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CYP Isoforms (cyp + isoform)
Selected AbstractsMetabolic drug interactions with new psychotropic agentsFUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 5 2003Edoardo Spina Abstract New psychotropic drugs introduced in clinical practice in recent years include new antidepressants, such as selective serotonin reuptake inhibitors (SSRI) and ,third generation' antidepressants, and atypical antipsychotics, i.e. clozapine, risperidone, olanzapine, quetiapine, ziprasidone and amisulpride. These agents are extensively metabolized in the liver by cytochrome P450 (CYP) enzymes and are therefore susceptible to metabolically based drug interactions with other psychotropic medications or with compounds used for the treatment of concomitant somatic illnesses. New antidepressants differ in their potential for metabolic drug interactions. Fluoxetine and paroxetine are potent inhibitors of CYP2D6, fluvoxamine markedly inhibits CYP1A2 and CYP2C19, while nefazodone is a potent inhibitor of CYP3A4. These antidepressants may be involved in clinically significant interactions when coadministered with substrates of these isoforms, especially those with a narrow therapeutic index. Other new antidepressants including sertraline, citalopram, venlafaxine, mirtazapine and reboxetine are weak in vitro inhibitors of the different CYP isoforms and appear to have less propensity for important metabolic interactions. The new atypical antipsychotics do not affect significantly the activity of CYP isoenzymes and are not expected to impair the elimination of other medications. Conversely, coadministration of inhibitors or inducers of the CYP isoenzymes involved in metabolism of the various antipsychotic compounds may alter their plasma concentrations, possibly leading to clinically significant effects. The potential for metabolically based drug interactions of any new psychotropic agent may be anticipated on the basis of knowledge about the CYP enzymes responsible for its metabolism and about its effect on the activity of these enzymes. This information is essential for rational prescribing and may guide selection of an appropriate compound which is less likely to interact with already taken medication(s). [source] Inhibition of fipronil and nonane metabolism in human liver microsomes and human cytochrome P450 isoforms by chlorpyrifosJOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 2 2007Hyun Joo Abstract Previous studies have established that chlorpyrifos (CPS), fipronil, and nonane can all be metabolized by human liver microsomes (HLM) and a number of cytochrome P450 (CYP) isoforms. However, metabolic interactions between these three substrates have not been described. In this study the effect of either coincubation or preincubation of CPS with HLM or CYP isoforms with either fipronil or nonane as substrate was investigated. In both co- and preincubation experiments, CPS significantly inhibited the metabolism of fipronil or nonane by HLM although CPS inhibited the metabolism of fipronil more effectively than that of nonane. CPS significantly inhibited the metabolism of fipronil by CYP3A4 as well as the metabolism of nonane by CYP2B6. In both cases, preincubation with CPS caused greater inhibition than coincubation, suggesting that the inhibition is mechanism based. © 2007 Wiley Periodicals, Inc. J Biochem Mol Toxicol 21:76,80, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20161 [source] Quantification of the expression and inducibility of 12 rat cytochrome P450 isoforms by quantitative RT,PCRJOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 6 2006Etienne Caron Abstract The administration of xenobiotics may significantly alter the expression of cytochromes P450 (CYPs), thereby leading to potentially toxic cellular, physiologic, and pharmacologic responses. Indeed, an important task in the development of new therapeutic entities is to evaluate efficiently and quantitatively their potential effects on the expression level of different CYPs. In this report, reverse transcriptase polymerase chain reaction (RT,PCR) was used to measure basal and induced mRNA of a wide range of rat CYP isoforms. Rats (n = 3 per treatment) were treated with five prototype inducers of CYP isoforms or with vehicle only. RT and PCR efficiencies were determined using appropriate RNA and DNA standards. Messenger RNA was quantified by PicoGreen standard curves and normalized to cyclophilin. Quantitative RT,PCR was used successfully to demonstrate that CYP isoforms were induced at the mRNA level following drug administration. Notably, phenobarbital resulted in significant induction of CYP2B1, CYP2B2, CYP2C6, CYP2C13, CYP2E1, CYP3A1, and CYP3A2. 