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Meng A, Ameroso D, Rios M. mGluR5 in Astrocytes in the Ventromedial Hypothalamus Regulates Pituitary Adenylate Cyclase-Activating Polypeptide Neurons and Glucose Homeostasis. J Neurosci 2023; 43:5918-5935. [PMID: 37507231 PMCID: PMC10436691 DOI: 10.1523/jneurosci.0193-23.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 05/09/2023] [Accepted: 07/16/2023] [Indexed: 07/30/2023] Open
Abstract
The ventromedial hypothalamus (VMH) is a functionally heterogeneous nucleus critical for systemic energy, glucose, and lipid balance. We showed previously that the metabotropic glutamate receptor 5 (mGluR5) plays essential roles regulating excitatory and inhibitory transmission in SF1+ neurons of the VMH and facilitating glucose and lipid homeostasis in female mice. Although mGluR5 is also highly expressed in VMH astrocytes in the mature brain, its role there influencing central metabolic circuits is unknown. In contrast to the glucose intolerance observed only in female mice lacking mGluR5 in VMH SF1 neurons, selective depletion of mGluR5 in VMH astrocytes enhanced glucose tolerance without affecting food intake or body weight in both adult female and male mice. The improved glucose tolerance was associated with elevated glucose-stimulated insulin release. Astrocytic mGluR5 male and female mutants also exhibited reduced adipocyte size and increased sympathetic tone in gonadal white adipose tissue. Diminished excitatory drive and synaptic inputs onto VMH Pituitary adenylate cyclase-activating polypeptide (PACAP+) neurons and reduced activity of these cells during acute hyperglycemia underlie the observed changes in glycemic control. These studies reveal an essential role of astrocytic mGluR5 in the VMH regulating the excitatory drive onto PACAP+ neurons and activity of these cells facilitating glucose homeostasis in male and female mice.SIGNIFICANCE STATEMENT Neuronal circuits within the VMH play chief roles in the regulation of whole-body metabolic homeostasis. It remains unclear how astrocytes influence neurotransmission in this region to facilitate energy and glucose balance control. Here, we explored the role of the metabotropic glutamate receptor, mGluR5, using a mouse model with selective depletion of mGluR5 from VMH astrocytes. We show that astrocytic mGluR5 critically regulates the excitatory drive and activity of PACAP-expressing neurons in the VMH to control glucose homeostasis in both female and male mice. Furthermore, mGluR5 in VMH astrocytes influences adipocyte size and sympathetic tone in white adipose tissue. These studies provide novel insight toward the importance of hypothalamic astrocytes participating in central circuits regulating peripheral metabolism.
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Affiliation(s)
- Alice Meng
- Graduate Program in Cell, Molecular and Developmental Biology, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Dominique Ameroso
- Graduate Program in Neuroscience, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts 02111, United States
| | - Maribel Rios
- Graduate Program in Cell, Molecular and Developmental Biology, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts 02111
- Graduate Program in Neuroscience, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts 02111, United States
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
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2
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Eraso‐Pichot A, Pouvreau S, Olivera‐Pinto A, Gomez‐Sotres P, Skupio U, Marsicano G. Endocannabinoid signaling in astrocytes. Glia 2023; 71:44-59. [PMID: 35822691 PMCID: PMC9796923 DOI: 10.1002/glia.24246] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Revised: 06/28/2022] [Accepted: 07/04/2022] [Indexed: 01/07/2023]
Abstract
The study of the astrocytic contribution to brain functions has been growing in popularity in the neuroscience field. In the last years, and especially since the demonstration of the involvement of astrocytes in synaptic functions, the astrocyte field has revealed multiple functions of these cells that seemed inconceivable not long ago. In parallel, cannabinoid investigation has also identified different ways by which cannabinoids are able to interact with these cells, modify their functions, alter their communication with neurons and impact behavior. In this review, we will describe the expression of different endocannabinoid system members in astrocytes. Moreover, we will relate the latest findings regarding cannabinoid modulation of some of the most relevant astroglial functions, namely calcium (Ca2+ ) dynamics, gliotransmission, metabolism, and inflammation.
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Affiliation(s)
- Abel Eraso‐Pichot
- U1215 Neurocentre MagendieInstitut national de la santé et de la recherche médicale (INSERM)BordeauxFrance,University of BordeauxBordeauxFrance
| | - Sandrine Pouvreau
- U1215 Neurocentre MagendieInstitut national de la santé et de la recherche médicale (INSERM)BordeauxFrance,University of BordeauxBordeauxFrance
| | - Alexandre Olivera‐Pinto
- U1215 Neurocentre MagendieInstitut national de la santé et de la recherche médicale (INSERM)BordeauxFrance,University of BordeauxBordeauxFrance
| | - Paula Gomez‐Sotres
- U1215 Neurocentre MagendieInstitut national de la santé et de la recherche médicale (INSERM)BordeauxFrance,University of BordeauxBordeauxFrance
| | - Urszula Skupio
- U1215 Neurocentre MagendieInstitut national de la santé et de la recherche médicale (INSERM)BordeauxFrance,University of BordeauxBordeauxFrance
| | - Giovanni Marsicano
- U1215 Neurocentre MagendieInstitut national de la santé et de la recherche médicale (INSERM)BordeauxFrance,University of BordeauxBordeauxFrance
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3
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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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Dias L, Madeira D, Dias R, Tomé ÂR, Cunha RA, Agostinho P. Aβ 1-42 peptides blunt the adenosine A 2A receptor-mediated control of the interplay between P 2X 7 and P 2Y 1 receptors mediated calcium responses in astrocytes. Cell Mol Life Sci 2022; 79:457. [PMID: 35907034 PMCID: PMC11071907 DOI: 10.1007/s00018-022-04492-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 06/22/2022] [Accepted: 07/15/2022] [Indexed: 12/21/2022]
Abstract
The contribution of astrocytes to Alzheimer's disease (AD) is still ill defined. AD involves an abnormal accumulation of amyloid-β peptides (Aβ) and increased production of danger signals such as ATP. ATP can direct or indirectly, through its metabolism into adenosine, trigger adaptive astrocytic responses resulting from intracellular Ca2+ oscillations. AD also triggers an upregulation of astrocytic adenosine A2A receptors (A2AR), which blockade prevents memory dysfunction in AD. We now investigated how Aβ peptides affect ATP-mediated Ca2+ responses in astrocytes measured by fluorescence live-cell imaging and whether A2AR control astrocytic Ca2+ responses mediated by ATP receptors, mainly P2X7R and P2Y1R. In primary cultures of rat astrocytes exposed to Aβ1-42, ATP-evoked Ca2+ responses had a lower amplitude but a longer duration than in control astrocytes and involved P2X7R and P2Y1R, the former potentiating the later. Moreover, Aβ1-42 exposure increased protein levels of P2Y1R in astrocytes. A2AR antagonism with SCH58261 controlled in a protein kinase A-dependent manner both P2X7R- and P2Y1R-mediated Ca2+ responses in astrocytes. The interplay between these purinoceptors in astrocytes was blunted upon exposure to Aβ1-42. These findings uncover the ability of A2AR to regulate the inter-twinned P2X7R- and P2Y1R-mediated Ca2+ dynamics in astrocytes, which is disrupted in conditions of early AD.
