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Fernandes E, Ledo A, Gerhardt GA, Barbosa RM. Amperometric bio-sensing of lactate and oxygen concurrently with local field potentials during status epilepticus. Talanta 2024; 268:125302. [PMID: 37826935 PMCID: PMC11164042 DOI: 10.1016/j.talanta.2023.125302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Revised: 10/03/2023] [Accepted: 10/07/2023] [Indexed: 10/14/2023]
Abstract
Epilepsy is a prevalent neurological disorder with a complex pathogenesis and unpredictable nature, presenting limited treatment options in >30 % of affected individuals. Neurometabolic abnormalities have been observed in epilepsy patients, suggesting a disruption in the coupling between neural activity and energy metabolism in the brain. In this study, we employed amperometric biosensors based on a modified carbon fiber microelectrode platform to directly and continuously measure lactate and oxygen dynamics in the brain extracellular space. These biosensors demonstrated high sensitivity, selectivity, and rapid response time, enabling in vivo measurements with high temporal and spatial resolution. In vivo recordings in the cortex of anaesthetized rats revealed rapid and multiphasic fluctuations in extracellular lactate and oxygen levels following neuronal stimulation with high potassium. Furthermore, real-time measurement of lactate and oxygen concentration dynamics concurrently with network electrical activity during status epilepticus induced by 4-aminopyridine (4-AP) demonstrated phasic changes in lactate levels that correlated with bursts of electrical activity, while tonic levels of lactate remained stable during seizures. This study highlights the complex interplay between lactate dynamics, electrical activity, and oxygen utilization in epileptic seizures.
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Affiliation(s)
- Eliana Fernandes
- University of Coimbra, Faculty of Pharmacy, Health Sciences Campus, Azinhaga de Santa Comba, 3000-548, Coimbra, Portugal; Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504, Coimbra, Portugal
| | - Ana Ledo
- University of Coimbra, Faculty of Pharmacy, Health Sciences Campus, Azinhaga de Santa Comba, 3000-548, Coimbra, Portugal; Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504, Coimbra, Portugal
| | - Greg A Gerhardt
- Center for Microelectrode Technology (CenMeT), Department of Neuroscience, University of Kentucky Medical Center, Lexington, KY, 40536, United States
| | - Rui M Barbosa
- University of Coimbra, Faculty of Pharmacy, Health Sciences Campus, Azinhaga de Santa Comba, 3000-548, Coimbra, Portugal; Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504, Coimbra, Portugal.
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2
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Abulseoud OA, Alasmari F, Hussein AM, Sari Y. Ceftriaxone as a Novel Therapeutic Agent for Hyperglutamatergic States: Bridging the Gap Between Preclinical Results and Clinical Translation. Front Neurosci 2022; 16:841036. [PMID: 35864981 PMCID: PMC9294323 DOI: 10.3389/fnins.2022.841036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Accepted: 06/07/2022] [Indexed: 12/02/2022] Open
Abstract
Dysregulation of glutamate homeostasis is a well-established core feature of neuropsychiatric disorders. Extracellular glutamate concentration is regulated by glutamate transporter 1 (GLT-1). The discovery of a beta-lactam antibiotic, ceftriaxone (CEF), as a safe compound with unique ability to upregulate GLT-1 sparked the interest in testing its efficacy as a novel therapeutic agent in animal models of neuropsychiatric disorders with hyperglutamatergic states. Indeed, more than 100 preclinical studies have shown the efficacy of CEF in attenuating the behavioral manifestations of various hyperglutamatergic brain disorders such as ischemic stroke, amyotrophic lateral sclerosis (ALS), seizure, Huntington’s disease, and various aspects of drug use disorders. However, despite rich and promising preclinical data, only one large-scale clinical trial testing the efficacy of CEF in patients with ALS is reported. Unfortunately, in that study, there was no significant difference in survival between placebo- and CEF-treated patients. In this review, we discussed the translational potential of preclinical efficacy of CEF based on four different parameters: (1) initiation of CEF treatment in relation to induction of the hyperglutamatergic state, (2) onset of response in preclinical models in relation to onset of GLT-1 upregulation, (3) mechanisms of action of CEF on GLT-1 expression and function, and (4) non-GLT-1-mediated mechanisms for CEF. Our detailed review of the literature brings new insights into underlying molecular mechanisms correlating the preclinical efficacy of CEF. We concluded here that CEF may be clinically effective in selected cases in acute and transient hyperglutamatergic states such as early drug withdrawal conditions.
