Effects of suplatast tosilate, a new type of anti-allergic agent, on airway cough hypersensitivity induced by airway allergy in guinea-pigs

Background Cough receptor hypersensitivity is a fundamental feature of some conditions presenting with chronic non-productive cough. Suplatast tosilate, an anti-allergic agent, is a T helper (Th)2 cytokine inhibitor that inhibits the synthesis of interleukin (IL)-4, IL-5, immunoglobulin (Ig)E production, and local eosinophil accumulation. Objective The purpose of this study was to investigate the effect of suplatast on antigen-induced airway cough hypersensitivity and eosinophil infiltration into the airway. Methods Number of coughs elicited by inhalation of increasing concentrations of capsaicin (10(-8), 10(-6) and 10(-4) M) was counted 24 h after an antigen challenge in conscious guinea-pigs and then bronchoalveolar lavage was performed. We investigated the effect of single (before antigen challenge or capsaicin provocation) or repetitive treatment with intraperitoneal suplatast at a dose of 10 or 30 mg/kg on anti gen-induced cough hypersensitivity. Results Twenty-four hours after antigen challenge, guinea-pigs developed an increase in cough receptor sensitivity to inhaled capsaicin and eosinophil infiltration in the airways. After a 2-week treatment with suplatast, but not after only a single treatment before antigen challenge or capsaicin provocation, the antigen-induced early phase bronchoconstriction, cough hypersensitivity, and airway eosinophilia were inhibited in a dose-dependent mariner. Conclusion These results indicate that suplatast inhibits airway cough hypersensitivity underlying allergic eosinophilic inflammation.