Oxidative Damage of DNA Induced by Ferritin and Hydrogen Peroxide

摘要

Excess free iron generates oxidative stress that may contribute to the pathogenesis of various causes of neurodegenerative diseases. Previous studies have shown that one of the primary causes of increased brain iron may be the release of excess iron from intracellular iron storage molecules. In this study, we attempted to characterize the oxidative damage of DNA induced by the reaction of ferritin with H2O2. When DNA was incubated with ferritin and H2O2, DNA strand breakage increased in a time-dependent manner. Hydroxyl radical scavengers strongly inhibited the ferritin/H2O2 system-induced DNA cleavage. We investigated the generation of hydroxyl radical in the reaction of ferritin with H2O2 using a chromogen, 2,2'-azinobis-(2-ethylbenzthiazoline-6-sulfonate) (ABTS), which reacted with ·OH to form ABTS~(+·). The initial rate of ABTS~(+·) formation increased as a function of incubation time. These results suggest that DNA strand breakage is mediated in the reaction of ferritin with H2O2 via the generation of hydroxyl radicals. The iron-specific chelator, deferoxamine, also inhibited DNA cleavage. Spectrophotometric study using a color reagent showed that the release of iron from H2O2-treated ferritin increased in a time-dependent manner. Ferritin enhanced mutation of the lacZ gene in the presence of H2O2 when measured as a loss of α-comple-mentation. These results indicate that ferritin/H2O2 system-mediated DNA cleavage and mutation may be attributable to hydroxyl radical generation via aFenton-like reaction of free iron ions released from oxidatively damaged ferritin.