Platelet activity markers, like P-selectin and mean platelet volume (MPV), also highlight a pro-thrombotic state in COPD patients (30, 31), while other generical markers of oxidative stress, such as peroxynitrite, ADMA, vascular cell adhesion molecule-1 (VCAM-1), and malondialdehyde have been used to assess ED, alongside circulating endothelial cells (CECs), EPCs, or endothelin-1 (ET-1), which are deemed to be more specific to endothelial function (32). This evidence concerns the gene EDN1 and chronic obstructive pulmonary disease.