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Brenner M, Parpura V. The Role of Astrocytes in CNS Disorders: Historic and Contemporary Views. Cells 2024; 13:1388. [PMID: 39195276 DOI: 10.3390/cells13161388] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2024] [Accepted: 07/29/2024] [Indexed: 08/29/2024] Open
Abstract
This Special Issue of Cells presents a collection of 22 published, peer-reviewed articles on the theme of "Astrocytes in CNS Disorders," including 9 reviews of the evidence implicating astrocytes in the etiology of specific disorders, and 13 original research papers providing such evidence [...].
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Affiliation(s)
- Michael Brenner
- Department of Neurobiology, The University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Vladimir Parpura
- International Translational Neuroscience Research Institute, Zhejiang Chinese Medical University, Hangzhou 310053, China
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2
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Rao GN, Jupudi S, Justin A. A Review on Neuroinflammatory Pathway Mediating Through Ang-II/AT1 Receptors and a Novel Approach for the Treatment of Cerebral Ischemia in Combination with ARB's and Ceftriaxone. Ann Neurosci 2024; 31:53-62. [PMID: 38584983 PMCID: PMC10996871 DOI: 10.1177/09727531231182554] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Accepted: 05/16/2023] [Indexed: 04/09/2024] Open
Abstract
Background Ischemic stroke is one of the prevalent neurodegenerative disorders; it is generally characterized by sudden abruption of blood flow due to thromboembolism and vascular abnormalities, eventually impairing the supply of oxygen and nutrients to the brain for its metabolic needs. Oxygen-glucose deprived conditions provoke the release of excessive glutamate, which causes excitotoxicity. Summary Recent studies suggest that circulatory angiotensin-II (Ang-II) has an imperative role in initiating detrimental events through binding central angiotensin 1 (AT1) receptors. Insufficient energy metabolites and essential ions often lead to oxidative stress during ischemic reperfusion, which leads to the release of proinflammatory mediators such as interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and cytokines like interleukin-18 (IL-18) and interleukin- 1beta (IL-1β). The transmembrane glutamate transporters, excitatory amino acid transporter-2 (EAAT-2), which express in astroglial cells, have a crucial role in the clearance of glutamate from its releasing site and convert glutamate into glutamine in normal circumstances of brain physiology. Key Message During cerebral ischemia, an impairment or dysfunction of EAAT-2 attributes the risk of delayed neuronal cell death. Earlier studies evidencing that angiotensin receptor blockers (ARB) attenuate neuroinflammation by inhibiting the Ang-II/AT1 receptor-mediated inflammatory pathway and that ceftriaxone ameliorates the excitotoxicity-induced neuronal deterioration by enhancing the transcription and expression of EAAT-2 via the nuclear transcriptional factor kappa-B (NF-kB) signaling pathway. The present review will briefly discuss the mechanisms involved in Ang-II/AT1-mediated neuroinflammation, ceftriaxone-induced EAAT-2 expression, and the repurposing hypothesis of the novel combination of ARBs and ceftriaxone for the treatment of cerebral ischemia.
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Affiliation(s)
- Gaddam Narasimha Rao
- Department of Pharmacology, JSS College of Pharmacy, JSS Academy of Higher Education & Research, Ooty, Nilgiris, Tamil Nadu, India
| | - Srikanth Jupudi
- Department of Pharmaceutical Chemistry, JSS College of Pharmacy, JSS Academy of Higher Education & Research, Ooty, Nilgiris, Tamil Nadu, India
| | - Antony Justin
- Department of Pharmacology, JSS College of Pharmacy, JSS Academy of Higher Education & Research, Ooty, Nilgiris, Tamil Nadu, India
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3
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Gebicke-Haerter PJ. The computational power of the human brain. Front Cell Neurosci 2023; 17:1220030. [PMID: 37608987 PMCID: PMC10441807 DOI: 10.3389/fncel.2023.1220030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Accepted: 07/05/2023] [Indexed: 08/24/2023] Open
Abstract
At the end of the 20th century, analog systems in computer science have been widely replaced by digital systems due to their higher computing power. Nevertheless, the question keeps being intriguing until now: is the brain analog or digital? Initially, the latter has been favored, considering it as a Turing machine that works like a digital computer. However, more recently, digital and analog processes have been combined to implant human behavior in robots, endowing them with artificial intelligence (AI). Therefore, we think it is timely to compare mathematical models with the biology of computation in the brain. To this end, digital and analog processes clearly identified in cellular and molecular interactions in the Central Nervous System are highlighted. But above that, we try to pinpoint reasons distinguishing in silico computation from salient features of biological computation. First, genuinely analog information processing has been observed in electrical synapses and through gap junctions, the latter both in neurons and astrocytes. Apparently opposed to that, neuronal action potentials (APs) or spikes represent clearly digital events, like the yes/no or 1/0 of a Turing machine. However, spikes are rarely uniform, but can vary in amplitude and widths, which has significant, differential effects on transmitter release at the presynaptic terminal, where notwithstanding the quantal (vesicular) release itself is digital. Conversely, at the dendritic site of the postsynaptic neuron, there are numerous analog events of computation. Moreover, synaptic transmission of information is not only neuronal, but heavily influenced by astrocytes tightly ensheathing the majority of synapses in brain (tripartite synapse). At least at this point, LTP and LTD modifying synaptic plasticity and believed to induce short and long-term memory processes including consolidation (equivalent to RAM and ROM in electronic devices) have to be discussed. The present knowledge of how the brain stores and retrieves memories includes a variety of options (e.g., neuronal network oscillations, engram cells, astrocytic syncytium). Also epigenetic features play crucial roles in memory formation and its consolidation, which necessarily guides to molecular events like gene transcription and translation. In conclusion, brain computation is not only digital or analog, or a combination of both, but encompasses features in parallel, and of higher orders of complexity.
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Affiliation(s)
- Peter J. Gebicke-Haerter
- Institute of Psychopharmacology, Central Institute of Mental Health, Faculty of Medicine, University of Heidelberg, Mannheim, Germany
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4
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Bonifacino T, Mingardi J, Facchinetti R, Sala N, Frumento G, Ndoj E, Valenza M, Paoli C, Ieraci A, Torazza C, Balbi M, Guerinoni M, Muhammad N, Russo I, Milanese M, Scuderi C, Barbon A, Steardo L, Bonanno G, Popoli M, Musazzi L. Changes at glutamate tripartite synapses in the prefrontal cortex of a new animal model of resilience/vulnerability to acute stress. Transl Psychiatry 2023; 13:62. [PMID: 36806044 PMCID: PMC9938874 DOI: 10.1038/s41398-023-02366-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Revised: 02/08/2023] [Accepted: 02/10/2023] [Indexed: 02/20/2023] Open
Abstract
Stress represents a main risk factor for psychiatric disorders. Whereas it is known that even a single trauma may induce psychiatric disorders in humans, the mechanisms of vulnerability to acute stressors have been little investigated. In this study, we generated a new animal model of resilience/vulnerability to acute footshock (FS) stress in rats and analyzed early functional, molecular, and morphological determinants of stress vulnerability at tripartite glutamate synapses in the prefrontal cortex (PFC). We found that adult male rats subjected to FS can be deemed resilient (FS-R) or vulnerable (FS-V), based on their anhedonic phenotype 24 h after stress exposure, and that these two populations are phenotypically distinguishable up to two weeks afterwards. Basal presynaptic glutamate release was increased in the PFC of FS-V rats, while depolarization-evoked glutamate release and synapsin I phosphorylation at Ser9 were increased in both FS-R and FS-V. In FS-R and FS-V rats the synaptic expression of GluN2A and apical dendritic length of prelimbic PFC layers II-III pyramidal neurons were decreased, while BDNF expression was selectively reduced in FS-V. Depolarization-evoked (carrier-mediated) glutamate release from astroglia perisynaptic processes (gliosomes) was selectively increased in the PFC of FS-V rats, while GLT1 and xCt levels were higher and GS expression reduced in purified PFC gliosomes from FS-R. Overall, we show for the first time that the application of the sucrose intake test to rats exposed to acute FS led to the generation of a novel animal model of resilience/vulnerability to acute stress, which we used to identify early determinants of maladaptive response related to behavioral vulnerability to stress.
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Affiliation(s)
- Tiziana Bonifacino
- grid.5606.50000 0001 2151 3065Department of Pharmacy, Unit of Pharmacology and Toxicology, University of Genoa, Genoa, Italy
| | - Jessica Mingardi
- grid.7563.70000 0001 2174 1754School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy ,grid.7637.50000000417571846Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - Roberta Facchinetti
- grid.7841.aDepartment of Physiology and Pharmacology “Vittorio Erspamer”, SAPIENZA University of Rome, Rome, Italy
| | - Nathalie Sala
- grid.4708.b0000 0004 1757 2822Laboratory of Neuropsychopharmacology and Functional Neurogenomics, Dipartimento di Scienze Farmaceutiche, Università Degli Studi di Milano, Milano, Italy
| | - Giulia Frumento
- grid.5606.50000 0001 2151 3065Department of Pharmacy, Unit of Pharmacology and Toxicology, University of Genoa, Genoa, Italy
| | - Elona Ndoj
- grid.7637.50000000417571846Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - Marta Valenza
- grid.7841.aDepartment of Physiology and Pharmacology “Vittorio Erspamer”, SAPIENZA University of Rome, Rome, Italy
| | - Caterina Paoli
- grid.7563.70000 0001 2174 1754School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy ,grid.5602.10000 0000 9745 6549Pharmacology Unit, School of Pharmacy, University of Camerino, Camerino, Italy
| | - Alessandro Ieraci
- grid.4708.b0000 0004 1757 2822Laboratory of Neuropsychopharmacology and Functional Neurogenomics, Dipartimento di Scienze Farmaceutiche, Università Degli Studi di Milano, Milano, Italy ,grid.449889.00000 0004 5945 6678Department of Theoretical and Applied Sciences, eCampus University, Novedrate, Como, Italy
| | - Carola Torazza
- grid.5606.50000 0001 2151 3065Department of Pharmacy, Unit of Pharmacology and Toxicology, University of Genoa, Genoa, Italy
| | - Matilde Balbi
- grid.5606.50000 0001 2151 3065Department of Pharmacy, Unit of Pharmacology and Toxicology, University of Genoa, Genoa, Italy
| | - Michele Guerinoni
- grid.4708.b0000 0004 1757 2822Laboratory of Neuropsychopharmacology and Functional Neurogenomics, Dipartimento di Scienze Farmaceutiche, Università Degli Studi di Milano, Milano, Italy
| | - Nadeem Muhammad
- grid.5606.50000 0001 2151 3065Department of Pharmacy, Unit of Pharmacology and Toxicology, University of Genoa, Genoa, Italy
| | - Isabella Russo
- grid.7637.50000000417571846Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy ,Genetics Unit, IRCCS Istituto Centro S. Giovanni di Dio, Fatebenefratelli, 25125 Brescia, Italy
| | - Marco Milanese
- grid.5606.50000 0001 2151 3065Department of Pharmacy, Unit of Pharmacology and Toxicology, University of Genoa, Genoa, Italy ,grid.410345.70000 0004 1756 7871IRCCS Ospedale Policlinico San Martino, Genoa, Italy
| | - Caterina Scuderi
- grid.7841.aDepartment of Physiology and Pharmacology “Vittorio Erspamer”, SAPIENZA University of Rome, Rome, Italy
| | - Alessandro Barbon
- grid.7637.50000000417571846Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - Luca Steardo
- grid.7841.aDepartment of Physiology and Pharmacology “Vittorio Erspamer”, SAPIENZA University of Rome, Rome, Italy
| | - Giambattista Bonanno
- grid.5606.50000 0001 2151 3065Department of Pharmacy, Unit of Pharmacology and Toxicology, University of Genoa, Genoa, Italy ,grid.410345.70000 0004 1756 7871IRCCS Ospedale Policlinico San Martino, Genoa, Italy
| | - Maurizio Popoli
- Laboratory of Neuropsychopharmacology and Functional Neurogenomics, Dipartimento di Scienze Farmaceutiche, Università Degli Studi di Milano, Milano, Italy.
| | - Laura Musazzi
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy.
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Boikov SI, Sibarov DA, Stepanenko YD, Karelina TV, Antonov SM. Calcium-Dependent Interplay of Lithium and Tricyclic Antidepressants, Amitriptyline and Desipramine, on N-methyl-D-aspartate Receptors. Int J Mol Sci 2022; 23:ijms232416177. [PMID: 36555818 PMCID: PMC9787943 DOI: 10.3390/ijms232416177] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 12/13/2022] [Accepted: 12/15/2022] [Indexed: 12/23/2022] Open
Abstract
The facilitated activity of N-methyl-D-aspartate receptors (NMDARs) in the central and peripheral nervous systems promotes neuropathic pain. Amitriptyline (ATL) and desipramine (DES) are tricyclic antidepressants (TCAs) whose anti-NMDAR properties contribute to their analgetic effects. At therapeutic concentrations <1 µM, these medicines inhibit NMDARs by enhancing their calcium-dependent desensitization (CDD). Li+, which suppresses the sodium−calcium exchanger (NCX) and enhances NMDAR CDD, also exhibits analgesia. Here, the effects of different [Li+]s on TCA inhibition of currents through native NMDARs in rat cortical neurons recorded by the patch-clamp technique were investigated. We demonstrated that the therapeutic [Li+]s of 0.5−1 mM cause an increase in ATL and DES IC50s of ~10 folds and ~4 folds, respectively, for the Ca2+-dependent NMDAR inhibition. The Ca2+-resistant component of NMDAR inhibition by TCAs, the open-channel block, was not affected by Li+. In agreement, clomipramine providing exclusively the NMDAR open-channel block is not sensitive to Li+. This Ca2+-dependent interplay between Li+, ATL, and DES could be determined by their competition for the same molecular target. Thus, submillimolar [Li+]s may weaken ATL and DES effects during combined therapy. The data suggest that Li+, ATL, and DES can enhance NMDAR CDD through NCX inhibition. This ability implies a drug−drug or ion−drug interaction when these medicines are used together therapeutically.
