Specific Induction of TSLP by the Viral RNA Analogue Poly(I:C) in Primary Epithelial Cells Derived from Nasal Polyps

Introduction

Chronic rhinosinusitis with nasal polyposis is an inflammatory disease that, although not directly linked to allergy, often displays a Th2-skewed inflammation characterized by elevated local IgE and IL-5 levels. The nasal cavity is constantly exposed to bacteria and viruses that may trigger epithelial inflammatory responses. To gain more insight into mechanisms by which such a biased inflammation might arise, we have investigated the epithelial expression of the Th2 skewing mediators (TSLP, IL-25, and IL-33) in relationship to disease and microbial triggers.

Methods

Epithelial cells were obtained from polyp tissues of nasal polyposis patients and from inferior turbinates of non-diseased controls. Cells were exposed to various TLR-specific triggers to study the effect on mRNA and protein expression level of TSLP, IL-25, and IL-33 and the potential regulatory mechanisms through the expression profile the transcription factors ATF-3, DUSP-1, EGR-1, and NFKB-1.

Results

The TLR3 agonist and viral analogue poly(I:C) induced TSLP mRNA 13.0 ± 3.1 fold (p < 0.05) and protein expression by 12.1 ± 2.3-fold (p < 0.05) higher in epithelium isolated from nasal polyposis patients than in epithelium form healthy controls. This enhanced induction of TSLP may be a consequence of a down-regulated expression of DUSP-1 in polyp epithelium.

Conclusion

The TLR3 induced expression of TSLP introduces a mechanism by which the Th2-skewed tissue environment might arise in nasal polyps and invites a further evaluation of the potential contribution of current or past viral infections to polyposis pathogenesis.

Synergy between TLR-2 and TLR-3 signaling in primary human nasal epithelial cells

INTRODUCTION

Although we have a detailed understanding of how single microbial derived triggers activate specialized Toll-like receptors (TLR) on airway epithelial cells, we know little of how these receptors react in a more complex environment. In everyday life, nasal epithelial cells are exposed to multiple TLR agonists, therefore we explored whether exposure to one trigger could affect the responsiveness to another TLR trigger.

METHODS

Primary nasal epithelium from healthy individuals and the bronchial epithelium cell line NCI-H292 were exposed in vitro to different TLR specific agonists. The effect on the expression of different TLRs was determined using the q-PCR. We also evaluated the effect of TLR-3 stimulation on TLR-2, functionally using ELISA to determine levels of secreted mediators.

RESULTS

Stimulation of airway epithelial cells with a specific TLR agonist affects gene expression of other TLRs. In primary nasal epithelium, poly(I:C) challenge results in an up-regulation of the TLR-1, TLR-2, and TLR-3 genes and reduction of expression of TLR-5. Poly(I:C) induced activation of TLR-2 contributes to stronger cell responses to a TLR-2 agonist and regulation of these synergistic responses may take place at the mRNA level of IL-6 and IL-8. The effect of TLR-3 stimulation on TLR-2 functionality and most of the effects on the expression of other TLRs could be replicated in NCI-H292. Poly(I:C) failed to up-regulate TLR-1 and showed an additional up-regulation of TLR-4.

CONCLUSION

Our data suggest that to better understand TLR mediated innate responses we need to consider the impact of the presence of multiple triggers.