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Nascimento AA, Pereira-Figueiredo D, Borges-Martins VP, Kubrusly RC, Calaza KC. GABAergic system and chloride cotransporters as potential therapeutic targets to mitigate cell death in ischemia. J Neurosci Res 2024; 102:e25355. [PMID: 38808645 DOI: 10.1002/jnr.25355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Revised: 04/17/2024] [Accepted: 05/06/2024] [Indexed: 05/30/2024]
Abstract
Gamma aminobutyric acid (GABA) is a critical inhibitory neurotransmitter in the central nervous system that plays a vital role in modulating neuronal excitability. Dysregulation of GABAergic signaling, particularly involving the cotransporters NKCC1 and KCC2, has been implicated in various pathologies, including epilepsy, schizophrenia, autism spectrum disorder, Down syndrome, and ischemia. NKCC1 facilitates chloride influx, whereas KCC2 mediates chloride efflux via potassium gradient. Altered expression and function of these cotransporters have been associated with excitotoxicity, inflammation, and cellular death in ischemic events characterized by reduced cerebral blood flow, leading to compromised tissue metabolism and subsequent cell death. NKCC1 inhibition has emerged as a potential therapeutic approach to attenuate intracellular chloride accumulation and mitigate neuronal damage during ischemic events. Similarly, targeting KCC2, which regulates chloride efflux, holds promise for improving outcomes and reducing neuronal damage under ischemic conditions. This review emphasizes the critical roles of GABA, NKCC1, and KCC2 in ischemic pathologies and their potential as therapeutic targets. Inhibiting or modulating the activity of these cotransporters represents a promising strategy for reducing neuronal damage, preventing excitotoxicity, and improving neurological outcomes following ischemic events. Furthermore, exploring the interactions between natural compounds and NKCC1/KCC2 provides additional avenues for potential therapeutic interventions for ischemic injury.
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Affiliation(s)
- A A Nascimento
- Neurobiology of the Retina Laboratory, Department of Neurobiology and Graduate Program of Neurosciences, Institute of Biology, Fluminense Federal University, Niterói, Brazil
| | - D Pereira-Figueiredo
- Graduate Program in Biomedical Sciences (Physiology and Pharmacology), Fluminense Federal University, Niterói, Brazil
| | - V P Borges-Martins
- Laboratory of Neuropharmacology, Department of Physiology and Pharmacology, Biomedical Institute, Fluminense Federal University, Niterói, Brazil
| | - R C Kubrusly
- Laboratory of Neuropharmacology, Department of Physiology and Pharmacology, Biomedical Institute, Fluminense Federal University, Niterói, Brazil
| | - K C Calaza
- Neurobiology of the Retina Laboratory, Department of Neurobiology and Graduate Program of Neurosciences, Institute of Biology, Fluminense Federal University, Niterói, Brazil
- Graduate Program in Biomedical Sciences (Physiology and Pharmacology), Fluminense Federal University, Niterói, Brazil
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2
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Chu MC, Mao WC, Wu HF, Chang YC, Lu TI, Lee CW, Chung YJ, Hsieh TH, Chang HS, Chen YF, Lin CH, Tang CW, Lin HC. Transient plasticity response is regulated by histone deacetylase inhibitor in oxygen-glucose deprivation condition. Pharmacol Rep 2023; 75:1200-1210. [PMID: 37695500 DOI: 10.1007/s43440-023-00525-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 08/25/2023] [Accepted: 08/25/2023] [Indexed: 09/12/2023]
Abstract
BACKGROUND The pathological form of synaptic plasticity, ischemic long-term potentiation (iLTP), induced by oxygen and glucose deprivation (OGD), is implicated in the acute phase of stroke with the potentiation of N-methyl-D-aspartate receptor (NMDAR). While there has been widespread attention on the excitatory system, a recent study reported that γ-aminobutyric acid (GABA)ergic system is also involved in iLTP. Valproic acid (VPA), a histone deacetylase inhibitor, protects against ischemic damage. However, whether VPA regulates early phase plasticity in ischemic stroke remains unknown. The present study aims to investigate the potential role and mechanism of VPA in ischemic stroke. METHODS A brief exposure of OGD on the hippocampal slices and the induction of photothrombotic ischemia (PTI) were used as ex vivo and in vivo models of ischemic stroke, respectively. RESULTS Using extracellular recordings, iLTP was induced in the hippocampal Schaffer collateral pathway following OGD exposure. VPA treatment abolished hippocampal iLTP via GABAA receptor enhancement and extracellular signal-regulated kinase (ERK) phosphorylation. Administration of VPA reduced brain infarct volume and motor dysfunction in mice with PTI. Moreover, VPA protected against ischemic injury by upregulating the GABAergic system and ERK phosphorylation, as well as by reducing of matrix metalloproteinase in a PTI-induced ischemic stroke model. CONCLUSIONS Together, this study revealed the protection of VPA in ex vivo OGD-induced pathological form of neuroplasticity and in vivo PTI-induced brain damage and motor dysfunction through rescuing GABAergic deficiency and the pathological hallmarks of ischemia.
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Affiliation(s)
- Ming-Chia Chu
- Department and Institute of Physiology, College of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Wei-Chang Mao
- Department of Psychiatry, Cheng-Hsin General Hospital, Taipei, Taiwan
| | - Han-Fang Wu
- Department of Optometry, MacKay Medical College, New Taipei City, Taiwan
| | - Yun-Chi Chang
- Department and Institute of Physiology, College of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Ting-I Lu
- Department and Institute of Physiology, College of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Chi-Wei Lee
- Department and Institute of Physiology, College of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Yueh-Jung Chung
- Department and Institute of Physiology, College of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Tsung-Han Hsieh
- Department and Institute of Physiology, College of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Hsun-Shuo Chang
- School of Pharmacy, College of Pharmacy, Kaoshiung Medical University, Kaoshiung, Taiwan
| | - Yih-Fung Chen
- School of Pharmacy, College of Pharmacy, Kaoshiung Medical University, Kaoshiung, Taiwan
- Graduate Institute of Natural Products, College of Pharmacy, Kaoshiung Medical University, Kaoshiung, Taiwan
| | - Chia-Hsien Lin
- Department of Health Industry Management, Kainan University, Taoyuan, Taiwan
| | - Chih-Wei Tang
- Department of Neurology, Far Eastern Memorial Hospital, New Taipei City, Taiwan.
| | - Hui-Ching Lin
- Department and Institute of Physiology, College of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan.
- Brain Research Center, National Yang Ming Chiao Tung University, Taipei, Taiwan.
- Ph.D. Program in Medical Neuroscience, College of Medical Science and Technology, Taipei Medical University and National Health Research Institute, Taipei, Taiwan.
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3
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Depressive-like behaviors induced by chronic cerebral hypoperfusion associate with a dynamic change of GABA B1/B2 receptors expression in hippocampal CA1 region. Physiol Behav 2022; 254:113887. [PMID: 35724927 DOI: 10.1016/j.physbeh.2022.113887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 05/07/2022] [Accepted: 06/16/2022] [Indexed: 11/21/2022]
Abstract
Cerebral ischemia could induce depressive-like behaviors; however, the alteration of gamma-aminobutyric acid receptors type B (GABAB) receptors in these pathological processes has not been extensively investigated. The aim of the current study was to document the behavioral change and the alteration of GABAB receptors in chronic cerebral hypoperfusion. The permanent occlusion of the bilateral common carotid arteries (two-vessel occlusion, 2VO) was performed to induce chronic cerebral ischemia (CCH). The depressive-like behaviors were evaluated with sucrose preference test, novelty suppress feeding test as well as forced swim test at 4, 8, and 12 weeks after the 2VO surgery. The total, surface and intracellular expressions of GABAB subunit 1 (GABAB1) and subunit 2 (GABAB2) in hippocampal CA1 were quantified by western blot. The depressive-like behaviors were observed in rats suffered from 4, 8, and 12 weeks 2VO in sucrose preference test, novelty suppress feeding test and forced swim test. In addition, the surface and total expression of GABAB1 in CA1 was reduced at 4 weeks after 2VO rather than 8 or 12 weeks. While the surface and total expression of GABAB2 in CA1 was decreased throughout the ischemia timeline (4, 8, and 12 weeks). Taken together, our findings suggested the potential roles of GABAB1 and GABAB2 subunits involved in depressive-like behaviors caused by chronic cerebral hypoperfusion.
