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Fabbri R, Spennato D, Conte G, Konstantoulaki A, Lazzarini C, Saracino E, Nicchia GP, Frigeri A, Zamboni R, Spray DC, Benfenati V. The emerging science of Glioception: Contribution of glia in sensing, transduction, circuit integration of interoception. Pharmacol Ther 2023; 245:108403. [PMID: 37024060 DOI: 10.1016/j.pharmthera.2023.108403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 03/29/2023] [Accepted: 03/30/2023] [Indexed: 04/08/2023]
Abstract
Interoception is the process by which the nervous system regulates internal functions to achieve homeostasis. The role of neurons in interoception has received considerable recent attention, but glial cells also contribute. Glial cells can sense and transduce signals including osmotic, chemical, and mechanical status of extracellular milieu. Their ability to dynamically communicate "listening" and "talking" to neurons is necessary to monitor and regulate homeostasis and information integration in the nervous system. This review introduces the concept of "Glioception" and focuses on the process by which glial cells sense, interpret and integrate information about the inner state of the organism. Glial cells are ideally positioned to act as sensors and integrators of diverse interoceptive signals and can trigger regulatory responses via modulation of the activity of neuronal networks, both in physiological and pathological conditions. We believe that understanding and manipulating glioceptive processes and underlying molecular mechanisms provide a key path to develop new therapies for the prevention and alleviation of devastating interoceptive dysfunctions, among which pain is emphasized here with more focused details.
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Affiliation(s)
- Roberta Fabbri
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Via P. Gobetti 101, I-40129 Bologna, Italy; Department of Electrical, Electronic, and Information Engineering "Guglielmo Marconi", University of Bologna, viale del Risorgimento 2, 40136 Bologna, Italy.
| | - Diletta Spennato
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Via P. Gobetti 101, I-40129 Bologna, Italy; Department of Bioscience, Biotechnologies and Biopharmaceutics, Centre of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, BA, Italy
| | - Giorgia Conte
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Via P. Gobetti 101, I-40129 Bologna, Italy
| | - Aikaterini Konstantoulaki
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Via P. Gobetti 101, I-40129 Bologna, Italy; Department of Chemistry "Giacomo Ciamician", University of Bologna, Via Selmi, 2, 40126 Bologna, BO, Italy
| | - Chiara Lazzarini
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Via P. Gobetti 101, I-40129 Bologna, Italy
| | - Emanuela Saracino
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Via P. Gobetti 101, I-40129 Bologna, Italy
| | - Grazia Paola Nicchia
- School of Medicine, Basic Medical Sciences, Neuroscience and Sense Organs, University of Bari "Aldo Moro", Bari, BA, Italy; Department of Bioscience, Biotechnologies and Biopharmaceutics, Centre of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, BA, Italy
| | - Antonio Frigeri
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA; Department of Bioscience, Biotechnologies and Biopharmaceutics, Centre of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, BA, Italy
| | - Roberto Zamboni
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Via P. Gobetti 101, I-40129 Bologna, Italy
| | - David C Spray
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| | - Valentina Benfenati
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Via P. Gobetti 101, I-40129 Bologna, Italy.
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Sun C, Ye Y, Tan Z, Liu Y, Li Y, Hu W, Liang K, Egranov SD, Huang LA, Zhang Z, Zhang Y, Yao J, Nguyen TK, Zhao Z, Wu A, Marks JR, Caudle AS, Sahin AA, Gao J, Gammon ST, Piwnica-Worms D, Hu J, Chiao PJ, Yu D, Hung MC, Curran MA, Calin GA, Ying H, Han L, Lin C, Yang L. Tumor-associated nonmyelinating Schwann cell-expressed PVT1 promotes pancreatic cancer kynurenine pathway and tumor immune exclusion. SCIENCE ADVANCES 2023; 9:eadd6995. [PMID: 36724291 PMCID: PMC9891701 DOI: 10.1126/sciadv.add6995] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Accepted: 01/03/2023] [Indexed: 05/16/2023]
Abstract
One of the major obstacles to treating pancreatic ductal adenocarcinoma (PDAC) is its immunoresistant microenvironment. The functional importance and molecular mechanisms of Schwann cells in PDAC remains largely elusive. We characterized the gene signature of tumor-associated nonmyelinating Schwann cells (TASc) in PDAC and indicated that the abundance of TASc was correlated with immune suppressive tumor microenvironment and the unfavorable outcome of patients with PDAC. Depletion of pancreatic-specific TASc promoted the tumorigenesis of PDAC tumors. TASc-expressed long noncoding RNA (lncRNA) plasmacytoma variant translocation 1 (PVT1) was triggered by the tumor cell-produced interleukin-6. Mechanistically, PVT1 modulated RAF proto-oncogene serine/threonine protein kinase-mediated phosphorylation of tryptophan 2,3-dioxygenase in TASc, facilitating its enzymatic activities in catalysis of tryptophan to kynurenine. Depletion of TASc-expressed PVT1 suppressed PDAC tumor growth. Furthermore, depletion of TASc using a small-molecule inhibitor effectively sensitized PDAC to immunotherapy, signifying the important roles of TASc in PDAC immune resistance.
