Computational Analysis of AMPK-Mediated Neuroprotection Suggests Acute Excitotoxic Bioenergetics and Glucose Dynamics Are Regulated by a Minimal Set of Critical Reactions.

PubMed

Connolly, Niamh M C; D'Orsi, Beatrice; Monsefi, Naser; Huber, Heinrich J; Prehn, Jochen H M

2016-01-01

Loss of ionic homeostasis during excitotoxic stress depletes ATP levels and activates the AMP-activated protein kinase (AMPK), re-establishing energy production by increased expression of glucose transporters on the plasma membrane. Here, we develop a computational model to test whether this AMPK-mediated glucose import can rapidly restore ATP levels following a transient excitotoxic insult. We demonstrate that a highly compact model, comprising a minimal set of critical reactions, can closely resemble the rapid dynamics and cell-to-cell heterogeneity of ATP levels and AMPK activity, as confirmed by single-cell fluorescence microscopy in rat primary cerebellar neurons exposed to glutamate excitotoxicity. The model further correctly predicted an excitotoxicity-induced elevation of intracellular glucose, and well resembled the delayed recovery and cell-to-cell heterogeneity of experimentally measured glucose dynamics. The model also predicted necrotic bioenergetic collapse and altered calcium dynamics following more severe excitotoxic insults. In conclusion, our data suggest that a minimal set of critical reactions may determine the acute bioenergetic response to transient excitotoxicity and that an AMPK-mediated increase in intracellular glucose may be sufficient to rapidly recover ATP levels following an excitotoxic insult.

Computational Analysis of AMPK-Mediated Neuroprotection Suggests Acute Excitotoxic Bioenergetics and Glucose Dynamics Are Regulated by a Minimal Set of Critical Reactions

PubMed Central

Connolly, Niamh M. C.; D’Orsi, Beatrice; Monsefi, Naser; Huber, Heinrich J.; Prehn, Jochen H. M.

2016-01-01

Loss of ionic homeostasis during excitotoxic stress depletes ATP levels and activates the AMP-activated protein kinase (AMPK), re-establishing energy production by increased expression of glucose transporters on the plasma membrane. Here, we develop a computational model to test whether this AMPK-mediated glucose import can rapidly restore ATP levels following a transient excitotoxic insult. We demonstrate that a highly compact model, comprising a minimal set of critical reactions, can closely resemble the rapid dynamics and cell-to-cell heterogeneity of ATP levels and AMPK activity, as confirmed by single-cell fluorescence microscopy in rat primary cerebellar neurons exposed to glutamate excitotoxicity. The model further correctly predicted an excitotoxicity-induced elevation of intracellular glucose, and well resembled the delayed recovery and cell-to-cell heterogeneity of experimentally measured glucose dynamics. The model also predicted necrotic bioenergetic collapse and altered calcium dynamics following more severe excitotoxic insults. In conclusion, our data suggest that a minimal set of critical reactions may determine the acute bioenergetic response to transient excitotoxicity and that an AMPK-mediated increase in intracellular glucose may be sufficient to rapidly recover ATP levels following an excitotoxic insult. PMID:26840769

Hydrogen-rich saline protects retina against glutamate-induced excitotoxic injury in guinea pig.

PubMed

Wei, Lihua; Ge, Li; Qin, Shucun; Shi, Yunzhi; Du, Changqing; Du, Hui; Liu, Liwei; Yu, Yang; Sun, Xuejun

2012-01-01

Molecular hydrogen (H(2)) is an efficient antioxidant that can selectively reduce hydroxyl radicals and inhibit oxidative stress-induced injuries. We investigated the protective effects and mechanism of hydrogen-rich saline in a glutamate-induced retinal injury model. Retinal excitotoxicity was induced in healthy guinea pigs by injecting glutamate into the vitreous cavity. After 30 min, hydrogen-rich saline was injected into the vitreous cavity, the peritoneal cavity or both. Seven days later, the retinal stress response was evaluated by examining the stress biomarkers, inducible nitric-oxide synthase (iNOS) and glucose-regulated protein 78 (GRP78). The impaired glutamate uptake was assessed by the expression of the excitatory amino acid transporter 1(EAAT-1). The retinal histopathological changes were investigated, focusing on the thicknesses of the entire retina and its inner layer, the number of cells in the retinal ganglion cell layer (GCL) and the ultrastructure of the retinal ganglion cells (RGCs) and glial cells. Compared with the glutamate-induced injury group, the hydrogen-rich saline treatment reduced the loss of cells in the GCL and thinning of the retina and attenuated cellular morphological damage. These improvements were greatest in animals that received H(2) injections into both the vitreous and the peritoneal cavities. The hydrogen-rich saline also inhibited the expression of glial fibrillary acidic protein (GFAP) in Müller cells, CD11b in microglia, and iNOS and GRP78 in glial cells. Moreover, the hydrogen-rich saline increased the expression of EAAT-1. In conclusion, the administration of hydrogen-rich saline through the intravitreal or/and intraperitoneal routes could reduce the retinal excitotoxic injury and promote retinal recovery. This result likely occurs by inhibiting the activation of glial cells, decreasing the production of the iNOS and GRP78 and promoting glutamate clearance. Copyright © 2011 Elsevier Ltd. All rights reserved.

Magnolol Reduces Glutamate-Induced Neuronal Excitotoxicity and Protects against Permanent Focal Cerebral Ischemia Up to 4 Hours

PubMed Central

Lee, E-Jian; Hung, Yu-Chang; Tai, Shih-Huang; Chen, Hung-Yi; Chen, Tsung-Ying; Wu, Tian-Shung

2012-01-01

Neuroprotective efficacy of magnolol, 5,5′-dially-2,2′-dihydroxydiphenyl, was investigated in a model of stroke and cultured neurons exposed to glutamate-induced excitotoxicity. Rats were subjected to permanent middle cerebral artery occlusion (pMCAO). Magnolol or vehicle was administered intraperitoneally, at 1 hr pre-insult or 1–6 hrs post-insult. Brain infarction was measured upon sacrifice. Relative to controls, animals pre-treated with magnolol (50–200 mg/kg) had significant infarct volume reductions by 30.9–37.8% and improved neurobehavioral outcomes (P<0.05, respectively). Delayed treatment with magnolol (100 mg/kg) also protected against ischemic brain damage and improved neurobehavioral scores, even when administered up to 4 hrs post-insult (P<0.05, respectively). Additionally, magnolol (0.1 µM) effectively attenuated the rises of intracellular Ca2+ levels, [Ca2+](i), in cultured neurons exposed to glutamate. Consequently, magnolol (0.1–1 µM) significantly attenuated glutamate-induced cytotoxicity and cell swelling (P<0.05). Thus, magnolol offers neuroprotection against permanent focal cerebral ischemia with a therapeutic window of 4 hrs. This neuroprotection may be, partly, mediated by its ability to limit the glutamate-induced excitotoxicity. PMID:22808077

Synthetic regulators of the 2-oxoglutarate oxidative decarboxylation alleviate the glutamate excitotoxicity in cerebellar granule neurons.

PubMed

Kabysheva, Maria S; Storozhevykh, Tatiana P; Pinelis, Vsevolod G; Bunik, Victoria I

2009-05-01

Impairment of the 2-oxoglutarate oxidative decarboxylation by the 2-oxoglutarate dehydrogenase complex (OGDHC) is associated with the glutamate accumulation, ROS production and neuropathologies. We hypothesized that correct function of OGDHC under metabolic stress is essential to overcome the glutamate excitotoxic action on neurons. We show that synthetic phosphono analogs of 2-oxoglutarate, succinyl phosphonate and its phosphono ethyl ester, improve the catalysis by brain OGDHC through inhibiting the side reaction of irreversible inactivation of its first component, 2-oxoglutarate dehydrogenase. Under the substrate and cofactor saturation, the component and complex undergo the inactivation during catalysis with the apparent rate constant 0.2 min(-1). The inactivation rate is reduced by 90% and 60% in the presence of 50 microM succinyl phosphonate and its phosphono ethyl ester, correspondingly. In cultured cerebellar granule neurons exposed to excitotoxic glutamate, the phosphonates (100 microM) protect from the irreversible impairment of mitochondrial function and delayed calcium deregulation. The deregulation amplitude is decreased by succinyl phosphonate and its phosphono ethyl ester by 50% and 30%, correspondingly. Thus, succinyl phosphonate is more potent than its phosphono ethyl ester in protecting both the isolated brain OGDHC from inactivation and cultured neurons from the glutamate-induced calcium deregulation. The correlation of the relative efficiency of the phosphonates in vitro and in situ indicates that their cellular effects are due to targeting OGDHC, which is in accord with independent studies. We conclude that the compounds preserving the 2-oxoglutarate dehydrogenase activity are of neuroprotective value upon metabolic disbalance induced by glutamate excess.

Glutamate-mediated excitotoxicity in neonatal hippocampal neurons is mediated by mGluR-induced release of Ca++ from intracellular stores and is prevented by estradiol

PubMed Central

Hilton, Genell D.; Nunez, Joseph L.; Bambrick, Linda; Thompson, Scott M.; McCarthy, Margaret M.

2008-01-01

Hypoxic/ischemic (HI) brain injury in newborn full-term and premature infants is a common and pervasive source of life time disabilities in cognitive and locomotor function. In the adult, HI induces glutamate release and excitotoxic cell death dependent on NMDA receptor activation. In animal models of the premature human infant, glutamate is also released following HI, but neurons are largely insensitive to NMDA or AMPA/kainic acid (KA) receptor-mediated damage. Using primary cultured hippocampal neurons we have determined that glutamate increases intracellular calcium much more than kainic acid. Moreover, glutamate induces cell death by activating Type I metabotropic glutamate receptors (mGluRs). Pretreatment of neurons with the gonadal steroid estradiol reduces the level of the Type I metabotropic glutamate receptors and completely prevents cell death, suggesting a novel therapeutic approach to excitotoxic brain damage in the neonate. PMID:17156362

Inhibition of the mitochondrial pyruvate carrier protects from excitotoxic neuronal death

PubMed Central

Wallace, Martina; Buren, Caodu; Martyniuk, Kelly; Andreyev, Alexander Y.; Li, Edward; Fields, Jerel A.; Cordes, Thekla; Reynolds, Ian J.; Bloodgood, Brenda L.; Metallo, Christian M.

2017-01-01

Glutamate is the dominant excitatory neurotransmitter in the brain, but under conditions of metabolic stress it can accumulate to excitotoxic levels. Although pharmacologic modulation of excitatory amino acid receptors is well studied, minimal consideration has been given to targeting mitochondrial glutamate metabolism to control neurotransmitter levels. Here we demonstrate that chemical inhibition of the mitochondrial pyruvate carrier (MPC) protects primary cortical neurons from excitotoxic death. Reductions in mitochondrial pyruvate uptake do not compromise cellular energy metabolism, suggesting neuronal metabolic flexibility. Rather, MPC inhibition rewires mitochondrial substrate metabolism to preferentially increase reliance on glutamate to fuel energetics and anaplerosis. Mobilizing the neuronal glutamate pool for oxidation decreases the quantity of glutamate released upon depolarization and, in turn, limits the positive-feedback cascade of excitotoxic neuronal injury. The finding links mitochondrial pyruvate metabolism to glutamatergic neurotransmission and establishes the MPC as a therapeutic target to treat neurodegenerative diseases characterized by excitotoxicity. PMID:28254829

Low dose of L-glutamic acid attenuated the neurological dysfunctions and excitotoxicity in bilateral common carotid artery occluded mice.

PubMed

Ramanathan, Muthiah; Abdul, Khadar K; Justin, Antony

2016-10-01

Glutamate, an excitatory neurotransmitter in the brain, produces excitotoxicity through its agonistic action on postsynaptic N-methyl-D-aspartate receptor, resulting in neurodegeneration. We hypothesized that the administration of low doses of glutamate in cerebral ischemia could attenuate the excitotoxicity in neurons through its autoreceptor regulatory mechanism, and thereby control neurodegeneration. To test the hypothesis, the effect of L-glutamic acid (L-GA) 400 μmol/l/kg was evaluated in a bilateral common carotid artery occlusion-induced global ischemic mouse model. Memantine was used as a positive control. Global ischemia in mice was induced by occlusion of both the common carotid artery (bilateral common carotid artery occlusion) for 20 min, followed by reperfusion injury. L-GA was infused slowly through the tail vein 30 min before the surgery and every 24 h thereafter until the end of the experiment. The time-dependent change in cerebral blood flow was monitored using a laser Doppler image analyzer. The neurotransmitters glutamate and γ-aminobutyric acid (GABA) and the neurobiochemicals ATP, glutathione, and nitric oxide were measured in the different regions of brain at 0, 24, 48, and 72 h after reperfusion injury. L-GA increased locomotor activity, muscle coordination, and cerebral blood flow in ischemic mice at 72 h after ischemic insult. L-GA reduced glutamate levels in the cortex, striatum, and hippocampus at 72 h, whereas GABA levels were elevated in all three brain regions studied. Further, L-GA elevated glutathione levels and attenuated nitric oxide levels, but failed to restore ATP levels 72 h after ischemia-reperfusion. We conclude that the gradual reduction of glutamate along with elevation of GABA in different brain regions could have contributed toward the neuroprotective effect of L-GA. Hence, a slow infusion of a low dose of L-GA could be beneficial in controlling excitotoxicity-induced neurodegeneration following ischemia.

In vivo and in vitro effects of multiple sclerosis immunomodulatory therapeutics on glutamatergic excitotoxicity.

PubMed

Luchtman, Dirk; Gollan, René; Ellwardt, Erik; Birkenstock, Jérôme; Robohm, Kerstin; Siffrin, Volker; Zipp, Frauke

2016-03-01

In multiple sclerosis (MS), a candidate downstream mechanism for neuronal injury is glutamate (Glu)-induced excitotoxicity, leading to toxic increases in intraneuronal Ca(2+) . Here, we used in vivo two-photon imaging in the brain of TN-XXL transgenic Ca(2+) reporter mice to test whether promising oral MS therapeutics, namely fingolimod, dimethyl fumarate, and their respective metabolites fingolimod-phosphate and monomethyl fumarate, can protect neurons against acute glutamatergic excitotoxic damage. We also assessed whether these drugs can protect against excitotoxicity in vitro using primary cortical neurons, and whether they can directly inhibit Glu release from pathogenic T-helper 17 lymphocytes. In vivo, direct and acute (1 h) administration of 100 mM Glu to the brainstem resulted in a rapid and significant up-regulation in neuronal Ca(2+) signaling as well as morphological excitotoxic changes that were attenuated by the NMDA-receptor antagonist MK801. Direct CNS administration of MS drugs prior to Glu significantly delayed or reduced, but did not prevent the neuronal Ca(2+) increase or morphological changes. In vitro, prolonged (24 h) treatment of primary neurons with the fumarates significantly protected against neurotoxicity induced by Glu as well as NMDA, similar to MK801. Furthermore, monomethyl fumerate significantly reduced Glu release from pathogenic T-helper 17 lymphocytes. Overall, these data suggest that MS drugs may mediate neuroprotection via excitotoxicity modulating effects. Evidence suggests MS pathogenesis may involve neuronal excitotoxicity, induced by local release of glutamate. However, current MS drugs, including dimethyl fumerate (DMF) and fingolimod (FTY720) are largely anti-inflammatory and not yet fully tested for their neuroprotective potential. Here, we show that the drugs, in particular DMF metabolite monomethyl fumerate (MMF), protect neurons by excitotoxicity modulating effects. Th17, T-helper 17. © 2015 International Society for

Developmental exposure to glyphosate-based herbicide and depressive-like behavior in adult offspring: Implication of glutamate excitotoxicity and oxidative stress.

PubMed

Cattani, Daiane; Cesconetto, Patrícia Acordi; Tavares, Mauren Kruger; Parisotto, Eduardo Benedetti; De Oliveira, Paulo Alexandre; Rieg, Carla Elise Heinz; Leite, Marina Concli; Prediger, Rui Daniel Schröder; Wendt, Nestor Cubas; Razzera, Guilherme; Filho, Danilo Wilhelm; Zamoner, Ariane

2017-07-15

We have previously demonstrated that maternal exposure to glyphosate-based herbicide (GBH) leads to glutamate excitotoxicity in 15-day-old rat hippocampus. The present study was conducted in order to investigate the effects of subchronic exposure to GBH on some neurochemical and behavioral parameters in immature and adult offspring. Rats were exposed to 1% GBH in drinking water (corresponding to 0.36% of glyphosate) from gestational day 5 until postnatal day (PND)-15 or PND60. Results showed that GBH exposure during both prenatal and postnatal periods causes oxidative stress, affects cholinergic and glutamatergic neurotransmission in offspring hippocampus from immature and adult rats. The subchronic exposure to the pesticide decreased L-[ 14 C]-glutamate uptake and increased 45 Ca 2+ influx in 60-day-old rat hippocampus, suggesting a persistent glutamate excitotoxicity from developmental period (PND15) to adulthood (PND60). Moreover, GBH exposure alters the serum levels of the astrocytic protein S100B. The effects of GBH exposure were associated with oxidative stress and depressive-like behavior in offspring on PND60, as demonstrated by the prolonged immobility time and decreased time of climbing observed in forced swimming test. The mechanisms underlying the GBH-induced neurotoxicity involve the NMDA receptor activation, impairment of cholinergic transmission, astrocyte dysfunction, ERK1/2 overactivation, decreased p65 NF-κB phosphorylation, which are associated with oxidative stress and glutamate excitotoxicity. These neurochemical events may contribute, at least in part, to the depressive-like behavior observed in adult offspring. Copyright © 2017 Elsevier B.V. All rights reserved.

Inhibition of the mitochondrial pyruvate carrier protects from excitotoxic neuronal death.

PubMed

Divakaruni, Ajit S; Wallace, Martina; Buren, Caodu; Martyniuk, Kelly; Andreyev, Alexander Y; Li, Edward; Fields, Jerel A; Cordes, Thekla; Reynolds, Ian J; Bloodgood, Brenda L; Raymond, Lynn A; Metallo, Christian M; Murphy, Anne N

2017-04-03

Glutamate is the dominant excitatory neurotransmitter in the brain, but under conditions of metabolic stress it can accumulate to excitotoxic levels. Although pharmacologic modulation of excitatory amino acid receptors is well studied, minimal consideration has been given to targeting mitochondrial glutamate metabolism to control neurotransmitter levels. Here we demonstrate that chemical inhibition of the mitochondrial pyruvate carrier (MPC) protects primary cortical neurons from excitotoxic death. Reductions in mitochondrial pyruvate uptake do not compromise cellular energy metabolism, suggesting neuronal metabolic flexibility. Rather, MPC inhibition rewires mitochondrial substrate metabolism to preferentially increase reliance on glutamate to fuel energetics and anaplerosis. Mobilizing the neuronal glutamate pool for oxidation decreases the quantity of glutamate released upon depolarization and, in turn, limits the positive-feedback cascade of excitotoxic neuronal injury. The finding links mitochondrial pyruvate metabolism to glutamatergic neurotransmission and establishes the MPC as a therapeutic target to treat neurodegenerative diseases characterized by excitotoxicity. © 2017 Divakaruni et al.

Chronic excitotoxicity in the guinea pig cochlea induces temporary functional deficits without disrupting otoacoustic emissions

NASA Astrophysics Data System (ADS)

Le Prell, Colleen G.; Yagi, Masao; Kawamoto, Kohei; Beyer, Lisa A.; Atkin, Graham; Raphael, Yehoash; Dolan, David F.; Bledsoe, Sanford C.; Moody, David B.

2004-08-01

Brief cochlear excitotoxicity produces temporary neural swelling and transient deficits in auditory sensitivity; however, the consequences of long-lasting excitotoxic insult have not been tested. Chronic intra-cochlear infusion of the glutamate agonist AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) resulted in functional deficits in the sound-evoked auditory brainstem response, as well as in behavioral measures of hearing. The electrophysiological deficits were similar to those observed following acute infusion of AMPA into the cochlea; however, the concentration-response curve was significantly shifted as a consequence of the slower infusion rate used with chronic cochlear administration. As observed following acute excitotoxic insult, complete functional recovery was evident within 7 days of discontinuing the AMPA infusion. Distortion product otoacoustic emissions were not affected by chronic AMPA infusion, suggesting that trauma to outer hair cells did not contribute to AMPA-induced deficits in acoustic sensitivity. Results from the current experiment address the permanence of deficits induced by chronic (14 day) excitotoxic insult as well as deficits in psychophysical detection of longer duration acoustic signals.

Defining external factors that determine neuronal survival, apoptosis and necrosis during excitotoxic injury using a high content screening imaging platform.

PubMed

Anilkumar, Ujval; Weisova, Petronela; Schmid, Jasmin; Bernas, Tytus; Huber, Heinrich J; Düssmann, Heiko; Connolly, Niamh M C; Prehn, Jochen H M

2017-01-01

Cell death induced by excessive glutamate receptor overactivation, excitotoxicity, has been implicated in several acute and chronic neurological disorders. While numerous studies have demonstrated the contribution of biochemically and genetically activated cell death pathways in excitotoxic injury, the factors mediating passive, excitotoxic necrosis are less thoroughly investigated. To address this question, we developed a high content screening (HCS) based assay to collect high volumes of quantitative cellular imaging data and elucidated the effects of intrinsic and external factors on excitotoxic necrosis and apoptosis. The analysis workflow consisted of robust nuclei segmentation, tracking and a classification algorithm, which enabled automated analysis of large amounts of data to identify and quantify viable, apoptotic and necrotic neuronal populations. We show that mouse cerebellar granule neurons plated at low or high density underwent significantly increased necrosis compared to neurons seeded at medium density. Increased extracellular Ca2+ sensitized neurons to glutamate-induced excitotoxicity, but surprisingly potentiated cell death mainly through apoptosis. We also demonstrate that inhibition of various cell death signaling pathways (including inhibition of calpain, PARP and AMPK activation) primarily reduced excitotoxic apoptosis. Excitotoxic necrosis instead increased with low extracellular glucose availability. Our study is the first of its kind to establish and implement a HCS based assay to investigate the contribution of external and intrinsic factors to excitotoxic apoptosis and necrosis.

Defining external factors that determine neuronal survival, apoptosis and necrosis during excitotoxic injury using a high content screening imaging platform

PubMed Central

Weisova, Petronela; Schmid, Jasmin; Bernas, Tytus; Huber, Heinrich J.; Düssmann, Heiko; Connolly, Niamh M. C.; Prehn, Jochen H. M.

2017-01-01

Cell death induced by excessive glutamate receptor overactivation, excitotoxicity, has been implicated in several acute and chronic neurological disorders. While numerous studies have demonstrated the contribution of biochemically and genetically activated cell death pathways in excitotoxic injury, the factors mediating passive, excitotoxic necrosis are less thoroughly investigated. To address this question, we developed a high content screening (HCS) based assay to collect high volumes of quantitative cellular imaging data and elucidated the effects of intrinsic and external factors on excitotoxic necrosis and apoptosis. The analysis workflow consisted of robust nuclei segmentation, tracking and a classification algorithm, which enabled automated analysis of large amounts of data to identify and quantify viable, apoptotic and necrotic neuronal populations. We show that mouse cerebellar granule neurons plated at low or high density underwent significantly increased necrosis compared to neurons seeded at medium density. Increased extracellular Ca2+ sensitized neurons to glutamate-induced excitotoxicity, but surprisingly potentiated cell death mainly through apoptosis. We also demonstrate that inhibition of various cell death signaling pathways (including inhibition of calpain, PARP and AMPK activation) primarily reduced excitotoxic apoptosis. Excitotoxic necrosis instead increased with low extracellular glucose availability. Our study is the first of its kind to establish and implement a HCS based assay to investigate the contribution of external and intrinsic factors to excitotoxic apoptosis and necrosis. PMID:29145487

Excitotoxicity in the pathogenesis of neurological and psychiatric disorders: Therapeutic implications.

PubMed

Olloquequi, Jordi; Cornejo-Córdova, Elizabeth; Verdaguer, Ester; Soriano, Francesc X; Binvignat, Octavio; Auladell, Carme; Camins, Antoni

2018-03-01

Neurological and psychiatric disorders are leading contributors to the global disease burden, having a serious impact on the quality of life of both patients and their relatives. Although the molecular events underlying these heterogeneous diseases remain poorly understood, some studies have raised the idea of common mechanisms involved. In excitotoxicity, there is an excessive activation of glutamate receptors by excitatory amino acids, leading to neuronal damage. Thus, the excessive release of glutamate can lead to a dysregulation of Ca 2+ homeostasis, triggering the production of free radicals and oxidative stress, mitochondrial dysfunction and eventually cell death. Although there is a consensus in considering excitotoxicity as a hallmark in most neurodegenerative diseases, increasing evidence points to the relevant role of this pathological mechanism in other illnesses affecting the central nervous system. Consequently, antagonists of glutamate receptors are used in current treatments or in clinical trials in both neurological and psychiatric disorders. However, drugs modulating other aspects of the excitotoxic mechanism could be more beneficial. This review discusses how excitotoxicity is involved in the pathogenesis of different neurological and psychiatric disorders and the promising strategies targeting the excitotoxic insult.

Biodegradable Spheres Protect Traumatically Injured Spinal Cord by Alleviating the Glutamate-Induced Excitotoxicity.

PubMed

Liu, Dongfei; Chen, Jian; Jiang, Tao; Li, Wei; Huang, Yao; Lu, Xiyi; Liu, Zehua; Zhang, Weixia; Zhou, Zheng; Ding, Qirui; Santos, Hélder A; Yin, Guoyong; Fan, Jin

2018-04-01

New treatment strategies for spinal cord injury with good therapeutic efficacy are actively pursued. Here, acetalated dextran (AcDX), a biodegradable polymer obtained by modifying vicinal diols of dextran, is demonstrated to protect the traumatically injured spinal cord. To facilitate its administration, AcDX is formulated into microspheres (≈7.2 µm in diameter) by the droplet microfluidic technique. Intrathecally injected AcDX microspheres effectively reduce the traumatic lesion volume and inflammatory response in the injured spinal cord, protect the spinal cord neurons from apoptosis, and ultimately, recover the locomotor function of injured rats. The neuroprotective feature of AcDX microspheres is achieved by sequestering glutamate and calcium ions in cerebrospinal fluid. The scavenging of glutamate and calcium ion reduces the influx of calcium ions into neurons and inhibits the formation of reactive oxygen species. Consequently, AcDX microspheres attenuate the expression of proapoptotic proteins, Calpain, and Bax, and enhance the expression of antiapoptotic protein Bcl-2. Overall, AcDX microspheres protect traumatically injured spinal cord by alleviating the glutamate-induced excitotoxicity. This study opens an exciting perspective toward the application of neuroprotective AcDX for the treatment of severe neurological diseases. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

KCa2 channels activation prevents [Ca2+]i deregulation and reduces neuronal death following glutamate toxicity and cerebral ischemia

PubMed Central

Dolga, A M; Terpolilli, N; Kepura, F; Nijholt, I M; Knaus, H-G; D'Orsi, B; Prehn, J H M; Eisel, U L M; Plant, T; Plesnila, N; Culmsee, C

2011-01-01

Exacerbated activation of glutamate receptor-coupled calcium channels and subsequent increase in intracellular calcium ([Ca2+]i) are established hallmarks of neuronal cell death in acute and chronic neurological diseases. Here we show that pathological [Ca2+]i deregulation occurring after glutamate receptor stimulation is effectively modulated by small conductance calcium-activated potassium (KCa2) channels. We found that neuronal excitotoxicity was associated with a rapid downregulation of KCa2.2 channels within 3 h after the onset of glutamate exposure. Activation of KCa2 channels preserved KCa2 expression and significantly reduced pathological increases in [Ca2+]i providing robust neuroprotection in vitro and in vivo. These data suggest a critical role for KCa2 channels in excitotoxic neuronal cell death and propose their activation as potential therapeutic strategy for the treatment of acute and chronic neurodegenerative disorders. PMID:21509037

KCa2 channels activation prevents [Ca2+]i deregulation and reduces neuronal death following glutamate toxicity and cerebral ischemia.

PubMed

Dolga, A M; Terpolilli, N; Kepura, F; Nijholt, I M; Knaus, H-G; D'Orsi, B; Prehn, J H M; Eisel, U L M; Plant, T; Plesnila, N; Culmsee, C

2011-04-21

Exacerbated activation of glutamate receptor-coupled calcium channels and subsequent increase in intracellular calcium ([Ca2+]i) are established hallmarks of neuronal cell death in acute and chronic neurological diseases. Here we show that pathological [Ca2+]i deregulation occurring after glutamate receptor stimulation is effectively modulated by small conductance calcium-activated potassium (KCa2) channels. We found that neuronal excitotoxicity was associated with a rapid downregulation of KCa2.2 channels within 3 h after the onset of glutamate exposure. Activation of KCa2 channels preserved KCa2 expression and significantly reduced pathological increases in [Ca2+]i providing robust neuroprotection in vitro and in vivo. These data suggest a critical role for KCa2 channels in excitotoxic neuronal cell death and propose their activation as potential therapeutic strategy for the treatment of acute and chronic neurodegenerative disorders.

Differential Molecular Targets for Neuroprotective Effect of Chlorogenic Acid and its Related Compounds Against Glutamate Induced Excitotoxicity and Oxidative Stress in Rat Cortical Neurons.

PubMed

Rebai, Olfa; Belkhir, Manel; Sanchez-Gomez, María Victoria; Matute, Carlos; Fattouch, Sami; Amri, Mohamed

2017-12-01

The present study has been designed to explore the molecular mechanism and signaling pathway targets of chlorogenic acid (CGA) and its main hydrolysates, caffeic (CA) and quinic acid in the protective effect against glutamate-excitotoxicity. For this purpose 8-DIV cortical neurons in primary culture were exposed to 50 μM L-glutamic acid plus 10 µM glycine, with or without 10-100 μM tested compounds. Chlorogenic acid and caffeic acid via their antioxidant properties inhibited cell death induced by glutamate in dose depended manner. However, quinic acid slightly protects neurons at a higher dose. DCF, JC-1 and Ca 2+ sensitive fluorescent dye fura-2, were used to measure intracellular ROS accumulation, mitochondrial membrane potential integration and intracellular calcium concentration [Ca 2+ ] i . Results indicate that similarly, CGA acts as a protective agent against glutamate-induced cortical neurons injury by suppressing the accumulation of endogenous ROS and restore the mitochondrial membrane potential, activate the enzymatic antioxidant system by the increase levels of SOD activity and modulate the rise of intracellular calcium levels by increasing the rise of intracellular concentrations of Ca 2+ caused by glutamate overstimulation. PKC signaling cascade appear to be engaged in this protective mechanism. Interseling, CGA and CA also exhibit antiapoptotic properties against glutamate-induced cleaved activation of pro-caspases; caspase 1,8 and 9 and calpain (PD 150606,Calpeptin and MDL 28170).These data suggest that neuroprotective activity of CGA ester may occurs throught its hydrolysate,the caffeic acid and its interaction with intracellular molecules suggesting that CGA exert its neuroprotection via its caffeoly acid group that might potentially be used as a therapeutic agent in neurodegeneratives disorders associated with glutamate excitotoxicity.

Ceftriaxone rescues hippocampal neurons from excitotoxicity and enhances memory retrieval in chronic hypobaric hypoxia.

PubMed

Hota, Sunil K; Barhwal, Kalpana; Ray, Koushik; Singh, Shashi B; Ilavazhagan, G

2008-05-01

Exposure to high altitude is known to cause impairment in cognitive functions in sojourners. The molecular events leading to this behavioral manifestation, however, still remain an enigma. The present study aims at exploring the nature of memory impairment occurring on chronic exposure to hypobaric hypoxia and the possible role of glutamate in mediating it. Increased ionotropic receptor stimulation by glutamate under hypobaric hypoxic conditions could lead to calcium mediated excitotoxic cell death resulting in impaired cognitive functions. Since glutamate is cleared from the synapse by the Glial Glutamate Transporter, upregulation of the transporter can be a good strategy in preventing excitotoxic cell death. Considering previous reports on upregulation of the expression of Glial Glutamate Transporter on ceftriaxone administration, the therapeutic potential of ceftriaxone in ameliorating hypobaric hypoxia induced memory impairment was investigated in male Sprague Dawley rats. Exposure to hypobaric hypoxia equivalent to an altitude of 7600 m for 14 days lead to oxidative stress, chromatin condensation and neuronal degeneration in the hippocampus. This was accompanied by delayed memory retrieval as evident from increased latency and pathlength in Morris Water Maze. Administration of ceftriaxone at a dose of 200 mg/kg for 7 days and 14 days during the exposure on the other hand improved the performance of rats in the water maze along with decreased oxidative stress and enhanced neuronal survival when compared to hypoxic group without drug administration. An increased expression of Glial Glutamate Transporter was also observed following drug administration indicating faster clearance of glutamate from the synapse. The present study not only brings to light the effect of longer duration of exposure to hypobaric hypoxia on the memory functions, but also indicates the pivotal role played by glutamate in mediating excitotoxic neuronal degeneration at high altitude. The

Blood glutamate grabbing does not reduce the hematoma in an intracerebral hemorrhage model but it is a safe excitotoxic treatment modality.

PubMed

da Silva-Candal, Andrés; Vieites-Prado, Alba; Gutiérrez-Fernández, María; Rey, Ramón I; Argibay, Bárbara; Mirelman, David; Sobrino, Tomás; Rodríguez-Frutos, Berta; Castillo, José; Campos, Francisco

2015-07-01

Recent studies have shown that blood glutamate grabbing is an effective strategy to reduce the excitotoxic effect of extracellular glutamate released during ischemic brain injury. The purpose of the study was to investigate the effect of two of the most efficient blood glutamate grabbers (oxaloacetate and recombinant glutamate oxaloacetate transaminase 1: rGOT1) in a rat model of intracerebral hemorrhage (ICH). Intracerebral hemorrhage was produced by injecting collagenase into the basal ganglia. Three treatment groups were developed: a control group treated with saline, a group treated with oxaloacetate, and a final group treated with human rGOT1. Treatments were given 1 hour after hemorrhage. Hematoma volume (analyzed by magnetic resonance imaging (MRI)), neurologic deficit, and blood glutamate and GOT levels were quantified over a period of 14 days after surgery. The results observed showed that the treatments used induced a significant reduction of blood glutamate levels; however, they did not reduce the hematoma, nor did they improve the neurologic deficit. In the present experimental study, we have shown that this novel therapeutic strategy is not effective in case of ICH pathology. More importantly, these findings suggest that blood glutamate grabbers are a safe treatment modality that can be given in cases of suspected ischemic stroke without previous neuroimaging.

Prolactin-induced neuroprotection against glutamate excitotoxicity is mediated by the reduction of [Ca2+]i overload and NF-κB activation

PubMed Central

Rivero-Segura, Nadia A.; Flores-Soto, Edgar; García de la Cadena, Selene; Coronado-Mares, Isabel; Gomez-Verjan, Juan C.; Ferreira, Diana G.; Cabrera-Reyes, Erika Alejandra; Lopes, Luísa V.; Massieu, Lourdes

2017-01-01

Prolactin (PRL) is a peptidic hormone that displays pleiotropic functions in the organism including different actions in the brain. PRL exerts a neuroprotective effect against excitotoxicity produced by glutamate (Glu) or kainic acid in both in vitro and in vivo models. It is well known that Glu excitotoxicity causes cell death through apoptotic or necrotic pathways due to intracellular calcium ([Ca2+] i) overload. Therefore, the aim of the present study was to assess the molecular mechanisms by which PRL maintains cellular viability of primary cultures of rat hippocampal neurons exposed to Glu excitotoxicity. We determined cell viability by monitoring mitochondrial activity and using fluorescent markers for viable and dead cells. The intracellular calcium level was determined by a fluorometric assay and proteins involved in the apoptotic pathway were determined by immunoblot. Our results demonstrated that PRL afforded neuroprotection against Glu excitotoxicity, as evidenced by a decrease in propidium iodide staining and by the decrease of the LDH activity. In addition, the MTT assay shows that PRL maintains normal mitochondrial activity even in neurons exposed to Glu. Furthermore, the Glu-induced intracellular [Ca2+]i overload was attenuated by PRL. These data correlate with the reduction found in the level of active caspase-3 and the pro-apoptotic ratio (Bax/Bcl-2). Concomitantly, PRL elicited the nuclear translocation of the transcriptional factor NF-κB, which was detected by immunofluorescence and confocal microscopy. To our knowledge, this is the first report demonstrating that PRL prevents Glu excitotoxicity by a mechanism involving the restoration of the intracellular calcium homeostasis and mitochondrial activity, as well as an anti-apoptotic action possibly mediated by the activity of NF-κB. Overall, the current results suggest that PRL could be of potential therapeutic advantage in the treatment of neurodegenerative diseases. PMID:28475602

Excitotoxicity Induced by Realgar in the Rat Hippocampus: the Involvement of Learning Memory Injury, Dysfunction of Glutamate Metabolism and NMDA Receptors.

PubMed

Huo, Tao-guang; Li, Wei-kai; Zhang, Ying-hua; Yuan, Jie; Gao, Lan-yue; Yuan, Yuan; Yang, Hui-lei; Jiang, Hong; Sun, Gui-fan

2015-01-01

Realgar is a type of mineral drug containing arsenic. The nervous system toxicity of realgar has received extensive attention. However, the underlying mechanisms of realgar-induced neurotoxicity have not been clearly elucidated. To explore the mechanisms that contribute to realgar-induced neurotoxicity, weanling rats were exposed to realgar (0, 0.3, 0.9, 2.7 g/kg) for 6 weeks, and cognitive ability was tested using the Morris water maze (MWM) test and object recognition task (ORT). The levels of arsenic in the blood and hippocampus were monitored. The ultrastructures of hippocampal neurons were observed. The levels of glutamate (Glu) and glutamine (Gln) in the hippocampus and hippocampal CA1 region; the activities of glutamine synthetase (GS) and phosphate-activated glutaminase (PAG); the mRNA and protein expression of glutamate transporter 1 (GLT-1), glutamate/aspartate transporter (GLAST), and N-methyl-D-aspartate (NMDA) receptors; and the level of intracellular Ca(2+) were also investigated. The results indicate that the rats developed deficiencies in cognitive ability after a 6-week exposure to realgar. The arsenic contained in realgar and the arsenic metabolites passed through the blood-brain barrier (BBB) and accumulated in the hippocampus, which resulted in the excessive accumulation of Glu in the extracellular space. The excessive accumulation of Glu in the extracellular space induced excitotoxicity, which was shown by enhanced GS and PAG activities, inhibition of GLT-1 mRNA and protein expression, alterations in NMDA receptor mRNA and protein expression, disturbance of intracellular Ca(2+) homeostasis, and ultrastructural changes in hippocampal neurons. In conclusion, the findings from our study indicate that exposure to realgar induces excitotoxicity and that the mechanism by which this occurs may be associated with disturbances in Glu metabolism and transportation and alterations in NMDA receptor expression.

Activation of NOX2 by the stimulation of ionotropic and metabotropic glutamate receptors contributes to glutamate neurotoxicity in vivo through the production of reactive oxygen species and calpain activation.

PubMed

Guemez-Gamboa, Alicia; Estrada-Sánchez, Ana María; Montiel, Teresa; Páramo, Blanca; Massieu, Lourdes; Morán, Julio

2011-11-01

Prolonged activation of glutamate receptors leads to excitotoxicity. Several processes such as reactive oxygen species (ROS) production and activation of the calcium-dependent protease, calpain, contribute to glutamate-induced damage. It has been suggested that the ROS-producing enzyme, NADPH oxidase (NOX), plays a role in excitotoxicity. Studies have reported NOX activation after NMDA receptor stimulation during excitotoxic damage, but the role of non-NMDA and metabotropic receptors is unknown. We evaluated the roles of different glutamate receptor subtypes on NOX activation and neuronal death induced by the intrastriatal administration of glutamate in mice. In wild-type mice, NOX2 immunoreactivity in neurons and microglia was stimulated by glutamate administration, and it progressively increased as microglia became activated; calpain activity was also induced. By contrast, mice lacking NOX2 were less vulnerable to excitotoxicity, and there was reduced ROS production and protein nitrosylation, microglial reactivity, and calpain activation. These results suggest that NOX2 is stimulated by glutamate in neurons and reactive microglia through the activation of ionotropic and metabotropic receptors. Neuronal damage involves ROS production by NOX2, which, in turn, contributes to calpain activation.

Calpains are downstream effectors of bax-dependent excitotoxic apoptosis.

PubMed

D'Orsi, Beatrice; Bonner, Helena; Tuffy, Liam P; Düssmann, Heiko; Woods, Ina; Courtney, Michael J; Ward, Manus W; Prehn, Jochen H M

2012-02-01

Excitotoxicity resulting from excessive Ca(2+) influx through glutamate receptors contributes to neuronal injury after stroke, trauma, and seizures. Increased cytosolic Ca(2+) levels activate a family of calcium-dependent proteases with papain-like activity, the calpains. Here we investigated the role of calpain activation during NMDA-induced excitotoxic injury in embryonic (E16-E18) murine cortical neurons that (1) underwent excitotoxic necrosis, characterized by immediate deregulation of Ca(2+) homeostasis, a persistent depolarization of mitochondrial membrane potential (Δψ(m)), and insensitivity to bax-gene deletion, (2) underwent excitotoxic apoptosis, characterized by recovery of NMDA-induced cytosolic Ca(2+) increases, sensitivity to bax gene deletion, and delayed Δψ(m) depolarization and Ca(2+) deregulation, or (3) that were tolerant to excitotoxic injury. Interestingly, treatment with the calpain inhibitor calpeptin, overexpression of the endogenous calpain inhibitor calpastatin, or gene silencing of calpain protected neurons against excitotoxic apoptosis but did not influence excitotoxic necrosis. Calpeptin failed to exert a protective effect in bax-deficient neurons but protected bid-deficient neurons similarly to wild-type cells. To identify when calpains became activated during excitotoxic apoptosis, we monitored calpain activation dynamics by time-lapse fluorescence microscopy using a calpain-sensitive Förster resonance energy transfer probe. We observed a delayed calpain activation that occurred downstream of mitochondrial engagement and directly preceded neuronal death. In contrast, we could not detect significant calpain activity during excitotoxic necrosis or in neurons that were tolerant to excitotoxic injury. Oxygen/glucose deprivation-induced injury in organotypic hippocampal slice cultures confirmed that calpains were specifically activated during bax-dependent apoptosis and in this setting function as downstream cell-death executioners.

The metabolic response to excitotoxicity - lessons from single-cell imaging.

PubMed

Connolly, Niamh M C; Prehn, Jochen H M

2015-04-01

Excitotoxicity is a pathological process implicated in neuronal death during ischaemia, traumatic brain injuries and neurodegenerative diseases. Excitotoxicity is caused by excess levels of glutamate and over-activation of NMDA or calcium-permeable AMPA receptors on neuronal membranes, leading to ionic influx, energetic stress and potential neuronal death. The metabolic response of neurons to excitotoxicity is complex and plays a key role in the ability of the neuron to adapt and recover from such an insult. Single-cell imaging is a powerful experimental technique that can be used to study the neuronal metabolic response to excitotoxicity in vitro and, increasingly, in vivo. Here, we review some of the knowledge of the neuronal metabolic response to excitotoxicity gained from in vitro single-cell imaging, including calcium and ATP dynamics and their effects on mitochondrial function, along with the contribution of glucose metabolism, oxidative stress and additional neuroprotective signalling mechanisms. Future work will combine knowledge gained from single-cell imaging with data from biochemical and computational techniques to garner holistic information about the metabolic response to excitotoxicity at the whole brain level and transfer this knowledge to a clinical setting.

Brain neuroprotection by scavenging blood glutamate.

PubMed

Zlotnik, Alexander; Gurevich, Boris; Tkachov, Sergei; Maoz, Ilana; Shapira, Yoram; Teichberg, Vivian I

2007-01-01

Excess glutamate in brain fluids characterizes acute brain insults such as traumatic brain injury and stroke. Its removal could prevent the glutamate excitotoxicity that causes long-lasting neurological deficits. As blood glutamate scavenging has been demonstrated to increase the efflux of excess glutamate from brain into blood, we tested the prediction that oxaloacetate-mediated blood glutamate scavenging causes neuroprotection in a pathological situation such as closed head injury (CHI), in which there is a well established deleterious increase of glutamate in brain fluids. We observed highly significant improvements of the neurological status of rats submitted to CHI following an intravenous treatment with 1 mmol oxaloacetate/100 g rat weight which decreases blood glutamate levels by 40%. No detectable therapeutic effect was obtained when rats were treated IV with 1 mmol oxaloacetate together with 1 mmol glutamate/100 g rat. The treatment with 0.005 mmol/100 g rat oxaloacetate was no more effective than saline but when it was combined with the intravenous administration of 0.14 nmol/100 g of recombinant glutamate-oxaloacetate transaminase, recovery was almost complete. Oxaloacetate provided neuroprotection when administered before CHI or at 60 min post CHI but not at 120 min post CHI. Since neurological recovery from CHI was highly correlated with the decrease of blood glutamate levels (r=0.89, P=0.001), we conclude that blood glutamate scavenging affords brain neuroprotection Blood glutamate scavenging may open now new therapeutic options.

Functional contributions of glutamate transporters at the parallel fibre to Purkinje neuron synapse-relevance for the progression of cerebellar ataxia.

PubMed

Power, Emmet M; Empson, Ruth M

2014-01-01

Rapid uptake of glutamate by neuronal and glial glutamate transporters (EAATs, a family of excitatory amino acid transporters) is critical for shaping synaptic responses and for preventing excitotoxicity. Two of these transporters, EAAT4 in Purkinje neurons (PN) and EAAT1 in Bergmann glia are both enriched within the cerebellum and altered in a variety of human ataxias. PN excitatory synaptic responses and firing behaviour following high frequency parallel fibre (PF) activity commonly encountered during sensory stimulation in vivo were adversely influenced by acute inhibition of glutamate transporters. In the presence of a non-transportable blocker of glutamate transporters we observed very large amplitude and duration excitatory postsynaptic currents accompanied by excessive firing of the PNs. A combination of AMPA and mGluR1, but not NMDA, type glutamate receptor activation powered the hyper-excitable PN state. The enhanced PN excitability also recruited a presynaptic mGluR4 dependent mechanism that modified short term plasticity at the PF synapse. Our findings indicate that reduced glutamate transporter activity, as occurs in the early stages of some forms of human cerebellar ataxias, excessively excites PNs and disrupts the timing of their output. Our findings raise the possibility that sustaining cerebellar glutamate uptake may provide a therapeutic approach to prevent this disruption and the glutamate excitotoxicity-induced PN death that signals the end point of the disease.

Researching glutamate – induced cytotoxicity in different cell lines: a comparative/collective analysis/study

PubMed Central

Kritis, Aristeidis A.; Stamoula, Eleni G.; Paniskaki, Krystallenia A.; Vavilis, Theofanis D.

2015-01-01

Although glutamate is one of the most important excitatory neurotransmitters of the central nervous system, its excessive extracellular concentration leads to uncontrolled continuous depolarization of neurons, a toxic process called, excitotoxicity. In excitotoxicity glutamate triggers the rise of intracellular Ca2+ levels, followed by up regulation of nNOS, dysfunction of mitochondria, ROS production, ER stress, and release of lysosomal enzymes. Excessive calcium concentration is the key mediator of glutamate toxicity through over activation of ionotropic and metabotropic receptors. In addition, glutamate accumulation can also inhibit cystine (CySS) uptake by reversing the action of the CySS/glutamate antiporter. Reversal of the antiporter action reinforces the aforementioned events by depleting neurons of cysteine and eventually glutathione’s reducing potential. Various cell lines have been employed in the pursuit to understand the mechanism(s) by which excitotoxicity affects the cells leading them ultimately to their demise. In some cell lines glutamate toxicity is exerted mainly through over activation of NMDA, AMPA, or kainate receptors whereas in other cell lines lacking such receptors, the toxicity is due to glutamate induced oxidative stress. However, in the greatest majority of the cell lines ionotropic glutamate receptors are present, co-existing to CySS/glutamate antiporters and metabotropic glutamate receptors, supporting the assumption that excitotoxicity effect in these cells is accumulative. Different cell lines differ in their responses when exposed to glutamate. In this review article the responses of PC12, SH-SY5Y, HT-22, NT-2, OLCs, C6, primary rat cortical neurons, RGC-5, and SCN2.2 cell systems are systematically collected and analyzed. PMID:25852482

A study of the potential neuroprotective effect of riluzole on locomotor networks of the neonatal rat spinal cord in vitro damaged by excitotoxicity.

PubMed

Sámano, C; Nasrabady, S E; Nistri, A

2012-10-11

Excitotoxicity triggered by over-stimulation of glutamatergic receptors is considered to be a major component of damage following acute spinal cord injury (SCI). Using an in vitro model of neonatal rat SCI caused by transient application (1h) of the glutamate agonist kainate (0.05-0.1 mM) to produce limited excitotoxicity, the present study investigated whether riluzole, a drug inhibiting glutamate release and neuronal excitability, could prevent neuronal loss and protect locomotor patterns 24 h later. Immunohistochemical analysis of neuronal and motoneuronal populations was associated with recording of fictive locomotion induced by neurochemicals or dorsal root stimuli. Riluzole (5 μM; 24 h application) per se exerted strong and persistent neurodepressant effects on network synaptic transmission from which recovery was very slow. When continuously applied after kainate, riluzole partially reduced the number of pyknotic cells in the gray matter, although motoneurons remained vulnerable and no fictive locomotion was present. In further experiments, riluzole per se was applied for 3 h (expected to coincide with kainate peak excitotoxicity) and washed out for 24 h with full return of fictive locomotion. When this protocol was implemented after kainate, no efficient histological or functional recovery was observed. No additional benefit was detected even when riluzole was co-applied with kainate and continued for the following 3 h. These results show that modest neuronal losses evoked by excitotoxicity have a severe impact on locomotor network function, and that they cannot be satisfactorily blocked by strong neurodepression with riluzole, suggesting the need for more effective pharmacological approaches. Copyright © 2012 IBRO. Published by Elsevier Ltd. All rights reserved.

Characterisation of neuroprotective efficacy of modified poly-arginine-9 (R9) peptides using a neuronal glutamic acid excitotoxicity model.

PubMed

Edwards, Adam B; Anderton, Ryan S; Knuckey, Neville W; Meloni, Bruno P

2017-02-01

In a recent study, we highlighted the importance of cationic charge and arginine residues for the neuroprotective properties of poly-arginine and arginine-rich peptides. In this study, using cortical neuronal cultures and an in vitro glutamic acid excitotoxicity model, we examined the neuroprotective efficacy of different modifications to the poly-arginine-9 peptide (R9). We compared an unmodified R9 peptide with R9 peptides containing the following modifications: (i) C-terminal amidation (R9-NH2); (ii) N-terminal acetylation (Ac-R9); (iii) C-terminal amidation with N-terminal acetylation (Ac-R9-NH2); and (iv) C-terminal amidation with D-amino acids (R9D-NH2). The three C-terminal amidated peptides (R9-NH2, Ac-R9-NH2, and R9D-NH2) displayed neuroprotective effects greater than the unmodified R9 peptide, while the N-terminal acetylated peptide (Ac-R9) had reduced efficacy. Using the R9-NH2 peptide, neuroprotection could be induced with a 10 min peptide pre-treatment, 1-6 h before glutamic acid insult, or when added to neuronal cultures up to 45 min post-insult. In addition, all peptides were capable of reducing glutamic acid-mediated neuronal intracellular calcium influx, in a manner that reflected their neuroprotective efficacy. This study further highlights the neuroprotective properties of poly-arginine peptides and provides insight into peptide modifications that affect efficacy.

A β-Lactam Antibiotic Dampens Excitotoxic Inflammatory CNS Damage in a Mouse Model of Multiple Sclerosis

PubMed Central

Torres-Salazar, Delany; Bittner, Stefan; Zozulya, Alla L.; Weidenfeller, Christian; Kotsiari, Alexandra; Stangel, Martin; Fahlke, Christoph; Wiendl, Heinz

2008-01-01

In multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE), impairment of glial “Excitatory Amino Acid Transporters” (EAATs) together with an excess glutamate-release by invading immune cells causes excitotoxic damage of the central nervous system (CNS). In order to identify pathways to dampen excitotoxic inflammatory CNS damage, we assessed the effects of a β-lactam antibiotic, ceftriaxone, reported to enhance expression of glial EAAT2, in “Myelin Oligodendrocyte Glycoprotein” (MOG)-induced EAE. Ceftriaxone profoundly ameliorated the clinical course of murine MOG-induced EAE both under preventive and therapeutic regimens. However, ceftriaxone had impact neither on EAAT2 protein expression levels in several brain areas, nor on the radioactive glutamate uptake capacity in a mixed primary glial cell-culture and the glutamate-induced uptake currents in a mammalian cell line mediated by EAAT2. Moreover, the clinical effect of ceftriaxone was preserved in the presence of the EAAT2-specific transport inhibitor, dihydrokainate, while dihydrokainate alone caused an aggravated EAE course. This demonstrates the need for sufficient glial glutamate uptake upon an excitotoxic autoimmune inflammatory challenge of the CNS and a molecular target of ceftriaxone other than the glutamate transporter. Ceftriaxone treatment indirectly hampered T cell proliferation and proinflammatory INFγ and IL17 secretion through modulation of myelin-antigen presentation by antigen-presenting cells (APCs) e.g. dendritic cells (DCs) and reduced T cell migration into the CNS in vivo. Taken together, we demonstrate, that a β-lactam antibiotic attenuates disease course and severity in a model of autoimmune CNS inflammation. The mechanisms are reduction of T cell activation by modulation of cellular antigen-presentation and impairment of antigen-specific T cell migration into the CNS rather than or modulation of central glutamate homeostasis. PMID:18773080

Glutathione and glutamate in schizophrenia: a 7T MRS study.

PubMed

Kumar, Jyothika; Liddle, Elizabeth B; Fernandes, Carolina C; Palaniyappan, Lena; Hall, Emma L; Robson, Siân E; Simmonite, Molly; Fiesal, Jan; Katshu, Mohammad Z; Qureshi, Ayaz; Skelton, Michael; Christodoulou, Nikolaos G; Brookes, Matthew J; Morris, Peter G; Liddle, Peter F

2018-06-22

In schizophrenia, abnormal neural metabolite concentrations may arise from cortical damage following neuroinflammatory processes implicated in acute episodes. Inflammation is associated with increased glutamate, whereas the antioxidant glutathione may protect against inflammation-induced oxidative stress. We hypothesized that patients with stable schizophrenia would exhibit a reduction in glutathione, glutamate, and/or glutamine in the cerebral cortex, consistent with a post-inflammatory response, and that this reduction would be most marked in patients with "residual schizophrenia", in whom an early stage with positive psychotic symptoms has progressed to a late stage characterized by long-term negative symptoms and impairments. We recruited 28 patients with stable schizophrenia and 45 healthy participants matched for age, gender, and parental socio-economic status. We measured glutathione, glutamate and glutamine concentrations in the anterior cingulate cortex (ACC), left insula, and visual cortex using 7T proton magnetic resonance spectroscopy (MRS). Glutathione and glutamate were significantly correlated in all three voxels. Glutamine concentrations across the three voxels were significantly correlated with each other. Principal components analysis (PCA) produced three clear components: an ACC glutathione-glutamate component; an insula-visual glutathione-glutamate component; and a glutamine component. Patients with stable schizophrenia had significantly lower scores on the ACC glutathione-glutamate component, an effect almost entirely leveraged by the sub-group of patients with residual schizophrenia. All three metabolite concentration values in the ACC were significantly reduced in this group. These findings are consistent with the hypothesis that excitotoxicity during the acute phase of illness leads to reduced glutathione and glutamate in the residual phase of the illness.

Mangifera indica L. extract attenuates glutamate-induced neurotoxicity on rat cortical neurons.

PubMed

Lemus-Molina, Yeny; Sánchez-Gómez, Maria Victoria; Delgado-Hernández, René; Matute, Carlos

2009-11-01

Overstimulation of ionotropic glutamate receptors causes excitotoxic neuronal death contributing to neurodegenerative disorders. Massive influx of calcium in excitotoxicity provokes alterations in the membrane potential of mitochondria and increases the production of reactive oxygen species. Here we report that Mangifera indica L. extracts (MiE) prevent glutamate-induced excitotoxicity in primary cultured neurons of the rat cerebral cortex. To evaluate the effects of MiE on excitotoxicity, cells were stimulated with L-glutamic acid (50 microM; 10 min) alone or in the presence of MiE. Maximal protection (56%) was obtained with 2.5 microg/mL of MiE. In turn, we measured the effects of MiE on excitotoxic-induced oxidative stress and mitochondrial depolarization by fluorimetry using 5,6-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate and tetramethylrhodamine, respectively. Both parameters were effectively reduced by MiE at concentrations which showed neuroprotection. Mangiferin, an antioxidant polyphenol which is a major component of MiE, was also effective in preventing neuronal death, oxidative stress and mitochondrial depolarization. Maximal protection (64%) was obtained at 12.5 microg/mL of mangiferin which also attenuated oxidative stress and mitochondrial depolarization at the neuroprotective concentrations. Together, these results indicate that MiE is an efficient neuroprotector of excitotoxic neuronal death, indicates that mangiferin carries a substantial part of the antioxidant and neuroprotective activity of MiE, and that this natural extract has therapeutic potential to treat neurodegenerative disorders.

Administration of a non-NMDA antagonist, GYKI 52466, increases excitotoxic Purkinje cell degeneration caused by ibogaine.

PubMed

O'Hearn, E; Molliver, M E

2004-01-01

Ibogaine is a tremorigenic hallucinogen that has been proposed for clinical use in treating addiction. We previously reported that ibogaine, administered systemically, produces degeneration of a subset of Purkinje cells in the cerebellum, primarily within the vermis. Ablation of the inferior olive affords protection against ibogaine-induced neurotoxicity leading to the interpretation that ibogaine itself is not directly toxic to Purkinje cells. We postulated that ibogaine produces sustained excitation of inferior olivary neurons that leads to excessive glutamate release at climbing fiber terminals, causing subsequent excitotoxic injury to Purkinje cells. The neuronal degeneration induced by ibogaine provides an animal model for studying excitotoxic injury in order to analyze the contribution of glutamate receptors to this injury and to evaluate neuroprotective strategies. Since non-N-methyl-D-aspartate (NMDA) receptors mediate Purkinje cell excitation by climbing fibers, we hypothesized that 1-4-aminophenyl-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine (GYKI-52466), which antagonizes non-NMDA receptors, may have a neuroprotective effect by blocking glutamatergic excitation at climbing fiber synapses. To test this hypothesis, rats were administered systemic ibogaine plus GYKI-52466 and the degree of neuronal injury was analyzed in cerebellar sections. The results indicate that the AMPA antagonist GYKI-52466 (10 mg/kg i.p. x 3) does not protect against Purkinje cell injury at the doses used. Rather, co-administration of GYKI-52466 with ibogaine produces increased toxicity evidenced by more extensive Purkinje cell degeneration. Several hypotheses that may underlie this result are discussed. Although the reason for the increased toxicity found in this study is not fully explained, the present results show that a non-NMDA antagonist can produce increased excitotoxic injury under some conditions. Therefore, caution should be exercised before employing glutamate

L-beta-ODAP alters mitochondrial Ca2+ handling as an early event in excitotoxicity.

PubMed

Van Moorhem, Marijke; Decrock, Elke; Coussee, Evelyne; Faes, Liesbeth; De Vuyst, Elke; Vranckx, Katleen; De Bock, Marijke; Wang, Nan; D'Herde, Katharina; Lambein, Fernand; Callewaert, Geert; Leybaert, Luc

2010-03-01

The neurotoxin beta-N-oxalyl-L-alpha,beta-diaminopropionic acid (L-beta-ODAP) is an L-glutamate analogue at alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)/kainate receptors in neurons and therefore acts as an excitotoxic substance. Chronic exposure to L-beta-ODAP present in Lathyrus sativus L. (L. sativus) seeds is proposed as the cause of the neurodegenerative disease neurolathyrism, but the mechanism of its action has not been conclusively identified. A key factor in excitotoxic neuronal cell death is a disturbance of the intracellular Ca2+ homeostasis, including changes in the capacity of intracellular Ca2+ stores like the endoplasmic reticulum (ER) or mitochondria. In this study, aequorin and other Ca2+ indicators were used in N2a neuroblastoma cells to investigate alterations of cellular Ca2+ handling after 24 h exposure to L-beta-ODAP. Our data demonstrate increased mitochondrial Ca2+ loading and hyperpolarization of the mitochondrial membrane potential (Psi(m)), which was specific for L-beta-ODAP and not observed with L-glutamate. We conclude that L-beta-ODAP disturbs the ER-mitochondrial Ca2+ signaling axis and thereby renders the cells more vulnerable to its excitotoxic effects that ultimately will lead to cell death. 2010 Elsevier Ltd. All rights reserved.

Ionotropic glutamate receptor expression in human white matter.

PubMed

Christensen, Pia Crone; Samadi-Bahrami, Zahra; Pavlov, Vlady; Stys, Peter K; Moore, G R Wayne

2016-09-06

Glutamate is the key excitatory neurotransmitter of the central nervous system (CNS). Its role in human grey matter transmission is well understood, but this is less clear in white matter (WM). Ionotropic glutamate receptors (iGluR) are found on both neuronal cell bodies and glia as well as on myelinated axons in rodents, and rodent WM tissue is capable of glutamate release. Thus, rodent WM expresses many of the components of the traditional grey matter neuron-to-neuron synapse, but to date this has not been shown for human WM. We demonstrate the presence of iGluRs in human WM by immunofluorescence employing high-resolution spectral confocal imaging. We found that the obligatory N-methyl-d-aspartic acid (NMDA) receptor subunit GluN1 and the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunit GluA4 co-localized with myelin, oligodendroglial cell bodies and processes. Additionally, GluA4 colocalized with axons, often in distinct clusters. These findings may explain why human WM is vulnerable to excitotoxic events following acute insults such as stroke and traumatic brain injury and in more chronic inflammatory conditions such as multiple sclerosis (MS). Further exploration of human WM glutamate signalling could pave the way for developing future therapies modulating the glutamate-mediated damage in these and other CNS disorders. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Grewia tiliaefolia and its active compound vitexin regulate the expression of glutamate transporters and protect Neuro2a cells from glutamate toxicity.

PubMed

Malar, Dicson Sheeja; Prasanth, Mani Iyer; Shafreen, Rajamohamed Beema; Balamurugan, Krishnaswamy; Devi, Kasi Pandima

2018-04-25

Glutamate is a major neurotransmitter involved in several brain functions and glutamate excitotoxicity is involved in Alzheimer's disease (AD). In the current study, the neuroprotective effect of the Indian medicinal plant Grewia tiliaefolia (GT) and its active component vitexin was evaluated in Neuro-2a cells against glutamate toxicity. Neuro-2a cells were exposed to glutamate to cause excitotoxicity and the neuroprotective effect of GT and vitexin were evaluated using biochemical studies (estimation of reactive oxygen species, reactive nitrogen species, protein carbonyl content, lipid peroxidation level, mitochondrial membrane potential and caspase-3 activity), molecular docking studies, gene expression and western blot analysis. Glutamate exposure to Neuro-2a cells induced oxidative stress, loss of membrane potential, suppressed the expression of antioxidant response genes (Nrf-2, HO-1, NQO-1), glutamate transporters (GLAST-1, GLT-1) and induced the expression of NMDAR, Calpain. However, pre-treatment of cells with GT/vitexin inhibited oxidative stress mediated damage by augmenting the expression of Nrf-2/HO-1 pathway, inducing the expression of glutamate transporters and downregulating Calpain, NMDAR. Molecular docking showed that vitexin effectively binds to NMDAR and GSK-3β and thereby can inhibit their activation. GT/vitexin also inhibited glutamate induced Bax expression. Methanol extract of G. tiliaefolia and its active component vitexin can act in an antioxidant dependent mechanism as well as by regulating glutamate in mitigating the toxicity exerted by glutamate in Neuro-2a cells. Our results conclude that GT/vitexin can act as potential drug leads for the therapeutic intervention of AD. Copyright © 2017. Published by Elsevier Inc.

In vivo Electrochemical Biosensor for Brain Glutamate Detection: A Mini Review

PubMed Central

HAMDAN, Siti Kartika; MOHD ZAIN, ainiharyati

2014-01-01

Glutamate is one of the most prominent neurotransmitters in mammalian brains, which plays an important role in neuronal excitation. High levels of neurotransmitter cause numerous alterations, such as calcium overload and the dysfunction of mitochondrial and oxidative stress. These alterations may lead to excitotoxicity and may trigger multiple neuronal diseases, such as Alzheimer’s disease, stroke, and epilepsy. Excitotoxicity is a pathological process that damages nerve cells and kills cells via excessive stimulation by neurotransmitters. Monitoring the concentration level of brain glutamate via an implantable microbiosensor is a promising alternative approach to closely investigate in the function of glutamate as a neurotransmitter. This review outlines glutamate microbiosensor designs to enhance the sensitivity of glutamate detection with less biofouling occurrence and minimal detection of interference species. There are many challenges in the development of a reproducible and stable implantable microbiosensor because many factors and limitations may affect the detection performance. However, the incorporation of multiple scales is needed to address the basic issues and combinations across the various disciplines needed to achieve the success of the system to overcome the challenges in the development of an implantable glutamate biosensor. PMID:25941459

Proton MRS in acute traumatic brain injury: role for glutamate/glutamine and choline for outcome prediction.

PubMed

Shutter, Lori; Tong, Karen A; Holshouser, Barbara A

2004-12-01

Proton magnetic resonance spectroscopy (MRS) is being used to evaluate individuals with acute traumatic brain injury and several studies have shown that changes in certain brain metabolites (N-acetylaspartate, choline) are associated with poor neurologic outcomes. The majority of previous MRS studies have been obtained relatively late after injury and none have examined the role of glutamate/ glutamine (Glx). We conducted a prospective MRS study of 42 severely injured adults to measure quantitative metabolite changes early (7 days) after injury in normal appearing brain. We used these findings to predict long-term neurologic outcome and to determine if MRS data alone or in combination with clinical outcome variables provided better prediction of long-term outcomes. We found that glutamate/glutamine (Glx) and choline (Cho) were significantly elevated in occipital gray and parietal white matter early after injury in patients with poor long-term (6-12-month) outcomes. Glx and Cho ratios predicted long-term outcome with 94% accuracy and when combined with the motor Glasgow Coma Scale score provided the highest predictive accuracy (97%). Somatosensory evoked potentials were not as accurate as MRS data in predicting outcome. Elevated Glx and Cho are more sensitive indicators of injury and predictors of poor outcome when spectroscopy is done early after injury. This may be a reflection of early excitotoxic injury (i.e., elevated Glx) and of injury associated with membrane disruption (i.e., increased Cho) secondary to diffuse axonal injury.

Neuroprotective effects of intrastriatal injection of rapamycin in a mouse model of excitotoxicity induced by quinolinic acid.

PubMed

Saliba, Soraya Wilke; Vieira, Erica Leandro Marciano; Santos, Rebeca Priscila de Melo; Candelario-Jalil, Eduardo; Fiebich, Bernd L; Vieira, Luciene Bruno; Teixeira, Antonio Lucio; de Oliveira, Antonio Carlos Pinheiro

2017-01-31

The mammalian target of rapamycin (mTOR) is a kinase involved in a variety of physiological and pathological functions. However, the exact role of mTOR in excitotoxicity is poorly understood. Here, we investigated the effects of mTOR inhibition with rapamycin against neurodegeneration, and motor impairment, as well as inflammatory profile caused by an excitotoxic stimulus. A single and unilateral striatal injection of quinolinic acid (QA) was used to induce excitotoxicity in mice. Rapamycin (250 nL of 0.2, 2, or 20 μM; intrastriatal route) was administered 15 min before QA injection. Forty-eight hours after QA administration, rotarod test was performed to evaluate motor coordination and balance. Fluoro-Jade C, Iba-1, and GFAP staining were used to evaluate neuronal cell death, microglia morphology, and astrocytes density, respectively, at this time point. Levels of cytokines and neurotrophic factors were measured by ELISA and Cytometric Bead Array 8 h after QA injection. Striatal synaptosomes were used to evaluate the release of glutamate. We first demonstrated that rapamycin prevented the motor impairment induced by QA. Moreover, mTOR inhibition also reduced the neurodegeneration and the production of interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α induced by excitotoxic stimulus. The lowest dose of rapamycin also increased the production of IL-10 and prevented the reduction of astrocyte density induced by QA. By using an in vitro approach, we demonstrated that rapamycin differently alters the release of glutamate from striatal synaptosomes induced by QA, reducing or enhancing the release of this neurotransmitter at low or high concentrations, respectively. Taken together, these data demonstrated a protective effect of rapamycin against an excitotoxic stimulus. Therefore, this study provides new evidence of the detrimental role of mTOR in neurodegeneration, which might represent an important target for the treatment of neurodegenerative

Melatonin improves neuroplasticity by upregulating the growth-associated protein-43 (GAP-43) and NMDAR postsynaptic density-95 (PSD-95) proteins in cultured neurons exposed to glutamate excitotoxicity and in rats subjected to transient focal cerebral ischemia even during a long-term recovery period.

PubMed

Juan, Wei-Sheng; Huang, Sheng-Yang; Chang, Che-Chao; Hung, Yu-Chang; Lin, Yu-Wen; Chen, Tsung-Ying; Lee, Ai-Hua; Lee, Ai-Chiang; Wu, Tian-Shung; Lee, E-Jian

2014-03-01

Recent evidence shows that the NMDAR postsynaptic density-95 (PSD-95), growth-associated protein-43 (GAP-43), and matrix metalloproteinase-9 (MMP-9) protein enhance neuroplasticity at the subacute stage of stroke. Here, we evaluated whether melatonin would modulate the PSD-95, GAP-43, and MMP-9 proteins in cultured neurons exposed to glutamate excitotoxicity and in rats subjected to experimental stroke. Adult male Sprague-Dawley rats were treated with melatonin (5 mg/kg) or vehicle at reperfusion onset after transient occlusion of the right middle cerebral artery (tMCAO) for 90 min. Animals were euthanized for Western immunoblot analyses for the PSD-95 and GAP-43 proteins and gelatin zymography for the MMP-9 activity at 7 days postinsult. Another set of animals was sacrificed for histologic and Golgi-Cox-impregnated sections at 28 days postinsult. In cultured neurons exposed to glutamate excitotoxicity, melatonin significantly upregulated the GAP-43 and PSD-95 expressions and improved dendritic aborizations (P<0.05, respectively). Relative to controls, melatonin-treated stroke animals caused a significant improvement in GAP-43 and PSD-95 expressions as well as the MMP-9 activity in the ischemic brain (P<0.05). Consequently, melatonin also significantly promoted the dendritic spine density and reduced infarction in the ischemic brain, and improved neurobehaviors as well at 28 days postinsult (P<0.05, respectively). Together, melatonin upregulates GAP-43, PSD-95, and MMP-9 proteins, which likely accounts for its actions to improve neuroplasticity in cultured neurons exposed to glutamate excitotoxicity and to enhance long-term neuroprotection, neuroplasticity, and brain remodeling in stroke rats. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Bacterial Cytolysin during Meningitis Disrupts the Regulation of Glutamate in the Brain, Leading to Synaptic Damage

PubMed Central

Wippel, Carolin; Maurer, Jana; Förtsch, Christina; Hupp, Sabrina; Bohl, Alexandra; Ma, Jiangtao; Mitchell, Timothy J.; Bunkowski, Stephanie; Brück, Wolfgang; Nau, Roland; Iliev, Asparouh I.

2013-01-01

Streptococcus pneumoniae (pneumococcal) meningitis is a common bacterial infection of the brain. The cholesterol-dependent cytolysin pneumolysin represents a key factor, determining the neuropathogenic potential of the pneumococci. Here, we demonstrate selective synaptic loss within the superficial layers of the frontal neocortex of post-mortem brain samples from individuals with pneumococcal meningitis. A similar effect was observed in mice with pneumococcal meningitis only when the bacteria expressed the pore-forming cholesterol-dependent cytolysin pneumolysin. Exposure of acute mouse brain slices to only pore-competent pneumolysin at disease-relevant, non-lytic concentrations caused permanent dendritic swelling, dendritic spine elimination and synaptic loss. The NMDA glutamate receptor antagonists MK801 and D-AP5 reduced this pathology. Pneumolysin increased glutamate levels within the mouse brain slices. In mouse astrocytes, pneumolysin initiated the release of glutamate in a calcium-dependent manner. We propose that pneumolysin plays a significant synapto- and dendritotoxic role in pneumococcal meningitis by initiating glutamate release from astrocytes, leading to subsequent glutamate-dependent synaptic damage. We outline for the first time the occurrence of synaptic pathology in pneumococcal meningitis and demonstrate that a bacterial cytolysin can dysregulate the control of glutamate in the brain, inducing excitotoxic damage. PMID:23785278

A new infectious encephalopathy syndrome, clinically mild encephalopathy associated with excitotoxicity (MEEX).

PubMed

Hirai, Nozomi; Yoshimaru, Daisuke; Moriyama, Yoko; Yasukawa, Kumi; Takanashi, Jun-Ichi

2017-09-15

Acute infectious encephalopathy is often observed in children in East Asia including Japan. More than 40% of the patients remain unclassified into specific syndromes. To investigate the underlying pathomechanisms in those with unclassified encephalopathy, we evaluated brain metabolism by MR spectroscopy. Among seven patients with acute encephalopathy admitted to our hospital from June 2016 to May 2017, three were classified into acute encephalopathy with biphasic seizures and late reduced diffusion (AESD). The other four showed consciousness disturbance lasting more than three days with no parenchymal lesion visible on MRI, which led to a diagnosis of unclassified encephalopathy. MR spectroscopy in these four patients, however, revealed an increase of glutamine with a normal N-acetyl aspartate level on days 5 to 8, which had normalized by follow-up studies on days 11 to 16. The four patients clinically recovered completely. Among 27 patients with encephalopathy, including the present seven patients, admitted to our hospital from January 2015 to March 2017, seven (26%) were classified into this type, which we propose is a new encephalopathy syndrome, clinically mild encephalopathy associated with excitotoxicity (MEEX). MEEX is the second most common subtype, following AESD (30%). This study suggests that excitotoxicity may be a common underlying pathomechanism of acute infectious encephalopathy, and prompt astrocytic neuroprotection from excitotoxicity may prevent progression of MEEX into AESD. Copyright © 2017 Elsevier B.V. All rights reserved.

Kainic Acid-Induced Excitotoxicity Experimental Model: Protective Merits of Natural Products and Plant Extracts

PubMed Central

Mohd Sairazi, Nur Shafika; Sirajudeen, K. N. S.; Asari, Mohd Asnizam; Muzaimi, Mustapha; Mummedy, Swamy; Sulaiman, Siti Amrah

2015-01-01

Excitotoxicity is well recognized as a major pathological process of neuronal death in neurodegenerative diseases involving the central nervous system (CNS). In the animal models of neurodegeneration, excitotoxicity is commonly induced experimentally by chemical convulsants, particularly kainic acid (KA). KA-induced excitotoxicity in rodent models has been shown to result in seizures, behavioral changes, oxidative stress, glial activation, inflammatory mediator production, endoplasmic reticulum stress, mitochondrial dysfunction, and selective neurodegeneration in the brain upon KA administration. Recently, there is an emerging trend to search for natural sources to combat against excitotoxicity-associated neurodegenerative diseases. Natural products and plant extracts had attracted a considerable amount of attention because of their reported beneficial effects on the CNS, particularly their neuroprotective effect against excitotoxicity. They provide significant reduction and/or protection against the development and progression of acute and chronic neurodegeneration. This indicates that natural products and plants extracts may be useful in protecting against excitotoxicity-associated neurodegeneration. Thus, targeting of multiple pathways simultaneously may be the strategy to maximize the neuroprotection effect. This review summarizes the mechanisms involved in KA-induced excitotoxicity and attempts to collate the various researches related to the protective effect of natural products and plant extracts in the KA model of neurodegeneration. PMID:26793262

Inducible Glutamate Oxaloacetate Transaminase as a Therapeutic Target Against Ischemic Stroke

PubMed Central

Khanna, Savita; Briggs, Zachary

2015-01-01

Abstract Significance: Glutamate serves multi-faceted (patho)physiological functions in the central nervous system as the most abundant excitatory neurotransmitter and under pathological conditions as a potent neurotoxin. Regarding the latter, elevated extracellular glutamate is known to play a central role in ischemic stroke brain injury. Recent Advances: Glutamate oxaloacetate transaminase (GOT) has emerged as a new therapeutic target in protecting against ischemic stroke injury. Oxygen-sensitive induction of GOT expression and activity during ischemic stroke lowers glutamate levels at the stroke site while sustaining adenosine triphosphate levels in brain. The energy demands of the brain are among the highest of all organs underscoring the need to quickly mobilize alternative carbon skeletons for metabolism in the absence of glucose during ischemic stroke. Recent work builds on the important observation of Hans Krebs that GOT-mediated metabolism of glutamate generates tri-carboxylic acid (TCA) cycle intermediates in brain tissue. Taken together, outcomes suggest GOT may enable the transformative switch of otherwise excitotoxic glutamate into life-sustaining TCA cycle intermediates during ischemic stroke. Critical Issues: Neuroprotective strategies that focus solely on blocking mechanisms of glutamate-mediated excitotoxicity have historically failed in clinical trials. That GOT can enable glutamate to assume the role of a survival factor represents a paradigm shift necessary to develop the overall significance of glutamate in stroke biology. Future Directions: Ongoing efforts are focused to develop the therapeutic significance of GOT in stroke-affected brain. Small molecules that target induction of GOT expression and activity in the ischemic penumbra are the focus of ongoing studies. Antioxid. Redox Signal. 22, 175–186. PMID:25343301

CORM-A1 prevents blood-brain barrier dysfunction caused by ionotropic glutamate receptor-mediated endothelial oxidative stress and apoptosis.

PubMed

Basuroy, Shyamali; Leffler, Charles W; Parfenova, Helena

2013-06-01

In cerebral microvascular endothelial cells (CMVEC) of newborn pigs, glutamate at excitotoxic concentrations (mM) causes apoptosis mediated by reactive oxygen species (ROS). Carbon monoxide (CO) produced by CMVEC or delivered by a CO-releasing molecule, CORM-A1, has antioxidant properties. We tested the hypothesis that CORM-A1 prevents cerebrovascular endothelial barrier dysfunction caused by glutamate excitotoxicity. First, we identified the glutamate receptors (GluRs) and enzymatic sources of ROS involved in the mechanism of endothelial apoptosis. In glutamate-exposed CMVEC, ROS formation and apoptosis were blocked by rotenone, 2-thenoyltrifluoroacetone (TTFA), and antimycin, indicating that mitochondrial complexes I, II, and III are the major sources of oxidative stress. Agonists of ionotropic GluRs (iGluRs) N-methyl-D-aspartate (NMDA), cis-ACPD, AMPA, and kainate increased ROS production and apoptosis, whereas iGluR antagonists exhibited antiapoptotic properties, suggesting that iGluRs mediate glutamate-induced endothelial apoptosis. The functional consequences of endothelial injury were tested in the model of blood-brain barrier (BBB) composed of CMVEC monolayer on semipermeable membranes. Glutamate and iGluR agonists reduced transendothelial electrical resistance and increased endothelial paracellular permeability to 3-kDa dextran. CORM-A1 exhibited potent antioxidant and antiapoptotic properties in CMVEC and completely prevented BBB dysfunction caused by glutamate and iGluR agonists. Overall, the endothelial component of the BBB is a cellular target for excitotoxic glutamate that, via a mechanism involving a iGluR-mediated activation of mitochondrial ROS production and apoptosis, leads to BBB opening that may be prevented by the antioxidant and antiapoptotic actions of CORMs. Antioxidant CORMs therapy may help preserve BBB functional integrity in neonatal cerebrovascular disease.

Bax-inhibiting peptide protects glutamate-induced cerebellar granule cell death by blocking Bax translocation.

