1
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Faissner A. Low-density lipoprotein receptor-related protein-1 (LRP1) in the glial lineage modulates neuronal excitability. FRONTIERS IN NETWORK PHYSIOLOGY 2023; 3:1190240. [PMID: 37383546 PMCID: PMC10293750 DOI: 10.3389/fnetp.2023.1190240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Accepted: 05/25/2023] [Indexed: 06/30/2023]
Abstract
The low-density lipoprotein related protein receptor 1 (LRP1), also known as CD91 or α-Macroglobulin-receptor, is a transmembrane receptor that interacts with more than 40 known ligands. It plays an important biological role as receptor of morphogens, extracellular matrix molecules, cytokines, proteases, protease inhibitors and pathogens. In the CNS, it has primarily been studied as a receptor and clearance agent of pathogenic factors such as Aβ-peptide and, lately, Tau protein that is relevant for tissue homeostasis and protection against neurodegenerative processes. Recently, it was found that LRP1 expresses the Lewis-X (Lex) carbohydrate motif and is expressed in the neural stem cell compartment. The removal of Lrp1 from the cortical radial glia compartment generates a strong phenotype with severe motor deficits, seizures and a reduced life span. The present review discusses approaches that have been taken to address the neurodevelopmental significance of LRP1 by creating novel, lineage-specific constitutive or conditional knockout mouse lines. Deficits in the stem cell compartment may be at the root of severe CNS pathologies.
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2
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Purushotham SS, Buskila Y. Astrocytic modulation of neuronal signalling. FRONTIERS IN NETWORK PHYSIOLOGY 2023; 3:1205544. [PMID: 37332623 PMCID: PMC10269688 DOI: 10.3389/fnetp.2023.1205544] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Accepted: 05/18/2023] [Indexed: 06/20/2023]
Abstract
Neuronal signalling is a key element in neuronal communication and is essential for the proper functioning of the CNS. Astrocytes, the most prominent glia in the brain play a key role in modulating neuronal signalling at the molecular, synaptic, cellular, and network levels. Over the past few decades, our knowledge about astrocytes and their functioning has evolved from considering them as merely a brain glue that provides structural support to neurons, to key communication elements. Astrocytes can regulate the activity of neurons by controlling the concentrations of ions and neurotransmitters in the extracellular milieu, as well as releasing chemicals and gliotransmitters that modulate neuronal activity. The aim of this review is to summarise the main processes through which astrocytes are modulating brain function. We will systematically distinguish between direct and indirect pathways in which astrocytes affect neuronal signalling at all levels. Lastly, we will summarize pathological conditions that arise once these signalling pathways are impaired focusing on neurodegeneration.
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Affiliation(s)
| | - Yossi Buskila
- School of Medicine, Western Sydney University, Campbelltown, NSW, Australia
- The MARCS Institute, Western Sydney University, Campbelltown, NSW, Australia
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3
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Ryner RF, Derera ID, Armbruster M, Kansara A, Sommer ME, Pirone A, Noubary F, Jacob M, Dulla CG. Cortical Parvalbumin-Positive Interneuron Development and Function Are Altered in the APC Conditional Knockout Mouse Model of Infantile and Epileptic Spasms Syndrome. J Neurosci 2023; 43:1422-1440. [PMID: 36717229 PMCID: PMC9987578 DOI: 10.1523/jneurosci.0572-22.2022] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 11/14/2022] [Accepted: 12/22/2022] [Indexed: 02/01/2023] Open
Abstract
Infantile and epileptic spasms syndrome (IESS) is a childhood epilepsy syndrome characterized by infantile or late-onset spasms, abnormal neonatal EEG, and epilepsy. Few treatments exist for IESS, clinical outcomes are poor, and the molecular and circuit-level etiologies of IESS are not well understood. Multiple human IESS risk genes are linked to Wnt/β-catenin signaling, a pathway that controls developmental transcriptional programs and promotes glutamatergic excitation via β-catenin's role as a synaptic scaffold. We previously showed that deleting adenomatous polyposis coli (APC), a component of the β-catenin destruction complex, in excitatory neurons (APC cKO mice, APCfl/fl x CaMKIIαCre) increased β-catenin levels in developing glutamatergic neurons and led to infantile behavioral spasms, abnormal neonatal EEG, and adult epilepsy. Here, we tested the hypothesis that the development of GABAergic interneurons (INs) is disrupted in APC cKO male and female mice. IN dysfunction is implicated in human IESS, is a feature of other rodent models of IESS, and may contribute to the manifestation of spasms and seizures. We found that parvalbumin-positive INs (PV+ INs), an important source of cortical inhibition, were decreased in number, underwent disproportionate developmental apoptosis, and had altered dendrite morphology at P9, the peak of behavioral spasms. PV+ INs received excessive excitatory input, and their intrinsic ability to fire action potentials was reduced at all time points examined (P9, P14, P60). Subsequently, GABAergic transmission onto pyramidal neurons was uniquely altered in the somatosensory cortex of APC cKO mice at all ages, with both decreased IPSC input at P14 and enhanced IPSC input at P9 and P60. These results indicate that inhibitory circuit dysfunction occurs in APC cKOs and, along with known changes in excitation, may contribute to IESS-related phenotypes.SIGNIFICANCE STATEMENT Infantile and epileptic spasms syndrome (IESS) is a devastating epilepsy with limited treatment options and poor clinical outcomes. The molecular, cellular, and circuit disruptions that cause infantile spasms and seizures are largely unknown, but inhibitory GABAergic interneuron dysfunction has been implicated in rodent models of IESS and may contribute to human IESS. Here, we use a rodent model of IESS, the APC cKO mouse, in which β-catenin signaling is increased in excitatory neurons. This results in altered parvalbumin-positive GABAergic interneuron development and GABAergic synaptic dysfunction throughout life, showing that pathology arising in excitatory neurons can initiate long-term interneuron dysfunction. Our findings further implicate GABAergic dysfunction in IESS, even when pathology is initiated in other neuronal types.
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Affiliation(s)
- Rachael F Ryner
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
- Cell, Molecular, and Developmental Biology Graduate Program, Tufts Graduate School of Biomedical Sciences, Boston, Massachusetts 02111
| | - Isabel D Derera
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Moritz Armbruster
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Anar Kansara
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Mary E Sommer
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Antonella Pirone
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Farzad Noubary
- Department of Health Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts 02115
| | - Michele Jacob
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Chris G Dulla
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
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4
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Brymer KJ, Hurley EP, Barron JC, Mukherjee B, Barnes JR, Nafar F, Parsons MP. Asymmetric dysregulation of glutamate dynamics across the synaptic cleft in a mouse model of Alzheimer's disease. Acta Neuropathol Commun 2023; 11:27. [PMID: 36788598 PMCID: PMC9926626 DOI: 10.1186/s40478-023-01524-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Accepted: 01/28/2023] [Indexed: 02/16/2023] Open
Abstract
Most research on glutamate spillover focuses on the deleterious consequences of postsynaptic glutamate receptor overactivation. However, two decades ago, it was noted that the glial coverage of hippocampal synapses is asymmetric: astrocytic coverage of postsynaptic sites exceeds coverage of presynaptic sites by a factor of four. The fundamental relevance of this glial asymmetry remains poorly understood. Here, we used the glutamate biosensor iGluSnFR, and restricted its expression to either CA3 or CA1 neurons to visualize glutamate dynamics at pre- and postsynaptic microenvironments, respectively. We demonstrate that inhibition of the primarily astrocytic glutamate transporter-1 (GLT-1) slows glutamate clearance to a greater extent at presynaptic compared to postsynaptic membranes. GLT-1 expression was reduced early in a mouse model of AD, resulting in slower glutamate clearance rates at presynaptic but not postsynaptic membranes that opposed presynaptic short-term plasticity. Overall, our data demonstrate that the presynapse is particularly vulnerable to GLT-1 dysfunction and may have implications for presynaptic impairments in a variety of brain diseases.
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Affiliation(s)
- Kyle J. Brymer
- grid.25055.370000 0000 9130 6822Division of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL A1B 3V6 Canada
| | - Emily P. Hurley
- grid.25055.370000 0000 9130 6822Division of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL A1B 3V6 Canada
| | - Jessica C. Barron
- grid.25055.370000 0000 9130 6822Division of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL A1B 3V6 Canada
| | - Bandhan Mukherjee
- grid.25055.370000 0000 9130 6822Division of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL A1B 3V6 Canada
| | - Jocelyn R. Barnes
- grid.25055.370000 0000 9130 6822Division of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL A1B 3V6 Canada
| | - Firoozeh Nafar
- grid.25055.370000 0000 9130 6822Division of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL A1B 3V6 Canada
| | - Matthew P. Parsons
- grid.25055.370000 0000 9130 6822Division of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL A1B 3V6 Canada
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5
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Armbruster M, Naskar S, Garcia JP, Sommer M, Kim E, Adam Y, Haydon PG, Boyden ES, Cohen AE, Dulla CG. Neuronal activity drives pathway-specific depolarization of peripheral astrocyte processes. Nat Neurosci 2022; 25:607-616. [PMID: 35484406 PMCID: PMC9988390 DOI: 10.1038/s41593-022-01049-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Accepted: 03/14/2022] [Indexed: 12/16/2022]
Abstract
Astrocytes are glial cells that interact with neuronal synapses via their distal processes, where they remove glutamate and potassium (K+) from the extracellular space following neuronal activity. Astrocyte clearance of both glutamate and K+ is voltage dependent, but astrocyte membrane potential (Vm) is thought to be largely invariant. As a result, these voltage dependencies have not been considered relevant to astrocyte function. Using genetically encoded voltage indicators to enable the measurement of Vm at peripheral astrocyte processes (PAPs) in mice, we report large, rapid, focal and pathway-specific depolarizations in PAPs during neuronal activity. These activity-dependent astrocyte depolarizations are driven by action potential-mediated presynaptic K+ efflux and electrogenic glutamate transporters. We find that PAP depolarization inhibits astrocyte glutamate clearance during neuronal activity, enhancing neuronal activation by glutamate. This represents a novel class of subcellular astrocyte membrane dynamics and a new form of astrocyte-neuron interaction.
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Affiliation(s)
- Moritz Armbruster
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA.
| | - Saptarnab Naskar
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Jacqueline P Garcia
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA.,Cell, Molecular, and Developmental Biology Program, Tufts Graduate School of Biomedical Sciences, Boston, MA, USA
| | - Mary Sommer
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Elliot Kim
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Yoav Adam
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA.,Edmond and Lily Safra Center for Brain Sciences, the Hebrew University of Jerusalem, Jerusalem, Israel
| | - Philip G Haydon
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Edward S Boyden
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA.,Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.,McGovern Institute, Massachusetts Institute of Technology, Cambridge, MA, USA.,Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, USA.,Koch Institute, Massachusetts Institute of Technology, Cambridge, MA, USA.,Center for Neurobiological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Adam E Cohen
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA.,Department of Physics, Harvard University, Cambridge, MA, USA
| | - Chris G Dulla
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA.
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6
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Ameroso D, Meng A, Chen S, Felsted J, Dulla CG, Rios M. Astrocytic BDNF signaling within the ventromedial hypothalamus regulates energy homeostasis. Nat Metab 2022; 4:627-643. [PMID: 35501599 PMCID: PMC9177635 DOI: 10.1038/s42255-022-00566-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Accepted: 03/28/2022] [Indexed: 11/12/2022]
Abstract
Brain-derived neurotrophic factor (BDNF) is essential for maintaining energy and glucose balance within the central nervous system. Because the study of its metabolic actions has been limited to effects in neuronal cells, its role in other cell types within the brain remains poorly understood. Here we show that astrocytic BDNF signaling within the ventromedial hypothalamus (VMH) modulates neuronal activity in response to changes in energy status. This occurs via the truncated TrkB.T1 receptor. Accordingly, either fasting or central BDNF depletion enhances astrocytic synaptic glutamate clearance, thereby decreasing neuronal activity in mice. Notably, selective depletion of TrkB.T1 in VMH astrocytes blunts the effects of energy status on excitatory transmission, as well as on responses to leptin, glucose and lipids. These effects are driven by increased astrocytic invasion of excitatory synapses, enhanced glutamate reuptake and decreased neuronal activity. We thus identify BDNF/TrkB.T1 signaling in VMH astrocytes as an essential mechanism that participates in energy and glucose homeostasis.
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Affiliation(s)
- Dominique Ameroso
- Graduate Program in Neuroscience, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, MA, USA
| | - Alice Meng
- Graduate Program in Cell, Molecular and Developmental Biology, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, MA, USA
| | - Stella Chen
- Graduate Program in Neuroscience, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, MA, USA
| | - Jennifer Felsted
- Graduate Program in Biochemical and Molecular Nutrition, Friedman School of Nutrition Science and Policy, Tufts University, Boston, MA, USA
| | - Chris G Dulla
- Graduate Program in Neuroscience, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, MA, USA
- Graduate Program in Cell, Molecular and Developmental Biology, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, MA, USA
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Maribel Rios
- Graduate Program in Neuroscience, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, MA, USA.