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Affiliation(s)
- Osama A. Abulseoud
- Department of Psychiatry and Psychology, Alex School of Medicine at Mayo Clinic, Phoenix, AZ, United States
- *Correspondence: Osama A. Abulseoud,
| | - Fawaz Alasmari
- Department of Pharmacology and Experimental Therapeutics, University of Toledo, Toledo, OH, United States
- Department of Pharmacology and Toxicology, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Abdelaziz M. Hussein
- Department of Medical Physiology, Faculty of Medicine, Mansoura University, Mansoura, Egypt
| | - Youssef Sari
- Department of Pharmacology and Experimental Therapeutics, University of Toledo, Toledo, OH, United States
- Youssef Sari,
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3
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Hascup ER, Sime LN, Peck MR, Hascup KN. Amyloid-β 42 stimulated hippocampal lactate release is coupled to glutamate uptake. Sci Rep 2022; 12:2775. [PMID: 35177691 PMCID: PMC8854608 DOI: 10.1038/s41598-022-06637-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Accepted: 02/03/2022] [Indexed: 12/05/2022] Open
Abstract
Since brain glucose hypometabolism is a feature of Alzheimer’s disease (AD) progression, lactate utilization as an energy source may become critical to maintaining central bioenergetics. We have previously shown that soluble amyloid-β (Aβ)42 stimulates glutamate release through the α7 nicotinic acetylcholine receptor (α7nAChR) and hippocampal glutamate levels are elevated in the APP/PS1 mouse model of AD. Accordingly, we hypothesized that increased glutamate clearance contributes to elevated extracellular lactate levels through activation of the astrocyte neuron lactate shuttle (ANLS). We utilized an enzyme-based microelectrode array (MEA) selective for measuring basal and phasic extracellular hippocampal lactate in male and female C57BL/6J mice. Although basal lactate was similar, transient lactate release varied across hippocampal subregions with the CA1 > CA3 > dentate for both sexes. Local application of Aβ42 stimulated lactate release throughout the hippocampus of male mice, but was localized to the CA1 of female mice. Coapplication with a nonselective glutamate or lactate transport inhibitor blocked these responses. Expression levels of SLC16A1, lactate dehydrogenase (LDH) A, and B were elevated in female mice which may indicate compensatory mechanisms to upregulate lactate production, transport, and utilization. Enhancement of the ANLS by Aβ42-stimulated glutamate release during AD progression may contribute to bioenergetic dysfunction in AD.
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Affiliation(s)
- Erin R Hascup
- Department of Neurology, Dale and Deborah Smith Center for Alzheimer's Research and Treatment, Neurosciences Institute, Southern Illinois University School of Medicine, P.O. Box 19628, Springfield, IL, 62794-9628, USA.,Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL, USA
| | - Lindsey N Sime
- Department of Neurology, Dale and Deborah Smith Center for Alzheimer's Research and Treatment, Neurosciences Institute, Southern Illinois University School of Medicine, P.O. Box 19628, Springfield, IL, 62794-9628, USA
| | - Mackenzie R Peck
- Department of Neurology, Dale and Deborah Smith Center for Alzheimer's Research and Treatment, Neurosciences Institute, Southern Illinois University School of Medicine, P.O. Box 19628, Springfield, IL, 62794-9628, USA
| | - Kevin N Hascup
- Department of Neurology, Dale and Deborah Smith Center for Alzheimer's Research and Treatment, Neurosciences Institute, Southern Illinois University School of Medicine, P.O. Box 19628, Springfield, IL, 62794-9628, USA. .,Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL, USA. .,Department of Medical Microbiology, Immunology and Cell Biology, Southern Illinois University School of Medicine, Springfield, IL, USA.
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4
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Jiao D, Qi L, Hu L, Hu D, Li X, Li G, Li Z, Liu S, Zhao C, Wu H. Changes in aging-induced kidney dysfunction in mice based on a metabolomics analysis. Front Endocrinol (Lausanne) 2022; 13:959311. [PMID: 36157455 PMCID: PMC9492839 DOI: 10.3389/fendo.2022.959311] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Accepted: 08/05/2022] [Indexed: 11/13/2022] Open
Abstract
Kidney dysfunction is particularly important in systemic organ injuries caused by aging. Metabolomics are utilized in this study to explore the mechanism of kidney dysfunction during aging by the identification of metabolites and the characterization of metabolic pathways. We analyzed the serum biochemistry and kidney histopathology of male Kunming mice aged 3 months and 24 months and found that the aged mice had inflammatory lesions, aggravated fibrosis, and functional impairment. A high-resolution untargeted metabolomics analysis revealed that the endogenous metabolites in the kidneys and urine of the mice were significantly changed by 25 and 20 metabolites, respectively. A pathway analysis of these differential metabolites revealed six key signaling pathways, namely, D-glutamine and D-glutamate metabolism, purine metabolism, the citrate cycle [tricarboxylic acid (TCA) cycle], histidine metabolism, pyruvate metabolism, and glyoxylate and dicarboxylate metabolism. These pathways are involved in amino acid metabolism, carbohydrate metabolism, and nucleotide metabolism, and these can lead to immune regulation, inflammatory responses, oxidative stress damage, cellular dysfunction, and bioenergy disorders, and they are closely associated with aging and kidney insufficiency. We also screened nine types of sensitive metabolites in the urine as potential biomarkers of kidney dysfunction during the aging process to confirm their therapeutic targets in senior-induced kidney dysfunction and to improve the level of risk assessment for senile kidney injury.
