OxyFile #429

Oxidants and antioxidants. Biological effects and therapeutic 
perspectives

Author
Urban T; Hurbain I; Urban M; Clement A; Housset B

Source
Ann Chir, 49: 5, 1995, 427-34

Abstract

The main oxidizing free radicals (FR) are oxygen-derived 
metabolites (superoxide anion O2-, hydrogen peroxide H2O2, 
hydroxyl radical OH (zero)), hypochloric acid, chloramines, 
nitrogen dioxide, ozone and lipid peroxides. They are produced 
continually by living organisms, either in the intracellular 
compartment by the mitochondrial respiratory chain and mixed 
function oxidase system, or in the extracellular compartment, 
especially by phagocytes. The body possesses complex protective 
antioxidant systems against this potentially toxic production, 
such as dismutase superoxides, catalase, the glutathione enzyme 
system, metallic ion sequestration, enzymes degrading proteins 
injured by FR, metabolising hydroperoxides, and repairing DNA, and 
vitamins E, C, P, and betacarotene. A physiological steady-state 
is established under normal conditions between the production of 
oxidants and their neutralization by antioxidants. Oxidative 
lesions result from a disturbance of the oxidant-antioxidant 
balance. Oxygen-derived metabolites act on polyunsaturated cell 
membrane lipids, induce genetic alterations, and oxidize 
sulfhydryl groups of proteins, thereby modifying their functions. 
FR are involved in major physiological mechanisms such as 
phagocytosis, the inflammatory reaction, and the reperfusion 
ischaemia phenomenon observed during organ storage. The 
therapeutic use of enzymatic (SOD, catalase, GSH) and nonenzymatic 
antioxidants (vitamins E, N-acetylcysteine, allopurinol and 
oxypurinol) has yet to be evaluated. The current state of our 
knowledge indicates the extreme complexity of these systems and 
calls for caution in the therapeutic use of antioxidant 
substances.