PubMed

Iriyama, Takayuki; Kamei, Yoshimasa; Kozuma, Shiro; Taketani, Yuji

2009-02-13

Glutamate-induced excitotoxicity has been implicated in the pathogenesis of various neurological damages and disorders. In the brain damage of immature animals such as neonatal hypoxic-ischemic brain injury, the excitotoxicity appears to be more intimately involved through apoptosis. Bax, a member of the Bcl-2 family proteins, plays a key role in the promotion of apoptosis by translocation from the cytosol to the mitochondria and the release of apoptogenic factors such as cytochrome c. Recently, Bax-inhibiting peptide (BIP), a novel membrane-permeable peptide which can bind Bax in the cytosol and inhibit its translocation to the mitochondria, was developed. To investigate the possibility of a new neuroprotection strategy targeting Bax translocation in glutamate-induced neuronal cell death, cerebellar granule neurons (CGNs) were exposed to glutamate with or without BIP. Pretreatment of CGNs with BIP elicited a dose-dependent reduction of glutamate-induced neuronal cell death as measured by MTT assay. BIP significantly suppressed both the number of TUNEL-positive cells and the increase in caspases 3 and 9 activities induced by glutamate. In addition, immunoblotting after subcellular fractionation revealed that BIP prevented the glutamate-induced Bax translocation to the mitochondria and the release of cytochrome c from the mitochondria. These results suggest that agents capable of inhibiting Bax activity such as BIP might lead to new drugs for glutamate-related diseases in the future.

Oxygen-Inducible Glutamate Oxaloacetate Transaminase as Protective Switch Transforming Neurotoxic Glutamate to Metabolic Fuel During Acute Ischemic Stroke

PubMed Central

Rink, Cameron; Gnyawali, Surya; Peterson, Laura

2011-01-01

Abstract This work rests on our previous report (J Cereb Blood Flow Metab 30: 1275–1287, 2010) recognizing that glutamate (Glu) oxaloacetate transaminase (GOT) is induced when brain tissue hypoxia is corrected during acute ischemic stroke (AIS). GOT can metabolize Glu into tricarboxylic acid cycle intermediates and may therefore be useful to harness excess neurotoxic extracellular Glu during AIS as a metabolic substrate. We report that in cultured neural cells challenged with hypoglycemia, extracellular Glu can support cell survival as long as there is sufficient oxygenation. This effect is abrogated by GOT knockdown. In a rodent model of AIS, supplemental oxygen (100% O2 inhaled) during ischemia significantly increased GOT expression and activity in the stroke-affected brain tissue and prevented loss of ATP. Biochemical analyses and in vivo magnetic resonance spectroscopy during stroke demonstrated that such elevated GOT decreased Glu levels at the stroke-affected site. In vivo lentiviral gene delivery of GOT minimized lesion volume, whereas GOT knockdown worsened stroke outcomes. Thus, brain tissue GOT emerges as a novel target in managing stroke outcomes. This work demonstrates that correction of hypoxia during AIS can help clear extracellular neurotoxic Glu by enabling utilization of this amino acid as a metabolic fuel to support survival of the hypoglycemic brain tissue. Strategies to mitigate extracellular Glu-mediated neurodegeneration via blocking receptor-mediated excitotoxicity have failed in clinical trials. We introduce the concept that under hypoglycemic conditions extracellular Glu can be transformed from a neurotoxin to a survival factor by GOT, provided there is sufficient oxygen to sustain cellular respiration. Antioxid. Redox Signal. 14, 1777–1785. PMID:21361730

Creatine affords protection against glutamate-induced nitrosative and oxidative stress.

PubMed

Cunha, Mauricio P; Lieberknecht, Vicente; Ramos-Hryb, Ana Belén; Olescowicz, Gislaine; Ludka, Fabiana K; Tasca, Carla I; Gabilan, Nelson H; Rodrigues, Ana Lúcia S

2016-05-01

Creatine has been reported to exert beneficial effects in several neurodegenerative diseases in which glutamatergic excitotoxicity and oxidative stress play an etiological role. The purpose of this study was to investigate the protective effects of creatine, as compared to the N-Methyl-d-Aspartate (NMDA) receptor antagonist dizocilpine (MK-801), against glutamate or hydrogen peroxide (H2O2)-induced injury in human neuroblastoma SH-SY5Y cells. Exposure of cells to glutamate (60-80 mM) or H2O2 (200-300 μM) for 24 h decreased cellular viability and increased dichlorofluorescein (DCF) fluorescence (indicative of increased reactive oxygen species, ROS) and nitric oxide (NO) production (assessed by mono-nitrogen oxides, NOx, levels). Creatine (1-10 mM) or MK-801 (0.1-10 μM) reduced glutamate- and H2O2-induced toxicity. The protective effect of creatine against glutamate-induced toxicity involves its antioxidant effect, since creatine, similar to MK-801, prevented the increase on DCF fluorescence induced by glutamate or H2O2. Furthermore, creatine or MK-801 blocked glutamate- and H2O2-induced increases in NOx levels. In another set of experiments, the repeated, but not acute, administration of creatine (300 mg/kg, po) in mice prevented the decreases on cellular viability and mitochondrial membrane potential (assessed by tetramethylrhodamine ethyl ester, TMRE, probe) of hippocampal slices incubated with glutamate (10 mM). Creatine concentration-dependent decreased the amount of nitrite formed in the reaction of oxygen with NO produced from sodium nitroprusside solution, suggesting that its protective effect against glutamate or H2O2-induced toxicity might be due to its scavenger activity. Overall, the results suggest that creatine may be useful as adjuvant therapy for neurodegenerative disease treatments. Copyright © 2016 Elsevier Ltd. All rights reserved.

Pregabalin attenuates excitotoxicity in diabetes.

PubMed

Huang, Chin-Wei; Lai, Ming-Chi; Cheng, Juei-Tang; Tsai, Jing-Jane; Huang, Chao-Ching; Wu, Sheng-Nan

2013-01-01

Diabetes can exacerbate seizures and worsen seizure-related brain damage. In the present study, we aimed to determine whether the standard antiepileptic drug pregabalin (PGB) protects against pilocarpine-induced seizures and excitotoxicity in diabetes. Adult male Sprague-Dawley rats were divided into either a streptozotocin (STZ)-induced diabetes group or a normal saline (NS) group. Both groups were further divided into subgroups that were treated intravenously with either PGB (15 mg/kg) or a vehicle; all groups were treated with subcutaneous pilocarpine (60 mg/kg) to induce seizures. To evaluate spontaneous recurrent seizures (SRS), PGB-pretreated rats were fed rat chow containing oral PGB (450 mg) for 28 consecutive days; vehicle-pretreated rats were fed regular chow. SRS frequency was monitored for 2 weeks from post-status epilepticus day 15. We evaluated both acute neuronal loss and chronic mossy fiber sprouting in the CA3 area. In addition, we performed patch clamp recordings to study evoked excitatory postsynaptic currents (eEPSCs) in hippocampal CA1 neurons for both vehicle-treated rats with SRS. Finally, we used an RNA interference knockdown method for Kir6.2 in a hippocampal cell line to evaluate PGB's effects in the presence of high-dose ATP. We found that compared to vehicle-treated rats, PGB-treated rats showed less severe acute seizure activity, reduced acute neuronal loss, and chronic mossy fiber sprouting. In the vehicle-treated STZ rats, eEPSC amplitude was significantly lower after PGB administration, but glibenclamide reversed this effect. The RNA interference study confirmed that PGB could counteract the ATP-sensitive potassium channel (KATP)-closing effect of high-dose ATP. By opening KATP, PGB protects against neuronal excitotoxicity, and is therefore a potential antiepileptogenic in diabetes. These findings might help develop a clinical algorithm for treating patients with epilepsy and comorbid metabolic disorders.

Biological Signatures of Brain Damage Associated with High Serum Ferritin Levels in Patients with Acute Ischemic Stroke and Thrombolytic Treatment

PubMed Central

Millán, Mónica; Sobrino, Tomás; Arenillas, Juan Francisco; Rodríguez-Yáñez, Manuel; García, María; Nombela, Florentino; Castellanos, Mar; de la Ossa, Natalia Pérez; Cuadras, Patricia; Serena, Joaquín; Castillo, José; Dávalos, Antoni

2008-01-01

Background and purpose: Increased body iron stores have been related to greater oxidative stress and brain injury in clinical and experimental cerebral ischemia and reperfusion. We aimed to investigate the biological signatures of excitotoxicity, inflammation and blood brain barrier disruption potentially associated with high serum ferritin levels-related damage in acute stroke patients treated with i.v. t-PA. Methods: Serum levels of ferritin (as index of increased cellular iron stores), glutamate, interleukin-6, matrix metalloproteinase-9 and cellular fibronectin were determined in 134 patients treated with i.v. t-PA within 3 hours from stroke onset in blood samples obtained before t-PA treatment, at 24 and 72 hours. Results: Serum ferritin levels before t-PA infusion correlated to glutamate (r = 0.59, p < 0.001) and interleukin-6 (r = 0.55, p <0.001) levels at baseline, and with glutamate (r = 0.57,p <0.001), interleukin-6 (r = 0.49,p <0.001), metalloproteinase-9 (r = 0.23, p = 0.007) and cellular fibronectin (r = 0.27, p = 0.002) levels measured at 24 hours and glutamate (r = 0.415, p < 0.001), interleukin-6 (r = 0.359, p < 0.001) and metalloproteinase-9 (r = 0.261, p = 0.004) at 72 hours. The association between ferritin and glutamate levels remained after adjustment for confounding factors in generalized linear models. Conclusions: Brain damage associated with increased iron stores in acute ischemic stroke patients treated with iv. tPA may be mediated by mechanisms linked to excitotoxic damage. The role of inflammation, blood brain barrier disruption and oxidative stress in this condition needs further research. PMID:19096131

Single-cell imaging of bioenergetic responses to neuronal excitotoxicity and oxygen and glucose deprivation.

PubMed

Connolly, Niamh M C; Düssmann, Heiko; Anilkumar, Ujval; Huber, Heinrich J; Prehn, Jochen H M

2014-07-30

Excitotoxicity is a condition occurring during cerebral ischemia, seizures, and chronic neurodegeneration. It is characterized by overactivation of glutamate receptors, leading to excessive Ca(2+)/Na(+) influx into neurons, energetic stress, and subsequent neuronal injury. We and others have previously investigated neuronal populations to study how bioenergetic parameters determine neuronal injury; however, such experiments are often confounded by population-based heterogeneity and the contribution of effects of non-neuronal cells. Hence, we here characterized bioenergetics during transient excitotoxicity in rat and mouse primary neurons at the single-cell level using fluorescent sensors for intracellular glucose, ATP, and activation of the energy sensor AMP-activated protein kinase (AMPK). We identified ATP depletion and recovery to energetic homeostasis, along with AMPK activation, as surprisingly rapid and plastic responses in two excitotoxic injury paradigms. We observed rapid recovery of neuronal ATP levels also in the absence of extracellular glucose, or when glycolytic ATP production was inhibited, but found mitochondria to be critical for fast and complete energetic recovery. Using an injury model of oxygen and glucose deprivation, we identified a similarly rapid bioenergetics response, yet with incomplete ATP recovery and decreased AMPK activity. Interestingly, excitotoxicity also induced an accumulation of intracellular glucose, providing an additional source of energy during and after excitotoxicity-induced energy depletion. We identified this to originate from extracellular, AMPK-dependent glucose uptake and from intracellular glucose mobilization. Surprisingly, cells recovering their elevated glucose levels faster to baseline survived longer, indicating that the plasticity of neurons to adapt to bioenergetic challenges is a key indicator of neuronal viability. Copyright © 2014 the authors 0270-6474/14/3410192-14$15.00/0.

Rotigotine protects against glutamate toxicity in primary dopaminergic cell culture.

PubMed

Oster, Sandra; Radad, Khaled; Scheller, Dieter; Hesse, Marlen; Balanzew, Wladimir; Reichmann, Heinz; Gille, Gabriele

2014-02-05

In Parkinson disease the degeneration of dopaminergic neurones is believed to lead to a disinhibition of the subthalamic nucleus thus increasing the firing rate of the glutamatergic excitatory projections to the substantia nigra. In consequence, excessive glutamatergic activity will cause excitotoxicity and oxidative stress. In the present study we investigated mechanisms of glutamate toxicity and the neuroprotective potential of the dopamine agonist rotigotine towards dopaminergic neurones in mouse mesencephalic primary culture. Glutamate toxicity was mediated by the N-methyl-d-aspartic acid (NMDA) receptor and accompanied by a strong calcium influx into dopaminergic neurones for which the L-type voltage-sensitive calcium channels play an important role. The rate of superoxide production in the culture was highly increased. Deleterious nitric oxide production did not participate in glutamate-mediated excitotoxicity. Pretreatment of cultures with rotigotine significantly increased the survival of dopaminergic neurones exposed to glutamate. Rotigotine exerted its protective effects via dopamine receptor stimulation (presumably via dopamine D3 receptor) and decreased significantly the production of superoxide radicals. When cultures were preincubated with Phosphoinositol 3-Kinase (PI3K) inhibitors the protective effect of rotigotine was abolished suggesting a decisive role of the PI3K/Akt pathway in rotigotine-mediated neuroprotection. Consistently, exposure to rotigotine induced the activation of Akt by phosphorylation followed by phosphorylation, and thus inactivation, of the pro-apoptotic factor glycogen synthase kinase-3-beta (GSK-3-β). Taken together, our work contributed to elucidating the mechanisms of glutamate toxicity in mesencephalic culture and unravelled the signalling pathways associated with rotigotine-induced neuroprotection against glutamate toxicity in primary dopaminergic cultures. Copyright © 2013 Elsevier B.V. All rights reserved.

Increase of extracellular glutamate concentration increases its oxidation and diminishes glucose oxidation in isolated mouse hippocampus: reversible by TFB-TBOA.

PubMed

Torres, Felipe Vasconcelos; Hansen, Fernanda; Locks-Coelho, Lucas Doridio

2013-08-01

Glutamate concentration at the synaptic level must be kept low in order to prevent excitotoxicity. Astrocytes play a key role in brain energetics, and also astrocytic glutamate transporters are responsible for the vast majority of glutamate uptake in CNS. Experiments with primary astrocytic cultures suggest that increased influx of glutamate cotransported with sodium at astrocytes favors its flux to the tricarboxylic acid cycle instead of the glutamate-glutamine cycle. Although metabolic coupling can be considered an emergent field of research with important recent discoveries, some basic aspects of glutamate metabolism still have not been characterized in brain tissue. Therefore, the aim of this study was to investigate whether the presence of extracellular glutamate is able to modulate the use of glutamate and glucose as energetic substrates. For this purpose, isolated hippocampi of mice were incubated with radiolabeled substrates, and CO2 radioactivity and extracellular lactate were measured. Our results point to a diminished oxidation of glucose with increasing extracellular glutamate concentration, glutamate presumably being the fuel, and might suggest that oxidation of glutamate could buffer excitotoxic conditions by high glutamate concentrations. In addition, these findings were reversed when glutamate uptake by astrocytes was impaired by the presence of (3S)-3-[[3-[[4-(trifluoromethyl)benzoyl]amino]phenyl]methoxy]-L-aspartic acid (TFB-TBOA). Taken together, our findings argue against the lactate shuttle theory, because glutamate did not cause any detectable increase in extracellular lactate content (or, presumably, in glycolysis), because the glutamate is being used as fuel instead of going to glutamine and back to neurons. Copyright © 2013 Wiley Periodicals, Inc.

Novel Application of Stem Cell-Derived Neurons to Evaluate the Time-and Dose-Dependent Progression of Excitotoxic Injury

DTIC Science & Technology

2013-05-14

enzymes . At sufficiently high doses of glutamate, this process culminates in excitogenic cell death [1]. Treatments to mitigate neuronal damage during...To evaluate the potential for therapeutic screening, we assessed the effect of several small molecule antagonists on excitotoxicity in a moderate...C. Current clamp recordings showing repeated overshooting action potentials are evoked by injection of a 75 pA current. D. Voltage-clamp recordings

Neuroprotective Effects of the Glutamate Transporter Activator (R)-(−)-5-methyl-1-nicotinoyl-2-pyrazoline (MS-153) following Traumatic Brain Injury in the Adult Rat

PubMed Central

Fox, Douglas P.; Zoubroulis, Argie; Valente Mortensen, Ole; Raghupathi, Ramesh

2016-01-01

Abstract Traumatic brain injury (TBI) in humans and in animals leads to an acute and sustained increase in tissue glutamate concentrations within the brain, triggering glutamate-mediated excitotoxicity. Excitatory amino acid transporters (EAATs) are responsible for maintaining extracellular central nervous system glutamate concentrations below neurotoxic levels. Our results demonstrate that as early as 5 min and up to 2 h following brain trauma in brain-injured rats, the activity (Vmax) of EAAT2 in the cortex and the hippocampus was significantly decreased, compared with sham-injured animals. The affinity for glutamate (KM) and the expression of glutamate transporter 1 (GLT-1) and glutamate aspartate transporter (GLAST) were not altered by the injury. Administration of (R)-(−)-5-methyl-1-nicotinoyl-2-pyrazoline (MS-153), a GLT-1 activator, beginning immediately after injury and continuing for 24 h, significantly decreased neurodegeneration, loss of microtubule-associated protein 2 and NeuN (+) immunoreactivities, and attenuated calpain activation in both the cortex and the hippocampus at 24 h after the injury; the reduction in neurodegeneration remained evident up to 14 days post-injury. In synaptosomal uptake assays, MS-153 up-regulated GLT-1 activity in the naïve rat brain but did not reverse the reduced activity of GLT-1 in traumatically-injured brains. This study demonstrates that administration of MS-153 in the acute post-traumatic period provides acute and long-term neuroprotection for TBI and suggests that the neuroprotective effects of MS-153 are related to mechanisms other than GLT-1 activation, such as the inhibition of voltage-gated calcium channels. PMID:26200170

Clinically mild infantile encephalopathy associated with excitotoxicity.

PubMed

Hirai, Nozomi; Yoshimaru, Daisuke; Moriyama, Yoko; Honda, Takafumi; Yasukawa, Kumi; Takanashi, Jun-Ichi

2017-02-15

Acute infectious encephalopathy is very frequently observed in children in East Asia including Japan. Acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) is the most common subtype in Japan; however, more than 40% of the patients remain unclassified into specific syndromes. To investigate the underlying pathomechanism in those with unclassified acute encephalopathy, we evaluated brain metabolism by MR spectroscopy. Among 20 patients with acute encephalopathy admitted to our hospital during January 2015 to May 2016, 12 could not be classified into specific syndromes. MR spectroscopy was performed in 8 of these 12 patients with unclassified encephalopathy. MR spectroscopy showed an increase of glutamine with a normal N-acetyl aspartate level on days 3 to 8 in three of the 8 patients, which had normalized by follow-up studies. The three patients clinically recovered completely. This study suggests that excitotoxicity may be the underlying pathomechanism in some patients with unclassified mild encephalopathy. Copyright © 2016 Elsevier B.V. All rights reserved.

A study of cannabinoid-1 receptors during the early phase of excitotoxic damage to rat spinal locomotor networks in vitro.

PubMed

Veeraraghavan, Priyadharishini; Dekanic, Ana; Nistri, Andrea

2016-10-01

Endocannabinoids acting on cannabinoid-1 receptors (CB1Rs) are proposed to protect brain and spinal neurons from excitotoxic damage. The ability to recover from spinal cord injury (SCI), in which excitotoxicity is a major player, is usually investigated at late times after modulation of CB1Rs whose role in the early phases of SCI remains unclear. Using the rat spinal cord in vitro as a model for studying SCI initial pathophysiology, we investigated if agonists or antagonists of CB1Rs might affect SCI induced by the excitotoxic agent kainate (KA) within 24h from a transient (1h) application of this glutamate agonist. The CB1 agonist anandamide (AEA or pharmacological block of its degradation) did not limit excitotoxic depolarization of spinal networks: cyclic adenosine monophosphate (cAMP) assay demonstrated that CB1Rs remained functional 24h later and similarly expressed among dead or survived cells. Locomotor-like network activity recorded from ventral roots could not recover with such treatments and was associated with persistent depression of synaptic transmission. Motoneurons, that are particularly vulnerable to KA, were not protected by AEA. Application of 2-arachidonoylglycerol also did not attenuate the electrophysiological and histological damage. The intensification of damage by the CB1 antagonist AM251 suggested that endocannabinoids were operative after excitotoxic stimulation, yet insufficient to contrast it efficiently. The present data indicate that the early phases of excitotoxic SCI could not be arrested by pharmacologically exploiting the endocannabinoid system, consistent with the notion that AEA and its derivatives are more useful to treat late SCI phases. Copyright © 2016 IBRO. Published by Elsevier Ltd. All rights reserved.

Atorvastatin and Fluoxetine Prevent Oxidative Stress and Mitochondrial Dysfunction Evoked by Glutamate Toxicity in Hippocampal Slices.

PubMed

Ludka, Fabiana K; Dal-Cim, Tharine; Binder, Luisa Bandeira; Constantino, Leandra Celso; Massari, Caio; Tasca, Carla I

2017-07-01

Atorvastatin has been shown to exert a neuroprotective action by counteracting glutamatergic toxicity. Recently, we have shown atorvastatin also exerts an antidepressant-like effect that depends on both glutamatergic and serotonergic systems modulation. Excitotoxicity is involved in several brain disorders including depression; thus, it is suggested that antidepressants may target glutamatergic system as a final common pathway. In this study, a comparison of the mechanisms involved in the putative neuroprotective effect of a repetitive atorvastatin or fluoxetine treatment against glutamate toxicity in hippocampal slices was performed. Adult Swiss mice were treated with atorvastatin (10 mg/kg, p.o.) or fluoxetine (10 mg/kg, p.o.), once a day during seven consecutive days. On the eighth day, animals were killed and hippocampal slices were obtained and subjected to an in vitro protocol of glutamate toxicity. An acute treatment of atorvastatin or fluoxetine was not neuroprotective; however, the repeated atorvastatin or fluoxetine treatment prevented the decrease in cellular viability induced by glutamate in hippocampal slices. The loss of cellular viability induced by glutamate was accompanied by increased D-aspartate release, increased reactive oxygen species (ROS) and nitric oxide (NO) production, and impaired mitochondrial membrane potential. Atorvastatin or fluoxetine repeated treatment also presented an antidepressant-like effect in the tail suspension test. Atorvastatin or fluoxetine treatment was effective in protecting mice hippocampal slices from glutamate toxicity by preventing the oxidative stress and mitochondrial dysfunction.

Memantine: targeting glutamate excitotoxicity in Alzheimer's disease and other dementias.

PubMed

Molinuevo, José L; Lladó, Albert; Rami, Lorena

2005-01-01

The management of dementia has changed since the development of new antidementia drugs. The benefits observed in Alzheimer's disease (AD) with selective cholinergic transmission treatments are mainly symptomatic, without clear evidence of neuroprotection. The hypothesis that glutamate-mediated neurotoxicity is involved in the pathogenesis of AD is finding increasingly more acceptance in the scientific community. Glutamate receptors are overactive, and N-methyl-D-aspartate (NMDA) receptor antagonists have therapeutic potential for the treatment of AD and other neurological disorders. Memantine is a noncompetitive NMDA antagonist that is considered a neuroprotective drug. Memantine's capacity has been demonstrated in preclinical studies, and it is considered a useful symptomatic treatment for AD. Memantine has been shown to benefit cognition, function, and global outcome in patients with moderate to severe AD, and it is currently approved by the US Food and Drug Administration (FDA) for the treatment of moderate to severe AD. Recently, memantine has also demonstrated efficacy in the initial stages of AD, although FDA authorization is pending. This review highlights the important pharmacological and clinical aspects of memantine, as well as some basic mechanisms mediating glutamatergic neurodegeneration.

Cellular Origin of [18F]FDG-PET Imaging Signals During Ceftriaxone-Stimulated Glutamate Uptake: Astrocytes and Neurons.

PubMed

Dienel, Gerald A; Behar, Kevin L; Rothman, Douglas L

2017-12-01

Ceftriaxone stimulates astrocytic uptake of the excitatory neurotransmitter glutamate, and it is used to treat glutamatergic excitotoxicity that becomes manifest during many brain diseases. Ceftriaxone-stimulated glutamate transport was reported to drive signals underlying [ 18 F]fluorodeoxyglucose-positron emission tomographic ([ 18 F]FDG-PET) metabolic images of brain glucose utilization and interpreted as supportive of the notion of lactate shuttling from astrocytes to neurons. This study draws attention to critical roles of astrocytes in the energetics and imaging of brain activity, but the results are provocative because (1) the method does not have cellular resolution or provide information about downstream pathways of glucose metabolism, (2) neuronal and astrocytic [ 18 F]FDG uptake were not separately measured, and (3) strong evidence against lactate shuttling was not discussed. Evaluation of potential metabolic responses to ceftriaxone suggests lack of astrocytic specificity and significant contributions by pre- and postsynaptic neuronal compartments. Indeed, astrocytic glycolysis may not make a strong contribution to the [ 18 F]FDG-PET signal because partial or complete oxidation of one glutamate molecule on its uptake generates enough ATP to fuel uptake of 3 to 10 more glutamate molecules, diminishing reliance on glycolysis. The influence of ceftriaxone on energetics of glutamate-glutamine cycling must be determined in astrocytes and neurons to elucidate its roles in excitotoxicity treatment.

Neuroprotection by GH against excitotoxic-induced cell death in retinal ganglion cells.

PubMed

Martínez-Moreno, Carlos G; Ávila-Mendoza, José; Wu, Yilun; Arellanes-Licea, Elvira Del Carmen; Louie, Marcela; Luna, Maricela; Arámburo, Carlos; Harvey, Steve

2016-08-01

Retinal growth hormone (GH) has been shown to promote cell survival in retinal ganglion cells (RGCs) during developmental waves of apoptosis during chicken embryonic development. The possibility that it might also against excitotoxicity-induced cell death was therefore examined in the present study, which utilized quail-derived QNR/D cells as an in vitro RGC model. QNR/D cell death was induced by glutamate in the presence of BSO (buthionine sulfoxamide) (an enhancer of oxidative stress), but this was significantly reduced (P<0.01) in the presence of exogenous recombinant chicken GH (rcGH). Similarly, QNR/D cells that had been prior transfected with a GH plasmid to overexpress secreted and non-secreted GH. This treatment reduced the number of TUNEL-labeled cells and blocked their release of lactate dehydrogenase (LDH). In a further experiment with dissected neuroretinal explants from ED (embryonic day) 10 embryos, rcGH treatment of the explants also reduced (P<0.01) the number of glutamate-BSO-induced apoptotic cells and blocked the explant release of LDH. This neuroprotective action was likely mediated by increased STAT5 phosphorylation and increased bcl-2 production, as induced by exogenous rcGH treatment and the media from GH-overexpressing QNR/D cells. As rcGH treatment and GH-overexpression cells also increased the content of IGF-1 and IGF-1 mRNA this neuroprotective action of GH is likely to be mediated, at least partially, through an IGF-1 mechanism. This possibility is supported by the fact that the siRNA knockdown of GH or IGF-1 significantly reduced QNR/D cell viability, as did the immunoneutralization of IGF-1. GH is therefore neuroprotective against excitotoxicity-induced RGC cell death by anti-apoptotic actions involving IGF-1 stimulation. Copyright © 2016 Elsevier Inc. All rights reserved.

TRANSCRIPTIONAL PROFILES FOR GLUTAMATE TRANSPORTERS REVEAL DIFFERENCES BETWEEN ORGANOPHOSPHATES BUT SIMILARITIES WITH UNRELATED NEUROTOXICANTS

PubMed Central

Slotkin, Theodore A.; Lobner, Doug; Seidler, Frederic J.

2010-01-01

The developmental neurotoxicity of organophosphates involves mechanisms other than their shared property as cholinesterase inhibitors, among which are excitotoxicity and oxidative stress. We used PC12 cells as a neurodevelopmental model to compare the effects of chlorpyrifos and diazinon on the expression of genes encoding glutamate transporters. Chlorpyrifos had a greater effect in cells undergoing nerve growth factor-induced neurodifferentiation as compared to undifferentiated PC12 cells, with peak sensitivity at the initiation of differentiation, reflecting a global upregulation of all the glutamate transporter genes expressed in this cell line. In differentiating cells, chlorpyrifos had a significantly greater effect than did diazinon and concordance analysis indicated no resemblance in their expression patterns. At the same time, the smaller effects of diazinon were highly concordant with those of an organochlorine pesticide (dieldrin) and a metal (divalent nickel). We also performed similar evaluations for the cystine/glutamate exchanger, which provides protection against oxidative stress by moving cystine into the cell; again, chlorpyrifos had the greatest effect, in this case reducing expression in undifferentiated and differentiating cells. Our results point to excitotoxicity and oxidative stress as major contributors to the noncholinesterase mechanisms that distinguish the neurodevelopmental outcomes betweem different organophosphates while providing a means whereby apparently unrelated neurotoxicants may produce similar outcomes. PMID:20600679

Melatonin protects against oxygen and glucose deprivation by decreasing extracellular glutamate and Nox-derived ROS in rat hippocampal slices.

PubMed

Patiño, Paloma; Parada, Esther; Farré-Alins, Victor; Molz, Simone; Cacabelos, Ramón; Marco-Contelles, José; López, Manuela G; Tasca, Carla I; Ramos, Eva; Romero, Alejandro; Egea, Javier

2016-12-01

Therapeutic interventions on pathological processes involved in the ischemic cascade, such as oxidative stress, neuroinflammation, excitotoxicity and/or apoptosis, are of urgent need for stroke treatment. Melatonin regulates a large number of physiological actions and its beneficial properties have been reported. The aim of this study was to investigate whether melatonin mediates neuroprotection in rat hippocampal slices subjected to oxygen-glucose-deprivation (OGD) and glutamate excitotoxicity. Thus, we describe here that melatonin significantly reduced the amount of lactate dehydrogenase released in the OGD-treated slices, reverted neuronal injury caused by OGD-reoxygenation in CA1 and CA3 hippocampal regions, restored the reduction of GSH content of the hippocampal slices induced by OGD, and diminished the oxidative stress produced in the reoxygenation period. Furthermore, melatonin afforded maximum protection against glutamate-induced toxicity and reversed the glutamate released almost basal levels, at 10 and 30μM concentration, respectively. Consequently, we propose that melatonin might strongly and positively influence the outcome of brain ischemia/reperfusion. Copyright © 2016 Elsevier B.V. All rights reserved.

Vesicular glutamate release from central axons contributes to myelin damage.

PubMed

Doyle, Sean; Hansen, Daniel Bloch; Vella, Jasmine; Bond, Peter; Harper, Glenn; Zammit, Christian; Valentino, Mario; Fern, Robert

2018-03-12

The axon myelin sheath is prone to injury associated with N-methyl-D-aspartate (NMDA)-type glutamate receptor activation but the source of glutamate in this context is unknown. Myelin damage results in permanent action potential loss and severe functional deficit in the white matter of the CNS, for example in ischemic stroke. Here, we show that in rats and mice, ischemic conditions trigger activation of myelinic NMDA receptors incorporating GluN2C/D subunits following release of axonal vesicular glutamate into the peri-axonal space under the myelin sheath. Glial sources of glutamate such as reverse transport did not contribute significantly to this phenomenon. We demonstrate selective myelin uptake and retention of a GluN2C/D NMDA receptor negative allosteric modulator that shields myelin from ischemic injury. The findings potentially support a rational approach toward a low-impact prophylactic therapy to protect patients at risk of stroke and other forms of excitotoxic injury.

Involvement of connexin43 in the infrasonic noise-induced glutamate release by cultured astrocytes.

PubMed

Jiang, Shan; Wang, Yong-Qiang; Xu, Cheng-Feng; Li, Ya-Na; Guo, Rong; Li, Ling

2014-05-01

Infrasonic noise/infrasound is a type of environmental noise that threatens public health as a nonspecific biological stressor. Glutamate-related excitotoxicity is thought to be responsible for infrasound-induced impairment of learning and memory. In addition to neurons, astrocytes are also capable of releasing glutamate. In the present study, to identify the effect of infrasound on astroglial glutamate release, cultured astrocytes were exposed to infrasound at 16 Hz, 130 dB for different times. We found that infrasound exposure caused a significant increase in glutamate levels in the extracellular fluid. Moreover, blocking the connexin43 (Cx43) hemichannel or gap junction, decreasing the probability of Cx43 being open or inhibiting of Cx43 expression blocked this increase. The results suggest that glutamate release by Cx43 hemichannels/gap junctions is involved in the response of cultured astrocytes to infrasound.

High blood glutamate oxaloacetate transaminase levels are associated with good functional outcome in acute ischemic stroke

PubMed Central

Campos, Francisco; Sobrino, Tomás; Ramos-Cabrer, Pedro; Castellanos, Mar; Blanco, Miguel; Rodríguez-Yáñez, Manuel; Serena, Joaquín; Leira, Rogelio; Castillo, José

2011-01-01

The capacity of the blood enzyme glutamate oxaloacetate transaminase (GOT) to remove glutamate from the brain by means of blood glutamate degradation has been shown in experimental models to be an efficient and novel neuroprotective tool against ischemic stroke; however, the beneficial effects of this enzyme should be tested in patients with stroke to validate these results. This study aims to investigate the association of GOT levels in blood with clinical outcome in patients with acute ischemic stroke. In two clinical independent studies, we found that patients with poor outcome show higher glutamate and lower GOT levels in blood at the time of admission. Lower GOT levels and higher glutamate levels were independently associated with poorer functional outcome at 3 months and higher infarct volume. These findings show a clear association between high blood glutamate levels and worse outcome and vice versa for GOT, presumably explained by the capacity of this enzyme to metabolize blood glutamate. PMID:21266984

Identification of Bax-interacting proteins in oligodendrocyte progenitors during glutamate excitotoxicity and perinatal hypoxia–ischemia

PubMed Central

Simonishvili, Sopio; Jain, Mohit Raja; Li, Hong; Levison, Steven W.; Wood, Teresa L.

2013-01-01

OPC (oligodendrocyte progenitor cell) death contributes significantly to the pathology and functional deficits following hypoxic-ischemic injury in the immature brain and to deficits resulting from demyelinating diseases, trauma and degenerative disorders in the adult CNS. Glutamate toxicity is a major cause of oligodendroglial death in diverse CNS disorders, and previous studies have demonstrated that AMPA/kainate receptors require the pro-apoptotic protein Bax in OPCs undergoing apoptosis. The goal of the present study was to define the pro-apoptotic and anti-apoptotic effectors that regulate Bax in healthy OPCs and after exposure to excess glutamate in vitro and following H–I (hypoxia–ischemia) in the immature rat brain. We show that Bax associates with a truncated form of Bid, a BH3-only domain protein, subsequent to glutamate treatment. Furthermore, glutamate exposure reduces Bax association with the anti-apoptotic Bcl family member, Bcl-xL. Cell fractionation studies demonstrated that both Bax and Bid translocate from the cytoplasm to mitochondria during the early stages of cell death consistent with a role for Bid as an activator, whereas Bcl-xL, which normally complexes with both Bax and Bid, disassociates from these complexes when OPCs are exposed to excess glutamate. Bax remained unactivated in the presence of insulin-like growth factor-1, and the Bcl-xL complexes were protected. Our data similarly demonstrate loss of Bcl-xL–Bax association in white matter following H–I and implicate active Bad in Bax-mediated OPC death. To identify other Bax-binding partners, we used proteomics and identified cofilin as a Bax-associated protein in OPCs. Cofilin and Bax associated in healthy OPCs, whereas the Bax–cofilin association was disrupted during glutamate-induced OPC apoptosis. PMID:24195677

Pilocarpine-Induced Status Epilepticus in Rats Involves Ischemic and Excitotoxic Mechanisms

PubMed Central

Fabene, Paolo Francesco; Merigo, Flavia; Galiè, Mirco; Benati, Donatella; Bernardi, Paolo; Farace, Paolo; Nicolato, Elena; Marzola, Pasquina; Sbarbati, Andrea

2007-01-01

The neuron loss characteristic of hippocampal sclerosis in temporal lobe epilepsy patients is thought to be the result of excitotoxic, rather than ischemic, injury. In this study, we assessed changes in vascular structure, gene expression, and the time course of neuronal degeneration in the cerebral cortex during the acute period after onset of pilocarpine-induced status epilepticus (SE). Immediately after 2 hr SE, the subgranular layers of somatosensory cortex exhibited a reduced vascular perfusion indicative of ischemia, whereas the immediately adjacent supragranular layers exhibited increased perfusion. Subgranular layers exhibited necrotic pathology, whereas the supergranular layers were characterized by a delayed (24 h after SE) degeneration apparently via programmed cell death. These results indicate that both excitotoxic and ischemic injuries occur during pilocarpine-induced SE. Both of these degenerative pathways, as well as the widespread and severe brain damage observed, should be considered when animal model-based data are compared to human pathology. PMID:17971868

The Sigma Receptor Ligand (+)-Pentazocine Prevents Apoptotic Retinal Ganglion Cell Death induced in vitro by Homocysteine and Glutamate

PubMed Central

Martin, Pamela Moore; Ola, Mohammad S.; Agarwal, Neeraj; Ganapathy, Vadivel; Smith, Sylvia B.

2013-01-01

Recent studies demonstrated that the excitotoxic amino acid homocysteine induces apoptotic death of retinal ganglion cells in vivo. In the present study, an in vitro rat retinal ganglion cell (RGC-5) culture system was used to analyze the toxicity of acute exposure to high levels of homocysteine, the mechanism of homocysteine-induced toxicity and the usefulness of σR1 ligands as neuroprotectants. When cultured RGC-5 cells were subjected to treatment with 1 mM D, L- homocysteine, a significant increase in cell death was detected by TUNEL analysis and analysis of activated caspase. When cells were treated with homocysteine- or glutamate in the presence of MK-801, an antagonist of the NMDA receptor, the cell death was inhibited significantly. In contrast, NBQX, an antagonist of the AMPA/Kainate receptor, and nifedipine, a calcium channel blocker, did not prevent the homocysteine- or glutamate-induced cell death. Semi-quantitative RT-PCR and immunocytochemical analysis demonstrated that RGC-5 cells exposed to homocysteine or glutamate express type 1 sigma receptor at levels similar to control cells. Treatment of RGC-5 cells with 3 µM or 10 µM concentrations of the σR1-specific ligand (+)-pentazocine inhibited significantly the apoptotic cell death induced by homocysteine or glutamate. The results suggest that homocysteine is toxic to ganglion cells in vitro, that the toxicity is mediated via NMDA receptor activation, and that the σR1-specific ligand (+)-pentazocine can block the RGC-5 cell death induced by homocysteine and glutamate. PMID:15046867

Acidosis-Induced Dysfunction of Cortical GABAergic Neurons through Astrocyte-Related Excitotoxicity

PubMed Central

Guan, Sudong; Zhu, Yan; Wang, Jin-Hui

2015-01-01

Background Acidosis impairs cognitions and behaviors presumably by acidification-induced changes in neuronal metabolism. Cortical GABAergic neurons are vulnerable to pathological factors and their injury leads to brain dysfunction. How acidosis induces GABAergic neuron injury remains elusive. As the glia cells and neurons interact each other, we intend to examine the role of the astrocytes in acidosis-induced GABAergic neuron injury. Results Experiments were done at GABAergic cells and astrocytes in mouse cortical slices. To identify astrocytic involvement in acidosis-induced impairment, we induced the acidification in single GABAergic neuron by infusing proton intracellularly or in both neurons and astrocytes by using proton extracellularly. Compared the effects of intracellular acidification and extracellular acidification on GABAergic neurons, we found that their active intrinsic properties and synaptic outputs appeared more severely impaired in extracellular acidosis than intracellular acidosis. Meanwhile, extracellular acidosis deteriorated glutamate transporter currents on the astrocytes and upregulated excitatory synaptic transmission on the GABAergic neurons. Moreover, the antagonists of glutamate NMDA-/AMPA-receptors partially reverse extracellular acidosis-induced injury in the GABAergic neurons. Conclusion Our studies suggest that acidosis leads to the dysfunction of cortical GABAergic neurons by astrocyte-mediated excitotoxicity, in addition to their metabolic changes as indicated previously. PMID:26474076

Cell Surface Translocation of Annexin A2 Facilitates Glutamate-induced Extracellular Proteolysis*

PubMed Central

Valapala, Mallika; Maji, Sayantan; Borejdo, Julian; Vishwanatha, Jamboor K.

2014-01-01

Glutamate-induced elevation in intracellular Ca2+ has been implicated in excitotoxic cell death. Neurons respond to increased glutamate levels by activating an extracellular proteolytic cascade involving the components of the plasmin-plasminogen system. AnxA2 is a Ca2+-dependent phospholipid binding protein and serves as an extracellular proteolytic center by recruiting the tissue plasminogen activator and plasminogen and mediating the localized generation of plasmin. Ratiometric Ca2+ imaging and time-lapse confocal microscopy demonstrated glutamate-induced Ca2+ influx. We showed that glutamate translocated both endogenous and AnxA2-GFP to the cell surface in a process dependent on the activity of the NMDA receptor. Glutamate-induced translocation of AnxA2 is dependent on the phosphorylation of tyrosine 23 at the N terminus, and mutation of tyrosine 23 to a non-phosphomimetic variant inhibits the translocation process. The cell surface-translocated AnxA2 forms an active plasmin-generating complex, and this activity can be neutralized by a hexapeptide directed against the N terminus. These results suggest an involvement of AnxA2 in potentiating glutamate-induced cell death processes. PMID:24742684

Implication of NMDA type glutamate receptors in neural regeneration and neoformation of synapses after excitotoxic injury in the guinea pig cochlea.

PubMed

d'Aldin, C G; Ruel, J; Assié, R; Pujol, R; Puel, J L

1997-07-01

In the adult mammalian cochlea, the ability of nerve fibres to regenerate has been observed following disruption of the organ of Corti by various means, or transsection of the cochlear nerve in the internal auditory meatus. Based upon the implication of glutamate as a neurotransmitter at synapses between sensory hair cells and terminal dendrites of the auditory nerve in the mammalian cochlea, we have developed, in a previous study, an in vivo model of neural regeneration and formation of synapses after the destruction of the afferent nerve endings by local application of the glutamate agonist alpha-amino-3-hydroxy-5-methyl-isoxazol-propionic acid (AMPA). In situ hybridization experiments performed during the re-innervation process revealed an overexpression of mRNA coding for NR1 subunit of N-methyl-D-aspartate (NMDA) receptors in the spiral ganglion neurons, suggesting that these receptors are implicated in neural regenerative processes. The present study has been designed to study the functional implication of NMDA receptors in the regrowth and synaptic repair of auditory dendrites in the guinea pig cochlea, by blocking the NMDA receptors during the period of normal functional recovery. In a first set of experiments, we recorded compound action potential after acute perilymphatic perfusion of cumulative doses (0.03-10mM) of DL 2-amino-5-phosphonovalerate (D-AP5), a NMDA antagonist, to determine the efficiency of the drug. In a second set of experiments, the auditory dendrites were destroyed by local application of the glutamate agonist AMPA. The blockage of NMDA by the antagonist D-AP5 applied with an osmotic micropump delayed the functional recovery and the regrowth of auditory dendrites. The findings of our study support the hypothesis that, in addition to acting as a fast transmitter, glutamate has a neurotrophic role via the activation of NMDA receptors.

GPR30 Regulates Glutamate Transporter GLT-1 Expression in Rat Primary Astrocytes*

PubMed Central

Lee, Eunsook; Sidoryk-Wêgrzynowicz, Marta; Wang, Ning; Webb, Anton; Son, Deok-Soo; Lee, Kyuwon; Aschner, Michael

2012-01-01

The G protein-coupled estrogen receptor GPR30 contributes to the neuroprotective effects of 17β-estradiol (E2); however, the mechanisms associated with this protection have yet to be elucidated. Given that E2 increases astrocytic expression of glutamate transporter-1 (GLT-1), which would prevent excitotoxic-induced neuronal death, we proposed that GPR30 mediates E2 action on GLT-1 expression. To investigate this hypothesis, we examined the effects of G1, a selective agonist of GPR30, and GPR30 siRNA on astrocytic GLT-1 expression, as well as glutamate uptake in rat primary astrocytes, and explored potential signaling pathways linking GPR30 to GLT-1. G1 increased GLT-1 protein and mRNA levels, subject to regulation by both MAPK and PI3K signaling. Inhibition of TGF-α receptor suppressed the G1-induced increase in GLT-1 expression. Silencing GPR30 reduced the expression of both GLT-1 and TGF-α and abrogated the G1-induced increase in GLT-1 expression. Moreover, the G1-induced increase in GLT-1 protein expression was abolished by a protein kinase A inhibitor and an NF-κB inhibitor. G1 also enhanced cAMP response element-binding protein (CREB), as well as both NF-κB p50 and NF-κB p65 binding to the GLT-1 promoter. Finally, to model dysfunction of glutamate transporters, manganese was used, and G1 was found to attenuate manganese-induced impairment in GLT-1 protein expression and glutamate uptake. Taken together, the present data demonstrate that activation of GPR30 increases GLT-1 expression via multiple pathways, suggesting that GPR30 is worthwhile as a potential target to be explored for developing therapeutics of excitotoxic neuronal injury. PMID:22645130

GSK-3 as a Target for Lithium-Induced Neuroprotection Against Excitotoxicity in Neuronal Cultures and Animal Models of Ischemic Stroke

PubMed Central

Chuang, De-Maw; Wang, Zhifei; Chiu, Chi-Tso

2011-01-01

The mood stabilizer lithium inhibits glycogen synthase kinase-3 (GSK-3) directly or indirectly by enhancing serine phosphorylation of both α and β isoforms. Lithium robustly protected primary brain neurons from glutamate-induced excitotoxicity; these actions were mimicked by other GSK-3 inhibitors or silencing/inhibiting GSK-3α and/or β isoforms. Lithium rapidly activated Akt to enhance GSK-3 serine phosphorylation and to block glutamate-induced Akt inactivation. Lithium also up-regulated Bcl-2 and suppressed glutamate-induced p53 and Bax. Induction of brain-derived neurotrophic factor (BDNF) was required for lithium’s neuroprotection to occur. BDNF promoter IV was activated by GSK-3 inhibition using lithium or other drugs, or through gene silencing/inactivation of either isoform. Further, lithium’s neuroprotective effects were associated with inhibition of NMDA receptor-mediated calcium influx and down-stream signaling. In rodent ischemic models, post-insult treatment with lithium decreased infarct volume, ameliorated neurological deficits, and improved functional recovery. Up-regulation of heat-shock protein 70 and Bcl-2 as well as down-regulation of p53 likely contributed to lithium’s protective effects. Delayed treatment with lithium improved functional MRI responses, which was accompanied by enhanced angiogenesis. Two GSK-3-regulated pro-angiogenic factors, matrix metalloproteinase-9 (MMP-9) and vascular endothelial growth factor were induced by lithium. Finally, lithium promoted migration of mesenchymal stem cells (MSCs) by up-regulation of MMP-9 through GSK-3β inhibition. Notably, transplantation of lithium-primed MSCs into ischemic rats enhanced MSC migration to the injured brain regions and improved the neurological performance. Several other GSK-3 inhibitors have also been reported to be beneficial in rodent ischemic models. Together, GSK-3 inhibition is a rational strategy to combat ischemic stroke and other excitotoxicity-related brain

Neuroprotection by Delta9-tetrahydrocannabinol, the main active compound in marijuana, against ouabain-induced in vivo excitotoxicity.

PubMed

van der Stelt, M; Veldhuis, W B; Bär, P R; Veldink, G A; Vliegenthart, J F; Nicolay, K

2001-09-01

Excitotoxicity is a paradigm used to explain the biochemical events in both acute neuronal damage and in slowly progressive, neurodegenerative diseases. Here, we show in a longitudinal magnetic resonance imaging study that Delta(9)-tetrahydrocannabinol (Delta(9)-THC), the main active compound in marijuana, reduces neuronal injury in neonatal rats injected intracerebrally with the Na(+)/K(+)-ATPase inhibitor ouabain to elicit excitotoxicity. In the acute phase Delta(9)-THC reduced the volume of cytotoxic edema by 22%. After 7 d, 36% less neuronal damage was observed in treated rats compared with control animals. Coadministration of the CB(1) cannabinoid receptor antagonist SR141716 prevented the neuroprotective actions of Delta(9)-THC, indicating that Delta(9)-THC afforded protection to neurons via the CB(1) receptor. In Delta(9)-THC-treated rats the volume of astrogliotic tissue was 36% smaller. The CB(1) receptor antagonist did not block this effect. These results provide evidence that the cannabinoid system can serve to protect the brain against neurodegeneration.

Amino acids as dietary excitotoxins: a contribution to understanding neurodegenerative disorders.

PubMed

Meldrum, B

1993-01-01

The possibility that some acidic amino acids occurring naturally or as additives in the diet can act as excitotoxins producing central nervous system pathology has been the subject of extensive debate in the last 20 years and is here reviewed. High doses of glutamate, aspartate or related excitatory amino acids given in isolation to neonatal rodents produce acute degeneration organs. Neuropathology resulting from consumption of glutamate or aspartate has not been described in man. Various unusual amino acids of plant origin can produce acute excitotoxic syndromes. In man domoate (consumed in mussels that have fed on (Nitschia pungens) can produce an acute syndrome associated with limbic system lesions and anterograde amnesia. Kainate and domoate produce similar syndromes in rodents; acromelate produces spinal pathology. The mechanisms and manifestations of chronic excitotoxicity are less clearly established. A combination of impaired energy metabolism or impaired buffering of calcium and free radicals and endogenous or exogenous excitotoxins may contribute to neuronal loss in human neurodegenerative disorders.

[Do the glutamate excitotoxicity theory and potential free radicals implication in schizophrenia aetiopathogenesis provide a new enlightenment to links between: genome, environment and biology in the determinism of that disorder?].

PubMed

Nguimfack Mbodie, P C

2002-01-01

The aetiopathogenesis of schizophrenia constitutes nowadays one of the major points of interest for researchers on this cosmopolitan disorder which involves about 1% of the world population and which significantly alters the social functioning of the individual. Numerous studies have focused on the role played by genome, environmental factors and biology in the development of symptoms. The neurodevelopmental theory is an illustration with the perinatal period considered as the main provider of environmental factors (hypertension, infections, bleedings during pregnancy, acute and chronic fetal distress.). Many authors found significant associations between such factors, the occurrence of brain lesions and finally schizophrenic symptoms. Although no convincing genetic model had been established to date for schizophrenia, nevertheless it appears that a predisposition not inheritable under the mendelian mode exists and authors showed that disease gets more and more severe over schizophrenic descendants. The risk to be schizophrenic being a first degree relative of the schizophrenic person is about ten time superior than in general population. Indeed, this risk is also about ten time superior in biological parents of schizophrenic adoptees than in biological parents of healthy adoptees. Studies done in monozygotic comparing to dizygotic twins are in favour of an important role played by genetic factors more than socioeducational or psychological factors. Concerning biology, the dopaminergic hypothesis remains shared by numerous authors although direct links with incriminated factors are not well established. Now is suspected the glutamate excitotoxicity with implication of free radicals in schizophrenia. These free radicals are products of various enzymatic activations led by overstimulation of post synaptic receptors (NMDA and AMPA) by the excess glutamate. Therefore, according to that concept, some amino acids as glutamate and derivatives could have through free

Glutamate antagonism fails to reverse mitochondrial dysfunction in late phase of experimental neonatal asphyxia in rats.

PubMed

Reddy, Nagannathahalli Ranga; Krishnamurthy, Sairam; Chourasia, Tapan Kumar; Kumar, Ashok; Joy, Keerikkattil Paily

2011-04-01

Neonatal asphyxia is a primary contributor to neonatal mortality and neuro-developmental disorders. It progresses in two distinct phases, as initial primary process and latter as the secondary process. A dynamic relationship exists between excitotoxicity and mitochondrial dysfunction during the progression of asphyxic injury. Study of status of glutamate and mitochondrial function in tandem during primary and secondary processes may give new leads to the treatment of asphyxia. Neonatal asphyxia was induced in rat pups on the day of birth by subjecting them to two episodes (10min each) of anoxia, 24h apart by passing 100% N(2) into an enclosed chamber. The NMDA antagonist ketamine (20mg/kg/day) was administered either for 1 day or 7 days after anoxic exposure. Tissue glutamate and nitric oxide were estimated in the cerebral cortex, extra-cortex and cerebellum. The mitochondria from the above brain regions were used for the estimation of malondialdehyde, and activities of superoxide dismutase and succinate dehydrogenase. Mitochondrial membrane potential was evaluated by using Rhodamine dye. Anoxia during the primary process increased glutamate and nitric oxide levels; however the mitochondrial function was unaltered in terms of succinate dehydrogenase and membrane potential. Acute ketamine treatment reversed the increase in both glutamate and nitric oxide levels and partially attenuated mitochondrial function in terms of succinate dehydrogenase activity. The elevated glutamate and nitric oxide levels were maintained during the secondary process but however with concomitant loss of mitochondrial function. Repeated ketamine administration reversed glutamate levels only in the cerebral cortex, where as nitric oxide was decreased in all the brain regions. However, repeated ketamine administration was unable to reverse anoxia-induced mitochondrial dysfunction. The failure of glutamate antagonism in the treatment of asphyxia may be due to persistence of mitochondrial

Na+,K+-ATPase functionally interacts with the plasma membrane Na+,Ca2+ exchanger to prevent Ca2+ overload and neuronal apoptosis in excitotoxic stress.

PubMed

Sibarov, Dmitry A; Bolshakov, Artemiy E; Abushik, Polina A; Krivoi, Igor I; Antonov, Sergei M

2012-12-01

Using a fluorescent viability assay, immunocytochemistry, patch-clamp recordings, and Ca(2+) imaging analysis, we report that ouabain, a specific ligand of the Na(+),K(+)-ATPase cardiac glycoside binding site, can prevent glutamate receptor agonist-induced apoptosis in cultured rat cortical neurons. In our model of excitotoxicity, a 240-min exposure to 30 μM N-methyl-d-aspartate (NMDA) or kainate caused apoptosis in ∼50% of neurons. These effects were accompanied by a significant decrease in the number of neurons that were immunopositive for the antiapoptotic peptide Bcl-2. Apoptotic injury was completely prevented when the agonists were applied together with 0.1 or 1 nM ouabain, resulting in a greater survival of neurons, and the percentage of neurons expressing Bcl-2 remained similar to those obtained without agonist treatments. In addition, subnanomolar concentrations of ouabain prevented the increase of spontaneous excitatory postsynaptic current's frequency and the intracellular Ca(2+) overload induced by excitotoxic insults. Loading neurons with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid or inhibition of the plasma membrane Na(+),Ca(2+)-exchanger by 2-(2-(4-(4-nitrobenzyloxy)phenyl)ethyl)isothiourea methanesulfonate (KB-R7943) eliminated ouabain's effects on NMDA- or kainite-evoked enhancement of spontaneous synaptic activity. Our data suggest that during excitotoxic insults ouabain accelerates Ca(2+) extrusion from neurons via the Na(+),Ca(2+) exchanger. Because intracellular Ca(2+) accumulation caused by the activation of glutamate receptors and boosted synaptic activity represents a key factor in triggering neuronal apoptosis, up-regulation of Ca(2+) extrusion abolishes its development. These antiapoptotic effects are independent of Na(+),K(+)-ATPase ion transport function and are initiated by concentrations of ouabain that are within the range of an endogenous analog, suggesting a novel functional role for Na(+),K(+)-ATPase in

alpha-Amino-3-hydroxy-5-methyl-4-isoxazole propionate attenuates glutamate-induced caspase-3 cleavage via regulation of glycogen synthase kinase 3beta.

PubMed

Nishimoto, Takaaki; Kihara, Takeshi; Akaike, Akinori; Niidome, Tetsuhiro; Sugimoto, Hachiro

2008-04-01

Preconditioning of sublethal ischemia exhibits neuroprotection against subsequent ischemia-induced neuronal death. It has been indicated that glutamate, an excitatory amino acid, is involved in the pathogenesis of ischemia-induced neuronal death or neurodegeneration. To elucidate whether prestimulation of glutamate receptor could counter ischemia-induced neuronal death or neurodegeneration, we examined the effect of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA), an ionotropic subtype of glutamate receptor, on excess glutamate-induced excitotoxicity using primary cortical neuronal cultures. We found that AMPA exerted a neuroprotective effect in a time- and concentration-dependent manner. A blocker of phosphatidylinositol-3 kinase (PI3K), LY294002 (10 microM), significantly attenuated AMPA-induced protection. In addition, Ser473 of Akt/PKB, a downstream target of PI3K, was phosphorylated by AMPA administration (10 microM). Glycogen synthase kinase 3beta (GSK3beta), which has been reported to be inactivated by Akt, was phosphorylated at Ser9 by AMPA. Ser9-phosphorylated GSK3beta or inactivated form would be a key molecule for neuroprotection, insofar as lithium chloride (100 microM) and SB216763 (10 microM), inhibitors of GSK3beta, also induced phosphorylation of GSK3beta at Ser9 and exerted neuroprotection, respectively. Glutamate (100 microM) increased cleaved caspase-3, an apoptosis-related cysteine protease, and caspase-3 inhibitor (Ac-DEVD-CHO; 1 microM) blocked glutamate-induced excitotoxicity in our culture. AMPA (10 microM, 24 hr) and SB216763 (10 microM) prominently decreased glutamate-induced caspase-3 cleavage. These findings suggest that AMPA activates PI3K-Akt and subsequently inhibits GSK3beta and that inactivated GSK3beta attenuates glutamate-induced caspase-3 cleavage and neurotoxicity.

Diadenosine tetraphosphate (Ap4A) inhibits ATP-induced excitotoxicity: a neuroprotective strategy for traumatic spinal cord injury treatment.

PubMed

Reigada, David; Navarro-Ruiz, Rosa María; Caballero-López, Marcos Javier; Del Águila, Ángela; Muñoz-Galdeano, Teresa; Maza, Rodrigo M; Nieto-Díaz, Manuel

2017-03-01

Reducing cell death during the secondary injury is a major priority in the development of a cure for traumatic spinal cord injury (SCI). One of the earliest processes that follow SCI is the excitotoxicity resulting from the massive release of excitotoxicity mediators, including ATP, which induce an excessive and/or prolonged activation of their receptors and a deregulation of the calcium homeostasis. Diadenosine tetraphosphate (Ap 4 A) is an endogenous purinergic agonist, present in both extracellular and intracellular fluids, with promising cytoprotective effects in different diseases including neurodegenerative processes. In a search for efficient neuroprotective strategies for SCI, we have tested the capability of Ap 4 A to reduce the excitotoxic death mediated by the ATP-induced deregulation of calcium homeostasis and its consequences on tissue preservation and functional recovery in a mouse model of moderate contusive SCI. Our analyses with the murine neural cell line Neuro2a demonstrate that treatment with Ap 4 A reduces ATP-dependent excitotoxic death by both lowering the intracellular calcium response and decreasing the expression of specific purinergic receptors. Follow-up analyses in a mouse model of contusive SCI showed that acute administration of Ap 4 A following SCI reduces tissue damage and improves motor function recovery. These results suggest that Ap 4 A cytoprotection results from a decrease of the purinergic tone preventing the effects of a massive release of ATP after SCI, probably together with a direct induction of anti-apoptotic and pro-survival pathways via activation of P2Y 2 proposed in previous studies. In conclusion, Ap 4 A may be a good candidate for an SCI therapy, particularly to reduce excitotoxicity in combination with other modulators and/or inhibitors of the excitotoxic process that are being tested.

Glutamate Neonatal Excitotoxicity Modifies VEGF-A, VEGF-B, VEGFR-1 and VEGFR-2 Protein Expression Profiles During Postnatal Development of the Cerebral Cortex and Hippocampus of Male Rats.

PubMed

Castañeda-Cabral, Jose Luis; Beas-Zarate, Carlos; Gudiño-Cabrera, Graciela; Ureña-Guerrero, Monica E

2017-09-01

Vascular endothelial growth factor (VEGF) exerts both neuroprotective and proinflammatory effects in the brain, depending on the VEGF (A-E) and VEGF receptor (VEGFR1-3) types involved. Neonatal monosodium glutamate (MSG) treatment triggers an excitotoxic degenerative process associated with several neuropathological conditions, and VEGF messenger RNA (mRNA) expression is increased at postnatal day (PD) 14 in rat hippocampus (Hp) following the treatment. The aim of this work was to establish the changes in immunoreactivity to VEGF-A, VEGF-B, VEGFR-1 and VEGFR-2 proteins induced by neonatal MSG treatment (4 g/kg, subcutaneous, at PD1, 3, 5 and 7) in the cerebral motor cortex (CMC) and Hp. Samples collected from PD2 to PD60 from control and MSG-treated male Wistar rats were assessed by western blotting for each protein. Considering that immunoreactivity measured by western blotting is related to the protein expression level, we found that each protein in each cerebral region has a specific expression profile throughout the studied ages, and all profiles were differentially modified by MSG. Specifically, neonatal MSG treatment significantly increased the immunoreactivity to the following: (1) VEGF-A at PD8-PD10 in the CMC and at PD6-PD8 in the Hp; (2) VEGF-B at PD2, PD6 and PD10 in the CMC and at PD8-PD9 in the Hp; and (3) VEGFR-2 at PD6-PD8 in the CMC and at PD21-PD60 in the Hp. Also, MSG significantly reduced the immunoreactivity to the following: (1) VEGF-B at PD8-PD9 and PD45-PD60 in the CMC; and (2) VEGFR-1 at PD4-PD6 and PD14-PD21 in the CMC and at PD4, PD9-PD10 and PD60 in the Hp. Our results indicate that VEGF-mediated signalling is involved in the excitotoxic process triggered by neonatal MSG treatment and should be further characterized.

Excitotoxic and Radiation Stress Increase TERT Levels in the Mitochondria and Cytosol of Cerebellar Purkinje Neurons.

PubMed

Eitan, Erez; Braverman, Carmel; Tichon, Ailone; Gitler, Daniel; Hutchison, Emmette R; Mattson, Mark P; Priel, Esther

2016-08-01

Telomerase reverse transcriptase (TERT) is the catalytic subunit of telomerase, an enzyme that elongates telomeres at the ends of chromosomes during DNA replication. Recently, it was shown that TERT has additional roles in cell survival, mitochondrial function, DNA repair, and Wnt signaling, all of which are unrelated to telomeres. Here, we demonstrate that TERT is enriched in Purkinje neurons, but not in the granule cells of the adult mouse cerebellum. TERT immunoreactivity in Purkinje neurons is present in the nucleus, mitochondria, and cytoplasm. Furthermore, TERT co-localizes with mitochondrial markers, and immunoblot analysis of protein extracts from isolated mitochondria and synaptosomes confirmed TERT localization in mitochondria. TERT expression in Purkinje neurons increased significantly in response to two stressors: a sub-lethal dose of X-ray radiation and exposure to a high glutamate concentration. While X-ray radiation increased TERT levels in the nucleus, glutamate exposure elevated TERT levels in mitochondria. Our findings suggest that in mature Purkinje neurons, TERT is present both in the nucleus and in mitochondria, where it may participate in adaptive responses of the neurons to excitotoxic and radiation stress.

Extracorporeal methods of blood glutamate scavenging: a novel therapeutic modality.

PubMed

Zhumadilov, Agzam; Boyko, Matthew; Gruenbaum, Shaun E; Brotfain, Evgeny; Bilotta, Federico; Zlotnik, Alexander

2015-05-01

Pathologically elevated glutamate concentrations in the brain's extracellular fluid are associated with several acute and chronic brain insults. Studies have demonstrated that by decreasing the concentration of glutamate in the blood, thereby increasing the concentration gradient between the brain and the blood, the rate of brain-to-blood glutamate efflux can be increased. Blood glutamate scavengers, pyruvate and oxaloacetate have shown great promise in providing neuroprotection in many animal models of acute brain insults. However, glutamate scavengers' potential systemic toxicity, side effects and pharmacokinetic properties may limit their use in clinical practice. In contrast, extracorporeal methods of blood glutamate reduction, in which glutamate is filtered from the blood and eliminated, may be an advantageous adjunct in treating acute brain insults. Here, we review the current evidence for the glutamate-lowering effects of hemodialysis, peritoneal dialysis and hemofiltration. The evidence reviewed here highlights the need for clinical trials.

Scavenging of blood glutamate for enhancing brain-to-blood glutamate efflux.

PubMed

Li, Yunhong; Hou, Xiaolin; Qi, Qi; Wang, Le; Luo, Lan; Yang, Shaoqi; Zhang, Yumei; Miao, Zhenhua; Zhang, Yanli; Wang, Fei; Wang, Hongyan; Huang, Weidong; Wang, Zhenhai; Shen, Ying; Wang, Yin

2014-01-01

The presence of excess glutamate in the brain interstitial fluid characterizes several acute pathological conditions of the brain, including traumatic brain injury and stroke. It has been demonstrated that it is possible to eliminate excess glutamate in the brain by decreasing blood glutamate levels and, accordingly, accelerating the brain-to-blood glutamate efflux. It is feasible to accomplish this process by activating blood resident enzymes in the presence of the respective glutamate cosubstrates. In the present study, several glutamate cosubstrates and cofactors were studied in an attempt to identify the optimal conditions to reduce blood glutamate levels. The administration of a mixture of 1 mM pyruvate and oxaloacetate (Pyr/Oxa) for 1 h decreased blood glutamate levels by ≤50%. The addition of lipoamide to this mixture resulted in a further reduction in blood glutamate levels of >80%. In addition, in vivo experiments showed that lipoamide together with Pyr/Oxa is able to decrease blood glutamate levels to a greater extent than Pyr/Oxa alone, and accordingly, this enhances the glutamate efflux from the brain to the blood. These results may outline a novel neuroprotective strategy with increased effectiveness for the removal of excess brain glutamate in various neurodegenerative conditions.

Glutamate release from activated microglia requires the oxidative burst and lipid peroxidation.

PubMed

Barger, Steven W; Goodwin, Mary E; Porter, Mandy M; Beggs, Marjorie L

2007-06-01

When activated by proinflammatory stimuli, microglia release substantial levels of glutamate, and mounting evidence suggests this contributes to neuronal damage during neuroinflammation. Prior studies indicated a role for the Xc exchange system, an amino acid transporter that antiports glutamate for cystine. Because cystine is used for synthesis of glutathione (GSH) synthesis, we hypothesized that glutamate release is an indirect consequence of GSH depletion by the respiratory burst, which produces superoxide from NADPH oxidase. Microglial glutamate release triggered by lipopolysaccharide was blocked by diphenylene iodonium chloride and apocynin, inhibitors of NADPH oxidase. This glutamate release was also blocked by vitamin E and elicited by lipid peroxidation products 4-hydroxynonenal and acrolein, suggesting that lipid peroxidation makes crucial demands on GSH. Although NADPH oxidase inhibitors also suppressed nitrite accumulation, vitamin E did not; moreover, glutamate release was largely unaffected by nitric oxide donors, inhibitors of nitric oxide synthase, or changes in gene expression. These findings indicate that a considerable degree of the neurodegenerative consequences of neuroinflammation may result from conversion of oxidative stress to excitotoxic stress. This phenomenon entails a biochemical chain of events initiated by a programmed oxidative stress and resultant mass-action amino acid transport. Indeed, some of the neuroprotective effects of antioxidants may be due to interference with these events rather than direct protection against neuronal oxidation.

Activation of ERK1/2 and PI3K/Akt by IGF-1 on GAP-43 expression in DRG neurons with excitotoxicity induced by glutamate in vitro.

PubMed

Liu, Zhen; Cai, Heng; Zhang, Ping; Li, Hao; Liu, Huaxiang; Li, Zhenzhong

2012-03-01

Insulin-like growth factor-1 (IGF-1) is a neurotrophic factor and plays an important role in promoting axonal growth from dorsal root ganglion (DRG) neurons. Whether IGF-1 influences growth-associated protein 43 (GAP-43) expression and activates the extracellular signal-regulated protein kinase (ERK1/2) and the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathways in DRG neurons with excitotoxicity induced by glutamate (Glu) remains unknown. In this study, embryonic 15-day-old rat DRG explants were cultured for 48 h and then exposed to IGF-1, Glu, Glu + IGF-1, Glu + IGF-1 + PD98059, Glu + IGF-1 + LY294002, Glu + IGF-1 + PD98059 + LY294002 for additional 12 h. The DRG explants were continuously exposed to growth media as control. The levels of GAP-43 mRNA were detected by real time-PCR analysis. The protein levels of GAP-43, phosphorylated ERK1/2, phosphorylated Akt, total ERK1/2, and total Akt were detected by Western blot assay. GAP-43 expression in situ was determined by immunofluorescent labeling. Apoptotic cell death was monitored by Hoechst 33342 staining. IGF-1 alone increased GAP-43 and its mRNA levels in the absence of Glu. The decreased GAP-43 and its mRNA levels caused by Glu could be partially reversed by the presence of IGF-1. IGF-1 rescued neuronal cell death caused by Glu. Neither the ERK1/2 inhibitor PD98059 nor the PI3K inhibitor LY294002 blocked the effect of IGF-1, but both inhibitors together were effective. To validate the impact of GAP-43 expression by IGF-1, GAP-43 induction was blocked by administration of dexamethasone (DEX). IGF-1 partially rescued the decrease of GAP-43 and its mRNA levels induced by DEX. DEX induced an increase of cell apoptosis. IGF-1 may play an important role in neuroprotective effects on DRG neurons through regulating GAP-43 expression with excitotoxicity induced by Glu and the process was involved in both ERK1/2 and PI3K/Akt signaling pathways.

SLC7A11 expression is associated with seizures and predicts poor survival in patients with malignant glioma

PubMed Central

Robert, Stephanie M.; Buckingham, Susan C.; Campbell, Susan L.; Robel, Stefanie; Holt, Kenneth T.; Ogunrinu-Babarinde, Toyin; Warren, Paula Province; White, David M.; Reid, Meredith A.; Eschbacher, Jenny M.; Berens, Michael E.; Lahti, Adrienne C.; Nabors, Louis B.; Sontheimer, Harald

2015-01-01

Glioma is the most common malignant primary brain tumor. Their rapid growth is aided by tumor-mediated release of glutamate, creating peritumoral excitotoxic cell death and vacating space for tumor expansion. Glioma glutamate release may also be responsible for seizures, which complicate the clinical course for many patients and are often the presenting symptom. A hypothesized glutamate release pathway is the cystine/glutamate transporter System xc− (SXC), responsible for the cellular synthesis of glutathione. However, the relationship of SXC-mediated glutamate release, seizures, and tumor growth remains unclear. Probing expression of SLC7A11/xCT, the catalytic subunit of SXC, in patient tissue and tissues propagated in mice, we found that approximately 50% of patient tumors have elevated SLC7A11 expression. Compared with tumors lacking this transporter, in vivo propagated and intracranially implanted SLC7A11-expressing tumors grew faster, produced pronounced peritumoral glutamate excitotoxicity, induced seizures, and shortened overall survival. In agreement with animal data, increased SLC7A11 expression predicted shorter patient survival according to annotated genomic data in the REMBRANDT database. In a clinical pilot study we used Magnetic Resonance Spectroscopy (MRS) to determine SXC-mediated glutamate release by measuring acute changes in glutamate after administration of the FDA-approved SXC inhibitor, sulfasalazine. In 9 glioma patients with biopsy-confirmed expression of SXC, we found that its expression positively correlates with glutamate release, which is acutely inhibited with oral sulfasalazine. These data suggest that SXC is the major pathway for glutamate release from gliomas and that SLC7A11 expression predicts accelerated growth and peritumoral seizures. PMID:26019222

Neuroprotection of the leaf and stem of Vitis amurensis and their active compounds against ischemic brain damage in rats and excitotoxicity in cultured neurons.

PubMed

Kim, Joo Youn; Jeong, Ha Yeon; Lee, Hong Kyu; Kim, SeungHwan; Hwang, Bang Yeon; Bae, KiHwan; Seong, Yeon Hee

2012-01-15

Vitis amurensis (Vitaceae) has been reported to have anti-oxidant and anti-inflammatory activities. The present study investigated a methanol extract from the leaf and stem of V. amurensis for neuroprotective effects on cerebral ischemic damage in rats and on excitotoxicity induced by glutamate in cultured rat cortical neurons. Transient focal cerebral ischemia was induced by 2h middle cerebral artery occlusion followed by 24h reperfusion (MCAO/reperfusion) in rats. Orally administered V. amurensis (25-100 mg/kg) reduced MCAO/reperfusion-induced infarct and edema formation, neurological deficits, and neuronal death. Depletion of glutathione (GSH) level and lipid peroxidation induced by MCAO/reperfusion was inhibited by administration of V. amurensis. The increase of phosphorylated mitogen-activated protein kinases (MAPKs), cyclooxygenase-2 (COX-2), and pro-apoptotic proteins and the decrease of anti-apoptotic protein in MCAO/reperfusion rats were significantly inhibited by treatment with V. amurensis. Exposure of cultured cortical neurons to 500 μM glutamate for 12h induced neuronal cell death. V. amurensis (1-50 μg/ml) and (+)-ampelopsin A, γ-2-viniferin, and trans-ε-viniferin isolated from the leaf and stem of V. amurensis inhibited glutamate-induced neuronal death, the elevation of intracellular calcium ([Ca(2+)](i)), the generation of reactive oxygen species (ROS), and changes of apoptosis-related proteins in cultured cortical neurons, suggesting that the neuroprotective effect of V. amurensis may be partially attributed to these compounds. These results suggest that the neuroprotective effect of V. amurensis against focal cerebral ischemic injury might be due to its anti-apoptotic effect, resulting from anti-excitotoxic, anti-oxidative, and anti-inflammatory effects and that the leaf and stem of V. amurensis have possible therapeutic roles for preventing neurodegeneration in stroke. Copyright © 2011 Elsevier GmbH. All rights reserved.

Naphthazarin protects against glutamate-induced neuronal death via activation of the Nrf2/ARE pathway

DOE Office of Scientific and Technical Information (OSTI.GOV)

Son, Tae Gen; Kawamoto, Elisa M.; Yu, Qian-Sheng

2013-04-19

Highlights: •Naphthazarin activates the Nrf2/ARE pathway. •Naphthazarin induces Nrf2-driven genes in neurons and astrocytes. •Naphthazarin protects neurons against excitotoxicity. -- Abstract: Nuclear factor E2-related factor 2 (Nrf2)/antioxidant response element (ARE) pathway is an important cellular stress response pathway involved in neuroprotection. We previously screened several natural phytochemicals and identified plumbagin as a novel activator of the Nrf2/ARE pathway that can protect neurons against ischemic injury. Here we extended our studies to natural and synthetic derivatives of plumbagin. We found that 5,8-dimethoxy-1,4-naphthoquinone (naphthazarin) is a potent activator of the Nrf2/ARE pathway, up-regulates the expression of Nrf2-driven genes in primary neuronal andmore » glial cultures, and protects neurons against glutamate-induced excitotoxicity.« less

Involvement of extrasynaptic glutamate in physiological and pathophysiological changes of neuronal excitability.

PubMed

Pál, Balázs

2018-05-15

Glutamate is the most abundant neurotransmitter of the central nervous system, as the majority of neurons use glutamate as neurotransmitter. It is also well known that this neurotransmitter is not restricted to synaptic clefts, but found in the extrasynaptic regions as ambient glutamate. Extrasynaptic glutamate originates from spillover of synaptic release, as well as from astrocytes and microglia. Its concentration is magnitudes lower than in the synaptic cleft, but receptors responding to it have higher affinity for it. Extrasynaptic glutamate receptors can be found in neuronal somatodendritic location, on astroglia, oligodendrocytes or microglia. Activation of them leads to changes of neuronal excitability with different amplitude and kinetics. Extrasynaptic glutamate is taken up by neurons and astrocytes mostly via EAAT transporters, and astrocytes, in turn metabolize it to glutamine. Extrasynaptic glutamate is involved in several physiological phenomena of the central nervous system. It regulates neuronal excitability and synaptic strength by involving astroglia; contributing to learning and memory formation, neurosecretory and neuromodulatory mechanisms, as well as sleep homeostasis.The extrasynaptic glutamatergic system is affected in several brain pathologies related to excitotoxicity, neurodegeneration or neuroinflammation. Being present in dementias, neurodegenerative and neuropsychiatric diseases or tumor invasion in a seemingly uniform way, the system possibly provides a common component of their pathogenesis. Although parts of the system are extensively discussed by several recent reviews, in this review I attempt to summarize physiological actions of the extrasynaptic glutamate on neuronal excitability and provide a brief insight to its pathology for basic understanding of the topic.

Downregulation of Glutamine Synthetase via GLAST Suppression Induces Retinal Axonal Swelling in a Rat Ex Vivo Hydrostatic Pressure Model

PubMed Central

Yoshitomi, Takeshi; Zorumski, Charles F.; Izumi, Yukitoshi

2011-01-01

Purpose. High levels of glutamate can be toxic to retinal GCs. Thus, effective buffering of extracellular glutamate is important in preserving retinal structure and function. GLAST, a major glutamate transporter in the retina, and glutamine synthetase (GS) regulate extracellular glutamate accumulation and prevent excitotoxicity. This study was an examination of changes in function and expression of GLAST and GS in ex vivo rat retinas exposed to acute increases in ambient pressure. Methods. Ex vivo rat retinas were exposed to elevated hydrostatic pressure for 24 hours. The expression of GLAST and GS were examined using immunochemistry and real-time PCR analysis. Also examined were the effects of (2S,3S)-3-[3-[4-(trifluoromethyl) benzoylamino] benzyloxy] aspartate (TFB-TBOA), an inhibitor of glutamate transporters, and l-methionine-S-sulfoximine (MSO), an inhibitor of GS. Results. In this acute model, Western blot and real-time RT-PCR analyses revealed that substantially (75 mm Hg), but not moderately (35 mm Hg), elevated pressure depressed GLAST expression, diminished GS activity, and induced axonal swelling between the GC layer and the inner limiting membrane. However, at the moderately elevated pressure (35 mm Hg), administration of either TFB-TBOA or MSO also induced axonal swelling and excitotoxic neuronal damage. MSO did not depress GLAST expression but TFB-TBOA significantly suppressed GS, suggesting that downregulation of GS during pressure loading may result from impaired GLAST expression. Conclusions. The retina is at risk during acute intraocular pressure elevation due to downregulation of GS activity resulting from depressed GLAST expression. PMID:21775659

Downregulation of glutamine synthetase via GLAST suppression induces retinal axonal swelling in a rat ex vivo hydrostatic pressure model.

PubMed

Ishikawa, Makoto; Yoshitomi, Takeshi; Zorumski, Charles F; Izumi, Yukitoshi

2011-08-22

PURPOSE. High levels of glutamate can be toxic to retinal GCs. Thus, effective buffering of extracellular glutamate is important in preserving retinal structure and function. GLAST, a major glutamate transporter in the retina, and glutamine synthetase (GS) regulate extracellular glutamate accumulation and prevent excitotoxicity. This study was an examination of changes in function and expression of GLAST and GS in ex vivo rat retinas exposed to acute increases in ambient pressure. METHODS. Ex vivo rat retinas were exposed to elevated hydrostatic pressure for 24 hours. The expression of GLAST and GS were examined using immunochemistry and real-time PCR analysis. Also examined were the effects of (2S,3S)-3-[3-[4-(trifluoromethyl) benzoylamino] benzyloxy] aspartate (TFB-TBOA), an inhibitor of glutamate transporters, and l-methionine-S-sulfoximine (MSO), an inhibitor of GS. RESULTS. In this acute model, Western blot and real-time RT-PCR analyses revealed that substantially (75 mm Hg), but not moderately (35 mm Hg), elevated pressure depressed GLAST expression, diminished GS activity, and induced axonal swelling between the GC layer and the inner limiting membrane. However, at the moderately elevated pressure (35 mm Hg), administration of either TFB-TBOA or MSO also induced axonal swelling and excitotoxic neuronal damage. MSO did not depress GLAST expression but TFB-TBOA significantly suppressed GS, suggesting that downregulation of GS during pressure loading may result from impaired GLAST expression. CONCLUSIONS. The retina is at risk during acute intraocular pressure elevation due to downregulation of GS activity resulting from depressed GLAST expression.