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Affiliation(s)
- Danli Jiao
- School of Acupuncture-Moxibustion and Tuina, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Li Qi
- Institute of Interdisciplinary Integrative Medicine Research, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Li Hu
- School of Acupuncture-Moxibustion and Tuina, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Dan Hu
- School of Acupuncture-Moxibustion and Tuina, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Xiao Li
- School of Acupuncture-Moxibustion and Tuina, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Guona Li
- School of Acupuncture-Moxibustion and Tuina, Shanghai University of Traditional Chinese Medicine, Shanghai, China
- Key Laboratory of Acupuncture and Immunological Effects, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Zheying Li
- School of Acupuncture-Moxibustion and Tuina, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Shimin Liu
- School of Acupuncture-Moxibustion and Tuina, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Chen Zhao
- School of Acupuncture-Moxibustion and Tuina, Shanghai University of Traditional Chinese Medicine, Shanghai, China
- *Correspondence: Chen Zhao, ; Huangan Wu,
| | - Huangan Wu
- Key Laboratory of Acupuncture and Immunological Effects, Shanghai University of Traditional Chinese Medicine, Shanghai, China
- *Correspondence: Chen Zhao, ; Huangan Wu,
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5
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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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6
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Kuhlmann L, Lehnertz K, Richardson MP, Schelter B, Zaveri HP. Seizure prediction - ready for a new era. Nat Rev Neurol 2019; 14:618-630. [PMID: 30131521 DOI: 10.1038/s41582-018-0055-2] [Citation(s) in RCA: 191] [Impact Index Per Article: 38.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Epilepsy is a common disorder characterized by recurrent seizures. An overwhelming majority of people with epilepsy regard the unpredictability of seizures as a major issue. More than 30 years of international effort have been devoted to the prediction of seizures, aiming to remove the burden of unpredictability and to couple novel, time-specific treatment to seizure prediction technology. A highly influential review published in 2007 concluded that insufficient evidence indicated that seizures could be predicted. Since then, several advances have been made, including successful prospective seizure prediction using intracranial EEG in a small number of people in a trial of a real-time seizure prediction device. In this Review, we examine advances in the field, including EEG databases, seizure prediction competitions, the prospective trial mentioned and advances in our understanding of the mechanisms of seizures. We argue that these advances, together with statistical evaluations, set the stage for a resurgence in efforts towards the development of seizure prediction methodologies. We propose new avenues of investigation involving a synergy between mechanisms, models, data, devices and algorithms and refine the existing guidelines for the development of seizure prediction technology to instigate development of a solution that removes the burden of the unpredictability of seizures.
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Affiliation(s)
- Levin Kuhlmann
- Centre for Human Psychopharmacology, Swinburne University of Technology, Melbourne, Victoria, Australia.,Department of Medicine - St. Vincent's, The University of Melbourne, Parkville, Victoria, Australia.,Department of Biomedical Engineering, The University of Melbourne, Parkville, Victoria, Australia
| | - Klaus Lehnertz
- Department of Epileptology, University of Bonn, Bonn, Germany. .,Interdisciplinary Center for Complex Systems, University of Bonn, Bonn, Germany.
| | - Mark P Richardson
- Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
| | - Björn Schelter
- Institute for Complex Systems and Mathematical Biology, University of Aberdeen, Aberdeen, UK
| | - Hitten P Zaveri
- Department of Neurology, Yale University, New Haven, CT, USA
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7
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Lieb A, Weston M, Kullmann DM. Designer receptor technology for the treatment of epilepsy. EBioMedicine 2019; 43:641-649. [PMID: 31078519 PMCID: PMC6558262 DOI: 10.1016/j.ebiom.2019.04.059] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 04/26/2019] [Accepted: 04/29/2019] [Indexed: 12/20/2022] Open
Abstract
Epilepsy remains refractory to medical treatment in ~30% of patients despite decades of new drug development. Neurosurgery to remove or disconnect the seizure focus is often curative but frequently contraindicated by risks of irreversible impairment to brain function. Novel therapies are therefore required that better balance seizure suppression against the risks of side effects. Among experimental gene therapies, chemogenetics has the major advantage that the action on the epileptogenic zone can be modulated on demand. Two broad approaches are to use a designer G-protein-coupled receptor or a modified ligand gated ion channel, targeted to specific neurons in the epileptogenic zone using viral vectors and cell-type selective promoters. The receptor can be activated on demand by either an exogenous compound or by pathological levels of extracellular glutamate that occur in epileptogenic tissue. We review the principal designer receptor technologies and their modes of action. We compare the drawbacks and benefits of each designer receptor with particular focus on the drug activators and the potential for clinical translation in epilepsy. Inhibitory designer receptors (DRs) allow on-demand suppression of seizures upon activation by exogenous drugs or endogenous neurotransmitters. DRs include modified G-protein coupled receptors, chimaeric ligand-gated ion channels, and mutated non-mammalian channels. Identification of drug activators of DRs that are already approved for use in humans significantly accelerates clinical translation.
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Affiliation(s)
- Andreas Lieb
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, University College London, UK
| | - Mikail Weston
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, University College London, UK
| | - Dimitri M Kullmann
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, University College London, UK.
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8
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Lieb A, Qiu Y, Dixon CL, Heller JP, Walker MC, Schorge S, Kullmann DM. Biochemical autoregulatory gene therapy for focal epilepsy. Nat Med 2018; 24:1324-1329. [PMID: 29988123 PMCID: PMC6152911 DOI: 10.1038/s41591-018-0103-x] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Accepted: 05/17/2018] [Indexed: 11/14/2022]
Abstract
Despite the introduction of more than one dozen new antiepileptic drugs in the past 20 years, approximately one-third of people who develop epilepsy continue to have seizures on mono- or polytherapy1. Viral-vector-mediated gene transfer offers the opportunity to design a rational treatment that builds on mechanistic understanding of seizure generation and that can be targeted to specific neuronal populations in epileptogenic foci2. Several such strategies have shown encouraging results in different animal models, although clinical translation is limited by possible effects on circuits underlying cognitive, mnemonic, sensory or motor function. Here, we describe an autoregulatory antiepileptic gene therapy, which relies on neuronal inhibition in response to elevations in extracellular glutamate. It is effective in a rodent model of focal epilepsy and is well tolerated, thus lowering the barrier to clinical translation.