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Affiliation(s)
- Liliana Dias
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Rua Larga, Polo I FMUC, 1st Floor, 3004-504, Coimbra, Portugal
- Faculty of Medicine, University of Coimbra, Rua Larga, Polo I FMUC, 1st Floor, 3004-504, Coimbra, Portugal
| | - Daniela Madeira
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Rua Larga, Polo I FMUC, 1st Floor, 3004-504, Coimbra, Portugal
- Faculty of Medicine, University of Coimbra, Rua Larga, Polo I FMUC, 1st Floor, 3004-504, Coimbra, Portugal
| | - Rafael Dias
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Rua Larga, Polo I FMUC, 1st Floor, 3004-504, Coimbra, Portugal
| | - Ângelo R Tomé
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Rua Larga, Polo I FMUC, 1st Floor, 3004-504, Coimbra, Portugal
- Department of Life Sciences, Faculty of Sciences and Technology, University of Coimbra, Coimbra, Portugal
| | - Rodrigo A Cunha
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Rua Larga, Polo I FMUC, 1st Floor, 3004-504, Coimbra, Portugal
- Faculty of Medicine, University of Coimbra, Rua Larga, Polo I FMUC, 1st Floor, 3004-504, Coimbra, Portugal
| | - Paula Agostinho
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Rua Larga, Polo I FMUC, 1st Floor, 3004-504, Coimbra, Portugal.
- Faculty of Medicine, University of Coimbra, Rua Larga, Polo I FMUC, 1st Floor, 3004-504, Coimbra, Portugal.
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5
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Bistability and Chaos Emergence in Spontaneous Dynamics of Astrocytic Calcium Concentration. MATHEMATICS 2022. [DOI: 10.3390/math10081337] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In this work, we consider a mathematical model describing spontaneous calcium signaling in astrocytes. Based on biologically relevant principles, this model simulates experimentally observed calcium oscillations and can predict the emergence of complicated dynamics. Using analytical and numerical analysis, various attracting sets were found and investigated. Employing bifurcation theory analysis, we examined steady state solutions, bistability, simple and complicated periodic limit cycles and also chaotic attractors. We found that astrocytes possess a variety of complex dynamical modes, including chaos and multistability, that can further provide different modulations of neuronal circuits, enhancing their plasticity and flexibility.
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Di Castro MA, Volterra A. Astrocyte control of the entorhinal cortex-dentate gyrus circuit: Relevance to cognitive processing and impairment in pathology. Glia 2021; 70:1536-1553. [PMID: 34904753 PMCID: PMC9299993 DOI: 10.1002/glia.24128] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Revised: 11/28/2021] [Accepted: 11/30/2021] [Indexed: 12/20/2022]
Abstract
The entorhinal cortex-dentate gyrus circuit is centrally involved in memory processing conveying to the hippocampus spatial and nonspatial context information via, respectively, medial and lateral perforant path (MPP and LPP) excitatory projections onto dentate granule cells (GCs). Here, we review work of several years from our group showing that astrocytes sense local synaptic transmission and exert in turn a presynaptic control at PP-GC synapses. Modulation of neurotransmitter release probability by astrocytes sets basal synaptic strength and dynamic range for long-term potentiation of PP-GC synapses. Intriguingly, this astrocyte control is circuit-specific, being present only at MPP-GC (not LPP-GC) synapses, which selectively express atypical presynaptic N-methyl-D-aspartate receptors (NMDAR) suitable to activation by astrocyte-released glutamate. Moreover, the astrocytic control is peculiarly dependent on the cytokine TNFα, which at constitutive levels acts as a gating factor for the astrocyte signaling. During inflammation/infection processes, increased levels of TNFα lead to uncontrolled astrocyte glutamate release, altered PP-GC circuit processing and, ultimately, impaired contextual memory performance. The TNFα-dependent pathological switch of the synaptic control from astrocytes and its deleterious consequences are observed in animal models of HIV brain infection and multiple sclerosis, conditions both known to cause cognitive disturbances in up to 50% of patients. The review also discusses open issues related to the identified astrocytic pathway: its role in contextual memory processing, potential damaging role in Alzheimer's disease, the existence of vesicular glutamate release from DG astrocytes, and the possible synaptic-like connectivity between astrocytic output sites and PP receptive sites.
