Last update: December 2023
2023
- Protonotarios, N. E., G. A. Kastis, A. D. Fotopoulos, A. G. Tzakos, D. Vlachos, and N. Dikaios. “Motion-compensated pet image reconstruction via separable parabolic surrogates.” Mathematics 11 (2023). doi:10.3390/math11010055
[BibTeX] [Abstract]
The effective resolution of positron emission tomography (PET) can be significantly degraded by patient motion during data acquisition. This is especially true in the thorax due to respiratory motion. This study concentrates on the improvement of motion correction algorithms both in terms of image quality and computational cost. In this paper, we present a novel motion-compensated image reconstruction (MCIR) algorithm based on a parabolic surrogate likelihood function instead of the loglikelihood function of the expectation maximization (EM) algorithm. The theoretical advantage of the parabolic surrogate algorithm lies within the fact that its loglikelihood is upper bounded by the EM loglikelihood, thus it will converge faster than EM. This is of particular importance in PET motion correction, where reconstructions are very computationally demanding. Relaxation parameters were also introduced to converge closer to the maximum likelihood (ML) solution and achieve lower noise levels. Image reconstructions with embedded relaxation parameters actually converged to better solutions than the corresponding ones without relaxation. Motion-compensated parabolic surrogates were indeed shown to accelerate convergence compared to EM, without reaching a limit cycle. Nonetheless, with the incorporation of ordered subsets in the reconstruction setting, the improvement was less evident.
@article{Protonotarios2023, abstract = {The effective resolution of positron emission tomography (PET) can be significantly degraded by patient motion during data acquisition. This is especially true in the thorax due to respiratory motion. This study concentrates on the improvement of motion correction algorithms both in terms of image quality and computational cost. In this paper, we present a novel motion-compensated image reconstruction (MCIR) algorithm based on a parabolic surrogate likelihood function instead of the loglikelihood function of the expectation maximization (EM) algorithm. The theoretical advantage of the parabolic surrogate algorithm lies within the fact that its loglikelihood is upper bounded by the EM loglikelihood, thus it will converge faster than EM. This is of particular importance in PET motion correction, where reconstructions are very computationally demanding. Relaxation parameters were also introduced to converge closer to the maximum likelihood (ML) solution and achieve lower noise levels. Image reconstructions with embedded relaxation parameters actually converged to better solutions than the corresponding ones without relaxation. Motion-compensated parabolic surrogates were indeed shown to accelerate convergence compared to EM, without reaching a limit cycle. Nonetheless, with the incorporation of ordered subsets in the reconstruction setting, the improvement was less evident.}, author = {N.E. Protonotarios and G.A. Kastis and A.D. Fotopoulos and A.G. Tzakos and D. Vlachos and N. Dikaios}, doi = {10.3390/math11010055}, issue = {1}, journal = {Mathematics}, title = {Motion-Compensated PET Image Reconstruction via Separable Parabolic Surrogates}, volume = {11}, year = {2023}, } - Kandyliari, A., P. Potsaki, P. Bousdouni, C. Kaloteraki, M. Christofilea, K. Almpounioti, A. Moutsou, C. K. Fasoulis, L. V. Polychronis, V. K. Gkalpinos, A. G. Tzakos, and A. E. Koutelidakis. “Development of dairy products fortified with plant extracts: antioxidant and phenolic content characterization.” Antioxidants 12 (2023). doi:10.3390/antiox12020500
[BibTeX] [Abstract]
In recent decades, there has been growing interest in the fortification of dairy products with antioxidants and phenolics derived from plant byproducts and herbs. The present study focused on the analysis of dairy products, including kefir, cream cheese, yogurt, and vegan yogurt, enhanced with aqueous extracts of plant byproducts (Citrus aurantium peel, Citrus limon peel and Rosa canina seed) and herbs (Sideritis spp., Hypericum perforatum, Origanum dictamnus, Mentha pulegium L., Melissa oficinallis, Mentha spicata L. and Lavandula angustifolia) to characterize their antioxidant content, phenolic profile, and organoleptic characteristics. Antioxidant and phenolic content were determined by Folin–Ciocalteu and ferric reducing antioxidant power (FRAP) assays and presented values up to 46.61 ± 7.22 mmol Fe2+/L and 82.97 ± 4.29 mg gallic acid (GAE)/g, respectively for the aqueous extracts, as well as up to 0.68 ± 0.06 mmol Fe2+/L and 2.82 ± 0.36 mg GAE/g for the fortified dairy products. The bioavailability of antioxidants and phenolics in fortified foods was determined after in vitro digestion and ranged between 4 and 68%. The phytochemical profile of the aqueous extracts was determined by mass spectrometry, and 162 phytochemicals were determined, from which 128 belong to the polyphenol family including flavonoids and phenolic acids. Furthermore, most of the identified compounds have been recorded to possess enhanced antioxidant capacity in correlation to the in vitro findings. Finally, organoleptic evaluation showed an overall acceptability around 3.0 ± 1.0 on a 5-point scale. In conclusion, the studied plants and herbal extracts can be used for the fortification of a variety of dairy products with potential positive effects on human health.
@article{Kandyliari2023, abstract = {In recent decades, there has been growing interest in the fortification of dairy products with antioxidants and phenolics derived from plant byproducts and herbs. The present study focused on the analysis of dairy products, including kefir, cream cheese, yogurt, and vegan yogurt, enhanced with aqueous extracts of plant byproducts (Citrus aurantium peel, Citrus limon peel and Rosa canina seed) and herbs (Sideritis spp., Hypericum perforatum, Origanum dictamnus, Mentha pulegium L., Melissa oficinallis, Mentha spicata L. and Lavandula angustifolia) to characterize their antioxidant content, phenolic profile, and organoleptic characteristics. Antioxidant and phenolic content were determined by Folin–Ciocalteu and ferric reducing antioxidant power (FRAP) assays and presented values up to 46.61 ± 7.22 mmol Fe2+/L and 82.97 ± 4.29 mg gallic acid (GAE)/g, respectively for the aqueous extracts, as well as up to 0.68 ± 0.06 mmol Fe2+/L and 2.82 ± 0.36 mg GAE/g for the fortified dairy products. The bioavailability of antioxidants and phenolics in fortified foods was determined after in vitro digestion and ranged between 4 and 68%. The phytochemical profile of the aqueous extracts was determined by mass spectrometry, and 162 phytochemicals were determined, from which 128 belong to the polyphenol family including flavonoids and phenolic acids. Furthermore, most of the identified compounds have been recorded to possess enhanced antioxidant capacity in correlation to the in vitro findings. Finally, organoleptic evaluation showed an overall acceptability around 3.0 ± 1.0 on a 5-point scale. In conclusion, the studied plants and herbal extracts can be used for the fortification of a variety of dairy products with potential positive effects on human health.}, author = {A. Kandyliari and P. Potsaki and P. Bousdouni and C. Kaloteraki and M. Christofilea and K. Almpounioti and A. Moutsou and C.K. Fasoulis and L.V. Polychronis and V.K. Gkalpinos and A.G. Tzakos and A.E. Koutelidakis}, doi = {10.3390/antiox12020500}, issue = {2}, journal = {Antioxidants}, title = {Development of Dairy Products Fortified with Plant Extracts: Antioxidant and Phenolic Content Characterization}, volume = {12}, year = {2023}, } - Gkalpinos, V. K., V. A. Anagnostou, G. Mitropoulou, V. Kompoura, I. Karapantzou, C. K. Fasoulis, E. P. Vasdekis, Y. Kourkoutas, and A. G. Tzakos. “Aloysia citrodora extracts cultivated in greece as antioxidants and potent regulators of food microbiota.” Applied sciences (switzerland) 13 (2023). doi:10.3390/app13063663
[BibTeX] [Abstract]
Featured Application: Recently, plant extracts have attracted scientific and industrial attention as growth stimulators of desired microbes (probiotics), although their antimicrobial properties are well-known. In our study, Aloysia citrodora extracts stimulated the growth of a wild-type and a commercial Lacticaseibacillus rhamnosus strain, while growth inhibitory activity against common food-spoilage and pathogenic microbes was documented. Thus, they may be considered potential candidates for functional regulation of food microbiota, provided that they are used at the optimum concentration in food systems. Plant extracts contain valuable sources of biologically active molecules and, lately, have attracted scientific and industrial interest as inhibitors of food-borne pathogens and growth stimulators of beneficial microbes. In this vein, the aim of this study was to explore and exploit the effect of Aloysia citrodora extracts as potent functional regulators of food microbiota by stimulating the growth of probiotic strains and by suppressing the evolution of common food-spoilage and pathogenic bacteria. Aqueous and ethanolic extracts of A. citrodora, rich in polyphenols, were prepared and their phytochemical composition was unveiled by LC-triple quadruple and LC-QToF mass spectrometry. The growth stimulatory activity of a wild-type Lacticaseibacillus rhamnosus strain, along with L. rhamnosus GG, used as a control, was assessed by monitoring cell growth in the presence of sodium chloride, bile salts, thermal stress, and alcohol. We found that the aqueous extract stimulated the growth of probiotic strains at 0.5 mg/mL. At the same concentration, stimulatory activity was observed for the wild-type L. rhamnosus in the presence of bile salts and alcohol and for L. rhamnosus GG in the presence of NaCl and under thermal stress. The ethanolic extract of A. citrodora exhibited prebiotic activity at 0.25 mg/mL, but did not promote the growth of the strains under the stress conditions tested. In addition, minimum inhibitory (MIC) and minimum bactericidal concentrations (MBC) against food-spoilage and pathogenic microbes were determined. The strongest growth inhibitory activity of foodborne pathogens was noted by the A. citrodora ethanolic extract, while the aqueous A. citrodora extract had no effect against Escherichia coli. Importantly, the spoilage and pathogenic microbes tested were more sensitive to the extracts than the probiotic strains, indicating a significant contribution to the functional regulation of food microbiota, provided that they are used at the optimum concentration.
@article{Gkalpinos2023, abstract = {Featured Application: Recently, plant extracts have attracted scientific and industrial attention as growth stimulators of desired microbes (probiotics), although their antimicrobial properties are well-known. In our study, Aloysia citrodora extracts stimulated the growth of a wild-type and a commercial Lacticaseibacillus rhamnosus strain, while growth inhibitory activity against common food-spoilage and pathogenic microbes was documented. Thus, they may be considered potential candidates for functional regulation of food microbiota, provided that they are used at the optimum concentration in food systems. Plant extracts contain valuable sources of biologically active molecules and, lately, have attracted scientific and industrial interest as inhibitors of food-borne pathogens and growth stimulators of beneficial microbes. In this vein, the aim of this study was to explore and exploit the effect of Aloysia citrodora extracts as potent functional regulators of food microbiota by stimulating the growth of probiotic strains and by suppressing the evolution of common food-spoilage and pathogenic bacteria. Aqueous and ethanolic extracts of A. citrodora, rich in polyphenols, were prepared and their phytochemical composition was unveiled by LC-triple quadruple and LC-QToF mass spectrometry. The growth stimulatory activity of a wild-type Lacticaseibacillus rhamnosus strain, along with L. rhamnosus GG, used as a control, was assessed by monitoring cell growth in the presence of sodium chloride, bile salts, thermal stress, and alcohol. We found that the aqueous extract stimulated the growth of probiotic strains at 0.5 mg/mL. At the same concentration, stimulatory activity was observed for the wild-type L. rhamnosus in the presence of bile salts and alcohol and for L. rhamnosus GG in the presence of NaCl and under thermal stress. The ethanolic extract of A. citrodora exhibited prebiotic activity at 0.25 mg/mL, but did not promote the growth of the strains under the stress conditions tested. In addition, minimum inhibitory (MIC) and minimum bactericidal concentrations (MBC) against food-spoilage and pathogenic microbes were determined. The strongest growth inhibitory activity of foodborne pathogens was noted by the A. citrodora ethanolic extract, while the aqueous A. citrodora extract had no effect against Escherichia coli. Importantly, the spoilage and pathogenic microbes tested were more sensitive to the extracts than the probiotic strains, indicating a significant contribution to the functional regulation of food microbiota, provided that they are used at the optimum concentration.}, author = {V.K. Gkalpinos and V.A. Anagnostou and G. Mitropoulou and V. Kompoura and I. Karapantzou and C.K. Fasoulis and E.P. Vasdekis and Y. Kourkoutas and A.G. Tzakos}, doi = {10.3390/app13063663}, issue = {6}, journal = {Applied Sciences (Switzerland)}, title = {Aloysia citrodora Extracts Cultivated in Greece as Antioxidants and Potent Regulators of Food Microbiota}, volume = {13}, year = {2023}, } - Diamantis, D., A. D. Tsiailanis, C. Papaemmanouil, M. -C. Nika, Z. Kanaki, Golic S. Grdadolnik, A. Babic, E. P. Tzakos, I. Fournier, M. Salzet, S. Gupta, and A. G. Tzakos. “Development of a novel apigenin prodrug programmed for alkaline-phosphatase instructed self-inhibition to combat cancer.” Journal of biomolecular structure and dynamics (2023). doi:10.1080/07391102.2023.2247083
[BibTeX] [Abstract]
Elevated levels of alkaline phosphatase (ALP) in the tumor microenvironment (TME) are a hallmark of cancer progression and thus inhibition of ALP could serve as an effective approach against cancer. Herein, we developed a novel prodrug approach to tackle cancer that bears self-inhibiting alkaline phosphatase-responsiveness properties that can enhance at the same time the solubility of the parent compound. To probe this novel concept, we selected apigenin as the cytotoxic agent since we first unveiled, that it directly interacts and inhibits ALP activity. Consequently, we rationally designed and synthesized, using a self-immolative linker, an ALP responsive apigenin-based phosphate prodrug, phospho-apigenin. Phospho-apigenin markedly increased the stability of the parent compound apigenin. Furthermore, the prodrug exhibited enhanced antiproliferative effect in malignant cells with elevated ALP levels, compared to apigenin. This recorded potency of the developed prodrug was further confirmed in vivo where phospho-apigenin significantly suppressed by 52.8% the growth of PC-3 xenograft tumors. Communicated by Ramaswamy H. Sarma.
@article{Diamantis2023, abstract = {Elevated levels of alkaline phosphatase (ALP) in the tumor microenvironment (TME) are a hallmark of cancer progression and thus inhibition of ALP could serve as an effective approach against cancer. Herein, we developed a novel prodrug approach to tackle cancer that bears self-inhibiting alkaline phosphatase-responsiveness properties that can enhance at the same time the solubility of the parent compound. To probe this novel concept, we selected apigenin as the cytotoxic agent since we first unveiled, that it directly interacts and inhibits ALP activity. Consequently, we rationally designed and synthesized, using a self-immolative linker, an ALP responsive apigenin-based phosphate prodrug, phospho-apigenin. Phospho-apigenin markedly increased the stability of the parent compound apigenin. Furthermore, the prodrug exhibited enhanced antiproliferative effect in malignant cells with elevated ALP levels, compared to apigenin. This recorded potency of the developed prodrug was further confirmed in vivo where phospho-apigenin significantly suppressed by 52.8% the growth of PC-3 xenograft tumors. Communicated by Ramaswamy H. Sarma.}, author = {D. Diamantis and A.D. Tsiailanis and C. Papaemmanouil and M.-C. Nika and Z. Kanaki and S. Golic Grdadolnik and A. Babic and E.P. Tzakos and I. Fournier and M. Salzet and S. Gupta and A.G. Tzakos}, doi = {10.1080/07391102.2023.2247083}, journal = {Journal of Biomolecular Structure and Dynamics}, title = {Development of a novel apigenin prodrug programmed for alkaline-phosphatase instructed self-inhibition to combat cancer}, year = {2023}, } - Zoi, V., M. Giannakopoulou, G. A. Alexiou, P. Bouziotis, S. Thalasselis, A. G. Tzakos, A. Fotopoulos, A. N. Papadopoulos, A. P. Kyritsis, and C. Sioka. “Nuclear medicine and cancer theragnostics: basic concepts.” Diagnostics 13 (2023). doi:10.3390/diagnostics13193064
[BibTeX] [Abstract]
Cancer theragnostics is a novel approach that combines diagnostic imaging and radionuclide therapy. It is based on the use of a pair of radiopharmaceuticals, one optimized for positron emission tomography imaging through linkage to a proper radionuclide, and the other bearing an alpha- or beta-emitter isotope that can induce significant damage to cancer cells. In recent years, the use of theragnostics in nuclear medicine clinical practice has increased considerably, and thus investigation has focused on the identification of novel radionuclides that can bind to molecular targets that are typically dysregulated in different cancers. The major advantages of the theragnostic approach include the elimination of multi-step procedures, reduced adverse effects to normal tissues, early diagnosis, better predictive responses, and personalized patient care. This review aims to discuss emerging theragnostic molecules that have been investigated in a series of human malignancies, including gliomas, thyroid cancer, neuroendocrine tumors, cholangiocarcinoma, and prostate cancer, as well as potent and recently introduced molecular targets, like cell-surface receptors, kinases, and cell adhesion proteins. Furthermore, special reference has been made to copper radionuclides as theragnostic agents and their radiopharmaceutical applications since they present promising alternatives to the well-studied gallium-68 and lutetium-177.
@article{Zoi2023, abstract = {Cancer theragnostics is a novel approach that combines diagnostic imaging and radionuclide therapy. It is based on the use of a pair of radiopharmaceuticals, one optimized for positron emission tomography imaging through linkage to a proper radionuclide, and the other bearing an alpha- or beta-emitter isotope that can induce significant damage to cancer cells. In recent years, the use of theragnostics in nuclear medicine clinical practice has increased considerably, and thus investigation has focused on the identification of novel radionuclides that can bind to molecular targets that are typically dysregulated in different cancers. The major advantages of the theragnostic approach include the elimination of multi-step procedures, reduced adverse effects to normal tissues, early diagnosis, better predictive responses, and personalized patient care. This review aims to discuss emerging theragnostic molecules that have been investigated in a series of human malignancies, including gliomas, thyroid cancer, neuroendocrine tumors, cholangiocarcinoma, and prostate cancer, as well as potent and recently introduced molecular targets, like cell-surface receptors, kinases, and cell adhesion proteins. Furthermore, special reference has been made to copper radionuclides as theragnostic agents and their radiopharmaceutical applications since they present promising alternatives to the well-studied gallium-68 and lutetium-177.}, author = {V. Zoi and M. Giannakopoulou and G.A. Alexiou and P. Bouziotis and S. Thalasselis and A.G. Tzakos and A. Fotopoulos and A.N. Papadopoulos and A.P. Kyritsis and C. Sioka}, doi = {10.3390/diagnostics13193064}, issue = {19}, journal = {Diagnostics}, title = {Nuclear Medicine and Cancer Theragnostics: Basic Concepts}, volume = {13}, year = {2023}, } - Christou, A., N. A. Parisis, T. Venianakis, A. Barbouti, A. G. Tzakos, I. P. Gerothanassis, and V. Goulas. “Ultrasound-assisted extraction of taro leaf antioxidants using natural deep eutectic solvents: an eco-friendly strategy for the valorization of crop residues.” Antioxidants 12 (2023). doi:10.3390/antiox12101801
[BibTeX] [Abstract]
Colocasia esculenta L. leaves are considered a by-product of taro cultivation and are discarded as environmental waste, despite their valuable phenolic composition. Their valorization to obtain value-added substances for medicinal, food, and cosmetic applications is the aim of the current work. An ultrasound-assisted extraction was developed for the environmentally friendly and sustainable isolation of taro leaf antioxidants using natural deep eutectic solvents (NaDESs). Among the utilized solvents, the NaDES based on betaine and ethylene glycol provided the best extraction efficiencies in terms of polyphenolic content and antioxidant activity. Multi-response optimization suggested a solvent-to-solid ratio of 10 mL g−1, a processing time of 60 min, an extraction temperature of 60 °C, and a water content of 33.8% (w/w) as optimal extraction parameters. Leaf extract obtained under these optimum operational parameters demonstrated a strong radical scavenging activity against 2,2-diphenyl-1-picrylhydrazyl (65.80 ± 0.87%), a high ferric reducing antioxidant power (126.62 ± 1.92 μmol TE g−1 sample), and significant protection against oxidative stress-induced DNA damage. The chromatographic characterization of the optimum extract revealed its richness in flavonoids (flavones and flavonols). The outcomes of the present study suggest that the proposed method could serve as a highly efficient and green alternative for the recovery of polyphenols from agricultural wastes.
@article{Christou2023, abstract = {Colocasia esculenta L. leaves are considered a by-product of taro cultivation and are discarded as environmental waste, despite their valuable phenolic composition. Their valorization to obtain value-added substances for medicinal, food, and cosmetic applications is the aim of the current work. An ultrasound-assisted extraction was developed for the environmentally friendly and sustainable isolation of taro leaf antioxidants using natural deep eutectic solvents (NaDESs). Among the utilized solvents, the NaDES based on betaine and ethylene glycol provided the best extraction efficiencies in terms of polyphenolic content and antioxidant activity. Multi-response optimization suggested a solvent-to-solid ratio of 10 mL g−1, a processing time of 60 min, an extraction temperature of 60 °C, and a water content of 33.8% (w/w) as optimal extraction parameters. Leaf extract obtained under these optimum operational parameters demonstrated a strong radical scavenging activity against 2,2-diphenyl-1-picrylhydrazyl (65.80 ± 0.87%), a high ferric reducing antioxidant power (126.62 ± 1.92 μmol TE g−1 sample), and significant protection against oxidative stress-induced DNA damage. The chromatographic characterization of the optimum extract revealed its richness in flavonoids (flavones and flavonols). The outcomes of the present study suggest that the proposed method could serve as a highly efficient and green alternative for the recovery of polyphenols from agricultural wastes.}, author = {A. Christou and N.A. Parisis and T. Venianakis and A. Barbouti and A.G. Tzakos and I.P. Gerothanassis and V. Goulas}, doi = {10.3390/antiox12101801}, issue = {10}, journal = {Antioxidants}, title = {Ultrasound-Assisted Extraction of Taro Leaf Antioxidants Using Natural Deep Eutectic Solvents: An Eco-Friendly Strategy for the Valorization of Crop Residues}, volume = {12}, year = {2023}, } - Tsiailanis, A. D., C. C. Tellis, P. Papakyriakopoulou, A. D. Kostagianni, V. Gkalpinos, C. M. Chatzigiannis, N. Kostomitsopoulos, G. Valsami, A. D. Tselepis, and A. G. Tzakos. “Development of a novel apigenin dosage form as a substitute for the modern triple antithrombotic regimen.” Molecules 28 (2023). doi:10.3390/molecules28052311
[BibTeX] [Abstract]
The simultaneous administration of three antiplatelet agents has been proposed as an efficient strategy for the secondary prevention of atherothrombotic events and is included in the European guidelines. However, this strategy presented an increased risk of bleeding; therefore, the identification of new antiplatelet agents, with improved efficacy and diminished side effects, is of great importance. In silico studies, UPLC/MS Q-TOF plasma stability, in vitro platelet aggregation experiments, and pharmacokinetic studies were exploited. In the present study, it has been predicted that the flavonoid apigenin could target different platelet activation pathways, including P2Y12, protease-activated receptor-1 (PAR-1), and cyclooxygenase 1 (COX-1). To enhance apigenin’s potency, hybridization with docosahexaenoic acid (DHA) was performed, as fatty acids have illustrated potent efficacy against cardiovascular diseases (CVDs). The new molecular hybrid, termed 4′-DHA-apigenin, demonstrated enhanced inhibitory activity against platelet aggregation induced by thrombin receptor activator peptide-6 (TRAP-6), adenosine diphosphate (ADP), and arachidonic acid (AA), with respect to the parent apigenin. The 4′-DHA-apigenin hybrid illustrated an almost 2-fold enhanced inhibitory activity, with respect to apigenin, and an almost 3-fold enhanced inhibitory activity, with respect to DHA, for the ADP-induced platelet aggregation. Additionally, the hybrid presented a more than 12-fold enhanced inhibitory activity with respect to DHA for the TRAP-6 induced platelet aggregation. Furthermore, a 2-fold enhanced inhibitory activity was recorded for the 4′-DHA-apigenin hybrid for the AA-induced platelet aggregation with respect to apigenin. To surmount the reduced LC-MS based plasma stability, a novel dosage form in olive oil has been developed. The 4′-DHA-apigenin olive oil-based formulation presented an enhanced antiplatelet inhibitory effect in three activation pathways. To further explore the pharmacokinetic profile of 4′-DHA-apigenin in olive oil formulations, a UPLC/MS Q-TOF protocol has been established to quantify the serum levels of apigenin after oral administration to C57BL/6J wild type mice. The olive oil-based formulation of 4′-DHA-apigenin demonstrated an increase in apigenin bioavailability of 262 %. This study may offer a new therapeutic strategy tailored to improve the treatment of CVDs.
@article{Tsiailanis2023, abstract = {The simultaneous administration of three antiplatelet agents has been proposed as an efficient strategy for the secondary prevention of atherothrombotic events and is included in the European guidelines. However, this strategy presented an increased risk of bleeding; therefore, the identification of new antiplatelet agents, with improved efficacy and diminished side effects, is of great importance. In silico studies, UPLC/MS Q-TOF plasma stability, in vitro platelet aggregation experiments, and pharmacokinetic studies were exploited. In the present study, it has been predicted that the flavonoid apigenin could target different platelet activation pathways, including P2Y12, protease-activated receptor-1 (PAR-1), and cyclooxygenase 1 (COX-1). To enhance apigenin’s potency, hybridization with docosahexaenoic acid (DHA) was performed, as fatty acids have illustrated potent efficacy against cardiovascular diseases (CVDs). The new molecular hybrid, termed 4′-DHA-apigenin, demonstrated enhanced inhibitory activity against platelet aggregation induced by thrombin receptor activator peptide-6 (TRAP-6), adenosine diphosphate (ADP), and arachidonic acid (AA), with respect to the parent apigenin. The 4′-DHA-apigenin hybrid illustrated an almost 2-fold enhanced inhibitory activity, with respect to apigenin, and an almost 3-fold enhanced inhibitory activity, with respect to DHA, for the ADP-induced platelet aggregation. Additionally, the hybrid presented a more than 12-fold enhanced inhibitory activity with respect to DHA for the TRAP-6 induced platelet aggregation. Furthermore, a 2-fold enhanced inhibitory activity was recorded for the 4′-DHA-apigenin hybrid for the AA-induced platelet aggregation with respect to apigenin. To surmount the reduced LC-MS based plasma stability, a novel dosage form in olive oil has been developed. The 4′-DHA-apigenin olive oil-based formulation presented an enhanced antiplatelet inhibitory effect in three activation pathways. To further explore the pharmacokinetic profile of 4′-DHA-apigenin in olive oil formulations, a UPLC/MS Q-TOF protocol has been established to quantify the serum levels of apigenin after oral administration to C57BL/6J wild type mice. The olive oil-based formulation of 4′-DHA-apigenin demonstrated an increase in apigenin bioavailability of 262 %. This study may offer a new therapeutic strategy tailored to improve the treatment of CVDs.}, author = {A.D. Tsiailanis and C.C. Tellis and P. Papakyriakopoulou and A.D. Kostagianni and V. Gkalpinos and C.M. Chatzigiannis and N. Kostomitsopoulos and G. Valsami and A.D. Tselepis and A.G. Tzakos}, doi = {10.3390/molecules28052311}, issue = {5}, journal = {Molecules}, title = {Development of a Novel Apigenin Dosage form as a Substitute for the Modern Triple Antithrombotic Regimen}, volume = {28}, year = {2023}, } - Leonis, G., V. Vakali, N. Zoupanou, N. Georgiou, D. A. Diamantis, A. G. Tzakos, T. Mavromoustakos, and D. Tzeli. “Computational and spectroscopic analysis of the quercetin encapsulation in (2hp-β-cd)
2 and (2,6me-β-cd)2 complexes.” Journal of molecular structure 1294 (2023). doi:10.1016/j.molstruc.2023.136430
[BibTeX] [Abstract]
Quercetin protects against many diseases due to its radical scavenging and anti-inflammatory properties. However, due to its poor bioavailability numerous types of nanocarriers have been evolved to increase quercetin solubility and to design tissue-specific delivery systems. Here, we study the entrapment of quercetin(QUE) in two dimeric assemblies formed by 2HP-β-CD and 2,6Me-β-CD, employing DFT calculations, NMR and fluorescent spectroscopy. Via NMR and fluorescent spectroscopy, it was revealed that the QUE:CDs stoichiometry for optimal complex formation follows a 1:2 pattern. DFT indicated that although both dimeric assemblies of 2HP-β-CD and 2,6Me-β-CD, as well as their encapsulation quercetin complexes are stable, the former dimer and the QUE@2HP-β-CD2 complex demonstrate the highest level of stability. The absorption spectrum of QUE in CD and CD2 was calculated. Encapsulation influences it, resulting in red and blue shifts, and in differences in the intensities. Only, the dimeric assemblies affect the electron density of QUE resulting in major peaks at about 250 nm, which are charge transfer (CT) or partially CT excitations. Finally, for the encapsulated QUE in CDs, the calculated T1→S0 vertical de-excitation is about 570 nm in the single CDs and about 800 nm in the dimeric complexes, making these complexes potential candidates for PDT.
@article{Leonis2023, abstract = {Quercetin protects against many diseases due to its radical scavenging and anti-inflammatory properties. However, due to its poor bioavailability numerous types of nanocarriers have been evolved to increase quercetin solubility and to design tissue-specific delivery systems. Here, we study the entrapment of quercetin(QUE) in two dimeric assemblies formed by 2HP-β-CD and 2,6Me-β-CD, employing DFT calculations, NMR and fluorescent spectroscopy. Via NMR and fluorescent spectroscopy, it was revealed that the QUE:CDs stoichiometry for optimal complex formation follows a 1:2 pattern. DFT indicated that although both dimeric assemblies of 2HP-β-CD and 2,6Me-β-CD, as well as their encapsulation quercetin complexes are stable, the former dimer and the QUE@2HP-β-CD2 complex demonstrate the highest level of stability. The absorption spectrum of QUE in CD and CD2 was calculated. Encapsulation influences it, resulting in red and blue shifts, and in differences in the intensities. Only, the dimeric assemblies affect the electron density of QUE resulting in major peaks at about 250 nm, which are charge transfer (CT) or partially CT excitations. Finally, for the encapsulated QUE in CDs, the calculated T1→S0 vertical de-excitation is about 570 nm in the single CDs and about 800 nm in the dimeric complexes, making these complexes potential candidates for PDT.}, author = {G. Leonis and V. Vakali and N. Zoupanou and N. Georgiou and D.A. Diamantis and A.G. Tzakos and T. Mavromoustakos and D. Tzeli}, doi = {10.1016/j.molstruc.2023.136430}, journal = {Journal of Molecular Structure}, title = {Computational and spectroscopic analysis of the Quercetin encapsulation in (2HP-β-CD)2 and (2,6Me-β-CD)2 complexes}, volume = {1294}, year = {2023}, } - Papandreou, C., C. Papagiannopoulos, M. Koutsonida, A. Kanellopoulou, G. Markozannes, G. Polychronidis, A. G. Tzakos, G. A. Fragkiadakis, E. Evangelou, E. Ntzani, E. Aretouli, and K. K. Tsilidis. “Mediterranean diet related metabolite profiles and cognitive performance.” Clinical nutrition 42 (2023): 173-181. doi:10.1016/j.clnu.2022.12.012
[BibTeX] [Abstract]
{Background & aims: Evidence suggests that adherence to the Mediterranean diet (MedDiet) affects human metabolism and may contribute to better cognitive performance. However, the underlying mechanisms are not clear. Objective: We generated a metabolite profile for adherence to MedDiet and evaluated its cross–sectional association with aspects of cognitive performance. Methods: A total of 1250 healthy Greek middle-aged adults from the Epirus Health Study cohort were included in the analysis. Adherence to the MedDiet was assessed using the 14-point Mediterranean Diet Adherence Screener (MEDAS); cognition was measured using the Trail Making Test, the Verbal Fluency test and the Logical Memory test. A targeted metabolite profiling (n = 250 metabolites) approach was applied, using a high-throughput nuclear magnetic resonance platform. We used elastic net regularized regressions, with a 10-fold cross-validation procedure, to identify a metabolite profile for MEDAS. We evaluated the associations of the identified metabolite profile and MEDAS with cognitive tests, using multivariable linear regression models. Results: We identified a metabolite profile composed of 42 metabolites, mainly lipoprotein subclasses and fatty acids, significantly correlated with MedDiet adherence (Pearson r = 0.35
@article{Papandreou2023, abstract = {Background & aims: Evidence suggests that adherence to the Mediterranean diet (MedDiet) affects human metabolism and may contribute to better cognitive performance. However, the underlying mechanisms are not clear. Objective: We generated a metabolite profile for adherence to MedDiet and evaluated its cross–sectional association with aspects of cognitive performance. Methods: A total of 1250 healthy Greek middle-aged adults from the Epirus Health Study cohort were included in the analysis. Adherence to the MedDiet was assessed using the 14-point Mediterranean Diet Adherence Screener (MEDAS); cognition was measured using the Trail Making Test, the Verbal Fluency test and the Logical Memory test. A targeted metabolite profiling (n = 250 metabolites) approach was applied, using a high-throughput nuclear magnetic resonance platform. We used elastic net regularized regressions, with a 10-fold cross-validation procedure, to identify a metabolite profile for MEDAS. We evaluated the associations of the identified metabolite profile and MEDAS with cognitive tests, using multivariable linear regression models. Results: We identified a metabolite profile composed of 42 metabolites, mainly lipoprotein subclasses and fatty acids, significantly correlated with MedDiet adherence (Pearson r = 0.35, P-value = 5.5 × 10−37). After adjusting for known risk factors and accounting for multiple testing, the metabolite profile and MEDAS were not associated with the cognitive tests. Conclusions: A plasma metabolite profile related to better adherence to the MedDiet was not associated with the tested aspects of cognitive performance, in a middle-aged Mediterranean population.}, author = {C. Papandreou and C. Papagiannopoulos and M. Koutsonida and A. Kanellopoulou and G. Markozannes and G. Polychronidis and A.G. Tzakos and G.A. Fragkiadakis and E. Evangelou and E. Ntzani and E. Aretouli and K.K. Tsilidis}, doi = {10.1016/j.clnu.2022.12.012}, issue = {2}, journal = {Clinical Nutrition}, pages = {173-181}, title = {Mediterranean diet related metabolite profiles and cognitive performance}, volume = {42}, year = {2023}, }
2022
- Chontzopoulou, E., C. D. Papaemmanouil, M. V. Chatziathanasiadou, D. Kolokouris, S. Kiriakidi, A. Konstantinidi, I. Gerogianni, T. Tselios, I. K. Kostakis, E. D. Chrysina, A. G. Tzakos, and T. Mavromoustakos. “Molecular investigation of artificial and natural sweeteners as potential anti-inflammatory agents.” Journal of biomolecular structure and dynamics 40 (2022): 12608-12620. doi:10.1080/07391102.2021.1973565
[BibTeX] [Abstract]
Repurposing existing drugs, as well as natural and artificial sweeteners for novel therapeutic indications could speed up the drug discovery process since numerous associated risks and costs for drug development can be surpassed. In this study, natural and artificial sweeteners have been evaluated by in silico and experimental studies for their potency to inhibit lipoxygenase enzyme, an enzyme participating in the inflammation pathway. A variety of different methods pinpointed that aspartame inhibits the lipoxygenase isoform 1 (LOX-1). In particular, “LOX-aspartame” complex, that was predicted by docking studies, was further evaluated by Molecular Dynamics (MD) simulations in order to assess the stability of the complex. The binding energy of the complex has been calculated after MD simulations using Molecular Mechanics/Generalized Born Surface Area (MM/GBSA) method. Furthermore, Quantum Mechanics/Molecular Mechanics (QM/MM) calculations have been applied for geometry optimization of the “enzyme-ligand” complex. After having fully characterized the “LOX-aspartame” complex in silico, followed in vitro biological assays confirmed that aspartame inhibits LOX-1 (IC50=50 ± 3.0 μΜ) and blocks its biological response. The atomic details of aspartame’s interaction profile with LOX-1 were revealed through Saturation Transfer Difference (STD) NMR (Nuclear Magnetic Resonance). Finally, aspartame was also tested with Molecular Docking and Molecular Dynamics studies for its potent binding to a number of different LOX isoforms of many organisms, including human. The in silico methods indicated that aspartame could serve as a novel starting point for drug design against LOX enzyme. Communicated by Ramaswamy H. Sarma.
@article{Chontzopoulou2022, abstract = {Repurposing existing drugs, as well as natural and artificial sweeteners for novel therapeutic indications could speed up the drug discovery process since numerous associated risks and costs for drug development can be surpassed. In this study, natural and artificial sweeteners have been evaluated by in silico and experimental studies for their potency to inhibit lipoxygenase enzyme, an enzyme participating in the inflammation pathway. A variety of different methods pinpointed that aspartame inhibits the lipoxygenase isoform 1 (LOX-1). In particular, “LOX-aspartame” complex, that was predicted by docking studies, was further evaluated by Molecular Dynamics (MD) simulations in order to assess the stability of the complex. The binding energy of the complex has been calculated after MD simulations using Molecular Mechanics/Generalized Born Surface Area (MM/GBSA) method. Furthermore, Quantum Mechanics/Molecular Mechanics (QM/MM) calculations have been applied for geometry optimization of the “enzyme-ligand” complex. After having fully characterized the “LOX-aspartame” complex in silico, followed in vitro biological assays confirmed that aspartame inhibits LOX-1 (IC50=50 ± 3.0 μΜ) and blocks its biological response. The atomic details of aspartame’s interaction profile with LOX-1 were revealed through Saturation Transfer Difference (STD) NMR (Nuclear Magnetic Resonance). Finally, aspartame was also tested with Molecular Docking and Molecular Dynamics studies for its potent binding to a number of different LOX isoforms of many organisms, including human. The in silico methods indicated that aspartame could serve as a novel starting point for drug design against LOX enzyme. Communicated by Ramaswamy H. Sarma.}, author = {E. Chontzopoulou and C.D. Papaemmanouil and M.V. Chatziathanasiadou and D. Kolokouris and S. Kiriakidi and A. Konstantinidi and I. Gerogianni and T. Tselios and I.K. Kostakis and E.D. Chrysina and A.G. Tzakos and T. Mavromoustakos}, doi = {10.1080/07391102.2021.1973565}, issue = {23}, journal = {Journal of Biomolecular Structure and Dynamics}, pages = {12608-12620}, title = {Molecular investigation of artificial and natural sweeteners as potential anti-inflammatory agents}, volume = {40}, year = {2022}, } - Tsiailanis, A. D., E. I. Vrettos, M. Choleva, S. Kiriakidi, A. M. Ganai, T. K. Patha, R. Karpoormath, T. Mavromoustakos, E. Fragopoulou, and A. G. Tzakos. “Development of a dha-losartan hybrid as a potent inhibitor of multiple pathway-induced platelet aggregation.” Journal of biomolecular structure and dynamics 40 (2022): 13889-13900. doi:10.1080/07391102.2021.1996461
[BibTeX] [Abstract]
Despite the scientific progression in the prevention and treatment of cardiovascular diseases (CVDs) they remain the leading cause of mortality and disability worldwide. The classic treatment involves the simultaneous dosing of two antiplatelet drugs, aspirin and clopidogrel/prasugrel. However, besides drug resistance, severe side effects have been also manifested including acute bleeding and toxicity. Thus, new therapeutic agents with enhanced efficacy and diminished side effects are of importance. Towards this end, omega-3 (ω-3) fatty acids have demonstrated potent efficacy against CVDs through inhibiting platelet aggregation that bears a pivotal role in atherothrombosis. Another factor that displays a critical role in the pathogenesis of cardiovascular diseases is the renin-angiotensin system (RAS), and especially the AT1R blocker losartan that has been reported to exert antiplatelet activity mediated by this receptor. Along these lines, we envisaged developing a molecular hybrid consisted of docosahexaenoic acid (ω-3 fatty acid) and losartan, that could exert a notable antiplatelet effect against CVDs. The design and synthesis of the new DHA-losartan hybrid, designated DHA-L, bestowed with the additive properties of the parent compounds, is reported. In silico studies were first exploited to validate the potential of DHA-L to retain losartan’s ability to bind AT1R. The antiplatelet activity of DHA-L was evaluated against in vitro platelet aggregation induced by several platelet agonists. Notably, the hybrid illustrated a pleiotropic antiplatelet profile inhibiting platelet aggregation through multiple platelet activation pathways including P2Y12, PAR-1 (Protease-Activated Receptor-1), PAF (Platelet Activating Factor), COX-1 (cyclooxygenase-1) and collagen receptors. The stability of DHA-L in human plasma and in a wide range of pH values was also evaluated over time using an HPLC protocol. The hybridization approach described herein could pave the way for the development of novel potent multitargeted therapeutics with enhanced antiplatelet profile. Communicated by Ramaswamy H. Sarma.
@article{Tsiailanis2022, abstract = {Despite the scientific progression in the prevention and treatment of cardiovascular diseases (CVDs) they remain the leading cause of mortality and disability worldwide. The classic treatment involves the simultaneous dosing of two antiplatelet drugs, aspirin and clopidogrel/prasugrel. However, besides drug resistance, severe side effects have been also manifested including acute bleeding and toxicity. Thus, new therapeutic agents with enhanced efficacy and diminished side effects are of importance. Towards this end, omega-3 (ω-3) fatty acids have demonstrated potent efficacy against CVDs through inhibiting platelet aggregation that bears a pivotal role in atherothrombosis. Another factor that displays a critical role in the pathogenesis of cardiovascular diseases is the renin-angiotensin system (RAS), and especially the AT1R blocker losartan that has been reported to exert antiplatelet activity mediated by this receptor. Along these lines, we envisaged developing a molecular hybrid consisted of docosahexaenoic acid (ω-3 fatty acid) and losartan, that could exert a notable antiplatelet effect against CVDs. The design and synthesis of the new DHA-losartan hybrid, designated DHA-L, bestowed with the additive properties of the parent compounds, is reported. In silico studies were first exploited to validate the potential of DHA-L to retain losartan’s ability to bind AT1R. The antiplatelet activity of DHA-L was evaluated against in vitro platelet aggregation induced by several platelet agonists. Notably, the hybrid illustrated a pleiotropic antiplatelet profile inhibiting platelet aggregation through multiple platelet activation pathways including P2Y12, PAR-1 (Protease-Activated Receptor-1), PAF (Platelet Activating Factor), COX-1 (cyclooxygenase-1) and collagen receptors. The stability of DHA-L in human plasma and in a wide range of pH values was also evaluated over time using an HPLC protocol. The hybridization approach described herein could pave the way for the development of novel potent multitargeted therapeutics with enhanced antiplatelet profile. Communicated by Ramaswamy H. Sarma.}, author = {A.D. Tsiailanis and E.I. Vrettos and M. Choleva and S. Kiriakidi and A.M. Ganai and T.K. Patha and R. Karpoormath and T. Mavromoustakos and E. Fragopoulou and A.G. Tzakos}, doi = {10.1080/07391102.2021.1996461}, issue = {24}, journal = {Journal of Biomolecular Structure and Dynamics}, pages = {13889-13900}, title = {Development of a DHA-Losartan hybrid as a potent inhibitor of multiple pathway-induced platelet aggregation}, volume = {40}, year = {2022}, } - Vlachou, M., A. -S. Foscolos, A. Siamidi, A. Syriopoulou, N. Georgiou, A. Dedeloudi, A. D. Tsiailanis, A. G. Tzakos, T. Mavromoustakos, and I. P. Papanastasiou. “Biophysical evaluation and in vitro controlled release of two isomeric adamantane phenylalkylamines with antiproliferative/anticancer and analgesic activity.” Molecules 27 (2022). doi:10.3390/molecules27010007
[BibTeX] [Abstract]
The aqueous dissolution profile of the isomeric synthetic adamantane phenylalkylamine hy-drochlorides I and II was probed. These adducts have shown significant antiproliferative/anticancer activity associated with an analgesic profile against neuropathic pain. They are both devoid of toxic effects and show appreciable enzymatic human plasma stability. The structures of these two compounds have been elucidated using 2D NMR experiments, which were used to study their predominant conformations. Compound II’s scaffold appeared more flexible, as shown by the NOE spatial interactions between the alkyl bridge chain, the aromatic rings, and the adamantane nucleus. Conversely, compound I appeared very rigid, as it did not share significant NOEs between the aforementioned structural segments. MD simulations confirmed the NOE results. The aqueous dissolution profile of both molecules fits well with their minimum energy conformers’ features, which stem from the NOE data; this was nicely demonstrated, especially in the case of compound II.
@article{Vlachou2022, abstract = {The aqueous dissolution profile of the isomeric synthetic adamantane phenylalkylamine hy-drochlorides I and II was probed. These adducts have shown significant antiproliferative/anticancer activity associated with an analgesic profile against neuropathic pain. They are both devoid of toxic effects and show appreciable enzymatic human plasma stability. The structures of these two compounds have been elucidated using 2D NMR experiments, which were used to study their predominant conformations. Compound II’s scaffold appeared more flexible, as shown by the NOE spatial interactions between the alkyl bridge chain, the aromatic rings, and the adamantane nucleus. Conversely, compound I appeared very rigid, as it did not share significant NOEs between the aforementioned structural segments. MD simulations confirmed the NOE results. The aqueous dissolution profile of both molecules fits well with their minimum energy conformers’ features, which stem from the NOE data; this was nicely demonstrated, especially in the case of compound II.}, author = {M. Vlachou and A.-S. Foscolos and A. Siamidi and A. Syriopoulou and N. Georgiou and A. Dedeloudi and A.D. Tsiailanis and A.G. Tzakos and T. Mavromoustakos and I.P. Papanastasiou}, doi = {10.3390/molecules27010007}, issue = {1}, journal = {Molecules}, title = {Biophysical evaluation and in vitro controlled release of two isomeric adamantane phenylalkylamines with antiproliferative/anticancer and analgesic activity}, volume = {27}, year = {2022}, } - Kyrkou, S. G., E. I. Vrettos, D. Gorpas, T. Crook, N. Syed, and A. G. Tzakos. “Design principles governing the development of theranostic anticancer agents and their nanoformulations with photoacoustic properties.” Pharmaceutics 14 (2022). doi:10.3390/pharmaceutics14020362
[BibTeX] [Abstract]
The unmet need to develop novel approaches for cancer diagnosis and treatment has led to the evolution of theranostic agents, which usually include, in addition to the anticancer drug, an imaging agent based mostly on fluorescent agents. Over the past few years, a non-invasive pho-toacoustic imaging modality has been effectively integrated into theranostic agents. Herein, we shed light on the design principles governing the development of theranostic agents with photoa-coustic properties, which can be formulated into nanocarriers to enhance their potency. Specifi-cally, we provide an extensive analysis of their individual constituents including the imaging dyes, drugs, linkers, targeting moieties, and their formulation into nanocarriers. Along these lines, we present numerous relevant paradigms. Finally, we discuss the clinical relevance of the specific strategy, as also the limitations and future perspectives, and through this review, we envisage paving the way for the development of theranostic agents endowed with photoacoustic properties as effective anticancer medicines.
@article{Kyrkou2022, abstract = {The unmet need to develop novel approaches for cancer diagnosis and treatment has led to the evolution of theranostic agents, which usually include, in addition to the anticancer drug, an imaging agent based mostly on fluorescent agents. Over the past few years, a non-invasive pho-toacoustic imaging modality has been effectively integrated into theranostic agents. Herein, we shed light on the design principles governing the development of theranostic agents with photoa-coustic properties, which can be formulated into nanocarriers to enhance their potency. Specifi-cally, we provide an extensive analysis of their individual constituents including the imaging dyes, drugs, linkers, targeting moieties, and their formulation into nanocarriers. Along these lines, we present numerous relevant paradigms. Finally, we discuss the clinical relevance of the specific strategy, as also the limitations and future perspectives, and through this review, we envisage paving the way for the development of theranostic agents endowed with photoacoustic properties as effective anticancer medicines.}, author = {S.G. Kyrkou and E.I. Vrettos and D. Gorpas and T. Crook and N. Syed and A.G. Tzakos}, doi = {10.3390/pharmaceutics14020362}, issue = {2}, journal = {Pharmaceutics}, title = {Design Principles Governing the Development of Theranostic Anticancer Agents and Their Nanoformulations with Photoacoustic Properties}, volume = {14}, year = {2022}, } - Hajji, N., J. Garcia-Revilla, M. S. Soto, R. Perryman, J. Symington, C. C. Quarles, D. R. Healey, Y. Guo, M. L. Orta-Vázquez, S. Mateos-Cordero, J. L. Venero, and N. Syed. “Arginine deprivation alters microglial polarity and synergizes with radiation to eradicate non-arginine-auxotrophic glioblastoma tumors.” Journal of clinical investigation 132 (2022). doi:10.1172/JCI142137
[BibTeX] [Abstract]
New approaches for the management of glioblastoma (GBM) are an urgent and unmet clinical need. Here, we illustrate that the efficacy of radiotherapy for GBM is strikingly potentiated by concomitant therapy with the arginine-depleting agent ADI-PEG20 in a non-arginine-auxotrophic cellular background (argininosuccinate synthetase 1 positive). Moreover, this combination led to durable and complete radiological and pathological response, with extended disease-free survival in an orthotopic immune-competent model of GBM, with no significant toxicity. ADI-PEG20 not only enhanced the cellular sensitivity of argininosuccinate synthetase 1–positive GBM to ionizing radiation by elevated production of nitric oxide (NO) and hence generation of cytotoxic peroxynitrites, but also promoted glioma-associated macrophage/microglial infiltration into tumors and turned their classical antiinflammatory (protumor) phenotype into a proinflammatory (antitumor) phenotype. Our results provide an effective, well-tolerated, and simple strategy to improve GBM treatment that merits consideration for early evaluation in clinical trials.
@article{Hajji2022, abstract = {New approaches for the management of glioblastoma (GBM) are an urgent and unmet clinical need. Here, we illustrate that the efficacy of radiotherapy for GBM is strikingly potentiated by concomitant therapy with the arginine-depleting agent ADI-PEG20 in a non-arginine-auxotrophic cellular background (argininosuccinate synthetase 1 positive). Moreover, this combination led to durable and complete radiological and pathological response, with extended disease-free survival in an orthotopic immune-competent model of GBM, with no significant toxicity. ADI-PEG20 not only enhanced the cellular sensitivity of argininosuccinate synthetase 1–positive GBM to ionizing radiation by elevated production of nitric oxide (NO) and hence generation of cytotoxic peroxynitrites, but also promoted glioma-associated macrophage/microglial infiltration into tumors and turned their classical antiinflammatory (protumor) phenotype into a proinflammatory (antitumor) phenotype. Our results provide an effective, well-tolerated, and simple strategy to improve GBM treatment that merits consideration for early evaluation in clinical trials.}, author = {N. Hajji and J. Garcia-Revilla and M.S. Soto and R. Perryman and J. Symington and C.C. Quarles and D.R. Healey and Y. Guo and M.L. Orta-Vázquez and S. Mateos-Cordero and J.L. Venero and N. Syed}, doi = {10.1172/JCI142137}, issue = {6}, journal = {Journal of Clinical Investigation}, title = {Arginine deprivation alters microglial polarity and synergizes with radiation to eradicate non-arginine-auxotrophic glioblastoma tumors}, volume = {132}, year = {2022}, } - Tsiailanis, A. D., C. Pateraki, M. Kyriazou, C. M. Chatzigiannis, M. Chatziathanasiadou, N. Parisis, I. Mandala, A. G. Tzakos, and A. Koutinas. “Chemical profiling, bioactivity evaluation and the discovery of a novel biopigment produced by penicillium purpurogenum cbs 113139.” Molecules 27 (2022). doi:10.3390/molecules27010069
[BibTeX] [Abstract]
Biobased pigments are environmentally friendly alternatives to synthetic variants with an increased market demand. Production of pigments via fermentation is a promising process, yet optimization of the production yield and rate is crucial. Herein, we evaluated the potential of Penicillium purpurogenum to produce biobased pigments. Optimum sugar concentration was 30 g/L and optimum C:N ratio was 36:1 resulting in the production of 4.1–4.5 AU (namely Pigment Complex A). Supplementation with ammonium nitrate resulted in the production of 4.1–4.9 AU (namely Pigment Complex B). Pigments showed excellent pH stability. The major biopigments in Pigment Complex A were N-threonyl-rubropunctamin or the acid form of PP-R (red pigment), N-GABA-PP-V (violet pigment), PP-O (orange pigment) and monascorubrin. In Pigment Complex B, a novel biopigment annotated as N-GLA-PP-V was identified. Its basic structure contains a polyketide azaphilone with the same carboxyl-monascorubramine base structure as PP-V (violet pigment) and γ-carboxyglutamic acid (GLA). The pigments were not cytotoxic up to 250 µg/mL.
@article{Tsiailanis2022, abstract = {Biobased pigments are environmentally friendly alternatives to synthetic variants with an increased market demand. Production of pigments via fermentation is a promising process, yet optimization of the production yield and rate is crucial. Herein, we evaluated the potential of Penicillium purpurogenum to produce biobased pigments. Optimum sugar concentration was 30 g/L and optimum C:N ratio was 36:1 resulting in the production of 4.1–4.5 AU (namely Pigment Complex A). Supplementation with ammonium nitrate resulted in the production of 4.1–4.9 AU (namely Pigment Complex B). Pigments showed excellent pH stability. The major biopigments in Pigment Complex A were N-threonyl-rubropunctamin or the acid form of PP-R (red pigment), N-GABA-PP-V (violet pigment), PP-O (orange pigment) and monascorubrin. In Pigment Complex B, a novel biopigment annotated as N-GLA-PP-V was identified. Its basic structure contains a polyketide azaphilone with the same carboxyl-monascorubramine base structure as PP-V (violet pigment) and γ-carboxyglutamic acid (GLA). The pigments were not cytotoxic up to 250 µg/mL.}, author = {A.D. Tsiailanis and C. Pateraki and M. Kyriazou and C.M. Chatzigiannis and M. Chatziathanasiadou and N. Parisis and I. Mandala and A.G. Tzakos and A. Koutinas}, doi = {10.3390/molecules27010069}, issue = {1}, journal = {Molecules}, title = {Chemical profiling, bioactivity evaluation and the discovery of a novel biopigment produced by penicillium purpurogenum cbs 113139}, volume = {27}, year = {2022}, } - Koprivica, I., N. Jonić, D. Diamantis, D. Gajić, T. Saksida, N. Pejnović, A. G. Tzakos, and I. Stojanović. “Phenethyl ester of rosmarinic acid attenuates autoimmune responses during type 1 diabetes development in mice.” Life sciences 288 (2022). doi:10.1016/j.lfs.2021.120184
[BibTeX] [Abstract]
Aims: Rosmarinic acid (RA) is a polyphenol that occurs in plants of the Lamiaceae family. Phenethyl ester of RA (PERA), a novel RA derivative, has been developed and evaluated in vivo in an animal model of type 1 diabetes (T1D). Methods: T1D was induced in male C57BL/6 mice using multiple low doses of streptozotocin (STZ) administered intraperitoneally for 5 consecutive days. Intraperitoneal administration of PERA (2.5 mg/kg bw) began from the first STZ injection and continued for 20 days. Key findings: PERA-treated mice exhibited lower incidence of T1D (monitored up to 38 days from the disease induction), and fluorescent histochemical analysis showed that their pancreatic islets expressed more insulin. PERA treatment significantly down-regulated the proportions of CD11b+ and CD11c+ myeloid cells in the immune cell infiltrates in the pancreatic islets early during T1D pathogenesis (on day 9 after T1D induction), while on day 15, PERA significantly reduced the proportions of CD11c+, CD8+, Th1 and Th17 cells. Simultaneously, it was found that the cells from the pancreatic infiltrates of PERA-treated mice produced significantly less reactive oxygen species than cells from the control group. Significance: These findings suggest that PERA efficiently prevented T1D development in mice. Interestingly, PERA attenuated the inflammatory process in the islets through temporally specific interference with the innate and adaptive immune response and therefore shows great promise for further clinical evaluation as a novel T1D therapeutic.
@article{Koprivica2022, abstract = {Aims: Rosmarinic acid (RA) is a polyphenol that occurs in plants of the Lamiaceae family. Phenethyl ester of RA (PERA), a novel RA derivative, has been developed and evaluated in vivo in an animal model of type 1 diabetes (T1D). Methods: T1D was induced in male C57BL/6 mice using multiple low doses of streptozotocin (STZ) administered intraperitoneally for 5 consecutive days. Intraperitoneal administration of PERA (2.5 mg/kg bw) began from the first STZ injection and continued for 20 days. Key findings: PERA-treated mice exhibited lower incidence of T1D (monitored up to 38 days from the disease induction), and fluorescent histochemical analysis showed that their pancreatic islets expressed more insulin. PERA treatment significantly down-regulated the proportions of CD11b+ and CD11c+ myeloid cells in the immune cell infiltrates in the pancreatic islets early during T1D pathogenesis (on day 9 after T1D induction), while on day 15, PERA significantly reduced the proportions of CD11c+, CD8+, Th1 and Th17 cells. Simultaneously, it was found that the cells from the pancreatic infiltrates of PERA-treated mice produced significantly less reactive oxygen species than cells from the control group. Significance: These findings suggest that PERA efficiently prevented T1D development in mice. Interestingly, PERA attenuated the inflammatory process in the islets through temporally specific interference with the innate and adaptive immune response and therefore shows great promise for further clinical evaluation as a novel T1D therapeutic.}, author = {I. Koprivica and N. Jonić and D. Diamantis and D. Gajić and T. Saksida and N. Pejnović and A.G. Tzakos and I. Stojanović}, doi = {10.1016/j.lfs.2021.120184}, journal = {Life Sciences}, title = {Phenethyl ester of rosmarinic acid attenuates autoimmune responses during type 1 diabetes development in mice}, volume = {288}, year = {2022}, } - Hernychova, L., E. Alexandri, A. G. Tzakos, M. Zatloukalová, A. Primikyri, I. P. Gerothanassis, L. Uhrik, M. Šebela, D. Kopečný, L. Jedinák, L. Jedinák, and J. Vacek. “Serum albumin as a primary non-covalent binding protein for nitro-oleic acid.” International journal of biological macromolecules 203 (2022): 116-129. doi:10.1016/j.ijbiomac.2022.01.050
[BibTeX] [Abstract]
This work explores the interaction of 9/10-nitro-oleic acid (NO2-OA) with human serum albumin (HSA). The molecular mechanism of the biological action of NO2-OA is to our knowledge based on a reversible covalent reaction–Michael addition of nucleophilic amino acid residues of proteins. Since HSA is an important fatty acid transporter, a key question is whether NO2-OA can bind covalently or non-covalently to HSA, similarly to oleic acid (OA), which can interact with the FA1-FA7 binding sites of the HSA molecule. 1H NMR studies and competition analysis with OA and the drugs ibuprofen and warfarin were used to investigate a potential non-covalent binding mode. NO2-OA/HSA binding was confirmed to compete with warfarin for FA-7 with significantly higher affinity. NO2-OA competes with ibuprofen for FA-3 and FA-6, however, in contrast to the situation with warfarin, the binding affinities are not significantly different. The described interactions are based exclusively on non-covalent binding. No covalent binding of NO2-OA to HSA was detected by MS/MS. More detailed studies based on MALDI-TOF-MS and Ellman’s assay indicated that HSA can be covalently modified in the presence of NO2-OA to a very limited extent. It was also shown that NO2-OA has a higher affinity to HSA than that of OA.
@article{Hernychova2022, abstract = {This work explores the interaction of 9/10-nitro-oleic acid (NO2-OA) with human serum albumin (HSA). The molecular mechanism of the biological action of NO2-OA is to our knowledge based on a reversible covalent reaction–Michael addition of nucleophilic amino acid residues of proteins. Since HSA is an important fatty acid transporter, a key question is whether NO2-OA can bind covalently or non-covalently to HSA, similarly to oleic acid (OA), which can interact with the FA1-FA7 binding sites of the HSA molecule. 1H NMR studies and competition analysis with OA and the drugs ibuprofen and warfarin were used to investigate a potential non-covalent binding mode. NO2-OA/HSA binding was confirmed to compete with warfarin for FA-7 with significantly higher affinity. NO2-OA competes with ibuprofen for FA-3 and FA-6, however, in contrast to the situation with warfarin, the binding affinities are not significantly different. The described interactions are based exclusively on non-covalent binding. No covalent binding of NO2-OA to HSA was detected by MS/MS. More detailed studies based on MALDI-TOF-MS and Ellman's assay indicated that HSA can be covalently modified in the presence of NO2-OA to a very limited extent. It was also shown that NO2-OA has a higher affinity to HSA than that of OA.}, author = {L. Hernychova and E. Alexandri and A.G. Tzakos and M. Zatloukalová and A. Primikyri and I.P. Gerothanassis and L. Uhrik and M. Šebela and D. Kopečný and L. Jedinák and L. Jedinák and J. Vacek}, doi = {10.1016/j.ijbiomac.2022.01.050}, journal = {International Journal of Biological Macromolecules}, pages = {116-129}, title = {Serum albumin as a primary non-covalent binding protein for nitro-oleic acid}, volume = {203}, year = {2022}, } - Ganai, A. M., T. K. Pathan, N. Sayyad, B. Kushwaha, N. D. Kushwaha, A. G. Tzakos, and R. Karpoormath. “Dbu mediated one-pot synthesis of triazolo triazines: via dimroth type rearrangement.” Rsc advances 12 (2022): 2102-2106. doi:10.1039/d1ra07749j
[BibTeX] [Abstract]
Herein we report an efficient one-pot synthesis of [1,2,4]triazolo[1,5 a][1,3,5]triazines from commercially available substituted aryl/heteroaryl aldehydes and substituted 2-hydrazinyl-1,3,5-triazines via N-bromosuccinimide (NBS) mediated oxidative C-N bond formation. Isomerisation of [1,2,4]triazolo[4,3-a][1,3,5]triazines to [1,2,4]triazolo[1,5-a][1,3,5]triazines is driven by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) affording both isomers with good to excellent yields (70-96%).
