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Vellucci L, Mazza B, Barone A, Nasti A, De Simone G, Iasevoli F, de Bartolomeis A. The Role of Astrocytes in the Molecular Pathophysiology of Schizophrenia: Between Neurodevelopment and Neurodegeneration. Biomolecules 2025; 15:615. [PMID: 40427508 PMCID: PMC12109222 DOI: 10.3390/biom15050615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2025] [Revised: 04/05/2025] [Accepted: 04/22/2025] [Indexed: 05/29/2025] Open
Abstract
Schizophrenia is a chronic and severe psychiatric disorder affecting approximately 1% of the global population, characterized by disrupted synaptic plasticity and brain connectivity. While substantial evidence supports its classification as a neurodevelopmental disorder, non-canonical neurodegenerative features have also been reported, with increasing attention given to astrocytic dysfunction. Overall, in this study, we explore the role of astrocytes as a structural and functional link between neurodevelopment and neurodegeneration in schizophrenia. Specifically, we examine how astrocytes contribute to forming an aberrant substrate during early neurodevelopment, potentially predisposing individuals to later neurodegeneration. Astrocytes regulate neurotransmitter homeostasis and synaptic plasticity, influencing early vulnerability and disease progression through their involvement in Ca2⁺ signaling and dopamine-glutamate interaction-key pathways implicated in schizophrenia pathophysiology. Astrocytes differentiate via nuclear factor I-A, Sox9, and Notch pathways, occurring within a neuronal environment that may already be compromised in the early stages due to the genetic factors associated with the 'two-hits' model of schizophrenia. As a result, astrocytes may contribute to the development of an altered neural matrix, disrupting neuronal signaling, exacerbating the dopamine-glutamate imbalance, and causing excessive synaptic pruning and demyelination. These processes may underlie both the core symptoms of schizophrenia and the increased susceptibility to cognitive decline-clinically resembling neurodegeneration but driven by a distinct, poorly understood molecular substrate. Finally, astrocytes are emerging as potential pharmacological targets for antipsychotics such as clozapine, which may modulate their function by regulating glutamate clearance, redox balance, and synaptic remodeling.
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Affiliation(s)
- Licia Vellucci
- Section of Psychiatry, Laboratory of Translational and Molecular Psychiatry, Unit of Treatment-Resistant Psychosis, Department of Neuroscience, Reproductive Sciences and Dentistry, University Medical School of Naples “Federico II”, Via Pansini 5, 80131 Naples, Italy
- Department of Translational Medical Sciences, University of Naples “Federico II”, Via S. Pansini 5, 80131 Naples, Italy
| | - Benedetta Mazza
- Section of Psychiatry, Laboratory of Translational and Molecular Psychiatry, Unit of Treatment-Resistant Psychosis, Department of Neuroscience, Reproductive Sciences and Dentistry, University Medical School of Naples “Federico II”, Via Pansini 5, 80131 Naples, Italy
| | - Annarita Barone
- Section of Psychiatry, Laboratory of Translational and Molecular Psychiatry, Unit of Treatment-Resistant Psychosis, Department of Neuroscience, Reproductive Sciences and Dentistry, University Medical School of Naples “Federico II”, Via Pansini 5, 80131 Naples, Italy
| | - Anita Nasti
- Section of Psychiatry, Laboratory of Translational and Molecular Psychiatry, Unit of Treatment-Resistant Psychosis, Department of Neuroscience, Reproductive Sciences and Dentistry, University Medical School of Naples “Federico II”, Via Pansini 5, 80131 Naples, Italy
| | - Giuseppe De Simone
- Section of Psychiatry, Laboratory of Translational and Molecular Psychiatry, Unit of Treatment-Resistant Psychosis, Department of Neuroscience, Reproductive Sciences and Dentistry, University Medical School of Naples “Federico II”, Via Pansini 5, 80131 Naples, Italy
- Departament de Medicina, Facultat de Medicina i Ciències de la Salut, Institut de Neurociències, Universitat de Barcelona (UB), c. Casanova, 143, 08036 Barcelona, Spain
- Institut d’Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), c. Villarroel, 170, 08036 Barcelona, Spain
- Bipolar and Depressive Disorders Unit, Hospìtal Clinic de Barcelona. c. Villarroel, 170, 08036 Barcelona, Spain
| | - Felice Iasevoli
- Section of Psychiatry, Laboratory of Translational and Molecular Psychiatry, Unit of Treatment-Resistant Psychosis, Department of Neuroscience, Reproductive Sciences and Dentistry, University Medical School of Naples “Federico II”, Via Pansini 5, 80131 Naples, Italy
| | - Andrea de Bartolomeis
- Section of Psychiatry, Laboratory of Translational and Molecular Psychiatry, Unit of Treatment-Resistant Psychosis, Department of Neuroscience, Reproductive Sciences and Dentistry, University Medical School of Naples “Federico II”, Via Pansini 5, 80131 Naples, Italy
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2
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Zonca L, Bellier FC, Milior G, Aymard P, Visser J, Rancillac A, Rouach N, Holcman D. Unveiling the functional connectivity of astrocytic networks with AstroNet, a graph reconstruction algorithm coupled to image processing. Commun Biol 2025; 8:114. [PMID: 39856404 PMCID: PMC11759710 DOI: 10.1038/s42003-024-07390-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Accepted: 12/09/2024] [Indexed: 01/27/2025] Open
Abstract
Astrocytes form extensive networks with diverse calcium activity, yet the organization and connectivity of these networks across brain regions remain largely unknown. To address this, we developed AstroNet, a data-driven algorithm that uses two-photon calcium imaging to map temporal correlations in astrocyte activation. By organizing individual astrocyte activation events chronologically, our method reconstructs functional networks and extracts local astrocyte correlations. We create a graph of the astrocyte network by tallying direct co-activations between pairs of cells along these activation pathways. Applied to the CA1 hippocampus and motor cortex, AstroNet reveals notable differences: astrocytes in the hippocampus display stronger connectivity, while cortical astrocytes form sparser networks. In both regions, smaller, tightly connected sub-networks are embedded within a larger, loosely connected structure. This method not only identifies astrocyte activation paths and connectivity but also reveals distinct, region-specific network patterns, providing new insights into the functional organization of astrocytic networks in the brain.
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Affiliation(s)
- L Zonca
- Applied Mathematics and Computational Biology, IBENS, Ecole Normale Supérieure, PSL University, Paris, France
- Center for Brain and Cognition, University Pompeu Fabra, Barcelona, Spain
| | - F C Bellier
- Neuroglial Interactions in Cerebral Physiology and Pathologies, Center for Interdisciplinary Research in Biology, Collège de France, CNR UMR 7241, INSERM U1050, PSL, Paris, France
| | - G Milior
- Neuroglial Interactions in Cerebral Physiology and Pathologies, Center for Interdisciplinary Research in Biology, Collège de France, CNR UMR 7241, INSERM U1050, PSL, Paris, France
| | - P Aymard
- Applied Mathematics and Computational Biology, IBENS, Ecole Normale Supérieure, PSL University, Paris, France
| | - J Visser
- Neuroglial Interactions in Cerebral Physiology and Pathologies, Center for Interdisciplinary Research in Biology, Collège de France, CNR UMR 7241, INSERM U1050, PSL, Paris, France
| | - A Rancillac
- Neuroglial Interactions in Cerebral Physiology and Pathologies, Center for Interdisciplinary Research in Biology, Collège de France, CNR UMR 7241, INSERM U1050, PSL, Paris, France
| | - N Rouach
- Neuroglial Interactions in Cerebral Physiology and Pathologies, Center for Interdisciplinary Research in Biology, Collège de France, CNR UMR 7241, INSERM U1050, PSL, Paris, France
| | - D Holcman
- Applied Mathematics and Computational Biology, IBENS, Ecole Normale Supérieure, PSL University, Paris, France.
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3
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Lana D, Ugolini F, Iovino L, Attorre S, Giovannini MG. Astrocytes phenomics as new druggable targets in healthy aging and Alzheimer's disease progression. Front Cell Neurosci 2025; 18:1512985. [PMID: 39835288 PMCID: PMC11743640 DOI: 10.3389/fncel.2024.1512985] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2024] [Accepted: 12/13/2024] [Indexed: 01/22/2025] Open
Abstract
For over a century after their discovery astrocytes were regarded merely as cells located among other brain cells to hold and give support to neurons. Astrocytes activation, "astrocytosis" or A1 functional state, was considered a detrimental mechanism against neuronal survival. Recently, the scientific view on astrocytes has changed. Accumulating evidence indicate that astrocytes are not homogeneous, but rather encompass heterogeneous subpopulations of cells that differ from each other in terms of transcriptomics, molecular signature, function and response in physiological and pathological conditions. In this review, we report and discuss the recent literature on the phenomic differences of astrocytes in health and their modifications in disease conditions, focusing mainly on the hippocampus, a region involved in learning and memory encoding, in the age-related memory impairments, and in Alzheimer's disease (AD) dementia. The morphological and functional heterogeneity of astrocytes in different brain regions may be related to their different housekeeping functions. Astrocytes that express diverse transcriptomics and phenomics are present in strictly correlated brain regions and they are likely responsible for interactions essential for the formation of the specialized neural circuits that drive complex behaviors. In the contiguous and interconnected hippocampal areas CA1 and CA3, astrocytes show different, finely regulated, and region-specific heterogeneity. Heterogeneous astrocytes have specific activities in the healthy brain, and respond differently to physiological or pathological stimuli, such as inflammaging present in normal brain aging or beta-amyloid-dependent neuroinflammation typical of AD. To become reactive, astrocytes undergo transcriptional, functional, and morphological changes that transform them into cells with different properties and functions. Alterations of astrocytes affect the neurovascular unit, the blood-brain barrier and reverberate to other brain cell populations, favoring or dysregulating their activities. It will be of great interest to understand whether the differential phenomics of astrocytes in health and disease can explain the diverse vulnerability of the hippocampal areas to aging or to different damaging insults, in order to find new astrocyte-targeted therapies that might prevent or treat neurodegenerative disorders.
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Affiliation(s)
- Daniele Lana
- Section of Clinical Pharmacology and Oncology, Department of Health Sciences, University of Florence, Florence, Italy
| | - Filippo Ugolini
- Section of Pathological Anatomy, Department of Health Sciences, University of Florence, Florence, Italy
| | - Ludovica Iovino
- Institute of Neuroscience, National Research Council (CNR), Pisa, Italy
| | - Selene Attorre
- Section of Pathological Anatomy, Department of Health Sciences, University of Florence, Florence, Italy
| | - Maria Grazia Giovannini
- Section of Clinical Pharmacology and Oncology, Department of Health Sciences, University of Florence, Florence, Italy
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4
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Seifert G, Sommer E, Passlick S, Henneberger C. Super-resolution Analysis of Astrocyte Morphology Using Expansion Microscopy. Methods Mol Biol 2025; 2896:165-179. [PMID: 40111604 DOI: 10.1007/978-1-0716-4366-2_12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/22/2025]
Abstract
Analyzing the structure of astrocytes, their specific morphological features, and their remodeling is important for understanding how this cell type fulfils its many functions. This is because cell shape determines the propagation of intracellular signals and their subcellular compartmentalization. At the same time, it determines which other cells in the neuropil an astrocyte is closely in contact with and can most effectively exchange signals with. One experimental challenge has been that the most abundant small astrocytic processes cannot be resolved with diffraction-limited microscopy. Typically, this obstacle was overcome by using electron microscopy, but the continuous development of super-resolution microscopy has produced many alternative techniques. One is expansion microscopy (ExM) [1]. ExM, in principle, expands the tissue while preserving the relative positioning of labels that mark structures of interest (e.g., fluorescent labels), which increases the effective spatial resolution of light microscopy without improving the spatial resolution of the microscope itself. The advantage of ExM is that it requires only a little more laboratory infrastructure than immunohistochemistry combined with confocal fluorescence microscopy. We have previously applied this universal technique to the analysis of the structure of astrocytes and of their fine processes and their perisynaptic arrangement. Here, we present a comprehensive protocol for visualizing and localizing astrocytes, synaptic structures, and synaptic and astrocytic proteins in fixed brain tissue.