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Affiliation(s)
- Maria Amalia Di Castro
- Department of Fundamental Neuroscience, University of Lausanne, Lausanne, Switzerland.,Department of Physiology and Pharmacology, Sapienza University of Rome, Rome, Italy
| | - Andrea Volterra
- Department of Fundamental Neuroscience, University of Lausanne, Lausanne, Switzerland
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7
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Caudal LC, Gobbo D, Scheller A, Kirchhoff F. The Paradox of Astroglial Ca 2 + Signals at the Interface of Excitation and Inhibition. Front Cell Neurosci 2020; 14:609947. [PMID: 33324169 PMCID: PMC7726216 DOI: 10.3389/fncel.2020.609947] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Accepted: 11/03/2020] [Indexed: 12/15/2022] Open
Abstract
Astroglial networks constitute a non-neuronal communication system in the brain and are acknowledged modulators of synaptic plasticity. A sophisticated set of transmitter receptors in combination with distinct secretion mechanisms enables astrocytes to sense and modulate synaptic transmission. This integrative function evolved around intracellular Ca2+ signals, by and large considered as the main indicator of astrocyte activity. Regular brain physiology meticulously relies on the constant reciprocity of excitation and inhibition (E/I). Astrocytes are metabolically, physically, and functionally associated to the E/I convergence. Metabolically, astrocytes provide glutamine, the precursor of both major neurotransmitters governing E/I in the central nervous system (CNS): glutamate and γ-aminobutyric acid (GABA). Perisynaptic astroglial processes are structurally and functionally associated with the respective circuits throughout the CNS. Astonishingly, in astrocytes, glutamatergic as well as GABAergic inputs elicit similar rises in intracellular Ca2+ that in turn can trigger the release of glutamate and GABA as well. Paradoxically, as gliotransmitters, these two molecules can thus strengthen, weaken or even reverse the input signal. Therefore, the net impact on neuronal network function is often convoluted and cannot be simply predicted by the nature of the stimulus itself. In this review, we highlight the ambiguity of astrocytes on discriminating and affecting synaptic activity in physiological and pathological state. Indeed, aberrant astroglial Ca2+ signaling is a key aspect of pathological conditions exhibiting compromised network excitability, such as epilepsy. Here, we gather recent evidence on the complexity of astroglial Ca2+ signals in health and disease, challenging the traditional, neuro-centric concept of segregating E/I, in favor of a non-binary, mutually dependent perspective on glutamatergic and GABAergic transmission.
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Affiliation(s)
- Laura C Caudal
- Department of Molecular Physiology, Center for Integrative Physiology and Molecular Medicine, University of Saarland, Homburg, Germany
| | - Davide Gobbo
- Department of Molecular Physiology, Center for Integrative Physiology and Molecular Medicine, University of Saarland, Homburg, Germany
| | - Anja Scheller
- Department of Molecular Physiology, Center for Integrative Physiology and Molecular Medicine, University of Saarland, Homburg, Germany
| | - Frank Kirchhoff
- Department of Molecular Physiology, Center for Integrative Physiology and Molecular Medicine, University of Saarland, Homburg, Germany
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8
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Schmidt E, Oheim M. Infrared Excitation Induces Heating and Calcium Microdomain Hyperactivity in Cortical Astrocytes. Biophys J 2020; 119:2153-2165. [PMID: 33130118 DOI: 10.1016/j.bpj.2020.10.027] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 10/01/2020] [Accepted: 10/07/2020] [Indexed: 11/16/2022] Open
Abstract
Unraveling how neural networks process and represent sensory information and how these cellular signals instruct behavioral output is a main goal in neuroscience. Two-photon activation of optogenetic actuators and calcium (Ca2+) imaging with genetically encoded indicators allow, respectively, the all-optical stimulation and readout of activity from genetically identified cell populations. However, these techniques locally expose the brain to high near-infrared light doses, raising the concern of light-induced adverse effects on the biology under study. Combining 2P imaging of Ca2+ transients in GCaMP6f-expressing cortical astrocytes and unbiased machine-based event detection, we demonstrate the subtle build-up of aberrant microdomain Ca2+ transients in the fine astroglial processes that depended on the average rather than peak laser power. Illumination conditions routinely being used in biological 2P microscopy (920-nm excitation, ∼100-fs, and ∼10 mW average power) increased the frequency of microdomain Ca2+ events but left their amplitude, area, and duration largely unchanged. Ca2+ transients in the otherwise silent soma were secondary to this peripheral hyperactivity that occurred without overt morphological damage. Continuous-wave (nonpulsed) 920-nm illumination at the same average power was as damaging as femtosecond pulses, unraveling the dominance of a heating-mediated damage mechanism. In an astrocyte-specific inositol 3-phosphate receptor type-2 knockout mouse, near-infrared light-induced Ca2+ microdomains persisted in the small processes, underpinning their resemblance to physiological inositol 3-phosphate receptor type-2-independent Ca2+ signals, whereas somatic hyperactivity was abolished. We conclude that, contrary to what has generally been believed in the field, shorter pulses and lower average power can help to alleviate damage and allow for longer recording windows at 920 nm.
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Affiliation(s)
- Elke Schmidt
- Université de Paris, SPPIN - Saints-Pères Paris Institute for the Neurosciences, CNRS, Paris, France
| | - Martin Oheim
- Université de Paris, SPPIN - Saints-Pères Paris Institute for the Neurosciences, CNRS, Paris, France.
