Pyrazinamide-induced hepatotoxicity mediated by aldehyde oxidase and xanthine oxidase.

Pyrazinamide (PZA) has been approved for the treatment of tuberculosis in clinical practice. However, its adverse effects, particularly hepatotoxicity, have raised concerns. The present study aimed at exploring the potential relationship between PZA-induced hepatotoxicity and its metabolites resulting from metabolic activation. Glutathione (GSH) conjugates with confirmed structures were detected in mouse cytosol incubations containing PZA or pyrazinoic acid (POA, a major metabolite of PZA) supplemented with glutathione (GSH). Such GSH metabolites were also observed in both liver homogenates from mice administered with PZA and mouse primary hepatocytes exposed to PZA. Aldehyde oxidase (AO) and xanthine oxidase (XOD) were identified as key enzymes in the metabolic activation of PZA and POA. Both vitamin C (VC) and N-acetylcysteine (NAC) were found to reduce the generation of GSH conjugates derived from PZA and POA in incubation systems. Additionally, VC alleviated the susceptibility of hepatocytes to PZA-induced cytotoxicity. Consecutive administration of PZA for 7 days resulted in a marked elevation of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in mice, and PZA-derived hepatic protein adduction was detected. Allopurinol administration attenuated the elevated serum ALT and AST in company with a reduction in the formation of GSH conjugates. This work provides solid evidence for the correlation between the metabolic activation of PZA and PZA-induced hepatotoxicity, enhancing the understanding of the underlying mechanisms of PZA toxicity in terms of molecular chemical structure.