Unraveling the therapeutic mechanisms of Polygonum cuspidatum in pulmonary fibrosis: Modulation of M2 macrophage polarization and glycolysis pathways.

Abstract

ETHNOPHARMACOLOGICAL RELEVANCE: Polygonum cuspidatum (PC), a plant widely distributed in East Asia, is traditionally used for respiratory diseases and is documented in the "Compendium of Materia Medica" as having heat-clearing properties. AIM OF THE STUDY: This study aimed to evaluate the therapeutic effects, molecular targets, and mechanisms of PC in mediating Idiopathic pulmonary fibrosis (IPF). MATERIALS AND METHODS: A bleomycin-induced IPF mouse model was established. Histopathological examination, hydroxyproline quantification, and extracellular matrix (ECM) marker analysis evaluated PC's anti-fibrotic effects in vivo. Macrophage infiltration and polarization were assessed using qRT-PCR, western blotting, and immunohistochemistry. Network pharmacology identified PC-modulated IPF pathways, and molecular docking assessed interactions with predicted molecular targets. Pathway effects on PC were verified through qRT-PCR, immunoblotting, and immunofluorescence. A co-culture model involving M2-polarized macrophages and MRC-5 fibroblasts further validated PC's antifibrotic activity. RESULTS: PC lowered hydroxyproline levels, preserved lung structure, and reduced E-cadherin, α-SMA, and fibronectin expression. PC inhibited M2 macrophage infiltration in vivo and suppressed M2 markers (CD206, Arginase1) and Spp1. Network pharmacology identified HIF-1 signaling as a core pathway, supported by strong binding affinity between PC compounds and HIF-1α. In vitro and in vivo studies showed that PC suppressed IL-4- and IL-13-induced activation of the HIF-1α/STAT3 signaling pathway in M2 macrophages. By reducing glycolytic enzymes (HK2, GLUT1, PFKFB3, LDHA), PC attenuated HIF-1α-dependent glycolysis and improved myofibroblast activation in MRC-5 cells. CONCLUSION: PC exerted anti-fibrotic effects by targeting the HIF-1α/STAT3 pathway in macrophages, suppressing M2 polarization and associated glycolytic programming, disrupting the feedback loop between macrophages and fibroblasts.