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Perez-Zoghbi JF, Sajorda DR, Webb DA, Arnold LA, Emala CW, Yocum GT. Imidazobenzodiazepine PI320 Relaxes Mouse Peripheral Airways by Inhibiting Calcium Mobilization. Am J Respir Cell Mol Biol 2022; 67:482-490. [PMID: 35776523 PMCID: PMC9564932 DOI: 10.1165/rcmb.2022-0084oc] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Asthma is a common respiratory disease characterized, in part, by excessive airway smooth muscle (ASM) contraction (airway hyperresponsiveness). Various GABAAR (γ-aminobutyric acid type A receptor) activators, including benzodiazepines, relax ASM. The GABAAR is a ligand-operated Cl- channel best known for its role in inhibitory neurotransmission in the central nervous system. Although ASM cells express GABAARs, affording a seemingly logical site of action, the mechanism(s) by which GABAAR ligands relax ASM remains unclear. PI320, a novel imidazobenzodiazepine designed for tissue selectivity, is a promising asthma drug candidate. Here, we show that PI320 alleviates methacholine (MCh)-induced bronchoconstriction in vivo and relaxes peripheral airways preconstricted with MCh ex vivo using the forced oscillation technique and precision-cut lung slice experiments, respectively. Surprisingly, the peripheral airway relaxation demonstrated in precision-cut lung slices does not appear to be GABAAR-dependent, as it is not inhibited by the GABAAR antagonist picrotoxin or the benzodiazepine antagonist flumazenil. Furthermore, we demonstrate here that PI320 inhibits MCh-induced airway constriction in the absence of external Ca2, suggesting that PI320-mediated relaxation is not mediated by inhibition of Ca2+ influx in ASM. However, PI320 does inhibit MCh-induced intracellular Ca2+ oscillations in peripheral ASM, a key mediator of contraction that is dependent on sarcoplasmic reticulum Ca2+ mobilization. Furthermore, PI320 inhibits peripheral airway constriction induced by experimentally increasing the intracellular concentration of inositol triphosphate (IP3). These novel data suggest that PI320 relaxes murine peripheral airways by inhibiting intracellular Ca2+ mobilization in ASM, likely by inhibiting Ca2+ release through IP3Rs (IP3 receptors).
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Affiliation(s)
- Jose F. Perez-Zoghbi
- Department of Anesthesiology, Vagelos College of Physicians and Surgeons, Columbia University, New York, New York; and
| | - Dannah Rae Sajorda
- Department of Anesthesiology, Vagelos College of Physicians and Surgeons, Columbia University, New York, New York; and
| | - Daniel A. Webb
- Department of Chemistry and Biochemistry and,Milwaukee Institute for Drug Discovery, University of Wisconsin–Milwaukee, Milwaukee, Wisconsin
| | - Leggy A. Arnold
- Department of Chemistry and Biochemistry and,Milwaukee Institute for Drug Discovery, University of Wisconsin–Milwaukee, Milwaukee, Wisconsin
| | - Charles W. Emala
- Department of Anesthesiology, Vagelos College of Physicians and Surgeons, Columbia University, New York, New York; and
| | - Gene T. Yocum
- Department of Anesthesiology, Vagelos College of Physicians and Surgeons, Columbia University, New York, New York; and
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2
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Zahn N, Roni MSR, Yocum GT, Meyer MJ, Webb DA, Mian MY, Cook JM, Stafford DC, Emala CW, Arnold LA. Development of Inhaled GABA A Receptor Modulators to Improve Airway Function in Bronchoconstrictive Disorders. ACS Pharmacol Transl Sci 2022; 5:80-88. [PMID: 35187417 PMCID: PMC8844962 DOI: 10.1021/acsptsci.1c00238] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Indexed: 02/03/2023]
Abstract
We report the modification of MIDD0301, an imidazodiazepine GABAA receptor (GABAAR) ligand, using two alkyl substituents. We developed PI310 with a 6-(4-phenylbutoxy)hexyl chain as used in the long-acting β2-agonist salmeterol and PI320 with a poly(ethylene glycol) chain as used to improve the brain:plasma ratio of naloxegol, a naloxone analogue. Both imidazodiazepines showed affinity toward the GABAAR binding site of clonazepam, with IC50 values of 576 and 242 nM, respectively. Molecular docking analysis, using the available α1β3γ2 GABAAR structural data, suggests binding of the diazepine core between the α1+/γ2- interface, whereas alkyl substituents are located outside the binding site and thus interact with the protein surface and solvent molecules. The physicochemical properties of these compounds are very different. The solubility of PI310 is low in water. PEGylation of PI320 significantly improves aqueous solubility and cell permeability. Neither compound is toxic in HEK293 cells following exposure at >300 μM for 18 h. Ex vivo studies using guinea pig tracheal rings showed that PI310 was unable to relax the constricted airway smooth muscle. In contrast, PI320 induced muscle relaxation at organ bath concentrations as low as 5 μM, with rapid onset (15 min) at 25 μM. PI320 also reduced airway hyper-responsiveness in vivo in a mouse model of steroid-resistant lung inflammation induced by intratracheal challenge with INFγ and lipopolysaccharide (LPS). At nebulized doses of 7.2 mg/kg, PI320 and albuterol were equally effective in reducing airway hyper-responsiveness. Ten minutes after nebulization, the lung concentration of PI320 was 50-fold that of PI310, indicating superior availability of PI320 when nebulized as an aqueous solution. Overall, PI320 is a promising inhaled drug candidate to quickly relax airway smooth muscle in bronchoconstrictive disorders, such as asthma. Future studies will evaluate the pharmacokinetic/pharmacodynamic properties of PI320 when administered orally.
