EDN1 and endothelial dysfunction: Recently, it has been suggested that endothelial cells are more involved than alveolar epithelial cells in alveolar gas exchange and have a greater impact on COPD pathogenesis.[21] ET-1 is a marker of endothelial dysfunction that acts as a vasoactive mediator, leading to vasoconstriction and vascular wall proliferation.[20,22] In smokers, accelerated lung aging, influenced by cigarette smoking, plays an important role in the development of COPD.