Innate immune responses to LPS in mouse lung are suppressed and reversed by neutralization of GM-CSF via repression of TLR-4.
The innate immune inflammatory response to lipopolysaccharide (LPS, an endotoxin) is essential for lung host defense against infection by gram-negative bacteria but is also implicated in the pathogenesis of some lung diseases. Studies on genetically altered mice implicate granulocyte-macrophage colony-stimulating factor (GM-CSF) in lung responses to LPS; however, the physiological effects of GM-CSF neutralization are poorly characterized. We performed detailed kinetic and dose-response analyses of the lung inflammation response to LPS in the presence of the specific GM-CSF-neutralizing antibody 22E9. LPS instilled into the lungs of BALB/c mice induced a dose-dependent inflammation comprised of intense neutrophilia, macrophage infiltration and proliferation, TNF-alpha and matrix metalloproteinase release, and macrophage inflammatory protein-2 induction. The neutralization of anti-GM-CSF in a dose-dependent fashion suppressed these inflammatory indexes by 85% when given before or after LPS or after repeat LPS challenges. Here we report for the first time that the physiological expression of Toll-like receptor-4 in lung is reduced by anti-GM-CSF. We observed that lower Toll-like receptor-4 expression correlated with a similar decline in peak TNF- levels in response to endotoxin. Consequently, sustained expression of key inflammatory mediators over 24 h was reduced. These data expand the understanding of the contribution of GM-CSF to innate immune responses in lung and suggest that blocking GM-CSF might benefit some lung diseases where LPS has been implicated in etiology.
Bozinovski
Steven
S
Lung Disease Research Group, Dept. of Pharmacology, Cooperative Research Center for Chronic Inflammatory Diseases, Univ. of Melbourne, Parkville 3010, Victoria, Australia. gpa@unimelb.edu.au
Jones
Jessica
J
Beavitt
Sarah-Jane
SJ
Cook
Andrew D
AD
Hamilton
John A
JA
Anderson
Gary P
GP
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000276:immunology* / Q000378:metabolism; D018836:Inflammation Mediators / Q000276:immunology / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008168:Lung / Q000276:immunology / Q000378:metabolism; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D009000:Monocytes / Q000276:immunology; D009504:Neutrophils / Q000276:immunology; D011014:Pneumonia / Q000276:immunology* / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D013047:Specific Pathogen-Free Organisms; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors
D000906:Antibodies; D018836:Inflammation Mediators; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D016178:Granulocyte-Macrophage Colony-Stimulating Factor