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Kyi CW, Garcia VB, Garcia ML, Schulz DJ. Spinal cord injury is associated with changes in synaptic properties of the mouse major pelvic ganglion. J Neurophysiol 2022; 128:892-909. [PMID: 36069457 DOI: 10.1152/jn.00477.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Spinal cord injury (SCI) has substantial impacts on autonomic function. In part, SCI results in loss of normal autonomic activity that contributes to injury-associated pathology such as neurogenic bladder, bowel, and sexual dysfunction. Yet little is known of the impacts of SCI on peripheral autonomic neurons that directly innervate these target organs. In this study, we measured changes in synaptic properties of neurons of the mouse major pelvic ganglion (MPG) associated with acute and chronic SCI. Our data show that functional and physiological properties of synapses onto MPG neurons are altered after SCI, and differ between acute and chronic injury. After acute injury, excitatory post-synaptic potentials (EPSPs) show increased rise and decay time constants leading to overall broader and longer EPSPs, while in chronic injured animals EPSPs are reduced in amplitude and show faster rise and decay leading to shorter EPSPs. Synaptic depression and low pass filtering are also altered in injured animals. Lastly, cholinergic currents are smaller in acute injured animals, but larger in chronic injured animals relative to controls. These changes in synaptic properties are associated with differences in nicotinic receptor subunit expression as well. MPG CHRNA3 mRNA levels decreased after injury, while CHRNA4 mRNAs increased. Further, changes in the correlations of alpha- and beta-subunit mRNAs suggests that nicotinic receptor subtype composition is altered after injury. Taken together, our data demonstrate that peripheral autonomic neurons are fundamentally altered after SCI, suggesting that longer-term therapeutic approaches could target these neurons directly to potentially help ameliorate neurogenic target organ dysfunction.
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Affiliation(s)
- Cindy W Kyi
- Division of Biological Sciences, University of Missouri, Columbia, MO, United States
| | - Virginia B Garcia
- Division of Biological Sciences, University of Missouri, Columbia, MO, United States
| | - Michael L Garcia
- Division of Biological Sciences, University of Missouri, Columbia, MO, United States
| | - David J Schulz
- Division of Biological Sciences, University of Missouri, Columbia, MO, United States
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2
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Menshov VA, Trofimov AV, Zagurskaya AV, Berdnikova NG, Yablonskaya OI, Platonova AG. Influence of Nicotine from Diverse Delivery Tools on the Autonomic Nervous and Hormonal Systems. Biomedicines 2022; 10:biomedicines10010121. [PMID: 35052800 PMCID: PMC8773565 DOI: 10.3390/biomedicines10010121] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Revised: 01/02/2022] [Accepted: 01/03/2022] [Indexed: 02/01/2023] Open
Abstract
Background: Through measurements of the heart rate variability (HRV) accompanied by the pertinent biomarker assays, the effects of nicotine and byproducts derived from alternative nicotine delivery systems (ANDS) on the autonomic nervous system (ANS) and hormonal system have been investigated. Methods: HRV was studied in a group of volunteers (17 people), involving non-smokers, i.e., who never smoked before (11), ex-smokers (4) and active smokers (2). ANDS and smoking simulators, including regular, nicotine-free and electronic cigarettes; tobacco heating systems; chewing gums and nicotine packs of oral fixation (nic-packs), were used. Blood pressure, levels of stress hormones in saliva and catecholamines in the blood were also monitored. Results: HRV analysis showed relatively small changes in HRV and in the other studied parameters with the systemic use of nic-packs with low and moderate nicotine contents (up to 6 mg) compared to other ANDS. Conclusions: The HRV method is proven to be a promising technique for evaluation of the risks associated with smoking, dual use of various ANDS and studying the biomedical aspects of smoking cessation. Nic-packs are shown to be leaders in biological safety among the studied ANDS. A sharp surge in the activity of the sympathetic division of the ANS within the first minutes of the use of nicotine packs implies that nicotine begins to act already at very low doses (before entering the blood physically in any significant amount) through fast signal transmission to the brain from the nicotinic and taste buds located in the mouth area.
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Affiliation(s)
- Valerii A. Menshov
- Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, 119334 Moscow, Russia; (N.G.B.); (O.I.Y.)
- Correspondence: (V.A.M.); (A.V.T.); Tel.: +7-495-9397358 (A.V.T.); Fax: +7-499-1374101 (V.A.M. & A.V.T.)
| | - Aleksei V. Trofimov
- Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, 119334 Moscow, Russia; (N.G.B.); (O.I.Y.)
- Moscow Institute of Physics and Technology (National Research University), 141701 Dolgoprudny, Russia
- Correspondence: (V.A.M.); (A.V.T.); Tel.: +7-495-9397358 (A.V.T.); Fax: +7-499-1374101 (V.A.M. & A.V.T.)
| | | | - Nadezda G. Berdnikova
- Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, 119334 Moscow, Russia; (N.G.B.); (O.I.Y.)
- Department of Clinical Pharmacology, I.M. Sechenov First Moscow State Medical University, 119991 Moscow, Russia
| | - Olga I. Yablonskaya
- Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, 119334 Moscow, Russia; (N.G.B.); (O.I.Y.)
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3
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Cytisine and cytisine derivatives. More than smoking cessation aids. Pharmacol Res 2021; 170:105700. [PMID: 34087351 DOI: 10.1016/j.phrs.2021.105700] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/01/2021] [Revised: 05/29/2021] [Accepted: 05/29/2021] [Indexed: 12/12/2022]
Abstract
Cytisine, a natural bioactive compound that is mainly isolated from plants of the Leguminosae family (especially the seeds of Laburnum anagyroides), has been marketed in central and eastern Europe as an aid in the clinical management of smoking cessation for more than 50 years. Its main targets are neuronal nicotinic acetylcholine receptors (nAChRs), and pre-clinical studies have shown that its interactions with various nAChR subtypes located in different areas of the central and peripheral nervous systems are neuroprotective, have a wide range of biological effects on nicotine and alcohol addiction, regulate mood, food intake and motor activity, and influence the autonomic and cardiovascular systems. Its relatively rigid conformation makes it an attractive template for research of new derivatives. Recent studies of structurally modified cytisine have led to the development of new compounds and for some of them the biological activities are mediated by still unidentified targets other than nAChRs, whose mechanisms of action are still being investigated. The aim of this review is to describe and discuss: 1) the most recent pre-clinical results obtained with cytisine in the fields of neurological and non-neurological diseases; 2) the effects and possible mechanisms of action of the most recent cytisine derivatives; and 3) the main areas warranting further research.
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4
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Silva EAP, Carvalho JS, Dos Santos DM, Oliveira AMS, de Souza Araújo AA, Serafini MR, Oliveira Santos LAB, Batista MVDA, Viana Santos MR, Siqueira Quintans JDS, Quintans-Júnior LJ, Barreto AS. Cardiovascular effects of farnesol and its β-cyclodextrin complex in normotensive and hypertensive rats. Eur J Pharmacol 2021; 901:174060. [PMID: 33819466 DOI: 10.1016/j.ejphar.2021.174060] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 03/12/2021] [Accepted: 03/17/2021] [Indexed: 10/21/2022]
Abstract
Farnesol (FAR) is a sesquiterpene alcohol with a range of reported biological effects including cardioprotective, antioxidant and antiarrhythmic properties. However, due to its volatility, the use of drug incorporation systems, such as cyclodextrins, have been proposed to improve its pharmacological properties. Thus, the aim of this study was to evaluate and characterize the cardiovascular effects of FAR alone, and to investigate the antihypertensive effects of FAR complexed with β-cyclodextrin (βCD) in rats. Mean arterial pressure (MAP) and heart rate (HR) were measured before and after intravenous administration of FAR (0,5; 2,5; 5 and 7,5 mg/kg) in normotensive rats, and after oral acute administration (200 mg/kg) of FAR and FAR/βCD complex in NG-nitro-L-arginine-methyl-ester (L-NAME) hypertensive rats. In normotensive animals, FAR induced dose-dependent hypotension associated with bradycardia. These effects were not affected by pre-treatment with L-NAME or indomethacin (INDO), but were partially attenuated by atropine. Pre-treatment with hexamethonium (HEXA) only affected hypotension. In the hypertensive rats, FAR/βCD potentialized the antihypertensive effect when compared to FAR alone. Molecular docking experiments demonstrated for the first time that FAR has affinity to bind to the M3 and M2 muscarinic, and nicotinic receptors through hydrogen bonds in the same residues as known ligands. In conclusion, our results demonstrated that FAR induced hypotension associated with bradycardia, possibly through the muscarinic and nicotinic receptors. The inclusion complex with βCD improved the antihypertensive effects of FAR, which can be relevant to improve current cardiovascular therapy using volatile natural components.
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Affiliation(s)
- Eric Aian P Silva
- Department of Physiology, Federal University of Sergipe, São Cristovão, Sergipe, Brazil; Biotechnology Graduate Program - Rede Nordeste de Biotecnologia (RENORBIO), Federal University of Sergipe, São Cristovão, Sergipe, Brazil
| | - Jéssica S Carvalho
- Department of Physiology, Federal University of Sergipe, São Cristovão, Sergipe, Brazil
| | - Danillo M Dos Santos
- Department of Physiology, Federal University of Sergipe, São Cristovão, Sergipe, Brazil; Health Sciences Graduate Program, Federal University of Sergipe, Aracaju, Sergipe, Brazil
| | - Ana Maria S Oliveira
- Department of Pharmacy, Federal University of Sergipe, São Cristovão, Sergipe, Brazil
| | - Adriano A de Souza Araújo
- Department of Pharmacy, Federal University of Sergipe, São Cristovão, Sergipe, Brazil; Health Sciences Graduate Program, Federal University of Sergipe, Aracaju, Sergipe, Brazil
| | - Mairim R Serafini
- Department of Pharmacy, Federal University of Sergipe, São Cristovão, Sergipe, Brazil; Health Sciences Graduate Program, Federal University of Sergipe, Aracaju, Sergipe, Brazil
| | | | - Marcus V de A Batista
- Department of Biology, Federal University of Sergipe, São Cristovão, Sergipe, Brazil
| | - Márcio R Viana Santos
- Department of Physiology, Federal University of Sergipe, São Cristovão, Sergipe, Brazil; Biotechnology Graduate Program - Rede Nordeste de Biotecnologia (RENORBIO), Federal University of Sergipe, São Cristovão, Sergipe, Brazil; Health Sciences Graduate Program, Federal University of Sergipe, Aracaju, Sergipe, Brazil
| | - Jullyana de S Siqueira Quintans
- Department of Physiology, Federal University of Sergipe, São Cristovão, Sergipe, Brazil; Biotechnology Graduate Program - Rede Nordeste de Biotecnologia (RENORBIO), Federal University of Sergipe, São Cristovão, Sergipe, Brazil; Department of Health Education, Federal University of Sergipe, Lagarto, Sergipe, Brazil
| | - Lucindo J Quintans-Júnior
- Department of Physiology, Federal University of Sergipe, São Cristovão, Sergipe, Brazil; Biotechnology Graduate Program - Rede Nordeste de Biotecnologia (RENORBIO), Federal University of Sergipe, São Cristovão, Sergipe, Brazil; Health Sciences Graduate Program, Federal University of Sergipe, Aracaju, Sergipe, Brazil
| | - André S Barreto
- Department of Health Education, Federal University of Sergipe, Lagarto, Sergipe, Brazil; Health Sciences Graduate Program, Federal University of Sergipe, Aracaju, Sergipe, Brazil.
