Epigenetic Activation of Endothelial Smurf1 via EP300-Mediated H3K27ac Disrupts BMPR2 Signaling in Pulmonary Arterial Hypertension

BackgroundPulmonary arterial hypertension (PAH) is a progressive vascular disease characterized by pulmonary endothelial dysfunction, vascular remodeling, and right ventricular failure. Despite recent advances, the underlying molecular mechanisms remain incompletely understood, and curative treatments are still lacking. Loss of BMPR2 signaling is a hallmark of PAH pathogenesis, yet the mechanisms leading to BMPR2 destabilization are not fully defined. Smad ubiquitination regulatory factor 1 (Smurf1), an E3 ubiquitin ligase, has been implicated in the degradation of BMPR2 and downstream signaling proteins; however, the regulation of Smurf1 and its therapeutic potential remain largely unexplored. MethodsWe assessed Smurf1 expression in lung tissues from PAH patients, experimental animal models, and pulmonary artery endothelial cells (PAECs). Epigenetic regulation of Smurf1 was examined using ChIP-qPCR, EP300 gain- and loss-of-function studies, and pharmacological inhibition with the selective EP300 inhibitor A485. Functional consequences of Smurf1 inhibition were evaluated in vitro using transcriptomic profiling, proliferation assays, and BMPR2-Smad signaling analyses. In vivo therapeutic efficacy was tested in monocrotaline (MCT)-induced PAH rats treated with the selective Smurf1 inhibitor Smurf1-IN-A01. ResultsSmurf1 expression was elevated in PAH patient lungs, experimental models, and PAECs. Increased histone H3K27 acetylation and EP300 occupancy at the Smurf1 promoter implicated epigenetic activation. EP300 inhibition reduced H3K27ac enrichment, suppressed Smurf1 expression, and restored BMPR2 signaling. Smurf1 blockade with Smurf1-IN-A01 reprogrammed the transcriptomic landscape of PAH-PAECs, downregulating inflammatory, fibrotic, and angiogenic gene networks. Functionally, Smurf1 inhibition decreased pathological endothelial proliferation and enhanced BMPR2-mediated Smad1/5/9 activation. In vivo, Smurf1- IN-A01 improved pulmonary hemodynamics, reduced vascular remodeling and fibrosis, and restored BMPR2 signaling in MCT-PAH rats. ConclusionsOur study identifies Smurf1 as an epigenetically regulated driver of endothelial dysfunction and vascular remodeling in PAH. Targeting Smurf1 restores BMPR2 signaling, reprograms pathogenic processes, and offers a novel therapeutic strategy for PAH.