title: Doxorubicin-mediated free radical generation in intact human tumor cells enhances nitroxide electron paramagnetic resonance absorption intensity decay.
abstract: The decay of nitroxide spin label electron paramagnetic resonance (EPR) absorption intensity was used to investigate the doxorubicin-mediated intracellular generation of free radicals. The effects of 50-500 micrograms/ml doxorubicin on human tumor cells (MCF-7, breast cancer cells, and HL-60, promyelocytic leukemia, cells) were studied by measuring 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) absorption intensity decay (TAID) at a TEMPO concentration of 10 microM. Doxorubicin accelerated the TAID in both cell lines with a detection limit of 50 micrograms/ml for MCF-7 cells and 500 micrograms/ml doxorubicin for HL-60 cells. Preincubation of cells with the iron chelating agent, deferoxamine (5 mM), partially prevented the effects of doxorubicin on the TAID. Catalase and copper, zinc-superoxide dismutase (Cu,Zn-SOD) had no influence on the effects of doxorubicin on the TAID in intact cells. However, Cu,Zn-SOD completely abolished the effects of doxorubicin on the TAID in a MCF-7 cell-free system. Our findings suggest that doxorubicin mediates the intracellular generation of O2.- and that iron is involved in this process.
authors.affiliation: Department of Internal Medicine, University Hospital Utrecht, The Netherlands.
authors.forename: E E
authors.initials: EE
authors.lastname: Voest
authors.forename: E
authors.initials: E
authors.lastname: Van Faassen
authors.forename: J P
authors.initials: JP
authors.lastname: Neijt
authors.forename: J J
authors.initials: JJ
authors.lastname: Marx
authors.forename: B S
authors.initials: BS
authors.lastname: Van Asbeck
mesh_terms: D003497:Cyclic N-Oxides; D004317:Doxorubicin / Q000494:pharmacology*; D004578:Electron Spin Resonance Spectroscopy; D005434:Flow Cytometry; D005609:Free Radicals; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D013113:Spin Labels; D014407:Tumor Cells, Cultured / Q000187:drug effects* / Q000378:metabolism
chemical_list: D003497:Cyclic N-Oxides; D005609:Free Radicals; D013113:Spin Labels; D004317:Doxorubicin; D006861:Hydrogen Peroxide; C003959:TEMPO