Kinins mediate important if not critical steps in the development of asthma. Our ability to define their role is limited however by the lack of a detailed understanding of the molecular mechanisms underlying their effects. We hypothesize that the coordinated transcriptional effects of Lys-bradykinin (BK) and Lys-des-Arg-BK orchestrate local airway events, including epithelial cell activation and expression of chemokine receptors, thereby focusing the recruitment of inflammatory cells. The resulting cytokine and chemokine array associated with locally activated and recruited cells favor the proinflammatory Th2 adaptive immune response associated with the clinical expression of asthma. As the kinin system functions as a sentinel of airway injury and inflammation, interventions designed to limit kinin-mediated effects in the airway may be uniquely beneficial for preventing the development of the asthmatic phenotype.
Our specific aims are to: (1) analyze the expression of BK receptors in the airways of asthmatic subjects; B2 BK receptors are constitutively expressed in many tissues. B1 receptors, in contrast, are inducibly expressed during injury or inflammation. We propose to examine the in vivo expression of B2 and B1 BK receptor in isolated airway cells obtained from mucosal biopsies of atopic/asthmatic, atopic/non-asthmatic, and non-atopic/non-asthmatic subjects. In addition, we will analyze the regulatory mechanisms controlling kinase receptor expression using cultured primary human airway cells; (2) assess the consequences of kinin challenge on gene expression and signaling pathways in airway cells of asthmatic subjects. We hypothesize that kinins will activate NF-kappaB and AP-1 in the airway of asthmatic subjects, thereby modulating gene expression, including cytokines, chemokines and chemokine receptors. We propose to analyze the effects of kinin inhalation on in vivo gene expression in human bronchial epithelial cells and identify the predominant signaling pathway mediating these in vivo effects; and (3) extend the analysis of the impact of BK receptors on gene expression and airway inflammation using a murine model of asthma. We hypothesize that full expression of airway inflammation and airway hyperresponsiveness requires the coordinate effects of signaling through B2 and B1 BK receptors. We propose to use the B2 BK receptor knockout mice as well as specific B2 and B1 BK receptor antagonists in this murine model to explore how the individual and combined effects of kinins contribute to airway inflammation. In summary, this application proposes to examine the role of kinins in human asthma and to primarily address this question using molecular approaches to study the human airway in vivo.
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