Nitrite generation and antioxidant effects during neutrophil apoptosis.
Neutrophil apoptosis is important for the resolution of airway inflammation in a number of lung diseases. Inflammatory mediators, endogenous reactive oxygen and nitrogen species, and intracellular and extracellular antioxidants may all influence neutrophil apoptosis. This study investigated the involvement of these factors during apoptosis of neutrophils cultured in vitro. Neutrophils undergoing spontaneous apoptosis in culture as assessed by annexin V binding generated significant amounts of nitrite. Incubation with agonistic anti-Fas monoclonal antibody or tumor necrosis factor-alpha (TNF-alpha) enhanced neutrophil apoptosis at 6 h, although it decreased nitrite accumulation. Although granulocyte-macrophage colony-stimulating factor significantly reduced neutrophil apoptosis, this was also associated with decreased nitrite accumulation. In contrast, inhibition of apoptosis at 16 h by dibutyryl cyclic adenosine monophosphate was associated with increased nitrite accumulation. Exogenous glutathione (GSH) or N-acetylcysteine significantly enhanced neutrophil apoptosis at 6 h and stimulated the production of H(2)O(2), which may mediate apoptosis through intracellular hydroxyl radical production. Intracellular GSH concentrations decreased in neutrophils undergoing apoptosis, and this was more marked in neutrophils treated with anti-Fas or TNF-alpha. These results suggest a causal association between reduced endogenous nitric oxide production, reduced intracellular GSH, and Fas- and TNF-alpha-mediated neutrophil apoptosis, whereas enhanced neutrophil survival mediated by dibutyryl cyclic adenosine monophosphate is associated with increased nitrite generation and maintenance of intracellular GSH. The interaction of endogenous reactive oxygen species with extracellular antioxidants such as GSH could also contribute to the complex processes regulating neutrophil apoptosis and hence the resolution of inflammation in the lung.
Misso
N L
NL
Asthma and Allergy Research Institute and Department of Medicine, The University of Western Australia, Sir Charles Gairdner Hospital, Perth, Australia.
Peacock
C D
CD
Watkins
D N
DN
Thompson
P J
PJ
D000111:Acetylcysteine / Q000494:pharmacology; D000328:Adult; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D000975:Antioxidants / Q000378:metabolism*; D017209:Apoptosis / Q000187:drug effects*; D003994:Bucladesine / Q000494:pharmacology; D053938:DNA Fragmentation; D005260:Female; D005978:Glutathione / Q000494:pharmacology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D008168:Lung / Q000473:pathology; D008297:Male; D009504:Neutrophils / Q000187:drug effects*; D009573:Nitrites / Q000378:metabolism*; D011485:Protein Binding; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D019014:fas Receptor / Q000276:immunology
D000911:Antibodies, Monoclonal; D000975:Antioxidants; D009573:Nitrites; D014409:Tumor Necrosis Factor-alpha; D019014:fas Receptor; D003994:Bucladesine; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D006861:Hydrogen Peroxide; D005978:Glutathione; D000111:Acetylcysteine