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Evolving targets for anti-epileptic drug discovery. Eur J Pharmacol 2020; 887:173582. [DOI: 10.1016/j.ejphar.2020.173582] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 09/14/2020] [Accepted: 09/15/2020] [Indexed: 12/27/2022]
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2
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Riquelme J, Wellmann M, Sotomayor-Zárate R, Bonansco C. Gliotransmission: A Novel Target for the Development of Antiseizure Drugs. Neuroscientist 2020; 26:293-309. [PMID: 31976817 DOI: 10.1177/1073858420901474] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
For more than a century, epilepsy has remained an incapacitating neurological disorder with a high incidence worldwide. Mesial temporal lobe epilepsy (TLE) is a common type of epilepsy without an effective pharmacological treatment. An increase in excitability and hypersynchrony of electrical neuronal activity during development are typically associated with an excitatory/inhibitory imbalance in the neuronal network. Astrocytes release gliotransmitters, which can regulate neuronal excitability and synaptic transmission; therefore, the classical neurocentric vision of the cellular basis of epileptogenesis has begun to change. Growing evidence suggests that the key contribution of astrocyte-to-neuron signaling in the mechanisms underlies the initiation, propagation, and recurrence of seizure activity. The aim of this review was to summarize current evidence obtained from experimental models that suggest how alterations in astroglial modulation of synaptic transmission and neuronal activity contribute to the development of this brain disease. In this article, we will summarize the main pharmacological, Ca2+-imaging, and electrophysiological findings in the gliotransmitter-mediated modulation of neuronal activity and their possible regulation as a novel cellular target for the development of pharmacological strategies for treating refractory epilepsies.
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Affiliation(s)
- Julio Riquelme
- Escuela de Medicina, Facultad de Medicina, Universidad de Valparaíso, Valparaíso, Chile.,Servicio de Neurología, Hospital Carlos Van Buren, Valparaíso, Chile
| | - Mario Wellmann
- Escuela de Fonoaudiología, Facultad de Medicina, Universidad de Valparaíso, Valparaíso, Chile.,Centro de Neurobiología y Fisiología Integrativa (CENFI), Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Ramón Sotomayor-Zárate
- Centro de Neurobiología y Fisiología Integrativa (CENFI), Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Christian Bonansco
- Centro de Neurobiología y Fisiología Integrativa (CENFI), Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
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3
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Krishna G, Beitchman JA, Bromberg CE, Currier Thomas T. Approaches to Monitor Circuit Disruption after Traumatic Brain Injury: Frontiers in Preclinical Research. Int J Mol Sci 2020; 21:ijms21020588. [PMID: 31963314 PMCID: PMC7014469 DOI: 10.3390/ijms21020588] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Revised: 01/03/2020] [Accepted: 01/13/2020] [Indexed: 12/19/2022] Open
Abstract
Mild traumatic brain injury (TBI) often results in pathophysiological damage that can manifest as both acute and chronic neurological deficits. In an attempt to repair and reconnect disrupted circuits to compensate for loss of afferent and efferent connections, maladaptive circuitry is created and contributes to neurological deficits, including post-concussive symptoms. The TBI-induced pathology physically and metabolically changes the structure and function of neurons associated with behaviorally relevant circuit function. Complex neurological processing is governed, in part, by circuitry mediated by primary and modulatory neurotransmitter systems, where signaling is disrupted acutely and chronically after injury, and therefore serves as a primary target for treatment. Monitoring of neurotransmitter signaling in experimental models with technology empowered with improved temporal and spatial resolution is capable of recording in vivo extracellular neurotransmitter signaling in behaviorally relevant circuits. Here, we review preclinical evidence in TBI literature that implicates the role of neurotransmitter changes mediating circuit function that contributes to neurological deficits in the post-acute and chronic phases and methods developed for in vivo neurochemical monitoring. Coupling TBI models demonstrating chronic behavioral deficits with in vivo technologies capable of real-time monitoring of neurotransmitters provides an innovative approach to directly quantify and characterize neurotransmitter signaling as a universal consequence of TBI and the direct influence of pharmacological approaches on both behavior and signaling.
