NOS3 and endothelial dysfunction: Nitric oxide (NO) produced from L-arginine by endothelial nitric oxide synthase (eNOS) exerts multiple beneficial functions, such as vasorelaxation, anti-inflammation and anti-apoptosis, in the vasculature and thus plays a critical role in vascular homeostasis and disorders.1 Abnormally decreased eNOS expression and activity, leading to impairment of the NO/cGMP pathway, are considered major contributors to the pathogenesis of various human diseases associated with endothelial dysfunction, such as hypertension, atherosclerosis and preeclampsia.1, 2, 3