Neutrophils induce apoptosis of lung epithelial cells via release of soluble Fas ligand.
Serrao, Karl L., James D. Fortenberry, Marilyn L. Owens, Frank L. Harris, and Lou Ann
S. Brown.
Divisions of 1Critical Care and 2Neonatology, Department of Pediatrics, Emory
University School of Medicine, and 3Division of Critical Care Medicine, Children's
Healthcare of Atlanta at Egleston, Atlanta, Georgia 30322
APStracts 7:0260L, 2000.
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 media 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.
Received 3 December 1999; accepted in final form 7 September 2000
APS Manuscript Number L387-9.
Article publication pending Am J Physiol Lung Cell Mol Physiol
ISSN 1080-4757 Copyright 2000 The American Physiological Society.
Published in APStracts on 30 November 2000