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Affiliation(s)
- Nicolas
M. Zahn
- Department
of Chemistry and Biochemistry and the Milwaukee Institute for Drug
Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53211, United States
| | - M. S. Rashid Roni
- Department
of Chemistry and Biochemistry and the Milwaukee Institute for Drug
Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53211, United States
| | - Gene T. Yocum
- Department
of Anesthesiology, Columbia University, New York, New York 10032, United States
| | - Michelle J. Meyer
- Department
of Chemistry and Biochemistry and the Milwaukee Institute for Drug
Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53211, United States
| | - Daniel A. Webb
- Department
of Chemistry and Biochemistry and the Milwaukee Institute for Drug
Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53211, United States
| | - Md Yeunus Mian
- Department
of Chemistry and Biochemistry and the Milwaukee Institute for Drug
Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53211, United States
| | - James M. Cook
- Department
of Chemistry and Biochemistry and the Milwaukee Institute for Drug
Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53211, United States
| | | | - Charles W. Emala
- Department
of Anesthesiology, Columbia University, New York, New York 10032, United States
| | - Leggy A. Arnold
- Department
of Chemistry and Biochemistry and the Milwaukee Institute for Drug
Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53211, United States,Pantherics
Incorporated, La Jolla, California 92037, United States,
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3
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Yim PD, Gallos G, Lee-Kong SA, Dan W, Wu AD, Xu D, Berkowitz DE, Emala CW. Novel Expression of GABAA Receptors on Resistance Arteries That Modulate Myogenic Tone. J Vasc Res 2020; 57:113-125. [PMID: 32097943 DOI: 10.1159/000505456] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Accepted: 12/16/2019] [Indexed: 01/17/2023] Open
Abstract
The clinical administration of GABAergic medications leads to hypotension which has classically been attributed to the modulation of neuronal activity in the central and peripheral nervous systems. However, certain types of peripheral smooth muscle cells have been shown to express GABAA receptors, which modulate smooth muscle tone, by the activation of these chloride channels on smooth muscle cell plasma membranes. Limited prior studies demonstrate that non-human large-caliber capacitance blood vessels mounted on a wire myograph are responsive to GABAA ligands. We questioned whether GABAA receptors are expressed in human resistance arteries and whether they modulate myogenic tone. We demonstrate the novel expression of GABAA subunits on vascular smooth muscle from small-caliber human omental and mouse tail resistance arteries. We show that GABAA receptors modulate both plasma membrane potential and calcium responses in primary cultured cells from human resistance arteries. Lastly, we demonstrate functional physiologic modulation of myogenic tone via GABAA receptor activation in human and mouse arteries. Together, these studies demonstrate a previously unrecognized role for GABAA receptors in the modulation of myogenic tone in mouse and human resistance arteries.
