Oxidative stress and cardiovascular disease: the enemy within

Normally the body maintains a balance between its antioxidant defences and free radicals. But an imbalance can be dangerous...

Biochemical processes in the body generate reactive oxygen species (ROS) that are normally mopped up by antioxidant defence mechanisms. Under certain conditions
an imbalance can develop between the antioxidant defences and the formation of ROS. The resulting accumulation of ROS, called oxidative stress, enables them to interact with physiological mediators in the body. Such an interaction inactivates those mediators and can result in the formation of toxic products. An example of this is nitric oxide (NO), a blood vessel dilator and anti-thrombotic agent generated in the lining of blood vessels, which reacts with superoxide anion (O2-). This interaction inactivates NO, leading to a condition in which the blood vessels fail to respond normally to the beneficial stimuli of the blood vessel dilators. This condition is predictive of cardiovascular disease and occurs in subjects with risk factors but no overt symptoms of disease. The reaction between NO and O2- also leads to the formation of peroxynitrite, a powerful oxidant species that has been implicated in conditions such as hypercholesterolaemia, diabetes and coronary artery disease. Another example is prostacyclin, the generation of which is decreased by lipid peroxides produced by the interaction between normal lipids in the body and ROS.

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