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Affiliation(s)
- Gerald Seifert
- Institute of Cellular Neurosciences I, Medical Faculty, University of Bonn, Bonn, Germany
| | - Erik Sommer
- Institute of Cellular Neurosciences I, Medical Faculty, University of Bonn, Bonn, Germany
| | - Stefan Passlick
- Institute of Cellular Neurosciences I, Medical Faculty, University of Bonn, Bonn, Germany
| | - Christian Henneberger
- Institute of Cellular Neurosciences I, Medical Faculty, University of Bonn, Bonn, Germany.
- German Center for Neurodegenerative Diseases, Bonn, Germany.
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5
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Squadrani L, Wert-Carvajal C, Müller-Komorowska D, Bohmbach K, Henneberger C, Verzelli P, Tchumatchenko T. Astrocytes enhance plasticity response during reversal learning. Commun Biol 2024; 7:852. [PMID: 38997325 PMCID: PMC11245475 DOI: 10.1038/s42003-024-06540-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2023] [Accepted: 07/03/2024] [Indexed: 07/14/2024] Open
Abstract
Astrocytes play a key role in the regulation of synaptic strength and are thought to orchestrate synaptic plasticity and memory. Yet, how specifically astrocytes and their neuroactive transmitters control learning and memory is currently an open question. Recent experiments have uncovered an astrocyte-mediated feedback loop in CA1 pyramidal neurons which is started by the release of endocannabinoids by active neurons and closed by astrocytic regulation of the D-serine levels at the dendrites. D-serine is a co-agonist for the NMDA receptor regulating the strength and direction of synaptic plasticity. Activity-dependent D-serine release mediated by astrocytes is therefore a candidate for mediating between long-term synaptic depression (LTD) and potentiation (LTP) during learning. Here, we show that the mathematical description of this mechanism leads to a biophysical model of synaptic plasticity consistent with the phenomenological model known as the BCM model. The resulting mathematical framework can explain the learning deficit observed in mice upon disruption of the D-serine regulatory mechanism. It shows that D-serine enhances plasticity during reversal learning, ensuring fast responses to changes in the external environment. The model provides new testable predictions about the learning process, driving our understanding of the functional role of neuron-glia interaction in learning.
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Affiliation(s)
- Lorenzo Squadrani
- Institute of Experimental Epileptology and Cognition Research, Medical Faculty, University of Bonn, Bonn, Germany
| | - Carlos Wert-Carvajal
- Institute of Experimental Epileptology and Cognition Research, Medical Faculty, University of Bonn, Bonn, Germany
| | | | - Kirsten Bohmbach
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Christian Henneberger
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
| | - Pietro Verzelli
- Institute of Experimental Epileptology and Cognition Research, Medical Faculty, University of Bonn, Bonn, Germany.
| | - Tatjana Tchumatchenko
- Institute of Experimental Epileptology and Cognition Research, Medical Faculty, University of Bonn, Bonn, Germany.
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6
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Bohmbach K, Henneberger C. Activity-induced reactivity of astrocytes impairs cognition. PLoS Biol 2024; 22:e3002712. [PMID: 38996200 PMCID: PMC11245315 DOI: 10.1371/journal.pbio.3002712] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/14/2024] Open
Abstract
Glial cells such as astrocytes can modulate neuronal signaling. Astrocytes can also acquire a reactive phenotype that correlates with cognitive impairments in brain diseases. A study in PLOS Biology shows that prolonged activation of astrocytes can trigger both cognitive impairments and a reactive astrocyte phenotype.
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Affiliation(s)
- Kirsten Bohmbach
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Christian Henneberger
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
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7
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Zhang LY, Hu YY, Liu XY, Wang XY, Li SC, Zhang JG, Xian XH, Li WB, Zhang M. The Role of Astrocytic Mitochondria in the Pathogenesis of Brain Ischemia. Mol Neurobiol 2024; 61:2270-2282. [PMID: 37870679 DOI: 10.1007/s12035-023-03714-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Accepted: 10/03/2023] [Indexed: 10/24/2023]
Abstract
The morbidity rate of ischemic stroke is increasing annually with the growing aging population in China. Astrocytes are ubiquitous glial cells in the brain and play a crucial role in supporting neuronal function and metabolism. Increasing evidence shows that the impairment or loss of astrocytes contributes to neuronal dysfunction during cerebral ischemic injury. The mitochondrion is increasingly recognized as a key player in regulating astrocyte function. Changes in astrocytic mitochondrial function appear to be closely linked to the homeostasis imbalance defects in glutamate metabolism, Ca2+ regulation, fatty acid metabolism, reactive oxygen species, inflammation, and copper regulation. Here, we discuss the role of astrocytic mitochondria in the pathogenesis of brain ischemic injury and their potential as a therapeutic target.
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Affiliation(s)
- Ling-Yan Zhang
- Department of Pathophysiology, Hebei Medical University, 361 Zhongshan East Road, Shijiazhuang, 050017, Hebei, People's Republic of China
- Hebei Key Laboratory of Critical Disease Mechanism and Intervention, Shijiazhuang, 050017, People's Republic of China
| | - Yu-Yan Hu
- Department of Pathophysiology, Hebei Medical University, 361 Zhongshan East Road, Shijiazhuang, 050017, Hebei, People's Republic of China
- Hebei Key Laboratory of Critical Disease Mechanism and Intervention, Shijiazhuang, 050017, People's Republic of China
| | - Xi-Yun Liu
- Department of Pathophysiology, Hebei Medical University, 361 Zhongshan East Road, Shijiazhuang, 050017, Hebei, People's Republic of China
| | - Xiao-Yu Wang
- Department of Pathophysiology, Hebei Medical University, 361 Zhongshan East Road, Shijiazhuang, 050017, Hebei, People's Republic of China
| | - Shi-Chao Li
- Department of Pathophysiology, Hebei Medical University, 361 Zhongshan East Road, Shijiazhuang, 050017, Hebei, People's Republic of China
| | - Jing-Ge Zhang
- Department of Pathophysiology, Hebei Medical University, 361 Zhongshan East Road, Shijiazhuang, 050017, Hebei, People's Republic of China
- Hebei Key Laboratory of Critical Disease Mechanism and Intervention, Shijiazhuang, 050017, People's Republic of China
| | - Xiao-Hui Xian
- Department of Pathophysiology, Hebei Medical University, 361 Zhongshan East Road, Shijiazhuang, 050017, Hebei, People's Republic of China
- Hebei Key Laboratory of Critical Disease Mechanism and Intervention, Shijiazhuang, 050017, People's Republic of China
| | - Wen-Bin Li
- Department of Pathophysiology, Hebei Medical University, 361 Zhongshan East Road, Shijiazhuang, 050017, Hebei, People's Republic of China
- Hebei Key Laboratory of Critical Disease Mechanism and Intervention, Shijiazhuang, 050017, People's Republic of China
| | - Min Zhang
- Department of Pathophysiology, Hebei Medical University, 361 Zhongshan East Road, Shijiazhuang, 050017, Hebei, People's Republic of China.
- Hebei Key Laboratory of Critical Disease Mechanism and Intervention, Shijiazhuang, 050017, People's Republic of China.
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Montalant A, Kiehn O, Perrier JF. Dopamine and noradrenaline activate spinal astrocyte endfeet via D1-like receptors. Eur J Neurosci 2024; 59:1278-1295. [PMID: 38052454 DOI: 10.1111/ejn.16205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Revised: 11/02/2023] [Accepted: 11/10/2023] [Indexed: 12/07/2023]
Abstract
Astrocytes, the most abundant glial cells in the central nervous system, respond to a wide variety of neurotransmitters binding to metabotropic receptors. Here, we investigated the intracellular calcium responses of spinal cord astrocytes to dopamine and noradrenaline, two catecholamines released by specific descending pathways. In a slice preparation from the spinal cord of neonatal mice, puff application of dopamine resulted in intracellular calcium responses that remained in the endfeet. Noradrenaline induced stronger responses that also started in the endfeet but spread to neighbouring compartments. The intracellular calcium responses were unaffected by blocking neuronal activity or inhibiting various neurotransmitter receptors, suggesting a direct effect of dopamine and noradrenaline on astrocytes. The intracellular calcium responses induced by noradrenaline and dopamine were inhibited by the D1 receptor antagonist SCH 23390. We assessed the functional consequences of these astrocytic responses by examining changes in arteriole diameter. Puff application of dopamine or noradrenaline resulted in vasoconstriction of spinal arterioles. However, blocking D1 receptors or manipulating astrocytic intracellular calcium levels did not abolish the vasoconstrictions, indicating that the observed intracellular calcium responses in astrocyte endfeet were not responsible for the vascular changes. Our findings demonstrate a compartmentalized response of spinal cord astrocytes to catecholamines and expand our understanding of astrocyte-neurotransmitter interactions and their potential roles in the physiology of the central nervous system.
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Affiliation(s)
- Alexia Montalant
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Ole Kiehn
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jean-François Perrier
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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9
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Barnett D, Bohmbach K, Grelot V, Charlet A, Dallérac G, Ju YH, Nagai J, Orr AG. Astrocytes as Drivers and Disruptors of Behavior: New Advances in Basic Mechanisms and Therapeutic Targeting. J Neurosci 2023; 43:7463-7471. [PMID: 37940585 PMCID: PMC10634555 DOI: 10.1523/jneurosci.1376-23.2023] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 08/13/2023] [Accepted: 08/22/2023] [Indexed: 11/10/2023] Open
Abstract
Astrocytes are emerging as key regulators of cognitive function and behavior. This review highlights some of the latest advances in the understanding of astrocyte roles in different behavioral domains across lifespan and in disease. We address specific molecular and circuit mechanisms by which astrocytes modulate behavior, discuss their functional diversity and versatility, and highlight emerging astrocyte-targeted treatment strategies that might alleviate behavioral and cognitive dysfunction in pathologic conditions. Converging evidence across different model systems and manipulations is revealing that astrocytes regulate behavioral processes in a precise and context-dependent manner. Improved understanding of these astrocytic functions may generate new therapeutic strategies for various conditions with cognitive and behavioral impairments.
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Affiliation(s)
- Daniel Barnett
- Appel Alzheimer's Disease Research Institute, Weill Cornell Medicine, New York, New York 10021
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, New York 10021
- Neuroscience Graduate Program, Weill Cornell Medicine, New York, New York 10021
| | - Kirsten Bohmbach
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53127 Bonn, Germany
| | - Valentin Grelot
- Institute of Cellular and Integrative Neuroscience, Centre National de la Recherche Scientifique and University of Strasbourg, Strasbourg, 67000, France
| | - Alexandre Charlet
- Institute of Cellular and Integrative Neuroscience, Centre National de la Recherche Scientifique and University of Strasbourg, Strasbourg, 67000, France
| | - Glenn Dallérac
- Centre National de la Recherche Scientifique and Paris-Saclay University, Paris-Saclay Institute for Neurosciences, Paris, 91400, France
| | - Yeon Ha Ju
- Department of Psychiatry and Neuroscience, University of Texas-Austin Dell Medical School, Austin, Texas 78712
| | - Jun Nagai
- RIKEN Center for Brain Science, Laboratory for Glia-Neuron Circuit Dynamics, Saitama, 351-0198, Japan
| | - Anna G Orr
- Appel Alzheimer's Disease Research Institute, Weill Cornell Medicine, New York, New York 10021
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, New York 10021
- Neuroscience Graduate Program, Weill Cornell Medicine, New York, New York 10021
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10
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Murphy-Royal C, Ching S, Papouin T. A conceptual framework for astrocyte function. Nat Neurosci 2023; 26:1848-1856. [PMID: 37857773 PMCID: PMC10990637 DOI: 10.1038/s41593-023-01448-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Accepted: 09/01/2023] [Indexed: 10/21/2023]
Abstract
The participation of astrocytes in brain computation was hypothesized in 1992, coinciding with the discovery that these cells display a form of intracellular Ca2+ signaling sensitive to neuroactive molecules. This finding fostered conceptual leaps crystalized around the idea that astrocytes, once thought to be passive, participate actively in brain signaling and outputs. A multitude of disparate roles of astrocytes has since emerged, but their meaningful integration has been muddied by the lack of consensus and models of how we conceive the functional position of these cells in brain circuitry. In this Perspective, we propose an intuitive, data-driven and transferable conceptual framework we coin 'contextual guidance'. It describes astrocytes as 'contextual gates' that shape neural circuitry in an adaptive, state-dependent fashion. This paradigm provides fresh perspectives on principles of astrocyte signaling and its relevance to brain function, which could spur new experimental avenues, including in computational space.
