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Chen, Yongmei. "Excitotoxicity in neurodegenerative disorders." free to MU campus, to others for purchase, 1998. http://wwwlib.umi.com/cr/mo/fullcit?p9901225.
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Scott, Michael Murray. "Development of in vitro models of NMDA excitotoxicity and assessment of excitotoxicity modulation by neurosteroids." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ36079.pdf.
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Giardina, Sarah Filippa 1974. "Neuropharmacology of kainate receptor-mediated excitotoxicity." Monash University, Dept. of Pharmacology, 2001. http://arrow.monash.edu.au/hdl/1959.1/8980.
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Soundarapandian, Mangala Meenakshi. "Glutamate Excitotoxicity in Epilepsy and Ischemia." Doctoral diss., University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3169.
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'Excitotoxicity' represents the excitatory amino acid mediated degeneration of neurons. Glutamate is the major excitatory neurotransmitter in the brain. Glutamate excitotoxicity has been implicated in a number of neurodegenerative disorders like Stroke, Epilepsy, Alzheimer's disease and traumatic brain injury. This neurotoxicity is summed up by the 'glutamate hypothesis' which describes the cause of neuronal cell death as an excessive release of glutamate causing over excitation of the glutamate receptors and subsequent increase in influx of calcium leading to cell death. An effort to counteract this neurotoxicity has lead to the development of glutamate receptor antagonists that can effectively serve as neuroprotective agents. Nevertheless, the downside to these drugs has been the side effects observed in clinical trial patients due to their disruptive action on the physiological function of these receptors like learning and memory. This work was undertaken to identify targets that can effectively be used to treat excitotoxicity without affecting any normal physiological functions. In one approach, (chapter I) we have identified the KATP channels as an effective modulator of epileptogenesis. In another approach, (Chapter II) we show that targeting the AMPA receptor subunit GluR2 is a practical strategy for stroke therapy. KATP channels that are gated by intracellular ATP/ADP concentrations are a unique subtype of potassium channels and play an essential role in coupling intracellular metabolic events to electrical activity. Opening of KATP channels during energy deficits in the central nervous system (CNS) induces efflux of potassium ions and in turn hyperpolarizes neurons. Thus, activation of KATP channels is thought to be able to counteract excitatory insults and protect against neuronal death. Here, we show that, functional Kir6.1 channels are located at excitatory pre-synaptic terminals as a complex with type-1 Sulfonylurea receptors (SUR1) in the hippocampus. The mutant mice with deficiencies in expressing the Kir6.1 or the SUR1 gene are more vulnerable to generation of epileptic form of seizures, compared to wild-type controls. Whole-cell patch clamp recordings demonstrate that genetic deletion of the Kir6.1/SUR1 channels enhances glutamate release at CA3 synapses. Hence, expression of functional Kir6.1/SUR1 channels inhibits seizure responses and possibly acts via limiting excitatory glutamate release. In addition to epilepsy, ischemic stroke is a leading cause of death in developed countries. A critical feature of this disease is a highly selective pattern of neuronal loss; certain identifiable subsets of neurons, particularly CA1 pyramidal neurons in the hippocampus are severely damaged, whereas others remain intact. A key step in this selective neuronal injury is Ca2+/Zn2+ entry into vulnerable neurons through [alpha]-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor channels, a principle subtype of glutamate receptors. AMPA receptor channels are assembled from glutamate receptor (GluR) -1, -2, -3, and -4 subunits. Circumstance data have indicated that the GluR2 subunits dictate Ca2+/Zn2+ permeability of AMPA receptor channels and gate injurious Ca2+/Zn2+ signals in vulnerable neurons. Here we show that ischemic insults induce toxic Ca2+ entry through AMPA receptors into vulnerable neurons by modification of GluR2 RNA editing. Thus, targeting of GluR2 subunit can be considered as a promising target for stroke therapy.Ph.D.
Department of Biomolecular Science
Burnett College of Biomedical Sciences
Biomolecular Sciences PhD
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Gladbach, Philip Amadeus Wilhelm. "The role of tau in excitotoxicity." Thesis, The University of Sydney, 2013. http://hdl.handle.net/2123/9557.
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Stroke is a leading cause of death. The majority are ischemic strokes resulting from acute focal brain infarction with sudden and persisting neurological deficits. This primary brain damage is followed by more substantial secondary destruction of surrounding areas (=penumbra). A major pathomechanism underlying penumbra formation is excitotoxicity, which results from over-excitation of glutaminergic synapses involving N-methyl-D-aspartate receptor signaling. Excitotoxicity also contributes to neurodegeneration in Alzheimer’s disease (AD), where the microtubule-associated protein tau deposits in neurons. Here, I show that reducing tau levels can prevent deficits in different AD mouse models. Furthermore, I show that tau-deficient mice (tau-/-) are protected from excitotoxic brain damage following induced seizure and stroke by middle cerebral artery occlusion and from progression of neurological deficits. Gene profiling indicated differential mitogen-activated protein kinase (MAPK) signaling induced by excitotoxic stress in tau-/- mice, with absent Ras and subsequent extracellular signal-regulated kinase (ERK) activation and immediate early gene induction. Accordingly, inhibition of MAP/ERK kinase 1/2 reduced MCAO-induced infarct size and neurological deficits in wild-type mice to the same degree as tau-depletion. Hence, my findings suggest tau dependent Ras/ERK activation drives excitotoxic secondary brain damage in stroke, implicating tau as a possible therapeutic target in acute brain damage beyond AD.
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Zhu, Shanshan. "Factors in glutamate excitotoxicity, inflammation and epilepsy." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/39844.
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Studying the mechanisms underlying glutamate excitotoxicity and inflammatory responses provides hints to the pathology of neurological diseases such as epilepsy. In this dissertation I investigated the expression and function of Krüppel-like factor 4 (KLF4) in glutamate excitotoxicity. I also studied the distribution and the role of progranulin (PGRN) in inflammatory stimulation, in epilepsy and in astrocytes subjected to glutamate excitotoxicity. First, I studied the role of KLF4 and found that NMDA induced KLF4 expression in cultured neurons and in brain slices. Overexpression of KLF4 upregulated cyclin D1 and downregulated p21Waf1/Cip1, suggesting the neuron’s progression into cell cycle. KLF4 expression also induced the cleavage of caspase-3 under conditions of a subtoxic dose of NMDA. Thus our work suggests that KLF4 might play a role in NMDA-induced apoptosis. Second, I studied the function of PGRN and observed that PGRN was enhanced in activated microglia after pilocarpine-induced epilepsy. In mixed cultures, lipopolysaccharide (LPS) also induced PGRN expression. Recombinant PGRN protein promoted microglial activation in the dentate gyrus after epilepsy and in purified microglial cell culture. PGRN was also required for LPS-induced microglial migration. Our work suggests that PGRN may contribute to microglial activation after epileptic and inflammatory insults.
Third, I performed a preliminary study on the role of PGRN in purified culture of astrocytes. I found that our cultured astrocytes express PGRN, and PGRN was required for glutamate-induced lactate release. PGRN was also involved in glutamate-induced glucose uptake and participated in the regulation of monocarboxylate transporter 1 (MCT1) expression in excitotoxic conditions. Our findings suggest that PGRN may be involved in glutamate-evoked increase of glycolysis in cultured astrocytes. In conclusion, our findings provide insights into factors involved in glutamate excitotoxicity, inflammation, and epilepsy.
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Bakshi, Deeksha. "The role of NMDA receptors in excitotoxicity." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/43907.
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NMDA receptors are glutamate-gated cation channels named after their prototypical selective agonist NMDA. The channels occur as multiple subtypes, which are formed from interactions between different receptor subunits. NMDA receptor subunits are classified into three families: NR1, NR2A-D, and NR3A, B.
NMDA receptors are implicated in HD pathology. During HD, a subset of medium-sized aspiny interneurons in the striatum that co-localize SST, NPY, and the enzyme NOS are selectively spared. In contrast, medium-sized spiny cells that constitute 80 % of all striatal neurons undergo selective neurodegeneration. While it was suggested that the interneurons survive because they lack NMDA receptors, studies including from our lab have shown the presence of NR1 in SST-positive striatal neurons. The finding of NR1 expression and co-localization with SST-positive neurons indicates that NMDA receptor-induced toxicity may be regulated in a receptor-specific manner. Therefore, the present study was conducted to investigate whether NMDA application leads to toxicity that is receptor-specific in HEK293 cells stably transfected with NR1, NR2A, or NR2B.
The main findings of this study indicate that NMDA application causes cell death, which varies in intensity and nature, depending upon the NMDA concentration applied, and the receptor-type expressed by the cells. Cells expressing NR1 were found to undergo apoptosis but not necrosis, while cells expressing NR2A/NR2B underwent both apoptosis and necrosis in a receptor-specific manner. In cells expressing NR2A/NR2B, exposure to low concentrations of NMDA resulted in cell death that was predominantly apoptotic. In contrast, exposure to high concentrations of NMDA produced mostly necrosis. In cells expressing NR1, NMDA application caused apoptosis, which exhibited a gradual increase in response to greater concentrations of NMDA. In addition, cell death through apoptosis and/or necrosis was determined to be the greatest at all NMDA concentrations in cells expressing NR2B, followed by those expressing NR2A, and then NR1. Taken together, these results indicate that the activation of receptors formed by NR1, NR2A, or NR2B have different toxic consequences. Thus, the selective neurodegeneration observed during HD may be due to the variation in expression levels of NR1, NR2A, and NR2B between medium-sized aspiny interneurons and medium-sized spiny projection neurons.