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Kilb W, Kirischuk S. GABA Release from Astrocytes in Health and Disease. Int J Mol Sci 2022; 23:ijms232415859. [PMID: 36555501 PMCID: PMC9784789 DOI: 10.3390/ijms232415859] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Revised: 12/06/2022] [Accepted: 12/10/2022] [Indexed: 12/15/2022] Open
Abstract
Astrocytes are the most abundant glial cells in the central nervous system (CNS) mediating a variety of homeostatic functions, such as spatial K+ buffering or neurotransmitter reuptake. In addition, astrocytes are capable of releasing several biologically active substances, including glutamate and GABA. Astrocyte-mediated GABA release has been a matter of debate because the expression level of the main GABA synthesizing enzyme glutamate decarboxylase is quite low in astrocytes, suggesting that low intracellular GABA concentration ([GABA]i) might be insufficient to support a non-vesicular GABA release. However, recent studies demonstrated that, at least in some regions of the CNS, [GABA]i in astrocytes might reach several millimoles both under physiological and especially pathophysiological conditions, thereby enabling GABA release from astrocytes via GABA-permeable anion channels and/or via GABA transporters operating in reverse mode. In this review, we summarize experimental data supporting both forms of GABA release from astrocytes in health and disease, paying special attention to possible feedback mechanisms that might govern the fine-tuning of astrocytic GABA release and, in turn, the tonic GABAA receptor-mediated inhibition in the CNS.
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Coppi E, Gibb AJ. Selective block of adenosine A 2A receptors prevents ischaemic-like effects induced by oxygen and glucose deprivation in rat medium spiny neurons. Br J Pharmacol 2022; 179:4844-4856. [PMID: 35817954 PMCID: PMC9796695 DOI: 10.1111/bph.15922] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 05/20/2022] [Accepted: 06/26/2022] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND AND PURPOSE Ischaemia is known to cause massive neuronal depolarization, termed anoxic depolarization (AD), due to energy failure and loss of membrane ion gradients. The neuromodulator adenosine accumulates extracellularly during ischaemia and activates four metabotropic receptors: A1 , A2A , A2B and A3 . Striatal medium spiny neurons (MSNs) express high levels of A2A receptors and are particularly vulnerable to ischaemic insults. A2A Receptor blockade reduces acute striatal post-ischaemic damage but the cellular mechanisms involved are still unknown. EXPERIMENTAL APPROACH We performed patch-clamp recordings of MSNs in rat striatal slices subjected to oxygen and glucose deprivation (OGD) to investigate the effects of A2A receptor ligands or ion channel blockers on AD and OGD-induced ionic imbalance, measured as a positive shift in Erev of ramp currents. KEY RESULTS Our data indicate that the A2A receptor antagonist SCH58261 (10 μM) significantly attenuated ionic imbalance and AD appearance in MSNs exposed to OGD. The K+ channel blocker Ba2+ (2 mM) or the Na+ channel blocker tetrodotoxin (1 μM) exacerbated and attenuated, respectively, OGD-induced changes. Spontaneous excitatory post-synaptic current (sEPSC) analysis in MSNs revealed that the A2A receptor agonist CGS21680 (1 μM) prevented OGD-induced decrease of sEPSCs within the first 5 min of the insult, an effect shared by the K+ channel blocker Ba2+ , indicating facilitated glutamate release. CONCLUSION AND IMPLICATIONS Adenosine, released during striatal OGD, activates A2A receptors that may exacerbate OGD-induced damage through K+ channel inhibition. Our results could help to develop A2A receptor-selective therapeutic tools for the treatment of brain ischaemia.
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Affiliation(s)
- Elisabetta Coppi
- Department of Neuroscience, Psychology, Drug Research and Child HealthUniversity of FlorenceFlorenceItaly
| | - Alasdair J. Gibb
- Department of Neuroscience, Physiology and PharmacologyUniversity College LondonLondonUK
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8
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The Involvement of Polyamines Catabolism in the Crosstalk between Neurons and Astrocytes in Neurodegeneration. Biomedicines 2022; 10:biomedicines10071756. [PMID: 35885061 PMCID: PMC9312548 DOI: 10.3390/biomedicines10071756] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Revised: 07/18/2022] [Accepted: 07/19/2022] [Indexed: 11/19/2022] Open
Abstract
In mammalian cells, the content of polyamines is tightly regulated. Polyamines, including spermine, spermidine and putrescine, are involved in many cellular processes. Spermine oxidase specifically oxidizes spermine, and its deregulated activity has been reported to be linked to brain pathologies involving neuron damage. Spermine is a neuromodulator of a number of ionotropic glutamate receptors and types of ion channels. In this respect, the Dach-SMOX mouse model overexpressing spermine oxidase in the neocortex neurons was revealed to be a model of chronic oxidative stress, excitotoxicity and neuronal damage. Reactive astrocytosis, chronic oxidative and excitotoxic stress, neuron loss and the susceptibility to seizure in the Dach-SMOX are discussed here. This genetic model would help researchers understand the linkage between polyamine dysregulation and neurodegeneration and unveil the roles of polyamines in the crosstalk between astrocytes and neurons in neuroprotection or neurodegeneration.
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Andrew RD, Farkas E, Hartings JA, Brennan KC, Herreras O, Müller M, Kirov SA, Ayata C, Ollen-Bittle N, Reiffurth C, Revah O, Robertson RM, Dawson-Scully KD, Ullah G, Dreier JP. Questioning Glutamate Excitotoxicity in Acute Brain Damage: The Importance of Spreading Depolarization. Neurocrit Care 2022; 37:11-30. [PMID: 35194729 PMCID: PMC9259542 DOI: 10.1007/s12028-021-01429-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Accepted: 12/20/2021] [Indexed: 02/02/2023]
Abstract
BACKGROUND Within 2 min of severe ischemia, spreading depolarization (SD) propagates like a wave through compromised gray matter of the higher brain. More SDs arise over hours in adjacent tissue, expanding the neuronal damage. This period represents a therapeutic window to inhibit SD and so reduce impending tissue injury. Yet most neuroscientists assume that the course of early brain injury can be explained by glutamate excitotoxicity, the concept that immediate glutamate release promotes early and downstream brain injury. There are many problems with glutamate release being the unseen culprit, the most practical being that the concept has yielded zero therapeutics over the past 30 years. But the basic science is also flawed, arising from dubious foundational observations beginning in the 1950s METHODS: Literature pertaining to excitotoxicity and to SD over the past 60 years is critiqued. RESULTS Excitotoxicity theory centers on the immediate and excessive release of glutamate with resulting neuronal hyperexcitation. This instigates poststroke cascades with subsequent secondary neuronal injury. By contrast, SD theory argues that although SD evokes some brief glutamate release, acute neuronal damage and the subsequent cascade of injury to neurons are elicited by the metabolic stress of SD, not by excessive glutamate release. The challenge we present here is to find new clinical targets based on more informed basic science. This is motivated by the continuing failure by neuroscientists and by industry to develop drugs that can reduce brain injury following ischemic stroke, traumatic brain injury, or sudden cardiac arrest. One important step is to recognize that SD plays a central role in promoting early neuronal damage. We argue that uncovering the molecular biology of SD initiation and propagation is essential because ischemic neurons are usually not acutely injured unless SD propagates through them. The role of glutamate excitotoxicity theory and how it has shaped SD research is then addressed, followed by a critique of its fading relevance to the study of brain injury. CONCLUSIONS Spreading depolarizations better account for the acute neuronal injury arising from brain ischemia than does the early and excessive release of glutamate.
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Affiliation(s)
| | - Eszter Farkas
- Hungarian Centre of Excellence for Molecular Medicine-University of Szeged, Cerebral Blood Flow and Metabolism Research Group, Department of Cell Biology and Molecular Medicine, University of Szeged, Szeged, Hungary
| | | | | | | | | | | | - Cenk Ayata
- Harvard Medical School, Harvard University, Boston, MA USA
| | | | - Clemens Reiffurth
- Center for Stroke Research Berlin, Berlin, Germany
- Department of Experimental Neurology, Charité – Universitätsmedizin Berlin, Berlin, Germany
| | - Omer Revah
- School of Medicine, Stanford University, Stanford, CA USA
| | | | | | | | - Jens P. Dreier
- Center for Stroke Research Berlin, Berlin, Germany
- Department of Experimental Neurology, Charité – Universitätsmedizin Berlin, Berlin, Germany
- Department of Neurology, Charité – Universitätsmedizin Berlin, Berlin, Germany
- Department of Neurology, Corporate Member of Freie Universität Berlin, Berlin, Germany
- Department of Neurology, Humboldt-Universität zu Berlin, Berlin, Germany
- Department of Neurology, Berlin Institute of Health, Berlin, Germany
- Bernstein Center for Computational Neuroscience Berlin, Berlin, Germany
- Einstein Center for Neurosciences Berlin, Berlin, Germany
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10
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Menyhárt Á, Frank R, Farkas AE, Süle Z, Varga VÉ, Nyúl-Tóth Á, Meiller A, Ivánkovits-Kiss O, Lemale CL, Szabó Í, Tóth R, Zölei-Szénási D, Woitzik J, Marinesco S, Krizbai IA, Bari F, Dreier JP, Farkas E. Malignant astrocyte swelling and impaired glutamate clearance drive the expansion of injurious spreading depolarization foci. J Cereb Blood Flow Metab 2022; 42:584-599. [PMID: 34427145 PMCID: PMC8943616 DOI: 10.1177/0271678x211040056] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Spreading depolarizations (SDs) indicate injury progression and predict worse clinical outcome in acute brain injury. We demonstrate in rodents that acute brain swelling upon cerebral ischemia impairs astroglial glutamate clearance and increases the tissue area invaded by SD. The cytotoxic extracellular glutamate accumulation (>15 µM) predisposes an extensive bulk of tissue (4-5 mm2) for a yet undescribed simultaneous depolarization (SiD). We confirm in rat brain slices exposed to osmotic stress that SiD is the pathological expansion of prior punctual SD foci (0.5-1 mm2), is associated with astrocyte swelling, and triggers oncotic neuron death. The blockade of astrocytic aquaporin-4 channels and Na+/K+/Cl- co-transporters, or volume-regulated anion channels mitigated slice edema, extracellular glutamate accumulation (<10 µM) and SiD occurrence. Reversal of slice swelling by hyperosmotic mannitol counteracted glutamate accumulation and prevented SiD. In contrast, inhibition of glial metabolism or inhibition of astrocyte glutamate transporters reproduced the SiD phenotype. Finally, we show in the rodent water intoxication model of cytotoxic edema that astrocyte swelling and altered astrocyte calcium waves are central in the evolution of SiD. We discuss our results in the light of evidence for SiD in the human cortex. Our results emphasize the need of preventive osmotherapy in acute brain injury.
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Affiliation(s)
- Ákos Menyhárt
- Department of Medical Physics and Informatics, Faculty of Medicine and Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
| | - Rita Frank
- Department of Medical Physics and Informatics, Faculty of Medicine and Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
| | - Attila E Farkas
- Neurovascular Unit Research Group, Molecular Neurobiology Research Unit, Institute of Biophysics, Biological Research Centre, Szeged, Hungary
| | - Zoltán Süle
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Viktória É Varga
- Department of Medical Physics and Informatics, Faculty of Medicine and Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
| | - Ádám Nyúl-Tóth
- Neurovascular Unit Research Group, Molecular Neurobiology Research Unit, Institute of Biophysics, Biological Research Centre, Szeged, Hungary.,Vascular Cognitive Impairment and Neurodegeneration Program, Reynolds Oklahoma Center on Aging/Oklahoma Center for Geroscience, Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Anne Meiller
- Lyon Neuroscience Research Center, Inserm U1028, CNRS UMR 5292, University Claude Bernard Lyon I, Lyon, France
| | - Orsolya Ivánkovits-Kiss
- Department of Medical Physics and Informatics, Faculty of Medicine and Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
| | - Coline L Lemale
- Center for Stroke Research Berlin, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany.,Department of Experimental Neurology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Írisz Szabó
- Department of Medical Physics and Informatics, Faculty of Medicine and Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
| | - Réka Tóth
- Department of Medical Physics and Informatics, Faculty of Medicine and Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
| | - Dániel Zölei-Szénási
- Department of Medical Physics and Informatics, Faculty of Medicine and Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
| | - Johannes Woitzik
- Department of Neurosurgery, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Stephane Marinesco
- Lyon Neuroscience Research Center, Inserm U1028, CNRS UMR 5292, University Claude Bernard Lyon I, Lyon, France
| | - István A Krizbai
- Neurovascular Unit Research Group, Molecular Neurobiology Research Unit, Institute of Biophysics, Biological Research Centre, Szeged, Hungary.,Institute of Life Sciences, Vasile Goldis Western University, Arad, Romania
| | - Ferenc Bari
- Department of Medical Physics and Informatics, Faculty of Medicine and Faculty of Science and Informatics, University of Szeged, Szeged, Hungary
| | - Jens P Dreier
- Center for Stroke Research Berlin, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany.,Department of Experimental Neurology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany.,Department of Neurology, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany.,Bernstein Center for Computational Neuroscience Berlin, Berlin, Germany.,Einstein Center for Neurosciences Berlin, Berlin, Germany
| | - Eszter Farkas
- HCEMM-USZ Cerebral Blood Flow and Metabolism Research Group, Szeged, Hungary.,Department of Cell Biology and Molecular Medicine, Faculty of Medicine and Faculty of Science and Informatics, University of Szeged,Szeged, Hungary
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11
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Marcoli M, Cervetto C, Amato S, Fiorucci C, Maura G, Mariottini P, Cervelli M. Transgenic Mouse Overexpressing Spermine Oxidase in Cerebrocortical Neurons: Astrocyte Dysfunction and Susceptibility to Epileptic Seizures. Biomolecules 2022; 12:204. [PMID: 35204705 PMCID: PMC8961639 DOI: 10.3390/biom12020204] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 01/20/2022] [Accepted: 01/21/2022] [Indexed: 02/06/2023] Open
Abstract
Polyamines are organic polycations ubiquitously present in living cells. Polyamines are involved in many cellular processes, and their content in mammalian cells is tightly controlled. Among their function, these molecules modulate the activity of several ion channels. Spermine oxidase, specifically oxidized spermine, is a neuromodulator of several types of ion channel and ionotropic glutamate receptors, and its deregulated activity has been linked to several brain pathologies, including epilepsy. The Dach-SMOX mouse line was generated using a Cre/loxP-based recombination approach to study the complex and critical functions carried out by spermine oxidase and spermine in the mammalian brain. This mouse genetic model overexpresses spermine oxidase in the neocortex and is a chronic model of excitotoxic/oxidative injury and neuron vulnerability to oxidative stress and excitotoxic, since its phenotype revealed to be more susceptible to different acute oxidative insults. In this review, the molecular mechanisms underlined the Dach-SMOX phenotype, linked to reactive astrocytosis, neuron loss, chronic oxidative and excitotoxic stress, and susceptibility to seizures have been discussed in detail. The Dach-SMOX mouse model overexpressing SMOX may help in shedding lights on the susceptibility to epileptic seizures, possibly helping to understand the mechanisms underlying epileptogenesis in vulnerable individuals and contributing to provide new molecular mechanism targets to search for novel antiepileptic drugs.