3-Methylcholanthrene induced CYP1A1, CYP1A2, and CYP1B1. CYP2C11 expression was highly variable and suppressed by pyridine, whereas the expression of CYP2E1 was suppressed by dexamethasone. We demonstrated that quantitative RT,PCR can be used to evaluate efficiently the effect of compounds on the expression of a wide range of CYP isoforms. The technique is advantageous over others in that it is very sensitive, efficient and applicable to highly homologous CYP isoforms. © 2005 Wiley Periodicals, Inc. J Biochem Mol Toxicol 19:368,378, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20103 [source] Inhibition of human cytochrome P450 isoforms and NADPH-CYP reductase in vitro by 15 herbal medicines, including Epimedii herbaJOURNAL OF CLINICAL PHARMACY & THERAPEUTICS, Issue 1 2006K. H. Liu PhD Summary Objective:, We evaluated the potential of 15 herbal medicines (HMs), commonly used in Korea, to inhibit the catalytic activities of several cytochrome P450 (CYP) isoforms and microsomal NADPH-CYP reductase. Methods:, The abilities of 1,1000 ,g/mL of freeze-dried aqueous extracts of 15 HMs to inhibit phenacetin O -deethylation (CYP1A2), tolbutamide 4-methylhydroxylation (CYP2C9), S -mephenytoin 4,-hydroxylation (CYP2C19), dextromethorphan O -demethylation (CYP2D6), chlorzoxazone 6-hydroxylation (CYP2E1), midazolam 1-hydroxylation (CYP3A4) and NADPH-CYP reductase were tested using human liver microsomes. Results:, The HMs Epimedii herba, Glycyrrhizae radix and Leonuri herba inhibited one or more of the CYP isoforms or NADPH-CYP reductase. Of the three HMs, Epimedii herba extracts were the most potent inhibitors of several CYP isoforms (IC50 67·5 ,g/mL for CYP2C19, 104·8 ,g/mL for CYP2E1, 110·9 ,g/mL for CYP2C9, 121·9 ,g/mL for CYP3A4, 157·8 ,g/mL for CYP2D6 and 168·7 ,g/mL for CYP1A2) and NADPH-CYP reductase (IC50 185·9 ,g/mL). Conclusion:, These results suggest that some of the HMs used in Korea have the potential to inhibit CYP isoforms in vitro. Although the plasma concentrations of the active constituents of the HMs were not determined, some herbs could cause clinically significant interactions because the usual doses of those individual herbs are several grams of freeze-dried extracts. Controlled trials to test the significance of these results are necessary. [source] Contributions of human cytochrome P450 enzymes to glyburide metabolismBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 4 2010Lin Zhou Abstract Glyburide (GLB) is a widely used oral sulfonylurea for the treatment of gestational diabetes. The therapeutic use of GLB is often complicated by a substantial inter-individual variability in the pharmacokinetics and pharmacodynamics of the drug in human populations, which might be caused by inter-individual variations in factors such as GLB metabolism. Therefore, there has been a continued interest in identifying human cytochrome P450 (CYP) isoforms that play a major role in the metabolism of GLB. However, contrasting data are available in the present literature in this regard. The present study systematically investigated the contributions of various human CYP isoforms (CYP3A4, CYP3A5, CYP2C8, CYP2C9 and CYP2C19) to in vitro metabolism of GLB. GLB depletion and metabolite formation in human liver microsomes were most significantly inhibited by the CYP3A inhibitor ketoconazole compared with the inhibitors of other CYP isoforms. Furthermore, multiple correlation analysis between GLB depletion and individual CYP activities was performed, demonstrating a significant correlation between GLB depletion and the CYP3A probe activity in 16 individual human liver microsomal preparations, but not between GLB depletion and the CYP2C19, CYP2C8 or CYP2C9 probe activity. By using recombinant supersomes overexpressing individual human CYP isoforms, it was found that GLB could be depleted by all the enzymes tested; however, the intrinsic clearance (Vmax/Km) of CYP3A4 for GLB depletion was 4,17 times greater than that of other CYP isoforms. These results confirm that human CYP3A4 is the major enzyme involved in the in vitro metabolism of GLB. Copyright © 2010 John Wiley & Sons, Ltd. [source] Evaluation of SupermixTM as an in vitro model of human liver microsomal drug metabolismBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 5 2002Karthik Venkatakrishnan Abstract SUPERMIXTM is a commercially available formulation of insect cell-expressed human drug-metabolizing cytochrome P450 (CYP) isoforms, mixed in proportions that are optimized to parallel their relative activities in human liver microsomes. We have evaluated the apparent functional affinity and capacity of individual CYP isoforms in SUPERMIXTM in comparison with microsomes from a panel of 12 human livers, using enzyme kinetic studies of isoform-selective index reactions. In addition, we have measured the concentration