Emodin Alleviates Liver Fibrosis of Mice by Reducing Infiltration of Gr1^hi Monocytes

Emodin, as a major active component of Rheum palmatum L. and Polygonum cuspidatum, has been reported to have antifibrotic effect. However, the mechanism of emodin on antifibrotic effect for liver fibrosis was still obscure. In the present study, we aimed to investigate whether emodin can alleviate carbon tetrachloride- (CCl₄-) induced liver fibrosis through reducing infiltration of Gr1^hi monocytes. Liver fibrosis was induced by intraperitoneal CCl₄ injection in mice. Mice in the emodin group received emodin treatment by gavage. Pretreatment with emodin significantly protected mice from liver inflammation and fibrosis revealed by the decreased elevation of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST), as well as reduced hepatic necrosis and fibrosis by analysis of hematoxylin-eosin (HE) staining, Masson staining, α-smooth muscle actin (α-SMA), and collagen-I immunohistochemistry staining. Further, compared to CCl₄ group, mice in the emodin group showed significantly less intrahepatic infiltration of Gr1^hi monocytes. Moreover, emodin significantly inhibited hepatic expression of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), transforming growth factor-β1 (TGF-β1), granulin (GRN), monocyte chemoattractant protein 1 (MCP-1), and chemokine ligand 7 (CCL7), which was in line with the decreased numbers of intrahepatic Gr1^hi monocytes. In conclusion, emodin can alleviate the degree of liver fibrosis by reducing infiltration of Gr1^hi monocytes. These results suggest that emodin is a promising candidate to prevent and treat liver fibrosis.