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Sample records for astrocyte glutamine transporter

  1. Astrocytes and glutamate homoeostasis in Alzheimer's disease: a decrease in glutamine synthetase, but not in glutamate transporter-1, in the prefrontal cortex

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    Alexei Verkhratsky

    2013-10-01

    Full Text Available Astrocytes control tissue equilibrium and hence define the homoeostasis and function of the CNS (central nervous system. Being principal homoeostatic cells, astroglia are fundamental for various forms of neuropathology, including AD (Alzheimer's disease. AD is a progressive neurodegenerative disorder characterized by the loss of cognitive functions due to specific lesions in mnesic-associated regions, including the mPFC (medial prefrontal cortex. Here, we analyzed the expression of GS (glutamine synthetase and GLT-1 (glutamate transporter-1 in astrocytes in the mPFC during the progression of AD in a triple-transgenic mouse model (3xTg-AD. GS is an astrocyte-specific enzyme, responsible for the intracellular conversion of glutamate into glutamine, whereas the removal of glutamate from the extracellular space is accomplished mainly by astroglia-specific GLT-1. We found a significant decrease in the numerical density (Nv, cells/mm3 of GS-positive astrocytes from early to middle ages (1–9 months; at the age of 1 month by 17%, 6 months by 27% and 9 months by 27% when compared with control animals in parallel with a reduced expression of GS (determined by Western blots, which started at the age of 6 months and was sustained up to 12 months of age. We did not, however, find any changes in the expression of GLT-1, which implies an intact glutamate uptake mechanism. Our results indicate that the decrease in GS expression may underlie a gradual decline in the vital astrocyte-dependent glutamate–glutamine conversion pathway, which in turn may compromise glutamate homoeostasis, leading towards failures in synaptic connectivity with deficient cognition and memory.

  2. Reduced density of glutamine synthetase immunoreactive astrocytes in different cortical areas in major depression but not in bipolar I disorder

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    Hans-Gert eBernstein

    2015-08-01

    Full Text Available There is increasing evidence for disturbances within the glutamate system in patients with affective disorders, which involve disruptions of the glutamate-glutamine- cycle. The mainly astroglia-located enzyme glutamine synthetase catalyzes the ATP-dependent condensation of ammonia and glutamate to form glutamine, thus playing a central role in glutamate and glutamine homoeostasis. However, glutamine synthetase is also expressed in numerous oligodendrocytes, another class of glial cells implicated in mood disorder pathology. To learn more about the role of glia-associated glutamine synthetase in mental illnesses, we decided to find out if numerical densities of glial cells immunostained for the enzyme protein differ between subjects with major depressive disorder, bipolar disorder and psychically healthy control cases. Counting of glutamine synthetase expressing astrocytes and oligodendrocytes in eight cortical and two subcortical brain regions of subjects with mood disorder (N=14, bipolar disorder (N=15 and controls (N=16 revealed that in major depression the densities of astrocytes were significantly reduced in some cortical but not subcortical gray matter areas, whereas no changes were found for oligodendrocytes. In bipolar disorder no alterations of glutamine synthetase-immunoreactive glia were found. From our findings we conclude that (1 glutamine synthetase expressing astrocytes are prominently involved in glutamate-related disturbances in major depression, but not in bipolar disorder and (2 glutamine synthetase expressing oligodendrocytes, though being present in significant numbers in prefrontal cortical areas, play a minor (if any role in mood disorder pathology. The latter assumption is supported by findings of others showing that - at least in the mouse brain cortex - glutamine synthetase immunoreactive oligodendroglial cells are unable to contribute to the glutamate-glutamine cycle due to the complete lack of amino acid transporters

  3. Expression of glutamine transporter isoforms in cerebral cortex of rats with chronic hepatic encephalopathy

    DEFF Research Database (Denmark)

    Leke, Renata; Escobar, Thayssa D.C.; Rama Rao, Kakulavarapu V.;

    2015-01-01

    Hepatic encephalopathy (HE) is a neuropsychiatric disorder that occurs due to acute and chronic liver diseases, the hallmark of which is the increased levels of ammonia and subsequent alterations in glutamine synthesis, i.e. conditions associated with the pathophysiology of HE. Under physiological...... conditions, glutamine is fundamental for replenishment of the neurotransmitter pools of glutamate and GABA. The different isoforms of glutamine transporters play an important role in the transfer of this amino acid between astrocytes and neurons. A disturbance in the GABA biosynthetic pathways has been...... described in bile duct ligated (BDL) rats, a well characterized model of chronic HE. Considering that glutamine is important for GABA biosynthesis, altered glutamine transport and the subsequent glutamate/GABA–glutamine cycle efficacy might influence these pathways. Given this potential outcome, the aim of...

  4. Knockout of GAD65 has major impact on synaptic GABA synthesized from astrocyte-derived glutamine

    DEFF Research Database (Denmark)

    Walls, Anne Byriel; Eyjolfsson, Elvar M.; Smeland, Olav B.;

    2011-01-01

    65 for maintenance of the highly compartmentalized intracellular and intercellular GABA homeostasis, GAD65 knockout and corresponding wild-type mice were injected with [1-(13)C]glucose and the astrocyte-specific substrate [1,2-(13)C]acetate. Synthesis of GABA from glutamine in the GABAergic synapses...... cortex and hippocampus. The GABA content in both brain regions was reduced by ∼20%. Moreover, it was revealed that GAD65 is crucial for maintenance of biosynthesis of synaptic GABA particularly by direct synthesis from astrocytic glutamine via glutamate. The GAD67 was found to be important for synthesis...... of GABA from glutamine both via direct synthesis and via a pathway involving mitochondrial metabolism. Furthermore, a severe neuronal hypometabolism, involving glycolysis and tricarboxylic acid (TCA) cycle activity, was observed in cerebral cortex of GAD65 knockout mice....

  5. Dexamethasone enhances glutamine synthetase activity and reduces N-methyl-D-aspartate neurotoxicity in mixed cultures of neurons and astrocytes

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    Edith Debroas

    2015-05-01

    Full Text Available Astrocytes are claimed to protect neurons against excitotoxicity by clearing glutamate from the extracellular space and rapidly converting it into glutamine. Glutamine, is then released into the extracellular medium, taken up by neurons and transformed back into glutamate which is then stored into synaptic vesicles. Glutamine synthetase (GS, the key enzyme that governs this glutamate/glutamine cycle, is known to be upregulated by glucocorticoids. In the present work we have thus studied in parallel the effects of dexamethasone on glutamine synthetase activity and NMDA-induced neuronal death in cultures derived from the brain cortex of murine embryos. We showed that dexamethasone was able to markedly enhance GS activity in cultures of astrocytes but not in near pure neuronal cultures. The pharmacological characteristics of the dexamethasone action strongly suggest that it corresponds to a typical receptor-mediated effect. We also observed that long lasting incubation (72 h of mixed astrocyte-neuron cultures in the presence of 100 nM dexamethasone significantly reduced the toxicity of NMDA treatment. Furthermore we demonstrated that methionine sulfoximine, a selective inhibitor of GS, abolished the dexamethasone-induced increase in GS activity and also markedly potentiated NMDA toxicity. Altogether these results suggest that dexamethasone may promote neuroprotection through a stimulation of astrocyte glutamine synthetase.

  6. Activity of the lactate-alanine shuttle is independent of glutamate-glutamine cycle activity in cerebellar neuronal-astrocytic cultures

    DEFF Research Database (Denmark)

    Bak, Lasse K; Sickmann, Helle M; Schousboe, Arne;

    2004-01-01

    The glutamate-glutamine cycle describes the neuronal release of glutamate into the synaptic cleft, astrocytic uptake, and conversion into glutamine, followed by release for use as a neuronal glutamate precursor. This only explains the fate of the carbon atoms, however, and not that of the ammonia......]/[5-(15)N]glutamine (0.25 mM), and [(15)N]ammonia (0.3 mM) were used as precursors and cell extracts were analyzed by mass spectrometry. Labeling from [(15)N]alanine in glutamine, aspartate, and glutamate in cerebellar cocultures was independent of depolarization of the neurons. Employing glutamine...... with the amino group labeled ([2-(15)N]glutamine) as the precursor, an activity-dependent increase in the labeling of both glutamate and aspartate (but not alanine) was observed in the cerebellar neurons. When the amide group of glutamine was labeled ([5-(15)N]glutamine), no labeling could be detected...

  7. Glial glutamate transporter and glutamine synthetase regulate GABAergic synaptic strength in the spinal dorsal horn.

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    Jiang, Enshe; Yan, Xisheng; Weng, Han-Rong

    2012-05-01

    Decreased GABAergic synaptic strength ('disinhibition') in the spinal dorsal horn is a crucial mechanism contributing to the development and maintenance of pathological pain. However, mechanisms leading to disinhibition in the spinal dorsal horn remain elusive. We investigated the role of glial glutamate transporters (GLT-1 and GLAST) and glutamine synthetase in maintaining GABAergic synaptic activity in the spinal dorsal horn. Electrically evoked GABAergic inhibitory post-synaptic currents (eIPSCs), spontaneous IPSCs (sIPSCs) and miniature IPSCs were recorded in superficial spinal dorsal horn neurons of spinal slices from young adult rats. We used (2S,3S)-3-[3-[4-(trifluoromethyl)benzoylamino]benzyloxy]aspartate (TFB-TBOA), to block both GLT-1 and GLAST and dihydrokainic acid to block only GLT-1. We found that blockade of both GLAST and GLT-1 and blockade of only GLT-1 in the spinal dorsal horn decreased the amplitude of GABAergic eIPSCs, as well as both the amplitude and frequency of GABAergic sIPSCs or miniature IPSCs. Pharmacological inhibition of glial glutamine synthetase had similar effects on both GABAergic eIPSCs and sIPSCs. We provided evidence demonstrating that the reduction in GABAergic strength induced by the inhibition of glial glutamate transporters is due to insufficient GABA synthesis through the glutamate-glutamine cycle between astrocytes and neurons. Thus, our results indicate that deficient glial glutamate transporters and glutamine synthetase significantly attenuate GABAergic synaptic strength in the spinal dorsal horn, which may be a crucial synaptic mechanism underlying glial-neuronal interactions caused by dysfunctional astrocytes in pathological pain conditions. PMID:22339645

  8. Role of astrocytic transport processes in glutamatergic and GABAergic neurotransmission

    DEFF Research Database (Denmark)

    Schousboe, A; Sarup, A; Bak, L K;

    2004-01-01

    The fine tuning of both glutamatergic and GABAergic neurotransmission is to a large extent dependent upon optimal function of astrocytic transport processes. Thus, glutamate transport in astrocytes is mandatory to maintain extrasynaptic glutamate levels sufficiently low to prevent excitotoxic...... neuronal damage. In GABA synapses hyperactivity of astroglial GABA uptake may lead to diminished GABAergic inhibitory activity resulting in seizures. As a consequence of this the expression and functional activity of astrocytic glutamate and GABA transport is regulated in a number of ways at...

  9. Astrocytic glutamate transport regulates a Drosophila CNS synapse that lacks astrocyte ensheathment.

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    MacNamee, Sarah E; Liu, Kendra E; Gerhard, Stephan; Tran, Cathy T; Fetter, Richard D; Cardona, Albert; Tolbert, Leslie P; Oland, Lynne A

    2016-07-01

    Anatomical, molecular, and physiological interactions between astrocytes and neuronal synapses regulate information processing in the brain. The fruit fly Drosophila melanogaster has become a valuable experimental system for genetic manipulation of the nervous system and has enormous potential for elucidating mechanisms that mediate neuron-glia interactions. Here, we show the first electrophysiological recordings from Drosophila astrocytes and characterize their spatial and physiological relationship with particular synapses. Astrocyte intrinsic properties were found to be strongly analogous to those of vertebrate astrocytes, including a passive current-voltage relationship, low membrane resistance, high capacitance, and dye-coupling to local astrocytes. Responses to optogenetic stimulation of glutamatergic premotor neurons were correlated directly with anatomy using serial electron microscopy reconstructions of homologous identified neurons and surrounding astrocytic processes. Robust bidirectional communication was present: neuronal activation triggered astrocytic glutamate transport via excitatory amino acid transporter 1 (Eaat1), and blocking Eaat1 extended glutamatergic interneuron-evoked inhibitory postsynaptic currents in motor neurons. The neuronal synapses were always located within 1 μm of an astrocytic process, but none were ensheathed by those processes. Thus, fly astrocytes can modulate fast synaptic transmission via neurotransmitter transport within these anatomical parameters. J. Comp. Neurol. 524:1979-1998, 2016. © 2016 Wiley Periodicals, Inc. PMID:27073064

  10. Glutamine transport. From energy supply to sensing and beyond.

    Science.gov (United States)

    Scalise, Mariafrancesca; Pochini, Lorena; Galluccio, Michele; Indiveri, Cesare

    2016-08-01

    Glutamine is the most abundant amino acid in plasma and is actively involved in many biosynthetic and regulatory processes. It can be synthesized endogenously but becomes "conditionally essential" in physiological or pathological conditions of high proliferation rate. To accomplish its functions glutamine has to be absorbed and distributed in the whole body. This job is efficiently carried out by a network of membrane transporters that differ in transport mechanisms and energetics, belonging to families SLC1, 6, 7, 38, and possibly, 25. Some of the transporters are involved in glutamine traffic across different membranes for metabolic purposes; others are involved in specific signaling functions through mTOR. Structure/function relationships and regulatory aspects of glutamine transporters are still at infancy. In the while, insights in involvement of these transporters in cell redox control, cancer metabolism and drug interactions are arising, stimulating basic research to uncover molecular mechanisms of transport and regulation. This article is part of a Special Issue entitled 'EBEC 2016: 19th European Bioenergetics Conference, Riva del Garda, Italy, July 2-6, 2016', edited by Prof. Paolo Bernardi. PMID:26951943

  11. Inhibition of glutamine synthesis induces glutamate dehydrogenase-dependent ammonia fixation into alanine in co-cultures of astrocytes and neurons

    DEFF Research Database (Denmark)

    Dadsetan, Sherry; Bak, Lasse Kristoffer; Sørensen, Michael;

    2011-01-01

    It has been previously demonstrated that ammonia exposure of neurons and astrocytes in co-culture leads to net synthesis not only of glutamine but also of alanine. The latter process involves the concerted action of glutamate dehydrogenase (GDH) and alanine aminotransferase (ALAT). In the present...... study it was investigated if the glutamine synthetase (GS) inhibitor methionine sulfoximine (MSO) would enhance alanine synthesis by blocking the GS-dependent ammonia scavenging process. Hence, co-cultures of neurons and astrocytes were incubated for 2.5h with [U-(13)C]glucose to monitor de novo...... synthesis of alanine and glutamine in the absence and presence of 5.0 mM NH(4)Cl and 10 mM MSO. Ammonia exposure led to increased incorporation of label but not to a significant increase in the amount of these amino acids. However, in the presence of MSO, glutamine synthesis was blocked and synthesis of...

  12. Hypoosmotic swelling modifies glutamate-glutamine cycle in the cerebral cortex and in astrocyte cultures

    OpenAIRE

    Hyzinski-García, María C.; Vincent, Melanie Y.; Haskew-Layton, Renée E.; Dohare, Preeti; Keller, Richard W.; Mongin, Alexander A.

    2011-01-01

    In our previous work, we found that perfusion of the rat cerebral cortex with hypoosmotic medium triggers massive release of the excitatory amino acid L-glutamate but decreases extracellular levels of L-glutamine (R.E. Haskew-Layton et al., PLoS ONE, 3: e3543). The release of glutamate was linked to activation of volume-regulated anion channels (VRAC), while mechanism(s) responsible for alterations in extracellular glutamine remained unclear. When mannitol was added to the hypoosmotic medium ...

  13. The Rho kinase inhibitor Fasudil up-regulates astrocytic glutamate transport subsequent to actin remodelling in murine cultured astrocytes

    DEFF Research Database (Denmark)

    Lau, Cl; O'Shea, Rd; Bischof, L;

    2011-01-01

    BACKGROUND AND PURPOSE Glutamate transporters play a major role in maintaining brain homeostasis and the astrocytic transporters, EAAT1 and EAAT2, are functionally dominant. Astrocytic excitatory amino acid transporters (EAATs) play important roles in various neuropathologies wherein astrocytes...... undergo cytoskeletal changes. Astrocytic plasticity is well documented, but the interface between EAAT function, actin and the astrocytic cytoskeleton is poorly understood. Because Rho kinase (ROCK) is a key determinant of actin polymerization, we investigated the effects of ROCK inhibitors on EAAT...... activity and astrocytic morphology. EXPERIMENTAL APPROACH The functional activity of glutamate transport was determined in murine cultured astrocytes after exposure to the ROCK inhibitors Fasudil (HA-1077) and Y27632 using biochemical, molecular and morphological approaches. Cytochemical analyses assessed...

  14. The glutamate/GABA-glutamine cycle

    DEFF Research Database (Denmark)

    Bak, Lasse K; Schousboe, Arne; Waagepetersen, Helle S

    2006-01-01

    Neurons are metabolically handicapped in the sense that they are not able to perform de novo synthesis of neurotransmitter glutamate and gamma-aminobutyric acid (GABA) from glucose. A metabolite shuttle known as the glutamate/GABA-glutamine cycle describes the release of neurotransmitter glutamate...... or GABA from neurons and subsequent uptake into astrocytes. In return, astrocytes release glutamine to be taken up into neurons for use as neurotransmitter precursor. In this review, the basic properties of the glutamate/GABA-glutamine cycle will be discussed, including aspects of transport and...... metabolism. Discussions of stoichiometry, the relative role of glutamate vs. GABA and pathological conditions affecting the glutamate/GABA-glutamine cycling are presented. Furthermore, a section is devoted to the accompanying ammonia homeostasis of the glutamate/GABA-glutamine cycle, examining the possible...

  15. Substrate-dependent regulation of ascorbate transport in astrocytes

    International Nuclear Information System (INIS)

    Astrocytes possess a concentrative L-ascorbate (vitamin C) uptake mechanism involving a Na+-dependent L-ascorbate transporter in the plasma membrane. The present study examined the effects of ascorbate deprivation and supplementation on the activity of the transport system. Initial rates of L-ascorbate uptake were measured by incubating primary cultures of rat astrocytes with L-[14C]ascorbate for 1 minute at 37C. They observed that the maximal uptake rate, Vmax, rapidly (m) of the transport system for ascorbate. Vmax returned to normal following addition of L-ascorbate, but not D-isoascorbate, to the medium. The authors conclude that astrocytes adapt ascorbate transport rates to changes in substrate availability. Furthermore, the data suggest that the transport system located in the astroglial plasma membrane regulates intracellular ascorbate concentration, because changes in transport rate may compensate for regional differences and temporal fluctuations in extracellular ascorbate levels

  16. Glutamine transporters in mammalian cells and their functions in physiology and cancer.

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    Bhutia, Yangzom D; Ganapathy, Vadivel

    2016-10-01

    The SLC (solute carrier)-type transporters (~400 in number) in mammalian cells consist of 52 distinct gene families, grouped solely based on the amino acid sequence (primary structure) of the transporter proteins and not on their transport function. Among them are the transporters for amino acids. Fourteen of them, capable of transporting glutamine across the plasma membrane, are found in four families: SLC1, SLC6, SLC7, and SLC38. However, it is generally thought that the members of the SLC38 family are the principal transporters for glutamine. Some of the glutamine transporters are obligatory exchangers whereas some function as active transporters in one direction. While most glutamine transporters mediate the influx of the amino acid into cells, some actually mediate the efflux of the amino acid out of the cells. Glutamine transporters play important roles in a variety of tissues, including the liver, brain, kidney, and placenta, as clearly evident from the biological and biochemical phenotypes resulting from the deletion of specific glutamine transporters in mice. Owing to the obligatory role of glutamine in growth and proliferation of tumor cells, there is increasing attention on glutamine transporters in cancer biology as potential drug targets for cancer treatment. Selective blockers of certain glutamine transporters might be effective in preventing the entry of glutamine and other important amino acids into tumor cells, thus essentially starving these cells to death. This could represent the beginning of a new era in the discovery of novel anticancer drugs with a previously unexplored mode of action. This article is part of a Special Issue entitled: Mitochondrial Channels edited by Pierre Sonveaux, Pierre Maechler and Jean-Claude Martinou. PMID:26724577

  17. Effect of exercise on glutamine synthesis and transport in skeletal muscle from rats.

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    dos Santos, Ronaldo V T; Caperuto, Erico C; de Mello, Marco T; Batista, Miguel L; Rosa, Luis F B P C

    2009-08-01

    1. Reductions in plasma glutamine are observed after prolonged exercise. Three hypotheses can explain such a decrease: (i) high demand by the liver and kidney; (ii) impaired release from muscles; and (iii) decreased synthesis in skeletal muscle. The present study investigated the effects of exercise on glutamine synthesis and transport in rat skeletal muscle. 2. Rats were divided into three groups: (i) sedentary (SED; n = 12); (ii) rats killed 1 h after the last exercise bout (EX-1; n = 15); and (iii) rats killed 24 h after the last exercise bout (EX-24; n = 15). Rats in the trained groups swam 1 h/day, 5 days/week for 6 weeks with a load equivalent to 5.5% of their bodyweight. 3. Plasma glutamine and insulin were lower and corticosterone was higher in EX-1 compared with SED rats (P exercise (EX-24), plasma glutamine was restored to levels seen in SED rats, whereas insulin levels were higher (P glutamine, glutamate and ammonia levels were lower in EX-24 than in SED and EX-1 rats (P glutamine synthetase (GS) activity was increased in EX-1 and was decreased in EX-24 compared with SED rats (both P glutamine concentration in EX-1 is not mediated by GS or glutamine transport in skeletal muscle. However, 24 h after exercise, lower GS may contribute to the decrease in glutamine concentration in muscle. PMID:19207717

  18. Astrocytes.

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    Kimelberg, Harold K.; Norenberg, Michael D.

    1989-01-01

    Describes the astrocytes' function as equal partners with neurons in both the normal and the abnormal brain. Discusses the developmental scaffolds, inert scar tissue, Huntington's disease, psychiatric disorders, and the identification of these brain cells. (RT)

  19. Transport of 3-hydroxybutyrate by cultured rat brain astrocytes

    International Nuclear Information System (INIS)

    Studies by a number of investigators have shown that 3-hydroxybutyrate is a preferred energy substrate for brain during early development. Since recent studies by the authors group suggest that the utilization of oxidizable substrates by brain may be regulated in part by transport across the plasma membrane, the authors investigated the transport of [3H] D- and L-3-hydroxybutyrate and 3-hydroxy-[3-14C] butyrate by primary cultures of rat brain astrocytes. The data is consistent with the hypothesis that 3-hydroxybutyrate is taken up into cultured rat brain astrocytes by both diffusion and a carrier mediated transport system, and further support the concept that transport at the cellular level contributes to the regulation of substrate utilization by brain cells

  20. Proton-dependent glutamine uptake by aphid bacteriocyte amino acid transporter ApGLNT1.

    Science.gov (United States)

    Price, Daniel R G; Wilson, Alex C C; Luetje, Charles W

    2015-10-01

    Aphids house large populations of the gammaproteobacterial symbiont Buchnera aphidicola in specialized bacteriocyte cells. The combined biosynthetic capability of the holobiont (Acyrthosiphon pisum and Buchnera) is sufficient for biosynthesis of all twenty protein coding amino acids, including amino acids that animals alone cannot synthesize; and that are present at low concentrations in A. pisum's plant phloem sap diet. Collaborative holobiont amino acid biosynthesis depends on glutamine import into bacteriocytes, which serves as a nitrogen-rich amino donor for biosynthesis of other amino acids. Recently, we characterized A. pisum glutamine transporter 1 (ApGLNT1), a member of the amino acid/auxin permease family, as the dominant bacteriocyte plasma membrane glutamine transporter. Here we show ApGLNT1 to be structurally and functionally related to mammalian proton-dependent amino acid transporters (PATs 1-4). Using functional expression in Xenopus laevis oocytes, combined with two-electrode voltage clamp electrophysiology we demonstrate that ApGLNT1 is electrogenic and that glutamine induces large inward currents. ApGLNT1 glutamine induced currents are dependent on external glutamine concentration, proton (H+) gradient across the membrane, and membrane potential. Based on these transport properties, ApGLNT1-mediated glutamine uptake into A. pisum bacteriocytes can be regulated by changes in either proton gradients across the plasma membrane or membrane potential. PMID:26028424

  1. SAT1, a glutamine transporter, is preferentially expressed in GABAergic neurons

    Directory of Open Access Journals (Sweden)

    Tom Tallak Solbu

    2010-02-01

    Full Text Available Subsets of GABAergic neurons are able to maintain high frequency discharge patterns, which requires efficient replenishment of the releasable pool of GABA. Although glutamine is considered a preferred precursor of GABA, the identity of transporters involved in glutamine uptake by GABAergic neurons remains elusive. Molecular analyses revealed that SAT1 (Slc38a1 features system A characteristics with a preferential affinity for glutamine, and that SAT1 mRNA expression is associated with GABAergic neurons. By generating specific antibodies against SAT1 we show that this glutamine carrier is particularly enriched in GABAergic neurons. Cellular SAT1 distribution resembles that of GAD67, an essential GABA synthesis enzyme, suggesting that SAT1 can be involved in translocating glutamine into GABAergic neurons to facilitate inhibitory neurotransmitter generation.

  2. Prefrontal changes in the glutamate-glutamine cycle and neuronal/glial glutamate transporters in depression with and without suicide

    NARCIS (Netherlands)

    Zhao, J; Verwer, R W H; van Wamelen, D J; Qi, X-R; Gao, S-F; Lucassen, P J; Swaab, D F

    2016-01-01

    There are indications for changes in glutamate metabolism in relation to depression or suicide. The glutamate-glutamine cycle and neuronal/glial glutamate transporters mediate the uptake of the glutamate and glutamine. The expression of various components of the glutamate-glutamine cycle and the neu

  3. Modulation of Astrocyte Glutamate Transporters Decreases Seizures in a Mouse Model of Tuberous Sclerosis Complex

    OpenAIRE

    Zeng, Ling-Hui; Bero, Adam W.; Bo ZHANG; Holtzman, David M.; Wong, Michael

    2010-01-01

    Astrocyte dysfunction may contribute to epileptogenesis and other neurological deficits in Tuberous Sclerosis Complex (TSC). In particular, decreased expression and function of astrocyte glutamate transporters have been implicated in causing elevated extracellular glutamate levels, neuronal death, and epilepsy in a mouse model of TSC (Tsc1GFAPCKO mice), involving inactivation of the Tsc1 gene primarily in astrocytes. Here, we tested whether pharmacological induction of astrocyte glutamate tra...

  4. Glutamine deprivation enhances antitumor activity of 3-bromopyruvate through the stabilization of monocarboxylate transporter-1.

    Science.gov (United States)

    Cardaci, Simone; Rizza, Salvatore; Filomeni, Giuseppe; Bernardini, Roberta; Bertocchi, Fabio; Mattei, Maurizio; Paci, Maurizio; Rotilio, Giuseppe; Ciriolo, Maria Rosa

    2012-09-01

    Anticancer drug efficacy might be leveraged by strategies to target certain biochemical adaptations of tumors. Here we show how depriving cancer cells of glutamine can enhance the anticancer properties of 3-bromopyruvate, a halogenated analog of pyruvic acid. Glutamine deprival potentiated 3-bromopyruvate chemotherapy by increasing the stability of the monocarboxylate transporter-1, an effect that sensitized cells to metabolic oxidative stress and autophagic cell death. We further elucidated mechanisms through which resistance to chemopotentiation by glutamine deprival could be circumvented. Overall, our findings offer a preclinical proof-of-concept for how to employ 3-bromopyruvate or other monocarboxylic-based drugs to sensitize tumors to chemotherapy. PMID:22773663

  5. Substrate regulation of ascorbate transport activity in astrocytes

    International Nuclear Information System (INIS)

    Astrocytes possess a concentrative L-ascorbate (vitamin C) uptake mechanism involving a Na(+)-dependent L-ascorbate transporter located in the plasma membrane. The present experiments examined the effects of deprivation and supplementation of extracellular L-ascorbate on the activity of this transport system. Initial rates of L-ascorbate uptake were measured by incubating primary cultures of rat astrocytes with L-[14C]ascorbate for 1 min at 37 degrees C. We observed that the apparent maximal rate of uptake (Vmax) increased rapidly (less than 1 h) when cultured cells were deprived of L-ascorbate. In contrast, there was no change in the apparent affinity of the transport system for L-[14C]ascorbate. The increase in Vmax was reversed by addition of L-ascorbate, but not D-isoascorbate, to the medium. The effects of external ascorbate on ascorbate transport activity were specific in that preincubation of cultures with L-ascorbate did not affect uptake of 2-deoxy-D-[3H(G)]glucose. We conclude that the astroglial ascorbate transport system is modulated by changes in substrate availability. Regulation of transport activity may play a role in intracellular ascorbate homeostasis by compensating for regional differences and temporal fluctuations in external ascorbate levels

  6. Dopamine denervation of the prefrontal cortex increases expression of the astrocytic glutamate transporter GLT-1

    OpenAIRE

    Vollbrecht, Peter J.; Simmler, Linda D.; Blakely, Randy D.; Deutch, Ariel Y.

    2014-01-01

    Both dopamine and glutamate are critically involved in cognitive processes such as working memory. Astrocytes, which express dopamine receptors, are essential elements in the termination of glutamatergic signaling: the astrocytic glutamate transporter GLT-1 is responsible for >90% of cortical glutamate uptake. The effect of dopamine depletion on glutamate transporters in the prefrontal cortex (PFC) is unknown. In an effort to determine if astrocytes are a locus of cortical dopamine-glutamate ...

  7. Astrocyte-neuron lactate transport is required for long-term memory formation

    OpenAIRE

    Suzuki, Akinobu; Stern, Sarah A.; Bozdagi, Ozlem; Huntley, George W.; Walker, Ruth H.; Magistretti, Pierre J.; Alberini, Cristina M

    2011-01-01

    We report that in the rat hippocampus learning leads to a significant increase in extracellular lactate levels, which derive from glycogen, an energy reserve selectively localized in astrocytes. Astrocytic glycogen breakdown and lactate release are essential for long-term but not short-term memory formation, and for the maintenance of long-term potentiation (LTP) of synaptic strength elicited in-vivo. Disrupting the expression of the astrocytic lactate transporters monocarboxylate transporter...

  8. Leptin regulates glutamate and glucose transporters in hypothalamic astrocytes

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    Fuente-Martín, Esther; García-Cáceres, Cristina; Granado, Miriam; de Ceballos, María L.; Sánchez-Garrido, Miguel Ángel; Sarman, Beatrix; Liu, Zhong-Wu; Dietrich, Marcelo O.; Tena-Sempere, Manuel; Argente-Arizón, Pilar; Díaz, Francisca; Argente, Jesús; Horvath, Tamas L.; Chowen, Julie A.

    2012-01-01

    Glial cells perform critical functions that alter the metabolism and activity of neurons, and there is increasing interest in their role in appetite and energy balance. Leptin, a key regulator of appetite and metabolism, has previously been reported to influence glial structural proteins and morphology. Here, we demonstrate that metabolic status and leptin also modify astrocyte-specific glutamate and glucose transporters, indicating that metabolic signals influence synaptic efficacy and glucose uptake and, ultimately, neuronal function. We found that basal and glucose-stimulated electrical activity of hypothalamic proopiomelanocortin (POMC) neurons in mice were altered in the offspring of mothers fed a high-fat diet. In adulthood, increased body weight and fasting also altered the expression of glucose and glutamate transporters. These results demonstrate that whole-organism metabolism alters hypothalamic glial cell activity and suggest that these cells play an important role in the pathology of obesity. PMID:23064363

  9. Membrane transporters for the special amino acid glutamine: Structure/function relationships and relevance to human health.

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    Pochini, Lorena; Scalise, Mariafrancesca; Galluccio, Michele; Indiveri, Cesare

    2014-08-01

    Glutamine together with glucose is essential for body’s homeostasis. It is the most abundant amino acid and is involved in many biosynthetic, regulatory and energy production processes. Several membrane transporters which differ in transport modes, ensure glutamine homeostasis by coordinating its absorption, reabsorption and delivery to tissues. These transporters belong to different protein families, are redundant and ubiquitous. Their classification, originally based on functional properties, has recently been associated with the SLC nomenclature. Function of glutamine transporters is studied in cells over-expressing the transporters or, more recently in proteoliposomes harboring the proteins extracted from animal tissues or over-expressed in microorganisms. The role of the glutamine transporters is linked to their transport modes and coupling with Na+ and H+. Most transporters share specificity for other neutral or cationic amino acids. Na+-dependent co-transporters efficiently accumulate glutamine while antiporters regulate the pools of glutamine and other amino acids. The most acknowledged glutamine transporters belong to the SLC1, 6, 7 and 38 families. The members involved in the homeostasis are the co-transporters B0AT1 and the SNAT members 1, 2, 3, 5 and 7; the antiporters ASCT2, LAT1 and 2. The last two are associated to the ancillary CD98 protein. Some information on regulation of the glutamine transporters exist, which, however, need to be deepened. No information at all is available on structures, besides some homology models obtained using similar bacterial transporters as templates. Some models of rat and human glutamine transporters highlight very similar structures between the orthologues. Moreover the presence of glycosylation and/or phosphorylation sites located at the extracellular or intracellular faces has been predicted. ASCT2 and LAT1 are over-expressed in several cancers, thus representing potential targets for pharmacological intervention.

  10. Regulation of the Glutamate-Glutamine Transport System by Intracellular pH in Streptococcus lactis

    NARCIS (Netherlands)

    POOLMAN, B; HELLINGWERF, KJ; KONINGS, WN

    1987-01-01

    Various methods of manipulation of the intracellular pH in Streptococcus lactis result in a unique relationship between the rate of glutamate and glutamine transport and the cytoplasmic pH. The initial rate of glutamate uptake by S. lactis cells increases more than 30-fold when the intracellular pH

  11. Redistribution of monocarboxylate transporter 2 on the surface of astrocytes in the human epileptogenic hippocampus

    DEFF Research Database (Denmark)

    Lauritzen, Fredrik; Heuser, Kjell; de Lanerolle, Nihal C;

    2012-01-01

    astrocyte endfeet, respectively, facilitate the transport of monocarboxylates and protons across cell membranes. Recently, we reported that the density of MCT1 protein is reduced on endothelial cells and increased on astrocyte plasma membranes in the hippocampal formation in patients with MTLE and in...... several animal models of the disorder. Because the perivascular astrocyte endfeet comprise an important part of the neurovascular unit, we now assessed the distribution of the MCT2 in hippocampal formations in TLE patients with (MTLE) or without hippocampal sclerosis (non-MTLE). Light microscopic...... perivascular astrocyte endfeet. Interestingly, the loss of MCT2 on astrocyte endfeet in MTLE (n = 3) was accompanied by an upregulation of the protein on astrocyte membranes facing synapses in the neuropil, when compared with non-MTLE (n = 3). We propose that the altered distribution of MCT1 and MCT2 in TLE...

  12. Role of astrocytic glutamate transporter in alcohol use disorder.

    Science.gov (United States)

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

    2016-03-22

    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

  13. N-acetylcysteine prevents HIV gp 120-related damage of human cultured astrocytes: correlation with glutamine synthase dysfunction

    Directory of Open Access Journals (Sweden)

    Costa Nicola

    2007-12-01

    Full Text Available Abstract Background HIV envelope gp 120 glycoprotein is released during active HIV infection of brain macrophages thereby generating inflammation and oxidative stress which contribute to the development of the AIDS-Dementia Complex (ADC. Gp120 has also been found capable to generate excitotoxic effect on brain tissue via enhancement of glutamatergic neurotransmission, leading to neuronal and astroglial damage, though the mechanism is still to be better understood. Here we investigated on the effect of N-acetylcysteine (NAC, on gp120-induced damage in human cultured astroglial cells and the possible contribution of gp120-related reacting oxygen species (ROS in the imbalanced activity of glutamine synthase (GS, the enzyme that metabolizes glutamate into glutamine within astroglial cells playing a neuroprotective role in brain disorders. Results Incubation of Lipari human cultured astroglial cells with gp 120 (0.1–10 nM produced a significant reduction of astroglial cell viability and apoptosis as evaluated by TUNEL reaction and flow cytometric analysis (FACS. This effect was accompanied by lipid peroxidation as detected by means of malondialdehyde assay (MDA. In addition, gp 120 reduced both glutamine concentration in astroglial cell supernatants and GS expression as detected by immunocytochemistry and western blotting analysis. Pre-treatment of cells with NAC (0.5–5 mM, dose-dependently antagonised astroglial apoptotic cell death induced by gp 120, an effect accompanied by significant attenuation of MDA accumulation. Furthermore, both effects were closely associated with a significant recovery of glutamine levels in cell supernatants and by GS expression, thus suggesting that overproduction of free radicals might contribute in gp 120-related dysfunction of GS in astroglial cells. Conclusion In conclusion, the present experiments demonstrate that gp 120 is toxic to astroglial cells, an effect accompanied by lipid peroxidation and by altered

  14. Spatial relationship of lectin-labelled extracellular matrix and glutamine synthetase-immunoreactive astrocytes in rat cortical forebrain regions.

    OpenAIRE

    Derouiche, A.; Härtig, W.; Brauer, K; Brückner, G.

    1996-01-01

    Extracellular matrix proteoglycans have previously been revealed by immunocytochemical and lectin-histochemical methods as distinct perineuronal nets in the microenvironment of different types of neurons, but also as a diffuse stain throughout the neuropil in region-dependent patterns. Ultrastructural investigations of perineuronal nets in subcortical regions have demonstrated glycan components in the close vicinity of astrocyte processes, suggesting that the extracellular matrix contributes ...

  15. Advances in the research of intestinal glutamine transporters%肠道谷氨酰胺转运载体研究进展

    Institute of Scientific and Technical Information of China (English)

    吴炜; 彭曦

    2014-01-01

    Glutamine,the most abundant amino acid in bloodstream,is the preferred fuel source for enterocytes.Glutamine exerts its functions through the activity of its transporters,which are located in cytomembrane,to transport it into or out of intestinal epithelial cells.Intestine is the primary center for glutamine metabolism in the body.As ASCT2 and B0AT1 are the most important glutamine transporters in the intestine,it wound be helpful to gain the knowledge of the structure,function,and pathologic changes and control strategy of the two transporters in order to have a better understanding of the metabolism and function of glutamine.

  16. The Glutamine-Glutamate/GABA Cycle

    DEFF Research Database (Denmark)

    Walls, Anne B; Waagepetersen, Helle S; Bak, Lasse Kristoffer;

    2015-01-01

    The operation of a glutamine-glutamate/GABA cycle in the brain consisting of the transfer of glutamine from astrocytes to neurons and neurotransmitter glutamate or GABA from neurons to astrocytes is a well-known concept. In neurons, glutamine is not only used for energy production and protein...... synthesis, as in other cells, but is also an essential precursor for biosynthesis of amino acid neurotransmitters. An excellent tool for the study of glutamine transfer from astrocytes to neurons is [(14)C]acetate or [(13)C]acetate and the glial specific enzyme inhibitors, i.e. the glutamine synthetase...... information about glutamine transfer. The present review will give information about glutamine trafficking and the tools used to map it as exemplified by discussions of published work employing brain cell cultures as well as intact animals. It will be documented that considerably more glutamine is transferred...