Glutamine synthetase activity and glutamate uptake in hippocampus and frontal cortex in portal hypertensive rats

PubMed Central

Acosta, Gabriela Beatriz; Fernández, María Alejandra; Roselló, Diego Martín; Tomaro, María Luján; Balestrasse, Karina; Lemberg, Abraham

2009-01-01

AIM: To study glutamine synthetase (GS) activity and glutamate uptake in the hippocampus and frontal cortex (FC) from rats with prehepatic portal vein hypertension. METHODS: Male Wistar rats were divided into sham-operated group and a portal hypertension (PH) group with a regulated stricture of the portal vein. Animals were sacrificed by decapitation 14 d after portal vein stricture. GS activity was determined in the hippocampus and FC. Specific uptake of radiolabeled L-glutamate was studied using synaptosome-enriched fractions that were freshly prepared from both brain areas. RESULTS: We observed that the activity of GS increased in the hippocampus of PH rats, as compared to control animals, and decreased in the FC. A significant decrease in glutamate uptake was found in both brain areas, and was more marked in the hippocampus. The decrease in glutamate uptake might have been caused by a deficient transport function, significantly and persistent increase in this excitatory neurotransmitter activity. CONCLUSION: The presence of moderate ammonia blood levels may add to the toxicity of excitotoxic glutamate in the brain, which causes alterations in brain function. Portal vein stricture that causes portal hypertension modifies the normal function in some brain regions. PMID:19533812

In vitro evidence for the brain glutamate efflux hypothesis: brain endothelial cells cocultured with astrocytes display a polarized brain-to-blood transport of glutamate.

PubMed

Helms, Hans Christian; Madelung, Rasmus; Waagepetersen, Helle Sønderby; Nielsen, Carsten Uhd; Brodin, Birger

2012-05-01

The concentration of the excitotoxic amino acid, L-glutamate, in brain interstitial fluid is tightly regulated by uptake transporters and metabolism in astrocytes and neurons. The aim of this study was to investigate the possible role of the blood-brain barrier endothelium in brain L-glutamate homeostasis. Transendothelial transport- and accumulation studies of (3) H-L-glutamate, (3) H-L-aspartate, and (3) H-D-aspartate in an electrically tight bovine endothelial/rat astrocyte blood-brain barrier coculture model were performed. After 6 days in culture, the endothelium displayed transendothelial resistance values of 1014 ± 70 Ω cm(2) , and (14) C-D-mannitol permeability values of 0.88 ± 0.13 × 10(-6) cm s(-1) . Unidirectional flux studies showed that L-aspartate and L-glutamate, but not D-aspartate, displayed polarized transport in the brain-to-blood direction, however, all three amino acids accumulated in the cocultures when applied from the abluminal side. The transcellular transport kinetics were characterized with a K(m) of 69 ± 15 μM and a J(max) of 44 ± 3.1 pmol min(-1) cm(-2) for L-aspartate and a K(m) of 138 ± 49 μM and J(max) of 28 ± 3.1 pmol min(-1) cm(-2) for L-glutamate. The EAAT inhibitor, DL-threo-ß-Benzyloxyaspartate, inhibited transendothelial brain-to-blood fluxes of L-glutamate and L-aspartate. Expression of EAAT-1 (Slc1a3), -2 (Slc1a2), and -3 (Slc1a1) mRNA in the endothelial cells was confirmed by conventional PCR and localization of EAAT-1 and -3 in endothelial cells was shown with immunofluorescence. Overall, the findings suggest that the blood-brain barrier itself may participate in regulating brain L-glutamate concentrations. Copyright © 2012 Wiley Periodicals, Inc.

Excitotoxicity in the Lung: N-Methyl-D-Aspartate-Induced, Nitric Oxide-Dependent, Pulmonary Edema is Attenuated by Vasoactive Intestinal Peptide and by Inhibitors of Poly(ADP-Ribose) Polymerase

NASA Astrophysics Data System (ADS)

Said, Sami I.; Berisha, Hasan I.; Pakbaz, Hedayatollah

1996-05-01

Excitatory amino acid toxicity, resulting from overactivation of N-methyl-D-aspartate (NMDA) glutamate receptors, is a major mechanism of neuronal cell death in acute and chronic neurological diseases. We have investigated whether excitotoxicity may occur in peripheral organs, causing tissue injury, and report that NMDA receptor activation in perfused, ventilated rat lungs triggered acute injury, marked by increased pressures needed to ventilate and perfuse the lung, and by high-permeability edema. The injury was prevented by competitive NMDA receptor antagonists or by channel-blocker MK-801, and was reduced in the presence of Mg2+. As with NMDA toxicity to central neurons, the lung injury was nitric oxide (NO) dependent: it required L-arginine, was associated with increased production of NO, and was attenuated by either of two NO synthase inhibitors. The neuropeptide vasoactive intestinal peptide and inhibitors of poly(ADP-ribose) polymerase also prevented this injury, but without inhibiting NO synthesis, both acting by inhibiting a toxic action of NO that is critical to tissue injury. The findings indicate that: (i) NMDA receptors exist in the lung (and probably elsewhere outside the central nervous system), (ii) excessive activation of these receptors may provoke acute edematous lung injury as seen in the ``adult respiratory distress syndrome,'' and (iii) this injury can be modulated by blockade of one of three critical steps: NMDA receptor binding, inhibition of NO synthesis, or activation of poly(ADP-ribose) polymerase.

Lycopene depresses glutamate release through inhibition of voltage-dependent Ca2+ entry and protein kinase C in rat cerebrocortical nerve terminals.

PubMed

Lu, Cheng-Wei; Hung, Chi-Feng; Jean, Wei-Horng; Lin, Tzu-Yu; Huang, Shu-Kuei; Wang, Su-Jane

2018-05-01

Lycopene is a natural dietary carotenoid that was reported to exhibit a neuroprotective profile. Considering that excitotoxicity and cell death induced by glutamate are involved in many brain disorders, the effect of lycopene on glutamate release in rat cerebrocortical nerve terminals and the possible mechanism involved in such effect was investigated. We observed here that lycopene inhibited 4-aminopyridine (4-AP)-evoked glutamate release and intrasynaptosomal Ca 2+ concentration elevation. The inhibitory effect of lycopene on 4-AP-evoked glutamate release was markedly reduced in the presence of the Ca v 2.2 (N-type) and Ca v 2.1 (P/Q-type) channel blocker ω-conotoxin MVIIC, but was insensitive to the intracellular Ca 2+ -release inhibitors dantrolene and CGP37157. Furthermore, in the presence of the protein kinase C inhibitors GF109203X and Go6976, the action of lycopene on evoked glutamate release was prevented. These results are the first to suggest that lycopene inhibits glutamate release from rat cortical synaptosomes by suppressing presynaptic Ca 2+ entry and protein kinase C activity.

Glutamate release and uptake processes are altered in a new mouse model of amyotrophic lateral sclerosis.

PubMed

Grigoriev, V V; Efimova, A D; Ustyugov, A A; Shevchenko, V P; Bachurin, S O; Myasoedov, N F

2016-05-01

In this paper, we showed that in the cortex of mice expressing an abberant form of FUS protein that model amyotrophic lateral sclerosis (ALS), the processes of KCl-induced and basal [(3)H]glutamate release and uptake are altered at the presymptomatic stage as compared to the non-transgenic littermates. The change in these three parameters in transgenic animals causes excitotoxicity, which, in turn, may lead to massive loss of motor neurons and the onset of ALS symptoms.

The volatile anesthetic methoxyflurane protects motoneurons against excitotoxicity in an in vitro model of rat spinal cord injury.

PubMed

Shabbir, A; Bianchetti, E; Nistri, A

2015-01-29

Neuroprotection of the spinal cord during the early phase of injury is an important goal to determine a favorable outcome by prevention of delayed pathological events, including excitotoxicity, which otherwise extend the primary damage and amplify the often irreversible loss of motor function. While intensive care and neurosurgical intervention are important treatments, effective neuroprotection requires further experimental studies focused to target vulnerable neurons, particularly motoneurons. The present investigation examined whether the volatile general anesthetic methoxyflurane might protect spinal locomotor networks from kainate-evoked excitotoxicity using an in vitro rat spinal cord preparation as a model. The protocols involved 1h excitotoxic stimulation on day 1 followed by electrophysiological and immunohistochemical testing on day 2. A single administration of methoxyflurane applied together with kainate (1h), or 30 or even 60 min later prevented any depression of spinal reflexes, loss of motoneuron excitability, and histological damage. Methoxyflurane per se temporarily decreased synaptic transmission and motoneuron excitability, effects readily reversible on washout. Spinal locomotor activity recorded as alternating electrical discharges from lumbar motor pools was fully preserved on the second day after application of methoxyflurane together with (or after) kainate. These data suggest that a volatile general anesthetic could provide strong electrophysiological and histological neuroprotection that enabled expression of locomotor network activity 1 day after the excitotoxic challenge. It is hypothesized that the benefits of early neurosurgery for acute spinal cord injury (SCI) might be enhanced if, in addition to injury decompression and stabilization, the protective role of general anesthesia is exploited. Copyright © 2014 IBRO. Published by Elsevier Ltd. All rights reserved.

Modulation of taurine release by glutamate receptors and nitric oxide.

PubMed

Oja, S S; Saransaari, P

2000-11-01

Taurine is held to function as a modulator and osmoregulator in the central nervous system, being of particular importance in the immature brain. In view of the possible involvement of excitatory pathways in the regulation of taurine function in the brain, the interference of glutamate receptors with taurine release from different tissue preparations in vitro and from the brain in vivo is of special interest. The release of taurine from the brain is enhanced by glutamate receptor agonists. This enhancement is inhibited by the respective receptor antagonists both in vitro and in vivo. The ionotropic N-methyl-D-aspartate (NMDA) and 2-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor agonists appear to be the most effective in enhancing taurine release, their effects being receptor-mediated. Kainate is less effective, particularly in adults. Of the glutamate receptors, the NMDA class seems to be the most susceptible to modulation by nitric oxide. Nitric oxide also modulates taurine release, enhancing the basal release in both immature and mature hippocampus, whereas the K(+)-stimulated release is generally inhibited. Metabotropic glutamate receptors also participate in the regulation of taurine release, group I metabotropic glutamate receptors potentiating the release in the developing hippocampus, while group III receptors may be involved in the adult. Under various cell-damaging conditions, including ischemia, hypoxia and hypoglycemia, taurine release is enhanced, together with an enhanced release of excitatory amino acids. The increase in extracellular taurine upon excessive stimulation of glutamate receptors and under cell-damaging conditions may serve as an important protective mechanism against excitotoxicity, being particularly effective in the immature brain.

Glutamate Increases In Vitro Survival and Proliferation and Attenuates Oxidative Stress-Induced Cell Death in Adult Spinal Cord-Derived Neural Stem/Progenitor Cells via Non-NMDA Ionotropic Glutamate Receptors.

PubMed

Hachem, Laureen D; Mothe, Andrea J; Tator, Charles H

2016-08-15

Traumatic spinal cord injury (SCI) leads to a cascade of secondary chemical insults, including oxidative stress and glutamate excitotoxicity, which damage host neurons and glia. Transplantation of exogenous neural stem/progenitor cells (NSPCs) has shown promise in enhancing regeneration after SCI, although survival of transplanted cells remains poor. Understanding the response of NSPCs to the chemical mediators of secondary injury is essential in finding therapies to enhance survival. We examined the in vitro effects of glutamate and glutamate receptor agonists on adult rat spinal cord-derived NSPCs. NSPCs isolated from the periventricular region of the adult rat spinal cord were exposed to various concentrations of glutamate for 96 h. We found that glutamate treatment (500 μM) for 96 h significantly increased live cell numbers, reduced cell death, and increased proliferation, but did not significantly alter cell phenotype. Concurrent glutamate treatment (500 μM) in the setting of H2O2 exposure (500 μM) for 10 h increased NSPC survival compared to H2O2 exposure alone. The effects of glutamate on NSPCs were blocked by the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate receptor antagonist GYKI-52466, but not by the N-methyl-D-aspartic acid receptor antagonist MK-801 or DL-AP5, or the mGluR3 antagonist LY-341495. Furthermore, treatment of NSPCs with AMPA, kainic acid, or the kainate receptor-specific agonist (RS)-2-amino-3-(3-hydroxy-5-tert-butylisoxazol-4-yl)propanoic acid mimicked the responses seen with glutamate both alone and in the setting of oxidative stress. These findings offer important insights into potential mechanisms to enhance NSPC survival and implicate a potential role for glutamate in promoting NSPC survival and proliferation after traumatic SCI.

Mitochondrial fragmentation in excitotoxicity requires ROCK activation.

PubMed

Martorell-Riera, Alejandro; Segarra-Mondejar, Marc; Reina, Manuel; Martínez-Estrada, Ofelia M; Soriano, Francesc X

2015-01-01

Mitochondria morphology constantly changes through fission and fusion processes that regulate mitochondrial function, and it therefore plays a prominent role in cellular homeostasis. Cell death progression is associated with mitochondrial fission. Fission is mediated by the mainly cytoplasmic Drp1, which is activated by different post-translational modifications and recruited to mitochondria to perform its function. Our research and other studies have shown that in the early moments of excitotoxic insult Drp1 must be nitrosylated to mediate mitochondrial fragmentation in neurons. Nonetheless, mitochondrial fission is a multistep process in which filamentous actin assembly/disassembly and myosin-mediated mitochondrial constriction play prominent roles. Here we establish that in addition to nitric oxide production, excitotoxicity-induced mitochondrial fragmentation also requires activation of the actomyosin regulator ROCK. Although ROCK1 has been shown to phosphorylate and activate Drp1, experiments using phosphor-mutant forms of Drp1 in primary cortical neurons indicate that in excitotoxic conditions, ROCK does not act directly on Drp1 to mediate fission, but may act on the actomyosin complex. Thus, these data indicate that a wider range of signaling pathways than those that target Drp1 are amenable to be inhibited to prevent mitochondrial fragmentation as therapeutic option.

Intrathecal infusion of a Ca(2+)-permeable AMPA channel blocker slows loss of both motor neurons and of the astrocyte glutamate transporter, GLT-1 in a mutant SOD1 rat model of ALS.

PubMed

Yin, Hong Z; Tang, Darryl T; Weiss, John H

2007-10-01

Elevated extracellular glutamate, resulting from a loss of astrocytic glutamate transport capacity, may contribute to excitotoxic motor neuron (MN) damage in ALS. Accounting for their high excitotoxic vulnerability, MNs possess large numbers of unusual Ca(2+)-permeable AMPA channels (Ca-AMPA channels), the activation of which triggers mitochondrial Ca(2+) overload and strong reactive oxygen species (ROS) generation. However, the causes of the astrocytic glutamate transport loss remain unexplained. To assess the role of Ca-AMPA channels on the evolution of pathology in vivo, we have examined effects of prolonged intrathecal infusion of the Ca-AMPA channel blocker, 1-naphthyl acetylspermine (NAS), in G93A transgenic rat models of ALS. In wild-type animals, immunoreactivity for the astrocytic glutamate transporter, GLT-1, was particularly strong around ventral horn MNs. However, a marked loss of ventral horn GLT-1 was observed, along with substantial MN damage, prior to onset of symptoms (90-100 days) in the G93A rats. Conversely, labeling with the oxidative marker, nitrotyrosine, was increased in the neuropil surrounding MNs in the transgenic animals. Compared to sham-treated G93A animals, 30-day NAS infusions (starting at 67+/-2 days of age) markedly diminished the loss of both MNs and of astrocytic GLT-1 labeling. These observations are compatible with the hypothesis that activation of Ca-AMPA channels on MNs contributes, likely in part through oxidative mechanisms, to loss of glutamate transporter in surrounding astrocytes.

Functional role of NT-3 in synapse regeneration by spiral ganglion neurons on inner hair cells after excitotoxic trauma in vitro

PubMed Central

Wang, Qiong; Green, Steven H.

2011-01-01

Spiral ganglion neurons (SGNs) are postsynaptic to hair cells and project to the brainstem. The inner hair cell (IHC) to SGN synapse is susceptible to glutamate excitotoxicity and to acoustic trauma, with potentially adverse consequences to long-term SGN survival. We used a cochlear explant culture from P6 rat pups consisting of a portion of organ of Corti maintained intact with the corresponding portion of spiral ganglion to investigate excitotoxic damage to IHC-SGN synapses in vitro. The normal innervation pattern is preserved in vitro. Brief treatment with NMDA and kainate results in loss of IHC–SGN synapses and degeneration of the distal type 1 SGN peripheral axons, mimicking damage to SGN peripheral axons caused by excitotoxicity or noise in vivo. The number of IHC presynaptic ribbons is not significantly altered. Reinnervation of IHCs occurs and regenerating axons remain restricted to the IHC row. However, the number of postsynaptic densities (PSDs) does not fully recover and not all axons regrow to the IHCs. Addition of either NT-3 or BDNF increases axon growth and synaptogenesis. Selective blockade of endogenous NT-3 signaling with TrkC-IgG reduced regeneration of axons and PSDs, but TrkB-IgG, which blocks BDNF, has no such effect, indicating that endogenous NT-3 is necessary for SGN axon growth and synaptogenesis. Remarkably, TrkC-IgG reduced axon growth and synaptogenesis even in the presence of BDNF, indicating that endogenous NT-3 has a distinctive role, not mimicked by BDNF, in promoting SGN axon growth in the organ of Corti and synaptogenesis on IHCs. PMID:21613508

Role of astrocytic glutamate transporter in alcohol use disorder

PubMed Central

Ayers-Ringler, Jennifer R; Jia, Yun-Fang; Qiu, Yan-Yan; Choi, Doo-Sup

2016-01-01

Alcohol use disorder (AUD) is one of the most widespread neuropsychiatric conditions, having a significant health and socioeconomic impact. According to the 2014 World Health Organization global status report on alcohol and health, the harmful use of alcohol is responsible for 5.9% of all deaths worldwide. Additionally, 5.1% of the global burden of disease and injury is ascribed to alcohol (measured in disability adjusted life years, or disability adjusted life years). Although the neurobiological basis of AUD is highly complex, the corticostriatal circuit contributes significantly to the development of addictive behaviors. In-depth investigation into the changes of the neurotransmitters in this circuit, dopamine, gamma-aminobutyricacid, and glutamate, and their corresponding neuronal receptors in AUD and other addictions enable us to understand the molecular basis of AUD. However, these discoveries have also revealed a dearth of knowledge regarding contributions from non-neuronal sources. Astrocytes, though intimately involved in synaptic function, had until recently been noticeably overlooked in their potential role in AUD. One major function of the astrocyte is protecting neurons from excitotoxicity by removing glutamate from the synapse via excitatory amino acid transporter type 2. The importance of this key transporter in addiction, as well as ethanol withdrawal, has recently become evident, though its regulation is still under investigation. Historically, pharmacotherapy for AUD has been focused on altering the activity of neuronal glutamate receptors. However, recent clinical evidence has supported the animal-based findings, showing that regulating glutamate homeostasis contributes to successful management of recovery from AUD. PMID:27014596

Chronic postnatal stress induces voluntary alcohol intake and modifies glutamate transporters in adolescent rats.

PubMed

Odeon, María Mercedes; Andreu, Marcela; Yamauchi, Laura; Grosman, Mauricio; Acosta, Gabriela Beatriz

2015-01-01

Postnatal stress alters stress responses for life, with serious consequences on the central nervous system (CNS), involving glutamatergic neurotransmission and development of voluntary alcohol intake. Several drugs of abuse, including alcohol and cocaine, alter glutamate transport (GluT). Here, we evaluated effects of chronic postnatal stress (CPS) on alcohol intake and brain glutamate uptake and transporters in male adolescent Wistar rats. For CPS from postnatal day (PD) 7, pups were separated from their mothers and exposed to cold stress (4 °C) for 1 h daily for 20 days; controls remained with their mothers. Then they were exposed to either voluntary ethanol (6%) or dextrose (1%) intake for 7 days (5-7 rats per group), then killed. CPS: (1) increased voluntary ethanol intake, (2) did not affect body weight gain or produce signs of toxicity with alcohol exposure, (3) increased glutamate uptake by hippocampal synaptosomes in vitro and (4) reduced protein levels (Western measurements) in hippocampus and frontal cortex of glial glutamate transporter-1 (GLT-1) and excitatory amino-acid transporter-3 (EAAT-3) but increased glutamate aspartate transporter (GLAST) levels. We propose that CPS-induced decrements in GLT-1 and EAAT-3 expression levels are opposed by activation of a compensatory mechanism to prevent excitotoxicity. A greater role for GLAST in total glutamate uptake to prevent enlarged extracellular glutamate levels is inferred. Although CPS strongly increased intake of ethanol, this had little impact on effects of CPS on brain glutamate uptake or transporters. However, the impact of early life adverse events on glutamatergic neurotransmission may underlie increased alcohol consumption in adulthood.

Pu-erh Tea Protects the Nervous System by Inhibiting the Expression of Metabotropic Glutamate Receptor 5.

PubMed

Li, Chunjie; Chai, Shaomeng; Ju, Yongzhi; Hou, Lu; Zhao, Hang; Ma, Wei; Li, Tian; Sheng, Jun; Shi, Wei

2017-09-01

Glutamate is one of the major excitatory neurotransmitters of the CNS and is essential for numerous key neuronal functions. However, excess glutamate causes massive neuronal death and brain damage owing to excitotoxicity via the glutamate receptors. Metabotropic glutamate receptor 5 (mGluR5) is one of the glutamate receptors and represents a promising target for studying neuroprotective agents of potential application in neurodegenerative diseases. Pu-erh tea, a fermented tea, mainly produced in Yunnan province, China, has beneficial effects, including the accommodation of the CNS. In this study, pu-erh tea markedly decreased the transcription and translation of mGluR5 compared to those by black and green teas. Pu-erh tea also inhibited the expression of Homer, one of the synaptic scaffolding proteins binding to mGluR5. Pu-erh tea protected neural cells from necrosis via blocked Ca 2+ influx and inhibited protein kinase C (PKC) activation induced by excess glutamate. Pu-erh tea relieved rat epilepsy induced by LiCl-pilocarpine in behavioural and physiological assays. Pu-erh tea also decreased the expression of mGluR5 in the hippocampus. These results show that the inhibition of mGluR5 plays a role in protecting neural cells from glutamate. The results also indicate that pu-erh tea contains biological compounds binding transcription factors and inhibiting the expression of mGluR5 and identify pu-erh tea as a novel natural neuroprotective agent.

Anthocyanins abrogate glutamate-induced AMPK activation, oxidative stress, neuroinflammation, and neurodegeneration in postnatal rat brain.

PubMed

Shah, Shahid Ali; Amin, Faiz Ul; Khan, Mehtab; Abid, Muhammad Noman; Rehman, Shafiq Ur; Kim, Tae Hyun; Kim, Min Woo; Kim, Myeong Ok

2016-11-08

Glutamate-induced excitotoxicity, oxidative damage, and neuroinflammation are believed to play an important role in the development of a number of CNS disorders. We recently reported that a high dose of glutamate could induce AMPK-mediated neurodegeneration in the postnatal day 7 (PND7) rat brain. Yet, the mechanism of glutamate-induced oxidative stress and neuroinflammation in the postnatal brain is not well understood. Here, we report for the first time the mechanism of glutamate-induced oxidative damage, neuroinflammation, and neuroprotection by polyphenolic anthocyanins in PND7. PND7 rat brains, SH-SY5Y, and BV2 cells treated either alone with glutamate or in combination with anthocyanins and compound C were examined with Western blot and immunofluorescence techniques. Additionally, reactive oxygen species (ROS) assay and other ELISA kit assays were employed to know the therapeutic efficacy of anthocyanins against glutamate. A single injection of glutamate to developing rats significantly increased brain glutamate levels, activated and phosphorylated AMPK induction, and inhibited nuclear factor-E2-related factor 2 (Nrf2) after 2, 3, and 4 h in a time-dependent manner. In contrast, anthocyanin co-treatment significantly reduced glutamate-induced AMPK induction, ROS production, neuroinflammation, and neurodegeneration in the developing rat brain. Most importantly, anthocyanins increased glutathione (GSH and GSSG) levels and stimulated the endogenous antioxidant system, including Nrf2 and heme oxygenase-1 (HO-1), against glutamate-induced oxidative stress. Interestingly, blocking AMPK with compound C in young rats abolished glutamate-induced neurotoxicity. Similarly, all these experiments were replicated in SH-SY5Y cells by silencing AMPK with siRNA, which suggests that AMPK is the key mediator in glutamate-induced neurotoxicity. Here, we report for the first time that anthocyanins can potentially decrease glutamate-induced neurotoxicity in young rats. Our work

E-p-Methoxycinnamic acid protects cultured neuronal cells against neurotoxicity induced by glutamate

PubMed Central

Kim, So Ra; Sung, Sang Hyun; Jang, Young Pyo; Markelonis, George J; Oh, Tae H; Kim, Young Choong

2002-01-01

We previously reported that four new phenylpropanoid glycosides and six known cinnamate derivatives isolated from roots of Scrophularia buergeriana Miquel (Scrophulariaceae) protected cultured cortical neurons from neurotoxicity induced by glutamate. Here, we have investigated the structure-activity relationships in the phenylpropanoids using our primary culture system. The α,β-unsaturated ester moiety and the para-methoxy group in the phenylpropanoids appeared to play a vital role in neuroprotective activity. This suggested that E-p-methoxycinnamic acid (E-p-MCA) might be a crucial component for their neuroprotective activity within the phenylpropanoid compounds. E-p-MCA significantly attenuated glutamate-induced neurotoxicity when added prior to an excitotoxic glutamate challenge. The neuroprotective activity of E-p-MCA appeared to be more effective in protecting neurons against neurotoxicity induced by NMDA than from that induced by kainic acid. E-p-MCA inhibited the binding of [propyl-2,3-3H]-CGP39653 and [2-3H]-glycine to their respective binding sites on rat cortical membranes. However, even high concentrations of E-p-MCA failed to inhibit completely [propyl-2,3-3H]-CGP39653 and [2-3H]-glycine binding. Indeed, E-p-MCA diminished the calcium influx that routinely accompanies glutamate-induced neurotoxicity, and inhibited the subsequent overproduction of nitric oxide and cellular peroxide in glutamate-injured neurons. Thus, our results suggest that E-p-MCA exerts significant protective effects against neurodegeneration induced by glutamate in primary cultures of cortical neurons by an action suggestive of partial glutamatergic antagonism. PMID:11877337

Auditory hindbrain atrophy and anomalous calcium binding protein expression after neonatal exposure to monosodium glutamate.

PubMed

Foran, Lindsey; Blackburn, Kaitlyn; Kulesza, Randy J

2017-03-06

Glutamate is the most abundant excitatory neurotransmitter in the central nervous system, and is stored and released by both neurons and astrocytes. Despite the important role of glutamate as a neurotransmitter, elevated extracellular glutamate can result in excitotoxicity and apoptosis. Monosodium glutamate (MSG) is a naturally occurring sodium salt of glutamic acid that is used as a flavor enhancer in many processed foods. Previous studies have shown that MSG administration during the early postnatal period results in neurodegenerative changes in several forebrain regions, characterized by neuronal loss and neuroendocrine abnormalities. Systemic delivery of MSG during the neonatal period and induction of glutamate neurotoxicity in the cochlea have both been shown to result in fewer neurons in the spiral ganglion. We hypothesized that an MSG-induced loss of neurons in the spiral ganglion would have a significant impact on the number of neurons in the cochlear nuclei and superior olivary complex (SOC). Indeed, we found that exposure to MSG from postnatal days 4 through 10 resulted in significantly fewer neurons in the cochlear nuclei and SOC and significant dysmorphology in surviving neurons. Moreover, we found that neonatal MSG exposure resulted in a significant decrease in the expression of both calretinin and calbindin. These results suggest that neonatal exposure to MSG interferes with early development of the auditory brainstem and impacts expression of calcium binding proteins, both of which may lead to diminished auditory function. Copyright © 2017 IBRO. Published by Elsevier Ltd. All rights reserved.

Chronic Desipramine Prevents Acute Stress-Induced Reorganization of Medial Prefrontal Cortex Architecture by Blocking Glutamate Vesicle Accumulation and Excitatory Synapse Increase

PubMed Central

Treccani, Giulia; Liebenberg, Nico; Chen, Fenghua; Popoli, Maurizio; Wegener, Gregers; Nyengaard, Jens Randel

2015-01-01

Background: Although a clear negative influence of chronic exposure to stressful experiences has been repeatedly demonstrated, the outcome of acute stress on key brain regions has only just started to be elucidated. Although it has been proposed that acute stress may produce enhancement of brain plasticity and that antidepressants may prevent such changes, we still lack ultrastructural evidence that acute stress-induced changes in neurotransmitter physiology are coupled with structural synaptic modifications. Methods: Rats were pretreated chronically (14 days) with desipramine (10mg/kg) and then subjected to acute foot-shock stress. By means of serial section electron microscopy, the structural remodeling of medial prefrontal cortex glutamate synapses was assessed soon after acute stressor cessation and stress hormone levels were measured. Results: Foot-shock stress induced a remarkable increase in the number of docked vesicles and small excitatory synapses, partially and strongly prevented by desipramine pretreatment, respectively. Acute stress-induced corticosterone elevation was not affected by drug treatment. Conclusions: Since desipramine pretreatment prevented the stress-induced structural plasticity but not the hormone level increase, we hypothesize that the preventing action of desipramine is located on pathways downstream of this process and/or other pathways. Moreover, because enhancement of glutamate system remodeling may contribute to overexcitation dysfunctions, this aspect could represent a crucial component in the pathophysiology of stress-related disorders. PMID:25522419

GABA and glutamate in schizophrenia: a 7 T ¹H-MRS study.

PubMed

Marsman, Anouk; Mandl, René C W; Klomp, Dennis W J; Bohlken, Marc M; Boer, Vincent O; Andreychenko, Anna; Cahn, Wiepke; Kahn, René S; Luijten, Peter R; Hulshoff Pol, Hilleke E

2014-01-01

Schizophrenia is characterized by loss of brain volume, which may represent an ongoing pathophysiological process. This loss of brain volume may be explained by reduced neuropil rather than neuronal loss, suggesting abnormal synaptic plasticity and cortical microcircuitry. A possible mechanism is hypofunction of the NMDA-type of glutamate receptor, which reduces the excitation of inhibitory GABAergic interneurons, resulting in a disinhibition of glutamatergic pyramidal neurons. Disinhibition of pyramidal cells may result in excessive stimulation by glutamate, which in turn could cause neuronal damage or death through excitotoxicity. In this study, GABA/creatine ratios, and glutamate, NAA, creatine and choline concentrations in the prefrontal and parieto-occipital cortices were measured in 17 patients with schizophrenia and 23 healthy controls using proton magnetic resonance spectroscopy at an ultra-high magnetic field strength of 7 T. Significantly lower GABA/Cr ratios were found in patients with schizophrenia in the prefrontal cortex as compared to healthy controls, with GABA/Cr ratios inversely correlated with cognitive functioning in the patients. No significant change in the GABA/Cr ratio was found between patients and controls in the parieto-occipital cortex, nor were levels of glutamate, NAA, creatine, and choline differed in patients and controls in the prefrontal and parieto-occipital cortices. Our findings support a mechanism involving altered GABA levels distinguished from glutamate levels in the medial prefrontal cortex in schizophrenia, particularly in high functioning patients. A (compensatory) role for GABA through altered inhibitory neurotransmission in the prefrontal cortex may be ongoing in (higher functioning) patients with schizophrenia.

Spinal cord-specific deletion of the glutamate transporter GLT1 causes motor neuron death in mice.

PubMed

Sugiyama, Kaori; Tanaka, Kohichi

2018-03-04

Amyotrophic lateral sclerosis (ALS) is a chronic neurodegenerative disorder characterized by the selective loss of motor neurons. The precise mechanisms that cause the selective death of motor neurons remain unclear, but a growing body of evidence suggests that glutamate-mediated excitotoxicity has been considered to play an important role in the mechanisms of motor neuron degeneration in ALS. Reductions in glutamate transporter GLT1 have been reported in animal models of ALS and the motor cortex and spinal cord of ALS patients. However, it remains unknown whether the reduction in GLT1 has a primary role in the induction of motor neuron degeneration in ALS. Here, we generated conditional knockout mice that lacked GLT1 specifically in the spinal cord by crossing floxed-GLT1 mice and Hoxb8-Cre mice. Hoxb8-Cre/GLT1 flox/flox mice showed motor deficits and motor neuron loss. Thus, loss of the glial glutamate transporter GLT1 is sufficient to cause motor neuron death in mice. Copyright © 2018 Elsevier Inc. All rights reserved.

BDNF heightens the sensitivity of motor neurons to excitotoxic insults through activation of TrkB

NASA Technical Reports Server (NTRS)

Hu, Peter; Kalb, Robert G.; Walton, K. D. (Principal Investigator)

2003-01-01

The survival promoting and neuroprotective actions of brain-derived neurotrophic factor (BDNF) are well known but under certain circumstances this growth factor can also exacerbate excitotoxic insults to neurons. Prior exploration of the receptor through which BDNF exerts this action on motor neurons deflects attention away from p75. Here we investigated the possibility that BDNF acts through the receptor tyrosine kinase, TrkB, to confer on motor neurons sensitivity to excitotoxic challenge. We blocked BDNF activation of TrkB using a dominant negative TrkB mutant or a TrkB function blocking antibody, and found that this protected motor neurons against excitotoxic insult in cultures of mixed spinal cord neurons. Addition of a function blocking antibody to BDNF to mixed spinal cord neuron cultures is also neuroprotective indicating that endogenously produced BDNF participates in vulnerability to excitotoxicity. We next examined the intracellular signaling cascades that are engaged upon TrkB activation. Previously we found that inhibition of the phosphatidylinositide-3'-kinase (PI3'K) pathway blocks BDNF-induced excitotoxic sensitivity. Here we show that expression of a constitutively active catalytic subunit of PI3'K, p110, confers excitotoxic sensitivity (ES) upon motor neurons not incubated with BDNF. Parallel studies with purified motor neurons confirm that these events are likely to be occuring specifically within motor neurons. The abrogation of BDNF's capacity to accentuate excitotoxic insults may make it a more attractive neuroprotective agent.

Canonical Transient Receptor Channel 5 (TRPC5) and TRPC1/4 Contribute to Seizure and Excitotoxicity by Distinct Cellular Mechanisms

PubMed Central

Phelan, Kevin D.; Shwe, U Thaung; Abramowitz, Joel; Wu, Hong; Rhee, Sung W.; Howell, Matthew D.; Gottschall, Paul E.; Freichel, Marc; Flockerzi, Veit; Birnbaumer, Lutz

2013-01-01

Seizures are the manifestation of highly synchronized burst firing of a large population of cortical neurons. Epileptiform bursts with an underlying plateau potential in neurons are a cellular correlate of seizures. Emerging evidence suggests that the plateau potential is mediated by neuronal canonical transient receptor potential (TRPC) channels composed of members of the TRPC1/4/5 subgroup. We previously showed that TRPC1/4 double-knockout (DKO) mice lack epileptiform bursting in lateral septal neurons and exhibit reduced seizure-induced neuronal cell death, but surprisingly have unaltered pilocarpine-induced seizures. Here, we report that TRPC5 knockout (KO) mice exhibit both significantly reduced seizures and minimal seizure-induced neuronal cell death in the hippocampus. Interestingly, epileptiform bursting induced by agonists for metabotropic glutamate receptors in the hippocampal CA1 area is unaltered in TRPC5 KO mice, but is abolished in TRPC1 KO and TRPC1/4 DKO mice. In contrast, long-term potentiation is greatly reduced in TRPC5 KO mice, but is normal in TRPC1 KO and TRPC1/4 DKO mice. The distinct changes from these knockouts suggest that TRPC5 and TRPC1/4 contribute to seizure and excitotoxicity by distinct cellular mechanisms. Furthermore, the reduced seizure and excitotoxicity and normal spatial learning exhibited in TRPC5 KO mice suggest that TRPC5 is a promising novel molecular target for new therapy. PMID:23188715

Canonical transient receptor channel 5 (TRPC5) and TRPC1/4 contribute to seizure and excitotoxicity by distinct cellular mechanisms.

PubMed

Phelan, Kevin D; Shwe, U Thaung; Abramowitz, Joel; Wu, Hong; Rhee, Sung W; Howell, Matthew D; Gottschall, Paul E; Freichel, Marc; Flockerzi, Veit; Birnbaumer, Lutz; Zheng, Fang

2013-02-01

Seizures are the manifestation of highly synchronized burst firing of a large population of cortical neurons. Epileptiform bursts with an underlying plateau potential in neurons are a cellular correlate of seizures. Emerging evidence suggests that the plateau potential is mediated by neuronal canonical transient receptor potential (TRPC) channels composed of members of the TRPC1/4/5 subgroup. We previously showed that TRPC1/4 double-knockout (DKO) mice lack epileptiform bursting in lateral septal neurons and exhibit reduced seizure-induced neuronal cell death, but surprisingly have unaltered pilocarpine-induced seizures. Here, we report that TRPC5 knockout (KO) mice exhibit both significantly reduced seizures and minimal seizure-induced neuronal cell death in the hippocampus. Interestingly, epileptiform bursting induced by agonists for metabotropic glutamate receptors in the hippocampal CA1 area is unaltered in TRPC5 KO mice, but is abolished in TRPC1 KO and TRPC1/4 DKO mice. In contrast, long-term potentiation is greatly reduced in TRPC5 KO mice, but is normal in TRPC1 KO and TRPC1/4 DKO mice. The distinct changes from these knockouts suggest that TRPC5 and TRPC1/4 contribute to seizure and excitotoxicity by distinct cellular mechanisms. Furthermore, the reduced seizure and excitotoxicity and normal spatial learning exhibited in TRPC5 KO mice suggest that TRPC5 is a promising novel molecular target for new therapy.

Amelioration of ischemic brain damage by peritoneal dialysis

PubMed Central

Godino, María del Carmen; Romera, Victor G.; Sánchez-Tomero, José Antonio; Pacheco, Jesus; Canals, Santiago; Lerma, Juan; Vivancos, José; Moro, María Angeles; Torres, Magdalena; Lizasoain, Ignacio; Sánchez-Prieto, José

2013-01-01

Ischemic stroke is a devastating condition, for which there is still no effective therapy. Acute ischemic stroke is associated with high concentrations of glutamate in the blood and interstitial brain fluid. The inability of the tissue to retain glutamate within the cells of the brain ultimately provokes neuronal death. Increased concentrations of interstitial glutamate exert further excitotoxic effects on healthy tissue surrounding the infarct zone. We developed a strategy based on peritoneal dialysis to reduce blood glutamate levels, thereby accelerating brain-to-blood glutamate clearance. In a rat model of stroke, this simple procedure reduced the transient increase in glutamate, consequently decreasing the size of the infarct area. Functional magnetic resonance imaging demonstrated that the rescued brain tissue remained functional. Moreover, in patients with kidney failure, peritoneal dialysis significantly decreased glutamate concentrations. Our results suggest that peritoneal dialysis may represent a simple and effective intervention for human stroke patients. PMID:23999426

Glutamate metabolism in HIV-1 infected macrophages: Role of HIV-1 Vpr.

PubMed

Datta, Prasun K; Deshmane, Satish; Khalili, Kamel; Merali, Salim; Gordon, John C; Fecchio, Chiara; Barrero, Carlos A

2016-09-01

HIV-1 infected macrophages play a significant role in the neuropathogenesis of AIDS. HIV-1 viral protein R (Vpr) not only facilitates HIV-1 infection but also contribute to long-lived persistence in macrophages. Our previous studies using SILAC-based proteomic analysis showed that the expression of critical metabolic enzymes in the glycolytic pathway and tricarboxylic acid (TCA) cycle were altered in response to Vpr expression in macrophages. We hypothesized that Vpr-induced modulation of glycolysis and TCA cycle regulates glutamate metabolism and release in HIV-1 infected macrophages. We assessed the amount of specific metabolites induced by Vpr and HIV-1 in macrophages at the intracellular and extracellular level in a time-dependent manner utilizing multiple reaction monitoring (MRM) targeted metabolomics. In addition, stable isotope-labeled glucose and an MRM targeted metabolomics assay were used to evaluate the de novo synthesis and release of glutamate in Vpr overexpressing macrophages and HIV-1 infected macrophages, throughout the metabolic flux of glycolytic pathway and TCA cycle activation. The metabolic flux studies demonstrated an increase in glucose uptake, glutamate release and accumulation of α-ketoglutarate (α-KG) and glutamine in the extracellular milieu in Vpr expressing and HIV-1 infected macrophages. Interestingly, glutamate pools and other intracellular intermediates (glucose-6-phosphate (G6P), fructose-6-phosphate (F6P), citrate, malate, α-KG, and glutamine) showed a decreased trend except for fumarate, in contrast to the glutamine accumulation observed in the extracellular space in Vpr overexpressing macrophages. Our studies demonstrate that dysregulation of mitochondrial glutamate metabolism induced by Vpr in HIV-1 infected macrophages commonly seen, may contribute to neurodegeneration via excitotoxic mechanisms in the context of NeuroAIDS.

Cerebrovascular Acute Radiation Syndrome : Radiation Neurotoxins, Mechanisms of Toxicity, Neuroimmune Interactions.

NASA Astrophysics Data System (ADS)

Popov, Dmitri; Maliev, Slava

. Radiation Toxins (SRD-1)had been isolated from Central Lymph of irradiated animals (cows, sheep, pigs). Experiments to study toxicity of Radiation Neurotoxins had been performed. Intravenous (IV) and intramuscular (IM) administration of RT SRD-1 to radiation naive animals had induced acute toxicity which referred to the harmful effects generated by high doses of radiation. In-jection of toxic doses of RT SRD-1 (Toxic doses: 0,1 mg/kg, 0,5mg/kg, 1 mg/kg, 10mg/kg,30 mg/kg, 50mg/kg,70 mg/kg,100 mg/kg, 110mg/kg)were compared to the similar effects caused by high doses of radiation. Results: Injection of SRD-1 ( Neurotoxin Cv ARS)of all ten tested toxic doses had caused a death of radiation naive animals within the first hours after admin-istration of toxins. For all animals in all experiments, a short period of extreme agitation was replaced by deep coma, and suppression of blood circulation and breathing. The results of postmortem section had showed characteristics of intra-cortical hemorrhage. Conclusions: Acute radiation injury induces a disorder of blood supply of the Central Nervous System (CNS). However, administration of SRD-1 Radiation Toxins to radiation naive animals produces crit-ically important inflammatory reactions with hemorrhagic stroke development. Neurotoxicity and Excitotoxicity are two stages of the pathological processes resulted in damaging and killing nerve cells thorough apoptotic necrosis. Excitotoxicity is well known as a pathological process that occurs when important excitatory neurotransmitters (glutamate, serotonin) over-activate the receptors -NMDA, AMPA, 5HT1, 5HT2, 5H3. Radiation Neurotoxins possibly act on the same receptors and activate the cell death mechanisms through direct or indirect excessive activation of same receptors.

Agmatine protects against cell damage induced by NMDA and glutamate in cultured hippocampal neurons

PubMed Central

Wang, Wei-Ping; Iyo, Abiye H.; Miguel-Hidalgo, Javier; Regunathan, Soundar; Zhu, Meng-Yang

2010-01-01

Agmatine is a polyamine and has been considered as a novel neurotransmitter or neuromodulator in the central nervous system. In the present study, the neuroprotective effect of agmatine against cell damage caused by N-methyl-d-aspartate (NMDA) and glutamate was investigated in cultured rat hippocampal neurons. Lactate dehydrogenase (LDH) activity assay, β-tubulin III immunocytochemical staining and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (dUTP) nick end-labeling (TUNEL) assay were conducted to detect cell damage. Exposure of 12-day neuronal cultures of rat hippocampus to NMDA or glutamate for 1 h caused a concentration-dependent neurotoxicity, as indicated by the significant increase in released LDH activities. Addition of 100 µM agmatine into media ablated the neurotoxicity induced by NMDA or glutamate, an effect also produced by the specific NMDA receptor antagonist dizocilpine hydrogen maleate (MK801). Arcaine, an analog of agmatine with similar structure as agmatine, fully prevented the NMDA- or glutamate-induced neuronal damage. Spermine and putrescine, the endogenous polyamine and metabolic products of agmatine without the guanidine moiety of agmatine, failed to show this effect, indicating a structural relevance for this neuroprotection. Immunocytochemical staining and TUNEL assay confirmed the findings in the LDH measurement. That is, agmatine and MK801 markedly attenuated NMDA-induced neuronal death and significantly reduced TUNEL-positive cell numbers induced by exposure of cultured hippocampal neurons to NMDA. Taken together, these results demonstrate that agmatine can protect cultured hippocampal neurons from NMDA- or glutamate-induced excitotoxicity, through a possible blockade of the NMDA receptor channels or a potential anti-apoptotic property. PMID:16546145

Marked synergism between mutant SOD1 and glutamate transport inhibition in the induction of motor neuronal degeneration in spinal cord slice cultures.

PubMed

Yin, Hong Z; Weiss, John H

2012-04-11

Loss of astrocytic glutamate transport capacity in ALS spinal cord supports an excitotoxic contribution to motor neuron (MN) damage in the disease, and dominant gain of function mutations in Cu/Zn superoxide dismutase (SOD1) cause certain familial forms of ALS. We have used organotypic slice cultures from wild type and G93A SOD1 mutant rat spinal cords to examine interactions between excitotoxicity and the presence of mutant SOD1 in the induction of MN degeneration. Slice cultures were prepared from 1 week old pups, and after an additional week in vitro, some were exposed to either a low level (30 μM) of the glutamate uptake inhibitor, trans-pyrrolidine-2,4-dicarboxylic acid (PDC) for 3 weeks, or a higher level (50 μM) for 48 h, followed by histochemical labeling to assess MN injury. In wild type animals these exposures caused relatively little MN degeneration. Similarly, little MN degeneration was seen in slices from SOD1 mutant animals that were not exposed to PDC. However, addition of PDC to SOD1 mutant slices resulted in substantial MN injury, which was markedly attenuated by a Ca2+ permeable AMPA-type (Ca-AMPA) glutamate channel blocker, or by a nitric oxide synthase antagonist. These observations illustrate the utility of the organotypic culture model for the investigation of intracellular interactions underlying MN degeneration in ALS, and support the hypothesis that activation of Ca-AMPA channels on MNs provides a metabolic burden that synergizes with deleterious effects of mutant SOD1 in the induction of MN injury. Copyright © 2012 Elsevier B.V. All rights reserved.

CCL11 enhances excitotoxic neuronal death by producing reactive oxygen species in microglia.

PubMed

Parajuli, Bijay; Horiuchi, Hiroshi; Mizuno, Tetsuya; Takeuchi, Hideyuki; Suzumura, Akio

2015-12-01

The chemokine CCL11 (also known as eotaxin-1) is a potent eosinophil chemoattractant that mediates allergic diseases such as asthma, atopic dermatitis, and inflammatory bowel diseases. Previous studies demonstrated that concentrations of CCL11 are elevated in the sera and cerebrospinal fluids (CSF) of patients with neuroinflammatory disorders, including multiple sclerosis. Moreover, the levels of CCL11 in plasma and CSF increase with age, and CCL11 suppresses adult neurogenesis in the central nervous system (CNS), resulting in memory impairment. However, the precise source and function of CCL11 in the CNS are not fully understood. In this study, we found that activated astrocytes release CCL11, whereas microglia predominantly express the CCL11 receptor. CCL11 significantly promoted the migration of microglia, and induced microglial production of reactive oxygen species by upregulating nicotinamide adenine dinucleotide phosphate-oxidase 1 (NOX1), thereby promoting excitotoxic neuronal death. These effects were reversed by inhibition of NOX1. Our findings suggest that CCL11 released from activated astrocytes triggers oxidative stress via microglial NOX1 activation and potentiates glutamate-mediated neurotoxicity, which may be involved in the pathogenesis of various neurological disorders. © 2015 Wiley Periodicals, Inc.

Mitochondria and NMDA Receptor-Dependent Toxicity of Berberine Sensitizes Neurons to Glutamate and Rotenone Injury

PubMed Central

Kysenius, Kai; Brunello, Cecilia A.; Huttunen, Henri J.

2014-01-01

The global incidence of metabolic and age-related diseases, including type 2 diabetes and Alzheimer's disease, is on the rise. In addition to traditional pharmacotherapy, drug candidates from complementary and alternative medicine are actively being pursued for further drug development. Berberine, a nutraceutical traditionally used as an antibiotic, has recently been proposed to act as a multi-target protective agent against type 2 diabetes, dyslipidemias, ischemic brain injury and neurodegenerative diseases, such as Parkinson's and Alzheimer's disease. However, the safety profile of berberine remains controversial, as isolated reports suggest risks with acute toxicity, bradycardia and exacerbation of neurodegeneration. We report that low micromolar berberine causes rapid mitochondria-dependent toxicity in primary neurons characterized by mitochondrial swelling, increased oxidative stress, decreased mitochondrial membrane potential and depletion of ATP content. Berberine does not induce caspase-3 activation and the resulting neurotoxicity remains unaffected by pan-caspase inhibitor treatment. Interestingly, inhibition of NMDA receptors by memantine and MK-801 completely blocked berberine-induced neurotoxicity. Additionally, subtoxic nanomolar concentrations of berberine were sufficient to sensitize neurons to glutamate excitotoxicity and rotenone injury. Our study highlights the need for further safety assessment of berberine, especially due to its tendency to accumulate in the CNS and the risk of potential neurotoxicity as a consequence of increasing bioavailability of berberine. PMID:25192195

Protective Effect of Resveratrol on the Brain in a Rat Model of Epilepsy.

PubMed

Li, Zhen; You, Zhuyan; Li, Min; Pang, Liang; Cheng, Juan; Wang, Liecheng

2017-06-01

Accumulating evidence has suggested resveratrol as a promising drug candidate for the treatment of epilepsy. To validate this, we tested the protective effect of resveratrol on a kainic acid (KA)-induced epilepsy model in rats and investigated the underlying mechanism. We found that acute resveratrol application partially inhibited evoked epileptiform discharges in the hippocampal CA1 region. During acute, silent and chronic phases of epilepsy, the expression of hippocampal kainate glutamate receptor (GluK2) and the GABA A receptor alpha1 subunit (GABA A R-alpha1) was up-regulated and down-regulated, respectively. Resveratrol reversed these effects and induced an antiepileptic effect. Furthermore, in the chronic phase, resveratrol treatment inhibited the KA-induced increased glutamate/GABA ratio in the hippocampus. The antiepileptic effects of resveratrol may be partially attributed to the reduction of glutamate-induced excitotoxicity and the enhancement in GABAergic inhibition.

A Molecular Determinant of Subtype-Specific Desensitization in Ionotropic Glutamate Receptors.

PubMed

Alsaloum, Matthew; Kazi, Rashek; Gan, Quan; Amin, Johansen; Wollmuth, Lonnie P

2016-03-02

AMPA and NMDA receptors are glutamate-gated ion channels that mediate fast excitatory synaptic transmission throughout the nervous system. In the continual presence of glutamate, AMPA and NMDA receptors containing the GluN2A or GluN2B subunit enter into a nonconducting, desensitized state that can impact synaptic responses and glutamate-mediated excitotoxicity. The process of desensitization is dramatically different between subtypes, but the basis for these differences is unknown. We generated an extensive sequence alignment of ionotropic glutamate receptors (iGluRs) from diverse animal phyla and identified a highly conserved motif, which we termed the "hydrophobic box," located at the extracellular interface of transmembrane helices. A single position in the hydrophobic box differed between mammalian AMPA and NMDA receptors. Surprisingly, we find that an NMDAR-to-AMPAR exchange mutation at this position in the rat GluN2A or GluN2B subunit had a dramatic and highly specific effect on NMDAR desensitization, making it AMPAR-like. In contrast, a reverse exchange mutation in AMPARs had minimal effects on desensitization. These experiments highlight differences in desensitization between iGluR subtypes and the highly specific contribution of the GluN2 subunit to this process. Rapid communication between cells in the nervous system depends on ion channels that are directly activated by neurotransmitter molecules. Here, we studied ionotropic glutamate receptors (iGluRs), which are ion channels activated by the neurotransmitter glutamate. By comparing the sequences of a vast number of iGluR proteins from diverse animal species, assisted by available structural information, we identified a highly conserved motif. We showed that a single amino acid difference in this motif between mammalian iGluR subtypes has dramatic effects on receptor function. These results have implications in both the evolution of synaptic function, as well as the role of iGluRs in health and disease

Glutamate metabolism in HIV-1 infected macrophages: Role of HIV-1 Vpr

PubMed Central

Datta, Prasun K.; Deshmane, Satish; Khalili, Kamel; Merali, Salim; Gordon, John C.; Fecchio, Chiara; Barrero, Carlos A.

2016-01-01

ABSTRACT HIV-1 infected macrophages play a significant role in the neuropathogenesis of AIDS. HIV-1 viral protein R (Vpr) not only facilitates HIV-1 infection but also contribute to long-lived persistence in macrophages. Our previous studies using SILAC-based proteomic analysis showed that the expression of critical metabolic enzymes in the glycolytic pathway and tricarboxylic acid (TCA) cycle were altered in response to Vpr expression in macrophages. We hypothesized that Vpr-induced modulation of glycolysis and TCA cycle regulates glutamate metabolism and release in HIV-1 infected macrophages. We assessed the amount of specific metabolites induced by Vpr and HIV-1 in macrophages at the intracellular and extracellular level in a time-dependent manner utilizing multiple reaction monitoring (MRM) targeted metabolomics. In addition, stable isotope-labeled glucose and an MRM targeted metabolomics assay were used to evaluate the de novo synthesis and release of glutamate in Vpr overexpressing macrophages and HIV-1 infected macrophages, throughout the metabolic flux of glycolytic pathway and TCA cycle activation. The metabolic flux studies demonstrated an increase in glucose uptake, glutamate release and accumulation of α-ketoglutarate (α-KG) and glutamine in the extracellular milieu in Vpr expressing and HIV-1 infected macrophages. Interestingly, glutamate pools and other intracellular intermediates (glucose-6-phosphate (G6P), fructose-6-phosphate (F6P), citrate, malate, α-KG, and glutamine) showed a decreased trend except for fumarate, in contrast to the glutamine accumulation observed in the extracellular space in Vpr overexpressing macrophages. Our studies demonstrate that dysregulation of mitochondrial glutamate metabolism induced by Vpr in HIV-1 infected macrophages commonly seen, may contribute to neurodegeneration via excitotoxic mechanisms in the context of NeuroAIDS. PMID:27245560

Hypothermia protects against oxygen-glucose deprivation-induced neuronal injury by down-regulating the reverse transport of glutamate by astrocytes as mediated by neurons.

PubMed

Wang, D; Zhao, Y; Zhang, Y; Zhang, T; Shang, X; Wang, J; Liu, Y; Kong, Q; Sun, B; Mu, L; Liu, X; Wang, G; Li, H

2013-05-01

Glutamate is the major mediator of excitotoxic neuronal death following cerebral ischemia. Under severe ischemic conditions, glutamate transporters can functionally reverse to release glutamate, thereby inducing further neuronal injury. Hypothermia has been shown to protect neurons from brain ischemia. However, the mechanism(s) involved remain unclear. Therefore, the aim of this study was to investigate the mechanism(s) mediating glutamate release during brain ischemia-reperfusion injury under hypothermic conditions. Neuron/astrocyte co-cultures were exposed to oxygen-glucose deprivation (OGD) at various temperatures for 2h, and cell viability was assayed 12h after reoxygenation. PI and MAP-2 staining demonstrated that hypothermia significantly decreased neuronal injury. Furthermore, [(3)H]-glutamate uptake assays showed that hypothermia protected rat primary cortical cultures against OGD reoxygenation-induced injury. Protein levels of the astrocytic glutamate transporter, GLT-1, which is primarily responsible for the clearance of extracellular glutamate, were also found to be reduced in a temperature-dependent manner. In contrast, expression of GLT-1 in astrocyte-enriched cultures was found to significantly increase following the addition of neuron-conditioned medium maintained at 37 °C, and to a lesser extent with neuron-conditioned medium at 33 °C. In conclusion, the neuroprotective effects of hypothermia against brain ischemia-reperfusion injury involve down-regulation of astrocytic GLT-1, which mediates the reverse transport of glutamate. Moreover, this process may be regulated by molecules secreted by stressed neurons. Copyright © 2013 IBRO. Published by Elsevier Ltd. All rights reserved.

Increases in Brain 1H-MR Glutamine and Glutamate Signals Following Acute Exhaustive Endurance Exercise in the Rat

PubMed Central

Świątkiewicz, Maciej; Fiedorowicz, Michał; Orzeł, Jarosław; Wełniak-Kamińska, Marlena; Bogorodzki, Piotr; Langfort, Józef; Grieb, Paweł

2017-01-01

Objective: Proton magnetic resonance spectroscopy (1H-MRS) in ultra-high magnetic field can be used for non-invasive quantitative assessment of brain glutamate (Glu) and glutamine (Gln) in vivo. Glu, the main excitatory neurotransmitter in the central nervous system, is efficiently recycled between synapses and presynaptic terminals through Glu-Gln cycle which involves glutamine synthase confined to astrocytes, and uses 60–80% of energy in the resting human and rat brain. During voluntary or involuntary exercise many brain areas are significantly activated, which certainly intensifies Glu-Gln cycle. However, studies on the effects of exercise on 1H-MRS Glu and/or Gln signals from the brain provided divergent results. The present study on rats was performed to determine changes in 1H-MRS signals from three brain regions engaged in motor activity consequential to forced acute exercise to exhaustion. Method: After habituation to treadmill running, rats were subjected to acute treadmill exercise continued to exhaustion. Each animal participating in the study was subject to two identical imaging sessions performed under light isoflurane anesthesia, prior to, and following the exercise bout. In control experiments, two imaging sessions separated by the period of rest instead of exercise were performed. 1H-NMR spectra were recorded from the cerebellum, striatum, and hippocampus using a 7T small animal MR scanner. Results: Following exhaustive exercise statistically significant increases in the Gln and Glx signals were found in all three locations, whereas increases in the Glu signal were found in the cerebellum and hippocampus. In control experiments, no changes in 1H-MRS signals were found. Conclusion: Increase in glutamine signals from the brain areas engaged in motor activity may reflect a disequilibrium caused by increased turnover in the glutamate-glutamine cycle and a delay in the return of glutamine from astrocytes to neurons. Increased turnover of Glu-Gln cycle

Studies of locomotor network neuroprotection by the selective poly(ADP-ribose) polymerase-1 inhibitor PJ-34 against excitotoxic injury to the rat spinal cord in vitro.

PubMed

Nasrabady, Sara E; Kuzhandaivel, Anujaianthi; Nistri, Andrea

2011-06-01

Delayed neuronal destruction after acute spinal injury is attributed to excitotoxicity mediated by hyperactivation of poly(ADP-ribose) polymerase-1 (PARP-1) that induces 'parthanatos', namely a non-apoptotic cell death mechanism. With an in vitro model of excitotoxicity, we have previously observed parthanatos of rat spinal cord locomotor networks to be decreased by a broad spectrum PARP-1 inhibitor. The present study investigated whether the selective PARP-1 inhibitor N-(6-oxo-5,6-dihydrophenanthridin-2-yl)-(N,N-dimethylamino)acetamide.HCl (PJ-34) not only protected networks from kainate-evoked excitotoxicity, but also prevented loss of locomotor patterns recorded as fictive locomotion from lumbar (L) ventral roots (VRs) 24 h later. PJ-34 (60 μm) blocked PARP-1 activation and preserved dorsal, central and ventral gray matter with maintained reflex activity even after a large dose of kainate. Fictive locomotion could not, however, be restored by either electrical stimulation or bath-applied neurochemicals (N-methyl-D-aspartate plus 5-hydroxytryptamine). A low kainate concentration induced less histological damage that was widely prevented by PJ-34. Nonetheless, fictive locomotion was observed in just over 50% of preparations whose histological profile did not differ (except for the dorsal horn) from those lacking such a rhythm. Our data show that inhibition of PARP-1 could amply preserve spinal network histology after excitotoxicity, with return of locomotor patterns only when the excitotoxic stimulus was moderate. These results demonstrated divergence between histological and functional outcome, implying a narrow borderline between loss of fictive locomotion and neuronal preservation. Our data suggest that either damage of a few unidentified neurons or functional network inhibition was critical for ensuring locomotor cycles. © 2011 The Authors. European Journal of Neuroscience © 2011 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.

ΔN-Bcl-xL, a therapeutic target for neuroprotection

PubMed Central

Park, Han-A; Jonas, Elizabeth A.

2017-01-01

The B-cell lymphoma-extra large (Bcl-xL) is a mitochondrial anti-apoptotic protein that plays a role in neuroprotection. However, during excitotoxic stimulation, Bcl-xL undergoes caspase-dependent cleavage and produces a fragmented form, ΔN-Bcl-xL. Accumulation of ΔN-Bcl-xL is associated with mitochondrial dysfunction and neuronal death. Therefore, strategies to inhibit the activity or formation of ΔN-Bcl-xL protect the brain against excitotoxic injuries. Our team found that the pharmacological inhibitor ABT-737 exerts dose dependent effects in primary neurons. When primary hippocampal neurons were treated with 1 μM ABT-737, glutamate-mediated mitochondrial damage and neuronal death were exacerbated, whereas 10 nM ABT-737, a 100-fold lower concentration, protected mitochondrial function and enhanced neuronal viability against glutamate toxicity. In addition, we suggested acute vs. prolonged formation of ΔN-Bcl-xL may have different effects on mitochondrial or neuronal functions. Unlike acute production of ΔN-Bcl-xL by glutamate, overexpression of ΔN-Bcl-xL did not cause drastic changes in neuronal viability. We predicted that neurons undergo adaptation and may activate altered metabolism to compensate for ΔN-Bcl-xL-mediated mitochondrial dysfunction. Although the detailed mechanism of ABT-mediated neurotoxicity neuroprotection is still unclear, our study shows that the mitochondrial membrane protein ΔN-Bcl-xL is a central target for interventions. PMID:29239317

Glutamate receptor antibodies in neurological diseases: anti-AMPA-GluR3 antibodies, anti-NMDA-NR1 antibodies, anti-NMDA-NR2A/B antibodies, anti-mGluR1 antibodies or anti-mGluR5 antibodies are present in subpopulations of patients with either: epilepsy, encephalitis, cerebellar ataxia, systemic lupus erythematosus (SLE) and neuropsychiatric SLE, Sjogren's syndrome, schizophrenia, mania or stroke. These autoimmune anti-glutamate receptor antibodies can bind neurons in few brain regions, activate glutamate receptors, decrease glutamate receptor's expression, impair glutamate-induced signaling and function, activate blood brain barrier endothelial cells, kill neurons, damage the brain, induce behavioral/psychiatric/cognitive abnormalities and ataxia in animal models, and can be removed or silenced in some patients by immunotherapy.

PubMed

Levite, Mia

2014-08-01

Glutamate is the major excitatory neurotransmitter of the Central Nervous System (CNS), and it is crucially needed for numerous key neuronal functions. Yet, excess glutamate causes massive neuronal death and brain damage by excitotoxicity--detrimental over activation of glutamate receptors. Glutamate-mediated excitotoxicity is the main pathological process taking place in many types of acute and chronic CNS diseases and injuries. In recent years, it became clear that not only excess glutamate can cause massive brain damage, but that several types of anti-glutamate receptor antibodies, that are present in the serum and CSF of subpopulations of patients with a kaleidoscope of human neurological diseases, can undoubtedly do so too, by inducing several very potent pathological effects in the CNS. Collectively, the family of anti-glutamate receptor autoimmune antibodies seem to be the most widespread, potent, dangerous and interesting anti-brain autoimmune antibodies discovered up to now. This impression stems from taking together the presence of various types of anti-glutamate receptor antibodies in a kaleidoscope of human neurological and autoimmune diseases, their high levels in the CNS due to intrathecal production, their multiple pathological effects in the brain, and the unique and diverse mechanisms of action by which they can affect glutamate receptors, signaling and effects, and subsequently impair neuronal signaling and induce brain damage. The two main families of autoimmune anti-glutamate receptor antibodies that were already found in patients with neurological and/or autoimmune diseases, and that were already shown to be detrimental to the CNS, include the antibodies directed against ionotorpic glutamate receptors: the anti-AMPA-GluR3 antibodies, anti-NMDA-NR1 antibodies and anti-NMDA-NR2 antibodies, and the antibodies directed against Metabotropic glutamate receptors: the anti-mGluR1 antibodies and the anti-mGluR5 antibodies. Each type of these anti-glutamate

Alteration of glutamate/GABA balance during acute alcohol intoxication in rats: effect of Xingnaojing injection.

PubMed

Wei, Jingjing; Yao, Limei; Yang, Lei; Zhao, Wei; Shi, Si; Cai, Qingyan; Chen, Dingsheng; Li, Weirong; Wang, Qi

2015-05-26

Xingnaojing Injection (XNJI) is a modern Chinese formula came from famous Chinese medicine An Gong Niu Huang Pill. XNJI has been used for treatment of cerebral diseases and stroke in China, and is approved by the State Food and Drug Administration of China for the treatment of acute alcohol intoxication (AAI). XNJI belongs to the ethnopharmacological family of medicines. In this study, we investigated the mechanisms of the XNJI effect on AAI. To investigate the effects of XNJI on glutamate, gamma-aminobutyric acid (GABA) and related receptor in lateral hypothalamic area (LHA) of AAI rat. Adult male Sprague-Dawley rats were implanted with microdialysis probes in LHA. Rats were randomly divided into control, model, 1.36mg/kg XNJI, 0.68mg/kg XNJI and 0.34mg/kg XNJI groups. During microdialysis, baseline samples were collected from 1h to 2.5h; thereafter, the rats were given an intraperitoneal injection of 52% ethanol, 5.2g/kg, or saline for control group. Twenty minutes later, three doses of XNJI was given by unilateral injection respectively, while saline for control and model groups, and samples were collected for the next 4h. The extracellular glutamate and GABA levels were measured in the LHA by a high performance liquid chromatography coupled with fluorescence detector (HPLC-FLU). The expression levels of related receptors N-methyl-d-aspartate receptor (NR) subunit NR2A, NR2B and GABAA were analyzed by reverse transcription polymerase chain reaction (RT-PCR). Ethanol (5.2g/kg) significantly decreased the extracellular levels of glutamate and increased extracellular GABA in LHA. On the other hand ethanol significantly decreased NR2A and NR2B mRNAs expression, and increase GABAA mRNA expression. XNJI could increase the extracellular level of glutamate and decrease that of GABA; moreover, induced an increase in NR2A and NR2B mRNA expression, and a decrease in GABAA mRNA expression in LHA. The current changes in glutamate, GABA and mRNA expressions of related

An optimized fluorescent probe for visualizing glutamate neurotransmission.

PubMed

Marvin, Jonathan S; Borghuis, Bart G; Tian, Lin; Cichon, Joseph; Harnett, Mark T; Akerboom, Jasper; Gordus, Andrew; Renninger, Sabine L; Chen, Tsai-Wen; Bargmann, Cornelia I; Orger, Michael B; Schreiter, Eric R; Demb, Jonathan B; Gan, Wen-Biao; Hires, S Andrew; Looger, Loren L

2013-02-01

We describe an intensity-based glutamate-sensing fluorescent reporter (iGluSnFR) with signal-to-noise ratio and kinetics appropriate for in vivo imaging. We engineered iGluSnFR in vitro to maximize its fluorescence change, and we validated its utility for visualizing glutamate release by neurons and astrocytes in increasingly intact neurological systems. In hippocampal culture, iGluSnFR detected single field stimulus-evoked glutamate release events. In pyramidal neurons in acute brain slices, glutamate uncaging at single spines showed that iGluSnFR responds robustly and specifically to glutamate in situ, and responses correlate with voltage changes. In mouse retina, iGluSnFR-expressing neurons showed intact light-evoked excitatory currents, and the sensor revealed tonic glutamate signaling in response to light stimuli. In worms, glutamate signals preceded and predicted postsynaptic calcium transients. In zebrafish, iGluSnFR revealed spatial organization of direction-selective synaptic activity in the optic tectum. Finally, in mouse forelimb motor cortex, iGluSnFR expression in layer V pyramidal neurons revealed task-dependent single-spine activity during running.

Human recombinant glutamate oxaloacetate transaminase 1 (GOT1) supplemented with oxaloacetate induces a protective effect after cerebral ischemia.

PubMed

Pérez-Mato, M; Ramos-Cabrer, P; Sobrino, T; Blanco, M; Ruban, A; Mirelman, D; Menendez, P; Castillo, J; Campos, F

2014-01-09

Blood glutamate scavenging is a novel and attractive protecting strategy to reduce the excitotoxic effect of extracellular glutamate released during ischemic brain injury. Glutamate oxaloacetate transaminase 1 (GOT1) activation by means of oxaloacetate administration has been used to reduce the glutamate concentration in the blood. However, the protective effect of the administration of the recombinant GOT1 (rGOT1) enzyme has not been yet addressed in cerebral ischemia. The aim of this study was to analyze the protective effect of an effective dose of oxaloacetate and the human rGOT1 alone and in combination with a non-effective dose of oxaloacetate in an animal model of ischemic stroke. Sixty rats were subjected to a transient middle cerebral artery occlusion (MCAO). Infarct volumes were assessed by magnetic resonance imaging (MRI) before treatment administration, and 24 h and 7 days after MCAO. Brain glutamate levels were determined by in vivo MR spectroscopy (MRS) during artery occlusion (80 min) and reperfusion (180 min). GOT activity and serum glutamate concentration were analyzed during the occlusion and reperfusion period. Somatosensory test was performed at baseline and 7 days after MCAO. The three treatments tested induced a reduction in serum and brain glutamate levels, resulting in a reduction in infarct volume and sensorimotor deficit. Protective effect of rGOT1 supplemented with oxaloacetate at 7 days persists even when treatment was delayed until at least 2 h after onset of ischemia. In conclusion, our findings indicate that the combination of human rGOT1 with low doses of oxaloacetate seems to be a successful approach for stroke treatment.

Human recombinant glutamate oxaloacetate transaminase 1 (GOT1) supplemented with oxaloacetate induces a protective effect after cerebral ischemia

PubMed Central

Pérez-Mato, M; Ramos-Cabrer, P; Sobrino, T; Blanco, M; Ruban, A; Mirelman, D; Menendez, P; Castillo, J; Campos, F

2014-01-01

Blood glutamate scavenging is a novel and attractive protecting strategy to reduce the excitotoxic effect of extracellular glutamate released during ischemic brain injury. Glutamate oxaloacetate transaminase 1 (GOT1) activation by means of oxaloacetate administration has been used to reduce the glutamate concentration in the blood. However, the protective effect of the administration of the recombinant GOT1 (rGOT1) enzyme has not been yet addressed in cerebral ischemia. The aim of this study was to analyze the protective effect of an effective dose of oxaloacetate and the human rGOT1 alone and in combination with a non-effective dose of oxaloacetate in an animal model of ischemic stroke. Sixty rats were subjected to a transient middle cerebral artery occlusion (MCAO). Infarct volumes were assessed by magnetic resonance imaging (MRI) before treatment administration, and 24 h and 7 days after MCAO. Brain glutamate levels were determined by in vivo MR spectroscopy (MRS) during artery occlusion (80 min) and reperfusion (180 min). GOT activity and serum glutamate concentration were analyzed during the occlusion and reperfusion period. Somatosensory test was performed at baseline and 7 days after MCAO. The three treatments tested induced a reduction in serum and brain glutamate levels, resulting in a reduction in infarct volume and sensorimotor deficit. Protective effect of rGOT1 supplemented with oxaloacetate at 7 days persists even when treatment was delayed until at least 2 h after onset of ischemia. In conclusion, our findings indicate that the combination of human rGOT1 with low doses of oxaloacetate seems to be a successful approach for stroke treatment PMID:24407245

The Pharmacological Inhibition of Fatty Acid Amide Hydrolase Prevents Excitotoxic Damage in the Rat Striatum: Possible Involvement of CB1 Receptors Regulation.

PubMed

Aguilera-Portillo, Gabriela; Rangel-López, Edgar; Villeda-Hernández, Juana; Chavarría, Anahí; Castellanos, Pilar; Elmazoglu, Zubeyir; Karasu, Çimen; Túnez, Isaac; Pedraza, Gibrán; Königsberg, Mina; Santamaría, Abel

2018-05-25

The endocannabinoid system (ECS) actively participates in several physiological processes within the central nervous system. Among such, its involvement in the downregulation of the N-methyl-D-aspartate receptor (NMDAr) through a modulatory input at the cannabinoid receptors (CBr) has been established. After its production via the kynurenine pathway (KP), quinolinic acid (QUIN) can act as an excitotoxin through the selective overactivation of NMDAr, thus participating in the onset and development of neurological disorders. In this work, we evaluated whether the pharmacological inhibition of fatty acid amide hydrolase (FAAH) by URB597, and the consequent increase in the endogenous levels of anandamide, can prevent the excitotoxic damage induced by QUIN. URB597 (0.3 mg/kg/day × 7 days, administered before, during and after the striatal lesion) exerted protective effects on the QUIN-induced motor (asymmetric behavior) and biochemical (lipid peroxidation and protein carbonylation) alterations in rats. URB597 also preserved the structural integrity of the striatum and prevented the neuronal loss (assessed as microtubule-associated protein-2 and glutamate decarboxylase localization) induced by QUIN (1 μL intrastriatal, 240 nmol/μL), while modified the early localization patterns of CBr1 (CB1) and NMDAr subunit 1 (NR1). Altogether, these findings support the concept that the pharmacological manipulation of the endocannabinoid system plays a neuroprotective role against excitotoxic insults in the central nervous system.

[Glutamate dehydrogenase activity in the pancreatic tissue in acute experimental pancreatitis and under the action of sodium thiosulphate].

PubMed

Simavorian, P S; Saakian, I L; Gevorkian, D A

1991-04-01

It has been established that the development of acute pancreatitis is accompanied by the reduced activity of glutamate dehydrogenase in the mitochondrial fraction of pancreas, pronounced in the focus of tissue necrosis and less expressed in the reactive inflammation focus. Besides this in the pancreas redistribution of enzyme, activity in the subcellular organelles takes place and enzyme activity emerges in the cytosol and further--in the blood and peritoneum liquid. Sodium thiosulfate has a marked correlation effect.

[A case of acute cerebellar ataxia following infectious mononucleosis accompanied by intrathecal anti-glutamate receptor δ2 antibody].

PubMed

Murakami, Hidetomo; Iijima, Shoji; Kawamura, Mitsuru; Takahashi, Yukitoshi; Ichikawa, Hiroo

2013-01-01

An 18-year-old woman was admitted because of sore throat and pain in the epigastric region. On admission, she presented with swollen tonsils and hepatosplenomegaly. Blood examinations revealed the presence of atypical lymphocytes, liver damage and anti-VCA IgM and IgG antibodies. These findings led to diagnosis of infectious mononucleosis. After admission, her condition improved, but on hospital day 4, she suddenly developed cerebellar ataxia in the trunk and four limbs. Cranial MRI findings were normal. Cerebrospinal fluid (CSF) collected on hospital day 6 showed normal cell counts and normal concentrations of protein and glucose. EB virus DNA and anti-VCA IgM and IgG antibodies were negative and glutamate receptor δ2 antibody was positive in CSF collected on hospital day 11. We diagnosed acute cerebellar ataxia (ACA) and performed methylprednisolone pulse therapy. After this therapy, her cerebellar ataxia improved over a few days. This is the first reported case of ACA after EB virus infection presenting with glutamate receptor δ2 antibody in CSF. The glutamate receptor δ2 subunit is expressed on cerebellar Purkinje cells. Therefore, the presence of the antibody may be associated with cerebellar dysfunction. In the present case, secondary immune reactions after EB virus infection may have produced the antibody.

[60]Fullerene derivative modulates adenosine and metabotropic glutamate receptors gene expression: a possible protective effect against hypoxia

PubMed Central

2014-01-01

Background Glutamate, the main excitatory neurotransmitter, is involved in learning and memory processes but at higher concentration results excitotoxic causing degeneration and neuronal death. Adenosine is a nucleoside that exhibit neuroprotective effects by modulating of glutamate release. Hypoxic and related oxidative conditions, in which adenosine and metabotropic glutamate receptors are involved, have been demonstrated to contribute to neurodegenerative processes occurring in certain human pathologies. Results Human neuroblastoma cells (SH-SY5Y) were used to evaluate the long time (24, 48 and 72 hours) effects of a [60]fullerene hydrosoluble derivative (t3ss) as potential inhibitor of hypoxic insult. Low oxygen concentration (5% O2) caused cell death, which was avoided by t3ss exposure in a concentration dependent manner. In addition, gene expression analysis by real time PCR of adenosine A1, A2A and A2B and metabotropic glutamate 1 and 5 receptors revealed that t3ss significantly increased A1 and mGlu1 expression in hypoxic conditions. Moreover, t3ss prevented the hypoxia-induced increase in A2A mRNA expression. Conclusions As t3ss causes overexpression of adenosine A1 and metabotropic glutamate receptors which have been shown to be neuroprotective, our results point to a radical scavenger protective effect of t3ss through the enhancement of these neuroprotective receptors expression. Therefore, the utility of these nanoparticles as therapeutic target to avoid degeneration and cell death of neurodegenerative diseases is suggested. PMID:25123848

The Neuroprotective Effects of SIRT1 on NMDA-Induced Excitotoxicity

PubMed Central

Si, Peipei; Qin, Huaping; Yin, Litian

2017-01-01

Silent information regulator 1 (SIRT1), an NAD+-dependent deacetylase, is involved in the regulation of gene transcription, energy metabolism, and cellular aging and has become an important therapeutic target across a range of diseases. Recent research has demonstrated that SIRT1 possesses neuroprotective effects; however, it is unknown whether it protects neurons from NMDA-mediated neurotoxicity. In the present study, by activation of SIRT1 using resveratrol (RSV) in cultured cortical neurons or by overexpression of SIRT1 in SH-SY5Y cell, we aimed to evaluate the roles of SIRT1 in NMDA-induced excitotoxicity. Our results showed that RSV or overexpression of SIRT1 elicited inhibitory effects on NMDA-induced excitotoxicity including a decrease in cell viability, an increase in lactate dehydrogenase (LDH) release, and a decrease in the number of living cells as measured by CCK-8 assay, LDH test, and Calcein-AM and PI double staining. RSV or overexpression of SIRT1 significantly improved SIRT1 deacetylase activity in the excitotoxicity model. Further study suggests that overexpression of SIRT1 partly suppressed an NMDA-induced increase in p53 acetylation. These results indicate that SIRT1 activation by either RSV or overexpression of SIRT1 can exert neuroprotective effects partly by inhibiting p53 acetylation in NMDA-induced neurotoxicity. PMID:29081884

Neuroprotective effects of α-iso-cubebene against glutamate-induced damage in the HT22 hippocampal neuronal cell line.

PubMed

Park, Sun Young; Jung, Won Jung; Kang, Jum Soon; Kim, Cheol-Min; Park, Geuntae; Choi, Young-Whan

2015-02-01

Since oxidative stress is critically involved in excitotoxic damage, we sought to determine whether the activation of the transcription factors, cAMP-responsive element binding protein (CREB) and nuclear factor (erythroid-derived 2)-like 2 (Nrf2, also known as NFE2L2), by α-iso-cubebene is involved in its protective effects against glutamate-induced neuronal cell death. Pre-treatment with α-iso-cubebene significantly attenuated glutamate-induced cytotoxicity in mouse hippocampus-derived neuronal cells. α-iso-cubebene also reduced the glutamate-induced generation of reactive oxygen species and calcium influx, thus preventing apoptotic cell death. α-iso-cubebene inhibited glutamate-induced mitochondrial membrane depolarization and, consequently, inhibited the release of the apoptosis-inducing factor from the mitochondria. Immunoblot anlaysis revealed that the phosphorylation of extracellular signal-regulated kinase (ERK) by glutamate was reduced in the presence of α-iso-cubebene. α-iso-cubebene activated protein kinase A (PKA), CREB and Nrf2, which mediate the expression of the antioxidant enzymes, heme oxygenase-1 (HO-1) and NAD(P)H dehydrogenase [quinone] 1 (NQO1), involved in neuroprotection. In addition, α-iso-cubebene induced the expression of antioxidant responsive element and CRE transcriptional activity, thus conferring neuroprotection against glutamate-induced oxidative injury. α-iso-cubebene also induced the expression of Nrf2-dependent genes encoding HO-1 and NQO1. Furthermore, the knockdown of CREB and Nrf2 by small interfering RNA attenuated the neuroprotective effects of α-iso-cubebene. Taken together, our results indicate that α-iso-cubebene protects HT22 cells from glutamate-induced oxidative damage through the activation of Nrf2/HO-1/NQO-1, as well as through the PKA and CREB signaling pathways.