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Affiliation(s)
- Ciaran Murphy-Royal
- Centre de Recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM) & Département de Neurosciences, Université de Montréal, Montréal, Quebec, Canada
| | - ShiNung Ching
- Electrical and Systems Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Thomas Papouin
- Department of Neuroscience, Washington University School of Medicine, St. Louis, MO, USA.
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11
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Brazhe A, Verisokin A, Verveyko D, Postnov D. Astrocytes: new evidence, new models, new roles. Biophys Rev 2023; 15:1303-1333. [PMID: 37975000 PMCID: PMC10643736 DOI: 10.1007/s12551-023-01145-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Accepted: 09/08/2023] [Indexed: 11/19/2023] Open
Abstract
Astrocytes have been in the limelight of active research for about 3 decades now. Over this period, ideas about their function and role in the nervous system have evolved from simple assistance in energy supply and homeostasis maintenance to a complex informational and metabolic hub that integrates data on local neuronal activity, sensory and arousal context, and orchestrates many crucial processes in the brain. Rapid progress in experimental techniques and data analysis produces a growing body of data, which can be used as a foundation for formulation of new hypotheses, building new refined mathematical models, and ultimately should lead to a new level of understanding of the contribution of astrocytes to the cognitive tasks performed by the brain. Here, we highlight recent progress in astrocyte research, which we believe expands our understanding of how low-level signaling at a cellular level builds up to processes at the level of the whole brain and animal behavior. We start our review with revisiting data on the role of noradrenaline-mediated astrocytic signaling in locomotion, arousal, sensory integration, memory, and sleep. We then briefly review astrocyte contribution to the regulation of cerebral blood flow regulation, which is followed by a discussion of biophysical mechanisms underlying astrocyte effects on different brain processes. The experimental section is closed by an overview of recent experimental techniques available for modulation and visualization of astrocyte dynamics. We then evaluate how the new data can be potentially incorporated into the new mathematical models or where and how it already has been done. Finally, we discuss an interesting prospect that astrocytes may be key players in important processes such as the switching between sleep and wakefulness and the removal of toxic metabolites from the brain milieu.
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Affiliation(s)
- Alexey Brazhe
- Department of Biophysics, Biological Faculty, Lomonosov Moscow State University, Leninskie Gory, 1/24, Moscow, 119234 Russia
- Department of Molecular Neurobiology, Institute of Bioorganic Chemistry RAS, GSP-7, Miklukho-Maklay Str., 16/10, Moscow, 117997 Russia
| | - Andrey Verisokin
- Department of Theoretical Physics, Kursk State University, Radishcheva st., 33, Kursk, 305000 Russia
| | - Darya Verveyko
- Department of Theoretical Physics, Kursk State University, Radishcheva st., 33, Kursk, 305000 Russia
| | - Dmitry Postnov
- Department of Optics and Biophotonics, Saratov State University, Astrakhanskaya st., 83, Saratov, 410012 Russia
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12
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Henning L, Unichenko P, Bedner P, Steinhäuser C, Henneberger C. Overview Article Astrocytes as Initiators of Epilepsy. Neurochem Res 2023; 48:1091-1099. [PMID: 36244037 PMCID: PMC10030460 DOI: 10.1007/s11064-022-03773-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Revised: 08/22/2022] [Accepted: 09/27/2022] [Indexed: 10/17/2022]
Abstract
Astrocytes play a dual role in the brain. On the one hand, they are active signaling partners of neurons and can for instance control synaptic transmission and its plasticity. On the other hand, they fulfill various homeostatic functions such as clearance of glutamate and K+ released from neurons. The latter is for instance important for limiting neuronal excitability. Therefore, an impairment or failure of glutamate and K+ clearance will lead to increased neuronal excitability, which could trigger or aggravate brain diseases such as epilepsy, in which neuronal hyperexcitability plays a role. Experimental data indicate that astrocytes could have such a causal role in epilepsy, but the role of astrocytes as initiators of epilepsy and the relevant mechanisms are under debate. In this overview, we will discuss the potential mechanisms with focus on K+ clearance, glutamate uptake and homoeostasis and related mechanisms, and the evidence for their causative role in epilepsy.
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Affiliation(s)
- Lukas Henning
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53127, Bonn, Germany
| | - Petr Unichenko
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53127, Bonn, Germany
| | - Peter Bedner
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53127, Bonn, Germany
| | - Christian Steinhäuser
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53127, Bonn, Germany.
| | - Christian Henneberger
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53127, Bonn, Germany.
- German Center for Neurodegenerative Diseases (DZNE), 53127, Bonn, Germany.
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13
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Domingos C, Müller FE, Passlick S, Wachten D, Ponimaskin E, Schwarz MK, Schoch S, Zeug A, Henneberger C. Induced Remodelling of Astrocytes In Vitro and In Vivo by Manipulation of Astrocytic RhoA Activity. Cells 2023; 12:331. [PMID: 36672265 PMCID: PMC9856770 DOI: 10.3390/cells12020331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2022] [Revised: 01/05/2023] [Accepted: 01/11/2023] [Indexed: 01/17/2023] Open
Abstract
Structural changes of astrocytes and their perisynaptic processes occur in response to various physiological and pathophysiological stimuli. They are thought to profoundly affect synaptic signalling and neuron-astrocyte communication. Understanding the causal relationship between astrocyte morphology changes and their functional consequences requires experimental tools to selectively manipulate astrocyte morphology. Previous studies indicate that RhoA-related signalling can play a major role in controlling astrocyte morphology, but the direct effect of increased RhoA activity has not been documented in vitro and in vivo. Therefore, we established a viral approach to manipulate astrocytic RhoA activity. We tested if and how overexpression of wild-type RhoA, of a constitutively active RhoA mutant (RhoA-CA), and of a dominant-negative RhoA variant changes the morphology of cultured astrocytes. We found that astrocytic expression of RhoA-CA induced robust cytoskeletal changes and a withdrawal of processes in cultured astrocytes. In contrast, overexpression of other RhoA variants led to more variable changes of astrocyte morphology. These induced morphology changes were reproduced in astrocytes of the hippocampus in vivo. Importantly, astrocytic overexpression of RhoA-CA did not alter the branching pattern of larger GFAP-positive processes of astrocytes. This indicates that a prolonged increase of astrocytic RhoA activity leads to a distinct morphological phenotype in vitro and in vivo, which is characterized by an isolated reduction of fine peripheral astrocyte processes in vivo. At the same time, we identified a promising experimental approach for investigating the functional consequences of astrocyte morphology changes.
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Affiliation(s)
- Cátia Domingos
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53127 Bonn, Germany
| | | | - Stefan Passlick
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53127 Bonn, Germany
| | - Dagmar Wachten
- Institute of Innate Immunity, Medical Faculty, University of Bonn, 53127 Bonn, Germany
| | - Evgeni Ponimaskin
- Cellular Neurophysiology, Hannover Medical School, 30625 Hannover, Germany
| | - Martin K. Schwarz
- Institute of Experimental Epileptology and Cognition Research (EECR), Medical Faculty, University of Bonn, 53127 Bonn, Germany
| | - Susanne Schoch
- Institute of Neuropathology, University of Bonn Medical School, 53127 Bonn, Germany
| | - André Zeug
- Cellular Neurophysiology, Hannover Medical School, 30625 Hannover, Germany
| | - Christian Henneberger
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53127 Bonn, Germany
- German Center for Neurodegenerative Diseases (DZNE), 53127 Bonn, Germany
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14
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Kruyer A, Kalivas PW, Scofield MD. Astrocyte regulation of synaptic signaling in psychiatric disorders. Neuropsychopharmacology 2023; 48:21-36. [PMID: 35577914 PMCID: PMC9700696 DOI: 10.1038/s41386-022-01338-w] [Citation(s) in RCA: 39] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2022] [Revised: 04/27/2022] [Accepted: 05/01/2022] [Indexed: 02/07/2023]
Abstract
Over the last 15 years, the field of neuroscience has evolved toward recognizing the critical role of astroglia in shaping neuronal synaptic activity and along with the pre- and postsynapse is now considered an equal partner in tripartite synaptic transmission and plasticity. The relative youth of this recognition and a corresponding deficit in reagents and technologies for quantifying and manipulating astroglia relative to neurons continues to hamper advances in understanding tripartite synaptic physiology. Nonetheless, substantial advances have been made and are reviewed herein. We review the role of astroglia in synaptic function and regulation of behavior with an eye on how tripartite synapses figure into brain pathologies underlying behavioral impairments in psychiatric disorders, both from the perspective of measures in postmortem human brains and more subtle influences on tripartite synaptic regulation of behavior in animal models of psychiatric symptoms. Our goal is to provide the reader a well-referenced state-of-the-art understanding of current knowledge and predict what we may discover with deeper investigation of tripartite synapses using reagents and technologies not yet available.
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Affiliation(s)
- Anna Kruyer
- Department of Neuroscience, Medical University of South Carolina, Charleston, SC, USA
| | - Peter W Kalivas
- Department of Neuroscience, Medical University of South Carolina, Charleston, SC, USA.
- Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC, USA.
| | - Michael D Scofield
- Department of Neuroscience, Medical University of South Carolina, Charleston, SC, USA.
- Department of Anesthesia & Perioperative Medicine, Medical University of South Carolina, Charleston, SC, USA.
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15
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Aghighi Z, Ghorbani Z, Moghaddam MH, Fathi M, Abdollahifar MA, Soleimani M, Karimzadeh F, Rasoolijazi H, Aliaghaei A. Melittin ameliorates motor function and prevents autophagy-induced cell death and astrogliosis in rat models of cerebellar ataxia induced by 3-acetylpyridine. Neuropeptides 2022; 96:102295. [PMID: 36280441 DOI: 10.1016/j.npep.2022.102295] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 10/10/2022] [Accepted: 10/11/2022] [Indexed: 11/06/2022]
Abstract
BACKGROUND Cerebellar ataxia (CA) is a form of ataxia that adversely affects the cerebellum. This study aims to investigate the therapeutic effects of melittin (MEL) on a 3-acetylpyridine-induced (3-AP) cerebellar ataxia (CA) rat model. METHODS Initially, CA rat models were generated by 3-AP administration followed by the subcutaneous injection of MEL. The open-field test was used for the evaluation of locomotion and anxiety. Immunohistochemistry was also conducted for the autophagy markers of LC3 and Beclin1. In the next step, the morphology of the astrocyte, the cell responsible for maintaining homeostasis in the CNS, was evaluated by the Sholl analysis. RESULTS The findings suggested that the administration of MEL in a 3-AP model of ataxia improved locomotion and anxiety (P < 0.001), decreased the expression of LC3 (P < 0.01) and Beclin1 (P < 0.05), increased astrocyte complexity (P < 0.05) and reduced astrocyte cell soma size (P < 0.001). CONCLUSIONS Overall, the findings imply that the MEL attenuates the 3-AP-induced autophagy, causes cell death and improves motor function. As such, it could be used as a therapeutic procedure for CA due to its neuroprotective effects.