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9
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Semyanov A, Henneberger C, Agarwal A. Making sense of astrocytic calcium signals — from acquisition to interpretation. Nat Rev Neurosci 2020; 21:551-564. [DOI: 10.1038/s41583-020-0361-8] [Citation(s) in RCA: 79] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/29/2020] [Indexed: 12/31/2022]
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10
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Structural basis of astrocytic Ca 2+ signals at tripartite synapses. Nat Commun 2020; 11:1906. [PMID: 32312988 PMCID: PMC7170846 DOI: 10.1038/s41467-020-15648-4] [Citation(s) in RCA: 86] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Accepted: 03/19/2020] [Indexed: 02/07/2023] Open
Abstract
Astrocytic Ca2+ signals can be fast and local, supporting the idea that astrocytes have the ability to regulate single synapses. However, the anatomical basis of such specific signaling remains unclear, owing to difficulties in resolving the spongiform domain of astrocytes where most tripartite synapses are located. Using 3D-STED microscopy in living organotypic brain slices, we imaged the spongiform domain of astrocytes and observed a reticular meshwork of nodes and shafts that often formed loop-like structures. These anatomical features were also observed in acute hippocampal slices and in barrel cortex in vivo. The majority of dendritic spines were contacted by nodes and their sizes were correlated. FRAP experiments and Ca2+ imaging showed that nodes were biochemical compartments and Ca2+ microdomains. Mapping astrocytic Ca2+ signals onto STED images of nodes and dendritic spines showed they were associated with individual synapses. Here, we report on the nanoscale organization of astrocytes, identifying nodes as a functional astrocytic component of tripartite synapses that may enable synapse-specific communication between neurons and astrocytes. Astrocytic Ca2+ signals can be fast and local, supporting the idea that astrocytes have the ability to regulate single synapses. Here, the authors report the organization of astrocytes at nanoscale level and identify nodes as a functional astrocytic component of tripartite synapses.
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Denizot A, Arizono M, Nägerl UV, Soula H, Berry H. Simulation of calcium signaling in fine astrocytic processes: Effect of spatial properties on spontaneous activity. PLoS Comput Biol 2019; 15:e1006795. [PMID: 31425510 PMCID: PMC6726244 DOI: 10.1371/journal.pcbi.1006795] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Revised: 09/04/2019] [Accepted: 07/08/2019] [Indexed: 12/20/2022] Open
Abstract
Astrocytes, a glial cell type of the central nervous system, have emerged as detectors and regulators of neuronal information processing. Astrocyte excitability resides in transient variations of free cytosolic calcium concentration over a range of temporal and spatial scales, from sub-microdomains to waves propagating throughout the cell. Despite extensive experimental approaches, it is not clear how these signals are transmitted to and integrated within an astrocyte. The localization of the main molecular actors and the geometry of the system, including the spatial organization of calcium channels IP3R, are deemed essential. However, as most calcium signals occur in astrocytic ramifications that are too fine to be resolved by conventional light microscopy, most of those spatial data are unknown and computational modeling remains the only methodology to study this issue. Here, we propose an IP3R-mediated calcium signaling model for dynamics in such small sub-cellular volumes. To account for the expected stochasticity and low copy numbers, our model is both spatially explicit and particle-based. Extensive simulations show that spontaneous calcium signals arise in the model via the interplay between excitability and stochasticity. The model reproduces the main forms of calcium signals and indicates that their frequency crucially depends on the spatial organization of the IP3R channels. Importantly, we show that two processes expressing exactly the same calcium channels can display different types of calcium signals depending on the spatial organization of the channels. Our model with realistic process volume and calcium concentrations successfully reproduces spontaneous calcium signals that we measured in calcium micro-domains with confocal microscopy and predicts that local variations of calcium indicators might contribute to the diversity of calcium signals observed in astrocytes. To our knowledge, this model is the first model suited to investigate calcium dynamics in fine astrocytic processes and to propose plausible mechanisms responsible for their variability.
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Affiliation(s)
- Audrey Denizot
- INRIA, F-69603, Villeurbanne, France
- Univ Lyon, LIRIS, UMR5205 CNRS, F-69621, Villeurbanne, France
| | - Misa Arizono
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, Bordeaux, France
- Interdisciplinary Institute for Neuroscience, CNRS UMR 5297, Bordeaux, France
| | - U. Valentin Nägerl
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, Bordeaux, France
- Interdisciplinary Institute for Neuroscience, CNRS UMR 5297, Bordeaux, France
| | - Hédi Soula
- INRIA, F-69603, Villeurbanne, France
- Univ P&M Curie, CRC, INSERM UMRS 1138, F-75006, Paris, France
| | - Hugues Berry
- INRIA, F-69603, Villeurbanne, France
- Univ Lyon, LIRIS, UMR5205 CNRS, F-69621, Villeurbanne, France
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12
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Semyanov A. Spatiotemporal pattern of calcium activity in astrocytic network. Cell Calcium 2019; 78:15-25. [DOI: 10.1016/j.ceca.2018.12.007] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 12/16/2018] [Accepted: 12/16/2018] [Indexed: 12/22/2022]
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13
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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: 194] [Impact Index Per Article: 38.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 08/01/2017] [Accepted: 08/29/2017] [Indexed: 01/09/2023] Open
Abstract
Astrocytes are highly complex cells with many emerging putative roles in brain function. Of these, gliotransmission (active information transfer from glia to neurons) has probably the widest implications on our understanding of how the brain works: do astrocytes really contribute to information processing within the neural circuitry? "Positive evidence" for this stems from work of multiple laboratories reporting many examples of modulatory chemical signaling from astrocytes to neurons in the timeframe of hundreds of milliseconds to several minutes. This signaling involves, but is not limited to, Ca2+-dependent vesicular transmitter release, and results in a variety of regulatory effects at synapses in many circuits that are abolished by preventing Ca2+ elevations or blocking exocytosis selectively in astrocytes. In striking contradiction, methodologically advanced studies by a few laboratories produced "negative evidence," triggering a heated debate on the actual existence and properties of gliotransmission. In this context, a skeptics' camp arose, eager to dismiss the whole positive evidence based on a number of assumptions behind the negative data, such as the following: (1) deleting a single Ca2+ release pathway (IP3R2) removes all the sources for Ca2+-dependent gliotransmission; (2) stimulating a transgenically expressed Gq-GPCR (MrgA1) mimics the physiological Ca2+ signaling underlying gliotransmitter release; (3) age-dependent downregulation of an endogenous GPCR (mGluR5) questions gliotransmitter release in adulthood; and (4) failure by transcriptome analysis to detect vGluts or canonical synaptic SNAREs in astrocytes proves inexistence/functional irrelevance of vesicular gliotransmitter release. We here discuss how the above assumptions are likely wrong and oversimplistic. In light of the most recent literature, we argue that gliotransmission is a more complex phenomenon than originally thought, possibly consisting of multiple forms and signaling processes, whose correct study and understanding require more sophisticated tools and finer scientific experiments than done until today. Under this perspective, the opposing camps can be reconciled and the field moved forward. Along the path, a more cautious mindset and an attitude to open discussion and mutual respect between opponent laboratories will be good companions.Dual Perspectives Companion Paper: Multiple Lines of Evidence Indicate That Gliotransmission Does Not Occur under Physiological Conditions, by Todd A. Fiacco and Ken D. McCarthy.
