1
|
Dadwal S, Heneka MT. Microglia heterogeneity in health and disease. FEBS Open Bio 2024; 14:217-229. [PMID: 37945346 PMCID: PMC10839410 DOI: 10.1002/2211-5463.13735] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Revised: 10/12/2023] [Accepted: 11/08/2023] [Indexed: 11/12/2023] Open
Abstract
Microglia, the resident immune cells of the central nervous system (CNS), have received significant attention due to their critical roles in maintaining brain homeostasis and mediating cerebral immune responses. Understanding the origin of microglia has been a subject of great interest, and emerging evidence suggests that microglia consist of multiple subpopulations with unique molecular and functional characteristics. These subpopulations of microglia may exhibit specialized roles in response to different environmental cues as in disease conditions. The newfound understanding of microglial heterogeneity has significant implications for elucidating their roles in both physiological and pathological conditions. In the context of disease, microglia have been studied rigorously as they play a very important role in neuroinflammation. Dysregulated microglial activation and function contribute to chronic inflammation. Further exploration of microglial heterogeneity and their interactions with other cell types in the CNS will undoubtedly pave the way to novel therapeutic strategies targeting microglia-mediated pathologies. In this review, we discuss the latest advances in the field of microglia research, focusing specifically on the origin and subpopulations of microglia, the populations of microglia types in the brains of patients with neurodegenerative diseases, and how microglia are regulated in the healthy CNS.
Collapse
Affiliation(s)
- Shilauni Dadwal
- Luxembourg Centre for Systems BiomedicineUniversity of LuxembourgBelvalLuxembourg
| | - Michael T. Heneka
- Luxembourg Centre for Systems BiomedicineUniversity of LuxembourgBelvalLuxembourg
- Division of Infectious Diseases and ImmunologyUniversity of Massachusetts Medical SchoolWorcesterMAUSA
| |
Collapse
|
2
|
Gajewski MP, Barger SW. Design, synthesis, and characterization of novel system x C- transport inhibitors: inhibition of microglial glutamate release and neurotoxicity. J Neuroinflammation 2023; 20:292. [PMID: 38057869 PMCID: PMC10702053 DOI: 10.1186/s12974-023-02972-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2023] [Accepted: 11/28/2023] [Indexed: 12/08/2023] Open
Abstract
Neuroinflammation appears to involve some degree of excitotoxicity promulgated by microglia, which release glutamate via the system xC- (SxC-) cystine-glutamate antiporter. With the aim of mitigating this source of neuronal stress and toxicity, we have developed a panel of inhibitors of the SxC- antiporter. The compounds were based on L-tyrosine, as elements of its structure align with those of glutamate, a primary physiological substrate of the SxC- antiporter. In addition to 3,5-dibromotyrosine, ten compounds were synthesized via amidation of that parent molecule with a selection of acyl halides. These agents were tested for the ability to inhibit release of glutamate from microglia activated with lipopolysaccharide (LPS), an activity exhibited by eight of the compounds. To confirm that the compounds were inhibitors of SxC-, two of them were further tested for the ability to inhibit cystine uptake. Finally, these agents were shown to protect primary cortical neurons from the toxicity exhibited by activated microglia. These agents may hold promise in reducing the neurodegenerative effects of neuroinflammation in conditions, such as encephalitis, traumatic brain injury, stroke, or neurodegenerative diseases.
Collapse
Affiliation(s)
- Mariusz P Gajewski
- Department of Physical and Earth Sciences, Arkansas Tech University, McEver Building, 1701 N Boulder Ave, Russellville, AR, 72801, USA.
| | - Steven W Barger
- Departments of Geriatrics and Neurobiology and Developmental Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, USA
- Geriatric Research Education and Clinical Center, Central Arkansas Veterans Healthcare System, Little Rock, AR, USA
| |
Collapse
|
3
|
Salavatian S, Robbins EM, Kuwabara Y, Castagnola E, Cui XT, Mahajan A. Real-time in vivo thoracic spinal glutamate sensing during myocardial ischemia. Am J Physiol Heart Circ Physiol 2023; 325:H1304-H1317. [PMID: 37737733 PMCID: PMC10908408 DOI: 10.1152/ajpheart.00299.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 09/18/2023] [Accepted: 09/18/2023] [Indexed: 09/23/2023]
Abstract
In the spinal cord, glutamate serves as the primary excitatory neurotransmitter. Monitoring spinal glutamate concentrations offers valuable insights into spinal neural processing. Consequently, spinal glutamate concentration has the potential to emerge as a useful biomarker for conditions characterized by increased spinal neural network activity, especially when uptake systems become dysfunctional. In this study, we developed a multichannel custom-made flexible glutamate-sensing probe for the large-animal model that is capable of measuring extracellular glutamate concentrations in real time and in vivo. We assessed the probe's sensitivity and specificity through in vitro and ex vivo experiments. Remarkably, this developed probe demonstrates nearly instantaneous glutamate detection and allows continuous monitoring of glutamate concentrations. Furthermore, we evaluated the mechanical and sensing performance of the probe in vivo, within the pig spinal cord. Moreover, we applied the glutamate-sensing method using the flexible probe in the context of myocardial ischemia-reperfusion (I/R) injury. During I/R injury, cardiac sensory neurons in the dorsal root ganglion transmit excitatory signals to the spinal cord, resulting in sympathetic activation that potentially leads to fatal arrhythmias. We have successfully shown that our developed glutamate-sensing method can detect this spinal network excitation during myocardial ischemia. This study illustrates a novel technique for measuring spinal glutamate at different spinal cord levels as a surrogate for the spinal neural network activity during cardiac interventions that engage the cardio-spinal neural pathway.NEW & NOTEWORTHY In this study, we have developed a new flexible sensing probe to perform an in vivo measurement of spinal glutamate signaling in a large animal model. Our initial investigations involved precise testing of this probe in both in vitro and ex vivo environments. We accurately assessed the sensitivity and specificity of our glutamate-sensing probe and demonstrated its performance. We also evaluated the performance of our developed flexible probe during the insertion and compared it with the stiff probe during animal movement. Subsequently, we used this innovative technique to monitor the spinal glutamate signaling during myocardial ischemia and reperfusion that can cause fatal ventricular arrhythmias. We showed that glutamate concentration increases during the myocardial ischemia, persists during the reperfusion, and is associated with sympathoexcitation and increases in myocardial substrate excitability.
Collapse
Affiliation(s)
- Siamak Salavatian
- Department of Anesthesiology and Perioperative Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
- Division of Cardiology, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Elaine Marie Robbins
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Yuki Kuwabara
- Department of Anesthesiology and Perioperative Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Elisa Castagnola
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Xinyan Tracy Cui
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
- Center for Neural Basis of Cognition, Pittsburgh, Pennsylvania, United States
- McGowan Institute for Regenerative Medicine, Pittsburgh, Pennsylvania, United States
| | - Aman Mahajan
- Department of Anesthesiology and Perioperative Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| |
Collapse
|
4
|
Gajewski M, Barger S. Design, synthesis, and characterization of novel Xc- transport inhibitors: Inhibition of microglial glutamate release and neurotoxicity. RESEARCH SQUARE 2023:rs.3.rs-2932128. [PMID: 37292591 PMCID: PMC10246248 DOI: 10.21203/rs.3.rs-2932128/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Neuroinflammation appears to involve some degree of excitotoxicity promulgated by microglia, which release glutamate via the system Xc- cystine-glutamate antiporter. With the aim of mitigating this source of neuronal stress and toxicity, we have developed a panel of inhibitors of the Xc- antiporter. The compounds were based on L-tyrosine, as elements of its structure align with those of glutamate, a primary physiological substrate of the Xc- antiporter. In addition to 3,5-dibromotyrosine, ten compounds were synthesized via amidation of that parent molecule with a selection of acyl halides. These agents were tested for the ability to inhibit release of glutamate from microglia activated with lipopolysaccharide (LPS), an activity exhibited by eight of the compounds. Two of these were further tested for the ability to inhibit death of primary cortical neurons in the presence of activated microglia. While both showed some neuroprotective activity, they were quantitatively distinct with a compound we refer to as "35DBTA7" showing the greatest effi cacy. This agent may hold promise in reducing the neurodegenerative effects of neuroinflammation in conditions such as encephalitis, traumatic brain injury, stroke, or neurodegenerative diseases.