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Affiliation(s)
- Zahra Aghighi
- Department of Anatomy, School of Medicine, Iran University of Medical Sciences, Tehran, Iran; Cellular and Molecular Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Zeynab Ghorbani
- Department of Anatomy, School of Medicine, Iran University of Medical Sciences, Tehran, Iran; Cellular and Molecular Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Meysam Hassani Moghaddam
- Department of Anatomical Sciences, Faculty of Medicine, AJA University of Medical Sciences, Tehran, Iran
| | - Mobina Fathi
- Student Research Committee, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Mohammad-Amin Abdollahifar
- Department of Biology and Anatomical Sciences, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Mansoureh Soleimani
- Department of Anatomy, School of Medicine, Iran University of Medical Sciences, Tehran, Iran; Cellular and Molecular Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Fariba Karimzadeh
- Cellular and Molecular Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Homa Rasoolijazi
- Department of Anatomy, School of Medicine, Iran University of Medical Sciences, Tehran, Iran; Cellular and Molecular Research Center, Iran University of Medical Sciences, Tehran, Iran.
| | - Abbas Aliaghaei
- Hearing Disorders Research Center, Loghman Hakim Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran; Department of Biology and Anatomical Sciences, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
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16
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Brunskine C, Passlick S, Henneberger C. Structural Heterogeneity of the GABAergic Tripartite Synapse. Cells 2022; 11:cells11193150. [PMID: 36231112 PMCID: PMC9563275 DOI: 10.3390/cells11193150] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 09/29/2022] [Accepted: 10/04/2022] [Indexed: 11/22/2022] Open
Abstract
The concept of the tripartite synapse describes the close interaction of pre- and postsynaptic elements and the surrounding astrocyte processes. For glutamatergic synapses, it is established that the presence of astrocytic processes and their structural arrangements varies considerably between and within brain regions and between synapses of the same neuron. In contrast, less is known about the organization of astrocytic processes at GABAergic synapses although bi-directional signaling is known to exist at these synapses too. Therefore, we established super-resolution expansion microscopy of GABAergic synapses and nearby astrocytic processes in the stratum radiatum of the mouse hippocampal CA1 region. By visualizing the presynaptic vesicular GABA transporter and the postsynaptic clustering protein gephyrin, we documented the subsynaptic heterogeneity of GABAergic synaptic contacts. We then compared the volume distribution of astrocytic processes near GABAergic synapses between individual synapses and with glutamatergic synapses. We made two novel observations. First, astrocytic processes were more abundant at the GABAergic synapses with large postsynaptic gephyrin clusters. Second, astrocytic processes were less abundant in the vicinity of GABAergic synapses compared to glutamatergic, suggesting that the latter may be selectively approached by astrocytes. Because of the GABA transporter distribution, we also speculate that this specific arrangement enables more efficient re-uptake of GABA into presynaptic terminals.
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Affiliation(s)
- Cindy Brunskine
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53127 Bonn, Germany
| | - Stefan Passlick
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53127 Bonn, Germany
| | - Christian Henneberger
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, 53127 Bonn, Germany
- German Center for Neurodegenerative Diseases (DZNE), 53127 Bonn, Germany
- Correspondence:
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17
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Astrocytes mediate analogous memory in a multi-layer neuron–astrocyte network. Neural Comput Appl 2022. [DOI: 10.1007/s00521-022-06936-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
AbstractModeling the neuronal processes underlying short-term working memory remains the focus of many theoretical studies in neuroscience. In this paper, we propose a mathematical model of a spiking neural network (SNN) which simulates the way a fragment of information is maintained as a robust activity pattern for several seconds and the way it completely disappears if no other stimuli are fed to the system. Such short-term memory traces are preserved due to the activation of astrocytes accompanying the SNN. The astrocytes exhibit calcium transients at a time scale of seconds. These transients further modulate the efficiency of synaptic transmission and, hence, the firing rate of neighboring neurons at diverse timescales through gliotransmitter release. We demonstrate how such transients continuously encode frequencies of neuronal discharges and provide robust short-term storage of analogous information. This kind of short-term memory can store relevant information for seconds and then completely forget it to avoid overlapping with forthcoming patterns. The SNN is inter-connected with the astrocytic layer by local inter-cellular diffusive connections. The astrocytes are activated only when the neighboring neurons fire synchronously, e.g., when an information pattern is loaded. For illustration, we took grayscale photographs of people’s faces where the shades of gray correspond to the level of applied current which stimulates the neurons. The astrocyte feedback modulates (facilitates) synaptic transmission by varying the frequency of neuronal firing. We show how arbitrary patterns can be loaded, then stored for a certain interval of time, and retrieved if the appropriate clue pattern is applied to the input.
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18
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Rusakov DA, Giese KP, Sandi C, Dommett E, Overton PG. Remembering Mike Stewart. Neuropharmacology 2022; 207:108962. [PMID: 35051447 DOI: 10.1016/j.neuropharm.2022.108962] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Dmitri A Rusakov
- UCL Queen Square Institute of Neurology, University College London, Queen Square, London, WC1N 3BG, UK.
| | - Karl Peter Giese
- Institute of Psychiatry, Physiology and Neuroscience, King's College London, De Crespigny Park, London, SE5 8AF, UK
| | - Carmen Sandi
- Swiss Federal Institute of Technology in Lausanne (EPFL), Rte Cantonale, 1015, Lausanne, Switzerland
| | - Eleanore Dommett
- Institute of Psychiatry, Physiology and Neuroscience, King's College London, De Crespigny Park, London, SE5 8AF, UK
| | - Paul G Overton
- Department of Psychology, University of Sheffield, Vicar Lane, Sheffield, S1 2LT, UK
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19
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Rusakov DA. Obituary for Professor Michael G. Stewart: Life in Neurosciences. Brain Res Bull 2022; 180:147-149. [DOI: 10.1016/j.brainresbull.2022.01.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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20
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Abstract
Drug addiction remains a key biomedical challenge facing current neuroscience research. In addition to neural mechanisms, the focus of the vast majority of studies to date, astrocytes have been increasingly recognized as an "accomplice." According to the tripartite synapse model, astrocytes critically regulate nearby pre- and postsynaptic neuronal substrates to craft experience-dependent synaptic plasticity, including synapse formation and elimination. Astrocytes within brain regions that are implicated in drug addiction exhibit dynamic changes in activity upon exposure to cocaine and subsequently undergo adaptive changes themselves during chronic drug exposure. Recent results have identified several key astrocytic signaling pathways that are involved in cocaine-induced synaptic and circuit adaptations. In this review, we provide a brief overview of the role of astrocytes in regulating synaptic transmission and neuronal function, and discuss how cocaine influences these astrocyte-mediated mechanisms to induce persistent synaptic and circuit alterations that promote cocaine seeking and relapse. We also consider the therapeutic potential of targeting astrocytic substrates to ameliorate drug-induced neuroplasticity for behavioral benefits. While primarily focusing on cocaine-induced astrocytic responses, we also include brief discussion of other drugs of abuse where data are available.
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21
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Lalo U, Koh W, Lee CJ, Pankratov Y. The tripartite glutamatergic synapse. Neuropharmacology 2021; 199:108758. [PMID: 34433089 DOI: 10.1016/j.neuropharm.2021.108758] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Revised: 07/25/2021] [Accepted: 08/20/2021] [Indexed: 12/31/2022]
Abstract
Astroglial cells were long considered as structural and metabolic supporting cells are which do not directly participate in information processing in the brain. Discoveries of responsiveness of astrocytes to synaptically-released glutamate and their capability to release agonists of glutamate receptors awakened extensive studies of glia-neuron communications and led to the revolutionary changes in our understanding of brain cellular networks. Nowadays, astrocytes are widely acknowledged as inseparable element of glutamatergic synapses and role for glutamatergic astrocyte-neuron interactions in the brain computation is emerging. Astroglial glutamate receptors, in particular of NMDA, mGluR3 and mGluR5 types, can activate a variety of molecular cascades leading astroglial-driven modulation of extracellular levels of glutamate and activity of neuronal glutamate receptors. Their preferential location to the astroglial perisynaptic processes facilitates interaction of astrocytes with individual excitatory synapses. Bi-directional glutamatergic communication between astrocytes and neurons underpins a complex, spatially-distributed modulation of synaptic signalling thus contributing to the enrichment of information processing by the neuronal networks. Still, further research is needed to bridge the substantial gaps in our understanding of mechanisms and physiological relevance of astrocyte-neuron glutamatergic interactions, in particular ability of astrocytes directly activate neuronal glutamate receptors by releasing glutamate and, arguably, d-Serine. An emerging roles for aberrant changes in glutamatergic astroglial signalling, both neuroprotective and pathogenic, in neurological and neurodegenerative diseases also require further investigation. This article is part of the special Issue on 'Glutamate Receptors - The Glutamatergic Synapse'.
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Affiliation(s)
- Ulyana Lalo
- School of Life Sciences, Immanuel Kant Baltic Federal University, Kaliningrad, Russia
| | - Wuhyun Koh
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon, 34126, South Korea
| | - C Justin Lee
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon, 34126, South Korea
| | - Yuriy Pankratov
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL, United Kingdom.
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22
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Müller FE, Schade SK, Cherkas V, Stopper L, Breithausen B, Minge D, Varbanov H, Wahl-Schott C, Antoniuk S, Domingos C, Compan V, Kirchhoff F, Henneberger C, Ponimaskin E, Zeug A. Serotonin receptor 4 regulates hippocampal astrocyte morphology and function. Glia 2020; 69:872-889. [PMID: 33156956 DOI: 10.1002/glia.23933] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 10/15/2020] [Accepted: 10/19/2020] [Indexed: 12/25/2022]
Abstract
Astrocytes are an important component of the multipartite synapse and crucial for proper neuronal network function. Although small GTPases of the Rho family are powerful regulators of cellular morphology, the signaling modules of Rho-mediated pathways in astrocytes remain enigmatic. Here we demonstrated that the serotonin receptor 4 (5-HT4 R) is expressed in hippocampal astrocytes, both in vitro and in vivo. Through fluorescence microscopy, we established that 5-HT4 R activation triggered RhoA activity via Gα13 -mediated signaling, which boosted filamentous actin assembly, leading to morphological changes in hippocampal astrocytes. We investigated the effects of these 5-HT4 R-mediated changes in mixed cultures and in acute slices, in which 5-HT4 R was expressed exclusively in astrocytes. In both systems, 5-HT4 R-RhoA signaling changed glutamatergic synaptic transmission: It increased the frequency of miniature excitatory postsynaptic currents (mEPSCs) in mixed cultures and reduced the paired-pulse-ratio (PPR) of field excitatory postsynaptic potentials (fEPSPs) in acute slices. Overall, our present findings demonstrate that astrocytic 5-HT4 R-Gα13 -RhoA signaling is a previously unrecognized molecular pathway involved in the functional regulation of excitatory synaptic circuits.
