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Zarate SM, Huntington TE, Bagher P, Srinivasan R. Aging reduces calreticulin expression and alters spontaneous calcium signals in astrocytic endfeet of the mouse dorsolateral striatum. NPJ AGING 2023; 9:5. [PMID: 37002232 PMCID: PMC10066375 DOI: 10.1038/s41514-023-00102-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2022] [Accepted: 03/15/2023] [Indexed: 04/03/2023]
Abstract
Aging-related impairment of the blood brain barrier (BBB) and neurovascular unit (NVU) increases the risk for neurodegeneration. Among various cells that participate in BBB and NVU function, calcium signals in astrocytic endfeet are crucial for maintaining BBB and NVU integrity. To assess if aging is associated with altered calcium signals within astrocytic endfeet of the dorsolateral striatum (DLS), we expressed GCaMP6f in DLS astrocytes of young (3-4 months), middle-aged (12-15 months) and aging (20-30 months) mice. Compared to endfeet in young mice, DLS endfeet in aging mice demonstrated decreased calreticulin expression, and alterations to both spontaneous membrane-associated and mitochondrial calcium signals. While young mice required both extracellular and endoplasmic reticulum calcium sources for endfoot signals, middle-aged and aging mice showed heavy dependence on endoplasmic reticulum calcium. Thus, astrocytic endfeet show significant changes in calcium buffering and sources throughout the lifespan, which is important for understanding mechanisms by which aging impairs the BBB and NVU.
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Affiliation(s)
- Sara M Zarate
- Department of Neuroscience & Experimental Therapeutics, Texas A&M University School of Medicine, 8447 Riverside Pkwy, Bryan, TX, 77807, USA
| | - Taylor E Huntington
- Department of Neuroscience & Experimental Therapeutics, Texas A&M University School of Medicine, 8447 Riverside Pkwy, Bryan, TX, 77807, USA
- Texas A&M Institute for Neuroscience (TAMIN), Texas A&M University, College Station, TX, 77843, USA
| | - Pooneh Bagher
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, NE, 68198, USA
| | - Rahul Srinivasan
- Department of Neuroscience & Experimental Therapeutics, Texas A&M University School of Medicine, 8447 Riverside Pkwy, Bryan, TX, 77807, USA.
- Texas A&M Institute for Neuroscience (TAMIN), Texas A&M University, College Station, TX, 77843, USA.
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2
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Kruyer A, Kalivas PW, Scofield MD. Astrocyte regulation of synaptic signaling in psychiatric disorders. Neuropsychopharmacology 2023; 48:21-36. [PMID: 35577914 PMCID: PMC9700696 DOI: 10.1038/s41386-022-01338-w] [Citation(s) in RCA: 28] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2022] [Revised: 04/27/2022] [Accepted: 05/01/2022] [Indexed: 02/07/2023]
Abstract
Over the last 15 years, the field of neuroscience has evolved toward recognizing the critical role of astroglia in shaping neuronal synaptic activity and along with the pre- and postsynapse is now considered an equal partner in tripartite synaptic transmission and plasticity. The relative youth of this recognition and a corresponding deficit in reagents and technologies for quantifying and manipulating astroglia relative to neurons continues to hamper advances in understanding tripartite synaptic physiology. Nonetheless, substantial advances have been made and are reviewed herein. We review the role of astroglia in synaptic function and regulation of behavior with an eye on how tripartite synapses figure into brain pathologies underlying behavioral impairments in psychiatric disorders, both from the perspective of measures in postmortem human brains and more subtle influences on tripartite synaptic regulation of behavior in animal models of psychiatric symptoms. Our goal is to provide the reader a well-referenced state-of-the-art understanding of current knowledge and predict what we may discover with deeper investigation of tripartite synapses using reagents and technologies not yet available.
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Affiliation(s)
- Anna Kruyer
- Department of Neuroscience, Medical University of South Carolina, Charleston, SC, USA
| | - Peter W Kalivas
- Department of Neuroscience, Medical University of South Carolina, Charleston, SC, USA.
- Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC, USA.
| | - Michael D Scofield
- Department of Neuroscience, Medical University of South Carolina, Charleston, SC, USA.
- Department of Anesthesia & Perioperative Medicine, Medical University of South Carolina, Charleston, SC, USA.
