HMGB1 induced endothelial to mesenchymal transition in liver fibrosis: The key regulation of early growth response factor 1

Liver fibrosis has been the focus and difficulty of medical research in the world and its concrete pathogenesis remains unclear. This study aims to observe the high-mobility group box 1 (HMGB1)-induced hepatic endothelial to mesenchymal transition (EndoMT) during the development of hepatic fibrosis, and further to explore the crucial involvement of Egr1 in this process.Carbon tetrachloride (CCl4), diosbulbin B (DB), N-acetyl-p-aminophenol (APAP) and bile duct ligation (BDL) were used to induce liver fibrosis in mice. Serum HMGB1 content, the occurrence of EndoMT and the production of extracellular matrix (ECM) in vitro and in vivo were detected by Western-blot.The elevated serum HMGB1 content, the occurrence of EndoMT, the production of ECM and the activation of Egr1 were observed in mice with liver fibrosis induced by CCl4, DB, APAP or BDL. HMGB1 induced EndoMT and ECM production in human hepatic sinusoidal endothelial cells (HHSECs), and then HHSECs lost the ability to inhibit the activation of hepatic stellate cells (HSCs). The hepatic deposition of collagen, the increased serum HMGB1 content and hepatic EndoMT were further aggravated in Egr1 knockout mice. Natural compound silymarin attenuated liver fibrosis in mice induced by CCl4 via increasing Egr1 nuclear accumulation, decreasing serum HMGB1 content and inhibiting hepatic EndoMT.Egr1 regulated the expression of HMGB1 that induced hepatic EndoMT, which plays an important role in the development of liver fibrosis.This study provides a novel therapeutic strategy for the treatment of liver fibrosis in clinic.