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Affiliation(s)
- Gokul Krishna
- Barrow Neurological Institute at Phoenix Children’s Hospital, Phoenix, AZ 85016, USA; (G.K.); (J.A.B.); (C.E.B.)
- Department of Child Health, University of Arizona College of Medicine-Phoenix, Phoenix, AZ 85004, USA
| | - Joshua A. Beitchman
- Barrow Neurological Institute at Phoenix Children’s Hospital, Phoenix, AZ 85016, USA; (G.K.); (J.A.B.); (C.E.B.)
- Department of Child Health, University of Arizona College of Medicine-Phoenix, Phoenix, AZ 85004, USA
- College of Graduate Studies, Midwestern University, Glendale, AZ 85308, USA
| | - Caitlin E. Bromberg
- Barrow Neurological Institute at Phoenix Children’s Hospital, Phoenix, AZ 85016, USA; (G.K.); (J.A.B.); (C.E.B.)
- Department of Child Health, University of Arizona College of Medicine-Phoenix, Phoenix, AZ 85004, USA
| | - Theresa Currier Thomas
- Barrow Neurological Institute at Phoenix Children’s Hospital, Phoenix, AZ 85016, USA; (G.K.); (J.A.B.); (C.E.B.)
- Department of Child Health, University of Arizona College of Medicine-Phoenix, Phoenix, AZ 85004, USA
- Phoenix VA Healthcare System, Phoenix, AZ 85012, USA
- Correspondence: ; Tel.: +1-602-827-2348
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Butler CR, Boychuk JA, Pomerleau F, Alcala R, Huettl P, Ai Y, Jakobsson J, Whiteheart SW, Gerhardt GA, Smith BN, Slevin JT. Modulation of epileptogenesis: A paradigm for the integration of enzyme-based microelectrode arrays and optogenetics. Epilepsy Res 2019; 159:106244. [PMID: 31816591 DOI: 10.1016/j.eplepsyres.2019.106244] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2019] [Revised: 10/22/2019] [Accepted: 11/22/2019] [Indexed: 02/03/2023]
Abstract
BACKGROUND Genesis of acquired epilepsy includes transformations spanning genetic-to- network-level modifications, disrupting the regional excitatory/inhibitory balance. Methodology concurrently tracking changes at multiple levels is lacking. Here, viral vectors are used to differentially express two opsin proteins in neuronal populations within dentate gyrus (DG) of hippocampus. When activated, these opsins induced excitatory or inhibitory neural output that differentially affected neural networks and epileptogenesis. In vivo measures included behavioral observation coupled to real-time measures of regional glutamate flux using ceramic-based amperometric microelectrode arrays (MEAs). RESULTS Using MEA technology, phasic increases of extracellular glutamate were recorded immediately upon application of blue light/488 nm to DG of rats previously transfected with an AAV 2/5 vector containing an (excitatory) channelrhodopsin-2 transcript. Rats receiving twice-daily 30-sec light stimulation to DG ipsilateral to viral transfection progressed through Racine seizure stages. AAV 2/5 (inhibitory) halorhodopsin-transfected rats receiving concomitant amygdalar kindling and DG light stimuli were kindled significantly more slowly than non-stimulated controls. In in vitro slice preparations, both excitatory and inhibitory responses were independently evoked in dentate granule cells during appropriate light stimulation. Latency to response and sensitivity of responses suggest a degree of neuron subtype-selective functional expression of the transcripts. CONCLUSIONS This study demonstrates the potential for coupling MEA technology and optogenetics for real-time neurotransmitter release measures and modification of seizure susceptibility in animal models of epileptogenesis. This microelectrode/optogenetic technology could prove useful for characterization of network and system level dysfunction in diseases involving imbalanced excitatory/inhibitory control of neuron populations and guide development of future treatment strategies.
