1
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Chalmers N, Masouti E, Beckervordersandforth R. Astrocytes in the adult dentate gyrus-balance between adult and developmental tasks. Mol Psychiatry 2024; 29:982-991. [PMID: 38177351 PMCID: PMC11176073 DOI: 10.1038/s41380-023-02386-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Revised: 12/12/2023] [Accepted: 12/14/2023] [Indexed: 01/06/2024]
Abstract
Astrocytes, a major glial cell type in the brain, are indispensable for the integration, maintenance and survival of neurons during development and adulthood. Both life phases make specific demands on the molecular and physiological properties of astrocytes, and most research projects traditionally focus on either developmental or adult astrocyte functions. In most brain regions, the generation of brain cells and the establishment of neural circuits ends with postnatal development. However, few neurogenic niches exist in the adult brain in which new neurons and glial cells are produced lifelong, and the integration of new cells into functional circuits represent a very special form of plasticity. Consequently, in the neurogenic niche, the astrocytes must be equipped to execute both mature and developmental tasks in order to integrate newborn neurons into the circuit and yet maintain overall homeostasis without affecting the preexisting neurons. In this review, we focus on astrocytes of the hippocampal dentate gyrus (DG), and discuss specific features of the astrocytic compartment that may allow the execution of both tasks. Firstly, astrocytes of the adult DG are molecularly, morphologically and functionally diverse, and the distinct astrocytes subtypes are characterized by their localization to DG layers. This spatial separation may lead to a functional specification of astrocytes subtypes according to the neuronal structures they are embedded in, hence a division of labor. Secondly, the astrocytic compartment is not static, but steadily increasing in numbers due to lifelong astrogenesis. Interestingly, astrogenesis can adapt to environmental and behavioral stimuli, revealing an unexpected astrocyte dynamic that allows the niche to adopt to changing demands. The diversity and dynamic of astrocytes in the adult DG implicate a vital contribution to hippocampal plasticity and represent an interesting model to uncover mechanisms how astrocytes simultaneously fulfill developmental and adult tasks.
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Affiliation(s)
- Nicholas Chalmers
- Institute of Biochemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Evangelia Masouti
- Institute of Biochemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
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2
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Handy G, Borisyuk A. Investigating the ability of astrocytes to drive neural network synchrony. PLoS Comput Biol 2023; 19:e1011290. [PMID: 37556468 PMCID: PMC10441806 DOI: 10.1371/journal.pcbi.1011290] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 08/21/2023] [Accepted: 06/21/2023] [Indexed: 08/11/2023] Open
Abstract
Recent experimental works have implicated astrocytes as a significant cell type underlying several neuronal processes in the mammalian brain, from encoding sensory information to neurological disorders. Despite this progress, it is still unclear how astrocytes are communicating with and driving their neuronal neighbors. While previous computational modeling works have helped propose mechanisms responsible for driving these interactions, they have primarily focused on interactions at the synaptic level, with microscale models of calcium dynamics and neurotransmitter diffusion. Since it is computationally infeasible to include the intricate microscale details in a network-scale model, little computational work has been done to understand how astrocytes may be influencing spiking patterns and synchronization of large networks. We overcome this issue by first developing an "effective" astrocyte that can be easily implemented to already established network frameworks. We do this by showing that the astrocyte proximity to a synapse makes synaptic transmission faster, weaker, and less reliable. Thus, our "effective" astrocytes can be incorporated by considering heterogeneous synaptic time constants, which are parametrized only by the degree of astrocytic proximity at that synapse. We then apply our framework to large networks of exponential integrate-and-fire neurons with various spatial structures. Depending on key parameters, such as the number of synapses ensheathed and the strength of this ensheathment, we show that astrocytes can push the network to a synchronous state and exhibit spatially correlated patterns.
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Affiliation(s)
- Gregory Handy
- Departments of Neurobiology and Statistics, University of Chicago, Chicago, Illinois, United States of America
- Grossman Center for Quantitative Biology and Human Behavior, University of Chicago, Chicago, Illinois, United States of America
| | - Alla Borisyuk
- Department of Mathematics, University of Utah, Salt Lake City, Utah, United States of America
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3
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Warsinger-Pepe N, Chang C, Desroberts CR, Akbari OS. Polycomb response elements reduce leaky expression of Cas9 under temperature-inducible Hsp70Bb promoter in Drosophila melanogaster. G3 (BETHESDA, MD.) 2023; 13:jkad024. [PMID: 36705519 PMCID: PMC10085756 DOI: 10.1093/g3journal/jkad024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 12/15/2022] [Accepted: 01/19/2023] [Indexed: 01/28/2023]
Abstract
Heat-shock-inducible expression of genes through the use of heat-inducible promoters is commonly used in research despite leaky expression of downstream genes of interest without targeted induction (i.e. heat shock). The development of non-leaky inducible expression systems is of broad interest for both basic and applied studies, to precisely control gene expression. Here we characterize the use of Polycomb response elements and the inducible Heat-shock protein 70Bb promoter, previously described as a non-leaky inducible system, to regulate Cas9 endonuclease levels and function in Drosophila melanogaster after varying both heat-shock durations and rearing temperatures. We show that Polycomb response elements can significantly reduce expression of Cas9 under Heat-shock protein 70Bb promoter control using a range of conditions, corroborating previously published results. We further demonstrate that this low transcript level of heat-induced Cas9 is sufficient to induce mutant mosaic phenotypes. Incomplete suppression of an inducible Cas9 system by Polycomb response elements with no heat-shock suggests that further regulatory elements are required to precisely control Cas9 expression and abundance.
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Affiliation(s)
- Natalie Warsinger-Pepe
- School of Biological Sciences, Department of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Carly Chang
- School of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Connor R Desroberts
- School of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Omar S Akbari
- School of Biological Sciences, Department of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA 92093, USA
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4
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Manninen T, Aćimović J, Linne ML. Analysis of Network Models with Neuron-Astrocyte Interactions. Neuroinformatics 2023; 21:375-406. [PMID: 36959372 PMCID: PMC10085960 DOI: 10.1007/s12021-023-09622-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/01/2023] [Indexed: 03/25/2023]
Abstract
Neural networks, composed of many neurons and governed by complex interactions between them, are a widely accepted formalism for modeling and exploring global dynamics and emergent properties in brain systems. In the past decades, experimental evidence of computationally relevant neuron-astrocyte interactions, as well as the astrocytic modulation of global neural dynamics, have accumulated. These findings motivated advances in computational glioscience and inspired several models integrating mechanisms of neuron-astrocyte interactions into the standard neural network formalism. These models were developed to study, for example, synchronization, information transfer, synaptic plasticity, and hyperexcitability, as well as classification tasks and hardware implementations. We here focus on network models of at least two neurons interacting bidirectionally with at least two astrocytes that include explicitly modeled astrocytic calcium dynamics. In this study, we analyze the evolution of these models and the biophysical, biochemical, cellular, and network mechanisms used to construct them. Based on our analysis, we propose how to systematically describe and categorize interaction schemes between cells in neuron-astrocyte networks. We additionally study the models in view of the existing experimental data and present future perspectives. Our analysis is an important first step towards understanding astrocytic contribution to brain functions. However, more advances are needed to collect comprehensive data about astrocyte morphology and physiology in vivo and to better integrate them in data-driven computational models. Broadening the discussion about theoretical approaches and expanding the computational tools is necessary to better understand astrocytes' roles in brain functions.
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Affiliation(s)
- Tiina Manninen
- Faculty of Medicine and Health Technology, Tampere University, Korkeakoulunkatu 3, FI-33720, Tampere, Finland.
| | - Jugoslava Aćimović
- Faculty of Medicine and Health Technology, Tampere University, Korkeakoulunkatu 3, FI-33720, Tampere, Finland
| | - Marja-Leena Linne
- Faculty of Medicine and Health Technology, Tampere University, Korkeakoulunkatu 3, FI-33720, Tampere, Finland.
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5
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Baudon A, Clauss Creusot E, Charlet A. [Emergent role of astrocytes in oxytocin-mediated modulatory control of neuronal circuits and brain functions]. Biol Aujourdhui 2023; 216:155-165. [PMID: 36744981 DOI: 10.1051/jbio/2022022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Indexed: 02/07/2023]
Abstract
The neuropeptide oxytocin has been in the focus of scientists for decades due to its profound and pleiotropic effects on physiology, activity of neuronal circuits and behaviors. Until recently, it was believed that oxytocinergic action exclusively occurs through direct activation of neuronal oxytocin receptors. However, several studies demonstrated the existence and functional relevance of astroglial oxytocin receptors in various brain regions in the mouse and rat brain. Astrocytic signaling and activity are critical for many important physiological processes including metabolism, neurotransmitter clearance from the synaptic cleft and integrated brain functions. While it can be speculated that oxytocinergic action on astrocytes predominantly facilitates neuromodulation via the release of gliotransmitters, the precise role of astrocytic oxytocin receptors remains elusive. In this review, we discuss the latest studies on the interaction between the oxytocinergic system and astrocytes, and give details of underlying intracellular cascades.
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Affiliation(s)
- Angel Baudon
- Centre National de la Recherche Scientifique et Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, 8 allée du Général Rouvillois, 67000 Strasbourg, France
| | - Etienne Clauss Creusot
- Centre National de la Recherche Scientifique et Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, 8 allée du Général Rouvillois, 67000 Strasbourg, France
| | - Alexandre Charlet
- Centre National de la Recherche Scientifique et Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, 8 allée du Général Rouvillois, 67000 Strasbourg, France
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6
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Iqbal Z, Lei Z, Ramkrishnan AS, Liu S, Hasan M, Akter M, Lam YY, Li Y. Adrenergic signalling to astrocytes in anterior cingulate cortex contributes to pain-related aversive memory in rats. Commun Biol 2023; 6:10. [PMID: 36604595 PMCID: PMC9816175 DOI: 10.1038/s42003-022-04405-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 12/23/2022] [Indexed: 01/06/2023] Open
Abstract
Pain contains both sensory and affective dimensions. We identify the role of norepinephrine in colorectal distention (sub-threshold for acute pain) induced conditioned place avoidance and plasticity gene expression in the anterior cingulate cortex (ACC). Activating locus coeruleus (LC)-projecting ACC neurons facilitates pain-evoked aversive consolidation and memory, while inhibiting LC-projecting ACC neurons reversibly blocks it. Optogenetic activation of ACC astrocytes facilitates aversive behaviour. ACC astrocytic Gi manipulation suppressed aversive behaviour and early plasticity gene expression induced by opto-activation of LC neurons projecting to ACC. Evidences for the critical role of β2AR in ACC astrocytes were provided using AAV encoding β2AR miRNAi to knockdown β2AR in astrocytes. In contrast, opto-activation of ACC astrocytic β2ARs promotes aversion memory. Our findings suggest that projection-specific adrenergic astrocytic signalling in ACC is integral to system-wide neuromodulation in response to visceral stimuli, and plays a key role in mediating pain-related aversion consolidation and memory formation.
