Preventive effects of interleukin-6 in lipopolysaccharide/d-galactosamine induced acute liver injuryviaregulating inflammatory response in hepatic macrophages
Lipopolysaccharide/d-Galactosamine (LPS/d-Gal)-induced acute liver injury is characterized by significant inflammatory responses including TNF-α and interleukin-6 (IL-6) and is a widely applied experimental model for inflammation research. TNF-α is critical in the progression of LPS/d-Gal-induced liver injury. However, the role of IL-6 in this model is still unknown. In the present study, we aim to elucidate the involvement of IL-6 in the pathogenesis of acute liver injury induced by LPS/d-Gal in mice and its underlying mechanism. To induce acute liver injury, LPS (50 μg/kg body weight) and d-Gal (400 mg/kg body weight) were injected intraperitoneally in the C57BL/6 mice. The vehicle (saline) or a single dose of recombinant IL-6 (200 μg/kg body weight) was administered 2 h prior to LPS/d-Gal injection. Mice were sacrificed 2 h and 6 h after LPS/d-Gal injection. The results indicated that IL-6 treatment could protect mice from LPS/d-Gal-induced tissue damage, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) elevation, as well as hepatocyte apoptosis and inflammation. Furthermore, in vitro study showed that IL-6 treatment could significantly suppress LPS-triggered expression of proinflammatory cytokines and chemokines, TNF-α, RANTES and MCP-1 in macrophages while promoting the expression of M2 markers, such as Arg-1 and Mrc-1 in macrophages. Taken together, these findings revealed a novel and unexpected role of IL-6 in ameliorating LPS/d-Gal-induced acute liver injury via regulating inflammatory responses in hepatic macrophages.