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Jones, Paul A. "Modulation of kainate-induced excitotoxicity in rats." Thesis, University of Glasgow, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244361.
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Serzysko, Malgorzata. "Endocannabinoids and excitotoxicity: lessons from hypoglossal motoneurons." Doctoral thesis, SISSA, 2015. http://hdl.handle.net/20.500.11767/3908.
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Brainstem hypoglossal motoneurons (HMs) exclusively innervate tongue muscles and are severely damaged in the neurodegenerative disease called amyotrophic lateral sclerosis (ALS). One mechanism leading to such cell death is proposed to be glutamate-mediated excitotoxic stress. HMs are particularly vulnerable to excitotoxicity due to their expression of calcium-permeable α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptors and scarcity of intracellular Ca2+ binding proteins like parvalbumin and calbindin. Indeed, blocking glutamate uptake in medullary slices can lead to pathological bursting and motoneuron damage.
The endocannabinoid system is widely distributed in the brain and is believed to be an important regulator of synaptic transmission. Several studies reported neuroprotection mediated by the endocannabinoid system in such pathological insults like brain ischemia, traumatic brain injury or excitotoxicity. Moreover, in ALS animal models, up-regulation of the endocannabinoid system has been detected, suggesting it can play a role during disease development. Thus, detailed information on how the endocannabinoid system can affect cells during pathological insults like excitotoxicity is a valuable asset for future investigations of novel therapy approaches for ALS.
The objective of this work was to investigate the effect of modulation of the endocannabinoid system during excitotoxic stress in hypoglossal motoneurons in vitro. Thin medullary slices (for electrophysiology and viability assay) or whole brainstem isolates (for Western Blot) from postnatal Wistar rats were used. Each slice/brainstem containing hypoglossal nuclei was transferred to a recording/incubation chamber and superfused with oxygenated Krebs solution. Excitotoxic stress was evoked by application of DL-TBOA (DL-threo-β-benzyloxyaspartic acid, 50 μM), a potent and selective inhibitor of excitatory amino acid transporters, with consequent build-up of extracellular glutamate.
It was observed that modulation of endocannabinoid CB1 receptor (CB1R) function affected TBOA-evoked bursting, an event previously correlated with TBOA toxicity. Co-application of the endocannabinoid anandamide (AEA, 10 μM), a CB1R agonist, with TBOA resulted in lowered probability of the occurrence of pathological bursting, whereas co-application of the CB1R antagonist AM251 (10 μM) disrupted TBOA-induced bursts, leading to their “fragmentation”. Furthermore, AEA significantly decreased the frequency of spontaneous excitatory postsynaptic currents (sEPSCs) isolated by co-application of bicuculline and strychnine (10 μM and 0.4 μM, respectively) and caused occurrence of biphasic activity in spontaneous inhibitory postsynaptic currents (sIPSCs; isolated by co-application of DNQX and APV at 10 μM and 50 μM, respectively) in some of the recorded cells. AM251 caused a decrease in the frequency of sIPSCs, but during application of bicuculline and strychnine it evoked activity which partly resembled bursting observed during TBOA application. Moreover, co-application of AEA with TBOA significantly decreased the number of damaged propidium iodide-positive cells with respect to counterstained Hoechst 33342-positive cells, which suggests a protective effect of this CB1R agonist against TBOA-induced toxicity. In addition, Western blot analysis showed a significant increase in CB1R protein levels after only 4 hours of TBOA incubation, indicating that the endocannabinoid system is activated during this excitotoxic insult. We suggest that a likely role of the endocannabinoid system in our brainstem preparation is to counteract the effects and consequences of elevated glutamate levels in the extracellular compartment.
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Tannenberg, Rudi. "Excitotoxicity in Alzheimer disease : a synaptic terminal study /." [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18741.pdf.
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Vladimirov, Andrew A. "Metabolic receptor cross-talk and excitotoxicity in astrocytes." Thesis, University of Bristol, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399955.
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Carrier, Raeann Lynn. "Excitotoxicity and bioenergetics in Huntington's disease transgenic neurons." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1213361299.
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Bordiga, Pierrick. "Caractérisation des mécanismes de réparation synaptique de l'oreille interne." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0625.
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Les connexions entre les cellules sensorielles et les neurones primaires de l’oreille interne, appelées synapses sont essentielles à l’encodage et la transmission des informations auditives et vestibulaires vers le cerveau. C’est aussi une zone extrêmement exposée et fragile qui semble impliquée dans de nombreuses atteintes de l’audition et de l’équilibration, mais également au cours du vieillissement. Des récupérations spontanées de l’audition et de l’équilibre ont été observées suite à ces différentes atteintes chez l’Homme. Dans le cadre de ma thèse, j’ai étudié d’une part, comment des atteintes sélectives de ces synapses pouvaient générer des troubles de l’oreille interne chez l’animal, et d’autre part, comment des mécanismes de réparation spontanée de ces synapses supportent la récupération des fonctions auditives et vestibulaires. Nous avons constaté qu’il existe une hétérogénéité dans les capacités de réparations synaptiques entre la cochlée et le vestibule. L’étude des mécanismes moléculaires mis en jeu dans cette réparation synaptique pourrait ouvrir la voie au développement de nouvelles stratégies thérapeutiques pour les atteintes de l’oreille interneInner ear connections between primary neurons and sensory cells, called synapses are essential for encoding and transmitting auditory and vestibular information to the brain. It is also an extremely exposed and fragile area that is involved in many hearing and balance disorders, but also during aging. Spontaneous hearing and balance recoveries have been observed following these different injuries in humans. In the context of my thesis, I studied, on the one hand, how selective lesions of these synapses could generate inner ear disorders in animals, and on the other hand, how spontaneous repair mechanisms of these synapses support auditory and vestibular functions recovery. We found that there is heterogeneity in synaptic repair capabilities between the cochlea and the vestibule. The study of the molecular mechanisms involved in this synaptic repair could pave the way for the development of new therapeutic strategies against various inner ear disorders
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Rogers, Derek Charles. "The effects of neuroprotective agents on in vitro and in vivo models of neurotoxicity." Thesis, University of Hertfordshire, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283890.
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Smith, Andrew John. "Excitotoxicity, oxidative stress and neuroprotection in cerebellar granule neurones." Thesis, Connect to e-thesis, 2008. http://theses.gla.ac.uk/305/.
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Olivieri, Dario. "New Spinal cord models: Characterization of Excitotoxicity and Neuroprotection." Doctoral thesis, SISSA, 2015. http://hdl.handle.net/20.500.11767/3892.
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Group III metabotropic glutamate receptors (mGluR III) are known to decrease glutamate release and to play an important role in controlling pain as documented in neuropathic pain models. Much less is known about their potential neuroprotective effect against excitotoxicity that is considered important for damage onset of spinal cord injury. Using rat spinal cord organotypic slices model, we investigated if mGluR III receptor activation might contrast excitotoxic cell death evoked by kainic acid (0.1 mM) applied for 1h and followed by wash for further 24h. The specific agonist of mGluR III receptors L-(+)-2-amino-4-phosphonobutyric acid (L-AP4; 1 µM) was either co-applied with kainic acid or administered during washout. Cell death was quantified in terms of percentage of pyknotic nuclei, total number of neurons, motoneurons and astrocytes.
Furthermore we developed for future long-term studies an in vitro model of Spinal Cord Isolated from newborn rats maintained for 3 days in medium. We characterize this model using both immunohistochemistry and electrophysiological recordings.
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Brun-Salabert, Anne-Sophie. "Développement préclinique de sondes fluorées utilisées dans l'imagerie moléculaire des pathologies neurodégénératives." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30371/document.
