Ozone-induced airway hyperresponsiveness and loss of neuronal M2 muscarinic receptor function

1994 ◽  
Vol 76 (3) ◽  
pp. 1088-1097 ◽  
Author(s):  
A. H. Schultheis ◽  
D. J. Bassett ◽  
A. D. Fryer
Keyword(s):  
Muscarinic Receptor ◽  
Muscarinic Receptors ◽  
Ozone Exposure ◽  
Muscarinic Agonist ◽  
Receptor Function ◽  
Vagus Nerves ◽  
Parasympathetic Nerves ◽  
M2 Muscarinic Receptor ◽  
Release Of Acetylcholine ◽  
M2 Muscarinic Receptors

The effect of acute ozone exposure on the function of efferent parasympathetic nerves, M3 muscarinic receptors on airway smooth muscle, and inhibitory M2 muscarinic receptors on the parasympathetic nerves was studied. Immediately after exposure to 2.0 ppm ozone for 4 h, guinea pigs became hyperresponsive to electrical stimulation of the vagus nerves. The normal airway response to intravenous cholinergic agonists at this time demonstrates normal M3 receptor function. M2 muscarinic receptors on the nerves, which normally inhibit release of acetylcholine, were dysfunctional after ozone exposure, as demonstrated by the failure of the muscarinic agonist pilocarpine to inhibit, and the failure of the M2 antagonist gallamine to potentiate, vagally mediated bronchoconstriction. Thus, loss of inhibitory M2 muscarinic receptor function after ozone exposure potentiates release of acetylcholine from the vagus nerves, increasing vagally mediated bronchoconstriction. By 14 days, postozone responses to vagal nerve stimulation were not different from those of air-exposed animals and the function of the neuronal M2 muscarinic receptor was normal, confirming that ozone-induced hyperresponsiveness is reversible.

Ozone-induced loss of neuronal M2 muscarinic receptor function is prevented by cyclophosphamide

1994 ◽  
Vol 77 (3) ◽  
pp. 1492-1499 ◽  
Author(s):  
L. M. Gambone ◽  
C. L. Elbon ◽  
A. D. Fryer
Keyword(s):  
Muscarinic Receptor ◽  
Muscarinic Receptors ◽  
Guinea Pigs ◽  
Inflammatory Cells ◽  
Lavage Fluid ◽  
Ozone Exposure ◽  
Muscarinic Agonist ◽  
Receptor Function ◽  
M2 Muscarinic Receptor ◽  
M2 Muscarinic Receptors

We tested the hypothesis that inflammatory cells mediate the loss of neuronal M2 muscarinic receptors in the lung after ozone exposure. Pathogen-free guinea pigs treated with cyclophosphamide (30 mg.kg-1.day-1 i.p. for 7 days) before exposure to ozone were compared with untreated ozone-exposed animals. This dose of cyclophosphamide significantly reduced leukocytes in peripheral blood and bronchoalveolar lavage fluid. Twenty-four hours after ozone, muscarinic receptor function was tested in anesthetized animals. In air-exposed guinea pigs, vagally induced bronchoconstriction was attenuated by the muscarinic agonist pilocarpine (0.1–100 micrograms/kg i.v.) and potentiated by the selective M2 antagonist gallamine (0.1–10 mg/kg i.v.), indicating that the neuronal M2 muscarinic receptors were functioning. These responses were significantly reduced after ozone, indicating loss of neuronal M2 muscarinic receptor function. However, in those animals treated with cyclophosphamide, M2 muscarinic receptor function was not altered by ozone. These data suggest that ozone-induced loss of neuronal muscarinic receptor function is mediated via inflammatory cells and that the link between ozone-induced hyperresponsiveness and inflammation may be the neuronal M2 muscarinic receptor.

Dysfunction of M2-muscarinic receptors in pulmonary parasympathetic nerves after antigen challenge

1991 ◽  
Vol 71 (6) ◽  
pp. 2255-2261 ◽  
Author(s):  
A. D. Fryer ◽  
M. Wills-Karp
Keyword(s):  
Muscarinic Receptors ◽  
Guinea Pigs ◽  
Antigen Challenge ◽  
Saline Control ◽  
Control Group ◽  
Vagus Nerves ◽  
Parasympathetic Nerves ◽  
Volume Blood ◽  
M2 Muscarinic Receptors ◽  
Stimulation Of