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Affiliation(s)
- Peter D Yim
- Department of Anesthesiology, Columbia University, New York, New York, USA,
| | - George Gallos
- Department of Anesthesiology, Columbia University, New York, New York, USA
| | | | - William Dan
- Department of Anesthesiology, Columbia University, New York, New York, USA
| | - Amy D Wu
- Department of Anesthesiology, Columbia University, New York, New York, USA
| | - Dingbang Xu
- Department of Anesthesiology, Columbia University, New York, New York, USA
| | - Dan E Berkowitz
- Department of Anesthesiology and Perioperative Medicine, University of Alabama, Birmingham, Alabama, USA
| | - Charles W Emala
- Department of Anesthesiology, Columbia University, New York, New York, USA
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4
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Yocum GT, Perez-Zoghbi JF, Danielsson J, Kuforiji AS, Zhang Y, Li G, Rashid Roni MS, Kodali R, Stafford DC, Arnold LA, Cook JM, Emala CW. A novel GABA A receptor ligand MIDD0301 with limited blood-brain barrier penetration relaxes airway smooth muscle ex vivo and in vivo. Am J Physiol Lung Cell Mol Physiol 2018; 316:L385-L390. [PMID: 30489155 DOI: 10.1152/ajplung.00356.2018] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Airway smooth muscle (ASM) cells express GABA A receptors (GABAARs), and previous reports have demonstrated that GABAAR activators relax ASM. However, given the activity of GABAARs in central nervous system inhibitory neurotransmission, concern exists that these activators may lead to undesirable sedation. MIDD0301 is a novel imidazobenzodiazepine and positive allosteric modulator of the GABAAR with limited brain distribution, thus eliminating the potential for sedation. Here, we demonstrate that MIDD0301 relaxes histamine-contracted guinea pig ( P < 0.05, n = 6-9) and human ( P < 0.05, n = 6-10) tracheal smooth muscle ex vivo in organ bath experiments, dilates mouse peripheral airways ex vivo in precision-cut lung-slice experiments ( P < 0.001, n = 16 airways from three mice), and alleviates bronchoconstriction in vivo in mice, as assessed by the forced-oscillation technique ( P < 0.05, n = 6 mice). Only trace concentrations of the compound were detected in the brains of mice after inhalation of nebulized 5 mM MIDD0301. Given its favorable pharmacokinetic properties and demonstrated ability to relax ASM in a number of clinically relevant experimental paradigms, MIDD0301 is a promising drug candidate for bronchoconstrictive diseases, such as asthma.
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Affiliation(s)
- Gene T Yocum
- Department of Anesthesiology, Vagelos College of Physicians and Surgeons, Columbia University , New York, New York
| | - Jose F Perez-Zoghbi
- Department of Anesthesiology, Vagelos College of Physicians and Surgeons, Columbia University , New York, New York
| | - Jennifer Danielsson
- Department of Anesthesiology, Vagelos College of Physicians and Surgeons, Columbia University , New York, New York
| | - Aisha S Kuforiji
- Department of Anesthesiology, Vagelos College of Physicians and Surgeons, Columbia University , New York, New York
| | - Yi Zhang
- Department of Anesthesiology, Vagelos College of Physicians and Surgeons, Columbia University , New York, New York
| | - Guanguan Li
- Department of Chemistry and Biochemistry, University of Wisconsin , Milwaukee, Wisconsin
| | - M S Rashid Roni
- Department of Chemistry and Biochemistry, University of Wisconsin , Milwaukee, Wisconsin
| | - Revathi Kodali
- Department of Chemistry and Biochemistry, University of Wisconsin , Milwaukee, Wisconsin
| | - Douglas C Stafford
- Milwaukee Institute for Drug Discovery, University of Wisconsin , Milwaukee, Wisconsin
| | - Leggy A Arnold
- Department of Chemistry and Biochemistry, University of Wisconsin , Milwaukee, Wisconsin.,Milwaukee Institute for Drug Discovery, University of Wisconsin , Milwaukee, Wisconsin
| | - James M Cook
- Department of Chemistry and Biochemistry, University of Wisconsin , Milwaukee, Wisconsin.,Milwaukee Institute for Drug Discovery, University of Wisconsin , Milwaukee, Wisconsin
| | - Charles W Emala
- Department of Anesthesiology, Vagelos College of Physicians and Surgeons, Columbia University , New York, New York
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5
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Dealing with Ophthalmic Chemosurgery Complications. Anesthesiology 2017; 127:586-587. [PMID: 28816788 DOI: 10.1097/aln.0000000000001762] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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6
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Prakash YS. Emerging concepts in smooth muscle contributions to airway structure and function: implications for health and disease. Am J Physiol Lung Cell Mol Physiol 2016; 311:L1113-L1140. [PMID: 27742732 DOI: 10.1152/ajplung.00370.2016] [Citation(s) in RCA: 99] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 10/06/2016] [Indexed: 12/15/2022] Open
Abstract
Airway structure and function are key aspects of normal lung development, growth, and aging, as well as of lung responses to the environment and the pathophysiology of important diseases such as asthma, chronic obstructive pulmonary disease, and fibrosis. In this regard, the contributions of airway smooth muscle (ASM) are both functional, in the context of airway contractility and relaxation, as well as synthetic, involving production and modulation of extracellular components, modulation of the local immune environment, cellular contribution to airway structure, and, finally, interactions with other airway cell types such as epithelium, fibroblasts, and nerves. These ASM contributions are now found to be critical in airway hyperresponsiveness and remodeling that occur in lung diseases. This review emphasizes established and recent discoveries that underline the central role of ASM and sets the stage for future research toward understanding how ASM plays a central role by being both upstream and downstream in the many interactive processes that determine airway structure and function in health and disease.
