Remodeling and airway hyperresponsiveness but not cellular inflammation persist after allergen challenge in asthma

RATIONALE: Airway hyperresponsiveness (AHR) increases up to 2 weeks after allergen inhalational challenge of subjects with asthma who show a late-phase asthmatic reaction (dual responders). Cellular inflammation and airway remodeling are increased 24 hours after allergen challenge. OBJECTIVES: To determine whether persistence of increased AHR is associated with persistent activation of remodeling and enhanced inflammation. METHODS: Fiberoptic bronchoscopy was performed at baseline and at 24 hours and 7 days after allergen inhalational challenge of dual responders with mild-moderate asthma. At each time point, AHR, spirometry, and expression of tenascin (extracellular matrix protein), procollagen I, procollagen III, and heat shock protein (HSP)-47 (markers of collagen synthesis), and alpha-smooth muscle actin (myofibroblasts) were evaluated as markers of activation of airway remodeling, together with numbers of mucosal major basic protein-positive eosinophils, CD68(+) macrophages, CD3(+), CD4(+), CD8(+) T cells, elastase-positive neutrophils, and tryptase-positive mast cells. MEASUREMENTS AND MAIN RESULTS: AHR was increased from baseline at 24 hours and 7 days after allergen challenge. Reticular basement membrane tenascin expression was elevated at 24 hours and returned to baseline levels at 7 days. Reticular basement membrane procollagen III expression was significantly elevated at 7 days. Expression of procollagen I, HSP-47, and alpha-smooth muscle actin were all higher at 7 days compared with 24 hours. At 24 hours, eosinophil, macrophage, neutrophil, and CD3(+) T cells were increased but had returned to baseline by 7 days. CONCLUSIONS: In dual responders with asthma, the 24-hour increase in airway wall cellular inflammation after allergen challenge resolves by 7 days, whereas the increases in AHR and markers of remodeling persist.