  17. Lipopolysaccharide-Induced Apoptosis of Astrocytes: Therapeutic Intervention by Minocycline.

    Science.gov (United States)

    Sharma, Arpita; Patro, Nisha; Patro, Ishan K

    2016-05-01

    Astrocytes are most abundant glial cell type in the brain and play a main defensive role in central nervous system against glutamate-induced toxicity by virtue of numerous transporters residing in their membranes and an astrocyte-specific enzyme glutamine synthetase (GS). In view of that, a dysregulation in the astrocytic activity following an insult may result in glutamate-mediated toxicity accompanied with astrocyte and microglial activation. The present study suggests that the lipopolysaccharide (LPS)-induced inflammation results in significant astrocytic apoptosis compared to other cell types in hippocampus and minocycline could not efficiently restrict the glutamate-mediated toxicity and apoptosis of astrocytes. Upon LPS exposure 76 % astrocytes undergo degeneration followed by 44 % oligodendrocytes, 26 % neurons and 10 % microglia. The pronounced astrocytic apoptosis resulted from the LPS-induced glutamate excitotoxicity leading to their hyperactivation as evident from their hypertrophied morphology, glutamate transporter 1 upregulation and downregulation of GS. Therapeutic minocycline treatment to LPS-infused rats efficiently restricted the inflammatory response and degeneration of other cell types but could not significantly combat with the apoptosis of astrocytes. Our study demonstrates a novel finding on cellular degeneration in the hippocampus revealing more of astrocytic death and suggests a more careful consideration on the protective efficacy of minocycline. PMID:26188416

  18. Luminal leptin inhibits L-glutamine transport in rat small intestine: involvement of ASCT2 and B0AT1

    OpenAIRE

    Ducroc, R. (Robert); Sakar, Y. (Yassine); Fanjul, C. (Carmen); Barber, A. (Ana); Bado, A.; Lostao, M.P. (María Pilar)

    2010-01-01

    International audience l-glutamine is the primary metabolic fuel for enterocytes. Glutamine from the diet is transported into the absorptive cells by two sodium-dependent neutral amino acid transporters present at the apical membrane: ASCT2/SLC1A5 and B(0)AT1/SLC6A19. We have demonstrated that leptin is secreted into the stomach lumen after a meal and modulates the transport of sugars after binding to its receptors located at the brush border of the enterocytes. The present study was desig...

  19. PEPT2-mediated transport of 5-aminolevulinic acid and carnosine in astrocytes

    OpenAIRE

    Xiang, Jianming; Hu, Yongjun; Smith, David E.; Keep, Richard F

    2006-01-01

    5-Aminolevulinic acid (ALA) and carnosine have important physiological and pathophysiological roles in the CNS. Both are substrates for the proton-coupled oligopeptide transporter PEPT2. The purpose of the current study was to determine the importance of PEPT2 in the uptake of ALA and carnosine in rat and mouse (PEPT2+/+ and PEPT2−/−) cultured neonatal astrocytes. Although neonatal astrocytes are known to express PEPT2, its quantitative importance in the transport of these compounds is not kn...

  20. Functional deficits in glutamate transporters and astrocyte biophysical properties in a rodent model of focal cortical dysplasia

    Directory of Open Access Journals (Sweden)

    John J Hablitz

    2014-12-01

    Full Text Available Cortical dysplasia is associated with intractable epilepsy and developmental delay in young children. Recent work with the rat freeze-induced focal cortical dysplasia (FCD model has demonstrated that hyperexcitability in the dysplastic cortex is due in part to higher levels of extracellular glutamate. Astrocyte glutamate transporters play a pivotal role in cortical maintaining extracellular glutamate concentrations. Here we examined the function of astrocytic glutamate transporters in a FCD model in rats. Neocortical freeze lesions were made in postnatal day (PN 1 rat pups and whole cell electrophysiological recordings and biochemical studies were performed at PN 21-28. Synaptically evoked glutamate transporter currents in astrocytes showed a near 10-fold reduction in amplitude compared to sham operated controls. Astrocyte glutamate transporter currents from lesioned animals were also significantly reduced when challenged exogenously applied glutamate. Reduced astrocytic glutamate transport clearance contributed to increased NMDA receptor-mediated current decay kinetics in lesioned animals. The electrophysiological profile of astrocytes in the lesion group was also markedly changed compared to sham operated animals. Control astrocytes demonstrate large-amplitude linear leak currents in response to voltage-steps whereas astrocytes in lesioned animals demonstrated significantly smaller voltage-activated inward and outward currents. Significant decreases in astrocyte resting membrane potential and increases in input resistance were observed in lesioned animals. However, Western blotting, immunohistochemistry and quantitative PCR demonstrated no differences in the expression of the astrocytic glutamate transporter GLT-1 in lesioned animals relative to controls. These data suggest that, in the absence of changes in protein or mRNA expression levels, functional changes in astrocytic glutamate transporters contribute to neuronal hyperexcitability in

  1. The glutamate aspartate transporter (GLAST) mediates L-glutamate-stimulated ascorbate-release via swelling-activated anion channels in cultured neonatal rodent astrocytes.

    Science.gov (United States)

    Lane, Darius J R; Lawen, Alfons

    2013-03-01

    Vitamin C (ascorbate) plays important neuroprotective and neuromodulatory roles in the mammalian brain. Astrocytes are crucially involved in brain ascorbate homeostasis and may assist in regenerating extracellular ascorbate from its oxidised forms. Ascorbate accumulated by astrocytes can be released rapidly by a process that is stimulated by the excitatory amino acid, L-glutamate. This process is thought to be neuroprotective against excitotoxicity. Although of potential clinical interest, the mechanism of this stimulated ascorbate-release remains unknown. Here, we report that primary cultures of mouse and rat astrocytes release ascorbate following initial uptake of dehydroascorbate and accumulation of intracellular ascorbate. Ascorbate-release was not due to cellular lysis, as assessed by cellular release of the cytosolic enzyme lactate dehydrogenase, and was stimulated by L-glutamate and L-aspartate, but not the non-excitatory amino acid L-glutamine. This stimulation was due to glutamate-induced cellular swelling, as it was both attenuated by hypertonic and emulated by hypotonic media. Glutamate-stimulated ascorbate-release was also sensitive to inhibitors of volume-sensitive anion channels, suggesting that the latter may provide the conduit for ascorbate efflux. Glutamate-stimulated ascorbate-release was not recapitulated by selective agonists of either ionotropic or group I metabotropic glutamate receptors, but was completely blocked by either of two compounds, TFB-TBOA and UCPH-101, which non-selectively and selectively inhibit the glial Na(+)-dependent excitatory amino acid transporter, GLAST, respectively. These results suggest that an impairment of astrocytic ascorbate-release may exacerbate neuronal dysfunction in neurodegenerative disorders and acute brain injury in which excitotoxicity and/or GLAST deregulation have been implicated. PMID:22886112

  2. Altered microtubule dynamics and vesicular transport in mouse and human MeCP2-deficient astrocytes.

    Science.gov (United States)

    Delépine, Chloé; Meziane, Hamid; Nectoux, Juliette; Opitz, Matthieu; Smith, Amos B; Ballatore, Carlo; Saillour, Yoann; Bennaceur-Griscelli, Annelise; Chang, Qiang; Williams, Emily Cunningham; Dahan, Maxime; Duboin, Aurélien; Billuart, Pierre; Herault, Yann; Bienvenu, Thierry

    2016-01-01

    Rett syndrome (RTT) is a rare X-linked neurodevelopmental disorder, characterized by normal post-natal development followed by a sudden deceleration in brain growth with progressive loss of acquired motor and language skills, stereotypic hand movements and severe cognitive impairment. Mutations in the methyl-CpG-binding protein 2 (MECP2) cause more than 95% of classic cases. Recently, it has been shown that the loss of Mecp2 from glia negatively influences neurons in a non-cell-autonomous fashion, and that in Mecp2-null mice, re-expression of Mecp2 preferentially in astrocytes significantly improved locomotion and anxiety levels, restored respiratory abnormalities to a normal pattern and greatly prolonged lifespan compared with globally null mice. We now report that microtubule (MT)-dependent vesicle transport is altered in Mecp2-deficient astrocytes from newborn Mecp2-deficient mice compared with control wild-type littermates. Similar observation has been made in human MECP2 p.Arg294* iPSC-derived astrocytes. Importantly, administration of Epothilone D, a brain-penetrant MT-stabilizing natural product, was found to restore MT dynamics in Mecp2-deficient astrocytes and in MECP2 p.Arg294* iPSC-derived astrocytes in vitro. Finally, we report that relatively low weekly doses of Epothilone D also partially reversed the impaired exploratory behavior in Mecp2(308/y) male mice. These findings represent a first step toward the validation of an innovative treatment for RTT. PMID:26604147

  3. Glutamine supplementation.

    Science.gov (United States)

    Wernerman, Jan

    2011-01-01

    Intravenous glutamine supplementation is standard care when parenteral nutrition is given for critical illness. There are data of a reduced mortality when glutamine supplementation is given. In addition, standard commercial products for parenteral nutrition do not contain any glutamine due to glutamine instability in aqueous solutions. For the majority of critical ill patients who are fed enterally, the available evidence is insufficient to recommend glutamine supplementation. Standard formulation of enteral nutrition contains some glutamine: 2-4 g/L. However, this dose is insufficient to normalize glutamine plasma concentration.Plasma concentration of glutamine is low in many patients with critical illness and a low level is an independent risk factor for mortality. A low plasma glutamine concentration is the best indicator of glutamine depletion. Data are emerging about how the endogenous production of glutamine is regulated. We know that skeletal muscle is the major producer of glutamine and that a part of the profound depletion of skeletal muscle seen in critical illness is a reflection of the need to produce glutamine.Glutamine is utilized in rapidly dividing cells in the splanchnic area. Quantitatively most glutamine is oxidized, but the availability of glutamine in surplus is important for the de novo synthesis of nucleotides and necessary for cell division and protein synthesis. More knowledge about the regulation of the endogenous production of glutamine is needed to outline better guidelines for glutamine supplementation in the future. PMID:21906372

  4. Molecular identification and characterisation of the glycine transporter (GLYT1) and the glutamine/glutamate transporter (ASCT2) in the rat lens

    DEFF Research Database (Denmark)

    Lim, Julie; Lorentzen, Karen Axelgaard; Kistler, Joerg;

    2006-01-01

    Glutathione (GSH) is an essential antioxidant required for the maintenance of lens transparency. In the lens, GSH is maintained at unusually high concentrations as a result of direct GSH uptake and/or intracellular de novo synthesis from its precursor amino acids; cysteine, glycine and glutamine...... Transporters (EAATs) in the rat lens. In this current study, we have identified and localised additional uptake systems that contribute to GSH synthesis. Transcripts for GLYT1 (glycine transporter) and ASCT2 (glutamine/glutamate transporter) were detected in rat lens fiber cells using the reverse transcription...... fiber cells of the lens core. The molecular identification and localisation of GLYT1 and ASCT2 in the lens suggests that these transporters may be responsible for the uptake of the precursor amino acids, glycine and glutamine, which are involved in GSH synthesis. Moreover, the presence of ASCT2 in the...

  5. Cell-specific abnormalities of glutamate transporters in schizophrenia: sick astrocytes and compensating relay neurons?

    Science.gov (United States)

    McCullumsmith, R E; O'Donovan, S M; Drummond, J B; Benesh, F S; Simmons, M; Roberts, R; Lauriat, T; Haroutunian, V; Meador-Woodruff, J H

    2016-06-01

    Excitatory amino-acid transporters (EAATs) bind and transport glutamate, limiting spillover from synapses due to their dense perisynaptic expression primarily on astroglia. Converging evidence suggests that abnormalities in the astroglial glutamate transporter localization and function may underlie a disease mechanism with pathological glutamate spillover as well as alterations in the kinetics of perisynaptic glutamate buffering and uptake contributing to dysfunction of thalamo-cortical circuits in schizophrenia. We explored this hypothesis by performing cell- and region-level studies of EAAT1 and EAAT2 expression in the mediodorsal nucleus of the thalamus in an elderly cohort of subjects with schizophrenia. We found decreased protein expression for the typically astroglial-localized glutamate transporters in the mediodorsal and ventral tier nuclei. We next used laser-capture microdissection and quantitative polymerase chain reaction to assess cell-level expression of the transporters and their splice variants. In the mediodorsal nucleus, we found lower expression of transporter transcripts in a population of cells enriched for astrocytes, and higher expression of transporter transcripts in a population of cells enriched for relay neurons. We confirmed expression of transporter protein in neurons in schizophrenia using dual-label immunofluorescence. Finally, the pattern of transporter mRNA and protein expression in rodents treated for 9 months with antipsychotic medication suggests that our findings are not due to the effects of antipsychotic treatment. We found a compensatory increase in transporter expression in neurons that might be secondary to a loss of transporter expression in astrocytes. These changes suggest a profound abnormality in astrocyte functions that support, nourish and maintain neuronal fidelity and synaptic activity. PMID:26416546

  6. Glutamine supplementation

    OpenAIRE

    Wernerman, Jan

    2011-01-01

    Intravenous glutamine supplementation is standard care when parenteral nutrition is given for critical illness. There are data of a reduced mortality when glutamine supplementation is given. In addition, standard commercial products for parenteral nutrition do not contain any glutamine due to glutamine instability in aqueous solutions. For the majority of critical ill patients who are fed enterally, the available evidence is insufficient to recommend glutamine supplementation. Standard formul...

  7. Functional changes in glutamate transporters and astrocyte biophysical properties in a rodent model of focal cortical dysplasia

    OpenAIRE

    Campbell, Susan L.; Hablitz, John J.; Olsen, Michelle L.

    2014-01-01

    Cortical dysplasia is associated with intractable epilepsy and developmental delay in young children. Recent work with the rat freeze-induced focal cortical dysplasia (FCD) model has demonstrated that hyperexcitability in the dysplastic cortex is due in part to higher levels of extracellular glutamate. Astrocyte glutamate transporters play a pivotal role in cortical maintaining extracellular glutamate concentrations. Here we examined the function of astrocytic glutamate transporters in a FCD ...

  8. Functional deficits in glutamate transporters and astrocyte biophysical properties in a rodent model of focal cortical dysplasia

    OpenAIRE

    Hablitz, John J.; Olsen, Michelle L.

    2014-01-01

    Cortical dysplasia is associated with intractable epilepsy and developmental delay in young children. Recent work with the rat freeze-induced focal cortical dysplasia (FCD) model has demonstrated that hyperexcitability in the dysplastic cortex is due in part to higher levels of extracellular glutamate. Astrocyte glutamate transporters play a pivotal role in cortical maintaining extracellular glutamate concentrations. Here we examined the function of astrocytic glutamate transporters in a FCD ...

  9. Brain-derived neurotrophic factor (BDNF) enhances GABA transport by modulating the trafficking of GABA transporter-1 (GAT-1) from the plasma membrane of rat cortical astrocytes

    DEFF Research Database (Denmark)

    Vaz, Sandra H; Jørgensen, Trine Nygaard; Cristóvão-Ferreira, Sofia;

    2011-01-01

    /MAPK pathway and requires active adenosine A(2A) receptors. Transport through GAT-3 is not affected by BDNF. To elucidate if BDNF affects trafficking of GAT-1 in astrocytes, we generated and infected astrocytes with a functional mutant of the rat GAT-1 (rGAT-1) in which the hemagglutinin (HA) epitope was...

  10. Promotion of both proliferation and neuronal differentiation in pluripotent P19 cells with stable overexpression of the glutamine transporter slc38a1.

    Directory of Open Access Journals (Sweden)

    Masato Ogura

    Full Text Available BACKGROUND: We previously demonstrated the functional expression in newborn rat neocortical astrocytes of glutamine transporter (GlnT = slc38a1 believed to predominate in neurons over astroglia in the brain. In order to evaluate the possible role of this transporter in neurogenesis, we attempted to establish stable transfectants of GlnT in mouse embryonal carcinoma P19 cells endowed to proliferate for self-renewal and differentiate into progeny cells such as neurons and astroglia, in addition to in vitro pharmacological profiling of the green tea ingredient theanine, which is shown to be a potent inhibitor of glutamine transport mediated by GlnT in cultured neurons and astroglia. METHODOLOGY/PRINCIPAL FINDINGS: The full-length coding region of rat GlnT was inserted into a vector for gene transfection along with selection by G418, followed by culture with all-trans retinoic acid under floating conditions and subsequent dispersion for spontaneous differentiation under adherent conditions. Stable overexpression of GlnT led to marked increases in the size of round spheres formed during the culture for 4 days and 3-(4,5-dimethyl-2-thiazolyl-2,5-diphenyl-2H-tetrazolium bromide reduction, with concomitant promotion of subsequent differentiation into cells immunoreactive for a neuronal marker protein. In these stable GlnT transfectants before differentiation, drastic upregulation was seen for mRNA expression of several proneural genes with a basic helix-loop-helix domain such as NeuroD1. Although a drastic increase was seen in NeuroD1 promoter activity in stable GlnT transfectants, theanine doubled NeuroD1 promoter activity in stable transfectants of empty vector (EV, without affecting the promoter activity already elevated in GlnT transfectants. Similarly, theanine promoted cellular proliferation and neuronal differentiation in stable EV transfectants, but failed to further stimulate the acceleration of both proliferation and neuronal differentiation

  11. A novel human astrocyte cell line (A735) with astrocyte-specific neurotransmitter function.

    Science.gov (United States)

    Price, T N; Burke, J F; Mayne, L V

    1999-05-01

    Studies of brain cell function and physiology are hampered by the limited availability of immortal human brain-derived cell lines, as a result of the technical difficulties encountered in establishing immortal human cells in culture. In this study, we demonstrate the application of recombinant DNA vectors expressing SV40 T antigen for the development of immortal human cell cultures, with morphological, growth, and functional properties of astrocytes. Primary human astrocytes were transfected with the SV40 T antigen expression vectors, pSV3neo or p735.6, and cultures were established with an extended lifespan. One of these cultures gave rise to an immortal cell line, designated A735. All the human SV40-derived lines retained morphological features and growth properties of type 1 astrocytes. Immunohistochemical studies and Western blot analysis of the intermediate filament proteins and glutamine synthetase demonstrated a differentiated but immature astrocyte phenotype. Transport of gamma-amino butyric acid and glutamate were examined and found to be by a glial-specific mechanism, consistent with the cell lines' retaining aspects of normal glial function. We conclude that methods based on the use of SV40 T antigen can successfully immortalize human astrocytes, retaining key astrocyte functions, but T antigen-induced proliferation appeared to interfere with expression of glial fibrillary acidic protein. We believe A735 is the first documented nontumor-derived human glial cell line which is immortal. PMID:10475274

  12. Copper Metabolism of Astrocytes

    OpenAIRE

    Ralf Dringen; Scheiber, Ivo F.; Julian FB Mercer

    2013-01-01

    This short review will summarize the current knowledge on the uptake, storage, and export of copper ions by astrocytes and will address the potential roles of astrocytes in copper homeostasis in the normal and diseased brain. Astrocytes in culture efficiently accumulate copper by processes that include both the copper transporter Ctr1 and Ctr1-independent mechanisms. Exposure of astrocytes to copper induces an increase in cellular glutathione (GSH) content as well as synthesis of metallothion...

  13. Reduced expression of glutamate transporter EAAT2 and impaired glutamate transport in human primary astrocytes exposed to HIV-1 or gp120

    International Nuclear Information System (INIS)

    L-Glutamate is the major excitatory neurotransmitter in the brain. Astrocytes maintain low levels of synaptic glutamate by high-affinity uptake and defects in this function may lead to neuronal cell death by excitotoxicity. We tested the effects of HIV-1 and its envelope glycoprotein gp120 upon glutamate uptake and expression of glutamate transporters EAAT1 and EAAT2 in fetal human astrocytes in vitro. Astrocytes isolated from fetal tissues between 16 and 19 weeks of gestation expressed EAAT1 and EAAT2 RNA and proteins as detected by Northern blot analysis and immunoblotting, respectively, and the cells were capable of specific glutamate uptake. Exposure of astrocytes to HIV-1 or gp120 significantly impaired glutamate uptake by the cells, with maximum inhibition within 6 h, followed by gradual decline during 3 days of observation. HIV-1-infected cells showed a 59% reduction in Vmax for glutamate transport, indicating a reduction in the number of active transporter sites on the cell surface. Impaired glutamate transport after HIV-1 infection or gp120 exposure correlated with a 40-70% decline in steady-state levels of EAAT2 RNA and protein. EAAT1 RNA and protein levels were less affected. Treatment of astrocytes with tumor necrosis factor-α (TNF-α) decreased the expression of both EAAT1 and EAAT2, but neither HIV-1 nor gp120 were found to induce TNF-α production by astrocytes. These findings demonstrate that HIV-1 and gp120 induce transcriptional downmodulation of the EAAT2 transporter gene in human astrocytes and coordinately attenuate glutamate transport by the cells. Reduction of the ability of HIV-1-infected astrocytes to take up glutamate may contribute to the development of neurological disease

  14. Neuronal activity mediated regulation of glutamate transporter GLT-1 surface diffusion in rat astrocytes in dissociated and slice cultures.

    Science.gov (United States)

    Al Awabdh, Sana; Gupta-Agarwal, Swati; Sheehan, David F; Muir, James; Norkett, Rosalind; Twelvetrees, Alison E; Griffin, Lewis D; Kittler, Josef T

    2016-07-01

    The astrocytic GLT-1 (or EAAT2) is the major glutamate transporter for clearing synaptic glutamate. While the diffusion dynamics of neurotransmitter receptors at the neuronal surface are well understood, far less is known regarding the surface trafficking of transporters in subcellular domains of the astrocyte membrane. Here, we have used live-cell imaging to study the mechanisms regulating GLT-1 surface diffusion in astrocytes in dissociated and brain slice cultures. Using GFP-time lapse imaging, we show that GLT-1 forms stable clusters that are dispersed rapidly and reversibly upon glutamate treatment in a transporter activity-dependent manner. Fluorescence recovery after photobleaching and single particle tracking using quantum dots revealed that clustered GLT-1 is more stable than diffuse GLT-1 and that glutamate increases GLT-1 surface diffusion in the astrocyte membrane. Interestingly, the two main GLT-1 isoforms expressed in the brain, GLT-1a and GLT-1b, are both found to be stabilized opposed to synapses under basal conditions, with GLT-1b more so. GLT-1 surface mobility is increased in proximity to activated synapses and alterations of neuronal activity can bidirectionally modulate the dynamics of both GLT-1 isoforms. Altogether, these data reveal that astrocytic GLT-1 surface mobility, via its transport activity, is modulated during neuronal firing, which may be a key process for shaping glutamate clearance and glutamatergic synaptic transmission. GLIA 2016;64:1252-1264. PMID:27189737

  15. Crucial role of astrocytes in temporal lobe epilepsy.

    Science.gov (United States)

    Steinhäuser, C; Grunnet, M; Carmignoto, G

    2016-05-26

    Astrocytes sense and respond to synaptic activity through activation of different neurotransmitter receptors and transporters. Astrocytes are also coupled by gap junctions, which allow these cells to redistribute through the glial network the K(+) ions excessively accumulated at sites of intense neuronal activity. Work over the past two decades has revealed important roles for astrocytes in brain physiology, and it is therefore not surprising that recent studies unveiled their involvement in the etiology of neurological disorders such as epilepsy. Investigation of specimens from patients with pharmacoresistant temporal lobe epilepsy and epilepsy models revealed alterations in expression, localization and function of astrocytic connexins, K(+) and water channels. In addition, disturbed gliotransmission as well as malfunction of glutamate transporters and of the astrocytic glutamate- and adenosine-converting enzymes - glutamine synthetase and adenosine kinase, respectively - have been observed in epileptic tissues. Accordingly, increasing evidence indicates that dysfunctional astrocytes are crucially involved in processes leading to epilepsy. These new insights might foster the search for new targets for the development of new, more efficient anti-epileptogenic therapies. PMID:25592426

  16. The amino acid transporters of the glutamate/GABA-glutamine cycle and their impact on insulin and glucagon secretion

    Directory of Open Access Journals (Sweden)

    MonicaJenstad

    2013-12-01

    Full Text Available Intercellular communication is pivotal in optimising and synchronising cellular responses to keep internal homeostasis and to respond adequately to external stimuli. In the central nervous system (CNS, glutamatergic and GABAergic signals are postulated to be dependent on the glutamate/GABA-glutamine (GGG cycle for vesicular loading of neurotransmitters, for inactivating the signal and for the replenishment of the neurotransmitters. Islets of Langerhans release the hormones insulin and glucagon, but share similarities with CNS cells in for example transcriptional control of development and differentiation, and chromatin methylation. Interestingly, proteins involved in the CNS in secretion of the neurotransmitters and emitting their responses as well as the regulation of these processes, are also found in islet cells. Moreover, high levels of glutamate, GABA and glutamine and their respective vesicular and plasma membrane transporters have been shown in the islet cells and there is emerging support for these amino acids and their transporters playing important roles in the maturation and secretion of insulin and glucagon. In this review, we will discuss the feasibility of recent data in the field in relation to the biophysical properties of the transporters (Slc1, Slc17, Slc32 and Slc38 and physiology of hormone secretion in islets of Langerhans.

  17. Homeostasis of the astrocytic glutamate transporter GLT-1 is altered in mouse models of Lafora disease.

    Science.gov (United States)

    Muñoz-Ballester, Carmen; Berthier, Arnaud; Viana, Rosa; Sanz, Pascual

    2016-06-01

    Lafora disease (LD, OMIM 254780) is a fatal rare disorder characterized by epilepsy and neurodegeneration. Although in recent years a lot of information has been gained on the molecular basis of the neurodegeneration that accompanies LD, the molecular basis of epilepsy is poorly understood. Here, we present evidence indicating that the homeostasis of glutamate transporter GLT-1 (EAAT2) is compromised in mouse models of LD. Our results indicate that primary astrocytes from LD mice have reduced capacity of glutamate transport, probably because they present a reduction in the levels of the glutamate transporter at the plasma membrane. On the other hand, the overexpression in cellular models of laforin and malin, the two proteins related to LD, results in an accumulation of GLT-1 (EAAT2) at the plasma membrane and in a severe reduction of the ubiquitination of the transporter. All these results suggest that the laforin/malin complex slows down the endocytic recycling of the GLT-1 (EAAT2) transporter. Since, defects in the function of this transporter lead to excitotoxicity and epilepsy, we suggest that the epilepsy that accompanies LD could be due, at least in part, to deficiencies in the function of the GLT-1 (EAAT2) transporter. PMID:26976331

  18. Characterization of Amino Acid Profile and Enzymatic Activity in Adult Rat Astrocyte Cultures.

    Science.gov (United States)

    Souza, Débora Guerini; Bellaver, Bruna; Hansel, Gisele; Arús, Bernardo Assein; Bellaver, Gabriela; Longoni, Aline; Kolling, Janaina; Wyse, Angela T S; Souza, Diogo Onofre; Quincozes-Santos, André

    2016-07-01

    Astrocytes are multitasking players in brain complexity, possessing several receptors and mechanisms to detect, participate and modulate neuronal communication. The functionality of astrocytes has been mainly unraveled through the study of primary astrocyte cultures, and recently our research group characterized a model of astrocyte cultures derived from adult Wistar rats. We, herein, aim to characterize other basal functions of these cells to explore the potential of this model for studying the adult brain. To characterize the astrocytic phenotype, we determined the presence of GFAP, GLAST and GLT 1 proteins in cells by immunofluorescence. Next, we determined the concentrations of thirteen amino acids, ATP, ADP, adenosine and calcium in astrocyte cultures, as well as the activities of Na(+)/K(+)-ATPase and acetylcholine esterase. Furthermore, we assessed the presence of the GABA transporter 1 (GAT 1) and cannabinoid receptor 1 (CB 1) in the astrocytes. Cells demonstrated the presence of glutamine, consistent with their role in the glutamate-glutamine cycle, as well as glutamate and D-serine, amino acids classically known to act as gliotransmitters. ATP was produced and released by the cells and ADP was consumed. Calcium levels were in agreement with those reported in the literature, as were the enzymatic activities measured. The presence of GAT 1 was detected, but the presence of CB 1 was not, suggesting a decreased neuroprotective capacity in adult astrocytes under in vitro conditions. Taken together, our results show cellular functionality regarding the astrocytic role in gliotransmission and neurotransmitter management since they are able to produce and release gliotransmitters and to modulate the cholinergic and GABAergic systems. PMID:26915106

  19. Multi-walled carbon nanotubes affect drug transport across cell membrane in rat astrocytes

    Energy Technology Data Exchange (ETDEWEB)

    Chen Xiao [School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Hangkong Road 13, 430030, Wuhan (China); Schluesener, Hermann J, E-mail: mornsmile@yahoo.com [Institute of Brain Research, University of Tuebingen, Calwerstrasse 3, D-72076, Tuebingen (Germany)

    2010-03-12

    The impact of carbon nanotubes on the cell membrane is an aspect of particular importance and interest in the study of carbon nanotubes' interactions with living systems. One of the many functions of the cell membrane is to execute substance transport into and out of the cell. We investigated the influence of multi-walled carbon nanotubes (MWCNTs) on the transport of several compounds across in the cell membrane of rat astrocytes using flow cytometry. These compounds are fluorescein diacetate, carboxyfluorescein diacetate, rhodamine 123 and doxorubicin, which are prosubstrate/substrates of multidrug transporter proteins. Results showed that MWCNTs significantly inhibited cellular uptake of doxorubicin but not the other drugs and the mode of loading made a significant difference in doxorubicin uptake. Retention of fluorescein, carboxyfluorescein and rhodamine 123 was remarkably higher in MWCNT-exposed cells after an efflux period. A kinetics study also demonstrated slower efflux of intracellular fluorescein and rhodamine 123. Data presented in this paper suggest that MWCNTs could affect drug transport across cell membranes. The implications of the findings are discussed.

  20. Multi-walled carbon nanotubes affect drug transport across cell membrane in rat astrocytes

    Science.gov (United States)

    Chen, Xiao; Schluesener, Hermann J.

    2010-03-01

    The impact of carbon nanotubes on the cell membrane is an aspect of particular importance and interest in the study of carbon nanotubes' interactions with living systems. One of the many functions of the cell membrane is to execute substance transport into and out of the cell. We investigated the influence of multi-walled carbon nanotubes (MWCNTs) on the transport of several compounds across in the cell membrane of rat astrocytes using flow cytometry. These compounds are fluorescein diacetate, carboxyfluorescein diacetate, rhodamine 123 and doxorubicin, which are prosubstrate/substrates of multidrug transporter proteins. Results showed that MWCNTs significantly inhibited cellular uptake of doxorubicin but not the other drugs and the mode of loading made a significant difference in doxorubicin uptake. Retention of fluorescein, carboxyfluorescein and rhodamine 123 was remarkably higher in MWCNT-exposed cells after an efflux period. A kinetics study also demonstrated slower efflux of intracellular fluorescein and rhodamine 123. Data presented in this paper suggest that MWCNTs could affect drug transport across cell membranes. The implications of the findings are discussed.

  1. Multi-walled carbon nanotubes affect drug transport across cell membrane in rat astrocytes

    International Nuclear Information System (INIS)

    The impact of carbon nanotubes on the cell membrane is an aspect of particular importance and interest in the study of carbon nanotubes' interactions with living systems. One of the many functions of the cell membrane is to execute substance transport into and out of the cell. We investigated the influence of multi-walled carbon nanotubes (MWCNTs) on the transport of several compounds across in the cell membrane of rat astrocytes using flow cytometry. These compounds are fluorescein diacetate, carboxyfluorescein diacetate, rhodamine 123 and doxorubicin, which are prosubstrate/substrates of multidrug transporter proteins. Results showed that MWCNTs significantly inhibited cellular uptake of doxorubicin but not the other drugs and the mode of loading made a significant difference in doxorubicin uptake. Retention of fluorescein, carboxyfluorescein and rhodamine 123 was remarkably higher in MWCNT-exposed cells after an efflux period. A kinetics study also demonstrated slower efflux of intracellular fluorescein and rhodamine 123. Data presented in this paper suggest that MWCNTs could affect drug transport across cell membranes. The implications of the findings are discussed.

  2. Pre-conditioning induces the precocious differentiation of neonatal astrocytes to enhance their neuroprotective properties

    Directory of Open Access Journals (Sweden)

    Sandra J Hewett

    2011-07-01

    Full Text Available Hypoxic preconditioning reprogrammes the brain's response to subsequent H/I (hypoxia–ischaemia injury by enhancing neuroprotective mechanisms. Given that astrocytes normally support neuronal survival and function, the purpose of the present study was to test the hypothesis that a hypoxic preconditioning stimulus would activate an adaptive astrocytic response. We analysed several functional parameters 24 h after exposing rat pups to 3 h of systemic hypoxia (8% O2. Hypoxia increased neocortical astrocyte maturation as evidenced by the loss of GFAP (glial fibrillary acidic protein-positive cells with radial morphologies and the acquisition of multipolar GFAP-positive cells. Interestingly, many of these astrocytes had nuclear S100B. Accompanying their differentiation, there was increased expression of GFAP, GS (glutamine synthetase, EAAT-1 (excitatory amino acid transporter-1; also known as GLAST, MCT-1 (monocarboxylate transporter-1 and ceruloplasmin. A subsequent H/I insult did not result in any further astrocyte activation. Some responses were cell autonomous, as levels of GS and MCT-1 increased subsequent to hypoxia in cultured forebrain astrocytes. In contrast, the expression of GFAP, GLAST and ceruloplasmin remained unaltered. Additional experiments utilized astrocytes exposed to exogenous dbcAMP (dibutyryl-cAMP, which mimicked several aspects of the preconditioning response, to determine whether activated astrocytes could protect neurons from subsequent excitotoxic injury. dbcAMP treatment increased GS and glutamate transporter expression and function, and as hypothesized, protected neurons from glutamate excitotoxicity. Taken altogether, these results indicate that a preconditioning stimulus causes the precocious differentiation of astrocytes and increases the acquisition of multiple astrocytic functions that will contribute to the neuroprotection conferred by a sublethal preconditioning stress.

  3. Regulation of astrocyte glutamate transporter-1 (GLT1) and aquaporin-4 (AQP4) expression in a model of epilepsy.

    Science.gov (United States)

    Hubbard, Jacqueline A; Szu, Jenny I; Yonan, Jennifer M; Binder, Devin K

    2016-09-01

    Astrocytes regulate extracellular glutamate and water homeostasis through the astrocyte-specific membrane proteins glutamate transporter-1 (GLT1) and aquaporin-4 (AQP4), respectively. The role of astrocytes and the regulation of GLT1 and AQP4 in epilepsy are not fully understood. In this study, we investigated the expression of GLT1 and AQP4 in the intrahippocampal kainic acid (IHKA) model of temporal lobe epilepsy (TLE). We used real-time polymerase chain reaction (RT-PCR), Western blot, and immunohistochemical analysis at 1, 4, 7, and 30days after kainic acid-induced status epilepticus (SE) to determine hippocampal glial fibrillary acidic protein (GFAP, a marker for reactive astrocytes), GLT1, and AQP4 expression changes during the development of epilepsy (epileptogenesis). Following IHKA, all mice had SE and progressive increases in GFAP immunoreactivity and GFAP protein expression out to 30days post-SE. A significant initial increase in dorsal hippocampal GLT1 immunoreactivity and protein levels were observed 1day post SE and followed by a marked downregulation at 4 and 7days post SE with a return to near control levels by 30days post SE. AQP4 dorsal hippocampal protein expression was significantly downregulated at 1day post SE and was followed by a gradual return to baseline levels with a significant increase in ipsilateral protein levels by 30days post SE. Transient increases in GFAP and AQP4 mRNA were also observed. Our findings suggest that specific molecular changes in astrocyte glutamate transporters and water channels occur during epileptogenesis in this model, and suggest the novel therapeutic strategy of restoring glutamate and water homeostasis. PMID:27155358

  4. Effect of 8-bromo-cAMP and dexamethasone on glutamate metabolism in rat astrocytes

    International Nuclear Information System (INIS)

    Glutamine synthetase (GS) activity in cultured rat astrocytes was measured in extracts and compared to the intracellular rate of glutamine synthesis by intact control astrocytes or astrocytes exposed to 1 mM 8-bromo-cAMP (8Br-cAMP) + 1 microM dexamethasone (DEX) for 4 days. GS activity in extracts of astrocytes treated with 8Br-cAMP + DEX was 7.5 times greater than the activity in extracts of control astrocytes. In contrast, the intracellular rate of glutamine synthesis by intact cells increased only 2-fold, suggesting that additional intracellular effectors regulate the expression of GS activity inside the intact cell. The rate of glutamine synthesis by astrocytes was 4.3 times greater in MEM than in HEPES buffered Hank's salts. Synthesis of glutamine by intact astrocytes cultured in MEM was independent of the external glutamine or ammonia concentrations but was increased by higher extracellular glutamate concentrations. In studies with intact astrocytes 80% of the original [U-14C]glutamate was recovered in the medium as radioactive glutamine, 2-3% as aspartate, and 7% as glutamate after 2 hours for both control and treated astrocytes. The results suggest: (1) astrocytes are highly efficient in the conversion of glutamate to glutamine; (2) induction of GS activity increases the rate of glutamate conversion to glutamine by astrocytes and the rate of glutamine release into the medium; (3) endogenous intracellular regulators of GS activity control the flux of glutamate through this enzymatic reaction; and (4) the composition of the medium alters the rate of glutamine synthesis from external glutamate

  5. Dysfunctional TCA-Cycle Metabolism in Glutamate Dehydrogenase Deficient Astrocytes.

    Science.gov (United States)

    Nissen, Jakob D; Pajęcka, Kamilla; Stridh, Malin H; Skytt, Dorte M; Waagepetersen, Helle S

    2015-12-01

    Astrocytes take up glutamate in the synaptic area subsequent to glutamatergic transmission by the aid of high affinity glutamate transporters. Glutamate is converted to glutamine or metabolized to support intermediary metabolism and energy production. Glutamate dehydrogenase (GDH) and aspartate aminotransferase (AAT) catalyze the reversible reaction between glutamate and α-ketoglutarate, which is the initial step for glutamate to enter TCA cycle metabolism. In contrast to GDH, AAT requires a concomitant interconversion of oxaloacetate and aspartate. We have investigated the role of GDH in astrocyte glutamate and glucose metabolism employing siRNA mediated knock down (KD) of GDH in cultured astrocytes using stable and radioactive isotopes for metabolic mapping. An increased level of aspartate was observed upon exposure to [U-(13) C]glutamate in astrocytes exhibiting reduced GDH activity. (13) C Labeling of aspartate and TCA cycle intermediates confirmed that the increased amount of aspartate is associated with elevated TCA cycle flux from α-ketoglutarate to oxaloacetate, i.e. truncated TCA cycle. (13) C Glucose metabolism was elevated in GDH deficient astrocytes as observed by increased de novo synthesis of aspartate via pyruvate carboxylation. In the absence of glucose, lactate production from glutamate via malic enzyme was lower in GDH deficient astrocytes. In conclusions, our studies reveal that metabolism via GDH serves an important anaplerotic role by adding net carbon to the TCA cycle. A reduction in GDH activity seems to cause the astrocytes to up-regulate activity in pathways involved in maintaining the amount of TCA cycle intermediates such as pyruvate carboxylation as well as utilization of alternate substrates such as branched chain amino acids. PMID:26221781

  6. Copper Metabolism of Astrocytes

    Directory of Open Access Journals (Sweden)

    Ralf eDringen

    2013-03-01

    Full Text Available This short review will summarize the current knowledge on the uptake, storage and export of copper ions by astrocytes and will address the potential roles of astrocytes in copper homeostasis in the normal and diseased brain. Astrocytes in culture efficiently accumulate copper by processes that include both the copper transporter Ctr1 and Ctr1-independent mechanisms. Exposure of astrocytes to copper induces an increase in cellular glutathione (GSH content as well as synthesis of metallothioneins, suggesting that excess of copper is stored as complex with GSH and in metallothioneins. Furthermore, exposure of astrocytes to copper accelerates the release of GSH and of glycolytically generated lactate. Astrocytes are able to export copper and express the Menkes protein ATP7A. This protein undergoes reversible, copper-dependent trafficking between the trans-Golgi network and vesicular structures. The ability of astrocytes to efficiently take up, store and export copper suggests that astrocytes play a key role in the supply of neurons with copper and that astrocytes should be considered as target for therapeutic inventions that aim to correct disturbances in brain copper homeostasis.

