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(·)) production and elevated levels of endothelin-1. Endothelin-1 is known to stimulate endothelial nitric oxide synthase (eNOS) via the endothelin-B receptor (ET(B)), 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(·) levels. We hypothesized that aldosterone modulates PAH by disrupting ET(B)-eNOS signaling through a mechanism involving increased pulmonary endothelial oxidant stress.


RESULTS
In rats with PAH, elevated endothelin-1 levels were associated with elevated aldosterone levels in plasma and lung tissue and decreased lung NO(·) 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-1α/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 ET(B) to decrease endothelin-1-stimulated eNOS activity. Substitution of ET(B)-Cys405 with alanine improved ET(B)-dependent NO(·) synthesis under conditions of oxidant stress, confirming that Cys405 is a redox-sensitive thiol that is necessary for ET(B)-eNOS signaling. In human pulmonary artery endothelial cells, mineralocorticoid receptor antagonism with spironolactone decreased aldosterone-mediated reactive oxygen species generation and restored ET(B)-dependent NO(·) 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 ET(B) cysteinyl thiol redox switch to decrease pulmonary endothelium-derived NO(·) and promote PAH.
Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital & Harvard Medical School, 75 Francis St, PBB-1, Boston, MA 02115, USA. bmaron@partners.org
Bradley A
BA
Maron
Ying-Yi
YY
Zhang
Kevin
K
White
Stephen Y
SY
Chan
Diane E
DE
Handy
Christopher E
CE
Mahoney
Joseph
J
Loscalzo
Jane A
JA
Leopold
D000450:Aldosterone / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D003545:Cysteine / Q000378:metabolism; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D019332:Endothelin-1 / Q000378:metabolism / Q000494:pharmacology; D065627:Familial Primary Pulmonary Hypertension; D006801:Humans; D006976:Hypertension, Pulmonary / Q000378:metabolism* / Q000473:pathology; D008297:Male; D000451:Mineralocorticoid Receptor Antagonists / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism*; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D011651:Pulmonary Artery / Q000166:cytology; D011669:Pulmonary Wedge Pressure / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D044023:Receptor, Endothelin B / Q000378:metabolism*; D013148:Spironolactone / Q000494:pharmacology; D013438:Sulfhydryl Compounds / Q000378:metabolism
D019332:Endothelin-1; D000451:Mineralocorticoid Receptor Antagonists; D044023:Receptor, Endothelin B; D013438:Sulfhydryl Compounds; D013148:Spironolactone; D009569:Nitric Oxide; D000450:Aldosterone; C496314:NOS3 protein, human; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat; D003545:Cysteine