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5
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Nicotinic Acetylcholine Receptor Involvement in Inflammatory Bowel Disease and Interactions with Gut Microbiota. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2021; 18:ijerph18031189. [PMID: 33572734 PMCID: PMC7908252 DOI: 10.3390/ijerph18031189] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 01/22/2021] [Accepted: 01/25/2021] [Indexed: 12/12/2022]
Abstract
The gut-brain axis describes a complex interplay between the central nervous system and organs of the gastrointestinal tract. Sensory neurons of dorsal root and nodose ganglia, neurons of the autonomic nervous system, and immune cells collect and relay information about the status of the gut to the brain. A critical component in this bi-directional communication system is the vagus nerve which is essential for coordinating the immune system’s response to the activities of commensal bacteria in the gut and to pathogenic strains and their toxins. Local control of gut function is provided by networks of neurons in the enteric nervous system also called the ‘gut-brain’. One element common to all of these gut-brain systems is the expression of nicotinic acetylcholine receptors. These ligand-gated ion channels serve myriad roles in the gut-brain axis including mediating fast synaptic transmission between autonomic pre- and postganglionic neurons, modulation of neurotransmitter release from peripheral sensory and enteric neurons, and modulation of cytokine release from immune cells. Here we review the role of nicotinic receptors in the gut-brain axis with a focus on the interplay of these receptors with the gut microbiome and their involvement in dysregulation of gut function and inflammatory bowel diseases.
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6
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Rodríguez-Núñez I, Pontes RB, Romero F, Campos RR. Effects of physical exercise on baroreflex sensitivity and renal sympathetic nerve activity in chronic nicotine-treated rats. Can J Physiol Pharmacol 2020; 99:786-794. [PMID: 33290163 DOI: 10.1139/cjpp-2020-0381] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Chronic nicotine exposure may increase cardiovascular risk by impairing the cardiac autonomic function. Besides, physical exercise (PE) has shown to improve cardiovascular health. Thus, we aimed to investigate the effects of PE on baroreflex sensitivity (BRS), heart rate variability (HRV), and sympathetic nerve activity (SNA) in chronically nicotine-exposed rats. Male Wistar rats were assigned to four independent groups: Control (treated with saline solution), Control+Ex (treated with saline and submitted to treadmill training), Nicotine (treated with Nicotine), and Nicotine+Ex (treated with nicotine and submitted to treadmill training). Nicotine (1 mg·kg-1) was administered daily for 28 consecutive days. PE consisted of running exercise (60%-70% of maximal aerobic capacity) for 45 min, 5 days per week, for 4 weeks. At the end of the protocol, cardiac BRS, HRV, renal SNA (rSNA), and renal BRS were assessed. Nicotine treatment decreased absolute values of HRV indexes, increased low frequency/high frequency ratio of HRV, reduced the bradycardic and sympatho-inhibitory baroreceptor reflex responses, and reduced the rSNA. PE effectively restored time-domain HRV indexes, the bradycardic and sympatho-inhibitory reflex responses, and the rSNA in chronic nicotine-treated rats. PE was effective in preventing the deterioration of time-domain parameters of HRV, arterial baroreceptor dysfunction, and the rSNA after nicotine treatment.
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Affiliation(s)
- Iván Rodríguez-Núñez
- Departamento de Fisiologia, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil.,Departamento de Kinesiología, Facultad de Medicina, Universidad de Concepción, Chile
| | - Roberto B Pontes
- Departamento de Fisiologia, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil
| | - Fernando Romero
- Programa de Doctorado en Ciencias Médicas, Departamento de Cirugía, Facultad de Medicina, Universidad de La Frontera, Temuco. Chile
| | - Ruy R Campos
- Departamento de Fisiologia, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil
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7
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Abstract
Human behavior can be controlled by physical or psychological dependencies associated with addiction. One of the most insidious addictions in our society is the use of tobacco products which contain nicotine. This addiction can be associated with specific receptors in the brain that respond to the natural neurotransmitter acetylcholine. These nicotinic acetylcholine receptors (nAChR) are ligand-gated ion channels formed by the assembly of one or multiple types of nAChR receptor subunits. In this paper, we review the structure and diversity of nAChR subunits and our understanding for how different nAChR subtypes play specific roles in the phenomenon of nicotine addiction. We focus on receptors containing β2 and/or α6 subunits and the special significance of α5-containing receptors. These subtypes all have roles in regulating dopamine-mediated neurotransmission in the mesolimbic reward pathways of the brain. We also discuss the unique roles of homomeric α7 nAChR in behavioral responses to nicotine and how our knowledge of nAChR functional diversity may help guide pharmacotherapeutic approaches for treating nicotine addiction. While nicotine addiction is a truly global problem, the use of areca nut (betel) products is also a serious addiction associated with public health issues across most of South Asia, impacting as many as 600 million people. We discuss how cholinergic receptors of the brain are also involved with areca addiction and the unique challenges for dealing with addiction to this substance.
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8
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Rollema H, Hurst RS. The contribution of agonist and antagonist activities of α4β2* nAChR ligands to smoking cessation efficacy: a quantitative analysis of literature data. Psychopharmacology (Berl) 2018; 235:2479-2505. [PMID: 29980822 DOI: 10.1007/s00213-018-4921-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/26/2017] [Accepted: 04/29/2018] [Indexed: 12/14/2022]
Abstract
RATIONALE AND OBJECTIVE Two mechanisms underlie smoking cessation efficacies of α4β2* nicotinic acetylcholine receptor (nAChR) agonists: a "nicotine-like" agonist activity reduces craving by substituting for nicotine during a quit attempt, and a "nicotine-blocking" antagonist activity attenuates reinforcement by competing with inhaled nicotine during a relapse. To evaluate the contribution of each mechanism to clinical efficacy, we estimated the degree of agonist and antagonist activities of nicotine replacement therapy (NRT), varenicline, cytisine, and the discontinued nAChR agonists dianicline, ABT-418, ABT-089, CP-601927, and CP-601932, relative to the functional effects of nicotine from smoking. METHODS Functional activities that occur in vivo with clinical doses were predicted from literature data on binding and functional potencies at the target α4β2 nAChR, as well as at α6β2* nAChRs, and from estimates of free drug exposures in human brain. Agonist activity is comprised of nAChR activation and desensitization, which were expressed as percentages of desensitization and activation by nicotine from smoking. Antagonist activity was expressed as the reduction in nAChR occupancy by nicotine during smoking in the presence of an agonist. RESULTS Comparisons with odds ratios at end of treatment suggest that extensive α4β2 and α6β2* nAChR desensitization combined with α6β2* nAChR activation at similar levels as nicotine from smoking is associated with clinical efficacy (NRT, varenicline, cytisine, ABT-418). Effective competition with inhaled nicotine for α4β2 and α6β2* nAChRs further improves clinical efficacy (varenicline). Other discontinued nAChR agonists have lower agonist and antagonist activities at α4β2 nAChRs and are inactive or less efficacious than NRT (dianicline, ABT-089, CP-601927, CP-601932). CONCLUSION Three pharmacological effects appear to be key factors underlying smoking cessation efficacy: the degree of activation of α6β2* nAChRs, desensitization of α4β2 and α6β2* nAChRs (agonist activity), and the reduction of nicotine occupancy at α4β2 and α6β2* nAChRs (antagonist activity). No single activity is dominant, and the level of smoking cessation efficacy depends on the profile of these activities achieved at clinical doses. While adequate agonist activity alone seems sufficient for a clinical effect (e.g., NRT, cytisine), clinical efficacy is improved with substantial competitive antagonism of α4β2 nAChRs, i.e., if the drug has a dual agonist-antagonist mechanism of action (e.g., varenicline).
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Affiliation(s)
- Hans Rollema
- Rollema Biomedical Consulting, 20 Holdridge Court, Mystic, CT, 06355, USA.
| | - Raymond S Hurst
- Hurst Neuropharmacology Consulting, 30 Brook Trail Road, Wayland, MA, 01778, USA
- Concert Pharmaceuticals, Inc., 99 Hayden Avenue, Suite 500, Lexington, MA, 02421, USA
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Crespi A, Plutino S, Sciaccaluga M, Righi M, Borgese N, Fucile S, Gotti C, Colombo SF. The fifth subunit in α3β4 nicotinic receptor is more than an accessory subunit. FASEB J 2018; 32:4190-4202. [PMID: 29505300 DOI: 10.1096/fj.201701377r] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The α3β4 subtype is the predominant neuronal nicotinic acetylcholine receptor present in the sensory and autonomic ganglia and in a subpopulation of brain neurons. This subtype can form pentameric receptors with either 2 or 3 β4 subunits that have different pharmacologic and functional properties. To further investigate the role of the fifth subunit, we coexpressed a dimeric construct coding for a single polypeptide containing the β4 and α3 subunit sequences, with different monomeric subunits. With this strategy, which allowed the formation of single populations of receptors with unique stoichiometry, we demonstrated with immunofluorescence and biochemical and functional assays that only the receptors with 3 β4 subunits are efficiently expressed at the plasma membrane. Moreover, the LFM export motif of β4 subunit in the fifth position exerts a unique function in the regulation of the intracellular trafficking of the receptors, their exposure at the cell surface, and consequently, their function, whereas the same export motif present in the β4 subunits forming the acetylcholine binding site is dispensable.-Crespi, A., Plutino, S., Sciaccaluga, M., Righi, M., Borgese, N., Fucile, S., Gotti, C., Colombo, S. F. The fifth subunit in α3β4 nicotinic receptor is more than an accessory subunit.
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Affiliation(s)
- Arianna Crespi
- Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy.,Consiglio Nazionale delle Ricerche (CNR) Institute of Neuroscience, Milan, Italy
| | - Simona Plutino
- Dipartimento di Fisiologia e Farmacologia, Università di Roma La Sapienza, Rome, Italy; and
| | - Miriam Sciaccaluga
- Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Neuromed, Istituto Neurologico Mediterraneo, Pozzilli, Italy
| | - Marco Righi
- Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy.,Consiglio Nazionale delle Ricerche (CNR) Institute of Neuroscience, Milan, Italy
| | - Nica Borgese
- Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy.,Consiglio Nazionale delle Ricerche (CNR) Institute of Neuroscience, Milan, Italy
| | - Sergio Fucile
- Dipartimento di Fisiologia e Farmacologia, Università di Roma La Sapienza, Rome, Italy; and.,Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Neuromed, Istituto Neurologico Mediterraneo, Pozzilli, Italy
| | - Cecilia Gotti
- Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy.,Consiglio Nazionale delle Ricerche (CNR) Institute of Neuroscience, Milan, Italy
| | - Sara Francesca Colombo
- Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy.,Consiglio Nazionale delle Ricerche (CNR) Institute of Neuroscience, Milan, Italy
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10
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Gahring LC, Myers EJ, Dunn DM, Weiss RB, Rogers SW. Nicotinic alpha 7 receptor expression and modulation of the lung epithelial response to lipopolysaccharide. PLoS One 2017; 12:e0175367. [PMID: 28384302 PMCID: PMC5383308 DOI: 10.1371/journal.pone.0175367] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Accepted: 03/26/2017] [Indexed: 01/14/2023] Open
Abstract
Nicotine modulates multiple inflammatory responses in the lung through the nicotinic acetylcholine receptor subtype alpha7 (α7). Previously we reported that α7 modulates both the hematopoietic and epithelium responses in the lung to the bacterial inflammogen, lipopolysaccharide (LPS). Here we apply immunohistochemistry, flow cytometry and RNA-Seq analysis of isolated distal lung epithelium to further define α7-expression and function in this tissue. Mouse lines were used that co-express a bicistronic tau-green fluorescent protein (tGFP) as a reporter of α7 (α7G) expression and that harbor an α7 with a specific point mutation (α7E260A:G) that selectively uncouples it from cell calcium-signaling mechanisms. The tGFP reporter reveals strong cell-specific α7-expression by alveolar macrophages (AM), Club cells and ATII cells. Ciliated cells do not express detectible tGFP, but their numbers decrease by one-third in the α7E260A:G lung compared to controls. Transcriptional comparisons (RNA-Seq) between α7G and α7E260A:G enriched lung epithelium 24 hours after challenge with either intra-nasal (i.n.) saline or LPS reveals a robust α7-genotype impact on both the stasis and inflammatory response of this tissue. Overall the α7E260A:G lung epithelium exhibits reduced inflammatory cytokine/chemokine expression to i.n. LPS. Transcripts specific to Club cells (e.g., CC10, secretoglobins and Muc5b) or to ATII cells (e.g., surfactant proteins) were constitutively decreased in in the α7E260A:G lung, but they were strongly induced in response to i.n. LPS. Protein analysis applying immunohistochemistry and ELISA also revealed α7-associated differences suggested by RNA-Seq including altered mucin protein 5b (Muc5b) accumulation in the α7E260A:G bronchia, that in some cases appeared to form airway plugs, and a substantial increase in extracellular matrix deposits around α7E260A:G airway bronchia linings that was not seen in controls. Our results show that α7 is an important modulator of normal gene expression stasis and the response to an inhaled inflammogen in the distal lung epithelium. Further, when normal α7 signaling is disrupted, changes in lung gene expression resemble those associated with long-term lung pathologies seen in humans who use inhaled nicotine products.
