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He F, Qiu Y, Wu X, Xia Y, Yang L, Wu C, Li P, Zhang R, Fang R, Li N, Peng Y. Slc6a13 Deficiency Attenuates Pasteurella multocida Infection-Induced Inflammation via Glycine-Inflammasome Signaling. J Innate Immun 2022; 15:107-121. [PMID: 35797984 PMCID: PMC10643921 DOI: 10.1159/000525089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Accepted: 05/07/2022] [Indexed: 11/19/2022] Open
Abstract
We have previously demonstrated that Slc6a13-deficient (Slc6a13-/-; KO) mice are resistant to P. multocida infection, which might be in connection with macrophage-mediated inflammation; however, the specific metabolic mechanism is still enigmatic. Here we reproduce the less sensitive to P. multocida infection in overall survival assays as well as reduced bacterial loads, tissue lesions, and inflammation of lungs in KO mice. The transcriptome sequencing analysis of wild-type (WT) and KO mice shows a large number of differentially expressed genes that are enriched in amino acid metabolism by functional analysis. Of note, glycine levels are substantially increased in the lungs of KO mice with or without P. multocida infection in comparison to the WT controls. Interestingly, exogenous glycine supplementation alleviates P. multocida infection-induced inflammation. Mechanistically, glycine reduces the production of inflammatory cytokines in macrophages by blocking the activation of inflammasome (NALP1, NLRP3, NLRC4, AIM2, and Caspase-1). Together, Slc6a13 deficiency attenuates P. multocida infection through lessening the excessive inflammatory responses of macrophages involving glycine-inflammasome signaling.
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Affiliation(s)
- Fang He
- College of Veterinary Medicine, Southwest University, Chongqing, China
- College of Animal Science, South China Agricultural University, Guangzhou, China
| | - Yangyang Qiu
- College of Veterinary Medicine, Southwest University, Chongqing, China
| | - Xiaoyan Wu
- College of Animal Science, South China Agricultural University, Guangzhou, China
| | - Yaoyao Xia
- College of Animal Science, South China Agricultural University, Guangzhou, China
| | - Liu Yang
- College of Veterinary Medicine, Southwest University, Chongqing, China
| | - Chenlu Wu
- College of Veterinary Medicine, Southwest University, Chongqing, China
| | - Pan Li
- College of Veterinary Medicine, Southwest University, Chongqing, China
| | - Rui Zhang
- College of Veterinary Medicine, Southwest University, Chongqing, China
| | - Rendong Fang
- College of Veterinary Medicine, Southwest University, Chongqing, China
| | - Nengzhang Li
- College of Veterinary Medicine, Southwest University, Chongqing, China
| | - Yuanyi Peng
- College of Veterinary Medicine, Southwest University, Chongqing, China
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Breitinger U, Sticht H, Breitinger HG. Modulation of recombinant human alpha 1 glycine receptor by flavonoids and gingerols. Biol Chem 2021; 402:825-838. [PMID: 33752269 DOI: 10.1515/hsz-2020-0360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Accepted: 03/09/2021] [Indexed: 11/15/2022]
Abstract
The inhibitory glycine receptor (GlyR) is a principal mediator of fast synaptic inhibition in mammalian spinal cord, brainstem, and higher brain centres. Flavonoids are secondary plant metabolites that exhibit many beneficial physiological effects, including modulatory action on neuronal receptors. Using whole-cell current recordings from recombinant human α1 GlyRs, expressed in HEK293 cells, we compared the flavonols kaempferol and quercetin, the flavanone naringenin, the flavones apigenin and nobiletin, the isoflavone genistein, and two gingerols, 6-gingerol and 8-gingerol for their modulation of receptor currents. All compounds were inhibitors of the GlyR with IC50 values ranging between 9.3 ± 2.6 µM (kaempferol) and 46.7 ± 6.5 µM (genistein), following a mixed mode of inhibition. Co-application of two inhibitors revealed distinct binding sites for flavonoids and gingerols. Pore-lining mutants T258A and T258S were strongly inhibited by quercetin and naringenin, but not by 6-gingerol, confirming the existence of distinct binding sites for flavonoids and gingerols. Apigenin, kaempferol, nobiletin, naringenin and 6-gingerol showed biphasic action, potentiating glycine-induced currents at low concentration of both, modulator and glycine, and inhibiting at higher concentrations. Identification of distinct modulatory sites for flavonoids and related compounds may present pharmacological target sites and aid the discovery of novel glycinergic drugs.
