Tetramethylpyrazine reduces glucose and insulin-induced activation of hepatic stellate cells by inhibiting insulin receptor-mediated PI3K/AKT and ERK pathways

Abstract

Hepatic stellate cell (HSC) activation is the central event during liver fibrogenesis. Metabolic syndrome characterized by hyperglycemia and hyperinsulinemia contributes to nonalcoholic steatohepatitis-associated liver fibrosis. This study was to investigate the effects of tetramethylpyrazine (TMP) on HSC activation induced by glucose and insulin (Glu/Ins) and the underlying mechanisms. Results showed that Glu/Ins significantly stimulated proliferation, invasion, adhesion, and extracellular matrix (ECM) production in HSCs. TMP inhibited HSC proliferation, invasion and adhesion, and reduced the expression of marker genes related to HSC activation in Glu/Ins-activated HSCs. Mechanistic evidence revealed that TMP reduced insulin receptor (InsR) expression and blocked the downstream phosphatidylinositol-3-kinase (PI3K)/AKT and extracellular signal-regulated kinase (ERK) cascades, which was required for TMP attenuation of HSC activation. Moreover, TMP modulated the genes relevant to ECM homeostasis favoring ECM degradation. It could be concluded that TMP inhibited Glu/Ins-stimulated HSC activation and ECM production by inhibiting InsR-mediated PI3K/AKT and ERK pathways.

Keywords: 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfo-phenyl)-2H-tetrazolium; BSA; CTGF; DMEM; Dulbecco’s modified eagle medium; ECM; ERK; Extracellular matrix; FBS; GAPDH; Glu/Ins; HSC; Hepatic stellate cell; InsR; Insulin receptor; JNK; Liver fibrosis; MAPK; MMP; MTS; NAFLD; NASH; PBS; PI3K; T2DM; TIMP; TMP; Tetramethylpyrazine; bovine serum albumin; c-Jun N-terminal kinase; connective tissue growth factor; extracellular matrix; extracellular signal-regulated kinase; fetal bovine serum; glucose and insulin; glyceraldehyde phosphate dehydrogenase; hepatic stellate cell; insulin receptor; matrix metalloproteinase; mitogen-activated protein kinase; non-alcoholic fatty liver disease; non-alcoholic steatohepatitis; phosphate buffered saline; phosphatidylinositol-3-kinase; tetramethylpyrazine; tissue inhibitor of metalloproteinase; type II diabetes mellitus; α-SMA; α-smooth muscle actin.