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Affiliation(s)
- Corwin R Butler
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY, 40536, United States
| | - Jeffery A Boychuk
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY, 40536, United States; Epilepsy Center, University of Kentucky, Lexington, KY, 40536, United States
| | - Francois Pomerleau
- Department of Neuroscience, College of Medicine, University of Kentucky, Lexington, KY, 40536, United States; Brain Restoration Center, University of Kentucky, Lexington, KY, 40356, United States
| | - Ramona Alcala
- Department of Neurology, College of Medicine, University of Kentucky, Lexington, KY, 40536, United States
| | - Peter Huettl
- Department of Neuroscience, College of Medicine, University of Kentucky, Lexington, KY, 40536, United States; Brain Restoration Center, University of Kentucky, Lexington, KY, 40356, United States
| | - Yi Ai
- Department of Neuroscience, College of Medicine, University of Kentucky, Lexington, KY, 40536, United States
| | - Johan Jakobsson
- Wallenburg Neuroscience Center, Lund Stem Cell Center, Lund University, Lund, Sweden
| | - Sidney W Whiteheart
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY, 40536, United States; Veterans Affairs Medical Center, Lexington, KY, 40536, United States
| | - Greg A Gerhardt
- Epilepsy Center, University of Kentucky, Lexington, KY, 40536, United States; Spinal Cord and Brain Injury Research Center (SCoBIRC), University of Kentucky, Lexington, KY, 40536, United States; Department of Neuroscience, College of Medicine, University of Kentucky, Lexington, KY, 40536, United States; Department of Neurology, College of Medicine, University of Kentucky, Lexington, KY, 40536, United States; Brain Restoration Center, University of Kentucky, Lexington, KY, 40356, United States
| | - Bret N Smith
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY, 40536, United States; Epilepsy Center, University of Kentucky, Lexington, KY, 40536, United States; Spinal Cord and Brain Injury Research Center (SCoBIRC), University of Kentucky, Lexington, KY, 40536, United States; Department of Neuroscience, College of Medicine, University of Kentucky, Lexington, KY, 40536, United States
| | - John T Slevin
- Epilepsy Center, University of Kentucky, Lexington, KY, 40536, United States; Department of Neurology, College of Medicine, University of Kentucky, Lexington, KY, 40536, United States; Veterans Affairs Medical Center, Lexington, KY, 40536, United States; Brain Restoration Center, University of Kentucky, Lexington, KY, 40356, United States.
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Differential expression of SV2A in hippocampal glutamatergic and GABAergic terminals during postnatal development. Brain Res 2019; 1715:73-83. [PMID: 30905653 DOI: 10.1016/j.brainres.2019.03.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Revised: 03/08/2019] [Accepted: 03/20/2019] [Indexed: 01/15/2023]
Abstract
The function of synaptic vesicle protein 2A (SV2A) has not been clearly identified, although it has an essential role in normal neurotransmission. Changes in SV2A expression have been linked to several diseases that could implicate an imbalance between excitation and inhibition, such as epilepsy. Although it is known that SV2A expression is necessary for survival, SV2A expression and its relationship with γ-aminobutyric acid (GABA) and glutamate neurotransmitter systems along development has not been addressed. This report follows SV2A expression levels in the rat hippocampus and their association with glutamatergic and GABAergic terminals along postnatal development. Total SV2A expression was assessed by real time PCR and western blot, while immunofluorescence was used to identify SV2A protein in the different hippocampal layers and its co-localization with GABA or glutamate vesicular transporters. SV2A was dynamically regulated along development and its association with GABA or glutamate transporters varied in the different hippocampal layers. In the principal cells layers (granular and pyramidal), SV2A protein was preferentially localized to GABAergic terminals, while in the hilus and stratum lucidum SV2A was associated mainly to glutamatergic terminals. Although SV2A was ubiquitously expressed in the entire hippocampus, it established a differential association with excitatory or inhibitory terminals, which could contribute to the maturation of excitatory/inhibitory balance.
