Viral infection is the leading cause of acute asthma exacerbations, with consequent enhanced morbidity and mortality. Recent results from our laboratories suggest a novel mechanism to explain susceptibility to viral provoked asthma exacerbations. We propose that the asthmatic airway is placed at risk for exacerbations by two abnormalities that synergistically augment viral-induced NF-kappaB activation. First, increased expression of Toll-like receptors (TLRs) on airway cells transduce enhanced NF-kappaB activation in response to acute viral infection. Second, reduced expression of the endogenous anti-inflammatory protein glucocorticoid-induced leucine zipper (GILZ) augments NF-kappaB mediated inflammatory gene transcription of cytokines, chemokines and co-stimulatory molecules. Our hypothesis is that these abnormalities in the expression of TLRs and GILZ have complementary effects on NF-kB activation that together increase susceptibility to asthma exacerbations.
Aim 1 will investigate the relationships between expression of TLRs and GILZ with virus-induced asthma exacerbations in human volunteers. In vivo TLR and GILZ expression in resident airway cells will be measured in normal and asthmatic subjects, then the functional consequences on TLR-mediated NF-kappaB activity determined in isolated bronchial epithelial cells and alveolar macrophages. Their relationship to acute asthma exacerbations will be analyzed prospectively.
Aim 2 will analyze the mechanisms underlying the ability of TLRs and GILZ to influence NF-kappaB activity. Potential synergistic activation of NF-kappaB will be analyzed at the level of the critical signaling steps; and the ability of GILZ to modulate NF-kappaB activity in airway cells assessed.
The final aim will use mice with targeted gene disruption to test the importance of TLRs and GILZ in a murine model of asthma. Our approach will employ complementary studies involving human in vivo, in vitro cell, and murine in vivo models. We anticipate that this proposal will provide novel and clinically relevant data regarding the mechanisms of acute asthma exacerbations.
| Christiansen, Sandra C; Eddleston, Jane; Bengtson, Sara H et al. (2008) Experimental rhinovirus infection increases human tissue kallikrein activation in allergic subjects. Int Arch Allergy Immunol 147:299-304 |
| Bengtson, S H; Eddleston, J; Christiansen, S C et al. (2007) Double-stranded RNA increases kinin B1 receptor expression and function in human airway epithelial cells. Int Immunopharmacol 7:1880-7 |
