rs-5186 and Bronchial-Hyperreactivity

The effects of CS-518, a thromboxane A2 synthase inhibitor, on antigen-induced dual bronchial responses, airway hyperresponsiveness (AHR) and airway eosinophilia were investigated in an experimental guinea pig model of the late asthmatic response. Oral CS-518 (1 and 10 mg/kg) inhibited immediate and late asthmatic responses dose-dependently. It also inhibited AHR and eosinophil accumulation after antigen challenge. Therefore, thromboxane A2 is possibly involved in development of the late asthmatic response and AHR, and CS-518 was inferred to inhibit these via inhibition of eosinophil accumulation and thromboxane production.

Topics: Animals; Asthma; Bronchial Hyperreactivity; Bronchial Provocation Tests; Bronchoalveolar Lavage Fluid; Chemotaxis, Leukocyte; Disease Models, Animal; Dose-Response Relationship, Drug; Enzyme Inhibitors; Eosinophils; Guinea Pigs; Male; Methacholine Chloride; Ovalbumin; Pulmonary Eosinophilia; Thiophenes; Thromboxane-A Synthase

The anti-asthmatic effects of CS-518 (sodium 2-(1-imidazolylmethyl)-4,5-dihydrobenzo[b]thiophene-6-carboxylate) , a specific thromboxane A2 (TXA2) synthase inhibitor, were investigated in the ovalbumin-sensitized guinea pig asthmatic model. Although CS-518 slightly inhibited (about 25%) whole bronchoconstriction, it significantly inhibited the antigen-induced bronchoconstriction mediated by slow-reacting substance of anaphylaxis (SRS-A), which was not reduced by chlorpheniramine, a histamine H1 antagonist. On the other hand, indomethacin, a cyclooxygenase inhibitor, potentiated the SRS-A-mediated constriction. CS-518 strongly, and indomethacin slightly, suppressed the leukotriene D4-induced bronchoconstriction. CS-518 clearly inhibited the antigen-induced airway hyperresponsiveness, but this compound had no effect on the airway hyperresponsiveness induced by U-46619, a TXA2-mimetic agent, and propranolol. These results suggest that CS-518 suppresses the development of bronchoconstriction and airway hyperresponsiveness in asthmatic models by inhibition of TXA2 synthesis with the concomitant increase in bronchodilating prostaglandins such as prostaglandin E2 and prostaglandin I2.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Asthma; Bronchial Hyperreactivity; Bronchoconstriction; Chlorpheniramine; Disease Models, Animal; Guinea Pigs; Indomethacin; Male; Methacrylates; Ovalbumin; Propranolol; Prostaglandin Endoperoxides, Synthetic; SRS-A; Thiophenes; Thromboxane A2; Thromboxane-A Synthase; Vasoconstrictor Agents