Reactive oxygen species limit neutrophil life span by activating death receptor signaling.
Neutrophils are abundant, short-lived leukocytes, and their death by apoptosis is central to hemostasis and the resolution of inflammation, yet the trigger for their entry into apoptosis is unknown. We show here that death receptor signaling, including CD95 death-inducing signaling complex (DISC) formation and caspase 8 activation, occurred early in neutrophil apoptosis. However, death receptor ligation was not required for apoptosis, suggesting a novel mechanism for caspase 8 activation. We detected ceramide generation and clustering of CD95 in lipid rafts early in neutrophil apoptosis, and neutrophil apoptosis and ceramide generation were both significantly inhibited in acid sphingomyelinase knockout (ASM(-/-)) mice compared to wild-type littermates. Further studies revealed that ceramide generation, CD95 clustering, and neutrophil apoptosis were dependent on reactive oxygen species (ROSs) and were preceded by a fall in reduced glutathione levels. We propose that accumulation of ROSs, as a consequence of altered redox status, initiates ligand-independent death receptor signaling via activation of ASM and clustering of preformed DISC components in lipid rafts and is therefore a primary factor limiting neutrophil life span.
Scheel-Toellner
Dagmar
D
MRC Centre for Immune Regulation, Division of Immunity and Infection, The Medical School, University of Birmingham, Birmingham B15 2TT, United Kingdom.
Wang
Keqing
K
Craddock
Rachel
R
Webb
Paul R
PR
McGettrick
Helen M
HM
Assi
Lakhvir Kaur
LK
Parkes
Neal
N
Clough
Louise E
LE
Gulbins
Erich
E
Salmon
Mike
M
Lord
Janet M
JM
D000818:Animals; D017209:Apoptosis; D051023:BH3 Interacting Domain Death Agonist Protein; D002352:Carrier Proteins / Q000378:metabolism; D053181:Caspase 8; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D002518:Ceramides / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D021962:Membrane Microdomains / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008928:Mitochondria / Q000378:metabolism; D009504:Neutrophils / Q000166:cytology* / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction; D013108:Sphingomyelin Phosphodiesterase / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D019014:fas Receptor / Q000378:metabolism*
D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; C494815:Bid protein, mouse; D002352:Carrier Proteins; D002518:Ceramides; D017382:Reactive Oxygen Species; D019014:fas Receptor; D013108:Sphingomyelin Phosphodiesterase; C505530:CASP8 protein, human; C505526:Casp8 protein, mouse; D053181:Caspase 8; D020169:Caspases