Synergistic Proinflammatory Responses by IL-17A and Toll-Like Receptor 3 in Human Airway Epithelial Cells.

Abstract

Viral respiratory infections activate the innate immune response in the airway epithelium through Toll-like receptors (TLRs) and induce airway inflammation, which causes acute exacerbation of asthma. Although increases in IL-17A expression were observed in the airway of severe asthma patients, the interaction between IL-17A and TLR activation in airway epithelium remains poorly understood. In this study, we demonstrated that IL-17A and polyI:C, the ligand of TLR3, synergistically induced the expression of proinflammatory cytokines and chemokines (G-CSF, IL-8, CXCL1, CXCL5, IL-1F9), but not type I interferon (IFN-α1, -β) in primary culture of normal human bronchial epithelial cells. Synergistic induction after co-stimulation with IL-17A and polyI:C was observed from 2 to 24 hours after stimulation. Treatment with cycloheximide or actinomycin D had no effect, suggesting that the synergistic induction occurred without de novo protein synthesis or mRNA stabilization. Inhibition of the TLR3, TLR/TIR-domain-containing adaptor-inducing interferon β (TRIF), NF-κB, and IRF3 pathways decreased the polyI:C- and IL-17A/polyI:C-induced G-CSF and IL-8 mRNA expression. Comparing the levels of mRNA induction between co-treatment with IL-17A/polyI:C and treatment with polyI:C alone, blocking the of NF-κB pathway significantly attenuated the observed synergism. In western blotting analysis, activation of both NF-κB and IRF3 was observed in treatment with polyI:C and co-treatment with IL-17A/polyI:C; moreover, co-treatment with IL-17A/polyI:C augmented IκB-α phosphorylation as compared to polyI:C treatment alone. Collectively, these findings indicate that IL-17A and TLR3 activation cooperate to induce proinflammatory responses in the airway epithelium via TLR3/TRIF-mediated NF-κB/IRF3 activation, and that enhanced activation of the NF-κB pathway plays an essential role in synergistic induction after co-treatment with IL-17A and polyI:C in vitro.

• Authors: Kazutaka Mori, Tomoyuki Fujisawa, Hideki Kusagaya, Katsumasa Yamanaka, Dai Hashimoto, Noriyuki Enomoto, Naoki Inui, Yutaro Nakamura, Masato Maekawa, Takafumi Suda
• Journal: PloS one (PLoS One) Vol. 10 Issue 9 Pg. e0139491 ( 2015) ISSN: 1932-6203 [Electronic] United States
• PMID: 26418032 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Adaptor Proteins, Vesicular Transport
• Cytokines
• IRF3 protein, human
• Interferon Regulatory Factor-3
• Interleukin-17
• Interleukin-8
• NF-kappa B
• TICAM1 protein, human
• TLR3 protein, human
• Toll-Like Receptor 3
• Granulocyte Colony-Stimulating Factor
• Poly I-C

Topics

• Adaptor Proteins, Vesicular Transport (genetics, metabolism)
• Blotting, Western
• Bronchi (cytology)
• Cell Line
• Cells, Cultured
• Cytokines (genetics, metabolism)
• Drug Synergism
• Epithelial Cells (drug effects, metabolism)
• Gene Expression (drug effects)
• Granulocyte Colony-Stimulating Factor (genetics, metabolism)
• Humans
• Interferon Regulatory Factor-3 (genetics, metabolism)
• Interleukin-17 (pharmacology)
• Interleukin-8 (genetics, metabolism)
• NF-kappa B (metabolism)
• Poly I-C (pharmacology)
• RNA Interference
• Reverse Transcriptase Polymerase Chain Reaction
• Toll-Like Receptor 3 (agonists, genetics, metabolism)