[Oxidative stress and endothelial dysfunction].

Endothelial dysfunction and oxidative stress are the main pathophysiological mechanisms of several diseases such as hypertension, atherosclerosis, dyslipidemia, diabetes mellitus, cardiovascular disease, renal failure and ischemia-reperfusion injury. Reactive oxygen species (ROS) can modulate cellular function, receptor signals and immune responses in physiological conditions, but when present in excess, they mediate progressive endothelial damage through growth and migration of vascular smooth muscle and inflammatory cells, alteration of extracellular matrix, apoptosis of endothelial cells, activation of transcription factors (NFkB, AP-1), over-expression of inflammatory cytokines and adhesion molecules (ICAM-1, VCAM-1 , E-selectin). Recent evidences suggest that the major source of ROS is the NADPH-oxidase, especially activated by angiotensin II, shear stress and hyperglycemia. The unbalance between production of free radicals and the ability to neutralize them by antioxidant systems causes a condition of "oxidative stress". ROS alter vascular tone by increasing concentration of cytosolic calcium and especially causing a decreased availability of nitric oxide, the principal agent of endothelial function with vasodilating action. The data emerged from experimental and clinical studies confirm that endothelium-dependent vasodilation is altered in many diseases.