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Les mécanismes physiopathologiques liés aux maladies neurodégénératives restent encore largement méconnus. Deux processus semblent être particulièrement en cause dans les phénomènes de neurodégénérescence : la neurotoxicité par afflux massif de calcium due à une activation excessive des récepteurs NMDA (GluN) et la neurotoxicité par déstabilisation du cytosquelette du neurone par le biais de la phosphorylation anormale de la protéine tau. L'imagerie moléculaire par le biais de la tomographie par émission de positons (TEP) et de radiotraceurs, en étudiant les mécanismes moléculaires in vivo, permet de détecter et quantifier ces phénomènes. Ce travail a eu pour objet d'étudier un dérivé de la mémantine, un antagoniste des GluN se fixant sur un site intra-canal accessible uniquement lorsque ces récepteurs sont activés ce qui en fait donc un vecteur d'imagerie intéressant pour étudier leur activation. Nous avons mis au point la synthèse d'un nouveau radiotraceur dérivé de la mémantine : la [18F]-FNM (Fluoroéthylnormémantine). Il s'agit d'une synthèse par substitution nucléophile d'un groupement tosylate par du [18F], suivie d'une hydrolyse acide. Cette synthèse est reproductible avec un rendement de 10%, son activité spécifique est > 355 GBq/µmol. Chez le rat, le traceur passe la barrière hémato-encéphalique et sa distribution cérébrale est bien corrélée avec la localisation des GluN (r=0.622, p<0.0001). Sa cinétique de fixation (40 minutes) est compatible avec son utilisation en TEP. En ce qui concerne les tauopathies, la protéine tau stabilise l'organisation microtubulaire. Lors d'une phosphorylation anormale, l'interaction avec les microtubules diminue et les protéines tau vont s'accumuler en formant des Paires de Filaments en Hélice (PHF). Nous avons optimisé la radiosynthèse de l' [18F]-AV1451 ciblant les PHF. Notre rendement de synthèse est de 30% et l'activité spécifique du traceur > 10 GBq/µmol. Nous avons réalisé des autoradiographies sur des coupes de cerveaux atteints de tauopathie et nous avons constaté la capacité du traceur à différencier les coupes saines des coupes malades. La production de cet outil dans notre centre va nous permettre d'étudier la présence de PHF chez le marmouset, un primate particulièrement intéressant dans l'étude du vieillissement. Nous avons donc réalisé la synthèse de deux radiotraceurs innovants : la [18F]-FNM et le [18F]-AV1451, les synthèses sont reproductibles et les rendements compatibles avec des productions de doses en recherche pré-clinique et cliniqueThe pathophysiological mechanisms associated with neurodegenerative diseases remain largely unknown. Two processes appear to be particularly involved in the phenomena of neurodegeneration: neurotoxicity induced by massive influx of calcium caused by excessive activation of NMDA receptors (GluN) and neurotoxicity by destabilization of neuron cytoskeleton through abnormal protein tau phosphorylation. Molecular imaging through positron emission tomography (PET) and radiotracers, by studying the molecular mechanisms in vivo, allows to detect and quantify these phenomena. This work was intended to study a memantine derivative, a GluN antagonist. We chose to develop a ligand that selectively binds to the ion channel in the open and active state which therefore makes it an interesting vector to study their overactivation. We have developed the synthesis of a new memantine analogue radiotracer: the [18F]-FNM (Fluoroéthylnormémantine). This is a synthesis by nucleophilic substitution of a tosylate with [18F], followed by acid hydrolysis. This synthesis is reproducible with a yield of 10%, its specific activity was> 355 GBq / µmol. In rats, the tracer cross the blood-brain barrier and brain distribution correlates well with the location of GluN (r = 0.622, p <0.0001). The binding kinetics (40 minutes) is compatible with its use in PET. Regarding tauopathies, the tau protein stabilizes microtubule organization. During abnormal phosphorylation, interaction with microtubules and tau proteins decreases and tau will accumulate to form Paired helical Filament (PHF). We optimized the radiosynthesis of [18F] AV1451 targeting 3 tau PHF. Our yield of synthesis is 30% and the specific activity of the tracer> 10 GBq / µmol. We made autoradiography on brains sections and have shown tracer ability to differentiate healthy and pathological slices. This tool will allow us to study the presence of PHF in marmosets, a particularly interesting primate in the study of aging. So we performed the synthesis of two innovative radiotracers: the [18F]-FNM and [18F]-AV1451, syntheses are reproducible and yields compatible with doses manufacturing in pre-clinical and clinical research
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Vaur, Pauline Magda Marie. "Caractérisation des effets protecteurs du NAD+ et du Nicotinamide Riboside lors de la dégénérescence axonale dans le système nerveux central : Implications dans les processus neurodégénératifs." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066594/document.
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Les maladies neurodégénératives se caractérisent par une déconnexion synaptique et une dégénérescence des axones (DA) précoces, menant à la mort spécifique d’une population neuronale. Les niveaux intracellulaires de NAD+, co-facteur essentiel dans le maintien de l’intégrité axonale, sont fortement diminués lors de ces pathologies. L’augmentation des taux de NAD+ est ainsi une stratégie thérapeutique dans la prévention de ces maladies. La capacité du nicotinamide riboside (NR) à retarder la DA dans le système nerveux périphérique (SNP) ainsi que la récente mise en évidence d'une conversion extracellulaire du NAD+ en NR dans des lignées cellulaires et dans le SNP soulignent l'intérêt de ce précurseur du NAD+. Mon projet de thèse repose sur la caractérisation des effets du NAD+ et du NR lors de la DA dans des neurones du système nerveux central (SNC). A partir d'un modèle d'excitotoxicité mis au point en dispositifs microfluidiques, nous montrons pour la première fois que le NR protège de la DA dans des neurones corticaux de manière plus efficace que le NAD+. Cet effet différentiel a également été validé dans un modèle ischémique in vivo. De manière surprenante, lors d'une neurodégénérescence induite par une déplétion aigüe en NAD+, un effet protecteur total à la fois du NAD+ et du NR a été mis en évidence. L'analyse de la voie de conversion extracellulaire a ainsi révélée une adaptation du métabolisme du NAD+ et de sa conversion en NR en fonction du paradigme neurotoxique. En conclusion, ce travail démontre un fort effet protecteur du NR dans le SNC et ouvre de nouvelles voies thérapeutiques dans la prévention des processus neurodégénératifsSynaptic and axonal degeneration (AxD) are major events in neurodegenerative diseases. Levels of NAD+, an important coenzyme for axonal integrity, are strongly reduced in different degeneration models so enhancing cellular NAD+ is one of the numerous therapeutic strategies against neuronal pathologies. Nicotinamide riboside (NR) is a good NAD+ precursor as it has already been shown to delay AxD in peripheral nervous system (PNS) and extracellular NAD+ conversion to NR was previously described in cell lines and in PNS. During my thesis project, we analyzed the role of NR metabolism to prevent degeneration processes in cortical neurons. Using an excitotoxicity model developed in microfluidic devices, we showed for the first time that both NAD+ and NR delay AxD in cortical neurons, with a more potent effect for NR. We confirm this differential effect in an in vivo ischemic model. Moreover, NR effect is mainly restricted to the axonal compartment and intracellular NAD+ depletion is reverted after NR application, suggesting that axonal integrity is totally dependent on NAD+ local metabolism. Furthermore, in a complete NAD+ depletion paradigm, NAD+ and NR have surprisingly the same strong effect, protecting equally neuronal death and AxD. Examination of the extracellular pathway suggest that NAD+ conversion to NR is limited in excitotoxicity but effective in the NAD+ depletion model. These results reveal that NR and NAD+ metabolism depend on the neurotoxic paradigm. Our results demonstrate that NR has a strong and local neuroprotective effect on AxD in several neurotoxic processes. These findings open new therapeutic strategies to prevent neurodegenerative diseases
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Miller, Brandon Andrew. "The effects of excitotoxicity and microglial activation on oligodendrocyte survival." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1177537595.
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Mizielinska, Sarah. "Rapid neuronal responses to glutamate-induced excitotoxicity and morphological change." Thesis, University of Dundee, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.521697.
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Tan, Hiang Khoon. "Investigating the effects of TIMPs on excitotoxicity and neurite regeneration." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247230.
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Zou, Shenglong. "Crosstalk between somatostatin receptor subtypes and cannabinoid receptor 1 in excitotoxicity." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/64231.
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Miranda, Allan F. "Modulation of quinolinic acid-induced excitotoxicity by endogenous kynurenine pathway intermediates." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/nq22484.pdf.
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Murphy, Michael Paul. "Interactions between excitotoxicity and lysosomal inhibition, implications for Alzheimer's disease pathogenesis." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ35262.pdf.
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Evans, Gary Lee. "The induction of long-term potentiation attenuates kainic acid-induced excitotoxicity." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/777.
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The activation of N-methyl-D-aspartate glutamate receptors (NMDARs) is required for the long term potentiation (LTP) and long term depression (LTD) of excitatory synaptic transmission at hippocampal CA1 synapses, and plays an important role in learning and memory. In addition, it is accepted that the over-activation of NMDARs leads to the neurotoxicity associated with stroke and other neurodegenerative disorders. Thus, the NMDAR provides a logical starting point to investigate a possible relationship between synaptic plasticity and the cell-signalling pathways which ultimately determine neuronal fate. Research in our lab has indicated that NR2A-containing NMDARs are essential for LTP induction whereas NR2B-containing NMDARs are crucial for the production of LTD in vitro, and the results of this study support these findings in the anaesthetized rat. Furthermore, using the kainic acid (KA) model of neurotoxicity, this research has explored the opposing roles that activity-dependent synaptic plasticity, through different NMDAR subtypes, can play in determining neuronal outcome in an excitotoxic environment. In these experiments, it is shown that (1) the induction of LTP using high-frequency stimulation (HFS) promotes the phosphorylation of Akt, which plays a critical role in controlling cell survival and apoptosis, (2) the induction of LTP using HFS attenuates kainic acid (KA) induced neurodegeneration while the induction of LTD using low-frequency stimulation (LFS) has no incremental effect on the degree of cell death resulting from exposure to KA, (3) the blockade of NR2B-containing NMDARs using Ro25-6981 attenuates KA-induced neurodegeneration while the blockade of NR2A-containing NMDARs using NVP-AAM077 does not influence KA-induced neurotoxicity, (4) pre-treatment with NR2A antagonists blocks both the induction of LTP and its neuroprotective effect against KA while NR2B antagonists neither block the induction of LTP nor the neuroprotection that this can provide against KA, (5) the administration of NR2A antagonists after the induction of LTP has no effect on the expression of LTP or its neuroprotective effect against KA, and (6) pre-treatment with a high dose (2.4mg/kg) of NVP-AAM077 leads to the induction of LTD rather than LTP as a result of HFS. Altogether this research supports the hypothesis that the production of LTP via the activation of NR2A-containing NMDARs protects neurons against excitotoxic neuronal death by promoting cell survival signalling. Furthermore, because NR2A antagonists applied after the production of LTP do not block neuroprotection, it can be concluded that LTP itself, and not NR2A activation, is responsible for this neuroprotective effect.
