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Fontana ACK, Poli AN, Gour J, Srikanth YV, Anastasi N, Ashok D, Khatiwada A, Reeb KL, Cheng MH, Bahar I, Rawls SM, Salvino JM. Synthesis and Structure-Activity Relationships for Glutamate Transporter Allosteric Modulators. J Med Chem 2024; 67:6119-6143. [PMID: 38626917 PMCID: PMC11056993 DOI: 10.1021/acs.jmedchem.3c01909] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Revised: 03/23/2024] [Accepted: 03/27/2024] [Indexed: 04/19/2024]
Abstract
Excitatory amino acid transporters (EAATs) are essential CNS proteins that regulate glutamate levels. Excess glutamate release and alteration in EAAT expression are associated with several CNS disorders. Previously, we identified positive allosteric modulators (PAM) of EAAT2, the main CNS transporter, and have demonstrated their neuroprotective properties in vitro. Herein, we report on the structure-activity relationships (SAR) for the analogs identified from virtual screening and from our medicinal chemistry campaign. This work identified several selective EAAT2 positive allosteric modulators (PAMs) such as compounds 4 (DA-023) and 40 (NA-014) from a library of analogs inspired by GT949, an early generation compound. This series also provides nonselective EAAT PAMs, EAAT inhibitors, and inactive compounds that may be useful for elucidating the mechanism of EAAT allosteric modulation.
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Affiliation(s)
- Andréia C. K. Fontana
- Department
of Pharmacology and Physiology, Drexel University
College of Medicine, Philadelphia, Pennsylvania 19102, United States
| | - Adi N.R. Poli
- Medicinal
Chemistry, Molecular and Cellular Oncogenesis (MCO) Program, The Wistar Institute, Philadelphia, Pennsylvania 19104, United States
| | - Jitendra Gour
- Medicinal
Chemistry, Molecular and Cellular Oncogenesis (MCO) Program, The Wistar Institute, Philadelphia, Pennsylvania 19104, United States
| | - Yellamelli V.V. Srikanth
- Medicinal
Chemistry, Molecular and Cellular Oncogenesis (MCO) Program, The Wistar Institute, Philadelphia, Pennsylvania 19104, United States
| | - Nicholas Anastasi
- Medicinal
Chemistry, Molecular and Cellular Oncogenesis (MCO) Program, The Wistar Institute, Philadelphia, Pennsylvania 19104, United States
| | - Devipriya Ashok
- Medicinal
Chemistry, Molecular and Cellular Oncogenesis (MCO) Program, The Wistar Institute, Philadelphia, Pennsylvania 19104, United States
| | - Apeksha Khatiwada
- Department
of Pharmacology and Physiology, Drexel University
College of Medicine, Philadelphia, Pennsylvania 19102, United States
| | - Katelyn L. Reeb
- Department
of Pharmacology and Physiology, Drexel University
College of Medicine, Philadelphia, Pennsylvania 19102, United States
| | - Mary Hongying Cheng
- Laufer
Center for Physical & Quantitative Biology, Stony Brook University, Stony
Brook, New York 11794, United States
| | - Ivet Bahar
- Department
of Biochemistry and Cell Biology, College of Arts & Sciences and
School of Medicine, Stony Brook University, Stony Brook, New York 11794, United States
- Laufer
Center for Physical & Quantitative Biology, Stony Brook University, Stony
Brook, New York 11794, United States
| | - Scott M. Rawls
- Center
for Substance Abuse Research, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania 19140United States
| | - Joseph M. Salvino
- Medicinal
Chemistry, Molecular and Cellular Oncogenesis (MCO) Program, The Wistar Institute, Philadelphia, Pennsylvania 19104, United States
- The
Wistar
Cancer Center Molecular Screening, The Wistar
Institute, Philadelphia, Pennsylvania 19104, United States
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2
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Soto-Verdugo J, Siva-Parra J, Hernández-Kelly LC, Ortega A. Acute Manganese Exposure Modifies the Translation Machinery via PI3K/Akt Signaling in Glial Cells. ASN Neuro 2022; 14:17590914221131452. [PMID: 36203371 PMCID: PMC9551334 DOI: 10.1177/17590914221131452] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
SUMMARY STATEMENT We demonstrate herein that short-term exposure of radial glia cells to Manganese, a neurotoxic metal, induces an effect on protein synthesis, altering the protein repertoire of these cells.
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Affiliation(s)
| | | | | | - Arturo Ortega
- Arturo Ortega, Departamento de Toxicología,
Centro de Investigación y de Estudios Avanzados del Instituto Politécnico
Nacional, México City, México, 07360.
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3
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Iovino L, Giusti V, Pischedda F, Giusto E, Plotegher N, Marte A, Battisti I, Di Iacovo A, Marku A, Piccoli G, Bandopadhyay R, Perego C, Bonifacino T, Bonanno G, Roseti C, Bossi E, Arrigoni G, Bubacco L, Greggio E, Hilfiker S, Civiero L. Trafficking of the glutamate transporter is impaired in LRRK2-related Parkinson's disease. Acta Neuropathol 2022; 144:81-106. [PMID: 35596783 PMCID: PMC9217889 DOI: 10.1007/s00401-022-02437-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 05/11/2022] [Accepted: 05/11/2022] [Indexed: 12/02/2022]
Abstract
The Excitatory Amino Acid Transporter 2 (EAAT2) accounts for 80% of brain glutamate clearance and is mainly expressed in astrocytic perisynaptic processes. EAAT2 function is finely regulated by endocytic events, recycling to the plasma membrane and degradation. Noteworthy, deficits in EAAT2 have been associated with neuronal excitotoxicity and neurodegeneration. In this study, we show that EAAT2 trafficking is impaired by the leucine-rich repeat kinase 2 (LRRK2) pathogenic variant G2019S, a common cause of late-onset familial Parkinson’s disease (PD). In LRRK2 G2019S human brains and experimental animal models, EAAT2 protein levels are significantly decreased, which is associated with elevated gliosis. The decreased expression of the transporter correlates with its reduced functionality in mouse LRRK2 G2019S purified astrocytic terminals and in Xenopus laevis oocytes expressing human LRRK2 G2019S. In LRRK2 G2019S knock-in mouse brain, the correct surface localization of the endogenous transporter is impaired, resulting in its interaction with a plethora of endo-vesicular proteins. Mechanistically, we report that pathogenic LRRK2 kinase activity delays the recycling of the transporter to the plasma membrane via Rabs inactivation, causing its intracellular re-localization and degradation. Taken together, our results demonstrate that pathogenic LRRK2 interferes with the physiology of EAAT2, pointing to extracellular glutamate overload as a possible contributor to neurodegeneration in PD.
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Bobermin LD, de Souza Almeida RR, Weber FB, Medeiros LS, Medeiros L, Wyse ATS, Gonçalves CA, Quincozes-Santos A. Lipopolysaccharide Induces Gliotoxicity in Hippocampal Astrocytes from Aged Rats: Insights About the Glioprotective Roles of Resveratrol. Mol Neurobiol 2022; 59:1419-1439. [PMID: 34993844 DOI: 10.1007/s12035-021-02664-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 11/23/2021] [Indexed: 12/13/2022]
Abstract
Astrocytes may undergo a functional remodeling with aging, acquiring a pro-inflammatory state. In line with this, resveratrol represents an interesting strategy for a healthier brain aging since it can improve glial functions. In the present study, we investigated the glioprotective role of resveratrol against lipopolysaccharide (LPS)-induced gliotoxicity in hippocampal aged astrocytes. Astrocyte cultures were obtained from aged rats (365 days old) and challenged in vitro with LPS in the presence of resveratrol. Cultured astrocytes from newborn rats were used as an age comparative for evaluating LPS gliotoxicity. In addition, aged rats were submitted to an acute systemic inflammation with LPS. Hippocampal astrocyte cultures were also obtained from these LPS-stimulated aged animals to further investigate the glioprotective effects of resveratrol in vitro. Overall, our results show that LPS induced a higher inflammatory response in aged astrocytes, compared to newborn astrocytes. Several inflammatory and gene expression alterations promoted by LPS in aged astrocyte cultures were similar in hippocampal tissue from aged animals submitted to in vivo LPS injection, corroborating our in vitro findings. Resveratrol, in turn, presented anti-inflammatory effects in aged astrocyte cultures, which were associated with downregulation of p21 and pro-inflammatory cytokines, Toll-like receptors (TLRs), and nuclear factor κB (NFκB). Resveratrol also improved astroglial functions. Upregulation of sirtuin 1 (SIRT1), nuclear factor erythroid 2-related factor 2 (Nrf2), and heme oxygenase 1 (HO-1) represent potential molecular mechanisms associated with resveratrol-mediated glioprotection. In summary, our data show that resveratrol can prime aged astrocytes against gliotoxic stimuli, contributing to a healthier brain aging.
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Affiliation(s)
- Larissa Daniele Bobermin
- Programa de Pós-Graduação Em Ciências Biológicas: Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal Do Rio Grande Do Sul, Porto Alegre, RS, Brazil
| | - Rômulo Rodrigo de Souza Almeida
- Programa de Pós-Graduação Em Ciências Biológicas: Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal Do Rio Grande Do Sul, Porto Alegre, RS, Brazil
| | - Fernanda Becker Weber
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul- UFRGS, Rua Ramiro Barcelos, 2600 - Anexo Bairro Santa Cecília, Porto Alegre, RS, Brazil
| | - Lara Scopel Medeiros
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul- UFRGS, Rua Ramiro Barcelos, 2600 - Anexo Bairro Santa Cecília, Porto Alegre, RS, Brazil
| | - Lívia Medeiros
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul- UFRGS, Rua Ramiro Barcelos, 2600 - Anexo Bairro Santa Cecília, Porto Alegre, RS, Brazil
| | - Angela T S Wyse
- Programa de Pós-Graduação Em Ciências Biológicas: Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal Do Rio Grande Do Sul, Porto Alegre, RS, Brazil.,Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul- UFRGS, Rua Ramiro Barcelos, 2600 - Anexo Bairro Santa Cecília, Porto Alegre, RS, Brazil
| | - Carlos-Alberto Gonçalves
- Programa de Pós-Graduação Em Ciências Biológicas: Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal Do Rio Grande Do Sul, Porto Alegre, RS, Brazil.,Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul- UFRGS, Rua Ramiro Barcelos, 2600 - Anexo Bairro Santa Cecília, Porto Alegre, RS, Brazil
| | - André Quincozes-Santos
- Programa de Pós-Graduação Em Ciências Biológicas: Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal Do Rio Grande Do Sul, Porto Alegre, RS, Brazil. .,Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul- UFRGS, Rua Ramiro Barcelos, 2600 - Anexo Bairro Santa Cecília, Porto Alegre, RS, Brazil.
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5
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Rodríguez-Campuzano AG, Ortega A. Glutamate transporters: Critical components of glutamatergic transmission. Neuropharmacology 2021; 192:108602. [PMID: 33991564 DOI: 10.1016/j.neuropharm.2021.108602] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 04/09/2021] [Accepted: 04/27/2021] [Indexed: 02/06/2023]
Abstract
Glutamate is the major excitatory neurotransmitter in the vertebrate central nervous system. Once released, it binds to specific membrane receptors and transporters activating a wide variety of signal transduction cascades, as well as its removal from the synaptic cleft in order to avoid its extracellular accumulation and the overstimulation of extra-synaptic receptors that might result in neuronal death through a process known as excitotoxicity. Although neurodegenerative diseases are heterogenous in clinical phenotypes and genetic etiologies, a fundamental mechanism involved in neuronal degeneration is excitotoxicity. Glutamate homeostasis is critical for brain physiology and Glutamate transporters are key players in maintaining low extracellular Glutamate levels. Therefore, the characterization of Glutamate transporters has been an active area of glutamatergic research for the last 40 years. Transporter activity its regulated at different levels: transcriptional and translational control, transporter protein trafficking and membrane mobility, and through extensive post-translational modifications. The elucidation of these mechanisms has emerged as an important piece to shape our current understanding of glutamate actions in the nervous system.
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Affiliation(s)
- Ada G Rodríguez-Campuzano
- Departamento de Toxicología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Apartado Postal 14-740, Ciudad de México, 07000, Mexico
| | - Arturo Ortega
- Departamento de Toxicología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Apartado Postal 14-740, Ciudad de México, 07000, Mexico.
