Nitroxide-mediated protection against X-ray-and neocarzinostatin-induced DNA damage

• Published in: Free radical biology & medicine Vol. 13; no. 5; pp. 479 - 487
• Main Authors: DeGraff, William G., Krishna, Murali C., Kaufman, Dwight, Mitchell, James B.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.11.1992; Elsevier Science
• Subjects: Animals; Antimutagenicity; Biological and medical sciences; Cell Line; Cell Survival - drug effects; Cell Survival - radiation effects; CHO Cells; Cricetinae; Cyclic N-Oxides - pharmacology; DNA - drug effects; DNA - radiation effects; DNA Damage; Dose-Response Relationship, Drug; Dose-Response Relationship, Radiation; Effects of various physical factors on living matter (vibrations, electric field, ultrasound, sound...); Electron spin resonance; Free radicals; Fundamental and applied biological sciences. Psychology; Kinetics; Mutagenesis; Neocarzinostatin; Nitroxide; Pulsed field gel electrophoresis; Radiation; Radiation-Protective Agents - pharmacology; Spin Labels; Tissues, organs and organisms biophysics; X-Rays; Zinostatin - pharmacology; Free radicals; Electron spin resonance; Neocarzinostatin; Radiation; Nitroxide; Pulsed field gel electrophoresis; Antimutagenicity; Antimutagen; Gel electrophoresis; Rodentia; Spin wave resonance; Cytotoxicity; X ray; Free radical; Vertebrata; Mammalia; Cell line; DNA; Nitrogen monoxide; Damage; Protection; Hamster
• ISSN: 0891-5849; 1873-4596
• DOI: 10.1016/0891-5849(92)90142-4

The stable free radical Tempol (4-hydroxy-2,2,6,6-tetramethyl-piperidinyloxy) has been shown to protect against X-ray-unduced cytotoxicity and hydrogen peroxide- or xanthine oxidase-induced cytotoxicity and mutagenicity. The ability of Tempol to protect against X-ray- or neocarzinostatin (NCS)-induced mutagenicity or DNA double-strand breaks (dsb) was studied in Chinese hamster cells. Tempol (50 mM) provided a protection factor of 2.7 against X-ray-induced mutagenicity in Chinese hamster ovary (CHO) AS52 cells, with a protection factor against cytotoxicity of 3.5. Using the field inversion gel electrophoresis technique of measuring DNA dsb, 50 mM Tempol provides a threefold reduction in DNA damage at an X-ray dose of 40 Gy. For NCS-induced damage, Tempol increased survival from 9% to 80% at 60 ng/mL NCS and reduced mutation induction by a factor of approximately 3. DNA dsb were reduced by a factor of approximately 7 at 500 ng/mL NCS. Tempol is representative of a class of stable nitroxide free radical compounds that have superoxide dismutase-mimetic activity, can oxidize metal ions such as ferrous iron that are complexed to DNA, and may also detoxify radiation-induced organoperoxide radicals by competitive scavenging. The NCS chromophore is reduced by sulfhydryls to an active form. Electron spin resonance (ESR) spectroscopy shows that 2-mercaptoethanol-activated NCS reacts with Tempol 3.5 times faster than does unactivated NCS. Thus, Tempol appears to inactivate the NCS chromophore before a substantial amount of DNA damage occurs.