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Affiliation(s)
- Zafar Iqbal
- Department of Neuroscience, College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon, Hong Kong
- Department of Biomedical Sciences, College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon, Hong Kong
- Centre for Regenerative Medicine and Health, Hong Kong Institute of Science & Innovation, Chinese Academy of Sciences, Hong Kong SAR, China
| | - Zhuogui Lei
- Department of Neuroscience, College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon, Hong Kong
- Department of Biomedical Sciences, College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon, Hong Kong
- Centre for Regenerative Medicine and Health, Hong Kong Institute of Science & Innovation, Chinese Academy of Sciences, Hong Kong SAR, China
| | - Aruna S Ramkrishnan
- Department of Neuroscience, College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon, Hong Kong
- Department of Biomedical Sciences, College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon, Hong Kong
| | - Shu Liu
- Department of Neuroscience, College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon, Hong Kong
- Department of Biomedical Sciences, College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon, Hong Kong
| | - Mahadi Hasan
- Department of Neuroscience, College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon, Hong Kong
- Department of Biomedical Sciences, College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon, Hong Kong
| | - Mastura Akter
- Department of Neuroscience, College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon, Hong Kong
- Department of Biomedical Sciences, College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon, Hong Kong
| | - Yuk Yan Lam
- Department of Neuroscience, College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon, Hong Kong
- Department of Biomedical Sciences, College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon, Hong Kong
- Centre for Regenerative Medicine and Health, Hong Kong Institute of Science & Innovation, Chinese Academy of Sciences, Hong Kong SAR, China
| | - Ying Li
- Department of Neuroscience, College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon, Hong Kong.
- Department of Biomedical Sciences, College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon, Hong Kong.
- Centre for Regenerative Medicine and Health, Hong Kong Institute of Science & Innovation, Chinese Academy of Sciences, Hong Kong SAR, China.
- Centre for Biosystems, Neuroscience, and Nanotechnology, City University of Hong Kong, Kowloon, Hong Kong.
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7
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Goenaga J, Araque A, Kofuji P, Herrera Moro Chao D. Calcium signaling in astrocytes and gliotransmitter release. Front Synaptic Neurosci 2023; 15:1138577. [PMID: 36937570 PMCID: PMC10017551 DOI: 10.3389/fnsyn.2023.1138577] [Citation(s) in RCA: 17] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Accepted: 02/16/2023] [Indexed: 03/06/2023] Open
Abstract
Glia are as numerous in the brain as neurons and widely known to serve supportive roles such as structural scaffolding, extracellular ionic and neurotransmitter homeostasis, and metabolic support. However, over the past two decades, several lines of evidence indicate that astrocytes, which are a type of glia, play active roles in neural information processing. Astrocytes, although not electrically active, can exhibit a form of excitability by dynamic changes in intracellular calcium levels. They sense synaptic activity and release neuroactive substances, named gliotransmitters, that modulate neuronal activity and synaptic transmission in several brain areas, thus impacting animal behavior. This "dialogue" between astrocytes and neurons is embodied in the concept of the tripartite synapse that includes astrocytes as integral elements of synaptic function. Here, we review the recent work and discuss how astrocytes via calcium-mediated excitability modulate synaptic information processing at various spatial and time scales.
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8
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Baudon A, Clauss Creusot E, Althammer F, Schaaf CP, Charlet A. Emerging role of astrocytes in oxytocin-mediated control of neural circuits and brain functions. Prog Neurobiol 2022; 217:102328. [PMID: 35870680 DOI: 10.1016/j.pneurobio.2022.102328] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 07/01/2022] [Accepted: 07/18/2022] [Indexed: 11/19/2022]
Abstract
The neuropeptide oxytocin has been in the focus of scientists for decades due to its profound and pleiotropic effects on physiology, activity of neuronal circuits and behaviors, among which sociality. Until recently, it was believed that oxytocinergic action exclusively occurs through direct activation of neuronal oxytocin receptors. However, several studies demonstrated the existence and functional relevance of astroglial oxytocin receptors in various brain regions in the mouse and rat brain. Astrocytic signaling and activity is critical for many important physiological processes including metabolism, neurotransmitter clearance from the synaptic cleft and integrated brain functions. While it can be speculated that oxytocinergic action on astrocytes predominantly facilitates neuromodulation via the release of specific gliotransmitters, the precise role of astrocytic oxytocin receptors remains elusive. In this review, we discuss the latest studies on the interaction between the oxytocinergic system and astrocytes, including detailed information about intracellular cascades, and speculate about future research directions on astrocytic oxytocin signaling.
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Affiliation(s)
- Angel Baudon
- Centre National de la Recherche Scientifique and University of Strasbourg, Institute of Cellular and Integrative Neuroscience, Strasbourg 67000 France
| | - Etienne Clauss Creusot
- Centre National de la Recherche Scientifique and University of Strasbourg, Institute of Cellular and Integrative Neuroscience, Strasbourg 67000 France
| | | | | | - Alexandre Charlet
- Centre National de la Recherche Scientifique and University of Strasbourg, Institute of Cellular and Integrative Neuroscience, Strasbourg 67000 France.
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9
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Linne ML, Aćimović J, Saudargiene A, Manninen T. Neuron-Glia Interactions and Brain Circuits. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2022; 1359:87-103. [PMID: 35471536 DOI: 10.1007/978-3-030-89439-9_4] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Recent evidence suggests that glial cells take an active role in a number of brain functions that were previously attributed solely to neurons. For example, astrocytes, one type of glial cells, have been shown to promote coordinated activation of neuronal networks, modulate sensory-evoked neuronal network activity, and influence brain state transitions during development. This reinforces the idea that astrocytes not only provide the "housekeeping" for the neurons, but that they also play a vital role in supporting and expanding the functions of brain circuits and networks. Despite this accumulated knowledge, the field of computational neuroscience has mostly focused on modeling neuronal functions, ignoring the glial cells and the interactions they have with the neurons. In this chapter, we introduce the biology of neuron-glia interactions, summarize the existing computational models and tools, and emphasize the glial properties that may be important in modeling brain functions in the future.
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Affiliation(s)
- Marja-Leena Linne
- Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland.
| | - Jugoslava Aćimović
- Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
| | - Ausra Saudargiene
- Neuroscience Institute, Lithuanian University of Health Sciences, Kaunas, Lithuania.,Department of Informatics, Vytautas Magnus University, Kaunas, Lithuania
| | - Tiina Manninen
- Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
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10
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Danjo Y, Shigetomi E, Hirayama YJ, Kobayashi K, Ishikawa T, Fukazawa Y, Shibata K, Takanashi K, Parajuli B, Shinozaki Y, Kim SK, Nabekura J, Koizumi S. Transient astrocytic mGluR5 expression drives synaptic plasticity and subsequent chronic pain in mice. J Exp Med 2022; 219:213089. [PMID: 35319723 PMCID: PMC8952801 DOI: 10.1084/jem.20210989] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Revised: 01/03/2022] [Accepted: 01/31/2022] [Indexed: 01/02/2023] Open
Abstract
Activation of astrocytes has a profound effect on brain plasticity and is critical for the pathophysiology of several neurological disorders including neuropathic pain. Here, we show that metabotropic glutamate receptor 5 (mGluR5), which reemerges in astrocytes in a restricted time frame, is essential for these functions. Although mGluR5 is absent in healthy adult astrocytes, it transiently reemerges in astrocytes of the somatosensory cortex (S1). During a limited spatiotemporal time frame, astrocytic mGluR5 drives Ca2+ signals; upregulates multiple synaptogenic molecules such as Thrombospondin-1, Glypican-4, and Hevin; causes excess excitatory synaptogenesis; and produces persistent alteration of S1 neuronal activity, leading to mechanical allodynia. All of these events were abolished by the astrocyte-specific deletion of mGluR5. Astrocytes dynamically control synaptic plasticity by turning on and off a single molecule, mGluR5, which defines subsequent persistent brain functions, especially under pathological conditions.
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Affiliation(s)
- Yosuke Danjo
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan.,Yamanashi GLIA Center, University of Yamanashi, Yamanashi, Japan
| | - Eiji Shigetomi
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan.,Yamanashi GLIA Center, University of Yamanashi, Yamanashi, Japan
| | - Yukiho J Hirayama
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan
| | - Kenji Kobayashi
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan.,Yamanashi GLIA Center, University of Yamanashi, Yamanashi, Japan
| | - Tatsuya Ishikawa
- Department of Functional Anatomy, Graduate School of Medical Science, Kanazawa University, Kanazawa, Japan
| | - Yugo Fukazawa
- Division of Brain Structure and Function, Faculty of Medical Sciences, University of Fukui, Fukui, Japan
| | - Keisuke Shibata
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan
| | - Kenta Takanashi
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan
| | - Bijay Parajuli
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan.,Yamanashi GLIA Center, University of Yamanashi, Yamanashi, Japan
| | - Youichi Shinozaki
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan.,Yamanashi GLIA Center, University of Yamanashi, Yamanashi, Japan
| | - Sun Kwang Kim
- Department of Physiology, College of Korean Medicine, Kyung Hee University, Seoul, Korea
| | - Junichi Nabekura
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki, Aichi, Japan.,Department of Physiological Sciences, The Graduate School for Advanced Study, Hayama, Kanagawa, Japan
| | - Schuichi Koizumi
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan.,Yamanashi GLIA Center, University of Yamanashi, Yamanashi, Japan
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11
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O'Donovan B, Neugornet A, Neogi R, Xia M, Ortinski P. Cocaine experience induces functional adaptations in astrocytes: Implications for synaptic plasticity in the nucleus accumbens shell. Addict Biol 2021; 26:e13042. [PMID: 33864336 DOI: 10.1111/adb.13042] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 03/22/2021] [Accepted: 03/26/2021] [Indexed: 11/24/2022]
Abstract
Astrocytes have become established as an important regulator of neuronal activity in the brain. Accumulating literature demonstrates that cocaine self-administration in rodent models induces structural changes within astrocytes that may influence their interaction with the surrounding neurons. Here, we provide evidence that cocaine impacts astrocytes at the functional level and alters neuronal sensitivity to astrocyte-derived glutamate. We report that a 14-day period of short access to cocaine (2 h/day) decreases spontaneous astrocytic Ca2+ transients and precipitates changes in astrocyte network activity in the nucleus accumbens shell. This is accompanied by increased prevalence of slow inward currents, a physiological marker of neuronal activation by astrocytic glutamate, in a subset of medium spiny neurons. Within, but not outside, of this subset, we observe an increase in duration and frequency of N-methyl-D-aspartate (NMDA) receptor-mediated synaptic events. Additionally, we find that the link between synaptic NMDA receptor plasticity and neuron sensitivity to astrocytic glutamate is maintained independent of drug exposure and is observed in both cocaine and saline control animals. Imaging analyses of neuronal Ca2+ activity show no effect of cocaine self-administration on individual cells or on neuronal network activity in brain slices. Therefore, our data indicate that cocaine self-administration promotes astrocyte-specific functional changes that can be linked to increased glutamate-mediated coupling with principal neurons in the nucleus accumbens. Such coupling may be spatially restricted as it does not result in a broad impact on network structure of local neuronal circuits.
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Affiliation(s)
- Bernadette O'Donovan
- Department of Neuroscience, College of Medicine University of Kentucky Lexington Kentucky USA
| | - Austin Neugornet
- Department of Neuroscience, College of Medicine University of Kentucky Lexington Kentucky USA
| | - Richik Neogi
- Department of Neuroscience, College of Medicine University of Kentucky Lexington Kentucky USA
- Integrated Biomedical Sciences University of Kentucky Lexington Kentucky USA
| | - Mengfan Xia
- Department of Neuroscience, College of Medicine University of Kentucky Lexington Kentucky USA
| | - Pavel Ortinski
- Department of Neuroscience, College of Medicine University of Kentucky Lexington Kentucky USA
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12
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Mielnicka A, Michaluk P. Exocytosis in Astrocytes. Biomolecules 2021; 11:1367. [PMID: 34572580 PMCID: PMC8471187 DOI: 10.3390/biom11091367] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 09/10/2021] [Accepted: 09/14/2021] [Indexed: 12/17/2022] Open
Abstract
Until recently, astrocytes were thought to be a part of a simple "brain glue" providing only a supporting role for neurons. However, the discoveries of the last two decades have proven astrocytes to be dynamic partners participating in brain metabolism and actively influencing communication between neurons. The means of astrocyte-neuron communication are diverse, although regulated exocytosis has received the most attention but also caused the most debate. Similar to most of eukaryotic cells, astrocytes have a complex range of vesicular organelles which can undergo exocytosis as well as intricate molecular mechanisms that regulate this process. In this review, we focus on the components needed for regulated exocytosis to occur and summarise the knowledge about experimental evidence showing its presence in astrocytes.