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Batten SR, Matveeva EA, Whiteheart SW, Vanaman TC, Gerhardt GA, Slevin JT. Linking kindling to increased glutamate release in the dentate gyrus of the hippocampus through the STXBP5/tomosyn-1 gene. Brain Behav 2017; 7:e00795. [PMID: 28948088 PMCID: PMC5607557 DOI: 10.1002/brb3.795] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Revised: 06/29/2017] [Accepted: 07/02/2017] [Indexed: 12/19/2022] Open
Abstract
INTRODUCTION In kindling, repeated electrical stimulation of certain brain areas causes progressive and permanent intensification of epileptiform activity resulting in generalized seizures. We focused on the role(s) of glutamate and a negative regulator of glutamate release, STXBP5/tomosyn-1, in kindling. METHODS Stimulating electrodes were implanted in the amygdala and progression to two successive Racine stage 5 seizures was measured in wild-type and STXBP5/tomosyn-1-/- (Tom-/-) animals. Glutamate release measurements were performed in distinct brain regions using a glutamate-selective microelectrode array (MEA). RESULTS Naïve Tom-/- mice had significant increases in KCl-evoked glutamate release compared to naïve wild type as measured by MEA of presynaptic release in the hippocampal dentate gyrus (DG). Kindling progression was considerably accelerated in Tom-/- mice, requiring fewer stimuli to reach a fully kindled state. Following full kindling, MEA measurements of both kindled Tom+/+ and Tom-/- mice showed significant increases in KCl-evoked and spontaneous glutamate release in the DG, indicating a correlation with the fully kindled state independent of genotype. Resting glutamate levels in all hippocampal subregions were significantly lower in the kindled Tom-/- mice, suggesting possible changes in basal control of glutamate circuitry in the kindled Tom-/- mice. CONCLUSIONS Our studies demonstrate that increased glutamate release in the hippocampal DG correlates with acceleration of the kindling process. Although STXBP5/tomosyn-1 loss increased evoked glutamate release in naïve animals contributing to their prokindling phenotype, the kindling process can override any attenuating effect of STXBP5/tomosyn-1. Loss of this "braking" effect of STXBP5/tomosyn-1 on kindling progression may set in motion an alternative but ultimately equally ineffective compensatory response, detected here as reduced basal glutamate release.
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Affiliation(s)
- Seth R. Batten
- Department of PsychologyUniversity of KentuckyCollege of Arts and SciencesLexingtonKYUSA
| | - Elena A. Matveeva
- Department of Molecular & Cellular BiochemistryUniversity of Kentucky Medical CenterLexingtonKYUSA
| | - Sidney W. Whiteheart
- Department of Molecular & Cellular BiochemistryUniversity of Kentucky Medical CenterLexingtonKYUSA
| | - Thomas C. Vanaman
- Department of Molecular & Cellular BiochemistryUniversity of Kentucky Medical CenterLexingtonKYUSA
| | - Greg A. Gerhardt
- Department of NeuroscienceUniversity of Kentucky Medical CenterLexingtonKYUSA
- Department of NeurologyUniversity of Kentucky Medical CenterLexingtonKYUSA
| | - John T. Slevin
- Neurology ServiceVeterans Affairs Medical CenterLexingtonKYUSA
- Department of NeurologyUniversity of Kentucky Medical CenterLexingtonKYUSA
- Department of Pharmacology and Nutritional SciencesUniversity of Kentucky Medical CenterLexingtonKYUSA
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7
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Calcineurin/NFAT Signaling in Activated Astrocytes Drives Network Hyperexcitability in Aβ-Bearing Mice. J Neurosci 2017; 37:6132-6148. [PMID: 28559377 DOI: 10.1523/jneurosci.0877-17.2017] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Revised: 05/12/2017] [Accepted: 05/16/2017] [Indexed: 12/25/2022] Open
Abstract