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Affiliation(s)
- Manuela Marcoli
- Department of Pharmacy, Section of Pharmacology and Toxicology, University of Genova, Viale Cembrano 4, 16148 Genoa, Italy; (S.A.); (G.M.)
- Interuniversity Center for the Promotion of the 3Rs Principles in Teaching and Research (Centro 3R), Lucio Lazzarino 1, 56122 Pisa, Italy
| | - Chiara Cervetto
- Department of Pharmacy, Section of Pharmacology and Toxicology, University of Genova, Viale Cembrano 4, 16148 Genoa, Italy; (S.A.); (G.M.)
- Interuniversity Center for the Promotion of the 3Rs Principles in Teaching and Research (Centro 3R), Lucio Lazzarino 1, 56122 Pisa, Italy
| | - Sarah Amato
- Department of Pharmacy, Section of Pharmacology and Toxicology, University of Genova, Viale Cembrano 4, 16148 Genoa, Italy; (S.A.); (G.M.)
| | - Cristian Fiorucci
- Department of Science, University of Rome “Roma Tre”, Viale Marconi 446, 00146 Rome, Italy; (C.F.); (P.M.)
| | - Guido Maura
- Department of Pharmacy, Section of Pharmacology and Toxicology, University of Genova, Viale Cembrano 4, 16148 Genoa, Italy; (S.A.); (G.M.)
| | - Paolo Mariottini
- Department of Science, University of Rome “Roma Tre”, Viale Marconi 446, 00146 Rome, Italy; (C.F.); (P.M.)
| | - Manuela Cervelli
- Department of Science, University of Rome “Roma Tre”, Viale Marconi 446, 00146 Rome, Italy; (C.F.); (P.M.)
- Neurodevelopment, Neurogenetics and Molecular Neurobiology Unit, IRCCS Fondazione Santa Lucia, Via del Fosso di Fiorano 64, 00143 Rome, Italy
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12
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Beckers P, Lara O, Belo do Nascimento I, Desmet N, Massie A, Hermans E. Validation of a System xc– Functional Assay in Cultured Astrocytes and Nervous Tissue Samples. Front Cell Neurosci 2022; 15:815771. [PMID: 35095428 PMCID: PMC8793334 DOI: 10.3389/fncel.2021.815771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Accepted: 12/24/2021] [Indexed: 11/13/2022] Open
Abstract
Disruption of the glutamatergic homeostasis is commonly observed in neurological diseases and has been frequently correlated with the altered expression and/or function of astrocytic high-affinity glutamate transporters. There is, however, a growing interest for the role of the cystine-glutamate exchanger system xc– in controlling glutamate transmission. This exchanger is predominantly expressed in glial cells, especially in microglia and astrocytes, and its dysregulation has been documented in diverse neurological conditions. While most studies have focused on measuring the expression of its specific subunit xCT by RT-qPCR or by Western blotting, the activity of this exchanger in tissue samples remains poorly examined. Indeed, the reported use of sulfur- and carbon-radiolabeled cystine in uptake assays shows several drawbacks related to its short radioactive half-life and its relatively high cost. We here report on the elaborate validation of a method using tritiated glutamate as a substrate for the reversed transport mediated by system xc–. The uptake assay was validated in primary cultured astrocytes, in transfected cells as well as in crude synaptosomes obtained from fresh nervous tissue samples. Working in buffers containing defined concentrations of Na+, allowed us to differentiate the glutamate uptake supported by system xc– or by high-affinity glutamate transporters, as confirmed by using selective pharmacological inhibitors. The specificity was further demonstrated in primary astrocyte cultures from transgenic mice lacking xCT or in cell lines where xCT expression was genetically induced or reduced. As such, this assay appears to be a robust and cost-efficient solution to investigate the activity of this exchanger in physiological and pathological conditions. It also provides a reliable tool for the screening and characterization of new system xc– inhibitors which have been frequently cited as valuable drugs for nervous disorders and cancer.
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Affiliation(s)
- Pauline Beckers
- Group of Neuropharmacology, Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium
| | - Olaya Lara
- Neuro-Aging & Viro-Immunotherapy, Center for Neurosciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Ines Belo do Nascimento
- Group of Neuropharmacology, Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium
| | - Nathalie Desmet
- Group of Neuropharmacology, Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium
| | - Ann Massie
- Neuro-Aging & Viro-Immunotherapy, Center for Neurosciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Emmanuel Hermans
- Group of Neuropharmacology, Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium
- *Correspondence: Emmanuel Hermans,
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13
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Andrew RD, Hartings JA, Ayata C, Brennan KC, Dawson-Scully KD, Farkas E, Herreras O, Kirov SA, Müller M, Ollen-Bittle N, Reiffurth C, Revah O, Robertson RM, Shuttleworth CW, Ullah G, Dreier JP. The Critical Role of Spreading Depolarizations in Early Brain Injury: Consensus and Contention. Neurocrit Care 2022; 37:83-101. [PMID: 35257321 PMCID: PMC9259543 DOI: 10.1007/s12028-021-01431-w] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Accepted: 12/29/2021] [Indexed: 02/02/2023]
Abstract
BACKGROUND When a patient arrives in the emergency department following a stroke, a traumatic brain injury, or sudden cardiac arrest, there is no therapeutic drug available to help protect their jeopardized neurons. One crucial reason is that we have not identified the molecular mechanisms leading to electrical failure, neuronal swelling, and blood vessel constriction in newly injured gray matter. All three result from a process termed spreading depolarization (SD). Because we only partially understand SD, we lack molecular targets and biomarkers to help neurons survive after losing their blood flow and then undergoing recurrent SD. METHODS In this review, we introduce SD as a single or recurring event, generated in gray matter following lost blood flow, which compromises the Na+/K+ pump. Electrical recovery from each SD event requires so much energy that neurons often die over minutes and hours following initial injury, independent of extracellular glutamate. RESULTS We discuss how SD has been investigated with various pitfalls in numerous experimental preparations, how overtaxing the Na+/K+ ATPase elicits SD. Elevated K+ or glutamate are unlikely natural activators of SD. We then turn to the properties of SD itself, focusing on its initiation and propagation as well as on computer modeling. CONCLUSIONS Finally, we summarize points of consensus and contention among the authors as well as where SD research may be heading. In an accompanying review, we critique the role of the glutamate excitotoxicity theory, how it has shaped SD research, and its questionable importance to the study of early brain injury as compared with SD theory.
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Affiliation(s)
- R. David Andrew
- grid.410356.50000 0004 1936 8331Queen’s University, Kingston, ON Canada
| | - Jed A. Hartings
- grid.24827.3b0000 0001 2179 9593University of Cincinnati, Cincinnati, OH USA
| | - Cenk Ayata
- grid.38142.3c000000041936754XHarvard Medical School, Harvard University, Boston, MA USA
| | - K. C. Brennan
- grid.223827.e0000 0001 2193 0096The University of Utah, Salt Lake City, UT USA
| | | | - Eszter Farkas
- grid.9008.10000 0001 1016 96251HCEMM-USZ Cerebral Blood Flow and Metabolism Research Group, and the Department of Cell Biology and Molecular Medicine, Faculty of Science and Informatics & Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Oscar Herreras
- grid.419043.b0000 0001 2177 5516Instituto de Neurobiologia Ramon Y Cajal (Consejo Superior de Investigaciones Científicas), Madrid, Spain
| | - Sergei. A. Kirov
- grid.410427.40000 0001 2284 9329Medical College of Georgia, Augusta, GA USA
| | - Michael Müller
- grid.411984.10000 0001 0482 5331University of Göttingen, University Medical Center Göttingen, Göttingen, Germany
| | - Nikita Ollen-Bittle
- grid.39381.300000 0004 1936 8884University of Western Ontario, London, ON Canada
| | - Clemens Reiffurth
- grid.7468.d0000 0001 2248 7639Center for Stroke Research Berlin, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health; and the Department of Experimental Neurology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health., Berlin, Germany
| | - Omer Revah
- grid.168010.e0000000419368956School of Medicine, Stanford University, Stanford, CA USA
| | | | | | - Ghanim Ullah
- grid.170693.a0000 0001 2353 285XUniversity of South Florida, Tampa, FL USA
| | - Jens P. Dreier
- grid.7468.d0000 0001 2248 7639Center for Stroke Research Berlin, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health; and the Department of Experimental Neurology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health., Berlin, Germany
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14
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Abstract
Drug addiction remains a key biomedical challenge facing current neuroscience research. In addition to neural mechanisms, the focus of the vast majority of studies to date, astrocytes have been increasingly recognized as an "accomplice." According to the tripartite synapse model, astrocytes critically regulate nearby pre- and postsynaptic neuronal substrates to craft experience-dependent synaptic plasticity, including synapse formation and elimination. Astrocytes within brain regions that are implicated in drug addiction exhibit dynamic changes in activity upon exposure to cocaine and subsequently undergo adaptive changes themselves during chronic drug exposure. Recent results have identified several key astrocytic signaling pathways that are involved in cocaine-induced synaptic and circuit adaptations. In this review, we provide a brief overview of the role of astrocytes in regulating synaptic transmission and neuronal function, and discuss how cocaine influences these astrocyte-mediated mechanisms to induce persistent synaptic and circuit alterations that promote cocaine seeking and relapse. We also consider the therapeutic potential of targeting astrocytic substrates to ameliorate drug-induced neuroplasticity for behavioral benefits. While primarily focusing on cocaine-induced astrocytic responses, we also include brief discussion of other drugs of abuse where data are available.
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15
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Wang J, Zhang K, Goyal P, Grewer C. Mechanism and potential sites of potassium interaction with glutamate transporters. J Gen Physiol 2021; 152:152037. [PMID: 32835376 PMCID: PMC7537348 DOI: 10.1085/jgp.202012577] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Accepted: 08/03/2020] [Indexed: 12/21/2022] Open
Abstract
In the mammalian glutamate transporters, countertransported intracellular K+ is essential for relocating the glutamate binding site to the extracellular side of the membrane. This K+-dependent process is believed to be rate limiting for the transport cycle. In contrast, extracellular K+ induces glutamate release upon transporter reversal. Here, we analyzed potential K+ binding sites using molecular dynamics (MD) simulations and site-directed mutagenesis. Two candidate sites were identified by spontaneous K+ binding in MD simulations, one site (K1 site) overlapping with the Na1 Na+ binding site and the K2 site being localized under hairpin loop 2 (HP2). Mutations to conserved amino acid residues in these sites resulted in several transporters that were defective in K+-induced reverse transport and which bound K+ with reduced apparent affinity compared with the wild-type transporter. However, external K+ interaction was abolished in only one mutant transporter EAAC1D454A in the K1 site. Our results, for the first time, directly demonstrate effects of K1-site mutations on K+ binding, in contrast to previous reports on K+ binding sites based on indirect evidence. We propose that K+ binding to the K1 site is responsible for catalyzing the relocation step, whereas binding to the K2 site may have an as-of-yet unidentified regulatory function.
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Affiliation(s)
- Jiali Wang
- Department of Chemistry, Binghamton University, Binghamton, NY
| | - Kaiqi Zhang
- Department of Chemistry, Binghamton University, Binghamton, NY
| | - Puja Goyal
- Department of Chemistry, Binghamton University, Binghamton, NY
| | - Christof Grewer
- Department of Chemistry, Binghamton University, Binghamton, NY
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16
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Sergeeva EG, Rosenberg PA, Benowitz LI. Non-Cell-Autonomous Regulation of Optic Nerve Regeneration by Amacrine Cells. Front Cell Neurosci 2021; 15:666798. [PMID: 33935656 PMCID: PMC8085350 DOI: 10.3389/fncel.2021.666798] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 03/19/2021] [Indexed: 11/13/2022] Open
Abstract
Visual information is conveyed from the eye to the brain through the axons of retinal ganglion cells (RGCs) that course through the optic nerve and synapse onto neurons in multiple subcortical visual relay areas. RGCs cannot regenerate their axons once they are damaged, similar to most mature neurons in the central nervous system (CNS), and soon undergo cell death. These phenomena of neurodegeneration and regenerative failure are widely viewed as being determined by cell-intrinsic mechanisms within RGCs or to be influenced by the extracellular environment, including glial or inflammatory cells. However, a new concept is emerging that the death or survival of RGCs and their ability to regenerate axons are also influenced by the complex circuitry of the retina and that the activation of a multicellular signaling cascade involving changes in inhibitory interneurons - the amacrine cells (AC) - contributes to the fate of RGCs. Here, we review our current understanding of the role that interneurons play in cell survival and axon regeneration after optic nerve injury.
