IL-17RA Signaling in Airway Inflammation and Bronchial Hyperreactivity in Allergic Asthma

Asthma is a heterogeneous disease characterized by airway inflammation and hyperreactivity. IL-17 receptor A (IL-17RA) is a shared receptor subunit required for activity of IL-17 family cytokines, including IL-17A and IL-25. IL-17A and IL-25 induce different proinflammatory responses, and concentrations are elevated in subjects with asthma. However, the individual contributions of IL-17A and IL-25 to disease pathogenesis are unclear. We explored proinflammatory activities of the IL-17 pathway in models of pulmonary inflammation and assessed its effects on contractility of human bronchial airway smooth muscle. In two mouse models, IL-17RA, IL-17RB, or IL-25 blockade reduced airway inflammation and airway hyperreactivity. Individually, IL-17A and IL-25 enhanced contractility of human bronchial smooth muscle induced by methacholine or carbachol. IL-17A had more pronounced effects on methacholine-induced contractility in bronchial rings from donors with asthma compared with donors without asthma. Blocking the IL-17 pathway via IL-17RA may be a useful therapy for some patients with asthma by reducing pulmonary inflammation and airway hyperreactivity.