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Bhat MA, Esmaeili A, Neumann E, Balakrishnan K, Benke D. Targeting the Interaction of GABA B Receptors With CHOP After an Ischemic Insult Restores Receptor Expression and Inhibits Progressive Neuronal Death. Front Pharmacol 2022; 13:870861. [PMID: 35422706 PMCID: PMC9002115 DOI: 10.3389/fphar.2022.870861] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 03/14/2022] [Indexed: 01/01/2023] Open
Abstract
GABAB receptors control neuronal excitability via slow and prolonged inhibition in the central nervous system. One important function of GABAB receptors under physiological condition is to prevent neurons from shifting into an overexcitation state which can lead to excitotoxic death. However, under ischemic conditions, GABAB receptors are downregulated, fostering over-excitation and excitotoxicity. One mechanism downregulating GABAB receptors is mediated via the interaction with the endoplasmic reticulum (ER) stress-induced transcription factor CHOP. In this study, we investigated the hypothesis that preventing the interaction of CHOP with GABAB receptors after an ischemic insult restores normal expression of GABAB receptors and reduces neuronal death. For this, we designed an interfering peptide (R2-Pep) that restored the CHOP-induced downregulation of cell surface GABAB receptors in cultured cortical neurons subjected to oxygen and glucose deprivation (OGD). Administration of R2-Pep after OGD restored normal cell surface expression of GABAB receptors as well as GABAB receptor-mediated inhibition. As a result, R2-Pep reduced enhanced neuronal activity and inhibited progressive neuronal death in OGD stressed cultures. Thus, targeting diseases relevant protein-protein interactions might be a promising strategy for developing highly specific novel therapeutics.
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Affiliation(s)
- Musadiq A Bhat
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
| | - Abolghasem Esmaeili
- Department of Cell and Molecular Biology & Microbiology, Faculty of Biological Science and Technology, University of Isfahan, Isfahan, Iran
| | - Elena Neumann
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
| | - Karthik Balakrishnan
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
| | - Dietmar Benke
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland.,Neuroscience Center Zurich, University of Zurich and ETH Zurich, Zurich, Switzerland.,Drug Discovery Network Zurich (DDNZ), Zurich, Switzerland
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5
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Hleihil M, Vaas M, Bhat MA, Balakrishnan K, Benke D. Sustained Baclofen-Induced Activation of GABA B Receptors After Cerebral Ischemia Restores Receptor Expression and Function and Limits Progressing Loss of Neurons. Front Mol Neurosci 2021; 14:726133. [PMID: 34539344 PMCID: PMC8440977 DOI: 10.3389/fnmol.2021.726133] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 08/12/2021] [Indexed: 11/13/2022] Open
Abstract
One important function of GABAB receptors is the control of neuronal activity to prevent overexcitation and thereby excitotoxic death, which is a hallmark of cerebral ischemia. Consequently, sustained activation of GABAB receptors with the selective agonist baclofen provides neuroprotection in in vitro and in vivo models of cerebral ischemia. However, excitotoxic conditions severely downregulate the receptors, which would compromise the neuroprotective effectiveness of baclofen. On the other hand, recent work suggests that sustained activation of GABAB receptors stabilizes receptor expression. Therefore, we addressed the question whether sustained activation of GABAB receptors reduces downregulation of the receptor under excitotoxic conditions and thereby preserves GABAB receptor-mediated inhibition. In cultured neurons subjected to oxygen and glucose deprivation (OGD), to mimic cerebral ischemia, GABAB receptors were severely downregulated. Treatment of the cultures with baclofen after OGD restored GABAB receptor expression and reduced loss of neurons. Restoration of GABAB receptors was due to enhanced fast recycling of the receptors, which reduced OGD-induced sorting of the receptors to lysosomal degradation. Utilizing the middle cerebral artery occlusion (MCAO) mouse model of cerebral ischemia, we verified the severe downregulation of GABAB receptors in the affected cortex and a partial restoration of the receptors after systemic injection of baclofen. Restored receptor expression recovered GABAB receptor-mediated currents, normalized the enhanced neuronal excitability observed after MCAO and limited progressive loss of neurons. These results suggest that baclofen-induced restoration of GABAB receptors provides the basis for the neuroprotective activity of baclofen after an ischemic insult. Since GABAB receptors regulate multiple beneficial pathways, they are promising targets for a neuroprotective strategy in acute cerebral ischemia.
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Affiliation(s)
- Mohammad Hleihil
- Institute of Pharmacology and Toxicology, University Zurich, Zurich, Switzerland.,Neuroscience Center Zurich, ETH Zurich, University of Zurich, Zurich, Switzerland
| | - Markus Vaas
- Institute of Pharmacology and Toxicology, University Zurich, Zurich, Switzerland
| | - Musadiq A Bhat
- Institute of Pharmacology and Toxicology, University Zurich, Zurich, Switzerland
| | - Karthik Balakrishnan
- Institute of Pharmacology and Toxicology, University Zurich, Zurich, Switzerland
| | - Dietmar Benke
- Institute of Pharmacology and Toxicology, University Zurich, Zurich, Switzerland.,Neuroscience Center Zurich, ETH Zurich, University of Zurich, Zurich, Switzerland
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6
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The Effects of GABAergic System under Cerebral Ischemia: Spotlight on Cognitive Function. Neural Plast 2020; 2020:8856722. [PMID: 33061952 PMCID: PMC7539123 DOI: 10.1155/2020/8856722] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Accepted: 09/23/2020] [Indexed: 12/31/2022] Open
Abstract
In this review, we present evidence about the changes of the GABAergic system on the hippocampus under the ischemic environment, which may be an underlying mechanism to the ischemia-induced cognitive deficit. GABAergic system, in contrast to the glutamatergic system, is considered to play an inhibitory effect on the central nervous system over the past several decades. It has received widespread attention in the area of schizophrenia and epilepsy. The GABAergic system has a significant effect in promoting neural development and formation of local neural circuits of the brain, which is the structural basis of cognitive function. There have been a number of reviews describing changes in the GABAergic system in cerebral ischemia in recent years. However, no study has investigated the changes in the system in the hippocampus during cerebral ischemic injury, which results in cognitive impairment, particularly at the chronic ischemic stage and the late phase of ischemia. We present a review of the changes of the GABAergic system in the hippocampus under ischemia, including GABA interneurons, extracellular GABA neurotransmitter, and GABA receptors. Several studies are also listed correlating amelioration of cognitive impairment by regulating the GABAergic system in the hippocampus damaged under ischemia. Furthermore, exogenous cell transplantation, which improves cognition by modulating the GABAergic system, will also be described in this review to bring new insight and strategy on solving cognitive deficits caused by cerebral ischemia.
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7
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Orts-Del'Immagine A, Pugh JR. Activity-dependent plasticity of presynaptic GABA B receptors at parallel fiber synapses. Synapse 2018; 72:e22027. [PMID: 29360168 DOI: 10.1002/syn.22027] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 01/05/2018] [Accepted: 01/21/2018] [Indexed: 01/10/2023]
Abstract
Parallel fiber synapses in the cerebellum express a wide range of presynaptic receptors. However, presynaptic receptor expression at individual parallel fiber synapses is quite heterogeneous, suggesting physiological mechanisms regulate presynaptic receptor expression. We investigated changes in presynaptic GABAB receptors at parallel fiber-stellate cell synapses in acute cerebellar slices from juvenile mice. GABAB receptor-mediated inhibition of excitatory postsynaptic currents (EPSCs) is remarkably diverse at these synapses, with transmitter release at some synapses inhibited by >50% and little or no inhibition at others. GABAB receptor-mediated inhibition was significantly reduced following 4 Hz parallel fiber stimulation but not after stimulation at other frequencies. The reduction in GABAB receptor-mediated inhibition was replicated by bath application of forskolin and blocked by application of a PKA inhibitor, suggesting activation of adenylyl cyclase and PKA are required. Immunolabeling for an extracellular domain of the GABAB2 subunit revealed reduced surface expression in the molecular layer after exposure to forskolin. GABAB receptor-mediated inhibition of action potential evoked calcium transients in parallel fiber varicosities was also reduced following bath application of forskolin, confirming presynaptic receptors are responsible for the reduced EPSC inhibition. These data demonstrate that presynaptic GABAB receptor expression can be a plastic property of synapses, which may compliment other forms of synaptic plasticity. This opens the door to novel forms of receptor plasticity previously confined primarily to postsynaptic receptors.
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Affiliation(s)
- Adeline Orts-Del'Immagine
- Department of Cellular and Integrative Physiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas, 78229
| | - Jason R Pugh
- Department of Cellular and Integrative Physiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas, 78229
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8
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Abstract
Among various methods now available to isolate distinct cell populations or even single cells for DNA/RNA and proteomic analysis, laser capture microdissection (LCM) offers a unique opportunity to study cells in their topological contexts. This chapter focuses on the preparation of LCM membrane slides, tissue staining and laser microdissection of cells of interest from frozen or formalin-fixed, paraffin-embedded glioblastoma tissue.