The effect of antigen challenge on the function of neuronal M2-muscarinic autoreceptors in the lungs was studied in anesthetized guinea pigs. Guinea pigs were injected intraperitoneally with saline (control group) or ovalbumin (10 mg/kg) on days 1, 3, and 5. One group of sensitized animals was challenged on days 20–25 with aerosolized ovalbumin for 5 min/day (challenged group), while another group of the sensitized animals was not challenged (sensitized group). On day 26 the animals were anesthetized, paralyzed, tracheostomized, and artificially ventilated. Pulmonary inflation pressure (Ppi), tidal volume, blood pressure, and heart rate were recorded. Both vagus nerves were cut, and electrical stimulation of the distal portions caused bronchoconstriction (measured as an increase in Ppi) and bradycardia. In the control group, pilocarpine (1–100 micrograms/kg iv) attenuated vagally induced bronchoconstriction by stimulating inhibitory M2-muscarinic receptors on parasympathetic nerves in the lungs. Conversely, blockade of these receptors with the antagonist gallamine (0.1–10 mg/kg iv) produced a marked potentiation of vagally induced bronchoconstriction. These results confirm previous findings. In the challenged guinea pigs, pilocarpine did not inhibit vagally induced bronchoconstriction. Furthermore, gallamine did not potentiate vagally induced bronchoconstriction to the same degree as in the controls. In the group of animals that was sensitized but not challenged, the potentiation of vagally induced bronchoconstriction by gallamine was identical to the controls. There was no increase in baseline Ppi in the sensitized or challenged animals compared with the controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuromuscular Relaxants as Antagonists for M2and M3Muscarinic Receptors 

1998 ◽  
Vol 88 (3) ◽  
pp. 744-750 ◽  
Author(s):  
Vivian Y. Hou ◽  
Carol A. Hirshman ◽  
Charles W. Emala
Keyword(s):  
Muscarinic Receptor ◽  
Muscarinic Receptors ◽  
Radioligand Binding ◽  
Chinese Hamster ◽  
Neuromuscular Relaxants ◽  
Ovary Cell ◽  
Relative Order ◽  
Parasympathetic Nerves ◽  
M2 Muscarinic Receptor ◽  
M3 Muscarinic Receptor

Background Neuromuscular relaxants such as pancuronium bind to M2 and M3 muscarinic receptors as antagonists. Blockade of muscarinic receptors in atria of the M2 subtype mediates tachycardia. In the lung, blockade of M2 receptors on parasympathetic nerves potentiates vagally induced bronchospasm, whereas blockade of M3 receptors on bronchial smooth muscle inhibits bronchospasm. The current study was designed to quantify the affinity of a series of neuromuscular relaxants for the M2 and M3 muscarinic receptors, which were individually stably transfected in Chinese hamster ovary cell lines. Methods Competitive radioligand binding assays determined the relative binding affinities of the neuromuscular relaxants pancuronium, succinylcholine, mivacurium, doxacurium, atracurium, rocuronium, gallamine, and pipecuronium for the muscarinic receptor in the presence of a muscarinic receptor antagonist (3H-QNB) in membranes prepared from cells individually expressing either the M2 or M3 muscarinic receptor. Results All muscle relaxants evaluated displaced 3H-QNB from muscarinic receptors. The relative order of potency for the M2 muscarinic receptor (highest to lowest) was pancuronium, gallamine, rocuronium, atracurium, pipecuronium, doxacurium, mivacurium, and succinylcholine. The relative order of potency for the M3 muscarinic receptor (highest to lowest) was pancuronium, atracurium, pipecuronium, rocuronium, mivacurium, gallamine, succinylcholine, and doxacurium. Conclusions All neuromuscular relaxants studied had affinities for the M2 and M3 muscarinic receptor, but only pancuronium and gallamine had affinities within the range of concentrations achieved with clinical use. The high affinities of gallamine and pancuronium for the M2 muscarinic receptor are consistent with a mechanism of M2 receptor blockade in relaxant-induced tachycardia.

Localization of eosinophils to airway nerves and effect on neuronal M2 muscarinic receptor function

1997 ◽  
Vol 273 (1) ◽  
pp. L93-L103 ◽  
Author(s):  
R. W. Costello ◽  
B. H. Schofield ◽  
G. M. Kephart ◽  
G. J. Gleich ◽  
D. B. Jacoby ◽  
...  
Keyword(s):  
Guinea Pigs ◽  
Acetylcholine Release ◽  
Basic Protein ◽  
Receptor Function ◽  
Major Basic Protein ◽  
Parasympathetic Nerves ◽  
M2 Muscarinic Receptor ◽  
Fatal Asthma ◽  
Eosinophil Major Basic Protein ◽  
M2 Muscarinic Receptors

Neuronal M2 muscarinic receptors inhibit acetylcholine release from pulmonary parasympathetic nerves but are dysfunctional in antigen-challenged animals and asthmatics. Deletion of pulmonary eosinophils protects M2 receptor function in antigen-challenged guinea pigs. Therefore, the association of eosinophils with airway nerves was investigated. Nerve-associated eosinophils were significantly increased in challenged animals compared with controls (0.75 +/- 0.05 vs. 0.28 +/- 0.05 eosinophils/nerve). In antigen-challenged animals, eosinophil density was greatest around airway nerves, suggesting recruitment to the nerves. M2 receptor function was inversely correlated with the number of eosinophils per nerve, thus eosinophils are associated with airway nerves in antigen-challenged guinea pigs, where they impair M2 receptor function. In airways from three patients with fatal asthma, 196 of 637 eosinophils (30%) were associated with nerves, and release of eosinophil major basic protein was evident; conversely, in three control patients 1 of 11 (9%) eosinophils were in contact with nerves. Thus eosinophils and their granule proteins are also seen in association with airway nerves in patients with asthma.

scholarly journals Immunocytochemical localization of M2 muscarinic receptors in rat ventricles with anti-peptide antibodies.

