Pub Date : 2017-01-01DOI: 10.2174/1872312810666161227145358
Chiaki Tanoue, K. Sugihara, Y. Tayama, Naoto Uramaru, Yoko Watanabe, S. Ohta, S. Kitamura
BACKGROUND Zaleplon (ZAL) is a sedative-hypnotic agent, which is mainly metabolized to inactive 5-oxidized zaleplon (5-oxo-ZAL) and N-des-ethylated ZAL (des-ethyl-ZAL) in mice and humans. The former reaction is considered to be catalyzed by aldehyde oxidase present in liver cytosol. METHODS Here, we examined sex and strain differences of ZAL metabolism to 5-oxo-ZAL among four strains of mice, as well as the inter-individual variation in humans, in order to evaluate the variability of 5-oxo-ZAL-forming activity and its relationship with aldehyde oxidase activity. In mice, the activity in C57BL/6J strain was the highest, followed by C3H/He and BALB/c. The activity in DBA/2J was the lowest, being 2.3-fold lower than that of C57BL/6J mice. The activity of male mice was higher than that of female mice. Large inter-individual variations were observed among humans, with a range of 10- fold. Raloxifene, an inhibitor of aldehyde oxidase, markedly decreased the formation of 5-oxo-ZAL by liver cytosol of mice and humans. Further, the plasma level of 5-oxo-ZAL in mice was decreased when raloxifene was co-administered with ZAL. RESULTS Our results indicate that the formation of 5-oxo-ZAL from ZAL is mainly catalyzed by aldehyde oxidase in mice and humans, and the variability of 5-oxo-ZAL formation is due primarily to differences of aldehyde oxidase activity. CONCLUSION High inter-individual variability of ZAL 5-oxidase activity and potential for interaction of ZAL with other medicines that are inhibitors of aldehyde oxidase should be taken into consideration in clinical usage of ZAL.
{"title":"Variability of Zaleplon 5-Oxidase Activity in Mice and Humans, and Inhibition by Raloxifene.","authors":"Chiaki Tanoue, K. Sugihara, Y. Tayama, Naoto Uramaru, Yoko Watanabe, S. Ohta, S. Kitamura","doi":"10.2174/1872312810666161227145358","DOIUrl":"https://doi.org/10.2174/1872312810666161227145358","url":null,"abstract":"BACKGROUND Zaleplon (ZAL) is a sedative-hypnotic agent, which is mainly metabolized to inactive 5-oxidized zaleplon (5-oxo-ZAL) and N-des-ethylated ZAL (des-ethyl-ZAL) in mice and humans. The former reaction is considered to be catalyzed by aldehyde oxidase present in liver cytosol. METHODS Here, we examined sex and strain differences of ZAL metabolism to 5-oxo-ZAL among four strains of mice, as well as the inter-individual variation in humans, in order to evaluate the variability of 5-oxo-ZAL-forming activity and its relationship with aldehyde oxidase activity. In mice, the activity in C57BL/6J strain was the highest, followed by C3H/He and BALB/c. The activity in DBA/2J was the lowest, being 2.3-fold lower than that of C57BL/6J mice. The activity of male mice was higher than that of female mice. Large inter-individual variations were observed among humans, with a range of 10- fold. Raloxifene, an inhibitor of aldehyde oxidase, markedly decreased the formation of 5-oxo-ZAL by liver cytosol of mice and humans. Further, the plasma level of 5-oxo-ZAL in mice was decreased when raloxifene was co-administered with ZAL. RESULTS Our results indicate that the formation of 5-oxo-ZAL from ZAL is mainly catalyzed by aldehyde oxidase in mice and humans, and the variability of 5-oxo-ZAL formation is due primarily to differences of aldehyde oxidase activity. CONCLUSION High inter-individual variability of ZAL 5-oxidase activity and potential for interaction of ZAL with other medicines that are inhibitors of aldehyde oxidase should be taken into consideration in clinical usage of ZAL.","PeriodicalId":11339,"journal":{"name":"Drug metabolism letters","volume":"10 4 1","pages":"278-285"},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68049348","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-11-01DOI: 10.2174/1872312811666170127160931
T. Sasabe, Shinichiro Maeda, K. Kishida, M. Yamano, Y. Miwa, T. Sugiyama
Objective: Drug therapy is occasionally accompanied by an idiosyncratic severe toxicity, which occurs very rarely, but can lead to patient mortality. Methazolamide, an anti-glaucomatous agent, could cause severe skin eruptions called Stevens-Johnson syndrome/toxic epidermal necrolyis (SJS/TEN). Its precise etiology is still uncertain. In this study, the metabolism of methazolamide was investigated in immortalized human keratinocytes to reveal the possible mechanism which causes SJS/TEN. Methods: The metabolism of methazolamide was studied using immortalized human keratinocytes, HaCaT cells. HPLC was used to isolate a metabolite from the culture medium. Mass spectrometry (LC-MS/MS) was employed for its characterization. Three typical chemical inducers were assessed for the inducibility of cytochrome P450, and methimazole was used as the inhibitor of flavin-containing monooxygenase (FMO). Results: A sulfonic acid, N-[3-methyl-5-sulfo-1,3,4-thiadiazol-2(3H)-ylidene]acetamide (MSO) was identified as the final metabolite. Dexamethasone and β-naphthoflavone behaved as an inducer of cytochrome P450 in the metabolism, but isoniazid did not. The effect of methimazole was not consistent. We did not detect any glucuronide nor any mercapturic acid (N-acetylcysteine conjugate). Conclusion: N-[3-methyl-5-sulfo-1,3,4-thiadiazol-2(3H)-ylidene]acetamide (MSO) is not considered to be a direct product of an enzymatic reaction, but rather an auto-oxidation product of N-[3-methyl-5-sulfe-1,3,4-thiadiazol-2(3H)-ylidene]acetamide, a chemically unstable sulfenic acid, which is produced by cytochrome P450 from the β-lyase product of cysteine conjugate of methazolamide. MSO is considered to be susceptible to glutathione and to return to glutathione conjugate of methazolamide, forming a futile cycle. A hypothetical scenario is presented as to the onset of the disease.