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Affiliation(s)
- Lorise C. Gahring
- Geriatric Research, Education, and Clinical Center, Salt Lake City Veterans Administration Medical Center, Salt Lake City, Utah, United States of America
- Division of Geriatrics, Department of Internal Medicine, University of Utah School of Medicine, Salt Lake City, Utah, United States of America
- * E-mail: (LCG); (SWR)
| | - Elizabeth J. Myers
- Division of Geriatrics, Department of Internal Medicine, University of Utah School of Medicine, Salt Lake City, Utah, United States of America
| | - Diane M. Dunn
- Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, Utah, United States of America
| | - Robert B. Weiss
- Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, Utah, United States of America
| | - Scott W. Rogers
- Geriatric Research, Education, and Clinical Center, Salt Lake City Veterans Administration Medical Center, Salt Lake City, Utah, United States of America
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah, United States of America
- * E-mail: (LCG); (SWR)
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11
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Fox-Loe AM, Dwoskin LP, Richards CI. Nicotinic Acetylcholine Receptors as Targets for Tobacco Cessation Therapeutics: Cutting-Edge Methodologies to Understand Receptor Assembly and Trafficking. NEUROMETHODS 2016; 117:119-132. [PMID: 28025590 DOI: 10.1007/978-1-4939-3768-4_7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Tobacco dependence is a chronic relapsing disorder and nicotine, the primary alkaloid in tobacco, acts at nicotinic receptors to stimulate dopamine release in brain, which is responsible for the reinforcing properties of nicotine, leading to addiction. Although the majority of tobacco users express the desire to quit, only a small percentage of those attempting to quit are successful using the currently available pharmacotherapies. Nicotine upregulates the number of specific nicotinic receptors on the neuronal cell surface. An increase in receptor trafficking or preferential stoichiometric assembly of receptor subunits involves changes in assembly, endoplasmic reticulum export, vesicle transport, decreased degradation, desensitization, enhanced maturation of functional pentamers, and pharmacological chaperoning. Understanding these changes on a mechanistic level is important to the development of nicotinic receptors as drug targets. For this reason, cutting-edge methodologies are being developed and employed to pinpoint distinct changes in localization, assembly, export, vesicle trafficking, and stoichiometry in order to further understand the physiology of these receptors and to evaluate the action of novel therapeutics for smoking cessation.
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12
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Modification of the anabaseine pyridine nucleus allows achieving binding and functional selectivity for the α3β4 nicotinic acetylcholine receptor subtype. Eur J Med Chem 2016; 108:392-405. [DOI: 10.1016/j.ejmech.2015.11.045] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Revised: 11/23/2015] [Accepted: 11/25/2015] [Indexed: 11/19/2022]
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13
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Alpha2-adrenoceptor-independent inhibition of acetylcholine receptor channel and sodium channel by dexmedetomidine in rat superior cervical ganglion neurons. Neuroscience 2015; 289:9-18. [DOI: 10.1016/j.neuroscience.2014.12.045] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Revised: 12/29/2014] [Accepted: 12/30/2014] [Indexed: 01/03/2023]
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Zhang C, Wang Z, Dong J, Pan R, Qiu H, Zhang J, Zhang P, Zheng J, Yu W. Bilirubin modulates acetylcholine receptors in rat superior cervical ganglionic neurons in a bidirectional manner. Sci Rep 2014; 4:7475. [PMID: 25503810 PMCID: PMC4265787 DOI: 10.1038/srep07475] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Accepted: 11/24/2014] [Indexed: 01/08/2023] Open
Abstract
Autonomic dysfunction as a partial contributing factor to cardiovascular instability in jaundiced patients is often associated with increased serum bilirubin levels. Whether increased serum bilirubin levels could directly inhibit sympathetic ganglion transmission by blocking neuronal nicotinic acetylcholine receptors (nAChRs) remains to be elucidated. Conventional patch-clamp recordings were used to study the effect of bilirubin on nAChRs currents from enzymatically dissociated rat superior cervical ganglia (SCG) neurons. The results showed that low concnetrations (0.5 and 2 μM) of bilirubin enhanced the peak ACh-evoked currents, while high concentrations (3 to 5.5 µM) of bilirubin suppressed the currents with an IC50 of 4 ± 0.5 μM. In addition, bilirubin decreased the extent of desensitization of nAChRs in a concentration-dependent manner. This inhibitory effect of bilirubin on nAChRs channel currents was non-competitive and voltage independent. Bilirubin partly improved the inhibitory effect of forskolin on ACh-induced currents without affecting the action of H-89. These data suggest that the dual effects of enhancement and suppression of bilirubin on nAChR function may be ascribed to the action mechanism of positive allosteric modulation and direct blockade. Thus, suppression of sympathetic ganglionic transmission through postganglionic nAChRs inhibition may partially contribute to the adverse cardiovascular effects in jaundiced patients.
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Affiliation(s)
- Chengmi Zhang
- 1] Department of Anesthesiology, Eastern Hepatobiliary Surgery Hospital, the Second Military Medical University, Shanghai, China [2] Department of Anesthesiology, Xinhua Hospital, Shanghai Jiaotong University, Shanghai, China
| | - Zhenmeng Wang
- Department of Anesthesiology, Eastern Hepatobiliary Surgery Hospital, the Second Military Medical University, Shanghai, China
| | - Jing Dong
- Department of Anesthesiology, Shanghai First People's Hospital, Shanghai Jiaotong University, Shanghai, China
| | - Ruirui Pan
- Department of Anesthesiology, Eastern Hepatobiliary Surgery Hospital, the Second Military Medical University, Shanghai, China
| | - Haibo Qiu
- Department of Anesthesiology, Eastern Hepatobiliary Surgery Hospital, the Second Military Medical University, Shanghai, China
| | - Jinmin Zhang
- Department of Anesthesiology, Eastern Hepatobiliary Surgery Hospital, the Second Military Medical University, Shanghai, China
| | - Peng Zhang
- Department of Clinical Diagnosis, Changhai Hospital, the Second Military Medical University, Shanghai, China
| | - Jijian Zheng
- Department of Anesthesiology, Shanghai First People's Hospital, Shanghai Jiaotong University, Shanghai, China
| | - Weifeng Yu
- Department of Anesthesiology, Eastern Hepatobiliary Surgery Hospital, the Second Military Medical University, Shanghai, China
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Gahring LC, Myers E, Palumbos S, Rogers SW. Nicotinic receptor Alpha7 expression during mouse adrenal gland development. PLoS One 2014; 9:e103861. [PMID: 25093893 PMCID: PMC4122369 DOI: 10.1371/journal.pone.0103861] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Accepted: 07/07/2014] [Indexed: 11/23/2022] Open
Abstract
The nicotinic acetylcholine receptor alpha 7 (α7) is a ligand-activated ion channel that contributes to a diversity of cellular processes involved in development, neurotransmission and inflammation. In this report the expression of α7 was examined in the mouse developing and adult adrenal gland that expresses a green fluorescent protein (GFP) reporter as a bi-cistronic extension of the endogenous α7 transcript (α7(G)). At embryonic day 12.5 (E12.5) α7(G) expression was associated with the suprarenal ganglion and precursor cells of the adrenal gland. The α7(G) cells are catecholaminergic chromaffin cells as reflected by their progressive increase in the co-expression of tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH) that is complete by E18.5. In the adult, α7(G) expression is limited to a subset of chromaffin cells in the adrenal medulla that cluster near the border with the adrenal cortex. These chromaffin cells co-express α7(G), TH and DBH, but they lack phenylethanolamine N-methyltransferase (PNMT) consistent with only norepinephrine (NE) synthesis. These cell groups appear to be preferentially innervated by pre-ganglionic afferents identified by the neurotrophin receptor p75. No afferents identified by beta-III tubulin, neurofilament proteins or p75 co-expressed α7(G). Occasional α7(G) cells in the pre-E14.5 embryos express neuronal markers consistent with intrinsic ganglion cells and in the adult some α7(G) cells co-express glutamic acid decarboxylase. The transient expression of α7 during adrenal gland development and its prominent co-expression by a subset of NE chromaffin cells in the adult suggests that the α7 receptor contributes to multiple aspects of adrenal gland development and function that persist into adulthood.
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Affiliation(s)
- Lorise C. Gahring
- Salt Lake City VA Geriatric Research, Education and Clinical Center, Salt Lake City, Utah, United States of America
- Department of Internal Medicine, Division of Geriatrics, University of Utah, Salt Lake City, Utah, United States of America
| | - Elizabeth Myers
- Department of Internal Medicine, Division of Geriatrics, University of Utah, Salt Lake City, Utah, United States of America
| | - Sierra Palumbos
- Department of Neurobiology and Anatomy, University of Utah, Salt Lake City, Utah, United States of America
| | - Scott W. Rogers
- Salt Lake City VA Geriatric Research, Education and Clinical Center, Salt Lake City, Utah, United States of America
- Department of Neurobiology and Anatomy, University of Utah, Salt Lake City, Utah, United States of America
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16
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De Biasi M, McLaughlin I, Perez EE, Crooks PA, Dwoskin LP, Bardo MT, Pentel PR, Hatsukami D. Scientific overview: 2013 BBC plenary symposium on tobacco addiction. Drug Alcohol Depend 2014; 141:107-17. [PMID: 24934691 PMCID: PMC4227301 DOI: 10.1016/j.drugalcdep.2014.05.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Revised: 05/12/2014] [Accepted: 05/16/2014] [Indexed: 12/13/2022]
Abstract
Nicotine dependence plays a critical role in addiction to tobacco products, and thus contributes to a variety of devastating tobacco-related diseases (SGR 2014). Annual costs associated with smoking in the US are estimated to be between $289 and $333 billion. Effective interventions for nicotine dependence, especially in smokers, are a critical barrier to the eradication of tobacco-related diseases. This overview highlights research presented at the Plenary Symposium of Behavior, Biology and Chemistry: Translational Research in Addiction Conference (BBC), hosted by the UT Health Science Center San Antonio, on March 9-10, 2013. The Plenary Symposium focused on tobacco addiction, and covered topics ranging from basic science to national policy. As in previous years, the meeting brought together globally-renowned scientists, graduate student recruits, and young scientists from underrepresented populations in Texas and other states with the goal of fostering interest in drug addiction research in young generations.
