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Xu JF, Xia J, Wan Y, Yang Y, Wu JJ, Peng C, Ao H. Vasorelaxant Activities and its Underlying Mechanisms of Magnolia Volatile Oil on Rat Thoracic Aorta Based on Network Pharmacology. Front Pharmacol 2022; 13:812716. [PMID: 35308213 PMCID: PMC8926352 DOI: 10.3389/fphar.2022.812716] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Accepted: 01/24/2022] [Indexed: 02/04/2023] Open
Abstract
Objective: Magnolia volatile oil (MVO) is a mixture mainly containing eudesmol and its isomers. This study was to investigate the vasorelaxant effects and the underlying mechanism of MVO in rat thoracic aortas. Method: The present study combined gas chromatography–mass spectrometry (GC-MS) and network pharmacology analysis with in vitro experiments to clarify the mechanisms of MVO against vessel contraction. A compound–target network, compound–target–disease network, protein–protein interaction network, compound–target–pathway network, gene ontology, and pathway enrichment for hypertension were applied to identify the potential active compounds, drug targets, and pathways. Additionally, the thoracic aortic rings with or without endothelium were prepared to explore the underlying mechanisms. The roles of the PI3K-Akt-NO pathways, neuroreceptors, K+ channels, and Ca2+ channels on the vasorelaxant effects of MVO were evaluated through the rat thoracic aortic rings. Results: A total of 29 compounds were found in MVO, which were identified by GC-MS, of which 21 compounds with a content of more than 0.1% were selected for further analysis. The network pharmacology research predicted that beta-caryophyllene, palmitic acid, and (+)-β-selinene might act as the effective ingredients of MVO for the treatment of hypertension. Several hot targets, mainly involving TNF, CHRM1, ACE, IL10, PTGS2, REN, and F2, and pivotal pathways, such as the neuroactive ligand–receptor interaction, the calcium signaling pathway, and the PI3K-Akt signaling, were responsible for the vasorelaxant effect of MVO. As expected, MVO exerted a vasorelaxant effect on the aortic rings pre-contracted by KCl and phenylephrine in an endothelium-dependent and non-endothelium-dependent manner. Importantly, a pre-incubation with indomethacin (Indo), N-nitro-L-arginine methyl ester, methylene blue, wortmannin, and atropine sulfate as well as 4-aminopyridione diminished MVO-induced vasorelaxation, suggesting that the activation of the PI3K-Akt-NO pathway and KV channel were involved in the vasorelaxant effect of MVO, which was consistent with the results of the Kyoto Encyclopedia of Genes and the Genomes. Additionally, MVO could significantly inhibit Ca2+ influx resulting in the contraction of aortic rings, revealing that the inhibition of the calcium signaling pathway exactly participated in the vasorelaxant activity of MVO as predicted by network pharmacology. Conclusion: MVO might be a potent treatment of diseases with vascular dysfunction like hypertension. The underlying mechanisms were related to the PI3K-Akt-NO pathway, KV pathway, as well as Ca2+ channel, which were predicted by the network pharmacology and verified by the experiments in vitro. This study based on network pharmacology provided experimental support for the clinical application of MVO in the treatment of hypertension and afforded a novel research method to explore the activity and mechanism of traditional Chinese medicine.
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Affiliation(s)
- Jin-Feng Xu
- Key Laboratory of Southwestern Chinese Medicine Resources, Chengdu University of Traditional Chinese Medicine, Chengdu, China
| | - Jia Xia
- Key Laboratory of Southwestern Chinese Medicine Resources, Chengdu University of Traditional Chinese Medicine, Chengdu, China
| | - Yan Wan
- Key Laboratory of Southwestern Chinese Medicine Resources, Chengdu University of Traditional Chinese Medicine, Chengdu, China
| | - Yu Yang
- Key Laboratory of Southwestern Chinese Medicine Resources, Chengdu University of Traditional Chinese Medicine, Chengdu, China
| | - Jiao-Jiao Wu
- Key Laboratory of Southwestern Chinese Medicine Resources, Chengdu University of Traditional Chinese Medicine, Chengdu, China
| | - Cheng Peng
- Key Laboratory of Southwestern Chinese Medicine Resources, Chengdu University of Traditional Chinese Medicine, Chengdu, China
- *Correspondence: Cheng Peng, ; Hui Ao,
| | - Hui Ao
- Key Laboratory of Southwestern Chinese Medicine Resources, Chengdu University of Traditional Chinese Medicine, Chengdu, China
- Innovative Institute of Chinese Medicine and Pharmacy, Chengdu University of Traditional Chinese Medicine, Chengdu, China
- *Correspondence: Cheng Peng, ; Hui Ao,
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Role of Airway Smooth Muscle in Inflammation Related to Asthma and COPD. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1303:139-172. [PMID: 33788192 DOI: 10.1007/978-3-030-63046-1_9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Airway smooth muscle contributes to both contractility and inflammation in the pathophysiology of asthma and COPD. Airway smooth muscle cells can change the degree of a variety of functions, including contraction, proliferation, migration, and the secretion of inflammatory mediators (phenotype plasticity). Airflow limitation, airway hyperresponsiveness, β2-adrenergic desensitization, and airway remodeling, which are fundamental characteristic features of these diseases, are caused by phenotype changes in airway smooth muscle cells. Alterations between contractile and hyper-contractile, synthetic/proliferative phenotypes result from Ca2+ dynamics and Ca2+ sensitization. Modulation of Ca2+ dynamics through the large-conductance Ca2+-activated K+ channel/L-type voltage-dependent Ca2+ channel linkage and of Ca2+ sensitization through the RhoA/Rho-kinase pathway contributes not only to alterations in the contractile phenotype involved in airflow limitation, airway hyperresponsiveness, and β2-adrenergic desensitization but also to alteration of the synthetic/proliferative phenotype involved in airway remodeling. These Ca2+ signal pathways are also associated with synergistic effects due to allosteric modulation between β2-adrenergic agonists and muscarinic antagonists. Therefore, airway smooth muscle may be a target tissue in the therapy for these diseases. Moreover, the phenotype changing in airway smooth muscle cells with focuses on Ca2+ signaling may provide novel strategies for research and development of effective remedies against both bronchoconstriction and inflammation.
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Tanahashi Y, Komori S, Matsuyama H, Kitazawa T, Unno T. Functions of Muscarinic Receptor Subtypes in Gastrointestinal Smooth Muscle: A Review of Studies with Receptor-Knockout Mice. Int J Mol Sci 2021; 22:E926. [PMID: 33477687 PMCID: PMC7831928 DOI: 10.3390/ijms22020926] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 01/12/2021] [Accepted: 01/14/2021] [Indexed: 01/25/2023] Open
Abstract
Parasympathetic signalling via muscarinic acetylcholine receptors (mAChRs) regulates gastrointestinal smooth muscle function. In most instances, the mAChR population in smooth muscle consists mainly of M2 and M3 subtypes in a roughly 80% to 20% mixture. Stimulation of these mAChRs triggers a complex array of biochemical and electrical events in the cell via associated G proteins, leading to smooth muscle contraction and facilitating gastrointestinal motility. Major signalling events induced by mAChRs include adenylyl cyclase inhibition, phosphoinositide hydrolysis, intracellular Ca2+ mobilisation, myofilament Ca2+ sensitisation, generation of non-selective cationic and chloride currents, K+ current modulation, inhibition or potentiation of voltage-dependent Ca2+ currents and membrane depolarisation. A lack of ligands with a high degree of receptor subtype selectivity and the frequent contribution of multiple receptor subtypes to responses in the same cell type have hampered studies on the signal transduction mechanisms and functions of individual mAChR subtypes. Therefore, novel strategies such as genetic manipulation are required to elucidate both the contributions of specific AChR subtypes to smooth muscle function and the underlying molecular mechanisms. In this article, we review recent studies on muscarinic function in gastrointestinal smooth muscle using mAChR subtype-knockout mice.
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Affiliation(s)
- Yasuyuki Tanahashi
- Department of Advanced Life Sciences, Faculty of Life Sciences, Kyoto Sangyo University, Kyoto 603-8555, Japan;
| | - Seiichi Komori
- Laboratory of Veterinary Pharmacology, Department of Veterinary Medicine, Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan; (S.K.); (H.M.)
| | - Hayato Matsuyama
- Laboratory of Veterinary Pharmacology, Department of Veterinary Medicine, Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan; (S.K.); (H.M.)
| | - Takio Kitazawa
- Department of Veterinary Science, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501, Japan;
| | - Toshihiro Unno
- Laboratory of Veterinary Pharmacology, Department of Veterinary Medicine, Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan; (S.K.); (H.M.)
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Abstract
Asthma is a heterogeneous inflammatory disease of the airways that is associated with airway hyperresponsiveness and airflow limitation. Although asthma was once simply categorized as atopic or nonatopic, emerging analyses over the last few decades have revealed a variety of asthma endotypes that are attributed to numerous pathophysiological mechanisms. The classification of asthma by endotype is primarily routed in different profiles of airway inflammation that contribute to bronchoconstriction. Many asthma therapeutics target G protein-coupled receptors (GPCRs), which either enhance bronchodilation or prevent bronchoconstriction. Short-acting and long-acting β 2-agonists are widely used bronchodilators that signal through the activation of the β 2-adrenergic receptor. Short-acting and long-acting antagonists of muscarinic acetylcholine receptors are used to reduce bronchoconstriction by blocking the action of acetylcholine. Leukotriene antagonists that block the signaling of cysteinyl leukotriene receptor 1 are used as an add-on therapy to reduce bronchoconstriction and inflammation induced by cysteinyl leukotrienes. A number of GPCR-targeting asthma drug candidates are also in different stages of development. Among them, antagonists of prostaglandin D2 receptor 2 have advanced into phase III clinical trials. Others, including antagonists of the adenosine A2B receptor and the histamine H4 receptor, are in early stages of clinical investigation. In the past decade, significant research advancements in pharmacology, cell biology, structural biology, and molecular physiology have greatly deepened our understanding of the therapeutic roles of GPCRs in asthma and drug action on these GPCRs. This review summarizes our current understanding of GPCR signaling and pharmacology in the context of asthma treatment. SIGNIFICANCE STATEMENT: Although current treatment methods for asthma are effective for a majority of asthma patients, there are still a large number of patients with poorly controlled asthma who may experience asthma exacerbations. This review summarizes current asthma treatment methods and our understanding of signaling and pharmacology of G protein-coupled receptors (GPCRs) in asthma therapy, and discusses controversies regarding the use of GPCR drugs and new opportunities in developing GPCR-targeting therapeutics for the treatment of asthma.
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Affiliation(s)
- Stacy Gelhaus Wendell
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania (S.G.W., C.Z.); Bioinformatics Institute, Agency for Science, Technology, and Research, Singapore (H.F.); and Department of Biological Sciences, National University of Singapore, and Center for Computational Biology, DUKE-NUS Medical School, Singapore (H.F.)
| | - Hao Fan
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania (S.G.W., C.Z.); Bioinformatics Institute, Agency for Science, Technology, and Research, Singapore (H.F.); and Department of Biological Sciences, National University of Singapore, and Center for Computational Biology, DUKE-NUS Medical School, Singapore (H.F.)
| | - Cheng Zhang
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania (S.G.W., C.Z.); Bioinformatics Institute, Agency for Science, Technology, and Research, Singapore (H.F.); and Department of Biological Sciences, National University of Singapore, and Center for Computational Biology, DUKE-NUS Medical School, Singapore (H.F.)
