Effect of curcumin on the non-alcoholic steatohepatitis via inhibiting the M1 polarization of macrophages

Background Non-alcoholic steatohepatitis (NASH) is a global medical problem and macrophages' activation is closely related to the pathogenesis of NASH. Curcumin is a polyphenol from turmeric with significant anti-inflammatory activity. Objective The objective of present study was to observe the effect of curcumin on macrophages' activation and secretion of pro-inflammatory cytokines in NASH. Methods Hematoxylin and eosin and TUNEL staining were used to observe the hepatic function. RT-PCR was conducted to evaluate the hepatic mRNA expression of tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta). Flow cytometry was adopted to detect the M1 polarization of macrophages. The RAW264.7 macrophage was pretreated with different doses of curcumin, and then lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma) were given to activate the M1 macrophage. The activation ratio of M1 macrophage was observed by flow cytometry, and IL-1 beta and TNF-alpha expression was detected by RT-PCR and ELISA. Results After treatment with curcumin, the activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), the mRNA expression of TNF-alpha and IL-1 beta, and M1 polarization of macrophages were significantly decreased. Hematoxylin and eosin and TUNEL staining showed that inflammation and apoptosis in the liver were improved. What is more, curcumin can effectively inhibit M1 macrophage activation induced by lipopolysaccharide and IFN-gamma and reduce the secretion of IL-1 beta and TNF-alpha. Conclusion Curcumin can effectively improve NASH and reduce hepatic cell necrosis by inhibiting the M1 polarization of macrophages and the secretion of inflammatory factors.