Characterization of the survival effect of tumour necrosis factor-alpha in human neutrophils.
Granulocyte apoptosis has been proposed as a fundamental, injury-limiting granulocyte-clearance mechanism. As such, inhibition of this process may prevent the resolution of inflammation. Our previous studies have shown that TNFalpha (tumour necrosis factor-alpha) has a bi-modal influence on the rate of constitutive neutrophil apoptosis in vitro, causing early acceleration and late inhibition of this process. The pro-apoptotic effect is uniquely TNFR1 (TNF receptor 1) and TNFR2-dependent and the latter survival process is mediated via phosphoinositide 3-kinase and NF-kappaB (nuclear factor-kappaB) activation. In the present study, we show that, in contrast with GM-CSF (granulocyte/macrophage colony-stimulating factor), the delayed addition (i.e. at 6 h) of TNFalpha increases its survival effect despite substantial loss of neutrophil TNFR1 and TNFR2 at that time. This paradox was resolved using PBMC (peripheral blood mononuclear cell)-deplete and 5% PBMC-replete neutrophil cultures, where the enhanced survival effect observed after delayed TNFalpha addition was shown to be PBMC-dependent. TNFR2-blocking antibodies had no effect on the late survival effect of TNFalpha, implying a TNFR1-dependent process. Finally, I-kappaBalpha (inhibitory kappaB-alpha) and NF-kappaB time-course studies demonstrated that the survival effects of both GM-CSF and TNFalpha could be explained by maintenance of functional NF-kappaB.
Walmsley
S R
SR
Respiratory Medicine Division, Department of Medicine, University of Cambridge School of Clinical Medicine, Addenbrooke's and Papworth Hospitals, Hills Road, Cambridge CB2 2QQ, UK.
Cowburn
A S
AS
Sobolewski
A
A
Murray
J
J
Farahi
N
N
Sabroe
I
I
Chilvers
E R
ER
D017209:Apoptosis; D015153:Blotting, Western; D002470:Cell Survival; D002478:Cells, Cultured; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000378:metabolism; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D008954:Models, Biological; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism; D009504:Neutrophils / Q000166:cytology* / Q000378:metabolism / Q000473:pathology; D047889:Receptors, Tumor Necrosis Factor, Type II / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000502:physiology*
D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D047889:Receptors, Tumor Necrosis Factor, Type II; D014409:Tumor Necrosis Factor-alpha; D000072000:NF-KappaB Inhibitor alpha; D016178:Granulocyte-Macrophage Colony-Stimulating Factor