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Affiliation(s)
| | - Piotr Michaluk
- BRAINCITY, Laboratory of Neurobiology, The Nencki Institute of Experimental Biology, PAS, 02-093 Warsaw, Poland;
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13
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Sancho L, Contreras M, Allen NJ. Glia as sculptors of synaptic plasticity. Neurosci Res 2021; 167:17-29. [PMID: 33316304 PMCID: PMC8513541 DOI: 10.1016/j.neures.2020.11.005] [Citation(s) in RCA: 74] [Impact Index Per Article: 24.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 11/05/2020] [Accepted: 11/09/2020] [Indexed: 12/16/2022]
Abstract
Glial cells are non-neuronal cells in the nervous system that are crucial for proper brain development and function. Three major classes of glia in the central nervous system (CNS) include astrocytes, microglia and oligodendrocytes. These cells have dynamic morphological and functional properties and constantly surveil neural activity throughout life, sculpting synaptic plasticity. Astrocytes form part of the tripartite synapse with neurons and perform many homeostatic functions essential to proper synaptic function including clearing neurotransmitter and regulating ion balance; they can modify these properties, in addition to additional mechanisms such as gliotransmitter release, to influence short- and long-term plasticity. Microglia, the resident macrophage of the CNS, monitor synaptic activity and can eliminate synapses by phagocytosis or modify synapses by release of cytokines or neurotrophic factors. Oligodendrocytes regulate speed of action potential conduction and efficiency of information exchange through the formation of myelin, having important consequences for the plasticity of neural circuits. A deeper understanding of how glia modulate synaptic and circuit plasticity will further our understanding of the ongoing changes that take place throughout life in the dynamic environment of the CNS.
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Affiliation(s)
- Laura Sancho
- Molecular Neurobiology Laboratory, Salk Institute for Biological Studies, 10010 North Torrey Pines Rd, La Jolla, CA, 92037, USA
| | - Minerva Contreras
- Molecular Neurobiology Laboratory, Salk Institute for Biological Studies, 10010 North Torrey Pines Rd, La Jolla, CA, 92037, USA
| | - Nicola J Allen
- Molecular Neurobiology Laboratory, Salk Institute for Biological Studies, 10010 North Torrey Pines Rd, La Jolla, CA, 92037, USA.
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Slc1a3-2A-CreERT2 mice reveal unique features of Bergmann glia and augment a growing collection of Cre drivers and effectors in the 129S4 genetic background. Sci Rep 2021; 11:5412. [PMID: 33686166 PMCID: PMC7940647 DOI: 10.1038/s41598-021-84887-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2020] [Accepted: 02/22/2021] [Indexed: 12/26/2022] Open
Abstract
Genetic variation is a primary determinant of phenotypic diversity. In laboratory mice, genetic variation can be a serious experimental confounder, and thus minimized through inbreeding. However, generalizations of results obtained with inbred strains must be made with caution, especially when working with complex phenotypes and disease models. Here we compared behavioral characteristics of C57Bl/6—the strain most widely used in biomedical research—with those of 129S4. In contrast to 129S4, C57Bl/6 demonstrated high within-strain and intra-litter behavioral hyperactivity. Although high consistency would be advantageous, the majority of disease models and transgenic tools are in C57Bl/6. We recently established six Cre driver lines and two Cre effector lines in 129S4. To augment this collection, we genetically engineered a Cre line to study astrocytes in 129S4. It was validated with two Cre effector lines: calcium indicator gCaMP5g-tdTomato and RiboTag—a tool widely used to study cell type-specific translatomes. These reporters are in different genomic loci, and in both the Cre was functional and astrocyte-specific. We found that calcium signals lasted longer and had a higher amplitude in cortical compared to hippocampal astrocytes, genes linked to a single neurodegenerative disease have highly divergent expression patterns, and that ribosome proteins are non-uniformly expressed across brain regions and cell types.
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15
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Manninen T, Saudargiene A, Linne ML. Astrocyte-mediated spike-timing-dependent long-term depression modulates synaptic properties in the developing cortex. PLoS Comput Biol 2020; 16:e1008360. [PMID: 33170856 PMCID: PMC7654831 DOI: 10.1371/journal.pcbi.1008360] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Accepted: 09/22/2020] [Indexed: 12/26/2022] Open
Abstract
Astrocytes have been shown to modulate synaptic transmission and plasticity in specific cortical synapses, but our understanding of the underlying molecular and cellular mechanisms remains limited. Here we present a new biophysicochemical model of a somatosensory cortical layer 4 to layer 2/3 synapse to study the role of astrocytes in spike-timing-dependent long-term depression (t-LTD) in vivo. By applying the synapse model and electrophysiological data recorded from rodent somatosensory cortex, we show that a signal from a postsynaptic neuron, orchestrated by endocannabinoids, astrocytic calcium signaling, and presynaptic N-methyl-D-aspartate receptors coupled with calcineurin signaling, induces t-LTD which is sensitive to the temporal difference between post- and presynaptic firing. We predict for the first time the dynamics of astrocyte-mediated molecular mechanisms underlying t-LTD and link complex biochemical networks at presynaptic, postsynaptic, and astrocytic sites to the time window of t-LTD induction. During t-LTD a single astrocyte acts as a delay factor for fast neuronal activity and integrates fast neuronal sensory processing with slow non-neuronal processing to modulate synaptic properties in the brain. Our results suggest that astrocytes play a critical role in synaptic computation during postnatal development and are of paramount importance in guiding the development of brain circuit functions, learning and memory.
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Affiliation(s)
- Tiina Manninen
- Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
- Department of Neurobiology, Stanford University, Stanford, CA, USA
| | - Ausra Saudargiene
- Neuroscience Institute, Lithuanian University of Health Sciences, Kaunas, Lithuania
- Department of Informatics, Vytautas Magnus University, Kaunas, Lithuania
| | - Marja-Leena Linne
- Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
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16
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Octeau JC, Gangwani MR, Allam SL, Tran D, Huang S, Hoang-Trong TM, Golshani P, Rumbell TH, Kozloski JR, Khakh BS. Transient, Consequential Increases in Extracellular Potassium Ions Accompany Channelrhodopsin2 Excitation. Cell Rep 2020; 27:2249-2261.e7. [PMID: 31116972 PMCID: PMC6582980 DOI: 10.1016/j.celrep.2019.04.078] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 03/04/2019] [Accepted: 04/17/2019] [Indexed: 12/13/2022] Open
Abstract
Channelrhodopsin2 (ChR2) optogenetic excitation is widely used to study neurons, astrocytes, and circuits. Using complementary approaches in situ and in vivo, we found that ChR2 stimulation leads to significant transient elevation of extracellular potassium ions by ~5 mM. Such elevations were detected in ChR2-expressing mice, following local in vivo expression of ChR2(H134R) with adeno-associated viruses (AAVs), in different brain areas and when ChR2 was expressed in neurons or astrocytes. In particular, ChR2-mediated excitation of striatal astrocytes was sufficient to increase medium spiny neuron (MSN) excitability and immediate early gene expression. The effects on MSN excitability were recapitulated in silico with a computational MSN model and detected in vivo as increased action potential firing in awake, behaving mice. We show that transient, physiologically consequential increases in extracellular potassium ions accompany ChR2 optogenetic excitation. This coincidental effect may be important to consider during astrocyte studies employing ChR2 to interrogate neural circuits and animal behavior. Using multiple approaches, Octeau et al. discover that optogenetic excitation of ChR2-expressing cells leads to significant transient extracellular potassium ion elevations that increase neuronal excitability and immediate early gene expression in neurons following in vivo stimulation.
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Affiliation(s)
- J Christopher Octeau
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Mohitkumar R Gangwani
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Sushmita L Allam
- IBM T.J. Watson Research Center, P.O. Box 218, 1101 Kitchawan Road, Yorktown Heights, NY 10598, USA
| | - Duy Tran
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Shuhan Huang
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Tuan M Hoang-Trong
- IBM T.J. Watson Research Center, P.O. Box 218, 1101 Kitchawan Road, Yorktown Heights, NY 10598, USA
| | - Peyman Golshani
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Intellectual and Developmental Disabilities Research Center, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Center for Neurobehavioral Genetics, Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Timothy H Rumbell
- IBM T.J. Watson Research Center, P.O. Box 218, 1101 Kitchawan Road, Yorktown Heights, NY 10598, USA
| | - James R Kozloski
- IBM T.J. Watson Research Center, P.O. Box 218, 1101 Kitchawan Road, Yorktown Heights, NY 10598, USA
| | - Baljit S Khakh
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA.
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17
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Allen SP, Hall B, Castelli LM, Francis L, Woof R, Siskos AP, Kouloura E, Gray E, Thompson AG, Talbot K, Higginbottom A, Myszczynska M, Allen CF, Stopford MJ, Hemingway J, Bauer CS, Webster CP, De Vos KJ, Turner MR, Keun HC, Hautbergue GM, Ferraiuolo L, Shaw PJ. Astrocyte adenosine deaminase loss increases motor neuron toxicity in amyotrophic lateral sclerosis. Brain 2020; 142:586-605. [PMID: 30698736 PMCID: PMC6391613 DOI: 10.1093/brain/awy353] [Citation(s) in RCA: 71] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Revised: 10/25/2018] [Accepted: 11/22/2018] [Indexed: 12/12/2022] Open
Abstract
As clinical evidence supports a negative impact of dysfunctional energy metabolism on the disease progression in amyotrophic lateral sclerosis, it is vital to understand how the energy metabolic pathways are altered and whether they can be restored to slow disease progression. Possible approaches include increasing or rerouting catabolism of alternative fuel sources to supplement the glycolytic and mitochondrial pathways such as glycogen, ketone bodies and nucleosides. To analyse the basis of the catabolic defect in amyotrophic lateral sclerosis we used a novel phenotypic metabolic array. We profiled fibroblasts and induced neuronal progenitor-derived human induced astrocytes from C9orf72 amyotrophic lateral sclerosis patients compared to normal controls, measuring the rates of production of reduced nicotinamide adenine dinucleotides from 91 potential energy substrates. This approach shows for the first time that C9orf72 human induced astrocytes and fibroblasts have an adenosine to inosine deamination defect caused by reduction of adenosine deaminase, which is also observed in induced astrocytes from sporadic patients. Patient-derived induced astrocyte lines were more susceptible to adenosine-induced toxicity, which could be mimicked by inhibiting adenosine deaminase in control lines. Furthermore, adenosine deaminase inhibition in control induced astrocytes led to increased motor neuron toxicity in co-cultures, similar to the levels observed with patient derived induced astrocytes. Bypassing metabolically the adenosine deaminase defect by inosine supplementation was beneficial bioenergetically in vitro, increasing glycolytic energy output and leading to an increase in motor neuron survival in co-cultures with induced astrocytes. Inosine supplementation, in combination with modulation of the level of adenosine deaminase may represent a beneficial therapeutic approach to evaluate in patients with amyotrophic lateral sclerosis.