- Graduate Program in Cell, Molecular and Developmental Biology, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, MA, USA.
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA.
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7
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Ung K, Huang TW, Lozzi B, Woo J, Hanson E, Pekarek B, Tepe B, Sardar D, Cheng YT, Liu G, Deneen B, Arenkiel BR. Olfactory bulb astrocytes mediate sensory circuit processing through Sox9 in the mouse brain. Nat Commun 2021; 12:5230. [PMID: 34471129 PMCID: PMC8410770 DOI: 10.1038/s41467-021-25444-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Accepted: 08/11/2021] [Indexed: 01/07/2023] Open
Abstract
The role of transcription factors during astrocyte development and their subsequent effects on neuronal development has been well studied. Less is known about astrocytes contributions towards circuits and behavior in the adult brain. Astrocytes play important roles in synaptic development and modulation, however their contributions towards neuronal sensory function and maintenance of neuronal circuit architecture remain unclear. Here, we show that loss of the transcription factor Sox9 results in both anatomical and functional changes in adult mouse olfactory bulb (OB) astrocytes, affecting sensory processing. Indeed, astrocyte-specific deletion of Sox9 in the OB results in decreased odor detection thresholds and discrimination and it is associated with aberrant neuronal sensory response maps. At functional level, loss of astrocytic Sox9 impairs the electrophysiological properties of mitral and tufted neurons. RNA-sequencing analysis reveals widespread changes in the gene expression profiles of OB astrocytes. In particular, we observe reduced GLT-1 expression and consequential alterations in glutamate transport. Our findings reveal that astrocytes are required for physiological sensory processing and we identify astrocytic Sox9 as an essential transcriptional regulator of mature astrocyte function in the mouse OB.
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Affiliation(s)
- Kevin Ung
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX, USA
| | - Teng-Wei Huang
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX, USA
| | - Brittney Lozzi
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX, USA
| | - Junsung Woo
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX, USA
| | - Elizabeth Hanson
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Brandon Pekarek
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Burak Tepe
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX, USA
| | - Debosmita Sardar
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX, USA
| | - Yi-Ting Cheng
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX, USA
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX, USA
| | - Gary Liu
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX, USA
- Medical Scientist Training Program, Baylor College of Medicine, Houston, TX, USA
| | - Benjamin Deneen
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX, USA.
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX, USA.
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA.
- Department of Neurosurgery, Baylor College of Medicine, Houston, TX, USA.
| | - Benjamin R Arenkiel
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX, USA.
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA.
- Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital, Houston, TX, USA.
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8
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Crivellaro G, Tottene A, Vitale M, Melone M, Casari G, Conti F, Santello M, Pietrobon D. Specific activation of GluN1-N2B NMDA receptors underlies facilitation of cortical spreading depression in a genetic mouse model of migraine with reduced astrocytic glutamate clearance. Neurobiol Dis 2021; 156:105419. [PMID: 34111520 DOI: 10.1016/j.nbd.2021.105419] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 05/29/2021] [Accepted: 06/04/2021] [Indexed: 01/28/2023] Open
Abstract
Migraine is a common but poorly understood sensory circuit disorder. Mouse models of familial hemiplegic migraine (FHM, a rare monogenic form of migraine with aura) show increased susceptibility to cortical spreading depression (CSD, the phenomenon that underlies migraine aura and can activate migraine headache mechanisms), allowing an opportunity to investigate the mechanisms of CSD and migraine onset. In FHM type 2 (FHM2) knock-in mice with reduced expression of astrocytic Na+, K+-ATPases, the reduced rate of glutamate uptake into astrocytes can account for the facilitation of CSD initiation. Here, we investigated the underlying mechanisms and show that the reduced rate of glutamate clearance in FHM2 mice results in increased amplitude and slowing of rise time and decay of the NMDA receptor (NMDAR) excitatory postsynaptic current (EPSC) elicited in layer 2/3 pyramidal cells by stimulation of neuronal afferents in somatosensory cortex slices. The relative increase in NMDAR activation in FHM2 mice is activity-dependent, being larger after high-frequency compared to low-frequency afferent activity. Inhibition of GluN1-N2B NMDARs, which hardly affected the NMDAR EPSC in wild-type mice, rescued the increased and prolonged activation of NMDARs as well as the facilitation of CSD induction and propagation in FHM2 mice. Our data suggest that the enhanced susceptibility to CSD in FHM2 is mainly due to specific activation of extrasynaptic GluN1-N2B NMDARs and point to these receptors as possible therapeutic targets for prevention of CSD and migraine.
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Affiliation(s)
- Giovanna Crivellaro
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Angelita Tottene
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Marina Vitale
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Marcello Melone
- Department of Experimental and Clinical Medicine, Università Politecnica delle Marche, Italy Center for Neurobiology of Aging, INRCA IRCCS, Ancona, Italy
| | - Giorgio Casari
- Vita Salute San Raffaele University and San Raffaele Scientific Institute, Milano, Italy
| | - Fiorenzo Conti
- Department of Experimental and Clinical Medicine, Università Politecnica delle Marche, Italy Center for Neurobiology of Aging, INRCA IRCCS, Ancona, Italy; Fondazione di Medicina Molecolare, Università Politecnica delle Marche, Ancona, Italy
| | - Mirko Santello
- Institute of Pharmacology and Toxicology and Neuroscience Center Zurich, University of Zurich, CH-8057 Zurich, Switzerland
| | - Daniela Pietrobon
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy; Padova Neuroscience Center, University of Padova, CNR Institute of Neuroscience, 35131 Padova, Italy.
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9
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Sipe GO, Petravicz J, Rikhye RV, Garcia R, Mellios N, Sur M. Astrocyte glutamate uptake coordinates experience-dependent, eye-specific refinement in developing visual cortex. Glia 2021; 69:1723-1735. [PMID: 33675674 DOI: 10.1002/glia.23987] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 02/17/2021] [Accepted: 02/24/2021] [Indexed: 12/25/2022]
Abstract
The uptake of glutamate by astrocytes actively shapes synaptic transmission, however its role in the development and plasticity of neuronal circuits remains poorly understood. The astrocytic glutamate transporter, GLT1 is the predominant source of glutamate clearance in the adult mouse cortex. Here, we examined the structural and functional development of the visual cortex in GLT1 heterozygous (HET) mice using two-photon microscopy, immunohistochemistry and slice electrophysiology. We find that though eye-specific thalamic axonal segregation is intact, binocular refinement in the primary visual cortex is disrupted. Eye-specific responses to visual stimuli in GLT1 HET mice show altered binocular matching, with abnormally high responses to ipsilateral compared to contralateral eye stimulation and a greater mismatch between preferred orientation selectivity of ipsilateral and contralateral eye responses. Furthermore, we observe an increase in dendritic spine density in the basal dendrites of layer 2/3 excitatory neurons suggesting aberrant spine pruning. Monocular deprivation induces atypical ocular dominance plasticity in GLT1 HET mice, with an unusual depression of ipsilateral open eye responses; however, this change in ipsilateral responses correlates well with an upregulation of GLT1 protein following monocular deprivation. These results demonstrate that a key function of astrocytic GLT1 function during development is the experience-dependent refinement of ipsilateral eye inputs relative to contralateral eye inputs in visual cortex.
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Affiliation(s)
- Grayson O Sipe
- Department of Brain and Cognitive Sciences, Picower Institute of Learning and Memory, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Jeremy Petravicz
- Department of Brain and Cognitive Sciences, Picower Institute of Learning and Memory, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Rajeev V Rikhye
- Department of Brain and Cognitive Sciences, Picower Institute of Learning and Memory, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Rodrigo Garcia
- Department of Brain and Cognitive Sciences, Picower Institute of Learning and Memory, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Nikolaos Mellios
- Department of Neurosciences, University of New Mexico School of Medicine, Albuquerque, New Mexico, USA.,Autophagy Inflammation and Metabolism (AIM) Center, Albuquerque, New Mexico, USA
| | - Mriganka Sur
- Department of Brain and Cognitive Sciences, Picower Institute of Learning and Memory, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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10
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Brymer KJ, Barnes JR, Parsons MP. Entering a new era of quantifying glutamate clearance in health and disease. J Neurosci Res 2021; 99:1598-1617. [PMID: 33618436 DOI: 10.1002/jnr.24810] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 01/22/2021] [Accepted: 02/01/2021] [Indexed: 12/21/2022]
Abstract
Glutamate transporter proteins, expressed on both neurons and glia, serve as the main gatekeepers that dictate the spatial and temporal actions of extracellular glutamate. Glutamate is essential to the function of the healthy brain yet paradoxically contributes to the toxicity associated with many neurodegenerative diseases. Rapid transporter-mediated glutamate uptake, primarily occurring at astrocytic processes, tightens the efficiency of excitatory network activity and prevents toxic glutamate build-up in the extracellular space. Glutamate transporter dysfunction is thought to underlie myriad central nervous system (CNS) diseases including Alzheimer and Huntington disease. Over the past few decades, techniques such as biochemical uptake assays and electrophysiological recordings of transporter currents from individual astrocytes have revealed the remarkable ability of the CNS to efficiently clear extracellular glutamate. In more recent years, the rapidly evolving glutamate-sensing "sniffers" now allow researchers to visualize real-time glutamate transients on a millisecond time scale with single synapse spatial resolution in defined cell populations. As we transition to an increased reliance on optical-based methods of glutamate visualization and quantification, it is of utmost importance to understand not only the advantages that glutamate biosensors bring to the table but also the associated caveats and their implications for data interpretation. In this review, we summarize the strengths and limitations of the commonly used methods to quantify glutamate uptake. We then discuss what these techniques, when viewed as a complementary whole, have told us about the brain's ability to regulate glutamate levels, in both health and in the context of neurodegenerative disease.
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Affiliation(s)
- Kyle J Brymer
- Faculty of Medicine, Division of Biomedical Sciences, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Jocelyn R Barnes
- Faculty of Medicine, Division of Biomedical Sciences, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Matthew P Parsons
- Faculty of Medicine, Division of Biomedical Sciences, Memorial University of Newfoundland, St. John's, NL, Canada
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11
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Zhou Y, Eid T, Hassel B, Danbolt NC. Novel aspects of glutamine synthetase in ammonia homeostasis. Neurochem Int 2020; 140:104809. [DOI: 10.1016/j.neuint.2020.104809] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2020] [Revised: 07/08/2020] [Accepted: 07/09/2020] [Indexed: 02/07/2023]
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12
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Ung K, Tepe B, Pekarek B, Arenkiel BR, Deneen B. Parallel astrocyte calcium signaling modulates olfactory bulb responses. J Neurosci Res 2020; 98:1605-1618. [PMID: 32426930 PMCID: PMC8147697 DOI: 10.1002/jnr.24634] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 03/27/2020] [Accepted: 04/10/2020] [Indexed: 12/17/2022]
Abstract
Astrocytes are the most abundant glial cell in the central nervous system. They modulate synaptic function through a variety of mechanisms, and yet remain relatively understudied with respect to overall neuronal circuit function. Exploiting the tractability of the mouse olfactory system, we manipulated astrocyte activity and examined how astrocytes modulate olfactory bulb responses. Toward this, we genetically targeted both astrocytes and neurons for in vivo widefield imaging of Ca2+ responses to odor stimuli. We found that astrocytes exhibited odor response maps that overlap with excitatory neuronal activity. By manipulating Ca2+ activity in astrocytes using chemical genetics we found that odor-evoked neuronal activity was reciprocally affected, suggesting that astrocyte activation inhibits neuronal odor responses. Subsequently, behavioral experiments revealed that astrocyte manipulations affect both odor detection threshold and discrimination, suggesting that astrocytes play an active role in olfactory sensory processing circuits. Together, these studies show that astrocyte calcium signaling contributes to olfactory behavior through modulation of sensory circuits.