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9
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Miller AP, Shah AS, Aperi BV, Kurpad SN, Stemper BD, Glavaski-Joksimovic A. Acute death of astrocytes in blast-exposed rat organotypic hippocampal slice cultures. PLoS One 2017; 12:e0173167. [PMID: 28264063 PMCID: PMC5338800 DOI: 10.1371/journal.pone.0173167] [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: 02/25/2016] [Accepted: 02/16/2017] [Indexed: 01/06/2023] Open
Abstract
Blast traumatic brain injury (bTBI) affects civilians, soldiers, and veterans worldwide and presents significant health concerns. The mechanisms of neurodegeneration following bTBI remain elusive and current therapies are largely ineffective. It is important to better characterize blast-evoked cellular changes and underlying mechanisms in order to develop more effective therapies. In the present study, our group utilized rat organotypic hippocampal slice cultures (OHCs) as an in vitro system to model bTBI. OHCs were exposed to either 138 ± 22 kPa (low) or 273 ± 23 kPa (high) overpressures using an open-ended helium-driven shock tube, or were assigned to sham control group. At 2 hours (h) following injury, we have characterized the astrocytic response to a blast overpressure. Immunostaining against the astrocytic marker glial fibrillary acidic protein (GFAP) revealed acute shearing and morphological changes in astrocytes, including clasmatodendrosis. Moreover, overlap of GFAP immunostaining and propidium iodide (PI) indicated astrocytic death. Quantification of the number of dead astrocytes per counting area in the hippocampal cornu Ammonis 1 region (CA1), demonstrated a significant increase in dead astrocytes in the low- and high-blast, compared to sham control OHCs. However only a small number of GFAP-expressing astrocytes were co-labeled with the apoptotic marker Annexin V, suggesting necrosis as the primary type of cell death in the acute phase following blast exposure. Moreover, western blot analyses revealed calpain mediated breakdown of GFAP. The dextran exclusion additionally indicated membrane disruption as a potential mechanism of acute astrocytic death. Furthermore, although blast exposure did not evoke significant changes in glutamate transporter 1 (GLT-1) expression, loss of GLT-1-expressing astrocytes suggests dysregulation of glutamate uptake following injury. Our data illustrate the profound effect of blast overpressure on astrocytes in OHCs at 2 h following injury and suggest increased calpain activity and membrane disruption as potential underlying mechanisms.
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Affiliation(s)
- Anna P. Miller
- Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
- Department of Cell Biology, Neurobiology & Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
- Clement J. Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin, United States of America
| | - Alok S. Shah
- Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
- Clement J. Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin, United States of America
| | - Brandy V. Aperi
- Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
- Clement J. Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin, United States of America
| | - Shekar N. Kurpad
- Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
- Department of Cell Biology, Neurobiology & Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
- Clement J. Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin, United States of America
| | - Brian D. Stemper
- Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
- Clement J. Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin, United States of America
| | - Aleksandra Glavaski-Joksimovic
- Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
- Department of Cell Biology, Neurobiology & Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
- Clement J. Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin, United States of America
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Öz P, Saybaşılı H. In vitro detection of oxygen and glucose deprivation-induced neurodegeneration and pharmacological neuroprotection based on hippocampal stratum pyramidale width. Neurosci Lett 2016; 636:196-204. [PMID: 27845243 DOI: 10.1016/j.neulet.2016.11.027] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 10/23/2016] [Accepted: 11/10/2016] [Indexed: 12/30/2022]
Abstract
Ischemia is one of the most prominent risk factors of neurodegenerative diseases such as Alzheimer's disease. The effects of oxygen and glucose depletion in hippocampal tissue due to ischemia can be mimicked in vitro using the oxygen and glucose deprivation (OGD) model. In this study, we applied OGD on acute rat hippocampal slices in order to design an elementary yet quantitative histological technique that compares the neuroprotective effects of (l)-carnitine to known neuroprotectors, such as the N-methyl-d-aspartate (NMDA) receptor antagonist memantine and the gamma-aminobutyric acid (GABA)-B receptor agonist baclofen. The level of neurodegeneration and the efficiency of pharmacological applications were estimated via stratum pyramidale width measurements in CA1 and CA3 regions of Nissl-stained 200-μm thick hippocampal slices. We demonstrated that (l)-carnitine is an effective pharmacological target against the neurodegeneration induced by in vitro ischemia in a narrow range of concentrations. Even though the effect of chemical neuroprotection was significant, full recovery was not achieved in the dose interval of 5-100μM. In addition to chemical applications, hypothermia was used as a physical neuroprotection against ischemia-related neurodegeneration. Our results showed that incubation of slices for 60min at 4°C provided the same level of neuroprotection as the most effective doses of memantine, baclofen, and (l)-carnitine.
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Affiliation(s)
- Pınar Öz
- Neuropsychopharmacology Application and Research Center, Üsküdar University Central Campus, Altunizade Mah. Haluk Türksoy Sk. No:14 34662, Istanbul, Turkey; Institute of Biomedical Engineering, Boğaziçi Üniversity Kandilli Campus, Kandilli Mah., 34684 Istanbul, Turkey
| | - Hale Saybaşılı
- Institute of Biomedical Engineering, Boğaziçi Üniversity Kandilli Campus, Kandilli Mah., 34684 Istanbul, Turkey.
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11
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Lu Y, Li CJ, Chen C, Luo P, Zhou M, Li C, Xu XL, Lu Q, He Z, Guo LJ. Activation of GABAB2 subunits alleviates chronic cerebral hypoperfusion-induced anxiety-like behaviours: A role for BDNF signalling and Kir3 channels. Neuropharmacology 2016; 110:308-321. [PMID: 27515806 DOI: 10.1016/j.neuropharm.2016.08.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2015] [Revised: 07/30/2016] [Accepted: 08/06/2016] [Indexed: 12/15/2022]
Abstract
Anxiety is an affective disorder that is commonly observed after irreversible brain damage induced by cerebral ischemia and can delay the physical and cognitive recovery, which affects the quality of life of both the patient and family members. However, anxiety after ischemia has received less attention, and mechanisms underlying anxiety-like behaviours induced by chronic cerebral ischemia are under-investigated. In the present study, the chronic cerebral hypoperfusion model was established by the permanent occlusion of the bilateral common carotid arteries (two-vessel occlusion, 2VO) in rats, and anxiety-related behaviours were evaluated. Results indicated that 2VO induced obvious anxiety-like behaviours; the surface expressions of GABAB2 subunits were down-regulated; Brain derived neurotrophic factor (BDNF), tyrosine kinase B (TrkB) and neural cell adhesion molecule (NCAM) were reduced; Meanwhile, the surface expressions of G protein-activated inwardly rectifying potassium (GIRK, Kir3) channels were up-regulated in hippocampal CA1 in 2VO rats. Baclofen, a GABAB receptor agonist, significantly ameliorated the anxiety-like behaviours. It also improved the down-regulation of GABAB2 surface expressions, restored the levels of BDNF, TrkB and NCAM, and reversed the increased surface expressions of Kir3 in hippocampal CA1 in 2VO rats. However, the effects of baclofen were absent in shRNA-GABAB2 infected 2VO rats. These results suggested that activation of GABAB2 subunits could improve BDNF signalling and reverse Kir3 channel surface expressions in hippocampal CA1, which may alleviate the anxiety-like behaviours in rats with chronic cerebral hypoperfusion.
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Affiliation(s)
- Yun Lu
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Chang-Jun Li
- Neurology Department, Tongji Medical College, Huazhong University of Science and Technology, The Central Hospital of Wuhan, Wuhan 430030, China
| | - Cheng Chen
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Pan Luo
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Mei Zhou
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Cai Li
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Xu-Lin Xu
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China; Institute of Brain Research, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Qing Lu
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China; Institute of Brain Research, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Zhi He
- Department of Neuropsychopharmacology, Medical School of China Three Gorges University, Yichang 443002, China.
| | - Lian-Jun Guo
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China; Institute of Brain Research, Huazhong University of Science and Technology, Wuhan 430030, China.
