Mechanisms of Beta-blocker Induced Improvements in Asthma

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DESCRIPTION (provided by applicant): Asthma is characterized by reversible airway obstruction, airway hyperresponsiveness (AHR) and airway inflammation. The medications used for control and acute relief of asthma vary in their effectiveness and may produce serious side effects. Thus, there is a need to develop new and improved medications for asthma. Our research has shown that, unexpectedly, activation of the ¿2AR is necessary for the development of the asthma phenotype produced by antigen challenge or by direct intra-tracheal administration of IL-13. We have also shown that chronic treatment of mouse models of asthma with ¿2AR-inverse agonists produced broad anti- inflammatory effects in the airways, including dramatic changes in airway epithelium mucus production and morphology. These data suggest that ¿2ARs located on the airway epithelium may be a key target for the effect of ¿2AR inverse agonists. Our long-range goal is to determine the mechanism of the proasthamtic effect of ¿2AR signaling. To do this we need to understand the signaling pathways and their sites of action. In this project, we will: Aim 1. Test the hypothesis that an important target of ¿2AR-inverse agonists is the airway epithelium, and determine what components of the asthma phenotype are due to lung parenchymal cells versus hematopoietic cells by using genetically altered mice and bone marrow transplantation experiments. Aim 2. Determine the role of ¿2AR-¿-arrestin-2-MAPK signaling, in mediating the pro-asthmatic effects of the ¿2AR using genetically altered mice and human bronchial airway epithelial cells, and Aim 3. Using pharmacological and genetic 'sympathectomy', as well as bone marrow transplant experiments, determine the cellular source of the epinephrine activating the ¿2AR allowing its various pro-asthmatic effects, and because weeks of treatment required for the anti-asthmatic effect of ¿2AR-inverse agonists, we will perform microarray analysis for gene expression changes as a lead for possible mechanisms of action. This research could lead to safer and more efficacious drugs for the treatment of asthma, and alter our understanding of asthma at a paradigm-shifting level.