Aminopeptidase N (CD13) regulates tumor necrosis factor-alpha-induced apoptosis in human neutrophils.
Neutrophil apoptosis plays a central role in the resolution of granulocytic inflammation. We have shown previously that tumor necrosis factor-alpha (TNFalpha) enhances the rate of neutrophil apoptosis at early time points via a mechanism involving both TNF receptor (TNFR) I and TNFRII. Here we reveal a marked but consistent variation in the magnitude of the pro-apoptotic effect of TNFalpha in neutrophils isolated from healthy donors, and we show that inhibition of cell surface aminopeptidase N (APN) using actinonin, bestatin, or inhibitory peptides significantly enhanced the efficacy of TNFalpha-induced killing. Notably, an inverse correlation is shown to exist between neutrophil APN activity and the sensitivity of donor cells to TNFalpha-induced apoptosis. Inhibition of cell surface APN appears to interfere with the shedding of TNFRI, and as a consequence results in augmented TNFalpha-induced apoptosis, cell polarization, and TNFalpha-primed, formyl-methionyl-leucyl-phenylalanine-stimulated respiratory burst. Of note, actinonin and bestatin had no effect on TNFRII expression under resting or TNFalpha-stimulated conditions and did not alter CXCRI or CXCRII expression. These data suggest significant variation in the activity of APN/CD13 on the cell surface of neutrophils in normal individuals and reveal a novel mechanism whereby APN/CD13 regulates TNFalpha-induced apoptosis via inhibition of TNFRI shedding. This has therapeutic relevance for driving neutrophil apoptosis in vivo.
Cowburn
Andrew S
AS
Respiratory Medicine Division, Department of Medicine, University of Cambridge School of Clinical Medicine, Addenbrooke's Hospital, Cambridge CB2 2QQ, United Kingdom. asc32@cam.ac.uk
Sobolewski
Anastasia
A
Reed
Ben J
BJ
Deighton
John
J
Murray
Joanna
J
Cadwallader
Karen A
KA
Bradley
John R
JR
Chilvers
Edwin R
ER
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D017209:Apoptosis; D018826:CD13 Antigens / Q000096:biosynthesis* / Q000378:metabolism; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D066298:In Vitro Techniques; D007930:Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D009504:Neutrophils / Q000378:metabolism* / Q000473:pathology; D023062:Receptors, Interleukin-8A / Q000378:metabolism; D023063:Receptors, Interleukin-8B / Q000378:metabolism; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000378:metabolism; D047889:Receptors, Tumor Necrosis Factor, Type II / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
D000900:Anti-Bacterial Agents; D006877:Hydroxamic Acids; D023062:Receptors, Interleukin-8A; D023063:Receptors, Interleukin-8B; D047888:Receptors, Tumor Necrosis Factor, Type I; D047889:Receptors, Tumor Necrosis Factor, Type II; D014409:Tumor Necrosis Factor-alpha; D018826:CD13 Antigens; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D007930:Leucine; C012211:ubenimex; C010531:actinonin