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6
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Voss TD, Gerget M, Linkus B, von Einem B, Landwehrmeyer GB, Lewerenz J. Ubiquitination and the proteasome rather than caspase-3-mediated C-terminal cleavage are involved in the EAAT2 degradation by staurosporine-induced cellular stress. J Neurochem 2020; 157:1284-1299. [PMID: 33180957 DOI: 10.1111/jnc.15237] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Revised: 03/09/2020] [Accepted: 11/03/2020] [Indexed: 01/01/2023]
Abstract
Diminished glutamate (Glu) uptake via the excitatory amino acid transporter EAAT2, which normally accounts for ~90% of total forebrain EAAT activity, may contribute to neurodegeneration via Glu-mediated excitotoxicity. C-terminal cleavage by caspase-3 (C3) was reported to mediate EAAT2 inactivation and down-regulation in the context of neurodegeneration. For a detailed analysis of C3-dependent EAAT2 degradation, we employed A172 glioblastoma as well as hippocampal HT22 cells and murine astrocytes over-expressing VSV-G-tagged EAAT2 constructs. C3 activation was induced by staurosporine (STR). In HT22 cells, STR-induced C3 activation-induced rapid EAAT2 protein degradation. The mutation of asparagine 504 to aspartate (D504N), which should inactivate the putative C3 cleavage site, increased EAAT2 activity in A172 cells. In contrast, the D504N mutation did not protect EAAT2 protein against STR-induced degradation in HT22 cells, whereas inhibition of caspases, ubiquitination and the proteasome did. Similar results were obtained in astrocytes. Phylogenetic analysis showed that C-terminal ubiquitin acceptor sites-but not the putative C3 cleavage site-exhibit a high degree of conservation. Moreover, C-terminal truncation mimicking C3 cleavage increased rather than decreased EAAT2 activity and stability as well as protected EAAT2 against STR-induced ubiquitination-dependent degradation. We conclude that cellular stress associated with endogenous C3 activation degrades EAAT2 via a pathway involving ubiquitination and the proteasome but not direct C3-mediated cleavage. In addition, C3 cleavage of EAAT2, described to occur in other models, is unlikely to inactivate EAAT2. However, mutation of the highly conserved D504 within the putative C3 cleavage site increases EAAT2 activity via an unknown mechanism.
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Affiliation(s)
| | - Maria Gerget
- Department of Neurology, Ulm University, Ulm, Germany
| | - Birgit Linkus
- Department of Neurology, Ulm University, Ulm, Germany
| | | | | | - Jan Lewerenz
- Department of Neurology, Ulm University, Ulm, Germany
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7
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Powers B, Joyce C, Kleinman JE, Hyde TM, Ajilore O, Leow A, Sodhi MS. Sex differences in the transcription of glutamate transporters in major depression and suicide. J Affect Disord 2020; 277:244-252. [PMID: 32836031 DOI: 10.1016/j.jad.2020.07.055] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 05/29/2020] [Accepted: 07/05/2020] [Indexed: 11/28/2022]
Abstract
BACKGROUND Accumulating evidence indicates that the glutamate system contributes to the pathophysiology of major depressive disorder (MDD) and suicide. We previously reported higher mRNA expression of glutamate receptors in the dorsolateral prefrontal cortex (DLPFC) of females with MDD. METHODS In the current study, we measured the expression of mRNAs encoding glutamate transporters in the DLPFC of MDD subjects who died by suicide (MDD-S, n = 51), MDD non-suicide subjects (MDD-NS, n = 28), and individuals who did not have a history of neurological illness (CTRL, n = 32). RESULTS Females but not males with MDD showed higher expression of EAATs and VGLUTs relative to CTRLs. VGLUT expression was significantly higher in the female MDD-S group, relative to the other groups. EAAT expression was lower in the male violent suicides. LIMITATIONS This study has limitations common to most human studies, including medication history and demographic differences between the diagnostic groups. We mitigated the effects of confounders by including them as covariates in our analyses. CONCLUSIONS We report sex differences in the expression of glutamate transporter genes in the DLPFC in MDD. Increased neuronal glutamate transporter expression may increase synaptic glutamate, leading to neuronal and glial loss in the DLPFC in MDD. These deficits may lower DLPFC activity, impair problem solving and impair executive function in depression, perhaps increasing vulnerability to suicidal behavior. These data add to accumulating support for the hypothesis that glutamatergic transmission is dysregulated in MDD and suicide. Glutamate transporters may be novel targets for the development of rapidly acting antidepressant therapies.
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Affiliation(s)
- Brian Powers
- Department of Molecular Pharmacology & Neuroscience, Stritch School of Medicine, Loyola University Chicago, Maywood, IL 60153, United States
| | - Cara Joyce
- Biostatistics Collaborative Core, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, United States
| | - Joel E Kleinman
- Lieber Institute for Brain Development and Department of Psychiatry & Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Thomas M Hyde
- Lieber Institute for Brain Development and Department of Psychiatry & Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, United States; Johns Hopkins University School of Medicine, Department of Neurology, Baltimore, MD, United States
| | - Olusola Ajilore
- Dept. Psychiatry, University of Illinois at Chicago, Chicago, IL, United States
| | - Alex Leow
- Dept. Psychiatry, University of Illinois at Chicago, Chicago, IL, United States
| | - Monsheel S Sodhi
- Department of Molecular Pharmacology & Neuroscience, Stritch School of Medicine, Loyola University Chicago, Maywood, IL 60153, United States; Dept. Psychiatry, University of Illinois at Chicago, Chicago, IL, United States.
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8
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Neurobiology, Functions, and Relevance of Excitatory Amino Acid Transporters (EAATs) to Treatment of Refractory Epilepsy. CNS Drugs 2020; 34:1089-1103. [PMID: 32926322 DOI: 10.1007/s40263-020-00764-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Epilepsy is one of the most prevalent and devastating neurological disorders characterized by episodes of unusual sensations, loss of awareness, and reoccurring seizures. The frequency and intensity of epileptic fits can vary to a great degree, with almost a third of all cases resistant to available therapies. At present, there is a major unmet need for effective and specific therapeutic intervention. Impairments of the exquisite balance between excitatory and inhibitory synaptic processes in the brain are considered key in the onset and pathophysiology of the disease. As the primary excitatory neurotransmitter in the central nervous system, glutamate has been implicated in the process, with the glutamatergic system holding center stage in the pathobiology as well as in developing disease-modifying therapies. Emerging data pinpoint impairments of glutamate clearance as one of the key causative factors in drug-resistant disease forms. Reinstatement of glutamate homeostasis using pharmacological and genetic modulation of glutamate clearance is therefore considered to be of major translational relevance. In this article, we review the neurobiological and clinical evidence suggesting complex aberrations in the activity and functions of excitatory amino acid transporters (EAATs) in epilepsy, with knock-on effects on glutamate homeostasis as a leading cause for the development of refractory forms. We consider the emerging data on pharmacological and genetic manipulations of EAATs, with reference to seizures and glutamate dyshomeostasis, and review their fundamental and translational relevance. We discuss the most recent advances in the EAATs research in human and animal models, along with numerous questions that remain open for debate and critical appraisal. Contrary to the widely held view on EAATs as a promising therapeutic target for management of refractory epilepsy as well as other neurological and psychiatric conditions related to glutamatergic hyperactivity and glutamate-induced cytotoxicity, we stress that the true relevance of EAAT2 as a target for medical intervention remains to be fully appreciated and verified. Despite decades of research, the emerging properties and functional characteristics of glutamate transporters and their relationship with neurophysiological and behavioral correlates of epilepsy challenge the current perception of this disease and fit unambiguously in neither EAATs functional deficit nor in reversal models. We stress the pressing need for new approaches and models for research and restoration of the physiological activity of glutamate transporters and synaptic transmission to achieve much needed therapeutic effects. The complex mechanism of EAATs regulation by multiple factors, including changes in the electrochemical environment and ionic gradients related to epileptic hyperactivity, impose major therapeutic challenges. As a final note, we consider the evolving views and present a cautious perspective on the key areas of future progress in the field towards better management and treatment of refractory disease forms.
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Elmatboly AM, Sherif AM, Deeb DA, Benmelouka A, Bin-Jumah MN, Aleya L, Abdel-Daim MM. The impact of proteostasis dysfunction secondary to environmental and genetic causes on neurodegenerative diseases progression and potential therapeutic intervention. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2020; 27:11461-11483. [PMID: 32072427 DOI: 10.1007/s11356-020-07914-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Accepted: 01/28/2020] [Indexed: 06/10/2023]
Abstract
Aggregation of particular proteins in the form of inclusion bodies or plaques followed by neuronal death is a hallmark of neurodegenerative proteopathies such as primary Parkinsonism, Alzheimer's disease, Lou Gehrig's disease, and Huntington's chorea. Complex polygenic and environmental factors implicated in these proteopathies. Accumulation of proteins in these disorders indicates a substantial disruption in protein homeostasis (proteostasis). Proteostasis or cellular proteome homeostasis is attained by the synchronization of a group of cellular mechanisms called the proteostasis network (PN), which is responsible for the stability of the proteome and achieves the equilibrium between synthesis, folding, and degradation of proteins. In this review, we will discuss the different types of PN and the impact of PN component dysfunction on the four major neurodegenerative diseases mentioned earlier. Graphical abstract.
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Affiliation(s)
| | - Ahmed M Sherif
- Faculty of Medicine, Zagazig University, El-Sharkia, Egypt
| | - Dalia A Deeb
- Faculty of Medicine, Zagazig University, El-Sharkia, Egypt
| | - Amira Benmelouka
- Faculty of Medicine, University of Algiers, Sidi M'Hamed, Algeria
| | - May N Bin-Jumah
- Biology Department, College Of Science, Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia
| | - Lotfi Aleya
- Chrono-Environnement Laboratory, UMR CNRS 6249, Bourgogne Franche-Comté University, Besançon Cedex, France
| | - Mohamed M Abdel-Daim
- Department of Zoology, Science College, King Saud University, Riyadh, 11451, Saudi Arabia.
- Pharmacology Department, Faculty of Veterinary Medicine, Suez Canal University, Ismailia, 41522, Egypt.
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10
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Ceftriaxone Treatment Affects EAAT2 Expression and Glutamatergic Neurotransmission and Exerts a Weak Anticonvulsant Effect in Young Rats. Int J Mol Sci 2019; 20:ijms20235852. [PMID: 31766528 PMCID: PMC6928884 DOI: 10.3390/ijms20235852] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Revised: 11/13/2019] [Accepted: 11/20/2019] [Indexed: 01/03/2023] Open
Abstract
Epilepsy is a common neurological disorder. Despite the availability of a wide range of antiepileptic drugs, these are unsuccessful in preventing seizures in 20–30% of patients. Therefore, new pharmacological strategies are urgently required to control seizures. Modulation of glutamate uptake may have potential in the treatment of pharmacoresistant forms of epilepsy. Previous research showed that the antibiotic ceftriaxone (CTX) increased the expression and functional activity of excitatory amino acid transporter 2 (EAAT2) and exerted considerable anticonvulsant effects. However, other studies did not confirm a significant anticonvulsant effect of CTX administration. We investigated the impacts of CTX treatment on EAAT expression and glutamatergic neurotransmission, as well its anticonvulsant action, in young male Wistar rats. As shown by a quantitative real-time polymerase chain reaction (qPCR) assay and a Western blot analysis, the mRNA but not the protein level of EAAT2 increased in the hippocampus following CTX treatment. Repetitive CTX administration had only a mild anticonvulsant effect on pentylenetetrazol (PTZ)-induced convulsions in a maximal electroshock threshold test (MEST). CTX treatment did not affect the glutamatergic neurotransmission, including synaptic efficacy, short-term facilitation, or the summation of excitatory postsynaptic potentials (EPSPs) in the hippocampus and temporal cortex. However, it decreased the field EPSP (fEPSP) amplitudes evoked by intense electrical stimulation. In conclusion, in young rats, CTX treatment did not induce overexpression of EAAT2, therefore exerting only a weak antiseizure effect. Our data provide new insight into the effects of modulation of EAAT2 expression on brain functioning.
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11
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Foster JB, Lashley R, Zhao F, Wang X, Kung N, Askwith CC, Lin L, Shultis MW, Hodgetts KJ, Lin CLG. Enhancement of tripartite synapses as a potential therapeutic strategy for Alzheimer's disease: a preclinical study in rTg4510 mice. ALZHEIMERS RESEARCH & THERAPY 2019; 11:75. [PMID: 31439023 PMCID: PMC6706914 DOI: 10.1186/s13195-019-0530-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Accepted: 08/15/2019] [Indexed: 12/20/2022]
Abstract
Background The lack of effective treatment options for Alzheimer’s disease (AD) is of momentous societal concern. Synaptic loss is the hallmark of AD that correlates best with impaired memory and occurs early in the disease process, before the onset of clinical symptoms. We have developed a small-molecule, pyridazine-based series that enhances the structure and function of both the glial processes and the synaptic boutons that form the tripartite synapse. Previously, we have shown that these pyridazine derivatives exhibit profound efficacy in an amyloid precursor protein AD model. Here, we evaluated the efficacy of an advanced compound, LDN/OSU-0215111, in rTg4510 mice—an aggressive tauopathy model. Methods rTg4510 mice were treated orally with vehicle or LDN/OSU-0215111 (10 mg/kg) daily from the early symptomatic stage (2 months old) to moderate (4 months old) and severe (8 months old) disease stages. At each time point, mice were subjected to a battery of behavioral tests to assess the activity levels and cognition. Also, tissue collections were performed on a subset of mice to analyze the tripartite synaptic changes, neurodegeneration, gliosis, and tau phosphorylation as assessed by immunohistochemistry and Western blotting. At 8 months of age, a subset of rTg4510 mice treated with compound was switched to vehicle treatment and analyzed behaviorally and biochemically 30 days after treatment cessation. Results At both the moderate and severe disease stages, compound treatment normalized cognition and behavior as well as reduced synaptic loss, neurodegeneration, tau hyperphosporylation, and neuroinflammation. Importantly, after 30 days of treatment cessation, the benefits of compound treatment were sustained, indicating disease modification. We also found that compound treatment rapidly and robustly reduced tau hyperphosphorylation/deposition possibly via the inhibition of GSK3β. Conclusions The results show that LDN/OSU-0215111 provides benefits for multiple aspects of tauopathy-dependent pathology found in Alzheimer’s disease including tripartite synapse normalization and reduction of toxic tau burden, which, in turn, likely accounted for normalized cognition and activity levels in compound-treated rTg4510 mice. This study, in combination with our previous work regarding the benefit of pyridazine derivatives against amyloid-dependent pathology, strongly supports pyridazine derivatives as a viable, clinically relevant, and disease-modifying treatment for many of the facets of Alzheimer’s disease. Electronic supplementary material The online version of this article (10.1186/s13195-019-0530-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Joshua B Foster
- Department of Neuroscience, College of Medicine, The Ohio State University, Columbus, OH, USA
| | - Rashelle Lashley
- Department of Neuroscience, College of Medicine, The Ohio State University, Columbus, OH, USA
| | - Fangli Zhao
- Department of Neuroscience, College of Medicine, The Ohio State University, Columbus, OH, USA
| | - Xueqin Wang
- Department of Neuroscience, College of Medicine, The Ohio State University, Columbus, OH, USA
| | - Nydia Kung
- Department of Neuroscience, College of Medicine, The Ohio State University, Columbus, OH, USA
| | - Candice C Askwith
- Department of Neuroscience, College of Medicine, The Ohio State University, Columbus, OH, USA
| | - Lin Lin
- Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Cambridge, MA, USA
| | - Michael W Shultis
- Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Cambridge, MA, USA
| | - Kevin J Hodgetts
- Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Cambridge, MA, USA
| | - Chien-Liang Glenn Lin
- Department of Neuroscience, College of Medicine, The Ohio State University, Columbus, OH, USA.