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Bradley E, Large RJ, Bihun VV, Mullins ND, Hollywood MA, Sergeant GP, Thornbury KD. Inhibitory effects of openers of large-conductance Ca 2+-activated K + channels on agonist-induced phasic contractions in rabbit and mouse bronchial smooth muscle. Am J Physiol Cell Physiol 2018; 315:C818-C829. [PMID: 30257105 DOI: 10.1152/ajpcell.00068.2018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Airway smooth muscle expresses abundant BKCa channels, but their role in regulating contractions remains controversial. This study examines the effects of two potent BKCa channel openers on agonist-induced phasic contractions in rabbit and mouse bronchi. First, we demonstrated the ability of 10 μM GoSlo-SR5-130 to activate BKCa channels in inside-out patches from rabbit bronchial myocytes, where it shifted the activation V1/2 by -88 ± 11 mV (100 nM Ca2+, n = 7). In mouse airway smooth muscle cells, GoSlo-SR5-130 dose dependently shifted V1/2 by 12-83 mV over a concentration range of 1-30 μM. Compound X, a racemic mixture of two enantiomers, reported to be potent BKCa channel openers, shifted V1/2 by 20-79 mV over a concentration range of 0.3-3 μM. In rabbit bronchial rings, exposure to histamine (1 μM) induced phasic contractions after a delay of ~35 min. These were abolished by GoSlo-SR5-130 (30 μM). Nifedipine (100 nM) and CaCCinhA01 (10 μM), a TMEM16A blocker, also abolished histamine-induced phasic contractions. In mouse bronchi, similar phasic contractions were evoked by exposure to U46619 (100 nM) and carbachol (100 nM). In each case, these were inhibited by concentrations of GoSlo-SR5-130 and compound X that shifted the activation V1/2 of BKCa channels in the order of -80 mV. In conclusion, membrane potential-dependent regulation of L-type Ca2+ channels appears to be important for histamine-, U46619-, and carbachol-induced phasic contractions in airway smooth muscle. Contractions can be abolished by BKCa channel openers, suggesting that these channels are potential targets for treating some causes of airway obstruction.
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Affiliation(s)
- Eamonn Bradley
- Smooth Muscle Research Centre, Dundalk Institute of Technology , Dundalk , Ireland
| | - Roddy J Large
- Smooth Muscle Research Centre, Dundalk Institute of Technology , Dundalk , Ireland
| | | | - Nicolas D Mullins
- Smooth Muscle Research Centre, Dundalk Institute of Technology , Dundalk , Ireland
| | - Mark A Hollywood
- Smooth Muscle Research Centre, Dundalk Institute of Technology , Dundalk , Ireland
| | - Gerard P Sergeant
- Smooth Muscle Research Centre, Dundalk Institute of Technology , Dundalk , Ireland
| | - Keith D Thornbury
- Smooth Muscle Research Centre, Dundalk Institute of Technology , Dundalk , Ireland
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Kume H, Nishiyama O, Isoya T, Higashimoto Y, Tohda Y, Noda Y. Involvement of Allosteric Effect and K Ca Channels in Crosstalk between β₂-Adrenergic and Muscarinic M₂ Receptors in Airway Smooth Muscle. Int J Mol Sci 2018; 19:ijms19071999. [PMID: 29987243 PMCID: PMC6073859 DOI: 10.3390/ijms19071999] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Revised: 06/24/2018] [Accepted: 07/04/2018] [Indexed: 12/17/2022] Open
Abstract
To advance the development of bronchodilators for asthma and chronic obstructive pulmonary disease (COPD), this study was designed to investigate the mechanism of functional antagonism between β2-adrenergic and muscarinic M2 receptors, focusing on allosteric effects and G proteins/ion channels coupling. Muscarinic receptor antagonists (tiotropium, glycopyrronium, atropine) synergistically enhanced the relaxant effects of β2-adrenergic receptor agonists (procaterol, salbutamol, formoterol) in guinea pig trachealis. This crosstalk was inhibited by iberitoxin, a large-conductance Ca2+-activated K+ (KCa) channel inhibitor, whereas it was increased by verapamil, a L-type voltage-dependent Ca2+ (VDC) channel inhibitor; additionally, it was enhanced after tissues were incubated with pertussis or cholera toxin. This synergism converges in the G proteins (Gi, Gs)/KCa channel/VDC channel linkages. Muscarinic receptor antagonists competitively suppressed, whereas, β2-adrenergic receptor agonists noncompetitively suppressed muscarinic contraction. In concentration-inhibition curves for β2-adrenergic receptor agonists with muscarinic receptor antagonists, EC50 was markedly decreased, and maximal inhibition was markedly increased. Hence, muscarinic receptor antagonists do not bind to allosteric sites on muscarinic receptors. β2-Adrenergic receptor agonists bind to allosteric sites on these receptors; their intrinsic efficacy is attenuated by allosteric modulation (partial agonism). Muscarinic receptor antagonists enhance affinity and efficacy of β2-adrenergic action via allosteric sites in β2-adrenergic receptors (synergism). In conclusion, KCa channels and allosterism may be novel targets of bronchodilator therapy for diseases such as asthma and COPD.
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Affiliation(s)
- Hiroaki Kume
- Department of Respiratory Medicine and Allergology, Faculty of Medicine, Kindai University, 377-2 Ohnohigashi, Osakasayama 589-8511, Japan.
| | - Osamu Nishiyama
- Department of Respiratory Medicine and Allergology, Faculty of Medicine, Kindai University, 377-2 Ohnohigashi, Osakasayama 589-8511, Japan.
| | - Takaaki Isoya
- Department of Respiratory Medicine and Allergology, Faculty of Medicine, Kindai University, 377-2 Ohnohigashi, Osakasayama 589-8511, Japan.
| | - Yuji Higashimoto
- Department of Respiratory Medicine and Allergology, Faculty of Medicine, Kindai University, 377-2 Ohnohigashi, Osakasayama 589-8511, Japan.
| | - Yuji Tohda
- Department of Respiratory Medicine and Allergology, Faculty of Medicine, Kindai University, 377-2 Ohnohigashi, Osakasayama 589-8511, Japan.
| | - Yukihiro Noda
- Division of Clinical Sciences and Neuropsychopharmacology, Graduate School of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya 468-8503, Japan.
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Menozzi A, Pozzoli C, Poli E, Bontempi G, Serventi P, Meucci V, Intorre L, Bertini S. Role of muscarinic receptors in the contraction of jejunal smooth muscle in the horse: An in vitro study. Res Vet Sci 2017; 115:387-392. [PMID: 28711697 DOI: 10.1016/j.rvsc.2017.07.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 06/09/2017] [Accepted: 07/08/2017] [Indexed: 11/19/2022]
Abstract
Nonselective antimuscarinic drugs are clinically useful in several pathologic conditions of horses, but, blocking all muscarinic receptor (MR) subtypes, may cause several side effects. The availability of selective antimuscarinic drugs could improve therapeutic efficacy and safety. We aimed to enlighten the role of different MR subtypes by evaluating the effects of nonselective, and selective M1, M2 and M3 MR antagonists on the contractions of horse jejunum. Segments of circular muscle of equine jejunum, were put into organ baths, connected to isotonic transducers, and the effects on ACh concentration-response curves, and on electrical field stimulation (EFS)-evoked contractions of intestinal preparations, induced by nonselective or selective MR antagonists, compared to pre-drug level, were studied. Atropine (nonselective MR antagonist), pirenzepine (selective M1 antagonist), and p-FHHSiD (selective M3 antagonist) competitively antagonized ACh (pA2=9.78±0.21; 7.14±0.25 and 7.56±0.17, respectively). Methoctramine (selective M2 antagonist) antagonized ACh in a concentration-unrelated fashion; however, it competitively antagonized carbachol, a nonselective muscarinic agonist (pA2=6.42±0.23). Atropine dose-dependently reduced EFS-evoked contractions, reaching a maximal effect of -45.64±6.54%; the simultaneous block of neurokinin receptors, almost completely abolished the atropine-insensitive contractions. p-FHHSiD dose-dependently reduced EFS-induced contractions, while pirenzepine caused a minor decrease. Methoctramine, ineffective up to 10-7M, enhanced the contractions at 10-6M; the block of neurokinin receptors abolished the increase of contraction. Cholinergic contractions of horse jejunum are mainly mediated by M3 receptors; M2 selective antagonists seem to scarcely affect cholinergic, and to enhance neurokininergic contractions of equine jejunum, thus their use entails a lower risk of causing intestinal hypomotility, compared to nonselective drugs.
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Affiliation(s)
- Alessandro Menozzi
- Department of Veterinary Science, University of Parma, Strada del Taglio 10, 43126 Parma, Italy.
| | - Cristina Pozzoli
- Department of Neuroscience, University of Parma, Via Volturno 39, 43125 Parma, Italy
| | - Enzo Poli
- Department of Neuroscience, University of Parma, Via Volturno 39, 43125 Parma, Italy
| | - Giada Bontempi
- Department of Veterinary Science, University of Parma, Strada del Taglio 10, 43126 Parma, Italy
| | - Paolo Serventi
- Department of Veterinary Science, University of Parma, Strada del Taglio 10, 43126 Parma, Italy
| | - Valentina Meucci
- Department of Veterinary Science, University of Pisa, Via Livornese, S. Piero a Grado, Pisa, Italy
| | - Luigi Intorre
- Department of Veterinary Science, University of Pisa, Via Livornese, S. Piero a Grado, Pisa, Italy
| | - Simone Bertini
- Department of Veterinary Science, University of Parma, Strada del Taglio 10, 43126 Parma, Italy
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Involvement of Ca 2+ Signaling in the Synergistic Effects between Muscarinic Receptor Antagonists and β₂-Adrenoceptor Agonists in Airway Smooth Muscle. Int J Mol Sci 2016; 17:ijms17091590. [PMID: 27657061 PMCID: PMC5037855 DOI: 10.3390/ijms17091590] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 09/02/2016] [Accepted: 09/08/2016] [Indexed: 12/25/2022] Open
Abstract
Long-acting muscarinic antagonists (LAMAs) and short-acting β2-adrenoceptor agonists (SABAs) play important roles in remedy for COPD. To propel a translational research for development of bronchodilator therapy, synergistic effects between SABAs with LAMAs were examined focused on Ca2+ signaling using simultaneous records of isometric tension and F340/F380 in fura-2-loaded tracheal smooth muscle. Glycopyrronium (3 nM), a LAMA, modestly reduced methacholine (1 μM)-induced contraction. When procaterol, salbutamol and SABAs were applied in the presence of glycopyrronium, relaxant effects of these SABAs are markedly enhanced, and percent inhibition of tension was much greater than the sum of those for each agent and those expected from the BI theory. In contrast, percent inhibition of F340/F380 was not greater than those values. Bisindolylmaleimide, an inhibitor of protein kinase C (PKC), significantly increased the relaxant effect of LAMA without reducing F340/F380. Iberiotoxin, an inhibitor of large-conductance Ca2+-activated K+ (KCa) channels, significantly suppressed the effects of these combined agents with reducing F340/F380. In conclusion, combination of SABAs with LAMAs synergistically enhances inhibition of muscarinic contraction via decreasing both Ca2+ sensitization mediated by PKC and Ca2+ dynamics mediated by KCa channels. PKC and KCa channels may be molecular targets for cross talk between β2-adrenoceptors and muscarinic receptors.
