Fas activation in alveolar epithelial cells induces KC (CXCL1) release by a MyD88-dependent mechanism.
Activation of the Fas/Fas ligand (FasL) system is associated with activation of apoptotic and proinflammatory pathways that lead to the development of acute lung injury. Previous studies in chimeric mice and macrophage-depleted mice suggested that the main effector cell in Fas-mediated lung injury is not a myeloid cell, but likely an epithelial cell. The goal of this study was to determine whether epithelial cells release proinflammatory cytokines after Fas activation, and to identify the relevant pathways. Incubation of the murine alveolar epithelial cell line, MLE-12, with the Fas-activating monoclonal antibody, Jo2, resulted in release of the CXC chemokine, KC, in a dose-dependent manner. KC release was not prevented by the pan-caspase inhibitor, zVAD.fmk. Silencing of the adaptor protein, MyD88, with small interfering (si)RNA resulted in attenuation of KC release in response to Jo2. Fas activation resulted in phosphorylation of the mitogen-activated kinases extracellular signal-regulated kinase (ERK) and c-Jun-N-terminal kinase (JNK), and pharmacologic inhibition of ERK and JNK attenuated KC release in a dose-response manner. Similarly, primary human small airways epithelial cells released IL-8 in response to soluble FasL, and this was abrogated by inhibition of JNK and ERK. In vivo confirmatory studies showed that MyD88-null mice are protected from Fas-induced acute lung injury. In summary, we conclude that Fas induces KC release in MLE-12 cells by a mechanism requiring MyD88, mitogen-activated protein kinases, and likely activator protein-1.
Center for Lung Biology, Division of Pulmonary & Critical Care Medicine, University of Washington School of Medicine, Seattle, Washington, USA.
Alex W
AW
Farnand
Alison J
AJ
Eastman
Raquel
R
Herrero
Josiah F
JF
Hanson
Steve
S
Mongovin
William A
WA
Altemeier
Gustavo
G
Matute-Bello
D000818:Animals; D054360:Chemokine CXCL1 / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000166:cytology*; D053222:Fas Ligand Protein / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D053594:Myeloid Differentiation Factor 88 / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000166:cytology*; D034741:RNA, Small Interfering / Q000378:metabolism; D014162:Transfection; D019014:fas Receptor / Q000378:metabolism*
C475829:CXCL1 protein, human; D054360:Chemokine CXCL1; D053222:Fas Ligand Protein; D016209:Interleukin-8; C507779:MYD88 protein, human; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; D034741:RNA, Small Interfering; D019014:fas Receptor
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