Abstract

Endothelial cell (EC) dysfunction plays a role in the pathobiology of occlusive vasculopathy in pulmonary arterial hypertension (PAH). Purinergic signalling pathways, which consists of extracellular nucleotide and nucleoside mediated cell signalling through specific receptors, are known to be important regulators of vascular tone and remodelling. Therefore, we hypothesized that abnormalities in the vascular purinergic microenvironment are associated with PAH. Enzymatic clearance is crucial to terminate unnecessary cell activation; one of the most abundantly expressed enzyme on EC surface is E-NTPDase1/CD39, which hydrolyses ATP and ADP to AMP. We used histological samples from patients and healthy donors, radioisotope labelled substrates to measure ecto-enzyme activity, and a variety of in vitro approaches to study the role of CD39 in PAH. Immunohistochemistry on human idiopathic PAH patients' lungs demonstrated that CD39 was significantly down-regulated in the endothelium of diseased small arteries. Similarly, CD39 expression and activity were decreased in cultured pulmonary ECs from IPAH patients. Suppression of CD39 in vitro resulted in EC phenotypic switch that gave rise to apoptosis resistant pulmonary arterial endothelial cells, and promoted a microenvironment that induced vascular smooth muscle cell migration. We also identified that the ATP receptor P2Y11 is essential for ATP-mediated EC survival. Furthermore, we report that apelin, a known regulator of pulmonary vascular homeostasis, can potentiate the activity of CD39 both in vitro and in vivo. We conclude that sustained attenuation of CD39 activity through ATP accumulation is tightly linked to vascular dysfunction and remodelling in PAH and could represent a novel target for therapy.

View details for DOI 10.1152/ajplung.00340.2014

View details for PubMedID 25820525