Effects of antioxidant enzymes in the molecular control of reactive oxygenspecies toxicology

Reactive Oxygen Species (ROS) are produced during normal cellular function. ROS include hydroxyl radicals, superoxide anion, hydrogen peroxide and nit ric oxide. They are very transient species due to their high chemical react ivity that leads to lipid peroxidation and oxidation of DNA and proteins. W hen ROS generation is increased to an extent that overcomes the cellular an tioxidants, the result is oxidative stress. It is now clear that several bi ological molecules, which are involved in cell signaling and gene regulatio n systems are very sensitive to redox statue of the cell. The various antio xidants exert their effect by scavenging superoxide, or by activating of a battery of detoxifying/defensive proteins. The prevention of oxidation is a n essential process in all the aerobic organisms, as decreased antioxidant protection may lead to cytotoxicity, mutagenicity and/or carcinogenicity. T his article also focuses on the mechanisms by which antioxidants and xenobi otics induce the gene expression of detoxifying enzymes. On the other hand, small molecules that mimic antioxidant enzymes are becoming new tools for the treatment of many diseases.