NOS3 and pulmonary hypertension: eNOS was shown to be downregulated by hypoxia in vitro, in cultured human umbilical vein endothelial cells (HUVECs) [79,80,81,82,83], human coronary artery endothelial cells (HCAECs) [84], bovine pulmonary artery endothelial cells (PAECs) [85], human saphenous vein endothelial cells [86], as well as in vivo in the lungs of patients with pulmonary hypertension [87] or in aortas and mesenteric arteries of mice exposed to chronic intermittent hypoxia [88].