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Wu YW, Gordleeva S, Tang X, Shih PY, Dembitskaya Y, Semyanov A. Morphological profile determines the frequency of spontaneous calcium events in astrocytic processes. Glia 2018; 67:246-262. [DOI: 10.1002/glia.23537] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Revised: 08/19/2018] [Accepted: 09/03/2018] [Indexed: 11/08/2022]
Affiliation(s)
- Yu-Wei Wu
- Brain Science Institute (BSI), RIKEN; Wako-shi Saitama Japan
- Institute of Molecular Biology, Academia Sinica; Nankang Taipei Taiwan
| | - Susan Gordleeva
- Institute of Neuroscience, University of Nizhny Novgorod; Nizhny Novgorod Russia
| | - Xiaofang Tang
- Brain Science Institute (BSI), RIKEN; Wako-shi Saitama Japan
| | - Pei-Yu Shih
- Brain Science Institute (BSI), RIKEN; Wako-shi Saitama Japan
| | - Yulia Dembitskaya
- Brain Science Institute (BSI), RIKEN; Wako-shi Saitama Japan
- Institute of Neuroscience, University of Nizhny Novgorod; Nizhny Novgorod Russia
| | - Alexey Semyanov
- Brain Science Institute (BSI), RIKEN; Wako-shi Saitama Japan
- Institute of Neuroscience, University of Nizhny Novgorod; Nizhny Novgorod Russia
- Department of Molecular Neurobiology, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences; Moscow Russia
- All-Russian Research Institute of Medicinal and Aromatic Plants; Moscow Russia
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15
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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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16
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Heredia DJ, Feng CY, Hennig GW, Renden RB, Gould TW. Activity-induced Ca 2+ signaling in perisynaptic Schwann cells of the early postnatal mouse is mediated by P2Y 1 receptors and regulates muscle fatigue. eLife 2018; 7:30839. [PMID: 29384476 PMCID: PMC5798932 DOI: 10.7554/elife.30839] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Accepted: 01/09/2018] [Indexed: 12/28/2022] Open
Abstract
Perisynaptic glial cells respond to neural activity by increasing cytosolic calcium, but the significance of this pathway is unclear. Terminal/perisynaptic Schwann cells (TPSCs) are a perisynaptic glial cell at the neuromuscular junction that respond to nerve-derived substances such as acetylcholine and purines. Here, we provide genetic evidence that activity-induced calcium accumulation in neonatal TPSCs is mediated exclusively by one subtype of metabotropic purinergic receptor. In P2ry1 mutant mice lacking these responses, postsynaptic, rather than presynaptic, function was altered in response to nerve stimulation. This impairment was correlated with a greater susceptibility to activity-induced muscle fatigue. Interestingly, fatigue in P2ry1 mutants was more greatly exacerbated by exposure to high potassium than in control mice. High potassium itself increased cytosolic levels of calcium in TPSCs, a response which was also reduced P2ry1 mutants. These results suggest that activity-induced calcium responses in TPSCs regulate postsynaptic function and muscle fatigue by regulating perisynaptic potassium. A muscle that contracts over and over again will become tired. This can sometimes occur after vigorous exercise, but abnormal muscle fatigue is also a feature of various clinical disorders. These include conditions that affect muscles directly, such as muscular dystrophy, as well as disorders of the motor nerves that control muscles, such as Guillain-Barré syndrome. Nerves make contact with muscles at specialized sites called neuromuscular junctions. Failing to send the correct signals to the muscles at these junctions can lead to muscle fatigue. Studies to date have focused on the role of nerve cells and muscle cells in these communication failures. But there is also a third cell type present at the neuromuscular junction, known as the terminal/perisynaptic Schwann cell (TPSC). Stimulating motor nerves in a way that produces muscle fatigue also activates TPSCs. To investigate whether TPSCs contribute to or counteract muscle fatigue, Heredia et al. studied the responses of these cells at the neuromuscular junctions of young mice. Stimulating motor nerves caused TPSCs to release calcium ions from their internal calcium stores. However, this did not occur in mice that lacked a protein called the P2Y1 receptor. In normal mice, activating the P2Y1 receptor directly also made the TPSCs release calcium. This calcium release in turn prompted the TPSCs to take up potassium ions. Nerve and muscle cells release potassium during intense activity, and removal of potassium by TPSCs helped to prevent muscle fatigue. Therapeutic strategies that make TPSCs release more of their internal calcium stores – and thus increase their potassium uptake – could help ease muscle fatigue. A valuable first step would be to use drugs and genetic techniques to show this effect in mice. The results could then guide the development of corresponding strategies in patients.