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Affiliation(s)
- Ulrike Breitinger
- Department of Biochemistry, The German University in Cairo, Main Entrance of Al Tagamoa Al Khames, New Cairo11835, Egypt
| | - Heinrich Sticht
- Bioinformatics, Institute of Biochemistry, Friedrich-Alexander-Universität Erlangen-Nümberg, Fahrstrasse 17, D-91054Erlangen, Germany
| | - Hans-Georg Breitinger
- Department of Biochemistry, The German University in Cairo, Main Entrance of Al Tagamoa Al Khames, New Cairo11835, Egypt
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Abstract
The inhibitory glycine receptor is a member of the Cys-loop superfamily of ligand-gated ion channels. It is the principal mediator of rapid synaptic inhibition in the spinal cord and brainstem and plays an important role in the modulation of higher brain functions including vision, hearing, and pain signaling. Glycine receptor function is controlled by only a few agonists, while the number of antagonists and positive or biphasic modulators is steadily increasing. These modulators are important for the study of receptor activation and regulation and have found clinical interest as potential analgesics and anticonvulsants. High-resolution structures of the receptor have become available recently, adding to our understanding of structure-function relationships and revealing agonistic, inhibitory, and modulatory sites on the receptor protein. This Review presents an overview of compounds that activate, inhibit, or modulate glycine receptor function in vitro and in vivo.
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Affiliation(s)
- Ulrike Breitinger
- Department of Biochemistry, German University in Cairo, New Cairo 11835, Egypt
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Kirson D, Oleata CS, Roberto M. Taurine Suppression of Central Amygdala GABAergic Inhibitory Signaling via Glycine Receptors Is Disrupted in Alcohol Dependence. Alcohol Clin Exp Res 2019; 44:445-454. [PMID: 31782155 DOI: 10.1111/acer.14252] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Accepted: 11/18/2019] [Indexed: 11/28/2022]
Abstract
BACKGROUND Alcohol use disorder (AUD) increases brain stress systems while suppressing reward system functioning. One expression of stress system recruitment is elevated GABAergic activity in the central amygdala (CeA), which is involved in the excessive drinking seen with AUD. The sulfonic amino acid taurine, a glycine receptor partial agonist, modulates GABAergic activity in the rewarding effects of alcohol. Despite taurine abundance in the amygdala, its role in the dysregulation of GABAergic activity associated with AUD has not been studied. Thus, here, we evaluated the effects of taurine on locally stimulated GABAergic neurotransmission in the CeA of naïve- and alcohol-dependent rats. METHODS We recorded intracellularly from CeA neurons of naïve- and alcohol-dependent rats, quantifying locally evoked GABAA receptor-mediated inhibitory postsynaptic potentials (eIPSP). We examined the effects of taurine and alcohol on CeA eIPSP to characterize potential alcohol dependence-induced changes in the effects of taurine. RESULTS We found that taurine decreased amplitudes of eIPSP in CeA neurons of naïve rats, without affecting the acute alcohol-induced facilitation of GABAergic responses. In CeA neurons from dependent rats, taurine no longer had an effect on eIPSP, but now blocked the ethanol (EtOH)-induced increase in eIPSP amplitude normally seen. Additionally, preapplication of the glycine receptor-specific antagonist strychnine blocked the EtOH-induced increase in eIPSP amplitude in neurons from naïve rats. CONCLUSIONS These data suggest taurine may act to oppose the effects of acute alcohol via the glycine receptor in the CeA of naïve rats, and this modulatory system is altered in the CeA of dependent rats.
