Role of flavin-containing-monooxygenase-dependent neutrophil activation in thioacetamide-induced hepatic inflammation in rats

Thioacetamide is widely used in industry and is known to be one of the most potent hepatotoxicants in experimental animals. We investigated the involvement of flavin-containing monooxygenase (FMO)-dependent hepatic-neutrophil activation and the release of proinflammatory mediators in thioacetamide-induced hepatic injury in rats. Thioacetamide (100 mg/kg, intraperitoneally) increased, within 12 h, hepatic serum aspartate transferase and alanine transferase levels, tumor necrosis factor-α production, interleukin-1β and nitrite levels, and myeloperoxidase activity. Rabbit anti-neutrophil serum markedly inhibited all thioacetamide-altered parameters. In addition, FMO-competitive inhibitor methimazole reduced thioacetamide-induced myeloperoxidase activity, hepatic tumor necrosis factor-α, interleukin-1β, nitrite, inducible nitric oxide synthase, and hepatic damage in thioacetamide-treated rats. Thus, we conclude that FMO-dependent hepatic neutrophil activation initiates the release of proinflammatory mediators in thioacetamide-treated rats.