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Affiliation(s)
- Kevin Ung
- Program in Developmental Biology, Houston, TX 77030, USA
| | - Burak Tepe
- Program in Developmental Biology, Houston, TX 77030, USA
| | - Brandon Pekarek
- Department of Molecular and Human Genetics, Houston, TX 77030, USA
| | - Benjamin R. Arenkiel
- Program in Developmental Biology, Houston, TX 77030, USA
- Department of Molecular and Human Genetics, Houston, TX 77030, USA
- Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital, Houston, TX 77030, USA
| | - Benjamin Deneen
- Program in Developmental Biology, Houston, TX 77030, USA
- Center for Cell and Gene Therapy, Houston, TX 77030, USA
- Department of Neurosurgery, Baylor College of Medicine, Houston, TX 77030, USA
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13
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Liu XX, Yang L, Shao LX, He Y, Wu G, Bao YH, Lu NN, Gong DM, Lu YP, Cui TT, Sun NH, Chen DY, Shi WX, Fukunaga K, Chen HS, Chen Z, Han F, Lu YM. Endothelial Cdk5 deficit leads to the development of spontaneous epilepsy through CXCL1/CXCR2-mediated reactive astrogliosis. J Exp Med 2020; 217:jem.20180992. [PMID: 31699822 PMCID: PMC7037235 DOI: 10.1084/jem.20180992] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2018] [Revised: 05/06/2019] [Accepted: 07/10/2019] [Indexed: 12/15/2022] Open
Abstract
Liu et al. reveal a key mechanism that mediating the transition from cerebrovascular damage to epilepsy. They identify the endothelial cyclin-dependent kinase 5 (CDK5) regulates astrocytic glutamate reuptake and increased glutamate synaptic function through CXCL1/CXCR2-mediated astrogliosis. Blood–brain barrier (BBB) dysfunction has been suggested to play an important role in epilepsy. However, the mechanism mediating the transition from cerebrovascular damage to epilepsy remains unknown. Here, we report that endothelial cyclin-dependent kinase 5 (CDK5) is a central regulator of neuronal excitability. Endothelial-specific Cdk5 knockout led to spontaneous seizures in mice. Knockout mice showed increased endothelial chemokine (C-X-C motif) ligand 1 (Cxcl1) expression, decreased astrocytic glutamate reuptake through the glutamate transporter 1 (GLT1), and increased glutamate synaptic function. Ceftriaxone restored astrocytic GLT1 function and inhibited seizures in endothelial Cdk5-deficient mice, and these effects were also reversed after silencing Cxcl1 in endothelial cells and its receptor chemokine (C-X-C motif) receptor 2 (Cxcr2) in astrocytes, respectively, in the CA1 by AAV transfection. These results reveal a previously unknown link between cerebrovascular factors and epileptogenesis and provide a rationale for targeting endothelial signaling as a potential treatment for epilepsy.
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Affiliation(s)
- Xiu-Xiu Liu
- Key Laboratory of Cardiovascular & Cerebrovascular Medicine, School of Pharmacy, Nanjing Medical University, Nanjing, China.,Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Lin Yang
- Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China.,Department of Physiology, School of Basic Medical Sciences, Nanjing Medical University, Nanjing, China.,School of Medicine, Zhejiang University City College, Hangzhou, Zhejiang, China
| | - Ling-Xiao Shao
- Key Laboratory of Cardiovascular & Cerebrovascular Medicine, School of Pharmacy, Nanjing Medical University, Nanjing, China.,Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Yang He
- Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Gang Wu
- Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Yu-Huan Bao
- Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China.,Department of Physiology, School of Basic Medical Sciences, Nanjing Medical University, Nanjing, China.,School of Medicine, Zhejiang University City College, Hangzhou, Zhejiang, China
| | - Nan-Nan Lu
- Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Dong-Mei Gong
- Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China.,Department of Physiology, School of Basic Medical Sciences, Nanjing Medical University, Nanjing, China.,School of Medicine, Zhejiang University City College, Hangzhou, Zhejiang, China
| | - Ya-Ping Lu
- Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China.,Department of Physiology, School of Basic Medical Sciences, Nanjing Medical University, Nanjing, China.,School of Medicine, Zhejiang University City College, Hangzhou, Zhejiang, China
| | - Tian-Tian Cui
- Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Ning-He Sun
- Key Laboratory of Cardiovascular & Cerebrovascular Medicine, School of Pharmacy, Nanjing Medical University, Nanjing, China.,Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Dan-Yang Chen
- Key Laboratory of Cardiovascular & Cerebrovascular Medicine, School of Pharmacy, Nanjing Medical University, Nanjing, China.,Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Wei-Xing Shi
- Departments of Pharmaceutical, Administrative, and Basic Sciences, Schools of Pharmacy and Medicine, Loma Linda University Health, Loma Linda, CA
| | - Kohji Fukunaga
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - Hong-Shan Chen
- Key Laboratory of Cardiovascular & Cerebrovascular Medicine, School of Pharmacy, Nanjing Medical University, Nanjing, China
| | - Zhong Chen
- Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Feng Han
- Key Laboratory of Cardiovascular & Cerebrovascular Medicine, School of Pharmacy, Nanjing Medical University, Nanjing, China.,Center for Global Health of Nanjing Medical University, Nanjing, China
| | - Ying-Mei Lu
- Department of Physiology, School of Basic Medical Sciences, Nanjing Medical University, Nanjing, China
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14
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Bres EE, Safina D, Müller J, Bedner P, Yang H, Helluy X, Shchyglo O, Jansen S, Mark MD, Esser A, Steinhäuser C, Herlitze S, Pietrzik CU, Sirko S, Manahan-Vaughan D, Faissner A. Lipoprotein receptor loss in forebrain radial glia results in neurological deficits and severe seizures. Glia 2020; 68:2517-2549. [PMID: 32579270 DOI: 10.1002/glia.23869] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Revised: 05/19/2020] [Accepted: 05/22/2020] [Indexed: 02/06/2023]
Abstract
The Alzheimer disease-associated multifunctional low-density lipoprotein receptor-related protein-1 is expressed in the brain. Recent studies uncovered a role of this receptor for the appropriate functioning of neural stem cells, oligodendrocytes, and neurons. The constitutive knock-out (KO) of the receptor is embryonically lethal. To unravel the receptors' role in the developing brain we generated a mouse mutant by specifically targeting radial glia stem cells of the dorsal telencephalon. The low-density lipoprotein receptor-related protein-1 lineage-restricted KO female and male mice, in contrast to available models, developed a severe neurological phenotype with generalized seizures during early postnatal development. The mechanism leading to a buildup of hyperexcitability and emergence of seizures was traced to a failure in adequate astrocyte development and deteriorated postsynaptic density integrity. The detected impairments in the astrocytic lineage: precocious maturation, reactive gliosis, abolished tissue plasminogen activator uptake, and loss of functionality emphasize the importance of this glial cell type for synaptic signaling in the developing brain. Together, the obtained results highlight the relevance of astrocytic low-density lipoprotein receptor-related protein-1 for glutamatergic signaling in the context of neuron-glia interactions and stage this receptor as a contributing factor for epilepsy.
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Affiliation(s)
- Ewa E Bres
- Department of Cell Morphology and Molecular Neurobiology, Ruhr University Bochum, Bochum, Germany.,International Graduate School of Neuroscience, Ruhr University Bochum, Bochum, Germany
| | - Dina Safina
- Department of Cell Morphology and Molecular Neurobiology, Ruhr University Bochum, Bochum, Germany.,International Graduate School of Neuroscience, Ruhr University Bochum, Bochum, Germany
| | - Julia Müller
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Peter Bedner
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Honghong Yang
- Department of Neurophysiology, Medical Faculty, Ruhr University Bochum, Bochum, Germany
| | - Xavier Helluy
- Department of Neurophysiology, Medical Faculty, Ruhr University Bochum, Bochum, Germany.,Department of Psychology, Institute of Cognitive Neuroscience, Biopsychology, Ruhr University Bochum, Bochum, Germany
| | - Olena Shchyglo
- Department of Neurophysiology, Medical Faculty, Ruhr University Bochum, Bochum, Germany
| | - Stephan Jansen
- Department of Neurophysiology, Medical Faculty, Ruhr University Bochum, Bochum, Germany
| | - Melanie D Mark
- Behavioral Neuroscience, Ruhr University Bochum, Bochum, Germany
| | | | - Christian Steinhäuser
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Stefan Herlitze
- Department of General Zoology and Neurobiology, Ruhr University Bochum, Bochum, Germany
| | - Claus U Pietrzik
- Institute of Pathobiochemistry, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Swetlana Sirko
- Department of Physiological Genomics, Biomedical Center (BMC), Ludwig-Maximilians University, Planegg-Martinsried, Germany.,Institute for Stem Cell Research, Helmholtz Zentrum Munich, Neuherberg, Germany
| | | | - Andreas Faissner
- Department of Cell Morphology and Molecular Neurobiology, Ruhr University Bochum, Bochum, Germany
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15
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Felix L, Stephan J, Rose CR. Astrocytes of the early postnatal brain. Eur J Neurosci 2020; 54:5649-5672. [PMID: 32406559 DOI: 10.1111/ejn.14780] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 04/30/2020] [Accepted: 05/06/2020] [Indexed: 12/21/2022]
Abstract
In the rodent forebrain, the majority of astrocytes are generated during the early postnatal phase. Following differentiation, astrocytes undergo maturation which accompanies the development of the neuronal network. Neonate astrocytes exhibit a distinct morphology and domain size which differs to their mature counterparts. Moreover, many of the plasma membrane proteins prototypical for fully developed astrocytes are only expressed at low levels at neonatal stages. These include connexins and Kir4.1, which define the low membrane resistance and highly negative membrane potential of mature astrocytes. Newborn astrocytes moreover express only low amounts of GLT-1, a glutamate transporter critical later in development. Furthermore, they show specific differences in the properties and spatio-temporal pattern of intracellular calcium signals, resulting from differences in their repertoire of receptors and signalling pathways. Therefore, roles fulfilled by mature astrocytes, including ion and transmitter homeostasis, are underdeveloped in the young brain. Similarly, astrocytic ion signalling in response to neuronal activity, a process central to neuron-glia interaction, differs between the neonate and mature brain. This review describes the unique functional properties of astrocytes in the first weeks after birth and compares them to later stages of development. We conclude that with an immature neuronal network and wider extracellular space, astrocytic support might not be as demanding and critical compared to the mature brain. The delayed differentiation and maturation of astrocytes in the first postnatal weeks might thus reflect a reduced need for active, energy-consuming regulation of the extracellular space and a less tight control of glial feedback onto synaptic transmission.
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Affiliation(s)
- Lisa Felix
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Duesseldorf, Duesseldorf, Germany
| | - Jonathan Stephan
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Duesseldorf, Duesseldorf, Germany
| | - Christine R Rose
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Duesseldorf, Duesseldorf, Germany
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16
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Armbruster M, Dulla CG, Diamond JS. Effects of fluorescent glutamate indicators on neurotransmitter diffusion and uptake. eLife 2020; 9:54441. [PMID: 32352378 PMCID: PMC7255799 DOI: 10.7554/elife.54441] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2019] [Accepted: 04/29/2020] [Indexed: 01/10/2023] Open
Abstract
Genetically encoded fluorescent glutamate indicators (iGluSnFRs) enable neurotransmitter release and diffusion to be visualized in intact tissue. Synaptic iGluSnFR signal time courses vary widely depending on experimental conditions, often lasting 10–100 times longer than the extracellular lifetime of synaptically released glutamate estimated with uptake measurements. iGluSnFR signals typically also decay much more slowly than the unbinding kinetics of the indicator. To resolve these discrepancies, here we have modeled synaptic glutamate diffusion, uptake and iGluSnFR activation to identify factors influencing iGluSnFR signal waveforms. Simulations suggested that iGluSnFR competes with transporters to bind synaptically released glutamate, delaying glutamate uptake. Accordingly, synaptic transporter currents recorded from iGluSnFR-expressing astrocytes in mouse cortex were slower than those in control astrocytes. Simulations also suggested that iGluSnFR reduces free glutamate levels in extrasynaptic spaces, likely limiting extrasynaptic receptor activation. iGluSnFR and lower affinity variants, nonetheless, provide linear indications of vesicle release, underscoring their value for optical quantal analysis.
