Correlation between troglitazone cytotoxicity and drug metabolic enzyme activities in cryopreserved human hepatocytes.
Troglitazone (TRO) was developed for the treatment of type II diabetes. It was withdrawn from use due to idiosyncratic liver damage and failure. The mechanism of toxicity is still not determined, moreover, it is still not clear whether toxicity is due to the parent compound or its metabolite(s). The cytotoxicity of TRO was evaluated in human hepatocytes using previously cryopreserved hepatocyte suspensions from 27 human donors. Cellular adenosine triphosphate content was used as a viability endpoint. To investigate the role of xenobiotic metabolism in TRO toxicity, the correlation between the drug metabolism activities of the hepatocytes from each donor to EC(50) values TRO cytotoxicity. The activities examined were cytochrome P450 (CYP) isoform activities (CYP2A6, CYP2D6, CYP2C19, CYP1A2, CYP2E1, CYP3A4 and CYP2C9) and phase 2 conjugation enzyme activities (phenol sulfotransferase (PST) and glucuronyl transferase (UGT)). Taken individually, none of the phase 1 or 2 enzyme activities correlated to the EC(50). However, when three enzyme activities ((CYP3A4 x UGT)/PST) were taken into account, a correlation was made (r(2)=0.53). Based on the correlation, we hypothesize that TRO and TRO sulfate are direct acting toxicants, whereas CYP3A4 oxidation and glucuronidation are detoxification pathways.
Hewitt
Nicola J
NJ
In Vitro Technologies, Inc., 1450 South Rolling Road, Baltimore, MD 21227, USA. hewittn@invitrotech.com
Lloyd
Scott
S
Hayden
Mike
M
Butler
Ryan
R
Sakai
Yumiko
Y
Springer
Ryan
R
Fackett
Andrew
A
Li
Albert P
AP
D000255:Adenosine Triphosphate / Q000378:metabolism; D015239:Arylsulfotransferase / Q000378:metabolism; D002839:Chromans / Q000378:metabolism / Q000633:toxicity*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D014453:Glucuronosyltransferase / Q000378:metabolism; D022781:Hepatocytes / Q000187:drug effects* / Q000201:enzymology*; D006801:Humans; D007004:Hypoglycemic Agents / Q000378:metabolism / Q000633:toxicity*; D007527:Isoenzymes / Q000378:metabolism; D013844:Thiazoles / Q000378:metabolism / Q000633:toxicity*; D045162:Thiazolidinediones; D000077288:Troglitazone
D002839:Chromans; D007004:Hypoglycemic Agents; D007527:Isoenzymes; D013844:Thiazoles; D045162:Thiazolidinediones; D000255:Adenosine Triphosphate; D003577:Cytochrome P-450 Enzyme System; D014453:Glucuronosyltransferase; D015239:Arylsulfotransferase; D000077288:Troglitazone