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Affiliation(s)
- Dante J Heredia
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, United States
| | - Cheng-Yuan Feng
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, United States
| | - Grant W Hennig
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, United States
| | - Robert B Renden
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, United States
| | - Thomas W Gould
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, United States
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17
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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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18
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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: 916] [Impact Index Per Article: 152.7] [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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19
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Murphy TR, Davila D, Cuvelier N, Young LR, Lauderdale K, Binder DK, Fiacco TA. Hippocampal and Cortical Pyramidal Neurons Swell in Parallel with Astrocytes during Acute Hypoosmolar Stress. Front Cell Neurosci 2017; 11:275. [PMID: 28979186 PMCID: PMC5611379 DOI: 10.3389/fncel.2017.00275] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 08/28/2017] [Indexed: 01/08/2023] Open
Abstract
Normal nervous system function is critically dependent on the balance of water and ions in the extracellular space (ECS). Pathological reduction in brain interstitial osmolarity results in osmotically-driven flux of water into cells, causing cellular edema which reduces the ECS and increases neuronal excitability and risk of seizures. Astrocytes are widely considered to be particularly susceptible to cellular edema due to selective expression of the water channel aquaporin-4 (AQP4). The apparent resistance of pyramidal neurons to osmotic swelling has been attributed to lack of functional water channels. In this study we report rapid volume changes in CA1 pyramidal cells in hypoosmolar ACSF (hACSF) that are equivalent to volume changes in astrocytes across a variety of conditions. Astrocyte and neuronal swelling was significant within 1 min of exposure to 17 or 40% hACSF, was rapidly reversible upon return to normosmolar ACSF, and repeatable upon re-exposure to hACSF. Neuronal swelling was not an artifact of patch clamp, occurred deep in tissue, was similar at physiological vs. room temperature, and occurred in both juvenile and adult hippocampal slices. Neuronal swelling was neither inhibited by TTX, nor by antagonists of NMDA or AMPA receptors, suggesting that it was not occurring as a result of excitotoxicity. Surprisingly, genetic deletion of AQP4 did not inhibit, but rather augmented, astrocyte swelling in severe hypoosmolar conditions. Taken together, our results indicate that neurons are not osmoresistant as previously reported, and that osmotic swelling is driven by an AQP4-independent mechanism.
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Affiliation(s)
- Thomas R. Murphy
- Division of Biomedical Sciences, School of Medicine, University of California, RiversideRiverside, CA, United States
- Center for Glial-Neuronal Interactions, University of California, RiversideRiverside, CA, United States
| | - David Davila
- Center for Glial-Neuronal Interactions, University of California, RiversideRiverside, CA, United States
- Department of Cell Biology and Neuroscience, University of California, RiversideRiverside, CA, United States
| | - Nicholas Cuvelier
- Center for Glial-Neuronal Interactions, University of California, RiversideRiverside, CA, United States
- Department of Cell Biology and Neuroscience, University of California, RiversideRiverside, CA, United States
| | - Leslie R. Young
- Center for Glial-Neuronal Interactions, University of California, RiversideRiverside, CA, United States
- Department of Cell Biology and Neuroscience, University of California, RiversideRiverside, CA, United States
| | - Kelli Lauderdale
- Division of Biomedical Sciences, School of Medicine, University of California, RiversideRiverside, CA, United States
- Center for Glial-Neuronal Interactions, University of California, RiversideRiverside, CA, United States
| | - Devin K. Binder
- Division of Biomedical Sciences, School of Medicine, University of California, RiversideRiverside, CA, United States
- Center for Glial-Neuronal Interactions, University of California, RiversideRiverside, CA, United States
| | - Todd A. Fiacco
- Center for Glial-Neuronal Interactions, University of California, RiversideRiverside, CA, United States
- Department of Cell Biology and Neuroscience, University of California, RiversideRiverside, CA, United States
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20
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Oheim M, Schmidt E, Hirrlinger J. Local energy on demand: Are 'spontaneous' astrocytic Ca 2+-microdomains the regulatory unit for astrocyte-neuron metabolic cooperation? Brain Res Bull 2017; 136:54-64. [PMID: 28450076 DOI: 10.1016/j.brainresbull.2017.04.011] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 03/18/2017] [Accepted: 04/21/2017] [Indexed: 12/21/2022]
Abstract
Astrocytes are a neural cell type critically involved in maintaining brain energy homeostasis as well as signaling. Like neurons, astrocytes are a heterogeneous cell population. Cortical astrocytes show a complex morphology with a highly branched aborization and numerous fine processes ensheathing the synapses of neighboring neurons, and typically extend one process connecting to blood vessels. Recent studies employing genetically encoded fluorescent calcium (Ca2+) indicators have described 'spontaneous' localized Ca2+-transients in the astrocyte periphery that occur asynchronously, independently of signals in other parts of the cells, and that do not involve somatic Ca2+ transients; however, neither it is known whether these Ca2+-microdomains occur at or near neuronal synapses nor have their molecular basis nor downstream effector(s) been identified. In addition to Ca2+ microdomains, sodium (Na+) transients occur in astrocyte subdomains, too, most likely as a consequence of Na+ co-transport with the neurotransmitter glutamate, which also regulates mitochondrial movements locally - as do cytoplasmic Ca2+ levels. In this review, we cover various aspects of these local signaling events and discuss how structural and biophysical properties of astrocytes might foster such compartmentation. Astrocytes metabolically interact with neurons by providing energy substrates to active neurons. As a single astrocyte branch covers hundreds to thousands of synapses, it is tempting to speculate that these metabolic interactions could occur localized to specific subdomains of astrocytes, perhaps even at the level of small groups of synapses. We discuss how astrocytic metabolism might be regulated at this scale and which signals might contribute to its regulation. We speculate that the astrocytic structures that light up transiently as Ca2+-microdomains might be the functional units of astrocytes linking signaling and metabolic processes to adapt astrocytic function to local energy demands. The understanding of these local regulatory and metabolic interactions will be fundamental to fully appreciate the complexity of brain energy homeostasis as well as its failure in disease and may shed new light on the controversy about neuron-glia bi-directional signaling at the tripartite synapse.