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12
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Jiang LL, Zhu B, Zhao Y, Li X, Liu T, Pina-Crespo J, Zhou L, Xu W, Rodriguez MJ, Yu H, Cleveland DW, Ravits J, Da Cruz S, Long T, Zhang D, Huang TY, Xu H. Membralin deficiency dysregulates astrocytic glutamate homeostasis leading to ALS-like impairment. J Clin Invest 2019; 129:3103-3120. [PMID: 31112137 DOI: 10.1172/jci127695] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Mechanisms underlying motor neuron degeneration in amyotrophic lateral sclerosis (ALS) are yet unclear. Specific deletion of the ER-component membralin in astrocytes manifested postnatal motor defects and lethality in mice, causing the accumulation of extracellular glutamate through reducing the glutamate transporter EAAT2. Restoring EAAT2 levels in membralin KO astrocytes limited astrocyte-dependent excitotoxicity in motor neurons. Transcriptomic profiles from mouse astrocytic membralin KO motor cortex indicated significant perturbation in KEGG pathway components related to ALS, including downregulation of Eaat2 and upregulation of Tnfrsf1a. Changes in gene expression with membralin deletion also overlapped with mouse ALS models and reactive astrocytes. Our results shown that activation of TNF receptor (TNFR1)-NFκB pathway known to suppress Eaat2 transcription was upregulated with membralin deletion. Further, reduced membralin and EAAT2 levels correlated with disease progression in spinal cord from SOD1-mutant mouse models, and reductions in membralin/EAAT2 were observed in human ALS spinal cord. Importantly, overexpression of membralin in SOD1G93A astrocytes decreased TNFR1 levels and increased EAAT2 expression, and improved motor neuron survival. Importantly, upregulation of membralin in SOD1G93A mice significantly prolonged mouse survival. Together, our study provided a mechanism for ALS pathogenesis where membralin limited glutamatergic neurotoxicity, suggesting that modulating membralin had potentials in ALS therapy.
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Affiliation(s)
- Lu-Lin Jiang
- Neuroscience Initiative, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, USA
| | - Bing Zhu
- Neuroscience Initiative, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, USA
| | - Yingjun Zhao
- Neuroscience Initiative, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, USA
| | - Xiaoguang Li
- Neuroscience Initiative, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, USA
| | - Tongfei Liu
- Neuroscience Initiative, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, USA
| | - Juan Pina-Crespo
- Neuroscience Initiative, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, USA
| | - Lisa Zhou
- Neuroscience Initiative, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, USA
| | - Wenxi Xu
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, USA
| | - Maria J Rodriguez
- Department of Neurosciences, UCSD, La Jolla, California, USA.,ALS Translational Research Program, Department of Neurosciences, UCSD, La Jolla, California, USA
| | - Haiyang Yu
- Ludwig Institute for Cancer Research, UCSD, La Jolla, California, USA
| | - Don W Cleveland
- Department of Neurosciences, UCSD, La Jolla, California, USA.,Ludwig Institute for Cancer Research, UCSD, La Jolla, California, USA.,Department of Cellular and Molecular Medicine, UCSD, La Jolla, California, USA
| | - John Ravits
- Department of Neurosciences, UCSD, La Jolla, California, USA.,ALS Translational Research Program, Department of Neurosciences, UCSD, La Jolla, California, USA
| | - Sandrine Da Cruz
- Ludwig Institute for Cancer Research, UCSD, La Jolla, California, USA
| | - Tao Long
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, USA
| | - Dongxian Zhang
- Neuroscience Initiative, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, USA
| | - Timothy Y Huang
- Neuroscience Initiative, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, USA
| | - Huaxi Xu
- Neuroscience Initiative, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, USA
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13
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Tertil M, Skupio U, Barut J, Dubovyk V, Wawrzczak-Bargiela A, Soltys Z, Golda S, Kudla L, Wiktorowska L, Szklarczyk K, Korostynski M, Przewlocki R, Slezak M. Glucocorticoid receptor signaling in astrocytes is required for aversive memory formation. Transl Psychiatry 2018; 8:255. [PMID: 30487639 PMCID: PMC6261947 DOI: 10.1038/s41398-018-0300-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 09/15/2018] [Accepted: 10/18/2018] [Indexed: 12/16/2022] Open
Abstract
Stress elicits the release of glucocorticoids (GCs) that regulate energy metabolism and play a role in emotional memory. Astrocytes express glucocorticoid receptors (GR), but their contribution to cognitive effects of GC's action in the brain is unknown. To address this question, we studied how astrocyte-specific elimination of GR affects animal behavior known to be regulated by stress. Mice with astrocyte-specific ablation of GR presented impaired aversive memory expression in two different paradigms of Pavlovian learning: contextual fear conditioning and conditioned place aversion. These mice also displayed compromised regulation of genes encoding key elements of the glucose metabolism pathway upon GR stimulation. In particular, we identified that the glial, but not the neuronal isoform of a crucial stress-response molecule, Sgk1, undergoes GR-dependent regulation in vivo and demonstrated the involvement of SGK1 in regulation of glucose uptake in astrocytes. Together, our results reveal astrocytes as a central element in GC-dependent formation of aversive memory and suggest their relevance for stress-induced alteration of brain glucose metabolism. Consequently, astrocytes should be considered as a cellular target of therapies of stress-induced brain diseases.
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Affiliation(s)
- Magdalena Tertil
- 0000 0001 1958 0162grid.413454.3Department of Molecular Neuropharmacology, Institute of Pharmacology, Polish Academy of Sciences, Cracow, 31-343 Poland
| | - Urszula Skupio
- 0000 0001 1958 0162grid.413454.3Department of Molecular Neuropharmacology, Institute of Pharmacology, Polish Academy of Sciences, Cracow, 31-343 Poland
| | - Justyna Barut
- 0000 0001 1958 0162grid.413454.3Department of Molecular Neuropharmacology, Institute of Pharmacology, Polish Academy of Sciences, Cracow, 31-343 Poland
| | - Valentyna Dubovyk
- Team Brain Microcircuits in Psychiatric Diseases, BioMed X Innovation Center, Heidelberg, 69120 Germany
| | - Agnieszka Wawrzczak-Bargiela
- 0000 0001 1958 0162grid.413454.3Department of Molecular Neuropharmacology, Institute of Pharmacology, Polish Academy of Sciences, Cracow, 31-343 Poland
| | - Zbigniew Soltys
- 0000 0001 2162 9631grid.5522.0Department of Neuroanatomy, Institute of Zoology and Biomedical Research, Jagiellonian University, Cracow, 30-387 Poland
| | - Slawomir Golda
- 0000 0001 1958 0162grid.413454.3Department of Molecular Neuropharmacology, Institute of Pharmacology, Polish Academy of Sciences, Cracow, 31-343 Poland
| | - Lucja Kudla
- 0000 0001 1958 0162grid.413454.3Department of Molecular Neuropharmacology, Institute of Pharmacology, Polish Academy of Sciences, Cracow, 31-343 Poland
| | - Lucja Wiktorowska
- 0000 0001 1958 0162grid.413454.3Department of Molecular Neuropharmacology, Institute of Pharmacology, Polish Academy of Sciences, Cracow, 31-343 Poland
| | - Klaudia Szklarczyk
- 0000 0001 1958 0162grid.413454.3Department of Molecular Neuropharmacology, Institute of Pharmacology, Polish Academy of Sciences, Cracow, 31-343 Poland
| | - Michal Korostynski
- 0000 0001 1958 0162grid.413454.3Department of Molecular Neuropharmacology, Institute of Pharmacology, Polish Academy of Sciences, Cracow, 31-343 Poland
| | - Ryszard Przewlocki
- 0000 0001 1958 0162grid.413454.3Department of Molecular Neuropharmacology, Institute of Pharmacology, Polish Academy of Sciences, Cracow, 31-343 Poland
| | - Michal Slezak
- Department of Molecular Neuropharmacology, Institute of Pharmacology, Polish Academy of Sciences, Cracow, 31-343, Poland. .,Team Brain Microcircuits in Psychiatric Diseases, BioMed X Innovation Center, Heidelberg, 69120, Germany.
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14
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Yang Z, Wang J, Yu C, Xu P, Zhang J, Peng Y, Luo Z, Huang H, Zeng J, Xu Z. Inhibition of p38 MAPK Signaling Regulates the Expression of EAAT2 in the Brains of Epileptic Rats. Front Neurol 2018; 9:925. [PMID: 30429824 PMCID: PMC6220601 DOI: 10.3389/fneur.2018.00925] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2018] [Accepted: 10/11/2018] [Indexed: 01/03/2023] Open
Abstract
Seizures induce the release of excitatory amino acids (EAAs) from the intracellular fluid to the extracellular fluid, and the released EAAs primarily comprise glutamic acid (Glu) and asparaginic acid (Asp). Glu neurotransmission functions via EAA transporters (EAATs) to maintain low concentrations of Glu in the extracellular space and avoid excitotoxicity. EAAT2, the most abundant Glu transporter subtype in the central nervous system (CNS), plays a key role in the regulation of glutamate transmission. Previous studies have shown that SB203580 promotes EAAT2 expression by inhibiting the p38 mitogen-activated protein kinase (MAPK) signaling pathway, but whether SB203580 upregulates EAAT2 expression in epileptic rats is unknown. This study demonstrated that EAAT2 expression was increased in the brain tissue of epileptic rats. Intraperitoneal injection of a specific inhibitor of p38 MAPK, SB203580, reduced the time to the first epileptic seizure and attenuated the seizure severity. In addition, SB203580 treatment increased the EAAT2 expression levels in the brain tissue of epileptic rats. These results suggest that SB203580 could regulate epileptic seizures via EAAT2.
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Affiliation(s)
- Zhang Yang
- Department of Neurology, Affiliated Hospital of Zunyi Medical University, Zunyi, China.,Department of Neurology, Affiliated Hospital of Guizhou Medical University, Guiyang, China
| | - Jing Wang
- Department of Prevention and Health Care, Affiliated Hospital of Zunyi Medical University, Zunyi, China
| | - Changyin Yu
- Department of Neurology, Affiliated Hospital of Zunyi Medical University, Zunyi, China
| | - Ping Xu
- Department of Neurology, Affiliated Hospital of Zunyi Medical University, Zunyi, China
| | - Jun Zhang
- Department of Neurology, Affiliated Hospital of Zunyi Medical University, Zunyi, China
| | - Yan Peng
- Department of Neurology, Affiliated Hospital of Zunyi Medical University, Zunyi, China
| | - Zhong Luo
- Department of Neurology, Affiliated Hospital of Zunyi Medical University, Zunyi, China
| | - Hao Huang
- Department of Neurology, Affiliated Hospital of Zunyi Medical University, Zunyi, China
| | - Junwei Zeng
- Department of Physiology, Zunyi Medical University, Zunyi, China
| | - Zucai Xu
- Department of Neurology, Affiliated Hospital of Zunyi Medical University, Zunyi, China.,Key Laboratory of Brain Science, Zunyi Medical University, Zunyi, China
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15
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Foster JB, Zhao F, Wang X, Xu Z, Lin K, Askwith CC, Hodgetts KJ, Lin CLG. Pyridazine-derivatives Enhance Structural and Functional Plasticity of Tripartite Synapse Via Activation of Local Translation in Astrocytic Processes. Neuroscience 2018; 388:224-238. [PMID: 30056115 DOI: 10.1016/j.neuroscience.2018.07.028] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 06/19/2018] [Accepted: 07/17/2018] [Indexed: 12/19/2022]
Abstract
Excitatory amino acid transporter 2 (EAAT2) is primarily located in perisynaptic astrocytic processes (PAP) where it plays a critical role in synaptic glutamate homeostasis. Dysregulation of EAAT2 at the translational level has been implicated in a myriad of neurological diseases. We previously discovered that pyridazine analogs can activate EAAT2 translation. Here, we sought to further refine the site and mechanism of compound action. We found that in vivo, compound treatment increased EAAT2 expression only in the PAP of astrocytes where EAAT2 mRNA also was identified. Direct application of compound to isolated PAP induced de novo EAAT2 protein synthesis, indicating that compound activates translation locally in the PAP. Using a screening process, we identified a set of PAP proteins that are rapidly up-regulated following compound treatment and a subset of these PAP proteins may be locally synthesized in the PAP. Importantly, these identified proteins are associated with the structural and functional capacity of the PAP, indicating compound enhanced plasticity of the PAP. Concomitantly, we found that pyridazine analogs increase synaptic protein expression in the synapse and enhance hippocampal long-term potentiation. This was not dependent upon compound-mediated local translation in neurons. This suggests that compound enhances the structural and functional capacity of the PAP which in turn facilitates enhanced plasticity of the tripartite synapse. Overall, this provides insight into the mechanism action site of pyridazine derivatives as well as the growing appreciation of the dynamic regulation and functional aspects of the PAP at the tripartite synapse.
