title: Role of macrophages in virus-induced airway hyperresponsiveness and neuronal M2 muscarinic receptor dysfunction.
abstract: Viral infections exacerbate asthma. One of the pathways by which viruses trigger bronchoconstriction and hyperresponsiveness is by causing dysfunction of inhibitory M(2) muscarinic receptors on the airway parasympathetic nerves. These receptors normally limit acetylcholine (ACh) release from the parasympathetic nerves. Loss of M(2) receptor function increases ACh release, thereby increasing vagally mediated bronchoconstriction. Because viral infection causes an influx of macrophages into the lungs, we tested the role of macrophages in virus-induced airway hyperresponsiveness and M(2) receptor dysfunction. Guinea pigs infected with parainfluenza virus were hyperresponsive to electrical stimulation of the vagus nerves but not to intravenous ACh, indicating that hyperresponsiveness was due to increased release of ACh from the nerves. In addition, the muscarinic agonist pilocarpine no longer inhibited vagally induced bronchoconstriction, indicating M(2) receptor dysfunction. Treating animals with liposome-encapsulated dichloromethylene-diphosphonate depleted macrophages as assessed histologically. In these animals, viral infection did not cause airway hyperresponsiveness or M(2) receptor dysfunction. These data suggest that macrophages mediate virus-induced M(2) receptor dysfunction and airway hyperresponsiveness.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Johns Hopkins University, Baltimore, Maryland 21205, USA.
authors.forename: Ann M
authors.initials: AM
authors.lastname: Lee
authors.forename: Allison D
authors.initials: AD
authors.lastname: Fryer
authors.forename: Nico
authors.initials: N
authors.lastname: van Rooijen
authors.forename: David B
authors.initials: DB
authors.lastname: Jacoby
mesh_terms: D000818:Animals; D000963:Antimetabolites / Q000494:pharmacology; D016535:Bronchial Hyperreactivity / Q000276:immunology* / Q000821:virology; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology / Q000276:immunology; D016084:Bronchoconstriction / Q000276:immunology; D004002:Clodronic Acid / Q000494:pharmacology; D005260:Female; D006168:Guinea Pigs; D008081:Liposomes; D016676:Macrophages, Alveolar / Q000276:immunology*; D009474:Neurons / Q000502:physiology; D010275:Parasympathetic Nervous System / Q000166:cytology / Q000276:immunology / Q000503:physiopathology; D043585:Receptor, Muscarinic M2 / Q000502:physiology*; D043587:Receptor, Muscarinic M3 / Q000502:physiology; D010253:Respirovirus Infections / Q000276:immunology* / Q000503:physiopathology; D029082:Sendai virus; D013047:Specific Pathogen-Free Organisms; D014630:Vagus Nerve / Q000166:cytology / Q000276:immunology* / Q000503:physiopathology
chemical_list: D000963:Antimetabolites; D008081:Liposomes; D043585:Receptor, Muscarinic M2; D043587:Receptor, Muscarinic M3; D004002:Clodronic Acid