Reactive oxygen species in tissue injury.

Reactive oxygen species (free radicals) are constantly formed in biological systems. They are removed by enzymatic and non-enzymatic defense systems such as superoxide dismutases, catalase, glutathione peroxidases, vitamin E, glutathione and vitamin C. Tissue injury such as lipid peroxidation results from an increased formation of reactive oxygen species, e.g. by the mitochondrial respiratory chain or by activated phagocytic cells, and/or a decreased antioxidant defense including a decreased repair capacity. In antioxidant therapy several specific and potent antioxidants are required.