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Tortarolo, Massimo. "Role of excitotoxicity in the degeneration of motor neurones in ALS." Thesis, Open University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412382.
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Urenjak, Jutta A., and Tihomir P. Obrenovitch. "Accumulation of quinolinic acid with euro-inflammation: does it mean excitotoxicity?" Thesis, Kluwer Academic, Plenum Publishers, New York, 2003. http://hdl.handle.net/10454/2833.
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Houlihan, Patrick Ryan. "The role of mitochondrial restructuring in neuronal calcium homeostasis and excitotoxicity." Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/2522.
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Mitochondrial Ca2+ buffering is an important physiological modulator of neuronal signaling and bioenergetics, but this propensity toward Ca2+ regulation proves pathological during excitotoxic insult. Specifically, excessive mitochondrial Ca2+ uptake is a key component of glutamate toxicity within the penumbra surrounding the ischemic core following stroke. This mitochondrial toxicity and Ca2+ dyshomeostasis may be visualized in real time as delayed calcium deregulation (DCD). DCD is a predictor of neuronal, excitoxic death, and is composed of three phases: 1) an initial response; 2) a latent period of elevated, but stable cytosolic Ca2+; and 3) failure of mitochondrial Ca2+ retention, termed deregulation. The duration of the latent period is an index of neuronal resistance.
Mitochondria are dynamic organelles that rapidly and reversibly undergo fission and fusion (MFF). MFF is tightly regulated by the phosphoregulation of fission inducing Drp1 at serine 656. Drp1-S656 phosphorelation is mediated by PKA/AKAP1, and it is dephosphorylated by PP2A/Bβ2. Phosphorylation of Drp1-S656 inactivates this contractile GTPase resulting in inhibition of mitochondrial fission and a shift toward elongated mitochondria. This PKA/AKAP1 dependent Drp1-S656 phosphorylation has proven to be neuroprotective. Likewise, attenuation of PP2A/Bβ2 signaling enhances neuronal survival during ischemia and excitotoxic insult.
Based on the mitochondrial buffering role in excitotoxicity and MFF modulation of neuronal survival, we began investigating the role of Ca2+ buffering as a function of MFF during glutamate toxicity. Noted above, resistance to excitoticity is visualized by the duration of the DCD latent period. Overexpression of AKAP1 in cultured hippocampal neurons greatly prolonged DCD latency in a PKA dependent manner, while Bβ2 ablation prolonged DCD latency by hours. Pharmacological modulation of PKA required PDE4 inhibition to reproduce the AKAP1 observations. Preliminary experiments studying the effect of Bβ2 overexpression on matrix Ca2+ load suggests possible mechanism of MFF regulated of matrix Ca2+ accumulation. Using mtPericam DRG neurons as a model system for individual mitochondrial Ca2+ recording, we discovered impaired extrusion kinetics in mitochondria fragmented by both Drp1 and Bβ2 overexpression. Ca2+ uptake was comparable to that of control. Extreme elongation of mitochondria via dominant negative Drp1-K38A enhanced recovery.
Understanding these observations, however, requires knowledge of the mitochondrial Ca2+ buffering mechanism. Mitochondrial uptake candidates include MCU and ccdc109b. Our neuronal characterization of MCU confirms a role in mitochondrial Ca2+ buffering, but not a requirement; other components must be involved. Ccdc109b remains an inconclusive candidate, but may be an important regulator of MCU. Mitochondrial efflux transporters include Letm1 and NCLX. Though Letm1 observations are hindered by control artifact, preliminary evidence supports a role in extrusion. The role of NCLX is complicated by possible tissue specificity. Functional expression experiments utilizing Na+ free Li+ external solution suggests absence of NCLX in hippocampal neurons; DRG neurons were capable of Li+ exchange. The above observations confirm the significance of mitochondrial Ca2+ extrusion in neuronal survival. Understanding the mechanisms and regulation of mitochondrial Ca2+ transport has the potential to provide novel therapeutic targets in pathologies of excitotoxic etiology.
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Li, Shuxin. "Excitotoxicity and sodium(+)-dependent glutamate transport in spinal cord white matter injury." Thesis, University of Ottawa (Canada), 2000. http://hdl.handle.net/10393/9231.
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Spinal cord injury (SCI) is a devastating condition, with much of the clinical disability resulting from disruption of ascending and descending white matter tracts. Recent reports suggest that a component of axonal dysfunction during SCI involves glutamate-mediated white matter damage, but the cellular targets of excitotoxicity and the precise mechanisms of glutamate release from non-synaptic white matter are not understood. In the present study, using combined techniques including electrophysiology, pharmacology, immunohistochemistry and confocal microscopy, we demonstrate that myelinated axons in isolated dorsal columns are vulnerable to irreversible excitotoxic injury, which is primarily dependent on Ca2+-permeable AMPA receptors. The cellular components susceptible to glutamate include oligodendrocytes, astrocytes and the myelin sheath, consistent with the distribution of GluR3 and GluR4 in these cell types in situ, but not GluR2. We also demonstrate that reduced transmembrane Na+ and K+ gradients induced by inhibiting Na+-K+-ATPase with ouabain plus high K+ could drive Na+-dependent glutamate transporters to operate in a reverse mode, resulting in glutamate release from intracellular compartments and functional failure in white matter tracts by activation of AMPA receptors. Using injury models of anoxia or trauma, we further show that the ionic and membrane potential perturbations induced during in vitro anoxia or trauma are sufficient to cause toxic glutamate efflux via reverse Na+-dependent glutamate transport, resulting in damage to the myelin sheath and possibly other structures by activation of AMPA receptors. Semiquantitative measurement of intracellular glutamate indicates that axon cylinders, and to a lesser extent oligodendrocytes, are the major cellular sources of endogenous glutamate release. Our findings are consistent with the immunolocalization of Na+-dependent transporters (GLT1, EAAC1 and GLAST) in dorsal columns. We conclude that white matter, especially glial elements including myelin, is vulnerable to excitotoxins acting via AMPA receptors; release of glutamate by reversal of Na+-dependent glutamate transport with subsequent activation of these receptors is an important mechanism in anoxic and traumatic injury of spinal cord white matter.
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Li, Shuxin. "Excitotoxicity and Na§+-dependent glutamate transport in spinal cord white matter injury." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0015/NQ58289.pdf.
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Utan, Aneli <1974>. "Effects of cannabidiol and cannabis extracts in models of convulsion and excitotoxicity." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/824/1/Tesi_Utan_Aneli.pdf.
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Utan, Aneli <1974>. "Effects of cannabidiol and cannabis extracts in models of convulsion and excitotoxicity." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/824/.
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Berry, Jennifer Nicole. "TIME-DEPENDENCE OF DISTAL-TO-PROXIMAL HIPPOCAMPAL NEURODEGENERATION PRODUCED BY N-METHYL-D-ASPARTATE RECEPTOR ACTIVATION." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_theses/72.
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Excitotoxicity is the overexcitation of neurons due to the excessive activation of excitatory amino acid receptors and is thought to be involved in many neurodegenerative states. The manner in which the neuron breaks down during excitotoxicity is still unclear. The current study used the organotypic hippocampal slice culture model to examine the time-dependent loss of the synaptic vesicular protein synaptophysin and the loss of N-methyl-D-aspartate (NMDA) receptor NR1 subunit availability following an excitotoxic insult (20 μM NMDA) to provide a better understanding of the topographical nature of neuronal death following NMDA receptor activation. Significant NMDA-induced cytotoxicity in the CA1 region of the hippocampus (as measured by propidium iodide uptake) was evident early (15 minutes after exposure) while significant loss of the NR1 subunit and synaptophysin was found at later timepoints (72 and 24 hours, respectively), suggesting delayed downregulation or degradation in axons and dendrites as compared to the soma. The addition of the competitive NMDA receptor antagonist 2-amino-7-phosphonovaleric acid (APV) significantly attenuated all NMDA-induced effects. These results suggest that NR1 and synaptophysin levels as measured by immunoreactivity are not reliable indicators of early cell death.