Collapse
|
5
|
Sah N, Zhang Z, Chime A, Fowler A, Mendez-Trendler A, Sharma A, Kannan RM, Slusher B, Kannan S. Dendrimer-Conjugated Glutamate Carboxypeptidase II Inhibitor Restores Microglial Changes in a Rabbit Model of Cerebral Palsy. Dev Neurosci 2023; 45:268-275. [PMID: 36990069 PMCID: PMC10614263 DOI: 10.1159/000530389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Accepted: 03/17/2023] [Indexed: 03/31/2023] Open
Abstract
We have previously shown that maternal endotoxin exposure leads to a phenotype of cerebral palsy and pro-inflammatory microglia in the brain in neonatal rabbits. "Activated" microglia overexpress the enzyme glutamate carboxypeptidase II (GCPII) that hydrolyzes N-acetylaspartylglutamate to N-acetylaspartate and glutamate, and we have shown previously that inhibiting microglial GCPII is neuroprotective. Glutamate-induced injury and associated immune signaling can alter microglial responses including microglial process movements for surveillance and phagocytosis. We hypothesize that inhibition of GCPII activity could alter microglial phenotype and normalize microglial process movement/dynamics. Newborn rabbit kits exposed to endotoxin in utero, when treated with dendrimer-conjugated 2-(phosphonomethyl)-pentanedioic acid (D-2PMPA), a potent and selective inhibitor of microglial GCPII, showed profound changes in microglial phenotype within 48 h of treatment. Live imaging of hippocampal microglia in ex vivo brain slice preparations revealed larger cell body and phagocytic cup sizes with less stable microglia processes in CP kits compared to healthy controls. D-2PMPA treatment led to significant reversal of microglial process stability to healthy control levels. Our results emphasize the importance of microglial process dynamics in determining the state of microglial function in the developing brain and demonstrate how GCPII inhibition specifically in microglia can effectively change the microglial process motility to healthy control levels, potentially impacting migration, phagocytosis, and inflammatory functions.
Collapse
Affiliation(s)
- Nirnath Sah
- Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Zhi Zhang
- Department of Natural Sciences, University of Michigan-Dearborn, Dearborn, MI, USA
| | - Alicia Chime
- Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Amanda Fowler
- Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Antonio Mendez-Trendler
- Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Anjali Sharma
- Center for Nanomedicine at the Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Department of Chemistry, Washington State University, Pullman, WA, USA
| | - Rangaramanujam M. Kannan
- Center for Nanomedicine at the Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Barbara Slusher
- Johns Hopkins Drug Discovery Program, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Sujatha Kannan
- Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| |
Collapse
|
6
|
Vadisiute A, Meijer E, Szabó F, Hoerder-Suabedissen A, Kawashita E, Hayashi S, Molnár Z. The role of snare proteins in cortical development. Dev Neurobiol 2022; 82:457-475. [PMID: 35724379 PMCID: PMC9539872 DOI: 10.1002/dneu.22892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 05/18/2022] [Accepted: 05/25/2022] [Indexed: 12/01/2022]
Abstract
Neural communication in the adult nervous system is mediated primarily through chemical synapses, where action potentials elicit Ca2+ signals, which trigger vesicular fusion and neurotransmitter release in the presynaptic compartment. At early stages of development, the brain is shaped by communication via trophic factors and other extracellular signaling, and by contact-mediated cell-cell interactions including chemical synapses. The patterns of early neuronal impulses and spontaneous and regulated neurotransmitter release guide the precise topography of axonal projections and contribute to determining cell survival. The study of the role of specific proteins of the synaptic vesicle release machinery in the establishment, plasticity, and maintenance of neuronal connections during development has only recently become possible, with the advent of mouse models where various members of the N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex have been genetically manipulated. We provide an overview of these models, focusing on the role of regulated vesicular release and/or cellular excitability in synaptic assembly, development and maintenance of cortical circuits, cell survival, circuit level excitation-inhibition balance, myelination, refinement, and plasticity of key axonal projections from the cerebral cortex. These models are important for understanding various developmental and psychiatric conditions, and neurodegenerative diseases.
Collapse
Affiliation(s)
- Auguste Vadisiute
- Department of Physiology, Anatomy and Genetics, Sherrington Building, University of Oxford, Oxford, UK
| | - Elise Meijer
- Department of Physiology, Anatomy and Genetics, Sherrington Building, University of Oxford, Oxford, UK
| | - Florina Szabó
- Department of Physiology, Anatomy and Genetics, Sherrington Building, University of Oxford, Oxford, UK
| | - Anna Hoerder-Suabedissen
- Department of Physiology, Anatomy and Genetics, Sherrington Building, University of Oxford, Oxford, UK
| | - Eri Kawashita
- Department of Physiology, Anatomy and Genetics, Sherrington Building, University of Oxford, Oxford, UK
- Department of Pathological Biochemistry, Kyoto Pharmaceutical University, Yamashina-ku, Kyoto, Japan
| | - Shuichi Hayashi
- Department of Physiology, Anatomy and Genetics, Sherrington Building, University of Oxford, Oxford, UK
- Department of Anatomy, Kawasaki Medical School, Kurashiki, Okayama, Japan
| | - Zoltán Molnár
- Department of Physiology, Anatomy and Genetics, Sherrington Building, University of Oxford, Oxford, UK
| |
Collapse
|
7
|
Hendrix RD, Ou Y, Davis JE, Odle AK, Groves TR, Allen AR, Childs GV, Barger SW. Alzheimer amyloid-β- peptide disrupts membrane localization of glucose transporter 1 in astrocytes: implications for glucose levels in brain and blood. Neurobiol Aging 2020; 97:73-88. [PMID: 33161213 PMCID: PMC7736209 DOI: 10.1016/j.neurobiolaging.2020.10.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Revised: 08/25/2020] [Accepted: 10/02/2020] [Indexed: 12/12/2022]
Abstract
Alzheimer’s disease (AD) is associated with disturbances in blood glucose regulation, and type-2 diabetes elevates the risk for dementia. A role for amyloid-β peptide (Aβ) in linking these age-related conditions has been proposed, tested primarily in transgenic mouse lines that overexpress mutated amyloid precursor protein (APP). Because APP has its own impacts on glucose regulation, we examined the BRI-Aβ42 line (“Aβ42-tg”), which produces extracellular Aβ1–42 in the CNS without elevation of APP. We also looked for interactions with diet-induced obesity (DIO) resulting from a high-fat, high-sucrose (“western”) diet. Aβ42-tg mice were impaired in both spatial memory and glucose tolerance. Although DIO induced insulin resistance, Aβ1–42 accumulation did not, and the impacts of DIO and Aβ on glucose tolerance were merely additive. Aβ42-tg mice exhibited no significant differences from wild-type in insulin production, body weight, lipidemia, appetite, physical activity, respiratory quotient, an-/orexigenic factors, or inflammatory factors. These negative findings suggested that the phenotype in these mice arose from perturbation of glucose excursion in an insulin-independent tissue. To wit, cerebral cortex of Aβ42-tg mice had reduced glucose utilization, similar to human patients with AD. This was associated with insufficient trafficking of glucose transporter 1 to the plasma membrane in parenchymal brain cells, a finding also documented in human AD tissue. Together, the lower cerebral metabolic rate of glucose and diminished function of parenchymal glucose transporter 1 indicate that aberrant regulation of blood glucose in AD likely reflects a central phenomenon, resulting from the effects of Aβ on cerebral parenchyma, rather than a generalized disruption of hypothalamic or peripheral endocrinology. The involvement of a specific glucose transporter in this deficit provides a new target for the design of AD therapies.
