title: Hepatocellular toxicity of clopidogrel: mechanisms and risk factors.
abstract: Clopidogrel is a prodrug used widely as a platelet aggregation inhibitor. After intestinal absorption, approximately 90% is converted to inactive clopidogrel carboxylate and 10% via a two-step procedure to the active metabolite containing a mercapto group. Hepatotoxicity is a rare but potentially serious adverse reaction associated with clopidogrel. The aim of this study was to find out the mechanisms and susceptibility factors for clopidogrel-associated hepatotoxicity. In primary human hepatocytes, clopidogrel (10 and 100 μM) was cytotoxic only after cytochrome P450 (CYP) induction by rifampicin. Clopidogrel (10 and 100 μM) was also toxic for HepG2 cells expressing human CYP3A4 (HepG2/CYP3A4) and HepG2 cells co-incubated with CYP3A4 supersomes (HepG2/CYP3A4 supersome), but not for wild-type HepG2 cells (HepG2/wt). Clopidogrel (100 μM) decreased the cellular glutathione content in HepG2/CYP3A4 supersome and triggered an oxidative stress reaction (10 and 100 µM) in HepG2/CYP3A4, but not in HepG2/wt. Glutathione depletion significantly increased the cytotoxicity of clopidogrel (10 and 100 µM) in HepG2/CYP3A4 supersome. Co-incubation with 1 μM ketoconazole or 10mM glutathione almost completely prevented the cytotoxic effect of clopidogrel in HepG2/CYP3A4 and HepG2/CYP3A4 supersome. HepG2/CYP3A4 incubated with 100 μM clopidogrel showed mitochondrial damage and cytochrome c release, eventually promoting apoptosis and/or necrosis. In contrast to clopidogrel, clopidogrel carboxylate was not toxic for HepG2/wt or HepG2/CYP3A4 up to 100 µM. In conclusion, clopidogrel incubated with CYP3A4 is associated with the formation of metabolites that are toxic for hepatocytes and can be trapped by glutathione. High CYP3A4 activity and low cellular glutathione stores may be risk factors for clopidogrel-associated hepatocellular toxicity.
authors.affiliation: Division of Clinical Pharmacology & Toxicology and Department of Biomedicine, University Hospital, CH-4031 Basel, Switzerland.
authors.forename: Anja
authors.initials: A
authors.lastname: Zahno
authors.affiliation: Division of Clinical Pharmacology & Toxicology and Department of Biomedicine, University Hospital, CH-4031 Basel, Switzerland.
authors.forename: Jamal
authors.initials: J
authors.lastname: Bouitbir
authors.affiliation: Division of Clinical Pharmacology & Toxicology and Department of Biomedicine, University Hospital, CH-4031 Basel, Switzerland.
authors.forename: Swarna
authors.initials: S
authors.lastname: Maseneni
authors.affiliation: Division of Clinical Pharmacology & Toxicology and Department of Biomedicine, University Hospital, CH-4031 Basel, Switzerland.
authors.forename: Peter W
authors.initials: PW
authors.lastname: Lindinger
authors.affiliation: Division of Clinical Pharmacology & Toxicology and Department of Biomedicine, University Hospital, CH-4031 Basel, Switzerland.
authors.forename: Karin
authors.initials: K
authors.lastname: Brecht
authors.affiliation: Division of Clinical Pharmacology & Toxicology and Department of Biomedicine, University Hospital, CH-4031 Basel, Switzerland. Electronic address: kraehenbuehl@uhbs.ch.
authors.forename: Stephan
authors.initials: S
authors.lastname: Krähenbühl
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D000077144:Clopidogrel; D051544:Cytochrome P-450 CYP3A / Q000378:metabolism; D005434:Flow Cytometry; D005978:Glutathione / Q000378:metabolism; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D008856:Microscopy, Fluorescence; D010975:Platelet Aggregation Inhibitors / Q000378:metabolism / Q000494:pharmacology*; D012307:Risk Factors; D013988:Ticlopidine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology
chemical_list: D010975:Platelet Aggregation Inhibitors; D000077144:Clopidogrel; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D005978:Glutathione; D013988:Ticlopidine
keywords: 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid; Apoptosis; CYP; CYP3A4; Clopidogrel activation; DEM; Free radicals; GSH; Glutathione; Hepes; Idiosyncrasy; Liver injury; Mitochondria; ROS; cytochrome P450; diethyl maleate; reactive oxygen species; reduced glutathione