@article{Ganai2022, abstract = {Herein we report an efficient one-pot synthesis of [1,2,4]triazolo[1,5 a][1,3,5]triazines from commercially available substituted aryl/heteroaryl aldehydes and substituted 2-hydrazinyl-1,3,5-triazines via N-bromosuccinimide (NBS) mediated oxidative C-N bond formation. Isomerisation of [1,2,4]triazolo[4,3-a][1,3,5]triazines to [1,2,4]triazolo[1,5-a][1,3,5]triazines is driven by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) affording both isomers with good to excellent yields (70-96%).}, author = {A.M. Ganai and T.K. Pathan and N. Sayyad and B. Kushwaha and N.D. Kushwaha and A.G. Tzakos and R. Karpoormath}, doi = {10.1039/d1ra07749j}, issue = {4}, journal = {RSC Advances}, pages = {2102-2106}, title = {DBU mediated one-pot synthesis of triazolo triazines: Via Dimroth type rearrangement}, volume = {12}, year = {2022}, } - Tsiailanis, A. D., C. M. Chatzigiannis, C. D. Papaemmanouil, M. V. Chatziathanasiadou, P. Chaloulos, I. Riba, G. Mullard, W. Wiczkowski, A. Koutinas, I. Mandala, I. Mandala, and A. G. Tzakos. “Exploration of betalains and determination of the antioxidant and cytotoxicity profile of orange and purple opuntia spp. cultivars in greece.” Plant foods for human nutrition 77 (2022): 198-205. doi:10.1007/s11130-022-00962-7
[BibTeX] [Abstract]
Replacing synthetic dyes with natural pigments has gained great attention over the past years in the food industry, due to the increased alertness of consumers for nontoxic and natural additives. Betalains are water-soluble nitrogenous natural pigments that are used as natural colorants in food industries, due to their applicability and their rich pharmacological profile including antioxidant, antimicrobial, and anticancer properties. Therefore, there is a need for a detailed exploration of betalains to fully exploit their properties. Opuntia spp. plants are one of the primary sources of betalains. The objective of this study was to identify betalain phytochemical content in prickly pear cactus of two different Opuntia species from Greece (an Opuntia ficus-indica (L.) Mill (OFI) orange prickly pear cultivar and an Opuntia spp. purple prickly pear cultivar) using modern analytical techniques as also to evaluate their antioxidant and cytotoxicity profile. To achieve this we used an array of analytical techniques, including ultra-violet-vis (UV-Vis) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and liquid chromatography-high resolution mass spectrometry (LC-HRMS) as also cell based in vitro assays. These enabled us to establish a rapid approach that can distinguish the different Opuntia spp. cultivars based on their phytochemical constituents through untargeted metabolomics analysis using ultra-high performance liquid chromatography-mass spectrometry – quadrupole time-of-flight (UPLC/MS Q-TOF). These findings could allow a further exploitation of Opuntia species and especially their enriched betalain phytochemical profile as viable source of natural food colorants.
@article{Tsiailanis2022, abstract = {Replacing synthetic dyes with natural pigments has gained great attention over the past years in the food industry, due to the increased alertness of consumers for nontoxic and natural additives. Betalains are water-soluble nitrogenous natural pigments that are used as natural colorants in food industries, due to their applicability and their rich pharmacological profile including antioxidant, antimicrobial, and anticancer properties. Therefore, there is a need for a detailed exploration of betalains to fully exploit their properties. Opuntia spp. plants are one of the primary sources of betalains. The objective of this study was to identify betalain phytochemical content in prickly pear cactus of two different Opuntia species from Greece (an Opuntia ficus-indica (L.) Mill (OFI) orange prickly pear cultivar and an Opuntia spp. purple prickly pear cultivar) using modern analytical techniques as also to evaluate their antioxidant and cytotoxicity profile. To achieve this we used an array of analytical techniques, including ultra-violet-vis (UV-Vis) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and liquid chromatography-high resolution mass spectrometry (LC-HRMS) as also cell based in vitro assays. These enabled us to establish a rapid approach that can distinguish the different Opuntia spp. cultivars based on their phytochemical constituents through untargeted metabolomics analysis using ultra-high performance liquid chromatography-mass spectrometry - quadrupole time-of-flight (UPLC/MS Q-TOF). These findings could allow a further exploitation of Opuntia species and especially their enriched betalain phytochemical profile as viable source of natural food colorants.}, author = {A.D. Tsiailanis and C.M. Chatzigiannis and C.D. Papaemmanouil and M.V. Chatziathanasiadou and P. Chaloulos and I. Riba and G. Mullard and W. Wiczkowski and A. Koutinas and I. Mandala and I. Mandala and A.G. Tzakos}, doi = {10.1007/s11130-022-00962-7}, issue = {2}, journal = {Plant Foods for Human Nutrition}, pages = {198-205}, title = {Exploration of Betalains and Determination of the Antioxidant and Cytotoxicity Profile of Orange and Purple Opuntia spp. Cultivars in Greece}, volume = {77}, year = {2022}, } - Vakali, V., M. Papadourakis, N. Georgiou, N. Zoupanou, D. A. Diamantis, U. Javornik, P. Papakyriakopoulou, J. Plavec, G. Valsami, A. G. Tzakos, Z. Cournia, and T. Mauromoustakos. “Comparative interaction studies of quercetin with 2-hydroxyl-propyl-β-cyclodextrin and 2,6-methylated-β-cyclodextrin.” Molecules 27 (2022). doi:10.3390/molecules27175490
[BibTeX] [Abstract]
Quercetin (QUE) is a well-known natural product that can exert beneficial properties on human health. However, due to its low solubility its bioavailability is limited. In the present study, we examine whether its formulation with two cyclodextrins (CDs) may enhance its pharmacological profile. Comparative interaction studies of quercetin with 2-hydroxyl-propyl-β-cyclodextrin (2HP-β-CD) and 2,6-methylated cyclodextrin (2,6Me-β-CD) were performed using NMR spectroscopy, DFT calculations, and in silico molecular dynamics (MD) simulations. Using T1 relaxation experiments and 2D DOSY it was illustrated that both cyclodextrin vehicles can host quercetin. Quantum mechanical calculations showed the formation of hydrogen bonds between QUE with 2HP-β-CD and 2,6Μe-β-CD. Six hydrogen bonds are formed ranging between 2 to 2.8 Å with 2HP-β-CD and four hydrogen bonds within 2.8 Å with 2,6Μe-β-CD. Calculations of absolute binding free energies show that quercetin binds favorably to both 2,6Me-β-CD and 2HP-β-CD. MM/GBSA results show equally favorable binding of quercetin in the two CDs. Fluorescence spectroscopy shows moderate binding of quercetin in 2HP-β-CD (520 M−1) and 2,6Me-β-CD (770 M−1). Thus, we propose that both formulations (2HP-β-CD:quercetin, 2,6Me-β-CD:quercetin) could be further explored and exploited as small molecule carriers in biological studies.
@article{Vakali2022, abstract = {Quercetin (QUE) is a well-known natural product that can exert beneficial properties on human health. However, due to its low solubility its bioavailability is limited. In the present study, we examine whether its formulation with two cyclodextrins (CDs) may enhance its pharmacological profile. Comparative interaction studies of quercetin with 2-hydroxyl-propyl-β-cyclodextrin (2HP-β-CD) and 2,6-methylated cyclodextrin (2,6Me-β-CD) were performed using NMR spectroscopy, DFT calculations, and in silico molecular dynamics (MD) simulations. Using T1 relaxation experiments and 2D DOSY it was illustrated that both cyclodextrin vehicles can host quercetin. Quantum mechanical calculations showed the formation of hydrogen bonds between QUE with 2HP-β-CD and 2,6Μe-β-CD. Six hydrogen bonds are formed ranging between 2 to 2.8 Å with 2HP-β-CD and four hydrogen bonds within 2.8 Å with 2,6Μe-β-CD. Calculations of absolute binding free energies show that quercetin binds favorably to both 2,6Me-β-CD and 2HP-β-CD. MM/GBSA results show equally favorable binding of quercetin in the two CDs. Fluorescence spectroscopy shows moderate binding of quercetin in 2HP-β-CD (520 M−1) and 2,6Me-β-CD (770 M−1). Thus, we propose that both formulations (2HP-β-CD:quercetin, 2,6Me-β-CD:quercetin) could be further explored and exploited as small molecule carriers in biological studies.}, author = {V. Vakali and M. Papadourakis and N. Georgiou and N. Zoupanou and D.A. Diamantis and U. Javornik and P. Papakyriakopoulou and J. Plavec and G. Valsami and A.G. Tzakos and Z. Cournia and T. Mauromoustakos}, doi = {10.3390/molecules27175490}, issue = {17}, journal = {Molecules}, title = {Comparative Interaction Studies of Quercetin with 2-Hydroxyl-propyl-β-cyclodextrin and 2,6-Methylated-β-cyclodextrin}, volume = {27}, year = {2022}, } - Perryman, R., A. Renziehausen, H. Shaye, A. D. Kostagianni, A. D. Tsiailanis, T. Thorne, M. V. Chatziathanasiadou, G. B. Sivolapenko, El M. A. Mubarak, G. W. Han, A. G. Tzakos, and N. Syed. “Inhibition of the angiotensin ii type 2 receptor at2r is a novel therapeutic strategy for glioblastoma.” Proceedings of the national academy of sciences of the united states of america 119 (2022). doi:10.1073/pnas.2116289119
[BibTeX] [Abstract]
Glioblastoma (GBM) is an aggressive malignant primary brain tumor with limited therapeutic options. We show that the angiotensin II (AngII) type 2 receptor (AT2R) is a therapeutic target for GBM and that AngII, endogenously produced in GBM cells, promotes proliferation through AT2R. We repurposed EMA401, an AT2R antagonist originally developed as a peripherally restricted analgesic, for GBM and showed that it inhibits the proliferation of AT2R-expressing GBM spheroids and blocks their invasiveness and angiogenic capacity. The crystal structure of AT2R bound to EMA401 was determined and revealed the receptor to be in an active-like conformation with helix- VIII blocking G-protein or β-arrestin recruitment. The architecture and interactions of EMA401 in AT2R differ drastically from complexes of AT2R with other relevant compounds. To enhance central nervous system (CNS) penetration of EMA401, we exploited the crystal structure to design an angiopep-2-tethered EMA401 derivative, A3E. A3E exhibited enhanced CNS penetration, leading to reduced tumor volume, inhibition of proliferation, and increased levels of apoptosis in an orthotopic xenograft model of GBM.
@article{Perryman2022, abstract = {Glioblastoma (GBM) is an aggressive malignant primary brain tumor with limited therapeutic options. We show that the angiotensin II (AngII) type 2 receptor (AT2R) is a therapeutic target for GBM and that AngII, endogenously produced in GBM cells, promotes proliferation through AT2R. We repurposed EMA401, an AT2R antagonist originally developed as a peripherally restricted analgesic, for GBM and showed that it inhibits the proliferation of AT2R-expressing GBM spheroids and blocks their invasiveness and angiogenic capacity. The crystal structure of AT2R bound to EMA401 was determined and revealed the receptor to be in an active-like conformation with helix- VIII blocking G-protein or β-arrestin recruitment. The architecture and interactions of EMA401 in AT2R differ drastically from complexes of AT2R with other relevant compounds. To enhance central nervous system (CNS) penetration of EMA401, we exploited the crystal structure to design an angiopep-2-tethered EMA401 derivative, A3E. A3E exhibited enhanced CNS penetration, leading to reduced tumor volume, inhibition of proliferation, and increased levels of apoptosis in an orthotopic xenograft model of GBM.}, author = {R. Perryman and A. Renziehausen and H. Shaye and A.D. Kostagianni and A.D. Tsiailanis and T. Thorne and M.V. Chatziathanasiadou and G.B. Sivolapenko and M.A. El Mubarak and G.W. Han and A.G. Tzakos and N. Syed}, doi = {10.1073/pnas.2116289119}, issue = {32}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, title = {Inhibition of the angiotensin II type 2 receptor AT2R is a novel therapeutic strategy for glioblastoma}, volume = {119}, year = {2022}, } - Tomou, E. -M., K. Lytra, S. Rallis, A. G. Tzakos, and H. Skaltsa. “An updated review of genus cistus l. since 2014: traditional uses, phytochemistry, and pharmacological properties.” Phytochemistry reviews 21 (2022): 2049-2087. doi:10.1007/s11101-022-09827-y
[BibTeX] [Abstract]
Genus Cistus L. (Cistaceae) occurs mainly in the Mediterranean region. Many plants of this genus have been used in different folk medicines since ancient times, mainly against peptic ailments and skin disorders, such as burns, wounds, and infections. Over the last years, Cistus species have attracted great interest due to the variety of their bioactive compounds and pharmacological activities. Comprehensive research of previously published literature was performed for the collection of the available data on the traditional uses, phytochemistry, and pharmacological properties of the genus Cistus since 2014, using electronic databases with several key search words. A total of 66 published scientific studies was examined. Over the last years, 111 secondary metabolites have been described in Cistus taxa. In vitro and in vivo studies, as well as a clinical study are included, highlighting the interesting pharmacological aspects of these plants. This review summarizes and discusses the current knowledge of the traditional uses, phytochemistry, and biological activities of Cistus plants, revealing the uncharted scientific territory and may provide critical information for future perspectives on these plants. Graphical abstract: [Figure not available: see fulltext.].
@article{Tomou2022, abstract = {Genus Cistus L. (Cistaceae) occurs mainly in the Mediterranean region. Many plants of this genus have been used in different folk medicines since ancient times, mainly against peptic ailments and skin disorders, such as burns, wounds, and infections. Over the last years, Cistus species have attracted great interest due to the variety of their bioactive compounds and pharmacological activities. Comprehensive research of previously published literature was performed for the collection of the available data on the traditional uses, phytochemistry, and pharmacological properties of the genus Cistus since 2014, using electronic databases with several key search words. A total of 66 published scientific studies was examined. Over the last years, 111 secondary metabolites have been described in Cistus taxa. In vitro and in vivo studies, as well as a clinical study are included, highlighting the interesting pharmacological aspects of these plants. This review summarizes and discusses the current knowledge of the traditional uses, phytochemistry, and biological activities of Cistus plants, revealing the uncharted scientific territory and may provide critical information for future perspectives on these plants. Graphical abstract: [Figure not available: see fulltext.].}, author = {E.-M. Tomou and K. Lytra and S. Rallis and A.G. Tzakos and H. Skaltsa}, doi = {10.1007/s11101-022-09827-y}, issue = {6}, journal = {Phytochemistry Reviews}, pages = {2049-2087}, title = {An updated review of genus Cistus L. since 2014: traditional uses, phytochemistry, and pharmacological properties}, volume = {21}, year = {2022}, } - Stegnjaić, G., A. D. Tsiailanis, M. Lazarević, V. K. Gkalpinos, N. Djedovic, T. Antoniou, S. Stanisavljević, M. Dimitrijević, M. Momčilović, Đ. Miljković, A. G. Tzakos, and B. Jevtić. “Phenethyl ester of gallic acid ameliorates experimental autoimmune encephalomyelitis.” Molecules 27 (2022). doi:10.3390/molecules27248770
[BibTeX] [Abstract]
Gallic acid is a phenolic acid present in various plants, nuts, and fruits. It is well known for its anti-oxidative and anti-inflammatory properties. The phenethyl ester of gallic acid (PEGA) was synthesized with the aim of increasing the bioavailability of gallic acid, and thus its pharmacological potential. Here, the effects of PEGA on encephalitogenic cells were examined, and PEGA was found to modulate the inflammatory activities of T cells and macrophages/microglia. Specifically, PEGA reduced the release of interleukin (IL)-17 and interferon (IFN)-γ from T cells, as well as NO, and IL-6 from macrophages/microglia. Importantly, PEGA ameliorated experimental autoimmune encephalomyelitis, an animal model of chronic inflammatory disease of the central nervous system (CNS)—multiple sclerosis. Thus, PEGA is a potent anti-inflammatory compound with a perspective to be further explored in the context of CNS autoimmunity and other chronic inflammatory disorders.
@article{, abstract = {Gallic acid is a phenolic acid present in various plants, nuts, and fruits. It is well known for its anti-oxidative and anti-inflammatory properties. The phenethyl ester of gallic acid (PEGA) was synthesized with the aim of increasing the bioavailability of gallic acid, and thus its pharmacological potential. Here, the effects of PEGA on encephalitogenic cells were examined, and PEGA was found to modulate the inflammatory activities of T cells and macrophages/microglia. Specifically, PEGA reduced the release of interleukin (IL)-17 and interferon (IFN)-γ from T cells, as well as NO, and IL-6 from macrophages/microglia. Importantly, PEGA ameliorated experimental autoimmune encephalomyelitis, an animal model of chronic inflammatory disease of the central nervous system (CNS)—multiple sclerosis. Thus, PEGA is a potent anti-inflammatory compound with a perspective to be further explored in the context of CNS autoimmunity and other chronic inflammatory disorders.}, author = {G. Stegnjaić and A.D. Tsiailanis and M. Lazarević and V.K. Gkalpinos and N. Djedovic and T. Antoniou and S. Stanisavljević and M. Dimitrijević and M. Momčilović and Đ. Miljković and A.G. Tzakos and B. Jevtić}, doi = {10.3390/molecules27248770}, issue = {24}, journal = {Molecules}, title = {Phenethyl Ester of Gallic Acid Ameliorates Experimental Autoimmune Encephalomyelitis}, volume = {27}, year = {2022}, } - Stegnjaić, G., M. Lazarević, D. A. Diamantis, N. Djedović, B. Jevtić, S. Stanisavljević, M. Dimitrijević, M. Momčilović, A. G. Tzakos, and Miljković. “Phenethyl ester of rosmarinic acid ameliorates experimental autoimmune encephalomyelitis.” Immunology letters 251-252 (2022): 9-19. doi:10.1016/j.imlet.2022.09.006
[BibTeX] [Abstract]
Rosmarinic acid is a polyphenolic compound, abundantly present in herbs of the Lamiaceae family. The aim of the study was to evaluate the immunomodulatory properties of a recently developed phenethyl ester derivative of rosmarinic acid (PERA), with enhanced ability of diffusion through biological membranes, in an animal model of the central nervous system (CNS) autoimmunity. To this end, experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis was used. Daily subcutaneous administration of PERA (30 mg/kg) from day 7 to day 22 after immunization successfully ameliorated EAE induced in Dark Agouti rats, shortening the disease duration and reducing maximal, cumulative and mean clinical score. PERA efficiently reduced production of major encephalitogenic cytokines, interferon (IFN)-γ and interleukin (IL)-17, in immune cells from the CNS or the lymph nodes draining the site of immunization of EAE rats, as well as in CD4+ T cells purified from the lymph nodes. Also, PERA inhibited NO production in the CNS and the lymph nodes, as well as in macrophages and microglial cells. Finally, microglial ability to produce pro-inflammatory cytokines IL-6, and tumor necrosis factor (TNF) were also reduced by PERA. Our results clearly imply that PERA possesses anti-encephalitogenic properties. Thus, further studies on the relevance of the observed effects for the therapy of multiple sclerosis are warranted.
@article{, abstract = {Rosmarinic acid is a polyphenolic compound, abundantly present in herbs of the Lamiaceae family. The aim of the study was to evaluate the immunomodulatory properties of a recently developed phenethyl ester derivative of rosmarinic acid (PERA), with enhanced ability of diffusion through biological membranes, in an animal model of the central nervous system (CNS) autoimmunity. To this end, experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis was used. Daily subcutaneous administration of PERA (30 mg/kg) from day 7 to day 22 after immunization successfully ameliorated EAE induced in Dark Agouti rats, shortening the disease duration and reducing maximal, cumulative and mean clinical score. PERA efficiently reduced production of major encephalitogenic cytokines, interferon (IFN)-γ and interleukin (IL)-17, in immune cells from the CNS or the lymph nodes draining the site of immunization of EAE rats, as well as in CD4+ T cells purified from the lymph nodes. Also, PERA inhibited NO production in the CNS and the lymph nodes, as well as in macrophages and microglial cells. Finally, microglial ability to produce pro-inflammatory cytokines IL-6, and tumor necrosis factor (TNF) were also reduced by PERA. Our results clearly imply that PERA possesses anti-encephalitogenic properties. Thus, further studies on the relevance of the observed effects for the therapy of multiple sclerosis are warranted.}, author = {G. Stegnjaić and M. Lazarević and D.A. Diamantis and N. Djedović and B. Jevtić and S. Stanisavljević and M. Dimitrijević and M. Momčilović and A.G. Tzakos and Miljković}, doi = {10.1016/j.imlet.2022.09.006}, journal = {Immunology Letters}, pages = {9-19}, title = {Phenethyl ester of rosmarinic acid ameliorates experimental autoimmune encephalomyelitis}, volume = {251-252}, year = {2022}, } - Alexandri, E., A. Primikyri, G. Papamokos, T. Venianakis, V. K. Gkalpinos, A. G. Tzakos, A. Karydis-Messinis, D. Moschovas, A. Avgeropoulos, and I. P. Gerothanassis. “Nmr and computational studies reveal novel aspects in molecular recognition of unsaturated fatty acids with non-labelled serum albumin.” Febs journal 289 (2022): 5617-5636. doi:10.1111/febs.16453
[BibTeX] [Abstract]
An approach based on the combined use of saturation transfer difference (STD), Tr-NOESY and Inter-ligand NOEs for PHArmacophore Mapping (INPHARMA) NMR techniques and docking calculations is reported, for the first time, for mapping interactions and specific binding sites of caproleic acid (10 : 1 cis-9), oleic acid (18 : 1 cis-9), linoleic acid (18 : 2 cis-9,12) and linolenic (18 : 3, cis-9,12,15) free fatty acids (FFAs) with non-labelled serum albumin (BSA/HSA). Significant negative inter-ligand NOEs between the FFAs and the drugs ibuprofen and warfarin, through competition experiments, were observed. The inter-ligand NOEs and docking calculations were interpreted in terms of competitive binding mode, the significant folding of the bis allylic region and the presence of two orientations of the FFAs in the warfarin binding site (FA7), due to two potential distinctive anchoring polar groups of amino acids. This conformational flexibility is the reason that, the location and conformational states of the FFAs in the binding site of warfarin could not be determined accurately, despite numerous available X-ray structural studies. α-Linolenic acid competes favourably with warfarin at the binding site FA7. Isothermal titration calorimetry experiments of the preformed HSA/α-linolenic acid complex upon titration with warfarin show a significant reduction in the binding constant of warfarin, in very good agreement with NMR and computational data. The combined use, therefore, of STD, Tr-NOESY and INPHARMA NMR, ITC and docking calculations may find promising applications in the field of protein–lipid recognition research.
@article{Alexandri2022, abstract = {An approach based on the combined use of saturation transfer difference (STD), Tr-NOESY and Inter-ligand NOEs for PHArmacophore Mapping (INPHARMA) NMR techniques and docking calculations is reported, for the first time, for mapping interactions and specific binding sites of caproleic acid (10 : 1 cis-9), oleic acid (18 : 1 cis-9), linoleic acid (18 : 2 cis-9,12) and linolenic (18 : 3, cis-9,12,15) free fatty acids (FFAs) with non-labelled serum albumin (BSA/HSA). Significant negative inter-ligand NOEs between the FFAs and the drugs ibuprofen and warfarin, through competition experiments, were observed. The inter-ligand NOEs and docking calculations were interpreted in terms of competitive binding mode, the significant folding of the bis allylic region and the presence of two orientations of the FFAs in the warfarin binding site (FA7), due to two potential distinctive anchoring polar groups of amino acids. This conformational flexibility is the reason that, the location and conformational states of the FFAs in the binding site of warfarin could not be determined accurately, despite numerous available X-ray structural studies. α-Linolenic acid competes favourably with warfarin at the binding site FA7. Isothermal titration calorimetry experiments of the preformed HSA/α-linolenic acid complex upon titration with warfarin show a significant reduction in the binding constant of warfarin, in very good agreement with NMR and computational data. The combined use, therefore, of STD, Tr-NOESY and INPHARMA NMR, ITC and docking calculations may find promising applications in the field of protein–lipid recognition research.}, author = {E. Alexandri and A. Primikyri and G. Papamokos and T. Venianakis and V.K. Gkalpinos and A.G. Tzakos and A. Karydis-Messinis and D. Moschovas and A. Avgeropoulos and I.P. Gerothanassis}, doi = {10.1111/febs.16453}, issue = {18}, journal = {FEBS Journal}, pages = {5617-5636}, title = {NMR and computational studies reveal novel aspects in molecular recognition of unsaturated fatty acids with non-labelled serum albumin}, volume = {289}, year = {2022}, } - Papaemmanouil, C. D., J. Peña-García, A. J. Banegas-Luna, A. D. Kostagianni, I. P. Gerothanassis, H. Pérez-Sánchez, and A. G. Tzakos. “Antiage-db: a database and server for the prediction of anti-aging compounds targeting elastase, hyaluronidase, and tyrosinase.” Antioxidants 11 (2022). doi:10.3390/antiox11112268
[BibTeX] [Abstract]
Natural products bear a multivariate biochemical profile with antioxidant, anti-inflammatory, antibacterial, and antitumoral properties. Along with their natural sources, they have been widely used both as anti-aging and anti-melanogenic agents due to their effective contribution in the elimination of reactive oxygen species (ROS) caused by oxidative stress. Their anti-aging activity is mainly related to their capacity of inhibiting enzymes like Human Neutrophil Elastase (HNE), Hyaluronidase (Hyal) and Tyrosinase (Tyr). Herein, we accumulated literature information (covering the period 1965–2020) on the inhibitory activity of natural products and their natural sources towards these enzymes. To navigate this information, we developed a database and server termed ANTIAGE-DB that allows the prediction of the anti-aging potential of target compounds. The server operates in two axes. First a comparison of compounds by shape similarity can be performed against our curated database of natural products whose inhibitory potential has been established in the literature. In addition, inverse virtual screening can be performed for a chosen molecule against the three targeted enzymes. The server is open access, and a detailed report with the prediction results is emailed to the user. ANTIAGE-DB could enable researchers to explore the chemical space of natural based products, but is not limited to, as anti-aging compounds and can predict their anti-aging potential. ANTIAGE-DB is accessed online.
@article{Papaemmanouil2022, abstract = {Natural products bear a multivariate biochemical profile with antioxidant, anti-inflammatory, antibacterial, and antitumoral properties. Along with their natural sources, they have been widely used both as anti-aging and anti-melanogenic agents due to their effective contribution in the elimination of reactive oxygen species (ROS) caused by oxidative stress. Their anti-aging activity is mainly related to their capacity of inhibiting enzymes like Human Neutrophil Elastase (HNE), Hyaluronidase (Hyal) and Tyrosinase (Tyr). Herein, we accumulated literature information (covering the period 1965–2020) on the inhibitory activity of natural products and their natural sources towards these enzymes. To navigate this information, we developed a database and server termed ANTIAGE-DB that allows the prediction of the anti-aging potential of target compounds. The server operates in two axes. First a comparison of compounds by shape similarity can be performed against our curated database of natural products whose inhibitory potential has been established in the literature. In addition, inverse virtual screening can be performed for a chosen molecule against the three targeted enzymes. The server is open access, and a detailed report with the prediction results is emailed to the user. ANTIAGE-DB could enable researchers to explore the chemical space of natural based products, but is not limited to, as anti-aging compounds and can predict their anti-aging potential. ANTIAGE-DB is accessed online.}, author = {C.D. Papaemmanouil and J. Peña-García and A.J. Banegas-Luna and A.D. Kostagianni and I.P. Gerothanassis and H. Pérez-Sánchez and A.G. Tzakos}, doi = {10.3390/antiox11112268}, issue = {11}, journal = {Antioxidants}, title = {ANTIAGE-DB: A Database and Server for the Prediction of Anti-Aging Compounds Targeting Elastase, Hyaluronidase, and Tyrosinase}, volume = {11}, year = {2022}, }
2021
- Pritsas, A., E. -M. Tomou, E. Tsitsigianni, C. D. Papaemmanouil, D. A. Diamantis, P. Chatzopoulou, A. G. Tzakos, and H. Skaltsa. “Valorisation of stachysetin from cultivated stachys iva griseb. as anti-diabetic agent: a multi-spectroscopic and molecular docking approach.” Journal of biomolecular structure and dynamics 39 (2021): 6452-6466. doi:10.1080/07391102.2020.1799864
[BibTeX] [Abstract]
Stachys species are considered as important medicinal plants with numerous health benefit effects. In continuation of our research on the Greek Stachys species, the chemical profile of the aerial parts of cultivated S. iva Griseb. has been explored. The NMR profiles of the plant extract/infusion were used to guide the isolation process, leading to the targeted isolation of seventeen known compounds. The rare acylated flavonoid, stachysetin, was isolated for the third time from plant species in the international literature. Identification of the characteristic signals of stachysetin in the 1D 1H-NMR spectrum of the crude extract was presented. In order to evaluate the potential of the identified chemical space in Stachys to bear possible bioactivity against diabetes, we performed an in silico screening against 17 proteins implicated in diabetes, as also ligand based similarity metrics against established anti-diabetic drugs. The results capitalized the anti-diabetic potency of stachysetin. Its binding profile to the major drug carrier plasma protein serum albumin was also explored along with its photophysical properties suggesting that stachysetin could be recognized and delivered in plasma through serum albumin and also could be tracked through near-infrared imaging. Communicated by Ramaswamy H. Sarma.
@article{Pritsas2021, abstract = {Stachys species are considered as important medicinal plants with numerous health benefit effects. In continuation of our research on the Greek Stachys species, the chemical profile of the aerial parts of cultivated S. iva Griseb. has been explored. The NMR profiles of the plant extract/infusion were used to guide the isolation process, leading to the targeted isolation of seventeen known compounds. The rare acylated flavonoid, stachysetin, was isolated for the third time from plant species in the international literature. Identification of the characteristic signals of stachysetin in the 1D 1H-NMR spectrum of the crude extract was presented. In order to evaluate the potential of the identified chemical space in Stachys to bear possible bioactivity against diabetes, we performed an in silico screening against 17 proteins implicated in diabetes, as also ligand based similarity metrics against established anti-diabetic drugs. The results capitalized the anti-diabetic potency of stachysetin. Its binding profile to the major drug carrier plasma protein serum albumin was also explored along with its photophysical properties suggesting that stachysetin could be recognized and delivered in plasma through serum albumin and also could be tracked through near-infrared imaging. Communicated by Ramaswamy H. Sarma.}, author = {A. Pritsas and E.-M. Tomou and E. Tsitsigianni and C.D. Papaemmanouil and D.A. Diamantis and P. Chatzopoulou and A.G. Tzakos and H. Skaltsa}, doi = {10.1080/07391102.2020.1799864}, issue = {17}, journal = {Journal of Biomolecular Structure and Dynamics}, pages = {6452-6466}, title = {Valorisation of stachysetin from cultivated Stachys iva Griseb. as anti-diabetic agent: a multi-spectroscopic and molecular docking approach}, volume = {39}, year = {2021}, } - Chatziathanasiadou, M. V., T. Mavromoustakos, and A. G. Tzakos. Unveiling the thermodynamic aspects of drug-cyclodextrin interactions through isothermal titration calorimetry. Vol. 2207. 2021. doi:10.1007/978-1-0716-0920-0_15
[BibTeX] [Abstract]
Due to their low toxicity and high aqueous solubility, cyclodextrins have emerged as a distinctive class of supramolecules with wide application in the pharmaceutical and food industry. Their ability to improve the water solubility, stability and pharmacokinetic profile of small molecules has established them as a rich toolkit for drug formulation. In order to improve the physicochemical characteristics and the pharmacokinetic profile of a drug through cyclodextrin inclusion, the proper cyclodextrin type has to be selected among the existing great variety consisting of both natural and synthetic variants. The selection of the most proper cyclodextrin variant comes after drug-cyclodextrin screening studies targeting the characterization of the complex formation and evaluation of the affinity and interaction forces participating in the complexation. Numerous analytical, spectroscopic, separation and electrochemical techniques have been applied to elucidate the interaction profile in a cyclodextrin-drug complex. Herein, we describe the application of Isothermal Titration Calorimetry (ITC) on cyclodextrin-drug complexes that enables the charting of the binding affinity and the thermodynamic profile of the inclusion complexes. We focus on the experimental design and present technical tips of the ITC application. To better illustrate the technique’s rationale, the interaction between 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) and the antihypertensive drug losartan is investigated.
@book{Chatziathanasiadou2021, abstract = {Due to their low toxicity and high aqueous solubility, cyclodextrins have emerged as a distinctive class of supramolecules with wide application in the pharmaceutical and food industry. Their ability to improve the water solubility, stability and pharmacokinetic profile of small molecules has established them as a rich toolkit for drug formulation. In order to improve the physicochemical characteristics and the pharmacokinetic profile of a drug through cyclodextrin inclusion, the proper cyclodextrin type has to be selected among the existing great variety consisting of both natural and synthetic variants. The selection of the most proper cyclodextrin variant comes after drug-cyclodextrin screening studies targeting the characterization of the complex formation and evaluation of the affinity and interaction forces participating in the complexation. Numerous analytical, spectroscopic, separation and electrochemical techniques have been applied to elucidate the interaction profile in a cyclodextrin-drug complex. Herein, we describe the application of Isothermal Titration Calorimetry (ITC) on cyclodextrin-drug complexes that enables the charting of the binding affinity and the thermodynamic profile of the inclusion complexes. We focus on the experimental design and present technical tips of the ITC application. To better illustrate the technique’s rationale, the interaction between 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) and the antihypertensive drug losartan is investigated.}, author = {M.V. Chatziathanasiadou and T. Mavromoustakos and A.G. Tzakos}, doi = {10.1007/978-1-0716-0920-0_15}, journal = {Methods in Molecular Biology}, pages = {187-198}, title = {Unveiling the Thermodynamic Aspects of Drug-Cyclodextrin Interactions Through Isothermal Titration Calorimetry}, volume = {2207}, year = {2021}, } - Vrettos, E. I. and A. G. Tzakos. Construction of peptide-drug conjugates for selective targeting of malignant tumor cells. Vol. 2207. 2021. doi:10.1007/978-1-0716-0920-0_23
[BibTeX] [Abstract]
Cancer constitutes a major threat to humanity, while its incidence and mortality rates are increasing rapidly worldwide. To tackle cancer, numerous strategies have been exploited, including the development of peptide–drug conjugates (PDCs), which are considered an appealing approach to selectively populate malignant tumors with toxic substances. The general architecture of a PDC usually includes three parts: the tumor-targeting peptide, the cytotoxic drug, and the biodegradable linker. Due to the fact that peptides possess fast renal clearance, affecting the bioavailability of the PDC, a nanodrug formation concept can be exploited to ameliorate this pitfall. Herein, we present methodologies to develop PDCs, along with certain basic principles governing such constructs. In addition, we highlight possible problems that may appear during the synthesis of PDCs, as also solutions to overcome them.
@book{Vrettos2021, abstract = {Cancer constitutes a major threat to humanity, while its incidence and mortality rates are increasing rapidly worldwide. To tackle cancer, numerous strategies have been exploited, including the development of peptide–drug conjugates (PDCs), which are considered an appealing approach to selectively populate malignant tumors with toxic substances. The general architecture of a PDC usually includes three parts: the tumor-targeting peptide, the cytotoxic drug, and the biodegradable linker. Due to the fact that peptides possess fast renal clearance, affecting the bioavailability of the PDC, a nanodrug formation concept can be exploited to ameliorate this pitfall. Herein, we present methodologies to develop PDCs, along with certain basic principles governing such constructs. In addition, we highlight possible problems that may appear during the synthesis of PDCs, as also solutions to overcome them.}, author = {E.I. Vrettos and A.G. Tzakos}, doi = {10.1007/978-1-0716-0920-0_23}, journal = {Methods in Molecular Biology}, pages = {327-338}, title = {Construction of Peptide-Drug Conjugates for Selective Targeting of Malignant Tumor Cells}, volume = {2207}, year = {2021}, } - Andreadelis, I., Μ. V. Chatziathanasiadou, D. Ntountaniotis, G. Valsami, C. Papaemmanouil, E. Christodoulou, G. Mitropoulou, Y. Kourkoutas, A. G. Tzakos, and T. Mavromoustakos. “Charting the structural and thermodynamic determinants in phenolic acid natural product–cyclodextrin encapsulations.” Journal of biomolecular structure and dynamics 39 (2021): 2642-2658. doi:10.1080/07391102.2020.1751716
[BibTeX] [Abstract]
Cyclodextrins are pliable platforms that have served to optimize the pharmaceutic profile of numerous compounds and to enhance the stability of natural food additives. Caffeic and rosmarinic acid are natural products with proven health benefits, though their full therapeutic potential has not been exploited. To enhance their pharmaceutic profile, we developed cyclodextrin-based formulates and unveiled their thermodynamic and structural principles. The complexes’ stoichiometry was determined by ESI-MS. Solid-state and liquid NMR spectroscopy revealed the interactions and the topographical location of the caffeic and rosmarinic acid inside the cyclodextrin cavity. The theoretically analyzed HP-β-CD’s degree of substitution (DS) of caffeic and rosmarinic acids can explain the intensities obtained by 2D NOESY experiments. The thermodynamics and the affinity of the complexes were evaluated through isothermal titration calorimetry. In addition, the rosmarinic and caffeic acids as, also, their complexes showed considerable antimicrobial activity against common food spoilage and pathogenic bacteria. The generated data could provide the basis to understand the structural and thermodynamic determinants implicated in natural products–CD recognition and to develop platforms for the optimization of their pharmaceutical and stability profiles in order to be utilized as safe and stable natural antimicrobial food additives. Communicated by Ramaswamy H. Sarma.
@article{Andreadelis2021, abstract = {Cyclodextrins are pliable platforms that have served to optimize the pharmaceutic profile of numerous compounds and to enhance the stability of natural food additives. Caffeic and rosmarinic acid are natural products with proven health benefits, though their full therapeutic potential has not been exploited. To enhance their pharmaceutic profile, we developed cyclodextrin-based formulates and unveiled their thermodynamic and structural principles. The complexes’ stoichiometry was determined by ESI-MS. Solid-state and liquid NMR spectroscopy revealed the interactions and the topographical location of the caffeic and rosmarinic acid inside the cyclodextrin cavity. The theoretically analyzed HP-β-CD’s degree of substitution (DS) of caffeic and rosmarinic acids can explain the intensities obtained by 2D NOESY experiments. The thermodynamics and the affinity of the complexes were evaluated through isothermal titration calorimetry. In addition, the rosmarinic and caffeic acids as, also, their complexes showed considerable antimicrobial activity against common food spoilage and pathogenic bacteria. The generated data could provide the basis to understand the structural and thermodynamic determinants implicated in natural products–CD recognition and to develop platforms for the optimization of their pharmaceutical and stability profiles in order to be utilized as safe and stable natural antimicrobial food additives. Communicated by Ramaswamy H. Sarma.}, author = {I. Andreadelis and Μ.V. Chatziathanasiadou and D. Ntountaniotis and G. Valsami and C. Papaemmanouil and E. Christodoulou and G. Mitropoulou and Y. Kourkoutas and A.G. Tzakos and T. Mavromoustakos}, doi = {10.1080/07391102.2020.1751716}, issue = {7}, journal = {Journal of Biomolecular Structure and Dynamics}, pages = {2642-2658}, title = {Charting the structural and thermodynamic determinants in phenolic acid natural product–cyclodextrin encapsulations}, volume = {39}, year = {2021}, } - Tsiailanis, A. D., A. Renziehausen, S. Karakurt, T. Crook, N. Syed, and A. G. Tzakos. Encapsulation of small drugs in a supramolecule enhances solubility, stability, and therapeutic efficacy against glioblastoma multiforme. Vol. 2207. 2021. doi:10.1007/978-1-0716-0920-0_14
[BibTeX] [Abstract]
Cancer occupies a high rank in the global morbidity and mortality scale with glioblastoma multiforme (GBM) accounting for almost 80% of all primary tumors of the brain. Despite the increasing availability of targeted and immunotherapeutic agents, chemotherapy still plays an important role in the treatment of neoplastic diseases. Limitations to the effective use of chemotherapy such as low aqueous solubility and high toxicity have directed the scientific community’s interest to the development of new therapeutic agents with enhanced efficacy and limited toxicity. Supramolecular chemistry has offered an alternative way on the design and development of new therapeutic agents as a result of their unique properties. Supramolecules can be used as drug carriers since their cavities can host a wide range of small drugs and surpass in this way the drawbacks of current therapeutic agents. Herein, we present the principles that should be followed for the encapsulation of small drugs in supramolecules with enhanced physicochemical properties and increased efficacy against glioblastoma multiforme.
@book{Tsiailanis2021, abstract = {Cancer occupies a high rank in the global morbidity and mortality scale with glioblastoma multiforme (GBM) accounting for almost 80% of all primary tumors of the brain. Despite the increasing availability of targeted and immunotherapeutic agents, chemotherapy still plays an important role in the treatment of neoplastic diseases. Limitations to the effective use of chemotherapy such as low aqueous solubility and high toxicity have directed the scientific community’s interest to the development of new therapeutic agents with enhanced efficacy and limited toxicity. Supramolecular chemistry has offered an alternative way on the design and development of new therapeutic agents as a result of their unique properties. Supramolecules can be used as drug carriers since their cavities can host a wide range of small drugs and surpass in this way the drawbacks of current therapeutic agents. Herein, we present the principles that should be followed for the encapsulation of small drugs in supramolecules with enhanced physicochemical properties and increased efficacy against glioblastoma multiforme.}, author = {A.D. Tsiailanis and A. Renziehausen and S. Karakurt and T. Crook and N. Syed and A.G. Tzakos}, doi = {10.1007/978-1-0716-0920-0_14}, journal = {Methods in Molecular Biology}, pages = {175-186}, title = {Encapsulation of Small Drugs in a Supramolecule Enhances Solubility, Stability, and Therapeutic Efficacy Against Glioblastoma Multiforme}, volume = {2207}, year = {2021}, } - Chatzigiannis, C. M., S. Kiriakidi, A. G. Tzakos, and T. Mavromoustakos. 2d dosy nmr: a valuable tool to confirm the complexation in drug delivery systems. Vol. 2207. 2021. doi:10.1007/978-1-0716-0920-0_18
[BibTeX] [Abstract]
Many bioactive substances face the problem of limited bioavailability, mainly due to low aqueous solubility and poor metabolic stability. Their complexation with drug delivery systems offers a more optimum pharmacological profile. Some of these drug delivery systems that have promising potential form complexes with bioactive compounds such as cyclodextrins and calixarenes. The monitoring of the success and the type of the complexation are of great importance and two-dimensional diffusion-ordered NMR spectroscopy (2D DOSY) is a valuable tool for the studying of these complexes and described as “NMR chromatography.” Herein we report the procedure for the complexation of the natural product quercetin in 2-hydroxypropyl-β-cyclodextrin and the anticancer drug temozolomide in p-sulfonatocalix[4]arene and the determination of the complexation with 2D DOSY spectroscopy.
@book{Chatzigiannis2021, abstract = {Many bioactive substances face the problem of limited bioavailability, mainly due to low aqueous solubility and poor metabolic stability. Their complexation with drug delivery systems offers a more optimum pharmacological profile. Some of these drug delivery systems that have promising potential form complexes with bioactive compounds such as cyclodextrins and calixarenes. The monitoring of the success and the type of the complexation are of great importance and two-dimensional diffusion-ordered NMR spectroscopy (2D DOSY) is a valuable tool for the studying of these complexes and described as “NMR chromatography.” Herein we report the procedure for the complexation of the natural product quercetin in 2-hydroxypropyl-β-cyclodextrin and the anticancer drug temozolomide in p-sulfonatocalix[4]arene and the determination of the complexation with 2D DOSY spectroscopy.}, author = {C.M. Chatzigiannis and S. Kiriakidi and A.G. Tzakos and T. Mavromoustakos}, doi = {10.1007/978-1-0716-0920-0_18}, journal = {Methods in Molecular Biology}, pages = {235-246}, title = {2D DOSY NMR: A Valuable Tool to Confirm the Complexation in Drug Delivery Systems}, volume = {2207}, year = {2021}, } - Tsiailanis, A. D., A. G. Tzakos, and T. Mavromoustakos. “Advancing the therapeutic efficacy of bioactive molecules by delivery vehicle platforms.” Current medicinal chemistry 28 (2021): 2697-2706. doi:10.2174/0929867327666200605154506
[BibTeX] [Abstract]
Drugs have to overcome numerous barriers to reach their desired therapeutic tar-gets. In several cases, drugs, especially the highly lipophilic molecules, suffer from low solubility and bioavailability and therefore their desired targeting is hampered. In addition, unde-sired metabolic products might be produced or off-targets could be recognized. Along these lines, nanopharmacology has provided new technological platforms, to overcome these boundaries. Specifically, numerous vehicle platforms such as cyclodextrins and calixarenes have been widely utilized to host lipophilic drugs such as antagonists of the angiotensin II AT1 receptor (AT1R), as well as quercetin and silibinin. The encapsulation of these drugs in supramolecules or other systems refines their solubility and metabolic stability, increases their selectivity and therefore decreases their effective dose and improves their therapeutic index. In this mini review we report on the formulations of silibinin and AT1R antagonist candesar-tan in a 2-HP-β-cyclodextrin host molecule, which displayed enhanced cytotoxicity and increased silibinin’s and candesartan’s stability, respectively. Moreover, we describe the encapsulation of quercetin in gold nanoparticles bearing a calixarene supramolecular host. Also, the encapsulation of temozolomide in a calixarene nanocapsule has been described. Finally, we report on the activity enhancement that has been achieved upon using these formulations as well as the analytical and computational methods we used to characterize these formulations and explore the molecular interactions between the host and quest molecules.
@article{Tsiailanis2021, abstract = {Drugs have to overcome numerous barriers to reach their desired therapeutic tar-gets. In several cases, drugs, especially the highly lipophilic molecules, suffer from low solubility and bioavailability and therefore their desired targeting is hampered. In addition, unde-sired metabolic products might be produced or off-targets could be recognized. Along these lines, nanopharmacology has provided new technological platforms, to overcome these boundaries. Specifically, numerous vehicle platforms such as cyclodextrins and calixarenes have been widely utilized to host lipophilic drugs such as antagonists of the angiotensin II AT1 receptor (AT1R), as well as quercetin and silibinin. The encapsulation of these drugs in supramolecules or other systems refines their solubility and metabolic stability, increases their selectivity and therefore decreases their effective dose and improves their therapeutic index. In this mini review we report on the formulations of silibinin and AT1R antagonist candesar-tan in a 2-HP-β-cyclodextrin host molecule, which displayed enhanced cytotoxicity and increased silibinin’s and candesartan’s stability, respectively. Moreover, we describe the encapsulation of quercetin in gold nanoparticles bearing a calixarene supramolecular host. Also, the encapsulation of temozolomide in a calixarene nanocapsule has been described. Finally, we report on the activity enhancement that has been achieved upon using these formulations as well as the analytical and computational methods we used to characterize these formulations and explore the molecular interactions between the host and quest molecules.}, author = {A.D. Tsiailanis and A.G. Tzakos and T. Mavromoustakos}, doi = {10.2174/0929867327666200605154506}, issue = {14}, journal = {Current Medicinal Chemistry}, pages = {2697-2706}, title = {Advancing the therapeutic efficacy of bioactive molecules by delivery vehicle platforms}, volume = {28}, year = {2021}, } - Syriopoulou, A., I. Markopoulos, A. G. Tzakos, and T. Mavromoustakos. Ligand–receptor interactions and drug design. Vol. 2266. 2021. doi:10.1007/978-1-0716-1209-5_5
[BibTeX] [Abstract]
In silico rational drug design is one of the major pylons in the drug discovery process. Drugs usually act on specific targets such as proteins, DNA, and lipid bilayers. Thus, molecular docking is an essential part of the rational drug design process. Molecular docking uses specific algorithms and scoring functions to reveal the strength of the interaction of the ligand to its target. AutoDock is a molecular docking suite that offers a variety of algorithms to tackle specific problems. These algorithms include Monte Carlo Simulated Annealing (SA), a Genetic Algorithm (GA), and a hybrid local search GA, also known as the Lamarckian Genetic Algorithm (LGA). This chapter aims to acquaint the reader with the docking process using AutoDockTools (GUI of AutoDock). Furthermore, herein is described the docking process of calf thymus DNA with three metal complexes, as a potential metallo-therapeutics as also the docking process of the plant flavonoid quercetin to the antiapoptotic protein BcL-xL.
@book{Syriopoulou2021, abstract = {In silico rational drug design is one of the major pylons in the drug discovery process. Drugs usually act on specific targets such as proteins, DNA, and lipid bilayers. Thus, molecular docking is an essential part of the rational drug design process. Molecular docking uses specific algorithms and scoring functions to reveal the strength of the interaction of the ligand to its target. AutoDock is a molecular docking suite that offers a variety of algorithms to tackle specific problems. These algorithms include Monte Carlo Simulated Annealing (SA), a Genetic Algorithm (GA), and a hybrid local search GA, also known as the Lamarckian Genetic Algorithm (LGA). This chapter aims to acquaint the reader with the docking process using AutoDockTools (GUI of AutoDock). Furthermore, herein is described the docking process of calf thymus DNA with three metal complexes, as a potential metallo-therapeutics as also the docking process of the plant flavonoid quercetin to the antiapoptotic protein BcL-xL.}, author = {A. Syriopoulou and I. Markopoulos and A.G. Tzakos and T. Mavromoustakos}, doi = {10.1007/978-1-0716-1209-5_5}, journal = {Methods in Molecular Biology}, pages = {89-104}, title = {Ligand–Receptor Interactions and Drug Design}, volume = {2266}, year = {2021}, } - Mavromoustakos, T., A. G. Tzakos, and S. Durdagi. Preface. Vol. 2207. 2021.
[BibTeX]@book{Mavromoustakos2021, author = {T. Mavromoustakos and A.G. Tzakos and S. Durdagi}, journal = {Methods in Molecular Biology}, pages = {v}, title = {Preface}, volume = {2207}, year = {2021}, } - Tomou, E. -M., C. D. Papaemmanouil, D. A. Diamantis, A. D. Kostagianni, P. Chatzopoulou, T. Mavromoustakos, A. G. Tzakos, and H. Skaltsa. “Anti-ageing potential of s. euboea heldr. phenolics.” Molecules 26 (2021). doi:10.3390/molecules26113151
[BibTeX] [Abstract]
In recent years, the use of Sideritis species as bioactive agents is increasing exponentially. The present study aimed to investigate the chemical constituents, as well as the anti-ageing potential of the cultivated Sideritis euboea Heldr. The chemical fingerprinting of the ethyl acetate residue of this plant was studied using 1D and 2D-NMR spectra. Isomeric compounds belonging to acylated flavone derivatives and phenylethanoid glycosides were detected in the early stage of the experimental process through 2D-NMR techniques. Overall, thirty-three known compounds were isolated and identified. Some of them are reported for the first time not only in S. euboea, but also in genus Sideritis L. The anti-ageing effect of the ethyl acetate residue and the isolated specialized products was assessed as anti-hyaluronidase activity. In silico docking simulation revealed the interactions of the isolated compounds with hyaluronidase. Furthermore, the in vitro study on the inhibition of hyaluronidase unveiled the potent inhibitory properties of ethyl acetate residue and apigenin 7-O-β-D-glucopyranoside. Though, the isomers of apigenin 7-O-p-coumaroyl-glucosides and also the 4′-methyl-hypolaetin 7-O-[6′′′-O-acetyl-β-D-allopyranosyl]-(1→2)-β-D-glucopyranoside exerted moderate hyaluronidase inhibition. This research represents the first study to report on the anti-hyaluronidase activity of Sideritis species, confirming its anti-inflammatory, cytotoxic and anti-ageing effects and its importance as an agent for cosmetic formulations as also anticancer potential.
@article{Tomou2021, abstract = {In recent years, the use of Sideritis species as bioactive agents is increasing exponentially. The present study aimed to investigate the chemical constituents, as well as the anti-ageing potential of the cultivated Sideritis euboea Heldr. The chemical fingerprinting of the ethyl acetate residue of this plant was studied using 1D and 2D-NMR spectra. Isomeric compounds belonging to acylated flavone derivatives and phenylethanoid glycosides were detected in the early stage of the experimental process through 2D-NMR techniques. Overall, thirty-three known compounds were isolated and identified. Some of them are reported for the first time not only in S. euboea, but also in genus Sideritis L. The anti-ageing effect of the ethyl acetate residue and the isolated specialized products was assessed as anti-hyaluronidase activity. In silico docking simulation revealed the interactions of the isolated compounds with hyaluronidase. Furthermore, the in vitro study on the inhibition of hyaluronidase unveiled the potent inhibitory properties of ethyl acetate residue and apigenin 7-O-β-D-glucopyranoside. Though, the isomers of apigenin 7-O-p-coumaroyl-glucosides and also the 4′-methyl-hypolaetin 7-O-[6′′′-O-acetyl-β-D-allopyranosyl]-(1→2)-β-D-glucopyranoside exerted moderate hyaluronidase inhibition. This research represents the first study to report on the anti-hyaluronidase activity of Sideritis species, confirming its anti-inflammatory, cytotoxic and anti-ageing effects and its importance as an agent for cosmetic formulations as also anticancer potential.}, author = {E.-M. Tomou and C.D. Papaemmanouil and D.A. Diamantis and A.D. Kostagianni and P. Chatzopoulou and T. Mavromoustakos and A.G. Tzakos and H. Skaltsa}, doi = {10.3390/molecules26113151}, issue = {11}, journal = {Molecules}, title = {Anti-ageing potential of S. Euboea heldr. phenolics}, volume = {26}, year = {2021}, } - Vrettos, E. I., T. Karampelas, N. Sayyad, A. Kougioumtzi, N. Syed, T. Crook, C. Murphy, C. Tamvakopoulos, and A. G. Tzakos. “Development of programmable gemcitabine-gnrh pro-drugs bearing linker controllable “click” oxime bond tethers and preclinical evaluation against prostate cancer.” European journal of medicinal chemistry 211 (2021). doi:10.1016/j.ejmech.2020.113018
[BibTeX] [Abstract]
Peptide-drug conjugates (PDCs) are gaining considerable attention as anti-neoplastic agents. However, their development is often laborious and time-consuming. Herein, we have developed and preclinically evaluated three PDCs with gemcitabine as the anticancer cytotoxic unit and D-Lys6-GnRH (gonadotropin-releasing hormone; GnRH) as the cancer-targeting unit. These units were tethered via acid-labile programmable linkers to guide a differential drug release rate from the PDC through a combination of ester or amide and “click” type oxime ligations. The pro-drugs were designed to enable the selective targeting of malignant tumor cells with linker guided differential drug release rates. We exploited the oxime bond responsiveness against the acidic pH of the tumor microenvironment and the GnRH endocytosis via the GnRH-R GPCR which is overexpressed on cancer cells. The challenging metabolic properties of gemcitabine were addressed during design of the PDCs. We developed a rapid (1 hour) and cost-effective “click” oxime bond ligation platform to assemble in one-pot the 3 desired PDCs that does not require purification, surpassing traditional time-ineffective and low yield methods. The internalization of the tumor-homing peptide unit in cancer cells, overexpressing the GnRH-R, was first validated through confocal laser microscopy and flow cytometry analysis. Subsequently, the three PDCs were evaluated for their in vitro antiproliferative effect in prostate cancer cells. Their stability and the release of gemcitabine over time were monitored in vitro in cell culture and in human plasma using LC-MS/MS. We then assessed the ability of the developed PDCs to internalize in prostate cancer cells and to release gemcitabine. The most potent analog, designated GOXG1, was used for pharmacokinetic studies in mice. The metabolism of GOXG1 was examined in liver microsomes, as well as in buffers mimicking the pH of intracellular organelles, resulting in the identification of two metabolites. The major metabolite at low pH emanated from the cleavage of the pH-labile oxime bond, validating our design approach. NMR spectroscopy and in vitro radioligand binding assays were exploited for GOXG1 to validate that upon conjugating the drug to the peptide, the peptide microenvironment responsible for its GnRH-R binding is not perturbed and to confirm its high binding potency to the GnRH-R. Finally, the binding of GOXG1 to the GnRH-R and the associated elicitation of testosterone release in mice were also determined. The facile platform established herein for the rapid assembly of PDCs with linker controllable characteristics from aldehyde and aminooxy units through rapid “click” oxime ligation, that does not require purification steps, could pave the way for a new generation of potent cancer therapeutics, diagnostics and theranostics.
@article{Vrettos2021, abstract = {Peptide-drug conjugates (PDCs) are gaining considerable attention as anti-neoplastic agents. However, their development is often laborious and time-consuming. Herein, we have developed and preclinically evaluated three PDCs with gemcitabine as the anticancer cytotoxic unit and D-Lys6-GnRH (gonadotropin-releasing hormone; GnRH) as the cancer-targeting unit. These units were tethered via acid-labile programmable linkers to guide a differential drug release rate from the PDC through a combination of ester or amide and “click” type oxime ligations. The pro-drugs were designed to enable the selective targeting of malignant tumor cells with linker guided differential drug release rates. We exploited the oxime bond responsiveness against the acidic pH of the tumor microenvironment and the GnRH endocytosis via the GnRH-R GPCR which is overexpressed on cancer cells. The challenging metabolic properties of gemcitabine were addressed during design of the PDCs. We developed a rapid (1 hour) and cost-effective “click” oxime bond ligation platform to assemble in one-pot the 3 desired PDCs that does not require purification, surpassing traditional time-ineffective and low yield methods. The internalization of the tumor-homing peptide unit in cancer cells, overexpressing the GnRH-R, was first validated through confocal laser microscopy and flow cytometry analysis. Subsequently, the three PDCs were evaluated for their in vitro antiproliferative effect in prostate cancer cells. Their stability and the release of gemcitabine over time were monitored in vitro in cell culture and in human plasma using LC-MS/MS. We then assessed the ability of the developed PDCs to internalize in prostate cancer cells and to release gemcitabine. The most potent analog, designated GOXG1, was used for pharmacokinetic studies in mice. The metabolism of GOXG1 was examined in liver microsomes, as well as in buffers mimicking the pH of intracellular organelles, resulting in the identification of two metabolites. The major metabolite at low pH emanated from the cleavage of the pH-labile oxime bond, validating our design approach. NMR spectroscopy and in vitro radioligand binding assays were exploited for GOXG1 to validate that upon conjugating the drug to the peptide, the peptide microenvironment responsible for its GnRH-R binding is not perturbed and to confirm its high binding potency to the GnRH-R. Finally, the binding of GOXG1 to the GnRH-R and the associated elicitation of testosterone release in mice were also determined. The facile platform established herein for the rapid assembly of PDCs with linker controllable characteristics from aldehyde and aminooxy units through rapid “click” oxime ligation, that does not require purification steps, could pave the way for a new generation of potent cancer therapeutics, diagnostics and theranostics.}, author = {E.I. Vrettos and T. Karampelas and N. Sayyad and A. Kougioumtzi and N. Syed and T. Crook and C. Murphy and C. Tamvakopoulos and A.G. Tzakos}, doi = {10.1016/j.ejmech.2020.113018}, journal = {European Journal of Medicinal Chemistry}, title = {Development of programmable gemcitabine-GnRH pro-drugs bearing linker controllable “click” oxime bond tethers and preclinical evaluation against prostate cancer}, volume = {211}, year = {2021}, } - Kiriakidi, S., C. Chatzigiannis, C. Papaemmanouil, A. G. Tzakos, Z. Cournia, and T. Mavromoustakos. “Interplay of cholesterol, membrane bilayers and the at1r: a cholesterol consensus motif on at1r is revealed.” Computational and structural biotechnology journal 19 (2021): 110-120. doi:10.1016/j.csbj.2020.11.042
[BibTeX] [Abstract]
Hypertension, mediated by the Angiotensin II receptor type 1 (AT1R), is still the major cause of premature death despite the discovery of novel therapeutics, highlighting the importance of an in depth understanding of the drug-AT1R recognition mechanisms coupled with the impact of the membrane environment on the interaction of drugs with AT1R. Herein, we examine the interplay of cholesterol-lipid-candesartan and the AT1R using Molecular Dynamics simulations of a model membrane consisting of 60:40 mol%. DPPC:cholesterol, candesartan and the AT1R, mimicking the physiological cholesterol concentration in sarcolemma membranes. The simulations of the model membrane of 60:40 mol%. DPPC:cholesterol were further validated using DOSY NMR experiments. Interestingly, our results suggest a significant role of cholesterol in the AT1R function imposed through a Cholesterol Consensus Motif (CCM) in the receptor, which could be crucial in the drug binding process. Candesartan diffusion towards AT1R through incorporation into lipid bilayers, appears to be retarded by the presence of cholesterol. However, its direct approach towards AT1R may be facilitated through the mobility induced on the N-terminus by the cholesterol binding on the CCM these novel insights could pave the way towards the development of more potent pharmaceutical agents to combat hypertension more effectively.
