Potential Role of Interleukin-25/Interleukin-33/Thymic Stromal Lymphopoietin-Fibrocyte Axis in the Pathogenesis of Allergic Airway Diseases

OBJECTIVE: Allergic airway diseases (AADs) are a group of heterogeneous disease mediated by T-helper type 2 (Th2) immune response and characterized with airway inflammation and remodeling, including allergic asthma, allergic rhinitis, and chronic rhinosinusitis with allergic background. This review aimed to discuss the abnormal epithelial-mesenchymal crosstalk in the pathogenesis of AADs. DATA SOURCES: Articles referred in this review were collected from the database of PubMed published in English up to January 2018. STUDY SELECTION: We had done a literature search using the following terms “allergic airway disease OR asthma OR allergic rhinitis OR chronic sinusitis AND IL-25 OR IL-33 OR thymic stromal lymphopoietin OR fibrocyte”. Related original or review articles were included and carefully analyzed. RESULTS: It is now believed that abnormal epithelial-mesenchymal crosstalk underlies the pathogenesis of AADs. However, the key regulatory factors and molecular events involved in this process still remain unclear. Epithelium-derived triple cytokines, including interleukin (IL)-25, IL-33, and thymic stromal lymphopoietin (TSLP), are shown to act on various target cells and promote the Th2 immune response. Circulating fibrocyte is an important mesenchymal cell that can mediate tissue remodeling. We previously found that IL-25-circulating fibrocyte axis was significantly upregulated in patients with asthma, which may greatly contribute to asthmatic airway inflammation and remodeling. CONCLUSIONS: In view of the redundancy of cytokines and “united airway” theory, we propose a new concept that IL-25/IL-33/TSLP-fibrocyte axis may play a vital role in the abnormal epithelial-mesenchymal crosstalk in some endotypes of AADs. This novel idea will guide potential new intervention schema for the common treatment of AADs sharing common pathogenesis in the future.