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Affiliation(s)
- Chengcao Sun
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Youqiong Ye
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston McGovern Medical School, Houston, TX 77030, USA
| | - Zhi Tan
- Center for Drug Discovery, Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Yuan Liu
- Center for Epigenetics and Disease Prevention, Institute of Biosciences and Technology, Texas A&M University, Houston, TX 77030, USA
| | - Yajuan Li
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Wei Hu
- Institute of Translational Medicine, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 201620, China
| | - Ke Liang
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Sergey D. Egranov
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Lisa Angela Huang
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Zhao Zhang
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston McGovern Medical School, Houston, TX 77030, USA
| | - Yaohua Zhang
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Jun Yao
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Tina K. Nguyen
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Zilong Zhao
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Andrew Wu
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Jeffrey R. Marks
- Division of Surgical Science, Department of Surgery, Duke University, School of Medicine, Durham, NC 27710, USA
| | - Abigail S. Caudle
- Department of Breast Surgical Oncology, Division of Surgery, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Aysegul A. Sahin
- Department of Pathology, Division of Pathology and Laboratory Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Jianjun Gao
- Department of Genitourinary Medical Oncology, Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Seth T. Gammon
- Department of Cancer Systems Imaging, Division of Diagnostic Imaging, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - David Piwnica-Worms
- Department of Cancer Systems Imaging, Division of Diagnostic Imaging, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Jian Hu
- Department of Cancer Biology, Division of Basic Sciences, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
- The Graduate School of Biomedical Sciences, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Paul J. Chiao
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
- The Graduate School of Biomedical Sciences, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Dihua Yu
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
- The Graduate School of Biomedical Sciences, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Mien-Chie Hung
- Graduate Institute of Biomedical Sciences, Research Center for Cancer Biology, and Center for Molecular Medicine, China Medical University, Taichung 404, Taiwan
- Department of Biotechnology, Asia University, Taichung 413, Taiwan
| | - Michael A. Curran
- The Graduate School of Biomedical Sciences, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
- Department of Immunology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - George A. Calin
- Department of Translational Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
- Center for RNA Interference and Non-Coding RNAs, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Haoqiang Ying
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
- The Graduate School of Biomedical Sciences, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Leng Han
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston McGovern Medical School, Houston, TX 77030, USA
- Center for Epigenetics and Disease Prevention, Institute of Biosciences and Technology, Texas A&M University, Houston, TX 77030, USA
| | - Chunru Lin
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
- The Graduate School of Biomedical Sciences, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Liuqing Yang
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
- The Graduate School of Biomedical Sciences, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
- Center for RNA Interference and Non-Coding RNAs, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
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Glial Modulation of Energy Balance: The Dorsal Vagal Complex Is No Exception. Int J Mol Sci 2022; 23:ijms23020960. [PMID: 35055143 PMCID: PMC8779587 DOI: 10.3390/ijms23020960] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Revised: 01/11/2022] [Accepted: 01/13/2022] [Indexed: 02/04/2023] Open
Abstract
The avoidance of being overweight or obese is a daily challenge for a growing number of people. The growing proportion of people suffering from a nutritional imbalance in many parts of the world exemplifies this challenge and emphasizes the need for a better understanding of the mechanisms that regulate nutritional balance. Until recently, research on the central regulation of food intake primarily focused on neuronal signaling, with little attention paid to the role of glial cells. Over the last few decades, our understanding of glial cells has changed dramatically. These cells are increasingly regarded as important neuronal partners, contributing not just to cerebral homeostasis, but also to cerebral signaling. Our understanding of the central regulation of energy balance is part of this (r)evolution. Evidence is accumulating that glial cells play a dynamic role in the modulation of energy balance. In the present review, we summarize recent data indicating that the multifaceted glial compartment of the brainstem dorsal vagal complex (DVC) should be considered in research aimed at identifying feeding-related processes operating at this level.
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Clyburn C, Browning KN. Glutamatergic plasticity within neurocircuits of the dorsal vagal complex and the regulation of gastric functions. Am J Physiol Gastrointest Liver Physiol 2021; 320:G880-G887. [PMID: 33730858 PMCID: PMC8202199 DOI: 10.1152/ajpgi.00014.2021] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The meticulous regulation of the gastrointestinal (GI) tract is required for the coordination of gastric motility and emptying, intestinal secretion, absorption, and transit as well as for the overarching management of food intake and energy homeostasis. Disruption of GI functions is associated with the development of severe GI disorders and the alteration of food intake and caloric balance. Functional GI disorders as well as the dysregulation of energy balance and food intake are frequently associated with, or result from, alterations in the central regulation of GI control. The faithful and rapid transmission of information from the stomach and upper GI tract to second-order neurons of the nucleus of the tractus solitarius (NTS) relies on the delicate modulation of excitatory glutamatergic transmission, as does the relay of integrated signals from the NTS to parasympathetic efferent neurons of the dorsal motor nucleus of the vagus (DMV). Many studies have focused on understanding the physiological and pathophysiological modulation of these glutamatergic synapses, although their role in the control and regulation of GI functions has lagged behind that of cardiovascular and respiratory functions. The purpose of this review is to examine the current literature exploring the role of glutamatergic transmission in the DVC in the regulation of GI functions.
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Affiliation(s)
- Courtney Clyburn
- Department of Neural and Behavioral Sciences, Penn State University College of Medicine, Hershey, Pennsylvania
| | - Kirsteen N. Browning
- Department of Neural and Behavioral Sciences, Penn State University College of Medicine, Hershey, Pennsylvania
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5
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Martinez D, Kline DD. The role of astrocytes in the nucleus tractus solitarii in maintaining central control of autonomic function. Am J Physiol Regul Integr Comp Physiol 2021; 320:R418-R424. [PMID: 33439770 PMCID: PMC8238142 DOI: 10.1152/ajpregu.00254.2020] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 12/16/2020] [Accepted: 01/07/2021] [Indexed: 12/24/2022]
Abstract
The nucleus tractus solitarii (nTS) is the first central site for the termination and integration of autonomic and respiratory sensory information. Sensory afferents terminating in the nTS as well as the embedded nTS neurocircuitry release and utilize glutamate that is critical for maintenance of baseline cardiorespiratory parameters and initiating cardiorespiratory reflexes, including those activated by bouts of hypoxia. nTS astrocytes contribute to synaptic and neuronal activity through a variety of mechanisms, including gliotransmission and regulation of glutamate in the extracellular space via membrane-bound transporters. Here, we aim to highlight recent evidence for the role of astrocytes within the nTS and their regulation of autonomic and cardiorespiratory processes under normal and hypoxic conditions.