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12
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Hannan S, Gerrow K, Triller A, Smart TG. Phospho-dependent Accumulation of GABABRs at Presynaptic Terminals after NMDAR Activation. Cell Rep 2016; 16:1962-73. [PMID: 27498877 PMCID: PMC4987283 DOI: 10.1016/j.celrep.2016.07.021] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Revised: 04/19/2016] [Accepted: 07/09/2016] [Indexed: 11/24/2022] Open
Abstract
Here, we uncover a mechanism for regulating the number of active presynaptic GABAB receptors (GABABRs) at nerve terminals, an important determinant of neurotransmitter release. We find that GABABRs gain access to axon terminals by lateral diffusion in the membrane. Their relative accumulation is dependent upon agonist activation and the presence of the two distinct sushi domains that are found only in alternatively spliced GABABR1a subunits. Following brief activation of NMDA receptors (NMDARs) using glutamate, GABABR diffusion is reduced, causing accumulation at presynaptic terminals in a Ca(2+)-dependent manner that involves phosphorylation of GABABR2 subunits at Ser783. This signaling cascade indicates how synaptically released glutamate can initiate, via a feedback mechanism, increased levels of presynaptic GABABRs that limit further glutamate release and excitotoxicity.
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Affiliation(s)
- Saad Hannan
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK
| | - Kim Gerrow
- Biologie Cellulaire de la Synapse, Inserm U1024, Institute of Biology, École Normale Supérieure (ENS), 46 rue d'Ulm, Paris 75005, France
| | - Antoine Triller
- Biologie Cellulaire de la Synapse, Inserm U1024, Institute of Biology, École Normale Supérieure (ENS), 46 rue d'Ulm, Paris 75005, France
| | - Trevor G Smart
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK.
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Jiang Y, Yang S, Tao J, Lin Z, Ye X, You Y, Peng J, Hong Z, Chen L. Opposing needling promotes behavior recovery and exerts neuroprotection via the cAMP/PKA/CREB signal transduction pathway in transient MCAO rats. Mol Med Rep 2016; 13:2060-70. [PMID: 26780954 PMCID: PMC4768950 DOI: 10.3892/mmr.2016.4773] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Accepted: 10/28/2015] [Indexed: 01/02/2023] Open
Abstract
The aim of the present study was to investigate whether the cyclic adenosine 3′,5′-monophosphate (cAMP)/protein kinase A(PKA)/cAMP-responsive element binding protein (CREB) signal transduction pathway triggered by γ-aminobutyric acid class B (GABAB) receptor activation is involved in neuroprotection against ischemia and behavioral recovery induced by opposing needling (ON). A total of 80 rats were randomly divided into four groups: A sham operation group, an ischemia group, an ON group and an ON group effectively inhibited by the GABAB receptor antagonist, CGP35384 (n=20/group). The behavior of the rats was assessed by their neurological deficit score, whereas the impairment of gait was examined using the CatWalk system. The volume of cerebral infarction was examined upon treatment with 2,3,5-triphenyltetrazolium chloride. The expression levels of CREB, GABAB1 and GABAB2 were examined by western blotting and reverse transcription-quantitative polymerase chain reaction, and the activity of adenylyl cyclase (AC), cAMP and PKA in the serum was detected using an enzyme-linked immunosorbent assay. In the present study, in comparison with other groups, the ON group exhibited a reduced score for the neurological deficit, the stride length and swing speed were improved, and the volume of infarction was reduced. However, these effects were reversed upon administration of CGP35384. Additionally, the expression levels of CREB, GABAB1 and GABAB2 were increased in the ON group. The levels of AC, cAMP and PKA in the serum were also increased in the ON group, whereas the addition of CGP35384 reversed these effects. The results of the present study demonstrated that ON markedly protected the brain against transient cerebral ischemic injury, and this effect was possibly mediated by the activation of the GABAB/cAMP/PKA/CREB signal transduction pathway. These findings implied that ON may be a potential therapeutic method for treating stroke.
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Affiliation(s)
- Yijing Jiang
- Department of Rehabilitation Medicine, Rehabilitation Hospital, Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian 350001, P.R. China
| | - Shanli Yang
- Department of Rehabilitation Medicine, Rehabilitation Hospital, Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian 350001, P.R. China
| | - Jing Tao
- College of Rehabilitation Medicine, Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian 350122, P.R. China
| | - Zhicheng Lin
- Department of Rehabilitation Medicine, Rehabilitation Hospital, Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian 350001, P.R. China
| | - Xiaoqian Ye
- College of Rehabilitation Medicine, Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian 350122, P.R. China
| | - Yongmei You
- College of Rehabilitation Medicine, Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian 350122, P.R. China
| | - Jun Peng
- College of Rehabilitation Medicine, Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian 350122, P.R. China
| | - Zhenfeng Hong
- College of Rehabilitation Medicine, Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian 350122, P.R. China
| | - Lidian Chen
- College of Rehabilitation Medicine, Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian 350122, P.R. China
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Vavers E, Zvejniece L, Svalbe B, Volska K, Makarova E, Liepinsh E, Rizhanova K, Liepins V, Dambrova M. The neuroprotective effects of R-phenibut after focal cerebral ischemia. Pharmacol Res 2015; 113:796-801. [PMID: 26621244 DOI: 10.1016/j.phrs.2015.11.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Revised: 11/19/2015] [Accepted: 11/20/2015] [Indexed: 11/25/2022]
Abstract
R-phenibut is a γ-aminobutyric acid (GABA)-B receptor and α2-δ subunit of the voltage-dependent calcium channel (VDCC) ligand. The aim of the present study was to test the effects of R-phenibut on the motor, sensory and tactile functions and histological outcomes in rats following transient middle cerebral artery occlusion (MCAO). In this study, MCAO was induced by filament insertion (f-MCAO) or endothelin-1 (ET1) microinjection (ET1-MCAO) in male Wistar or CD rats, respectively. R-phenibut was administrated at doses of 10 and 50mg/kg for 14 days in the f-MCAO or 7 days in the ET1-MCAO. The vibrissae-evoked forelimb-placing and limb-placing tests were used to assess sensorimotor, tactile and proprioceptive function. Quantitative reverse transcriptase-PCR was used to detect brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF) gene expression in the damaged brain hemisphere. Both f-MCAO and ET1-MCAO resulted in statistically significant impairment of sensorimotor function and brain infarction. R-phenibut at a dose of 10mg/kg significantly improved histological outcome at day 7 in the ET1-MCAO. R-phenibut treatment at a dose of 50mg/kg significantly alleviated reduction of brain volume in damaged hemisphere in both f-MCAO and ET1-MCAO. In R-phenibut treated animals a trend of recovery of tactile and proprioceptive stimulation in the vibrissae-evoked forelimb-placing test was observed. After R-phenibut treatment at a dose of 50mg/kg statistically significant increase of BDNF and VEGF gene expression was found in damaged brain hemisphere. Taken together, obtained results provide evidence for the neuroprotective activity of R-phenibut in experimental models of stroke. These effects might be related to the modulatory effects of the drug on the GABA-B receptor and α2-δ subunit of VDCC.
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Affiliation(s)
- Edijs Vavers
- Latvian Institute of Organic Synthesis, Riga, Latvia; Riga Stradins University, Riga, Latvia.
| | | | - Baiba Svalbe
- Latvian Institute of Organic Synthesis, Riga, Latvia
| | - Kristine Volska
- Latvian Institute of Organic Synthesis, Riga, Latvia; Riga Stradins University, Riga, Latvia
| | | | | | | | | | - Maija Dambrova
- Latvian Institute of Organic Synthesis, Riga, Latvia; Riga Stradins University, Riga, Latvia
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15
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The modulatory effect of CA1 GABAb receptors on ketamine-induced spatial and non-spatial novelty detection deficits with respect to Ca2+. Neuroscience 2015; 305:157-68. [DOI: 10.1016/j.neuroscience.2015.07.083] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Revised: 07/24/2015] [Accepted: 07/30/2015] [Indexed: 11/18/2022]
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16
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Liu L, Li CJ, Lu Y, Zong XG, Luo C, Sun J, Guo LJ. Baclofen mediates neuroprotection on hippocampal CA1 pyramidal cells through the regulation of autophagy under chronic cerebral hypoperfusion. Sci Rep 2015; 5:14474. [PMID: 26412641 PMCID: PMC4585985 DOI: 10.1038/srep14474] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Accepted: 09/01/2015] [Indexed: 12/13/2022] Open
Abstract
GABA receptors play an important role in ischemic brain injury. Studies have indicated that autophagy is closely related to neurodegenerative diseases. However, during chronic cerebral hypoperfusion, the changes of autophagy in the hippocampal CA1 area, the correlation between GABA receptors and autophagy, and their influences on hippocampal neuronal apoptosis have not been well established. Here, we found that chronic cerebral hypoperfusion resulted in rat hippocampal atrophy, neuronal apoptosis, enhancement and redistribution of autophagy, down-regulation of Bcl-2/Bax ratio, elevation of cleaved caspase-3 levels, reduction of surface expression of GABAA receptor α1 subunit and an increase in surface and mitochondrial expression of connexin 43 (CX43) and CX36. Chronic administration of GABAB receptors agonist baclofen significantly alleviated neuronal damage. Meanwhile, baclofen could up-regulate the ratio of Bcl-2/Bax and increase the activation of Akt, GSK-3β and ERK which suppressed cytodestructive autophagy. The study also provided evidence that baclofen could attenuate the decrease in surface expression of GABAA receptor α1 subunit, and down-regulate surface and mitochondrial expression of CX43 and CX36, which might enhance protective autophagy. The current findings suggested that, under chronic cerebral hypoperfusion, the effects of GABAB receptors activation on autophagy regulation could reverse neuronal damage.