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Affiliation(s)
- Moritz Armbruster
- Department of Neuroscience, Tufts University School of Medicine, Boston, United States
| | - Chris G Dulla
- Department of Neuroscience, Tufts University School of Medicine, Boston, United States
| | - Jeffrey S Diamond
- Synaptic Physiology Section, NINDS Intramural Research Program, National Institutes of Health, Bethesda, United States
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17
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Huang Y, Hu L, Li H, Huang Y, Li Y, Yang J, Gu J, Xu H. PKA-mediated phosphorylation of CREB and NMDA receptor 2B in the hippocampus of offspring rats is involved in transmission of mental disorders across a generation. Psychiatry Res 2019; 280:112497. [PMID: 31419724 DOI: 10.1016/j.psychres.2019.112497] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Revised: 07/28/2019] [Accepted: 07/28/2019] [Indexed: 02/05/2023]
Abstract
This study is aimed at the mechanism of transmission of mental disorders across a generation. We used 10 different stressors to establish an animal model of chronic unpredictable stress (CUS) before pregnancy. Forced swimming test (FST) and open field test (OFT) were used to analyze the behavior of 30-day-old adolescent offspring rats born to stress mothers. Magnetic resonance spectroscopy was used to measure glutamate, gamma-aminobutyric acid (GABA), and glutamine. Phosphate-activated glutaminase (PAG), glutamate decarboxylase (GAD), GABA-transaminase (GABA-T), protein kinase A (PKA), cAMP response element-binding protein (CREB), and N-methyl-D-aspartate (NMDA) receptor 2B (NR2B) were detected by western blot. Adolescent offspring rats in the CUS group exhibited depressive-like behavior in the FST and anxious behavior in the OFT. GAD was increased and GABA-T was decreased, which resulted in an increase in GABA levels and decrease of the glutamate/GABA ratio in the hippocampus of CUS offspring rats. Disruption of the glutamate/GABA-glutamine cycle was related to decrease PKA-mediated phosphorylation of CREB and NR2B in the hippocampus. These findings highlight the importance of mental health of females before pregnancy and suggest that CUS before pregnancy reduces p-CREB and p-NR2B in the offspring hippocampus, which could be responsible for behavioral disorders in the adolescent offspring.
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Affiliation(s)
- Yuejun Huang
- Department of Pediatrics, Second Affiliated Hospital of Shantou University Medical College, North Dongxia Road, Shantou 515041, Guangdong, China
| | - Liu Hu
- Department of Pediatrics, Second Affiliated Hospital of Shantou University Medical College, North Dongxia Road, Shantou 515041, Guangdong, China
| | - Hui Li
- Department of Psychiatry and Psychology, Mental Health Center of Shantou University, Taishan Road, Shantou 515041, Guangdong, China
| | - Yanhong Huang
- Department of Psychiatry and Psychology, Mental Health Center of Shantou University, Taishan Road, Shantou 515041, Guangdong, China
| | - Yuewa Li
- Department of Pediatrics, Second Affiliated Hospital of Shantou University Medical College, North Dongxia Road, Shantou 515041, Guangdong, China
| | - Jianhui Yang
- Department of Pediatrics, Second Affiliated Hospital of Shantou University Medical College, North Dongxia Road, Shantou 515041, Guangdong, China
| | - Jiajie Gu
- Department of Neurosurgery, First Affiliated Hospital of Shantou University Medical College, Changping Road, Shantou 515041, Guangdong, China
| | - Hongwu Xu
- Department of Neurosurgery, First Affiliated Hospital of Shantou University Medical College, Changping Road, Shantou 515041, Guangdong, China.
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18
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Beenhakker M. A Brief Boost of Positive Energy When Young Makes for a Healthy Adult Interneuron. Epilepsy Curr 2019; 19:321-324. [PMID: 31456436 PMCID: PMC6864565 DOI: 10.1177/1535759719871315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Tonic Activation of GluN2C/GluN2D-Containing NMDA Receptors by Ambient Glutamate Facilitates Cortical Interneuron Maturation Hanson E, Armbruster M, Lau LA, Sommer ME, Klaft ZJ, Swanger SA, Traynelis SF, Moss SJ, Noubary F, Chadchankar J, Dulla CG. J Neurosci. 2019;39(19):3611-3626. doi:10.1523/JNEUROSCI.1392-18.2019. PMID: 30846615. Epub Mar 7, 2019. Developing cortical GABAergic interneurons rely on genetic programs, neuronal activity, and environmental cues to construct inhibitory circuits during early postnatal development. Disruption of these events can cause long-term changes in cortical inhibition and may be involved in neurological disorders associated with inhibitory circuit dysfunction. We hypothesized that tonic glutamate signaling in the neonatal cortex contributes to, and is necessary for, the maturation of cortical interneurons. To test this hypothesis, we used mice of both sexes to quantify extracellular glutamate concentrations in the cortex during development, measure ambient glutamate-mediated activation of developing cortical interneurons, and manipulate tonic glutamate signaling using subtype-specific N-methyl-d-aspartic acid (NMDA) receptor antagonists in vitro and in vivo. We report that ambient glutamate levels are high (≈100 nm) in the neonatal cortex and decrease (to ≈50 nm) during the first weeks of life, coincident with increases in astrocytic glutamate uptake. Consistent with elevated ambient glutamate, putative parvalbumin-positive interneurons in the cortex (identified using G42: GAD1-eGFP reporter mice) exhibit a transient, tonic NMDA current at the end of the first postnatal week. GluN2C/GluN2D-containing NMDA receptors mediate the majority of this current and contribute to the resting membrane potential and intrinsic properties of developing putative parvalbumin interneurons. Pharmacological blockade of GluN2C/GluN2D-containing NMDA receptors in vivo during the period of tonic interneuron activation, but not later, leads to lasting decreases in interneuron morphological complexity and causes deficits in cortical inhibition later in life. These results demonstrate that dynamic ambient glutamate signaling contributes to cortical interneuron maturation via tonic activation of GluN2C/GluN2D-containing NMDA receptors. Significance statement: Inhibitory GABAergic interneurons make up 20% of cortical neurons and are critical to controlling cortical network activity. Dysfunction of cortical inhibition is associated with multiple neurological disorders, including epilepsy. Establishing inhibitory cortical networks requires in utero proliferation, differentiation, and migration of immature GABAergic interneurons and subsequent postnatal morphological maturation and circuit integration. Here, we demonstrate that ambient glutamate provides tonic activation of immature, putative parvalbumin-positive GABAergic interneurons in the neonatal cortex via high-affinity NMDA receptors. When this activation is blocked, GABAergic interneuron maturation is disrupted, and cortical networks exhibit lasting abnormal hyperexcitability. We conclude that temporally precise activation of developing cortical interneurons by ambient glutamate is critically important for establishing normal cortical inhibition.
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19
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Zhao CC, Jiang MY, Zhang LY, Hu YY, Hu ZJ, Zhang MY, Qi J, Su AC, Lou N, Xian XH, Zhang JG, Li WB, Zhang M. Peroxisome proliferator-activated receptor gamma participates in the acquisition of brain ischemic tolerance induced by ischemic preconditioning via glial glutamate transporter 1 in vivo and in vitro. J Neurochem 2019; 151:608-625. [PMID: 31314916 DOI: 10.1111/jnc.14824] [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: 12/05/2018] [Revised: 03/08/2019] [Accepted: 07/11/2019] [Indexed: 01/29/2023]
Abstract
Glial glutamate transporter 1 (GLT-1) plays a vital role in the induction of brain ischemic tolerance (BIT) by ischemic preconditioning (IPC). However, the mechanism still needs to be further explained. The aim of this study was to investigate whether peroxisome proliferator-activated receptor gamma (PPARγ) participates in regulating GLT-1 during the acquisition of BIT induced by IPC. Initially, cerebral IPC induced BIT and enhanced PPARγ and GLT-1 expression in the CA1 hippocampus in rats. The ratio of nuclear/cytoplasmic PPARγ was also increased. At the same time, the up-regulation of PPARγ expression in astrocytes in the CA1 hippocampus was revealed by double immunofluorescence for PPARγ and glial fibrillary acidic protein. Then, the mechanism by which PPARγ regulates GLT-1 was studied in rat cortical astrocyte-neuron cocultures. We found that IPC [45 min of oxygen glucose deprivation (OGD)] protected neuronal survival after lethal OGD (4 h of OGD), which usually leads to neuronal death. The activation of PPARγ occurred earlier than the up-regulation of GLT-1 in astrocytes after IPC, as determined by western blot and immunofluorescence. Moreover, the preadministration of the PPARγ antagonist T0070907 or PPARγ siRNA significantly attenuated GLT-1 up-regulation and the neuroprotective effects induced by IPC in vitro. Finally, the effect of the PPARγ antagonist on GLT-1 expression and BIT was verified in vivo. We observed that the preadministration of T0070907 by intracerebroventricular injection dose-dependently attenuated the up-regulation of GLT-1 and BIT induced by cerebral IPC in rats. In conclusion, PPARγ participates in regulating GLT-1 during the acquisition of BIT induced by IPC. Cover Image for this issue: doi: 10.1111/jnc.14532. Open Science: This manuscript was awarded with the Open Materials Badge For more information see: https://cos.io/our-services/open-science-badges/.
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Affiliation(s)
- Cong-Cong Zhao
- Department of Pathophysiology, Hebei Medical University, Shijiazhuang, People's Republic of China.,Department of Intensive Care Unit, The Fourth Hospital of Hebei Medical University, Shijiazhuang, People's Republic of China
| | - Meng-Yang Jiang
- Department of Pathophysiology, Hebei Medical University, Shijiazhuang, People's Republic of China
| | - Ling-Yan Zhang
- Department of Pathophysiology, Hebei Medical University, Shijiazhuang, People's Republic of China
| | - Yu-Yan Hu
- Department of Pathophysiology, Hebei Medical University, Shijiazhuang, People's Republic of China
| | - Zhen-Jie Hu
- Department of Intensive Care Unit, The Fourth Hospital of Hebei Medical University, Shijiazhuang, People's Republic of China
| | - Meng-Yue Zhang
- Clinical Medicine, Hebei Medical University, Shijiazhuang, People's Republic of China
| | - Jie Qi
- Department of Pathophysiology, Hebei Medical University, Shijiazhuang, People's Republic of China
| | - A-Chou Su
- Department of Pathophysiology, Hebei Medical University, Shijiazhuang, People's Republic of China
| | - Nan Lou
- Department of Pathophysiology, Hebei Medical University, Shijiazhuang, People's Republic of China
| | - Xiao-Hui Xian
- Department of Pathophysiology, Hebei Medical University, Shijiazhuang, People's Republic of China
| | - Jing-Ge Zhang
- Department of Pathophysiology, Hebei Medical University, Shijiazhuang, People's Republic of China
| | - Wen-Bin Li
- Department of Pathophysiology, Hebei Medical University, Shijiazhuang, People's Republic of China.,Aging and Cognition Neuroscience Laboratory of Hebei Province, Shijiazhuang, People's Republic of China
| | - Min Zhang
- Department of Pathophysiology, Hebei Medical University, Shijiazhuang, People's Republic of China.,Aging and Cognition Neuroscience Laboratory of Hebei Province, Shijiazhuang, People's Republic of China
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20
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Hanson E, Armbruster M, Lau LA, Sommer ME, Klaft ZJ, Swanger SA, Traynelis SF, Moss SJ, Noubary F, Chadchankar J, Dulla CG. Tonic Activation of GluN2C/GluN2D-Containing NMDA Receptors by Ambient Glutamate Facilitates Cortical Interneuron Maturation. J Neurosci 2019; 39:3611-3626. [PMID: 30846615 PMCID: PMC6510335 DOI: 10.1523/jneurosci.1392-18.2019] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Revised: 01/29/2019] [Accepted: 02/26/2019] [Indexed: 02/03/2023] Open
Abstract
Developing cortical GABAergic interneurons rely on genetic programs, neuronal activity, and environmental cues to construct inhibitory circuits during early postnatal development. Disruption of these events can cause long-term changes in cortical inhibition and may be involved in neurological disorders associated with inhibitory circuit dysfunction. We hypothesized that tonic glutamate signaling in the neonatal cortex contributes to, and is necessary for, the maturation of cortical interneurons. To test this hypothesis, we used mice of both sexes to quantify extracellular glutamate concentrations in the cortex during development, measure ambient glutamate-mediated activation of developing cortical interneurons, and manipulate tonic glutamate signaling using subtype-specific NMDA receptor antagonists in vitro and in vivo We report that ambient glutamate levels are high (≈100 nm) in the neonatal cortex and decrease (to ≈50 nm) during the first weeks of life, coincident with increases in astrocytic glutamate uptake. Consistent with elevated ambient glutamate, putative parvalbumin-positive interneurons in the cortex (identified using G42:GAD1-eGFP reporter mice) exhibit a transient, tonic NMDA current at the end of the first postnatal week. GluN2C/GluN2D-containing NMDA receptors mediate the majority of this current and contribute to the resting membrane potential and intrinsic properties of developing putative parvalbumin interneurons. Pharmacological blockade of GluN2C/GluN2D-containing NMDA receptors in vivo during the period of tonic interneuron activation, but not later, leads to lasting decreases in interneuron morphological complexity and causes deficits in cortical inhibition later in life. These results demonstrate that dynamic ambient glutamate signaling contributes to cortical interneuron maturation via tonic activation of GluN2C/GluN2D-containing NMDA receptors.SIGNIFICANCE STATEMENT Inhibitory GABAergic interneurons make up 20% of cortical neurons and are critical to controlling cortical network activity. Dysfunction of cortical inhibition is associated with multiple neurological disorders, including epilepsy. Establishing inhibitory cortical networks requires in utero proliferation, differentiation, and migration of immature GABAergic interneurons, and subsequent postnatal morphological maturation and circuit integration. Here, we demonstrate that ambient glutamate provides tonic activation of immature, putative parvalbumin-positive GABAergic interneurons in the neonatal cortex via high-affinity NMDA receptors. When this activation is blocked, GABAergic interneuron maturation is disrupted, and cortical networks exhibit lasting abnormal hyperexcitability. We conclude that temporally precise activation of developing cortical interneurons by ambient glutamate is critically important for establishing normal cortical inhibition.