of NADPH cytochrome P450 oxidoreductase (OR) in SUPERMIXTM and compared it with the concentrations of this accessory electron transfer protein in human liver microsomes. No important differences were evident in the catalytic activities of CYPs 1A2, 2C8, 2C9, 2C19, 2D6 and 3A4 between SUPERMIXTM and human liver microsomes. However, SUPERMIXTM lacks CYP2B6 activity and did not hydroxylate the antidepressant bupropion, a clinically relevant substrate of this enzyme. In addition, the concentration of OR in SUPERMIXTM (1198 pmol mg protein,1) is 17-fold higher than the mean value in human liver microsomes (70 pmol mg protein,1). In conclusion, SUPERMIXTM lacks CYP2B6 activity and contains supraphysiological concentrations of the accessory electron transfer protein OR. These factors should be considered when this formulation is used as an in vitro model in human liver microsomal drug metabolism studies. Copyright © 2002 John Wiley & Sons, Ltd. [source] In Vitro/in Vivo scaling of alprazolam metabolism by CYP3A4 and CYP3A5 in humansBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 2 2001Noriko Hirota Abstract We attempted to predict the in vivo metabolic clearance of alprazolam from in vitro metabolic studies using human liver microsomes and human CYP recombinants. Good correlations were observed between the intrinsic clearance (CLint) for 4-hydroxylation and CYP3A4 content and between the CLint for ,-hydroxylation and CYP3A5 content in ten human liver microsomal samples. Using the recombinant CYP isoforms expressed in insect cells, the CLint for CYP3A4 was about 2-fold higher than the CLint for CYP3A5 in the case of 4-hydroxylation. However, the CLint for CYP3A5 was about 3-fold higher than the CLint for CYP3A4 in the case of ,-hydroxylation. The metabolic rates for 4- and ,-hydroxylation increased as the added amount of cytochrome b5 increased, and their maximum values were 3- to 4-fold higher than those without cytochrome b5. The values of CLint, in vivo predicted from in vitro studies using human liver microsomes and CYP3A4 and CYP3A5 recombinants were within 2.5 times of the observed value calculated from literature data. The average CLint value (sum of 4- and ,-hydroxylation) obtained using three human liver microsomal samples was 4-fold higher than that obtained using three small intestinal microsomal samples from the same donors, indicating the minor contribution of intestinal metabolism to alprazolam disposition. The area under the plasma concentration-time curve (AUC) of alprazolam is reported to increase following co-administration of ketoconazole and the magnitude of the increase predicted from the in vitroKi values and reported pharmacokinetic parameters of ketoconazole was 2.30,2.45, which is close to the value observed in vivo (3.19). A quantitative prediction of the AUC increase by cimetidine was also successful (1.73,1.79 vs 1.58,1.64), considering the active transport of cimetidine into the liver. In conclusion, we have succeeded in carrying out an in vitro/in vivo scaling of alprazolam metabolism using human liver microsomes and human CYP3A4 and CYP3A5 recombinants. Copyright © 2001 John Wiley & Sons, Ltd. [source] Pharmacokinetic assessment of a five-probe cocktail for CYPs 1A2, 2C9, 2C19, 2D6 and 3ABRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 6 2009Sandrine Turpault WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT , Numerous cocktails using concurrent administration of several cytochrome P450 (CYP) isoform-selective probe drugs have been reported to investigate drug,drug interactions in vivo. , This approach has several advantages: characterize the inhibitory or induction potential of compounds in development toward the CYP enzymes identified in vitro in an in vivo situation, assess several enzymes in the same trial, and have complete in vivo information about potential CYP-based drug interactions. WHAT THIS STUDY ADDS , This study describes a new cocktail containing five probe drugs that has never been published. , This cocktail can be used to test the effects of a new chemical entity on multiple CYP isoforms in a single clinical study: CYP1A2 (caffeine), CYP2C9 (warfarin), CYP2C19 (omeprazole), CYP2D6 (metoprolol), and CYP3A (midazolam) and was designed to overcome potential liabilities of other reported cocktails. AIMS To assess the pharmacokinetics (PK) of selective substrates of CYP1A2 (caffeine), CYP2C9 (S-warfarin), CYP2C19 (omeprazole), CYP2D6 (metoprolol) and CYP3A (midazolam) when administered orally and concurrently as a cocktail relative to the drugs administered alone. METHODS This was an open-label, single-dose, randomized, six-treatment six-period six-sequence William's design study with a wash-out of 7 or 14 days. Thirty healthy male subjects received 100 mg