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Affiliation(s)
- Joshua B Foster
- Department of Neuroscience, College of Medicine, The Ohio State University, Columbus, OH, United States
| | - Fangli Zhao
- Department of Neuroscience, College of Medicine, The Ohio State University, Columbus, OH, United States
| | - Xueqin Wang
- Department of Neuroscience, College of Medicine, The Ohio State University, Columbus, OH, United States
| | - Zan Xu
- Department of Neuroscience, College of Medicine, The Ohio State University, Columbus, OH, United States
| | - Kuanhung Lin
- Department of Neuroscience, College of Medicine, The Ohio State University, Columbus, OH, United States
| | - Candice C Askwith
- Department of Neuroscience, College of Medicine, The Ohio State University, Columbus, OH, United States
| | - Kevin J Hodgetts
- Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Cambridge, MA, United States
| | - Chien-Liang Glenn Lin
- Department of Neuroscience, College of Medicine, The Ohio State University, Columbus, OH, United States.
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16
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Parkin GM, Udawela M, Gibbons A, Dean B. Glutamate transporters, EAAT1 and EAAT2, are potentially important in the pathophysiology and treatment of schizophrenia and affective disorders. World J Psychiatry 2018; 8:51-63. [PMID: 29988908 PMCID: PMC6033743 DOI: 10.5498/wjp.v8.i2.51] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 05/15/2018] [Accepted: 06/09/2018] [Indexed: 02/05/2023] Open
Abstract
Glutamate is the predominant excitatory neurotransmitter in the human brain and it has been shown that prolonged activation of the glutamatergic system leads to nerve damage and cell death. Following release from the pre-synaptic neuron and synaptic transmission, glutamate is either taken up into the pre-synaptic neuron or neighbouring glia by transmembrane glutamate transporters. Excitatory amino acid transporter (EAAT) 1 and EAAT2 are Na+-dependant glutamate transporters expressed predominantly in glia cells of the central nervous system. As the most abundant glutamate transporters, their primary role is to modulate levels of glutamatergic excitability and prevent spill over of glutamate beyond the synapse. This role is facilitated through the binding and transportation of glutamate into astrocytes and microglia. The function of EAAT1 and EAAT2 is heavily regulated at the levels of gene expression, post-transcriptional splicing, glycosylation states and cell-surface trafficking of the protein. Both glutamatergic dysfunction and glial dysfunction have been proposed to be involved in psychiatric disorder. This review will present an overview of the roles that EAAT1 and EAAT2 play in modulating glutamatergic activity in the human brain, and mount an argument that these two transporters could be involved in the aetiologies of schizophrenia and affective disorders as well as represent potential drug targets for novel therapies for those disorders.
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Affiliation(s)
- Georgia M Parkin
- Molecular Psychiatry Laboratory, the Florey Institute of Neuroscience and Mental Health, Parkville VIC 3052, Australia
- CRC for Mental Health, Carlton VIC 3053, Australia
| | - Madhara Udawela
- Molecular Psychiatry Laboratory, the Florey Institute of Neuroscience and Mental Health, Parkville VIC 3052, Australia
- CRC for Mental Health, Carlton VIC 3053, Australia
| | - Andrew Gibbons
- Molecular Psychiatry Laboratory, the Florey Institute of Neuroscience and Mental Health, Parkville VIC 3052, Australia
| | - Brian Dean
- Molecular Psychiatry Laboratory, the Florey Institute of Neuroscience and Mental Health, Parkville VIC 3052, Australia
- CRC for Mental Health, Carlton VIC 3053, Australia
- Research Centre for Mental Health, the Faculty of Health, Arts and Design, Swinburne University, Hawthorne VIC 3122, Australia
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17
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Yin X, Wang S, Qi Y, Wang X, Jiang H, Wang T, Yang Y, Wang Y, Zhang C, Feng H. Astrocyte elevated gene-1 is a novel regulator of astrogliosis and excitatory amino acid transporter-2 via interplaying with nuclear factor-κB signaling in astrocytes from amyotrophic lateral sclerosis mouse model with hSOD1 G93A mutation. Mol Cell Neurosci 2018; 90:1-11. [PMID: 29777762 DOI: 10.1016/j.mcn.2018.05.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2018] [Revised: 05/14/2018] [Accepted: 05/14/2018] [Indexed: 12/16/2022] Open
Abstract
AEG-1 has received extensive attention on cancer research. However, little is known about its roles in astrogliosis of Amyotrophic lateral sclerosis (ALS). In this study, we detected AEG-1 expression in hSOD1G93A-positive (mut-SOD1) astrocytes and wild type (wt-SOD1) astrocytes, and intend to elucidate its potential functions in ALS related astrogliosis and the always accompanied dysregulated glutamate clearance. Results showed elevated protein and mRNA levels of AEG-1 in mut-SOD1 astrocytes; Also, NF-κB signaling pathway related proteins and inflammatory cytokines were upregulated in mut-SOD1 astrocytes; AEG-1 knockdown attenuated astrocytes proliferation and pro-inflammatory release; also we found that AEG-1 silence inhibited translocation of p65 from cytoplasma to nuclear, which was associated with inhibited NF-κB signaling. Besides, excitatory amino acid transporter-2 (EAAT2) expression levels were significantly decreased, accompanied by impaired glutamate clearance ability, in mut-SOD1 astrocytes; yin yang 1 (YY1), a transcriptional inhibitor for EAAT2, increased in nucleus of mut-SOD1 astrocytes. AEG-1 silence inhibited translocation of YY1 to nucleus, increased EAAT2 expression levels, and enhanced astrocytic ability of glutamate clearance, ultimately exerted the neuronal protection. Findings from this study implicate potential function of AEG-1 in mut-SOD1 related astrogliosis and the accompanied excitatory cytotoxic mechanism in ALS.
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Affiliation(s)
- Xiang Yin
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin 150001, PR China; Department of Neurology and Neuroscience Center, The First Hospital of Jilin University, Changchun 130021, People's Republic of China
| | - Shuyu Wang
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin 150001, PR China
| | - Yan Qi
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin 150001, PR China
| | - Xudong Wang
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin 150001, PR China
| | - Hongquan Jiang
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin 150001, PR China
| | - Tianhang Wang
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin 150001, PR China
| | - Yueqing Yang
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin 150001, PR China
| | - Ying Wang
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin 150001, PR China
| | - Chunting Zhang
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin 150001, PR China
| | - Honglin Feng
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin 150001, PR China.
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18
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Laquinimod ameliorates excitotoxic damage by regulating glutamate re-uptake. J Neuroinflammation 2018; 15:5. [PMID: 29304807 PMCID: PMC5756343 DOI: 10.1186/s12974-017-1048-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Accepted: 12/21/2017] [Indexed: 11/10/2022] Open
Abstract
Background Laquinimod is an immunomodulatory drug under clinical investigation for the treatment of the progressive form of multiple sclerosis (MS) with both anti-inflammatory and neuroprotective effects. Excitotoxicity, a prominent pathophysiological feature of MS and of its animal model, experimental autoimmune encephalomyelitis (EAE), involves glutamate transporter (GluT) dysfunction in glial cells. The aim of this study was to assess whether laquinimod might exert direct neuroprotective effects by interfering with the mechanisms of excitotoxicity linked to GluT function impairments in EAE. Methods Osmotic minipumps allowing continuous intracerebroventricular (icv) infusion of laquinimod for 4 weeks were implanted into C57BL/6 mice before EAE induction. EAE cerebella were taken to perform western blot and qPCR experiments. For ex vivo experiments, EAE cerebellar slices were incubated with laquinimod before performing electrophysiology, western blot, and qPCR. Results In vivo treatment with laquinimod attenuated EAE clinical score at the peak of the disease, without remarkable effects on inflammatory markers. In vitro application of laquinimod to EAE cerebellar slices prevented EAE-linked glutamatergic alterations without mitigating astrogliosis and inflammation. Moreover, such treatment induced an increase of Slcla3 mRNA coding for the glial glutamate–aspartate transporter (GLAST) without affecting the protein content. Concomitantly, laquinimod significantly increased the levels of the glial glutamate transporter 1 (GLT-1) protein and pharmacological blockade of GLT-1 function fully abolished laquinimod anti-excitotoxic effect. Conclusions Overall, our results suggest that laquinimod protects against glutamate excitotoxicity of the cerebellum of EAE mice by bursting the expression of glial glutamate transporters, independently of its anti-inflammatory effects.
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19
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Drugs to Alter Extracellular Concentration of Glutamate: Modulators of Glutamate Uptake Systems. ACTA ACUST UNITED AC 2017. [DOI: 10.1007/978-1-4939-7228-9_7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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20
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Spencer S, Kalivas PW. Glutamate Transport: A New Bench to Bedside Mechanism for Treating Drug Abuse. Int J Neuropsychopharmacol 2017; 20:797-812. [PMID: 28605494 PMCID: PMC5632313 DOI: 10.1093/ijnp/pyx050] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Accepted: 06/09/2017] [Indexed: 02/06/2023] Open
Abstract
Drug addiction has often been described as a "hijacking" of the brain circuits involved in learning and memory. Glutamate is the principal excitatory neurotransmitter in the brain, and its contribution to synaptic plasticity and learning processes is well established in animal models. Likewise, over the past 20 years the addiction field has ascribed a critical role for glutamatergic transmission in the development of addiction. Chronic drug use produces enduring neuroadaptations in corticostriatal projections that are believed to contribute to a maladaptive deficit in inhibitory control over behavior. Much of this research focuses on the role played by ionotropic glutamate receptors directly involved in long-term potentiation and depression or metabotropic receptors indirectly modulating synaptic plasticity. Importantly, the balance between glutamate release and clearance tightly regulates the patterned activation of these glutamate receptors, emphasizing an important role for glutamate transporters in maintaining extracellular glutamate levels. Five excitatory amino acid transporters participate in active glutamate reuptake. Recent evidence suggests that these glutamate transporters can be modulated by chronic drug use at a variety of levels. In this review, we synopsize the evidence and mechanisms associated with drug-induced dysregulation of glutamate transport. We then summarize the preclinical and clinical data suggesting that glutamate transporters offer an effective target for the treatment of drug addiction. In particular, we focus on the role that altered glutamate transporters have in causing drug cues and contexts to develop an intrusive quality that guides maladaptive drug seeking behaviors.
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Affiliation(s)
- Sade Spencer
- Department of Neurosciences, Medical University of South Carolina, Charleston, South Carolina.,Correspondence: Sade Spencer, PhD, Medical University of South Carolina, 173 Ashley Avenue, BSB, 403- MSC 510, Charleston, SC 29425 ()
| | - Peter W Kalivas
- Department of Neurosciences, Medical University of South Carolina, Charleston, South Carolina.
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21
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Chelini A, Brogi S, Paolino M, Di Capua A, Cappelli A, Giorgi G, Farzad M, Di Cesare Mannelli L, Micheli L, Ghelardini C, Anzini M. Synthesis and Biological Evaluation of Novel Neuroprotective Pyridazine Derivatives as Excitatory Amino Acid Transporter 2 (EAAT2) Activators. J Med Chem 2017; 60:5216-5221. [DOI: 10.1021/acs.jmedchem.7b00383] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Alessia Chelini
- Dipartimento
di Biotecnologie, Chimica e Farmacia, Università di Siena, Via A. Moro
2, 53100 Siena, Italy
| | - Simone Brogi
- Dipartimento
di Biotecnologie, Chimica e Farmacia, Università di Siena, Via A. Moro
2, 53100 Siena, Italy
| | - Marco Paolino
- Dipartimento
di Biotecnologie, Chimica e Farmacia, Università di Siena, Via A. Moro
2, 53100 Siena, Italy
| | - Angela Di Capua
- Dipartimento
di Biotecnologie, Chimica e Farmacia, Università di Siena, Via A. Moro
2, 53100 Siena, Italy
- Griffith
Institute for Drug Discovery, Griffith University, Nathan 4111, Queensland, Australia
| | - Andrea Cappelli
- Dipartimento
di Biotecnologie, Chimica e Farmacia, Università di Siena, Via A. Moro
2, 53100 Siena, Italy
| | - Gianluca Giorgi
- Dipartimento
di Biotecnologie, Chimica e Farmacia, Università di Siena, Via A. Moro
2, 53100 Siena, Italy
| | - Mersedeh Farzad
- Oncological
Clinical Trials and Medical Oncology Unit, Alta Valdelsa Hospital, 53036 Campostaggia, Siena, Italy
| | - Lorenzo Di Cesare Mannelli
- Dipartimento
di Neuroscienze, Area del Farmaco e Salute del Bambino (NEUROFARBA), Viale Pieraccini, 6, 50139 Firenze, Italy
| | - Laura Micheli
- Dipartimento
di Neuroscienze, Area del Farmaco e Salute del Bambino (NEUROFARBA), Viale Pieraccini, 6, 50139 Firenze, Italy
| | - Carla Ghelardini
- Dipartimento
di Neuroscienze, Area del Farmaco e Salute del Bambino (NEUROFARBA), Viale Pieraccini, 6, 50139 Firenze, Italy
| | - Maurizio Anzini
- Dipartimento
di Biotecnologie, Chimica e Farmacia, Università di Siena, Via A. Moro
2, 53100 Siena, Italy
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22
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EAAT2 and the Molecular Signature of Amyotrophic Lateral Sclerosis. ADVANCES IN NEUROBIOLOGY 2017; 16:117-136. [PMID: 28828608 DOI: 10.1007/978-3-319-55769-4_6] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) is a rapid and fatal neurodegenerative disease, primarily affecting upper and lower motor neurons. It is an extremely heterogeneous disease in both cause and symptom development, and its mechanisms of pathogenesis remain largely unknown. Excitotoxicity, a process caused by excessive glutamate signaling, is believed to play a substantial role, however. Excessive glutamate release, changes in postsynaptic glutamate receptors, and reduction of functional astrocytic glutamate transporters contribute to excitotoxicity in ALS. Here, we explore the roles of each, with a particular emphasis on glutamate transporters and attempts to increase them as therapy for ALS. Screening strategies have been employed to find compounds that increase the functional excitatory amino acid transporter EAAT2 (GLT1), which is responsible for the vast majority of glutamate clearance. One such compound, ceftriaxone, was recently tested in clinical trials but unfortunately did not modify disease course, though its effect on EAAT2 expression in patients was not measured.