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Affiliation(s)
- Y S Prakash
- Departments of Anesthesiology, and Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
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7
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Danielsson J, Zaidi S, Kim B, Funayama H, Yim PD, Xu D, Worgall TS, Gallos G, Emala CW. Airway Epithelial Cell Release of GABA is Regulated by Protein Kinase A. Lung 2016; 194:401-8. [PMID: 26989055 DOI: 10.1007/s00408-016-9867-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Accepted: 03/09/2016] [Indexed: 01/05/2023]
Abstract
INTRODUCTION γ-amino butyric acid (GABA) is not only the major inhibitory neurotransmitter in the central nervous system (CNS), but it also plays an important role in the lung, mediating airway smooth muscle relaxation and mucus production. As kinases such as protein kinase A (PKA) are known to regulate the release and reuptake of GABA in the CNS by GABA transporters, we hypothesized that β-agonists would affect GABA release from airway epithelial cells through activation of PKA. METHODS C57/BL6 mice received a pretreatment of a β-agonist or vehicle (PBS), followed by methacholine or PBS. Bronchoalveolar lavage (BAL) was collected and the amount of GABA was quantified using HPLC mass spectrometry. For in vitro studies, cultured BEAS-2B human airway epithelial cells were loaded with (3)H-GABA. (3)H-GABA released was measured during activation and inhibition of PKA and tyrosine kinase signaling pathways. RESULTS β-agonist pretreatment prior to methacholine challenge attenuated in vivo GABA release in mouse BAL and (3)H-GABA release from depolarized BEAS-2B cells. GABA release was also decreased in BEAS-2B cells by increases in cAMP but not by Epac or tyrosine kinase activation. CONCLUSION β-agonists decrease GABA release from airway epithelium through the activation of cAMP and PKA. This has important therapeutic implications as β-agonists and GABA are important mediators of both mucus production and airway smooth muscle tone.
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Affiliation(s)
- Jennifer Danielsson
- Department of Anesthesiology, Columbia University, 630 W 168th St., P&S Box 46, New York, NY, 10032, USA.
| | - Sarah Zaidi
- Department of Pediatrics, Columbia University, New York, NY, 10032, USA
| | - Benjamin Kim
- Department of Pathology and Cell Biology, Columbia University, New York, NY, 10032, USA
| | - Hiromi Funayama
- Department of Anesthesiology, Columbia University, 630 W 168th St., P&S Box 46, New York, NY, 10032, USA
- Department of Pediatric Dentistry, Tsurumi University School of Dental Medicine, Yokohama, Japan
| | - Peter D Yim
- Department of Anesthesiology, Columbia University, 630 W 168th St., P&S Box 46, New York, NY, 10032, USA
| | - Dingbang Xu
- Department of Anesthesiology, Columbia University, 630 W 168th St., P&S Box 46, New York, NY, 10032, USA
| | - Tilla S Worgall
- Department of Pathology and Cell Biology, Columbia University, New York, NY, 10032, USA
| | - George Gallos
- Department of Anesthesiology, Columbia University, 630 W 168th St., P&S Box 46, New York, NY, 10032, USA
| | - Charles W Emala
- Department of Anesthesiology, Columbia University, 630 W 168th St., P&S Box 46, New York, NY, 10032, USA
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8
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Lauer R, Vadi M, Mason L. Anaesthetic management of the child with co-existing pulmonary disease. Br J Anaesth 2013; 109 Suppl 1:i47-i59. [PMID: 23242751 DOI: 10.1093/bja/aes392] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Children with co-existing pulmonary disease have a wide range of clinical manifestations with significant implications for anaesthetists. Although there are a number of pulmonary diseases in children, this review focuses on two of the most common pulmonary disorders, asthma and bronchopulmonary dysplasia (BPD). These diseases share the physiology of bronchoconstriction and variably decreased flow in the airways, but also have unique physiological consequences. The anaesthetist can make a difference in outcomes with proper preoperative evaluation and appropriate preparation for surgery in the context of a team approach to perioperative care with implementation of a stepwise approach to disease management. An understanding of the importance of minimizing the risk for bronchoconstriction and having the tools at hand to treat it when necessary is paramount in the care of these patients. Unique challenges exist in the management of pulmonary hypertension in BPD patients. This review covers medical treatment, intraoperative management, and postoperative care for both patient populations.