{"title":"The Metabolism of Methazolamide in Immortalized Human Keratinocytes, HaCaT Cells","authors":"T. Sasabe, Shinichiro Maeda, K. Kishida, M. Yamano, Y. Miwa, T. Sugiyama","doi":"10.2174/1872312811666170127160931","DOIUrl":"https://doi.org/10.2174/1872312811666170127160931","url":null,"abstract":"Objective: Drug therapy is occasionally accompanied by an idiosyncratic severe toxicity, which occurs very rarely, but can lead to patient mortality. Methazolamide, an anti-glaucomatous agent, could cause severe skin eruptions called Stevens-Johnson syndrome/toxic epidermal necrolyis (SJS/TEN). Its precise etiology is still uncertain. In this study, the metabolism of methazolamide was investigated in immortalized human keratinocytes to reveal the possible mechanism which causes SJS/TEN. Methods: The metabolism of methazolamide was studied using immortalized human keratinocytes, HaCaT cells. HPLC was used to isolate a metabolite from the culture medium. Mass spectrometry (LC-MS/MS) was employed for its characterization. Three typical chemical inducers were assessed for the inducibility of cytochrome P450, and methimazole was used as the inhibitor of flavin-containing monooxygenase (FMO). Results: A sulfonic acid, N-[3-methyl-5-sulfo-1,3,4-thiadiazol-2(3H)-ylidene]acetamide (MSO) was identified as the final metabolite. Dexamethasone and β-naphthoflavone behaved as an inducer of cytochrome P450 in the metabolism, but isoniazid did not. The effect of methimazole was not consistent. We did not detect any glucuronide nor any mercapturic acid (N-acetylcysteine conjugate). Conclusion: N-[3-methyl-5-sulfo-1,3,4-thiadiazol-2(3H)-ylidene]acetamide (MSO) is not considered to be a direct product of an enzymatic reaction, but rather an auto-oxidation product of N-[3-methyl-5-sulfe-1,3,4-thiadiazol-2(3H)-ylidene]acetamide, a chemically unstable sulfenic acid, which is produced by cytochrome P450 from the β-lyase product of cysteine conjugate of methazolamide. MSO is considered to be susceptible to glutathione and to return to glutathione conjugate of methazolamide, forming a futile cycle. A hypothetical scenario is presented as to the onset of the disease.","PeriodicalId":11339,"journal":{"name":"Drug metabolism letters","volume":"10 1","pages":"295 - 305"},"PeriodicalIF":0.0,"publicationDate":"2016-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2174/1872312811666170127160931","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68049414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-05-31DOI: 10.2174/1872312810666160303112012
Lorraine Thong, John Macsharry, D. Murphy
BACKGROUND Statins have been long known for their lipid-lowering properties however there has been recent interest in their potential to positively influence clinical outcomes in pulmonary disease processes manifesting primarily as airway disorders. OBJECTIVES We review the potential use of statin therapy in respiratory medicine, with particular emphasis on airway disease. We also explore the possible mechanisms for the observed benefits of statins in conditions of the airway. METHOD A literary review of published articles related to defining the potential scientific basis for touted clinical efficacy, pertinent clinical data and review articles of statin therapy in airway disease. RESULTS There was a vast quantity of publications available pertaining to the topic of interest. CONCLUSION Statins may have beneficial pleiotropic effects in addition to their actions as potent lipid-lowering agents particularly in patients with chronic obstructive pulmonary disease and post lung transplantation. Further human studies are required to substantiate their possible potential as many of the clinical trials performed to date have not demonstrated the translation of results of these promising scientific and observational studies into positive outcomes in well-designed, randomized, placebo-controlled human trials.