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Glutamate Transport System as a Novel Therapeutic Target in Chronic Pain: Molecular Mechanisms and Pharmacology. ADVANCES IN NEUROBIOLOGY 2017; 16:225-253. [PMID: 28828613 DOI: 10.1007/978-3-319-55769-4_11] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The vast majority of peripheral neurons sensing noxious stimuli and conducting pain signals to the dorsal horn of the spinal cord utilize glutamate as a chemical transmitter of excitation. High-affinity glutamate transporter subtypes GLAST/EAAT1, GLT1/EAAT2, EAAC1/EAAT3, and EAAT4, differentially expressed on sensory neurons, postsynaptic spinal interneurons, and neighboring glia, ensure fine modulation of glutamate neurotransmission in the spinal cord. The glutamate transport system seems to play important roles in molecular mechanisms underlying chronic pain and analgesia. Downregulation of glutamate transporters (GluTs) often precedes or occurs simultaneously with development of hypersensitivity to thermal or tactile stimuli in various models of chronic pain. Moreover, antisense knockdown or pharmacological inhibition of these membrane proteins can induce or aggravate pain. In contrast, upregulation of GluTs by positive pharmacological modulators or by viral gene transfer to the spinal cord can reverse the development of such pathological hypersensitivity. Furthermore, some multi-target drugs displaying analgesic properties (e.g., tricyclic antidepressant amitriptyline, riluzole, anticonvulsant valproate, tetracycline antibiotic minocycline, β-lactam antibiotic ceftriaxone and its structural analog devoid of antibacterial activity, clavulanic acid) can significantly increase the spinal glutamate uptake. Thus, mounting evidence points at GluTs as prospective therapeutic target for chronic pain treatment. However, design and development of new analgesics based on the modulation of glutamate uptake will require more precise knowledge of molecular mechanisms underlying physiological or aberrant functioning of this transport system in the spinal cord.
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Vartak-Sharma N, Nooka S, Ghorpade A. Astrocyte elevated gene-1 (AEG-1) and the A(E)Ging HIV/AIDS-HAND. Prog Neurobiol 2016; 157:133-157. [PMID: 27090750 DOI: 10.1016/j.pneurobio.2016.03.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2015] [Revised: 03/11/2016] [Accepted: 03/19/2016] [Indexed: 12/23/2022]
Abstract
Recent attempts to analyze human immunodeficiency virus (HIV)-1-induced gene expression changes in astrocytes uncovered a multifunctional oncogene, astrocyte elevated gene-1 (AEG-1). Our previous studies revealed that AEG-1 regulates reactive astrocytes proliferation, migration and inflammation, hallmarks of aging and CNS injury. Moreover, the involvement of AEG-1 in neurodegenerative disorders, such as Huntington's disease and migraine, and its induction in the aged brain suggest a plausible role in regulating overall CNS homeostasis and aging. Therefore, it is important to investigate AEG-1 specifically in aging-associated cognitive decline. In this study, we decipher the common mechanistic links in cancer, aging and HIV-1-associated neurocognitive disorders that likely contribute to AEG-1-based regulation of astrocyte responses and function. Despite AEG-1 incorporation into HIV-1 virions and its induction by HIV-1, tumor necrosis factor-α and interleukin-1β, the specific role(s) of AEG-1 in astrocyte-driven HIV-1 neuropathogenesis are incompletely defined. We propose that AEG-1 plays a central role in a multitude of cellular stress responses involving mitochondria, endoplasmic reticulum and the nucleolus. It is thus important to further investigate AEG-1-based cellular and molecular regulation in order to successfully develop better therapeutic approaches that target AEG-1 to combat cancer, HIV-1 and aging.
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Affiliation(s)
- Neha Vartak-Sharma
- Department of Cell Biology and Immunology, University of North Texas Health Science Center, Fort Worth, TX, 76107-2699, USA; Institute for Integrated Cell-Material Sciences, Kyoto University, Japan; Institute for Stem Cell Research and Regenerative Medicine, National Center for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India
| | - Shruthi Nooka
- Department of Cell Biology and Immunology, University of North Texas Health Science Center, Fort Worth, TX, 76107-2699, USA
| | - Anuja Ghorpade
- Department of Cell Biology and Immunology, University of North Texas Health Science Center, Fort Worth, TX, 76107-2699, USA.
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Martinez-Lozada Z, Guillem AM, Robinson MB. Transcriptional Regulation of Glutamate Transporters: From Extracellular Signals to Transcription Factors. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2016; 76:103-45. [PMID: 27288076 DOI: 10.1016/bs.apha.2016.01.004] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Glutamate is the predominant excitatory neurotransmitter in the mammalian CNS. It mediates essentially all rapid excitatory signaling. Dysfunction of glutamatergic signaling contributes to developmental, neurologic, and psychiatric diseases. Extracellular glutamate is cleared by a family of five Na(+)-dependent glutamate transporters. Two of these transporters (GLAST and GLT-1) are relatively selectively expressed in astrocytes. Other of these transporters (EAAC1) is expressed by neurons throughout the nervous system. Expression of the last two members of this family (EAAT4 and EAAT5) is almost exclusively restricted to specific populations of neurons in cerebellum and retina, respectively. In this review, we will discuss our current understanding of the mechanisms that control transcriptional regulation of the different members of this family. Over the last two decades, our understanding of the mechanisms that regulate expression of GLT-1 and GLAST has advanced considerably; several specific transcription factors, cis-elements, and epigenetic mechanisms have been identified. For the other members of the family, little or nothing is known about the mechanisms that control their transcription. It is assumed that by defining the mechanisms involved, we will advance our understanding of the events that result in cell-specific expression of these transporters and perhaps begin to define the mechanisms by which neurologic diseases are changing the biology of the cells that express these transporters. This approach might provide a pathway for developing new therapies for a wide range of essentially untreatable and devastating diseases that kill neurons by an excitotoxic mechanism.
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Affiliation(s)
- Z Martinez-Lozada
- Children's Hospital of Philadelphia Research Institute, University of Pennsylvania, Philadelphia, PA, United States
| | - A M Guillem
- Children's Hospital of Philadelphia Research Institute, University of Pennsylvania, Philadelphia, PA, United States
| | - M B Robinson
- Children's Hospital of Philadelphia Research Institute, University of Pennsylvania, Philadelphia, PA, United States.
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Recent Advance in the Relationship between Excitatory Amino Acid Transporters and Parkinson's Disease. Neural Plast 2016; 2016:8941327. [PMID: 26981287 PMCID: PMC4769779 DOI: 10.1155/2016/8941327] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Revised: 01/05/2016] [Accepted: 01/18/2016] [Indexed: 01/12/2023] Open
Abstract
Parkinson's disease (PD) is the most common movement disorder disease in the elderly and is characterized by degeneration of dopamine neurons and formation of Lewy bodies. Glutamate is the major excitatory neurotransmitter in the central nervous system (CNS). If glutamate is not removed promptly in the synaptic cleft, it will excessively stimulate the glutamate receptors and induce excitotoxic effects on the CNS. With lack of extracellular enzyme to decompose glutamate, glutamate uptake in the synaptic cleft is mainly achieved by the excitatory amino acid transporters (EAATs, also known as high-affinity glutamate transporters). Current studies have confirmed that decreased expression and function of EAATs appear in PD animal models. Moreover, single unilateral administration of EAATs inhibitor in the substantia nigra mimics several PD features and this is a solid evidence supporting that decreased EAATs contribute to the process of PD. Drugs or treatments promoting the expression and function of EAATs are shown to attenuate dopamine neurons death in the substantia nigra and striatum, ameliorate the behavior disorder, and improve cognitive abilities in PD animal models. EAATs are potential effective drug targets in treatment of PD and thus study of relationship between EAATs and PD has predominant medical significance currently.
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Abousaab A, Warsi J, Elvira B, Lang F. Caveolin-1 Sensitivity of Excitatory Amino Acid Transporters EAAT1, EAAT2, EAAT3, and EAAT4. J Membr Biol 2015; 249:239-49. [PMID: 26690923 DOI: 10.1007/s00232-015-9863-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 12/07/2015] [Indexed: 10/22/2022]
Abstract
Excitatory amino acid transporters EAAT1 (SLC1A3), EAAT2 (SLC1A2), EAAT3 (SLC1A1), and EAAT4 (SLC1A6) serve to clear L-glutamate from the synaptic cleft and are thus important for the limitation of neuronal excitation. EAAT3 has previously been shown to form complexes with caveolin-1, a major component of caveolae, which participate in the regulation of transport proteins. The present study explored the impact of caveolin-1 on electrogenic transport by excitatory amino acid transporter isoforms EAAT1-4. To this end cRNA encoding EAAT1, EAAT2, EAAT3, or EAAT4 was injected into Xenopus oocytes without or with additional injection of cRNA encoding caveolin-1. The L-glutamate (2 mM)-induced inward current (I Glu) was taken as a measure of glutamate transport. As a result, I Glu was observed in EAAT1-, EAAT2-, EAAT3-, or EAAT4-expressing oocytes but not in water-injected oocytes, and was significantly decreased by coexpression of caveolin-1. Caveolin-1 decreased significantly the maximal transport rate. Treatment of EAATs-expressing oocytes with brefeldin A (5 µM) was followed by a decrease in conductance, which was similar in oocytes expressing EAAT together with caveolin-1 as in oocytes expressing EAAT1-4 alone. Thus, caveolin-1 apparently does not accelerate transporter protein retrieval from the cell membrane. In conclusion, caveolin-1 is a powerful negative regulator of the excitatory glutamate transporters EAAT1, EAAT2, EAAT3, and EAAT4.
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Affiliation(s)
- Abeer Abousaab
- Department of Physiology I, University of Tübingen, Gmelinstr. 5, 72076, Tübingen, Germany
| | - Jamshed Warsi
- Department of Physiology I, University of Tübingen, Gmelinstr. 5, 72076, Tübingen, Germany
| | - Bernat Elvira
- Department of Physiology I, University of Tübingen, Gmelinstr. 5, 72076, Tübingen, Germany
| | - Florian Lang
- Department of Physiology I, University of Tübingen, Gmelinstr. 5, 72076, Tübingen, Germany.
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Takahashi K, Foster JB, Lin CLG. Glutamate transporter EAAT2: regulation, function, and potential as a therapeutic target for neurological and psychiatric disease. Cell Mol Life Sci 2015; 72:3489-506. [PMID: 26033496 PMCID: PMC11113985 DOI: 10.1007/s00018-015-1937-8] [Citation(s) in RCA: 108] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Revised: 05/22/2015] [Accepted: 05/26/2015] [Indexed: 12/12/2022]
Abstract
Glutamate is the predominant excitatory neurotransmitter in the central nervous system. Excitatory amino acid transporter 2 (EAAT2) is primarily responsible for clearance of extracellular glutamate to prevent neuronal excitotoxicity and hyperexcitability. EAAT2 plays a critical role in regulation of synaptic activity and plasticity. In addition, EAAT2 has been implicated in the pathogenesis of many central nervous system disorders. In this review, we summarize current understanding of EAAT2, including structure, pharmacology, physiology, and functions, as well as disease relevancy, such as in stroke, Parkinson's disease, epilepsy, amyotrophic lateral sclerosis, Alzheimer's disease, major depressive disorder, and addiction. A large number of studies have demonstrated that up-regulation of EAAT2 protein provides significant beneficial effects in many disease models suggesting EAAT2 activation is a promising therapeutic approach. Several EAAT2 activators have been identified. Further understanding of EAAT2 regulatory mechanisms could improve development of drug-like compounds that spatiotemporally regulate EAAT2.
