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Salmon CK, Syed TA, Kacerovsky JB, Alivodej N, Schober AL, Sloan TFW, Pratte MT, Rosen MP, Green M, Chirgwin-Dasgupta A, Mehta S, Jilani A, Wang Y, Vali H, Mandato CA, Siddiqi K, Murai KK. Organizing principles of astrocytic nanoarchitecture in the mouse cerebral cortex. Curr Biol 2023; 33:957-972.e5. [PMID: 36805126 DOI: 10.1016/j.cub.2023.01.043] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 12/01/2022] [Accepted: 01/20/2023] [Indexed: 02/18/2023]
Abstract
Astrocytes are increasingly understood to be important regulators of central nervous system (CNS) function in health and disease; yet, we have little quantitative understanding of their complex architecture. While broad categories of astrocytic structures are known, the discrete building blocks that compose them, along with their geometry and organizing principles, are poorly understood. Quantitative investigation of astrocytic complexity is impeded by the absence of high-resolution datasets and robust computational approaches to analyze these intricate cells. To address this, we produced four ultra-high-resolution datasets of mouse cerebral cortex using serial electron microscopy and developed astrocyte-tailored computer vision methods for accurate structural analysis. We unearthed specific anatomical building blocks, structural motifs, connectivity hubs, and hierarchical organizations of astrocytes. Furthermore, we found that astrocytes interact with discrete clusters of synapses and that astrocytic mitochondria are distributed to lie closer to larger clusters of synapses. Our findings provide a geometrically principled, quantitative understanding of astrocytic nanoarchitecture and point to an unexpected level of complexity in how astrocytes interact with CNS microanatomy.
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Affiliation(s)
- Christopher K Salmon
- Centre for Research in Neuroscience, Department of Neurology & Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, 1650 Cedar Avenue, Montreal, QC H3G 1A4, Canada
| | - Tabish A Syed
- School of Computer Science and Centre for Intelligent Machines, McGill University, 3480 Rue University, Montreal, QC H3A 2A7, Canada; MILA - Québec AI Institute, 6666 Rue Saint-Urbain, Montreal, QC H2S 3H1, Canada
| | - J Benjamin Kacerovsky
- Centre for Research in Neuroscience, Department of Neurology & Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, 1650 Cedar Avenue, Montreal, QC H3G 1A4, Canada
| | - Nensi Alivodej
- Centre for Research in Neuroscience, Department of Neurology & Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, 1650 Cedar Avenue, Montreal, QC H3G 1A4, Canada
| | - Alexandra L Schober
- Centre for Research in Neuroscience, Department of Neurology & Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, 1650 Cedar Avenue, Montreal, QC H3G 1A4, Canada
| | | | - Michael T Pratte
- Centre for Research in Neuroscience, Department of Neurology & Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, 1650 Cedar Avenue, Montreal, QC H3G 1A4, Canada
| | - Michael P Rosen
- Centre for Research in Neuroscience, Department of Neurology & Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, 1650 Cedar Avenue, Montreal, QC H3G 1A4, Canada
| | - Miranda Green
- Centre for Research in Neuroscience, Department of Neurology & Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, 1650 Cedar Avenue, Montreal, QC H3G 1A4, Canada
| | - Adario Chirgwin-Dasgupta
- Centre for Research in Neuroscience, Department of Neurology & Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, 1650 Cedar Avenue, Montreal, QC H3G 1A4, Canada
| | - Shaurya Mehta
- School of Computer Science and Centre for Intelligent Machines, McGill University, 3480 Rue University, Montreal, QC H3A 2A7, Canada
| | - Affan Jilani
- School of Computer Science and Centre for Intelligent Machines, McGill University, 3480 Rue University, Montreal, QC H3A 2A7, Canada
| | - Yanan Wang
- School of Computer Science and Centre for Intelligent Machines, McGill University, 3480 Rue University, Montreal, QC H3A 2A7, Canada
| | - Hojatollah Vali
- Department of Anatomy & Cell Biology, McGill University, 3640 Rue University, Montreal, QC H3A 0C7, Canada
| | - Craig A Mandato
- Department of Anatomy & Cell Biology, McGill University, 3640 Rue University, Montreal, QC H3A 0C7, Canada
| | - Kaleem Siddiqi
- School of Computer Science and Centre for Intelligent Machines, McGill University, 3480 Rue University, Montreal, QC H3A 2A7, Canada; MILA - Québec AI Institute, 6666 Rue Saint-Urbain, Montreal, QC H2S 3H1, Canada.
| | - Keith K Murai
- Centre for Research in Neuroscience, Department of Neurology & Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, 1650 Cedar Avenue, Montreal, QC H3G 1A4, Canada.
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Zhou Y, Ding M, Nagel G, Konrad KR, Gao S. Advances and prospects of rhodopsin-based optogenetics in plant research. PLANT PHYSIOLOGY 2021; 187:572-589. [PMID: 35237820 PMCID: PMC8491038 DOI: 10.1093/plphys/kiab338] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Accepted: 07/05/2021] [Indexed: 05/20/2023]
Abstract
Microbial rhodopsins have advanced optogenetics since the discovery of channelrhodopsins almost two decades ago. During this time an abundance of microbial rhodopsins has been discovered, engineered, and improved for studies in neuroscience and other animal research fields. Optogenetic applications in plant research, however, lagged largely behind. Starting with light-regulated gene expression, optogenetics has slowly expanded into plant research. The recently established all-trans retinal production in plants now enables the use of many microbial opsins, bringing extra opportunities to plant research. In this review, we summarize the recent advances of rhodopsin-based plant optogenetics and provide a perspective for future use, combined with fluorescent sensors to monitor physiological parameters.
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Affiliation(s)
- Yang Zhou
- Institute of Physiology, Department of Neurophysiology, Biocenter, University of Wuerzburg, Wuerzburg 97070, Germany
| | - Meiqi Ding
- Institute for Molecular Plant Physiology and Biophysics, Julius-von-Sachs-Institute, Biocenter, University of Wuerzburg, Wuerzburg 97082, Germany
| | - Georg Nagel
- Institute of Physiology, Department of Neurophysiology, Biocenter, University of Wuerzburg, Wuerzburg 97070, Germany
| | - Kai R. Konrad
- Institute for Molecular Plant Physiology and Biophysics, Julius-von-Sachs-Institute, Biocenter, University of Wuerzburg, Wuerzburg 97082, Germany
| | - Shiqiang Gao
- Institute of Physiology, Department of Neurophysiology, Biocenter, University of Wuerzburg, Wuerzburg 97070, Germany
- Author for communication:
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Ung K, Huang TW, Lozzi B, Woo J, Hanson E, Pekarek B, Tepe B, Sardar D, Cheng YT, Liu G, Deneen B, Arenkiel BR. Olfactory bulb astrocytes mediate sensory circuit processing through Sox9 in the mouse brain. Nat Commun 2021; 12:5230. [PMID: 34471129 PMCID: PMC8410770 DOI: 10.1038/s41467-021-25444-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Accepted: 08/11/2021] [Indexed: 01/07/2023] Open
Abstract
The role of transcription factors during astrocyte development and their subsequent effects on neuronal development has been well studied. Less is known about astrocytes contributions towards circuits and behavior in the adult brain. Astrocytes play important roles in synaptic development and modulation, however their contributions towards neuronal sensory function and maintenance of neuronal circuit architecture remain unclear. Here, we show that loss of the transcription factor Sox9 results in both anatomical and functional changes in adult mouse olfactory bulb (OB) astrocytes, affecting sensory processing. Indeed, astrocyte-specific deletion of Sox9 in the OB results in decreased odor detection thresholds and discrimination and it is associated with aberrant neuronal sensory response maps. At functional level, loss of astrocytic Sox9 impairs the electrophysiological properties of mitral and tufted neurons. RNA-sequencing analysis reveals widespread changes in the gene expression profiles of OB astrocytes. In particular, we observe reduced GLT-1 expression and consequential alterations in glutamate transport. Our findings reveal that astrocytes are required for physiological sensory processing and we identify astrocytic Sox9 as an essential transcriptional regulator of mature astrocyte function in the mouse OB.
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Affiliation(s)
- Kevin Ung
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX, USA
| | - Teng-Wei Huang
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX, USA
| | - Brittney Lozzi
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX, USA
| | - Junsung Woo
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX, USA
| | - Elizabeth Hanson
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Brandon Pekarek
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Burak Tepe
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX, USA
| | - Debosmita Sardar
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX, USA
| | - Yi-Ting Cheng
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX, USA
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX, USA
| | - Gary Liu
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX, USA
- Medical Scientist Training Program, Baylor College of Medicine, Houston, TX, USA
| | - Benjamin Deneen
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX, USA.
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX, USA.
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA.
- Department of Neurosurgery, Baylor College of Medicine, Houston, TX, USA.
| | - Benjamin R Arenkiel
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX, USA.
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA.
- Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital, Houston, TX, USA.
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Lohr C, Beiersdorfer A, Fischer T, Hirnet D, Rotermund N, Sauer J, Schulz K, Gee CE. Using Genetically Encoded Calcium Indicators to Study Astrocyte Physiology: A Field Guide. Front Cell Neurosci 2021; 15:690147. [PMID: 34177468 PMCID: PMC8226001 DOI: 10.3389/fncel.2021.690147] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Accepted: 05/06/2021] [Indexed: 01/14/2023] Open
Abstract
Ca2+ imaging is the most frequently used technique to study glial cell physiology. While chemical Ca2+ indicators served to visualize and measure changes in glial cell cytosolic Ca2+ concentration for several decades, genetically encoded Ca2+ indicators (GECIs) have become state of the art in recent years. Great improvements have been made since the development of the first GECI and a large number of GECIs with different physical properties exist, rendering it difficult to select the optimal Ca2+ indicator. This review discusses some of the most frequently used GECIs and their suitability for glial cell research.
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Affiliation(s)
- Christian Lohr
- Division of Neurophysiology, University of Hamburg, Hamburg, Germany
| | | | - Timo Fischer
- Division of Neurophysiology, University of Hamburg, Hamburg, Germany
| | - Daniela Hirnet
- Division of Neurophysiology, University of Hamburg, Hamburg, Germany
| | - Natalie Rotermund
- Division of Neurophysiology, University of Hamburg, Hamburg, Germany
| | - Jessica Sauer
- Division of Neurophysiology, University of Hamburg, Hamburg, Germany
| | - Kristina Schulz
- Division of Neurophysiology, University of Hamburg, Hamburg, Germany
| | - Christine E Gee
- Institute of Synaptic Physiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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Mo SY, Bai SS, Xu XX, Liu Y, Fu KY, Sessle BJ, Cao Y, Xie QF. Astrocytes in the rostral ventromedial medulla contribute to the maintenance of oro-facial hyperalgesia induced by late removal of dental occlusal interference. J Oral Rehabil 2021; 49:207-218. [PMID: 34042200 DOI: 10.1111/joor.13211] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 04/29/2021] [Accepted: 05/18/2021] [Indexed: 11/27/2022]
Abstract
BACKGROUND Astrocytes in the rostral ventromedial medulla (RVM) contribute to descending pain modulation, but their role in oro-facial pain induced by persistent experimental dental occlusal interference (PEOI) or following EOI removal (REOI) is unknown. OBJECTIVE To explore the involvement of RVM astrocytes in PEOI-induced oro-facial hyperalgesia or its maintenance following REOI. METHODS Male rats were randomly assigned into five groups: sham-EOI, postoperative day 6 and 14 of PEOI (PEOI 6 d and PEOI 14 d), postoperative day 6 following REOI on day 3 (REOI 3 d) and postoperative day 14 following REOI on day 8 (REOI 8 d). The nociceptive head withdrawal threshold (HWT) and activities of RVM ON- or OFF-cells were recorded before and after intra-RVM astrocyte gap junction blocker carbenoxolone (CBX) microinjection. RVM astrocytes were labelled immunohistochemically with glial fibrillary acidic protein (GFAP) and analysed semi-quantitatively. RESULTS Persistent experimental dental occlusal interference-induced oro-facial hyperalgesia, as reflected in decreased HWTs, was partially inhibited by REOI at day 3 but not at day 8 after EOI placement. Increased GFAP-staining area occurred only in REOI 8 d group in which CBX could inhibit the maintained hyperalgesia; CBX was ineffective in inhibiting hyperalgesia in PEOI 14 d group. OFF-cell activities showed no change, but the spontaneous activity and responses of ON-cells were significantly enhanced that could be suppressed by CBX in REOI 8 d group. CONCLUSION Rostral ventromedial medulla astrocytes may not participate in PEOI-induced oro-facial hyperalgesia or hyperalgesia inhibition by early REOI but are involved in the maintenance of oro-facial hyperalgesia by late REOI.
