The effects of repeated allergen challenge on airway smooth muscle structural and molecular remodeling in a rat model of allergic asthma

• Published in: American journal of physiology. Lung cellular and molecular physiology 2009-10, Vol.297 (4), p.L698-L705
• Main Authors: Labonte, Isabelle, Hassan, Muhannad, Risse, Paul-Andre, Tsuchiya, Kimitake, Laviolette, Michel, Lauzon, Anne-Marie, Martin, James G
• Format: Article
• Language: English
• Subjects: Airway management; Allergens - pharmacology; Allergies; Animals; Asthma - drug therapy; Asthma - immunology; Asthma - metabolism; Blotting, Western; Bronchial Hyperreactivity - immunology; Bronchial Hyperreactivity - metabolism; Bronchial Hyperreactivity - pathology; Bronchoconstrictor Agents - pharmacology; Cells; Disease Models, Animal; Lungs; Male; Methacholine Chloride - pharmacology; Muscle, Smooth - drug effects; Muscle, Smooth - immunology; Muscle, Smooth - pathology; Ovalbumin - physiology; Rats; Rats, Inbred BN; Receptor, Muscarinic M3 - genetics; Receptor, Muscarinic M3 - metabolism; Respiratory System - immunology; Respiratory System - metabolism; Respiratory System - pathology; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - genetics; RNA, Messenger - metabolism; Rodents; Studies
• ISSN: 1040-0605; 1522-1504
• DOI: 10.1152/ajplung.00142.2009

Meakins-Christie Laboratories, Department of Medicine, McGill University, Montreal, Quebec, Canada Submitted 29 April 2009 ; accepted in final form 29 July 2009 The effects of remodeling of airway smooth muscle (SM) by hyperplasia on airway SM contractility in vivo are poorly explored. The aim of this study was to investigate the relationship between allergen-induced airway SM hyperplasia and its contractile phenotype. Brown Norway rats were sensitized with ovalbumin (OVA) or saline on day 0 and then either OVA-challenged once on day 14 and killed 24 h later or OVA-challenged 3 times (on days 14 , 19 , and 24 ) and killed 2 or 7 days later. Changes in SM mass, expression of total myosin, SM myosin heavy chain fast isoform (SM-B) and myosin light chain kinase (MLCK), tracheal contractions ex vivo, and airway responsiveness to methacholine (MCh) in vivo were assessed. One day after a single OVA challenge, the number of SM cells positive for PCNA was greater than for control animals, whereas the SM mass, contractile phenotype, and tracheal contractility were unchanged. Two days after three challenges, SM mass and PCNA immunoreactive cells were increased (3- and 10-fold, respectively; P < 0.05), but airway responsiveness to MCh was unaffected. Lower expression in total myosin, SM-B, and MLCK was observed at the mRNA level ( P < 0.05), and total myosin and MLCK expression were lower at the protein level ( P < 0.05) after normalization for SM mass. Normalized tracheal SM force generation was also significantly lower 2 days after repeated challenges ( P < 0.05). Seven days after repeated challenges, features of remodeling were restored toward control levels. Allergen-induced hyperplasia of SM cells was associated with a loss of contractile phenotype, which was offset by the increase in mass. phenotype; animal model; myosin heavy chain isoform Address for reprint requests and other correspondence: J. G. Martin, Meakins-Christie Laboratories, 3626 St. Urbain St., Montreal, QC, Canada H2X 2P2 (e-mail: james.martin{at}mcgill.ca ).