IL-6-deficient Mice Are Susceptible to Ethanol-induced Hepatic Steatosis:IL-6 Protects against Ethanol-induced Oxidative Stress and Mitochondrial Permeability Transition in the Liver

Interleukin-6(IL-6)-deficient mice are prone to ethanol-induced apoptosis and steatosis in the liver;however,the underlying mechanism is not fully understood.Mitochondrial dysfunction caused by oxidative stress is anearly event that plays an important role in the pathogenesis of alcoholic liver disease.Therefore,we hypothesizethat the protective role of IL-6 in ethanol-induced liver injury is mediated via suppression of ethanol-inducedoxidative stress and mitochondrial dysfunction.To test this hypothesis,we examined the effects of IL-6 onethanol-induced oxidative stress,mitochondrial injury,and energy depletion in the livers of IL-6(-/-)mice andhepatocytes from ethanol-fed rats.Ethanol consumption leads to stronger induction of malondialdehyde(MDA)in IL-6(-/-)mice compared to wild-type control mice,which can be corrected by administration of IL-6.In vitro,IL-6 treatment prevents ethanol-mediated induction of reactive oxygen species(ROS),MDA,mitochondrialpermeability transition(MPT),and ethanol-mediated depletion of adenosine triphosphate(ATP)in hepatocytesfrom ethanol-fed rats.Administration of IL-6 in vivo also reverses ethanol-induced MDA and ATP depletion inhepatocytes.Finally,IL-6 treatment induces metallothionein protein expression,but not superoxide dismutaseand glutathione peroxidase in cultured hepatocytes.In conclusion,IL-6 protects against ethanol-inducedoxidative stress and mitochondrial dysfunction in hepatocytes via induction of metailothionein proteinexpression,which may account for the protective role of IL-6 in alcoholic liver disease.Cellular & MolecularImmunology.2004;1(3):205-211.