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Affiliation(s)
- Si-Yi Mo
- Center for Oral and Jaw Functional Diagnosis, Treatment and Research, Department of Prosthodontics, Peking University School and Hospital of Stomatology & National Engineering Laboratory for Digital and Material Technology of Stomatology & Beijing Key Laboratory of Digital Stomatology, Beijing, China
| | - Shan-Shan Bai
- Center for Oral and Jaw Functional Diagnosis, Treatment and Research, Department of Prosthodontics, Peking University School and Hospital of Stomatology & National Engineering Laboratory for Digital and Material Technology of Stomatology & Beijing Key Laboratory of Digital Stomatology, Beijing, China
| | - Xiao-Xiang Xu
- Center for Oral and Jaw Functional Diagnosis, Treatment and Research, Department of Prosthodontics, Peking University School and Hospital of Stomatology & National Engineering Laboratory for Digital and Material Technology of Stomatology & Beijing Key Laboratory of Digital Stomatology, Beijing, China
| | - Yun Liu
- Center for Oral and Jaw Functional Diagnosis, Treatment and Research, Department of Prosthodontics, Peking University School and Hospital of Stomatology & National Engineering Laboratory for Digital and Material Technology of Stomatology & Beijing Key Laboratory of Digital Stomatology, Beijing, China
| | - Kai-Yuan Fu
- Center for TMD & Orofacial Pain, Peking University School & Hospital of Stomatology, Beijing, China
| | - Barry J Sessle
- Faculty of Dentistry, and Department of Physiology, Faculty of Medicine, and Centre for the Study of Pain, University of Toronto, Toronto, ON, Canada
| | - Ye Cao
- Center for Oral and Jaw Functional Diagnosis, Treatment and Research, Department of Prosthodontics, Peking University School and Hospital of Stomatology & National Engineering Laboratory for Digital and Material Technology of Stomatology & Beijing Key Laboratory of Digital Stomatology, Beijing, China
| | - Qiu-Fei Xie
- Center for Oral and Jaw Functional Diagnosis, Treatment and Research, Department of Prosthodontics, Peking University School and Hospital of Stomatology & National Engineering Laboratory for Digital and Material Technology of Stomatology & Beijing Key Laboratory of Digital Stomatology, Beijing, China
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6
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Gao W, Wang Z, Wang H, Li H, Huang C, Shen Y, Ma X, Sun H. Neurons and Astrocytes in Ventrolateral Periaqueductal Gray Contribute to Restraint Water Immersion Stress-Induced Gastric Mucosal Damage via the ERK1/2 Signaling Pathway. Int J Neuropsychopharmacol 2021; 24:666-676. [PMID: 34000028 PMCID: PMC8378083 DOI: 10.1093/ijnp/pyab028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 03/15/2021] [Accepted: 05/12/2021] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND The restraint water immersion stress (RWIS) model includes both psychological and physical stimulation, which may lead to gastrointestinal disorders and cause gastric mucosal damage. The ventrolateral periaqueductal gray (VLPAG) contributes to gastrointestinal function, but whether it is involved in RWIS-induced gastric mucosal damage has not yet been reported. METHODS The expression of glial fibrillary acidic protein, neuronal c-Fos, and phosphorylated extracellular signal regulated kinase 1/2 in the VLPAG after RWIS was assessed using western blotting and immunocytochemical staining methods. Lateral ventricle injection of astrocytic toxin L-a-aminoadipate and treatment with extracellular signal-regulated kinase (ERK)1/2 signaling pathway inhibitor PD98059 were further used to study protein expression and distribution in the VLPAG after RWIS. RESULTS The expression of c-Fos, glial fibrillary acidic protein, and phosphorylated extracellular signal regulated kinase 1/2 in the VLPAG significantly increased following RWIS and peaked at 1 hour after RWIS. Lateral ventricle injection of the astrocytic toxin L-a-aminoadipate significantly alleviated gastric mucosal injury and decreased the activation of neurons and astrocytes. Treatment with the ERK1/2 signaling pathway inhibitor PD98059 obviously suppressed gastric mucosal damage as well as the RWIS-induced activation of neurons and astrocytes in the VLPAG. CONCLUSIONS These results suggested that activation of VLPAG neurons and astrocytes induced by RWIS through the ERK1/2 signaling pathway may play a critical role in RWIS-induced gastric mucosa damage.
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Affiliation(s)
- Wenting Gao
- Key Laboratory of Animal Resistance Biology of Shandong Province, College of Life Science, Shandong Normal University, Jinan, China
| | - Zepeng Wang
- Key Laboratory of Animal Resistance Biology of Shandong Province, College of Life Science, Shandong Normal University, Jinan, China
| | - Hui Wang
- Key Laboratory of Animal Resistance Biology of Shandong Province, College of Life Science, Shandong Normal University, Jinan, China
| | - Huimin Li
- Key Laboratory of Animal Resistance Biology of Shandong Province, College of Life Science, Shandong Normal University, Jinan, China
| | - Chenxu Huang
- Key Laboratory of Animal Resistance Biology of Shandong Province, College of Life Science, Shandong Normal University, Jinan, China
| | - Yangyang Shen
- Key Laboratory of Animal Resistance Biology of Shandong Province, College of Life Science, Shandong Normal University, Jinan, China
| | - Xiaoli Ma
- Research Center of Basic Medicine, Jinan Central Hospital, Cheeloo College of Medicine, Shandong University, Jinan, China,Correspondence: Xiaoli Ma, PhD, Jinan Central Hospital, Cheeloo College of Medicine, Shandong University ()
| | - Haiji Sun
- Key Laboratory of Animal Resistance Biology of Shandong Province, College of Life Science, Shandong Normal University, Jinan, China,Haiji Sun, PhD, College of Life Science, Shandong Normal University ()
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A morphological analysis of activity-dependent myelination and myelin injury in transitional oligodendrocytes. Sci Rep 2021; 11:9588. [PMID: 33953273 PMCID: PMC8099889 DOI: 10.1038/s41598-021-88887-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Accepted: 04/07/2021] [Indexed: 12/13/2022] Open
Abstract
Neuronal activity is established as a driver of oligodendrocyte (OL) differentiation and myelination. The concept of activity-dependent myelin plasticity, and its role in cognition and disease, is gaining support. Methods capable of resolving changes in the morphology of individual myelinating OL would advance our understanding of myelin plasticity and injury, thus we adapted a labelling approach involving Semliki Forest Virus (SFV) vectors to resolve and quantify the 3-D structure of OL processes and internodes in cerebellar slice cultures. We first demonstrate the utility of the approach by studying changes in OL morphology after complement-mediated injury. SFV vectors injected into cerebellar white matter labelled transitional OL (TOL), whose characteristic mixture of myelinating and non-myelinating processes exhibited significant degeneration after complement injury. The method was also capable of resolving finer changes in morphology related to neuronal activity. Prolonged suppression of neuronal activity, which reduced myelination, selectively decreased the length of putative internodes, and the proportion of process branches that supported them, while leaving other features of process morphology unaltered. Overall this work provides novel information on the morphology of TOL, and their response to conditions that alter circuit function or induce demyelination.
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8
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Wang Y, Fu AKY, Ip NY. Instructive roles of astrocytes in hippocampal synaptic plasticity: neuronal activity-dependent regulatory mechanisms. FEBS J 2021; 289:2202-2218. [PMID: 33864430 PMCID: PMC9290076 DOI: 10.1111/febs.15878] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 03/02/2021] [Accepted: 04/12/2021] [Indexed: 12/22/2022]
Abstract
In the adult hippocampus, synaptic plasticity is important for information processing, learning, and memory encoding. Astrocytes, the most common glial cells, play a pivotal role in the regulation of hippocampal synaptic plasticity. While astrocytes were initially described as a homogenous cell population, emerging evidence indicates that in the adult hippocampus, astrocytes are highly heterogeneous and can differentially respond to changes in neuronal activity in a subregion‐dependent manner to actively modulate synaptic plasticity. In this review, we summarize how local neuronal activity changes regulate the interactions between astrocytes and synapses, either by modulating the secretion of gliotransmitters and synaptogenic proteins or via contact‐mediated signaling pathways. In turn, these specific responses induced in astrocytes mediate the interactions between astrocytes and neurons, thus shaping synaptic communication in the adult hippocampus. Importantly, the activation of astrocytic signaling is required for memory performance including memory acquisition and recall. Meanwhile, the dysregulation of this signaling can cause hippocampal circuit dysfunction in pathological conditions, resulting in cognitive impairment and neurodegeneration. Indeed, reactive astrocytes, which have dysregulated signaling associated with memory, are induced in the brains of patients with Alzheimer's disease (AD) and transgenic mouse model of AD. Emerging technologies that can precisely manipulate and monitor astrocytic signaling in vivo enable the examination of the specific actions of astrocytes in response to neuronal activity changes as well as how they modulate synaptic connections and circuit activity. Such findings will clarify the roles of astrocytes in hippocampal synaptic plasticity and memory in health and disease.
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Affiliation(s)
- Ye Wang
- Division of Life Science, The Hong Kong University of Science and Technology, China.,Molecular Neuroscience Center, The Hong Kong University of Science and Technology, China.,State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, China.,Hong Kong Center for Neurodegenerative Diseases, China
| | - Amy K Y Fu
- Division of Life Science, The Hong Kong University of Science and Technology, China.,Molecular Neuroscience Center, The Hong Kong University of Science and Technology, China.,State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, China.,Hong Kong Center for Neurodegenerative Diseases, China.,Guangdong Provincial Key Laboratory of Brain Science, Disease and Drug Development, HKUST Shenzhen Research Institute, Shenzhen-Hong Kong Institute of Brain Science, Shenzhen, China
| | - Nancy Y Ip
- Division of Life Science, The Hong Kong University of Science and Technology, China.,Molecular Neuroscience Center, The Hong Kong University of Science and Technology, China.,State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, China.,Hong Kong Center for Neurodegenerative Diseases, China.,Guangdong Provincial Key Laboratory of Brain Science, Disease and Drug Development, HKUST Shenzhen Research Institute, Shenzhen-Hong Kong Institute of Brain Science, Shenzhen, China
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Astrocyte-secreted IL-33 mediates homeostatic synaptic plasticity in the adult hippocampus. Proc Natl Acad Sci U S A 2020; 118:2020810118. [PMID: 33443211 PMCID: PMC7817131 DOI: 10.1073/pnas.2020810118] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Synaptic plasticity in the hippocampus is important for learning and memory formation. In particular, homeostatic synaptic plasticity enables neurons to restore their activity levels in response to chronic neuronal activity changes. While astrocytes modulate synaptic functions via the secretion of factors, the underlying molecular mechanisms remain unclear. Here, we show that suppression of hippocampal neuronal activity increases cytokine IL-33 release from astrocytes in the CA1 region. Activation of IL-33 and its neuronal ST2 receptor complex promotes functional excitatory synapse formation. Moreover, IL-33/ST2 signaling is important for the neuronal activity blockade-induced increase of CA1 excitatory synapses in vivo and spatial memory formation. This study suggests that astrocyte-secreted IL-33 acts as a negative feedback control signal to regulate hippocampal homeostatic synaptic plasticity. Hippocampal synaptic plasticity is important for learning and memory formation. Homeostatic synaptic plasticity is a specific form of synaptic plasticity that is induced upon prolonged changes in neuronal activity to maintain network homeostasis. While astrocytes are important regulators of synaptic transmission and plasticity, it is largely unclear how they interact with neurons to regulate synaptic plasticity at the circuit level. Here, we show that neuronal activity blockade selectively increases the expression and secretion of IL-33 (interleukin-33) by astrocytes in the hippocampal cornu ammonis 1 (CA1) subregion. This IL-33 stimulates an increase in excitatory synapses and neurotransmission through the activation of neuronal IL-33 receptor complex and synaptic recruitment of the scaffold protein PSD-95. We found that acute administration of tetrodotoxin in hippocampal slices or inhibition of hippocampal CA1 excitatory neurons by optogenetic manipulation increases IL-33 expression in CA1 astrocytes. Furthermore, IL-33 administration in vivo promotes the formation of functional excitatory synapses in hippocampal CA1 neurons, whereas conditional knockout of IL-33 in CA1 astrocytes decreases the number of excitatory synapses therein. Importantly, blockade of IL-33 and its receptor signaling in vivo by intracerebroventricular administration of its decoy receptor inhibits homeostatic synaptic plasticity in CA1 pyramidal neurons and impairs spatial memory formation in mice. These results collectively reveal an important role of astrocytic IL-33 in mediating the negative-feedback signaling mechanism in homeostatic synaptic plasticity, providing insights into how astrocytes maintain hippocampal network homeostasis.
