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 antigen‐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 manner. Conclusion These results indicate that suplatast inhibits airway cough hypersensitivity underlying allergic eosinophilic inflammation.