TMEM16A Antagonism: Therapeutic Potential with Desensitization of β-agonist Responsiveness in Asthma.

The efficacy of β-agonists in asthma is severely limited by β-adrenoceptor desensitization which results in poorly managed symptoms and refractory bronchoconstriction. Thus, there is a need to identify novel therapeutic pathways and to clarify the relationship between novel therapeutics and functional β-adrenoceptor responsiveness. We have previously demonstrated that acute antagonism of the calcium activated chloride channel, transmembrane member 16A (TMEM16A), relaxes airway smooth muscle (ASM). We sought to determine the efficacy and role of TMEM16A antagonism in the context of desensitization β - adrenoceptor responsiveness. For these studies, we exposed murine tracheal rings on wire myography and precision cut lung slices to contractile mediators in the presence or absence of TMEM16A antagonists and β-agonists with or without prior β-adrenoceptor desensitization. Contractile studies were also performed with human tracheal and bronchial ASM. Finally, the ability of TMEM16A antagonism to prevent desensitization of β₂-adrenoceptor-induced cyclic AMP synthesis was measured in human ASM cells. From these studies we demonstrate that acute TMEM16A antagonism is effective in relaxing β-agonist desensitized ASM in central and peripheral murine ASM and human ASM. Furthermore, we demonstrate that chronic pretreatment with TMEM16A antagonists prevents functional desensitization of β-agonist responsiveness in mouse and human upper airways and prevents desensitization of β-agonist-mediated cyclic AMP production in human ASM cells. Taken together, the present study demonstrates a favorable therapeutic profile of TMEM16A antagonism for airway smooth muscle relaxation despite functional desensitization of β-agonist responsiveness which may be a novel therapeutic approach in the face of β-adrenoceptor tachyphylaxis.