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Affiliation(s)
- Kou Takahashi
- Department of Neuroscience, The Ohio State University, 333 West 10th Avenue, Columbus, OH 43210 USA
| | - Joshua B. Foster
- Department of Neuroscience, The Ohio State University, 333 West 10th Avenue, Columbus, OH 43210 USA
| | - Chien-Liang Glenn Lin
- Department of Neuroscience, The Ohio State University, 333 West 10th Avenue, Columbus, OH 43210 USA
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Fontana ACK. Current approaches to enhance glutamate transporter function and expression. J Neurochem 2015; 134:982-1007. [DOI: 10.1111/jnc.13200] [Citation(s) in RCA: 105] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2015] [Revised: 05/19/2015] [Accepted: 05/20/2015] [Indexed: 12/12/2022]
Affiliation(s)
- Andréia C. K. Fontana
- Department of Pharmacology and Physiology; Drexel University College of Medicine; Philadelphia Pennsylvania USA
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30
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Abousaab A, Warsi J, Elvira B, Alesutan I, Hoseinzadeh Z, Lang F. Down-Regulation of Excitatory Amino Acid Transporters EAAT1 and EAAT2 by the Kinases SPAK and OSR1. J Membr Biol 2015; 248:1107-19. [PMID: 26233565 DOI: 10.1007/s00232-015-9826-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Accepted: 07/24/2015] [Indexed: 11/27/2022]
Abstract
SPAK (SPS1-related proline/alanine-rich kinase) and OSR1 (oxidative stress-responsive kinase 1) are cell volume-sensitive kinases regulated by WNK (with-no-K[Lys]) kinases. SPAK/OSR1 regulate several channels and carriers. SPAK/OSR1 sensitive functions include neuronal excitability. Orchestration of neuronal excitation involves the excitatory glutamate transporters EAAT1 and EAAT2. Sensitivity of those carriers to SPAK/OSR1 has never been shown. The present study thus explored whether SPAK and/or OSR1 contribute to the regulation of EAAT1 and/or EAAT2. To this end, cRNA encoding EAAT1 or EAAT2 was injected into Xenopus oocytes without or with additional injection of cRNA encoding wild-type SPAK or wild-type OSR1, constitutively active (T233E)SPAK, WNK insensitive (T233A)SPAK, catalytically inactive (D212A)SPAK, constitutively active (T185E)OSR1, WNK insensitive (T185A)OSR1 or catalytically inactive (D164A)OSR1. The glutamate (2 mM)-induced inward current (I Glu) was taken as a measure of glutamate transport. As a result, I Glu was observed in EAAT1- and in EAAT2-expressing oocytes but not in water-injected oocytes, and was significantly decreased by coexpression of SPAK and OSR1. As shown for EAAT2, SPAK, and OSR1 decreased significantly the maximal transport rate but significantly enhanced the affinity of the carrier. The effect of wild-type SPAK/OSR1 on EAAT1 and EAAT2 was mimicked by (T233E)SPAK and (T185E)OSR1, but not by (T233A)SPAK, (D212A)SPAK, (T185A)OSR1, or (D164A)OSR1. Coexpression of either SPAK or OSR1 decreased the EAAT2 protein abundance in the cell membrane of EAAT2-expressing oocytes. In conclusion, SPAK and OSR1 are powerful negative regulators of the excitatory glutamate transporters EAAT1 and EAAT2.
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Affiliation(s)
- Abeer Abousaab
- Department of Physiology, University of Tübingen, Gmelinstr. 5, 72076, Tübingen, Germany
| | - Jamshed Warsi
- Department of Physiology, University of Tübingen, Gmelinstr. 5, 72076, Tübingen, Germany
| | - Bernat Elvira
- Department of Physiology, University of Tübingen, Gmelinstr. 5, 72076, Tübingen, Germany
| | - Ioana Alesutan
- Department of Physiology, University of Tübingen, Gmelinstr. 5, 72076, Tübingen, Germany
| | - Zohreh Hoseinzadeh
- Department of Physiology, University of Tübingen, Gmelinstr. 5, 72076, Tübingen, Germany
| | - Florian Lang
- Department of Physiology, University of Tübingen, Gmelinstr. 5, 72076, Tübingen, Germany.
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Association of rare variation in the glutamate receptor gene SLC1A2 with susceptibility to bipolar disorder and schizophrenia. Eur J Hum Genet 2014; 23:1200-6. [PMID: 25406999 PMCID: PMC4351899 DOI: 10.1038/ejhg.2014.261] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Revised: 09/30/2014] [Accepted: 10/04/2014] [Indexed: 01/23/2023] Open
Abstract
The SLC1A2 gene encodes the excitatory amino acid transporter 2 (EAAT2). Glutamate is the major mediator of excitatory neurotransmission and EAAT2 is responsible for clearing the neurotransmitter from the synaptic cleft. Genetic variation in SLC1A2 has been implicated in a range of neurological and neuropsychiatric conditions including schizophrenia (SZ), autism and in core phenotypes of bipolar disorder (BD). The coding and putative regulatory regions of SLC1A2 gene were screened for variants using high resolution melting or sequenced in 1099 or in 32 BD subjects. Thirty-two variants were detected in the SLC1A2 gene. Fifteen potentially etiological variants were selected for genotyping in 1099 BD and 1095 control samples. Five amino acid changing variants were also genotyped in 630 participants suffering from SZ. None of the variants were found to be associated with BD or SZ or with the two diseases combined. However, two recurrent missense variants (rs145827578:G>A, p.(G6S); rs199599866:G>A, p.(R31Q)) and one recurrent 5′-untranslated region (UTR) variant (ss825678885:G>T) were detected in cases only. Combined analysis of the recurrent-case-only missense variants and of the case-only missense and 5′-UTR variants showed nominal evidence for association with the combined diseases (Fisher's P=0.019 and 0.0076). These findings are exploratory in nature and await replication in larger cohorts, however, they provide intriguing evidence that potentially functional rare variants in the SLC1A2 gene may confer susceptibility to psychotic disorders.
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Gegelashvili G, Bjerrum OJ. High-affinity glutamate transporters in chronic pain: an emerging therapeutic target. J Neurochem 2014; 131:712-30. [DOI: 10.1111/jnc.12957] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 09/18/2014] [Accepted: 09/25/2014] [Indexed: 01/13/2023]
Affiliation(s)
- Georgi Gegelashvili
- Department of Drug Design and Pharmacology; Faculty of Health and Medical Sciences; University of Copenhagen; Copenhagen Denmark
- Institute of Chemical Biology; Ilia State University; Tbilisi Georgia
| | - Ole J. Bjerrum
- Department of Drug Design and Pharmacology; Faculty of Health and Medical Sciences; University of Copenhagen; Copenhagen Denmark
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Cisneros IE, Ghorpade A. Methamphetamine and HIV-1-induced neurotoxicity: role of trace amine associated receptor 1 cAMP signaling in astrocytes. Neuropharmacology 2014; 85:499-507. [PMID: 24950453 PMCID: PMC4315503 DOI: 10.1016/j.neuropharm.2014.06.011] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2013] [Revised: 06/05/2014] [Accepted: 06/10/2014] [Indexed: 01/01/2023]
Abstract
Methamphetamine (METH) is abused by about 5% of the United States population with approximately 10-15% of human immunodeficiency virus-1 (HIV-1) patients reporting its use. METH abuse accelerates the onset and severity of HIV-associated neurocognitive disorders (HAND) and astrocyte-induced neurotoxicity. METH activates G-protein coupled receptors such as trace amine associated receptor 1 (TAAR1) increasing intracellular cyclic adenosine monophosphate (cAMP) levels in presynaptic cells of monoaminergic systems. In the present study, we investigated the effects of METH and HIV-1 on primary human astrocyte TAAR1 expression, function and glutamate clearance. Our results demonstrate combined conditions increased TAAR1 mRNA levels 7-fold and increased intracellular cAMP levels. METH and beta-phenylethylamine (β-PEA), known TAAR1 agonists, increased intracellular cAMP levels in astrocytes. Further, TAAR1 knockdown significantly reduced intracellular cAMP levels in response to METH/β-PEA, indicating signaling through astrocyte TAAR1. METH±HIV-1 decreased excitatory amino acid transporter-2 (EAAT-2) mRNA and significantly decreased glutamate clearance. RNA interference for TAAR1 prevented METH-mediated decreases in EAAT-2. TAAR1 knockdown significantly increased glutamate clearance, which was further heightened significantly by METH. Moreover, TAAR1 overexpression significantly decreased EAAT-2 levels and glutamate clearance that were further reduced by METH. Taken together, our data show that METH treatment activated TAAR1 leading to intracellular cAMP in human astrocytes and modulated glutamate clearance abilities. Furthermore, molecular alterations in astrocyte TAAR1 levels correspond to changes in astrocyte EAAT-2 levels and function. To our knowledge this is the first report implicating astrocyte TAAR1 as a novel receptor for METH during combined injury in the context of HAND.
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Affiliation(s)
- Irma E Cisneros
- Department of Cell Biology and Immunology, University of North Texas Health Science Center, 3500 Camp Bowie Blvd., Fort Worth, TX 76107, USA.
| | - Anuja Ghorpade
- Department of Cell Biology and Immunology, University of North Texas Health Science Center, 3500 Camp Bowie Blvd., Fort Worth, TX 76107, USA.
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Genetic dys-regulation of astrocytic glutamate transporter EAAT2 and its implications in neurological disorders and manganese toxicity. Neurochem Res 2014; 40:380-8. [PMID: 25064045 DOI: 10.1007/s11064-014-1391-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Revised: 07/09/2014] [Accepted: 07/15/2014] [Indexed: 12/14/2022]
Abstract
Astrocytic glutamate transporters, the excitatory amino acid transporter (EAAT) 2 and EAAT1 (glutamate transporter 1 and glutamate aspartate transporter in rodents, respectively), are the main transporters for maintaining optimal glutamate levels in the synaptic clefts by taking up more than 90% of glutamate from extracellular space thus preventing excitotoxic neuronal death. Reduced expression and function of these transporters, especially EAAT2, has been reported in numerous neurological disorders, including amyotrophic lateral sclerosis, Alzheimer's disease, Parkinson's disease, schizophrenia and epilepsy. The mechanism of down-regulation of EAAT2 in these diseases has yet to be fully established. Genetic as well as transcriptional dys-regulation of these transporters by various modes, such as single nucleotide polymorphisms and epigenetics, resulting in impairment of their functions, might play an important role in the etiology of neurological diseases. Consequently, there has been an extensive effort to identify molecular targets for enhancement of EAAT2 expression as a potential therapeutic approach. Several pharmacological agents increase expression of EAAT2 via nuclear factor κB and cAMP response element binding protein at the transcriptional level. However, the negative regulatory mechanisms of EAAT2 have yet to be identified. Recent studies, including those from our laboratory, suggest that the transcriptional factor yin yang 1 plays a critical role in the repressive effects of various neurotoxins, such as manganese (Mn), on EAAT2 expression. In this review, we will focus on transcriptional epigenetics and translational regulation of EAAT2.
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Chotibut T, Davis RW, Arnold JC, Frenchek Z, Gurwara S, Bondada V, Geddes JW, Salvatore MF. Ceftriaxone increases glutamate uptake and reduces striatal tyrosine hydroxylase loss in 6-OHDA Parkinson's model. Mol Neurobiol 2014; 49:1282-92. [PMID: 24297323 PMCID: PMC4618839 DOI: 10.1007/s12035-013-8598-0] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Accepted: 11/19/2013] [Indexed: 12/18/2022]
Abstract
Excess glutamatergic neurotransmission may contribute to excitotoxic loss of nigrostriatal neurons in Parkinson's disease (PD). Here, we determined if increasing glutamate uptake could reduce the extent of tyrosine hydroxylase (TH) loss in PD progression. The beta-lactam antibiotic, ceftriaxone, increases the expression of glutamate transporter 1 (GLT-1), a glutamate transporter that plays a major role in glutamate clearance in central nervous system and may attenuate adverse behavioral or neurobiological function in other neurodegenerative disease models. In association with >80% TH loss, we observed a significant decrease in glutamate uptake in the established 6-hydroxydopamine (6-OHDA) PD model. Ceftriaxone (200 mg/kg, i.p.) increased striatal glutamate uptake with >5 consecutive days of injection in nonlesioned rats and lasted out to 14 days postinjection, a time beyond that required for 6-OHDA to produce >70% TH loss (∼9 days). When ceftriaxone was given at the time of 6-OHDA, TH loss was ∼57% compared to ∼85% in temporally matched vehicle-injected controls and amphetamine-induced rotation was reduced about 2-fold. This attenuation of TH loss was associated with increased glutamate uptake, increased GLT-1 expression, and reduced Serine 19 TH phosphorylation, a calcium-dependent target specific for nigrostriatal neurons. These results reveal that glutamate uptake can be targeted in a PD model, decrease the rate of TH loss in a calcium-dependent manner, and attenuate locomotor behavior associated with 6-OHDA lesion. Given that detection of reliable PD markers will eventually be employed in susceptible populations, our results give credence to the possibility that increasing glutamate uptake may prolong the time period before locomotor impairment occurs.