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Affiliation(s)
- Scott P Allen
- Sheffield Institute for Translational Neuroscience (SITraN), University of Sheffield, 385 Glossop Road, Sheffield, UK
- Correspondence to: Dr Scott Allen Sheffield Institute for Translational Neuroscience (SITraN), University of Sheffield, 385 Glossop Road, Sheffield S10 2HQ, UK E-mail:
| | - Benjamin Hall
- Sheffield Institute for Translational Neuroscience (SITraN), University of Sheffield, 385 Glossop Road, Sheffield, UK
| | - Lydia M Castelli
- Sheffield Institute for Translational Neuroscience (SITraN), University of Sheffield, 385 Glossop Road, Sheffield, UK
| | - Laura Francis
- The Living Systems Institute, University of Exeter, Stocker Road, Exeter, UK
| | - Ryan Woof
- Sheffield Institute for Translational Neuroscience (SITraN), University of Sheffield, 385 Glossop Road, Sheffield, UK
| | - Alexandros P Siskos
- Department of Surgery and Cancer, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Eirini Kouloura
- Department of Surgery and Cancer, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Elizabeth Gray
- Nuffield Department of Clinical Neurosciences, Oxford University, John Radcliffe Hospital, West Wing Level 6, Oxford, UK
| | - Alexander G Thompson
- Nuffield Department of Clinical Neurosciences, Oxford University, John Radcliffe Hospital, West Wing Level 6, Oxford, UK
| | - Kevin Talbot
- Nuffield Department of Clinical Neurosciences, Oxford University, John Radcliffe Hospital, West Wing Level 6, Oxford, UK
| | - Adrian Higginbottom
- Sheffield Institute for Translational Neuroscience (SITraN), University of Sheffield, 385 Glossop Road, Sheffield, UK
| | - Monika Myszczynska
- Sheffield Institute for Translational Neuroscience (SITraN), University of Sheffield, 385 Glossop Road, Sheffield, UK
| | - Chloe F Allen
- Sheffield Institute for Translational Neuroscience (SITraN), University of Sheffield, 385 Glossop Road, Sheffield, UK
| | - Matthew J Stopford
- Sheffield Institute for Translational Neuroscience (SITraN), University of Sheffield, 385 Glossop Road, Sheffield, UK
| | - Jordan Hemingway
- Sheffield Institute for Translational Neuroscience (SITraN), University of Sheffield, 385 Glossop Road, Sheffield, UK
| | - Claudia S Bauer
- Sheffield Institute for Translational Neuroscience (SITraN), University of Sheffield, 385 Glossop Road, Sheffield, UK
| | - Christopher P Webster
- Sheffield Institute for Translational Neuroscience (SITraN), University of Sheffield, 385 Glossop Road, Sheffield, UK
| | - Kurt J De Vos
- Sheffield Institute for Translational Neuroscience (SITraN), University of Sheffield, 385 Glossop Road, Sheffield, UK
| | - Martin R Turner
- Nuffield Department of Clinical Neurosciences, Oxford University, John Radcliffe Hospital, West Wing Level 6, Oxford, UK
| | - Hector C Keun
- Department of Surgery and Cancer, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Guillaume M Hautbergue
- Sheffield Institute for Translational Neuroscience (SITraN), University of Sheffield, 385 Glossop Road, Sheffield, UK
| | - Laura Ferraiuolo
- Sheffield Institute for Translational Neuroscience (SITraN), University of Sheffield, 385 Glossop Road, Sheffield, UK
| | - Pamela J Shaw
- Sheffield Institute for Translational Neuroscience (SITraN), University of Sheffield, 385 Glossop Road, Sheffield, UK
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18
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Spatiotemporal model of tripartite synapse with perinodal astrocytic process. J Comput Neurosci 2019; 48:1-20. [DOI: 10.1007/s10827-019-00734-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2019] [Revised: 10/11/2019] [Accepted: 10/21/2019] [Indexed: 12/30/2022]
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19
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Mizuno GO, Wang Y, Shi G, Wang Y, Sun J, Papadopoulos S, Broussard GJ, Unger EK, Deng W, Weick J, Bhattacharyya A, Chen CY, Yu G, Looger LL, Tian L. Aberrant Calcium Signaling in Astrocytes Inhibits Neuronal Excitability in a Human Down Syndrome Stem Cell Model. Cell Rep 2019; 24:355-365. [PMID: 29996097 PMCID: PMC6631348 DOI: 10.1016/j.celrep.2018.06.033] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Revised: 05/04/2018] [Accepted: 06/07/2018] [Indexed: 11/25/2022] Open
Abstract
Down syndrome (DS) is a genetic disorder that causes cognitive impairment. The staggering effects associated with an extra copy of human chromosome 21 (HSA21) complicates mechanistic understanding of DS pathophysiology. We examined the neuron-astrocyte interplay in a fully recapitulated HSA21 trisomy cellular model differentiated from DS-patient-derived induced pluripotent stem cells (iPSCs). By combining calcium imaging with genetic approaches, we discovered the functional defects of DS astroglia and their effects on neuronal excitability. Compared with control isogenic astroglia, DS astroglia exhibited more-frequent spontaneous calcium fluctuations, which reduced the excitability of co-cultured neurons. Furthermore, suppressed neuronal activity could be rescued by abolishing astrocytic spontaneous calcium activity either chemically by blocking adenosine-mediated signaling or genetically by knockdown of inositol triphosphate (IP3) receptors or S100B, a calcium binding protein coded on HSA21. Our results suggest a mechanism by which DS alters the function of astrocytes, which subsequently disturbs neuronal excitability. To understand how Down syndrome (DS) affects neural networks, Mizuno et al. used a DS-patient-derived stem cell model and calcium imaging to investigate the functional defects of DS astrocytes and their effects on neuronal excitability. Their study reveals that DS astroglia exhibited more frequent spontaneous calcium fluctuations, which impair neuronal excitability.
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Affiliation(s)
- Grace O Mizuno
- Department of Biochemistry and Molecular Medicine, Department of Psychiatry and Behavioral Sciences, University of California, Davis, Davis, CA, USA
| | - Yinxue Wang
- Bradley Department of Electrical and Computer Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA
| | - Guilai Shi
- Department of Biochemistry and Molecular Medicine, Department of Psychiatry and Behavioral Sciences, University of California, Davis, Davis, CA, USA
| | - Yizhi Wang
- Bradley Department of Electrical and Computer Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA
| | - Junqing Sun
- Department of Pharmacology, University of California, Davis, Davis, CA, USA
| | - Stelios Papadopoulos
- Department of Biochemistry and Molecular Medicine, Department of Psychiatry and Behavioral Sciences, University of California, Davis, Davis, CA, USA
| | - Gerard J Broussard
- Department of Biochemistry and Molecular Medicine, Department of Psychiatry and Behavioral Sciences, University of California, Davis, Davis, CA, USA
| | - Elizabeth K Unger
- Department of Biochemistry and Molecular Medicine, Department of Psychiatry and Behavioral Sciences, University of California, Davis, Davis, CA, USA
| | - Wenbin Deng
- Department of Biochemistry and Molecular Medicine, Shriner's Hospital, University of California, Davis, Davis, CA, USA
| | - Jason Weick
- Department of Neuroscience, University of New Mexico, Albuquerque, NM, USA
| | | | - Chao-Yin Chen
- Department of Pharmacology, University of California, Davis, Davis, CA, USA
| | - Guoqiang Yu
- Bradley Department of Electrical and Computer Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA
| | - Loren L Looger
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Lin Tian
- Department of Biochemistry and Molecular Medicine, Department of Psychiatry and Behavioral Sciences, University of California, Davis, Davis, CA, USA.
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Astrocytic p38α MAPK drives NMDA receptor-dependent long-term depression and modulates long-term memory. Nat Commun 2019; 10:2968. [PMID: 31273206 PMCID: PMC6609681 DOI: 10.1038/s41467-019-10830-9] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 06/04/2019] [Indexed: 11/08/2022] Open
Abstract
NMDA receptor-dependent long-term depression (LTD) in the hippocampus is a well-known form of synaptic plasticity that has been linked to different cognitive functions. The core mechanism for this form of plasticity is thought to be entirely neuronal. However, we now demonstrate that astrocytic activity drives LTD at CA3-CA1 synapses. We have found that LTD induction enhances astrocyte-to-neuron communication mediated by glutamate, and that Ca2+ signaling and SNARE-dependent vesicular release from the astrocyte are required for LTD expression. In addition, using optogenetic techniques, we show that low-frequency astrocytic activation, in the absence of presynaptic activity, is sufficient to induce postsynaptic AMPA receptor removal and LTD expression. Using cell-type-specific gene deletion, we show that astrocytic p38α MAPK is required for the increased astrocytic glutamate release and astrocyte-to-neuron communication during low-frequency stimulation. Accordingly, removal of astrocytic (but not neuronal) p38α abolishes LTD expression. Finally, this mechanism modulates long-term memory in vivo. How astrocytes influence neuronal plasticity remains unclear, as they are typically considered as modulators of core mechanisms driven by neuronal components. Here, authors show that Long-term depression (LTD) induction in the hippocampus triggers calcium signaling in the astrocyte and enhances SNARE-dependent astrocytic glutamate release, which is then responsible for the activation of postsynaptic NMDA receptors and synaptic depression.
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21
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Mu Y, Bennett DV, Rubinov M, Narayan S, Yang CT, Tanimoto M, Mensh BD, Looger LL, Ahrens MB. Glia Accumulate Evidence that Actions Are Futile and Suppress Unsuccessful Behavior. Cell 2019; 178:27-43.e19. [PMID: 31230713 DOI: 10.1016/j.cell.2019.05.050] [Citation(s) in RCA: 139] [Impact Index Per Article: 27.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Revised: 01/31/2019] [Accepted: 05/23/2019] [Indexed: 11/29/2022]
Abstract
When a behavior repeatedly fails to achieve its goal, animals often give up and become passive, which can be strategic for preserving energy or regrouping between attempts. It is unknown how the brain identifies behavioral failures and mediates this behavioral-state switch. In larval zebrafish swimming in virtual reality, visual feedback can be withheld so that swim attempts fail to trigger expected visual flow. After tens of seconds of such motor futility, animals became passive for similar durations. Whole-brain calcium imaging revealed noradrenergic neurons that responded specifically to failed swim attempts and radial astrocytes whose calcium levels accumulated with increasing numbers of failed attempts. Using cell ablation and optogenetic or chemogenetic activation, we found that noradrenergic neurons progressively activated brainstem radial astrocytes, which then suppressed swimming. Thus, radial astrocytes perform a computation critical for behavior: they accumulate evidence that current actions are ineffective and consequently drive changes in behavioral states. VIDEO ABSTRACT.
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Affiliation(s)
- Yu Mu
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA.
| | - Davis V Bennett
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA; Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL, USA
| | - Mikail Rubinov
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA; Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA
| | - Sujatha Narayan
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Chao-Tsung Yang
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Masashi Tanimoto
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Brett D Mensh
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Loren L Looger
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Misha B Ahrens
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA.