Collapse
Affiliation(s)
- Rachel D Hendrix
- Department of Neurobiology & Developmental Sciences, Little Rock, AR, USA
| | - Yang Ou
- Department of Geriatrics, Little Rock, AR, USA
| | - Jakeira E Davis
- Graduate Program in Interdisciplinary Biomedical Sciences, Little Rock, AR, USA
| | - Angela K Odle
- Department of Neurobiology & Developmental Sciences, Little Rock, AR, USA
| | - Thomas R Groves
- Department of Neurobiology & Developmental Sciences, Little Rock, AR, USA
| | - Antiño R Allen
- Department of Neurobiology & Developmental Sciences, Little Rock, AR, USA; Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Gwen V Childs
- Department of Neurobiology & Developmental Sciences, Little Rock, AR, USA
| | - Steven W Barger
- Department of Neurobiology & Developmental Sciences, Little Rock, AR, USA; Department of Geriatrics, Little Rock, AR, USA; Geriatric Research, Education & Clinical Center, Central Arkansas Veterans Healthcare System, Little Rock, AR, USA.
| |
Collapse
|
8
|
Pereira V, Goudet C. Emerging Trends in Pain Modulation by Metabotropic Glutamate Receptors. Front Mol Neurosci 2019; 11:464. [PMID: 30662395 PMCID: PMC6328474 DOI: 10.3389/fnmol.2018.00464] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Accepted: 11/30/2018] [Indexed: 12/20/2022] Open
Abstract
Pain is an essential protective mechanism meant to prevent tissue damages in organisms. On the other hand, chronic or persistent pain caused, for example, by inflammation or nerve injury is long lasting and responsible for long-term disability in patients. Therefore, chronic pain and its management represents a major public health problem. Hence, it is critical to better understand chronic pain molecular mechanisms to develop innovative and efficient drugs. Over the past decades, accumulating evidence has demonstrated a pivotal role of glutamate in pain sensation and transmission, supporting glutamate receptors as promising potential targets for pain relieving drug development. Glutamate is the most abundant excitatory neurotransmitter in the brain. Once released into the synapse, glutamate acts through ionotropic glutamate receptors (iGluRs), which are ligand-gated ion channels triggering fast excitatory neurotransmission, and metabotropic glutamate receptors (mGluRs), which are G protein-coupled receptors modulating synaptic transmission. Eight mGluRs subtypes have been identified and are divided into three classes based on their sequence similarities and their pharmacological and biochemical properties. Of note, all mGluR subtypes (except mGlu6 receptor) are expressed within the nociceptive pathways where they modulate pain transmission. This review will address the role of mGluRs in acute and persistent pain processing and emerging pharmacotherapies for pain management.
Collapse
Affiliation(s)
- Vanessa Pereira
- IGF, CNRS, INSERM, Univ. de Montpellier, Montpellier, France
| | - Cyril Goudet
- IGF, CNRS, INSERM, Univ. de Montpellier, Montpellier, France
| |
Collapse
|
9
|
Younger D, Murugan M, Rama Rao KV, Wu LJ, Chandra N. Microglia Receptors in Animal Models of Traumatic Brain Injury. Mol Neurobiol 2018; 56:5202-5228. [DOI: 10.1007/s12035-018-1428-7] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Accepted: 11/13/2018] [Indexed: 02/07/2023]
|
10
|
Spampinato SF, Copani A, Nicoletti F, Sortino MA, Caraci F. Metabotropic Glutamate Receptors in Glial Cells: A New Potential Target for Neuroprotection? Front Mol Neurosci 2018; 11:414. [PMID: 30483053 PMCID: PMC6243036 DOI: 10.3389/fnmol.2018.00414] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Accepted: 10/25/2018] [Indexed: 12/14/2022] Open
Abstract
Neurodegenerative disorders are characterized by excitotoxicity and neuroinflammation that finally lead to slow neuronal degeneration and death. Although neurons are the principal target, glial cells are important players as they contribute by either exacerbating or dampening the events that lead to neuroinflammation and neuronal damage. A dysfunction of the glutamatergic system is a common event in the pathophysiology of these diseases. Metabotropic glutamate (mGlu) receptors belong to a large family of G protein-coupled receptors largely expressed in neurons as well as in glial cells. They often appear overexpressed in areas involved in neurodegeneration, where they can modulate glutamatergic transmission. Of note, mGlu receptor upregulation may involve microglia or, even more frequently, astrocytes, where their activation causes release of factors potentially able to influence neuronal death. The expression of mGlu receptors has been also reported on oligodendrocytes, a glial cell type specifically involved in the development of multiple sclerosis. Here we will provide a general overview on the possible involvement of mGlu receptors expressed on glial cells in the pathogenesis of different neurodegenerative disorders and the potential use of subtype-selective mGlu receptor ligands as candidate drugs for the treatment of neurodegenerative disorders. Negative allosteric modulators (NAM) of mGlu5 receptors might represent a relevant pharmacological tool to develop new neuroprotective strategies in these diseases. Recent evidence suggests that targeting astrocytes and microglia with positive allosteric modulators (PAM) of mGlu3 receptor or oligodendrocytes with mGlu4 PAMS might represent novel pharmacological approaches for the treatment of neurodegenerative disorders.
Collapse
Affiliation(s)
| | - Agata Copani
- Department of Drug Sciences, University of Catania, Catania, Italy.,Institute of Biostructure and Bioimaging, National Research Council, Catania, Italy
| | - Ferdinando Nicoletti
- Department of Physiology and Pharmacology, Sapienza University of Rome, Rome, Italy.,Neuromed, Istituto di Ricovero e Cura a Carattere Scientifico, Pozzilli, Italy
| | - Maria Angela Sortino
- Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy
| | - Filippo Caraci
- Department of Drug Sciences, University of Catania, Catania, Italy.,Oasi Research Institute, Istituto di Ricovero e Cura a Carattere Scientifico, Troina, Italy
| |
Collapse
|
11
|
Pál B. Involvement of extrasynaptic glutamate in physiological and pathophysiological changes of neuronal excitability. Cell Mol Life Sci 2018; 75:2917-2949. [PMID: 29766217 PMCID: PMC11105518 DOI: 10.1007/s00018-018-2837-5] [Citation(s) in RCA: 79] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Revised: 04/27/2018] [Accepted: 05/07/2018] [Indexed: 12/14/2022]
Abstract
Glutamate is the most abundant neurotransmitter of the central nervous system, as the majority of neurons use glutamate as neurotransmitter. It is also well known that this neurotransmitter is not restricted to synaptic clefts, but found in the extrasynaptic regions as ambient glutamate. Extrasynaptic glutamate originates from spillover of synaptic release, as well as from astrocytes and microglia. Its concentration is magnitudes lower than in the synaptic cleft, but receptors responding to it have higher affinity for it. Extrasynaptic glutamate receptors can be found in neuronal somatodendritic location, on astroglia, oligodendrocytes or microglia. Activation of them leads to changes of neuronal excitability with different amplitude and kinetics. Extrasynaptic glutamate is taken up by neurons and astrocytes mostly via EAAT transporters, and astrocytes, in turn metabolize it to glutamine. Extrasynaptic glutamate is involved in several physiological phenomena of the central nervous system. It regulates neuronal excitability and synaptic strength by involving astroglia; contributing to learning and memory formation, neurosecretory and neuromodulatory mechanisms, as well as sleep homeostasis.The extrasynaptic glutamatergic system is affected in several brain pathologies related to excitotoxicity, neurodegeneration or neuroinflammation. Being present in dementias, neurodegenerative and neuropsychiatric diseases or tumor invasion in a seemingly uniform way, the system possibly provides a common component of their pathogenesis. Although parts of the system are extensively discussed by several recent reviews, in this review I attempt to summarize physiological actions of the extrasynaptic glutamate on neuronal excitability and provide a brief insight to its pathology for basic understanding of the topic.