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Gattineni J, Baum M. Developmental changes in renal tubular transport-an overview. Pediatr Nephrol 2015; 30:2085-98. [PMID: 24253590 PMCID: PMC4028442 DOI: 10.1007/s00467-013-2666-6] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Revised: 10/01/2013] [Accepted: 10/11/2013] [Indexed: 10/26/2022]
Abstract
The adult kidney maintains a constant volume and composition of extracellular fluid despite changes in water and salt intake. The neonate is born with a kidney that has a small fraction of the glomerular filtration rate of the adult and immature tubules that function at a lower capacity than that of the mature animal. Nonetheless, the neonate is also able to maintain a constant extracellular fluid volume and composition. Postnatal renal tubular development was once thought to be due to an increase in the transporter abundance to meet the developmental increase in glomerular filtration rate. However, postnatal renal development of each nephron segment is quite complex. There are isoform changes of several transporters as well as developmental changes in signal transduction that affect the capacity of renal tubules to reabsorb solutes and water. This review will discuss neonatal tubular function with an emphasis on the differences that have been found between the neonate and adult. We will also discuss some of the factors that are responsible for the maturational changes in tubular transport that occur during postnatal renal development.
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Affiliation(s)
- Jyothsna Gattineni
- Department of Pediatrics, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390-9061, USA
| | - Michel Baum
- Department of Pediatrics, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390-9061, USA.
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA.
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Kume H, Fukunaga K, Oguma T. Research and development of bronchodilators for asthma and COPD with a focus on G protein/KCa channel linkage and β2-adrenergic intrinsic efficacy. Pharmacol Ther 2015; 156:75-89. [PMID: 26432616 DOI: 10.1016/j.pharmthera.2015.09.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Bronchodilators are used to improve symptoms and lung function in asthma and COPD. Airway smooth muscle tone is regulated by both muscarinic and β2-adrenergic receptor activity. Large-conductance Ca(2+)-activated K(+) (KCa) channels are activated by β2-adrenergic receptor agonists, via Gs, and suppressed by muscarinic receptor antagonists via Gi. This functional antagonism converges on the G protein/KCa channel linkages. Membrane potential regulated by KCa channels contributes to airway smooth muscle tension via Ca(2+) influx passing through voltage-dependent Ca(2+) (VDC) channels. The Gs/KCa/VDC channel linkage is a key process in not only physiological effects, but also in dysfunction of β2-adrenergic receptors and airway remodeling. Moreover, this pathway is involved in the synergistic effects between β2-adrenergic receptor agonists and muscarinic receptor antagonists. Intrinsic efficacy is also an important characteristic for both maintenance and loss of β2-adrenergic action. Allosteric modulators of G protein-coupled receptors contribute not only to this synergistic effect between β2-adrenergic and muscarinic M2 receptors, but also to intrinsic efficacy. The effects of weak partial agonists are suppressed by lowering receptor number, disordering receptor function, and enhancing functional antagonism; in contrast, those of full or strong partial agonists are not suppressed. Excessive exposure to full agonists causes β2-adrenergic desensitization; in contrast, exposure to partial agonists does not cause desensitization. Intrinsic efficacy may provide the rationale for the clinical use of β2-adrenergic receptor agonists in asthma and COPD. In conclusion, the G protein/KCa linkage and intrinsic efficacy (allosteric effects) may be therapeutic targets for research and development of novel agents against both airway obstruction and airway remodeling.
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Affiliation(s)
- Hiroaki Kume
- Department of Respiratory Medicine and Allergology, Kinki University Faculty of Medicine, Japan.
| | - Kentaro Fukunaga
- Division of Respiratory Medicine, Department of Internal Medicine, Shiga University of Medical Science, Japan
| | - Tetsuya Oguma
- Division of Respiratory Medicine, Department of Internal Medicine, Shiga University of Medical Science, Japan
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Toro L, Li M, Zhang Z, Singh H, Wu Y, Stefani E. MaxiK channel and cell signalling. Pflugers Arch 2014; 466:875-86. [PMID: 24077696 DOI: 10.1007/s00424-013-1359-0] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Revised: 09/09/2013] [Accepted: 09/10/2013] [Indexed: 01/23/2023]
Abstract
The large-conductance Ca2+- and voltage-activated K+ (MaxiK, BK, BKCa, Slo1, KCa1.1) channel role in cell signalling is becoming apparent as we learn how the channel interacts with a multiplicity of proteins not only at the plasma membrane but also in intracellular organelles including the endoplasmic reticulum, nucleus, and mitochondria. In this review, we focus on the interactions of MaxiK channels with seven-transmembrane G protein-coupled receptors and discuss information suggesting that, the channel big C-terminus may act as the nucleus of signalling molecules including kinases relevant for cell death and survival. Increasing evidence indicates that the channel is able to associate with a variety of receptors including β-adrenergic receptors, G protein-coupled estrogen receptors, acetylcholine receptors, thromboxane A2 receptors, and angiotensin II receptors, which highlights the varied functions that the channel has (or may have) not only in regulating contraction/relaxation of muscle cells or neurotransmission in the brain but also in cell metabolism, proliferation, migration, and gene expression. In line with this view, MaxiK channels have been implicated in obesity and in brain, prostate, and mammary cancers. A better understanding on the molecular mechanisms underlying or triggered by MaxiK channel abnormalities like overexpression in certain cancers may lead to new therapeutics to prevent devastating diseases.
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Ahounou JF, Ouedraogo GG, Gbenou JD, Ouedraogo S, Agbodjogbe WK, Dansou PH, Moudachirou M. Spasmolytic effects of aqueous extract of mixture from Aframomumum melegueta (K Schum) - Citrus aurantifolia (Christm and Panzer) on isolated trachea from rat. AFRICAN JOURNAL OF TRADITIONAL, COMPLEMENTARY, AND ALTERNATIVE MEDICINES : AJTCAM 2014; 9:228-33. [PMID: 23983339 DOI: 10.4314/ajtcam.v9i2.7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The spasmolytic properties of the aqueous extract of Aframomum melegueta (K Schum) and Citrus aurantifolia (Christm and Panzer) (AMCA) mixture were tested on isolated rat trachea. Inhibition of the contraction was observed the in presence of the AMCA (EC 50 = 1.80 ± 0.48 mg/mL) after a pre contraction of the trachea by acetylcholine (10⁻⁵ M). With propranolol (10⁻⁶ M), the spasmolytic activity of the mixture was inhibited and the concentration-response curve shifted to the right. The EC50 value was then 2.60 ± 0.41 mg/mL. AMCA also inhibited contraction induced by KCl (4.10⁻² M) with EC50 value = 1.86 ± 0.65 mg/mL. These results clearly show the relaxing effect of the aqueous extract on the isolated rat trachea. This effect involved some β-adrenergic receptor inhibition.
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Affiliation(s)
- Judith F Ahounou
- Laboratoire de Pharmacognosie et des Huiles Essentielles, Faculté des Sciences de la Santé, Faculté des Sciences et Techniques, Université d'Abomey Calavi 01 BP 918 Cotonou Bénin
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13
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Menozzi A, Pozzoli C, Poli E, Delvescovo B, Serventi P, Bertini S. Pharmacological characterization of muscarinic receptors in the contractions of isolated bronchi in the horse. J Vet Pharmacol Ther 2014; 37:325-31. [DOI: 10.1111/jvp.12108] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Accepted: 01/08/2014] [Indexed: 11/26/2022]
Affiliation(s)
- A. Menozzi
- Dipartimento di Scienze Medico-Veterinarie; Università di Parma; Parma Italy
| | - C. Pozzoli
- Dipartimento di Neuroscienze; Università di Parma; Parma Italy
| | - E. Poli
- Dipartimento di Neuroscienze; Università di Parma; Parma Italy
| | - B. Delvescovo
- Dipartimento di Scienze Medico-Veterinarie; Università di Parma; Parma Italy
| | - P. Serventi
- Dipartimento di Scienze Medico-Veterinarie; Università di Parma; Parma Italy
| | - S. Bertini
- Dipartimento di Scienze Medico-Veterinarie; Università di Parma; Parma Italy
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14
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Jin Q, Davis RS, Bullion AM, Jin J, Wang Y, Widdowson KL, Palovich MR, Foley JJ, Schmidt DB, Buckley PT, Webb EF, Salmon M, Belmonte KE, Sarau HM, Busch-Petersen J. Tyrosine urea muscarinic acetylcholine receptor antagonists: achiral quaternary ammonium groups. Bioorg Med Chem Lett 2012; 22:7087-91. [PMID: 23099092 DOI: 10.1016/j.bmcl.2012.09.085] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Revised: 09/21/2012] [Accepted: 09/25/2012] [Indexed: 11/25/2022]
Abstract
Tyrosine ureas had been identified as potent muscarinic receptor antagonists with promising in vivo activity. Controlling the stereochemistry of the chiral quaternary ammonium center had proved to be a serious issue for this series, however. Herein we describe the preparation and SAR of tyrosine urea antagonists containing achiral quaternary ammonium centers. The most successful such moiety was the 2-methylimidazo[2,1-b][1,3]thiazol-7-ium group which yielded highly potent antagonists with long duration of action in an inhaled animal model of bronchoconstriction.
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Affiliation(s)
- Qi Jin
- GlaxoSmithKline, 709 Swedeland Road, PO Box 1539, King of Prussia, PA 19406-0939, USA
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15
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Meurs H, Dekkers BGJ, Maarsingh H, Halayko AJ, Zaagsma J, Gosens R. Muscarinic receptors on airway mesenchymal cells: novel findings for an ancient target. Pulm Pharmacol Ther 2012; 26:145-55. [PMID: 22842340 DOI: 10.1016/j.pupt.2012.07.003] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Revised: 07/15/2012] [Accepted: 07/17/2012] [Indexed: 01/25/2023]
Abstract
Since ancient times, anticholinergics have been used as a bronchodilator therapy for obstructive lung diseases. Targets of these drugs are G-protein-coupled muscarinic M(1), M(2) and M(3) receptors in the airways, which have long been recognized to regulate vagally-induced airway smooth muscle contraction and mucus secretion. However, recent studies have revealed that acetylcholine also exerts pro-inflammatory, pro-proliferative and pro-fibrotic actions in the airways, which may involve muscarinic receptor stimulation on mesenchymal, epithelial and inflammatory cells. Moreover, acetylcholine in the airways may not only be derived from vagal nerves, but also from non-neuronal cells, including epithelial and inflammatory cells. Airway smooth muscle cells seem to play a major role in the effects of acetylcholine on airway function. It has become apparent that these cells are multipotent cells that may reversibly adopt (hyper)contractile, proliferative and synthetic phenotypes, which are all under control of muscarinic receptors and differentially involved in bronchoconstriction, airway remodeling and inflammation. Cholinergic contractile tone is increased by airway inflammation associated with asthma and COPD, resulting from exaggerated acetylcholine release as well as increased expression of contraction related proteins in airway smooth muscle. Moreover, muscarinic receptor stimulation promotes proliferation of airway smooth muscle cells as well as fibroblasts, and regulates cytokine, chemokine and extracellular matrix production by these cells, which may contribute to airway smooth muscle growth, airway fibrosis and inflammation. In line, animal models of chronic allergic asthma and COPD have recently demonstrated that tiotropium may potently inhibit airway inflammation and remodeling. These observations indicate that muscarinic receptors have a much larger role in the pathophysiology of obstructive airway diseases than previously thought, which may have important therapeutic implications.
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Affiliation(s)
- Herman Meurs
- Department of Molecular Pharmacology, University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands.
