Cellular DNA damage by hydrogen peroxide is attenuated by hypotonicity

• Published in: Biochemical journal Vol. 299; no. 1; pp. 137 - 140
• Main Authors: MARTINS, E. A. L, MENEGHINI, R
• Format: Journal Article
• Language: English
• Published: Colchester Portland Press 01-04-1994
• Subjects: Animals; Biological and medical sciences; Cell Line; Cell physiology; Cricetinae; Cricetulus; DNA Damage; Effects of physical and chemical agents; Fibroblasts - drug effects; Fibroblasts - metabolism; Fundamental and applied biological sciences. Psychology; Hydrogen Peroxide - toxicity; Molecular and cellular biology; Osmolar Concentration; Cell culture; Oxidative stress; Hypotonic solution; Lung; Rodentia; Environmental factor; Hydrogen Peroxides; Vertebrata; Cell line; Mammalia; Sensitivity resistance; DNA; Lesion; Hamster
• DOI: 10.1042/bj2990137
• EISSN: 1470-8728
• ISSN: 0264-6021

Chinese hamster fibroblasts (line V79) withstand well exposure for 30 min to hypotonic medium, corresponding to 25% physiological phosphate-buffered saline (PBS). Under these conditions, the cells become resistant to two effects of H2O2: DNA damage and inhibition of cell clone formation. The normal sensitivity to the DNA-damaging action of H2O2 is restored if, after exposure to hypotonic PBS, the cells are incubated in isotonic cell-culture medium. However, restoration of sensitivity is not observed on incubation in isotonic PBS. The normal sensitivity to H2O2 is also restored if one of the following reducing agents is added to hypotonic PBS: ascorbate, NADH and NADPH, in this order of decreasing efficiency. The recovery of sensitivity to H2O2 by ascorbate is completely inhibited by 1,10-phenanthroline, indicating that ascorbate is mediating the reduction of Fe(III). The decrease in the sensitivity to the DNA-damaging action of H2O2 is not a peculiarity of hypotonic PBS, since it appears to be caused by hypo-osmolarity in general: it is also observed in culture medium of 25% the isotonic concentration, and in 0.07 M sucrose. One explanation for this phenomenon is that hypotonic stress leads to a depletion of reducing species, in particular ascorbate. Under these conditions Fe(II) tends to be oxidized to Fe(III) and the Fenton chemistry is mitigated. However, other possibilities are that hypotonicity brings about structural modifications in the chromatin, rendering it less accessible to H2O2, or that it attenuates the Ca(2+)-activation of endonuclease, induced by oxidative stress.