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Affiliation(s)
- Diana Martinez
- Department of Biomedical Sciences and Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
| | - David D Kline
- Department of Biomedical Sciences and Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
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6
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Cawthon CR, Kirkland RA, Pandya S, Brinson NA, de La Serre CB. Non-neuronal crosstalk promotes an inflammatory response in nodose ganglia cultures after exposure to byproducts from gram positive, high-fat-diet-associated gut bacteria. Physiol Behav 2020; 226:113124. [PMID: 32763334 PMCID: PMC7530053 DOI: 10.1016/j.physbeh.2020.113124] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2019] [Revised: 07/31/2020] [Accepted: 08/03/2020] [Indexed: 02/06/2023]
Abstract
Vagal afferent neurons (VAN) projecting to the lamina propria of the digestive tract are the primary source of gut-originating signals to the central nervous system (CNS). VAN cell bodies are found in the nodose ganglia (NG). Responsiveness of VAN to gut-originating signals is altered by feeding status with sensitivity to satiety signals such as cholecystokinin (CCK) increasing in the fed state. Chronic high-fat (HF) feeding results in inflammation at the level of the NG associated with a loss of VAN ability to switch phenotype from the fasted to the fed state. HF feeding also leads to compositional changes in the gut microbiota. HF diet consumption notably drives increased Firmicutes to Bacteroidetes phyla ratio and increased members of the Actinobacteria phylum. Firmicutes and Actinobacteria are largely gram positive (GP). In this study, we aimed to determine if byproducts from GP bacteria can induce an inflammatory response in cultured NG and to characterize the mechanism and cell types involved in the response. NG were collected from male Wistar rats and cultured for a total of 72 hours. At 48-68 hours after plating, cultures were treated with neuronal culture media in which Serinicoccus chungangensis had been grown and removed (SUP), lipoteichoic acid (LTA), or meso-diaminopimelic acid (meso-DAP). Some treatments included the glial inhibitors minocycline (MINO) and/or fluorocitrate (FC). The responses were evaluated using immunocytochemistry, qPCR, and electrochemiluminescence. We found that SUP induced an inflammatory response characterized by increased interleukin (IL)-6 staining and increased expression of genes for IL-6, interferon (IFN)γ, and tumor necrosis factor (TNF)α along with genes associated with cell-to-cell communication such as C-C motif chemokine ligand-2 (CCL2). Inclusion of inhibitors attenuated some responses but failed to completely normalize all indications of response, highlighting the role of immunocompetent cellular crosstalk in regulating the inflammatory response. LTA and meso-DAP produced responses that shared characteristics with SUP but were not identical. Our results support a role for HF associated GP bacterial byproducts' ability to contribute to vagal inflammation and to engage signaling from nonneuronal cells.
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Affiliation(s)
- Carolina R Cawthon
- Department of Foods and Nutrition, The University of Georgia, Athens, Georgia30602, United States
| | - Rebecca A Kirkland
- Department of Foods and Nutrition, The University of Georgia, Athens, Georgia30602, United States
| | - Shreya Pandya
- Department of Foods and Nutrition, The University of Georgia, Athens, Georgia30602, United States
| | - Nigel A Brinson
- Department of Foods and Nutrition, The University of Georgia, Athens, Georgia30602, United States
| | - Claire B de La Serre
- Department of Foods and Nutrition, The University of Georgia, Athens, Georgia30602, United States.
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Dorsal vagal complex and hypothalamic glia differentially respond to leptin and energy balance dysregulation. Transl Psychiatry 2020; 10:90. [PMID: 32152264 PMCID: PMC7062837 DOI: 10.1038/s41398-020-0767-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 02/18/2020] [Accepted: 02/25/2020] [Indexed: 01/16/2023] Open
Abstract
Previous studies identify a role for hypothalamic glia in energy balance regulation; however, a narrow hypothalamic focus provides an incomplete understanding of how glia throughout the brain respond to and regulate energy homeostasis. We examined the responses of glia in the dorsal vagal complex (DVC) to the adipokine leptin and high fat diet-induced obesity. DVC astrocytes functionally express the leptin receptor; in vivo pharmacological studies suggest that DVC astrocytes partly mediate the anorectic effects of leptin in lean but not diet-induced obese rats. Ex vivo calcium imaging indicated that these changes were related to a lower proportion of leptin-responsive cells in the DVC of obese versus lean animals. Finally, we investigated DVC microglia and astroglia responses to leptin and energy balance dysregulation in vivo: obesity decreased DVC astrogliosis, whereas the absence of leptin signaling in Zucker rats was associated with extensive astrogliosis in the DVC and decreased hypothalamic micro- and astrogliosis. These data uncover a novel functional heterogeneity of astrocytes in different brain nuclei of relevance to leptin signaling and energy balance regulation.
