Research

Differential effects of cytokines and corticosteroids on Toll-like receptor 2 expression and activity in human airway epithelia

Audra A Winder¹ , Christine Wohlford-Lenane¹ , Todd E Scheetz^2,5 , Brie N Nardy³ , Lori J Manzel³ , Dwight C Look³ and Paul B McCray Jr^1,3,4

¹  Department of Pediatrics, Carver College of Medicine, University of Iowa, Iowa City, IA USA

²  Department of Opthalmology, Carver College of Medicine, University of Iowa, Iowa City, IA USA

³  Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA USA

⁴  Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, IA USA

⁵  College of Engineering, University of Iowa, Iowa City, IA USA

author email corresponding author email

Respiratory Research 2009, 10:96doi:10.1186/1465-9921-10-96

Published:	16 October 2009

Abstract

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-α and IFN-γ) 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-α and IFN-γ), 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-κB, 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-α and IFN-γ may serve as a dynamic means to amplify epithelial innate immune responses during infectious or inflammatory pulmonary diseases.