DNA damages induced by selenite in the presence of glutathione

• Published in: Biomedical research on trace elements Vol. 19; no. 4; p. 317
• Main Authors: Saito, Yoshihiro, Baba, Yoshiko, Sato, Takaji, Chikuma, Masahiko
• Format: Journal Article
• Language: English
• Published: Osaka Japan Science and Technology Agency 01.10.2008
• ISSN: 0916-717X; 1880-1404

Reactive chemical species involved in the single strand breaks of plasmid DNA, which was induced by sodium selenite and excess amount of reduced glutathione (GSH), were investigated. DNA damages were analyzed by agarose gel electrophoresis after DNA was incubated with selenite and glutathione in the presence or absence of several reagents to modify the level of reactive oxygen species which may be produced during the incubation in Tris-borate-EDTA (TBE) buffer (pH8.2). The addition of neither superoxide dismutase nor catalase affected the DNA damages, and the treatment of DNA with superoxide anion produced by hypoxanthine-xanthine oxidase system or exogenous hydrogen peroxide did not reproduce DNA damages induced by selenite and GSH. The results suggested that superoxide anion and hydrogen peroxide may not be the species responsible for DNA damages. Both mannitol and deferoxamine, which are expected to scavenge hydroxyl radical or inhibit hydroxyl radical production, lowered the electrophoretic band strength corresponding to open circular form, indicating that they protected the DNA from single strand breaks. DNA damages were induced by hydroxyl radical generating system of hydrogen peroxide and iron(II) ion. It was suggested that hydroxyl radical may be a species which causes DNA damages induced by selenite and GSH. In the study with isolated selenodiglutathione (GSSeSG), which is the intermediate formed by the reaction of selenite and GSH, single strand break of DNA was observed when DNA was incubated with GSSeSG and excess amount of GSH though it was not when DNA was incubated with GSSeSG alone. These results indicated that GSSeSG itself is not a species responsible for DNA damages induced by selenite and excess amount of GSH and that hydroxyl radical produced in the processes of GSSeSG decomposition with excess GSH may be a major species causing single strand breaks of DNA.