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

Area of Science:

• Pharmacology
• Hepatotoxicity
• Drug Metabolism

Background:

• Atorvastatin calcium (ATV) is a widely prescribed statin for managing hyperlipidemia and preventing cardiovascular diseases.
• Patient reports indicate a risk of liver injury associated with ATV use, necessitating investigation into its hepatotoxic mechanisms.

Purpose of the Study:

• To elucidate the association between atorvastatin-induced hepatotoxicity and its metabolic activation by cytochrome P450 enzymes.
• To identify specific metabolites and reactive intermediates involved in ATV's toxic effects.

Main Methods:

• In vitro studies using NADPH-supplemented systems with glutathione (GSH) and cysteine (Cys) as trapping agents.
• Liquid chromatography-tandem mass spectrometry (LC-MS/MS) for metabolite and conjugate detection.
• In vivo studies in mice, including intragastric administration of ATV and analysis of primary hepatocytes.
• Assessment of CYP3A involvement using the inhibitor ketoconazole (KTC).

Main Results:

• Two phase I metabolites (M1, M2) and corresponding GSH (M3, M4) and Cys (M5, M6) conjugates were identified, indicating electrophilic quinone-imine intermediate formation.
• In vivo and in vitro studies confirmed GSH conjugation and protein adduction following ATV exposure.
• CYP3A was identified as the primary enzyme responsible for ATV metabolic activation.
• Ketoconazole pre-treatment significantly reduced ATV-induced protein adduction and hepatocyte cytotoxicity.

Conclusions:

• The study systematically characterizes the CYP3A-mediated bioactivation process of atorvastatin.
• Findings provide mechanistic insights into the idiosyncratic hepatotoxicity of atorvastatin.