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Affiliation(s)
- Martin Oheim
- CNRS UMR 8118, Brain Physiology Laboratory, F-75006 Paris, France; Fédération de Recherche en Neurosciences FR3636, Faculté de Sciences Fondamentales et Biomédicales, Université Paris Descartes, PRES Université Sorbonne Paris Cité (USPC), F-75006 Paris, France.
| | - Elke Schmidt
- CNRS UMR 8118, Brain Physiology Laboratory, F-75006 Paris, France; Fédération de Recherche en Neurosciences FR3636, Faculté de Sciences Fondamentales et Biomédicales, Université Paris Descartes, PRES Université Sorbonne Paris Cité (USPC), F-75006 Paris, France
| | - Johannes Hirrlinger
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, D-04103 Leipzig, Germany; Dept. of Neurogenetics, Max-Planck-Institute for Experimental Medicine, D-37075 Göttingen, Germany.
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21
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Pappas AC, Koide M, Wellman GC. Purinergic signaling triggers endfoot high-amplitude Ca2+ signals and causes inversion of neurovascular coupling after subarachnoid hemorrhage. J Cereb Blood Flow Metab 2016; 36:1901-1912. [PMID: 27207166 PMCID: PMC5094310 DOI: 10.1177/0271678x16650911] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 04/25/2016] [Indexed: 01/09/2023]
Abstract
Neurovascular coupling supports brain metabolism by matching focal increases in neuronal activity with local arteriolar dilation. Previously, we demonstrated that an emergence of spontaneous endfoot high-amplitude Ca2+ signals (eHACSs) caused a pathologic shift in neurovascular coupling from vasodilation to vasoconstriction in brain slices obtained from subarachnoid hemorrhage model animals. Extracellular purine nucleotides (e.g., ATP) can trigger astrocyte Ca2+ oscillations and may be elevated following subarachnoid hemorrhage. Here, the role of purinergic signaling in subarachnoid hemorrhage-induced eHACSs and inversion of neurovascular coupling was examined by imaging parenchymal arteriolar diameter and astrocyte Ca2+ signals in rat brain slices using two-photon fluorescent and infrared-differential interference contrast microscopy. We report that broad-spectrum inhibition of purinergic (P2) receptors using suramin blocked eHACSs and restored vasodilatory neurovascular coupling after subarachnoid hemorrhage. Importantly, eHACSs were also abolished using a cocktail of inhibitors targeting Gq-coupled P2Y receptors. Further, activation of P2Y receptors in brain slices from un-operated animals triggered high-amplitude Ca2+ events resembling eHACSs and disrupted neurovascular coupling. Neither tetrodotoxin nor bafilomycin A1 affected eHACSs suggesting that purine nucleotides are not released by ongoing neurotransmission and/or vesicular release after subarachnoid hemorrhage. These results indicate that purinergic signaling via P2Y receptors contributes to subarachnoid hemorrhage-induced eHACSs and inversion of neurovascular coupling.
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Affiliation(s)
- Anthony C Pappas
- Department of Pharmacology, University of Vermont, Burlington, VT, USA
| | - Masayo Koide
- Department of Pharmacology, University of Vermont, Burlington, VT, USA
| | - George C Wellman
- Department of Pharmacology, University of Vermont, Burlington, VT, USA .,Department of Surgery, Division of Neurosurgery, University of Vermont, Burlington, VT, USA
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22
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Astrocyte-mediated metaplasticity in the hippocampus: Help or hindrance? Neuroscience 2015; 309:113-24. [DOI: 10.1016/j.neuroscience.2015.08.035] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Revised: 08/03/2015] [Accepted: 08/17/2015] [Indexed: 12/22/2022]
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23
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Asada A, Ujita S, Nakayama R, Oba S, Ishii S, Matsuki N, Ikegaya Y. Subtle modulation of ongoing calcium dynamics in astrocytic microdomains by sensory inputs. Physiol Rep 2015; 3:3/10/e12454. [PMID: 26438730 PMCID: PMC4632942 DOI: 10.14814/phy2.12454] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Astrocytes communicate with neurons through their processes. In vitro experiments have demonstrated that astrocytic processes exhibit calcium activity both spontaneously and in response to external stimuli; however, it has not been fully determined whether and how astrocytic subcellular domains respond to sensory input in vivo. We visualized the calcium signals in astrocytes in the primary visual cortex of awake, head-fixed mice. Bias-free analyses of two-photon imaging data revealed that calcium activity prevailed in astrocytic subcellular domains, was coordinated with variable spot-like patterns, and was dominantly spontaneous. Indeed, visual stimuli did not affect the frequency of calcium domain activity, but it increased the domain size, whereas tetrodotoxin reduced the sizes of spontaneous calcium domains and abolished their visual responses. The “evoked” domain activity exhibited no apparent orientation tuning and was distributed unevenly within the cell, constituting multiple active hotspots that were often also recruited in spontaneous activity. The hotspots existed dominantly in the somata and endfeet of astrocytes. Thus, the patterns of astrocytic calcium dynamics are intrinsically constrained and are subject to minor but significant modulation by sensory input.
