title: Antigen-induced airway inflammation in the Brown Norway rat results in airway smooth muscle hyperplasia.
abstract: Asthma is characterized by chronic airways inflammation, airway wall remodeling, and airway hyperresponsiveness (AHR). An increase in airway smooth muscle has been proposed to explain a major part of AHR in asthma. We have used unbiased stereological methods to determine whether airway smooth muscle hyperplasia and AHR occurred in sensitized, antigen-challenged Brown Norway (BN) rats. Ovalbumin (OA)-sensitized BN rats chronically exposed to OA aerosol displayed airway inflammation and a modest level of AHR to intravenously administered ACh 24 h after the last antigen challenge. However, these animals did not show an increase in smooth muscle cell (SMC) number in the left main bronchus, suggesting that short-lived inflammatory mechanisms caused the acute AHR. In contrast, 7 days after the last aerosol challenge, there was a modest increase in SMC number, but no AHR to ACh. Addition of FCS to the chronic OA challenge protocol had no effect on the degree of inflammation but resulted in a marked increase in both SMC number and a persistent (7-day) AHR. These results raise the possibility that increases in airway SMC number rather than, or in addition to, chronic inflammation contribute to the persistent AHR detected in this model.
authors.affiliation: Bernard O'Brien Institute of Microsurgery, St. Vincent's Hospital, Fitzroy, Victoria 3065, Australia.
authors.forename: K F
authors.initials: KF
authors.lastname: Xu
authors.forename: R
authors.initials: R
authors.lastname: Vlahos
authors.forename: A
authors.initials: A
authors.lastname: Messina
authors.forename: T L
authors.initials: TL
authors.lastname: Bamford
authors.forename: J F
authors.initials: JF
authors.lastname: Bertram
authors.forename: A G
authors.initials: AG
authors.lastname: Stewart
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000403:Airway Resistance; D000818:Animals; D001980:Bronchi / Q000187:drug effects / Q000473:pathology*; D016535:Bronchial Hyperreactivity / Q000276:immunology* / Q000503:physiopathology; D001991:Bronchitis / Q000276:immunology* / Q000473:pathology* / Q000503:physiopathology; D002452:Cell Count; D006965:Hyperplasia; D006969:Hypersensitivity, Immediate / Q000276:immunology / Q000503:physiopathology; D008297:Male; D009130:Muscle, Smooth / Q000473:pathology*; D010047:Ovalbumin / Q000276:immunology*; D051381:Rats; D011914:Rats, Inbred BN
chemical_list: D010047:Ovalbumin; D000109:Acetylcholine