Oxidant-induced DNA damage of target cells.

Abstract

In this study we examined the leukocytic oxidant species that induce oxidant damage of DNA in whole cells. H202 added extracellularly in micromolar concentrations (10-100 MM) induced DNA strand breaks in various target cells. The sensitivity of a specific target cell was inversely correlated to its catalase content and the rate of removal of H202 by the target cell. Oxidant species produced by xanthine oxidase/purine or phorbol myristate acetate-stimulated monocytes induced DNA breakage of target cells in proportion to the amount of H202 generated. These DNA strand breaks were prevented by extracellular catalase, but not by superoxide dismutase.Cytotoxic doses of HOCI, added to target cells, did not induce DNA strand breakage, and myeloperoxidase added extracellularly in the presence of an H202-generating system, prevented the formation of DNA strand breaks in proportion to its H202 degrading capacity.The studies also indicated that H202 formed hydroxyl radical (OH) intracellularly, which appeared to be the most likely free radical responsible for DNA damage: OH was detected in cells exposed to H202; the DNA base, deoxyguanosine, was hydroxylated in cells exposed to H202; and intracellular iron was essential for induction of DNA strand breaks.

Stimulated human leukocytes cause activating mutations in the K-ras proto-oncogene

“…Following incubation, DNA mixtures were centrifuged at 10 000 g for 5 s to pellet neutrophils; and supernatants were transferred to clean tubes. To determine if an enzymatic O 2 7 ⋅ and H 2 O 2 -generating system can cause K-ras oncogene activation, 10 mg of K-ras 4B plasmid DNA was incubated with purine (7H-Imidazo[4,5-d]pyrimidine, 2 mM) and xanthine oxidase (0.005 m/ml) (Schraufstatter et al, 1988), in a ®nal volume of 100 ml of PBS for 1 h at 378C.…”

“…Stimulated leukocytes release superoxide anion (O 2 7 ⋅ ) and hydrogen peroxide (H 2 O 2 ) (Babior, 1978). Although neither of these oxygen metabolites appear to be directly toxic to DNA (Halliwell and Aruoma, 1991), H 2 O 2 can di use into target cells and react with iron (or other transition metals) that is either bound to or in close proximity to DNA (Schraufstatter et al, 1988;Halliwell, 1987). Reaction of H 2 O 2 with iron generates the very potent oxidant, hydroxyl radical ( .…”

Mobilization of iron from cellular ferritin by ascorbic acid in neuroblastoma SK‐N‐SH cells: an EPR study

“…If iron is released unspecifically from the ferritin core it would catalyze -like any other form of adventitious cellular iron the formation of hydroxyl radicals via Haber-Weiss-Fenton reaction cycles [14]. The hydroxyl radical gives rise to a radical reaction chain inducing, e.g., DNA strand breaks [15,16] and generating lipid peroxidation products [17]. Such a process eventually could lead to cell death.…”

DNA strand breakage and base modification induced by hydrogen peroxide treatment of human respiratory tract epithelial cells

“…Damage to DNA, usually measured as strand breakage, has been shown to occur in many cell types in response to oxidative stress [1][2][3][4][5]. However, little is known about the mechanism of this damage.…”

“…Possible mechanisms include rises in intracellular free Ca 2+ that are sufficient to activate endonucleases [6] and direct attack on DNA by highly reactive radicals, such as hydroxyl, OH ° [2,7,8]. Consistent with direct free radical attack on DNA, several groups have reported increases in 8-hydroxy-2'-deoxyguanosine (8OHdG) in mammalian cells exposed to oxidative stress [1,5,[9][10][11]. However, the extent of the increase is often small (sometimes less than the reported variability between measurements of 'normal' levels of 8OHdG in cells [12]), which has led several authors to doubt the significance of oxidative base modification in causing DNA damage.…”