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Affiliation(s)
- Elizabeth Hanson
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
- Neuroscience Program, Tufts Sackler School of Biomedical Sciences, Boston, Massachusetts 02111
| | - Moritz Armbruster
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Lauren A Lau
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
- Neuroscience Program, Tufts Sackler School of Biomedical Sciences, Boston, Massachusetts 02111
| | - Mary E Sommer
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Zin-Juan Klaft
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Sharon A Swanger
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Stephen F Traynelis
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Stephen J Moss
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
- AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111, and
| | - Farzad Noubary
- Department of Health Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts 02115
| | - Jayashree Chadchankar
- AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111, and
| | - Chris G Dulla
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111,
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21
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Koenig JB, Cantu D, Low C, Sommer M, Noubary F, Croker D, Whalen M, Kong D, Dulla CG. Glycolytic inhibitor 2-deoxyglucose prevents cortical hyperexcitability after traumatic brain injury. JCI Insight 2019; 5:126506. [PMID: 31038473 DOI: 10.1172/jci.insight.126506] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Traumatic brain injury (TBI) causes cortical dysfunction and can lead to post-traumatic epilepsy. Multiple studies demonstrate that GABAergic inhibitory network function is compromised following TBI, which may contribute to hyperexcitability and motor, behavioral, and cognitive deficits. Preserving the function of GABAergic interneurons, therefore, is a rational therapeutic strategy to preserve cortical function after TBI and prevent long-term clinical complications. Here, we explored an approach based on the ketogenic diet, a neuroprotective and anticonvulsant dietary therapy which results in reduced glycolysis and increased ketosis. Utilizing a pharmacologic inhibitor of glycolysis (2-deoxyglucose, or 2-DG), we found that acute in vitro application of 2-DG decreased the excitability of excitatory neurons, but not inhibitory interneurons, in cortical slices from naïve mice. Employing the controlled cortical impact (CCI) model of TBI in mice, we found that in vitro 2-DG treatment rapidly attenuated epileptiform activity seen in acute cortical slices 3 to 5 weeks after TBI. One week of in vivo 2-DG treatment immediately after TBI prevented the development of epileptiform activity, restored excitatory and inhibitory synaptic activity, and attenuated the loss of parvalbumin-expressing inhibitory interneurons. In summary, 2-DG may have therapeutic potential to restore network function following TBI.
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Affiliation(s)
- Jenny B Koenig
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts, USA.,Neuroscience Program, Tufts University Sackler School of Graduate Biomedical Sciences, Boston, Massachusetts, USA
| | - David Cantu
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Cho Low
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts, USA.,Cellular, Molecular, and Developmental Biology Program, Tufts University Sackler School of Graduate Biomedical Sciences, Boston, Massachusetts, USA
| | - Mary Sommer
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Farzad Noubary
- Department of Health Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts, USA
| | - Danielle Croker
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Michael Whalen
- Neuroscience Center, Harvard Medical School, Massachusetts General Hospital, Charlestown, Massachusetts, USA.,Department of Pediatrics, Harvard Medical School, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Dong Kong
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Chris G Dulla
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts, USA
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22
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Gegelashvili G, Bjerrum OJ. Glutamate transport system as a key constituent of glutamosome: Molecular pathology and pharmacological modulation in chronic pain. Neuropharmacology 2019; 161:107623. [PMID: 31047920 DOI: 10.1016/j.neuropharm.2019.04.029] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 04/26/2019] [Accepted: 04/28/2019] [Indexed: 01/07/2023]
Abstract
Neural uptake of glutamate is executed by the structurally related members of the SLC1A family of solute transporters: GLAST/EAAT1, GLT-1/EAAT2, EAAC1/EAAT3, EAAT4, ASCT2. These plasma membrane proteins ensure supply of glutamate, aspartate and some neutral amino acids, including glutamine and cysteine, for synthetic, energetic and signaling purposes, whereas effective removal of glutamate from the synaptic cleft shapes excitatory neurotransmission and prevents glutamate toxicity. Glutamate transporters (GluTs) possess also receptor-like properties and can directly initiate signal transduction. GluTs are physically linked to other glutamate signaling-, transporting- and metabolizing molecules (e.g., glutamine transporters SNAT3 and ASCT2, glutamine synthetase, NMDA receptor, synaptic vesicles), as well as cellular machineries fueling the transmembrane transport of glutamate (e.g., ion gradient-generating Na/K-ATPase, glycolytic enzymes, mitochondrial membrane- and matrix proteins, glucose transporters). We designate this supramolecular functional assembly as 'glutamosome'. GluTs play important roles in the molecular pathology of chronic pain, due to the predominantly glutamatergic nature of nociceptive signaling in the spinal cord. Down-regulation of GluTs often precedes or occurs simultaneously with development of pain hypersensitivity. Pharmacological inhibition or gene knock-down of spinal GluTs can induce/aggravate pain, whereas enhancing expression of GluTs by viral gene transfer can mitigate chronic pain. Thus, functional up-regulation of GluTs is turning into a prospective pharmacotherapeutic approach for the management of chronic pain. A number of novel positive pharmacological regulators of GluTs, incl. pyridazine derivatives and β-lactams, have recently been introduced. However, design and development of new analgesics based on this principle will require more precise knowledge of molecular mechanisms underlying physiological or aberrant functioning of the glutamate transport system in nociceptive circuits. This article is part of the issue entitled 'Special Issue on Neurotransmitter Transporters'.
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Affiliation(s)
- Georgi Gegelashvili
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark; Institute of Chemical Biology, Ilia State University, Tbilisi, Georgia.
| | - Ole Jannik Bjerrum
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
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23
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Yang P, Li L, Xia S, Zhou B, Zhu Y, Zhou G, Tu E, Huang T, Huang H, Li F. Effect of Clozapine on Anti-N-Methyl-D-Aspartate Receptor Encephalitis With Psychiatric Symptoms: A Series of Three Cases. Front Neurosci 2019; 13:315. [PMID: 31024238 PMCID: PMC6465601 DOI: 10.3389/fnins.2019.00315] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 03/19/2019] [Indexed: 01/29/2023] Open
Abstract
The main clinical manifestations of anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis are acute or subacute seizures, cognition impairment, and psychiatric symptoms. Nowadays, the scheme of antipsychotic therapy for this disease has not been established. This study reports three cases of anti-NMDAR encephalitis with psychiatric symptoms. The anti-NMDAR antibodies in cerebrospinal fluid (CSF) and serum were positive. The psychiatric symptoms still existed after intravenous immunoglobulin (IVIG) treatment; thus, clozapine was used for antipsychotic therapy. Case 1 was a 37-year-old man who suffered from bad mood and suicide behaviors for 1 month. Hallucination and delusion still existed after IVIG treatment and hormone therapy, and the symptoms were relieved when given clozapine for 12 months. Case 2 was a 28-year-old man who was admitted to our hospital due to injuring other people and destructive behaviors for 2 days. He showed irritability, bad temper, declined cognition, and severe delusion of persecution after IVIG treatment and hormone therapy, but the psychiatric symptoms disappeared when given clozapine for 3 months. Case 3 was a 23-year-old man who suffered from headache and babbing for 7 days. Symptoms such as irritability, bad temper, babbing, and injuring other people still existed after IVIG treatment and hormone therapy, but they disappeared when given clozapine for 2 months. Therefore, we suggest that during the treatment of anti-NMDAR encephalitis with psychiatric symptoms, if the anti-NMDAR antibodies in CSF and serum were positive, and psychiatric symptoms could not be controlled after IVIG and hormone therapy, clozapine may work.
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Affiliation(s)
- Ping Yang
- Department of Psychiatry, Hunan Brain Hospital, Clinical Medical School, Hunan University of Chinese Medicine, Changsha, China
| | - Liang Li
- Provincial Key Laboratory of TCM Diagnostics, Hunan University of Chinese Medicine, Changsha, China
| | - Shuaishuai Xia
- Provincial Key Laboratory of TCM Diagnostics, Hunan University of Chinese Medicine, Changsha, China
| | - Bin Zhou
- Department of Psychiatry, Hunan Brain Hospital, Clinical Medical School, Hunan University of Chinese Medicine, Changsha, China
| | - Yong Zhu
- Department of Psychiatry, Hunan Brain Hospital, Clinical Medical School, Hunan University of Chinese Medicine, Changsha, China
| | - Gaoya Zhou
- Department of Psychiatry, Hunan Brain Hospital, Clinical Medical School, Hunan University of Chinese Medicine, Changsha, China
| | - Erwen Tu
- Department of Psychiatry, Hunan Brain Hospital, Clinical Medical School, Hunan University of Chinese Medicine, Changsha, China
| | - Tianhao Huang
- Shanghai Institute of Measurement and Testing Technology, Shanghai, China
| | - Huiyong Huang
- Provincial Key Laboratory of TCM Diagnostics, Hunan University of Chinese Medicine, Changsha, China
| | - Feng Li
- Provincial Key Laboratory of TCM Diagnostics, Hunan University of Chinese Medicine, Changsha, China.,School of Dentistry, University of California, Los Angeles, Los Angeles, CA, United States
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24
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Romanos J, Benke D, Saab AS, Zeilhofer HU, Santello M. Differences in glutamate uptake between cortical regions impact neuronal NMDA receptor activation. Commun Biol 2019; 2:127. [PMID: 30963115 PMCID: PMC6451009 DOI: 10.1038/s42003-019-0367-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Accepted: 03/05/2019] [Indexed: 01/06/2023] Open
Abstract
Removal of synaptically-released glutamate by astrocytes is necessary to spatially and temporally limit neuronal activation. Recent evidence suggests that astrocytes may have specialized functions in specific circuits, but the extent and significance of such specialization are unclear. By performing direct patch-clamp recordings and two-photon glutamate imaging, we report that in the somatosensory cortex, glutamate uptake by astrocytes is slower during sustained synaptic stimulation when compared to lower stimulation frequencies. Conversely, glutamate uptake capacity is increased in the frontal cortex during higher frequency synaptic stimulation, thereby limiting extracellular buildup of glutamate and NMDA receptor activation in layer 5 pyramidal neurons. This efficient glutamate clearance relies on Na+/K+-ATPase function and both GLT-1 and non-GLT-1 transporters. Thus, by enhancing their glutamate uptake capacity, astrocytes in the frontal cortex may prevent excessive neuronal excitation during intense synaptic activity. These results may explain why diseases associated with network hyperexcitability differentially affect individual brain areas.