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Affiliation(s)
- Dean Kirson
- Department of Molecular Medicine, and Alcohol Research Center, The Scripps Research Institute, La Jolla, California
| | - Christopher S Oleata
- Department of Molecular Medicine, and Alcohol Research Center, The Scripps Research Institute, La Jolla, California
| | - Marisa Roberto
- Department of Molecular Medicine, and Alcohol Research Center, The Scripps Research Institute, La Jolla, California
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Kirson D, Todorovic J, Mihic SJ. Single Channel Analysis of Isoflurane and Ethanol Enhancement of Taurine-Activated Glycine Receptors. J Pharmacol Exp Ther 2017; 364:70-76. [PMID: 29118035 DOI: 10.1124/jpet.117.243840] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2017] [Accepted: 10/26/2017] [Indexed: 02/05/2023] Open
Abstract
The amino acid taurine is an endogenous ligand acting on glycine receptors (GlyRs), which is released by astrocytes in many brain regions, such as the nucleus accumbens and prefrontal cortex. Taurine is a partial agonist with an efficacy significantly lower than that of glycine. Allosteric modulators such as ethanol and isoflurane produce leftward shifts of glycine concentration-response curves but have no effects at saturating glycine concentrations. In contrast, in whole-cell electrophysiology studies these modulators increase the effects of saturating taurine concentrations. A number of possible mechanisms may explain these enhancing effects, including modulator effects on conductance, channel open times, or channel closed times. We used outside-out patch-clamp single channel electrophysiology to investigate the mechanism of action of 200 mM ethanol and 0.55 mM isoflurane in enhancing the effects of a saturating concentration of taurine. Neither modulator enhanced taurine-mediated conductance. Isoflurane increased the probability of channel opening. Isoflurane also increased the lifetimes of the two shortest open dwell times while both agents decreased the likelihood of occurrence of the longest-lived intracluster channel-closing events. The mechanism of enhancement of GlyR functioning by these modulators is dependent on the efficacy of the agonist activating the receptor and the concentration of agonist tested.
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Affiliation(s)
- Dean Kirson
- Department of Neuroscience, Division of Pharmacology and Toxicology, Waggoner Center for Alcohol & Addiction Research, Institutes for Neuroscience and Cell & Molecular Biology, University of Texas at Austin, Austin, Texas
| | - Jelena Todorovic
- Department of Neuroscience, Division of Pharmacology and Toxicology, Waggoner Center for Alcohol & Addiction Research, Institutes for Neuroscience and Cell & Molecular Biology, University of Texas at Austin, Austin, Texas
| | - S John Mihic
- Department of Neuroscience, Division of Pharmacology and Toxicology, Waggoner Center for Alcohol & Addiction Research, Institutes for Neuroscience and Cell & Molecular Biology, University of Texas at Austin, Austin, Texas
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Söderpalm B, Lidö HH, Ericson M. The Glycine Receptor-A Functionally Important Primary Brain Target of Ethanol. Alcohol Clin Exp Res 2017; 41:1816-1830. [PMID: 28833225 DOI: 10.1111/acer.13483] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2017] [Accepted: 08/15/2017] [Indexed: 12/27/2022]
Abstract
Identification of ethanol's (EtOH) primary molecular brain targets and determination of their functional role is an ongoing, important quest. Pentameric ligand-gated ion channels, that is, the nicotinic acetylcholine receptor, the γ-aminobutyric acid type A receptor, the 5-hydroxytryptamine3 , and the glycine receptor (GlyR), are such targets. Here, aspects of the structure and function of these receptors and EtOH's interaction with them are briefly reviewed, with special emphasis on the GlyR and the importance of this receptor and its ligands for EtOH pharmacology. It is suggested that GlyRs are involved in (i) the dopamine-activating effect of EtOH, (ii) regulating EtOH intake, and (iii) the relapse preventing effect of acamprosate. Exploration of the GlyR subtypes involved and efforts to develop subtype specific agonists or antagonists may offer new pharmacotherapies for alcohol use disorders.
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Affiliation(s)
- Bo Söderpalm
- Addiction Biology Unit, Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, the Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Helga H Lidö
- Addiction Biology Unit, Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, the Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Mia Ericson
- Addiction Biology Unit, Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, the Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
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Allosteric modulation of the glycine receptor activated by agonists differing in efficacy. Brain Res 2015; 1606:95-101. [PMID: 25721789 DOI: 10.1016/j.brainres.2015.02.024] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Revised: 02/12/2015] [Accepted: 02/13/2015] [Indexed: 01/29/2023]
Abstract
The glycine receptor (GlyR) is the predominant inhibitory neurotransmitter receptor in the brainstem and spinal cord but is also found in higher brain regions. GlyR function is affected by a variety of allosteric modulators including drugs of abuse, such as ethanol and inhalants and the ubiquitous divalent cation zinc. Two-electrode voltage-clamp experiments were conducted on Xenopus laevis oocytes expressing wild-type α1 homomeric glycine receptors to compare the degree of enhancement produced by zinc on GlyR activated by two agonists (glycine vs. taurine) that vary markedly in their efficacies. Zinc potentiation of both glycine- and taurine-evoked currents was the same at the concentrations of agonists that produced the same currents, corresponding to 6% of the maximal effect of glycine compared to 23% of the maximal effect of taurine. Similar results were seen with 50 and 200 mM ethanol. A direct comparison of agonist concentration-response curves showed that zinc enhancement was greater, overall, for taurine-activated than glycine-activated receptors. In addition, zinc only enhanced taurine- but not glycine-activated GlyR when agonists were applied at saturating concentrations. These data suggest that zinc affects taurine affinity, as well as the probability of channel opening at sub-maximal taurine concentrations, and that the magnitude of allosteric modulation at the GlyR depends on the efficacy of the agonist tested. This has implications for mutagenesis studies in which changes in the degree of allosteric modulation observed may result from mutation-induced changes in agonist efficacy.