Hyperexcitable neuronal networks are mechanistically linked to the pathologic and clinical features of Alzheimer's disease (AD). Astrocytes are a primary defense against hyperexcitability, but their functional phenotype during AD is poorly understood. Here, we found that activated astrocytes in the 5xFAD mouse model were strongly associated with proteolysis of the protein phosphatase calcineurin (CN) and the elevated expression of the CN-dependent transcription factor nuclear factor of activated T cells 4 (NFAT4). Intrahippocampal injections of adeno-associated virus vectors containing the astrocyte-specific promoter Gfa2 and the NFAT inhibitory peptide VIVIT reduced signs of glutamate-mediated hyperexcitability in 5xFAD mice, measured in vivo with microelectrode arrays and ex vivo brain slices, using whole-cell voltage clamp. VIVIT treatment in 5xFAD mice led to increased expression of the astrocytic glutamate transporter GLT-1 and to attenuated changes in dendrite morphology, synaptic strength, and NMDAR-dependent responses. The results reveal astrocytic CN/NFAT4 as a key pathologic mechanism for driving glutamate dysregulation and neuronal hyperactivity during AD.SIGNIFICANCE STATEMENT Neuronal hyperexcitability and excitotoxicity are increasingly recognized as important mechanisms for neurodegeneration and dementia associated with Alzheimer's disease (AD). Astrocytes are profoundly activated during AD and may lose their capacity to regulate excitotoxic glutamate levels. Here, we show that a highly active calcineurin (CN) phosphatase fragment and its substrate transcription factor, nuclear factor of activated T cells (NFAT4), appear in astrocytes in direct proportion to the extent of astrocyte activation. The blockade of astrocytic CN/NFAT signaling in a common mouse model of AD, using adeno-associated virus vectors normalized glutamate signaling dynamics, increased astrocytic glutamate transporter levels and alleviated multiple signs of neuronal hyperexcitability. The results suggest that astrocyte activation drives hyperexcitability during AD through a mechanism involving aberrant CN/NFAT signaling and impaired glutamate transport.
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Hunsberger HC, Setti SE, Heslin RT, Quintero JE, Gerhardt GA, Reed MN. Using Enzyme-based Biosensors to Measure Tonic and Phasic Glutamate in Alzheimer's Mouse Models. J Vis Exp 2017. [PMID: 28518111 DOI: 10.3791/55418] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Neurotransmitter disruption is often a key component of diseases of the central nervous system (CNS), playing a role in the pathology underlying Alzheimer's disease, Parkinson's disease, depression, and anxiety. Traditionally, microdialysis has been the most common (lauded) technique to examine neurotransmitter changes that occur in these disorders. But because microdialysis has the ability to measure slow 1-20 minute changes across large areas of tissue, it has the disadvantage of invasiveness, potentially destroying intrinsic connections within the brain and a slow sampling capability. A relatively newer technique, the microelectrode array (MEA), has numerous advantages for measuring specific neurotransmitter changes within discrete brain regions as they occur, making for a spatially and temporally precise approach. In addition, using MEAs is minimally invasive, allowing for measurement of neurotransmitter alterations in vivo. In our laboratory, we have been specifically interested in changes in the neurotransmitter, glutamate, related to Alzheimer's disease pathology. As such, the method described here has been used to assess potential hippocampal disruptions in glutamate in a transgenic mouse model of Alzheimer's disease. Briefly, the method used involves coating a multi-site microelectrode with an enzyme very selective for the neurotransmitter of interest and using self-referencing sites to subtract out background noise and interferents. After plating and calibration, the MEA can be constructed with a micropipette and lowered into the brain region of interest using a stereotaxic device. Here, the method described involves anesthetizing rTg(TauP301L)4510 mice and using a stereotaxic device to precisely target sub-regions (DG, CA1, and CA3) of the hippocampus.
