iron and its sensitive balance in the cell.pdf

Mutation Research 475 (2001) 153–159 Review Iron and its sensitive balance in the cell Jeane M. De Freitas, Rogerio Meneghini ? Departamento de Bioquimica, Instituto de Quimica, Universidade de S?o Paulo, CP 26077, 05599-970 S?o Paulo, SP, Brazil Received 18 March 2000; received in revised form 12 June 2000; accepted 13 June 2000 Abstract Iron is vital in life because it is an important component of molecules that undergoes redox reactions or transport oxygen. However, the existence of two stable and inter-convertible forms of iron, iron(III) and iron(II), makes possible one electron being transferred to or captured from other species to form radicals. In particular, superoxide and hydroxyl radicals may be formed in these reactions, both with capacity of attacking other molecules. DNA is one important target and a vast literature exists showing that attack of hydroxyl radical to DNA leads to cell death cellular necrosis, apoptosis, mutation and malignant transformation. Therefore, a fine balance must exist at various levels of an organism to maintain iron concentration in a narrow range, above and bellow which deleterious effects of distinct nature occur. This review will deal with the formation of oxygen reactive species in iron participating reactions, defenses in the organism against these species, the different mechanisms of iron homeostasis and iron deficiency and iron overload related diseases. ? 2001 Elsevier Science B.V. All rights reserved. Keywords: Iron; Reactive oxygen species; Antioxidant enzymes; Oxidative stress 1. Introduction Iron is vital in life because it is an important component of molecules that undergoes redox reac- tions in cells. However, this property also makes iron potentially toxic, since redox reactions may generate reactive oxygen species (ROS) [1,2]. In fact, ROS are known to damage proteins, lipids and DNA [3,4]. As a consequence, cells and organisms have developed several mechanisms to reduce toxicity by iron ions, which include a