Corilagin alleviates liver fibrosis in zebrafish and mice by repressing IDO1-mediated M2 macrophage repolarization.

Background: Liver fibrosis caused by chronic liver injury, eventually develops into liver cirrhosis and hepatocellular carcinoma. Currently, there are no effective drugs to relieve liver fibrosis due to the lack of molecular pathogenesis characteristics. Former research demonstrates that the hepatic immune microenvironment plays a key role in the pathogenesis of liver fibrosis, thus macrophages are important immune cells in the liver. Our previous study has found that IDO1 plays an important role in the liver immune microenvironment. CRG is a gallic acid tannin found in medicinal plants of many ethnicities that protects against inflammation, tumors and chronic liver disease. However, the mechanism of by which CRG mediates the interaction of IDO1 with macrophages during hepatic immune maturation is not clear.

Purpose: To investigate the regulatory mechanism of CRG in liver fibrosis and the intrinsic relationship between IDO1 and macrophage differentiation.

Methods: Zebrafish, RAW264.7 cells and mice were used in the study. IDO1 overexpression and knockdown cell lines were constructed using lentiviral techniques.

Results: We discovered that CRG remarkably reduced the AST and ALT serum levels. Histological examination revealed that CRG ameliorates CCL4-induced liver fibrosis and depressed the expression of α-SMA, Lamimin, Collagen-Ι and fibronectin. Besides, we found that CRG promoted increased MerTK expression on partly macrophages. Interestingly, in vitro, we found that CRG suppressed IDO1 expression and regulated macrophage differentiation by upregulating CD86, CD80 and iNOS, while downregulating CD206, CD163, IL-4 and IL-10 expression. Additionally, we found that CRG could inhibit hepatic stellate cell activation by direct or indirect action.

Conclusion: Our findings suggest that CRG alleviates liver fibrosis by mediating IDO1-mediated M2 macrophage repolarization.