Differential protection by nitroxides and hydroxylamines to radiation-induced and metal ion-catalyzed oxidative damage.
Modulation of radiation- and metal ion-catalyzed oxidative-induced damage using plasmid DNA, genomic DNA, and cell survival, by three nitroxides and their corresponding hydroxylamines, were examined. The antioxidant property of each compound was independently determined by reacting supercoiled DNA with copper II/1,10-phenanthroline complex fueled by the products of hypoxanthine/xanthine oxidase (HX/XO) and noting the protective effect as assessed by agarose gel electrophoresis. The nitroxides and their corresponding hydroxylamines protected approximately to the same degree (33-47% relaxed form) when compared to 76.7% relaxed form in the absence of protectors. Likewise, protection by both the nitroxide and corresponding hydroxylamine were observed for Chinese hamster V79 cells exposed to hydrogen peroxide. In contrast, when plasmid DNA damage was induced by ionizing radiation (100 Gy), only nitroxides (10 mM) provide protection (32.4-38.5% relaxed form) when compared to radiation alone or in the presence of hydroxylamines (10 mM) (79.8% relaxed form). Nitroxide protection was concentration dependent. Radiation cell survival studies and DNA double-strand break (DBS) assessment (pulse field electrophoresis) showed that only the nitroxide protected or prevented damage, respectively. Collectively, the results show that nitroxides and hydroxylamines protect equally against the damage mediated by oxidants generated by the metal ion-catalyzed Haber-Weiss reaction, but only nitroxides protect against radiation damage, suggesting that nitroxides may more readily react with intermediate radical species produced by radiation than hydroxylamines.
Xavier
Sandhya
S
Radiation Biology Branch, National Cancer Institute, Bldg. 10, Room B3/B69, 9000 Rockville Pike, Bethesda, MD 20892-1002, USA.
Yamada
Ken-ichi
K
Samuni
Ayelet M
AM
Samuni
Amram
A
DeGraff
William
W
Krishna
Murali C
MC
Mitchell
James B
JB
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D002460:Cell Line; D002470:Cell Survival; D003300:Copper; D003497:Cyclic N-Oxides / Q000494:pharmacology; D004247:DNA / Q000032:analysis / Q000187:drug effects / Q000528:radiation effects; D004249:DNA Damage; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D004586:Electrophoresis / Q000379:methods; D006861:Hydrogen Peroxide; D006898:Hydroxylamines / Q000494:pharmacology*; D009589:Nitrogen Oxides / Q000494:pharmacology*; D010084:Oxidation-Reduction; D010618:Phenanthrolines; D010957:Plasmids; D011837:Radiation-Protective Agents / Q000494:pharmacology*; D013113:Spin Labels; D014216:Triacetoneamine-N-Oxyl / Q000494:pharmacology
D000975:Antioxidants; D003497:Cyclic N-Oxides; D006898:Hydroxylamines; D009589:Nitrogen Oxides; D010618:Phenanthrolines; D011837:Radiation-Protective Agents; D013113:Spin Labels; C015527:4-amino-TEMPO; D014216:Triacetoneamine-N-Oxyl; D003300:Copper; D004247:DNA; D006861:Hydrogen Peroxide; C039900:nitroxyl; C001803:tempol; C025205:1,10-phenanthroline