Protein covalent modification and hepatic cytotoxicity of atorvastatin resulting from its metabolic activation.

Atorvastatin calcium (ATV) is a statin drug that reduces low-density lipoprotein cholesterol and is widely used for the prevention and treatment of hyperlipidemia and cardiovascular and cerebrovascular diseases. However, its liver injury reported in patients has brought attention to the risk of hepatic adverse effects. This study is the first to elucidate the association between ATV-induced hepatotoxicity and its P450-mediated metabolic activation. In an NADPH-supplemented incubation system, two phase I metabolites (M1 and M2) were detected. Using nucleophilic small molecules glutathione (GSH) and cysteine (Cys) as trapping agents, two GSH conjugates (M3 and M4) and two Cys conjugates (M5 and M6) were detected by LC-MS/MS. The observation of M3-M6 indicates the generation electrophilic quinone-imine intermediates. Furthermore, following intragastric administration of ATV (16.4 mg/kg) to mice, the corresponding GSH conjugation and protein adduction were observed in vivo. Following exposure to ATV, GSH conjugation and protein adduction were also detected in mouse primary hepatocytes. CYP3A was the enzyme predominantly responsible for the metabolic activation of ATV. Pre-treatment with CYP3A inhibitor ketoconazole (KTC) significantly reduced both ATV-derived protein adduction and hepatocyte susceptibility to ATV cytotoxicity. The findings facilitate the understanding of the mechanisms involved in ATV's idiosyncratic toxicity through systematic characterization of a CYP3A-mediated bioactivation process.