title: Sites of allergic airway smooth muscle remodeling and hyperresponsiveness are not associated in the rat.
abstract: The cause-and-effect relationship between airway smooth muscle (ASM) remodeling and airway hyperresponsiveness (AHR) following allergen challenge is not well established. Using a rat model of allergen-induced ASM remodeling we explored the relationship between the site of ASM remodeling and AHR. Brown Norway rats, sensitized and challenged (3 times at 5-day intervals) with ovalbumin, were intranasally administered 0.1 mg/kg budesonide 24 and 1 h before challenge. Airway responses to aerosolized methacholine were assessed 48 h or 1 wk after three challenges. Airways were stained and analyzed for total airway wall area, area of smooth muscle-specific α-actin, and goblet cell hyperplasia, and the constant-phase model was used to resolve the changes in respiratory system mechanics into large airway and peripheral lung responses. After three ovalbumin challenges, there was a significant increase in ASM area and in the total wall area in all sized airways as well as an increase in goblet cells in the central airways. Budesonide inhibited ASM growth and central airway goblet cell hyperplasia following ovalbumin challenges. Budesonide also inhibited small but not large airway total wall area. AHR was attributable to excessive responses of the small airways, whereas responsiveness of the large airways was unchanged. Budesonide did not inhibit AHR after repeated challenge. We conclude that ASM remodeling induced by repeated allergen challenges involves the entire bronchial tree, whereas AHR reflects alterations in the lung periphery. Prevention of ASM remodeling by corticosteroid does not abrogate AHR.
authors.affiliation: Meakins Christie Laboratories, Department of Medicine, McGill University, Montreal, Quebec, Canada.
authors.forename: Sana
authors.initials: S
authors.lastname: Siddiqui
authors.forename: Taisuke
authors.initials: T
authors.lastname: Jo
authors.forename: Meiyo
authors.initials: M
authors.lastname: Tamaoka
authors.forename: Karim H
authors.initials: KH
authors.lastname: Shalaby
authors.forename: Heberto
authors.initials: H
authors.lastname: Ghezzo
authors.forename: Maria
authors.initials: M
authors.lastname: Bernabeu
authors.forename: James G
authors.initials: JG
authors.lastname: Martin
mesh_terms: D056151:Airway Remodeling / Q000187:drug effects; D000818:Animals; D001249:Asthma / Q000188:drug therapy / Q000276:immunology / Q000473:pathology / Q000503:physiopathology*; D016535:Bronchial Hyperreactivity / Q000188:drug therapy / Q000276:immunology / Q000473:pathology / Q000503:physiopathology*; D001985:Bronchial Provocation Tests; D001992:Bronchoalveolar Lavage Fluid / Q000276:immunology; D001993:Bronchodilator Agents / Q000494:pharmacology; D019819:Budesonide / Q000494:pharmacology; D049109:Cell Proliferation; D018925:Chemokines / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism; D004195:Disease Models, Animal; D020397:Goblet Cells / Q000473:pathology; D006965:Hyperplasia; D018836:Inflammation Mediators / Q000378:metabolism; D008168:Lung / Q000187:drug effects / Q000276:immunology / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects / Q000276:immunology / Q000473:pathology / Q000503:physiopathology*; D010047:Ovalbumin; D051381:Rats; D011914:Rats, Inbred BN; D013997:Time Factors
chemical_list: D001993:Bronchodilator Agents; D018925:Chemokines; D016207:Cytokines; D018836:Inflammation Mediators; D019819:Budesonide; D010047:Ovalbumin