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Affiliation(s)
- M De Biasi
- Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA; Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA; Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA.
| | - I McLaughlin
- Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA; Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - E E Perez
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - P A Crooks
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - L P Dwoskin
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, KY, USA
| | - M T Bardo
- Department of Psychology, University of Kentucky, Lexington, KY, USA
| | - P R Pentel
- Department of Medicine, Hennepin County Medical Center, University of Minnesota, Minneapolis, MN, USA
| | - D Hatsukami
- Department of Psychiatry, University of Minnesota, Minneapolis, MN, USA
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17
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Muraki K, Hatano N, Suzuki H, Muraki Y, Iwajima Y, Maeda Y, Ono H. Oseltamivir blocks human neuronal nicotinic acetylcholine receptor-mediated currents. Basic Clin Pharmacol Toxicol 2014; 116:87-95. [PMID: 24965031 DOI: 10.1111/bcpt.12290] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Accepted: 06/12/2014] [Indexed: 11/30/2022]
Abstract
The effects of oseltamivir, a neuraminidase inhibitor, were tested on the function of neuronal nicotinic acetylcholine receptors (nAChRs) in a neuroblastoma cell line IMR32 derived from human peripheral neurons and on recombinant human α3β4 nAChRs expressed in HEK cells. IMR32 cells predominately express α3β4 nAChRs. Nicotine (nic, 30 μm)-evoked currents recorded at -90 mV in IMR32 cells using the whole-cell patch clamp technique were reversibly blocked by oseltamivir in a concentration-dependent manner. In contrast, an active metabolite of oseltamivir, oseltamivir carboxylate (OC) at 30 μm had little effect on the nic-evoked currents. Oseltamivir also blocked nic-evoked currents derived from HEK cells with recombinant α3β4 nAChRs. This blockade was voltage-dependent with 10, 30 and 100 μm oseltamivir inhibiting ~50% at -100, -60 and -40 mV, respectively. Non-inactivating currents in IMR32 cells and in HEK cells with α3β4 nAChRs, which were evoked by an endogenous nicotinic agonist, ACh (5 μm), were reversibly blocked by oseltamivir. These data demonstrate that oseltamivir blocks nAChRs, presumably via binding to a site in the channel pore.
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Affiliation(s)
- Katsuhiko Muraki
- Laboratory of Cellular Pharmacology, School of Pharmacy, Aichi-Gakuin University, Chikusa, Japan
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Rollema H, Russ C, Lee TC, Hurst RS, Bertrand D. Functional interactions of varenicline and nicotine with nAChR subtypes implicated in cardiovascular control. Nicotine Tob Res 2014; 16:733-42. [PMID: 24406270 DOI: 10.1093/ntr/ntt208] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
INTRODUCTION It has been suggested that varenicline-induced activation of nicotinic acetylcholine receptors (nAChRs) could play a role in the cardiovascular (CV) safety of varenicline. However, since preclinical studies showed that therapeutic varenicline concentrations have no effect in models of CV function, this study examined in vitro profiles of varenicline and nicotine at nAChR subtypes possibly involved in CV control. METHODS Concentration-dependent functional effects of varenicline and nicotine at human α3β4, α3α5β4, α7, and α4β2 nAChRs expressed in oocytes were determined by electrophysiology. The proportion of nAChRs predicted to be activated and inhibited by concentrations of varenicline (1mg b.i.d.) and of nicotine in smokers was derived from activation-inhibition curves for each nAChR subtype. RESULTS Human varenicline and nicotine concentrations can desensitize and inhibit nAChRs but cause only low-level activation of α3β4, α4β2 (<2%), α7 (<0.05%), and α3α5β4 (<0.01%) nAChRs, which is consistent with literature data. Nicotine concentrations in smokers are predicted to inhibit larger fractions of α3β4 (48%) and α3α5β4 (10%) nAChRs than therapeutic varenicline concentrations (11% and 0.6%, respectively) and to inhibit comparable fractions of α4β2 nAChRs (42%-56%) and α7 nAChRs (16%) as varenicline. CONCLUSIONS Nicotine and varenicline concentrations in patients and smokers are predicted to cause minimal activation of ganglionic α3β4* nAChRs, while their functional profiles at α3β4, α3α5β4, α7, and α4β2 nAChRs cannot explain that substituting nicotine from tobacco with varenicline would cause CV adverse events in smokers who try to quit. Other pharmacological properties that could mediate varenicline-induced CV effects have not been identified.
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Nicotine-modulated subunit stoichiometry affects stability and trafficking of α3β4 nicotinic receptor. J Neurosci 2013; 33:12316-28. [PMID: 23884938 DOI: 10.1523/jneurosci.2393-13.2013] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Heteromeric nAChRs are pentameric cation channels, composed of combinations of two or three α and three or two β subunits, which play key physiological roles in the central and peripheral nervous systems. The prototypical agonist nicotine acts intracellularly to upregulate many nAChR subtypes, a phenomenon that is thought to contribute to the nicotine dependence of cigarette smokers. The α3β4 subtype has recently been genetically linked to nicotine dependence and lung cancer; however, the mode of action of nicotine on this receptor subtype has been incompletely investigated. Here, using transfected mammalian cells as model system, we characterized the response of the human α3β4 receptor subtype to nicotine and the mechanism of action of the drug. Nicotine, when present at 1 mm concentration, elicited a ∼5-fold increase of cell surface α3β4 and showed a more modest upregulatory effect also at concentrations as low as 10 μM. Upregulation was obtained if nicotine was present during, but not after, pentamer assembly and was caused by increased stability and trafficking of receptors assembled in the presence of the drug. Experimental determinations as well as computational studies of subunit stoichiometry showed that nicotine favors assembly of pentamers with (α3)2(β4)3 stoichiometry; these are less prone than (α3)3(β4)2 receptors to proteasomal degradation and, because of the presence in the β subunit of an endoplasmic reticulum export motif, more efficiently transported to the plasma membrane. Our findings uncover a novel mechanism of nicotine-induced α3β4 nAChR upregulation that may be relevant also for other nAChR subtypes.
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20
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Mc Laughlin D, Puri P. Familial megacystis microcolon intestinal hypoperistalsis syndrome: a systematic review. Pediatr Surg Int 2013; 29:947-51. [PMID: 23955298 DOI: 10.1007/s00383-013-3357-x] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
BACKGROUND Megacystis microcolon intestinal hypoperistalsis syndrome (MMIHS) is a rare and severe disorder of functional obstruction affecting bladder and bowel, usually diagnosed in the neonatal period. Over 230 cases have been reported since Berdon and colleagues first described this clinical entity in 1976. The exact pathogenesis of MMIHS is unknown. Familial occurrence of MMIHS has been reported and could offer insight into the aetiology of this disease. The purpose of this study was to systematically review the published literature for the evidence of familial MMIHS and to characterise these presentations. METHODS A literature search was performed using the keywords "megacystis microcolon intestinal hypoperistalsis" (1976-2013). Retrieved articles, including additional studies from reference lists, were reviewed for consanguinity between parents and recurrence of MMIHS between siblings. Data were extracted for cases where familial MMIHS was present. RESULTS A total of 47 patients were reported in which familial MMIHS was likely or confirmed. 15 sibling sets were definitively diagnosed with MMIHS (14 pairs and one set of three siblings). Four further index patients with a confirmed diagnosis and also one of the sibling pairs were reported to have a sibling in which MMIHS was probable. Consanguinity between parents was present in four of the confirmed sibling sets and in an additional seven individual cases. The outcome for familial MMIHS is generally poor. Multiple sibling fatalities were frequent and in only one family were both siblings' survivors at the time of reporting. CONCLUSION Consanguinity between parents and recurrence in siblings indicate that MMIHS is inherited in an autosomal recessive manner. With the advent of next generation sequencing, these familial clusters may be key to determining the genetic basis for MMIHS.
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Affiliation(s)
- Danielle Mc Laughlin
- National Children's Research Centre, Our Lady's Children's Hospital, Crumlin, Dublin 12, Ireland
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21
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Anticholinergic therapy for overactive bladder: A nicotinic modality? Med Hypotheses 2013; 81:456-8. [DOI: 10.1016/j.mehy.2013.06.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Revised: 05/24/2013] [Accepted: 06/11/2013] [Indexed: 12/17/2022]
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22
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Expression of Acetylcholine and Its Receptor in Human Sympathetic Ganglia in Primary Hyperhidrosis. Ann Thorac Surg 2013; 95:465-70. [DOI: 10.1016/j.athoracsur.2012.10.068] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/18/2012] [Revised: 10/21/2012] [Accepted: 10/25/2012] [Indexed: 02/05/2023]
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23
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Mazurov AA, Miao L, Bhatti BS, Strachan JP, Akireddy S, Murthy S, Kombo D, Xiao YD, Hammond P, Zhang J, Hauser TA, Jordan KG, Miller CH, Speake JD, Gatto GJ, Yohannes D. Discovery of 3-(5-chloro-2-furoyl)-3,7-diazabicyclo[3.3.0]octane (TC-6683, AZD1446), a novel highly selective α4β2 nicotinic acetylcholine receptor agonist for the treatment of cognitive disorders. J Med Chem 2012; 55:9181-94. [PMID: 22793665 DOI: 10.1021/jm3006542] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Diversification of essential nicotinic cholinergic pharmacophoric elements, i.e., cationic center and hydrogen bond acceptor, resulted in the discovery of novel potent α4β2 nAChR selective agonists comprising a series of N-acyldiazabicycles. Core characteristics of the series are an exocyclic carbonyl moiety as a hydrogen bond acceptor and endocyclic secondary amino group. These features are positioned at optimal distance and with optimal relative spatial orientation to provide near optimal interactions with the receptor. A novel potent and highly selective α4β2 nAChR agonist 3-(5-chloro-2-furoyl)-3,7-diazabicyclo[3.3.0]octane (56, TC-6683, AZD1446) with favorable pharmaceutical properties and in vivo efficacy in animal models has been identified as a potential treatment for cognitive deficits associated with psychiatric or neurological conditions and is currently being progressed to phase 2 clinical trials as a treatment for Alzheimer's disease.
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Affiliation(s)
- Anatoly A Mazurov
- Targacept, Inc., Winston Salem, North Carolina 27101, United States.
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de Moura Júnior NB, das-Neves-Pereira JC, de Campos JRM, de Oliveira FRG, Wolosker N, Parra ER, Capelozzi VL, Jatene FB. Preservation of α-3 neuronal nicotinic acetylcholine receptor expression in sympathetic ganglia after brain death. Mol Neurobiol 2012; 45:362-5. [PMID: 22274960 DOI: 10.1007/s12035-012-8235-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Accepted: 01/06/2012] [Indexed: 02/06/2023]
Abstract
The goal of this study was to evaluate if the immunohistochemical expression of alpha-3 neuronal nicotinic acetylcholine receptor subunit in sympathetic ganglia remains stable after brain death, determining the possible use of sympathetic thoracic ganglia from subjects after brain death as study group. The third left sympathetic ganglion was resected from patients divided in two groups: BD-organ donors after brain death and CON-patients submitted to sympathectomy for hyperhidrosis (control group). Immunohistochemical staining for alpha-3 neuronal nicotinic acetylcholine receptor subunit was performed; strong and weak expression areas were quantified in both groups. The BD group showed strong alpha-3 neuronal nicotinic acetylcholine receptor expression in 6.55% of the total area, whereas the CON group showed strong expression in 5.91% (p = 0.78). Weak expression was found in 6.47% of brain-dead subjects and in 7.23% of control subjects (p = 0.31). Brain death did not affect the results of the immunohistochemical analysis of sympathetic ganglia, and its use as study group is feasible.
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Affiliation(s)
- Nabor Bezerra de Moura Júnior
- Division of Thoracic Surgery, Heart Institute, University of São Paulo, Av. Dr. Eneas de Carvalho Aguiar, 44, 2° andar, 05403-900 São Paulo, São Paulo, Brazil.
