title: Glutathione propagates oxidative stress triggered by myeloperoxidase in HL-60 cells. Evidence for glutathionyl radical-induced peroxidation of phospholipids and cytotoxicity.
abstract: Glutathione acts as a universal scavenger of free radicals at the expense of the formation of the glutathionyl radicals (GS*). Here we demonstrated that GS* radicals specifically interact with a reporter molecule, paramagnetic and non-fluorescent 4-((9-acridinecarbonyl)-amino)-2,2,6,6-tetramethylpiperidine-1-oxyl (Ac-Tempo), and convert it into a non-paramagnetic fluorescent product, identified as 4-((9-acridinecarbonyl)amino)-2,2,6,6-tetramethylpiperidine (Ac-piperidine). Horseradish peroxidase-, myeloperoxidase-, and cyclooxygenasecatalyzed oxidation of phenol in the presence of H2O2 and GSH caused the generation of phenoxyl radicals and GS* radicals, of which only the latter reacted with Ac-Tempo. Oxidation of several other phenolic compounds (e.g. etoposide and tyrosine) was accompanied by the formation of GS* radicals along with a characteristic fluorescence response from Ac-Tempo. In myeloperoxidase-rich HL-60 cells treated with H2O2 and phenol, fluorescence microscopic imaging of Ac-Tempo revealed the production of GS* radicals. A thiol-blocking reagent, N-ethylmaleimide, as well as myeloperoxidase inhibitors (succinyl acetone and azide), blocked formation of fluorescent acridine-piperidine. H2O2/phenolinduced peroxidation of major classes of phospholipids in HL-60 cells was completely inhibited by Ac-Tempo, indicating that GS* radicals were responsible for phospholipid peroxidation. Thus, GSH, commonly viewed as a universal free radical scavenger and major intracellular antioxidant, acts as a pro-oxidant during myeloperoxidase-catalyzed metabolism of phenol in HL-60 cells.
authors.affiliation: Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA. grigoryb@yahoo.com
authors.forename: Grigory G
authors.initials: GG
authors.lastname: Borisenko
authors.forename: Ian
authors.initials: I
authors.lastname: Martin
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhao
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Amoscato
authors.forename: Yulia Y
authors.initials: YY
authors.lastname: Tyurina
authors.forename: Valerian E
authors.initials: VE
authors.lastname: Kagan
mesh_terms: D002470:Cell Survival; D016166:Free Radical Scavengers; D005609:Free Radicals / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism*; D018922:HL-60 Cells; D006801:Humans; D015227:Lipid Peroxidation; D018384:Oxidative Stress / Q000502:physiology*; D009195:Peroxidase / Q000378:metabolism*
chemical_list: D016166:Free Radical Scavengers; D005609:Free Radicals; D009195:Peroxidase; D005978:Glutathione