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22
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Luo H, Wu PF, Han QQ, Cao Y, Deng SL, Wang J, Deng Q, Wang F, Chen JG. Reactive Sulfur Species Emerge as Gliotransmitters to Support Memory via Sulfuration-Dependent Gating of NR2A-Containing N-Methyl-d-Aspartate Subtype Glutamate Receptor Function. Antioxid Redox Signal 2019; 30:1880-1899. [PMID: 30187770 DOI: 10.1089/ars.2018.7503] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
AIMS Astrocytes have been revealed as a controller of synaptic plasticity and memory via releasing gliotransmitters. Our recent findings showed that reactive sulfur species (RSS), including hydrogen sulfide (H2S) and polysulfide (H2Sn), regulated the availability of d-serine, which is a well-known gliotransmitter that is involved in synaptic plasticity. An interesting question is whether RSS, which are small molecules, can function as direct gliotransmitters to integrate astrocyte-neuron interactions throughout the memory process. RESULTS We found that hippocampal RSS level increased significantly in response to learning. We further demonstrated that the activity-triggered RSS signal controlled memory formation by using pharmacological and genetic approaches. The RSS-supporting memory was primarily conferred by enzymes that were mainly located in astrocytes, including cystathionine β-synthase (CBS) and mercaptopyruvate sulfurtransferase (3-MST), and the memory-promoting effects were mostly dependent on sulfration of the NR2A subunit of N-methyl-d-aspartate subtype glutamate receptors (NMDARs). Further, RSS were demonstrated to buffer the strong inhibitory effect of synaptically released zinc on NR2A-containing NMDARs. Innovation and Conclusion: These results suggest that glial-derived RSS signals can serve as direct gliotransmitters that regulate memory formation through the redox modulation of postsynaptic receptors; this conclusion will enrich the gliotransmission hypothesis.
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Affiliation(s)
- Han Luo
- 1 Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Peng-Fei Wu
- 1 Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Qian-Qian Han
- 1 Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yu Cao
- 1 Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Si-Long Deng
- 1 Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Ji Wang
- 1 Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Qiao Deng
- 1 Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Fang Wang
- 1 Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.,2 Key Laboratory of Neurological Diseases (HUST), Ministry of Education of China, Wuhan, China.,3 The Key Laboratory for Drug Target Researches and Pharmacodynamic Evaluation of Hubei Province, Wuhan, China.,4 Laboratory of Neuropsychiatric Diseases, The Institute of Brain Research, Huazhong University of Science and Technology, Wuhan, China.,5 The Collaborative-Innovation Center for Brain Science, Wuhan, China
| | - Jian-Guo Chen
- 1 Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.,2 Key Laboratory of Neurological Diseases (HUST), Ministry of Education of China, Wuhan, China.,3 The Key Laboratory for Drug Target Researches and Pharmacodynamic Evaluation of Hubei Province, Wuhan, China.,4 Laboratory of Neuropsychiatric Diseases, The Institute of Brain Research, Huazhong University of Science and Technology, Wuhan, China.,5 The Collaborative-Innovation Center for Brain Science, Wuhan, China
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23
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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: 185] [Impact Index Per Article: 37.0] [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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Guttenplan KA, Liddelow SA. Astrocytes and microglia: Models and tools. J Exp Med 2018; 216:71-83. [PMID: 30541903 PMCID: PMC6314517 DOI: 10.1084/jem.20180200] [Citation(s) in RCA: 88] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Revised: 08/16/2018] [Accepted: 11/26/2018] [Indexed: 01/05/2023] Open
Abstract
An amazing array of tools both old and new are available to investigate the function of astrocytes and microglia. Guttenplan and Liddelow discuss tools available to study the physiology and pathophysiology of these cells both in vivo and in culture systems. Glial cells serve as fundamental regulators of the central nervous system in development, homeostasis, and disease. Discoveries into the function of these cells have fueled excitement in glial research, with enthusiastic researchers addressing fundamental questions about glial biology and producing new scientific tools for the community. Here, we outline the pros and cons of in vivo and in vitro techniques to study astrocytes and microglia with the goal of helping researchers quickly identify the best approach for a given research question in the context of glial biology. It is truly a great time to be a glial biologist.
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Affiliation(s)
| | - Shane A Liddelow
- Neuroscience Institute, NYU Langone Medical Center, New York, NY.,Department of Neuroscience and Physiology, NYU Langone Medical Center, New York, NY.,Department of Pharmacology and Therapeutics, The University of Melbourne, Melbourne, Australia
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Conditional Knock-out of mGluR5 from Astrocytes during Epilepsy Development Impairs High-Frequency Glutamate Uptake. J Neurosci 2018; 39:727-742. [PMID: 30504280 DOI: 10.1523/jneurosci.1148-18.2018] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2018] [Revised: 11/11/2018] [Accepted: 11/18/2018] [Indexed: 11/21/2022] Open
Abstract
Astrocyte expression of metabotropic glutamate receptor 5 (mGluR5) is consistently observed in resected tissue from patients with epilepsy and is equally prevalent in animal models of epilepsy. However, little is known about the functional signaling properties or downstream consequences of astrocyte mGluR5 activation during epilepsy development. In the rodent brain, astrocyte mGluR5 expression is developmentally regulated and confined in expression/function to the first weeks of life, with similar observations made in human control tissue. Herein, we demonstrate that mGluR5 expression and function dramatically increase in a mouse model of temporal lobe epilepsy. Interestingly, in both male and female mice, mGluR5 function persists in the astrocyte throughout the process of epileptogenesis following status epilepticus. However, mGluR5 expression and function are transient in animals that do not develop epilepsy over an equivalent time period, suggesting that patterns of mGluR5 expression may signify continuing epilepsy development or its resolution. We demonstrate that, during epileptogenesis, astrocytes reacquire mGluR5-dependent calcium transients following agonist application or synaptic glutamate release, a feature of astrocyte-neuron communication absent since early development. Finally, we find that the selective and conditional knock-out of mGluR5 signaling from astrocytes during epilepsy development slows the rate of glutamate clearance through astrocyte glutamate transporters under high-frequency stimulation conditions, a feature that suggests astrocyte mGluR5 expression during epileptogenesis may recapitulate earlier developmental roles in regulating glutamate transporter function.SIGNIFICANCE STATEMENT In development, astrocyte mGluR5 signaling plays a critical role in regulating structural and functional interactions between astrocytes and neurons at the tripartite synapse. Notably, mGluR5 signaling is a positive regulator of astrocyte glutamate transporter expression and function, an essential component of excitatory signaling regulation in hippocampus. After early development, astrocyte mGluR5 expression is downregulated, but reemerges in animal models of temporal lobe epilepsy (TLE) development and patient epilepsy samples. We explored the hypothesis that astrocyte mGluR5 reemergence recapitulates earlier developmental roles during TLE acquisition. Our work demonstrates that astrocytes with mGluR5 signaling during TLE development perform faster glutamate uptake in hippocampus, revealing a previously unexplored role for astrocyte mGluR5 signaling in hypersynchronous pathology.
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Yu X, Taylor AMW, Nagai J, Golshani P, Evans CJ, Coppola G, Khakh BS. Reducing Astrocyte Calcium Signaling In Vivo Alters Striatal Microcircuits and Causes Repetitive Behavior. Neuron 2018; 99:1170-1187.e9. [PMID: 30174118 PMCID: PMC6450394 DOI: 10.1016/j.neuron.2018.08.015] [Citation(s) in RCA: 199] [Impact Index Per Article: 33.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Revised: 05/23/2018] [Accepted: 08/10/2018] [Indexed: 01/01/2023]
Abstract
Astrocytes tile the central nervous system, but their functions in neural microcircuits in vivo and their roles in mammalian behavior remain incompletely defined. We used two-photon laser scanning microscopy, electrophysiology, MINIscopes, RNA-seq, and a genetic approach to explore the effects of reduced striatal astrocyte Ca2+ signaling in vivo. In wild-type mice, reducing striatal astrocyte Ca2+-dependent signaling increased repetitive self-grooming behaviors by altering medium spiny neuron (MSN) activity. The mechanism involved astrocyte-mediated neuromodulation facilitated by ambient GABA and was corrected by blocking astrocyte GABA transporter 3 (GAT-3). Furthermore, in a mouse model of Huntington's disease, dysregulation of GABA and astrocyte Ca2+ signaling accompanied excessive self-grooming, which was relieved by blocking GAT-3. Assessments with RNA-seq revealed astrocyte genes and pathways regulated by Ca2+ signaling in a cell-autonomous and non-cell-autonomous manner, including Rab11a, a regulator of GAT-3 functional expression. Thus, striatal astrocytes contribute to neuromodulation controlling mouse obsessive-compulsive-like behavior.
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Affiliation(s)
- Xinzhu Yu
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Anna M W Taylor
- Hatos Center for Neuropharmacology, Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Jun Nagai
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Peyman Golshani
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Intellectual and Developmental Disabilities Research Center, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; West Los Angeles VA Medical Center, Los Angeles, CA 90073, USA
| | - Christopher J Evans
- Hatos Center for Neuropharmacology, Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Giovanni Coppola
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Intellectual and Developmental Disabilities Research Center, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Center for Neurobehavioral Genetics, Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Baljit S Khakh
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA.
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Perez-Nievas BG, Serrano-Pozo A. Deciphering the Astrocyte Reaction in Alzheimer's Disease. Front Aging Neurosci 2018; 10:114. [PMID: 29922147 PMCID: PMC5996928 DOI: 10.3389/fnagi.2018.00114] [Citation(s) in RCA: 174] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Accepted: 04/03/2018] [Indexed: 12/24/2022] Open
Abstract
Reactive astrocytes were identified as a component of senile amyloid plaques in the cortex of Alzheimer's disease (AD) patients several decades ago. However, their role in AD pathophysiology has remained elusive ever since, in part owing to the extrapolation of the literature from primary astrocyte cultures and acute brain injury models to a chronic neurodegenerative scenario. Recent accumulating evidence supports the idea that reactive astrocytes in AD acquire neurotoxic properties, likely due to both a gain of toxic function and a loss of their neurotrophic effects. However, the diversity and complexity of this glial cell is only beginning to be unveiled, anticipating that astrocyte reaction might be heterogeneous as well. Herein we review the evidence from mouse models of AD and human neuropathological studies and attempt to decipher the main conundrums that astrocytes pose to our understanding of AD development and progression. We discuss the morphological features that characterize astrocyte reaction in the AD brain, the consequences of astrocyte reaction for both astrocyte biology and AD pathological hallmarks, and the molecular pathways that have been implicated in this reaction.
