We hypothesized that MR contributes to pulmonary vascular and right ventricular (RV) remodeling of pulmonary hypertension (PH). We evaluated the efficacy of MR antagonism by spironolactone in two experimental PH models; mouse chronic hypoxia-induced PH (prevention model) and rat monocrotaline-induced PH (prevention and treatment models). Last, the biological function of the MR was analyzed in cultured distal pulmonary artery smooth muscle cells (PASMCs). In hypoxic PH mice, spironolactone attenuated the increase in RV systolic pressure, pulmonary arterial muscularization, and RV fibrosis. In rat monocrotaline-induced PH (prevention arm), spironolactone attenuated pulmonary vascular resistance and pulmonary vascular remodeling. In the established disease (treatment arm), spironolactone decreased RV systolic pressure and pulmonary vascular resistance with no significant effect on histological measures of pulmonary vascular remodeling, or RV fibrosis. Spironolactone decreased RV cardiomyocyte size modestly with no significant effect on RV mass, systemic blood pressure, cardiac output, or body weight, suggesting a predominantly local pulmonary vascular effect. In distal PASMCs, MR was expressed and localized diffusely. Treatment with the MR agonist aldosterone, hypoxia, or plateletderived growth factor promoted MR translocation to the nucleus, activated MR transcriptional function, and stimulated PASMC proliferation, while spironolactone blocked these effects. In summary, MR is active in distal PASMCs, and its antagonism prevents PASMC proliferation and attenuates experimental PH. These data suggest that MR is involved in the pathogenesis of PH via effects on PASMCs and that MR antagonism may represent a novel therapeutic target for this disease.aldosterone; hypoxia; monocrotaline; pulmonary vascular remodeling; spironolactone PULMONARY ARTERIAL HYPERTENSION (PAH) is a progressive, fatal disease. In its idiopathic form, mortality is 30 -50% at five years, even with recent advances in available therapies. In its secondary forms, pulmonary hypertension (PH) contributes significantly to the morbidity and mortality of chronic lung and heart diseases. The pathological changes include medial thickening of the pulmonary vasculature due to smooth muscle cell (SMC) hyperplasia and hypertrophy (12

Inhaled nitric oxide (iNO) is used for acute vasoreactivity testing in pulmonary arterial hypertension (PAH) patients. Inhaled epoprostenol (iPGI2) has pulmonary selectivity and is less costly. We sought to compare acute hemodynamic effects of iNO (20 ppm) and iPGI2 (50 ng/kg/min) and determine whether their combination has additive effects. We conducted a prospective, single center, randomized, cross-over study in 12 patients with PAH and seven with heart failure with preserved ejection fraction (HFpEF). In PAH patients, iNO lowered mean pulmonary artery pressure (mPAP) by 9 ± 12% and pulmonary vascular resistance (PVR) by 14 ± 32% (mean ± SD). iPGI2 decreased mPAP by 10 ± 12% and PVR by 12 ± 36%. Responses to iNO and iPGI2 in mPAP and PVR were directly correlated (r2 = 0.68, 0.70, respectively, P < 0.001). In HFpEF patients, mPAP dropped by 4 ± 7% with each agent, and PVR dropped by 33 ± 23% with iNO, and by 25 ± 29% with iPGI2 (P = NS). Pulmonary artery wedge pressure (PAWP) increased significantly with iPGI2 versus baseline (20 ± 3 vs. 17 ± 2 mmHg, P = 0.02) and trended toward an increase with iNO and the combination (20 ± 2, 19 ± 4 mmHg, respectively). There were no additive effects in either group. In PAH patients, the vasodilator effects of iNO and iPGI2 correlated at the doses used, making iPGI2 a possible alternative for testing acute vasoreactivity, but their combination lacks additive effect. Exposure of HFpEF patients to inhaled vasodilators worsens the PAWP without hemodynamic benefit.

This study aimed to characterize alterations in select eicosanoids in experimental and human pulmonary arterial hypertension (PAH) and to assess their potential utility as predictors of outcome. Using liquid chromatography-mass spectrometry, we performed targeted lipidomic analyses of the lungs and right ventricles (RVs) of chronically hypoxic rats and plasma of consecutive PAH patients and healthy controls. In rat lungs, chronic hypoxia was associated with significantly decreased lung prostacyclin (PGI 2 )/thromboxane B 2 (TXB 2 ) ratio and elevated lung 8-hydroxyeicosanoid (HETE) acid concentrations. RV eicosanoids did not exhibit any changes with chronic hypoxia. PAH treatment-naïve patients had significantly increased plasma concentrations of TXB 2 and 5-, 8-, 12-, and 15-HETE. The PGI 2 /TXB 2 ratio was lower in PAH patients than in controls, especially in the treatment-naïve cohort (median: 2.1, 0.3, and 1.3 in controls, treatment-naïve, and treated patients, respectively, P = 0.001). Survival was significantly worse in PAH patients with 12-HETE high (≥57 pg/mL) and 15-HETE high (≥256 pg/mL) in unadjusted and adjusted analyses (hazard ratio [HR]: 2.8 [95% confidence interval (CI): 1.1-7.3], P = 0.04 and HR: 4.3 [95% CI: 1.6-11.8], P = 0.004, respectively; adjustment was performed with the REVEAL [Registry to Evaluate Early and Long-Term PAH Disease Management] risk score). We demonstrate significant alterations in eicosanoid pathways in experimental and human PAH. We found that 12-and 15-HETE were independent predictors of survival in human PAH, even after adjusting for the REVEAL score, suggesting their potential role as novel biomarkers.