Airway inflammation plays a critical role in the pathogenesis of chronic asthma. Glucocorticoid (GC)s are the cornerstone of anti-inflammatory therapy in this disease. However, not all asthmatics improve their pulmonary function following GC therapy. These patients are subjected to the unwanted side effects of prolonged systemic GC therapy, often in situations where there is no evidence that it is exerting any appreciable benefit. Recent analyses of the economic burden of asthma suggest that the costs of asthma are largely attributable to uncontrolled disease. Although patients with severe asthma represent a minority of asthmatics, they account for much of the morbidity and cost of the disease due to use of costly medications, emergency room visits and frequent hospitalizations. The present proposal will use cellular and molecular approaches to study the pathogenesis of steroid resistant (CR) vs corticosteroid sensitive (CS) asthma. The central hypothesis which we will pursue is that airway macrophages from CR, as compared to CS, asthmatics are steroid resistant, have a distinct phenotype and demonstrate an orchestrated increase in expression of multiple proinflammatory cytokines and chemokines involved in """"""""classical"""""""" macrophage activation. Preliminary data suggests that endotoxin may be one important ongoing environmental trigger for steroid resistance and airway inflammation in CR asthma.
Our specific aims are to use molecular and cellular approaches to characterize airway macrophages in CR, as compared to CS, asthma (specific aim 1);determine whether loss of inhibitory signaling contributes to the chronic activation of monocyte/macrophages from CR, as compared to CS, asthmatics (specific aim 2);determine the mechanism(s) resulting in loss of corticosteroid response in monocyte/macrophages of CR asthmatics (specific aim 3);and determine whether LPS contributes to the increased macrophage activation in CR asthma (specific aim 4). The elucidation of mechanisms underlying steroid resistance will have important consequences for development of biomarkers to diagnose and monitor steroid resistance, and develop novel therapeutic modalities in the treatment of CR asthma and other chronic inflammatory conditions where altered corticosteroid responsiveness contributes to persistent tissue inflammation.
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