  7. Induction of inducible nitric oxide synthase expression in ammonia-exposed cultured astrocytes is coupled to increased arginine transport by upregulated y(+) LAT2 transporter.

    Science.gov (United States)

    Zielińska, Magdalena; Milewski, Krzysztof; Skowrońska, Marta; Gajos, Anna; Ziemińska, Elżbieta; Beręsewicz, Andrzej; Albrecht, Jan

    2015-12-01

    One of the aspects of ammonia toxicity to brain cells is increased production of nitric oxide (NO) by NO synthases (NOSs). Previously we showed that ammonia increases arginine (Arg) uptake in cultured rat cortical astrocytes specifically via y(+) L amino acid transport system, by activation of its member, a heteromeric y(+) LAT2 transporter. Here, we tested the hypothesis that up-regulation of y(+) LAT2 underlies ammonia-dependent increase of NO production via inducible NOS (iNOS) induction, and protein nitration. Treatment of rat cortical astrocytes for 48 with 5 mM ammonium chloride ('ammonia') (i) increased the y(+) L-mediated Arg uptake, (ii) raised the expression of iNOS and endothelial NOS (eNOS), (iii) stimulated NO production, as manifested by increased nitrite+nitrate (Griess) and/or nitrite alone (chemiluminescence), and consequently, (iv) evoked nitration of tyrosine residues of proteins in astrocytes. Except for the increase of eNOS, all the above described effects of ammonia were abrogated by pre-treatment of astrocytes with either siRNA silencing of the Slc7a6 gene coding for y(+) LAT2 protein, or antibody to y(+) LAT2, indicating their strict coupling to y(+) LAT2 activity. Moreover, induction of y(+) LAT2 expression by ammonia was sensitive to Nf-κB inhibitor, BAY 11-7085, linking y(+) LAT2 upregulation to the Nf-κB activation in this experimental setting as reported earlier and here confirmed. Importantly, ammonia did not affect y(+) LAT2 expression nor y(+) L-mediated Arg uptake activity in the cultured cerebellar neurons, suggesting astroglia-specificity of the above described mechanism. The described coupling of up-regulation of y(+) LAT2 transporter with iNOS in ammonia-exposed astrocytes may be considered as a mechanism to ensure NO supply for protein nitration. Ammonia (NH4(+) ) increases the expression and activity of the L-arginine (Arg) transporter (Arg/neutral amino acids [NAA] exchanger) y(+) LAT2 in cultured rat cortical astrocytes

  8. Regulation of the High-Affinity Nitrate Transport System in Wheat Roots by Exogenous Abscisic Acid and Glutamine

    Institute of Scientific and Technical Information of China (English)

    Chao Cai; Xue-Qiang Zhao; Yong-Guan Zhu; Bin Li; Yi-Ping Tong; Zhen-Sheng Li

    2007-01-01

    Nitrate is a major nitrogen (N) source for most crops.Nitrate uptake by root cells is a key step of nitrogen metabolism and has been widely studied at the physiological and molecular levels.Understanding how nitrate uptake is regulated will help us engineer crops with improved nitrate uptake efficiency.The present study investigated the regulation of the high-affinity nitrate transport system (HATS) by exogenous abscisic acid (ABA) and glutamine (Gin) in wheat (Triticum aestivum L.) roots.Wheat seedlings grown in nutrient solution containing 2 mmollL nitrate as the only nitrogen source for 2 weeks were deprived of N for 4d and were then transferred to nutrient solution containing 50 μmol/L ABA, and 1 mmol/L Gin in the presence or absence of 2 mmol/L nitrate for 0, 0.5, 1, 2, 4, and 8 h.Treated wheat plants were then divided into two groups.One group of plants was used to investigate the mRNA levels of the HATS components NRT2 and NAR2 genes in roots through semi-quantitative RT-PCR approach, and the other set of plants were used to measure high-affinity nitrate influx rates in a nutrient solution containing 0.2 mmol/L 15 N-labeled nitrate.The results showed that exogenous ABA induced the expression of the TaNRT2.1, TaNRT2.2, TaNRT2.3, TaNAR2.1, and TaNAR2.2 genes in roots when nitrate was not present in the nutrient solution, but did not further enhance the induction of these genes by nitrate.Glutamine, which has been shown to inhibit the expression of NRT2 genes when nitrate is present in the growth media, did not inhibit this induction.When Gin was supplied to a nitrate-free nutrient solution, the expression of these five genes in roots was induced.These results imply that the inhibition by Gin of NRT2 expression occurs only when nitrate is present in the growth media.Although exogenous ABA and Gin induced HATS genes in the roots of wheat, they did not induce nitrate influx.

  9. Glutamate metabolism of astrocytes during hyperbaric oxygen exposure and its effects on central nervous system oxygen toxicity.

    Science.gov (United States)

    Chen, Yu-Liang; Li, Dan; Wang, Zhong-Zhuang; Xu, Wei-Gang; Li, Run-Ping; Zhang, Jun-Dong

    2016-01-20

    Hyperbaric oxygen (HBO) has been used widely in many underwater missions and clinical work. However, exposure to extremely high oxygen pressure may cause central nervous system oxygen toxicity (CNS-OT). The regulation of astrocyte glutamate metabolism is closely related to epilepsy. This study aimed to observe the effects of HBO exposure on glutamate metabolism in astrocytes and confirm the role of glutamate metabolism in CNS-OT. Anesthetized rats were exposed to 5 atmosphere absolute HBO for 80 min and microdialysis samples of brain interstitial fluid were continuously collected. Extracellular glutamate and glutamine concentrations were also detected. Freely moving rats were exposed to HBO of the same pressure for 20 min and glutamine synthetase (GS) activity in brain tissues was measured. Finally, we observed the effects of different doses of drugs related to glutamate metabolism on the latency of CNS-OT. Results showed that HBO exposure significantly increased glutamate content, whereas glutamine content was significantly reduced. Moreover, HBO exposure significantly reduced GS activity. Glutamate transporter-1 (GLT-1) selective antagonist ceftriaxone prolonged CNS-OT latency, whereas GLT-1 selective inhibitor dihydrokainate shortened CNS-OT latency. In summary, HBO exposure improved glutamate concentration and reduced glutamine concentration by inhibition of GS activity. GLT-1 activation also participated in the prevention of HBO-induced CNS-OT. Our research will provide a potential new target to terminate or attenuate CNS-OT. PMID:26619231

  10. Inactivation of the glutamine/amino acid transporter ASCT2 by 1,2,3-dithiazoles: proteoliposomes as a tool to gain insights in the molecular mechanism of action and of antitumor activity

    Energy Technology Data Exchange (ETDEWEB)

    Oppedisano, Francesca [Dipartimento di Biologia Cellulare Università della Calabria, via P. Bucci 4 c, 87036 Arcavacata di Rende (CS) (Italy); Catto, Marco [Dipartimento Farmaco-Chimico, Università degli Studi “Aldo Moro,”, via Orabona 4, 70125 Bari (Italy); Koutentis, Panayiotis A. [Department of Chemistry, University of Cyprus, P.O. Box 20537, 1678 Nicosia (Cyprus); Nicolotti, Orazio [Dipartimento Farmaco-Chimico, Università degli Studi “Aldo Moro,”, via Orabona 4, 70125 Bari (Italy); Pochini, Lorena [Dipartimento di Biologia Cellulare Università della Calabria, via P. Bucci 4 c, 87036 Arcavacata di Rende (CS) (Italy); Koyioni, Maria [Department of Chemistry, University of Cyprus, P.O. Box 20537, 1678 Nicosia (Cyprus); Introcaso, Antonellina [Dipartimento Farmaco-Chimico, Università degli Studi “Aldo Moro,”, via Orabona 4, 70125 Bari (Italy); Michaelidou, Sophia S. [Department of Chemistry, University of Cyprus, P.O. Box 20537, 1678 Nicosia (Cyprus); Carotti, Angelo, E-mail: carotti@farmchim.uniba.it [Dipartimento Farmaco-Chimico, Università degli Studi “Aldo Moro,”, via Orabona 4, 70125 Bari (Italy); Indiveri, Cesare, E-mail: indiveri@unical.it [Dipartimento di Biologia Cellulare Università della Calabria, via P. Bucci 4 c, 87036 Arcavacata di Rende (CS) (Italy)

    2012-11-15

    The ASCT2 transport system catalyses a sodium-dependent antiport of glutamine and other neutral amino acids which is involved in amino acid metabolism. A library of 1,2,3-dithiazoles was designed, synthesized and evaluated as inhibitors of the glutamine/amino acid ASCT2 transporter in the model system of proteoliposomes reconstituted with the rat liver transporter. Fifteen of the tested compounds at concentration of 20 μM or below, inhibited more than 50% the glutamine/glutamine antiport catalysed by the reconstituted transporter. These good inhibitors bear a phenyl ring with electron withdrawing substituents. The inhibition was reversed by 1,4-dithioerythritol indicating that the effect was likely owed to the formation of mixed sulfides with the protein's Cys residue(s). A dose–response analysis of the most active compounds gave IC{sub 50} values in the range of 3–30 μM. Kinetic inhibition studies indicated a non-competitive inhibition, presumably because of a potential covalent interaction of the dithiazoles with cysteine thiol groups that are not located at the substrate binding site. Indeed, computational studies using a homology structural model of ASCT2 transporter, suggested as possible binding targets, Cys-207 or Cys-210, that belong to the CXXC motif of the protein. -- Highlights: ► Non‐competitive inhibition of ASCT2 by 1,2,3-dithiazoles was studied in proteoliposomes. ► Different 1,2,3-dithiazoles were synthesized and evaluated as transporter inhibitors. ► Many compounds potently inhibited the glutamine/glutamine antiport catalyzed by ASCT2. ► The inhibition was reversed by DTE indicating reaction with protein Cys. ► The most active compounds gave IC{sub 50} in the range of 3–30 μM.

  11. Inactivation of the glutamine/amino acid transporter ASCT2 by 1,2,3-dithiazoles: proteoliposomes as a tool to gain insights in the molecular mechanism of action and of antitumor activity

    International Nuclear Information System (INIS)

    The ASCT2 transport system catalyses a sodium-dependent antiport of glutamine and other neutral amino acids which is involved in amino acid metabolism. A library of 1,2,3-dithiazoles was designed, synthesized and evaluated as inhibitors of the glutamine/amino acid ASCT2 transporter in the model system of proteoliposomes reconstituted with the rat liver transporter. Fifteen of the tested compounds at concentration of 20 μM or below, inhibited more than 50% the glutamine/glutamine antiport catalysed by the reconstituted transporter. These good inhibitors bear a phenyl ring with electron withdrawing substituents. The inhibition was reversed by 1,4-dithioerythritol indicating that the effect was likely owed to the formation of mixed sulfides with the protein's Cys residue(s). A dose–response analysis of the most active compounds gave IC50 values in the range of 3–30 μM. Kinetic inhibition studies indicated a non-competitive inhibition, presumably because of a potential covalent interaction of the dithiazoles with cysteine thiol groups that are not located at the substrate binding site. Indeed, computational studies using a homology structural model of ASCT2 transporter, suggested as possible binding targets, Cys-207 or Cys-210, that belong to the CXXC motif of the protein. -- Highlights: ► Non‐competitive inhibition of ASCT2 by 1,2,3-dithiazoles was studied in proteoliposomes. ► Different 1,2,3-dithiazoles were synthesized and evaluated as transporter inhibitors. ► Many compounds potently inhibited the glutamine/glutamine antiport catalyzed by ASCT2. ► The inhibition was reversed by DTE indicating reaction with protein Cys. ► The most active compounds gave IC50 in the range of 3–30 μM.

  12. A three-dimensional model of the human blood-brain barrier to analyse the transport of nanoparticles and astrocyte/endothelial interactions [version 2; referees: 2 approved

    Directory of Open Access Journals (Sweden)

    Peddagangannagari Sreekanthreddy

    2016-01-01

    Full Text Available The aim of this study was to develop a three-dimensional (3D model of the human blood-brain barrier in vitro, which mimics the cellular architecture of the CNS and could be used to analyse the delivery of nanoparticles to cells of the CNS. The model includes human astrocytes set in a collagen gel, which is overlaid by a monolayer of human brain endothelium (hCMEC/D3 cell line. The model was characterised by transmission electron microscopy (TEM, immunofluorescence microscopy and flow cytometry. A collagenase digestion method could recover the two cell types separately at 92-96% purity.  Astrocytes grown in the gel matrix do not divide and they have reduced expression of aquaporin-4 and the endothelin receptor, type B compared to two-dimensional cultures, but maintain their expression of glial fibrillary acidic protein. The effects of conditioned media from these astrocytes on the barrier phenotype of the endothelium was compared with media from astrocytes grown conventionally on a two-dimensional (2D substratum. Both induce the expression of tight junction proteins zonula occludens-1 and claudin-5 in hCMEC/D3 cells, but there was no difference between the induced expression levels by the two media. The model has been used to assess the transport of glucose-coated 4nm gold nanoparticles and for leukocyte migration. TEM was used to trace and quantitate the movement of the nanoparticles across the endothelium and into the astrocytes. This blood-brain barrier model is very suitable for assessing delivery of nanoparticles and larger biomolecules to cells of the CNS, following transport across the endothelium.

  13. Relationship between Increase in Astrocytic GLT-1 Glutamate Transport and Late-LTP

    Science.gov (United States)

    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…

  14. Astrocytes revisited: concise historic outlook on glutamate homeostasis and signaling

    OpenAIRE

    Parpura, Vladimir; VERKHRATSKY, ALEXEI

    2012-01-01

    Astroglia is a main type of brain neuroglia, which includes many cell sub-types that differ in their morphology and physiological properties and yet are united by the main function, which is the maintenance of brain homeostasis. Astrocytes employ a variety of mechanisms for communicating with neuronal networks. The communication mediated by neurotransmitter glutamate has received a particular attention. Glutamate is de novo synthesized exclusively in astrocytes; astroglia-derived glutamine is...

  15. In vitro growth environment produces lipidomic and electron transport chain abnormalities in mitochondria from non-tumorigenic astrocytes and brain tumours

    Directory of Open Access Journals (Sweden)

    Thomas N Seyfried

    2009-05-01

    Full Text Available The mitochondrial lipidome influences ETC (electron transport chain and cellular bioenergetic efficiency. Brain tumours are largely dependent on glycolysis for energy due to defects in mitochondria and oxidative phosphorylation. In the present study, we used shotgun lipidomics to compare the lipidome in highly purified mitochondria isolated from normal brain, from brain tumour tissue, from cultured tumour cells and from non-tumorigenic astrocytes. The tumours included the CT-2A astrocytoma and an EPEN (ependymoblastoma, both syngeneic with the C57BL/6J (B6 mouse strain. The mitochondrial lipidome in cultured CT-2A and EPEN tumour cells were compared with those in cultured astrocytes and in solid tumours grown in vivo. Major differences were found between normal tissue and tumour tissue and between in vivo and in vitro growth environments for the content or composition of ethanolamine glycerophospholipids, phosphatidylglycerol and cardiolipin. The mitochondrial lipid abnormalities in solid tumours and in cultured cells were associated with reductions in multiple ETC activities, especially Complex I. The in vitro growth environment produced lipid and ETC abnormalities in cultured non-tumorigenic astrocytes that were similar to those associated with tumorigenicity. It appears that the culture environment obscures the boundaries of the Crabtree and the Warburg effects. These results indicate that in vitro growth environments can produce abnormalities in mitochondrial lipids and ETC activities, thus contributing to a dependency on glycolysis for ATP production.

  16. Astrocytes and glutamate homeostasis in Alzheimer's disease: a decrease in glutamine synthetase but not in glutamate transporter-1 in the prefrontal cortex.

    Czech Academy of Sciences Publication Activity Database

    Kulijewicz-Nawrot, Magdaléna; Syková, Eva; Chvátal, Alexandr; Verkhratsky, A.; Rodríguez, J. J.

    2013-01-01

    Roč. 5, č. 4 (2013), s. 273-282. ISSN 1759-0914 R&D Projects: GA ČR(CZ) GAP304/11/0184; GA ČR(CZ) GBP304/12/G069; GA ČR GA309/09/1696; GA ČR GA305/08/1384 Institutional support: RVO:68378041 Keywords : Alzheimer's disease * astroglia * GLT-1 Subject RIV: FH - Neurology Impact factor: 4.436, year: 2013

  17. Glutamate metabolism in the brain focusing on astrocytes

    DEFF Research Database (Denmark)

    Schousboe, Arne; Scafidi, Susanna; Bak, Lasse Kristoffer;

    2014-01-01

    Metabolism of glutamate, the main excitatory neurotransmitter and precursor of GABA, is exceedingly complex and highly compartmentalized in brain. Maintenance of these neurotransmitter pools is strictly dependent on the de novo synthesis of glutamine in astrocytes which requires both the anaplero...

  18. Concerted hexose transport curb by tunicamycin is rendered irreversible by glucose or allose in medium containing L-glutamine.

    OpenAIRE

    Ullrey, D B; Kalckar, H M

    1989-01-01

    The hexose transport in a hamster fibroblast mutant (DS7), unable to use glucose for generation of energy, is nevertheless subject to a marked down-regulation ("curb") after prolonged incubation of monolayer cultures with glucose; fructose is unable to exert any curb. D-Allose, an all-cis hexose, mediates a vigorous curb of the transport system. Moreover, prolonged coincubation of glucose or allose with tunicamycin (TM) brings about an additional effect that is not an inhibition of the transp...

  19. A subconvulsive dose of kainate selectively compromises astrocytic metabolism in the mouse brain in vivo

    DEFF Research Database (Denmark)

    Walls, Anne B; Eyjolfsson, Elvar M; Schousboe, Arne;

    2014-01-01

    cerebral metabolism and particularly that associated with astrocytes. We investigated astrocytic and neuronal metabolism in the cerebral cortex of adult mice after treatment with saline (controls), a subconvulsive or a mildly convulsive dose of kainate. A combination of [1,2-(13)C]acetate and [1-(13)C......]glucose was injected and subsequent nuclear magnetic resonance spectroscopy of cortical extracts was employed to distinctively map astrocytic and neuronal metabolism. The subconvulsive dose of kainate led to an instantaneous increase in the cortical lactate content, a subsequent reduction in the amount of [4......,5-(13)C]glutamine and an increase in the calculated astrocytic TCA cycle activity. In contrast, the convulsive dose led to decrements in the cortical content and (13)C labeling of glutamate, glutamine, GABA, and aspartate. Evidence is provided that astrocytic metabolism is affected by a subconvulsive dose...

  20. Glutamine Modulates Macrophage Lipotoxicity

    Directory of Open Access Journals (Sweden)

    Li He

    2016-04-01

    Full Text Available Obesity and diabetes are associated with excessive inflammation and impaired wound healing. Increasing evidence suggests that macrophage dysfunction is responsible for these inflammatory defects. In the setting of excess nutrients, particularly dietary saturated fatty acids (SFAs, activated macrophages develop lysosome dysfunction, which triggers activation of the NLRP3 inflammasome and cell death. The molecular pathways that connect lipid stress to lysosome pathology are not well understood, but may represent a viable target for therapy. Glutamine uptake is increased in activated macrophages leading us to hypothesize that in the context of excess lipids glutamine metabolism could overwhelm the mitochondria and promote the accumulation of toxic metabolites. To investigate this question we assessed macrophage lipotoxicity in the absence of glutamine using LPS-activated peritoneal macrophages exposed to the SFA palmitate. We found that glutamine deficiency reduced lipid induced lysosome dysfunction, inflammasome activation, and cell death. Under glutamine deficient conditions mTOR activation was decreased and autophagy was enhanced; however, autophagy was dispensable for the rescue phenotype. Rather, glutamine deficiency prevented the suppressive effect of the SFA palmitate on mitochondrial respiration and this phenotype was associated with protection from macrophage cell death. Together, these findings reveal that crosstalk between activation-induced metabolic reprogramming and the nutrient microenvironment can dramatically alter macrophage responses to inflammatory stimuli.

  1. Effect of glutamine synthetase inhibition on brain and interorgan ammonia metabolism in bile duct ligated rats

    DEFF Research Database (Denmark)

    Fries, Andreas W; Dadsetan, Sherry; Keiding, Susanne;

    2014-01-01

    Ammonia has a key role in the development of hepatic encephalopathy (HE). In the brain, glutamine synthetase (GS) rapidly converts blood-borne ammonia into glutamine which in high concentrations may cause mitochondrial dysfunction and osmolytic brain edema. In astrocyte-neuron cocultures and brains...... of healthy rats, inhibition of GS by methionine sulfoximine (MSO) reduced glutamine synthesis and increased alanine synthesis. Here, we investigate effects of MSO on brain and interorgan ammonia metabolism in sham and bile duct ligated (BDL) rats. Concentrations of glutamine, glutamate, alanine, and...... aspartate and incorporation of (15)NH4(+) into these amino acids in brain, liver, muscle, kidney, and plasma were similar in sham and BDL rats treated with saline. Methionine sulfoximine reduced glutamine concentrations in liver, kidney, and plasma but not in brain and muscle; MSO reduced incorporation of...

  2. Effects of atrial and brain natriuretic peptides upon cyclic GMP levels, potassium transport, and receptor binding in rat astrocytes

    Energy Technology Data Exchange (ETDEWEB)

    Beaumont, K.; Tan, P.K. (Univ. of California, San Diego, La Jolla (USA))

    1990-02-01

    The ability of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) to alter cyclic GMP levels and NaKCl cotransport in rat neocortical astrocytes was determined. At concentrations of 10(-9)-10(-6) M, rat ANP99-126 (rANF), rat ANP102-126 (auriculin B), and rat ANP103-126 (atriopeptin III) stimulated 6- to 100-fold increases in cyclic GMP levels. Porcine BNP (pBNP) and rat BNP (rBNP) were 20%-90% as effective as rANF over most of this concentration range, although 10(-6) M pBNP produced a greater effect than rANF. NaKCl cotransport as measured by bumetanide-sensitive 86Rb+ influx was not altered by exposure of astrocytes to 10(-6)M rANF, pBNP, or rBNP. Both pBNP and rBNP, as well as rat ANP103-123 (atriopeptin I) and des(gl18, ser19, gly20, leu21, gly22) ANF4-23-NH2 (C-ANF4-23) strongly competed for specific 125I-rANF binding sites in astrocyte membranes with affinities ranging from 0.03 to 0.4 nM, suggesting that virtually all binding sites measured at subnanomolar concentrations of 125I-rANF were of the ANP-C (ANF-R2) receptor subtype. These receptors are thought to serve a clearance function and may be linked to a guanylate cyclase activity that is chemically and pharmacologically distinct from that coupled to ANP-A (ANF-R1) receptors. ANP receptors on astrocytes may function in limiting the access of ANP and BNP to neurons involved in body fluid and cardiovascular regulation.

  3. Effects of atrial and brain natriuretic peptides upon cyclic GMP levels, potassium transport, and receptor binding in rat astrocytes

    International Nuclear Information System (INIS)

    The ability of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) to alter cyclic GMP levels and NaKCl cotransport in rat neocortical astrocytes was determined. At concentrations of 10(-9)-10(-6) M, rat ANP99-126 (rANF), rat ANP102-126 (auriculin B), and rat ANP103-126 (atriopeptin III) stimulated 6- to 100-fold increases in cyclic GMP levels. Porcine BNP (pBNP) and rat BNP (rBNP) were 20%-90% as effective as rANF over most of this concentration range, although 10(-6) M pBNP produced a greater effect than rANF. NaKCl cotransport as measured by bumetanide-sensitive 86Rb+ influx was not altered by exposure of astrocytes to 10(-6)M rANF, pBNP, or rBNP. Both pBNP and rBNP, as well as rat ANP103-123 (atriopeptin I) and des[gl18, ser19, gly20, leu21, gly22] ANF4-23-NH2 (C-ANF4-23) strongly competed for specific 125I-rANF binding sites in astrocyte membranes with affinities ranging from 0.03 to 0.4 nM, suggesting that virtually all binding sites measured at subnanomolar concentrations of 125I-rANF were of the ANP-C (ANF-R2) receptor subtype. These receptors are thought to serve a clearance function and may be linked to a guanylate cyclase activity that is chemically and pharmacologically distinct from that coupled to ANP-A (ANF-R1) receptors. ANP receptors on astrocytes may function in limiting the access of ANP and BNP to neurons involved in body fluid and cardiovascular regulation

  4. Trafficking of astrocytic vesicles in hippocampal slices

    International Nuclear Information System (INIS)

    The increasingly appreciated role of astrocytes in neurophysiology dictates a thorough understanding of the mechanisms underlying the communication between astrocytes and neurons. In particular, the uptake and release of signaling substances into/from astrocytes is considered as crucial. The release of different gliotransmitters involves regulated exocytosis, consisting of the fusion between the vesicle and the plasma membranes. After fusion with the plasma membrane vesicles may be retrieved into the cytoplasm and may continue to recycle. To study the mobility implicated in the retrieval of secretory vesicles, these structures have been previously efficiently and specifically labeled in cultured astrocytes, by exposing live cells to primary and secondary antibodies. Since the vesicle labeling and the vesicle mobility properties may be an artifact of cell culture conditions, we here asked whether the retrieving exocytotic vesicles can be labeled in brain tissue slices and whether their mobility differs to that observed in cell cultures. We labeled astrocytic vesicles and recorded their mobility with two-photon microscopy in hippocampal slices from transgenic mice with fluorescently tagged astrocytes (GFP mice) and in wild-type mice with astrocytes labeled by Fluo4 fluorescence indicator. Glutamatergic vesicles and peptidergic granules were labeled by the anti-vesicular glutamate transporter 1 (vGlut1) and anti-atrial natriuretic peptide (ANP) antibodies, respectively. We report that the vesicle mobility parameters (velocity, maximal displacement and track length) recorded in astrocytes from tissue slices are similar to those reported previously in cultured astrocytes.

  5. Trafficking of astrocytic vesicles in hippocampal slices

    Energy Technology Data Exchange (ETDEWEB)

    Potokar, Maja; Kreft, Marko [Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloska 4, 1000 Ljubljana (Slovenia); Celica Biomedical Center, Technology Park 24, 1000 Ljubljana (Slovenia); Lee, So-Young; Takano, Hajime; Haydon, Philip G. [Department of Neuroscience, Room 215, Stemmler Hall, University of Pennsylvania, School of Medicine, Philadelphia, PA 19104 (United States); Zorec, Robert, E-mail: Robert.Zorec@mf.uni-lj.si [Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloska 4, 1000 Ljubljana (Slovenia); Celica Biomedical Center, Technology Park 24, 1000 Ljubljana (Slovenia)

    2009-12-25

    The increasingly appreciated role of astrocytes in neurophysiology dictates a thorough understanding of the mechanisms underlying the communication between astrocytes and neurons. In particular, the uptake and release of signaling substances into/from astrocytes is considered as crucial. The release of different gliotransmitters involves regulated exocytosis, consisting of the fusion between the vesicle and the plasma membranes. After fusion with the plasma membrane vesicles may be retrieved into the cytoplasm and may continue to recycle. To study the mobility implicated in the retrieval of secretory vesicles, these structures have been previously efficiently and specifically labeled in cultured astrocytes, by exposing live cells to primary and secondary antibodies. Since the vesicle labeling and the vesicle mobility properties may be an artifact of cell culture conditions, we here asked whether the retrieving exocytotic vesicles can be labeled in brain tissue slices and whether their mobility differs to that observed in cell cultures. We labeled astrocytic vesicles and recorded their mobility with two-photon microscopy in hippocampal slices from transgenic mice with fluorescently tagged astrocytes (GFP mice) and in wild-type mice with astrocytes labeled by Fluo4 fluorescence indicator. Glutamatergic vesicles and peptidergic granules were labeled by the anti-vesicular glutamate transporter 1 (vGlut1) and anti-atrial natriuretic peptide (ANP) antibodies, respectively. We report that the vesicle mobility parameters (velocity, maximal displacement and track length) recorded in astrocytes from tissue slices are similar to those reported previously in cultured astrocytes.

  6. L-glutamate released from activated microglia downregulates astrocytic L-glutamate transporter expression in neuroinflammation: the ‘collusion’ hypothesis for increased extracellular L-glutamate concentration in neuroinflammation

    Directory of Open Access Journals (Sweden)

    Takaki Junpei

    2012-12-01

    Full Text Available Abstract Background In the central nervous system, astrocytic L-glutamate (L-Glu transporters maintain extracellular L-Glu below neurotoxic levels, but their function is impaired with neuroinflammation. Microglia become activated with inflammation; however, the correlation between activated microglia and the impairment of L-Glu transporters is unknown. Methods We used a mixed culture composed of astrocytes, microglia, and neurons. To quantify L-Glu transporter function, we measured the extracellular L-Glu that remained 30 min after an application of L-Glu to the medium (the starting concentration was 100 μM. We determined the optimal conditions of lipopolysaccharide (LPS treatment to establish an inflammation model without cell death. We examined the predominant subtypes of L-Glu transporters and the changes in the expression levels of these transporters in this inflammation model. We then investigated the role of activated microglia in the changes in L-Glu transporter expression and the underlying mechanisms in this inflammation model. Results Because LPS (10 ng/mL, 72 h caused a significant increase in the levels of L-Glu remaining but did not affect cell viability, we adopted this condition for our inflammation model without cell death. GLAST was the predominant L-Glu transporter subtype, and its expression decreased in this inflammation model. As a result of their release of L-Glu, activated microglia were shown to be essential for the significant decrease in L-Glu uptake. The serial application of L-Glu caused a significant decrease in L-Glu uptake and GLAST expression in the astrocyte culture. The hemichannel inhibitor carbenoxolone (CBX inhibited L-Glu release from activated microglia and ameliorated the decrease in GLAST expression in the inflammation model. In addition, the elevation of the astrocytic intracellular L-Glu itself caused the downregulation of GLAST. Conclusions Our findings suggest that activated microglia trigger the

  7. Troglitazone suppresses glutamine metabolism through a PPAR-independent mechanism.

    Science.gov (United States)

    Reynolds, Miriam R; Clem, Brian F

    2015-08-01

    Enhanced glutamine metabolism is required for tumor cell growth and survival, which suggests that agents targeting glutaminolysis may have utility within anti-cancer therapies. Troglitazone, a PPARγ agonist, exhibits significant anti-tumor activity and can alter glutamine metabolism in multiple cell types. Therefore, we examined whether troglitazone would disrupt glutamine metabolism in tumor cells and whether its action was reliant on PPARγ activity. We found that troglitazone treatment suppressed glutamine uptake and the expression of the glutamine transporter, ASCT2, and glutaminase. In addition, troglitazone reduced 13C-glutamine incorporation into the TCA cycle, decreased [ATP], and resulted in an increase in reactive oxygen species (ROS). Further, troglitazone treatment decreased tumor cell growth, which was partially rescued with the addition of the TCA-intermediate, α-ketoglutarate, or the antioxidant N-acetylcysteine. Importantly, troglitazone's effects on glutamine uptake or viable cell number were found to be PPARγ-independent. In contrast, troglitazone caused a decrease in c-Myc levels, while the proteasomal inhibitor, MG132, rescued c-Myc, ASCT2 and GLS1 expression, as well as glutamine uptake and cell number. Lastly, combinatorial treatment of troglitazone and metformin resulted in a synergistic decrease in cell number. Therefore, characterizing new anti-tumor properties of previously approved FDA therapies supports the potential for repurposing of these agents. PMID:25872876

  8. High-affinity glutamate transporter and glutamine synthetase content in longissimus dorsi and adipose tissues of growing Angus steers differs among suckling, weanling, backgrounding, and finishing production stages.

    Science.gov (United States)

    Matthews, J C; Huang, J; Rentfrow, G

    2016-03-01

    Skeletal muscle and adipose tissues play important roles in maintaining whole-body Glu and N homeostasis by the uptake of Glu and release of Gln. To test the hypothesis that expression of high-affinity Glu transporters (GLAST1, EAAT4, EAAC1, GLT-1) and glutamine synthetase (GS) would increase in longissimus dorsi and adipose tissue of newborn Angus steers randomly assigned ( = 6) to develop through suckling (S; 32 d) and/or weanling (W; 184 d), backgrounding (B; 248 d), and finishing (F; 423 d) production stages. Carcass quality was determined at slaughter to verify shifts in adipose and lean deposition with development. Expression of mRNA (RT-PCR/Southern) and relative protein abundance (Western analysis) were determined in tissue homogenates isolated from longissimus dorsi, and kidney and subcutaneous adipose. The effect of production stage or tissue type on carcass and protein abundance was assessed by 1-way ANOVA using the GLM procedure of SAS, and Fisher's protected LSD procedure was used to separate data means. Neither GLAST1 nor EAAT4 mRNA or protein was detected. EAAC1, GLT-1, and GS mRNA were identified in all tissues, but GLT-1 and GS protein were not detected in kidney or subcutaneous adipose, and GS protein was not detected in longissimus dorsi. The EAAC1 content of subcutaneous ( = 0.06) and kidney ( = 0.02) adipose was 2 times greater in B and F than W steers, whereas GS was 5 times greater ( F). For longissimus dorsi, EAAC1 ( W > B = F, S = W > B = F, respectively). Within F steers, EAAC1 and GLT-1 mRNA was expressed by subcutaneous, kidney, omental, mesenchymal, and intramuscular adipose tissues, whereas GS mRNA was expressed by all except for intramuscular. Only EAAC1 protein was detected in any adipose tissue, with EAAC1 content being 104% and 112% greater ( 0.45) from omental or mesenchymal adipose. These data demonstrate (1) longissimus dorsi and adipose tissues of steers developing through typical production stages have different capacities for

  9. Cytosolic glutamine synthetase

    DEFF Research Database (Denmark)

    Thomsen, Hanne Cecilie; Eriksson, Ulf Dennis; Møller, Inge Skrumsager;

    2014-01-01

    Overexpression of the cytosolic enzyme glutamine synthetase 1 (GS1) has been investigated in numerous cases with the goal of improving crop nitrogen use efficiency. However, the outcome has generally been inconsistent. Here, we review possible reasons underlying the lack of success and conclude...

  10. Striatal Astrocytes Act as a Reservoir for L-DOPA

    OpenAIRE

    Masato Asanuma; Ikuko Miyazaki; Shinki Murakami; Diaz-Corrales, Francisco J.; Norio Ogawa

    2014-01-01

    L-DOPA is therapeutically efficacious in patients with Parkinson's disease (PD), although dopamine (DA) neurons are severely degenerated. Since cortical astrocytes express neutral amino acid transporter (LAT) and DA transporter (DAT), the uptake and metabolism of L-DOPA and DA in striatal astrocytes may influence their availability in the dopaminergic system of PD. To assess possible L-DOPA- and DA-uptake and metabolic properties of striatal astrocytes, we examined the expression of L-DOPA, D...

  11. Differentiation of purified astrocytes in a chemically defined medium

    Energy Technology Data Exchange (ETDEWEB)

    Morrison, R.S.; de Vellis, J.

    1981-01-01

    Homogeneous cultures of astrocytes and oligodendrocytes provide an excellent model system for studying the regulation of glial structure and function. Recently, a chemically defined (CD) medium was developed for purified cultures of astrocytes, thus eliminating the requirement for serum and providing a controlled system for the study of astroglial properties. Due to the widespread use of astrocyte cultures and the potential benefits to be gained from using a defined medium, astrocyte cultures raised in CD medium were analyzed for purity as well as morphological and biochemical properties. Purity was assessed using immunocytochemical staining for glial fibrillary acidic protein (GFAP) and fibronectin. Astrocytes raised in CD medium are 95% pure using the expression of GFAP as a criterion. Fewer than 1% of the cells in CD medium stained positive for fibronectin eliminating the possibility that CD medium is selective for meningeal or endothelial cells. Astrocytes raised in CD medium exhibit a striking degree of morphological differentiation as seen in scanning electron micrographs. They also exhibit a high degree of biochemical differentiation illustrated by increases in the specific activity of S-100 protein and the induction of glutamine synthetase by glucocorticoids. A defined medium that supports the proliferation of rat astrocytes and enhances numerous morphological and biochemical properties should greatly facilitate the study of factors controlling glial proliferation and differentiation.

  12. Human T-cell lymphotropic virus type 1-infected T lymphocytes impair catabolism and uptake of glutamate by astrocytes via Tax-1 and tumor necrosis factor alpha.

    Science.gov (United States)

    Szymocha, R; Akaoka, H; Dutuit, M; Malcus, C; Didier-Bazes, M; Belin, M F; Giraudon, P

    2000-07-01

    Human T-cell lymphotropic virus type 1 (HTLV-1) is the causative agent of a chronic progressive myelopathy called tropical spastic paraparesis/HTLV-1-associated myelopathy (TSP/HAM). In this disease, lesions of the central nervous system (CNS) are associated with perivascular infiltration by lymphocytes. We and others have hypothesized that these T lymphocytes infiltrating the CNS may play a prominent role in TSP/HAM. Here, we show that transient contact of human or rat astrocytes with T lymphocytes chronically infected by HTLV-1 impairs some of the major functions of brain astrocytes. Uptake of extracellular glutamate by astrocytes was significantly decreased after transient contact with infected T cells, while the expression of the glial transporters GLAST and GLT-1 was decreased. In two-compartment cultures avoiding direct cell-to-cell contact, similar results were obtained, suggesting possible involvement of soluble factors, such as cytokines and the viral protein Tax-1. Recombinant Tax-1 and tumor necrosis factor alpha (TNF-alpha) decreased glutamate uptake by astrocytes. Tax-1 probably acts by inducing TNF-alpha, as the effect of Tax-1 was abolished by anti-TNF-alpha antibody. The expression of glutamate-catabolizing enzymes in astrocytes was increased for glutamine synthetase and decreased for glutamate dehydrogenase, the magnitudes of these effects being correlated with the level of Tax-1 transcripts. In conclusion, Tax-1 and cytokines produced by HTLV-1-infected T cells impair the ability of astrocytes to manage the steady-state level of glutamate, which in turn may affect neuronal and oligodendrocytic functions and survival. PMID:10864655

  13. Primary cultures of astrocytes

    DEFF Research Database (Denmark)

    Lange, Sofie C; Bak, Lasse Kristoffer; Waagepetersen, Helle S;

    2012-01-01

    subsequently found in vivo. Nevertheless, primary cultures of astrocytes are an in vitro model that does not fully mimic the complex events occurring in vivo. Here we present an overview of the numerous contributions generated by the use of primary astrocyte cultures to uncover the diverse functions of......During the past few decades of astrocyte research it has become increasingly clear that astrocytes have taken a central position in all central nervous system activities. Much of our new understanding of astrocytes has been derived from studies conducted with primary cultures of astrocytes. Such...... cultures have been an invaluable tool for studying roles of astrocytes in physiological and pathological states. Many central astrocytic functions in metabolism, amino acid neurotransmission and calcium signaling were discovered using this tissue culture preparation and most of these observations were...

  14. Glutamine and glutamate as vital metabolites

    Directory of Open Access Journals (Sweden)

    Newsholme P.