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Affiliation(s)
- Andreas Lieb
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, University College London, London, UK.
| | - Yichen Qiu
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, University College London, London, UK
| | - Christine L Dixon
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, University College London, London, UK
| | - Janosch P Heller
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, University College London, London, UK
| | - Matthew C Walker
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, University College London, London, UK
| | - Stephanie Schorge
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, University College London, London, UK
| | - Dimitri M Kullmann
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, University College London, London, UK.
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9
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Batten SR, Pomerleau F, Quintero J, Gerhardt GA, Beckmann JS. The role of glutamate signaling in incentive salience: second-by-second glutamate recordings in awake Sprague-Dawley rats. J Neurochem 2018; 145:276-286. [PMID: 29315659 DOI: 10.1111/jnc.14298] [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: 08/16/2017] [Revised: 01/02/2018] [Accepted: 01/04/2018] [Indexed: 11/29/2022]
Abstract
The attribution of incentive salience to reward-predictive stimuli has been shown to be associated with substance abuse-like behavior such as increased drug taking. Evidence suggests that glutamate neurotransmission and sequential N-methyl-D-aspartate (NMDA) activation are involved in the attribution of incentive salience. Here, we further explore the role of second-by-second glutamate neurotransmission in the attribution of incentive salience to reward-predictive stimuli by measuring sign-tracking behavior during a Pavlovian conditioned approach procedure using ceramic-based microelectrode arrays configured for sensitive measures of extracellular glutamate in awake behaving Sprague-Dawley rats. Specifically, we show that there is an increase in extracellular glutamate levels in the prelimbic cortex (PrL) and the nucleus accumbens core (NAcC) during sign-tracking behavior to a food-predictive conditioned stimulus (CS+) compared to the presentation of a non-predictive conditioned stimulus (CS-). Furthermore, the results indicate greater increases in extracellular glutamate levels in the PrL compared to NAcC in response to the CS+, including differences in glutamate release and signal decay. Taken together, the present research suggests that there is differential glutamate signaling in the NAcC and PrL during sign-tracking behavior to a food-predictive CS+.
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Affiliation(s)
- Seth R Batten
- Department of Psychology, University of Kentucky, College of Arts and Sciences, Lexington, Kentucky, USA
| | - Francois Pomerleau
- Department of Neuroscience, University of Kentucky, College of Medicine, Lexington, Kentucky, USA
| | - Jorge Quintero
- Department of Neuroscience, University of Kentucky, College of Medicine, Lexington, Kentucky, USA
| | - Greg A Gerhardt
- Department of Neuroscience, University of Kentucky, College of Medicine, Lexington, Kentucky, USA
| | - Joshua S Beckmann
- Department of Psychology, University of Kentucky, College of Arts and Sciences, Lexington, Kentucky, USA
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10
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Setti SE, Hunsberger HC, Reed MN. Alterations in Hippocampal Activity and Alzheimer's Disease. TRANSLATIONAL ISSUES IN PSYCHOLOGICAL SCIENCE 2017; 3:348-356. [PMID: 29862310 DOI: 10.1037/tps0000124] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The aging population and those with amnestic mild cognitive impairment (aMCI) are at increased risk for developing Alzheimer's disease (AD). Individuals with aMCI in particular may display pathological changes in brain function that may ultimately result in a diagnosis of AD. This review focuses specifically on hippocampal hyperexcitability, a pathology that is sometimes detectable years before diagnosis, which has been observed in individuals with aMCI. We describe how changes in hippocampal activity are associated with, or in some cases may be permissive for, the development of AD. Finally, we describe how lifestyle changes, including exercise and dietary changes can attenuate cognitive decline and hippocampal hyperexcitability, potentially reducing the risk of developing AD.
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Affiliation(s)
- Sharay E Setti
- Department of Drug Discovery & Development, Auburn University
| | - Holly C Hunsberger
- Department of Psychiatry, Columbia University.,Department of Psychology, West Virginia University
| | - Miranda N Reed
- Department of Drug Discovery & Development, Auburn University
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11
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Li DH, Yang XF. Remote modulation of network excitability during deep brain stimulation for epilepsy. Seizure 2017; 47:42-50. [DOI: 10.1016/j.seizure.2017.02.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Revised: 01/20/2017] [Accepted: 02/28/2017] [Indexed: 12/18/2022] Open
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12
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Hunsberger HC, Konat GW, Reed MN. Peripheral viral challenge elevates extracellular glutamate in the hippocampus leading to seizure hypersusceptibility. J Neurochem 2017; 141:341-346. [PMID: 28244106 DOI: 10.1111/jnc.13999] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 01/25/2017] [Accepted: 02/21/2017] [Indexed: 12/27/2022]
Abstract
Peripheral viral infections increase seizure propensity and intensity in susceptible individuals. We have modeled this comorbidity by demonstrating that the acute phase response instigated by an intraperitoneal (i.p.) injection of a viral mimetic, polyinosinic-polycytidylic acid (PIC), induces protracted hypersusceptibility to kainic acid-induced seizures. We have further demonstrated that PIC challenge robustly increases the level of tonic extracellular glutamate and neuronal excitability in the hippocampus. This study was undertaken to determine a relationship between tonic glutamate and seizure susceptibility following PIC challenge. Briefly, glutamate-sensing microelectrodes were permanently implanted into the CA1 of 8-week-old female C57BL/6 mice. Following a 3-day recovery, acute phase response was induced by i.p. injection of 12 mg/kg of PIC, while saline-injected mice served as controls. Tonic glutamate was measured at 1, 2, 3 and 4 days after PIC challenge. PIC challenge induced an approximately fourfold increase in tonic glutamate levels measured after 24 h. The levels gradually declined to the baseline values within 4 days. Twenty-four hours after PIC challenge, the mice featured an approximately threefold increase in cumulative seizure scores and twofold increase in the duration of status epilepticus induced by subcutaneous injection of 12 mg/kg of kainic acid. Seizure scores positively correlated with pre-seizure tonic glutamate. Moreover, seizures resulted in a profound (76%) elevation of extracellular glutamate in the CA1 of PIC-challenged but not saline-injected mice. Our results implicate the increase in extracellular glutamate as a mediator of seizure hypersusceptibility induced by peripheral viral challenge.
