BTG1 Mediates the Proliferation and Activation of Hepatic Stellate Cells via the JAK2/STAT3 Pathway in Liver Fibrosis.

Liver fibrosis is pathologically characterized by excessive extracellular matrix (ECM) deposition induced by diverse etiological factors, which is associated with hepatic stellate cell (HSC) activation and proliferation. B-cell translocation gene 1 (BTG1) contributes to the regulation of cellular proliferation, differentiation, and development. The biological role of BTG1 in HSC activation and liver fibrosis remains incompletely understood. To clarify the regulatory role of BTG1, carbon tetrachloride (CCl4)-induced rat liver fibrosis models and platelet-derived growth factor-BB (PDGF-BB)-activated HSC-T6 cells were used. For in vivo studies, rats were injected with BTG1-overexpressing recombinant adeno-associated virus (AAV). siRNA or overexpression vectors targeting BTG1 were transfected into HSC-T6 cells in vitro, respectively. Rat serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were measured using biochemical assays. Liver histopathological alterations were evaluated by histological staining. 5-ethynyl-2'-deoxyuridine (EdU) assays and flow cytometry were used to assess cell proliferation and apoptosis. Immunohistochemistry, Western blotting, and quantitative real-time polymerase chain reaction (RT-qPCR) were performed to quantify the levels of α-smooth muscle actin (α-SMA), collagen I, interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α), as well as proliferation- and apoptosis-related proteins. Furthermore, a specific JAK2 inhibitor was used to further clarify the underlying molecular mechanism. BTG1 was significantly downregulated in CCl4-induced fibrotic liver tissues and activated HSCs. AAV-mediated BTG1 overexpression markedly alleviated liver fibrosis in rats. siRNA-mediated BTG1 knockdown resulted in the significant upregulation of collagen I, α-SMA, IL-6, and TNF-α expression in HSC-T6 cells. BTG1 deficiency enhanced HSC-T6 cell proliferation induced by PDGF-BB as evidenced by increased expression of proliferating cell nuclear antigen (PCNA) and Ki67, while inhibiting apoptotic death, as evidenced by reduced levels of Bax and cleaved caspase-3, and by enhanced Bcl-2 expression. BTG1 overexpression had the opposite effects. Mechanistically, BTG1 deficiency enhanced JAK2/STAT3 signaling by upregulating the phosphorylation of these signaling intermediaries, whereas BTG1 overexpression inhibited this signaling pathway. Notably, pretreatment with the JAK2 inhibitor ruxolitinib neutralized BTG1 knockdown-induced JAK2/STAT3 hyperactivation. BTG1 suppresses HSC activation by modulating the JAK2/STAT3 signaling axis and retards liver fibrosis progression, suggesting that it may represent a promising therapeutic target for anti-fibrotic intervention.