Vascular oxidant stress: Molecular mechanisms and pathophysiological implications

The term oxidative stress refers to a situation in which cells are exposed to excessive levels of either molecular oxygen or chemical derivatives of o xygen tie, reactive oxygen species). Three enzyme systems produce reactive oxygen species in the vascular wall: NADH/NADPH oxidase, xanthine oxidoredu ctase, and endothelial nitric oxide synthase. Among vascular reactive oxyge n species superoxide anion plays a critical role in vascular biology becaus e it is the source for many other reactive oxygen species and various vascu lar cell functions. It is currently thought that increases in oxidant stres s, namely excessive production of superoxide anion, are involved in the pat hophysiology of endothelial dysfunction that accompanies a number of cardio vascular risk factors including hypercholesterolemia, hypertension and ciga rette smoking. On the other hand, vascular oxidant stress plays a pivotal r ole in the evolution of clinical conditions such as atherosclerosis, diabet es and heart failure.