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Affiliation(s)
- Jennifer Romanos
- Institute of Pharmacology and Toxicology, University of Zurich, CH-8057 Zurich, Switzerland
- Neuroscience Center Zurich, University of Zurich and ETH Zurich, CH-8057 Zurich, Switzerland
| | - Dietmar Benke
- Institute of Pharmacology and Toxicology, University of Zurich, CH-8057 Zurich, Switzerland
- Neuroscience Center Zurich, University of Zurich and ETH Zurich, CH-8057 Zurich, Switzerland
| | - Aiman S. Saab
- Institute of Pharmacology and Toxicology, University of Zurich, CH-8057 Zurich, Switzerland
- Neuroscience Center Zurich, University of Zurich and ETH Zurich, CH-8057 Zurich, Switzerland
| | - Hanns Ulrich Zeilhofer
- Institute of Pharmacology and Toxicology, University of Zurich, CH-8057 Zurich, Switzerland
- Neuroscience Center Zurich, University of Zurich and ETH Zurich, CH-8057 Zurich, Switzerland
- Institute of Pharmaceutical Sciences, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Mirko Santello
- Institute of Pharmacology and Toxicology, University of Zurich, CH-8057 Zurich, Switzerland
- Neuroscience Center Zurich, University of Zurich and ETH Zurich, CH-8057 Zurich, Switzerland
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25
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Heterogeneity of Activity-Induced Sodium Transients between Astrocytes of the Mouse Hippocampus and Neocortex: Mechanisms and Consequences. J Neurosci 2019; 39:2620-2634. [PMID: 30737311 DOI: 10.1523/jneurosci.2029-18.2019] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Revised: 01/07/2019] [Accepted: 01/23/2019] [Indexed: 01/09/2023] Open
Abstract
Activity-related sodium transients induced by glutamate uptake represent a special form of astrocyte excitability. Astrocytes of the neocortex, as opposed to the hippocampus proper, also express ionotropic glutamate receptors, which might provide additional sodium influx. We compared glutamate-related sodium transients in astrocytes and neurons in slices of the neocortex and hippocampus of juvenile mice of both sexes, using widefield and multiphoton imaging. Stimulation of glutamatergic afferents or glutamate application induced sodium transients that were twice as large in neocortical as in hippocampal astrocytes, despite similar neuronal responses. Astrocyte sodium transients were reduced by ∼50% upon blocking NMDA receptors in the neocortex, but not hippocampus. Neocortical, but not hippocampal, astrocytes exhibited marked sodium increases in response to NMDA. These key differences in sodium signaling were also observed in neonates and in adults. NMDA application evoked local calcium transients in processes of neocortical astrocytes, which were dampened upon blocking sodium/calcium exchange (NCX) with KB-R7943 or SEA0400. Mathematical computation based on our data predict that NMDA-induced sodium increases drive the NCX into reverse mode, resulting in calcium influx. Together, our study reveals a considerable regional heterogeneity in astrocyte sodium transients, which persists throughout postnatal development. Neocortical astrocytes respond with much larger sodium elevations to glutamatergic activity than hippocampal astrocytes. Moreover, neocortical astrocytes experience NMDA-receptor-mediated sodium influx, which hippocampal astrocytes lack, and which drives calcium import through reverse NCX. This pathway thereby links sodium to calcium signaling and represents a new mechanism for the generation of local calcium influx in neocortical astrocytes.SIGNIFICANCE STATEMENT Astrocyte calcium signals play a central role in neuron-glia interaction. Moreover, activity-related sodium transients may represent a new form of astrocyte excitability. Here we show that activation of NMDA receptors results in prominent sodium transients in neocortical, but not hippocampal, astrocytes in the mouse brain. NMDA receptor activation is accompanied by local calcium signaling in processes of neocortical astrocytes, which is augmented by sodium-driven reversal of the sodium/calcium exchanger. Our data demonstrate a significant regional heterogeneity in the magnitude and mechanisms of astrocyte sodium transients. They also suggest a close interrelation between NMDA-receptor-mediated sodium influx and calcium signaling through the reversal of sodium/calcium exchanger, thereby establishing a new pathway for the generation of local calcium signaling in astrocyte processes.
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26
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Guo W, Imai S, Zou S, Yang J, Watanabe M, Wang J, Dubner R, Wei F, Ren K. Altered glial glutamate transporter expression in descending circuitry and the emergence of pain chronicity. Mol Pain 2019; 15:1744806918825044. [PMID: 30799685 PMCID: PMC6348548 DOI: 10.1177/1744806918825044] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND The glutamate type 1 transporter (GLT1) plays a major role in glutamate homeostasis in the brain. Although alterations of GLT1 activity have been linked to persistent pain, the significance of these changes is poorly understood. Focusing on the rostral ventromedial medulla, a key site in pain modulation, we examined the expression and function of GLT1 and related transcription factor kappa B-motif binding phosphoprotein (KBBP) in rats after adjuvant-induced hind paw inflammation. RESULTS After inflammation, GLT1 and KBBP showed an early upregulation and gradual transition to downregulation that lasted throughout the eight-week observation period. Nitration of GLT1 was reduced at 30 min and increased at eight weeks after inflammation, suggesting an initial increase and later decrease in transporter activity. Mechanical hyperalgesia and paw edema exhibited an initial developing phase with peak hyperalgesia at 4 to 24 h, a subsequent attenuating phase, followed by a late persistent phase that lasted for months. The downregulation of GLT1 occurred at a time when hyperalgesia transitioned into the persistent phase. In the rostral ventromedial medulla, pharmacological block with dihydrokainic acid and RNAi of GLT1 and KBBP increased nociception and overexpression of GLT1 reversed persistent hyperalgesia. Further, the initial upregulation of GLT1 and KBBP was blocked by local anesthetic block, and pretreatment with dihydrokainic acid facilitated the development of hyperalgesia. CONCLUSIONS These results suggest that the initial increased GLT1 activity depends on injury input and serves to dampen the development of hyperalgesia. However, later downregulation of GLT1 fosters the net descending facilitation as injury persists, leading to the emergence of persistent pain.
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Affiliation(s)
- Wei Guo
- 1 Department of Neural and Pain Sciences, School of Dentistry, University of Maryland, Baltimore, MD, USA
- 2 Program in Neuroscience, University of Maryland, Baltimore, MD, USA
| | - Satoshi Imai
- 1 Department of Neural and Pain Sciences, School of Dentistry, University of Maryland, Baltimore, MD, USA
- 2 Program in Neuroscience, University of Maryland, Baltimore, MD, USA
| | - Shiping Zou
- 1 Department of Neural and Pain Sciences, School of Dentistry, University of Maryland, Baltimore, MD, USA
- 2 Program in Neuroscience, University of Maryland, Baltimore, MD, USA
| | - Jiale Yang
- 1 Department of Neural and Pain Sciences, School of Dentistry, University of Maryland, Baltimore, MD, USA
- 2 Program in Neuroscience, University of Maryland, Baltimore, MD, USA
| | - Mineo Watanabe
- 1 Department of Neural and Pain Sciences, School of Dentistry, University of Maryland, Baltimore, MD, USA
- 2 Program in Neuroscience, University of Maryland, Baltimore, MD, USA
- 3 Department of Oral Biology, Division of Molecular Medical Science, Hiroshima, Japan
| | - Jing Wang
- 1 Department of Neural and Pain Sciences, School of Dentistry, University of Maryland, Baltimore, MD, USA
- 2 Program in Neuroscience, University of Maryland, Baltimore, MD, USA
- 4 Key Laboratory of Bone and Joint Diseases of Gansu province, Institute of Orthopedics, the Second Hospital of Lanzhou University, Lanzhou, China
| | - Ronald Dubner
- 1 Department of Neural and Pain Sciences, School of Dentistry, University of Maryland, Baltimore, MD, USA
- 2 Program in Neuroscience, University of Maryland, Baltimore, MD, USA
| | - Feng Wei
- 1 Department of Neural and Pain Sciences, School of Dentistry, University of Maryland, Baltimore, MD, USA
- 2 Program in Neuroscience, University of Maryland, Baltimore, MD, USA
| | - Ke Ren
- 1 Department of Neural and Pain Sciences, School of Dentistry, University of Maryland, Baltimore, MD, USA
- 2 Program in Neuroscience, University of Maryland, Baltimore, MD, USA
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27
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Wang X, Shan Y, Tang Z, Gao L, Liu H. Neuroprotective effects of dexmedetomidine against isoflurane-induced neuronal injury via glutamate regulation in neonatal rats. DRUG DESIGN DEVELOPMENT AND THERAPY 2018; 13:153-160. [PMID: 30613136 PMCID: PMC6306062 DOI: 10.2147/dddt.s163197] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Background Considerable evidences support the finding that the anesthesia reagent isoflurane increases neuronal cell death in young rats. Recent studies have shown that dexmedetomidine can reduce isoflurane-induced neuronal injury, but the mechanism remains unclear. We investigated whether isoflurane cause neurotoxicity to the central nervous system by regulating the N-methyl-D-aspartate receptor (NMDAR) and excitatory amino acid transporter1 (EAAT1) in young rats. Furthermore, we examined if dexmedetomidine could decrease isoflurane-induced neurotoxicity. Methods Neonatal rats (postnatal day 7, n=144) were randomly divided into four groups of 36 animals each: control (saline injection without isoflurane); isoflurane (2% for 4 h); isoflurane + single dose of dexmedetomidine (75 µg/kg, 20 min before the start of 2% isoflurane for 4 h); and isoflurane + dual doses of dexmedetomidine (25 µg/kg, 20 min before and 2 h after start of isoflurane at 2% for 4 h). Six neonates from each group were euthanatized at 2 h, 12 h, 24 h, 3 days, 7 days and 28 days post-anesthesia. Hippocampi were collected and processed for protein extraction. Expression levels of the NMDAR subunits NR2A and NR2B, EAAT1 and caspase-3 were measured by western blot analysis. Results Protein levels of NR2A, EAAT1 and caspase-3 were significantly increased in hippocampus of the isoflurane group from 2 h to 3 days, while NR2B levels were decreased. However, the -induced increase in NR2A, EAAT1 and caspase-3 and the decrease in NR2B in isoflurane-exposed rats were ameliorated in the rats treated with single or dual doses of dexmedetomidine. Isoflurane-induced neuronal damage in neonatal rats is due in part to the increase in NR2A and EAAT1 and the decrease in NR2B in the hippocampus. Conclusion Dexmedetomidine protects the brain against the use of isoflurane through the regulation of NR2A, NR2B and EAAT1. However, using the same amount of dexmedetomidine, the trend of protection is basically the same.
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Affiliation(s)
- Xue Wang
- Department of Anesthesiology, Shengjing Hospital, China Medical University, Shenyang 110004, China, .,Department of Anesthesiology, Xiangyang Central Hospital, Affiliated Hospital of Hubei University of Arts and Sciences, Xiangyang 441000, China
| | - Yangyang Shan
- Department of Anesthesiology, Shengjing Hospital, China Medical University, Shenyang 110004, China,
| | - Zhiyin Tang
- Department of Anesthesiology, Shengjing Hospital, China Medical University, Shenyang 110004, China,
| | - Linlin Gao
- Department of Medical Research, Shengjing Hospital, China Medical University, Shenyang 110004, China
| | - Hongtao Liu
- Department of Anesthesiology, Shengjing Hospital, China Medical University, Shenyang 110004, China,
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28
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Kurauchi Y, Noma K, Hisatsune A, Seki T, Katsuki H. Na +, K +-ATPase inhibition induces neuronal cell death in rat hippocampal slice cultures: Association with GLAST and glial cell abnormalities. J Pharmacol Sci 2018; 138:167-175. [PMID: 30322800 DOI: 10.1016/j.jphs.2018.09.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 08/27/2018] [Accepted: 09/11/2018] [Indexed: 12/20/2022] Open
Abstract
Na+, K+-ATPase is a highly expressed membrane protein. Dysfunction of Na+, K+-ATPase has been implicated in the pathophysiology of several neurodegenerative and psychiatric disorders, however, the underlying mechanism of neuronal cell death resulting from Na+, K+-ATPase dysfunction is poorly understood. Here, we investigated the mechanism of neurotoxicity due to Na+, K+-ATPase inhibition using rat organotypic hippocampal slice cultures. Treatment with ouabain, a Na+, K+-ATPase inhibitor, increased the ratio of propidium iodide-positive cells among NeuN-positive cells in the hippocampal CA1 region, which was prevented by MK-801 and d-AP5, specific blockers of the N-methyl-d-aspartate (NMDA) receptor. EGTA, a Ca2+-chelating agent, also protected neurons from ouabain-induced injury. We observed that astrocytes expressed the glutamate aspartate transporter (GLAST), and ouabain changed the immunoreactive area of GFAP-positive astrocytes as well as GLAST. We also observed that ouabain increased the number of Iba1-positive microglial cells in a time-dependent manner. Furthermore, lithium carbonate, a mood-stabilizing drug, protected hippocampal neurons and reduced disturbances of astrocytes and microglia after ouabain treatment. Notably, lithium carbonate improved ouabain-induced decreases in GLAST intensity in astrocytes. These results suggest that glial cell abnormalities resulting in excessive extracellular concentrations of glutamate contribute to neurotoxicity due to Na+, K+-ATPase dysfunction in the hippocampal CA1 region.
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Affiliation(s)
- Yuki Kurauchi
- Department of Chemico-Pharmacological Sciences, Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto 862-0973, Japan
| | - Kazuki Noma
- Department of Chemico-Pharmacological Sciences, Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto 862-0973, Japan
| | - Akinori Hisatsune
- Priority Organization for Innovation and Excellence, Kumamoto University, Kumamoto 860-8555, Japan; Program for Leading Graduate Schools "HIGO (Health Life Science: Interdisciplinary and Glocal Oriented) Program", Kumamoto University, Kumamoto 862-0973, Japan
| | - Takahiro Seki
- Department of Chemico-Pharmacological Sciences, Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto 862-0973, Japan
| | - Hiroshi Katsuki
- Department of Chemico-Pharmacological Sciences, Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto 862-0973, Japan.
