Mammalian Cells Are Not Killed by DNA Single-Strand Breaks Caused by Hydroxyl Radicals from Hydrogen Peroxide

Cell killing by ionizing radiation has been shown to be caused by hydroxyl free radicals formed by water radiolysis. We have previously suggested that the killing is not caused by individual OH free radicals but by the interaction of volumes of high radical density with DNA to cause locally multiply...

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Bibliographic Details
Published in:Radiation research 1985-09, Vol.103 (3), p.383-392
Main Authors: Ward, John F., Blakely, William F., Joner, Eva I.
Format: Article
Language:English
Subjects:
Animals
Biological and medical sciences
Cell Line
Cell physiology
Cell Survival - drug effects
Cricetinae
Cricetulus
DNA
DNA damage
DNA, Single-Stranded
Dose-Response Relationship, Drug
Effects of physical and chemical agents
Flood damage
Free radicals
Fundamental and applied biological sciences. Psychology
Hydrogen
Hydrogen Peroxide - pharmacology
Hydroxides - pharmacology
Hydroxyl Radical
Hydroxyl radicals
In Vitro Techniques
Ionizing radiation
Metal ions
Molecular and cellular biology
Peroxides
Radiation damage
Space life sciences
Time Factors
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Summary:Cell killing by ionizing radiation has been shown to be caused by hydroxyl free radicals formed by water radiolysis. We have previously suggested that the killing is not caused by individual OH free radicals but by the interaction of volumes of high radical density with DNA to cause locally multiply damaged sites (LMDS) (J. F. Ward, Radiat. Res. 86, 185-195, 1985). Here we test this hypothesis using hydrogen peroxide as an alternate source of OH radicals. The route to OH production from H2 O2 is expected to cause singly damaged sites rather than LMDS. Chinese hamster V79-171 cells were treated with H2 O2 at varying concentrations for varying times at 0°C. DNA damage produced intracellularly was measured by alkaline elution and quantitated in terms of Gray-equivalent damage by comparing the rate of its elution with that of DNA from γ-irradiated cells. The yield of DNA damage produced increases with increasing concentration of H2 O2 and with time of exposure. H2 O2 is efficient in producing single-strand breaks; treatment with 50 μM for 30 min produces damage equivalent to that formed by 10 Gy of γ irradiation. In the presence of a hydroxyl radical scavenger, dimethyl sulfoxide (DMSO), the yield of damage decreases with increasing DMSO concentration consistent with the scavenging of hydroxyl radicals traveling an average of 15 Å prior to reacting with the DNA. In contrast to DNA damage production, cell killing by H2 O2 treatment at 0°C is inefficient. Concentrations of $5\times 10^{-2}\ M\ {\rm H}_{2}{\rm O}_{2}$ for 10 min are required to produce significant cell killing; the DNA damage yield from this treatment can be calculated to be equivalent to 6000 Gy of γ irradiation. The conclusion drawn is that individual DNA damage sites are ineffectual in killing cells. Mechanisms are suggested for killing at 0°C at high concentrations and for the efficient cell killing by H2 O2 at 37°C at much lower concentrations.
ISSN:0033-7587
1938-5404
DOI:10.2307/3576760