Glycyrrhizic acid alleviates liver fibrosis in vitro and in vivo via activating CUGBP1-mediated IFN-γ/STAT1/Smad7 pathway

Hepatic fibrosis, a common pathological feature of chronic liver injuries, is a serious public health problem and lacks effective therapy. Glycyrrhizic acid (GA) is a bioactive ingredient in the root of traditional Chinese medicine licorice, and exhibits remarkable anti-viral, anti-inflammatory and hepatoprotective actions.Here we aimed to investigated whether GA provided a therapeutic efficacy in hepatic fibrosis and uncover its molecular mechanisms.We investigated the anti-fibrosis effects of GA using CCl4-induced mouse mode of liver fibrosis as well as TGF-β1-activated human LX-2 cells and primary hepatic stellate cells (HSCs). CUGBP1-mediated IFN-γ/STAT1/Smad7 signaling was examined with immunofluorescence staining and western blot analysis. We designed and studied the binding of GA to CUGBP1 using in silico docking, and validated by microscale thermophoresis (MST) assay.GA obviously attenuated CCl4-induced liver histological damage, and reduced serum ALT and AST levels. Meanwhile, GA decreased liver fibrogenesis markers such as α-SMA, collagen α1, HA, COL-III, and LN in the hepatic tissues. Mechanistically, GA remarkably elevated the levels of IFN-γ, p-STAT1, Smad7, and decreased CUGBP1 in vivo and in vitro. Over-expression of CUGBP1 completely abolished the anti-fibrotic effect of GA and regulation on IFN-γ/STAT1/Smad7 pathway in LX-2 cells and primary HSCs, confirming CUGBP1 played a pivotal role in the protection by GA from liver fibrosis. Further molecular docking and MST assay indicated that GA had a good binding affinity with the CUGBP1 protein. The dissociation constant (Kd) of GA and CUGBP1 was 0.293 μM.Our study demonstrated for the first time that GA attenuated liver fibrosis and hepatic stellate cell activation by promoting CUGBP1-mediated IFN-γ/STAT1/Smad7 signalling pathways. GA may be a potential candidate compound for preventing or reliving liver fibrosis.