caffeine, 100 mg metoprolol, 0.03 mg kg,1 midazolam, 20 mg omeprazole and 10 mg warfarin individually and in combination (cocktail). Poor metabolizers of CYP2C9, 2C19 and 2D6 were excluded. Plasma samples were obtained up to 48 h for caffeine, metoprolol and omeprazole, 12 h for midazolam, 312 h for warfarin and the cocktail. Three different validated liquid chromatography tandem mass spectrometry methods were used. Noncompartmental PK parameters were calculated. Log-transformed Cmax, AUClast and AUC for each analyte were analysed with a linear mixed effects model with fixed term for treatment, sequence and period, and random term for subject within sequence. Point estimates (90% CI) for treatment ratios (individual/cocktail) were computed for each analyte Cmax, AUClast and AUC. RESULTS There was no PK interaction between the probe drugs when administered in combination as a cocktail, relative to the probes administered alone, as the 90% CI of the PK parameters was within the prespecified bioequivalence limits of 0.80, 1.25. CONCLUSION The lack of interaction between probes indicates that this cocktail could be used to evaluate the potential for multiple drug,drug interactions in vivo. [source] The influence of CYP2B6, CYP2C9 and CYP2D6 genotypes on the formation of the potent antioestrogen Z-4-hydroxy-tamoxifen in human liverBRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 2 2002Janet K. Coller Aims, To investigate in a large panel of 50 human liver samples the contribution of CYP2C9, CYP2D6, and CYP3A4 to the overall formation of the potent antioestrogen Z-4-hydroxy-tamoxifen, and how various genotypes affect its formation from tamoxifen. Methods, The formation of Z-4-hydroxy-tamoxifen from 10 µm tamoxifen was studied in human liver microsomes (n=50), characterized for CYP2B6, CYP2C9, CYP2D6 and CYP3A4 expression, and CYP2B6, CYP2C9 and CYP2D6 genotype. The effect of chemical and monoclonal antibody inhibitors, and the formation in supersomes expressing recombinant CYP isoforms was also investigated. Z-4-hydroxy-tamoxifen was quantified using LC-MS analysis. Results, Z-4-hydroxy-tamoxifen was formed by supersomes expressing CYP2B6, CYP2C9, CYP2C19 and CYP2D6, but not CYP3A4. In agreement with these data, the mean formation of Z-4-hydroxy-tamoxifen was inhibited 49% by sulphaphenazole (P=0.001), 38% by quinidine (P<0.05) and 13% by monoclonal antibody against CYP2B6 (MAB-2B6, P<0.05). Furthermore, Z-4-hydroxy-tamoxifen formation significantly correlated with both CYP2C9 expression (rs=0.256, P<0.05) and CYP2D6 expression (rs=0.309, P<0.05). Genotypes of CYP2D6, CYP2B6 and CYP2C9 had an effect on metabolite formation in such a way that samples with two nonfunctional CYP2D6, or two variant CYP2C9 or CYP2B6 alleles, showed lower enzyme activity compared with those with two functional or wild-type alleles, (5.0 vs 9.9 pmol mg,1 protein min,1, P=0.046, 5.1 vs 9.9 pmol mg,1 protein min,1, P=0.053, and 6.8 vs 9.4 pmol mg,1 protein min,1, P=0.054, respectively). CYP2D6 and CYP2C9 contribute on average 45 and 46%, respectively, to the overall formation of Z-4-hydroxy-tamoxifen. Conclusions,CYP2B6, CYP2C9 and CYP2D6 genotypes all affected Z-4-hydroxy-tamoxifen formation and can predict individual ability to catalyse this reaction. [source] Immunohistochemical analysis of CYP2A13 in various types of human lung cancersCANCER SCIENCE, Issue 4 2010Tatsuki Fukami Human CYP2A13, which is expressed in the respiratory tract, is the most efficient enzyme for the metabolic activation of tobacco-specific nitrosamines such as 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). The relevance of CYP2A13 in carcinogenicity and toxicity in the respiratory tract has been suggested, but the expression of CYP2A13 protein in lung cancer tissues remains to be determined. We first prepared a mouse monoclonal antibody against human CYP2A13. The antibody showed no cross reactivity with the other CYP isoforms including CYP2A6. Using the specific antibody, we performed immunohistochemical analysis for human lung carcinomas. In adenocarcinomas (n = 15), all specimens were positive for the staining and five samples showed strong staining. In squamous cell carcinomas (n = 15) and large cell carcinomas (n = 15), each 14 samples were positive for the staining and two and three samples showed strong staining, respectively. In small cell carcinoma samples (n = 15), eight samples were negative for the staining and five samples showed weak or moderate staining. In conclusion, we first found that the expression of CYP2A13 was markedly increased in non-small cell lung carcinomas. The high expression might be associated with the tumor development and progression in non-small cell lung carcinomas. (Cancer Sci 2010; 101: 1024,1028) [source] | ||||||||||