{"title":"The Effects of Statin Therapy on the Human Airway.","authors":"Lorraine Thong, John Macsharry, D. Murphy","doi":"10.2174/1872312810666160303112012","DOIUrl":"https://doi.org/10.2174/1872312810666160303112012","url":null,"abstract":"BACKGROUND\u0000Statins have been long known for their lipid-lowering properties however there has been recent interest in their potential to positively influence clinical outcomes in pulmonary disease processes manifesting primarily as airway disorders.\u0000\u0000\u0000OBJECTIVES\u0000We review the potential use of statin therapy in respiratory medicine, with particular emphasis on airway disease. We also explore the possible mechanisms for the observed benefits of statins in conditions of the airway.\u0000\u0000\u0000METHOD\u0000A literary review of published articles related to defining the potential scientific basis for touted clinical efficacy, pertinent clinical data and review articles of statin therapy in airway disease.\u0000\u0000\u0000RESULTS\u0000There was a vast quantity of publications available pertaining to the topic of interest.\u0000\u0000\u0000CONCLUSION\u0000Statins may have beneficial pleiotropic effects in addition to their actions as potent lipid-lowering agents particularly in patients with chronic obstructive pulmonary disease and post lung transplantation. Further human studies are required to substantiate their possible potential as many of the clinical trials performed to date have not demonstrated the translation of results of these promising scientific and observational studies into positive outcomes in well-designed, randomized, placebo-controlled human trials.","PeriodicalId":11339,"journal":{"name":"Drug metabolism letters","volume":"10 2 1","pages":"75-82"},"PeriodicalIF":0.0,"publicationDate":"2016-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68049621","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-05-31DOI: 10.2174/1872312810666160219121415
A. Varghese, J. Savai, Shruti Mistry, Preeti K. Khandare, K. Barve, N. Pandita, R. Gaud
BACKGROUND Terminalia arjuna Wight & Arn. (Combretaceae) is a tree having an extensive medicinal potential in cardiovascular disorders. T. arjuna bark extract has been reported to play a significant role as a cardiac stimulant for its beneficial effects in angina. Herb - drug interactions (HDI) are one of the most important clinical concerns in the concomitant consumption of herbs and prescription drugs. Our study was to investigate the in vitro CYP2D inhibition potential of Terminalia arjuna (T. arjuna) extracts in rat liver microsomes and to study the influence of aqueous bark extract of T. arjuna on the oral pharmacokinetics and pharmacodynamics of metoprolol succinate in rats. METHODS The CYP2D inhibition potential of herbal extracts of T. arjuna was investigated in rat liver microsomes. Pharmacokinetic-pharmacodynamic interaction of aqueous extract of T. arjuna with metoprolol succinate was investigated in rats. RESULTS The ethyl acetate, alcoholic & aqueous bark extracts of T. arjuna showed potent reversible non-competitive inhibition CYP2D enzyme in rat liver microsomes with IC50 values less than 40 μg/mL. Arjunic acid, arjunetin and arjungenin did not show significant inhibition of CYP2D enzyme in rat liver microsomes. Pharmacokinetic studies showed that aqueous bark extract of T. arjuna led to a significant reduction (P < 0.05) in AUC0-24h and Cmax of metoprolol succinate in rats, when co-administered. Pharmacodynamic studies reveal a significant reduction in therapeutic activity of metoprolol succinate on co-administration with aqueous bark extract of T. arjuna. CONCLUSION Based on our in vitro and in vivo findings and until further clinical drug interaction experiments are conducted, the co-administration of drugs, especially those primarily cleared via CYP2D catalyzed metabolism, with T. arjuna extracts should be done with caution.