Collapse
Affiliation(s)
- Balázs Pál
- Department of Physiology, Faculty of Medicine, University of Debrecen, Nagyerdei krt 98, Debrecen, 4012, Hungary.
| |
Collapse
|
12
|
Osipova ED, Semyachkina-Glushkovskaya OV, Morgun AV, Pisareva NV, Malinovskaya NA, Boitsova EB, Pozhilenkova EA, Belova OA, Salmin VV, Taranushenko TE, Noda M, Salmina AB. Gliotransmitters and cytokines in the control of blood-brain barrier permeability. Rev Neurosci 2018; 29:567-591. [DOI: 10.1515/revneuro-2017-0092] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Accepted: 11/26/2017] [Indexed: 11/15/2022]
Abstract
AbstractThe contribution of astrocytes and microglia to the regulation of neuroplasticity or neurovascular unit (NVU) is based on the coordinated secretion of gliotransmitters and cytokines and the release and uptake of metabolites. Blood-brain barrier (BBB) integrity and angiogenesis are influenced by perivascular cells contacting with the abluminal side of brain microvessel endothelial cells (pericytes, astrocytes) or by immune cells existing (microglia) or invading the NVU (macrophages) under pathologic conditions. The release of gliotransmitters or cytokines by activated astroglial and microglial cells is provided by distinct mechanisms, affects intercellular communication, and results in the establishment of microenvironment controlling BBB permeability and neuroinflammation. Glial glutamate transporters and connexin and pannexin hemichannels working in the tight functional coupling with the purinergic system serve as promising molecular targets for manipulating the intercellular communications that control BBB permeability in brain pathologies associated with excessive angiogenesis, cerebrovascular remodeling, and BBB-mediated neuroinflammation. Substantial progress in deciphering the molecular mechanisms underlying the (patho)physiology of perivascular glia provides promising approaches to novel clinically relevant therapies for brain disorders. The present review summarizes the current understandings on the secretory machinery expressed in glial cells (glutamate transporters, connexin and pannexin hemichannels, exocytosis mechanisms, membrane-derived microvesicles, and inflammasomes) and the role of secreted gliotransmitters and cytokines in the regulation of NVU and BBB permeability in (patho)physiologic conditions.
Collapse
|
13
|
Fazio F, Ulivieri M, Volpi C, Gargaro M, Fallarino F. Targeting metabotropic glutamate receptors for the treatment of neuroinflammation. Curr Opin Pharmacol 2018; 38:16-23. [PMID: 29471184 DOI: 10.1016/j.coph.2018.01.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2017] [Accepted: 01/31/2018] [Indexed: 12/15/2022]
Abstract
A large body of evidence suggests that neuroinflammation lies at the core of nearly all CNS disorders, including psychiatric disorders. Invading and local immune cells orchestrate the series of events that lead to either tissue repair or damage in response to neuroinflammation. Both lymphocytes and microglia express metabotropic glutamate (mGlu) receptors, which respond to glutamate or other endogenous activators (e.g. some kynurenine metabolites of tryptophan metabolism) influencing immune phenotype and the balance between pro-inflammatory and anti-inflammatory cytokines. Here, we offer an up-to-date on the role of individual mGlu receptor subtypes in the regulation of innate and adaptive immune response, highlighting the relevance of this information in the development of subtype-selective mGlu receptor ligands for treatment of CNS disorders.
Collapse
Affiliation(s)
| | - Martina Ulivieri
- Department of Physiology and Pharmacology, Sapienza University, Rome, Italy
| | - Claudia Volpi
- Department of Experimental Medicine, University of Perugia, Polo Unico Sant'Andrea delle Fratte, Piazzale Gambuli, 06132 Perugia, Italy
| | - Marco Gargaro
- Department of Experimental Medicine, University of Perugia, Polo Unico Sant'Andrea delle Fratte, Piazzale Gambuli, 06132 Perugia, Italy
| | - Francesca Fallarino
- Department of Experimental Medicine, University of Perugia, Polo Unico Sant'Andrea delle Fratte, Piazzale Gambuli, 06132 Perugia, Italy
| |
Collapse
|
14
|
Haraguchi Y, Mizoguchi Y, Ohgidani M, Imamura Y, Murakawa-Hirachi T, Nabeta H, Tateishi H, Kato TA, Monji A. Donepezil suppresses intracellular Ca 2+ mobilization through the PI3K pathway in rodent microglia. J Neuroinflammation 2017; 14:258. [PMID: 29273047 PMCID: PMC5741946 DOI: 10.1186/s12974-017-1033-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Accepted: 12/11/2017] [Indexed: 12/17/2022] Open
Abstract
Background Microglia are resident innate immune cells which release many factors including proinflammatory cytokines or nitric oxide (NO) when they are activated in response to immunological stimuli. Pathophysiology of Alzheimer’s disease (AD) is related to the inflammatory responses mediated by microglia. Intracellular Ca2+ signaling is important for microglial functions such as release of NO and cytokines. In addition, alteration of intracellular Ca2+ signaling underlies the pathophysiology of AD, while it remains unclear how donepezil, an acetylcholinesterase inhibitor, affects intracellular Ca2+ mobilization in microglial cells. Methods We examined whether pretreatment with donepezil affects the intracellular Ca2+ mobilization using fura-2 imaging and tested the effects of donepezil on phagocytic activity by phagocytosis assay in rodent microglial cells. Results In this study, we observed that pretreatment with donepezil suppressed the TNFα-induced sustained intracellular Ca2+ elevation in both rat HAPI and mouse primary microglial cells. On the other hand, pretreatment with donepezil did not suppress the mRNA expression of both TNFR1 and TNFR2 in rodent microglia we used. Pretreatment with acetylcholine but not donepezil suppressed the TNFα-induced intracellular Ca2+ elevation through the nicotinic α7 receptors. In addition, sigma 1 receptors were not involved in the donepezil-induced suppression of the TNFα-mediated intracellular Ca2+ elevation. Pretreatment with donepezil suppressed the TNFα-induced intracellular Ca2+ elevation through the PI3K pathway in rodent microglial cells. Using DAF-2 imaging, we also found that pretreatment with donepezil suppressed the production of NO induced by TNFα treatment and the PI3K pathway could be important for the donepezil-induced suppression of NO production in rodent microglial cells. Finally, phagocytosis assay showed that pretreatment with donepezil promoted phagocytic activity of rodent microglial cells through the PI3K but not MAPK/ERK pathway. Conclusions These suggest that donepezil could directly modulate the microglial function through the PI3K pathway in the rodent brain, which might be important to understand the effect of donepezil in the brain. Electronic supplementary material The online version of this article (10.1186/s12974-017-1033-0) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Yoshinori Haraguchi
- Department of Psychiatry, Faculty of Medicine, Saga University, 5-1-1 Nabeshima, Saga, 849-8501, Japan
| | - Yoshito Mizoguchi
- Department of Psychiatry, Faculty of Medicine, Saga University, 5-1-1 Nabeshima, Saga, 849-8501, Japan.
| | - Masahiro Ohgidani
- Department of Neuropsychiatry, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan
| | - Yoshiomi Imamura
- Department of Psychiatry, Faculty of Medicine, Saga University, 5-1-1 Nabeshima, Saga, 849-8501, Japan
| | - Toru Murakawa-Hirachi
- Department of Psychiatry, Faculty of Medicine, Saga University, 5-1-1 Nabeshima, Saga, 849-8501, Japan
| | - Hiromi Nabeta
- Department of Psychiatry, Faculty of Medicine, Saga University, 5-1-1 Nabeshima, Saga, 849-8501, Japan
| | - Hiroshi Tateishi
- Department of Psychiatry, Faculty of Medicine, Saga University, 5-1-1 Nabeshima, Saga, 849-8501, Japan
| | - Takahiro A Kato
- Department of Neuropsychiatry, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan
| | - Akira Monji
- Department of Psychiatry, Faculty of Medicine, Saga University, 5-1-1 Nabeshima, Saga, 849-8501, Japan
| |
Collapse
|
15
|
Opere CA, Heruye S, Njie-Mbye YF, Ohia SE, Sharif NA. Regulation of Excitatory Amino Acid Transmission in the Retina: Studies on Neuroprotection. J Ocul Pharmacol Ther 2017; 34:107-118. [PMID: 29267132 DOI: 10.1089/jop.2017.0085] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Excitotoxicity occurs in neurons due to the accumulation of excitatory amino acids such as glutamate in the synaptic and extrasynaptic locations. In the retina, excessive glutamate concentrations trigger a neurotoxic cascade involving several mechanisms, including the elevation of intracellular calcium (Ca2+) and the activation of α-amino-3-hydroxy 5-methyl-4-iso-xazole-propionic acid/kainate (AMPA/KA) and N-methyl-d-aspartate (NMDA) receptors leading to retinal degeneration. Both ionotropic glutamate receptors (iGluRs) and metabotropic glutamate receptors (mGluRs) are present in the mammalian retina. Indeed, due to the abundant expression of GluRs, the mammalian retina is highly susceptible to excitotoxic neurodegeneration. Excitotoxicity has been postulated to present a common downstream mechanism for several stimuli, including hypoglycemia, hypoxia, ischemia, and chronic neurodegenerative diseases. Experimental approaches to the study of neuroprotection in the retina have utilized insults that trigger hypoxia, hypoglycemia, or excitotoxicity. Using these experimental approaches, the neuroprotective potential of GluR agents, including the NMDA receptor modulators (MK801, ifenprodil, memantine); AMPA/KA receptor antagonist (CNQX); Group II and III mGluR agonists (LY354740, quisqualate); and Ca2+-channel blockers (diltiazem, lomerizine, verapamil, ω-conotoxin), and others (pituitary adenylate cyclase activating polypeptide, neuropeptide Y, acetylcholine receptor agonists) have been elucidated. In addition to corroborating the exocytotic role of excitatory amino acids in retinal degeneration, these studies affirm that multiple mechanism/s contribute to the prevention of damage caused by excitotoxicity in the retina. Therefore, it is feasible that several pathways are involved in protecting the retina from toxic insults in ocular neurodegenerative conditions such as glaucoma and retinal ischemia. Furthermore, these experimental models are viable tools for evaluating therapeutic candidates in ocular neuropathies.
