Allergic airway inflammation and beta-adrenoceptor dysfunction

A reduced response to beta-adrenoceptor agonists has been reported in airways of asthmatic subjects. Mechanisms for beta-adrenoceptor dysfunction are (1) inactivation or downregulation of beta-adrenoceptors by specific agonists (homologous desensitization) or by inflammatory mediations (heterologous desensitization), (2) inactivation or downregulation of second messengers of beta-adrenoceptor pathway. Studies from our laboratory have shown that allergen challenge of passively sensitized human bronchi causes a beta-adrenoceptor dysfunction as a result of reduced activity of the receptor-coupled Gs protein. The dysfunction was prevented by leukotriene-receptor antagonists or a cell membrane stabilizer, but not by an antihistimine or indomethacin, suggesting a central role of leukotrienes released from resident inflammatory cells in its genesis. Furthermore, the beta-adrenoceptor response and Gs protein function after allergen exposure were restored by short-term (3 h) incubation with beclomethasone dipropionate, suggesting an effect independent of gene transcription. Restoration of the intracellular beta-adrenoceptor effector pathway may contribute to the efficacy of corticosteroids in the acute treatment of asthma.