Neutrophils induce apoptosis of lung epithelial cells via release of soluble Fas ligand.
Neutrophils release soluble Fas ligand (sFasL), which can induce apoptosis in certain Fas-bearing cell types (Liles WC, Kiener PA, Ledbetter JA, Aruffo A, and Klebanoff SJ. J Exp Med 184: 429-440, 1996). We hypothesized that neutrophils could induce alveolar epithelial apoptosis via release of sFasL. A549 pulmonary adenocarcinoma cells expressed surface Fas and underwent cell death (10 +/- 7% viability) and DNA fragmentation (354 +/- 98% of control cells) when incubated with agonistic CD95/Fas monoclonal antibody (P < 0.05). Coincubation with human neutrophils induced significant A549 cell death at 48 (51 +/- 9% viability; P < 0.05) and 72 h (25 +/- 10%; P < 0.05) and increased DNA fragmentation (178 +/- 42% of control cells; P < 0.05), with morphological characteristics of apoptosis. The addition of antioxidants did not inhibit apoptosis. sFasL concentrations were maximally increased in coculture medium at 24 h (4.9 +/- 0.7 ng/ml; P < 0.05). Neutrophil-induced A549 cell apoptosis was blocked by inhibitory anti-Fas (42 +/- 6% of control cells; P < 0.05) and anti-FasL monoclonal antibodies (29 +/- 3%; P < 0.05). Human neutrophils and Fas similarly affected murine primary alveolar epithelial cell bilayers, and caspase activation occurred in response to Fas exposure. We conclude that neutrophils undergoing spontaneous apoptosis induce A549 cell death and DNA fragmentation, independent of the oxidative burst, that is mediated by sFasL.
Serrao
K L
KL
Division of Critical Care, Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, USA.
Fortenberry
J D
JD
Owens
M L
ML
Harris
F L
FL
Brown
L A
LA
D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D017209:Apoptosis; D002374:Catalase / Q000378:metabolism / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D018920:Coculture Techniques; D053938:DNA Fragmentation / Q000187:drug effects; D015194:Diffusion Chambers, Culture; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D053222:Fas Ligand Protein; D006801:Humans; D020287:In Situ Nick-End Labeling; D008168:Lung / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D009504:Neutrophils / Q000166:cytology / Q000378:metabolism*; D012128:Respiratory Distress Syndrome / Q000378:metabolism / Q000473:pathology; D013482:Superoxide Dismutase / Q000378:metabolism / Q000494:pharmacology; D019014:fas Receptor / Q000187:drug effects / Q000378:metabolism
D000911:Antibodies, Monoclonal; C505661:FASLG protein, human; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D008562:Membrane Glycoproteins; D019014:fas Receptor; D002374:Catalase; D013482:Superoxide Dismutase