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10
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Purinergic signaling orchestrating neuron-glia communication. Pharmacol Res 2020; 162:105253. [PMID: 33080321 DOI: 10.1016/j.phrs.2020.105253] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 09/29/2020] [Accepted: 10/09/2020] [Indexed: 12/12/2022]
Abstract
This review discusses the evidence supporting a role for ATP signaling (operated by P2X and P2Y receptors) and adenosine signaling (mainly operated by A1 and A2A receptors) in the crosstalk between neurons, astrocytes, microglia and oligodendrocytes. An initial emphasis will be given to the cooperation between adenosine receptors to sharpen information salience encoding across synapses. The interplay between ATP and adenosine signaling in the communication between astrocytes and neurons will then be presented in context of the integrative properties of the astrocytic syncytium, allowing to implement heterosynaptic depression processes in neuronal networks. The process of microglia 'activation' and its control by astrocytes and neurons will then be analyzed under the perspective of an interplay between different P2 receptors and adenosine A2A receptors. In spite of these indications of a prominent role of purinergic signaling in the bidirectional communication between neurons and glia, its therapeutical exploitation still awaits obtaining an integrated view of the spatio-temporal action of ATP signaling and adenosine signaling, clearly distinguishing the involvement of both purinergic signaling systems in the regulation of physiological processes and in the control of pathogenic-like responses upon brain dysfunction or damage.
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11
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Ung K, Tepe B, Pekarek B, Arenkiel BR, Deneen B. Parallel astrocyte calcium signaling modulates olfactory bulb responses. J Neurosci Res 2020; 98:1605-1618. [PMID: 32426930 PMCID: PMC8147697 DOI: 10.1002/jnr.24634] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 03/27/2020] [Accepted: 04/10/2020] [Indexed: 12/17/2022]
Abstract
Astrocytes are the most abundant glial cell in the central nervous system. They modulate synaptic function through a variety of mechanisms, and yet remain relatively understudied with respect to overall neuronal circuit function. Exploiting the tractability of the mouse olfactory system, we manipulated astrocyte activity and examined how astrocytes modulate olfactory bulb responses. Toward this, we genetically targeted both astrocytes and neurons for in vivo widefield imaging of Ca2+ responses to odor stimuli. We found that astrocytes exhibited odor response maps that overlap with excitatory neuronal activity. By manipulating Ca2+ activity in astrocytes using chemical genetics we found that odor-evoked neuronal activity was reciprocally affected, suggesting that astrocyte activation inhibits neuronal odor responses. Subsequently, behavioral experiments revealed that astrocyte manipulations affect both odor detection threshold and discrimination, suggesting that astrocytes play an active role in olfactory sensory processing circuits. Together, these studies show that astrocyte calcium signaling contributes to olfactory behavior through modulation of sensory circuits.
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Affiliation(s)
- Kevin Ung
- Program in Developmental Biology, Houston, TX 77030, USA
| | - Burak Tepe
- Program in Developmental Biology, Houston, TX 77030, USA
| | - Brandon Pekarek
- Department of Molecular and Human Genetics, Houston, TX 77030, USA
| | - Benjamin R. Arenkiel
- Program in Developmental Biology, Houston, TX 77030, USA
- Department of Molecular and Human Genetics, Houston, TX 77030, USA
- Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital, Houston, TX 77030, USA
| | - Benjamin Deneen
- Program in Developmental Biology, Houston, TX 77030, USA
- Center for Cell and Gene Therapy, Houston, TX 77030, USA
- Department of Neurosurgery, Baylor College of Medicine, Houston, TX 77030, USA
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12
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Kastanenka KV, Moreno-Bote R, De Pittà M, Perea G, Eraso-Pichot A, Masgrau R, Poskanzer KE, Galea E. A roadmap to integrate astrocytes into Systems Neuroscience. Glia 2020; 68:5-26. [PMID: 31058383 PMCID: PMC6832773 DOI: 10.1002/glia.23632] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Revised: 04/08/2019] [Accepted: 04/09/2019] [Indexed: 12/14/2022]
Abstract
Systems neuroscience is still mainly a neuronal field, despite the plethora of evidence supporting the fact that astrocytes modulate local neural circuits, networks, and complex behaviors. In this article, we sought to identify which types of studies are necessary to establish whether astrocytes, beyond their well-documented homeostatic and metabolic functions, perform computations implementing mathematical algorithms that sub-serve coding and higher-brain functions. First, we reviewed Systems-like studies that include astrocytes in order to identify computational operations that these cells may perform, using Ca2+ transients as their encoding language. The analysis suggests that astrocytes may carry out canonical computations in a time scale of subseconds to seconds in sensory processing, neuromodulation, brain state, memory formation, fear, and complex homeostatic reflexes. Next, we propose a list of actions to gain insight into the outstanding question of which variables are encoded by such computations. The application of statistical analyses based on machine learning, such as dimensionality reduction and decoding in the context of complex behaviors, combined with connectomics of astrocyte-neuronal circuits, is, in our view, fundamental undertakings. We also discuss technical and analytical approaches to study neuronal and astrocytic populations simultaneously, and the inclusion of astrocytes in advanced modeling of neural circuits, as well as in theories currently under exploration such as predictive coding and energy-efficient coding. Clarifying the relationship between astrocytic Ca2+ and brain coding may represent a leap forward toward novel approaches in the study of astrocytes in health and disease.
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Affiliation(s)
- Ksenia V. Kastanenka
- Department of Neurology, MassGeneral Institute for Neurodegenerative Diseases, Massachusetts General Hospital and Harvard Medical School, Massachusetts 02129, USA
| | - Rubén Moreno-Bote
- Department of Information and Communications Technologies, Center for Brain and Cognition and Universitat Pompeu Fabra, 08018 Barcelona, Spain
- ICREA, 08010 Barcelona, Spain
| | | | | | - Abel Eraso-Pichot
- Departament de Bioquímica, Institut de Neurociències i Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, Spain
| | - Roser Masgrau
- Departament de Bioquímica, Institut de Neurociències i Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, Spain
| | - Kira E. Poskanzer
- Department of Biochemistry & Biophysics, Neuroscience Graduate Program, and Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, California 94143, USA
- Equally contributing authors
| | - Elena Galea
- ICREA, 08010 Barcelona, Spain
- Departament de Bioquímica, Institut de Neurociències i Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, Spain
- Equally contributing authors
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13
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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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14
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Greenhalgh AD, Zarruk JG, Healy LM, Baskar Jesudasan SJ, Jhelum P, Salmon CK, Formanek A, Russo MV, Antel JP, McGavern DB, McColl BW, David S. Peripherally derived macrophages modulate microglial function to reduce inflammation after CNS injury. PLoS Biol 2018; 16:e2005264. [PMID: 30332405 PMCID: PMC6205650 DOI: 10.1371/journal.pbio.2005264] [Citation(s) in RCA: 139] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Revised: 10/29/2018] [Accepted: 10/01/2018] [Indexed: 12/19/2022] Open
Abstract
Infiltrating monocyte-derived macrophages (MDMs) and resident microglia dominate central nervous system (CNS) injury sites. Differential roles for these cell populations after injury are beginning to be uncovered. Here, we show evidence that MDMs and microglia directly communicate with one another and differentially modulate each other's functions. Importantly, microglia-mediated phagocytosis and inflammation are suppressed by infiltrating macrophages. In the context of spinal cord injury (SCI), preventing such communication increases microglial activation and worsens functional recovery. We suggest that macrophages entering the CNS provide a regulatory mechanism that controls acute and long-term microglia-mediated inflammation, which may drive damage in a variety of CNS conditions.
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Affiliation(s)
- Andrew D. Greenhalgh
- Centre for Research in Neuroscience, The Research Institute of the McGill University Health Center, Quebec, Canada
- Laboratory of Nutrition and Integrated Neurobiology, UMR INRA 1286, University of Bordeaux, Bordeaux, France
| | - Juan G. Zarruk
- Centre for Research in Neuroscience, The Research Institute of the McGill University Health Center, Quebec, Canada
| | - Luke M. Healy
- Neuroimmunology Unit, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Sam J. Baskar Jesudasan
- Centre for Research in Neuroscience, The Research Institute of the McGill University Health Center, Quebec, Canada
| | - Priya Jhelum
- Centre for Research in Neuroscience, The Research Institute of the McGill University Health Center, Quebec, Canada
| | - Christopher K. Salmon
- Centre for Research in Neuroscience, The Research Institute of the McGill University Health Center, Quebec, Canada
| | - Albert Formanek
- Centre for Research in Neuroscience, The Research Institute of the McGill University Health Center, Quebec, Canada
| | - Matthew V. Russo
- Viral Immunology and Intravital Imaging Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Jack P. Antel
- Neuroimmunology Unit, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Dorian B. McGavern
- Viral Immunology and Intravital Imaging Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Barry W. McColl
- UK Dementia Research Institute, University of Edinburgh, Edinburgh, United Kingdom
| | - Samuel David
- Centre for Research in Neuroscience, The Research Institute of the McGill University Health Center, Quebec, Canada
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15
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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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16
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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: 899] [Impact Index Per Article: 149.8] [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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17
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Lind BL, Jessen SB, Lønstrup M, Joséphine C, Bonvento G, Lauritzen M. Fast Ca 2+ responses in astrocyte end-feet and neurovascular coupling in mice. Glia 2017; 66:348-358. [PMID: 29058353 DOI: 10.1002/glia.23246] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Revised: 09/28/2017] [Accepted: 09/29/2017] [Indexed: 01/09/2023]
Abstract
Cerebral blood flow (CBF) is regulated by the activity of neurons and astrocytes. Understanding how these cells control activity-dependent increases in CBF is crucial to interpreting functional neuroimaging signals. The relative importance of neurons and astrocytes is debated, as are the functional implications of fast Ca2+ changes in astrocytes versus neurons. Here, we used two-photon microscopy to assess Ca2+ changes in neuropil, astrocyte processes, and astrocyte end-feet in response to whisker pad stimulation in mice. We also developed a pixel-based analysis to improve the detection of rapid Ca2+ signals in the subcellular compartments of astrocytes. Fast Ca2+ responses were observed using both chemical and genetically encoded Ca2+ indicators in astrocyte end-feet prior to dilation of arterioles and capillaries. A low dose of the NMDA receptor antagonist (5R,10s)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine-hydrogen-maleate (MK801) attenuated fast Ca2+ responses in the neuropil and astrocyte processes, but not in astrocyte end-feet, and the evoked CBF response was preserved. In addition, a low dose of 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP), an agonist for the extrasynaptic GABAA receptor (GABAA R), increased CBF responses and the fast Ca2+ response in astrocyte end-feet but did not affect Ca2+ responses in astrocyte processes and neuropil. These results suggest that fast Ca2+ increases in the neuropil and astrocyte processes are not necessary for an evoked CBF response. In contrast, as local fast Ca2+ responses in astrocyte end-feet are unaffected by MK801 but increase via GABAA R-dependent mechanisms that also increased CBF responses, we hypothesize that the fast Ca2+ increases in end-feet adjust CBF during synaptic activity.