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3
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Grienberger C, Giovannucci A, Zeiger W, Portera-Cailliau C. Two-photon calcium imaging of neuronal activity. NATURE REVIEWS. METHODS PRIMERS 2022; 2:67. [PMID: 38124998 PMCID: PMC10732251 DOI: 10.1038/s43586-022-00147-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 07/07/2022] [Indexed: 12/23/2023]
Abstract
In vivo two-photon calcium imaging (2PCI) is a technique used for recording neuronal activity in the intact brain. It is based on the principle that, when neurons fire action potentials, intracellular calcium levels rise, which can be detected using fluorescent molecules that bind to calcium. This Primer is designed for scientists who are considering embarking on experiments with 2PCI. We provide the reader with a background on the basic concepts behind calcium imaging and on the reasons why 2PCI is an increasingly powerful and versatile technique in neuroscience. The Primer explains the different steps involved in experiments with 2PCI, provides examples of what ideal preparations should look like and explains how data are analysed. We also discuss some of the current limitations of the technique, and the types of solutions to circumvent them. Finally, we conclude by anticipating what the future of 2PCI might look like, emphasizing some of the analysis pipelines that are being developed and international efforts for data sharing.
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Affiliation(s)
- Christine Grienberger
- Department of Biology and Volen National Center for Complex Systems, Brandeis University, Waltham, MA, USA
| | - Andrea Giovannucci
- Joint Department of Biomedical Engineering University of North Carolina at Chapel Hill and North Carolina State University, Chapel Hill, NC, USA
- UNC Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - William Zeiger
- Department of Neurology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Carlos Portera-Cailliau
- Department of Neurology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
- Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
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4
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Tran CHT. Toolbox for studying neurovascular coupling in vivo, with a focus on vascular activity and calcium dynamics in astrocytes. NEUROPHOTONICS 2022; 9:021909. [PMID: 35295714 PMCID: PMC8920490 DOI: 10.1117/1.nph.9.2.021909] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Accepted: 02/23/2022] [Indexed: 05/14/2023]
Abstract
Significance: Insights into the cellular activity of each member of the neurovascular unit (NVU) is critical for understanding their contributions to neurovascular coupling (NVC)-one of the key control mechanisms in cerebral blood flow regulation. Advances in imaging and genetic tools have enhanced our ability to observe, manipulate and understand the cellular activity of NVU components, namely neurons, astrocytes, microglia, endothelial cells, vascular smooth muscle cells, and pericytes. However, there are still many unresolved questions. Since astrocytes are considered electrically unexcitable, Ca 2 + signaling is the main parameter used to monitor their activity. It is therefore imperative to study astrocytic Ca 2 + dynamics simultaneously with vascular activity using tools appropriate for the question of interest. Aim: To highlight currently available genetic and imaging tools for studying the NVU-and thus NVC-with a focus on astrocyte Ca 2 + dynamics and vascular activity, and discuss the utility, technical advantages, and limitations of these tools for elucidating NVC mechanisms. Approach: We draw attention to some outstanding questions regarding the mechanistic basis of NVC and emphasize the role of astrocytic Ca 2 + elevations in functional hyperemia. We further discuss commonly used genetic, and optical imaging tools, as well as some newly developed imaging modalities for studying NVC at the cellular level, highlighting their advantages and limitations. Results: We provide an overview of the current state of NVC research, focusing on the role of astrocytic Ca 2 + elevations in functional hyperemia; summarize recent advances in genetically engineered Ca 2 + indicators, fluorescence microscopy techniques for studying NVC; and discuss the unmet challenges for future imaging development. Conclusions: Advances in imaging techniques together with improvements in genetic tools have significantly contributed to our understanding of NVC. Many pieces of the puzzle have been revealed, but many more remain to be discovered. Ultimately, optimizing NVC research will require a concerted effort to improve imaging techniques, available genetic tools, and analytical software.
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Affiliation(s)
- Cam Ha T. Tran
- University of Nevada, Reno School of Medicine, Department of Physiology and Cell Biology, Reno, Nevada, United States
- Address all correspondence to Cam Ha T. Tran,
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5
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McNeill J, Rudyk C, Hildebrand ME, Salmaso N. Ion Channels and Electrophysiological Properties of Astrocytes: Implications for Emergent Stimulation Technologies. Front Cell Neurosci 2021; 15:644126. [PMID: 34093129 PMCID: PMC8173131 DOI: 10.3389/fncel.2021.644126] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2020] [Accepted: 04/26/2021] [Indexed: 12/12/2022] Open
Abstract
Astrocytes comprise a heterogeneous cell population characterized by distinct morphologies, protein expression and function. Unlike neurons, astrocytes do not generate action potentials, however, they are electrically dynamic cells with extensive electrophysiological heterogeneity and diversity. Astrocytes are hyperpolarized cells with low membrane resistance. They are heavily involved in the modulation of K+ and express an array of different voltage-dependent and voltage-independent channels to help with this ion regulation. In addition to these K+ channels, astrocytes also express several different types of Na+ channels; intracellular Na+ signaling in astrocytes has been linked to some of their functional properties. The physiological hallmark of astrocytes is their extensive intracellular Ca2+ signaling cascades, which vary at the regional, subregional, and cellular levels. In this review article, we highlight the physiological properties of astrocytes and the implications for their function and influence of network and synaptic activity. Furthermore, we discuss the implications of these differences in the context of optogenetic and DREADD experiments and consider whether these tools represent physiologically relevant techniques for the interrogation of astrocyte function.