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Affiliation(s)
- R Lauer
- Department of Anesthesiology, Loma Linda University, 11234 Anderson Street, Loma Linda, CA 92354, USA.
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9
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Billington CK, Ojo OO, Penn RB, Ito S. cAMP regulation of airway smooth muscle function. Pulm Pharmacol Ther 2013; 26:112-20. [PMID: 22634112 PMCID: PMC3574867 DOI: 10.1016/j.pupt.2012.05.007] [Citation(s) in RCA: 154] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Revised: 05/14/2012] [Accepted: 05/17/2012] [Indexed: 12/11/2022]
Abstract
Agonists activating β(2)-adrenoceptors (β(2)ARs) on airway smooth muscle (ASM) are the drug of choice for rescue from acute bronchoconstriction in patients with both asthma and chronic obstructive pulmonary disease (COPD). Moreover, the use of long-acting β-agonists combined with inhaled corticosteroids constitutes an important maintenance therapy for these diseases. β-Agonists are effective bronchodilators due primarily to their ability to antagonize ASM contraction. The presumed cellular mechanism of action involves the generation of intracellular cAMP, which in turn can activate the effector molecules cAMP-dependent protein kinase (PKA) and Epac. Other agents such as prostaglandin E(2) and phosphodiesterase inhibitors that also increase intracellular cAMP levels in ASM, can also antagonize ASM contraction, and inhibit other ASM functions including proliferation and migration. Therefore, β(2)ARs and cAMP are key players in combating the pathophysiology of airway narrowing and remodeling. However, limitations of β-agonist therapy due to drug tachyphylaxis related to β(2)AR desensitization, and recent findings regarding the manner in which β(2)ARs and cAMP signal, have raised new and interesting questions about these well-studied molecules. In this review we discuss current concepts regarding β(2)ARs and cAMP in the regulation of ASM cell functions and their therapeutic roles in asthma and COPD.
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Affiliation(s)
- Charlotte K Billington
- Division of Therapeutics and Molecular Medicine, The University of Nottingham, Nottingham NG7 2UH, UK.
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10
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Vanhoutte PM. Airway epithelium-derived relaxing factor: myth, reality, or naivety? Am J Physiol Cell Physiol 2013; 304:C813-20. [PMID: 23325407 DOI: 10.1152/ajpcell.00013.2013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The presence of a healthy epithelium can moderate the contraction of the underlying airway smooth muscle. This is, in part, because epithelial cells generate inhibitory messages, whether diffusible substances, electrophysiological signals, or both. The epithelium-dependent inhibitory effect can be tonic (basal), synergistic, or evoked. Rather than a unique epithelium-derived relaxing factor (EpDRF), several known endogenous bronchoactive mediators, including nitric oxide and prostaglandin E2, contribute. The early concept that EpDRF diffuses all the way through the subepithelial layers to directly relax the airway smooth muscle appears unlikely. It is more plausible that the epithelial cells release true messenger molecules, which alter the production of endogenous substances (nitric oxide and/or metabolites of arachidonic acid) by the subepithelial layers. These substances then diffuse to the airway smooth muscle cells, conveying epithelium dependency.
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Affiliation(s)
- Paul M Vanhoutte
- Department of Pharmacology and Pharmacy, University of Hong Kong, Hong Kong, China.
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11
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Gallos G, Townsend E, Yim P, Virag L, Zhang Y, Xu D, Bacchetta M, Emala CW. Airway epithelium is a predominant source of endogenous airway GABA and contributes to relaxation of airway smooth muscle tone. Am J Physiol Lung Cell Mol Physiol 2012. [PMID: 23204068 DOI: 10.1152/ajplung.00274.2012] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Chronic obstructive pulmonary disease and asthma are characterized by hyperreactive airway responses that predispose patients to episodes of acute airway constriction. Recent studies suggest a complex paradigm of GABAergic signaling in airways that involves GABA-mediated relaxation of airway smooth muscle. However, the cellular source of airway GABA and mechanisms regulating its release remain unknown. We questioned whether epithelium is a major source of GABA in the airway and whether the absence of epithelium-derived GABA contributes to greater airway smooth muscle force. Messenger RNA encoding glutamic acid decarboxylase (GAD) 65/67 was quantitatively measured in human airway epithelium and smooth muscle. HPLC quantified GABA levels in guinea pig tracheal ring segments under basal or stimulated conditions with or without epithelium. The role of endogenous GABA in the maintenance of an acetylcholine contraction in human airway and guinea pig airway smooth muscle was assessed in organ baths. A 37.5-fold greater amount of mRNA encoding GAD 67 was detected in human epithelium vs. airway smooth muscle cells. HPLC confirmed that guinea pig airways with intact epithelium have a higher constitutive elution of GABA under basal or KCl-depolarized conditions compared with epithelium-denuded airway rings. Inhibition of GABA transporters significantly suppressed KCl-mediated release of GABA from epithelium-intact airways, but tetrodotoxin was without effect. The presence of intact epithelium had a significant GABAergic-mediated prorelaxant effect on the maintenance of contractile tone. Airway epithelium is a predominant cellular source of endogenous GABA in the airway and contributes significant prorelaxant GABA effects on airway smooth muscle force.