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Affiliation(s)
- Barbara Lykke Lind
- Department of Neuroscience and Center for Healthy Aging, University of Copenhagen, Denmark
| | - Sanne Barsballe Jessen
- Department of Neuroscience and Center for Healthy Aging, University of Copenhagen, Denmark
| | - Micael Lønstrup
- Department of Neuroscience and Center for Healthy Aging, University of Copenhagen, Denmark
| | - Charlène Joséphine
- Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Département de la Recherche Fondamentale (DRF), Institut de Biologie François-Jacob, Molecular Imaging Research Center (MIRCen), CNRS UMR 9199, Université Paris-Sud, Université Paris-Saclay, Fontenay-aux-Roses, France
| | - Gilles Bonvento
- Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Département de la Recherche Fondamentale (DRF), Institut de Biologie François-Jacob, Molecular Imaging Research Center (MIRCen), CNRS UMR 9199, Université Paris-Sud, Université Paris-Saclay, Fontenay-aux-Roses, France
| | - Martin Lauritzen
- Department of Neuroscience and Center for Healthy Aging, University of Copenhagen, Denmark.,Department of Clinical Neurophysiology, Glostrup Hospital, Denmark
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18
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Pseudo-typed Semliki Forest virus delivers EGFP into neurons. J Neurovirol 2016; 23:205-215. [PMID: 27739033 DOI: 10.1007/s13365-016-0486-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2016] [Revised: 09/22/2016] [Accepted: 09/26/2016] [Indexed: 12/14/2022]
Abstract
Semliki Forest virus (SFV), a neurotropic virus, has been used to deliver heterologous genes into cells in vitro and in vivo. In this study, we constructed a reporter SFV4-FL-EGFP and found that it can deliver EGFP into neurons located at the injection site without disseminating throughout the brain. Lacking of the capsid gene of SFV4-FL-EGFP does not block its life cycle, while forming replication-competent virus-like particles (VLPs). These VLPs hold subviral genome by using the packaging sequence (PS) located within the nsP2 gene, and can transfer their genome into cells. In addition, we found that the G protein of vesicular stomatitis virus (VSVG) can package SFV subviral genome, which is consistent with the previous reports. The G protein of rabies virus (RVG) could also package SFV subviral genome. These pseudo-typed SFV can deliver EGFP gene into neurons. Taken together, these findings may be used to construct various SFV-based delivery systems for virological studies, gene therapy, and neural circuit labeling.
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19
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Greenhalgh AD, Passos Dos Santos R, Zarruk JG, Salmon CK, Kroner A, David S. Arginase-1 is expressed exclusively by infiltrating myeloid cells in CNS injury and disease. Brain Behav Immun 2016; 56:61-7. [PMID: 27126514 DOI: 10.1016/j.bbi.2016.04.013] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Revised: 04/14/2016] [Accepted: 04/23/2016] [Indexed: 11/28/2022] Open
Abstract
Resident microglia and infiltrating myeloid cells play important roles in the onset, propagation, and resolution of inflammation in central nervous system (CNS) injury and disease. Identifying cell type-specific mechanisms will help to appropriately target interventions for tissue repair. Arginase-1 (Arg-1) is a well characterised modulator of tissue repair and its expression correlates with recovery after CNS injury. Here we assessed the cellular localisation of Arg-1 in two models of CNS damage. Using microglia specific antibodies, P2ry12 and Fc receptor-like S (FCRLS), we show the LysM-EGFP reporter mouse is an excellent model to distinguish infiltrating myeloid cells from resident microglia. We show that Arg-1 is expressed exclusively in infiltrating myeloid cells but not microglia in models of spinal cord injury (SCI) and experimental autoimmune encephalomyelitis (EAE). Our in vitro studies suggest that factors in the CNS environment prevent expression of Arg-1 in microglia in vivo. This work suggests different functional roles for these cells in CNS injury and repair and shows that such repair pathways can be switched on in infiltrating myeloid cells in pro-inflammatory environments.
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Affiliation(s)
- Andrew D Greenhalgh
- Centre for Research in Neuroscience, The Research Institute of the McGill University Health Centre, 1650 Cedar Ave., Montreal, Quebec H3G 1A4, Canada
| | - Rosmarini Passos Dos Santos
- Centre for Research in Neuroscience, The Research Institute of the McGill University Health Centre, 1650 Cedar Ave., Montreal, Quebec H3G 1A4, Canada
| | - Juan Guillermo Zarruk
- Centre for Research in Neuroscience, The Research Institute of the McGill University Health Centre, 1650 Cedar Ave., Montreal, Quebec H3G 1A4, Canada
| | - Christopher K Salmon
- Centre for Research in Neuroscience, The Research Institute of the McGill University Health Centre, 1650 Cedar Ave., Montreal, Quebec H3G 1A4, Canada
| | - Antje Kroner
- Centre for Research in Neuroscience, The Research Institute of the McGill University Health Centre, 1650 Cedar Ave., Montreal, Quebec H3G 1A4, Canada
| | - Samuel David
- Centre for Research in Neuroscience, The Research Institute of the McGill University Health Centre, 1650 Cedar Ave., Montreal, Quebec H3G 1A4, Canada.
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20
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Bazargani N, Attwell D. Astrocyte calcium signaling: the third wave. Nat Neurosci 2016; 19:182-9. [PMID: 26814587 DOI: 10.1038/nn.4201] [Citation(s) in RCA: 559] [Impact Index Per Article: 69.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2015] [Accepted: 11/10/2015] [Indexed: 02/06/2023]
Abstract
The discovery that transient elevations of calcium concentration occur in astrocytes, and release 'gliotransmitters' which act on neurons and vascular smooth muscle, led to the idea that astrocytes are powerful regulators of neuronal spiking, synaptic plasticity and brain blood flow. These findings were challenged by a second wave of reports that astrocyte calcium transients did not mediate functions attributed to gliotransmitters and were too slow to generate blood flow increases. Remarkably, the tide has now turned again: the most important calcium transients occur in fine astrocyte processes not resolved in earlier studies, and new mechanisms have been discovered by which astrocyte [Ca(2+)]i is raised and exerts its effects. Here we review how this third wave of discoveries has changed our understanding of astrocyte calcium signaling and its consequences for neuronal function.
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Affiliation(s)
- Narges Bazargani
- Department of Neuroscience, Physiology &Pharmacology, University College London, London, UK
| | - David Attwell
- Department of Neuroscience, Physiology &Pharmacology, University College London, London, UK
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21
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Hu X, Yuan Y, Wang D, Su Z. Heterogeneous astrocytes: Active players in CNS. Brain Res Bull 2016; 125:1-18. [PMID: 27021168 DOI: 10.1016/j.brainresbull.2016.03.017] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Revised: 03/22/2016] [Accepted: 03/24/2016] [Indexed: 12/12/2022]
Abstract
Astrocytes, the predominant cell type that are broadly distributed in the brain and spinal cord, play key roles in maintaining homeostasis of the central nerve system (CNS) in physiological and pathological conditions. Increasing evidence indicates that astrocytes are a complex colony with heterogeneity on morphology, gene expression, function and many other aspects depending on their spatio-temporal distribution and activation level. In pathological conditions, astrocytes differentially respond to all kinds of insults, including injury and disease, and participate in the neuropathological process. Based on current studies, we here give an overview of the roles of heterogeneous astrocytes in CNS, especially in neuropathologies, which focuses on biological and functional diversity of astrocytes. We propose that a precise understanding of the heterogeneous astrocytes is critical to unlocking the secrets about pathogenesis and treatment of the mazy CNS.
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Affiliation(s)
- Xin Hu
- Institute of Neuroscience and Key Laboratory of Molecular Neurobiology of Ministry of Education, Second Military Medical University, Shanghai, China
| | - Yimin Yuan
- Institute of Neuroscience and Key Laboratory of Molecular Neurobiology of Ministry of Education, Second Military Medical University, Shanghai, China
| | - Dan Wang
- Institute of Neuroscience and Key Laboratory of Molecular Neurobiology of Ministry of Education, Second Military Medical University, Shanghai, China
| | - Zhida Su
- Institute of Neuroscience and Key Laboratory of Molecular Neurobiology of Ministry of Education, Second Military Medical University, Shanghai, China.
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22
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Tanamoto R, Shindo Y, Niwano M, Matsumoto Y, Miki N, Hotta K, Oka K. Qualitative and quantitative estimation of comprehensive synaptic connectivity in short- and long-term cultured rat hippocampal neurons with new analytical methods inspired by Scatchard and Hill plots. Biochem Biophys Res Commun 2016; 471:486-91. [PMID: 26896767 DOI: 10.1016/j.bbrc.2016.02.048] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Accepted: 02/14/2016] [Indexed: 02/04/2023]
Abstract
To investigate comprehensive synaptic connectivity, we examined Ca(2+) responses with quantitative electric current stimulation by indium-tin-oxide (ITO) glass electrode with transparent and high electro-conductivity. The number of neurons with Ca(2+) responses was low during the application of stepwise increase of electric current in short-term cultured neurons (less than 17 days in-vitro (DIV)). The neurons cultured over 17 DIV showed two-type responses: S-shaped (sigmoid) and monotonous saturated responses, and Scatchard plots well illustrated the difference of these two responses. Furthermore, sigmoid like neural network responses over 17 DIV were altered to the monotonous saturated ones by the application of the mixture of AP5 and CNQX, specific blockers of NMDA and AMPA receptors, respectively. This alternation was also characterized by the change of Hill coefficients. These findings indicate that the neural network with sigmoid-like responses has strong synergetic or cooperative synaptic connectivity via excitatory glutamate synapses.
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Affiliation(s)
- Ryo Tanamoto
- Department of Biosciences and Informatics, Faculty of Science and Technology, Keio University, Japan
| | - Yutaka Shindo
- Department of Biosciences and Informatics, Faculty of Science and Technology, Keio University, Japan
| | - Mariko Niwano
- Department of Biosciences and Informatics, Faculty of Science and Technology, Keio University, Japan
| | - Yoshinori Matsumoto
- Department of Applied Physics and Physico-Informatics, Faculty of Science and Technology, Keio University, Japan
| | - Norihisa Miki
- Department of Mechanical Engineering, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa, 223-8522, Japan
| | - Kohji Hotta
- Department of Biosciences and Informatics, Faculty of Science and Technology, Keio University, Japan
| | - Kotaro Oka
- Department of Biosciences and Informatics, Faculty of Science and Technology, Keio University, Japan.
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23
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Reciprocal Regulation of Mitochondrial Dynamics and Calcium Signaling in Astrocyte Processes. J Neurosci 2016; 35:15199-213. [PMID: 26558789 DOI: 10.1523/jneurosci.2049-15.2015] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED We recently showed that inhibition of neuronal activity, glutamate uptake, or reversed-Na(+)/Ca(2+)-exchange with TTX, TFB-TBOA, or YM-244769, respectively, increases mitochondrial mobility in astrocytic processes. In the present study, we examined the interrelationships between mitochondrial mobility and Ca(2+) signaling in astrocyte processes in organotypic cultures of rat hippocampus. All of the treatments that increase mitochondrial mobility decreased basal Ca(2+). As recently reported, we observed spontaneous Ca(2+) spikes with half-lives of ∼1 s that spread ∼6 μm and are almost abolished by a TRPA1 channel antagonist. Virtually all of these Ca(2+) spikes overlap mitochondria (98%), and 62% of mitochondria are overlapped by these spikes. Although tetrodotoxin, TFB-TBOA, or YM-244769 increased Ca(2+) signaling, the specific effects on peak, decay time, and/or frequency were different. To more specifically manipulate mitochondrial mobility, we explored the effects of Miro motor adaptor proteins. We show that Miro1 and Miro2 are both expressed in astrocytes and that exogenous expression of Ca(2+)-insensitive Miro mutants (KK) nearly doubles the percentage of mobile mitochondria. Expression of Miro1(KK) had a modest effect on the frequency of these Ca(2+) spikes but nearly doubled the decay half-life. The mitochondrial proton ionophore, FCCP, caused a large, prolonged increase in cytosolic Ca(2+) followed by an increase in the decay time and the spread of the spontaneous Ca(2+) spikes. Photo-ablation of mitochondria in individual astrocyte processes has similar effects on Ca(2+). Together, these studies show that Ca(2+) regulates mitochondrial mobility, and mitochondria in turn regulate Ca(2+) signals in astrocyte processes. SIGNIFICANCE STATEMENT In neurons, the movement and positioning of mitochondria at sites of elevated activity are important for matching local energy and Ca(2+) buffering capacity. Previously, we demonstrated that mitochondria are immobilized in astrocytes in response to neuronal activity and glutamate uptake. Here, we demonstrate a mechanism by which mitochondria are immobilized in astrocytes subsequent to increases in intracellular [Ca(2+)] and provide evidence that mitochondria contribute to the compartmentalization of spontaneous Ca(2+) signals in astrocyte processes. Immobilization of mitochondria at sites of glutamate uptake in astrocyte processes provides a mechanism to coordinate increases in activity with increases in mitochondrial metabolism.