1994 ◽  
Vol 42 (3) ◽  
pp. 337-343 ◽  
Author(s):  
M Fu ◽  
W Schulze ◽  
W P Wolf ◽  
A Hjalmarson ◽  
J Hoebeke
Keyword(s):  
Muscarinic Receptor ◽  
Muscarinic Receptors ◽  
Receptor Protein ◽  
Extracellular Loop ◽  
Electron Microscopic ◽  
Major Band ◽  
Rat Cardiomyocytes ◽  
M2 Muscarinic Receptor ◽  
T Tubules ◽  
M2 Muscarinic Receptors

We produced antibodies against a synthetic peptide corresponding to amino acids 168-192 of the second extracellular loop of the M2 human muscarinic receptor in rabbits. In immunoblot, affinity-purified antibodies specifically recognized a major band of rat ventricular muscarinic receptor protein with a molecular weight of about 80 KD. This recognition could be blocked by pre-incubation with peptide. Moreover, with both light (LM) and electron microscopic (EM) immunocytochemistry techniques, muscarinic receptors were detected on sarcolemma and T-tubules of rat cardiomyocytes. In addition, immunoreactions were localized in membranes of capillaries. Likewise, these reactivities were abolished by pre-incubation with peptide. These results suggest that the antibodies against the second extracellular loop of human M2 muscarinic receptor could specifically recognize rat ventricular muscarinic receptor protein and could be a powerful tool to study the fate of this receptor under different pathological or physiological conditions.

Ozone-induced hyperresponsiveness and blockade of M2 muscarinic receptors by eosinophil major basic protein

1999 ◽  
Vol 87 (4) ◽  
pp. 1272-1278 ◽  
Author(s):  
Bethany L. Yost ◽  
Gerald J. Gleich ◽  
Allison D. Fryer
Keyword(s):  
Muscarinic Receptors ◽  
Guinea Pigs ◽  
Basic Protein ◽  
Muscarinic Agonist ◽  
Receptor Function ◽  
Major Basic Protein ◽  
Interleukin 5 ◽  
Parasympathetic Nerves ◽  
Eosinophil Major Basic Protein

Control of airway smooth muscle is provided by parasympathetic nerves that release acetylcholine onto M3 muscarinic receptors. Acetylcholine release is limited by inhibitory M2 muscarinic receptors. In antigen-challenged guinea pigs, hyperresponsiveness is due to blockade of neuronal M2 receptors by eosinophil major basic protein (MBP). Because exposure of guinea pigs to ozone also causes M2dysfunction and airway hyperresponsiveness, the role of eosinophils in ozone-induced hyperresponsiveness was tested. Animals were exposed to filtered air or to 2 parts/million ozone for 4 h. Twenty-four hours later, the muscarinic agonist pilocarpine no longer inhibited vagally induced bronchoconstriction in ozone-exposed animals, indicating M2 dysfunction. M2 receptor function in ozone-exposed animals was protected by depletion of eosinophils with antibody to interleukin-5 and by pretreatment with antibody to guinea pig MBP. M2 function was acutely restored by removal of MBP with heparin. Ozone-induced hyperreactivity was also prevented by antibody to MBP and was reversed by heparin. These data show that loss of neuronal M2 receptor function after ozone is due to release of eosinophil MBP.

Role of macrophages in virus-induced airway hyperresponsiveness and neuronal M2 muscarinic receptor dysfunction

2004 ◽  
Vol 286 (6) ◽  
pp. L1255-L1259 ◽  
Author(s):  
Ann M. Lee ◽  
Allison D. Fryer ◽  
Nico van Rooijen ◽  
David B. Jacoby
Keyword(s):  
Viral Infection ◽  
Airway Hyperresponsiveness ◽  
Viral Infections ◽  
Muscarinic Agonist ◽  
Vagus Nerves ◽  
Ach Release ◽  
Parasympathetic Nerves ◽  
M2 Muscarinic Receptor ◽  
Stimulation Of

Viral infections exacerbate asthma. One of the pathways by which viruses trigger bronchoconstriction and hyperresponsiveness is by causing dysfunction of inhibitory M2 muscarinic receptors on the airway parasympathetic nerves. These receptors normally limit acetylcholine (ACh) release from the parasympathetic nerves. Loss of M2 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 M2 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 M2 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 M2 receptor dysfunction. These data suggest that macrophages mediate virus-induced M2 receptor dysfunction and airway hyperresponsiveness.

