Oxygen free radicals in nephrology

For living creatures with an aerobic metabolism, the univalent reduction of oxygen can lead to formation within the cell of intermediate products with marked chemical instability and strong potential toxicity. These are the free radicals (FR) superoxide and hydroxyl, hydrogen peroxide and the singlet ¹O₂. Their toxicity is primarily expressed through the peroxidation of membrane lipids, resulting in mitochondrial, lysosomal and parietal damage. It is enhanced by the presence of metals in trace amounts. Imbalance between the production of FR and the availability of FR scavengers (superoxide dismutase, catalase, glutathione peroxidase, etc.) may underlie different human pathologies. FR have been thought to play a part in inflammation, the aging process, carcinomatous transformations, damage due to recirculation and autoimmune diseases. As far as the kidney is concerned, the intervention of FR has been demonstrated or can be postulated in various contexts in the light of what has been observed in other pathologies: immunological nephritis, toxic nephropathies, microthrombotic and microangiopathic processes, damage caused by postischemic reflow, and problems in the preservation and rejection of transplants. FR have also been incriminated in lung lesions following intradialytic leukostasis and some aspects of toxicity ascribable to uremia. Subjects to the precautions imposed by the need for theoretical, experimental and clinical verification, FR biochemistry offers new keys to the interpretation of a variety of kidney pathologies and opens up new prospects for treatment, both through a better understanding of the mechanism of action of drugs already known and employed, and with regard to the practical possibility of using alternative or combined forms of therapy.