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Affiliation(s)
- Jessica McNeill
- Department of Neuroscience, Carleton University, Ottawa, ON, Canada
| | | | | | - Natalina Salmaso
- Department of Neuroscience, Carleton University, Ottawa, ON, Canada
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6
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Badia-Soteras A, Octeau JC, Verheijen MHG, Khakh BS. Assessing Neuron-Astrocyte Spatial Interactions Using the Neuron-Astrocyte Proximity Assay. CURRENT PROTOCOLS IN NEUROSCIENCE 2020; 91:e91. [PMID: 32068967 PMCID: PMC7123847 DOI: 10.1002/cpns.91] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Astrocytes are morphologically complex cells with numerous close contacts with neurons at the level of their somata, branches, and branchlets. The smallest astrocyte processes make discrete contacts with synapses at scales that cannot be observed by standard light microscopy. At such contact points, astrocytes are thought to perform both homeostatic and neuromodulatory roles-functions that are proposed to be determined by their close spatial apposition. To study such spatial interactions, we previously developed a Förster resonance energy transfer (FRET)-based approach, which enables observation and tracking of the static and dynamic proximity of astrocyte processes with synapses. The approach is compatible with standard imaging techniques such as confocal microscopy and permits assessment of the most proximate contacts between astrocytes and neurons in live tissues. In this protocol article we describe the approach to analyze the contacts between striatal astrocyte processes and corticostriatal neuronal projection terminals onto medium spiny neurons. We report the required protocols in detail, including adeno-associated virus microinjections, acute brain slice preparation, imaging, and post hoc FRET quantification. The article provides a detailed description that can be used to characterize and study astrocyte process proximity to synapses in living tissue. © 2020 by John Wiley & Sons, Inc. Basic Protocol 1: Förster resonance energy transfer imaging in cultured cells Basic Protocol 2: Förster resonance energy transfer imaging with the neuron-astrocyte proximity assay in acute brain slices.
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Affiliation(s)
- Aina Badia-Soteras
- Department of Molecular & Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, Amsterdam Neuroscience, VU University Amsterdam, Amsterdam, 1081 HV, The Netherlands
| | - J. Christopher Octeau
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Mark H. G. Verheijen
- Department of Molecular & Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, Amsterdam Neuroscience, VU University Amsterdam, Amsterdam, 1081 HV, The Netherlands
| | - 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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7
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Khakh BS. Astrocyte-Neuron Interactions in the Striatum: Insights on Identity, Form, and Function. Trends Neurosci 2019; 42:617-630. [PMID: 31351745 PMCID: PMC6741427 DOI: 10.1016/j.tins.2019.06.003] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Revised: 06/22/2019] [Accepted: 06/28/2019] [Indexed: 01/09/2023]
Abstract
The physiological functions of astrocytes within neural circuits remain incompletely understood. There has been progress in this regard from recent work on striatal astrocytes, where detailed studies are emerging. In this review, findings on striatal astrocyte identity, form, and function, are summarized with a focus on how astrocytes regulate striatal neurons, circuits, and behavior. Specific features of striatal astrocytes are highlighted to illustrate how they may be specialized to regulate medium spiny neurons (MSNs) by responding to, and altering, excitation and inhibition. Further experiments should reveal additional mechanisms for astrocyte-neuron interactions in the striatum and potentially reveal insights into the functions of astrocytes in neural circuits more generally.
