Environmental exposure to viruses, noxious stimuli and allergens leads to the rapid generation of kinins in the airway. Kinins then mediate important functions in the initiation and propagation of allergic airway inflammation. While kinin receptor antagonists have demonstrated potent anti-asthma actions in both experimental animals and human asthmatic subjects, mice lacking the bradykinin B2 receptor (B2R) exhibit enhanced bronchial hyperresponsiveness, inflammation, and airway remodeling in the OVA model of allergic airway inflammation. Thus, the B2R appears to be capable of mediating both pro-inflammatory and anti-inflammatory effects on allergic airway inflammation. The overall hypothesis of this project is that the B2R mediates distinct and opposing effects in a temporal-spatial manner;specifically that B2R mediates tolerance to innocuous antigens during the immunologic induction phase through actions on lymphocytes and/or dendritic cells, but then mediates pro-inflammatory effects during the effector phase of inflammation through actions on airway epithelial cells. This application will address the following key questions: 1) What is/are the mechanism(s) that underlie the enhanced allergic airway inflammation in B2R knockout mice? 2) Is it possible to separate the pro- and anti-inflammatory effects of B2R inhibition in a temporal-spatial manner;and 3) Could the information gained from answering the above questions allow B2R acting drugs to be used in a manner that would optimize their therapeutic benefit? Two aims are proposed.
Aim 1 will analyze the underlying mechanism(s) of the enhanced Th2 polarization observed in the B2R knockout mice, and assess the impact of this on allergic airway inflammation. First, the antigen specific T cell responses in knockout and normal mice will be elucidated. Next, the differentiation and migration of specific dendritic cell subpopulations to the lung will be analyzed in wild-type and knockout mice. Third, the impact of B2R knockout on the development of inhalational tolerance will be assessed. Finally, adoptive transfer of dendritic cells from wild-type mice into B2R knockout mice will be performed to show whether this can correct the abnormal T cell polarization.
Aim 2 will then analyze how alterations in the temporal-spatial pattern of bradykinin signaling influences the ultimate airway allergic inflammation phenotype in this model. First, the role of the B1R in mediating the phenotype will be deconstructed. Next, the ability of wild-type polarized T cells to abrogate or reverse the phenotype will be tested. Finally, the impact of varying both the timing and route of administration of pharmacologic agents affecting the bradykinin system will be explored to better understand the clinical relevance of the findings in the murine knockout model.
7. Project Narrative The overall goal of this project is to identify the mechanisms responsible for the ability of bradykinin B2 receptors to mediate either pro-inflammatory or anti-inflammatory consequences during allergic airway inflammation. By elucidating these mechanisms we anticipate learning more about how the airway innate immune system interacts with the adaptive immune system and using this information to help maximize the clinical benefit of novel bradykinin B2 receptor acting drugs that are nearing clinical deployment. Asthma is a common disease both in the Veterans population as well as in the general population, and these studies should help develop more effective asthma treatments.