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Beckel JM, Birder LA. Differential expression and function of nicotinic acetylcholine receptors in the urinary bladder epithelium of the rat. J Physiol 2012; 590:1465-80. [PMID: 22250215 DOI: 10.1113/jphysiol.2011.226860] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
It has been previously determined that the epithelial lining of the urinary bladder, or urothelium, expresses two subtypes of nicotinic acetylcholine receptors (nAChRs) that mediate distinct physiological effects in vivo. These effects include inhibition of bladder reflexes through α7 receptors and an excitation of bladder reflexes through α3-containing (α3*) receptors. It is believed that urothelial receptors mediate their effects through modulating the release of neurotransmitters such as ATP that subsequently influence bladder afferent nerve excitability. Therefore, we examined the distribution of nAChRs in the urothelium, as well as their ability to influence the release of the neurotransmitter ATP. Immunofluorescent staining of both whole bladder tissue and primary urothelial cultures from the rat demonstrated that the urothelium contains both α3* and α7 receptors. In primary urothelial cultures, α7 stimulation with choline (10 μM to 1 mM) caused a decrease in basal ATP release while α3* stimulation with cytisine (1–100 μM) caused a concentration-dependent, biphasic response, with low concentrations (1–10 μM) inhibiting release and higher concentrations (50–100 μM) increasing release. These responses were mirrored in an in vitro, whole bladder preparation. In vivo, excitation of bladder reflexes in response to intravesical cytisine (100 μM) is blocked by systemic administration of the purinergic antagonist PPADS (1 or 3 μg kg(−1)). We also examined how each receptor subtype influenced intracellular Ca2+ levels in cultured urothelial cells. nAChR stimulation increased [Ca2+]i through distinct mechanisms: α7 through a ryanodine-sensitive intracellular mechanism and α3* through extracellular influx. In addition, our findings suggest interactions between nAChR subtypes whereby activation of α7 receptors inhibited the response to a subsequent activation of α3* receptors, preventing the increase in [Ca2+]i previously observed. This inhibitory effect appears to be mediated through protein kinase A- or protein kinase C-mediated pathways.
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Affiliation(s)
- Jonathan M Beckel
- Department of Pharmacology and Biological Chemistry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
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Ferrari MFR, Coelho EF, Farizatto KLG, Chadi G, Fior-Chadi DR. Modulation of tyrosine hydroxylase, neuropeptide y, glutamate, and substance p in Ganglia and brain areas involved in cardiovascular control after chronic exposure to nicotine. Int J Hypertens 2011; 2011:216464. [PMID: 21822476 PMCID: PMC3147125 DOI: 10.4061/2011/216464] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2011] [Revised: 06/03/2011] [Accepted: 06/14/2011] [Indexed: 11/20/2022] Open
Abstract
Considering that nicotine instantly interacts with central and peripheral nervous systems promoting cardiovascular effects after tobacco smoking, we evaluated the modulation of glutamate, tyrosine hydroxylase (TH), neuropeptide Y (NPY), and substance P (SP) in nodose/petrosal and superior cervical ganglia, as well as TH and NPY in nucleus tractus solitarii (NTS) and hypothalamic paraventricular nucleus (PVN) of normotensive Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR) after 8 weeks of nicotine exposure. Immunohistochemical and in situ hybridization data demonstrated increased expression of TH in brain and ganglia related to blood pressure control, preferentially in SHR, after nicotine exposure. The alkaloid also increased NPY immunoreactivity in ganglia, NTS, and PVN of SHR, in spite of decreasing its receptor (NPY1R) binding in NTS of both strains. Nicotine increased SP and glutamate in ganglia. In summary, nicotine positively modulated the studied variables in ganglia while its central effects were mainly constrained to SHR.
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Affiliation(s)
- Merari F R Ferrari
- Departamento de Genetica e Biologia Evolutiva, Instituto de Biociencias, Universidade de São Paulo, Rua do Matao 277, 05508-090 São Paulo, SP, Brazil
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Pucci L, Grazioso G, Dallanoce C, Rizzi L, De Micheli C, Clementi F, Bertrand S, Bertrand D, Longhi R, De Amici M, Gotti C. Engineering of α-conotoxin MII-derived peptides with increased selectivity for native α6β2* nicotinic acetylcholine receptors. FASEB J 2011; 25:3775-89. [PMID: 21778325 DOI: 10.1096/fj.10-179853] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
α6β2* Nicotinic acetylcholine receptors are expressed in selected central nervous system areas, where they are involved in striatal dopamine (DA) release and its behavioral consequences, and other still uncharacterized brain activities. α6β2* receptors are selectively blocked by the α-conotoxins MII and PIA, which bear a characteristic N-terminal amino acid tail [arginine (R), aspartic acid (D), and proline (P)]. We synthesized a group of PIA-related peptides in which R1 was mutated or the RDP motif gradually removed. Binding and striatal DA release assays of native rat α6β2* receptors showed that the RDP sequence, and particularly residue R1, is essential for the activity of PIA. On the basis of molecular modeling analyses, we synthesized a hybrid peptide (RDP-MII) that had increased potency (7-fold) and affinity (13-fold) for α6β2* receptors but not for the very similar α3β2* subtype. As docking studies also suggested that E11 of MII might be a key residue engendering α6β2* vs. α3β2* selectivity, we prepared MII[E11R] and RDP-MII[E11R] peptides. Their affinity and potency for native α6β2* receptors were similar to those of their parent analogues, whereas, for the oocyte expressed rat α3β2* subtype, they showed a 31- and 14-fold lower affinity and 21- and 3.5-fold lower potency. Thus, MII[E11R] and RDP-MII[E11R] are potent antagonists showing a degree of α6β2* vs. α3β2* selectivity in vivo.
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Affiliation(s)
- Luca Pucci
- Consiglio Nazionale delle Ricerche, Istituto di Neuroscienze, Farmacologia Cellulare e Molecolare e Dipartimento di Farmacologia, Chemioterapia e Tossicologia Medica, Milan, Italy
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28
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Bellier JP, Kimura H. Peripheral type of choline acetyltransferase: biological and evolutionary implications for novel mechanisms in cholinergic system. J Chem Neuroanat 2011; 42:225-35. [PMID: 21382474 DOI: 10.1016/j.jchemneu.2011.02.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2010] [Revised: 02/23/2011] [Accepted: 02/24/2011] [Indexed: 01/29/2023]
Abstract
The peripheral type of choline acetyltransferase (pChAT) is an isoform of the well-studied common type of choline acetyltransferase (cChAT), the synthesizing enzyme of acetylcholine. Since pChAT arises by exons skipping, its amino acid sequence is similar to that of cChAT, except the lack of a continuous peptide sequence encoded by all the four exons from 6 to 9. While cChAT expression has been observed in both the central and peripheral nervous systems, pChAT is preferentially expressed in the peripheral nervous system. pChAT appears to be a reliable marker for the visualization of peripheral cholinergic neurons and their processes, whereas other conventional markers including cChAT have not been used successfully for it. In mammals like rodents, pChAT immunoreactivity has been observed in most, if not all, physiologically identified peripheral cholinergic structures such as all parasympathetic postganglionic neurons and most neurons of the enteric nervous system. In addition, pChAT has been found in many peripheral neurons that are derived from the neural crest. These include sensory neurons of the trigeminal ganglion and the dorsal root ganglion, and sympathetic postganglionic neurons. Recent studies moreover indicate that pChAT, as well as cChAT, appears ubiquitously expressed among various species not only of vertebrate mammals but also of invertebrate mollusks. This finding implies that the alternative splicing mechanism to generate pChAT and cChAT has been preserved during evolution, probably for some functional benefits.
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Affiliation(s)
- J-P Bellier
- Molecular Neuroscience Research Center, Shiga University of Medical Science, Seta Tsukinowa-cho, Otsu, Shiga 520-2192, Japan.
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David R, Ciuraszkiewicz A, Simeone X, Orr-Urtreger A, Papke RL, McIntosh JM, Huck S, Scholze P. Biochemical and functional properties of distinct nicotinic acetylcholine receptors in the superior cervical ganglion of mice with targeted deletions of nAChR subunit genes. Eur J Neurosci 2010; 31:978-93. [PMID: 20377613 DOI: 10.1111/j.1460-9568.2010.07133.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) mediate fast synaptic transmission in ganglia of the autonomic nervous system. Here, we determined the subunit composition of hetero-pentameric nAChRs in the mouse superior cervical ganglion (SCG), the function of distinct receptors (obtained by deletions of nAChR subunit genes) and mechanisms at the level of nAChRs that might compensate for the loss of subunits. As shown by immunoprecipitation and Western blots, wild-type (WT) mice expressed: alpha 3 beta 4 (55%), alpha 3 beta 4 alpha 5 (24%) and alpha 3 beta 4 beta 2 (21%) nAChRs. nAChRs in beta 4 knockout (KO) mice were reduced to < 15% of controls and no longer contained the alpha 5 subunit. Compound action potentials, recorded from the postganglionic (internal carotid) nerve and induced by preganglionic nerve stimulation, did not differ between alpha 5 beta 4 KO and WT mice, suggesting that the reduced number of receptors in the KO mice did not impair transganglionic transmission. Deletions of alpha 5 or beta2 did not affect the overall number of receptors and we found no evidence that the two subunits substitute for each other. In addition, dual KOs allowed us to study the functional properties of distinct alpha 3 beta4 and alpha 3 beta 2 receptors that have previously only been investigated in heterologous expression systems. The two receptors strikingly differed in the decay of macroscopic currents, the efficacy of cytisine, and their responses to the alpha-conotoxins AuIB and MII. Our data, based on biochemical and functional experiments and several mouse KO models, clarify and significantly extend previous observations on the function of nAChRs in heterologous systems and the SCG.
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Affiliation(s)
- Reinhard David
- Department of Biochemistry and Molecular Biology, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, A-1090 Vienna, Austria
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30
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Li YF, Lacroix C, Freeling J. Cytisine induces autonomic cardiovascular responses via activations of different nicotinic receptors. Auton Neurosci 2009; 154:14-9. [PMID: 19887306 DOI: 10.1016/j.autneu.2009.09.023] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2009] [Revised: 09/15/2009] [Accepted: 09/28/2009] [Indexed: 02/05/2023]
Abstract
Nicotinic cholinergic receptors mediate autonomic transmission at ganglia. However, whether different subtypes of nicotinic cholinergic receptors expressed in autonomic ganglia elicit distinct roles in mediating sympathetic and parasympathetic regulations remain to be defined. In this study, we observed that different subtypes of nicotinic receptors were responsible for the sympathetic and parasympathetic cardiovascular responses. In urethane anesthetized mice, intravenous injection with cytisine, a non-selective nicotinic agonist, induced a brief but pronounced decrease in heart rate, followed by increases in heart rate and arterial blood pressure. The bradycardic response was blocked by atropine, and the pressor response was blocked by prazosin, confirming that these responses were parasympathetic and sympathetic activities, respectively. Hexamethonium, a ganglionic blocker, blocked both sympathetic and parasympathetic responses. Pretreatment with methyllycaconitine citrate, a selective alpha7 nicotinic receptor antagonist, significantly attenuated cytisine-induced sympathetic response with little effect on the parasympathetic response. In contrast, pretreatment with dihydro-beta-erythroidine hydrobromide, a selective alpha4beta2 nicotinic receptor antagonist, blocked cytisine-induced parasympathetic response but not the sympathetic response. Pretreatment with dihydro-beta-erythroidine hydrobromide also blocked baroreflex associated parasympathetic bradycardic response. Moreover, treatment with nicotine induced a bradycardic response without a significant pressor response, which was also attenuated by dihydro-beta-erythroidine hydrobromide. Collectively, these data suggest that different nicotinic receptors play distinct roles in sympathetic and parasympathetic ganglia. Specifically, activations of alpha7 and alpha4beta2 nicotinic receptors are involved in cytisine-induced cardiovascular sympathetic and parasympathetic responses, respectively.
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Affiliation(s)
- Yi-Fan Li
- Division of Basic Biomedical Sciences, Sanford School of Medicine, The University of South Dakota, Vermillion, SD 57069, USA.