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Affiliation(s)
- 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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8
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Nagai J, Rajbhandari AK, Gangwani MR, Hachisuka A, Coppola G, Masmanidis SC, Fanselow MS, Khakh BS. Hyperactivity with Disrupted Attention by Activation of an Astrocyte Synaptogenic Cue. Cell 2019; 177:1280-1292.e20. [PMID: 31031006 PMCID: PMC6526045 DOI: 10.1016/j.cell.2019.03.019] [Citation(s) in RCA: 185] [Impact Index Per Article: 37.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2018] [Revised: 02/08/2019] [Accepted: 03/07/2019] [Indexed: 11/19/2022]
Abstract
Hyperactivity and disturbances of attention are common behavioral disorders whose underlying cellular and neural circuit causes are not understood. We report the discovery that striatal astrocytes drive such phenotypes through a hitherto unknown synaptic mechanism. We found that striatal medium spiny neurons (MSNs) triggered astrocyte signaling via γ-aminobutyric acid B (GABAB) receptors. Selective chemogenetic activation of this pathway in striatal astrocytes in vivo resulted in acute behavioral hyperactivity and disrupted attention. Such responses also resulted in upregulation of the synaptogenic cue thrombospondin-1 (TSP1) in astrocytes, increased excitatory synapses, enhanced corticostriatal synaptic transmission, and increased MSN action potential firing in vivo. All of these changes were reversed by blocking TSP1 effects. Our data identify a form of bidirectional neuron-astrocyte communication and demonstrate that acute reactivation of a single latent astrocyte synaptogenic cue alters striatal circuits controlling behavior, revealing astrocytes and the TSP1 pathway as therapeutic targets in hyperactivity, attention deficit, and related psychiatric disorders.
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Affiliation(s)
- Jun Nagai
- Department of Physiology, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Abha K Rajbhandari
- Department of Psychology, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Mohitkumar R Gangwani
- Department of Physiology, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Ayaka Hachisuka
- Department of Neurobiology, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Giovanni Coppola
- Department of Neurology, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Center for Neurobehavioral Genetics, Semel Institute for Neuroscience and Human Behavior, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Sotiris C Masmanidis
- Department of Neurobiology, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Michael S Fanselow
- Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Department of Psychology, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Baljit S Khakh
- Department of Physiology, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Department of Neurobiology, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA.
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9
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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: 219] [Impact Index Per Article: 36.5] [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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10
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Kelly P, Hudry E, Hou SS, Bacskai BJ. In Vivo Two Photon Imaging of Astrocytic Structure and Function in Alzheimer's Disease. Front Aging Neurosci 2018; 10:219. [PMID: 30072889 PMCID: PMC6060286 DOI: 10.3389/fnagi.2018.00219] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 06/26/2018] [Indexed: 12/17/2022] Open
Abstract
The physiological function of the neurovascular unit is critically dependent upon the complex structure and functions of astrocytes for optimal preservation of cerebral homeostasis. While it has been shown that astrocytes exhibit aberrant changes in both structure and function in transgenic murine models of Alzheimer’s disease (AD), it is not fully understood how this altered phenotype contributes to the pathogenesis of AD or whether this alteration predicts a therapeutic target in AD. The mechanisms underlying the spatiotemporal relationship between astrocytes, neurons and the vasculature in their orchestrated regulation of local cerebral flow in active brain regions has not been fully elucidated in brain physiology and in AD. As there is an incredible urgency to identify therapeutic targets that are well-tolerated and efficacious in protecting the brain against the pathological impact of AD, here we use the current body of literature to evaluate the hypothesis that pathological changes in astrocytes are central to the pathogenesis of AD. We also examine the current tools available to assess astrocytic calcium signaling in the living murine brain as it has an important role in the complex interaction between astrocytes, neurons and the vasculature. Furthermore, we discuss the altered function of astrocytes in their interaction with neurons in the preservation of glutamate homeostasis and additionally address the role of astrocytes at the vascular interface and their contribution to functional hyperemia within the living murine brain in health and in AD.
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Affiliation(s)
- Patricia Kelly
- Massachusetts Institute for Neurodegenerative Disease, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Harvard University, Boston, MA, United States
| | - Eloise Hudry
- Massachusetts Institute for Neurodegenerative Disease, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Harvard University, Boston, MA, United States
| | - Steven S Hou
- Massachusetts Institute for Neurodegenerative Disease, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Harvard University, Boston, MA, United States
| | - Brian J Bacskai
- Massachusetts Institute for Neurodegenerative Disease, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Harvard University, Boston, MA, United States
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11
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Marina N, Turovsky E, Christie IN, Hosford PS, Hadjihambi A, Korsak A, Ang R, Mastitskaya S, Sheikhbahaei S, Theparambil SM, Gourine AV. Brain metabolic sensing and metabolic signaling at the level of an astrocyte. Glia 2018; 66:1185-1199. [PMID: 29274121 PMCID: PMC5947829 DOI: 10.1002/glia.23283] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 10/04/2017] [Accepted: 11/29/2017] [Indexed: 12/18/2022]
Abstract
Astrocytes support neuronal function by providing essential structural and nutritional support, neurotransmitter trafficking and recycling and may also contribute to brain information processing. In this article we review published results and report new data suggesting that astrocytes function as versatile metabolic sensors of central nervous system (CNS) milieu and play an important role in the maintenance of brain metabolic homeostasis. We discuss anatomical and functional features of astrocytes that allow them to detect and respond to changes in the brain parenchymal levels of metabolic substrates (oxygen and glucose), and metabolic waste products (carbon dioxide). We report data suggesting that astrocytes are also sensitive to circulating endocrine signals-hormones like ghrelin, glucagon-like peptide-1 and leptin, that have a major impact on the CNS mechanisms controlling food intake and energy balance. We discuss signaling mechanisms that mediate communication between astrocytes and neurons and consider how these mechanisms are recruited by astrocytes activated in response to various metabolic challenges. We review experimental data suggesting that astrocytes modulate the activities of the respiratory and autonomic neuronal networks that ensure adaptive changes in breathing and sympathetic drive in order to support the physiological and behavioral demands of the organism in ever-changing environmental conditions. Finally, we discuss evidence suggesting that altered astroglial function may contribute to the pathogenesis of disparate neurological, respiratory and cardiovascular disorders such as Rett syndrome and systemic arterial hypertension.