@article{Kiriakidi2021, abstract = {Hypertension, mediated by the Angiotensin II receptor type 1 (AT1R), is still the major cause of premature death despite the discovery of novel therapeutics, highlighting the importance of an in depth understanding of the drug-AT1R recognition mechanisms coupled with the impact of the membrane environment on the interaction of drugs with AT1R. Herein, we examine the interplay of cholesterol-lipid-candesartan and the AT1R using Molecular Dynamics simulations of a model membrane consisting of 60:40 mol%. DPPC:cholesterol, candesartan and the AT1R, mimicking the physiological cholesterol concentration in sarcolemma membranes. The simulations of the model membrane of 60:40 mol%. DPPC:cholesterol were further validated using DOSY NMR experiments. Interestingly, our results suggest a significant role of cholesterol in the AT1R function imposed through a Cholesterol Consensus Motif (CCM) in the receptor, which could be crucial in the drug binding process. Candesartan diffusion towards AT1R through incorporation into lipid bilayers, appears to be retarded by the presence of cholesterol. However, its direct approach towards AT1R may be facilitated through the mobility induced on the N-terminus by the cholesterol binding on the CCM these novel insights could pave the way towards the development of more potent pharmaceutical agents to combat hypertension more effectively.}, author = {S. Kiriakidi and C. Chatzigiannis and C. Papaemmanouil and A.G. Tzakos and Z. Cournia and T. Mavromoustakos}, doi = {10.1016/j.csbj.2020.11.042}, journal = {Computational and Structural Biotechnology Journal}, pages = {110-120}, title = {Interplay of cholesterol, membrane bilayers and the AT1R: A cholesterol consensus motif on AT1R is revealed}, volume = {19}, year = {2021}, } - Chontzopoulou, E., A. G. Tzakos, and T. Mavromoustakos. “On the rational drug design for hypertension through nmr spectroscopy.” Molecules 26 (2021). doi:10.3390/molecules26010012
[BibTeX] [Abstract]
Antagonists of the AT1receptor (AT1R) are beneficial molecules that can prevent the peptide hormone angiotensin II from binding and activating the specific receptor causing hypertension in pathological states. This review article summarizes the multifaced applications of solid and liquid state high resolution nuclear magnetic resonance (NMR) spectroscopy in antihypertensive commercial drugs that act as AT1R antagonists. The 3D architecture of these compounds is explored through 2D NOESY spectroscopy and their interactions with micelles and lipid bilayers are described using solid state 13CP/MAS, 31P and 2H static solid state NMR spectroscopy. Due to their hydrophobic character, AT1R antagonists do not exert their optimum profile on the AT1R. Therefore, various vehicles are explored so as to effectively deliver these molecules to the site of action and to enhance their pharmaceutical efficacy. Cyclodextrins and polymers comprise successful examples of effective drug delivery vehicles, widely used for the delivery of hydrophobic drugs to the active site of the receptor. High resolution NMR spectroscopy provides valuable information on the physical-chemical forces that govern these drug:vehicle interactions, knowledge required to get a deeper understanding on the stability of the formed complexes and therefore the appropriateness and usefulness of the drug delivery system. In addition, it provides valuable information on the rational design towards the synthesis of more stable and efficient drug formulations.
@article{Chontzopoulou2021, abstract = {Antagonists of the AT1receptor (AT1R) are beneficial molecules that can prevent the peptide hormone angiotensin II from binding and activating the specific receptor causing hypertension in pathological states. This review article summarizes the multifaced applications of solid and liquid state high resolution nuclear magnetic resonance (NMR) spectroscopy in antihypertensive commercial drugs that act as AT1R antagonists. The 3D architecture of these compounds is explored through 2D NOESY spectroscopy and their interactions with micelles and lipid bilayers are described using solid state 13CP/MAS, 31P and 2H static solid state NMR spectroscopy. Due to their hydrophobic character, AT1R antagonists do not exert their optimum profile on the AT1R. Therefore, various vehicles are explored so as to effectively deliver these molecules to the site of action and to enhance their pharmaceutical efficacy. Cyclodextrins and polymers comprise successful examples of effective drug delivery vehicles, widely used for the delivery of hydrophobic drugs to the active site of the receptor. High resolution NMR spectroscopy provides valuable information on the physical-chemical forces that govern these drug:vehicle interactions, knowledge required to get a deeper understanding on the stability of the formed complexes and therefore the appropriateness and usefulness of the drug delivery system. In addition, it provides valuable information on the rational design towards the synthesis of more stable and efficient drug formulations.}, author = {E. Chontzopoulou and A.G. Tzakos and T. Mavromoustakos}, doi = {10.3390/molecules26010012}, issue = {1}, journal = {Molecules}, title = {On the rational drug design for hypertension through NMR spectroscopy}, volume = {26}, year = {2021}, } - Diamantis, D. A., A. Agalou, M. V. Chatziathanasiadou, G. S. Markopoulos, S. Bellou, Z. Kanaki, T. Crook, N. Syed, T. Rampias, A. Klinakis, D. Beis, and A. G. Tzakos. “Biotin-yellow a biotin guided nir turn-on fluorescent probe for cancer targeted diagnosis.” Sensors and actuators, b: chemical 337 (2021). doi:10.1016/j.snb.2021.129807
[BibTeX] [Abstract]
A dicyanomethylene-4H-pyran based tumor-targeting and biothiol activatable fluorescent and colorimetric probe, named Biotin-Yellow, has been developed with unprecedented turn-on near-infrared fluorescence properties. Biotin-Yellow is non-toxic and can effectively recognize and discriminate human lung adenocarcinoma cells and urothelial (bladder) carcinoma cells from embryonic kidney cells and embryonic fibroblasts. Biotin-Yellow can also be employed for real-time bioimaging tracking of upregulated biothiol activity in cancer cells. The efficacy and biothiol responsiveness of Biotin-Yellow was further validated in vivo in zebrafish and mice xenografts.
@article{Diamantis2021, abstract = {A dicyanomethylene-4H-pyran based tumor-targeting and biothiol activatable fluorescent and colorimetric probe, named Biotin-Yellow, has been developed with unprecedented turn-on near-infrared fluorescence properties. Biotin-Yellow is non-toxic and can effectively recognize and discriminate human lung adenocarcinoma cells and urothelial (bladder) carcinoma cells from embryonic kidney cells and embryonic fibroblasts. Biotin-Yellow can also be employed for real-time bioimaging tracking of upregulated biothiol activity in cancer cells. The efficacy and biothiol responsiveness of Biotin-Yellow was further validated in vivo in zebrafish and mice xenografts.}, author = {D.A. Diamantis and A. Agalou and M.V. Chatziathanasiadou and G.S. Markopoulos and S. Bellou and Z. Kanaki and T. Crook and N. Syed and T. Rampias and A. Klinakis and D. Beis and A.G. Tzakos}, doi = {10.1016/j.snb.2021.129807}, journal = {Sensors and Actuators, B: Chemical}, title = {Biotin-Yellow a biotin guided NIR turn-on fluorescent probe for cancer targeted diagnosis}, volume = {337}, year = {2021}, } - Georgiou, N., V. K. Gkalpinos, S. D. Katsakos, S. Vassiliou, A. G. Tzakos, and T. Mavromoustakos. “Rational design and synthesis of at1r antagonists.” Molecules 26 (2021). doi:10.3390/molecules26102927
[BibTeX] [Abstract]
Hypertension is one of the most common diseases nowadays and is still the major cause of premature death despite of the continuous discovery of novel therapeutics. The discovery of the Renin Angiotensin System (RAS) unveiled a path to develop efficient drugs to fruitfully combat hypertension. Several compounds that prevent the Angiotensin II hormone from binding and activating the AT1R, named sartans, have been developed. Herein, we report a comprehensive review of the synthetic paths followed for the development of different sartans since the discovery of the first sartan, Losartan.
@article{Georgiou2021, abstract = {Hypertension is one of the most common diseases nowadays and is still the major cause of premature death despite of the continuous discovery of novel therapeutics. The discovery of the Renin Angiotensin System (RAS) unveiled a path to develop efficient drugs to fruitfully combat hypertension. Several compounds that prevent the Angiotensin II hormone from binding and activating the AT1R, named sartans, have been developed. Herein, we report a comprehensive review of the synthetic paths followed for the development of different sartans since the discovery of the first sartan, Losartan.}, author = {N. Georgiou and V.K. Gkalpinos and S.D. Katsakos and S. Vassiliou and A.G. Tzakos and T. Mavromoustakos}, doi = {10.3390/molecules26102927}, issue = {10}, journal = {Molecules}, title = {Rational design and synthesis of at1r antagonists}, volume = {26}, year = {2021}, } - Tsagogiannis, E., E. Vandera, A. Primikyri, S. Asimakoula, A. G. Tzakos, I. P. Gerothanassis, and A. -I. Koukkou. “Characterization of protocatechuate 4,5-dioxygenase from pseudarthrobacter phenanthrenivorans sphe3 and in situ reaction monitoring in the nmr tube.” International journal of molecular sciences 22 (2021). doi:10.3390/ijms22179647
[BibTeX] [Abstract]
The current study aims at the functional and kinetic characterization of protocatechuate (PCA) 4,5-dioxygenase (PcaA) from Pseudarthrobacter phenanthrenivorans Sphe3. This is the first single subunit Type II dioxygenase characterized in Actinobacteria. RT-PCR analysis demonstrated that pcaA and the adjacent putative genes implicated in the PCA meta-cleavage pathway comprise a single transcriptional unit. The recombinant PcaA is highly specific for PCA and exhibits Michae-lis–Menten kinetics with Km and Vmax values of 21 ± 1.6 μM and 44.8 ± 4.0 U × mg−1, respectively, in pH 9.5 and at 20 °C. PcaA also converted gallate from a broad range of substrates tested. The enzy-matic reaction products were identified and characterized, for the first time, through in situ bio-transformation monitoring inside an NMR tube. The PCA reaction product demonstrated a keto-enol tautomerization, whereas the gallate reaction product was present only in the keto form. More-over, the transcriptional levels of pcaA and pcaR (gene encoding a LysR-type regulator of the path-way) were also determined, showing an induction when cells were grown on PCA and phenan-threne. Studying key enzymes in biodegradation pathways is significant for bioremediation and for efficient biocatalysts development.
@article{Tsagogiannis2021, abstract = {The current study aims at the functional and kinetic characterization of protocatechuate (PCA) 4,5-dioxygenase (PcaA) from Pseudarthrobacter phenanthrenivorans Sphe3. This is the first single subunit Type II dioxygenase characterized in Actinobacteria. RT-PCR analysis demonstrated that pcaA and the adjacent putative genes implicated in the PCA meta-cleavage pathway comprise a single transcriptional unit. The recombinant PcaA is highly specific for PCA and exhibits Michae-lis–Menten kinetics with Km and Vmax values of 21 ± 1.6 μM and 44.8 ± 4.0 U × mg−1, respectively, in pH 9.5 and at 20 °C. PcaA also converted gallate from a broad range of substrates tested. The enzy-matic reaction products were identified and characterized, for the first time, through in situ bio-transformation monitoring inside an NMR tube. The PCA reaction product demonstrated a keto-enol tautomerization, whereas the gallate reaction product was present only in the keto form. More-over, the transcriptional levels of pcaA and pcaR (gene encoding a LysR-type regulator of the path-way) were also determined, showing an induction when cells were grown on PCA and phenan-threne. Studying key enzymes in biodegradation pathways is significant for bioremediation and for efficient biocatalysts development.}, author = {E. Tsagogiannis and E. Vandera and A. Primikyri and S. Asimakoula and A.G. Tzakos and I.P. Gerothanassis and A.-I. Koukkou}, doi = {10.3390/ijms22179647}, issue = {17}, journal = {International Journal of Molecular Sciences}, title = {Characterization of protocatechuate 4,5-dioxygenase from pseudarthrobacter phenanthrenivorans sphe3 and in situ reaction monitoring in the NMR tube}, volume = {22}, year = {2021}, } - Sayyad, N., R. Maji, C. A. Omolo, A. M. Ganai, U. H. Ibrahim, T. K. Pathan, N. Devnarain, R. Karpoormath, S. Dhawan, V. A. Obakachi, A. G. Tzakos, and S. Singh. “Development of niosomes for encapsulating captopril-quercetin prodrug to combat hypertension.” International journal of pharmaceutics 609 (2021). doi:10.1016/j.ijpharm.2021.121191
[BibTeX] [Abstract]
Novel and effective anti-hypertensive agents are required to manage hypertension; therefore, we synthesised a novel antihypertensive drug from captopril and quercetin (cap-que) and explored its antihypertensive potential in a niosomal formulation via molecular hybridisation. The cap-que hybrid was synthesised, and its structure was characterised via NMR, FTIR, and HRMS. Niosomes were then loaded with cap-que using the thin-film hydration method. The particle size, polydispersity index, surface charge and drug entrapment efficiency (EE%) of the formulation were 418.8 ± 4.21 nm, 0.393 ± 0.063, 16.25 ± 0.21 mV, and 87.74 ± 2.82%, respectively. The drug release profile showed a sustained release of the active compound (43 ± 0.09%) from the niosomal formulation, compared to the parent drug (80.7 ± 4.68%), over 24 h. The cell viability study confirmed the biosafety of the formulation. The in vivo study in a rat model showed enhanced antihypertensive activity of the hybrid molecule and niosomal formulation which reduced systolic and diastolic pressure when compared to the individual, bare drugs. The findings of this study concluded that the antihypertensive potential of captopril can be enhanced by its hybridisation with quercetin, followed by niosomal nano drug delivery.
@article{Sayyad2021, abstract = {Novel and effective anti-hypertensive agents are required to manage hypertension; therefore, we synthesised a novel antihypertensive drug from captopril and quercetin (cap-que) and explored its antihypertensive potential in a niosomal formulation via molecular hybridisation. The cap-que hybrid was synthesised, and its structure was characterised via NMR, FTIR, and HRMS. Niosomes were then loaded with cap-que using the thin-film hydration method. The particle size, polydispersity index, surface charge and drug entrapment efficiency (EE%) of the formulation were 418.8 ± 4.21 nm, 0.393 ± 0.063, 16.25 ± 0.21 mV, and 87.74 ± 2.82%, respectively. The drug release profile showed a sustained release of the active compound (43 ± 0.09%) from the niosomal formulation, compared to the parent drug (80.7 ± 4.68%), over 24 h. The cell viability study confirmed the biosafety of the formulation. The in vivo study in a rat model showed enhanced antihypertensive activity of the hybrid molecule and niosomal formulation which reduced systolic and diastolic pressure when compared to the individual, bare drugs. The findings of this study concluded that the antihypertensive potential of captopril can be enhanced by its hybridisation with quercetin, followed by niosomal nano drug delivery.}, author = {N. Sayyad and R. Maji and C.A. Omolo and A.M. Ganai and U.H. Ibrahim and T.K. Pathan and N. Devnarain and R. Karpoormath and S. Dhawan and V.A. Obakachi and A.G. Tzakos and S. Singh}, doi = {10.1016/j.ijpharm.2021.121191}, journal = {International Journal of Pharmaceutics}, title = {Development of niosomes for encapsulating captopril-quercetin prodrug to combat hypertension}, volume = {609}, year = {2021}, } - Matsoukas, J., G. Deraos, K. Kelaidonis, M. K. Hossain, J. Feehan, A. G. Tzakos, E. Matsoukas, E. Topoglidis, and V. Apostolopoulos. “Myelin peptide–mannan conjugate multiple sclerosis vaccines: conjugation efficacy and stability of vaccine ingredient.” Vaccines 9 (2021). doi:10.3390/vaccines9121456
[BibTeX] [Abstract]
Myelin peptide–mannan conjugates have been shown to be potential vaccines in the immunotherapy of multiple sclerosis. The conjugates are comprised from the epitope peptide and the polysaccharide mannan which transfers as a carrier the antigenic peptide to dendritic cells that process and present antigenic peptides at their surface in complex with MHC class I or class II resulting in T-cell stimulation. The conjugation of antigenic peptide with mannan occurs through the linker (Lys–Gly)5, which connects the peptide with the oxidized mannose units of mannan. This study describes novel methods for the quantification of the vaccine ingredient peptide within the conjugate, a prerequisite for approval of clinical trials in the pursuit of multiple sclerosis therapeutics. Myelin peptides, such as MOG35–55, MBP83–99, and PLP131–145 in linear or cyclic form, as altered peptide ligands or conjugated to appropriate carriers, possess immunomodulatory properties in experimental models and are potential candidates for clinical trials.
@article{Matsoukas2021, abstract = {Myelin peptide–mannan conjugates have been shown to be potential vaccines in the immunotherapy of multiple sclerosis. The conjugates are comprised from the epitope peptide and the polysaccharide mannan which transfers as a carrier the antigenic peptide to dendritic cells that process and present antigenic peptides at their surface in complex with MHC class I or class II resulting in T-cell stimulation. The conjugation of antigenic peptide with mannan occurs through the linker (Lys–Gly)5, which connects the peptide with the oxidized mannose units of mannan. This study describes novel methods for the quantification of the vaccine ingredient peptide within the conjugate, a prerequisite for approval of clinical trials in the pursuit of multiple sclerosis therapeutics. Myelin peptides, such as MOG35–55, MBP83–99, and PLP131–145 in linear or cyclic form, as altered peptide ligands or conjugated to appropriate carriers, possess immunomodulatory properties in experimental models and are potential candidates for clinical trials.}, author = {J. Matsoukas and G. Deraos and K. Kelaidonis and M.K. Hossain and J. Feehan and A.G. Tzakos and E. Matsoukas and E. Topoglidis and V. Apostolopoulos}, doi = {10.3390/vaccines9121456}, issue = {12}, journal = {Vaccines}, title = {Myelin peptide–mannan conjugate multiple sclerosis vaccines: Conjugation efficacy and stability of vaccine ingredient}, volume = {9}, year = {2021}, } - Kougioumtzi, A., M. V. Chatziathanasiadou, E. I. Vrettos, N. Sayyad, M. Sakka, P. Stathopoulos, M. D. Mantzaris, A. M. Ganai, R. Karpoormath, G. Vartholomatos, C. Murphy, and A. G. Tzakos. “Development of novel gnrh and tat48-60based luminescent probes with enhanced cellular uptake and bioimaging profile.” Dalton transactions 50 (2021): 9215-9224. doi:10.1039/d1dt00060h
[BibTeX] [Abstract]
There is a clear need to develop photostable chromophores for bioimaging with respect to the classically utilized green fluorescent dye fluorescein. Along these lines, we utilized a phosphorescent carboxy-substituted ruthenium(ii) polypyridyl [Ru(bipy)2(mcb)]2+(bipy = 2,2′-bipyridyl and mcb = 4-carboxy-4′-methyl-2,2′-bipyridyl) complex. We developed two luminescent peptide conjugates of the cell-penetrating peptide Tat48-60consisting of either [Ru(bipy)2(mcb)]2+or 5(6)-carboxyfluorescein (5(6)-FAM) tethered on the Lys50of the peptide through amide bond. We confirmed the efficient cellular uptake of both bioconjugates in HeLa cells by confocal microscopy and flow cytometry and proved that the ruthenium-based chromophore possesses enhanced photostability compared to a 5(6)-FAM-based peptide, after continuous laser scanning. Furthermore, we designed and developed a luminescent agent with high photostability, based on the ruthenium core, that could be selectively localized in cancer cells overexpressing the GnRH receptor (GnRH-R). To achieve this, we took advantage of the tumor-homing character ofd-Lys6-GnRH which selectively recognizes the GnRH-R. The [Ru(bipy)2(mcb)]2+-d-Lys6-GnRH peptide conjugate was synthesized, and its cellular uptake was evaluated through flow cytometric analysis and live-cell imaging in HeLa and T24 bladder cancer cells as negative and positive controls of GnRH-R, respectively. Besides the selective targeting that the specific conjugate could offer, we also recorded high internalization levels in T24 bladder cancer cells. The ruthenium(ii) polypyridyl peptide-based conjugates we developed is an intriguing approach that offers targeted cell imaging in the Near Infrared region, and simultaneously paves the way for further advancements in the dynamic studies on cellular imaging.
@article{Kougioumtzi2021, abstract = {There is a clear need to develop photostable chromophores for bioimaging with respect to the classically utilized green fluorescent dye fluorescein. Along these lines, we utilized a phosphorescent carboxy-substituted ruthenium(ii) polypyridyl [Ru(bipy)2(mcb)]2+(bipy = 2,2′-bipyridyl and mcb = 4-carboxy-4′-methyl-2,2′-bipyridyl) complex. We developed two luminescent peptide conjugates of the cell-penetrating peptide Tat48-60consisting of either [Ru(bipy)2(mcb)]2+or 5(6)-carboxyfluorescein (5(6)-FAM) tethered on the Lys50of the peptide through amide bond. We confirmed the efficient cellular uptake of both bioconjugates in HeLa cells by confocal microscopy and flow cytometry and proved that the ruthenium-based chromophore possesses enhanced photostability compared to a 5(6)-FAM-based peptide, after continuous laser scanning. Furthermore, we designed and developed a luminescent agent with high photostability, based on the ruthenium core, that could be selectively localized in cancer cells overexpressing the GnRH receptor (GnRH-R). To achieve this, we took advantage of the tumor-homing character ofd-Lys6-GnRH which selectively recognizes the GnRH-R. The [Ru(bipy)2(mcb)]2+-d-Lys6-GnRH peptide conjugate was synthesized, and its cellular uptake was evaluated through flow cytometric analysis and live-cell imaging in HeLa and T24 bladder cancer cells as negative and positive controls of GnRH-R, respectively. Besides the selective targeting that the specific conjugate could offer, we also recorded high internalization levels in T24 bladder cancer cells. The ruthenium(ii) polypyridyl peptide-based conjugates we developed is an intriguing approach that offers targeted cell imaging in the Near Infrared region, and simultaneously paves the way for further advancements in the dynamic studies on cellular imaging.}, author = {A. Kougioumtzi and M.V. Chatziathanasiadou and E.I. Vrettos and N. Sayyad and M. Sakka and P. Stathopoulos and M.D. Mantzaris and A.M. Ganai and R. Karpoormath and G. Vartholomatos and C. Murphy and A.G. Tzakos}, doi = {10.1039/d1dt00060h}, issue = {26}, journal = {Dalton Transactions}, pages = {9215-9224}, title = {Development of novel GnRH and Tat48-60based luminescent probes with enhanced cellular uptake and bioimaging profile}, volume = {50}, year = {2021}, } - Tourwé, D., A. D. Tsiailanis, N. Parisis, B. Hirmiz, Del M. Borgo, M. -I. Aguilar, Van O. der Poorten, S. Ballet, R. E. Widdop, and A. G. Tzakos. “Using conformational constraints at position 6 of angiotensin ii to generate compounds with enhanced at2r selectivity and proteolytic stability.” Bioorganic and medicinal chemistry letters 43 (2021). doi:10.1016/j.bmcl.2021.128086
[BibTeX] [Abstract]
The Renin-Angiotensin System (RAS) plays a crucial role in numerous pathological conditions. Two of the critical RAS players, the angiotensin receptors AT1R and AT2R, possess differential functional profiles, although they share high sequence similarity. Although the main focus has been placed on AT1R, several epidemiological studies have evidenced that activation of AT2R could operate as a multimodal therapeutic target for different diseases. Thus, the development of selective AT2R ligands could have a high clinical potential for different therapeutic directions. Furthermore, they could serve as a powerful tool to interrogate the molecular mechanisms that are mediated by AT2R. Based on our recently established high affinity and AT2R selective compound [Y]6-AII we developed several analogues through modifying aminoacids located at positions 6 and 7 with various conformationally constrained analogues to enhance both the selectivity and stability. We report the development of high-affinity AT2R binders, which displayed high selectivity for AT2R versus AT1R. Furthermore, all analogues presented enhanced stability in human plasma with respect to the parent hormone Angiotensin II as also [Y]6-AII.
@article{, abstract = {The Renin-Angiotensin System (RAS) plays a crucial role in numerous pathological conditions. Two of the critical RAS players, the angiotensin receptors AT1R and AT2R, possess differential functional profiles, although they share high sequence similarity. Although the main focus has been placed on AT1R, several epidemiological studies have evidenced that activation of AT2R could operate as a multimodal therapeutic target for different diseases. Thus, the development of selective AT2R ligands could have a high clinical potential for different therapeutic directions. Furthermore, they could serve as a powerful tool to interrogate the molecular mechanisms that are mediated by AT2R. Based on our recently established high affinity and AT2R selective compound [Y]6-AII we developed several analogues through modifying aminoacids located at positions 6 and 7 with various conformationally constrained analogues to enhance both the selectivity and stability. We report the development of high-affinity AT2R binders, which displayed high selectivity for AT2R versus AT1R. Furthermore, all analogues presented enhanced stability in human plasma with respect to the parent hormone Angiotensin II as also [Y]6-AII.}, author = {D. Tourwé and A.D. Tsiailanis and N. Parisis and B. Hirmiz and M. Del Borgo and M.-I. Aguilar and O. Van der Poorten and S. Ballet and R.E. Widdop and A.G. Tzakos}, doi = {10.1016/j.bmcl.2021.128086}, journal = {Bioorganic and Medicinal Chemistry Letters}, title = {Using conformational constraints at position 6 of Angiotensin II to generate compounds with enhanced AT2R selectivity and proteolytic stability}, volume = {43}, year = {2021}, } - Zoi, V., V. Galani, E. Vartholomatos, N. Zacharopoulou, E. Tsoumeleka, G. Gkizas, G. Bozios, P. Tsekeris, I. Chousidis, I. Leonardos, A. P. Kyritsis, and G. A. Alexiou. “Curcumin and radiotherapy exert synergistic anti-glioma effect in vitro.” Biomedicines 9 (2021). doi:10.3390/biomedicines9111562
[BibTeX] [Abstract]
Curcumin, a bioactive polyphenol, is known to have anticancer properties. In this study, the effectiveness of curcumin pretreatment as a strategy for radio-sensitizing glioblastoma cell lines was explored. For this, U87 and T98 cells were treated with curcumin, exposed to 2 Gy or 4 Gy of irradiation, and the combined effect was compared to the antiproliferative effect of each agent when given individually. Cell viability and proliferation were evaluated with the trypan blue exclusion assay and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The synergistic effects of the combination treatment were analyzed with CompuSyn software. To examine how the co-treatment affected different phases of cell-cycle progression, a cell-cycle analysis via flow cytometry was performed. Treatment with curcumin and radiation significantly reduced cell viability in both U87 and T98 cell lines. The combination treatment arrested both cell lines at the G2/M phase to a higher extent than radiation or curcumin treatment alone. The synergistic effect of curcumin when combined with temozolomide resulted in increased tumor cell death. Our results demonstrate for the first time that low doses of curcumin and irradiation exhibit a strong synergistic anti-proliferative effect on glioblastoma cells in vitro. Therefore, this combination may represent an innovative and promising strategy for the treatment of glioblastoma, and further studies are needed to fully understand the molecular mechanism underlying this effect.
@article{Zoi2021, abstract = {Curcumin, a bioactive polyphenol, is known to have anticancer properties. In this study, the effectiveness of curcumin pretreatment as a strategy for radio-sensitizing glioblastoma cell lines was explored. For this, U87 and T98 cells were treated with curcumin, exposed to 2 Gy or 4 Gy of irradiation, and the combined effect was compared to the antiproliferative effect of each agent when given individually. Cell viability and proliferation were evaluated with the trypan blue exclusion assay and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The synergistic effects of the combination treatment were analyzed with CompuSyn software. To examine how the co-treatment affected different phases of cell-cycle progression, a cell-cycle analysis via flow cytometry was performed. Treatment with curcumin and radiation significantly reduced cell viability in both U87 and T98 cell lines. The combination treatment arrested both cell lines at the G2/M phase to a higher extent than radiation or curcumin treatment alone. The synergistic effect of curcumin when combined with temozolomide resulted in increased tumor cell death. Our results demonstrate for the first time that low doses of curcumin and irradiation exhibit a strong synergistic anti-proliferative effect on glioblastoma cells in vitro. Therefore, this combination may represent an innovative and promising strategy for the treatment of glioblastoma, and further studies are needed to fully understand the molecular mechanism underlying this effect.}, author = {V. Zoi and V. Galani and E. Vartholomatos and N. Zacharopoulou and E. Tsoumeleka and G. Gkizas and G. Bozios and P. Tsekeris and I. Chousidis and I. Leonardos and A.P. Kyritsis and G.A. Alexiou}, doi = {10.3390/biomedicines9111562}, issue = {11}, journal = {Biomedicines}, title = {Curcumin and radiotherapy exert synergistic anti-glioma effect in vitro}, volume = {9}, year = {2021}, }
2020
- Kiriakidi, S., C. Chatzigiannis, C. Papaemmanouil, A. G. Tzakos, and T. Mavromoustakos. “Exploring the role of the membrane bilayer in the recognition of candesartan by its gpcr at1 receptor.” Biochimica et biophysica acta – biomembranes 1862 (2020). doi:10.1016/j.bbamem.2019.183142
[BibTeX] [Abstract]
Cardiovascular diseases and hypertension in particular are major health risks worldwide and the improvement on their treatment will be beneficial for the human health. AT1R antagonists belong to the sartans family that targets the renin-angiotensin aldosterone system (RAAS) through blocking the hormone angiotensin II to exert its detrimental effects in pathological states. As a consequence, they are beneficial to treat hypertension, diabetes related kidney failure and hyperaemic episodes. Long unbiased Molecular Dynamics (MD) simulations are performed in order to explore candesartan’s possible 2D and 3D diffusion mechanisms towards AT1R receptor. 3D diffusion mechanism is referred to the direct binding of the AT1 antagonist candesartan to the AT1R 3D structure (PDB ID: 4YAY). 2D diffusion mechanism involves first, the incorporation of candesartan in the bilayer core and then its localization on the AT1R binding cavity, through a diffusion mechanism. The obtained results indicate that membranes interact significantly with the neutral form of candesartan, which is indeed approaching the receptors’ active site through diffusion via the lipids. On the other hand, the deprotonated form of the drug is interacting with AT1R’s extracellular loop and fails to enter the membrane, pointing out the importance of the pH microenvironment around the receptor. To validate the calculated diffusion coefficients of the drug in the lipid bilayers 2D DOSY NMR experiments were recorded and they were in good agreement. Information on the impact that has the interaction of candesartan with the membrane is very important for the rationally design and development of potent ARBs. Thus, its conformational features as well as its localization in the membrane core have to be thoroughly explored.
@article{Kiriakidi2020, abstract = {Cardiovascular diseases and hypertension in particular are major health risks worldwide and the improvement on their treatment will be beneficial for the human health. AT1R antagonists belong to the sartans family that targets the renin-angiotensin aldosterone system (RAAS) through blocking the hormone angiotensin II to exert its detrimental effects in pathological states. As a consequence, they are beneficial to treat hypertension, diabetes related kidney failure and hyperaemic episodes. Long unbiased Molecular Dynamics (MD) simulations are performed in order to explore candesartan's possible 2D and 3D diffusion mechanisms towards AT1R receptor. 3D diffusion mechanism is referred to the direct binding of the AT1 antagonist candesartan to the AT1R 3D structure (PDB ID: 4YAY). 2D diffusion mechanism involves first, the incorporation of candesartan in the bilayer core and then its localization on the AT1R binding cavity, through a diffusion mechanism. The obtained results indicate that membranes interact significantly with the neutral form of candesartan, which is indeed approaching the receptors' active site through diffusion via the lipids. On the other hand, the deprotonated form of the drug is interacting with AT1R's extracellular loop and fails to enter the membrane, pointing out the importance of the pH microenvironment around the receptor. To validate the calculated diffusion coefficients of the drug in the lipid bilayers 2D DOSY NMR experiments were recorded and they were in good agreement. Information on the impact that has the interaction of candesartan with the membrane is very important for the rationally design and development of potent ARBs. Thus, its conformational features as well as its localization in the membrane core have to be thoroughly explored.}, author = {S. Kiriakidi and C. Chatzigiannis and C. Papaemmanouil and A.G. Tzakos and T. Mavromoustakos}, doi = {10.1016/j.bbamem.2019.183142}, issue = {3}, journal = {Biochimica et Biophysica Acta - Biomembranes}, title = {Exploring the role of the membrane bilayer in the recognition of candesartan by its GPCR AT1 receptor}, volume = {1862}, year = {2020}, } - Chatzikonstantinou, A. V., A. C. Polydera, E. Thomou, N. Chalmpes, T. N. Baroud, A. Enotiadis, L. Estevez, M. Patila, M. A. Hammami, K. Spyrou, D. Gournis, and H. Stamatis. “Lipase immobilized on magnetic hierarchically porous carbon materials as a versatile tool for the synthesis of bioactive quercetin derivatives.” Bioresource technology reports 9 (2020). doi:10.1016/j.biteb.2019.100372
[BibTeX] [Abstract]
The preparation, characterization and application of a novel robust nanobiocatalyst, developed through the covalent binding of lipase B from Pseudozyma antarctica on magnetic hierarchically porous carbon materials (HPCFe), is reported. The nanobiocatalyst was characterized by combination of spectroscopic and microscopic techniques. Structural and catalytic characterization indicates that HPCFe nanostructures create a microenvironment which stabilizes the structure of the immobilized enzyme, resulting in enhanced activity and stability in non-aqueous media over other forms of the biocatalyst. The nanobiocatalyst was effectively applied for the selective deacetylation of peracetylated quercetin towards the synthesis of 3,5,7-triacetoxy-3′,4′-dihydroxyflavone, a compound with high antiproliferative activity. At the optimum bioprocess conditions, the produced amount of the bioactive quercetin derivative in a single-step process reached values up to 3.48 g L−1 which is 13 times higher than that reported to date. The immobilized enzyme retains ~100% of its catalytic activity after 10 repeated reaction cycles.
@article{Chatzikonstantinou2020, abstract = {The preparation, characterization and application of a novel robust nanobiocatalyst, developed through the covalent binding of lipase B from Pseudozyma antarctica on magnetic hierarchically porous carbon materials (HPCFe), is reported. The nanobiocatalyst was characterized by combination of spectroscopic and microscopic techniques. Structural and catalytic characterization indicates that HPCFe nanostructures create a microenvironment which stabilizes the structure of the immobilized enzyme, resulting in enhanced activity and stability in non-aqueous media over other forms of the biocatalyst. The nanobiocatalyst was effectively applied for the selective deacetylation of peracetylated quercetin towards the synthesis of 3,5,7-triacetoxy-3′,4′-dihydroxyflavone, a compound with high antiproliferative activity. At the optimum bioprocess conditions, the produced amount of the bioactive quercetin derivative in a single-step process reached values up to 3.48 g L−1 which is 13 times higher than that reported to date. The immobilized enzyme retains ~100% of its catalytic activity after 10 repeated reaction cycles.}, author = {A.V. Chatzikonstantinou and A.C. Polydera and E. Thomou and N. Chalmpes and T.N. Baroud and A. Enotiadis and L. Estevez and M. Patila and M.A. Hammami and K. Spyrou and D. Gournis and H. Stamatis}, doi = {10.1016/j.biteb.2019.100372}, journal = {Bioresource Technology Reports}, title = {Lipase immobilized on magnetic hierarchically porous carbon materials as a versatile tool for the synthesis of bioactive quercetin derivatives}, volume = {9}, year = {2020}, } - Manta, K., P. Papakyriakopoulou, M. Chountoulesi, D. A. Diamantis, D. Spaneas, V. Vakali, N. Naziris, M. V. Chatziathanasiadou, I. Andreadelis, K. Moschovou, A. G. Tzakos, and G. Valsami. “Preparation and biophysical characterization of quercetin inclusion complexes with β-cyclodextrin derivatives to be formulated as possible nose-to-brain quercetin delivery systems.” Molecular pharmaceutics 17 (2020): 4241-4255. doi:10.1021/acs.molpharmaceut.0c00672
[BibTeX] [Abstract]
Quercetin (Que) is a flavonoid associated with high oxygen radical scavenging activity and potential neuroprotective activity against Alzheimer’s disease. Que’s oral bioavailability is limited by its low water solubility and extended peripheral metabolism; thus, nasal administration may be a promising alternative to achieve effective Que concentrations in the brain. The formation of Que-2-hydroxypropylated-β-cyclodextrin (Que/HP-β-CD) complexes was previously found to increase the molecule’s solubility and stability in aqueous media. Que-methyl-β-cyclodextrin (Que/Me-β-CD) inclusion complexes were prepared, characterized, and compared with the Que/HP-β-CD complex using biophysical and computational methods (phase solubility, fluorescence and NMR spectroscopy, differential scanning calorimetry (DSC), and molecular dynamics simulations (MDS)) as candidates for the preparation of nose-to-brain Que’s delivery systems. DSC thermograms, NMR, fluorescence spectroscopy, and MDS confirmed the inclusion complex formation of Que with both CDs. Differences between the two preparations were observed regarding their thermodynamic stability and inclusion mode governing the details of molecular interactions. Que’s solubility in aqueous media at pH 1.2 and 4.5 was similar and linearly increased with both CD concentrations. At pH 6.8, Que’s solubility was higher and positively deviated from linearity in the presence of HP-β-CD more than with Me-β-CD, possibly revealing the presence of more than one HP-β-CD molecule involved in the complex. Overall, water solubility of lyophilized Que/Me-β-CD and Que/HP-β-CD products was approximately 7-40 times and 14-50 times as high as for pure Que at pH 1.2-6.8. In addition, the proof of concept experiment on ex vivo permeation across rabbit nasal mucosa revealed measurable and similar Que permeability profiles with both CDs and negligible permeation of pure Que. These results are quite encouraging for further ex vivo and in vivo evaluation toward nasal administration and nose-to-brain delivery of Que.
@article{Manta2020, abstract = {Quercetin (Que) is a flavonoid associated with high oxygen radical scavenging activity and potential neuroprotective activity against Alzheimer's disease. Que's oral bioavailability is limited by its low water solubility and extended peripheral metabolism; thus, nasal administration may be a promising alternative to achieve effective Que concentrations in the brain. The formation of Que-2-hydroxypropylated-β-cyclodextrin (Que/HP-β-CD) complexes was previously found to increase the molecule's solubility and stability in aqueous media. Que-methyl-β-cyclodextrin (Que/Me-β-CD) inclusion complexes were prepared, characterized, and compared with the Que/HP-β-CD complex using biophysical and computational methods (phase solubility, fluorescence and NMR spectroscopy, differential scanning calorimetry (DSC), and molecular dynamics simulations (MDS)) as candidates for the preparation of nose-to-brain Que's delivery systems. DSC thermograms, NMR, fluorescence spectroscopy, and MDS confirmed the inclusion complex formation of Que with both CDs. Differences between the two preparations were observed regarding their thermodynamic stability and inclusion mode governing the details of molecular interactions. Que's solubility in aqueous media at pH 1.2 and 4.5 was similar and linearly increased with both CD concentrations. At pH 6.8, Que's solubility was higher and positively deviated from linearity in the presence of HP-β-CD more than with Me-β-CD, possibly revealing the presence of more than one HP-β-CD molecule involved in the complex. Overall, water solubility of lyophilized Que/Me-β-CD and Que/HP-β-CD products was approximately 7-40 times and 14-50 times as high as for pure Que at pH 1.2-6.8. In addition, the proof of concept experiment on ex vivo permeation across rabbit nasal mucosa revealed measurable and similar Que permeability profiles with both CDs and negligible permeation of pure Que. These results are quite encouraging for further ex vivo and in vivo evaluation toward nasal administration and nose-to-brain delivery of Que.}, author = {K. Manta and P. Papakyriakopoulou and M. Chountoulesi and D.A. Diamantis and D. Spaneas and V. Vakali and N. Naziris and M.V. Chatziathanasiadou and I. Andreadelis and K. Moschovou and A.G. Tzakos and G. Valsami}, doi = {10.1021/acs.molpharmaceut.0c00672}, issue = {11}, journal = {Molecular Pharmaceutics}, pages = {4241-4255}, title = {Preparation and Biophysical Characterization of Quercetin Inclusion Complexes with β-Cyclodextrin Derivatives to be Formulated as Possible Nose-to-Brain Quercetin Delivery Systems}, volume = {17}, year = {2020}, } - Koukoulitsa, C., E. Chontzopoulou, S. Kiriakidi, A. G. Tzakos, and T. Mavromoustakos. “A journey to the conformational analysis of t-cell epitope peptides involved in multiple sclerosis.” Brain sciences 10 (2020): 1-16. doi:10.3390/brainsci10060356
[BibTeX] [Abstract]
Multiple sclerosis (MS) is a serious central nervous system (CNS) disease responsible for disability problems and deterioration of the quality of life. Several approaches have been applied to medications entering the market to treat this disease. However, no effective therapy currently exists, and the available drugs simply ameliorate the destructive disability effects of the disease. In this review article, we report on the efforts that have been conducted towards establishing the conformational properties of wild-type myelin basic protein (MBP), myelin proteolipid protein (PLP), myelin oligodendrocyte glycoprotein (MOG) epitopes or altered peptide ligands (ALPs). These efforts have led to the aim of discovering some non-peptide mimetics possessing considerable activity against the disease. These efforts have contributed also to unveiling the molecular basis of the molecular interactions implicated in the trimolecular complex, T-cell receptor (TCR)–peptide–major histocompatibility complex (MHC) or human leucocyte antigen (HLA).
@article{Koukoulitsa2020, abstract = {Multiple sclerosis (MS) is a serious central nervous system (CNS) disease responsible for disability problems and deterioration of the quality of life. Several approaches have been applied to medications entering the market to treat this disease. However, no effective therapy currently exists, and the available drugs simply ameliorate the destructive disability effects of the disease. In this review article, we report on the efforts that have been conducted towards establishing the conformational properties of wild-type myelin basic protein (MBP), myelin proteolipid protein (PLP), myelin oligodendrocyte glycoprotein (MOG) epitopes or altered peptide ligands (ALPs). These efforts have led to the aim of discovering some non-peptide mimetics possessing considerable activity against the disease. These efforts have contributed also to unveiling the molecular basis of the molecular interactions implicated in the trimolecular complex, T-cell receptor (TCR)–peptide–major histocompatibility complex (MHC) or human leucocyte antigen (HLA).}, author = {C. Koukoulitsa and E. Chontzopoulou and S. Kiriakidi and A.G. Tzakos and T. Mavromoustakos}, doi = {10.3390/brainsci10060356}, issue = {6}, journal = {Brain Sciences}, pages = {1-16}, title = {A journey to the conformational analysis of T-cell epitope peptides involved in multiple sclerosis}, volume = {10}, year = {2020}, } - Chatzigiannis, C. and A. Tzakos. “A theragnostic device with photo regulated drug dosing and cancer microenvironment sensing character.” Review of clinical pharmacology and pharmacokinetics, international edition 34 (2020): 79-80.
[BibTeX]@article{Chatzigiannis2020, author = {C. Chatzigiannis and A. Tzakos}, issue = {2}, journal = {Review of Clinical Pharmacology and Pharmacokinetics, International Edition}, pages = {79-80}, title = {A theragnostic device with photo regulated drug dosing and cancer microenvironment sensing character}, volume = {34}, year = {2020}, } - Chatzikonstantinou, A. V., A. D. Tsiailanis, I. P. Gerothanassis, H. Stamatis, E. Ravera, M. Fragai, C. Luchinat, G. Parigi, and A. G. Tzakos. The nmr tube bioreactor. Vol. 633. 2020. doi:10.1016/bs.mie.2019.10.032
[BibTeX] [Abstract]
Enzymes are pliable systems and core cellular components allowing the performance of several processes. They can also be utilized as “green” synthetic factories to generate bioactive therapeutic, diagnostic or theranostic compounds. Methods to enable the mapping of enzyme substrates as well as the understanding of the interactions of the formed products with target proteins could be of importance. This chapter describes the utilization of the “NMR tube bioreactor” method. This method, carried out inside an NMR tube, can allow for the prediction of compounds that are able to serve as potential enzyme substrates, and also exploit the regioselectivity of the enzymatic reactions. Furthermore, it enables the real time monitoring of multiple-biotransformation products in the NMR tube without the need of fractionation or isolation of each individual component. Finally, it allows for the screening of the resulting biotransformation products as ligands for protein targets.
@book{Chatzikonstantinou2020, abstract = {Enzymes are pliable systems and core cellular components allowing the performance of several processes. They can also be utilized as “green” synthetic factories to generate bioactive therapeutic, diagnostic or theranostic compounds. Methods to enable the mapping of enzyme substrates as well as the understanding of the interactions of the formed products with target proteins could be of importance. This chapter describes the utilization of the “NMR tube bioreactor” method. This method, carried out inside an NMR tube, can allow for the prediction of compounds that are able to serve as potential enzyme substrates, and also exploit the regioselectivity of the enzymatic reactions. Furthermore, it enables the real time monitoring of multiple-biotransformation products in the NMR tube without the need of fractionation or isolation of each individual component. Finally, it allows for the screening of the resulting biotransformation products as ligands for protein targets.}, author = {A.V. Chatzikonstantinou and A.D. Tsiailanis and I.P. Gerothanassis and H. Stamatis and E. Ravera and M. Fragai and C. Luchinat and G. Parigi and A.G. Tzakos}, doi = {10.1016/bs.mie.2019.10.032}, isbn = {9780128191286}, journal = {Methods in Enzymology}, pages = {71-101}, title = {The NMR tube bioreactor}, volume = {633}, year = {2020}, } - Tomou, E. -M., M. V. Chatziathanasiadou, P. Chatzopoulou, A. G. Tzakos, and H. Skaltsa. “Nmr-based chemical profiling, isolation and evaluation of the cytotoxic potential of the diterpenoid siderol from cultivated sideritis euboea heldr.” Molecules 25 (2020). doi:10.3390/molecules25102382
[BibTeX] [Abstract]
Diterpenes are characteristic compounds from the genus Sideritis L., possessing an array of biological activities. Siderol is the main constituent of the ent-kaurene diterpenes in Sideritis species. In order to isolate the specific compound and evaluate for the first time its cytotoxic activity, we explored the dichloromethane extract of cultivated Sideritis euboea Heldr. To track the specific natural bioactive agent, we applied NMR spectroscopy to the crude plant extract, since NMR can serve as a powerful and rapid tool both to navigate the targeted isolation process of bioactive constituents, and to also reveal the identity of bioactive components. Along these lines, from the rapid 1D 1H NMR spectrum of the total crude plant extract, we were able to determine the characteristic proton NMR signals of siderol. Furthermore, with the same NMR spectrum, we were able to categorize several secondary metabolites into chemical groups as a control of the isolation process. Therefore, this non-polar extract was explored, for the first time, revealing eleven compounds—one fatty acid ester; 2-(p-hydroxyphenyl)ethylstearate (1), three phytosterols; β-sitosterol (2), stigmasterol (3), and campesterol (4); one triterpenoid; ursolic acid (5), four diterpenoids; siderol (6), eubol (7), eubotriol (8), 7-epicandicandiol (9) and two flavonoids; xanthomicrol (10) and penduletin (11). The main isolated constituent was siderol. The antiproliferative potential of siderol was evaluated, using the MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) assay, on three human cancer cell lines DLD1, HeLa, and A549, where the IC50 values were estimated at 26.4 ± 3.7, 44.7 ± 7.2, and 46.0 ± 4.9 µM, respectively. The most potent activity was recorded in the human colon cancer cell line DLD1, where siderol exhibited the lowest IC50. Our study unveiled the beneficial potential of siderol as a remarkable cytotoxic agent and the significant contribution of NMR spectroscopy towards the isolation and identification of this potent anticancer agent.
@article{Tomou2020, abstract = {Diterpenes are characteristic compounds from the genus Sideritis L., possessing an array of biological activities. Siderol is the main constituent of the ent-kaurene diterpenes in Sideritis species. In order to isolate the specific compound and evaluate for the first time its cytotoxic activity, we explored the dichloromethane extract of cultivated Sideritis euboea Heldr. To track the specific natural bioactive agent, we applied NMR spectroscopy to the crude plant extract, since NMR can serve as a powerful and rapid tool both to navigate the targeted isolation process of bioactive constituents, and to also reveal the identity of bioactive components. Along these lines, from the rapid 1D 1H NMR spectrum of the total crude plant extract, we were able to determine the characteristic proton NMR signals of siderol. Furthermore, with the same NMR spectrum, we were able to categorize several secondary metabolites into chemical groups as a control of the isolation process. Therefore, this non-polar extract was explored, for the first time, revealing eleven compounds—one fatty acid ester; 2-(p-hydroxyphenyl)ethylstearate (1), three phytosterols; β-sitosterol (2), stigmasterol (3), and campesterol (4); one triterpenoid; ursolic acid (5), four diterpenoids; siderol (6), eubol (7), eubotriol (8), 7-epicandicandiol (9) and two flavonoids; xanthomicrol (10) and penduletin (11). The main isolated constituent was siderol. The antiproliferative potential of siderol was evaluated, using the MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) assay, on three human cancer cell lines DLD1, HeLa, and A549, where the IC50 values were estimated at 26.4 ± 3.7, 44.7 ± 7.2, and 46.0 ± 4.9 µM, respectively. The most potent activity was recorded in the human colon cancer cell line DLD1, where siderol exhibited the lowest IC50. Our study unveiled the beneficial potential of siderol as a remarkable cytotoxic agent and the significant contribution of NMR spectroscopy towards the isolation and identification of this potent anticancer agent.}, author = {E.-M. Tomou and M.V. Chatziathanasiadou and P. Chatzopoulou and A.G. Tzakos and H. Skaltsa}, doi = {10.3390/molecules25102382}, issue = {10}, journal = {Molecules}, title = {NMR-based chemical profiling, isolation and evaluation of the cytotoxic potential of the diterpenoid siderol from cultivated sideritis euboea heldr}, volume = {25}, year = {2020}, } - Vrettos, E. I., I. E. Valverde, A. Mascarin, P. N. Pallier, L. Cerofolini, M. Fragai, G. Parigi, B. Hirmiz, N. Bekas, N. M. Grob, T. L. Mindt, and A. G. Tzakos. “Single peptide backbone surrogate mutations to regulate angiotensin gpcr subtype selectivity.” Chemistry – a european journal 26 (2020): 10690-10694. doi:10.1002/chem.202000924
[BibTeX] [Abstract]
Mutating the side-chains of amino acids in a peptide ligand, with unnatural amino acids, aiming to mitigate its short half-life is an established approach. However, it is hypothesized that mutating specific backbone peptide bonds with bioisosters can be exploited not only to enhance the proteolytic stability of parent peptides, but also to tune its receptor subtype selectivity. Towards this end, four [Y]6-Angiotensin II analogues are synthesized where amide bonds have been replaced by 1,4-disubstituted 1,2,3-triazole isosteres in four different backbone locations. All the analogues possessed enhanced stability in human plasma in comparison with the parent peptide, whereas only two of them achieved enhanced AT2R/AT1R subtype selectivity. This diversification has been studied through 2D NMR spectroscopy and unveiled a putative more structured microenvironment for the two selective ligands accompanied with increased number of NOE cross-peaks. The most potent analogue, compound 2, has been explored regarding its neurotrophic potential and resulted in an enhanced neurite growth with respect to the established agent C21.
@article{Vrettos2020, abstract = {Mutating the side-chains of amino acids in a peptide ligand, with unnatural amino acids, aiming to mitigate its short half-life is an established approach. However, it is hypothesized that mutating specific backbone peptide bonds with bioisosters can be exploited not only to enhance the proteolytic stability of parent peptides, but also to tune its receptor subtype selectivity. Towards this end, four [Y]6-Angiotensin II analogues are synthesized where amide bonds have been replaced by 1,4-disubstituted 1,2,3-triazole isosteres in four different backbone locations. All the analogues possessed enhanced stability in human plasma in comparison with the parent peptide, whereas only two of them achieved enhanced AT2R/AT1R subtype selectivity. This diversification has been studied through 2D NMR spectroscopy and unveiled a putative more structured microenvironment for the two selective ligands accompanied with increased number of NOE cross-peaks. The most potent analogue, compound 2, has been explored regarding its neurotrophic potential and resulted in an enhanced neurite growth with respect to the established agent C21.}, author = {E.I. Vrettos and I.E. Valverde and A. Mascarin and P.N. Pallier and L. Cerofolini and M. Fragai and G. Parigi and B. Hirmiz and N. Bekas and N.M. Grob and T.L. Mindt and A.G. Tzakos}, doi = {10.1002/chem.202000924}, issue = {47}, journal = {Chemistry - A European Journal}, pages = {10690-10694}, title = {Single Peptide Backbone Surrogate Mutations to Regulate Angiotensin GPCR Subtype Selectivity}, volume = {26}, year = {2020}, } - Papaemmanouil, C., M. V. Chatziathanasiadou, C. Chatzigiannis, E. Chontzopoulou, T. Mavromoustakos, S. G. Grdadolnik, and A. G. Tzakos. “Unveiling the interaction profile of rosmarinic acid and its bioactive substructures with serum albumin.” Journal of enzyme inhibition and medicinal chemistry 35 (2020): 786-804. doi:10.1080/14756366.2020.1740923
[BibTeX] [Abstract]
Rosmarinic acid, a phytochemical compound, bears diverse pharmaceutical profile. It is composed by two building blocks: caffeic acid and a salvianic acid unit. The interaction profile, responsible for the delivery of rosmarinic acid and its two substructure components by serum albumin remains unexplored. To unveil this, we established a novel low-cost and efficient method to produce salvianic acid from the parent compound. To probe the interaction profile of rosmarinic acid and its two substructure constituents with the different serum albumin binding sites we utilised fluorescence spectroscopy and competitive saturation transfer difference NMR experiments. These studies were complemented with transfer NOESY NMR experiments. The thermodynamics of the binding profile of rosmarinic acid and its substructures were addressed using isothermal titration calorimetry. In silico docking studies, driven by the experimental data, have been used to deliver further atomic details on the binding mode of rosmarinic acid and its structural components.
@article{Papaemmanouil2020, abstract = {Rosmarinic acid, a phytochemical compound, bears diverse pharmaceutical profile. It is composed by two building blocks: caffeic acid and a salvianic acid unit. The interaction profile, responsible for the delivery of rosmarinic acid and its two substructure components by serum albumin remains unexplored. To unveil this, we established a novel low-cost and efficient method to produce salvianic acid from the parent compound. To probe the interaction profile of rosmarinic acid and its two substructure constituents with the different serum albumin binding sites we utilised fluorescence spectroscopy and competitive saturation transfer difference NMR experiments. These studies were complemented with transfer NOESY NMR experiments. The thermodynamics of the binding profile of rosmarinic acid and its substructures were addressed using isothermal titration calorimetry. In silico docking studies, driven by the experimental data, have been used to deliver further atomic details on the binding mode of rosmarinic acid and its structural components.}, author = {C. Papaemmanouil and M.V. Chatziathanasiadou and C. Chatzigiannis and E. Chontzopoulou and T. Mavromoustakos and S.G. Grdadolnik and A.G. Tzakos}, doi = {10.1080/14756366.2020.1740923}, issue = {1}, journal = {Journal of Enzyme Inhibition and Medicinal Chemistry}, pages = {786-804}, title = {Unveiling the interaction profile of rosmarinic acid and its bioactive substructures with serum albumin}, volume = {35}, year = {2020}, } - Liapakis, G., V. Karageorgos, I. Andreadelis, G. G. Holz, E. Dermitzaki, G. G. Kordopati, E. Κ. Stylos, K. Spyridaki, S. Poulaki, D. Ntountaniotis, A. G. Tzakos, and T. Mavromoustakos. “Discovery of a stable tripeptide targeting the n-domain of crf1 receptor.” Amino acids 52 (2020): 1337-1351. doi:10.1007/s00726-020-02895-4
[BibTeX] [Abstract]
The corticotropin-releasing factor (CRF) and its CRF1 receptor (CRF1R) play a central role in the maintenance of homeostasis. Malfunctioning of the CRF/CRF1R unit is associated with several disorders, such as anxiety and depression. Non-peptide CRF1R-selective antagonists have been shown to exert anxiolytic and antidepressant effects on experimental animals. However, none of them is in clinical use today because of several side effects, thus demonstrating the need for the development of other more suitable CRF1R antagonists. In an effort to develop novel CRF1R antagonists we designed, synthesized and chemically characterized two tripeptide analogues of CRF, namely (R)-LMI and (S)-LMI, having their Leu either in R (or D) or in S (or L) configuration, respectively. Their design was based on the crystal structure of the N-extracellular domain (N-domain) of CRF1R/CRF complex, using a relevant array of computational methods. Experimental evaluation of the stability of synthetic peptides in human plasma has revealed that (R)-LMI is proteolytically more stable than (S)-LMI. Based on this finding, (R)-LMI was selected for pharmacological characterization. We have found that (R)-LMI is a CRF antagonist, inhibiting (1) the CRF-stimulated accumulation of cAMP in HEK 293 cells expressing the CRF1R, (2) the production of interleukins by adipocytes and (3) the proliferation rate of RAW 264.7 cells. (R)-LMI likely blocked agonist actions by interacting with the N-domain of CRF1R as suggested by data using a constitutively active chimera of CRF1R. We propose that (R)-LMI can be used as an optimal lead compound in the rational design of novel CRF antagonists.
@article{Liapakis2020, abstract = {The corticotropin-releasing factor (CRF) and its CRF1 receptor (CRF1R) play a central role in the maintenance of homeostasis. Malfunctioning of the CRF/CRF1R unit is associated with several disorders, such as anxiety and depression. Non-peptide CRF1R-selective antagonists have been shown to exert anxiolytic and antidepressant effects on experimental animals. However, none of them is in clinical use today because of several side effects, thus demonstrating the need for the development of other more suitable CRF1R antagonists. In an effort to develop novel CRF1R antagonists we designed, synthesized and chemically characterized two tripeptide analogues of CRF, namely (R)-LMI and (S)-LMI, having their Leu either in R (or D) or in S (or L) configuration, respectively. Their design was based on the crystal structure of the N-extracellular domain (N-domain) of CRF1R/CRF complex, using a relevant array of computational methods. Experimental evaluation of the stability of synthetic peptides in human plasma has revealed that (R)-LMI is proteolytically more stable than (S)-LMI. Based on this finding, (R)-LMI was selected for pharmacological characterization. We have found that (R)-LMI is a CRF antagonist, inhibiting (1) the CRF-stimulated accumulation of cAMP in HEK 293 cells expressing the CRF1R, (2) the production of interleukins by adipocytes and (3) the proliferation rate of RAW 264.7 cells. (R)-LMI likely blocked agonist actions by interacting with the N-domain of CRF1R as suggested by data using a constitutively active chimera of CRF1R. We propose that (R)-LMI can be used as an optimal lead compound in the rational design of novel CRF antagonists.}, author = {G. Liapakis and V. Karageorgos and I. Andreadelis and G.G. Holz and E. Dermitzaki and G.G. Kordopati and E.Κ. Stylos and K. Spyridaki and S. Poulaki and D. Ntountaniotis and A.G. Tzakos and T. Mavromoustakos}, doi = {10.1007/s00726-020-02895-4}, issue = {9}, journal = {Amino Acids}, pages = {1337-1351}, title = {Discovery of a stable tripeptide targeting the N-domain of CRF1 receptor}, volume = {52}, year = {2020}, } - Pérez-Sánchez, H., H. den-Haan, J. Peña-García, J. Lozano-Sánchez, Martínez M. E. Moreno, A. Sánchez-Pérez, A. Muñoz, P. Ruiz-Espinosa, A. S. P. Pereira, A. Katsikoudi, A. S. Carretero, and A. G. Tzakos. “Dia-db: a database and web server for the prediction of diabetes drugs.” Journal of chemical information and modeling 60 (2020): 4124-4130. doi:10.1021/acs.jcim.0c00107
[BibTeX] [Abstract]
The DIA-DB is a web server for the prediction of diabetes drugs that uses two different and complementary approaches: (a) comparison by shape similarity against a curated database of approved antidiabetic drugs and experimental small molecules and (b) inverse virtual screening of the input molecules chosen by the users against a set of therapeutic protein targets identified as key elements in diabetes. As a proof of concept DIA-DB was successfully applied in an integral workflow for the identification of the antidiabetic chemical profile in a complex crude plant extract. To this end, we conducted the extraction and LC-MS based chemical profile analysis of Sclerocarya birrea and subsequently utilized this data as input for our server. The server is open to all users, registration is not necessary, and a detailed report with the results of the prediction is sent to the user by email once calculations are completed. This is a novel public domain database and web server specific for diabetes drugs and can be accessed online through http://bio-hpc.eu/software/dia-db/.
@article{, abstract = {The DIA-DB is a web server for the prediction of diabetes drugs that uses two different and complementary approaches: (a) comparison by shape similarity against a curated database of approved antidiabetic drugs and experimental small molecules and (b) inverse virtual screening of the input molecules chosen by the users against a set of therapeutic protein targets identified as key elements in diabetes. As a proof of concept DIA-DB was successfully applied in an integral workflow for the identification of the antidiabetic chemical profile in a complex crude plant extract. To this end, we conducted the extraction and LC-MS based chemical profile analysis of Sclerocarya birrea and subsequently utilized this data as input for our server. The server is open to all users, registration is not necessary, and a detailed report with the results of the prediction is sent to the user by email once calculations are completed. This is a novel public domain database and web server specific for diabetes drugs and can be accessed online through http://bio-hpc.eu/software/dia-db/.}, author = {H. Pérez-Sánchez and H. den-Haan and J. Peña-García and J. Lozano-Sánchez and M.E. Martínez Moreno and A. Sánchez-Pérez and A. Muñoz and P. Ruiz-Espinosa and A.S.P. Pereira and A. Katsikoudi and A.S. Carretero and A.G. Tzakos}, doi = {10.1021/acs.jcim.0c00107}, issue = {9}, journal = {Journal of Chemical Information and Modeling}, pages = {4124-4130}, title = {DIA-DB: A database and web server for the prediction of diabetes drugs}, volume = {60}, year = {2020}, } - Chayrov, R., N. A. Parisis, M. V. Chatziathanasiadou, E. Vrontaki, K. Moschovou, G. Melagraki, H. Sbirkova-Dimitrova, B. Shivachev, M. Schmidtke, Y. Mitrev, A. G. Tzakos, and I. Stankova. “Synthetic analogues of aminoadamantane as influenza viral inhibitors—in vitro, in silico and qsar studies.” Molecules 25 (2020). doi:10.3390/molecules25173989
[BibTeX] [Abstract]
A series of nineteen amino acid analogues of amantadine (Amt) and rimantadine (Rim) were synthesized and their antiviral activity was evaluated against influenza virus A (H3N2). Among these analogues, the conjugation of rimantadine with glycine illustrated high antiviral activity combined with low cytotoxicity. Moreover, this compound presented a profoundly high stability after in vitro incubation in human plasma for 24 h. Its thermal stability was established using differential and gravimetric thermal analysis. The crystal structure of glycyl-rimantadine revealed that it crystallizes in the orthorhombic Pbca space group. The structure–activity relationship for this class of compounds was established, with CoMFA (Comparative Molecular Field Analysis) 3D-Quantitative Structure Activity Relationships (3D-QSAR) studies predicting the activities of synthetic molecules. In addition, molecular docking studies were conducted, revealing the structural requirements for the activity of the synthetic molecules.
