ABSTRACT
The induction of enzymes is a defensive mechanism for some xenobiotics, but it may alter the drug's safety and efficacy by altering the activity of metabolic enzymes. One of the major families of enzymes involved in phase I metabolism is Cytochrome P450 (CYP) enzymes which may get induced by certain drugs. Concomitant administration of drugs due to chronic disease or polypharmacy, inducers among them may cause toxicity or reduce the plasma concentration at a sub-therapeutic level. This is one of the dangerous types of drug-drug interactions, but predictable & preventable. The CYPs get induced by three nuclear receptors, including the aryl hydrocarbon receptor (AhR); constitutive androstane receptor (CAR); the pregnane X receptor (PXR). Without identification during drug development, enzyme induction phenomenon of a new drug molecule may get noticed only during pharmacovigilance. Though, this CYP induction may not be a barrier for drug development, it may cause possible DDI and treatment failure. According to FDA guidelines, pharmaceutical industries adopted In-vitro, Ex-vivoand In-vivotechniques based on different developmental stages. The results are also interpreted based on regulatory bodies guidelines. For In-vitroassay best accepted method is using primary hepatocytes either fresh or cryopreserved, for Ex-vivoliver slices of different species and in-vivo, clinical investigations are the extreme option. This paper reviews current industry approaches of CYP induction assays to evaluate potentiality for a new drug molecule as an inducer
ABSTRACT
CAT3 is a promising anti-brain tumor agent that has significant anti-tumor activity on Daoy or U87MG orthotopic xenograft in nude mice. This study was carried out to investigate the metabolic profiles of CAT3 in mouse/dog/human blood and microsome as well as in humanized recombinant enzymes. All animal care and experimental procedures were reviewed and approved by the Animal Ethics Committee of Chinese Academy of Medical Sciences. Our findings showed that CAT3 could be hydrolyzed to active metabolite PF403 by carboxylesterase, butyrylcholinesterase and serine hydrolase in mouse/dog/ human blood. PF403 could be further metabolized to M1 oxidative dehydration product, M2 double oxidation dehydration product, M3 methylation oxidative dehydration product, M4 oxidation product and M5 demethylation product, which were mainly catalyzed by CYP1A2, 1A1, 2C9 and 3A4, and slightly by CYP2B6, 2C8, 2C19 and 2D6. Besides oxidative metabolism, PF403 also was transformed into glucuronylation metabolites GLU-PF403 by Phase II enzymes UGT1A1, 1A3 and 1A9. Taken together, the metabolism of CAT3 was a multiple enzyme catalytic reaction. These results could provide valuable information for potential enzyme-mediated DDI in clinic studies.
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Objective To study the inhibitory effects ofisorhamnetin on six kinds of CYPs of liver in vitro,and the toxic effect on rat hepatocytes Methods This report uses warm incubation of human liver microsomes in vitro to investigate the inhibition of isorhamnetin on 6 kinds of CYPs (CYP2C19,CYP2D6,CYP3A4,CYP2E1,CYP1A2 and CYP2C9),and using HPLC-MS/MS to detect product of metabolism as well as analysing of the pathways of metabolic.At the same time,using rat primary hepatocytes which has low CYPs activity in vitro to explore whether the use of isorhamnetin will cause effects on the ALT,AST and LDH of hepatocytes.Results Isorhamnetin has inhibition effects on CYP2E1 and CYP1A2,the inhibition rate were 59.48％ and 39.91％,respectively.Methylated metabolite is produced after incubating of isorhamnetin and HLMs.The isorhmnetin becomes high polarity and water solubility metabolite 3,3',4',5,7-hydroxyflavone.Isorhamnetin of 30,100 and 300 μmol/L cause a significant rise of ALT and LDH in primary cultured rat hepatocytes cultured (P ＜ 0.01).isorharnnetin of 100 μmol/L cause a rise of AST in primary cultured rat hepatocytes cultured (P ＜ 0.05) and 300 μmol/L cause a significant rise (P ＜ 0.01).It was a dose-dependent manner.Conclusion Isorhamnetin in vitro mainly metabolized by HLMs,and at the same time have a certain inhibitory effect on CYP2E1 and CYP1A2,which may cause the drugs which are metabolized by CYP2E1 and CYP1A2 in vivo accumulation that lead to a series of drug interactions.The results also indicate that heavy use of isorhamnetin cause some adverse effects on hepatocytes,and it was a dose-dependent manner.Individuals need to pay attention to the dose ofisorhamnetin and the potential drug interactions.
ABSTRACT
Aim Toinvestigatingtheinductionof CYPs in hepatocytes or HepG2 cells by triptolide(TP) andthepossiblemechanism.Methods AfterTPtreat-ment,the expression of CYPs in rat primary hepato-cytes or human HepG2 cells was detected by real-time PCR and Western blot assays.Specific inhibitors or gene knockdown method were employed to analyze the possiblemechanism.Results Theexpressionof CYP1A2,2C7,2C11,2C12,2D2,2E1 and 3A1 in rat primary hepatocytes was induced by TP.The fold was 19,2,31,3,21,88 and 34 at 50 nmol·L-1, respectively while at 100 nmol·L-1 it was 20,5,30,23,61,83 and 38,respectively.In HepG2 cells,the expression of human CYP1A1,2B6,2C9,2C19, 2D6,2E1 and 3A4 was also induced by TP.The ac-tivities of nuclear receptor PXR and CAR were inhibi-ted.TP upregulated p53 expression,and the induction of several CYPs caused by TP was blocked when p53 wasinhibited.Conclusions TPinducesCYPsexpres-sion in rat hepatocytes and HepG2 cells.Nuclear re-ceptors may not be involved in TP induced CYPs, while the mechanism may partly attribute to p53.