NOX1 and pulmonary arterial hypertension: Indeed, recently it has been shown that GKT137831, an inhibitor of Nox1 and Nox4, attenuated hypoxia-induced TGF-β1 expression and proliferation of human pulmonary artery endothelial and smooth muscle cells in vitro, as well as attenuated pulmonary artery wall thickening and vascular remodelling in vivo, features which are all characteristic of idiopathic pulmonary hypertension [6].