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Affiliation(s)
- Elena G. Sergeeva
- Department of Neurology, Boston Children’s Hospital, Boston, MA, United States
- Kirby Center for Neuroscience, Boston Children’s Hospital, Boston, MA, United States
- Department of Neurology, Harvard Medical School, Boston, MA, United States
| | - Paul A. Rosenberg
- Department of Neurology, Boston Children’s Hospital, Boston, MA, United States
- Kirby Center for Neuroscience, Boston Children’s Hospital, Boston, MA, United States
- Department of Neurology, Harvard Medical School, Boston, MA, United States
| | - Larry I. Benowitz
- Kirby Center for Neuroscience, Boston Children’s Hospital, Boston, MA, United States
- Laboratories for Neuroscience Research in Neurosurgery, Boston Children’s Hospital, Boston, MA, United States
- Department of Neurosurgery, Boston Children’s Hospital, Boston, MA, United States
- Department of Neurosurgery, Harvard Medical School, Boston, MA, United States
- Department of Ophthalmology, Harvard Medical School, Boston, MA, United States
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17
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Sears SM, Hewett SJ. Influence of glutamate and GABA transport on brain excitatory/inhibitory balance. Exp Biol Med (Maywood) 2021; 246:1069-1083. [PMID: 33554649 DOI: 10.1177/1535370221989263] [Citation(s) in RCA: 76] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
An optimally functional brain requires both excitatory and inhibitory inputs that are regulated and balanced. A perturbation in the excitatory/inhibitory balance-as is the case in some neurological disorders/diseases (e.g. traumatic brain injury Alzheimer's disease, stroke, epilepsy and substance abuse) and disorders of development (e.g. schizophrenia, Rhett syndrome and autism spectrum disorder)-leads to dysfunctional signaling, which can result in impaired cognitive and motor function, if not frank neuronal injury. At the cellular level, transmission of glutamate and GABA, the principle excitatory and inhibitory neurotransmitters in the central nervous system control excitatory/inhibitory balance. Herein, we review the synthesis, release, and signaling of GABA and glutamate followed by a focused discussion on the importance of their transport systems to the maintenance of excitatory/inhibitory balance.
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Affiliation(s)
- Sheila Ms Sears
- Department of Biology, Program in Neuroscience, 2029Syracuse University, Syracuse, NY 13244, USA
| | - Sandra J Hewett
- Department of Biology, Program in Neuroscience, 2029Syracuse University, Syracuse, NY 13244, USA
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18
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Wang J, Zielewicz L, Dong Y, Grewer C. Pre-Steady-State Kinetics and Reverse Transport in Rat Glutamate Transporter EAAC1 with an Immobilized Transport Domain. Neurochem Res 2021; 47:148-162. [PMID: 33550531 DOI: 10.1007/s11064-021-03247-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Revised: 01/15/2021] [Accepted: 01/18/2021] [Indexed: 01/01/2023]
Abstract
Plasma membrane glutamate transporters move glutamate across the cell membrane in a process that is thought to involve elevator-like movement of the transport domain relative to the static trimerization domain. Conformational changes associated with this elevator-like movement have been blocked by covalent crosslinking of cysteine pairs inserted strategically in several positions in the transporter structure, resulting in inhibition of steady-state transport activity. However, it is not known how these crosslinking restraints affect other partial reactions of the transporter that were identified based on pre-steady-state kinetic analysis. Here, we re-examine two different introduced cysteine pairs in the rat glutamate transporter EAAC1 recombinantely expressed in HEK293 cells, W440C/K268C and K64C/V419C, with respect to the molecular mechanism of their impairment of transporter function. Pre-steady-state kinetic studies of glutamate-induced partial reactions were performed using laser photolysis of caged glutamate to achieve sub-millisecond time resolution. Crosslinking of both cysteine pairs abolished steady-state transport current, as well as the majority of pre-steady-state glutamate-induced charge movements, in both forward and reverse transport mode, suggesting that it is not only the elevator-like movement associated with translocation, but also other transporter partial reactions that are inhibited. In contrast, sodium binding to the empty transporter, and glutamate-induced anion conductance were still intact after the W440C/K268C crosslink. Our results add to the previous mechanistic view of how covalent restraints of the transporter affect function and structural changes linked to individual steps in the transport cycle.
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Affiliation(s)
- Jiali Wang
- Department of Chemistry, Binghamton University, 4400 Vestal Parkway East, Binghamton, NY, 13902, USA
| | - Laura Zielewicz
- Department of Chemistry, Binghamton University, 4400 Vestal Parkway East, Binghamton, NY, 13902, USA
| | - Yang Dong
- Department of Chemistry, Binghamton University, 4400 Vestal Parkway East, Binghamton, NY, 13902, USA
| | - Christof Grewer
- Department of Chemistry, Binghamton University, 4400 Vestal Parkway East, Binghamton, NY, 13902, USA.
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19
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Verhoog QP, Holtman L, Aronica E, van Vliet EA. Astrocytes as Guardians of Neuronal Excitability: Mechanisms Underlying Epileptogenesis. Front Neurol 2020; 11:591690. [PMID: 33324329 PMCID: PMC7726323 DOI: 10.3389/fneur.2020.591690] [Citation(s) in RCA: 73] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Accepted: 10/26/2020] [Indexed: 12/11/2022] Open
Abstract
Astrocytes are key homeostatic regulators in the central nervous system and play important roles in physiology. After brain damage caused by e.g., status epilepticus, traumatic brain injury, or stroke, astrocytes may adopt a reactive phenotype. This process of reactive astrogliosis is important to restore brain homeostasis. However, persistent reactive astrogliosis can be detrimental for the brain and contributes to the development of epilepsy. In this review, we will focus on physiological functions of astrocytes in the normal brain as well as pathophysiological functions in the epileptogenic brain, with a focus on acquired epilepsy. We will discuss the role of astrocyte-related processes in epileptogenesis, including reactive astrogliosis, disturbances in energy supply and metabolism, gliotransmission, and extracellular ion concentrations, as well as blood-brain barrier dysfunction and dysregulation of blood flow. Since dysfunction of astrocytes can contribute to epilepsy, we will also discuss their role as potential targets for new therapeutic strategies.
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Affiliation(s)
- Quirijn P. Verhoog
- Leiden Academic Center for Drug Research, Leiden University, Leiden, Netherlands
- Department of Neuropathology, Amsterdam Neuroscience, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Linda Holtman
- Leiden Academic Center for Drug Research, Leiden University, Leiden, Netherlands
| | - Eleonora Aronica
- Department of Neuropathology, Amsterdam Neuroscience, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
- Stichting Epilepsie Instellingen Nederland (SEIN), Heemstede, Netherlands
| | - Erwin A. van Vliet
- Department of Neuropathology, Amsterdam Neuroscience, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
- Center for Neuroscience, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, Netherlands
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20
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Kim HB, Yoo JY, Yoo SY, Lee JH, Chang W, Kim HS, Baik TK, Woo RS. Neuregulin-1 inhibits CoCl 2-induced upregulation of excitatory amino acid carrier 1 expression and oxidative stress in SH-SY5Y cells and the hippocampus of mice. Mol Brain 2020; 13:153. [PMID: 33187547 PMCID: PMC7664014 DOI: 10.1186/s13041-020-00686-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Accepted: 10/09/2020] [Indexed: 11/10/2022] Open
Abstract
Excitatory amino acid carrier 1 (EAAC1) is an important subtype of excitatory amino acid transporters (EAATs) and is the route for neuronal cysteine uptake. CoCl2 is not only a hypoxia-mimetic reagent but also an oxidative stress inducer. Here, we found that CoCl2 induced significant EAAC1 overexpression in SH-SY5Y cells and the hippocampus of mice. Transient transfection of EAAC1 reduced CoCl2-induced cytotoxicity in SH-SY5Y cells. Based on this result, upregulation of EAAC1 expression by CoCl2 is thought to represent a compensatory response against oxidative stress in an acute hypoxic state. We further demonstrated that pretreatment with Neuregulin-1 (NRG1) rescued CoCl2-induced upregulation of EAAC1 and tau expression. NRG1 plays a protective role in the CoCl2-induced accumulation of reactive oxygen species (ROS) and reduction in antioxidative enzyme (SOD and GPx) activity. Moreover, NRG1 attenuated CoCl2-induced apoptosis and cell death. NRG1 inhibited the CoCl2-induced release of cleaved caspase-3 and reduction in Bcl-XL levels. Our novel finding suggests that NRG1 may play a protective role in hypoxia through the inhibition of oxidative stress and thereby maintain normal EAAC1 expression levels.
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Affiliation(s)
- Han-Byeol Kim
- Department of Anatomy and Neuroscience, College of Medicine, Eulji University, 143-5Jung-Gu, Yongdu-Dong, Daejeon, 301-746, Republic of Korea
| | - Ji-Young Yoo
- Department of Anatomy and Neuroscience, College of Medicine, Eulji University, 143-5Jung-Gu, Yongdu-Dong, Daejeon, 301-746, Republic of Korea
| | - Seung-Yeon Yoo
- Department of Anatomy and Neuroscience, College of Medicine, Eulji University, 143-5Jung-Gu, Yongdu-Dong, Daejeon, 301-746, Republic of Korea
| | - Jun-Ho Lee
- Department of Emergency Medical Technology, Daejeon University, Daejeon, 34520, Republic of Korea
| | - Wonseok Chang
- Department of Physiology, College of Medicine, Eulji University, Daejeon, 301-746, Republic of Korea
| | - Hye-Sun Kim
- Department of Pharmacology, College of Medicine, Seoul National University, Seoul, 110-799, Korea.,Seoul National University College of Medicine, Bundang Hospital, Sungnam, 13620, Republic of Korea
| | - Tai-Kyoung Baik
- Department of Anatomy and Neuroscience, College of Medicine, Eulji University, 143-5Jung-Gu, Yongdu-Dong, Daejeon, 301-746, Republic of Korea.
| | - Ran-Sook Woo
- Department of Anatomy and Neuroscience, College of Medicine, Eulji University, 143-5Jung-Gu, Yongdu-Dong, Daejeon, 301-746, Republic of Korea.
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21
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Li C, Huang L, Jia X, Zhao B, Chen L, Liu Y. Functional glutamate transporters are expressed in the carotid chemoreceptor. Respir Res 2020; 21:208. [PMID: 32771007 PMCID: PMC7414757 DOI: 10.1186/s12931-020-01468-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 07/23/2020] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND The carotid body (CB) plays a critical role in cyclic intermittent hypoxia (CIH)-induced chemosensitivity; however, the underlying mechanism remains uncertain. We have demonstrated the presence of multiple inotropic glutamate receptors (iGluRs) in CB, and that CIH exposure alters the level of some iGluRs in CB. This result implicates glutamatergic signaling in the CB response to hypoxia. The glutamatergic neurotransmission is not only dependent on glutamate and glutamate receptors, but is also dependent on glutamate transporters, including vesicular glutamate transporters (VGluTs) and excitatory amino acid transporters (EAATs). Here, we have further assessed the expression and distribution of VGluTs and EAATs in human and rat CB and the effect of CIH exposure on glutamate transporters expression. METHODS The mRNA of VGluTs and EAATs in the human CB were detected by RT-PCR. The protein expression of VGluTs and EAATs in the human and rat CB were detected by Western blot. The distribution of VGluT3, EAAT2 and EAAT3 were observed by immunohistochemistry staining and immunofluorescence staining. Male Sprague-Dawley (SD) rats were exposed to CIH (FIO2 10-21%, 3 min/3 min for 8 h per day) for 2 weeks. The unpaired Student's t-test was performed. RESULTS Here, we report on the presence of mRNAs for VGluT1-3 and EAAT1-3 in human CB, which is consistent with our previous results in rat CB. The proteins of VGluT1 and 3, EAAT2 and 3, but not VGluT2 and EAAT1, were detected with diverse levels in human and rat CB. Immunostaining showed that VGluT3, the major type of VGluTs in CB, was co-localized with tyrosine hydroxylase (TH) in type I cells. EAAT2 and EAAT3 were distributed not only in type I cells, but also in glial fibrillary acidic protein (GFAP) positive type II cells. Moreover, we found that exposure of SD rats to CIH enhanced the protein level of EAAT3 as well as TH, but attenuated the levels of VGluT3 and EAAT2 in CB. CONCLUSIONS Our study suggests that glutamate transporters are expressed in the CB, and that glutamate transporters may contribute to glutamatergic signaling-dependent carotid chemoreflex to CIH.
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Affiliation(s)
- Chaohong Li
- The First Affiliated Hospital of Xinxiang Medical University, Henan Key Laboratory of Neural Regeneration and Repairment, Henan Neurology Institute, 88 Jiankang Road, Weihui, 453100, Henan, China
| | - Lu Huang
- The First Affiliated Hospital of Xinxiang Medical University, Henan Key Laboratory of Neural Regeneration and Repairment, Henan Neurology Institute, 88 Jiankang Road, Weihui, 453100, Henan, China
| | - Xianglei Jia
- The First Affiliated Hospital of Xinxiang Medical University, Henan Key Laboratory of Neural Regeneration and Repairment, Henan Neurology Institute, 88 Jiankang Road, Weihui, 453100, Henan, China
| | - Baosheng Zhao
- Department of Thoracic Surgery, The First Affiliated Hospital of Xinxiang Medical University, Weihui, Henan, China
| | - Lingyun Chen
- Operating Room, The First Affiliated Hospital of Xinxiang Medical University, Weihui, Henan, China
| | - Yuzhen Liu
- The First Affiliated Hospital of Xinxiang Medical University, Henan Key Laboratory of Neural Regeneration and Repairment, Henan Neurology Institute, 88 Jiankang Road, Weihui, 453100, Henan, China.
