Published ahead of print on February 1, 2007, doi:10.1164/rccm.200609-1260OC Am. J. Respir. Crit. Care Med., Volume 175, Number 9, May 2007, 896-904 A more recent version of this article appeared on May 1, 2007
Submitted on September 4, 2006 Remodelling and AHR but not Cellular Inflammation Persist After Allergen Challenge in AsthmaHarsha H Kariyawasam1,1 Allergy and Clinical Immunology Section, Imperial College London, National Heart and Lung Institute, London, United Kingdom; Leukocyte Biology Section, Imperial College London, National Heart and Lung Institute, London, United Kingdom; MRC and Asthma UK Centre in Allergic Mechanisms of Asthma, Imperial College London, National Heart and Lung Institute, London, United Kingdom, 2 Allergy and Clinical Immunology Section, Imperial College London, National Heart and Lung Institute, London, United Kingdom; MRC and Asthma UK Centre in Allergic Mechanisms of Asthma, Imperial College London, National Heart and Lung Institute, London, United Kingdom, 3 Leukocyte Biology Section, Imperial College London, National Heart and Lung Institute, London, United Kingdom; MRC and Asthma UK Centre in Allergic Mechanisms of Asthma, Imperial College London, National Heart and Lung Institute, London, United Kingdom * To whom correspondence should be addressed. E-mail: a.b.kay{at}imperial.ac.uk.
Rationale. Airway hyper-responsiveness increases up to 2 weeks after allergen inhalational challenge of asthmatics who show a late phase asthmatic reaction (dual responders). Cellular inflammation and airway remodelling are increased 24 hours after allergen challenge.
Objectives. To determine whether persistence of increased AHR is associated with persistent activation of remodelling and enhanced inflammation. Methods. Fibreoptic bronchoscopy was performed at baseline and at 24 hours and 7 days following allergen inhalational challenge of mild-moderate asthmatic dual responders. At each time point airway hyper-responsiveness, spirometry and expression of tenascin (extracellular matrix protein), procollagen I, procollagen III and HSP-47 (markers of collagen synthesis) and Key words: asthma, airway hyper-responsiveness (AHR), inflammation
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-smooth muscle actin (myofibroblasts) were evaluated as markers of activation of airway remodelling, together with numbers of mucosal MBP+ eosinophils, CD68+macrophages, CD3+, CD4+, CD8+ T cells, elastase+ neutrophils and tryptase+ mast cells. Measurements and Main Results. Airway hyper-responsiveness was increased from baseline at 24 hours and 7 days after allergen challenge. Reticular basement membrane (RBM) tenascin expression was elevated at 24 hours and returned to baseline levels at 7 days. RBM 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 to 24 hours. At 24 hours eosinophil, macrophage, neutrophil and CD3+ T cells were increased but had returned to baseline by 7 days. Conclusion. In dual asthmatic responders the 24 hour increase in airway wall cellular inflammation after allergen challenge resolves by 7 days whereas the increases in AHR and markers of remodelling persist.
