S100A4 promotes inflammation but suppresses lipid accumulation via the STAT3 pathway in chronic ethanol-induced fatty liver.

S100A4, a member of the S100 calcium-binding protein family, has been identified in a subpopulation of liver macrophages and promotes liver fibrosis via hepatic stellate cell activation. However, the specific role of S100A4 in alcoholic liver disease (ALD) has not been well investigated. Here, S100A4 knockout (S100A4-/-) mice were used in a chronic-binge ethanol model for studying the role of S100A4 and its related molecular mechanism in ALD. S100A4 expression was increased in ethanol-induced liver tissues of wild-type (WT) mice. Macrophage-derived S100A4 promoted liver inflammation but suppressed lipid accumulation under the ethanol feeding condition. S100A4 deficiency promoted ethanol-induced liver injury and hepatic fat accumulation. Further mechanistic studies found that S100A4 inhibited liver fat accumulation mainly by activating the STAT3 pathway and downregulating lipogenic gene expression, especially that of SREBP-1c. In AML-12 cells, a STAT3 inhibitor abolished STAT3 levels and decreased the expression of SREBP1c. Furthermore, the administration of a neutralizing S100A4 antibody to WT mice significantly promoted ethanol-induced liver injury and fatty accumulation. Thus, S100A4 may represent a potential candidate target for the prevention and treatment of ethanol-induced fatty liver. In this study, we discovered the special role of S100A4 in alcoholic liver disease. S100A4 deficiency attenuated ethanol-induced hepatitis and promoted hepatic fat accumulation in ethanol-induced liver tissues. Further mechanistic studies have found that S100A4 promotes early alcoholic hepatitis mainly by activating the STAT3 pathway and its downstream proinflammatory gene expression. Interestingly, activation of the STAT3 pathway downregulates lipogenic gene expression, especially SREBP-1c. KEY MESSAGES: In this study, we discovered the special role of S100A4 in alcoholic liver disease. S100A4 deficiency attenuated ethanol-induced hepatitis and promoted hepatic fat accumulation in ethanol-induced liver tissues. Further mechanistic studies have found that S100A4 promotes early alcoholic hepatitis mainly by activating the STAT3 pathway and its downstream proinflammatory gene expression. Interestingly, activation of the STAT3 pathway downregulates lipogenic gene expression, especially SREBP-1c.