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Morud J, Adermark L, Ericson M, Söderpalm B. Alterations in ethanol-induced accumbal transmission after acute and long-term zinc depletion. Addict Biol 2015; 20:170-81. [PMID: 24102995 DOI: 10.1111/adb.12096] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Alcoholism is subject to extensive research, but the role of changes in metabolism caused by alcohol consumption has been poorly investigated. Zinc (Zn(2+) ) deficiency is a common metabolic aberration among alcoholics and Zn(2+) influences the function of ligand-gated ion channels, known pharmacological targets of ethanol (EtOH). Here, we investigate whether manipulation of extracellular levels of Zn(2+) modulates EtOH-induced increases of dopamine (DA) output, as measured by in vivo microdialysis in the rat, and whether voluntary EtOH consumption is altered by Zn(2+) deficiency. Our findings show that the Zn(2+) -chelating agent tricine slowly raises DA levels when perfused in the nucleus accumbens (nAc), whereas the more potent Zn(2+) chelator TPEN reduces DA levels. We also show that pre-treatment with either tricine or TPEN blocks the EtOH-induced DA elevation. Chronic Zn(2+) deficiency induced by a Zn(2+) -free diet did not affect EtOH consumption, but excitatory transmission, assessed by striatal field-potential recordings in the nAc shell, was significantly modulated both by Zn(2+) -free diet and by EtOH consumption, as compared with the EtOH naïve controls. The present study indicates that Zn(2+) influences EtOH's interaction with the brain reward system, possibly by interfering with glycine receptor and GABAA receptor function. This also implies that Zn(2+) deficiency among alcoholics may be important to correct in order to normalize important aspects of brain function.
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Affiliation(s)
- Julia Morud
- Addiction Biology Unit; Department of Psychiatry and Neurochemistry; Institute of Neuroscience and Physiology; The Sahlgrenska Academy at University of Gothenburg; Sweden
| | - Louise Adermark
- Addiction Biology Unit; Department of Psychiatry and Neurochemistry; Institute of Neuroscience and Physiology; The Sahlgrenska Academy at University of Gothenburg; Sweden
| | - Mia Ericson
- Addiction Biology Unit; Department of Psychiatry and Neurochemistry; Institute of Neuroscience and Physiology; The Sahlgrenska Academy at University of Gothenburg; Sweden
| | - Bo Söderpalm
- Addiction Biology Unit; Department of Psychiatry and Neurochemistry; Institute of Neuroscience and Physiology; The Sahlgrenska Academy at University of Gothenburg; Sweden
- Beroendekliniken; Sahlgrenska University Hospital; Sweden
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Bell RL, Franklin KM, Hauser SR, Zhou FC. Introduction to the special issue "Pharmacotherapies for the treatment of alcohol abuse and dependence" and a summary of patents targeting other neurotransmitter systems. RECENT PATENTS ON CNS DRUG DISCOVERY 2012; 7:93-112. [PMID: 22574678 PMCID: PMC3868366 DOI: 10.2174/157488912800673155] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Revised: 03/02/2012] [Accepted: 03/13/2012] [Indexed: 12/19/2022]
Abstract
This paper introduces the Special Section: Pharmacotherapies for the Treatment of Alcohol Abuse and Dependence and provides a summary of patents targeting neurotransmitter systems not covered in the other four chapters. The World Health Organization notes that alcoholic-type drinking results in 2.5 million deaths per year, and these deaths occur to a disproportionately greater extent among adolescents and young adults. Developing a pharmacological treatment targeting alcohol abuse and dependence is complicated by (a) the heterogeneous nature of the disease(s), (b) alcohol affecting multiple neurotransmitter and neuromodulator systems, and (c) alcohol affecting multiple organ systems which in turn influence the function of the central nervous system. Presently, the USA Federal Drug Administration has approved three pharmacotherapies for alcoholism: disulfiram, naltrexone, and acamprosate. This chapter provides a summary of the following systems, which are not covered in the accompanying chapters; alcohol and acetaldehyde metabolism, opioid, glycinergic, GABA-A, neurosteroid, dopaminergic, serotonergic, and endocannabinoid, as well as patents targeting these systems for the treatment of alcoholism. Finally, an overview is presented on the use of pharmacogenetics and pharmacogenomics in tailoring treatments for certain subpopulations of alcoholics, which is expected to continue in the future.