{"title":"In Vitro CYP2D Inhibitory Effect and Influence on Pharmacokinetics and Pharmacodynamic Parameters of Metoprolol Succinate by Terminalia arjuna in Rats.","authors":"A. Varghese, J. Savai, Shruti Mistry, Preeti K. Khandare, K. Barve, N. Pandita, R. Gaud","doi":"10.2174/1872312810666160219121415","DOIUrl":"https://doi.org/10.2174/1872312810666160219121415","url":null,"abstract":"BACKGROUND\u0000Terminalia arjuna Wight & Arn. (Combretaceae) is a tree having an extensive medicinal potential in cardiovascular disorders. T. arjuna bark extract has been reported to play a significant role as a cardiac stimulant for its beneficial effects in angina. Herb - drug interactions (HDI) are one of the most important clinical concerns in the concomitant consumption of herbs and prescription drugs. Our study was to investigate the in vitro CYP2D inhibition potential of Terminalia arjuna (T. arjuna) extracts in rat liver microsomes and to study the influence of aqueous bark extract of T. arjuna on the oral pharmacokinetics and pharmacodynamics of metoprolol succinate in rats.\u0000\u0000\u0000METHODS\u0000The CYP2D inhibition potential of herbal extracts of T. arjuna was investigated in rat liver microsomes. Pharmacokinetic-pharmacodynamic interaction of aqueous extract of T. arjuna with metoprolol succinate was investigated in rats.\u0000\u0000\u0000RESULTS\u0000The ethyl acetate, alcoholic & aqueous bark extracts of T. arjuna showed potent reversible non-competitive inhibition CYP2D enzyme in rat liver microsomes with IC50 values less than 40 μg/mL. Arjunic acid, arjunetin and arjungenin did not show significant inhibition of CYP2D enzyme in rat liver microsomes. Pharmacokinetic studies showed that aqueous bark extract of T. arjuna led to a significant reduction (P < 0.05) in AUC0-24h and Cmax of metoprolol succinate in rats, when co-administered. Pharmacodynamic studies reveal a significant reduction in therapeutic activity of metoprolol succinate on co-administration with aqueous bark extract of T. arjuna.\u0000\u0000\u0000CONCLUSION\u0000Based on our in vitro and in vivo findings and until further clinical drug interaction experiments are conducted, the co-administration of drugs, especially those primarily cleared via CYP2D catalyzed metabolism, with T. arjuna extracts should be done with caution.","PeriodicalId":11339,"journal":{"name":"Drug metabolism letters","volume":"10 2 1","pages":"124-35"},"PeriodicalIF":0.0,"publicationDate":"2016-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68048538","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-05-31DOI: 10.2174/1872312810666160303112212
Pengcheng Wang, Amina I. Shehu, Ke Liu, Jie Lu, Xiaochao Ma
BACKGROUND Cobicistat (COBI) is a pharmacoenhancer for antiretroviral therapy. OBJECTIVE The current study was designed to profile the metabolic pathways of COBI and to determine the enzymes that contribute to COBI metabolism. METHOD We screened COBI metabolites in mice and human liver microsomes. We also used cDNAexpressed human cytochromes P450 (CYPs) to explore the role of human enzymes in COBI metabolism. RESULTS Twenty new and three known metabolites of COBI were identified in mouse urine and feces. These new metabolic pathways of COBI include glycine conjugation, N-acetyl cysteine conjugation, morpholine ring-opening, and thiazole ring-opening. Twelve of COBI metabolites were further confirmed in mouse and human liver microsomes, including nine new metabolites. Consistent with the previous report, CYP3A4 and CYP2D6 were determined as the major enzymes that contribute to COBI metabolism. CONCLUSION This study provided a full map of COBI metabolism. These results can be used to manage CYP-mediated drug-drug interactions and adverse drug reactions that are associated with COBI-containing regimens in human.
{"title":"Biotransformation of Cobicistat: Metabolic Pathways and Enzymes.","authors":"Pengcheng Wang, Amina I. Shehu, Ke Liu, Jie Lu, Xiaochao Ma","doi":"10.2174/1872312810666160303112212","DOIUrl":"https://doi.org/10.2174/1872312810666160303112212","url":null,"abstract":"BACKGROUND\u0000Cobicistat (COBI) is a pharmacoenhancer for antiretroviral therapy.\u0000\u0000\u0000OBJECTIVE\u0000The current study was designed to profile the metabolic pathways of COBI and to determine the enzymes that contribute to COBI metabolism.\u0000\u0000\u0000METHOD\u0000We screened COBI metabolites in mice and human liver microsomes. We also used cDNAexpressed human cytochromes P450 (CYPs) to explore the role of human enzymes in COBI metabolism.\u0000\u0000\u0000RESULTS\u0000Twenty new and three known metabolites of COBI were identified in mouse urine and feces. These new metabolic pathways of COBI include glycine conjugation, N-acetyl cysteine conjugation, morpholine ring-opening, and thiazole ring-opening. Twelve of COBI metabolites were further confirmed in mouse and human liver microsomes, including nine new metabolites. Consistent with the previous report, CYP3A4 and CYP2D6 were determined as the major enzymes that contribute to COBI metabolism.\u0000\u0000\u0000CONCLUSION\u0000This study provided a full map of COBI metabolism. These results can be used to manage CYP-mediated drug-drug interactions and adverse drug reactions that are associated with COBI-containing regimens in human.","PeriodicalId":11339,"journal":{"name":"Drug metabolism letters","volume":"10 2 1","pages":"111-23"},"PeriodicalIF":0.0,"publicationDate":"2016-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68049652","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-05-31DOI: 10.2174/1872312810666160219121217
Jian Shi, Lijun J. Zhu, Ye Li, Haihui Zheng, Jia Yu, Linlin Lu, Zhongqiu Liu
C-glycosides are important flavonoids with significant pharmacological activities implicated in anticancer and antioxidative effects. However, their characteristics of metabolism and transportation have been rarely investigated. This research aimed to examine the metabolic characteristics of two active C-glycosides, namely, orientin and isoorientin, in human liver microsomes (HLMs) and rat liver microsomes (RLMs) and to confirm the specific uridine 5'-diphospho glucuronosyltransferase (UGT) isoforms involved in glucuronidation by HLMs. Furthermore, the permeability of orientin and isoorientin was also determined by using Caco-2 cell monolayers. Results revealed that orientin and isoorientin could generate two metabolites, which were identified as monoglucuronides. HLM- and RLM-mediated glucuronide formations were in accordance with typical Michaelis-Menten kinetics. Conversely, RLM initially metabolized orientin to its corresponding metabolite, and this process was consistent with biphasic kinetics. Among the UGT isoform, UGT1A1, 1A8, 1A9 and 1A10 exhibited the highest enzyme activity. Passive diffusion was the predominant orientin and isoorientin transportation mechanism in Caco-2 cell monolayers, and their apparent permeability further confirmed that orientin and isoorientin were well absorbed. Therefore, orientin and isoorientin can be metabolized by UGT isoforms and microsomes; these flavonoids can also be transported via passive diffusion in Caco-2 cells, which are relatively permeable.