@article{Chayrov2020, abstract = {A series of nineteen amino acid analogues of amantadine (Amt) and rimantadine (Rim) were synthesized and their antiviral activity was evaluated against influenza virus A (H3N2). Among these analogues, the conjugation of rimantadine with glycine illustrated high antiviral activity combined with low cytotoxicity. Moreover, this compound presented a profoundly high stability after in vitro incubation in human plasma for 24 h. Its thermal stability was established using differential and gravimetric thermal analysis. The crystal structure of glycyl-rimantadine revealed that it crystallizes in the orthorhombic Pbca space group. The structure–activity relationship for this class of compounds was established, with CoMFA (Comparative Molecular Field Analysis) 3D-Quantitative Structure Activity Relationships (3D-QSAR) studies predicting the activities of synthetic molecules. In addition, molecular docking studies were conducted, revealing the structural requirements for the activity of the synthetic molecules.}, author = {R. Chayrov and N.A. Parisis and M.V. Chatziathanasiadou and E. Vrontaki and K. Moschovou and G. Melagraki and H. Sbirkova-Dimitrova and B. Shivachev and M. Schmidtke and Y. Mitrev and A.G. Tzakos and I. Stankova}, doi = {10.3390/molecules25173989}, issue = {17}, journal = {Molecules}, title = {Synthetic Analogues of Aminoadamantane as Influenza Viral Inhibitors—In Vitro, in Silico and QSAR Studies}, volume = {25}, year = {2020}, } - Leonis, G., E. Christodoulou, D. Ntountaniotis, M. V. Chatziathanasiadou, T. Mavromoustakos, N. Naziris, M. Chountoulesi, C. Demetzos, G. Valsami, D. E. Damalas, V. Karageorgos, and G. Liapakis. “Antihypertensive activity and molecular interactions of irbesartan in complex with 2-hydroxypropyl-β-cyclodextrin.” Chemical biology and drug design 96 (2020): 668-683. doi:10.1111/cbdd.13664
[BibTeX] [Abstract]
Irbesartan (IRB) exerts beneficial effects either alone or in combination with other drugs on numerous diseases, such as cancer, diabetes, and hypertension. However, due to its high lipophilicity, IRB does not possess the optimum pharmacological efficiency. To circumvent this problem, a drug delivery system with 2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD) was explored. The 1:1 complex between IRB and 2-HP-β-CD was identified through ESI QTF HRMS. Dissolution studies showed a higher dissolution rate of the lyophilized IRB–2-HP-β-CD complex than the tablet containing IRB at pH = 1.2. DSC results revealed the differences of the thermal properties between the complex and various mixtures consisting of the two components, namely IRB and 2-HP-β-CD. Interestingly, depending on the way the mixture preparation was conducted, different association between the two components was observed. Molecular dynamics (MD) simulations predicted the favorable formation of the above complex and identified the dominant interactions between IRB and 2-HP-β-CD. In vitro pharmacological results verified that the inclusion complex not only preserves the binding affinity of IRB for AT1R receptor, but also it slightly increases it. As the complex formulation lacks the problems of the tablet, our approach is a promising new way to improve the efficiency of IRB.
@article{Leonis2020, abstract = {Irbesartan (IRB) exerts beneficial effects either alone or in combination with other drugs on numerous diseases, such as cancer, diabetes, and hypertension. However, due to its high lipophilicity, IRB does not possess the optimum pharmacological efficiency. To circumvent this problem, a drug delivery system with 2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD) was explored. The 1:1 complex between IRB and 2-HP-β-CD was identified through ESI QTF HRMS. Dissolution studies showed a higher dissolution rate of the lyophilized IRB–2-HP-β-CD complex than the tablet containing IRB at pH = 1.2. DSC results revealed the differences of the thermal properties between the complex and various mixtures consisting of the two components, namely IRB and 2-HP-β-CD. Interestingly, depending on the way the mixture preparation was conducted, different association between the two components was observed. Molecular dynamics (MD) simulations predicted the favorable formation of the above complex and identified the dominant interactions between IRB and 2-HP-β-CD. In vitro pharmacological results verified that the inclusion complex not only preserves the binding affinity of IRB for AT1R receptor, but also it slightly increases it. As the complex formulation lacks the problems of the tablet, our approach is a promising new way to improve the efficiency of IRB.}, author = {G. Leonis and E. Christodoulou and D. Ntountaniotis and M.V. Chatziathanasiadou and T. Mavromoustakos and N. Naziris and M. Chountoulesi and C. Demetzos and G. Valsami and D.E. Damalas and V. Karageorgos and G. Liapakis}, doi = {10.1111/cbdd.13664}, issue = {1}, journal = {Chemical Biology and Drug Design}, pages = {668-683}, title = {Antihypertensive activity and molecular interactions of irbesartan in complex with 2-hydroxypropyl-β-cyclodextrin}, volume = {96}, year = {2020}, } - Tsiailanis, A. D., A. Renziehausen, S. Kiriakidi, E. I. Vrettos, G. S. Markopoulos, N. Sayyad, B. Hirmiz, M. -I. Aguilar, Del M. P. Borgo, E. Kolettas, N. Syed, and A. G. Tzakos. “Enhancement of glioblastoma multiforme therapy through a novel quercetin-losartan hybrid.” Free radical biology and medicine 160 (2020): 391-402. doi:10.1016/j.freeradbiomed.2020.08.007
[BibTeX] [Abstract]
Glioblastoma multiforme (GBM) is the most common and aggressive primary malignant brain tumor. Maximal surgical resection followed by radiotherapy and concomitant chemotherapy with temozolomide remains the first-line therapy, prolonging the survival of patients by an average of only 2.5 months. There is therefore an urgent need for novel therapeutic strategies to improve clinical outcomes. Reactive oxygen species (ROS) are an important contributor to GBM development. Here, we describe the rational design and synthesis of a stable hybrid molecule tethering two ROS regulating moieties, with the aim of constructing a chemopreventive and anticancer chemical entity that retains the properties of the parent compounds. We utilized the selective AT1R antagonist losartan, leading to the inhibition of ROS levels, and the antioxidant flavonoid quercetin. In GBM cells, we show that this hybrid retains the binding potential of losartan to the AT1R through competition-binding experiments and simultaneously exhibits ROS inhibition and antioxidant capacity similar to native quercetin. In addition, we demonstrate that the hybrid is able to alter the cell cycle distribution of GBM cells, leading to cell cycle arrest and to the induction of cytotoxic effects. Last, the hybrid significantly and selectively reduces cancer cell proliferation and angiogenesis in primary GBM cultures with respect to the isolated parent components or their simple combination, further emphasizing the potential utility of the current hybridization approach in GBM.
@article{Tsiailanis2020, abstract = {Glioblastoma multiforme (GBM) is the most common and aggressive primary malignant brain tumor. Maximal surgical resection followed by radiotherapy and concomitant chemotherapy with temozolomide remains the first-line therapy, prolonging the survival of patients by an average of only 2.5 months. There is therefore an urgent need for novel therapeutic strategies to improve clinical outcomes. Reactive oxygen species (ROS) are an important contributor to GBM development. Here, we describe the rational design and synthesis of a stable hybrid molecule tethering two ROS regulating moieties, with the aim of constructing a chemopreventive and anticancer chemical entity that retains the properties of the parent compounds. We utilized the selective AT1R antagonist losartan, leading to the inhibition of ROS levels, and the antioxidant flavonoid quercetin. In GBM cells, we show that this hybrid retains the binding potential of losartan to the AT1R through competition-binding experiments and simultaneously exhibits ROS inhibition and antioxidant capacity similar to native quercetin. In addition, we demonstrate that the hybrid is able to alter the cell cycle distribution of GBM cells, leading to cell cycle arrest and to the induction of cytotoxic effects. Last, the hybrid significantly and selectively reduces cancer cell proliferation and angiogenesis in primary GBM cultures with respect to the isolated parent components or their simple combination, further emphasizing the potential utility of the current hybridization approach in GBM.}, author = {A.D. Tsiailanis and A. Renziehausen and S. Kiriakidi and E.I. Vrettos and G.S. Markopoulos and N. Sayyad and B. Hirmiz and M.-I. Aguilar and M.P. Del Borgo and E. Kolettas and N. Syed and A.G. Tzakos}, doi = {10.1016/j.freeradbiomed.2020.08.007}, journal = {Free Radical Biology and Medicine}, pages = {391-402}, title = {Enhancement of glioblastoma multiforme therapy through a novel Quercetin-Losartan hybrid}, volume = {160}, year = {2020}, } - Diamantis, D. A., M. Oblukova, M. V. Chatziathanasiadou, A. Gemenetzi, C. Papaemmanouil, P. S. Gerogianni, N. Syed, T. Crook, D. Galaris, Y. Deligiannakis, R. Sokolova, and A. G. Tzakos. “Bioinspired tailoring of fluorogenic thiol responsive antioxidant precursors to protect cells against h
2 o2 -induced dna damage.” Free radical biology and medicine 160 (2020): 540-551. doi:10.1016/j.freeradbiomed.2020.08.025
[BibTeX] [Abstract]
Natural antioxidants, like phenolic acids, possess a unique chemical space that can protect cellular components from oxidative stress. However, their polar carboxylic acid chemotype reduces full intracellular antioxidant potential due to limited diffusion through biological membranes. Here, we have designed and developed a new generation of hydrophobic turn-on fluorescent antioxidant precursors that upon penetration of the cell membrane, reveal a more polar and more potent antioxidant core and simultaneously become fluorescent allowing their intracellular tracking. Their activation is stimulated by polarity alteration by sensing intracellular signals and specifically biothiols. In our design, the carboxylic group of phenolic acids that originally restricts cell entrance is derivatized and conjugated through Copper (I)-catalyzed azide-alkyne cycloaddition (CuAAC) to a coumarin derivative that its fluorescence properties are quenched with a biothiol activatable element. This more hydrophobic precursor readily penetrates cell membrane and once inside the cell the antioxidant core is revealed upon sensing glutathione, its fluorescence is restored in a turn-on manner and the generation of a more polar character traps the molecule inside the cell. This turn-on fluorescent antioxidant precursor that can be applied to phenolic acids, was developed for rosmarinic acid and the conjugate was named as RCG. The selectivity and responsiveness of RCG towards the most abundant biothiols was monitored through a variety of biophysical techniques including UV–Vis, fluorescence and NMR spectroscopy. The electrochemical behavior and free radical scavenging capacity of the precursor RCG and the active compound (RC) was evaluated and compared with the parent compound (rosmarinic acid) through cyclic voltammetry and EPR spectroscopy, respectively. The stability of the newly synthesized bioactive conjugate RC was found significantly higher than the parent rosmarinic acid when exposed to oxygen. Cell uptake experiments were conducted and revealed the internalization of RCG. The degree of intracellular DNA protection offered by RCG and its active drug (RC) on exposure to H2O2 was also evaluated in Jurkat cells.
@article{Diamantis2020, abstract = {Natural antioxidants, like phenolic acids, possess a unique chemical space that can protect cellular components from oxidative stress. However, their polar carboxylic acid chemotype reduces full intracellular antioxidant potential due to limited diffusion through biological membranes. Here, we have designed and developed a new generation of hydrophobic turn-on fluorescent antioxidant precursors that upon penetration of the cell membrane, reveal a more polar and more potent antioxidant core and simultaneously become fluorescent allowing their intracellular tracking. Their activation is stimulated by polarity alteration by sensing intracellular signals and specifically biothiols. In our design, the carboxylic group of phenolic acids that originally restricts cell entrance is derivatized and conjugated through Copper (I)-catalyzed azide-alkyne cycloaddition (CuAAC) to a coumarin derivative that its fluorescence properties are quenched with a biothiol activatable element. This more hydrophobic precursor readily penetrates cell membrane and once inside the cell the antioxidant core is revealed upon sensing glutathione, its fluorescence is restored in a turn-on manner and the generation of a more polar character traps the molecule inside the cell. This turn-on fluorescent antioxidant precursor that can be applied to phenolic acids, was developed for rosmarinic acid and the conjugate was named as RCG. The selectivity and responsiveness of RCG towards the most abundant biothiols was monitored through a variety of biophysical techniques including UV–Vis, fluorescence and NMR spectroscopy. The electrochemical behavior and free radical scavenging capacity of the precursor RCG and the active compound (RC) was evaluated and compared with the parent compound (rosmarinic acid) through cyclic voltammetry and EPR spectroscopy, respectively. The stability of the newly synthesized bioactive conjugate RC was found significantly higher than the parent rosmarinic acid when exposed to oxygen. Cell uptake experiments were conducted and revealed the internalization of RCG. The degree of intracellular DNA protection offered by RCG and its active drug (RC) on exposure to H2O2 was also evaluated in Jurkat cells.}, author = {D.A. Diamantis and M. Oblukova and M.V. Chatziathanasiadou and A. Gemenetzi and C. Papaemmanouil and P.S. Gerogianni and N. Syed and T. Crook and D. Galaris and Y. Deligiannakis and R. Sokolova and A.G. Tzakos}, doi = {10.1016/j.freeradbiomed.2020.08.025}, journal = {Free Radical Biology and Medicine}, pages = {540-551}, title = {Bioinspired tailoring of fluorogenic thiol responsive antioxidant precursors to protect cells against H2 O2 -induced DNA damage}, volume = {160}, year = {2020}, }
2019
- Chatzigiannis, C. and A. Tzakos. “A theragnostic device with photo regulated drug dosing and cancer microenvironment sensing character.” Review of clinical pharmacology and pharmacokinetics, international edition 33 (2019): 98.
[BibTeX]@article{Chatzigiannis2019, author = {C. Chatzigiannis and A. Tzakos}, issue = {3}, journal = {Review of Clinical Pharmacology and Pharmacokinetics, International Edition}, pages = {98}, title = {A theragnostic device with photo regulated drug dosing and cancer microenvironment sensing character}, volume = {33}, year = {2019}, } - Vrettos, E. I. and A. G. Tzakos. “Design and synthesis of peptide-drug conjugates selectively targeting cancer cells.” Review of clinical pharmacology and pharmacokinetics, international edition 33 (2019): 77.
[BibTeX]@article{Vrettos2019, author = {E.I. Vrettos and A.G. Tzakos}, issue = {3}, journal = {Review of Clinical Pharmacology and Pharmacokinetics, International Edition}, pages = {77}, title = {Design and synthesis of peptide-drug conjugates selectively targeting cancer cells}, volume = {33}, year = {2019}, } - Magafa, V., M. -T. Matsoukas, V. Karageorgos, E. Dermitzaki, R. Exarchakou, E. Κ. Stylos, M. Pardalos, A. N. Margioris, G. Varvounis, A. G. Tzakos, G. A. Spyroulias, and G. Liapakis. “Novel stable analogues of the neurotensin c-terminal hexapeptide containing unnatural amino acids.” Amino acids 51 (2019): 1009-1022. doi:10.1007/s00726-019-02741-2
[BibTeX] [Abstract]
Neurotensin (NT) (pGlu–Leu–Tyr–Glu–Asn–Lys–Pro–Arg–Arg–Pro–Tyr–Ile–Leu) exerts a dual function as a neurotransmitter/neuromodulator in the central nervous system and as a hormone/cellular mediator in periphery. This dual function of NT establishes a connection between brain and peripheral tissues that renders this peptide a central player in energy homeostasis. Many biological actions of NT are mediated through its interaction with three types of NT receptors (NTS receptors). Despite its role in energy homeostasis, NT has a short half-life that hampers further determination of the biological actions of this peptide and its receptors in brain and periphery. The short half-life of NT is due to the proteolytic degradation of its C-terminal side by several endopeptidases. Therefore, it is important to synthesize NT analogues with resistant bonds against metabolic deactivation. Based on these findings, we herein report the synthesis of ten linear, two cyclic and two dimeric analogues of NT with modifications in its structure that improve their metabolic stability, while retaining the ability to bind to NTS receptors. Modifications at position 11 (introduction of d-Tyrosine (OEthyl) [d-Tyr(Et)] or d-1-naphtylalanine [d-1-Nal] were combined with introduction of a l-Lysine or a d-Arginine at positions 8 or 9, and 1-[2-(aminophenyl)-2-oxoethyl]-1H-pyrrole-2-carboxylic acid (AOPC) at positions 7 or 8, resulting in compounds NT4-NT21. AOPC is an unnatural amino acid with promise in applications as a building block for the synthesis of peptidomimetic compounds. To biologically evaluate these analogues, we determined their plasma stability and their binding affinities to type 1 NT receptor (NTS1), endogenously expressed in HT-29 cells, Among the fourteen NT analogues, compounds, NT5, NT6, and NT8, which have d-Tyr(Et) at position 11, bound to NTS1 in a dose–response manner and with relatively high affinity but still lower than that of the natural peptide. Despite their lower binding affinities compared to NT, the NT5, NT6, and NT8 exhibited a remarkably higher stability, as a result of their chemistry, which provides protection from enzymatic activity. These results will set the basis for the rational design of novel NT molecules with improved pharmacological properties and enhanced enzymatic stability.
@article{Magafa2019, abstract = {Neurotensin (NT) (pGlu–Leu–Tyr–Glu–Asn–Lys–Pro–Arg–Arg–Pro–Tyr–Ile–Leu) exerts a dual function as a neurotransmitter/neuromodulator in the central nervous system and as a hormone/cellular mediator in periphery. This dual function of NT establishes a connection between brain and peripheral tissues that renders this peptide a central player in energy homeostasis. Many biological actions of NT are mediated through its interaction with three types of NT receptors (NTS receptors). Despite its role in energy homeostasis, NT has a short half-life that hampers further determination of the biological actions of this peptide and its receptors in brain and periphery. The short half-life of NT is due to the proteolytic degradation of its C-terminal side by several endopeptidases. Therefore, it is important to synthesize NT analogues with resistant bonds against metabolic deactivation. Based on these findings, we herein report the synthesis of ten linear, two cyclic and two dimeric analogues of NT with modifications in its structure that improve their metabolic stability, while retaining the ability to bind to NTS receptors. Modifications at position 11 (introduction of d-Tyrosine (OEthyl) [d-Tyr(Et)] or d-1-naphtylalanine [d-1-Nal] were combined with introduction of a l-Lysine or a d-Arginine at positions 8 or 9, and 1-[2-(aminophenyl)-2-oxoethyl]-1H-pyrrole-2-carboxylic acid (AOPC) at positions 7 or 8, resulting in compounds NT4-NT21. AOPC is an unnatural amino acid with promise in applications as a building block for the synthesis of peptidomimetic compounds. To biologically evaluate these analogues, we determined their plasma stability and their binding affinities to type 1 NT receptor (NTS1), endogenously expressed in HT-29 cells, Among the fourteen NT analogues, compounds, NT5, NT6, and NT8, which have d-Tyr(Et) at position 11, bound to NTS1 in a dose–response manner and with relatively high affinity but still lower than that of the natural peptide. Despite their lower binding affinities compared to NT, the NT5, NT6, and NT8 exhibited a remarkably higher stability, as a result of their chemistry, which provides protection from enzymatic activity. These results will set the basis for the rational design of novel NT molecules with improved pharmacological properties and enhanced enzymatic stability.}, author = {V. Magafa and M.-T. Matsoukas and V. Karageorgos and E. Dermitzaki and R. Exarchakou and E.Κ. Stylos and M. Pardalos and A.N. Margioris and G. Varvounis and A.G. Tzakos and G.A. Spyroulias and G. Liapakis}, doi = {10.1007/s00726-019-02741-2}, issue = {7}, journal = {Amino Acids}, pages = {1009-1022}, title = {Novel stable analogues of the neurotensin C-terminal hexapeptide containing unnatural amino acids}, volume = {51}, year = {2019}, } - Mubarak, El M. A., E. K. Stylos, M. V. Chatziathanasiadou, C. Danika, G. A. Alexiou, P. Tsekeris, A. Renziehausen, T. Crook, N. Syed, G. B. Sivolapenko, G. B. Sivolapenko, and A. G. Tzakos. “Development and validation of simple step protein precipitation uhplc-ms/ms methods for quantitation of temozolomide in cancer patient plasma samples.” Journal of pharmaceutical and biomedical analysis 162 (2019): 164-170. doi:10.1016/j.jpba.2018.09.019
[BibTeX] [Abstract]
Temozolomide (TEMODAL™) (TMZ) is an antineoplastic agent that is primarily used for the treatment of glioblastoma and anaplastic gliomas, two aggressive forms of brain cancer. Due to the poor prognosis of brain tumour patients, there is an increasing body of research into improving the stability and delivery of TMZ past the blood brain barrier using carrier molecules. These require accurate determination of TMZ levels for biodistribution and pharmacokinetic evaluation. Unfortunately, current methodologies for the determination of TMZ in human plasma suffer from low reproducibility, recovery, sensitivity or cost ineffective procedures associated with extensive sample cleaning. To surpass these disadvantages, we developed two bioanalytical methods with high sensitivity and excellent recovery for the determination of TMZ in human plasma at minimum cost. Liquid chromatography coupled with tandem mass spectrometry (LC–MS/MS) was used and both methods were validated under US Food and Drug Administration (FDA) and the European Medicines Agency (EMEA) guidelines. The two methods had minor differences in the sample pre-treatment and each method was developed and applied in separate laboratories. Theophylline was selected as internal standard (IS). Calibration curves were linear over the range of 10–500 ng/mL with extraction recovery ranging from 77.3 to 97.3% while all validation parameters met the acceptance criteria and proved the methods’ reliability. The validated methods were successfully applied to plasma samples donated from cancer patient following treatment with temozolomide.
@article{, abstract = {Temozolomide (TEMODAL™) (TMZ) is an antineoplastic agent that is primarily used for the treatment of glioblastoma and anaplastic gliomas, two aggressive forms of brain cancer. Due to the poor prognosis of brain tumour patients, there is an increasing body of research into improving the stability and delivery of TMZ past the blood brain barrier using carrier molecules. These require accurate determination of TMZ levels for biodistribution and pharmacokinetic evaluation. Unfortunately, current methodologies for the determination of TMZ in human plasma suffer from low reproducibility, recovery, sensitivity or cost ineffective procedures associated with extensive sample cleaning. To surpass these disadvantages, we developed two bioanalytical methods with high sensitivity and excellent recovery for the determination of TMZ in human plasma at minimum cost. Liquid chromatography coupled with tandem mass spectrometry (LC–MS/MS) was used and both methods were validated under US Food and Drug Administration (FDA) and the European Medicines Agency (EMEA) guidelines. The two methods had minor differences in the sample pre-treatment and each method was developed and applied in separate laboratories. Theophylline was selected as internal standard (IS). Calibration curves were linear over the range of 10–500 ng/mL with extraction recovery ranging from 77.3 to 97.3% while all validation parameters met the acceptance criteria and proved the methods’ reliability. The validated methods were successfully applied to plasma samples donated from cancer patient following treatment with temozolomide.}, author = {M.A. El Mubarak and E.K. Stylos and M.V. Chatziathanasiadou and C. Danika and G.A. Alexiou and P. Tsekeris and A. Renziehausen and T. Crook and N. Syed and G.B. Sivolapenko and G.B. Sivolapenko and A.G. Tzakos}, doi = {10.1016/j.jpba.2018.09.019}, journal = {Journal of Pharmaceutical and Biomedical Analysis}, pages = {164-170}, title = {Development and validation of simple step protein precipitation UHPLC-MS/MS methods for quantitation of temozolomide in cancer patient plasma samples}, volume = {162}, year = {2019}, } - Renziehausen, A., H. Wang, B. Rao, L. Weir, C. L. Nigro, L. Lattanzio, M. Merlano, A. Vega-Rioja, Carmen M. del Fernandez-Carranco, N. Hajji, N. Syed, and T. Crook. “The renin angiotensin system (ras) mediates bifunctional growth regulation in melanoma and is a novel target for therapeutic intervention.” Oncogene 38 (2019): 2320-2336. doi:10.1038/s41388-018-0563-y
[BibTeX] [Abstract]
Despite emergence of new systemic therapies, metastatic melanoma remains a challenging and often fatal form of skin cancer. The renin–angiotensin system (RAS) is a major physiological regulatory pathway controlling salt–water equilibrium, intravascular volume and blood pressure. Biological effects of the RAS are mediated by the vasoactive hormone angiotensin II (AngII) via two receptor subtypes, AT1R (encoded by AGTR1) and AT2R (encoded by AGTR2). We report decreasing expression and increasing CpG island methylation of AGTR1 in metastatic versus primary melanoma and detection in serum of methylated genomic DNA from the AGTR1 CpG island in metastatic melanoma implying that AGTR1 encodes a tumour suppressor function in melanoma. Consistent with this hypothesis, antagonism of AT1R using losartan or shRNA-mediated knockdown in melanoma cell lines expressing AGTR1 resulted in acquisition of the ability to proliferate in serum-free conditions. Conversely, ectopic expression of AGTR1 in cell lines lacking endogenous expression inhibits proliferation irrespective of the presence of AngII implying a ligand-independent suppressor function for AT1R. Treatment of melanoma cell lines expressing endogenous AT2R with either AngII or the AT2R-selective agonist Y6AII induces proliferation in serum-free conditions whereas the AT2R-specific antagonists PD123319 and EMA401 inhibit melanoma growth and angiogenesis and potentiate inhibitors of BRAF and MEK in cells with BRAF V600 mutations. Our results demonstrate that the RAS has both oncogenic and tumour suppressor functions in melanoma. Pharmacological inhibition of AT2R may provide therapeutic opportunities in melanomas expressing this receptor and AGTR1 CpG island methylation in serum may serve as a novel biomarker of metastatic melanoma.
@article{Renziehausen2019, abstract = {Despite emergence of new systemic therapies, metastatic melanoma remains a challenging and often fatal form of skin cancer. The renin–angiotensin system (RAS) is a major physiological regulatory pathway controlling salt–water equilibrium, intravascular volume and blood pressure. Biological effects of the RAS are mediated by the vasoactive hormone angiotensin II (AngII) via two receptor subtypes, AT1R (encoded by AGTR1) and AT2R (encoded by AGTR2). We report decreasing expression and increasing CpG island methylation of AGTR1 in metastatic versus primary melanoma and detection in serum of methylated genomic DNA from the AGTR1 CpG island in metastatic melanoma implying that AGTR1 encodes a tumour suppressor function in melanoma. Consistent with this hypothesis, antagonism of AT1R using losartan or shRNA-mediated knockdown in melanoma cell lines expressing AGTR1 resulted in acquisition of the ability to proliferate in serum-free conditions. Conversely, ectopic expression of AGTR1 in cell lines lacking endogenous expression inhibits proliferation irrespective of the presence of AngII implying a ligand-independent suppressor function for AT1R. Treatment of melanoma cell lines expressing endogenous AT2R with either AngII or the AT2R-selective agonist Y6AII induces proliferation in serum-free conditions whereas the AT2R-specific antagonists PD123319 and EMA401 inhibit melanoma growth and angiogenesis and potentiate inhibitors of BRAF and MEK in cells with BRAF V600 mutations. Our results demonstrate that the RAS has both oncogenic and tumour suppressor functions in melanoma. Pharmacological inhibition of AT2R may provide therapeutic opportunities in melanomas expressing this receptor and AGTR1 CpG island methylation in serum may serve as a novel biomarker of metastatic melanoma.}, author = {A. Renziehausen and H. Wang and B. Rao and L. Weir and C.L. Nigro and L. Lattanzio and M. Merlano and A. Vega-Rioja and M. del Carmen Fernandez-Carranco and N. Hajji and N. Syed and T. Crook}, doi = {10.1038/s41388-018-0563-y}, issue = {13}, journal = {Oncogene}, pages = {2320-2336}, title = {The renin angiotensin system (RAS) mediates bifunctional growth regulation in melanoma and is a novel target for therapeutic intervention}, volume = {38}, year = {2019}, } - Heřmánková, E., M. Zatloukalová, M. Biler, R. Sokolová, M. Bancířová, A. G. Tzakos, V. Křen, M. Kuzma, P. Trouillas, and J. Vacek. “Redox properties of individual quercetin moieties.” Free radical biology and medicine 143 (2019): 240-251. doi:10.1016/j.freeradbiomed.2019.08.001
[BibTeX] [Abstract]
Quercetin is one of the most prominent and widely studied flavonoids. Its oxidation has been previously investigated only indirectly by comparative analyses of structurally analogous compounds, e.g. dihydroquercetin (taxifolin). To provide direct evidence about the mechanism of quercetin oxidation, we employed selective alkylation procedures for the step-by-step blocking of individual redox active sites, i.e. the catechol, resorcinol and enol C-3 hydroxyls, as represented by newly prepared quercetin derivatives 1–3. Based on the structure-activity relationship (SAR), electrochemical, and computational (density functional theory) studies, we can clearly confirm that quercetin is oxidized in the following steps: the catechol moiety is oxidized first, forming the benzofuranone derivative via intramolecular rearrangement mechanism; therefore the quercetin C-3 hydroxy group cannot be involved in further oxidation reactions or other biochemical processes. The benzofuranone is oxidized subsequently, followed by oxidation of the resorcinol motif to complete the electrochemical cascade of reactions. Derivatization of individual quercetin hydroxyls has a significant effect on its redox behavior, and, importantly, on its antiradical and stability properties, as shown in DPPH/ABTS radical scavenging assays and UV–Vis spectrophotometry, respectively. The SAR data reported here are instrumental for future studies on the oxidation of biologically or technologically important flavonoids and other polyphenols or polyhydroxy substituted aromatics. This is the first complete and direct study mapping redox properties of individual moieties in quercetin structure.
@article{, abstract = {Quercetin is one of the most prominent and widely studied flavonoids. Its oxidation has been previously investigated only indirectly by comparative analyses of structurally analogous compounds, e.g. dihydroquercetin (taxifolin). To provide direct evidence about the mechanism of quercetin oxidation, we employed selective alkylation procedures for the step-by-step blocking of individual redox active sites, i.e. the catechol, resorcinol and enol C-3 hydroxyls, as represented by newly prepared quercetin derivatives 1–3. Based on the structure-activity relationship (SAR), electrochemical, and computational (density functional theory) studies, we can clearly confirm that quercetin is oxidized in the following steps: the catechol moiety is oxidized first, forming the benzofuranone derivative via intramolecular rearrangement mechanism; therefore the quercetin C-3 hydroxy group cannot be involved in further oxidation reactions or other biochemical processes. The benzofuranone is oxidized subsequently, followed by oxidation of the resorcinol motif to complete the electrochemical cascade of reactions. Derivatization of individual quercetin hydroxyls has a significant effect on its redox behavior, and, importantly, on its antiradical and stability properties, as shown in DPPH/ABTS radical scavenging assays and UV–Vis spectrophotometry, respectively. The SAR data reported here are instrumental for future studies on the oxidation of biologically or technologically important flavonoids and other polyphenols or polyhydroxy substituted aromatics. This is the first complete and direct study mapping redox properties of individual moieties in quercetin structure.}, author = {E. Heřmánková and M. Zatloukalová and M. Biler and R. Sokolová and M. Bancířová and A.G. Tzakos and V. Křen and M. Kuzma and P. Trouillas and J. Vacek}, doi = {10.1016/j.freeradbiomed.2019.08.001}, journal = {Free Radical Biology and Medicine}, pages = {240-251}, title = {Redox properties of individual quercetin moieties}, volume = {143}, year = {2019}, } - Kostagianni, A., A. Tsiailanis, E. Giannopoulou, S. Pappas, K. Siatis, A. Lampropoulou, M. Sakka, A. Kougioumtzi, E. Mpriasoulis, C. Kalofonos, C. Kalofonos, and A. Tzakos. “Synthesis of cell penetrating peptides for targeting tumors.” Review of clinical pharmacology and pharmacokinetics, international edition 33 (2019): 82.
[BibTeX]@article{Kostagianni2019, author = {A. Kostagianni and A. Tsiailanis and E. Giannopoulou and S. Pappas and K. Siatis and A. Lampropoulou and M. Sakka and A. Kougioumtzi and E. Mpriasoulis and C. Kalofonos and C. Kalofonos and A. Tzakos}, issue = {3}, journal = {Review of Clinical Pharmacology and Pharmacokinetics, International Edition}, pages = {82}, title = {Synthesis of cell penetrating peptides for targeting tumors}, volume = {33}, year = {2019}, } - Chatziathanasiadou, M. V., E. K. Stylos, E. Giannopoulou, M. -H. Spyridaki, E. Briasoulis, H. P. Kalofonos, T. Crook, N. Syed, G. B. Sivolapenko, and A. G. Tzakos. “Development of a validated lc-ms/ms method for the in vitro and in vivo quantitation of sunitinib in glioblastoma cells and cancer patients.” Journal of pharmaceutical and biomedical analysis 164 (2019): 690-697. doi:10.1016/j.jpba.2018.11.030
[BibTeX] [Abstract]
Sunitinib is a multi-targeted tyrosine kinase inhibitor approved for the treatment of renal cell carcinoma and imatinib-resistant gastrointestinal stromal tumor and is currently being investigated against other forms of malignant tumors. Recently great interest has emerged for the application of sunitinib to glioblastoma treatment. In order to have a method with broad applicability it will be of importance to have access to a method that could be applied both in human plasma and cell uptake studies. No method has been reported thus far for the estimation of sunitinib uptake in glioma cells. We therefore set out to develop a method that could be applied for quantifying sunitinib in human plasma and in cell uptake studies. The method was validated and accredited according to ISO 17025:2005 guideline in human plasma and successfully applied to cancer patient plasma. Also, the method was effectively recruited to establish a protocol for the evaluation of sunitinib accumulation into M095K glioma cells. This method could significantly contribute to developmental phases in repurposing this drug in different cancer types.
@article{Chatziathanasiadou2019, abstract = {Sunitinib is a multi-targeted tyrosine kinase inhibitor approved for the treatment of renal cell carcinoma and imatinib-resistant gastrointestinal stromal tumor and is currently being investigated against other forms of malignant tumors. Recently great interest has emerged for the application of sunitinib to glioblastoma treatment. In order to have a method with broad applicability it will be of importance to have access to a method that could be applied both in human plasma and cell uptake studies. No method has been reported thus far for the estimation of sunitinib uptake in glioma cells. We therefore set out to develop a method that could be applied for quantifying sunitinib in human plasma and in cell uptake studies. The method was validated and accredited according to ISO 17025:2005 guideline in human plasma and successfully applied to cancer patient plasma. Also, the method was effectively recruited to establish a protocol for the evaluation of sunitinib accumulation into M095K glioma cells. This method could significantly contribute to developmental phases in repurposing this drug in different cancer types.}, author = {M.V. Chatziathanasiadou and E.K. Stylos and E. Giannopoulou and M.-H. Spyridaki and E. Briasoulis and H.P. Kalofonos and T. Crook and N. Syed and G.B. Sivolapenko and A.G. Tzakos}, doi = {10.1016/j.jpba.2018.11.030}, journal = {Journal of Pharmaceutical and Biomedical Analysis}, pages = {690-697}, title = {Development of a validated LC-MS/MS method for the in vitro and in vivo quantitation of sunitinib in glioblastoma cells and cancer patients}, volume = {164}, year = {2019}, } - Pavlos, D., T. Mavromoustakos, and A. Tzakos. “Improving the pharmacological profile of natural products using cyclodextrins as encapsulation agents.” Pharmakeftiki 31 (2019): 179-191.
[BibTeX] [Abstract]
Lipophilic compounds such as many bioactive compounds do not present their optimum pharmacological profile because they mainly exhibit metabolic instability and toxicity, they lack selectivity and suffer from low bioavailability. Their complexes with cyclodextrins improves these disadvantages and transform them to improved molecules of pharmacological interest with good prospects for human health. In this review paper, are presented examples of representative molecules, natural products, whose properties were improved when hosted by various cyclodextrins.
@article{Pavlos2019, abstract = {Lipophilic compounds such as many bioactive compounds do not present their optimum pharmacological profile because they mainly exhibit metabolic instability and toxicity, they lack selectivity and suffer from low bioavailability. Their complexes with cyclodextrins improves these disadvantages and transform them to improved molecules of pharmacological interest with good prospects for human health. In this review paper, are presented examples of representative molecules, natural products, whose properties were improved when hosted by various cyclodextrins.}, author = {D. Pavlos and T. Mavromoustakos and A. Tzakos}, issue = {4}, journal = {Pharmakeftiki}, pages = {179-191}, title = {Improving the pharmacological profile of natural products using cyclodextrins as encapsulation agents}, volume = {31}, year = {2019}, } - Sayyad, N., E. I. Vrettos, T. Karampelas, C. M. Chatzigiannis, K. Spyridaki, G. Liapakis, C. Tamvakopoulos, and A. G. Tzakos. “Development of bioactive gemcitabine-d-lys6-gnrh prodrugs with linker-controllable drug release rate and enhanced biopharmaceutical profile.” European journal of medicinal chemistry 166 (2019): 256-266. doi:10.1016/j.ejmech.2019.01.041
[BibTeX] [Abstract]
Peptide-drug conjugates have emerged as a potent approach to enhance the targeting and pharmacokinetic profiles of drugs. However, the impact of the linker unit has not been explored/exploited in depth. Gemcitabine (dFdC) is an anticancer agent used against a variety of solid tumours. Despite its potency, gemcitabine suffers mostly due to its unspecific toxicity, lack of targeting and rapid metabolic inactivation. To minimize these limitations and enable its targeting to tumours overexpressing the GnRH receptor, we examined the peptide-drug conjugation approach. Our design hypothesis was driven by the impact that the linker unit could have on the peptide-drug conjugate efficacy. Along these lines, in order to exploit the potential to manipulate the potency of gemcitabine through altering the linker unit we constructed three different novel peptide-drug conjugates assembled of gemcitabine, the tumour-homing peptide D-Lys6-GnRH and modified linker building blocks. Specifically, the linker was sculpted to either allow slow drug release (utilizing carbamate bond) or rapid disassociation (using amide and ester bonds). Notably, the new analogues possessed up to 95.5-fold enhanced binding affinity for the GnRH receptor (GnRH-R) compared to the natural peptide ligand D-Lys6-GnRH. Additionally, their in vitro cytotoxicity was evaluated in four different cancer cell lines. Their cellular uptake, release of gemcitabine and inactivation of gemcitabine to its inactive metabolite (dFdU) was explored in a representative cell line. In vitro stability and the consequent drug release were evaluated in cell culture medium and human plasma. In vivo pharmacokinetic studies were performed in mice, summarizing the relative stability of the three conjugates and the released levels of gemcitabine in comparison with dFdU. These studies suggest that the fine tuning of the linkage within a peptide-drug conjugate affects the drug release rate and its overall pharmaceutical profile. This could eventually emerge as an intriguing medicinal chemistry approach to optimize bio-profiles of prodrugs.
@article{Sayyad2019, abstract = {Peptide-drug conjugates have emerged as a potent approach to enhance the targeting and pharmacokinetic profiles of drugs. However, the impact of the linker unit has not been explored/exploited in depth. Gemcitabine (dFdC) is an anticancer agent used against a variety of solid tumours. Despite its potency, gemcitabine suffers mostly due to its unspecific toxicity, lack of targeting and rapid metabolic inactivation. To minimize these limitations and enable its targeting to tumours overexpressing the GnRH receptor, we examined the peptide-drug conjugation approach. Our design hypothesis was driven by the impact that the linker unit could have on the peptide-drug conjugate efficacy. Along these lines, in order to exploit the potential to manipulate the potency of gemcitabine through altering the linker unit we constructed three different novel peptide-drug conjugates assembled of gemcitabine, the tumour-homing peptide D-Lys6-GnRH and modified linker building blocks. Specifically, the linker was sculpted to either allow slow drug release (utilizing carbamate bond) or rapid disassociation (using amide and ester bonds). Notably, the new analogues possessed up to 95.5-fold enhanced binding affinity for the GnRH receptor (GnRH-R) compared to the natural peptide ligand D-Lys6-GnRH. Additionally, their in vitro cytotoxicity was evaluated in four different cancer cell lines. Their cellular uptake, release of gemcitabine and inactivation of gemcitabine to its inactive metabolite (dFdU) was explored in a representative cell line. In vitro stability and the consequent drug release were evaluated in cell culture medium and human plasma. In vivo pharmacokinetic studies were performed in mice, summarizing the relative stability of the three conjugates and the released levels of gemcitabine in comparison with dFdU. These studies suggest that the fine tuning of the linkage within a peptide-drug conjugate affects the drug release rate and its overall pharmaceutical profile. This could eventually emerge as an intriguing medicinal chemistry approach to optimize bio-profiles of prodrugs.}, author = {N. Sayyad and E.I. Vrettos and T. Karampelas and C.M. Chatzigiannis and K. Spyridaki and G. Liapakis and C. Tamvakopoulos and A.G. Tzakos}, doi = {10.1016/j.ejmech.2019.01.041}, journal = {European Journal of Medicinal Chemistry}, pages = {256-266}, title = {Development of bioactive gemcitabine-D-Lys6-GnRH prodrugs with linker-controllable drug release rate and enhanced biopharmaceutical profile}, volume = {166}, year = {2019}, } - Mihailidou, A. S., A. G. Tzakos, and A. W. Ashton. Non-genomic effects of aldosterone. Vol. 109. 2019. doi:10.1016/bs.vh.2018.12.001
[BibTeX] [Abstract]
Encouraging changes in the steroid hormone receptor field from initially questioning the role of non-genomic actions of steroid hormones to acceptance of the concept that the acute, membrane-centric actions are linked and/or regulate the nuclear actions. The focus of this chapter is how the non-genomic effects are linked to the longer lasting, genomic actions of aldosterone. By non-genomic we refer to the rapid actions that occur within minutes do not require transcription or translation and occur in both classical MR target organs (kidney and colon) and non-epithelial tissues (blood vessels, heart, and adipose). The mechanism of rapid non-genomic actions of aldosterone varies between tissues. As a result, this chapter is viewed through the lens of how the non-genomic and genomic actions of aldosterone are linked in cardiovascular disease. Specifically, regulation of sodium flux in the myocardium has an important role in pathogenesis of cardiac arrhythmia. Since there are now recognized gender differences in cardiovascular disease, we also include preliminary studies to investigate the interaction of sex steroid hormones with the ligand binding pocket of the mineralocorticoid receptor. Overall, we aim to showcase how the non-genomic effects of aldosterone potentially modulate the genomic effects and represent additional targets for intervention.
@book{Mihailidou2019, abstract = {Encouraging changes in the steroid hormone receptor field from initially questioning the role of non-genomic actions of steroid hormones to acceptance of the concept that the acute, membrane-centric actions are linked and/or regulate the nuclear actions. The focus of this chapter is how the non-genomic effects are linked to the longer lasting, genomic actions of aldosterone. By non-genomic we refer to the rapid actions that occur within minutes do not require transcription or translation and occur in both classical MR target organs (kidney and colon) and non-epithelial tissues (blood vessels, heart, and adipose). The mechanism of rapid non-genomic actions of aldosterone varies between tissues. As a result, this chapter is viewed through the lens of how the non-genomic and genomic actions of aldosterone are linked in cardiovascular disease. Specifically, regulation of sodium flux in the myocardium has an important role in pathogenesis of cardiac arrhythmia. Since there are now recognized gender differences in cardiovascular disease, we also include preliminary studies to investigate the interaction of sex steroid hormones with the ligand binding pocket of the mineralocorticoid receptor. Overall, we aim to showcase how the non-genomic effects of aldosterone potentially modulate the genomic effects and represent additional targets for intervention.}, author = {A.S. Mihailidou and A.G. Tzakos and A.W. Ashton}, doi = {10.1016/bs.vh.2018.12.001}, isbn = {9780128177822}, journal = {Vitamins and Hormones}, pages = {133-149}, title = {Non-Genomic Effects of Aldosterone}, volume = {109}, year = {2019}, } - Ntountaniotis, D., I. Andreadelis, T. F. Kellici, V. Karageorgos, G. Leonis, E. Christodoulou, S. Kiriakidi, J. Becker-Baldus, E. K. Stylos, M. V. Chatziathanasiadou, G. Liapakis, and T. Mavromoustakos. “Host-guest interactions between candesartan and its prodrug candesartan cilexetil in complex with 2-hydroxypropyl-β-cyclodextrin: on the biological potency for angiotensin ii antagonism.” Molecular pharmaceutics 16 (2019): 1255-1271. doi:10.1021/acs.molpharmaceut.8b01212
[BibTeX] [Abstract]
Renin-angiotensin aldosterone system inhibitors are for a long time extensively used for the treatment of cardiovascular and renal diseases. AT1 receptor blockers (ARBs or sartans) act as antihypertensive drugs by blocking the octapeptide hormone Angiotensin II to stimulate AT1 receptors. The antihypertensive drug candesartan (CAN) is the active metabolite of candesartan cilexetil (Atacand, CC). Complexes of candesartan and candesartan cilexetil with 2-hydroxylpropyl-β-cyclodextrin (2-HP-β-CD) were characterized using high-resolution electrospray ionization mass spectrometry and solid state 13 C cross-polarization/magic angle spinning nuclear magnetic resonance (CP/MAS NMR) spectroscopy. The 13 C CP/MAS results showed broad peaks especially in the aromatic region, thus confirming the strong interactions between cyclodextrin and drugs. This experimental evidence was in accordance with molecular dynamics simulations and quantum mechanical calculations. The synthesized and characterized complexes were evaluated biologically in vitro. It was shown that as a result of CAN’s complexation, CAN exerts higher antagonistic activity than CC. Therefore, a formulation of CC with 2-HP-β-CD is not indicated, while the formulation with CAN is promising and needs further investigation. This intriguing result is justified by the binding free energy calculations, which predicted efficient CC binding to 2-HP-β-CD, and thus, the molecule’s availability for release and action on the target is diminished. In contrast, CAN binding was not favored, and this may allow easy release for the drug to exert its bioactivity.
@article{Ntountaniotis2019, abstract = {Renin-angiotensin aldosterone system inhibitors are for a long time extensively used for the treatment of cardiovascular and renal diseases. AT1 receptor blockers (ARBs or sartans) act as antihypertensive drugs by blocking the octapeptide hormone Angiotensin II to stimulate AT1 receptors. The antihypertensive drug candesartan (CAN) is the active metabolite of candesartan cilexetil (Atacand, CC). Complexes of candesartan and candesartan cilexetil with 2-hydroxylpropyl-β-cyclodextrin (2-HP-β-CD) were characterized using high-resolution electrospray ionization mass spectrometry and solid state 13 C cross-polarization/magic angle spinning nuclear magnetic resonance (CP/MAS NMR) spectroscopy. The 13 C CP/MAS results showed broad peaks especially in the aromatic region, thus confirming the strong interactions between cyclodextrin and drugs. This experimental evidence was in accordance with molecular dynamics simulations and quantum mechanical calculations. The synthesized and characterized complexes were evaluated biologically in vitro. It was shown that as a result of CAN's complexation, CAN exerts higher antagonistic activity than CC. Therefore, a formulation of CC with 2-HP-β-CD is not indicated, while the formulation with CAN is promising and needs further investigation. This intriguing result is justified by the binding free energy calculations, which predicted efficient CC binding to 2-HP-β-CD, and thus, the molecule's availability for release and action on the target is diminished. In contrast, CAN binding was not favored, and this may allow easy release for the drug to exert its bioactivity.}, author = {D. Ntountaniotis and I. Andreadelis and T.F. Kellici and V. Karageorgos and G. Leonis and E. Christodoulou and S. Kiriakidi and J. Becker-Baldus and E.K. Stylos and M.V. Chatziathanasiadou and G. Liapakis and T. Mavromoustakos}, doi = {10.1021/acs.molpharmaceut.8b01212}, issue = {3}, journal = {Molecular Pharmaceutics}, pages = {1255-1271}, title = {Host-Guest Interactions between Candesartan and Its Prodrug Candesartan Cilexetil in Complex with 2-Hydroxypropyl-β-cyclodextrin: On the Biological Potency for Angiotensin II Antagonism}, volume = {16}, year = {2019}, } - Renziehausen, A., A. D. Tsiailanis, R. Perryman, E. K. Stylos, C. Chatzigiannis, K. O’Neill, T. Crook, A. G. Tzakos, and N. Syed. “Encapsulation of temozolomide in a calixarene nanocapsule improves its stability and enhances its therapeutic efficacy against glioblastoma.” Molecular cancer therapeutics 18 (2019): 1497-1505. doi:10.1158/1535-7163.MCT-18-1250
[BibTeX] [Abstract]
The alkylating agent temozolomide (TMZ) is the first-line chemotherapeutic for glioblastoma (GBM), a common and aggressive primary brain tumor in adults. However, its poor stability and unfavorable pharmacokinetic profile limit its clinical efficacy. There is an unmet need to tailor the therapeutic window of TMZ, either through complex derivatization or by utilizing pharmaceutical excipients. To enhance stability and aqueous solubility, we encapsulated TMZ in a p-sulphonatocalix[4]arene (Calix) nanocapsule and used 1H-NMR, LC-MS, and UV–Vis spectroscopy to chart the stability of this novel TMZ@Calix complex according to FDA and European Medicines Agency guidelines. LC-MS/MS plasma stability assays were conducted in mice to further explore the stability profile of TMZ@Calix in vivo. The therapeutic efficacy of TMZ@Calix was compared with that of unbound TMZ in GBM cell lines and patient-derived primary cells with known O6-methylguanine-DNA methyltransferase (MGMT) expression status and in vivo in an intracranial U87 xenograft mouse model. Encapsulation significantly enhanced the stability of TMZ in all conditions tested. TMZ@Calix was more potent than native TMZ at inhibiting the growth of established GBM cell lines and patient-derived primary lines expressing MGMT and highly resistant to TMZ. In vivo, native TMZ was rapidly degraded in mouse plasma, whereas the stability of TMZ@Calix was enhanced threefold with increased therapeutic efficacy in an orthotopic model. In the absence of new effective therapies, this novel formulation is of clinical importance, serving as an inexpensive and highly efficient treatment that could be made readily available to patients with GBM and warrants further preclinical and clinical evaluation.
@article{Renziehausen2019, abstract = {The alkylating agent temozolomide (TMZ) is the first-line chemotherapeutic for glioblastoma (GBM), a common and aggressive primary brain tumor in adults. However, its poor stability and unfavorable pharmacokinetic profile limit its clinical efficacy. There is an unmet need to tailor the therapeutic window of TMZ, either through complex derivatization or by utilizing pharmaceutical excipients. To enhance stability and aqueous solubility, we encapsulated TMZ in a p-sulphonatocalix[4]arene (Calix) nanocapsule and used 1H-NMR, LC-MS, and UV–Vis spectroscopy to chart the stability of this novel TMZ@Calix complex according to FDA and European Medicines Agency guidelines. LC-MS/MS plasma stability assays were conducted in mice to further explore the stability profile of TMZ@Calix in vivo. The therapeutic efficacy of TMZ@Calix was compared with that of unbound TMZ in GBM cell lines and patient-derived primary cells with known O6-methylguanine-DNA methyltransferase (MGMT) expression status and in vivo in an intracranial U87 xenograft mouse model. Encapsulation significantly enhanced the stability of TMZ in all conditions tested. TMZ@Calix was more potent than native TMZ at inhibiting the growth of established GBM cell lines and patient-derived primary lines expressing MGMT and highly resistant to TMZ. In vivo, native TMZ was rapidly degraded in mouse plasma, whereas the stability of TMZ@Calix was enhanced threefold with increased therapeutic efficacy in an orthotopic model. In the absence of new effective therapies, this novel formulation is of clinical importance, serving as an inexpensive and highly efficient treatment that could be made readily available to patients with GBM and warrants further preclinical and clinical evaluation.}, author = {A. Renziehausen and A.D. Tsiailanis and R. Perryman and E.K. Stylos and C. Chatzigiannis and K. O'Neill and T. Crook and A.G. Tzakos and N. Syed}, doi = {10.1158/1535-7163.MCT-18-1250}, issue = {9}, journal = {Molecular Cancer Therapeutics}, pages = {1497-1505}, title = {Encapsulation of temozolomide in a calixarene nanocapsule improves its stability and enhances its therapeutic efficacy against glioblastoma}, volume = {18}, year = {2019}, } - Goulas, V., L. Hadjivasileiou, A. Primikyri, C. Michael, G. Botsaris, A. G. Tzakos, and I. P. Gerothanassis. “Valorization of carob fruit residues for the preparation of novel bi-functional polyphenolic coating for food packaging applications.” Molecules 24 (2019). doi:10.3390/molecules24173162
[BibTeX] [Abstract]
The food industry has become interested in the development of innovative biomaterials with antioxidant and antimicrobial properties. Although several biopolymers have been evaluated for food packaging, the use of polyphenolic coatings has been unexplored. The purpose of this work was to develop an antioxidant and antimicrobial coating for food packaging through the polymerization of carob phenolics. At first, the polyphenolic coatings were deposited in glass surfaces polymerizing different concentrations of carob extracts (2 and 4 mg mL−1) at three pH values (7, 8 and 9). Results demonstrated that the coating produced at pH 8 and at a concentration of 4 mg mL−1 had the most potent antioxidant and antimicrobial potential. Then, the coating was applied directly on the salmon fillet (coating) and on the plastic container (active packaging). Peroxide and thiobarbituric acid-reactive substances (TBARS) methods were used to measure the potency to inhibit lipid oxidation in salmon fillets. Furthermore, the anti-Listeria activity of coatings was also assessed. Results showed a significant decrease of lipid oxidation during cold storage of salmon fillets for both treatments; the superiority of applied coating directly on the salmon fillets was also highlighted. Regarding the antimicrobial potency, the polyphenolic coating depleted the growth of Listeria monocytogenes after 10 days storage; while the active packaging had no effect on Listeria monocytogenes. Overall, we describe the use of low-cost carob polyphenols as precursors for the formation of bifunctional coatings with promising applications in food packaging.
@article{Goulas2019, abstract = {The food industry has become interested in the development of innovative biomaterials with antioxidant and antimicrobial properties. Although several biopolymers have been evaluated for food packaging, the use of polyphenolic coatings has been unexplored. The purpose of this work was to develop an antioxidant and antimicrobial coating for food packaging through the polymerization of carob phenolics. At first, the polyphenolic coatings were deposited in glass surfaces polymerizing different concentrations of carob extracts (2 and 4 mg mL−1) at three pH values (7, 8 and 9). Results demonstrated that the coating produced at pH 8 and at a concentration of 4 mg mL−1 had the most potent antioxidant and antimicrobial potential. Then, the coating was applied directly on the salmon fillet (coating) and on the plastic container (active packaging). Peroxide and thiobarbituric acid-reactive substances (TBARS) methods were used to measure the potency to inhibit lipid oxidation in salmon fillets. Furthermore, the anti-Listeria activity of coatings was also assessed. Results showed a significant decrease of lipid oxidation during cold storage of salmon fillets for both treatments; the superiority of applied coating directly on the salmon fillets was also highlighted. Regarding the antimicrobial potency, the polyphenolic coating depleted the growth of Listeria monocytogenes after 10 days storage; while the active packaging had no effect on Listeria monocytogenes. Overall, we describe the use of low-cost carob polyphenols as precursors for the formation of bifunctional coatings with promising applications in food packaging.}, author = {V. Goulas and L. Hadjivasileiou and A. Primikyri and C. Michael and G. Botsaris and A.G. Tzakos and I.P. Gerothanassis}, doi = {10.3390/molecules24173162}, issue = {17}, journal = {Molecules}, title = {Valorization of carob fruit residues for the preparation of novel bi-functional polyphenolic coating for food packaging applications}, volume = {24}, year = {2019}, } - Yilmaz, M., A. A. Karanastasis, M. V. Chatziathanasiadou, M. Oguz, A. Kougioumtzi, N. Clemente, T. F. Kellici, N. E. Zafeiropoulos, A. Avgeropoulos, T. Mavromoustakos, S. Karakurt, and A. G. Tzakos. “Inclusion of quercetin in gold nanoparticles decorated with supramolecular hosts amplifies its tumor targeting properties.” Acs applied bio materials 2 (2019): 2715-2725. doi:10.1021/acsabm.8b00748
[BibTeX] [Abstract]
Despite the anticancer potential of natural products (NPs), their limited bioavailability necessitates laborious derivatization or covalent conjugation to delivery vehicles. To unleash their potential, we developed a nanohybrid delivery platform with a noncovalently tunable surface. Initially, the active compound was encapsulated in a macrocycle, p-sulfonatocalix[4]arene, enabling a 62â000-fold aqueous solubility amplification as also a 2.9-fold enhancement in its cytotoxicity with respect to the parent compound in SW-620 colon cancer cells. A pH stimuli responsive behavior was recorded for this formulate, where a programmable release of quercetin from the macrocycle was monitored in an acidic environment. Then, a nanoparticle gold core was decorated with calixarene hosts to accommodate noncovalently NPs. The loaded nanocarrier with the NP quercetin dramatically enhanced the cytotoxicity (>50-fold) of the parent NP in colon cancer and altered its cell membrane transport mode. In vivo experiments in a mouse 4T1 tumor model showed a reduction of tumor volume in mice treated with quercetin-loaded nanoparticles without apparent toxic effects. Further analysis of the tumor-derived RNA highlighted that treatment with quercetin-loaded nanoparticles altered the expression of 27 genes related to apoptosis.
@article{Yilmaz2019, abstract = {Despite the anticancer potential of natural products (NPs), their limited bioavailability necessitates laborious derivatization or covalent conjugation to delivery vehicles. To unleash their potential, we developed a nanohybrid delivery platform with a noncovalently tunable surface. Initially, the active compound was encapsulated in a macrocycle, p-sulfonatocalix[4]arene, enabling a 62â000-fold aqueous solubility amplification as also a 2.9-fold enhancement in its cytotoxicity with respect to the parent compound in SW-620 colon cancer cells. A pH stimuli responsive behavior was recorded for this formulate, where a programmable release of quercetin from the macrocycle was monitored in an acidic environment. Then, a nanoparticle gold core was decorated with calixarene hosts to accommodate noncovalently NPs. The loaded nanocarrier with the NP quercetin dramatically enhanced the cytotoxicity (>50-fold) of the parent NP in colon cancer and altered its cell membrane transport mode. In vivo experiments in a mouse 4T1 tumor model showed a reduction of tumor volume in mice treated with quercetin-loaded nanoparticles without apparent toxic effects. Further analysis of the tumor-derived RNA highlighted that treatment with quercetin-loaded nanoparticles altered the expression of 27 genes related to apoptosis.}, author = {M. Yilmaz and A.A. Karanastasis and M.V. Chatziathanasiadou and M. Oguz and A. Kougioumtzi and N. Clemente and T.F. Kellici and N.E. Zafeiropoulos and A. Avgeropoulos and T. Mavromoustakos and S. Karakurt and A.G. Tzakos}, doi = {10.1021/acsabm.8b00748}, issue = {7}, journal = {ACS Applied Bio Materials}, pages = {2715-2725}, title = {Inclusion of Quercetin in Gold Nanoparticles Decorated with Supramolecular Hosts Amplifies Its Tumor Targeting Properties}, volume = {2}, year = {2019}, } - Kellici, T. F., D. Ntountaniotis, G. Liapakis, A. G. Tzakos, and T. Mavromoustakos. “The dynamic properties of angiotensin ii type 1 receptor inverse agonists in solution and in the receptor site.” Arabian journal of chemistry 12 (2019): 5062-5078. doi:10.1016/j.arabjc.2016.11.014
[BibTeX] [Abstract]
In this article, the conformational properties of olmesartan and its methylated analogue were charted using a combination of NMR spectroscopy and molecular modeling. For the molecular docking experiments three different forms of angiotensin II type 1 receptor (AT1R) have been used: (a) crystal structure; (b) homology model based on CXCR4 and (c) homology model based on rhodopsin. The aim of this study was to possibly explain the differences between the experimental findings derived from mutagenesis studies on this receptor and the crystal structure of the AT1R-olmesartan complex. Molecular Dynamics (MD) experiments were performed to illustrate the stability of the AT1R-inverse agonist complex and the most prominent interactions during the simulated trajectory. The obtained results showed that olmesartan and its methyl ether exert similar interactions with critical residues justifying their almost identical in vitro activity. However, the docking and MD experiments failed to justify the mutation findings in a satisfactory matter, indicating that the real system is more complex and crystal structure or homology models of AT1R receptors cannot simulate it sufficiently. Various conformations of olmesartan and olmesartan methyl ether were simulated to provide chemical shifts. These are compared with the experimental NMR results. Useful information regarding the putative bioactive conformations of olmesartan and its methylated analogue has been obtained. Finally, comparative data regarding the binding poses and energies of olmesartan, olmesartan methyl ether and three derivative compounds of olmesartan (R239470, R781253, and R794847) were acquired using Prime/MM-GBSA calculations.