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Affiliation(s)
- Holly C Hunsberger
- Department of Neurobiology and Anatomy, School of Medicine, West Virginia University, Morgantown, West Virginia, USA
| | - Gregory W Konat
- Drug Discovery and Development, School of Pharmacy, Auburn University, Auburn, Alabama, USA
| | - Miranda N Reed
- Department of Neurobiology and Anatomy, School of Medicine, West Virginia University, Morgantown, West Virginia, USA
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Deeb W, Giordano JJ, Rossi PJ, Mogilner AY, Gunduz A, Judy JW, Klassen BT, Butson CR, Van Horne C, Deny D, Dougherty DD, Rowell D, Gerhardt GA, Smith GS, Ponce FA, Walker HC, Bronte-Stewart HM, Mayberg HS, Chizeck HJ, Langevin JP, Volkmann J, Ostrem JL, Shute JB, Jimenez-Shahed J, Foote KD, Wagle Shukla A, Rossi MA, Oh M, Pourfar M, Rosenberg PB, Silburn PA, de Hemptine C, Starr PA, Denison T, Akbar U, Grill WM, Okun MS. Proceedings of the Fourth Annual Deep Brain Stimulation Think Tank: A Review of Emerging Issues and Technologies. Front Integr Neurosci 2016; 10:38. [PMID: 27920671 PMCID: PMC5119052 DOI: 10.3389/fnint.2016.00038] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Accepted: 11/01/2016] [Indexed: 02/02/2023] Open
Abstract
This paper provides an overview of current progress in the technological advances and the use of deep brain stimulation (DBS) to treat neurological and neuropsychiatric disorders, as presented by participants of the Fourth Annual DBS Think Tank, which was convened in March 2016 in conjunction with the Center for Movement Disorders and Neurorestoration at the University of Florida, Gainesveille FL, USA. The Think Tank discussions first focused on policy and advocacy in DBS research and clinical practice, formation of registries, and issues involving the use of DBS in the treatment of Tourette Syndrome. Next, advances in the use of neuroimaging and electrochemical markers to enhance DBS specificity were addressed. Updates on ongoing use and developments of DBS for the treatment of Parkinson's disease, essential tremor, Alzheimer's disease, depression, post-traumatic stress disorder, obesity, addiction were presented, and progress toward innovation(s) in closed-loop applications were discussed. Each section of these proceedings provides updates and highlights of new information as presented at this year's international Think Tank, with a view toward current and near future advancement of the field.
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Affiliation(s)
- Wissam Deeb
- Department of Neurology, Center for Movement Disorders and Neurorestoration, University of Florida Gainesville, FL, USA
| | - James J Giordano
- Department of Neurology, and Neuroethics Studies Program, Pellegrino Center for Clinical Bioethics, Georgetown University Medical Center Washington, DC, USA
| | - Peter J Rossi
- Department of Neurology, Center for Movement Disorders and Neurorestoration, University of Florida Gainesville, FL, USA
| | - Alon Y Mogilner
- Department of Neurosurgery, Center for Neuromodulation, New York University Langone Medical Center New York, NY, USA
| | - Aysegul Gunduz
- Department of Neurology, Center for Movement Disorders and Neurorestoration, University of FloridaGainesville, FL, USA; J. Crayton Pruitt Family Department of Biomedical Engineering, University of FloridaGainesville, FL, USA
| | - Jack W Judy
- Department of Neurology, Center for Movement Disorders and Neurorestoration, University of FloridaGainesville, FL, USA; J. Crayton Pruitt Family Department of Biomedical Engineering, University of FloridaGainesville, FL, USA
| | | | - Christopher R Butson
- Department of Bioengineering, Scientific Computing and Imaging Institute, University of Utah Salt Lake City, UT, USA
| | - Craig Van Horne
- Department of Neurosurgery, University of Kentucky Chandler Medical Center Lexington, KY, USA
| | - Damiaan Deny
- Department of Psychiatry, Academic Medical Center, University of Amsterdam Amsterdam, Netherlands
| | - Darin D Dougherty
- Department of Psychiatry, Massachusetts General Hospital Boston, MA, USA
| | - David Rowell
- Asia Pacific Centre for Neuromodulation, Queensland Brain Institute, The University of Queensland Brisbane, QLD, Australia
| | - Greg A Gerhardt
- Department of Anatomy and Neurobiology, University of Kentucky Chandler Medical Center Lexington, KY, USA
| | - Gwenn S Smith
- Departments of Psychiatry and Behavioral Sciences and Radiology and Radiological Sciences, Johns Hopkins University School of Medicine Baltimore, MD, USA
| | - Francisco A Ponce
- Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center Phoenix Arizona, AZ, USA
| | - Harrison C Walker
- Department of Neurology and Department of Biomedical Engineering, University of Alabama at Birmingham Birmingham, AL, USA
| | - Helen M Bronte-Stewart
- Departments of Neurology and Neurological Sciences and Neurosurgery, Stanford University Stanford, CA, USA
| | - Helen S Mayberg
- Department of Psychiatry, Emory University School of Medicine Atlanta, GA, USA