Metabotropic glutamate receptors as therapeutic targets in Parkinson's disease: An update from the last 5 years of research.

PubMed

Litim, Nadhir; Morissette, Marc; Di Paolo, Thérèse

2017-03-15

Disturbance of glutamate neurotransmission in Parkinson's disease (PD) and l-DOPA induced dyskinesia (LID) is well documented. This review focuses on advances during the past five years on pharmacological modulation of metabotropic glutamate (mGlu) receptors in relation to anti-parkinsonian activity, LID attenuation, and neuroprotection. Drug design and characterization have led to the development of orthosteric agonists binding the same site as glutamate and Positive and Negative Allosteric modulators (PAMs and NAMs) binding sites different from the orthosteric site and offering subtype selectivity. Inhibition of group I (mGlu1 and mGlu5) receptors with NAMs and activation of group II (mGlu2 and 3 receptors) and group III (mGlu 4, 7 and 8 receptors) with PAMs and orthosteric agonists have shown their potential to inhibit glutamate release and attenuate excitotoxicity. Earlier and recent studies have led to the development of mGlu5 receptors NAMs to reduce LID and for neuroprotection, mGlu3 receptor agonists for neuroprotection while mGlu4 receptor PAMs and agonists for antiparkinsonian effects and neuroprotection. Furthermore, homo- and heterodimers of mGlu receptors are documented and highlight the complexity of the functioning of these receptors. Research on partial allosteric modulators and biased mGlu receptor allosteric modulators offer new glutamatergic drugs with better therapeutic effects and less off target adverse activity. Thus these various mGlu receptor targets will enable the development of novel drugs with improved clinical effects for normalization of glutamate transmission, treat PD and LID relief. This article is part of the Special Issue entitled 'Metabotropic Glutamate Receptors, 5 years on'. Copyright © 2016 Elsevier Ltd. All rights reserved.

Local and downstream effects of excitotoxic lesions in the rat medial prefrontal cortex on In vivo 1H-MRS signals.

PubMed

Roffman, J L; Lipska, B K; Bertolino, A; Van Gelderen, P; Olson, A W; Khaing, Z Z; Weinberger, D R

2000-04-01

The rat medial prefrontal cortex (mPFC) regulates subcortical dopamine transmission via projections to the striatum and ventral tegmental area. We used in vivo proton magnetic resonance spectroscopy (1H-MRS) at 4.7 T to determine whether excitotoxic lesions of the mPFC result in alterations of N-acetylaspartate (NAA), a marker of neuronal integrity, both locally and downstream in the striatum. Lesioned rats exhibited persistent reductions of NAA and other metabolites within the prefrontal cortex; selective reductions of NAA were seen in the striatum, but not in the parietal cortex. Consistent with earlier reports, lesioned rats exhibited a transient enhancement in amphetamine-induced hyperlocomotion. Prefrontal NAA losses correlated with lesion extent. In the striatum, while there was no change in tissue volume, expression of striatal glutamic acid decarboxylase-67 mRNA was significantly reduced. In vivo NAA levels thus appear sensitive to both local and downstream alterations in neuronal integrity, and may signal meaningful effects at cellular and behavioral levels.

Effects of Excitotoxic Lesion with Inhaled Anesthetics on Nervous System Cells of Rodents.

PubMed

Quiroz-Padilla, Maria Fernanda; Guillazo-Blanch, Gemma; Sanchez, Magdy Y; Dominguez-Sanchez, Maria Andrea; Gomez, Rosa Margarita

2018-01-01

Different anesthesia methods can variably influence excitotoxic lesion effects on the brain. The main purpose of this review is to identify potential differences in the toxicity to nervous system cells of two common inhalation anesthesia methods, isoflurane and sevoflurane, used in combination with an excitotoxic lesion procedure in rodents. The use of bioassays in animal models has provided the opportunity to examine the role of specific molecules and cellular interactions that underlie important aspects of neurotoxic effects relating to calcium homeostasis and apoptosis activation. Processes induced by NMDA antagonist drugs involve translocation of Bax protein to mitochondrial membranes, allowing extra-mitochondrial leakage of cytochrome C, followed by sequence of changes that ending in activation of CASP-3. The literature demonstrates that the use of these anesthetics in excitotoxic surgery increases neuroinflammation activity facilitating the effects of apoptosis and necrosis on nervous system cells, depending on the concentration and exposure duration of the anesthetic. High numbers of microglia and astrocytes and high levels of proinflammatory cytokines and caspase activation possibly mediate these inflammatory responses. However, it is necessary to continue studies in rodents to understand the effect of the use of inhaled anesthetics with excitotoxic lesions in different developmental stages, including newborns, juveniles and adults. Understanding the mechanisms of regulation of cell death during development can potentially provide tools to promote neuroprotection and eventually achieve the repair of the nervous system in pathological conditions. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Mice lacking glutamate carboxypeptidase II develop normally, but are less susceptible to traumatic brain injury.

PubMed

Gao, Yang; Xu, Siyi; Cui, Zhenwen; Zhang, Mingkun; Lin, Yingying; Cai, Lei; Wang, Zhugang; Luo, Xingguang; Zheng, Yan; Wang, Yong; Luo, Qizhong; Jiang, Jiyao; Neale, Joseph H; Zhong, Chunlong

2015-07-01

Glutamate carboxypeptidase II (GCPII) is a transmembrane zinc metallopeptidase found mainly in the nervous system, prostate and small intestine. In the nervous system, glia-bound GCPII mediates the hydrolysis of the neurotransmitter N-acetylaspartylglutamate (NAAG) into glutamate and N-acetylaspartate. Inhibition of GCPII has been shown to attenuate excitotoxicity associated with enhanced glutamate transmission under pathological conditions. However, different strains of mice lacking the GCPII gene are reported to exhibit striking phenotypic differences. In this study, a GCPII gene knockout (KO) strategy involved removing exons 3-5 of GCPII. This generated a new GCPII KO mice line with no overt differences in standard neurological behavior compared to their wild-type (WT) littermates. However, GCPII KO mice were significantly less susceptible to moderate traumatic brain injury (TBI). GCPII gene KO significantly lessened neuronal degeneration and astrocyte damage in the CA2 and CA3 regions of the hippocampus 24 h after moderate TBI. In addition, GCPII gene KO reduced TBI-induced deficits in long-term spatial learning/memory tested in the Morris water maze and motor balance tested via beam walking. Knockout of the GCPII gene is not embryonic lethal and affords histopathological protection with improved long-term behavioral outcomes after TBI, a result that further validates GCPII as a target for drug development consistent with results from studies using GCPII peptidase inhibitors. © 2015 International Society for Neurochemistry.

Nicergoline enhances glutamate re-uptake and protects against brain damage in rat global brain ischemia.

PubMed

Asai, S; Zhao, H; Yamashita, A; Jike, T; Kunimatsu, T; Nagata, T; Kohno, T; Ishikawa, K

1999-11-03

Whereas a 2-3 degrees C decrease in intraischemic brain temperature can be neuroprotective, mild brain hyperthermia significantly worsens outcome. Our previous study suggested that an ischemic injury mechanism which is sensitive to temperature may not actually increase the extracellular glutamate concentration ([Glu](e)) during the intraischemic period, but rather impairs the Glu re-uptake system, which has been suggested to be involved in the reversed uptake of Glu. We speculated that enhancing Glu re-uptake, pharmacologically or hypothermically, may shorten exposure to high [Glu](e) in the postischemic period and thereby decrease its deleterious excitotoxic effect on neuronal cells. In the present study, rats treated with nicergoline (32 mg/kg, i.p.), an ergot alkaloid derivative, showed minimal inhibition of the [Glu](e) elevation which characteristically occurs during the 10-min intraischemic period, while Glu re-uptake was dramatically improved in the postischemic period, when severe transient global ischemia was caused by mild hyperthermia. Moreover, the nicergoline (32 mg/kg, i.p.) treated rats showed reduced cell death morphologically and clearly had a far lower mortality. The present study suggests that the development of therapeutic strategies aimed at inhibition or prevention of the reversed uptake of glutamate release during ischemia, i.e., activation of the glutamate uptake mechanism, is a promising approach to reduce neural damage occurring in response to brain ischemia.

Potentiation of lead-induced cell death in PC12 cells by glutamate: Protection by N-acetylcysteine amide (NACA), a novel thiol antioxidant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Penugonda, Suman; Mare, Suneetha; Lutz, P.

2006-10-15

Oxidative stress has been implicated as an important factor in many neurological diseases. Oxidative toxicity in a number of these conditions is induced by excessive glutamate release and subsequent glutamatergic neuronal stimulation. This, in turn, causes increased generation of reactive oxygen species (ROS), oxidative stress, excitotoxicity, and neuronal damage. Recent studies indicate that the glutamatergic neurotransmitter system is involved in lead-induced neurotoxicity. Therefore, this study aimed to (1) investigate the potential effects of glutamate on lead-induced PC12 cell death and (2) elucidate whether the novel thiol antioxidant N-acetylcysteine amide (NACA) had any protective abilities against such cytotoxicity. Our results suggestmore » that glutamate (1 mM) potentiates lead-induced cytotoxicity by increased generation of ROS, decreased proliferation (MTS), decreased glutathione (GSH) levels, and depletion of cellular adenosine-triphosphate (ATP). Consistent with its ability to decrease ATP levels and induce cell death, lead also increased caspase-3 activity, an effect potentiated by glutamate. Exposure to glutamate and lead elevated the cellular malondialdehyde (MDA) levels and phospholipase-A{sub 2} (PLA{sub 2}) activity and diminished the glutamine synthetase (GS) activity. NACA protected PC12 cells from the cytotoxic effects of glutamate plus lead, as evaluated by MTS assay. NACA reduced the decrease in the cellular ATP levels and restored the intracellular GSH levels. The increased levels of ROS and MDA in glutamate-lead treated cells were significantly decreased by NACA. In conclusion, our data showed that glutamate potentiated the effects of lead-induced PC12 cell death by a mechanism involving mitochondrial dysfunction (ATP depletion) and oxidative stress. NACA had a protective role against the combined toxic effects of glutamate and lead by inhibiting lipid peroxidation and scavenging ROS, thus preserving intracellular GSH.« less

Exploration of the role of reactive oxygen species in glutamate neurotoxicity in rat hippocampal neurones in culture.

PubMed

Vergun, O; Sobolevsky, A I; Yelshansky, M V; Keelan, J; Khodorov, B I; Duchen, M R

2001-02-15

1. Exposure of hippocampal neurones to glutamate at toxic levels is associated with a profound collapse of mitochondrial potential and deregulation of calcium homeostasis. We have explored the contributions of reactive oxygen species (ROS) to these events, considered to represent the first steps in the progression to cell death. 2. Digital imaging techniques were used to monitor changes in cytosolic Ca2+ concentration ([Ca2+]c; fura-2FF) and mitochondrial potential (Deltapsim; rhodamine 123); rates of ROS generation were assessed using hydroethidium (HEt); and membrane currents were measured with the whole-cell configuration of the patch clamp technique. 3. Inhibitors of lipid peroxidation (trolox plus ascorbate) and scavengers of superoxide or hydrogen peroxide (manganese(III) tetrakis(4-benzoic acid) porphyrin (MnTBAP) and TEMPO plus catalase), had only minimal impact on the mitochondrial depolarisation and the sustained increase in [Ca2+]c during and following a 10 min exposure to glutamate. 4. The antioxidants completely suppressed ROS generated by xanthine with xanthine oxidase. No significant increase in ROS production was detected with HEt during a 10 min glutamate exposure. 5. A combination of antioxidants (TEMPO, catalase, trolox and ascorbate) delayed but did not prevent the glutamate-induced mitochondrial depolarisation and the secondary [Ca2+]c rise. However, this was attributable to a transient inhibition of the NMDA current by the antioxidants. 6. Despite their inability to attenuate the glutamate-induced collapse of Deltapsim and destabilisation of [Ca2+]c homeostasis, the antioxidants conferred significant protection in assays of cell viability at 24 h after a 10 min excitotoxic challenge. The data obtained suggest that antioxidants exert their protective effect against glutamate-induced neuronal death through steps downstream of a sustained increase in [Ca2+]c associated with the collapse of Deltapsi(m).

Nicotinamide riboside, a form of vitamin B3, protects against excitotoxicity-induced axonal degeneration.

PubMed

Vaur, Pauline; Brugg, Bernard; Mericskay, Mathias; Li, Zhenlin; Schmidt, Mark S; Vivien, Denis; Orset, Cyrille; Jacotot, Etienne; Brenner, Charles; Duplus, Eric

2017-12-01

NAD + depletion is a common phenomenon in neurodegenerative pathologies. Excitotoxicity occurs in multiple neurologic disorders and NAD + was shown to prevent neuronal degeneration in this process through mechanisms that remained to be determined. The activity of nicotinamide riboside (NR) in neuroprotective models and the recent description of extracellular conversion of NAD + to NR prompted us to probe the effects of NAD + and NR in protection against excitotoxicity. Here, we show that intracortical administration of NR but not NAD + reduces brain damage induced by NMDA injection. Using cortical neurons, we found that provision of extracellular NR delays NMDA-induced axonal degeneration (AxD) much more strongly than extracellular NAD + Moreover, the stronger effect of NR compared to NAD + depends of axonal stress since in AxD induced by pharmacological inhibition of nicotinamide salvage, both NAD + and NR prevent neuronal death and AxD in a manner that depends on internalization of NR. Taken together, our findings demonstrate that NR is a better neuroprotective agent than NAD + in excitotoxicity-induced AxD and that axonal protection involves defending intracellular NAD + homeostasis.-Vaur, P., Brugg, B., Mericskay, M., Li, Z., Schmidt, M. S., Vivien, D., Orset, C., Jacotot, E., Brenner, C., Duplus, E. Nicotinamide riboside, a form of vitamin B 3 , protects against excitotoxicity-induced axonal degeneration. © FASEB.

Glutamate mediates cell death and increases the Bax to Bcl-2 ratio in a differentiated neuronal cell line.

PubMed

Schelman, William R; Andres, Robert D; Sipe, Kimberly J; Kang, Evan; Weyhenmeyer, James A

2004-09-28

control. Taken together, these findings provide additional evidence for the reciprocal regulation of Bcl-2 and Bax expression by glutamate and suggest that neuronal excitotoxicity may, in part, result from the inverse regulation of these proteins.

Involvement of metabotropic glutamate receptors in taurine release in the adult and developing mouse hippocampus.

PubMed

Saransaari, P; Oja, S S

1999-01-01

The inhibitory amino acid taurine has been held to function as an osmoregulator and modulator of neural activity, being particularly important in the immature brain. Ionotropic glutamate receptor agonists are known markedly to potentiate taurine release. The effects of different metabotropic glutamate receptor (mGluR) agonists and antagonists on the basal and K(+)-stimulated release of [3H]taurine from hippocampal slices from 3-month-old (adult) and 7-day-old mice were now investigated using a superfusion system. Of group I metabotropic glutamate receptor agonists, quisqualate potentiated basal taurine release in both age groups, more markedly in the immature hippocampus. This action was not antagonized by the specific antagonists of group I but by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and 6-nitro-7-sulphamoylbenzo[f]quinoxaline-2,3-dione (NBQX), which would suggest an involvement of ionotropic glutamate receptors. (S)-3,5-dihydroxyphenylglycine (DHPG) potentiated the basal release by a receptor-mediated mechanism in the immature hippocampus. The group II agonist (2S, 2'R, 3'R)-2-(2',3'-dicarboxycyclopropyl)glycine (DCG IV) markedly potentiated basal taurine release at both ages. These effects were antagonized by dizocilpine, indicating again the participation of ionotropic receptors. Group III agonists slightly potentiated basal taurine release, as did several antagonists of the three metabotropic receptor groups. Potassium-stimulated (50 mM K+) taurine release was generally significantly reduced by mGluR agents, mainly by group I and II compounds. This may be harmful to neurons in hyperexcitatory states. On the other hand, the potentiation by mGluRs of basal taurine release, particularly in the immature hippocampus, together with the earlier demonstrated pronounced enhancement by activation of ionotropic glutamate receptors, may protect neurons against excitotoxicity.

Dopamine neuron dependent behaviors mediated by glutamate cotransmission

PubMed Central

Mingote, Susana; Chuhma, Nao; Kalmbach, Abigail; Thomsen, Gretchen M; Wang, Yvonne; Mihali, Andra; Sferrazza, Caroline; Zucker-Scharff, Ilana; Siena, Anna-Claire; Welch, Martha G; Lizardi-Ortiz, José; Sulzer, David; Moore, Holly; Gaisler-Salomon, Inna; Rayport, Stephen

2017-01-01

Dopamine neurons in the ventral tegmental area use glutamate as a cotransmitter. To elucidate the behavioral role of the cotransmission, we targeted the glutamate-recycling enzyme glutaminase (gene Gls1). In mice with a dopamine transporter (Slc6a3)-driven conditional heterozygous (cHET) reduction of Gls1 in their dopamine neurons, dopamine neuron survival and transmission were unaffected, while glutamate cotransmission at phasic firing frequencies was reduced, enabling a selective focus on the cotransmission. The mice showed normal emotional and motor behaviors, and an unaffected response to acute amphetamine. Strikingly, amphetamine sensitization was reduced and latent inhibition potentiated. These behavioral effects, also seen in global GLS1 HETs with a schizophrenia resilience phenotype, were not seen in mice with an Emx1-driven forebrain reduction affecting most brain glutamatergic neurons. Thus, a reduction in dopamine neuron glutamate cotransmission appears to mediate significant components of the GLS1 HET schizophrenia resilience phenotype, and glutamate cotransmission appears to be important in attribution of motivational salience. DOI: http://dx.doi.org/10.7554/eLife.27566.001 PMID:28703706

Regulation of Mitochondrial Function and Glutamatergic System Are the Target of Guanosine Effect in Traumatic Brain Injury.

PubMed

Dobrachinski, Fernando; da Rosa Gerbatin, Rogério; Sartori, Gláubia; Ferreira Marques, Naiani; Zemolin, Ana Paula; Almeida Silva, Luiz Fernando; Franco, Jeferson Luis; Freire Royes, Luiz Fernando; Rechia Fighera, Michele; Antunes Soares, Félix Alexandre

2017-04-01

Traumatic brain injury (TBI) is a highly complex multi-factorial disorder. Experimental trauma involves primary and secondary injury cascades that underlie delayed neuronal dysfunction and death. Mitochondrial dysfunction and glutamatergic excitotoxicity are the hallmark mechanisms of damage. Accordingly, a successful pharmacological intervention requires a multi-faceted approach. Guanosine (GUO) is known for its neuromodulator effects in various models of brain pathology, specifically those that involve the glutamatergic system. The aim of the study was to investigate the GUO effects against mitochondrial damage in hippocampus and cortex of rats subjected to TBI, as well as the relationship of this effect with the glutamatergic system. Adult male Wistar rats were subjected to a unilateral moderate fluid percussion brain injury (FPI) and treated 15 min later with GUO (7.5 mg/kg) or vehicle (saline 0.9%). Analyses were performed in hippocampus and cortex 3 h post-trauma and revealed significant mitochondrial dysfunction, characterized by a disrupted membrane potential, unbalanced redox system, decreased mitochondrial viability, and complex I inhibition. Further, disruption of Ca 2+ homeostasis and increased mitochondrial swelling was also noted. Our results showed that mitochondrial dysfunction contributed to decreased glutamate uptake and levels of glial glutamate transporters (glutamate transporter 1 and glutamate aspartate transporter), which leads to excitotoxicity. GUO treatment ameliorated mitochondrial damage and glutamatergic dyshomeostasis. Thus, GUO might provide a new efficacious strategy for the treatment acute physiological alterations secondary to TBI.

Protective effect of methanol extract of Uncaria rhynchophylla against excitotoxicity induced by N-methyl-D-aspartate in rat hippocampus.

PubMed

Lee, Jongseok; Son, Dongwook; Lee, Pyeongjae; Kim, Dae-Keun; Shin, Min-Chul; Jang, Mi-Hyeon; Kim, Chang-Ju; Kim, Yong-Sik; Kim, Sun-Yeou; Kim, Hocheol

2003-05-01

Uncaria rhynchophylla is a medicinal herb used for convulsive disorders in Oriental medicine. In this study, the effect of the methanol extract of Uncaria rhynchophylla against N-methyl-D-aspartate (NMDA)-induced excitotoxicity was investigated. Pretreatment with the extract of Uncaria rhynchopylla reduced the degree of neuronal damage induced by NMDA exposure in cultured hippocampal slices. In the patch clamp study, Uncaria rhynchophylla significantly inhibited NMDA receptor-activated ion current in acutely dissociated hippocampal CA1 neurons. These results indicate that Uncaria rhynchophylla offers protection against NMDA-induced neuronal injury and inhibitory action on NMDA receptor-mediated ion current may be a mechanism behind the neuroprotective effect of Uncaria rhynchophylla.

A New Transgenic Mouse Model for Studying the Neurotoxicity of Spermine Oxidase Dosage in the Response to Excitotoxic Injury

PubMed Central

Cervelli, Manuela; Bellavia, Gabriella; D'Amelio, Marcello; Cavallucci, Virve; Moreno, Sandra; Berger, Joachim; Nardacci, Roberta; Marcoli, Manuela; Maura, Guido; Piacentini, Mauro; Amendola, Roberto; Cecconi, Francesco; Mariottini, Paolo

2013-01-01

Spermine oxidase is a FAD-containing enzyme involved in polyamines catabolism, selectively oxidizing spermine to produce H2O2, spermidine, and 3-aminopropanal. Spermine oxidase is highly expressed in the mouse brain and plays a key role in regulating the levels of spermine, which is involved in protein synthesis, cell division and cell growth. Spermine is normally released by neurons at synaptic sites where it exerts a neuromodulatory function, by specifically interacting with different types of ion channels, and with ionotropic glutamate receptors. In order to get an insight into the neurobiological roles of spermine oxidase and spermine, we have deregulated spermine oxidase gene expression producing and characterizing the transgenic mouse model JoSMOrec, conditionally overexpressing the enzyme in the neocortex. We have investigated the effects of spermine oxidase overexpression in the mouse neocortex by transcript accumulation, immunohistochemical analysis, enzymatic assays and polyamine content in young and aged animals. Transgenic JoSMOrec mice showed in the neocortex a higher H2O2 production in respect to Wild-Type controls, indicating an increase of oxidative stress due to SMO overexpression. Moreover, the response of transgenic mice to excitotoxic brain injury, induced by kainic acid injection, was evaluated by analysing the behavioural phenotype, the immunodistribution of neural cell populations, and the ultrastructural features of neocortical neurons. Spermine oxidase overexpression and the consequently altered polyamine levels in the neocortex affects the cytoarchitecture in the adult and aging brain, as well as after neurotoxic insult. It resulted that the transgenic JoSMOrec mouse line is more sensitive to KA than Wild-Type mice, indicating an important role of spermine oxidase during excitotoxicity. These results provide novel evidences of the complex and critical functions carried out by spermine oxidase and spermine in the mammalian brain. PMID

Methylglyoxal Induces Changes in the Glyoxalase System and Impairs Glutamate Uptake Activity in Primary Astrocytes

PubMed Central

Galland, Fabiana; Lirio, Franciane; de Souza, Daniela Fraga; Da Ré, Carollina; Pacheco, Rafaela Ferreira; Vizuete, Adriana Fernanda; Quincozes-Santos, André; Leite, Marina Concli; Gonçalves, Carlos-Alberto

2017-01-01

The impairment of astrocyte functions is associated with diabetes mellitus and other neurodegenerative diseases. Astrocytes have been proposed to be essential cells for neuroprotection against elevated levels of methylglyoxal (MG), a highly reactive aldehyde derived from the glycolytic pathway. MG exposure impairs primary astrocyte viability, as evaluated by different assays, and these cells respond to MG elevation by increasing glyoxalase 1 activity and glutathione levels, which improve cell viability and survival. However, C6 glioma cells have shown strong signs of resistance against MG, without significant changes in the glyoxalase system. Results for aminoguanidine coincubation support the idea that MG toxicity is mediated by glycation. We found a significant decrease in glutamate uptake by astrocytes, without changes in the expression of the major transporters. Carbenoxolone, a nonspecific inhibitor of gap junctions, prevented the cytotoxicity induced by MG in astrocyte cultures. Thus, our data reinforce the idea that astrocyte viability depends on gap junctions and that the impairment induced by MG involves glutamate excitotoxicity. The astrocyte susceptibility to MG emphasizes the importance of this compound in neurodegenerative diseases, where the neuronal damage induced by MG may be aggravated by the commitment of the cells charged with MG clearance. PMID:28685011

Methylglyoxal Induces Changes in the Glyoxalase System and Impairs Glutamate Uptake Activity in Primary Astrocytes.

PubMed

Hansen, Fernanda; Galland, Fabiana; Lirio, Franciane; de Souza, Daniela Fraga; Da Ré, Carollina; Pacheco, Rafaela Ferreira; Vizuete, Adriana Fernanda; Quincozes-Santos, André; Leite, Marina Concli; Gonçalves, Carlos-Alberto

2017-01-01

The impairment of astrocyte functions is associated with diabetes mellitus and other neurodegenerative diseases. Astrocytes have been proposed to be essential cells for neuroprotection against elevated levels of methylglyoxal (MG), a highly reactive aldehyde derived from the glycolytic pathway. MG exposure impairs primary astrocyte viability, as evaluated by different assays, and these cells respond to MG elevation by increasing glyoxalase 1 activity and glutathione levels, which improve cell viability and survival. However, C6 glioma cells have shown strong signs of resistance against MG, without significant changes in the glyoxalase system. Results for aminoguanidine coincubation support the idea that MG toxicity is mediated by glycation. We found a significant decrease in glutamate uptake by astrocytes, without changes in the expression of the major transporters. Carbenoxolone, a nonspecific inhibitor of gap junctions, prevented the cytotoxicity induced by MG in astrocyte cultures. Thus, our data reinforce the idea that astrocyte viability depends on gap junctions and that the impairment induced by MG involves glutamate excitotoxicity. The astrocyte susceptibility to MG emphasizes the importance of this compound in neurodegenerative diseases, where the neuronal damage induced by MG may be aggravated by the commitment of the cells charged with MG clearance.

The ratio of N-acetyl aspartate to glutamate correlates with disease duration of amyotrophic lateral sclerosis.

PubMed

Sako, Wataru; Abe, Takashi; Izumi, Yuishin; Harada, Masafumi; Kaji, Ryuji

2016-05-01

Glutamate (Glu)-induced excitotoxicity has been implicated in the neuronal loss of amyotrophic lateral sclerosis. To test the hypothesis that Glu in the primary motor cortex contributes to disease severity and/or duration, the Glu level was investigated using MR spectroscopy. Seventeen patients with amyotrophic lateral sclerosis were diagnosed according to the El Escorial criteria for suspected, possible, probable or definite amyotrophic lateral sclerosis, and enrolled in this cross-sectional study. We measured metabolite concentrations, including N-acetyl aspartate (NAA), creatine, choline, inositol, Glu and glutamine, and performed partial correlation between each metabolite concentration or NAA/Glu ratio and disease severity or duration using age as a covariate. Considering our hypothesis that Glu is associated with neuronal cell death in amyotrophic lateral sclerosis, we investigated the ratio of NAA to Glu, and found a significant correlation between NAA/Glu and disease duration (r=-0.574, p=0.02). The "suspected" amyotrophic lateral sclerosis patients showed the same tendency as possible, probable and definite amyotrophic lateral sclerosis patients in regard to correlation of NAA/Glu ratio with disease duration. The other metabolites showed no significant correlation. Our findings suggested that glutamatergic neurons are less vulnerable compared to other neurons and this may be because inhibitory receptors are mainly located presynaptically, which supports the notion of Glu-induced excitotoxicity. Copyright © 2015 Elsevier Ltd. All rights reserved.

Glutamate as a neurotransmitter in the brain: review of physiology and pathology.

PubMed

Meldrum, B S

2000-04-01

Glutamate is the principal excitatory neurotransmitter in brain. Our knowledge of the glutamatergic synapse has advanced enormously in the last 10 years, primarily through application of molecular biological techniques to the study of glutamate receptors and transporters. There are three families of ionotropic receptors with intrinsic cation permeable channels [N-methyl-D-aspartate (NMDA), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and kainate]. There are three groups of metabotropic, G protein-coupled glutamate receptors (mGluR) that modify neuronal and glial excitability through G protein subunits acting on membrane ion channels and second messengers such as diacylglycerol and cAMP. There are also two glial glutamate transporters and three neuronal transporters in the brain. Glutamate is the most abundant amino acid in the diet. There is no evidence for brain damage in humans resulting from dietary glutamate. A kainate analog, domoate, is sometimes ingested accidentally in blue mussels; this potent toxin causes limbic seizures, which can lead to hippocampal and related pathology and amnesia. Endogenous glutamate, by activating NMDA, AMPA or mGluR1 receptors, may contribute to the brain damage occurring acutely after status epilepticus, cerebral ischemia or traumatic brain injury. It may also contribute to chronic neurodegeneration in such disorders as amyotrophic lateral sclerosis and Huntington's chorea. In animal models of cerebral ischemia and traumatic brain injury, NMDA and AMPA receptor antagonists protect against acute brain damage and delayed behavioral deficits. Such compounds are undergoing testing in humans, but therapeutic efficacy has yet to be established. Other clinical conditions that may respond to drugs acting on glutamatergic transmission include epilepsy, amnesia, anxiety, hyperalgesia and psychosis.

Multimodal use of calcitonin gene-related peptide and substance P in itch and acute pain uncovered by the elimination of vesicular glutamate transporter 2 from transient receptor potential cation channel subfamily V member 1 neurons.

PubMed

Rogoz, Katarzyna; Andersen, Helena H; Lagerström, Malin C; Kullander, Klas

2014-10-15

Primary afferents are known to use glutamate as their principal fast neurotransmitter. However, it has become increasingly clear that peptides have an influential role in both mediating and modulating sensory transmission. Here we describe the transmission accounting for different acute pain states and itch transmitted via the transient receptor potential cation channel subfamily V member 1 (TRPV1) population by either ablating Trpv1-Cre-expressing neurons or inducing vesicular glutamate transporter 2 (VGLUT2) deficiency in Trpv1-Cre-expressing neurons. Furthermore, by pharmacological inhibition of substance P or calcitonin gene-related peptide (CGRP) signaling in Vglut2-deficient mice, we evaluated the contribution of substance P or CGRP to these sensory modulations, with or without the presence of VGLUT2-mediated glutamatergic transmission in Trpv1-Cre neurons. This examination, together with c-Fos analyses, showed that glutamate via VGLUT2 in the Trpv1-Cre population together with substance P mediate acute cold pain, whereas glutamate together with CGRP mediate noxious heat. Moreover, we demonstrate that glutamate together with both substance P and CGRP mediate tissue-injury associated pain. We further show that itch, regulated by the VGLUT2-mediated transmission via the Trpv1-Cre population, depends on CGRP and gastrin-releasing peptide receptor (GRPR) transmission because pharmacological blockade of the CGRP or GRPR pathway, or genetic ablation of Grpr, led to a drastically attenuated itch. Our study reveals how different neurotransmitters combined can cooperate with each other to transmit or regulate various acute sensations, including itch. Copyright © 2014 the authors 0270-6474/14/3414055-14$15.00/0.

S-Nitrosylation and uncompetitive/fast off-rate (UFO) drug therapy in neurodegenerative disorders of protein misfolding.

PubMed

Nakamura, T; Lipton, S A

2007-07-01

Although activation of glutamate receptors is essential for normal brain function, excessive activity leads to a form of neurotoxicity known as excitotoxicity. Key mediators of excitotoxic damage include overactivation of N-methyl-D-aspartate (NMDA) receptors, resulting in excessive Ca(2+) influx with production of free radicals and other injurious pathways. Overproduction of free radical nitric oxide (NO) contributes to acute and chronic neurodegenerative disorders. NO can react with cysteine thiol groups to form S-nitrosothiols and thus change protein function. S-nitrosylation can result in neuroprotective or neurodestructive consequences depending on the protein involved. Many neurodegenerative diseases manifest conformational changes in proteins that result in misfolding and aggregation. Our recent studies have linked nitrosative stress to protein misfolding and neuronal cell death. Molecular chaperones - such as protein-disulfide isomerase, glucose-regulated protein 78, and heat-shock proteins - can provide neuroprotection by facilitating proper protein folding. Here, we review the effect of S-nitrosylation on protein function under excitotoxic conditions, and present evidence that NO contributes to degenerative conditions by S-nitrosylating-specific chaperones that would otherwise prevent accumulation of misfolded proteins and neuronal cell death. In contrast, we also review therapeutics that can abrogate excitotoxic damage by preventing excessive NMDA receptor activity, in part via S-nitrosylation of this receptor to curtail excessive activity.

L-phenylalanyl-L-glutamate-stimulated, chloride-dependent glutamate binding represents glutamate sequestration mediated by an exchange system.

PubMed

Kessler, M; Petersen, G; Vu, H M; Baudry, M; Lynch, G

1987-04-01

Stimulation of glutamate binding by the dipeptide L-phenylalanyl-L-glutamate (Phe-Glu) was inhibited by the peptidase inhibitor bestatin, suggesting that the stimulation was caused by glutamate liberated from the dipeptide and not by the dipeptide itself. It further suggests that this form of glutamate binding should be reinterpreted as glutamate sequestration and that stimulation of binding both by dipeptides and after preincubation with high concentrations of glutamate is likely to be due to counterflow accumulation. Several other criteria indicate that most of glutamate binding stimulated by chloride represents glutamate sequestration: Binding is reduced when the osmolarity of the incubation medium is increased, when membranes incubated with [3H]glutamate are lysed before filtration, and when membranes are made permeable by transient exposure to saponin. Moreover, dissociation of bound glutamate after a 100-fold dilution of the incubation medium is accelerated about 50 times by the addition of glutamate to the dilution medium. This result would be anomalous if glutamate were bound to a receptor site; it suggests instead that glutamate is transported in and out of membrane vesicles by a transport system that preferentially mediates exchange between internal and external glutamate. Glutamate binding contains a component of glutamate sequestration even when measured in the absence of chloride. Sequestration is adequately abolished only after treating membranes with detergents; even extensive lysis, sonication, and freezing/thawing may be insufficient.

Excitotoxicity-induced prostaglandin D2 production induces sustained microglial activation and delayed neuronal death.

PubMed

Iwasa, Kensuke; Yamamoto, Shinji; Yagishita, Sosuke; Maruyama, Kei; Yoshikawa, Keisuke

2017-04-01

Excitotoxicity is the pivotal mechanism of neuronal death. Prostaglandins (PGs) produced during excitotoxicity play important roles in neurodegenerative conditions. Previously, we demonstrated that initial burst productions of PGD 2 , PGE 2 , and PGF 2α are produced by cyclooxygenase-2 (COX-2) in the hippocampus following a single systemic kainic acid (KA) administration. In addition, we showed that blocking of all PG productions ameliorated hippocampal delayed neuronal death at 30 days after KA administration. To investigate the role of individual PGs in the delayed neuronal death, we performed intracerebroventricular injection of PGD 2 , PGE 2 , or PGF 2α in rats whose hippocampal PG productions were entirely blocked by pretreatment of NS398, a COX-2 selective inhibitor. Administration of PGD 2 and PGF 2α had a latent contribution to the delayed neuronal death, sustained over 30 days after a single KA treatment. Furthermore, PGD 2 enhanced microglial activation, which may be involved in the delayed neuronal death in the hippocampus. These findings suggest that excitotoxic delayed neuronal death is mediated through microglia activated by PGD 2 . Copyright © 2017 by the American Society for Biochemistry and Molecular Biology, Inc.

Neurotransmitters and pathophysiology of stroke: evidence for the release of glutamate and other transmitters/mediators in animals and humans.

PubMed

Dávalos, A; Shuaib, A; Wahlgren, N G

2000-11-01

a lag of approximately 4 hours before the concentration of glutamate in the blood rises. Therefore, it may be possible to detect the ongoing release of glutamate into the brain as a result of cerebral ischemia, which may aid in the selection of the most appropriate treatment. The results of microdialysis and plasma EAA analyses suggest that excitotoxic damage can occur over many hours. This implies that effective neuroprotectant strategies could provide clinical benefits over similarly prolonged periods.

Effects of Cannabidiol and Hypothermia on Short-Term Brain Damage in New-Born Piglets after Acute Hypoxia-Ischemia

PubMed Central

Lafuente, Hector; Pazos, Maria R.; Alvarez, Antonia; Mohammed, Nagat; Santos, Martín; Arizti, Maialen; Alvarez, Francisco J.; Martinez-Orgado, Jose A.

2016-01-01

Hypothermia is a standard treatment for neonatal encephalopathy, but nearly 50% of treated infants have adverse outcomes. Pharmacological therapies can act through complementary mechanisms with hypothermia improving neuroprotection. Cannabidiol could be a good candidate. Our aim was to test whether immediate treatment with cannabidiol and hypothermia act through complementary brain pathways in hypoxic-ischemic newborn piglets. Hypoxic-ischemic animals were randomly divided into four groups receiving 30 min after the insult: (1) normothermia and vehicle administration; (2) normothermia and cannabidiol administration; (3) hypothermia and vehicle administration; and (4) hypothermia and cannabidiol administration. Six hours after treatment, brains were processed to quantify the number of damaged neurons by Nissl staining. Proton nuclear magnetic resonance spectra were obtained and analyzed for lactate, N-acetyl-aspartate and glutamate. Metabolite ratios were calculated to assess neuronal damage (lactate/N-acetyl-aspartate) and excitotoxicity (glutamate/Nacetyl-aspartate). Western blot studies were performed to quantify protein nitrosylation (oxidative stress), content of caspase-3 (apoptosis) and TNFα (inflammation). Individually, the hypothermia and the cannabidiol treatments reduced the glutamate/Nacetyl-aspartate ratio, as well as TNFα and oxidized protein levels in newborn piglets subjected to hypoxic-ischemic insult. Also, both therapies reduced the number of necrotic neurons and prevented an increase in lactate/N-acetyl-aspartate ratio. The combined effect of hypothermia and cannabidiol on excitotoxicity, inflammation and oxidative stress, and on cell damage, was greater than either hypothermia or cannabidiol alone. The present study demonstrated that cannabidiol and hypothermia act complementarily and show additive effects on the main factors leading to hypoxic-ischemic brain damage if applied shortly after the insult. PMID:27462203

Pre- and postsynaptic type-1 cannabinoid receptors control the alterations of glutamate transmission in experimental autoimmune encephalomyelitis.

PubMed

Musella, Alessandra; Sepman, Helena; Mandolesi, Georgia; Gentile, Antonietta; Fresegna, Diego; Haji, Nabila; Conrad, Andrea; Lutz, Beat; Maccarrone, Mauro; Centonze, Diego

2014-04-01

Type-1 cannabinoid receptors (CB1R) are important regulators of the neurodegenerative damage in multiple sclerosis (MS) and in experimental autoimmune encephalomyelitis (EAE). In GABAergic striatal neurons, CB1R stimulation exerts protective effects by limiting inflammation-induced potentiation of glutamate-mediated spontaneous excitatory postsynaptic currents (sEPSCs). Here we show that CB1R located on GABAergic or on glutamatergic neurons are differentially involved in the pre- and postsynaptic alterations of sEPSCs caused by EAE in the striatum. After induction of EAE, mice selectively lacking CB1R on GABAergic neurons (GABA-CB1R-KO) showed exacerbated alterations of sEPSC duration in GABAergic medium spiny neurons (MSN). On the other hand, EAE-induced alterations of corticostriatal sEPSC frequency were exacerbated only in mice lacking CB1R on glutamatergic neurons (Glu-CB1R-KO), indicating that this subset of receptors controls the effects of inflammation on glutamate release. While EAE severity was enhanced in whole CB1R-KO mice, GABA-CB1R-KO and Glu-CB1R-KO mice had similar motor deficits as the respective wild-type (WT) counterparts. Our results provide further evidence that CB1R are involved in EAE pathophysiology, and suggest that both pre- and postsynaptic alterations of glutamate transmission are important to drive excitotoxic neurodegeneration typical of this disorder. Copyright © 2014 Elsevier Ltd. All rights reserved.

Dual regulation of Ca2+-dependent glutamate release from astrocytes: vesicular glutamate transporters and cytosolic glutamate levels.

PubMed

Ni, Yingchun; Parpura, Vladimir

2009-09-01

Vesicular glutamate transporters (VGLUTs) are responsible for vesicular glutamate storage and exocytotic glutamate release in neurons and astrocytes. Here, we selectively and efficiently overexpressed individual VGLUT proteins (VGLUT1, 2, or 3) in solitary astrocytes and studied their effects on mechanical stimulation-induced Ca2+-dependent glutamate release. Neither VGLUT1 nor VGLUT2 overexpression changed the amount of glutamate release, whereas overexpression of VGLUT3 significantly enhanced Ca2+-dependent glutamate release from astrocytes. None of the VGLUT overexpression affected mechanically induced intracellular Ca2+ increase. Inhibition of glutamine synthetase activity by L-methionine sulfoximine in astrocytes, which leads to increased cytosolic glutamate concentration, greatly increased their mechanically induced Ca2+-dependent glutamate release, without affecting intracellular Ca2+ dynamics. Taken together, these data indicate that both VGLUT3 and the cytosolic concentration of glutamate are key limiting factors in regulating the Ca2+-dependent release of glutamate from astrocytes.

Nicergoline enhances glutamate uptake via glutamate transporters in rat cortical synaptosomes.

PubMed

Nishida, Atsushi; Iwata, Hiroshi; Kudo, Yukitsuka; Kobayashi, Tsutomu; Matsuoka, Yuzo; Kanai, Yoshikatsu; Endou, Hitoshi

2004-06-01

To elucidate the mechanisms of neuroprotective action of nicergoline, we examined its effect on glutamate transport in rat cortical synaptosomes and cloned glutamate transporters. In synaptosomes, nicergoline enhanced the glutamate uptake at 1-10 microM in standard medium and suppressed the increase of extracellular glutamate by reversed transport in low Na(+) medium. Apparent increase of extracellular glutamate concentration by dihydrokinate, an inhibitor of glial glutamate transporter GLT-1, was antagonized by nicergoline. In Xenopus oocytes expressing mouse neuronal glutamate transporter (mEAAC1), the glutamate-induced inward current was enhanced by nicergoline. These results suggest that nicergoline reduces the extracellular glutamate concentration through its effect on glutamate transporters.

Improved Synthesis of Caged Glutamate and Caging Each Functional Group.

PubMed

Guruge, Charitha; Ouedraogo, Yannick P; Comitz, Richard L; Ma, Jingxuan; Losonczy, Attila; Nesnas, Nasri

2018-05-25

Glutamate is an excitatory neurotransmitter that controls numerous pathways in the brain. Neuroscientists make use of photoremovable protecting groups, also known as cages, to release glutamate with precise spatial and temporal control. Various cage designs have been developed and among the most effective has been the nitroindolinyl caging of glutamate. We, hereby, report an improved synthesis of one of the current leading molecules of caged glutamate, 4-carboxymethoxy-5,7-dinitroindolinyl glutamate (CDNI-Glu), which possesses efficiencies with the highest reported quantum yield of at least 0.5. We present the shortest route, to date, for the synthesis of CDNI-Glu in 4 steps, with a total reaction time of 40 h and an overall yield of 20%. We also caged glutamate at the other two functional groups, thereby, introducing two new cage designs: α-CDNI-Glu and N-CDNI-Glu. We included a study of their photocleavage properties using UV-vis, NMR, as well as a physiology experiment of a two-photon uncaging of CDNI-Glu in acute hippocampal brain slices. The newly introduced cage designs may have the potential to minimize the interference that CDNI-Glu has with the GABA A receptor. We are broadly disseminating this to enable neuroscientists to use these photoactivatable tools.

Arctigenin reduces neuronal responses in the somatosensory cortex via the inhibition of non-NMDA glutamate receptors.

PubMed

Borbély, Sándor; Jócsák, Gergely; Moldován, Kinga; Sedlák, Éva; Preininger, Éva; Boldizsár, Imre; Tóth, Attila; Atlason, Palmi T; Molnár, Elek; Világi, Ildikó

2016-07-01

Lignans are biologically active phenolic compounds related to lignin, produced in different plants. Arctigenin, a dibenzylbutyrolactone-type lignan, has been used as a neuroprotective agent for the treatment of encephalitis. Previous studies of cultured rat cerebral cortical neurones raised the possibility that arctigenin inhibits kainate-induced excitotoxicity. The aims of the present study were: 1) to analyse the effect of arctigenin on normal synaptic activity in ex vivo brain slices, 2) to determine its receptor binding properties and test the effect of arctigenin on AMPA/kainate receptor activation and 3) to establish its effects on neuronal activity in vivo. Arctigenin inhibited glutamatergic transmission and reduced the evoked field responses. The inhibitory effect of arctigenin on the evoked field responses proved to be substantially dose dependent. Our results indicate that arctigenin exerts its effects under physiological conditions and not only on hyper-excited neurons. Furthermore, arctigenin can cross the blood-brain barrier and in the brain it interacts with kainate sensitive ionotropic glutamate receptors. These results indicate that arctigenin is a potentially useful new pharmacological tool for the inhibition of glutamate-evoked responses in the central nervous system in vivo. Copyright © 2016 Elsevier Ltd. All rights reserved.

Glutamate/glutamine concentrations in the dorsal anterior cingulate vary with Post-Traumatic Stress Disorder symptoms.

PubMed

Harnett, Nathaniel G; Wood, Kimberly H; Ference, Edward W; Reid, Meredith A; Lahti, Adrienne C; Knight, Amy J; Knight, David C

2017-08-01

Trauma and stress-related disorders (e.g., Acute Stress Disorder; ASD and Post-Traumatic Stress Disorder; PTSD) that develop following a traumatic event are characterized by cognitive-affective dysfunction. The cognitive and affective functions disrupted by stress disorder are mediated, in part, by glutamatergic neural systems. However, it remains unclear whether neural glutamate concentrations, measured acutely following trauma, vary with ASD symptoms and/or future PTSD symptom expression. Therefore, the current study utilized proton magnetic resonance spectroscopy ( 1 H-MRS) to investigate glutamate/glutamine (Glx) concentrations within the dorsal anterior cingulate cortex (ACC) of recently (i.e., within one month) traumatized individuals and non-traumatized controls. Although Glx concentrations within dorsal ACC did not differ between recently traumatized and non-traumatized control groups, a positive linear relationship was observed between Glx concentrations and current stress disorder symptoms in traumatized individuals. Further, Glx concentrations showed a positive linear relationship with future stress disorder symptoms (i.e., assessed 3 months post-trauma). The present results suggest glutamate concentrations may play a role in both acute and future post-traumatic stress symptoms following a traumatic experience. The current results expand our understanding of the neurobiology of stress disorder and suggest glutamate within the dorsal ACC plays an important role in cognitive-affective dysfunction following a traumatic experience. Copyright © 2017 Elsevier Ltd. All rights reserved.

Contribution of Cystine-Glutamate Antiporters to the Psychotomimetic Effects of Phencyclidine

PubMed Central

Baker, David. A.; Madayag, Aric; Kristiansen, Lars V.; Meador-Woodruff, James H.; Haroutunian, Vahram; Raju, Ilangovan

2014-01-01

Altered glutamate signaling contributes to a myriad of neural disorders, including schizophrenia. While synaptic levels are intensely studied, nonvesicular release mechanisms, including cystine-glutamate exchange, maintain high steady-state glutamate levels in the extrasynaptic space. The existence of extrasynaptic receptors, including metabotropic group II glutamate receptors (mGluR), pose nonvesicular release mechanisms as unrecognized targets capable of contributing to pathological glutamate signaling. We tested the hypothesis that activation of cystine-glutamate antiporters using the cysteine prodrug N-acetylcysteine would blunt psychotomimetic effects in the rodent phencyclidine (PCP) model of schizophrenia. First, we demonstrate that PCP elevates extracellular glutamate in the prefrontal cortex; an effect that is blocked by N-acetylcysteine pretreatment. To determine the relevance of the above finding, we assessed social interaction and found that N-acetylcysteine reverses social withdrawal produced by repeated PCP. In a separate paradigm, acute PCP resulted in working memory deficits assessed using a discrete trial T-maze task, and this effect was also reversed by N-acetylcysteine pretreatment. The capacity of N-acetylcysteine to restore working memory was blocked by infusion of the cystine-glutamate antiporter inhibitor (S)-4-carboxyphenylglycine into the prefrontal cortex or systemic administration of the group II mGluR antagonist LY341495 indicating that the effects of N-acetylcysteine requires cystine-glutamate exchange and group II mGluR activation. Lastly, protein levels from post mortem tissue obtained from schizophrenic patients revealed significant changes in the level of xCT, the active subunit for cystine-glutamate exchange, in the dorsolateral prefrontal cortex. These data advance cystine-glutamate antiporters as novel targets capable of reversing the psychotomimetic effects of PCP. PMID:17728701

Poly-arginine and arginine-rich peptides are neuroprotective in stroke models

PubMed Central

Meloni, Bruno P; Brookes, Laura M; Clark, Vince W; Cross, Jane L; Edwards, Adam B; Anderton, Ryan S; Hopkins, Richard M; Hoffmann, Katrin; Knuckey, Neville W

2015-01-01

Using cortical neuronal cultures and glutamic acid excitotoxicity and oxygen-glucose deprivation (OGD) stroke models, we demonstrated that poly-arginine and arginine-rich cell-penetrating peptides (CPPs), are highly neuroprotective, with efficacy increasing with increasing arginine content, have the capacity to reduce glutamic acid-induced neuronal calcium influx and require heparan sulfate preotoglycan-mediated endocytosis to induce a neuroprotective effect. Furthermore, neuroprotection could be induced with immediate peptide treatment or treatment up to 2 to 4 hours before glutamic acid excitotoxicity or OGD, and with poly-arginine-9 (R9) when administered intravenously after stroke onset in a rat model. In contrast, the JNKI-1 peptide when fused to the (non-arginine) kFGF CPP, which does not rely on endocytosis for uptake, was not neuroprotective in the glutamic acid model; the kFGF peptide was also ineffective. Similarly, positively charged poly-lysine-10 (K10) and R9 fused to the negatively charged poly-glutamic acid-9 (E9) peptide (R9/E9) displayed minimal neuroprotection after excitotoxicity. These results indicate that peptide positive charge and arginine residues are critical for neuroprotection, and have led us to hypothesize that peptide-induced endocytic internalization of ion channels is a potential mechanism of action. The findings also question the mode of action of different neuroprotective peptides fused to arginine-rich CPPs. PMID:25669902

Chronic stress enhances calcium mobilization and glutamate exocytosis in cerebrocortical synaptosomes from mice.

PubMed

Satoh, Eiki; Tada, Yuichi; Matsuhisa, Fumikazu

2011-11-01

Our previous study showed that acute restraint stress enhances depolarization-induced increases in intrasynaptosomal free calcium (Ca(2+)) concentration ([Ca(2+)](i)) and Ca(2+)-dependent glutamate release in mouse cerebrocortical nerve terminals (synaptosomes). In the present study, we investigated the effects of chronic stress on [Ca(2+)](i) and glutamate release in cerebrocortical synaptosomes from mice. Male ddY strain mice were randomly assigned to one of two experimental groups: control group and chronic stressed group. Mice in the chronic stressed group were subjected to immobilization stress for 2 hours daily for a period of 21 days. [Ca(2+)](i) and glutamate release in cerebrocortical synaptosomes isolated from the mice were determined by fura-2 fluorescence assay and enzyme-linked fluorometric assay, respectively. Chronic stress caused a significant increase in resting [Ca(2+)](i) and significantly enhanced the ability of the depolarizing agents K(+) and 4-aminopyridine (4-AP) to increase [Ca(2+)](i). It also brought about a significant increase in spontaneous (unstimulated) glutamate release and significantly enhanced K(+)- and 4-AP-evoked Ca(2+)-dependent glutamate release. Synaptosomes were more sensitive to the depolarizing agents at lower concentrations following chronic stress than after acute stress. The pretreatment of synaptosomes with a combination of omega-agatoxin IVA (a P-type Ca(2+) channel blocker) and omega-conotoxin GVIA (an N-type Ca(2+) channel blocker) completely suppressed the enhancements of [Ca(2+)](i) and Ca(2+)-dependent glutamate release in chronic stressed mice. These results indicate that chronic stress enhances depolarization-evoked glutamate release by increasing [Ca(2+)](i) via stimulation of Ca(2+) entry through P- and N-type Ca(2+) channels, and that chronic stress increases the sensitivity to depolarizing agents.

Characterization and Expression of Glutamate Dehydrogenase in Response to Acute Salinity Stress in the Chinese Mitten Crab, Eriocheir sinensis

PubMed Central

Wang, Yueru; Li, Erchao; Yu, Na; Wang, Xiaodan; Cai, Chunfang; Tang, Boping; Chen, Liqiao; Van Wormhoudt, Alain

2012-01-01

Background Glutamate dehydrogenase (GDH) is a key enzyme for the synthesis and catabolism of glutamic acid, proline and alanine, which are important osmolytes in aquatic animals. However, the response of GDH gene expression to salinity alterations has not yet been determined in macro-crustacean species. Methodology/Principal Findings GDH cDNA was isolated from Eriocheir sinensis. Then, GDH gene expression was analyzed in different tissues from normal crabs and the muscle of crabs following transfer from freshwater (control) directly to water with salinities of 16‰ and 30‰, respectively. Full-length GDH cDNA is 2,349 bp, consisting of a 76 bp 5′- untranslated region, a 1,695 bp open reading frame encoding 564 amino acids and a 578 bp 3′- untranslated region. E. sinensis GDH showed 64–90% identity with protein sequences of mammalian and crustacean species. Muscle was the dominant expression source among all tissues tested. Compared with the control, GDH expression significantly increased at 6 h in crabs transferred to 16‰ and 30‰ salinity, and GDH expression peaked at 48 h and 12 h, respectively, with levels approximately 7.9 and 8.5 fold higher than the control. The free amino acid (FAA) changes in muscle, under acute salinity stress (16‰ and 30‰ salinities), correlated with GDH expression levels. Total FAA content in the muscle, which was based on specific changes in arginine, proline, glycine, alanine, taurine, serine and glutamic acid, tended to increase in crabs following transfer to salt water. Among these, arginine, proline and alanine increased significantly during salinity acclimation and accounted for the highest proportion of total FAA. Conclusions E. sinensis GDH is a conserved protein that serves important functions in controlling osmoregulation. We observed that higher GDH expression after ambient salinity increase led to higher FAA metabolism, especially the synthesis of glutamic acid, which increased the synthesis of proline and

Distribution of the branched-chain α-ketoacid dehydrogenase complex E1α subunit and glutamate dehydrogenase in the human brain and their role in neuro-metabolism.

PubMed

Hull, Jonathon; Usmari Moraes, Marcela; Brookes, Emma; Love, Seth; Conway, Myra E

2018-01-01

Glutamate is the major excitatory neurotransmitter of the central nervous system, with the branched-chain amino acids (BCAAs) acting as key nitrogen donors for de novo glutamate synthesis. Despite the importance of these major metabolites, their metabolic pathway in the human brain is still not well characterised. The metabolic pathways that influence the metabolism of BCAAs have been well characterised in rat models. However, the expression of key proteins such as the branched-chain α-ketoacid dehydrogenase (BCKD) complex and glutamate dehydrogenase isozymes (GDH) in the human brain is still not well characterised. We have used specific antibodies to these proteins to analyse their distribution within the human brain and report, for the first time, that the E1α subunit of the BCKD is located in both neurons and vascular endothelial cells. We also demonstrate that GDH is localised to astrocytes, although vascular immunolabelling does occur. The labelling of GDH was most intense in astrocytes adjacent to the hippocampus, in keeping with glutamatergic neurotransmission in this region. GDH was also present in astrocyte processes abutting vascular endothelial cells. Previously, we demonstrated that the branched-chain aminotransferase (hBCAT) proteins were most abundant in vascular cells (hBCATm) and neurons (hBCATc). Present findings are further evidence that BCAAs are metabolised within both the vasculature and neurons in the human brain. We suggest that GDH, hBCAT and the BCKD proteins operate in conjunction with astrocytic glutamate transporters and glutamine synthetase to regulate the availability of glutamate. This has important implications given that the dysregulation of glutamate metabolism, leading to glutamate excitotoxicity, is an important contributor to the pathogenesis of several neurodegenerative conditions such as Alzheimer's disease. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

Neuroprotective effect and mechanism of daucosterol palmitate in ameliorating learning and memory impairment in a rat model of Alzheimer's disease.

PubMed

Ji, Zhi-Hong; Xu, Zhong-Qi; Zhao, Hong; Yu, Xin-Yu

2017-03-01

Alzheimer's disease (AD) is an age-related neurodegenerative disorder characterized by progressive memory decline and cognitive impairment. Amyloid beta (Aβ) has been proposed as the causative role for the pathogenesis of AD. Accumulating evidence demonstrates that Aβ neurotoxicity is mediated by glutamate excitotoxicity. Daucosterol palmitate (DSP), a plant steroid with anti-glutamate excitotoxicity effect, was isolated from the anti-aging traditional Chinese medicinal herb Alpinia oxyphylla Miq. in our previous study. Based on the anti-glutamate excitotoxicity effect of DSP, in this study we investigated potential benefit and mechanism of DSP in ameliorating learning and memory impairment in AD model rats. Results from this study showed that DSP administration effectively ameliorated Aβ-induced learning and memory impairment in rats, markedly inhibited Aβ-induced hippocampal ROS production, effectively prevented Aβ-induced hippocampal neuronal damage and significantly restored hippocampal synaptophysin expression level. This study suggests that DSP may be a potential candidate for development as a therapeutic agent for AD cognitive decline. Copyright © 2017 Elsevier Inc. All rights reserved.

Resveratrol Prevents Ammonia Toxicity in Astroglial Cells

PubMed Central

Guerra, Maria Cristina; Leite, Marina Concli; Souza, Diogo Onofre; Gonçalves, Carlos-Alberto; Gottfried, Carmem

2012-01-01

Ammonia is implicated as a neurotoxin in brain metabolic disorders associated with hyperammonemia. Acute ammonia toxicity can be mediated by an excitotoxic mechanism, oxidative stress and nitric oxide (NO) production. Astrocytes interact with neurons, providing metabolic support and protecting against oxidative stress and excitotoxicity. Astrocytes also convert excess ammonia and glutamate into glutamine via glutamine synthetase (GS). Resveratrol, a polyphenol found in grapes and red wines, exhibits antioxidant and anti-inflammatory properties and modulates glial functions, such as glutamate metabolism. We investigated the effect of resveratrol on the production of reactive oxygen species (ROS), GS activity, S100B secretion, TNF-α, IL-1β and IL-6 levels in astroglial cells exposed to ammonia. Ammonia induced oxidative stress, decreased GS activity and increased cytokines release, probably by a mechanism dependent on protein kinase A (PKA) and extracellular signal-regulated kinase (ERK) pathways. Resveratrol prevented ammonia toxicity by modulating oxidative stress, glial and inflammatory responses. The ERK and nuclear factor-κB (NF-κB) are involved in the protective effect of resveratrol on cytokines proinflammatory release. In contrast, other antioxidants (e.g., ascorbic acid and trolox) were not effective against hyperammonemia. Thus, resveratrol could be used to protect against ammonia-induced neurotoxicity. PMID:23284918

Effects of Chronic Alcohol Exposure on the Modulation of Ischemia-Induced Glutamate Release via Cannabinoid Receptors in the Dorsal Hippocampus.

PubMed

Zheng, Lei; Wu, Xiaoda; Dong, Xiao; Ding, Xinli; Song, Cunfeng

2015-10-01

Chronic alcohol consumption is a critical contributing factor to ischemic stroke, as it enhances ischemia-induced glutamate release, leading to more severe excitotoxicity and brain damage. But the neural mechanisms underlying this phenomenon are poorly understood. We evaluated the effects of chronic alcohol exposure on the modulation of ischemia-induced glutamate release via CB1 and CB2 cannabinoid receptors during middle cerebral artery occlusion, using in vivo microdialysis coupled with high-performance liquid chromatography, in alcohol-naïve rats or rats after 1 or 30 days of withdrawal from chronic ethanol intake (6% v/v for 14 days). Intra-dorsal hippocampus (DH) infusions of ACEA or JWH133, selective CB1 or CB2 receptor agonists, respectively, decreased glutamate release in the DH in alcohol-naïve rats in a dose-dependent manner. Such an effect was reversed by co-infusions of SR141716A or AM630, selective CB1 or CB2 receptor antagonists, respectively. After 30 days, but not 1 day of withdrawal, ischemia induced an enhancement in glutamate release in the DH, as compared with non-alcohol-treated control group. Intra-DH infusions of JWH133, but not ACEA, inhibited ischemia-induced glutamate release in the DH after 30 days of withdrawal. Finally, 1 day of withdrawal did not alter the protein level of CB1 or CB2 receptors in the DH, as compared to non-alcohol-treated control rats. Whereas 30 days of withdrawal robustly decreased the protein level of CB1 receptors, but failed to alter the protein level of CB2 receptors, in the DH, as compared to non-alcohol-treated control rats. Together, these findings suggest that loss of expression/function of CB1 receptors, but not CB2 receptors in the DH, is correlated with the enhancement of ischemia-induced glutamate release after prolonged alcohol withdrawal. Copyright © 2015 by the Research Society on Alcoholism.

Synaptic Glutamate Spillover Due to Impaired Glutamate Uptake Mediates Heroin Relapse

PubMed Central

Scofield, Michael D.; Boger, Heather; Hensley, Megan; Kalivas, Peter W.

2014-01-01

Reducing the enduring vulnerability to relapse is a therapeutic goal in treating drug addiction. Studies with animal models of drug addiction show a marked increase in extrasynaptic glutamate in the core subcompartment of the nucleus accumbens (NAcore) during reinstated drug seeking. However, the synaptic mechanisms linking drug-induced changes in extrasynaptic glutamate to relapse are poorly understood. Here, we discovered impaired glutamate elimination in rats extinguished from heroin self-administration that leads to spillover of synaptically released glutamate into the nonsynaptic extracellular space in NAcore and investigated whether restoration of glutamate transport prevented reinstated heroin seeking. Through multiple functional assays of glutamate uptake and analyzing NMDA receptor-mediated currents, we show that heroin self-administration produced long-lasting downregulation of glutamate uptake and surface expression of the transporter GLT-1. This downregulation was associated with spillover of synaptic glutamate to extrasynaptic NMDA receptors within the NAcore. Ceftriaxone restored glutamate uptake and prevented synaptic glutamate spillover and cue-induced heroin seeking. Ceftriaxone-induced inhibition of reinstated heroin seeking was blocked by morpholino-antisense targeting GLT-1 synthesis. These data reveal that the synaptic glutamate spillover in the NAcore results from reduced glutamate transport and is a critical pathophysiological mechanism underling reinstated drug seeking in rats extinguished from heroin self-administration. PMID:24741055

Intracellular synthesis of glutamic acid in Bacillus methylotrophicus SK19.001, a glutamate-independent poly(γ-glutamic acid)-producing strain.

PubMed

Peng, Yingyun; Zhang, Tao; Mu, Wanmeng; Miao, Ming; Jiang, Bo

2016-01-15

Bacillus methylotrophicus SK19.001 is a glutamate-independent strain that produces poly(γ-glutamic acid) (γ-PGA), a polymer of D- and L-glutamic acids that possesses applications in food, the environment, agriculture, etc. This study was undertaken to explore the synthetic pathway of intracellular L- and D-glutamic acid in SK19.001 by investigating the effects of tricarboxylic acid cycle intermediates and different amino acids as metabolic precursors on the production of γ-PGA and analyzing the activities of the enzymes involved in the synthesis of L- and D-glutamate. Tricarboxylic acid cycle intermediates and amino acids could participate in the synthesis of γ-PGA via independent pathways in SK19.001. L-Aspartate aminotransferase, L-glutaminase and L-glutamate synthase were the enzymatic sources of L-glutamate. Glutamate racemase was responsible for the formation of D-glutamate for the synthesis of γ-PGA, and the synthetase had stereoselectivity for glutamate substrate. The enzymatic sources of L-glutamate were investigated for the first time in the glutamate-independent γ-PGA-producing strain, and multiple enzymatic sources of L-glutamate were verified in SK19.001, which will benefit efforts to improve production of γ-PGA with metabolic engineering strategies. © 2015 Society of Chemical Industry.

A study of oxidative stress, cytokines and glutamate in Wilson disease and their asymptomatic siblings.

PubMed

Kalita, Jayantee; Kumar, Vijay; Misra, Usha K; Ranjan, Abhay; Khan, Hamidullah; Konwar, Rituraj

2014-09-15

Free copper in Wilson disease (WD) is toxic and may reduce antioxidant, increase oxidative stress marker and thereby cytokine release and excitotoxic injury, but there is paucity of studies in humans. We report oxidative stress markers, cytokines and glutamate in neurologic WD and correlate these with their clinical severity, laboratory findings and extent of Magnetic resonance imaging (MRI) changes. 29 patients with neurologic WD and 9 asymptomatic WD siblings were included and their clinical, treatment history, disease severity, biochemical findings and MRI changes were noted. Glutathione (GSH), total antioxidant capacity (TAC) and malonodialdehyde (MDA) were measured by spectrophotometer, cytokines by cytokine bead array and glutamate by the fluorometer. In WD patients, the glutathione (mean±SEM, 2.20±0.06 vs. 2.73±0.04mg/dl, P<0.001) and TAC (1.70±0.03 vs. 2.29±0.02 Trolox_Eq_mmol/l, P<0.001) were reduced, and MDA and glutamate (23.93±0.54 vs. 19.96±0.27μmol/l; P<0.001) were increased (4.7±0.11 vs. 3.03±0.52nmol/ml, P<0.001) compared to controls. The serum IL6 {median (IQRs), 9.42(10.92) vs. 5.2(5.34) pg/ml; P=0.001}, IL8 {12.37(10.92) vs. 5.63(5.52) pg/ml; P<0.001}, IL10 {8.33(8.3) vs. 2.05(1.37) pg/ml; P=0.001} and TNFα {6.14(8.95) vs. 3.61(3.58) pg/ml; P<0.001} were also increased in WD patients compared to controls. These changes were more marked in the neurologic WD compared to asymptomatic WD and in the untreated compared to treated patients. TAC correlated with duration of illness, serum free copper, 24hour urinary copper and serum ceruloplasmin, and glutamate with MDA, TNFα, ceruloplasmin and 24-hour urinary copper. In WD patients, antioxidants are reduced and MDA, cytokines and glutamate are increased which are more marked in symptomatic neurologic WD than asymptomatic patients. Copyright © 2014 Elsevier B.V. All rights reserved.

Live Imaging of Kv7.2/7.3 Cell Surface Dynamics at the Axon Initial Segment: High Steady-State Stability and Calpain-Dependent Excitotoxic Downregulation Revealed.

PubMed

Benned-Jensen, Tau; Christensen, Rasmus Kordt; Denti, Federico; Perrier, Jean-Francois; Rasmussen, Hanne Borger; Olesen, Søren-Peter

2016-02-17

The voltage-gated K(+) channels Kv7.2 and Kv7.3 are located at the axon initial segment (AIS) and exert strong control over action potential generation. Therefore, changes in their localization or cell surface numbers are likely to influence neuronal signaling. However, nothing is known about the cell surface dynamics of Kv7.2/7.3 at steady state or during short-term neuronal stimulation. This is primarily attributable to their membrane topology, which hampers extracellular epitope tagging. Here we circumvent this limitation by fusing an extra phluorin-tagged helix to the N terminus of human Kv7.3. This seven transmembrane chimera, named super ecliptic phluorin (SEP)-TAC-7.3, functions and traffics as a wild-type (WT) channel. We expressed SEP-TAC-7.3 in dissociated rat hippocampal neurons to examine the lateral mobility, surface numbers, and localization of AIS Kv7.2/7.3 heteromers using live imaging. We discovered that they are extraordinarily stable and exhibit a very low surface mobility both during steady state and neuronal stimulation. In the latter case, we also found that neither localization nor cell surface numbers were changed. However, at high glutamate loads, we observed a rapid irreversible endocytosis of Kv7.2/7.3, which required the activation of NR2B-containing NMDA receptors, Ca(2+) influx, and calpain activation. This excitotoxic mechanism may be specific to ankyrin G-bound AIS proteins because Nav1.2 channels, but not AIS GABAA receptors, were also endocytosed. In conclusion, we have, for the first time, characterized the cell surface dynamics of a full-length Kv7 channel using a novel chimeric strategy. This approach is likely also applicable to other Kv channels and thus of value for the additional characterization of this ion channel subfamily. The voltage-gated K(+) channels Kv7.2 and Kv7.3 exert strong control over action potential generation, but little is known about their cell surface dynamics. Using a novel phluorin-based approach, we

IGF-1-Involved Negative Feedback of NR2B NMDA Subunits Protects Cultured Hippocampal Neurons Against NMDA-Induced Excitotoxicity.

PubMed

Li, Yun; Sun, Wei; Han, Song; Li, Jianing; Ding, Shu; Wang, Wei; Yin, Yanling

2017-01-01

Insulin-like growth factor 1 (IGF-1) is a multifunctional protein involved in neuronal polarity and axonal guidance. In our previous study, it was discovered that IGF-1 alleviated 50-μM NMDA-induced excitotoxicity against neuronal autophagy via depression of NR2B p-Ser1303 activation. However, it was found that NMDA at a higher dose did not cause neuronal autophagy. And, the performance of IGF-1 under severe excitotoxicity still needs to be clarified. In this study, we observed that IGF-1 can salvage the hippocampal neurons in an autophagy-independent manner after 150-μM NMDA exposure using thiazolyl blue tetrazolium bromide (MTT), lactate dehydrogenase (LDH), Western blot assay, and transmission electron microscopy. In addition, over-activation of post-synaptic NMDARs was found with the whole-cell patch clamp recording method. In order to explore whether there is a positive feedback way for post-synaptic NMDARs and the different pathway caused by 150 μM NMDA, the phosphorylation level of Fyn and the phosphorylation site of NR2B were investigated. It was observed that NR2B p-Tyr1472 was increased by the activation of Fyn after 150-μM NMDA exposure. When the neutralizing antibody against NR2B p-Ser1303 was added into the medium, both the activations of Fyn and NR2B p-Tyr1472 were blocked, suggesting NR2B p-Ser1303 may be the initial step of NMDA-induced excitotoxicity. In addition, since IGF-1 can block the initial step of NR2B activation, its effect is concluded to continue with the development of excitotoxicity. Overall, this study strongly indicates that the relationship between different phosphorylation sites of NR2B should be laid more emphasis on, which may be a vital target for the NR2B-involved excitotoxicity.

Protective effects of N-acetylcysteine against monosodium glutamate-induced astrocytic cell death.

PubMed

Park, Euteum; Yu, Kyoung Hwan; Kim, Do Kyung; Kim, Seung; Sapkota, Kumar; Kim, Sung-Jun; Kim, Chun Sung; Chun, Hong Sung

2014-05-01

Monosodium glutamate (MSG) is a flavor enhancer, largely used in the food industry and it was reported to have excitotoxic effects. Higher amounts of MSG consumption have been related with increased risk of many diseases, including Chinese restaurant syndrome and metabolic syndromes in human. This study investigated the protective effects of N-acetylcysteine (NAC) on MSG-induced cytotoxicity in C6 astrocytic cells. MSG (20 mM)-induced reactive oxygen species (ROS) generation and apoptotic cell death were significantly attenuated by NAC (500 μM) pretreatment. NAC effectively inhibited the MSG-induced mitochondrial membrane potential (MMP) loss and intracellular reduced glutathione (GSH) depletion. In addition, NAC significantly attenuated MSG-induced endoplasmic reticulum (ER) stress markers, such as XBP1 splicing and CHOP, PERK, and GRP78 up-regulation. Furthermore, NAC prevented the changes of MSG-induced Bcl-2 expression level. These results suggest that NAC can protect C6 astrocytic cells against MSG-induced oxidative stress, mitochondrial dysfunction, and ER stress. Copyright © 2014 Elsevier Ltd. All rights reserved.

Myricetin Inhibits the Release of Glutamate in Rat Cerebrocortical Nerve Terminals

PubMed Central

Chang, Yi; Chang, Chia-Ying; Huang, Shu-Kuei

2015-01-01

Abstract The excessive release of glutamate is a critical element in the neuropathology of acute and chronic brain disorders. The purpose of the present study was to investigate the effect and possible mechanism of myricetin, a naturally occurring flavonoid with a neuroprotective profile, on endogenous glutamate release in the nerve terminals (synaptosomes) of the rat cerebral cortex. The release of glutamate was evoked by the K+ channel blocker 4-aminopyridine (4-AP) and measured by one-line enzyme-coupled fluorometric assay. We also used a membrane potential-sensitive dye to assay the synaptosomal plasma membrane potential, and a Ca2+ indicator Fura-2 to monitor cytosolic Ca2+ concentrations ([Ca2+]C). Results show that myricetin inhibited 4-AP-evoked glutamate release, and this effect was prevented by chelating extracellular Ca2+ ions and the vesicular transporter inhibitor bafilomycin A1. However, the glutamate transporter inhibitor dl-threo-beta-benzyl-oxyaspartate had no effect on myricetin action. Myricetin did not alter the synaptosomal membrane potential, but decreased 4-AP-induced increases in the cytosolic free Ca2+ concentration. Furthermore, the myricetin effect on 4-AP-evoked glutamate release was prevented by blocking the Cav2.2 (N-type) and Cav2.1 (P/Q-type) channels, but not by blocking intracellular Ca2+ release. These results suggest that myricetin inhibits glutamate release from cerebrocortical synaptosomes by attenuating voltage-dependent Ca2+ entry. This implies that the inhibition of glutamate release is an important pharmacological activity of myricetin that may play a critical role in the apparent clinical efficacy of this compound. PMID:25340625

Monosodium glutamate neurotoxicity increases beta amyloid in the rat hippocampus: a potential role for cyclic AMP protein kinase.

PubMed

Dief, Abeer E; Kamha, Eman S; Baraka, Azza M; Elshorbagy, Amany K

2014-05-01

Glutamate excitotoxicity and cyclic AMP-activated protein kinase (AMPK) are both recognized as important mediators in neurodegenerative disorders including Alzheimer's disease (AD). To investigate whether oral or subcutaneous monosodium glutamate (MSG) neurotoxicity mimics some features of AD and whether these can be reversed by the AMPK activator Pioglitazone. Male Wistar rats aged 5 weeks were administered oral or subcutaneous MSG for 10 days with or without daily oral Pioglitazone. Two additional groups given only saline orally or subcutaneously acted as controls. At age 10 weeks the rats were subjected to neurobehavioral testing, then sacrificed for measurement of AMPK, β-amyloid and Fas ligand in the hippocampus. Oral and subcutaneous MSG both induced a lowering of hippocampal AMPK by 43% and 31% respectively (P<0.05 for both) and >2-fold increase in hippocampal Fas ligand, a mediator of apoptosis (P<0.001 for both). MSG treatment also induced a significant increase in β-amyloid in the hippocampus by >4-fold and >5-fold in the oral and subcutaneous groups. This was associated with increased latency before crossing to the white half in the black-white alley and before the first rear in the holeboard test, suggesting increased anxiety. Pioglitazone decreased hippocampal β-amyloid accumulation and Fas ligand, but did not ameliorate the neurobehavioural deficits induced by MSG. MSG treatment enhances β-amyloid accumulation in the rat hippocampus. Our results suggest a role for AMPK reduction in mediating the neurotoxic effects of glutamate, including β-amyloid accumulation. Copyright © 2014 Elsevier Inc. All rights reserved.

Does acute or habitual protein deprivation influence liking for monosodium glutamate?

PubMed

Masic, Una; Yeomans, Martin R

2017-03-15

The umami flavour generated by monosodium glutamate (MSG) has been proposed as the marker for the presence of protein in foods. As protein is the most closely regulated macronutrient in the diet, the present study addressed whether acute protein deprivation, habitual protein intake or a combination of the two influenced liking for the taste of MSG. 24 low-restraint male participants (mean age: 22; BMI: 23) consumed either their habitual breakfast (baseline), a low protein breakfast (breakfast meal with low protein milk and milkshake) or a high protein breakfast (breakfast meal with high protein milk and milkshake) on three different days, and then evaluated the acceptability of umami (MSG), salty (NaCl) or sweet (Acesulphame K) tastes at low or high concentrations in a soup context at lunchtime. Participants also completed a habitual protein intake questionnaire (39-item protein Food Frequency Questionnaire). Liking for all tastes was higher on the low than on the high protein day, and NaCl and Acesulphame K were liked less on both protein manipulation days when compared to the no added flavour control. Habitual protein intake was not related to liking for MSG stimuli alone but habitual high protein consumers rated a high concentration of MSG as more pleasant than any other taste when in protein deficit. Overall, these findings suggest that liking for high MSG concentrations may be moderated by nutritional need in high protein consumers. Crown Copyright © 2017. Published by Elsevier Inc. All rights reserved.

NMDA Receptor Activation Underlies the Loss of Spinal Dorsal Horn Neurons and the Transition to Persistent Pain after Peripheral Nerve Injury.

PubMed

Inquimbert, Perrine; Moll, Martin; Latremoliere, Alban; Tong, Chi-Kun; Whang, John; Sheehan, Gregory F; Smith, Brendan M; Korb, Erica; Athié, Maria C P; Babaniyi, Olusegun; Ghasemlou, Nader; Yanagawa, Yuchio; Allis, C David; Hof, Patrick R; Scholz, Joachim

2018-05-29

Peripheral nerve lesions provoke apoptosis in the dorsal horn of the spinal cord. The cause of cell death, the involvement of neurons, and the relevance for the processing of somatosensory information are controversial. Here, we demonstrate in a mouse model of sciatic nerve injury that glutamate-induced neurodegeneration and loss of γ-aminobutyric acid (GABA)ergic interneurons in the superficial dorsal horn promote the transition from acute to chronic neuropathic pain. Conditional deletion of Grin1, the essential subunit of N-methyl-d-aspartate-type glutamate receptors (NMDARs), protects dorsal horn neurons from excitotoxicity and preserves GABAergic inhibition. Mice deficient in functional NMDARs exhibit normal nociceptive responses and acute pain after nerve injury, but this initial increase in pain sensitivity is reversible. Eliminating NMDARs fully prevents persistent pain-like behavior. Reduced pain in mice lacking proapoptotic Bax confirmed the significance of neurodegeneration. We conclude that NMDAR-mediated neuron death contributes to the development of chronic neuropathic pain. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Simultaneous two-voxel localized 1H-observed 13C-edited spectroscopy for in vivo MRS on rat brain at 9.4 T: Application to the investigation of excitotoxic lesions

NASA Astrophysics Data System (ADS)

Doan, Bich-Thuy; Autret, Gwennhael; Mispelter, Joël; Méric, Philippe; Même, William; Montécot-Dubourg, Céline; Corrèze, Jean-Loup; Szeremeta, Frédéric; Gillet, Brigitte; Beloeil, Jean-Claude

2009-05-01

13C spectroscopy combined with the injection of 13C-labeled substrates is a powerful method for the study of brain metabolism in vivo. Since highly localized measurements are required in a heterogeneous organ such as the brain, it is of interest to augment the sensitivity of 13C spectroscopy by proton acquisition. Furthermore, as focal cerebral lesions are often encountered in animal models of disorders in which the two brain hemispheres are compared, we wished to develop a bi-voxel localized sequence for the simultaneous bilateral investigation of rat brain metabolism, with no need for external additional references. Two sequences were developed at 9.4 T: a bi-voxel 1H-( 13C) STEAM-POCE (Proton Observed Carbon Edited) sequence and a bi-voxel 1H-( 13C) PRESS-POCE adiabatically decoupled sequence with Hadamard encoding. Hadamard encoding allows both voxels to be recorded simultaneously, with the same acquisition time as that required for a single voxel. The method was validated in a biological investigation into the neuronal damage and the effect on the Tri Carboxylic Acid cycle in localized excitotoxic lesions. Following an excitotoxic quinolinate-induced localized lesion in the rat cortex and the infusion of U- 13C glucose, two 1H-( 13C) spectra of distinct (4 × 4 × 4 mm 3) voxels, one centred on the injured hemisphere and the other on the contralateral hemisphere, were recorded simultaneously. Two 1H bi-voxel spectra were also recorded and showed a significant decrease in N-acetyl aspartate, and an accumulation of lactate in the ipsilateral hemisphere. The 1H-( 13C) spectra could be recorded dynamically as a function of time, and showed a fall in the glutamate/glutamine ratio and the presence of a stable glutamine pool, with a permanent increase of lactate in the ipsilateral hemisphere. This bi-voxel 1H-( 13C) method can be used to investigate simultaneously both brain hemispheres, and to perform dynamic studies. We report here the neuronal damage and the

Chronic Mild Stress Alters Kynurenine Pathways Changing the Glutamate Neurotransmission in Frontal Cortex of Rats.

