TNAP-induced CD47 membrane expression enhances TGF-β1 conversion in liver fibrosis

Tissue-nonspecific alkaline phosphatase (TNAP) expression increases after liver injury, but its role in liver fibrosis remains unclear. This study investigated the effect of TNAP on liver fibrosis and its mechanism in regulating TGF-β1 signaling.

Human liver samples and a CCl4-induced liver fibrosis mouse model with adv-TNAP and a TNAP inhibitor (tetramisole, Tetra) were used to study the function of TNAP in liver fibrosis. Primary HSCs were used to study the mechanism of TNAP in regulating the TGF-β1 signal.

Elevated TNAP expression was observed in human and murine fibrotic liver tissues, correlating with increased fibrotic markers. In vivo experiments using TNAP overexpression and inhibition in a CCl4-induced liver fibrosis mouse model demonstrated that TNAP exacerbated, while its inhibition alleviated, liver fibrosis. In vitro studies revealed that TNAP regulated TGF-β1 conversion and HSCs activation through the TGF-β1/SMAD pathway. TNAP facilitated TGF-β1 conversion by promoting the interaction between CD47 and thrombospondin-1 (TSP1). Membrane expression of CD47 modulated by TNAP might contribute to the binding effect of CD47 and TSP1.

TNAP plays a critical regulatory role in TGF-β1-mediated liver fibrosis, probably by promoting the binding of CD47/TSP1. Targeting TNAP-mediated pathways may offer new therapeutic strategies for liver fibrosis.