Abstract 16770: The Epigenetic Modifier EP300: A New Corner Stone in the Regulation of Both Vascular Remodeling and Right Ventricle Failure in Pulmonary Arterial Hypertension

Abstract

Introduction: Pulmonary Arterial Hypertension (PAH) is characterized by excessive proliferation and resistance to apoptosis of pulmonary artery (PA) smooth muscle cells (PASMCs), leading to progressive increases in pulmonary vascular resistance, and ultimately right ventricular (RV) failure and death. Thanks to omics technologies, we made tremendous progress in understanding gene misregulation during disease processes and identified the epigenetic factor EP300 as a critical player in pathological processes like proliferation/apoptosis and hypertrophy/fibrosis all of which are critical features of both PA remodeling and RV failure in PAH. We hypothesized that EP300 is upregulated in PAH and contributes to both PA remodeling and RV failure. Methods and Results: By Western blot (WB) and immunofluorescence (IF), we found that EP300 is up-regulated in isolated PASMCs and distal PAs from PAH patients (n=11-14) compared to controls (n=8-10) (p<0.01). Similar results were observed in 3 PAH animal models, namely the monocrotaline (MCT), the Sugen/Hypoxia (Su/Hx) and the Fawn-Hooded rat (FHR) (p<0.05). In vitro, pharmacological inhibition of EP300 using CCS-1477 reduces PAH-PASMC proliferation (Ki67 labeling & WB PCNA; p<0.05) and resistance to apoptosis (Annexin V assay & WB Survivin; p<0.05). These effects were confirmed at the molecular level by RNA-Seq analysis. In addition, increased EP300 expression was observed in hypertrophied and failed RV from PAH patients, as well as in rats injected with MCT or subjected to pulmonary artery banding (WB, p<0.05). In animal models, EP300 negatively correlates with CO and positively correlates with RVEDP, cardiomyocyte surface area and fibrosis. Finally, we demonstrated that inhibition of EP300 using CCS-1477 or SGC-CBP30 significantly improved established PAH (right heart catheterization) in two animal models (MCT and FHR). Conclusion: EP300 upregulation contributes to both pulmonary vascular remodeling and RV dysfunction seen in PAH and its inhibition represents a promising therapeutic avenue.