PubMed

Martín-Hernández, David; Tendilla-Beltrán, Hiram; Madrigal, José L M; García-Bueno, Borja; Leza, Juan C; Caso, Javier R

2018-05-03

Immune stimulation might be involved in the pathophysiology of major depressive disorder (MDD). This stimulation induces indoleamine 2,3-dioxygenase (IDO), an enzyme that reduces the tryptophan bioavailability to synthesize serotonin. IDO products, kynurenine metabolites, exert neurotoxic/neuroprotective actions through glutamate receptors. Thus, we study elements of these pathways linked to kynurenine metabolite activity examining whether antidepressants (ADs) can modulate them. Male Wistar rats were exposed to chronic mild stress (CMS), and some of them were treated with ADs. The expression of elements of the IDO pathway, including kynurenine metabolites, and their possible modulation by ADs was studied in the frontal cortex (FC). CMS increased IDO expression in FC compared to control group, and ADs restored the IDO expression levels to control values. CMS-induced IDO expression led to increased levels of the excitotoxic quinolinic acid (QUINA) compared to control, and ADs prevented the rise in such levels. Neither CMS nor ADs changed significantly the antiexcitotoxic kynurenic acid (KYNA) levels. The QUINA/KYNA ratio, calculated as excitotoxicity risk indicator, increased after CMS and ADs prevented this increase. CMS lowered excitatory amino acid transporter (EAAT)-1 and EAAT-4 expression, and some ADs restored their expression levels. Furthermore, CMS decreased N-methyl-D-aspartate receptor (NMDAR)-2A and 2B protein expression, and ADs mitigated this decrease. Our research examines the link between CMS-induced pro-inflammatory cytokines and the kynurenine pathway; it shows that CMS alters the kynurenine pathway in rat FC. Importantly, it also reveals the ability of classic ADs to prevent potentially harmful situations related to the brain scenario caused by CMS.

The use of propidium iodide to assess excitotoxic neuronal death in primary mixed cortical cultures.

PubMed

Lau, Anthony C; Cui, Hong; Tymianski, Michael

2007-01-01

Neurodegenerative disorders are subjects of intense scrutiny in biomedical research because of their often-debilitating effects. Currently, many laboratories are engaged in developing or testing drugs to prevent neuronal loss in a variety of these pathologies. A key to testing such drugs is the use of a fast, reliable, and easily reproducible model of neurodegeneration and neuroprotection. Our laboratory has previously used propidium iodide (PI) to assess the degree of neurodegeneration and neuroprotection under a variety of conditions. Ultimately, efforts are underway in the laboratory to prevent delayed neuronal loss following acute ischemic insults using drug therapies. It is now believed that a key mechanism of neurodegeneration following acute ischemia or anoxia is a result of excitotoxicity via N-methyl-D-aspartate receptors (NMDARs) and subsequent overproduction of nitric oxide via neuronal nitric oxide synthase (nNOS). Thus, for the purposes of this chapter, the insult used to induce cell death will be various concentrations of NMDA and the compound used to demonstrate neuroprotection will be the nonspecific NOS inhibitor No-nitro-L-arginine methyl ester (L-NAME). Assessment of neuronal death is accomplished by measuring changes in PI fluorescence using a fluorescent plate reader. This chapter will outline the necessary steps required to (1) produce primary mixed cortical cultures, (2) apply PT and NMDA to these cultures, (3) quantify the results obtained from these cultures, and (4) image these cultures in conjunction with Hoechst 33342 and immunocytochemistry using fluorescence microscopy.

ACUTE ETHANOL MODULATES GLUTAMATERGIC AND SEROTONERGIC PHASE SHIFTS OF THE MOUSE CIRCADIAN LOCK IN VITRO

PubMed Central

Prosser, Rebecca A.; Mangrum, Charles A.; Glass, J. David

2008-01-01

Alcohol abuse is associated with sleep problems, which are often linked to circadian rhythm disturbances. However, there is no information on the direct effects of ethanol on the mammalian circadian clock. Acute ethanol inhibits glutamate signaling, which is the primary mechanism through which light resets the mammalian clock in the suprachiasmatic nucleus (SCN). Glutamate and light also inhibit circadian clock resetting induced by non-photic signals, including serotonin. Thus, we investigated the effects of acute ethanol on both glutamatergic and serotoninergic resetting of the SCN clock in vitro. We show that ethanol dose-dependently inhibits glutamate-induced phase shifts and enhances serotonergic phase shifts. The inhibition of glutamate-induced phase shifts is not affected by excess glutamate, glycine or D-serine, but is prevented by excess brain-derived neurotrophic factor (BDNF). BDNF is known to augment glutamate signaling in the SCN and to be necessary for glutamate/light-induced phase shifts. Thus, ethanol may inhibit glutamate-induced clock resetting at least in part by blocking BDNF enhancement of glutamate signaling. Ethanol enhancement of serotonergic phase shifts is mimicked by treatments that suppress glutamate signaling in the SCN, including antagonists of glutamate receptors, BDNF signaling and nitric oxide synthase. The combined effect of ethanol with these treatments is not additive, suggesting they act through a common pathway. Our data indicate further that the interaction between serotonin and glutamate in the SCN may occur downstream from nitric oxide synthase activation. Thus, acute ethanol disrupts normal circadian clock phase regulation, which could contribute to the physiological and psychological problems associated with alcohol abuse. PMID:18313227

Taurine release from the developing and ageing hippocampus: stimulation by agonists of ionotropic glutamate receptors.

PubMed

Saransaari, P; Oja, S S

1997-12-30

The inhibitory amino acid taurine has been held to function as a modulator and osmoregulator in the brain, being of particular importance in the immature brain. The release of preloaded [3H]taurine was now studied in hippocampal slices from developing (7-day-old), adult (3-month-old) and ageing (6-24-month-old) mice focussing on the effects of agonists of ionotropic glutamate receptors. N-methyl-D-aspartate (NMDA), kainate and 2-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) potentiated taurine release concentration-dependently at each age, more so in the immature than in the adult and ageing hippocampus. The effect of kainate was blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) in the developing and aged hippocampus and those of AMPA and NMDA by 6-nitro-7-sulphamoylbenzo[f]quinoxaline-2,3-dione (NBQX) and dizocilpine a(MK-801) at every age studied. This indicates the involvement of NMDA and AMPA receptors in taurine release throughout the life-span of mice, while the kainate-receptor-mediated release does not appear to function in adults. The increased hippocampal taurine release evoked by ionotropic glutamate receptors could act neuroprotectively, counteracting by several mechanisms the harmful effects of the simultaneous release of excitatory amino acids. The substantial release of taurine in the immature hippocampus might be particularly significant in view of the vulnerability of brain tissue to excitotoxicity at early age.

Neuroprotective effects of NAP against excitotoxic brain damage in the newborn mice: implications for cerebral palsy.

PubMed

Sokolowska, P; Passemard, S; Mok, A; Schwendimann, L; Gozes, I; Gressens, P

2011-01-26

Activity-dependent neuroprotective protein (ADNP) was shown to be essential for embryogenesis and brain development while NAP, an active motif of ADNP, is neuroprotective in a broad range of neurodegenerative disorders. In the present study, we examined the protective potential of ADNP/NAP in a mouse model of excitotoxic brain lesion mimicking brain damage associated with cerebral palsy. We demonstrated that NAP had a potent neuroprotective effect against ibotenate-induced excitotoxic damage in the cortical plate and the white matter of P5 mice, and moderate against brain lesions of P0 mice. In contrast, endogenous ADNP appears not to be involved in the response to excitotoxic challenge in the studied model. Our findings further show that NAP reduced the number of apoptotic neurons through activation of PI-3K/Akt pathway in the cortical plate or both PI-3K/Akt and MAPK/MEK1 kinases in the white matter. In addition, NAP prevented ibotenate-induced loss of pre-oligodendrocytes without affecting the number of astrocytes or activated microglia around the site of injection. These findings indicate that protective actions of NAP are mediated by triggering transduction pathways that are crucial for neuronal and oligodendroglial survival, thus, NAP might be a promising therapeutic agent for treating developing brain damage. © 2011 IBRO. Published by Elsevier Ltd. All rights reserved.

Cardiovascular responses to microinjection of L-glutamate into the NTS in AV3V-lesioned rats.

PubMed

Vieira, Alexandre Antonio; Colombari, Eduardo; De Luca, Laurival A; de Almeida Colombari, Débora Simões; Menani, José V

2004-10-29

The excitatory amino acid L-glutamate injected into the nucleus of the solitary tract (NTS) in unanesthetized rats similar to peripheral chemoreceptor activation increases mean arterial pressure (MAP) and reduces heart rate. In this study, we investigated the effects of acute (1 day) and chronic (15 days) electrolytic lesions of the preoptic-periventricular tissue surrounding the anteroventral third ventricle (AV3V region) on the pressor and bradycardic responses induced by injections of L-glutamate into the NTS or peripheral chemoreceptor activation in unanesthetized rats. Male Holtzman rats with sham or electrolytic AV3V lesions and a stainless steel cannula implanted into the NTS were used. Differently from the pressor responses (28+/-3 mm Hg) produced by injections into the NTS of sham-lesioned rats, L-glutamate (5 nmol/100 nl) injected into the NTS reduced MAP (-26+/-8 mm Hg) or produced no effect (2+/-7 mm Hg) in acute and chronic AV3V-lesioned rats, respectively. The bradycardia to l-glutamate into the NTS and the cardiovascular responses to chemoreflex activation with intravenous potassium cyanide or to baroreflex activation with intravenous phenylephrine or sodium nitroprusside were not modified by AV3V lesions. The results show that the integrity of the AV3V region is essential for the pressor responses to L-glutamate into the NTS but not for the pressor responses to chemoreflex activation, suggesting dissociation between the central mechanisms involved in these responses.

Time-lapse imaging of p65 and IκBα translocation kinetics following Ca2+-induced neuronal injury reveals biphasic translocation kinetics in surviving neurons.

PubMed

Schwamborn, Robert; Düssmann, Heiko; König, Hans-Georg; Prehn, Jochen H M

2017-04-01

The transcription factor nuclear factor-κB (NF-κB) regulates neuronal differentiation, plasticity and survival. It is well established that excitatory neurotransmitters such as glutamate control NF-κB activity. Glutamate receptor overactivation is also involved in ischemic- and seizure-induced neuronal injury and neurodegeneration. However, little is known at the single cell-level how NF-κB signaling relates to neuronal survival during excitotoxic injury. We found that silencing of p65/NF-κB delayed N-methyl-d-aspartate (NMDA)-induced excitotoxic injury in hippocampal neurons, suggesting a functional role of p65 in excitotoxicity. Time-lapse imaging of p65 and its inhibitor IκBα using GFP and Cerulean fusion proteins revealed specific patterns of excitotoxic NF-κB activation. Nuclear translocation of p65 began on average 8±3min following 15min of NMDA treatment and was observed in up to two thirds of hippocampal neurons. Nuclear translocation of IκBα preceded that of p65 suggesting independent translocation processes. In surviving neurons, the onset of p65 nuclear export correlated with mitochondrial membrane potential recovery. Dying neurons exhibited persistent nuclear accumulation of p65-eGFP until plasma membrane permeabilization. Our data demonstrate an important role for p65 activation kinetics in neuronal cell death decisions following excitotoxic injury. Copyright © 2017 Elsevier Inc. All rights reserved.

In Vitro Neuroprotective and Anti-Inflammatory Activities of Natural and Semi-Synthetic Spirosteroid Analogues.

PubMed

García-Pupo, Laura; Zaldo-Castro, Armando; Exarchou, Vassiliki; Tacoronte-Morales, Juan Enrique; Pieters, Luc; Vanden Berghe, Wim; Nuñez-Figueredo, Yanier; Delgado-Hernández, René

2016-07-29

Two spirosteroid analogues were synthesized and evaluated for their in vitro neuroprotective activities in PC12 cells, against glutamate-induced excitotoxicity and mitochondrial damage in glucose deprivation conditions, as well as their anti-inflammatory potential in LPS/IFNγ-stimulated microglia primary cultures. We also evaluated the in vitro anti-excitotoxic and anti-inflammatory activities of natural and endogenous steroids. Our results show that the plant-derived steroid solasodine decreased PC12 glutamate-induced excitotoxicity, but not the cell death induced by mitochondrial damage and glucose deprivation. Among the two synthetic spirosteroid analogues, only the (25R)-5α-spirostan-3,6-one (S15) protected PC12 against ischemia-related in vitro models and inhibited NO production, as well as the release of IL-1β by stimulated primary microglia. These findings provide further insights into the role of specific modifications of the A and B rings of sapogenins for their neuroprotective potential.

Acute Alcohol Intoxication Exacerbates Rhabdomyolysis-Induced Acute Renal Failure in Rats.

PubMed

Tsai, Jen-Pi; Lee, Chung-Jen; Subeq, Yi-Maun; Lee, Ru-Ping; Hsu, Bang-Gee

2017-01-01

Traumatic and nontraumatic rhabdomyolysis can lead to acute renal failure (ARF), and acute alcohol intoxication can lead to multiple abnormalities of the renal tubules. We examined the effect of acute alcohol intoxication in a rat model of rhabdomyolysis and ARF. Intravenous injections of 5 g/kg ethanol were given to rats over 3 h, followed by glycerol-induced rhabdomyolysis. Biochemical parameters, including blood urea nitrogen (BUN), creatinine (Cre), glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), and creatine phosphokinase (CPK), were measured before and after induction of rhabdomyolysis. Renal tissue injury score, renal tubular cell expression of E-cadherin, nuclear factor-κB (NF-κB), and inducible nitric oxide synthase (iNOS) were determined. Relative to rats in the vehicle group, rats in the glycerol-induced rhabdomyolysis group had significantly increased serum levels of BUN, Cre, GOT, GPT, and CPK, elevated renal tissue injury scores, increased expression of NF-κB and iNOS, and decreased expression of E-cadherin. Ethanol exacerbated all of these pathological responses. Our results suggest that acute alcohol intoxication exacerbates rhabdomyolysis-induced ARF through its pro-oxidant and inflammatory effects.

Acute Alcohol Intoxication Exacerbates Rhabdomyolysis-Induced Acute Renal Failure in Rats

PubMed Central

Tsai, Jen-Pi; Lee, Chung-Jen; Subeq, Yi-Maun; Lee, Ru-Ping; Hsu, Bang-Gee

2017-01-01

Traumatic and nontraumatic rhabdomyolysis can lead to acute renal failure (ARF), and acute alcohol intoxication can lead to multiple abnormalities of the renal tubules. We examined the effect of acute alcohol intoxication in a rat model of rhabdomyolysis and ARF. Intravenous injections of 5 g/kg ethanol were given to rats over 3 h, followed by glycerol-induced rhabdomyolysis. Biochemical parameters, including blood urea nitrogen (BUN), creatinine (Cre), glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), and creatine phosphokinase (CPK), were measured before and after induction of rhabdomyolysis. Renal tissue injury score, renal tubular cell expression of E-cadherin, nuclear factor-κB (NF-κB), and inducible nitric oxide synthase (iNOS) were determined. Relative to rats in the vehicle group, rats in the glycerol-induced rhabdomyolysis group had significantly increased serum levels of BUN, Cre, GOT, GPT, and CPK, elevated renal tissue injury scores, increased expression of NF-κB and iNOS, and decreased expression of E-cadherin. Ethanol exacerbated all of these pathological responses. Our results suggest that acute alcohol intoxication exacerbates rhabdomyolysis-induced ARF through its pro-oxidant and inflammatory effects. PMID:28824301

Oxaloacetate restores the long-term potentiation impaired in rat hippocampus CA1 region by 2-vessel occlusion.

PubMed

Marosi, Máté; Fuzik, János; Nagy, Dávid; Rákos, Gabriella; Kis, Zsolt; Vécsei, László; Toldi, József; Ruban-Matuzani, Angela; Teichberg, Vivian I; Farkas, Tamás

2009-02-14

Various acute brain pathological conditions are characterized by the presence of elevated glutamate concentrations in the brain interstitial fluids. It has been established that a decrease in the blood glutamate level enhances the brain-to-blood efflux of glutamate, removal of which from the brain may prevent glutamate excitotoxicity and its contribution to the long-lasting neurological deficits seen in stroke. A decrease in blood glutamate level can be achieved by exploiting the glutamate-scavenging properties of the blood-resident enzyme glutamate-oxaloacetate transaminase, which transforms glutamate into 2-ketoglutarate in the presence of the glutamate co-substrate oxaloacetate. The present study had the aim of an evaluation of the effects of the blood glutamate scavenger oxaloacetate on the impaired long-term potentiation (LTP) induced in the 2-vessel occlusion ischaemic model in rat. Transient (30-min) incomplete forebrain ischaemia was produced 72 h before LTP induction. Although the short transient brain hypoperfusion did not induce histologically identifiable injuries in the CA1 region (Fluoro-Jade B, S-100 and cresyl violet), it resulted in an impaired LTP function in the hippocampal CA1 region without damaging the basal synaptic transmission between the Schaffer collaterals and the pyramidal neurons. This impairment could be fended off in a dose-dependent manner by the intravenous administration of oxaloacetate in saline (at doses between 1.5 mmol and 0.1 mumol) immediately after the transient hypoperfusion. Our results suggest that oxaloacetate-mediated blood and brain glutamate scavenging contributes to the restoration of the LTP after its impairment by brain ischaemia.

Role of CCR5 and its ligands in the control of vascular inflammation and leukocyte recruitment required for acute excitotoxic seizure induction and neural damage

PubMed Central

Louboutin, Jean-Pierre; Chekmasova, Alena; Marusich, Elena; Agrawal, Lokesh; Strayer, David S.

2011-01-01

Chemokines may play a role in leukocyte migration across the blood-brain barrier (BBB) during neuroinflammation and other neuropathological processes, such as epilepsy. We investigated the role of the chemokine receptor CCR5 in seizures. We used a rat model based on intraperitoneal kainic acid (KA) administration. Four months before KA injection, adult rats were given femoral intramarrow inoculations of SV (RNAiR5-RevM10.AU1), which carries an interfering RNA (RNAi) against CCR5, plus a marker epitope (AU1), or its monofunctional RNAi-carrying homologue, SV(RNAiR5). This treatment lowered expression of CCR5 in circulating cells. In control rats, seizures induced elevated expression of CCR5 ligands MIP-1α and RANTES in the microvasculature, increased BBB leakage and CCR5+ cells, as well as neuronal loss, inflammation, and gliosis in the hippocampi. Animals given either the bifunctional or the monofunctional vector were largely protected from KA-induced seizures, neuroinflammation, BBB damage, and neuron loss. Brain CCR5 mRNA was reduced. Rats receiving RNAiR5-bearing vectors showed far greater repair responses: increased neuronal proliferation, and decreased production of MIP-1α and RANTES. Controls received unrelated SV(BUGT) vectors. Decrease in CCR5 in circulating cells strongly protected from excitotoxin-induced seizures, BBB leakage, CNS injury, and inflammation, and facilitated neurogenic repair.—Louboutin, J.-P., Chekmasova, A., Marusich, E., Agrawal, L., Strayer, D. S. Role of CCR5 and its ligands in the control of vascular inflammation and leukocyte recruitment required for acute excitotoxic seizure induction and neural damage. PMID:20940264

Connexin-deficiency affects expression levels of glial glutamate transporters within the cerebrum.

PubMed

Unger, Tina; Bette, Stefanie; Zhang, Jiong; Theis, Martin; Engele, Jürgen

2012-01-06

The glial glutamate transporter subtypes, GLT-1/EAAT-2 and GLAST/EAAT-1 clear the bulk of extracellular glutamate and are severely dysregulated in various acute and chronic brain diseases. Despite the previous identification of several extracellular factors modulating glial glutamate transporter expression, our knowledge of the regulatory network controlling glial glutamate transport in health and disease still remains incomplete. In studies with cultured cortical astrocytes, we previously obtained evidence that glial glutamate transporter expression is also affected by gap junctions/connexins. To assess whether gap junctions would likewise control the in vivo expression of glial glutamate transporters, we have now assessed their expression levels in brains of conditional Cx43 knockout mice, total Cx30 knockouts, as well as Cx43/Cx30 double knockouts. We found that either knocking out Cx30, Cx43, or both increases GLT-1/EAAT-2 protein levels in the cerebral cortex to a similar extent. By contrast, GLAST/EAAT-1 protein levels maximally increased in cerebral cortices of Cx30/Cx43 double knockouts, implying that gap junctions differentially affect the expression of GLT-1/EAAT-2 and GLAST/EAAT-1. Quantitative PCR analysis further revealed that increases in glial glutamate transporter expression are brought about by transcriptional and translational/posttranslational processes. Moreover, GLT-1/EAAT-2- and GLAST/EAAT-1 protein levels remained unchanged in the hippocampi of Cx43/Cx30 double knockouts when compared to Cx43fl/fl controls, indicating brain region-specific effects of gap junctions on glial glutamate transport. Since astrocytic gap junction coupling is affected in various forms of brain injuries, our findings point to gap junctions/connexins as important regulators of glial glutamate turnover in the diseased cerebral cortex. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Nonvesicular Release of Glutamate by Glial xCT Transporters Suppresses Glutamate Receptor Clustering In Vivo

PubMed Central

Augustin, Hrvoje; Grosjean, Yael; Chen, Kaiyun; Sheng, Qi; Featherstone, David E.

2008-01-01

We hypothesized that cystine/glutamate transporters (xCTs) might be critical regulators of ambient extracellular glutamate levels in the nervous system and that misregulation of this glutamate pool might have important neurophysiological and/or behavioral consequences. To test this idea, we identified and functionally characterized a novel Drosophila xCT gene, which we subsequently named “genderblind” (gb). Genderblind is expressed in a previously overlooked subset of peripheral and central glia. Genetic elimination of gb causes a 50% reduction in extracellular glutamate concentration, demonstrating that xCT transporters are important regulators of extracellular glutamate. Consistent with previous studies showing that extracellular glutamate regulates postsynaptic glutamate receptor clustering, gb mutants show a large (200–300%) increase in the number of postsynaptic glutamate receptors. This increase in postsynaptic receptor abundance is not accompanied by other obvious synaptic changes and is completely rescued when synapses are cultured in wild-type levels of glutamate. Additional in situ pharmacology suggests that glutamate-mediated suppression of glutamate receptor clustering depends on receptor desensitization. Together, our results suggest that (1) xCT transporters are critical for regulation of ambient extracellular glutamate in vivo; (2) ambient extracellular glutamate maintains some receptors constitutively desensitized in vivo; and (3) constitutive desensitization of ionotropic glutamate receptors suppresses their ability to cluster at synapses. PMID:17202478

Modification of hippocampal markers of synaptic plasticity by memantine in animal models of acute and repeated restraint stress: implications for memory and behavior.

PubMed

Amin, Shaimaa Nasr; El-Aidi, Ahmed Amro; Ali, Mohamed Mostafa; Attia, Yasser Mahmoud; Rashed, Laila Ahmed

2015-06-01

Stress is any condition that impairs the balance of the organism physiologically or psychologically. The response to stress involves several neurohormonal consequences. Glutamate is the primary excitatory neurotransmitter in the central nervous system, and its release is increased by stress that predisposes to excitotoxicity in the brain. Memantine is an uncompetitive N-methyl D-aspartate glutamatergic receptors antagonist and has shown beneficial effect on cognitive function especially in Alzheimer's disease. The aim of the work was to investigate memantine effect on memory and behavior in animal models of acute and repeated restraint stress with the evaluation of serum markers of stress and the expression of hippocampal markers of synaptic plasticity. Forty-two male rats were divided into seven groups (six rats/group): control, acute restraint stress, acute restraint stress with Memantine, repeated restraint stress, repeated restraint stress with Memantine and Memantine groups (two subgroups as positive control). Spatial working memory and behavior were assessed by performance in Y-maze. We evaluated serum cortisol, tumor necrotic factor, interleukin-6 and hippocampal expression of brain-derived neurotrophic factor, synaptophysin and calcium-/calmodulin-dependent protein kinase II. Our results revealed that Memantine improved spatial working memory in repeated stress, decreased serum level of stress markers and modified the hippocampal synaptic plasticity markers in both patterns of stress exposure; in ARS, Memantine upregulated the expression of synaptophysin and brain-derived neurotrophic factor and downregulated the expression of calcium-/calmodulin-dependent protein kinase II, and in repeated restraint stress, it upregulated the expression of synaptophysin and downregulated calcium-/calmodulin-dependent protein kinase II expression.

Glutamate transporter-dependent mTOR phosphorylation in Müller glia cells

PubMed Central

María López-Colomé, Ana; Martínez-Lozada, Zila; Guillem, Alain M; López, Edith; Ortega, Arturo

2012-01-01

Glu (glutamate), the excitatory transmitter at the main signalling pathway in the retina, is critically involved in changes in the protein repertoire through the activation of signalling cascades, which regulate protein synthesis at transcriptional and translational levels. Activity-dependent differential gene expression by Glu is related to the activation of ionotropic and metabotropic Glu receptors; however, recent findings suggest the involvement of Na+-dependent Glu transporters in this process. Within the retina, Glu uptake is aimed at the replenishment of the releasable pool, and for the prevention of excitotoxicity and is carried mainly by the GLAST/EAAT-1 (Na+-dependent glutamate/aspartate transporter/excitatory amino acids transporter-1) located in Müller radial glia. Based on the previous work showing the alteration of GLAST expression induced by Glu, the present work investigates the involvement of GLAST signalling in the regulation of protein synthesis in Müller cells. To this end, we explored the effect of D-Asp (D-aspartate) on Ser-2448 mTOR (mammalian target of rapamycin) phosphorylation in primary cultures of chick Müller glia. The results showed that D-Asp transport induces the time- and dose-dependent phosphorylation of mTOR, mimicked by the transportable GLAST inhibitor THA (threo-β-hydroxyaspartate). Signalling leading to mTOR phosphorylation includes Ca2+ influx, the activation of p60src, phosphatidylinositol 3-kinase, protein kinase B, mTOR and p70S6K. Interestingly, GLAST activity promoted AP-1 (activator protein-1) binding to DNA, supporting a function for transporter signalling in retinal long-term responses. These results add a novel receptor-independent pathway for Glu signalling in Müller glia, and further strengthen the critical involvement of these cells in the regulation of glutamatergic transmission in the retina. PMID:22817638

Glucose and Intermediary Metabolism and Astrocyte-Neuron Interactions Following Neonatal Hypoxia-Ischemia in Rat.

PubMed

Brekke, Eva; Berger, Hester Rijkje; Widerøe, Marius; Sonnewald, Ursula; Morken, Tora Sund

2017-01-01

Neonatal hypoxia-ischemia (HI) and the delayed injury cascade that follows involve excitotoxicity, oxidative stress and mitochondrial failure. The susceptibility to excitotoxicity of the neonatal brain may be related to the capacity of astrocytes for glutamate uptake. Furthermore, the neonatal brain is vulnerable to oxidative stress, and the pentose phosphate pathway (PPP) may be of particular importance for limiting this kind of injury. Also, in the neonatal brain, neurons depend upon de novo synthesis of neurotransmitters via pyruvate carboxylase in astrocytes to increase neurotransmitter pools during normal brain development. Several recent publications describing intermediary brain metabolism following neonatal HI have yielded interesting results: (1) Following HI there is a prolonged depression of mitochondrial metabolism in agreement with emerging evidence of mitochondria as vulnerable targets in the delayed injury cascade. (2) Astrocytes, like neurons, are metabolically impaired following HI, and the degree of astrocytic malfunction may be an indicator of the outcome following hypoxic and hypoxic-ischemic brain injury. (3) Glutamate transfer from neurons to astrocytes is not increased following neonatal HI, which may imply that astrocytes fail to upregulate glutamate uptake in response to the massive glutamate release during HI, thus contributing to excitotoxicity. (4) In the neonatal brain, the activity of the PPP is reduced following HI, which may add to the susceptibility of the neonatal brain to oxidative stress. The present review aims to discuss the metabolic temporal alterations observed in the neonatal brain following HI.

Exposure to Enriched Environment Decreases Neurobehavioral Deficits Induced by Neonatal Glutamate Toxicity

PubMed Central

Horvath, Gabor; Reglodi, Dora; Vadasz, Gyongyver; Farkas, Jozsef; Kiss, Peter

2013-01-01

Environmental enrichment is a popular strategy to enhance motor and cognitive performance and to counteract the effects of various harmful stimuli. The protective effects of enriched environment have been shown in traumatic, ischemic and toxic nervous system lesions. Monosodium glutamate (MSG) is a commonly used taste enhancer causing excitotoxic effects when given in newborn animals. We have previously demonstrated that MSG leads to a delay in neurobehavioral development, as shown by the delayed appearance of neurological reflexes and maturation of motor coordination. In the present study we aimed at investigating whether environmental enrichment is able to decrease the neurobehavioral delay caused by neonatal MSG treatment. Newborn pups were treated with MSG subcutaneously on postnatal days 1, 5 and 9. For environmental enrichment, we placed rats in larger cages, supplemented with different toys that were altered daily. Normal control and enriched control rats received saline treatment only. Physical parameters such as weight, day of eye opening, incisor eruption and ear unfolding were recorded. Animals were observed for appearance of reflexes such as negative geotaxis, righting reflexes, fore- and hindlimb grasp, fore- and hindlimb placing, sensory reflexes and gait. In cases of negative geotaxis, surface righting and gait, the time to perform the reflex was also recorded daily. For examining motor coordination, we performed grid walking, footfault, rope suspension, rota-rod, inclined board and walk initiation tests. We found that enriched environment alone did not lead to marked alterations in the course of development. On the other hand, MSG treatment caused a slight delay in reflex development and a pronounced delay in weight gain and motor coordination maturation. This delay in most signs and tests could be reversed by enriched environment: MSG-treated pups kept under enriched conditions showed no weight retardation, no reflex delay in some signs and

Inducible Nitric Oxide Inhibitors Block NMDA Antagonist-Stimulated Motoric Behaviors and Medial Prefrontal Cortical Glutamate Efflux

PubMed Central

Bergstrom, Hadley C.; Darvesh, Altaf S.; Berger, S. P.

2015-01-01

Nitric oxide (NO) plays a critical role in the motoric and glutamate releasing action of N-methyl-D-aspartate (NMDA)-antagonist stimulants. Earlier studies utilized neuronal nitric oxide synthase inhibitors (nNOS) for studying the neurobehavioral effects of non-competitive NMDA-antagonist stimulants such as dizocilpine (MK-801) and phencyclidine (PCP). This study explores the role of the inducible nitric oxide synthase inhibitors (iNOS) aminoguanidine (AG) and (-)-epigallocatechin-3-gallate (EGCG) in NMDA-antagonist induced motoric behavior and prefrontal cortical glutamate efflux. Adult male rats were administered a dose range of AG, EGCG, or vehicle prior to receiving NMDA antagonists MK-801, PCP, or a conventional psychostimulant (cocaine) and tested for motoric behavior in an open arena. Glutamate in the medial prefrontal cortex (mPFC) was measured using in vivo microdialysis after a combination of AG or EGCG prior to MK-801. Acute administration of AG or EGCG dose-dependently attenuated the locomotor and ataxic properties of MK-801 and PCP. Both AG and EGCG were unable to block the motoric effects of cocaine, indicating the acute pharmacologic action of AG and EGCG is specific to NMDA antagonism and not generalizable to all stimulant class drugs. AG and EGCG normalized MK-801-stimulated mPFC glutamate efflux. These data demonstrate that AG and EGCG attenuates NMDA antagonist-stimulated motoric behavior and cortical glutamate efflux. Our results suggest that EGCG-like polyphenol nutraceuticals (contained in “green tea” and chocolate) may be clinically useful in protecting against the adverse behavioral dissociative and cortical glutamate stimulating effects of NMDA antagonists. Medications that interfere with NMDA antagonists such as MK-801 and PCP have been proposed as treatments for schizophrenia. PMID:26696891

Different pools of glutamate receptors mediate sensitivity to ambient glutamate in the cochlear nucleus.

PubMed

Yang, Yang; Xu-Friedman, Matthew A

2015-06-01

Ambient glutamate plays an important role in pathological conditions, such as stroke, but its role during normal activity is not clear. In addition, it is not clear how ambient glutamate acts on glutamate receptors with varying affinities or subcellular localizations. To address this, we studied "endbulb of Held" synapses, which are formed by auditory nerve fibers onto bushy cells (BCs) in the anteroventral cochlear nucleus. When ambient glutamate was increased by applying the glutamate reuptake inhibitor TFB-TBOA, BCs depolarized as a result of activation of N-methyl-D-aspartate receptors (NMDARs) and group I metabotropic glutamate receptors (mGluRs). Application of antagonists against NMDARs (in 0 Mg(2+)) or mGluRs caused hyperpolarization, indicating that these receptors were bound by a tonic source of glutamate. AMPA receptors did not show these effects, consistent with their lower glutamate affinity. We also evaluated the subcellular localization of the receptors activated by ambient glutamate. The mGluRs were not activated by synaptic stimulation and thus appear to be exclusively extrasynaptic. By contrast, NMDARs in both synaptic and extrasynaptic compartments were activated by ambient glutamate, as shown using the use-dependent antagonist MK-801. Levels of ambient glutamate appeared to be regulated in a spike-independent manner, and glia likely play a major role. These low levels of ambient glutamate likely have functional consequences, as even low concentrations of TBOA caused significant increases in BC spiking following synaptic stimulation. These results indicate that normal resting potential appears to be poised in the region of maximal sensitivity to small changes in ambient glutamate. Copyright © 2015 the American Physiological Society.

Different pools of glutamate receptors mediate sensitivity to ambient glutamate in the cochlear nucleus

PubMed Central

Yang, Yang

2015-01-01

Ambient glutamate plays an important role in pathological conditions, such as stroke, but its role during normal activity is not clear. In addition, it is not clear how ambient glutamate acts on glutamate receptors with varying affinities or subcellular localizations. To address this, we studied “endbulb of Held” synapses, which are formed by auditory nerve fibers onto bushy cells (BCs) in the anteroventral cochlear nucleus. When ambient glutamate was increased by applying the glutamate reuptake inhibitor TFB-TBOA, BCs depolarized as a result of activation of N-methyl-d-aspartate receptors (NMDARs) and group I metabotropic glutamate receptors (mGluRs). Application of antagonists against NMDARs (in 0 Mg2+) or mGluRs caused hyperpolarization, indicating that these receptors were bound by a tonic source of glutamate. AMPA receptors did not show these effects, consistent with their lower glutamate affinity. We also evaluated the subcellular localization of the receptors activated by ambient glutamate. The mGluRs were not activated by synaptic stimulation and thus appear to be exclusively extrasynaptic. By contrast, NMDARs in both synaptic and extrasynaptic compartments were activated by ambient glutamate, as shown using the use-dependent antagonist MK-801. Levels of ambient glutamate appeared to be regulated in a spike-independent manner, and glia likely play a major role. These low levels of ambient glutamate likely have functional consequences, as even low concentrations of TBOA caused significant increases in BC spiking following synaptic stimulation. These results indicate that normal resting potential appears to be poised in the region of maximal sensitivity to small changes in ambient glutamate. PMID:25855696

Prevention of Noise Damage to Cochlear Synapses

DTIC Science & Technology

2016-10-01

significantly less susceptible to synaptopathy than are males, suggesting that sex hormone provide protection. Second, we have shown effective protection... Sex Differences, Spiral Ganglion Neuron, Synapse, Synaptopathy 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES 19a...Cochlea Excitotoxicity Sex Differences Glutamate Agonist Glutamate Receptor Hair Cell Hearing Threshold Noise-Induced Hearing Loss Organotypic

Ionotropic glutamate receptors activate cell signaling in response to glutamate in Schwann cells.

PubMed

Campana, Wendy M; Mantuano, Elisabetta; Azmoon, Pardis; Henry, Kenneth; Banki, Michael A; Kim, John H; Pizzo, Donald P; Gonias, Steven L

2017-04-01

In the peripheral nervous system, Schwann cells (SCs) demonstrate surveillance activity, detecting injury and undergoing trans -differentiation to support repair. SC receptors that detect peripheral nervous system injury remain incompletely understood. We used RT-PCR to profile ionotropic glutamate receptor expression in cultured SCs. We identified subunits required for assembly of N -methyl-d-aspartic acid (NMDA) receptors (NMDA-Rs), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors, and kainate receptors. Treatment of SCs with 40-100 µM glutamate or with 0.5-1.0 µM NMDA robustly activated Akt and ERK1/2. The response was transient and bimodal; glutamate concentrations that exceeded 250 µM failed to activate cell signaling. Phosphoprotein profiling identified diverse phosphorylated proteins in glutamate-treated SCs in addition to ERK1/2 and Akt, including p70 S6-kinase, glycogen synthase kinase-3, ribosomal S6 kinase, c-Jun, and cAMP response element binding protein. Activation of SC signaling by glutamate was blocked by EGTA and dizocilpine and by silencing expression of the NMDA-R NR1 subunit. Phosphoinositide 3-kinase/PI3K functioned as an essential upstream activator of Akt and ERK1/2 in glutamate-treated SCs. When glutamate or NMDA was injected directly into crush-injured rat sciatic nerves, ERK1/2 phosphorylation was observed in myelinated and nonmyelinating SCs. Glutamate promoted SC migration by a pathway that required PI3K and ERK1/2. These results identified ionotropic glutamate receptors and NMDA-Rs, specifically, as potentially important cell signaling receptors in SCs.-Campana, W. M., Mantuano, E., Azmoon, P., Henry, K., Banki, M. A., Kim, J. H., Pizzo, D. P., Gonias, S. L. Ionotropic glutamate receptors activate cell signaling in response to glutamate in Schwann cells. © FASEB.

[Pharmacology of glutamate sensitive synapses (I). Glutamate agonists (author's transl)].

PubMed

Shinozaki, H

1982-04-01

The actions of kainic acid, quisqualic acid, and ibotenic acid on the crayfish neuromuscular junction were described, and it was particularly interesting that the discrepancy between glutamate responses and EJPs was revealed by the use of kainic acid. On the other hand, there is increasing evidence showing that glutamate is an excitatory transmitter at the crayfish neuromuscular junction. At this stage, we are unable as yet to definitively support or reject glutamate's candidacy as the excitatory transmitter at the crayfish neuromuscular junction. The discrepancy revealed by the use of kainic acid may bring up some questions. Certainly, the differential action of kainic acid on the glutamate current and the excitatory synaptic current opens to doubt the transmitter role of glutamate. In the case of the study on a transmitter role for a substance of doubt status, the value of pharmacological studies seems to be greater in disproving than in asserting such the role. However, we have to consider the matter of the extra-junctional receptor postulated on the crayfish postsynaptic membrane as one of the major problems for pharmacological identification.

Extending the role of peritoneal dialysis: can we win hearts and minds?

PubMed

Davies, Simon; Lally, Frank; Satchithananda, Duwarakan; Kadam, Umesh; Roffe, Christine

2014-09-01

The ability of peritoneal dialysis (PD) to achieve low-molecular weight solute clearance and ultrafiltration at low haemodynamic cost makes it an attractive therapy in situations where more aggressive therapy may be undesirable due to sudden reductions in cerebral, coronary or renal blood flow. We undertook a review of the literature to examine the recent evidence for this in two specific examples: the removal of glutamate following acute stroke and ultrafiltration for the treatment of diuretic resistant heart failure. In acute stroke, glutamate, when released into the extracellular tissues, causes neuronal cell death due to its excitotoxic properties. Experimental evidence from animal models indicates that its removal, including via PD, can reduce infarct size and restore functional brain tissue. PD is effective in removing glutamate in patients treated for renal failure. In heart failure, PD has a number of both theoretical and practical advantages for extending treatment, especially as an established home therapy. Several recent cohort studies describing its use in approaching 300 patients with diuretic resistance show consistent benefits in hospitalization and severity. Both these applications require substantial further clinical evaluation before they can justify wider adoption but their potential to alleviate morbidity on a large and potentially highly cost-effective scale demands further study. © The Author 2014. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved.

The cystine-glutamate exchanger (xCT, Slc7a11) is expressed in significant concentrations in a subpopulation of astrocytes in the mouse brain.

PubMed

Ottestad-Hansen, Sigrid; Hu, Qiu Xiang; Follin-Arbelet, Virgine Veronique; Bentea, Eduard; Sato, Hideyo; Massie, Ann; Zhou, Yun; Danbolt, Niels Christian

2018-05-01

The cystine-glutamate exchanger (xCT) promotes glutathione synthesis by catalyzing cystine uptake and glutamate release. The released glutamate may modulate normal neural signaling and contribute to excitotoxicity in pathological situations. Uncertainty, however, remains as neither the expression levels nor the distribution of xCT have been unambiguously determined. In fact, xCT has been reported in astrocytes, neurons, oligodendrocytes and microglia, but most of the information derives from cell cultures. Here, we show by immunohistochemistry and by Western blotting that xCT is widely expressed in the central nervous system of both sexes. The labeling specificity was validated using tissue from xCT knockout mice as controls. Astrocytes were selectively labeled, but showed greatly varying labeling intensities. This astroglial heterogeneity resulted in an astrocyte domain-like labeling pattern. Strong xCT labeling was also found in the leptomeninges, along some blood vessels, in selected circumventricular organs and in a subpopulation of tanycytes residing the lateral walls of the ventral third ventricle. Neurons, oligodendrocytes and resting microglia, as well as reactive microglia induced by glutamine synthetase deficiency, were unlabeled. The concentration of xCT protein in hippocampus was compared with that of the EAAT3 glutamate transporter by immunoblotting using a chimeric xCT-EAAT3 protein to normalize xCT and EAAT3 labeling intensities. The immunoblots suggested an xCT/EAAT3 ratio close to one (0.75 ± 0.07; average ± SEM; n = 4) in adult C57BL6 mice. xCT is present in select blood/brain/CSF interface areas and in an astrocyte subpopulation, in sufficient quantities to support the notion that system xc- provides physiologically relevant transport activity. © 2018 Wiley Periodicals, Inc.

Prevention of Noise Damage to Cochlear Synapses

DTIC Science & Technology

2015-10-01

AWARD NUMBER: W81XWH-14-1-0494 TITLE: Prevention of Noise Damage to Cochlear Synapses PRINCIPAL INVESTIGATOR: Steven Green CONTRACTING...to Cochlear Synapses 5a. CONTRACT NUMBER 5b. GRANT NUMBER W81XWH-14-1-0494 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Steven Green 5d. PROJECT...ABSTRACT Noise-induced synaptopathy is the result of excitotoxic trauma to cochlear synapses due to glutamate released from the hair cells. Excitotoxic

Extracellular glutamate and other amino acids in experimental intracerebral hemorrhage: an in vivo microdialysis study.

PubMed

Qureshi, Adnan I; Ali, Zulfiqar; Suri, M Fareed K; Shuaib, Asfhaq; Baker, Glen; Todd, Kathryn; Guterman, Lee R; Hopkins, L Nelson

2003-05-01

To determine whether extracellular concentrations of glutamate and other amino acids are significantly elevated after intracerebral hemorrhage and, if so, the temporal characteristics of these changes. Although the role of excitotoxic amino acids, particularly that of glutamate, has been described in ischemic stroke and head trauma, no information exists regarding their possible contribution to the pathogenesis of neuronal injury in intracerebral hemorrhage. Prospective, controlled, laboratory trial. Animal research laboratory. Sixteen anesthetized New Zealand rabbits. We introduced intracerebral hemorrhage in each of eight anesthetized New Zealand rabbits by injecting 0.4 mL of autologous blood under arterial pressure into the deep gray matter of the cerebrum. Extracellular fluid samples were collected from the perihematoma region and contralateral (right) hemisphere by in vivo microdialysis at 30-min intervals for 6 hrs. Corresponding samples were similarly collected from both hemispheres in each of eight control animals that underwent needle placement without introduction of a hematoma. Concentrations of amino acids (glutamate, aspartate, asparagine, glycine, taurine, and gamma-aminobutyric acid) in the samples were measured by use of high-pressure liquid chromatography with fluorescence detection. Glutamate concentrations (mean +/- sem) were significantly higher in the hemisphere ipsilateral to the hematoma than in the contralateral hemisphere (92 +/- 22 pg/microL vs. 22 +/- 6 pg/microL) at 30 mins after hematoma creation. A significant increase was observed at 30 mins posthematoma creation in the hemisphere ipsilateral to the hematoma compared with the baseline value. A nonsignificant increase in glutamate concentration persisted in the hemisphere ipsilateral to the hematoma, ranging from 134% to 187% of baseline value between 1 and 5 hrs after hematoma creation. In the hemisphere ipsilateral to the hematoma, a three-fold increase in the concentration of

Involvement of Glutamate NMDA Receptors in the Acute, Long-Term, and Conditioned Effects of Amphetamine on Rat 50kHz Ultrasonic Vocalizations

PubMed Central

Costa, Giulia; Morelli, Micaela

2015-01-01

Background: Rats emit 50kHz ultrasonic vocalizations (USVs) in response to either natural or pharmacological pleasurable stimuli, and these USVs have emerged as a new behavioral measure for investigating the motivational properties of drugs. Earlier studies have indicated that activation of the dopaminergic system is critically involved in 50kHz USV emissions. However, evidence also exists that non-dopaminergic neurotransmitters participate in this behavioral response. Methods: To ascertain whether glutamate transmission plays a role in 50kHz USV emissions stimulated by amphetamine, rats received five amphetamine (1–2mg/kg, i.p.) administrations on alternate days in a test cage, either alone or combined with the glutamate N-methyl-D-aspartate receptor antagonist MK-801 (0.1–0.5mg/kg, i.p.). Seven days after treatment discontinuation, rats were re-exposed to the test cage to assess drug conditioning, and afterwards received a drug challenge. USVs and locomotor activity were evaluated, along with immunofluorescence for Zif-268 in various brain regions and spontaneous alternation in a Y maze. Results: Amphetamine-treated rats displayed higher 50kHz USV emissions and locomotor activity than vehicle-treated rats, and emitted conditioned vocalizations on test cage re-exposure. Rats co-administered amphetamine and MK-801 displayed lower and dose-dependent 50kHz USV emissions, but not lower locomotor activity, during repeated treatment and challenge, and scarce conditioned vocalization compared with amphetamine-treated rats. These effects were associated with lower levels of Zif-268 after amphetamine challenge and spontaneous alternation deficits. Conclusions: These results indicate that glutamate transmission participates in the acute, long-term, and conditioned effects of amphetamine on 50kHz USVs, possibly by influencing amphetamine-induced long-term neuronal changes and/or amphetamine-associated memories. PMID:25991653

50 Hz hippocampal stimulation in refractory epilepsy: Higher level of basal glutamate predicts greater release of glutamate.

PubMed

Cavus, Idil; Widi, Gabriel A; Duckrow, Robert B; Zaveri, Hitten; Kennard, Jeremy T; Krystal, John; Spencer, Dennis D

2016-02-01

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. 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. 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. Electrical stimulation of the epileptic hippocampus either increased extracellular glutamate efflux or induced seizures. The magnitude of stimulated

Effects of monosodium glutamate supplementation on glutamine metabolism in adult rats.

PubMed

Boutry, Claire; Bos, Cecile; Matsumoto, Hideki; Even, Patrick; Azzout-Marniche, Dalila; Tome, Daniel; Blachier, Francois

2011-01-01

Monosodium glutamate (MSG) is a worldwide used flavor enhancer. Supplemental glutamate may impact physiological functions. The aim of this study was to document the metabolic and physiological consequences of supplementation with 2% MSG (w/w) in rats. After 15 days-supplementation and following the ingestion of a test meal containing 2% MSG, glutamic acid accumulated for 5h in the stomach and for 1h in the small intestine. This coincided with a significant decrease of intestinal glutaminase activity, a marked specific increase in plasma glutamine concentration and a transient increase of plasma insulin concentration. MSG after chronic or acute supplementation had no effect on food intake, body weight, adipose tissue masses, gastric emptying rate, incorporation of dietary nitrogen in gastrointestinal and other tissues, and protein synthesis in intestinal mucosa, liver and muscles. The only significant effects of chronic supplementation were a slightly diminished gastrocnemius muscle mass, increased protein mass in intestinal mucosa and decreased protein synthesis in stomach. It is concluded that MSG chronic supplementation promotes glutamine synthesis in the body but has little effect on the physiological functions examined.

The dichotomy of memantine treatment for ischemic stroke: dose-dependent protective and detrimental effects

PubMed Central

Trotman, Melissa; Vermehren, Philipp; Gibson, Claire L; Fern, Robert

2015-01-01

Excitotoxicity is a major contributor to cell death during the acute phase of ischemic stroke but aggressive pharmacological targeting of excitotoxicity has failed clinically. Here we investigated whether pretreatment with low doses of memantine, within the range currently used and well tolerated for the treatment of Alzheimer's disease, produce a protective effect in stroke. A coculture preparation exposed to modeled ischemia showed cell death associated with rapid glutamate rises and cytotoxic Ca2+ influx. Cell death was significantly enhanced in the presence of high memantine concentrations. However, low memantine concentrations significantly protected neurons and glia via excitotoxic cascade interruption. Mice were systemically administered a range of memantine doses (0.02, 0.2, 2, 10, and 20 mg/kg/day) starting 24 hours before 60 minutes reversible focal cerebral ischemia and continuing for a 48-hour recovery period. Low dose (0.2 mg/kg/day) memantine treatment significantly reduced lesion volume (by 30% to 50%) and improved behavioral outcomes in stroke lesions that had been separated into either small/striatal or large/striatocortical infarcts. However, higher doses of memantine (20 mg/kg/day) significantly increased injury. These results show that clinically established low doses of memantine should be considered for patients ‘at risk' of stroke, while higher doses are contraindicated. PMID:25407270

Ectopic vesicular glutamate release at the optic nerve head and axon loss in mouse experimental glaucoma.

PubMed

Fu, Christine T; Sretavan, David W

2012-11-07

Although clinical and experimental observations indicate that the optic nerve head (ONH) is a major site of axon degeneration in glaucoma, the mechanisms by which local retinal ganglion cell (RGC) axons are injured and damage spreads among axons remain poorly defined. Using a laser-induced ocular hypertension (LIOH) mouse model of glaucoma, we found that within 48 h of intraocular pressure elevation, RGC axon segments within the ONH exhibited ectopic accumulation and colocalization of multiple components of the glutamatergic presynaptic machinery including the vesicular glutamate transporter VGLUT2, several synaptic vesicle marker proteins, glutamate, the soluble N-ethylmaleimide-sensitive factor attachment protein receptor complex and active zone cytomatrix components, as well as ultrastructurally identified, synaptophysin-containing vesicles. Ectopic vesicle exocytosis and glutamate release were detected in acute preparations of the LIOH ONH. Immunolocalization and analysis using the ionotropic receptor channel-permeant cation agmatine indicated that ONH axon segments and glia expressed glutamate receptors, and these receptors were more active after LIOH compared with controls. Pharmacological antagonism of glutamate receptors and neuronal activity resulted in increased RGC axon sparing in vivo. Furthermore, in vivo RGC-specific genetic disruption of the vesicular glutamate transporter VGLUT2 or the obligatory NMDA receptor subunit NR1 promoted axon survival in experimental glaucoma. As the inhibition of ectopic glutamate vesicular release or glutamate receptivity can independently modify the severity of RGC axon loss, synaptic release mechanisms may provide useful therapeutic entry points into glaucomatous axon degeneration.

Effect of cannabis on glutamate signalling in the brain: A systematic review of human and animal evidence.

PubMed

Colizzi, Marco; McGuire, Philip; Pertwee, Roger G; Bhattacharyya, Sagnik

2016-05-01

Use of cannabis or delta-9-tetrahydrocannabinol (Δ9-THC), its main psychoactive ingredient, is associated with psychotic symptoms or disorder. However, the neurochemical mechanism that may underlie this psychotomimetic effect is poorly understood. Although dopaminergic dysfunction is generally recognized as the final common pathway in psychosis, evidence of the effects of Δ9-THC or cannabis use on dopaminergic measures in the brain is equivocal. In fact, it is thought that cannabis or Δ9-THC may not act on dopamine firing directly but indirectly by altering glutamate neurotransmission. Here we systematically review all studies examining acute and chronic effects of cannabis or Δ9-THC on glutamate signalling in both animals and man. Limited research carried out in humans tends to support the evidence that chronic cannabis use reduces levels of glutamate-derived metabolites in both cortical and subcortical brain areas. Research in animals tends to consistently suggest that Δ9-THC depresses glutamate synaptic transmission via CB1 receptor activation, affecting glutamate release, inhibiting receptors and transporters function, reducing enzyme activity, and disrupting glutamate synaptic plasticity after prolonged exposure. Copyright © 2016 Elsevier Ltd. All rights reserved.

Riluzole But Not Melatonin Ameliorates Acute Motor Neuron Degeneration and Moderately Inhibits SOD1-Mediated Excitotoxicity Induced Disrupted Mitochondrial Ca2+ Signaling in Amyotrophic Lateral Sclerosis

PubMed Central

Jaiswal, Manoj Kumar

2017-01-01

Selective motoneurons (MNs) degeneration in the brain stem, hypoglossal motoneurons (HMNs), and the spinal cord resulting in patients paralysis and eventual death are prominent features of amyotrophic lateral sclerosis (ALS). Previous studies have suggested that mitochondrial respiratory impairment, low Ca2+ buffering and homeostasis and excitotoxicity are the pathological phenotypes found in mice, and cell culture models of familial ALS (fALS) linked with Cu/Zn-superoxide dismutase 1 (SOD1) mutation. In our study, we aimed to understand the impact of riluzole and melatonin on excitotoxicity, neuronal protection and Ca2+ signaling in individual HMNs ex vivo in symptomatic adult ALS mouse brain stem slice preparations and in WT and SOD1-G93A transfected SH-SY5Y neuroblastoma cell line using fluorescence microscopy, calcium imaging with high speed charged coupled device camera, together with immunohistochemistry, cell survival assay and histology. In our experiments, riluzole but not melatonin ameliorates MNs degeneration and moderately inhibit excitotoxicity and cell death in SH-SY5YWT or SH-SY5YG93A cell lines induced by complex IV blocker sodium azide. In brain stem slice preparations, riluzole significantly inhibit HMNs cell death induced by inhibiting the mitochondrial electron transport chain by Na-azide. In the HMNs of brainstem slice prepared from adult (14–15 weeks) WT, and corresponding symptomatic SOD1G93A mice, we measured the effect of riluzole and melatonin on [Ca2+]i using fura-2 AM ratiometric calcium imaging in individual MNs. Riluzole caused a significant decrease in [Ca2+]i transients and reversibly inhibited [Ca2+]i transients in Fura-2 AM loaded HMNs exposed to Na-azide in adult symptomatic SOD1G93A mice. On the contrary, melatonin failed to show similar effects in the HMNs of WT and SOD1G93A mice. Intrinsic nicotinamide adenine dinucleotide (NADH) fluorescence, an indicator of mitochondrial metabolism and health in MNs, showed enhanced

Glutamate dehydrogenase (RocG) in Bacillus licheniformis WX-02: Enzymatic properties and specific functions in glutamic acid synthesis for poly-γ-glutamic acid production.

PubMed

Tian, Guangming; Wang, Qin; Wei, Xuetuan; Ma, Xin; Chen, Shouwen

2017-04-01

Poly-γ-glutamic acid (γ-PGA), a natural biopolymer, is widely used in cosmetics, medicine, food, water treatment, and agriculture owing to its features of moisture sequestration, cation chelation, non-toxicity and biodegradability. Intracellular glutamic acid, the substrate of γ-PGA, is a limiting factor for high yield in γ-PGA production. Bacillus subtilis and Bacillus licheniformis are both important γ-PGA producing strains, and B. subtilis synthesizes glutamic acid in vivo using the unique GOGAT/GS pathway. However, little is known about the glutamate synthesis pathway in B. licheniformis. The aim of this work was to characterize the glutamate dehydrogenase (RocG) in glutamic acid synthesis from B. licheniformis with both in vivo and in vitro experiments. By re-directing the carbon flux distribution, the rocG gene deletion mutant WX-02ΔrocG produced intracellular glutamic acid with a concentration of 90ng/log(CFU), which was only 23.7% that of the wild-type WX-02 (380ng/log(CFU)). Furthermore, the γ-PGA yield of mutant WX-02ΔrocG was 5.37g/L, a decrease of 45.3% compared to the wild type (9.82g/L). In vitro enzymatic assays of RocG showed that RocG has higher affinity for 2-oxoglutarate than glutamate, and the glutamate synthesis rate was far above degradation. This is probably the first study to reveal the glutamic acid synthesis pathway and the specific functions of RocG in B. licheniformis. The results indicate that γ-PGA production can be enhanced through improving intracellular glutamic acid synthesis. Copyright © 2017 Elsevier Inc. All rights reserved.

AMP kinase–mediated activation of the BH3-only protein Bim couples energy depletion to stress-induced apoptosis

PubMed Central

Concannon, Caoimhín G.; Tuffy, Liam P.; Weisová, Petronela; Bonner, Helena P.; Dávila, David; Bonner, Caroline; Devocelle, Marc C.; Strasser, Andreas; Ward, Manus W.

2010-01-01

Excitotoxicity after glutamate receptor overactivation induces disturbances in cellular ion gradients, resulting in necrosis or apoptosis. Excitotoxic necrosis is triggered by rapid, irreversible ATP depletion, whereas the ability to recover cellular bioenergetics is suggested to be necessary for the activation of excitotoxic apoptosis. In this study, we demonstrate that even a transient decrease in cellular bioenergetics and an associated activation of adenosine monophosphate–activated protein kinase (AMPK) is necessary for the activation of excitotoxic apoptosis. We show that the Bcl-2 homology domain 3 (BH3)–only protein Bim, a proapoptotic Bcl-2 family member, is activated in multiple excitotoxicity paradigms, mediates excitotoxic apoptosis, and inhibits delayed Ca2+ deregulation, mitochondrial depolarization, and apoptosis-inducing factor translocation. We demonstrate that bim activation required the activation of AMPK and that prolonged AMPK activation is sufficient to induce bim gene expression and to trigger a bim-dependent cell death. Collectively, our data demonstrate that AMPK activation and the BH3-only protein Bim couple transient energy depletion to stress-induced neuronal apoptosis. PMID:20351066

Glutamate and Neurodegenerative Disease

NASA Astrophysics Data System (ADS)

Schaeffer, Eric; Duplantier, Allen

As the main excitatory neurotransmitter in the mammalian central nervous system, glutamate is critically involved in most aspects of CNS function. Given this critical role, it is not surprising that glutamatergic dysfunction is associated with many CNS disorders. In this chapter, we review the literature that links aberrant glutamate neurotransmission with CNS pathology, with a focus on neurodegenerative diseases. The biology and pharmacology of the various glutamate receptor families are discussed, along with data which links these receptors with neurodegenerative conditions. In addition, we review progress that has been made in developing small molecule modulators of glutamate receptors and transporters, and describe how these compounds have helped us understand the complex pharmacology of glutamate in normal CNS function, as well as their potential for the treatment of neurodegenerative diseases.

Kainate Receptors in the Striatum: Implications for Excitotoxicity in Huntington’s Disease

DTIC Science & Technology

2005-08-01

called ionotropic glutamate receptors. Using specific antibodies and glutamate-related compounds, we have achieved successfully a series of studies of the...them from AMPA receptors. However, the recent development of specific antibodies and selective AMPA receptor antagonists allowed various groups to...highly specific antibodies and/or cDNA probes allowed the better characterization of the cellular localization of various GABA and glutamate receptor

Neurotoxicity and reactive astrogliosis in the anterior cingulate cortex in acute ciguatera poisoning.

PubMed

Zhang, Xu; Cao, Bing; Wang, Jun; Liu, Jin; Tung, Vivian Oi Vian; Lam, Paul Kwan Sing; Chan, Leo Lai; Li, Ying

2013-06-01

Ciguatoxins (CTXs) cause long-term disturbance of cerebral functions. The primary mechanism of neurotoxicity is related to their interaction with voltage-gated sodium channels. However, until now, the neurological targets for CTXs in the brain of intact animals have not been described. In our study, 1 day following oral exposure to 0.26 ng/g of Pacific ciguatoxin 1 (P-CTX-1), we performed in vivo electrophysiological recordings in the rat anterior cingulate cortex (ACC) and identified the increase in spontaneous firings and enhanced responses to visceral noxious stimulation. Local field recordings characterized the P-CTX-1-induced synaptic potentiation and blockage of the induction of electrical stimulation-induced long-term potentiation in the medial thalamus (MT)-ACC pathway. Furthermore, intracerebroventricular administration of P-CTX-1 at doses of 1.0, 5.0, and 10 nM produced a dose-dependent increase in ACC neuronal firings and MT-ACC synaptic transmission. Further studies showed upregulated Na(+) channel expression in astrocytes under pathological conditions. We hypothesized that the astrocytes might have been activated in the ciguatera poisoning in vivo. Increases in glial fibrillary acid protein expression were detected in reactive astrocytes in the rat ACC. The activation of astroglia was further indicated by activation of the gap junction protein connexin 43 and upregulation of excitatory amino acid transporter 2 expression suggesting that glutamate was normally rapidly cleared from the synaptic cleft during acute ciguatera poisoning. However, neurotoxicity and reactive astrogliosis were not detected in the ACC after 7 days of P-CTX-1 exposure. The present results are the first characterization of P-CTX-1-invoked brain cortex neuronal excitotoxicity in vivo and supported the theme that neuron and astroglia signals might play roles in acute ciguatera poisoning.

Reciprocal regulation between taurine and glutamate response via Ca2+- dependent pathways in retinal third-order neurons

PubMed Central

2010-01-01

Although taurine and glutamate are the most abundant amino acids conducting neural signals in the central nervous system, the communication between these two neurotransmitters is largely unknown. This study explores the interaction of taurine and glutamate in the retinal third-order neurons. Using specific antibodies, both taurine and taurine transporters were localized in photoreceptors and Off-bipolar cells, glutamatergic neurons in retinas. It is possible that Off-bipolar cells release juxtaposed glutamate and taurine to activate the third-order neurons in retina. The interaction of taurine and glutamate was studied in acutely dissociated third-order neurons in whole-cell patch-clamp recording and Ca2+ imaging. We find that taurine effectively reduces glutamate-induced Ca2+ influx via ionotropic glutamate receptors and voltage-dependent Ca2+ channels in the neurons, and the effect of taurine was selectively inhibited by strychnine and picrotoxin, but not GABA receptor antagonists, although GABA receptors are present in the neurons. A CaMKII inhibitor partially reversed the effect of taurine, suggesting that a Ca2+/calmodulin-dependent pathway is involved in taurine regulation. On the other hand, a rapid influx of Ca2+ through ionotropic glutamate receptors could inhibit the amplitude and kinetics of taurine-elicited currents in the third-order neurons, which could be controlled with intracellular application of BAPTA a fast Ca2+ chelator. This study indicates that taurine is a potential neuromodulator in glutamate transmission. The reciprocal inhibition between taurine and glutamate in the postsynaptic neurons contributes to computation of visual signals in the retinal neurons. PMID:20804625

Oligomers of Amyloid β Prevent Physiological Activation of the Cellular Prion Protein-Metabotropic Glutamate Receptor 5 Complex by Glutamate in Alzheimer Disease.

PubMed

Haas, Laura T; Strittmatter, Stephen M

2016-08-12

The dysfunction and loss of synapses in Alzheimer disease are central to dementia symptoms. We have recently demonstrated that pathological Amyloid β oligomer (Aβo) regulates the association between intracellular protein mediators and the synaptic receptor complex composed of cellular prion protein (PrP(C)) and metabotropic glutamate receptor 5 (mGluR5). Here we sought to determine whether Aβo alters the physiological signaling of the PrP(C)-mGluR5 complex upon glutamate activation. We provide evidence that acute exposure to Aβo as well as chronic expression of familial Alzheimer disease mutant transgenes in model mice prevents protein-protein interaction changes of the complex induced by the glutamate analog 3,5-dihydroxyphenylglycine. We further show that 3,5-dihydroxyphenylglycine triggers the phosphorylation and activation of protein-tyrosine kinase 2-β (PTK2B, also referred to as Pyk2) and of calcium/calmodulin-dependent protein kinase II in wild-type brain slices but not in Alzheimer disease transgenic brain slices or wild-type slices incubated with Aβo. This study further distinguishes two separate Aβo-dependent signaling cascades, one dependent on extracellular Ca(2+) and Fyn kinase activation and the other dependent on the release of Ca(2+) from intracellular stores. Thus, Aβo triggers multiple distinct PrP(C)-mGluR5-dependent events implicated in neurodegeneration and dementia. We propose that targeting the PrP(C)-mGluR5 complex will reverse aberrant Aβo-triggered states of the complex to allow physiological fluctuations of glutamate signaling. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Glutamic acid as anticancer agent: An overview

PubMed Central

Dutta, Satyajit; Ray, Supratim; Nagarajan, K.

2013-01-01

The objective of the article is to highlight various roles of glutamic acid like endogenic anticancer agent, conjugates to anticancer agents, and derivatives of glutamic acid as possible anticancer agents. Besides these emphases are given especially for two endogenous derivatives of glutamic acid such as glutamine and glutamate. Glutamine is a derivative of glutamic acid and is formed in the body from glutamic acid and ammonia in an energy requiring reaction catalyzed by glutamine synthase. It also possesses anticancer activity. So the transportation and metabolism of glutamine are also discussed for better understanding the role of glutamic acid. Glutamates are the carboxylate anions and salts of glutamic acid. Here the roles of various enzymes required for the metabolism of glutamates are also discussed. PMID:24227952

Glutamic acid as anticancer agent: An overview.

PubMed

Dutta, Satyajit; Ray, Supratim; Nagarajan, K

2013-10-01

The objective of the article is to highlight various roles of glutamic acid like endogenic anticancer agent, conjugates to anticancer agents, and derivatives of glutamic acid as possible anticancer agents. Besides these emphases are given especially for two endogenous derivatives of glutamic acid such as glutamine and glutamate. Glutamine is a derivative of glutamic acid and is formed in the body from glutamic acid and ammonia in an energy requiring reaction catalyzed by glutamine synthase. It also possesses anticancer activity. So the transportation and metabolism of glutamine are also discussed for better understanding the role of glutamic acid. Glutamates are the carboxylate anions and salts of glutamic acid. Here the roles of various enzymes required for the metabolism of glutamates are also discussed.

Brain ischaemia induces shedding of a BDNF-scavenger ectodomain from TrkB receptors by excitotoxicity activation of metalloproteinases and γ-secretases.

PubMed

Tejeda, Gonzalo S; Ayuso-Dolado, Sara; Arbeteta, Raquel; Esteban-Ortega, Gema M; Vidaurre, Oscar G; Díaz-Guerra, Margarita

2016-04-01

Stroke remains a leading cause of death and disability in the world with limited therapies available to restrict brain damage or improve functional recovery after cerebral ischaemia. A promising strategy currently under investigation is the promotion of brain-derived neurotrophic factor (BDNF) signalling through tropomyosin-related kinase B (TrkB) receptors, a pathway essential for neuronal survival and function. However, TrkB and BDNF-signalling are impaired by excitotoxicity, a primary pathological process in stroke also associated with neurodegenerative diseases. Pathological imbalance of TrkB isoforms is critical in neurodegeneration and is caused by calpain processing of BDNF high affinity full-length receptor (TrkB-FL) and an inversion of the transcriptional pattern of the Ntrk2 gene, to favour expression of the truncated isoform TrkB-T1 over TrkB-FL. We report here that both TrkB-FL and neuronal TrkB-T1 also undergo ectodomain shedding by metalloproteinases activated after ischaemic injury or excitotoxic damage of cortical neurons. Subsequently, the remaining membrane-bound C-terminal fragments (CTFs) are cleaved by γ-secretases within the transmembrane region, releasing their intracellular domains (ICDs) into the cytosol. Therefore, we identify TrkB-FL and TrkB-T1 as new substrates of regulated intramembrane proteolysis (RIP), a mechanism that highly contributes to TrkB-T1 regulation in ischaemia but is minor for TrkB-FL which is mainly processed by calpain. However, since the secreted TrkB ectodomain acts as a BDNF scavenger and significantly alters BDNF/TrkB signalling, the mechanism of RIP could contribute to neuronal death in excitotoxicity. These results are highly relevant since they reveal new targets for the rational design of therapies to treat stroke and other pathologies with an excitotoxic component. Copyright © 2015 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Amperometric L-glutamate biosensor based on bacterial cell-surface displayed glutamate dehydrogenase.

PubMed

Liang, Bo; Zhang, Shu; Lang, Qiaolin; Song, Jianxia; Han, Lihui; Liu, Aihua

2015-07-16

A novel L-glutamate biosensor was fabricated using bacteria surface-displayed glutamate dehydrogenase (Gldh-bacteria). Here the cofactor NADP(+)-specific dependent Gldh was expressed on the surface of Escherichia coli using N-terminal region of ice nucleation protein (INP) as the anchoring motif. The cell fractionation assay and SDS-PAGE analysis indicated that the majority of INP-Gldh fusion proteins were located on the surface of cells. The biosensor was fabricated by successively casting polyethyleneimine (PEI)-dispersed multi-walled carbon nanotubes (MWNTs), Gldh-bacteria and Nafion onto the glassy carbon electrode (Nafion/Gldh-bacteria/PEI-MWNTs/GCE). The MWNTs could not only significantly lower the oxidation overpotential towards NAPDH, which was the product of NADP(+) involving in the oxidation of glutamate by Gldh, but also enhanced the current response. Under the optimized experimental conditions, the current-time curve of the Nafion/Gldh-bacteria/PEI-MWNTs/GCE was performed at +0.52 V (vs. SCE) by amperometry varying glutamate concentration. The current response was linear with glutamate concentration in two ranges (10 μM-1 mM and 2-10 mM). The low limit of detection was estimated to be 2 μM glutamate (S/N=3). Moreover, the proposed biosensor is stable, specific, reproducible and simple, which can be applied to real samples detection. Copyright © 2015 Elsevier B.V. All rights reserved.

Depletion of substance P and glutamate by capsaicin blocks respiratory rhythm in neonatal rat in vitro

PubMed Central

Morgado-Valle, Consuelo; Feldman, Jack L

2004-01-01

The specific role of the neuromodulator substance P (SP) and its target, the neurokinin 1 receptor (NK1R), in the generation and regulation of respiratory activity is not known. The preBötzinger complex (preBötC), an essential site for respiratory rhythm generation, contains glutamatergic NK1R-expressing neurones that are strongly modulated by exogenously applied SP or acute pharmacological blockade of NK1Rs. We investigated the effects of capsaicin, which depletes neuropeptides (including SP) and glutamate from presynaptic terminals, on respiratory motor output in medullary slice preparations of neonatal rat that generate respiratory-related activity. Bath application of capsaicin slowed respiratory motor output in a dose- and time-dependent manner. Respiratory rhythm could be restored by bath application of SP or glutamate transporter blockers. Capsaicin also evoked dose-dependent glutamate release and depleted SP in fibres within the preBötC. Our results suggest that depletion of SP (or other peptides) and/or glutamate by capsaicin causes a cessation of respiratory rhythm in neonatal rat slices. PMID:14724197

Depletion of substance P and glutamate by capsaicin blocks respiratory rhythm in neonatal rat in vitro.

PubMed

Morgado-Valle, Consuelo; Feldman, Jack L

2004-03-16

The specific role of the neuromodulator substance P (SP) and its target, the neurokinin 1 receptor (NK1R), in the generation and regulation of respiratory activity is not known. The preBötzinger complex (preBötC), an essential site for respiratory rhythm generation, contains glutamatergic NK1R-expressing neurones that are strongly modulated by exogenously applied SP or acute pharmacological blockade of NK1Rs. We investigated the effects of capsaicin, which depletes neuropeptides (including SP) and glutamate from presynaptic terminals, on respiratory motor output in medullary slice preparations of neonatal rat that generate respiratory-related activity. Bath application of capsaicin slowed respiratory motor output in a dose- and time-dependent manner. Respiratory rhythm could be restored by bath application of SP or glutamate transporter blockers. Capsaicin also evoked dose-dependent glutamate release and depleted SP in fibres within the preBötC. Our results suggest that depletion of SP (or other peptides) and/or glutamate by capsaicin causes a cessation of respiratory rhythm in neonatal rat slices.

The neuroprotective properties of the superoxide dismutase mimetic tempol correlate with its ability to reduce pathological glutamate release in a rodent model of stroke

PubMed Central

Dohare, Preeti; Hyzinski-García, María C.; Vipani, Aarshi; Bowens, Nicole H.; Nalwalk, Julia W.; Feustel, Paul J.; Keller, Richard W.; Jourd’heuil, David; Mongin, Alexander A.

2014-01-01

The contribution of oxidative stress to ischemic brain damage is well established. Nevertheless, for unknown reasons, several clinically tested antioxidant therapies failed to show benefits in human stroke. Based on our previous in vitro work, we hypothesized that the neuroprotective potency of antioxidants is related to their ability to limit release of the excitotoxic amino acids, glutamate and aspartate. We explored the effects of two antioxidants, tempol and edaravone, on amino acid release in the brain cortex, in a rat model of transient occlusion of the middle cerebral artery (MCAo). Amino acid levels were quantified using a microdialysis approach, with the probe positioned in the ischemic penumbra as verified by a laser Doppler technique. Two-hour MCAo triggered a dramatic increase in the levels of glutamate, aspartate, taurine and alanine. Microdialysate delivery of 10 mM tempol reduced the amino acid release by 60–80%, while matching levels of edaravone had no effect. In line with these latter data, an intracerebroventri-cular injection of tempol but not edaravone (500 nmols each, 15 minutes prior to MCAo) reduced infarction volumes by ~50% and improved neurobehavioral outcomes. In vitro assays showed that tempol was superior in removing superoxide anion, whereas edaravone was more potent in scavenging hydrogen peroxide, hydroxyl radical, and peroxynitrite. Overall, our data suggests that the neuroprotective properties of tempol are likely related to its ability to reduce tissue levels of the superoxide anion and pathological glutamate release, and, in such a way, limit progression of brain infarction within ischemic penumbra. These new findings may be instrumental in developing new antioxidant therapies for treatment of stroke. PMID:25224033

Untargeted Metabolomic Analysis of Rat Neuroblastoma Cells as a Model System to Study the Biochemical Effects of the Acute Administration of Methamphetamine.

PubMed

Maker, Garth L; Green, Tobias; Mullaney, Ian; Trengove, Robert D

2018-06-07

Methamphetamine is an illicit psychostimulant drug that is linked to a number of diseases of the nervous system. The downstream biochemical effects of its primary mechanisms are not well understood, and the objective of this study was to investigate whether untargeted metabolomic analysis of an in vitro model could generate data relevant to what is already known about this drug. Rat B50 neuroblastoma cells were treated with 1 mM methamphetamine for 48 h, and both intracellular and extracellular metabolites were profiled using gas chromatography⁻mass spectrometry. Principal component analysis of the data identified 35 metabolites that contributed most to the difference in metabolite profiles. Of these metabolites, the most notable changes were in amino acids, with significant increases observed in glutamate, aspartate and methionine, and decreases in phenylalanine and serine. The data demonstrated that glutamate release and, subsequently, excitotoxicity and oxidative stress were important in the response of the neuronal cell to methamphetamine. Following this, the cells appeared to engage amino acid-based mechanisms to reduce glutamate levels. The potential of untargeted metabolomic analysis has been highlighted, as it has generated biochemically relevant data and identified pathways significantly affected by methamphetamine. This combination of technologies has clear uses as a model for the study of neuronal toxicology.

The interplay between inflammatory cytokines and the endocannabinoid system in the regulation of synaptic transmission.

PubMed

Rossi, Silvia; Motta, Caterina; Musella, Alessandra; Centonze, Diego

2015-09-01

Excessive glutamate-mediated synaptic transmission and secondary excitotoxicity have been proposed as key determinants of neurodegeneration in many neurological diseases. Soluble mediators of inflammation have recently gained attention owing to their ability to enhance glutamate transmission and affect synaptic sensitivity to neurotransmitters. In the complex crosstalk between soluble immunoactive molecules and synapses, the endocannabinoid system (ECS) plays a central role, exerting an indirect neuroprotective action by inhibiting cytokine-dependent synaptic alterations, and a direct neuroprotective effect by limiting glutamate transmission and excitotoxic damage. On the other hand, the endocannabinoid (eCB)-mediated control of synaptic transmission is altered by proinflammatory cytokines with consequent effects in central nervous system (CNS) disorders. In this review, we summarize the interactions, at the pre- and postsynaptic level, between major inflammatory cytokines and the ECS. In addition, the behavioral and clinical consequences of the modulation of synaptic transmission during neuroinflammation are discussed. This article is part of a Special Issue entitled 'Neuroimmunology and Synaptic Function'. Copyright © 2014 Elsevier Ltd. All rights reserved.

Creatine Protects against Excitoxicity in an In Vitro Model of Neurodegeneration

PubMed Central

Genius, Just; Geiger, Johanna; Bender, Andreas; Möller, Hans-Jürgen; Klopstock, Thomas; Rujescu, Dan

2012-01-01

Creatine has been shown to be neuroprotective in aging, neurodegenerative conditions and brain injury. As a common molecular background, oxidative stress and disturbed cellular energy homeostasis are key aspects in these conditions. Moreover, in a recent report we could demonstrate a life-enhancing and health-promoting potential of creatine in rodents, mainly due to its neuroprotective action. In order to investigate the underlying pharmacology mediating these mainly neuroprotective properties of creatine, cultured primary embryonal hippocampal and cortical cells were challenged with glutamate or H2O2. In good agreement with our in vivo data, creatine mediated a direct effect on the bioenergetic balance, leading to an enhanced cellular energy charge, thereby acting as a neuroprotectant. Moreover, creatine effectively antagonized the H2O2-induced ATP depletion and the excitotoxic response towards glutamate, while not directly acting as an antioxidant. Additionally, creatine mediated a direct inhibitory action on the NMDA receptor-mediated calcium response, which initiates the excitotoxic cascade. Even excessive concentrations of creatine had no neurotoxic effects, so that high-dose creatine supplementation as a health-promoting agent in specific pathological situations or as a primary prophylactic compound in risk populations seems feasible. In conclusion, we were able to demonstrate that the protective potential of creatine was primarily mediated by its impact on cellular energy metabolism and NMDA receptor function, along with reduced glutamate spillover, oxidative stress and subsequent excitotoxicity. PMID:22347384

Ciprofloxacin triggered glutamate production by Corynebacterium glutamicum.