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Affiliation(s)
| | - Sophie K Schade
- Cellular Neurophysiology, Hannover Medical School, Hannover, Germany
| | - Volodymyr Cherkas
- Cellular Neurophysiology, Hannover Medical School, Hannover, Germany
| | - Laura Stopper
- Department of Molecular Physiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), University of Saarland, Homburg, Germany
| | - Björn Breithausen
- Institute of Cellular Neurosciences, Medical School, University of Bonn, Bonn, Germany
| | - Daniel Minge
- Institute of Cellular Neurosciences, Medical School, University of Bonn, Bonn, Germany
| | - Hristo Varbanov
- Institute of Neurophysiology, Hannover Medical School, Hannover, Germany
| | | | - Svitlana Antoniuk
- Cellular Neurophysiology, Hannover Medical School, Hannover, Germany.,Nencki Institute of Experimental Biology of the Polish Academy of Science, Warsaw, Poland
| | - Catia Domingos
- Institute of Cellular Neurosciences, Medical School, University of Bonn, Bonn, Germany
| | - Valérie Compan
- Department of Sciences, Brain, Anorexia & Addiction, Nîmes University, Nîmes, France
| | - Frank Kirchhoff
- Department of Molecular Physiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), University of Saarland, Homburg, Germany
| | - Christian Henneberger
- Institute of Cellular Neurosciences, Medical School, University of Bonn, Bonn, Germany.,German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany.,Institute of Neurology, University College London, London, UK
| | - Evgeni Ponimaskin
- Cellular Neurophysiology, Hannover Medical School, Hannover, Germany.,Institute of Neuroscience, Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod, Russia
| | - Andre Zeug
- Cellular Neurophysiology, Hannover Medical School, Hannover, Germany
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23
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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: 16] [Impact Index Per Article: 3.2] [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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24
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Kofuji P, Araque A. G-Protein-Coupled Receptors in Astrocyte-Neuron Communication. Neuroscience 2020; 456:71-84. [PMID: 32224231 DOI: 10.1016/j.neuroscience.2020.03.025] [Citation(s) in RCA: 156] [Impact Index Per Article: 31.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 03/13/2020] [Accepted: 03/18/2020] [Indexed: 12/11/2022]
Abstract
Astrocytes, a major type of glial cell, are known to play key supportive roles in brain function, contributing to ion and neurotransmitter homeostasis, maintaining the blood-brain barrier and providing trophic and metabolic support for neurons. Besides these support functions, astrocytes are emerging as important elements in brain physiology through signaling exchange with neurons at tripartite synapses. Astrocytes express a wide variety of neurotransmitter transporters and receptors that allow them to sense and respond to synaptic activity. Principal among them are the G-protein-coupled receptors (GPCRs) in astrocytes because their activation by synaptically released neurotransmitters leads to mobilization of intracellular calcium. In turn, activated astrocytes release neuroactive substances called gliotransmitters, such as glutamate, GABA, and ATP/adenosine that lead to synaptic regulation through activation of neuronal GPCRs. In this review we will present and discuss recent evidence demonstrating the critical roles played by GPCRs in the bidirectional astrocyte-neuron signaling, and their crucial involvement in the astrocyte-mediated regulation of synaptic transmission and plasticity.
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Affiliation(s)
- Paulo Kofuji
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA.
| | - Alfonso Araque
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA.
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25
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King CM, Bohmbach K, Minge D, Delekate A, Zheng K, Reynolds J, Rakers C, Zeug A, Petzold GC, Rusakov DA, Henneberger C. Local Resting Ca 2+ Controls the Scale of Astroglial Ca 2+ Signals. Cell Rep 2020; 30:3466-3477.e4. [PMID: 32160550 PMCID: PMC7068654 DOI: 10.1016/j.celrep.2020.02.043] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Revised: 12/21/2019] [Accepted: 02/06/2020] [Indexed: 02/07/2023] Open
Abstract
Astroglia regulate neurovascular coupling while engaging in signal exchange with neurons. The underlying cellular machinery is thought to rely on astrocytic Ca2+ signals, but what controls their amplitude and waveform is poorly understood. Here, we employ time-resolved two-photon excitation fluorescence imaging in acute hippocampal slices and in cortex in vivo to find that resting [Ca2+] predicts the scale (amplitude) and the maximum (peak) of astroglial Ca2+ elevations. We bidirectionally manipulate resting [Ca2+] by uncaging intracellular Ca2+ or Ca2+ buffers and use ratiometric imaging of a genetically encoded Ca2+ indicator to establish that alterations in resting [Ca2+] change co-directionally the peak level and anti-directionally the amplitude of local Ca2+ transients. This relationship holds for spontaneous and for induced (for instance by locomotion) Ca2+ signals. Our findings uncover a basic generic rule of Ca2+ signal formation in astrocytes, thus also associating the resting Ca2+ level with the physiological "excitability" state of astroglia.
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Affiliation(s)
- Claire M King
- Institute of Neurology, University College London, London, UK
| | - Kirsten Bohmbach
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Daniel Minge
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Andrea Delekate
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
| | - Kaiyu Zheng
- Institute of Neurology, University College London, London, UK
| | - James Reynolds
- Institute of Neurology, University College London, London, UK
| | - Cordula Rakers
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
| | - Andre Zeug
- Cellular Neurophysiology, Hannover Medical School, Hannover, Germany
| | - Gabor C Petzold
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany; Department of Neurology, University Hospital Bonn, Bonn, Germany
| | | | - Christian Henneberger
- Institute of Neurology, University College London, London, UK; Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany; German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany.
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26
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Nikolic L, Nobili P, Shen W, Audinat E. Role of astrocyte purinergic signaling in epilepsy. Glia 2019; 68:1677-1691. [DOI: 10.1002/glia.23747] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Revised: 10/08/2019] [Accepted: 10/25/2019] [Indexed: 12/26/2022]
Affiliation(s)
- Ljiljana Nikolic
- Institute for Biological Research Siniša Stanković, University of Belgrade Serbia
| | | | - Weida Shen
- Zhejiang University City College Zhejiang Hangzhou China
| | - Etienne Audinat
- Institute for Functional Genomics (IGF), University of Montpellier, CNRS, INSERM Montpellier France
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27
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Reiner A, Levitz J. Glutamatergic Signaling in the Central Nervous System: Ionotropic and Metabotropic Receptors in Concert. Neuron 2019; 98:1080-1098. [PMID: 29953871 DOI: 10.1016/j.neuron.2018.05.018] [Citation(s) in RCA: 407] [Impact Index Per Article: 67.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Revised: 04/19/2018] [Accepted: 05/10/2018] [Indexed: 12/28/2022]
Abstract
Glutamate serves as both the mammalian brain's primary excitatory neurotransmitter and as a key neuromodulator to control synapse and circuit function over a wide range of spatial and temporal scales. This functional diversity is decoded by two receptor families: ionotropic glutamate receptors (iGluRs) and metabotropic glutamate receptors (mGluRs). The challenges posed by the complexity and physiological importance of each of these subtypes has limited our appreciation and understanding of how these receptors work in concert. In this review, by comparing both receptor families with a focus on their crosstalk, we argue for a more holistic understanding of neural glutamate signaling.
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Affiliation(s)
- Andreas Reiner
- Department of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany.
| | - Joshua Levitz
- Department of Biochemistry, Weill Cornell Medicine, New York, NY, USA.
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28
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Zhang Z, Ma Z, Zou W, Zhang L, Li Y, Zhang J, Liu M, Hou W, Ma Y. N-myc downstream-regulated gene 2 controls astrocyte morphology via Rho-GTPase signaling. J Cell Physiol 2019; 234:20847-20858. [PMID: 31004356 DOI: 10.1002/jcp.28689] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 03/25/2019] [Accepted: 04/05/2019] [Indexed: 01/16/2023]
Abstract
Astrocyte undergoes morphology changes that are closely associated with the signaling communications at synapses. N-myc downstream-regulated gene 2 (NDRG2) is specifically expressed in astrocytes and is associated with several important astrocyte functions, but its potential role(s) relating to astrocyte morphological changes remain unknown. Here, primary astrocytes were prepared from neonatal Ndrg2+/+ and Ndrg2-/- pups, and the drug Y27632 was used to induce stellation. We then used a variety of methods to measure the levels of NDRG2, α-Actinin4, and glial fibrillary acidic protein (GFAP), and the activity of RhoA, Rac1, and Cdc42 in Y27632-treated astrocytes as well as in Ndrg2+/+ , Ndrg2-/- , or Ndrg2-/- + lentivirus (restore NDRG2 expression) astrocytes. We also conducted live-imaging and proteomics studies of the cultured astrocytes. We found that induction of astrocytes stellation (characterized by cytoplasmic retraction and process outgrowth) resulted in increased NDRG2 protein expression and Rac1 activity and in reduced α-Actinin4 protein expression and RhoA activity. Ndrg2 deletion induced astrocyte flattening, whereas the restoration of NDRG2 expression induced stellation. Ndrg2 deletion also significantly increased α-Actinin4 protein expression and RhoA activity yet reduced GFAP protein expression and Rac1 activity, and these trends were reversed by restoration of NDRG2 expression. Collectively, our results showed that Ndrg2 deletion promoted cell proliferation, interrupted stellation capability, and extensively altered the protein expression profiles of proteins that function in Rho-GTPase signaling. These findings suggest that NDRG2 functions to regulate astrocytes morphology via altering the accumulation of the Rho-GTPase signaling pathway components, thereby supporting that NDRG2 should be understood as a regulator of synaptic plasticity and thus neuronal communications.
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Affiliation(s)
- Zengli Zhang
- Department of Anesthesiology, Xiangya Hospital, Central South University, Changsha, China.,Department of Anesthesiology and Perioperative Medicine, Xijing Hospital, The Fourth Military Medical University, Xi'an, China
| | - Zhi Ma
- Department of Anesthesiology, Center for Brain Science, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Wangyuan Zou
- Department of Anesthesiology, Xiangya Hospital, Central South University, Changsha, China
| | - Lixia Zhang
- Department of Burn and Plastic Surgery, The Fourth Medical Center to Chinese PLA General Hospital, Beijing, China
| | - Yan Li
- Department of Anesthesiology, Center for Brain Science, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Jian Zhang
- Department of Biochemistry and Molecular Biology, The Fourth Military Medical University, Xi'an, China
| | - Min Liu
- Anesthesia and Operation Center, The First Medical Center to Chinese PLA General Hospital, Beijing, China
| | - Wugang Hou
- Department of Anesthesiology and Perioperative Medicine, Xijing Hospital, The Fourth Military Medical University, Xi'an, China
| | - Yulong Ma
- Anesthesia and Operation Center, The First Medical Center to Chinese PLA General Hospital, Beijing, China
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29
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Gliotransmission: Beyond Black-and-White. J Neurosci 2019; 38:14-25. [PMID: 29298905 DOI: 10.1523/jneurosci.0017-17.2017] [Citation(s) in RCA: 215] [Impact Index Per Article: 35.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 08/01/2017] [Accepted: 08/29/2017] [Indexed: 01/09/2023] Open
Abstract
Astrocytes are highly complex cells with many emerging putative roles in brain function. Of these, gliotransmission (active information transfer from glia to neurons) has probably the widest implications on our understanding of how the brain works: do astrocytes really contribute to information processing within the neural circuitry? "Positive evidence" for this stems from work of multiple laboratories reporting many examples of modulatory chemical signaling from astrocytes to neurons in the timeframe of hundreds of milliseconds to several minutes. This signaling involves, but is not limited to, Ca2+-dependent vesicular transmitter release, and results in a variety of regulatory effects at synapses in many circuits that are abolished by preventing Ca2+ elevations or blocking exocytosis selectively in astrocytes. In striking contradiction, methodologically advanced studies by a few laboratories produced "negative evidence," triggering a heated debate on the actual existence and properties of gliotransmission. In this context, a skeptics' camp arose, eager to dismiss the whole positive evidence based on a number of assumptions behind the negative data, such as the following: (1) deleting a single Ca2+ release pathway (IP3R2) removes all the sources for Ca2+-dependent gliotransmission; (2) stimulating a transgenically expressed Gq-GPCR (MrgA1) mimics the physiological Ca2+ signaling underlying gliotransmitter release; (3) age-dependent downregulation of an endogenous GPCR (mGluR5) questions gliotransmitter release in adulthood; and (4) failure by transcriptome analysis to detect vGluts or canonical synaptic SNAREs in astrocytes proves inexistence/functional irrelevance of vesicular gliotransmitter release. We here discuss how the above assumptions are likely wrong and oversimplistic. In light of the most recent literature, we argue that gliotransmission is a more complex phenomenon than originally thought, possibly consisting of multiple forms and signaling processes, whose correct study and understanding require more sophisticated tools and finer scientific experiments than done until today. Under this perspective, the opposing camps can be reconciled and the field moved forward. Along the path, a more cautious mindset and an attitude to open discussion and mutual respect between opponent laboratories will be good companions.Dual Perspectives Companion Paper: Multiple Lines of Evidence Indicate That Gliotransmission Does Not Occur under Physiological Conditions, by Todd A. Fiacco and Ken D. McCarthy.