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Affiliation(s)
- George Gallos
- Department of Anesthesiology, College of Physicians and Surgeons, Columbia University, 622 W. 168 St., P&S Box 46, New York, NY 10032, USA.
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12
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Chen Q, Yim PD, Yuan N, Johnson J, Cook JM, Smith S, Ionescu-Zanetti C, Wang ZJ, Arnold LA, Emala CW. Comparison of cell expression formats for the characterization of GABA(A) channels using a microfluidic patch clamp system. Assay Drug Dev Technol 2012; 10:325-35. [PMID: 22574655 DOI: 10.1089/adt.2011.415] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Ensemble recording and microfluidic perfusion are recently introduced techniques aimed at removing the laborious nature and low recording success rates of manual patch clamp. Here, we present assay characteristics for these features integrated into one automated electrophysiology platform as applied to the study of GABA(A) channels. A variety of cell types and methods of GABA(A) channel expression were successfully studied (defined as I(GABA)>500 pA), including stably transfected human embryonic kidney (HEK) cells expressing α(1)β(3)γ(2) GABA(A) channels, frozen ready-to-assay (RTA) HEK cells expressing α(1)β(3)γ(2) or α(3)β(3)γ(2) GABA(A) channels, transiently transfected HEK293T cells expressing α(1)β(3)γ(2) GABA(A) channels, and immortalized cultures of human airway smooth muscle cells endogenously expressing GABA(A) channels. Current measurements were successfully studied in multiple cell types with multiple modes of channel expression in response to several classic GABA(A) channel agonists, antagonists, and allosteric modulators. We obtained success rates above 95% for transiently or stably transfected HEK cells and frozen RTA HEK cells expressing GABA(A) channels. Tissue-derived immortalized cultures of airway smooth muscle cells exhibited a slightly lower recording success rate of 75% using automated patch, which was much higher than the 5% success rate using manual patch clamp technique by the same research group. Responses to agonists, antagonists, and allosteric modulators compared well to previously reported manual patch results. The data demonstrate that both the biophysics and pharmacologic characterization of GABA(A) channels in a wide variety of cell formats can be performed using this automated patch clamp system.
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Affiliation(s)
- Qin Chen
- Fluxion Biosciences, South San Francisco, California, USA
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13
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Gallos G, Yim P, Chang S, Zhang Y, Xu D, Cook JM, Gerthoffer WT, Emala CW. Targeting the restricted α-subunit repertoire of airway smooth muscle GABAA receptors augments airway smooth muscle relaxation. Am J Physiol Lung Cell Mol Physiol 2011; 302:L248-56. [PMID: 21949156 DOI: 10.1152/ajplung.00131.2011] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The prevalence of asthma has taken on pandemic proportions. Since this disease predisposes patients to severe acute airway constriction, novel mechanisms capable of promoting airway smooth muscle relaxation would be clinically valuable. We have recently demonstrated that activation of endogenous airway smooth muscle GABA(A) receptors potentiates β-adrenoceptor-mediated relaxation, and molecular analysis of airway smooth muscle reveals that the α-subunit component of these GABA(A) receptors is limited to the α(4)- and α(5)-subunits. We questioned whether ligands with selective affinity for these GABA(A) receptors could promote relaxation of airway smooth muscle. RT-PCR analysis of GABA(A) receptor subunits was performed on RNA isolated by laser capture microdissection from human and guinea pig airway smooth muscle. Membrane potential and chloride-mediated current were measured in response to GABA(A) subunit-selective agonists in cultured human airway smooth muscle cells. Functional relaxation of precontracted guinea pig tracheal rings was assessed in the absence and presence of the α(4)-subunit-selective GABA(A) receptor agonists: gaboxadol, taurine, and a novel 8-methoxy imidazobenzodiazepine (CM-D-45). Only messenger RNA encoding the α(4)- and α(5)-GABA(A) receptor subunits was identified in RNA isolated by laser capture dissection from guinea pig and human airway smooth muscle tissues. Activation of airway smooth muscle GABA(A) receptors with agonists selective for these subunits resulted in appropriate membrane potential changes and chloride currents and promoted relaxation of airway smooth muscle. In conclusion, selective subunit targeting of endogenous airway smooth muscle-specific GABA(A) receptors may represent a novel therapeutic option for patients in severe bronchospasm.