Collapse
Affiliation(s)
- Catherine A Opere
- 1 Department of Pharmacy Sciences, School of Pharmacy and Health Professions, Creighton University , Omaha, Nebraska
| | - Segewkal Heruye
- 1 Department of Pharmacy Sciences, School of Pharmacy and Health Professions, Creighton University , Omaha, Nebraska
| | - Ya-Fatou Njie-Mbye
- 2 Department of Environmental and Pharmaceutical Sciences, College of Pharmacy and Health Sciences, Texas Southern University , Houston, Texas
| | - Sunny E Ohia
- 2 Department of Environmental and Pharmaceutical Sciences, College of Pharmacy and Health Sciences, Texas Southern University , Houston, Texas
| | - Najam A Sharif
- 2 Department of Environmental and Pharmaceutical Sciences, College of Pharmacy and Health Sciences, Texas Southern University , Houston, Texas.,3 Santen Incorporated , Emeryville, California
| |
Collapse
|
16
|
Elmann A, Beit-Yannai E, Telerman A, Ofir R, Mordechay S, Erlank H, Borochov-Neori H. Pulicaria incisa infusion attenuates inflammatory responses of brain microglial cells. J Funct Foods 2016. [DOI: 10.1016/j.jff.2016.05.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
|
17
|
Liu H, Leak RK, Hu X. Neurotransmitter receptors on microglia. Stroke Vasc Neurol 2016; 1:52-58. [PMID: 28959464 PMCID: PMC5435193 DOI: 10.1136/svn-2016-000012] [Citation(s) in RCA: 106] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2016] [Revised: 04/29/2016] [Accepted: 04/30/2016] [Indexed: 12/21/2022] Open
Abstract
As the resident immune cells in the central nervous system, microglia have long been hypothesised to promote neuroinflammation and exacerbate neurotoxicity. However, this traditional view has undergone recent revision as evidence has accumulated that microglia exert beneficial and detrimental effects depending on activation status, polarisation phenotype and cellular context. A variety of neurotransmitter receptors are expressed on microglia and help mediate the bidirectional communication between neurons and microglia. Here we review data supporting the importance of neurotransmitter receptors on microglia, with a special emphasis on glutamate, γ-aminobutyric acid (GABA), norepinephrine, cannabinoid and acetylcholine receptors. We summarise evidence favouring a significant role for neurotransmitter receptors in modulating microglial activation, phagocytic clearance and phenotypic polarisation. Elucidating the effects of neurotransmitter receptors on microglia and dissecting the underlying mechanisms may help accelerate the discovery of novel drugs that tap the therapeutic potential of microglia.
Collapse
Affiliation(s)
- Huan Liu
- Center of Cerebrovascular Disease Research, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Rehana K Leak
- Division of Pharmaceutical Sciences, Duquesne University, Pittsburgh, Pennsylvania, USA
| | - Xiaoming Hu
- Center of Cerebrovascular Disease Research, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| |
Collapse
|
18
|
Peterlik D, Flor PJ, Uschold-Schmidt N. The Emerging Role of Metabotropic Glutamate Receptors in the Pathophysiology of Chronic Stress-Related Disorders. Curr Neuropharmacol 2016; 14:514-39. [PMID: 27296643 PMCID: PMC4983752 DOI: 10.2174/1570159x13666150515234920] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2015] [Revised: 04/04/2015] [Accepted: 05/12/2015] [Indexed: 12/28/2022] Open
Abstract
Chronic stress-related psychiatric conditions such as anxiety, depression, and alcohol abuse are an enormous public health concern. The etiology of these pathologies is complex, with psychosocial stressors being among the most frequently discussed risk factors. The brain glutamatergic neurotransmitter system has often been found involved in behaviors and pathophysiologies resulting from acute stress and fear. Despite this, relatively little is known about the role of glutamatergic system components in chronic psychosocial stress, neither in rodents nor in humans. Recently, drug discovery efforts at the metabotropic receptor subtypes of the glutamatergic system (mGlu1-8 receptors) led to the identification of pharmacological tools with emerging potential in psychiatric conditions. But again, the contribution of individual mGlu subtypes to the manifestation of physiological, molecular, and behavioral consequences of chronic psychosocial stress remains still largely unaddressed. The current review will describe animal models typically used to analyze acute and particularly chronic stress conditions, including models of psychosocial stress, and there we will discuss the emerging roles for mGlu receptor subtypes. Indeed, accumulating evidence indicates relevance and potential therapeutic usefulness of mGlu2/3 ligands and mGlu5 receptor antagonists in chronic stress-related disorders. In addition, a role for further mechanisms, e.g. mGlu7-selective compounds, is beginning to emerge. These mechanisms are important to be analyzed in chronic psychosocial stress paradigms, e.g. in the chronic subordinate colony housing (CSC) model. We summarize the early results and discuss necessary future investigations, especially for mGlu5 and mGlu7 receptor blockers, which might serve to suggest improved therapeutic strategies to treat stress-related disorders.
Collapse
Affiliation(s)
| | - Peter J Flor
- Faculty of Biology and Preclinical Medicine, University of Regensburg, D-93053 Regensburg, Germany.
| | - Nicole Uschold-Schmidt
- Faculty of Biology and Preclinical Medicine, University of Regensburg, D-93053 Regensburg, Germany.
| |
Collapse
|
19
|
Abstract
Neuroglia, the "glue" that fills the space between neurons in the central nervous system, takes active part in nerve cell signaling. Neuroglial cells, astroglia, oligodendroglia, and microglia, are together about as numerous as neurons in the brain as a whole, and in the cerebral cortex grey matter, but the proportion varies widely among brain regions. Glial volume, however, is less than one-fifth of the tissue volume in grey matter. When stimulated by neurons or other cells, neuroglial cells release gliotransmitters by exocytosis, similar to neurotransmitter release from nerve endings, or by carrier-mediated transport or channel flux through the plasma membrane. Gliotransmitters include the common neurotransmitters glutamate and GABA, the nonstandard amino acid d-serine, the high-energy phosphate ATP, and l-lactate. The latter molecule is a "buffer" between glycolytic and oxidative metabolism as well as a signaling substance recently shown to act on specific lactate receptors in the brain. Complementing neurotransmission at a synapse, neuroglial transmission often implies diffusion of the transmitter over a longer distance and concurs with the concept of volume transmission. Transmission from glia modulates synaptic neurotransmission based on energetic and other local conditions in a volume of tissue surrounding the individual synapse. Neuroglial transmission appears to contribute significantly to brain functions such as memory, as well as to prevalent neuropathologies.