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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: 41] [Impact Index Per Article: 6.8] [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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31
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Montagna E, Crux S, Luckner M, Herber J, Colombo AV, Marinković P, Tahirovic S, Lichtenthaler SF, Wanner G, Müller UC, Sgobio C, Herms J. In vivo
Ca
2+
imaging of astrocytic microdomains reveals a critical role of the amyloid precursor protein for mitochondria. Glia 2019; 67:985-998. [DOI: 10.1002/glia.23584] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Revised: 12/17/2018] [Accepted: 12/20/2018] [Indexed: 01/04/2023]
Affiliation(s)
- Elena Montagna
- Division of Translational Brain Research, German Center for Neurodegenerative Diseases (DZNE) Munich Germany
- Division of Translational Brain Research, Center for Neuropathology and Prion ResearchLudwig–Maximilians University Munich Germany
- Munich Cluster of Systems Neurology (SyNergy)Ludwig‐Maximilians University Munich Germany
| | - Sophie Crux
- Division of Translational Brain Research, German Center for Neurodegenerative Diseases (DZNE) Munich Germany
- Division of Translational Brain Research, Center for Neuropathology and Prion ResearchLudwig–Maximilians University Munich Germany
- Munich Cluster of Systems Neurology (SyNergy)Ludwig‐Maximilians University Munich Germany
| | - Manja Luckner
- Department Biology I, BiocenterLudwig‐Maximilians University Munich Martinsried Germany
| | - Julia Herber
- Division of Translational Brain Research, German Center for Neurodegenerative Diseases (DZNE) Munich Germany
- Neuroproteomics, School of Medicine, Klinikum rechts der Isar and Institute for Advanced StudyTechnische Universität München Munich Germany
| | - Alessio V. Colombo
- Division of Translational Brain Research, German Center for Neurodegenerative Diseases (DZNE) Munich Germany
| | - Petar Marinković
- Division of Translational Brain Research, German Center for Neurodegenerative Diseases (DZNE) Munich Germany
| | - Sabina Tahirovic
- Division of Translational Brain Research, German Center for Neurodegenerative Diseases (DZNE) Munich Germany
| | - Stefan F. Lichtenthaler
- Division of Translational Brain Research, German Center for Neurodegenerative Diseases (DZNE) Munich Germany
- Munich Cluster of Systems Neurology (SyNergy)Ludwig‐Maximilians University Munich Germany
- Neuroproteomics, School of Medicine, Klinikum rechts der Isar and Institute for Advanced StudyTechnische Universität München Munich Germany
| | - Gerhard Wanner
- Department Biology I, BiocenterLudwig‐Maximilians University Munich Martinsried Germany
| | - Ulrike C. Müller
- Department of Functional Genomics, Institute of Pharmacy and Molecular BiotechnologyHeidelberg University Heidelberg Germany
| | - Carmelo Sgobio
- Division of Translational Brain Research, German Center for Neurodegenerative Diseases (DZNE) Munich Germany
| | - Jochen Herms
- Division of Translational Brain Research, German Center for Neurodegenerative Diseases (DZNE) Munich Germany
- Division of Translational Brain Research, Center for Neuropathology and Prion ResearchLudwig–Maximilians University Munich Germany
- Munich Cluster of Systems Neurology (SyNergy)Ludwig‐Maximilians University Munich Germany
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32
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Reynolds JP, Zheng K, Rusakov DA. Multiplexed calcium imaging of single-synapse activity and astroglial responses in the intact brain. Neurosci Lett 2019; 689:26-32. [PMID: 29908948 PMCID: PMC6335263 DOI: 10.1016/j.neulet.2018.06.024] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Revised: 06/11/2018] [Accepted: 06/13/2018] [Indexed: 10/28/2022]
Abstract
All-optical registration of neuronal and astrocytic activities within the intact mammalian brain has improved significantly with recent advances in optical sensors and biophotonics. However, relating single-synapse release events and local astroglial responses to sensory stimuli in an intact animal has not hitherto been feasible. Here, we present a multiplexed multiphoton excitation imaging approach for assessing the relationship between presynaptic Ca2+ entry at thalamocortical axonal boutons and perisynaptic astrocytic Ca2+ elevations, induced by whisker stimulation in the barrel cortex of C57BL/6 mice. We find that, unexpectedly, Ca2+ elevations in the perisynaptic astrocytic regions consistently precede local presynaptic Ca2+ signals during spontaneous brain activity associated with anaesthesia. The methods described here can be adapted to a variety of optical sensors and are compatible with experimental designs that might necessitate repeated sampling of single synapses over a longitudinal behavioural paradigm.
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Affiliation(s)
- James P Reynolds
- UCL Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK.
| | - Kaiyu Zheng
- UCL Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK
| | - Dmitri A Rusakov
- UCL Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK.
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33
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Heller JP, Rusakov DA. A Method to Visualize the Nanoscopic Morphology of Astrocytes In Vitro and In Situ. Methods Mol Biol 2019; 1938:69-84. [PMID: 30617973 DOI: 10.1007/978-1-4939-9068-9_5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
In recent years it has become apparent that astroglia are not only essential players in brain development, homeostasis, and metabolic support but are also important for the formation and regulation of synaptic circuits. Fine astrocytic processes that can be found in the vicinity of synapses undergo considerable structural plasticity associated with age- and use-dependent changes in neural circuitries. However, due to the extraordinary complex, essentially nanoscopic morphology of astroglia, the underlying cellular mechanisms remain poorly understood.Here we detail a super-resolution microscopy approach, based on the single-molecule localisation microscopy (SMLM) technique direct stochastic optical reconstruction microscopy (dSTORM) to visualize astroglial morphology on the nanoscale. This approach enables visualization of key morphological changes that occur in nanoscopic astrocyte processes, whose characteristic size falls below the diffraction limit of conventional optical microscopy.
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Affiliation(s)
- Janosch P Heller
- UCL Queen Square Institute of Neurology, University College London, Queen Square, London, UK.
| | - Dmitri A Rusakov
- UCL Queen Square Institute of Neurology, University College London, Queen Square, London, UK.
- Laboratory of Brain Microcircuits, Institute of Neuroscience, University of Nizhny Novgorod, Nizhny Novgorod, Russia.
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Cresswell-Clay E, Crock N, Tabak J, Erlebacher G. A Compartmental Model to Investigate Local and Global Ca 2+ Dynamics in Astrocytes. Front Comput Neurosci 2018; 12:94. [PMID: 30555315 PMCID: PMC6284150 DOI: 10.3389/fncom.2018.00094] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 11/08/2018] [Indexed: 01/20/2023] Open
Abstract
Intracellular Ca2+ dynamics in astrocytes can be triggered by neuronal activity and in turn regulate a variety of downstream processes that modulate neuronal function. In this fashion, astrocytic Ca2+ signaling is regarded as a processor of neural network activity by means of complex spatial and temporal Ca2+ dynamics. Accordingly, a key step is to understand how different patterns of neural activity translate into spatiotemporal dynamics of intracellular Ca2+ in astrocytes. Here, we introduce a minimal compartmental model for astrocytes that can qualitatively reproduce essential hierarchical features of spatiotemporal Ca2+ dynamics in astrocytes. We find that the rate of neuronal firing determines the rate of Ca2+ spikes in single individual processes as well as in the soma of the cell, while correlations of incoming neuronal activity are important in determining the rate of “global” Ca2+ spikes that can engulf soma and the majority of processes. Significantly, our model predicts that whether the endoplasmic reticulum is shared between soma and processes or not determines the relationship between the firing rate of somatic Ca2+ events and the rate of neural network activity. Together these results provide intuition about how neural activity in combination with inherent cellular properties shapes spatiotemporal astrocytic Ca2+ dynamics, and provide experimentally testable predictions.
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Affiliation(s)
- Evan Cresswell-Clay
- Computational Intelligence Lab, Department of Scientific Computing, Florida State University, Tallahassee, FL, United States
| | - Nathan Crock
- Computational Intelligence Lab, Department of Scientific Computing, Florida State University, Tallahassee, FL, United States
| | - Joël Tabak
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, United Kingdom
| | - Gordon Erlebacher
- Computational Intelligence Lab, Department of Scientific Computing, Florida State University, Tallahassee, FL, United States
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35
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Durkee CA, Araque A. Diversity and Specificity of Astrocyte-neuron Communication. Neuroscience 2018; 396:73-78. [PMID: 30458223 DOI: 10.1016/j.neuroscience.2018.11.010] [Citation(s) in RCA: 227] [Impact Index Per Article: 32.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Revised: 11/08/2018] [Accepted: 11/09/2018] [Indexed: 01/30/2023]
Abstract
Astrocytes are emerging as important players in synaptic function, and, consequently, on brain function and animal behavior. According to the Tripartite Synapse concept, astrocytes are integral elements involved in synaptic function. They establish bidirectional communication with neurons, whereby they respond to synaptically released neurotransmitters and, in turn, release gliotransmitters that influence neuronal and synaptic activity. Accumulating evidence is revealing that the mechanisms and functional consequences of astrocyte-neuron signaling are more complex than originally thought. Furthermore, astrocyte-neuron signaling is not based on broad, unspecific interaction; rather, it is a synapse-, cell- and circuit-specific phenomenon that presents a high degree of complexity. This diversity and complexity of astrocyte-synapse interactions greatly enhance the degrees of freedom of the neural circuits and the consequent computational power of the neural systems.
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Affiliation(s)
- Caitlin A Durkee
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
| | - Alfonso Araque
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA.
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36
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Li Q, Li QQ, Jia JN, Liu ZQ, Zhou HH, Mao XY. Targeting gap junction in epilepsy: Perspectives and challenges. Biomed Pharmacother 2018; 109:57-65. [PMID: 30396092 DOI: 10.1016/j.biopha.2018.10.068] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 10/08/2018] [Accepted: 10/12/2018] [Indexed: 12/21/2022] Open
Abstract
Gap junctions (GJs) are multiple cellular intercellular connections that allow ions to pass directly into the cytoplasm of neighboring cells. Electrical coupling mediated by GJs plays a role in the generation of highly synchronous electrical activity. Accumulative investigations show that GJs in the brain are involved in the generation, synchronization and maintenance of seizure events. At the same time, GJ blockers exert potent curative potential on epilepsy in vivo or in vitro. This review aims to shed light on the role of GJs in epileptogenesis. Targeting GJs is likely to be served as a novel therapeutic approach on epileptic patients.
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Affiliation(s)
- Qin Li
- Department of Clinical Pharmacology, Xiangya Hospital, Central South University, Changsha 410008, China; Institute of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, Central South University, Changsha 410078, Hunan, China
| | - Qiu-Qi Li
- Department of Clinical Pharmacology, Xiangya Hospital, Central South University, Changsha 410008, China; Institute of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, Central South University, Changsha 410078, Hunan, China
| | - Ji-Ning Jia
- Department of Clinical Pharmacology, Xiangya Hospital, Central South University, Changsha 410008, China; Institute of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, Central South University, Changsha 410078, Hunan, China
| | - Zhao-Qian Liu
- Department of Clinical Pharmacology, Xiangya Hospital, Central South University, Changsha 410008, China; Institute of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, Central South University, Changsha 410078, Hunan, China
| | - Hong-Hao Zhou
- Department of Clinical Pharmacology, Xiangya Hospital, Central South University, Changsha 410008, China; Institute of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, Central South University, Changsha 410078, Hunan, China
| | - Xiao-Yuan Mao
- Department of Clinical Pharmacology, Xiangya Hospital, Central South University, Changsha 410008, China; Institute of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, Central South University, Changsha 410078, Hunan, China.
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37
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Savtchenko LP, Bard L, Jensen TP, Reynolds JP, Kraev I, Medvedev N, Stewart MG, Henneberger C, Rusakov DA. Disentangling astroglial physiology with a realistic cell model in silico. Nat Commun 2018; 9:3554. [PMID: 30177844 PMCID: PMC6120909 DOI: 10.1038/s41467-018-05896-w] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Accepted: 07/10/2018] [Indexed: 12/05/2022] Open
Abstract
Electrically non-excitable astroglia take up neurotransmitters, buffer extracellular K+ and generate Ca2+ signals that release molecular regulators of neural circuitry. The underlying machinery remains enigmatic, mainly because the sponge-like astrocyte morphology has been difficult to access experimentally or explore theoretically. Here, we systematically incorporate multi-scale, tri-dimensional astroglial architecture into a realistic multi-compartmental cell model, which we constrain by empirical tests and integrate into the NEURON computational biophysical environment. This approach is implemented as a flexible astrocyte-model builder ASTRO. As a proof-of-concept, we explore an in silico astrocyte to evaluate basic cell physiology features inaccessible experimentally. Our simulations suggest that currents generated by glutamate transporters or K+ channels have negligible distant effects on membrane voltage and that individual astrocytes can successfully handle extracellular K+ hotspots. We show how intracellular Ca2+ buffers affect Ca2+ waves and why the classical Ca2+ sparks-and-puffs mechanism is theoretically compatible with common readouts of astroglial Ca2+ imaging.