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22
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Octeau JC, Gangwani MR, Allam SL, Tran D, Huang S, Hoang-Trong TM, Golshani P, Rumbell TH, Kozloski JR, Khakh BS. Transient, Consequential Increases in Extracellular Potassium Ions Accompany Channelrhodopsin2 Excitation. Cell Rep 2020; 27:2249-2261.e7. [PMID: 31116972 PMCID: PMC6582980 DOI: 10.1016/j.celrep.2019.04.078] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 03/04/2019] [Accepted: 04/17/2019] [Indexed: 12/13/2022] Open
Abstract
Channelrhodopsin2 (ChR2) optogenetic excitation is widely used to study neurons, astrocytes, and circuits. Using complementary approaches in situ and in vivo, we found that ChR2 stimulation leads to significant transient elevation of extracellular potassium ions by ~5 mM. Such elevations were detected in ChR2-expressing mice, following local in vivo expression of ChR2(H134R) with adeno-associated viruses (AAVs), in different brain areas and when ChR2 was expressed in neurons or astrocytes. In particular, ChR2-mediated excitation of striatal astrocytes was sufficient to increase medium spiny neuron (MSN) excitability and immediate early gene expression. The effects on MSN excitability were recapitulated in silico with a computational MSN model and detected in vivo as increased action potential firing in awake, behaving mice. We show that transient, physiologically consequential increases in extracellular potassium ions accompany ChR2 optogenetic excitation. This coincidental effect may be important to consider during astrocyte studies employing ChR2 to interrogate neural circuits and animal behavior. Using multiple approaches, Octeau et al. discover that optogenetic excitation of ChR2-expressing cells leads to significant transient extracellular potassium ion elevations that increase neuronal excitability and immediate early gene expression in neurons following in vivo stimulation.
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Affiliation(s)
- J Christopher Octeau
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Mohitkumar R Gangwani
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Sushmita L Allam
- IBM T.J. Watson Research Center, P.O. Box 218, 1101 Kitchawan Road, Yorktown Heights, NY 10598, USA
| | - Duy Tran
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Shuhan Huang
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Tuan M Hoang-Trong
- IBM T.J. Watson Research Center, P.O. Box 218, 1101 Kitchawan Road, Yorktown Heights, NY 10598, USA
| | - Peyman Golshani
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Intellectual and Developmental Disabilities Research Center, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Center for Neurobehavioral Genetics, Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Timothy H Rumbell
- IBM T.J. Watson Research Center, P.O. Box 218, 1101 Kitchawan Road, Yorktown Heights, NY 10598, USA
| | - James R Kozloski
- IBM T.J. Watson Research Center, P.O. Box 218, 1101 Kitchawan Road, Yorktown Heights, NY 10598, USA
| | - Baljit S Khakh
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA.
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23
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Niello M, Gradisch R, Loland CJ, Stockner T, Sitte HH. Allosteric Modulation of Neurotransmitter Transporters as a Therapeutic Strategy. Trends Pharmacol Sci 2020; 41:446-463. [PMID: 32471654 PMCID: PMC7610661 DOI: 10.1016/j.tips.2020.04.006] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 04/21/2020] [Accepted: 04/22/2020] [Indexed: 12/11/2022]
Abstract
Neurotransmitter transporters (NTTs) are involved in the fine-tuning of brain neurotransmitter homeostasis. As such, they are implicated in a plethora of complex behaviors, including reward, movement, and cognition. During recent decades, compounds that modulate NTT functions have been developed. Some of them are in clinical use for the management of different neuropsychiatric conditions. The majority of these compounds have been found to selectively interact with the orthosteric site of NTTs. Recently, diverse allosteric sites have been described in a number of NTTs, modulating their function. A more complex NTT pharmacology may be useful in the development of novel therapeutics. Here, we summarize current knowledge on such modulatory allosteric sites, with specific focus on their pharmacological and therapeutic potential.
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Affiliation(s)
- Marco Niello
- Centre for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Ralph Gradisch
- Centre for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Claus Juul Loland
- Laboratory for Membrane Protein Dynamics. Department of Neuroscience. University of Copenhagen, Copenhagen, Denmark
| | - Thomas Stockner
- Centre for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Harald H Sitte
- Centre for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Vienna, Austria; AddRess, Centre for Addiction Research and Science, Medical University of Vienna, Vienna, Austria.
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24
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Aizawa H, Sun W, Sugiyama K, Itou Y, Aida T, Cui W, Toyoda S, Terai H, Yanagisawa M, Tanaka K. Glial glutamate transporter GLT-1 determines susceptibility to spreading depression in the mouse cerebral cortex. Glia 2020; 68:2631-2642. [PMID: 32585762 DOI: 10.1002/glia.23874] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 06/01/2020] [Accepted: 06/04/2020] [Indexed: 12/26/2022]
Abstract
Cortical spreading depression (CSD) is a pathological neural excitation that underlies migraine pathophysiology. Since glutamate receptor antagonists impair CSD propagation, susceptibility to CSD might be determined by any of the neuronal (excitatory amino acid carrier 1 [EAAC1]) and glial (GLutamate ASpartate Transporter [GLAST] and glial glutamate transporter 1 [GLT-1]) glutamate transporters, which are responsible for clearing extracellular glutamate. To investigate this hypothesis, we performed electrophysiological, hemodynamic, and electrochemical analyses using EAAC1- (EAAC1 KO), GLAST- (GLAST KO), and conditional GLT1-1-knockout mice (GLT-1 cKO) to assess altered susceptibility to CSD. Despite the incomplete deletion of the gene in the cerebral cortex, GLT-1 cKO mice exhibited significant reduction of GLT-1 protein in the brain without apparent alteration of the cytoarchitecture in the cerebral cortex. Physiological analysis revealed that GLT-1 cKO showed enhanced susceptibility to CSD elicited by chemical stimulation with increased CSD frequency and velocity compared to GLT-1 control. In contrast, the germ-line EAAC1 and GLAST KOs showed no such effect. Intriguingly, both field potential and cerebral blood flow showed faster dynamics with narrower CSD than the controls. An enzyme-based biosensor revealed more rapid accumulation of glutamate in the extracellular space in GLT-1 cKO mice during the early phase of CSD than in GLT-1 control, resulting in an increased susceptibility to CSD. These results provided the first evidence for a novel role of GLT-1 in determining susceptibility to CSD.
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Affiliation(s)
- Hidenori Aizawa
- Laboratory of Molecular Neuroscience, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan.,Department of Neurobiology, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Weinan Sun
- Laboratory of Molecular Neuroscience, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Kaori Sugiyama
- Laboratory of Molecular Neuroscience, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Yukiko Itou
- Laboratory of Molecular Neuroscience, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Tomomi Aida
- Laboratory of Molecular Neuroscience, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Wanpeng Cui
- Laboratory of Molecular Neuroscience, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan.,Department of Neurobiology, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Saori Toyoda
- Laboratory of Molecular Neuroscience, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Haruhi Terai
- Department of Neurobiology, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Michiko Yanagisawa
- Laboratory of Molecular Neuroscience, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Kohichi Tanaka
- Laboratory of Molecular Neuroscience, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan.,Center for Brain Integration Research, Tokyo Medical and Dental University, Tokyo, Japan
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25
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Pathway analysis of glutamate-mediated, calcium-related signaling in glioma progression. Biochem Pharmacol 2020; 176:113814. [PMID: 31954716 DOI: 10.1016/j.bcp.2020.113814] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Accepted: 01/13/2020] [Indexed: 12/18/2022]
Abstract
Brain tumors, particularly high-grade glioblastomas, are a crucial public health issue due to poor prognosis and an extremely low survival rate. The glioblastoma multiforme (GBM) grows rapidly within its unique microenvironment that is characterized by active neural communications. Therefore, diverse neurotransmitters not only maintain normal brain functions but also influence glioma progression. To fully appreciate the relationship between neurotransmitters and glioma progression, we reviewed potential neurotransmitter contributors in human GBM and the much less aggressive Low-grade glioma (LGG) by combining previously published data from gene-mutation/mRNA sequencing databases together with protein-protein interaction (PPI) network analysis results. The summarized results indicate that glutamatergic and calcium signaling may provide positive feedback to promote glioma formation through 1) metabolic reprogramming and genetic switching to accelerate glioma duplication and progression; 2) upregulation of cytoskeleton proteins and elevation of intracellular Ca2+ levels to increase glutamate release and facilitate formation of synaptic-like connections with surrounding cells in their microenvironment. The upregulated glutamatergic neuronal activities in turn stimulate glioma growth and signaling. Importantly, the enhanced electrical and molecular signals from both neurons and glia propagate out to enable glioma symptoms such as epilepsy and migraine. The elevated intracellular Ca2+ also activates nitric oxide synthase to produce nitric oxide (NO) that can either promote or inhibit tumorigenesis. By analyzing the network effects for complex interaction among neurotransmitters such as glutamate, Ca2+ and NO in brain tumor progression, especially GBM, we identified the glutamatergic signaling as the potential therapeutic targets and suggest manipulation of glutamatergic signaling may be an effective treatment strategy for this aggressive brain cancer.
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26
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Abstract
In the peripheral nervous system, the vast majority of axons are accommodated within the fibre bundles that constitute the peripheral nerves. Axons within the nerves are in close contact with myelinating glia, the Schwann cells that are ideally placed to respond to, and possibly shape, axonal activity. The mechanisms of intercellular communication in the peripheral nerves may involve direct contact between the cells, as well as signalling via diffusible substances. Neurotransmitter glutamate has been proposed as a candidate extracellular molecule mediating the cross-talk between cells in the peripheral nerves. Two types of experimental findings support this idea: first, glutamate has been detected in the nerves and can be released upon electrical or chemical stimulation of the nerves; second, axons and Schwann cells in the peripheral nerves express glutamate receptors. Yet, the studies providing direct experimental evidence that intercellular glutamatergic signalling takes place in the peripheral nerves during physiological or pathological conditions are largely missing. Remarkably, in the central nervous system, axons and myelinating glia are involved in glutamatergic signalling. This signalling occurs via different mechanisms, the most intriguing of which is fast synaptic communication between axons and oligodendrocyte precursor cells. Glutamate receptors and/or synaptic axon-glia signalling are involved in regulation of proliferation, migration, and differentiation of oligodendrocyte precursor cells, survival of oligodendrocytes, and re-myelination of axons after damage. Does synaptic signalling exist between axons and Schwann cells in the peripheral nerves? What is the functional role of glutamate receptors in the peripheral nerves? Is activation of glutamate receptors in the nerves beneficial or harmful during diseases? In this review, we summarise the limited information regarding glutamate release and glutamate receptors in the peripheral nerves and speculate about possible mechanisms of glutamatergic signalling in the nerves. We highlight the necessity of further research on this topic because it should help to understand the mechanisms of peripheral nervous system development and nerve regeneration during diseases.
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Affiliation(s)
- Ting-Jiun Chen
- Center for Neuroscience Research, Children's Research Institute, Children's National Medical Centre, Washington, DC, USA
| | - Maria Kukley
- Group of Neuron Glia Interaction, University of Tübingen; Research Institute of Ophthalmology, Tübingen University Hospital, Tübingen, Germany
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27
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Verkhratsky A, Rose CR. Na +-dependent transporters: The backbone of astroglial homeostatic function. Cell Calcium 2019; 85:102136. [PMID: 31835178 DOI: 10.1016/j.ceca.2019.102136] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2019] [Revised: 11/30/2019] [Accepted: 11/30/2019] [Indexed: 01/30/2023]
Abstract
Astrocytes are the principal homeostatic cells of the central nerves system (CNS) that support the CNS function at all levels of organisation, from molecular to organ. Several fundamental homeostatic functions of astrocytes are mediated through plasmalemmal pumps and transporters; most of which are also regulated by the transplasmalemmal gradient of Na+ ions. Neuronal activity as well as mechanical or chemical stimulation of astrocytes trigger plasmalemmal Na+ fluxes, which in turn generate spatio-temporally organised transient changes in the cytosolic Na+ concentration, which represent the substrate of astroglial Na+ signalling. Astroglial Na+ signals link and coordinate neuronal activity and CNS homeostatic demands with the astroglial homeostatic response.
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Affiliation(s)
- Alexei Verkhratsky
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, M13 9PT, UK; Achucarro Centre for Neuroscience, IKERBASQUE, Basque Foundation for Science, 48011, Bilbao, Spain.
| | - Christine R Rose
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Düsseldorf, Universitätsstrasse 1, D-40225, Düsseldorf, Germany
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28
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Prabhu D, Khan SM, Blackburn K, Marshall JP, Ashpole NM. Loss of insulin-like growth factor-1 signaling in astrocytes disrupts glutamate handling. J Neurochem 2019; 151:689-702. [PMID: 31563149 DOI: 10.1111/jnc.14879] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2019] [Revised: 09/04/2019] [Accepted: 09/17/2019] [Indexed: 12/25/2022]
Abstract
Insulin-like Growth Factor-1 (IGF-1) has been studied extensively for its ability to promote neuronal growth and excitability. Declining levels of IGF-1 have been correlated with impaired learning and memory as well as an increased risk of neurodegenerative diseases. While neuronal regulation by IGF-1 is well understood, the role of IGF-1 in influencing astrocyte function requires further exploration. Astrocytes regulate many aspects of the brain microenvironment, including controlling glutamate-glutamine cycling, which ultimately supports neuronal metabolism, neurotransmission, and protection from over stimulation. In this study, we examined whether IGF-1 acts through its cognate receptor, IGFR, to alter astrocytic glutamate handling. We utilized both small molecule IGFR inhibitors and Cre-driven genetic approaches to reduce IGFR in vivo and in cultured rodent astrocytes. When IGFR was knocked out of primary astrocytes derived from igfrf/f mice using AAV5-CMV-Cre, significant reductions in glutamate uptake were observed. Similarly, inhibition of IGFR with picropodophyllotoxin for 2 h, as well as 24 h, reduced glutamate uptake in vitro. Mechanistically, short-term inhibition of IGFR resulted in a significant decrease in glutamate transporter availability on the cell surface, as assessed by biotinylation. Long-term inhibition of IGFR led to significant reductions in mRNA expression of glutamate transport machinery, as assessed with qPCR. Reduced glutamate transporter mRNA was also observed in the brains of astrocyte-specific IGFR-deficient mice, three to four months after knock-out was induced with tamoxifen. Interestingly, long-term IGF-1 inhibition also resulted in an increase in adenosine triphosphate-stimulated glutamate release, though no change in adenosine triphosphate-stimulated calcium flux was observed nor were any changes in purinergic receptor protein expression. Together, these data suggest that reduced IGF-1 signaling will favor an accumulation of extrasynaptic glutamate, which may contribute to neurodegeneration in disease states where IGF-1 levels are low. Cover Image for this issue: doi: 10.1111/jnc.14534.
