title: Free radical modes of cytotoxicity of adriamycin and streptonigrin.
abstract: Free radical modes of cytotoxicity of streptonigrin (STN) and Adriamycin (ADR) in Chinese hamster V79 cells under aerobic conditions were evaluated using 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TP), a low molecular weight stable nitroxide free radical with antioxidant properties and desferrioxamine (DF), a transition metal chelator. In addition, exogenous superoxide dismutase (SOD, EC 1.15.1.1) and catalase (CAT, EC 1.11.1.6), were tested for cytoprotective effects. EPR studies showed that TP reacts with the semiquinones of both ADR and STN and also with O2- radicals generated during aerobic redox cycling of the respective semiquinone radicals. Pulsed field gel electrophoresis studies confirmed that DNA double-strand breaks (dsb) induced by STN in V79 cells were inhibited completely by TP, whereas ADR-induced DNA dsb were not affected by TP. Clonogenic cell survival studies showed that STN-induced cytotoxicity could be inhibited completely by DF or TP. Both agents were ineffective in inhibiting ADR-induced cytotoxicity. SOD and CAT were ineffective in protecting against both STN and ADR cytotoxicity. Our results are consistent with a mechanism requiring the semiquinone radical intermediate of STN for cytotoxicity and minimal free radical involvement in ADR-induced V79 cell cytotoxicity.
authors.affiliation: Radiation Biology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.
authors.forename: W
authors.initials: W
authors.lastname: DeGraff
authors.forename: S M
authors.initials: SM
authors.lastname: Hahn
authors.forename: J B
authors.initials: JB
authors.lastname: Mitchell
authors.forename: M C
authors.initials: MC
authors.lastname: Krishna
mesh_terms: D000818:Animals; D002374:Catalase / Q000494:pharmacology; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D006224:Cricetinae; D003412:Cricetulus; D003497:Cyclic N-Oxides / Q000037:antagonists & inhibitors / Q000494:pharmacology; D004249:DNA Damage; D003676:Deferoxamine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin / Q000494:pharmacology*; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D009245:NADH Dehydrogenase; D011809:Quinones / Q000737:chemistry; D013113:Spin Labels; D013308:Streptonigrin / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D013482:Superoxide Dismutase / Q000494:pharmacology
chemical_list: D003497:Cyclic N-Oxides; D005609:Free Radicals; D011809:Quinones; D013113:Spin Labels; D013308:Streptonigrin; D004317:Doxorubicin; D002374:Catalase; D013482:Superoxide Dismutase; D009245:NADH Dehydrogenase; D003676:Deferoxamine; C001803:tempol