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Affiliation(s)
- George Gallos
- Dept. of Anesthesiology, College of Physicians and Surgeons of Columbia University, 622 W. 168 St.; P&S Box 46, New York, NY 10032, USA.
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14
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Zaidi S, Gallos G, Yim PD, Xu D, Sonett JR, Panettieri RA, Gerthoffer W, Emala CW. Functional expression of γ-amino butyric acid transporter 2 in human and guinea pig airway epithelium and smooth muscle. Am J Respir Cell Mol Biol 2010; 45:332-9. [PMID: 21057105 DOI: 10.1165/rcmb.2010-0177oc] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
γ-Amino butyric acid (GABA) is a primary inhibitory neurotransmitter in the central nervous system, and is classically released by fusion of synaptic vesicles with the plasma membrane or by egress via GABA transporters (GATs). Recently, a GABAergic system comprised of GABA(A) and GABA(B) receptors has been identified on airway epithelial and smooth muscle cells that regulate mucus secretion and contractile tone of airway smooth muscle (ASM). In addition, the enzyme that synthesizes GABA, glutamic acid decarboxylase, has been identified in airway epithelial cells; however, the mechanism(s) by which this synthesized GABA is released from epithelial intracellular stores is unknown. We questioned whether any of the four known isoforms of GATs are functionally expressed in ASM or epithelial cells. We detected mRNA and protein expression of GAT2 and -4, and isoforms of glutamic acid decarboxylase in native and cultured human ASM and epithelial cells. In contrast, mRNA encoding vesicular GAT (VGAT), the neuronal GABA transporter, was not detected. Functional inhibition of (3)H-GABA uptake was demonstrated using GAT2 and GAT4/betaine-GABA transporter 1 (BGT1) inhibitors in both human ASM and epithelial cells. These results demonstrate that two isoforms of GATs, but not VGAT, are expressed in both airway epithelial and smooth muscle cells. They also provide a mechanism by which locally synthesized GABA can be released from these cells into the airway to activate GABA(A) channels and GABA(B) receptors, with subsequent autocrine and/or paracrine signaling effects on airway epithelium and ASM.
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Affiliation(s)
- Sarah Zaidi
- Department of Pediatrics, College of Physicians and Surgeons of Columbia University, New York, New York 10032, USA
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Propofol preferentially relaxes neurokinin receptor-2-induced airway smooth muscle contraction in guinea pig trachea. Anesthesiology 2010; 112:1335-44. [PMID: 20461005 DOI: 10.1097/aln.0b013e3181d3d7f6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND Propofol is the anesthetic of choice for patients with reactive airway disease and is thought to reduce intubation- or irritant-induced bronchoconstriction by decreasing the cholinergic component of vagal nerve activation. However, additional neurotransmitters, including neurokinins, play a role in irritant-induced bronchoconstriction. We questioned the mechanistic assumption that the clinically recognized protective effect of propofol against irritant-induced bronchoconstriction during intubation was due to attenuation of airway cholinergic reflexes. METHODS Muscle force was continuously recorded from isolated guinea pig tracheal rings in organ baths. Rings were subjected to exogenous contractile agonists (acetylcholine, histamine, endothelin-1, substance P, acetyl-substance P, and neurokinin A) or to electrical field stimulation (EFS) to differentiate cholinergic or nonadrenergic, noncholinergic nerve-mediated contraction with or without cumulatively increasing concentrations of propofol, thiopental, etomidate, or ketamine. RESULTS Propofol did not attenuate the cholinergic component of EFS-induced contraction at clinically relevant concentrations. In contrast, propofol relaxed nonadrenergic, noncholinergic-mediated EFS contraction at concentrations within the clinical range (20-100 mum, n = 9; P < 0.05), and propofol was more potent against an exogenous selective neurokinin-2 receptor versus neurokinin-1 receptor agonist contraction (n = 6, P < 0.001). CONCLUSIONS Propofol, at clinically relevant concentrations, relaxes airway smooth muscle contracted by nonadrenergic, noncholinergic-mediated EFS and exogenous neurokinins but not contractions elicited by the cholinergic component of EFS. These findings suggest that the mechanism of protective effects of propofol against irritant-induced bronchoconstriction involves attenuation of tachykinins released from nonadrenergic, noncholinergic nerves acting at neurokinin-2 receptors on airway smooth muscle.