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Rogers RC, Burke SJ, Collier JJ, Ritter S, Hermann GE. Evidence that hindbrain astrocytes in the rat detect low glucose with a glucose transporter 2-phospholipase C-calcium release mechanism. Am J Physiol Regul Integr Comp Physiol 2020; 318:R38-R48. [PMID: 31596114 PMCID: PMC6985801 DOI: 10.1152/ajpregu.00133.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Astrocytes generate robust cytoplasmic calcium signals in response to reductions in extracellular glucose. This calcium signal, in turn, drives purinergic gliotransmission, which controls the activity of catecholaminergic (CA) neurons in the hindbrain. These CA neurons are critical to triggering glucose counter-regulatory responses (CRRs) that, ultimately, restore glucose homeostasis via endocrine and behavioral means. Although the astrocyte low-glucose sensor involvement in CRR has been accepted, it is not clear how astrocytes produce an increase in intracellular calcium in response to a decrease in glucose. Our ex vivo calcium imaging studies of hindbrain astrocytes show that the glucose type 2 transporter (GLUT2) is an essential feature of the astrocyte glucosensor mechanism. Coimmunoprecipitation assays reveal that the recombinant GLUT2 binds directly with the recombinant Gq protein subunit that activates phospholipase C (PLC). Additional calcium imaging studies suggest that GLUT2 may be connected to a PLC-endoplasmic reticular-calcium release mechanism, which is amplified by calcium-induced calcium release (CICR). Collectively, these data help outline a potential mechanism used by astrocytes to convert information regarding low-glucose levels into intracellular changes that ultimately regulate the CRR.
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Affiliation(s)
- Richard C. Rogers
- 1Laboratory of Autonomic Neuroscience, Pennington Biomedical Research Center, Baton Rouge, Louisiana
| | - Susan J. Burke
- 2Laboratory of Immunogenetics, Pennington Biomedical Research Center, Baton Rouge, Louisiana
| | - J. Jason Collier
- 3Laboratory of Islet Biology and Inflammation, Pennington Biomedical Research Center, Baton Rouge, Louisiana
| | - Sue Ritter
- 4Department of Veterinary and Comparative Anatomy, Pharmacology and Physiology, Washington State University, Pullman, Washington
| | - Gerlinda E. Hermann
- 1Laboratory of Autonomic Neuroscience, Pennington Biomedical Research Center, Baton Rouge, Louisiana
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Rogers RC, Hermann GE. Hindbrain astrocytes and glucose counter-regulation. Physiol Behav 2019; 204:140-150. [PMID: 30797812 PMCID: PMC7145321 DOI: 10.1016/j.physbeh.2019.02.025] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2018] [Revised: 02/11/2019] [Accepted: 02/20/2019] [Indexed: 12/31/2022]
Abstract
Hindbrain astrocytes are emerging as critical components in the regulation of homeostatic functions by either modulating synaptic activity or serving as primary detectors of physiological parameters. Recent studies have suggested that the glucose counter-regulation response (CRR), a critical defense against hypoglycemic emergencies, is dependent on glucoprivation-sensitive astrocytes in the hindbrain. This subpopulation of astrocytes produces a robust calcium signal in response to glucopenic stimuli. Both ex vivo and in vivo evidence suggest that low-glucose sensitive astrocytes utilize purinergic gliotransmission to activate catecholamine neurons in the hindbrain that are critical to the generation of the integrated CRR. Lastly, reports in the clinical literature suggest that an uncontrolled activation of CRR may as part of the pathology of severe traumatic injury. Work in our laboratory also suggests that this pathological hyperglycemia resulting from traumatic injury may be caused by the action of thrombin (generated by tissue trauma or bleeding) on hindbrain astrocytes. Similar to their glucopenia-sensitive neighbors, these hindbrain astrocytes may trigger hyperglycemic responses by their interactions with catecholaminergic neurons.
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Affiliation(s)
- Richard C Rogers
- Pennington Biomedical Research Center, 6400 Perkins Rd, Baton Rouge, LA 70808, USA
| | - Gerlinda E Hermann
- Pennington Biomedical Research Center, 6400 Perkins Rd, Baton Rouge, LA 70808, USA.
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10
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De Bernardis Murat C, Leão RM. A voltage-dependent depolarization induced by low external glucose in neurons of the nucleus of the tractus solitarius: interaction with K ATP channels. J Physiol 2019; 597:2515-2532. [PMID: 30927460 DOI: 10.1113/jp277729] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Accepted: 03/21/2019] [Indexed: 12/18/2022] Open
Abstract
KEY POINTS Neurons from the brainstem nucleus of the tractus solitarius (NTS) participate in the counter-regulatory mechanisms in response to hypoglycaemia. ATP-sensitive potassium (KATP ) channels are expressed in NTS neurons, and are partially open at rest in normoglycaemic 5 mM glucose. In normoglycaemic conditions, most NTS neurons depolarize in response to low external glucose (0.5 mM), via a voltage-dependent mechanism. Conversely, most NTS neurons incubated in hyperglycaemic 10 mM glucose do not respond to low glucose due to a more positive resting membrane potential caused by the closure of KATP channels following increased intracellular metabolic ATP. Our findings show that in hyperglycaemic conditions, NTS neurons failed to sense rapid changes in external glucose, which could be related to hypoglycaemia-associated autonomic failure. ABSTRACT The nucleus of the tractus solitarius (NTS) is an integrative centre for autonomic counter-regulatory responses to hypoglycaemia. KATP channels link the metabolic status of the neuron to its excitability. Here we investigated the influence of KATP channels on the membrane potential of NTS neurons in normo- and hyperglycaemic external glucose concentrations, and after switching to a hypoglycaemic concentration, using in vitro electrophysiological recordings in brainstem slices. We found that in normoglycaemic (5 mM) glucose, tolbutamide, a KATP channel antagonist, depolarized the membrane of most neurons, and this effect was observed in more hyperpolarized neurons. All neurons hyperpolarized after pharmacological activation of KATP channels. Most NTS neurons depolarized in the presence of low glucose (0.5 mM), and this effect was only seen in hyperpolarized neurons. The effect of glucose was caused by a cationic current with a reversal potential around -50 mV. In the presence of hyperglycaemic glucose (10 mM), neurons were more depolarized, and fewer neurons responded to KATP blockage. Application of 0.5 mM glucose solution to these neurons depolarized the membrane only in more hyperpolarized neurons. We conclude that NTS neurons present with KATP channels open at rest in normoglycaemic conditions, and their membrane potential is affected by extracellular glucose. Moreover, NTS neurons depolarize the membrane in response to the application of a low glucose solution, but this effect is occluded by membrane depolarization triggered by KATP blockage. Our data suggest a homeostatic regulation of the membrane potential by external glucose, and a possible mechanism related to the hypoglycaemia-associated autonomic failure.
