Differential effects of cytokines and corticosteroids on toll-like receptor 2 expression and activity in human airway epithelia.
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-kappaB, 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.


CONCLUSIONS
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.
Winder
Audra A
AA
Department of Pediatrics, Carver College of Medicine, University of Iowa, Iowa City, IA, USA. audra.winder@marshfieldclinic.org
Wohlford-Lenane
Christine
C
Scheetz
Todd E
TE
Nardy
Brie N
BN
Manzel
Lori J
LJ
Look
Dwight C
DC
McCray
Paul B
PB
D000305:Adrenal Cortex Hormones / Q000494:pharmacology*; D002478:Cells, Cultured; D054418:Chemokine CCL20 / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology*; D004847:Epithelial Cells / Q000187:drug effects* / Q000276:immunology; D004926:Escherichia coli / Q000276:immunology; D020869:Gene Expression Profiling / Q000379:methods; D006801:Humans; D007113:Immunity, Innate / Q000187:drug effects*; D018836:Inflammation Mediators / Q000378:metabolism*; D007371:Interferon-gamma / Q000378:metabolism; D053583:Interleukin-1beta / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D008024:Ligands; D055666:Lipopeptides / Q000494:pharmacology; D008089:Listeria monocytogenes / Q000276:immunology; D020411:Oligonucleotide Array Sequence Analysis; D011550:Pseudomonas aeruginosa / Q000276:immunology; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D020545:Respiratory Mucosa / Q000187:drug effects* / Q000276:immunology; D051195:Toll-Like Receptor 2 / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D000305:Adrenal Cortex Hormones; C108355:CCL20 protein, human; C508606:CXCL8 protein, human; D054418:Chemokine CCL20; D016207:Cytokines; D018836:Inflammation Mediators; D053583:Interleukin-1beta; D016209:Interleukin-8; D008024:Ligands; D055666:Lipopeptides; C508075:Pam(3)CSK(4) peptide; D012333:RNA, Messenger; D011994:Recombinant Proteins; C495342:TLR2 protein, human; D051195:Toll-Like Receptor 2; D014409:Tumor Necrosis Factor-alpha; D003907:Dexamethasone; D007371:Interferon-gamma