Upregulation of Steroidogenic Acute Regulatory Protein by Hypoxia Stimulates Aldosterone Synthesis in Pulmonary Artery Endothelial Cells to Promote Pulmonary Vascular Fibrosis

Abstract

Background The molecular mechanism(s) regulating hypoxia-induced vascular fibrosis are unresolved. Hyperaldosteronism correlates positively with vascular remodeling in pulmonary arterial hypertension (PAH), suggesting that aldosterone may contribute to the pulmonary vasculopathy of hypoxia. The hypoxia-sensitive transcription factors c-Fos/c-Jun regulate steroidogenic acute regulatory protein (StAR), which facilitates the rate-limiting step of aldosterone steroidogenesis. We hypothesized that c-Fos/c-Jun upregulation by hypoxia activates StAR-dependent aldosterone synthesis in human pulmonary artery endothelial cells (HPAECs) to promote vascular fibrosis in PAH. Methods and Results Patients with PAH, rats with Sugen/hypoxia-PAH, and mice exposed to chronic hypoxia expressed increased StAR in remodeled pulmonary arterioles, providing a basis for investigating hypoxia-StAR signaling in HPAECs. Hypoxia (2.0% FiO2) increased aldosterone levels selectively in HPAECs, which was confirmed by liquid chromatography-mass spectrometry. Increased aldosterone by hypoxia resulted from enhanced c-Fos/c-Jun binding to the proximal activator protein (AP-1) site of the StAR promoter in HPAECs, which increased StAR expression and activity. In HPAECs transfected with StAR-siRNA or treated with the AP-1 inhibitor, SR-11302, hypoxia failed to increase aldosterone, confirming that aldosterone biosynthesis required StAR activation by c-Fos/c-Jun. The functional consequences of aldosterone were confirmed by pharmacological inhibition of the mineralocorticoid receptor with spironolactone or eplerenone, which attenuated hypoxia-induced upregulation of the fibrogenic protein connective tissue growth factor and collagen III in vitro, and decreased pulmonary vascular fibrosis to improve pulmonary hypertension in Conclusions Our findings identify autonomous aldosterone synthesis in HPAECs due to hypoxia-mediated upregulation of StAR as a novel molecular mechanism that promotes pulmonary vascular remodeling and fibrosis.

Pulmonary Vascular and Ventricular Dysfunction in the Susceptible Patient (2015 Grover Conference Series)

“…154 However, diethylaminoethylcellulose chromatography and other sensitive methods have confirmed detectable expression levels of (fibrillar) collagen III and the profibrotic protein connective tissue growth factor (CTGF) in PAECs under basal conditions. 155,156 Importantly, however, CTGF-collagen III signaling is increased in PAECs exposed to hypoxia for 24 hours, 157 which is a time point well in advance of the 3-7-day duration necessary to complete EndMT. 152 Observations from coculture systems in vitro that demonstrate upregulation of fibrillar collagen synthesis in PASMCs and resident fibroblasts induced by PAECs overexpressing CTGF lend additional evidence indicating that EndMT is not required for vascular or perivascular fibrosis.…”

Absence of the inflammasome adaptor ASC reduces hypoxia-induced pulmonary hypertension in mice

“…Embedded tissue was sectioned transversely (5 m), and three slides from each animal were stained with hematoxylin and eosin, acid fuchsin orange G stain (AFOG), and Sirius red to assess collagen content around blood vessels. Image J software (NIH, Bethesda, MD) was used to measure the luminal area of small arteries stained with AFOG by subtracting the area of the lesser curvature from the greater curvature and dividing by the lesser curvature ϫ 100 (29).…”

Emerging Roles of the Mineralocorticoid Receptor in Pathology: Toward New Paradigms in Clinical Pharmacology

“…Spironolactone was also shown to limit skin (dermal) fibrosis (Mitts et al, 2010). In the lung, hypoxia-induced local secretion of aldosterone by pulmonary artery endothelial cells leads to pulmonary vascular fibrosis (Maron et al, 2014). Thus fibrotic actions of MR appear as a general feature that can be prevented by MRA.…”

“…-in the heart of rodents with myocardial infarction (Milik et al, 2007;Takeda et al, 2007), with diastolic heart failure (Ohtani et al, 2007), or with hypertension (Silvestre et al, 2000;Konishi et al, 2003); -in vessels of hypertensive animals (SHR) (DeLano and Schmid-Schonbein, 2004) or vascular cells in a model of normal aging (30-month-old Fisher344 cross-bred Brown Norway rats) (Krug et al, 2010); -in hypoxic pulmonary artery vascular endothelial cells (Maron et al, 2014); -in the kidney of Brown Norway rats (Cavallari et al, 2008) and in the renal collecting duct of spontaneously hypertensive rats (Farman and Bonvalet, 1985); -in adipose tissue from diabetic animal models (obese db/db and ob/ob mice, HFD) (Guo et al, 2008;Hirata et al, 2009Hirata et al, , 2012; in kidney from db/db mice and streptozotocin-treated rats (Guo et al, 2006); -in skin of mice with ultraviolet irradiation and metabolic syndrome .…”