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Lo, Edmund. "The development of a method to deliver neuroprotective peptides specifically into stroke-affected neurons." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/233.
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Stroke is a pathological condition that causes extensive brain damage. During ischemic stroke, an excess of the excitatory neurotransmitter glutamate exerts many deleterious effects, which leads to cellular damage and cell death, a phenomenon appropriately termed excitotoxicity. Among the events triggered is the activation of the enzyme calpain, a protease whose action is dependent on the intracellular concentration of calcium, which is known to be elevated during excitotoxicity. In this thesis, I hypothesize that neuroprotective drugs can be better accumulated into stroke-affected regions by utilizing the actions of calpain. The extent of calpain activation was first investigated, and it was found to increase over time in both in vitro and in vivo models of stroke. Different amino acid sequences recognized and cleaved by calpain were then incorporated into the neuroprotective Tat-GluR2/3Y peptide. Although in vivo detection of modified Tat-GluR2/3Y peptides was unsuccessful due to technical difficulties, the accumulation of the therapeutic 3Y peptide fragments in neurons under excitotoxic conditions in vitro was found to increase with the CP-3 peptide, a peptide that is a modified version of the Tat-GluR2/3Y, with a sequence cleavable by calpain from the protein Collapsin Response Mediator Protein-3 (CRMP-3). These results suggest that it is possible to concentrate therapeutic agents into stroke-affected neurons, and this may translate into enhanced neuroprotective properties in both in vitro and in vivo animal stroke models.
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Karmarkar, Sumedha. "MECHANISMS OF NEUROPROTECTION IN SCN2.2 CELLS." OpenSIUC, 2012. https://opensiuc.lib.siu.edu/dissertations/476.
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As the major excitatory neurotransmitter, glutamate (Glu) is physiologically important in brain function. Excessive Glu release, however, is a critical underlying pathological mechanism in neurodegenerative disease, especially stroke. Strategies to protect neurons from cell death under these conditions are scarce; in part because of incomplete understanding of inherent neuroprotective mechanisms. The suprachiasmatic nucleus (SCN) is a region of the brain that exhibits endogenous resistance to Glu excitotoxicity. A previous study demonstrated that SCN2.2 cells (an immortalized SCN cell line) were resistant to Glu excitotoxicity as compared to GT1-7 neurons (from the neighboring hypothalamus). This thesis explored the cellular mechanisms underlying this endogenous neuroprotection in SCN2.2 cells. Extracellular regulated kinase (ERK) is expressed in the SCN, activated by Glu, and is anti-apoptotic in other systems. Therefore, this thesis was designed to test the following central hypothesis: SCN2.2 cells are dependent on ERK signaling for survival in the presence of an excitotoxic insult. Glu increased ERK activity in SCN2.2 cells and importantly, resistance to Glu excitotoxicity in SCN2.2 cells was compromised by pre-treatment with an ERK inhibitor (PD98059; PD). ERK inhibition + Glu mediated SCN2.2 cell death in an N-methyl-D-aspartate receptor (NMDAR)-dependent manner; specifically via the NMDAR 2B (NR2B) subunit. Glu treatment increased expression of NR2B, phosphorylated NR2B and NR1 proteins and decreased NR2A and NR2D mRNA in the GT1-7 cells. Glu-treated SCN2.2 cells showed decreased NR2B, phosphorylated NR2B, increased NR2C proteins and increased NR2A and NR2D mRNA levels. These data are consistent with varied NMDAR responses to Glu in GT1-7 vs. SCN2.2 cells, which might underlie the different physiological responses to Glu in the two cell types. Further experiments investigated the role of several signaling kinases, e.g. protein kinase A (PKA), protein kinase C (PKC), calcium/calmodulin-dependent kinase II (CaMK-II) and c-Jun N-terminal kinase-II (JNK-II) in regulation of ERK activation and on SCN2.2 cell fate. PKA and PKC inhibition together, CaMK-II inhibition and JNK-II inhibition resulted in SCN2.2 cell death in the presence of Glu. PKA + PKC inhibition and CaMK-II inhibition resulted in a corresponding decrease in Glu-induced ERK phosphorylation. Combined inhibition of ERK, CaMK-II and JNK-II resulted in exacerbation of cell death as compared to when the inhibitors were used individually. These results suggest that ERK activity is regulated by a number of different kinases. Glu treatment resulted in a persistent increase in ERK phosphorylation (activation) for up to 48 h in the SCN2.2 cells whereas the pro-apoptotic p38 was phosphorylated (activated) in the GT1-7 cells exposed to Glu. JNK-II was transiently phosphorylated (activated) in the SCN2.2 cells. This suggests an activation of a short-term stress response which can result in activation of a long-term neuroprotective response in these cells. Pro-apoptotic Bid mRNA and cleaved Bid protein levels were increased in the Glu-treated GT1-7 cells. The effect of Glu treatment on the expression of several downstream effector molecules of ERK activation was also explored. Neuritin mRNA was increased with Glu treatment in the SCN2.2, but not in the GT1-7 cells. However, there was no change in the neuritin protein levels in either cell type with Glu treatment. Bcl2 levels remained unchanged in the Glu-treated GT1-7 cells. Although there was no change in the Bcl2 mRNA levels in the SCN2.2 cells, Bcl2 protein was significantly increased with Glu treatment, thus suggesting a post-translational mechanism of neuroprotection involving Bcl2. Taken together, these results are consistent with activation of an apoptotic mechanism in the GT1-7 cells exposed to Glu as opposed to a pro-survival effect in similarly treated SCN2.2 cells. Future studies should be able to take advantage of these mechanisms in developing therapeutic strategies in the treatment of neurodegenerative disorders.
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Tsai, Wang Wei Vicky. "The role of group I metabotropic glutamate receptors in neuronal excitotoxicity in Alzheimer's disease /." [St. Lucia, Qld.], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18689.pdf.
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Oberländer, Kristin [Verfasser], and Hilmar [Akademischer Betreuer] Bading. "Neuronal activity-dependent gene expression in learning and excitotoxicity / Kristin Oberländer ; Betreuer: Hilmar Bading." Heidelberg : Universitätsbibliothek Heidelberg, 2019. http://d-nb.info/117978216X/34.
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Tischbein, Maeve. "FUS and Excitotoxicity Cross Paths in ALS: New Insights into Cellular Stress and Disease." eScholarship@UMMS, 2018. https://escholarship.umassmed.edu/gsbs_diss/990.
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Amyotrophic lateral sclerosis (ALS) is an incurable and fatal neurodegenerative disease characterized by motor neuron loss. Although pathological mutations exist in >15 genes, the mechanism(s) underlying ALS are unknown. FUS is one such gene and encodes the nuclear RNA-binding protein (RBP), fused in sarcoma (FUS), which actively shuttles between the nucleus and cytoplasm. Intriguingly, nearly half of the ALS mutations identified in FUS cause this protein to mislocalize, suggesting that FUS localization is relevant to disease.
Here, we found that excitotoxicity, a neuronal stress caused by aberrant glutamate signaling, induces the rapid redistribution of FUS and additional disease-linked RBPs from the nucleus to the cytoplasm. As excitotoxicity is pathologically associated with ALS, it was notable that the nuclear egress of FUS was particularly robust. Further, ALS-FUS variants that predominantly localize to the nucleus also undergo redistribution. Thus, we sought to understand the purpose underlying FUS translocation and the potential relevance of this response to disease. As calcium dysregulation is strongly associated with neurodegenerative disorders, we examined the contribution of calcium to FUS egress. In addition to global changes to nucleocytoplasmic transport following excitotoxic insult, we observed that FUS translocation caused by excitotoxicity is calcium mediated. Moreover, we found that dendritic expression of Gria2, a transcript encoding an α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunit responsible for regulating calcium permeability, is FUS-dependent under conditions of stress. Together, these observations support the premise that FUS has a normal function during excitotoxic stress and that glutamatergic signaling may be dysregulated in FUS-mediated ALS.
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Sharrett-Field, Lynda. "SOMATIC INJURY PRECEDES DISTAL ATROPHY FOLLOWING EXCITOTOXIC HIPPOCAMPAL INSULT." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_theses/70.
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Excitotoxicity can lead to increases in intracellular Na+ and Ca2+ concentrations via the glutamatergic NMDA receptors, which can lead to cell death. Detailing the time-dependent degradation of neuronal components in response to excitotoxic challenge may help elucidate the sequence in which these signaling pathways are initiated and further, associate these pathways with topographic cellular demise. Using organotypic hippocampal slice culture technique, tissue from neonatal rat pups was exposed to NMDA, APV, or co-exposed for 24, 72 or 120 hours. Fluorescent microscopy of propidium iodide (PI) was used to evaluate neuronal membrane damage, changes in the density of mature soma (NeuN) and NMDA NR2B subunits were measured using immunohistochemical procedures. After 24 hours of exposure, the CA1 showed an increased PI signal and a decrease in NeuN marker, indicating somatic injury occurs shortly after excitotoxic challenge; these effects were blocked by co-administration of APV. Also in the CA1, loss of NR2B subunits, heavily expressed in dendritic processes, declined following 72 hours of exposure. Because somatic injury precedes loss of distal NR2B subunits, it is possible that these events involve different mechanisms, findings that may be relevant in the development of therapies to target neurodegeneration resulting from excitotoxicity.