c -糖苷是一类重要的类黄酮，具有重要的抗癌和抗氧化作用。然而，对其代谢和运输特性的研究却很少。本研究旨在检测两种活性c -糖苷，即东方苷和异东方苷在人肝微粒体(HLMs)和大鼠肝微粒体(rlm)中的代谢特征，并确定尿苷5′-二磷酸葡萄糖醛酸转移酶(UGT)在HLMs中参与糖醛酸化的特异性亚型。此外，还利用Caco-2细胞单层膜测定了定向蛋白和异定向蛋白的通透性。结果表明，荭草苷和异荭草苷可产生两种代谢产物，鉴定为单lucuronides。HLM-和rlm -介导的葡萄糖醛酸生成符合典型的Michaelis-Menten动力学。相反，RLM最初将orientin代谢为相应的代谢物，这一过程符合双相动力学。在UGT亚型中，UGT1A1、1A8、1A9和1A10的酶活性最高。被动扩散是Caco-2细胞单层中主要的取向蛋白和异取向蛋白运输机制，其明显的通透性进一步证实了取向蛋白和异取向蛋白具有良好的吸收作用。因此，荭草苷和异荭草苷可以被UGT异构体和微粒体代谢;这些类黄酮也可以通过Caco-2细胞的被动扩散进行运输，Caco-2细胞具有相对的渗透性。
{"title":"In Vitro Study of UGT Metabolism and Permeability of Orientin and Isoorientin, Two Active flavonoid C-glycosides.","authors":"Jian Shi, Lijun J. Zhu, Ye Li, Haihui Zheng, Jia Yu, Linlin Lu, Zhongqiu Liu","doi":"10.2174/1872312810666160219121217","DOIUrl":"https://doi.org/10.2174/1872312810666160219121217","url":null,"abstract":"C-glycosides are important flavonoids with significant pharmacological activities implicated in anticancer and antioxidative effects. However, their characteristics of metabolism and transportation have been rarely investigated. This research aimed to examine the metabolic characteristics of two active C-glycosides, namely, orientin and isoorientin, in human liver microsomes (HLMs) and rat liver microsomes (RLMs) and to confirm the specific uridine 5'-diphospho glucuronosyltransferase (UGT) isoforms involved in glucuronidation by HLMs. Furthermore, the permeability of orientin and isoorientin was also determined by using Caco-2 cell monolayers. Results revealed that orientin and isoorientin could generate two metabolites, which were identified as monoglucuronides. HLM- and RLM-mediated glucuronide formations were in accordance with typical Michaelis-Menten kinetics. Conversely, RLM initially metabolized orientin to its corresponding metabolite, and this process was consistent with biphasic kinetics. Among the UGT isoform, UGT1A1, 1A8, 1A9 and 1A10 exhibited the highest enzyme activity. Passive diffusion was the predominant orientin and isoorientin transportation mechanism in Caco-2 cell monolayers, and their apparent permeability further confirmed that orientin and isoorientin were well absorbed. Therefore, orientin and isoorientin can be metabolized by UGT isoforms and microsomes; these flavonoids can also be transported via passive diffusion in Caco-2 cells, which are relatively permeable.","PeriodicalId":11339,"journal":{"name":"Drug metabolism letters","volume":"10 2 1","pages":"101-10"},"PeriodicalIF":0.0,"publicationDate":"2016-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68048525","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-05-01DOI: 10.2174/1872312810666160223121836
Samantha J. Richardson, April Bai, A. Kulkarni, M. Moghaddam
Background: A rapid and comprehensive metabolic stability screen at the top of a drug discovery flow chart serves as an effective gate in eliminating low value compounds. This imparts a significant level of efficiency and saves valuable resources. While microsomes are amenable to high throughput automation and are cost effective, their enzymatic make-up is limited to that which is contained in endoplasmic reticulum, thereby informing only on Phase I metabolism. Lack of Phase II metabolism data can become a potential liability later in the process, adversely affecting discovery projects’ timelines and budget. Hepatocytes offer a full complement of metabolic enzymes and retain their cellular compartments, better representing liver metabolic function. However, hepatocyte screens are relatively expensive, labor intensive, and not easily automatable. Liver S9 fractions include Phase I and II metabolic enzymes, are relatively inexpensive, easy to use, and amenable to automation, making them a more appropriate screening system. We compare the data from the three systems and present the results. Results: Liver S9 and hepatocyte stability assays binned into the same category 70-84% of the time. Microsome and hepatocyte data were in agreement 73-82% of the time. The true rate for stability versus plasma clearance was 45% for hepatocytes and 43% for S9. Conclusion: In our opinion, replacing liver microsome and hepatocyte assays with S9 assay for high throughput metabolic screening purposes provides the combined benefit of comprehensive and high quality data at a reasonable expense for drug discovery programs.
