Elafin Reverses Pulmonary Hypertension via Caveolin-1–Dependent Bone Morphogenetic Protein Signaling

Abstract

Rationale: Pulmonary arterial hypertension is characterized by endothelial dysfunction, impaired bone morphogenetic protein receptor 2 (BMPR2) signaling, and increased elastase activity. Synthetic elastase inhibitors reverse experimental pulmonary hypertension but cause hepatotoxicity in clinical studies. The endogenous elastase inhibitor elafin attenuates hypoxic pulmonary hypertension in mice, but its potential to improve endothelial function and BMPR2 signaling, and to reverse severe experimental pulmonary hypertension or vascular pathology in the human disease was unknown.Objectives: To assess elafin-mediated regression of pulmonary vascular pathology in rats and in lung explants from patients with pulmonary hypertension. To determine if elafin amplifies BMPR2 signaling in pulmonary artery endothelial cells and to elucidate the underlying mechanism.Methods: Rats with pulmonary hypertension induced by vascular endothelial growth factor receptor blockade and hypoxia (Sugen/ hypoxia) as well as lung organ cultures from patients with pulmonary hypertension were used to assess elafin-mediated reversibility of pulmonary vascular disease. Pulmonary arterial endothelial cells from patients and control subjects were used to determine the efficacy and mechanism of elafin-mediated BMPR2 signaling. Measurements and Main Results:In Sugen/hypoxia rats, elafin reduced elastase activity and reversed pulmonary hypertension, judged by regression of right ventricular systolic pressure and hypertrophy and pulmonary artery occlusive changes. Elafin improved endothelial function by increasing apelin, a BMPR2 target. Elafin induced apoptosis in human pulmonary arterial smooth muscle cells and decreased neointimal lesions in lung organ culture. In normal and patient pulmonary artery endothelial cells, elafin promoted angiogenesis by increasing pSMAD-dependent and -independent BMPR2 signaling. This was linked mechanistically to augmented interaction of BMPR2 with caveolin-1 via elafin-mediated stabilization of endothelial surface caveolin-1.Conclusions: Elafin reverses obliterative changes in pulmonary arteries via elastase inhibition and caveolin-1-dependent amplification of BMPR2 signaling.

RNA Sequencing Analysis Detection of a Novel Pathway of Endothelial Dysfunction in Pulmonary Arterial Hypertension

“…The new data suggest that optimizing BMPR2 receptor function (5,20) may allow for normalization of a wide range of targets. n Author disclosures are available with the text of this article at www.atsjournals.org.…”

“…Cardiac function and output were assessed by echocardiography and right ventricular (RV) systolic pressure was measured by closed chest technique (20). RV hypertrophy was assessed as the weight of the RV relative to left ventricle (LV) plus septum.…”

“…Lungs were perfused with normal saline and fixed for routine histology, and morphometric analysis performed as previously described (5). Mouse lung tissue sections were stained with fluorescent antibodies for von Willebrand factor and a-smooth muscle actin as previously described (20).…”

Induced Pluripotent Stem Cell Model of Pulmonary Arterial Hypertension Reveals Novel Gene Expression and Patient Specificity

“…Both in humans with PAH and in experimental pulmonary hypertension (PH), there is pulmonary arterial (PA) endothelial cell (EC) dysfunction characterized by susceptibility to apoptosis associated with loss of peripheral arteries (3), reduced adhesion related to impaired regeneration (4), decreased migration (5) and tube formation in angiogenesis assays (3), as well as heightened glycolysis, and emergence of apoptosis-resistant cells (6).…”

“…Reduced BMPR2 is associated with impaired adhesion and migration of PA endothelial cells (PAEC) related to decreased expression of downstream targets collagen (COL) 4A1 and A2 and Ephrin A1 (5), heightened susceptibility to inflammation (7), and defects in cytoskeletal protein phosphorylation (8). In addition, decreased BMPR2 suppresses downstream activation of mothers against decapentaplegic homolog proteins (SMAD)1/5 and transcription of the early response gene inhibitor of DNA binding 1 (ID1) (9) that regulates angiogenesis (10), and SMAD1/5 independent signaling (3,9).…”