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Michalski K, Kawate T. Carbenoxolone inhibits Pannexin1 channels through interactions in the first extracellular loop. ACTA ACUST UNITED AC 2016; 147:165-74. [PMID: 26755773 PMCID: PMC4727946 DOI: 10.1085/jgp.201511505] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 12/18/2015] [Indexed: 12/15/2022]
Abstract
A chimeric approach combined with extensive site-directed mutagenesis reveals new information about the interaction of the toxin carbenoxolone with the ATP release channel Pannexin1 and the role of the first extracellular loop in channel gating. Pannexin1 (Panx1) is an ATP release channel important for controlling immune responses and synaptic strength. Various stimuli including C-terminal cleavage, a high concentration of extracellular potassium, and voltage have been demonstrated to activate Panx1. However, it remains unclear how Panx1 senses and integrates such diverse stimuli to form an open channel. To provide a clue on the mechanism underlying Panx1 channel gating, we investigated the action mechanism of carbenoxolone (CBX), the most commonly used small molecule for attenuating Panx1 function triggered by a wide range of stimuli. Using a chimeric approach, we discovered that CBX reverses its action polarity and potentiates the voltage-gated channel activity of Panx1 when W74 in the first extracellular loop is mutated to a nonaromatic residue. A systematic mutagenesis study revealed that conserved residues in this loop also play important roles in CBX function, potentially by mediating CBX binding. We extended our experiments to other Panx1 inhibitors such as probenecid and ATP, which also potentiate the voltage-gated channel activity of a Panx1 mutant at position 74. Notably, probenecid alone can activate this mutant at a resting membrane potential. These data suggest that CBX and other inhibitors, including probenecid, attenuate Panx1 channel activity through modulation of the first extracellular loop. Our experiments are the first step toward identifying a previously unknown mode of CBX action, which provide insight into the role of the first extracellular loop in Panx1 channel gating.
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Affiliation(s)
- Kevin Michalski
- Department of Molecular Medicine, Field of Biochemistry, Molecular, and Cell Biology, Cornell University, Ithaca, NY 14853
| | - Toshimitsu Kawate
- Department of Molecular Medicine, Field of Biochemistry, Molecular, and Cell Biology, Cornell University, Ithaca, NY 14853
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Kubik LL, Philbert MA. The role of astrocyte mitochondria in differential regional susceptibility to environmental neurotoxicants: tools for understanding neurodegeneration. Toxicol Sci 2015; 144:7-16. [PMID: 25740792 DOI: 10.1093/toxsci/kfu254] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
In recent decades, there has been a significant expansion in our understanding of the role of astrocytes in neuroprotection, including spatial buffering of extracellular ions, secretion of metabolic coenzymes, and synaptic regulation. Astrocytic neuroprotective functions require energy, and therefore require a network of functional mitochondria. Disturbances to astrocytic mitochondrial homeostasis and their ability to produce ATP can negatively impact neural function. Perturbations in astrocyte mitochondrial function may accrue as the result of physiological aging processes or as a consequence of neurotoxicant exposure. Hydrophobic environmental neurotoxicants, such as 1,3-dinitrobenzene and α-chlorohydrin, cause regionally specific spongiform lesions mimicking energy deprivation syndromes. Astrocyte involvement includes mitochondrial damage that either precedes or is accompanied by neuronal damage. Similarly, environmental neurotoxicants that are implicated in the etiology of age-related neurodegenerative conditions cause regionally specific damage in the brain. Based on the regioselective nature of age-related neurodegenerative lesions, chemically induced models of regioselective lesions targeting astrocyte mitochondria can provide insight into age-related susceptibilities in astrocyte mitochondria. Most of the available research to date focuses on neuronal damage in cases of age-related neurodegeneration; however, there is a body of evidence that supports a central mechanistic role for astrocyte mitochondria in the expression of neural injury. Regional susceptibility to neuronal damage induced by aging by exposure to neurotoxicants may be a reflection of highly variable regional energy requirements. This review identifies region-specific vulnerabilities in astrocyte mitochondria in examples of exposure to neurotoxicants and in age-related neurodegeneration.
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Affiliation(s)
- Laura L Kubik
- Toxicology Program, Department of Environmental Health Sciences, School of Public Health, University of Michigan, Ann Arbor, MI 48109
| | - Martin A Philbert
- Toxicology Program, Department of Environmental Health Sciences, School of Public Health, University of Michigan, Ann Arbor, MI 48109
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Kim JH, Kwon SJ, Stankewich MC, Huh GY, Glantz SB, Morrow JS. Reactive protoplasmic and fibrous astrocytes contain high levels of calpain-cleaved alpha 2 spectrin. Exp Mol Pathol 2015; 100:1-7. [PMID: 26551084 DOI: 10.1016/j.yexmp.2015.11.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Accepted: 11/04/2015] [Indexed: 12/13/2022]
Abstract
Calpain, a family of calcium-dependent neutral proteases, plays important roles in neurophysiology and pathology through the proteolytic modification of cytoskeletal proteins, receptors and kinases. Alpha 2 spectrin (αII spectrin) is a major substrate for this protease family, and the presence of the αII spectrin breakdown product (αΙΙ spectrin BDP) in a cell is evidence of calpain activity triggered by enhanced intracytoplasmic Ca(2+) concentrations. Astrocytes, the most dynamic CNS cells, respond to micro-environmental changes or noxious stimuli by elevating intracytoplasmic Ca(2+) concentration to become activated. As one measure of whether calpains are involved with reactive glial transformation, we examined paraffin sections of the human cerebral cortex and white matter by immunohistochemistry with an antibody specific for the calpain-mediated αΙΙ spectrin BDP. We also performed conventional double immunohistochemistry as well as immunofluorescent studies utilizing antibodies against αΙΙ spectrin BDP as well as glial fibrillary acidic protein (GFAP). We found strong immunopositivity in selected protoplasmic and fibrous astrocytes, and in transitional forms that raise the possibility of some of fibrous astrocytes emerging from protoplasmic astrocytes. Immunoreactive astrocytes were numerous in brain sections from cases with severe cardiac and/or respiratory diseases in the current study as opposed to our previous study of cases without significant clinical conditions that failed to reveal such remarkable immunohistochemical alterations. Our study suggests that astrocytes become αΙΙ spectrin BDP immunopositive in various stages of activation, and that spectrin cleavage product persists even in fully reactive astrocytes. Immunohistochemistry for αΙΙ spectrin BDP thus marks reactive astrocytes, and highlights the likelihood that calpains and their proteolytic processing of spectrin participate in the morphologic and physiologic transition from resting protoplasmic astrocytes to reactive fibrous astrocytes.
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Affiliation(s)
- Jung H Kim
- Department of Pathology, Yale Univ. School of Medicine, 310 Cedar Street, New Haven, CT 06510-8023, USA.
| | - Soojung J Kwon
- Department of Pathology, Yale Univ. School of Medicine, 310 Cedar Street, New Haven, CT 06510-8023, USA
| | - Michael C Stankewich
- Department of Pathology, Yale Univ. School of Medicine, 310 Cedar Street, New Haven, CT 06510-8023, USA
| | - Gi-Yeong Huh
- Department of Forensic Medicine, School of Medicine, Pusan National University, Pusan, Korea
| | - Susan B Glantz
- Department of Pathology, Yale Univ. School of Medicine, 310 Cedar Street, New Haven, CT 06510-8023, USA
| | - Jon S Morrow
- Department of Pathology, Yale Univ. School of Medicine, 310 Cedar Street, New Haven, CT 06510-8023, USA
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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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Development of a microfluidic platform with integrated power splitting waveguides for optogenetic neural cell stimulation. Biomed Microdevices 2015; 17:101. [DOI: 10.1007/s10544-015-0008-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Benjamin Kacerovsky J, Murai KK. Stargazing: Monitoring subcellular dynamics of brain astrocytes. Neuroscience 2015; 323:84-95. [PMID: 26162237 DOI: 10.1016/j.neuroscience.2015.07.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Revised: 06/28/2015] [Accepted: 07/01/2015] [Indexed: 01/21/2023]
Abstract
Astrocytes are major non-neuronal cell types in the central nervous system that regulate a variety of processes in the brain including synaptic transmission, neurometabolism, and cerebrovasculature tone. Recent discoveries have revealed that astrocytes perform very specialized and heterogeneous roles in brain homeostasis and function. Exactly how astrocytes fulfill such diverse roles in the brain remains to be fully understood and is an active area of research. In this review, we focus on the complex subcellular anatomical features of protoplasmic gray matter astrocytes in the mature, healthy brain that likely empower these cells with the ability to detect and respond to changes in neuronal and synaptic activity. In particular, we discuss how intricate processes on astrocytes allow these cells to communicate with neurons and their synapses and strategically deliver specific cellular organelles such as mitochondria and ribosomes to active compartments within the neuropil. Understanding the properties of these structural elements will lead to a better understanding of how astrocytes function in the healthy and diseased brain.
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Affiliation(s)
- J Benjamin Kacerovsky
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec H3G 1A4, Canada
| | - K K Murai
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec H3G 1A4, Canada.
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Renault R, Sukenik N, Descroix S, Malaquin L, Viovy JL, Peyrin JM, Bottani S, Monceau P, Moses E, Vignes M. Combining microfluidics, optogenetics and calcium imaging to study neuronal communication in vitro. PLoS One 2015; 10:e0120680. [PMID: 25901914 PMCID: PMC4406441 DOI: 10.1371/journal.pone.0120680] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Accepted: 02/05/2015] [Indexed: 11/19/2022] Open
Abstract
In this paper we report the combination of microfluidics, optogenetics and calcium imaging as a cheap and convenient platform to study synaptic communication between neuronal populations in vitro. We first show that Calcium Orange indicator is compatible in vitro with a commonly used Channelrhodopsine-2 (ChR2) variant, as standard calcium imaging conditions did not alter significantly the activity of transduced cultures of rodent primary neurons. A fast, robust and scalable process for micro-chip fabrication was developed in parallel to build micro-compartmented cultures. Coupling optical fibers to each micro-compartment allowed for the independent control of ChR2 activation in the different populations without crosstalk. By analyzing the post-stimuli activity across the different populations, we finally show how this platform can be used to evaluate quantitatively the effective connectivity between connected neuronal populations.