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Affiliation(s)
- Nephtali Marina
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & PharmacologyUniversity College LondonLondonWC1E 6BTUnited Kingdom
- Research Department of Metabolism and Experimental Therapeutics, Division of MedicineUniversity College LondonLondonWC1E 6JJUnited Kingdom
| | - Egor Turovsky
- Laboratory of Intracellular SignallingInstitute of Cell Biophysics, Russian Academy of SciencesPushchinoRussia
| | - Isabel N Christie
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & PharmacologyUniversity College LondonLondonWC1E 6BTUnited Kingdom
| | - Patrick S Hosford
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & PharmacologyUniversity College LondonLondonWC1E 6BTUnited Kingdom
| | - Anna Hadjihambi
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & PharmacologyUniversity College LondonLondonWC1E 6BTUnited Kingdom
| | - Alla Korsak
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & PharmacologyUniversity College LondonLondonWC1E 6BTUnited Kingdom
| | - Richard Ang
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & PharmacologyUniversity College LondonLondonWC1E 6BTUnited Kingdom
| | - Svetlana Mastitskaya
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & PharmacologyUniversity College LondonLondonWC1E 6BTUnited Kingdom
| | - Shahriar Sheikhbahaei
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & PharmacologyUniversity College LondonLondonWC1E 6BTUnited Kingdom
| | - Shefeeq M Theparambil
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & PharmacologyUniversity College LondonLondonWC1E 6BTUnited Kingdom
| | - Alexander V Gourine
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & PharmacologyUniversity College LondonLondonWC1E 6BTUnited Kingdom
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12
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Savtchouk I, Carriero G, Volterra A. Studying Axon-Astrocyte Functional Interactions by 3D Two-Photon Ca 2+ Imaging: A Practical Guide to Experiments and "Big Data" Analysis. Front Cell Neurosci 2018; 12:98. [PMID: 29706870 PMCID: PMC5908897 DOI: 10.3389/fncel.2018.00098] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 03/22/2018] [Indexed: 01/06/2023] Open
Abstract
Recent advances in fast volumetric imaging have enabled rapid generation of large amounts of multi-dimensional functional data. While many computer frameworks exist for data storage and analysis of the multi-gigabyte Ca2+ imaging experiments in neurons, they are less useful for analyzing Ca2+ dynamics in astrocytes, where transients do not follow a predictable spatio-temporal distribution pattern. In this manuscript, we provide a detailed protocol and commentary for recording and analyzing three-dimensional (3D) Ca2+ transients through time in GCaMP6f-expressing astrocytes of adult brain slices in response to axonal stimulation, using our recently developed tools to perform interactive exploration, filtering, and time-correlation analysis of the transients. In addition to the protocol, we release our in-house software tools and discuss parameters pertinent to conducting axonal stimulation/response experiments across various brain regions and conditions. Our software tools are available from the Volterra Lab webpage at https://wwwfbm.unil.ch/dnf/group/glia-an-active-synaptic-partner/member/volterra-andrea-volterra in the form of software plugins for Image J (NIH)—a de facto standard in scientific image analysis. Three programs are available: MultiROI_TZ_profiler for interactive graphing of several movable ROIs simultaneously, Gaussian_Filter5D for Gaussian filtering in several dimensions, and Correlation_Calculator for computing various cross-correlation parameters on voxel collections through time.