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31
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The ubiquitin-proteasome system regulates the stability of neuronal nicotinic acetylcholine receptors. J Mol Neurosci 2009; 40:177-84. [PMID: 19693707 DOI: 10.1007/s12031-009-9272-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2009] [Accepted: 07/20/2009] [Indexed: 12/16/2022]
Abstract
Ubiquitination is a key event for protein degradation by the proteasome system, membrane protein internalization, and protein trafficking among cellular compartments. Few data are available on the role of the ubiquitin-proteasome system (UPS) in the trafficking of neuronal nicotinic acetylcholine receptors (nAChRs). Experiments conducted in neuron-like differentiated rat pheochromocytoma cells (PC12 cells) show that the alpha3, beta2, and beta4 nAChR subunits are ubiquitinated and that their ubiquitination is necessary for degradation. A 24-h treatment with the proteasome inhibitor PS-341 increased the total levels of alpha3 and the two beta subunits in both whole cell lysates and fractions enriched for the ER/Golgi compartment. nAChR subunit upregulation was also detected in plasma membrane-enriched fractions. Inhibition of the lysosomal degradation machinery by E-64 had a significantly smaller effect on nAChR turnover. The present data, together with previous results showing that the alpha7 nAChR subunit is a target of the UPS, point to a prominent role of the proteasome in nAChR trafficking.
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32
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Li YF, LaCroix C, Freeling J. Specific subtypes of nicotinic cholinergic receptors involved in sympathetic and parasympathetic cardiovascular responses. Neurosci Lett 2009; 462:20-3. [PMID: 19573576 DOI: 10.1016/j.neulet.2009.06.081] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2009] [Revised: 06/20/2009] [Accepted: 06/24/2009] [Indexed: 11/28/2022]
Abstract
Various subtypes of nicotinic cholinergic receptors are expressed in autonomic ganglia. The distinct functional roles of these receptors in autonomic ganglionic transmission to different target organs remain to be elucidated. In this study, we tested the sympathetic and parasympathetic cardiovascular responses to nicotinic agonist and antagonists in urethane-anesthetized mice. Intravenous injection with a nicotinic agonist, 1,1-dimethyl-4-phenylpiperazinium iodide, induced a brief but pronounced decrease in heart rate, followed by significant increases in heart rate and arterial blood pressure. The bradycardic response was blocked by atropine whereas the pressor response was blocked by prazosine, confirming those responses were parasympathetic and sympathetic activities, respectively. The sympathetic response was blocked by methyllycaconitine citrate, a selective alpha 7 nicotinic cholinergic receptor (nAchR) antagonist. The parasympathetic response was blocked by a selective alpha 4 beta 2 nAchR antagonist, dihydro-beta-erythroidine hydrobromide. Moreover, injection with a selective alpha 4 beta 2 nAchR agonist, RJR2403 oxalate, induced a pronounced parasympathetic response with a smaller sympathetic response. Collectively, these data show that activations of alpha 4 beta 2 nAchRs elicits a parasympathetic cardiovascular response and activation of alpha 7 nAchRs elicits a sympathetic cardiovascular response. These data suggest that specific subtypes of nicotinic receptors at the level of the ganglia may play distinct roles in mediating sympathetic or parasympathetic activation.
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Affiliation(s)
- Yi-Fan Li
- Division of Basic Biomedical Sciences, Sanford School of Medicine, The University of South Dakota, Vermillion, SD 57069, USA.
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33
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UBXD4, a UBX-containing protein, regulates the cell surface number and stability of alpha3-containing nicotinic acetylcholine receptors. J Neurosci 2009; 29:6883-96. [PMID: 19474315 DOI: 10.1523/jneurosci.4723-08.2009] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Adaptor proteins are likely to modulate spatially and temporally the trafficking of a number of membrane proteins, including neuronal nicotinic acetylcholine receptors (nAChRs). A yeast two-hybrid screen identified a novel UBX-containing protein, UBXD4, as one of the cytosolic proteins that interact directly with the alpha3 and alpha4 nAChR subunits. The function of UBX-containing proteins is largely unknown. Immunoprecipitation and confocal microscopy confirmed the interaction of UBXD4 with alpha3-containing nAChRs (alpha3* nAChRs) expressed in HEK293 cells, PC12 cells, and rat cortical neurons. Overexpression of UBXD4 in differentiated PC12 cells (dPC12) increased nAChR cell surface expression, especially that of the alpha3beta2 subtype. These findings were corroborated by electrophysiology, immunofluorescent staining, and biotinylation of surface receptors. Silencing of UBXD4 led to a significant reduction of alpha3* nAChRs in rat cortical neurons and dPC12 cells. Biochemical and immunofluorescence studies of endogenous UBXD4 showed that the protein is located in both the ER and cis-Golgi compartments. Our investigations also showed that the alpha3 subunit is ubiquitinated and that UBXD4 can interfere with its ubiquitination and consequent degradation by the proteasome. Our data suggest that UBXD4 modulates the distribution of alpha3* nAChRs between specialized intracellular compartments and the plasma membrane. This effect is achieved by controlling the stability of the alpha3 subunit and, consequently, the number of receptors at the cell surface.
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34
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Cellular events in nicotine addiction. Semin Cell Dev Biol 2009; 20:418-31. [PMID: 19560047 DOI: 10.1016/j.semcdb.2009.01.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2008] [Revised: 12/19/2008] [Accepted: 01/09/2009] [Indexed: 11/23/2022]
Abstract
In the 25 years since the observation that chronic exposure to nicotine could regulate the number and function of high affinity nicotine binding sites in the brain there has been a major effort to link alterations in nicotinic acetylcholine receptors (nAChRs) to nicotine-induced behaviors that drive the addiction to tobacco products. Here we review the proposed roles of various nAChR subtypes in the addiction process, with emphasis on how they are regulated by nicotine and the implications for understanding the cellular neurobiology of addiction to this drug.
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Decker MW, Gopalakrishnan M, Meyer MD. The potential of neuronal nicotinic acetylcholine receptor agonists for treating CNS conditions. Expert Opin Drug Discov 2008; 3:1027-40. [DOI: 10.1517/17460441.3.9.1027] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Abdrakhmanova GR, Carroll FI, Damaj MI, Martin BR. 3'-Fluoro substitution in the pyridine ring of epibatidine improves selectivity and efficacy for alpha4beta2 versus alpha3beta4 nAChRs. Neuropharmacology 2008; 55:1287-92. [PMID: 18775444 DOI: 10.1016/j.neuropharm.2008.08.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2008] [Revised: 07/31/2008] [Accepted: 08/06/2008] [Indexed: 10/21/2022]
Abstract
The analog of epibatidine having a fluoro substituent at the 3' position of the pyridine ring has been recently developed and shown to possess binding affinity in the pM range to alpha4beta2 nAChRs and in the nM range to alpha7 nAChRs and to exhibit potent agonist activity in nicotine-induced analgesia tests. Here we used patch-clamp technique in a whole-cell configuration to compare functional activity of 3'-fluoroepibatidine to that of epibatidine by itself on recombinant alpha4beta2, alpha7 and alpha3beta4 neuronal nAChRs. The agonist effect of (+/-)-epibatidine was partial and yielded comparable EC50s of 0.012 microM (72% efficacy) and 0.027 microM (81% efficacy) at alpha4beta2 and alpha3beta4 nAChRs, respectively, but was full at alpha7 nAChRs with an EC50 of 4.8 muM. Testing of the analog at different concentrations revealed that it acts as a full agonist with an EC50 of 0.36 microM at alpha4beta2 nAChRs and induces partial agonist effect (66% efficacy) at alpha7 nAChRs with an EC50 of 9.8 microM and an IC50 corresponding to 225 microM. In contrast, the analog caused only 24% maximal activation at the range of concentrations from 0.1 to 100 microM and, in addition, induced an inhibition of alpha3beta4 nAChR function with an IC50 of 8.3 microM. Our functional data, which are in agreement with previous binding and behavioral findings, demonstrate that 3'-fluoro substitution in the pyridine ring of epibatidine results in an improved pharmacological profile as observed by an increased efficacy and selectivity for alpha4beta2 versus alpha3beta4 nAChRs.
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Affiliation(s)
- Galya R Abdrakhmanova
- Department of Pharmacology and Toxicology (G.R.A., M.I.D., B.R.M.), Virginia Commonwealth University, Richmond, VA 23298, United States.
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37
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Mitochondrial reactive oxygen species inactivate neuronal nicotinic acetylcholine receptors and induce long-term depression of fast nicotinic synaptic transmission. J Neurosci 2008; 28:1733-44. [PMID: 18272694 DOI: 10.1523/jneurosci.5130-07.2008] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Neuronal nicotinic acetylcholine receptors (nAChRs), ligand-gated ion channels implicated in a variety of cognitive, motor, and sensory behaviours, are targeted to compartments rich in mitochondria, particularly postsynaptic domains and presynaptic terminals, exposing these receptors to reactive oxygen species (ROS) generated by oxidative phosphorylation. In addition, these receptors can become exposed to ROS during the progression of certain neurodegenerative diseases. Because ROS are known to modify several membrane proteins, including some types of ion channels, it raises the question of whether elevations in cytosolic ROS alter the function of nAChRs. To address this, we elevated ROS in cultured sympathetic neurons, directly by perfusing neurons intracellularly with ROS, indirectly by blocking the mitochondrial electron transport chain, or noninvasively by transient NGF removal; we then simultaneously measured changes in cytosolic ROS levels and whole-cell ACh-evoked currents. In addition, we elevated cytosolic ROS in postganglionic neurons in intact ganglia and measured changes in nerve-evoked EPSPs. Our experiments indicate that mild elevations in cytosolic ROS, including that produced by transient interruption of NGF signaling, induce a use-dependent, long-lasting rundown of ACh-evoked currents on cultured sympathetic neurons and a long-lasting depression of fast nerve-evoked EPSPs. We show that these effects of cytosolic ROS are specific to nAChRs on neurons and do not cause rundown of ACh-evoked currents on muscle. Our results demonstrate that elevations in cytosolic ROS inactivate neuronal nAChRs in a use-dependent manner and suggest that mild oxidative stress impairs mechanisms mediated by cholinergic nicotinic signaling at neuronal-neuronal synapses.
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38
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Azam L, Yoshikami D, McIntosh JM. Amino acid residues that confer high selectivity of the alpha6 nicotinic acetylcholine receptor subunit to alpha-conotoxin MII[S4A,E11A,L15A]. J Biol Chem 2008; 283:11625-32. [PMID: 18299323 DOI: 10.1074/jbc.m710288200] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) containing alpha3 and beta2 subunits are found in autonomic ganglia and mediate ganglionic transmission. The closely related alpha6 nAChR subtype is found in the central nervous system where changes in its level of expression are observed in Parkinson's disease. To obtain a ligand that discriminates between these two receptors, we designed and synthesized a novel analog ofalpha-conotoxin MII, MII[S4A,E11A,L15A], and tested it on nAChRs expressed in Xenopus oocytes. The peptide blocked chimeric alpha6/alpha3beta2beta3 nAChRs with an IC(50) of 1.2 nm; in contrast, its IC(50) on the closely related alpha3beta2 as well as non-alpha6 nAChRs was three orders of magnitude higher. We identified the residues in the receptors that are responsible for their differential sensitivity to the peptide. We constructed chimeras with increasingly longer fragments of the N-terminal ligand binding domain of the alpha3 subunit inserted into the homologous positions of the alpha6 subunit, and these were used to determine that the region downstream of the first 140 amino acids was involved. Further mutagenesis of this region revealed that the alpha6 subunit residues Glu-152, Asp-184, and Thr-195 were critical, and replacement of these three residues with their homologs from the alpha3 subunit increased the IC(50) of the peptide by >1000-fold. Conversely, when these key residues inalpha3 were replaced with those fromalpha6, the IC(50) decreased by almost 150-fold. Similar effects were seen with other alpha6-selective conotoxins, suggesting the general importance of thesealpha6 residues in conferring selective binding.
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Affiliation(s)
- Layla Azam
- Department of Biology, University of Utah, Salt Lake City, Utah 84112, USA.