PubMed

Lubitz, Dorit; Wendisch, Volker F

2016-10-07

Corynebacterium glutamicum is a well-studied bacterium which naturally overproduces glutamate when induced by an elicitor. Glutamate production is accompanied by decreased 2-oxoglutatate dehydrogenase activity. Elicitors of glutamate production by C. glutamicum analyzed to molecular detail target the cell envelope. Ciprofloxacin, an inhibitor of bacterial DNA gyrase and topoisomerase IV, was shown to inhibit growth of C. glutamicum wild type with concomitant excretion of glutamate. Enzyme assays showed that 2-oxoglutarate dehydrogenase activity was decreased due to ciprofloxacin addition. Transcriptome analysis revealed that this inhibitor of DNA gyrase increased RNA levels of genes involved in DNA synthesis, repair and modification. Glutamate production triggered by ciprofloxacin led to glutamate titers of up to 37 ± 1 mM and a substrate specific glutamate yield of 0.13 g/g. Even in the absence of the putative glutamate exporter gene yggB, ciprofloxacin effectively triggered glutamate production. When C. glutamicum wild type was cultivated under nitrogen-limiting conditions, 2-oxoglutarate rather than glutamate was produced as consequence of exposure to ciprofloxacin. Recombinant C. glutamicum strains overproducing lysine, arginine, ornithine, and putrescine, respectively, secreted glutamate instead of the desired amino acid when exposed to ciprofloxacin. Ciprofloxacin induced DNA synthesis and repair genes, reduced 2-oxoglutarate dehydrogenase activity and elicited glutamate production by C. glutamicum. Production of 2-oxoglutarate could be triggered by ciprofloxacin under nitrogen-limiting conditions.

[60]Fullerene-based monolayers as neuroprotective biocompatible hybrid materials.

PubMed

Giust, Davide; Albasanz, José Luis; Martín, Mairena; Marega, Riccardo; Delforge, Arnaud; Bonifazi, Davide

2011-10-14

Here we report on the surface immobilization of redox-active [60]fullerene derivatives and the consequent neuroprotective effects toward l-glutamate induced excitotoxicity in human derived undifferentiated neuroblastoma cells. This journal is © The Royal Society of Chemistry 2011

Clostridium perfringens epsilon toxin targets granule cells in the mouse cerebellum and stimulates glutamate release.

PubMed

Lonchamp, Etienne; Dupont, Jean-Luc; Wioland, Laetitia; Courjaret, Raphaël; Mbebi-Liegeois, Corinne; Jover, Emmanuel; Doussau, Frédéric; Popoff, Michel R; Bossu, Jean-Louis; de Barry, Jean; Poulain, Bernard

2010-09-30

Epsilon toxin (ET) produced by C. perfringens types B and D is a highly potent pore-forming toxin. ET-intoxicated animals express severe neurological disorders that are thought to result from the formation of vasogenic brain edemas and indirect neuronal excitotoxicity. The cerebellum is a predilection site for ET damage. ET has been proposed to bind to glial cells such as astrocytes and oligodendrocytes. However, the possibility that ET binds and attacks the neurons remains an open question. Using specific anti-ET mouse polyclonal antibodies and mouse brain slices preincubated with ET, we found that several brain structures were labeled, the cerebellum being a prominent one. In cerebellar slices, we analyzed the co-staining of ET with specific cell markers, and found that ET binds to the cell body of granule cells, oligodendrocytes, but not astrocytes or nerve endings. Identification of granule cells as neuronal ET targets was confirmed by the observation that ET induced intracellular Ca(2+) rises and glutamate release in primary cultures of granule cells. In cultured cerebellar slices, whole cell patch-clamp recordings of synaptic currents in Purkinje cells revealed that ET greatly stimulates both spontaneous excitatory and inhibitory activities. However, pharmacological dissection of these effects indicated that they were only a result of an increased granule cell firing activity and did not involve a direct action of the toxin on glutamatergic nerve terminals or inhibitory interneurons. Patch-clamp recordings of granule cell somata showed that ET causes a decrease in neuronal membrane resistance associated with pore-opening and depolarization of the neuronal membrane, which subsequently lead to the firing of the neuronal network and stimulation of glutamate release. This work demonstrates that a subset of neurons can be directly targeted by ET, suggesting that part of ET-induced neuronal damage observed in neuronal tissue is due to a direct effect of ET on

Clostridium perfringens Epsilon Toxin Targets Granule Cells in the Mouse Cerebellum and Stimulates Glutamate Release

PubMed Central

Lonchamp, Etienne; Dupont, Jean-Luc; Wioland, Laetitia; Courjaret, Raphaël; Mbebi-Liegeois, Corinne; Jover, Emmanuel; Doussau, Frédéric; Popoff, Michel R.; Bossu, Jean-Louis; de Barry, Jean; Poulain, Bernard

2010-01-01

Epsilon toxin (ET) produced by C. perfringens types B and D is a highly potent pore-forming toxin. ET-intoxicated animals express severe neurological disorders that are thought to result from the formation of vasogenic brain edemas and indirect neuronal excitotoxicity. The cerebellum is a predilection site for ET damage. ET has been proposed to bind to glial cells such as astrocytes and oligodendrocytes. However, the possibility that ET binds and attacks the neurons remains an open question. Using specific anti-ET mouse polyclonal antibodies and mouse brain slices preincubated with ET, we found that several brain structures were labeled, the cerebellum being a prominent one. In cerebellar slices, we analyzed the co-staining of ET with specific cell markers, and found that ET binds to the cell body of granule cells, oligodendrocytes, but not astrocytes or nerve endings. Identification of granule cells as neuronal ET targets was confirmed by the observation that ET induced intracellular Ca2+ rises and glutamate release in primary cultures of granule cells. In cultured cerebellar slices, whole cell patch-clamp recordings of synaptic currents in Purkinje cells revealed that ET greatly stimulates both spontaneous excitatory and inhibitory activities. However, pharmacological dissection of these effects indicated that they were only a result of an increased granule cell firing activity and did not involve a direct action of the toxin on glutamatergic nerve terminals or inhibitory interneurons. Patch-clamp recordings of granule cell somata showed that ET causes a decrease in neuronal membrane resistance associated with pore-opening and depolarization of the neuronal membrane, which subsequently lead to the firing of the neuronal network and stimulation of glutamate release. This work demonstrates that a subset of neurons can be directly targeted by ET, suggesting that part of ET-induced neuronal damage observed in neuronal tissue is due to a direct effect of ET on neurons

The Degradation of 14C-Glutamic Acid by L-Glutamic Acid Decarboxylase.

ERIC Educational Resources Information Center

Dougherty, Charles M; Dayan, Jean

1982-01-01

Describes procedures and semi-micro reaction apparatus (carbon dioxide trap) to demonstrate how a particular enzyme (L-Glutamic acid decarboxylase) may be used to determine the site or sites of labeling in its substrate (carbon-14 labeled glutamic acid). Includes calculations, solutions, and reagents used. (Author/SK)

Effect of starch ingestion on plasma glutamate concentrations in humans ingesting monosodium L-glutamate in soup.

PubMed

Stegink, L D; Filer, L J; Baker, G L

1985-02-01

Plasma glutamate concentrations in human subjects are markedly lower when monosodium L-glutamate is ingested in a water solution containing partially hydrolyzed starch than when ingested in water alone. This study was carried out to investigate whether starch ingested as crackers had a similar effect. Eight normal adult subjects (four male, four female) ingested three servings of a beef consommé providing 50 mg/kg body weight monosodium L-glutamate. One serving was consommé alone, the other two were accompanied by sufficient crackers to provide 0.25 or 0.5 g starch per kilogram body weight, respectively. Ingestion of consommé containing glutamate significantly increased the mean plasma glutamate concentration above baseline to a mean peak value 30 min later. The peak after consumption of 0.5 g starch per kilogram body weight, but not 0.25 g/kg body weight, was significantly lower than when consommé alone was ingested. These data indicate that simultaneous ingestion of metabolizable carbohydrate with glutamate has a marked effect on the plasma glutamate response and indicate that the threshold value for carbohydrate is greater than 0.25 g/kg body weight.

Targeting Glia with N-Acetylcysteine Modulates Brain Glutamate and Behaviors Relevant to Neurodevelopmental Disorders in C57BL/6J Mice

PubMed Central

Durieux, Alice M. S.; Fernandes, Cathy; Murphy, Declan; Labouesse, Marie Anais; Giovanoli, Sandra; Meyer, Urs; Li, Qi; So, Po-Wah; McAlonan, Grainne

2015-01-01

An imbalance between excitatory (E) glutamate and inhibitory (I) GABA transmission may underlie neurodevelopmental conditions such as autism spectrum disorder (ASD) and schizophrenia. This may be direct, through alterations in synaptic genes, but there is increasing evidence for the importance of indirect modulation of E/I balance through glial mechanisms. Here, we used C57BL/6J mice to test the hypothesis that striatal glutamate levels can be shifted by N-acetylcysteine (NAC), which acts at the cystine-glutamate antiporter of glial cells. Striatal glutamate was quantified in vivo using proton magnetic resonance spectroscopy. The effect of NAC on behaviors relevant to ASD was examined in a separate cohort. NAC induced a time-dependent decrease in striatal glutamate, which recapitulated findings of lower striatal glutamate reported in ASD. NAC-treated animals were significantly less active and more anxious in the open field test; and NAC-treated females had significantly impaired prepulse inhibition of startle response. This at least partly mimics greater anxiety and impaired sensorimotor gating reported in neurodevelopmental disorders. Thus glial mechanisms regulate glutamate acutely and have functional consequences even in adulthood. Glial cells may be a potential drug target for the development of new therapies for neurodevelopmental disorders across the life-span. PMID:26696857

NBQX, a highly selective competitive antagonist of AMPA and KA ionotropic glutamate receptors, increases seizures and mortality following picornavirus infection.

PubMed

Libbey, Jane E; Hanak, Tyler J; Doty, Daniel J; Wilcox, Karen S; Fujinami, Robert S

2016-06-01

Seizures occur due to an imbalance between excitation and inhibition, with the balance tipping towards excitation, and glutamate is the predominant excitatory neurotransmitter in the central nervous system of mammals. Since upregulation of expression and/or function of glutamate receptors can contribute to seizures we determined the effects of three antagonists, NBQX, GYKI-52466 and MK 801, of the various ionotropic glutamate receptors, AMPA, NMDA and KA, on acute seizure development in the Theiler's murine encephalomyelitis virus (TMEV)-induced seizure model. We found that only NBQX had an effect on acute seizure development, resulting in a significantly higher number of mice experiencing seizures, an increase in the number of seizures per mouse, a greater cumulative seizure score per mouse and a significantly higher mortality rate among the mice. Although NBQX has previously been shown to be a potent anticonvulsant in animal seizure models, seizures induced by electrical stimulation, drug administration or as a result of genetic predisposition may differ greatly in terms of mechanism of seizure development from our virus-induced seizure model, which could explain the opposite, proconvulsant effect of NBQX observed in the TMEV-induced seizure model. Copyright © 2016 Elsevier Inc. All rights reserved.

NBQX, a highly selective competitive antagonist of AMPA and KA ionotropic glutamate receptors, increases seizures and mortality following picornavirus infection

PubMed Central

Libbey, Jane E.; Hanak, Tyler J.; Doty, Daniel J.; Wilcox, Karen S.; Fujinami, Robert S.

2016-01-01

Seizures occur due to an imbalance between excitation and inhibition, with the balance tipping towards excitation, and glutamate is the predominant excitatory neurotransmitter in the central nervous system of mammals. Since upregulation of expression and/or function of glutamate receptors can contribute to seizures we determined the effects of three antagonists, NBQX, GYKI-52466 and MK 801, of the various ionotropic glutamate receptors, AMPA, NMDA and KA, on acute seizure development in the Theiler’s murine encephalomyelitis virus (TMEV)-induced seizure model. We found that only NBQX had an effect on acute seizure development, resulting in a significantly higher number of mice experiencing seizures, an increase in the number of seizures per mouse, a greater cumulative seizure score per mouse and a significantly higher mortality rate among the mice. Although NBQX has previously been shown to be a potent anticonvulsant in animal seizure models, seizures induced by electrical stimulation, drug administration or as a result of genetic predisposition may differ greatly in terms of mechanism of seizure development from our virus-induced seizure model, which could explain the opposite, proconvulsant effect of NBQX observed in the TMEV-induced seizure model. PMID:27072529

Acute brown adipose tissue temperature response to cold in monosodium glutamate-treated Siberian hamsters

PubMed Central

Leitner, Claudia; Bartness, Timothy J.

2014-01-01

Neonatal monosodium glutamate (MSG) administration increases adiposity, decreases energy expenditure and is associated with arcuate nucleus (Arc) destruction. Disrupted brown adipose tissue (BAT) thermogenesis underlies some of these effects, although, interscapular BAT temperature (TIBAT) has not been measured. Therefore, we tested the effects of neonatal MSG or vehicle administration in Siberian hamsters and, when they were adults, measured TIBAT during acute cold exposure. The Arc and its projection to the hypothalamic paraventricular nucleus (PVH) are both components of the CNS outflow circuits to IBAT, with the latter implicated in BAT thermogenesis that could be compromised by MSG treatment. Using a viral transneuronal tract tracer, pseudorabies virus (PRV), we also tested whether the components of these circuits were intact. As adults, MSG-treated hamsters had significantly increased body mass and some white fat pad masses, markedly reduced Arc Nissl and neuropeptide staining, and PVH neuropeptide fiber staining. Cold-exposed (18 h at 5 °C) MSG- and vehicle-treated hamsters initially maintained TIBAT, but the ability of the former waned after 2 h being significantly decreased by 18 h. PRV immunoreactive fibers/cells were not altered by neonatal MSG treatment despite substantial Arc and PVH destruction. MSG- and vehicle-treated hamsters given an exogenous norepinephrine challenge showed identical increases in the duration and peak of TIBAT. Thus, the inability of MSG-treated animals to sustain TIBAT in the cold is not due to any obvious MSG-induced deletions of central sympathetic outflow circuits to IBAT, but appears to be extrinsic to the tissue nevertheless. PMID:19643091

Taste responses to monosodium glutamate after alcohol exposure.

PubMed

Wrobel, Elzbieta; Skrok-Wolska, Dominika; Ziolkowski, Marcin; Korkosz, Agnieszka; Habrat, Boguslaw; Woronowicz, Bohdan; Kukwa, Andrzej; Kostowski, Wojciech; Bienkowski, Przemyslaw; Scinska, Anna

2005-01-01

The aim of the present study was to evaluate the effects of acute and chronic exposure to alcohol on taste responses to a prototypic umami substance, monosodium glutamate (MSG). The rated intensity and pleasantness of MSG taste (0.03-10.0%) was compared in chronic male alcoholics (n = 35) and control subjects (n = 25). In a separate experiment, the effects of acute exposure of the oral mucosa to ethanol rinse (0.5-4.0%) on MSG taste (0.3-3.0%) were studied in 10 social drinkers. The alcoholic and control group did not differ in terms of the rated intensity and pleasantness of MSG taste. Electrogustometric thresholds were significantly (P < 0.01) higher, i.e. worse, in the alcohol-dependent subjects. The difference remained significant after controlling for between-group differences in cigarette smoking and coffee drinking. Rinsing with ethanol did not alter either intensity or pleasantness of MSG taste in social drinkers. The present results suggest that: (i) neither acute nor chronic alcohol exposure modifies taste responses to MSG; (ii) alcohol dependence may be associated with deficit in threshold taste reactivity, as assessed by electrogustometry.

Metabotropic Glutamate Receptors in the Trafficking of Ionotropic Glutamate and GABAA Receptors at Central Synapses

PubMed Central

Xiao, Min-Yi; Gustafsson, Bengt; Niu, Yin-Ping

2006-01-01

The trafficking of ionotropic glutamate (AMPA, NMDA and kainate) and GABAA receptors in and out of, or laterally along, the postsynaptic membrane has recently emerged as an important mechanism in the regulation of synaptic function, both under physiological and pathological conditions, such as information processing, learning and memory formation, neuronal development, and neurodegenerative diseases. Non-ionotropic glutamate receptors, primarily group I metabotropic glutamate receptors (mGluRs), co-exist with the postsynaptic ionotropic glutamate and GABAA receptors. The ability of mGluRs to regulate postsynaptic phosphorylation and Ca2+ concentration, as well as their interactions with postsynaptic scaffolding/signaling proteins, makes them well suited to influence the trafficking of ionotropic glutamate and GABAA receptors. Recent studies have provided insights into how mGluRs may impose such an influence at central synapses, and thus how they may affect synaptic signaling and the maintenance of long-term synaptic plasticity. In this review we will discuss some of the recent progress in this area: i) long-term synaptic plasticity and the involvement of mGluRs; ii) ionotropic glutamate receptor trafficking and long-term synaptic plasticity; iii) the involvement of postsynaptic group I mGluRs in regulating ionotropic glutamate receptor trafficking; iv) involvement of postsynaptic group I mGluRs in regulating GABAA receptor trafficking; v) and the trafficking of postsynaptic group I mGluRs themselves. PMID:18615134

Possible involvements of glutamate and adrenergic receptors on acute toxicity of methylphenidate in isolated hippocampus and cerebral cortex of adult rats.

PubMed

Motaghinejad, Majid; Motevalian, Manijeh; Shabab, Behnaz

2017-04-01

Neurodegeneration induced by methylphenidate (MPH), as a central stimulant with unknown long-term consequences, in adult rats' brain and the possible mechanisms involved were studied. Rats were acutely treated with MPH in the presence and absence of some receptor antagonists such as ketamine, topiramate, yohimbine, and haloperidol. Motor activity and anxiety level in rats were monitored. Antioxidant and inflammatory parameters were also measured in isolated hippocampus and cerebral cortex. MPH-treated groups (10 and 20 mg/kg) demonstrated anxiety-like behavior and increased motor activity. MPH significantly increased lipid peroxidation, GSSG content, IL-1β and TNF-α levels in isolated tissues, and also significantly reduced GSH content, superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione reductase (GR) activities in hippocampus and cerebral cortex. Pretreatment of animals by receptor antagonists caused inhibition of MPH-induced motor activity disturbances and anxiety-like behavior. Pretreatment of animals by ketamine, topiramate, and yohimbine inhibited the MPH-induced oxidative stress and inflammation; it significantly decreased lipid peroxidation, GSSG level, IL-1β and TNF-α levels and increased GSH content, SOD, GPx, and GR activities in hippocampus and cerebral cortex of acutely MPH-treated rats. Pretreatment with haloperidol did not cause any change in MPH-induced oxidative stress and inflammation. In conclusion, acute administration of high doses of MPH can cause oxidative and inflammatory changes in brain cells and induce neurodegeneration in hippocampus and cerebral cortex of adult rats and these changes might probably be mediated by glutamate (NMDA or AMPA) and/or α 2 -adrenergic receptors. © 2016 Société Française de Pharmacologie et de Thérapeutique.

Glutamate: Tastant and Neuromodulator in Taste Buds.

PubMed

Vandenbeuch, Aurelie; Kinnamon, Sue C

2016-07-01

In taste buds, glutamate plays a double role as a gustatory stimulus and neuromodulator. The detection of glutamate as a tastant involves several G protein-coupled receptors, including the heterodimer taste receptor type 1, member 1 and 3 as well as metabotropic glutamate receptors (mGluR1 and mGluR4). Both receptor types participate in the detection of glutamate as shown with knockout animals and selective antagonists. At the basal part of taste buds, ionotropic glutamate receptors [N-methyl-d-aspartate (NMDA) and non-NMDA] are expressed and participate in the modulation of the taste signal before its transmission to the brain. Evidence suggests that glutamate has an efferent function on taste cells and modulates the release of other neurotransmitters such as serotonin and ATP. This short article reviews the recent developments in the field with regard to glutamate receptors involved in both functions as well as the influence of glutamate on the taste signal. © 2016 American Society for Nutrition.

Ca2+-Permeable AMPARs Mediate Glutamatergic Transmission and Excitotoxic Damage at the Hair Cell Ribbon Synapse.

PubMed

Sebe, Joy Y; Cho, Soyoun; Sheets, Lavinia; Rutherford, Mark A; von Gersdorff, Henrique; Raible, David W

2017-06-21

We report functional and structural evidence for GluA2-lacking Ca 2+ -permeable AMPARs (CP-AMPARs) at the mature hair cell ribbon synapse. By using the methodological advantages of three species (of either sex), we demonstrate that CP-AMPARs are present at the hair cell synapse in an evolutionarily conserved manner. Via a combination of in vivo electrophysiological and Ca 2+ imaging approaches in the larval zebrafish, we show that hair cell stimulation leads to robust Ca 2+ influx into afferent terminals. Prolonged application of AMPA caused loss of afferent terminal responsiveness, whereas blocking CP-AMPARs protects terminals from excitotoxic swelling. Immunohistochemical analysis of AMPAR subunits in mature rat cochlea show regions within synapses lacking the GluA2 subunit. Paired recordings from adult bullfrog auditory synapses demonstrate that CP-AMPARs mediate a major component of glutamatergic transmission. Together, our results support the importance of CP-AMPARs in mediating transmission at the hair cell ribbon synapse. Further, excess Ca 2+ entry via CP-AMPARs may underlie afferent terminal damage following excitotoxic challenge, suggesting that limiting Ca 2+ levels in the afferent terminal may protect against cochlear synaptopathy associated with hearing loss. SIGNIFICANCE STATEMENT A single incidence of noise overexposure causes damage at the hair cell synapse that later leads to neurodegeneration and exacerbates age-related hearing loss. A first step toward understanding cochlear neurodegeneration is to identify the cause of initial excitotoxic damage to the postsynaptic neuron. Using a combination of immunohistochemical, electrophysiological, and Ca 2+ imaging approaches in evolutionarily divergent species, we demonstrate that Ca 2+ -permeable AMPARs (CP-AMPARs) mediate glutamatergic transmission at the adult auditory hair cell synapse. Overexcitation of the terminal causes Ca 2+ accumulation and swelling that can be prevented by blocking CP

Effect of biotin on transcription levels of key enzymes and glutamate efflux in glutamate fermentation by Corynebacterium glutamicum.

PubMed

Cao, Yan; Duan, Zuoying; Shi, Zhongping

2014-02-01

Biotin is an important factor affecting the performance of glutamate fermentation by biotin auxotrophic Corynebacterium glutamicum and glutamate is over-produced only when initial biotin content is controlled at suitable levels or initial biotin is excessive but with Tween 40 addition during fermentation. The transcription levels of key enzymes at pyruvate, isocitrate and α-ketoglutarate metabolic nodes, as well as transport protein (TP) of glutamate were investigated under the conditions of varied biotin contents and Tween 40 supplementation. When biotin was insufficient, the genes encoding key enzymes and TP were down-regulated in the early production phase, in particular, the transcription level of isocitrate dehydrogenase (ICDH) which was only 2% of that of control. Although the cells' morphology transformation and TP level were not affected, low transcription level of ICDH led to lower final glutamate concentration (64 g/L). When biotin was excessive, the transcription levels of key enzymes were at comparable levels as those of control with ICDH as an exception, which was only 3-22% of control level throughout production phase. In this case, little intracellular glutamate accumulation (1.5 mg/g DCW) and impermeable membrane resulted in non glutamate secretion into broth, even though the quantity of TP was more than 10-folds of control level. Addition of Tween 40 when biotin was excessive stimulated the expression of all key enzymes and TP, intracellular glutamate content was much higher (10-12 mg/g DCW), and final glutamate concentration reached control level (75-80 g/L). Hence, the membrane alteration and TP were indispensable in glutamate secretion. Biotin and Tween 40 influenced the expression level of ICDH and glutamate efflux, thereby influencing glutamate production.

Enzymatic production of α-ketoglutaric acid from l-glutamic acid via l-glutamate oxidase.

PubMed

Niu, Panqing; Dong, Xiaoxiang; Wang, Yuancai; Liu, Liming

2014-06-10

In this study, a novel strategy for α-ketoglutaric acid (α-KG) production from l-glutamic acid using recombinant l-glutamate oxidase (LGOX) was developed. First, by analyzing the molecular structure characteristics of l-glutamic acid and α-KG, LGOX was found to be the best catalyst for oxidizing the amino group of l-glutamic acid to a ketonic group without the need for exogenous cofactor. Then the LGOX gene was expressed in Escherichia coli BL21 (DE3) in a soluble and active form, and the recombinant LGOX activity reached to a maximum value of 0.59U/mL at pH 6.5, 30°C. Finally, the maximum α-KG concentration reached 104.7g/L from 110g/L l-glutamic acid in 24h, under the following optimum conditions: 1.5U/mL LGOX, 250U/mL catalase, 3mM MnCl2, 30°C, and pH 6.5. Copyright © 2014. Published by Elsevier B.V.

Neuroprotective effect of pyruvate and oxaloacetate during pilocarpine induced status epilepticus in rats.

PubMed

Carvalho, Andrezza Sossai Rodrigues; Torres, Laila Brito; Persike, Daniele Suzete; Fernandes, Maria José Silva; Amado, Debora; Naffah-Mazzacoratti, Maria da Graça; Cavalheiro, Esper Abrão; da Silva, Alexandre Valotta

2011-02-01

Recent research data have shown that systemic administration of pyruvate and oxaloacetate causes an increased brain-to-blood glutamate efflux. Since increased release of glutamate during epileptic seizures can lead to excitotoxicity and neuronal cell death, we tested the hypothesis that glutamate scavenging mediated by pyruvate and oxaloacetate systemic administration could have a neuroprotective effect in rats subjected to status epilepticus (SE). SE was induced by a single dose of pilocarpine (350mg/kgi.p.). Thirty minutes after SE onset, a single dose of pyruvate (250mg/kgi.p.), oxaloacetate (1.4mg/kgi.p.), or both substances was administrated. Acute neuronal loss in hippocampal regions CA1 and hilus was quantitatively determined five hours after SE onset, using the optical fractionator method for stereological cell counting. Apoptotic cascade in the hippocampus was also investigated seven days after SE using caspase-1 and -3 activity assays. SE-induced neuronal loss in CA1 was completely prevented in rats treated with pyruvate plus oxaloacetate. The SE-induced caspase-1 activation was significantly reduced when rats were treated with oxaloacetate or pyruvate plus oxaloacetate. The treatment with pyruvate and oxaloacetate caused a neuroprotective effect in rats subjected to pilocarpine-induced SE. Copyright © 2010 Elsevier Ltd. All rights reserved.

GDH3 encodes a glutamate dehydrogenase isozyme, a previously unrecognized route for glutamate biosynthesis in Saccharomyces cerevisiae.

PubMed Central

Avendaño, A; Deluna, A; Olivera, H; Valenzuela, L; Gonzalez, A

1997-01-01

It has been considered that the yeast Saccharomyces cerevisiae, like many other microorganisms, synthesizes glutamate through the action of NADP+-glutamate dehydrogenase (NADP+-GDH), encoded by GDH1, or through the combined action of glutamine synthetase and glutamate synthase (GOGAT), encoded by GLN1 and GLT1, respectively. A double mutant of S. cerevisiae lacking NADP+-GDH and GOGAT activities was constructed. This strain was able to grow on ammonium as the sole nitrogen source and thus to synthesize glutamate through an alternative pathway. A computer search for similarities between the GDH1 nucleotide sequence and the complete yeast genome was carried out. In addition to identifying its cognate sequence at chromosome XIV, the search found that GDH1 showed high identity with a previously recognized open reading frame (GDH3) of chromosome I. Triple mutants impaired in GDH1, GLT1, and GDH3 were obtained. These were strict glutamate auxotrophs. Our results indicate that GDH3 plays a significant physiological role, providing glutamate when GDH1 and GLT1 are impaired. This is the first example of a microorganism possessing three pathways for glutamate biosynthesis. PMID:9287019

21 CFR 182.1045 - Glutamic acid.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Glutamic acid. 182.1045 Section 182.1045 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN....1045 Glutamic acid. (a) Product. Glutamic acid. (b) [Reserved] (c) Limitations, restrictions, or...

21 CFR 182.1045 - Glutamic acid.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Glutamic acid. 182.1045 Section 182.1045 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN....1045 Glutamic acid. (a) Product. Glutamic acid. (b) [Reserved] (c) Limitations, restrictions, or...

Role of glutamate receptors in the dorsal reticular nucleus in formalin-induced secondary allodynia.

PubMed

Ambriz-Tututi, Mónica; Palomero-Rivero, Marcela; Ramirez-López, Fernanda; Millán-Aldaco, Diana; Drucker-Colín, And René

2013-10-01

The role of glutamate receptors present in the medullary dorsal reticular nucleus (DRt) in the formalin test and formalin-induced secondary nociception was studied in rats. Secondary mechanical allodynia was assessed with von Frey filaments applied to the rat's hindpaw, and secondary thermal hyperalgesia was evaluated with the tail-immersion test. The selective glutamate receptor antagonists MK801 (N-methyl-D-aspartate receptor antagonist), 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) (AMPA/KA receptor antagonist) and A841720 (metabotropic glutamate 1 receptor antagonist) were injected into the DRt before or 6 days after formalin injection in the rat. In the formalin test, the three antagonists significantly reduced the number of flinches in both phases of the test. DRt microinjection of MK801 or A841720, but not of CNQX, reduced both secondary nociceptive behaviors. Moreover, pre-treatment with the three antagonists injected into the DRt prevented the development of secondary mechanical allodynia and secondary thermal hyperalgesia. Similarly, in these rats, the number of c-Fos-like immunoreactive neurons were markedly reduced in both the superficial and deep lamina of the dorsal horn. Our findings support the role of DRt as a pain facilitator in acute and chronic pain states, and suggest a key role of glutamate receptors during the development and maintenance of formalin-induced secondary allodynia. © 2013 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

The utility of ionotropic glutamate receptor antagonists in the treatment of nociception induced by epidural glutamate infusion in rats.

PubMed

Osgood, Doreen B; Harrington, William F; Kenney, Elizabeth V; Harrington, J Frederick

2013-01-01

The authors have previously demonstrated that human herniated disc material contains high concentrations of free glutamate. In an experimental model, elevated epidural glutamate concentrations in the lumbar spine can cause a focal hyperesthetic state. Rats underwent epidural glutamate infusion in the lumbar spine by a miniosmotic pump over a 72-hour period. Some rats underwent coinfusion with glutamate and ionotropic glutamate antagonists. Nociception was assessed by von Frey fibers and by assessment of glutamate receptor expression in the corresponding dorsal horn of the spinal cord. The kainic acid antagonist, UBP 301, decreased epidural glutamate-based hyperesthesia in a dose dependent manner. Concordant with these findings, there was significant decrease in kainate receptor expression in the dorsal horn. The N-Methyl-4-isoxazoleproionic acid (NMDA) antagonist Norketamine also significantly diminished hyperesthesia and decreased receptor expression in the dorsal horn. Both UBP 301, the kainic acid receptor antagonist and Norketamine, an NMDA receptor antagonist, dampened epidural glutamate-based nociception. Focal epidural injections of Kainate or NMDA receptor antagonists could be effective treatments for disc herniation-based lumbar radiculopathy.

Metabotropic glutamate receptors in the trafficking of ionotropic glutamate and GABA(A) receptors at central synapses.

PubMed

Xiao, Min-Yi; Gustafsson, Bengt; Niu, Yin-Ping

2006-01-01

The trafficking of ionotropic glutamate (AMPA, NMDA and kainate) and GABA(A) receptors in and out of, or laterally along, the postsynaptic membrane has recently emerged as an important mechanism in the regulation of synaptic function, both under physiological and pathological conditions, such as information processing, learning and memory formation, neuronal development, and neurodegenerative diseases. Non-ionotropic glutamate receptors, primarily group I metabotropic glutamate receptors (mGluRs), co-exist with the postsynaptic ionotropic glutamate and GABA(A) receptors. The ability of mGluRs to regulate postsynaptic phosphorylation and Ca(2+) concentration, as well as their interactions with postsynaptic scaffolding/signaling proteins, makes them well suited to influence the trafficking of ionotropic glutamate and GABA(A) receptors. Recent studies have provided insights into how mGluRs may impose such an influence at central synapses, and thus how they may affect synaptic signaling and the maintenance of long-term synaptic plasticity. In this review we will discuss some of the recent progress in this area: i) long-term synaptic plasticity and the involvement of mGluRs; ii) ionotropic glutamate receptor trafficking and long-term synaptic plasticity; iii) the involvement of postsynaptic group I mGluRs in regulating ionotropic glutamate receptor trafficking; iv) involvement of postsynaptic group I mGluRs in regulating GABA(A) receptor trafficking; v) and the trafficking of postsynaptic group I mGluRs themselves.

Astroglial Glutamate Signaling and Uptake in the Hippocampus

PubMed Central

Rose, Christine R.; Felix, Lisa; Zeug, Andre; Dietrich, Dirk; Reiner, Andreas; Henneberger, Christian

2018-01-01

Astrocytes have long been regarded as essentially unexcitable cells that do not contribute to active signaling and information processing in the brain. Contrary to this classical view, it is now firmly established that astrocytes can specifically respond to glutamate released from neurons. Astrocyte glutamate signaling is initiated upon binding of glutamate to ionotropic and/or metabotropic receptors, which can result in calcium signaling, a major form of glial excitability. Release of so-called gliotransmitters like glutamate, ATP and D-serine from astrocytes in response to activation of glutamate receptors has been demonstrated to modulate various aspects of neuronal function in the hippocampus. In addition to receptors, glutamate binds to high-affinity, sodium-dependent transporters, which results in rapid buffering of synaptically-released glutamate, followed by its removal from the synaptic cleft through uptake into astrocytes. The degree to which astrocytes modulate and control extracellular glutamate levels through glutamate transporters depends on their expression levels and on the ionic driving forces that decrease with ongoing activity. Another major determinant of astrocytic control of glutamate levels could be the precise morphological arrangement of fine perisynaptic processes close to synapses, defining the diffusional distance for glutamate, and the spatial proximity of transporters in relation to the synaptic cleft. In this review, we will present an overview of the mechanisms and physiological role of glutamate-induced ion signaling in astrocytes in the hippocampus as mediated by receptors and transporters. Moreover, we will discuss the relevance of astroglial glutamate uptake for extracellular glutamate homeostasis, focusing on how activity-induced dynamic changes of perisynaptic processes could shape synaptic transmission at glutamatergic synapses. PMID:29386994

Microbial production of poly-γ-glutamic acid.

PubMed

Sirisansaneeyakul, Sarote; Cao, Mingfeng; Kongklom, Nuttawut; Chuensangjun, Chaniga; Shi, Zhongping; Chisti, Yusuf

2017-09-05

Poly-γ-glutamic acid (γ-PGA) is a natural, biodegradable and water-soluble biopolymer of glutamic acid. This review is focused on nonrecombinant microbial production of γ-PGA via fermentation processes. In view of its commercial importance, the emphasis is on L-glutamic acid independent producers (i.e. microorganisms that do not require feeding with the relatively expensive amino acid L-glutamic acid to produce γ-PGA), but glutamic acid dependent production is discussed for comparison. Strategies for improving production, reducing costs and using renewable feedstocks are discussed.

Propolis ameliorates tumor nerosis factor-α, nitric oxide levels, caspase-3 and nitric oxide synthase activities in kainic acid mediated excitotoxicity in rat brain.

PubMed

Swamy, Mummedy; Suhaili, Dian; Sirajudeen, K N S; Mustapha, Zulkarnain; Govindasamy, Chandran

2014-01-01

Increased nitric oxide (NO), neuronal inflammation and apoptosis have been proposed to be involved in excitotoxicity plays a part in many neurodegenerative diseases. To understand the neuro-protective effects of propolis, activities of Nitric oxide synthase (NOS) and caspase-3 along with NO and tumor necrosis factor-α (TNF-α) levels were studied in cerebral cortex (CC), cerebellum (CB) and brain stem (BS) in rats supplemented with propolis prior to excitotoxic injury with kainic acid (KA). Male Sprague-Dawley rats were divided into four groups (n=6 rats per group) as Control, KA, Propolis and KA+Propolis. The control group and KA group have received vehicle and saline. Propolis group and propolis + KA group were orally administered with propolis (150 mg/kg body weight), five times every 12 hours. KA group and propolis +KA group were injected subcutaneously with kainic acid (15 mg/kg body weight) and were sacrificed after 2 hrs. CC, CB and BS were separated, homogenized and used for estimation of NOS, caspase-3, NO and TNF-α by commercial kits. Results were analyzed by one way ANOVA, reported as mean + SD (n=6 rats), and p<0.05 was considered statistically significant. The concentration of NO, TNF-α, NOS and caspase-3 activity were increased significantly (p<0.001) in all the three brain regions tested in KA group compared to the control. Propolis supplementation significantly (p<0.001) prevented the increase in NOS, NO, TNF-α and caspase-3 due to KA. Results of this study clearly demonstrated that the propolis supplementation attenuated the NOS, caspase-3 activities, NO, and TNF-α concentration and in KA mediated excitotoxicity. Hence propolis can be a possible potential protective agent against excitotoxicity and neurodegenerative disorders.

Vaccination for protection of retinal ganglion cells against death from glutamate cytotoxicity and ocular hypertension: Implications for glaucoma

NASA Astrophysics Data System (ADS)

Schori, Hadas; Kipnis, Jonathan; Yoles, Eti; Woldemussie, Elizabeth; Ruiz, Guadalupe; Wheeler, Larry A.; Schwartz, Michal

2001-03-01

Our group recently demonstrated that autoimmune T cells directed against central nervous system-associated myelin antigens protect neurons from secondary degeneration. We further showed that the synthetic peptide copolymer 1 (Cop-1), known to suppress experimental autoimmune encephalomyelitis, can be safely substituted for the natural myelin antigen in both passive and active immunization for neuroprotection of the injured optic nerve. Here we attempted to determine whether similar immunizations are protective from retinal ganglion cell loss resulting from a direct biochemical insult caused, for example, by glutamate (a major mediator of degeneration in acute and chronic optic nerve insults) and in a rat model of ocular hypertension. Passive immunization with T cells reactive to myelin basic protein or active immunization with myelin oligodendrocyte glycoprotein-derived peptide, although neuroprotective after optic nerve injury, was ineffective against glutamate toxicity in mice and rats. In contrast, the number of surviving retinal ganglion cells per square millimeter in glutamate-injected retinas was significantly larger in mice immunized 10 days previously with Cop-1 emulsified in complete Freund's adjuvant than in mice injected with PBS in the same adjuvant (2,133 ± 270 and 1,329 ± 121, respectively, mean ± SEM; P < 0.02). A similar pattern was observed when mice were immunized on the day of glutamate injection (1,777 ± 101 compared with 1,414 ± 36; P <0.05), but not when they were immunized 48h later. These findings suggest that protection from glutamate toxicity requires reinforcement of the immune system by antigens that are different from those associated with myelin. The use of Cop-1 apparently circumvents this antigen specificity barrier. In the rat ocular hypertension model, which simulates glaucoma, immunization with Cop-1 significantly reduced the retinal ganglion cell loss from 27.8%±6.8% to 4.3%±1.6%, without affecting the intraocular pressure

Immunoexcitotoxicity as the central mechanism of etiopathology and treatment of autism spectrum disorders: A possible role of fluoride and aluminum

PubMed Central

Strunecka, Anna; Blaylock, Russell L.; Patocka, Jiri; Strunecky, Otakar

2018-01-01

Our review suggests that most autism spectrum disorder (ASD) risk factors are connected, either directly or indirectly, to immunoexcitotoxicity. Chronic brain inflammation is known to enhance the sensitivity of glutamate receptors and interfere with glutamate removal from the extraneuronal space, where it can trigger excitotoxicity over a prolonged period. Neuroscience studies have clearly shown that sequential systemic immune stimulation can activate the brain's immune system, microglia, and astrocytes, and that with initial immune stimulation, there occurs CNS microglial priming. Children are exposed to such sequential immune stimulation via a growing number of environmental excitotoxins, vaccines, and persistent viral infections. We demonstrate that fluoride and aluminum (Al3+) can exacerbate the pathological problems by worsening excitotoxicity and inflammation. While Al3+ appears among the key suspicious factors of ASD, fluoride is rarely recognized as a causative culprit. A long-term burden of these ubiquitous toxins has several health effects with a striking resemblance to the symptoms of ASD. In addition, their synergistic action in molecules of aluminofluoride complexes can affect cell signaling, neurodevelopment, and CNS functions at several times lower concentrations than either Al3+ or fluoride acting alone. Our review opens the door to a number of new treatment modes that naturally reduce excitotoxicity and microglial priming. PMID:29721353

Enhancing poly-γ-glutamic acid production in Bacillus amyloliquefaciens by introducing the glutamate synthesis features from Corynebacterium glutamicum.

PubMed

Feng, Jun; Quan, Yufen; Gu, Yanyan; Liu, Fenghong; Huang, Xiaozhong; Shen, Haosheng; Dang, Yulei; Cao, Mingfeng; Gao, Weixia; Lu, Xiaoyun; Wang, Yi; Song, Cunjiang; Wang, Shufang

2017-05-22

Poly-γ-glutamic acid (γ-PGA) is a valuable polymer with glutamate as its sole precursor. Enhancement of the intracellular glutamate synthesis is a very important strategy for the improvement of γ-PGA production, especially for those glutamate-independent γ-PGA producing strains. Corynebacterium glutamicum has long been used for industrial glutamate production and it exhibits some unique features for glutamate synthesis; therefore introduction of these metabolic characters into the γ-PGA producing strain might lead to increased intracellular glutamate availability, and thus ultimate γ-PGA production. In this study, the unique glutamate synthesis features from C. glutamicum was introduced into the glutamate-independent γ-PGA producing Bacillus amyloliquefaciens NK-1 strain. After introducing the energy-saving NADPH-dependent glutamate dehydrogenase (NADPH-GDH) pathway, the NK-1 (pHT315-gdh) strain showed slightly increase (by 9.1%) in γ-PGA production. Moreover, an optimized metabolic toggle switch for controlling the expression of ɑ-oxoglutarate dehydrogenase complex (ODHC) was introduced into the NK-1 strain, because it was previously shown that the ODHC in C. glutamicum was completely inhibited when glutamate was actively produced. The obtained NK-PO1 (pHT01-xylR) strain showed 66.2% higher γ-PGA production than the NK-1 strain. However, the further combination of these two strategies (introducing both NADPH-GDH pathway and the metabolic toggle switch) did not lead to further increase of γ-PGA production but rather the resultant γ-PGA production was even lower than that in the NK-1 strain. We proposed new metabolic engineering strategies to improve the γ-PGA production in B. amyloliquefaciens. The NK-1 (pHT315-gdh) strain with the introduction of NADPH-GDH pathway showed 9.1% improvement in γ-PGA production. The NK-PO1 (pHT01-xylR) strain with the introduction of a metabolic toggle switch for controlling the expression of ODHC showed 66.2% higher �

Guanosine-5'-monophosphate induces cell death in rat hippocampal slices via ionotropic glutamate receptors activation and glutamate uptake inhibition.

PubMed

Molz, Simone; Dal-Cim, Tharine; Tasca, Carla I

2009-12-01

Guanine derivatives modulate the glutamatergic system through displacement of binding of glutamate to its receptors acting as antagonist of glutamate receptors in moderate to high micromolar concentrations. Guanosine-5'-monophosphate (GMP) is shown to be neuroprotective against glutamate- or oxygen/glucose deprivation-induced neurotoxicity and also against NMDA-induced apoptosis in hippocampal slices. However, in this study we are showing that high extracellular GMP concentrations (5mM) reduced cell viability in hippocampal brain slices. The toxic effect of GMP was not blocked by dipyridamole, a nucleoside transport inhibitor, nor mimicked by guanosine, suggesting an extracellular mode of action to GMP which does not involve its hydrolysis to guanosine. GMP-dependent cell damage was not blocked by P1 purinergic receptor antagonists, neither altered by adenosine A(1) or A(2A) receptor agonists. The blockage of the ionotropic glutamate receptors AMPA or NMDA, but not KA or metabotropic glutamate receptors, reversed the toxicity induced by GMP. GMP (5mM) induced a decrease in glutamate uptake into hippocampal slices, which was reversed by dl-TBOA. Therefore, GMP-induced hippocampal cell damage involves activation of ionotropic glutamate receptors and inhibition of glutamate transporters activity.

Glial glutamate transporters expression, glutamate uptake, and oxidative stress in an experimental rat model of intracerebral hemorrhage.

PubMed

Neves, J D; Vizuete, A F; Nicola, F; Da Ré, C; Rodrigues, A F; Schmitz, F; Mestriner, R G; Aristimunha, D; Wyse, A T S; Netto, C A

2018-06-01

Glial glutamate transporters (EAAT1 and EAAT2), glutamate uptake, and oxidative stress are important players in the pathogenesis of ischemic brain injury. However, the changes in EAAT1 and EAAT2 expression, glutamate uptake and the oxidative profile during intracerebral hemorrhage (ICH) development have not been described. The present study sought to investigate the changes of the above-mentioned variables, as well as the Na + /K + -ATP ase and glutamine synthetase activities (as important contributors of glutamate homeostasis) and the percentage of neuronal cells after 6 h, 24 h, 72 h and 7 days of ICH. An injection of 0.2U of bacterial collagenase in the ipsilateral striatum was used to induce ICH in male Wistar rats; naïve animals were used as controls. EAAT1 and EAAT2 expression and glutamate uptake in the ipsilateral striatum were assessed. Additionally, the percentage of MAP2+ cells, Na + /K + -ATP ase and GS activities, as well as the oxidative profile were analyzed. It is shown a decrease of EAAT1 expression and glutamate uptake 6 h post-ICH, whereas EAAT2 decreased 72 h after the event; conversely EAAT2 and glutamate uptake were increased after 7 days. The oxidative stress and endogenous defense system exhibited a remarkable response at 72 h of injury. ICH also increased Na + /K + -ATP ase activity and selectively decreased GS activity, variables known to be important contributors of glial glutamate transporters activities. Altogether, present findings indicate that ICH induces different temporal EAAT1 and EAAT2 responses, culminating with an imbalance of glutamate uptake capacity, increased oxidative stress and sustained neuronal loss. Copyright © 2018 Elsevier Ltd. All rights reserved.

Glutamate Dehydrogenase from Apodachlya (Oomycetes) 1

PubMed Central

Price, Jeffrey S.; Gleason, Frank H.

1972-01-01

A glutamate dehydrogenase specific for nicotinamide-adenine-dinucleotide has been purified 50-fold from Apodachlya brachynema (Leptomitales). Certain physical, chemical, and kinetic properties of this enzyme have been studied, particularly specificity for coenzymes and substrates. With glucose as the sole carbon source, the synthesis of glutamate dehydrogenase was repressed, whereas glutamate, proline, alanine, or ornithine plus aspartate as sole carbon sources induced synthesis of the enzyme. These data indicate that the function of this enzyme is primarily degradative, although there is no evidence for a nicotinamide-adenine-dinucleotide-phosphate-specific biosynthetic glutamate dehydrogenase in Apodachlya. PMID:16657902

NO-producing compounds transform neuron responses to glutamate.

PubMed

D'yakonova, T L

2000-01-01

We have previously shown that NO increases the excitatory effects of glutamate and blocks the desensitization of neurons to glutamate in the brain of the common snail. The aim of the present work was to identify the possible effect of NO on inhibitory responses to glutamate in the neurons of this mollusk. Electrophysiological investigations were performed on three identified neurons. The results showed that glutamate (0.05-0.1 mM) initially induced hyperpolarization and blocked the spike activity of these neurons. Simultaneous exposure to glutamate and the NO donor nitroprusside or preincubation with an NO donor had the effect that cells again responded to glutamate with depolarization and excitation. The transformed excitatory response lasted several minutes and could be reproduced even after 24 h of washing. The NO synthase blocker monomethylarginine blocked the excitatory response to glutamate. Another agonist of glutamate receptors, N-methyl-D-aspartate (NMDA, 0.1-1 mM), initially had excitatory effects on these neurons; this effect was significantly enhanced after transformation of the response to glutamate by NO donors. The results obtained here show that NO is involved in transforming the inhibitory responses to glutamate to excitatory responses, and that this effect may be mediated by NMDA-type receptors.

Activation of NMDA receptor by elevated homocysteine in chronic liver disease contributes to encephalopathy.

PubMed

Choudhury, Sabanum; Borah, Anupom

2015-07-01

Liver diseases lead to a complex syndrome characterized by neurological, neuro-psychiatric and motor complications, called hepatic encephalopathy, which is prevalent in patients and animal models of acute, sub-chronic and chronic liver failure. Although alterations in GABAergic, glutamatergic, cholinergic and serotonergic neuronal functions have been implicated in HE, the molecular mechanisms that lead to HE in chronic liver disease (CLD) is least illustrated. Due to hepatocellular failure, levels of ammonia and homocysteine (Hcy), in addition to others, are found to increase in the brain as well as plasma. Hcy, a non-protein forming amino acid and an excitotoxin, activates ionotropic glutamate (n-methyl-d-aspartate; NMDA) receptors, and thereby leads to influx of Ca(2+) into neurons, which in turn activates several pathways that trigger oxidative stress, inflammation and apoptosis, collectively called excitotoxicity. Elevated levels of Hcy in the plasma and brain, a condition called Hyperhomocysteinemia (HHcy), and the resultant NMDA receptor-mediated excitotoxicity has been implicated in several diseases, including Parkinson's disease and Alzheimer's disease. Although, hyperammonemia has been shown to cause excitotoxicity, the role of HHcy in the development of behavioral and neurochemical alterations that occur in HE has not been illustrated yet. It is hypothesized that CLD-induced HHcy plays a major role in the development of HE through activation of NMDA receptors. It is further hypothesized that HHcy synergizes with hyperammonemia to activate NMDA receptor in the brain, and thereby cause oxidative stress, inflammation and apoptosis, and neuronal loss that leads to HE. Copyright © 2015 Elsevier Ltd. All rights reserved.

[NO donors transform neuronal response to glutamate].

PubMed

D'iakonova, T L

1998-10-01

Electrophysiological experiments on three identified neurones were performed. Two NO donors, sodium nitroprusside (SNP) and sodium nitrite, as well as NO synthase inhibitor, were used. In each neurone, bath application of glutamate caused hyperpolarization and suppression of firing. Combined application of glutamate and SNP resulted in that the same cells responded to identical glutamate solutions with depolarization and excitation. Application of N-monomethyl-L-arginin (NMMA) arrested the glutamate-induced firing and depolarization. The findings suggest involvement of NO in the mechanism of transformation of glutamate-induced inhibition into excitation and a mediation of the latter by the N-methyl-D-aspartate-like receptors in the Helix brain.

Direct stimulation of pituitary prolactin release by glutamate.

PubMed

Login, I S

1990-01-01

The ability of glutamate and other excitatory amino acids to stimulate prolactin secretion when administered to adult animals is hypothesized to depend on a central site of action in the brain, but there are no data to support this position. An alternative hypothesis was tested that glutamate would stimulate prolactin release when applied directly to primary cultures of dispersed adult female rat anterior pituitary cells studied in a perifusion protocol. Glutamate increased the rate of prolactin release within two minutes in a self-limited manner. Glutamate-stimulated prolactin release was augmented about 4-fold by elimination of magnesium from the perfusate and was associated with stimulation of pituitary calcium flux. Ketamine and MK-801 both reduced the basal rate of prolactin release and abolished the effects of glutamate. Pituitary cells of 10-day-old rats responded similarly to glutamate. Exposure to glutamate did not influence subsequent responses to physiological hypothalamic secretagogues, thus the likelihood of toxicity was minimized. These results suggest that the N-methyl-D-aspartate (NMDA) subclass of the glutamate receptor complex is involved. Prolactin secretion may be regulated physiologically through a functional glutamate receptor on pituitary cells.

Pharmacological Treatment of Glutamate Excitotoxicity Following Traumatic Brain Injury

DTIC Science & Technology

2009-01-14

31.5%) associated with TBI. In a subsequent study, Rao, et al. (2001) found that treatment with the non-competitive NMDA blocker, memantine ...Dogan A, Todd KG, Bowen KK, Dempsey RJ. Neuroprotection by memantine , a non-competitive NMDA receptor antagonist after traumatic brain injury in...R, Stöffler A, Schmitt F, Ferris S, Möbius HJ; Memantine Study Group. Memantine in moderate-to-severe Alzheimer’s disease. N Engl J Med. 2003 Apr

Correlation between afferent rearrangements and behavioral deficits after local excitotoxic insult in the mammalian vestibule: a rat model of vertigo symptoms.

PubMed

Gaboyard-Niay, Sophie; Travo, Cécile; Saleur, Aurélie; Broussy, Audrey; Brugeaud, Aurore; Chabbert, Christian

2016-10-01

Damage to inner ear afferent terminals is believed to result in many auditory and vestibular dysfunctions. The sequence of afferent injuries and repair, as well as their correlation with vertigo symptoms, remains poorly documented. In particular, information on the changes that take place at the primary vestibular endings during the first hours following a selective insult is lacking. In the present study, we combined histological analysis with behavioral assessments of vestibular function in a rat model of unilateral vestibular excitotoxic insult. Excitotoxicity resulted in an immediate but transient alteration of the balance function that was resolved within a week. Concomitantly, vestibular primary afferents underwent a sequence of structural changes followed by spontaneous repair. Within the first two hours after the insult, a first phase of pronounced vestibular dysfunction coincided with extensive swelling of afferent terminals. In the next 24 h, a second phase of significant but incomplete reduction of the vestibular dysfunction was accompanied by a resorption of swollen terminals and fiber retraction. Eventually, within 1 week, a third phase of complete balance restoration occurred. The slow and progressive withdrawal of the balance dysfunction correlated with full reconstitution of nerve terminals. Competitive re-innervation by afferent and efferent terminals that mimicked developmental synaptogenesis resulted in full re-afferentation of the sensory epithelia. By deciphering the sequence of structural alterations that occur in the vestibule during selective excitotoxic impairment, this study offers new understanding of how a vestibular insult develops in the vestibule and how it governs the heterogeneity of vertigo symptoms. © 2016. Published by The Company of Biologists Ltd.

Modafinil attenuates reinstatement of cocaine seeking: role for cystine-glutamate exchange and metabotropic glutamate receptors.

PubMed

Mahler, Stephen V; Hensley-Simon, Megan; Tahsili-Fahadan, Pouya; LaLumiere, Ryan T; Thomas, Charles; Fallon, Rebecca V; Kalivas, Peter W; Aston-Jones, Gary

2014-01-01

Modafinil may be useful for treating stimulant abuse, but the mechanisms by which it acts to do so are unknown. Indeed, a primary effect of modafinil is to inhibit dopamine transport, which typically promotes rather than inhibits motivated behavior. Therefore, we examined the role of nucleus accumbens extracellular glutamate and the group II metabotropic glutamate receptor (mGluR2/3) in modafinil effects. One group of rats was trained to self-administer cocaine for 10 days and extinguished, then given priming injections of cocaine to elicit reinstatement. Modafinil (300 mg/kg, intraperitoneal) inhibited reinstated cocaine seeking (but did not alter extinction responding by itself), and this effect was prevented by pre-treatment with bilateral microinjections of the mGluR2/3 antagonist LY-341495 (LY) into nucleus accumbens core. No reversal of modafinil effects was seen after unilateral accumbens core LY, or bilateral LY in the rostral pole of accumbens. Next, we sought to explore effects of modafinil on extracellular glutamate levels in accumbens after chronic cocaine. Separate rats were administered non-contingent cocaine, and after 3 weeks of withdrawal underwent accumbens microdialysis. Modafinil increased extracellular accumbens glutamate in chronic cocaine, but not chronic saline-pre-treated animals. This increase was prevented by reverse dialysis of cystine-glutamate exchange or voltage-dependent calcium channel antagonists. Voltage-dependent sodium channel blockade partly attenuated the increase in glutamate, but mGluR1 blockade did not. We conclude that modafinil increases extracellular glutamate in nucleus accumbens from glial and neuronal sources in cocaine-exposed rats, which may be important for its mGluR2/3-mediated antirelapse properties. © 2012 The Authors, Addiction Biology © 2012 Society for the Study of Addiction.

Integration between Glycolysis and Glutamate-Glutamine Cycle Flux May Explain Preferential Glycolytic Increase during Brain Activation, Requiring Glutamate

PubMed Central

Hertz, Leif; Chen, Ye

2017-01-01

The 1988 observation by Fox et al. (1988) that brief intense brain activation increases glycolysis (pyruvate formation from glucose) much more than oxidative metabolism has been abundantly confirmed. Specifically glycolytic increase was unexpected because the amount of ATP it generates is much smaller than that formed by subsequent oxidative metabolism of pyruvate. The present article shows that preferential glycolysis can be explained by metabolic processes associated with activation of the glutamate-glutamine cycle. The flux in this cycle, which is essential for production of transmitter glutamate and GABA, equals 75% of brain glucose utilization and each turn is associated with utilization of ~1 glucose molecule. About one half of the association between cycle flux and glucose metabolism occurs during neuronal conversion of glutamine to glutamate in a process similar to the malate-aspartate shuttle (MAS) except that glutamate is supplied from glutamine, not formed from α-ketoglutarate (αKG) as during operation of conventional MAS. Regular MAS function is triggered by one oxidative process in the cytosol during glycolysis causing NAD+ reduction to NADH. Since NADH cannot cross the mitochondrial membrane (MEM) for oxidation NAD+ is re-generated by conversion of cytosolic oxaloacetate (OAA) to malate, which enters the mitochondria for oxidation and in a cyclic process regenerates cytosolic OAA. Therefore MAS as well as the “pseudo-MAS” necessary for neuronal glutamate formation can only operate together with cytosolic reduction of NAD+ to NADH. The major process causing NAD+ reduction is glycolysis which therefore also must occur during neuronal conversion of glutamine to glutamate and may energize vesicular glutamate uptake which preferentially uses glycolytically derived energy. Another major contributor to the association between glutamate-glutamine cycle and glucose utilization is the need for astrocytic pyruvate to generate glutamate. Although some

Glutamate and Brain Glutaminases in Drug Addiction.

PubMed

Márquez, Javier; Campos-Sandoval, José A; Peñalver, Ana; Matés, José M; Segura, Juan A; Blanco, Eduardo; Alonso, Francisco J; de Fonseca, Fernando Rodríguez

2017-03-01

Glutamate is the principal excitatory neurotransmitter in the central nervous system and its actions are related to the behavioral effects of psychostimulant drugs. In the last two decades, basic neuroscience research and preclinical studies with animal models are suggesting a critical role for glutamate transmission in drug reward, reinforcement, and relapse. Although most of the interest has been centered in post-synaptic glutamate receptors, the presynaptic synthesis of glutamate through brain glutaminases may also contribute to imbalances in glutamate homeostasis, a key feature of the glutamatergic hypothesis of addiction. Glutaminases are the main glutamate-producing enzymes in brain and dysregulation of their function have been associated with neurodegenerative diseases and neurological disorders; however, the possible implication of these enzymes in drug addiction remains largely unknown. This mini-review focuses on brain glutaminase isozymes and their alterations by in vivo exposure to drugs of abuse, which are discussed in the context of the glutamate homeostasis theory of addiction. Recent findings from mouse models have shown that drugs induce changes in the expression profiles of key glutamatergic transmission genes, although the molecular mechanisms that regulate drug-induced neuronal sensitization and behavioral plasticity are not clear.

Inhibiting Src family tyrosine kinase activity blocks glutamate signalling to ERK1/2 and Akt/PKB but not JNK in cultured striatal neurones.

PubMed

Crossthwaite, Andrew J; Valli, Haseeb; Williams, Robert J

2004-03-01

Glutamate receptor activation of mitogen-activated protein (MAP) kinase signalling cascades has been implicated in diverse neuronal functions such as synaptic plasticity, development and excitotoxicity. We have previously shown that Ca2+-influx through NMDA receptors in cultured striatal neurones mediates the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) and Akt/protein kinase B (PKB) through a phosphatidylinositol 3-kinase (PI 3-kinase)-dependent pathway. Exposing neurones to the Src family tyrosine kinase inhibitor PP2, but not the inactive analogue PP3, inhibited NMDA receptor-induced phosphorylation of ERK1/2 and Akt/PKB in a concentration-dependent manner, and reduced cAMP response element-binding protein (CREB) phosphorylation. To establish a link between Src family tyrosine kinase-mediated phosphorylation and PI 3-kinase signalling, affinity precipitation experiments were performed with the SH2 domains of the PI 3-kinase regulatory subunit p85. This revealed a Src-dependent phosphorylation of a focal adhesion kinase (FAK)-p85 complex on glutamate stimulation. Demonstrating that PI3-kinase is not ubiquitously involved in NMDA receptor signal transduction, the PI 3-kinase inhibitors wortmannin and LY294002 did not prevent NMDA receptor Ca2+-dependent phosphorylation of c-Jun N-terminal kinase 1/2 (JNK1/2). Further, inhibiting Src family kinases increased NMDA receptor-dependent JNK1/2 phosphorylation, suggesting that Src family kinase-dependent cascades may physiologically limit signalling to JNK. These results demonstrate that Src family tyrosine kinases and PI3-kinase are pivotal regulators of NMDA receptor signalling to ERK/Akt and JNK in striatal neurones.

The Group 2 Metabotropic Glutamate Receptor Agonist LY379268 Rescues Neuronal, Neurochemical and Motor Abnormalities in R6/2 Huntington’s Disease Mice

PubMed Central

Reiner, A.; Lafferty, D.C.; Wang, H.B.; Del Mar, N.; Deng, Y.P.

2012-01-01

Excitotoxic injury to striatum by dysfunctional cortical input or aberrant glutamate uptake may contribute to Huntington’s Disease (HD) pathogenesis. Since corticostriatal terminals possess mGluR2/3 autoreceptors, whose activation dampens glutamate release, we tested the ability of the mGluR2/3 agonist LY379268 to improve the phenotype in R6/2 HD mice with 120–125 CAG repeats. Daily subcutaneous injection of a maximum tolerated dose (MTD) of LY379268 (20mg/kg) had no evident adverse effects in WT mice, and diverse benefits in R6/2 mice, both in a cohort of mice tested behaviorally until the end of R6/2 lifespan and in a cohort sacrificed at 10 weeks of age for blinded histological analysis. MTD LY379268 yielded a significant 11% increase in R6/2 survival, an improvement on rotarod, normalization and/or improvement in locomotor parameters measured in open field (activity, speed, acceleration, endurance, and gait), a rescue of a 15–20% cortical and striatal neuron loss, normalization of SP striatal neuron neurochemistry, and to a lesser extent enkephalinergic striatal neuron neurochemistry. Deficits were greater in male than female R6/2 mice, and drug benefit tended to be greater in males. The improvements in SP striatal neurons, which facilitate movement, are consistent with the improved movement in LY379268-treated R6/2 mice. Our data indicate that mGluR2/3 agonists may be particularly useful for ameliorating the morphological, neurochemical and motor defects observed in HD. PMID:22472187

Glutamate mediates platelet activation through the AMPA receptor

PubMed Central

Morrell, Craig N.; Sun, Henry; Ikeda, Masahiro; Beique, Jean-Claude; Swaim, Anne Marie; Mason, Emily; Martin, Tanika V.; Thompson, Laura E.; Gozen, Oguz; Ampagoomian, David; Sprengel, Rolf; Rothstein, Jeffrey; Faraday, Nauder; Huganir, Richard; Lowenstein, Charles J.

2008-01-01

Glutamate is an excitatory neurotransmitter that binds to the kainate receptor, the N-methyl-D-aspartate (NMDA) receptor, and the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor (AMPAR). Each receptor was first characterized and cloned in the central nervous system (CNS). Glutamate is also present in the periphery, and glutamate receptors have been identified in nonneuronal tissues, including bone, heart, kidney, pancreas, and platelets. Platelets play a central role in normal thrombosis and hemostasis, as well as contributing greatly to diseases such as stroke and myocardial infarction. Despite the presence of glutamate in platelet granules, the role of glutamate during hemostasis is unknown. We now show that activated platelets release glutamate, that platelets express AMPAR subunits, and that glutamate increases agonist-induced platelet activation. Furthermore, we demonstrate that glutamate binding to the AMPAR increases intracellular sodium concentration and depolarizes platelets, which are important steps in platelet activation. In contrast, platelets treated with the AMPAR antagonist CNQX or platelets derived from GluR1 knockout mice are resistant to AMPA effects. Importantly, mice lacking GluR1 have a prolonged time to thrombosis in vivo. Our data identify glutamate as a regulator of platelet activation, and suggest that the AMPA receptor is a novel antithrombotic target. PMID:18283118

Glutamate receptors in the nucleus tractus solitarius contribute to ventilatory acclimatization to hypoxia in rat.

PubMed

Pamenter, Matthew E; Carr, J Austin; Go, Ariel; Fu, Zhenxing; Reid, Stephen G; Powell, Frank L

2014-04-15

When exposed to a hypoxic environment the body's first response is a reflex increase in ventilation, termed the hypoxic ventilatory response (HVR). With chronic sustained hypoxia (CSH), such as during acclimatization to high altitude, an additional time-dependent increase in ventilation occurs, which increases the HVR. This secondary increase persists after exposure to CSH and involves plasticity within the circuits in the central nervous system that control breathing. Currently these mechanisms of HVR plasticity are unknown and we hypothesized that they involve glutamatergic synapses in the nucleus tractus solitarius (NTS), where afferent endings from arterial chemoreceptors terminate. To test this, we treated rats held in normoxia (CON) or 10% O2 (CSH) for 7 days and measured ventilation in conscious, unrestrained animals before and after microinjecting glutamate receptor agonists and antagonists into the NTS. In normoxia, AMPA increased ventilation 25% and 50% in CON and CSH, respectively, while NMDA doubled ventilation in both groups (P < 0.05). Specific AMPA and NMDA receptor antagonists (NBQX and MK801, respectively) abolished these effects. MK801 significantly decreased the HVR in CON rats, and completely blocked the acute HVR in CSH rats but had no effect on ventilation in normoxia. NBQX decreased ventilation whenever it was increased relative to normoxic controls; i.e. acute hypoxia in CON and CSH, and normoxia in CSH. These results support our hypothesis that glutamate receptors in the NTS contribute to plasticity in the HVR with CSH. The mechanism underlying this synaptic plasticity is probably glutamate receptor modification, as in CSH rats the expression of phosphorylated NR1 and GluR1 proteins in the NTS increased 35% and 70%, respectively, relative to that in CON rats.

The neuroprotective efficacy of cell-penetrating peptides TAT, penetratin, Arg-9, and Pep-1 in glutamic acid, kainic acid, and in vitro ischemia injury models using primary cortical neuronal cultures.

PubMed

Meloni, Bruno P; Craig, Amanda J; Milech, Nadia; Hopkins, Richard M; Watt, Paul M; Knuckey, Neville W

2014-03-01

Cell-penetrating peptides (CPPs) are small peptides (typically 5-25 amino acids), which are used to facilitate the delivery of normally non-permeable cargos such as other peptides, proteins, nucleic acids, or drugs into cells. However, several recent studies have demonstrated that the TAT CPP has neuroprotective properties. Therefore, in this study, we assessed the TAT and three other CPPs (penetratin, Arg-9, Pep-1) for their neuroprotective properties in cortical neuronal cultures following exposure to glutamic acid, kainic acid, or in vitro ischemia (oxygen-glucose deprivation). Arg-9, penetratin, and TAT-D displayed consistent and high level neuroprotective activity in both the glutamic acid (IC50: 0.78, 3.4, 13.9 μM) and kainic acid (IC50: 0.81, 2.0, 6.2 μM) injury models, while Pep-1 was ineffective. The TAT-D isoform displayed similar efficacy to the TAT-L isoform in the glutamic acid model. Interestingly, Arg-9 was the only CPP that displayed efficacy when washed-out prior to glutamic acid exposure. Neuroprotection following in vitro ischemia was more variable with all peptides providing some level of neuroprotection (IC50; Arg-9: 6.0 μM, TAT-D: 7.1 μM, penetratin/Pep-1: >10 μM). The positive control peptides JNKI-1D-TAT (JNK inhibitory peptide) and/or PYC36L-TAT (AP-1 inhibitory peptide) were neuroprotective in all models. Finally, in a post-glutamic acid treatment experiment, Arg-9 was highly effective when added immediately after, and mildly effective when added 15 min post-insult, while the JNKI-1D-TAT control peptide was ineffective when added post-insult. These findings demonstrate that different CPPs have the ability to inhibit neurodamaging events/pathways associated with excitotoxic and ischemic injuries. More importantly, they highlight the need to interpret neuroprotection studies when using CPPs as delivery agents with caution. On a positive note, the cytoprotective properties of CPPs suggests they are ideal carrier molecules to

21 CFR 182.1047 - Glutamic acid hydrochloride.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Glutamic acid hydrochloride. 182.1047 Section 182.1047 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Food Substances § 182.1047 Glutamic acid hydrochloride. (a) Product. Glutamic acid hydrochloride. (b...

21 CFR 182.1047 - Glutamic acid hydrochloride.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Glutamic acid hydrochloride. 182.1047 Section 182.1047 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Food Substances § 182.1047 Glutamic acid hydrochloride. (a) Product. Glutamic acid hydrochloride. (b...

Introduction to the Glutamate-Glutamine Cycle.

PubMed

Sonnewald, Ursula; Schousboe, Arne

2016-01-01

The term 'glutamate-glutamine cycle' was coined several decades ago based on the observation that using certain 14 C-labeled precursors for studies of brain metabolism the specific radioactivity of glutamine generated from glutamate was higher than that of glutamate, its immediate precursor. This is metabolically impossible unless it is assumed that at least two distinct pools of these amino acids exist. This combined with the finding that the enzyme synthesizing glutamine from glutamate was expressed in astrocytes but not in neurons formed the basis of the notion that a cycle must exist in which glutamate released from neurons is transported into astrocytes, converted to glutamine which is subsequently returned to neurons and converted to glutamate by an enzyme the activity of which is much higher in neurons than in astrocytes. Originally this cycle was supposed to function in a stoichiometric fashion but more recent research has seriously questioned this.This volume of Advances in Neurobiology is intended to provide a detailed discussion of recent developments in research aimed at delineating the functional roles of the cycle taking into account that in order for this system to work there must be a tight coupling between metabolism of glutamate in astrocytes, transfer of glutamine to neurons and de novo synthesis of glutamine in astrocytes. To understand this, knowledge about the activity and regulation of the enzymes and transporters involved in these processes is required and as can be seen from the table of contents these issues will be dealt with in detail in the individual chapters of the book.

The role of glutamate and its receptors in autism and the use of glutamate receptor antagonists in treatment

PubMed Central

Rojas, Donald C.

2014-01-01

Glutamate is the major excitatory neurotransmitter in the brain and may be a key neurotransmitter involved in autism. Literature pertaining to glutamate and autism or related disorders (e.g., Fragile X syndrome) is reviewed in this article. Interest in glutamatergic dysfunction in autism is high due to increasing convergent evidence implicating the system in the disorder from peripheral biomarkers, neuroimaging, protein expression, genetics and animal models. Currently, there are no pharmaceutical interventions approved for autism that address glutamate deficits in the disorder. New treatments related to glutamatergic neurotransmission, however, are emerging. In addition, older glutamate-modulating medications with approved indications for use in other disorders are being investigated for re-tasking as treatments for autism. This review presents evidence in support of glutamate abnormalities in autism and the potential for translation into new treatments for the disorder. PMID:24752754

Exploring the role of MKK7 in excitotoxicity and cerebral ischemia: a novel pharmacological strategy against brain injury

PubMed Central

Vercelli, A; Biggi, S; Sclip, A; Repetto, I E; Cimini, S; Falleroni, F; Tomasi, S; Monti, R; Tonna, N; Morelli, F; Grande, V; Stravalaci, M; Biasini, E; Marin, O; Bianco, F; di Marino, D; Borsello, T

2015-01-01

Excitotoxicity following cerebral ischemia elicits a molecular cascade, which leads to neuronal death. c-Jun-N-terminal kinase (JNK) has a key role in excitotoxic cell death. We have previously shown that JNK inhibition by a specific cell-permeable peptide significantly reduces infarct size and neuronal death in an in vivo model of cerebral ischemia. However, systemic inhibition of JNK may have detrimental side effects, owing to blockade of its physiological function. Here we designed a new inhibitor peptide (growth arrest and DNA damage-inducible 45β (GADD45β-I)) targeting mitogen-activated protein kinase kinase 7 (MKK7), an upstream activator of JNK, which exclusively mediates JNK's pathological activation. GADD45β-I was engineered by optimizing the domain of the GADD45β, able to bind to MKK7, and by linking it to the TAT peptide sequence, to allow penetration of biological membranes. Our data clearly indicate that GADD45β-I significantly reduces neuronal death in excitotoxicity induced by either N-methyl-D-aspartate exposure or by oxygen–glucose deprivation in vitro. Moreover, GADD45β-I exerted neuroprotection in vivo in two models of ischemia, obtained by electrocoagulation and by thromboembolic occlusion of the middle cerebral artery (MCAo). Indeed, GADD45β-I reduced the infarct size when injected 30 min before the lesion in both models. The peptide was also effective when administrated 6 h after lesion, as demonstrated in the electrocoagulation model. The neuroprotective effect of GADD45β-I is long lasting; in fact, 1 week after MCAo the infarct volume was still reduced by 49%. Targeting MKK7 could represent a new therapeutic strategy for the treatment of ischemia and other pathologies involving MKK7/JNK activation. Moreover, this new inhibitor can be useful to further dissect the physiological and pathological role of the JNK pathway in the brain. PMID:26270349

Effect of acute and chronic MK-801 administration on extracellular glutamate and ascorbic acid release in the prefrontal cortex of freely moving mice on line with open-field behavior.

PubMed

Zuo, Dai-Ying; Zhang, Ya-Hong; Cao, Yue; Wu, Chun-Fu; Tanaka, Masatoshi; Wu, Ying-Liang

2006-04-04

The present study was designed to investigate the effects of acute and chronic administration of MK-801 (0.6 mg/kg), a noncompetitive NMDA-receptor antagonist on extracellular glutamate (Glu) and ascorbic acid (AA) release in the prefrontal cortex (PFC) of freely moving mice using in vivo microdialysis with open-field behavior. In line with earlier studies, acute administration of MK-801 induced an increase of Glu in the PFC. We also observed single MK-801 treatment increased AA release in the PFC. In addition, our results indicated that the basal AA levels in the PFC after MK-801 administration for 7 consecutive days were significantly decreased, and basal Glu levels also had a decreased tendency. After chronic administration (0.6 mg/kg, 7 days), MK-801 (0.6 mg/kg) challenge significantly decreased dialysate levels of AA and Glu. Our study also found that both acute and chronic administration of MK-801 induced hyperactivity in mice, but the intensity of acute administration was more than that of chronic administration. Furthermore, in all acute treatment mice, individual changes in Glu dialysate concentrations and the numbers of locomotion were positively correlated. In conclusion, this study may provide new evidence that a single MK-801 administration induces increases of dialysate AA and Glu concentrations in the PFC of freely moving mice, which are opposite to those induced by repeated MK-801 administration, with an unknown mechanism. Our results suggested that redox-response might play an important role in the model of schizophrenic symptoms induced by MK-801.

N-Acetylcysteine improves mitochondrial function and ameliorates behavioral deficits in the R6/1 mouse model of Huntington's disease

PubMed Central

Wright, D J; Renoir, T; Smith, Z M; Frazier, A E; Francis, P S; Thorburn, D R; McGee, S L; Hannan, A J; Gray, L J

2015-01-01

Huntington's disease (HD) is a neurodegenerative disorder, involving psychiatric, cognitive and motor symptoms, caused by a CAG-repeat expansion encoding an extended polyglutamine tract in the huntingtin protein. Oxidative stress and excitotoxicity have previously been implicated in the pathogenesis of HD. We hypothesized that N-acetylcysteine (NAC) may reduce both excitotoxicity and oxidative stress through its actions on glutamate reuptake and antioxidant capacity. The R6/1 transgenic mouse model of HD was used to investigate the effects of NAC on HD pathology. It was found that chronic NAC administration delayed the onset and progression of motor deficits in R6/1 mice, while having an antidepressant-like effect on both R6/1 and wild-type mice. A deficit in the astrocytic glutamate transporter protein, GLT-1, was found in R6/1 mice. However, this deficit was not ameliorated by NAC, implying that the therapeutic effect of NAC is not due to rescue of the GLT-1 deficit and associated glutamate-induced excitotoxicity. Assessment of mitochondrial function in the striatum and cortex revealed that R6/1 mice show reduced mitochondrial respiratory capacity specific to the striatum. This deficit was rescued by chronic treatment with NAC. There was a selective increase in markers of oxidative damage in mitochondria, which was rescued by NAC. In conclusion, NAC is able to delay the onset of motor deficits in the R6/1 model of Huntington's disease and it may do so by ameliorating mitochondrial dysfunction. Thus, NAC shows promise as a potential therapeutic agent in HD. Furthermore, our data suggest that NAC may also have broader antidepressant efficacy. PMID:25562842

Glutamate and Its Receptors as Therapeutic Targets for Migraine.

PubMed

Hoffmann, Jan; Charles, Andrew

2018-04-01

There is substantial evidence indicating a role for glutamate in migraine. Levels of glutamate are higher in the brain and possibly also in the peripheral circulation in migraine patients, particularly during attacks. Altered blood levels of kynurenines, endogenous modulators of glutamate receptors, have been reported in migraine patients. Population genetic studies implicate genes that are involved with glutamate signaling in migraine, and gene mutations responsible for familial hemiplegic migraine and other familial migraine syndromes may influence glutamate signaling. Animal studies indicate that glutamate plays a key role in pain transmission, central sensitization, and cortical spreading depression. Multiple therapies that target glutamate receptors including magnesium, topiramate, memantine, and ketamine have been reported to have efficacy in the treatment of migraine, although with the exception of topiramate, the evidence for the efficacy of these therapies is not strong. Also, because all of these therapies have other mechanisms of action, it is not possible to conclude that the efficacy of these drugs is entirely due to their effects on glutamate receptors. Further studies are needed to more clearly delineate the possible roles of glutamate and its specific receptor subtypes in migraine and to identify new ways of targeting glutamate for migraine therapy.

Using glutamate homeostasis as a target for treating addictive disorders

PubMed Central

Reissner, Kathryn J.; Kalivas, Peter W.

2010-01-01

Well-developed cellular mechanisms exist to preserve glutamate homeostasis and regulate extrasynaptic glutamate levels. Accumulating evidence indicates that disruptions in glutamate homeostasis are associated with addictive disorders. The disruptions in glutamate concentrations observed following prolonged exposure to drugs of abuse are associated with changes in the function and activity of several key components within the homeostatic control mechanism, including the cystine/glutamate exchanger xc− and the glial glutamate transporter EAAT2/GLT-1. Changes in the balance between synaptic and extrasynaptic glutamate levels in turn influence signaling through pre- and postsynaptic glutamate receptors, and thus affect synaptic plasticity and circuit-level activity. In this review we describe the evidence for impaired glutamate homestasis as a critical mediator of long-term drug-seeking behaviors, how chronic neuroadaptations in xc− and GLT-1 mediate a disruption in glutamate homeostasis, and how targeting these components restores glutamate levels and inhibits drug-seeking behaviors. PMID:20634691

Patch-clamp, ion-sensing, and glutamate-sensing techniques to study glutamate transport in isolated retinal glial cells.

PubMed

Billups, B; Szatkowski, M; Rossi, D; Attwell, D

1998-01-01

We have described how a combination of electrical, ion-sensing, and glutamate-sensing techniques has advanced our understanding of glutamate uptake into isolated salamander retinal glial cells. The next steps in understanding glutamate transport will inevitably depend strongly on molecular biological methods, as described elsewhere in this book, but will also require more detailed study of transporters in their normal environment, perhaps by using patch-clamping or imaging techniques to study cells in situ.

Differential effects of repetitive oral administration of monosodium glutamate on interstitial glutamate concentration and muscle pain sensitivity.

PubMed

Shimada, Akiko; Baad-Hansen, Lene; Castrillon, Eduardo; Ghafouri, Bijar; Stensson, Niclas; Gerdle, Björn; Ernberg, Malin; Cairns, Brian; Svensson, Peter; Svensson Odont, Peter

2015-02-01

The aim of this study was to determine the relationship of high daily monosodium glutamate (MSG) consumption with glutamate concentrations in jaw muscle, saliva, and serum, and muscle pain sensitivity in healthy participants. A randomized, double-blinded, placebo-controlled study was conducted to investigate the effect of repetitive consumption of high-dose MSG on glutamate concentration in the masseter muscles measured by microdialysis and muscle pain sensitivity. In five contiguous experimental daily sessions, 32 healthy participants drank MSG (150 mg/kg) or NaCl (24 mg/kg) diluted with a 400 mL soda. The concentrations of glutamate before and after the ingestion were assessed in dialysate and plasma samples on the first and last days. Saliva glutamate concentration was assessed every day. Pressure pain threshold, pressure pain tolerance, autonomic parameters (heart rate, systolic and diastolic blood pressures) and reported side effects also were assessed. No significant change was noted in the baseline concentration of glutamate in the masseter muscle, blood, or saliva, but the peak concentration in the masseter muscle increased significantly between day 1 and 5. A statistically significant increase in systolic and diastolic blood pressures after MSG administration was observed, as well as a significantly higher frequency of reports of nausea and headache in the MSG group. No robust effect of MSG on muscle sensitivity was found. Interstitial glutamate concentration in the masseter muscle is not highly disturbed by excessive repetitive intake of MSG in healthy man. Copyright © 2015 Elsevier Inc. All rights reserved.

