Journal
RESPIRATORY RESEARCH
Volume 10, Issue -, Pages -Publisher
BMC
DOI: 10.1186/1465-9921-10-96
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Funding
- NIH [T32 AI007343, P50 HL-61234, N01 AI-30040]
- Roy J. Carver Charitable Trust
- Research to Prevent Blindness [HL-082505, HL-075559]
- Cell and Tissues and Cell Morphology Cores
- Center for Gene Therapy for Cystic Fibrosis [NIH P30 DK-54759]
- Cystic Fibrosis Foundation
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Background: The recognition of microbial molecular patterns via Toll-like receptors (TLRs) is critical for mucosal defenses. Methods: Using well-differentiated primary cultures of human airway epithelia, we investigated the effects of exposure of the cells to cytokines (TNF-alpha and IFN-gamma) and dexamethasone (dex) on responsiveness to the TLR2/TLR1 ligand Pam3CSK4. Production of IL-8, CCL20, and airway surface liquid antimicrobial activity were used as endpoints. Results: Microarray expression profiling in human airway epithelia revealed that first response cytokines markedly induced TLR2 expression. Real-time PCR confirmed that cytokines (TNF-alpha and IFN-gamma), dexamethasone (dex), or cytokines + dex increased TLR2 mRNA abundance. A synergistic increase was seen with cytokines + dex. To assess TLR2 function, epithelia pre-treated with cytokines +/- dex were exposed to the TLR2/TLR1 ligand Pam3CSK4 for 24 hours. While cells pre-treated with cytokines alone exhibited significantly enhanced IL-8 and CCL20 secretion following Pam3CSK4, mean IL-8 and CCL20 release decreased in Pam3CSK4 stimulated cells following cytokines + dex pre-treatment. This marked increase in inflammatory gene expression seen after treatment with cytokines followed by the TLR2 ligand did not correlate well with NF-kappa B, Stat1, or p38 MAP kinase pathway activation. Cytokines also enhanced TLR2 agonist-induced beta-defensin 2 mRNA expression and increased the antimicrobial activity of airway surface liquid. Dex blocked these effects. Conclusion: While dex treatment enhanced TLR2 expression, co-administration of dex with cytokines inhibited airway epithelial cell responsiveness to TLR2/TLR1 ligand over cytokines alone. Enhanced functional TLR2 expression following exposure to TNF-alpha and IFN-gamma may serve as a dynamic means to amplify epithelial innate immune responses during infectious or inflammatory pulmonary diseases.
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