Orcinol glucoside ameliorates pulmonary fibrosis by suppressing hyaluronic acid synthesis and macrophage M2 polarization via targeting hyaluronic acid synthase 2

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive lung disorder characterized by unexplained fibrosis and limited therapeutic options, highlighting the urgent need for innovative treatments. Hyaluronic acid (HA), which is upregulated in IPF and correlates with disease severity, plays an undefined role in its pathogenesis. Hyaluronic acid synthase 2 (HAS2), a key enzyme in HA production, has an unclear function in IPF progression, particularly regarding its involvement in macrophage polarization. Understanding this mechanism is essential for identifying novel therapeutic targets and developing effective drugs for IPF. The present study investigated the roles of HAS2 and HA in IPF and identified potential therapeutic agents. Transcriptomic analysis revealed HAS2 as a critical IPF‑associated gene in patient samples, bleomycin (BLM)‑induced mouse models, and transforming growth factor β1 (TGF‑β1)‑induced myofibroblasts. Single‑cell RNA sequencing further confirmed the fibroblast‑specific upregulation of HAS2 in fibrotic lungs. Experimental validation showed elevated HAS2 expression and HA accumulation in fibrosis models. HA facilitated macrophage M2 polarization and TGF‑β1 secretion through CD44‑dependent STAT6 activation, with CD44 inhibition blocking this effect. Knockdown of HAS2 in fibroblasts decreased HA release and impaired their ability to promote M2 polarization, suggesting that fibroblast‑derived HA drives this process. High‑throughput virtual screening, coupled with absorption, distribution, metabolism and excretion (ADME) profiling, identified orcinol glucoside (OG) as a potential HAS2 inhibitor, which was validated through surface plasmon resonance, cellular thermal shift assays, and molecular dynamics simulations. OG suppressed HA synthesis in TGF‑β1‑induced and HAS2‑overexpressing myofibroblasts in a dose‑dependent manner, inhibiting M2 polarization induction. <i>In vivo</i>, OG reduced collagen deposition, HA, and TGF‑β1 levels in BLM‑induced fibrotic mice. These findings established HAS2 as a central pathogenic factor in IPF and suggested OG as a promising therapeutic candidate, providing a novel approach for IPF treatment by targeting HA synthesis and macrophage polarization.