Open Access

ARTICLE

Long-term exposure to IL-1β enhances Toll-IL-1 receptor-mediated inflammatory signaling in murine airway hyperresponsiveness

Yaping Zhang¹, Cang-Bao Xu², Lars-Olaf Cardell¹

1 Division of ENT Diseases, Department of CLINTEC, Karolinska Institutet, Karolinska University Hospital, Huddinge, Sweden
2 Division of Experimental Vascular Research, Institute of Clinical Science in Lund, Lund University, Lund, Sweden

* Corresponding Author: Y. Zhang,

European Cytokine Network 2009, 20(3), 148-156. https://doi.org/10.1684/ecn.2009.0156

Accepted 28 May 2009;

Abstract

Toll-interleukin-1 (Toll-IL-1) receptor signaling may play a key role in the development of airway hyperreactivity (AHR) and chronic airway inflammatory diseases such as asthma. Previously, we have demon-strated that pro-inflammatory cytokines, tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), induce AHR. However, the underlying intracellular signaling mechanisms that lead to AHR remain elusive. In order to see if the Toll-IL-1 receptor-mediated inflammatory signal pathways are involved in the development of AHR, the present study was designed to use a real-time PCR array, a sensitive and powerful tool, consisting of 84 genes related to Toll-IL-1 receptor signal pathways. Murine tracheal segments were organ cultured for four days in the presence and absence of IL-1β. The Toll-IL-1 receptor-mediated inflammatory signal gene profile was studied using the real-time PCR-based cDNA array. The key gene expressions that were altered were veri-fied by immunohistochemistry using confocal microscopy. Tracheal ring segment contractile responsiveness to the inflammatory mediator bradykinin was monitored using a sensitive myograph system. The results showed that after exposed to IL-1β for four days, the tracheal segments exhibited increased mRNA expression of 67 genes (out of the 84 genes in the array), although expression reached statistical significance for only 16 of these genes. There were 14 genes that showed only a tendency towards a decrease in mRNA expression following IL-1β treatment. Immunohistochemistry confirmed that protein expression for CD14, RP105, MCP-1 and phos-phorylated IκB-α were increased in both the airway epithelial and smooth muscle cells. In order to link the acti-vation of Toll-IL-1 receptor-mediated inflammatory signal mechanisms to the AHR, the anti-inflammatory drug dexamethasone, was used. Dexamethasone not only completely abolished the IL-1β-induced AHR to bradykinin, but also abrogated the increased mRNA expression for inflammatory mediators, IL-6, IFN-γ and Cox-2. In con-clusion, long-term exposure of murine airway to IL-1β induces up- and down-regulation of mRNA expression for Toll-IL-1 receptor signal molecules, with a significant increase in the expression of 16 genes that contribute to the development of airway inflammation and AHR. Understanding cytokine-induced activation of the Toll-IL-1 receptor-mediated inflammatory signaling mechanisms may provide new options for the treatment of air-way inflammation and AHR.

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Keywords

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