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16
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Sashio T, Kume H, Takeda N, Asano T, Tsuji S, Kondo M, Hasegawa Y, Shimokata K. Possible Involvement of Sphingosine-1-Phosphate/G(i)/RhoA pathways in adherence of eosinophils to pulmonary endothelium. Allergol Int 2012; 61:283-93. [PMID: 22361510 DOI: 10.2332/allergolint.10-oa-0299] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Accepted: 11/06/2011] [Indexed: 11/20/2022] Open
Abstract
BACKGROUND Sphingosine-1-phosphate (S1P), a lysophospholipid released from inflammatory cells, causes cell migration by increasing cytokines and chemokines. This study was designed to determine whether S1P causes adherence of eosinophils to pulmonary endothelial cells via enhancement of adhesion molecule expression. METHODS Expression of VCAM-1 and ICAM-1 was assessed by RT-PCR and Western blot analysis in human pulmonary microvasucular endothelial cells (HPMVECs). The number of adherent eosinophils to HPMVECs was calculated according to adhesion assay. RESULTS Pre-treatment of HPMVECs with S1P increased mRNA and protein expression of VCAM-1, in contrast, did not dramatically increase those expression of ICAM-1. The maximal expression of these adhesion molecules in mRNA and protein was observed 4 and 8h after exposure to S1P, respectively. Pre-treatment with S1P also activated RhoA, a monomeric G protein; the ability of S1P to enhance the expression of VCAM-1 was attenuated by RhoA related inhibitors such as Y-27632, C3 exoenzyme, and GGTI-286. The effects of S1P on VCAM-1 were attenuated by pre-incubation with pertussis toxin, which catalyzes the ADP-ribosylation of G(i), a heterotrimeric G protein. After HPMVECs were treated with S1P, adhesion of human eosinophilic leukemic cell line (EoL-1) cells to HPMVECs was enhanced in a concentration-dependent manner. Augmented adherence of EoL-1 cells by S1P was also attenuated by Y-27632 and pertussis toxin. S1P causes adherence of eosinophils to pulmonary endothelium via RhoA activation. CONCLUSIONS S1P may act as a lipid mediator in asthma. The RhoA/Rho-kinase pathway may be a therapeutic target for preventing eosinophil infiltration to the airway.
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Affiliation(s)
- Toyokazu Sashio
- Department of Respiratory Medicine, Nagoya University Graduate School of Medicine, Aichi, Japan
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17
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Pharmacogenetics of asthma controller treatment. THE PHARMACOGENOMICS JOURNAL 2012; 13:242-50. [PMID: 22370858 DOI: 10.1038/tpj.2012.5] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The interpatient variability in response to asthma controllers is significant and associates with pharmacogenomic variability. The goal of the present study was to identify novel variants that associate with response to common asthma controllers: fluticasone, combination of fluticasone + salmeterol and montelukast with single nucleotide polymorphisms (SNPs) in β2-adrenergic receptor, corticosteroid and leukotriene pathway candidate genes. Participants in a large clinical trial of step-down strategies volunteered for this pharmacogenetic study. A total of 169 SNPs in 26 candidate genes were genotyped in 189 Caucasian participants with asthma who took either fluticasone (100 μg bid), fluticasone propionate (100 μg) + salmeterol (50 μg) (FP/Salm) or montelukast (5 or 10 mg) each night for 16 weeks. Primary outcomes were the slopes of plots of Asthma Control Questionnaire (ACQ) scores versus time following randomization; and the percent change in percent predicted FEV1 (ΔFEV1%pred) from enrollment to the end of the study. Associations between SNPs and outcomes were analyzed using general linear models. False discovery rate and Bonferroni corrections were used to correct for multiple comparisons. In all, 16 SNPs in seven genes were significantly associated with outcomes. For FP/Salm, three SNPs in CHRM2 associated with ACQ slope (P=2.8 × 10⁻⁵), and rs1461496 in HSPA8 associated with ΔFEV1%pred. For fluticasone, five SNPs in CRHR1 (P=1.9 × 10⁻⁴), and three SNPs in COL2A1 associated with ACQ slope and ΔFEV1%pred, respectively. For montelukast, four SNPs in CHRM2 associated with ΔFEV1%pred and predicted an opposite effect compared with fluticasone (P=9 × 10⁻³). The present study indentified several novel SNPs that associate with response to common asthma controllers, and support further pharmacogenomic study and the use of genetic variants to personalize asthma treatment.
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18
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Vahabi B, Lawson K, McKay NG, Sellers DJ. Phasic activity of urinary bladder smooth muscle in the streptozotocin-induced diabetic rat: effect of potassium channel modulators. Eur J Pharmacol 2011; 660:431-7. [PMID: 21497590 DOI: 10.1016/j.ejphar.2011.03.053] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2010] [Revised: 03/09/2011] [Accepted: 03/28/2011] [Indexed: 02/07/2023]
Abstract
Increased phasic activity in the bladder smooth muscle of animal models and patients with detrusor overactivity has been suggested to underlie the pathophysiology of overactive bladder. Potassium (K+) channels are key regulators of bladder smooth muscle tone and thus may play a role in this altered phasic activity. In this study the effects of K+ channel modulators on the phasic activity of bladder strips from the streptozotocin-induced diabetic rat model of bladder dysfunction were investigated. Bladder strips from rats 1 week following streptozotocin administration and age-matched controls were mounted in tissue baths at 37 °C and the effects of K+ channel modulators on resting basal tension or phasic activity induced by a low concentration of carbachol (0.5 μM) were investigated. Activation of BKCa channels by NS1619 had a minor inhibitory effect on carbachol-induced phasic activity of bladder strips from control and diabetic rats, and significantly inhibited amplitude only at 30 μM. Activation of KATP channels by cromakalim inhibited the frequency of carbachol-induced phasic activity of bladder strips, although strips from diabetic rats showed a trend towards being less sensitive to cromakalim. The BKCa channel blocker iberiotoxin was able to induce phasic activity in resting tissues, with diabetic bladder strips demonstrating significantly enhanced phasic activity compared to controls. In contrast, inhibition of SKCa and KATP channels did not induce phasic activity in resting tissues. In conclusion, responses of diabetic rat bladder to BKCa and KATP channel modulators are altered, suggesting altered function and/or expression of channels which may contribute to bladder dysfunction in this model.
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Affiliation(s)
- Bahareh Vahabi
- Biomedical Research Centre, Sheffield Hallam University, Howard Street, Sheffield S1 1WB, UK.
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19
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Zhou XB, Wulfsen I, Lutz S, Utku E, Sausbier U, Ruth P, Wieland T, Korth M. M2 muscarinic receptors induce airway smooth muscle activation via a dual, Gbetagamma-mediated inhibition of large conductance Ca2+-activated K+ channel activity. J Biol Chem 2008; 283:21036-44. [PMID: 18524769 PMCID: PMC3258941 DOI: 10.1074/jbc.m800447200] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2008] [Revised: 04/24/2008] [Indexed: 11/06/2022] Open
Abstract
Airway smooth muscle is richly endowed with muscarinic receptors of the M(2) and M(3) subtype. Stimulation of these receptors inhibits large conductance calcium-activated K(+) (BK) channels, a negative feed back regulator, in a pertussis toxin-sensitive manner and thus facilitates contraction. The underlying mechanism, however, is unknown. We therefore studied the activity of bovine trachea BK channels in HEK293 cells expressing the M(2) or M(3) receptor (M(2)R or M(3)R). In M(2)R- but not M(3)R-expressing cells, maximal effective concentrations of carbamoylcholine (CCh) inhibited whole cell BK currents by 53%. This M(2)R-induced inhibition was abolished by pertussis toxin treatment or overexpression of the Gbetagamma scavenger transducin-alpha. In inside-out patches, direct application of 300 nm purified Gbetagamma decreased channel open probability by 55%. The physical interaction of Gbetagamma with BK channels was confirmed by co-immunoprecipitation. Interestingly, inhibition of phospholipase C as well as protein kinase C activities also reversed the CCh effect but to a smaller (approximately 20%) extent. Mouse tracheal cells responded similarly to CCh, purified Gbetagamma and phospholipase C/protein kinase C inhibition as M(2)R-expressing HEK293 cells. Our results demonstrate that airway M(2)Rs inhibit BK channels by a dual, Gbetagamma-mediated mechanism, a direct membrane-delimited interaction, and the activation of the phospholipase C/protein kinase C pathway.
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Affiliation(s)
- Xiao-Bo Zhou
- Institut für Pharmakologie für
Pharmazeuten, Universitätsklinikum Hamburg-Eppendorf, 20246 Hamburg,
Germany, the Pharmakologie und Toxikologie,
Pharmazeutisches Institut, Universität Tübingen, 72076
Tübingen, Germany, and the Institut
für Experimentelle und Klinische Pharmakologie und Toxikologie,
Medizinische Fakultät Mannheim, Universität Heidelberg, 68169
Mannheim, Germany
| | - Iris Wulfsen
- Institut für Pharmakologie für
Pharmazeuten, Universitätsklinikum Hamburg-Eppendorf, 20246 Hamburg,
Germany, the Pharmakologie und Toxikologie,
Pharmazeutisches Institut, Universität Tübingen, 72076
Tübingen, Germany, and the Institut
für Experimentelle und Klinische Pharmakologie und Toxikologie,
Medizinische Fakultät Mannheim, Universität Heidelberg, 68169
Mannheim, Germany
| | - Susanne Lutz
- Institut für Pharmakologie für
Pharmazeuten, Universitätsklinikum Hamburg-Eppendorf, 20246 Hamburg,
Germany, the Pharmakologie und Toxikologie,
Pharmazeutisches Institut, Universität Tübingen, 72076
Tübingen, Germany, and the Institut
für Experimentelle und Klinische Pharmakologie und Toxikologie,
Medizinische Fakultät Mannheim, Universität Heidelberg, 68169
Mannheim, Germany
| | - Emine Utku
- Institut für Pharmakologie für
Pharmazeuten, Universitätsklinikum Hamburg-Eppendorf, 20246 Hamburg,
Germany, the Pharmakologie und Toxikologie,
Pharmazeutisches Institut, Universität Tübingen, 72076
Tübingen, Germany, and the Institut
für Experimentelle und Klinische Pharmakologie und Toxikologie,
Medizinische Fakultät Mannheim, Universität Heidelberg, 68169
Mannheim, Germany
| | - Ulrike Sausbier
- Institut für Pharmakologie für
Pharmazeuten, Universitätsklinikum Hamburg-Eppendorf, 20246 Hamburg,
Germany, the Pharmakologie und Toxikologie,
Pharmazeutisches Institut, Universität Tübingen, 72076
Tübingen, Germany, and the Institut
für Experimentelle und Klinische Pharmakologie und Toxikologie,
Medizinische Fakultät Mannheim, Universität Heidelberg, 68169
Mannheim, Germany
| | - Peter Ruth
- Institut für Pharmakologie für
Pharmazeuten, Universitätsklinikum Hamburg-Eppendorf, 20246 Hamburg,
Germany, the Pharmakologie und Toxikologie,
Pharmazeutisches Institut, Universität Tübingen, 72076
Tübingen, Germany, and the Institut
für Experimentelle und Klinische Pharmakologie und Toxikologie,
Medizinische Fakultät Mannheim, Universität Heidelberg, 68169
Mannheim, Germany
| | - Thomas Wieland
- Institut für Pharmakologie für
Pharmazeuten, Universitätsklinikum Hamburg-Eppendorf, 20246 Hamburg,
Germany, the Pharmakologie und Toxikologie,
Pharmazeutisches Institut, Universität Tübingen, 72076
Tübingen, Germany, and the Institut
für Experimentelle und Klinische Pharmakologie und Toxikologie,
Medizinische Fakultät Mannheim, Universität Heidelberg, 68169
Mannheim, Germany
| | - Michael Korth
- Institut für Pharmakologie für
Pharmazeuten, Universitätsklinikum Hamburg-Eppendorf, 20246 Hamburg,
Germany, the Pharmakologie und Toxikologie,
Pharmazeutisches Institut, Universität Tübingen, 72076
Tübingen, Germany, and the Institut
für Experimentelle und Klinische Pharmakologie und Toxikologie,
Medizinische Fakultät Mannheim, Universität Heidelberg, 68169
Mannheim, Germany
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20
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Lee HK, Lim MY, Bok SM, Cho ES, Lee EM, Kim SW, Kim YH, Kim HW. Age differences in cholinergic airway responsiveness in relation with muscarinic receptor subtypes. Life Sci 2007; 81:204-9. [PMID: 17568623 DOI: 10.1016/j.lfs.2007.05.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2007] [Revised: 04/30/2007] [Accepted: 05/02/2007] [Indexed: 11/28/2022]
Abstract
Children seem more susceptible to increased airway reactivity than adults. Such an age-dependent discrepancy in airway reactivity may involve different airway smooth muscle functions. Therefore, we compared the in vivo and in vitro responsiveness of airway smooth muscles between two age groups of animals. Rats of 6 and 21 weeks old were challenged in vivo with acetylcholine (ACh) infused intravenously and airway resistance (R(aw)) was measured. Tracheal muscle was also isolated and the isometric force developed to ACh or KCl was measured. Furthermore, the level of genes encoding muscarinic receptor subtypes (M(1-3)) and acetylcholinesterase (AChE) expressed in the tracheal muscle was determined by RT-PCR. In results, the basal R(aw) was similar in the two age groups. The R(aw) at each ACh dose was significantly greater in young rats than older rats (p<0.05, n=22-27). Tracheal muscles from young rats were more sensitive to ACh than older rats (p<0.05, n=20-21), while receptor-independent muscle contraction to KCl was greater in older rats (p<0.05, n=10-19). Genes encoding AChE, M(2) and M(3) muscarinic receptors were more highly expressed in the tracheal muscles from young than older rats (p<0.05, n=4-6). In conclusion, airway smooth muscle in young rat is more sensitive to cholinergic stimulation in vivo and in vitro compared to older rats, which may be due to a higher expression of M(2) and M(3) muscarinic receptors in airway smooth muscle.
