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A7177 - Interleukin 17a Induces Corticosteroid Insensitivity in Bronchial Epithelial Cells from Severe Neutrophilic Asthmatic Patients
Author Block: N. Dauletbaev1, R. Hamed2, A. L. Panariti3, J. G. Martin4, C. Fugere5, R. Olivenstein6, L. C. Lands7; 1Research Institute, McGill University Health Centre, Montreal, QC, Canada, 2McGill University, Montreal, QC, Canada, 3The Research Institute of McGill University Health Centre, Montreal, QC, Canada, 4Research Institute of the MUHC, McGill University, Montreal, QC, Canada, 5Montreal Chest Institute, Montreal, QC, Canada, 6McGill University Health Centre, Montreal, QC, Canada, 7Montreal Childrens Hospital-McGill University Health Centre, Montreal, QC, Canada.
Rationale Severe corticosteroid-insensitive asthma comprises a heterogeneous patient population, including eosinophilic and neutrophilic phenotypes. Unlike in severe eosinophilic asthma, the search for valid therapeutic targets is still ongoing in severe neutrophilic asthma. The airways in severe neutrophilic asthma exhibit high levels of Interleukin (IL)-17a, a pro-inflammatory cytokine produced by T cells. This cytokine may stimulate or potentiate production of IL-8, the major neutrophil chemoattractant, in bronchial epithelial cells. Alternatively, IL-17a may affect corticosteroid sensitivity of bronchial epithelial cells. Here we tested the effects of IL-17a on IL-8 production in bronchial epithelial cells, with or without co-inflammatory stimulation by Tumor Necrosis Factor (TNF)-α, which is also abundant in severe asthma. We further evaluated potential effects of IL-17a on corticosteroid sensitivity of bronchial epithelial cells. Methods The main cell model was the bronchial epithelial cell line BEAS-2B. Key experiments were confirmed in primary bronchial epithelial cells from healthy individuals and severe neutrophilic asthmatic patients. Cells were stimulated for up to 24 hours with IL-17a (10 ng/ml; Peprotech), with or without co-stimulation with TNF-α (10 ng/ml; BD Biosciences). Parallel cells were stimulated with IL-17a and TNF-α, and post-treated with the corticosteroid Budesonide (10-10 M – 10-6 M; Sigma-Aldrich). Alternative to Budesonide, a combination of Budesonide with Formoterol (Selleck Chemicals; a 10 : 1 concentration ratio of Budesonide/Formoterol; respective concetnrations of 10-8/10-9 M and 10-9/10-10 M), a long acting beta-adrenoceptor agonist, was tested. Supernatant levels of secreted IL-8 were quantified by ELISA. Results In BEAS-2B cells, IL-17a showed weak IL-8 stimulating effects. This was in marked contrast to potent effects of TNF-α. Co-stimulation with IL-17a and TNF-α mildly potentiated the IL-8 stimulating effects of the latter. Interestingly, pre-treatment with IL-17a significantly decreased the sensitivity to Budesonide (p = 0.0079 vs. without IL-17a pre-treatment) in TNF-α stimulated BEAS-2B cells. A similar trend of IL-17a induced corticosteroid insensitivity was observed in TNF-α stimulated primary bronchial epithelial cells from healthy individuals and severe neutrophilic asthmatic patients. A combination of Budesonide with Formoterol did not reverse the IL-17a induced corticosteroid insensitivity in BEAS-2B or primary cells. Conclusions IL-17a has a limited pro-IL-8 effect on its own and only mildly potentiates IL-8 stimulating effects of other inflammatory stimuli. However, IL-17a induces substantial corticosteroid insensitivity in bronchial epithelium, applicable to both healthy and severe asthmatic cells. Thereby, IL-17a may be a drug target to restore corticosteroid sensitivity in severe neutrophilic asthma. ND and RH: co-first authors