Plasma 12- and 15-hydroxyeicosanoids are predictors of survival in pulmonary arterial hypertension.

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 (PGI2)/thromboxane B2 (TXB2) 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 TXB2 and 5-, 8-, 12-, and 15-HETE. The PGI2/TXB2 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-HETEhigh (≥57 pg/mL) and 15-HETEhigh (≥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.

Comparison of acute hemodynamic effects of inhaled nitric oxide and inhaled epoprostenol in patients with pulmonary hypertension.

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 (r(2) = 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.

Differences between basal lung levels of select eicosanoids in rat and mouse.

Metabolites of arachidonic acid play an important role in mediating inflammation, cell proliferation, and oxidative stress that contribute to many pulmonary diseases. We hypothesized that the substantial differences between rats and mice in their responses to experimental pulmonary hypertensive stimuli would be associated with parallel differences in their basal eicosanoid profile. Rat and mouse lung extracts were subjected to liquid chromatography tandem mass spectrometry that was optimized for simultaneous separation and rapid quantification of the major hydroxyeicosatetraenoic acids (HETEs) and prostaglandins (PGs). Basal levels (pg/µg protein) of arachidonic acid metabolites differed significantly between rat and mouse lungs. Median values of the following major eicosanoids were significantly higher in mouse than in rat lungs: 5-HETE, 8-HETE, 12-HETE, 15-HETE, PGE2, and PGI2, as well as isoprostane-E2 and -F2α. In addition, the PGI2/TXB2 ratio was increased in mouse relative to rat lungs. On the basis of the important roles that these compounds play in determining pulmonary vascular tone, the differences in select eicosanoid profiles, especially the PGI2/TXB2 ratio, between rat and mouse lungs may underlie the interspecies differences in susceptibility to the development of pulmonary hypertension.

Mineralocorticoid receptor antagonism attenuates experimental pulmonary hypertension.

Mineralocorticoid receptor (MR) activation stimulates systemic vascular and left ventricular remodeling. 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 platelet-derived 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.