Effects of (a Combination of) the Beta2-Adrenoceptor Agonist Indacaterol and the Muscarinic Receptor Antagonist Glycopyrrolate on Intrapulmonary Airway Constriction

Expression of bronchodilatory beta(2)-adrenoceptors and bronchoconstrictive muscarinic M-3-receptors alter with airway size. In COPD, (a combination of) beta(2)-agonists and muscarinic M-3-antagonists (anticholinergics) are used as bronchodilators. We studied whether differential receptor expression in large and small airways affects the response to beta(2)-agonists and anticholinergics in COPD. Bronchoprotection by indacaterol (beta(2)-agonist) and glycopyrrolate (anticholinergic) against methacholine- and EFS-induced constrictions of large and small airways was measured in guinea pig and human lung slices using video-assisted microscopy. In guinea pig lung slices, glycopyrrolate (1, 3 and 10 nM) concentration-dependently protected against methacholine- and EFS-induced constrictions, with no differences between large and small intrapulmonary airways. Indacaterol (0.01, 0.1, 1 and 10 mu M) also provided concentration-dependent protection, which was greater in large airways against methacholine and in small airways against EFS. Indacaterol (10 mu M) and glycopyrrolate (10 nM) normalized small airway hyperresponsiveness in COPD lung slices. Synergy of low indacaterol (10 nM) and glycopyrrolate (1 nM) concentrations was greater in LPS-challenged guinea pigs (COPD model) compared to saline-challenged controls. In conclusion, glycopyrrolate similarly protects large and small airways, whereas the protective effect of indacaterol in the small, but not the large, airways depends on the contractile stimulus used. Moreover, findings in a guinea pig model indicate that the synergistic bronchoprotective effect of indacaterol and glycopyrrolate is enhanced in COPD.

Automated summary

The expression of bronchodilatory beta(2)-adrenoceptors and bronchoconstrictive muscarinic M-3-receptors varies with the size of the airways. In COPD, beta(2)-agonists and muscarinic M-3-antagonists (anticholinergics) are commonly used as bronchodilators. Studies have shown that glycopyrrolate provides protection for both large and small airways, while the protective effect of indacaterol is dependent on the type of contractile stimulus in small airways. Additionally, in a guinea pig model, it was observed that the synergistic bronchoprotective effect of indacaterol and glycopyrrolate is enhanced in COPD.