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Affiliation(s)
- Renaud Renault
- MSC (Université Paris-Diderot, CNRS-UMR 7057), 5 Rue Thomas Mann, 75013 Paris, France
- Physicochimie Curie (Institut Curie, CNRS-UMR 168, UPMC), Institut Curie, Centre de Recherche, 26 rue d’Ulm, 75248 Paris Cedex 05, France
- Department of Complex Systems, Weizmann Institute, Rehovot, Israel
| | - Nirit Sukenik
- Department of Complex Systems, Weizmann Institute, Rehovot, Israel
| | - Stéphanie Descroix
- Physicochimie Curie (Institut Curie, CNRS-UMR 168, UPMC), Institut Curie, Centre de Recherche, 26 rue d’Ulm, 75248 Paris Cedex 05, France
| | - Laurent Malaquin
- Physicochimie Curie (Institut Curie, CNRS-UMR 168, UPMC), Institut Curie, Centre de Recherche, 26 rue d’Ulm, 75248 Paris Cedex 05, France
| | - Jean-Louis Viovy
- Physicochimie Curie (Institut Curie, CNRS-UMR 168, UPMC), Institut Curie, Centre de Recherche, 26 rue d’Ulm, 75248 Paris Cedex 05, France
| | - Jean-Michel Peyrin
- Biological Adaptation and Ageing (CNRS, UMR 8256), F-75005, Paris, France
- Sorbonne Universités, UPMC Univ Paris 06, UMR 8256, B2A, Institut de Biologie Paris Seine, F-75005, Paris, France
| | - Samuel Bottani
- MSC (Université Paris-Diderot, CNRS-UMR 7057), 5 Rue Thomas Mann, 75013 Paris, France
| | - Pascal Monceau
- MSC (Université Paris-Diderot, CNRS-UMR 7057), 5 Rue Thomas Mann, 75013 Paris, France
| | - Elisha Moses
- Department of Complex Systems, Weizmann Institute, Rehovot, Israel
| | - Maéva Vignes
- Physicochimie Curie (Institut Curie, CNRS-UMR 168, UPMC), Institut Curie, Centre de Recherche, 26 rue d’Ulm, 75248 Paris Cedex 05, France
- Biological Adaptation and Ageing (CNRS, UMR 8256), F-75005, Paris, France
- Sorbonne Universités, UPMC Univ Paris 06, UMR 8256, B2A, Institut de Biologie Paris Seine, F-75005, Paris, France
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Zhou Y, Lu Y, Fang X, Zhang J, Li J, Li S, Deng X, Yu Y, Xu R. An Astrocyte Regenerative Response from Vimentin-Containing Cells in the Spinal Cord of Amyotrophic Lateral Sclerosis's Disease-Like Transgenic (G93A SOD1) Mice. NEURODEGENER DIS 2015; 15:1-12. [DOI: 10.1159/000369466] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Accepted: 10/27/2014] [Indexed: 11/19/2022] Open
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Glutamate mediated astrocytic filtering of neuronal activity. PLoS Comput Biol 2014; 10:e1003964. [PMID: 25521344 PMCID: PMC4270452 DOI: 10.1371/journal.pcbi.1003964] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Accepted: 10/06/2014] [Indexed: 02/02/2023] Open
Abstract
Neuron-astrocyte communication is an important regulatory mechanism in various brain functions but its complexity and role are yet to be fully understood. In particular, the temporal pattern of astrocyte response to neuronal firing has not been fully characterized. Here, we used neuron-astrocyte cultures on multi-electrode arrays coupled to Ca2+ imaging and explored the range of neuronal stimulation frequencies while keeping constant the amount of stimulation. Our results reveal that astrocytes specifically respond to the frequency of neuronal stimulation by intracellular Ca2+ transients, with a clear onset of astrocytic activation at neuron firing rates around 3-5 Hz. The cell-to-cell heterogeneity of the astrocyte Ca2+ response was however large and increasing with stimulation frequency. Astrocytic activation by neurons was abolished with antagonists of type I metabotropic glutamate receptor, validating the glutamate-dependence of this neuron-to-astrocyte pathway. Using a realistic biophysical model of glutamate-based intracellular calcium signaling in astrocytes, we suggest that the stepwise response is due to the supralinear dynamics of intracellular IP3 and that the heterogeneity of the responses may be due to the heterogeneity of the astrocyte-to-astrocyte couplings via gap junction channels. Therefore our results present astrocyte intracellular Ca2+ activity as a nonlinear integrator of glutamate-dependent neuronal activity.
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Nakae K, Ikegaya Y, Ishikawa T, Oba S, Urakubo H, Koyama M, Ishii S. A statistical method of identifying interactions in neuron-glia systems based on functional multicell Ca2+ imaging. PLoS Comput Biol 2014; 10:e1003949. [PMID: 25393874 PMCID: PMC4230777 DOI: 10.1371/journal.pcbi.1003949] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Accepted: 09/29/2014] [Indexed: 11/18/2022] Open
Abstract
Crosstalk between neurons and glia may constitute a significant part of information processing in the brain. We present a novel method of statistically identifying interactions in a neuron-glia network. We attempted to identify neuron-glia interactions from neuronal and glial activities via maximum-a-posteriori (MAP)-based parameter estimation by developing a generalized linear model (GLM) of a neuron-glia network. The interactions in our interest included functional connectivity and response functions. We evaluated the cross-validated likelihood of GLMs that resulted from the addition or removal of connections to confirm the existence of specific neuron-to-glia or glia-to-neuron connections. We only accepted addition or removal when the modification improved the cross-validated likelihood. We applied the method to a high-throughput, multicellular in vitro Ca2+ imaging dataset obtained from the CA3 region of a rat hippocampus, and then evaluated the reliability of connectivity estimates using a statistical test based on a surrogate method. Our findings based on the estimated connectivity were in good agreement with currently available physiological knowledge, suggesting our method can elucidate undiscovered functions of neuron-glia systems.
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Affiliation(s)
- Ken Nakae
- Integrated Systems Biology Laboratory, Graduate School of Informatics, Kyoto University, Sakyo-ku, Kyoto, Japan
| | - Yuji Ikegaya
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
- Center for Information and Neural Networks, Suita City, Osaka, Japan
- * E-mail: (YI); (SI)
| | - Tomoe Ishikawa
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Shigeyuki Oba
- Integrated Systems Biology Laboratory, Graduate School of Informatics, Kyoto University, Sakyo-ku, Kyoto, Japan
| | - Hidetoshi Urakubo
- Integrated Systems Biology Laboratory, Graduate School of Informatics, Kyoto University, Sakyo-ku, Kyoto, Japan
| | - Masanori Koyama
- Integrated Systems Biology Laboratory, Graduate School of Informatics, Kyoto University, Sakyo-ku, Kyoto, Japan
| | - Shin Ishii
- Integrated Systems Biology Laboratory, Graduate School of Informatics, Kyoto University, Sakyo-ku, Kyoto, Japan
- * E-mail: (YI); (SI)
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Oheim M, van 't Hoff M, Feltz A, Zamaleeva A, Mallet JM, Collot M. New red-fluorescent calcium indicators for optogenetics, photoactivation and multi-color imaging. BIOCHIMICA ET BIOPHYSICA ACTA 2014; 1843:2284-306. [PMID: 24681159 DOI: 10.1016/j.bbamcr.2014.03.010] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Accepted: 03/09/2014] [Indexed: 01/15/2023]
Abstract
Most chemical and, with only a few exceptions, all genetically encoded fluorimetric calcium (Ca(2+)) indicators (GECIs) emit green fluorescence. Many of these probes are compatible with red-emitting cell- or organelle markers. But the bulk of available fluorescent-protein constructs and transgenic animals incorporate green or yellow fluorescent protein (GFP and YFP respectively). This is, in part, not only heritage from the tendency to aggregate of early-generation red-emitting FPs, and due to their complicated photochemistry, but also resulting from the compatibility of green-fluorescent probes with standard instrumentation readily available in most laboratories and core imaging facilities. Photochemical constraints like limited water solubility and low quantum yield have contributed to the relative paucity of red-emitting Ca(2+) probes compared to their green counterparts, too. The increasing use of GFP and GFP-based functional reporters, together with recent developments in optogenetics, photostimulation and super-resolution microscopies, has intensified the quest for red-emitting Ca(2+) probes. In response to this demand more red-emitting chemical and FP-based Ca(2+)-sensitive indicators have been developed since 2009 than in the thirty years before. In this topical review, we survey the physicochemical properties of these red-emitting Ca(2+) probes and discuss their utility for biological Ca(2+) imaging. Using the spectral separability index Xijk (Oheim M., 2010. Methods in Molecular Biology 591: 3-16) we evaluate their performance for multi-color excitation/emission experiments, involving the identification of morphological landmarks with GFP/YFP and detecting Ca(2+)-dependent fluorescence in the red spectral band. We also establish a catalog of criteria for evaluating Ca(2+) indicators that ideally should be made available for each probe. This article is part of a Special Issue entitled: Calcium signaling in health and disease. Guest Editors: Geert Bultynck, Jacques Haiech, Claus W. Heizmann, Joachim Krebs, and Marc Moreau.
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Affiliation(s)
- Martin Oheim
- CNRS, UMR 8154, Paris F-75006, France; INSERM, U603, Paris F-75006, France; University Paris Descartes, PRES Sorbonne Paris Cité, Laboratory of Neurophysiology and New Microscopies, 45 rue des Saints Pères, Paris F-75006, France.
| | - Marcel van 't Hoff
- CNRS, UMR 8154, Paris F-75006, France; INSERM, U603, Paris F-75006, France; University Paris Descartes, PRES Sorbonne Paris Cité, Laboratory of Neurophysiology and New Microscopies, 45 rue des Saints Pères, Paris F-75006, France; University of Florence, LENS - European Laboratory for Non-linear Spectroscopy, Via Nello Carrara 1, I-50019 Sesto Fiorentino, Italy
| | - Anne Feltz
- Ecole Normale Supérieure, Institut de Biologie de l'ENS (IBENS), Paris F-75005, France; INSERM U1024, Paris F-75005, France; CNRS UMR 8197, Paris F-75005, France
| | - Alsu Zamaleeva
- Ecole Normale Supérieure, Institut de Biologie de l'ENS (IBENS), Paris F-75005, France; INSERM U1024, Paris F-75005, France; CNRS UMR 8197, Paris F-75005, France
| | - Jean-Maurice Mallet
- UPMC Université́ Paris 06, Ecole Normale Supérieure (ENS), 24 rue Lhomond, Paris F-75005, France; CNRS UMR 7203, Paris F-75005, France
| | - Mayeul Collot
- UPMC Université́ Paris 06, Ecole Normale Supérieure (ENS), 24 rue Lhomond, Paris F-75005, France; CNRS UMR 7203, Paris F-75005, France
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Activity-dependent structural plasticity of perisynaptic astrocytic domains promotes excitatory synapse stability. Curr Biol 2014; 24:1679-88. [PMID: 25042585 DOI: 10.1016/j.cub.2014.06.025] [Citation(s) in RCA: 245] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Revised: 06/05/2014] [Accepted: 06/10/2014] [Indexed: 11/21/2022]
Abstract
BACKGROUND Excitatory synapses in the CNS are highly dynamic structures that can show activity-dependent remodeling and stabilization in response to learning and memory. Synapses are enveloped with intricate processes of astrocytes known as perisynaptic astrocytic processes (PAPs). PAPs are motile structures displaying rapid actin-dependent movements and are characterized by Ca(2+) elevations in response to neuronal activity. Despite a debated implication in synaptic plasticity, the role of both Ca(2+) events in astrocytes and PAP morphological dynamics remain unclear. RESULTS In the hippocampus, we found that PAPs show extensive structural plasticity that is regulated by synaptic activity through astrocytic metabotropic glutamate receptors and intracellular calcium signaling. Synaptic activation that induces long-term potentiation caused a transient PAP motility increase leading to an enhanced astrocytic coverage of the synapse. Selective activation of calcium signals in individual PAPs using exogenous metabotropic receptor expression and two-photon uncaging reproduced these effects and enhanced spine stability. In vivo imaging in the somatosensory cortex of adult mice revealed that increased neuronal activity through whisker stimulation similarly elevates PAP movement. This in vivo PAP motility correlated with spine coverage and was predictive of spine stability. CONCLUSIONS This study identifies a novel bidirectional interaction between synapses and astrocytes, in which synaptic activity and synaptic potentiation regulate PAP structural plasticity, which in turn determines the fate of the synapse. This mechanism may represent an important contribution of astrocytes to learning and memory processes.