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Affiliation(s)
- Akiko Asada
- Graduate School of Pharmaceutical Sciences University of Tokyo, Tokyo, Japan
| | - Sakiko Ujita
- Graduate School of Pharmaceutical Sciences University of Tokyo, Tokyo, Japan
| | - Ryota Nakayama
- Graduate School of Pharmaceutical Sciences University of Tokyo, Tokyo, Japan
| | - Shigeyuki Oba
- Graduate School of Informatics Kyoto University, Kyoto, Japan
| | - Shin Ishii
- Graduate School of Informatics Kyoto University, Kyoto, Japan
| | - Norio Matsuki
- Graduate School of Pharmaceutical Sciences University of Tokyo, Tokyo, Japan
| | - Yuji Ikegaya
- Graduate School of Pharmaceutical Sciences University of Tokyo, Tokyo, Japan Center for Information and Neural Networks, Suita City Osaka, Japan
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24
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Panatier A, Robitaille R. Astrocytic mGluR5 and the tripartite synapse. Neuroscience 2015; 323:29-34. [PMID: 25847307 DOI: 10.1016/j.neuroscience.2015.03.063] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Revised: 03/19/2015] [Accepted: 03/26/2015] [Indexed: 11/27/2022]
Abstract
In the brain, astrocytes occupy a key position between vessels and synapses. Among their numerous functions, these glial cells are key partners of neurons during synaptic transmission. Astrocytes detect transmitter release through receptors and transporters at the level of their processes, which are in close proximity to the tow neuronal elements of synapses. In response to transmitter-mediated activation, glial cells in turn regulate synaptic transmission and neuronal excitability. This process has been reported to involve several glial receptors. One of the best known of such receptors is the metabotropic glutamatergic receptor subtype 5 (mGluR5). In the present review we will discuss the implication of mGluR5s as detectors of synaptic transmission. In particular, we will discuss how the functional properties and localization of these receptors permit the detection of the synaptic signal in a defined temporal window and a given spatial area around the synapse. Furthermore, we will review the impact of their activation on synaptic transmission.
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Affiliation(s)
- A Panatier
- Neurocentre Magendie, INSERM U862, Bordeaux, France; Université de Bordeaux, Bordeaux, France.
| | - R Robitaille
- Groupe de recherche sur le système nerveux central, Université de Montréal, Canada; Département de neurosciences, Université de Montréal, PO Box 6128, Station centre-ville, Montréal, Québec H3C 3J7, Canada
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25
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Astrocytic Gq-GPCR-linked IP3R-dependent Ca2+ signaling does not mediate neurovascular coupling in mouse visual cortex in vivo. J Neurosci 2014; 34:13139-50. [PMID: 25253859 DOI: 10.1523/jneurosci.2591-14.2014] [Citation(s) in RCA: 149] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Local blood flow is modulated in response to changing patterns of neuronal activity (Roy and Sherrington, 1890), a process termed neurovascular coupling. It has been proposed that the central cellular pathway driving this process is astrocytic Gq-GPCR-linked IP3R-dependent Ca(2+) signaling, though in vivo tests of this hypothesis are largely lacking. We examined the impact of astrocytic Gq-GPCR and IP3R-dependent Ca(2+) signaling on cortical blood flow in awake, lightly sedated, responsive mice using multiphoton laser-scanning microscopy and novel genetic tools that enable the selective manipulation of astrocytic signaling pathways in vivo. Selective stimulation of astrocytic Gq-GPCR cascades and downstream Ca(2+) signaling with the hM3Dq DREADD (designer receptors exclusively activated by designer drugs) designer receptor system was insufficient to modulate basal cortical blood flow. We found no evidence of observable astrocyte endfeet Ca(2+) elevations following physiological visual stimulation despite robust dilations of adjacent arterioles using cyto-GCaMP3 and Lck-GCaMP6s, the most sensitive Ca(2+) indicator available. Astrocytic Ca(2+) elevations could be evoked when inducing the startle response with unexpected air puffs. However, startle-induced astrocytic Ca(2+) signals did not precede corresponding startle-induced hemodynamic changes. Further, neurovascular coupling was intact in lightly sedated, responsive mice genetically lacking astrocytic IP3R-dependent Ca(2+) signaling (IP3R2 KO). These data demonstrate that astrocytic Gq-GPCR-linked IP3R-dependent Ca(2+) signaling does not mediate neurovascular coupling in visual cortex of awake, lightly sedated, responsive mice.
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26
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Liu H, Zhou B, Yan W, Lei Z, Zhao X, Zhang K, Guo A. Astrocyte-like glial cells physiologically regulate olfactory processing through the modification of ORN-PN synaptic strength in Drosophila. Eur J Neurosci 2014; 40:2744-54. [PMID: 24964821 DOI: 10.1111/ejn.12646] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Revised: 04/26/2014] [Accepted: 05/02/2014] [Indexed: 11/29/2022]
Abstract
Astrocyte-like glial cells are abundant in the central nervous system of adult Drosophila and exhibit morphology similar to astrocytes of mammals. Previous evidence has shown that astrocyte-like glial cells are strongly associated with synapses in the antennal lobe (AL), the first relay of the olfactory system, where olfactory receptor neurons (ORNs) transmit information into projection neurons (PNs). However, the function of astrocyte-like glia in the AL remains obscure. In this study, using in vivo calcium imaging, we found that astrocyte-like glial cells exhibited spontaneous microdomain calcium elevations. Using simultaneous manipulation of glial activity and monitoring of neuronal function, we found that the astrocyte-like glial activation, but not ensheathing glial activation, could inhibit odor-evoked responses of PNs. Ensheathing glial cells are another subtype of glia, and are of functional importance in the AL. Electrophysiological experiments indicated that astrocyte-like glial activation decreased the amplitude and slope of excitatory postsynaptic potentials evoked through electrical stimulation of the antennal nerve. These results suggest that astrocyte-like glial cells may regulate olfactory processing through negative regulation of ORN-PN synaptic strength. Beyond the antennal lobe we observed astrocyte-like glial spontaneous calcium activities in the ventromedial protocerebrum, indicating that astrocyte-like glial spontaneous calcium elevations might be general in the adult fly brain. Overall, our study demonstrates a new function for astrocyte-like glial cells in the physiological modulation of olfactory information transmission, possibly through regulating ORN-PN synapse strength.
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Affiliation(s)
- He Liu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, Shanghai, China; University of Chinese Academy of Sciences, Shanghai, China
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