Collapse
Affiliation(s)
- Vidar Gundersen
- SN-Lab, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, and CMBN/SERTA/Healthy Brain Ageing Centre, University of Oslo, Oslo, Norway; Department of Neurology, Oslo University Hospital-Rikshospitalet, Oslo, Norway; Center for Healthy Aging, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark; and Brain and Muscle Energy Group, Department of Oral Biology and Division of Anatomy, Department of Molecular Medicine, University of Oslo, Oslo, Norway
| | - Jon Storm-Mathisen
- SN-Lab, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, and CMBN/SERTA/Healthy Brain Ageing Centre, University of Oslo, Oslo, Norway; Department of Neurology, Oslo University Hospital-Rikshospitalet, Oslo, Norway; Center for Healthy Aging, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark; and Brain and Muscle Energy Group, Department of Oral Biology and Division of Anatomy, Department of Molecular Medicine, University of Oslo, Oslo, Norway
| | - Linda Hildegard Bergersen
- SN-Lab, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, and CMBN/SERTA/Healthy Brain Ageing Centre, University of Oslo, Oslo, Norway; Department of Neurology, Oslo University Hospital-Rikshospitalet, Oslo, Norway; Center for Healthy Aging, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark; and Brain and Muscle Energy Group, Department of Oral Biology and Division of Anatomy, Department of Molecular Medicine, University of Oslo, Oslo, Norway
| |
Collapse
|
20
|
Thomas AG, Sattler R, Tendyke K, Loiacono KA, Hansen H, Sahni V, Hashizume Y, Rojas C, Slusher BS. High-Throughput Assay Development for Cystine-Glutamate Antiporter (xc-) Highlights Faster Cystine Uptake than Glutamate Release in Glioma Cells. PLoS One 2015; 10:e0127785. [PMID: 26252954 PMCID: PMC4529246 DOI: 10.1371/journal.pone.0127785] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Accepted: 04/19/2015] [Indexed: 01/22/2023] Open
Abstract
The cystine-glutamate antiporter (system xc-) is a Na+-independent amino acid transporter that exchanges extracellular cystine for intracellular glutamate. It is thought to play a critical role in cellular redox processes through regulation of intracellular glutathione synthesis via cystine uptake. In gliomas, system xc- expression is universally up-regulated while that of glutamate transporters down-regulated, leading to a progressive accumulation of extracellular glutamate and excitotoxic cell death of the surrounding non-tumorous tissue. Additionally, up-regulation of system xc- in activated microglia has been implicated in the pathogenesis of several neurodegenerative disorders mediated by excess glutamate. Consequently, system xc- is a new drug target for brain cancer and neuroinflammatory diseases associated with excess extracellular glutamate. Unfortunately no potent and selective small molecule system xc- inhibitors exist and to our knowledge, no high throughput screening (HTS) assay has been developed to identify new scaffolds for inhibitor design. To develop such an assay, various neuronal and non-neuronal human cells were evaluated as sources of system xc-. Human glioma cells were chosen based on their high system xc- activity. Using these cells, [14C]-cystine uptake and cystine-induced glutamate release assays were characterized and optimized with respect to cystine and protein concentrations and time of incubation. A pilot screen of the LOPAC/NINDS libraries using glutamate release demonstrated that the logistics of the assay were in place but unfortunately, did not yield meaningful pharmacophores. A larger, HTS campaign using the 384-well cystine-induced glutamate release as primary assay and the 96-well 14C-cystine uptake as confirmatory assay is currently underway. Unexpectedly, we observed that the rate of cystine uptake was significantly faster than the rate of glutamate release in human glioma cells. This was in contrast to the same rates of cystine uptake and glutamate release previously reported in normal human fibroblast cells.
Collapse
Affiliation(s)
- Ajit G. Thomas
- Brain Science Institute, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, United States of America
| | - Rita Sattler
- Brain Science Institute, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, United States of America
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, United States of America
| | - Karen Tendyke
- Next Generation Systems CFU, Eisai Inc., Andover, MA, 01810, United States of America
| | - Kara A. Loiacono
- Next Generation Systems CFU, Eisai Inc., Andover, MA, 01810, United States of America
| | - Hans Hansen
- Next Generation Systems CFU, Eisai Inc., Andover, MA, 01810, United States of America
| | - Vishal Sahni
- Neuroscience and General Medicine PCU, Eisai Inc., Andover, MA, 01810, United States of America
| | - Yutaka Hashizume
- Neuroscience and General Medicine PCU, Eisai Inc., Andover, MA, 01810, United States of America
| | - Camilo Rojas
- Brain Science Institute, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, United States of America
- Department of Comparative Medicine and Molecular Pathobiology, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, United States of America
- * E-mail: (CR); (BSS)
| | - Barbara S. Slusher
- Brain Science Institute, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, United States of America
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, United States of America
- Department of Psychiatry, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, United States of America
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, United States of America
- * E-mail: (CR); (BSS)
| |
Collapse
|
21
|
Kritis AA, Stamoula EG, Paniskaki KA, Vavilis TD. Researching glutamate - induced cytotoxicity in different cell lines: a comparative/collective analysis/study. Front Cell Neurosci 2015; 9:91. [PMID: 25852482 PMCID: PMC4362409 DOI: 10.3389/fncel.2015.00091] [Citation(s) in RCA: 230] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 02/26/2015] [Indexed: 12/21/2022] Open
Abstract
Although glutamate is one of the most important excitatory neurotransmitters of the central nervous system, its excessive extracellular concentration leads to uncontrolled continuous depolarization of neurons, a toxic process called, excitotoxicity. In excitotoxicity glutamate triggers the rise of intracellular Ca2+ levels, followed by up regulation of nNOS, dysfunction of mitochondria, ROS production, ER stress, and release of lysosomal enzymes. Excessive calcium concentration is the key mediator of glutamate toxicity through over activation of ionotropic and metabotropic receptors. In addition, glutamate accumulation can also inhibit cystine (CySS) uptake by reversing the action of the CySS/glutamate antiporter. Reversal of the antiporter action reinforces the aforementioned events by depleting neurons of cysteine and eventually glutathione’s reducing potential. Various cell lines have been employed in the pursuit to understand the mechanism(s) by which excitotoxicity affects the cells leading them ultimately to their demise. In some cell lines glutamate toxicity is exerted mainly through over activation of NMDA, AMPA, or kainate receptors whereas in other cell lines lacking such receptors, the toxicity is due to glutamate induced oxidative stress. However, in the greatest majority of the cell lines ionotropic glutamate receptors are present, co-existing to CySS/glutamate antiporters and metabotropic glutamate receptors, supporting the assumption that excitotoxicity effect in these cells is accumulative. Different cell lines differ in their responses when exposed to glutamate. In this review article the responses of PC12, SH-SY5Y, HT-22, NT-2, OLCs, C6, primary rat cortical neurons, RGC-5, and SCN2.2 cell systems are systematically collected and analyzed.
Collapse
Affiliation(s)
- Aristeidis A Kritis
- Laboratory of Physiology, Department of Physiology and Pharmacology, School of Medicine, Faculty of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki Greece
| | - Eleni G Stamoula
- Laboratory of Physiology, Department of Physiology and Pharmacology, School of Medicine, Faculty of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki Greece
| | - Krystallenia A Paniskaki
- Laboratory of Physiology, Department of Physiology and Pharmacology, School of Medicine, Faculty of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki Greece
| | - Theofanis D Vavilis
- Laboratory of Physiology, Department of Physiology and Pharmacology, School of Medicine, Faculty of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki Greece
| |
Collapse
|
22
|
Spampinato SF, Merlo S, Chisari M, Nicoletti F, Sortino MA. Glial metabotropic glutamate receptor-4 increases maturation and survival of oligodendrocytes. Front Cell Neurosci 2015; 8:462. [PMID: 25642169 PMCID: PMC4294134 DOI: 10.3389/fncel.2014.00462] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 12/18/2014] [Indexed: 11/22/2022] Open
Abstract
Group III metabotropic glutamate (mGlu) receptors mediate important neuroprotective and anti-inflammatory effects. Stimulation of mGlu4 receptor reduces neuroinflammation in a mouse model of experimental autoimmune encephalomyelitis (EAE) whereas mGlu4 knockout mice display exacerbated EAE clinical scores. We now show that mGlu4 receptors are expressed in oligodendrocytes, astrocytes and microglia in culture. Oligodendrocytes express mGlu4 receptors only at early stages of maturation (O4 positive), but not when more differentiated (myelin basic protein, MBP positive). Treatment of immature oligodendrocytes with the mGlu4 receptor agonist L-2-Amino-4-phosphonobutyrate (L-AP4; 50 μM for 48 h) accelerates differentiation with enhanced branching and earlier appearance of MBP staining. Oligodendrocyte death induced by exposure to 1 mM kainic acid for 24 h is significantly reduced by a 30-min pretreatment with L-AP4 (50 μM), an effect observed only in the presence of astrocytes, mimicked by the specific mGlu4 receptor positive allosteric modulator N-Phenyl-7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxamide (PHCCC) (30 μM) and prevented by pretreatment with the mGlu4 receptor antagonist, cyclopropyl-4-phosphonophenylglycine (CPPG) (100 μM). In astrocytes, mGlu4 receptor is the most expressed among group III mGlu receptors, as by Quantitative real time PCR (QRT-PCR), and its silencing prevents protective effects. Protection is also observed when conditioned medium (CM) from L-AP4-pretreated astrocytes is transferred to oligodendrocytes challenged with kainic acid. Transforming growth factor β (TGF-β) mediates the increased oligodendrocyte survival as the effect of L-AP4 is mimicked by addition of 10 ng/ml TGF-β and prevented by incubation with a neutralizing anti-TGF-β antibody. In contrast, despite the expression of mGlu4 receptor in resting and activated microglia, CM from L-AP4-stimulated microglia does not modify kainate-induced oligodendrocyte toxicity. Our results suggest that mGlu4 receptors expressed in astrocytes mediate enhanced survival of oligodendrocytes under conditions of excitotoxicity.