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Affiliation(s)
- Cahuê De Bernardis Murat
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Ricardo Mauricio Leão
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
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Inhibition of activated astrocyte ameliorates lipopolysaccharide- induced depressive-like behaviors. J Affect Disord 2019; 242:52-59. [PMID: 30172225 DOI: 10.1016/j.jad.2018.08.015] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Revised: 07/05/2018] [Accepted: 08/07/2018] [Indexed: 12/19/2022]
Abstract
BACKGROUND Numerous studies indicate that inflammation plays important roles in the development of depression. Astrocytes are crucial regulators of immune response in the central nervous system, and strongly activated by pro-inflammatory cytokines. We hypothesized that inhibition of activated astrocytes contributed to ameliorate depressive-like symptoms. METHODS This study evaluated the antidepressant-like effect of inhibition of activated astrocytes, by a well-established astrocyte inactivator fluorocitrate (FC), on a lipopolysaccharide (LPS)-induced model of depression. Forced swim test (FST), tail suspension test (TST) and sucrose preference test were used to assess depressive-like behaviors. The expression of fibrillary acidic protein (GFAP), brain-derived neurotrophic factor (BDNF) and neuroinflammation were determined in the hippocampus and cortex. RESULTS The results demonstrated that LPS increased immobility time in the TST and FST, reduced sucrose preference as well. LPS also enhanced the expression of IL-1β, TNF-α, iNOS and GFAP, accompanying with decreased expression of BDNF in the hippocampus and cortex. Inhibition of activated astrocytes by FC significantly prevented LPS- induced alteration in the FST, TST and sucrose preference test. Moreover, in the hippocampus and cortex, inhibition of activated astrocytes by FC significantly attenuated increases of neuroinflammation and GFAP whereas reversed decrease of BDNF in LPS- challenged depression. CONCLUSIONS Taken together, the results suggest that inhibition of activated astrocytes ameliorates LPS-induced depressive-like behavior, providing the first evidence that inhibition of activated astrocytes might represent a novel therapeutic target for depression.
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McDougal DH, Darpolor MM, DuVall MA, Sutton EF, Morrison CD, Gadde KM, Redman LM, Carmichael OT. Glial acetate metabolism is increased following a 72-h fast in metabolically healthy men and correlates with susceptibility to hypoglycemia. Acta Diabetol 2018; 55:1029-1036. [PMID: 29931424 PMCID: PMC6153507 DOI: 10.1007/s00592-018-1180-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2017] [Accepted: 06/11/2018] [Indexed: 12/02/2022]
Abstract
AIMS Prior exposure to insulin-induced hypoglycemia was shown to increase glial acetate metabolism (GAM) during subsequent exposure to hypoglycemia in diabetic individuals. However, it remained unclear whether this effect was dependent on the disease state or the antecedent cause of hypoglycemia. We aimed to establish whether exposure to fasting-induced hypoglycemia was sufficient to produce alterations in GAM in non-diabetic individuals. METHODS GAM was measured via carbon-13 magnetic resonance spectroscopy during infusion of [1-13C] acetate before and after a 72-h fast in six metabolically healthy men. All participants were male, aged 18-40 years, with a Body Mass Index of 20.0-27.9 kg/m2, who consented to reside at Pennington Biomedical Research Center for 4 days. The main outcome measure was the percent enhancement of cerebral [1-13C] bicarbonate (the primary metabolic byproduct of glial oxidation of [1-13C] acetate). Continuous glucose monitoring was used to measure hypoglycemic episodes during the 72-h fast. RESULTS As expected, 72 h of fasting significantly reduced blood glucose levels and resulted in a high frequency of hypoglycemic episodes. Steady-state GAM increased from 53.5 ± 3.7 to 61.9 ± 1.7% following the 72-h fast (p = 0.005). This increase correlated with greater duration of hypoglycemia experienced during the fast (r = 0.967). In addition, subjects with greater GAM at baseline experienced a greater increase in the duration of hypoglycemia experienced during the 72-h fast (r = 0.979). CONCLUSIONS GAM has potential as a biomarker for susceptibility to hypoglycemic episodes. TRAIL REGISTRATION Clinicaltrials.gov ID: NCT02690168.