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Affiliation(s)
- Disha Prabhu
- Department of BioMolecular Sciences, University of Mississippi School of Pharmacy, University, Mississippi, USA
| | - Sariya M Khan
- Department of BioMolecular Sciences, University of Mississippi School of Pharmacy, University, Mississippi, USA
| | - Katherine Blackburn
- Department of BioMolecular Sciences, University of Mississippi School of Pharmacy, University, Mississippi, USA
| | - Jessica P Marshall
- Department of BioMolecular Sciences, University of Mississippi School of Pharmacy, University, Mississippi, USA
| | - Nicole M Ashpole
- Department of BioMolecular Sciences, University of Mississippi School of Pharmacy, University, Mississippi, USA.,Research Institute of Pharmaceutical Sciences, University of Mississippi School of Pharmacy, University, Mississippi, USA
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29
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Prabhu D, Khan SM, Blackburn K, Marshall JP, Ashpole NM. Loss of insulin-like growth factor-1 signaling in astrocytes disrupts glutamate handling. J Neurochem 2019. [PMID: 31563149 DOI: 10.1111/jnc.14534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Insulin-like Growth Factor-1 (IGF-1) has been studied extensively for its ability to promote neuronal growth and excitability. Declining levels of IGF-1 have been correlated with impaired learning and memory as well as an increased risk of neurodegenerative diseases. While neuronal regulation by IGF-1 is well understood, the role of IGF-1 in influencing astrocyte function requires further exploration. Astrocytes regulate many aspects of the brain microenvironment, including controlling glutamate-glutamine cycling, which ultimately supports neuronal metabolism, neurotransmission, and protection from over stimulation. In this study, we examined whether IGF-1 acts through its cognate receptor, IGFR, to alter astrocytic glutamate handling. We utilized both small molecule IGFR inhibitors and Cre-driven genetic approaches to reduce IGFR in vivo and in cultured rodent astrocytes. When IGFR was knocked out of primary astrocytes derived from igfrf/f mice using AAV5-CMV-Cre, significant reductions in glutamate uptake were observed. Similarly, inhibition of IGFR with picropodophyllotoxin for 2 h, as well as 24 h, reduced glutamate uptake in vitro. Mechanistically, short-term inhibition of IGFR resulted in a significant decrease in glutamate transporter availability on the cell surface, as assessed by biotinylation. Long-term inhibition of IGFR led to significant reductions in mRNA expression of glutamate transport machinery, as assessed with qPCR. Reduced glutamate transporter mRNA was also observed in the brains of astrocyte-specific IGFR-deficient mice, three to four months after knock-out was induced with tamoxifen. Interestingly, long-term IGF-1 inhibition also resulted in an increase in adenosine triphosphate-stimulated glutamate release, though no change in adenosine triphosphate-stimulated calcium flux was observed nor were any changes in purinergic receptor protein expression. Together, these data suggest that reduced IGF-1 signaling will favor an accumulation of extrasynaptic glutamate, which may contribute to neurodegeneration in disease states where IGF-1 levels are low. Cover Image for this issue: doi: 10.1111/jnc.14534.
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Affiliation(s)
- Disha Prabhu
- Department of BioMolecular Sciences, University of Mississippi School of Pharmacy, University, Mississippi, USA
| | - Sariya M Khan
- Department of BioMolecular Sciences, University of Mississippi School of Pharmacy, University, Mississippi, USA
| | - Katherine Blackburn
- Department of BioMolecular Sciences, University of Mississippi School of Pharmacy, University, Mississippi, USA
| | - Jessica P Marshall
- Department of BioMolecular Sciences, University of Mississippi School of Pharmacy, University, Mississippi, USA
| | - Nicole M Ashpole
- Department of BioMolecular Sciences, University of Mississippi School of Pharmacy, University, Mississippi, USA.,Research Institute of Pharmaceutical Sciences, University of Mississippi School of Pharmacy, University, Mississippi, USA
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30
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Glia-neuron interactions underlie state transitions to generalized seizures. Nat Commun 2019; 10:3830. [PMID: 31444362 PMCID: PMC6707163 DOI: 10.1038/s41467-019-11739-z] [Citation(s) in RCA: 74] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Accepted: 07/31/2019] [Indexed: 11/08/2022] Open
Abstract
Brain activity and connectivity alter drastically during epileptic seizures. The brain networks shift from a balanced resting state to a hyperactive and hypersynchronous state. It is, however, less clear which mechanisms underlie the state transitions. By studying neural and glial activity in zebrafish models of epileptic seizures, we observe striking differences between these networks. During the preictal period, neurons display a small increase in synchronous activity only locally, while the gap-junction-coupled glial network was highly active and strongly synchronized across large distances. The transition from a preictal state to a generalized seizure leads to an abrupt increase in neural activity and connectivity, which is accompanied by a strong alteration in glia-neuron interactions and a massive increase in extracellular glutamate. Optogenetic activation of glia excites nearby neurons through the action of glutamate and gap junctions, emphasizing a potential role for glia-glia and glia-neuron connections in the generation of epileptic seizures. During epileptic seizures, neural activity across the brain switches into a hyperactive and hypersynchronized state. Here, the authors report on the role of glia-glia and glia-neuron interactions in mediating the changes that result in the ictal state in a zebrafish model of epilepsy.
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31
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Wang J, Zielewicz L, Grewer C. A K +/Na + co-binding state: Simultaneous versus competitive binding of K + and Na + to glutamate transporters. J Biol Chem 2019; 294:12180-12190. [PMID: 31235523 DOI: 10.1074/jbc.ra119.009421] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Revised: 06/17/2019] [Indexed: 01/09/2023] Open
Abstract
Plasma membrane-associated glutamate transporters play a key role in signaling by the major excitatory neurotransmitter glutamate. Uphill glutamate uptake into cells is energetically driven by coupling to co-transport of three Na+ ions. In exchange, one K+ ion is counter-transported. Currently accepted transport mechanisms assume that Na+ and K+ effects are exclusive, resulting from competition of these cations at the binding level. Here, we used electrophysiological analysis to test the effects of K+ and Na+ on neuronal glutamate transporter excitatory amino acid carrier 1 (EAAC1; the rat homologue of human excitatory amino acid transporter 3 (EAAT3)). Unexpectedly, extracellular K+ application to EAAC1 induced anion current, but only in the presence of Na+ This result could be explained with a K+/Na+ co-binding state in which the two cations simultaneously bind to the transporter. We obtained further evidence for this co-binding state, and its anion conductance, by analyzing transient currents when Na+ was exchanged for K+ and effects of the [K+]/[Na+] ratio on glutamate affinity. Interestingly, we observed the K+/Na+ co-binding state not only in EAAC1 but also in the subtypes EAAT1 and -2, which, unlike EAAC1, conducted anions in response to K+ only. We incorporated these experimental findings in a revised transport mechanism, including the K+/Na+ co-binding state and the ability of K+ to activate anion current. Overall, these results suggest that differentiation between Na+ and K+ does not occur at the binding level but is conferred by coupling of cation binding to conformational changes. These findings have implications also for other exchangers.
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Affiliation(s)
- Jiali Wang
- Department of Chemistry, Binghamton University, Binghamton, New York 13902
| | - Laura Zielewicz
- Department of Chemistry, Binghamton University, Binghamton, New York 13902
| | - Christof Grewer
- Department of Chemistry, Binghamton University, Binghamton, New York 13902.
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32
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Nordström T, Andersson LC, Åkerman KE. Regulation of intracellular pH by electrogenic Na+/HCO3– co-transporters in embryonic neural stem cell-derived radial glia-like cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:1037-1048. [DOI: 10.1016/j.bbamem.2019.03.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 03/11/2019] [Accepted: 03/14/2019] [Indexed: 01/19/2023]
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33
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Maguire G, Paler L, Green L, Mella R, Valcarcel M, Villace P. Rescue of degenerating neurons and cells by stem cell released molecules: using a physiological renormalization strategy. Physiol Rep 2019; 7:e14072. [PMID: 31050222 PMCID: PMC6497969 DOI: 10.14814/phy2.14072] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Revised: 03/26/2019] [Accepted: 03/31/2019] [Indexed: 12/13/2022] Open
Abstract
Evidence suggests that adult stem cell types and progenitor cells act collectively in a given tissue to maintain and heal organs, such as muscle, through a release of a multitude of molecules packaged into exosomes from the different cell types. Using this principle for the development of bioinspired therapeutics that induces homeostatic renormalization, here we show that the collection of molecules released from four cell types, including mesenchymal stem cells, fibroblast, neural stem cells, and astrocytes, rescues degenerating neurons and cells. Specifically, oxidative stress induced in a human recombinant TDP-43- or FUS-tGFP U2OS cell line by exposure to sodium arsenite was shown to be significantly reduced by our collection of molecules using in vitro imaging of FUS and TDP-43 stress granules. Furthermore, we also show that the collective secretome rescues cortical neurons from glutamate toxicity as evidenced by increased neurite outgrowth, reduced LDH release, and reduced caspase 3/7 activity. These data are the first in a series supporting the development of stem cell-based exosome systems therapeutics that uses a physiological renormalization strategy to treat neurodegenerative diseases.
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Affiliation(s)
- Greg Maguire
- BioRegenerative Sciences, Inc.San DiegoCalifornia
- Auditory Sound Waves, LLCSan DiegoCalifornia
| | - Lee Paler
- BioRegenerative Sciences, Inc.San DiegoCalifornia
- Auditory Sound Waves, LLCSan DiegoCalifornia
| | - Linda Green
- BioRegenerative Sciences, Inc.San DiegoCalifornia
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Pregnolato S, Chakkarapani E, Isles AR, Luyt K. Glutamate Transport and Preterm Brain Injury. Front Physiol 2019; 10:417. [PMID: 31068830 PMCID: PMC6491644 DOI: 10.3389/fphys.2019.00417] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Accepted: 03/27/2019] [Indexed: 12/19/2022] Open
Abstract
Preterm birth complications are the leading cause of child death worldwide and a top global health priority. Among the survivors, the risk of life-long disabilities is high, including cerebral palsy and impairment of movement, cognition, and behavior. Understanding the molecular mechanisms of preterm brain injuries is at the core of future healthcare improvements. Glutamate excitotoxicity is a key mechanism in preterm brain injury, whereby the accumulation of extracellular glutamate damages the delicate immature oligodendrocytes and neurons, leading to the typical patterns of injury seen in the periventricular white matter. Glutamate excitotoxicity is thought to be induced by an interaction between environmental triggers of injury in the perinatal period, particularly cerebral hypoxia-ischemia and infection/inflammation, and developmental and genetic vulnerabilities. To avoid extracellular build-up of glutamate, the brain relies on rapid uptake by sodium-dependent glutamate transporters. Astrocytic excitatory amino acid transporter 2 (EAAT2) is responsible for up to 95% of glutamate clearance, and several lines of evidence suggest that it is essential for brain functioning. While in the adult EAAT2 is predominantly expressed by astrocytes, EAAT2 is transiently upregulated in the immature oligodendrocytes and selected neuronal populations during mid-late gestation, at the peak time for preterm brain injury. This developmental upregulation may interact with perinatal hypoxia-ischemia and infection/inflammation and contribute to the selective vulnerability of the immature oligodendrocytes and neurons in the preterm brain. Disruption of EAAT2 may involve not only altered expression but also impaired function with reversal of transport direction. Importantly, elevated EAAT2 levels have been found in the reactive astrocytes and macrophages of human infant post-mortem brains with severe white matter injury (cystic periventricular leukomalacia), potentially suggesting an adaptive mechanism against excitotoxicity. Interestingly, EAAT2 is suppressed in animal models of acute hypoxic-ischemic brain injury at term, pointing to an important and complex role in newborn brain injuries. Enhancement of EAAT2 expression and transport function is gathering attention as a potential therapeutic approach for a variety of adult disorders and awaits exploration in the context of the preterm brain injuries.
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Affiliation(s)
- Silvia Pregnolato
- Department of Neonatal Neurology, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom
| | - Elavazhagan Chakkarapani
- Department of Neonatal Neurology, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom
| | - Anthony R Isles
- Behavioural Genetics Group, MRC Centre for Neuropsychiatric Genetics and Genomics, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | - Karen Luyt
- Department of Neonatal Neurology, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom
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Kula B, Chen T, Kukley M. Glutamatergic signaling between neurons and oligodendrocyte lineage cells: Is it synaptic or non‐synaptic? Glia 2019; 67:2071-2091. [DOI: 10.1002/glia.23617] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 03/12/2019] [Accepted: 03/18/2019] [Indexed: 12/18/2022]
Affiliation(s)
- Bartosz Kula
- Group of Neuron Glia InteractionUniversity of Tübingen Tübingen Germany
- Graduate Training Centre for NeuroscienceUniversity of Tübingen Tübingen Germany
| | - Ting‐Jiun Chen
- Center for Neuroscience ResearchChildren's Research Institute, Children's National Medical Center Washington District of Columbia
| | - Maria Kukley
- Group of Neuron Glia InteractionUniversity of Tübingen Tübingen Germany
- Research Institute for OphthalmologyUniversity Hospital Tübingen Tübingen Germany
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Cellular and Molecular Differences Between Area CA1 and the Dentate Gyrus of the Hippocampus. Mol Neurobiol 2019; 56:6566-6580. [PMID: 30874972 DOI: 10.1007/s12035-019-1541-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Accepted: 02/27/2019] [Indexed: 12/16/2022]
Abstract
A distinct feature of the hippocampus of the brain is its unidirectional tri-synaptic pathway originating from the entorhinal cortex and projecting to the dentate gyrus (DG) then to area CA3 and subsequently, area CA1 of the Ammon's horn. Each of these areas of the hippocampus has its own cellular structure and distinctive function. The principal neurons in these areas are granule cells in the DG and pyramidal cells in the Ammon's horn's CA1 and CA3 areas with a vast network of interneurons. This review discusses the fundamental differences between the CA1 and DG areas regarding cell morphology, synaptic plasticity, signaling molecules, ability for neurogenesis, vulnerability to various insults and pathologies, and response to pharmacological agents.