| | - Howard J Chizeck
- Electrical Engineering Department, University of WashingtonSeattle, WA, USA; NSF Engineering Research Center for Sensorimotor Neural EngineeringSeattle, WA, USA
| | - Jean-Philippe Langevin
- Department of Neurosurgery, VA Greater Los Angeles Healthcare System Los Angeles, CA, USA
| | - Jens Volkmann
- Department of Neurology, University Clinic of Würzburg Würzburg, Germany
| | - Jill L Ostrem
- Department of Neurology, University of California San Francisco San Francisco, CA, USA
| | - Jonathan B Shute
- J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida Gainesville, FL, USA
| | | | - Kelly D Foote
- Department of Neurology, Center for Movement Disorders and Neurorestoration, University of FloridaGainesville, FL, USA; Department of Neurological Sciences, University of FloridaGainesville, FL, USA
| | - Aparna Wagle Shukla
- Department of Neurology, Center for Movement Disorders and Neurorestoration, University of Florida Gainesville, FL, USA
| | - Marvin A Rossi
- Departments of Neurological Sciences, Diagnostic Radiology, and Nuclear Medicine, Rush University Medical Center Chicago, IL, USA
| | - Michael Oh
- Division of Functional Neurosurgery, Department of Neurosurgery, Allegheny General Hospital Pittsburgh, PA, USA
| | - Michael Pourfar
- Department of Neurology, New York University Langone Medical Center New York, NY, USA
| | - Paul B Rosenberg
- Psychiatry and Behavioral Sciences, Johns Hopkins Bayview Medical Center, Johns Hopkins School of Medicine Baltimore, MD, USA
| | - Peter A Silburn
- Asia Pacific Centre for Neuromodulation, Queensland Brain Institute, The University of Queensland Brisbane, QLD, Australia
| | - Coralie de Hemptine
- Graduate Program in Neuroscience, Department of Neurological Surgery, Kavli Institute for Fundamental Neuroscience, University of California, San Francisco San Francisco, CA, USA
| | - Philip A Starr
- Graduate Program in Neuroscience, Department of Neurological Surgery, Kavli Institute for Fundamental Neuroscience, University of California, San Francisco San Francisco, CA, USA
| | | | - Umer Akbar
- Movement Disorders Program, Department of Neurology, Alpert Medical School, Rhode Island Hospital, Brown University Providence, RI, USA
| | - Warren M Grill
- Department of Biomedical Engineering, Duke University Durham, NC, USA
| | - Michael S Okun
- Department of Neurology, Center for Movement Disorders and Neurorestoration, University of Florida Gainesville, FL, USA
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Hunsberger HC, Wang D, Petrisko TJ, Alhowail A, Setti SE, Suppiramaniam V, Konat GW, Reed MN. Peripherally restricted viral challenge elevates extracellular glutamate and enhances synaptic transmission in the hippocampus. J Neurochem 2016; 138:307-16. [PMID: 27168075 PMCID: PMC4936939 DOI: 10.1111/jnc.13665] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 05/05/2016] [Accepted: 05/09/2016] [Indexed: 01/23/2023]
Abstract
Peripheral infections increase the propensity and severity of seizures in susceptible populations. We have previously shown that intraperitoneal injection of a viral mimic, polyinosinic-polycytidylic acid (PIC), elicits hypersusceptibility of mice to kainic acid (KA)-induced seizures. This study was undertaken to determine whether this seizure hypersusceptibility entails alterations in glutamate signaling. Female C57BL/6 mice were intraperitoneally injected with PIC, and after 24 h, glutamate homeostasis in the hippocampus was monitored using the enzyme-based microelectrode arrays. PIC challenge robustly increased the level of resting extracellular glutamate. While pre-synaptic potassium-evoked glutamate release was not affected, glutamate uptake was profoundly impaired and non-vesicular glutamate release was augmented, indicating functional alterations of astrocytes. Electrophysiological examination of hippocampal slices from PIC-challenged mice revealed a several fold increase in the basal synaptic transmission as compared to control slices. PIC challenge also increased the probability of pre-synaptic glutamate release as seen from a reduction of paired-pulse facilitation and synaptic plasticity as seen from an enhancement of long-term potentiation. Altogether, our results implicate a dysregulation of astrocytic glutamate metabolism and an alteration of excitatory synaptic transmission as the underlying mechanism for the development of hippocampal hyperexcitability, and consequently seizure hypersusceptibility following peripheral PIC challenge. Peripheral infections/inflammations enhance seizure susceptibility. Here, we explored the effect of peritoneal inflammation induced by a viral mimic on glutamate homeostasis and glutamatergic neurotransmission in the mouse hippocampus. We found that peritoneal inflammation elevated extracellular glutamate concentration and enhanced the probability of pre-synaptic glutamate release resulting in hyperexcitability of neuronal networks. These mechanisms are likely to underlie the enhanced seizure propensity.
