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Cellular DNA damage by hydrogen peroxide is attenuated by hypotonicity
1Department of Biochemistry, University of São Paulo, Brazil.
The Biochemical Journal
|April 1, 1994
Summary
Hypotonic stress protects Chinese hamster V79 cells from hydrogen peroxide (H2O2) DNA damage and clone formation inhibition. This protective effect is reversed by incubation in normal medium or by adding reducing agents like ascorbate.
Area of Science:
- Cell Biology
- Oxidative Stress Research
- Genotoxicology
Background:
- Chinese hamster V79 fibroblasts exhibit resistance to hydrogen peroxide (H2O2) under hypotonic conditions.
- Hypotonic stress protects cells from H2O2-induced DNA damage and impaired cell clone formation.
Purpose of the Study:
- To investigate the protective mechanisms of hypotonic stress against H2O2 toxicity in V79 cells.
- To identify factors influencing the restoration of H2O2 sensitivity after hypotonic exposure.
Main Methods:
- Exposure of V79 cells to hypotonic phosphate-buffered saline (PBS) and subsequent treatment with H2O2.
- Incubation in isotonic media or PBS with and without reducing agents (ascorbate, NADH, NADPH) post-hypotonic stress.
- Assessment of DNA damage and cell clone formation inhibition.
Main Results:
- Hypotonic stress (25% PBS) confers resistance to H2O2, reducing DNA damage and clone formation inhibition.
- Sensitivity is restored by incubation in isotonic cell-culture medium but not isotonic PBS.
- Reducing agents (ascorbate, NADH, NADPH) restore H2O2 sensitivity, with ascorbate's effect inhibited by 1,10-phenanthroline, suggesting Fe(III) reduction.
- Hypo-osmolarity in general, not just hypotonic PBS, causes this protective effect.
Conclusions:
- Hypotonic stress-induced resistance to H2O2 may involve depletion of reducing species, oxidation of Fe(II) to Fe(III), and mitigation of Fenton chemistry.
- Alternative explanations include hypotonicity-induced chromatin structural changes or attenuation of oxidative stress-induced endonuclease activation.