Effect of superoxide dismutase mimics on radical adduct formation during the reaction between peroxynitrite and thiols--an ESR-spin trapping study.
We have reexamined the formation and reactions of radicals formed from peroxynitrite (ONOO-)-mediated oxidation of glutathione (GSH), L-cysteine (Cys), N-acetyl-D,L-penicillamine (NAP), and sodium bisulfite (NaHSO3). Sulfur-centered and superoxide union radicals were trapped using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and the radical adducts were analyzed by electron spin resonance (ESR) spectroscopy. The following sulfur-centered radicals were detected: glutathionyl radical (GS') from GSH, L-cysteinyl radical ('Scys) from L-cysteine, N-acetyl-D,L-penicillamine thiyl radical ('SNAP) from NAP, and sulfite anion radical (SO3-.) from NaHSO3. Additionally the formation of the hydroxyl radical adduct of DMPO (DMPO/'OH) was observed. DMPO/'OH formation was totally inhibited by low-molecular-weight superoxide dismutase (SOD) mimics. This suggests that DMPO/'OH was formed from the decay of the superoxide radical adduct of DMPO. In the presence of SOD mimics, the DMPO-sulfur-centered adducts were more persistent, suggesting that O2-. is partially responsible for the instability of DMPO-thiyl adducts. Sulfur-centered radicals formed during oxidation of thiols and sulfite by peroxynitrite react with ammonium formate to form the carbon dioxide anion radical (CO2-.). We conclude that sulfur-centered radicals produced from the oxidation of thiols and sulfite by peroxynitrite arise from a hydroxyl-radical-independent mechanism. Biological implications of peroxynitrite-mediated oxidation of thiols as well as the use of SOD mimics in biological spin-trapping are discussed.
Karoui
H
H
Biophysics Research Institute, Medical College of Wisconsin, Milwaukee 53226, USA.
Hogg
N
N
Joseph
J
J
Kalyanaraman
B
B
D003497:Cyclic N-Oxides; D003545:Cysteine / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D016166:Free Radical Scavengers; D005609:Free Radicals; D005978:Glutathione / Q000031:analogs & derivatives / Q000737:chemistry; D019803:Glutathione Disulfide; D007700:Kinetics; D009566:Nitrates / Q000737:chemistry*; D009942:Organometallic Compounds; D010100:Oxygen; D010396:Penicillamine / Q000031:analogs & derivatives / Q000737:chemistry; D013113:Spin Labels; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013447:Sulfites / Q000737:chemistry; D013482:Superoxide Dismutase / Q000378:metabolism*; D013481:Superoxides
D003497:Cyclic N-Oxides; D016166:Free Radical Scavengers; D005609:Free Radicals; D009566:Nitrates; D009942:Organometallic Compounds; D013113:Spin Labels; D013438:Sulfhydryl Compounds; D013447:Sulfites; D013481:Superoxides; C089774:SC 52608; C039642:peroxynitric acid; C010005:N-acetylpenicillamine; C017245:5,5-dimethyl-1-pyrroline-1-oxide; D013482:Superoxide Dismutase; D005978:Glutathione; D010396:Penicillamine; D003545:Cysteine; D010100:Oxygen; C009279:sodium bisulfite; D019803:Glutathione Disulfide