@article{Kellici2019, abstract = {In this article, the conformational properties of olmesartan and its methylated analogue were charted using a combination of NMR spectroscopy and molecular modeling. For the molecular docking experiments three different forms of angiotensin II type 1 receptor (AT1R) have been used: (a) crystal structure; (b) homology model based on CXCR4 and (c) homology model based on rhodopsin. The aim of this study was to possibly explain the differences between the experimental findings derived from mutagenesis studies on this receptor and the crystal structure of the AT1R-olmesartan complex. Molecular Dynamics (MD) experiments were performed to illustrate the stability of the AT1R-inverse agonist complex and the most prominent interactions during the simulated trajectory. The obtained results showed that olmesartan and its methyl ether exert similar interactions with critical residues justifying their almost identical in vitro activity. However, the docking and MD experiments failed to justify the mutation findings in a satisfactory matter, indicating that the real system is more complex and crystal structure or homology models of AT1R receptors cannot simulate it sufficiently. Various conformations of olmesartan and olmesartan methyl ether were simulated to provide chemical shifts. These are compared with the experimental NMR results. Useful information regarding the putative bioactive conformations of olmesartan and its methylated analogue has been obtained. Finally, comparative data regarding the binding poses and energies of olmesartan, olmesartan methyl ether and three derivative compounds of olmesartan (R239470, R781253, and R794847) were acquired using Prime/MM-GBSA calculations.}, author = {T.F. Kellici and D. Ntountaniotis and G. Liapakis and A.G. Tzakos and T. Mavromoustakos}, doi = {10.1016/j.arabjc.2016.11.014}, issue = {8}, journal = {Arabian Journal of Chemistry}, pages = {5062-5078}, title = {The dynamic properties of angiotensin II type 1 receptor inverse agonists in solution and in the receptor site}, volume = {12}, year = {2019}, }
2018
- Chayrov, R. L., E. K. Stylos, M. V. Chatziathanasiadou, K. N. Chuchkov, A. I. Tencheva, A. D. Kostagianni, T. S. Milkova, A. L. Angelova, A. S. Galabov, S. A. Shishkov, A. G. Tzakos, and I. G. Stankova. “Tailoring acyclovir prodrugs with enhanced antiviral activity: rational design, synthesis, human plasma stability and in vitro evaluation.” Amino acids 50 (2018): 1131-1143. doi:10.1007/s00726-018-2590-y
[BibTeX] [Abstract]
Bile acid prodrugs have served as a viable strategy for refining the pharmaceutical profile of parent drugs through utilizing bile acid transporters. A series of three ester prodrugs of the antiherpetic drug acyclovir (ACV) with the bile acids cholic, chenodeoxycholic and deoxycholic were synthesized and evaluated along with valacyclovir for their in vitro antiviral activity against herpes simplex viruses type 1 and type 2 (HSV-1, HSV-2). The in vitro antiviral activity of the three bile acid prodrugs was also evaluated against Epstein–Barr virus (EBV). Plasma stability assays, utilizing ultra-high performance liquid chromatography coupled with tandem mass spectrometry, in vitro cytotoxicity and inhibitory experiments were conducted in order to establish the biological profile of ACV prodrugs. The antiviral assays demonstrated that ACV-cholate had slightly better antiviral activity than ACV against HSV-1, while it presented an eight-fold higher activity with respect to ACV against HSV-2. ACV-chenodeoxycholate presented a six-fold higher antiviral activity against HSV-2 with respect to ACV. Concerning EBV, the highest antiviral effect was demonstrated by ACV-chenodeoxycholate. Human plasma stability assays revealed that ACV-deoxycholate was more stable than the other two prodrugs. These results suggest that decorating the core structure of ACV with bile acids could deliver prodrugs with amplified antiviral activity.
@article{Chayrov2018, abstract = {Bile acid prodrugs have served as a viable strategy for refining the pharmaceutical profile of parent drugs through utilizing bile acid transporters. A series of three ester prodrugs of the antiherpetic drug acyclovir (ACV) with the bile acids cholic, chenodeoxycholic and deoxycholic were synthesized and evaluated along with valacyclovir for their in vitro antiviral activity against herpes simplex viruses type 1 and type 2 (HSV-1, HSV-2). The in vitro antiviral activity of the three bile acid prodrugs was also evaluated against Epstein–Barr virus (EBV). Plasma stability assays, utilizing ultra-high performance liquid chromatography coupled with tandem mass spectrometry, in vitro cytotoxicity and inhibitory experiments were conducted in order to establish the biological profile of ACV prodrugs. The antiviral assays demonstrated that ACV-cholate had slightly better antiviral activity than ACV against HSV-1, while it presented an eight-fold higher activity with respect to ACV against HSV-2. ACV-chenodeoxycholate presented a six-fold higher antiviral activity against HSV-2 with respect to ACV. Concerning EBV, the highest antiviral effect was demonstrated by ACV-chenodeoxycholate. Human plasma stability assays revealed that ACV-deoxycholate was more stable than the other two prodrugs. These results suggest that decorating the core structure of ACV with bile acids could deliver prodrugs with amplified antiviral activity.}, author = {R.L. Chayrov and E.K. Stylos and M.V. Chatziathanasiadou and K.N. Chuchkov and A.I. Tencheva and A.D. Kostagianni and T.S. Milkova and A.L. Angelova and A.S. Galabov and S.A. Shishkov and A.G. Tzakos and I.G. Stankova}, doi = {10.1007/s00726-018-2590-y}, issue = {8}, journal = {Amino Acids}, pages = {1131-1143}, title = {Tailoring acyclovir prodrugs with enhanced antiviral activity: rational design, synthesis, human plasma stability and in vitro evaluation}, volume = {50}, year = {2018}, } - Tsiailanis, A., M. Tsoumani, E. K. Stylos, M. V. Chatziathanasiadou, T. F. Kellici, T. Mavromoustakos, A. D. Tselepis, and A. G. Tzakos. Designing natural product hybrids bearing triple antiplatelet profile and evaluating their human plasma stability. Vol. 1824. 2018. doi:10.1007/978-1-4939-8630-9_22
[BibTeX] [Abstract]
Cardiovascular diseases (CVDs) are becoming major contributors to the burden of disease due to genetic and environmental factors. Despite current standard oral care, cardiovascular risk remains relatively high. A triple antiplatelet therapy with a cyclooxygenase-1 (COX-1) inhibitor, a P2Y 12 receptor antagonist, and a protease-activated receptor-1 (PAR-1) antagonist has been established in the secondary prevention of atherothrombosis in patients with acute myocardial infraction and in those with peripheral artery disease. However, due to the combinatorial use of three different drugs, patients receiving this triple therapy are exposed to enhanced risk of bleeding. Conforming to polypharmacology principles, the discovery of a single compound that can simultaneously block the three platelet activation pathways (PAR-1, P2Y 12 , and COX-1) is of importance. Natural products have served as an inexhaustible source of bioactive compounds presenting a diverse pharmaceutical profile, including anti-inflammatory, antioxidant, anticancer, and antithrombotic activity. Indeed, principal component analysis indicated that natural products have the potential to inhibit the three aforementioned pathways, though existed reports refer to single inhibition mechanism on specific receptor(s) implicated in platelet activation. We thus set out to explore possibilities that take advantage of this potential of natural products and shape the basis to produce novel compounds that could simultaneously target PAR-1, P2Y 12 , and COX-1 platelet activation pathways. Polyunsaturated fatty acids (PUFAs) have multiple effects leading to improvements in blood pressure and cardiac function and arterial compliance. A promising approach to achieve the desirable goal is the bioconjugation of natural products with PUFAs. Herein, we describe the principles that should be followed to develop molecular hybrids bearing triple antiplatelet activity profile.
@book{Tsiailanis2018, abstract = {Cardiovascular diseases (CVDs) are becoming major contributors to the burden of disease due to genetic and environmental factors. Despite current standard oral care, cardiovascular risk remains relatively high. A triple antiplatelet therapy with a cyclooxygenase-1 (COX-1) inhibitor, a P2Y 12 receptor antagonist, and a protease-activated receptor-1 (PAR-1) antagonist has been established in the secondary prevention of atherothrombosis in patients with acute myocardial infraction and in those with peripheral artery disease. However, due to the combinatorial use of three different drugs, patients receiving this triple therapy are exposed to enhanced risk of bleeding. Conforming to polypharmacology principles, the discovery of a single compound that can simultaneously block the three platelet activation pathways (PAR-1, P2Y 12 , and COX-1) is of importance. Natural products have served as an inexhaustible source of bioactive compounds presenting a diverse pharmaceutical profile, including anti-inflammatory, antioxidant, anticancer, and antithrombotic activity. Indeed, principal component analysis indicated that natural products have the potential to inhibit the three aforementioned pathways, though existed reports refer to single inhibition mechanism on specific receptor(s) implicated in platelet activation. We thus set out to explore possibilities that take advantage of this potential of natural products and shape the basis to produce novel compounds that could simultaneously target PAR-1, P2Y 12 , and COX-1 platelet activation pathways. Polyunsaturated fatty acids (PUFAs) have multiple effects leading to improvements in blood pressure and cardiac function and arterial compliance. A promising approach to achieve the desirable goal is the bioconjugation of natural products with PUFAs. Herein, we describe the principles that should be followed to develop molecular hybrids bearing triple antiplatelet activity profile.}, author = {A. Tsiailanis and M. Tsoumani and E.K. Stylos and M.V. Chatziathanasiadou and T.F. Kellici and T. Mavromoustakos and A.D. Tselepis and A.G. Tzakos}, doi = {10.1007/978-1-4939-8630-9_22}, journal = {Methods in Molecular Biology}, pages = {371-386}, title = {Designing natural product hybrids bearing triple antiplatelet profile and evaluating their human plasma stability}, volume = {1824}, year = {2018}, } - Ishiguro, S., A. Kawabata, A. Zulbaran-Rojas, K. Monson, D. Uppalapati, N. Ohta, M. Inui, C. G. Pappas, A. G. Tzakos, and M. Tamura. “Co-treatment with a c1b5 peptide of protein kinase cγ and a low dose of gemcitabine strongly attenuated pancreatic cancer growth in mice through t cell activation.” Biochemical and biophysical research communications 495 (2018): 962-968. doi:10.1016/j.bbrc.2017.11.102
[BibTeX] [Abstract]
Although gemcitabine is an effective chemotherapeutic for pancreatic cancer, severe side effects often accompany its use. Since we have discovered that locally administered C1B domain peptides effectively control tumor growth without any side effects, the efficacy of co-treatment with this peptide and a low dose of gemcitabine on the growth of pancreatic cancer was examined. Two- and three-dimensional cell culture studies clarified that a co-treatment with C1B5 peptide and gemcitabine significantly attenuated growth of PAN02 mouse and PANC-1 human pancreatic cancer cells in 2D and 3D cultures. Although treatment with the low dose of gemcitabine alone (76%) or the C1B5 peptide alone (39%) inhibited tumor growth moderately, a co-treatment with C1B5 peptide and a low dose of gemcitabine markedly inhibited the growth of PAN02 autografts in the mouse peritoneal cavity (94% inhibition) without any noticeable adverse effect. The number of peritoneal cavity-infiltrating neutrophils and granzyme B+ lymphocytes was significantly higher in the co-treatment group than in the control group. A significant increase of granzyme B mRNA expression was also detected in human T cells by the co-treatment. Taken together, the current study suggests that C1B5 peptide offers a remarkably effective combination treatment strategy to reduce side effects associated with gemcitabine, without losing its tumoricidal effect.
@article{Ishiguro2018, abstract = {Although gemcitabine is an effective chemotherapeutic for pancreatic cancer, severe side effects often accompany its use. Since we have discovered that locally administered C1B domain peptides effectively control tumor growth without any side effects, the efficacy of co-treatment with this peptide and a low dose of gemcitabine on the growth of pancreatic cancer was examined. Two- and three-dimensional cell culture studies clarified that a co-treatment with C1B5 peptide and gemcitabine significantly attenuated growth of PAN02 mouse and PANC-1 human pancreatic cancer cells in 2D and 3D cultures. Although treatment with the low dose of gemcitabine alone (76%) or the C1B5 peptide alone (39%) inhibited tumor growth moderately, a co-treatment with C1B5 peptide and a low dose of gemcitabine markedly inhibited the growth of PAN02 autografts in the mouse peritoneal cavity (94% inhibition) without any noticeable adverse effect. The number of peritoneal cavity-infiltrating neutrophils and granzyme B+ lymphocytes was significantly higher in the co-treatment group than in the control group. A significant increase of granzyme B mRNA expression was also detected in human T cells by the co-treatment. Taken together, the current study suggests that C1B5 peptide offers a remarkably effective combination treatment strategy to reduce side effects associated with gemcitabine, without losing its tumoricidal effect.}, author = {S. Ishiguro and A. Kawabata and A. Zulbaran-Rojas and K. Monson and D. Uppalapati and N. Ohta and M. Inui and C.G. Pappas and A.G. Tzakos and M. Tamura}, doi = {10.1016/j.bbrc.2017.11.102}, issue = {1}, journal = {Biochemical and Biophysical Research Communications}, pages = {962-968}, title = {Co-treatment with a C1B5 peptide of protein kinase Cγ and a low dose of gemcitabine strongly attenuated pancreatic cancer growth in mice through T cell activation}, volume = {495}, year = {2018}, } - Kyriakou, E., A. D. Kostagianni, T. F. Kellici, E. Giannopoulou, K. E. Siatis, N. Sayyad, H. P. Kalofonos, T. Mavromoustakos, H. Stamatis, and A. G. Tzakos. “Three regioselectively acylated flavonoid aglycone derivatives in equimolar yield at one blow.” Chemistryselect 3 (2018): 5207-5211. doi:10.1002/slct.201703002
[BibTeX] [Abstract]
A simple and time-effective chemoenzymatic process to obtain three regioselective acylated quercetin analogues in a 1:1:1 ratio in one pot is described. This process overcomes the inherent scaffold intricacy and synthetic complexity of quercetin. Cell proliferation experiments in three breast cancers cell lines pinpoint the high potency of the generated compounds.
@article{Kyriakou2018, abstract = {A simple and time-effective chemoenzymatic process to obtain three regioselective acylated quercetin analogues in a 1:1:1 ratio in one pot is described. This process overcomes the inherent scaffold intricacy and synthetic complexity of quercetin. Cell proliferation experiments in three breast cancers cell lines pinpoint the high potency of the generated compounds.}, author = {E. Kyriakou and A.D. Kostagianni and T.F. Kellici and E. Giannopoulou and K.E. Siatis and N. Sayyad and H.P. Kalofonos and T. Mavromoustakos and H. Stamatis and A.G. Tzakos}, doi = {10.1002/slct.201703002}, issue = {18}, journal = {ChemistrySelect}, pages = {5207-5211}, title = {Three Regioselectively Acylated Flavonoid Aglycone Derivatives in Equimolar Yield at One Blow}, volume = {3}, year = {2018}, } - Diamantis, D. A., S. Ramesova, C. M. Chatzigiannis, I. Degano, P. S. Gerogianni, K. E. Karadima, S. Perikleous, D. Rekkas, I. P. Gerothanassis, D. Galaris, R. Sokolova, and A. G. Tzakos. “Exploring the oxidation and iron binding profile of a cyclodextrin encapsulated quercetin complex unveiled a controlled complex dissociation through a chemical stimulus.” Biochimica et biophysica acta – general subjects 1862 (2018): 1913-1924. doi:10.1016/j.bbagen.2018.06.006
[BibTeX] [Abstract]
Background: Flavonoids possess a rich polypharmacological profile and their biological role is linked to their oxidation state protecting DNA from oxidative stress damage. However, their bioavailability is hampered due to their poor aqueous solubility. This can be surpassed through encapsulation to supramolecular carriers as cyclodextrin (CD). A quercetin- 2HP-β-CD complex has been formerly reported by us. However, once the flavonoid is in its 2HP-β-CD encapsulated state its oxidation potential, its decomplexation mechanism, its potential to protect DNA damage from oxidative stress remained elusive. To unveil this, an array of biophysical techniques was used. Methods: The quercetin-2HP-β-CD complex was evaluated through solubility and dissolution experiments, electrochemical and spectroelectrochemical studies (Cyclic Voltammetry), UV–Vis spectroscopy, HPLC-ESI-MS/MS and HPLC-DAD, fluorescence spectroscopy, NMR Spectroscopy, theoretical calculations (density functional theory (DFT)) and biological evaluation of the protection offered against H 2 O 2 -induced DNA damage. Results: Encapsulation of quercetin inside the supramolecule’s cavity enhanced its solubility and retained its oxidation profile. Although the protective ability of the quercetin-2HP-β-CD complex against H 2 O 2 was diminished, iron serves as a chemical stimulus to dissociate the complex and release quercetin. Conclusions: We found that in a quercetin-2HP-β-CD inclusion complex quercetin retains its oxidation profile similarly to its native state, while iron can operate as a chemical stimulus to release quercetin from its host cavity. General significance: The oxidation profile of a natural product once it is encapsulated in a supramolecular carrier was unveiled as also it was discovered that decomplexation can be triggered by a chemical stimilus.
@article{Diamantis2018, abstract = {Background: Flavonoids possess a rich polypharmacological profile and their biological role is linked to their oxidation state protecting DNA from oxidative stress damage. However, their bioavailability is hampered due to their poor aqueous solubility. This can be surpassed through encapsulation to supramolecular carriers as cyclodextrin (CD). A quercetin- 2HP-β-CD complex has been formerly reported by us. However, once the flavonoid is in its 2HP-β-CD encapsulated state its oxidation potential, its decomplexation mechanism, its potential to protect DNA damage from oxidative stress remained elusive. To unveil this, an array of biophysical techniques was used. Methods: The quercetin-2HP-β-CD complex was evaluated through solubility and dissolution experiments, electrochemical and spectroelectrochemical studies (Cyclic Voltammetry), UV–Vis spectroscopy, HPLC-ESI-MS/MS and HPLC-DAD, fluorescence spectroscopy, NMR Spectroscopy, theoretical calculations (density functional theory (DFT)) and biological evaluation of the protection offered against H 2 O 2 -induced DNA damage. Results: Encapsulation of quercetin inside the supramolecule's cavity enhanced its solubility and retained its oxidation profile. Although the protective ability of the quercetin-2HP-β-CD complex against H 2 O 2 was diminished, iron serves as a chemical stimulus to dissociate the complex and release quercetin. Conclusions: We found that in a quercetin-2HP-β-CD inclusion complex quercetin retains its oxidation profile similarly to its native state, while iron can operate as a chemical stimulus to release quercetin from its host cavity. General significance: The oxidation profile of a natural product once it is encapsulated in a supramolecular carrier was unveiled as also it was discovered that decomplexation can be triggered by a chemical stimilus.}, author = {D.A. Diamantis and S. Ramesova and C.M. Chatzigiannis and I. Degano and P.S. Gerogianni and K.E. Karadima and S. Perikleous and D. Rekkas and I.P. Gerothanassis and D. Galaris and R. Sokolova and A.G. Tzakos}, doi = {10.1016/j.bbagen.2018.06.006}, issue = {9}, journal = {Biochimica et Biophysica Acta - General Subjects}, pages = {1913-1924}, title = {Exploring the oxidation and iron binding profile of a cyclodextrin encapsulated quercetin complex unveiled a controlled complex dissociation through a chemical stimulus}, volume = {1862}, year = {2018}, } - Gerogianni, P. S., M. V. Chatziathanasiadou, D. A. Diamantis, A. G. Tzakos, and D. Galaris. “Lipophilic ester and amide derivatives of rosmarinic acid protect cells against h
2 o2 -induced dna damage and apoptosis: the potential role of intracellular accumulation and labile iron chelation.” Redox biology 15 (2018): 548-556. doi:10.1016/j.redox.2018.01.014
[BibTeX] [Abstract]
Phenolic acids represent abundant components contained in human diet. However, the negative charge in their carboxylic group limits their capacity to diffuse through biological membranes, thus hindering their access to cell interior. In order to promote the diffusion of rosmarinic acid through biological membranes, we synthesized several lipophilic ester- and amide-derivatives of this compound and evaluated their capacity to prevent H2O2-induced DNA damage and apoptosis in cultured human cells. Esterification of the carboxylic moiety with lipophilic groups strongly enhanced the capacity of rosmarinic acid to protect cells. On the other hand, the amide-derivatives were somewhat less effective but exerted less cytotoxicity at high concentrations. Cell uptake experiments, using ultra-high performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS), illustrated different levels of intracellular accumulation among the ester- and amide-derivatives, with the first being more effectively accumulated, probably due to their extensive hydrolysis inside the cells. In conclusion, these results highlight the hitherto unrecognized fundamental importance of derivatization of diet-derived phenolic acids to unveil their biological potential.
@article{Gerogianni2018, abstract = {Phenolic acids represent abundant components contained in human diet. However, the negative charge in their carboxylic group limits their capacity to diffuse through biological membranes, thus hindering their access to cell interior. In order to promote the diffusion of rosmarinic acid through biological membranes, we synthesized several lipophilic ester- and amide-derivatives of this compound and evaluated their capacity to prevent H2O2-induced DNA damage and apoptosis in cultured human cells. Esterification of the carboxylic moiety with lipophilic groups strongly enhanced the capacity of rosmarinic acid to protect cells. On the other hand, the amide-derivatives were somewhat less effective but exerted less cytotoxicity at high concentrations. Cell uptake experiments, using ultra-high performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS), illustrated different levels of intracellular accumulation among the ester- and amide-derivatives, with the first being more effectively accumulated, probably due to their extensive hydrolysis inside the cells. In conclusion, these results highlight the hitherto unrecognized fundamental importance of derivatization of diet-derived phenolic acids to unveil their biological potential.}, author = {P.S. Gerogianni and M.V. Chatziathanasiadou and D.A. Diamantis and A.G. Tzakos and D. Galaris}, doi = {10.1016/j.redox.2018.01.014}, journal = {Redox Biology}, pages = {548-556}, title = {Lipophilic ester and amide derivatives of rosmarinic acid protect cells against H2 O2 -induced DNA damage and apoptosis: The potential role of intracellular accumulation and labile iron chelation}, volume = {15}, year = {2018}, } - Chatzikonstantinou, A. V., M. V. Chatziathanasiadou, E. Ravera, M. Fragai, G. Parigi, I. P. Gerothanassis, C. Luchinat, H. Stamatis, and A. G. Tzakos. “Enriching the biological space of natural products and charting drug metabolites, through real time biotransformation monitoring: the nmr tube bioreactor.” Biochimica et biophysica acta – general subjects 1862 (2018): 1-8. doi:10.1016/j.bbagen.2017.09.021
[BibTeX] [Abstract]
Background Natural products offer a wide range of biological activities, but they are not easily integrated in the drug discovery pipeline, because of their inherent scaffold intricacy and the associated complexity in their synthetic chemistry. Enzymes may be used to perform regioselective and stereoselective incorporation of functional groups in the natural product core, avoiding harsh reaction conditions, several protection/deprotection and purification steps. Methods Herein, we developed a three step protocol carried out inside an NMR-tube. 1st-step: STD-NMR was used to predict the: i) capacity of natural products as enzyme substrates and ii) possible regioselectivity of the biotransformations. 2nd-step: The real-time formation of multiple-biotransformation products in the NMR-tube bioreactor was monitored in-situ. 3rd-step: STD-NMR was applied in the mixture of the biotransformed products to screen ligands for protein targets. Results Herein, we developed a simple and time-effective process, the “NMR-tube bioreactor” that is able to: (i) predict which component of a mixture of natural products can be enzymatically transformed, (ii) monitor in situ the transformation efficacy and regioselectivity in crude extracts and multiple substrate biotransformations without fractionation and (iii) simultaneously screen for interactions of the biotransformation products with pharmaceutical protein targets. Conclusions We have developed a green, time-, and cost-effective process that provide a simple route from natural products to lead compounds for drug discovery. General significanse This process can speed up the most crucial steps in the early drug discovery process, and reduce the chemical manipulations usually involved in the pipeline, improving the environmental compatibility.
@article{Chatzikonstantinou2018, abstract = {Background Natural products offer a wide range of biological activities, but they are not easily integrated in the drug discovery pipeline, because of their inherent scaffold intricacy and the associated complexity in their synthetic chemistry. Enzymes may be used to perform regioselective and stereoselective incorporation of functional groups in the natural product core, avoiding harsh reaction conditions, several protection/deprotection and purification steps. Methods Herein, we developed a three step protocol carried out inside an NMR-tube. 1st-step: STD-NMR was used to predict the: i) capacity of natural products as enzyme substrates and ii) possible regioselectivity of the biotransformations. 2nd-step: The real-time formation of multiple-biotransformation products in the NMR-tube bioreactor was monitored in-situ. 3rd-step: STD-NMR was applied in the mixture of the biotransformed products to screen ligands for protein targets. Results Herein, we developed a simple and time-effective process, the “NMR-tube bioreactor” that is able to: (i) predict which component of a mixture of natural products can be enzymatically transformed, (ii) monitor in situ the transformation efficacy and regioselectivity in crude extracts and multiple substrate biotransformations without fractionation and (iii) simultaneously screen for interactions of the biotransformation products with pharmaceutical protein targets. Conclusions We have developed a green, time-, and cost-effective process that provide a simple route from natural products to lead compounds for drug discovery. General significanse This process can speed up the most crucial steps in the early drug discovery process, and reduce the chemical manipulations usually involved in the pipeline, improving the environmental compatibility.}, author = {A.V. Chatzikonstantinou and M.V. Chatziathanasiadou and E. Ravera and M. Fragai and G. Parigi and I.P. Gerothanassis and C. Luchinat and H. Stamatis and A.G. Tzakos}, doi = {10.1016/j.bbagen.2017.09.021}, issue = {1}, journal = {Biochimica et Biophysica Acta - General Subjects}, pages = {1-8}, title = {Enriching the biological space of natural products and charting drug metabolites, through real time biotransformation monitoring: The NMR tube bioreactor}, volume = {1862}, year = {2018}, } - Primikyri, A., N. Sayyad, G. Quilici, E. I. Vrettos, K. Lim, S. -W. Chi, G. Musco, I. P. Gerothanassis, and A. G. Tzakos. “Probing the interaction of a quercetin bioconjugate with bcl-2 in living human cancer cells with in-cell nmr spectroscopy.” Febs letters 592 (2018): 3367-3379. doi:10.1002/1873-3468.13250
[BibTeX] [Abstract]
In-cell NMR spectroscopy has emerged as a powerful technique for monitoring biomolecular interactions at an atomic level inside intact cells. However, current methodologies are inadequate at charting intracellular interactions of nonlabeled proteins and require their prior isotopic labeling. Herein, we describe for the first time the monitoring of the quercetin-alanine bioconjugate interaction with the nonlabeled antiapoptotic protein Bcl-2 inside living human cancer cells. STD and Tr-NOESY in-cell NMR methodologies were successfully applied in the investigation of the binding, which was further validated in vitro. In-cell NMR proved a very promising strategy for the real-time probing of the interaction profile of potential drugs with their therapeutic targets in native cellular environments and could, thus, open a new avenue in drug discovery.
@article{Primikyri2018, abstract = {In-cell NMR spectroscopy has emerged as a powerful technique for monitoring biomolecular interactions at an atomic level inside intact cells. However, current methodologies are inadequate at charting intracellular interactions of nonlabeled proteins and require their prior isotopic labeling. Herein, we describe for the first time the monitoring of the quercetin-alanine bioconjugate interaction with the nonlabeled antiapoptotic protein Bcl-2 inside living human cancer cells. STD and Tr-NOESY in-cell NMR methodologies were successfully applied in the investigation of the binding, which was further validated in vitro. In-cell NMR proved a very promising strategy for the real-time probing of the interaction profile of potential drugs with their therapeutic targets in native cellular environments and could, thus, open a new avenue in drug discovery.}, author = {A. Primikyri and N. Sayyad and G. Quilici and E.I. Vrettos and K. Lim and S.-W. Chi and G. Musco and I.P. Gerothanassis and A.G. Tzakos}, doi = {10.1002/1873-3468.13250}, issue = {20}, journal = {FEBS Letters}, pages = {3367-3379}, title = {Probing the interaction of a quercetin bioconjugate with Bcl-2 in living human cancer cells with in-cell NMR spectroscopy}, volume = {592}, year = {2018}, } - Mubarak, El M. A., I. Leontari, G. Efstathia, E. I. Vrettos, A. K. Shaikh, S. E. Konstantinos, C. Danika, H. P. Kalofonos, A. G. Tzakos, and G. B. Sivolapenko. “Development of a novel conjugatable sunitinib analogue validated through in vitro and in vivo preclinical settings.” Journal of chromatography b: analytical technologies in the biomedical and life sciences 1092 (2018): 515-523. doi:10.1016/j.jchromb.2018.05.050
[BibTeX] [Abstract]
Sunitinib is an oral FDA/EMEA approved multi-targeted tyrosine kinase inhibitor. It possesses anti-angiogenic and antitumor activity against a variety of advanced solid tumors. However, its chemical core does not allow a potential linkage to tumor-homing elements that could eventually enhance its potency. Therefore, a novel linkable sunitinib derivative, designated SB1, was rationally designed and synthesized. The pharmaceutical profile of SB1 was explored both in vitro and in vivo. Mass spectrometry and NMR spectroscopy were utilized for characterization, while MTT assays and LC-MS/MS validated protocols were used to explore its antiproliferative effect and stability, respectively. Cytotoxicity evaluation in three glioma cells showed that SB1 preserved the antiproliferative effect of sunitinib. SB1 was stable in vitro after 24 h incubation in mouse plasma, while both agents exhibited bioequivalent pharmacokinetic characteristics after i.v. administration in Balb/c mice. To evaluate the levels of SB1 in mouse plasma, a novel analytical method was developed and validated in accordance to the US FDA and the EU EMA guidelines. We formulated a novel linkable sunitinib analog exhibiting similar antiproliferative and apoptotic properties with native sunitinib in glioma cell lines. Both SB1 and native sunitinib showed identical in vitro stability in mouse plasma and pharmacokinetics after i.v. administration in Balb/c mice.
@article{, abstract = {Sunitinib is an oral FDA/EMEA approved multi-targeted tyrosine kinase inhibitor. It possesses anti-angiogenic and antitumor activity against a variety of advanced solid tumors. However, its chemical core does not allow a potential linkage to tumor-homing elements that could eventually enhance its potency. Therefore, a novel linkable sunitinib derivative, designated SB1, was rationally designed and synthesized. The pharmaceutical profile of SB1 was explored both in vitro and in vivo. Mass spectrometry and NMR spectroscopy were utilized for characterization, while MTT assays and LC-MS/MS validated protocols were used to explore its antiproliferative effect and stability, respectively. Cytotoxicity evaluation in three glioma cells showed that SB1 preserved the antiproliferative effect of sunitinib. SB1 was stable in vitro after 24 h incubation in mouse plasma, while both agents exhibited bioequivalent pharmacokinetic characteristics after i.v. administration in Balb/c mice. To evaluate the levels of SB1 in mouse plasma, a novel analytical method was developed and validated in accordance to the US FDA and the EU EMA guidelines. We formulated a novel linkable sunitinib analog exhibiting similar antiproliferative and apoptotic properties with native sunitinib in glioma cell lines. Both SB1 and native sunitinib showed identical in vitro stability in mouse plasma and pharmacokinetics after i.v. administration in Balb/c mice.}, author = {M.A. El Mubarak and I. Leontari and G. Efstathia and E.I. Vrettos and A.K. Shaikh and S.E. Konstantinos and C. Danika and H.P. Kalofonos and A.G. Tzakos and G.B. Sivolapenko}, doi = {10.1016/j.jchromb.2018.05.050}, journal = {Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences}, pages = {515-523}, title = {Development of a novel conjugatable sunitinib analogue validated through in vitro and in vivo preclinical settings}, volume = {1092}, year = {2018}, } - Chatziathanasiadou, M. V., E. G. Geromichalou, N. Sayyad, E. I. Vrettos, A. Katsikoudi, E. Stylos, S. Bellou, G. D. Geromichalos, and A. G. Tzakos. “Amplifying and broadening the cytotoxic profile of quercetin in cancer cell lines through bioconjugation.” Amino acids 50 (2018): 279-291. doi:10.1007/s00726-017-2514-2
[BibTeX] [Abstract]
Quercetin is a flavonoid presenting cytotoxicity against different cancer cell lines. We hypothesized that its core could serve as a scaffold for generating more potent compounds. A quercetin–alanine bioconjugate was synthesized, its cellular internalization was monitored through confocal microscopy and its cytotoxic activity was explored against ten different cell lines. The bioconjugate consistently illustrated enhanced cytotoxic activity with respect to the parent compound. A threefold enhancement in its cytotoxicity was revealed for HeLa, A549, MCF-7 and LNCaP cells. In silico studies suggested that quercetin–alanine possesses enhanced binding affinity to human estrogen receptor alpha corroborating to its activity to MCF-7, overexpressing this receptor. Spectrofluorimetric, calorimetric and in silico studies revealed that quercetin–alanine binds primarily to Sudlow site I of serum albumin mainly through hydrogen bonding. Through this array of experiments we discovered that the specific compound bears a more refined pharmaceutical profile in contrast to quercetin in terms of cytotoxicity, while at the same time preserves its affinity to serum albumin. Natural products could thus offer a potent scaffold to develop bioconjugates with amplified therapeutic window.
@article{Chatziathanasiadou2018, abstract = {Quercetin is a flavonoid presenting cytotoxicity against different cancer cell lines. We hypothesized that its core could serve as a scaffold for generating more potent compounds. A quercetin–alanine bioconjugate was synthesized, its cellular internalization was monitored through confocal microscopy and its cytotoxic activity was explored against ten different cell lines. The bioconjugate consistently illustrated enhanced cytotoxic activity with respect to the parent compound. A threefold enhancement in its cytotoxicity was revealed for HeLa, A549, MCF-7 and LNCaP cells. In silico studies suggested that quercetin–alanine possesses enhanced binding affinity to human estrogen receptor alpha corroborating to its activity to MCF-7, overexpressing this receptor. Spectrofluorimetric, calorimetric and in silico studies revealed that quercetin–alanine binds primarily to Sudlow site I of serum albumin mainly through hydrogen bonding. Through this array of experiments we discovered that the specific compound bears a more refined pharmaceutical profile in contrast to quercetin in terms of cytotoxicity, while at the same time preserves its affinity to serum albumin. Natural products could thus offer a potent scaffold to develop bioconjugates with amplified therapeutic window.}, author = {M.V. Chatziathanasiadou and E.G. Geromichalou and N. Sayyad and E.I. Vrettos and A. Katsikoudi and E. Stylos and S. Bellou and G.D. Geromichalos and A.G. Tzakos}, doi = {10.1007/s00726-017-2514-2}, issue = {2}, journal = {Amino Acids}, pages = {279-291}, title = {Amplifying and broadening the cytotoxic profile of quercetin in cancer cell lines through bioconjugation}, volume = {50}, year = {2018}, } - Vrettos, E. I., G. Mező, and A. G. Tzakos. “On the design principles of peptide–drug conjugates for targeted drug delivery to the malignant tumor site.” Beilstein journal of organic chemistry 14 (2018): 930-954. doi:10.3762/BJOC.14.80
[BibTeX] [Abstract]
Cancer is the second leading cause of death affecting nearly one in two people, and the appearance of new cases is projected to rise by >70% by 2030. To effectively combat the menace of cancer, a variety of strategies have been exploited. Among them, the development of peptide–drug conjugates (PDCs) is considered as an inextricable part of this armamentarium and is continuously explored as a viable approach to target malignant tumors. The general architecture of PDCs consists of three building blocks: the tumor-homing peptide, the cytotoxic agent and the biodegradable connecting linker. The aim of the current review is to provide a spherical perspective on the basic principles governing PDCs, as also the methodology to construct them. We aim to offer basic and integral knowledge on the rational design towards the construction of PDCs through analyzing each building block, as also to highlight the overall progress of this rapidly growing field. Therefore, we focus on several intriguing examples from the recent literature, including important PDCs that have progressed to phase III clinical trials. Last, we address possible difficulties that may emerge during the synthesis of PDCs, as also report ways to overcome them.
@article{Vrettos2018, abstract = {Cancer is the second leading cause of death affecting nearly one in two people, and the appearance of new cases is projected to rise by >70% by 2030. To effectively combat the menace of cancer, a variety of strategies have been exploited. Among them, the development of peptide–drug conjugates (PDCs) is considered as an inextricable part of this armamentarium and is continuously explored as a viable approach to target malignant tumors. The general architecture of PDCs consists of three building blocks: the tumor-homing peptide, the cytotoxic agent and the biodegradable connecting linker. The aim of the current review is to provide a spherical perspective on the basic principles governing PDCs, as also the methodology to construct them. We aim to offer basic and integral knowledge on the rational design towards the construction of PDCs through analyzing each building block, as also to highlight the overall progress of this rapidly growing field. Therefore, we focus on several intriguing examples from the recent literature, including important PDCs that have progressed to phase III clinical trials. Last, we address possible difficulties that may emerge during the synthesis of PDCs, as also report ways to overcome them.}, author = {E.I. Vrettos and G. Mező and A.G. Tzakos}, doi = {10.3762/BJOC.14.80}, journal = {Beilstein Journal of Organic Chemistry}, pages = {930-954}, title = {On the design principles of peptide–drug conjugates for targeted drug delivery to the malignant tumor site}, volume = {14}, year = {2018}, }
2017
- Moschonas, I. C., T. F. Kellici, T. Mavromoustakos, P. Stathopoulos, V. Tsikaris, V. Magafa, A. G. Tzakos, and A. D. Tselepis. “Molecular requirements involving the human platelet protease-activated receptor-4 mechanism of activation by peptide analogues of its tethered-ligand.” Platelets 28 (2017): 812-821. doi:10.1080/09537104.2017.1282607
[BibTeX] [Abstract]
Thrombin is the most potent agonist of human platelets and its effects are primarily mediated through the protease-activated receptors (PARs)-1 and -4. Although PAR-1 has higher affinity for thrombin than PAR-4, both receptors contribute to thrombin-mediated actions on platelets. Recently, a potent and selective PAR-1 antagonist (vorapaxar) was approved for clinical use in selected patients. In contrast, despite the fact that several PAR-4 antagonists have been developed, few of them have been tested in clinical trials. The aim of the present study was to elucidate the molecular requirements involving the PAR-4 mechanism of activation by peptide analogues of its tethered-ligand. Eight synthetic PAR-4 tethered-ligand peptide analogues were synthesized and studied for their agonistic/antagonistic potency and selectivity toward human washed platelet aggregation, using light transmittance aggregometry. In addition, in silico studies were conducted to describe the receptor–peptide interactions that are developed following PAR-4 exposure to the above analogues. To provide a first structure-activity relationship rationale on the bioactivity profiles recorded for the studied analogues, molecular docking was applied in a homology model of PAR-4, derived using the crystal structure of PAR-1. The following peptide analogues were synthesized: AYPGKF-NH2 (1), GYPGKF-NH2 (2), Ac-AYPGKF-NH2 (3), trans-cinnamoyl-AYPGKF-NH2 (4), YPGKF-NH2 (5), Ac-YPGKF-NH2 (6), trans-cinnamoyl-YPGKF-NH2 (7), and caffeoyl-YPGKF-NH2 (8). Peptide (1) is a selective PAR-4 agonist inducing platelet aggregation with an IC50 value of 26.2 μM. Substitution of Ala-1 with Gly-1 resulted in peptide (2), which significantly reduces the agonistic potency of peptide (1) by 25-fold. Importantly, substitution of Ala-1 with trans-cinnamoyl-1 resulted in peptide (7), which completely abolishes the agonistic activity of peptide (1) and renders it with a potent antagonistic activity toward peptide (1)-induced platelet aggregation. All other peptides tested were inactive. Tyr-2, residue, along with its neighboring environment was a key determinant in the PAR-4 recognition mode. When the neighboring residues to Tyr-2 provided an optimum spatial ability for the ligand to enter into the binding site of the transmembrane receptor, a biological response was propagated. These results were compared with the predicted binding poses of small molecule antagonists of PAR-4, denoted as YD-3, ML-354, and BMS-986120. π–π stacking interaction with Tyr-183 appears to be critical and common for both small molecules antagonists and the peptide trans-cinnamoyl-YPGKF-NH2. Conclusively, the lipophilicity, size, and aromatic nature of the residue preceding Tyr-2 are determining factors on whether a human platelet PAR-4 tethered-ligand peptide analogue will exert an agonistic or antagonistic activity.
@article{Moschonas2017, abstract = {Thrombin is the most potent agonist of human platelets and its effects are primarily mediated through the protease-activated receptors (PARs)-1 and -4. Although PAR-1 has higher affinity for thrombin than PAR-4, both receptors contribute to thrombin-mediated actions on platelets. Recently, a potent and selective PAR-1 antagonist (vorapaxar) was approved for clinical use in selected patients. In contrast, despite the fact that several PAR-4 antagonists have been developed, few of them have been tested in clinical trials. The aim of the present study was to elucidate the molecular requirements involving the PAR-4 mechanism of activation by peptide analogues of its tethered-ligand. Eight synthetic PAR-4 tethered-ligand peptide analogues were synthesized and studied for their agonistic/antagonistic potency and selectivity toward human washed platelet aggregation, using light transmittance aggregometry. In addition, in silico studies were conducted to describe the receptor–peptide interactions that are developed following PAR-4 exposure to the above analogues. To provide a first structure-activity relationship rationale on the bioactivity profiles recorded for the studied analogues, molecular docking was applied in a homology model of PAR-4, derived using the crystal structure of PAR-1. The following peptide analogues were synthesized: AYPGKF-NH2 (1), GYPGKF-NH2 (2), Ac-AYPGKF-NH2 (3), trans-cinnamoyl-AYPGKF-NH2 (4), YPGKF-NH2 (5), Ac-YPGKF-NH2 (6), trans-cinnamoyl-YPGKF-NH2 (7), and caffeoyl-YPGKF-NH2 (8). Peptide (1) is a selective PAR-4 agonist inducing platelet aggregation with an IC50 value of 26.2 μM. Substitution of Ala-1 with Gly-1 resulted in peptide (2), which significantly reduces the agonistic potency of peptide (1) by 25-fold. Importantly, substitution of Ala-1 with trans-cinnamoyl-1 resulted in peptide (7), which completely abolishes the agonistic activity of peptide (1) and renders it with a potent antagonistic activity toward peptide (1)-induced platelet aggregation. All other peptides tested were inactive. Tyr-2, residue, along with its neighboring environment was a key determinant in the PAR-4 recognition mode. When the neighboring residues to Tyr-2 provided an optimum spatial ability for the ligand to enter into the binding site of the transmembrane receptor, a biological response was propagated. These results were compared with the predicted binding poses of small molecule antagonists of PAR-4, denoted as YD-3, ML-354, and BMS-986120. π–π stacking interaction with Tyr-183 appears to be critical and common for both small molecules antagonists and the peptide trans-cinnamoyl-YPGKF-NH2. Conclusively, the lipophilicity, size, and aromatic nature of the residue preceding Tyr-2 are determining factors on whether a human platelet PAR-4 tethered-ligand peptide analogue will exert an agonistic or antagonistic activity.}, author = {I.C. Moschonas and T.F. Kellici and T. Mavromoustakos and P. Stathopoulos and V. Tsikaris and V. Magafa and A.G. Tzakos and A.D. Tselepis}, doi = {10.1080/09537104.2017.1282607}, issue = {8}, journal = {Platelets}, pages = {812-821}, title = {Molecular requirements involving the human platelet protease-activated receptor-4 mechanism of activation by peptide analogues of its tethered-ligand}, volume = {28}, year = {2017}, } - Vrettos, E. I., N. Sayyad, E. M. Mavrogiannaki, E. Stylos, A. D. Kostagianni, S. Papas, T. Mavromoustakos, V. Theodorou, and A. G. Tzakos. “Unveiling and tackling guanidinium peptide coupling reagent side reactions towards the development of peptide-drug conjugates.” Rsc advances 7 (2017): 50519-50526. doi:10.1039/c7ra06655d
[BibTeX] [Abstract]
Peptide coupling reagents and especially uronium/guanidinium salts have been extensively utilized in solid-phase peptide synthesis. However, the impact of these reagents in solution phase synthesis, normally used in the formation of peptide-drug conjugates (PDCs), has not been fully explored. Herein, we identified that when guanidinium salts are used in classical peptide coupling conditions, besides leading to the formation of amide bonds, a uronium derivative can also be installed on specific amino acid scaffolds. The formation of this side product depends on the reaction conditions, as also on the nucleophilicity of the susceptible groups. Conditions to avoid this side product formation and a putative reaction mechanism describing its formation are reported.
@article{Vrettos2017, abstract = {Peptide coupling reagents and especially uronium/guanidinium salts have been extensively utilized in solid-phase peptide synthesis. However, the impact of these reagents in solution phase synthesis, normally used in the formation of peptide-drug conjugates (PDCs), has not been fully explored. Herein, we identified that when guanidinium salts are used in classical peptide coupling conditions, besides leading to the formation of amide bonds, a uronium derivative can also be installed on specific amino acid scaffolds. The formation of this side product depends on the reaction conditions, as also on the nucleophilicity of the susceptible groups. Conditions to avoid this side product formation and a putative reaction mechanism describing its formation are reported.}, author = {E.I. Vrettos and N. Sayyad and E.M. Mavrogiannaki and E. Stylos and A.D. Kostagianni and S. Papas and T. Mavromoustakos and V. Theodorou and A.G. Tzakos}, doi = {10.1039/c7ra06655d}, issue = {80}, journal = {RSC Advances}, pages = {50519-50526}, title = {Unveiling and tackling guanidinium peptide coupling reagent side reactions towards the development of peptide-drug conjugates}, volume = {7}, year = {2017}, } - Kellici, T. F., M. V. Chatziathanasiadou, M. -S. Lee, N. Sayyad, E. G. Geromichalou, E. I. Vrettos, A. D. Tsiailanis, S. -W. Chi, G. D. Geromichalos, T. Mavromoustakos, T. Mavromoustakos, and A. G. Tzakos. “Rational design and structure-activity relationship studies of quercetin-amino acid hybrids targeting the anti-apoptotic protein bcl-xl.” Organic and biomolecular chemistry 15 (2017): 7956-7976. doi:10.1039/c7ob02045g
[BibTeX] [Abstract]
Anti-apoptotic proteins, like the Bcl-2 family proteins, present an important therapeutic cancer drug target. Their activity is orchestrated through neutralization upon interaction of pro-apoptotic protein counterparts that leads to immortality of cancer cells. Therefore, generating compounds targeting these proteins is of immense therapeutic importance. Herein, Induced Fit Docking (IFD) and Molecular Dynamics (MD) simulations were performed to rationally design quercetin analogues that bind in the BH3 site of the Bcl-xL protein. IFD calculations determined their binding cavity while Molecular Mechanics Poisson Boltzmann Surface Area (MM-PBSA) and Molecular Mechanics Generalised Born Surface Area (MM-GBSA) calculations provided an insight into the binding enthalpies of the analogues. The quercetin analogues were synthesized and their binding to Bcl-xL was verified with fluorescence spectroscopy. The binding affinity and the thermodynamic parameters between Bcl-xL and quercetin-glutamic acid were estimated through Isothermal Titration Calorimetry. 2D 1H-15N HSQC NMR chemical shift perturbation mapping was used to chart the binding site of the quercetin analogues in the Bcl-xL that overlapped with the predicted poses generated by both IFD and MD calculations. Furthermore, evaluation of the four conjugates against the prostate DU-145 and PC-3 cancer cell lines, revealed quercetin-glutamic acid and quercetin-alanine as the most potent conjugates bearing the higher cytostatic activity. This pinpoints that the chemical space of natural products can be tailored to exploit new hits for difficult tractable targets such as protein-protein interactions.
@article{Kellici2017, abstract = {Anti-apoptotic proteins, like the Bcl-2 family proteins, present an important therapeutic cancer drug target. Their activity is orchestrated through neutralization upon interaction of pro-apoptotic protein counterparts that leads to immortality of cancer cells. Therefore, generating compounds targeting these proteins is of immense therapeutic importance. Herein, Induced Fit Docking (IFD) and Molecular Dynamics (MD) simulations were performed to rationally design quercetin analogues that bind in the BH3 site of the Bcl-xL protein. IFD calculations determined their binding cavity while Molecular Mechanics Poisson Boltzmann Surface Area (MM-PBSA) and Molecular Mechanics Generalised Born Surface Area (MM-GBSA) calculations provided an insight into the binding enthalpies of the analogues. The quercetin analogues were synthesized and their binding to Bcl-xL was verified with fluorescence spectroscopy. The binding affinity and the thermodynamic parameters between Bcl-xL and quercetin-glutamic acid were estimated through Isothermal Titration Calorimetry. 2D 1H-15N HSQC NMR chemical shift perturbation mapping was used to chart the binding site of the quercetin analogues in the Bcl-xL that overlapped with the predicted poses generated by both IFD and MD calculations. Furthermore, evaluation of the four conjugates against the prostate DU-145 and PC-3 cancer cell lines, revealed quercetin-glutamic acid and quercetin-alanine as the most potent conjugates bearing the higher cytostatic activity. This pinpoints that the chemical space of natural products can be tailored to exploit new hits for difficult tractable targets such as protein-protein interactions.}, author = {T.F. Kellici and M.V. Chatziathanasiadou and M.-S. Lee and N. Sayyad and E.G. Geromichalou and E.I. Vrettos and A.D. Tsiailanis and S.-W. Chi and G.D. Geromichalos and T. Mavromoustakos and T. Mavromoustakos and A.G. Tzakos}, doi = {10.1039/c7ob02045g}, issue = {37}, journal = {Organic and Biomolecular Chemistry}, pages = {7956-7976}, title = {Rational design and structure-activity relationship studies of quercetin-amino acid hybrids targeting the anti-apoptotic protein Bcl-xL}, volume = {15}, year = {2017}, } - Stylos, E., M. V. Chatziathanasiadou, A. Tsiailanis, T. F. Kellici, M. Tsoumani, A. D. Kostagianni, M. Deligianni, A. D. Tselepis, and A. G. Tzakos. “Tailoring naringenin conjugates with amplified and triple antiplatelet activity profile: rational design, synthesis, human plasma stability and in vitro evaluation.” Biochimica et biophysica acta – general subjects 1861 (2017): 2609-2618. doi:10.1016/j.bbagen.2017.08.018
[BibTeX] [Abstract]
Background The current standard-of-care antiplatelet therapy in cardiovascular disease patients is consisted of cyclooxygenase-1 (COX-1) inhibitor aspirin, along with a platelet receptor P2Y12 antagonist. Recently, the triple antiplatelet therapy with aspirin, a P2Y12 receptor antagonist and a protease activated receptor-1 (PAR-1) antagonist, has been suggested for the secondary prevention of atherothrombotic events, however presented an increased risk of bleeding. Therefore, the quest for novel antiplatelet agents simultaneously targeting the three pathways with improved efficacy/safety profile is of immense importance. Flavonoids as pre-validated ligands for numerous targets could serve as scaffolds targeting the three platelet activation pathways. Methods Computational methods, Ultra High Performance Liquid Chromatography-Tandem Mass Spectrometry (UHPLC-MS/MS) plasma stability and in vitro platelet aggregation experiments were used to establish the antiplatelet activity of the flavonoid naringenin and its conjugates. Results In silico studies indicated that naringenin could bear a potent triple antiplatelet activity by inhibiting different platelet aggregation mechanisms. However, we found that in human platelets naringenin has diminished activity. We rationally designed and synthesized different naringenin conjugates aiming to amplify the antiplatelet activity of the parent compound. UHPLC-MS/MS revealed a slow degradation rate for a docosahexaenoic acid (DHA) – naringenin conjugate in human plasma. The antiplatelet profile of the new analogues was evaluated against in vitro platelet aggregation induced by several platelet agonists. Conclusions The DHA – naringenin hybrid presented triple antiplatelet activity simultaneously targeting PAR-1, P2Y12 and COX-1 platelet activation pathways. General significance Natural products could offer a rich source for novel bioactives as a powerful alternative to the current combinatorial use of three different antiplatelet drugs.
@article{Stylos2017, abstract = {Background The current standard-of-care antiplatelet therapy in cardiovascular disease patients is consisted of cyclooxygenase-1 (COX-1) inhibitor aspirin, along with a platelet receptor P2Y12 antagonist. Recently, the triple antiplatelet therapy with aspirin, a P2Y12 receptor antagonist and a protease activated receptor-1 (PAR-1) antagonist, has been suggested for the secondary prevention of atherothrombotic events, however presented an increased risk of bleeding. Therefore, the quest for novel antiplatelet agents simultaneously targeting the three pathways with improved efficacy/safety profile is of immense importance. Flavonoids as pre-validated ligands for numerous targets could serve as scaffolds targeting the three platelet activation pathways. Methods Computational methods, Ultra High Performance Liquid Chromatography-Tandem Mass Spectrometry (UHPLC-MS/MS) plasma stability and in vitro platelet aggregation experiments were used to establish the antiplatelet activity of the flavonoid naringenin and its conjugates. Results In silico studies indicated that naringenin could bear a potent triple antiplatelet activity by inhibiting different platelet aggregation mechanisms. However, we found that in human platelets naringenin has diminished activity. We rationally designed and synthesized different naringenin conjugates aiming to amplify the antiplatelet activity of the parent compound. UHPLC-MS/MS revealed a slow degradation rate for a docosahexaenoic acid (DHA) – naringenin conjugate in human plasma. The antiplatelet profile of the new analogues was evaluated against in vitro platelet aggregation induced by several platelet agonists. Conclusions The DHA – naringenin hybrid presented triple antiplatelet activity simultaneously targeting PAR-1, P2Y12 and COX-1 platelet activation pathways. General significance Natural products could offer a rich source for novel bioactives as a powerful alternative to the current combinatorial use of three different antiplatelet drugs.}, author = {E. Stylos and M.V. Chatziathanasiadou and A. Tsiailanis and T.F. Kellici and M. Tsoumani and A.D. Kostagianni and M. Deligianni and A.D. Tselepis and A.G. Tzakos}, doi = {10.1016/j.bbagen.2017.08.018}, issue = {11}, journal = {Biochimica et Biophysica Acta - General Subjects}, pages = {2609-2618}, title = {Tailoring naringenin conjugates with amplified and triple antiplatelet activity profile: Rational design, synthesis, human plasma stability and in vitro evaluation}, volume = {1861}, year = {2017}, } - Liossi, A. S., D. Ntountaniotis, T. F. Kellici, M. V. Chatziathanasiadou, G. Megariotis, M. Mania, J. Becker-Baldus, M. Kriechbaum, A. Krajnc, E. Christodoulou, A. G. Tzakos, and T. Mavromoustakos. “Exploring the interactions of irbesartan and irbesartan–2-hydroxypropyl-β-cyclodextrin complex with model membranes.” Biochimica et biophysica acta – biomembranes 1859 (2017): 1089-1098. doi:10.1016/j.bbamem.2017.03.003
[BibTeX] [Abstract]
The interactions of irbesartan (IRB) and irbesartan–2-hydroxypropyl-β-cyclodextrin (HP-β-CD) complex with dipalmitoyl phosphatidylcholine (DPPC) bilayers have been explored utilizing an array of biophysical techniques ranging from differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS), ESI mass spectrometry (ESI-MS) and solid state nuclear magnetic resonance (ssNMR). Molecular dynamics (MD) calculations have been also conducted to complement the experimental results. Irbesartan was found to be embedded in the lipid membrane core and to affect the phase transition properties of the DPPC bilayers. SAXS studies revealed that irbesartan alone does not display perfect solvation since some coexisting irbesartan crystallites are present. In its complexed form IRB gets fully solvated in the membranes showing that encapsulation of IRB in HP-β-CD may have beneficial effects in the ADME properties of this drug. MD experiments revealed the topological and orientational integration of irbesartan into the phospholipid bilayer being placed at about 1 nm from the membrane centre.
@article{Liossi2017, abstract = {The interactions of irbesartan (IRB) and irbesartan–2-hydroxypropyl-β-cyclodextrin (HP-β-CD) complex with dipalmitoyl phosphatidylcholine (DPPC) bilayers have been explored utilizing an array of biophysical techniques ranging from differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS), ESI mass spectrometry (ESI-MS) and solid state nuclear magnetic resonance (ssNMR). Molecular dynamics (MD) calculations have been also conducted to complement the experimental results. Irbesartan was found to be embedded in the lipid membrane core and to affect the phase transition properties of the DPPC bilayers. SAXS studies revealed that irbesartan alone does not display perfect solvation since some coexisting irbesartan crystallites are present. In its complexed form IRB gets fully solvated in the membranes showing that encapsulation of IRB in HP-β-CD may have beneficial effects in the ADME properties of this drug. MD experiments revealed the topological and orientational integration of irbesartan into the phospholipid bilayer being placed at about 1 nm from the membrane centre.}, author = {A.S. Liossi and D. Ntountaniotis and T.F. Kellici and M.V. Chatziathanasiadou and G. Megariotis and M. Mania and J. Becker-Baldus and M. Kriechbaum and A. Krajnc and E. Christodoulou and A.G. Tzakos and T. Mavromoustakos}, doi = {10.1016/j.bbamem.2017.03.003}, issue = {6}, journal = {Biochimica et Biophysica Acta - Biomembranes}, pages = {1089-1098}, title = {Exploring the interactions of irbesartan and irbesartan–2-hydroxypropyl-β-cyclodextrin complex with model membranes}, volume = {1859}, year = {2017}, } - Stylos, E., M. V. Chatziathanasiadou, A. Syriopoulou, and A. G. Tzakos. “Liquid chromatography coupled with tandem mass spectrometry (lc–ms/ms) based bioavailability determination of the major classes of phytochemicals.” Journal of chromatography b: analytical technologies in the biomedical and life sciences 1047 (2017): 15-38. doi:10.1016/j.jchromb.2016.12.022
[BibTeX] [Abstract]
Natural products derived from plants have served as an inexhausted source for drug discovery and drug development. They have been evolutionary amplified with drug-like properties and have already illustrated immense therapeutic potential over an array of different diseases. However, their incorporation in the drug discovery pipeline has been diminished the last two decades. This was probably due to barriers related to their inherent difficulties to be integrated in high-throughput screening assays as also their largely unexplored bioavailability. Analytical procedures have come into the spotlight, a result of the continuous development of the instrumentation’s capabilities as far as detection and separation is concerned. Integral part of this technological evolution is LC–MS instrumentation and its extended use for the determination of various compounds. The fact that it provides extra sensitivity, specificity and good separation in complex samples, makes LC–MS/MS the ultimate tool in the determination of many types of chemical compounds, such as phytochemicals. Herein, we focus on the achievements of the last five years in quantitative analysis of the major classes of phytochemicals (flavonoids, alkaloids, terpenes, glycosides and saponins) in plasma, through LC–MS/MS, as also their bioavailability.
@article{Stylos2017, abstract = {Natural products derived from plants have served as an inexhausted source for drug discovery and drug development. They have been evolutionary amplified with drug-like properties and have already illustrated immense therapeutic potential over an array of different diseases. However, their incorporation in the drug discovery pipeline has been diminished the last two decades. This was probably due to barriers related to their inherent difficulties to be integrated in high-throughput screening assays as also their largely unexplored bioavailability. Analytical procedures have come into the spotlight, a result of the continuous development of the instrumentation's capabilities as far as detection and separation is concerned. Integral part of this technological evolution is LC–MS instrumentation and its extended use for the determination of various compounds. The fact that it provides extra sensitivity, specificity and good separation in complex samples, makes LC–MS/MS the ultimate tool in the determination of many types of chemical compounds, such as phytochemicals. Herein, we focus on the achievements of the last five years in quantitative analysis of the major classes of phytochemicals (flavonoids, alkaloids, terpenes, glycosides and saponins) in plasma, through LC–MS/MS, as also their bioavailability.}, author = {E. Stylos and M.V. Chatziathanasiadou and A. Syriopoulou and A.G. Tzakos}, doi = {10.1016/j.jchromb.2016.12.022}, journal = {Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences}, pages = {15-38}, title = {Liquid chromatography coupled with tandem mass spectrometry (LC–MS/MS) based bioavailability determination of the major classes of phytochemicals}, volume = {1047}, year = {2017}, } - Charisiadis, P., V. G. Kontogianni, C. G. Tsiafoulis, A. G. Tzakos, and I. P. Gerothanassis. “Determination of polyphenolic phytochemicals using highly deshielded –oh 1h-nmr signals.” Phytochemical analysis 28 (2017): 159-170. doi:10.1002/pca.2656
[BibTeX] [Abstract]
Introduction: Quantitative analysis of plant extracts is a tedious and time consuming process requiring chromatographic techniques and/or the use of specilised hyphenated spectroscopic methods. Thus, investigation of a rapid method capable for the determination of bioactive constituents is of major importance. Objective: To employ high resolution 1H-NMR spectroscopy of the –OH spectral region, as a rapid method for the simultaneous determination and quantification of polyphenolic phytochemicals in crude oregano and olive leaf extracts without any prior isolation step. Methodology: A critical overview of experimental parameters that influence the resolution of the –OH groups is provided with emphasis on the nature of the extraction solvent, effects of dilution, pH, temperature and nature of the NMR solvent. The compounds were assigned with the use of 1H-NMR, 2D 1H-13C HMBC NMR and spiking experiments with model compounds. Results: The method was applied for the NMR analysis of natural product extracts and the results were found to be in good agreement with those obtained with the use of the time consuming HPLC-DAD, preparative LC and LC-SPE-NMR. Conclusion: The method is rapid, selective, with very good analytical performance characteristics, which support the efficiency of the suggested methodology. Copyright © 2016 John Wiley & Sons, Ltd.