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Affiliation(s)
- Hye Kyung Lee
- Department of Pharmacology, University of Ulsan College of Medicine, Songpagu, Seoul, South Korea.
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21
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Abstract
The large conductance calcium-activated potassium channel, or BKCa channel, plays an important feedback role in a variety of physiological processes, including neurotransmitter release and smooth muscle contraction. Some reports have suggested that this channel forms a stable complex with regulators of its function, including several kinases and phosphatases. To further define such signaling complexes, we used the yeast two-hybrid system to screen a human aorta cDNA library for proteins that bind to the BKCa channel's intracellular, COOH-terminal “tail”. One of the interactors we identified is the protein receptor for activated C kinase 1 (RACK1). RACK1 is a member of the WD40 protein family, which also includes the G protein β-subunits. Consistent with an important role in BKCa-channel regulation, RACK1 has been shown to be a scaffolding protein that interacts with a wide variety of signaling molecules, including cSRC and PKC. We have confirmed the interaction between RACK1 and the BKCa channel biochemically with GST pull-down and coimmunoprecipitation experiments. We have observed some co-localization of RACK1 with the BKCa channel in vascular smooth muscle cells with immunocytochemical experiments, and we have found that RACK1 has effects on the BKCa channel's biophysical properties. Thus RACK1 binds to the BKCa channel and it may form part of a BKCa-channel regulatory complex in vascular smooth muscle.
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Affiliation(s)
- Christina Kaldany Isacson
- Molecular Cardiology Research Institute, Tufts-New England Medical Center, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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22
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Kume H, Takeda N, Oguma T, Ito S, Kondo M, Ito Y, Shimokata K. Sphingosine 1-phosphate causes airway hyper-reactivity by rho-mediated myosin phosphatase inactivation. J Pharmacol Exp Ther 2006; 320:766-73. [PMID: 17105828 DOI: 10.1124/jpet.106.110718] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In the present study, we investigated whether extracellular sphingosine 1-phosphate (S1P) is involved in airway hyper-reactivity in bronchial asthma. The effects of S1P on the response to methacholine was examined in the fura-2-loaded strips of guinea pig tracheal smooth muscle using simultaneous recording of the isometric tension and the ratio of fluorescence intensities at 340 and 380 nm (F(340)/F(380)). A 15-min pretreatment with S1P (>100 nM) markedly enhanced methacholine-induced contraction without elevating F(340)/F(380). This effect of S1P was suppressed in the presence of Y-27632 [(R)-(+)-trans-N-(4-pyridyl)-4-(1-aminoethyl)-cyclohexane-carboxamide], a selective inhibitor of Rho-kinase, in a concentration-dependent manner. Moreover, pretreatment with pertussis toxin caused an inhibition in S1P-induced hyper-reactivity to methacholine in a time- and concentration-dependent manner. In contrast, although S1P-induced Ca(2+) mobilization was attenuated by SKF96365 and verapamil, the subsequent response to methacholine was unaffected. A 15-min pretreatment with lower concentrations of S1P (<100 nM), which is clinically attainable, did not increase methacholine-induced contraction. However, when the incubation was lengthened to 6 h, S1P (<100 nM) enhanced the subsequent response to methacholine. Next, application of S1P to cultured human bronchial smooth muscle cells increased the proportion of active RhoA (GTP-RhoA) and phosphorylation of myosin phosphatase target subunit 1 (MYPT1). This phosphorylation of MYPT1 was significantly inhibited by application of Y-27632 and by pretreatment with pertussis toxin. Our findings demonstrate that exposure of airway smooth muscle to S1P results in airway hyper-reactivity mediated by Ca(2+) sensitization via inactivation of myosin phosphatase, which links G(i) and RhoA/Rho-kinase processes.
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Affiliation(s)
- Hiroaki Kume
- Department of Respiratory Medicine, Nagoya University Graduate School of Medicine, 65 Tsrumai-cho, Showa-ku, Nagoya 466-8550, Japan.
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23
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Eglen RM. Muscarinic Receptor Subtype Pharmacology and Physiology. PROGRESS IN MEDICINAL CHEMISTRY 2005; 43:105-36. [PMID: 15850824 DOI: 10.1016/s0079-6468(05)43004-0] [Citation(s) in RCA: 152] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Affiliation(s)
- Richard M Eglen
- DiscoveRx Corporation, Albrae Street, Fremont, CA 94538, USA
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24
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Racké K, Matthiesen S. The airway cholinergic system: physiology and pharmacology. Pulm Pharmacol Ther 2004; 17:181-98. [PMID: 15219263 DOI: 10.1016/j.pupt.2004.03.001] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2003] [Revised: 01/23/2004] [Accepted: 03/16/2004] [Indexed: 11/22/2022]
Abstract
The present review summarizes the current knowledge of the cholinergic systems in the airways with special emphasis on the role of acetylcholine both as neurotransmitter in ganglia and postganglionic parasympathetic nerves and as non-neuronal paracrine mediator. The different cholinoceptors, various nicotinic and muscarinic receptors, as well as their signalling mechanisms are presented. The complex ganglionic and prejunctional mechanisms controlling the release of acetylcholine are explained, and it is discussed whether changes in transmitter release could be involved in airway dysfunctions. The effects of acetylcholine on different target cells, smooth muscles, nerves, surface epithelial and secretory cells as well as mast cells are described in detail, including the receptor subtypes involved in signal transmission.
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Affiliation(s)
- K Racké
- Institute of Pharmacology and Toxicology, University of Bonn, Reuterstrasse 2b, D-53113 Bonn, Germany.
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25
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Zholos AV, Bolton TB, Dresvyannikov AV, Kustov MV, Tsvilovskii VV, Shuba MF. Cholinergic excitation of smooth muscles: Multiple signaling pathways linking M2 and M3 muscarinic receptors to cationic channels. NEUROPHYSIOLOGY+ 2004. [DOI: 10.1007/s11062-005-0034-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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26
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Walker JKL, Gainetdinov RR, Feldman DS, McFawn PK, Caron MG, Lefkowitz RJ, Premont RT, Fisher JT. G protein-coupled receptor kinase 5 regulates airway responses induced by muscarinic receptor activation. Am J Physiol Lung Cell Mol Physiol 2003; 286:L312-9. [PMID: 14565944 DOI: 10.1152/ajplung.00255.2003] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
G protein-coupled receptors (GPCRs) transduce extracellular signals into intracellular events. The waning responsiveness of GPCRs in the face of persistent agonist stimulation, or desensitization, is a necessary event that ensures physiological homeostasis. GPCR kinases (GRKs) are important regulators of GPCR desensitization. GRK5, one member of the GRK family, desensitizes central M(2) muscarinic receptors in mice. We questioned whether GRK5 might also be an important regulator of peripheral muscarinic receptor responsiveness in the cardiopulmonary system. Specifically, we wanted to determine the role of GRK5 in regulating muscarinic receptor-mediated control of airway smooth muscle tone or regulation of cholinergic-induced bradycardia. Tracheal pressure, heart rate, and tracheal smooth muscle tension were measured in mice having a targeted deletion of the GRK5 gene (GRK5(-/-)) and littermate wild-type (WT) control mice. Both in vivo and in vitro results showed that the airway contractile response to a muscarinic receptor agonist was not different between GRK5(-/-) and WT mice. However, the relaxation component of bilateral vagal stimulation and the airway smooth muscle relaxation resulting from beta(2)-adrenergic receptor activation were diminished in GRK5(-/-) mice. These data suggest that M(2) muscarinic receptor-mediated opposition of airway smooth muscle relaxation is regulated by GRK5 and is, therefore, excessive in GRK5(-/-) mice. In addition, this study shows that GRK5 regulates pulmonary responses in a tissue- and receptor-specific manner but does not regulate peripheral cardiac muscarinic receptors. GRK5 regulation of airway responses may have implications in obstructive airway diseases such as asthma or chronic obstructive pulmonary disease.
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Affiliation(s)
- J K L Walker
- Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA.
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Rezzonico R, Cayatte C, Bourget-Ponzio I, Romey G, Belhacene N, Loubat A, Rocchi S, Van Obberghen E, Girault JA, Rossi B, Schmid-Antomarchi H. Focal adhesion kinase pp125FAK interacts with the large conductance calcium-activated hSlo potassium channel in human osteoblasts: potential role in mechanotransduction. J Bone Miner Res 2003; 18:1863-71. [PMID: 14584897 DOI: 10.1359/jbmr.2003.18.10.1863] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
UNLABELLED Molecular events of mechanotransduction in osteoblasts are poorly defined. We show that the mechanosensitive BK channels open and recruit the focal adhesion kinase FAK in osteoblasts on hypotonic shock. This could convert mechanical signals in biochemical events, leading to osteoblast activation. INTRODUCTION Mechanical strains applied to the skeleton influence bone remodeling and architecture mainly through the osteoblast lineage. The molecular mechanisms involved in osteoblastic mechanotransduction include opening of mechanosensitive cation channels and the activation of protein tyrosine kinases, notably FAK, but their interplay remains poorly characterized. The large conductance K+ channel (BK) seems likely as a bone mechanoreceptor candidate because of its high expression in osteoblasts and its ability to open in response to membrane stretch or hypotonic shock. Propagation of the signals issued from the mechanosensitivity of BK channels inside the cell likely implies complex interactions with molecular partners involved in mechanotransduction, notably FAK. METHODS Interaction of FAK with the C terminus of the hSlo alpha-subunit of BK was investigated using the yeast two-hybrid system as well as immunofluorescence microscopy and coimmunoprecipitation experiments with a rabbit anti-hslo antibody on MG63 and CAL72 human osteosarcoma cell lines and on normal human osteoblasts. Mapping of the FAK region interacting with hSlo was approached by testing the ability of hSlo to recruit mutated ot truncated FAK proteins. RESULTS To the best of our knowledge, we provide the first evidence of the physical association of FAK with the intracellular part of hslo. We show that FAK/hSlo interaction likely takes place through the Pro-1-rich domain situated in the C-terminal region of the kinase. FAK/hSlo association occurs constitutively at a low, but appreciable, level in human osteosarcoma cells and normal human osteoblasts that express endogenous FAK and hSlo. In addition, we found that application of an hypo-osmotic shock to these cells induced a sustained activation of BK channels associated to a marked increase in the recruitment of FAK on hSlo. CONCLUSIONS Based on these data, we propose that BK channels might play a triggering role in the signaling cascade induced by mechanical strains in osteoblasts.