    2003-01-01

    Full Text Available Glucose is widely accepted as the primary nutrient for the maintenance and promotion of cell function. This metabolite leads to production of ATP, NADPH and precursors for the synthesis of macromolecules such as nucleic acids and phospholipids. We propose that, in addition to glucose, the 5-carbon amino acids glutamine and glutamate should be considered to be equally important for maintenance and promotion of cell function. The functions of glutamine/glutamate are many, i.e., they are substrates for protein synthesis, anabolic precursors for muscle growth, they regulate acid-base balance in the kidney, they are substrates for ureagenesis in the liver and for hepatic and renal gluconeogenesis, they act as an oxidative fuel for the intestine and cells of the immune system, provide inter-organ nitrogen transport, and act as precursors of neurotransmitter synthesis, of nucleotide and nucleic acid synthesis and of glutathione production. Many of these functions are interrelated with glucose metabolism. The specialized aspects of glutamine/glutamate metabolism of different glutamine-utilizing cells are discussed in the context of glucose requirements and cell function.

  15. Interrelationships between glutamine and citrulline metabolism

    Science.gov (United States)

    This article analyzes the contribution of glutamine to the synthesis of citrulline and reviews the evidence that glutamine supplementation increases citrulline production. Glutamine supplementation has been proposed in the treatment of critically ill patients; however, a recent large multicenter ran...

  16. Astrocytic Ion Dynamics: Implications for Potassium Buffering and Liquid Flow

    OpenAIRE

    Halnes, Geir; Pettersen, Klas H.; Øyehaug, Leiv; Rognes, Marie E.; Langtangen, Hans Petter; Einevoll, Gaute T.

    2016-01-01

    We review modeling of astrocyte ion dynamics with a specific focus on the implications of so-called spatial potassium buffering, where excess potassium in the extracellular space (ECS) is transported away to prevent pathological neural spiking. The recently introduced Kirchoff-Nernst-Planck (KNP) scheme for modeling ion dynamics in astrocytes (and brain tissue in general) is outlined and used to study such spatial buffering. We next describe how the ion dynamics of astrocytes may regulate mic...

  17. Characterization of primary and secondary cultures of astrocytes prepared from mouse cerebral cortex

    DEFF Research Database (Denmark)

    Skytt, Dorte Marie; Madsen, Karsten Kirkegaard; Pajecka, Kamilla;

    2010-01-01

    Astrocyte cultures were prepared from cerebral cortex of new-born and 7-day-old mice and additionally, the cultures from new-born animals were passaged as secondary cultures. The cultures were characterized by immunostaining for the astrocyte markers glutamine synthetase (GS), glial fibrillary...... of the astrocyte marker proteins. The metabolic pattern of the cultures from 7-day-old animals of the labeled substrates was comparable to that seen previously in astrocyte cultures prepared from new-born mouse brain showing pronounced glycolytic and oxidative metabolism of glucose. Glutamate was...... prepared from cerebral cortex of 7-day-old mice have metabolic and functional properties indistinguishable from those of classical astrocyte cultures prepared from neocortex of new-born animals. This provides flexibility with regard to preparation and use of these cultures for a variety of purposes....

  18. Control of glutamine metabolism by the tumor suppressor Rb.

    Science.gov (United States)

    Reynolds, M R; Lane, A N; Robertson, B; Kemp, S; Liu, Y; Hill, B G; Dean, D C; Clem, B F

    2014-01-30

    Retinoblastoma (Rb) protein is a tumor suppressor that is dysregulated in a majority of human cancers. Rb functions to inhibit cell cycle progression in part by directly disabling the E2F family of cell cycle-promoting transcription factors. Because the de novo synthesis of multiple glutamine-derived anabolic precursors is required for cell cycle progression, we hypothesized that Rb also may directly regulate proteins involved in glutamine metabolism. We examined glutamine metabolism in mouse embryonic fibroblasts (MEFs) isolated from mice that have triple knock-outs (TKO) of all three Rb family members (Rb-1, Rbl1 and Rbl2) and found that loss of global Rb function caused a marked increase in (13)C-glutamine uptake and incorporation into glutamate and tricarboxylic acid cycle (TCA) intermediates in part via upregulated expression of the glutamine transporter ASCT2 and the activity of glutaminase 1 (GLS1). The Rb-controlled transcription factor E2F-3 altered glutamine uptake by direct regulation of ASCT2 mRNA and protein expression, and E2F-3 was observed to associate with the ASCT2 promoter. We next examined the functional consequences of the observed increase in glutamine uptake and utilization and found that glutamine exposure potently increased oxygen consumption, whereas glutamine deprivation selectively decreased ATP concentration in the Rb TKO MEFs but not the wild-type (WT) MEFs. In addition, TKO MEFs exhibited elevated production of glutathione from exogenous glutamine and had increased expression of gamma-glutamylcysteine ligase relative to WT MEFs. Importantly, this metabolic shift towards glutamine utilization was required for the proliferation of Rb TKO MEFs but not for the proliferation of the WT MEFs. Last, addition of the TCA cycle intermediate α-ketoglutarate to the Rb TKO MEFs reversed the inhibitory effects of glutamine deprivation on ATP, GSH levels and viability. Taken together, these studies demonstrate that the Rb/E2F cascade directly

  19. Astrocytes optimize synaptic fidelity

    Science.gov (United States)

    Nadkarni, Suhita; Jung, Peter; Levine, Herbert

    2007-03-01

    Most neuronal synapses in the central nervous system are enwrapped by an astrocytic process. This relation allows the astrocyte to listen to and feed back to the synapse and to regulate synaptic transmission. We combine a tested mathematical model for the Ca^2+ response of the synaptic astrocyte and presynaptic feedback with a detailed model for vesicle release of neurotransmitter at active zones. The predicted Ca^2+ dependence of the presynaptic synaptic vesicle release compares favorably for several types of synapses, including the Calyx of Held. We hypothesize that the feedback regulation of the astrocyte onto the presynaptic terminal optimizes the fidelity of the synapse in terms of information transmission.

  20. Striatal astrocytes act as a reservoir for L-DOPA.

    Science.gov (United States)

    Asanuma, Masato; Miyazaki, Ikuko; Murakami, Shinki; Diaz-Corrales, Francisco J; Ogawa, Norio

    2014-01-01

    L-DOPA is therapeutically efficacious in patients with Parkinson's disease (PD), although dopamine (DA) neurons are severely degenerated. Since cortical astrocytes express neutral amino acid transporter (LAT) and DA transporter (DAT), the uptake and metabolism of L-DOPA and DA in striatal astrocytes may influence their availability in the dopaminergic system of PD. To assess possible L-DOPA- and DA-uptake and metabolic properties of striatal astrocytes, we examined the expression of L-DOPA, DA and DAT in striatal astrocytes of hemi-parkinsonian model rats after repeated L-DOPA administration, and measured the contents of L-DOPA, DA and their metabolite in primary cultured striatal astrocytes after L-DOPA/DA treatment. Repeated injections of L-DOPA induced apparent L-DOPA- and DA-immunoreactivities and marked expression of DAT in reactive astrocytes on the lesioned side of the striatum in hemi-parkinsonian rats. Exposure to DA for 4h significantly increased the levels of DA and its metabolite DOPAC in cultured striatal astrocytes. L-DOPA was also markedly increased in cultured striatal astrocytes after 4-h L-DOPA exposure, but DA was not detected 4 or 8h after L-DOPA treatment, despite the expression of aromatic amino acid decarboxylase in astrocytes. Furthermore, the intracellular level of L-DOPA in cultured striatal astrocytes decreased rapidly after removal of extracellular L-DOPA. The results suggest that DA uptaken into striatal astrocytes is rapidly metabolized and that striatal astrocytes act as a reservoir of L-DOPA that govern the uptake or release of L-DOPA depending on extracellular L-DOPA concentration, but are less capable of converting L-DOPA to DA. PMID:25188235

  1. Glutamine synthetase immunor present in oligodendroglia of regions of the central nervous system

    Science.gov (United States)

    D'Amelio, Fernando; Eng, Lawrence F.; Gibbs, Michael A.

    1990-01-01

    Glutamine synthetase immunoreactive oligodendrocytes were identified in the cerebral cortex, cerebellum, brain stem, and spinal cord. They were mostly confined to the gray matter, particularly close to neurons and processes. The white matter showed few immunoreactive oligodendroglia. It was suggested that some type of oligodendrocytes, specially those in perineuronal location, might fulfill a functional role more akin to astrocytes than to the normally myelinating oligodendroglia.

  2. Astrocytic Vesicle Mobility in Health and Disease

    Directory of Open Access Journals (Sweden)

    Robert Zorec

    2013-05-01

    Full Text Available Astrocytes are no longer considered subservient to neurons, and are, instead, now understood to play an active role in brain signaling. The intercellular communication of astrocytes with neurons and other non-neuronal cells involves the exchange of molecules by exocytotic and endocytotic processes through the trafficking of intracellular vesicles. Recent studies of single vesicle mobility in astrocytes have prompted new views of how astrocytes contribute to information processing in nervous tissue. Here, we review the trafficking of several types of membrane-bound vesicles that are specifically involved in the processes of (i intercellular communication by gliotransmitters (glutamate, adenosine 5'-triphosphate, atrial natriuretic peptide, (ii plasma membrane exchange of transporters and receptors (EAAT2, MHC-II, and (iii the involvement of vesicle mobility carrying aquaporins (AQP4 in water homeostasis. The properties of vesicle traffic in astrocytes are discussed in respect to networking with neighboring cells in physiologic and pathologic conditions, such as amyotrophic lateral sclerosis, multiple sclerosis, and states in which astrocytes contribute to neuroinflammatory conditions.

  3. Breathless cancer cells get fat on glutamine

    Institute of Scientific and Technical Information of China (English)

    Dimitrios Anastasiou; Lewis C Cantley

    2012-01-01

    Many cancer cells depend on glutamine as a fuel for proliferation,yet the mechanisms by which glutamine supports cancer metabolism are not fully understood.Two recent studies highlight an important role for glutamine in the synthesis of lipids and provide novel insights into how glutamine metabolism could be targeted for cancer therapy.

  4. Rapamycin prevents the mutant huntingtin-suppressed GLT-1 expression in cultured astrocytes

    OpenAIRE

    Chen, Lei-lei; Wu, Jun-Chao; Wang, Lin-Hui; Wang, Jin; Qin, Zheng-hong; Difiglia, Marian; Lin, Fang

    2012-01-01

    Aim: To investigate the effects of rapamycin on glutamate uptake in cultured rat astrocytes expressing N-terminal 552 residues of mutant huntingtin (Htt-552). Methods: Methods: Primary astrocyte cultures were prepared from the cortex of postnatal rat pups. An astrocytes model of Huntington's disease was established using the astrocytes infected with adenovirus carrying coden gene of N-terminal 552 residues of Huntingtin. The protein levels of glutamate transporters GLT-1 and GLAST, the autoph...

  5. Astrocytes Potentiate Synaptic Transmission

    Science.gov (United States)

    Nadkarni, Suhita

    2005-03-01

    A recent experimental study shows that astrocytes, a subtype of glia, are able to influence the spontaneous activity in the brain via calcium dependent glutamate release. We model the coupling mechanism between an astrocyte and a neuron based on experimental data. This coupling is dynamic and bi-directional, such that the modulations in intracellular calcium concentrations in astrocytes affect neuronal excitability and vice versa via a glutamatergic pathway. We demonstrate through simple neural-glial circuits that increases in the intracellular calcium concentration in astrocytes nearby can enhance spontaneous activity in a neuron, a significant mechanism said to be involved in plasticity and learning. The pattern of this marked increase in spontaneous firing rate in our model quantitatively follows that observed in the experiment. Further, depending on the type of synaptic connections diverging from the neuron, it can either inhibit or excite the ensuing dynamics and potentiate synaptic transmission, thus reinstating the integral role played by astrocytes in normal neuronal dynamics.

  6. Astroglial glutamate-glutamine cycle is involved in the modulation of inflammatory nociception in rats

    Institute of Scientific and Technical Information of China (English)

    Tiancheng Wang; Jing Wang; Bin Geng; Hongyu Guo; Haili Shen; Yayi Xia

    2011-01-01

    Our previous behavioral studies have indicated that the astroglial glutamate-glutamine cycle is involved in the process of formalin-induced spinal cord central sensitization, but there was little morphological evidence. In this study, double-labeling immunofluorescence techniques showed that after rats were intrathecally injected with PBS and plantarly injected with formalin, glial fibrillary acidic protein (GFAP) and glutamine synthesase (GS) expression were increased and GFAP/GS coexpression was changed to include layers III and IV. After intrathecal injection of methionine sulfoximine, a GS specific inhibitor, the formalin-induced change in expression and coexpression of GFAP and GS in spinal cord dorsal horns was inhibited. The morphology, distribution and quantity of astrocytes recovered to normal levels. An intrathecal glutamine injection reversed the inhibitory effect of methionine sulfoximine. Astrocytes showed significant activation and distribution extended to layers V and VI. The present study provides morphological evidence that the astroglial glutamate-glutamine cycle is involved in the process of formalin-induced spinal cord central sensitization.

  7. Astrocytes drive upregulation of the multidrug resistance transporter ABCB1 (P-Glycoprotein) in endothelial cells of the blood-brain barrier in mutant superoxide dismutase 1-linked amyotrophic lateral sclerosis.

    Science.gov (United States)

    Qosa, Hisham; Lichter, Jessica; Sarlo, Mark; Markandaiah, Shashirekha S; McAvoy, Kevin; Richard, Jean-Philippe; Jablonski, Michael R; Maragakis, Nicholas J; Pasinelli, Piera; Trotti, Davide

    2016-08-01

    The efficacy of drugs targeting the CNS is influenced by their limited brain access, which can lead to complete pharmacoresistance. Recently a tissue-specific and selective upregulation of the multidrug efflux transporter ABCB1 or P-glycoprotein (P-gp) in the spinal cord of both patients and the mutant SOD1-G93A mouse model of amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease that prevalently kills motor neurons has been reported. Here, we extended the analysis of P-gp expression in the SOD1-G93A ALS mouse model and found that P-gp upregulation was restricted to endothelial cells of the capillaries, while P-gp expression was not detected in other cells of the spinal cord parenchyma such as astrocytes, oligodendrocytes, and neurons. Using both in vitro human and mouse models of the blood-brain barrier (BBB), we found that mutant SOD1 astrocytes were driving P-gp upregulation in endothelial cells. In addition, a significant increase in reactive oxygen species production, Nrf2 and NFκB activation in endothelial cells exposed to mutant SOD1 astrocytes in both human and murine BBB models were observed. Most interestingly, astrocytes expressing FUS-H517Q, a different familial ALS-linked mutated gene, also drove NFκB-dependent upregulation of P-gp. However, the pathway was not dependent on oxidative stress but rather involved TNF-α release. Overall, these findings indicated that nuclear translocation of NFκB was a converging mechanism used by endothelial cells of the BBB to upregulate P-gp expression in mutant SOD1-linked ALS and possibly other forms of familial ALS. GLIA 2016 GLIA 2016;64:1298-1313. PMID:27158936

  8. Functional metabolic interactions of human neuron-astrocyte 3D in vitro networks.

    Science.gov (United States)

    Simão, Daniel; Terrasso, Ana P; Teixeira, Ana P; Brito, Catarina; Sonnewald, Ursula; Alves, Paula M

    2016-01-01

    The generation of human neural tissue-like 3D structures holds great promise for disease modeling, drug discovery and regenerative medicine strategies. Promoting the establishment of complex cell-cell interactions, 3D culture systems enable the development of human cell-based models with increased physiological relevance, over monolayer cultures. Here, we demonstrate the establishment of neuronal and astrocytic metabolic signatures and shuttles in a human 3D neural cell model, namely the glutamine-glutamate-GABA shuttle. This was indicated by labeling of neuronal GABA following incubation with the glia-specific substrate [2-(13)C]acetate, which decreased by methionine sulfoximine-induced inhibition of the glial enzyme glutamine synthetase. Cell metabolic specialization was further demonstrated by higher pyruvate carboxylase-derived labeling in glutamine than in glutamate, indicating its activity in astrocytes and not in neurons. Exposure to the neurotoxin acrylamide resulted in intracellular accumulation of glutamate and decreased GABA synthesis. These results suggest an acrylamide-induced impairment of neuronal synaptic vesicle trafficking and imbalanced glutamine-glutamate-GABA cycle, due to loss of cell-cell contacts at synaptic sites. This work demonstrates, for the first time to our knowledge, that neural differentiation of human cells in a 3D setting recapitulates neuronal-astrocytic metabolic interactions, highlighting the relevance of these models for toxicology and better understanding the crosstalk between human neural cells. PMID:27619889

  9. Glutamine acts as a neuroprotectant against DNA damage, beta-amyloid and H2O2-induced stress.

    Directory of Open Access Journals (Sweden)

    Jianmin Chen

    Full Text Available Glutamine is the most abundant free amino acid in the human blood stream and is 'conditionally essential' to cells. Its intracellular levels are regulated both by the uptake of extracellular glutamine via specific transport systems and by its intracellular synthesis by glutamine synthetase (GS. Adding to the regulatory complexity, when extracellular glutamine is reduced GS protein levels rise. Unfortunately, this excess GS can be maladaptive. GS overexpression is neurotoxic especially if the cells are in a low-glutamine medium. Similarly, in low glutamine, the levels of multiple stress response proteins are reduced rendering cells hypersensitive to H(2O(2, zinc salts and DNA damage. These altered responses may have particular relevance to neurodegenerative diseases of aging. GS activity and glutamine levels are lower in the Alzheimer's disease (AD brain, and a fraction of AD hippocampal neurons have dramatically increased GS levels compared with control subjects. We validated the importance of these observations by showing that raising glutamine levels in the medium protects cultured neuronal cells against the amyloid peptide, Aβ. Further, a 10-day course of dietary glutamine supplementation reduced inflammation-induced neuronal cell cycle activation, tau phosphorylation and ATM-activation in two different mouse models of familial AD while raising the levels of two synaptic proteins, VAMP2 and synaptophysin. Together, our observations suggest that healthy neuronal cells require both intracellular and extracellular glutamine, and that the neuroprotective effects of glutamine supplementation may prove beneficial in the treatment of AD.

  10. Characterization of Glutamine-Requiring Mutants of Pseudomonas aeruginosa

    NARCIS (Netherlands)

    Janssen, Dick B.; Joosten, Han M.L.J.; Herst, Patricia M.; Drift, Chris van der

    1982-01-01

    Revertants were isolated from a glutamine-requiring mutant of Pseudomonas aeruginosa PAO. One strain showed thermosensitive glutamine requirement and formed thermolabile glutamine synthetase, suggesting the presence of a mutation in the structural gene for glutamine synthetase. The mutation conferri

  11. Bipotential precursors of putative fibrous astrocytes and oligodendrocytes in rat cerebellar cultures express distinct surface features and neuron-like γ-aminobutyric acid transport

    International Nuclear Information System (INIS)

    When postnatal rat cerebellar cells were cultured in a chemically defined, serum-free medium, the only type of astrocyte present was unable to accumulate γ-[3H]aminobutyric acid (GABA), did not express surface antigens recognized by two monoclonal antibodies, A2B5 and LB1, and showed minimal proliferation. In these cultures, nonneuronal A2B5+, LB1+ stellate cells exhibiting neuron-like [3H]GABA uptake formed cell colonies of increasing size and were GFAP-. After about one week of culturing, the A2B5+, LB1+, GABA-uptake positive cell groups became galactocerebroside (GalCer) positive. Immunocytolysis of the A2B5+ cells at 3 and 4 days in vitro prevented the appearance of the A2B5+, LB1+, GABA-uptake positive cell colonies, and also of the GalCer+ cell groups. If 10% (vol/vol) fetal calf serum was added to 6-day cultures, the A2B5+, LB1+, GABA-uptake positive cell groups expressed GFAP and not GalCer. If the serum was added to the cultures 2 days after lysing the A2B5+ cells, only A2B5-, LB1-, GABA-uptake negative astrocytes proliferated. It is concluded that the putative fibrous astrocytes previously described in serum-containing cultures derive from bipotential precursors that differentiate into oligodendrocytes (GalCer+) in serum-free medium or into astrocytes (GFAP+) in the presence of serum, while the epithelioid A2B5-, LB1-, GABA-uptake negative astrocytes originate from a different precursor not yet identified

  12. Amino Acid transporters in cancer and their relevance to "glutamine addiction": novel targets for the design of a new class of anticancer drugs.

    Science.gov (United States)

    Bhutia, Yangzom D; Babu, Ellappan; Ramachandran, Sabarish; Ganapathy, Vadivel

    2015-05-01

    Tumor cells have an increased demand for amino acids because of their rapid proliferation rate. In addition to their need in protein synthesis, several amino acids have other roles in supporting cancer growth. There are approximately two-dozen amino acid transporters in humans, and tumor cells must upregulate one or more of these transporters to satisfy their demand for amino acids. If the transporters that specifically serve this purpose in tumor cells are identified, they can be targeted for the development of a brand new class of anticancer drugs; the logical basis of such a strategy would be to starve the tumor cells of an important class of nutrients. To date, four amino acid transporters have been found to be expressed at high levels in cancer: SLC1A5, SLC7A5, SLC7A11, and SLC6A14. Their induction occurs in a cancer type-specific manner with a direct or indirect involvement of the oncogene c-Myc. Further, these transporters are functionally coupled, thus maximizing their ability to promote cancer growth and chemoresistance. Progress has been made in preclinical studies, exploiting these transporters as drug targets in cancer therapy. These transporters also show promise in development of new tumor-imaging probes and in tumor-specific delivery of appropriately designed chemotherapeutic agents. PMID:25855379

  13. The effect of glutamine supplementation and physical exercise on neutrophil function.

    Science.gov (United States)

    Lagranha, C J; Levada-Pires, A C; Sellitti, D F; Procopio, J; Curi, R; Pithon-Curi, T C

    2008-04-01

    Glutamine is the most abundant free amino acid in the body. Its primary source is skeletal muscle, from where it is released into the bloodstream and transported to a variety of tissues. Several studies have shown that glutamine is important for rat and human neutrophil function and that these cells utilize glutamine at high rates. Physical exercise has also been shown to induce considerable changes in neutrophil metabolism and function. As neutrophils represent 50-60% of the total circulating leukocyte pool and play a key role in inflammation, both physical exercise and glutamine might be expected to regulate the inflammatory process. In this review, the changes in neutrophil function induced by physical exercise and glutamine supplementation are compared. PMID:17928941

  14. Age-dependent decrease in glutamine synthetase expression in the hippocampal astroglia of the triple transgenic Alzheimer's disease mouse model: mechanism for deficient glutamatergic transmission?

    Directory of Open Access Journals (Sweden)

    Verkhratsky Alexei

    2011-07-01

    Full Text Available Abstract Astrocytes are fundamental for brain homeostasis and the progression and outcome of many neuropathologies including Alzheimer's disease (AD. In the triple transgenic mouse model of AD (3xTg-AD generalised hippocampal astroglia atrophy precedes a restricted and specific β-amyloid (Aβ plaque-related astrogliosis. Astrocytes are critical for CNS glutamatergic transmission being the principal elements of glutamate homeostasis through maintaining its synthesis, uptake and turnover via glutamate-glutamine shuttle. Glutamine synthetase (GS, which is specifically expressed in astrocytes, forms glutamine by an ATP-dependent amination of glutamate. Here, we report changes in GS astrocytic expression in two major cognitive areas of the hippocampus (the dentate gyrus, DG and the CA1 in 3xTg-AD animals aged between 9 and 18 months. We found a significant reduction in Nv (number of cell/mm3 of GS immunoreactive (GS-IR astrocytes starting from 12 months (28.59% of age in the DG, and sustained at 18 months (31.65%. CA1 decrease of GS-positive astrocytes Nv (33.26% occurs at 18 months. This Nv reduction of GS-IR astrocytes is paralleled by a decrease in overall GS expression (determined by its optical density that becomes significant at 18 months (21.61% and 19.68% in DG and CA1, respectively. GS-IR Nv changes are directly associated with the presence of Aβ deposits showing a decrease of 47.92% as opposed to 23.47% in areas free of Aβ. These changes in GS containing astrocytes and GS-immunoreactivity indicate AD-related impairments of glutamate homeostatic system, at the advanced and late stages of the disease, which may affect the efficacy of glutamatergic transmission in the diseased brain that may contribute to the cognitive deficiency.

  15. Astrocytes Grown in Alvetex(®) Three Dimensional Scaffolds Retain a Non-reactive Phenotype.

    Science.gov (United States)

    Ugbode, Christopher I; Hirst, Warren D; Rattray, Marcus

    2016-08-01

    Protocols which permit the extraction of primary astrocytes from either embryonic or postnatal mice are well established however astrocytes in culture are different to those in the mature CNS. Three dimensional (3D) cultures, using a variety of scaffolds may enable better phenotypic properties to be developed in culture. We present data from embryonic (E15) and postnatal (P4) murine primary cortical astrocytes grown on coated coverslips or a 3D polystyrene scaffold, Alvetex. Growth of both embryonic and postnatal primary astrocytes in the 3D scaffold changed astrocyte morphology to a mature, protoplasmic phenotype. Embryonic-derived astrocytes in 3D expressed markers of mature astrocytes, namely the glutamate transporter GLT-1 with low levels of the chondroitin sulphate proteoglycans, NG2 and SMC3. Embryonic astrocytes derived in 3D show lower levels of markers of reactive astrocytes, namely GFAP and mRNA levels of LCN2, PTX3, Serpina3n and Cx43. Postnatal-derived astrocytes show few protein changes between 2D and 3D conditions. Our data shows that Alvetex is a suitable scaffold for growth of astrocytes, and with appropriate choice of cells allows the maintenance of astrocytes with the properties of mature cells and a non-reactive phenotype. PMID:27099962

  16. Ketogenic diet and astrocyte/neuron metabolic interactions

    Directory of Open Access Journals (Sweden)

    Vamecq Joseph

    2007-05-01

    Full Text Available The ketogenic diet is an anticonvulsant diet enriched in fat. It provides the body with a minimal protein requirement and a restricted carbohydrate supply, the vast majority of calories (more than 80-90% being given by fat. Though anticonvulsant activity of ketogenic diet has been well documented by a large number of experimental and clinical studies, underlying mechanisms still remain partially unclear. Astrocyte-neuron interactions, among which metabolic shuttles, may influence synaptic activity and hence anticonvulsant protection. The astrocyte-neuron metabolic shuttles may be themselves influenced by the availability in energetic substrates such as hydrates of carbon and fats. Historically, ketogenic diet had been designed to mimic changes such as ketosis occurring upon starvation, a physiological state already known to exhibit anticonvulsant protection and sometimes referred to as “water diet”. For this reason, a special attention should be paid to metabolic features shared in common by ketogenic diet and starvation and especially those features that might result in anticonvulsant protection. Compared to feeding by usual mixed diet, starvation and ketogenic diet are both characterised by increased fat, lowered glucose and aminoacid supplies to cells. The resulting impact of these changes in energetic substrates on astrocyte/neuron metabolic shuttles might have anticonvulsant and/or neuroprotective properties. This is the aim of this communication to review some important astrocyte/neuron metabolic interactions (astrocyte/neuron lactate shuttle, glutamateinduced astrocytic glycolysis activation, glutamate/glutamine cycle along with the neurovascular coupling and the extent to which the way of their alteration by starvation and/or ketogenic diet might result in seizure and/or brain protection.

  17. α7 Nicotinic Receptor Promotes the Neuroprotective Functions of Astrocytes against Oxaliplatin Neurotoxicity

    Directory of Open Access Journals (Sweden)

    Lorenzo Di Cesare Mannelli

    2015-01-01

    Full Text Available Neuropathies are characterized by a complex response of the central nervous system to injuries. Glial cells are recruited to maintain neuronal homeostasis but dysregulated activation leads to pain signaling amplification and reduces the glial neuroprotective power. Recently, we highlighted the property of α7 nicotinic-acetylcholine-receptor (nAChR agonists to relieve pain and induce neuroprotection simultaneously with a strong increase in astrocyte density. Aimed to study the role of α7 nAChR in the neuron-glia cross-talk, we treated primary rat neurons and astrocytes with the neurotoxic anticancer drug oxaliplatin evaluating the effect of the α7 nAChR agonist PNU-282987 (PNU. Oxaliplatin (1 μM, 48 h reduced cell viability and increased caspase-3 activity of neuron monocultures without damaging astrocytes. In cocultures, astrocytes were not able to protect neurons by oxaliplatin even if glial cell metabolism was stimulated (pyruvate increase. On the contrary, the coculture incubation with 10 μM PNU improved neuron viability and inhibited apoptosis. In the absence of astrocytes, the protection disappeared. Furthermore, PNU promoted the release of the anti-inflammatory cytokine TGF-β1 and the expression of the glutamate-detoxifying enzyme glutamine synthetase. The α7 nAChR stimulation protects neurons from oxaliplatin toxicity through an astrocyte-mediated mechanism. α7 nAChR is suggested for recovering the homeostatic role of astrocytes.

  18. Protective Effects of Gastrodin Against Autophagy-Mediated Astrocyte Death.

    Science.gov (United States)

    Wang, Xin-Shang; Tian, Zhen; Zhang, Nan; Han, Jing; Guo, Hong-Liang; Zhao, Ming-Gao; Liu, Shui-Bing

    2016-03-01

    Gastrodin is an active ingredient derived from the rhizome of Gastrodia elata. This compound is usually used to treat convulsive illness, dizziness, vertigo, and headache. This study aimed to investigate the effect of gastrodin on the autophagy of glial cells exposed to lipopolysaccharides (LPS, 1 µg/mL). Autophagy is a form of programmed cell death, although it also promotes cell survival. In cultured astrocytes, LPS exposure induced excessive autophagy and apoptosis, which were significantly prevented by the pretreatment cells with gastrodin (10 μM). The protective effects of gastrodin via autophagy inhibition were verified by the decreased levels of LC3-II, P62, and Beclin-1, which are classical markers for autophagy. Furthermore, gastrodin protected astrocytes from apoptosis through Bcl-2 and Bax signaling pathway. The treatment of astrocytes with rapamycin (500 nM), wortmannin (100 nM), and LY294002 (10 μM), which are inhibitors of mTOR and PI3K, respectively, eliminated the known effects of gastrodin on the inhibited Beclin-1 expression. Furthermore, gastrodin blocked the down-regulation of glutamine synthetase induced by LPS exposure in astrocytes. Our results suggest that gastrodin can be used as a preventive agent for the excessive autophagy induced by LPS. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26643508

  19. Glutamate reduces experimental intestinal hyperpermeability and facilitates glutamine support of gut integrity

    Institute of Scientific and Technical Information of China (English)

    Mechteld AR Vermeulen; Jeffrey de Jong; Mathijs J Vaessen; Paul AM van Leeuwen; Alexander PJ Houdijk

    2011-01-01

    AIM: To assess whether glutamate plays a similar role to glutamine in preserving gut wall integrity. METHODS: The effects of glutamine and glutamate on induced hyperpermeability in intestinal cell lines were studied. Paracellular hyperpermeability was induced in Caco2.BBE and HT-29CL.19A cell lines by adding phorbol-12,13-dibutyrate (PDB) apically, after which the effects of glutamine and glutamate on horseradish peroxidase (HRP) diffusion were studied. An inhibitor of glutamate transport (L-trans-pyrrolidine-2,4-dicarboxylic acid: trans-PDC) and an irreversible blocker (acivicin) of the extracellular glutamine to glutamate converting enzyme, γ-glutamyltransferase, were used. RESULTS: Apical to basolateral HRP flux increased significantly compared to controls not exposed to PDB (n = 30, P < 0.001). Glutamine application reduced hyperpermeability by 19% and 39% in the respective cell lines. Glutamate application reduced hyperpermeability by 30% and 20%, respectively. Incubation of HT29CL.19A cells with acivicin and subsequent PDB and glutamine addition increased permeability levels. Incubation of Caco2.BBE cells with trans-PDC followed by PDB and glutamate addition also resulted in high permeability levels. CONCLUSION: Apical glutamate -similar to glutaminecan decrease induced paracellular hyperpermeability. Extracellular conversion of glutamine to glutamate and subsequent uptake of glutamate could be a pivotal step in the mechanism underlying the protective effect of glutamine.

  20. Glutamine synthetase is a genetic determinant of cell type-specific glutamine independence in breast epithelia.

    Directory of Open Access Journals (Sweden)

    Hsiu-Ni Kung

    2011-08-01

    Full Text Available Although significant variations in the metabolic profiles exist among different cells, little is understood in terms of genetic regulations of such cell type-specific metabolic phenotypes and nutrient requirements. While many cancer cells depend on exogenous glutamine for survival to justify the therapeutic targeting of glutamine metabolism, the mechanisms of glutamine dependence and likely response and resistance of such glutamine-targeting strategies among cancers are largely unknown. In this study, we have found a systematic variation in the glutamine dependence among breast tumor subtypes associated with mammary differentiation: basal- but not luminal-type breast cells are more glutamine-dependent and may be susceptible to glutamine-targeting therapeutics. Glutamine independence of luminal-type cells is associated mechanistically with lineage-specific expression of glutamine synthetase (GS. Luminal cells can also rescue basal cells in co-culture without glutamine, indicating a potential for glutamine symbiosis within breast ducts. The luminal-specific expression of GS is directly induced by GATA3 and represses glutaminase expression. Such distinct glutamine dependency and metabolic symbiosis is coupled with the acquisition of the GS and glutamine independence during the mammary differentiation program. Understanding the genetic circuitry governing distinct metabolic patterns is relevant to many symbiotic relationships among different cells and organisms. In addition, the ability of GS to predict patterns of glutamine metabolism and dependency among tumors is also crucial in the rational design and application of glutamine and other metabolic pathway targeted therapies.

  1. Cytosolic glutamine synthetase in barley

    DEFF Research Database (Denmark)

    Thomsen, Hanne Cecilie

    fertilizer requirement. The enzyme glutamine synthetase (GS) has been a major topic in plant nitrogen research for decades due to its central role in plant N metabolism. The cytosolic version of this enzyme (GS1) plays an important role in relation to primary N assimilation as well as in relation to N...

  2. Targeting astrocytes in major depression

    OpenAIRE

    Verkhratsky, Alexej; Peng, Liang; Gu, Li; Li, Baoman

    2015-01-01

    Astrocytes represent a highly heterogeneous population of neural cells primarily responsible for the homeostasis of the central nervous system. Astrocytes express multiple receptors for neurotransmitters, including the serotonin 5-HT2B receptors and interact with neurones at the synapse. Astroglia contribute to neurological diseases through homeostatic response, neuroprotection and reactivity. In major depression, astrocytes show signs of degeneration and are decreased in numbe...

  3. L-glutamine supplementations enhance liver glutamine-glutathione axis and heat shock factor-1 expression in endurance-exercise trained rats.

    Science.gov (United States)

    Petry, Éder Ricardo; Cruzat, Vinicius Fernandes; Heck, Thiago Gomes; Homem de Bittencourt, Paulo Ivo; Tirapegui, Julio

    2015-04-01

    Liver L-glutamine is an important vehicle for the transport of ammonia and intermediary metabolism of amino acids between tissues, particularly under catabolic situations, such as high-intensity exercise. Hence, the aim of this study was to investigate the effects of oral supplementations with L-glutamine in its free or dipeptide forms (with L-alanine) on liver glutamine-glutathione (GSH) axis, and 70 kDa heat shock proteins (HSP70)/heat shock transcription factor 1 (HSF1) expressions. Adult male Wistar rats were 8-week trained (60 min/day, 5 days/week) on a treadmill. During the last 21 days, the animals were daily supplemented with 1 g of L-glutamine/kg body weight per day in either l-alanyl-L-glutamine dipeptide (DIP) form or a solution containing L-glutamine and l-alanine in their free forms (GLN+ALA) or water (controls). Exercise training increased cytosolic and nuclear HSF1 and HSP70 expression, as compared with sedentary animals. However, both DIP and GLN+ALA supplements enhanced HSF1 expression (in both cytosolic and nuclear fractions) in relation to exercised controls. Interestingly, HSF1 rises were not followed by enhanced HSP70 expression. DIP and GLN+ALA supplements increased plasma glutamine concentrations (by 62% and 59%, respectively) and glutamine to glutamate plasma ratio in relation to trained controls. This was in parallel with a decrease in plasma ammonium levels. Supplementations increased liver GSH (by 90%), attenuating the glutathione disulfide (GSSG) to GSH ratio, suggesting a redox state protection. In conclusion, oral administration with DIP and GLN+ALA supplements in endurance-trained rats improve liver glutamine-GSH axis and modulate HSF1 pathway. PMID:25202991

  4. Expression and cellular function of vSNARE proteins in brain astrocytes.

    Science.gov (United States)

    Ropert, N; Jalil, A; Li, D

    2016-05-26

    Gray matter protoplasmic astrocytes, a major type of glial cell in the mammalian brain, extend thin processes ensheathing neuronal synaptic terminals. Albeit electrically silent, astrocytes respond to neuronal activity with Ca(2+) signals that trigger the release of gliotransmitters, such as glutamate, d-serine, and ATP, which modulate synaptic transmission. It has been suggested that the astrocytic processes, together with neuronal pre- and post-synaptic elements, constitute a tripartite synapse, and that astrocytes actively regulate information processing. Astrocytic vesicles expressing VAMP2 and VAMP3 vesicular SNARE (vSNARE) proteins have been suggested to be a key feature of the tripartite synapse and mediate gliotransmitter release through Ca(2+)-regulated exocytosis. However, the concept of exocytotic release of gliotransmitters by astrocytes has been challenged. Here we review studies investigating the expression profile of VAMP2 and VAMP3 vSNARE proteins in rodent astrocytes, and the functional implication of VAMP2/VAMP3 vesicles in astrocyte signaling. We also discuss our recent data suggesting that astrocytic VAMP3 vesicles regulate the trafficking of glutamate transporters at the plasma membrane and glutamate uptake. A better understanding of the functional consequences of the astrocytic vSNARE vesicles on glutamate signaling, neuronal excitability and plasticity, will require the development of new strategies to selectively interrogate the astrocytic vesicles trafficking in vivo. PMID:26518463

  5. Astrocytes in Alzheimer's Disease

    Czech Academy of Sciences Publication Activity Database

    Verkhratsky, Alexei; Olabarria, M.; Noristani, H. N.; Yeh, C. Y.; Rodríguez Arellano, Jose Julio

    2010-01-01

    Roč. 7, č. 4 (2010), s. 399-412. ISSN 1933-7213 R&D Projects: GA ČR GA309/09/1696; GA ČR GA305/08/1384 Institutional research plan: CEZ:AV0Z50390703 Keywords : Astrocytes * neuroglia * neurodegeneration Subject RIV: FH - Neurology Impact factor: 6.084, year: 2010

  6. White-matter astrocytes, axonal energy metabolism, and axonal degeneration in multiple sclerosis

    Science.gov (United States)

    Cambron, Melissa; D'Haeseleer, Miguel; Laureys, Guy; Clinckers, Ralph; Debruyne, Jan; De Keyser, Jacques

    2012-01-01

    In patients with multiple sclerosis (MS), a diffuse axonal degeneration occurring throughout the white matter of the central nervous system causes progressive neurologic disability. The underlying mechanism is unclear. This review describes a number of pathways by which dysfunctional astrocytes in MS might lead to axonal degeneration. White-matter astrocytes in MS show a reduced metabolism of adenosine triphosphate-generating phosphocreatine, which may impair the astrocytic sodium potassium pump and lead to a reduced sodium-dependent glutamate uptake. Astrocytes in MS white matter appear to be deficient in β2 adrenergic receptors, which are involved in stimulating glycogenolysis and suppressing inducible nitric oxide synthase (NOS2). Glutamate toxicity, reduced astrocytic glycogenolysis leading to reduced lactate and glutamine production, and enhanced nitric oxide (NO) levels may all impair axonal mitochondrial metabolism, leading to axonal degeneration. In addition, glutamate-mediated oligodendrocyte damage and impaired myelination caused by a decreased production of N-acetylaspartate by axonal mitochondria might also contribute to axonal loss. White-matter astrocytes may be considered as a potential target for neuroprotective MS therapies. PMID:22214904

  7. Glutamine metabolism in uricotelic species: variation in skeletal muscle glutamine synthetase, glutaminase, glutamine levels and rates of protein synthesis.

