Atropine pretreatment enhances airway hyperreactivity in antigen-challenged guinea pigs through an eosinophil-dependent mechanism

2007 ◽  
Vol 292 (5) ◽  
pp. L1126-L1135 ◽  
Author(s):  
Norah G. Verbout ◽  
Jesse K. Lorton ◽  
David B. Jacoby ◽  
Allison D. Fryer
Keyword(s):  
Muscarinic Receptors ◽  
Guinea Pigs ◽  
Airway Hyperreactivity ◽  
Antigen Challenge ◽  
Receptor Function ◽  
Airway Reactivity ◽  
Parasympathetic Nerves ◽  
Eosinophil Activation ◽  
Eosinophil Major Basic Protein ◽  
Eosinophil Accumulation

Airway hyperreactivity in antigen-challenged animals is mediated by eosinophil major basic protein (MBP) that blocks inhibitory M2 muscarinic receptors on parasympathetic nerves, increasing acetylcholine release onto M3 muscarinic receptors on airway smooth muscle. Acutely, anticholinergics block hyperreactivity in antigen-challenged animals and reverse asthma exacerbations in the human, but are less effective in chronic asthma. We tested whether atropine, given before antigen challenge, affected hyperreactivity, M2 receptor function, eosinophil accumulation, and activation. Sensitized guinea pigs received atropine (1 mg/kg ip) 1 h before challenge and 6 h later. Twenty-four hours after challenge, animals were anesthetized, vagotomized, paralyzed, and ventilated. Airway reactivity to electrical stimulation of the vagi and to intravenous acetylcholine was not altered by atropine pretreatment in nonsensitized animals, indicating that atropine was no longer blocking postjunctional muscarinic receptors. Antigen challenge induced airway hyperreactivity to vagal stimulation that was significantly potentiated by atropine pretreatment. Bronchoconstriction induced by acetylcholine was not changed by antigen challenge or by atropine pretreatment. M2 receptor function was lost in challenged animals but protected by atropine pretreatment. Eosinophils in bronchoalveolar lavage and within airway tissues were significantly increased by challenge but significantly reduced by atropine pretreatment. However, extracellular MBP in challenged airways was significantly increased by atropine pretreatment, which may account for reduced eosinophils. Depleting eosinophils with antibody to IL-5 before challenge prevented hyperreactivity and significantly reduced MBP in airways of atropine-pretreated animals. Thus atropine pretreatment potentiated airway hyperreactivity by increasing eosinophil activation and degranulation. These data suggest that anticholinergics enhance eosinophil interactions with airway nerves.

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.

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)

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 Atropine-enhanced, antigen challenge-induced airway hyperreactivity in guinea pigs is mediated by eosinophils and nerve growth factor

2009 ◽  
Vol 297 (2) ◽  
pp. L228-L237 ◽  
Author(s):  
Norah G. Verbout ◽  
David B. Jacoby ◽  
Gerald J. Gleich ◽  
Allison D. Fryer
Keyword(s):  
Nerve Growth Factor ◽  
Growth Factor ◽  
Guinea Pigs ◽  
Inflammatory Cells ◽  
Airway Hyperreactivity ◽  
Antigen Challenge ◽  
Vagus Nerves ◽  
Nerve Growth ◽  
Anticholinergic Therapy ◽  
Eosinophil Activation

Although anticholinergic therapy inhibits bronchoconstriction in asthmatic patients and antigen-challenged animals, administration of atropine 1 h before antigen challenge significantly potentiates airway hyperreactivity and eosinophil activation measured 24 h later. This potentiation in airway hyperreactivity is related to increased eosinophil activation and is mediated at the level of the airway nerves. Since eosinophils produce nerve growth factor (NGF), which is known to play a role in antigen-induced airway hyperreactivity, we tested whether NGF mediates atropine-enhanced, antigen challenge-induced hyperreactivity. Antibody to NGF (Ab NGF) was administered to sensitized guinea pigs with and without atropine pretreatment (1 mg/kg iv) 1 h before challenge. At 24 h after challenge, animals were anesthetized, vagotomized, paralyzed, and ventilated. Electrical stimulation of both vagus nerves caused bronchoconstriction that was increased in challenged animals. Atropine pretreatment potentiated antigen challenge-induced hyperreactivity. Ab NGF did not affect eosinophils or inflammatory cells in any group, nor did it prevent hyperreactivity in challenged animals that were not pretreated with atropine. However, Ab NGF did prevent atropine-enhanced, antigen challenge-induced hyperreactivity and eosinophil activation (assessed by immunohistochemistry). This effect was specific to NGF, since animals given control IgG remained hyperreactive. These data suggest that anticholinergic therapy amplifies eosinophil interactions with airway nerves via NGF. Therefore, therapeutic strategies that target both eosinophil activation and NGF-mediated inflammatory processes in allergic asthma are likely to be beneficial.

Role of insulin in antigen-induced airway eosinophilia and neuronal M2 muscarinic receptor dysfunction

1998 ◽  
Vol 85 (5) ◽  
pp. 1708-1718 ◽  
Author(s):  
K. E. Belmonte ◽  
A. D. Fryer ◽  
R. W. Costello
Keyword(s):  
Muscarinic Receptor ◽  
Fold Increase ◽  
Diabetic Rats ◽  
Antigen Challenge ◽  
Diabetic Patients ◽  
Receptor Function ◽  
Ach Release ◽  
Parasympathetic Nerves ◽  
Low Incidence ◽  
Eosinophil Accumulation

In the lungs, neuronal M2 muscarinic receptors limit ACh release from parasympathetic nerves. In antigen-challenged animals, eosinophil proteins block these receptors, resulting in increased ACh release and vagally mediated hyperresponsiveness. In contrast, diabetic rats are hyporesponsive and have increased M2 receptor function. Because there is a low incidence of asthma among diabetic patients, we investigated whether diabetes protects neuronal M2 receptor function in antigen-challenged rats. Antigen challenge of sensitized rats decreased M2 receptor function, increased vagally mediated hyperreactivity by 75%, and caused a 10-fold increase in eosinophil accumulation around airway nerves. In antigen-challenged diabetic rats, neuronal M2receptor function was preserved and there was no eosinophil accumulation around airway nerves. Insulin treatment of diabetic rats completely restored loss of M2receptor function, vagally mediated hyperresponsiveness, and eosinophilia after antigen challenge. These data demonstrate that insulin is required for development of airway inflammation, loss of neuronal M2 muscarinic receptor function, and subsequent hyperresponsiveness in antigen-challenged rats and may explain decreased incidence of asthma among diabetic humans.

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.

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.

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