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Samson, Andrew James. "Rapid neuronal responses during spreading neurotoxic and neuroprotective network activity." Thesis, University of Dundee, 2016. https://discovery.dundee.ac.uk/en/studentTheses/8c797952-eda1-4c03-a38a-15c2679e984f.
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Glutamate is the major excitatory neurotransmitter in the mammalian central nervous system, playing critical roles in basal synaptic transmission and the molecular correlates of learning and memory, long-term potentiation and long-term depression. However, glutamate is also neurotoxic during prolonged exposure and the dysfunction of the glutamatergic system has been implicated in most neurological disorders, including stroke and epilepsy, and in certain neurodegenerative diseases, including Alzheimer’s disease. In these conditions, an increased concentration of extracellular glutamate causes an over-activation of local ionotropic glutamate receptors that trigger neuronal cell death (excitotoxicity). In this study, we have used dissociated hippocampal neurons cultured on coverslips and within novel microfluidic devices to study neuronal responses, both functional and morphological, to prolonged exposure to glutamate. We find that high glutamate concentrations evoke a rapid retraction of dendritic spines, the collapse of microtubules, the formation of dendritic beads and the inhibition of basal neurotransmitter release. These responses have been identified in many neurological disorders where excitotoxicity is reported, suggesting they may be a sign of imminent cell death. However, the development of dendritic beads and the inhibition of network activity also occurs at subtoxic concentrations of glutamate and neuronal morphological changes recover rapidly post-insult. We therefore hypothesised that beading and the inhibition of neurotransmitter release may be a protective mechanism and render neurons resistant to subsequent glutamatergic insults. However, a subtoxic stimulation is not protective against a subsequent excitotoxic insult delivered immediately afterwards. However, given that neurotransmitter release can confer protection to neurons, it is possible that protection is realised, not on the neurons exposed to the subtoxic insult, but on those neurons with which they communicate, as a ‘warning’ signal. To assess the impact of a localised insult to a wider neuronal network, hippocampal neurons were cultured in novel microfluidic devices, to environmentally isolate neuronal populations, whilst preserving synaptic contacts between them. We observe that bystander naïve neurons downstream of a localised excitotoxic insult succumb to a secondary, activity-dependent, spreading toxicity. In addition, we reveal a novel mechanism by which neuronal networks also transmit a rapid and robust (albeit transient) protection from excitotoxicity. The protective phenotype acquired by neurons during this protective process requires neuronal inhibitory activity to quench overexcitation, along with the retraction of dendritic spines and/or dendritic beading. Therefore, we highlight a dichotomous role that dendritic beading plays following a direct glutamatergic insult (large beads) and as a result of GABAergic recruitment in downstream neurons (small beads). We determine that a network neuroprotective capacity exists that limits spreading toxicity, which may be recruited from a distal site even after an excitotoxic insult has occurred. Together, we may have identified a new therapeutic opportunity to limit on-going brain damage in conditions of acute neuronal injury.
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Akins, Mark S. "The Role of the Neuronal gap Junction Protein Connexin36 in Kainic Acid Induced Hippocampal Excitotoxicity." Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/30392.
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Kainic acid induced excitotoxicity causes pyramidal cell death in the CA3a/b region of the hippocampus. Electrical synapses, gap junctional communication, and single membrane channels in non-junctional membranes (hemichannels) composed of connexin36 (Cx36) have been implicated in both seizure propagation and the spread of excitotoxic cell death. In rats, Cx36 protein is expressed by pyramidal neurons. Localization of protein in mouse, however, is highly controversial. Expression is reported to be restricted to hippocampal interneurons yet the same excitotoxic mechanisms (electrical and metabolic coupling between pyramidal neurons) are invoked to explain the role of Cx36 in excitotoxic pyramidal loss in murine brain. To address this controversy, I show by confocal immunofluorescence and in situ hybridization that Cx36 protein expression is restricted to interneurons and microglia in murine hippocampus and is not expressed by, or is below level of detection in pyramidal neurons. Using behavioural and electrophysiological measures, seizure propagation was found to be moderately enhanced in the absence of Cx36 likely due to the loss of interneuron-mediated synchronous inhibition of the pyramidal cells. Further, CA3a/b neurons die post kainic acid injury in the presence of Cx36 but are protected in Cx36-/- mice. When delayed excitotoxic cell death is maximal, Cx36 is primarily expressed by activated microglia as demonstrated by confocal immunofluorescence, in situ hybridization, and Western blotting. These activated microglia are located in the direct vicinity of, and surrounding cells in the damaged Ca3a/b region. Finally, I show that loss of Cx36 from activated microglia in mice is sufficient to prevent excitotoxic cell death in the CA3a/b with surviving neurons functional as assessed by both electrophysiological and behavioural measures. Together, these data identify a new mechanism of excitotoxic injury, mediated by neuronal-glial interactions, and dependent on microglial Cx36 expression.
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Cuthill, Daniel. "Involvement of excitotoxicity or oxidative stress in the pathophysiology of white and grey matter injury." Thesis, University of Glasgow, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414444.
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Ting, Ka Ka Clinical School St Vincent's Hospital Faculty of Medicine UNSW. "Quinolinic acid and its effect on the astrocyte with relevance to the pathogenesis of Alzheimer??s disease." Publisher:University of New South Wales. Clinical School - St Vincent's Hospital, 2008. http://handle.unsw.edu.au/1959.4/41288.
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There is evidence that the excitotoxin quinolinic acid (QUIN) synthesized through the kynurenine pathway (KP) by activated microglia may play a role in the pathogenesis of several major neuroinflammatory diseases and more particularly in Alzheimer??s disease (AD). The hypothesis of this project is QUIN affects the function and morphology of astrocytes. In this study I used human foetal astrocytes stimulated with AD associated cytokines including IFN-gamma, TNF-alpha, TGF-alpha and different concentrations of QUIN ranging from low physiological to high excitotoxic concentrations. I found that QUIN induces IL-1beta expression in human astrocytes and subsequently, contribute to the inflammatory cascade that is present in AD pathology. Glial fibrillary acid protein (GFAP) and vimentin protein expression were complementary in expression to each other after 24 hr stimulation with different QUIN doses. However, there were marked increases in GFAP levels and reduction in vimentin levels compared to controls with QUIN treatment indicating that QUIN can trigger astrogliosis in human astrocytes. Glutamine synthetase (GS) activity was used as a functional metabolic test for astrocytes and I found a dose-dependent inhibition of GS activity by QUIN. This inhibition was inversely correlated with iNOS expression whereby reduced GS activity is accompanied with an increase expression of iNOS in human astrocytes. These results suggest that reduction in GS activity can lead to accumulation of extracellular glutamate then leading to exacerbated excitotoxicity via NMDA receptor over-activation and ultimately neuronal death. PCR array results showed that at least four different pathways were activated with pathological concentration of QUIN including p38 MAPK that is associated with pro-inflammatory cytokine production, ERK/MAPK growth and differentiation that can modulate structural proteins, mitochondrial-induced apoptotic cascade and cell cycle control pathway. QUIN-induced astrogliosis and excitotoxicity could lead to glial scar formation and prevention of axonal growth thus exacerbation of neurodegeneration via synaptosomal NMDA receptor over-activation. All together, this study showed that, in the context of AD, QUIN is an important factor for astroglial activation, dysregulation and death, which can be mediated by the previously mentioned pathways.
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Puddifoot, Clare Anne. "Neuroprotection from the huntingtin-repressed transcriptional coactivator PGC-1α." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/8055.
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The transcriptional coactivator PPARgamma coactivator 1alpha (PGC-1α) is a regulator of mitochondrial biogenesis and function and is decreased in the striatum of patients with Huntington’s Disease (HD). HD is an autosomal dominant neurological disorder caused by a polyglutamine repeat in the huntingtin protein which leads to degeneration of striatal and cortical tissues. PGC-1α undergoes targeted downregulation by mutant huntingtin protein (mtHtt) and PGC-1α knockout mice have striatal lesions similar to HD transgenic mice. Exogenous PGC-1α partially reverses the toxic effects of mutant huntingtin in cultured striatal neurons while in vivo administration of PGC-1α to the striatum in a mouse model of HD reduces neuronal volume loss. Synaptic N-methyl-D-aspartate receptor (NMDAR)- activity can drive the expression of PGC-1α which is neuroprotective against oxidative and excitotoxic stress in vitro whereas extrasynaptic NMDAR expression is increased in HD. Excessive NMDAR activity, specifically through extrasynaptic rather than synaptic NMDARs, leads to excitotoxic death in neurons and its regulation has been targeted in the search for therapeutic interventions for multiple neurological disorders. The data presented in this thesis show that the repression of PGC-1α by mtHtt may be significant in the dysregulation of NMDARs in HD. Both PGC-1α knockdown and mutant huntingtin are found to increase extrasynaptic NMDAR activity and excitotoxicity in a non-additive way, suggesting common regulatory mechanisms. Furthermore exogenous PGC- 1α expression is sufficient to reverse this increase in extrasynaptic NMDAR currents and excitotoxicity by mtHtt. This thesis adds mechanistic insight into previous understanding of the synergistic roles of mtHtt, NMDAR activity and PGC-1α in HD. Finally, we show that chronic knockout of PGC-1α in the PGC-1α(-/-) mouse causes distinct alterations in glutamatergic signaling that do not mimic the observation of acute knockdown of PGC-1α. We propose that the loss of PGC-1α in a number of neurological disorders contributes to concurrent increases in aberrant glutamate signaling and excitotoxicity in these diseases.