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Ashhad S, Narayanan R. Stores, Channels, Glue, and Trees: Active Glial and Active Dendritic Physiology. Mol Neurobiol 2019; 56:2278-2299. [PMID: 30014322 PMCID: PMC6394607 DOI: 10.1007/s12035-018-1223-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Accepted: 07/03/2018] [Indexed: 02/07/2023]
Abstract
Glial cells and neuronal dendrites were historically assumed to be passive structures that play only supportive physiological roles, with no active contribution to information processing in the central nervous system. Research spanning the past few decades has clearly established this assumption to be far from physiological realities. Whereas the discovery of active channel conductances and their localized plasticity was the turning point for dendritic structures, the demonstration that glial cells release transmitter molecules and communicate across the neuroglia syncytium through calcium wave propagation constituted path-breaking discoveries for glial cell physiology. An additional commonality between these two structures is the ability of calcium stores within their endoplasmic reticulum (ER) to support active propagation of calcium waves, which play crucial roles in the spatiotemporal integration of information within and across cells. Although there have been several demonstrations of regulatory roles of glial cells and dendritic structures in achieving common physiological goals such as information propagation and adaptability through plasticity, studies assessing physiological interactions between these two active structures have been few and far. This lacuna is especially striking given the strong connectivity that is known to exist between these two structures through several complex and tightly intercoupled mechanisms that also recruit their respective ER structures. In this review, we present brief overviews of the parallel literatures on active dendrites and active glial physiology and make a strong case for future studies to directly assess the strong interactions between these two structures in regulating physiology and pathophysiology of the brain.
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Affiliation(s)
- Sufyan Ashhad
- Department of Neurobiology, University of California at Los Angeles, Los Angeles, CA, 90095, USA
| | - Rishikesh Narayanan
- Cellular Neurophysiology Laboratory, Molecular Biophysics Unit, Indian Institute of Science, Bangalore, 560012, India.
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Zhang LN, Hao L, Guo YS, Wang HY, Li LL, Liu LZ, Li WB. Are glutamate transporters neuroprotective or neurodegenerative during cerebral ischemia? J Mol Med (Berl) 2019; 97:281-289. [PMID: 30675649 DOI: 10.1007/s00109-019-01745-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Revised: 01/10/2019] [Accepted: 01/14/2019] [Indexed: 12/14/2022]
Abstract
The accumulation of glutamate (Glu) in the synaptic cleft during cerebral ischemia triggers the death of neurons, causing mental or physical handicap. However, the mechanisms of the alteration in Glu homeostasis and the imbalance between the release and clearance of Glu in ischemia are not yet completely understood. Additionally, the role of Glu transporters in regulating Glu concentration in the synaptic cleft is controversial. This review aims to provide readers with an in-depth understanding of Glu transporters in the early or later stages of ischemic events, or in mild or severe cerebral ischemia via alteration of Glu transporter expression, reversal of Glu transporters function, and trafficking between membrane and cytoplasm, to further clarify whether the Glu transporters are neuroprotective or neurodegenerative during cerebral ischemia. We provide the insights for deeper understanding of the mechanism of Glu transporters regulation after different periods and severities of cerebral ischemia.
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Affiliation(s)
- Li-Nan Zhang
- Department of Pathophysiology, Hebei Medical University, 361 Zhongshan East Road, Shijiazhuang, 050017, Hebei, China
| | - Liang Hao
- Department of Neurosurgery, Third Hospital of Shijiazhuang, Beijing, 050011, Hebei, China
| | - Yu-Song Guo
- Department of Traumatology, Third Hospital of Shijiazhuang, Beijing, 050011, Hebei, China
| | - Hai-Yan Wang
- Pharmaceutical Preparation Section, Third Hospital of Shijiazhuang, Beijing, 050011, Hebei, China
| | - Lin-Lin Li
- Clinical Medicine, College of Basic Medicine, Hebei Medical University, Beijing, 050017, Hebei, China
| | - Li-Zhe Liu
- Department of Pathophysiology, Hebei Medical University, 361 Zhongshan East Road, Shijiazhuang, 050017, Hebei, China
| | - Wen-Bin Li
- Department of Pathophysiology, Hebei Medical University, 361 Zhongshan East Road, Shijiazhuang, 050017, Hebei, China.
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Corbetta C, Di Ianni N, Bruzzone MG, Patanè M, Pollo B, Cantini G, Cominelli M, Zucca I, Pisati F, Poliani PL, Finocchiaro G, Pellegatta S. Altered function of the glutamate–aspartate transporter GLAST, a potential therapeutic target in glioblastoma. Int J Cancer 2019; 144:2539-2554. [DOI: 10.1002/ijc.31985] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Revised: 10/17/2018] [Accepted: 10/31/2018] [Indexed: 01/07/2023]
Affiliation(s)
- Cristina Corbetta
- Unit of Molecular Neuro‐OncologyFondazione IRCCS Istituto Neurologico Carlo Besta Milan Italy
| | - Natalia Di Ianni
- Unit of Molecular Neuro‐OncologyFondazione IRCCS Istituto Neurologico Carlo Besta Milan Italy
| | - Maria Grazia Bruzzone
- Experimental Imaging and Neuro‐RadiologyFondazione IRCCS Istituto Neurologico Carlo Besta Milan Italy
| | - Monica Patanè
- Unit of PathologyFondazione IRCCS Istituto Neurologico Carlo Besta Milan Italy
| | - Bianca Pollo
- Unit of PathologyFondazione IRCCS Istituto Neurologico Carlo Besta Milan Italy
| | - Gabriele Cantini
- Unit of Molecular Neuro‐OncologyFondazione IRCCS Istituto Neurologico Carlo Besta Milan Italy
| | | | - Ileana Zucca
- Experimental Imaging and Neuro‐RadiologyFondazione IRCCS Istituto Neurologico Carlo Besta Milan Italy
| | - Federica Pisati
- Unit of Molecular Neuro‐OncologyFondazione IRCCS Istituto Neurologico Carlo Besta Milan Italy
| | | | - Gaetano Finocchiaro
- Unit of Molecular Neuro‐OncologyFondazione IRCCS Istituto Neurologico Carlo Besta Milan Italy
| | - Serena Pellegatta
- Unit of Molecular Neuro‐OncologyFondazione IRCCS Istituto Neurologico Carlo Besta Milan Italy
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Mahan VL. Neurointegrity and neurophysiology: astrocyte, glutamate, and carbon monoxide interactions. Med Gas Res 2019; 9:24-45. [PMID: 30950417 PMCID: PMC6463446 DOI: 10.4103/2045-9912.254639] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 02/15/2019] [Indexed: 12/27/2022] Open
Abstract
Astrocyte contributions to brain function and prevention of neuropathologies are as extensive as that of neurons. Astroglial regulation of glutamate, a primary neurotransmitter, is through uptake, release through vesicular and non-vesicular pathways, and catabolism to intermediates. Homeostasis by astrocytes is considered to be of primary importance in determining normal central nervous system health and central nervous system physiology - glutamate is central to dynamic physiologic changes and central nervous system stability. Gasotransmitters may affect diverse glutamate interactions positively or negatively. The effect of carbon monoxide, an intrinsic central nervous system gasotransmitter, in the complex astrocyte homeostasis of glutamate may offer insights to normal brain development, protection, and its use as a neuromodulator and neurotherapeutic. In this article, we will review the effects of carbon monoxide on astrocyte homeostasis of glutamate.
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Affiliation(s)
- Vicki L. Mahan
- Division of Pediatric Cardiothoracic Surgery in the Department of Surgery, St. Christopher's Hospital for Children/Drexel University College of Medicine, Philadelphia, PA, USA
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41
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Fang Y, Jiang D, Wang Y, Wang Q, Lv D, Liu J, Liu C. Neuroprotection of rhGLP‐1 in diabetic rats with cerebral ischemia/reperfusion injury via regulation of oxidative stress, EAAT2, and apoptosis. Drug Dev Res 2018; 79:249-259. [PMID: 30222190 DOI: 10.1002/ddr.21439] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 06/05/2018] [Accepted: 06/07/2018] [Indexed: 12/22/2022]
Affiliation(s)
- Yi Fang
- Department of Pharmacy Peking University People's Hospital Beijing People's Republic of China
| | - Daoli Jiang
- Department of Pharmacy The Affiliated Hospital of Xuzhou Medical University Xuzhou People's Republic of China
| | - Yitong Wang
- Department of Pharmacy Peking University People's Hospital Beijing People's Republic of China
- Department of Pharmacy Administration and Clinical Pharmacy Peking University Health Science Center Beijing People's Republic of China
| | - Qian Wang
- Department of Pharmacy Peking University People's Hospital Beijing People's Republic of China
| | - Dongmei Lv
- Department of Pharmacy The Affiliated Hospital of Xuzhou Medical University Xuzhou People's Republic of China
| | - Jichao Liu
- Animal Experimental Center Peking University People's Hospital Beijing People's Republic of China
| | - Chang Liu
- Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy Xuzhou Medical University Xuzhou People's Republic of China
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42
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Wilson CS, Mongin AA. Cell Volume Control in Healthy Brain and Neuropathologies. CURRENT TOPICS IN MEMBRANES 2018; 81:385-455. [PMID: 30243438 DOI: 10.1016/bs.ctm.2018.07.006] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Regulation of cellular volume is a critical homeostatic process that is intimately linked to ionic and osmotic balance in the brain tissue. Because the brain is encased in the rigid skull and has a very complex cellular architecture, even minute changes in the volume of extracellular and intracellular compartments have a very strong impact on tissue excitability and function. The failure of cell volume control is a major feature of several neuropathologies, such as hyponatremia, stroke, epilepsy, hyperammonemia, and others. There is strong evidence that such dysregulation, especially uncontrolled cell swelling, plays a major role in adverse pathological outcomes. To protect themselves, brain cells utilize a variety of mechanisms to maintain their optimal volume, primarily by releasing or taking in ions and small organic molecules through diverse volume-sensitive ion channels and transporters. In principle, the mechanisms of cell volume regulation are not unique to the brain and share many commonalities with other tissues. However, because ions and some organic osmolytes (e.g., major amino acid neurotransmitters) have a strong impact on neuronal excitability, cell volume regulation in the brain is a surprisingly treacherous process, which may cause more harm than good. This topical review covers the established and emerging information in this rapidly developing area of physiology.
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Affiliation(s)
- Corinne S Wilson
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY, United States
| | - Alexander A Mongin
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY, United States; Department of Biophysics and Functional Diagnostics, Siberian State Medical University, Tomsk, Russian Federation
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43
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Pál B. Involvement of extrasynaptic glutamate in physiological and pathophysiological changes of neuronal excitability. Cell Mol Life Sci 2018; 75:2917-2949. [PMID: 29766217 PMCID: PMC11105518 DOI: 10.1007/s00018-018-2837-5] [Citation(s) in RCA: 79] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Revised: 04/27/2018] [Accepted: 05/07/2018] [Indexed: 12/14/2022]
Abstract
Glutamate is the most abundant neurotransmitter of the central nervous system, as the majority of neurons use glutamate as neurotransmitter. It is also well known that this neurotransmitter is not restricted to synaptic clefts, but found in the extrasynaptic regions as ambient glutamate. Extrasynaptic glutamate originates from spillover of synaptic release, as well as from astrocytes and microglia. Its concentration is magnitudes lower than in the synaptic cleft, but receptors responding to it have higher affinity for it. Extrasynaptic glutamate receptors can be found in neuronal somatodendritic location, on astroglia, oligodendrocytes or microglia. Activation of them leads to changes of neuronal excitability with different amplitude and kinetics. Extrasynaptic glutamate is taken up by neurons and astrocytes mostly via EAAT transporters, and astrocytes, in turn metabolize it to glutamine. Extrasynaptic glutamate is involved in several physiological phenomena of the central nervous system. It regulates neuronal excitability and synaptic strength by involving astroglia; contributing to learning and memory formation, neurosecretory and neuromodulatory mechanisms, as well as sleep homeostasis.The extrasynaptic glutamatergic system is affected in several brain pathologies related to excitotoxicity, neurodegeneration or neuroinflammation. Being present in dementias, neurodegenerative and neuropsychiatric diseases or tumor invasion in a seemingly uniform way, the system possibly provides a common component of their pathogenesis. Although parts of the system are extensively discussed by several recent reviews, in this review I attempt to summarize physiological actions of the extrasynaptic glutamate on neuronal excitability and provide a brief insight to its pathology for basic understanding of the topic.
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Affiliation(s)
- Balázs Pál
- Department of Physiology, Faculty of Medicine, University of Debrecen, Nagyerdei krt 98, Debrecen, 4012, Hungary.
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Turnaturi R, Montenegro L, Marrazzo A, Parenti R, Pasquinucci L, Parenti C. Benzomorphan skeleton, a versatile scaffold for different targets: A comprehensive review. Eur J Med Chem 2018; 155:492-502. [PMID: 29908442 DOI: 10.1016/j.ejmech.2018.06.017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 03/23/2018] [Accepted: 06/06/2018] [Indexed: 12/21/2022]
Abstract
Despite the fact that the benzomorphan skeleton has mainly been employed in medicinal chemistry for the development of opioid analgesics, it is a versatile structure. Its stereochemistry, as well as opportune modifications at the phenolic hydroxyl group and at the basic nitrogen, play a pivotal role addressing the benzomorphan-based compounds to a specific target. In this review, we describe the structure activity-relationships (SARs) of benzomorphan-based compounds acting at sigma 1 receptor (σ1R), sigma 2 receptor (σ2R), voltage-dependent sodium channel, N-Methyl-d-Aspartate (NMDA) receptor-channel complex and other targets. Collectively, the SARs data have highlighted that the benzomorphan nucleus could be regarded as a useful template for the synthesis of drug candidates for different targets.