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Voituron N, Zanella S, Menuet C, Lajard AM, Dutschmann M, Hilaire G. Early abnormalities of post-sigh breathing in a mouse model of Rett syndrome. Respir Physiol Neurobiol 2009; 170:173-82. [PMID: 20040383 DOI: 10.1016/j.resp.2009.12.009] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2009] [Revised: 12/18/2009] [Accepted: 12/21/2009] [Indexed: 01/07/2023]
Abstract
Rett syndrome is a neurodevelopmental disease accompanied by complex, disabling symptoms, including breathing symptoms. Because Rett syndrome is caused by mutations in the transcriptional repressor methyl-CpG-binding protein 2 (MeCP2), Mecp2-deficient mice have been generated as experimental model. Males of Mecp2-deficient mice (Mecp2(-/y)) breathe normally at birth but show abnormal respiratory responses to hypoxia and hypercapnia from postnatal day 25 (P25). After P30, Mecp2(-/y) mice develop breathing symptoms reminiscent of Rett syndrome, aggravating until premature death at around P60. Using plethysmography, we analyzed the sighs and the post-sigh breathing pattern of unrestrained wild type male mice (WT) and Mecp2(-/y) mice from P15 to P60. Sighs are spontaneous large inspirations known to prevent lung atelectasis and to improve alveolar oxygenation. However, Mecp2(-/y) mice show early abnormalities of post-sigh breathing, with long-lasting post-sigh apnoeas, reduced tidal volume when eupnoea resumes and lack of post-sigh bradypnoea which develop from P15, aggravate with age and possibly contribute to breathing symptoms to come.
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Affiliation(s)
- N Voituron
- Maturation, Plasticity, Physiology and Pathology of Respiration (mp3-resp team), Unité Mixte de Recherche 6231 CNRS, Faculté Saint-Jérôme, Service 362, 13397 Marseilles Cedex 20, France
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17
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Choi IG, Choi YS, Min JH, Kim YH, Chae YK, Lee WK, Lee YK, Lee AR, Cho HR, Chae HS. The effects of lidocaine and fentanyl on airway irritability during inhalation induction with desflurane. Korean J Anesthesiol 2009; 57:693-697. [PMID: 30625950 DOI: 10.4097/kjae.2009.57.6.693] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Inhalation induction with desflurane can cause airway irritability and sympathetic stimulation. The aim of this study was to investigate whether lidocaine and fentanyl could reduce these unwanted reactions. METHODS Seventy-five patients who had premedication with midazolam were randomly allocated to one of three groups to receive intravenous saline (S group), lidocaine 1.5 mg/kg (L group), fentanyl 1 microgram/kg (F group), respectively, before tidal volume induction with desflurane in oxygen and nitrous oxide. We recorded airway irritability such as cough, apnea, laryngospasm and excitatory movement and hemodynamic changes. RESULTS Airway irritability was not significantly different between the groups. In F group, mean blood pressure at LOC ver and LOC BIS and heart rate at LOC ver, LOC BIS and just before intubation were lower than those of S group (P < 0.05). Other results were not significantly different. CONCLUSIONS The results of the study showed that intravenous fentanyl and lidocaine had no beneficial effects to reduce airway irritability, but intravenous fentanyl could significantly reduce hemodynamic stimulation during inhalation induction with desflurane in the patients who were premedicated with midazolam.
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Affiliation(s)
- In Gyu Choi
- Department of Anesthesiology and Pain Medicine, Kwandong University, College of Medicine, Goyang, Korea.
| | - Young Soon Choi
- Department of Anesthesiology and Pain Medicine, Kwandong University, College of Medicine, Goyang, Korea.
| | - Jin Hye Min
- Department of Anesthesiology and Pain Medicine, Kwandong University, College of Medicine, Goyang, Korea.
| | - Yong Ho Kim
- Department of Anesthesiology and Pain Medicine, Kwandong University, College of Medicine, Goyang, Korea.
| | - Young Keun Chae
- Department of Anesthesiology and Pain Medicine, Kwandong University, College of Medicine, Goyang, Korea.
| | - Woo Kyung Lee
- Department of Anesthesiology and Pain Medicine, Kwandong University, College of Medicine, Goyang, Korea.
| | - Yong Kyung Lee
- Department of Anesthesiology and Pain Medicine, Kwandong University, College of Medicine, Goyang, Korea.
| | - Ae Re Lee
- Department of Anesthesiology and Pain Medicine, Kwandong University, College of Medicine, Goyang, Korea.
| | - Hyong Rae Cho
- Department of Anesthesiology and Pain Medicine, Kwandong University, College of Medicine, Goyang, Korea.
| | - Hong Seok Chae
- Department of Anesthesiology and Pain Medicine, Kwandong University, College of Medicine, Goyang, Korea.
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