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Affiliation(s)
| | - Sharay E Setti
- Department of Drug Discovery & Development, Auburn University
| | - Ryan T Heslin
- Department of Drug Discovery & Development, Auburn University
| | - Jorge E Quintero
- Department of Neuroscience, University of Kentucky Medical Center
| | - Greg A Gerhardt
- Department of Neuroscience, University of Kentucky Medical Center
| | - Miranda N Reed
- Department of Drug Discovery & Development, Auburn University;
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Xi Z, Deng W, Wang L, Xiao F, Li J, Wang Z, Wang X, Mi X, Wang N, Wang X. Association of Alpha-Soluble NSF Attachment Protein with Epileptic Seizure. J Mol Neurosci 2015; 57:417-25. [DOI: 10.1007/s12031-015-0596-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2015] [Accepted: 06/02/2015] [Indexed: 01/02/2023]
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10
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DiNuzzo M, Mangia S, Maraviglia B, Giove F. Physiological bases of the K+ and the glutamate/GABA hypotheses of epilepsy. Epilepsy Res 2014; 108:995-1012. [PMID: 24818957 DOI: 10.1016/j.eplepsyres.2014.04.001] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Revised: 03/20/2014] [Accepted: 04/01/2014] [Indexed: 01/19/2023]
Abstract
Epilepsy is a heterogeneous family of neurological disorders that manifest as seizures, i.e. the hypersynchronous activity of large population of neurons. About 30% of epileptic patients do not respond to currently available antiepileptic drugs. Decades of intense research have elucidated the involvement of a number of possible signaling pathways, however, at present we do not have a fundamental understanding of epileptogenesis. In this paper, we review the literature on epilepsy under a wide-angle perspective, a mandatory choice that responds to the recurrent and unanswered question about what is epiphenomenal and what is causal to the disease. While focusing on the involvement of K+ and glutamate/GABA in determining neuronal hyperexcitability, emphasis is given to astrocytic contribution to epileptogenesis, and especially to loss-of-function of astrocytic glutamine synthetase following reactive astrogliosis, a hallmark of epileptic syndromes. We finally introduce the potential involvement of abnormal glycogen synthesis induced by excess glutamate in increasing susceptibility to seizures.
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Affiliation(s)
- Mauro DiNuzzo
- MARBILab, Museo storico della fisica e Centro di studi e ricerche "Enrico Fermi", Rome, Italy.
| | - Silvia Mangia
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, USA
| | - Bruno Maraviglia
- Dipartimento di Fisica, Sapienza Università di Roma, Rome, Italy; Fondazione Santa Lucia IRCCS, Rome, Italy
| | - Federico Giove
- MARBILab, Museo storico della fisica e Centro di studi e ricerche "Enrico Fermi", Rome, Italy; Dipartimento di Fisica, Sapienza Università di Roma, Rome, Italy
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Burmeister JJ, Davis VA, Quintero JE, Pomerleau F, Huettl P, Gerhardt GA. Glutaraldehyde cross-linked glutamate oxidase coated microelectrode arrays: selectivity and resting levels of glutamate in the CNS. ACS Chem Neurosci 2013; 4:721-8. [PMID: 23650904 DOI: 10.1021/cn4000555] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Glutaraldehyde is widely used as a cross-linking agent for enzyme immobilization onto microelectrodes. Recent studies and prior reports indicate changes in enzyme activity and selectivity with certain glutaraldehyde cross-linking procedures that may jeopardize the performance of microelectrode recordings and lead to falsely elevated responses in biological systems. In this study, the sensitivity of glutaraldehyde cross-linked glutamate oxidase-based microelectrode arrays to 22 amino acids was tested and compared to glutamate. As expected, responses to electroactive amino acids (Cys, Tyr, Trp) were detected at both nonenzyme-coated and enzyme-coated microelectrodes sites, while the remaining amino acids yielded no detectable responses. Electroactive amino acids were effectively blocked with a m-phenylene diamine (mPD) layer and, subsequently, no responses were detected. Preliminary results on the use of poly(ethylene glycol) diglycidyl ether (PEGDE) as a potentially more reliable cross-linking agent for the immobilization of glutamate oxidase onto ceramic-based microelectrode arrays are reported and show no significant advantages over glutaraldehyde as we observe comparable selectivities and responses. These results support that glutaraldehyde-cross-linked glutamate oxidase retains sufficient enzyme specificity for accurate in vivo brain measures of tonic and phasic glutamate levels when immobilized using specific "wet" coating procedures.
