Metabolic activation and cytotoxicity of 4-methylquinoline mediated by CYP3A4 and sulfotransferases in rats

4-Methylquinoline (4-MQ) is a quinoline derivative widely present in groundwater and soil and has been reported to be genotoxic. The mechanisms of the toxic action remain unknown. This study aimed to elucidate the metabolic activation of 4-MQ and to determine the possible role of reactive metabolites in 4-MQ-induced liver injury in rats. In the present study, a hydroxylation metabolite (M1), a GSH conjugate (M2) and an NAC conjugate (M3) derived from 4-MQ were detected in vitro and in vivo . The structures of the two conjugates were verified by chemical synthesis, mass spectrometry, and nuclear magnetic resonance. CYP3A4 was found to dominate the hydroxylation of 4-MQ. Sulfotransferases also participated in the metabolic activation of 4-MQ. Pretreatment of primary hepatocytes with ketoconazole (KTC) or 2,6-dichloro-4-nitrophenol (DCNP) not only reduced the production of GSH conjugate M2 but also decreased the susceptibility of hepatocytes to the cytotoxicity of 4-MQ. Urinary NAC conjugate M3 was found in rats given 4-MQ, and M3 may be a potential biomarker for 4-MQ exposure.