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29
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Region- and Activity-Dependent Regulation of Extracellular Glutamate. J Neurosci 2018; 38:5351-5366. [PMID: 29760178 DOI: 10.1523/jneurosci.3213-17.2018] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Revised: 04/19/2018] [Accepted: 05/03/2018] [Indexed: 11/21/2022] Open
Abstract
Transporter-mediated glutamate uptake plays an essential role in shaping synaptic neurotransmission. The rapid removal of synaptically released glutamate ensures the high temporal dynamics characteristic of fast excitatory chemical neurotransmission and prevents the overexcitation of extrasynaptic NMDA receptors that have been implicated in synaptic plasticity impairments and cell death. Despite clear regional differences in plasticity and excitotoxic thresholds, few studies have compared extracellular glutamate dynamics across different brain regions and in response to a range of neural activity including plasticity-inducing stimuli. Here, we used the rapid extracellular fluorescent glutamate sensor iGluSnFR (intensity-based glutamate-sensing fluorescent reporter) and high-speed imaging (205 frames per second) to quantify relative differences in glutamate clearance rates over a wide range of presynaptic activity in situ in the hippocampus, cortex, and striatum of male C57/BL6NCrl mice. We found that the hippocampus was significantly more efficient than the cortex and striatum at clearing synaptically released glutamate and that this efficiency could be attributed, at least in part, to faster glutamate diffusion away from the release site. In addition, we found that pharmacological inhibition of GLT-1, the brain's most abundant glutamate transporter, slowed clearance rates to only a fraction (∼20-25%) of the effect induced by nonselective transporter blockade, regardless of the brain region and the duration of presynaptic activity. In all, our data reveal clear regional differences in glutamate dynamics after neural activity and suggest that non-GLT-1 transporters can make a large contribution to the rate of glutamate clearance in the hippocampus, cortex, and striatum.SIGNIFICANCE STATEMENT Glutamate is the brain's most abundant neurotransmitter, and although essential for rapid cell-cell communication, too much glutamate can negatively impact cellular health. Extracellular glutamate levels are tightly regulated by membrane-bound transporters that rapidly remove the glutamate that is released during neural activity, thereby shaping both the spatial and temporal dynamics of excitatory neurotransmission. Using high-speed imaging of an optical sensor of extracellular glutamate, we show that glutamate dynamics vary widely from one brain region to the next and are highly dependent on the duration of synaptic activity. Our data demonstrate the heterogeneous nature of glutamate regulation in the brain and suggest that such regional differences can dramatically affect both the localization and duration of postsynaptic receptor activation during synaptic neurotransmission.
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30
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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: 122] [Impact Index Per Article: 20.3] [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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31
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Abstract
Astrocytes are neural cells of ectodermal, neuroepithelial origin that provide for homeostasis and defense of the central nervous system (CNS). Astrocytes are highly heterogeneous in morphological appearance; they express a multitude of receptors, channels, and membrane transporters. This complement underlies their remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue; astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
| | - Maiken Nedergaard
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
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32
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Verkhratsky A, Nedergaard M. Physiology of Astroglia. Physiol Rev 2018; 98:239-389. [PMID: 29351512 PMCID: PMC6050349 DOI: 10.1152/physrev.00042.2016] [Citation(s) in RCA: 876] [Impact Index Per Article: 146.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 03/22/2017] [Accepted: 04/27/2017] [Indexed: 02/07/2023] Open
Abstract
Astrocytes are neural cells of ectodermal, neuroepithelial origin that provide for homeostasis and defense of the central nervous system (CNS). Astrocytes are highly heterogeneous in morphological appearance; they express a multitude of receptors, channels, and membrane transporters. This complement underlies their remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue; astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
| | - Maiken Nedergaard
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
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33
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Hameed MQ, Dhamne SC, Gersner R, Kaye HL, Oberman LM, Pascual-Leone A, Rotenberg A. Transcranial Magnetic and Direct Current Stimulation in Children. Curr Neurol Neurosci Rep 2017; 17:11. [PMID: 28229395 DOI: 10.1007/s11910-017-0719-0] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Promising results in adult neurologic and psychiatric disorders are driving active research into transcranial brain stimulation techniques, particularly transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS), in childhood and adolescent syndromes. TMS has realistic utility as an experimental tool tested in a range of pediatric neuropathologies such as perinatal stroke, depression, Tourette syndrome, and autism spectrum disorder (ASD). tDCS has also been tested as a treatment for a number of pediatric neurologic conditions, including ASD, attention-deficit/hyperactivity disorder, epilepsy, and cerebral palsy. Here, we complement recent reviews with an update of published TMS and tDCS results in children, and discuss developmental neuroscience considerations that should inform pediatric transcranial stimulation.
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Affiliation(s)
- Mustafa Q Hameed
- Neuromodulation Program, Division of Epilepsy and Clinical Neurophysiology, Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA, 02115, USA
- F.M. Kirby Neurobiology Center, Department of Neurology, Boston Children's Hospital Harvard Medical School, 300 Longwood Avenue, Boston, MA, 02115, USA
- Department of Neurosurgery, Boston Children's Hospital Harvard Medical School, Boston, MA, 02115, USA
| | - Sameer C Dhamne
- Neuromodulation Program, Division of Epilepsy and Clinical Neurophysiology, Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA, 02115, USA
- F.M. Kirby Neurobiology Center, Department of Neurology, Boston Children's Hospital Harvard Medical School, 300 Longwood Avenue, Boston, MA, 02115, USA
| | - Roman Gersner
- Neuromodulation Program, Division of Epilepsy and Clinical Neurophysiology, Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA, 02115, USA
- F.M. Kirby Neurobiology Center, Department of Neurology, Boston Children's Hospital Harvard Medical School, 300 Longwood Avenue, Boston, MA, 02115, USA
| | - Harper L Kaye
- Neuromodulation Program, Division of Epilepsy and Clinical Neurophysiology, Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA, 02115, USA
- F.M. Kirby Neurobiology Center, Department of Neurology, Boston Children's Hospital Harvard Medical School, 300 Longwood Avenue, Boston, MA, 02115, USA
| | - Lindsay M Oberman
- Neuroplasticity and Autism Spectrum Disorder Program and Department of Psychiatry and Human Behavior, E.P. Bradley Hospital and Warren Alpert Medical School, Brown University, Providence, RI, USA
| | - Alvaro Pascual-Leone
- Berenson-Allen Center for Noninvasive Brain Stimulation and Division for Cognitive Neurology, Beth Israel Deaconness Medical Center Harvard Medical School, Boston, MA, USA
- Institut Guttmann, Universitat Autonoma, Barcelona, Spain
| | - Alexander Rotenberg
- Neuromodulation Program, Division of Epilepsy and Clinical Neurophysiology, Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA, 02115, USA.
- F.M. Kirby Neurobiology Center, Department of Neurology, Boston Children's Hospital Harvard Medical School, 300 Longwood Avenue, Boston, MA, 02115, USA.
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34
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Glutamate Clearance Is Locally Modulated by Presynaptic Neuronal Activity in the Cerebral Cortex. J Neurosci 2017; 36:10404-10415. [PMID: 27707974 DOI: 10.1523/jneurosci.2066-16.2016] [Citation(s) in RCA: 83] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Accepted: 08/18/2016] [Indexed: 02/02/2023] Open
Abstract
Excitatory amino acid transporters (EAATs) are abundantly expressed by astrocytes, rapidly remove glutamate from the extracellular environment, and restrict the temporal and spatial extent of glutamate signaling. Studies probing EAAT function suggest that their capacity to remove glutamate is large and does not saturate, even with substantial glutamate challenges. In contrast, we report that neuronal activity rapidly and reversibly modulates EAAT-dependent glutamate transport. To date, no physiological manipulation has shown changes in functional glutamate uptake in a nonpathological state. Using iGluSnFr-based glutamate imaging and electrophysiology in the adult mouse cortex, we show that glutamate uptake is slowed up to threefold following bursts of neuronal activity. The slowing of glutamate uptake depends on the frequency and duration of presynaptic neuronal activity but is independent of the amount of glutamate released. The modulation of glutamate uptake is brief, returning to normal within 50 ms after stimulation ceases. Interestingly, the slowing of glutamate uptake is specific to activated synapses, even within the domain of an individual astrocyte. Activity-induced slowing of glutamate uptake, and the increased persistence of glutamate in the extracellular space, is reflected by increased decay times of neuronal NR2A-mediated NMDA currents. These results show that astrocytic clearance of extracellular glutamate is slowed in a temporally and spatially specific manner following bursts of neuronal activity ≥30 Hz and that these changes affect the neuronal response to released glutamate. This suggests a previously unreported form of neuron-astrocyte interaction. SIGNIFICANCE STATEMENT We report the first fast, physiological modulation of astrocyte glutamate clearance kinetics. We show that presynaptic activity in the cerebral cortex increases the persistence of glutamate in the extracellular space by slowing its clearance by astrocytes. Because of abundant EAAT expression, glutamate clearance from the extracellular space has been thought to have invariant kinetics. While multiple studies report experimental manipulations resulting in altered EAAT expression, our findings show that astrocytic glutamate uptake is dynamic on a fast time-scale. This shows rapid plasticity of glutamate clearance, which locally modulates synaptic signaling in the cortex. As astrocytic glutamate uptake is a fundamental and essential mechanism for neurotransmission, this work has implications for neurotransmission, extrasynaptic receptor activation, and synaptic plasticity.
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35
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Rose CR, Ziemens D, Untiet V, Fahlke C. Molecular and cellular physiology of sodium-dependent glutamate transporters. Brain Res Bull 2016; 136:3-16. [PMID: 28040508 DOI: 10.1016/j.brainresbull.2016.12.013] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 12/20/2016] [Accepted: 12/21/2016] [Indexed: 02/04/2023]
Abstract
Glutamate is the major excitatory transmitter in the vertebrate brain. After its release from presynaptic nerve terminals, it is rapidly taken up by high-affinity sodium-dependent plasma membrane transporters. While both neurons and glial cells express these excitatory amino acid transporters (EAATs), the majority of glutamate uptake is accomplished by astrocytes, which convert synaptically-released glutamate to glutamine or feed it into their own metabolism. Glutamate uptake by astrocytes not only shapes synaptic transmission by regulating the availability of glutamate to postsynaptic neuronal receptors, but also protects neurons from hyper-excitability and subsequent excitotoxic damage. In the present review, we provide an overview of the molecular and cellular characteristics of sodium-dependent glutamate transporters and their associated anion permeation pathways, with a focus on astrocytic glutamate transport. We summarize their functional properties and roles within tripartite synapses under physiological and pathophysiological conditions, exemplifying the intricate interactions and interrelationships between neurons and glial cells in the brain.
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Affiliation(s)
- Christine R Rose
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Düsseldorf, Germany.
| | - Daniel Ziemens
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Düsseldorf, Germany
| | - Verena Untiet
- Institute of Complex Systems, Zelluläre Biophysik (ICS-4), Forschungszentrum Jülich, Germany
| | - Christoph Fahlke
- Institute of Complex Systems, Zelluläre Biophysik (ICS-4), Forschungszentrum Jülich, Germany
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36
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Orexin-A promotes Glu uptake by OX1R/PKCα/ERK1/2/GLT-1 pathway in astrocytes and protects co-cultured astrocytes and neurons against apoptosis in anoxia/hypoglycemic injury in vitro. Mol Cell Biochem 2016; 425:103-112. [DOI: 10.1007/s11010-016-2866-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Accepted: 11/02/2016] [Indexed: 12/31/2022]
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37
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Trabelsi Y, Amri M, Becq H, Molinari F, Aniksztejn L. The conversion of glutamate by glutamine synthase in neocortical astrocytes from juvenile rat is important to limit glutamate spillover and peri/extrasynaptic activation of NMDA receptors. Glia 2016; 65:401-415. [PMID: 27862359 DOI: 10.1002/glia.23099] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Revised: 10/25/2016] [Accepted: 10/26/2016] [Indexed: 12/31/2022]
Abstract
Glutamate transporters (EAATs) are important to maintain spatial and temporal specificity of synaptic transmission. Their efficiency to uptake and transport glutamate into the intracellular space depends on several parameters including the intracellular concentrations of Na+ and glutamate, the elevations of which may slow down the cycling rate of EAATs. In astrocytes, glutamate is maintained at low concentration due to the presence of specific enzymes such as glutamine synthase (GS). GS inhibition results in cytosolic accumulation of glutamate suggesting that the conversion of glutamate by GS is important for EAATs operation. Here we recorded astrocytes from juvenile rat neocortical slices and analyzed the consequences of elevated intracellular glutamate concentrations and of GS inhibition on the time course of synaptically evoked transporter current (STC). In slices from rats treated with methionine sulfoximine (MSO), a GS inhibitor, STC evoked by short burst of high frequency stimulation (HFS; 100 Hz for 100 ms) but not by low frequency stimulation (LFS; 0.1 Hz) was twice slower than STC evoked from saline injected rats. Same results were obtained for astrocytes recorded with pipette containing 3-10 mM glutamate and compared with cells recorded with 0 or1 mM glutamate in the patch pipette. We also showed that HFS elicited significantly larger NMDAR-excitatory postsynaptic currents (EPSCs) with a stronger peri/extrasynaptic component in pyramidal cells from MSO-treated compared with saline treated rats. Taken together our data demonstrate that the conversion of glutamate by GS is fundamental to ensure an efficient clearance of glutamate by EAATs and to prevent glutamate spillover. GLIA 2017;65:401-415.