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Affiliation(s)
- Iaroslav Savtchouk
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
| | - Giovanni Carriero
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
| | - Andrea Volterra
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
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13
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Octeau JC, Chai H, Jiang R, Bonanno SL, Martin KC, Khakh BS. An Optical Neuron-Astrocyte Proximity Assay at Synaptic Distance Scales. Neuron 2018; 98:49-66.e9. [PMID: 29621490 PMCID: PMC5916847 DOI: 10.1016/j.neuron.2018.03.003] [Citation(s) in RCA: 83] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 01/21/2018] [Accepted: 03/02/2018] [Indexed: 02/06/2023]
Abstract
Astrocytes are complex bushy cells that serve important functions through close contacts between their processes and synapses. However, the spatial interactions and dynamics of astrocyte processes relative to synapses have proven problematic to study in adult living brain tissue. Here, we report a genetically targeted neuron-astrocyte proximity assay (NAPA) to measure astrocyte-synapse spatial interactions within intact brain preparations and at synaptic distance scales. The method exploits resonance energy transfer between extracellularly displayed fluorescent proteins targeted to synapses and astrocyte processes. We validated the method in the striatal microcircuitry following in vivo expression. We determined the proximity of striatal astrocyte processes to distinct neuronal input pathways, to D1 and D2 medium spiny neuron synapses, and we evaluated how astrocyte-to-excitatory synapse proximity changed following cortical afferent stimulation, during ischemia and in a model of Huntington's disease. NAPA provides a simple approach to measure astrocyte-synapse spatial interactions in a variety of experimental scenarios. VIDEO ABSTRACT.
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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
| | - Hua Chai
- Department of Physiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Ruotian Jiang
- Department of Physiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Shivan L Bonanno
- Department of Biological Chemistry, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Kelsey C Martin
- Department of Biological Chemistry, 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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14
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Chai H, Diaz-Castro B, Shigetomi E, Monte E, Octeau JC, Yu X, Cohn W, Rajendran PS, Vondriska TM, Whitelegge JP, Coppola G, Khakh BS. Neural Circuit-Specialized Astrocytes: Transcriptomic, Proteomic, Morphological, and Functional Evidence. Neuron 2017; 95:531-549.e9. [PMID: 28712653 PMCID: PMC5811312 DOI: 10.1016/j.neuron.2017.06.029] [Citation(s) in RCA: 479] [Impact Index Per Article: 68.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Revised: 05/14/2017] [Accepted: 06/16/2017] [Indexed: 12/15/2022]
Abstract
Astrocytes are ubiquitous in the brain and are widely held to be largely identical. However, this view has not been fully tested, and the possibility that astrocytes are neural circuit specialized remains largely unexplored. Here, we used multiple integrated approaches, including RNA sequencing (RNA-seq), mass spectrometry, electrophysiology, immunohistochemistry, serial block-face-scanning electron microscopy, morphological reconstructions, pharmacogenetics, and diffusible dye, calcium, and glutamate imaging, to directly compare adult striatal and hippocampal astrocytes under identical conditions. We found significant differences in electrophysiological properties, Ca2+ signaling, morphology, and astrocyte-synapse proximity between striatal and hippocampal astrocytes. Unbiased evaluation of actively translated RNA and proteomic data confirmed significant astrocyte diversity between hippocampal and striatal circuits. We thus report core astrocyte properties, reveal evidence for specialized astrocytes within neural circuits, and provide new, integrated database resources and approaches to explore astrocyte diversity and function throughout the adult brain. VIDEO ABSTRACT.
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Affiliation(s)
- Hua Chai
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Blanca Diaz-Castro
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Eiji Shigetomi
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi 409-3898, Japan, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Emma Monte
- Department of Anesthesiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - J Christopher Octeau
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Xinzhu Yu
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Whitaker Cohn
- Pasarow Mass Spectrometry Laboratory, Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Brain Research Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Pradeep S Rajendran
- UCLA Cardiac Arrhythmia Center, Neurocardiology Research Center for Excellence, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Thomas M Vondriska
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Department of Anesthesiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA
| | - Julian P Whitelegge
- Pasarow Mass Spectrometry Laboratory, Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1751, USA; Brain Research Institute, 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; 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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15
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Rougon G, Brasselet S, Debarbieux F. Advances in Intravital Non-Linear Optical Imaging of the Central Nervous System in Rodents. Brain Plast 2016; 2:31-48. [PMID: 29765847 PMCID: PMC5928564 DOI: 10.3233/bpl-160028] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Purpose of review: Highly coordinated cellular interactions occur in the healthy or pathologic adult rodent central nervous system (CNS). Until recently, technical challenges have restricted the analysis of these events to largely static modes of study such as immuno-fluorescence and electron microscopy on fixed tissues. The development of intravital imaging with subcellular resolution is required to probe the dynamics of these events in their natural context, the living brain. Recent findings: This review focuses on the recently developed live non-linear optical imaging modalities, the core principles involved, the identified technical challenges that limit their use and the scope of their applications. We highlight some practical applications for these modalities with a specific attention given to Experimental Autoimmune Encephalomyelitis (EAE), a rodent model of a chronic inflammatory disease of the CNS characterized by the formation of disseminated demyelinating lesions accompanied by axonal degeneration. Summary: We conclude that label-free nonlinear optical imaging combined to two photon imaging will continue to contribute richly to comprehend brain function and pathogenesis and to develop effective therapeutic strategies.
