β-Adrenoceptor signaling in airway epithelial cells promotes eosinophilic inflammation, mucous metaplasia, and airway contractility.

The mostly widely used bronchodilators in asthma therapy are β-adrenoreceptor (βAR) agonists, but their chronic use causes paradoxical adverse effects. We have previously determined that βAR activation is required for expression of the asthma phenotype in mice, but the cell types involved are unknown. We now demonstrate that βAR signaling in the airway epithelium is sufficient to mediate key features of the asthmatic responses to IL-13 in murine models. Our data show that inhibition of βAR signaling with an aerosolized antagonist attenuates airway hyperresponsiveness (AHR), eosinophilic inflammation, and mucus-production responses to IL-13, whereas treatment with an aerosolized agonist worsens these phenotypes, suggesting that βAR signaling on resident lung cells modulates the asthma phenotype. Labeling with a fluorescent βAR ligand shows the receptors are highly expressed in airway epithelium. In βAR mice, transgenic expression of βARs only in airway epithelium is sufficient to rescue IL-13-induced AHR, inflammation, and mucus production, and transgenic overexpression in WT mice exacerbates these phenotypes. Knockout of β-arrestin-2 (βarr-2) attenuates the asthma phenotype as in βAR mice. In contrast to eosinophilic inflammation, neutrophilic inflammation was not promoted by βAR signaling. Together, these results suggest βARs on airway epithelial cells promote the asthma phenotype and that the proinflammatory pathway downstream of the βAR involves βarr-2. These results identify βAR signaling in the airway epithelium as capable of controlling integrated responses to IL-13 and affecting the function of other cell types such as airway smooth muscle cells.