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Affiliation(s)
- Li Liu
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, PR China
| | - Chang-jun Li
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, PR China
- Neurology Department, Huanggang central hospital, Hubei Province, Huanggang, 438000, PR China
| | - Yun Lu
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, PR China
| | - Xian-gang Zong
- Center for Integrated Protein Science (CIPSM) and Zentrum für Pharmaforschung, Department Pharmazie, Ludwig-Maximilians-Universität München, 80539 Munich, Germany
| | - Chao Luo
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, PR China
| | - Jun Sun
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, PR China
| | - Lian-jun Guo
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, PR China
- Key Laboratory of Drug Target Research and Pharmacodynamic Evaluation, Hubei Province, Wuhan 430030, China
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Kantamneni S. Cross-talk and regulation between glutamate and GABAB receptors. Front Cell Neurosci 2015; 9:135. [PMID: 25914625 PMCID: PMC4392697 DOI: 10.3389/fncel.2015.00135] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Accepted: 03/23/2015] [Indexed: 12/16/2022] Open
Abstract
Brain function depends on co-ordinated transmission of signals from both excitatory and inhibitory neurotransmitters acting upon target neurons. NMDA, AMPA and mGluR receptors are the major subclasses of glutamate receptors that are involved in excitatory transmission at synapses, mechanisms of activity dependent synaptic plasticity, brain development and many neurological diseases. In addition to canonical role of regulating presynaptic release and activating postsynaptic potassium channels, GABAB receptors also regulate glutamate receptors. There is increasing evidence that metabotropic GABAB receptors are now known to play an important role in modulating the excitability of circuits throughout the brain by directly influencing different types of postsynaptic glutamate receptors. Specifically, GABAB receptors affect the expression, activity and signaling of glutamate receptors under physiological and pathological conditions. Conversely, NMDA receptor activity differentially regulates GABAB receptor subunit expression, signaling and function. In this review I will describe how GABAB receptor activity influence glutamate receptor function and vice versa. Such a modulation has widespread implications for the control of neurotransmission, calcium-dependent neuronal function, pain pathways and in various psychiatric and neurodegenerative diseases.
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Affiliation(s)
- Sriharsha Kantamneni
- Bradford School of Pharmacy, School of Life Sciences, University of Bradford Bradford, West Yorkshire, UK
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18
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Benke D, Balakrishnan K, Zemoura K. Regulation of Cell Surface GABAB Receptors. DIVERSITY AND FUNCTIONS OF GABA RECEPTORS: A TRIBUTE TO HANNS MÖHLER, PART B 2015; 73:41-70. [DOI: 10.1016/bs.apha.2014.11.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Tasca CI, Dal-Cim T, Cimarosti H. In vitro oxygen-glucose deprivation to study ischemic cell death. Methods Mol Biol 2015; 1254:197-210. [PMID: 25431067 DOI: 10.1007/978-1-4939-2152-2_15] [Citation(s) in RCA: 105] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Oxygen-glucose deprivation (OGD ) is widely used as an in vitro model for stroke, showing similarities with the in vivo models of brain ischemia. In order to perform OGD, cell or tissue cultures, such as primary neurons or organotypic slices, and acutely prepared tissue slices are usually incubated in a glucose-free medium under a deoxygenated atmosphere, for example in a hypoxic chamber. Here, we describe the step-by-step procedure to expose cultures and acute slices to OGD, focusing on the most suitable methods for assessing cellular death and/or viability. OGD is a simple yet highly useful technique, not only for the elucidation of the role of key cellular and molecular mechanisms underlying brain ischemia, but also for the development of novel neuroprotective strategies.
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Affiliation(s)
- Carla I Tasca
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Campus Universitário - Trindade 88040-900, Florianópolis, SC, Brazil
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20
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Gao XY, Huang JO, Hu YF, Gu Y, Zhu SZ, Huang KB, Chen JY, Pan SY. Combination of mild hypothermia with neuroprotectants has greater neuroprotective effects during oxygen-glucose deprivation and reoxygenation-mediated neuronal injury. Sci Rep 2014; 4:7091. [PMID: 25404538 PMCID: PMC4665348 DOI: 10.1038/srep07091] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Accepted: 10/29/2014] [Indexed: 12/02/2022] Open
Abstract
Co-treatment of neuroprotective reagents may improve the therapeutic efficacy of hypothermia in protecting neurons during ischemic stroke. This study aimed to find promising drugs that enhance the neuroprotective effect of mild hypothermia (MH). 26 candidate drugs were selected based on different targets. Primary cultured cortical neurons were exposed to oxygen-glucose deprivation and reoxygenation (OGD/R) to induce neuronal damage, followed by either single treatment (a drug or MH) or a combination of a drug and MH. Results showed that, compared with single treatment, combination of MH with brain derived neurotrophic factor, glibenclamide, dizocilpine, human urinary kallidinogenase or neuroglobin displayed higher proportion of neuronal cell viability. The latter three drugs also caused less apoptosis rate in combined treatment. Furthermore, co-treatment of those three drugs and MH decreased the level of reactive oxygen species (ROS) and intracellular calcium accumulation, as well as stabilized mitochondrial membrane potential (MMP), indicating the combined neuroprotective effects are probably via inhibiting mitochondrial apoptosis pathway. Taken together, the study suggests that combined treatment with hypothermia and certain neuroprotective reagents provide a better protection against OGD/R-induced neuronal injury.
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Affiliation(s)
- Xiao-Ya Gao
- 1] Department of Neurology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, P. R. China [2] Department of Neurology, Zhujiang Hospital, Southern Medical University, Guangzhou, Guangdong, P. R. China
| | - Jian-Ou Huang
- 1] Department of Neurology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, P. R. China [2] Department of Neurology, the 421 Hospital, Guangzhou, Guangdong, P. R. China
| | - Ya-Fang Hu
- Department of Neurology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, P. R. China
| | - Yong Gu
- Department of Neurology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, P. R. China
| | - Shu-Zhen Zhu
- Department of Neurology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, P. R. China
| | - Kai-Bin Huang
- Department of Neurology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, P. R. China
| | - Jin-Yu Chen
- Department of Neurology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, P. R. China
| | - Su-Yue Pan
- Department of Neurology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, P. R. China
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21
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Kim JY, Ho H, Kim N, Liu J, Tu CL, Yenari MA, Chang W. Calcium-sensing receptor (CaSR) as a novel target for ischemic neuroprotection. Ann Clin Transl Neurol 2014; 1:851-66. [PMID: 25540800 PMCID: PMC4265057 DOI: 10.1002/acn3.118] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Revised: 08/14/2014] [Accepted: 08/15/2014] [Indexed: 01/04/2023] Open
Abstract
Object Ischemic brain injury is the leading cause for death and long-term disability in patients who suffer cardiac arrest and embolic stroke. Excitotoxicity and subsequent Ca2+-overload lead to ischemic neuron death. We explore a novel mechanism concerning the role of the excitatory extracellular calcium-sensing receptor (CaSR) in the induction of ischemic brain injury. Method Mice were exposed to forebrain ischemia and the actions of CaSR were determined after its genes were ablated specifically in hippocampal neurons or its activities were inhibited pharmacologically. Since the CaSR forms a heteromeric complex with the inhibitory type B γ-aminobutyric acid receptor 1 (GABABR1), we compared neuronal responses to ischemia in mice deficient in CaSR, GABABR1, or both, and in mice injected locally or systemically with a specific CaSR antagonist (or calcilytic) in the presence or absence of a GABABR1 agonist (baclofen). Results Both global and focal brain ischemia led to CaSR overexpression and GABABR1 downregulation in injured neurons. Genetic ablation of Casr genes or blocking CaSR activities by calcilytics rendered robust neuroprotection and preserved learning and memory functions in ischemic mice, partly by restoring GABABR1 expression. Concurrent ablation of Gabbr1 gene blocked the neuroprotection caused by the Casr gene knockout. Coinjection of calcilytics with baclofen synergistically enhanced neuroprotection. This combined therapy remained robust when given 6 h after ischemia. Interpretation Our study demonstrates a novel receptor interaction, which contributes to ischemic neuron death through CaSR upregulation and GABABR1 downregulation, and feasibility of neuroprotection by concurrently targeting these two receptors.
