Dioscin reduces lipopolysaccharide-induced inflammatory liver injury via regulating TLR4/MyD88 signal pathway

We previously reported the effects of dioscin against carbon tetrachloride-, acetaminophen- and alcohol-induced acute liver damage. However, its effect on lipopolysaccharide (LPS)-induced inflammatory liver injury remains unknown. In the present work, liver injury in mice and rats was induced by LPS, and dioscin was intragastrically administered for 7 days. In vitro, the AML-12 cells and HepG-2 cells were treated with LPS after dioscin treatment The results showed that dioscin not only markedly reduced serum ALT, AST levels and relative liver weights, but also restored cell injury caused by LPS. In mechanism study, dioscin significantly attenuated inflammation through down-regulating the levels of toll-like receptor (TLR) 4, myeloid differentiation factor 88 (MyD88), interleukin-1 receptor-associated kinase 1 (IRAK1), tumor necrosis factor receptor-associated factor 6 (TRAF6), phosphorylated inhibitor of nuclear factor kappa B kinase (p-IKK), phosphorylated inhibitor of nuclear factor kappa B alpha (p-I kappa B alpha), phosphorylated nuclear factor kappa B p65 (p-NF-kappa B p65), high-mobility group protein 1 (HMGB-1), interleuldn (IL)-1, IL-6 and tumor necrosis factor-alpha (TNF-alpha). TLR4 overexpression was also decreased by dioscin, leading to the markedly decreased levels of MyD88, IRAK1, TRAF6, p-IKK, p-I kappa B alpha, p-NF-kappa B p65 and HMGB-1. Suppression of MyD88 by ST2825 eliminated the inhibitory effects of dioscin on the levels of IRAK1, TRAF6, p-IKK, p-I kappa B alpha, p-NF-kappa B p65, HMGB-1, IL-1 beta, IL-6 and TNF-alpha. Our results suggested that dioscin exhibited protective effect against LPS-induced liver injury via altering TLR4/MyD88 pathway, which should be developed as one potent candidate for the treatment of acute inflammatory liver injury in the future. (C) 2016 Elsevier B.V. All rights reserved.