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Affiliation(s)
- Yosra Trabelsi
- Institut de Neurobiologie de la Méditerranée (INMED), Aix-Marseille Université, Marseille, 13009, France.,INSERM, UMR_S 901, Marseille, 13009, France
| | - Mohamed Amri
- Laboratoire de Neurophysiologie Fonctionnelle et Pathologies, Tunis, UR11ES09, Tunisie
| | - Hélène Becq
- Institut de Neurobiologie de la Méditerranée (INMED), Aix-Marseille Université, Marseille, 13009, France.,INSERM, UMR_S 901, Marseille, 13009, France
| | - Florence Molinari
- Institut de Neurobiologie de la Méditerranée (INMED), Aix-Marseille Université, Marseille, 13009, France.,INSERM, UMR_S 901, Marseille, 13009, France
| | - Laurent Aniksztejn
- Institut de Neurobiologie de la Méditerranée (INMED), Aix-Marseille Université, Marseille, 13009, France.,INSERM, UMR_S 901, Marseille, 13009, France
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38
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Wanke E, Gullo F, Dossi E, Valenza G, Becchetti A. Neuron-glia cross talk revealed in reverberating networks by simultaneous extracellular recording of spikes and astrocytes' glutamate transporter and K+ currents. J Neurophysiol 2016; 116:2706-2719. [PMID: 27683885 PMCID: PMC5133298 DOI: 10.1152/jn.00509.2016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Accepted: 09/22/2016] [Indexed: 01/11/2023] Open
Abstract
In neocortex networks, we simultaneously captured spikes and the slower astrocytes' K+and glutamate transporter (GluT) currents with the use of individual MEA electrodes. Inward and outward K+currents in different regions of the glial syncytium suggested that spatial buffering was operant. Moreover, in organotypic slices from ventral tegmental area and prefrontal cortex, the large GluT current amplitudes allowed to measure transporter currents with a single electrode. Our method allows direct study of the dynamic interplay of different cell types in excitable and nonexcitable tissue. Astrocytes uptake synaptically released glutamate with electrogenic transporters (GluT) and buffer the spike-dependent extracellular K+ excess with background K+ channels. We studied neuronal spikes and the slower astrocytic signals on reverberating neocortical cultures and organotypic slices from mouse brains. Spike trains and glial responses were simultaneously captured from individual sites of multielectrode arrays (MEA) by splitting the recorded traces into appropriate filters and reconstructing the original signal by deconvolution. GluT currents were identified by using dl-threo-β-benzyloxyaspartate (TBOA). K+ currents were blocked by 30 μM Ba2+, suggesting a major contribution of inwardly rectifying K+ currents. Both types of current were tightly correlated with the spike rate, and their astrocytic origin was tested in primary cultures by blocking glial proliferation with cytosine β-d-arabinofuranoside (AraC). The spike-related, time-locked inward and outward K+ currents in different regions of the astrocyte syncytium were consistent with the assumptions of the spatial K+ buffering model. In organotypic slices from ventral tegmental area and prefrontal cortex, the GluT current amplitudes exceeded those observed in primary cultures by several orders of magnitude, which allowed to directly measure transporter currents with a single electrode. Simultaneously measuring cell signals displaying widely different amplitudes and kinetics will help clarify the neuron-glia interplay and make it possible to follow the cross talk between different cell types in excitable as well as nonexcitable tissue.
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Affiliation(s)
- Enzo Wanke
- Department of Biotechnologies and Biosciences and Milan Center For Neuroscience (NeuroMI), University of Milano-Bicocca, Milan, Italy; and
| | - Francesca Gullo
- Department of Biotechnologies and Biosciences and Milan Center For Neuroscience (NeuroMI), University of Milano-Bicocca, Milan, Italy; and
| | - Elena Dossi
- Department of Biotechnologies and Biosciences and Milan Center For Neuroscience (NeuroMI), University of Milano-Bicocca, Milan, Italy; and
| | - Gaetano Valenza
- Research Centre "E. Piaggio" and Department of Information Engineering, School of Engineering, University of Pisa, Pisa, Italy
| | - Andrea Becchetti
- Department of Biotechnologies and Biosciences and Milan Center For Neuroscience (NeuroMI), University of Milano-Bicocca, Milan, Italy; and
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39
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Macht VA. Neuro-immune interactions across development: A look at glutamate in the prefrontal cortex. Neurosci Biobehav Rev 2016; 71:267-280. [PMID: 27593444 DOI: 10.1016/j.neubiorev.2016.08.039] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Revised: 07/26/2016] [Accepted: 08/31/2016] [Indexed: 02/07/2023]
Abstract
Although the primary role for the immune system is to respond to pathogens, more recently, the immune system has been demonstrated to have a critical role in signaling developmental events. Of particular interest for this review is how immunocompetent microglia and astrocytes interact with glutamatergic systems to influence the development of neural circuits in the prefrontal cortex (PFC). Microglia are the resident macrophages of the brain, and astrocytes mediate both glutamatergic uptake and coordinate with microglia to respond to the general excitatory state of the brain. Cross-talk between microglia, astrocytes, and glutamatergic neurons forms a quad-partite synapse, and this review argues that interactions within this synapse have critical implications for the maturation of PFC-dependent cognitive function. Similarly, understanding developmental shifts in immune signaling may help elucidate variations in sensitivities to developmental disruptions.
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Affiliation(s)
- Victoria A Macht
- University of South Carolina, 1512 Pendleton St., Department of Psychology, Columbia, SC 29208, United States.
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40
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Glia plasma membrane transporters: Key players in glutamatergic neurotransmission. Neurochem Int 2016; 98:46-55. [DOI: 10.1016/j.neuint.2016.04.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Revised: 03/07/2016] [Accepted: 04/06/2016] [Indexed: 12/27/2022]
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41
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Danbolt NC, Zhou Y, Furness DN, Holmseth S. Strategies for immunohistochemical protein localization using antibodies: What did we learn from neurotransmitter transporters in glial cells and neurons. Glia 2016; 64:2045-2064. [PMID: 27458697 DOI: 10.1002/glia.23027] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Revised: 06/19/2016] [Accepted: 06/21/2016] [Indexed: 12/11/2022]
Abstract
Immunocytochemistry and Western blotting are still major methods for protein localization, but they rely on the specificity of the antibodies. Validation of antibody specificity remains challenging mostly because ideal negative controls are often unavailable. Further, immunochemical labeling patterns are also influenced by a number of other factors such as postmortem changes, fixation procedures and blocking agents as well as the general assay conditions (e.g., buffers, temperature, etc.). Western blotting similarly depends on tissue collection and sample preparation as well as the electrophoretic separation, transfer to blotting membranes and the immunochemical probing of immobilized molecules. Publication of inaccurate information on protein distribution has downstream consequences for other researchers because the interpretation of physiological and pharmacological observations depends on information on where ion channels, receptors, enzymes or transporters are located. Despite numerous reports, some of which are strongly worded, erroneous localization data are being published. Here we describe the extent of the problem and illustrate the nature of the pitfalls with examples from studies of neurotransmitter transporters. We explain the importance of supplementing immunochemical observations with other measurements (e.g., mRNA levels and distribution, protein activity, mass spectrometry, electrophysiological recordings, etc.) and why quantitative considerations are integral parts of the quality control. Further, we propose a practical strategy for researchers who plan to embark on a localization study. We also share our thoughts about guidelines for quality control. GLIA 2016;64:2045-2064.
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Affiliation(s)
- Niels Christian Danbolt
- Neurotransporter Group, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.
| | - Yun Zhou
- Neurotransporter Group, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - David N Furness
- School of Life Sciences, Keele University, Keele, Staffs, United Kingdom
| | - Silvia Holmseth
- Neurotransporter Group, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
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42
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Danbolt NC, Furness DN, Zhou Y. Neuronal vs glial glutamate uptake: Resolving the conundrum. Neurochem Int 2016; 98:29-45. [PMID: 27235987 DOI: 10.1016/j.neuint.2016.05.009] [Citation(s) in RCA: 141] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Revised: 05/03/2016] [Accepted: 05/17/2016] [Indexed: 12/30/2022]
Abstract
Neither normal brain function nor the pathological processes involved in neurological diseases can be adequately understood without knowledge of the release, uptake and metabolism of glutamate. The reason for this is that glutamate (a) is the most abundant amino acid in the brain, (b) is at the cross-roads between several metabolic pathways, and (c) serves as the major excitatory neurotransmitter. In fact most brain cells express glutamate receptors and are thereby influenced by extracellular glutamate. In agreement, brain cells have powerful uptake systems that constantly remove glutamate from the extracellular fluid and thereby limit receptor activation. It has been clear since the 1970s that both astrocytes and neurons express glutamate transporters. However the relative contribution of neuronal and glial transporters to the total glutamate uptake activity, however, as well as their functional importance, has been hotly debated ever since. The present short review provides (a) an overview of what we know about neuronal glutamate uptake as well as an historical description of how we got there, and (b) a hypothesis reconciling apparently contradicting observations thereby possibly resolving the paradox.
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Affiliation(s)
- N C Danbolt
- The Neurotransporter Group, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.
| | - D N Furness
- School of Life Sciences, Keele University, Keele, Staffs. ST5 5BG, UK
| | - Y Zhou
- The Neurotransporter Group, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
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43
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Hanson E, Danbolt NC, Dulla CG. Astrocyte membrane properties are altered in a rat model of developmental cortical malformation but single-cell astrocytic glutamate uptake is robust. Neurobiol Dis 2016; 89:157-68. [PMID: 26875663 PMCID: PMC4794447 DOI: 10.1016/j.nbd.2016.02.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Revised: 02/03/2016] [Accepted: 02/09/2016] [Indexed: 12/31/2022] Open
Abstract
Developmental cortical malformations (DCMs) are linked with severe epilepsy and are caused by both genetic and environmental insults. DCMs include several neurological diseases, such as focal cortical dysplasia, polymicrogyria, schizencephaly, and others. Human studies have implicated astrocyte reactivity and dysfunction in the pathophysiology of DCMs, but their specific role is unknown. As astrocytes powerfully regulate glutamate neurotransmission, and glutamate levels are known to be increased in human epileptic foci, understanding the role of astrocytes in the pathological sequelae of DCMs is extremely important. Additionally, recent studies examining astrocyte glutamate uptake in DCMs have reported conflicting results, adding confusion to the field. In this study we utilized the freeze lesion (FL) model of DCM, which is known to induce reactive astrocytosis and cause significant changes in astrocyte morphology, proliferation, and distribution. Using whole-cell patch clamp recording from astrocytes, we recorded both UV-uncaging and synaptically evoked glutamate transporter currents (TCs), widely accepted assays of functional glutamate transport by astrocytes. With this approach, we set out to test the hypothesis that astrocyte membrane properties and glutamate transport were disrupted in this model of DCM. Though we found that the developmental maturation of astrocyte membrane resistance was disrupted by FL, glutamate uptake by individual astrocytes was robust throughout FL development. Interestingly, using an immunolabeling approach, we observed spatial and developmental differences in excitatory amino acid transporter (EAAT) expression in FL cortex. Spatially specific differences in EAAT2 (GLT-1) and EAAT1 (GLAST) expression suggest that the relative contribution of each EAAT to astrocytic glutamate uptake may be altered in FL cortex. Lastly, we carefully analyzed the amplitudes and onset times of both synaptically- and UV uncaging-evoked TCs. We found that in the FL cortex, synaptically-evoked, but not UV uncaging-evoked TCs, were larger in amplitude. Additionally, we found that the amount of electrical stimulation required to evoke a synaptic TC was significantly reduced in the FL cortex. Both of these findings are consistent with increased excitatory input to the FL cortex, but not with changes in how individual astrocytes remove glutamate. Taken together, our results demonstrate that the maturation of astrocyte membrane resistance, local distribution of glutamate transporters, and glutamatergic input to the cortex are altered in the FL model, but that single-cell astrocytic glutamate uptake is robust.
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Affiliation(s)
- Elizabeth Hanson
- Department of Neuroscience, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA; Neuroscience Program, Tufts Sackler School of Biomedical Sciences, 136 Harrison Avenue, Boston, MA 02111, USA
| | - Niels Christian Danbolt
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, P.O. Box 1105 Blindern, N-0317 Oslo, Norway
| | - Chris G Dulla
- Department of Neuroscience, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA; Neuroscience Program, Tufts Sackler School of Biomedical Sciences, 136 Harrison Avenue, Boston, MA 02111, USA
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