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Affiliation(s)
- Geneviève Rougon
- Aix-Marseille Université, CNRS, Institut des Neurosciences de la Timone, UMR 7289, Marseille, France
| | - Sophie Brasselet
- Aix-Marseille Université, CNRS, Centrale Marseille, Institut Fresnel, UMR 7249, Marseille, France
| | - Franck Debarbieux
- Aix-Marseille Université, CNRS, Institut des Neurosciences de la Timone, UMR 7289, Marseille, France
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16
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Dysfunctional Calcium and Glutamate Signaling in Striatal Astrocytes from Huntington's Disease Model Mice. J Neurosci 2016; 36:3453-70. [PMID: 27013675 DOI: 10.1523/jneurosci.3693-15.2016] [Citation(s) in RCA: 152] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Accepted: 01/07/2016] [Indexed: 01/14/2023] Open
Abstract
UNLABELLED Astrocytes tile the entire CNS, but their functions within neural circuits in health and disease remain incompletely understood. We used genetically encoded Ca(2+)and glutamate indicators to explore the rules for astrocyte engagement in the corticostriatal circuit of adult wild-type (WT) and Huntington's disease (HD) model mice at ages not accompanied by overt astrogliosis (at approximately postnatal days 70-80). WT striatal astrocytes displayed extensive spontaneous Ca(2+)signals, but did not respond to cortical stimulation, implying that astrocytes were largely disengaged from cortical input in healthy tissue. In contrast, in HD model mice, spontaneous Ca(2+)signals were significantly reduced in frequency, duration, and amplitude, but astrocytes responded robustly to cortical stimulation with evoked Ca(2+)signals. These action-potential-dependent astrocyte Ca(2+)signals were mediated by neuronal glutamate release during cortical stimulation, accompanied by prolonged extracellular glutamate levels near astrocytes and tightly gated by Glt1 glutamate transporters. Moreover, dysfunctional Ca(2+)and glutamate signaling that was observed in HD model mice was largely, but not completely, rescued by astrocyte specific restoration of Kir4.1, emphasizing the important contributions of K(+)homeostatic mechanisms that are known to be reduced in HD model mice. Overall, our data show that astrocyte engagement in the corticostriatal circuit is markedly altered in HD. Such prodromal astrocyte dysfunctions may represent novel therapeutic targets in HD and other brain disorders. SIGNIFICANCE STATEMENT We report how early-onset astrocyte dysfunction without detectable astrogliosis drives disease-related processes in a mouse model of Huntington's disease (HD). The cellular mechanisms involve astrocyte homeostasis and signaling mediated by Kir4.1, Glt1, and Ca(2+) The data show that the rules for astrocyte engagement in a neuronal circuit are fundamentally altered in a brain disease caused by a known molecular defect and that fixing early homeostasis dysfunction remedies additional cellular deficits. Overall, our data suggest that key aspects of altered striatal function associated with HD may be triggered, at least in part, by dysfunctional astrocytes, thereby providing details of an emerging striatal microcircuit mechanism in HD. Such prodromal changes in astrocytes may represent novel therapeutic targets.
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17
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Shigetomi E, Patel S, Khakh BS. Probing the Complexities of Astrocyte Calcium Signaling. Trends Cell Biol 2016; 26:300-312. [PMID: 26896246 PMCID: PMC4946798 DOI: 10.1016/j.tcb.2016.01.003] [Citation(s) in RCA: 168] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 01/12/2016] [Accepted: 01/14/2016] [Indexed: 01/08/2023]
Abstract
Astrocytes are abundant glial cells that tile the entire central nervous system and mediate well-established functions for neurons, blood vessels, and other glia. These ubiquitous cells display intracellular Ca(2+) signals, which have been intensely studied for 25 years. Recently, the use of improved methods has unearthed the panoply of astrocyte Ca(2+) signals and a variable landscape of basal Ca(2+) levels. In vivo studies have started to reveal the settings under which astrocytes display behaviorally relevant Ca(2+) signaling. Studies in mice have emphasized how astrocyte Ca(2+) signaling is altered in distinct neurodegenerative diseases. Progress in the past few years, fueled by methodological advances, has thus reignited interest in astrocyte Ca(2+) signaling for brain function and dysfunction.
