Troglitazone thiol adduct formation in human liver microsomes: enzyme kinetics and reaction phenotyping.
Troglitazone (TGZ) induced hepatotoxicity has been linked to cytochrome P450 (CYP)-catalyzed reactive metabolite formation. Therefore, the kinetics and CYP specificity of reactive metabolite formation were studied using dansyl glutathione (dGSH) as a trapping agent after incubation of TGZ with human liver microsomes (HLM) and recombinant human CYP proteins. CYP2C8 exhibited the highest rate of TGZ adduct (TGZ-dGS) formation, followed by CYP3A4, CYP3A5, and CYP2C19. The involvement of CYP2C8 and CYP3A4 was confirmed with CYP form-selective chemical inhibitors. The impact of TGZ concentration on the rate of TGZ-dGS formation was also evaluated. In this instance, two distinctly different profiles were observed with recombinant CYP3A4 and CYP2C8. It is concluded that both CYP3A4/5 and CYP2C8 play a major role in the formation of TGZ adduct in HLM. However, the contribution of these CYPs varies depending on their relative expression and the concentration of TGZ.
Department of Pharmaceutical Candidate Optimization, Bristol-Myers Squibb Research and Development, Princeton, NJ 08543, USA. jinping.gan@bms.com
Jinping
J
Gan
Qinling
Q
Qu
Bing
B
He
Wen C
WC
Shyu
A David
AD
Rodrigues
Kan
K
He
D001189:Aryl Hydrocarbon Hydroxylases / Q000378:metabolism; D002839:Chromans / Q000008:administration & dosage / Q000378:metabolism*; D065727:Cytochrome P-450 CYP2C8; D051544:Cytochrome P-450 CYP3A / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D003619:Dansyl Compounds / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D015971:Gene Expression Regulation, Enzymologic; D005978:Glutathione / Q000737:chemistry; D006801:Humans; D007004:Hypoglycemic Agents / Q000008:administration & dosage / Q000378:metabolism*; D008862:Microsomes, Liver / Q000201:enzymology*; D010641:Phenotype; D013438:Sulfhydryl Compounds / Q000378:metabolism; D045162:Thiazolidinediones / Q000008:administration & dosage / Q000378:metabolism*; D000077288:Troglitazone
D002839:Chromans; D003619:Dansyl Compounds; D007004:Hypoglycemic Agents; D013438:Sulfhydryl Compounds; D045162:Thiazolidinediones; D003577:Cytochrome P-450 Enzyme System; D001189:Aryl Hydrocarbon Hydroxylases; C450259:CYP2C8 protein, human; C510164:CYP3A5 protein, human; D065727:Cytochrome P-450 CYP2C8; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D005978:Glutathione; D000077288:Troglitazone