Abrogation of PDE7A ameliorates alveolar epithelial EMT-Driven pulmonary fibrosis.

Epithelial-mesenchymal transition (EMT) is a key driver of idiopathic pulmonary fibrosis (IPF), yet therapies specifically targeting epithelial cells remain limited. The role of phosphodiesterase 7A (PDE7A) in IPF and its mechanism in regulating EMT are still largely unknown. This study aims to investigate the anti-fibrotic effect of BRL-50481, focusing on its target PDE7A and the associated molecular mechanism in regulating epithelial cell fibrosis and EMT. BRL-50481 was identified as a top candidate compound targeting pathogenic alveolar epithelial cells through bioinformatic screening. Its efficacy was evaluated in both a bleomycin-induced murine pulmonary fibrosis model and a TGF-β-induced A549 cell model. Drug-target interaction was characterized using molecular docking, cellular thermal shift assay (CETSA), and site-directed mutagenesis. Downstream signaling pathways were predicted via the TRRUST database and experimentally validated. PDE7A was found to be highly expressed in alveolar epithelial cells of IPF patients and mice. BRL-50481 directly bound to the ILE323 residue of PDE7A, specifically inhibiting JAK2/STAT3 signaling pathway activation. This inhibition suppressed EMT, inflammatory factor release, and collagen deposition, ultimately alleviating pulmonary fibrosis in both in vivo and in vitro models. PDE7A acts as a key upstream regulator driving JAK2/STAT3 signaling activation and the EMT process in alveolar epithelial cells. BRL-50481 exerts anti-fibrotic effects by precisely targeting this mechanism, providing novel insights into IPF pathogenesis and establishing a theoretical foundation for developing innovative therapies targeting PDE7A.