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Affiliation(s)
| | | | | | - Elizabeth Frost Sutton
- Pennington Biomedical Research Center, Baton Rouge, LA, 70808, USA
- Magee-Womens Research Institute, 204 Craft Ave, Pittsburgh, PA, 15213, USA
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Rogers RC, McDougal DH, Ritter S, Qualls-Creekmore E, Hermann GE. Response of catecholaminergic neurons in the mouse hindbrain to glucoprivic stimuli is astrocyte dependent. Am J Physiol Regul Integr Comp Physiol 2018; 315:R153-R164. [PMID: 29590557 PMCID: PMC6087883 DOI: 10.1152/ajpregu.00368.2017] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Hindbrain catecholaminergic (CA) neurons are required for critical autonomic, endocrine, and behavioral counterregulatory responses (CRRs) to hypoglycemia. Recent studies suggest that CRR initiation depends on hindbrain astrocyte glucose sensors (McDougal DH, Hermann GE, Rogers RC. Front Neurosci 7: 249, 2013; Rogers RC, Ritter S, Hermann GE. Am J Physiol Regul Integr Comp Physiol 310: R1102-R1108, 2016). To test the proposition that hindbrain CA responses to glucoprivation are astrocyte dependent, we utilized transgenic mice in which the calcium reporter construct (GCaMP5) was expressed selectively in tyrosine hydroxylase neurons (TH-GCaMP5). We conducted live cell calcium-imaging studies on tissue slices containing the nucleus of the solitary tract (NST) or the ventrolateral medulla, critical CRR initiation sites. Results show that TH-GCaMP5 neurons are robustly activated by a glucoprivic challenge and that this response is dependent on functional astrocytes. Pretreatment of hindbrain slices with fluorocitrate (an astrocytic metabolic suppressor) abolished TH-GCaMP5 neuronal responses to glucoprivation, but not to glutamate. Pharmacologic results suggest that the astrocytic connection with hindbrain CA neurons is purinergic via P2 receptors. Parallel imaging studies on hindbrain slices of NST from wild-type C57BL/6J mice, in which astrocytes and neurons were prelabeled with a calcium reporter dye and an astrocytic vital dye, show that both cell types are activated by glucoprivation but astrocytes responded significantly sooner than neurons. Pretreatment of these hindbrain slices with P2 antagonists abolished neuronal responses to glucoprivation without interruption of astrocyte responses; pretreatment with fluorocitrate eliminated both astrocytic and neuronal responses. These results support earlier work suggesting that the primary detection of glucoprivic signals by the hindbrain is mediated by astrocytes.
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Affiliation(s)
| | | | - Sue Ritter
- 2Department of Veterinary and Comparative Anatomy, Pharmacology and Physiology, Washington State University, Pullman, Washington
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Astrocytes activation contributes to the antidepressant-like effect of ketamine but not scopolamine. Pharmacol Biochem Behav 2018; 170:1-8. [DOI: 10.1016/j.pbb.2018.05.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Revised: 04/25/2018] [Accepted: 05/02/2018] [Indexed: 12/15/2022]
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Rogers RC, McDougal D, Ritter S, Qualls‐Creekmore E, Hermann GE. Glucoprivic sensitivity of hindbrain catecholamine neurons is astrocyte‐dependent. FASEB J 2018. [DOI: 10.1096/fasebj.2018.32.1_supplement.738.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Collares EF, Vinagre AM, Collares-Buzato CB. Dipyrone in association with atropine inhibits the effect on gastric emptying induced by hypoglycemia in rats. Braz J Med Biol Res 2017; 50:e5948. [PMID: 28876363 PMCID: PMC5579963 DOI: 10.1590/1414-431x20175948] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2016] [Accepted: 06/27/2017] [Indexed: 11/21/2022] Open
Abstract
Atropine (AT) and dipyrone (Dp) induce a delay of gastric emptying (GE) of liquids in rats by inhibiting muscarinic receptors and activating β2-adrenergic receptors, respectively. The objective of the present study was to determine the effects of pretreatment with AT and Dp, given alone or in combination, on the effect of hypoglycemia in the liquid GE in rats. Male Wistar adult rats (280-310 g) were pretreated intravenously with AT, Dp, AT plus Dp or their vehicle and then treated 30 min later with iv insulin or its vehicle (n=8-10 animals/group). Thirty min after treatment, GE was evaluated by determining, in awake rats, the percent gastric retention (%GR) of a saline meal labeled with phenol red administered by gavage. The results indicated that insulin induced hypoglycemia in a dose-dependent manner resulting in a significant reduction in %GR of liquid only at the highest dose tested (1 U/kg). Pretreatment with AT significantly increased %GR in the rats treated with 1 U/kg insulin. Surprisingly, after pretreatment with AT, the group treated with the lowest dose of insulin (0.25 U/kg) displayed significantly lower %GR compared to its control (vehicle-treated group), which was not seen in the non-pretreated animals. Pretreatment with Dp alone at the dose of 40 mg/kg induced an increase in %GR in both vehicle and 0.25 U/kg-treated rats. A higher dose of Dp alone (80 mg/kg) significantly reduced the effect of a marked hypoglycemia induced by 1 U/kg of insulin on GE while in combination with AT the effect was completely abolished. The results with AT suggest that moderate hypoglycemia may render the inhibitory mechanisms of GE ineffective while Dp alone and in combination with AT significantly overcame the effect of hypoglycemia on GE.
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Affiliation(s)
- E F Collares
- Departamento de Pediatria, Faculdade de Ciências Médicas, Universidade Estadual de Campinas, Campinas, SP, Brasil.,Núcleo de Medicina e Cirurgia Experimental, Universidade Estadual de Campinas, Campinas, SP, Brasil
| | - A M Vinagre
- Núcleo de Medicina e Cirurgia Experimental, Universidade Estadual de Campinas, Campinas, SP, Brasil
| | - C B Collares-Buzato
- Departamento de Bioquímica e Biologia Tecidual, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, SP, Brasil
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Sevgili AM, Balkanci DZ, Erdem A. Potential excitatory role of nitric oxide on 2-deoxy- d-glucose-induced gastric motility in rats. Clin Exp Pharmacol Physiol 2017; 44:693-699. [DOI: 10.1111/1440-1681.12749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 02/28/2017] [Accepted: 03/03/2017] [Indexed: 11/29/2022]
Affiliation(s)
- Ayse M. Sevgili
- Department of Pharmacology; Faculty of Medicine; Hacettepe University, Sıhhiye; Ankara Turkey
| | - Dicle Z. Balkanci
- Department of Pharmacology; Faculty of Medicine; Hacettepe University, Sıhhiye; Ankara Turkey
| | - Aysen Erdem
- Department of Pharmacology; Faculty of Medicine; Hacettepe University, Sıhhiye; Ankara Turkey
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Grubišić V, Parpura V. Two modes of enteric gliotransmission differentially affect gut physiology. Glia 2017; 65:699-711. [PMID: 28168732 DOI: 10.1002/glia.23121] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2016] [Revised: 01/07/2017] [Accepted: 01/10/2017] [Indexed: 11/08/2022]
Abstract
Enteric glia (EG) in the enteric nervous system can modulate neuronally regulated gut functions. Using molecular genetics, we assessed the effects that molecular entities expressed in EG and otherwise mediating two distinct mechanisms of gliotransmitter release, connexin 43 (Cx43) hemichannel vs. Ca2+ -dependent exocytosis, have on gut function. The expression of mutated Cx43G138R (which favors hemichannel, as opposed to gap-junctional activity) in EG increased gut motility in vivo, while a knock-down of Cx43 in EG resulted in the reduction of gut motility. However, inhibition of Ca2+ -dependent exocytosis in EG did not affect gut motility in vivo; rather, it increased the fecal pellet fluid content. Hampering either Cx43 expression or Ca2+ -dependent exocytosis in EG had an effect on colonic migrating motor complexes, mainly decreasing frequency and velocity of contractions ex vivo. Thus, EG can differentially modulate gut reflexes using the above two distinct mechanisms of gliotransmission.