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Affiliation(s)
- Richard L. Bell
- Indiana University School of Medicine, Department of Psychiatry, Institute of Psychiatric Research, 791 Union Drive, Indianapolis, Indiana, 46202, USA
| | - Kelle M. Franklin
- Indiana University School of Medicine, Department of Psychiatry, Institute of Psychiatric Research, 791 Union Drive, Indianapolis, Indiana, 46202, USA
| | - Sheketha R. Hauser
- Indiana University School of Medicine, Department of Psychiatry, Institute of Psychiatric Research, 791 Union Drive, Indianapolis, Indiana, 46202, USA
| | - Feng C. Zhou
- Indiana University School of Medicine, Department of Anatomy and Cell Biology, 635 Barnhill Drive MS-508, Indian-apolis, Indiana, 46202, USA
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Tipps ME, Iyer SV, John Mihic S. Trifluoroacetate is an allosteric modulator with selective actions at the glycine receptor. Neuropharmacology 2012; 63:368-73. [PMID: 22548713 DOI: 10.1016/j.neuropharm.2012.04.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2011] [Revised: 03/20/2012] [Accepted: 04/04/2012] [Indexed: 11/30/2022]
Abstract
Trifluoroacetic acid is a metabolite of the inhaled anesthetics halothane, desflurane and isoflurane as well as a major contaminant in HPLC-purified peptides. Ligand-gated ion channels, including cys-loop receptors such as the glycine receptor, have been the targets of peptide-based drug design and are considered to be likely candidates for mediating the effects of anesthetics in vivo, but the possible secondary contributions of contaminants and metabolites to these effects have not been studied. We used two-electrode voltage-clamp electrophysiology to test glycine, GABA(A) and 5-HT3 receptors expressed in Xenopus oocytes for their sensitivities to sodium trifluoroacetate. Trifluoroacetate (100 μM-3mM) enhanced the currents elicited by low concentrations of glycine applied to α1 homomeric and α1β heteromeric glycine receptors, but it had no effects when co-applied with a maximally-effective glycine concentration. Trifluoroacetate had no effects on α1β2γ2S GABA(A) or 5-HT3A receptors at any GABA or serotonin concentration tested. The results demonstrate that trifluoroacetate acts as an allosteric modulator at the glycine receptor with greater specificity than other known modulators. These results have important implications for both the secondary effects of volatile anesthetics and the presence of contaminating trifluoroacetate in HPLC-purified peptides, which is potentially an important source of experimental variability or error that requires control.
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Affiliation(s)
- Megan E Tipps
- Division of Pharmacology and Toxicology, Waggoner Center for Alcohol & Addiction Research, Institutes for Neuroscience and Cell & Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA
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Kirson D, Todorovic J, Mihic SJ. Positive allosteric modulators differentially affect full versus partial agonist activation of the glycine receptor. J Pharmacol Exp Ther 2012; 342:61-70. [PMID: 22473615 DOI: 10.1124/jpet.112.191486] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Taurine acts as a partial agonist at the glycine receptor (GlyR) in some brain regions such as the hippocampus, striatum, and nucleus accumbens. Ethanol, volatile anesthetics, and inhaled drugs of abuse are all known positive allosteric modulators of GlyRs, but their effects on taurine-activated GlyRs remain poorly understood, especially their effects on the high concentrations of taurine likely to be found after synaptic release. Two-electrode voltage-clamp electrophysiology in Xenopus laevis oocytes was used to compare the enhancing effects of ethanol, anesthetics, and inhalants on human homomeric α1-GlyR activated by saturating concentrations of glycine versus taurine. Allosteric modulators had negligible effects on glycine-activated GlyR while potentiating taurine-activated currents. In addition, inhaled anesthetics markedly enhanced desensitization rates of taurine- but not glycine-activated receptors. Our findings suggest that ethanol, volatile anesthetics, and inhalants differentially affect the time courses of synaptic events at GlyR, depending on whether the receptor is activated by a full or partial agonist.