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Affiliation(s)
- Jason J. Burmeister
- Department
of Anatomy and Neurobiology, Parkinson’s Disease Translational
Research Center of Excellence, ‡Center for Microelectrode Technology, University of Kentucky, Lexington, Kentucky 40536-0098, United States
| | - Verda A. Davis
- Department
of Anatomy and Neurobiology, Parkinson’s Disease Translational
Research Center of Excellence, ‡Center for Microelectrode Technology, University of Kentucky, Lexington, Kentucky 40536-0098, United States
| | - Jorge E. Quintero
- Department
of Anatomy and Neurobiology, Parkinson’s Disease Translational
Research Center of Excellence, ‡Center for Microelectrode Technology, University of Kentucky, Lexington, Kentucky 40536-0098, United States
| | - Francois Pomerleau
- Department
of Anatomy and Neurobiology, Parkinson’s Disease Translational
Research Center of Excellence, ‡Center for Microelectrode Technology, University of Kentucky, Lexington, Kentucky 40536-0098, United States
| | - Peter Huettl
- Department
of Anatomy and Neurobiology, Parkinson’s Disease Translational
Research Center of Excellence, ‡Center for Microelectrode Technology, University of Kentucky, Lexington, Kentucky 40536-0098, United States
| | - Greg A. Gerhardt
- Department
of Anatomy and Neurobiology, Parkinson’s Disease Translational
Research Center of Excellence, ‡Center for Microelectrode Technology, University of Kentucky, Lexington, Kentucky 40536-0098, United States
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12
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Persistent receptor activity underlies group I mGluR-mediated cellular plasticity in CA3 neuron. J Neurosci 2013; 33:2526-40. [PMID: 23392681 DOI: 10.1523/jneurosci.3338-12.2013] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Plastic changes in cortical activities induced by group I metabotropic glutamate receptor (mGluR) stimulation include epileptogenesis, expressed in vitro as the conversion of normal neuronal activity to persistent, prolonged synchronized (ictal) discharges. At present, the mechanism that maintains group I mGluR-induced plasticity is not known. We examined this issue using hippocampal slices from guinea pigs and mice. Agonist [(S)-3,5-dihydroxyphenylglycine (DHPG), 30-50 μm)] stimulation of group I mGluRs induces persistent prolonged synchronized (ictal-like) discharges in CA3 that are associated with three identified excitatory cellular responses-suppression of spike afterhyperpolarizations, activation of a voltage-dependent cationic current, and increase in neuronal input resistance. Persistent prolonged synchronized discharges and the underlying excitatory cellular responses maintained following induction were reversibly blocked by mGluR1 antagonists [(S)-+-α-amino-4-carboxy-2-methylbenzeneacetic acid (LY 367385), 50, 100 μm; CPCCOEt (hydroxyimino)cyclopropa[b]chromen-1a-carboxylate ethyl ester, 100 μm], and to a lesser extent by the mGluR5 antagonist MPEP [2-methyl-6-(phenylethynyl)pyridine hydrochloride, 50 μm]. Activation of persistent cellular responses to DHPG were unaffected by tetrodotoxin (0.5-1 μm) or perfusion with low Ca(2+)(0.2 mm)-Mn(2+)(0.5 mm) media-conditions that suppress endogenous glutamate release. The pharmacological profile of the blocking action of the group I mGluR antagonist MCPG [(RS)-α-methyl-4-carboxyphenylglycine, 50-500 μm] on persistent cellular responses was different from that on cellular responses directly activated by DHPG. These data indicate that transient stimulation of group I mGluRs alters receptor properties, rendering them persistently active in the absence of applied agonist or endogenous glutamate activation. Persistent receptor activities, primarily involving mGluR1, maintain excitatory cellular responses and emergent prolonged synchronized discharges.