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Affiliation(s)
- Rita Turnaturi
- Department of Drug Sciences, Medicinal Chemistry Section, University of Catania, Viale A. Doria, 6, 95100, Catania, Italy.
| | - Lucia Montenegro
- Department of Drug Sciences, Pharmaceutical Technology Section, University of Catania, Viale A. Doria 6, 95125, Catania, Italy
| | - Agostino Marrazzo
- Department of Drug Sciences, Medicinal Chemistry Section, University of Catania, Viale A. Doria, 6, 95100, Catania, Italy
| | - Rosalba Parenti
- Department of Biomedical and Biotechnological Sciences, Physiology Section, University of Catania, Catania, Italy
| | - Lorella Pasquinucci
- Department of Drug Sciences, Medicinal Chemistry Section, University of Catania, Viale A. Doria, 6, 95100, Catania, Italy
| | - Carmela Parenti
- Department of Drug Sciences, Pharmacology Section, University of Catania, Viale A. Doria, 6, 95100, Catania, Italy
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Parkin GM, Udawela M, Gibbons A, Dean B. Glutamate transporters, EAAT1 and EAAT2, are potentially important in the pathophysiology and treatment of schizophrenia and affective disorders. World J Psychiatry 2018; 8:51-63. [PMID: 29988908 PMCID: PMC6033743 DOI: 10.5498/wjp.v8.i2.51] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 05/15/2018] [Accepted: 06/09/2018] [Indexed: 02/05/2023] Open
Abstract
Glutamate is the predominant excitatory neurotransmitter in the human brain and it has been shown that prolonged activation of the glutamatergic system leads to nerve damage and cell death. Following release from the pre-synaptic neuron and synaptic transmission, glutamate is either taken up into the pre-synaptic neuron or neighbouring glia by transmembrane glutamate transporters. Excitatory amino acid transporter (EAAT) 1 and EAAT2 are Na+-dependant glutamate transporters expressed predominantly in glia cells of the central nervous system. As the most abundant glutamate transporters, their primary role is to modulate levels of glutamatergic excitability and prevent spill over of glutamate beyond the synapse. This role is facilitated through the binding and transportation of glutamate into astrocytes and microglia. The function of EAAT1 and EAAT2 is heavily regulated at the levels of gene expression, post-transcriptional splicing, glycosylation states and cell-surface trafficking of the protein. Both glutamatergic dysfunction and glial dysfunction have been proposed to be involved in psychiatric disorder. This review will present an overview of the roles that EAAT1 and EAAT2 play in modulating glutamatergic activity in the human brain, and mount an argument that these two transporters could be involved in the aetiologies of schizophrenia and affective disorders as well as represent potential drug targets for novel therapies for those disorders.
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Affiliation(s)
- Georgia M Parkin
- Molecular Psychiatry Laboratory, the Florey Institute of Neuroscience and Mental Health, Parkville VIC 3052, Australia
- CRC for Mental Health, Carlton VIC 3053, Australia
| | - Madhara Udawela
- Molecular Psychiatry Laboratory, the Florey Institute of Neuroscience and Mental Health, Parkville VIC 3052, Australia
- CRC for Mental Health, Carlton VIC 3053, Australia
| | - Andrew Gibbons
- Molecular Psychiatry Laboratory, the Florey Institute of Neuroscience and Mental Health, Parkville VIC 3052, Australia
| | - Brian Dean
- Molecular Psychiatry Laboratory, the Florey Institute of Neuroscience and Mental Health, Parkville VIC 3052, Australia
- CRC for Mental Health, Carlton VIC 3053, Australia
- Research Centre for Mental Health, the Faculty of Health, Arts and Design, Swinburne University, Hawthorne VIC 3122, Australia
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46
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Kv1.3 activity perturbs the homeostatic properties of astrocytes in glioma. Sci Rep 2018; 8:7654. [PMID: 29769580 PMCID: PMC5955950 DOI: 10.1038/s41598-018-25940-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 05/02/2018] [Indexed: 01/06/2023] Open
Abstract
Glial cells actively maintain the homeostasis of brain parenchyma, regulating neuronal excitability and preserving the physiological composition of the extracellular milieu. Under pathological conditions, some functions of glial cells could be compromised, exacerbating the neurotoxic processes. We investigated if the homeostatic activities of astrocytes and microglia could be modulated by the voltage-gated K+ channel Kv1.3. To this end we used in vitro and in vivo systems to model cell-to-cell interactions in tumoral conditions, using a specific inhibitor of Kv1.3 channels, 5-(4-phenoxybutoxy) psoralen (PAP-1). We demonstrated that PAP-1 increases astrocytic glutamate uptake, reduces glioma-induced neurotoxicity, and decreases microglial migration and phagocytosis. We also found in a tumor blood brain barrier model that Kv1.3 activity is required for its integrity. The crucial role of Kv1.3 channels as modulators of glial cell activity was confirmed in a mouse model of glioma, where PAP-1 treatment reduces tumor volume only in the presence of active glutamate transporters GLT-1. In the same mouse model, PAP-1 reduces astrogliosis and microglial infiltration. PAP-1 also reduces tumor cell invasion. All these findings point to Kv1.3 channels as potential targets to re-instruct glial cells toward their homeostatic functions, in the context of brain tumors.
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47
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Shalaby HN, El-Tanbouly DM, Zaki HF. Topiramate mitigates 3-nitropropionic acid-induced striatal neurotoxicity via modulation of AMPA receptors. Food Chem Toxicol 2018; 118:227-234. [PMID: 29753867 DOI: 10.1016/j.fct.2018.05.022] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Revised: 05/01/2018] [Accepted: 05/08/2018] [Indexed: 01/10/2023]
Abstract
Prevalence of glutamate receptor subunit 2 (GluR2)-lacking alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors is a hallmark of excitotoxicity-related neurodegenerative diseases. Topiramate (TPM) is a structurally novel anticonvulsant with a well-known modulatory effects on AMPA/kainate subtypes of glutamate receptors. The present study aimed at investigating the neuroprotective potential of TPM on 3-nitropropionic acid (3-NP)-induced striatal neurodegeneration and Huntington's disease-like symptoms. Rats were injected with 3-NP (10 mg/kg/i.p.) for 14 days. TPM (50 mg/kg/p.o.) was given once a day, 1 h before 3-NP. TPM amended 3-NP induced changes in neurobehavioral performance, striatal neurotransmitters levels and histopathological injury. 3-NP control rats showed a significant ablation in the mRNA expression of Ca2+-impermeable Glu2R subunit along with an elevation in its regulatory protein (protein interacting with C kinase-1) PICK1, an effect that was largely reversed by TPM. TPM in addition, enhanced the phosphorylation of the protein kinase B/glycogen synthase kinase-3β/cAMP response element binding protein (Akt/GSK-3β/CREB) cue. Moreover, improvement in oxidative status, suppression of caspase-3 activity and restoration of striatal BDNF were noticed following treatment with TPM. The current study revealed that TPM boosted the neuroprotective (Akt/GSK-3β/CREB) pathway by its negative modulatory effect on AMPA glutamate receptors as well as its direct antioxidant property.
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Affiliation(s)
- Heba N Shalaby
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Cairo University, Cairo, Egypt
| | - Dalia M El-Tanbouly
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Cairo University, Cairo, Egypt.
| | - Hala F Zaki
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Cairo University, Cairo, Egypt
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48
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Hayashi MK. Structure-Function Relationship of Transporters in the Glutamate-Glutamine Cycle of the Central Nervous System. Int J Mol Sci 2018; 19:ijms19041177. [PMID: 29649168 PMCID: PMC5979278 DOI: 10.3390/ijms19041177] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 04/09/2018] [Accepted: 04/10/2018] [Indexed: 12/12/2022] Open
Abstract
Many kinds of transporters contribute to glutamatergic excitatory synaptic transmission. Glutamate is loaded into synaptic vesicles by vesicular glutamate transporters to be released from presynaptic terminals. After synaptic vesicle release, glutamate is taken up by neurons or astrocytes to terminate the signal and to prepare for the next signal. Glutamate transporters on the plasma membrane are responsible for transporting glutamate from extracellular fluid to cytoplasm. Glutamate taken up by astrocyte is converted to glutamine by glutamine synthetase and transported back to neurons through glutamine transporters on the plasma membranes of the astrocytes and then on neurons. Glutamine is converted back to glutamate by glutaminase in the neuronal cytoplasm and then loaded into synaptic vesicles again. Here, the structures of glutamate transporters and glutamine transporters, their conformational changes, and how they use electrochemical gradients of various ions for substrate transport are summarized. Pharmacological regulations of these transporters are also discussed.
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Affiliation(s)
- Mariko Kato Hayashi
- School of Medicine, International University of Health and Welfare, 4-3 Kozunomori, Narita, Chiba 286-8686, Japan.
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49
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Rimmele TS, Rocher AB, Wellbourne-Wood J, Chatton JY. Control of Glutamate Transport by Extracellular Potassium: Basis for a Negative Feedback on Synaptic Transmission. Cereb Cortex 2018; 27:3272-3283. [PMID: 28369311 DOI: 10.1093/cercor/bhx078] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 03/15/2017] [Indexed: 01/07/2023] Open
Abstract
Glutamate and K+, both released during neuronal firing, need to be tightly regulated to ensure accurate synaptic transmission. Extracellular glutamate and K+ ([K+]o) are rapidly taken up by glutamate transporters and K+-transporters or channels, respectively. Glutamate transport includes the exchange of one glutamate, 3 Na+, and one proton, in exchange for one K+. This K+ efflux allows the glutamate binding site to reorient in the outwardly facing position and start a new transport cycle. Here, we demonstrate the sensitivity of the transport process to [K+]o changes. Increasing [K+]o over the physiological range had an immediate and reversible inhibitory action on glutamate transporters. This K+-dependent transporter inhibition was revealed using microspectrofluorimetry in primary astrocytes, and whole-cell patch-clamp in acute brain slices and HEK293 cells expressing glutamate transporters. Previous studies demonstrated that pharmacological inhibition of glutamate transporters decreases neuronal transmission via extrasynaptic glutamate spillover and subsequent activation of metabotropic glutamate receptors (mGluRs). Here, we demonstrate that increasing [K+]o also causes a decrease in neuronal mEPSC frequency, which is prevented by group II mGluR inhibition. These findings highlight a novel, previously unreported physiological negative feedback mechanism in which [K+]o elevations inhibit glutamate transporters, unveiling a new mechanism for activity-dependent modulation of synaptic activity.
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Affiliation(s)
- Theresa S Rimmele
- Department of Fundamental Neurosciences, University of Lausanne, CH-1005 Lausanne, Switzerland
| | - Anne-Bérengère Rocher
- Department of Fundamental Neurosciences, University of Lausanne, CH-1005 Lausanne, Switzerland
| | - Joel Wellbourne-Wood
- Department of Fundamental Neurosciences, University of Lausanne, CH-1005 Lausanne, Switzerland
| | - Jean-Yves Chatton
- Department of Fundamental Neurosciences, University of Lausanne, CH-1005 Lausanne, Switzerland.,Cellular Imaging Facility, University of Lausanne, CH-1005 Lausanne, Switzerland
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50
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Rose CR, Felix L, Zeug A, Dietrich D, Reiner A, Henneberger C. Astroglial Glutamate Signaling and Uptake in the Hippocampus. Front Mol Neurosci 2018; 10:451. [PMID: 29386994 PMCID: PMC5776105 DOI: 10.3389/fnmol.2017.00451] [Citation(s) in RCA: 128] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Accepted: 12/22/2017] [Indexed: 12/22/2022] Open
Abstract
Astrocytes have long been regarded as essentially unexcitable cells that do not contribute to active signaling and information processing in the brain. Contrary to this classical view, it is now firmly established that astrocytes can specifically respond to glutamate released from neurons. Astrocyte glutamate signaling is initiated upon binding of glutamate to ionotropic and/or metabotropic receptors, which can result in calcium signaling, a major form of glial excitability. Release of so-called gliotransmitters like glutamate, ATP and D-serine from astrocytes in response to activation of glutamate receptors has been demonstrated to modulate various aspects of neuronal function in the hippocampus. In addition to receptors, glutamate binds to high-affinity, sodium-dependent transporters, which results in rapid buffering of synaptically-released glutamate, followed by its removal from the synaptic cleft through uptake into astrocytes. The degree to which astrocytes modulate and control extracellular glutamate levels through glutamate transporters depends on their expression levels and on the ionic driving forces that decrease with ongoing activity. Another major determinant of astrocytic control of glutamate levels could be the precise morphological arrangement of fine perisynaptic processes close to synapses, defining the diffusional distance for glutamate, and the spatial proximity of transporters in relation to the synaptic cleft. In this review, we will present an overview of the mechanisms and physiological role of glutamate-induced ion signaling in astrocytes in the hippocampus as mediated by receptors and transporters. Moreover, we will discuss the relevance of astroglial glutamate uptake for extracellular glutamate homeostasis, focusing on how activity-induced dynamic changes of perisynaptic processes could shape synaptic transmission at glutamatergic synapses.
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Affiliation(s)
- Christine R Rose
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Duesseldorf, Duesseldorf, Germany
| | - Lisa Felix
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Duesseldorf, Duesseldorf, Germany
| | - Andre Zeug
- Cellular Neurophysiology, Hannover Medical School, Hannover, Germany
| | - Dirk Dietrich
- Department of Neurosurgery, University of Bonn Medical School, Bonn, Germany
| | - Andreas Reiner
- Cellular Neurobiology, Faculty of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany
| | - Christian Henneberger
- Institute of Cellular Neurosciences, University of Bonn Medical School, Bonn, Germany.,German Center for Degenerative Diseases (DZNE), Bonn, Germany.,Institute of Neurology, University College London, London, United Kingdom
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