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Affiliation(s)
- Jong Youl Kim
- Endocrine Unit, University of California San Francisco and Veterans Affairs Medical Center San Francisco, California, 94121 ; Department of Neurology, University of California San Francisco and Veterans Affairs Medical Center San Francisco, California, 94121
| | - Hanson Ho
- Endocrine Unit, University of California San Francisco and Veterans Affairs Medical Center San Francisco, California, 94121
| | - Nuri Kim
- Department of Neurology, University of California San Francisco and Veterans Affairs Medical Center San Francisco, California, 94121
| | - Jialing Liu
- Neurological Surgery, University of California San Francisco and Veterans Affairs Medical Center San Francisco, California, 94121
| | - Chia-Ling Tu
- Endocrine Unit, University of California San Francisco and Veterans Affairs Medical Center San Francisco, California, 94121
| | - Midori A Yenari
- Department of Neurology, University of California San Francisco and Veterans Affairs Medical Center San Francisco, California, 94121
| | - Wenhan Chang
- Endocrine Unit, University of California San Francisco and Veterans Affairs Medical Center San Francisco, California, 94121
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Hsu WCJ, Nilsson CL, Laezza F. Role of the axonal initial segment in psychiatric disorders: function, dysfunction, and intervention. Front Psychiatry 2014; 5:109. [PMID: 25191280 PMCID: PMC4139700 DOI: 10.3389/fpsyt.2014.00109] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/21/2014] [Accepted: 08/06/2014] [Indexed: 12/22/2022] Open
Abstract
The progress of developing effective interventions against psychiatric disorders has been limited due to a lack of understanding of the underlying cellular and functional mechanisms. Recent research findings focused on exploring novel causes of psychiatric disorders have highlighted the importance of the axonal initial segment (AIS), a highly specialized neuronal structure critical for spike initiation of the action potential. In particular, the role of voltage-gated sodium channels, and their interactions with other protein partners in a tightly regulated macromolecular complex has been emphasized as a key component in the regulation of neuronal excitability. Deficits and excesses of excitability have been linked to the pathogenesis of brain disorders. Identification of the factors and regulatory pathways involved in proper AIS function, or its disruption, can lead to the development of novel interventions that target these mechanistic interactions, increasing treatment efficacy while reducing deleterious off-target effects for psychiatric disorders.
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Affiliation(s)
- Wei-Chun Jim Hsu
- Department of Biochemistry and Molecular Biology, The University of Texas Medical Branch at Galveston, Galveston, TX, USA
- Graduate Program in Biochemistry and Molecular Biology, The University of Texas Medical Branch at Galveston, Galveston, TX, USA
- M.D.–Ph.D. Combined Degree Program, The University of Texas Medical Branch at Galveston, Galveston, TX, USA
| | - Carol Lynn Nilsson
- Department of Pharmacology and Toxicology, The University of Texas Medical Branch at Galveston, Galveston, TX, USA
- Sealy Center for Molecular Medicine, The University of Texas Medical Branch at Galveston, Galveston, TX, USA
| | - Fernanda Laezza
- Department of Pharmacology and Toxicology, The University of Texas Medical Branch at Galveston, Galveston, TX, USA
- Center for Addiction Research, The University of Texas Medical Branch at Galveston, Galveston, TX, USA
- Center for Biomedical Engineering, The University of Texas Medical Branch at Galveston, Galveston, TX, USA
- Mitchell Center for Neurodegenerative Diseases, The University of Texas Medical Branch at Galveston, Galveston, TX, USA
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Li CJ, Lu Y, Zhou M, Zong XG, Li C, Xu XL, Guo LJ, Lu Q. Activation of GABAB receptors ameliorates cognitive impairment via restoring the balance of HCN1/HCN2 surface expression in the hippocampal CA1 area in rats with chronic cerebral hypoperfusion. Mol Neurobiol 2014; 50:704-20. [PMID: 24838625 DOI: 10.1007/s12035-014-8736-3] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Accepted: 04/29/2014] [Indexed: 11/30/2022]
Abstract
Hyperpolarization-activated cyclic-nucleotide-gated cation nonselective (HCN) channels are involved in the pathology of nervous system diseases. HCN channels and γ-aminobutyric acid (GABA) receptors can mutually co-regulate the function of neurons in many brain areas. However, little is known about the co-regulation of HCN channels and GABA receptors in the chronic ischemic rats with possible features of vascular dementia. Protein kinase A (PKA) and TPR containing Rab8b interacting protein (TRIP8b) can modulate GABAB receptors cell surface stability and HCN channel trafficking, respectively, and adaptor-associated kinase 1 (AAK1) inhibits the function of the major TRIP8b-interacting protein adaptor protein 2 (AP2) via phosphorylating the AP2 μ2 subunit. Until now, the role of these regulatory factors in chronic cerebral hypoperfusion is unclear. In the present study, we evaluated whether and how HCN channels and GABAB receptors were pathologically altered and investigated neuroprotective effects of GABAB receptors activation and cross-talk networks between GABAB receptors and HCN channels in the hippocampal CA1 area in chronic cerebral hypoperfusion rat model. We found that cerebral hypoperfusion for 5 weeks by permanent occlusion of bilateral common carotid arteries (two-vessel occlusion, 2VO) induced marked spatial and nonspatial learning and memory deficits, significant neuronal loss and decrease in dendritic spine density, impairment of long-term potentiation (LTP) at the Schaffer collateral-CA1 synapses, and reduction of surface expression of GABAB R1, GABAB R2, and HCN1, but increase in HCN2 surface expression. Meanwhile, the protein expression of TRIP8b (1a-4), TRIP8b (1b-2), and AAK1 was significantly decreased. Baclofen, a GABAB receptor agonist, markedly improved the memory impairment and alleviated neuronal damage. Besides, baclofen attenuated the decrease of surface expression of GABAB R1, GABAB R2, and HCN1, but downregulated HCN2 surface expression. Furthermore, baclofen could restore expression of AAK1 protein and significantly increase p-PKA, TRIP8b (1a-4), TRIP8b (1b-2), and p-AP2 μ2 expression. Those findings suggested that, under chronic cerebral hypoperfusion, activation of PKA could attenuate baclofen-induced decrease in surface expression of GABAB R1 and GABAB R2, and activation of GABAB receptors not only increased the expression of TRIP8b (1a-4) and TRIP8b (1b-2) but also regulated the function of TRIP8b via AAK1 and p-AP2 μ2, which restored the balance of HCN1/HCN2 surface expression in rat hippocampal CA1 area, and thus ameliorated cognitive impairment.
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Affiliation(s)
- Chang-jun Li
- Department of Pharmacology, School of Basic Medical Sciences, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, People's Republic of China
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Maier PJ, Zemoura K, Acuña MA, Yévenes GE, Zeilhofer HU, Benke D. Ischemia-like oxygen and glucose deprivation mediates down-regulation of cell surface γ-aminobutyric acidB receptors via the endoplasmic reticulum (ER) stress-induced transcription factor CCAAT/enhancer-binding protein (C/EBP)-homologous protein (CHOP). J Biol Chem 2014; 289:12896-907. [PMID: 24668805 DOI: 10.1074/jbc.m114.550517] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Cerebral ischemia frequently leads to long-term disability and death. Excitotoxicity is believed to be the main cause for ischemia-induced neuronal death. Although a role of glutamate receptors in this process has been firmly established, the contribution of metabotropic GABAB receptors, which control excitatory neurotransmission, is less clear. A prominent characteristic of ischemic insults is endoplasmic reticulum (ER) stress associated with the up-regulation of the transcription factor CCAAT/enhancer-binding protein-homologous protein (CHOP). After inducing ER stress in cultured cortical neurons by sustained Ca(2+) release from intracellular stores or by a brief episode of oxygen and glucose deprivation (in vitro model of cerebral ischemia), we observed an increased expression of CHOP accompanied by a strong reduction of cell surface GABAB receptors. Our results indicate that down-regulation of cell surface GABAB receptors is caused by the interaction of the receptors with CHOP in the ER. Binding of CHOP prevented heterodimerization of the receptor subunits GABAB1 and GABAB2 and subsequent forward trafficking of the receptors to the cell surface. The reduced level of cell surface receptors diminished GABAB receptor signaling and, thus, neuronal inhibition. These findings indicate that ischemia-mediated up-regulation of CHOP down-regulates cell surface GABAB receptors by preventing their trafficking from the ER to the plasma membrane. This mechanism leads to diminished neuronal inhibition and may contribute to excitotoxicity in cerebral ischemia.
