The impairment of vasodilator NO production is well accepted as a typical marker of endothelial dysfunction in vascular diseases, including in the pathophysiology of Pulmonary Arterial Hypertension (PAH), but the molecular mechanisms accounting for loss of NO production are unknown. We hypothesized that low NO production by pulmonary arterial endothelial cells in PAH is due to inactivation of eNOS by aberrant phosphorylation of the protein. To test the hypothesis, we evaluated eNOS levels, dimerization and phosphorylation in the vascular endothelial cells and lungs of patients with PAH in comparison to controls. In mechanistic studies, eNOS activity in endothelial cells in PAH lungs was found to be inhibited due to phosphorylation at T495. Evidence pointed to greater phosphorylation/activation of Protein Kinase C (PKC) α and its greater association with eNOS as the source of greater phosphorylation at T495. The presence of greater amounts of pT495-eNOS in plexiform lesions in lungs of patients with PAH confirmed the pathobiologic mechanism in vivo. Transfection of the activating mutation of eNOS (T495A/S1177D) restored NO production in PAH cells. Pharmacologic blockade of PKC activity by β-blocker also restored NO formation by PAH cells, identifying one mechanism by which β-blockers may benefit PAH and cardiovascular diseases through recovery of endothelial functions.
- Endothelial cells
- Nitric oxide
- Protein kinases
- Copyright © 2016, American Journal of Physiology - Lung Cellular and Molecular Physiology