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Affiliation(s)
| | - Alberto Serrano-Pozo
- Alzheimer's Research Unit, MassGeneral Institute for Neurodegenerative Diseases (MIND), Department of Neurology, Massachusetts General Hospital, Boston, MA, United States
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Flanagan B, McDaid L, Wade J, Wong-Lin K, Harkin J. A computational study of astrocytic glutamate influence on post-synaptic neuronal excitability. PLoS Comput Biol 2018; 14:e1006040. [PMID: 29659572 PMCID: PMC5919689 DOI: 10.1371/journal.pcbi.1006040] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 04/26/2018] [Accepted: 02/15/2018] [Indexed: 11/18/2022] Open
Abstract
The ability of astrocytes to rapidly clear synaptic glutamate and purposefully release the excitatory transmitter is critical in the functioning of synapses and neuronal circuits. Dysfunctions of these homeostatic functions have been implicated in the pathology of brain disorders such as mesial temporal lobe epilepsy. However, the reasons for these dysfunctions are not clear from experimental data and computational models have been developed to provide further understanding of the implications of glutamate clearance from the extracellular space, as a result of EAAT2 downregulation: although they only partially account for the glutamate clearance process. In this work, we develop an explicit model of the astrocytic glutamate transporters, providing a more complete description of the glutamate chemical potential across the astrocytic membrane and its contribution to glutamate transporter driving force based on thermodynamic principles and experimental data. Analysis of our model demonstrates that increased astrocytic glutamate content due to glutamine synthetase downregulation also results in increased postsynaptic quantal size due to gliotransmission. Moreover, the proposed model demonstrates that increased astrocytic glutamate could prolong the time course of glutamate in the synaptic cleft and enhances astrocyte-induced slow inward currents, causing a disruption to the clarity of synaptic signalling and the occurrence of intervals of higher frequency postsynaptic firing. Overall, our work distilled the necessity of a low astrocytic glutamate concentration for reliable synaptic transmission of information and the possible implications of enhanced glutamate levels as in epilepsy. The role of astrocytes in the excitability and hyperexcitability of neurons is a subject which has gained a lot of attention, particularly in the pathology of neurological disorders including epilepsy. Although not completely understood, the control of glutamate homeostasis is believed to play a role in paroxysmal neuronal hyperexcitability known to precede seizure activity. We have developed a computational model which explores two of the astrocytic homeostatic mechanisms, namely glutamate clearance and gliotransmission, and connect them with a common controlling factor, astrocytic cytoplasmic glutamate concentration. In our model simulations we demonstrate both a slower clearance rate of synaptic glutamate and enhanced astrocytic glutamate release where cytoplasmic glutamate is elevated, both of which contribute to high frequency neuronal firing and conditions for seizure generation. We also describe a viable role for astrocytes as a “high pass” filter, where astrocytic activation in the form of intracellular calcium oscillations is possible for only a certain range of presynaptic neuronal firing rates, the lower bound of the range being reduced where astrocytic glutamate is elevated. In physiological terms this perhaps indicates not only neuronal but also astrocytic glutamate-mediated excitation in the neural-astrocytic network.
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Affiliation(s)
- Bronac Flanagan
- Intelligent Systems Research Centre, University of Ulster, Magee Campus, Derry~Londonderry, Northern Ireland, United Kingdom
- * E-mail:
| | - Liam McDaid
- Intelligent Systems Research Centre, University of Ulster, Magee Campus, Derry~Londonderry, Northern Ireland, United Kingdom
| | - John Wade
- Intelligent Systems Research Centre, University of Ulster, Magee Campus, Derry~Londonderry, Northern Ireland, United Kingdom
| | - KongFatt Wong-Lin
- Intelligent Systems Research Centre, University of Ulster, Magee Campus, Derry~Londonderry, Northern Ireland, United Kingdom
| | - Jim Harkin
- Intelligent Systems Research Centre, University of Ulster, Magee Campus, Derry~Londonderry, Northern Ireland, United Kingdom
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30
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Manninen T, Havela R, Linne ML. Computational Models for Calcium-Mediated Astrocyte Functions. Front Comput Neurosci 2018; 12:14. [PMID: 29670517 PMCID: PMC5893839 DOI: 10.3389/fncom.2018.00014] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Accepted: 02/28/2018] [Indexed: 12/16/2022] Open
Abstract
The computational neuroscience field has heavily concentrated on the modeling of neuronal functions, largely ignoring other brain cells, including one type of glial cell, the astrocytes. Despite the short history of modeling astrocytic functions, we were delighted about the hundreds of models developed so far to study the role of astrocytes, most often in calcium dynamics, synchronization, information transfer, and plasticity in vitro, but also in vascular events, hyperexcitability, and homeostasis. Our goal here is to present the state-of-the-art in computational modeling of astrocytes in order to facilitate better understanding of the functions and dynamics of astrocytes in the brain. Due to the large number of models, we concentrated on a hundred models that include biophysical descriptions for calcium signaling and dynamics in astrocytes. We categorized the models into four groups: single astrocyte models, astrocyte network models, neuron-astrocyte synapse models, and neuron-astrocyte network models to ease their use in future modeling projects. We characterized the models based on which earlier models were used for building the models and which type of biological entities were described in the astrocyte models. Features of the models were compared and contrasted so that similarities and differences were more readily apparent. We discovered that most of the models were basically generated from a small set of previously published models with small variations. However, neither citations to all the previous models with similar core structure nor explanations of what was built on top of the previous models were provided, which made it possible, in some cases, to have the same models published several times without an explicit intention to make new predictions about the roles of astrocytes in brain functions. Furthermore, only a few of the models are available online which makes it difficult to reproduce the simulation results and further develop the models. Thus, we would like to emphasize that only via reproducible research are we able to build better computational models for astrocytes, which truly advance science. Our study is the first to characterize in detail the biophysical and biochemical mechanisms that have been modeled for astrocytes.
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Affiliation(s)
- Tiina Manninen
- Computational Neuroscience Group, BioMediTech Institute and Faculty of Biomedical Sciences and Engineering, Tampere University of Technology, Tampere, Finland
| | | | - Marja-Leena Linne
- Computational Neuroscience Group, BioMediTech Institute and Faculty of Biomedical Sciences and Engineering, Tampere University of Technology, Tampere, Finland
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31
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Abstract
Astrocytes are neural cells of ectodermal, neuroepithelial origin that provide for homeostasis and defense of the central nervous system (CNS). Astrocytes are highly heterogeneous in morphological appearance; they express a multitude of receptors, channels, and membrane transporters. This complement underlies their remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue; astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
| | - Maiken Nedergaard
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
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32
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Verkhratsky A, Nedergaard M. Physiology of Astroglia. Physiol Rev 2018; 98:239-389. [PMID: 29351512 PMCID: PMC6050349 DOI: 10.1152/physrev.00042.2016] [Citation(s) in RCA: 888] [Impact Index Per Article: 148.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 03/22/2017] [Accepted: 04/27/2017] [Indexed: 02/07/2023] Open
Abstract
Astrocytes are neural cells of ectodermal, neuroepithelial origin that provide for homeostasis and defense of the central nervous system (CNS). Astrocytes are highly heterogeneous in morphological appearance; they express a multitude of receptors, channels, and membrane transporters. This complement underlies their remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue; astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
| | - Maiken Nedergaard
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
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34
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Cell Biology of Astrocyte-Synapse Interactions. Neuron 2017; 96:697-708. [PMID: 29096081 DOI: 10.1016/j.neuron.2017.09.056] [Citation(s) in RCA: 565] [Impact Index Per Article: 80.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Revised: 09/24/2017] [Accepted: 09/28/2017] [Indexed: 12/25/2022]
Abstract
Astrocytes, the most abundant glial cells in the mammalian brain, are critical regulators of brain development and physiology through dynamic and often bidirectional interactions with neuronal synapses. Despite the clear importance of astrocytes for the establishment and maintenance of proper synaptic connectivity, our understanding of their role in brain function is still in its infancy. We propose that this is at least in part due to large gaps in our knowledge of the cell biology of astrocytes and the mechanisms they use to interact with synapses. In this review, we summarize some of the seminal findings that yield important insight into the cellular and molecular basis of astrocyte-neuron communication, focusing on the role of astrocytes in the development and remodeling of synapses. Furthermore, we pose some pressing questions that need to be addressed to advance our mechanistic understanding of the role of astrocytes in regulating synaptic development.
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35
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Acton D, Miles GB. Gliotransmission and adenosinergic modulation: insights from mammalian spinal motor networks. J Neurophysiol 2017; 118:3311-3327. [PMID: 28954893 DOI: 10.1152/jn.00230.2017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Astrocytes are proposed to converse with neurons at tripartite synapses, detecting neurotransmitter release and responding with release of gliotransmitters, which in turn modulate synaptic strength and neuronal excitability. However, a paucity of evidence from behavioral studies calls into question the importance of gliotransmission for the operation of the nervous system in healthy animals. Central pattern generator (CPG) networks in the spinal cord and brain stem coordinate the activation of muscles during stereotyped activities such as locomotion, inspiration, and mastication and may therefore provide tractable models in which to assess the contribution of gliotransmission to behaviorally relevant neural activity. We review evidence for gliotransmission within spinal locomotor networks, including studies indicating that adenosine derived from astrocytes regulates the speed of locomotor activity via metamodulation of dopamine signaling.
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Affiliation(s)
- David Acton
- School of Psychology and Neuroscience, University of St Andrews, St Andrews, Fife , United Kingdom
| | - Gareth B Miles
- School of Psychology and Neuroscience, University of St Andrews, St Andrews, Fife , United Kingdom
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36
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Astrocyte-Mediated Neuronal Synchronization Properties Revealed by False Gliotransmitter Release. J Neurosci 2017; 37:9859-9870. [PMID: 28899919 PMCID: PMC5637115 DOI: 10.1523/jneurosci.2761-16.2017] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Revised: 06/14/2017] [Accepted: 06/27/2017] [Indexed: 12/21/2022] Open
Abstract
Astrocytes spontaneously release glutamate (Glut) as a gliotransmitter (GT), resulting in the generation of extrasynaptic NMDAR-mediated slow inward currents (SICs) in neighboring neurons, which can increase local neuronal excitability. However, there is a deficit in our knowledge of the factors that control spontaneous astrocyte GT release and the extent of its influence. We found that, in rat brain slices, increasing the supply of the physiological transmitter Glut increased the frequency and signaling charge of SICs over an extended period. This phenomenon was replicated by exogenous preexposure to the amino acid D-aspartate (D-Asp). Using D-Asp as a “false” GT, we determined the extent of local neuron excitation by GT release in ventrobasal thalamus, CA1 hippocampus, and somatosensory cortex. By analyzing synchronized neuronal NMDAR-mediated excitation, we found that the properties of the excitation were conserved in different brain areas. In the three areas, astrocyte-derived GT release synchronized groups of neurons at distances of >;200 μm. Individual neurons participated in more than one synchronized population, indicating that individual neurons can be excited by more than one astrocyte and that individual astrocytes may determine a neuron's synchronized network. The results confirm that astrocytes can act as excitatory nodes that can influence neurons over a significant range in a number of brain regions. Our findings further suggest that chronic elevation of ambient Glut levels can lead to increased GT Glut release, which may be relevant in some pathological states. SIGNIFICANCE STATEMENT Astrocytes spontaneously release glutamate (Glut) and other gliotransmitters (GTs) that can modify neuronal activity. Exposing brain slices to Glut and D-aspartate (D-Asp) before recording resulted in an increase in frequency of GT-mediated astrocyte–neuron signaling. Using D-Asp, it was possible to investigate the effects of specific GT release at neuronal NMDARs. Calcium imaging showed synchronized activity in groups of neurons in cortex, hippocampus, and thalamus. The size of these populations was similar in all areas and some neurons were involved in more than one synchronous group. The findings show that GT release is supply dependent and that the properties of the signaling and activated networks are largely conserved between different brain areas.
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37
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Modulation of Central Synapses by Astrocyte-Released ATP and Postsynaptic P2X Receptors. Neural Plast 2017; 2017:9454275. [PMID: 28845311 PMCID: PMC5563405 DOI: 10.1155/2017/9454275] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Accepted: 07/10/2017] [Indexed: 01/14/2023] Open
Abstract
Communication between neuronal and glial cells is important for neural plasticity. P2X receptors are ATP-gated cation channels widely expressed in the brain where they mediate action of extracellular ATP released by neurons and/or glia. Recent data show that postsynaptic P2X receptors underlie slow neuromodulatory actions rather than fast synaptic transmission at brain synapses. Here, we review these findings with a particular focus on the release of ATP by astrocytes and the diversity of postsynaptic P2X-mediated modulation of synaptic strength and plasticity in the CNS.