{"title":"Efficiency in Drug Discovery: Liver S9 Fraction Assay As a Screen for Metabolic Stability","authors":"Samantha J. Richardson, April Bai, A. Kulkarni, M. Moghaddam","doi":"10.2174/1872312810666160223121836","DOIUrl":"https://doi.org/10.2174/1872312810666160223121836","url":null,"abstract":"Background: A rapid and comprehensive metabolic stability screen at the top of a drug discovery flow chart serves as an effective gate in eliminating low value compounds. This imparts a significant level of efficiency and saves valuable resources. While microsomes are amenable to high throughput automation and are cost effective, their enzymatic make-up is limited to that which is contained in endoplasmic reticulum, thereby informing only on Phase I metabolism. Lack of Phase II metabolism data can become a potential liability later in the process, adversely affecting discovery projects’ timelines and budget. Hepatocytes offer a full complement of metabolic enzymes and retain their cellular compartments, better representing liver metabolic function. However, hepatocyte screens are relatively expensive, labor intensive, and not easily automatable. Liver S9 fractions include Phase I and II metabolic enzymes, are relatively inexpensive, easy to use, and amenable to automation, making them a more appropriate screening system. We compare the data from the three systems and present the results. Results: Liver S9 and hepatocyte stability assays binned into the same category 70-84% of the time. Microsome and hepatocyte data were in agreement 73-82% of the time. The true rate for stability versus plasma clearance was 45% for hepatocytes and 43% for S9. Conclusion: In our opinion, replacing liver microsome and hepatocyte assays with S9 assay for high throughput metabolic screening purposes provides the combined benefit of comprehensive and high quality data at a reasonable expense for drug discovery programs.","PeriodicalId":11339,"journal":{"name":"Drug metabolism letters","volume":"31 1","pages":"83 - 90"},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2174/1872312810666160223121836","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68048666","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-02-29DOI: 10.2174/187231281001160212150630
A. Muhammad, M. Ibrahim, O. Erukainure, N. Habila, A. Idowu, U. Ndidi, I. Malami, H. Zailani, Zeenat Bello Kudan, Bilal Abdullahi Muhammad
BACKGROUND Antimalarial drugs are medicines that are used to prevent or treat malaria effectively at different stages in the life cycle of the malarial parasites. In spite of this, a good number of these drugs have the potential to cause harm when they are misused or abused. OBJECTIVE This study was undertaken to evaluate the effects of commonly-used antimalarial drugs in the North Western region of Nigeria on haemolysis and DNA fragmentation in the blood of normal and malarial infected humans ex vivo. METHOD The drugs used were artemisinine, artesunate, chloroquine, coartem and quinine (0.5-8.0 mg/ml). Haemolysis, haemoglobin status and DNA fragmentations were assayed for using standard procedures. RESULTS It was observed that all the drugs induced a remarkable dose-dependent haemolysis with more pronounced effects on apparently healthy humans. There was a significant (P < 0.05) decrease in the level of haemoglobin in normal blood samples when compared with control samples. Contrariwise, in the malaria-infected blood, the haemoglobin level significantly (P < 0.05) increased as compared with control. The drugs caused an exceptional significant (P < 0.05) induction of DNA fragmentation when compared with control. CONCLUSION Commonly-used antimalarial drugs induced haemolysis and altered haemoglobin status which may spontaneously increases the cellular iron levels; a substrate for Fenton and Haber Weiss reactions, and eventually induces DNA fragmentation. Hence, adequate care should be taken during prescription with total avoidance for self medications and/or drugs abuse as a result of their adverse effects within the red blood cells and its immediate microenvironment.
