The dual role of osteopontin in acetaminophen hepatotoxicity.

Aim: Osteopontin (OPN), a multifunctional protein, has been reported to be protoxicant in acetaminophen hepatotoxicity. In this study, the mechanisms underlying the detrimental role of OPN in acetaminophen toxicity were explored.

Methods: Male C57BL/6 (wild-type, WT) and OPN(-/-) mice were administered with acetaminophen (500 mg/kg, ip). After the treatment, serum transaminase (ALT), as well as OPN expression, histology changes, oxidative stress and inflammation response in liver tissue were studied. Freshly isolated hepatocytes of WT and OPN(-/-) mice were prepared.

Results: Acetaminophen administration significantly increased OPN protein level in livers of WT mice. OPN expression was mainly localized in hepatic macrophages 6 h after the administration. In OPN(-/-) mice, acetaminophen-induced serum ALT release was reduced, but the centrilobular hepatic necrosis was increased. In OPN(-/-) mice, the expression of CYP2E1 and CYP1A2 in livers was significantly increased; GSH depletion and lipid peroxidation in livers were enhanced. On the other hand, OPN(-/-) mice exhibited less macrophage and neutrophil infiltration and reduced expression of proinflammatory cytokines TNF-α and IL-1α in livers. An anti-OPN neutralizing antibody significantly reduced acetaminophen-induced serum ALT level and inflammatory infiltration in livers of WT mice.

Conclusion: OPN plays a dual role in acetaminophen toxicity: OPN in hepatocytes inhibits acetaminophen metabolism, while OPN in macrophages enhances acetaminophen toxicity via recruitment of inflammatory cells and production of proinflammatory cytokines.