Mechanisms of asthma and allergic inflammation
IL-17E upregulates the expression of proinflammatory cytokines in lung fibroblasts

https://doi.org/10.1016/j.jaci.2005.10.025Get rights and content

Background

IL-17E is a new TH2 cytokine that promotes airway eosinophilia in mice. IL-17E proinflammatory activity has been proposed to involve induction of cytokine and chemokine production. Recruitment of inflammatory cells may be mediated by tissue-resident cells.

Objective

This study aimed to evaluate whether fibroblasts represent a target of IL-17E for the production of eosinophil active mediators in the lung.

Methods

Expression of IL-17B receptor (IL-17BR), a receptor for IL-17E, was evaluated by immunofluorescent staining, Western blot, and real-time PCR in human primary lung fibroblasts. Mediator production was analyzed by using real-time PCR and ELISA after stimulation of fibroblasts with IL-17E alone or in combination with TNF-α and TGF-β1. Expression of IL-17E and of eosinophil major basic protein was evaluated by immunohistochemistry in bronchial biopsies from subjects with asthma.

Results

Human primary lung fibroblasts constitutively expressed IL-17BR. IL-17BR mRNA levels were increased in cells stimulated with TNF-α and decreased with TGF-β1. IL-17E slightly upregulated CC chemokine ligand (CCL)–5, CCL-11, GM-CSF, and CXC chemokine ligand (CXCL)–8 mRNA in fibroblasts. Moreover, IL-17E and TNF-α synergistically induced GM-CSF and CXCL-8 mRNA. IL-17E also potentiated the upregulation of CXCL-8 transcripts observed with TGF-β1. In contrast, TGF-β1 decreased IL-17E–induced CCL-11 mRNA. The capacity of IL-17E to enhance GM-CSF and CXCL-8 responses to TNF-α was accompanied by production and secretion of both proteins by lung fibroblasts. Finally, IL-17E was detected in asthma in eosinophil-infiltrated bronchial submucosa.

Conclusion

IL-17E may contribute to the induction and maintenance of eosinophilic inflammation in the airways by acting on lung fibroblasts. This study supports a role for IL-17E in asthma pathophysiology.

Section snippets

Cell culture

The human normal lung fibroblasts CCD-8Lu were purchased from American Type Culture Collection (Rockville, Md) and studied at passages 4-7. Cells were cultured in Dulbecco's modified Eagle Medium containing 100 U/mL penicillin, 100 μg/mL streptomycin (GIBCO, Grand Island, NY), and 10% FCS (HyClone Laboratories, Logan, Utah). Unless otherwise specified, fibroblasts were seeded in 6-well plates and grown to confluence. Cells were washed in PBS and serum-deprived for 24 hours before stimulation

Expression and regulation of a receptor for IL-17E, IL-17BR, in human lung fibroblasts

By using cultured fibroblasts obtained from human lung, we demonstrated a constitutive expression of IL-17BR, as shown by immunofluorescent staining using a specific mAb directed against the extracellular domain of the receptor (Fig 1, A, left panel). No staining was observed when an irrelevant isotype-matched antibody was used (Fig 1, A, right panel).

The presence of IL-17BR in fibroblasts was confirmed by Western blot analysis. The mAb detected a 56-kd protein corresponding to the full length

Discussion

The recently described cytokine IL-17E may play a role in allergic inflammation and remodeling of the airways. To date, however, very little is known about its involvement in human disease, particularly in asthma. This study demonstrates for the first time the constitutive expression of a receptor for IL-17E, IL-17BR, in human primary lung fibroblasts, and supports a role for IL-17E in allergic airway inflammation.

We show that IL-17E stimulates the production of several mediators known to favor

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    Supported by a grant from the Canadian Institutes of Health Research. Dr Létuvé is funded by a fellowship from the Canadian Lung Association and Merck Frosst Canada.

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