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Affiliation(s)
- Dean Kirson
- Waggoner Center for Alcohol and Addiction Research, and Institute for Neuroscience, University of Texas at Austin, Austin, Texas, USA
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Huang KH, Chang CC, Ho JD, Lu RH, Tsai LH. Role of taurine on acid secretion in the rat stomach. J Biomed Sci 2011; 18:11. [PMID: 21294907 PMCID: PMC3042912 DOI: 10.1186/1423-0127-18-11] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Accepted: 02/05/2011] [Indexed: 11/10/2022] Open
Abstract
Background Taurine has chemical structure similar to an inhibitory neurotransmitter, γ-aminobutyric acid (GABA). Previous studies on GABA in the stomach suggest GABAergic neuron is involved in acid secretion, but the effects of taurine are poor understood. Methods The effects of taurine on acid secretion, signal transduction, and localization of taurinergic neurons were determined in the rat stomach using everted whole stomach, RIA kit and immunohistochemical methods. Results We used antibodies against taurine-synthesizing enzyme, cysteine sulfuric acid decarboxylase (CSAD), and taurine. CSAD- and taurine-positive cells were found in the muscle and mucosal layers. Distributions of CSAD- and taurine-positive cells in both mucosal and muscle layers were heterogeneous in the stomach. Taurine at 10-9~10-4 M induced acid secretion, and the maximum secretion was at 10-5 M, 1.6-fold higher than the spontaneous secretion. Taurine-induced acid secretion was completely inhibited by bicuculline and atropine but not by cimetidine, proglumide, or strychnine. Atropine and tetrodotoxin (TTX) completely inhibited the acid secretion induced by low concentrations of taurine and partially inhibited induced by high concentrations. Verapamil, a calcium blocker agent, inhibited acid output elicited by taurine. We assumed all Ca2+ channels involved in the response to these secretagogues were equally affected by verapamil. Intracellular cAMP (adenosine 3', 5'-monophosphat) in the stomach significantly increased with taurine treatment in a dose-dependent manner. High correlation (r=0.859, p < 0.001) of taurine concentrations with cAMP was observed. Conclusions Our results demonstrated for the first time in taurine-induced acid secretion due to increase intracellular calcium may act through the A type of GABA receptors, which are mainly located on cholinergic neurons though cAMP pathway and partially on nonneuronal cells in the rat stomach.
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Affiliation(s)
- Kai-Han Huang
- Department of Ophthalmology, Taipei Medical University Hospital, Taipei Taiwan
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Lee MR, Hinton DJ, Wu J, Mishra PK, Port JD, Macura SI, Choi DS. Acamprosate reduces ethanol drinking behaviors and alters the metabolite profile in mice lacking ENT1. Neurosci Lett 2010; 490:90-5. [PMID: 21172405 DOI: 10.1016/j.neulet.2010.12.033] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2010] [Revised: 12/10/2010] [Accepted: 12/12/2010] [Indexed: 10/18/2022]
Abstract
Acamprosate is clinically used to treat alcoholism. However, the precise molecular functionality of acamprosate in the central nervous system remains unclear, although it is known to antagonize glutamate action in the brain. Since elevated glutamate signaling, especially in the nucleus accumbens (NAc), is implicated in several aspects of alcoholism, we utilized mice lacking type 1 equilibrative nucleoside transporter (ENT1), which exhibit increased glutamate levels in the NAc as well as increased ethanol drinking behaviors. We found that acamprosate significantly reduced ethanol drinking of mice lacking ENT1 (ENT1(-/-)) while having no such effect in wild-type littermates. We then analyzed the basal and acamprosate-treated accumbal metabolite profiles of ENT1(-/-) and wild-type mice using in vivo 16.4T proton magnetic resonance spectroscopy (MRS). Our data show that basal glutamate+glutamine (Glx), glutamate, glutamine and N-acetylaspartatic acid (NAA) levels are increased in the nucleus accumbens (NAc) of ENT1(-/-) compared to wild-type mice. We then found that acamprosate treatment significantly reduced Glx and glutamine levels while increasing taurine levels in the NAc of only ENT1(-/-) compared to their saline-treated group while normalizing other metabolite compared to wild-type mice. This study will be useful in the understanding of the molecular basis of acamprosate in the brain.
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Affiliation(s)
- Moonnoh R Lee
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
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