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Leroi AM, Le Normand L. Physiologie de l’appareil sphinctérien urinaire et anal pour la continence. Prog Urol 2007. [DOI: 10.1016/s1166-7087(07)92325-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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40
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Smith JW, Mogg A, Tafi E, Peacey E, Pullar IA, Szekeres P, Tricklebank M. Ligands selective for alpha4beta2 but not alpha3beta4 or alpha7 nicotinic receptors generalise to the nicotine discriminative stimulus in the rat. Psychopharmacology (Berl) 2007; 190:157-70. [PMID: 17115136 DOI: 10.1007/s00213-006-0596-8] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2006] [Accepted: 09/19/2006] [Indexed: 02/06/2023]
Abstract
RATIONALE Nicotine produces behavioural effects that are potentially related to its interaction with diverse nicotinic acetylcholine receptor populations. Evidence from gene deletion studies suggests that the interoceptive stimulus properties of nicotine are mediated by heteromeric high-affinity receptors containing alpha4beta2 subunits. Mice lacking beta2 subunits do not discriminate nicotine (Shoaib et al., Neuropharmacology, 42:530-539, 2002), and nicotine does not elicit dopamine release in these animals (Grady et al., J Neurochem, 76:258-268, 2001). The stimulus properties of nicotine can be detected in rats using a two-lever operant drug discrimination paradigm, allowing them to be classified pharmacologically using ligands with selectivity for receptors containing alpha4beta2, alpha3beta4 or alpha7 subunits. MATERIALS AND METHODS Rats trained to discriminate 0.4 mg/kg nicotine from vehicle were given the nicotinic receptor agonists, cytisine, varenicline, TC2559, ABT-594, A-85380 (all having high affinity but varying selectivity for alpha4beta2-containing receptors), and WO 03/062224 and WO 01/60821A1 (selective for beta4- and alpha7-containing receptors, respectively). In separate studies, WO 03/062224 was used as the training stimulus. RESULTS Nicotine, TC-2559, A-85380 and ABT-594 showed dose-dependent and complete stimulus substitution, whilst WO 03/062224 and WO 01/60821A1 were completely without effect. Cytisine and varenicline showed partial generalisation, consistent with their partial agonist activity at nicotinic receptors eliciting dopamine release in rat striatal slices. After almost 50 training sessions with WO 03/062224, there was no clear evidence that an alpha3beta4 receptor agonist could sustain a discriminable stimulus. CONCLUSION Substitution to the nicotine discriminative stimulus required high-affinity and high intrinsic activity at beta2 but not at beta4- or at alpha7-containing nicotinic receptors.
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Affiliation(s)
- Janice W Smith
- Eli Lilly & Co Ltd, Lilly Research Centre, Sunninghill Road, Windlesham, Surrey, UK.
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41
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Park KS, Cha SK, Kim MJ, Kim DR, Jeong SW, Lee JW, Kong ID. An α3β4 subunit combination acts as a major functional nicotinic acetylcholine receptor in male rat pelvic ganglion neurons. Pflugers Arch 2006; 452:775-83. [PMID: 16715294 DOI: 10.1007/s00424-006-0086-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2006] [Accepted: 03/31/2006] [Indexed: 10/24/2022]
Abstract
We identified major subunits of the nicotinic acetylcholine receptor (nAChR) involved in excitatory postsynaptic potential and intracellular Ca(2+) ([Ca(2+)]i) increase in the major pelvic ganglion (MPG) neurons of the male rat. ACh elicited fast inward currents in both sympathetic and parasympathetic MPG neurons. Mecamylamine, a selective antagonist for alpha3beta4 nAChR, potently inhibited the ACh-induced currents in sympathetic and parasympathetic neurons (IC(50); 0.53 and 0.22 microM, respectively). Furthermore, alpha-conotoxin AuIB (10 microM), a new selective antagonist for alpha3beta4 nAChR, blocked more than 80% of the ACh-induced currents in MPG neurons. Conversely, alpha-bungarotoxin, alpha-methyllycaconitine, and dihydro-beta-erythroidine, known as blockers of the alpha7 or alpha4beta2, did not show selective blocking effects on MPG neurons. ACh transiently increased [Ca(2+)]i which was subsequently abolished in the extracellular Ca(2+)-free environment. Simultaneous recording of [Ca(2+)]i and ionic currents revealed that ACh increased [Ca(2+)]i under the conditions of the voltage-clamped (at -80 mV) state, and this resulted from the influx through nAChR itself. ACh-induced [Ca(2+)]i increase was blocked by mecamylamine (10 microM), but was not affected by atropine (1 microM). RT-PCR analysis showed that, among subunits of nAChR, alpha3 and beta4 were predominantly expressed in MPG. We suggest that activation of alpha3 and beta4 nAChR subunits in MPG neurons induce fast inward currents and [Ca(2+)]i increase, possibly mediating a major role in pelvic autonomic synaptic transmission.
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MESH Headings
- Acetylcholine/antagonists & inhibitors
- Acetylcholine/pharmacology
- Animals
- Calcium/metabolism
- Calcium/physiology
- Calcium Channel Blockers
- Conotoxins/pharmacology
- Electrophysiology
- Ganglia, Parasympathetic/cytology
- Ganglia, Parasympathetic/drug effects
- Ganglia, Parasympathetic/physiology
- Ganglia, Sympathetic/cytology
- Ganglia, Sympathetic/drug effects
- Ganglia, Sympathetic/physiology
- In Vitro Techniques
- Male
- Membrane Potentials/physiology
- Neurons/drug effects
- Neurons/physiology
- Nicotinic Antagonists/pharmacology
- Patch-Clamp Techniques
- Rats
- Receptors, Nicotinic/drug effects
- Receptors, Nicotinic/genetics
- Receptors, Nicotinic/physiology
- Reverse Transcriptase Polymerase Chain Reaction
- Spectrometry, Fluorescence
- Synaptic Transmission/physiology
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Affiliation(s)
- Kyu-Sang Park
- Department of Physiology and Institute of Basic Medical Science, Yonsei University Wonju College of Medicine, Wonju, South Korea
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Salas R, Pieri F, De Biasi M. Decreased signs of nicotine withdrawal in mice null for the beta4 nicotinic acetylcholine receptor subunit. J Neurosci 2005; 24:10035-9. [PMID: 15537871 PMCID: PMC6730195 DOI: 10.1523/jneurosci.1939-04.2004] [Citation(s) in RCA: 183] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Withdrawal from chronic exposure to nicotine, the main addictive component of tobacco, produces distinctive symptoms in humans. The appearance of these symptoms is a major deterrent when people try to quit smoking. To study which type of nicotine receptor is relevant for the onset of the withdrawal syndrome, we used a mouse model of nicotine withdrawal. Wild-type mice and mice null for the beta4 (beta4-/-) or the beta2 (beta2-/-) nicotinic acetylcholine receptor subunits were implanted with osmotic minipumps delivering 24 mg x kg(-1) x d(-1) nicotine for 13 d. Subsequently, a single intraperitoneal injection of the nicotinic receptor antagonist mecamylamine induced behavioral symptoms of withdrawal measured as increased grooming, chewing, scratching, and shaking, plus the appearance of some unique behaviors such as jumping, leg tremors, and cage scratching. Mecamylamine injection triggered comparable withdrawal signs in wild-type and in beta2-/- mice, whereas the beta4-/- mice displayed significantly milder somatic symptoms. In addition, nicotine withdrawal produced hyperalgesia in wild-type but not beta4-/- mice. Finally, chronic nicotine produced an increase in epibatidine binding in several areas of the brain in both wild-type and in beta4-/- mice, but such receptor upregulation did not correlate with the severity of withdrawal signs. Our results demonstrate a major role for beta4-containing nicotinic acetylcholine receptors in the appearance of nicotine withdrawal symptoms. In contrast, the beta2 subunit does not seem to greatly influence this phenomenon. We also show that the upregulation of epibatidine binding sites attributable to chronic nicotine, an effect associated with beta2-containing receptors, is probably not related to the mechanisms underlying withdrawal.
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Affiliation(s)
- Ramiro Salas
- Division of Neuroscience, Baylor College of Medicine, Houston, Texas 77030, USA
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43
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Azam L, Dowell C, Watkins M, Stitzel JA, Olivera BM, McIntosh JM. Alpha-conotoxin BuIA, a novel peptide from Conus bullatus, distinguishes among neuronal nicotinic acetylcholine receptors. J Biol Chem 2004; 280:80-7. [PMID: 15520009 DOI: 10.1074/jbc.m406281200] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) are pentameric ligand-gated ion channels. Alpha subunits, together with beta 2 and/or beta 4 subunits, form ligand-binding sites at alpha/beta subunit interfaces. Predatory marine snails of the genus Conus are a rich source of nAChR-targeted peptides. Using conserved features of the alpha-conotoxin signal sequence and 3'-untranslated sequence region, we have cloned a novel gene from the fish-eating snail, Conus bullatus; the gene codes for a previously unreported alpha-conotoxin with unusual 4/4 spacing of amino acids in the two disulfide loops. Chemical synthesis of the predicted mature toxin was performed. The resulting peptide, alpha-conotoxin BuIA, was tested on cloned nAChRs expressed in Xenopus oocytes. The peptide potently blocks numerous rat nAChR subtypes, with highest potency for alpha 3- and chimeric alpha 6-containing nAChRs; BuIA blocks alpha 6/alpha 3 beta 2 nAChRs with a 40,000-fold lower IC(50) than alpha 4 beta 2 nAChRs. The kinetics of toxin unblock are dependent on the beta subunit. nAChRs with a beta 4 subunit have very slow off-times, compared with the corresponding beta 2 subunit-containing nAChR. In each instance, rat alpha x beta 4 may be distinguished from rat alpha x beta 2 by the large difference in time to recover from toxin block. Similar results are obtained when comparing mouse alpha 3 beta 2 to mouse alpha 3 beta 4, and human alpha 3 beta2 to human alpha 3 beta 4, indicating that the beta subunit dependence extends across species. Thus, alpha-conotoxin BuIA also represents a novel probe for distinguishing between beta 2- and beta 4-containing nAChRs.
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Affiliation(s)
- Layla Azam
- Department of Biology, University of Utah, Salt Lake City, Utah 84112, USA
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Del Signore A, Gotti C, Rizzo A, Moretti M, Paggi P. Nicotinic acetylcholine receptor subtypes in the rat sympathetic ganglion: pharmacological characterization, subcellular distribution and effect of pre- and postganglionic nerve crush. J Neuropathol Exp Neurol 2004; 63:138-50. [PMID: 14989600 DOI: 10.1093/jnen/63.2.138] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) mediate fast synaptic transmission in autonomic ganglia, which innervate and control the activity of most visceral organs. By combining ultrastructural, immunocytochemical, and pharmacological analyses, we characterized the nAChR subtypes in the rat superior cervical ganglion (SCG) and the effect of pre- and postganglionic nerve crush on their number in the ganglion and their distribution at the intraganglionic synapses. Binding with radioactive nicotinic ligands, immunoprecipitation, and immunolocalization experiments revealed the presence of different nAChR subtypes: those containing the alpha3 subunit associated with beta4 and/or beta2 subunits that bind 3H-Epibatidine with high affinity, and those containing the alpha7 subunit that bind 125I-alphaBungarotoxin. After postganglionic nerve crush, the number of nicotinic receptors and immunopositive intraganglionic synapses for each nAChR subunit strongly decreased. Both the number of nAChRs and immunoreactivity recovered 26 days after injury, when regenerating postganglionic fibers had reinnervated the peripheral target organs, as shown by the restoration of tyrosine hydroxylase immunoreactivity in the iris. This observation and the lack of any effect of preganglionic nerve crush on the number of nicotinic receptors suggest that the peripheral targets affect the organization of intraganglionic synapses in adult SCG.