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38
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Single vector non-leaky gene expression system for Drosophila melanogaster. Sci Rep 2017; 7:6899. [PMID: 28761084 PMCID: PMC5537222 DOI: 10.1038/s41598-017-07282-w] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Accepted: 06/23/2017] [Indexed: 12/28/2022] Open
Abstract
An ideal transgenic gene expression system is inducible, non-leaky, and well tolerated by the target organism. While the former has been satisfactorily realized, leakiness and heavy physiological burden imposed by the existing systems are still prominent hurdles in their successful implementation. Here we describe a new system for non-leaky expression of transgenes in Drosophila. PRExpress is based on a single transgenic construct built from endogenous components, the inducible hsp70 promoter and a multimerized copy of a Polycomb response element (PRE) controlled by epigenetic chromatin regulators of the Polycomb group. We show that this system is non-leaky, rapidly and strongly inducible, and reversible. To make the application of PRExpress user-friendly, we deliver the construct via site-specific integration.
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39
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Taschenberger G, Tereshchenko J, Kügler S. A MicroRNA124 Target Sequence Restores Astrocyte Specificity of gfaABC 1D-Driven Transgene Expression in AAV-Mediated Gene Transfer. MOLECULAR THERAPY-NUCLEIC ACIDS 2017; 8:13-25. [PMID: 28918015 PMCID: PMC5476465 DOI: 10.1016/j.omtn.2017.03.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Revised: 03/21/2017] [Accepted: 03/28/2017] [Indexed: 12/03/2022]
Abstract
Experimentally restricting transgene expression exclusively to astrocytes has proven difficult. Using adeno-associated-virus-mediated gene transfer, we assessed two commonly used glial fibrillary acidic protein promoters: the full-length version gfa2 (2,210-bp human glial fibrillary acidic protein [GFAP] promoter) and the truncated variant gfaABC1D (681-bp GFAP promoter). The capacity to drive efficient, but also cell-type specific, expression of the EGFP in astrocytes was tested both in vitro in rat primary cortical cultures as well as in vivo in the rat striatum. We observed an efficient, but not entirely astrocyte-specific, gfa2-driven reporter expression. gfaABC1D exhibited a weaker activity, and most importantly, off-target, neuronal expression of the transgene occurred in a larger fraction of cells. Therefore, we explored the potential of a microRNA (miR)-specific target-sequence-based approach for abolishing off-target expression. When miR124 target sequences were incorporated into the 3′ UTR, neuronal gene expression was effectively silenced. However, unexpectedly, the insertion of an additional sequence in the 3′ UTR clearly diminished transgene expression. In conclusion, the gfaABC1D promoter on its own is not sufficient to specifically target transgene expression to astrocytes and is not well suited for AAV-based gene targeting, even if short promoter sequences are required. The combination with a miR de-targeting sequence represents a promising experimental strategy that eliminates off-target, neuronal expression.
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Affiliation(s)
- Grit Taschenberger
- Center of Nanoscale Microscopy and Molecular Physiology of the Brain, Humboldtallee 23, 37073 Goettingen, Germany; Department of Neurology, University Medical Center Goettingen, Waldweg 33, 37073 Goettingen, Germany.
| | - Julia Tereshchenko
- Department of Neurology, University Medical Center Goettingen, Waldweg 33, 37073 Goettingen, Germany
| | - Sebastian Kügler
- Center of Nanoscale Microscopy and Molecular Physiology of the Brain, Humboldtallee 23, 37073 Goettingen, Germany; Department of Neurology, University Medical Center Goettingen, Waldweg 33, 37073 Goettingen, Germany
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Jorgačevski J, Potokar M, Kreft M, Guček A, Mothet JP, Zorec R. Astrocytic Vesicle-based Exocytosis in Cultures and Acutely Isolated Hippocampal Rodent Slices. J Neurosci Res 2017; 95:2152-2158. [PMID: 28370180 DOI: 10.1002/jnr.24051] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Revised: 02/02/2017] [Accepted: 02/22/2017] [Indexed: 01/05/2023]
Abstract
Astrocytes are excitable neural cells that contribute to brain information processing via bidirectional communication with neurons. This involves the release of gliosignaling molecules that affect synapses patterning and activity. Mechanisms mediating the release of these molecules likely consist of non-vesicular and vesicular-based mechanisms. It is the vesicle-based regulated exocytosis that is an evolutionary more complex process. It is well established that the release of gliosignaling molecules has profound effects on information processing in different brain regions (e.g., hippocampal astrocytes contribute to long-term potentiation [LTP]), which has traditionally been considered as one of the cellular mechanisms underlying learning and memory. However, the paradigm of vesicle-based regulated release of gliosignaling molecules from astrocytes is still far from being unanimously accepted. One of the most important questions is to what extent can the conclusions obtained from cultured astrocytes be translated to in vivo conditions. Here, we overview the properties of vesicle mobility and their fusion with the plasma membrane in cultured astrocytes and compare these parameters to those recorded in astrocytes from acute brain hippocampal slices. The results from both experimental models are similar, which validates experiments on isolated astrocytes and further supports arguments in favor of in vivo vesicle-based exocytotic release of gliosignaling molecules. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Jernej Jorgačevski
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000, Ljubljana, Slovenia.,Celica Biomedical, Tehnološki Park 24, 1000, Ljubljana, Slovenia
| | - Maja Potokar
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000, Ljubljana, Slovenia.,Celica Biomedical, Tehnološki Park 24, 1000, Ljubljana, Slovenia
| | - Marko Kreft
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000, Ljubljana, Slovenia.,Celica Biomedical, Tehnološki Park 24, 1000, Ljubljana, Slovenia.,Department of Biology, Biotechnical Faculty, University of Ljubljana, Večna pot 111, 1000, Ljubljana, Slovenia
| | - Alenka Guček
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000, Ljubljana, Slovenia
| | - Jean-Pierre Mothet
- Team Gliotransmission and Synaptopathies, Aix-Marseille Université, CNRS, CRN2M UMR7286, Marseille, France
| | - Robert Zorec
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000, Ljubljana, Slovenia.,Celica Biomedical, Tehnološki Park 24, 1000, Ljubljana, Slovenia
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41
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Kardos J, Héja L, Jemnitz K, Kovács R, Palkovits M. The nature of early astroglial protection-Fast activation and signaling. Prog Neurobiol 2017; 153:86-99. [PMID: 28342942 DOI: 10.1016/j.pneurobio.2017.03.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Revised: 09/22/2016] [Accepted: 03/05/2017] [Indexed: 12/14/2022]
Abstract
Our present review is focusing on the uniqueness of balanced astroglial signaling. The balance of excitatory and inhibitory signaling within the CNS is mainly determined by sharp synaptic transients of excitatory glutamate (Glu) and inhibitory γ-aminobutyrate (GABA) acting on the sub-second timescale. Astroglia is involved in excitatory chemical transmission by taking up i) Glu through neurotransmitter-sodium transporters, ii) K+ released due to presynaptic action potential generation, and iii) water keeping osmotic pressure. Glu uptake-coupled Na+ influx may either ignite long-range astroglial Ca2+ transients or locally counteract over-excitation via astroglial GABA release and increased tonic inhibition. Imbalance of excitatory and inhibitory drives is associated with a number of disease conditions, including prevalent traumatic and ischaemic injuries or the emergence of epilepsy. Therefore, when addressing the potential of early therapeutic intervention, astroglial signaling functions combating progress of Glu excitotoxicity is of critical importance. We suggest, that excitotoxicity is linked primarily to over-excitation induced by the impairment of astroglial Glu uptake and/or GABA release. Within this framework, we discuss the acute alterations of Glu-cycling and metabolism and conjecture the therapeutic promise of regulation. We also confer the role played by key carrier proteins and enzymes as well as their interplay at the molecular, cellular, and organ levels. Moreover, based on our former studies, we offer potential prospect on the emerging theme of astroglial succinate sensing in course of Glu excitotoxicity.
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Affiliation(s)
- Julianna Kardos
- Functional Pharmacology Research Group, Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Hungary.
| | - László Héja
- Functional Pharmacology Research Group, Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Hungary
| | - Katalin Jemnitz
- Functional Pharmacology Research Group, Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Hungary
| | - Richárd Kovács
- Institute of Neurophysiology, Charité - Universitätsmedizin, Berlin, Germany
| | - Miklós Palkovits
- Human Brain Tissue Bank and Laboratory, Semmelweis University, Budapest, Hungary
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Srinivasan R, Lu TY, Chai H, Xu J, Huang BS, Golshani P, Coppola G, Khakh BS. New Transgenic Mouse Lines for Selectively Targeting Astrocytes and Studying Calcium Signals in Astrocyte Processes In Situ and In Vivo. Neuron 2016; 92:1181-1195. [PMID: 27939582 PMCID: PMC5403514 DOI: 10.1016/j.neuron.2016.11.030] [Citation(s) in RCA: 237] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 10/14/2016] [Accepted: 11/15/2016] [Indexed: 11/23/2022]
Abstract
Astrocytes exist throughout the nervous system and are proposed to affect neural circuits and behavior. However, studying astrocytes has proven difficult because of the lack of tools permitting astrocyte-selective genetic manipulations. Here, we report the generation of Aldh1l1-Cre/ERT2 transgenic mice to selectively target astrocytes in vivo. We characterized Aldh1l1-Cre/ERT2 mice using imaging, immunohistochemistry, AAV-FLEX-GFP microinjections, and crosses to RiboTag, Ai95, and new Cre-dependent membrane-tethered Lck-GCaMP6f knockin mice that we also generated. Two to three weeks after tamoxifen induction, Aldh1l1-Cre/ERT2 selectively targeted essentially all adult (P80) brain astrocytes with no detectable neuronal contamination, resulting in expression of cytosolic and Lck-GCaMP6f, and permitting subcellular astrocyte calcium imaging during startle responses in vivo. Crosses with RiboTag mice allowed sequencing of actively translated mRNAs and determination of the adult cortical astrocyte transcriptome. Thus, we provide well-characterized, easy-to-use resources with which to selectively study astrocytes in situ and in vivo in multiple experimental scenarios.
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Affiliation(s)
- Rahul Srinivasan
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Tsai-Yi Lu
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Hua Chai
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Ji Xu
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Ben S Huang
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Peyman Golshani
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Integrative Center for Learning and Memory, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; West Los Angeles VA Medical Center, Los Angeles, CA 90073, USA
| | - Giovanni Coppola
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Center for Neurobehavioral Genetics, Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Baljit S Khakh
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA.
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Vignoli B, Battistini G, Melani R, Blum R, Santi S, Berardi N, Canossa M. Peri-Synaptic Glia Recycles Brain-Derived Neurotrophic Factor for LTP Stabilization and Memory Retention. Neuron 2016; 92:873-887. [PMID: 27746130 DOI: 10.1016/j.neuron.2016.09.031] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Revised: 07/24/2016] [Accepted: 09/08/2016] [Indexed: 10/20/2022]
Abstract
Glial cells respond to neuronal activation and release neuroactive molecules (termed "gliotransmitters") that can affect synaptic activity and modulate plasticity. In this study, we used molecular genetic tools, ultra-structural microscopy, and electrophysiology to assess the role of brain-derived neurotrophic factor (BDNF) on cortical gliotransmission in vivo. We find that glial cells recycle BDNF that was previously secreted by neurons as pro-neurotrophin following long-term potentiation (LTP)-inducing electrical stimulation. Upon BDNF glial recycling, we observed tight, temporal, highly localized TrkB phosphorylation on adjacent neurons, a process required to sustain LTP. Engagement of BDNF recycling by astrocytes represents a novel mechanism by which cortical synapses can expand BDNF action and provide synaptic changes that are relevant for the acquisition of new memories. Accordingly, mice deficient in BDNF glial recycling fail to recognize familiar from novel objects, indicating a physiological requirement for this process in memory consolidation.