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Affiliation(s)
- Tanya Chotibut
- Department of Pharmacology, Toxicology, & Neuroscience, Louisiana State University Health Sciences Center-Shreveport, Shreveport, LA 71130, USA
| | - Richard W. Davis
- Department of Pharmacology, Toxicology, & Neuroscience, Louisiana State University Health Sciences Center-Shreveport, Shreveport, LA 71130, USA
| | - Jennifer C. Arnold
- Department of Pharmacology, Toxicology, & Neuroscience, Louisiana State University Health Sciences Center-Shreveport, Shreveport, LA 71130, USA
| | - Zachary Frenchek
- Department of Pharmacology, Toxicology, & Neuroscience, Louisiana State University Health Sciences Center-Shreveport, Shreveport, LA 71130, USA
| | - Shawn Gurwara
- Department of Pharmacology, Toxicology, & Neuroscience, Louisiana State University Health Sciences Center-Shreveport, Shreveport, LA 71130, USA
| | - Vimala Bondada
- Spinal Cord & Brain Injury Research Center, University of Kentucky Medical Center, Lexington, KY 40536, USA
| | - James W. Geddes
- Spinal Cord & Brain Injury Research Center, University of Kentucky Medical Center, Lexington, KY 40536, USA
| | - Michael F. Salvatore
- Department of Pharmacology, Toxicology, & Neuroscience, Louisiana State University Health Sciences Center, 1501 Kings Highway, Shreveport, LA 71106, USA
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Kong Q, Chang LC, Takahashi K, Liu Q, Schulte DA, Lai L, Ibabao B, Lin Y, Stouffer N, Das Mukhopadhyay C, Xing X, Seyb KI, Cuny GD, Glicksman MA, Lin CLG. Small-molecule activator of glutamate transporter EAAT2 translation provides neuroprotection. J Clin Invest 2014; 124:1255-67. [PMID: 24569372 DOI: 10.1172/jci66163] [Citation(s) in RCA: 106] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Accepted: 11/27/2013] [Indexed: 12/31/2022] Open
Abstract
Glial glutamate transporter EAAT2 plays a major role in glutamate clearance in synaptic clefts. Several lines of evidence indicate that strategies designed to increase EAAT2 expression have potential for preventing excitotoxicity, which contributes to neuronal injury and death in neurodegenerative diseases. We previously discovered several classes of compounds that can increase EAAT2 expression through translational activation. Here, we present efficacy studies of the compound LDN/OSU-0212320, which is a pyridazine derivative from one of our lead series. In a murine model, LDN/OSU-0212320 had good potency, adequate pharmacokinetic properties, no observed toxicity at the doses examined, and low side effect/toxicity potential. Additionally, LDN/OSU-0212320 protected cultured neurons from glutamate-mediated excitotoxic injury and death via EAAT2 activation. Importantly, LDN/OSU-0212320 markedly delayed motor function decline and extended lifespan in an animal model of amyotrophic lateral sclerosis (ALS). We also found that LDN/OSU-0212320 substantially reduced mortality, neuronal death, and spontaneous recurrent seizures in a pilocarpine-induced temporal lobe epilepsy model. Moreover, our study demonstrated that LDN/OSU-0212320 treatment results in activation of PKC and subsequent Y-box-binding protein 1 (YB-1) activation, which regulates activation of EAAT2 translation. Our data indicate that the use of small molecules to enhance EAAT2 translation may be a therapeutic strategy for the treatment of neurodegenerative diseases.
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Wang D, Zhao Y, Zhang Y, Zhang T, Shang X, Wang J, Liu Y, Kong Q, Sun B, Mu L, Liu X, Wang G, Li H. Hypothermia protects against oxygen-glucose deprivation-induced neuronal injury by down-regulating the reverse transport of glutamate by astrocytes as mediated by neurons. Neuroscience 2013; 237:130-8. [PMID: 23402854 DOI: 10.1016/j.neuroscience.2013.01.056] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Revised: 01/25/2013] [Accepted: 01/27/2013] [Indexed: 11/29/2022]
Abstract
Glutamate is the major mediator of excitotoxic neuronal death following cerebral ischemia. Under severe ischemic conditions, glutamate transporters can functionally reverse to release glutamate, thereby inducing further neuronal injury. Hypothermia has been shown to protect neurons from brain ischemia. However, the mechanism(s) involved remain unclear. Therefore, the aim of this study was to investigate the mechanism(s) mediating glutamate release during brain ischemia-reperfusion injury under hypothermic conditions. Neuron/astrocyte co-cultures were exposed to oxygen-glucose deprivation (OGD) at various temperatures for 2h, and cell viability was assayed 12h after reoxygenation. PI and MAP-2 staining demonstrated that hypothermia significantly decreased neuronal injury. Furthermore, [(3)H]-glutamate uptake assays showed that hypothermia protected rat primary cortical cultures against OGD reoxygenation-induced injury. Protein levels of the astrocytic glutamate transporter, GLT-1, which is primarily responsible for the clearance of extracellular glutamate, were also found to be reduced in a temperature-dependent manner. In contrast, expression of GLT-1 in astrocyte-enriched cultures was found to significantly increase following the addition of neuron-conditioned medium maintained at 37 °C, and to a lesser extent with neuron-conditioned medium at 33 °C. In conclusion, the neuroprotective effects of hypothermia against brain ischemia-reperfusion injury involve down-regulation of astrocytic GLT-1, which mediates the reverse transport of glutamate. Moreover, this process may be regulated by molecules secreted by stressed neurons.
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Affiliation(s)
- D Wang
- Department of Neurobiology, Harbin Medical University Provincial Key Lab of Neurobiology, Harbin Medical University, Heilongjiang, China
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Morel L, Regan M, Higashimori H, Ng SK, Esau C, Vidensky S, Rothstein J, Yang Y. Neuronal exosomal miRNA-dependent translational regulation of astroglial glutamate transporter GLT1. J Biol Chem 2013; 288:7105-16. [PMID: 23364798 DOI: 10.1074/jbc.m112.410944] [Citation(s) in RCA: 281] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Perisynaptic astrocytes express important glutamate transporters, especially excitatory amino acid transporter 2 (EAAT2, rodent analog GLT1) to regulate extracellular glutamate levels and modulate synaptic activation. In this study, we investigated an exciting new pathway, the exosome-mediated transfer of microRNA (in particular, miR-124a), in neuron-to-astrocyte signaling. Exosomes isolated from neuron-conditioned medium contain abundant microRNAs and small RNAs. These exosomes can be directly internalized into astrocytes and increase astrocyte miR-124a and GLT1 protein levels. Direct miR-124a transfection also significantly and selectively increases protein (but not mRNA) expression levels of GLT1 in cultured astrocytes. Consistent with our in vitro findings, intrastriatal injection of specific antisense against miR-124a into adult mice dramatically reduces GLT1 protein expression and glutamate uptake levels in striatum without reducing GLT1 mRNA levels. MiR-124a-mediated regulation of GLT1 expression appears to be indirect and is not mediated by its suppression of the putative GLT1 inhibitory ligand ephrinA3. Moreover, miR-124a is selectively reduced in the spinal cord tissue of end-stage SOD1 G93A mice, the mouse model of ALS. Subsequent exogenous delivery of miR-124a in vivo through stereotaxic injection significantly prevents further pathological loss of GLT1 proteins, as determined by GLT1 immunoreactivity in SOD1 G93A mice. Together, our study characterized a new neuron-to-astrocyte communication pathway and identified miRNAs that modulate GLT1 protein expression in astrocytes in vitro and in vivo.
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Affiliation(s)
- Lydie Morel
- Department of Neuroscience, Tufts University, Boston, Massachusetts 02111, USA
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39
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Lin CLG, Kong Q, Cuny GD, Glicksman MA. Glutamate transporter EAAT2: a new target for the treatment of neurodegenerative diseases. Future Med Chem 2012; 4:1689-700. [PMID: 22924507 PMCID: PMC3580837 DOI: 10.4155/fmc.12.122] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Glutamate is the primary excitatory amino acid neurotransmitter in the CNS. The concentration of glutamate in the synaptic cleft is tightly controlled by interplay between glutamate release and glutamate clearance. Abnormal glutamate release and/or dysfunction of glutamate clearance can cause overstimulation of glutamate receptors and result in neuronal injury known as excitotoxicity. The glial glutamate transporter EAAT2 plays a major role in glutamate clearance. Dysfunction or reduced expression of EAAT2 has been documented in many neurodegenerative diseases. In addition, many studies in animal models of disease indicate that increased EAAT2 expression provides neuronal protection. Here, we summarize these studies and suggest that EAAT2 is a potential target for the prevention of excitotoxicity. EAAT2 can be upregulated by transcriptional or translational activation. We discuss current progress in the search for EAAT2 activators, which is a promising direction for the treatment of neurodegenerative diseases.
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40
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Cisneros IE, Ghorpade A. HIV-1, methamphetamine and astrocyte glutamate regulation: combined excitotoxic implications for neuro-AIDS. Curr HIV Res 2012; 10:392-406. [PMID: 22591363 PMCID: PMC3580828 DOI: 10.2174/157016212802138832] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Revised: 04/18/2012] [Accepted: 04/18/2012] [Indexed: 02/08/2023]
Abstract
Glutamate, the most abundant excitatory transmitter in the brain can lead to neurotoxicity when not properly regulated. Excitotoxicity is a direct result of abnormal regulation of glutamate concentrations in the synapse, and is a common neurotoxic mediator associated with neurodegenerative disorders. It is well accepted that methamphetamine (METH), a potent central nervous stimulant with high abuse potential, and human immunodeficiency virus (HIV)-1 are implicated in the progression of neurocognitive malfunction. Both have been shown to induce common neurodegenerative effects such as astrogliosis, compromised blood brain barrier integrity, and excitotoxicity in the brain. Reduced glutamate uptake from neuronal synapses likely leads to the accumulation of glutamate in the extracellular spaces. Astrocytes express the glutamate transporters responsible for majority of the glutamate uptake from the synapse, as well as for vesicular glutamate release. However, the cellular and molecular mechanisms of astrocyte-mediated excitotoxicity in the context of METH and HIV-1 are undefined. Topics reviewed include dysregulation of the glutamate transporters, specifically excitatory amino acid transporter-2, metabotropic glutamate receptor(s) expression and the release of glutamate by vesicular exocytosis. We also discuss glutamate concentration dysregulation through astrocytic expression of enzymes for glutamate synthesis and metabolism. Lastly, we discuss recent evidence of various astrocyte and neuron crosstalk mechanisms implicated in glutamate regulation. Astrocytes play an essential role in the neuropathologies associated with METH/HIV-1-induced excitotoxicity. We hope to shed light on common cellular and molecular pathways astrocytes share in glutamate regulation during drug abuse and HIV-1 infection.
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Affiliation(s)
| | - Anuja Ghorpade
- University of North Texas Health Science Center, Fort Worth, TX, USA
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41
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Kerdsan W, Thanoi S, Nudmamud-Thanoi S, Reynolds GP. An association between genotypic variations and protein expression of the glial glutamate transporter 2 in the human nucleus accumbens. Neurosci Lett 2012; 523:108-10. [PMID: 22750157 DOI: 10.1016/j.neulet.2012.06.052] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Revised: 06/13/2012] [Accepted: 06/19/2012] [Indexed: 11/30/2022]
Abstract
The glial glutamate transporter EAAT2 is responsible for the majority of synaptic glutamate clearance. Dysfunction of EAAT2 is strongly implicated in neuropsychiatric disorders. Single nucleotide polymorphisms (SNPs) in the EAAT2 gene have been associated with an increased risk of pathological conditions that may result from changes in extracellular glutamate levels. Genetic variation in the metabotropic glutamate receptor 3 (GRM3) gene has been reported to affect EAAT2 mRNA. Therefore, the aim of this study was to investigate the association of EAAT2 (rs4755404 and rs1885343) and GRM3 (rs6465084) SNPs and EAAT2 protein expression in healthy subjects. Postmortem nucleus accumbens tissue from 37 normal subjects had EAAT2 protein determined and was genotyped for three SNPs. Expression of EAAT2 protein was observed in both monomeric (70kDa) and multimeric (150kDa) forms. A significantly lower expression of the monomer (P=0.037) was observed with the GG genotype than in A allele carriers of rs1885343. However, there were no differences in EAAT2 expression associated with genotypes or alleles of rs4755404 and rs6465084. This finding indicates an association between EAAT2 protein expression in the human nucleus accumbens and a genetic polymorphism of EAAT2.
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Affiliation(s)
- Walailuk Kerdsan
- Department of Anatomy, Faculty of Medical Science, Naresuan University, Phitsanulok 65000, Thailand
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42
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Chan TJ, Her LS, Liaw HJ, Chen MC, Tzeng SF. Retinoic acid mediates the expression of glutamate transporter-1 in rat astrocytes through genomic RXR action and non-genomic protein kinase C signaling pathway. J Neurochem 2012; 121:537-50. [PMID: 22380620 DOI: 10.1111/j.1471-4159.2012.07715.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Astrocytic glutamate transporter-1 (GLT-1) is responsible for 90% of forebrain glutamate uptake in the adult CNS. Retinoic acid (RA) is a potent regulator of neural cell differentiation and neuronal maturation in the developing CNS through activation of RA receptors/retinoic X receptors (RXRs) or non-genomic mechanisms. Although rat GLT-1 contains several RXR binding regions, RA-triggered RXR mechanisms regulating GLT-1 expression remain unknown. RA applied at submicromolar concentrations for 24 h significantly reduced GLT-1 mRNA and membrane levels in astrocytes and dibutyryl cAMP (dbcAMP)-primed astrocytes. An RXR agonist reduced astrocytic GLT-1 mRNA expression, whereas an RXR antagonist blocked the effects of RA on the reduction of astrocytic GLT-1 mRNA expression. Electrophoresis motility shift assay indicated that RA-treatment increased astrocytic RXR-DNA binding activity. RA-induced reduction in GLT-1 mRNA expression was also observed in dbcAMP-primed astrocytes. Through lentivirus-mediated astrocytic over-expression of rat GLT-1, levels of GLT-1 in the processes of dbcAMP-treated astrocytes were attenuated by exposure to RA. The protein kinase C inhibitor, Bis I, restored GLT-1 distribution in the processes of RA-treated dbcAMP-primed astrocytes. These results suggest that RA reduces astrocytic GLT-1 levels through both RXR-mediated inhibition at the transcriptional level and triggering activation of protein kinase C which reduces cell surface GLT-1 levels.