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Nutritional state-dependent ghrelin activation of vasopressin neurons via retrograde trans-neuronal-glial stimulation of excitatory GABA circuits. J Neurosci 2014; 34:6201-13. [PMID: 24790191 DOI: 10.1523/jneurosci.3178-13.2014] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Behavioral and physiological coupling between energy balance and fluid homeostasis is critical for survival. The orexigenic hormone ghrelin has been shown to stimulate the secretion of the osmoregulatory hormone vasopressin (VP), linking nutritional status to the control of blood osmolality, although the mechanism of this systemic crosstalk is unknown. Here, we show using electrophysiological recordings and calcium imaging in rat brain slices that ghrelin stimulates VP neurons in the hypothalamic paraventricular nucleus (PVN) in a nutritional state-dependent manner by activating an excitatory GABAergic synaptic input via a retrograde neuronal-glial circuit. In slices from fasted rats, ghrelin activation of a postsynaptic ghrelin receptor, the growth hormone secretagogue receptor type 1a (GHS-R1a), in VP neurons caused the dendritic release of VP, which stimulated astrocytes to release the gliotransmitter adenosine triphosphate (ATP). ATP activation of P2X receptors excited presynaptic GABA neurons to increase GABA release, which was excitatory to the VP neurons. This trans-neuronal-glial retrograde circuit activated by ghrelin provides an alternative means of stimulation of VP release and represents a novel mechanism of neuronal control by local neuronal-glial circuits. It also provides a potential cellular mechanism for the physiological integration of energy and fluid homeostasis.
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Sheridan GK, Moeendarbary E, Pickering M, O'Connor JJ, Murphy KJ. Theta-burst stimulation of hippocampal slices induces network-level calcium oscillations and activates analogous gene transcription to spatial learning. PLoS One 2014; 9:e100546. [PMID: 24950243 PMCID: PMC4065069 DOI: 10.1371/journal.pone.0100546] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Accepted: 05/28/2014] [Indexed: 01/24/2023] Open
Abstract
Over four decades ago, it was discovered that high-frequency stimulation of the dentate gyrus induces long-term potentiation (LTP) of synaptic transmission. LTP is believed to underlie how we process and code external stimuli before converting it to salient information that we store as 'memories'. It has been shown that rats performing spatial learning tasks display theta-frequency (3–12 Hz) hippocampal neural activity. Moreover, administering theta-burst stimulation (TBS) to hippocampal slices can induce LTP. TBS triggers a sustained rise in intracellular calcium [Ca2+]i in neurons leading to new protein synthesis important for LTP maintenance. In this study, we measured TBS-induced [Ca2+]i oscillations in thousands of cells at increasing distances from the source of stimulation. Following TBS, a calcium wave propagates radially with an average speed of 5.2 µm/s and triggers multiple and regular [Ca2+]i oscillations in the hippocampus. Interestingly, the number and frequency of [Ca2+]i fluctuations post-TBS increased with respect to distance from the electrode. During the post-tetanic phase, 18% of cells exhibited 3 peaks in [Ca2+]i with a frequency of 17 mHz, whereas 2.3% of cells distributed further from the electrode displayed 8 [Ca2+]i oscillations at 33 mHz. We suggest that these observed [Ca2+]i oscillations could lead to activation of transcription factors involved in synaptic plasticity. In particular, the transcription factor, NF-κB, has been implicated in memory formation and is up-regulated after LTP induction. We measured increased activation of NF-κB 30 min post-TBS in CA1 pyramidal cells and also observed similar temporal up-regulation of NF-κB levels in CA1 neurons following water maze training in rats. Therefore, TBS of hippocampal slice cultures in vitro can mimic the cell type-specific up-regulations in activated NF-κB following spatial learning in vivo. This indicates that TBS may induce similar transcriptional changes to spatial learning and that TBS-triggered [Ca2+]i oscillations could activate memory-associated gene expression.
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Affiliation(s)
- Graham K. Sheridan
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
- * E-mail:
| | | | - Mark Pickering
- School of Medicine and Medical Science, Health Sciences Centre, University College Dublin, Dublin, Ireland
| | - John J. O'Connor
- UCD School of Biomolecular and Biomedical Science, Conway Institute, University College Dublin, Dublin, Ireland
| | - Keith J. Murphy
- Neurotherapeutics Research Group, UCD School of Biomolecular and Biomedical Science, Conway Institute, University College Dublin, Dublin, Ireland
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38
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Lee L, Kosuri P, Arancio O. Picomolar amyloid-β peptides enhance spontaneous astrocyte calcium transients. J Alzheimers Dis 2014; 38:49-62. [PMID: 23948929 DOI: 10.3233/jad-130740] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Amyloid-β (Aβ) peptides are constitutively produced in the brain throughout life via mechanisms that can be regulated by synaptic activity. Although Aβ has been extensively studied as the pathological plaque-forming protein species in Alzheimer's disease (AD), little is known about the normal physiological function(s) and signaling pathway(s). We previously discovered that physiologically-relevant, low picomolar amounts of Aβ can enhance synaptic plasticity and hippocampal-dependent cognition in mice. In this study, we demonstrated that astrocytes are cellular candidates for participating in this type of Aβ signaling. Using calcium imaging of primary astrocyte cultures, we observed that picomolar amounts of Aβ peptides can enhance spontaneous intracellular calcium transient signaling. After application of 200 pM Aβ42 peptides, the frequency and amplitude averages of spontaneous cytosolic calcium transients were significantly increased. These effects were dependent on α7 nicotinic acetylcholine receptors (α7-nAChRs), as the enhancement effects were blocked by a pharmacological α7-nAChR inhibitor and in astrocytes from an α7 deficient mouse strain. We additionally examined evoked intercellular calcium wave signaling but did not detect significant picomolar Aβ-induced alterations in propagation parameters. Overall, these results indicate that at a physiologically-relevant low picomolar concentration, Aβ peptides can enhance spontaneous astrocyte calcium transient signaling via α7-nAChRs. Since astrocyte-mediated gliotransmission has been previously found to have neuromodulatory roles, Aβ peptides may have a normal physiological function in regulating neuron-glia signaling. Dysfunction of this signaling process may underlie glia-based aspects of AD pathogenesis.
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Affiliation(s)
- Linda Lee
- Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University, New York, NY, USA Department of Pathology and Cell Biology, Columbia University, New York, NY, USA Center for Neurobiology and Behavior, Columbia University, New York, NY, USA
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39
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Sasaki T, Ishikawa T, Abe R, Nakayama R, Asada A, Matsuki N, Ikegaya Y. Astrocyte calcium signalling orchestrates neuronal synchronization in organotypic hippocampal slices. J Physiol 2014; 592:2771-83. [PMID: 24710057 DOI: 10.1113/jphysiol.2014.272864] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Astrocytes are thought to detect neuronal activity in the form of intracellular calcium elevations; thereby, astrocytes can regulate neuronal excitability and synaptic transmission. Little is known, however, about how the astrocyte calcium signal regulates the activity of neuronal populations. In this study, we addressed this issue using functional multineuron calcium imaging in hippocampal slice cultures. Under normal conditions, CA3 neuronal networks exhibited temporally correlated activity patterns, occasionally generating large synchronization among a subset of cells. The synchronized neuronal activity was correlated with astrocyte calcium events. Calcium buffering by an intracellular injection of a calcium chelator into multiple astrocytes reduced the synaptic strength of unitary transmission between pairs of surrounding pyramidal cells and caused desynchronization of the neuronal networks. Uncaging the calcium in the astrocytes increased the frequency of neuronal synchronization. These data suggest an essential role of the astrocyte calcium signal in the maintenance of basal neuronal function at the circuit level.
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Affiliation(s)
- Takuya Sasaki
- Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan
| | - Tomoe Ishikawa
- Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan
| | - Reimi Abe
- Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan
| | - Ryota Nakayama
- Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan
| | - Akiko Asada
- Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, 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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40
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Xie AX, Lauderdale K, Murphy T, Myers TL, Fiacco TA. Inducing plasticity of astrocytic receptors by manipulation of neuronal firing rates. J Vis Exp 2014. [PMID: 24686723 PMCID: PMC4155624 DOI: 10.3791/51458] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Close to two decades of research has established that astrocytes in situ and in vivo express numerous G protein-coupled receptors (GPCRs) that can be stimulated by neuronally-released transmitter. However, the ability of astrocytic receptors to exhibit plasticity in response to changes in neuronal activity has received little attention. Here we describe a model system that can be used to globally scale up or down astrocytic group I metabotropic glutamate receptors (mGluRs) in acute brain slices. Included are methods on how to prepare parasagittal hippocampal slices, construct chambers suitable for long-term slice incubation, bidirectionally manipulate neuronal action potential frequency, load astrocytes and astrocyte processes with fluorescent Ca(2+) indicator, and measure changes in astrocytic Gq GPCR activity by recording spontaneous and evoked astrocyte Ca(2+) events using confocal microscopy. In essence, a "calcium roadmap" is provided for how to measure plasticity of astrocytic Gq GPCRs. Applications of the technique for study of astrocytes are discussed. Having an understanding of how astrocytic receptor signaling is affected by changes in neuronal activity has important implications for both normal synaptic function as well as processes underlying neurological disorders and neurodegenerative disease.
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Affiliation(s)
- Alison X Xie
- Graduate Program in Neuroscience, University of California Riverside
| | - Kelli Lauderdale
- Graduate Program in Neuroscience, University of California Riverside
| | - Thomas Murphy
- Graduate Program in Neuroscience, University of California Riverside
| | - Timothy L Myers
- Graduate Program in Neuroscience, University of California Riverside
| | - Todd A Fiacco
- Department of Cell Biology and Neuroscience, University of California Riverside; Center for Glial-Neuronal Interactions, University of California Riverside;
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41
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Astrocyte calcium microdomains are inhibited by Bafilomycin A1 and cannot be replicated by low-level Schaffer collateral stimulation in situ. Cell Calcium 2014; 55:1-16. [DOI: 10.1016/j.ceca.2013.10.004] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Accepted: 10/09/2013] [Indexed: 11/20/2022]
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42
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Human stem cell-derived spinal cord astrocytes with defined mature or reactive phenotypes. Cell Rep 2013; 4:1035-1048. [PMID: 23994478 DOI: 10.1016/j.celrep.2013.06.021] [Citation(s) in RCA: 150] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Revised: 05/15/2013] [Accepted: 06/18/2013] [Indexed: 12/23/2022] Open
Abstract
Differentiation of astrocytes from human stem cells has significant potential for analysis of their role in normal brain function and disease, but existing protocols generate only immature astrocytes. Using early neuralization, we generated spinal cord astrocytes from mouse or human embryonic or induced pluripotent stem cells with high efficiency. Remarkably, short exposure to fibroblast growth factor 1 (FGF1) or FGF2 was sufficient to direct these astrocytes selectively toward a mature quiescent phenotype, as judged by both marker expression and functional analysis. In contrast, tumor necrosis factor alpha and interleukin-1β, but not FGFs, induced multiple elements of a reactive inflammatory phenotype but did not affect maturation. These phenotypically defined, scalable populations of spinal cord astrocytes will be important both for studying normal astrocyte function and for modeling human pathological processes in vitro.
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43
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De Pittà M, Volman V, Berry H, Parpura V, Volterra A, Ben-Jacob E. Computational quest for understanding the role of astrocyte signaling in synaptic transmission and plasticity. Front Comput Neurosci 2012; 6:98. [PMID: 23267326 PMCID: PMC3528083 DOI: 10.3389/fncom.2012.00098] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Accepted: 12/06/2012] [Indexed: 01/08/2023] Open
Abstract
The complexity of the signaling network that underlies astrocyte-synapse interactions may seem discouraging when tackled from a theoretical perspective. Computational modeling is challenged by the fact that many details remain hitherto unknown and conventional approaches to describe synaptic function are unsuitable to explain experimental observations when astrocytic signaling is taken into account. Supported by experimental evidence is the possibility that astrocytes perform genuine information processing by means of their calcium signaling and are players in the physiological setting of the basal tone of synaptic transmission. Here we consider the plausibility of this scenario from a theoretical perspective, focusing on the modulation of synaptic release probability by the astrocyte and its implications on synaptic plasticity. The analysis of the signaling pathways underlying such modulation refines our notion of tripartite synapse and has profound implications on our understanding of brain function.