Glutamate and GABA-metabolizing enzymes in post-mortem cerebellum in Alzheimer's disease: phosphate-activated glutaminase and glutamic acid decarboxylase.

PubMed

Burbaeva, G Sh; Boksha, I S; Tereshkina, E B; Savushkina, O K; Prokhorova, T A; Vorobyeva, E A

2014-10-01

Enzymes of glutamate and GABA metabolism in postmortem cerebellum from patients with Alzheimer's disease (AD) have not been comprehensively studied. The present work reports results of original comparative study on levels of phosphate-activated glutaminase (PAG) and glutamic acid decarboxylase isoenzymes (GAD65/67) in autopsied cerebellum samples from AD patients and matched controls (13 cases in each group) as well as summarizes published evidence for altered levels of PAG and GAD65/67 in AD brain. Altered (decreased) levels of these enzymes and changes in links between amounts of these enzymes and other glutamate-metabolizing enzymes (such as glutamate dehydrogenase and glutamine synthetase-like protein) in AD cerebella suggest significantly impaired glutamate and GABA metabolism in this brain region, which was previously regarded as not substantially involved in AD pathogenesis.

Chronic treatment with agomelatine or venlafaxine reduces depolarization-evoked glutamate release from hippocampal synaptosomes

PubMed Central

2013-01-01

Background Growing compelling evidence from clinical and preclinical studies has demonstrated the primary role of alterations of glutamatergic transmission in cortical and limbic areas in the pathophysiology of mood disorders. Chronic antidepressants have been shown to dampen endogenous glutamate release from rat hippocampal synaptic terminals and to prevent the marked increase of glutamate overflow induced by acute behavioral stress in frontal/prefrontal cortex. Agomelatine, a new antidepressant endowed with MT1/MT2 agonist and 5-HT2C serotonergic antagonist properties, has shown efficacy at both preclinical and clinical levels. Results Chronic treatment with agomelatine, or with the reference drug venlafaxine, induced a marked decrease of depolarization-evoked endogenous glutamate release from purified hippocampal synaptic terminals in superfusion. No changes were observed in GABA release. This effect was accompanied by reduced accumulation of SNARE protein complexes, the key molecular effector of vesicle docking, priming and fusion at presynaptic membranes. Conclusions Our data suggest that the novel antidepressant agomelatine share with other classes of antidepressants the ability to modulate glutamatergic transmission in hippocampus. Its action seems to be mediated by molecular mechanisms located on the presynaptic membrane and related with the size of the vesicle pool ready for release. PMID:23895555

Moclobemide attenuates anoxia and glutamate-induced neuronal damage in vitro independently of interaction with glutamate receptor subtypes.

PubMed

Verleye, Marc; Steinschneider, Remy; Bernard, François Xavier; Gillardin, Jean-Marie

2007-03-23

Recent data suggested the existence of a bidirectional relation between depression and neurodegenerative diseases resulting from cerebral ischemia injury. Glutamate, a major excitatory neurotransmitter, has long been recognised to play a key role in the pathophysiology of anoxia or ischemia, due to its excessive accumulation in the extracellular space and the subsequent activation of its receptors. A characteristic response to glutamate is the increase in cytosolic Na(+) and Ca(2+) levels which is due mainly to influx from the extracellular space, with a consequent cell swelling and oxidative metabolism dysfunction. The present study examined the in vitro effects of the antidepressant and type-A monoamine oxidase inhibitor, moclobemide, in neuronal-astroglial cultures from rat cerebral cortex exposed to anoxia (for 5 and 7 h) or to glutamate (2 mM for 6 h), two in vitro models of brain ischemia. In addition, the affinity of moclobemide for the different glutamate receptor subtypes and an interaction with the cell influx of Na(+) and of Ca(2+) enhanced by veratridine and K(+) excess, respectively, were evaluated. Moclobemide (10-100 microM) included in the culture medium during anoxia or with glutamate significantly increased in a concentration-dependent manner the amount of surviving neurons compared to controls. Moclobemide displayed no binding affinity for the different glutamate receptor subtypes (IC(50)>100 microM) and did not block up to 300 microM the entry of Na(+) and of Ca(2+) activated by veratridine and K(+), respectively. These results suggest that the neuroprotective properties of moclobemide imply neither the glutamate neurotransmission nor the Na(+) and Ca(2+) channels.

AV3V lesions reduce the pressor response to L-glutamate into the RVLM.

PubMed

Vieira, Alexandre Antonio; Colombari, Eduardo; De Luca, Laurival A; Colombari, Débora Simões de Almeida; Menani, José V

2006-05-01

Neurons from the rostral ventrolateral medulla (RVLM) directly activate sympathetic pre-ganglionic neurons in the spinal cord. Hypertensive responses and sympathetic activation produced by different stimuli are strongly affected by lesions of the preoptic periventricular tissue surrounding the anteroventral third ventricle (AV3V region). Therefore, in the present study, we investigated the effects of acute (1 day) and chronic (15 days) electrolytic lesions of the AV3V region on the pressor responses produced by injections of the excitatory amino acid L-glutamate into the RVLM of unanesthetized rats. Male Holtzman rats with sham or electrolytic AV3V lesions and a stainless steel cannula implanted into the RVLM were used. The pressor responses produced by injections of L-glutamate (1, 5 and 10 nmol/100 nl) into the RVLM were reduced 1 day (9 +/- 4, 39 +/- 6 and 37 +/- 4 mm Hg, respectively) and 15 days after AV3V lesions (13 +/- 6, 39 +/- 4 and 43 +/- 4 mm Hg, respectively, vs. sham lesions: 29 +/- 3, 50 +/- 2 and 58 +/- 3 mm Hg, respectively). Injections of L-glutamate into the RVLM in sham or AV3V-lesioned rats produced no significant change in the heart rate (HR). Baroreflex bradycardia and tachycardia produced by iv phenylephrine or sodium nitroprusside, respectively, and the pressor and bradycardic responses to chemoreflex activation with iv potassium cyanide were not modified by AV3V lesions. The results suggest that signals from the AV3V region are important for sympathetic activation induced by L-glutamate into the RVLM.

An examination of the roles of glutamate and sex in latent inhibition: Relevance to the glutamate hypothesis of schizophrenia?

PubMed

Huang, Andrew Chih Wei; Bo-Han He, Alan; Chen, Chih-Chung

2017-10-01

The present study examined the effects of the glutamate receptor antagonist MK-801, the glutamate receptor agonist N-methyl-D-aspartate (NMDA), and sexual dimorphism on latent inhibition to elucidate the glutamate hypothesis of schizophrenia. During the pre-exposure phase, 56 male and 65 female Wistar rats were intracerebroventricularly administered normal saline, MK-801 or NMDA, in the left ventricle and then exposed to a passive avoidance box (or a different context) in three trials over 3 days. Then, all of the rats were placed in the light compartment of the passive avoidance box and were allowed to enter the dark compartment, where they each received a footshock (1mA, 2s) in five trials over 5 days. Injections of the glutamate drugs NMDA and MK-801 did not affect latent inhibition. Sexual dimorphism did not occur in latent inhibition. The present data on the male rats indicated that the glutamate system did not affect latent inhibition, indicating that the glutamate system was not like the dopamine system in terms of mediating the positive symptoms of schizophrenia. The glutamate system might be involved in the negative and cognitive symptoms of schizophrenia. The results may provide information for novel treatments of the negative and cognitive symptoms of schizophrenia. Copyright © 2017 Elsevier B.V. All rights reserved.

Heteroreceptor Complexes Formed by Dopamine D1, Histamine H3, and N-Methyl-D-Aspartate Glutamate Receptors as Targets to Prevent Neuronal Death in Alzheimer's Disease.

PubMed

Rodríguez-Ruiz, Mar; Moreno, Estefanía; Moreno-Delgado, David; Navarro, Gemma; Mallol, Josefa; Cortés, Antonio; Lluís, Carme; Canela, Enric I; Casadó, Vicent; McCormick, Peter J; Franco, Rafael

2017-08-01

Alzheimer's disease (AD) is a neurodegenerative disorder causing progressive memory loss and cognitive dysfunction. Anti-AD strategies targeting cell receptors consider them as isolated units. However, many cell surface receptors cooperate and physically contact each other forming complexes having different biochemical properties than individual receptors. We here report the discovery of dopamine D 1 , histamine H 3 , and N-methyl-D-aspartate (NMDA) glutamate receptor heteromers in heterologous systems and in rodent brain cortex. Heteromers were detected by co-immunoprecipitation and in situ proximity ligation assays (PLA) in the rat cortex where H 3 receptor agonists, via negative cross-talk, and H 3 receptor antagonists, via cross-antagonism, decreased D 1 receptor agonist signaling determined by ERK1/2 or Akt phosphorylation, and counteracted D 1 receptor-mediated excitotoxic cell death. Both D 1 and H 3 receptor antagonists also counteracted NMDA toxicity suggesting a complex interaction between NMDA receptors and D 1 -H 3 receptor heteromer function. Likely due to heteromerization, H 3 receptors act as allosteric regulator for D 1 and NMDA receptors. By bioluminescence resonance energy transfer (BRET), we demonstrated that D 1 or H 3 receptors form heteromers with NR1A/NR2B NMDA receptor subunits. D 1 -H 3 -NMDA receptor complexes were confirmed by BRET combined with fluorescence complementation. The endogenous expression of complexes in mouse cortex was determined by PLA and similar expression was observed in wild-type and APP/PS1 mice. Consistent with allosteric receptor-receptor interactions within the complex, H 3 receptor antagonists reduced NMDA or D 1 receptor-mediated excitotoxic cell death in cortical organotypic cultures. Moreover, H 3 receptor antagonists reverted the toxicity induced by ß 1-42 -amyloid peptide. Thus, histamine H 3 receptors in D 1 -H 3 -NMDA heteroreceptor complexes arise as promising targets to prevent neurodegeneration.

Prefrontal glutamate correlates of methamphetamine sensitization and preference

PubMed Central

Lominac, Kevin D.; Quadir, Sema G.; Barrett, Hannah M.; McKenna, Courtney L.; Schwartz, Lisa M.; Ruiz, Paige N.; Wroten, Melissa G.; Campbell, Rianne R.; Miller, Bailey W.; Holloway, John J.; Travis, Katherine O.; Rajasekar, Ganesh; Maliniak, Dan; Thompson, Andrew B.; Urman, Lawrence E.; Kippin, Tod E.; Phillips, Tamara J.; Szumlinski, Karen K.

2016-01-01

Methamphetamine (MA) is a widely abused, highly addictive, psychostimulant that elicits pronounced deficits in neurocognitive function related to hypo-functioning of the prefrontal cortex (PFC). Our understanding of how repeated methamphetamine impacts excitatory glutamatergic transmission within the PFC is limited, as is information about the relation between PFC glutamate and addiction vulnerability/resiliency. In vivo microdialysis and immunoblotting studies characterized the effects of methamphetamine (10 injections of 2 mg/kg, IP) upon extracellular glutamate in C57BL/6J mice and upon glutamate receptor and transporter expression, within the medial PFC. Glutamatergic correlates of both genetic and idiopathic variance in MA preference/intake were determined through studies of high versus low MA-drinking selectively bred mouse lines (MAHDR versus MALDR, respectively) and inbred C57BL/6J mice exhibiting spontaneously divergent place-conditioning phenotypes. Repeated methamphetamine sensitized drug-induced glutamate release and lowered indices of NMDA receptor expression in C57BL/6J mice, but did not alter basal extracellular glutamate content or total protein expression of Homer proteins, or metabotropic or AMPA glutamate receptors. Elevated basal glutamate, blunted methamphetamine-induced glutamate release and ERK activation, as well as reduced protein expression of mGlu2/3 and Homer2a/b were all correlated biochemical traits of selection for high versus low methamphetamine drinking, and Homer2a/b levels were inversely correlated with the motivational valence of methamphetamine in C57BL/6J mice. These data provide novel evidence that repeated, low-dose, methamphetamine is sufficient to perturb pre- and post-synaptic aspects of glutamate transmission within the medial PFC and that glutamate anomalies within this region may contribute to both genetic and idiopathic variance in methamphetamine addiction vulnerability/resiliency. PMID:26742098

Glutamate receptors in the nucleus tractus solitarius contribute to ventilatory acclimatization to hypoxia in rat

PubMed Central

Pamenter, Matthew E; Carr, J Austin; Go, Ariel; Fu, Zhenxing; Reid, Stephen G; Powell, Frank L

2014-01-01

When exposed to a hypoxic environment the body's first response is a reflex increase in ventilation, termed the hypoxic ventilatory response (HVR). With chronic sustained hypoxia (CSH), such as during acclimatization to high altitude, an additional time-dependent increase in ventilation occurs, which increases the HVR. This secondary increase persists after exposure to CSH and involves plasticity within the circuits in the central nervous system that control breathing. Currently these mechanisms of HVR plasticity are unknown and we hypothesized that they involve glutamatergic synapses in the nucleus tractus solitarius (NTS), where afferent endings from arterial chemoreceptors terminate. To test this, we treated rats held in normoxia (CON) or 10% O2 (CSH) for 7 days and measured ventilation in conscious, unrestrained animals before and after microinjecting glutamate receptor agonists and antagonists into the NTS. In normoxia, AMPA increased ventilation 25% and 50% in CON and CSH, respectively, while NMDA doubled ventilation in both groups (P < 0.05). Specific AMPA and NMDA receptor antagonists (NBQX and MK801, respectively) abolished these effects. MK801 significantly decreased the HVR in CON rats, and completely blocked the acute HVR in CSH rats but had no effect on ventilation in normoxia. NBQX decreased ventilation whenever it was increased relative to normoxic controls; i.e. acute hypoxia in CON and CSH, and normoxia in CSH. These results support our hypothesis that glutamate receptors in the NTS contribute to plasticity in the HVR with CSH. The mechanism underlying this synaptic plasticity is probably glutamate receptor modification, as in CSH rats the expression of phosphorylated NR1 and GluR1 proteins in the NTS increased 35% and 70%, respectively, relative to that in CON rats. PMID:24492841

Differential effects of serotonin-specific and excitotoxic lesions of OFC on conditioned reinforcer devaluation and extinction in rats

PubMed Central

West, Elizabeth A.; Forcelli, Patrick A.; McCue, David L.; Malkova, Ludise

2013-01-01

The orbitofrontal cortex (OFC) is critical for behavioral adaptation in response to changes in reward value. Here we investigated, in rats, the role of OFC and, specifically, serotonergic neurotransmission within OFC in a reinforcer devaluation task (which measures behavioral flexibility). This task used two visual cues, each predicting one of two foods, with the spatial position (left-right) of the cues above two levers pseudorandomized across trials. An instrumental action (lever press) was required for reinforcer delivery. After training, rats received either excitotoxic OFC lesions made by NMDA (N-methyl-D-aspartic acid), serotonin-specific OFC lesions made by 5,7-DHT (5,7-dihydroxytryptamine), or sham lesions. In sham-lesioned rats, devaluation of one food (by feeding to satiety) significantly decreased responding to the cue associated with that food, when both cues were presented simultaneously during extinction. Both types of OFC lesions disrupted the devaluation effect. In contrast, extinction learning was not affected by serotonin-specific lesions and was only mildly retarded in rats with excitotoxic lesions. Thus, serotonin within OFC is necessary for appropriately adjusting behavior towards cues that predict reward but not for reducing responses in the absence of reward. Our results are the first to demonstrate that serotonin in OFC is necessary for reinforcer devaluation, but not extinction. PMID:23458741

The neuroprotective effects of oxaloacetate in closed head injury in rats is mediated by its blood glutamate scavenging activity: evidence from the use of maleate.

PubMed

Zlotnik, Alexander; Gruenbaum, Shaun E; Artru, Alan A; Rozet, Irene; Dubilet, Michael; Tkachov, Sergey; Brotfain, Evgeny; Klin, Yael; Shapira, Yoram; Teichberg, Vivian I

2009-07-01

Treatment with oxaloacetate after traumatic brain injury has been shown to decrease blood glutamate levels and protect against the neurotoxic effects of glutamate on the brain. A number of potential mechanisms have been suggested to explain oxaloacetate-induced neuroprotection. We hypothesize that the primary mechanism by which intravenous oxaloacetate provides neuroprotection is by activation of the blood glutamate-scavenging enzyme glutamate-oxaloacetate transaminase, increasing thereby the driving force for the efflux of excess glutamate from brain interstitial fluids into blood. If so, coadministration of maleate, a glutamate-oxaloacetate transaminase-blocker is expected to prevent the neuroprotective effects of oxaloacetate. A neurological severity score (NSS) was measured 1 hour after closed head injury (CHI) in rats. Then, rats received 30 microL/min/100 g infusion of saline, or 1 mmol/100 g solution of oxaloacetate, maleate, or a mixture of oxaloacetate and maleate. NSS was reassessed at 24 and 48 hour after CHI. Blood glutamate and glucose levels were measured at 0, 60, 90, and 120 minutes. NSS improved significantly at 24 hour (P<0.001) and 48 hour (P<0.001) only in the rats treated with oxaloacetate. Blood glutamate decreased significantly in the oxaloacetate-treated group at 90 minute (at the conclusion of oxaloacetate administration) (P<0.00001), but not in the control, maleate or oxaloacetate+maleate groups. A strong correlation r2=0.86 was found to exist between the percent decrease in blood glutamate levels and percent improvement in NSS. The results of this study demonstrate that the primary mechanism by which oxaloacetate provides neuroprotective activity after CHI is related to its blood glutamate scavenging activity. Management of blood glutamate concentration may have important implications in the treatment of acute brain conditions, including CHI and stroke.

The Influence of Glutamate on Axonal Compound Action Potential In Vitro.

PubMed

Abouelela, Ahmed; Wieraszko, Andrzej

2016-01-01

Background  Our previous experiments demonstrated modulation of the amplitude of the axonal compound action potential (CAP) by electrical stimulation. To verify assumption that glutamate released from axons could be involved in this phenomenon, the modification of the axonal CAP induced by glutamate was investigated. Objectives  The major objective of this research is to verify the hypothesis that axonal activity would trigger the release of glutamate, which in turn would interact with specific axonal receptors modifying the amplitude of the action potential. Methods  Segments of the sciatic nerve were exposed to exogenous glutamate in vitro, and CAP was recorded before and after glutamate application. In some experiments, the release of radioactive glutamate analog from the sciatic nerve exposed to exogenous glutamate was also evaluated. Results  The glutamate-induced increase in CAP was blocked by different glutamate receptor antagonists. The effect of glutamate was not observed in Ca-free medium, and was blocked by antagonists of calcium channels. Exogenous glutamate, applied to the segments of sciatic nerve, induced the release of radioactive glutamate analog, demonstrating glutamate-induced glutamate release. Immunohistochemical examination revealed that axolemma contains components necessary for glutamatergic neurotransmission. Conclusion  The proteins of the axonal membrane can under the influence of electrical stimulation or exogenous glutamate change membrane permeability and ionic conductance, leading to a change in the amplitude of CAP. We suggest that increased axonal activity leads to the release of glutamate that results in changes in the amplitude of CAPs.

Increased pain and muscle glutamate concentration after single ingestion of monosodium glutamate by myofascial temporomandibular disorders patients.

PubMed

Shimada, A; Castrillon, E E; Baad-Hansen, L; Ghafouri, B; Gerdle, B; Wåhlén, K; Ernberg, M; Cairns, B E; Svensson, P

2016-10-01

A randomized, double-blinded, placebo-controlled study was conducted to investigate if single monosodium glutamate (MSG) administration would elevate muscle/serum glutamate concentrations and affect muscle pain sensitivity in myofascial temporomandibular disorders (TMD) patients more than in healthy individuals. Twelve myofascial TMD patients and 12 sex- and age-matched healthy controls participated in two sessions. Participants drank MSG (150 mg/kg) or NaCl (24 mg/kg; control) diluted in 400 mL of soda. The concentration of glutamate in the masseter muscle, blood plasma and saliva was determined before and after the ingestion of MSG or control. At baseline and every 15 min after the ingestion, pain intensity was scored on a 0-10 numeric rating scale. Pressure pain threshold, pressure pain tolerance (PPTol) and autonomic parameters were measured. All participants were asked to report adverse effects after the ingestion. In TMD, interstitial glutamate concentration was significantly greater after the MSG ingestion when compared with healthy controls. TMD reported a mean pain intensity of 2.8/10 at baseline, which significantly increased by 40% 30 min post MSG ingestion. At baseline, TMD showed lower PPTols in the masseter and trapezius, and higher diastolic blood pressure and heart rate than healthy controls. The MSG ingestion resulted in reports of headache by half of the TMD and healthy controls, respectively. These findings suggest that myofascial TMD patients may be particularly sensitive to the effects of ingested MSG. WHAT DOES THIS STUDY ADD?': Elevation of interstitial glutamate concentration in the masseter muscle caused by monosodium glutamate (MSG) ingestion was significantly greater in myofascial myofascial temporomandibular disorders (TMD) patients than healthy individuals. This elevation of interstitial glutamate concentration in the masseter muscle significantly increased the intensity of spontaneous pain in myofascial TMD patients. © 2016

Ibogaine alters synaptosomal and glial glutamate release and uptake.

PubMed

Leal, M B; Emanuelli, T; Porciúncula, L D; Souza, D O; Elisabetsky, E

2001-02-12

Ibogaine has aroused expectations as a potentially innovative medication for drug addiction. It has been proposed that antagonism of the NMDA receptor by ibogaine may be one of the mechanisms underlying its antiaddictive properties; glutamate has also been implicated in ibogaine-induced neurotoxicity. We here report the effects of ibogaine on [3H]glutamate release and uptake in cortical and cerebellar synaptosomes, as well as in cortical astrocyte cultures, from mice and rats. Ibogaine (2-1000 microM) had no effects on glutamate uptake or release by rat synaptosomes. However, ibogaine (500-1000 microM) significantly inhibited the glutamate uptake and stimulated the release of glutamate by cortical (but not cerebellar) synaptosomes of mice. In addition, ibogaine (1000 microM) nearly abolished glutamate uptake by cortical astrocyte cultures from rats and mice. The data provide direct evidence of glutamate involvement in ibogaine-induced neurotoxicity.

Characterization of Human Hippocampal Neural Stem/Progenitor Cells and Their Application to Physiologically Relevant Assays for Multiple Ionotropic Glutamate Receptors.

PubMed

Fukushima, Kazuyuki; Tabata, Yoshikuni; Imaizumi, Yoichi; Kohmura, Naohiro; Sugawara, Michiko; Sawada, Kohei; Yamazaki, Kazuto; Ito, Masashi

2014-09-01

The hippocampus is an important brain region that is involved in neurological disorders such as Alzheimer disease, schizophrenia, and epilepsy. Ionotropic glutamate receptors-namely,N-methyl-D-aspartate (NMDA) receptors (NMDARs), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors (AMPARs), and kainic acid (KA) receptors (KARs)-are well known to be involved in these diseases by mediating long-term potentiation, excitotoxicity, or both. To predict the therapeutic efficacy and neuronal toxicity of drug candidates acting on these receptors, physiologically relevant systems for assaying brain region-specific human neural cells are necessary. Here, we characterized the functional differentiation of human fetal hippocampus-derived neural stem/progenitor cells-namely, HIP-009 cells. Calcium rise assay demonstrated that, after a 4-week differentiation, the cells responded to NMDA (EC50= 7.5 ± 0.4 µM; n= 4), AMPA (EC50= 2.5 ± 0.1 µM; n= 3), or KA (EC50= 33.5 ± 1.1 µM; n= 3) in a concentration-dependent manner. An AMPA-evoked calcium rise was observed in the absence of the desensitization inhibitor cyclothiazide. In addition, the calcium rise induced by these agonists was inhibited by antagonists for each receptor-namely, MK-801 for NMDA stimulation (IC50= 0.6 ± 0.1 µM; n= 4) and NBQX for AMPA and KA stimulation (IC50= 0.7 ± 0.1 and 0.7 ± 0.03 µM, respectively; n= 3). The gene expression profile of differentiated HIP-009 cells was distinct from that of undifferentiated cells and closely resembled that of the human adult hippocampus. Our results show that HIP-009 cells are a unique tool for obtaining human hippocampal neural cells and are applicable to systems for assay of ionotropic glutamate receptors as a physiologically relevant in vitro model. © 2014 Society for Laboratory Automation and Screening.

Inhibitory Effects of Pretreatment with Radon on Acute Alcohol-Induced Hepatopathy in Mice

PubMed Central

Toyota, Teruaki; Kataoka, Takahiro; Nishiyama, Yuichi; Taguchi, Takehito; Yamaoka, Kiyonori

2012-01-01

We previously reported that radon inhalation activates antioxidative functions in the liver and inhibits carbon tetrachloride-induced hepatopathy in mice. In addition, it has been reported that reactive oxygen species contribute to alcohol-induced hepatopathy. In this study, we examined the inhibitory effects of radon inhalation on acute alcohol-induced hepatopathy in mice. C57BL/6J mice were subjected to intraperitoneal injection of 50% alcohol (5 g/kg bodyweight) after inhaling approximately 4000 Bq/m3 radon for 24 h. Alcohol administration significantly increased the activities of glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT) in serum, and the levels of triglyceride and lipid peroxide in the liver, suggesting acute alcohol-induced hepatopathy. Radon inhalation activated antioxidative functions in the liver. Furthermore, pretreatment with radon inhibited the depression of hepatic functions and antioxidative functions. These findings suggested that radon inhalation activated antioxidative functions in the liver and inhibited acute alcohol-induced hepatopathy in mice. PMID:23213269

Inhibitory effects of pretreatment with radon on acute alcohol-induced hepatopathy in mice.

PubMed

Toyota, Teruaki; Kataoka, Takahiro; Nishiyama, Yuichi; Taguchi, Takehito; Yamaoka, Kiyonori

2012-01-01

We previously reported that radon inhalation activates antioxidative functions in the liver and inhibits carbon tetrachloride-induced hepatopathy in mice. In addition, it has been reported that reactive oxygen species contribute to alcohol-induced hepatopathy. In this study, we examined the inhibitory effects of radon inhalation on acute alcohol-induced hepatopathy in mice. C57BL/6J mice were subjected to intraperitoneal injection of 50% alcohol (5 g/kg bodyweight) after inhaling approximately 4000 Bq/m(3) radon for 24 h. Alcohol administration significantly increased the activities of glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT) in serum, and the levels of triglyceride and lipid peroxide in the liver, suggesting acute alcohol-induced hepatopathy. Radon inhalation activated antioxidative functions in the liver. Furthermore, pretreatment with radon inhibited the depression of hepatic functions and antioxidative functions. These findings suggested that radon inhalation activated antioxidative functions in the liver and inhibited acute alcohol-induced hepatopathy in mice.

Aprotinin, but not epsilon aminocaproic acid and tranexamic acid, exerts neuroprotection against excitotoxic injury in an in vitro neuronal cell culture model

PubMed Central

Lu, Zhaohui; Korotcova, Ludmila; Murata, Akira; Ishibashi, Nobuyuki; Jonas, Richard A.

2013-01-01

Objective Lack of availability of aprotinin has resulted in increased clinical use of the alternative antifibrinolytic agents epsilon aminocaproic acid (EACA) and tranexamic acid (TXA) which are known to be associated with an increased risk of seizures. In contrast aprotinin has previously been demonstrated to be neuroprotective through suppression of excitotoxicity-mediated neuronal degeneration via the extracellular plasminogen/plasmin system. We compared the impact of antifibrinolytic agents on neuronal and mixed glial/neuronal cell cultures. Methods Mixed cortical cultures containing neuronal and glial cells were prepared from fetal mice and plated on a layer of confluent astrocytes from postnatal pups. Primary neuronal culture was obtained from the same gestational stage and plated in multiwall vessels. Slowly triggered excitotoxicity was induced by 24-hour exposure to 12.5 mM N-methyl-D-aspartate (NMDA). Apoptotic neuronal cell death was induced by exposure of primary neural cultures to 24 hours of serum deprivation. Results Compared to NMDA alone, no significant changes in cell death were observed for any dose of TXA or EACA in mixed cultures. Conversely, a clinical dose of aprotinin significantly reduced cell death by -31% on average. Aprotinin reduced apoptotic neuronal cell death from 75% to 37.3%, and 34.1% at concentrations of 100 and 200 KIU/mL, and significantly decreased neuronal nuclear damage. These concentrations of aprotinin significantly inhibited caspase 9 and 3/7 activations. 250 KIU/ml aprotinin exerted maximal protection on primary cortical neurons. Conclusions In contrast to aprotinin, EACA and TXA exert no protective effect against excitotoxic neuronal injury that can occur during cardiac surgery. PMID:24237885

β-N-Methylamino-L-alanine (BMAA) perturbs alanine, aspartate and glutamate metabolism pathways in human neuroblastoma cells as determined by metabolic profiling.

PubMed

Engskog, Mikael K R; Ersson, Lisa; Haglöf, Jakob; Arvidsson, Torbjörn; Pettersson, Curt; Brittebo, Eva

2017-05-01

β-Methylamino-L-alanine (BMAA) is a non-proteinogenic amino acid that induces long-term cognitive deficits, as well as an increased neurodegeneration and intracellular fibril formation in the hippocampus of adult rodents following short-time neonatal exposure and in vervet monkey brain following long-term exposure. It has also been proposed to be involved in the etiology of neurodegenerative disease in humans. The aim of this study was to identify metabolic effects not related to excitotoxicity or oxidative stress in human neuroblastoma SH-SY5Y cells. The effects of BMAA (50, 250, 1000 µM) for 24 h on cells differentiated with retinoic acid were studied. Samples were analyzed using LC-MS and NMR spectroscopy to detect altered intracellular polar metabolites. The analysis performed, followed by multivariate pattern recognition techniques, revealed significant perturbations in protein biosynthesis, amino acid metabolism pathways and citrate cycle. Of specific interest were the BMAA-induced alterations in alanine, aspartate and glutamate metabolism and as well as alterations in various neurotransmitters/neuromodulators such as GABA and taurine. The results indicate that BMAA can interfere with metabolic pathways involved in neurotransmission in human neuroblastoma cells.

Bax regulates neuronal Ca2+ homeostasis.

PubMed

D'Orsi, Beatrice; Kilbride, Seán M; Chen, Gang; Perez Alvarez, Sergio; Bonner, Helena P; Pfeiffer, Shona; Plesnila, Nikolaus; Engel, Tobias; Henshall, David C; Düssmann, Heiko; Prehn, Jochen H M

2015-01-28

Excessive Ca(2+) entry during glutamate receptor overactivation ("excitotoxicity") induces acute or delayed neuronal death. We report here that deficiency in bax exerted broad neuroprotection against excitotoxic injury and oxygen/glucose deprivation in mouse neocortical neuron cultures and reduced infarct size, necrotic injury, and cerebral edema formation after middle cerebral artery occlusion in mice. Neuronal Ca(2+) and mitochondrial membrane potential (Δψm) analysis during excitotoxic injury revealed that bax-deficient neurons showed significantly reduced Ca(2+) transients during the NMDA excitation period and did not exhibit the deregulation of Δψm that was observed in their wild-type (WT) counterparts. Reintroduction of bax or a bax mutant incapable of proapoptotic oligomerization equally restored neuronal Ca(2+) dynamics during NMDA excitation, suggesting that Bax controlled Ca(2+) signaling independently of its role in apoptosis execution. Quantitative confocal imaging of intracellular ATP or mitochondrial Ca(2+) levels using FRET-based sensors indicated that the effects of bax deficiency on Ca(2+) handling were not due to enhanced cellular bioenergetics or increased Ca(2+) uptake into mitochondria. We also observed that mitochondria isolated from WT or bax-deficient cells similarly underwent Ca(2+)-induced permeability transition. However, when Ca(2+) uptake into the sarco/endoplasmic reticulum was blocked with the Ca(2+)-ATPase inhibitor thapsigargin, bax-deficient neurons showed strongly elevated cytosolic Ca(2+) levels during NMDA excitation, suggesting that the ability of Bax to support dynamic ER Ca(2+) handling is critical for cell death signaling during periods of neuronal overexcitation. Copyright © 2015 the authors 0270-6474/15/351706-17$15.00/0.

Mitochondrial Division Inhibitor 1 (mdivi-1) Protects Neurons against Excitotoxicity through the Modulation of Mitochondrial Function and Intracellular Ca2+ Signaling.

PubMed

Ruiz, Asier; Alberdi, Elena; Matute, Carlos

2018-01-01

Excessive dynamin related protein 1 (Drp1)-triggered mitochondrial fission contributes to apoptosis under pathological conditions and therefore it has emerged as a promising therapeutic target. Mitochondrial division inhibitor 1 (mdivi-1) inhibits Drp1-dependent mitochondrial fission and is neuroprotective in several models of brain ischemia and neurodegeneration. However, mdivi-1 also modulates mitochondrial function and oxidative stress independently of Drp1, and consequently the mechanisms through which it protects against neuronal injury are more complex than previously foreseen. In this study, we have analyzed the effects of mdivi-1 on mitochondrial dynamics, Ca 2+ signaling, mitochondrial bioenergetics and cell viability during neuronal excitotoxicity in vitro . Time-lapse fluorescence microscopy revealed that mdivi-1 blocked NMDA-induced mitochondrial fission but not that triggered by sustained AMPA receptor activation, showing that mdivi-1 inhibits excitotoxic mitochondrial fragmentation in a source specific manner. Similarly, mdivi-1 strongly reduced NMDA-triggered necrotic-like neuronal death and, to a lesser extent, AMPA-induced toxicity. Interestingly, neuroprotection provided by mdivi-1 against NMDA, but not AMPA, correlated with a reduction in cytosolic Ca 2+ ([Ca 2+ ] cyt ) overload and calpain activation indicating additional cytoprotective mechanisms. Indeed, mdivi-1 depolarized mitochondrial membrane and depleted ER Ca 2+ content, leading to attenuation of mitochondrial [Ca 2+ ] increase and enhancement of the integrated stress response (ISR) during NMDA receptor activation. Finally, lentiviral knockdown of Drp1 did not rescue NMDA-induced mitochondrial fission and toxicity, indicating that neuroprotective activity of mdivi-1 is Drp1-independent. Together, these results suggest that mdivi-1 induces a Drp1-independent protective phenotype that prevents predominantly NMDA receptor-mediated excitotoxicity through the modulation of mitochondrial

Opposite in vivo effects of agents that stimulate or inhibit the glutamate/cysteine exchanger system xc- on the inhibition of hippocampal LTP by Aß.

PubMed

Zhang, Dainan; Jin, Baozhe; Ondrejcak, Tomas; Rowan, Michael J

2016-12-01

Aggregated amyloid ß-protein (Aß) is pathognomonic of Alzheimer's disease and certain assemblies of Aß are synaptotoxic. Excess glutamate or diminished glutathione reserve are both implicated in mediating or modulating Aß-induced disruption of synaptic plasticity. The system xc- antiporter promotes Na + -independent exchange of cystine with glutamate thereby providing a major source of extracellular glutamate and intracellular glutathione concentrations. Here we probed the ability of two drugs with opposite effects on system xc-, the inhibitor sulfasalazine and facilitator N-acetylcysteine, to modulate the ability of Aß1-42 to inhibit long-term potentiation (LTP) in the CA1 area of the anaesthetized rat. Whereas acute systemic treatment with sulfasalazine lowered the threshold for Aß to interfere with synaptic plasticity, N-acetylcysteine prevented the inhibition of LTP by Aß alone or in combination with sulfasalazine. Moreover acute N-acetylcysteine also prevented the inhibition of LTP by TNFα, a putative mediator of Aß actions, and repeated systemic N-acetylcysteine treatment for 7 days reversed the delayed deleterious effect of Aß on LTP. Since both of these drugs are widely used clinically, further evaluation of their potential beneficial and deleterious actions in early Alzheimer's disease seems warranted. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Glutamate induces the elongation of early dendritic protrusions via mGluRs in wild type mice, but not in fragile X mice.

PubMed

Cruz-Martín, Alberto; Crespo, Michelle; Portera-Cailliau, Carlos

2012-01-01

Fragile X syndrome (FXS), the most common inherited from of autism and mental impairment, is caused by transcriptional silencing of the Fmr1 gene, resulting in the loss of the RNA-binding protein FMRP. Dendritic spines of cortical pyramidal neurons in affected individuals are abnormally immature and in Fmr1 knockout (KO) mice they are also abnormally unstable. This could result in defects in synaptogenesis, because spine dynamics are critical for synapse formation. We have previously shown that the earliest dendritic protrusions, which are highly dynamic and might serve an exploratory role to reach out for axons, elongate in response to glutamate. Here, we tested the hypothesis that this process is mediated by metabotropic glutamate receptors (mGluRs) and that it is defective in Fmr1 KO mice. Using time-lapse imaging with two-photon microscopy in acute brain slices from early postnatal mice, we find that early dendritic protrusions in layer 2/3 neurons become longer in response to application of glutamate or DHPG, a Group 1 mGluR agonist. Blockade of mGluR5 signaling, which reverses some adult phenotypes of KO mice, prevented the glutamate-mediated elongation of early protrusions. In contrast, dendritic protrusions from KO mice failed to respond to glutamate. Thus, absence of FMRP may impair the ability of cortical pyramidal neurons to respond to glutamate released from nearby pre-synaptic terminals, which may be a critical step to initiate synaptogenesis and stabilize spines.

[The role of non-NMDA glutamate receptors in the EEG effects of chronic administration of noopept GVS-111 in awake rats].

PubMed

Kovalev, G I; Vorob'ev, V V

2002-01-01

Participation of the non-NMDA glutamate receptor subtype in the formation of the EEG frequency spectrum was studied in wakeful rats upon a long-term (10 x 0.2 mg/kg, s.c.) administration of the nootropic dipeptide GVS-111 (noopept or N-phenylacetyl-L-prolyglycine ethylate). The EEGs were measured with electrodes implanted into somatosensor cortex regions, hippocampus, and a cannula in the lateral ventricle. The acute reactions (characteristic of nootropes) in the alpha and beta ranges of EEG exhibited inversion after the 6th injection of noopept and almost completely vanished after the 9th injection. Preliminary introduction of the non-NMDA antagonist GDEE (glutamic acid diethyl ester) in a dose of 1 mumole into the lateral ventricle restored the EEG pattern observed upon the 6th dose of GVS-111. The role of glutamate receptors in the course of a prolonged administration of nootropes, as well as the possible mechanisms accounting for a difference in the action of GVS-111 and piracetam are discussed.

A Novel Corynebacterium glutamicum l-Glutamate Exporter.

PubMed

Wang, Yu; Cao, Guoqiang; Xu, Deyu; Fan, Liwen; Wu, Xinyang; Ni, Xiaomeng; Zhao, Shuxin; Zheng, Ping; Sun, Jibin; Ma, Yanhe

2018-03-15

Besides metabolic pathways and regulatory networks, transport systems are also pivotal for cellular metabolism and hyperproduction of biochemicals using microbial cell factories. The identification and characterization of transporters are therefore of great significance for the understanding and engineering of transport reactions. Herein, a novel l-glutamate exporter, MscCG2, which exists extensively in Corynebacterium glutamicum strains but is distinct from the only known l-glutamate exporter, MscCG, was discovered in an industrial l-glutamate-producing C. glutamicum strain. MscCG2 was predicted to possess three transmembrane helices in the N-terminal region and located in the cytoplasmic membrane, which are typical structural characteristics of the mechanosensitive channel of small conductance. MscCG2 has a low amino acid sequence identity (23%) to MscCG and evolved separately from MscCG with four transmembrane helices. Despite the considerable differences between MscCG2 and MscCG in sequence and structure, gene deletion and complementation confirmed that MscCG2 also functioned as an l-glutamate exporter and an osmotic safety valve in C. glutamicum Besides, transcriptional analysis showed that MscCG2 and MscCG genes were transcribed in similar patterns and not induced by l-glutamate-producing conditions. It was also demonstrated that MscCG2-mediated l-glutamate excretion was activated by biotin limitation or penicillin treatment and that constitutive l-glutamate excretion was triggered by a gain-of-function mutation of MscCG2 (A151V). Discovery of MscCG2 will enrich the understanding of bacterial amino acid transport and provide additional targets for exporter engineering. IMPORTANCE The exchange of matter, energy, and information with surroundings is fundamental for cellular metabolism. Therefore, studying transport systems that are essential for these processes is of great significance. Besides, transport systems of bacterial cells are usually related to

Effects of Vinpocetine on mitochondrial function and neuroprotection in primary cortical neurons.

PubMed

Tárnok, K; Kiss, E; Luiten, P G M; Nyakas, C; Tihanyi, K; Schlett, K; Eisel, U L M

2008-12-01

Vinpocetine (ethyl apovincaminate), a synthetic derivative of the Vinca minor alkaloid vincamine, is widely used for the treatment of cerebrovascular-related diseases. One of the proposed mechanisms underlying its action is to protect against the cytotoxic effects of glutamate overexposure. Glutamate excitotoxicity leads to the disregulation of mitochondrial function and neuronal metabolism. As Vinpocetine has a binding affinity to the peripheral-type benzodiazepine receptor (PBR) involved in the mitochondrial transition pore complex, we investigated whether neuroprotection can be at least partially due to Vinpocetine's effects on PBRs. Neuroprotective effects of PK11195 and Ro5-4864, two drugs with selective and high affinity to PBR, were compared to Vinpocetine in glutamate excitotoxicity assays on primary cortical neuronal cultures. Vinpocetine exerted a neuroprotective action in a 1-50microM concentration range while PK11195 and Ro5-4864 were only slightly neuroprotective, especially in high (>25microM) concentrations. Combined pretreatment of neuronal cultures with Vinpocetine and PK11195 or Ro5-4864 showed increased neuroprotection in a dose-dependent manner, indicating that the different drugs may have different targets. To test this hypothesis, mitochondrial membrane potential (MMP) of cultured neurons was measured by flow cytometry. 25microM Vinpocetine reduced the decrease of mitochondrial inner membrane potential induced by glutamate exposure, but Ro5-4864 in itself was found to be more potent to block glutamate-evoked changes in MMP. Combination of Ro5-4864 and Vinpocetine treatment was found to be even more effective. In summary, the present results indicate that the neuroprotective action of vinpocetine in culture can not be explained by its effect on neuronal PBRs alone and that additional drug targets are involved.

Costimulation of AMPA and metabotropic glutamate receptors underlies phospholipase C activation by glutamate in hippocampus.

PubMed

Kim, Hye-Hyun; Lee, Kyu-Hee; Lee, Doyun; Han, Young-Eun; Lee, Suk-Ho; Sohn, Jong-Woo; Ho, Won-Kyung

2015-04-22

Glutamate, a major neurotransmitter in the brain, activates ionotropic and metabotropic glutamate receptors (iGluRs and mGluRs, respectively). The two types of glutamate receptors interact with each other, as exemplified by the modulation of iGluRs by mGluRs. However, the other way of interaction (i.e., modulation of mGluRs by iGluRs) has not received much attention. In this study, we found that group I mGluR-specific agonist (RS)-3,5-dihydroxyphenylglycine (DHPG) alone is not sufficient to activate phospholipase C (PLC) in rat hippocampus, while glutamate robustly activates PLC. These results suggested that additional mechanisms provided by iGluRs are involved in group I mGluR-mediated PLC activation. A series of experiments demonstrated that glutamate-induced PLC activation is mediated by mGluR5 and is facilitated by local Ca(2+) signals that are induced by AMPA-mediated depolarization and L-type Ca(2+) channel activation. Finally, we found that PLC and L-type Ca(2+) channels are involved in hippocampal mGluR-dependent long-term depression (mGluR-LTD) induced by paired-pulse low-frequency stimulation, but not in DHPG-induced chemical LTD. Together, we propose that AMPA receptors initiate Ca(2+) influx via the L-type Ca(2+) channels that facilitate mGluR5-PLC signaling cascades, which underlie mGluR-LTD in rat hippocampus. Copyright © 2015 the authors 0270-6474/15/356401-12$15.00/0.

Glutamate. Its applications in food and contribution to health.

PubMed

Jinap, S; Hajeb, P

2010-08-01

This article reviews application of glutamate in food and its benefits and role as one of the common food ingredients used. Monosodium glutamate is one of the most abundant naturally occurring amino acids which frequently added as a flavor enhancer. It produced a unique taste that cannot be provided by other basic taste (saltiness, sourness, sweetness and bitterness), referred to as a fifth taste (umami). Glutamate serves some functions in the body as well, serving as an energy source for certain tissues and as a substrate for glutathione synthesis. Glutamate has the potential to enhance food intake in older individuals and dietary free glutamate evoked a visceral sensation from the stomach, intestine and portal vein. Small quantities of glutamate used in combination with a reduced amount of table salt during food preparation allow for far less salt to be used during and after cooking. Because glutamate is one of the most intensely studied food ingredients in the food supply and has been found safe, the Joint Expert Committee on Food Additives of the United Nations Food and Agriculture Organization and World Health Organization placed it in the safest category for food additives. Despite a widespread belief that glutamate can elicit asthma, migraine headache and Chinese Restaurant Syndrome (CRS), there are no consistent clinical data to support this claim. In addition, findings from the literature indicate that there is no consistent evidence to suggest that individuals may be uniquely sensitive to glutamate. 2010 Elsevier Ltd. All rights reserved.

Therapeutic potential of metabotropic glutamate receptor modulators.

PubMed

Hovelsø, N; Sotty, F; Montezinho, L P; Pinheiro, P S; Herrik, K F; Mørk, A

2012-03-01

Glutamate is the main excitatory neurotransmitter in the central nervous system (CNS) and is a major player in complex brain functions. Glutamatergic transmission is primarily mediated by ionotropic glutamate receptors, which include NMDA, AMPA and kainate receptors. However, glutamate exerts modulatory actions through a family of metabotropic G-protein-coupled glutamate receptors (mGluRs). Dysfunctions of glutamatergic neurotransmission have been implicated in the etiology of several diseases. Therefore, pharmacological modulation of ionotropic glutamate receptors has been widely investigated as a potential therapeutic strategy for the treatment of several disorders associated with glutamatergic dysfunction. However, blockade of ionotropic glutamate receptors might be accompanied by severe side effects due to their vital role in many important physiological functions. A different strategy aimed at pharmacologically interfering with mGluR function has recently gained interest. Many subtype selective agonists and antagonists have been identified and widely used in preclinical studies as an attempt to elucidate the role of specific mGluRs subtypes in glutamatergic transmission. These studies have allowed linkage between specific subtypes and various physiological functions and more importantly to pathological states. This article reviews the currently available knowledge regarding the therapeutic potential of targeting mGluRs in the treatment of several CNS disorders, including schizophrenia, addiction, major depressive disorder and anxiety, Fragile X Syndrome, Parkinson's disease, Alzheimer's disease and pain.

Therapeutic Potential of Metabotropic Glutamate Receptor Modulators

PubMed Central

Hovelsø, N; Sotty, F; Montezinho, L.P; Pinheiro, P.S; Herrik, K.F; Mørk, A

2012-01-01

Glutamate is the main excitatory neurotransmitter in the central nervous system (CNS) and is a major player in complex brain functions. Glutamatergic transmission is primarily mediated by ionotropic glutamate receptors, which include NMDA, AMPA and kainate receptors. However, glutamate exerts modulatory actions through a family of metabotropic G-protein-coupled glutamate receptors (mGluRs). Dysfunctions of glutamatergic neurotransmission have been implicated in the etiology of several diseases. Therefore, pharmacological modulation of ionotropic glutamate receptors has been widely investigated as a potential therapeutic strategy for the treatment of several disorders associated with glutamatergic dysfunction. However, blockade of ionotropic glutamate receptors might be accompanied by severe side effects due to their vital role in many important physiological functions. A different strategy aimed at pharmacologically interfering with mGluR function has recently gained interest. Many subtype selective agonists and antagonists have been identified and widely used in preclinical studies as an attempt to elucidate the role of specific mGluRs subtypes in glutamatergic transmission. These studies have allowed linkage between specific subtypes and various physiological functions and more importantly to pathological states. This article reviews the currently available knowledge regarding the therapeutic potential of targeting mGluRs in the treatment of several CNS disorders, including schizophrenia, addiction, major depressive disorder and anxiety, Fragile X Syndrome, Parkinson’s disease, Alzheimer’s disease and pain. PMID:22942876

Cytoprotection by Endogenous Zinc in the Vertebrate Retina

PubMed Central

Anastassov, Ivan; Ripps, Harris; Chappell, Richard L.

2014-01-01

Our recent studies have shown that endogenous zinc, co-released with glutamate from the synaptic terminals of vertebrate retinal photoreceptors, provides a feedback mechanism that reduces calcium entry and the concomitant vesicular release of glutamate. We hypothesized that zinc feedback may serve to protect the retina from glutamate excitotoxicity, and conducted in vivo experiments on the retina of the skate (Raja erinacea) to determine the effects of removing endogenous zinc by chelation. These studies showed that removal of zinc by injecting the zinc chelator histidine results in inner retinal damage similar to that induced by the glutamate receptor agonist kainic acid. In contrast, when an equimolar quantity of zinc followed the injection of histidine, the retinal cells were unaffected. Our results are a good indication that zinc, co-released with glutamate by photoreceptors, provides an auto-feedback system that plays an important cytoprotective role in the retina. PMID:24286124

Role of aminotransferases in glutamate metabolism of human erythrocytes.

PubMed

Ellinger, James J; Lewis, Ian A; Markley, John L

2011-04-01

Human erythrocytes require a continual supply of glutamate to support glutathione synthesis, but are unable to transport this amino acid across their cell membrane. Consequently, erythrocytes rely on de novo glutamate biosynthesis from α-ketoglutarate and glutamine to maintain intracellular levels of glutamate. Erythrocytic glutamate biosynthesis is catalyzed by three enzymes, alanine aminotransferase (ALT), aspartate aminotransferase (AST), and glutamine aminohydrolase (GA). Although the presence of these enzymes in RBCs has been well documented, the relative contributions of each pathway have not been established. Understanding the relative contributions of each biosynthetic pathway is critical for designing effective therapies for sickle cell disease, hemolytic anemia, pulmonary hypertension, and other glutathione-related disorders. In this study, we use multidimensional (1)H-(13)C nuclear magnetic resonance (NMR) spectroscopy and multiple reaction mode mass spectrometry (MRM-MS) to measure the kinetics of de novo glutamate biosynthesis via AST, ALT, and GA in intact cells and RBC lysates. We show that up to 89% of the erythrocyte glutamate pool can be derived from ALT and that ALT-derived glutamate is subsequently used for glutathione synthesis.

Cocaine-induced neuroadaptations in glutamate transmission

PubMed Central

Schmidt, Heath D.; Pierce, R. Christopher

2017-01-01

A growing body of evidence indicates that repeated exposure to cocaine leads to profound changes in glutamate transmission in limbic nuclei, particularly the nucleus accumbens. This review focuses on preclinical studies of cocaine-induced behavioral plasticity, including behavioral sensitization, self-administration, and the reinstatement of cocaine seeking. Behavioral, pharmacological, neurochemical, electrophysiological, biochemical, and molecular biological changes associated with cocaine-induced plasticity in glutamate systems are reviewed. The ultimate goal of these lines of research is to identify novel targets for the development of therapies for cocaine craving and addiction. Therefore, we also outline the progress and prospects of glutamate modulators for the treatment of cocaine addiction. PMID:20201846

Activation of Pedunculopontine Glutamate Neurons Is Reinforcing

PubMed Central

Yoo, Ji Hoon; Zell, Vivien; Wu, Johnathan; Punta, Cindy; Ramajayam, Nivedita; Shen, Xinyi; Faget, Lauren; Lilascharoen, Varoth; Lim, Byung Kook

2017-01-01

Dopamine transmission from midbrain ventral tegmental area (VTA) neurons underlies behavioral processes related to motivation and drug addiction. The pedunculopontine tegmental nucleus (PPTg) is a brainstem nucleus containing glutamate-, acetylcholine-, and GABA-releasing neurons with connections to basal ganglia and limbic brain regions. Here we investigated the role of PPTg glutamate neurons in reinforcement, with an emphasis on their projections to VTA dopamine neurons. We used cell-type-specific anterograde tracing and optogenetic methods to selectively label and manipulate glutamate projections from PPTg neurons in mice. We used anatomical, electrophysiological, and behavioral assays to determine their patterns of connectivity and ascribe functional roles in reinforcement. We found that photoactivation of PPTg glutamate cell bodies could serve as a direct positive reinforcer on intracranial self-photostimulation assays. Further, PPTg glutamate neurons directly innervate VTA; photostimulation of this pathway preferentially excites VTA dopamine neurons and is sufficient to induce behavioral reinforcement. These results demonstrate that ascending PPTg glutamate projections can drive motivated behavior, and PPTg to VTA synapses may represent an important target relevant to drug addiction and other mental health disorders. SIGNIFICANCE STATEMENT Uncovering brain circuits underlying reward-seeking is an important step toward understanding the circuit bases of drug addiction and other psychiatric disorders. The dopaminergic system emanating from the ventral tegmental area (VTA) plays a key role in regulating reward-seeking behaviors. We used optogenetics to demonstrate that the pedunculopontine tegmental nucleus sends glutamatergic projections to VTA dopamine neurons, and that stimulation of this circuit promotes behavioral reinforcement. The findings support a critical role for pedunculopontine tegmental nucleus glutamate neurotransmission in modulating VTA dopamine

Functional reconstitution of Drosophila melanogaster NMJ glutamate receptors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, Tae Hee; Dharkar, Poorva; Mayer, Mark L.

The Drosophila larval neuromuscular junction (NMJ), at which glutamate acts as the excitatory neurotransmitter, is a widely used model for genetic analysis of synapse function and development. Despite decades of study, the inability to reconstitute NMJ glutamate receptor function using heterologous expression systems has complicated the analysis of receptor function, such that it is difficult to resolve the molecular basis for compound phenotypes observed in mutant flies. In this paper, we find that Drosophila Neto functions as an essential component required for the function of NMJ glutamate receptors, permitting analysis of glutamate receptor responses in Xenopus oocytes. Finally, in combinationmore » with a crystallographic analysis of the GluRIIB ligand binding domain, we use this system to characterize the subunit dependence of assembly, channel block, and ligand selectivity for Drosophila NMJ glutamate receptors.« less

Functional reconstitution of Drosophila melanogaster NMJ glutamate receptors

DOE PAGES

Han, Tae Hee; Dharkar, Poorva; Mayer, Mark L.; ...

2015-04-27

The Drosophila larval neuromuscular junction (NMJ), at which glutamate acts as the excitatory neurotransmitter, is a widely used model for genetic analysis of synapse function and development. Despite decades of study, the inability to reconstitute NMJ glutamate receptor function using heterologous expression systems has complicated the analysis of receptor function, such that it is difficult to resolve the molecular basis for compound phenotypes observed in mutant flies. In this paper, we find that Drosophila Neto functions as an essential component required for the function of NMJ glutamate receptors, permitting analysis of glutamate receptor responses in Xenopus oocytes. Finally, in combinationmore » with a crystallographic analysis of the GluRIIB ligand binding domain, we use this system to characterize the subunit dependence of assembly, channel block, and ligand selectivity for Drosophila NMJ glutamate receptors.« less

Emerging aspects of dietary glutamate metabolism in the developing gut

USDA-ARS?s Scientific Manuscript database

Glutamate is a major constituent of dietary protein and is also consumed in many prepared foods as a flavour additive in the form of monosodium glutamate (MSG). Evidence from human and animal studies indicates that glutamate is the major oxidative fuel for the gut and that dietary glutamate is exten...

Differential effects of serotonin-specific and excitotoxic lesions of OFC on conditioned reinforcer devaluation and extinction in rats.

PubMed

West, Elizabeth A; Forcelli, Patrick A; McCue, David L; Malkova, Ludise

2013-06-01

The orbitofrontal cortex (OFC) is critical for behavioral adaptation in response to changes in reward value. Here we investigated, in rats, the role of OFC and, specifically, serotonergic neurotransmission within OFC in a reinforcer devaluation task (which measures behavioral flexibility). This task used two visual cues, each predicting one of two foods, with the spatial position (left-right) of the cues above two levers pseudorandomized across trials. An instrumental action (lever press) was required for reinforcer delivery. After training, rats received either excitotoxic OFC lesions made by NMDA (N-methyl-d-aspartic acid), serotonin-specific OFC lesions made by 5,7-DHT (5,7-dihydroxytryptamine), or sham lesions. In sham-lesioned rats, devaluation of one food (by feeding to satiety) significantly decreased responding to the cue associated with that food, when both cues were presented simultaneously during extinction. Both types of OFC lesions disrupted the devaluation effect. In contrast, extinction learning was not affected by serotonin-specific lesions and was only mildly retarded in rats with excitotoxic lesions. Thus, serotonin within OFC is necessary for appropriately adjusting behavior toward cues that predict reward but not for reducing responses in the absence of reward. Our results are the first to demonstrate that serotonin in OFC is necessary for reinforcer devaluation, but not extinction. Copyright © 2013 Elsevier B.V. All rights reserved.

Aprotinin, but not ε-aminocaproic acid and tranexamic acid, exerts neuroprotection against excitotoxic injury in an in vitro neuronal cell culture model.

PubMed

Lu, Zhaohui; Korotcova, Ludmila; Murata, Akira; Ishibashi, Nobuyuki; Jonas, Richard A

2014-06-01

Lack of availability of aprotinin has resulted in increased clinical use of the alternative antifibrinolytic agents, ε-aminocaproic acid (EACA) and tranexamic acid (TXA), which are known to be associated with an increased risk of seizures. In contrast, aprotinin has previously been demonstrated to be neuroprotective through suppression of excitotoxicity-mediated neuronal degeneration via the extracellular plasminogen/plasmin system. This study compares the effect of antifibrinolytic agents on neuronal and mixed glial/neuronal cell cultures. Mixed cortical cultures containing neuronal and glial cells were prepared from fetal mice and plated on a layer of confluent astrocytes from postnatal pups. A primary neuronal culture was obtained from the same gestational stage and plated in multiwall vessels. Slowly triggered excitotoxicity was induced by 24-hour exposure to 12.5 mM N-methyl-D-aspartate (NMDA). Apoptotic neuronal cell death was induced by exposure of primary neural cultures to 24 hours of serum deprivation. Compared with NMDA alone, no significant changes in cell death were observed for any dose of TXA or EACA in mixed cultures. Conversely, a clinical dose of aprotinin significantly reduced cell death by -31% on average. Aprotinin reduced apoptotic neuronal cell death from 75% to 37.3%, and to 34.1% at concentrations of 100 and 200 kIU/mL, respectively, and significantly decreased neuronal nuclear damage. These concentrations of aprotinin significantly inhibited caspase 9 and 3/7 activations; 250 kIU/mL aprotinin exerted maximal protection on primary cortical neurons. In contrast to aprotinin, EACA and TXA exert no protective effect against excitotoxic neuronal injury that can occur during cardiac surgery. Copyright © 2014 The American Association for Thoracic Surgery. Published by Mosby, Inc. All rights reserved.

Glutamate spillover modulates GABAergic synaptic transmission in the rat midbrain periaqueductal grey via metabotropic glutamate receptors and endocannabinoid signaling.

PubMed

Drew, Geoffrey M; Mitchell, Vanessa A; Vaughan, Christopher W

2008-01-23

Glutamate spillover regulates GABAergic synaptic transmission at several CNS synapses via presynaptic ionotropic and metabotropic glutamate receptors (mGluRs). We have previously demonstrated that activation of group I-III mGluRs inhibits GABAergic transmission in the midbrain periaqueductal gray (PAG), a region involved in organizing behavioral responses to threat, stress, and pain. Here, we examined the role of glutamate spillover in the modulation of GABAergic transmission in the PAG. Using whole-cell recordings from rat PAG slices, we found that evoked IPSCs were reduced by the nonspecific glutamate transport blockers DL-threo-beta-benzyloxyaspartic acid (TBOA) and L-trans-pyrrolidine-2,4-dicarboxylic acid, but not by the glial GLT1-specific blocker dihydrokainate. In contrast, TBOA had no effect on evoked IPSCs when glutamate uptake into the postsynaptic neuron was selectively impaired. TBOA increased the paired-pulse ratio of evoked IPSCs and reduced the rate but not the amplitude of spontaneous miniature IPSCs. The effect of TBOA on evoked IPSCs was abolished by the broad-spectrum mGluR antagonist (2S)-2-amino-2-[(1S,2S)-2-carboxycycloprop-1-yl]-3-(xanth-9-yl) propanoic acid (100 microM), reduced by the mGluR5-specific antagonist 2-methyl-6-(phenylethynyl)pyridine hydrochloride (MPEP) and mimicked by the mGluR1/5 agonist (RS)-3,5-dihydroxyphenylglycine (DHPG). Furthermore, the effects of both TBOA and DHPG were reduced by the cannabinoid CB1 receptor antagonist 1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-1-piperidinyl-1H-pyrazole-3-carboxamide (AM251). Finally, although MPEP and AM251 had no effect on single evoked IPSCs, they increased evoked IPSCs during repetitive stimulation. These results indicate that neuronal glutamate transporters limit mGluR5 activation and endocannabinoid signaling, but may be overwhelmed during conditions of elevated glutamate release. Thus, neuronal glutamate transporters play a key role in regulating endocannabinoid

[Molecular organization of glutamate-sensitive chemoexcitable membranes of nerve cells. Function of glutamate-binding proteins of the central nervous system when incorporated into liposomes].

PubMed

Besedin, V I; Kuznetsov, A S; Dambinova, S A

1985-03-01

The functioning of the glutamate-binding protein of rat brain cortex synaptic membranes was studied by its incorporation into liposomes. The optimal conditions for the receptor protein incorporation were established and the kinetics of 22Na+ and 86Rb+ incorporation into the liposomes in the presence of L-glutamate were analyzed. Modelling of the CNS glutamate receptor functions was found to be dependent on the lipid composition and amount of the incorporated membrane protein. The selective transport of 22Na+ into the liposomes was stimulated in the presence of 10(-4) M glutamate. Addition of monoclonal antibodies against glutamate-binding proteins blocked the incorporation of Na+ into the liposomes. The experimental results are suggestive of the nativity of the liposome-incorporated membrane protein, which is capable of binding glutamate and regulating selective transport of Na+. It was assumed that the glutamate receptor macromolecule represents an integral complex made up of several low molecular weight subunits of glucoprotein nature that form a selective ionic channel.

Glutamate biosensors based on diamond and graphene platforms.

PubMed

Hu, Jingping; Wisetsuwannaphum, Sirikarn; Foord, John S

2014-01-01

l-Glutamate is one of the most important neurotransmitters in the mammalian central nervous system, playing a vital role in many physiological processes and implicated in several neurological disorders, for which monitoring of dynamic levels of extracellular glutamate in the living brain tissues may contribute to medical understanding and treatments. Electrochemical sensing of glutamate has been developed recently mainly using platinum, carbon fibre and carbon nanotube electrodes. In the present work, we explore the fabrication and properties of electrochemical glutamate sensors fabricated on doped chemical vapour deposition diamond electrodes and graphene nanoplatelet structures. The sensors incorporate platinum nanoparticles to catalyse the electrooxidation of hydrogen peroxide, glutamate oxidase to oxidise glutamate, and a layer of poly-phenylenediamine to impart selectivity. The performance of the devices was compared to a similar sensor fabricated on glassy carbon. Both the diamond and the graphene sensor showed very competitive performance compared to the majority of existing electrochemical sensors. The graphene based sensor showed the best performance of the three investigated in terms of sensitivity, linear dynamic range and long term stability, whereas it was found that the diamond device showed the best limit of detection.

Increased expression of the Drosophila vesicular glutamate transporter leads to excess glutamate release and a compensatory decrease in quantal content.

PubMed

Daniels, Richard W; Collins, Catherine A; Gelfand, Maria V; Dant, Jaime; Brooks, Elizabeth S; Krantz, David E; DiAntonio, Aaron

2004-11-17

Quantal size is a fundamental parameter controlling the strength of synaptic transmission. The transmitter content of synaptic vesicles is one mechanism that can affect the physiological response to the release of a single vesicle. At glutamatergic synapses, vesicular glutamate transporters (VGLUTs) are responsible for filling synaptic vesicles with glutamate. To investigate how VGLUT expression can regulate synaptic strength in vivo, we have identified the Drosophila vesicular glutamate transporter, which we name DVGLUT. DVGLUT mRNA is expressed in glutamatergic motoneurons and a large number of interneurons in the Drosophila CNS. DVGLUT protein resides on synaptic vesicles and localizes to the presynaptic terminals of all known glutamatergic neuromuscular junctions as well as to synapses throughout the CNS neuropil. Increasing the expression of DVGLUT in motoneurons leads to an increase in quantal size that is accompanied by an increase in synaptic vesicle volume. At synapses confronted with increased glutamate release from each vesicle, there is a compensatory decrease in the number of synaptic vesicles released that maintains normal levels of synaptic excitation. These results demonstrate that (1) expression of DVGLUT determines the size and glutamate content of synaptic vesicles and (2) homeostatic mechanisms exist to attenuate the excitatory effects of excess glutamate release.

Towards a glutamate hypothesis of depression

PubMed Central

Sanacora, Gerard; Treccani, Giulia; Popoli, Maurizio

2011-01-01

Half a century after the first formulation of the monoamine hypothesis, compelling evidence implies that long-term changes in an array of brain areas and circuits mediating complex cognitive-emotional behaviors represent the biological underpinnings of mood/anxiety disorders. A large number of clinical studies suggest that pathophysiology is associated with dysfunction of the predominant glutamatergic system, malfunction in the mechanisms regulating clearance and metabolism of glutamate, and cytoarchitectural/morphological maladaptive changes in a number of brain areas mediating cognitive-emotional behaviors. Concurrently, a wealth of data from animal models have shown that different types of environmental stress enhance glutamate release/transmission in limbic/cortical areas and exert powerful structural effects, inducing dendritic remodeling, reduction of synapses and possibly volumetric reductions resembling those observed in depressed patients. Because a vast majority of neurons and synapses in these areas and circuits use glutamate as neurotransmitter, it would be limiting to maintain that glutamate is in some way ‘involved’ in mood/anxiety disorders; rather it should be recognized that the glutamatergic system is a primary mediator of psychiatric pathology and, potentially, also a final common pathway for the therapeutic action of antidepressant agents. A paradigm shift from a monoamine hypothesis of depression to a neuroplasticity hypothesis focused on glutamate may represent a substantial advancement in the working hypothesis that drives research for new drugs and therapies. Importantly, despite the availability of multiple classes of drugs with monoamine-based mechanisms of action, there remains a large percentage of patients who fail to achieve a sustained remission of depressive symptoms. The unmet need for improved pharmacotherapies for treatment-resistant depression means there is a large space for the development of new compounds with novel

Neurochemical and behavioral characterization of neuronal glutamate transporter EAAT3 heterozygous mice.

PubMed

González, Luis F; Henríquez-Belmar, Francisca; Delgado-Acevedo, Claudia; Cisternas-Olmedo, Marisol; Arriagada, Gloria; Sotomayor-Zárate, Ramón; Murphy, Dennis L; Moya, Pablo R

2017-09-19

Obsessive-compulsive disorder (OCD) is a severe neuropsychiatric condition affecting 1-3% of the worldwide population. OCD has a strong genetic component, and the SLC1A1 gene that encodes neuronal glutamate transporter EAAT3 is a strong candidate for this disorder. To evaluate the impact of reduced EAAT3 expression in vivo, we studied male EAAT3 heterozygous and wild-type littermate mice using a battery of behavioral paradigms relevant to anxiety (open field test, elevated plus maze) and compulsivity (marble burying), as well as locomotor activity induced by amphetamine. Using high-performance liquid chromatography, we also determined tissue neurotransmitter levels in cortex, striatum and thalamus-brain areas that are relevant to OCD. Compared to wild-type littermates, EAAT3 heterozygous male mice have unaltered baseline anxiety-like, compulsive-like behavior and locomotor activity. Administration of acute amphetamine (5 mg/kg intraperitoneally) increased locomotion with no differences across genotypes. Tissue levels of glutamate, GABA, dopamine and serotonin did not vary between EAAT3 heterozygous and wild-type mice. Our results indicate that reduced EAAT3 expression does not impact neurotransmitter content in the corticostriatal circuit nor alter anxiety or compulsive-like behaviors.

Protons Regulate Vesicular Glutamate Transporters through an Allosteric Mechanism.

PubMed

Eriksen, Jacob; Chang, Roger; McGregor, Matt; Silm, Katlin; Suzuki, Toshiharu; Edwards, Robert H

2016-05-18

The quantal nature of synaptic transmission requires a mechanism to transport neurotransmitter into synaptic vesicles without promoting non-vesicular efflux across the plasma membrane. Indeed, the vesicular transport of most classical transmitters involves a mechanism of H(+) exchange, which restricts flux to acidic membranes such as synaptic vesicles. However, vesicular transport of the principal excitatory transmitter glutamate depends primarily on membrane potential, which would drive non-vesicular efflux, and the role of protons is unclear. Adapting electrophysiology to record currents associated with the vesicular glutamate transporters (VGLUTs), we characterize a chloride conductance that is gated by lumenal protons and chloride and supports glutamate uptake. Rather than coupling stoichiometrically to glutamate flux, lumenal protons and chloride allosterically activate vesicular glutamate transport. Gating by protons serves to inhibit what would otherwise be substantial non-vesicular glutamate efflux at the plasma membrane, thereby restricting VGLUT activity to synaptic vesicles. Copyright © 2016 Elsevier Inc. All rights reserved.

Neuroprotection of locomotor networks after experimental injury to the neonatal rat spinal cord in vitro.

PubMed

Margaryan, G; Mattioli, C; Mladinic, M; Nistri, A

2010-02-03

Treatment to block the pathophysiological processes triggered by acute spinal injury remains unsatisfactory as the underlying mechanisms are incompletely understood. Using as a model the in vitro spinal cord of the neonatal rat, we investigated the feasibility of neuroprotection of lumbar locomotor networks by the glutamate antagonists 6-cyano-7-nitroquinoxaline-2, 3-dione (CNQX) and aminophosphonovalerate (APV) against acute lesions induced by either a toxic solution (pathological medium (PM) to mimic the spinal injury hypoxic-dysmetabolic perturbation) or excitotoxicity with kainate. The study outcome was presence of fictive locomotion 24 h after the insult and its correlation with network histology. Inhibition of fictive locomotion by PM was contrasted by simultaneous and even delayed (1 h later) co-application of CNQX and APV with increased survival of ventral horn premotoneurons and lateral column white matter. Neither CNQX nor APV alone provided neuroprotection. Kainate-mediated excitotoxicity always led to loss of fictive locomotion and extensive neuronal damage. CNQX and APV co-applied with kainate protected one-third of preparations with improved motoneuron and dorsal horn neuronal counts, although they failed with delayed application. Our data suggest that locomotor network neuroprotection was possible when introduced very early during the pathological process of spinal injury, but also showed how the borderline between presence or loss of locomotor activity was a very narrow one that depended on the survival of a certain number of neurons or white matter elements. The present report provides a model not only for preclinical testing of novel neuroprotective agents, but also for estimating the minimal network membership compatible with functional locomotor output. Copyright 2010 IBRO. Published by Elsevier Ltd. All rights reserved.

Influence of glutamic acid enantiomers on C-mineralization.

PubMed

Formánek, Pavel; Vranová, Valerie; Lojková, Lea

2015-02-01

Seasonal dynamics in the mineralization of glutamic acid enantiomers in soils from selected ecosystems was determined and subjected to a range of treatments: ambient x elevated CO2 level and meadow x dense x thinned forest environment. Mineralization of glutamic acid was determined by incubation of the soil with 2 mg L- or D-glutamic acid g(-1) of dry soil to induce the maximum respiration rate. Mineralization of glutamic acid enantiomers in soils fluctuates over the course of a vegetation season, following a similar trend across a range of ecosystems. Mineralization is affected by environmental changes and management practices, including elevated CO2 level and thinning intensity. L-glutamic acid metabolism is more dependent on soil type as compared to metabolism of its D-enantiomer. The results support the hypothesis that the slower rate of D- compared to L- amino acid mineralization is due to different roles in anabolism and catabolism of the soil microbial community. © 2014 Wiley Periodicals, Inc.

Heteromeric Canonical Transient Receptor Potential 1 and 4 Channels Play a Critical Role in Epileptiform Burst Firing and Seizure-Induced Neurodegeneration

PubMed Central

Phelan, Kevin D.; Mock, Matthew M.; Kretz, Oliver; Shwe, U. Thaung; Kozhemyakin, Maxim; Greenfield, L. John; Dietrich, Alexander; Birnbaumer, Lutz; Freichel, Marc; Flockerzi, Veit

2012-01-01

Canonical transient receptor potential channels (TRPCs) are receptor-operated cation channels that are activated in response to phospholipase C signaling. Although TRPC1 is ubiquitously expressed in the brain, TRPC4 expression is the most restrictive, with the highest expression level limited to the lateral septum. The subunit composition of neuronal TRPC channels remains uncertain because of conflicting data from recombinant expression systems. Here we report that the large depolarizing plateau potential that underlies the epileptiform burst firing induced by metabotropic glutamate receptor agonists in lateral septal neurons was completely abolished in TRPC1/4 double-knockout mice, and was abolished in 74% of lateral septal neurons in TRPC1 knockout mice. Furthermore, neuronal cell death in the lateral septum and the cornu ammonis 1 region of hippocampus after pilocarpine-induced severe seizures was significantly ameliorated in TRPC1/4 double-knockout mice. Our data suggest that both TRPC1 and TRPC4 are essential for an intrinsic membrane conductance mediating the plateau potential in lateral septal neurons, possibly as heteromeric channels. Moreover, excitotoxic neuronal cell death, an underlying process for many neurological diseases, is not mediated merely by ionotropic glutamate receptors but also by heteromeric TRPC channels activated by metabotropic glutamate receptors. TRPC channels could be an unsuspected but critical molecular target for clinical intervention for excitotoxicity. PMID:22144671

Heteromeric canonical transient receptor potential 1 and 4 channels play a critical role in epileptiform burst firing and seizure-induced neurodegeneration.

PubMed

Phelan, Kevin D; Mock, Matthew M; Kretz, Oliver; Shwe, U Thaung; Kozhemyakin, Maxim; Greenfield, L John; Dietrich, Alexander; Birnbaumer, Lutz; Freichel, Marc; Flockerzi, Veit; Zheng, Fang

2012-03-01

Canonical transient receptor potential channels (TRPCs) are receptor-operated cation channels that are activated in response to phospholipase C signaling. Although TRPC1 is ubiquitously expressed in the brain, TRPC4 expression is the most restrictive, with the highest expression level limited to the lateral septum. The subunit composition of neuronal TRPC channels remains uncertain because of conflicting data from recombinant expression systems. Here we report that the large depolarizing plateau potential that underlies the epileptiform burst firing induced by metabotropic glutamate receptor agonists in lateral septal neurons was completely abolished in TRPC1/4 double-knockout mice, and was abolished in 74% of lateral septal neurons in TRPC1 knockout mice. Furthermore, neuronal cell death in the lateral septum and the cornu ammonis 1 region of hippocampus after pilocarpine-induced severe seizures was significantly ameliorated in TRPC1/4 double-knockout mice. Our data suggest that both TRPC1 and TRPC4 are essential for an intrinsic membrane conductance mediating the plateau potential in lateral septal neurons, possibly as heteromeric channels. Moreover, excitotoxic neuronal cell death, an underlying process for many neurological diseases, is not mediated merely by ionotropic glutamate receptors but also by heteromeric TRPC channels activated by metabotropic glutamate receptors. TRPC channels could be an unsuspected but critical molecular target for clinical intervention for excitotoxicity.

[Memantine: from the original brand to generics].

PubMed

Titova, N V

Memantine is the first clinically available glutamate antagonist, with an antagonist action at the N-methyl-D-aspartate receptors in the brain, for correction of cognitive and behavioral functions in neurodegenerative disorders. Glutamate mediated excitotoxic neuronal damage has been implicated in Alzheimer's disease (AD) and other parkinsonism-related dementias and, therefore, memantine represents a novel mode of action to counteract the glutamate-mediated excitotoxicity. In moderate to severe AD, 20 mg of memantine shows a positive effect on cognition, mood, behavior and the ability to perform activities of daily living. Long-term studies show good tolerability of memantine with an acceptable side-effect profile. In recent years, there have been a proliferation of a number of companies producing generic memantine with different trade names. In Russia, the first memantine generic drug noojerone was approved in 2010 and its use has since been supported by a growing evidence base of efficacy in real-life clinical practice. Postmarketing studies show that noojerone provides long-term and effective therapy in patients with moderate and severe Alzheimer's dementia. This observation is supported by the clinically significant therapeutic effect of noojerone on cognitive and daily functioning, behavioral and psychotic symptoms of dementia and a reduction of the burden on caregivers. This generic version of memantine is affordable and, therefore, reduces financial burden on patients and improves compliance with treatment.

Flavor Preferences Conditioned by Dietary Glutamate.

PubMed

Ackroff, Karen; Sclafani, Anthony

2016-07-01

Our understanding of the molecular basis of umami taste and its appetitive qualities has been greatly aided by studies in laboratory rodents. This review describes methods for testing responses to the prototypical umami substance monosodium glutamate (MSG) in rodents. Two techniques, forced exposure to MSG and 2-bottle choice tests with ascending concentrations, were used to evaluate the responses to the taste of umami itself, and 2 other methods used oral or postoral MSG to modify the responses to other flavors. Intake and preference for MSG are enhanced in mice by experience with MSG and with other nutrients with positive postoral effects. In addition, flavor preferences are enhanced in mice and rats by gastric or intestinal MSG infusions via an associative learning process. Even mice with an impaired or absent ability to taste MSG can learn to prefer a flavor added to an MSG solution, supporting the notion that glutamate acts postorally. The more complex flavor of dashi seasoning, which includes umami substances (inosinate, glutamate), is attractive to rodents, but dashi does not condition flavor preferences. Details of the postoral glutamate detection process and the nature of the signal involved in learned preferences are still uncertain but probably involve gastric or intestinal sensors or both and vagal transmission. Some findings suggest that postoral glutamate effects may enhance food preferences in humans, but this requires further study. © 2016 American Society for Nutrition.

Relationship between Increase in Astrocytic GLT-1 Glutamate Transport and Late-LTP

ERIC Educational Resources Information Center

Pita-Almenar, Juan D.; Zou, Shengwei; Colbert, Costa M.; Eskin, Arnold

2012-01-01

Na[superscript +]-dependent high-affinity glutamate transporters have important roles in the maintenance of basal levels of glutamate and clearance of glutamate during synaptic transmission. Interestingly, several studies have shown that basal glutamate transport displays plasticity. Glutamate uptake increases in hippocampal slices during early…

Neuroprotective Effects of Glutamate Antagonists and Extracellular Acidity

NASA Astrophysics Data System (ADS)

Kaku, David A.; Giffard, Rona G.; Choi, Dennis W.

1993-06-01

Glutamate antagonists protect neurons from hypoxic injury both in vivo and in vitro, but in vitro studies have not been done under the acidic conditions typical of hypoxia-ischemia in vivo. Consistent with glutamate receptor antagonism, extracellular acidity reduced neuronal death in murine cortical cultures that were deprived of oxygen and glucose. Under these acid conditions, N-methyl-D-aspartate and α-amino-3-hydroxy-5-methyl-4-isox-azolepropionate-kainate antagonists further reduced neuronal death, such that some neurons tolerated prolonged oxygen and glucose deprivation almost as well as did astrocytes. Neuroprotection induced by this combination exceeded that induced by glutamate antagonists alone, suggesting that extracellular acidity has beneficial effects beyond the attenuation of ionotropic glutamate receptor activation.

Ketone bodies and brain glutamate and GABA metabolism.