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Nascimento, Paula Hespanholo 1984. "Padrão de distribuição e localização de expressão das proteínas VILIP-1, receptor sensor de cálcio e receptor metabotrópico do glutamato 1 em tecidos de pacientes com epilepsia do lobo temporal." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/310395.
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Orientador: Lília Freira Rodrigues de Souza LiDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas
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Resumo: A esclerose hipocampal está associada à epilepsia de lobo temporal medial (ELT) e causa expressão alterada de receptores tais como o Receptor Metabotrópico de Glutamato (mGluR1). Contudo, ainda há controvérsias se sua expressão está aumentada ou diminuída em ELT. O Receptor Sensor de Cálcio (CASR), outro receptor da mesma família do mGluR1, é expresso em hipocampo, mas seu papel no cérebro ainda é desconhecido. VILIP-1 é uma proteína sensora de cálcio neuronal (NCS) expressa predominantemente no cérebro e em humanos e sua expressão foi mapeada por imunoistoquímica na subpopulação de neurônios piramidais em CA1 e CA4 de hipocampo. Sugere-se também que a ativação de mGluR possa regular a expressão de VILIP-1 durante a plasticidade hipocampal. No entanto, não há estudos associando VILIP-1 e esclerose hipocampal. Nós hipotetizamos que além do mGluR1, o CASR e o VILIP-1 estão associados a esclerose hipocampal em ELT. O objetivo deste trabalho foi analisar o padrão de expressão de VILIP-1, CASR e mGluR1, em hipocampo de pacientes com ELT submetidos a amigdalohipocampectomia. Nossos resultados demonstraram a presença de EH nos tecidos hipocampais de pacientes com ELT com redução no número de neurônios em CA1 e presença de intensa gliose. Pela análise da expressão dos transcritos VILIP-1, CASR e mGluR1 em hipocampo total utilizando PCR em tempo real não encontramos diferença na expressão dos RNAs mensageiros dos pacientes quando comparado com os controles. Entretanto, quando comparamos a expressão protéica em hipocampo de pacientes e controles, utilizando o método de imunoistoquímica, encontramos não somente redução significativa no número de neurônios presentes em CA1 de pacientes, mas também redução importante nos neurônios positivamente marcados para VILIP-1, CASR e mGluR1. Estes achados sugerem que não apenas mGluR1, mas também CASR e VILIP-1, estão associados à EH em pacientes com ELT
Abstract: Hippocampal sclerosis (HS) is associated to temporal lobe epilepsy (TLE) and cause altered expression of neurotransmitter receptors such as metabotropic glutamate receptor 1 (mGluR1). However, whether its expression level is increased or decreased in temporal lobe epilepsy is still controversial. Calcium-sensing receptor (CASR), another receptor from the same family of mGluR1, is expressed in hippocampus, but its role in brain is unknown. VILIP-1, a neuronal calcium sensing protein (NCS) is expressed predominantly in brain and in humans its expression was identified by immunohistochemistry in subpopulations of pyramidal neurons in CA1 and CA4 in hippocampus. Activation of mGluR1 is suggested that may regulates VILIP-1 expression during hippocampal plasticity. However, there are no studies associating VILIP-1 and hippocampal sclerosis. We hypothesized that not only mGluR1 but also VILIP and CASR is involved in hippocampal sclerosis in TLE patients. The objective of this study was to analyze the pattern of expression of VILIP-1, CASR and mGluR1 in hippocampal tissues from patients with TLE who underwent amygdalohippocampectomy. Our results demonstrated the presence of hippocampal sclerosis in hippocampal tissues in patients with TLE with reduction in the number of neurons in CA1 and gliosis. By the expression analysis of the transcripts of VILIP-1, CASR and mGluR1 in total hippocampus using real time PCR, we did not find differences on mRNAS expression of patients compared with controls. However, when we compared the protein expression from hippocampi from patients with controls, by immunohistochemistry, we not only found an important reduction on neuron cell number in patients, but also an important reduction on positively stained neurons for VILIP-1, CASR and mGluR1, suggesting that not only mGluR1, but also CASR and VILIP1 are associated to HS in patients with TLE
Mestrado
Saude da Criança e do Adolescente
Mestre em Saude da Criança e do Adolescente
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MAZZA, Roberta. "Neurotensin as Modulator of Glutamatergic Signalling: Relevance in Neurodegenerative Diseases." Doctoral thesis, Università degli studi di Ferrara, 2009. http://hdl.handle.net/11392/2389146.
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Rationale: Neurotensin (NT) is a tridecapeptide widely distributed in mammalian brain, where acts as a neurotransmitter or neuromodulator of classical neurotransmitters, mainly through the activation of its receptor NTS1. Several in vitro and in vivo studies have demonstrated the existence of close interactions between NT and dopamine (DA) systems both in limbic and striatal brain regions (Nemeroff CB., 1985; Binder EB., 2001; Caceda R., 2006). Because of the involvement of an over-activation of DA system in the development of neurological disorders such as schizophrenia, psychosis and dyskinesia, a strong attention was given to the study of complex interactions between NTS1 and D2 dopamine receptor, highlighting the existence of receptor-receptor interaction, potential target for developing new anti-schizophrenic drugs (Ferraro L., 2007). In addition, neurochemical and biochemical data indicate that NT plays a crucial role in regulating glutamatergic transmission, probably inducing an amplification of NMDA receptor signalling, even at threshold concentrations (lOnM) (Antonelli T., 2004).
Results I: The neuromodulatory function of NT on glutamatergic signalling was studied in an in vitro model of primary cortical cultures, highlighting a dose-dependent effect (NT 0.1-300 nM) on glutamate release. In addition, NT show the ability to amplify the NMDA-induced (lOOnM) increase of glutamate release. The use of the NTS1 receptor antagonists, SR48692 (lOOnM) and the NMDA receptor antagonist MK-801 (l[iM), in combination with an effective concentration of NT, made possible to hypothesize that the mechanism involved could be an NTSl/NMDA receptor-receptor interaction (Antonelli T., 2004; Ferraro L., 2008) both at striatal and cortical level. It has been postulated that the accumulation of extracellular glutamate level and the consequent excessive activation of NMDA receptors (excitotoxic mechanism) contributes to neuronal death associated with chronic and acute neurodegenerative diseases (Olney JW., 1978). Since the data obtained to date suggest a NT-mediated strengthening on several glutamatergic functions in the central nervous system, our work was intended to deepen its possible involvement in glutamate-induced neurodegenerative mechanisms. The in vitro model of cerebral ischemia obtained by oxygen and glucose deprivation (OGD) showed a significant increase in extracellular levels of glutamate. In addition, significant alterations of biochemical and morphological parameters measured were observed. Increase the release of LDH, reduction of mitochondrial oxidative capacity (MTT levels), increased activity of caspase-3, increased number of apoptotic (fragmented) nuclei, increasead level of AN(+)/PI(-) immunoreactive cells and MAP-2 dendritic aggregations was measured 24 hours after the ischemic insult. The addition of NT (lOOnM) to the culture medium showed a significant increase in the OGD-induced changes, while cells pre-exposure to the NTS1 antagonist SR48692 (lOOnM) blocked the effect of both the neuropeptide and OGD exposure, alone or in combination. The results obtained with this in vitro model of cerebral ischemia, stress the involvement of NT activity in the eziopathogenesis of an acute neurodegenerative disease (Antonelli T., 2008).
Results II: At basal ganglia level, NT induces an amplification of glutamate release, probably through a NTS1/D2 antagonistic interaction. This phenomenon could contribute to the degeneration of dopaminergic nigro-striatal neurons by the means of an excitotoxic mechanism, pathogenetic feature of Parkinson's disease (PD). In this contex, experiments were conducted with the in vivo microdialysis technique at striatal and cortical level, anatomical areas notoriously involved in PD. The results obtained again showed that a, potential, NTS1/NMDA receptor-receptor interaction induces a glutamatergic signalling amplification. The observed increase in glutamate extracellular levels induced by treatment with NMDA (100 and 500 uM) and NT (lO nM), showed once again to be partially blocked by treatment with NT antagonist SR48692 (Ferraro L., 2008). Given the potential neuroprotective role played SR48692, successive studies in an vivo model of PD achieved through unilateral lesion of the nigro-striatalpathway with the neurotoxin 6-idroxydopamine (6-OHDA) were done. Three experimental groups were tested for the turning rotation behaviour and by a challenge with NMDA lOOuM: lesioned rats, rats exposed only to vehicle and lesioned rats treated with the neurotensinergic antagonist. The animals exposed to SR48692 have shown a significant recovery for both the parameter of turning behaviour and responsiveness to pharmacological challenge with NMDA (Ferraro L., 2008). The results obtained can lead to the hypothesis that the use of selective NTS1 receptor antagonists, in combination with conventional drug treatments, could provide a new terapeutic approach for chronic and acute neurodegenerative diseases treatment, such as cerebral ischemia and Parkinson's disease.
