Sphingosine 1-phosphate/microRNA-1249-5p/MCP-1 axis is involved in macrophage-associated inflammation in fatty liver injury in mice.

Monocyte chemotactic protein-1 (MCP-1) is one of the most representative inflammatory cytokines, and has been proved to be markedly increased in injured liver and sphingosine 1-phosphate (S1P)-treated macrophages. However, microRNAs (miRNAs) targeting MCP-1 and the role of miRNA/MCP-1 axis in S1P-mediated liver inflammation remain largely unknown. Here, we demonstrate that MCP-1 expression is increased in the liver and isolated liver macrophages of MCDHF mice. Moreover, there is a positive correlation between the hepatic levels of S1P and MCP-1. We then predict miRNAs targeting MCP-1 by bioinformatics analysis and select miRNA-1249-5p (miR-1249-5p) from the intersection of TargetScan database and downregulated miRNAs in the injured liver. S1P significantly upregulates the expression of MCP-1 and decreases miR-1249-5p expression in macrophages. MiR-1249-5p directly targets 3'-UTR of MCP-1 and negatively regulates its expression in S1P-treated macrophages. Administration of miR-1249-5p agomir decreases hepatic MCP-1 levels and attenuates liver inflammation in MCDHF mice. Protein-protein interaction network by STRING displays that S1P system is closely associated with MCP-1/CCR2 axis in the network of inflammation. In conclusion, we characterize the vital role of miR-1249-5p in negatively regulating MCP-1 expression in vitro and in vivo, which may open new perspectives for pharmacological treatment of liver disease.