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Affiliation(s)
- Beatrice Vignoli
- European Brain Research Institute (EBRI) "Rita Levi-Montalcini", via del Fosso di Fiorano 64, 00143 Rome, Italy; Centre for Integrative Biology (CIBIO), University of Trento, via Sommarive 9, 38123 Povo (TN), Italy.
| | - Giulia Battistini
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, via San Donato 15, 40127 Bologna, Italy
| | - Riccardo Melani
- National Research Council (CNR), Institute of Neuroscience, via Moruzzi 1, 56100 Pisa, Italy
| | - Robert Blum
- Institute for Clinical Neurobiology, University Hospital, Julius Maximilians University, Versbacher Straße 5, 97078 Würzburg, Germany
| | - Spartaco Santi
- National Research Council (CNR), Institute of Molecular Genetics (IGM), Laboratory of Muscoloskeletal Cell Biology, IOR, via di Barbiano1/10, 40136 Bologna, Italy
| | - Nicoletta Berardi
- National Research Council (CNR), Institute of Neuroscience, via Moruzzi 1, 56100 Pisa, Italy; Department of Neuroscience, Psychology, Drug Research, and Child Health (NEUROFARBA), University of Florence, via di San Salvi 26, 50100 Florence, Italy
| | - Marco Canossa
- European Brain Research Institute (EBRI) "Rita Levi-Montalcini", via del Fosso di Fiorano 64, 00143 Rome, Italy; Centre for Integrative Biology (CIBIO), University of Trento, via Sommarive 9, 38123 Povo (TN), Italy.
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Wolosker H, Balu DT, Coyle JT. The Rise and Fall of the d-Serine-Mediated Gliotransmission Hypothesis. Trends Neurosci 2016; 39:712-721. [PMID: 27742076 DOI: 10.1016/j.tins.2016.09.007] [Citation(s) in RCA: 130] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Revised: 09/19/2016] [Accepted: 09/20/2016] [Indexed: 01/26/2023]
Abstract
d-Serine modulates N-methyl d-aspartate receptors (NMDARs) and regulates synaptic plasticity, neurodevelopment, and learning and memory. However, the primary site of d-serine synthesis and release remains controversial, with some arguing that it is a gliotransmitter and others defining it as a neuronal cotransmitter. Results from several laboratories using different strategies now show that the biosynthetic enzyme of d-serine, serine racemase (SR), is expressed almost entirely by neurons, with few astrocytes appearing to contain d-serine. Cell-selective suppression of SR expression demonstrates that neuronal, rather than astrocytic d-serine, modulates synaptic plasticity. Here, we propose an alternative conceptualization whereby astrocytes affect d-serine levels by synthesizing l-serine that shuttles to neurons to fuel the neuronal synthesis of d-serine.
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Affiliation(s)
- Herman Wolosker
- Department of Biochemistry, Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa 31096, Israel.
| | - Darrick T Balu
- Department of Psychiatry, Harvard Medical School, Boston, MA, USA; Translational Psychiatry Laboratory, McLean Hospital, Belmont, MA 02478, USA.
| | - Joseph T Coyle
- Department of Psychiatry, Harvard Medical School, Boston, MA, USA; Laboratory of Psychiatric and Molecular Neuroscience, McLean Hospital, Belmont, MA 02478, USA.
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Guček A, Jorgačevski J, Singh P, Geisler C, Lisjak M, Vardjan N, Kreft M, Egner A, Zorec R. Dominant negative SNARE peptides stabilize the fusion pore in a narrow, release-unproductive state. Cell Mol Life Sci 2016; 73:3719-31. [PMID: 27056575 PMCID: PMC11108528 DOI: 10.1007/s00018-016-2213-2] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Revised: 03/05/2016] [Accepted: 03/29/2016] [Indexed: 01/18/2023]
Abstract
Key support for vesicle-based release of gliotransmitters comes from studies of transgenic mice with astrocyte-specific expression of a dominant-negative domain of synaptobrevin 2 protein (dnSNARE). To determine how this peptide affects exocytosis, we used super-resolution stimulated emission depletion microscopy and structured illumination microscopy to study the anatomy of single vesicles in astrocytes. Smaller vesicles contained amino acid and peptidergic transmitters and larger vesicles contained ATP. Discrete increases in membrane capacitance, indicating single-vesicle fusion, revealed that astrocyte stimulation increases the frequency of predominantly transient fusion events in smaller vesicles, whereas larger vesicles transitioned to full fusion. To determine whether this reflects a lower density of SNARE proteins in larger vesicles, we treated astrocytes with botulinum neurotoxins D and E, which reduced exocytotic events of both vesicle types. dnSNARE peptide stabilized the fusion-pore diameter to narrow, release-unproductive diameters in both vesicle types, regardless of vesicle diameter.
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Affiliation(s)
- Alenka Guček
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, University of Ljubljana, 1000, Ljubljana, Slovenia
| | - Jernej Jorgačevski
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, University of Ljubljana, 1000, Ljubljana, Slovenia
- Celica BIOMEDICAL, 1000, Ljubljana, Slovenia
| | - Priyanka Singh
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, University of Ljubljana, 1000, Ljubljana, Slovenia
| | - Claudia Geisler
- Department of Optical Nanoscopy, Laser-Laboratory Göttingen e.V., 37077, Göttingen, Germany
| | - Marjeta Lisjak
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, University of Ljubljana, 1000, Ljubljana, Slovenia
| | - Nina Vardjan
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, University of Ljubljana, 1000, Ljubljana, Slovenia
- Celica BIOMEDICAL, 1000, Ljubljana, Slovenia
| | - Marko Kreft
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, University of Ljubljana, 1000, Ljubljana, Slovenia
- Celica BIOMEDICAL, 1000, Ljubljana, Slovenia
- Department of Biology, Biotechnical Faculty, University of Ljubljana, 1000, Ljubljana, Slovenia
| | - Alexander Egner
- Department of Optical Nanoscopy, Laser-Laboratory Göttingen e.V., 37077, Göttingen, Germany
| | - Robert Zorec
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, University of Ljubljana, 1000, Ljubljana, Slovenia.
- Celica BIOMEDICAL, 1000, Ljubljana, Slovenia.
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Chandrasekaran A, Avci HX, Leist M, Kobolák J, Dinnyés A. Astrocyte Differentiation of Human Pluripotent Stem Cells: New Tools for Neurological Disorder Research. Front Cell Neurosci 2016; 10:215. [PMID: 27725795 PMCID: PMC5035736 DOI: 10.3389/fncel.2016.00215] [Citation(s) in RCA: 99] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 08/30/2016] [Indexed: 12/22/2022] Open
Abstract
Astrocytes have a central role in brain development and function, and so have gained increasing attention over the past two decades. Consequently, our knowledge about their origin, differentiation and function has increased significantly, with new research showing that astrocytes cultured alone or co-cultured with neurons have the potential to improve our understanding of various central nervous system diseases, such as amyotrophic lateral sclerosis, Alzheimer’s disease, or Alexander disease. The generation of astrocytes derived from pluripotent stem cells (PSCs) opens up a new area for studying neurologic diseases in vitro; these models could be exploited to identify and validate potential drugs by detecting adverse effects in the early stages of drug development. However, as it is now known that a range of astrocyte populations exist in the brain, it will be important in vitro to develop standardized protocols for the in vitro generation of astrocyte subsets with defined maturity status and phenotypic properties. This will then open new possibilities for co-cultures with neurons and the generation of neural organoids for research purposes. The aim of this review article is to compare and summarize the currently available protocols and their strategies to generate human astrocytes from PSCs. Furthermore, we discuss the potential role of human-induced PSCs derived astrocytes in disease modeling.
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Affiliation(s)
| | - Hasan X Avci
- BioTalentum LtdGödöllő, Hungary; Department of Medical Chemistry, University of SzegedSzeged, Hungary
| | - Marcel Leist
- Dorenkamp-Zbinden Chair, Faculty of Mathematics and Sciences, University of Konstanz Konstanz, Germany
| | | | - Andras Dinnyés
- BioTalentum LtdGödöllő, Hungary; Molecular Animal Biotechnology Laboratory, Szent Istvan UniversityGödöllő, Hungary
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Skatchkov SN, Antonov SM, Eaton MJ. Glia and glial polyamines. Role in brain function in health and disease. BIOCHEMISTRY MOSCOW SUPPLEMENT SERIES A-MEMBRANE AND CELL BIOLOGY 2016. [DOI: 10.1134/s1990747816010116] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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48
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Bazargani N, Attwell D. Astrocyte calcium signaling: the third wave. Nat Neurosci 2016; 19:182-9. [PMID: 26814587 DOI: 10.1038/nn.4201] [Citation(s) in RCA: 559] [Impact Index Per Article: 69.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2015] [Accepted: 11/10/2015] [Indexed: 02/06/2023]
Abstract
The discovery that transient elevations of calcium concentration occur in astrocytes, and release 'gliotransmitters' which act on neurons and vascular smooth muscle, led to the idea that astrocytes are powerful regulators of neuronal spiking, synaptic plasticity and brain blood flow. These findings were challenged by a second wave of reports that astrocyte calcium transients did not mediate functions attributed to gliotransmitters and were too slow to generate blood flow increases. Remarkably, the tide has now turned again: the most important calcium transients occur in fine astrocyte processes not resolved in earlier studies, and new mechanisms have been discovered by which astrocyte [Ca(2+)]i is raised and exerts its effects. Here we review how this third wave of discoveries has changed our understanding of astrocyte calcium signaling and its consequences for neuronal function.
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Affiliation(s)
- Narges Bazargani
- Department of Neuroscience, Physiology &Pharmacology, University College London, London, UK
| | - David Attwell
- Department of Neuroscience, Physiology &Pharmacology, University College London, London, UK
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Abstract
The role of astrocytes in neuronal function has received increasing recognition, but disagreement remains about their function at the circuit level. Here we use in vivo two-photon calcium imaging of neocortical astrocytes while monitoring the activity state of the local neuronal circuit electrophysiologically and optically. We find that astrocytic calcium activity precedes spontaneous circuit shifts to the slow-oscillation-dominated state, a neocortical rhythm characterized by synchronized neuronal firing and important for sleep and memory. Further, we show that optogenetic activation of astrocytes switches the local neuronal circuit to this slow-oscillation state. Finally, using two-photon imaging of extracellular glutamate, we find that astrocytic transients in glutamate co-occur with shifts to the synchronized state and that optogenetically activated astrocytes can generate these glutamate transients. We conclude that astrocytes can indeed trigger the low-frequency state of a cortical circuit by altering extracellular glutamate, and therefore play a causal role in the control of cortical synchronizations.
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50
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Glial cell response after aneurysmal subarachnoid hemorrhage — Functional consequences and clinical implications. Biochim Biophys Acta Mol Basis Dis 2016; 1862:492-505. [DOI: 10.1016/j.bbadis.2015.10.013] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Revised: 10/12/2015] [Accepted: 10/15/2015] [Indexed: 12/17/2022]
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