Abstract 19580: Identification of a Pro-Hypertrophic Pathway With Chamber Specificity for the Right Ventricle; Implications for Right-Heart Dysfunction in Pulmonary Arterial Hypertension
Introduction: Decompensated right ventricle (RV) hypertrophy and failure is the leading cause of death from pulmonary arterial hypertension (PAH). The mechanisms remain unclear. In this work, we identify an RV-specific pathway involving ERM binding phosphoprotein 50 (EBP50) and NADPH oxidase 1 (Nox1).
Methods: Rat neonatal cardiomyocytes (RNCM) were isolated from 1-day-old pup hearts. RV pressure overload was induced in mice by pulmonary artery banding (PAB; 3wk).
Results: Angiotensin II (AngII, 1μM, 24hr) stimulated RNCM hypertrophy, Nox1 expression and production of reactive oxygen species (ROS) superoxide (O2•-). We showed that EBP50 regulates smooth muscle Nox1 and hypertrophy via binding Nox organizing subunit p47phox. In RNCM AngII-induced hypertrophy was attenuated by EBP50 or Nox1 siRNA supporting this link. Moreover, interruption of Ask1, which we previously reported to be downstream of Nox1, reduced AngII-induced RNCM hypertrophy. To test chamber specificity, RNCM isolated from RV or LV were treated with AngII ± NoxA1ds, a specific Nox1 inhibitor. NoxA1ds abolished hypertrophy in RV but not LV RNCM. In vivo, PAB induced an increase in EBP50, Nox1 and O2•-. In contrast, left ventricle pressure overload, induced by 3wk aortic banding, did not significantly affect Nox1 or O2•- levels. Furthermore, PAB-induced O2•- was attenuated in Nox1 and EBP50 null mice. This coincided with improvement in PAB-induced end diastolic volume (EDV) elevation in these animals. Gleaning mechanistic insight from smooth muscle data, we tested a link between RV EBP50 and p47phox. Co-IP reveals increased RV EBP50-p47phox association post-PAB, consistent with Nox regulation by EBP50. Finally, to gain translational insight, RV tissue samples from PAH vs. non-PAH patients were compared for O2•- and Nox1 protein. Both parameters were increased in PAH (O2•-: 2.4±0.15 vs 1.3±0.32 nmol/min/mg; Nox1/β-actin: 1.6±0.12 vs 1.1±0.15 for PAH vs non-PAH, respectively, n=3-5, p<0.05).
Conclusion: Taken together our data support a novel chamber-specific hypertrophic pathway in the RV involving EBP50, Nox1 and Ask1 following pressure overload. These data shed important light on RV dysfunction mechanisms in PAH and identify novel potential therapeutic targets.
Author Disclosures: I. Al Ghouleh: None. D. Meijles: None. J. Sembrat: None. M. Rojas: None. R.R. Vanderpool: None. J. Baust: None. A. Naqvi: None. P.J. Pagano: None.
- © 2016 by American Heart Association, Inc.