Abstract 10052: Endothelin-1 is a Potent Stimulus for Aldosterone Synthesis in Pulmonary Artery Endothelial Cells
Elevated levels of endothelin-1 (ET) are associated with increased pulmonary vascular tone; however, the role of ET-mediated synthesis of pressor hormones to account for this observation is unknown. We hypothesized that in human pulmonary artery endothelial cells (HPAECs), ETB receptor stimulation by ET induces the synthesis of aldosterone (ALDO). To test this hypothesis, HPAECs were incubated with ET (10-8 mol/L) or vehicle (V) for 24 hr. Compared to V, ET significantly increased ALDO levels in the media (88.5±20.8 vs. 239.9±24.1 pg/μg protein, p<0.04) whereas co-incubation of ET with the selective ETB receptor antagonist BQ-788 (1.5 μM) fully inhibited ET-induced ALDO synthesis (p=NS compared to V). ET increased ALDO levels by upregulating expression of ALDO synthase (CYP11B2) in HPAECs by 226% (p<0.05). To explore a mechanism by which ET increased ALDO synthase expression, we examined the transcription factors PPARγ coactivator 1-α (PGC1α) and steroidogenesis factor-1 (SF), previously shown to increase ALDO synthase expression in adrenal cells. We found that ET increased PGC1α protein expression by 496% compared to V (p<0.05), and co-immunoprecipitation revealed that ET enhanced binding of PGC1α to SF (1111±103 vs. 1881±179 arb. units, p<0.03). Chromatin immunopercipitation demonstrated that compared with V, ET significantly increased SF binding to the promoter region of ALDO synthase (16.3±9.8 vs. 61.6±9.3 arb. units, p<0.03). We further confirmed that PGC1α modulates ALDO synthesis by showing that compared with V, the PGC1α agonist pioglitazone (50 μM for 24 hr) increased ALDO levels by 330% (p<0.05). These data demonstrate that ET induces the synthesis of ALDO in HPAECs by increasing PGC1α-mediated binding of SF to ALDO synthase. Identifying ALDO as a novel product of ET signaling in HPAECs has important therapeutic implications for regulating pulmonary vascular tone in patients with pulmonary vascular disease.
- © 2011 by American Heart Association, Inc.