Double-stranded RNA causes airway hyperreactivity and neuronal M2 muscarinic receptor dysfunction

2002 ◽  
Vol 92 (4) ◽  
pp. 1417-1422 ◽  
Author(s):  
William M. L. Bowerfind ◽  
Allison D. Fryer ◽  
David B. Jacoby
Keyword(s):  
Muscarinic Receptors ◽  
Guinea Pigs ◽  
Interferon Γ ◽  
Airway Hyperreactivity ◽  
Vagus Nerves ◽  
Double Stranded Rna ◽  
Parasympathetic Nerves ◽  
M2 Muscarinic Receptor ◽  
Parasympathetic Neurons ◽  
Stimulation Of

Viral infection causes dysfunction of inhibitory M2 muscarinic receptors (M2Rs) on parasympathetic nerves, leading to airway hyperreactivity. The mechanisms of M2R dysfunction are incompletely understood. Double-stranded RNA (dsRNA), a product of viral replication, promotes the expression of interferons. Interferon-γ decreases M2R gene expression in cultured airway parasympathetic neurons. In this study, guinea pigs were treated with dsRNA (1 mg/kg ip) on 2 consecutive days. Twenty-four hours later, anesthetized guinea pigs had dysfunctional M2Rs and were hyperresponsive to electrical stimulation of the vagus nerves, in the absence of inflammation. DsRNA did not affect either cholinesterase or the function of postjunctional M3 muscarinic receptors on smooth muscle. M2Rs on the nerves supplying the heart were also dysfunctional, but M2Rs on the heart muscle itself functioned normally. Thus dsRNA causes increased bronchoconstriction and bradycardia via increased release of ACh from the vagus nerves because of loss of M2R function on parasympathetic nerves in the lungs and heart. Production of dsRNA may be a mechanism by which viruses cause dysfunction of neuronal M2Rs and airway hyperreactivity.

A Mechanism for Rapacuronium-induced Bronchospasm

2003 ◽  
Vol 98 (4) ◽  
pp. 906-911 ◽  
Author(s):  
Edmund Jooste ◽  
Farrah Klafter ◽  
Carol A. Hirshman ◽  
Charles W. Emala
Keyword(s):  
Smooth Muscle ◽  
Muscarinic Receptor ◽  
Airway Smooth Muscle ◽  
Muscarinic Receptors ◽  
Radioligand Binding ◽  
Neuromuscular Blocking ◽  
Parasympathetic Nerve ◽  
Release Of Acetylcholine ◽  
M3 Muscarinic Receptor ◽  
M2 Muscarinic Receptors

Background A safe and effective ultra-short-acting nondepolarizing neuromuscular blocking agent is required to block nicotinic receptors to facilitate intubation. Rapacuronium, which sought to fulfill these criteria, was withdrawn from clinical use due to a high incidence of bronchospasm resulting in death. Understanding the mechanism by which rapacuronium induces fatal bronchospasm is imperative so that newly synthesized neuromuscular blocking agents that share this mechanism will not be introduced clinically. Selective inhibition of M2 muscarinic receptors by muscle relaxants during periods of parasympathetic nerve stimulation (e.g., intubation) can result in the massive release of acetylcholine to act on unopposed M3 muscarinic receptors in airway smooth muscle, thereby facilitating bronchoconstriction. Methods Competitive radioligand binding determined the binding affinities of rapacuronium, vecuronium, cisatracurium, methoctramine (selective M2 antagonist), and 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP; selective M3 antagonist) for M2 and M3 muscarinic receptors. Results Rapacuronium competitively displaced 3H-QNB from the M2 muscarinic receptors but not from the M3 muscarinic receptors within clinically relevant concentrations. Fifty percent inhibitory concentrations (mean +/- SE) for rapacuronium were as follows: M2 muscarinic receptor, 5.10 +/- 1.5 microm (n = 6); M3 muscarinic receptor, 77.9 +/- 11 microm (n = 8). Cisatracurium and vecuronium competitively displaced 3H-QNB from both M2 and M3 muscarinic receptors but had affinities at greater than clinically achieved concentrations for these relaxants. Conclusions Rapacuronium in clinically significant doses has a higher affinity for M2 muscarinic receptors as compared with M3 muscarinic receptors. A potential mechanism by which rapacuronium may potentiate bronchoconstriction is by blockade of M2 muscarinic receptors on prejunctional parasympathetic nerves, leading to increased release of acetylcholine and thereby resulting in M3 muscarinic receptor-mediated airway smooth muscle constriction.

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