{"title":"Induction of Haemolysis and DNA Fragmentation in a Normal and Malarial-Infected Blood by Commonly - used Antimalarial Drugs in the North-Western Region of Nigeria.","authors":"A. Muhammad, M. Ibrahim, O. Erukainure, N. Habila, A. Idowu, U. Ndidi, I. Malami, H. Zailani, Zeenat Bello Kudan, Bilal Abdullahi Muhammad","doi":"10.2174/187231281001160212150630","DOIUrl":"https://doi.org/10.2174/187231281001160212150630","url":null,"abstract":"BACKGROUND\u0000Antimalarial drugs are medicines that are used to prevent or treat malaria effectively at different stages in the life cycle of the malarial parasites. In spite of this, a good number of these drugs have the potential to cause harm when they are misused or abused.\u0000\u0000\u0000OBJECTIVE\u0000This study was undertaken to evaluate the effects of commonly-used antimalarial drugs in the North Western region of Nigeria on haemolysis and DNA fragmentation in the blood of normal and malarial infected humans ex vivo.\u0000\u0000\u0000METHOD\u0000The drugs used were artemisinine, artesunate, chloroquine, coartem and quinine (0.5-8.0 mg/ml). Haemolysis, haemoglobin status and DNA fragmentations were assayed for using standard procedures.\u0000\u0000\u0000RESULTS\u0000It was observed that all the drugs induced a remarkable dose-dependent haemolysis with more pronounced effects on apparently healthy humans. There was a significant (P < 0.05) decrease in the level of haemoglobin in normal blood samples when compared with control samples. Contrariwise, in the malaria-infected blood, the haemoglobin level significantly (P < 0.05) increased as compared with control. The drugs caused an exceptional significant (P < 0.05) induction of DNA fragmentation when compared with control.\u0000\u0000\u0000CONCLUSION\u0000Commonly-used antimalarial drugs induced haemolysis and altered haemoglobin status which may spontaneously increases the cellular iron levels; a substrate for Fenton and Haber Weiss reactions, and eventually induces DNA fragmentation. Hence, adequate care should be taken during prescription with total avoidance for self medications and/or drugs abuse as a result of their adverse effects within the red blood cells and its immediate microenvironment.","PeriodicalId":11339,"journal":{"name":"Drug metabolism letters","volume":"10 1 1","pages":"49-55"},"PeriodicalIF":0.0,"publicationDate":"2016-02-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68048406","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-02-29DOI: 10.2174/1872312810666151204002456
H. Raunio, R. Juvonen, A. Poso, M. Lahtela-Kakkonen, Minna Rahnasto-Rilla
BACKGROUND Tobacco smoking is a leading cause of preventable disease and death globally. Nicotine is the main addictive component in tobacco. Nicotine is eliminated from the body by biotransformation in the liver to inactive metabolites. This reaction is catalyzed by the cytochrome P450 2A6 (CYP2A6) enzyme. Administering chemical inhibitors of CYP2A6 has been shown to slow down the elimination of nicotine with consequent reduction in number of cigarettes smoked. We have systematically developed small molecule CYP2A6 inhibitors with good balance between potency and CYP selectivity. OBJECTIVE During this process we have noticed that many potent CYP2A6 inhibitors also inhibit other human liver CYP forms, most notably CYP1A2 and CYP2B6. This study aimed at defining common and distinct features of ligand binding to CYP1A2, CYP2A6 and CYP2B6 active sites. METHODS We used our previous chemical inhibitor databases to construct improved 3-dimensional quantitative structureactivity relationship (3D-QSAR) models for CYP1A2, CYP2A6 and CYP2B6. RESULTS Combined 3D-QSAR and docking procedures yielded precise information about the common and distinct interactions of inhibitors and the enzyme active sites. Positioning of hydrogen bond donor/acceptor atoms and the shape and volume of the compound defined the potency and specificity of inhibition. A novel potent and selective CYP1A2 inhibitor was found. CONCLUSION This in silico approach will provide a means for very rapid and high throughput prediction of cross-inhibition of these three CYP enzymes.
