[Free radicals in human pathology].

The role of free radicals has been suggested in many different diseases; the molecular mechanisms of radical-induced damage have been widely investigated: the main effects on cellular components are lipid peroxidation, protein denaturation and DNA damage causing alteration in membrane functions, impaired enzyme activity and genetic alterations, including cancer. Since oxidative metabolism produces some radicals, aerobic organisms acquired a complex defensive system against radical attack, based on localization of oxidative reactions, enzymes that scavenge free radicals or their products and antioxidant vitamins. Diseases may arise from increased exposure to radicals or from impaired efficiency of protective systems. The role of oxygen radicals in cancerogenesis, alcoholic liver disease and the aging process is also briefly discussed.