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Affiliation(s)
- Patrick J Maier
- From the Institute of Pharmacology and Toxicology, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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Kantamneni S, Gonzàlez-Gonzàlez IM, Luo J, Cimarosti H, Jacobs SC, Jaafari N, Henley JM. Differential regulation of GABAB receptor trafficking by different modes of N-methyl-D-aspartate (NMDA) receptor signaling. J Biol Chem 2014; 289:6681-6694. [PMID: 24425870 PMCID: PMC3945329 DOI: 10.1074/jbc.m113.487348] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2013] [Revised: 12/24/2013] [Indexed: 12/31/2022] Open
Abstract
Inhibitory GABAB receptors (GABABRs) can down-regulate most excitatory synapses in the CNS by reducing postsynaptic excitability. Functional GABABRs are heterodimers of GABAB1 and GABAB2 subunits and here we show that the trafficking and surface expression of GABABRs is differentially regulated by synaptic or pathophysiological activation of NMDA receptors (NMDARs). Activation of synaptic NMDARs using a chemLTP protocol increases GABABR recycling and surface expression. In contrast, excitotoxic global activation of synaptic and extrasynaptic NMDARs by bath application of NMDA causes the loss of surface GABABRs. Intriguingly, exposing neurons to extreme metabolic stress using oxygen/glucose deprivation (OGD) increases GABAB1 but decreases GABAB2 surface expression. The increase in surface GABAB1 involves enhanced recycling and is blocked by the NMDAR antagonist AP5. The decrease in surface GABAB2 is also blocked by AP5 and by inhibiting degradation pathways. These results indicate that NMDAR activity is critical in GABABR trafficking and function and that the individual subunits can be separately controlled to regulate neuronal responsiveness and survival.
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Affiliation(s)
- Sriharsha Kantamneni
- School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, United Kingdom.
| | | | - Jia Luo
- School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Helena Cimarosti
- School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Susan C Jacobs
- School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Nadia Jaafari
- School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Jeremy M Henley
- School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, United Kingdom.
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Benke D. GABAB receptor trafficking and interacting proteins: Targets for the development of highly specific therapeutic strategies to treat neurological disorders? Biochem Pharmacol 2013; 86:1525-30. [DOI: 10.1016/j.bcp.2013.09.016] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Revised: 09/20/2013] [Accepted: 09/20/2013] [Indexed: 10/26/2022]
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Hoppe JB, Haag M, Whalley BJ, Salbego CG, Cimarosti H. Curcumin protects organotypic hippocampal slice cultures from Aβ1-42-induced synaptic toxicity. Toxicol In Vitro 2013; 27:2325-30. [PMID: 24134851 DOI: 10.1016/j.tiv.2013.10.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Revised: 09/25/2013] [Accepted: 10/03/2013] [Indexed: 11/28/2022]
Abstract
Increasing evidence demonstrates that beta-amyloid (Aβ) is toxic to synapses, resulting in the progressive dismantling of neuronal circuits. Counteract the synaptotoxic effects of Aβ could be particularly relevant for providing effective treatments for Alzheimer's disease (AD). Curcumin was recently reported to improve learning and memory in animal models of AD. Little is currently known about the specific mechanisms by which Aβ affects neuronal excitability and curcumin ameliorates synaptic transmission in the hippocampus. Organotypic hippocampal slice cultures exposed to Aβ1-42 were used to study the neuroprotective effects of curcumin through a spectral analysis of multi-electrode array (MEA) recordings of spontaneous neuronal activity. Curcumin counteracted both deleterious effects of Aβ; the initial synaptic dysfunction and the later neuronal death. The analysis of MEA recordings of spontaneous neuronal activity showed an attenuation of signal propagation induced by Aβ before cell death and curcumin-induced alterations to local field potential (LFP) phase coherence. Curcumin-mediated attenuation of Aβ-induced synaptic dysfunction involved regulation of synaptic proteins, namely phospho-CaMKII and phospho-synapsin I. Taken together, our results expand the neuroprotective role of curcumin to a synaptic level. The identification of these mechanisms underlying the effects of curcumin may lead to new targets for future therapies for AD.
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Affiliation(s)
- Juliana Bender Hoppe
- Reading School of Pharmacy, University of Reading, Whiteknights, Reading RG6 6UB, UK; Laboratory of Neuroprotection and Cell Signalling, Department of Biochemistry, Federal University of Rio Grande do Sul, Porto Alegre, RS 90035-003, Brazil.
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Therapeutic potential of GABA(B) receptor ligands in drug addiction, anxiety, depression and other CNS disorders. Pharmacol Biochem Behav 2013; 110:174-84. [PMID: 23872369 DOI: 10.1016/j.pbb.2013.07.003] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 06/27/2013] [Accepted: 07/05/2013] [Indexed: 01/06/2023]
Abstract
Glutamate and γ-aminobutyric acid (GABA) are the major excitatory and inhibitory neurotransmitter systems, respectively in the central nervous system (CNS). Dysregulation, in any of these or both, has been implicated in various CNS disorders. GABA acts via ionotropic (GABA(A) and GABA(C) receptor) and metabotropic (GABA(B)) receptor. Dysregulation of GABAergic signaling and alteration in GABA(B) receptor expression has been implicated in various CNS disorders. Clinically, baclofen-a GABA(B) receptor agonist is available for the treatment of spasticity, dystonia etc., associated with various neurological disorders. Moreover, GABAB receptor ligands has also been suggested to be beneficial in various neuropsychiatric and neurodegenerative disorders. The present review is aimed to discuss the role of GABA(B) receptors and the possible outcomes of GABA(B) receptor modulation in CNS disorders.
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Benke D, Zemoura K, Maier PJ. Modulation of cell surface GABA(B) receptors by desensitization, trafficking and regulated degradation. World J Biol Chem 2012; 3:61-72. [PMID: 22558486 PMCID: PMC3342575 DOI: 10.4331/wjbc.v3.i4.61] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2011] [Revised: 12/08/2011] [Accepted: 12/15/2011] [Indexed: 02/05/2023] Open
Abstract
Inhibitory neurotransmission ensures normal brain function by counteracting and integrating excitatory activity. γ-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the mammalian central nervous system, and mediates its effects via two classes of receptors: the GABA(A) and GABA(B) receptors. GABA(A) receptors are heteropentameric GABA-gated chloride channels and responsible for fast inhibitory neurotransmission. GABA(B) receptors are heterodimeric G protein coupled receptors (GPCR) that mediate slow and prolonged inhibitory transmission. The extent of inhibitory neurotransmission is determined by a variety of factors, such as the degree of transmitter release and changes in receptor activity by posttranslational modifications (e.g., phosphorylation), as well as by the number of receptors present in the plasma membrane available for signal transduction. The level of GABA(B) receptors at the cell surface critically depends on the residence time at the cell surface and finally the rates of endocytosis and degradation. In this review we focus primarily on recent advances in the understanding of trafficking mechanisms that determine the expression level of GABA(B) receptors in the plasma membrane, and thereby signaling strength.
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Affiliation(s)
- Dietmar Benke
- Dietmar Benke, Khaled Zemoura, Patrick J Maier, Institute of Pharmacology and Toxicology, University of Zürich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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Lodewyks C, Rodriguez J, Yan J, Lerner B, Lipschitz J, Nfon C, Rempel JD, Uhanova J, Minuk GY. GABA-B receptor activation inhibits the in vitro migration of malignant hepatocytes. Can J Physiol Pharmacol 2011; 89:393-400. [PMID: 21762014 DOI: 10.1139/y11-031] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
There are conflicting data regarding whether activation of γ-aminobutyric acid-B (GABA-B) receptors results in inhibition of tumor growth and invasion. The objectives of this study were to document the effects of the GABA-B receptor agonist baclofen on malignant hepatocyte proliferation and migration. We also sought to determine whether any effects on cell migration were mediated by changes in cyclic adenosine monophosphate (cAMP) signaling or matrix metalloproteinase (MMP) expression. Finally, GABA-B(1) and -B(2) receptor expression was documented in 2 malignant hepatocyte cell lines (PLC/PRF/5 and Huh-7) and 12 sets of human hepatocellular carcinoma and adjacent nontumor tissues. Cell proliferative activity was documented by WST-1 absorbance, migration by wound healing assays, cAMP levels by enzyme-linked immunoassay (ELISA), MMP by immunohistochemistry and ELISA, and GABA-B receptor expression by flow cytometry and reverse transcriptase - polymerase chain reaction. Although baclofen had no effect on cell proliferation, wound healing was delayed, an effect that was reversed by the GABA-B receptor antagonist CGP. cAMP levels were decreased in Huh-7 but not PLC cells exposed to baclofen. MMP expression remained unaltered in both cell lines. Finally, GABA-B(1) receptor expression was present and consistently expressed, but GABA-B(2) expression was limited and varied with the number of cell passages and (or) duration of culture. In conclusion, activation of GABA-B receptors has no effect on malignant hepatocyte proliferation but does decrease cell migration. This inhibitory effect may involve cAMP signaling but not MMP expression. GABA-B(2) receptor expression is limited and variable, which may help to explain discrepancies with previously published results.