    Science.gov (United States)

    Watford, Malcolm; Wu, Guoyao

    2005-04-01

    High intracellular glutamine levels have been implicated in promoting net protein synthesis and accretion in mammalian skeletal muscle. Little is known regarding glutamine metabolism in uricotelic species but chicken breast muscle exhibits high rates of protein accretion and would be predicted to maintain high glutamine levels. However, chicken breast muscle expresses high glutaminase activity and here we report that chicken breast muscle also expresses low glutamine synthetase activity (0.07+/-0.01 U/g) when compared to leg muscle (0.50+/-0.04 U/g). Free glutamine levels were 1.38+/-0.09 and 9.69+/-0.12 nmol/mg wet weight in breast and leg muscles of fed chickens, respectively. Glutamine levels were also lower in dove breast muscle (4.82+/-0.35 nmol/mg wet weight) when compared to leg muscle (16.2+/-1.0 nmol/mg wet weight) and much lower (1.80+/-0.46 nmol/mg wet weight) in lizard leg muscle. In fed chickens, rates of fractional protein synthesis were higher in leg than in breast muscle, and starvation (48 h) resulted in a decrease in both glutamine content and rate of protein synthesis in leg muscle. Thus, although tissue-specific glutamine metabolism in uricotelic species differs markedly from that in ureotelic animals, differences in rates of skeletal muscle protein synthesis are associated with corresponding differences in intramuscular glutamine content. PMID:15763516

  8. Neuron–astrocyte interactions in the medial nucleus of the trapezoid body

    OpenAIRE

    Reyes-Haro, D.; Mueller, J.; Boresch, M.; Pivneva, T.; Benedetti, B.; Scheller, A; Nolte, C.; Kettenmann, H.

    2010-01-01

    The calyx of Held (CoH) synapse serves as a model system to analyze basic mechanisms of synaptic transmission. Astrocyte processes are part of the synaptic structure and contact both pre- and postsynaptic membranes. In the medial nucleus of the trapezoid body (MNTB), midline stimulation evoked a current response that was not mediated by glutamate receptors or glutamate uptake, despite the fact that astrocytes express functional receptors and transporters. However, astrocytes showed spontaneou...

  9. Functional and phenotypic differences of pure populations of stem cell-derived astrocytes and neuronal precursor cells.

    Science.gov (United States)

    Kleiderman, Susanne; Sá, João V; Teixeira, Ana P; Brito, Catarina; Gutbier, Simon; Evje, Lars G; Hadera, Mussie G; Glaab, Enrico; Henry, Margit; Sachinidis, Agapios; Alves, Paula M; Sonnewald, Ursula; Leist, Marcel

    2016-05-01

    Availability of homogeneous astrocyte populations would facilitate research concerning cell plasticity (metabolic and transcriptional adaptations; innate immune responses) and cell cycle reactivation. Current protocols to prepare astrocyte cultures differ in their final content of immature precursor cells, preactivated cells or entirely different cell types. A new method taking care of all these issues would improve research on astrocyte functions. We found here that the exposure of a defined population of pluripotent stem cell-derived neural stem cells (NSC) to BMP4 results in pure, nonproliferating astrocyte cultures within 24-48 h. These murine astrocytes generated from embryonic stem cells (mAGES) expressed the positive markers GFAP, aquaporin 4 and GLT-1, supported neuronal function, and acquired innate immune functions such as the response to tumor necrosis factor and interleukin 1. The protocol was applicable to several normal or disease-prone pluripotent cell lines, and the corresponding mAGES all exited the cell cycle and lost most of their nestin expression, in contrast to astrocytes generated by serum-addition or obtained as primary cultures. Comparative gene expression analysis of mAGES and NSC allowed quantification of differences between the two cell types and a definition of an improved marker set to define astrocytes. Inclusion of several published data sets in this transcriptome comparison revealed the similarity of mAGES with cortical astrocytes in vivo. Metabolic analysis of homogeneous NSC and astrocyte populations revealed distinct neurochemical features: both cell types synthesized glutamine and citrate, but only mature astrocytes released these metabolites. Thus, the homogeneous cultures allowed an improved definition of NSC and astrocyte features. PMID:26689134

  10. Glutamine Synthetase Is a Genetic Determinant of Cell Type–Specific Glutamine Independence in Breast Epithelia

    OpenAIRE

    Hsiu-Ni Kung; Marks, Jeffrey R.; Jen-Tsan Chi

    2011-01-01

    Although significant variations in the metabolic profiles exist among different cells, little is understood in terms of genetic regulations of such cell type-specific metabolic phenotypes and nutrient requirements. While many cancer cells depend on exogenous glutamine for survival to justify the therapeutic targeting of glutamine metabolism, the mechanisms of glutamine dependence and likely response and resistance of such glutamine-targeting strategies among cancers are largely unknown. In th...

  11. Probing astrocytes with carbon nanotubes and assessing their effects on astrocytic structural and functional properties

    Science.gov (United States)

    Gottipati, Manoj K.

    Single-walled carbon nanotubes, chemically-functionalized with polyethylene glycol (SWCNT-PEG) have been shown to modulate the morphology and proliferation characteristics of astrocytes in culture, when applied to the cells as colloidal solutes or as films upon which the cells can attach and grow. These changes were associated with a change in the immunoreactivity of the astrocyte-specific protein, glial fibrillary acidic protein (GFAP); the solutes and films caused an increase and a decrease in GFAP levels, respectively. To assess if these morpho-functional changes induced by the SWCNT-PEG modalities are dependent on GFAP or if the changes in GFAP levels are independent events, I used astrocytes isolated from GFAP knockout mice and found that selected changes induced by the SWCNT-PEG modalities are mediated by GFAP, namely the changes in perimeter, shape and cell death for colloidal solutes and the rate of proliferation for films. Since the loss GFAP has been shown to hamper the trafficking of glutamate transporters to the surface of astrocytes, which plays a vital role in the uptake of extracellular glutamate and maintaining homeostasis in the brain and spinal cord, in a subsequent study, I assessed if the SWCNT-PEG solute causes any change in the glutamate uptake characteristics of astrocytes. Using a radioactive glutamate uptake assay and immunolabeling, I found that SWCNT-PEG solute causes an increase in the uptake of glutamate from the extracellular space along with an increase in the immunoreactivity of the glutamate transporter, L-glutamate L-aspartate transporter (GLAST), on their cell surface, a likely consequence of the increase in GFAP levels induced by the SWCNT-PEG solute. These results imply that SWCNT-PEG could potentially be used as a viable candidate in neural prosthesis applications to prevent glutamate excitotoxicity, a pathological process observed in brain and spinal cord injuries, and alleviate the death toll of neurons surrounding the injury

  12. Modeling presynapse-astrocyte interactions

    OpenAIRE

    Kerstin Lenk

    2015-01-01

    Astrocytes have gained an increased interest in neuroscience due to their ability to influence synaptic transmission through gliotransmitters. Many studies and models concentrate on tripartite synapses formed by two neurons and an astrocyte. The effects of tripartite synapse on paired pulse facilitation and depression were suggested for example by De Pittá et al. (PLoS Comput. Biol. 2011). In the presented work we concentrated on the pathway from the presynapse to the astrocyte and back to th...

  13. Astrocyte membrane properties are altered in a rat model of developmental cortical malformation but single-cell astrocytic glutamate uptake is robust.

    Science.gov (United States)

    Hanson, Elizabeth; Danbolt, Niels Christian; Dulla, Chris G

    2016-05-01

    Developmental cortical malformations (DCMs) are linked with severe epilepsy and are caused by both genetic and environmental insults. DCMs include several neurological diseases, such as focal cortical dysplasia, polymicrogyria, schizencephaly, and others. Human studies have implicated astrocyte reactivity and dysfunction in the pathophysiology of DCMs, but their specific role is unknown. As astrocytes powerfully regulate glutamate neurotransmission, and glutamate levels are known to be increased in human epileptic foci, understanding the role of astrocytes in the pathological sequelae of DCMs is extremely important. Additionally, recent studies examining astrocyte glutamate uptake in DCMs have reported conflicting results, adding confusion to the field. In this study we utilized the freeze lesion (FL) model of DCM, which is known to induce reactive astrocytosis and cause significant changes in astrocyte morphology, proliferation, and distribution. Using whole-cell patch clamp recording from astrocytes, we recorded both UV-uncaging and synaptically evoked glutamate transporter currents (TCs), widely accepted assays of functional glutamate transport by astrocytes. With this approach, we set out to test the hypothesis that astrocyte membrane properties and glutamate transport were disrupted in this model of DCM. Though we found that the developmental maturation of astrocyte membrane resistance was disrupted by FL, glutamate uptake by individual astrocytes was robust throughout FL development. Interestingly, using an immunolabeling approach, we observed spatial and developmental differences in excitatory amino acid transporter (EAAT) expression in FL cortex. Spatially specific differences in EAAT2 (GLT-1) and EAAT1 (GLAST) expression suggest that the relative contribution of each EAAT to astrocytic glutamate uptake may be altered in FL cortex. Lastly, we carefully analyzed the amplitudes and onset times of both synaptically- and UV uncaging-evoked TCs. We found that in

  14. Traumatically injured astrocytes release a proteomic signature modulated by STAT3-dependent cell survival.

    Science.gov (United States)

    Levine, Jaclynn; Kwon, Eunice; Paez, Pablo; Yan, Weihong; Czerwieniec, Gregg; Loo, Joseph A; Sofroniew, Michael V; Wanner, Ina-Beate

    2016-05-01

    Molecular markers associated with CNS injury are of diagnostic interest. Mechanical trauma generates cellular deformation associated with membrane permeability with unknown molecular consequences. We used an in vitro model of stretch-injury and proteomic analyses to determine protein changes in murine astrocytes and their surrounding fluids. Abrupt pressure-pulse stretching resulted in the rapid release of 59 astrocytic proteins with profiles reflecting cell injury and cell death, i.e., mechanoporation and cell lysis. This acute trauma-release proteome was overrepresented with metabolic proteins compared with the uninjured cellular proteome, bearing relevance for post-traumatic metabolic depression. Astrocyte-specific deletion of signal transducer and activator of transcription 3 (STAT3-CKO) resulted in reduced stretch-injury tolerance, elevated necrosis and increased protein release. Consistent with more lysed cells, more protein complexes, nuclear and transport proteins were released from STAT3-CKO versus nontransgenic astrocytes. STAT3-CKO astrocytes had reduced basal expression of GFAP, lactate dehydrogenase B (LDHB), aldolase C (ALDOC), and astrocytic phosphoprotein 15 (PEA15), and elevated levels of tropomyosin (TPM4) and α actinin 4 (ACTN4). Stretching caused STAT3-dependent cellular depletion of PEA15 and GFAP, and its filament disassembly in subpopulations of injured astrocytes. PEA15 and ALDOC signals were low in injured astrocytes acutely after mouse spinal cord crush injury and were robustly expressed in reactive astrocytes 1 day postinjury. In contrast, α crystallin (CRYAB) was present in acutely injured astrocytes, and absent from uninjured and reactive astrocytes, demonstrating novel marker differences among postinjury astrocytes. These findings reveal a proteomic signature of traumatically-injured astrocytes reflecting STAT3-dependent cellular survival with potential diagnostic value. GLIA 2016;64:668-694. PMID:26683444

  15. Spatiotemporal characteristics of calcium dynamics in astrocytes

    Science.gov (United States)

    Kang, Minchul; Othmer, Hans G.

    2009-09-01

    Although Cai2+ waves in networks of astrocytes in vivo are well documented, propagation in vivo is much more complex than in culture, and there is no consensus concerning the dominant roles of intercellular and extracellular messengers [inositol 1,4,5-trisphosphate (IP3) and adenosine-5'-triphosphate (ATP)] that mediate Cai2+ waves. Moreover, to date only simplified models that take very little account of the geometrical struture of the networks have been studied. Our aim in this paper is to develop a mathematical model based on realistic cellular morphology and network connectivity, and a computational framework for simulating the model, in order to address these issues. In the model, Cai2+ wave propagation through a network of astrocytes is driven by IP3 diffusion between cells and ATP transport in the extracellular space. Numerical simulations of the model show that different kinetic and geometric assumptions give rise to differences in Cai2+ wave propagation patterns, as characterized by the velocity, propagation distance, time delay in propagation from one cell to another, and the evolution of Ca2+ response patterns. The temporal Cai2+ response patterns in cells are different from one cell to another, and the Cai2+ response patterns evolve from one type to another as a Cai2+ wave propagates. In addition, the spatial patterns of Cai2+ wave propagation depend on whether IP3, ATP, or both are mediating messengers. Finally, two different geometries that reflect the in vivo and in vitro configuration of astrocytic networks also yield distinct intracellular and extracellular kinetic patterns. The simulation results as well as the linear stability analysis of the model lead to the conclusion that Cai2+ waves in astrocyte networks are probably mediated by both intercellular IP3 transport and nonregenerative (only the glutamate-stimulated cell releases ATP) or partially regenerative extracellular ATP signaling.

  16. Electrodiffusive model for astrocytic and neuronal ion concentration dynamics.

    Directory of Open Access Journals (Sweden)

    Geir Halnes

    Full Text Available The cable equation is a proper framework for modeling electrical neural signalling that takes place at a timescale at which the ionic concentrations vary little. However, in neural tissue there are also key dynamic processes that occur at longer timescales. For example, endured periods of intense neural signaling may cause the local extracellular K(+-concentration to increase by several millimolars. The clearance of this excess K(+ depends partly on diffusion in the extracellular space, partly on local uptake by astrocytes, and partly on intracellular transport (spatial buffering within astrocytes. These processes, that take place at the time scale of seconds, demand a mathematical description able to account for the spatiotemporal variations in ion concentrations as well as the subsequent effects of these variations on the membrane potential. Here, we present a general electrodiffusive formalism for modeling of ion concentration dynamics in a one-dimensional geometry, including both the intra- and extracellular domains. Based on the Nernst-Planck equations, this formalism ensures that the membrane potential and ion concentrations are in consistency, it ensures global particle/charge conservation and it accounts for diffusion and concentration dependent variations in resistivity. We apply the formalism to a model of astrocytes exchanging ions with the extracellular space. The simulations show that K(+-removal from high-concentration regions is driven by a local depolarization of the astrocyte membrane, which concertedly (i increases the local astrocytic uptake of K(+, (ii suppresses extracellular transport of K(+, (iii increases axial transport of K(+ within astrocytes, and (iv facilitates astrocytic relase of K(+ in regions where the extracellular concentration is low. Together, these mechanisms seem to provide a robust regulatory scheme for shielding the extracellular space from excess K(+.

  17. RNA Localization in Astrocytes

    DEFF Research Database (Denmark)

    Thomsen, Rune

    2012-01-01

    Messenger RNA (mRNA) localization is a mechanism by which polarized cells can regulate protein synthesis to specific subcellular compartments in a spatial and temporal manner, and plays a pivotal role in multiple physiological processes from embryonic development to cell differentiation and...... cell protrusions of both cell types. Moreover, the NGS analysis revealed that the mRNA of the intermediate filament proteins nestin and glial fibrilary acidic protein (GFAP) significantlyaccumulatedin astrocyte protrusions, which was examined in closer detail. Fluorescence in situ hybridization (FISH...

  18. Astrocytes: Orchestrating synaptic plasticity?

    Science.gov (United States)

    De Pittà, M; Brunel, N; Volterra, A

    2016-05-26

    Synaptic plasticity is the capacity of a preexisting connection between two neurons to change in strength as a function of neural activity. Because synaptic plasticity is the major candidate mechanism for learning and memory, the elucidation of its constituting mechanisms is of crucial importance in many aspects of normal and pathological brain function. In particular, a prominent aspect that remains debated is how the plasticity mechanisms, that encompass a broad spectrum of temporal and spatial scales, come to play together in a concerted fashion. Here we review and discuss evidence that pinpoints to a possible non-neuronal, glial candidate for such orchestration: the regulation of synaptic plasticity by astrocytes. PMID:25862587

  19. Plasma Glutamine Concentrations in Liver Failure.

    Directory of Open Access Journals (Sweden)

    Gunnel Helling

    Full Text Available Higher than normal plasma glutamine concentration at admission to an intensive care unit is associated with an unfavorable outcome. Very high plasma glutamine levels are sometimes seen in both acute and chronic liver failure. We aimed to systematically explore the relation between different types of liver failure and plasma glutamine concentrations.Four different groups of patients were studies; chronic liver failure (n = 40, acute on chronic liver failure (n = 20, acute fulminant liver failure (n = 20, and post-hepatectomy liver failure (n = 20. Child-Pugh and Model for End-stage Liver Disease (MELD scores were assessed as indices of liver function. All groups except the chronic liver failure group were followed longitudinally during hospitalisation. Outcomes were recorded up to 48 months after study inclusion.All groups had individuals with very high plasma glutamine concentrations. In the total group of patients (n = 100, severity of liver failure correlated significantly with plasma glutamine concentration, but the correlation was not strong.Liver failure, regardless of severity and course of illness, may be associated with a high plasma glutamine concentration. Further studies are needed to understand whether high glutamine levels should be regarded as a biomarker or as a contributor to symptomatology in liver failure.

  20. Astrocytes in multiple sclerosis.

    Science.gov (United States)

    Ludwin, Samuel K; Rao, Vijayaraghava Ts; Moore, Craig S; Antel, Jack P

    2016-08-01

    Recent experimental and clinical studies on astrocytes are unraveling the capabilities of these multi-functional cells in normal homeostasis, and in central nervous system (CNS) disease. This review focuses on understanding their behavior in all aspects of the initiation, evolution, and resolution of the multiple sclerosis (MS) lesion. Astrocytes display remarkable flexibility and variability of their physical structure and biochemical output, each aspect finely tuned to the specific stage and location of the disease, participating in both pathogenic and beneficial changes seen in acute and progressive forms. As examples, chemo-attractive or repulsive molecules may facilitate the entry of destructive immune cells but may also aid in the recruitment of oligodendrocyte precursors, essential for repair. Pro-inflammatory cytokines may attack pathogenic cells and also destroy normal oligodendrocytes, myelin, and axons. Protective trophic factors may also open the blood-brain barrier and modulate the extracellular matrix to favor recruitment and persistence of CNS-specific immune cells. A chronic glial scar may confer structural support following tissue loss and inhibit ingress of further noxious insults and also inhibit migration of reparative cells and molecules into the damaged tissue. Continual study into these processes offers the therapeutic opportunities to enhance the beneficial capabilities of these cells while limiting their destructive effects. PMID:27207458

  1. Rapamycin prevents the mutant huntingtin-suppressed GLT-1 expression in cultured astrocytes

    Institute of Scientific and Technical Information of China (English)

    Lei-lei CHEN; Jun-chao WU; Lin-hui WANG; Jin WANG; Zhen-hong QIN; Marian DIFIGLIA; Fang LIN

    2012-01-01

    To investigate the effects of rapamycin on glutamate uptake in cultured rat astrocytes expressing N-terminal 552 residues of mutant huntingtin (Htt-552).Methods:Primary astrocyte cultures were prepared from the cortex of postnatal rat pups.An astrocytes model of Huntington's diseasewas established using the astrocytes infected with adenovirus carrying coden gene of N-terminal 552 residues of Huntingtin.The protein levels of glutamate transporters GLT-1 and GLAST,the autophagic marker microtubule-associated protein 1A/1B-light chain 3(LC3) and the autophagy substrate p62 in the astrocytes were examined using Western blotting.The mRNA expression levels of GLT-1and GLAST in the astrocytes were determined using Real-time PCR.[3H]glutamate uptake by the astrocytes was measured with liquid scintillation counting.Results:The expression of mutant Htt-552 in the astrocytes significantly decreased both the mRNA and protein levels of GLT-1 but not those of GLAST.Furthermore,Htt-552 significantly reduced [3H]glutamate uptake by the astrocytes.Treatment with the autophagy inhibitor 3-MA (10 mmol/L) significantly increased the accumulation of mutant Htt-552,and reduced the expression of GLT-1 and [3H]glutamate uptake in the astrocytes.Treatment with the autophagy stimulator rapamycin (0.2 mg/mL) significantly reduced the accumulation of mutant Htt-552,and reversed the changes in GLT-1 expression and [3H]glutamate uptake in the astrocytes.Conclusion:Rapamcin,an autophagy stimulator,can prevent the suppression of GLT-1 expression and glutamate uptake by mutant Htt-552 in cultured astrocytes.

  2. Astrocyte morphology, heterogeneity and density in the developing African Giant Rat (Cricetomys gambianus

    Directory of Open Access Journals (Sweden)

    James Olukayode Olopade

    2015-05-01

    Full Text Available Astrocyte morphologies and heterogeneity were described in male African giant rats (AGR (Cricetomys gambianus, Waterhouse across three age groups (5 neonates, 5 juveniles and 5 adults using Silver impregnation method and immunohistochemistry against glia fibrillary acidic protein (GFAP. Immunopositive cell signaling, cell size and population were least in neonates, followed by adults and juveniles respectively. In neonates, astrocyte processes were mostly detected within the glia limitans of the mid and hind brain; their cell bodies measuring 32±4.8 µm in diameter against 91±5.4µm and 75± 1.9µm in juveniles and adults respectively. Astrocyte heterogeneity in juvenile and adult groups revealed eight subtypes to include fibrous astrocytes chiefly in the corpus callosum and brain stem, protoplasmic astrocytes in the cortex and dentate gyrus (DG; radial glia were found along the olfactory bulb (OB and subventricular zone (SVZ; velate astrocytes were mainly found in the cerebellum and hippocampus; marginal astrocytes close to the pia mater; Bergmann glia in the molecular layer of the cerebellum; perivascular and periventricular astrocytes in the cortex and third ventricle respectively. Cell counts from twelve anatomical regions of the brain were significantly higher in juveniles than in adults (p≤0.01 using unpaired student t-test in the cerebral cortex, pia, corpus callosum, rostral migratory stream (RMS, DG and cerebellum. Highest astrocyte count was found in the DG, while the least count was in the brain stem and sub cortex. Astrocytes along the periventricular layer of the OB are believed to be part of the radial glia system that transport newly formed cells towards the hippocampus and play roles in neurogenesis migration and homeostasis in the AGR. Therefore, astrocyte heterogeneity was examined across age groups in the AGR to determine whether age influences astrocytes population in different regions of the AGR brain and discuss

  3. Active Sulforhodamine 101 Uptake into Hippocampal Astrocytes

    OpenAIRE

    Christian Schnell; Yohannes Hagos; Swen Hülsmann

    2012-01-01

    Sulforhodamine 101 (SR101) is widely used as a marker of astrocytes. In this study we investigated labeling of astrocytes by SR101 in acute slices from the ventrolateral medulla and the hippocampus of transgenic mice expressing EGFP under the control of the astrocyte-specific human GFAP promoter. While SR101 efficiently and specifically labeled EGFP-expressing astrocytes in hippocampus, we found that the same staining procedure failed to label astrocytes efficiently in the ventrol...

  4. Heterogeneity of Astrocytic Form and Function

    OpenAIRE

    Oberheim, Nancy Ann; Goldman, Steven A.; NEDERGAARD, Maiken

    2012-01-01

    Astrocytes participate in all essential CNS functions, including blood flow regulation, energy metabolism, ion and water homeostasis, immune defence, neurotransmission, and adult neurogenesis. It is thus not surprising that astrocytic morphology and function differ between regions, and that different subclasses of astrocytes exist within the same brain region. Recent lines of work also show that the complexity of protoplasmic astrocytes increases during evolution. Human astrocytes are structu...

  5. Primary cultures of astrocytes: Their value in understanding astrocytes in health and disease

    OpenAIRE

    Lange, Sofie C.; Bak, Lasse K.; Helle S. Waagepetersen; Schousboe, Arne; Norenberg, Michael D.

    2012-01-01

    During the past decades of astrocyte research it has become increasingly clear that astrocytes have taken a central position in all central nervous system activities. Much of our new understanding of astrocytes has been derived from studies conducted with primary cultures of astrocytes. Such cultures have been an invaluable tool for studying roles of astrocytes in physiological and pathological states. Many central astrocytic functions in metabolism, amino acid neurotransmission and calcium s...

  6. Intracellular Polyamines Enhance Astrocytic Coupling

    OpenAIRE

    Benedikt, Jan; Inyushin, Mikhail; Yuriy V Kucheryavykh; Rivera, Yomarie; Kucheryavykh, Lilia Y.; Nichols, Colin G.; Eaton, Misty J.; Skatchkov, Serguei N.

    2012-01-01

    Spermine (SPM) and spermidine (SPD), endogenous polyamines (PA) with the ability to modulate various ion channels and receptors in the brain, exert neuroprotective, antidepressant, antioxidant and other effects in vivo such as increasing longevity. These PA are preferably accumulated in astrocytes, and we hypothesized that SPM increases glial intercellular communication by interacting with glial gap junctions. Results obtained in situ, using Lucifer yellow propagation in the astrocytic syncit...

  7. Inhibition of glycogenolysis in astrocytes interrupts memory consolidation in young chickens.

    Science.gov (United States)

    Gibbs, Marie E; Anderson, Damian G; Hertz, Leif

    2006-08-15

    Glycolysis and glycogenolysis are involved in memory processing in day-old chickens and, aside from the provision of energy for neuronal and astrocytic energy metabolism these pathways enable astrocytes to supply neurones with precursor for transmitter glutamate by glucose-based de novo synthesis. We have previously shown that memory processing for bead discrimination learning is dependent on glycolysis; however, the metabolic inhibitor used, iodoacetate, inhibits pyruvate formation from both glucose and glycogen. At specific time points after training transient reductions in brain glycogen content occur, mirrored by increases in glutamate/glutamine content. In the present study, we used intracerebral injection of a glycogen phosphorylase inhibitor, 1,4-dideoxy-1,4-imino-D-arabinitol (DAB), which does not affect glucose breakdown, to evaluate the role of glycogen metabolism in memory consolidation. Dose-dependent inhibition of learning occurred when DAB was administered at specific time periods in relation to training: (i) 5 min before training, (ii) around 30 min posttraining, and (iii) 55 min posttraining. After injection at either of the two earlier periods, memory disappeared after consolidation 30 min postlearning, and after injection 55 min after learning memory was absent at 70 min. The memory loss caused by early administration could be prevented after training by central injection of the glutamate precursor glutamine or the astrocyte-specific substrate acetate together with aspartate, substituting for pyruvate carboxylation. Thus, glycogenolysis is essential for learning in this paradigm and, aside from energy supply considerations, we suggest that an important role for glycogenolysis is to provide neurones with glutamine as the precursor for neuronal glutamate and GABA. PMID:16819764

  8. Insensitivity of astrocytes to interleukin 10 signaling following peripheral immune challenge results in prolonged microglial activation in the aged brain.

    Science.gov (United States)

    Norden, Diana M; Trojanowski, Paige J; Walker, Frederick R; Godbout, Jonathan P

    2016-08-01

    Immune-activated microglia from aged mice produce exaggerated levels of cytokines. Despite high levels of microglial interleukin (IL)-10 in the aged brain, neuroinflammation was prolonged and associated with depressive-like deficits. Because astrocytes respond to IL-10 and, in turn, attenuate microglial activation, we investigated if astrocyte-mediated resolution of microglial activation was impaired with age. Here, aged astrocytes had a dysfunctional profile with higher glial fibrillary acidic protein, lower glutamate transporter expression, and significant cytoskeletal re-arrangement. Moreover, aged astrocytes had reduced expression of growth factors and IL-10 receptor-1 (IL-10R1). After in vivo lipopolysaccharide immune challenge, aged astrocytes had a molecular signature associated with reduced responsiveness to IL-10. This IL-10 insensitivity of aged astrocytes resulted in a failure to induce IL-10R1 and transforming growth factor β and resolve microglial activation. In addition, adult astrocytes reduced microglial activation when co-cultured ex vivo, whereas aged astrocytes did not. Consistent with the aging studies, IL-10R(KO) astrocytes did not augment transforming growth factor β after immune challenge and failed to resolve microglial activation. Collectively, a major cytokine-regulatory loop between activated microglia and astrocytes is impaired in the aged brain. PMID:27318131

  9. A Computational Model to Investigate Astrocytic Glutamate Uptake Influence on Synaptic Transmission and Neuronal Spiking

    Directory of Open Access Journals (Sweden)

    Sushmita Lakshmi Allam

    2012-10-01

    Full Text Available Over the past decades, our view of astrocytes has switched from passive support cells to active processing elements in the brain. The current view is that astrocytes shape neuronal communication and also play an important role in many neurodegenerative diseases. Despite the growing awareness of the importance of astrocytes, the exact mechanisms underlying neuron-astrocyte communication and the physiological consequences of astrocytic-neuronal interactions remain largely unclear. In this work, we define a modeling framework that will permit to address unanswered questions regarding the role of astrocytes. Our computational model of a detailed glutamatergic synapse facilitates the analysis of neural system responses to various stimuli and conditions that are otherwise difficult to obtain experimentally, in particular the readouts at the sub-cellular level. In this paper, we extend a detailed glutamatergic synaptic model, to include astrocytic glutamate transporters. We demonstrate how these glial transporters, responsible for the majority of glutamate uptake, modulate synaptic transmission mediated by ionotropic AMPA and NMDA receptors at glutamatergic synapses. Furthermore, we investigate how these local signaling effects at the synaptic level are translated into varying spatio-temporal patterns of neuron firing. Paired pulse stimulation results reveal that the effect of astrocytic glutamate uptake is more apparent when the input inter-spike interval is sufficiently long to allow the receptors to recover from desensitization. These results suggest an important functional role of astrocytes in spike timing dependent processes and demand further investigation of the molecular basis of certain neurological diseases specifically related to alterations in astrocytic glutamate uptake, such as epilepsy.

  10. Latent KSHV Infected Endothelial Cells Are Glutamine Addicted and Require Glutaminolysis for Survival.

    Directory of Open Access Journals (Sweden)

    Erica L Sanchez

    2015-07-01

    Full Text Available Kaposi's Sarcoma-associated Herpesvirus (KSHV is the etiologic agent of Kaposi's Sarcoma (KS. KSHV establishes a predominantly latent infection in the main KS tumor cell type, the spindle cell, which is of endothelial cell origin. KSHV requires the induction of multiple metabolic pathways, including glycolysis and fatty acid synthesis, for the survival of latently infected endothelial cells. Here we demonstrate that latent KSHV infection leads to increased levels of intracellular glutamine and enhanced glutamine uptake. Depletion of glutamine from the culture media leads to a significant increase in apoptotic cell death in latently infected endothelial cells, but not in their mock-infected counterparts. In cancer cells, glutamine is often required for glutaminolysis to provide intermediates for the tri-carboxylic acid (TCA cycle and support for the production of biosynthetic and bioenergetic precursors. In the absence of glutamine, the TCA cycle intermediates alpha-ketoglutarate (αKG and pyruvate prevent the death of latently infected cells. Targeted drug inhibition of glutaminolysis also induces increased cell death in latently infected cells. KSHV infection of endothelial cells induces protein expression of the glutamine transporter, SLC1A5. Chemical inhibition of SLC1A5, or knockdown by siRNA, leads to similar cell death rates as glutamine deprivation and, similarly, can be rescued by αKG. KSHV also induces expression of the heterodimeric transcription factors c-Myc-Max and related heterodimer MondoA-Mlx. Knockdown of MondoA inhibits expression of both Mlx and SLC1A5 and induces a significant increase in cell death of only cells latently infected with KSHV, again, fully rescued by the supplementation of αKG. Therefore, during latent infection of endothelial cells, KSHV activates and requires the Myc/MondoA-network to upregulate the glutamine transporter, SLC1A5, leading to increased glutamine uptake for glutaminolysis. These findings

  11. Exercise Counteracts Aging-Related Memory Impairment: A Potential Role for the Astrocytic Metabolic Shuttle.

    Science.gov (United States)

    Tsai, Sheng-Feng; Chen, Pei-Chun; Calkins, Marcus J; Wu, Shih-Ying; Kuo, Yu-Min

    2016-01-01

    Age-related cognitive impairment has become one of the most common health threats in many countries. The biological substrate of cognition is the interconnection of neurons to form complex information processing networks. Experience-based alterations in the activities of these information processing networks lead to neuroadaptation, which is physically represented at the cellular level as synaptic plasticity. Although synaptic plasticity is known to be affected by aging, the underlying molecular mechanisms are not well described. Astrocytes, a glial cell type that is infrequently investigated in cognitive science, have emerged as energy suppliers which are necessary for meeting the abundant energy demand resulting from glutamatergic synaptic activity. Moreover, the concerted action of an astrocyte-neuron metabolic shuttle is essential for cognitive function; whereas, energetic incoordination between astrocytes and neurons may contribute to cognitive impairment. Whether altered function of the astrocyte-neuron metabolic shuttle links aging to reduced synaptic plasticity is unexplored. However, accumulated evidence documents significant beneficial effects of long-term, regular exercise on cognition and synaptic plasticity. Furthermore, exercise increases the effectiveness of astrocyte-neuron metabolic shuttle by upregulation of astrocytic lactate transporter levels. This review summarizes previous findings related to the neuronal activity-dependent astrocyte-neuron metabolic shuttle. Moreover, we discuss how aging and exercise may shape the astrocyte-neuron metabolic shuttle in cognition-associated brain areas. PMID:27047373

  12. Deprive to kill: glutamine closes the gate to anticancer monocarboxylic drugs.

    Science.gov (United States)

    Cardaci, Simone; Ciriolo, Maria Rosa

    2012-12-01

    Killing properties of antitumor drugs can be enhanced by strategies targeting biochemical adaptations of cancer cells. Recently, we reported that depriving cancer cells of glutamine is a feasible approach to enhance antitumor effects of the alkylating analog of pyruvic acid, 3-bromopyruvate, which rely on the induction of autophagic cell death by metabolic-oxidative stress. 3-bromopyruvate chemopotentiation is the result of its increased intracellular uptake mediated by the monocarboxylate transporter 1, whose expression is post-transcriptionally increased upon glutamine withdrawal. Overall, our results identified the metabolic condition able to increase the selectivity of 3-bromopyruvate targets in neoplastic tissues, thereby providing a stage for its use in clinical settings for targeting malignancies and represent a proof of principle that modulation of glutamine availability can influence the delivery of monocarboxylic drugs into tumors. PMID:22932475

  13. Memory in astrocytes: a hypothesis

    Directory of Open Access Journals (Sweden)

    Caudle Robert M

    2006-01-01

    Full Text Available Abstract Background Recent work has indicated an increasingly complex role for astrocytes in the central nervous system. Astrocytes are now known to exchange information with neurons at synaptic junctions and to alter the information processing capabilities of the neurons. As an extension of this trend a hypothesis was proposed that astrocytes function to store information. To explore this idea the ion channels in biological membranes were compared to models known as cellular automata. These comparisons were made to test the hypothesis that ion channels in the membranes of astrocytes form a dynamic information storage device. Results Two dimensional cellular automata were found to behave similarly to ion channels in a membrane when they function at the boundary between order and chaos. The length of time information is stored in this class of cellular automata is exponentially related to the number of units. Therefore the length of time biological ion channels store information was plotted versus the estimated number of ion channels in the tissue. This analysis indicates that there is an exponential relationship between memory and the number of ion channels. Extrapolation of this relationship to the estimated number of ion channels in the astrocytes of a human brain indicates that memory can be stored in this system for an entire life span. Interestingly, this information is not affixed to any physical structure, but is stored as an organization of the activity of the ion channels. Further analysis of two dimensional cellular automata also demonstrates that these systems have both associative and temporal memory capabilities. Conclusion It is concluded that astrocytes may serve as a dynamic information sink for neurons. The memory in the astrocytes is stored by organizing the activity of ion channels and is not associated with a physical location such as a synapse. In order for this form of memory to be of significant duration it is necessary

  14. The high-mobility group box 1 cytokine induces transporter-mediated release of glutamate from glial subcellular particles (gliosomes) prepared from in situ-matured astrocytes.

    Science.gov (United States)

    Bonanno, Giambattista; Raiteri, Luca; Milanese, Marco; Zappettini, Simona; Melloni, Edon; Pedrazzi, Marco; Passalacqua, Mario; Tacchetti, Carlo; Usai, Cesare; Sparatore, Bianca

    2007-01-01

    The multifunctional protein high-mobility group box 1 (HMGB1) is expressed in restricted areas of adult brain where it can act as a proinflammatory cytokine. We report here that HMGB1 affects CNS transmission by inducing glutamatergic release from glial (gliosomes) but not neuronal (synaptosomes) resealed subcellular particles isolated from mouse cerebellum and hippocampus. Confocal microscopy showed that gliosomes are enriched with glia-specific proteins such as GFAP and S-100, but not with neuronal proteins such as PSD-95, MAP-2, and beta-tubulin III. Furthermore, gliosomes exhibit labeling neither for integrin-alphaM nor for myelin basic protein, specific for microglia and oligodendrocytes, respectively. The gliosomal fraction contains proteins of the exocytotic machinery coexisting with GFAP. Consistent with ultrastructural analysis, several approximately 30-nm nonclustered vesicles are present in the gliosome cytoplasm. Finally, gliosomes represent functional organelles that actively export glutamate when subjected to releasing stimuli, such as ionomycin or ATP, by mechanisms involving extracellular Ca(2+) and Ca(2+) release from intracellular stores. HMGB1-induced release of the stable glutamate analogue [(3)H]d-aspartate and endogenous glutamate form gliosomes, whereas nerve terminals were insensitive to the protein. The HMGB1-evoked release of glutamate was independent on modifications of cytosolic Ca(2+) concentration, but it was blocked by dl-threo-beta-benzyloxyaspartate, suggesting the involvement of transporter-mediated release mechanisms. Moreover, dihydrokainic acid, a selective inhibitor of glutamate transporter 1 does not block the HMGB1 effect, indicating a role for the glial glutamate-aspartate transporter (GLAST) subtype in this response. HMGB1 bind to gliosomes but not to synaptosomes and can physically interact with GLAST and receptor for advanced glycation end products (RAGE). Taken together, these results suggest that the HMGB1 cytokine

  15. Laser-scanning astrocyte mapping reveals increased glutamate-responsive domain size and disrupted maturation of glutamate uptake following neonatal cortical freeze-lesion

    Directory of Open Access Journals (Sweden)

    Mortiz eArmbruster

    2014-09-01

    Full Text Available Astrocytic uptake of glutamate shapes extracellular neurotransmitter dynamics, receptor activation, and synaptogenesis. During development, glutamate transport becomes more robust. How neonatal brain insult affects the functional maturation of glutamate transport remains unanswered. Neonatal brain insult can lead to developmental delays, cognitive losses, and epilepsy; the disruption of glutamate transport is known to cause changes in synaptogenesis, receptor activation, and seizure. Using the neonatal freeze-lesion (FL model, we have investigated how insult affects the maturation of astrocytic glutamate transport. As lesioning occurs on the day of birth, a time when astrocytes are still functionally immature, this model is ideal for identifying changes in astrocyte maturation following insult. Reactive astrocytosis, astrocyte proliferation, and in vitro hyperexcitability are known to occur in this model. To probe astrocyte glutamate transport with better spatial precision we have developed a novel technique, Laser Scanning Astrocyte Mapping (LSAM, which combines glutamate transport current (TC recording from astrocytes with laser scanning glutamate photolysis. LSAM allows us to identify the area from which a single astrocyte can transport glutamate and to quantify spatial heterogeneity in the rate of glutamate clearance kinetics within that domain. Using LSAM, we report that cortical astrocytes have an increased glutamate-responsive area following FL and that TCs have faster decay times in distal, as compared to proximal processes. Furthermore, the developmental shift from GLAST- to GLT-1-dominated clearance is disrupted following FL. These findings introduce a novel method to probe astrocyte glutamate uptake and show that neonatal cortical FL disrupts the functional maturation of cortical astrocytes.