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Affiliation(s)
- Vladimir Grubišić
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, Alabama.,Department of Physiology, Neuroscience Program, Michigan State University, East Lansing, Michigan
| | - Vladimir Parpura
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, Alabama
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Astrocytes Regulate GLP-1 Receptor-Mediated Effects on Energy Balance. J Neurosci 2016; 36:3531-40. [PMID: 27013681 DOI: 10.1523/jneurosci.3579-15.2016] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2015] [Accepted: 02/02/2016] [Indexed: 01/19/2023] Open
Abstract
UNLABELLED Astrocytes are well established modulators of extracellular glutamate, but their direct influence on energy balance-relevant behaviors is largely understudied. As the anorectic effects of glucagon-like peptide-1 receptor (GLP-1R) agonists are partly mediated by central modulation of glutamatergic signaling, we tested the hypothesis that astrocytic GLP-1R signaling regulates energy balance in rats. Central or peripheral administration of a fluorophore-labeled GLP-1R agonist, exendin-4, localizes within astrocytes and neurons in the nucleus tractus solitarius (NTS), a hindbrain nucleus critical for energy balance control. This effect is mediated by GLP-1R, as the uptake of systemically administered fluorophore-tagged exendin-4 was blocked by central pretreatment with the competitive GLP-1R antagonist exendin-(9-39). Ex vivo analyses show prolonged exendin-4-induced activation (live cell calcium signaling) of NTS astrocytes and neurons; these effects are also attenuated by exendin-(9-39), indicating mediation by the GLP-1R. In vitro analyses show that the application of GLP-1R agonists increases cAMP levels in astrocytes. Immunohistochemical analyses reveal that endogenous GLP-1 axons form close synaptic apposition with NTS astrocytes. Finally, pharmacological inhibition of NTS astrocytes attenuates the anorectic and body weight-suppressive effects of intra-NTS GLP-1R activation. Collectively, data demonstrate a role for NTS astrocytic GLP-1R signaling in energy balance control. SIGNIFICANCE STATEMENT Glucagon-like peptide-1 receptor (GLP-1R) agonists reduce food intake and are approved by the Food and Drug Administration for the treatment of obesity, but the cellular mechanisms underlying the anorectic effects of GLP-1 require further investigation. Astrocytes represent a major cellular population in the CNS that regulates neurotransmission, yet the role of astrocytes in mediating energy balance is largely unstudied. The current data provide novel evidence that astrocytes within the NTS are relevant for energy balance control by GLP-1 signaling. Here, we report that GLP-1R agonists activate and internalize within NTS astrocytes, while behavioral data suggest the pharmacological relevance of NTS astrocytic GLP-1R activation for food intake and body weight. These findings support a previously unknown role for CNS astrocytes in energy balance control by GLP-1 signaling.
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Rogers RC, Ritter S, Hermann GE. Hindbrain cytoglucopenia-induced increases in systemic blood glucose levels by 2-deoxyglucose depend on intact astrocytes and adenosine release. Am J Physiol Regul Integr Comp Physiol 2016; 310:R1102-8. [PMID: 27101298 PMCID: PMC4935490 DOI: 10.1152/ajpregu.00493.2015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 04/07/2016] [Indexed: 01/16/2023]
Abstract
The hindbrain contains critical neurocircuitry responsible for generating defensive physiological responses to hypoglycemia. This counter-regulatory response (CRR) is evoked by local hindbrain cytoglucopenia that causes an autonomically mediated increase in blood glucose, feeding behavior, and accelerated digestion; that is, actions that restore glucose homeostasis. Recent reports suggest that CRR may be initially triggered by astrocytes in the hindbrain. The present studies in thiobutabarbital-anesthetized rats show that exposure of the fourth ventricle (4V) to 2-deoxyglucose (2DG; 15 μmol) produced a 35% increase in circulating glucose relative to baseline levels. While the 4V application of the astrocytic signal blocker, fluorocitrate (FC; 5 nmol), alone, had no effect on blood glucose levels, 2DG-induced increases in glucose were blocked by 4V FC. The 4V effect of 2DG to increase glycemia was also blocked by the pretreatment with caffeine (nonselective adenosine antagonist) or a potent adenosine A1 antagonist (8-cyclopentyl-1,3-dipropylxanthine; DPCPX) but not the NMDA antagonist (MK-801). These results suggest that CNS detection of glucopenia is mediated by astrocytes and that astrocytic release of adenosine that occurs after hypoglycemia may cause the activation of downstream neural circuits that drive CRR.