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Affiliation(s)
- Holly C. Hunsberger
- Behavioral Neuroscience, Department of Psychology, West Virginia University, Morgantown, 26506 WV, USA
- Department of Drug Discovery and Development, School of Pharmacy, Auburn University, Auburn, 36849 AL, USA
| | - Desheng Wang
- Blanchette Rockefeller Neurosciences Institute, Morgantown, 26506 WV, USA
| | - Tiffany J. Petrisko
- Department of Neurobiology and Anatomy, School of Medicine, West Virginia University, Morgantown, 26506 WV, USA
| | - Ahmad Alhowail
- Department of Drug Discovery and Development, School of Pharmacy, Auburn University, Auburn, 36849 AL, USA
| | - Sharay E. Setti
- Department of Drug Discovery and Development, School of Pharmacy, Auburn University, Auburn, 36849 AL, USA
| | - Vishnu Suppiramaniam
- Department of Drug Discovery and Development, School of Pharmacy, Auburn University, Auburn, 36849 AL, USA
| | - Gregory W. Konat
- Department of Neurobiology and Anatomy, School of Medicine, West Virginia University, Morgantown, 26506 WV, USA
| | - Miranda N. Reed
- Department of Drug Discovery and Development, School of Pharmacy, Auburn University, Auburn, 36849 AL, USA
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Neal A, Yuen T, Bjorksten AR, Kwan P, O'Brien TJ, Morokoff A. Peritumoural glutamate correlates with post-operative seizures in supratentorial gliomas. J Neurooncol 2016; 129:259-67. [PMID: 27311724 DOI: 10.1007/s11060-016-2169-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Accepted: 06/01/2016] [Indexed: 11/30/2022]
Abstract
To examine the impact of glutamate on post-operative seizures and survival in a cohort of patients with grade II to IV supratentorial glioma. A retrospective analysis was performed on 216 patients who underwent surgery for supratentorial gliomas. Primary explanatory variables were peritumoural and/or tumoural glutamate concentrations, glutamate transporter expression (EAAT2 and SXC). Univariate and multivariate survival analysis was performed with primary outcomes of time to first post-operative seizure and overall survival. Subgroup analysis was performed in patients with de novo glioblastomas who received adjuvant chemoradiotherapy. 47 (21.8 %), 34 (15.8 %) and 135 (62.5 %) WHO grade II, III and IV gliomas respectively were followed for a median of 15.8 months. Following multivariate analysis, there was a non-significant association between higher peritumoural glutamate concentrations and time to first post-operative seizure (HR 2.07, CI 0.98-4.37, p = 0.06). In subgroup analysis of 81 glioblastoma patients who received adjunct chemoradiotherapy, peritumoural glutamate concentration was significantly associated with time to first post-operative seizure (HR 3.10, CI 1.20-7.97, p = 0.02). In both the overall cohort and subgroup analysis no glutamate cycle biomarkers were predictive of overall survival. Increased concentrations of peritumoural glutamate were significantly associated with shorter periods of post-operative seizure freedom in patients with de novo glioblastomas treated with adjuvant chemoradiotherapy. No glutamate cycle biomarkers were predictive of overall survival. These results suggest that therapies targeting glutamate may be beneficial in tumour associated epilepsy.
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Affiliation(s)
- Andrew Neal
- Department of Neurology, Royal Melbourne Hospital, University of Melbourne, 3050, Parkville, VIC, Australia.
- Department of Medicine, Royal Melbourne Hospital, University of Melbourne, 3050, Parkville, VIC, Australia.
| | - Tanya Yuen
- Department of Neurosurgery, Royal Melbourne Hospital, University of Melbourne, 3050, Parkville, VIC, Australia
- Department of Surgery, Royal Melbourne Hospital, University of Melbourne, 3050, Parkville, VIC, Australia
| | - Andrew R Bjorksten
- Department of Anaesthesia and Pain Management, Royal Melbourne Hospital, 3050, Parkville, VIC, Australia
| | - Patrick Kwan
- Department of Neurology, Royal Melbourne Hospital, University of Melbourne, 3050, Parkville, VIC, Australia
- Department of Medicine, Royal Melbourne Hospital, University of Melbourne, 3050, Parkville, VIC, Australia
| | - Terence J O'Brien
- Department of Neurology, Royal Melbourne Hospital, University of Melbourne, 3050, Parkville, VIC, Australia
- Department of Medicine, Royal Melbourne Hospital, University of Melbourne, 3050, Parkville, VIC, Australia
| | - Andrew Morokoff
- Department of Neurosurgery, Royal Melbourne Hospital, University of Melbourne, 3050, Parkville, VIC, Australia
- Department of Surgery, Royal Melbourne Hospital, University of Melbourne, 3050, Parkville, VIC, Australia
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Hunsberger HC, Hickman JE, Reed MN. Riluzole rescues alterations in rapid glutamate transients in the hippocampus of rTg4510 mice. Metab Brain Dis 2016; 31:711-5. [PMID: 26744018 PMCID: PMC4864118 DOI: 10.1007/s11011-015-9783-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Accepted: 12/22/2015] [Indexed: 01/18/2023]
Abstract
Those at risk for Alzheimer's disease (AD) often exhibit hippocampal hyperexcitability in the years preceding diagnosis. Our previous work with the rTg(TauP301L)4510 tau mouse model of AD suggests that this increase in hyperexcitability is likely mediated by an increase in depolarization-evoked glutamate release and a decrease in glutamate uptake, alterations of which correlate with learning and memory deficits. Treatment with riluzole restored glutamate regulation and rescued memory deficits in the TauP301L model. Here, we used enzyme-based ceramic microelectrode array technology to measure real-time phasic glutamate release and uptake events in the hippocampal subregions of TauP301L mice. For the first time, we demonstrate that perturbations in glutamate transients (rapid, spontaneous bursts of glutamate) exist in a tau mouse model of AD mouse model and that riluzole mitigates these alterations. These results help to inform our understanding of how glutamate signaling is altered in the disease process and also suggest that riluzole may serve as a clinically applicable therapeutic approach in AD.