{"title":"Common and Distinct Interactions of Chemical Inhibitors with Cytochrome P450 CYP1A2, CYP2A6 and CYP2B6 Enzymes.","authors":"H. Raunio, R. Juvonen, A. Poso, M. Lahtela-Kakkonen, Minna Rahnasto-Rilla","doi":"10.2174/1872312810666151204002456","DOIUrl":"https://doi.org/10.2174/1872312810666151204002456","url":null,"abstract":"BACKGROUND\u0000Tobacco smoking is a leading cause of preventable disease and death globally. Nicotine is the main addictive component in tobacco. Nicotine is eliminated from the body by biotransformation in the liver to inactive metabolites. This reaction is catalyzed by the cytochrome P450 2A6 (CYP2A6) enzyme. Administering chemical inhibitors of CYP2A6 has been shown to slow down the elimination of nicotine with consequent reduction in number of cigarettes smoked. We have systematically developed small molecule CYP2A6 inhibitors with good balance between potency and CYP selectivity.\u0000\u0000\u0000OBJECTIVE\u0000During this process we have noticed that many potent CYP2A6 inhibitors also inhibit other human liver CYP forms, most notably CYP1A2 and CYP2B6. This study aimed at defining common and distinct features of ligand binding to CYP1A2, CYP2A6 and CYP2B6 active sites.\u0000\u0000\u0000METHODS\u0000We used our previous chemical inhibitor databases to construct improved 3-dimensional quantitative structureactivity relationship (3D-QSAR) models for CYP1A2, CYP2A6 and CYP2B6.\u0000\u0000\u0000RESULTS\u0000Combined 3D-QSAR and docking procedures yielded precise information about the common and distinct interactions of inhibitors and the enzyme active sites. Positioning of hydrogen bond donor/acceptor atoms and the shape and volume of the compound defined the potency and specificity of inhibition. A novel potent and selective CYP1A2 inhibitor was found.\u0000\u0000\u0000CONCLUSION\u0000This in silico approach will provide a means for very rapid and high throughput prediction of cross-inhibition of these three CYP enzymes.","PeriodicalId":11339,"journal":{"name":"Drug metabolism letters","volume":"10 1 1","pages":"56-64"},"PeriodicalIF":0.0,"publicationDate":"2016-02-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68048464","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-02-29DOI: 10.2174/1872312810666151223103208
Y. Masubuchi, S. Kondo
BACKGROUND Benzbromarone is a uricosuric drug in current clinical use that can cause serious hepatotoxicity. Chemically reactive and/or cytotoxic metabolites of benzbromarone have been identified; however there is a lack of available information on their role in benzbromarone hepatotoxicity. The reactive metabolites of some hepatotoxic drugs are known to covalently bind, or alternatively are targeted, to specific cytochrome P450 (P450) enzymes, a process that is often described as mechanism-based inhibition. OBJECTIVE We examined whether benzbromarone causes a mechanism-based inhibition of human P450 enzymes. METHOD Microsomes from human livers were preincubated with benzbromarone and NADPH, followed by evaluation of CYP2C9 and CYP3A4 activities. RESULTS Benzbromarone metabolism resulted in inhibition of CYP3A4 but not CYP2C9 in a time-dependent manner. Confirmation of pseudo-first order kinetics of inhibition, a requirement for NADPH, and a lack of protection by scavengers suggested that benzbromarone is a mechanism-based CYP3A4 inhibitor. CONCLUSION Modification of the P450 enzyme by the reactive metabolite is a common trait of drugs that induce idiosyncratic hepatotoxicity, and might provide a speculative, mechanistic model for the rare occurrences of this type of drug toxicity.
{"title":"Inactivation of CYP3A4 by Benzbromarone in Human Liver Microsomes.","authors":"Y. Masubuchi, S. Kondo","doi":"10.2174/1872312810666151223103208","DOIUrl":"https://doi.org/10.2174/1872312810666151223103208","url":null,"abstract":"BACKGROUND\u0000Benzbromarone is a uricosuric drug in current clinical use that can cause serious hepatotoxicity. Chemically reactive and/or cytotoxic metabolites of benzbromarone have been identified; however there is a lack of available information on their role in benzbromarone hepatotoxicity. The reactive metabolites of some hepatotoxic drugs are known to covalently bind, or alternatively are targeted, to specific cytochrome P450 (P450) enzymes, a process that is often described as mechanism-based inhibition.\u0000\u0000\u0000OBJECTIVE\u0000We examined whether benzbromarone causes a mechanism-based inhibition of human P450 enzymes.\u0000\u0000\u0000METHOD\u0000Microsomes from human livers were preincubated with benzbromarone and NADPH, followed by evaluation of CYP2C9 and CYP3A4 activities.\u0000\u0000\u0000RESULTS\u0000Benzbromarone metabolism resulted in inhibition of CYP3A4 but not CYP2C9 in a time-dependent manner. Confirmation of pseudo-first order kinetics of inhibition, a requirement for NADPH, and a lack of protection by scavengers suggested that benzbromarone is a mechanism-based CYP3A4 inhibitor.\u0000\u0000\u0000CONCLUSION\u0000Modification of the P450 enzyme by the reactive metabolite is a common trait of drugs that induce idiosyncratic hepatotoxicity, and might provide a speculative, mechanistic model for the rare occurrences of this type of drug toxicity.","PeriodicalId":11339,"journal":{"name":"Drug metabolism letters","volume":"10 1 1","pages":"16-21"},"PeriodicalIF":0.0,"publicationDate":"2016-02-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68048474","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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