PubMed

Daikhin, Y; Yudkoff, M

1998-01-01

The effects of ketone bodies on brain metabolism of glutamate and GABA were studied in three different systems: synaptosomes, cultured astrocytes and the whole animal. In synaptosomes the addition of either acetoacetate or 3-OH-butyrate was associated with diminished consumption of glutamate via transamination to aspartate and increased formation of labelled GABA from either L-[2H5-2,3,3,4, 4]glutamine or L-[15N]glutamine. There was no effect of ketone bodies on synaptosomal GABA transamination. An increase of total forebrain GABA and a diminution of aspartate was noted when mice were injected intraperitoneally with 3-OH-butyrate. In cultured astrocytes the addition of acetoacetate to the medium was associated with a significantly enhanced rate of citrate production and with a diminution in the rate of conversion of [15N]glutamate to [15N]aspartate. These data are consistent with the hypothesis that the metabolism of ketone bodies to acetyl-CoA results in a diminution of the pool of brain oxaloacetate, which is consumed in the citrate synthetase reaction (oxaloacetate + acetyl-CoA --> citrate). As less oxaloacetate is available to the aspartate aminotransferase reaction, thereby lowering the rate of glutamate transamination, more glutamate becomes accessible to the glutamate decarboxylase pathway, thereby favoring the synthesis of GABA.

Effects of orally administered Augmentin on glutamate transporter 1, cystine-glutamate exchanger expression and ethanol intake in alcohol-preferring rats.

PubMed

Hakami, Alqassem Y; Alshehri, Fahad S; Althobaiti, Yusuf S; Sari, Youssef

2017-03-01

Alcohol dependence is associated with deficits in glutamate uptake and impairment of glutamate homeostasis in different brain reward regions. Glutamate transporter subtype 1 (GLT-1), cystine-glutamate exchanger (xCT) and glutamate/aspartate transporter (GLAST) are one of the key players in regulating extracellular glutamate concentration in the brain. Parenteral treatment with ceftriaxone, β-lactam antibiotic, has been reported to attenuate ethanol consumption and reinstatement to cocaine-seeking behavior, in part, by restoring the expression of GLT-1 and xCT in mesocorticolimbic brain regions in rats. In this study, we focused to test Augmentin (amoxicillin/clavulanate), which can be administered orally to subjects. Therefore, we examined the effects of orally administered Augmentin on ethanol intake as well as GLT-1, xCT and GLAST expression in male alcohol-preferring (P) rats. We found that orally administered Augmentin significantly attenuated ethanol consumption in P rats as compared to the vehicle-treated group. Importantly, the attenuation in ethanol consumption was associated with a significant upregulation of GLT-1 and xCT expression in nucleus accumbens (NAc) and prefrontal cortex (PFC). There was no effect of orally administered Augmentin on GLAST expression in either NAc or PFC. These findings present strong evidence that oral administration of Augmentin can be used as an alternative to parenteral treatment. Copyright © 2016 Elsevier B.V. All rights reserved.

Glutamate-Dependent Translational Control of Glutamine Synthetase in Bergmann Glia Cells.

PubMed

Tiburcio-Félix, Reynaldo; Escalante-López, Miguel; López-Bayghen, Bruno; Martínez, Daniel; Hernández-Kelly, Luisa C; Zinker, Samuel; Hernández-Melchor, Dinorah; López-Bayghen, Esther; Olivares-Bañuelos, Tatiana N; Ortega, Arturo

2018-06-01

Glutamate is the major excitatory transmitter of the vertebrate brain. It exerts its actions through the activation of specific plasma membrane receptors expressed both in neurons and in glial cells. Recent evidence has shown that glutamate uptake systems, particularly enriched in glia cells, trigger biochemical cascades in a similar fashion as receptors. A tight regulation of glutamate extracellular levels prevents neuronal overstimulation and cell death, and it is critically involved in glutamate turnover. Glial glutamate transporters are responsible of the majority of the brain glutamate uptake activity. Once internalized, this excitatory amino acid is rapidly metabolized to glutamine via the astrocyte-enriched enzyme glutamine synthetase. A coupling between glutamate uptake and glutamine synthesis and release has been commonly known as the glutamate/glutamine shuttle. Taking advantage of the established model of cultured Bergmann glia cells, in this contribution, we explored the gene expression regulation of glutamine synthetase. A time- and dose-dependent regulation of glutamine synthetase protein and activity levels was found. Moreover, glutamate exposure resulted in the transient shift of glutamine synthetase mRNA from the monosomal to the polysomal fraction. These results demonstrate a novel mode of glutamate-dependent glutamine synthetase regulation and strengthen the notion of an exquisite glia neuronal interaction in glutamatergic synapses.

J-difference-edited MRS measures of γ-aminobutyric acid before and after acute caffeine administration.

PubMed

Oeltzschner, Georg; Zöllner, Helge J; Jonuscheit, Marc; Lanzman, Rotem S; Schnitzler, Alfons; Wittsack, Hans-Jörg

2018-05-12

The aim of this study was to investigate potential effects of acute caffeine intake on J-difference-edited MRS measures of the primary inhibitory neurotransmitter γ-aminobutyric acid (GABA). J-difference-edited Mescher-Garwood PRESS (MEGA-PRESS) and conventional PRESS data were acquired at 3T from voxels in the anterior cingulate and occipital area of the brain in 15 healthy subjects, before and after oral intake of a 200-mg caffeine dose. MEGA-PRESS data were analyzed with the MATLAB-based Gannet tool to estimate GABA+ macromolecule (GABA+) levels, while PRESS data were analyzed with LCModel to estimate levels of glutamate, glutamate+glutamine, N-acetylaspartate, and myo-inositol. All metabolites were quantified with respect to the internal reference compounds creatine and tissue water, and compared between the pre- and post-caffeine intake condition. For both MRS voxels, mean GABA+ estimates did not differ before and after caffeine intake. Slightly lower estimates of myo-inositol were observed after caffeine intake in both voxels. N-acetylaspartate, glutamate, and glutamate+glutamine did not show significant differences between conditions. Mean GABA+ estimates from J-difference-edited MRS in two different brain regions are not altered by acute oral administration of caffeine. These findings may increase subject recruitment efficiency for MRS studies. © 2018 International Society for Magnetic Resonance in Medicine.

Effects of acute versus repeated cocaine exposure on the expression of endocannabinoid signaling-related proteins in the mouse cerebellum.

PubMed

Palomino, Ana; Pavón, Francisco-Javier; Blanco-Calvo, Eduardo; Serrano, Antonia; Arrabal, Sergio; Rivera, Patricia; Alén, Francisco; Vargas, Antonio; Bilbao, Ainhoa; Rubio, Leticia; Rodríguez de Fonseca, Fernando; Suárez, Juan

2014-01-01

Growing awareness of cerebellar involvement in addiction is based on the cerebellum's intermediary position between motor and reward, potentially acting as an interface between motivational and cognitive functions. Here, we examined the impact of acute and repeated cocaine exposure on the two main signaling systems in the mouse cerebellum: the endocannabinoid (eCB) and glutamate systems. To this end, we investigated whether eCB signaling-related gene and protein expression {cannabinoid receptor type 1 receptors and enzymes that produce [diacylglycerol lipase alpha/beta (DAGLα/β) and N-acyl phosphatidylethanolamine phospholipase D (NAPE-PLD)] and degrade [monoacylglycerol lipase (MAGL) and fatty acid amino hydrolase (FAAH)] eCB} were altered. In addition, we analyzed the gene expression of relevant components of the glutamate signaling system [glutamate synthesizing enzymes liver-type glutaminase isoform (LGA) and kidney-type glutaminase isoform (KGA), metabotropic glutamatergic receptor (mGluR3/5), NMDA-ionotropic glutamatergic receptor (NR1/2A/2B/2C) and AMPA-ionotropic receptor subunits (GluR1/2/3/4)] and the gene expression of tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine biosynthesis, because noradrenergic terminals innervate the cerebellar cortex. Results indicated that acute cocaine exposure decreased DAGLα expression, suggesting a down-regulation of 2-arachidonylglycerol (2-AG) production, as well as gene expression of TH, KGA, mGluR3 and all ionotropic receptor subunits analyzed in the cerebellum. The acquisition of conditioned locomotion and sensitization after repeated cocaine exposure were associated with an increased NAPE-PLD/FAAH ratio, suggesting enhanced anandamide production, and a decreased DAGLβ/MAGL ratio, suggesting decreased 2-AG generation. Repeated cocaine also increased LGA gene expression but had no effect on glutamate receptors. These findings indicate that acute cocaine modulates the expression of the eCB and

Effects of acute versus repeated cocaine exposure on the expression of endocannabinoid signaling-related proteins in the mouse cerebellum

PubMed Central

Palomino, Ana; Pavón, Francisco-Javier; Blanco-Calvo, Eduardo; Serrano, Antonia; Arrabal, Sergio; Rivera, Patricia; Alén, Francisco; Vargas, Antonio; Bilbao, Ainhoa; Rubio, Leticia; Rodríguez de Fonseca, Fernando; Suárez, Juan

2014-01-01

Growing awareness of cerebellar involvement in addiction is based on the cerebellum’s intermediary position between motor and reward, potentially acting as an interface between motivational and cognitive functions. Here, we examined the impact of acute and repeated cocaine exposure on the two main signaling systems in the mouse cerebellum: the endocannabinoid (eCB) and glutamate systems. To this end, we investigated whether eCB signaling-related gene and protein expression {cannabinoid receptor type 1 receptors and enzymes that produce [diacylglycerol lipase alpha/beta (DAGLα/β) and N-acyl phosphatidylethanolamine phospholipase D (NAPE-PLD)] and degrade [monoacylglycerol lipase (MAGL) and fatty acid amino hydrolase (FAAH)] eCB} were altered. In addition, we analyzed the gene expression of relevant components of the glutamate signaling system [glutamate synthesizing enzymes liver-type glutaminase isoform (LGA) and kidney-type glutaminase isoform (KGA), metabotropic glutamatergic receptor (mGluR3/5), NMDA-ionotropic glutamatergic receptor (NR1/2A/2B/2C) and AMPA-ionotropic receptor subunits (GluR1/2/3/4)] and the gene expression of tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine biosynthesis, because noradrenergic terminals innervate the cerebellar cortex. Results indicated that acute cocaine exposure decreased DAGLα expression, suggesting a down-regulation of 2-arachidonylglycerol (2-AG) production, as well as gene expression of TH, KGA, mGluR3 and all ionotropic receptor subunits analyzed in the cerebellum. The acquisition of conditioned locomotion and sensitization after repeated cocaine exposure were associated with an increased NAPE-PLD/FAAH ratio, suggesting enhanced anandamide production, and a decreased DAGLβ/MAGL ratio, suggesting decreased 2-AG generation. Repeated cocaine also increased LGA gene expression but had no effect on glutamate receptors. These findings indicate that acute cocaine modulates the expression of the eCB and

Influence of glutamate-evoked pain and sustained elevated muscle activity on blood oxygenation in the human masseter muscle.

PubMed

Suzuki, Shunichi; Arima, Taro; Kitagawa, Yoshimasa; Svensson, Peter; Castrillon, Eduardo

2017-12-01

This study aimed to investigate the effect of glutamate-evoked masseter muscle pain on intramuscular oxygenation during rest and sustained elevated muscle activity (SEMA). Seventeen healthy individuals participated in two sessions in which they were injected with glutamate and saline in random order. Each session was divided into three, 10-min periods. During the first (period 1) and the last (period 3) 10-min periods, participants performed five intercalated 1-min bouts of masseter SEMA with 1-min periods of 'rest'. At onset of the second 10-min period, glutamate (0.5 ml, 1 M; Ajinomoto, Tokyo, Japan) or isotonic saline (0.5 ml; 0.9%) was injected into the masseter muscle and the participants kept the muscle relaxed in a resting position for 10 min (period 2). The hemodynamic characteristics of the masseter muscle were recorded simultaneously during the experiment by a laser blood-oxygenation monitor. The results demonstrated that glutamate injections caused significant levels of self-reported pain in the masseter muscle; however, this nociceptive input did not have robust effects on intramuscular oxygenation during rest or SEMA tasks. Interestingly, these findings suggest an uncoupling between acute nociceptive activity and hemodynamic parameters in both resting and low-level active jaw muscles. Further studies are needed to explore the pathophysiological significance of blood-flow changes for persistent jaw-muscle pain conditions. © 2017 Eur J Oral Sci.

Serum Glutamic-Oxaloacetic Transaminase (GOT) and Glutamic-Pyruvic Transaminase (GPT) Levels in Children and Adolescents with Intellectual Disabilities

ERIC Educational Resources Information Center

Lin, Jin-Ding; Lin, Pei-Ying; Chen, Li-Mei; Fang, Wen-Hui; Lin, Lan-Ping; Loh, Ching-Hui

2010-01-01

The elevated serum glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT) rate among people with intellectual disabilities (ID) is unknown and have not been sufficiently studies. The present paper aims to provide the profile of GOT and GPT, and their associated relationship with other biochemical levels of children or…

Decreased glutamate, glutamine and citrulline concentrations in plasma and muscle in endotoxemia cannot be reversed by glutamate or glutamine supplementation: a primary intestinal defect?

PubMed

Boutry, Claire; Matsumoto, Hideki; Bos, Cécile; Moinard, Christophe; Cynober, Luc; Yin, Yulong; Tomé, Daniel; Blachier, François

2012-10-01

Endotoxemia affects intestinal physiology. A decrease of circulating citrulline concentration is considered as a reflection of the intestinal function. Citrulline can be produced in enterocytes notably from glutamate and glutamine. The aim of this work was to determine if glutamate, glutamine and citrulline concentrations in blood, intestine and muscle are decreased by endotoxemia, and if supplementation with glutamate or glutamine can restore normal concentrations. We induced endotoxemia in rats by an intraperitoneal injection of 0.3 mg kg(-1) lipopolysaccharide (LPS). This led to a rapid anorexia, negative nitrogen balance and a transient increase of the circulating level of IL-6 and TNF-α. When compared with the values measured in pair fed (PF) animals, almost all circulating amino acids (AA) including citrulline decreased, suggesting a decrease of intestinal function. However, at D2 after LPS injection, most circulating AA concentrations were closed to the values recorded in the PF group. At that time, among AA, only glutamate, glutamine and citrulline were decreased in gastrocnemius muscle without change in intestinal mucosa. A supplementation with 4% monosodium glutamate (MSG) or an isomolar amount of glutamine failed to restore glutamate, glutamine and citrulline concentrations in plasma and muscle. However, MSG supplementation led to an accumulation of glutamate in the intestinal mucosa. In conclusion, endotoxemia rapidly but transiently decreased the circulating concentrations of almost all AA and more durably of glutamate, glutamine and citrulline in muscle. Supplementation with glutamate or glutamine failed to restore glutamate, glutamine and citrulline concentrations in plasma and muscles. The implication of a loss of the intestinal capacity for AA absorption and/or metabolism in endotoxemia (as judged from decreased citrulline plasma concentration) for explaining such results are discussed.

Effect of glutamate and blood glutamate scavengers oxaloacetate and pyruvate on neurological outcome and pathohistology of the hippocampus after traumatic brain injury in rats.

PubMed

Zlotnik, Alexander; Sinelnikov, Igor; Gruenbaum, Benjamin F; Gruenbaum, Shaun E; Dubilet, Michael; Dubilet, Elena; Leibowitz, Akiva; Ohayon, Sharon; Regev, Adi; Boyko, Matthew; Shapira, Yoram; Teichberg, Vivian I

2012-01-01

Decreasing blood glutamate concentrations after traumatic brain injury accelerates brain-to-blood glutamate efflux, leading to improved neurologic outcomes. The authors hypothesize that treatment with blood glutamate scavengers should reduce neuronal cell loss, whereas administration of glutamate should worsen outcomes. The authors performed histologic studies of neuronal survival in the rat hippocampus after traumatic brain injury and treatment with blood glutamate scavengers. Traumatic brain injury was induced on anesthetized male Sprague-Dawley rats by a standardized weight drop. Intravenous treatment groups included saline (control), oxaloacetate, pyruvate, and glutamate. Neurologic outcome was assessed using a Neurological Severity Score at 1 h, and 1, 2, 7, 14, 21, 28 days. Blood glutamate was determined at baseline and 90 min. Four weeks after traumatic brain injury, a histologic analysis of surviving neurons was performed. Oxaloacetate and pyruvate treatment groups demonstrated increased neuronal survival (oxaloacetate 2,200 ± 37, pyruvate 2,108 ± 137 vs. control 1,978 ± 46, P < 0.001, mean ± SD). Glutamate treatment revealed decreased neuronal survival (1,715 ± 48, P < 0.001). Treatment groups demonstrated favorable neurologic outcomes at 24 and 48 h (Neurological Severity Score at 24 and 48 h: 5.5 (1-8.25), 5 (1.75-7.25), P = 0.02 and 3(1-6.5), 4 (1.75-4.5), P = 0.027, median ± corresponding interquartile range). Blood glutamate concentrations were decreased in the oxaloacetate and pyruvate treatment groups. Administration of oxaloacetate and pyruvate was not shown to have any adverse effects. The authors demonstrate that the blood glutamate scavengers oxaloacetate and pyruvate provide neuroprotection after traumatic brain injury, expressed both by reduced neuronal loss in the hippocampus and improved neurologic outcomes. The findings of this study may bring about new therapeutic possibilities in a variety of clinical settings.

A Role for Glutamate Transporters in the Regulation of Insulin Secretion

PubMed Central

Gammelsaeter, Runhild; Coppola, Thierry; Marcaggi, Païkan; Storm-Mathisen, Jon; Chaudhry, Farrukh A.; Attwell, David; Regazzi, Romano; Gundersen, Vidar

2011-01-01

In the brain, glutamate is an extracellular transmitter that mediates cell-to-cell communication. Prior to synaptic release it is pumped into vesicles by vesicular glutamate transporters (VGLUTs). To inactivate glutamate receptor responses after release, glutamate is taken up into glial cells or neurons by excitatory amino acid transporters (EAATs). In the pancreatic islets of Langerhans, glutamate is proposed to act as an intracellular messenger, regulating insulin secretion from β-cells, but the mechanisms involved are unknown. By immunogold cytochemistry we show that insulin containing secretory granules express VGLUT3. Despite the fact that they have a VGLUT, the levels of glutamate in these granules are low, indicating the presence of a protein that can transport glutamate out of the granules. Surprisingly, in β-cells the glutamate transporter EAAT2 is located, not in the plasma membrane as it is in brain cells, but exclusively in insulin-containing secretory granules, together with VGLUT3. In EAAT2 knock out mice, the content of glutamate in secretory granules is higher than in wild type mice. These data imply a glutamate cycle in which glutamate is carried into the granules by VGLUT3 and carried out by EAAT2. Perturbing this cycle by knocking down EAAT2 expression with a small interfering RNA, or by over-expressing EAAT2 or a VGLUT in insulin granules, significantly reduced the rate of granule exocytosis. Simulations of granule energetics suggest that VGLUT3 and EAAT2 may regulate the pH and membrane potential of the granules and thereby regulate insulin secretion. These data suggest that insulin secretion from β-cells is modulated by the flux of glutamate through the secretory granules. PMID:21853059

Calcium regulates glutamate dehydrogenase and poly-γ-glutamic acid synthesis in Bacillus natto.

PubMed

Meng, Yonghong; Dong, Guiru; Zhang, Chen; Ren, Yuanyuan; Qu, Yuling; Chen, Weifeng

2016-04-01

To study the effect of Ca(2+) on glutamate dehydrogenase (GDH) and its role in poly-γ-glutamic acid (γ-PGA) synthesis in Bacillus natto HSF 1410. When the concentration of Ca(2+) varied from 0 to 0.1 g/l in the growth medium of B. natto HSF 1410, γ-PGA production increased from 6.8 to 9.7 g/l, while GDH specific activity and NH4Cl consumption improved from 183 to 295 U/mg and from 0.65 to 0.77 g/l, respectively. GDH with α-ketoglutarate as substrate primarily used NADPH as coenzyme with a K m of 0.08 mM. GDH was responsible for the synthesis of endogenous glutamate. The specific activity of GDH remained essentially unchanged in the presence of CaCl2 (0.05-0.2 g/l) in vitro. However, the specific activity of GDH and its expression was significantly increased by CaCl2 in vivo. Therefore, the regulation of GDH and PGA synthesis by Ca(2+) is an intracellular process. Calcium regulation may be an effective approach for producing γ-PGA on an industrial scale.

Evidence for increased expression of the vesicular glutamate transporter, VGLUT1, by a course of antidepressant treatment.

PubMed

Tordera, Rosa M; Pei, Qi; Sharp, Trevor

2005-08-01

The therapeutic effect of a course of antidepressant treatment is believed to involve a cascade of neuroadaptive changes in gene expression leading to increased neural plasticity. Because glutamate is linked to mechanisms of neural plasticity, this transmitter may play a role in these changes. This study investigated the effect of antidepressant treatment on expression of the vesicular glutamate transporters, VGLUT1-3 in brain regions of the rat. Repeated treatment with fluoxetine, paroxetine or desipramine increased VGLUT1 mRNA abundance in frontal, orbital, cingulate and parietal cortices, and regions of the hippocampus. Immunoautoradiography analysis showed that repeated antidepressant drug treatment increased VGLUT1 protein expression. Repeated electroconvulsive shock (ECS) also increased VGLUT1 mRNA abundance in regions of the cortex and hippocampus compared to sham controls. The antidepressant drugs and ECS did not alter VGLUT1 mRNA abundance after acute administration, and no change was detected after repeated treatment with the antipsychotic agents, haloperidol and chlorpromazine. In contrast to VGLUT1, the different antidepressant treatments did not commonly increase the expression of VGLUT2 or VGLUT3 mRNA. These data suggest that a course of antidepressant drug or ECS treatment increases expression of VGLUT1, a key gene involved in the regulation of glutamate secretion.

[Glutamate-binding membrane proteins from human platelets].

PubMed

Gurevich, V S; Popov, Iu G; Gorodinskiĭ, A I; Dambinova, S A

1991-09-01

Solubilization of the total membrane fraction of human platelets in a 2% solution of sodium deoxycholate and subsequent affinity chromatography on glutamate agarose resulted in two protein fractions possessing a glutamate-binding activity. As can be evidenced from radioligand binding data, the first fraction contains two types of binding sites (Kd1 = 1 microM, Bmax 1 = 100 pmol/mg of protein; Kd2 = 9.3 microMm Bmax2 = 395 pmol/mg of protein). The second fraction has only one type of binding sites (Kd = 1 microM, Bmax = = 110 pmol/mg of protein). SDS-PAAG electrophoresis revealed the presence in the first fraction of proteins with Mr of 14, 24, 56 and 155 kDa, whereas the second fraction was found to contain 14, 46, 71 and 155 kDa proteins. Solid phase immunoenzymatic analysis using poly- and monoclonal specific antibodies against mammalian brain glutamate-binding proteins revealed a marked immunochemical similarity of the isolated protein fractions with human brain synaptic membrane glutamate-binding proteins.

Glutamate-mediated protection of crayfish glial cells from PDT-induced apoptosis

NASA Astrophysics Data System (ADS)

Rudkovskii, M. V.; Romanenko, N. P.; Berezhnaya, E. V.; Kovaleva, V. D.; Uzdensky, A. B.

2011-03-01

Photodynamic treatment that causes intense oxidative stress and kills cells is currently used in neurooncology. However, along with tumor it damages surrounding healthy neurons and glial cells. In order to study the possible role of glutamate-related signaling pathways in photodynamic injury of neurons and glia, we investigated photodynamic effect of alumophthalocyanine Photosens on isolated crayfish stretch receptor that consists of a single neuron surrounded by glial cells. The laser diode (670 nm, 0.4 W/cm2) was used for dye photoexcitation. Application of glutamate increased photodynamically induced necrosis of neurons and glial cells but significantly decreased glial apoptosis. The natural neuroglial mediator N-acetylaspartylglutamate, which releases glutamate after cleavage in the extracellular space by glutamate carboxypeptidase II, also inhibited photoinduced apoptosis. Inhibition of glutamate carboxypeptidase II, oppositely, enhanced apoptosis of glial cells. These data confirm the anti-apoptotic activity of glutamate. Application of NMDA or inhibition of NMDA receptors by MK801 did not influence photodynamic death of neurons and glial cells that indicated nonparticipation of NMDA receptors in these processes. Inhibition of metabotropic glutamate receptors by AP-3 decreased PDT-induced apoptosis. One can suggest that crayfish neurons naturally secrete NAAG, which being cleaved by GCOP produces glutamate. Glutamate prevents photoinduced apoptosis of glial cells possibly through metabotropic but not ionotropic glutamate receptors.

Hyperbaric oxygen therapy ameliorates acute brain injury after porcine intracerebral hemorrhage at high altitude.

PubMed

Zhu, Hai-tao; Bian, Chen; Yuan, Ji-chao; Liao, Xiao-jun; Liu, Wei; Zhu, Gang; Feng, Hua; Lin, Jiang-kai

2015-06-15

Intracerebral hemorrhage (ICH) at high altitude is not well understood to date. This study investigates the effects of high altitude on ICH, and examines the acute neuroprotection of hyperbaric oxygen (HBO) therapy against high-altitude ICH. Minipigs were placed in a hypobaric chamber for 72 h before the operation. ICH was induced by an infusion of autologous arterial blood (3 ml) into the right basal ganglia. Animals in the high-altitude ICH group received HBO therapy (2.5 ATA for 60 min) 30 min after ICH. Blood gas, blood glucose and brain tissue oxygen partial pressure (PbtO2) were monitored continuously for animals from all groups, as were microdialysis products including glucose, lactate, pyruvate and glutamate in perihematomal tissue from 3 to 12 h post-ICH. High-altitude ICH animals showed significantly lower PbtO2, higher lactate/pyruvate ratio (LPR) and glutamate levels than low-altitude ICH animals. More severe neurological deficits, brain edema and neuronal damage were also observed in high-altitude ICH. After HBO therapy, PbtO2 was significantly increased and LPR and glutamate levels were significantly decreased. Brain edema, neurological deficits and neuronal damage were also ameliorated. The data suggested a more serious disturbance of tissue oxygenation and cerebral metabolism in the acute stage after ICH at high altitude. Early HBO treatment reduced acute brain injury, perhaps through a mechanism involving the amelioration of the derangement of cerebral oxygenation and metabolism following high-altitude ICH.

Distribution of Vesicular Glutamate Transporter 2 and Ionotropic Glutamate Receptors in the Auditory Ganglion and Cochlear Nuclei of Pigeons (Columba livia).

PubMed

Karim, M R; Atoji, Y

2016-02-01

Glutamate is a principal excitatory neurotransmitter in the auditory system. Our previous studies revealed localization of glutamate receptor mRNAs in the pigeon cochlear nuclei, suggesting the existence of glutamatergic input from the auditory nerve to the brainstem. This study demonstrated localization of mRNAs for vesicular glutamate transporter 2 (vGluT2) and ionotropic glutamate receptors (AMPA, kainate and NMDA) in the auditory ganglion (AG) and cochlear nuclei (magnocellular, angular and laminar nuclei). VGluT2 mRNA was intensely expressed in AG and intensely or moderately in the cochlear nuclei. The AG and cochlear nuclei showed intense-to-moderate mRNA signals for GluA2, GluA3, GluA4, GluK4 and GluN1. These results suggest that the pigeon AG neurons receives glutamatergic input from hair cells and in turn projects to the magnocellular and angular nuclei. Glutamate may play a pivotal role in the excitatory synapse transmission in the peripheral auditory pathway of birds. © 2015 Blackwell Verlag GmbH.

GLUTAMATE METABOLISM IN BRUCELLA ABORTUS STRAINS OF LOW AND HIGH VIRULENCE

PubMed Central

Dasinger, B. L.; Wilson, J. B.

1962-01-01

Dasinger, B. L. (University of Wisconsin, Madison) and J. B. Wilson. Glutamate metabolism in Brucella abortus strains of low and high virulence. J. Bacteriol. 84:911–915. 1962.—Brucella abortus strains of low virulence oxidize glutamate at a high rate, whereas strains of high virulence oxidize glutamate at a relatively low rate. Results indicated that this observation was not related to differences in pathway of glutamate oxidation or to differences in total enzyme activity. Permeability studies showed that the maximal rates of glutamate accumulation were 2.8 μmoles per 2 min per g (wet wt) for a strain of high virulence and 6.2 μmoles per 2 min per g for a strain of low virulence, but equal intracellular steady-state concentrations were attained by both types of strains. Evidence is presented which suggests that the site of glutamate oxidation is separate from the pool of glutamate being measured. Unequal rates of permeability at these sites could be the reason for the differences in rate of glutamate oxidation. PMID:14028057

Metabolic Control of Vesicular Glutamate Transport and Release

PubMed Central

Juge, Narinobu; Gray, John A.; Omote, Hiroshi; Miyaji, Takaaki; Inoue, Tsuyoshi; Hara, Chiaki; Uneyama, Hisayuki; Edwards, Robert H.; Nicoll, Roger A.; Moriyama, Yoshinori

2010-01-01

Fasting has been used to control epilepsy since antiquity, but the mechanism of coupling between metabolic state and excitatory neurotransmission remains unknown. Previous work has shown that the vesicular glutamate transporters (VGLUTs) required for exocytotic release of glutamate undergo an unusual form of regulation by Cl−. Using functional reconstitution of the purified VGLUTs into proteoliposomes, we now show that Cl− acts as an allosteric activator, and the ketone bodies that increase with fasting inhibit glutamate release by competing with Cl− at the site of allosteric regulation. Consistent with these observations, acetoacetate reduced quantal size at hippocampal synapses, and suppresses glutamate release and seizures evoked with 4-aminopyridine in the brain. The results indicate an unsuspected link between metabolic state and excitatory neurotransmission through anion-dependent regulation of VGLUT activity. PMID:20920794

Pharmacology of Glutamate Transport in the CNS: Substrates and Inhibitors of Excitatory Amino Acid Transporters (EAATs) and the Glutamate/Cystine Exchanger System x c -

NASA Astrophysics Data System (ADS)

Bridges, Richard J.; Patel, Sarjubhai A.

As the primary excitatory neurotransmitter in the mammalian CNS, l-glutamate participates not only in standard fast synaptic communication, but also contributes to higher order signal processing, as well as neuropathology. Given this variety of functional roles, interest has been growing as to how the extracellular concentrations of l-glutamate surrounding neurons are regulated by cellular transporter proteins. This review focuses on two prominent systems, each of which appears capable of influencing both the signaling and pathological actions of l-glutamate within the CNS: the sodium-dependent excitatory amino acid transporters (EAATs) and the glutamate/cystine exchanger, system x c - (Sx c -). While the family of EAAT subtypes limit access to glutamate receptors by rapidly and efficiently sequestering l-glutamate in neurons and glia, Sxc - provides a route for the export of glutamate from cells into the extracellular environment. The primary intent of this work is to provide an overview of the inhibitors and substrates that have been developed to delineate the pharmacological specificity of these transport systems, as well as be exploited as probes with which to selectively investigate function. Particular attention is paid to the development of small molecule templates that mimic the structural properties of the endogenous substrates, l-glutamate, l-aspartate and l-cystine and how strategic control of functional group position and/or the introduction of lipophilic R-groups can impact multiple aspects of the transport process, including: subtype selectivity, inhibitory potency, and substrate activity.

Update on food safety of monosodium l-glutamate (MSG).

PubMed

Henry-Unaeze, Helen Nonye

2017-12-01

This evidence-based safety review of the flavor enhancer monosodium l-glutamate (MSG) was triggered by its global use and recent studies expressing some safety concerns. This article obtained information through search of evidence-based scientific databases, especially the US National Library of Medicine NIH. (A) MSG is a water-soluble salt of glutamate, a non-essential amino acid, normally synthesized in the body and prevalent in protein foods. (B) MSG is utilized world-wide for its "umami" taste and flavor enhancement qualities, (C) the human body does not discriminate between glutamate present in food and that added as seasoning, (D) glutamate metabolism is compartmentalized in the human body without reported ethnic differences, (E) glutamate does not passively cross biological membranes, (F) food glutamate is completely metabolized by gut cells as energy source and serves as key substrate for other important metabolites in the liver, (G) normal food use of MSG is dose-dependent and self-limiting without elevation in plasma glutamate, (H) the recent EFSA acceptable daily intake (30mg/kg body weight/day) is not attainable when MSG is consumed at normal dietary level, (I) scientists have not been able to consistently elicit reactions in double-blind studies with 'sensitive' individuals using MSG or placebo in food. Based on the above observations (A-I), high quality MSG is safe for all life-cycle stages without respect to ethnic origin or culinary background. MSG researchers are advised to employ appropriate scientific methodologies, consider glutamate metabolism and its normal food use before extrapolating pharmacological rodent studies to humans. Copyright © 2017 Elsevier B.V. All rights reserved.

Flavor Preferences Conditioned by Dietary Glutamate123

PubMed Central

2016-01-01

Our understanding of the molecular basis of umami taste and its appetitive qualities has been greatly aided by studies in laboratory rodents. This review describes methods for testing responses to the prototypical umami substance monosodium glutamate (MSG) in rodents. Two techniques, forced exposure to MSG and 2-bottle choice tests with ascending concentrations, were used to evaluate the responses to the taste of umami itself, and 2 other methods used oral or postoral MSG to modify the responses to other flavors. Intake and preference for MSG are enhanced in mice by experience with MSG and with other nutrients with positive postoral effects. In addition, flavor preferences are enhanced in mice and rats by gastric or intestinal MSG infusions via an associative learning process. Even mice with an impaired or absent ability to taste MSG can learn to prefer a flavor added to an MSG solution, supporting the notion that glutamate acts postorally. The more complex flavor of dashi seasoning, which includes umami substances (inosinate, glutamate), is attractive to rodents, but dashi does not condition flavor preferences. Details of the postoral glutamate detection process and the nature of the signal involved in learned preferences are still uncertain but probably involve gastric or intestinal sensors or both and vagal transmission. Some findings suggest that postoral glutamate effects may enhance food preferences in humans, but this requires further study. PMID:27422522

Effects of Orally Administered Augmentin on Glutamate Transporter 1, Cystine-glutamate Exchanger Expression as well as Ethanol Intake in Alcohol-Preferring Rats

PubMed Central

Hakami, Alqassem Y.; Alshehri, Fahad S.; Althobaiti, Yusuf S.; Sari, Youssef

2016-01-01

Alcohol dependence is associated with deficits in glutamate uptake and impairment of glutamate homeostasis in different brain reward regions. Glutamate transporter subtype 1 (GLT-1), cystine-glutamate exchanger (xCT) and glutamate/aspartate transporter (GLAST) are the key players in regulating extracellular glutamate concentration in the brain. Parenteral treatment with ceftriaxone, β-lactam antibiotic, has been reported to attenuate ethanol consumption and reinstatement to cocaine-seeking behavior, in part, by restoring the expression of GLT-1 and xCT in mesocorticolimbic brain regions in rats. In this study, we focus to test Augmentin (amoxicillin/clavulanate), which can be administered orally to subjects. Therefore, we examined the effects of orally administered Augmentin on ethanol intake as well as GLT-1, xCT and GLAST expression in alcohol-preferring (P) rats. We found that orally administered Augmentin significantly attenuated ethanol consumption in P rats as compared to the vehicle-treated group. Importantly, the attenuation in ethanol consumption was associated with a significant upregulation of GLT-1 and xCT expression in nucleus accumbens (NAc) and prefrontal cortex (PFC). There was no effect of oral Augmentin on GLAST expression in either NAc or PFC. These findings present strong evidence that oral administration of Augmentin can be used as an alternative to parenteral administration. PMID:27993695

A modern ionotropic glutamate receptor with a K(+) selectivity signature sequence.

PubMed

Janovjak, H; Sandoz, G; Isacoff, E Y

2011-01-01

Glutamate is the major excitatory neurotransmitter in the mammalian central nervous system and gates non-selective cation channels. The origins of glutamate receptors are not well understood as they differ structurally and functionally from simple bacterial ligand-gated ion channels. Here we report the discovery of an ionotropic glutamate receptor that combines the typical eukaryotic domain architecture with the 'TXVGYG' signature sequence of the selectivity filter found in K(+) channels. This receptor exhibits functional properties intermediate between bacterial and eukaryotic glutamate-gated ion channels, suggesting a link in the evolution of ionotropic glutamate receptors.

[Determination of glutamic acid in biological material by capillary electrophoresis].

PubMed

Narezhnaya, E; Krukier, I; Avrutskaya, V; Degtyareva, A; Igumnova, E A

2015-01-01

The conditions for the identification and determination of Glutamic acid by capillary zone electrophoresis without their preliminary derivatization have been optimized. The effect of concentration of buffer electrolyte and pH on determination of Glutamic acid has been investigated. It is shown that the 5 Mm borate buffer concentration and a pH 9.15 are optimal. Quantitative determination of glutamic acid has been carried out using a linear dependence between the concentration of the analyte and the area of the peak. The accuracy and reproducibility of the determination are confirmed by the method "introduced - found". Glutamic acid has been determined in the placenta homogenate. The duration of analysis doesn't exceed 30 minutes. The results showed a decrease in the level of glutamic acid in cases of pregnancy complicated by placental insufficiency compared with the physiological, and this fact allows to consider the level of glutamic acid as a possible marker of complicated pregnancy.

Glucose, Lactate, β-Hydroxybutyrate, Acetate, GABA, and Succinate as Substrates for Synthesis of Glutamate and GABA in the Glutamine-Glutamate/GABA Cycle.

PubMed

Hertz, Leif; Rothman, Douglas L

2016-01-01

The glutamine-glutamate/GABA cycle is an astrocytic-neuronal pathway transferring precursors for transmitter glutamate and GABA from astrocytes to neurons. In addition, the cycle carries released transmitter back to astrocytes, where a minor fraction (~25 %) is degraded (requiring a similar amount of resynthesis) and the remainder returned to the neurons for reuse. The flux in the cycle is intense, amounting to the same value as neuronal glucose utilization rate or 75-80 % of total cortical glucose consumption. This glucose:glutamate ratio is reduced when high amounts of β-hydroxybutyrate are present, but β-hydroxybutyrate can at most replace 60 % of glucose during awake brain function. The cycle is initiated by α-ketoglutarate production in astrocytes and its conversion via glutamate to glutamine which is released. A crucial reaction in the cycle is metabolism of glutamine after its accumulation in neurons. In glutamatergic neurons all generated glutamate enters the mitochondria and its exit to the cytosol occurs in a process resembling the malate-aspartate shuttle and therefore requiring concomitant pyruvate metabolism. In GABAergic neurons one half enters the mitochondria, whereas the other one half is released directly from the cytosol. A revised concept is proposed for the synthesis and metabolism of vesicular and nonvesicular GABA. It includes the well-established neuronal GABA reuptake, its metabolism, and use for resynthesis of vesicular GABA. In contrast, mitochondrial glutamate is by transamination to α-ketoglutarate and subsequent retransamination to releasable glutamate essential for the transaminations occurring during metabolism of accumulated GABA and subsequent resynthesis of vesicular GABA.

Acute movement disorders in the medical setting.

PubMed

Zawar, Ifrah; Caro, Mario A; Feldman, Lara; Jimenez, Xavier F

2016-07-01

Objective Psychosomatic medicine psychiatrists are often tasked with the evaluation and treatment of complex neuropsychiatric states which may be motoric in phenotype. Little energy has been dedicated to understanding acute movement disorders in the hospital environment. Method Recognizing the importance of frontal-subcortical (corticostriatothalamocortical) circuitry and basal ganglia structures, we present a case series of acute movement disorder phenotypes resulting from underlying medical conditions, commonly-administered medications, or the interaction of both. We organize these scenarios into neurodegenerative disorders, primary psychiatric disorders, neuroinflammation, and polypharmacy, demonstrating a clinical example of each followed by background references on a variety of clinical states and medications contributing to acute movement disorders. In addition, we offer visual illustration of implicated neurocircuitry as well as proposed neurotransmitter imbalances involving glutamate, gamma aminobutyric acid, and dopamine. Furthermore, we review the various clinical syndromes and medications involved in the development of acute movement disorders. Results Acute movement disorder's involve complex interactions between frontal-subcortical circuits and acute events. Given the complexity of interactions, psychopharmacological considerations become critical, as some treatments may alleviate acute movement disorders while others will exacerbate them. Conclusion Integrating underlying medical conditions and acutely administered (or discontinued) pharmacological agents offers an interactional, neuromedical approach to acute movement disorders that is critical to the work of psychosomatic medicine.

Food Application of Newly Developed Handy-type Glutamate Sensor.

PubMed

Mukai, Yuuka; Oikawa, Tsutomu

2016-01-01

Tests on physiological functions of umami have been actively conducted and a need recognized for a high-performance quantification device that is simple and cost-effective, and whose use is not limited to a particular location or user. To address this need, Ajinomoto Co. and Tanita Corp. have jointly been researching and developing a simple device for glutamate measurement. The device uses L-glutamate oxidase immobilized on a hydrogen peroxide electrode. L-glutamate in the sample is converted to α-ketoglutaric acid, which produces hydrogen peroxide. Subsequently, the electrical current from the electrochemical reaction of hydrogen peroxide is measured to determine the L-glutamate concentration. In order to evaluate its basic performance, we used this device to measure the concentration of L-glutamate standard solutions. In a concentration range of 0-1.0%, the difference from the theoretical value was minimal. The coefficient of variation (CV) value of 3 measurements was 4% or less. This shows that the device has a reasonable level of precision and accuracy. The device was also used in trial measurements of L-glutamate concentrations in food. There was a good correlation between the results obtained using the developed device and those obtained with an amino acid analyzer; the correlation coefficient was R=0.997 (n=24). In this review, we demonstrate the use of our device to measure the glutamate concentration in miso soup served daily at a home for elderly people, and other foods and ingredients.

Neuroprotection by glutamate oxaloacetate transaminase in ischemic stroke: an experimental study.

PubMed

Campos, Francisco; Sobrino, Tomás; Ramos-Cabrer, Pedro; Argibay, Bárbara; Agulla, Jesús; Pérez-Mato, María; Rodríguez-González, Raquel; Brea, David; Castillo, José

2011-06-01

As ischemic stroke is associated with an excessive release of glutamate into the neuronal extracellular space, a decrease in blood glutamate levels could provide a mechanism to remove it from the brain tissue, by increasing the brain-blood gradient. In this regard, the ability of glutamate oxaloacetate transaminase (GOT) to metabolize glutamate in blood could represent a potential neuroprotective tool for ischemic stroke. This study aimed to determine the neuroprotective effects of GOT in an animal model of cerebral ischemia by means of a middle cerebral arterial occlusion (MCAO) following the Stroke Therapy Academic Industry Roundtable (STAIR) group guidelines. In this animal model, oxaloacetate-mediated GOT activation inhibited the increase of blood and cerebral glutamate after MCAO. This effect is reflected in a reduction of infarct size, smaller edema volume, and lower sensorimotor deficits with respect to controls. Magnetic resonance spectroscopy confirmed that the increase of glutamate levels in the brain parenchyma after MCAO is inhibited after oxaloacetate-mediated GOT activation. These findings show the capacity of the GOT to remove glutamate from the brain by means of blood glutamate degradation, and suggest the applicability of this enzyme as an efficient and novel neuroprotective tool against ischemic stroke.

Neuroprotective and anti-inflammatory effects of lidocaine in kainic acid-injected rats.

PubMed

Chiu, Kuan Ming; Lu, Cheng Wei; Lee, Ming Yi; Wang, Ming Jiuh; Lin, Tzu Yu; Wang, Su Jane

2016-05-04

Lidocaine, the most commonly used local anesthetic, inhibits glutamate release from nerve terminals. Given the involvement of glutamate neurotoxicity in the pathogenesis of various neurological disorders, this study investigated the role of lidocaine in hippocampal neuronal death and inflammatory events induced by an i.p. injection of kainic acid (KA) (15 mg/kg), a glutamate analog. The results showed that KA significantly led to neuronal death in the CA3 pyramidal layers of the hippocampus and this effect was attenuated by the systemic administration of lidocaine (0.8 or 4 mg/kg, i.p.) 30 min before KA injection. Moreover, KA-induced microglia activation and gene expression of proinflammatory cytokines, namely, interleukin-1β, interleukin-6, and tumor necrosis factor-α, in the hippocampus were reduced by the lidocaine pretreatment. Altogether, the results suggest that lidocaine can effectively treat glutamate excitotoxicity-related brain disorders.

Metabolic control of vesicular glutamate transport and release.

PubMed

Juge, Narinobu; Gray, John A; Omote, Hiroshi; Miyaji, Takaaki; Inoue, Tsuyoshi; Hara, Chiaki; Uneyama, Hisayuki; Edwards, Robert H; Nicoll, Roger A; Moriyama, Yoshinori

2010-10-06

Fasting has been used to control epilepsy since antiquity, but the mechanism of coupling between metabolic state and excitatory neurotransmission remains unknown. Previous work has shown that the vesicular glutamate transporters (VGLUTs) required for exocytotic release of glutamate undergo an unusual form of regulation by Cl(-). Using functional reconstitution of the purified VGLUTs into proteoliposomes, we now show that Cl(-) acts as an allosteric activator, and the ketone bodies that increase with fasting inhibit glutamate release by competing with Cl(-) at the site of allosteric regulation. Consistent with these observations, acetoacetate reduced quantal size at hippocampal synapses and suppresses glutamate release and seizures evoked with 4-aminopyridine in the brain. The results indicate an unsuspected link between metabolic state and excitatory neurotransmission through anion-dependent regulation of VGLUT activity. Copyright © 2010 Elsevier Inc. All rights reserved.

Noscapine protects OLN-93 oligodendrocytes from ischemia-reperfusion damage: Calcium and nitric oxide involvement.

PubMed

Nadjafi, S; Ebrahimi, S-A; Rahbar-Roshandel, N

2015-12-01

This study was carried out to evaluate the effects of noscapine, a benzylisoquinoline alkaloid from opium poppy, on oligodendrocyte during ischemia/reperfusion-induced excitotoxic injury. Changes in intracellular calcium levels due to chemical ischemia and nitric oxide (NO) production during ischemia/reperfusion were evaluated as the hallmarks of ischemia-derived excitotoxic event. OLN-93 cell line (a permanent immature rat oligodendrocyte) was used as a model of oligodendrocyte. 30- or 60-minute-oxygen-glucose deprivation/24 hours reperfusion were used to induce excitotoxicity. MTT (3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) assay was used to evaluate cell viability. Ratiometric fluorescence microscopy using Ca(2+)-sensitive indicator Fura-2/AM was utilized to assess intracellular calcium levels. NO production was evaluated by Griess method. Noscapine (4 μM) significantly attenuated intracellular Ca(2+) elevation (P < 0.001). Also, noscapine significantly decreased NO production during a 30-minute oxygen-glucose deprivation/reperfusion (P < 0.01). The inhibitory effect of noscapine (4 μM) on intracellular Ca(2+) was greater than ionotropic glutamate receptors antagonists. Noscapine is protective against ischemia/reperfusion-induced excitotoxic injury in OLN-93 oligodendrocyte. This protective effect seems to be related to attenuation of intracellular Ca(2+) overload and NO production.

Glutamate and asparagine cataplerosis underlie glutamine addiction in melanoma

PubMed Central

Ratnikov, Boris; Aza-Blanc, Pedro; Ronai, Ze'ev A.; Smith, Jeffrey W.; Osterman, Andrei L.; Scott, David A.

2015-01-01

Glutamine dependence is a prominent feature of cancer metabolism, and here we show that melanoma cells, irrespective of their oncogenic background, depend on glutamine for growth. A quantitative audit of how carbon from glutamine is used showed that TCA-cycle-derived glutamate is, in most melanoma cells, the major glutamine-derived cataplerotic output and product of glutaminolysis. In the absence of glutamine, TCA cycle metabolites were liable to depletion through aminotransferase-mediated α-ketoglutarate-to-glutamate conversion and glutamate secretion. Aspartate was an essential cataplerotic output, as melanoma cells demonstrated a limited capacity to salvage external aspartate. Also, the absence of asparagine increased the glutamine requirement, pointing to vulnerability in the aspartate-asparagine biosynthetic pathway within melanoma metabolism. In contrast to melanoma cells, melanocytes could grow in the absence of glutamine. Melanocytes use more glutamine for protein synthesis rather than secreting it as glutamate and are less prone to loss of glutamate and TCA cycle metabolites when starved of glutamine. PMID:25749035

Assessing the Psychedelic "After-Glow" in Ayahuasca Users: Post-Acute Neurometabolic and Functional Connectivity Changes Are Associated with Enhanced Mindfulness Capacities.

PubMed

Sampedro, Frederic; de la Fuente Revenga, Mario; Valle, Marta; Roberto, Natalia; Domínguez-Clavé, Elisabet; Elices, Matilde; Luna, Luís Eduardo; Crippa, José Alexandre S; Hallak, Jaime E C; de Araujo, Draulio B; Friedlander, Pablo; Barker, Steven A; Álvarez, Enrique; Soler, Joaquim; Pascual, Juan C; Feilding, Amanda; Riba, Jordi

2017-09-01

Ayahuasca is a plant tea containing the psychedelic 5-HT2A agonist N,N-dimethyltryptamine and harmala monoamine-oxidase inhibitors. Acute administration leads to neurophysiological modifications in brain regions of the default mode network, purportedly through a glutamatergic mechanism. Post-acutely, ayahuasca potentiates mindfulness capacities in volunteers and induces rapid and sustained antidepressant effects in treatment-resistant patients. However, the mechanisms underlying these fast and maintained effects are poorly understood. Here, we investigated in an open-label uncontrolled study in 16 healthy volunteers ayahuasca-induced post-acute neurometabolic and connectivity modifications and their association with mindfulness measures. Using 1H-magnetic resonance spectroscopy and functional connectivity, we compared baseline and post-acute neurometabolites and seed-to-voxel connectivity in the posterior and anterior cingulate cortex after a single ayahuasca dose. Magnetic resonance spectroscopy showed post-acute reductions in glutamate+glutamine, creatine, and N-acetylaspartate+N-acetylaspartylglutamate in the posterior cingulate cortex. Connectivity was increased between the posterior cingulate cortex and the anterior cingulate cortex, and between the anterior cingulate cortex and limbic structures in the right medial temporal lobe. Glutamate+glutamine reductions correlated with increases in the "nonjudging" subscale of the Five Facets Mindfulness Questionnaire. Increased anterior cingulate cortex-medial temporal lobe connectivity correlated with increased scores on the self-compassion questionnaire. Post-acute neural changes predicted sustained elevations in nonjudging 2 months later. These results support the involvement of glutamate neurotransmission in the effects of psychedelics in humans. They further suggest that neurometabolic changes in the posterior cingulate cortex, a key region within the default mode network, and increased connectivity between the

A computational study of astrocytic glutamate influence on post-synaptic neuronal excitability.

PubMed

Flanagan, Bronac; McDaid, Liam; Wade, John; Wong-Lin, KongFatt; Harkin, Jim

2018-04-01

The ability of astrocytes to rapidly clear synaptic glutamate and purposefully release the excitatory transmitter is critical in the functioning of synapses and neuronal circuits. Dysfunctions of these homeostatic functions have been implicated in the pathology of brain disorders such as mesial temporal lobe epilepsy. However, the reasons for these dysfunctions are not clear from experimental data and computational models have been developed to provide further understanding of the implications of glutamate clearance from the extracellular space, as a result of EAAT2 downregulation: although they only partially account for the glutamate clearance process. In this work, we develop an explicit model of the astrocytic glutamate transporters, providing a more complete description of the glutamate chemical potential across the astrocytic membrane and its contribution to glutamate transporter driving force based on thermodynamic principles and experimental data. Analysis of our model demonstrates that increased astrocytic glutamate content due to glutamine synthetase downregulation also results in increased postsynaptic quantal size due to gliotransmission. Moreover, the proposed model demonstrates that increased astrocytic glutamate could prolong the time course of glutamate in the synaptic cleft and enhances astrocyte-induced slow inward currents, causing a disruption to the clarity of synaptic signalling and the occurrence of intervals of higher frequency postsynaptic firing. Overall, our work distilled the necessity of a low astrocytic glutamate concentration for reliable synaptic transmission of information and the possible implications of enhanced glutamate levels as in epilepsy.

Post-Translational Modification Biology of Glutamate Receptors and Drug Addiction

PubMed Central

Mao, Li-Min; Guo, Ming-Lei; Jin, Dao-Zhong; Fibuch, Eugene E.; Choe, Eun Sang; Wang, John Q.

2011-01-01

Post-translational covalent modifications of glutamate receptors remain a hot topic. Early studies have established that this family of receptors, including almost all ionotropic and metabotropic glutamate receptor subtypes, undergoes active phosphorylation at serine, threonine, or tyrosine residues in their intracellular domains. Recent evidence identifies several glutamate receptor subtypes to be direct substrates for palmitoylation at cysteine residues. Other modifications such as ubiquitination and sumoylation at lysine residues also occur to certain glutamate receptors. These modifications are dynamic and reversible in nature and are regulatable by changing synaptic inputs. The regulated modifications significantly impact the receptor in many ways, including interrelated changes in biochemistry (synthesis, subunit assembling, and protein–protein interactions), subcellular redistribution (trafficking, endocytosis, synaptic delivery, and clustering), and physiology, usually associated with changes in synaptic plasticity. Glutamate receptors are enriched in the striatum and cooperate closely with dopamine to regulate striatal signaling. Emerging evidence shows that modification processes of striatal glutamate receptors are sensitive to addictive drugs, such as psychostimulants (cocaine and amphetamine). Altered modifications are believed to be directly linked to enduring receptor/synaptic plasticity and drug-seeking. This review summarizes several major types of modifications of glutamate receptors and analyzes the role of these modifications in striatal signaling and in the pathogenesis of psychostimulant addiction. PMID:21441996

40 CFR 721.3821 - L-Glutamic acid, N-(1-oxododecyl)-.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false L-Glutamic acid, N-(1-oxododecyl... Substances § 721.3821 L-Glutamic acid, N-(1-oxododecyl)-. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as L-Glutamic acid, N-(1-oxododecyl)- (PMN P...

Synthetic cathinone MDPV downregulates glutamate transporter subtype I (GLT-1) and produces rewarding and locomotor-activating effects that are reduced by a GLT-1 activator

PubMed Central

Gregg, Ryan A.; Hicks, Callum; Nayak, Sunil U.; Tallarida, Christopher S.; Nucero, Paul; Reitz, Allen B.; Smith, Garry R.; Rawls, Scott M.

2016-01-01

Synthetic cathinones produce dysregulation of monoamine systems, but their effects on the glutamate system and the influence of glutamate on behavioral effects related to cathinone abuse are unknown. A principal regulator of glutamate homeostasis is glutamate transporter subtype 1 (GLT-1), an astrocytic protein that clears glutamate from the extracellular space and influences behavioral effects of established psychostimulants. We hypothesized that repeated administration of the synthetic cathinone, MDPV (3,4-methylenedioxypyrovalerone), would affect GLT-1 expression in the corticolimbic circuit, and that a GLT-1 activator (ceftriaxone, CTX) would reduce rewarding and locomotor-stimulant effects of MDPV in rats. GLT-1 protein expression in the nucleus accumbens (NAcc), but not prefrontal cortex (PFC), was decreased following withdrawal (2, 5 and 10 days) from repeated MDPV treatment, but not immediately after the last MDPV injection. CTX (200 mg/kg) pretreatment did not affect acute locomotor activation produced by MDPV (0.5, 1, 3 mg/kg). However, CTX (200 mg/kg) administered during a 7-day MDPV treatment paradigm attenuated the development of MDPV-induced sensitization of repetitive movements in rats challenged with MDPV following 11 days of drug abstinence. Pretreatment with CTX (200 mg/kg) during a 4-day MDPV (2 mg/kg) conditioned place preference (CPP) paradigm reduced the development of place preference produced by MDPV. The present data demonstrate dysregulation of corticolimbic glutamate transport systems during withdrawal from chronic MDPV exposure, and show that a GLT-1 transporter activator disrupts behavioral effects of MDPV that are related to synthetic cathinone abuse. PMID:27085607

Effects of sarizotan on the corticostriatal glutamate pathways.

PubMed

Antonelli, Tiziana; Fuxe, Kjell; Tomasini, Maria C; Bartoszyk, Gerd D; Seyfried, Christoph A; Tanganelli, Sergio; Ferraro, Luca

2005-12-01

The effects of sarizotan, a 5-HT(1A) agonist with additional affinity for D(3) and D(4) receptors, have been studied on the corticostriatal glutamate pathways using dual-probe microdialysis in the awake rat. Sarizotan given systemically (0.1-10 mg/kg s.c.) or perfused into the motor cortex (10 microM) produced 20-30% reduction of cortical and striatal glutamate levels. The inhibitory effects of the systemic sarizotan on cortical and striatal glutamate levels were counteracted by intracortical perfusion with the 5-HT(1A) antagonist WAY100135 (10 microM). These findings suggest that the anti-dyskinetic properties of sarizotan could be mediated via its 5-HT(1A) agonist actions in the motor cortex, leading to reduced activity in the corticostriatal glutamate pathways with reduced activation of the striatopallidal GABA pathway mediating motor inhibition. Synapse 58:193-199, 2005. (c) 2005 Wiley-Liss, Inc.

Energetics of Glutamate Binding to an Ionotropic Glutamate Receptor.

PubMed

Yu, Alvin; Lau, Albert Y

2017-11-22

Ionotropic glutamate receptors (iGluRs) are ligand-gated ion channels that are responsible for the majority of excitatory transmission at the synaptic cleft. Mechanically speaking, agonist binding to the ligand binding domain (LBD) activates the receptor by triggering a conformational change that is transmitted to the transmembrane region, opening the ion channel pore. We use fully atomistic molecular dynamics simulations to investigate the binding process in the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor, an iGluR subtype. The string method with swarms of trajectories was applied to calculate the possible pathways glutamate traverses during ligand binding. Residues peripheral to the binding cleft are found to metastably bind the ligand prior to ligand entry into the binding pocket. Umbrella sampling simulations were performed to compute the free energy barriers along the binding pathways. The calculated free energy profiles demonstrate that metastable interactions contribute substantially to the energetics of ligand binding and form local minima in the overall free energy landscape. Protein-ligand interactions at sites outside of the orthosteric agonist-binding site may serve to lower the transition barriers of the binding process.

Cloning and characterization of the glutamate dehydrogenase gene in Streptococcus bovis.

PubMed

Ando, Tasuke; Sugawara, Yoko; Nishio, Ryohei; Murakami, Miho; Isogai, Emiko; Yoneyama, Hiroshi

2017-07-01

Streptococcus bovis, an etiologic agent of rumen acidosis in cattle, is a rumen bacterium that can grow in a chemically defined medium containing ammonia as a sole source of nitrogen. To understand its ability to assimilate inorganic ammonia, we focused on the function of glutamate dehydrogenase. In order to identify the gene encoding this enzyme, we first amplified an internal region of the gene by using degenerate primers corresponding to hexameric family I and NAD(P) + binding motifs. Subsequently, inverse PCR was used to identify the whole gene, comprising an open reading frame of 1350 bp that encodes 449 amino acid residues that appear to have the substrate binding site of glutamate dehydrogenase observed in other organisms. Upon introduction of a recombinant plasmid harboring the gene into an Escherichia coli glutamate auxotroph lacking glutamate dehydrogenase and glutamate synthase, the transformants gained the ability to grow on minimal medium without glutamate supplementation. When cell extracts of the transformant were resolved by blue native polyacrylamide gel electrophoresis followed by activity staining, a single protein band appeared that corresponded to the size of S. bovis glutamate dehydrogenase. Based on these results, we concluded that the gene obtained encodes glutamate dehydrogenase in S. bovis. © 2016 Japanese Society of Animal Science.

Neuroprotection by glutamate oxaloacetate transaminase in ischemic stroke: an experimental study

PubMed Central

Campos, Francisco; Sobrino, Tomás; Ramos-Cabrer, Pedro; Argibay, Bárbara; Agulla, Jesús; Pérez-Mato, María; Rodríguez-González, Raquel; Brea, David; Castillo, José

2011-01-01

As ischemic stroke is associated with an excessive release of glutamate into the neuronal extracellular space, a decrease in blood glutamate levels could provide a mechanism to remove it from the brain tissue, by increasing the brain–blood gradient. In this regard, the ability of glutamate oxaloacetate transaminase (GOT) to metabolize glutamate in blood could represent a potential neuroprotective tool for ischemic stroke. This study aimed to determine the neuroprotective effects of GOT in an animal model of cerebral ischemia by means of a middle cerebral arterial occlusion (MCAO) following the Stroke Therapy Academic Industry Roundtable (STAIR) group guidelines. In this animal model, oxaloacetate-mediated GOT activation inhibited the increase of blood and cerebral glutamate after MCAO. This effect is reflected in a reduction of infarct size, smaller edema volume, and lower sensorimotor deficits with respect to controls. Magnetic resonance spectroscopy confirmed that the increase of glutamate levels in the brain parenchyma after MCAO is inhibited after oxaloacetate-mediated GOT activation. These findings show the capacity of the GOT to remove glutamate from the brain by means of blood glutamate degradation, and suggest the applicability of this enzyme as an efficient and novel neuroprotective tool against ischemic stroke. PMID:21266983

The NR1-4 C-terminus interferes with N-methyl-D-aspartate receptor-mediated excitotoxicity: evidence against a typical T/SXV-PDZ interaction.

PubMed

Mattar, P A; Holmes, K D; Dekaban, G A

2005-01-01

The N-methyl-D-aspartate receptor (NMDAR) plays a key role in the neural plasticity that underlies learning and memory in vivo. The plasticity exhibited by NMDARs may also contribute to disease pathogenesis, as a number of disorders are caused or exacerbated by exaggerated NMDAR activity. The NMDAR is composed of two obligatory types of subunits, NR1 and NR2. These transmembrane proteins include large intracellular C-termini that have yet to be fully characterized. We have developed a three-color fluorescence system in order to visualize NMDAR expression in living cells. Using excitotoxicity as a proxy for exaggerated NMDAR activity, we analyzed the effect of over-expressing NR1-4 and NR2A C-terminal domains on exaggerated NMDAR function. We demonstrate that a determinant within the C-terminal domain of NR1-4 (C02') is important for NMDAR excitotoxicity, whereas no novel determinants were identified in the NR2A C-terminus. Through the use of heterologous cells, and by examining the interaction between the prototypical NMDAR-binding partner postsynaptic density-95 (PSD-95), we show that this effect is unlikely to be mediated through a classical interaction with PSD-95.

A Glutamic Acid-Producing Lactic Acid Bacteria Isolated from Malaysian Fermented Foods

PubMed Central

Zareian, Mohsen; Ebrahimpour, Afshin; Bakar, Fatimah Abu; Mohamed, Abdul Karim Sabo; Forghani, Bita; Ab-Kadir, Mohd Safuan B.; Saari, Nazamid

2012-01-01

l-glutamaic acid is the principal excitatory neurotransmitter in the brain and an important intermediate in metabolism. In the present study, lactic acid bacteria (218) were isolated from six different fermented foods as potent sources of glutamic acid producers. The presumptive bacteria were tested for their ability to synthesize glutamic acid. Out of the 35 strains showing this capability, strain MNZ was determined as the highest glutamic-acid producer. Identification tests including 16S rRNA gene sequencing and sugar assimilation ability identified the strain MNZ as Lactobacillus plantarum. The characteristics of this microorganism related to its glutamic acid-producing ability, growth rate, glucose consumption and pH profile were studied. Results revealed that glutamic acid was formed inside the cell and excreted into the extracellular medium. Glutamic acid production was found to be growth-associated and glucose significantly enhanced glutamic acid production (1.032 mmol/L) compared to other carbon sources. A concentration of 0.7% ammonium nitrate as a nitrogen source effectively enhanced glutamic acid production. To the best of our knowledge this is the first report of glutamic acid production by lactic acid bacteria. The results of this study can be further applied for developing functional foods enriched in glutamic acid and subsequently γ-amino butyric acid (GABA) as a bioactive compound. PMID:22754309

Two Pathways of Glutamate Fermentation by Anaerobic Bacteria

PubMed Central

Buckel, Wolfgang; Barker, H. A.

1974-01-01

Two pathways are involved in the fermentation of glutamate to acetate, butyrate, carbon dioxide, and ammonia—the methylaspartate and the hydroxyglutarate pathways which are used by Clostridium tetanomorphum and Peptococcus aerogenes, respectively. Although these pathways give rise to the same products, they are easily distinguished by different labeling patterns of the butyrate when [4-14C]glutamate is used as substrate. Schmidt degradation of the radioactive butyrate from C. tetanomorphum yielded equally labeled propionate and carbon dioxide, whereas nearly all the radioactivity of the butyrate from P. aerogenes was recovered in the corresponding propionate. This procedure was used as a test for the pathway of glutamate fermentation by 15 strains (9 species) of anaerobic bacteria. The labeling patterns of the butyrate indicate that glutamate is fermented via the methylaspartate pathway by C. tetani, C. cochlearium, and C. saccarobutyricum, and via the hydroxyglutarate pathway by Acidaminococcus fermentans, C. microsporum, Fusobacterium nucleatum, and F. fusiformis. Enzymes specific for each pathway were assayed in crude extracts of the above organisms. 3-Methylaspartase was found only in clostridia which use the methylaspartate pathway, including Clostridium SB4 and C. sticklandii, which probably degrade glutamate to acetate and carbon dioxide by using a second amino acid as hydrogen acceptor. High levels of 2-hydroxyglutarate dehydrogenase were found exclusively in organisms that use the hydroxyglutarate pathway. The data indicate that only two pathways are involved in the fermentation of glutamate by the bacteria analyzed. The methylaspartate pathway appears to be used only by species of Clostridium, whereas the hydroxyglutarate pathway is used by representatives of several genera. PMID:4813895

Thiopental sodium reduces glutamate extracellular levels in rat intact prefrontal cortex.

PubMed

Liu, Hongliang; Yao, Shanglong

2005-12-01

To investigate the effect of thiopental sodium on glutamate extracellular levels in the prefrontal cortex (PFC) of rats, a microdialysis probe was inserted into the PFC, the perfusate was collected every 10 min throughout the experiment with thiopental sodium ip or perfused into the PFC locally. The concentrations of glutamate in the perfusate were determined by reversed-phase high performance liquid chromatography. Thiopental sodium 30 mg kg(-1) ip significantly decreased glutamate levels in the perfusate after 10, 20, 30, and 40 min; glutamate levels in the perfusate were also decreased from 10 to 90 min after thiopental sodium 50 mg kg(-1) ip. Thiopental sodium with concentrations of 30, 100, or 300 microM perfused into the PFC also decreased glutamate levels in the perfusate significantly. The results suggest that thiopental sodium decreases glutamate extracellular levels in rat intact PFC.

Acute pancreatitis decreases the sensitivity of pancreas-projecting dorsal motor nucleus of the vagus neurones to group II metabotropic glutamate receptor agonists in rats

PubMed Central

Babic, Tanja; Travagli, R Alberto

2014-01-01

Recent studies have shown that pancreatic exocrine secretions (PES) are modulated by dorsal motor nucleus of the vagus (DMV) neurones, whose activity is finely tuned by GABAergic and glutamatergic synaptic inputs. Group II metabotropic glutamate receptors (mGluR) decrease synaptic transmission to pancreas-projecting DMV neurones and increase PES. In the present study, we used a combination of in vivo and in vitro approaches aimed at characterising the effects of caerulein-induced acute pancreatitis (AP) on the vagal neurocircuitry modulating pancreatic functions. In control rats, microinjection of bicuculline into the DMV increased PES, whereas microinjections of kynurenic acid had no effect. Conversely, in AP rats, microinjection of bicuculline had no effect, whereas kynurenic acid decreased PES. DMV microinjections of the group II mGluR agonist APDC and whole cell recordings of excitatory currents in identified pancreas-projecting DMV neurones showed a reduced functional response in AP rats compared to controls. Moreover, these changes persisted up to 3 weeks following the induction of AP. These data demonstrate that AP increases the excitatory input to pancreas-projecting DMV neurones by decreasing the response of excitatory synaptic terminals to group II mGluR agonist. PMID:24445314

Protein Modification: A Proposed Mechanism for the Long-Term Pathogenesis of Traumatic Brain Injury

DTIC Science & Technology

2015-06-04

two distinct phases: a first stage of “primary injury,” and subsequent “secondary injury.” Primary injury refers to the direct, physical disruption of...acid, is due to a number of post- injury effects, including the physical disruption of cell membranes and the impairment of energy-dependent...TBI. The pathophysiology of TBI is both complex and dynamic, involving physical injury, ischemia/reperfusion, hypoxia, glutamate excitotoxicity

Postmortem brain abnormalities of the glutamate neurotransmitter system in autism.

PubMed

Purcell, A E; Jeon, O H; Zimmerman, A W; Blue, M E; Pevsner, J

2001-11-13

Studies examining the brains of individuals with autism have identified anatomic and pathologic changes in regions such as the cerebellum and hippocampus. Little, if anything, is known, however, about the molecules that are involved in the pathogenesis of this disorder. To identify genes with abnormal expression levels in the cerebella of subjects with autism. Brain samples from a total of 10 individuals with autism and 23 matched controls were collected, mainly from the cerebellum. Two cDNA microarray technologies were used to identify genes that were significantly up- or downregulated in autism. The abnormal mRNA or protein levels of several genes identified by microarray analysis were investigated using PCR with reverse transcription and Western blotting. alpha-Amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid (AMPA)- and NMDA-type glutamate receptor densities were examined with receptor autoradiography in the cerebellum, caudate-putamen, and prefrontal cortex. The mRNA levels of several genes were significantly increased in autism, including excitatory amino acid transporter 1 and glutamate receptor AMPA 1, two members of the glutamate system. Abnormalities in the protein or mRNA levels of several additional molecules in the glutamate system were identified on further analysis, including glutamate receptor binding proteins. AMPA-type glutamate receptor density was decreased in the cerebellum of individuals with autism (p < 0.05). Subjects with autism may have specific abnormalities in the AMPA-type glutamate receptors and glutamate transporters in the cerebellum. These abnormalities may be directly involved in the pathogenesis of the disorder.

Activated microglia in acute encephalopathy with biphasic seizures and late reduced diffusion.

PubMed

Fujita, Yuji; Takanashi, Jun-Ichi; Takei, Haruka; Ota, Setsuo; Fujii, Katsunori; Sakuma, Hiroshi; Hayashi, Masaharu

2016-07-15

Acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) is the most common subtype of infectious pediatric encephalopathy in Japan. The exact pathogenesis of and the best therapeutic strategy for AESD are uncertain. We firstly performed a brain biopsy in a 2-year-old boy with AESD associated with RS viral infection, which revealed activated ameoboid microglia accumulation around degenerated neuron, and astrogliosis in the affected cortex. Glutamate released from activated microglia may play an important role in the pathogenesis of AESD, which is compatible with the previous report of magnetic resonance spectroscopy showing elevated glutamate. Copyright © 2016 Elsevier B.V. All rights reserved.

Assessing the Psychedelic “After-Glow” in Ayahuasca Users: Post-Acute Neurometabolic and Functional Connectivity Changes Are Associated with Enhanced Mindfulness Capacities

PubMed Central

Sampedro, Frederic; de la Fuente Revenga, Mario; Valle, Marta; Roberto, Natalia; Domínguez-Clavé, Elisabet; Elices, Matilde; Luna, Luís Eduardo; Crippa, José Alexandre S; Hallak, Jaime E C; de Araujo, Draulio B; Friedlander, Pablo; Barker, Steven A; Álvarez, Enrique; Soler, Joaquim; Pascual, Juan C; Feilding, Amanda

2017-01-01

Abstract Background Ayahuasca is a plant tea containing the psychedelic 5-HT2A agonist N,N-dimethyltryptamine and harmala monoamine-oxidase inhibitors. Acute administration leads to neurophysiological modifications in brain regions of the default mode network, purportedly through a glutamatergic mechanism. Post-acutely, ayahuasca potentiates mindfulness capacities in volunteers and induces rapid and sustained antidepressant effects in treatment-resistant patients. However, the mechanisms underlying these fast and maintained effects are poorly understood. Here, we investigated in an open-label uncontrolled study in 16 healthy volunteers ayahuasca-induced post-acute neurometabolic and connectivity modifications and their association with mindfulness measures. Methods Using 1H-magnetic resonance spectroscopy and functional connectivity, we compared baseline and post-acute neurometabolites and seed-to-voxel connectivity in the posterior and anterior cingulate cortex after a single ayahuasca dose. Results Magnetic resonance spectroscopy showed post-acute reductions in glutamate+glutamine, creatine, and N-acetylaspartate+N-acetylaspartylglutamate in the posterior cingulate cortex. Connectivity was increased between the posterior cingulate cortex and the anterior cingulate cortex, and between the anterior cingulate cortex and limbic structures in the right medial temporal lobe. Glutamate+glutamine reductions correlated with increases in the “nonjudging” subscale of the Five Facets Mindfulness Questionnaire. Increased anterior cingulate cortex-medial temporal lobe connectivity correlated with increased scores on the self-compassion questionnaire. Post-acute neural changes predicted sustained elevations in nonjudging 2 months later. Conclusions These results support the involvement of glutamate neurotransmission in the effects of psychedelics in humans. They further suggest that neurometabolic changes in the posterior cingulate cortex, a key region within the default

Agmatine reverses pain induced by inflammation, neuropathy, and spinal cord injury.

PubMed

Fairbanks, C A; Schreiber, K L; Brewer, K L; Yu, C G; Stone, L S; Kitto, K F; Nguyen, H O; Grocholski, B M; Shoeman, D W; Kehl, L J; Regunathan, S; Reis, D J; Yezierski, R P; Wilcox, G L

2000-09-12

Antagonists of glutamate receptors of the N-methyl-d-aspartate subclass (NMDAR) or inhibitors of nitric oxide synthase (NOS) prevent nervous system plasticity. Inflammatory and neuropathic pain rely on plasticity, presenting a clinical opportunity for the use of NMDAR antagonists and NOS inhibitors in chronic pain. Agmatine (AG), an endogenous neuromodulator present in brain and spinal cord, has both NMDAR antagonist and NOS inhibitor activities. We report here that AG, exogenously administered to rodents, decreased hyperalgesia accompanying inflammation, normalized the mechanical hypersensitivity (allodynia/hyperalgesia) produced by chemical or mechanical nerve injury, and reduced autotomy-like behavior and lesion size after excitotoxic spinal cord injury. AG produced these effects in the absence of antinociceptive effects in acute pain tests. Endogenous AG also was detected in rodent lumbosacral spinal cord in concentrations similar to those previously detected in brain. The evidence suggests a unique antiplasticity and neuroprotective role for AG in processes underlying persistent pain and neuronal injury.

Agmatine reverses pain induced by inflammation, neuropathy, and spinal cord injury

PubMed Central

Fairbanks, Carolyn A.; Schreiber, Kristin L.; Brewer, Kori L.; Yu, Chen-Guang; Stone, Laura S.; Kitto, Kelley F.; Nguyen, H. Oanh; Grocholski, Brent M.; Shoeman, Don W.; Kehl, Lois J.; Regunathan, Soundararajan; Reis, Donald J.; Yezierski, Robert P.; Wilcox, George L.

2000-01-01

Antagonists of glutamate receptors of the N-methyl-d-aspartate subclass (NMDAR) or inhibitors of nitric oxide synthase (NOS) prevent nervous system plasticity. Inflammatory and neuropathic pain rely on plasticity, presenting a clinical opportunity for the use of NMDAR antagonists and NOS inhibitors in chronic pain. Agmatine (AG), an endogenous neuromodulator present in brain and spinal cord, has both NMDAR antagonist and NOS inhibitor activities. We report here that AG, exogenously administered to rodents, decreased hyperalgesia accompanying inflammation, normalized the mechanical hypersensitivity (allodynia/hyperalgesia) produced by chemical or mechanical nerve injury, and reduced autotomy-like behavior and lesion size after excitotoxic spinal cord injury. AG produced these effects in the absence of antinociceptive effects in acute pain tests. Endogenous AG also was detected in rodent lumbosacral spinal cord in concentrations similar to those previously detected in brain. The evidence suggests a unique antiplasticity and neuroprotective role for AG in processes underlying persistent pain and neuronal injury. PMID:10984543

Transiently increased glutamate cycling in rat PFC is associated with rapid onset of antidepressant-like effects.

PubMed

Chowdhury, G M I; Zhang, J; Thomas, M; Banasr, M; Ma, X; Pittman, B; Bristow, L; Schaeffer, E; Duman, R S; Rothman, D L; Behar, K L; Sanacora, G

2017-01-01

Several drugs have recently been reported to induce rapid antidepressant effects in clinical trials and rodent models. Although the cellular mechanisms involved remain unclear, reports suggest that increased glutamate transmission contributes to these effects. Here, we demonstrate that the antidepressant-like efficacy of three unique drugs, with reported rapid onset antidepressant properties, is coupled with a rapid transient rise in glutamate cycling in the medial prefronal cortex (mPFC) of awake rats as measured by ex vivo 1 H-[ 13 C]-nuclear magnetic resonance spectroscopy. Rats were acutely pretreated by intraperitoneal injection with a single dose of ketamine (1, 3, 10, 30 and 80 mg kg -1 ), Ro 25-6981 (1, 3 and 10 mg kg -1 ), scopolamine (5, 25 and 100 μg kg -1 ) or vehicle (controls). At fixed times after drug injection, animals received an intravenous infusion of [1,6- 13 C 2 ]glucose for 8 min to enrich the amino-acid pools of the brain with 13 C, followed by rapid euthanasia. The mPFC was dissected, extracted with ethanol and metabolite 13 C enrichments were measured. We found a clear dose-dependent effect of ketamine and Ro 25-6981 on behavior and the percentage of 13 C enrichment of glutamate, glutamine and GABA (γ-aminobutyric acid). Further, we also found an effect of scopolamine on both cycling and behavior. These studies demonstrate that three pharmacologically distinct classes of drugs, clinically related through their reported rapid antidepressant actions, share the common ability to rapidly stimulate glutamate cycling at doses pertinent for their antidepressant-like efficacy. We conclude that increased cycling precedes the antidepressant action at behaviorally effective doses and suggest that the rapid change in cycling could be used to predict efficacy of novel agents or identify doses with antidepressant activity.

Glutamate-induced excitation and sensitization of nociceptors in rat glabrous skin.

PubMed

Du, J; Koltzenburg, M; Carlton, S M

2001-01-01

Anatomical studies demonstrate the presence of glutamate receptors on unmyelinated axons in peripheral cutaneous nerves. Pharmacological studies show that intraplantar injection of glutamate or glutamate agonists in the glabrous skin results in nociceptive behaviors. The present study describes a novel in vitro skin-nerve preparation using the glabrous skin from the rat hindpaw. In the first series of experiments, recordings were obtained from 141 fibers that responded to a strong mechanical search stimulus. Based on their conduction velocity they were classified as C (27%), A delta (28%) and A beta (45%) fibers. The C and A delta fibers typically exhibited sustained firing during suprathreshold mechanical stimuli whereas both rapidly (66%) and slowly (34%) adapting responses were obtained from A beta fibers. Noxious heat excited 46% of the C fibers but only 12% of the A delta units. In another series of experiments application of an ascending series of glutamate concentrations (10, 100, 300, and 1000 microM) to A delta (n=14) and C (n=19) nociceptors resulted in a significant excitation of 43% (6/14) A delta fibers and 68% (13/19) C fibers. At these concentrations, there was no excitation of A beta units (n=13). Superfusion of the receptive fields of either mechanoheat-sensitive A (AMH, n=10) or C fibers (CMH, n=12) for 2 min with 300 microM glutamate resulted in sensitization of 90% (9/10) AMH and 92% (11/12) CMH fibers to subsequent thermal stimulation. This was evidenced by a significant (1) decrease in thermal threshold for activation, (2) increase in discharge rate, and (3) increase in peak instantaneous frequencies during the second heat trial. Glutamate-induced sensitization to heat occurred in the absence of either a glutamate-induced excitation or an initial heat response. Exposure of A delta or C fibers to glutamate did not result in a decrease in von Frey thresholds. These data provide a physiological basis for the nociceptive behaviors that arise

GABA and Glutamate Uptake and Metabolism in Retinal Glial (Müller) Cells