Collapse
Affiliation(s)
- Simona Federica Spampinato
- Department of Biomedical and Biotechnological Sciences, Section of Pharmacology, University of Catania Catania, Italy
| | - Sara Merlo
- Department of Biomedical and Biotechnological Sciences, Section of Pharmacology, University of Catania Catania, Italy
| | - Mariangela Chisari
- Department of Biomedical and Biotechnological Sciences, Section of Pharmacology, University of Catania Catania, Italy
| | - Ferdinando Nicoletti
- Department of Physiology and Pharmacology, University of Rome Sapienza Rome, Italy ; IRCSS Neuromed Pozzilli, Italy
| | - Maria Angela Sortino
- Department of Biomedical and Biotechnological Sciences, Section of Pharmacology, University of Catania Catania, Italy
| |
Collapse
|
23
|
Lan YL, Zhao J, Li S. Estrogen receptors' neuroprotective effect against glutamate-induced neurotoxicity. Neurol Sci 2014; 35:1657-62. [PMID: 25228013 DOI: 10.1007/s10072-014-1937-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Accepted: 08/29/2014] [Indexed: 01/28/2023]
Abstract
Glutamate is the most abundant excitatory brain neurotransmitter that has important functional significance with respect to neurodegenerative conditions. Glutamate-mediated excitotoxicity and neurodegeneration in Alzheimer's disease (AD) has been gradually becoming elucidated recently. Excessive release of glutamate induces an increase in intracellular Ca(2+) levels, thus triggers a cascade of cellular responses, ultimately leading to neuronal cell death. This type of neuronal damage induced by over-excitation has been proposed to be involved in a number of neuropathological conditions, ranging from acute insults to chronic neurodegenerative disorders. Estrogen could be effective in modulating glutamate-induced neurotoxicity and the protective responsivenesses are mostly estrogen receptors (ERs)-dependent. However, the mechanism underlying estrogen's neuroprotective effect is not fully clarified and is complicated by the presence of several distinct ER types. So a deeper research into the neuroprotection of ERs might be informative about the positive effect that estrogen might have on ageing-related cognitive changes. Extensive studies have indicated the neuroprotective effects of ERs against glutamate-induced neurotoxicity. The purpose of this review is to elucidate ERs' neuroprotective effects against glutamate-induced cytotoxicity and explore new ways to prevent and cure neurotoxicity-associated neurodegenerative disorders.
Collapse
Affiliation(s)
- Yu-Long Lan
- Department of Physiology, Dalian Medical University, Dalian, 116044, China
| | | | | |
Collapse
|
24
|
Careaga M, Noyon T, Basuta K, Van de Water J, Tassone F, Hagerman RJ, Ashwood P. Group I metabotropic glutamate receptor mediated dynamic immune dysfunction in children with fragile X syndrome. J Neuroinflammation 2014; 11:110. [PMID: 24942544 PMCID: PMC4107617 DOI: 10.1186/1742-2094-11-110] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Accepted: 05/27/2014] [Indexed: 11/23/2022] Open
Abstract
Background Fragile X syndrome (FXS) is the leading cause of inheritable intellectual disability in male children, and is predominantly caused by a single gene mutation resulting in expanded trinucleotide CGG-repeats within the 5’ untranslated region of the fragile X mental retardation (FMR1) gene. Reports have suggested the presence of immune dysregulation in FXS with evidence of altered plasma cytokine levels; however, no studies have directly assessed functional cellular immune responses in children with FXS. In order to ascertain if immune dysregulation is present in children with FXS, dynamic cellular responses to immune stimulation were examined. Methods Peripheral blood mononuclear cells (PBMC) were from male children with FXS (n = 27) and from male aged-matched typically developing (TD) controls (n = 8). PBMC were cultured for 48 hours in media alone or with lipopolysaccharides (LPS; 1 μg/mL) to stimulate the innate immune response or with phytohemagglutinin (PHA; 8 μg/mL) to stimulate the adaptive T-cell response. Additionally, the group I mGluR agonist, DHPG, was added to cultures to ascertain the role of mGluR signaling in the immune response in subject with FXS. Supernatants were harvested and cytokine levels were assessed using Luminex multiplexing technology. Results Children with FXS displayed similar innate immune response following challenge with LPS alone when compared with TD controls; however, when LPS was added in the presence of a group I mGluR agonist, DHPG, increased immune response were observed in children with FXS for a number of pro-inflammatory cytokines including IL-6 (P = 0.02), and IL-12p40 (P < 0.01). Following PHA stimulation, with or without DHPG, no significant differences between subjects with FXS and TD were seen. Conclusions In unstimulated cultures, subjects with FXS did not display altered dynamic immune response to LPS or PHA alone; however, subjects with FXS showed an altered response to co-current stimulation of LPS and DHPG, such that subjects with FXS failed to inhibit production of pro-inflammatory cytokines, suggesting a role of group I mGluR signaling in innate immune responses in FXS.
Collapse
Affiliation(s)
| | | | | | | | | | | | - Paul Ashwood
- Department of Medical Microbiology and Immunology, and the MIND Institute, UC Davis, 2805, 50th Street, Sacramento, CA 95817, USA.
| |
Collapse
|
25
|
Pomierny-Chamioło L, Rup K, Pomierny B, Niedzielska E, Kalivas PW, Filip M. Metabotropic glutamatergic receptors and their ligands in drug addiction. Pharmacol Ther 2014; 142:281-305. [DOI: 10.1016/j.pharmthera.2013.12.012] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Accepted: 12/02/2013] [Indexed: 02/07/2023]
|
26
|
Williams CJ, Dexter DT. Neuroprotective and symptomatic effects of targeting group III mGlu receptors in neurodegenerative disease. J Neurochem 2013; 129:4-20. [PMID: 24224472 DOI: 10.1111/jnc.12608] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2013] [Revised: 10/28/2013] [Accepted: 11/06/2013] [Indexed: 12/21/2022]
Abstract
Neurodegenerative disorders possess common pathological mechanisms, such as protein aggregation, inflammation, oxidative stress (OS) and excitotoxicity, raising the possibility of shared therapeutic targets. As a result of the selective cellular and regional expression of group III metabotropic glutamate (mGlu) receptors, drugs targeting such receptors have demonstrated both neuroprotective properties and symptomatic improvements in several models of neurodegeneration. In recent years, the discovery and development of subtype-selective ligands for the group III mGlu receptors has gained pace, allowing further research into the functions of these receptors and revealing their roles in health and disease. Activation of this class of receptors results in neuroprotection, with a variety of underlying mechanisms implicated. Group III mGlu receptor stimulation prevents excitotoxicity by inhibiting glutamate release from neurons and microglia and increasing glutamate uptake by astrocytes. It also attenuates the neuroinflammatory response by reducing glial reactivity and encourages neurotrophic phenotypes. This article will review the current literature with regard to the neuroprotective and symptomatic effects of group III mGlu receptor activation and discuss their promise as therapeutic targets in neurodegenerative disease. We review the neuroprotective and symptomatic effects of targeting group III mGlu receptors in neurodegenerative disease: Excess extracellular glutamate causes overactivation of NMDA receptors resulting in excitotoxicity. Externalization of phosphatidylserine stimulates phagocytosis of neurons by activated microglia, which contribute to damage through glutamate and pro-inflammatory factor release. Reactive astrocytes produce cytotoxic factors enhancing neuronal cell death. Activation of group III mGlu receptors by glutamate and/or mGlu receptor ligands results in inhibition of glutamate release from presynaptic terminals and microglia, reducing excitotoxicity. Astrocytic glutamate uptake is increased and microglia produce neurotrophic factors.