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Affiliation(s)
- Richard C. Rogers
- 1Autonomic Neurosciences Laboratory, Pennington Biomedical Research Center, Baton Rouge, Louisiana; and
| | - Sue Ritter
- 2Integrative Physiology and Neuroscience, Washington State University, Pullman, Washington
| | - Gerlinda E. Hermann
- 1Autonomic Neurosciences Laboratory, Pennington Biomedical Research Center, Baton Rouge, Louisiana; and
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Lee CY, Dallérac G, Ezan P, Anderova M, Rouach N. Glucose Tightly Controls Morphological and Functional Properties of Astrocytes. Front Aging Neurosci 2016; 8:82. [PMID: 27148048 PMCID: PMC4834307 DOI: 10.3389/fnagi.2016.00082] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Accepted: 04/01/2016] [Indexed: 01/14/2023] Open
Abstract
The main energy source powering the brain is glucose. Strong energy needs of our nervous system are fulfilled by conveying this essential metabolite through blood via an extensive vascular network. Glucose then reaches brain tissues by cell uptake, diffusion and metabolization, processes primarily undertaken by astrocytes. Deprivation of glucose can however occur in various circumstances. In particular, ageing is associated with cognitive disturbances that are partly attributable to metabolic deficiency leading to brain glycopenia. Despite the crucial role of glucose and its metabolites in sustaining neuronal activity, little is known about its moment-to-moment contribution to astroglial physiology. We thus here investigated the early structural and functional alterations induced in astrocytes by a transient metabolic challenge consisting in glucose deprivation. Electrophysiological recordings of hippocampal astroglial cells of the stratum radiatumin situ revealed that shortage of glucose specifically increases astrocyte membrane capacitance, whilst it has no impact on other passive membrane properties. Consistent with this change, morphometric analysis unraveled a prompt increase in astrocyte volume upon glucose deprivation. Furthermore, characteristic functional properties of astrocytes are also affected by transient glucose deficiency. We indeed found that glucoprivation decreases their gap junction-mediated coupling, while it progressively and reversibly increases their intracellular calcium levels during the slow depression of synaptic transmission occurring simultaneously, as assessed by dual electrophysiological and calcium imaging recordings. Together, these data indicate that astrocytes rapidly respond to metabolic dysfunctions, and are therefore central to the neuroglial dialog at play in brain adaptation to glycopenia.
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Affiliation(s)
- Chun-Yao Lee
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, Collège de France, Centre National de la Recherche Scientifique UMR 7241, Institut National de la Santé et de la Recherche Médicale U1050, Labex Memolife, PSL Research University Paris, France
| | - Glenn Dallérac
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, Collège de France, Centre National de la Recherche Scientifique UMR 7241, Institut National de la Santé et de la Recherche Médicale U1050, Labex Memolife, PSL Research University Paris, France
| | - Pascal Ezan
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, Collège de France, Centre National de la Recherche Scientifique UMR 7241, Institut National de la Santé et de la Recherche Médicale U1050, Labex Memolife, PSL Research University Paris, France
| | - Miroslava Anderova
- Department of Cellular Neurophysiology, Institute of Experimental Medicine, Academy of Sciences of the Czech RepublicPrague, Czech Republic; Department of Neuroscience, 2nd Faculty of Medicine, Charles UniversityPrague, Czech Republic
| | - Nathalie Rouach
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, Collège de France, Centre National de la Recherche Scientifique UMR 7241, Institut National de la Santé et de la Recherche Médicale U1050, Labex Memolife, PSL Research University Paris, France
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PAR1-activated astrocytes in the nucleus of the solitary tract stimulate adjacent neurons via NMDA receptors. J Neurosci 2015; 35:776-85. [PMID: 25589770 DOI: 10.1523/jneurosci.3105-14.2015] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Severe autonomic dysfunction, including the loss of control of the cardiovascular, respiratory, and gastrointestinal systems, is a common comorbidity of stroke and other bleeding head injuries. Previous studies suggest that this collapse of autonomic control may be caused by thrombin acting on astrocytic protease-activated receptors (PAR1) in the hindbrain. Using calcium imaging and electrophysiological techniques, we evaluated the mechanisms by which astrocytic PAR1s modulate the activity of presynaptic vagal afferent terminals and postsynaptic neurons in the rat nucleus of the solitary tract (NST). Our calcium-imaging data show that astrocytic and neuronal calcium levels increase after brain slices are treated with the PAR1 agonist SFLLRN-NH2. This increase in activity is blocked by pretreating the slices with the glial metabolic blocker fluorocitrate. In addition, PAR1-activated astrocytes communicate directly with NST neurons by releasing glutamate. Calcium responses to SFLLRN-NH2 in the astrocytes and neurons significantly increase after bath application of the excitatory amino acid transporter blocker DL-threo-β-benzyloxyaspartic acid (TBOA) and significantly decrease after bath application of the NMDA receptor antagonist DL-2-amino-5-phosphonopentanoic acid (DL-AP5). Furthermore, astrocytic glutamate activates neuronal GluN2B-containing NMDA receptors. Voltage-clamp recordings of miniature EPSCs (mEPSCs) from NST neurons show that astrocytes control presynaptic vagal afferent excitability directly under resting and activated conditions. Fluorocitrate significantly decreases mEPSC frequency and SFLLRN-NH2 significantly increases mEPSC frequency. These data show that astrocytes act within a tripartite synapse in the NST, controlling the excitability of both postsynaptic NST neurons and presynaptic vagal afferent terminals.
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Teschemacher AG, Gourine AV, Kasparov S. A Role for Astrocytes in Sensing the Brain Microenvironment and Neuro-Metabolic Integration. Neurochem Res 2015; 40:2386-93. [DOI: 10.1007/s11064-015-1562-9] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Revised: 01/27/2015] [Accepted: 02/07/2015] [Indexed: 12/22/2022]
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