Characterization of sulfur-centered radical intermediates formed during the oxidation of thiols and sulfite by peroxynitrite. ESR-spin trapping and oxygen uptake studies.
Using a novel phosphorylated spin trap, 5-diethoxy-phosphoryl-5-methyl-1-pyrroline N-oxide (DEPMPO), an analog of the commonly used trap 5,5'-dimethyl-1-pyrroline N-oxide (DMPO), we have investigated the reactions of sulfur-centered radicals produced from the oxidation of thiols and sulfite by peroxynitrite. The predominant species trapped in all cases are the corresponding sulfur-centered radicals, i.e. glutathionyl radical (GS) from glutathione (GSH), N-acetyl-DL-penicillamine thiyl radical (S-NAP) from N-acetyl-DL-penicillamine (NAP) and sulfate anion radical (SO3-) from sulfite. These radicals consume molecular oxygen forming either peroxyl or superoxide anion radicals. GS, S-NAP, and (SO3-)-derived radicals react with ammonium formate to form the carbon dioxide anion radical (CO2-). Further support of spin adduct assignments and radical reactions are obtained from photolysis of S-nitrosoglutathione and S-nitroso-N-acetyl-DL-penicillamine. We conclude that the direct reaction of peroxynitrite with thiols and sulfate forms thiyl and sulfate anion radicals, respectively, by a hydroxyl radical-independent mechanism. Pathological implications of thiyl radical formation and subsequent oxyradical-mediated chain reactions are discussed. Oxygen activation by thiyl radicals formed during peroxynitrite-mediated oxidation of glutathione may limit the effectiveness of GSH against peroxynitrite-mediated toxicity in cellular systems.
Karoui
H
H
Biophysics Research Institute, Medical College of Wisconsin, Milwaukee 53226, USA.
Hogg
N
N
Fréjaville
C
C
Tordo
P
P
Kalyanaraman
B
B
D003497:Cyclic N-Oxides / Q000737:chemistry / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D005561:Formates / Q000737:chemistry / Q000378:metabolism; D005609:Free Radicals / Q000737:chemistry / Q000378:metabolism; D005978:Glutathione / Q000737:chemistry / Q000378:metabolism; D017665:Hydroxyl Radical / Q000737:chemistry / Q000378:metabolism; D066298:In Vitro Techniques; D015394:Molecular Structure; D009566:Nitrates / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction; D010396:Penicillamine / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism; D013113:Spin Labels; D013438:Sulfhydryl Compounds / Q000737:chemistry / Q000378:metabolism*; D013447:Sulfites / Q000737:chemistry / Q000378:metabolism*
D003497:Cyclic N-Oxides; D005561:Formates; D005609:Free Radicals; D009566:Nitrates; D013113:Spin Labels; D013438:Sulfhydryl Compounds; D013447:Sulfites; C030544:formic acid; C098505:5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide; C039642:peroxynitric acid; D017665:Hydroxyl Radical; C010005:N-acetylpenicillamine; C017245:5,5-dimethyl-1-pyrroline-1-oxide; D005978:Glutathione; D010396:Penicillamine