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Fan, Jing. "Signaling pathways involved in enhanced NMDA receptor-dependent excitotoxicity in a mouse model of Huntington disease." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/38094.
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Huntington disease (HD) is an inherited neurodegenerative disease lacking effective treatment, characterized by involuntary movements, psychiatric disorders, and cognitive symptoms. Pathology shows prominent degeneration of γ-aminobutyric acid (GABA)-ergic medium-sized spiny neurons (MSNs) of the striatum and certain cortical layers (Vonsattel and DiFiglia, 1998). HD is caused by a dominant mutation in the HD gene that leads to >35 glutamine repeats (polyQ) near the N-terminus of the protein huntingtin (htt) (The Huntington’s Disease Collaborative Research Group, 1993). Increasing evidence suggests that the N-methyl-D-aspartate (NMDA)-type glutamate receptor (NMDAR) plays a role in mediating death of MSNs observed in HD (Fan and Raymond, 2007). Previous results from our laboratory demonstrate that NMDAR-mediated current and toxicity are increased in MSNs from the Yeast Artificial Chromosome (YAC) transgenic mouse model expressing polyglutamine-expanded full-length human htt (Shehadeh et al., 2006; Zeron et al., 2002). However, the mechanism underlying altered function and enhanced toxicity of NMDAR in HD remains unknown.
Previous studies have shown that membrane-associated guanylate kinases (MAGUKs), such as postsynaptic density protein 95 (PSD-95) modulate NMDAR surface expression and excitotoxicity in rat hippocampal and cortical neurons (Aarts et al., 2002; Roche et al., 2001), and that htt interacts with PSD-95 in a polyglutamine dependent manner (Sun et al., 2001). Here, I tested the hypothesis that an altered association and/or regulation between PSD-95 and NMDARs in mutant htt-expressing cells contributes to increased susceptibility to excitotoxicity and investigated mechanism by which this occurs. Specifically, I investigated the association of PSD-95 with htt and the NMDAR GluN2 subunits; signaling downstream of activation of the NMDAR/PSD-95 complex; and NMDA-induced cell death. My results suggest that at the presymptomatic stage of HD, the enhanced interaction of PSD-95 with GluN2B, and its signaling through p38 mitogen-activated protein kinase (MAPK) but not neuronal nitric oxide synthase (nNOS) activation, contributes to mutant htt-mediated sensitivity to NMDAR-dependent excitotoxicity in YAC128 striatal neurons. This work contributes to the understanding of both NMDAR-dependent neuronal death mechanisms in striatal neurons and early synaptic changes in HD pathogenesis, as well as providing potential drug candidates for future HD treatment.
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Vasiljevic, Alexandre. "Caractérisation des fonctions neuroprotectives des interfaces sang-cerveau au cours du développement normal, dans les tumeurs périventriculaires et dans un modèle d’excitotoxicité périnatale." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1328/document.
Full textAbstract:
Les interfaces sang-cerveau comme la barrière hémato-encéphalique (BHE), les plexus choroïdes (PC) ou les organes circumventriculaires (OCV), constituent des barrières physiologiques nécessaires au fonctionnement du système nerveux central. Ces barrières sont à la fois « physiques », constituées de jonctions serrées, et « enzymatiques ». Longtemps considérées comme immatures chez le fœtus, ces barrières sont en réalité présentes précocement au cours du développement. Leurs caractéristiques et leurs propriétés restent peu connues chez l'homme. Nos travaux montrent que les PC expriment, précocement au cours du développement, des protéines de jonction serrée, les claudines (CLDN) 1, 2 et 3 chez le rat et chez l'homme. Cette expression est dynamique au cours du développement avec une apparition progressive de la CLDN2 pouvant avoir un lien avec la sécrétion du liquide céphalo-rachidien. Les CLDN 1 et 3 sont identifiées chez le fœtus humain au niveau de l'organe sous-commissural (OSC), un des OCV. La CLDN5 est exprimée précocement au niveau de la BHE chez le rat et chez l'homme et son expression est altérée dans un modèle d'excitotoxicité néonatale. Nos travaux montrent également que l'analyse du profil des CLDN est utile en pathologie tumorale notamment dans la compréhension et le diagnostic de tumeurs développées à partir des PC ou de l'OSC. Enfin, diverses enzymes antioxydantes et de détoxification dont l'époxyde hydrolase microsomale sont exprimées à 22 semaines d'aménorrhée principalement au niveau des PC du fœtus humain. Ces données suggèrent des capacités de détoxification des PC, d'installation précoce au cours du développement chez l'hommeBlood-brain interfaces including blood-brain barrier (BBB), choroid plexuses (CP) or circumventricular organs (CVO) are physiological barriers required for brain homeostasis. These barriers are “physical”, with tight junctions, and “enzymatic”. Though long considered immature in fetuses, these barriers are present from an early stage of development. Their characteristics and their properties are largely unknown in humans. Our work demonstrates that CP express tight junction-associated proteins claudins (CLDN) 1, 2, and 3 at early stages of development in rat and human. This expression is dynamic during development as shown by the progressive increase of CLDN2 immunopositivity that may follow increase in cerebrospinal fluid secretion. CLDN 1 and 3 are identified in human fetal subcommissural organ (SCO), one of the CVO. CLDN5 is early expressed in rat and human BBB and its expression is disrupted by excitotoxic injury. Our work also shows that CLDN immunohistochemical profile is useful in tumoral pathology, notably to better understand and diagnose tumors arising from CP or the SCO. Finally, various antioxidant and detoxifying enzymes such as the microsomal epoxide hydrolase are expressed at 22 weeks of gestation in the human fetus, mainly in CP. These results suggest a high detoxifying capacity for the CP during development in humans
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Isom, Amanda M. "The Cellular Consequences of Combining Antipsychotic Medications and Hypoglycemia." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1407407111.
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McKay, Sean. "Probing spatial and subunit-dependent signalling by the NMDA receptor." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/14225.
Full textAbstract:
NMDARs are ligand-gated cation channels which are activated by the neurotransmitter glutamate. NMDARs are essential in coupling electrical activity to biochemical signalling as a consequence of their high Ca2+ permeability. This Ca2+ influx acts as a secondary messenger to mediate neurodevelopment, synaptic plasticity, neuroprotection and neurodegeneration. The biological outcome of NMDAR activation is determined by a complicated interrelationship between the concentration of Ca2+ influx, NMDAR location (synaptic vs. extrasynaptic) as well as the subtype of the GluN2 subunit. Despite the recognition that NMDAR mediated physiology is multifaceted, tools used to study subunit and location dependent signalling are poorly characterized and in other cases, non-existent. Therefore, the aim of this thesis is to address this issue. Firstly, I assessed the current pharmacological approach used to selectively activate extrasynaptic NMDARs. Here, synaptic NMDARs are first blocked with MK-801 during phasic activation and then extrasynaptic NMDARs are tonically activated. This approach relies on the continual irreversible blockade of synaptic NMDARs by MK-801 yet contrary to the current dogma, I demonstrate this blockade is unstable during tonic agonist exposure and even more so when physiologically relevant concentrations of Mg2+ are present. This confines a temporal limit in which selective activation of extrasynaptic NMDARs can occur with significant consequences for studying synaptic vs. extrasynaptic NMDAR signalling. Dissecting subunit-dependent signalling mediated by the two major GluN2 subunits in the forebrain, GluN2A and GluN2B, has been advanced significantly by selective GluN2B antagonism yet a reciprocal GluN2A selective antagonist has been lacking. Utilizing novel GluN2A-specific antagonists, I demonstrate a developmental upregulation of GluN2A-mediated NMDA currents which concurrently dilutes the contribution of GluN2B-mediated currents. Moreover, I tested the hypothesis that the Cterminus of GluN2A and GluN2B are essential in controlling the developmental switch of GluN2 subunits utilizing knock-in mice whereby the C-terminus of GluN2A is replaced with that of GluN2B. Surprisingly, the exchange of the C-terminus does not impede the developmental switch in subunits nor the proportion of NMDARs at synaptic vs extrasynaptic sites. However, replacing the C-terminus of GluN2A with that of GluN2B induces a greater neuronal vulnerability to NMDA-dependent excitotoxicity. Collectively, this work enhances our understanding of the complex physiology mediated by the NMDAR by determining how pharmacological tools are best utilized to study the roles of NMDAR location and subunit composition in addition to revealing the importance of the GluN2 C-terminus in development and excitotoxicity.