Selective down-regulation of the expression of Kv α subunits (Kv1.1, Kv1.5, Kv2.1, Kv4.3, Kv9.3) in PASMC via HIF1α occurs during chronic hypoxia; this signalling pathway is abnormally potentiated by ROS during PAH [71,72]. The gene discussed is KCNA5; the disease is pulmonary arterial hypertension.