HMOX1 and pulmonary arterial hypertension: Indeed, in Prx2−/− we observed (i) increased expression of heme-oxygenase 1 (HO-1), a Nrf2 related cytoprotective system; (ii) markers of vascular endothelial activation such as endothelin-1 (ET-1) and vascular cell adhesion molecule -1 (VCAM-1) and (iii) marker of extracellular matrix remodeling as the platelet growth factor- B (PDGF-B) that has been recently function linked to the development of pulmonary artery hypertension (Fig. 2B).