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Affiliation(s)
- Leonid P Savtchenko
- UCL Institute of Neurology, University College London, London, WC1N 3BG, UK.
| | - Lucie Bard
- UCL Institute of Neurology, University College London, London, WC1N 3BG, UK
| | - Thomas P Jensen
- UCL Institute of Neurology, University College London, London, WC1N 3BG, UK
| | - James P Reynolds
- UCL Institute of Neurology, University College London, London, WC1N 3BG, UK
| | - Igor Kraev
- The Open University, Milton Keynes, MK7 6AA, UK
| | | | | | - Christian Henneberger
- UCL Institute of Neurology, University College London, London, WC1N 3BG, UK
- German Center of Neurodegenerative Diseases (DZNE), Bonn, 53127, Germany
- Institute of Cellular Neurosciences, University of Bonn Medical School, Bonn, 53127, Germany
| | - Dmitri A Rusakov
- UCL Institute of Neurology, University College London, London, WC1N 3BG, UK.
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38
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Montes de Oca Balderas P, Montes de Oca Balderas H. Synaptic neuron-astrocyte communication is supported by an order of magnitude analysis of inositol tris-phosphate diffusion at the nanoscale in a model of peri-synaptic astrocyte projection. BMC BIOPHYSICS 2018; 11:3. [PMID: 29456837 PMCID: PMC5809920 DOI: 10.1186/s13628-018-0043-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Accepted: 01/30/2018] [Indexed: 12/13/2022]
Abstract
Background Astrocytes were conceived for decades only as supporting cells of the brain. However, the observation of Ca2+ waves in astrocyte synctitia, their neurotransmitter receptor expression and gliotransmitter secretion suggested a role in information handling, conception that has some controversies. Synaptic Neuron-Astrocyte metabotropic communication mediated by Inositol tris-phosphate (SN-AmcIP3) is supported by different reports. However, some models contradict this idea and Ca2+ stores are 1000 ± 325 nm apart from the Postsynaptic Density in the Perisynaptic Astrocyte Projections (PAP’s), suggesting that SN-AmcIP3 is extrasynaptic. However, this assumption does not consider IP3 Diffusion Coefficient (Dab), that activates IP3 Receptor (IP3R) releasing Ca2+ from intracellular stores. Results In this work we idealized a model of a PAP (PAPm) to perform an order of magnitude analysis of IP3 diffusion using a transient mass diffusion model. This model shows that IP3 forms a concentration gradient along the PAPm that reaches the steady state in milliseconds, three orders of magnitude before IP3 degradation. The model predicts that IP3 concentration near the Ca2+ stores may activate IP3R, depending upon Phospholipase C (PLC) number and activity. Moreover, the PAPm supports that IP3 and extracellular Ca2+ entry synergize to promote global Ca2+ transients. Conclusion The model presented here indicates that Ca2+ stores position in PAP’s does not limit SN-AmcIP3. Electronic supplementary material The online version of this article (10.1186/s13628-018-0043-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Pavel Montes de Oca Balderas
- Unit of Dynamic Neurobiology, Neurochemistry Deprtment Instituto Nacional de Neurología y Neurocirugía, Insurgentes Sur #3877, Col. La Fama, C.P. 14269 Ciudad de México, Mexico
| | - Horacio Montes de Oca Balderas
- Unit of Dynamic Neurobiology, Neurochemistry Deprtment Instituto Nacional de Neurología y Neurocirugía, Insurgentes Sur #3877, Col. La Fama, C.P. 14269 Ciudad de México, Mexico
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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: 150] [Impact Index Per Article: 21.4] [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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40
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Guerra-Gomes S, Sousa N, Pinto L, Oliveira JF. Functional Roles of Astrocyte Calcium Elevations: From Synapses to Behavior. Front Cell Neurosci 2018; 11:427. [PMID: 29386997 PMCID: PMC5776095 DOI: 10.3389/fncel.2017.00427] [Citation(s) in RCA: 136] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 12/20/2017] [Indexed: 12/22/2022] Open
Abstract
Astrocytes are fundamental players in the regulation of synaptic transmission and plasticity. They display unique morphological and phenotypical features that allow to monitor and to dynamically respond to changes. One of the hallmarks of the astrocytic response is the generation of calcium elevations, which further affect downstream cellular processes. Technical advances in the field have allowed to spatially and to temporally quantify and qualify these elevations. However, the impact on brain function remains poorly understood. In this review, we discuss evidences of the functional impact of heterogeneous astrocytic calcium events in several brain regions, and their consequences in synapses, circuits, and behavior.
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Affiliation(s)
- Sónia Guerra-Gomes
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal
- ICVS/3B’s – PT Government Associate Laboratory, Braga, Portugal
| | - Nuno Sousa
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal
- ICVS/3B’s – PT Government Associate Laboratory, Braga, Portugal
| | - Luísa Pinto
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal
- ICVS/3B’s – PT Government Associate Laboratory, Braga, Portugal
| | - João F. Oliveira
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal
- ICVS/3B’s – PT Government Associate Laboratory, Braga, Portugal
- DIGARC, Polytechnic Institute of Cávado and Ave, Barcelos, Portugal
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41
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Tyurikova O, Zheng K, Rings A, Drews A, Klenerman D, Rusakov DA. Monitoring Ca 2+ elevations in individual astrocytes upon local release of amyloid beta in acute brain slices. Brain Res Bull 2018; 136:85-90. [PMID: 28011193 PMCID: PMC5766740 DOI: 10.1016/j.brainresbull.2016.12.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2016] [Revised: 12/12/2016] [Accepted: 12/19/2016] [Indexed: 11/28/2022]
Abstract
The pathogenesis of Alzheimer's disease (AD) is thought to involve acute neurotoxic effects exerted by oligomeric forms of amyloid-β 1-42 (Aβ). Application of Aβ oligomers in physiological concentrations have been shown to transiently elevate internal Ca2+ in cultured astroglia. While the cellular machinery involved has been extensively explored, to what degree this important signalling cascade occurs in organised brain tissue has remained unclear. Here we adapted two-photon excitation microscopy and calibrated time-resolved imaging (FLIM), coupled with patch-clamp electrophysiology, to monitor Ca2+ concentration ([Ca2+]) inside individual astrocytes and principal neurons in acute brain slices. Inside the slice tissue local micro-ejection of Aβ in sub-micromolar concentrations triggered prominent [Ca2+] elevations in an adjacent astrocyte translated as an approximately two-fold increase (averaged over ∼5min) in basal [Ca2+]. This elevation did not spread to neighbouring cells and appeared comparable in amplitude with commonly documented spontaneous [Ca2+] rises in astroglia. Principal nerve cells (pyramidal neurons) also showed Ca2+ sensitivity, albeit to a lesser degree. These observations shed light on the extent and dynamics of the acute physiological effects of Aβ on brain cells in situ, in the context of AD.
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Affiliation(s)
- Olga Tyurikova
- UCL Institute of Neurology, University College London, Queen Square, London WC1 3BG, UK; Institute of Neuroscience, University of Nizhny Novgorod, 603950 Nizhny Novgorod, Russia
| | - Kaiyu Zheng
- UCL Institute of Neurology, University College London, Queen Square, London WC1 3BG, UK
| | - Annika Rings
- UCL Institute of Neurology, University College London, Queen Square, London WC1 3BG, UK
| | - Anna Drews
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, UK
| | - David Klenerman
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, UK
| | - Dmitri A Rusakov
- UCL Institute of Neurology, University College London, Queen Square, London WC1 3BG, UK.
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42
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Heller JP, Rusakov DA. The Nanoworld of the Tripartite Synapse: Insights from Super-Resolution Microscopy. Front Cell Neurosci 2017; 11:374. [PMID: 29225567 PMCID: PMC5705901 DOI: 10.3389/fncel.2017.00374] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Accepted: 11/10/2017] [Indexed: 12/17/2022] Open
Abstract
Synaptic connections between individual nerve cells are fundamental to the process of information transfer and storage in the brain. Over the past decades a third key partner of the synaptic machinery has been unveiled: ultrathin processes of electrically passive astroglia which often surround pre- and postsynaptic structures. The recent advent of super-resolution (SR) microscopy has begun to uncover the dynamic nanoworld of synapses and their astroglial environment. Here we overview and discuss the current progress in our understanding of the synaptic nanoenvironment, as gleaned from the imaging methods that go beyond the diffraction limit of conventional light microscopy. We argue that such methods are essential to achieve a new level of comprehension pertinent to the principles of signal integration in the brain.
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Affiliation(s)
- Janosch P Heller
- UCL Institute of Neurology, University College London, London, United Kingdom
| | - Dmitri A Rusakov
- UCL Institute of Neurology, University College London, London, United Kingdom.,Institute of Neuroscience, University of Nizhny Novgorod, Nizhny Novgorod, Russia
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43
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Henneberger C. Molecular mechanisms of astrocyte-neuron signaling. Brain Res Bull 2017; 136:1-2. [PMID: 29126875 DOI: 10.1016/j.brainresbull.2017.11.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Christian Henneberger
- Institute of Cellular Neuroscience, University of Bonn Medical School, Bonn, Germany; German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany; Institute of Neurology, University College London, London, United Kingdom.
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44
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Jackson JG, Robinson MB. Regulation of mitochondrial dynamics in astrocytes: Mechanisms, consequences, and unknowns. Glia 2017; 66:1213-1234. [PMID: 29098734 DOI: 10.1002/glia.23252] [Citation(s) in RCA: 113] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Revised: 09/20/2017] [Accepted: 10/09/2017] [Indexed: 12/15/2022]
Abstract
Astrocytes are the major glial cell in the central nervous system. These polarized cells possess numerous processes that ensheath the vasculature and contact synapses. Astrocytes play important roles in synaptic signaling, neurotransmitter synthesis and recycling, control of nutrient uptake, and control of local blood flow. Many of these processes depend on local metabolism and/or energy utilization. While astrocytes respond to increases in neuronal activity and metabolic demand by upregulating glycolysis and glycogenolysis, astrocytes also possess significant capacity for oxidative (mitochondrial) metabolism. Mitochondria mediate energy supply and metabolism, cellular survival, ionic homeostasis, and proliferation. These organelles are dynamic structures undergoing extensive fission and fusion, directed movement along cytoskeletal tracts, and degradation. While many of the mechanisms underlying the dynamics of these organelles and their physiologic roles have been characterized in neurons and other cells, the roles that mitochondrial dynamics play in glial physiology is less well understood. Recent work from several laboratories has demonstrated that mitochondria are present within the fine processes of astrocytes, that their movement is regulated, and that they contribute to local Ca2+ signaling within the astrocyte. They likely play a role in local ATP production and metabolism, particularly that of glutamate. Here we will review these and other findings describing the mechanism by which mitochondrial dynamics are regulated in astrocytes, how mitochondrial dynamics might influence astrocyte and brain metabolism, and draw parallels to mitochondrial dynamics in neurons. Additionally, we present new analyses of the size, distribution, and dynamics of mitochondria in astrocytes performed using in vivo using 2-photon microscopy.
