Aldosterone Inactivates the Endothelin-B Receptor via a Cysteinyl Thiol Redox Switch to Decrease Pulmonary Endothelial Nitric Oxide Levels and Modulate Pulmonary Arterial Hypertension

Background-Pulmonary arterial hypertension (PAH) is characterized, in part, by decreased endothelial nitric oxide (NO center dot) production and elevated levels of endothelin-1. Endothelin-1 is known to stimulate endothelial nitric oxide synthase (eNOS) via the endothelin-B receptor (ETB), suggesting that this signaling pathway is perturbed in PAH. Endothelin-1 also stimulates adrenal aldosterone synthesis; in systemic blood vessels, hyperaldosteronism induces vascular dysfunction by increasing endothelial reactive oxygen species generation and decreasing NO center dot levels. We hypothesized that aldosterone modulates PAH by disrupting ETB-eNOS signaling through a mechanism involving increased pulmonary endothelial oxidant stress. Methods and Results-In rats with PAH, elevated endothelin-1 levels were associated with elevated aldosterone levels in plasma and lung tissue and decreased lung NO center dot metabolites in the absence of left-sided heart failure. In human pulmonary artery endothelial cells, endothelin-1 increased aldosterone levels via peroxisome proliferator-activated receptor gamma coactivator-1 alpha/steroidogenesis factor-1-dependent upregulation of aldosterone synthase. Aldosterone also increased reactive oxygen species production, which oxidatively modified cysteinyl thiols in the eNOS-activating region of ETB to decrease endothelin-1-stimulated eNOS activity. Substitution of ETB-Cys405 with alanine improved ETB-dependent NO center dot synthesis under conditions of oxidant stress, confirming that Cys405 is a redox-sensitive thiol that is necessary for ETB-eNOS signaling. In human pulmonary artery endothelial cells, mineralocorticoid receptor antagonism with spironolactone decreased aldosterone-mediated reactive oxygen species generation and restored ETB-dependent NO center dot production. Spironolactone or eplerenone prevented or reversed pulmonary vascular remodeling and improved cardiopulmonary hemodynamics in 2 animal models of PAH in vivo. Conclusions-Our findings demonstrate that aldosterone modulates an ETB cysteinyl thiol redox switch to decrease pulmonary endothelium-derived NO center dot and promote PAH. (Circulation. 2012;126:963-974.)