Collapse
Affiliation(s)
- Claire J Williams
- Parkinson's Disease Research Group, Centre for Neuroinflammation and Neurodegeneration, Division of Brain Sciences, Faculty of Medicine, Imperial College London, Hammersmith Hospital Campus, London, UK
| | | |
Collapse
|
27
|
Blaylock RL. Immunology primer for neurosurgeons and neurologists part 2: Innate brain immunity. Surg Neurol Int 2013; 4:118. [PMID: 24083053 PMCID: PMC3784951 DOI: 10.4103/2152-7806.118349] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Accepted: 06/18/2013] [Indexed: 12/27/2022] Open
Abstract
Over the past several decades we have learned a great deal about microglia and innate brain immunity. While microglia are the principle innate immune cells, other cell types also play a role, including invading macrophages, astrocytes, neurons, and endothelial cells. The fastest reacting cell is the microglia and despite its name, resting microglia (also called ramified microglia) are in fact quite active. Motion photomicrographs demonstrate a constant movement of ramified microglial foot processes, which appear to be testing the microenvironment for dangerous alteration in extracellular fluid content. These foot processes, in particular, interact with synapses and play a role in synaptic function. In event of excitatory overactivity, these foot processes can strip selected synapses, thus reducing activation states as a neuroprotective mechanism. They can also clear extracellular glutamate so as to reduce the risk of excitotoxicity. Microglia also appear to have a number of activation phenotypes, such as: (1) phagocytic, (2) neuroprotective and growth promoting, or (3) primarily neurodestructive. These innate immune cells can migrate a great distance under pathological conditions and appear to have anatomic specificity, meaning they can accumulate in specifically selected areas of the brain. There is some evidence that there are several types of microglia. Macrophage infiltration into the embryonic brain is the source of resident microglia and in adulthood macrophages can infiltrate the brain and are for the most part pathologically indistinguishable from resident microglia, but may react differently. Activation itself does not imply a destructive phenotype and can be mostly neuroprotective via phagocytosis of debris, neuron parts and dying cells and by the release of neurotrophins such as nerve growth factor (NGF) and brain derived neurotrophic factor (BDNF). Evidence is accumulating that microglia undergo dynamic fluctuations in phenotype as the neuropathology evolves. For example, in the early stages of neurotrauma and stroke, microglia play a mostly neuroprotective role and only later switch to a neurodestructive mode. A great number of biological systems alter microglia function, including neurohormones, cannabinoids, other neurotransmitters, adenosine triphosphate (ATP), adenosine, and corticosteroids. One can appreciate that with aging many of these systems are altered by the aging process itself or by disease thus changing the sensitivity of the innate immune system.
Collapse
Affiliation(s)
- Russell L Blaylock
- Theoretical Neurosciences Research, LLC, Neurosurgeon (Ret), Ridgeland, MS
| |
Collapse
|
28
|
Abstract
Microglia are critical nervous system-specific cells influencing brain development, maintenance of the neural environment, response to injury, and repair. They contribute to neuronal proliferation and differentiation, pruning of dying neurons, synaptic remodeling and clearance of debris and aberrant proteins. Colonization of the brain occurs during gestation with an expansion following birth with localization stimulated by programmed neuronal death, synaptic pruning, and axonal degeneration. Changes in microglia phenotype relate to cellular processes including specific neurotransmitter, pattern recognition, or immune-related receptor activation. Upon activation, microglia cells have the capacity to release a number of substances, e.g., cytokines, chemokines, nitric oxide, and reactive oxygen species, which could be detrimental or beneficial to the surrounding cells. With aging, microglia shift their morphology and may display diminished capacity for normal functions related to migration, clearance, and the ability to shift from a pro-inflammatory to an anti-inflammatory state to regulate injury and repair. This shift in microglia potentially contributes to increased susceptibility and neurodegeneration as a function of age. In the current review, information is provided on the colonization of the brain by microglia, the expression of various pattern recognition receptors to regulate migration and phagocytosis, and the shift in related functions that occur in normal aging.
Collapse
Affiliation(s)
- G Jean Harry
- National Toxicology Program Laboratory, National Institute of Environmental Health Sciences, MD C1-04, 111 T.W. Alexander Drive, Research Triangle Park, NC 27709, USA.
| |
Collapse
|
29
|
Miklós F, Mándity IM, Sillanpää R, Fülöp F. Stereocontrolled synthesis of five diastereomers of trimethyl 3-aminocyclopentane-1,2,4-tricarboxylates. Tetrahedron Lett 2013. [DOI: 10.1016/j.tetlet.2013.05.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
|
30
|
Gao Z, Zhu Q, Zhang Y, Zhao Y, Cai L, Shields CB, Cai J. Reciprocal modulation between microglia and astrocyte in reactive gliosis following the CNS injury. Mol Neurobiol 2013; 48:690-701. [PMID: 23613214 DOI: 10.1007/s12035-013-8460-4] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Accepted: 04/09/2013] [Indexed: 12/16/2022]
Abstract
Reactive gliosis, also known as glial scar formation, is an inflammatory response characterized by the proliferation of microglia and astrocytes as well as astrocytic hypertrophy following injury in the central nervous system (CNS). The glial scar forms a physical and molecular barrier to isolate the injured area from adjacent normal nervous tissue for re-establishing the integrity of the CNS. It prevents the further spread of cellular damage but represents an obstacle to regrowing axons. In this review, we integrated the current findings to elucidate the tightly reciprocal modulation between activated microglia and astrocytes in reactive gliosis and proposed that modification of cellular response to the injury or cellular reprogramming in the glial scar could lead advances in axon regeneration and functional recovery after the CNS injury.
Collapse
Affiliation(s)
- Zhongwen Gao
- Department of Spine Surgery, the First Hospital of Jilin University, 71 Xinmin Street, Changchun, Jilin, 130021, China
| | | | | | | | | | | | | |
Collapse
|
31
|
Domercq M, Vázquez-Villoldo N, Matute C. Neurotransmitter signaling in the pathophysiology of microglia. Front Cell Neurosci 2013; 7:49. [PMID: 23626522 PMCID: PMC3630369 DOI: 10.3389/fncel.2013.00049] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Accepted: 04/05/2013] [Indexed: 01/09/2023] Open
Abstract
Microglial cells are the resident immune cells of the central nervous system. In the resting state, microglia are highly dynamic and control the environment by rapidly extending and retracting motile processes. Microglia are closely associated with astrocytes and neurons, particularly at the synapses, and more recent data indicate that neurotransmission plays a role in regulating the morphology and function of surveying/resting microglia, as they are endowed with receptors for most known neurotransmitters. In particular, microglia express receptors for ATP and glutamate, which regulate microglial motility. After local damage, the release of ATP induces microgliosis and activated microglial cells migrate to the site of injury, proliferate, and phagocytose cells, and cellular compartments. However, excessive activation of microglia could contribute to the progression of chronic neurodegenerative diseases, though the underlying mechanisms are still unclear. Microglia have the capacity to release a large number of substances that can be detrimental to the surrounding neurons, including glutamate, ATP, and reactive oxygen species. However, how altered neurotransmission following acute insults or chronic neurodegenerative conditions modulates microglial functions is still poorly understood. This review summarizes the relevant data regarding the role of neurotransmitter receptors in microglial physiology and pathology.
Collapse
Affiliation(s)
- María Domercq
- Departamento de Neurociencias, Universidad del País Vasco-UPV/EHU Leioa, Spain ; Achucarro Basque Center for Neuroscience-UPV/EHU Zamudio, Spain ; Instituto de Salud Carlos III, Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas Leioa, Spain
| | | | | |
Collapse
|