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Affiliation(s)
- Joshua G Jackson
- Children's Hospital of Philadelphia Research Institute, University of Pennsylvania, Philadelphia, PA, 19104.,Departments of Pediatrics, University of Pennsylvania, Philadelphia, PA, 19104
| | - Michael B Robinson
- Children's Hospital of Philadelphia Research Institute, University of Pennsylvania, Philadelphia, PA, 19104.,Departments of Pediatrics, University of Pennsylvania, Philadelphia, PA, 19104.,Department of Pharmacology, University of Pennsylvania, Philadelphia, PA, 19104
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45
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Shen W, Nikolic L, Meunier C, Pfrieger F, Audinat E. An autocrine purinergic signaling controls astrocyte-induced neuronal excitation. Sci Rep 2017; 7:11280. [PMID: 28900295 PMCID: PMC5595839 DOI: 10.1038/s41598-017-11793-x] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Accepted: 08/29/2017] [Indexed: 12/30/2022] Open
Abstract
Astrocyte-derived gliotransmitters glutamate and ATP modulate neuronal activity. It remains unclear, however, how astrocytes control the release and coordinate the actions of these gliotransmitters. Using transgenic expression of the light-sensitive channelrhodopsin 2 (ChR2) in astrocytes, we observed that photostimulation reliably increases action potential firing of hippocampal pyramidal neurons. This excitation relies primarily on a calcium-dependent glutamate release by astrocytes that activates neuronal extra-synaptic NMDA receptors. Remarkably, our results show that ChR2-induced Ca2+ increase and subsequent glutamate release are amplified by ATP/ADP-mediated autocrine activation of P2Y1 receptors on astrocytes. Thus, neuronal excitation is promoted by a synergistic action of glutamatergic and autocrine purinergic signaling in astrocytes. This new mechanism may be particularly relevant for pathological conditions in which ATP extracellular concentration is increased and acts as a major danger signal.
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Affiliation(s)
- Weida Shen
- Inserm U1128, Paris Descartes University, 75006, Paris, France
| | | | - Claire Meunier
- Inserm U1128, Paris Descartes University, 75006, Paris, France
| | - Frank Pfrieger
- Institute of Cellular and Integrative Neurosciences, CNRS UPR 3212, University of Strasbourg, 67084, Strasbourg, France
| | - Etienne Audinat
- Inserm U1128, Paris Descartes University, 75006, Paris, France.
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46
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Abstract
Rapid advances in Ca2+ imaging techniques enable us to simultaneously monitor the activities of hundreds of astrocytes in the intact brain, thus providing a powerful tool for understanding the functions of both host and engrafted astrocytes in sensory processing in vivo. These techniques include both improved Ca2+ indicators and advanced optical recording methods. Astrocytes in multiple cortical and sub-cortical areas are able to respond to the corresponding sensory modalities. These sensory stimuli produce astrocytic Ca2+ responses through different cellular mechanisms. In addition, it has been suggested that astrocytic gene deficiencies in various sensory systems cause impairments in sensory circuits and cognition. Therefore, glial transplantation would be a potentially interesting approach for the cell-based therapy for glia-related disorders. There are multiple cell sources for glial transplantation, including neural stem cells, glial progenitors, and pluripotent stem cells. Both in vitro and in vivo studies have shown that engrafted astrocytes derived from these cell sources are capable of responding to sensory stimulation by elevating the intracellular Ca2+ concentration. These results indicate that engrafted astrocytes not only morphologically but also functionally integrate into the host neural network. Until now, many animal studies have proven that glial transplantation would be a good choice for treating multiple glial disorders. Together, these studies on the sensory responses of host and engrafted astrocytes have provided us a novel perspective in both neuron-glia circuit functions and future treatment strategies for glial disorders.
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Affiliation(s)
- Kuan Zhang
- Brain Research Center and State Key Laboratory of Trauma, Burns and Combined Injury, Third Military Medical University, Chongqing, China
| | - Xiaowei Chen
- Brain Research Center and State Key Laboratory of Trauma, Burns and Combined Injury, Third Military Medical University, Chongqing, China.,CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, China
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47
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Control of astrocyte morphology by Rho GTPases. Brain Res Bull 2017; 136:44-53. [PMID: 28502648 DOI: 10.1016/j.brainresbull.2017.05.003] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Revised: 05/05/2017] [Accepted: 05/10/2017] [Indexed: 12/15/2022]
Abstract
Astrocytes modulate and support neuronal and synapse function via numerous mechanisms that often rely on diffusion of signalling molecules, ions or metabolites through extracellular space. As a consequence, the spatial arrangement and the distance between astrocyte processes and neuronal structures are of functional importance. Likewise, changes of astrocyte structure will affect the ability of astrocytes to interact with neurons. In contrast to neurons, where rapid morphology changes are critically involved in many aspects of physiological brain function, a role of astrocyte restructuring in brain physiology is only beginning to emerge. In neurons, small GTPases of the Rho family are powerful initiators and modulators of structural changes. Less is known about the functional significance of these signalling molecules in astrocytes. Here, we review recent experimental evidence for the role of RhoA, Cdc42 and Rac1 in controlling dynamic astrocyte morphology as well as experimental tools and analytical approaches for studying astrocyte morphology changes.
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48
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Oheim M, Schmidt E, Hirrlinger J. Local energy on demand: Are 'spontaneous' astrocytic Ca 2+-microdomains the regulatory unit for astrocyte-neuron metabolic cooperation? Brain Res Bull 2017; 136:54-64. [PMID: 28450076 DOI: 10.1016/j.brainresbull.2017.04.011] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 03/18/2017] [Accepted: 04/21/2017] [Indexed: 12/21/2022]
Abstract
Astrocytes are a neural cell type critically involved in maintaining brain energy homeostasis as well as signaling. Like neurons, astrocytes are a heterogeneous cell population. Cortical astrocytes show a complex morphology with a highly branched aborization and numerous fine processes ensheathing the synapses of neighboring neurons, and typically extend one process connecting to blood vessels. Recent studies employing genetically encoded fluorescent calcium (Ca2+) indicators have described 'spontaneous' localized Ca2+-transients in the astrocyte periphery that occur asynchronously, independently of signals in other parts of the cells, and that do not involve somatic Ca2+ transients; however, neither it is known whether these Ca2+-microdomains occur at or near neuronal synapses nor have their molecular basis nor downstream effector(s) been identified. In addition to Ca2+ microdomains, sodium (Na+) transients occur in astrocyte subdomains, too, most likely as a consequence of Na+ co-transport with the neurotransmitter glutamate, which also regulates mitochondrial movements locally - as do cytoplasmic Ca2+ levels. In this review, we cover various aspects of these local signaling events and discuss how structural and biophysical properties of astrocytes might foster such compartmentation. Astrocytes metabolically interact with neurons by providing energy substrates to active neurons. As a single astrocyte branch covers hundreds to thousands of synapses, it is tempting to speculate that these metabolic interactions could occur localized to specific subdomains of astrocytes, perhaps even at the level of small groups of synapses. We discuss how astrocytic metabolism might be regulated at this scale and which signals might contribute to its regulation. We speculate that the astrocytic structures that light up transiently as Ca2+-microdomains might be the functional units of astrocytes linking signaling and metabolic processes to adapt astrocytic function to local energy demands. The understanding of these local regulatory and metabolic interactions will be fundamental to fully appreciate the complexity of brain energy homeostasis as well as its failure in disease and may shed new light on the controversy about neuron-glia bi-directional signaling at the tripartite synapse.
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Affiliation(s)
- Martin Oheim
- CNRS UMR 8118, Brain Physiology Laboratory, F-75006 Paris, France; Fédération de Recherche en Neurosciences FR3636, Faculté de Sciences Fondamentales et Biomédicales, Université Paris Descartes, PRES Université Sorbonne Paris Cité (USPC), F-75006 Paris, France.
| | - Elke Schmidt
- CNRS UMR 8118, Brain Physiology Laboratory, F-75006 Paris, France; Fédération de Recherche en Neurosciences FR3636, Faculté de Sciences Fondamentales et Biomédicales, Université Paris Descartes, PRES Université Sorbonne Paris Cité (USPC), F-75006 Paris, France
| | - Johannes Hirrlinger
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, D-04103 Leipzig, Germany; Dept. of Neurogenetics, Max-Planck-Institute for Experimental Medicine, D-37075 Göttingen, Germany.
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49
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Sakuragi S, Niwa F, Oda Y, Mikoshiba K, Bannai H. Astroglial Ca 2+ signaling is generated by the coordination of IP 3R and store-operated Ca 2+ channels. Biochem Biophys Res Commun 2017; 486:879-885. [PMID: 28336440 DOI: 10.1016/j.bbrc.2017.03.096] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Accepted: 03/19/2017] [Indexed: 12/21/2022]
Abstract
Astrocytes play key roles in the central nervous system and regulate local blood flow and synaptic transmission via intracellular calcium (Ca2+) signaling. Astrocytic Ca2+ signals are generated by multiple pathways: Ca2+ release from the endoplasmic reticulum (ER) via the inositol 1, 4, 5-trisphosphate receptor (IP3R) and Ca2+ influx through various Ca2+ channels on the plasma membrane. However, the Ca2+ channels involved in astrocytic Ca2+ homeostasis or signaling have not been fully characterized. Here, we demonstrate that spontaneous astrocytic Ca2+ transients in cultured hippocampal astrocytes were induced by cooperation between the Ca2+ release from the ER and the Ca2+ influx through store-operated calcium channels (SOCCs) on the plasma membrane. Ca2+ imaging with plasma membrane targeted GCaMP6f revealed that spontaneous astroglial Ca2+ transients were impaired by pharmacological blockade of not only Ca2+ release through IP3Rs, but also Ca2+ influx through SOCCs. Loss of SOCC activity resulted in the depletion of ER Ca2+, suggesting that SOCCs are activated without store depletion in hippocampal astrocytes. Our findings indicate that sustained SOCC activity, together with that of the sarco-endoplasmic reticulum Ca2+-ATPase, contribute to the maintenance of astrocytic Ca2+ store levels, ultimately enabling astrocytic Ca2+ signaling.
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Affiliation(s)
- Shigeo Sakuragi
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi, 464-8602, Japan
| | - Fumihiro Niwa
- Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute (BSI), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Yoichi Oda
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi, 464-8602, Japan
| | - Katsuhiko Mikoshiba
- Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute (BSI), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
| | - Hiroko Bannai
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi, 464-8602, Japan; Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute (BSI), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan; Nagoya Research Center for Brain & Neural Circuits, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi, 464-8602, Japan; Japan Science and Technology Agency, PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan.
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50
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Vasile F, Dossi E, Rouach N. Human astrocytes: structure and functions in the healthy brain. Brain Struct Funct 2017; 222:2017-2029. [PMID: 28280934 PMCID: PMC5504258 DOI: 10.1007/s00429-017-1383-5] [Citation(s) in RCA: 263] [Impact Index Per Article: 32.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 02/06/2017] [Indexed: 12/28/2022]
Abstract
Data collected on astrocytes’ physiology in the rodent have placed them as key regulators of synaptic, neuronal, network, and cognitive functions. While these findings proved highly valuable for our awareness and appreciation of non-neuronal cell significance in brain physiology, early structural and phylogenic investigations of human astrocytes hinted at potentially different astrocytic properties. This idea sparked interest to replicate rodent-based studies on human samples, which have revealed an analogous but enhanced involvement of astrocytes in neuronal function of the human brain. Such evidence pointed to a central role of human astrocytes in sustaining more complex information processing. Here, we review the current state of our knowledge of human astrocytes regarding their structure, gene profile, and functions, highlighting the differences with rodent astrocytes. This recent insight is essential for assessment of the relevance of findings using animal models and for comprehending the functional significance of species-specific properties of astrocytes. Moreover, since dysfunctional astrocytes have been described in many brain disorders, a more thorough understanding of human-specific astrocytic properties is crucial for better-adapted translational applications.
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Affiliation(s)
- Flora Vasile
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, Collège de France, CNRS UMR 7241, INSERM U1050, Labex Memolife, PSL Research University, Paris, France
| | - Elena Dossi
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, Collège de France, CNRS UMR 7241, INSERM U1050, Labex Memolife, PSL Research University, Paris, France
| | - Nathalie Rouach
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, Collège de France, CNRS UMR 7241, INSERM U1050, Labex Memolife, PSL Research University, Paris, France.
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