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Kume H, Ishikawa T, Oguma T, Ito S, Shimokata K, Kotlikoff MI. Involvement of Ca2+ mobilization in tachyphylaxis to beta-adrenergic receptors in trachealis. Am J Respir Cell Mol Biol 2003; 29:359-66. [PMID: 12663330 DOI: 10.1165/rcmb.2002-0197oc] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
We examined the mechanisms underlying tachyphylaxis to beta-adrenergic receptor agonists (beta-agonists) in tracheal smooth muscle. Simultaneous measurements of isometric tension and intracellular Ca2+ concentration ([Ca2+]i) using fura-2-loaded guinea pig tracheas showed that the inhibitory effects of isoproterenol (ISO) on tension and increases in [Ca2+]i induced by methacholine exhibited marked tachyphylaxis with repeated exposure to ISO at intervals of 15 min. Similarly, the activation of single Ca2+-activated K+ (KCa) channels in on-cell patches by 1 microM ISO was gradually attenuated after repeated extracellular application of ISO to single smooth cells of porcine tracheas. Desensitization of beta-adrenergic receptor/KCa channel stimulatory coupling and relaxation responses was prevented by separately antagonizing the voltage-dependent Ca2+ channel (VDCC) with verapamil, suggesting a surprising relationship between Ca2+ influx through VDCC and beta-adrenergic desensitization. Conversely, repeated exposure of 10 U/ml protein kinase A to inside-out patches did not result in desensitization of channel activation, and repeated exposure to 10 microM forskolin modestly augmented the inhibitory effects of forskolin on tension and [Ca2+]i by methacholine, indicating that the mechanism of desensitization is mediated by the beta-adrenergic receptor/G protein complex. These results indicate that an uncoupling of beta-adrenergic receptor from KCa channels augments Ca2+ mobilization through VDCC and stimulates tachyphylaxis.
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Affiliation(s)
- Hiroaki Kume
- Division of Respiratory Medicine, Department of Medicine, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan.
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Abstract
Parasympathetic nerves provide the dominant autonomic innervation of the airways. Release of acetylcholine from parasympathetic nerves activates postjunctional muscarinic receptors present on airway smooth muscle, submucosal glands, and blood vessels to cause bronchoconstriction, mucus secretion, and vasodilatation, respectively. Acetylcholine also feeds back onto prejunctional muscarinic receptors to enhance or inhibit further acetylcholine release. In asthma and chronic obstructive pulmonary disease, bronchoconstriction and mucus secretion is increased and the airways are hyperresponsive to contractile agents. These changes are due to increased parasympathetic nerve activity. The number and function of postjunctional muscarinic receptors in the airways are unchanged in animal models of asthma. Rather, it is the supply of acetylcholine to the postjunctional cells (smooth muscle and submucosal gland) that is increased. The increase in acetylcholine release occurs because prejunctional, inhibitory M(2) muscarinic receptors on the parasympathetic nerves are dysfunctional. M(2) muscarinic receptor dysfunction and subsequent airway hyperreactivity have been demonstrated to occur in animals in response to a variety of triggers, including antigen challenge, virus infection, ozone exposure, and vitamin A deficiency. In humans, there is evidence that loss of M(2) muscarinic receptor function is related to asthma. The mechanisms by which neuronal M(2) muscarinic receptor function is lost and its relevance to human airway disease are discussed in this review.
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Affiliation(s)
- Fiona R Coulson
- Department of Environmental Health Sciences, Bloomberg School of Public Health, Johns Hopkins University, 615 North Wolfe Street, Baltimore, MD 21205, USA
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Janssen LJ. Ionic mechanisms and Ca(2+) regulation in airway smooth muscle contraction: do the data contradict dogma? Am J Physiol Lung Cell Mol Physiol 2002; 282:L1161-78. [PMID: 12003770 DOI: 10.1152/ajplung.00452.2001] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In general, excitation-contraction coupling in muscle is dependent on membrane depolarization and hyperpolarization to regulate the opening of voltage-dependent Ca(2+) channels and, thereby, influence intracellular Ca(2+) concentration ([Ca(2+)](i)). Thus Ca(2+) channel blockers and K(+) channel openers are important tools in the arsenals against hypertension, stroke, and myocardial infarction, etc. Airway smooth muscle (ASM) also exhibits robust Ca(2+), K(+), and Cl(-) currents, and there are elaborate signaling pathways that regulate them. It is easy, then, to presume that these also play a central role in contraction/relaxation of ASM. However, several lines of evidence speak to the contrary. Also, too many researchers in the ASM field view the sarcoplasmic reticulum as being centrally located and displacing its contents uniformly throughout the cell, and they have focused almost exclusively on the initial single [Ca(2+)] spike evoked by excitatory agonists. Several recent studies have revealed complex spatial and temporal heterogeneity in [Ca(2+)](i), the significance of which is only just beginning to be appreciated. In this review, we will compare what is known about ion channels in ASM with what is believed to be their roles in ASM physiology. Also, we will examine some novel ionic mechanisms in the context of Ca(2+) handling and excitation-contraction coupling in ASM.
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Affiliation(s)
- Luke J Janssen
- Asthma Research Group, Firestone Institute for Respiratory Health, St. Joseph's Hospital, McMaster University, Hamilton, Ontario, Canada L8N 4A6.
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Abstract
Muscarinic acetylcholine receptor subtypes have been the subjects of research for at least a quarter of a century. Nonetheless, there are few selective muscarinic receptor ligands presently used as therapeutics. The extensive development of muscarinic M(1) receptor agonists for the treatment of cognitive dysfunction has culminated in a series of unsuccessful drug candidates, which reflects a lack of understanding of the disease and the role played by muscarinic cholinergic transmission. Paradoxically, the most successful antagonist approved for use in urinary incontinence is the nonselective muscarinic receptor antagonist tolterodine. This deficit in subtype-selective ligands could be circumvented by the development of transgenic mice, each lacking functional M(1), M(2), M(3), M(4) or M(5) receptors. In this article, the current status of muscarinic receptor research is critically assessed.
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Affiliation(s)
- R M Eglen
- DiscoveRx Corp, Fremont, CA 94538, USA.
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Ito S, Kume H, Honjo H, Katoh H, Kodama I, Yamaki K, Hayashi H. Possible involvement of Rho kinase in Ca2+ sensitization and mobilization by MCh in tracheal smooth muscle. Am J Physiol Lung Cell Mol Physiol 2001; 280:L1218-24. [PMID: 11350801 DOI: 10.1152/ajplung.2001.280.6.l1218] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We examined the effects of Rho kinase on contraction and intracellular Ca2+ concentration ([Ca2+](i)) in guinea pig trachealis by measuring isometric force and the fura 2 signal [340- to 380-nm fluorescence ratio (F340/F380)]. A Rho kinase inhibitor, Y-27632 (1-1,000 microM), inhibited methacholine (MCh)-induced contraction, with a reduction in F340/F380 in a concentration-dependent manner. The values of EC(50) for contraction and F340/F380 induced by 1 microM MCh with Y-27632 were 27.3 +/- 5.1 and 524.1 +/- 31.0 microM, respectively. With 0.1 microM MCh, the values for these parameters were decreased to 1.0 +/- 0.1 and 98.2 +/- 6.2 microM, respectively. Tension-F340/F380 curves for MCh indicated that Y-27632 caused an ~50% inhibition of MCh-induced contraction, without a reduction in F340/F380. These effects of Y-27632 were not inhibited by a protein kinase C inhibitor, GF-109203X. Our results indicate that inhibition of Rho kinase attenuates both Ca2+ sensitization and [Ca2+](i).
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Affiliation(s)
- S Ito
- The Second Department of Internal Medicine, School of Medicine, Nagoya University, Tsurumai-cho, Showa-ku, Nagoya 466-8560, Japan
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Swenson ER. Respiratory and renal roles of carbonic anhydrase in gas exchange and acid-base regulation. EXS 2001:281-341. [PMID: 11268521 DOI: 10.1007/978-3-0348-8446-4_15] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- E R Swenson
- VA Puget Sound Health Care System, 1660 S Columbian Way, Seattle, WA 98108, USA
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Yamanishi T, Chapple CR, Yasuda K, Chess-Williams R. The role of M(2)-muscarinic receptors in mediating contraction of the pig urinary bladder in vitro. Br J Pharmacol 2000; 131:1482-8. [PMID: 11090124 PMCID: PMC1572475 DOI: 10.1038/sj.bjp.0703719] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
1. In urinary bladder, M(2)-muscarinic receptors predominate, but it is the smaller population of M(3)-receptors which mediate detrusor contraction. This study examines the M(2) : M(3) ratio and the role of M(2)-receptors in contraction of pig urinary bladder. 2. Competition experiments with [(3)H]-QNB determined the ratio of M(2) : M(3). In functional studies, affinity values (pK(B)) for 4-DAMP, darifenacin and methoctramine were calculated. Similar experiments were performed on tissues following selective M(3)-inactivation (incubation with 40 nM 4-DAMP mustard in the presence of 1 microM methoctramine to protect M(2)-receptors), precontraction with 50 mM KCl and relaxation with isoprenaline (30 microM) or forskolin (1 microM). 3. In competition binding, displacement of [(3)H]-QNB by 4-DAMP, darifenacin and methoctramine best fitted a two-site model suggesting a predominant (70 - 80%) population of M(2)-receptors. 4. On normal detrusor in vitro, 4-DAMP and methoctramine caused surmountable antagonism of responses to carbachol with pK(B) values of 9.37+/-0.07 and 6.05+/-0.05 respectively. Darifenacin caused unsurmountable antagonism, the apparent pK(B) value being 8.61+/-0.10. 5. In tissues where the M(3)-receptors had been inactivated and cyclic AMP levels elevated, 4-DAMP and darifenacin were less potent, with apparent pK(B) values of 8.72+/-0.08 and 6.74+/-0.07. In contrast, methoctramine was more potent, the apparent pK(B) value increasing significantly to 6.86+/-0.06. 6. se data suggest that the pig bladder possesses a similar muscarinic receptor population to the human bladder and that the M(3)-receptor subtype mediates contraction of the normal detrusor muscle. However an involvement of M(2)-receptors in contraction can be observed following pharmacological manipulation of the receptor population.