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MESH Headings
- Animals
- Binding Sites
- Blotting, Western
- Bridged Bicyclo Compounds, Heterocyclic/pharmacokinetics
- Bungarotoxins/pharmacokinetics
- Cell Count
- Ganglia, Sympathetic/drug effects
- Ganglia, Sympathetic/injuries
- Ganglia, Sympathetic/metabolism
- Ganglia, Sympathetic/ultrastructure
- Humans
- Immunohistochemistry/methods
- Iodine Isotopes/pharmacokinetics
- Male
- Mice
- Microscopy, Immunoelectron
- Nerve Crush
- Nerve Regeneration/physiology
- Nicotinic Agonists/pharmacokinetics
- Protein Subunits/metabolism
- Pyridines/pharmacokinetics
- Rats
- Rats, Wistar
- Receptors, Nicotinic/classification
- Receptors, Nicotinic/metabolism
- Receptors, Nicotinic/ultrastructure
- Subcellular Fractions
- Superior Cervical Ganglion/drug effects
- Superior Cervical Ganglion/injuries
- Superior Cervical Ganglion/metabolism
- Superior Cervical Ganglion/ultrastructure
- Synapses/metabolism
- Synapses/pathology
- Synapses/ultrastructure
- Time Factors
- Tritium/pharmacokinetics
- Tyrosine 3-Monooxygenase/metabolism
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Affiliation(s)
- Arianna Del Signore
- Dipartimento di Biologia Cellulare e dello Sviluppo, Università "La Sapienza", Rome, Italy
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Abstract
Pharmacogenetics, the inherited basis for interindividual differences in drug response, has rapidly expanded with the advent of new molecular tools and the sequencing of the human genome, yielding pharmacogenomics. We review here recent ideas and findings regarding pharmacogenomics of components of the autonomic nervous system, in particular, neuronal nicotinic acetylcholine receptors, postsynaptic receptors with which the parasympathetic and sympathetic neurotransmitters, acetylcholine (ACh) and norepinephrine, respectively, interact. The receptor subtypes that mediate these responses, M(1-3) muscarinic cholinergic receptors (mAChRs), and alpha(1A,B,D)-, alpha(2A,B,C)-, and beta(1,2,3)-adrenergic receptors (AR), show highly variable expression of genetic variants; variants of mAChRs and alpha(1)-ARs are relatively rare, whereas alpha(2)-AR and beta-AR subtype variants are quite common. The largest amount of data is available regarding variants of the latter ARs and represents efforts to associate certain receptor genotypes, most commonly, single nucleotide polymorphisms, with particular phenotypes (e.g., cardiovascular and metabolic responses). In vitro and in vivo studies have yielded inconsistent results; definitive conclusions are limited. We identify several conceptual and methodological problems with available data: sample size, ethnicity, tissue differences, coding versus noncoding variants, limited studies of haplotypes, and interaction among variants. Thus, although progress has been made in identifying genetic variation that influences drug response fo autonomic nervous system components, we are still at the early stages of defining the most critical genetic determinants and their role in human physiology and pharmacology.
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Affiliation(s)
- Shelli L Kirstein
- Department of Pharmacology, University of California, San Diego, 9500 Gilman D., 0636, La Jolla, CA 92093-0636, USA
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Krivoshein AV, Hess GP. Mechanism-Based Approach to the Successful Prevention of Cocaine Inhibition of the Neuronal (α3β4) Nicotinic Acetylcholine Receptor. Biochemistry 2003; 43:481-9. [PMID: 14717603 DOI: 10.1021/bi034838l] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The nicotinic acetylcholine receptor (nAChR) belongs to a family of five channel-forming proteins that regulate communication between the approximately 10(12) cells of the nervous system. A minimum mechanism of inhibition of the muscle-type nAChR (1) by the noncompetitive inhibitors cocaine and MK-801 [(+)-dizocilpine, an anticonvulsant] indicated they bind to a regulatory site, with higher affinity for the closed-channel form than for the open-channel form, thus shifting the equilibrium toward the closed-channel form and inhibiting receptor function. The mechanism predicts that compounds that bind to this regulatory site with equal or higher affinity for the open-channel conformation than for the closed-channel conformation will prevent receptor inhibition (1). Does a neuronal form of the receptor behave similarly? The mechanism of inhibition of the neuronal nAChR by cocaine and MK-801 using rapid chemical kinetic techniques was investigated. The alpha3beta4 nAChR stably expressed in HEK 293 cells was used in these investigations. Whole-cell currents originated from a major and minor nAChR isoform. Only the major isoform has been characterized. For the dominant, rapidly desensitizing isoform, the carbamoylcholine dissociation constant for the site controlling receptor activation, Kd, is 2 mM; the channel-opening equilibrium constant, Phi(-1), is 4; and the dominant desensitization rate constant, k34, is 20 s(-1). Cocaine inhibits the receptor noncompetitively, with an apparent KI of 84 and 26 microM at high and low carbamoylcholine concentrations, at which concentrations the receptor is mainly in the open- or closed-channel form, respectively. Similar results were obtained with MK-801. A combinatorially synthesized RNA ligand and a cocaine analogue alleviated cocaine inhibition of this neuronal receptor.
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Affiliation(s)
- Arcadius V Krivoshein
- Department of Molecular Biology and Genetics, 216 Biotechnology Building, Cornell University, Ithaca, New York 14853-2703, USA
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Smulders CJGM, Bueters TJH, Van Kleef RGDM, Vijverberg HPM. Selective effects of carbamate pesticides on rat neuronal nicotinic acetylcholine receptors and rat brain acetylcholinesterase. Toxicol Appl Pharmacol 2003; 193:139-46. [PMID: 14644616 DOI: 10.1016/j.taap.2003.07.011] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Effects of commonly used carbamate pesticides on rat neuronal nicotinic acetylcholine receptors expressed in Xenopus laevis oocytes have been investigated using the two-electrode voltage clamp technique. The potencies of these effects have been compared to the potencies of the carbamates to inhibit rat brain acetylcholinesterase. The potency order of six carbamates to inhibit alpha4beta4 nicotinic receptors is fenoxycarb > EPTC > carbaryl, bendiocarb > propoxur > aldicarb with IC50 values ranging from 3 microM for fenoxycarb to 165 microM for propoxur and >1 mM for aldicarb. Conversely, the potency order of these carbamates to inhibit rat brain acetylcholinesterase is bendiocarb > propoxur, aldicarb > carbaryl > EPTC, fenoxycarb with IC50 values ranging from 1 microM for bendiocarb to 17 microM for carbaryl and > mM for EPTC and fenoxycarb. The alpha4beta2, alpha3beta4, and alpha3beta2 nicotinic acetylcholine receptors are inhibited by fenoxycarb, EPTC, and carbaryl with potency orders similar to that for alpha4beta4 receptors. Comparing the potencies of inhibition of the distinct subtypes of nicotinic acetylcholine receptors shows that the alpha3beta2 receptor is less sensitive to inhibition by fenoxycarb and EPTC. The potency of inhibition depends on the carbamate as well as on a combination of alpha and beta subunit properties. It is concluded that carbamate pesticides affect different subtypes of neuronal nicotinic receptors independently of acetylcholinesterase inhibition. This implicates that neuronal nicotinic receptors are additional targets for some carbamate pesticides and that these receptors may contribute to carbamate pesticide toxicology, especially after long-term exposure.
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Affiliation(s)
- Chantal J G M Smulders
- Institute for Risk Assessment Sciences, Utrecht University, P.O. Box 80176, NL-3508 TD Utrecht, The Netherlands
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Liu G, Iden JB, Kovithavongs K, Gulamhusein R, Duff HJ, Kavanagh KM. In vivo temporal and spatial distribution of depolarization and repolarization and the illusive murine T wave. J Physiol 2003; 555:267-79. [PMID: 14634200 PMCID: PMC1664824 DOI: 10.1113/jphysiol.2003.054064] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
This study assessed in vivo temporal and spatial electrophysiological properties of murine hearts and the effect of manipulation of transmural action potential durations (APDs) on T wave morphology. Monophasic action potentials (MAPs) were acquired from multiple left ventricular sites. All MAPs exhibited a plateau phase, with a spike and dome appearance being present in epicardial recordings. Activation occurred from endocardial apex to epicardial apex and apex to base while repolarization occurred from base (shortest 90 eta0 level of repolarization (MAP90), 95.4 +/- 8.9 ms) to apex and epicardium to endocardium (longest MAP90, 110.77 +/- 10.6 ms). The peak of phase 0 of the epicardial base MAP correlated with the return to baseline of the initial and usually dominant waveform of the QRS and the onset of the second usually smaller wave, which clearly occurred in early repolarization, thus establishing where depolarization ended and repolarization began on the murine ECG. This second waveform was similar to the J wave seen in larger animals. Despite temporal and spatial electrophysiological similarities, a T wave is frequently not seen on a murine ECG. There are several determinants of T wave morphology, including transmural activation time, slope of phase 3 repolarization and differences in epicardial, endocardial and M cell APDs. Experimental manipulation of murine transmural gradients by shortening epicardial MAP(90) to 84% of endocardial MAP90 the epicardial/endocardial ratio in larger mammals when a positive T wave is present, resulted in a positive murine T wave. Thus, manipulation of the transmural gradients such that they are similar to larger mammals can result in T waves with similar morphology.
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Affiliation(s)
- Gang Liu
- Department of Medicine, University of Alberta, Edmonton, Canada
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Tosaka T, Casimiro MC, Rong Q, Tella S, Oh M, Katchman AN, Pezzullo JC, Pfeifer K, Ebert SN. Nicotine induces a long QT phenotype in Kcnq1-deficient mouse hearts. J Pharmacol Exp Ther 2003; 306:980-7. [PMID: 12766260 DOI: 10.1124/jpet.103.053017] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We have previously shown that targeted disruption of the mouse Kcnq1 gene produces a long QT phenotype in vivo that requires extracardiac factors for manifestation (Casimiro et al., 2001). In the present study, we explore the hypothesis that autonomic neuroeffector transmission represents the "extra cardiac" stimulus that induces a long QT phenotype in mouse hearts lacking Kcnq1. Using the isolated perfused (Langendorff) mouse heart preparation, we challenged wild-type (Kcnq1+/+) and mutant (Kcnq1-/-) mouse hearts with nicotine, an autonomic stimulant. ECGs were recorded continuously, and QT intervals were compared at baseline and peak nicotine-induced heart rates. No significant differences in QT or any other ECG parameters were observed in Kcnq1+/+ versus Kcnq1-/- hearts at baseline. In the presence of nicotine, however, the JT, QT, and rate-corrected QT (QTc) intervals were significantly prolonged in Kcnq1-/- hearts relative to Kcnq1+/+ hearts (e.g., QTc = 92 +/- 11 ms versus 66 +/- 2 ms, respectively, p < 0.01). Similar findings were obtained when the hearts were challenged with either epinephrine or isoproterenol (0.1 microM each), thereby suggesting that sympathetic stimulation drives the long QT phenotype in Kcnq1-deficient hearts. This idea is supported by in vivo ECG data obtained from unrestrained conscious mice using radiotelemetry recording techniques. Again, no significant ECG differences were observed in Kcnq1-/- versus Kcnq1+/+ mice at baseline, but handling/injection stress led to significant QTc increases in Kcnq1-/- mice relative to wild-type controls (11 +/- 3 versus -1 +/- 1%, respectively, p < 0.05). These data suggest that sympathetic stimulation induces a long QT phenotype in Kcnq1-deficient mouse hearts.
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Affiliation(s)
- Toshimasa Tosaka
- Department of Pharmacology, Georgetown University Medical Center, Washington, DC 20057, USA
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50
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Gopalakrishnan M, Bitner RS. Neuronal nicotinic receptors: filling the void? Am J Physiol Regul Integr Comp Physiol 2003; 285:R21-2. [PMID: 12793987 DOI: 10.1152/ajpregu.00212.2003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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