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.
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
Andrew S
AS
Cowburn
Anastasia
A
Sobolewski
Ben J
BJ
Reed
John
J
Deighton
Joanna
J
Murray
Karen A
KA
Cadwallader
John R
JR
Bradley
Edwin R
ER
Chilvers
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