@article{Charisiadis2017, abstract = {Introduction: Quantitative analysis of plant extracts is a tedious and time consuming process requiring chromatographic techniques and/or the use of specilised hyphenated spectroscopic methods. Thus, investigation of a rapid method capable for the determination of bioactive constituents is of major importance. Objective: To employ high resolution 1H-NMR spectroscopy of the –OH spectral region, as a rapid method for the simultaneous determination and quantification of polyphenolic phytochemicals in crude oregano and olive leaf extracts without any prior isolation step. Methodology: A critical overview of experimental parameters that influence the resolution of the –OH groups is provided with emphasis on the nature of the extraction solvent, effects of dilution, pH, temperature and nature of the NMR solvent. The compounds were assigned with the use of 1H-NMR, 2D 1H-13C HMBC NMR and spiking experiments with model compounds. Results: The method was applied for the NMR analysis of natural product extracts and the results were found to be in good agreement with those obtained with the use of the time consuming HPLC-DAD, preparative LC and LC-SPE-NMR. Conclusion: The method is rapid, selective, with very good analytical performance characteristics, which support the efficiency of the suggested methodology. Copyright © 2016 John Wiley & Sons, Ltd.}, author = {P. Charisiadis and V.G. Kontogianni and C.G. Tsiafoulis and A.G. Tzakos and I.P. Gerothanassis}, doi = {10.1002/pca.2656}, issue = {3}, journal = {Phytochemical Analysis}, pages = {159-170}, title = {Determination of Polyphenolic Phytochemicals using Highly Deshielded –OH 1H-NMR Signals}, volume = {28}, year = {2017}, }
2016
- Kellici, T. F., M. V. Chatziathanasiadou, D. Diamantis, A. V. Chatzikonstantinou, I. Andreadelis, E. Christodoulou, G. Valsami, T. Mavromoustakos, and A. G. Tzakos. “Mapping the interactions and bioactivity of quercetin—(2-hydroxypropyl)-β-cyclodextrin complex.” International journal of pharmaceutics 511 (2016): 303-311. doi:10.1016/j.ijpharm.2016.07.008
[BibTeX] [Abstract]
Natural products have served as a rich source for drug discovery and development. In the last decade their fruitful integration in the drug discovery pipeline declined due to their reduced bioavailability, mainly attributed to their poor aqueous solubility. We synthesized a quercetin (QUE)—(2-hydroxypropyl)-β-cyclodextrin (HP-β-CD) complex that enabled amplification of its solubility and in the same time retained its bioactivity in T24 human bladder cancer cell line. The stability of the complex and the molecular basis of the interactions developed in this host-guest complex were assayed by incorporating an array of analytical techniques and Molecular Dynamics (MD) experiments. 2D DOSY NMR experiment revealed that the diffusion coefficient of free HP-β-CD was 3.55 × 10−10 m2s−1 while that of QUE–HP-β-CD inclusion complex 3.09 × 10−10 m2s−1, indicating the formation of a complex. Solid and liquid high resolution NMR spectroscopy data showed that the most pronounced differences in chemical shifts at carbons and protons correspondingly during complexation occur in the aromatic ring Α (bearing the two phenolic hydroxyl groups meta to each other). The chemical shift differences in the aromatic ring Β (bearing the two phenolic hydroxyl groups ortho to each other) were less pronounced. The MD results confirmed the experimental data.
@article{Kellici2016, abstract = {Natural products have served as a rich source for drug discovery and development. In the last decade their fruitful integration in the drug discovery pipeline declined due to their reduced bioavailability, mainly attributed to their poor aqueous solubility. We synthesized a quercetin (QUE)—(2-hydroxypropyl)-β-cyclodextrin (HP-β-CD) complex that enabled amplification of its solubility and in the same time retained its bioactivity in T24 human bladder cancer cell line. The stability of the complex and the molecular basis of the interactions developed in this host-guest complex were assayed by incorporating an array of analytical techniques and Molecular Dynamics (MD) experiments. 2D DOSY NMR experiment revealed that the diffusion coefficient of free HP-β-CD was 3.55 × 10−10 m2s−1 while that of QUE–HP-β-CD inclusion complex 3.09 × 10−10 m2s−1, indicating the formation of a complex. Solid and liquid high resolution NMR spectroscopy data showed that the most pronounced differences in chemical shifts at carbons and protons correspondingly during complexation occur in the aromatic ring Α (bearing the two phenolic hydroxyl groups meta to each other). The chemical shift differences in the aromatic ring Β (bearing the two phenolic hydroxyl groups ortho to each other) were less pronounced. The MD results confirmed the experimental data.}, author = {T.F. Kellici and M.V. Chatziathanasiadou and D. Diamantis and A.V. Chatzikonstantinou and I. Andreadelis and E. Christodoulou and G. Valsami and T. Mavromoustakos and A.G. Tzakos}, doi = {10.1016/j.ijpharm.2016.07.008}, issue = {1}, journal = {International Journal of Pharmaceutics}, pages = {303-311}, title = {Mapping the interactions and bioactivity of quercetin—(2-hydroxypropyl)-β-cyclodextrin complex}, volume = {511}, year = {2016}, } - Argyros, O., T. Karampelas, X. Asvos, A. Varela, N. Sayyad, A. Papakyriakou, C. H. Davos, A. G. Tzakos, D. Fokas, and C. Tamvakopoulos. “Peptide-drug conjugate gnrh-sunitinib targets angiogenesis selectively at the site of action to inhibit tumor growth.” Cancer research 76 (2016): 1181-1192. doi:10.1158/0008-5472.CAN-15-2138
[BibTeX] [Abstract]
The potential to heighten the efficacy of antiangiogenic agents was explored in this study based on active targeting of tumor cells overexpressing the gonadotropin-releasing hormone receptor (GnRH-R). The rational design pursued focused on five analogues of a clinically established antiangiogenic compound (sunitinib), from which a lead candidate (SAN1) was conjugated to the targeting peptide [D-Lys6]-GnRH, generating SAN1GSC. Conjugation of SAN1 did not disrupt any of its antiangiogenic or cytotoxic properties in GnRH-R-expressing prostate and breast tumor cells. Daily SAN1GSC treatments in mouse xenograft models of castration-resistant prostate cancer resulted in significant tumor growth delay compared with equimolar SAN1 or sunitinib alone. This efficacy correlated with inhibited phosphor-ylation of AKT and S6, together with reduced Ki-67 and CD31 expression. The superior efficacy of the peptide-drug conjugate was also attributed to the finding that higher amounts of SAN1 were delivered to the tumor site (∼4-fold) following dosing of SAN1GSC compared with equimolar amounts of nonconjugated SAN1. Importantly, treatment with SAN1GSC was associated with minimal hematotoxicity and cardiotoxicity based on measurements of the left ventricular systolic function in treated mice. Our results offer preclinical proof-of-concept for SAN1GSC as a novel molecule that selectively reaches the tumor site and downregulates angiogenesis with negligible cardiotoxicity, thus encouraging its further clinical development and evaluation.
@article{Argyros2016, abstract = {The potential to heighten the efficacy of antiangiogenic agents was explored in this study based on active targeting of tumor cells overexpressing the gonadotropin-releasing hormone receptor (GnRH-R). The rational design pursued focused on five analogues of a clinically established antiangiogenic compound (sunitinib), from which a lead candidate (SAN1) was conjugated to the targeting peptide [D-Lys6]-GnRH, generating SAN1GSC. Conjugation of SAN1 did not disrupt any of its antiangiogenic or cytotoxic properties in GnRH-R-expressing prostate and breast tumor cells. Daily SAN1GSC treatments in mouse xenograft models of castration-resistant prostate cancer resulted in significant tumor growth delay compared with equimolar SAN1 or sunitinib alone. This efficacy correlated with inhibited phosphor-ylation of AKT and S6, together with reduced Ki-67 and CD31 expression. The superior efficacy of the peptide-drug conjugate was also attributed to the finding that higher amounts of SAN1 were delivered to the tumor site (∼4-fold) following dosing of SAN1GSC compared with equimolar amounts of nonconjugated SAN1. Importantly, treatment with SAN1GSC was associated with minimal hematotoxicity and cardiotoxicity based on measurements of the left ventricular systolic function in treated mice. Our results offer preclinical proof-of-concept for SAN1GSC as a novel molecule that selectively reaches the tumor site and downregulates angiogenesis with negligible cardiotoxicity, thus encouraging its further clinical development and evaluation.}, author = {O. Argyros and T. Karampelas and X. Asvos and A. Varela and N. Sayyad and A. Papakyriakou and C.H. Davos and A.G. Tzakos and D. Fokas and C. Tamvakopoulos}, doi = {10.1158/0008-5472.CAN-15-2138}, issue = {5}, journal = {Cancer Research}, pages = {1181-1192}, title = {Peptide-Drug conjugate gnrh-sunitinib targets angiogenesis selectively at the site of action to inhibit tumor growth}, volume = {76}, year = {2016}, } - Siskos, M. G., M. I. Choudhary, A. G. Tzakos, and I. P. Gerothanassis. “1h νμr chemical shift assignment, structure and conformational elucidation of hypericin with the use of dft calculations – the challenge of accurate positions of labile hydrogens.” Tetrahedron 72 (2016): 8287-8293. doi:10.1016/j.tet.2016.10.072
[BibTeX] [Abstract]
Hypericin is one of the principal active constituents of Hypericium (Saint John’s wort). We present in this paper: (i) chemical shift assignment of the neutral and ionic form of hypericin based on DFT1H NMR calculations, and conflicting literature experimental OH1H NMR chemical shifts are critically evaluated; (ii) investigation of the cooperative nature of intra- and intermolecular hydrogen bonding of the bay OH groups in the neutral form of hypericin in acetone and DMSO; (iii) demonstration of a very strong intramolecular hydrogen bonding of the deprotonated bay OH…O-moiety in DMSO and (iv) excellent linear correlation between experimental and computed1H chemicals shifts for a variety of basis sets. Comparison of the literature X-ray structures with those obtained with DFT calculations clearly demonstrates the advantages of computation in investigating resonance assignments, ionization state, accurate labile hydrogen positions, and structural and conformational properties of natural products at an atomic level.
@article{Siskos2016, abstract = {Hypericin is one of the principal active constituents of Hypericium (Saint John's wort). We present in this paper: (i) chemical shift assignment of the neutral and ionic form of hypericin based on DFT1H NMR calculations, and conflicting literature experimental OH1H NMR chemical shifts are critically evaluated; (ii) investigation of the cooperative nature of intra- and intermolecular hydrogen bonding of the bay OH groups in the neutral form of hypericin in acetone and DMSO; (iii) demonstration of a very strong intramolecular hydrogen bonding of the deprotonated bay OH…O-moiety in DMSO and (iv) excellent linear correlation between experimental and computed1H chemicals shifts for a variety of basis sets. Comparison of the literature X-ray structures with those obtained with DFT calculations clearly demonstrates the advantages of computation in investigating resonance assignments, ionization state, accurate labile hydrogen positions, and structural and conformational properties of natural products at an atomic level.}, author = {M.G. Siskos and M.I. Choudhary and A.G. Tzakos and I.P. Gerothanassis}, doi = {10.1016/j.tet.2016.10.072}, issue = {50}, journal = {Tetrahedron}, pages = {8287-8293}, title = {1H ΝΜR chemical shift assignment, structure and conformational elucidation of hypericin with the use of DFT calculations – The challenge of accurate positions of labile hydrogens}, volume = {72}, year = {2016}, } - Sakka, M., G. Tzortzis, M. D. Mantzaris, N. Bekas, T. F. Kellici, A. Likas, D. Galaris, I. P. Gerothanassis, and A. G. Tzakos. “Press: protein s-sulfenylation server.” Bioinformatics 32 (2016): 2710-2712. doi:10.1093/bioinformatics/btw301
[BibTeX] [Abstract]
Motivation: Transient S-sulfenylation of cysteine thiols mediated by reactive oxygen species plays a critical role in pathology, physiology and cell signaling. Therefore, discovery of new S-sulfenylated sites in proteins is of great importance towards understanding how protein function is regulated upon redox conditions. Results: We developed PRESS (PRotEin S-Sulfenylation) web server, a server which can effectively predict the cysteine thiols of a protein that could undergo S-sulfenylation under redox conditions. We envisage that this server will boost and facilitate the discovery of new and currently unknown functions of proteins triggered upon redox conditions, signal regulation and transduction, thus uncovering the role of S-sulfenylation in human health and disease. Availability and implementation: The PRESS web server is freely available at http://press-sulfenylation.cse.uoi.gr/.
@article{Sakka2016, abstract = {Motivation: Transient S-sulfenylation of cysteine thiols mediated by reactive oxygen species plays a critical role in pathology, physiology and cell signaling. Therefore, discovery of new S-sulfenylated sites in proteins is of great importance towards understanding how protein function is regulated upon redox conditions. Results: We developed PRESS (PRotEin S-Sulfenylation) web server, a server which can effectively predict the cysteine thiols of a protein that could undergo S-sulfenylation under redox conditions. We envisage that this server will boost and facilitate the discovery of new and currently unknown functions of proteins triggered upon redox conditions, signal regulation and transduction, thus uncovering the role of S-sulfenylation in human health and disease. Availability and implementation: The PRESS web server is freely available at http://press-sulfenylation.cse.uoi.gr/.}, author = {M. Sakka and G. Tzortzis and M.D. Mantzaris and N. Bekas and T.F. Kellici and A. Likas and D. Galaris and I.P. Gerothanassis and A.G. Tzakos}, doi = {10.1093/bioinformatics/btw301}, issue = {17}, journal = {Bioinformatics}, pages = {2710-2712}, title = {PRESS: PRotEin S-Sulfenylation server}, volume = {32}, year = {2016}, } - Vujicic, M., I. Nikolic, V. G. Kontogianni, T. Saksida, P. Charisiadis, B. Vasic, S. Stosic-Grujicic, I. P. Gerothanassis, A. G. Tzakos, and I. Stojanovic. “Ethyl acetate extract of origanum vulgare l. ssp. hirtum prevents streptozotocin-induced diabetes in c57bl/6 mice.” Journal of food science 81 (2016): H1846-H1853. doi:10.1111/1750-3841.13333
[BibTeX] [Abstract]
Type 1 diabetes (T1D) is an autoimmune disease that develops as a consequence of pancreatic β-cell death induced by proinflammatory mediators. Because Origanum vulgare L. ssp. hirtum (Greek oregano) contains antiinflammatory molecules, we hypothesized that it might be beneficial for the treatment of T1D. An ethyl acetate extract of oregano (EAO) was prepared from the leaves by a polar extraction method. Phytochemical composition was determined by liquid chromatography-UV diode array coupled to ion-trap mass spectrometry with electrospray ionization interface (LC/DAD/ESI-MS(n) ). In vitro immunomodulatory effect of EAO was estimated by measuring proliferation (MTT) or cytokine secretion (ELISA) from immune cells. Diabetes was induced by multiple low doses of streptozotocin (MLDS) in male C57BL/6 mice and EAO was administered intraperitoneally for 10 d. Determination of cellular composition (flow cytometry) and cytokine production (ELISA) was performed on 12th d after diabetes induction. EAO suppressed the function of both macrophages and lymphocytes in vitro. In vivo, EAO treatment significantly preserved pancreatic islets and reduced diabetes incidence in MLDS-challenged mice. Besides down-modulatory effect on macrophages, EAO reduced the number of total CD4(+) and activated CD4(+) CD25(+) T cells. Furthermore, EAO affected the number of T helper 1 (Th1) and T helper 17 (Th17) cells through downregulation of their key transcription factors T-bet and RORγT. Because EAO treatment protects mice from development of hyperglycemia by reducing proinflammatory macrophage/Th1/Th17 response, this plant extract could represent a basis for future diabetes therapy.
@article{Vujicic2016, abstract = {Type 1 diabetes (T1D) is an autoimmune disease that develops as a consequence of pancreatic β-cell death induced by proinflammatory mediators. Because Origanum vulgare L. ssp. hirtum (Greek oregano) contains antiinflammatory molecules, we hypothesized that it might be beneficial for the treatment of T1D. An ethyl acetate extract of oregano (EAO) was prepared from the leaves by a polar extraction method. Phytochemical composition was determined by liquid chromatography-UV diode array coupled to ion-trap mass spectrometry with electrospray ionization interface (LC/DAD/ESI-MS(n) ). In vitro immunomodulatory effect of EAO was estimated by measuring proliferation (MTT) or cytokine secretion (ELISA) from immune cells. Diabetes was induced by multiple low doses of streptozotocin (MLDS) in male C57BL/6 mice and EAO was administered intraperitoneally for 10 d. Determination of cellular composition (flow cytometry) and cytokine production (ELISA) was performed on 12th d after diabetes induction. EAO suppressed the function of both macrophages and lymphocytes in vitro. In vivo, EAO treatment significantly preserved pancreatic islets and reduced diabetes incidence in MLDS-challenged mice. Besides down-modulatory effect on macrophages, EAO reduced the number of total CD4(+) and activated CD4(+) CD25(+) T cells. Furthermore, EAO affected the number of T helper 1 (Th1) and T helper 17 (Th17) cells through downregulation of their key transcription factors T-bet and RORγT. Because EAO treatment protects mice from development of hyperglycemia by reducing proinflammatory macrophage/Th1/Th17 response, this plant extract could represent a basis for future diabetes therapy.}, author = {M. Vujicic and I. Nikolic and V.G. Kontogianni and T. Saksida and P. Charisiadis and B. Vasic and S. Stosic-Grujicic and I.P. Gerothanassis and A.G. Tzakos and I. Stojanovic}, doi = {10.1111/1750-3841.13333}, issue = {7}, journal = {Journal of food science}, pages = {H1846-H1853}, title = {Ethyl Acetate Extract of Origanum vulgare L. ssp. hirtum Prevents Streptozotocin-Induced Diabetes in C57BL/6 Mice}, volume = {81}, year = {2016}, } - Kellici, T. F., D. Ntountaniotis, E. Kritsi, M. Zervou, P. Zoumpoulakis, C. Potamitis, S. Durdagi, R. E. Salmas, G. Ergun, E. Gokdemir, A. G. Tzakos, and T. Mavromoustakos. “Leveraging nmr and x-ray data of the free ligands to build better drugs targeting angiotensin ii type 1 g-protein coupled receptor.” Current medicinal chemistry 23 (2016): 36-59. doi:10.2174/0929867323666151117122116
[BibTeX] [Abstract]
The angiotensin II type 1 receptor (AT1R) has been recently crystallized. A new era has emerged for the structure-based rational drug design and the synthesis of novel AT1R antagonists. In this critical review, the X-ray crystallographic data of commercially available AT1R antagonists in free form are analyzed and compared with the conformational analysis results obtained using a combination of NMR spectroscopy and Molecular Modeling. The same AT1R antagonists are docked and compared in terms of their interactions in their binding site using homology models and the crystallized AT1R receptor. Various aspects derived from these comparisons regarding rational drug design are outlined.
@article{Kellici2016, abstract = {The angiotensin II type 1 receptor (AT1R) has been recently crystallized. A new era has emerged for the structure-based rational drug design and the synthesis of novel AT1R antagonists. In this critical review, the X-ray crystallographic data of commercially available AT1R antagonists in free form are analyzed and compared with the conformational analysis results obtained using a combination of NMR spectroscopy and Molecular Modeling. The same AT1R antagonists are docked and compared in terms of their interactions in their binding site using homology models and the crystallized AT1R receptor. Various aspects derived from these comparisons regarding rational drug design are outlined.}, author = {T.F. Kellici and D. Ntountaniotis and E. Kritsi and M. Zervou and P. Zoumpoulakis and C. Potamitis and S. Durdagi and R.E. Salmas and G. Ergun and E. Gokdemir and A.G. Tzakos and T. Mavromoustakos}, doi = {10.2174/0929867323666151117122116}, issue = {1}, journal = {Current Medicinal Chemistry}, pages = {36-59}, title = {Leveraging NMR and X-ray data of the free ligands to build better drugs targeting angiotensin II Type 1 G-Protein coupled receptor}, volume = {23}, year = {2016}, } - Goulas, V., E. Stylos, M. V. Chatziathanasiadou, T. Mavromoustakos, and A. G. Tzakos. “Functional components of carob fruit: linking the chemical and biological space.” International journal of molecular sciences 17 (2016). doi:10.3390/ijms17111875
[BibTeX] [Abstract]
The contribution of natural products to the drug-discovery pipeline has been remarkable since they have served as a rich source for drug development and discovery. Natural products have adapted, during the course of evolution, optimum chemical scaffolds against a wide variety of diseases, including cancer and diabetes. Advances in high-throughput screening assays, assisted by the continuous development on the instrumentation’s capabilities and omics, have resulted in charting a large chemical and biological space of drug-like compounds, originating from natural sources. Herein, we attempt to integrate the information on the chemical composition and the associated biological impact of carob fruit in regards to human health. The beneficial and health-promoting effects of carob along with the clinical trials and the drug formulations derived from carob’s natural components are presented in this review.
@article{Goulas2016, abstract = {The contribution of natural products to the drug-discovery pipeline has been remarkable since they have served as a rich source for drug development and discovery. Natural products have adapted, during the course of evolution, optimum chemical scaffolds against a wide variety of diseases, including cancer and diabetes. Advances in high-throughput screening assays, assisted by the continuous development on the instrumentation’s capabilities and omics, have resulted in charting a large chemical and biological space of drug-like compounds, originating from natural sources. Herein, we attempt to integrate the information on the chemical composition and the associated biological impact of carob fruit in regards to human health. The beneficial and health-promoting effects of carob along with the clinical trials and the drug formulations derived from carob’s natural components are presented in this review.}, author = {V. Goulas and E. Stylos and M.V. Chatziathanasiadou and T. Mavromoustakos and A.G. Tzakos}, doi = {10.3390/ijms17111875}, issue = {11}, journal = {International Journal of Molecular Sciences}, title = {Functional components of carob fruit: Linking the chemical and biological space}, volume = {17}, year = {2016}, } - Karakurt, S., T. F. Kellici, T. Mavromoustakos, A. G. Tzakos, and M. Yilmaz. “Calixarenes in lipase biocatalysis and cancer therapy.” Current organic chemistry 20 (2016): 1043-1057. doi:10.2174/1385272820666151211192249
[BibTeX] [Abstract]
Calixarenes are supramolecular structures characterized by their “calix” shape and their easy synthetic accessibility. They are amphiphilic in nature, thus they can bear in their structure both hydrophobic and hydrophilic features as well as charged groups. They are characterized by architectural plasticity responsible for their unique fine-tuned properties that can be shaped for an array of applications. Herein, we will focus, on their diverse available applications, and give special emphasis on biocatalysis and cancer therapy as two modern directions and emerging fields of interest that have been sporadically explored in the literature and can pave the way for the discovery of novel therapeutics. This review provides the first exhaustive examination on the enhanced catalytic activity and selectivity of calixarene-based encapsulated biocatalysts towards the synthesis of bioactive molecules. The application of functionalized calixarenes in cancer therapy is also analyzed towards the spatiotemporal control they can offer in targeted drug delivery.
@article{Karakurt2016, abstract = {Calixarenes are supramolecular structures characterized by their “calix” shape and their easy synthetic accessibility. They are amphiphilic in nature, thus they can bear in their structure both hydrophobic and hydrophilic features as well as charged groups. They are characterized by architectural plasticity responsible for their unique fine-tuned properties that can be shaped for an array of applications. Herein, we will focus, on their diverse available applications, and give special emphasis on biocatalysis and cancer therapy as two modern directions and emerging fields of interest that have been sporadically explored in the literature and can pave the way for the discovery of novel therapeutics. This review provides the first exhaustive examination on the enhanced catalytic activity and selectivity of calixarene-based encapsulated biocatalysts towards the synthesis of bioactive molecules. The application of functionalized calixarenes in cancer therapy is also analyzed towards the spatiotemporal control they can offer in targeted drug delivery.}, author = {S. Karakurt and T.F. Kellici and T. Mavromoustakos and A.G. Tzakos and M. Yilmaz}, doi = {10.2174/1385272820666151211192249}, issue = {10}, journal = {Current Organic Chemistry}, pages = {1043-1057}, title = {Calixarenes in lipase biocatalysis and cancer therapy}, volume = {20}, year = {2016}, } - Kontogianni, V. G., M. E. Tsoumani, T. F. Kellici, T. Mavromoustakos, I. P. Gerothanassis, A. D. Tselepis, and A. G. Tzakos. “Deconvoluting the dual antiplatelet activity of a plant extract.” Journal of agricultural and food chemistry 64 (2016): 4511-4521. doi:10.1021/acs.jafc.6b00544
[BibTeX] [Abstract]
A thorough evaluation of the antiplatelet activity profile of hexane olive leaf extract in human platelets indicated a potent activity accomplished through a two axis inhibition of platelet activation triggered both by ADP and thrombin. To delineate the extract components responsible for this dual activity, an NMR based method was established to determine and quantify the triterpenoid content leading to the characterization of uvaol, erythrodiol, and oleanolic acid. The antiplatelet profile of the total extract and of the 3 determined triterpenoids was evaluated against in vitro platelet aggregation induced by several platelet agonists as also on PAC-1 binding and P-selectin membrane expression both in healthy volunteers and in platelets from patients with an acute coronary syndrome receiving dual antiplatelet therapy with aspirin and ticagrelor. The extract was identified to inhibit ADP-induced platelet activation due to its erythrodiol content and TRAP-induced platelet activation due to the activity of uvaol and oleanolic acid.
@article{Kontogianni2016, abstract = {A thorough evaluation of the antiplatelet activity profile of hexane olive leaf extract in human platelets indicated a potent activity accomplished through a two axis inhibition of platelet activation triggered both by ADP and thrombin. To delineate the extract components responsible for this dual activity, an NMR based method was established to determine and quantify the triterpenoid content leading to the characterization of uvaol, erythrodiol, and oleanolic acid. The antiplatelet profile of the total extract and of the 3 determined triterpenoids was evaluated against in vitro platelet aggregation induced by several platelet agonists as also on PAC-1 binding and P-selectin membrane expression both in healthy volunteers and in platelets from patients with an acute coronary syndrome receiving dual antiplatelet therapy with aspirin and ticagrelor. The extract was identified to inhibit ADP-induced platelet activation due to its erythrodiol content and TRAP-induced platelet activation due to the activity of uvaol and oleanolic acid.}, author = {V.G. Kontogianni and M.E. Tsoumani and T.F. Kellici and T. Mavromoustakos and I.P. Gerothanassis and A.D. Tselepis and A.G. Tzakos}, doi = {10.1021/acs.jafc.6b00544}, issue = {22}, journal = {Journal of Agricultural and Food Chemistry}, pages = {4511-4521}, title = {Deconvoluting the dual antiplatelet activity of a plant extract}, volume = {64}, year = {2016}, }
2015
- Kellici, T. F., D. Ntountaniotis, G. Leonis, M. Chatziathanasiadou, A. V. Chatzikonstantinou, J. Becker-Baldus, C. Glaubitz, A. G. Tzakos, K. Viras, P. Chatzigeorgiou, M. G. Papadopoulos, and T. Mavromoustakos. “Investigation of the interactions of silibinin with 2-hydroxypropyl-β-cyclodextrin through biophysical techniques and computational methods.” Molecular pharmaceutics 12 (2015): 954-965. doi:10.1021/mp5008053
[BibTeX] [Abstract]
Cyclodextrins (CDs) are a well-known class of supermolecules that have been widely used to protect drugs against conjugation and metabolic inactivation as well as to enhance the aqueous solubility and hence to ameliorate the oral bioavailability of sparingly soluble drug molecules. The hepatoprotectant drug silibinin can be incorporated into CDs, and here we elucidate the interaction between the drug and the host at the molecular level. The complexation product of silibinin with 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) is characterized by Differential Scanning Calorimetry, mass spectrometry, solid and liquid high-resolution NMR spectroscopy. The chemical shift changes using 13C CP/MAS on the complexing of the guest with the host provided significant information on the molecular interactions, and they were in agreement with the 2D NOESY results. These results point out that in both solid and liquid forms, the drug is engulfed and interacts with HP-β-CD in identical manner. Molecular dynamics calculations have been performed to examine the thermodynamic characteristics associated with the silibinin-HP-β-CD interactions and to study the stability of the complex. To approximate the physiological conditions, the aqueous solubility and dissolution characteristics of the complex at pH states simulating those of the upper gastrointestinal tract have been applied. To evaluate the antiproliferative activity of silibinin-HP-β-CD complex comparatively to silibinin in MCF-7 human cancer cells, MTT assays have been performed. (Graph Presented).
@article{Kellici2015, abstract = {Cyclodextrins (CDs) are a well-known class of supermolecules that have been widely used to protect drugs against conjugation and metabolic inactivation as well as to enhance the aqueous solubility and hence to ameliorate the oral bioavailability of sparingly soluble drug molecules. The hepatoprotectant drug silibinin can be incorporated into CDs, and here we elucidate the interaction between the drug and the host at the molecular level. The complexation product of silibinin with 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) is characterized by Differential Scanning Calorimetry, mass spectrometry, solid and liquid high-resolution NMR spectroscopy. The chemical shift changes using 13C CP/MAS on the complexing of the guest with the host provided significant information on the molecular interactions, and they were in agreement with the 2D NOESY results. These results point out that in both solid and liquid forms, the drug is engulfed and interacts with HP-β-CD in identical manner. Molecular dynamics calculations have been performed to examine the thermodynamic characteristics associated with the silibinin-HP-β-CD interactions and to study the stability of the complex. To approximate the physiological conditions, the aqueous solubility and dissolution characteristics of the complex at pH states simulating those of the upper gastrointestinal tract have been applied. To evaluate the antiproliferative activity of silibinin-HP-β-CD complex comparatively to silibinin in MCF-7 human cancer cells, MTT assays have been performed. (Graph Presented).}, author = {T.F. Kellici and D. Ntountaniotis and G. Leonis and M. Chatziathanasiadou and A.V. Chatzikonstantinou and J. Becker-Baldus and C. Glaubitz and A.G. Tzakos and K. Viras and P. Chatzigeorgiou and M.G. Papadopoulos and T. Mavromoustakos}, doi = {10.1021/mp5008053}, issue = {3}, journal = {Molecular Pharmaceutics}, pages = {954-965}, title = {Investigation of the interactions of silibinin with 2-hydroxypropyl-β-cyclodextrin through biophysical techniques and computational methods}, volume = {12}, year = {2015}, } - Sánchez-Pérez, A., A. Muñoz, J. Peña-García, H. den-Haan, N. Bekas, A. Katsikoudi, A. G. Tzakos, and H. Péréz-Sánchez. Dia-db: a web-accessible database for the prediction of diabetes drugs. Vol. 9044. 2015. doi:10.1007/978-3-319-16480-9_63
[BibTeX] [Abstract]
Diabetes mellitus is the 8th leading cause of death worldwide, with 1.5million deaths in 2012, andmedical costs that reached 245$ billion in the US. Moreover, it is estimated that roughly 387 million people worldwide suffer from diabetes mellitus, with numbers growing rapidly. These facts demonstrate the importance of creating a completely new and innovative method for the fast development of novel anti-diabetic compounds. In silico prediction methods represent an efficient approach for the prediction of diabetes drugs, aiming to explaining preclinical drug development and therefore enabling the reduction of associated time, costs and experiments. We present hereDIA-DB, aweb server for the prediction of diabetes drugs that uses two different approaches; a) comparison by similarity with a curated database of anti-diabetic drugs and experimental compounds, and b) inverse virtual screening of the input molecules chosen by the users against a set of protein targets identified as key elements in diabetes. The server is open to all users and is accessible at http://bio-hpc.eu/dia-db, where registration is not necessary, and a detailed report with the prediction results are sent to the user by email once calculations are finished. This is the first public domain database for diabetes drugs.
@book{, abstract = {Diabetes mellitus is the 8th leading cause of death worldwide, with 1.5million deaths in 2012, andmedical costs that reached 245$ billion in the US. Moreover, it is estimated that roughly 387 million people worldwide suffer from diabetes mellitus, with numbers growing rapidly. These facts demonstrate the importance of creating a completely new and innovative method for the fast development of novel anti-diabetic compounds. In silico prediction methods represent an efficient approach for the prediction of diabetes drugs, aiming to explaining preclinical drug development and therefore enabling the reduction of associated time, costs and experiments. We present hereDIA-DB, aweb server for the prediction of diabetes drugs that uses two different approaches; a) comparison by similarity with a curated database of anti-diabetic drugs and experimental compounds, and b) inverse virtual screening of the input molecules chosen by the users against a set of protein targets identified as key elements in diabetes. The server is open to all users and is accessible at http://bio-hpc.eu/dia-db, where registration is not necessary, and a detailed report with the prediction results are sent to the user by email once calculations are finished. This is the first public domain database for diabetes drugs.}, author = {A. Sánchez-Pérez and A. Muñoz and J. Peña-García and H. den-Haan and N. Bekas and A. Katsikoudi and A.G. Tzakos and H. Péréz-Sánchez}, doi = {10.1007/978-3-319-16480-9_63}, isbn = {9783319164793}, journal = {Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)}, pages = {655-663}, title = {DIA-DB: A web-accessible database for the prediction of diabetes drugs}, volume = {9044}, year = {2015}, } - Kellici, T. F., A. G. Tzakos, and T. Mavromoustakos. “Rational drug design and synthesis of molecules targeting the angiotensin ii type 1 and type 2 receptors.” Molecules 20 (2015): 3868-3897. doi:10.3390/molecules20033868
[BibTeX] [Abstract]
The angiotensin II (Ang II) type 1 and type 2 receptors (AT
1 R and AT2 R) orchestrate an array of biological processes that regulate human health. Aberrant function of these receptors triggers pathophysiological responses that can ultimately lead to death. Therefore, it is important to design and synthesize compounds that affect beneficially these two receptors. Cardiovascular disease, which is attributed to the overactivation of the vasoactive peptide hormone Ang II, can now be treated with commercial AT1 R antagonists. Herein, recent achievements in rational drug design and synthesis of molecules acting on the two AT receptors are reviewed. Quantitative structure activity relationships (QSAR) and molecular modeling on the two receptors aim to assist the search for new active compounds. As AT1 R and AT2 R are GPCRs and drug action is localized in the transmembrane region the role of membrane bilayers is exploited. The future perspectives in this field are outlined. Tremendous progress in the field is expected if the two receptors are crystallized, as this will assist the structure based screening of the chemical space and lead to new potent therapeutic agents in cardiovascular and other diseases.@article{Kellici2015, abstract = {The angiotensin II (Ang II) type 1 and type 2 receptors (AT1 R and AT2 R) orchestrate an array of biological processes that regulate human health. Aberrant function of these receptors triggers pathophysiological responses that can ultimately lead to death. Therefore, it is important to design and synthesize compounds that affect beneficially these two receptors. Cardiovascular disease, which is attributed to the overactivation of the vasoactive peptide hormone Ang II, can now be treated with commercial AT1 R antagonists. Herein, recent achievements in rational drug design and synthesis of molecules acting on the two AT receptors are reviewed. Quantitative structure activity relationships (QSAR) and molecular modeling on the two receptors aim to assist the search for new active compounds. As AT1 R and AT2 R are GPCRs and drug action is localized in the transmembrane region the role of membrane bilayers is exploited. The future perspectives in this field are outlined. Tremendous progress in the field is expected if the two receptors are crystallized, as this will assist the structure based screening of the chemical space and lead to new potent therapeutic agents in cardiovascular and other diseases.}, author = {T.F. Kellici and A.G. Tzakos and T. Mavromoustakos}, doi = {10.3390/molecules20033868}, issue = {3}, journal = {Molecules}, pages = {3868-3897}, title = {Rational drug design and synthesis of molecules targeting the angiotensin II type 1 and type 2 receptors}, volume = {20}, year = {2015}, } - Kounnis, V., G. Chondrogiannis, M. D. Mantzaris, A. G. Tzakos, D. Fokas, N. A. Papanikolaou, V. Galani, I. Sainis, and E. Briasoulis. “Microcystin lr shows cytotoxic activity against pancreatic cancer cells expressing the membrane oatp1b1 and oatp1b3 transporters.” Anticancer research 35 (2015): 5857-5865.
[BibTeX] [Abstract]
Microcystin-LR (MC-LR) is a cyanobacterial cyclopeptide, known for its unique ability to cause acute liver injury. Its cellular uptake is facilitated by specific transmembrane organic anion-transporting polypeptides (OATPs) specifically OATP1B1 and 1B3. The objective of the present study was to investigate the expression of OATPs 1A2, 1B1 and 1B3 in pancreatic cancer cell lines BxPC-3 and MIA PACA-2 and assess their role in MC-LR-mediated cytotoxicity by using the novel xCELLigence system and flow cytometry. OATP1B1 and 1B3 were found to be expressed in both cell lines at both the mRNA and protein levels. The cytotoxic effects of MC-LR were proportionally related to the expression of these transporters. Moreover the cytotoxic potency of MC-LR was found superior to gemcitabine. Based on the expression of the organic anion transporting polypeptides 1B1 and 1B3 in pancreatic carcinoma tissue and cell lines and the potent cytotoxicity induced by MC-LR in vitro, we propose that this molecule could be held as structural basis for the development of novel targetedcompounds against pancreatic cancer.
@article{Kounnis2015, abstract = {Microcystin-LR (MC-LR) is a cyanobacterial cyclopeptide, known for its unique ability to cause acute liver injury. Its cellular uptake is facilitated by specific transmembrane organic anion-transporting polypeptides (OATPs) specifically OATP1B1 and 1B3. The objective of the present study was to investigate the expression of OATPs 1A2, 1B1 and 1B3 in pancreatic cancer cell lines BxPC-3 and MIA PACA-2 and assess their role in MC-LR-mediated cytotoxicity by using the novel xCELLigence system and flow cytometry. OATP1B1 and 1B3 were found to be expressed in both cell lines at both the mRNA and protein levels. The cytotoxic effects of MC-LR were proportionally related to the expression of these transporters. Moreover the cytotoxic potency of MC-LR was found superior to gemcitabine. Based on the expression of the organic anion transporting polypeptides 1B1 and 1B3 in pancreatic carcinoma tissue and cell lines and the potent cytotoxicity induced by MC-LR in vitro, we propose that this molecule could be held as structural basis for the development of novel targetedcompounds against pancreatic cancer.}, author = {V. Kounnis and G. Chondrogiannis and M.D. Mantzaris and A.G. Tzakos and D. Fokas and N.A. Papanikolaou and V. Galani and I. Sainis and E. Briasoulis}, issue = {11}, journal = {Anticancer Research}, pages = {5857-5865}, title = {Microcystin lr shows cytotoxic activity against pancreatic cancer cells expressing the membrane OATP1B1 and OATP1B3 transporters}, volume = {35}, year = {2015}, } - Prodromidis, M. I., E. M. Zahran, A. G. Tzakos, and L. G. Bachas. “Preorganized composite material of polyaniline-palladium nanoparticles with high electrocatalytic activity to methanol and ethanol oxidation.” International journal of hydrogen energy 40 (2015): 6745-6753. doi:10.1016/j.ijhydene.2015.03.102
[BibTeX] [Abstract]
We report a simple method for the preparation of a stabilized palladium nanoparticle-polyaniline composite by mixing aniline and PdCl42- in aqueous acidic solutions. Pd nanoparticles (Pd NP) were produced by subsequent reduction of the pre-organized material with different concentrations of NaBH4. Under optimum conditions (0.1 M NaBH4 in ethanol for 1 h at 0 °C), Pd NP with a size of 5-10 nm were obtained, as revealed by transmission electron microscopy. The so-formed pre-organized material was also characterized with scanning electron microscopy, X-ray diffraction, infrared spectroscopy, inductively coupled plasma atomic emission spectrometry, nuclear magnetic resonance spectroscopy, and cyclic voltammetry. The developed catalyst exhibited a large electrochemically active surface area (25.2 m2 g-1 catalyst) and remarkable mass activities for the electro-oxidation of methanol (602 A g-1 Pd) and ethanol (433 A g-1 Pd) in alkaline media. The excellent electrocatalytic performance of the developed polyaniline-Pd NP composite material renders it as a promising anode catalyst in alkaline fuel cells.
@article{Prodromidis2015, abstract = {We report a simple method for the preparation of a stabilized palladium nanoparticle-polyaniline composite by mixing aniline and PdCl42- in aqueous acidic solutions. Pd nanoparticles (Pd NP) were produced by subsequent reduction of the pre-organized material with different concentrations of NaBH4. Under optimum conditions (0.1 M NaBH4 in ethanol for 1 h at 0 °C), Pd NP with a size of 5-10 nm were obtained, as revealed by transmission electron microscopy. The so-formed pre-organized material was also characterized with scanning electron microscopy, X-ray diffraction, infrared spectroscopy, inductively coupled plasma atomic emission spectrometry, nuclear magnetic resonance spectroscopy, and cyclic voltammetry. The developed catalyst exhibited a large electrochemically active surface area (25.2 m2 g-1 catalyst) and remarkable mass activities for the electro-oxidation of methanol (602 A g-1 Pd) and ethanol (433 A g-1 Pd) in alkaline media. The excellent electrocatalytic performance of the developed polyaniline-Pd NP composite material renders it as a promising anode catalyst in alkaline fuel cells.}, author = {M.I. Prodromidis and E.M. Zahran and A.G. Tzakos and L.G. Bachas}, doi = {10.1016/j.ijhydene.2015.03.102}, issue = {21}, journal = {International Journal of Hydrogen Energy}, pages = {6745-6753}, title = {Preorganized composite material of polyaniline-palladium nanoparticles with high electrocatalytic activity to methanol and ethanol oxidation}, volume = {40}, year = {2015}, } - Geromichalou, E., N. Sayyad, E. Kyriakou, A. V. Chatzikonstantinou, E. Giannopoulou, N. Vrbjar, H. P. Kalofonos, H. Stamatis, and A. G. Tzakos. “Regioselective chemical and rapid enzymatic synthesis of a novel redox-antiproliferative molecular hybrid.” European journal of medicinal chemistry 96 (2015): 47-57. doi:10.1016/j.ejmech.2015.03.064
[BibTeX] [Abstract]
Recent science evidenced the interlinkage of oxidative stress and cancer. Due to the inherent complexity of cancer and its accompanying effect of oxidative stress, novel molecules, containing combinatorial functionalities should be targeted. Herein, we synthesized gemcitabine-5’2-O-lipoate derived from a regioselective coupling of the chemotherapeutic drug gemcitabine (GEM), a first-line agent for cancer therapy and ±-lipoic acid (LA), a potent antioxidant. gemcitabine-5’2-O-lipoate was obtained in 4 chemical steps. To avoid the tedious and laborious chemical steps we also utilized biocatalysis using immobilized Candida antarctica lipase B (CALB), and the optimum conditions for the regioselective and one-pot synthesis of gemcitabine-5’2-O-lipoate were established by exploiting different solvents (organic solvents and ionic liquids) and enzyme immobilization (acrylic resin and carbon nanotubes). Cytotoxic activity of co-administrating GEM and LA was proven to be synergistic against non-small cell lung cancer cells whereas antagonistic for bladder cancer cells. In contrast, the gemcitabine-5’2-O-lipoate hybrid was found to be superior to the parent compounds against both non-small cell lung cancer and bladder cancer cells as also was found to preserve the redox activity of the parent compound LA. The regioselective biotransformation mediated synthesis of the anticancer-antioxidant hybrid illustrates the capacity of biocatalysis to act as an asset in molecular hybridization techniques.
@article{Geromichalou2015, abstract = {Recent science evidenced the interlinkage of oxidative stress and cancer. Due to the inherent complexity of cancer and its accompanying effect of oxidative stress, novel molecules, containing combinatorial functionalities should be targeted. Herein, we synthesized gemcitabine-5'2-O-lipoate derived from a regioselective coupling of the chemotherapeutic drug gemcitabine (GEM), a first-line agent for cancer therapy and ±-lipoic acid (LA), a potent antioxidant. gemcitabine-5'2-O-lipoate was obtained in 4 chemical steps. To avoid the tedious and laborious chemical steps we also utilized biocatalysis using immobilized Candida antarctica lipase B (CALB), and the optimum conditions for the regioselective and one-pot synthesis of gemcitabine-5'2-O-lipoate were established by exploiting different solvents (organic solvents and ionic liquids) and enzyme immobilization (acrylic resin and carbon nanotubes). Cytotoxic activity of co-administrating GEM and LA was proven to be synergistic against non-small cell lung cancer cells whereas antagonistic for bladder cancer cells. In contrast, the gemcitabine-5'2-O-lipoate hybrid was found to be superior to the parent compounds against both non-small cell lung cancer and bladder cancer cells as also was found to preserve the redox activity of the parent compound LA. The regioselective biotransformation mediated synthesis of the anticancer-antioxidant hybrid illustrates the capacity of biocatalysis to act as an asset in molecular hybridization techniques.}, author = {E. Geromichalou and N. Sayyad and E. Kyriakou and A.V. Chatzikonstantinou and E. Giannopoulou and N. Vrbjar and H.P. Kalofonos and H. Stamatis and A.G. Tzakos}, doi = {10.1016/j.ejmech.2015.03.064}, journal = {European Journal of Medicinal Chemistry}, pages = {47-57}, title = {Regioselective chemical and rapid enzymatic synthesis of a novel redox-Antiproliferative molecular hybrid}, volume = {96}, year = {2015}, } - Ishiguro, S., K. Yoshimura, R. Tsunedomi, M. Oka, S. Takao, M. Inui, A. Kawabata, T. Wall, V. Magafa, P. Cordopatis, A. G. Tzakos, and M. Tamura. “Involvement of angiotensin ii type 2 receptor (at2r) signaling in human pancreatic ductal adenocarcinoma (pdac): a novel at2r agonist effectively attenuates growth of pdac grafts in mice.” Cancer biology and therapy 16 (2015): 307-316. doi:10.1080/15384047.2014.1002357
[BibTeX] [Abstract]
We have recently discovered the potential involvement of angiotensin II type 2 receptor (AT2R) signaling in pancreatic cancer using AT2R deficient mice. To examine the involvement of AT2R expression in human PDAC, expressions of AT2R as well as the major angiotensin II receptor (type 1 receptor, AT1R) in human PDAC and adjacent normal tissue was evaluated by immunohistochemistry and real time PCR using surgically dissected human PDAC specimens. In immunohistochemical analysis, relatively strong AT1R expression was detected consistently in both normal pancreas and PDAC areas, whereas moderate AT2R expression was detected in 78.5% of PDAC specimens and 100% of normal area of the pancreas. AT1R, but not AT2R, mRNA levels were significantly higher in the PDAC area than in the normal pancreas. AT2R mRNA levels showed a negative correlation trend with overall survival. In cell cultures, treatment with a novel AT2R agonist significantly attenuated both murine and human PDAC cell growth with negligible cytotoxicity in normal epithelial cells. In a mouse study, administrations of the AT2R agonist in tumor surrounding connective tissue markedly attenuated growth of only AT2R expressing PAN02 murine PDAC grafts in syngeneic mice. The AT2R agonist treatment induced apoptosis primarily in tumor cells but not in stromal cells. Taken together, our findings offer clinical and preclinical evidence for the involvement of AT2R signaling in PDAC development and pinpoint that the novel AT2R agonist could serve as an effective therapeutic for PDAC treatment.
@article{Ishiguro2015, abstract = {We have recently discovered the potential involvement of angiotensin II type 2 receptor (AT2R) signaling in pancreatic cancer using AT2R deficient mice. To examine the involvement of AT2R expression in human PDAC, expressions of AT2R as well as the major angiotensin II receptor (type 1 receptor, AT1R) in human PDAC and adjacent normal tissue was evaluated by immunohistochemistry and real time PCR using surgically dissected human PDAC specimens. In immunohistochemical analysis, relatively strong AT1R expression was detected consistently in both normal pancreas and PDAC areas, whereas moderate AT2R expression was detected in 78.5% of PDAC specimens and 100% of normal area of the pancreas. AT1R, but not AT2R, mRNA levels were significantly higher in the PDAC area than in the normal pancreas. AT2R mRNA levels showed a negative correlation trend with overall survival. In cell cultures, treatment with a novel AT2R agonist significantly attenuated both murine and human PDAC cell growth with negligible cytotoxicity in normal epithelial cells. In a mouse study, administrations of the AT2R agonist in tumor surrounding connective tissue markedly attenuated growth of only AT2R expressing PAN02 murine PDAC grafts in syngeneic mice. The AT2R agonist treatment induced apoptosis primarily in tumor cells but not in stromal cells. Taken together, our findings offer clinical and preclinical evidence for the involvement of AT2R signaling in PDAC development and pinpoint that the novel AT2R agonist could serve as an effective therapeutic for PDAC treatment.}, author = {S. Ishiguro and K. Yoshimura and R. Tsunedomi and M. Oka and S. Takao and M. Inui and A. Kawabata and T. Wall and V. Magafa and P. Cordopatis and A.G. Tzakos and M. Tamura}, doi = {10.1080/15384047.2014.1002357}, issue = {2}, journal = {Cancer Biology and Therapy}, pages = {307-316}, title = {Involvement of angiotensin II type 2 receptor (AT2R) signaling in human pancreatic ductal adenocarcinoma (PDAC): A novel AT2R agonist effectively attenuates growth of PDAC grafts in mice}, volume = {16}, year = {2015}, } - Kellici, T. F., G. Liapakis, A. G. Tzakos, and T. Mavromoustakos. “Pharmaceutical compositions for antihypertensive treatments: a patent review.” Expert opinion on therapeutic patents 25 (2015): 1305-1317. doi:10.1517/13543776.2015.1086337
[BibTeX] [Abstract]
Introduction: New drug formulations against hypertension have a vital role in the quality of human life, as this risk factor for cardiovascular disease can be life threatening. A modern life style characterized by less exercise, smoking, drinking and poor diet has increased the risk of developing hypertension, the so-called silent killer, in civilized communities and thus an urgent defense is needed against this enemy. Areas covered: In this review, the authors provide extensive information on pharmaceutical formulations containing anti-hypertensive drugs, as well as on general and specific patents. Thus, readers can understand the advances and new trends in the field. Expert opinion: A considerable effort has been made to provide new and improved formulations, comprising anti-hypertensive drugs with new excipients, appropriate particle size, containing alkaline salts or included in cyclodextrins in an attempt to avoid known existing problems. New types of formulations are expected to emerge in the near future that will allow for more effective and spatiotemporally controlled drug delivery, which will be better tolerated by the patients and will provide better pharmaceutical treatment. Such an example is the new cocktail formulations that contain more than one active component, act synergistically and therefore have optimized pharmacological benefits. Formulations using multitarget antihypertensive drugs are also expected to be commercially available in the near future.
@article{Kellici2015, abstract = {Introduction: New drug formulations against hypertension have a vital role in the quality of human life, as this risk factor for cardiovascular disease can be life threatening. A modern life style characterized by less exercise, smoking, drinking and poor diet has increased the risk of developing hypertension, the so-called silent killer, in civilized communities and thus an urgent defense is needed against this enemy. Areas covered: In this review, the authors provide extensive information on pharmaceutical formulations containing anti-hypertensive drugs, as well as on general and specific patents. Thus, readers can understand the advances and new trends in the field. Expert opinion: A considerable effort has been made to provide new and improved formulations, comprising anti-hypertensive drugs with new excipients, appropriate particle size, containing alkaline salts or included in cyclodextrins in an attempt to avoid known existing problems. New types of formulations are expected to emerge in the near future that will allow for more effective and spatiotemporally controlled drug delivery, which will be better tolerated by the patients and will provide better pharmaceutical treatment. Such an example is the new cocktail formulations that contain more than one active component, act synergistically and therefore have optimized pharmacological benefits. Formulations using multitarget antihypertensive drugs are also expected to be commercially available in the near future.}, author = {T.F. Kellici and G. Liapakis and A.G. Tzakos and T. Mavromoustakos}, doi = {10.1517/13543776.2015.1086337}, issue = {11}, journal = {Expert Opinion on Therapeutic Patents}, pages = {1305-1317}, title = {Pharmaceutical compositions for antihypertensive treatments: A patent review}, volume = {25}, year = {2015}, } - Ferlemi, A. -V., A. Katsikoudi, V. G. Kontogianni, T. F. Kellici, G. Iatrou, F. N. Lamari, A. G. Tzakos, and M. Margarity. “Rosemary tea consumption results to anxiolytic- and anti-depressant-like behavior of adult male mice and inhibits all cerebral area and liver cholinesterase activity; phytochemical investigation and in silico studies.” Chemico-biological interactions 237 (2015): 47-57. doi:10.1016/j.cbi.2015.04.013
[BibTeX] [Abstract]
Our aim was to investigate the possible effects of regular drinking of Rosmarinus officinalis L. leaf infusion on behavior and on AChE activity of mice. Rosemary tea (2% w/w) phytochemical profile was investigated through LC/DAD/ESI-MSn. Adult male mice were randomly divided into two groups: “Rosemary-treated” that received orally the rosemary tea for 4 weeks and “control” that received drinking water. The effects of regular drinking of rosemary tea on behavioral parameters were assessed by passive avoidance, elevated plus maze and forced swimming tests. Moreover, its effects on cerebral and liver cholinesterase (ChE) isoforms activity were examined colorimetricaly. Phytochemical analysis revealed the presence of diterpenes, flavonoids and hydroxycinnamic derivatives in rosemary tea; the major compounds were quantitatively determined. Its consumption rigorously affected anxiety/fear and depression-like behavior of mice, though memory/learning was unaffected. ChE isoforms activity was significantly decreased in brain and liver of “rosemary treated” mice. In order to explain the tissue ChE inhibition, principal component analysis, pharmacophore alignment and molecular docking were used to explore a possible relationship between main identified compounds of rosemary tea, i.e. rosmarinic acid, luteolin-7-O-glucuronide, caffeic acid and known AChE inhibitors. Results revealed potential common pharmacophores of the phenolic components with the inhibitors. Our findings suggest that rosemary tea administration exerts anxiolytic and antidepressant effects on mice and inhibits ChE activity; its main phytochemicals may function in a similar way as inhibitors.
@article{Ferlemi2015, abstract = {Our aim was to investigate the possible effects of regular drinking of Rosmarinus officinalis L. leaf infusion on behavior and on AChE activity of mice. Rosemary tea (2% w/w) phytochemical profile was investigated through LC/DAD/ESI-MSn. Adult male mice were randomly divided into two groups: "Rosemary-treated" that received orally the rosemary tea for 4 weeks and "control" that received drinking water. The effects of regular drinking of rosemary tea on behavioral parameters were assessed by passive avoidance, elevated plus maze and forced swimming tests. Moreover, its effects on cerebral and liver cholinesterase (ChE) isoforms activity were examined colorimetricaly. Phytochemical analysis revealed the presence of diterpenes, flavonoids and hydroxycinnamic derivatives in rosemary tea; the major compounds were quantitatively determined. Its consumption rigorously affected anxiety/fear and depression-like behavior of mice, though memory/learning was unaffected. ChE isoforms activity was significantly decreased in brain and liver of "rosemary treated" mice. In order to explain the tissue ChE inhibition, principal component analysis, pharmacophore alignment and molecular docking were used to explore a possible relationship between main identified compounds of rosemary tea, i.e. rosmarinic acid, luteolin-7-O-glucuronide, caffeic acid and known AChE inhibitors. Results revealed potential common pharmacophores of the phenolic components with the inhibitors. Our findings suggest that rosemary tea administration exerts anxiolytic and antidepressant effects on mice and inhibits ChE activity; its main phytochemicals may function in a similar way as inhibitors.}, author = {A.-V. Ferlemi and A. Katsikoudi and V.G. Kontogianni and T.F. Kellici and G. Iatrou and F.N. Lamari and A.G. Tzakos and M. Margarity}, doi = {10.1016/j.cbi.2015.04.013}, journal = {Chemico-Biological Interactions}, pages = {47-57}, title = {Rosemary tea consumption results to anxiolytic- and anti-depressant-like behavior of adult male mice and inhibits all cerebral area and liver cholinesterase activity; Phytochemical investigation and in silico studies}, volume = {237}, year = {2015}, } - Vujicic, M., I. Nikolic, V. G. Kontogianni, T. Saksida, P. Charisiadis, Z. Orescanin-Dusic, D. Blagojevic, S. Stosic-Grujicic, A. G. Tzakos, and I. Stojanovic. “Methanolic extract of origanum vulgare ameliorates type 1 diabetes through antioxidant, anti-inflammatory and anti-apoptotic activity.” British journal of nutrition 113 (2015): 770-782. doi:10.1017/S0007114514004048
[BibTeX] [Abstract]
Type 1 diabetes (T1D), an autoimmune inflammatory disorder, develops as a consequence of pancreatic β-cell destruction and results in hyperglycaemia. Since current T1D therapy mainly involves insulin replacement, the aim of the present study was to evaluate the therapeutic potential of Origanum vulgare L. ssp. hirtum (Greek oregano) leaf extract rich in biophenols for the treatment of T1D. The phytochemical profile of methanolic oregano extract (MOE) and aqueous oregano extract (AOE) was determined by liquid chromatography/electrospray ion-trap tandem MS (LC/DAD/ESI-MSn), while their main compounds were quantified by HPLC with diode array detection. After establishing their potent in vitro antioxidant activity, the extracts were administered to C57BL/6 mice treated with multiple low doses of streptozotocin for diabetes induction. While prophylactic AOE therapy had no impact on diabetes induction, MOE reduced diabetes incidence and preserved normal insulin secretion. In addition, MOE scavenged reactive oxygen and nitrogen species and, therefore, alleviated the need for the up-regulation of antioxidant enzymes. MOE treatment specifically attenuated the pro-inflammatory response mediated by T helper 17 cells and enhanced anti-inflammatory T helper 2 and T regulatory cells through the impact on specific signalling pathways and transcription factors. Importantly, MOE preserved β-cells from in vitro apoptosis via blockade of caspase 3. Finally, rosmarinic acid, a predominant compound in MOE, exhibited only partial protection from diabetes induction. In conclusion, acting as an antioxidant, immunomodulator and in an anti-apoptotic manner, MOE protected mice from diabetes development. Seemingly, there is more than one compound responsible for the beneficial effect of MOE.
@article{Vujicic2015, abstract = {Type 1 diabetes (T1D), an autoimmune inflammatory disorder, develops as a consequence of pancreatic β-cell destruction and results in hyperglycaemia. Since current T1D therapy mainly involves insulin replacement, the aim of the present study was to evaluate the therapeutic potential of Origanum vulgare L. ssp. hirtum (Greek oregano) leaf extract rich in biophenols for the treatment of T1D. The phytochemical profile of methanolic oregano extract (MOE) and aqueous oregano extract (AOE) was determined by liquid chromatography/electrospray ion-trap tandem MS (LC/DAD/ESI-MSn), while their main compounds were quantified by HPLC with diode array detection. After establishing their potent in vitro antioxidant activity, the extracts were administered to C57BL/6 mice treated with multiple low doses of streptozotocin for diabetes induction. While prophylactic AOE therapy had no impact on diabetes induction, MOE reduced diabetes incidence and preserved normal insulin secretion. In addition, MOE scavenged reactive oxygen and nitrogen species and, therefore, alleviated the need for the up-regulation of antioxidant enzymes. MOE treatment specifically attenuated the pro-inflammatory response mediated by T helper 17 cells and enhanced anti-inflammatory T helper 2 and T regulatory cells through the impact on specific signalling pathways and transcription factors. Importantly, MOE preserved β-cells from in vitro apoptosis via blockade of caspase 3. Finally, rosmarinic acid, a predominant compound in MOE, exhibited only partial protection from diabetes induction. In conclusion, acting as an antioxidant, immunomodulator and in an anti-apoptotic manner, MOE protected mice from diabetes development. Seemingly, there is more than one compound responsible for the beneficial effect of MOE.}, author = {M. Vujicic and I. Nikolic and V.G. Kontogianni and T. Saksida and P. Charisiadis and Z. Orescanin-Dusic and D. Blagojevic and S. Stosic-Grujicic and A.G. Tzakos and I. Stojanovic}, doi = {10.1017/S0007114514004048}, issue = {5}, journal = {British Journal of Nutrition}, pages = {770-782}, title = {Methanolic extract of Origanum vulgare ameliorates type 1 diabetes through antioxidant, anti-inflammatory and anti-apoptotic activity}, volume = {113}, year = {2015}, } - Kellici, T., D. Ntountaniotis, E. Vrontaki, G. Liapakis, P. Moutevelis-Minakakis, G. Kokotos, S. Hadjikakou, A. G. Tzakos, A. Afantitis, G. Melagraki, Di V. Marzo, and T. Mavromoustakos. “Rational drug design paradigms: the odyssey for designing better drugs.” Combinatorial chemistry and high throughput screening 18 (2015): 238-256. doi:10.2174/1386207318666150305125638
[BibTeX] [Abstract]
Due to the time and effort requirements for the development of a new drug, and the high attrition rates associated with this developmental process, there is an intense effort by academic and industrial researchers to find novel ways for more effective drug development schemes. The first step in the discovery process of a new drug is the identification of the lead compound. The modern research tendency is to avoid the synthesis of new molecules based on chemical intuition, which is time and cost consuming, and instead to apply in silico rational drug design. This approach reduces the consumables and human personnel involved in the initial steps of the drug design. In this review real examples from our research activity aiming to discover new leads will be given for various dire warnings diseases. There is no recipe to follow for discovering new leads. The strategy to be followed depends on the knowledge of the studied system and the experience of the researchers. The described examples constitute successful and unsuccessful efforts and reflect the reality which medicinal chemists have to face in drug design and development. The drug stability is also discussed in both organic molecules and metallotherapeutics. This is an important issue in drug discovery as drug metabolism in the body can lead to various toxic and undesired molecules.
