NEUTROPHIL ANTIOXIDANT CAPACITY DURING THE RESPIRATORY BURST - LOSS OF GLUTATHIONE INDUCED BY CHLORAMINES

Low-molecular weight antioxidants in rat peritoneal neutrophils underg o rapid redox recycling, so measurements were made of their initial co ntent and subsequent changes during the respiratory but-st, when super oxide formation is maximized. Endogenous vitamin E, ascorbate and tota l glutathione (reduced - oxidized) were not significantly changed duri ng 30 min of respiratory burst, which was stimulated by phorbol 12-myr istate 13-acetate (PMA). When de novo synthesis of glutathione was inh ibited by buthionine-[S,R] sulfoximine (BSO), the glutathione content rapidly decreased in activated neutrophils but not in resting cells. T he lost total glutathione was recovered neither from the incubation me dium nor as a protein-bound form, which suggests that irreversible oxi dation of glutathione occurs. Furthermore, the glutathione loss contin ues even 30 min after PMA stimulation, when the respiratory burst has almost ceased. The decrease of glutathione was prevented by added cata lase, or by addition of NaN3 or KCN which inhibits myeloperoxidase (MP O). Superoxide dismutase had no protective effects. These findings sug gest the involvement of an MPO-H2O2-halide system in the accelerated c onsumption of glutathione during the respiratory burst. Additional stu dies showed that neutrophil-derived chloramines found in the extracell ular medium could lead to intracellular glutathione loss. Incubation o f resting cells with chemically produced membrane permeable monochlora mine in the presence of BSO resulted in a decrease of glutathione, whe reas membrane-impermeable taurine-chloramine was less effective. We co nclude that chloramines are responsible for accelerated glutathione tu rnover in neutrophils during the respiratory burst. Permeable extracel lular chloramines derived from the respiratory burst activity, such as monochloramine, can reenter cells and react with thiols. (C) 1997 Els evier Science Inc.