The transcriptional response to lipopolysaccharide reveals a role for interferon-gamma in lung neutrophil recruitment.
Neutrophil recruitment to the lung after lipopolysaccharide (LPS; endotoxin) inhalation is primarily dependent on Toll-like receptor 4 (Tlr4) signaling, because it is virtually absent in mice deficient in Tlr4. However, among strains wild type for Tlr4, the magnitude of neutrophil recruitment to the lung after LPS inhalation is variable, suggesting the involvement of genes other than Tlr4. To identify genes associated with the inflammatory response to inhaled LPS, we evaluated the transcriptional response in lungs of 12 inbred strains of mice, 8 which are wild type for Tlr4 and 4 of which lack functional Tlr4. Using the promoter integration in microarray analysis algorithm, we scanned our gene list for transcription factor-binding sites significantly overrepresented among Tlr4 wild-type strains with high neutrophil influx in the lung after LPS inhalation. This analysis identified the interferon (IFN)-stimulated response element (ISRE) as the most overrepresented transcription factor (present in 24% of the promoters) associated with the neutrophil influx to the lower respiratory tract. To test the validity of this observation, we evaluated IFN-gamma-deficient mice and found that the presence of IFN-gamma is essential for robust neutrophil recruitment to the lower respiratory tract and modulation of key regulatory cytokines and chemokines after LPS inhalation. In conclusion, using a genomic approach, we identified the ISRE as a transcriptional element associated with the neutrophil response to inhaled LPS and demonstrated for the first time that IFN-gamma plays a critical role in LPS-induced neutrophil recruitment to the lower airways.
Burch
Lauranell H
LH
National Institute of Environmental Health Sciences, Division of Pulmonary, Allergy, and Critical Care Medicine, Research Triangle Park, NC 27709, USA. burchl@niehs.nih.gov
Yang
Ivana V
IV
Whitehead
Gregory S
GS
Chao
Frank G
FG
Berman
Katherine G
KG
Schwartz
David A
DA
D000280:Administration, Inhalation; D000818:Animals; D015870:Gene Expression / Q000187:drug effects; D007371:Interferon-gamma / Q000502:physiology*; D007372:Interferons / Q000502:physiology; D008070:Lipopolysaccharides / Q000008:administration & dosage / Q000494:pharmacology*; D008168:Lung / Q000187:drug effects / Q000502:physiology*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D018345:Mice, Knockout; D020556:Neutrophil Infiltration / Q000235:genetics / Q000502:physiology*; D011014:Pneumonia / Q000139:chemically induced / Q000235:genetics; D020218:Response Elements / Q000502:physiology; D051197:Toll-Like Receptor 4 / Q000172:deficiency / Q000502:physiology; D014157:Transcription Factors / Q000502:physiology; D014158:Transcription, Genetic / Q000187:drug effects*
D008070:Lipopolysaccharides; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D014157:Transcription Factors; D007371:Interferon-gamma; D007372:Interferons