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Affiliation(s)
- Ti-Ju Chan
- Department of Life Sciences, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan, Taiwan
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43
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Hosseinzadeh Z, Bhavsar SK, Sopjani M, Alesutan I, Saxena A, Dërmaku-Sopjani M, Lang F. Regulation of the glutamate transporters by JAK2. Cell Physiol Biochem 2011; 28:693-702. [PMID: 22178881 DOI: 10.1159/000335763] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/24/2011] [Indexed: 01/13/2023] Open
Abstract
The Janus-activated kinase-2 JAK2 is involved in the signaling of leptin and erythropoietin receptors and mediates neuroprotective effects of the hormones. In theory, JAK2 could be effective through modulation of the glutamate transporters, carriers accounting for the clearance of glutamate released during neurotransmission. The present study thus elucidated the effect of JAK2 on the glutamate transporters EAAT1, EAAT2, EAAT3 and EAAT4. To this end, cRNA encoding the carriers was injected into Xenopus oocytes with or without cRNA encoding JAK2 and glutamate transport was estimated from glutamate induced current (I(glu)). I(glu) was observed in Xenopus oocytes expressing EAAT1 or EAAT2 or EAAT3 or EAAT4, but not in water injected oocytes. Coexpression of JAK2 resulted in an increase of I(glu) by 83% (EAAT1), 67% (EAAT2), 42% (EAAT3) and 126% (EAAT4). As shown for EAAT4 expressing Xenopus oocytes, the effect of JAK2 was mimicked by gain of function mutation (V617F)JAK2 but not by the inactive mutant (K882E)JAK2. Incubation with JAK2 inhibitor AG490 (40 μM) resulted in a gradual decrease of I(glu) by 53%, 79% and 92% within 3, 6 and 24 hours. Confocal microscopy and chemiluminescence analysis revealed that JAK2 coexpression increased EAAT4 protein abundance in the cell membrane. Disruption of transcription did not appreciably modify the up-regulation of I(glu) in EAAT4 expressing oocytes. The decay of I(glu) following inhibition of carrier insertion with brefeldin A was similar in oocytes expressing EAAT4 + JAK2 and oocytes expressing EAAT4 alone, indicating that JAK2 did not appreciably affect carrier retrieval from the membrane. In conclusion, JAK2 is a novel powerful regulator of glutamate transporters and thus participates in the protection against excitotoxicity.
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Affiliation(s)
- Zohreh Hosseinzadeh
- Department of Physiology, University of Tübingen, Gmelinstrasse 5, Tübingen, Germany
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44
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Unger T, Bette S, Zhang J, Theis M, Engele J. Connexin-deficiency affects expression levels of glial glutamate transporters within the cerebrum. Neurosci Lett 2011; 506:12-6. [PMID: 22037505 DOI: 10.1016/j.neulet.2011.10.032] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2010] [Revised: 10/12/2011] [Accepted: 10/16/2011] [Indexed: 11/17/2022]
Abstract
The glial glutamate transporter subtypes, GLT-1/EAAT-2 and GLAST/EAAT-1 clear the bulk of extracellular glutamate and are severely dysregulated in various acute and chronic brain diseases. Despite the previous identification of several extracellular factors modulating glial glutamate transporter expression, our knowledge of the regulatory network controlling glial glutamate transport in health and disease still remains incomplete. In studies with cultured cortical astrocytes, we previously obtained evidence that glial glutamate transporter expression is also affected by gap junctions/connexins. To assess whether gap junctions would likewise control the in vivo expression of glial glutamate transporters, we have now assessed their expression levels in brains of conditional Cx43 knockout mice, total Cx30 knockouts, as well as Cx43/Cx30 double knockouts. We found that either knocking out Cx30, Cx43, or both increases GLT-1/EAAT-2 protein levels in the cerebral cortex to a similar extent. By contrast, GLAST/EAAT-1 protein levels maximally increased in cerebral cortices of Cx30/Cx43 double knockouts, implying that gap junctions differentially affect the expression of GLT-1/EAAT-2 and GLAST/EAAT-1. Quantitative PCR analysis further revealed that increases in glial glutamate transporter expression are brought about by transcriptional and translational/posttranslational processes. Moreover, GLT-1/EAAT-2- and GLAST/EAAT-1 protein levels remained unchanged in the hippocampi of Cx43/Cx30 double knockouts when compared to Cx43fl/fl controls, indicating brain region-specific effects of gap junctions on glial glutamate transport. Since astrocytic gap junction coupling is affected in various forms of brain injuries, our findings point to gap junctions/connexins as important regulators of glial glutamate turnover in the diseased cerebral cortex.
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Affiliation(s)
- Tina Unger
- Institute of Anatomy, University of Leipzig, Medical Faculty, Liebigstr. 13, 04103 Leipzig, Germany
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45
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Lee A, Anderson AR, Stevens MG, Pow DV. Exon 4-skipping GLT-1: a new form of an abundantly expressed glutamate transporter. Neurosci Lett 2011; 504:228-31. [PMID: 21964391 DOI: 10.1016/j.neulet.2011.09.029] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Revised: 09/14/2011] [Accepted: 09/15/2011] [Indexed: 11/26/2022]
Abstract
GLT-1 (EAAT2) is an abundant glial glutamate transporter in the mammalian brain. It plays important roles, especially in the termination of neurotransmitter signals at excitatory synapses in grey matter. In normal brain, alternative splicing of GLT-1 has been described, where exons in the GLT-1 gene are skipped or intronic sequences spliced in to generate new sequences. This study describes the isolation of a cDNA clone encoding a new splice variant of GLT-1 where exon 4 is skipped. This novel variant was isolated by RT-PCR cloning from adult rat brain and encodes a protein of 500 amino acids (MW ~54.5 kDa). RT-PCR analysis showed that mRNA was readily detectable in various brain regions of rat, primary astrocyte cultures and in tissues such as testis, but little mRNA was detectable in retina and liver. An antibody that selectively recognizes exon-4 skipping GLT-1 revealed strong signals in Western blots and labelled grey matter astrocytes. We conclude that exon-4 skipping GLT 1 is abundantly expressed in the brain and may represent either a functional glutamate transporter or a modulator of glutamate transporter function.
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Affiliation(s)
- Aven Lee
- The University of Queensland, Centre for Clinical Research, Queensland, Australia.
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46
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Xing X, Chang LC, Kong Q, Colton CK, Lai L, Glicksman MA, Lin CLG, Cuny GD. Structure-activity relationship study of pyridazine derivatives as glutamate transporter EAAT2 activators. Bioorg Med Chem Lett 2011; 21:5774-7. [PMID: 21875806 DOI: 10.1016/j.bmcl.2011.08.009] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Revised: 07/28/2011] [Accepted: 08/01/2011] [Indexed: 11/18/2022]
Abstract
Excitatory amino acid transporter 2 (EAAT2) is the major glutamate transporter and functions to remove glutamate from synapses. A thiopyridazine derivative has been found to increase EAAT2 protein levels in astrocytes. A structure-activity relationship study revealed that several components of the molecule were required for activity, such as the thioether and pyridazine. Modification of the benzylthioether resulted in several derivatives (7-13, 7-15 and 7-17) that enhanced EAAT2 levels by >6-fold at concentrations < 5 μM after 24h. In addition, one of the derivatives (7-22) enhanced EAAT2 levels 3.5-3.9-fold after 24h with an EC(50) of 0.5 μM.
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Affiliation(s)
- Xuechao Xing
- Laboratory for Drug Discovery in Neurodegeneration, Harvard NeuroDiscovery Center, Brigham & Women's Hospital and Harvard Medical School, 65 Landsdowne St., Cambridge, MA 02139, USA
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47
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Obulesu M, Dowlathabad MR, Bramhachari PV. Carotenoids and Alzheimer's disease: an insight into therapeutic role of retinoids in animal models. Neurochem Int 2011; 59:535-41. [PMID: 21672580 DOI: 10.1016/j.neuint.2011.04.004] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2011] [Revised: 03/16/2011] [Accepted: 04/20/2011] [Indexed: 01/09/2023]
Abstract
Carotenoids play a pivotal role in prevention of many degenerative diseases mediated by oxidative stress including neurodegenerative diseases like Alzheimer's Disease (AD). The involvement of retinoids in physiology, AD pathology and their therapeutic role in vitro and in vivo has been extensively studied. This review focuses on the role of carotenoids like retinoic acid (RA), all trans retinoic acid (ATRA), lycopene and β-carotene in prevention of AD symptoms primarily through inhibition of amyloid beta (Aβ) formation, deposition and fibril formation either by reducing the levels of p35 or inhibiting corresponding enzymes. The role of antioxidant micronutrients in prevention or delaying of AD symptoms has been included. This study emphasizes the dietary supplementation of carotenoids to combat AD and warrants further studies on animal models to unravel their mechanism of neuroprotection.
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Affiliation(s)
- M Obulesu
- Department of Biotechnology, Rayalaseema University, Kurnool, Andhra Pradesh, India.
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48
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Lee A, Pow DV. Astrocytes: Glutamate transport and alternate splicing of transporters. Int J Biochem Cell Biol 2010; 42:1901-6. [DOI: 10.1016/j.biocel.2010.09.016] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2010] [Revised: 09/14/2010] [Accepted: 09/21/2010] [Indexed: 10/19/2022]
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49
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Colton CK, Kong Q, Lai L, Zhu MX, Seyb KI, Cuny GD, Xian J, Glicksman MA, Lin CLG. Identification of translational activators of glial glutamate transporter EAAT2 through cell-based high-throughput screening: an approach to prevent excitotoxicity. ACTA ACUST UNITED AC 2010; 15:653-62. [PMID: 20508255 DOI: 10.1177/1087057110370998] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Excitotoxicity has been implicated as the mechanism of neuronal damage resulting from acute insults such as stroke, epilepsy, and trauma, as well as during the progression of adult-onset neurodegenerative disorders such as Alzheimer's disease and amyotrophic lateral sclerosis (ALS). Excitotoxicity is defined as excessive exposure to the neurotransmitter glutamate or overstimulation of its membrane receptors, leading to neuronal injury or death. One potential approach to protect against excitotoxic neuronal damage is enhanced glutamate reuptake. The glial glutamate transporter EAAT2 is the quantitatively dominant glutamate transporter and plays a major role in clearance of glutamate. Expression of EAAT2 protein is highly regulated at the translational level. In an effort to identify compounds that can induce translation of EAAT2 transcripts, a cell-based enzyme-linked immunosorbent assay was developed using a primary astrocyte line stably transfected with a vector designed to identify modulators of EAAT2 translation. This assay was optimized for high-throughput screening, and a library of approximately 140,000 compounds was tested. In the initial screen, 293 compounds were identified as hits. These 293 hits were retested at 3 concentrations, and a total of 61 compounds showed a dose-dependent increase in EAAT2 protein levels. Selected compounds were tested in full 12-point dose-response experiments in the screening assay to assess potency as well as confirmed by Western blot, immunohistochemistry, and glutamate uptake assays to evaluate the localization and function of the elevated EAAT2 protein. These hits provide excellent starting points for developing therapeutic agents to prevent excitotoxicity.
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Affiliation(s)
- Craig K Colton
- Department of Neuroscience, The Ohio State University, Columbus, OH 43210, USA
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50
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Tian G, Kong Q, Lai L, Ray-Chaudhury A, Lin CLG. Increased expression of cholesterol 24S-hydroxylase results in disruption of glial glutamate transporter EAAT2 association with lipid rafts: a potential role in Alzheimer's disease. J Neurochem 2010; 113:978-89. [PMID: 20193040 DOI: 10.1111/j.1471-4159.2010.06661.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The glial glutamate transporter EAAT2 (excitatory amino acid transporter 2) is the major mediator of glutamate clearance that terminates glutamate-mediated neurotransmission. Loss of EAAT2 and associated glutamate uptake function has been reported in the brains of patients with Alzheimer's disease (AD). We previously reported that EAAT2 is associated with lipid raft microdomains of the plasma membrane. In the present study, we demonstrated that association of EAAT2 with lipid rafts is disrupted in AD brains. This abnormality is not a consequence of neuron degeneration, oxidative stress, or amyloid beta toxicity. In AD brains, cholesterol 24S-hydroxylase (CYP46), a key enzyme in maintenance of cholesterol homeostasis in the brain, is markedly increased in astrocytes but decreased in neurons. We demonstrated that increased expression of CYP46 in primary astrocytes results in a reduction of membrane cholesterol levels and leads to the dissociation of EAAT2 from lipid rafts and the loss of EAAT2 and associated glutamate uptake function. These results suggest that a disturbance of cholesterol metabolism may contribute to loss of EAAT2 in AD.
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Affiliation(s)
- Guilian Tian
- Department of Neuroscience, The Ohio State University, Columbus, Ohio 43210, USA
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