Inhibiting VEGFC - mediated hepatocyte - macrophage regulatory axis contributes to protective effects of naringin against high - fat diet - induced hepatic fibrosis

Background: Naringin (NAR) has shown anti-fibrotic effects. This study found it alleviates non-alcoholic steatohepatitis (NASH)-associated liver fibrosis and downregulates vascular endothelial growth factor C (VEGFC). However, the pathophysiological role of VEGFC in NASH and its contribution to NAR's protection remain unclear.

Objective: To determine whether and how the downregulation of VEGFC contributes to the protective effect of NAR against NASH-associated hepatic fibrosis.

Methods: A mouse model of NASH fibrosis was induced by a 24-week high-fat diet (HFD). Mice were treated concomitantly with NAR-L (25 mg/kg/day), NAR-H (50 mg/kg/day), or SAR131675 (SAR, 30 mg/kg/day) from week 9 to 24 (16 weeks). Clinical serum VEGFC levels were measured in a hospital cohort (n = 165); human hepatic VEGFC expression was analyzed in using data from Gene Expression Omnibus (GEO) datasets (GSE162694, GSE130970). Hepatocyte-specific Vegfc knockout mice (Vegfc^Hep‑cKO) were generated by crossing Vegfc^flox/flox with Alb-CreERT2 (Albumin-CreERT2) mice. In vitro, AML12 hepatocytes were pretreated (oleic acid, recombinant VEGFC, or Vegfc genetic modulation); these cells or their conditioned medium were used to stimulate bone marrow-derived macrophages to assess macrophage migration and phenotypic switching.

Results: NAR and SAR131675 ameliorated liver inflammation and fibrosis in mice, downregulated VEGFC and CCL2/CCR2, reduced Ly6C^high monocyte infiltration, and promoted Ly6C^high-to-Ly6C^low macrophage phenotypic switch. Clinical data showed elevated VEGFC in NAFLD and NASH patients. Vegfc^Hep‑cKO mice exhibited similar therapeutic effects. In vitro, hepatocyte-derived VEGFC promoted macrophage migration via VEGFR3 and CCL2/CCR2; inhibited phenotypic transition via regulating IL-10 or CX3CR1. NAR disrupted this axis by suppressing VEGFC in hepatocytes.

Conclusion: Hepatocyte-derived VEGFC is a key contributor to NASH-related liver fibrosis, functioning by regulating macrophage migration and phenotypic switch. The hepatoprotective effect of NAR is partially mediated through the inhibition of the VEGFC-mediated hepatocyte-macrophage regulatory axis.

Hepatic fibrosis; Ly6C(high); Macrophage; NASH; Naringin; Phenotypic switch; VEGFC.