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Affiliation(s)
- Carly Lodewyks
- Section of Hepatology, Department of Medicine, University of Manitoba, Winnipeg, MB, Canada
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Maier PJ, Marin I, Grampp T, Sommer A, Benke D. Sustained glutamate receptor activation down-regulates GABAB receptors by shifting the balance from recycling to lysosomal degradation. J Biol Chem 2010; 285:35606-14. [PMID: 20826795 DOI: 10.1074/jbc.m110.142406] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Metabotropic GABA(B) receptors are abundantly expressed at glutamatergic synapses where they control excitability of the synapse. Here, we tested the hypothesis that glutamatergic neurotransmission may regulate GABA(B) receptors. We found that application of glutamate to cultured cortical neurons led to rapid down-regulation of GABA(B) receptors via lysosomal degradation. This effect was mimicked by selective activation of AMPA receptors and further accelerated by coactivation of group I metabotropic glutamate receptors. Inhibition of NMDA receptors, blockade of L-type Ca(2+) channels, and removal of extracellular Ca(2+) prevented glutamate-induced down-regulation of GABA(B) receptors, indicating that Ca(2+) influx plays a critical role. We further established that glutamate-induced down-regulation depends on the internalization of GABA(B) receptors. Glutamate did not affect the rate of GABA(B) receptor endocytosis but led to reduced recycling of the receptors back to the plasma membrane. Blockade of lysosomal activity rescued receptor recycling, indicating that glutamate redirects GABA(B) receptors from the recycling to the degradation pathway. In conclusion, the data indicate that sustained activation of AMPA receptors down-regulates GABA(B) receptors by sorting endocytosed GABA(B) receptors preferentially to lysosomes for degradation on the expense of recycling. This mechanism may relieve glutamatergic synapses from GABA(B) receptor-mediated inhibition resulting in increased synaptic excitability.
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Affiliation(s)
- Patrick J Maier
- Institute of Pharmacology and Toxicology, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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Guetg N, Aziz SA, Holbro N, Turecek R, Rose T, Seddik R, Gassmann M, Moes S, Jenoe P, Oertner TG, Casanova E, Bettler B. NMDA receptor-dependent GABAB receptor internalization via CaMKII phosphorylation of serine 867 in GABAB1. Proc Natl Acad Sci U S A 2010; 107:13924-9. [PMID: 20643921 PMCID: PMC2922270 DOI: 10.1073/pnas.1000909107] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
GABAB receptors are the G-protein-coupled receptors for GABA, the main inhibitory neurotransmitter in the brain. GABAB receptors are abundant on dendritic spines, where they dampen postsynaptic excitability and inhibit Ca2+ influx through NMDA receptors when activated by spillover of GABA from neighboring GABAergic terminals. Here, we show that an excitatory signaling cascade enables spines to counteract this GABAB-mediated inhibition. We found that NMDA application to cultured hippocampal neurons promotes dynamin-dependent endocytosis of GABAB receptors. NMDA-dependent internalization of GABAB receptors requires activation of Ca2+/Calmodulin-dependent protein kinase II (CaMKII), which associates with GABAB receptors in vivo and phosphorylates serine 867 (S867) in the intracellular C terminus of the GABAB1 subunit. Blockade of either CaMKII or phosphorylation of S867 renders GABAB receptors refractory to NMDA-mediated internalization. Time-lapse two-photon imaging of organotypic hippocampal slices reveals that activation of NMDA receptors removes GABAB receptors within minutes from the surface of dendritic spines and shafts. NMDA-dependent S867 phosphorylation and internalization is predominantly detectable with the GABAB1b subunit isoform, which is the isoform that clusters with inhibitory effector K+ channels in the spines. Consistent with this, NMDA receptor activation in neurons impairs the ability of GABAB receptors to activate K+ channels. Thus, our data support that NMDA receptor activity endocytoses postsynaptic GABAB receptors through CaMKII-mediated phosphorylation of S867. This provides a means to spare NMDA receptors at individual glutamatergic synapses from reciprocal inhibition through GABAB receptors.
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Affiliation(s)
- Nicole Guetg
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, 4056 Basel, Switzerland
| | - Said Abdel Aziz
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, 4056 Basel, Switzerland
| | - Niklaus Holbro
- Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland
| | - Rostislav Turecek
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, 4056 Basel, Switzerland
- Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, 142 20 Prague, Czech Republic; and
| | - Tobias Rose
- Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland
| | - Riad Seddik
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, 4056 Basel, Switzerland
| | - Martin Gassmann
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, 4056 Basel, Switzerland
| | - Suzette Moes
- Biozentrum, University of Basel, 4056 Basel, Switzerland
| | - Paul Jenoe
- Biozentrum, University of Basel, 4056 Basel, Switzerland
| | - Thomas G. Oertner
- Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland
| | - Emilio Casanova
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, 4056 Basel, Switzerland
| | - Bernhard Bettler
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, 4056 Basel, Switzerland
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Prolonged activation of NMDA receptors promotes dephosphorylation and alters postendocytic sorting of GABAB receptors. Proc Natl Acad Sci U S A 2010; 107:13918-23. [PMID: 20643948 DOI: 10.1073/pnas.1000853107] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Slow and persistent synaptic inhibition is mediated by metabotropic GABAB receptors (GABABRs). GABABRs are responsible for the modulation of neurotransmitter release from presynaptic terminals and for hyperpolarization at postsynaptic sites. Postsynaptic GABABRs are predominantly found on dendritic spines, adjacent to excitatory synapses, but the control of their plasma membrane availability is still controversial. Here, we explore the role of glutamate receptor activation in regulating the function and surface availability of GABABRs in central neurons. We demonstrate that prolonged activation of NMDA receptors (NMDA-Rs) leads to endocytosis, a diversion from a recycling route, and subsequent lysosomal degradation of GABABRs. These sorting events are paralleled by a reduction in GABABR-dependent activation of inwardly rectifying K+ channel currents. Postendocytic sorting is critically dependent on phosphorylation of serine 783 (S783) within the GABABR2 subunit, an established substrate of AMP-dependent protein kinase (AMPK). NMDA-R activation leads to a rapid increase in phosphorylation of S783, followed by a slower dephosphorylation, which results from the activity of AMPK and protein phosphatase 2A, respectively. Agonist activation of GABABRs counters the effects of NMDA. Thus, NMDA-R activation alters the phosphorylation state of S783 and acts as a molecular switch to decrease the abundance of GABABRs at the neuronal plasma membrane. Such a mechanism may be of significance during synaptic plasticity or pathological conditions, such as ischemia or epilepsy, which lead to prolonged activation of glutamate receptors.
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Benke D. Mechanisms of GABAB receptor exocytosis, endocytosis, and degradation. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2010; 58:93-111. [PMID: 20655479 DOI: 10.1016/s1054-3589(10)58004-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
GABA(B) receptors belong to the family of G-protein-coupled receptors, which mediate slow inhibitory neurotransmission in the central nervous system. They are promising drug targets for a variety of neurological disorders and play important functions in regulating synaptic plasticity. Signaling strength is critically dependent on the availability of the receptors at the cell surface. Several distinct highly regulated trafficking mechanisms ensure the presence of adequate receptor numbers in the plasma membrane. The rate of exocytosis of newly synthesized receptors from the endoplasmic reticulum via the Golgi apparatus to the cell surface as well as the rates of their endocytosis and degradation determines the retention time of receptors at the cell surface. This chapter focuses on the recently emerged mechanisms of GABA(B) receptor exocytosis, endocytosis, recycling, and degradation.
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Affiliation(s)
- Dietmar Benke
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
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