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Affiliation(s)
- Maurizio De Pittà
- School of Physics and Astronomy, Tel Aviv University Ramat Aviv, Israel
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44
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Min R, Santello M, Nevian T. The computational power of astrocyte mediated synaptic plasticity. Front Comput Neurosci 2012; 6:93. [PMID: 23125832 PMCID: PMC3485583 DOI: 10.3389/fncom.2012.00093] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Accepted: 10/15/2012] [Indexed: 12/05/2022] Open
Abstract
Research in the last two decades has made clear that astrocytes play a crucial role in the brain beyond their functions in energy metabolism and homeostasis. Many studies have shown that astrocytes can dynamically modulate neuronal excitability and synaptic plasticity, and might participate in higher brain functions like learning and memory. With the plethora of astrocyte mediated signaling processes described in the literature today, the current challenge is to identify, which of these processes happen under what physiological condition, and how this shapes information processing and, ultimately, behavior. To answer these questions will require a combination of advanced physiological, genetical, and behavioral experiments. Additionally, mathematical modeling will prove crucial for testing predictions on the possible functions of astrocytes in neuronal networks, and to generate novel ideas as to how astrocytes can contribute to the complexity of the brain. Here, we aim to provide an outline of how astrocytes can interact with neurons. We do this by reviewing recent experimental literature on astrocyte-neuron interactions, discussing the dynamic effects of astrocytes on neuronal excitability and short- and long-term synaptic plasticity. Finally, we will outline the potential computational functions that astrocyte-neuron interactions can serve in the brain. We will discuss how astrocytes could govern metaplasticity in the brain, how they might organize the clustering of synaptic inputs, and how they could function as memory elements for neuronal activity. We conclude that astrocytes can enhance the computational power of neuronal networks in previously unexpected ways.
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Affiliation(s)
- Rogier Min
- Department of Physiology, University of Berne Berne, Switzerland
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45
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Fellin T, Ellenbogen JM, De Pittà M, Ben-Jacob E, Halassa MM. Astrocyte regulation of sleep circuits: experimental and modeling perspectives. Front Comput Neurosci 2012; 6:65. [PMID: 22973222 PMCID: PMC3428699 DOI: 10.3389/fncom.2012.00065] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Accepted: 08/10/2012] [Indexed: 12/20/2022] Open
Abstract
Integrated within neural circuits, astrocytes have recently been shown to modulate brain rhythms thought to mediate sleep function. Experimental evidence suggests that local impact of astrocytes on single synapses translates into global modulation of neuronal networks and behavior. We discuss these findings in the context of current conceptual models of sleep generation and function, each of which have historically focused on neural mechanisms. We highlight the implications and the challenges introduced by these results from a conceptual and computational perspective. We further provide modeling directions on how these data might extend our knowledge of astrocytic properties and sleep function. Given our evolving understanding of how local cellular activities during sleep lead to functional outcomes for the brain, further mechanistic and theoretical understanding of astrocytic contribution to these dynamics will undoubtedly be of great basic and translational benefit.
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Affiliation(s)
- Tommaso Fellin
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia Genova, Italy
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46
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Imbe H, Kimura A, Donishi T, Kaneoke Y. Chronic restraint stress decreases glial fibrillary acidic protein and glutamate transporter in the periaqueductal gray matter. Neuroscience 2012; 223:209-18. [PMID: 22890077 DOI: 10.1016/j.neuroscience.2012.08.007] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Revised: 08/01/2012] [Accepted: 08/02/2012] [Indexed: 12/22/2022]
Abstract
Stress affects brain activity and promotes long-term changes in multiple neural systems. Exposure to stressors causes substantial effects on the perception and response to pain. In several animal models, chronic stress produces lasting hyperalgesia. Postmortem studies of stress-related psychiatric disorders have demonstrated a decrease in the number of astrocytes and the level of glial fibrillary acidic protein (GFAP), a marker for astrocyte, in the cerebral cortex. Since astrocytes play vital roles in maintaining neuroplasticity via synapse maintenance and secretion of neurotrophins, impairment of astrocytes is thought to be involved in the neuropathology. In the present study we examined GFAP and excitatory amino acid transporter 2 (EAAT2) protein levels in the periaqueductal gray matter (PAG) after subacute and chronic restraint stresses to clarify changes in descending pain modulatory system in the rat with stress-induced hyperalgesia. Chronic restraint stress (6h/day for 3 weeks), but not subacute restraint stress (6h/day for 3 days), caused a marked mechanical hypersensitivity and aggressive behavior. The chronic restraint stress induced a significant decrease of GFAP protein level in the PAG (32.0 ± 8.9% vs. control group, p<0.05). In immunohistochemical analysis the remarkable decrease of GFAP was observed in the ventrolateral PAG. The EAAT2 protein level in the 3 weeks stress group (79.6 ± 6.8%) was significantly lower compared to that in the control group (100.0 ± 6.1%, p<0.05). In contrast there was no significant difference in the GFAP and EAAT2 protein levels between the control and 3 days stress groups These findings suggest a dysfunction of the PAG that plays pivotal roles in the organization of strategies for coping with stressors and in pain modulation after chronic restraint stress.
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Affiliation(s)
- H Imbe
- Department of Physiology, Wakayama Medical University, Kimiidera 811-1, Wakayama City 641-8509, Japan.
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Barat E, Boisseau S, Bouyssières C, Appaix F, Savasta M, Albrieux M. Subthalamic nucleus electrical stimulation modulates calcium activity of nigral astrocytes. PLoS One 2012; 7:e41793. [PMID: 22848608 PMCID: PMC3407058 DOI: 10.1371/journal.pone.0041793] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Accepted: 06/25/2012] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The substantia nigra pars reticulata (SNr) is a major output nucleus of the basal ganglia, delivering inhibitory efferents to the relay nuclei of the thalamus. Pathological hyperactivity of SNr neurons is known to be responsible for some motor disorders e.g. in Parkinson's disease. One way to restore this pathological activity is to electrically stimulate one of the SNr input, the excitatory subthalamic nucleus (STN), which has emerged as an effective treatment for parkinsonian patients. The neuronal network and signal processing of the basal ganglia are well known but, paradoxically, the role of astrocytes in the regulation of SNr activity has never been studied. PRINCIPAL FINDINGS In this work, we developed a rat brain slice model to study the influence of spontaneous and induced excitability of afferent nuclei on SNr astrocytes calcium activity. Astrocytes represent the main cellular population in the SNr and display spontaneous calcium activities in basal conditions. Half of this activity is autonomous (i.e. independent of synaptic activity) while the other half is dependent on spontaneous glutamate and GABA release, probably controlled by the pace-maker activity of the pallido-nigral and subthalamo-nigral loops. Modification of the activity of the loops by STN electrical stimulation disrupted this astrocytic calcium excitability through an increase of glutamate and GABA releases. Astrocytic AMPA, mGlu and GABA(A) receptors were involved in this effect. SIGNIFICANCE Astrocytes are now viewed as active components of neural networks but their role depends on the brain structure concerned. In the SNr, evoked activity prevails and autonomous calcium activity is lower than in the cortex or hippocampus. Our data therefore reflect a specific role of SNr astrocytes in sensing the STN-GPe-SNr loops activity and suggest that SNr astrocytes could potentially feedback on SNr neuronal activity. These findings have major implications given the position of SNr in the basal ganglia network.
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Affiliation(s)
- Elodie Barat
- Institut National de la Santé et de la Recherche Médicale, U 836, Grenoble Institut des Neurosciences, Equipe Dynamique et Physiopathologie des Ganglions de la Base, Grenoble F-38043, France
- Université Joseph Fourier, Grenoble F- 38042, France
| | - Sylvie Boisseau
- Institut National de la Santé et de la Recherche Médicale, U 836, Grenoble Institut des Neurosciences, Equipe Dynamique et Physiopathologie des Ganglions de la Base, Grenoble F-38043, France
- Université Joseph Fourier, Grenoble F- 38042, France
| | - Céline Bouyssières
- Institut National de la Santé et de la Recherche Médicale, U 836, Grenoble Institut des Neurosciences, Equipe Dynamique et Physiopathologie des Ganglions de la Base, Grenoble F-38043, France
- Université Joseph Fourier, Grenoble F- 38042, France
| | - Florence Appaix
- Institut National de la Santé et de la Recherche Médicale, U 836, Grenoble Institut des Neurosciences, Equipe Dynamique et Physiopathologie des Ganglions de la Base, Grenoble F-38043, France
- Université Joseph Fourier, Grenoble F- 38042, France
| | - Marc Savasta
- Institut National de la Santé et de la Recherche Médicale, U 836, Grenoble Institut des Neurosciences, Equipe Dynamique et Physiopathologie des Ganglions de la Base, Grenoble F-38043, France
- Université Joseph Fourier, Grenoble F- 38042, France
- Centre Hospitalier Universitaire de Grenoble, BP217, Grenoble F-38043, France
| | - Mireille Albrieux
- Institut National de la Santé et de la Recherche Médicale, U 836, Grenoble Institut des Neurosciences, Equipe Dynamique et Physiopathologie des Ganglions de la Base, Grenoble F-38043, France
- Université Joseph Fourier, Grenoble F- 38042, France
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48
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Direct and glia-mediated effects of GABA on development of central olfactory neurons. ACTA ACUST UNITED AC 2012; 7:143-61. [PMID: 22874585 DOI: 10.1017/s1740925x12000075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Previously studied for its role in processing olfactory information in the antennal lobe, GABA also may shape development of the olfactory pathway, acting either through or on glial cells. Early in development, the dendrites of GABAergic neurons extend to the glial border that surrounds the nascent olfactory lobe neuropil. These neuropil glia express both GABAA and GABAB receptors, about half of the glia in acute cultures responded to GABA with small outward currents, and about a third responded with small transient increases in intracellular calcium. The neuronal classes that express GABA in vivo, the local interneurons and a subset of projection neurons, also do so in culture. Exposure to GABA in culture increased the size and complexity of local interneurons, but had no effect on glial morphology. The presence of glia alone did not affect neuronal morphology, but in the presence of both glia and GABA, the growth-enhancing effects of GABA on cultured antennal lobe neurons were eliminated. Contact between the glial cells and the neurons was not necessary. Operating in vivo, these antagonistic effects, one direct and one glia mediated, could help to sculpt the densely branched, tufted arbors that are characteristic of neurons innervating olfactory glomeruli.
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49
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Hemodynamic responses evoked by neuronal stimulation via channelrhodopsin-2 can be independent of intracortical glutamatergic synaptic transmission. PLoS One 2012; 7:e29859. [PMID: 22253807 PMCID: PMC3254633 DOI: 10.1371/journal.pone.0029859] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Accepted: 12/05/2011] [Indexed: 11/19/2022] Open
Abstract
Maintenance of neuronal function depends on the delivery of oxygen and glucose through changes in blood flow that are linked to the level of ongoing neuronal and glial activity, yet the underlying mechanisms remain unclear. Using transgenic mice expressing the light-activated cation channel channelrhodopsin-2 in deep layer pyramidal neurons, we report that changes in intrinsic optical signals and blood flow can be evoked by activation of a subset of channelrhodopsin-2-expressing neurons in the sensorimotor cortex. We have combined imaging and pharmacology to examine the importance of glutamatergic synaptic transmission in this form of neurovascular coupling. Blockade of ionotropic glutamate receptors with the antagonists CNQX and MK801 significantly reduced forepaw-evoked hemodynamic responses, yet resulted in no significant reduction of channelrhodopsin-evoked hemodynamic responses, suggesting that stimulus-dependent coupling of neuronal activity to blood flow can be independent of local excitatory synaptic transmission. Together, these results indicate that channelrhodopsin-2 activation of sensorimotor excitatory neurons produces changes in intrinsic optical signals and blood flow that can occur under conditions where synaptic activation of neurons or other cells through ionotropic glutamate receptors would be blocked.
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