  16. Glutamate Mediated Astrocytic Filtering of Neuronal Activity

    OpenAIRE

    Wallach, Gilad; Lallouette, Jules; Herzog, Nitzan; De Pittà, Maurizio; Ben Jacob, Eshel; Berry, Hugues; Hanein, Yael

    2014-01-01

    Neuron-astrocyte communication is an important regulatory mechanism in various brain functions but its complexity and role are yet to be fully understood. In particular, the temporal pattern of astrocyte response to neuronal firing has not been fully characterized. Here, we used neuron-astrocyte cultures on multi-electrode arrays coupled to Ca2+ imaging and explored the range of neuronal stimulation frequencies while keeping constant the amount of stimulation. Our results reveal that astrocyt...

  17. Astrocytic regulation of cortical UP states

    OpenAIRE

    Poskanzer, Kira E.; Yuste, Rafael

    2011-01-01

    The synchronization of neuronal assemblies during cortical UP states has been implicated in computational and homeostatic processes, but the mechanisms by which this occurs remain unknown. To investigate potential roles of astrocytes in synchronizing cortical circuits, we electrically activated astrocytes while monitoring the activity of the surrounding network with electrophysiological recordings and calcium imaging. Stimulating a single astrocyte activates other astrocytes in the local circ...

  18. Glutamine: the nonessential amino acid for performance enhancement.

    Science.gov (United States)

    Phillips, George C

    2007-07-01

    Glutamine is a popular dietary supplement consumed for purported ergogenic benefits of increased strength, quicker recovery, decreased frequency of respiratory infections, and prevention of overtraining. From a biochemical standpoint, glutamine does play a physiologic role in each of these areas, but it remains only one of a host of factors involved. This review examines the effects of glutamine on exercise and demonstrates a lack of evidence for definitive positive ergogenic benefits as a result of glutamine supplementation. PMID:17618004

  19. Low-frequency vibrational modes of glutamine

    Science.gov (United States)

    Wang, Wei-Ning; Wang, Guo; Zhang, Yan

    2011-12-01

    High-resolution terahertz absorption and Raman spectra of glutamine in the frequency region 0.2 THz-2.8 THz are obtained by using THz time domain spectroscopy and low-frequency Raman spectroscopy. Based on the experimental and the computational results, the vibration modes corresponding to the terahertz absorption and Raman scatting peaks are assigned and further verified by the theoretical calculations. Spectral investigation of the periodic structure of glutamine based on the sophisticated hybrid density functional B3LYP indicates that the vibrational modes come mainly from the inter-molecular hydrogen bond in this frequency region.

  20. Low-frequency vibrational modes of glutamine

    Institute of Scientific and Technical Information of China (English)

    Wang Wei-Ning; Wang Guo; Zhang Yan

    2011-01-01

    High-resolution terahertz absorption and Raman spectra of glutamine in the frequency region 0.2 THz-2.8 THz are obtained by using THz time domain spectroscopy and low-frequency Raman spectroscopy.Based on the experimental and the computational results,the vibration modes corresponding to the terahertz absorption and Raman scatting peaks are assigned and further verified by the theoretical calculations.Spectral investigation of the periodic structure of glutamine based on the sophisticated hybrid density functional B3LYP indicates that the vibrational modes come mainly from the inter-molecular hydrogen bond in this frequency region.

  1. Astrocytes and lysosomal storage diseases.

    Science.gov (United States)

    Rama Rao, K V; Kielian, T

    2016-05-26

    Lysosomal storage diseases (LSDs) encompass a wide range of disorders characterized by inborn errors of lysosomal function. The majority of LSDs result from genetic defects in lysosomal enzymes, although some arise from mutations in lysosomal proteins that lack known enzymatic activity. Neuropathological abnormalities are a feature of several LSDs and when severe, represent an important determinant in disease outcome. Glial dysfunction, particularly in astrocytes, is also observed in numerous LSDs and has been suggested to impact neurodegeneration. This review will discuss the potential role of astrocytes in LSDs and highlight the possibility of targeting glia as a beneficial strategy to counteract the neuropathology associated with LSDs. PMID:26037807

  2. Functional Oxygen Sensitivity of Astrocytes.

    Science.gov (United States)

    Angelova, Plamena R; Kasymov, Vitaliy; Christie, Isabel; Sheikhbahaei, Shahriar; Turovsky, Egor; Marina, Nephtali; Korsak, Alla; Zwicker, Jennifer; Teschemacher, Anja G; Ackland, Gareth L; Funk, Gregory D; Kasparov, Sergey; Abramov, Andrey Y; Gourine, Alexander V

    2015-07-22

    In terrestrial mammals, the oxygen storage capacity of the CNS is limited, and neuronal function is rapidly impaired if oxygen supply is interrupted even for a short period of time. However, oxygen tension monitored by the peripheral (arterial) chemoreceptors is not sensitive to regional CNS differences in partial pressure of oxygen (PO2 ) that reflect variable levels of neuronal activity or local tissue hypoxia, pointing to the necessity of a functional brain oxygen sensor. This experimental animal (rats and mice) study shows that astrocytes, the most numerous brain glial cells, are sensitive to physiological changes in PO2 . Astrocytes respond to decreases in PO2 a few millimeters of mercury below normal brain oxygenation with elevations in intracellular calcium ([Ca(2+)]i). The hypoxia sensor of astrocytes resides in the mitochondria in which oxygen is consumed. Physiological decrease in PO2 inhibits astroglial mitochondrial respiration, leading to mitochondrial depolarization, production of free radicals, lipid peroxidation, activation of phospholipase C, IP3 receptors, and release of Ca(2+) from the intracellular stores. Hypoxia-induced [Ca(2+)]i increases in astrocytes trigger fusion of vesicular compartments containing ATP. Blockade of astrocytic signaling by overexpression of ATP-degrading enzymes or targeted astrocyte-specific expression of tetanus toxin light chain (to interfere with vesicular release mechanisms) within the brainstem respiratory rhythm-generating circuits reveals the fundamental physiological role of astroglial oxygen sensitivity; in low-oxygen conditions (environmental hypoxia), this mechanism increases breathing activity even in the absence of peripheral chemoreceptor oxygen sensing. These results demonstrate that astrocytes are functionally specialized CNS oxygen sensors tuned for rapid detection of physiological changes in brain oxygenation. Significance statement: Most, if not all, animal cells possess mechanisms that allow them to

  3. Thyroid hormone action: Astrocyte-neuron communication.

    Directory of Open Access Journals (Sweden)

    BeatrizMorte

    2014-05-01

    Full Text Available Thyroid hormone action is exerted mainly through regulation of gene expression by binding of T3 to the nuclear receptors. T4 plays an important role as a source of intracellular T3 in the central nervous system via the action of the type 2 deiodinase, expressed in the astrocytes. A model of T3 availability to neural cells has been proposed and validated. The model contemplates that brain T3 has a double origin: a fraction is available directly from the circulation, and another is produced locally from T4 in the astrocytes by type 2 deiodinase. The fetal brain depends almost entirely on the T3 generated locally. The contribution of systemic T3 increases subsequently during development to account for approximately 50% of total brain T3 in the late postnatal and adult stages. In this article we review the experimental data in support of this model, and how the factors affecting T3 availability in the brain, such as deiodinases and transporters, play a decisive role in modulating local thyroid hormone action during development.

  4. Sulfonylurea Receptor 1 Contributes to the Astrocyte Swelling and Brain Edema in Acute Liver Failure

    OpenAIRE

    Jayakumar, A.R.; Valdes, V.; Tong, X. Y.; Shamaladevi, N.; W Gonzalez; Norenberg, M.D.

    2014-01-01

    Astrocyte swelling (cytotoxic brain edema) is the major neurological complication of acute liver failure (ALF), a condition in which ammonia has been strongly implicated in its etiology. Ion channels and transporters are known to be involved in cell volume regulation and a disturbance in these systems may result in cell swelling. One ion channel known to contribute to astrocyte swelling/brain edema in other neurological disorders is the ATP-dependent, non-selective cation channel (NCCa-ATP ch...

  5. Astrocyte/neuron ratio and its importance on glutamate toxicity: an in vitro voltammetric study.

    Science.gov (United States)

    Hacimuftuoglu, Ahmet; Tatar, Abdulgani; Cetin, Damla; Taspinar, Numan; Saruhan, Fatih; Okkay, Ufuk; Turkez, Hasan; Unal, Deniz; Stephens, Robert Louis; Suleyman, Halis

    2016-08-01

    The purpose of this study was to clarify the relationship between neuron cells and astrocyte cells in regulating glutamate toxicity on the 10th and 20th day in vitro. A mixed primary culture system from newborn rats that contain cerebral cortex neurons cells was employed to investigate the glutamate toxicity. All cultures were incubated with various glutamate concentrations, then viability tests and histological analyses were performed. The activities of glutamate transporters were determined by using in vitro voltammetry technique. Viable cell number was decreased significantly on the 10th day at 10(-7) M and at 10(-6) M glutamate applications, however, viable cell number was not decreased at 20th day. Astrocyte number was increased nearly six times on the 20th day as compared to the 10th day. The peak point of glutamate reuptake capacity was about 2 × 10(-4) M on the 10th day and 10(-3) M on the 20th day. According to our results, we suggested that astrocyte age was important to maintain neuronal survival against glutamate toxicity. Thus, we revealed activation or a trigger point of glutamate transporters on astrocytes due to time since more glutamate was taken up by astrocytes when glutamate transporters on the astrocyte were triggered with high exogenous glutamate concentrations. In conclusion, the present investigation is the first voltammetric study on the reuptake parameters of glutamate in vitro. PMID:26438331

  6. Astrocyte, the star avatar: redefined

    Indian Academy of Sciences (India)

    Pankaj Seth; Nitin Koul

    2008-09-01

    Until recently, the neuroscience community held the belief that glial cells such as astrocytes and oligodendrocytes functioned solely as “support” cells of the brain. In this role, glial cells simply provide physical support and housekeeping functions for the more important cells of the brain, the neurons. However, this view has changed radically in recent years with the discovery of previously unrecognized and surprising functions for this underappreciated cell type. In the past decade or so, emerging evidence has provided new insights into novel glial cell activities such as control of synapse formation and function, communication, cerebrovascular tone regulation, immune regulation and adult neurogenesis. Such advances in knowledge have effectively elevated the role of the astrocyte to one that is more important than previously realized. This review summarizes the past and present knowledge of glial cell functions that has evolved over the years, and has resulted in a new appreciation of astrocytes and their value in studying the neurobiology of human brain cells and their functions. In this review, we highlight recent advances in the role of glial cells in physiology, pathophysiology and, most importantly, in adult neurogenesis and “stemness”, with special emphasis on astrocytes.

  7. Astrocytes Underlie Neuroinflammatory Memory Impairment

    OpenAIRE

    Osso, LA; Chan, JR

    2015-01-01

    © 2015 Elsevier Inc. All rights reserved. Neuroinflammation is being increasingly recognized as a potential mediator of cognitive impairments in various neurological conditions. Habbas et al. demonstrate that the pro-inflammatory cytokine tumor necrosis factor alpha signals through astrocytes to alter synaptic transmission and impair cognition in a mouse model of multiple sclerosis.

  8. Central Role of Maladapted Astrocytic Plasticity in Ischemic Brain Edema Formation.

    Science.gov (United States)

    Wang, Yu-Feng; Parpura, Vladimir

    2016-01-01

    Brain edema formation and the ensuing brain damages are the major cause of high mortality and long term disability following the occurrence of ischemic stroke. In this process, oxygen and glucose deprivation and the resulting reperfusion injury play primary roles. In response to the ischemic insult, the neurovascular unit experiences both intracellular and extracellular edemas, associated with maladapted astrocytic plasticity. The astrocytic plasticity includes both morphological and functional plasticity. The former involves a reactive gliosis and the subsequent glial retraction. It relates to the capacity of astrocytes to buffer changes in extracellular chemical levels, particularly K(+) and glutamate, as well as the integrity of the blood-brain barrier (BBB). The latter involves the expression and activity of a series of ion and water transport proteins. These molecules are grouped together around glial fibrillary acidic protein (GFAP) and water channel protein aquaporin 4 (AQP4) to form functional networks, regulate hydromineral balance across cell membranes and maintain the integrity of the BBB. Intense ischemic challenges can disrupt these capacities of astrocytes and result in their maladaptation. The maladapted astrocytic plasticity in ischemic stroke cannot only disrupt the hydromineral homeostasis across astrocyte membrane and the BBB, but also leads to disorders of the whole neurovascular unit. This review focuses on how the maladapted astrocytic plasticity in ischemic stroke plays the central role in the brain edema formation. PMID:27242440

  9. Central role of maladapted astrocytic plasticity in ischemic brain edema formation

    Directory of Open Access Journals (Sweden)

    Yu-Feng eWang

    2016-05-01

    Full Text Available Brain edema formation and the ensuing brain damages are the major cause of high mortality and long term disability following the occurrence of ischemic stroke. In this process, oxygen and glucose deprivation and the ensuing reperfusion injury play primary roles. In response to the ischemic insult, the neurovascular unit experiences both intracellular and extracellular edemas; the two processes are interactive closely under the driving of maladapted astrocytic plasticity. The astrocytic plasticity includes both morphologic and functional plasticity. The former involves a reactive gliosis and the ensuing glial retraction. It relates to the capacity of astrocytes to buffer changes in extracellular chemical levels, particularly K+ and glutamate, as well as the integrity of the blood-brain barrier. The latter involves the expression and activity of a series of ion and water transport proteins. These molecules are grouped together around glial fibrillary acidic protein and water channel protein aquaporin 4 to form functional networks, regulate hydromineral balance across cell membranes and maintain the integrity of the blood-brain barrier. Intense ischemic challenges can disrupt these capacities of astrocytes and result in their maladaptation. The maladapted astrocytic plasticity in ischemic stroke cannot only disrupt the hydromineral homeostasis across astrocyte membrane and the blood-brain barrier, but also lead to disorders of the whole neurovascular unit. This review focuses on how the maladapted astrocytic plasticity in ischemic stroke plays the central role in the brain edema formation.

  10. Astrocyte Regulation of CNS Inflammation and Remyelination

    Directory of Open Access Journals (Sweden)

    Stephen J. Crocker

    2013-07-01

    Full Text Available Astrocytes regulate fundamentally important functions to maintain central nervous system (CNS homeostasis. Altered astrocytic function is now recognized as a primary contributing factor to an increasing number of neurological diseases. In this review, we provide an overview of our rapidly developing understanding of the basal and inflammatory functions of astrocytes as mediators of CNS responsiveness to inflammation and injury. Specifically, we elaborate on ways that astrocytes actively participate in the pathogenesis of demyelinating diseases of the CNS through their immunomodulatory roles as CNS antigen presenting cells, modulators of blood brain barrier function and as a source of chemokines and cytokines. We also outline how changes in the extracellular matrix can modulate astrocytes phenotypically, resulting in dysregulation of astrocytic responses during inflammatory injury. We also relate recent studies describing newly identified roles for astrocytes in leukodystrophies. Finally, we describe recent advances in how adapting this increasing breadth of knowledge on astrocytes has fostered new ways of thinking about human diseases, which offer potential to modulate astrocytic heterogeneity and plasticity towards therapeutic gain. In summary, recent studies have provided improved insight in a wide variety of neuroinflammatory and demyelinating diseases, and future research on astrocyte pathophysiology is expected to provide new perspectives on these diseases, for which new treatment modalities are increasingly necessary.

  11. Astrocytic mitochondrial membrane hyperpolarization following extended oxygen and glucose deprivation.

    Directory of Open Access Journals (Sweden)

    Andrej Korenić

    Full Text Available Astrocytes can tolerate longer periods of oxygen and glucose deprivation (OGD as compared to neurons. The reasons for this reduced vulnerability are not well understood. Particularly, changes in mitochondrial membrane potential (Δψ(m in astrocytes, an indicator of the cellular redox state, have not been investigated during reperfusion after extended OGD exposure. Here, we subjected primary mouse astrocytes to glucose deprivation (GD, OGD and combinations of both conditions varying in duration and sequence. Changes in Δψ(m, visualized by change in the fluorescence of JC-1, were investigated within one hour after reconstitution of oxygen and glucose supply, intended to model in vivo reperfusion. In all experiments, astrocytes showed resilience to extended periods of OGD, which had little effect on Δψ(m during reperfusion, whereas GD caused a robust Δψ(m negativation. In case no Δψ(m negativation was observed after OGD, subsequent chemical oxygen deprivation (OD induced by sodium azide caused depolarization, which, however, was significantly delayed as compared to normoxic group. When GD preceded OD for 12 h, Δψ(m hyperpolarization was induced by both GD and subsequent OD, but significant interaction between these conditions was not detected. However, when GD was extended to 48 h preceding OGD, hyperpolarization enhanced during reperfusion. This implicates synergistic effects of both conditions in that sequence. These findings provide novel information regarding the role of the two main substrates of electron transport chain (glucose and oxygen and their hyperpolarizing effect on Δψ(m during substrate deprivation, thus shedding new light on mechanisms of astrocyte resilience to prolonged ischemic injury.

  12. Effect of glutamine supplementation on neutrophil function in male judoists.

    Science.gov (United States)

    Sasaki, Eiji; Umeda, Takashi; Takahashi, Ippei; Arata, Kojima; Yamamoto, Yousuke; Tanabe, Masaru; Oyamada, Kazuyuki; Hashizume, Erika; Nakaji, Shigeyuki

    2013-01-01

    Glutamine is an important amino acid for immune function. Though high intensity and prolonged exercise decreases plasma glutamine concentration and causes immune suppression, the relationship between neutrophil functions and glutamine has not yet been found. The purpose of this study was to investigate the impacts of glutamine supplementation on neutrophil function. Twenty-six male university judoists were recruited. Subjects were classified into glutamine and control groups. The glutamine group ingested 3000 mg of glutamine per day and the control group ingested placebo for 2 weeks. Examinations were performed at the start of preunified loading exercise (pre-ULE), then 1 and 2 weeks after ULE (post-ULE). Reactive oxygen species (ROS) production, phagocytic activity, serum opsonic activity and serum myogenic enzymes were measured. Differences between the levels obtained in pre-ULE and post-ULE for the two groups were compared. In the glutamine group, ROS production activity increased 1 week after ULE, whereas it was not observed in the control group (P glutamine group remained unchanged by supplementation during ULE. Glutamine supplementation has prevented excessive muscle damage and suppression of neutrophil function, especially in ROS production activity, even during an intensive training period. PMID:23348981

  13. Weak mitochondrial targeting sequence determines tissue-specific subcellular localization of glutamine synthetase in liver and brain cells.

    Science.gov (United States)

    Matthews, Gideon D; Gur, Noa; Koopman, Werner J H; Pines, Ophry; Vardimon, Lily

    2010-02-01

    Evolution of the uricotelic system for ammonia detoxification required a mechanism for tissue-specific subcellular localization of glutamine synthetase (GS). In uricotelic vertebrates, GS is mitochondrial in liver cells and cytoplasmic in brain. Because these species contain a single copy of the GS gene, it is not clear how tissue-specific subcellular localization is achieved. Here we show that in chicken, which utilizes the uricotelic system, the GS transcripts of liver and brain cells are identical and, consistently, there is no difference in the amino acid sequence of the protein. The N-terminus of GS, which constitutes a 'weak' mitochondrial targeting signal (MTS), is sufficient to direct a chimeric protein to the mitochondria in hepatocytes and to the cytoplasm in astrocytes. Considering that a weak MTS is dependent on a highly negative mitochondrial membrane potential (DeltaPsi) for import, we examined the magnitude of DeltaPsi in hepatocytes and astrocytes. Our results unexpectedly revealed that DeltaPsi in hepatocytes is considerably more negative than that of astrocytes and that converting the targeting signal into 'strong' MTS abolished the capability to confer tissue-specific subcellular localization. We suggest that evolutional selection of weak MTS provided a tool for differential targeting of an identical protein by taking advantage of tissue-specific differences in DeltaPsi. PMID:20053634

  14. Involvement of astrocytes in neurovascular communication.

    Science.gov (United States)

    Nuriya, M; Hirase, H

    2016-01-01

    The vascular interface of the brain is distinct from that of the peripheral tissue in that astrocytes, the most numerous glial cell type in the gray matter, cover the vasculature with their endfeet. This morphological feature of the gliovascular junction has prompted neuroscientists to suggest possible functional roles of astrocytes including astrocytic modulation of the vasculature. Additionally, astrocytes develop an intricate morphology that intimately apposes neuronal synapses, making them an ideal cellular mediator of neurovascular coupling. In this article, we first introduce the classical anatomical and physiological findings that led to the proposal of various gliovascular interaction models. Next, we touch on the technological advances in the past few decades that enabled investigations and evaluations of neuro-glio-vascular interactions in situ. We then review recent experimental findings on the roles of astrocytes in neurovascular coupling from the viewpoints of intra- and intercellular signalings in astrocytes. PMID:27130410

  15. Astrocyte calcium signaling: the third wave.

    Science.gov (United States)

    Bazargani, Narges; Attwell, David

    2016-01-27

    The discovery that transient elevations of calcium concentration occur in astrocytes, and release 'gliotransmitters' which act on neurons and vascular smooth muscle, led to the idea that astrocytes are powerful regulators of neuronal spiking, synaptic plasticity and brain blood flow. These findings were challenged by a second wave of reports that astrocyte calcium transients did not mediate functions attributed to gliotransmitters and were too slow to generate blood flow increases. Remarkably, the tide has now turned again: the most important calcium transients occur in fine astrocyte processes not resolved in earlier studies, and new mechanisms have been discovered by which astrocyte [Ca(2+)]i is raised and exerts its effects. Here we review how this third wave of discoveries has changed our understanding of astrocyte calcium signaling and its consequences for neuronal function. PMID:26814587

  16. Astrocytes in the tempest of multiple sclerosis.

    Science.gov (United States)

    Miljković, Djordje; Timotijević, Gordana; Mostarica Stojković, Marija

    2011-12-01

    Astrocytes are the most abundant cell population within the CNS of mammals. Their glial role is perfectly performed in the healthy CNS as they support functions of neurons. The omnipresence of astrocytes throughout the white and grey matter and their intimate relation with blood vessels of the CNS, as well as numerous immunity-related actions that these cells are capable of, imply that astrocytes should have a prominent role in neuroinflammatory disorders, such as multiple sclerosis (MS). The role of astrocytes in MS is rather ambiguous, as they have the capacity to both stimulate and restrain neuroinflammation and tissue destruction. In this paper we present some of the proved and the proposed functions of astrocytes in neuroinflammation and discuss the effect of MS therapeutics on astrocytes. PMID:21443873

  17. Dynamic reactive astrocytes after focal ischemia

    Institute of Scientific and Technical Information of China (English)

    Shinghua Ding

    2014-01-01

    Astrocytes are specialized and most numerous glial cell type in the central nervous system and play important roles in physiology. Astrocytes are also critically involved in many neural disor-ders including focal ischemic stroke, a leading cause of brain injury and human death. One of the prominent pathological features of focal ischemic stroke is reactive astrogliosis and glial scar for-mation associated with morphological changes and proliferation. This review paper discusses the recent advances in spatial and temporal dynamics of morphology and proliferation of reactive astrocytes after ischemic stroke based on results from experimental animal studies. As reactive astrocytes exhibit stem cell-like properties, knowledge of dynamics of reactive astrocytes and glial scar formation will provide important insights for astrocyte-based cell therapy in stroke.

  18. Triptolide protects astrocytes from hypoxia/ reoxygenation injury

    Institute of Scientific and Technical Information of China (English)

    Minfang Guo; Hongcui Fan; Jiezhong Yu; Ning Ji; Yongsheng Sun; Liyun Liang; Baoguo Xiao; Cungen Ma

    2011-01-01

    Astrocytes in an in vitro murine astrocyte model of oxygen and glucose deprivation/hypoxia and reoxygenation were treated with different concentrations of triptolide (250, 500, 1 000 ng/mL) in a broader attempt to elucidate the protection and mechanism underlying triptolide treatment on astrocytes exposed to hypoxia/reoxygenation injury. The results showed that the matrix metalloproteinase-9, interleukin-1β, tumor necrosis factor α and interleukin-6 expressions were significantly decreased after triptolide treatment in the astrocytes exposed to hypoxia/ reoxygenation injury, while interleukin-10 expression was upregulated. In addition, the vitality of the injured astrocytes was enhanced, the triptolide's effect was apparent at 500 ng/mL. These experimental findings indicate that triptolide treatment could protect astrocytes against hypoxia/ reoxygenation injury through the inhibition of inflammatory response and the reduction of matrix metalloproteinase-9 expression.

  19. Rotational Study of Natural Amino Acid Glutamine

    Science.gov (United States)

    Varela, Marcelino; Cabezas, Carlos; Alonso, José L.

    2014-06-01

    Recent improvements in laser ablation molecular beam Fourier transform microwave spectroscopy (LA-MB-FTMW) have allowed the investigation of glutamine (COOH-CH(NH2)-CH2-CH2-CONH2), a natural amino acid with a long polar side chain. One dominant structure has been detected in the rotational spectrum. The nuclear quadrupole hyperfine structure of two 14N nuclei has been totally resolved allowing the conclusive identification of the observed species.

  20. Gap Junctions Couple Astrocytes and Oligodendrocytes

    OpenAIRE

    Orthmann-Murphy, Jennifer L.; ABRAMS, CHARLES K.; Scherer, Steven S.

    2008-01-01

    In vertebrates, a family of related proteins called connexins form gap junctions (GJs), which are intercellular channels. In the central nervous system (CNS), GJs couple oligodendrocytes and astrocytes (O/A junctions) and adjacent astrocytes (A/A junctions), but not adjacent oligodendrocytes, forming a “glial syncytium.” Oligodendrocytes and astrocytes each express different connexins. Mutations of these connexin genes demonstrate that the proper functioning of myelin and oligodendrocytes req...

  1. White matter astrocytes in health and disease

    OpenAIRE

    Lundgaard, Iben; Osório, Maria Joana; Kress, Benjamin; Sanggaard, Simon; NEDERGAARD, Maiken

    2013-01-01

    Myelination by oligodendrocytes is a highly specialized process that relies on intimate interactions between the axon and oligodendrocyte. Astrocytes also have an important part in facilitating myelination in the CNS, however, comparatively less is known about how they affect myelination. This review therefore summarizes the literature and explores lingering questions surrounding differences between white matter and grey matter astrocytes, how astrocytes support myelination, how their dysfunc...

  2. Glutamate Pays Its Own Way in Astrocytes

    OpenAIRE

    MaryC.McKenna

    2013-01-01

    In vitro and in vivo studies have shown that glutamate can be oxidized for energy by brain astrocytes. The ability to harvest the energy from glutamate provides astrocytes with a mechanism to offset the high ATP cost of the uptake of glutamate from the synaptic cleft. This brief review focuses on oxidative metabolism of glutamate by astrocytes, the specific pathways involved in the complete oxidation of glutamate and the energy provided by each reaction.

  3. Targeting astrocytes in bipolar disorder.

    Science.gov (United States)

    Peng, Liang; Li, Baoman; Verkhratsky, Alexei

    2016-06-01

    Astrocytes are homeostatic cells of the central nervous system, which are critical for development and maintenance of synaptic transmission and hence of synaptically connected neuronal ensembles. Astrocytic densities are reduced in bipolar disorder, and therefore deficient astroglial function may contribute to overall disbalance in neurotransmission and to pathological evolution. Classical anti-bipolar drugs (lithium salts, valproic acid and carbamazepine) affect expression of astroglial genes and modify astroglial signalling and homeostatic cascades. Many effects of both antidepressant and anti-bipolar drugs are exerted through regulation of glutamate homeostasis and glutamatergic transmission, through K(+) buffering, through regulation of calcium-dependent phospholipase A2 (that controls metabolism of arachidonic acid) or through Ca(2+) homeostatic and signalling pathways. Sometimes anti-depressant and anti-bipolar drugs exert opposite effects, and some effects on gene expression in drug treated animals are opposite in neurones vs. astrocytes. Changes in the intracellular pH induced by anti-bipolar drugs affect uptake of myo-inositol and thereby signalling via inositoltrisphosphate (InsP3), this being in accord with one of the main theories of mechanism of action for these drugs. PMID:27015045

  4. Astrocytic actions on extrasynaptic neuronal currents

    Directory of Open Access Journals (Sweden)

    Balazs ePal

    2015-12-01

    Full Text Available In the last few decades, knowledge about astrocytic functions has significantly increased. It was demonstrated that astrocytes are not passive elements of the central nervous system, but active partners of neurons. There is a growing body of knowledge about the calcium excitability of astrocytes, the actions of different gliotransmitters and their release mechanisms, as well as the participation of astrocytes in the regulation of synaptic functions and their contribution to synaptic plasticity. However, astrocytic functions are even more complex than being a partner of the 'tripartite synapse', as they can influence extrasynaptic neuronal currents either by releasing substances or regulating ambient neurotransmitter levels. Several types of currents or changes of membrane potential with different kinetics and via different mechanisms can be elicited by astrocytic activity. Astrocyte-dependent phasic or tonic, inward or outward currents were described in several brain areas. Such currents, together with the synaptic actions of astrocytes, can contribute to neuromodulatory mechanisms, neurosensory and –secretory processes, cortical oscillatory activity, memory and learning or overall neuronal excitability. This mini-review is an attempt to give a brief summary of astrocyte-dependent extrasynaptic neuronal currents and their possible functional significance.

  5. Lateral regulation of synaptic transmission by astrocytes.

    Science.gov (United States)

    Covelo, A; Araque, A

    2016-05-26

    Fifteen years ago the concept of the "tripartite synapse" was proposed to conceptualize the functional view that astrocytes are integral elements of synapses. The signaling exchange between astrocytes and neurons within the tripartite synapse results in the synaptic regulation of synaptic transmission and plasticity through an autocrine form of communication. However, recent evidence indicates that the astrocyte synaptic regulation is not restricted to the active tripartite synapse but can be manifested through astrocyte signaling at synapses relatively distant from active synapses, a process termed lateral astrocyte synaptic regulation. This phenomenon resembles the classical heterosynaptic modulation but is mechanistically different because it involves astrocytes and its properties critically depend on the morphological and functional features of astrocytes. Therefore, the functional concept of the tripartite synapse as a fundamental unit must be expanded to include the interaction between tripartite synapses. Through lateral synaptic regulation, astrocytes serve as an active processing bridge for synaptic interaction and crosstalk between synapses with no direct neuronal connectivity, supporting the idea that neural network function results from the coordinated activity of astrocytes and neurons. PMID:25732135

  6. Molecular diversity of astrocytes with implications for neurological disorders

    OpenAIRE

    Bachoo, Robert M.; Kim, Ryung S.; Ligon, Keith L.; Maher, Elizabeth A.; Brennan, Cameron; Billings, Nathan; Chan, Suzanne; Li, Cheng; Rowitch, David H.; Wing H. Wong; DePinho, Ronald A.

    2004-01-01

    The astrocyte represents the most abundant yet least understood cell type of the CNS. Here, we use a stringent experimental strategy to molecularly define the astrocyte lineage by integrating microarray datasets across several in vitro model systems of astrocyte differentiation, primary astrocyte cultures, and various astrocyterich CNS structures. The intersection of astrocyte data sets, coupled with the application of nonastrocytic exclusion filters, yielded many astrocyte-specific genes pos...

  7. Role of astrocytes in depolarization-coupled release of glutamate in cerebellar cultures

    DEFF Research Database (Denmark)

    Bak, Lasse K; Waagepetersen, Helle S; Schousboe, Arne

    2004-01-01

    astrocytes, and corresponding cocultures. Release from the vesicular and the cytoplasmic glutamate pools, respectively, was distinguished employing the competitive, non-transportable glutamate transport inhibitor DL-threo-beta-benzyloxyaspartate (DL-TBOA). The results indicate that the release in response to...... AMPA (30 microM) in the presence of cyclothiazide (50 microM) to block desensitization, was of a vesicular origin. Pulses of 55 mM K+ caused a DL-TBOA resistant efflux of preloaded D-[3H]aspartate from astrocytes, indicating that this release was not mediated by glutamate transporters. The results...... furthermore support the notion of an important function of the astrocytes in the uptake of released glutamate, because DL-TBOA caused a large, apparent increase in the depolarization-coupled release of preloaded D-[3H]aspartate in the cocultures, compared to neuronal monocultures....

  8. Glutamine uptake contributes to central sensitization in the medullary dorsal horn

    OpenAIRE

    Chiang, Chen Yu; Li, Zhaohui; Dostrovsky, Jonathan O.; Hu, James W.; Sessle, Barry J.

    2008-01-01

    Mustard oil application to tooth pulp produces central sensitization in rat medullary dorsal horn (MDH) nociceptive neurons, which has been implicated in persistent pain mechanisms. We found that superfusion onto MDH of methylaminoisobutyric acid, a competitive inhibitor of the neuronal system A transporter for presynaptic uptake of glutamine (a glutamate precursor released from astroglia), significantly depressed development of mustard oil-induced central sensitization in rat MDH nociceptive...

  9. Reconstruction and flux analysis of coupling between metabolic pathways of astrocytes and neurons: application to cerebral hypoxia

    Directory of Open Access Journals (Sweden)

    Akιn Ata

    2007-12-01

    Full Text Available Abstract Background It is a daunting task to identify all the metabolic pathways of brain energy metabolism and develop a dynamic simulation environment that will cover a time scale ranging from seconds to hours. To simplify this task and make it more practicable, we undertook stoichiometric modeling of brain energy metabolism with the major aim of including the main interacting pathways in and between astrocytes and neurons. Model The constructed model includes central metabolism (glycolysis, pentose phosphate pathway, TCA cycle, lipid metabolism, reactive oxygen species (ROS detoxification, amino acid metabolism (synthesis and catabolism, the well-known glutamate-glutamine cycle, other coupling reactions between astrocytes and neurons, and neurotransmitter metabolism. This is, to our knowledge, the most comprehensive attempt at stoichiometric modeling of brain metabolism to date in terms of its coverage of a wide range of metabolic pathways. We then attempted to model the basal physiological behaviour and hypoxic behaviour of the brain cells where astrocytes and neurons are tightly coupled. Results The reconstructed stoichiometric reaction model included 217 reactions (184 internal, 33 exchange and 216 metabolites (183 internal, 33 external distributed in and between astrocytes and neurons. Flux balance analysis (FBA techniques were applied to the reconstructed model to elucidate the underlying cellular principles of neuron-astrocyte coupling. Simulation of resting conditions under the constraints of maximization of glutamate/glutamine/GABA cycle fluxes between the two cell types with subsequent minimization of Euclidean norm of fluxes resulted in a flux distribution in accordance with literature-based findings. As a further validation of our model, the effect of oxygen deprivation (hypoxia on fluxes was simulated using an FBA-derivative approach, known as minimization of metabolic adjustment (MOMA. The results show the power of the

  10. GLUTAMINE AND HYPERAMMONEMIC CRISES IN PATIENTS WITH UREA CYCLE DISORDERS

    Science.gov (United States)

    Lee, B.; Diaz, G.A.; Rhead, W.; Lichter-Konecki, U.; Feigenbaum, A.; Berry, S.A.; Le Mons, C.; Bartley, J.; Longo, N.; Nagamani, S.C.; Berquist, W.; Gallagher, R.C.; Harding, C.O.; McCandless, S.E.; Smith, W.; Schulze, A.; Marino, M.; Rowell, R.; Coakley, D.F.; Mokhtarani, M.; Scharschmidt, B.F.

    2016-01-01

    Blood ammonia and glutamine levels are used as biomarkers of control in patients with urea cycle disorders (UCDs). This study was undertaken to evaluate glutamine variability and utility as a predictor of hyperammonemic crises (HACs) in UCD patients. Methods The relationships between glutamine and ammonia levels and the incidence and timing of HACs were evaluated in over 100 adult and pediatric UCD patients who participated in clinical trials of glycerol phenylbutyrate. Results The median (range) intra-subject 24-hour coefficient of variation for glutamine was 15% (8–29%) as compared with 56% (28%–154%) for ammonia, and the correlation coefficient between glutamine and concurrent ammonia levels varied from 0.17 to 0.29. Patients with baseline (fasting) glutamine values >900 µmol/L had higher baseline ammonia levels (mean [SD]: 39.6 [26.2] µmol/L) than patients with baseline glutamine ≤900 µmol/L (26.6 [18.0] µmol/L). Glutamine values >900 µmol/L during the study were associated with an approximately 2-fold higher HAC risk (odds ratio [OR]=1.98; p=0.173). However, glutamine lost predictive significance (OR=1.47; p=0.439) when concomitant ammonia was taken into account, whereas the predictive value of baseline ammonia ≥ 1.0 upper limit of normal (ULN) was highly statistically significant (OR=4.96; p=0.013). There was no significant effect of glutamine >900 µmol/L on time to first HAC crisis (hazard ratio [HR]=1.14; p=0.813), but there was a significant effect of baseline ammonia ≥ 1.0 ULN (HR=4.62; p=0.0011). Conclusions The findings in this UCD population suggest that glutamine is a weaker predictor of HACs than ammonia and that the utility of the predictive value of glutamine will need to take into account concurrent ammonia levels. PMID:26586473

  11. A Novel Preparation Method of C-Terminal Glutamine Dipeptides

    Institute of Scientific and Technical Information of China (English)

    QIAN Shao-Song; LIU Yi; CHEN Ran; LI Jia-You; WU Xiao-Yan; JIAO Qing-Cai

    2006-01-01

    A novel synthesis method of dipeptides containing glutamine is reported. Protected L-amino acids were prepared by using inexpensive phthaloyl as the protecting group. Then the phthaloyl-L-amino acids were condensed with glutamine salts by the mixed anhydride method to afford phthaloyl dipeptides. Subsequently, the phthaloyl was removed from the dipeptides with hydrazine hydrate. As a result, optically pure glutamine-containing dipeptides were obtained in good yields.

  12. When Is It Appropriate to Use Glutamine in Critical Illness?

    Science.gov (United States)

    Mundi, Manpreet S; Shah, Meera; Hurt, Ryan T

    2016-08-01

    Glutamine is a nonessential amino acid, which under trauma or critical illness can become essential. A number of historic small single-center randomized controlled trials (RCTs) have demonstrated positive treatment effects on clinical outcomes with glutamine supplementation. Meta-analyses based on these trials demonstrated a significant reduction in hospital mortality, intensive care unit (ICU) length of stay (LOS), and hospital LOS with intravenous (IV) glutamine. Similar results were not noted in 2 large multicenter RCTs (REDOXS and MetaPlus) assessing the efficacy of glutamine supplementation in ventilated ICU patients. The REDOXS trial of 40 ICUs randomized 1223 ventilated ICU patients to glutamine (IV and enteral), antioxidants, both glutamine and antioxidants, or placebo. The main conclusions were a trend toward increased 28-day mortality and significant increased hospital and 6-month mortality in those who received glutamine. The MetaPlus trial of 14 ICUs, which randomized 301 ventilated ICU patients to glutamine-enriched enteral vs an isocaloric diet, noted increased 6-month mortality in the glutamine-supplemented group. Newer RCTs have focused on specific populations and have demonstrated benefits in burn and elective surgery patients with glutamine supplementation. Whether larger studies will confirm these findings is yet to be determined. Recent American Society for Parenteral and Enteral Nutrition guidelines recommend that IV and enteral glutamine should not be used in the critical care setting based on the moderate quality of evidence available. We agree with these recommendations and would encourage larger multicenter studies to evaluate the risks and benefits of glutamine in burn and elective surgery patients. PMID:27246308

  13. ErbB receptor signaling in astrocytes: a mediator of neuron-glia communication in the mature central nervous system.

    Science.gov (United States)

    Sharif, Ariane; Prevot, Vincent

    2010-11-01

    Astrocytes are now recognized as active players in the developing and mature central nervous system. Each astrocyte contacts vascular structures and thousands of synapses within discrete territories. These cells receive a myriad of inputs and generate appropriate responses to regulate the function of brain microdomains. Emerging evidence has implicated receptors of the ErbB tyrosine kinase family in the integration and processing of neuronal inputs by astrocytes: ErbB receptors can be activated by a wide range of neuronal stimuli; they control critical steps of glutamate-glutamine metabolism; and they regulate the biosynthesis and release of various glial-derived neurotrophic factors, gliomediators and gliotransmitters. These key properties of astrocytic ErbB signaling in neuron-glia interactions have significance for the physiology of the mature central nervous system, as exemplified by the central control of reproduction within the hypothalamus, and are also likely to contribute to pathological situations, since both dysregulation of ErbB signaling and glial dysfunction occur in many neurological disorders. PMID:20685225

  14. Specialized contacts of astrocytes with astrocytes and with other cell types in the hypothalamus of the hamster.

    OpenAIRE

    Suarez Najera, I; Fernandez Ruiz, B; Garcia Segura, L M

    1980-01-01

    Adult hamsters were used for this electron microscopic study of the hypothalamic region. Specialized contacts between astrocytes and astrocytes, and between astrocytes and other cellular elements, are described and illustrated. The specialized inter-astrocytic junctions occur primarily in perivascular and subpial regions, but also in areas of high synaptic density. The junctions between astrocytic processes are of hemidesmosomal type. Astrocytes are connected to oligodendroglial cells by mean...

