Hepatocyte-derived macrophage migration inhibitory factor mediates alcohol-induced liver injury in mice and patients

Macrophage migration inhibitory factor (MIF) is a multi-potent cytokine that contributes to the inflammatory response to injury. MIF is expressed by multiple cell types; however, the cellular source and actions of MIF in alcoholic liver disease (ALD) are not well known. Here we tested the hypothesis that non-myeloid cells, specifically hepatocytes, are an important cellular source of MIF in ALD.

MIF expression was measured in HuH7 and differentiated THP-1 cells in response to ethanol. Ethanol-induced liver injury was assessed in C57BL/6 (WT) and Mif^-/- bone marrow chimeras. MIF was measured in peripheral and suprahepatic serum, as well as visualized by immunohistochemistry in liver biopsies, from patients with alcoholic hepatitis (AH).

HuH7 hepatocytes, but not THP-1 macrophages, released MIF in response to ethanol challenge in culture. In chimeric mice expressing MIF in non-myeloid cells (Mif^-/-→WT), chronic ethanol feeding increased ALT/AST, hepatic steatosis, and expression of cytokine/chemokine mRNA. In contrast, chimeric mice not expressing MIF in non-myeloid cells (WT→Mif^-/-) were protected from ethanol-induced liver injury. Immunohistochemical staining of liver biopsies from patients with AH revealed a predominant localization of MIF to hepatocytes. Interestingly, the concentration of MIF in suprahepatic serum, but not peripheral serum, was positively correlated with clinical indicators of disease severity and with an increased risk of mortality in patients with AH.

Taken together, these data provide evidence that hepatocyte-derived MIF is critical in the pathogenesis of ALD in mice and likely contributes to liver injury in patients with AH. Lay summary: Alcoholic liver disease is a major cause of preventable mortality worldwide, and lacks specific pharmacological therapies. Recent studies have recognized that macrophage migration inhibitor factor (MIF) has a critical role in the inflammatory response to liver damage. However, the cells that produce this protein are still unknown. Our present findings reveal that hepatocytes, the main cell type in the liver, are primarily responsible for MIF production in response to alcohol, which promotes liver injury. Our study suggests that drugs inhibiting MIF production could be beneficial in treating patients with liver disease due to excessive alcohol consumption.