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Affiliation(s)
- Tomonori Yamanishi
- Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN
- Department of Urology, Royal Hallamshire Hospital, Sheffield
| | | | - Kosaku Yasuda
- Department of Urology, Dokkyo University, Koshigaya Hospital, Japan
| | - Russell Chess-Williams
- Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN
- Author for correspondence:
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Ling S, Woronuk G, Sy L, Lev S, Braun AP. Enhanced activity of a large conductance, calcium-sensitive K+ channel in the presence of Src tyrosine kinase. J Biol Chem 2000; 275:30683-9. [PMID: 10893418 DOI: 10.1074/jbc.m004292200] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Large conductance, calcium-sensitive K(+) channels (BK(Ca) channels) contribute to the control of membrane potential in a variety of tissues, including smooth muscle, where they act as the target effector for intracellular "calcium sparks" and the endothelium-derived vasodilator nitric oxide. Various signal transduction pathways, including protein phosphorylation can regulate the activity of BK(Ca) channels, along with many other membrane ion channels. In our study, we have examined the regulation of BK(Ca) channels by the cellular Src gene product (cSrc), a soluble tyrosine kinase that has been implicated in the regulation of both voltage- and ligand-gated ion channels. Using a heterologous expression system, we observed that co-expression of murine BK(Ca) channel and the human cSrc tyrosine kinase in HEK 293 cells led to a calcium-sensitive enhancement of BK(Ca) channel activity in excised membrane patches. In contrast, co-expression with a catalytically inactive cSrc mutant produced no change in BK(Ca) channel activity, demonstrating the requirement for a functional cSrc molecule. Furthermore, we observed that BK(Ca) channels underwent direct tyrosine phosphorylation in cells co-transfected with BK(Ca) channels and active cSrc but not in cells co-transfected with the kinase inactive form of the enzyme. A single Tyr to Phe substitution in the C-terminal half of the channel largely prevented this observed phosphorylation. Given that cSrc may become activated by receptor tyrosine kinases or G-protein-coupled receptors, these findings suggest that cSrc-dependent tyrosine phosphorylation of BK(Ca) channels in situ may represent a novel regulatory mechanism for altering membrane potential and calcium entry.
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Affiliation(s)
- S Ling
- Smooth Muscle Research Group, Department of Pharmacology and Therapeutics, University of Calgary, Calgary, Alberta T2N 4N1, Canada
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36
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Properties, regulation, and role of potassium channels of smooth muscle. ACTA ACUST UNITED AC 2000. [DOI: 10.1016/s1569-2590(00)08010-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/27/2023]
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Silva BA, Nouailhetas VL, Aboulafia J. Desensitization to ANG II in guinea pig ileum depends on membrane repolarization: role of maxi-K(+) channel. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:C739-45. [PMID: 10516104 DOI: 10.1152/ajpcell.1999.277.4.c739] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Desensitization of ANG II tonic contractile response of the guinea pig ileum is related to membrane repolarization determined by Ca(2+)-activated K(+) (maxi-K(+)) channel opening. ANG II-stimulated depolarized myocytes presented sustained activation of maxi-K(+) channels, characterized by reduction from 415 to 12 ms of the closed time constant. ANG II desensitization was prevented by 100 nM iberiotoxin, being reversible within 30 min. Depolarization by KCl, higher than 4 mM, impaired desensitization, suggesting that the membrane potential must attain a threshold to counteract the repolarization induced by maxi-K(+) channel opening. Once this value is attained, there is no time dependency because the desensitization process was shut off by addition of KCl along the time course of the tonic response. In contrast, the sustained ACh tonic component was not altered by these maneuvers. We conclude that desensitization of the ANG II tonic component is foremost due to the opening of maxi-K(+) channels, leading to membrane repolarization, thus closing the voltage-dependent Ca(2+) channels responsible for the Ca(2+) influx that sustains the tonic component in this muscle.
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Affiliation(s)
- B A Silva
- Department of Biophysics, Universidade Federal de São Paulo, Escola Paulista de Medicina, 04023-062 São Paulo, Brazil
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39
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Bolton TB, Prestwich SA, Zholos AV, Gordienko DV. Excitation-contraction coupling in gastrointestinal and other smooth muscles. Annu Rev Physiol 1999; 61:85-115. [PMID: 10099683 DOI: 10.1146/annurev.physiol.61.1.85] [Citation(s) in RCA: 179] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The main contributors to increases in [Ca2+]i and tension are the entry of Ca2+ through voltage-dependent channels opened by depolarization or during action potential (AP) or slow-wave discharge, and Ca2+ release from store sites in the cell by the action of IP3 or by Ca(2+)-induced Ca(2+)-release (CICR). The entry of Ca2+ during an AP triggers CICR from up to 20 or more subplasmalemmal store sites (seen as hot spots, using fluorescent indicators); Ca2+ waves then spread from these hot spots, which results in a rise in [Ca2+]i throughout the cell. Spontaneous transient releases of store Ca2+, previously detected as spontaneous transient outward currents (STOCs), are seen as sparks when fluorescent indicators are used. Sparks occur at certain preferred locations--frequent discharge sites (FDSs)--and these and hot spots may represent aggregations of sarcoplasmic reticulum scattered throughout the cytoplasm. Activation of receptors for excitatory signal molecules generally depolarizes the cell while it increases the production of IP3 (causing calcium store release) and diacylglycerols (which activate protein kinases). Activation of receptors for inhibitory signal molecules increases the activity of protein kinases through increases in cAMP or cGMP and often hyperpolarizes the cell. Other receptors link to tyrosine kinases, which trigger signal cascades interacting with trimeric G-protein systems.
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Affiliation(s)
- T B Bolton
- Department of Pharmacology and Clinical Pharmacology, St George's Hospital Medical School, London, United Kingdom.
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40
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Abstract
M2 receptor stimulation results in the gating of nonselective cation channels in several smooth muscle cell types. However the requirement for current activation includes a rise in cytosolic calcium mediated by M3 receptor induced calcium release. This complex signaling system confers substantial complexity on the interpretation of pharmacological experiments. M2 and M3 receptor stimulation has also been linked to the inhibition of potassium channels in smooth muscle. These signaling events are likely to play important roles in excitation/contraction coupling.
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Affiliation(s)
- M I Kotlikoff
- Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia 19104-6046, USA
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Kume H, Takagi K. Inhibition of beta-adrenergic desensitization by KCa channels in human trachealis. Am J Respir Crit Care Med 1999; 159:452-60. [PMID: 9927357 DOI: 10.1164/ajrccm.159.2.9801006] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
We examined the reduced responsiveness to beta-adrenergic receptor agonists (beta-agonists) after exposure to beta-agonists, and the mechanisms underlying this phenomenon in isolated human tracheal smooth muscle, using isometric tension records to test the hypothesis that repeated inhalation of beta-agonists leads to reduced responsiveness to beta-agonists. The inhibitory effects of isoproterenol (ISO) on contraction by spasmogens participating in asthma attacks diminished markedly after continuous exposure to ISO (0.0003 to 3 microM) for 45 min; moreover, when ISO was repeatedly applied for 10 min to tissues precontracted by methacholine every 30 min, the relaxant effects of ISO gradually attenuated after these repeated applications. In contrast, reduced beta-adrenergic relaxation after continuous and repeated exposure to agonists did not occur when tissues were preincubated with 2 microg/ ml cholera toxin (CTX), which irreversibly activates guanosine triphosphate (GTP)-binding protein (Gs) coupled with beta-adrenergic receptors, for 6 h. However, the CTX inhibition disappeared in the presence of iberiotoxin, a selective inhibitor of large conductance Ca2+-activated K+ (KCa) channels. Our results demonstrate that continuous and repeated exposure to beta-agonists leads to beta-adrenergic desensitization, and that activation of KCa channels by Gs prevents this desensitization.
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Affiliation(s)
- H Kume
- Second Department of Internal Medicine, School of Medicine, Nagoya University, Nagoya, Japan
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Dumoulin M, Salvail D, Gaudreault SB, Cadieux A, Rousseau E. Epoxyeicosatrienoic acids relax airway smooth muscles and directly activate reconstituted KCa channels. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:L423-31. [PMID: 9728036 DOI: 10.1152/ajplung.1998.275.3.l423] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Epoxyeicosatrienoic acids (EETs) relax various smooth muscles by increasing outward K+ movement, but the molecular mode of action of EET regioisomers remains to be clarified. The effects of EETs were investigated on bovine airway smooth muscle tone and on reconstituted Ca2+-activated K+ (KCa) channels. 5,6-EET and 11, 12-EET induced dose-dependent relaxations of precontracted bronchial spirals. These effects were partly abolished by 10 nM iberiotoxin. Bilayer experiments have shown that 0.1-10 microM 11,12-EET produced up to fourfold increases in the open probability of KCa channels from the cis (extracellular) side by enhancing the mean open time constant and reducing the long closed time constant, without affecting the unitary conductance. EET-induced activations were blocked by 10 nM iberiotoxin. Addition of vehicles or other lipids as well as of GTP and guanosine 5'-O-(3-thiotriphosphate) in the absence of EET had no effect on channel activity. Thus EETs directly activate KCa channels from airway smooth muscle through an interaction with the extracellular face of the channel. We propose that EETs could represent candidate molecules as epithelium-derived hyperpolarizing factors.
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Affiliation(s)
- M Dumoulin
- Le Bilarium, Faculty of Medicine, University of Sherbrooke, Sherbrooke, Quebec, Canada J1H 5N4
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43
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Romero F, Silva BA, Nouailhetas VL, Aboulafia J. Activation of Ca(2+)-activated K+ (maxi-K+) channel by angiotensin II in myocytes of the guinea pig ileum. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:C983-91. [PMID: 9575795 DOI: 10.1152/ajpcell.1998.274.4.c983] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
We investigated the regulation of the Ca(2+)-activated K+ (maxi-K+) channel by angiotensin II (ANG II) and its synthetic analog, [Lys2]ANG II, in freshly dispersed intestinal myocytes. We identified a maxi-K+ channel population in the inside-out patch configuration on the basis of its conductance (257 +/- 4 pS in symmetrical 150 mM KCl solution), voltage and Ca2+ dependence of channel opening, low Na(+)-to-K+ and Cl(-)-to-K+ permeability ratios, and blockade by external Cs+ and tetraethylammonium chloride. ANG II and [Lys2]ANG II caused an indirect, reversible, Ca(2+)- and dose-dependent activation of maxi-K+ channels in cell-attached experiments when cells were bathed in high-K+ solution. This effect was reversibly blocked by DUP-753, being that it is mediated by the AT1 receptor. Evidences that activation of the maxi-K+ channel by ANG II requires a rise in intracellular Ca2+ concentration ([Ca2+]i) as an intermediate step were the shift of the open probability of the channel-membrane potential relationship to less positive membrane potentials and the sustained increase in [Ca2+]i in fura 2-loaded myocytes. The preservation of the pharmacomechanical coupling of ANG II in these cells provides a good model for the study of transmembrane signaling responses to ANG II and analogs in this tissue.