  15. Histamine (re)uptake by astrocytes: an experimental and computational study.

    Science.gov (United States)

    Perdan-Pirkmajer, Katja; Mavri, Janez; Krzan, Mojca

    2010-06-01

    Astrocytes participate in the clearance of neurotransmitters by their uptake and subsequent enzymatic degradation. Histamine as a polar and/or protonated molecule must use a carrier to be transported across the cell membrane, although a specific histamine transporter has not been elucidated, yet. In this work we upgraded the kinetic studies of histamine uptake into neonatal rat cultured type 1 astrocytes with quantum chemical calculations of histamine pKa values in conjunction with Langevin dipoles solvation model as the first step toward microscopic simulation of transport. Our results indicate that astrocytes transport histamine by at least two carrier mediated processes, a concentration gradient dependent passive and a sodium-dependent and ATP-driven active transport. We also demonstrated that histamine protonation states depend on the polarity of the environment. In conclusion we suggest that histamine, a polar molecule at physiological pH uses at least two different mechanisms for its uptake into astrocytes -an electrodiffusion and Na(+)-dependent and ouabain sensitive active process. We emphasize relevance of knowledge of histamines protonation states at the rate limiting step of its transport for microscopic simulation that will be possible when structure of histamine transporter is known. PMID:20013137

  16. Astrocyte sodium signaling and neuro-metabolic coupling in the brain.

    Science.gov (United States)

    Rose, C R; Chatton, J-Y

    2016-05-26

    At tripartite synapses, astrocytes undergo calcium signaling in response to release of neurotransmitters and this calcium signaling has been proposed to play a critical role in neuron-glia interaction. Recent work has now firmly established that, in addition, neuronal activity also evokes sodium transients in astrocytes, which can be local or global depending on the number of activated synapses and the duration of activity. Furthermore, astrocyte sodium signals can be transmitted to adjacent cells through gap junctions and following release of gliotransmitters. A main pathway for activity-related sodium influx into astrocytes is via high-affinity sodium-dependent glutamate transporters. Astrocyte sodium signals differ in many respects from the well-described glial calcium signals both in terms of their temporal as well as spatial distribution. There are no known buffering systems for sodium ions, nor is there store-mediated release of sodium. Sodium signals thus seem to represent rather direct and unbiased indicators of the site and strength of neuronal inputs. As such they have an immediate influence on the activity of sodium-dependent transporters which may even reverse in response to sodium signaling, as has been shown for GABA transporters for example. Furthermore, recovery from sodium transients through Na(+)/K(+)-ATPase requires a measurable amount of ATP, resulting in an activation of glial metabolism. In this review, we present basic principles of sodium regulation and the current state of knowledge concerning the occurrence and properties of activity-related sodium transients in astrocytes. We then discuss different aspects of the relationship between sodium changes in astrocytes and neuro-metabolic coupling, putting forward the idea that indeed sodium might serve as a new type of intracellular ion signal playing an important role in neuron-glia interaction and neuro-metabolic coupling in the healthy and diseased brain. PMID:25791228

  17. Neural control of glutamine synthetase activity in rat skeletal muscles.

    Science.gov (United States)

    Feng, B; Konagaya, M; Konagaya, Y; Thomas, J W; Banner, C; Mill, J; Max, S R

    1990-05-01

    The mechanism of glutamine synthetase induction in rat skeletal muscle after denervation or limb immobilization was investigated. Adult male rats were subjected to midthigh section of the sciatic nerve. At 1, 2, and 5 h and 1, 2, and 7 days after denervation, rats were killed and denervated, and contralateral control soleus and plantaris muscles were excised, weighted, homogenized, and assayed for glutamine synthetase. Glutamine synthetase activity increased approximately twofold 1 h after denervation in both muscles. By 7 days postdenervation enzyme activity had increased to three times the control level in plantaris muscle and to four times the control level in soleus muscle. Increased enzyme activity after nerve section was associated with increased maximum velocity with no change in apparent Michaelis constant. Immunotitration with an antiglutamine synthetase antibody suggested that denervation caused an increase in the number of glutamine synthetase molecules in muscle. However, Northern-blot analysis revealed no increase in the steady-state level of glutamine synthetase mRNA after denervation. A mixing experiment failed to yield evidence for the presence of a soluble factor involved in regulating the activity of glutamine synthetase in denervated muscle. A combination of denervation and dexamethasone injections resulted in additive increases in glutamine synthetase. Thus the mechanism underlying increased glutamine synthetase after denervation appears to be posttranscriptional and is distinct from that of the glucocorticoid-mediated glutamine synthetase induction previously described by us. PMID:1970709

  18. Astrocytic Ca2+ signals are required for the functional integrity of tripartite synapses

    Directory of Open Access Journals (Sweden)

    Tanaka Mika

    2013-01-01

    Full Text Available Abstract Background Neuronal activity alters calcium ion (Ca2+ dynamics in astrocytes, but the physiologic relevance of these changes is controversial. To examine this issue further, we generated an inducible transgenic mouse model in which the expression of an inositol 1,4,5-trisphosphate absorbent, “IP3 sponge”, attenuates astrocytic Ca2+ signaling. Results Attenuated Ca2+ activity correlated with reduced astrocytic coverage of asymmetric synapses in the hippocampal CA1 region in these animals. The decreased astrocytic ‘protection’ of the synapses facilitated glutamate ‘spillover’, which was reflected by prolonged glutamate transporter currents in stratum radiatum astrocytes and enhanced N-methyl-D-aspartate receptor currents in CA1 pyramidal neurons in response to burst stimulation. These mice also exhibited behavioral impairments in spatial reference memory and remote contextual fear memory, in which hippocampal circuits are involved. Conclusions Our findings suggest that IP3-mediated astrocytic Ca2+ signaling correlates with the formation of functional tripartite synapses in the hippocampus.

  19. Heterogeneity of astrocytes: from development to injury - single cell gene expression.

    Directory of Open Access Journals (Sweden)

    Vendula Rusnakova

    Full Text Available Astrocytes perform control and regulatory functions in the central nervous system; heterogeneity among them is still a matter of debate due to limited knowledge of their gene expression profiles and functional diversity. To unravel astrocyte heterogeneity during postnatal development and after focal cerebral ischemia, we employed single-cell gene expression profiling in acutely isolated cortical GFAP/EGFP-positive cells. Using a microfluidic qPCR platform, we profiled 47 genes encoding glial markers and ion channels/transporters/receptors participating in maintaining K(+ and glutamate homeostasis per cell. Self-organizing maps and principal component analyses revealed three subpopulations within 10-50 days of postnatal development (P10-P50. The first subpopulation, mainly immature glia from P10, was characterized by high transcriptional activity of all studied genes, including polydendrocytic markers. The second subpopulation (mostly from P20 was characterized by low gene transcript levels, while the third subpopulation encompassed mature astrocytes (mainly from P30, P50. Within 14 days after ischemia (D3, D7, D14, additional astrocytic subpopulations were identified: resting glia (mostly from P50 and D3, transcriptionally active early reactive glia (mainly from D7 and permanent reactive glia (solely from D14. Following focal cerebral ischemia, reactive astrocytes underwent pronounced changes in the expression of aquaporins, nonspecific cationic and potassium channels, glutamate receptors and reactive astrocyte markers.

  20. Circadian modulation of gene expression, but not glutamate uptake, in mouse and rat cortical astrocytes.

    Directory of Open Access Journals (Sweden)

    Christian Beaulé

    Full Text Available BACKGROUND: Circadian clocks control daily rhythms including sleep-wake, hormone secretion, and metabolism. These clocks are based on intracellular transcription-translation feedback loops that sustain daily oscillations of gene expression in many cell types. Mammalian astrocytes display circadian rhythms in the expression of the clock genes Period1 (Per1 and Period2 (Per2. However, a functional role for circadian oscillations in astrocytes is unknown. Because uptake of extrasynaptic glutamate depends on the presence of Per2 in astrocytes, we asked whether glutamate uptake by glia is circadian. METHODOLOGY/PRINCIPAL FINDINGS: We measured glutamate uptake, transcript and protein levels of the astrocyte-specific glutamate transporter, Glast, and the expression of Per1 and Per2 from cultured cortical astrocytes and from explants of somatosensory cortex. We found that glutamate uptake and Glast mRNA and protein expression were significantly reduced in Clock/Clock, Per2- or NPAS2-deficient glia. Uptake was augmented when the medium was supplemented with dibutyryl-cAMP or B27. Critically, glutamate uptake was not circadian in cortical astrocytes cultured from rats or mice or in cortical slices from mice. CONCLUSION/SIGNIFICANCE: We conclude that glutamate uptake levels are modulated by CLOCK, PER2, NPAS2, and the composition of the culture medium, and that uptake does not show circadian variations.

  1. Carnosine decreased neuronal cell death through targeting glutamate system and astrocyte mitochondrial bioenergetics in cultured neuron/astrocyte exposed to OGD/recovery.

    Science.gov (United States)

    Ouyang, Li; Tian, Yueyang; Bao, Yun; Xu, Huijuan; Cheng, Jiaoyan; Wang, Bingyu; Shen, Yao; Chen, Zhong; Lyu, Jianxin

    2016-06-01

    Previously, we showed that carnosine upregulated the expression level of glutamate transporter 1 (GLT-1), which has been recognized as an important participant in the astrocyte-neuron lactate shuttle (ANLS), with ischemic model in vitro and in vivo. This study was designed to investigate the protective effect of carnosine on neuron/astrocyte co-cultures exposed to OGD/recovery, and to explore whether the ANLS or any other mechanism contributes to carnosine-induced neuroprotection on neuron/astrocyte. Co-cultures were treated with carnosine and exposed to OGD/recovery. Cell death and the extracellular levels of glutamate and GABA were measured. The mitochondrial respiration and glycolysis were detected by Seahorse Bioscience XF96 Extracellular Flux Analyzer. Results showed that carnosine decreased neuronal cell death, increased extracellular GABA level, and abolished the increase in extracellular glutamate and reversed the mitochondrial energy metabolism disorder induced by OGD/recovery. Carnosine also upregulated the mRNA level of neuronal glutamate transporter EAAC1 at 2h after OGD. Dihydrokainate, a specific inhibitor of GLT-1, decreased glycolysis but it did not affect mitochondrial respiration of the cells, and it could not reverse the increase in mitochondrial OXPHOS induced by carnosine in the co-cultures. The levels of mRNAs for monocarboxylate transporter1, 4 (MCT1, 4), which were expressed in astrocytes, and MCT2, the main neuronal MCT, were significantly increased at the early stage of recovery. Carnosine only partly reversed the increased expression of astrocytic MCT1 and MCT4. These results suggest that regulating astrocytic energy metabolism and extracellular glutamate and GABA levels but not the ANLS are involved in the carnosine-induced neuroprotection. PMID:27040711

  2. Synthesis and Radiolabelling of DOTA-Linked Glutamine Analogues with 67,68Ga as Markers for Increased Glutamine Metabolism in Tumour Cells

    Directory of Open Access Journals (Sweden)

    Ivan Greguric

    2013-06-01

    Full Text Available DOTA-linked glutamine analogues with a C6- alkyl and polyethyleneglycol (PEG chain between the chelating group and the L-glutamine moiety were synthesised and labelled with 67,68Ga using established methods. High yields were achieved for the radiolabelling of the molecules with both radionuclides (>90%, although conversion of the commercially available 67Ga-citrate to the chloride species was a requirement for consistent high radiochemical yields. The generator produced 68Ga was in the [68Ga(OH4]− form. The 67Ga complexes and the 67Ga complexes were demonstrated to be stable in PBS buffer for a week. Uptake studies were performed with longer lived 67Ga analogues against four tumour cell lines, as well as uptake inhibition studies against L-glutamine, and two known amino acid transporter inhibitors. Marginal uptake was exhibited in the PEG variant radio-complex, and inhibition studies indicate this uptake is via a non-targeted amino acid pathway.

  3. Astrocytes and Developmental White Matter Disorders

    Science.gov (United States)

    Sen, Ellora; Levison, Steven W.

    2006-01-01

    There is an increasing awareness that the astrocytes in the immature periventricular white matter are vulnerable to ischemia and respond to inflammation. Here we provide a synopsis of the articles that have evaluated the causes and consequences of developmental brain injuries to white matter astrocytes as well as the consequences of several…

  4. Nitric Oxide in Astrocyte-Neuron Signaling

    Energy Technology Data Exchange (ETDEWEB)

    Nianzhen Li

    2002-06-27

    Astrocytes, a subtype of glial cell, have recently been shown to exhibit Ca{sup 2+} elevations in response to neurotransmitters. A Ca{sup 2+} elevation can propagate to adjacent astrocytes as a Ca{sup 2+} wave, which allows an astrocyte to communicate with its neighbors. Additionally, glutamate can be released from astrocytes via a Ca{sup 2+}-dependent mechanism, thus modulating neuronal activity and synaptic transmission. In this dissertation, the author investigated the roles of another endogenous signal, nitric oxide (NO), in astrocyte-neuron signaling. First the author tested if NO is generated during astrocytic Ca{sup 2+} signaling by imaging NO in purified murine cortical astrocyte cultures. Physiological concentrations of a natural messenger, ATP, caused a Ca{sup 2+}-dependent NO production. To test the roles of NO in astrocytic Ca{sup 2+} signaling, the author applied NO to astrocyte cultures via addition of a NO donor, S-nitrosol-N-acetylpenicillamine (SNAP). NO induced an influx of external Ca{sup 2+}, possibly through store-operated Ca{sup 2+} channels. The NO-induced Ca{sup 2+} signaling is cGMP-independent since 8-Br-cGMP, an agonistic analog of cGMP, did not induce a detectable Ca{sup 2+} change. The consequence of this NO-induced Ca{sup 2+} influx was assessed by simultaneously monitoring of cytosolic and internal store Ca{sup 2+} using fluorescent Ca{sup 2+} indicators x-rhod-1 and mag-fluo-4. Blockage of NO signaling with the NO scavenger PTIO significantly reduced the refilling percentage of internal stores following ATP-induced Ca{sup 2+} release, suggesting that NO modulates internal store refilling. Furthermore, locally photo-release of NO to a single astrocyte led to a Ca{sup 2+} elevation in the stimulated astrocyte and a subsequent Ca{sup 2+} wave to neighbors. Finally, the author tested the role of NO inglutamate-mediated astrocyte-neuron signaling by recording the astrocyte-evoked glutamate-dependent neuronal slow inward current (SIC

  5. Alkali metal ion binding to glutamine and glutamine derivatives investigated by infrared action spectroscopy and theory

    NARCIS (Netherlands)

    Bush, M. F.; Oomens, J.; Saykally, R. J.; Williams, E. R.

    2008-01-01

    The gas-phase structures of alkali-metal cationized glutamine are investigated by using both infrared multiple photon dissociation (TRMPD) action spectroscopy, utilizing light generated by a free electron laser, and theory. The IRMPD spectra contain many similarities that are most consistent with gl

  6. Podocalyxin expression in malignant astrocytic tumors

    International Nuclear Information System (INIS)

    Podocalyxin is an anti-adhesive mucin-like transmembrane sialoglycoprotein that has been implicated in the development of aggressive forms of cancer. Podocalyxin is also known as keratan sulfate (KS) proteoglycan. Recently, we revealed that highly sulfated KS or another mucin-like transmembrane sialoglycoprotein podoplanin/aggrus is upregulated in malignant astrocytic tumors. The aim of this study is to examine the relationship between podocalyxin expression and malignant progression of astrocytic tumors. In this study, 51 astrocytic tumors were investigated for podocalyxin expression using immunohistochemistry, Western blot analysis, and quantitative real-time PCR. Immunohistochemistry detected podocalyxin on the surface of tumor cells in six of 14 anaplastic astrocytomas (42.9%) and in 17 of 31 glioblastomas (54.8%), especially around proliferating endothelial cells. In diffuse astrocytoma, podocalyxin expression was observed only in vascular endothelial cells. Podocalyxin might be associated with the malignant progression of astrocytic tumors, and be a useful prognostic marker for astrocytic tumors

  7. Podocalyxin expression in malignant astrocytic tumors.

    Science.gov (United States)

    Hayatsu, Norihito; Kaneko, Mika Kato; Mishima, Kazuhiko; Nishikawa, Ryo; Matsutani, Masao; Price, Janet E; Kato, Yukinari

    2008-09-19

    Podocalyxin is an anti-adhesive mucin-like transmembrane sialoglycoprotein that has been implicated in the development of aggressive forms of cancer. Podocalyxin is also known as keratan sulfate (KS) proteoglycan. Recently, we revealed that highly sulfated KS or another mucin-like transmembrane sialoglycoprotein podoplanin/aggrus is upregulated in malignant astrocytic tumors. The aim of this study is to examine the relationship between podocalyxin expression and malignant progression of astrocytic tumors. In this study, 51 astrocytic tumors were investigated for podocalyxin expression using immunohistochemistry, Western blot analysis, and quantitative real-time PCR. Immunohistochemistry detected podocalyxin on the surface of tumor cells in six of 14 anaplastic astrocytomas (42.9%) and in 17 of 31 glioblastomas (54.8%), especially around proliferating endothelial cells. In diffuse astrocytoma, podocalyxin expression was observed only in vascular endothelial cells. Podocalyxin might be associated with the malignant progression of astrocytic tumors, and be a useful prognostic marker for astrocytic tumors. PMID:18639524

  8. Glucose and hypothalamic astrocytes: More than a fueling role?

    Science.gov (United States)

    Leloup, C; Allard, C; Carneiro, L; Fioramonti, X; Collins, S; Pénicaud, L

    2016-05-26

    Brain plays a central role in energy homeostasis continuously integrating numerous peripheral signals such as circulating nutrients, and in particular blood glucose level, a variable that must be highly regulated. Then, the brain orchestrates adaptive responses to modulate food intake and peripheral organs activity in order to achieve the fine tuning of glycemia. More than fifty years ago, the presence of glucose-sensitive neurons was discovered in the hypothalamus, but what makes them specific and identifiable still remains disconnected from their electrophysiological signature. On the other hand, astrocytes represent the major class of macroglial cells and are now recognized to support an increasing number of neuronal functions. One of these functions consists in the regulation of energy homeostasis through neuronal fueling and nutrient sensing. Twenty years ago, we discovered that the glucose transporter GLUT2, the canonical "glucosensor" of the pancreatic beta-cell together with the glucokinase, was also present in astrocytes and participated in hypothalamic glucose sensing. Since then, many studies have identified other actors and emphasized the astroglial participation in this mechanism. Growing evidence suggest that astrocytes form a complex network and have to be considered as spatially coordinated and regulated metabolic units. In this review we aim to provide an updated view of the molecular and respective cellular pathways involved in hypothalamic glucose sensing, and their relevance in physiological and pathological states. PMID:26071958

  9. Microglia trigger astrocyte-mediated neuroprotection via purinergic gliotransmission

    Science.gov (United States)

    Shinozaki, Youichi; Nomura, Masatoshi; Iwatsuki, Ken; Moriyama, Yoshinori; Gachet, Christian; Koizumi, Schuichi

    2014-03-01

    Microglia are highly sensitive to even small changes in the brain environment, such as invasion of non-hazardous toxicants or the presymptomatic state of diseases. However, the physiological or pathophysiological consequences of their responses remain unknown. Here, we report that cultured microglia sense low concentrations of the neurotoxicant methylmercury (MeHglow) and provide neuroprotection against MeHg, for which astrocytes are also required. When exposed to MeHglow, microglia exocytosed ATP via p38 MAPK- and vesicular nucleotide transporter (VNUT)-dependent mechanisms. Astrocytes responded to the microglia-derived ATP via P2Y1 receptors and released interleukin-6 (IL-6), thereby protecting neurons against MeHglow. These neuroprotective actions were also observed in organotypic hippocampal slices from wild-type mice, but not in slices prepared from VNUT knockout or P2Y1 receptor knockout mice. These findings suggest that microglia sense and respond to even non-hazardous toxicants such as MeHglow and change their phenotype into a neuroprotective one, for which astrocytic support is required.

  10. Glutamine: A novel approach to chemotherapy-induced toxicity

    Directory of Open Access Journals (Sweden)

    Kumar Gaurav

    2012-01-01

    Full Text Available Treatment of cancer is associated with short- and long-term side-effects. Cancer produces a state of glutamine deficiency, which is further aggravated by toxic effects of chemotherapeutic agents leading to increased tolerance of tumor to chemotherapy as well as reduced tolerance of normal tissues to the side-effects of chemotherapy. This article reviews the possible role of glutamine supplementation in reducing the serious adverse events in patients treated with anticancer drugs. The literature related to the possible role of glutamine in humans with cancer and the supportive evidence from animal studies was reviewed. Searches were made and the literature was retrieved using PUBMED, MEDLINE, COCHRANE LIBRARY, CENAHL and EMBASE, with a greater emphasis on the recent advances and clinical trials. Glutamine supplementation was found to protect against radiation-induced mucositis, anthracycline-induced cardiotoxicity and paclitaxel-related myalgias/arthralgias. Glutamine may prevent neurotoxicity of paclitaxel, cisplatin, oxaplatin bortezomib and lenolidamide, and is beneficial in the reduction of the dose-limiting gastrointestinal toxic effects of irinotecan and 5-FU-induced mucositis and stomatitis. Dietary glutamine reduces the severity of the immunosuppressive effect induced by methotrexate and improves the immune status of rats recovering from chemotherapy. In patients with acute myeloid leukemia requiring parenteral nutrition, glycyl-glutamine supplementation could hasten neutrophil recovery after intensive myelosuppressive chemotherapy. Current data supports the usefulness of glutamine supplementation in reducing complications of chemotherapy; however, paucity of clinical trials weakens the clear interpretation of these findings.

  11. Exogenous Glutamine in Respiratory Diseases: Myth or Reality?

    Directory of Open Access Journals (Sweden)

    Gisele P. Oliveira

    2016-02-01

    Full Text Available Several respiratory diseases feature increased inflammatory response and catabolic activity, which are associated with glutamine depletion; thus, the benefits of exogenous glutamine administration have been evaluated in clinical trials and models of different respiratory diseases. Recent reviews and meta-analyses have focused on the effects and mechanisms of action of glutamine in a general population of critical care patients or in different models of injury. However, little information is available about the role of glutamine in respiratory diseases. The aim of the present review is to discuss the evidence of glutamine depletion in cystic fibrosis (CF, asthma, chronic obstructive pulmonary disease (COPD, acute respiratory distress syndrome (ARDS, and lung cancer, as well as the results of exogenous glutamine administration in experimental and clinical studies. Exogenous glutamine administration might be beneficial in ARDS, asthma, and during lung cancer treatment, thus representing a potential therapeutic tool in these conditions. Further experimental and large randomized clinical trials focusing on the development and progression of respiratory diseases are necessary to elucidate the effects and possible therapeutic role of glutamine in this setting.

  12. A theoretical study of the role of astrocyte activity in neuronal hyperexcitability using a new neuro-glial mass model

    OpenAIRE

    Garnier, Aurélie; Vidal, Alexandre; Benali, Habib

    2015-01-01

    The investigation of the neuronal environment allows us to better understand the activity of a cerebral region as a whole. The recent experimental evidences of the presence of transporters for glutamate and GABA in both neuronal and astrocyte compartments raise the question of the functional importance of the astrocytes in the regulation of the neuronal activity. We propose a new computational model at the mesoscopic scale embedding the recent knowledge on the physiology of neuron and astrocy...

  13. Role of glutamine in cobinamide biosynthesis in Propionibacterium shermanii

    International Nuclear Information System (INIS)

    The role of glutamine as a possible donor of amide groups in the biosynthesis of vitamin B12 was investigated. In the incubation of P. shermanii cells preliminarily exhausted with respect to nitrogen on media containing ammonium sulfate or asparagine, the glutamine synthetase inhibitor methionine sulfoximine suppressed the formation of cobinamide (factor B) from the monoamide of cobiric acid (by 75 and 59%, respectively). At the same time, the inhibitor did not affect cobinamide synthesis on a medium with glutamine. The amide group of glutamine, labeled with 13N, was used for the amidation of corrinoids four times as efficiently as the amine group. It was concluded that a glutamine-dependent synthetase, which catalyzes the amidation of cobiric acids with the formation of cobinamide, functions in cells of propionic acid bacteria

  14. Complexation of asparagine and glutamine by dioxovanadium

    International Nuclear Information System (INIS)

    The complexation of pervanadyl ion (VO2+) with L-asparagine and L-glutamine has been investigated by spectrophotometric measurements in aqueous solution at 0.15 mol dm-3 ionic strength (NaCLO4) and 25 ± 0.1 Deg C in the pH 1.3 - 10.3 range. The stability constants of the formed complexes and their stoichiometries are given and interpreted. The logarithms of the cumulative stability constant, βxyz, of the complexes [(H)x(oxo metal)y(amino acid)z] are respectively: lgβ101 = 8.80 ± 0.08, lgβ011 = 9.47 ± 0.10, and lgβ012 = 14.57 ± 0.15 for asparagine and lgβ101 = 9.05 ± 0.10, lgβ011 9.54 ± 0.10, and lgβ012 = 14.81 ± 0.15 for glutamine. The mode coordination of the ligands in their protonated and deprotonated complexes is discussed on the basis of their parameters

  15. Induction of adult human bone marrow mesenchymal stromal cells into functional astrocyte-like cells: potential for restorative treatment in Parkinson's disease.

    Science.gov (United States)

    Bahat-Stroomza, Merav; Barhum, Yael; Levy, Yossef S; Karpov, Olga; Bulvik, Shlomo; Melamed, Eldad; Offen, Daniel

    2009-09-01

    Parkinson's disease (PD) is a neurodegenerative disorder with its motor phenomena due mostly to loss of dopamine-producing neurons in the substantia nigra. Pharmacological treatments aimed to increase the deficient dopaminergic neurotransmission are effective in ameliorating the cardinal symptoms, but none of these therapies is curative. It has been suggested that treatment with neurotrophic factors (NTFs) might protect and prevent death of the surviving dopaminergic neurons and induce proliferation of their axonal nerve terminals with reinnervations of the deafferented striatum. However, long-term delivery of such proteins into the CNS is problematic. We therefore aimed to differentiate ex vivo human bone marrow-derived mesenchymal stromal cells into astrocyte-like cells, capable of generating NTFs for future transplantation into basal ganglia of PD patients. Indeed, mesenchymal stromal cells treated with our novel astrocyte differentiation medium, present astrocyte-like morphology and express the astrocyte markers S100beta, glutamine synthetase and glial fibrillary acidic protein. Moreover, these astrocyte-like cells produce and secrete significant amounts of glial cell line-derived neurotrophic factor (GDNF), nerve growth factor (NGF), and brain-derived neurotrophic factor as indicated by messenger RNA, real-time polymerase chain reaction, ELISA, and Western blot analyses. Such NTF-producing cells transplanted into the striatum of 6-hydroxydopamine-lesioned rats, a model of PD, produced a progressive reduction in the apomorphine-induced contralateral rotations as well as behavioral improvement in rotor-rod and the "sunflower seeds" eating motor tests. Histological assessments revealed that the engrafted cells survived and expressed astrocyte and human markers and acted to regenerate the damaged dopaminergic nerve terminal system. Findings indicate that our novel procedure to induce NTF-producing astrocyte-like cells derived from human bone marrow stromal cells

  16. Loose excitation-secretion coupling in astrocytes.

    Science.gov (United States)

    Vardjan, Nina; Parpura, Vladimir; Zorec, Robert

    2016-05-01

    Astrocytes play an important housekeeping role in the central nervous system. Additionally, as secretory cells, they actively participate in cell-to-cell communication, which can be mediated by membrane-bound vesicles. The gliosignaling molecules stored in these vesicles are discharged into the extracellular space after the vesicle membrane fuses with the plasma membrane. This process is termed exocytosis, regulated by SNARE proteins, and triggered by elevations in cytosolic calcium levels, which are necessary and sufficient for exocytosis in astrocytes. For astrocytic exocytosis, calcium is sourced from the intracellular endoplasmic reticulum store, although its entry from the extracellular space contributes to cytosolic calcium dynamics in astrocytes. Here, we discuss calcium management in astrocytic exocytosis and the properties of the membrane-bound vesicles that store gliosignaling molecules, including the vesicle fusion machinery and kinetics of vesicle content discharge. In astrocytes, the delay between the increase in cytosolic calcium activity and the discharge of secretions from the vesicular lumen is orders of magnitude longer than that in neurons. This relatively loose excitation-secretion coupling is likely tailored to the participation of astrocytes in modulating neural network processing. PMID:26358496

  17. Artificial astrocytes improve neural network performance.

    Science.gov (United States)

    Porto-Pazos, Ana B; Veiguela, Noha; Mesejo, Pablo; Navarrete, Marta; Alvarellos, Alberto; Ibáñez, Oscar; Pazos, Alejandro; Araque, Alfonso

    2011-01-01

    Compelling evidence indicates the existence of bidirectional communication between astrocytes and neurons. Astrocytes, a type of glial cells classically considered to be passive supportive cells, have been recently demonstrated to be actively involved in the processing and regulation of synaptic information, suggesting that brain function arises from the activity of neuron-glia networks. However, the actual impact of astrocytes in neural network function is largely unknown and its application in artificial intelligence remains untested. We have investigated the consequences of including artificial astrocytes, which present the biologically defined properties involved in astrocyte-neuron communication, on artificial neural network performance. Using connectionist systems and evolutionary algorithms, we have compared the performance of artificial neural networks (NN) and artificial neuron-glia networks (NGN) to solve classification problems. We show that the degree of success of NGN is superior to NN. Analysis of performances of NN with different number of neurons or different architectures indicate that the effects of NGN cannot be accounted for an increased number of network elements, but rather they are specifically due to astrocytes. Furthermore, the relative efficacy of NGN vs. NN increases as the complexity of the network increases. These results indicate that artificial astrocytes improve neural network performance, and established the concept of Artificial Neuron-Glia Networks, which represents a novel concept in Artificial Intelligence with implications in computational science as well as in the understanding of brain function. PMID:21526157

  18. Artificial astrocytes improve neural network performance.

    Directory of Open Access Journals (Sweden)

    Ana B Porto-Pazos

    Full Text Available Compelling evidence indicates the existence of bidirectional communication between astrocytes and neurons. Astrocytes, a type of glial cells classically considered to be passive supportive cells, have been recently demonstrated to be actively involved in the processing and regulation of synaptic information, suggesting that brain function arises from the activity of neuron-glia networks. However, the actual impact of astrocytes in neural network function is largely unknown and its application in artificial intelligence remains untested. We have investigated the consequences of including artificial astrocytes, which present the biologically defined properties involved in astrocyte-neuron communication, on artificial neural network performance. Using connectionist systems and evolutionary algorithms, we have compared the performance of artificial neural networks (NN and artificial neuron-glia networks (NGN to solve classification problems. We show that the degree of success of NGN is superior to NN. Analysis of performances of NN with different number of neurons or different architectures indicate that the effects of NGN cannot be accounted for an increased number of network elements, but rather they are specifically due to astrocytes. Furthermore, the relative efficacy of NGN vs. NN increases as the complexity of the network increases. These results indicate that artificial astrocytes improve neural network performance, and established the concept of Artificial Neuron-Glia Networks, which represents a novel concept in Artificial Intelligence with implications in computational science as well as in the understanding of brain function.

  19. Metabolic gene expression changes in astrocytes in Multiple Sclerosis cerebral cortex are indicative of immune-mediated signaling

    KAUST Repository

    Zeis, T.

    2015-04-01

    Emerging as an important correlate of neurological dysfunction in Multiple Sclerosis (MS), extended focal and diffuse gray matter abnormalities have been found and linked to clinical manifestations such as seizures, fatigue and cognitive dysfunction. To investigate possible underlying mechanisms we analyzed the molecular alterations in histopathological normal appearing cortical gray matter (NAGM) in MS. By performing a differential gene expression analysis of NAGM of control and MS cases we identified reduced transcription of astrocyte specific genes involved in the astrocyte–neuron lactate shuttle (ANLS) and the glutamate–glutamine cycle (GGC). Additional quantitative immunohistochemical analysis demonstrating a CX43 loss in MS NAGM confirmed a crucial involvement of astrocytes and emphasizes their importance in MS pathogenesis. Concurrently, a Toll-like/IL-1β signaling expression signature was detected in MS NAGM, indicating that immune-related signaling might be responsible for the downregulation of ANLS and GGC gene expression in MS NAGM. Indeed, challenging astrocytes with immune stimuli such as IL-1β and LPS reduced their ANLS and GGC gene expression in vitro. The detected upregulation of IL1B in MS NAGM suggests inflammasome priming. For this reason, astrocyte cultures were treated with ATP and ATP/LPS as for inflammasome activation. This treatment led to a reduction of ANLS and GGC gene expression in a comparable manner. To investigate potential sources for ANLS and GGC downregulation in MS NAGM, we first performed an adjuvant-driven stimulation of the peripheral immune system in C57Bl/6 mice in vivo. This led to similar gene expression changes in spinal cord demonstrating that peripheral immune signals might be one source for astrocytic gene expression changes in the brain. IL1B upregulation in MS NAGM itself points to a possible endogenous signaling process leading to ANLS and GGC downregulation. This is supported by our findings that, among others

  20. Liposomal clodronate selectively eliminates microglia from primary astrocyte cultures

    OpenAIRE

    Kumamaru Hiromi; Saiwai Hirokazu; Kobayakawa Kazu; Kubota Kensuke; van Rooijen Nico; Inoue Kazuhide; Iwamoto Yukihide; Okada Seiji

    2012-01-01

    Abstract Background There is increasing interest in astrocyte biology because astrocytes have been demonstrated to play prominent roles in physiological and pathological conditions of the central nervous system, including neuroinflammation. To understand astrocyte biology, primary astrocyte cultures are most commonly used because of the direct accessibility of astrocytes in this system. However, this advantage can be hindered by microglial contamination. Although several authors have warned r...

  1. Neuronal modulation of calcium channel activity in cultured rat astrocytes.

    OpenAIRE

    Corvalan, V; Cole, R; de Vellis, J.; Hagiwara, S.

    1990-01-01

    The patch-clamp technique was used to study whether cocultivation of neurons and astrocytes modulates the expression of calcium channel activity in astrocytes. Whole-cell patch-clamp recordings from rat brain astrocytes cocultured with rat embryonic neurons revealed two types of voltage-dependent inward currents carried by Ca2+ and blocked by either Cd2+ or Co2+ that otherwise were not detected in purified astrocytes. This expression of calcium channel activity in astrocytes was neuron depend...

  2. Common astrocytic programs during brain development, injury and cancer

    OpenAIRE

    Silver, Daniel J.; Steindler, Dennis A.

    2009-01-01

    In addition to radial glial cells of neurohistogenesis, immature astrocytes with stem-cell-like properties cordon off emerging functional patterns in the developing brain. Astrocytes also can be stem cells during adult neurogenesis, and a proposed potency of injury-associated reactive astrocytes has recently been substantiated. Astrocytic cells might additionally be involved in cancer stem cell-associated gliomagenesis. Thus, there are distinguishing roles for stem-cell-like astrocytes during...

  3. Superantigen presenting capacity of human astrocytes

    DEFF Research Database (Denmark)

    Hassan-Zahraee, M; Ladiwala, U; Lavoie, P M;

    2000-01-01

    We found that human fetal astrocytes (HFA) are able to support superantigen (SAG) staphylococcal enterotoxin B (SEB) and toxic shock syndrome toxin-1 (TSST-1)-induced activation of immediately ex vivo allogenic human CD4 T cells. Using radiolabelled toxins, we demonstrate that both SEB and TSST-1...... bind with high affinity to MHC class II antigen expressing astrocytes; binding is displaceable with excess cold toxin. Competition experiments further indicate that TSST-1 and SEB at least partially compete with each other for binding to astrocytes suggesting they bind to the same HLA-DR region on...

  4. The glutamate-glutamine(GABA cycle: importance of late postnatal development and potential reciprocal interactions between biosynthesis and degradation

    Directory of Open Access Journals (Sweden)

    Leif eHertz

    2013-05-01

    Full Text Available The gold standard for studies of glutamate-glutamine(GABA cycling and its connections to brain biosynthesis from glucose of glutamate and GABA and their subsequent metabolism are the elegant in vivo studies by 13C magnetic resonance spectroscopy (NMR, showing the large fluxes in the cycle. However, simpler experiments in intact brain tissue (e.g. immunohistochemistry, brain slices, cultured brain cells and mitochondria have also made important contributions to the understanding of details, mechanisms and functional consequences of glutamate/GABA biosynthesis and degradation. The purpose of this review is to attempt to integrate evidence from different sources regarding i the enzyme(s responsible for the initial conversion of -ketoglutarate to glutamate; ii the possibility that especially glutamate oxidation is essentially confined to astrocytes; and iii the ontogenetically very late onset and maturation of glutamine-glutamate(GABA cycle function. Pathway models based on the functional importance of aspartate for glutamate synthesis suggest the possibility of interacting pathways for biosynthesis and degradation of glutamate and GABA and the use of transamination as the default mechanism for initiation of glutamate oxidation. The late development and maturation are related to the late cortical gliogenesis and convert brain cortical function from being purely neuronal to becoming neuronal-astrocytic. This conversion is associated with huge increases in energy demand and production, and the character of potentially incurred gains of function are discussed. These may include alterations in learning mechanisms, in mice indicated by lack of pairing of odor learning with aversive stimuli in newborn animals but the development of such an association 10-12 days later. The possibility is suggested that analogous maturational changes may contribute to differences in the way learning is accomplished in the newborn human brain and during later development.

  5. Isolation and Characterization of Ischemia-Derived Astrocytes (IDAs) with Ability to Transactivate Quiescent Astrocytes

    OpenAIRE

    Villarreal, Alejandro; Rosciszewski, Gerardo; Murta, Veronica; Cadena, Vanesa; Usach, Vanina; Dodes-Traian, Martin M.; Setton-Avruj, Patricia; Barbeito, Luis H.; Ramos, Alberto J.

    2016-01-01

    Reactive gliosis involving activation and proliferation of astrocytes and microglia, is a widespread but largely complex and graded glial response to brain injury. Astroglial population has a previously underestimated high heterogeneity with cells differing in their morphology, gene expression profile, and response to injury. Here, we identified a subset of reactive astrocytes isolated from brain focal ischemic lesions that show several atypical characteristics. Ischemia-derived astrocytes (I...

