Development of an inhaled endotoxin challenge protocol for characterizing evoked cell surface phenotype and genomic responses of airway cells in allergic individuals.
BACKGROUND
Environmental exposure to endotoxin is a known cause of exacerbation of asthma. Inhaled endotoxin protocols have been used to evaluate airway cell surface phenotypes associated with antigen presentation and innate immunity in healthy volunteers, but not in allergic volunteers.


OBJECTIVE
To establish the safety of challenge with low-dose endotoxin (10,000 endotoxin units) (lipopolysaccharide [LPS]) inhalation in allergic individuals, to measure airway cell surface phenotypes associated with antigen presentation and innate immunity in induced sputum (IS) after LPS challenge, and to conduct gene expression profiling in IS cells to determine which host genetic networks are modified by LPS inhalation.


METHODS
Induced sputum was obtained before and 6 hours after LPS inhalation in 10 allergic volunteers (8 with asthma and 2 with rhinitis). Flow cytometry was used to examine cell surface phenotypes on IS cells. Genomic expression was analyzed on a subset of IS samples (n = 10) using microarray and ingenuity pathway analysis.


RESULTS
A total of 10,000 endotoxin units of LPS induced significant up-regulation of membrane CD14, CD11b, CD16, HLA-DR, CD86, and Fcepsilon receptor 1 on sputum phagocytes and increased expression of genes that influence antigen-presenting surface molecules (HLA-DR, chemokine ligand 2 or monocyte chemoattractant protein 1, v-rel reticuloendotheliosis viral oncogene homolog, prostaglandin-endoperoxide synthase 2 or cyclooxygenase 2, and transforming growth factor beta), immune activation (CD14, interleukin 1beta, and regulated upon activation, normal T cell expressed and secreted), and inflammation (intracellular adhesion molecule 1 and inhibitory kappaBalpha). Gene profiles for nuclear factor kappaB, interleukin 1, and tumor necrosis factor pathways were also significantly affected.


CONCLUSIONS
Low-dose inhaled endotoxin challenge is safe in allergic individuals with mild to moderate disease. It enhances airway cell surface phenotypes and expression of genes associated with antigen presentation, innate immunity, and inflammation. Microarray with ingenuity pathway analysis can be successfully applied to sputum cells to characterize genetic responses to inhaled exacerbants.
Alexis
Neil E
NE
Center for Environmental Medicine, Asthma and Lung Biology, UNC School of Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA. Neil_Alexis@med.unc.edu
Brickey
Willie June
WJ
Lay
John C
JC
Wang
Ying
Y
Roubey
Robert A S
RA
Ting
Jenny P Y
JP
Peden
David B
DB
D000280:Administration, Inhalation; D000328:Adult; D017951:Antigen Presentation; D001249:Asthma / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D007113:Immunity, Innate; D018836:Inflammation Mediators / Q000276:immunology / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000008:administration & dosage / Q000276:immunology*; D008213:Lymphocyte Activation; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D012221:Rhinitis, Allergic, Perennial / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D013183:Sputum / Q000166:cytology* / Q000276:immunology / Q000378:metabolism*; D015854:Up-Regulation
D018836:Inflammation Mediators; D008070:Lipopolysaccharides