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Affiliation(s)
- F Romero
- Department of Biophysics, Universidade Federal de São Paulo, Escola Paulista de Medicina, Brazil
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44
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Wang ZW, Nara M, Wang YX, Kotlikoff MI. Redox regulation of large conductance Ca(2+)-activated K+ channels in smooth muscle cells. J Gen Physiol 1997; 110:35-44. [PMID: 9234169 PMCID: PMC2229357 DOI: 10.1085/jgp.110.1.35] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/1997] [Accepted: 04/14/1997] [Indexed: 02/04/2023] Open
Abstract
The effects of sulfhydryl reduction/oxidation on the gating of large-conductance, Ca(2+)-activated K+ (maxi-K) channels were examined in excised patches from tracheal myocytes. Channel activity was modified by sulfhydryl redox agents applied to the cytosolic surface, but not the extracellular surface, of membrane patches. Sulfhydryl reducing agents dithiothreitol, beta-mercaptoethanol, and GSH augmented, whereas sulfhydryl oxidizing agents diamide, thimerosal, and 2,2'-dithiodipyridine inhibited, channel activity in a concentration-dependent manner. Channel stimulation by reduction and inhibition by oxidation persisted following washout of the compounds, but the effects of reduction were reversed by subsequent oxidation, and vice versa. The thiol-specific reagents N-ethylmaleimide and (2-aminoethyl)methanethiosulfonate inhibited channel activity and prevented the effect of subsequent sulfhydryl oxidation. Measurements of macroscopic currents in inside-out patches indicate that reduction only shifted the voltage/nP0 relationship without an effect on the maximum conductance of the patch, suggesting that the increase in nP0 following reduction did not result from recruitment of more functional channels but rather from changes of channel gating. We conclude that redox modulation of cysteine thiol groups, which probably involves thiol/disulfide exchange, alters maxi-K channel gating, and that this modulation likely affects channel activity under physiological conditions.
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Affiliation(s)
- Z W Wang
- Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia 19104, USA
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45
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Li PL, Campbell WB. Epoxyeicosatrienoic acids activate K+ channels in coronary smooth muscle through a guanine nucleotide binding protein. Circ Res 1997; 80:877-84. [PMID: 9168791 DOI: 10.1161/01.res.80.6.877] [Citation(s) in RCA: 179] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Epoxyeicosatrienoic acids (EETs) are endothelium-derived arachidonic acid metabolites of cytochrome P450. They dilate coronary arteries, open K+ channels, and hyperpolarize vascular smooth muscles. However, the mechanisms of these smooth muscle actions remain unknown. This study examined the effects of EETs on the large-conductance Ca(2+)-activated K+ channel (KCa) in smooth muscle cells of small bovine coronary arteries. In cell-attached patch-clamp experiments, 11,12-EET produced a 0.5- to 10-fold increase in the activity of the KCa channels when added in concentrations of 1, 10, and 100 nmol/L. In the inside-out excised membrane patch mode, 11,12-EET was without effect on the activity of the KCa channel unless GTP (0.5 mmol/L) or GTP and ATP (1 mmol/L) were added to the bath solution. In the presence of GTP and ATP, the increase in the KCa channel activity with 11,12-EET in inside-out patches was comparable to that in cell-attached patches. This effect of 11,12-EET in inside-out patches was blocked by the addition of GDP-beta-S (100 mumol/L). In outside-out patches, 11,12-EET also increased the KCa channel activity when GTP and ATP were added to the pipette solution. The addition of a specific anti-Gs alpha antibody (100 nmol/L) in the pipette solution completely blocked the activation of the KCa channels induced by 11,12-EET. An anti-G beta gamma or anti-Gi alpha antibody was without effect. We conclude that 11,12-EET activates the KCa channels by a Gs alpha-mediated mechanism. This mechanism contributes to the effects of EETs as endothelium-derived hyperpolarizing factors to hyperpolarize and relax arterial smooth muscle.
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Affiliation(s)
- P L Li
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee 53226, USA
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46
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Abstract
Muscarinic M1, M2, and M3 receptor subtypes have been shown to be involved in the pre- and postjunctional control of airway diameter of various species, including man. In a guinea pig model of allergic asthma, the prejunctional M2 receptor was shown to become dysfunctional already during the early allergic reaction, thereby contributing to exaggerated vagal reflex activity and airway hyperreactivity. Moreover, a deficiency of endogenous nitric oxide was observed after allergen provocation, which may also contribute to an enhanced postjunctional M3 receptor-mediated cholinergic response. Both in human and in animal airway preparations it was shown that enhanced cholinergic contractions are relatively resistent to beta-adrenoceptor-mediated relaxation. The reduced beta-adrenoceptor function may primarily be due to transductional cross-talk between PI metabolism and adenylyl cyclase, including protein kinase C-induced uncoupling of the beta-adrenoceptor from the effector system. Cross-talk between postjunctional M2 receptor-mediated inhibition and beta-adrenoceptor-induced activation of adenylyl cyclase appears to be of minor functional importance, but could be enhanced in allergic asthma due to increased expression of the inhibitory G protein as induced by cytokines.
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Affiliation(s)
- J Zaagsma
- Department of Molecular Pharmacology, University Centre for Pharmacy, Groningen, The Netherlands
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47
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Beech DJ. Actions of neurotransmitters and other messengers on Ca2+ channels and K+ channels in smooth muscle cells. Pharmacol Ther 1997; 73:91-119. [PMID: 9131720 DOI: 10.1016/s0163-7258(97)87271-3] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Ion channels play key roles in determining smooth muscle tone by setting the membrane potential and allowing Ca2+ influx. Perhaps not surprisingly, therefore, they also provide targets for neurotransmitters and other messengers that act on smooth muscle. Application of patch-clamp and molecular biology techniques and the use of selective pharmacology has started to provide a wealth of information on the ion channel systems of smooth muscle cells, revealing complexity and functional significance. Reviewed are the actions of messengers (e.g., noradrenaline, acetylcholine, endothelin, angiotensin II, neuropeptide Y, 5-hydroxytryptamine, histamine, adenosine, calcitonin gene-related peptide, substance P, prostacyclin, nitric oxide and oxygen) on specific types of ion channel in smooth muscle, the L-type calcium channel, and the large conductance Ca(2+)-activated, ATP-sensitive, delayed rectifier and apamin-sensitive K+ channels.
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Affiliation(s)
- D J Beech
- Department of Pharmacology, University of Leeds, England
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48
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Graier WF, Holzmann S, Hoebel BG, Kukovetz WR, Kostner GM. Mechanisms of L-NG nitroarginine/indomethacin-resistant relaxation in bovine and porcine coronary arteries. Br J Pharmacol 1996; 119:1177-86. [PMID: 8937721 PMCID: PMC1915901 DOI: 10.1111/j.1476-5381.1996.tb16020.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
1. Coronary arteries from bovines (BCA) and pigs (PCA) were used for measuring endothelium-dependent relaxation in the presence of L-NG nitroarginine and indomethacin. As some compounds tested have been found to have an inhibitory effect on autacoid-activated endothelial Ca2+ signalling, endothelium-dependent relaxation was initiated with the Ca2+ ionophore A23187. 2. The common compounds for modulating arachidonic acid release/pathway, mepacrine and econazole only inhibited L-NG nitroarginine-resistant relaxation in BCA not in PCA. In contrast, proadifen (SKF 525A) diminished relaxation in BCA and PCA. Mepacrine and proadifen inhibited Hoe-234-initiated relaxation in BCA and PCA, while econazole only inhibited Hoe 234-induced relaxation in PCA. Due to the multiple effects of these compounds, caution is necessary in the interpretation of results obtained with these compounds. 3. The inhibitor of Ca(2+)-activated K+ channels, apamin, strongly attenuated A23187-induced L-NG nitroarginine-resistant relaxation in BCA while apamin did not affect L-NG nitroarginine-resistant relaxation in PCA. 4. Pertussis toxin blunted L-NG nitroarginine-resistant relaxation in BCA, while relaxation of PCA was not affected by pertussis toxin. 5. Thiopentone sodium inhibited endothelial cytochrome P450 epoxygenase (EPO) in PCA but not in BCA, while L-NG nitroarginine-resistant relaxation of BCA and PCA were unchanged. Protoporphyrine IX inhibited EPO in BCA and PCA and abolished L-NG nitroarginine-resistant relaxation of BCA not PCA. 6. An EPO-derived compound, 11,12-epoxy-eicosatrienoic acid (11,12-EET) yielded significant relaxation in BCA and PCA in three out of six experiments. 7. These findings suggest that L-NG nitroarginine-resistant relaxation in BCA and PCA constitutes two distinct pathways. In BCA, activation of Ca(2+)-activated K+ channels via a pertussis-toxin-sensitive G protein and EPO-derived compounds might be involved. In PCA, no selective inhibition of L-NG nitroarginine-resistant relaxation was found.
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Affiliation(s)
- W F Graier
- Department of Medical Biochemistry, University of Graz, Austria
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49
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Shieh CC, Petrini M, Dwyer T, Farley J. Effects of Elevated Cytosolic Calcium on ACh-Induced Swine Tracheal Smooth Muscle Contraction. J Biomed Sci 1996; 3:348-358. [PMID: 11725117 DOI: 10.1007/bf02257965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Increased intracellular calcium concentration ([Ca(2+)](i)) is required for smooth muscle contraction. In tracheal and other tonic smooth muscles, contraction and elevated [Ca(2+)](i) are maintained as long as an agonist is present. To evaluate the physiological role of steady-state increases in Ca(2+) on tension maintenance, [Ca(2+)](i) was elevated using ionomycin, a Ca(2+) ionophore or charybdotoxin, a large-conductance calcium-activated potassium channel (K(Ca)) blocker prior to or during exposure of tracheal smooth muscle strips to ACh (10(-9) to 10(-4) M). Ionomycin (5 &mgr;M) in resting muscles induced increases in [Ca(2+)](i) to 500 +/- 230 nM and small increases in force of 2.6 +/- 2.3 N/cm(2). This tension is only 10% of the maximal tension induced by ACh. Charybdotoxin had no effect on [Ca(2+)](i) or tension in resting muscle. After pretreatment of muscle with ionomycin, the concentration-response relationship for ACh-induced changes in tension shifted to the left (EC(50) = 0.07 +/- 0.05 &mgr;M ionomycin; 0.17 +/- 0.07 &mgr;M, control, p < 0.05). When applied to the muscles during steady-state responses to submaximal concentrations of ACh, both ionomycin and charybdotoxin induced further increases in tension. The same magnitude increase in tension occurs after ionomycin and charybdotoxin treatment, even though the increase in [Ca(2+)](i) induced by charybdotoxin is much smaller than that induced by ionomycin. We conclude that the resting muscle is much less sensitive to elevation of [Ca(2+)](i) when compared to muscles stimulated with ACh. Steady-state [Ca(2+)](i) limits tension development induced by submaximal concentrations of ACh. The activity of K(Ca) moderates the response of the muscle to ACh at concentrations less than 1 &mgr;M. Copyright 1996 S. Karger AG, Basel
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Affiliation(s)
- C.-C. Shieh
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, Miss., USA
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50
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Bauer RJ, Carl A, Kapicka CL, Kenyon JL. Determination of channel open probabilities from multichannel data. J Neurosci Methods 1996; 68:101-11. [PMID: 8884619 DOI: 10.1016/0165-0270(96)00013-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We developed a method for determining whether channels in a multichannel patch or bilayer have the same or statistically significantly different open probabilities. We use a maximum likelihood method to fit the distribution of (unbinned) current amplitudes and to provide estimates of individual channel open probabilities, single channel currents, and standard deviations of the channel currents. These parameters are used to compare models with increasing constraints on the open probabilities including the model where all channels have different open probabilities and the model where all channels have the same open probability. A chi 2 statistic is used to identify models that are statistically less likely to predict the data. The ability of multichannel data to determine individual open probabilities is limited by two factors: the signal to noise ratio of the record and the fact that changes in amplitude distributions caused by a 0.2 difference in open probabilities are comparable in magnitude to the variations caused by random channel gating. These limitations notwithstanding, we demonstrate the utility of our approach by using it to analyze the open probabilities of 3 large conductance Ca2(+)-activated K+ channels in an artificial lipid bilayer revealing the response of one of those channels to GTP gamma S.
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Affiliation(s)
- R J Bauer
- Department of Physiology/MS 352, University of Nevada School of Medicine, Reno 89557, USA
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