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.
Gan
Jinping
J
Department of Pharmaceutical Candidate Optimization, Bristol-Myers Squibb Research and Development, Princeton, NJ 08543, USA. jinping.gan@bms.com
Qu
Qinling
Q
He
Bing
B
Shyu
Wen C
WC
Rodrigues
A David
AD
He
Kan
K
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