Free radicals in health and disease

The biological efficacy of oxidants is based on a highly regulated equilibrium between the production of oxygen radicals and the counteracting defense mechanisms of antioxidant scavenging systems and repair enzymes for the elimination of the degraded bioproducts. Imbalance of this finely tuned, sophisticated equilibrium can result in oxidative stress unleashing a cascade of pathological processes. This review summarizes the general characteristics of oxidative reactions and gives examples of some groups of diseases in which free radicals and reactive oxygen species (ROS) are thought to play a pivotal role. General aspects of the analytical methods used for the detection of an excess of free radicals are discussed together with a critical evaluation of the results obtained by their application. Free radicals are very reactive, shortlived and react in non-specific way. In spite of the broad array of existing analytical methods no routine diagnostic in vivo procedures are available to date. The results of fundamental research and clinical investigations have none-the-less focused the attention to the probably crucial role of free radicals in aging and in the pathogenesis of many human diseases. The development of more site-specific in vivo methods will enable the elucidation of the exact role of these very reactive radicals and molecular species. For the time being, the most important task of physicians and surgeons is to prevent all catalytic reactions known to initiate pro-oxidative stress and counteract the absolute or relative lack of antioxidants.