LHPP deficiency aggravates liver fibrosis through TGF-β/Smad3 signaling

Liver fibrosis is characterized by a wound-healing response and may progress to liver cirrhosis and even hepatocellular carcinoma. Phospholysine phosphohistidine inorganic pyrophosphate phosphatase (LHPP) is a tumor suppressor that participates in malignant diseases. However, the role of LHPP in liver fibrosis has not been determined. Herein, the function and regulatory network of LHPP were explored in liver fibrosis. The expression of LHPP in human and murine fibrotic liver tissues was assessed via immunohistochemistry and Western blot analysis. In addition, liver fibrosis was induced in wild-type (WT) and LHPP^-/- (KO) mice after carbon tetrachloride (CCl₄) or thioacetamide (TAA) treatment. The effect of LHPP was systematically assessed by using specimens acquired from the above murine models. The functional role of LHPP was further explored by detecting the pathway activity of TGF-β/Smad3 and apoptosis after interfering with LHPP in vitro. To explore whether the function of LHPP depended on the TGF-β/Smad3 pathway in vivo, an inhibitor of the TGF-β/Smad3 pathway was used in CCl₄-induced WT and KO mice. LHPP expression was downregulated in liver tissue samples from fibrosis patients and fibrotic mice. LHPP deficiency aggravated CCl₄- and TAA-induced liver fibrosis. Moreover, through immunoblot analysis, we identified the TGF-β/Smad3 pathway as a key downstream pathway of LHPP in vivo and in vitro. The effect of LHPP deficiency was reversed by inhibiting the TGF-β/Smad3 pathway in liver fibrosis. These results revealed that LHPP deficiency exacerbates liver fibrosis through the TGF-β/Smad3 pathway. LHPP may be a potential therapeutic target in hepatic fibrosis.