@article{Kellici2015, abstract = {Due to the time and effort requirements for the development of a new drug, and the high attrition rates associated with this developmental process, there is an intense effort by academic and industrial researchers to find novel ways for more effective drug development schemes. The first step in the discovery process of a new drug is the identification of the lead compound. The modern research tendency is to avoid the synthesis of new molecules based on chemical intuition, which is time and cost consuming, and instead to apply in silico rational drug design. This approach reduces the consumables and human personnel involved in the initial steps of the drug design. In this review real examples from our research activity aiming to discover new leads will be given for various dire warnings diseases. There is no recipe to follow for discovering new leads. The strategy to be followed depends on the knowledge of the studied system and the experience of the researchers. The described examples constitute successful and unsuccessful efforts and reflect the reality which medicinal chemists have to face in drug design and development. The drug stability is also discussed in both organic molecules and metallotherapeutics. This is an important issue in drug discovery as drug metabolism in the body can lead to various toxic and undesired molecules.}, author = {T. Kellici and D. Ntountaniotis and E. Vrontaki and G. Liapakis and P. Moutevelis-Minakakis and G. Kokotos and S. Hadjikakou and A.G. Tzakos and A. Afantitis and G. Melagraki and V. Di Marzo and T. Mavromoustakos}, doi = {10.2174/1386207318666150305125638}, issue = {3}, journal = {Combinatorial Chemistry and High Throughput Screening}, pages = {238-256}, title = {Rational drug design paradigms: The odyssey for designing better drugs}, volume = {18}, year = {2015}, } - Papaemmanouil, C., C. G. Tsiafoulis, D. Alivertis, O. Tzamaloukas, D. Miltiadou, A. G. Tzakos, and I. P. Gerothanassis. “Selective one-dimensional total correlation spectroscopy nuclear magnetic resonance experiments for a rapid identification of minor components in the lipid fraction of milk and dairy products: toward spin chromatography?.” Journal of agricultural and food chemistry 63 (2015): 5381-5387. doi:10.1021/acs.jafc.5b01335
[BibTeX] [Abstract]
We report a rapid, direct, and unequivocal spin-chromatographic separation and identification of minor components in the lipid fraction of milk and common dairy products with the use of selective one-dimensional (1D) total correlation spectroscopy (TOCSY) nuclear magnetic resonance (NMR) experiments. The method allows for the complete backbone spin-coupling network to be elucidated even in strongly overlapped regions and in the presence of major components from 4 × 102 to 3 × 103 stronger NMR signal intensities. The proposed spin-chromatography method does not require any derivatization steps for the lipid fraction, is selective with excellent resolution, is sensitive with quantitation capability, and compares favorably to two-dimensional (2D) TOCSY and gas chromatography-mass spectrometry (GC-MS) methods of analysis. The results of the present study demonstrated that the 1D TOCSY NMR spin-chromatography method can become a procedure of primary interest in food analysis and generally in complex mixture analysis.
@article{Papaemmanouil2015, abstract = {We report a rapid, direct, and unequivocal spin-chromatographic separation and identification of minor components in the lipid fraction of milk and common dairy products with the use of selective one-dimensional (1D) total correlation spectroscopy (TOCSY) nuclear magnetic resonance (NMR) experiments. The method allows for the complete backbone spin-coupling network to be elucidated even in strongly overlapped regions and in the presence of major components from 4 × 102 to 3 × 103 stronger NMR signal intensities. The proposed spin-chromatography method does not require any derivatization steps for the lipid fraction, is selective with excellent resolution, is sensitive with quantitation capability, and compares favorably to two-dimensional (2D) TOCSY and gas chromatography-mass spectrometry (GC-MS) methods of analysis. The results of the present study demonstrated that the 1D TOCSY NMR spin-chromatography method can become a procedure of primary interest in food analysis and generally in complex mixture analysis.}, author = {C. Papaemmanouil and C.G. Tsiafoulis and D. Alivertis and O. Tzamaloukas and D. Miltiadou and A.G. Tzakos and I.P. Gerothanassis}, doi = {10.1021/acs.jafc.5b01335}, issue = {22}, journal = {Journal of Agricultural and Food Chemistry}, pages = {5381-5387}, title = {Selective One-Dimensional Total Correlation Spectroscopy Nuclear Magnetic Resonance Experiments for a Rapid Identification of Minor Components in the Lipid Fraction of Milk and Dairy Products: Toward Spin Chromatography?}, volume = {63}, year = {2015}, } - Primikyri, A., G. Mazzone, C. Lekka, A. G. Tzakos, N. Russo, and I. P. Gerothanassis. “Understanding zinc(ii) chelation with quercetin and luteolin: a combined nmr and theoretical study.” Journal of physical chemistry b 119 (2015): 83-95. doi:10.1021/jp509752s
[BibTeX] [Abstract]
The Zn(II) chelation with natural flavonoids, quercetin and luteolin, was investigated by the use of NMR spectroscopy and various levels of ab initio calculations. Very sharp phenolic OH 1H resonances in DMSO-d6 were observed for both free and complexed quercetin which allowed (i) the unequivocal assignment with the combined use of 1H-13C HSQC and HMBC experiments and (ii) the determination of complexation sites which were found to be the CO-4 carbonyl oxygen and the deprotonated C-5 OH group of quercetin and CO-4 carbonyl oxygen and the deprotonated C-5 OH group of luteolin. DOSY experiments allowed the determination of the effective molecular weight of the Zn-quercetin complex which was shown to be mainly 1:1. DFT calculations of the 1:1 complex in the gas phase demonstrated that the C-3 O- and CO-4 sites are favored for quercetin at both GGA and LDA approximations and the C-5 O- and CO-4 groups of luteolin at the LDA approximation. Quantum chemical calculations were also performed by means of the conductor polarizable model in DMSO by employing various functionals. The energetically favored Zn chelation sites of the 1:1 complex were found to be either the C-3 O- and CO-4 or C-5 O- and CO-4 sites, depending on the functional used, for quercetin and the C-5 O- and CO-4 sites for luteolin. (Figure Presented).
@article{Primikyri2015, abstract = {The Zn(II) chelation with natural flavonoids, quercetin and luteolin, was investigated by the use of NMR spectroscopy and various levels of ab initio calculations. Very sharp phenolic OH 1H resonances in DMSO-d6 were observed for both free and complexed quercetin which allowed (i) the unequivocal assignment with the combined use of 1H-13C HSQC and HMBC experiments and (ii) the determination of complexation sites which were found to be the CO-4 carbonyl oxygen and the deprotonated C-5 OH group of quercetin and CO-4 carbonyl oxygen and the deprotonated C-5 OH group of luteolin. DOSY experiments allowed the determination of the effective molecular weight of the Zn-quercetin complex which was shown to be mainly 1:1. DFT calculations of the 1:1 complex in the gas phase demonstrated that the C-3 O- and CO-4 sites are favored for quercetin at both GGA and LDA approximations and the C-5 O- and CO-4 groups of luteolin at the LDA approximation. Quantum chemical calculations were also performed by means of the conductor polarizable model in DMSO by employing various functionals. The energetically favored Zn chelation sites of the 1:1 complex were found to be either the C-3 O- and CO-4 or C-5 O- and CO-4 sites, depending on the functional used, for quercetin and the C-5 O- and CO-4 sites for luteolin. (Figure Presented).}, author = {A. Primikyri and G. Mazzone and C. Lekka and A.G. Tzakos and N. Russo and I.P. Gerothanassis}, doi = {10.1021/jp509752s}, issue = {1}, journal = {Journal of Physical Chemistry B}, pages = {83-95}, title = {Understanding zinc(II) chelation with quercetin and luteolin: A combined NMR and theoretical study}, volume = {119}, year = {2015}, } - Siskos, M. G., A. G. Tzakos, and I. P. Gerothanassis. “Accurate ab initio calculations of o-h⋯o and o-h⋯–o proton chemical shifts: towards elucidation of the nature of the hydrogen bond and prediction of hydrogen bond distances.” Organic and biomolecular chemistry 13 (2015): 8852-8868. doi:10.1039/c5ob00920k
[BibTeX] [Abstract]
The inability to determine precisely the location of labile protons in X-ray molecular structures has been a key barrier to progress in many areas of molecular sciences. We report an approach for predicting hydrogen bond distances beyond the limits of X-ray crystallography based on accurate ab initio calculations of O-H⋯O proton chemical shifts, using a combination of DFT and contactor-like polarizable continuum model (PCM). Very good linear correlation between experimental and computed (at the GIAO/B3LYP/6-311++G(2d,p) level of theory) chemical shifts were obtained with a large set of 43 compounds in CHCl3 exhibiting intramolecular O-H⋯O and intermolecular and intramolecular ionic O-H⋯-O hydrogen bonds. The calculated OH chemical shifts exhibit a strong linear dependence on the computed (O)H⋯O hydrogen bond length, in the region of 1.24 to 1.85 Å, of -19.8 ppm Å-1 and -20.49 ppm Å-1 with optimization of the structures at the M06-2X/6-31+G(d) and B3LYP/6-31+G(d) level of theory, respectively. A Natural Bond Orbitals (NBO) analysis demonstrates a very good linear correlation between the calculated 1H chemical shifts and (i) the second-order perturbation stabilization energies, corresponding to charge transfer between the oxygen lone pairs and σ∗OH antibonding orbital and (ii) Wiberg bond order of the O-H⋯O and O-H⋯-O hydrogen bond. Accurate ab initio calculations of O-H⋯O and O-H⋯-O 1H chemical shifts can provide improved structural and electronic description of hydrogen bonding and a highly accurate measure of distances of short and strong hydrogen bonds.
@article{Siskos2015, abstract = {The inability to determine precisely the location of labile protons in X-ray molecular structures has been a key barrier to progress in many areas of molecular sciences. We report an approach for predicting hydrogen bond distances beyond the limits of X-ray crystallography based on accurate ab initio calculations of O-H⋯O proton chemical shifts, using a combination of DFT and contactor-like polarizable continuum model (PCM). Very good linear correlation between experimental and computed (at the GIAO/B3LYP/6-311++G(2d,p) level of theory) chemical shifts were obtained with a large set of 43 compounds in CHCl3 exhibiting intramolecular O-H⋯O and intermolecular and intramolecular ionic O-H⋯-O hydrogen bonds. The calculated OH chemical shifts exhibit a strong linear dependence on the computed (O)H⋯O hydrogen bond length, in the region of 1.24 to 1.85 Å, of -19.8 ppm Å-1 and -20.49 ppm Å-1 with optimization of the structures at the M06-2X/6-31+G(d) and B3LYP/6-31+G(d) level of theory, respectively. A Natural Bond Orbitals (NBO) analysis demonstrates a very good linear correlation between the calculated 1H chemical shifts and (i) the second-order perturbation stabilization energies, corresponding to charge transfer between the oxygen lone pairs and σ∗OH antibonding orbital and (ii) Wiberg bond order of the O-H⋯O and O-H⋯-O hydrogen bond. Accurate ab initio calculations of O-H⋯O and O-H⋯-O 1H chemical shifts can provide improved structural and electronic description of hydrogen bonding and a highly accurate measure of distances of short and strong hydrogen bonds.}, author = {M.G. Siskos and A.G. Tzakos and I.P. Gerothanassis}, doi = {10.1039/c5ob00920k}, issue = {33}, journal = {Organic and Biomolecular Chemistry}, pages = {8852-8868}, title = {Accurate ab initio calculations of O-H⋯O and O-H⋯-O proton chemical shifts: Towards elucidation of the nature of the hydrogen bond and prediction of hydrogen bond distances}, volume = {13}, year = {2015}, }
2014
- Magnani, F., C. G. Pappas, T. Crook, V. Magafa, P. Cordopatis, S. Ishiguro, N. Ohta, J. Selent, S. Bosnyak, E. S. Jones, R. E. Widdop, and A. G. Tzakos. “Electronic sculpting of ligand-gpcr subtype selectivity: the case of angiotensin ii.” Acs chemical biology 9 (2014): 1420-1425. doi:10.1021/cb500063y
[BibTeX] [Abstract]
GPCR subtypes possess distinct functional and pharmacological profiles, and thus development of subtype-selective ligands has immense therapeutic potential. This is especially the case for the angiotensin receptor subtypes AT1R and AT2R, where a functional negative control has been described and AT2R activation highlighted as an important cancer drug target. We describe a strategy to fine-tune ligand selectivity for the AT2R/AT1R subtypes through electronic control of ligand aromatic-prolyl interactions. Through this strategy an AT2R high affinity (Ki = 3 nM) agonist analogue that exerted 18,000-fold higher selectivity for AT2R versus AT1R was obtained. We show that this compound is a negative regulator of AT1R signaling since it is able to inhibit MCF-7 breast carcinoma cellular proliferation in the low nanomolar range. © 2014 American Chemical Society.
@article{Magnani2014, abstract = {GPCR subtypes possess distinct functional and pharmacological profiles, and thus development of subtype-selective ligands has immense therapeutic potential. This is especially the case for the angiotensin receptor subtypes AT1R and AT2R, where a functional negative control has been described and AT2R activation highlighted as an important cancer drug target. We describe a strategy to fine-tune ligand selectivity for the AT2R/AT1R subtypes through electronic control of ligand aromatic-prolyl interactions. Through this strategy an AT2R high affinity (Ki = 3 nM) agonist analogue that exerted 18,000-fold higher selectivity for AT2R versus AT1R was obtained. We show that this compound is a negative regulator of AT1R signaling since it is able to inhibit MCF-7 breast carcinoma cellular proliferation in the low nanomolar range. © 2014 American Chemical Society.}, author = {F. Magnani and C.G. Pappas and T. Crook and V. Magafa and P. Cordopatis and S. Ishiguro and N. Ohta and J. Selent and S. Bosnyak and E.S. Jones and R.E. Widdop and A.G. Tzakos}, doi = {10.1021/cb500063y}, issue = {7}, journal = {ACS Chemical Biology}, pages = {1420-1425}, title = {Electronic sculpting of ligand-GPCR subtype selectivity: The case of angiotensin II}, volume = {9}, year = {2014}, } - Stathopoulos, P., S. Papas, M. Sakka, A. G. Tzakos, and V. Tsikaris. “A rapid and efficient method for the synthesis of selectively s-trt or s-mmt protected cys-containing peptides.” Amino acids 46 (2014): 1367-1376. doi:10.1007/s00726-014-1696-0
[BibTeX] [Abstract]
Selective removal of protecting groups under different cleavage mechanisms could be an asset in peptide synthesis, since it provides the feasibility to incorporate different functional groups in similar reactive centres. However, selective protection/deprotection of orthogonal protecting groups in peptides is still challenging, especially for Cys-containing peptides, where protection of the cysteine side-chain is mandatory since the nucleophilic thiol can be otherwise alkylated, acylated or oxidized. Herein, we established a protocol for the synthesis of Cys-selective S-Trt or S-Mmt protected Cys-containing peptides, in a rapid way. This was achieved by, simply fine-tuning the carbocation scavenger in the final acidolytic release of the peptide from the solid support in the classic SPPS. © 2014 Springer-Verlag Wien.
@article{Stathopoulos2014, abstract = {Selective removal of protecting groups under different cleavage mechanisms could be an asset in peptide synthesis, since it provides the feasibility to incorporate different functional groups in similar reactive centres. However, selective protection/deprotection of orthogonal protecting groups in peptides is still challenging, especially for Cys-containing peptides, where protection of the cysteine side-chain is mandatory since the nucleophilic thiol can be otherwise alkylated, acylated or oxidized. Herein, we established a protocol for the synthesis of Cys-selective S-Trt or S-Mmt protected Cys-containing peptides, in a rapid way. This was achieved by, simply fine-tuning the carbocation scavenger in the final acidolytic release of the peptide from the solid support in the classic SPPS. © 2014 Springer-Verlag Wien.}, author = {P. Stathopoulos and S. Papas and M. Sakka and A.G. Tzakos and V. Tsikaris}, doi = {10.1007/s00726-014-1696-0}, issue = {5}, journal = {Amino Acids}, pages = {1367-1376}, title = {A rapid and efficient method for the synthesis of selectively S-Trt or S-Mmt protected Cys-containing peptides}, volume = {46}, year = {2014}, } - Karampelas, T., O. Argyros, N. Sayyad, K. Spyridaki, C. Pappas, K. Morgan, G. Kolios, R. P. Millar, G. Liapakis, A. G. Tzakos, D. Fokas, and C. Tamvakopoulos. “Gnrh-gemcitabine conjugates for the treatment of androgen-independent prostate cancer: pharmacokinetic enhancements combined with targeted drug delivery.” Bioconjugate chemistry 25 (2014): 813-823. doi:10.1021/bc500081g
[BibTeX] [Abstract]
Gemcitabine, a drug with established efficacy against a number of solid tumors, has therapeutic limitations due to its rapid metabolic inactivation. The aim of this study was the development of an innovative strategy to produce a metabolically stable analogue of gemcitabine that could also be selectively delivered to prostate cancer (CaP) cells based on cell surface expression of the Gonadotropin Releasing Hormone-Receptor (GnRH-R). The synthesis and evaluation of conjugated molecules, consisting of gemcitabine linked to a GnRH agonist, is presented along with results in androgen-independent prostate cancer models. NMR and ligand binding assays were employed to verify conservation of microenvironments responsible for binding of novel GnRH-gemcitabine conjugates to the GnRH-R. In vitro cytotoxicity, cellular uptake, and metabolite formation of the conjugates were examined in CaP cell lines. Selected conjugates were efficacious in the in vitro assays with one of them, namely, GSG, displaying high antiproliferative activity in CaP cell lines along with significant metabolic and pharmacokinetic advantages in comparison to gemcitabine. Finally, treatment of GnRH-R positive xenografted mice with GSG showed a significant advantage in tumor growth inhibition when compared to gemcitabine. © 2014 American Chemical Society.
@article{Karampelas2014, abstract = {Gemcitabine, a drug with established efficacy against a number of solid tumors, has therapeutic limitations due to its rapid metabolic inactivation. The aim of this study was the development of an innovative strategy to produce a metabolically stable analogue of gemcitabine that could also be selectively delivered to prostate cancer (CaP) cells based on cell surface expression of the Gonadotropin Releasing Hormone-Receptor (GnRH-R). The synthesis and evaluation of conjugated molecules, consisting of gemcitabine linked to a GnRH agonist, is presented along with results in androgen-independent prostate cancer models. NMR and ligand binding assays were employed to verify conservation of microenvironments responsible for binding of novel GnRH-gemcitabine conjugates to the GnRH-R. In vitro cytotoxicity, cellular uptake, and metabolite formation of the conjugates were examined in CaP cell lines. Selected conjugates were efficacious in the in vitro assays with one of them, namely, GSG, displaying high antiproliferative activity in CaP cell lines along with significant metabolic and pharmacokinetic advantages in comparison to gemcitabine. Finally, treatment of GnRH-R positive xenografted mice with GSG showed a significant advantage in tumor growth inhibition when compared to gemcitabine. © 2014 American Chemical Society.}, author = {T. Karampelas and O. Argyros and N. Sayyad and K. Spyridaki and C. Pappas and K. Morgan and G. Kolios and R.P. Millar and G. Liapakis and A.G. Tzakos and D. Fokas and C. Tamvakopoulos}, doi = {10.1021/bc500081g}, issue = {4}, journal = {Bioconjugate Chemistry}, pages = {813-823}, title = {GnRH-gemcitabine conjugates for the treatment of androgen-independent prostate cancer: Pharmacokinetic enhancements combined with targeted drug delivery}, volume = {25}, year = {2014}, } - Primikyri, A., M. V. Chatziathanasiadou, E. Karali, E. Kostaras, M. D. Mantzaris, E. Hatzimichael, J. -S. Shin, S. -W. Chi, E. Briasoulis, E. Kolettas, I. P. Gerothanassis, and A. G. Tzakos. “Direct binding of bcl-2 family proteins by quercetin triggers its pro-apoptotic activity.” Acs chemical biology 9 (2014): 2737-2741. doi:10.1021/cb500259e
[BibTeX] [Abstract]
Bcl-2 family proteins are important regulators of apoptosis and its antiapoptotic members, which are overexpressed in many types of cancer, are of high prognostic significance, establishing them as attractive therapeutic targets. Quercetin, a natural flavonoid, has drawn much attention because it exerts anticancer effects, while sparing normal cells. A multidisciplinary approach has been employed herein, in an effort to reveal its mode of action including dose-response antiproliferative activity and induced apoptosis effect, biochemical and physicochemical assays, and computational calculations. It may be concluded that, quercetin binds directly to the BH3 domain of Bcl-2 and Bcl-xL proteins, thereby inhibiting their activity and promoting cancer cell apoptosis.
@article{Primikyri2014, abstract = {Bcl-2 family proteins are important regulators of apoptosis and its antiapoptotic members, which are overexpressed in many types of cancer, are of high prognostic significance, establishing them as attractive therapeutic targets. Quercetin, a natural flavonoid, has drawn much attention because it exerts anticancer effects, while sparing normal cells. A multidisciplinary approach has been employed herein, in an effort to reveal its mode of action including dose-response antiproliferative activity and induced apoptosis effect, biochemical and physicochemical assays, and computational calculations. It may be concluded that, quercetin binds directly to the BH3 domain of Bcl-2 and Bcl-xL proteins, thereby inhibiting their activity and promoting cancer cell apoptosis.}, author = {A. Primikyri and M.V. Chatziathanasiadou and E. Karali and E. Kostaras and M.D. Mantzaris and E. Hatzimichael and J.-S. Shin and S.-W. Chi and E. Briasoulis and E. Kolettas and I.P. Gerothanassis and A.G. Tzakos}, doi = {10.1021/cb500259e}, issue = {12}, journal = {ACS Chemical Biology}, pages = {2737-2741}, title = {Direct binding of Bcl-2 family proteins by quercetin triggers its pro-apoptotic activity}, volume = {9}, year = {2014}, } - Stamatopoulou, V., C. Toumpeki, A. Vourekas, M. Bikou, M. Tsitlaidou, A. G. Tzakos, A. Afendra, C. Drainas, and D. Drainas. “On the role of the appended p19 element in type a rnas of bacterial rnase p.” Biochemistry 53 (2014): 1810-1817. doi:10.1021/bi4011013
[BibTeX] [Abstract]
Comparative in silico analyses of bacterial RNase P enzymes clustered their RNA subunits in type A RNA, found in Escherichia coli, and in type B, found in Bacillus subtilis. Zymomonas mobilis RNase P consists of one protein (Zmo-RnpA) and one type A RNA (RPR) subunit containing the P19 element, present in many RNase P RNAs of any structure class but lacking in the E. coli RNase P RNA. To investigate the putative role of the P19 stem, we constructed a P19 deletion RNA mutant (ΔP19RPR) and performed detailed kinetic analysis of reconstituted enzymes in the presence of the homologous Zmo-RnpA protein or Eco-RnpA protein from E. coli. The deletion of P19 perturbs the monovalent ion requirements. The Mg2+ requirement for the ΔP19RPR holoenzyme was almost identical to that for the wtRPR holoenzyme at Mg2+ concentrations of ≤25 mM. Interestingly, enzymes reconstituted with Eco-RnpA protein, relative to those assembled with Zmo-RnpA, exhibited enhanced activity in the presence of ΔP19RPR, suggesting that Eco-RnpA protein can effectively replace its Z. mobilis counterpart. Homologous and heterologous reconstituted enzymes in the presence of ΔP19RPR exhibited differences in their Km values and catalytic efficacies. Overall, the presence of the P19 stem points toward an adaption during the co-evolution of Zmo-RnpA and RPR that is essential for stabilizing the overall structure of the Z. mobilis RNase P. Finally, our results are in line with existing structural data on RNase P enzymes and provide biochemical support for the possible role of appended domains in RNase P RNA subunits. © 2014 American Chemical Society.
@article{Stamatopoulou2014, abstract = {Comparative in silico analyses of bacterial RNase P enzymes clustered their RNA subunits in type A RNA, found in Escherichia coli, and in type B, found in Bacillus subtilis. Zymomonas mobilis RNase P consists of one protein (Zmo-RnpA) and one type A RNA (RPR) subunit containing the P19 element, present in many RNase P RNAs of any structure class but lacking in the E. coli RNase P RNA. To investigate the putative role of the P19 stem, we constructed a P19 deletion RNA mutant (ΔP19RPR) and performed detailed kinetic analysis of reconstituted enzymes in the presence of the homologous Zmo-RnpA protein or Eco-RnpA protein from E. coli. The deletion of P19 perturbs the monovalent ion requirements. The Mg2+ requirement for the ΔP19RPR holoenzyme was almost identical to that for the wtRPR holoenzyme at Mg2+ concentrations of ≤25 mM. Interestingly, enzymes reconstituted with Eco-RnpA protein, relative to those assembled with Zmo-RnpA, exhibited enhanced activity in the presence of ΔP19RPR, suggesting that Eco-RnpA protein can effectively replace its Z. mobilis counterpart. Homologous and heterologous reconstituted enzymes in the presence of ΔP19RPR exhibited differences in their Km values and catalytic efficacies. Overall, the presence of the P19 stem points toward an adaption during the co-evolution of Zmo-RnpA and RPR that is essential for stabilizing the overall structure of the Z. mobilis RNase P. Finally, our results are in line with existing structural data on RNase P enzymes and provide biochemical support for the possible role of appended domains in RNase P RNA subunits. © 2014 American Chemical Society.}, author = {V. Stamatopoulou and C. Toumpeki and A. Vourekas and M. Bikou and M. Tsitlaidou and A.G. Tzakos and A. Afendra and C. Drainas and D. Drainas}, doi = {10.1021/bi4011013}, issue = {11}, journal = {Biochemistry}, pages = {1810-1817}, title = {On the role of the appended P19 element in type A RNAs of bacterial RNase P}, volume = {53}, year = {2014}, } - Charisiadis, P., V. G. Kontogianni, C. G. Tsiafoulis, A. G. Tzakos, M. Siskos, and I. P. Gerothanassis. “1h-nmr as a structural and analytical tool of intra- and intermolecular hydrogen bonds of phenol-containing natural products and model compounds.” Molecules 19 (2014): 13643-13682. doi:10.3390/molecules190913643
[BibTeX] [Abstract]
Experimental parameters that influence the resolution of 1H-NMR phenol OH signals are critically evaluated with emphasis on the effects of pH, temperature and nature of the solvents. Extremely sharp peaks (Δν1/2≤ 2 Hz) can be obtained under optimized experimental conditions which allow the application of 1H-13C HMBC-NMR experiments to reveal long range coupling constants of hydroxyl protons and, thus, to provide unequivocal assignment of the OH signals even in cases of complex polyphenol natural products. Intramolecular and intermolecular hydrogen bonds have a very significant effect on 1H OH chemical shifts which cover a region from 4.5 up to 19 ppm. Solvent effects on -OH proton chemical shifts, temperature coefficients (Δδ/ΔT), OH diffusion coefficients, and nJ(13C, O1H) coupling constants are evaluated as indicators of hydrogen bonding and solvation state of phenol-OH groups. Accurate 1H chemical shifts of the OH groups can be calculated using a combination of DFT and discrete solute-solvent hydrogen bond interaction at relatively inexpensive levels of theory, namely, DFT/B3LYP/6-311++G (2d,p). Excellent correlations between experimental 1H chemical shifts and those calculated at the ab initio level can provide a method of primary interest in order to obtain structural and conformational description of solute-solvent interactions at a molecular level. The use of the high resolution phenol hydroxyl group 1H-NMR spectral region provides a general method for the analysis of complex plant extracts without the need for the isolation of the individual components.
@article{Charisiadis2014, abstract = {Experimental parameters that influence the resolution of 1H-NMR phenol OH signals are critically evaluated with emphasis on the effects of pH, temperature and nature of the solvents. Extremely sharp peaks (Δν1/2≤ 2 Hz) can be obtained under optimized experimental conditions which allow the application of 1H-13C HMBC-NMR experiments to reveal long range coupling constants of hydroxyl protons and, thus, to provide unequivocal assignment of the OH signals even in cases of complex polyphenol natural products. Intramolecular and intermolecular hydrogen bonds have a very significant effect on 1H OH chemical shifts which cover a region from 4.5 up to 19 ppm. Solvent effects on -OH proton chemical shifts, temperature coefficients (Δδ/ΔT), OH diffusion coefficients, and nJ(13C, O1H) coupling constants are evaluated as indicators of hydrogen bonding and solvation state of phenol-OH groups. Accurate 1H chemical shifts of the OH groups can be calculated using a combination of DFT and discrete solute-solvent hydrogen bond interaction at relatively inexpensive levels of theory, namely, DFT/B3LYP/6-311++G (2d,p). Excellent correlations between experimental 1H chemical shifts and those calculated at the ab initio level can provide a method of primary interest in order to obtain structural and conformational description of solute-solvent interactions at a molecular level. The use of the high resolution phenol hydroxyl group 1H-NMR spectral region provides a general method for the analysis of complex plant extracts without the need for the isolation of the individual components.}, author = {P. Charisiadis and V.G. Kontogianni and C.G. Tsiafoulis and A.G. Tzakos and M. Siskos and I.P. Gerothanassis}, doi = {10.3390/molecules190913643}, issue = {9}, journal = {Molecules}, pages = {13643-13682}, title = {1H-NMR as a structural and analytical tool of intra- and intermolecular hydrogen bonds of phenol-containing natural products and model compounds}, volume = {19}, year = {2014}, } - Ntountaniotis, D., T. Kellici, A. Tzakos, P. Kolokotroni, T. Tselios, J. Becker-Baldus, C. Glaubitz, S. Lin, A. Makriyannis, and T. Mavromoustakos. “The application of solid-state nmr spectroscopy to study candesartan cilexetil (tcv-116) membrane interactions. comparative study with the at1r antagonist drug olmesartan.” Biochimica et biophysica acta – biomembranes 1838 (2014): 2439-2450. doi:10.1016/j.bbamem.2014.06.003
[BibTeX] [Abstract]
AT1 receptor (AT1R) antagonists exert their antihypertensive effects by preventing the vasoconstrictive hormone AngII to bind to the AT1 receptor. It has been proposed that these biological effects are mediated through a two-step mechanism reaction. In the first step, they are incorporated in the core of the lipid bilayers and in the second step they reach the active site of the receptor through lateral diffusion. In this model, drug/membrane interactions are key elements for the drugs achieving inhibition at the AT1 receptor. In this work, the interactions of the prodrug candesartan cilexetil (TCV-116) with lipid bilayers are studied at molecular detail. Solid-state 13C-CP/MAS, 2D 1H-1H NOESY NMR spectroscopy and in silico calculations are used. TCV-116 and olmesartan, another drug which acts as an AT1R antagonist are compared for their dynamic effects in lipid bilayers using solid-state 2H-NMR. We find a similar localization of TCV-116 compared to other AT1 antagonists in the intermediate polar region. In addition, we can identify specific local interactions. These interactions may be associated in part with the discrete pharmacological profiles observed for different antagonists. © 2014 Elsevier B.V. All rights reserved.
@article{Ntountaniotis2014, abstract = {AT1 receptor (AT1R) antagonists exert their antihypertensive effects by preventing the vasoconstrictive hormone AngII to bind to the AT1 receptor. It has been proposed that these biological effects are mediated through a two-step mechanism reaction. In the first step, they are incorporated in the core of the lipid bilayers and in the second step they reach the active site of the receptor through lateral diffusion. In this model, drug/membrane interactions are key elements for the drugs achieving inhibition at the AT1 receptor. In this work, the interactions of the prodrug candesartan cilexetil (TCV-116) with lipid bilayers are studied at molecular detail. Solid-state 13C-CP/MAS, 2D 1H-1H NOESY NMR spectroscopy and in silico calculations are used. TCV-116 and olmesartan, another drug which acts as an AT1R antagonist are compared for their dynamic effects in lipid bilayers using solid-state 2H-NMR. We find a similar localization of TCV-116 compared to other AT1 antagonists in the intermediate polar region. In addition, we can identify specific local interactions. These interactions may be associated in part with the discrete pharmacological profiles observed for different antagonists. © 2014 Elsevier B.V. All rights reserved.}, author = {D. Ntountaniotis and T. Kellici and A. Tzakos and P. Kolokotroni and T. Tselios and J. Becker-Baldus and C. Glaubitz and S. Lin and A. Makriyannis and T. Mavromoustakos}, doi = {10.1016/j.bbamem.2014.06.003}, issue = {10}, journal = {Biochimica et Biophysica Acta - Biomembranes}, pages = {2439-2450}, title = {The application of solid-state NMR spectroscopy to study candesartan cilexetil (TCV-116) membrane interactions. Comparative study with the AT1R antagonist drug olmesartan}, volume = {1838}, year = {2014}, } - Charisiadis, P., C. G. Tsiafoulis, A. G. Tzakos, and I. P. Gerothanassis. “Dynamic changes in composition of extracts of natural products as monitored by in situ nmr.” Magnetic resonance in chemistry 52 (2014): 764-768. doi:10.1002/mrc.4128
[BibTeX] [Abstract]
The direct in situ NMR observation and quantification, based on the aldehyde -CH chemical shift region, of the inter-conversion of secoiridoid derivatives due to temperature and solvent effects is demonstrated in complex extracts of natural products without prior isolation of the individual components. The equilibrium between the aldehyde hydrate form and the dialdehyde form of the oleuropein aglycon of an olive leaf aqueous extract in D2O was shown to be temperature dependent. The resulting thermodynamic values of the Van’t Hoff plot with ΔHo=-26.34±1.00kJmol-1 and TΔS°(298K)=-24.70±1.00kJmol-1 demonstrate a significant entropy term which nearly compensates the effect of enthalpy at room temperature. The equilibrium between the two diastereomeric hemiacetal forms and the dialdehyde form of the oleuropein 6-O-β-d-glucopyranoside aglycon of an olive leaf aqueous extract in CD3OD was also shown to be strongly temperature dependent again because of the significant entropy term (TΔS°(298K)=-26.50±1.39kJmol-1) compared with that of the enthalpy term (ΔHo=-36.64±1.46kJmol-1). This is the first demonstration of the significant role of the entropy parameter in determining the equilibrium of chemical transformations in complex mixtures of natural products due to solvent and temperature effects.
@article{Charisiadis2014, abstract = {The direct in situ NMR observation and quantification, based on the aldehyde -CH chemical shift region, of the inter-conversion of secoiridoid derivatives due to temperature and solvent effects is demonstrated in complex extracts of natural products without prior isolation of the individual components. The equilibrium between the aldehyde hydrate form and the dialdehyde form of the oleuropein aglycon of an olive leaf aqueous extract in D2O was shown to be temperature dependent. The resulting thermodynamic values of the Van't Hoff plot with ΔHo=-26.34±1.00kJmol-1 and TΔS°(298K)=-24.70±1.00kJmol-1 demonstrate a significant entropy term which nearly compensates the effect of enthalpy at room temperature. The equilibrium between the two diastereomeric hemiacetal forms and the dialdehyde form of the oleuropein 6-O-β-d-glucopyranoside aglycon of an olive leaf aqueous extract in CD3OD was also shown to be strongly temperature dependent again because of the significant entropy term (TΔS°(298K)=-26.50±1.39kJmol-1) compared with that of the enthalpy term (ΔHo=-36.64±1.46kJmol-1). This is the first demonstration of the significant role of the entropy parameter in determining the equilibrium of chemical transformations in complex mixtures of natural products due to solvent and temperature effects.}, author = {P. Charisiadis and C.G. Tsiafoulis and A.G. Tzakos and I.P. Gerothanassis}, doi = {10.1002/mrc.4128}, issue = {12}, journal = {Magnetic Resonance in Chemistry}, pages = {764-768}, title = {Dynamic changes in composition of extracts of natural products as monitored by in situ NMR}, volume = {52}, year = {2014}, }
2013
- Froudarakis, M., E. Hatzimichael, L. Kyriazopoulou, K. Lagos, P. Pappas, A. G. Tzakos, V. Karavasilis, D. Daliani, C. Papandreou, and E. Briasoulis. “Revisiting bleomycin from pathophysiology to safe clinical use.” Critical reviews in oncology/hematology 87 (2013): 90-100. doi:10.1016/j.critrevonc.2012.12.003
[BibTeX] [Abstract]
Bleomycin is a key component of curative chemotherapy regimens employed in the treatment of curable cancers, such as Hodgkin lymphoma (HL) and testicular germ-cell tumours (GCT), yet its use may cause bleomycin-induced lung injury (BILI), which is associated with significant morbidity and a mortality rate of 1-3%. Diagnosis of BILI is one of exclusion and physicians involved in the care of HL and GCT patients should be alerted. Pharmacogenomic studies could contribute towards the identification of molecular predictors of bleomycin toxicity on the aim to optimize individual use of bleomycin. We review all existing data on bleomycin’s most recent integrated chemical biology, molecular pharmacology and mature clinical data and provide guidelines for its safe clinical use. © 2012 Elsevier Ireland Ltd.
@article{Froudarakis2013, abstract = {Bleomycin is a key component of curative chemotherapy regimens employed in the treatment of curable cancers, such as Hodgkin lymphoma (HL) and testicular germ-cell tumours (GCT), yet its use may cause bleomycin-induced lung injury (BILI), which is associated with significant morbidity and a mortality rate of 1-3%. Diagnosis of BILI is one of exclusion and physicians involved in the care of HL and GCT patients should be alerted. Pharmacogenomic studies could contribute towards the identification of molecular predictors of bleomycin toxicity on the aim to optimize individual use of bleomycin. We review all existing data on bleomycin's most recent integrated chemical biology, molecular pharmacology and mature clinical data and provide guidelines for its safe clinical use. © 2012 Elsevier Ireland Ltd.}, author = {M. Froudarakis and E. Hatzimichael and L. Kyriazopoulou and K. Lagos and P. Pappas and A.G. Tzakos and V. Karavasilis and D. Daliani and C. Papandreou and E. Briasoulis}, doi = {10.1016/j.critrevonc.2012.12.003}, issue = {1}, journal = {Critical Reviews in Oncology/Hematology}, pages = {90-100}, title = {Revisiting bleomycin from pathophysiology to safe clinical use}, volume = {87}, year = {2013}, } - Kontogianni, V. G., G. Tomic, I. Nikolic, A. A. Nerantzaki, N. Sayyad, S. Stosic-Grujicic, I. Stojanovic, I. P. Gerothanassis, and A. G. Tzakos. “Phytochemical profile of rosmarinus officinalis and salvia officinalis extracts and correlation to their antioxidant and anti-proliferative activity.” Food chemistry 136 (2013): 120-129. doi:10.1016/j.foodchem.2012.07.091
[BibTeX] [Abstract]
The goal of this study was to monitor the anti-proliferative activity of Rosmarinus officinalis and Salvia officinalis extracts against cancer cells and to correlate this activity with their phytochemical profiles using liquid chromatography/diode array detection/electrospray ion trap tandem mass spectrometry (LC/DAD/ESI-MSn). For the quantitative estimation of triterpenic acids in the crude extracts an NMR based methodology was used and compared with the HPLC measurements, both applied for the first time, for the case of betulinic acid. Both extracts exerted cytotoxic activity through dose-dependent impairment of viability and mitochondrial activity of rat insulinoma m5F (RINm5F) cells. Decrease of RINm5F viability was mediated by nitric oxide (NO)-induced apoptosis. Importantly, these extracts potentiated NO and TNF-α release from macrophages therefore enhancing their cytocidal action. The rosemary extract developed more pronounced antioxidant, cytotoxic and immunomodifying activities, probably due to the presence of betulinic acid and a higher concentration of carnosic acid in its phytochemical profile. © 2012 Elsevier Ltd. All rights reserved.
@article{Kontogianni2013, abstract = {The goal of this study was to monitor the anti-proliferative activity of Rosmarinus officinalis and Salvia officinalis extracts against cancer cells and to correlate this activity with their phytochemical profiles using liquid chromatography/diode array detection/electrospray ion trap tandem mass spectrometry (LC/DAD/ESI-MSn). For the quantitative estimation of triterpenic acids in the crude extracts an NMR based methodology was used and compared with the HPLC measurements, both applied for the first time, for the case of betulinic acid. Both extracts exerted cytotoxic activity through dose-dependent impairment of viability and mitochondrial activity of rat insulinoma m5F (RINm5F) cells. Decrease of RINm5F viability was mediated by nitric oxide (NO)-induced apoptosis. Importantly, these extracts potentiated NO and TNF-α release from macrophages therefore enhancing their cytocidal action. The rosemary extract developed more pronounced antioxidant, cytotoxic and immunomodifying activities, probably due to the presence of betulinic acid and a higher concentration of carnosic acid in its phytochemical profile. © 2012 Elsevier Ltd. All rights reserved.}, author = {V.G. Kontogianni and G. Tomic and I. Nikolic and A.A. Nerantzaki and N. Sayyad and S. Stosic-Grujicic and I. Stojanovic and I.P. Gerothanassis and A.G. Tzakos}, doi = {10.1016/j.foodchem.2012.07.091}, issue = {1}, journal = {Food Chemistry}, pages = {120-129}, title = {Phytochemical profile of Rosmarinus officinalis and Salvia officinalis extracts and correlation to their antioxidant and anti-proliferative activity}, volume = {136}, year = {2013}, } - Stathopoulos, P., S. Papas, C. Pappas, V. Mousis, N. Sayyad, V. Theodorou, A. G. Tzakos, and V. Tsikaris. “Side reactions in the spps of cys-containing peptides.” Amino acids 44 (2013): 1357-1363. doi:10.1007/s00726-013-1471-7
[BibTeX] [Abstract]
Alkylation of sensitive amino acids during synthesis of biologically important peptides is a common and well-documented problem in Fmoc-based strategy. Herein, we probed for the first time an unexpected S-alkylation of Cys-containing peptides that occur during the final TFA cleavage of peptides from the Wang solid support. Through a battery of approaches (NMR, UV and LC-MS) the formed by-product was assigned as the alkylation of the cysteine sulfydryl group by the p-hydroxyl benzyl group derived from the acidic Wang linker decomposition. Factors affecting this side reaction were monitored and a protocol that minimizes the presence of the by-product is reported. © 2013 Springer-Verlag Wien.
@article{Stathopoulos2013, abstract = {Alkylation of sensitive amino acids during synthesis of biologically important peptides is a common and well-documented problem in Fmoc-based strategy. Herein, we probed for the first time an unexpected S-alkylation of Cys-containing peptides that occur during the final TFA cleavage of peptides from the Wang solid support. Through a battery of approaches (NMR, UV and LC-MS) the formed by-product was assigned as the alkylation of the cysteine sulfydryl group by the p-hydroxyl benzyl group derived from the acidic Wang linker decomposition. Factors affecting this side reaction were monitored and a protocol that minimizes the presence of the by-product is reported. © 2013 Springer-Verlag Wien.}, author = {P. Stathopoulos and S. Papas and C. Pappas and V. Mousis and N. Sayyad and V. Theodorou and A.G. Tzakos and V. Tsikaris}, doi = {10.1007/s00726-013-1471-7}, issue = {5}, journal = {Amino Acids}, pages = {1357-1363}, title = {Side reactions in the SPPS of Cys-containing peptides}, volume = {44}, year = {2013}, } - Siskos, M. G., V. G. Kontogianni, C. G. Tsiafoulis, A. G. Tzakos, and I. P. Gerothanassis. “Investigation of solute-solvent interactions in phenol compounds: accurate ab initio calculations of solvent effects on 1h nmr chemical shifts.” Organic and biomolecular chemistry 11 (2013): 7400-7411. doi:10.1039/c3ob41556b
[BibTeX] [Abstract]
Accurate 1H chemical shifts of the -OH groups of polyphenol compounds can be calculated, compared to experimental values, using a combination of DFT, polarizable continuum model (PCM) and discrete solute-solvent hydrogen bond interactions. The study focuses on three molecular solutes: phenol, 4-methylcatechol and the natural product genkwanin in DMSO, acetone, acetonitrile, and chloroform. Excellent linear correlation between experimental and computed chemical shifts (with the GIAO method at the DFT/B3LYP/6-311++G(2d,p) level) was obtained with minimization of the solvation complexes at the DFT/B3LYP/6-31+G(d) and DFT/B3LYP/6-311++G(d,p) level of theory with a correlation coefficient of 0.991. The use of the DFT/B3LYP/6-31+G(d) level of theory for minimization could provide an excellent means for the accurate prediction of the experimental OH chemical shift range of over 8 ppm due to: (i) strong intramolecular and solute-solvent intermolecular hydrogen bonds, (ii) flip-flop intramolecular hydrogen bonds, and (iii) conformational effects of substituents of genkwanin. The combined use of ab initio calculations and experimental 1H chemical shifts of phenol -OH groups provides a method of primary interest in order to obtain detailed structural, conformation and electronic description of solute-solvent interactions at a molecular level. © 2013 The Royal Society of Chemistry.
@article{Siskos2013, abstract = {Accurate 1H chemical shifts of the -OH groups of polyphenol compounds can be calculated, compared to experimental values, using a combination of DFT, polarizable continuum model (PCM) and discrete solute-solvent hydrogen bond interactions. The study focuses on three molecular solutes: phenol, 4-methylcatechol and the natural product genkwanin in DMSO, acetone, acetonitrile, and chloroform. Excellent linear correlation between experimental and computed chemical shifts (with the GIAO method at the DFT/B3LYP/6-311++G(2d,p) level) was obtained with minimization of the solvation complexes at the DFT/B3LYP/6-31+G(d) and DFT/B3LYP/6-311++G(d,p) level of theory with a correlation coefficient of 0.991. The use of the DFT/B3LYP/6-31+G(d) level of theory for minimization could provide an excellent means for the accurate prediction of the experimental OH chemical shift range of over 8 ppm due to: (i) strong intramolecular and solute-solvent intermolecular hydrogen bonds, (ii) flip-flop intramolecular hydrogen bonds, and (iii) conformational effects of substituents of genkwanin. The combined use of ab initio calculations and experimental 1H chemical shifts of phenol -OH groups provides a method of primary interest in order to obtain detailed structural, conformation and electronic description of solute-solvent interactions at a molecular level. © 2013 The Royal Society of Chemistry.}, author = {M.G. Siskos and V.G. Kontogianni and C.G. Tsiafoulis and A.G. Tzakos and I.P. Gerothanassis}, doi = {10.1039/c3ob41556b}, issue = {42}, journal = {Organic and Biomolecular Chemistry}, pages = {7400-7411}, title = {Investigation of solute-solvent interactions in phenol compounds: Accurate ab initio calculations of solvent effects on 1H NMR chemical shifts}, volume = {11}, year = {2013}, } - Kontogianni, V. G., P. Charisiadis, A. Primikyri, C. G. Pappas, V. Exarchou, A. G. Tzakos, and I. P. Gerothanassis. “Hydrogen bonding probes of phenol -oh groups.” Organic and biomolecular chemistry 11 (2013): 1013-1025. doi:10.1039/c2ob27117f
[BibTeX] [Abstract]
Correlations between hydrogen bonds and solvent effects on phenol -OH proton shieldings, temperature coefficients (Δδ/ΔT) and effects on OH diffusion coefficients for numerous phenolic acids, flavonols, flavones, and oleuropein derivatives of biological interest were investigated in several organic solvents and were shown to serve as reliable indicators of hydrogen bonding and solvation state of -OH groups. The temperature coefficients span a range of -0.5 to -12.3 ppb K-1. Shielding differences of 2.0 to 2.9 ppm at 298 K were observed for solvent exposed OH groups between DMSO-d6 and CD3CN which should be compared with a shielding range of ∼7 ppm. This demonstrates that the solvation state of hydroxyl protons is a key factor in determining the value of the chemical shift. For -OH protons showing temperature gradients more positive than -2.5 ppb K-1, shielding changes between DMSO-d6 and CD 3CN below 0.6 ppm, and diffusion coefficients significantly different from those of traces of H2O, there is an intramolecular hydrogen bond predictivity value of 100%. The C-3 OH protons of flavonols show very significant negative temperature coefficients and shielding changes between DMSO-d6 and CD3CN of ∼2.3 ppm, which indicate the absence of persistent intramolecular hydrogen bonds, contrary to numerous X-ray structures. © 2013 The Royal Society of Chemistry.
@article{Kontogianni2013, abstract = {Correlations between hydrogen bonds and solvent effects on phenol -OH proton shieldings, temperature coefficients (Δδ/ΔT) and effects on OH diffusion coefficients for numerous phenolic acids, flavonols, flavones, and oleuropein derivatives of biological interest were investigated in several organic solvents and were shown to serve as reliable indicators of hydrogen bonding and solvation state of -OH groups. The temperature coefficients span a range of -0.5 to -12.3 ppb K-1. Shielding differences of 2.0 to 2.9 ppm at 298 K were observed for solvent exposed OH groups between DMSO-d6 and CD3CN which should be compared with a shielding range of ∼7 ppm. This demonstrates that the solvation state of hydroxyl protons is a key factor in determining the value of the chemical shift. For -OH protons showing temperature gradients more positive than -2.5 ppb K-1, shielding changes between DMSO-d6 and CD 3CN below 0.6 ppm, and diffusion coefficients significantly different from those of traces of H2O, there is an intramolecular hydrogen bond predictivity value of 100%. The C-3 OH protons of flavonols show very significant negative temperature coefficients and shielding changes between DMSO-d6 and CD3CN of ∼2.3 ppm, which indicate the absence of persistent intramolecular hydrogen bonds, contrary to numerous X-ray structures. © 2013 The Royal Society of Chemistry.}, author = {V.G. Kontogianni and P. Charisiadis and A. Primikyri and C.G. Pappas and V. Exarchou and A.G. Tzakos and I.P. Gerothanassis}, doi = {10.1039/c2ob27117f}, issue = {6}, journal = {Organic and Biomolecular Chemistry}, pages = {1013-1025}, title = {Hydrogen bonding probes of phenol -OH groups}, volume = {11}, year = {2013}, } - Kontogianni, V. G., P. Charisiadis, E. Margianni, F. N. Lamari, I. P. Gerothanassis, and A. G. Tzakos. “Olive leaf extracts are a natural source of advanced glycation end product inhibitors.” Journal of medicinal food 16 (2013): 817-822. doi:10.1089/jmf.2013.0016
[BibTeX] [Abstract]
Advanced glycation end products (AGEs), which are readily formed and accumulated with sustained hyperglycemia, contribute to the development of diabetic complications. As a consequence, inhibition of AGE formation constitutes an attractive therapeutic/preventive target. In the current study, we explored the phytochemical composition and the in vitro effect of two different olive leaf extracts (an aqueous and a methanolic) on AGE formation. The methanolic olive leaf extract inhibited fluorescent AGE formation in a bovine serum albumin (BSA)-ribose system, whereas the aqueous extract had no effect in both BSA-fructose and BSA-ribose systems. The phytochemical profile was investigated with liquid chromatography-ultraviolet-visible (UV-Vis) diode array coupled to electrospray ionization multistage mass spectrometry (LC/DAD/ESI-MSn). Quantification of the major phenolic compounds was performed with high performance liquid chromatography with UV-Vis diode array detection and nuclear magnetic resonance spectroscopy. Among the major phenolic components (luteolin, hydroxytyrosol, luteolin-4′-O-β-D- glucopyranoside, luteolin-7-O-β-D-glucopyranoside, and oleuropein), luteolin and luteolin-4′-O-β-D-glucopyranoside were assigned as potent inhibitors of AGE formation. The extraction procedure greatly affects the composition and therefore the anti-glycation potential of olive leaves. © Mary Ann Liebert, Inc., and Korean Society of Food Science and Nutrition.
@article{Kontogianni2013, abstract = {Advanced glycation end products (AGEs), which are readily formed and accumulated with sustained hyperglycemia, contribute to the development of diabetic complications. As a consequence, inhibition of AGE formation constitutes an attractive therapeutic/preventive target. In the current study, we explored the phytochemical composition and the in vitro effect of two different olive leaf extracts (an aqueous and a methanolic) on AGE formation. The methanolic olive leaf extract inhibited fluorescent AGE formation in a bovine serum albumin (BSA)-ribose system, whereas the aqueous extract had no effect in both BSA-fructose and BSA-ribose systems. The phytochemical profile was investigated with liquid chromatography-ultraviolet-visible (UV-Vis) diode array coupled to electrospray ionization multistage mass spectrometry (LC/DAD/ESI-MSn). Quantification of the major phenolic compounds was performed with high performance liquid chromatography with UV-Vis diode array detection and nuclear magnetic resonance spectroscopy. Among the major phenolic components (luteolin, hydroxytyrosol, luteolin-4′-O-β-D- glucopyranoside, luteolin-7-O-β-D-glucopyranoside, and oleuropein), luteolin and luteolin-4′-O-β-D-glucopyranoside were assigned as potent inhibitors of AGE formation. The extraction procedure greatly affects the composition and therefore the anti-glycation potential of olive leaves. © Mary Ann Liebert, Inc., and Korean Society of Food Science and Nutrition.}, author = {V.G. Kontogianni and P. Charisiadis and E. Margianni and F.N. Lamari and I.P. Gerothanassis and A.G. Tzakos}, doi = {10.1089/jmf.2013.0016}, issue = {9}, journal = {Journal of Medicinal Food}, pages = {817-822}, title = {Olive leaf extracts are a natural source of advanced glycation end product inhibitors}, volume = {16}, year = {2013}, } - Papadopoulou, A. A., M. H. Katsoura, A. Chatzikonstantinou, E. Kyriakou, A. C. Polydera, A. G. Tzakos, and H. Stamatis. “Enzymatic hybridization of α-lipoic acid with bioactive compounds in ionic solvents.” Bioresource technology 136 (2013): 41-48. doi:10.1016/j.biortech.2013.02.067
[BibTeX] [Abstract]
The lipase-catalyzed molecular hybridization of α-lipoic acid (LA) with bioactive compounds pyridoxine, tyrosol and tyramine was performed in ionic solvents and deep eutectic solvents. The biocatalytic reactions were catalyzed by Candida antarctica lipase B immobilized onto various functionalized multi-walled carbon nanotubes (f-CNTs-CaLB), as well as by commercial Novozym 435. The use of f-CNTs-CaLB leads, in most cases, to higher conversion yields as compared to Novozym 435. The nature and ion composition of ionic solvents affect the performance of the biocatalytic process. The highest conversion yield was observed in (mtoa)NTf2. The high enzyme stability and the relatively low solubility of substrates in specific media account for the improved biocatalytic synthesis of molecular hybrids of LA. Principal component analysis was used to screen for potential lipoxygenase inhibitors. In vitro studies showed that the synthesized compounds exhibit up to 10-fold increased inhibitory activity on lipoxygenase mediated lipid peroxidation as compared to parent molecules. © 2013 Elsevier Ltd.
@article{Papadopoulou2013, abstract = {The lipase-catalyzed molecular hybridization of α-lipoic acid (LA) with bioactive compounds pyridoxine, tyrosol and tyramine was performed in ionic solvents and deep eutectic solvents. The biocatalytic reactions were catalyzed by Candida antarctica lipase B immobilized onto various functionalized multi-walled carbon nanotubes (f-CNTs-CaLB), as well as by commercial Novozym 435. The use of f-CNTs-CaLB leads, in most cases, to higher conversion yields as compared to Novozym 435. The nature and ion composition of ionic solvents affect the performance of the biocatalytic process. The highest conversion yield was observed in (mtoa)NTf2. The high enzyme stability and the relatively low solubility of substrates in specific media account for the improved biocatalytic synthesis of molecular hybrids of LA. Principal component analysis was used to screen for potential lipoxygenase inhibitors. In vitro studies showed that the synthesized compounds exhibit up to 10-fold increased inhibitory activity on lipoxygenase mediated lipid peroxidation as compared to parent molecules. © 2013 Elsevier Ltd.}, author = {A.A. Papadopoulou and M.H. Katsoura and A. Chatzikonstantinou and E. Kyriakou and A.C. Polydera and A.G. Tzakos and H. Stamatis}, doi = {10.1016/j.biortech.2013.02.067}, journal = {Bioresource Technology}, pages = {41-48}, title = {Enzymatic hybridization of α-lipoic acid with bioactive compounds in ionic solvents}, volume = {136}, year = {2013}, } - Vasilopoulou, C. G., V. G. Kontogianni, Z. I. Linardaki, G. Iatrou, F. N. Lamari, A. A. Nerantzaki, I. P. Gerothanassis, A. G. Tzakos, and M. Margarity. “Phytochemical composition of “mountain tea” from sideritis clandestina subsp. clandestina and evaluation of its behavioral and oxidant/antioxidant effects on adult mice.” European journal of nutrition 52 (2013): 107-116. doi:10.1007/s00394-011-0292-2
[BibTeX] [Abstract]
Purpose: The goals of this study were to monitor the effect of drinking of herbal tea from Sideritis clandestina subsp. clandestina for 6 weeks on behavioral and oxidant/antioxidant parameters of adult male mice and also to evaluate its phytochemical composition. Methods: The phytochemical profile of the Sideritis tea was determined by liquid chromatography-UV diode array coupled to ion-trap mass spectrometry with electrospray ionization interface. The effects of two doses of the herbal infusion (2 and 4% w/v, daily) intake on anxiety-like state in mice were studied by the assessment of their thigmotactic behavior. The oxidant/antioxidant status of brain (-Ce), liver and heart of adult male Balb-c mice following the consumption of Sideritis tea was also evaluated via the measurement of malondialdehyde (MDA) and reduced glutathione (GSH) levels using fluorometric assays. Our study was further extended to determine the antioxidant effects of the herbal tea on specific brain regions (cerebral cortex, cerebellum and midbrain). Results: The identified compounds were classified into several natural product classes: quinic acid derivatives, iridoids, phenylethanol glycosides and flavonoids. Our results showed that only the 4% Sideritis tea exhibited anxiolytic-like properties as evidenced by statistically significant (p < 0.05) decrease in the thigmotaxis time and increase in the number of entries to the central zone in comparison with the control group. Consumption of both tea doses (2 and 4% w/v) elevated GSH (12 and 28%, respectively, p < 0.05) and decreased MDA (16 and 29%, p < 0.05) levels in brain (-Ce), while liver and heart remained unaffected. In regard to the effect of herbal tea drinking (2 and 4% w/v) on specific brain regions, it caused a significant increase in GSH of cerebellum (13 and 36%, respectively, p < 0.05) and midbrain (17 and 36%, p < 0.05). Similarly, MDA levels were decreased in cerebellum (45 and 79%, respectively, p < 0.05) and midbrain (50 and 63%, respectively, p < 0.05), whereas cerebral cortex remained unaffected. Conclusions: Mountain tea drinking prevents anxiety-related behaviors and confers antioxidant protection to rodent's tissues in a region-specific, dose-dependent manner, and its phytochemical constituents are shown for the first time. © 2011 Springer-Verlag.
@article{Vasilopoulou2013, abstract = {Purpose: The goals of this study were to monitor the effect of drinking of herbal tea from Sideritis clandestina subsp. clandestina for 6 weeks on behavioral and oxidant/antioxidant parameters of adult male mice and also to evaluate its phytochemical composition. Methods: The phytochemical profile of the Sideritis tea was determined by liquid chromatography-UV diode array coupled to ion-trap mass spectrometry with electrospray ionization interface. The effects of two doses of the herbal infusion (2 and 4% w/v, daily) intake on anxiety-like state in mice were studied by the assessment of their thigmotactic behavior. The oxidant/antioxidant status of brain (-Ce), liver and heart of adult male Balb-c mice following the consumption of Sideritis tea was also evaluated via the measurement of malondialdehyde (MDA) and reduced glutathione (GSH) levels using fluorometric assays. Our study was further extended to determine the antioxidant effects of the herbal tea on specific brain regions (cerebral cortex, cerebellum and midbrain). Results: The identified compounds were classified into several natural product classes: quinic acid derivatives, iridoids, phenylethanol glycosides and flavonoids. Our results showed that only the 4% Sideritis tea exhibited anxiolytic-like properties as evidenced by statistically significant (p < 0.05) decrease in the thigmotaxis time and increase in the number of entries to the central zone in comparison with the control group. Consumption of both tea doses (2 and 4% w/v) elevated GSH (12 and 28%, respectively, p < 0.05) and decreased MDA (16 and 29%, p < 0.05) levels in brain (-Ce), while liver and heart remained unaffected. In regard to the effect of herbal tea drinking (2 and 4% w/v) on specific brain regions, it caused a significant increase in GSH of cerebellum (13 and 36%, respectively, p < 0.05) and midbrain (17 and 36%, p < 0.05). Similarly, MDA levels were decreased in cerebellum (45 and 79%, respectively, p < 0.05) and midbrain (50 and 63%, respectively, p < 0.05), whereas cerebral cortex remained unaffected. Conclusions: Mountain tea drinking prevents anxiety-related behaviors and confers antioxidant protection to rodent's tissues in a region-specific, dose-dependent manner, and its phytochemical constituents are shown for the first time. © 2011 Springer-Verlag.}, author = {C.G. Vasilopoulou and V.G. Kontogianni and Z.I. Linardaki and G. Iatrou and F.N. Lamari and A.A. Nerantzaki and I.P. Gerothanassis and A.G. Tzakos and M. Margarity}, doi = {10.1007/s00394-011-0292-2}, issue = {1}, journal = {European Journal of Nutrition}, pages = {107-116}, title = {Phytochemical composition of "mountain tea" from Sideritis clandestina subsp. clandestina and evaluation of its behavioral and oxidant/antioxidant effects on adult mice}, volume = {52}, year = {2013}, }
2012
- Tzakos, A. G., V. G. Kontogianni, M. Tsoumani, E. Kyriakou, J. Hwa, F. A. Rodrigues, and A. D. Tselepis. "Exploration of the antiplatelet activity profile of betulinic acid on human platelets." Journal of agricultural and food chemistry 60 (2012): 6977-6983. doi:10.1021/jf3006728
[BibTeX] [Abstract]
Betulinic acid, a natural pentacyclic triterpene acid, presents a diverse mode of biological actions including antiretroviral, antibacterial, antimalarial, and anti-inflammatory activities. The potency of betulinic acid as an inhibitor of human platelet activation was evaluated, and its antiplatelet profile against in vitro platelet aggregation, induced by several platelet agonists (adenosine diphosphate, thrombin receptor activator peptide-14, and arachidonic acid), was explored. Flow cytometric analysis was performed to examine the effect of betulinic acid on P-selectin membrane expression and PAC-1 binding to activated platelets. Betulinic acid potently inhibits platelet aggregation and also reduced PAC-1 binding and the membrane expression of P-selectin. Principal component analysis was used to screen, on the chemical property space, for potential common pharmacophores of betulinic acid with approved antithrombotic drugs. A common pharmacophore was defined between the NMR-derived structure of betulinic acid and prostacyclin agonists (PGI2), and the importance of its carboxylate group in its antiplatelet activity was determined. The present results indicate that betulinic acid has potential use as an antithrombotic compound and suggest that the mechanism underlying the antiplatelet effects of betulinic acid is similar to that of the PGI2 receptor agonists, a hypothesis that deserves further investigation. © 2012 American Chemical Society.
