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Human CYP3A4 (human + cyp3a4)
Selected AbstractsIn vitro metabolism of a new H+/K+ ATPase inhibitor DBM-819 in liver microsomes using HPLC and electrospray mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 8 2001Sung Jin Choi The metabolism of 1-(2-methyl-4-methoxyphenyl)-4-[(3-hydroxypropyl)amino]-6-methyl-2,3-dihydropyrrolo[3,2c]quinoline (DBM-819), a new H+/K+ ATPase inhibitor, has been studied by HPLC with spectrometric detection and on-line LC-electrospray mass spectrometry. In vitro incubation of DBM-819 with rat liver microsomes in the presence of NADPH resulted in the production of four metabolites (M1-4), whereas DBM-819 was oxidized to two metabolites, M2 and M4, by human liver microsomes. M2, M3 and M4 were identified as O-demethyl-DBM-819, 8-hydroxy-DBM-819 and N-dehydroxypropyl-DBM-819, respectively, based on LC/MS/MS analysis with authentic standards. M1 was tentatively identified as 1-(hydroxy-2-methyl-4-methoxyphenyl)-4-[(3-hydroxypropyl)amino]-6-methyl-2,3-dihydropyrrolo[3,2c]quinoline. Rat liver CYP1A1/2 catalyzed the oxidation of DBM-819 to 8-hydroxy-DBM-819 and N-dehydroxypropyl-DBM-819. Human CYP3A4 was a major isozyme for the formation of O-demethyl-DBM-819 as well as N-dehydroxypropyl-DBM-819. Copyright © 2001 John Wiley & Sons, Ltd. [source] Effects of cysteine on the pharmacokinetics of itraconazole in rats with protein-calorie malnutritionBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 2 2003Ae K. Lee Abstract The effects of cysteine on the pharmacokinetics of itraconazole were investigated after intravenous, 20 mg/kg, and oral, 50 mg/kg, administration of the drug to control rats (fed for 4 weeks on 23% casein diet) and rats with PCM (protein-calorie malnutrition, fed for 4 weeks on 5% casein diet) and PCMC (PCM with oral cysteine supplementation, 250 mg/kg, twice daily during the fourth week). After intravenous administration of itraconazole to rats with PCM, the area under the plasma concentration,time curve from time zero to time infinity (AUC) of itraconazole was significantly greater (3580 compared with 2670 and 2980 µg min/ml) than those in control rats and rats with PCMC (the values between control rats and rats with PCMC were not significantly different). The above data suggested that metabolism of itraconazole decreased significantly in rats with PCM due to suppression of hepatic microsomal cytochrome P450 (CYP) 3A23 in the rats. The results could be expected since in rats with PCM, the level of CYP3A23 decreased significantly as compared to control. Itraconazole was reported to be metabolized via CYP3A4 to several metabolites, including hydroxyitraconazole, in human subjects. Human CYP3A4 and rat CYP3A1 (CYP3A23) proteins have 73% homology. By cysteine supplementation (rats with PCMC), the AUC of itraconazole was restored fully to control levels. Copyright © 2003 John Wiley & Sons, Ltd. [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] Human cytochromes mediating gepirone biotransformation at low substrate concentrationsBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 2 2003David J. Greenblatt Abstract Biotransformation of gepirone to 1-(2-pyrimidinyl)-piperazine (1-PP) and 3'-OH-gepirone, as well as two other hydroxylated metabolites, was studied in vitro using a human liver microsomal preparation and heterologously expressed human CYP3A4 and CYP2D6. The focus was on a low range of gepirone concentrations (1000 nM and below). Liver microsomes formed 1-PP and 3'-OH-gepirone with similar reaction velocities. Two other hydroxylated metabolites (2-OH- and 5-OH-gepirone) were also formed, but pure reference standards were not available for purposes of quantitative analysis. The CYP3A inhibitor ketoconazole completely eliminated 1-PP formation, reduced 3'-OH-gepirone formation to less than 20% of control, and reduced 2-OH-gepirone formation to 7% of control. All metabolites were formed by expressed CYP3A4; however, CYP2D6 formed 3'-OH- and 5-OH-gepirone, but not 1-PP or 2-OH-gepirone. Based on estimated relative abundances of the two isoforms in human liver, CYP3A4 was predicted to account for more than 95% of net clearance of gepirone in vivo at low concentrations approaching the therapeutic range. CYP2D6 would account for less than 5% of net clearance. The findings are consistent with previous in vitro studies of gepirone using higher substrate concentrations. Copyright © 2003 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] Enantioselectivity of inhibition of cytochrome P450 3A4 (CYP3A4) by ketoconazole: Testosterone and methadone as substratesCHIRALITY, Issue 2 2004Shahrzad Dilmaghanian Abstract Racemic ketoconazole (KTZ) was the first orally active azole antifungal agent used in clinical practice and has become widely used in the treatment of mucosal fungal infections associated with AIDS immunosuppression and cancer chemotherapy. However, the use of KTZ has been limited because of adverse drug,drug interactions. KTZ blocks ergosterol biosynthesis by inhibiting the fungal cytochrome P450 (CYP51). KTZ is also a potent inhibitor of human cytochrome P450 3A4 (CYP3A4) enzyme, the major drug-metabolizing CYP isozyme in the human liver. We examined the enantioselective differences of KTZ in the inhibition of human CYP3A4 and in antifungal action. Dextro - and levo -KTZ exhibited modest enantioselective differences with respect to CYP3A4 inhibition of testosterone and methadone metabolism. For both substrates levo -KTZ was approximately a 2-fold more potent inhibitor. We examined the enantioselective differences in the in vitro activity of KTZ against medically relevant species of Candida and Aspergillus, as well as Cryptococcus neoformans. Overall, levo -KTZ was 2,4-fold more active than dextro -KTZ. Therefore, levo -KTZ is a more potent inhibitor of CYP3A4 and has stronger in vitro antifungal activity. Chirality 16:79,85, 2004. © 2004 Wiley-Liss, Inc. [source] | ||||||||||