Biochemical aspects of cellular oxidative stress.

Oxidative stress, as proposed by H. Sies, indicates a change in the prooxidant/antioxidant balance of a biologic system in favour of the former. It is related to oxidative reactions that occur in aerobic metabolism which can damage biomolecules through generation of reactive oxygen species. The oxidative deterioration of polyunsaturated fatty acids of membrane phospholipids (lipid peroxidation) is one of the consequences of oxidative stress, and has been observed in the liver cell under the influence of ethanol or lindane intoxication, associated with the calorigenic action of thyroid hormones, induced by the rupture of t-butyl hydroperoxide by cellular hemoproteins, or in the autoxidation of a disrupted tissue. Apart from noxious challenges, oxidative free-radical processes are important in numerous physiological reactions, such as NADPH oxidase in the function of macrophages, ribonucleotide reduction in DNA metabolism, or in eicosanoids production.