title: Eosinophil-induced release of acetylcholine from differentiated cholinergic nerve cells.
abstract: One immunological component of asthma is believed to be the interaction of eosinophils with parasympathetic cholinergic nerves and a consequent inhibition of acetylcholine muscarinic M2 receptor activity, leading to enhanced acetylcholine release and bronchoconstriction. Here we have used an in vitro model of cholinergic nerve function, the human IMR32 cell line, to study this interaction. IMR32 cells, differentiated in culture for 7 days, expressed M2 receptors. Cells were radiolabeled with [3H]choline and electrically stimulated. The stimulation-induced release of acetylcholine was prevented by the removal of Ca2+. The muscarinic M1/M2 receptor agonist arecaidine reduced the release of acetylcholine after stimulation (to 82 +/- 2% of control at 10(-7) M), and the M2 receptor antagonist AF-DX 116 increased it (to 175 +/- 23% of control at 10(-5) M), indicating the presence of a functional M2 receptor that modulated acetylcholine release. When human eosinophils were added to IMR32 cells, they enhanced acetylcholine release by 36 +/- 10%. This effect was prevented by inhibitors of adhesion of the eosinophils to the IMR32 cells. Pretreatment of IMR32 cells with 10 mM carbachol, to desensitize acetylcholine receptors, prevented the potentiation of acetylcholine release by eosinophils or AF-DX 116. Acetylcholine release was similarly potentiated (by up to 45 +/- 7%) by degranulation products from eosinophils that had been treated with N-formyl-methionyl-leucyl-phenylalanine or that had been in contact with IMR32 cells. Contact between eosinophils and IMR32 cells led to an initial increase in expression of M2 receptors, whereas prolonged exposure reduced M2 receptor expression.
authors.affiliation: Department of Pharmacology and Therapeutics, University of Liverpool L69 3GE, United Kingdom.
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Sawatzky
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Kingham
authors.forename: Niamh
authors.initials: N
authors.lastname: Durcan
authors.forename: W Graham
authors.initials: WG
authors.lastname: McLean
authors.forename: Richard W
authors.initials: RW
authors.lastname: Costello
mesh_terms: D000109:Acetylcholine / Q000378:metabolism*; D001249:Asthma / Q000276:immunology / Q000378:metabolism; D002450:Cell Communication / Q000276:immunology; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D002794:Choline / Q000493:pharmacokinetics; D002799:Cholinergic Fibers / Q000378:metabolism*; D004804:Eosinophils / Q000378:metabolism*; D015870:Gene Expression / Q000276:immunology; D006801:Humans; D009447:Neuroblastoma; D009474:Neurons / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D010275:Parasympathetic Nervous System / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D043585:Receptor, Muscarinic M2 / Q000235:genetics / Q000378:metabolism; D014316:Tritium
chemical_list: D043585:Receptor, Muscarinic M2; D014316:Tritium; D002794:Choline; D000109:Acetylcholine