Expression of Vsig4 attenuates macrophage-mediated hepatic inflammation and fibrosis in high fat diet (HFD)-induced mice.

The innate immune response contributes to hepatic steatosis and nonalcoholic fatty liver disease (NAFLD). However, the pathogenic mechanism of NAFLD is still poorly understood. The costimulatory molecule V-set and immunoglobulin domain-containing protein-4 (Vsig4), which is exclusively expressed on macrophages, shows significant role in regulating macrophage-mediated inflammation. Here, we attempted to explore if Vsig4 expression was involved in high fat diet (HFD)-induced NAFLD. The results indicated that Vsig4 expression was markedly down-regulated in fatty livers of NAFLD patients and obese mice. Vsig4 knockout accelerated HFD-induced metabolic dysfunction. In addition, the loss of Vsig4 significantly promoted insulin resistance and lipid deposition in liver samples of HFD-challenged mice. Furthermore, HFD-induced inflammation was apparently accelerated in Vsig4 knockout mice by further activating nuclear factor-κB (NF-κB) signaling pathway. Also, Vsig4 deficient mice exhibited greater collagen accumulation in hepatic samples in HFD-challenged mice compared to the WT mice, which was through promoting transforming growth factor-β1 (TGFβ1) signaling. Importantly, we found that lipopolysaccharide (LPS)- or TGFβ1-stimulated inflammation and fibrosis in primary hepatocytes and hepatic stellate cells, respectively, were markedly exacerbated by co-culture with condition medium from bone marrow-derived macrophages (BMDMs) with Vsig4 deficiency. Finally, transplantation of bone marrow cells from control mice to Vsig4-knockout mice restored the severity of steatosis, inflammation and fibrosis after HFD feeding. Therefore, loss of Vsig4 accelerated the severity of lipid deposition, fibrosis and the inflammatory response. Vsig4 could be a therapeutic target for NAFLD treatment.

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