Interaction of neuropilin-1 and hepatocyte growth factor/C-Met pathway in liver fibrosis progression in hepatocyte-specific NRP-1 knockout mice.

BACKGROUND: Hepatocyte growth factor (HGF)/c-Met signaling critically influences liver fibrosis, but its interaction with neuropilin-1 (NRP-1) in hepatocytes remains unclear. We investigated the role of hepatocyte-specific NRP-1 deletion in liver fibrosis progression and its relationship with the HGF/c-Met pathway. METHODS: Hepatocyte-specific NRP-1 knockout mice were generated using the Cre-lox system, and liver fibrosis was induced by carbon tetrachloride injections or a methionine- and choline-deficient diet. Fibrosis severity, hepatocyte injury, and cytokine secretion were evaluated via histology, biochemical assays, and molecular analyses in isolated hepatocytes. In vitro experiments were conducted in primary hepatocytes and Huh7 cells using lentiviral overexpression and knockdown of NRP-1. Chromatin immunoprecipitation and dual-luciferase reporter assays were performed to analyze transcription factor binding to the NRP-1 promoter. RESULTS: Hepatocyte NRP-1 expression increased significantly during liver fibrosis and was positively correlated with HGF/c-Met expression and fibrosis severity. In vivo, NRP-1 inhibition reduced extracellular matrix accumulation and abnormal angiogenesis in Alb-Cre NRP-1(f/f) mice. In vitro, NRP-1 blockade inhibited c-Met activation and reduced transforming growth factor-beta and vascular endothelial growth factor secretion in hepatocytes. NRP-1 functioned as a co-receptor for HGF/c-Met, with HGF upregulating NRP-1 expression at transcript and protein levels. NRP-1 promoted fibrosis through the Met/extracellular signal-regulated kinase pathway. Furthermore, HGF increased retinoic acid receptor alpha expression, promoting NRP-1 transcription. CONCLUSIONS: HGF-induced upregulation of hepatocyte NRP-1, mediated by RARA binding to its promoter, drives liver fibrosis through c-Met pathway activation, highlighting NRP-1 as a potential therapeutic target for liver fibrosis.