Blockade of interleukin-6 signaling enhances hepatic steatosis but improves liver injury in methionine choline-deficient diet-fed mice

Abstract

Inflammatory processes have an important role in the development of hepatic steatosis and progression to nonalcoholic steatohepatitis (NASH). Interleukin-6 (IL-6) is known to be a proinflammatory cytokine, but also promotes liver regeneration and protects the liver against various forms of damage. The role of IL-6/Glycoprotein130 (GP130) in NASH remains unclear. In this study, we determined whether blocking IL-6/GP130 signaling prevents progression of steatohepatitis in a mouse NASH model. Six-week-old male C57/BL6 mice were fed either chow control or a methionine choline-deficient (MCD) diet for 8 weeks. Half of the MCD diet-fed mice were treated with 15 mg/kg rat anti-mouse IL-6 receptor antibody (MR16-1), intraperitoneally twice weekly, the remainder and chow-fed mice were injected with 15 mg/kg rat IgG as a control. Hepatic steatosis, injury, fibrosis, apoptosis, markers of lipid peroxidation/oxidant stress and IL-6-related gene expressions were evaluated. MR16-1 treatment decreased signal transducer and activator of transcription 3 activities and expression of suppressor of cytokine signaling 3 in MCD diet-treated mouse livers. Although this treatment enhanced intrahepatic lipid accumulation accompanied by increased sterol regulatory element-binding protein 1 and decreased peroxisome proliferator-activated receptor-α expression, elevated plasma alanine aminotransferase levels were improved with decreased plasma free fatty acid levels, lipid peroxidation/oxidant stress and hepatic apoptosis. Blocking IL-6/GP130 signaling by MR16-1 enhanced MCD diet-induced hepatic steatosis, but ameliorated liver injury. These findings suggest that hepatic IL-6 signaling has a protective role against the progression of hepatic steatosis but may enhance liver inflammation.