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Affiliation(s)
- Holly C Hunsberger
- Behavioral Neuroscience, Department of Psychology, West Virginia University, Morgantown, 26506, WV, USA
- Drug Discovery & Development Department, School of Pharmacy, Auburn University, 4306 Walker Building, Auburn, AL, 36849, USA
| | - James E Hickman
- Behavioral Neuroscience, Department of Psychology, West Virginia University, Morgantown, 26506, WV, USA
| | - Miranda N Reed
- Drug Discovery & Development Department, School of Pharmacy, Auburn University, 4306 Walker Building, Auburn, AL, 36849, USA.
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Cavus I, Widi GA, Duckrow RB, Zaveri H, Kennard JT, Krystal J, Spencer DD. 50 Hz hippocampal stimulation in refractory epilepsy: Higher level of basal glutamate predicts greater release of glutamate. Epilepsia 2016; 57:288-97. [PMID: 26749134 DOI: 10.1111/epi.13269] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/02/2015] [Indexed: 11/27/2022]
Abstract
OBJECTIVE The effect of electrical stimulation on brain glutamate release in humans is unknown. Glutamate is elevated at baseline in the epileptogenic hippocampus of patients with refractory epilepsy, and increases during spontaneous seizures. We examined the effect of 50 Hz stimulation on glutamate release and its relationship to interictal levels in the hippocampus of patients with epilepsy. In addition, we measured basal and stimulated glutamate levels in a subset of these patients where stimulation elicited a seizure. METHODS Subjects (n = 10) were patients with medically refractory epilepsy who were undergoing intracranial electroencephalography (EEG) evaluation in an epilepsy monitoring unit. Electrical stimulation (50 Hz) was delivered through implanted hippocampal electrodes (n = 11), and microdialysate samples were collected every 2 min. Basal glutamate, changes in glutamate efflux with stimulation, and the relationships between peak stimulation-associated glutamate concentrations, basal zero-flow levels, and stimulated seizures were examined. RESULTS Stimulation of epileptic hippocampi in patients with refractory epilepsy caused increases in glutamate efflux (p = 0.005, n = 10), and 4 of ten patients experienced brief stimulated seizures. Stimulation-induced increases in glutamate were not observed during the evoked seizures, but rather were related to the elevation in interictal basal glutamate (R(2) = 0.81, p = 0.001). The evoked-seizure group had lower basal glutamate levels than the no-seizure group (p = 0.04), with no stimulation-induced change in glutamate efflux (p = 0.47, n = 4). Conversely, increased glutamate was observed following stimulation in the no-seizure group (p = 0.005, n = 7). Subjects with an atrophic hippocampus had higher basal glutamate levels (p = 0.03, n = 7) and higher stimulation-induced glutamate efflux. SIGNIFICANCE Electrical stimulation of the epileptic hippocampus either increased extracellular glutamate efflux or induced seizures. The magnitude of stimulated glutamate increase was related to elevation in basal interictal glutamate, suggesting a common mechanism, possibly impaired glutamate metabolism. Divergent mechanisms may exist for seizure induction and increased glutamate in patients with epilepsy. These data highlight the potential risk of 50 Hz stimulation in patients with epilepsy.
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Affiliation(s)
- Idil Cavus
- Department of Neurosurgery, Yale University, New Haven, Connecticut, U.S.A.,Department of Psychiatry, Yale University, New Haven, Connecticut, U.S.A
| | - Gabriel A Widi
- Yale University School of Medicine, New Haven, Connecticut, U.S.A
| | - Robert B Duckrow
- Department of Neurosurgery, Yale University, New Haven, Connecticut, U.S.A.,Department of Neurology, Yale University, New Haven, Connecticut, U.S.A
| | - Hitten Zaveri
- Department of Neurology, Yale University, New Haven, Connecticut, U.S.A
| | - Jeremy T Kennard
- Department of Neurosurgery, Yale University, New Haven, Connecticut, U.S.A
| | - John Krystal
- Department of Psychiatry, Yale University, New Haven, Connecticut, U.S.A
| | - Dennis D Spencer
- Department of Neurosurgery, Yale University, New Haven, Connecticut, U.S.A
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