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13
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Schiro PG, Gadd JC, Yen GS, Chiu DT. High-throughput fluorescence-activated nanoscale subcellular sorter with single-molecule sensitivity. J Phys Chem B 2012; 116:10490-5. [PMID: 22574902 DOI: 10.1021/jp3019233] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Recent single-cell and single-molecule studies have shown that a variety of subpopulations exist within biological systems, such as synaptic vesicles, that have previously been overlooked in common bulk studies. By isolating and enriching these various subpopulations, detailed analysis with a variety of analytical techniques can be done to further understand the role that various subpopulations play in cellular dynamics and how alterations to these subpopulations affect the overall function of the biological system. Previous sorters lack the sensitivity, sorting speed, and efficiency to isolate synaptic vesicles and other nanoscale systems. This paper describes the development of a fluorescence-activated nanoscale subcellular sorter that can sort nearly 10 million objects per hour with single-molecule sensitivity. Utilizing a near-nanoscale channel system, we were able to achieve upward of 91% recovery of desired objects with a 99.7% purity.
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Affiliation(s)
- Perry G Schiro
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
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Matveeva EA, Price DA, Whiteheart SW, Vanaman TC, Gerhardt GA, Slevin JT. Reduction of vesicle-associated membrane protein 2 expression leads to a kindling-resistant phenotype in a murine model of epilepsy. Neuroscience 2011; 202:77-86. [PMID: 22183055 DOI: 10.1016/j.neuroscience.2011.11.055] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2011] [Revised: 11/23/2011] [Accepted: 11/24/2011] [Indexed: 11/13/2022]
Abstract
Our previous work has correlated permanent alterations in the rat neurosecretory machinery with epileptogenesis. Such findings highlighted the need for a greater understanding of the molecular mechanisms underlying epilepsy so that novel therapeutic regimens can be designed. To this end, we examined kindling in transgenic mice with a defined reduction of a key element of the neurosecretory machinery: the v-SNARE (vesicle-bound SNAP [soluble NSF attachment protein] receptor), synaptobrevin/vesicle-associated membrane protein 2 (VAMP2). Initial analysis of biochemical markers, which previously displayed kindling-dependent alterations in rat hippocampal synaptosomes, showed similar trends in both wild-type and VAMP2(+/-) mice, demonstrating that kindled rat and mouse models are comparable. This report focuses on the effects that a ~50% reduction of synaptosomal VAMP2 has on the progression of electrical kindling and on glutamate release in hippocampal subregions. Our studies show that epileptogenesis is dramatically attenuated in VAMP2(+/-) mice, requiring both higher current and more stimulations to reach a fully kindled state (two successive Racine stage 5 seizures). Progression through the five identifiable Racine stages was slower and more variable in the VAMP2(+/-) animals compared with the almost linear progression seen in wild-type littermates. Consistent with the expected effects of reducing a major neuronal v-SNARE, glutamate-selective, microelectrode array (MEA) measurements in specific hippocampal subregions of VAMP2(+/-) mice showed significant reductions in potassium-evoked glutamate release. Taken together these studies demonstrate that manipulating the levels of the neurosecretory machinery not only affects neurotransmitter release but also mitigates kindling-induced epileptogenesis.
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Affiliation(s)
- E A Matveeva
- Department of Molecular and Cellular Biochemistry, University of Kentucky Medical Center, Lexington, KY, USA
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