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Affiliation(s)
- Eiji Shigetomi
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi 409-3898, Japan
| | - Sandip Patel
- Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - 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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18
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Astrocyte scar formation aids central nervous system axon regeneration. Nature 2016; 532:195-200. [PMID: 27027288 DOI: 10.1038/nature17623] [Citation(s) in RCA: 1203] [Impact Index Per Article: 150.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 02/26/2016] [Indexed: 12/20/2022]
Abstract
Transected axons fail to regrow in the mature central nervous system. Astrocytic scars are widely regarded as causal in this failure. Here, using three genetically targeted loss-of-function manipulations in adult mice, we show that preventing astrocyte scar formation, attenuating scar-forming astrocytes, or ablating chronic astrocytic scars all failed to result in spontaneous regrowth of transected corticospinal, sensory or serotonergic axons through severe spinal cord injury (SCI) lesions. By contrast, sustained local delivery via hydrogel depots of required axon-specific growth factors not present in SCI lesions, plus growth-activating priming injuries, stimulated robust, laminin-dependent sensory axon regrowth past scar-forming astrocytes and inhibitory molecules in SCI lesions. Preventing astrocytic scar formation significantly reduced this stimulated axon regrowth. RNA sequencing revealed that astrocytes and non-astrocyte cells in SCI lesions express multiple axon-growth-supporting molecules. Our findings show that contrary to the prevailing dogma, astrocyte scar formation aids rather than prevents central nervous system axon regeneration.
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19
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Diversity of astrocyte functions and phenotypes in neural circuits. Nat Neurosci 2015; 18:942-52. [PMID: 26108722 DOI: 10.1038/nn.4043] [Citation(s) in RCA: 752] [Impact Index Per Article: 83.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 05/04/2015] [Indexed: 12/11/2022]
Abstract
Astrocytes tile the entire CNS. They are vital for neural circuit function, but have traditionally been viewed as simple, homogenous cells that serve the same essential supportive roles everywhere. Here, we summarize breakthroughs that instead indicate that astrocytes represent a population of complex and functionally diverse cells. Physiological diversity of astrocytes is apparent between different brain circuits and microcircuits, and individual astrocytes display diverse signaling in subcellular compartments. With respect to injury and disease, astrocytes undergo diverse phenotypic changes that may be protective or causative with regard to pathology in a context-dependent manner. These new insights herald the concept that astrocytes represent a diverse population of genetically tractable cells that mediate neural circuit-specific roles in health and disease.
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20
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Srinivasan R, Huang BS, Venugopal S, Johnston AD, Chai H, Zeng H, Golshani P, Khakh BS. Ca(2+) signaling in astrocytes from Ip3r2(-/-) mice in brain slices and during startle responses in vivo. Nat Neurosci 2015; 18:708-17. [PMID: 25894291 PMCID: PMC4429056 DOI: 10.1038/nn.4001] [Citation(s) in RCA: 331] [Impact Index Per Article: 36.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Accepted: 03/15/2015] [Indexed: 12/11/2022]
Abstract
Intracellular Ca2+ signaling is considered important for multiple astrocyte functions in neural circuits. However, mice devoid of inositol triphosphate type 2 receptors (IP3R2) reportedly lack all astrocyte Ca2+ signaling, but display no neuronal or neurovascular deficits, implying that astrocyte Ca2+ fluctuations play no role(s) in these functions. An assumption has been that loss of somatic Ca2+ fluctuations also reflects similar loss within astrocyte processes. Here, we tested this assumption and found diverse types of Ca2+ fluctuations within astrocytes, with most occurring within processes rather than in somata. These fluctuations were preserved in IP3R2−/− mice in brain slices and in vivo, occurred in endfeet, were increased by G-protein coupled receptor activation and by startle-induced neuromodulatory responses. Our data reveal novel Ca2+ fluctuations within astrocytes and highlight limitations of studies that used IP3R2−/− mice to evaluate astrocyte contributions to neural circuit function and mouse behavior.
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Affiliation(s)
- Rahul Srinivasan
- Department of Physiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA
| | - Ben S Huang
- Department of Neurology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA
| | - Sharmila Venugopal
- Department of Physiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA
| | - April D Johnston
- Department of Physiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA
| | - Hua Chai
- Department of Physiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA
| | - Hongkui Zeng
- Allen Institute for Brain Science, Seattle, Washington, USA
| | - Peyman Golshani
- 1] Department of Neurology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA. [2] Integrative Center for Learning and Memory, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA. [3] West Los Angeles VA Medical Center, Los Angeles, California, USA
| | - Baljit S Khakh
- 1] Department of Physiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA. [2] Department of Neurobiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA
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