Yin Yang 1 facilitates the activation, inflammation, and extracellular matrix deposition of hepatic stellate cells in hepatic fibrosis.

Chronic hepatic diseases often involve fibrosis as a pivotal factor in their progression. This study investigates the regulatory mechanisms of Yin Yang 1 (YY1) in hepatic fibrosis. Our data reveal that YY1 binds to the prolyl hydroxylase domain 1 (PHD1) promoter. Rats treated with carbon tetrachloride (CCl₄) display heightened fibrosis in liver tissues, accompanied by increased levels of YY1, PHD1, and the fibrosis marker alpha-smooth muscle actin (α-SMA). Elevated levels of YY1, PHD1, and α-SMA are observed in the liver tissues of CCl₄-treated rats, primary hepatic stellate cells (HSCs) isolated from fibrotic liver tissues, and transforming growth factor beta-1 (TGF-β1)-induced HSCs. The human HSC cell line LX-2, upon YY1 overexpression, exhibits enhanced TGF-β1-induced activation, leading to increased expression of extracellular matrix (ECM)-related proteins and inflammatory cytokines. YY1 silencing produces the opposite effect. YY1 exerts a positive regulatory effect on the activation of the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway and PHD1 expression. PHD1 silencing rescues the promotion of YY1 in cell activation, ECM-related protein expression, and inflammatory cytokine production in TGF-β1-treated LX-2 cells. Overall, our findings propose a model wherein YY1 facilitates TGF-β1-induced HSC activation, ECM-related protein expression, and inflammatory cytokine production by promoting PHD1 expression and activating the PI3K/AKT signaling pathway. This study positions YY1 as a promising therapeutic target for hepatic fibrosis.