@article{Tzakos2012, abstract = {Betulinic acid, a natural pentacyclic triterpene acid, presents a diverse mode of biological actions including antiretroviral, antibacterial, antimalarial, and anti-inflammatory activities. The potency of betulinic acid as an inhibitor of human platelet activation was evaluated, and its antiplatelet profile against in vitro platelet aggregation, induced by several platelet agonists (adenosine diphosphate, thrombin receptor activator peptide-14, and arachidonic acid), was explored. Flow cytometric analysis was performed to examine the effect of betulinic acid on P-selectin membrane expression and PAC-1 binding to activated platelets. Betulinic acid potently inhibits platelet aggregation and also reduced PAC-1 binding and the membrane expression of P-selectin. Principal component analysis was used to screen, on the chemical property space, for potential common pharmacophores of betulinic acid with approved antithrombotic drugs. A common pharmacophore was defined between the NMR-derived structure of betulinic acid and prostacyclin agonists (PGI2), and the importance of its carboxylate group in its antiplatelet activity was determined. The present results indicate that betulinic acid has potential use as an antithrombotic compound and suggest that the mechanism underlying the antiplatelet effects of betulinic acid is similar to that of the PGI2 receptor agonists, a hypothesis that deserves further investigation. © 2012 American Chemical Society.}, author = {A.G. Tzakos and V.G. Kontogianni and M. Tsoumani and E. Kyriakou and J. Hwa and F.A. Rodrigues and A.D. Tselepis}, doi = {10.1021/jf3006728}, issue = {28}, journal = {Journal of Agricultural and Food Chemistry}, pages = {6977-6983}, title = {Exploration of the antiplatelet activity profile of betulinic acid on human platelets}, volume = {60}, year = {2012}, } - Charisiadis, P., C. G. Tsiafoulis, V. Exarchou, A. G. Tzakos, and I. P. Gerothanassis. "Rapid and direct low micromolar nmr method for the simultaneous detection of hydrogen peroxide and phenolics in plant extracts." Journal of agricultural and food chemistry 60 (2012): 4508-4513. doi:10.1021/jf205003e
[BibTeX] [Abstract]
A rapid and direct low micromolar 1H NMR method for the simultaneous identification and quantification of hydrogen peroxide and phenolic compounds in plant extracts was developed. The method is based on the highly deshielded 1H NMR signal of H2O2 at â̂ 10.30 ppm in DMSO-d6 and the combined use of picric acid and low temperature, near the freezing point of the solution, in order to achieve the minimum proton exchange rate. Line widths of H2O 2 below 3.8 Hz were obtained for several Greek oregano extracts which resulted in a detection limit of 0.7 μmol L-1. Application of an array of NMR experiments, including 2D 1H-13C HMBC, spiking of the samples with H2O2, and variable temperature experiments, resulted in the unequivocal assignment of H2O 2 precluding any confusion with interferences from intrinsic phenolics in the extract. © 2012 American Chemical Society.
@article{Charisiadis2012, abstract = {A rapid and direct low micromolar 1H NMR method for the simultaneous identification and quantification of hydrogen peroxide and phenolic compounds in plant extracts was developed. The method is based on the highly deshielded 1H NMR signal of H2O2 at â̂ 10.30 ppm in DMSO-d6 and the combined use of picric acid and low temperature, near the freezing point of the solution, in order to achieve the minimum proton exchange rate. Line widths of H2O 2 below 3.8 Hz were obtained for several Greek oregano extracts which resulted in a detection limit of 0.7 μmol L-1. Application of an array of NMR experiments, including 2D 1H-13C HMBC, spiking of the samples with H2O2, and variable temperature experiments, resulted in the unequivocal assignment of H2O 2 precluding any confusion with interferences from intrinsic phenolics in the extract. © 2012 American Chemical Society.}, author = {P. Charisiadis and C.G. Tsiafoulis and V. Exarchou and A.G. Tzakos and I.P. Gerothanassis}, doi = {10.1021/jf205003e}, issue = {18}, journal = {Journal of Agricultural and Food Chemistry}, pages = {4508-4513}, title = {Rapid and direct low micromolar NMR method for the simultaneous detection of hydrogen peroxide and phenolics in plant extracts}, volume = {60}, year = {2012}, } - Koutsotoli, A. and A. G. Tzakos. "Host- pathogen crosstalking: the mastery of taking the helm of the host." Structure 20 (2012): 1613-1615. doi:10.1016/j.str.2012.09.006
[BibTeX] [Abstract]
How can pathogen proteins functionally hijack their hosts? In this issue of Structure, Aitio et al. reveal that the process involves coordinated intrinsic disorder in a short pathogen sequence that elegantly commandeers the tightly regulated cytoskeletal signaling in the host. © 2012 Elsevier Ltd.
@article{Koutsotoli2012, abstract = {How can pathogen proteins functionally hijack their hosts? In this issue of Structure, Aitio et al. reveal that the process involves coordinated intrinsic disorder in a short pathogen sequence that elegantly commandeers the tightly regulated cytoskeletal signaling in the host. © 2012 Elsevier Ltd.}, author = {A. Koutsotoli and A.G. Tzakos}, doi = {10.1016/j.str.2012.09.006}, issue = {10}, journal = {Structure}, pages = {1613-1615}, title = {Host- pathogen crosstalking: The mastery of taking the helm of the host}, volume = {20}, year = {2012}, } - Nagulapalli, M., G. Parigi, J. Yuan, J. Gsponer, G. Deraos, V. V. Bamm, G. Harauz, J. Matsoukas, De M. R. R. Planque, I. P. Gerothanassis, C. Luchinat, and A. G. Tzakos. "Recognition pliability is coupled to structural heterogeneity: a calmodulin intrinsically disordered binding region complex." Structure 20 (2012): 522-533. doi:10.1016/j.str.2012.01.021
[BibTeX] [Abstract]
Protein interactions within regulatory networks should adapt in a spatiotemporal-dependent dynamic environment, in order to process and respond to diverse and versatile cellular signals. However, the principles governing recognition pliability in protein complexes are not well understood. We have investigated a region of the intrinsically disordered protein myelin basic protein (MBP 145-165) that interacts with calmodulin, but that also promiscuously binds other biomolecules (membranes, modifying enzymes). To characterize this interaction, we implemented an NMR spectroscopic approach that calculates, for each conformation of the complex, the maximum occurrence based on recorded pseudocontact shifts and residual dipolar couplings. We found that the MBP 145-165-calmodulin interaction is characterized by structural heterogeneity. Quantitative comparative analysis indicated that distinct conformational landscapes of structural heterogeneity are sampled for different calmodulin-target complexes. Such structural heterogeneity in protein complexes could potentially explain the way that transient and promiscuous protein interactions are optimized and tuned in complex regulatory networks. © 2012 Elsevier Ltd All rights reserved.
@article{Nagulapalli2012, abstract = {Protein interactions within regulatory networks should adapt in a spatiotemporal-dependent dynamic environment, in order to process and respond to diverse and versatile cellular signals. However, the principles governing recognition pliability in protein complexes are not well understood. We have investigated a region of the intrinsically disordered protein myelin basic protein (MBP 145-165) that interacts with calmodulin, but that also promiscuously binds other biomolecules (membranes, modifying enzymes). To characterize this interaction, we implemented an NMR spectroscopic approach that calculates, for each conformation of the complex, the maximum occurrence based on recorded pseudocontact shifts and residual dipolar couplings. We found that the MBP 145-165-calmodulin interaction is characterized by structural heterogeneity. Quantitative comparative analysis indicated that distinct conformational landscapes of structural heterogeneity are sampled for different calmodulin-target complexes. Such structural heterogeneity in protein complexes could potentially explain the way that transient and promiscuous protein interactions are optimized and tuned in complex regulatory networks. © 2012 Elsevier Ltd All rights reserved.}, author = {M. Nagulapalli and G. Parigi and J. Yuan and J. Gsponer and G. Deraos and V.V. Bamm and G. Harauz and J. Matsoukas and M.R.R. De Planque and I.P. Gerothanassis and C. Luchinat and A.G. Tzakos}, doi = {10.1016/j.str.2012.01.021}, issue = {3}, journal = {Structure}, pages = {522-533}, title = {Recognition pliability is coupled to structural heterogeneity: A calmodulin intrinsically disordered binding region complex}, volume = {20}, year = {2012}, } - Primikyri, A., E. Kyriakou, P. Charisiadis, C. Tsiafoulis, H. Stamatis, A. G. Tzakos, and I. P. Gerothanassis. "Fine-tuning of the diffusion dimension of -oh groups for high resolution dosy nmr applications in crude enzymatic transformations and mixtures of organic compounds." Tetrahedron 68 (2012): 6887-6891. doi:10.1016/j.tet.2012.06.016
[BibTeX] [Abstract]
A convenient DOSY methodology was developed that can be applied directly in crude reaction products or mixtures containing polyphenol organic compounds, for the rapid identification of their various components without any prior separation or isolation. The method is based on the resolution enhancement of the resonances of the -OH protons and the fine-tuning of their diffusion coefficients to the molecular diffusion coefficient; this can be achieved in DMSO-d 6 in combination with the addition of picric acid and the use of temperatures near the freezing point of the solution. This method, which does not modify the apparent molecular diffusion, allowed the recording of high resolution DOSY spectra, both in crude enzymatic reactions and mixtures of organic compounds based on the phenolic OH NMR spectral region which is much less crowded and, thus, much more informative compared to the aromatic region. © 2012 Elsevier Ltd. All rights reserved.
@article{Primikyri2012, abstract = {A convenient DOSY methodology was developed that can be applied directly in crude reaction products or mixtures containing polyphenol organic compounds, for the rapid identification of their various components without any prior separation or isolation. The method is based on the resolution enhancement of the resonances of the -OH protons and the fine-tuning of their diffusion coefficients to the molecular diffusion coefficient; this can be achieved in DMSO-d 6 in combination with the addition of picric acid and the use of temperatures near the freezing point of the solution. This method, which does not modify the apparent molecular diffusion, allowed the recording of high resolution DOSY spectra, both in crude enzymatic reactions and mixtures of organic compounds based on the phenolic OH NMR spectral region which is much less crowded and, thus, much more informative compared to the aromatic region. © 2012 Elsevier Ltd. All rights reserved.}, author = {A. Primikyri and E. Kyriakou and P. Charisiadis and C. Tsiafoulis and H. Stamatis and A.G. Tzakos and I.P. Gerothanassis}, doi = {10.1016/j.tet.2012.06.016}, issue = {34}, journal = {Tetrahedron}, pages = {6887-6891}, title = {Fine-tuning of the diffusion dimension of -OH groups for high resolution DOSY NMR applications in crude enzymatic transformations and mixtures of organic compounds}, volume = {68}, year = {2012}, } - Kyriakou, E., A. Primikyri, P. Charisiadis, M. Katsoura, I. P. Gerothanassis, H. Stamatis, and A. G. Tzakos. "Unexpected enzyme-catalyzed regioselective acylation of flavonoid aglycones and rapid product screening." Organic and biomolecular chemistry 10 (2012): 1739-1742. doi:10.1039/c2ob06784f
[BibTeX] [Abstract]
Unprecedented regioselective acylation of flavonoid aglycones was achieved using Candida antarctica lipase B (CALB). The rapid screening of product formation was performed by the use of the high resolution phenol-type OH 1H NMR spectral region recorded after the addition of picric acid. © 2012 The Royal Society of Chemistry.
@article{Kyriakou2012, abstract = {Unprecedented regioselective acylation of flavonoid aglycones was achieved using Candida antarctica lipase B (CALB). The rapid screening of product formation was performed by the use of the high resolution phenol-type OH 1H NMR spectral region recorded after the addition of picric acid. © 2012 The Royal Society of Chemistry.}, author = {E. Kyriakou and A. Primikyri and P. Charisiadis and M. Katsoura and I.P. Gerothanassis and H. Stamatis and A.G. Tzakos}, doi = {10.1039/c2ob06784f}, issue = {9}, journal = {Organic and Biomolecular Chemistry}, pages = {1739-1742}, title = {Unexpected enzyme-catalyzed regioselective acylation of flavonoid aglycones and rapid product screening}, volume = {10}, year = {2012}, }
2011
- Tzakos, A. G., D. Fokas, C. Johannes, V. Moussis, E. Hatzimichael, and E. Briasoulis. "Targeting oncogenic protein-protein interactions by diversity oriented synthesis and combinatorial chemistry approaches." Molecules 16 (2011): 4408-4427. doi:10.3390/molecules16064408
[BibTeX] [Abstract]
We are currently witnessing a decline in the development of efficient new anticancer drugs, despite the salient efforts made on all fronts of cancer drug discovery. This trend presumably relates to the substantial heterogeneity and the inherent biological complexity of cancer, which hinder drug development success. Protein-protein interactions (PPIs) are key players in numerous cellular processes and aberrant interruption of this complex network provides a basis for various disease states, including cancer. Thus, it is now believed that cancer drug discovery, in addition to the design of single-targeted bioactive compounds, should also incorporate diversity-oriented synthesis (DOS) and other combinatorial strategies in order to exploit the ability of multi-functional scaffolds to modulate multiple protein-protein interactions (biological hubs). Throughout the review, we highlight the chemistry driven approaches to access diversity space for the discovery of small molecules that disrupt oncogenic PPIs, namely the p53-Mdm2, Bcl-2/Bcl-xL-BH3, Myc-Max, and p53-Mdmx/Mdm2 interactions. © 2011 by the authors; licensee MDPI, Basel, Switzerland.
@article{Tzakos2011, abstract = {We are currently witnessing a decline in the development of efficient new anticancer drugs, despite the salient efforts made on all fronts of cancer drug discovery. This trend presumably relates to the substantial heterogeneity and the inherent biological complexity of cancer, which hinder drug development success. Protein-protein interactions (PPIs) are key players in numerous cellular processes and aberrant interruption of this complex network provides a basis for various disease states, including cancer. Thus, it is now believed that cancer drug discovery, in addition to the design of single-targeted bioactive compounds, should also incorporate diversity-oriented synthesis (DOS) and other combinatorial strategies in order to exploit the ability of multi-functional scaffolds to modulate multiple protein-protein interactions (biological hubs). Throughout the review, we highlight the chemistry driven approaches to access diversity space for the discovery of small molecules that disrupt oncogenic PPIs, namely the p53-Mdm2, Bcl-2/Bcl-xL-BH3, Myc-Max, and p53-Mdmx/Mdm2 interactions. © 2011 by the authors; licensee MDPI, Basel, Switzerland.}, author = {A.G. Tzakos and D. Fokas and C. Johannes and V. Moussis and E. Hatzimichael and E. Briasoulis}, doi = {10.3390/molecules16064408}, issue = {6}, journal = {Molecules}, pages = {4408-4427}, title = {Targeting oncogenic protein-protein interactions by diversity oriented synthesis and combinatorial chemistry approaches}, volume = {16}, year = {2011}, } - Charisiadis, P., A. Primikyri, V. Exarchou, A. Tzakos, and I. P. Gerothanassis. "Unprecedented ultra-high-resolution hydroxy group 1h nmr spectroscopic analysis of plant extracts." Journal of natural products 74 (2011): 2462-2466. doi:10.1021/np200329a
[BibTeX] [Abstract]
A general method is demonstrated for obtaining ultra-high resolution in the phenolic hydroxy group 1H NMR spectroscopic region, in DMSO-d 6 solution, with the addition of picric acid. Line-width reduction by a factor of over 100 was observed, which resulted in line-widths ranging from 1.6 to 0.6 Hz. This unprecedented resolution, in combination with the shielding sensitivity of the hydroxy group absorptions to substituent effects at least up to 11 bonds distant and the application of 2D 1H- 13C HMBC techniques, allows the unequivocal structure analysis of natural products with phenolic hydroxy groups in complex plant extracts. © 2011 The American Chemical Society and American Society of Pharmacognosy.
@article{Charisiadis2011, abstract = {A general method is demonstrated for obtaining ultra-high resolution in the phenolic hydroxy group 1H NMR spectroscopic region, in DMSO-d 6 solution, with the addition of picric acid. Line-width reduction by a factor of over 100 was observed, which resulted in line-widths ranging from 1.6 to 0.6 Hz. This unprecedented resolution, in combination with the shielding sensitivity of the hydroxy group absorptions to substituent effects at least up to 11 bonds distant and the application of 2D 1H- 13C HMBC techniques, allows the unequivocal structure analysis of natural products with phenolic hydroxy groups in complex plant extracts. © 2011 The American Chemical Society and American Society of Pharmacognosy.}, author = {P. Charisiadis and A. Primikyri and V. Exarchou and A. Tzakos and I.P. Gerothanassis}, doi = {10.1021/np200329a}, issue = {11}, journal = {Journal of Natural Products}, pages = {2462-2466}, title = {Unprecedented ultra-high-resolution hydroxy group 1H NMR spectroscopic analysis of plant extracts}, volume = {74}, year = {2011}, } - Kounnis, V., E. Ioachim, M. Svoboda, A. Tzakos, I. Sainis, T. Thalhammer, G. Steiner, and E. Briasoulis. "Expression of organic anion-transporting polypeptides 1b3, 1b1, and 1a2 in human pancreatic cancer reveals a new class of potential therapeutic targets." Oncotargets and therapy 4 (2011): 27-32. doi:10.2147/OTT.S16706
[BibTeX] [Abstract]
Background: Organic anion-transporting polypeptides (OATPs) are influx transporters that mediate intracellular uptake of selective endogenous and xenobiotic compounds. Identification of new molecular targets and discovery of novel targeted therapies is top priority for pancreatic cancer, which lacks any effective therapy. Materials and methods: We studied expression of OATP 1A2, 1B1, and 1B3 in pancreatic cancer tissue and in cell lines. Formalin-fixed paraffin-embedded biopsy material of 12 human pancreatic cancers was immunohistochemically assessed for protein expression of the three studied influx transporters. Immunohistochemistry was evaluated by experienced pathologists and quantified by use of an automated image analysis system. BxPC-3 and MIA PaCa-2 pancreatic cancer cell lines were used to quantify transcripts of OATP 1B1 and 1B3. Results: OATP 1A2, 1B1, and 1B3 proteins were found ubiquitously expressed in all studied cases. Quantification performed by HistoQuest system revealed that mean intensity was 53 for 1A2, 45 for 1B1, and 167 for OATP 1B1/1B3 on a range scale 0-250 units. At mRNA level, 1B1 and 1B3 were overexpressed in both studied cancer cell lines but not in normal pancreatic tissue. Conclusion: OATPs 1A2, 1B1, and 1B3 are highly expressed in pancreatic adenocarcinoma. We suggest that expression of these transporters in pancreatic cancer justify research efforts towards discovery of novel therapeutics targeting OATPs. © 2011 Kounnis et al, publisher and licensee Dove Medical Press Ltd.
@article{Kounnis2011, abstract = {Background: Organic anion-transporting polypeptides (OATPs) are influx transporters that mediate intracellular uptake of selective endogenous and xenobiotic compounds. Identification of new molecular targets and discovery of novel targeted therapies is top priority for pancreatic cancer, which lacks any effective therapy. Materials and methods: We studied expression of OATP 1A2, 1B1, and 1B3 in pancreatic cancer tissue and in cell lines. Formalin-fixed paraffin-embedded biopsy material of 12 human pancreatic cancers was immunohistochemically assessed for protein expression of the three studied influx transporters. Immunohistochemistry was evaluated by experienced pathologists and quantified by use of an automated image analysis system. BxPC-3 and MIA PaCa-2 pancreatic cancer cell lines were used to quantify transcripts of OATP 1B1 and 1B3. Results: OATP 1A2, 1B1, and 1B3 proteins were found ubiquitously expressed in all studied cases. Quantification performed by HistoQuest system revealed that mean intensity was 53 for 1A2, 45 for 1B1, and 167 for OATP 1B1/1B3 on a range scale 0-250 units. At mRNA level, 1B1 and 1B3 were overexpressed in both studied cancer cell lines but not in normal pancreatic tissue. Conclusion: OATPs 1A2, 1B1, and 1B3 are highly expressed in pancreatic adenocarcinoma. We suggest that expression of these transporters in pancreatic cancer justify research efforts towards discovery of novel therapeutics targeting OATPs. © 2011 Kounnis et al, publisher and licensee Dove Medical Press Ltd.}, author = {V. Kounnis and E. Ioachim and M. Svoboda and A. Tzakos and I. Sainis and T. Thalhammer and G. Steiner and E. Briasoulis}, doi = {10.2147/OTT.S16706}, journal = {OncoTargets and Therapy}, pages = {27-32}, title = {Expression of organic anion-transporting polypeptides 1B3, 1B1, and 1A2 in human pancreatic cancer reveals a new class of potential therapeutic targets}, volume = {4}, year = {2011}, }
2010
- Sainis, I., D. Fokas, K. Vareli, A. G. Tzakos, V. Kounnis, and E. Briasoulis. "Cyanobacterial cyclopeptides as lead compounds to novel targeted cancer drugs." Marine drugs 8 (2010): 629-657. doi:10.3390/md8030629
[BibTeX] [Abstract]
Cyanobacterial cyclopeptides, including microcystins and nodularins, are considered a health hazard to humans due to the possible toxic effects of high consumption. From a pharmacological standpoint, microcystins are stable hydrophilic cyclic heptapeptides with a potential to cause cellular damage following uptake via organic anion-transporting polypeptides (OATP). Their intracellular biological effects involve inhibition of catalytic subunits of protein phosphatase 1 (PP1) and PP2, glutathione depletion and generation of reactive oxygen species (ROS). Interestingly, certain OATPs are prominently expressed in cancers as compared to normal tissues, qualifying MC as potential candidates for cancer drug development. In the era of targeted cancer therapy, cyanotoxins comprise a rich source of natural cytotoxic compounds with a potential to target cancers expressing specific uptake transporters. Moreover, their structure offers opportunities for combinatorial engineering to enhance the therapeutic index and resolve organ-specific toxicity issues. In this article, we revisit cyanobacterial cyclopeptides as potential novel targets for anticancer drugs by summarizing existing biomedical evidence, presenting structure-activity data and discussing developmental perspectives. © 2010 by the authors; licensee Molecular Diversity Preservation International.
@article{Sainis2010, abstract = {Cyanobacterial cyclopeptides, including microcystins and nodularins, are considered a health hazard to humans due to the possible toxic effects of high consumption. From a pharmacological standpoint, microcystins are stable hydrophilic cyclic heptapeptides with a potential to cause cellular damage following uptake via organic anion-transporting polypeptides (OATP). Their intracellular biological effects involve inhibition of catalytic subunits of protein phosphatase 1 (PP1) and PP2, glutathione depletion and generation of reactive oxygen species (ROS). Interestingly, certain OATPs are prominently expressed in cancers as compared to normal tissues, qualifying MC as potential candidates for cancer drug development. In the era of targeted cancer therapy, cyanotoxins comprise a rich source of natural cytotoxic compounds with a potential to target cancers expressing specific uptake transporters. Moreover, their structure offers opportunities for combinatorial engineering to enhance the therapeutic index and resolve organ-specific toxicity issues. In this article, we revisit cyanobacterial cyclopeptides as potential novel targets for anticancer drugs by summarizing existing biomedical evidence, presenting structure-activity data and discussing developmental perspectives. © 2010 by the authors; licensee Molecular Diversity Preservation International.}, author = {I. Sainis and D. Fokas and K. Vareli and A.G. Tzakos and V. Kounnis and E. Briasoulis}, doi = {10.3390/md8030629}, issue = {3}, journal = {Marine Drugs}, pages = {629-657}, title = {Cyanobacterial cyclopeptides as lead compounds to novel targeted cancer drugs}, volume = {8}, year = {2010}, } - Skobridis, K., M. Kinigopoulou, V. Theodorou, E. Giannousi, A. Russell, R. Chauhan, R. Sala, N. Brownlow, S. Kiriakidis, J. Domin, A. G. Tzakos, and N. J. Dibb. "Novel imatinib derivatives with altered specificity between bcr-abl and fms, kit, and pdgf receptors." Chemmedchem 5 (2010): 130-139. doi:10.1002/cmdc.200900394
[BibTeX] [Abstract]
Imatinib is a clinically important ATP analogue inhibitor that targets the tyrosine kinase domain of the intracellular Abl kinase and the PDGF receptor family. Imatinib has revolutionised the treatment of chronic myeloid leukaemia, which is caused by the oncogene Bcr-Abl and certain solid tumours that harbor oncogenic mutations of the PDGF receptor family. As a leading kinase inhibitor, imatinib also provides an excellent model system to investigate how changes in drug design impact biological activity, which is an important consideration for rational drug design. Herein we report a new series of imatinib derivatives that in general have greater activity against the family of PDGF receptors and poorer activity against Abl, as a result of modifications of the phenyl and N-methylpiperazine rings. These new compounds provide a platform for further drug development against the therapeutically important PDGF receptor family and they also provide insight into the engineering of drugs with altered biological activity. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.
@article{Skobridis2010, abstract = {Imatinib is a clinically important ATP analogue inhibitor that targets the tyrosine kinase domain of the intracellular Abl kinase and the PDGF receptor family. Imatinib has revolutionised the treatment of chronic myeloid leukaemia, which is caused by the oncogene Bcr-Abl and certain solid tumours that harbor oncogenic mutations of the PDGF receptor family. As a leading kinase inhibitor, imatinib also provides an excellent model system to investigate how changes in drug design impact biological activity, which is an important consideration for rational drug design. Herein we report a new series of imatinib derivatives that in general have greater activity against the family of PDGF receptors and poorer activity against Abl, as a result of modifications of the phenyl and N-methylpiperazine rings. These new compounds provide a platform for further drug development against the therapeutically important PDGF receptor family and they also provide insight into the engineering of drugs with altered biological activity. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.}, author = {K. Skobridis and M. Kinigopoulou and V. Theodorou and E. Giannousi and A. Russell and R. Chauhan and R. Sala and N. Brownlow and S. Kiriakidis and J. Domin and A.G. Tzakos and N.J. Dibb}, doi = {10.1002/cmdc.200900394}, issue = {1}, journal = {ChemMedChem}, pages = {130-139}, title = {Novel imatinib derivatives with altered specificity between Bcr-Abl and FMS, KIT, and PDGF receptors}, volume = {5}, year = {2010}, }
2009
- Janga, S. C. and A. Tzakos. "Structure and organization of drug-target networks: insights from genomic approaches for drug discovery." Molecular biosystems 5 (2009): 1536-1548. doi:10.1039/b908147j
[BibTeX] [Abstract]
Recent years have seen an explosion in the amount of "omics" data and the integration of several disciplines, which has influenced all areas of life sciences including that of drug discovery. Several lines of evidence now suggest that the traditional notion of "one drug-one protein" for one disease does not hold any more and that treatment for most complex diseases can best be attempted using polypharmacological approaches. In this review, we formalize the definition of a drug-target network by decomposing it into drug, target and disease spaces and provide an overview of our understanding in recent years about its structure and organizational principles. We discuss advances made in developing promiscuous drugs following the paradigm of polypharmacology and reveal their advantages over traditional drugs for targeting diseases such as cancer. We suggest that drug-target networks can be decomposed to be studied at a variety of levels and argue that such network-based approaches have important implications in understanding disease phenotypes and in accelerating drug discovery. We also discuss the potential and scope network pharmacology promises in harnessing the vast amount of data from high-throughput approaches for therapeutic advantage. © 2009 The Royal Society of Chemistry.
@article{Janga2009, abstract = {Recent years have seen an explosion in the amount of "omics" data and the integration of several disciplines, which has influenced all areas of life sciences including that of drug discovery. Several lines of evidence now suggest that the traditional notion of "one drug-one protein" for one disease does not hold any more and that treatment for most complex diseases can best be attempted using polypharmacological approaches. In this review, we formalize the definition of a drug-target network by decomposing it into drug, target and disease spaces and provide an overview of our understanding in recent years about its structure and organizational principles. We discuss advances made in developing promiscuous drugs following the paradigm of polypharmacology and reveal their advantages over traditional drugs for targeting diseases such as cancer. We suggest that drug-target networks can be decomposed to be studied at a variety of levels and argue that such network-based approaches have important implications in understanding disease phenotypes and in accelerating drug discovery. We also discuss the potential and scope network pharmacology promises in harnessing the vast amount of data from high-throughput approaches for therapeutic advantage. © 2009 The Royal Society of Chemistry.}, author = {S.C. Janga and A. Tzakos}, doi = {10.1039/b908147j}, issue = {12}, journal = {Molecular BioSystems}, pages = {1536-1548}, title = {Structure and organization of drug-target networks: Insights from genomic approaches for drug discovery}, volume = {5}, year = {2009}, } - Roukos, D. H., A. Tzakos, and G. Zografos. "Current concerns and challenges regarding tailored anti-angiogenic therapy in cancer." Expert review of anticancer therapy 9 (2009): 1413-1416. doi:10.1586/ERA.09.116
[BibTeX]@article{Roukos2009, author = {D.H. Roukos and A. Tzakos and G. Zografos}, doi = {10.1586/ERA.09.116}, issue = {10}, journal = {Expert Review of Anticancer Therapy}, pages = {1413-1416}, title = {Current concerns and challenges regarding tailored anti-angiogenic therapy in cancer}, volume = {9}, year = {2009}, }
2007
- Theodorou, V., K. Skobridis, A. G. Tzakos, and V. Ragoussis. "A simple method for the alkaline hydrolysis of esters." Tetrahedron letters 48 (2007): 8230-8233. doi:10.1016/j.tetlet.2007.09.074
[BibTeX] [Abstract]
A very mild and rapid procedure for the efficient alkaline hydrolysis of esters in non-aqueous conditions has been developed, by the use of dichloromethane/methanol (9:1) as solvent. This method conveniently provides both carboxylic acids and alcohols from the corresponding esters and sodium hydroxide in a few minutes at room temperature. A plausible reaction mechanism is proposed. © 2007 Elsevier Ltd. All rights reserved.
@article{Theodorou2007, abstract = {A very mild and rapid procedure for the efficient alkaline hydrolysis of esters in non-aqueous conditions has been developed, by the use of dichloromethane/methanol (9:1) as solvent. This method conveniently provides both carboxylic acids and alcohols from the corresponding esters and sodium hydroxide in a few minutes at room temperature. A plausible reaction mechanism is proposed. © 2007 Elsevier Ltd. All rights reserved.}, author = {V. Theodorou and K. Skobridis and A.G. Tzakos and V. Ragoussis}, doi = {10.1016/j.tetlet.2007.09.074}, issue = {46}, journal = {Tetrahedron Letters}, pages = {8230-8233}, title = {A simple method for the alkaline hydrolysis of esters}, volume = {48}, year = {2007}, }
2006
- Tzakos, A. G., N. Naqvi, K. Comporozos, R. Pierattelli, V. Theodorou, A. Husain, and I. P. Gerothanassis. "The molecular basis for the selection of captopril cis and trans conformations by angiotensin i converting enzyme." Bioorganic and medicinal chemistry letters 16 (2006): 5084-5087. doi:10.1016/j.bmcl.2006.07.034
[BibTeX] [Abstract]
Enzyme-inhibitor recognition is considered one of the most fundamental aspects in the area of drug discovery. However, the molecular mechanism of this recognition process (induced fit or prebinding and adaptive selection among multiple conformers) in several cases remains unexplored. In order to shed light toward this step of the recognition process in the case of human angiotensin I converting enzyme (hACE) and its inhibitor captopril, we have established a novel combinatorial approach exploiting solution NMR, flexible docking calculations, mutagenesis, and enzymatic studies. We provide evidence that an equimolar ratio of the cis and trans states of captopril exists in solution and that the enzyme selects only the trans state of the inhibitor that presents architectural and stereoelectronic complementarity with its substrate binding groove. © 2006 Elsevier Ltd. All rights reserved.
@article{Tzakos2006, abstract = {Enzyme-inhibitor recognition is considered one of the most fundamental aspects in the area of drug discovery. However, the molecular mechanism of this recognition process (induced fit or prebinding and adaptive selection among multiple conformers) in several cases remains unexplored. In order to shed light toward this step of the recognition process in the case of human angiotensin I converting enzyme (hACE) and its inhibitor captopril, we have established a novel combinatorial approach exploiting solution NMR, flexible docking calculations, mutagenesis, and enzymatic studies. We provide evidence that an equimolar ratio of the cis and trans states of captopril exists in solution and that the enzyme selects only the trans state of the inhibitor that presents architectural and stereoelectronic complementarity with its substrate binding groove. © 2006 Elsevier Ltd. All rights reserved.}, author = {A.G. Tzakos and N. Naqvi and K. Comporozos and R. Pierattelli and V. Theodorou and A. Husain and I.P. Gerothanassis}, doi = {10.1016/j.bmcl.2006.07.034}, issue = {19}, journal = {Bioorganic and Medicinal Chemistry Letters}, pages = {5084-5087}, title = {The molecular basis for the selection of captopril cis and trans conformations by angiotensin I converting enzyme}, volume = {16}, year = {2006}, }
2005
- Tzakos, A. G., A. Troganis, V. Theodorou, T. Tselios, C. Svarnas, J. Matsoukas, V. Apostolopoulos, and I. P. Gerothanassis. "Structure and function of the myelin proteins: current status and perspectives in relation to multiple sclerosis." Current medicinal chemistry 12 (2005): 1569-1587. doi:10.2174/0929867054039026
[BibTeX] [Abstract]
Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) characterized by demyelination and loss of neurological function, local macrophage infiltrate and neuroantigen-specific CD4+T cells. MS arises from complex interactions between genetic, immunological, infective and biochemical mechanisms. Although the circumstances of MS etiology remain hypothetical, one persistent theme involves immune system recognition of myelin-specific antigens derived from myelin basic protein, the most abundant extrinsic myelin membrane protein, and/or another equally suitable myelin protein or lipid. Knowledge of the biochemical and physico-chemical properties of myelin proteins and lipids, particularly their composition, organization, structure and accessibility with respect to the compacted myelin multilayers, becomes central to understanding how and why myelin-specific antigens become selected during the development of MS. This review focuses on the current understanding of the molecular basis of MS with emphasis: (i) on the physical-chemical properties, organization, morphology, and accessibility of the proteins and lipids within the myelin multilayers; (ii) on the structure-function relationships and characterization of the myelin proteins relevant to the manifestation and evolution of MS; (iii) on conformational relationships between myelin epitopes which might become selected during the development of MS; (iv) on the structure of MHC/HLA in complex with MBP peptides as well as with TCR, which is crucial to the understanding of the pathogenesis of MS with the ultimate goal of designed antigen-specific treatments. © 2005 Bentham Science Publishers Ltd.
@article{Tzakos2005, abstract = {Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) characterized by demyelination and loss of neurological function, local macrophage infiltrate and neuroantigen-specific CD4+T cells. MS arises from complex interactions between genetic, immunological, infective and biochemical mechanisms. Although the circumstances of MS etiology remain hypothetical, one persistent theme involves immune system recognition of myelin-specific antigens derived from myelin basic protein, the most abundant extrinsic myelin membrane protein, and/or another equally suitable myelin protein or lipid. Knowledge of the biochemical and physico-chemical properties of myelin proteins and lipids, particularly their composition, organization, structure and accessibility with respect to the compacted myelin multilayers, becomes central to understanding how and why myelin-specific antigens become selected during the development of MS. This review focuses on the current understanding of the molecular basis of MS with emphasis: (i) on the physical-chemical properties, organization, morphology, and accessibility of the proteins and lipids within the myelin multilayers; (ii) on the structure-function relationships and characterization of the myelin proteins relevant to the manifestation and evolution of MS; (iii) on conformational relationships between myelin epitopes which might become selected during the development of MS; (iv) on the structure of MHC/HLA in complex with MBP peptides as well as with TCR, which is crucial to the understanding of the pathogenesis of MS with the ultimate goal of designed antigen-specific treatments. © 2005 Bentham Science Publishers Ltd.}, author = {A.G. Tzakos and A. Troganis and V. Theodorou and T. Tselios and C. Svarnas and J. Matsoukas and V. Apostolopoulos and I.P. Gerothanassis}, doi = {10.2174/0929867054039026}, issue = {13}, journal = {Current Medicinal Chemistry}, pages = {1569-1587}, title = {Structure and function of the myelin proteins: Current status and perspectives in relation to multiple sclerosis}, volume = {12}, year = {2005}, } - Tzakos, A. G. and I. P. Gerothanassis. "Domain-selective ligand-binding modes and atomic level pharmacophore refinement in angiotensin i converting enzyme (ace) inhibitors." Chembiochem 6 (2005): 1089-1103. doi:10.1002/cbic.200400386
[BibTeX] [Abstract]
Somatic ACE (EC 3.4.15.1), a ZnII metalloproteinase, is composed of functionally active N and C domains resulting from tandem gene duplication. Despite the high degree of sequence similarity between the two domains, they differ in substrate and inhibitor specificity and in their activation by chloride ions. Because of the critical role of ACE in cardiovascular and renal diseases, both domains are attractive targets for drug design. Putative structural models have been generated for the interactions of ACE inhibitors (lisinopril, captoril, enalaprilat, keto-ACE, ramiprilat, quinaprilat, peridoprilat, fosinoprilat, and RXP 407) with both the ACE_C and the ACE_N domains. Inhibitor-domain selectivity was interpreted in terms of residue alterations observed in the four subsites of the binding grooves of the ACE_C/ACE_N domains (S1: V516/N494, V518/T496, S2: F391/Y369, E403/R381, S1′: D377/Q355, E162/D140, V379/S357, V380/T358, and S2′: D463/E431, T282/S260). The interactions governing the ligand-receptor recognition process in the ACE_C domain are: a salt bridge between D377, E162, and the NH 2 group (PT position), a hydrogen bond of the inhibitor with Q281, the presence of bulky hydrophobic groups in the P1 and P2′ sites, and a stacking interaction of F391 with a benzyl group in the P2 position, in ACE_N these interactions are: hydrogen bonds of the inhibitor with E431, Y369, and R381, and a salt bridge between the carboxy group in the P2 position of the inhibitor and R500. The calculated complexes were evaluated for their consistency with structure-activity relationships and site-directed mutagenesis data. A comparison between the calculated interaction free energies and the experimentally observed biological activities was also made. Pharmacophore refinement was achieved at an atomic level, and might provide an improved basis for structure-based rational design of second-generation, domain-selective inhibitors. © 2005 Wiley-VCH Verlag GmbH & Co. KGaA.
@article{Tzakos2005, abstract = {Somatic ACE (EC 3.4.15.1), a ZnII metalloproteinase, is composed of functionally active N and C domains resulting from tandem gene duplication. Despite the high degree of sequence similarity between the two domains, they differ in substrate and inhibitor specificity and in their activation by chloride ions. Because of the critical role of ACE in cardiovascular and renal diseases, both domains are attractive targets for drug design. Putative structural models have been generated for the interactions of ACE inhibitors (lisinopril, captoril, enalaprilat, keto-ACE, ramiprilat, quinaprilat, peridoprilat, fosinoprilat, and RXP 407) with both the ACE_C and the ACE_N domains. Inhibitor-domain selectivity was interpreted in terms of residue alterations observed in the four subsites of the binding grooves of the ACE_C/ACE_N domains (S1: V516/N494, V518/T496, S2: F391/Y369, E403/R381, S1′: D377/Q355, E162/D140, V379/S357, V380/T358, and S2′: D463/E431, T282/S260). The interactions governing the ligand-receptor recognition process in the ACE_C domain are: a salt bridge between D377, E162, and the NH 2 group (PT position), a hydrogen bond of the inhibitor with Q281, the presence of bulky hydrophobic groups in the P1 and P2′ sites, and a stacking interaction of F391 with a benzyl group in the P2 position, in ACE_N these interactions are: hydrogen bonds of the inhibitor with E431, Y369, and R381, and a salt bridge between the carboxy group in the P2 position of the inhibitor and R500. The calculated complexes were evaluated for their consistency with structure-activity relationships and site-directed mutagenesis data. A comparison between the calculated interaction free energies and the experimentally observed biological activities was also made. Pharmacophore refinement was achieved at an atomic level, and might provide an improved basis for structure-based rational design of second-generation, domain-selective inhibitors. © 2005 Wiley-VCH Verlag GmbH & Co. KGaA.}, author = {A.G. Tzakos and I.P. Gerothanassis}, doi = {10.1002/cbic.200400386}, issue = {6}, journal = {ChemBioChem}, pages = {1089-1103}, title = {Domain-selective ligand-binding modes and atomic level pharmacophore refinement in angiotensin I converting enzyme (ACE) inhibitors}, volume = {6}, year = {2005}, }
2004
- Tzakos, A. G., I. P. Gerothanassis, and A. N. Troganis. "On the structural basis of the hypertensive properties of angiotensin ii: a solved mystery or a controversial issue?." Current topics in medicinal chemistry 4 (2004): 431-444. doi:10.2174/1568026043451375
[BibTeX] [Abstract]
Angiotensin II (AII), Asp1- Arg2- Val3- Tyr4- Ile5- His6- Pro7-Phe8, the primary active hormone of the Renin-Angiotensin-System (RAS), is a major vasoconstrictor implicated in the cause of hypertension. To unravel the question of the biologically active conformation(s) of this flexible peptide hormone and to better understand the stereoelectronic requirements that lead to the molecular basis of hypertension, we will analyze research efforts in the identification of pharmacophoric groups of AII and three general approaches for structural characterisation: the free peptide - ligand approach, the receptor based approach, and approaches that target the peptide - receptor complex. The free peptide - ligand based approach can be further categorized to: (a) conformational analysis of AII and linear peptide analogues in aqueous solution; (b) the use of solvents of medium dielectric constants; (c) conformationally restricted analogues, with emphasis to cyclic analogues, (d) the use of receptor - simulating environments, and (e) non-peptide mimetics. The receptor and peptide - receptor based approaches can be categorised to: (a) The use of monoclonal antibodies and (b) the generic description of AII receptor sites through homology modelling and mutagenesis studies. These investigations, with particular emphasis to recent developments, have greatly assisted in the identification of pharmacophoric groups for receptor activation and the development of several models of AII - receptor complexes. © 2004 Bentham Science Publishers Ltd.
@article{Tzakos2004, abstract = {Angiotensin II (AII), Asp1- Arg2- Val3- Tyr4- Ile5- His6- Pro7-Phe8, the primary active hormone of the Renin-Angiotensin-System (RAS), is a major vasoconstrictor implicated in the cause of hypertension. To unravel the question of the biologically active conformation(s) of this flexible peptide hormone and to better understand the stereoelectronic requirements that lead to the molecular basis of hypertension, we will analyze research efforts in the identification of pharmacophoric groups of AII and three general approaches for structural characterisation: the free peptide - ligand approach, the receptor based approach, and approaches that target the peptide - receptor complex. The free peptide - ligand based approach can be further categorized to: (a) conformational analysis of AII and linear peptide analogues in aqueous solution; (b) the use of solvents of medium dielectric constants; (c) conformationally restricted analogues, with emphasis to cyclic analogues, (d) the use of receptor - simulating environments, and (e) non-peptide mimetics. The receptor and peptide - receptor based approaches can be categorised to: (a) The use of monoclonal antibodies and (b) the generic description of AII receptor sites through homology modelling and mutagenesis studies. These investigations, with particular emphasis to recent developments, have greatly assisted in the identification of pharmacophoric groups for receptor activation and the development of several models of AII - receptor complexes. © 2004 Bentham Science Publishers Ltd.}, author = {A.G. Tzakos and I.P. Gerothanassis and A.N. Troganis}, doi = {10.2174/1568026043451375}, issue = {4}, journal = {Current Topics in Medicinal Chemistry}, pages = {431-444}, title = {On the structural basis of the hypertensive properties of angiotensin II: A solved mystery or a controversial issue?}, volume = {4}, year = {2004}, } - Tzakos, A. G., P. Fuchs, Van N. A. J. Nuland, A. Troganis, T. Tselios, S. Deraos, J. Matsoukas, I. P. Gerothanassis, and A. M. J. J. Bonvin. "Nmr and molecular dynamics studies of an autoimmune myelin basic protein peptide and its antagonist: structural implications for the mhc ii (i-a u)-peptide complex from docking calculations." European journal of biochemistry 271 (2004): 3399-3413. doi:10.1111/j.1432-1033.2004.04274.x
[BibTeX] [Abstract]
Experimental autoimmune encephalomyelitis can be induced in susceptible animals by immunodominant determinants of myelin basic protein (MBP). To characterize the molecular features of antigenic sites important for designing experimental autoimmune encephalomyelitis suppressing molecules, we report structural studies, based on NMR experimental data in conjunction with molecular dynamic simulations, of the potent linear dodecapeptide epitope of guinea pig MBP, Gln74-Lys75-Ser76-Gln77-Arg78-Ser79-Gln80-Asp81-Glu82-Asn83-Pro84-Val85 [MBP(74-85)], and its antagonist analogue Ala81MBP(74-85). The two peptides were studied in both water and Me2SO in order to mimic solvent-dependent structural changes in MBP. The agonist MBP(74-85) adopts a compact conformation because of electrostatic interactions of Arg78 with the side chains of Asp81 and Glu82. Arg78 is 'locked' in a well-defined conformation, perpendicular to the peptide backbone which is practically solvent independent. These electrostatic interactions are, however, absent from the antagonist Ala81MBP(74-85), resulting in great flexibility of the side chain of Arg78. Sequence alignment of the two analogues with several species of MBP suggests a critical role for the positively charged residue Arg78, firstly, in the stabilization of the local microdomains (epitopes) of the integral protein, and secondly, in a number of post-translational modifications relevant to multiple sclerosis, such as the conversion of charged arginine residues to uncharged citrullines. Flexible docking calculations on the binding of the MBP(74-85) antigen to the MHC class II receptor site I-Au using HADDOCK indicate that Gln74, Ser76 and Ser79 are MHC II anchor residues. Lys75, Arg78 and Asp81 are prominent, solvent-exposed residues and, thus, may be of importance in the formation of the trimolecular T-cell receptor-MBP(74-85)-MHC II complex.
@article{Tzakos2004, abstract = {Experimental autoimmune encephalomyelitis can be induced in susceptible animals by immunodominant determinants of myelin basic protein (MBP). To characterize the molecular features of antigenic sites important for designing experimental autoimmune encephalomyelitis suppressing molecules, we report structural studies, based on NMR experimental data in conjunction with molecular dynamic simulations, of the potent linear dodecapeptide epitope of guinea pig MBP, Gln74-Lys75-Ser76-Gln77-Arg78-Ser79-Gln80-Asp81-Glu82-Asn83-Pro84-Val85 [MBP(74-85)], and its antagonist analogue Ala81MBP(74-85). The two peptides were studied in both water and Me2SO in order to mimic solvent-dependent structural changes in MBP. The agonist MBP(74-85) adopts a compact conformation because of electrostatic interactions of Arg78 with the side chains of Asp81 and Glu82. Arg78 is 'locked' in a well-defined conformation, perpendicular to the peptide backbone which is practically solvent independent. These electrostatic interactions are, however, absent from the antagonist Ala81MBP(74-85), resulting in great flexibility of the side chain of Arg78. Sequence alignment of the two analogues with several species of MBP suggests a critical role for the positively charged residue Arg78, firstly, in the stabilization of the local microdomains (epitopes) of the integral protein, and secondly, in a number of post-translational modifications relevant to multiple sclerosis, such as the conversion of charged arginine residues to uncharged citrullines. Flexible docking calculations on the binding of the MBP(74-85) antigen to the MHC class II receptor site I-Au using HADDOCK indicate that Gln74, Ser76 and Ser79 are MHC II anchor residues. Lys75, Arg78 and Asp81 are prominent, solvent-exposed residues and, thus, may be of importance in the formation of the trimolecular T-cell receptor-MBP(74-85)-MHC II complex.}, author = {A.G. Tzakos and P. Fuchs and N.A.J. Van Nuland and A. Troganis and T. Tselios and S. Deraos and J. Matsoukas and I.P. Gerothanassis and A.M.J.J. Bonvin}, doi = {10.1111/j.1432-1033.2004.04274.x}, issue = {16}, journal = {European Journal of Biochemistry}, pages = {3399-3413}, title = {NMR and molecular dynamics studies of an autoimmune myelin basic protein peptide and its antagonist: Structural implications for the MHC II (I-A u)-peptide complex from docking calculations}, volume = {271}, year = {2004}, }
2003
- Galanis, A. S., G. A. Spyroulias, R. Pierattelli, A. Tzakos, A. Troganis, I. P. Gerothanassis, G. Pairas, E. Manessi-Zoupa, and P. Cordopatis. "Zinc binding in peptide models of angiotensin-i converting enzyme active sites studied through 1h-nmr and chemical shift perturbation mapping." Biopolymers 69 (2003): 244-252. doi:10.1002/bip.10362
[BibTeX] [Abstract]
We report the design and synthesis through solid phase 9-flourenylmethoxycarbonyl (Fmoc) chemistry of the two angiotensin-I converting enzyme active sites possessing the general sequence HEMGHX23EAIGDX3. Their zinc-binding properties were monitored in solution through high-resolution 1H-NMR. The obtained data were analyzed in terms of chemical shift differences. The results indicate that zinc binds to the HEMGH and the EAIGD characteristic motifs, and suggest possible coordination modes of zinc in the native enzyme. © 2003 Wiley Periodicals, Inc.
@article{Galanis2003, abstract = {We report the design and synthesis through solid phase 9-flourenylmethoxycarbonyl (Fmoc) chemistry of the two angiotensin-I converting enzyme active sites possessing the general sequence HEMGHX23EAIGDX3. Their zinc-binding properties were monitored in solution through high-resolution 1H-NMR. The obtained data were analyzed in terms of chemical shift differences. The results indicate that zinc binds to the HEMGH and the EAIGD characteristic motifs, and suggest possible coordination modes of zinc in the native enzyme. © 2003 Wiley Periodicals, Inc.}, author = {A.S. Galanis and G.A. Spyroulias and R. Pierattelli and A. Tzakos and A. Troganis and I.P. Gerothanassis and G. Pairas and E. Manessi-Zoupa and P. Cordopatis}, doi = {10.1002/bip.10362}, issue = {2}, journal = {Biopolymers}, pages = {244-252}, title = {Zinc binding in peptide models of angiotensin-I converting enzyme active sites studied through 1H-NMR and chemical shift perturbation mapping}, volume = {69}, year = {2003}, } - Spyroulias, G. A., P. Nikolakopoulou, A. Tzakos, I. P. Gerothanassis, V. Magafa, E. Manessi-Zoupa, and P. Cordopatis. "Comparison of the solution structures of angiotensin i & ii implication for structure-function relationship." European journal of biochemistry 270 (2003): 2163-2173. doi:10.1046/j.1432-1033.2003.03573.x
[BibTeX] [Abstract]
Conformational analysis of angiotensin I (A/) and II (A/I) peptides has been performed through 2D 1H-NMR spectroscopy in dimethylsulfoxide and 2,2,2-trifluoroethanol/H2O. The solution structural models of AI and AII have been determined in dimethylsulfoxide using NOE distance and 3JHNHα, coupling constants. Finally, the AI family of models resulting from restrained energy minimization (REM) refinement, exhibits pairwise rmsd values for the family ensemble 0.26 ± 0.13 Å, 1.05 ± 0.23Å, for backbone and heavy atoms, respectively, and the distance penalty function is calculated at 0.075 ± 0.006 Å2. Comparable results have been afforded for AII ensemble (rmsd values 0.30 ± 0.22 Å, 1.38 ± 0.48 Å for backbone and heavy atoms, respectively; distance penalty function is 0.029 ± 0.003 Å2). The two peptides demonstrate similar N-terminal and different C-terminal conformation as a consequence of the presence/absence of the His9-Leul0 dipeptide, which plays an important role in the different biological function of the two peptides. Other conformational variations focused on the side-chain orientation of aromatic residues, which constitute a biologically relevant hydrophobic core and whose inter-residue contacts are strong in dimethylsulfoxide and are retained even in mixed organic-aqueous media. Detailed analysis of the peptide structural features attempts to elucidate the conformational role of the C-terminal dipeptide to the different binding affinity of AI and AII towards the AT1 receptor and sets the basis for understanding the factors that might govern free- or bound-depended AII structural differentiation.
@article{Spyroulias2003, abstract = {Conformational analysis of angiotensin I (A/) and II (A/I) peptides has been performed through 2D 1H-NMR spectroscopy in dimethylsulfoxide and 2,2,2-trifluoroethanol/H2O. The solution structural models of AI and AII have been determined in dimethylsulfoxide using NOE distance and 3JHNHα, coupling constants. Finally, the AI family of models resulting from restrained energy minimization (REM) refinement, exhibits pairwise rmsd values for the family ensemble 0.26 ± 0.13 Å, 1.05 ± 0.23Å, for backbone and heavy atoms, respectively, and the distance penalty function is calculated at 0.075 ± 0.006 Å2. Comparable results have been afforded for AII ensemble (rmsd values 0.30 ± 0.22 Å, 1.38 ± 0.48 Å for backbone and heavy atoms, respectively; distance penalty function is 0.029 ± 0.003 Å2). The two peptides demonstrate similar N-terminal and different C-terminal conformation as a consequence of the presence/absence of the His9-Leul0 dipeptide, which plays an important role in the different biological function of the two peptides. Other conformational variations focused on the side-chain orientation of aromatic residues, which constitute a biologically relevant hydrophobic core and whose inter-residue contacts are strong in dimethylsulfoxide and are retained even in mixed organic-aqueous media. Detailed analysis of the peptide structural features attempts to elucidate the conformational role of the C-terminal dipeptide to the different binding affinity of AI and AII towards the AT1 receptor and sets the basis for understanding the factors that might govern free- or bound-depended AII structural differentiation.}, author = {G.A. Spyroulias and P. Nikolakopoulou and A. Tzakos and I.P. Gerothanassis and V. Magafa and E. Manessi-Zoupa and P. Cordopatis}, doi = {10.1046/j.1432-1033.2003.03573.x}, issue = {10}, journal = {European Journal of Biochemistry}, pages = {2163-2173}, title = {Comparison of the solution structures of angiotensin I & II implication for structure-function relationship}, volume = {270}, year = {2003}, } - Tzakos, A. G., A. S. Galanis, G. A. Spyroulias, P. Cordopatis, E. Manessi-Zoupa, and I. P. Gerothanassis. "Structure-function discrimination of the n- and c- catalytic domains of human angiotensin-converting enzyme: implications for cl- activation and peptide hydrolysis mechanisms." Protein engineering 16 (2003): 993-1003. doi:10.1093/protein/gzg122
[BibTeX] [Abstract]
Human somatic angiotensin I-converting enzyme (sACE) has two active sites present in two sequence homologous protein domains (ACE_N and ACE_C) possessing several biochemical features that differentiate the two active sites (i.e. chloride ion activation). Based on the recently solved X-ray structure of testis angiotensin-converting enzyme (tACE), the 3D structure of ACE_N was modeled. Electrostatic potential calculations reveal that the ACE_N binding groove is significantly more positively charged than the ACE_C, which provides a first rationalization for their functional discrimination. The chloride ion pore for Cl2 (one of the two chloride ions revealed in the X-ray structure of tACE) that connects the external solution with the inner part of the protein was identified on the basis of an extended network of water molecules. Comparison of ACE_C with the X-ray structure of the prokaryotic CIC Cl - channel from Salmonella enterica serovar typhimurium demonstrates a common molecular basis of anion selectivity. The critical role for Cl2 as an ionic switch is emphasized. Sequence and structural comparison between ACE_N and ACE_C and of other proteins of the gluzincin family highlights key residues that could be responsible for the peptide hydrolysis mechanism. Currently available mutational and substrate hydrolysis data for both domains are evaluated and are consistent with the predicted model.
@article{Tzakos2003, abstract = {Human somatic angiotensin I-converting enzyme (sACE) has two active sites present in two sequence homologous protein domains (ACE_N and ACE_C) possessing several biochemical features that differentiate the two active sites (i.e. chloride ion activation). Based on the recently solved X-ray structure of testis angiotensin-converting enzyme (tACE), the 3D structure of ACE_N was modeled. Electrostatic potential calculations reveal that the ACE_N binding groove is significantly more positively charged than the ACE_C, which provides a first rationalization for their functional discrimination. The chloride ion pore for Cl2 (one of the two chloride ions revealed in the X-ray structure of tACE) that connects the external solution with the inner part of the protein was identified on the basis of an extended network of water molecules. Comparison of ACE_C with the X-ray structure of the prokaryotic CIC Cl - channel from Salmonella enterica serovar typhimurium demonstrates a common molecular basis of anion selectivity. The critical role for Cl2 as an ionic switch is emphasized. Sequence and structural comparison between ACE_N and ACE_C and of other proteins of the gluzincin family highlights key residues that could be responsible for the peptide hydrolysis mechanism. Currently available mutational and substrate hydrolysis data for both domains are evaluated and are consistent with the predicted model.}, author = {A.G. Tzakos and A.S. Galanis and G.A. Spyroulias and P. Cordopatis and E. Manessi-Zoupa and I.P. Gerothanassis}, doi = {10.1093/protein/gzg122}, issue = {12}, journal = {Protein Engineering}, pages = {993-1003}, title = {Structure-function discrimination of the N- and C- catalytic domains of human angiotensin-converting enzyme: Implications for Cl- activation and peptide hydrolysis mechanisms}, volume = {16}, year = {2003}, } - Tzakos, A. G., A. M. J. J. Bonvin, A. Troganis, P. Cordopatis, M. L. Amzel, I. P. Gerothanassis, and Van N. A. J. Nuland. "On the molecular basis of the recognition of angiotensin ii (aii) nmr structure of aii in solution compared with the x-ray structure of aii bound to the mab fab131." European journal of biochemistry 270 (2003): 849-860. doi:10.1046/j.1432-1033.2003.03441.x
[BibTeX] [Abstract]
The high-resolution 3D structure of the octapeptide hormone angiotensin II (AII) in aqueous solution has been obtained by simulated annealing calculations, using high-resolution NMR-derived restraints. After final refinement in explicit water, a family of 13 structures was obtained with a backbone RMSD of 0.73 ± 0.23 Å. AII adopts a fairly compact folded structure, with its C-terminus and N-terminus approaching to within ≈ 7.2 Å of each other. The side chains of Arg2, Tyr4, Ile5 and His6 are oriented on one side of a plane defined by the peptide backbone, and the Val3 and Pro7 are pointing in opposite directions. The stabilization of the folded conformation can be explained by the stacking of the Val3 side chain with the Pro7 ring and by a hydrophobic cluster formed by the Tyr4, Ile5 and His6 side chains. Comparison between the NMR-derived structure of AII in aqueous solution and the refined crystal structure of the complex of AII with a high-affinity mAb (Fab131) [Garcia, K.C., Ronco, P.M., Verroust, P.J., Brunger, A.T., Amzel, L.M. (1992) Science 257, 502-507] provides important quantitative information on two common structural features: (a) a U-shaped structure of the Tyr4-Ile5-His6-Pro7 sequence, which is the most immunogenic epitope of the peptide, with the Asp1 side chain oriented towards the interior of the turn approaching the C-terminus; (b) an Asx-turn-like motif with the side chain aspartate carboxyl group hydrogen-bonded to the main chain NH group of Arg2. It can be concluded that small rearrangements of the epitope 4-7 in the solution structure of AII are required by a mean value of 0.76 ± 0.03 Å for structure alignment and ≈ 1.27 ± 0.02 Å for sequence alignment with the X-ray structure of AII bound to the mAb Fab131. These data are interpreted in terms of a biological 'nucleus' conformation of the hormone in solution, which requires a limited number of structural rearrangements for receptor-antigen recognition and binding.
@article{Tzakos2003, abstract = {The high-resolution 3D structure of the octapeptide hormone angiotensin II (AII) in aqueous solution has been obtained by simulated annealing calculations, using high-resolution NMR-derived restraints. After final refinement in explicit water, a family of 13 structures was obtained with a backbone RMSD of 0.73 ± 0.23 Å. AII adopts a fairly compact folded structure, with its C-terminus and N-terminus approaching to within ≈ 7.2 Å of each other. The side chains of Arg2, Tyr4, Ile5 and His6 are oriented on one side of a plane defined by the peptide backbone, and the Val3 and Pro7 are pointing in opposite directions. The stabilization of the folded conformation can be explained by the stacking of the Val3 side chain with the Pro7 ring and by a hydrophobic cluster formed by the Tyr4, Ile5 and His6 side chains. Comparison between the NMR-derived structure of AII in aqueous solution and the refined crystal structure of the complex of AII with a high-affinity mAb (Fab131) [Garcia, K.C., Ronco, P.M., Verroust, P.J., Brunger, A.T., Amzel, L.M. (1992) Science 257, 502-507] provides important quantitative information on two common structural features: (a) a U-shaped structure of the Tyr4-Ile5-His6-Pro7 sequence, which is the most immunogenic epitope of the peptide, with the Asp1 side chain oriented towards the interior of the turn approaching the C-terminus; (b) an Asx-turn-like motif with the side chain aspartate carboxyl group hydrogen-bonded to the main chain NH group of Arg2. It can be concluded that small rearrangements of the epitope 4-7 in the solution structure of AII are required by a mean value of 0.76 ± 0.03 Å for structure alignment and ≈ 1.27 ± 0.02 Å for sequence alignment with the X-ray structure of AII bound to the mAb Fab131. These data are interpreted in terms of a biological 'nucleus' conformation of the hormone in solution, which requires a limited number of structural rearrangements for receptor-antigen recognition and binding.}, author = {A.G. Tzakos and A.M.J.J. Bonvin and A. Troganis and P. Cordopatis and M.L. Amzel and I.P. Gerothanassis and N.A.J. Van Nuland}, doi = {10.1046/j.1432-1033.2003.03441.x}, issue = {5}, journal = {European Journal of Biochemistry}, pages = {849-860}, title = {On the molecular basis of the recognition of angiotensin II (AII) NMR structure of AII in solution compared with the X-ray structure of AII bound to the mAB Fab131}, volume = {270}, year = {2003}, }