  6. Association of astrocytes with neurons and astrocytes derived from distinct progenitor domains in the subpallium

    OpenAIRE

    Makio Torigoe; Kenta Yamauchi; Yan Zhu; Hiroaki Kobayashi; Fujio Murakami

    2015-01-01

    Astrocytes play pivotal roles in metabolism and homeostasis as well as in neural development and function in a manner thought to depend on their region-specific diversity. In the mouse spinal cord, astrocytes and neurons, which are derived from a common progenitor domain (PD) and controlled by common PD-specific transcription factors, migrate radially and share their final positions. However, whether astrocytes can only interact with neurons from common PDs in the brain remains unknown. Here,...

  7. Glucose and glutamine fuel protein O-GlcNAcylation to control T cell self-renewal and malignancy.

    Science.gov (United States)

    Swamy, Mahima; Pathak, Shalini; Grzes, Katarzyna M; Damerow, Sebastian; Sinclair, Linda V; van Aalten, Daan M F; Cantrell, Doreen A

    2016-06-01

    Sustained glucose and glutamine transport are essential for activated T lymphocytes to support ATP and macromolecule biosynthesis. We found that glutamine and glucose also fuel an indispensable dynamic regulation of intracellular protein O-GlcNAcylation at key stages of T cell development, transformation and differentiation. Glucose and glutamine are precursors of uridine diphosphate N-acetylglucosamine (UDP-GlcNAc), a substrate for cellular glycosyltransferases. Immune-activated T cells contained higher concentrations of UDP-GlcNAc and increased intracellular protein O-GlcNAcylation controlled by the enzyme O-linked-β-N-acetylglucosamine (O-GlcNAc) glycosyltransferase as compared with naive cells. We identified Notch, the T cell antigen receptor and c-Myc as key controllers of T cell protein O-GlcNAcylation via regulation of glucose and glutamine transport. Loss of O-GlcNAc transferase blocked T cell progenitor renewal, malignant transformation and peripheral T cell clonal expansion. Nutrient-dependent signaling pathways regulated by O-GlcNAc glycosyltransferase are thus fundamental for T cell biology. PMID:27111141

  8. Transcriptomic analysis and 3D bioengineering of astrocytes indicate ROCK inhibition produces cytotrophic astrogliosis

    Directory of Open Access Journals (Sweden)

    Ross D O'Shea

    2015-02-01

    Full Text Available Astrocytes provide trophic, structural and metabolic support to neurons, and are considered genuine targets in regenerative neurobiology, as their phenotype arbitrates brain integrity during injury. Inhibitors of Rho kinase (ROCK cause stellation of cultured 2D astrocytes, increased L-glutamate transport, augmented G-actin, and elevated expression of BDNF and anti-oxidant genes. Here we further explored the signposts of a cytotrophic, healthy phenotype by data-mining of our astrocytic transcriptome in the presence of Fasudil. Gene expression profiles of motor and autophagic cellular cascades and inflammatory / angiogenic responses were all inhibited, favouring adoption of an anti-migratory phenotype. Like ROCK inhibition, tissue engineered bioscaffolds can influence the extracellular matrix. We built upon our evidence that astrocytes maintained on 3D poly-Ɛ-caprolactone (PCL electrospun scaffolds adopt a cytotrophic phenotype similar to that produced by Fasudil. Using these procedures, employing mature 3D cultured astrocytes, Fasudil (100 µM or Y27632 (30 µM added for the last 72 h of culture altered arborization, which featured numerous additional minor processes as shown by GFAP and AHNAK immunolabelling. Both ROCK inhibitors decreased F-actin, but increased G-actin labelling, indicative of disassembly of actin stress fibres. ROCK inhibitors provide additional beneficial effects for bioengineered 3D astrocytes, including enlargement of the overall arbour. Potentially, the combined strategy of bio-compatible scaffolds with ROCK inhibition offers unique advantages for the management of glial scarring. Overall these data emphasize that manipulation of the astrocyte phenotype to achieve a healthy biology offers new hope for the management of inflammation in neuropathologies.

  9. Calcium wave of Brain Astrocytes

    Science.gov (United States)

    Cornell Bell, A. H.

    1997-03-01

    Time lapse confocal scanning laser microscopy was used to study hippocampal astrocyte cultures loaded with a calcium indicator, Fluo3-AM (4 uM). kThe neurotransmitter kainate (100uM) overwhelms the Na+-buffering capacity of astrocytes within 100 sec resulting in reversal of the Na+/Ca2+ exchanger. This results in a subcellular site where Ca2+ entering the cytoplasm contributes to a long-distance Ca2+ wave which travels at 20 um/sec without decrement. Image analysis has shown calcium waves not only at a high Kainate dose, but also at a low Kainate dose, e.g. 10uM. These are, however, shortlived and burried in an extremely noisy background and only detectable by analyzing the calcium waves images for spatio-temporal coherence. As the kainate dose increases, more large scale coherent structures with visible geometric features (spiral waves and target waves) can be observed. Multiple spiral waves are produced when the Kainate dose increases to 100 uM. These waves travel at a constant velocity across entire microscope fields for long time periods (>30 mins). Na+ channels have no effect on the Kainate wave. Voltage-gated Ca2+ channels are not involved and Ca2+ enters through reversal of the exchanger. Ca2+ release from stores does not contribute to the kainate wave. Removal of Na+ or Ca2+ from outside and the specific Na+/Ca2+ exchange inhibitor benzamil (10 uM) inhibit the kainate wave. A functional antibody to alpha6-Integrin which is localized to membrane regions between cells inhibits the spread of the kainate wave in a dose and time-dependent manner. Fluorescence Recovery after Photobleach (FRAP) techniques indicate that gap junctions remain open between cells. This would imply that Ca2+ or IP3 need not pass through the gap junction, but reversal of the exchanger would propel the Ca2+ wave at the cell surface.

  10. Astrocytic expression of Parkinson's disease-related A53T α-synuclein causes neurodegeneration in mice

    Directory of Open Access Journals (Sweden)

    Gu Xing-Long

    2010-04-01

    Full Text Available Abstract Background Parkinson's disease (PD is the most common movement disorder. While neuronal deposition of α-synuclein serves as a pathological hallmark of PD and Dementia with Lewy Bodies, α-synuclein-positive protein aggregates are also present in astrocytes. The pathological consequence of astrocytic accumulation of α-synuclein, however, is unclear. Results Here we show that PD-related A53T mutant α-synuclein, when selectively expressed in astrocytes, induced rapidly progressed paralysis in mice. Increasing accumulation of α-synuclein aggregates was found in presymptomatic and symptomatic mouse brains and correlated with the expansion of reactive astrogliosis. The normal function of astrocytes was compromised as evidenced by cerebral microhemorrhage and down-regulation of astrocytic glutamate transporters, which also led to increased inflammatory responses and microglial activation. Interestingly, the activation of microglia was mainly detected in the midbrain, brainstem and spinal cord, where a significant loss of dopaminergic and motor neurons was observed. Consistent with the activation of microglia, the expression level of cyclooxygenase 1 (COX-1 was significantly up-regulated in the brain of symptomatic mice and in cultured microglia treated with conditioned medium derived from astrocytes over-expressing A53T α-synuclein. Consequently, the suppression of COX-1 activities extended the survival of mutant mice, suggesting that excess inflammatory responses elicited by reactive astrocytes may contribute to the degeneration of neurons. Conclusions Our findings demonstrate a critical involvement of astrocytic α-synuclein in initiating the non-cell autonomous killing of neurons, suggesting the viability of reactive astrocytes and microglia as potential therapeutic targets for PD and other neurodegenerative diseases.

  11. A widespread glutamine-sensing mechanism in the plant kingdom.

    Science.gov (United States)

    Chellamuthu, Vasuki-Ranjani; Ermilova, Elena; Lapina, Tatjana; Lüddecke, Jan; Minaeva, Ekaterina; Herrmann, Christina; Hartmann, Marcus D; Forchhammer, Karl

    2014-11-20

    Glutamine is the primary metabolite of nitrogen assimilation from inorganic nitrogen sources in microorganisms and plants. The ability to monitor cellular nitrogen status is pivotal for maintaining metabolic homeostasis and sustaining growth. The present study identifies a glutamine-sensing mechanism common in the entire plant kingdom except Brassicaceae. The plastid-localized PII signaling protein controls, in a glutamine-dependent manner, the key enzyme of the ornithine synthesis pathway, N-acetyl-l-glutamate kinase (NAGK), that leads to arginine and polyamine formation. Crystal structures reveal that the plant-specific C-terminal extension of PII, which we term the Q loop, forms a low-affinity glutamine-binding site. Glutamine binding alters PII conformation, promoting interaction and activation of NAGK. The binding motif is highly conserved in plants except Brassicaceae. A functional Q loop restores glutamine sensing in a recombinant Arabidopsis thaliana PII protein, demonstrating the modular concept of the glutamine-sensing mechanism adopted by PII proteins during the evolution of plant chloroplasts. PMID:25416954

  12. Preparation and characterization of electrospun nanofibers containing glutamine.

    Science.gov (United States)

    Tort, Serdar; Acartürk, Füsun

    2016-11-01

    Oral mucositis is a painful inflammation of mucous membranes commonly after chemotherapy or radiotherapy. The aim of this study was to develop mucoadhesive nanofibers containing glutamine via electrospinning and to characterize them for the treatment of oral mucositis. Different mucoadhesive polymers were tried for preparing nanofibers and sodium alginate nanofibers were chosen after the characterization studies. Glutamine-loaded nanofibers were produced and characterized. Glutamine loaded onto nanofibers was confirmed by differantial scanning calorimetry and fourier transform infrared spectroscopy analyses. As a result, scanning electron microscopy observations showed that the glutamine loaded nanofibers had average diameter of 160nm. Glutamine amount was found to be 0.452mg/cm(2). Work of mucoadhesion, tensile strength and elongation at break values of the glutamine loaded nanofibers were found to be 0.165mJ/cm(2), 2.61mPa and 6.62% respectively. In vitro dissolution tests showed that more than 85% of the drug was diffused from the nanofibers at the end of 4h. Stability studies showed that there was no significant changes at 4 and 25°C/65% relative humidity storage conditions. Therefore, these results demonstrate that glutamine loaded nanofibers could have potential as an oromucosal drug delivery system for the treatment oral mucositis. PMID:27516332

  13. Understanding the mechanisms of glutamine action in critically ill patients

    Directory of Open Access Journals (Sweden)

    Gisele P. Oliveira

    2010-06-01

    Full Text Available Glutamine (Gln is an important energy source and has been used as a supplementary energy substrate. Furthermore, Gln is an essential component for numerous metabolic functions, including acid-base homeostasis, gluconeogenesis, nitrogen transport and synthesis of proteins and nucleic acids. Therefore, glutamine plays a significant role in cell homeostasis and organ metabolism. This article aims to review the mechanisms of glutamine action during severe illnesses. In critically ill patients, the increase in mortality was associated with a decreased plasma Gln concentration. During catabolic stress, Gln consumption rate exceeds the supply, and both plasma and skeletal muscle pools of free Gln are severely reduced. The dose and route of Gln administration clearly influence its effectiveness: high-dose parenteral appears to be more beneficial than low-dose enteral administration. Experimental studies reported that Gln may protect cells, tissues, and whole organisms from stress and injury through the following mechanisms: attenuation of NF (nuclear factor-kB activation, a balance between pro- and anti-inflammatory cytokines, reduction in neutrophil accumulation, improvement in intestinal integrity and immune cell function, and enhanced of heat shock protein expression. In conclusion, high-doses of parenteral Gln (>0.50 g/kg/day demonstrate a greater potential to benefit in critically ill patients, although Gln pathophysiological mechanisms requires elucidation.A glutamina (Gln é uma importante fonte de energia e tem sido usada como substrato energético suplementar. Além disso, a Gln é um componente essencial para numerosas funções metabólicas tais como: homeostase ácido-base, gliconeogênese, transporte de nitrogênio e síntese de proteínas e ácidos nucléicos. Portanto, a glutamina desempenha um papel importante na homeostase celular e no metabolismo dos órgãos. Esse artigo objetiva rever os mecanismos de ação da glutamina na doen

  14. Astrocytes release ATP through lysosomal exocytosis

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ Astrocytes, the most abundant type of glial cells in the brain, have been found to release signaling molecules, including adenosine triphosphate(ATP), the most important energy carrier inside the cell as well as a universal extracellular signaling molecule.

  15. The glutamine synthetase gene family in Populus

    Directory of Open Access Journals (Sweden)

    Cánovas Francisco M

    2011-08-01

    Full Text Available Abstract Background Glutamine synthetase (GS; EC: 6.3.1.2, L-glutamate: ammonia ligase ADP-forming is a key enzyme in ammonium assimilation and metabolism of higher plants. The current work was undertaken to develop a more comprehensive understanding of molecular and biochemical features of GS gene family in poplar, and to characterize the developmental regulation of GS expression in various tissues and at various times during the poplar perennial growth. Results The GS gene family consists of 8 different genes exhibiting all structural and regulatory elements consistent with their roles as functional genes. Our results indicate that the family members are organized in 4 groups of duplicated genes, 3 of which code for cytosolic GS isoforms (GS1 and 1 which codes for the choroplastic GS isoform (GS2. Our analysis shows that Populus trichocarpa is the first plant species in which it was observed the complete GS family duplicated. Detailed expression analyses have revealed specific spatial and seasonal patterns of GS expression in poplar. These data provide insights into the metabolic function of GS isoforms in poplar and pave the way for future functional studies. Conclusions Our data suggest that GS duplicates could have been retained in order to increase the amount of enzyme in a particular cell type. This possibility could contribute to the homeostasis of nitrogen metabolism in functions associated to changes in glutamine-derived metabolic products. The presence of duplicated GS genes in poplar could also contribute to diversification of the enzymatic properties for a particular GS isoform through the assembly of GS polypeptides into homo oligomeric and/or hetero oligomeric holoenzymes in specific cell types.

  16. Astrocytes and Huntington’s Disease

    OpenAIRE

    Khakh, Baljit S.; Sofroniew, Michael V.

    2014-01-01

    In this Viewpoint, we summarize and discuss the recent serendipitous discovery of an astrocyte Kir4.1 potassium channel dysfunction in two mouse models of Huntington’s disease (HD). Restoration of Kir4.1 channels within astrocytes in vivo attenuated neuronal dysfunction, some aspects of motor dysfunction and increased survival time in a HD mouse model. Overall, the data show that aspects of altered neuronal excitability associated with HD may be secondary to changes in as...

  17. Relaxin Protects Astrocytes from Hypoxia In Vitro

    OpenAIRE

    Willcox, Jordan M.; Alastair J S Summerlee

    2014-01-01

    The peptide relaxin has recently been shown to protect brain tissues from the detrimental effects of ischemia. To date, the mechanisms for this remain unclear. In order to investigate the neuroprotective mechanisms by which relaxin may protect the brain, we investigated the possibility that relaxin protects astrocytes from hypoxia or oxygen/glucose deprivation (OGD). Cultured astrocytes were pre-treated with either relaxin-2 or relaxin-3 and exposed to OGD for 24 or 48 hours. Following OGD ex...

  18. Dynamic reactive astrocytes after focal ischemia

    OpenAIRE

    Ding, Shinghua

    2014-01-01

    Astrocytes are specialized and most numerous glial cell type in the central nervous system and play important roles in physiology. Astrocytes are also critically involved in many neural disorders including focal ischemic stroke, a leading cause of brain injury and human death. One of the prominent pathological features of focal ischemic stroke is reactive astrogliosis and glial scar formation associated with morphological changes and proliferation. This review paper discusses the recent advan...

  19. Astrocytic mechanisms explaining neural-activity-induced shrinkage of extraneuronal space.

    Directory of Open Access Journals (Sweden)

    Ivar Østby

    2009-01-01

    Full Text Available Neuronal stimulation causes approximately 30% shrinkage of the extracellular space (ECS between neurons and surrounding astrocytes in grey and white matter under experimental conditions. Despite its possible implications for a proper understanding of basic aspects of potassium clearance and astrocyte function, the phenomenon remains unexplained. Here we present a dynamic model that accounts for current experimental data related to the shrinkage phenomenon in wild-type as well as in gene knockout individuals. We find that neuronal release of potassium and uptake of sodium during stimulation, astrocyte uptake of potassium, sodium, and chloride in passive channels, action of the Na/K/ATPase pump, and osmotically driven transport of water through the astrocyte membrane together seem sufficient for generating ECS shrinkage as such. However, when taking into account ECS and astrocyte ion concentrations observed in connection with neuronal stimulation, the actions of the Na(+/K(+/Cl(- (NKCC1 and the Na(+/HCO(3 (- (NBC cotransporters appear to be critical determinants for achieving observed quantitative levels of ECS shrinkage. Considering the current state of knowledge, the model framework appears sufficiently detailed and constrained to guide future key experiments and pave the way for more comprehensive astroglia-neuron interaction models for normal as well as pathophysiological situations.

  20. Stargazing: Monitoring subcellular dynamics of brain astrocytes.

    Science.gov (United States)

    Benjamin Kacerovsky, J; Murai, K K

    2016-05-26

    Astrocytes are major non-neuronal cell types in the central nervous system that regulate a variety of processes in the brain including synaptic transmission, neurometabolism, and cerebrovasculature tone. Recent discoveries have revealed that astrocytes perform very specialized and heterogeneous roles in brain homeostasis and function. Exactly how astrocytes fulfill such diverse roles in the brain remains to be fully understood and is an active area of research. In this review, we focus on the complex subcellular anatomical features of protoplasmic gray matter astrocytes in the mature, healthy brain that likely empower these cells with the ability to detect and respond to changes in neuronal and synaptic activity. In particular, we discuss how intricate processes on astrocytes allow these cells to communicate with neurons and their synapses and strategically deliver specific cellular organelles such as mitochondria and ribosomes to active compartments within the neuropil. Understanding the properties of these structural elements will lead to a better understanding of how astrocytes function in the healthy and diseased brain. PMID:26162237

  1. Astrocyte response to St. Louis encephalitis virus.

    Science.gov (United States)

    Zuza, Adriano Lara; Barros, Heber Leão Silva; de Mattos Silva Oliveira, Thelma Fátima; Chávez-Pavoni, Juliana Helena; Zanon, Renata Graciele

    2016-06-01

    St. Louis encephalitis virus (SLEV), a flavivirus transmitted to humans by Culex mosquitoes, causes clinical symptoms ranging from acute febrile disorder to encephalitis. To reach the central nervous system (CNS) from circulating blood, the pathogen must cross the blood-brain barrier formed by endothelial cells and astrocytes. Because astrocytes play an essential role in CNS homeostasis, in this study these cells were infected with SLEV and investigated for astrogliosis, major histocompatibility complex (MHC)-I-dependent immune response, and apoptosis by caspase-3 activation. Cultures of Vero cells were used as a positive control for the viral infection. Cytopathic effects were observed in both types of cell cultures, and the cytotoxicity levels of the two were compared. Astrocytes infected with a dilution of 1E-01 (7.7E+08 PFU/mL) had a reduced mortality rate of more than 50% compared to the Vero cells. In addition, the astrocytes responded to the flavivirus infection with increased MHC-I expression and astrogliosis, characterized by intense glial fibrillary acidic protein expression and an increase in the number and length of cytoplasmic processes. When the astrocytes were exposed to higher viral concentrations, a proportional increase in caspase-3 expression was observed, as well as nuclear membrane destruction. SLEV immunostaining revealed a perinuclear location of the virus during the replication process. Together, these results suggest that mechanisms other than SLEV infection in astrocytes must be associated with the development of the neuroinvasive form of the disease. PMID:26975980

  2. Glucocorticoid regulation of astrocytic fate and function.

    Directory of Open Access Journals (Sweden)

    Shuang Yu

    Full Text Available Glial loss in the hippocampus has been suggested as a factor in the pathogenesis of stress-related brain disorders that are characterized by dysregulated glucocorticoid (GC secretion. However, little is known about the regulation of astrocytic fate by GC. Here, we show that astrocytes derived from the rat hippocampus undergo growth inhibition and display moderate activation of caspase 3 after exposure to GC. Importantly, the latter event, observed both in situ and in primary astrocytic cultures is not followed by either early- or late-stage apoptosis, as monitored by stage I or stage II DNA fragmentation. Thus, unlike hippocampal granule neurons, astrocytes are resistant to GC-induced apoptosis; this resistance is due to lower production of reactive oxygen species (ROS and a greater buffering capacity against the cytotoxic actions of ROS. We also show that GC influence hippocampal cell fate by inducing the expression of astrocyte-derived growth factors implicated in the control of neural precursor cell proliferation. Together, our results suggest that GC instigate a hitherto unknown dialog between astrocytes and neural progenitors, adding a new facet to understanding how GC influence the cytoarchitecture of the hippocampus.

  3. Astrocyte Aquaporin Dynamics in Health and Disease.

    Science.gov (United States)

    Potokar, Maja; Jorgačevski, Jernej; Zorec, Robert

    2016-01-01

    The family of aquaporins (AQPs), membrane water channels, consists of diverse types of proteins that are mainly permeable to water; some are also permeable to small solutes, such as glycerol and urea. They have been identified in a wide range of organisms, from microbes to vertebrates and plants, and are expressed in various tissues. Here, we focus on AQP types and their isoforms in astrocytes, a major glial cell type in the central nervous system (CNS). Astrocytes have anatomical contact with the microvasculature, pia, and neurons. Of the many roles that astrocytes have in the CNS, they are key in maintaining water homeostasis. The processes involved in this regulation have been investigated intensively, in particular regulation of the permeability and expression patterns of different AQP types in astrocytes. Three aquaporin types have been described in astrocytes: aquaporins AQP1 and AQP4 and aquaglyceroporin AQP9. The aim here is to review their isoforms, subcellular localization, permeability regulation, and expression patterns in the CNS. In the human CNS, AQP4 is expressed in normal physiological and pathological conditions, but astrocytic expression of AQP1 and AQP9 is mainly associated with a pathological state. PMID:27420057

  4. Effects of glutamine on performance and intestinal mucosa morphometry of broiler chickens vaccinated against coccidiosis

    OpenAIRE

    Brenda Carla Luquetti; Miguel Frederico Fernandez Alarcon; Raquel Lunedo; Daniel Mendes Borges Campos; Renato Luís Furlan; Marcos Macari

    2016-01-01

    ABSTRACT This study aimed to assess the effects of glutamine as feed additive on performance and intestinal mucosa morphometry of broiler chickens vaccinated against coccidiosis. A total of 400 day-old male chicks were randomly assigned to four treatments (NVNG – no vaccination, no glutamine supplementation; NVG – no vaccination, glutamine supplementation (10 g kg−1); VNG – vaccination, no glutamine supplementation; VG – vaccination, glutamine supplementation) replicated four times with 25 bi...

  5. Label-free optical activation of astrocyte in vivo

    Science.gov (United States)

    Choi, Myunghwan; Yoon, Jonghee; Ku, Taeyun; Choi, Kyungsun; Choi, Chulhee

    2011-07-01

    As the most abundant cell type in the central nervous system, astrocyte has been one of main research topics in neuroscience. Although various tools have been developed, at present, there is no tool that allows noninvasive activation of astrocyte in vivo without genetic or pharmacological perturbation. Here we report a noninvasive label-free optical method for physiological astrocyte activation in vivo using a femtosecond pulsed laser. We showed the laser stimulation robustly induced astrocytic calcium activation in vivo and further verified physiological relevance of the calcium increase by demonstrating astrocyte mediated vasodilation in the brain. This novel optical method will facilitate noninvasive physiological study on astrocyte function.

  6. Astrocyte elevated gene-1 regulates astrocyte responses to neural injury: implications for reactive astrogliosis and neurodegeneration

    Directory of Open Access Journals (Sweden)

    Vartak-Sharma Neha

    2012-08-01

    Full Text Available Abstract Background Reactive astrogliosis is a ubiquitous but poorly understood hallmark of central nervous system pathologies such as trauma and neurodegenerative diseases. In vitro and in vivo studies have identified proinflammatory cytokines and chemokines as mediators of astrogliosis during injury and disease; however, the molecular mechanism remains unclear. In this study, we identify astrocyte elevated gene-1 (AEG-1, a human immunodeficiency virus 1 or tumor necrosis factor α-inducible oncogene, as a novel modulator of reactive astrogliosis. AEG-1 has engendered tremendous interest in the field of cancer research as a therapeutic target for aggressive tumors. However, little is known of its role in astrocytes and astrocyte-mediated diseases. Based on its oncogenic role in several cancers, here we investigate the AEG-1-mediated regulation of astrocyte migration and proliferation during reactive astrogliosis. Methods An in vivo brain injury mouse model was utilized to show AEG-1 induction following reactive astrogliosis. In vitro wound healing and cell migration assays following AEG-1 knockdown were performed to analyze the role of AEG-1 in astrocyte migration. AEG-1-mediated regulation of astrocyte proliferation was assayed by quantifying the levels of cell proliferation markers, Ki67 and proliferation cell nuclear antigen, using immunocytochemistry. Confocal microscopy was used to evaluate nucleolar localization of AEG-1 in cultured astrocytes following injury. Results The in vivo mouse model for brain injury showed reactive astrocytes with increased glial fibrillary acidic protein and AEG-1 colocalization at the wound site. AEG-1 knockdown in cultured human astrocytes significantly reduced astrocyte migration into the wound site and cell proliferation. Confocal analysis showed colocalization of AEG-1 to the nucleolus of injured cultured human astrocytes. Conclusions The present findings report for the first time the novel role of AEG-1

  7. Metabolic alterations produced by 3-nitropropionic acid in rat striata and cultured astrocytes: quantitative in vitro 1H nuclear magnetic resonance spectroscopy and biochemical characterization

    International Nuclear Information System (INIS)

    Quantitative high resolution in vitro 1H nuclear magnetic resonance spectroscopy was employed to study the metabolic effects of 3-nitropropionic acid associated with aging from perchloric acid extracts of rat striata. Systemic injection of 3-nitropropionic acid in rats at a dose of 10 mg/kg/day for seven consecutive days significantly impaired energy metabolism in rats one, four and eight months of age, as evidenced by a marked elevation of succinate and lactate levels. However, a significant decrease in N-acetyl-l-aspartate level, a neuronal marker, was observed in four- and eight-month-old rats but not in one-month-old rats. This would indicate that rats at four to eight months are more susceptible to 3-nitropropionic acid than those at one month. A significant decrease in GABA level was observed in four-month-old 3-nitropropionic acid-treated rats, which is consistent with the literature that GABAergic neurons are particularly vulnerable to 3-nitropropionic acid treatment. In addition, glutamine and glutamate levels were markedly decreased at four and eight months in 3-nitropropionic acid-treated rats. Since glutamine is synthesized predominantly in glia, the observation above suggests that 3-nitropropionic acid intoxication may involve perturbation of energy metabolism, glial injury and consequent neuronal damage. Astrocytes which are essential in the metabolism of glutamate and glutamine were used to further assess 3-nitropropionic acid-induced toxicity. Glial proliferation, mitochondrial metabolism and glutamine synthetase activity were all reduced by 3-nitropropionic acid treatment with a concomitant increase, in a dose-dependent manner, of lactate levels, suggesting that 3-nitropropionic acid is also detrimental to astrocytes in vivo and thus may affect metabolic interaction between neurons and glia.These results not only imply that 3-nitropropionic acid blocks energy metabolism prior to exerting neurotoxic damage but also demonstrate that the degree of

  8. Supplementation with L-Glutamine and L-Alanyl-L-Glutamine Changes Biochemical Parameters and Jejunum Morphophysiology in Type 1 Diabetic Wistar Rats

    OpenAIRE

    da Rosa, Carlos Vinicius D.; Azevedo, Silvia C. S. F.; Bazotte, Roberto B.; Peralta, Rosane M.; Buttow, Nilza C.; Maria Montserrat D Pedrosa; Vilma A F de Godoi; Maria Raquel M Natali

    2015-01-01

    We evaluated the effects of the supplementation with L-glutamine and glutamine dipeptide (GDP) on biochemical and morphophysiological parameters in streptozotocin-diabetic rats. For this purpose, thirty animals were distributed into six groups treated orally (gavage) during thirty days: non diabetic rats (Control) + saline, diabetic + saline; Control + L-glutamine (248 mg/kg), Diabetic + L-glutamine (248 mg/kg), Control + GDP (400 mg/kg), Diabetic + GDP (400 mg/kg). Diabetes was induced by an...

  9. Isolation and Characterization of Ischemia-Derived Astrocytes (IDAs) with Ability to Transactivate Quiescent Astrocytes

    Science.gov (United States)

    Villarreal, Alejandro; Rosciszewski, Gerardo; Murta, Veronica; Cadena, Vanesa; Usach, Vanina; Dodes-Traian, Martin M.; Setton-Avruj, Patricia; Barbeito, Luis H.; Ramos, Alberto J.

    2016-01-01

    Reactive gliosis involving activation and proliferation of astrocytes and microglia, is a widespread but largely complex and graded glial response to brain injury. Astroglial population has a previously underestimated high heterogeneity with cells differing in their morphology, gene expression profile, and response to injury. Here, we identified a subset of reactive astrocytes isolated from brain focal ischemic lesions that show several atypical characteristics. Ischemia-derived astrocytes (IDAs) were isolated from early ischemic penumbra and core. IDA did not originate from myeloid precursors, but rather from pre-existing local progenitors. Isolated IDA markedly differ from primary astrocytes, as they proliferate in vitro with high cell division rate, show increased migratory ability, have reduced replicative senescence and grow in the presence of macrophages within the limits imposed by the glial scar. Remarkably, IDA produce a conditioned medium that strongly induced activation on quiescent primary astrocytes and potentiated the neuronal death triggered by oxygen-glucose deprivation. When re-implanted into normal rat brains, eGFP-IDA migrated around the injection site and induced focal reactive gliosis. Inhibition of gamma secretases or culture on quiescent primary astrocytes monolayers facilitated IDA differentiation to astrocytes. We propose that IDA represent an undifferentiated, pro-inflammatory, highly replicative and migratory astroglial subtype emerging from the ischemic microenvironment that may contribute to the expansion of reactive gliosis. Main Points: Ischemia-derived astrocytes (IDA) were isolated from brain ischemic tissue IDA show reduced replicative senescence, increased cell division and spontaneous migration IDA potentiate death of oxygen-glucose deprived cortical neurons IDA propagate reactive gliosis on quiescent astrocytes in vitro and in vivo Inhibition of gamma secretases facilitates IDA differentiation to astrocytes PMID:27313509

  10. Astroglial glutamate transporters coordinate excitatory signaling and brain energetics.

    Science.gov (United States)

    Robinson, Michael B; Jackson, Joshua G

    2016-09-01

    In the mammalian brain, a family of sodium-dependent transporters maintains low extracellular glutamate and shapes excitatory signaling. The bulk of this activity is mediated by the astroglial glutamate transporters GLT-1 and GLAST (also called EAAT2 and EAAT1). In this review, we will discuss evidence that these transporters co-localize with, form physical (co-immunoprecipitable) interactions with, and functionally couple to various 'energy-generating' systems, including the Na(+)/K(+)-ATPase, the Na(+)/Ca(2+) exchanger, glycogen metabolizing enzymes, glycolytic enzymes, and mitochondria/mitochondrial proteins. This functional coupling is bi-directional with many of these systems both being regulated by glutamate transport and providing the 'fuel' to support glutamate uptake. Given the importance of glutamate uptake to maintaining synaptic signaling and preventing excitotoxicity, it should not be surprising that some of these systems appear to 'redundantly' support the energetic costs of glutamate uptake. Although the glutamate-glutamine cycle contributes to recycling of neurotransmitter pools of glutamate, this is an over-simplification. The ramifications of co-compartmentalization of glutamate transporters with mitochondria for glutamate metabolism are discussed. Energy consumption in the brain accounts for ∼20% of the basal metabolic rate and relies almost exclusively on glucose for the production of ATP. However, the brain does not possess substantial reserves of glucose or other fuels. To ensure adequate energetic supply, increases in neuronal activity are matched by increases in cerebral blood flow via a process known as 'neurovascular coupling'. While the mechanisms for this coupling are not completely resolved, it is generally agreed that astrocytes, with processes that extend to synapses and endfeet that surround blood vessels, mediate at least some of the signal that causes vasodilation. Several studies have shown that either genetic deletion or

  11. Alteration of interaction between astrocytes and neurons in different stages of diabetes: a nuclear magnetic resonance study using [1-(13)C]glucose and [2-(13)C]acetate.

    Science.gov (United States)

    Wang, Na; Zhao, Liang-Cai; Zheng, Yong-Quan; Dong, Min-Jian; Su, Yongchao; Chen, Wei-Jian; Hu, Zi-Long; Yang, Yun-Jun; Gao, Hong-Chang

    2015-01-01

    Increasing evidence has shown that the brain is a site of diabetic end-organ damage. This study investigates cerebral metabolism and the interactions between astrocytes and neurons at different stages of diabetes to identify the potential pathogenesis of diabetic encephalopathy. [1-(13)C]glucose or [2-(13)C]acetate is infused into 1- and 15-week diabetic rats, the brain extracts of which are analyzed by using (1)H and (13)C magnetic resonance spectroscopy. The (13)C-labeling pattern and enrichment of cerebral metabolites are also investigated. The increased (13)C incorporation in the glutamine, glutamate, and γ-aminobutyric acid carbons from [2-(13)C]acetate suggests that the astrocytic mitochondrial metabolism is enhanced in 1-week diabetic rats. By contrast, the decreased labeling from [1-(13)C]glucose reflected that the neuronal mitochondrial metabolism is impaired. As diabetes developed to 15 weeks, glutamine and glutamate concentrations significantly decreased. The increased labeling of glutamine C4 but unchanged labeling of glutamate C4 from [2-(13)C]acetate suggests decreased astrocyte supply to the neurons. In addition, the enhanced pyruvate recycling pathway manifested by the increased lactate C2 enrichment in 1-week diabetic rats is weakened in 15-week diabetic rats. Our study demonstrates the overall metabolism disturbances, changes in specific metabolic pathways, and interaction between astrocytes and neurons during the onset and development of diabetes. These results contribute to the mechanistic understanding of diabetes pathogenesis and evolution. PMID:25048983

  12. Stretch induced endothelin-1 secretion by adult rat astrocytes involves calcium influx via stretch-activated ion channels (SACs)

    International Nuclear Information System (INIS)

    Highlights: → Endothelin-1 expression by adult rat astrocytes correlates with cell proliferation. → Stretch-induced ET-1 is inhibited by GsMtx-4, a specific inhibitor of Ca2+ permeant SACs. → The less specific SAC inhibitor streptomycin also inhibits ET-1 secretion. → Stretch-induced ET-1 production depends on a calcium influx. → SAC pharmacology may provide a new class of therapeutic agents for CNS pathology. -- Abstract: The expression of endothelins (ETs) and ET-receptors is often upregulated in brain pathology. ET-1, a potent vasoconstrictor, also inhibits the expression of astrocyte glutamate transporters and is mitogenic for astrocytes, glioma cells, neurons, and brain capillary endothelia. We have previously shown that mechanical stress stimulates ET-1 production by adult rat astrocytes. We now show in adult astrocytes that ET-1 production is driven by calcium influx through stretch-activated ion channels (SACs) and the ET-1 production correlates with cell proliferation. Mechanical stimulation using biaxial stretch (2+ threshold. This coupling of mechanical stress to the astrocyte endothelin system through SACs has treatment implications, since all pathology deforms the surrounding parenchyma.

  13. Astrocytes in physiological aging and Alzheimer's disease.

    Science.gov (United States)

    Rodríguez-Arellano, J J; Parpura, V; Zorec, R; Verkhratsky, A

    2016-05-26

    Astrocytes are fundamental for homoeostasis, defence and regeneration of the central nervous system. Loss of astroglial function and astroglial reactivity contributes to the aging of the brain and to neurodegenerative diseases. Changes in astroglia in aging and neurodegeneration are highly heterogeneous and region-specific. In animal models of Alzheimer's disease (AD) astrocytes undergo degeneration and atrophy at the early stages of pathological progression, which possibly may alter the homeostatic reserve of the brain and contribute to early cognitive deficits. At later stages of AD reactive astrocytes are associated with neurite plaques, the feature commonly found in animal models and in human diseased tissue. In animal models of the AD reactive astrogliosis develops in some (e.g. in the hippocampus) but not in all regions of the brain. For instance, in entorhinal and prefrontal cortices astrocytes do not mount gliotic response to emerging β-amyloid deposits. These deficits in reactivity coincide with higher vulnerability of these regions to AD-type pathology. Astroglial morphology and function can be regulated through environmental stimulation and/or medication suggesting that astrocytes can be regarded as a target for therapies aimed at the prevention and cure of neurodegenerative disorders. PMID:25595973

  14. Sodium signaling and astrocyte energy metabolism.

    Science.gov (United States)

    Chatton, Jean-Yves; Magistretti, Pierre J; Barros, L Felipe

    2016-10-01

    The Na(+) gradient across the plasma membrane is constantly exploited by astrocytes as a secondary energy source to regulate the intracellular and extracellular milieu, and discard waste products. One of the most prominent roles of astrocytes in the brain is the Na(+) -dependent clearance of glutamate released by neurons during synaptic transmission. The intracellular Na(+) load collectively generated by these processes converges at the Na,K-ATPase pump, responsible for Na(+) extrusion from the cell, which is achieved at the expense of cellular ATP. These processes represent pivotal mechanisms enabling astrocytes to increase the local availability of metabolic substrates in response to neuronal activity. This review presents basic principles linking the intracellular handling of Na(+) following activity-related transmembrane fluxes in astrocytes and the energy metabolic pathways involved. We propose a role of Na(+) as an energy currency and as a mediator of metabolic signals in the context of neuron-glia interactions. We further discuss the possible impact of the astrocytic syncytium for the distribution and coordination of the metabolic response, and the compartmentation of these processes in cellular microdomains and subcellular organelles. Finally, we illustrate future avenues of investigation into signaling mechanisms aimed at bridging the gap between Na(+) and the metabolic machinery. GLIA 2016;64:1667-1676. PMID:27027636

  15. Functional changes in astrocytes by human T-lymphotropic virus type-1 T-lymphocytes.

    Science.gov (United States)

    Akaoka, H; Szymocha, R; Beurton-Marduel, P; Bernard, A; Belin, M F; Giraudon, P

    2001-10-30

    The human T-lymphotropic virus type-1 (HTLV-1) is the causative agent of a chronic progressive myelopathy (TSP/HAM) in which lesions of the central nervous system (CNS) are associated with infiltration of HTLV-1-infected T-cells. In a model that mimics the interaction between glial and T-cells, we show that transient contact with T-lymphocytes chronically infected with HTLV-1 induce profound metabolic alterations in astrocytes. Within the first week post-contact, an overall activation of astrocyte metabolism was observed as assessed by enhanced uptake of glutamate and glucose, and lactate release. In contrast, longer examination showed a reduced astrocytic accumulation of glutamate. The time course of the change in glutamate uptake was in fact biphasic. Previous observations indicated that HTLV-1 protein Tax-1 was involved in this delayed decrease, via the induction of TNF-alpha. The expression of the glial glutamate transporters, GLAST and GLT-1 decreased in parallel. These decreases in glutamate uptake and transporters' expression were associated with an imbalance in the expression of the catabolic enzymes of glutamate, GS and GDH, presumably due to Tax-1. Given the fact that impairment of glutamate management in astrocytes is able to compromise the functional integrity of neurons and oligodendrocytes, our results altogether give new insights into the physiopathology of TSP/HAM. PMID:11520580

  16. Functions of astrocytes and their potential as therapeutic targets

    OpenAIRE

    Kimelberg, Harold K.; NEDERGAARD, Maiken

    2010-01-01

    Astrocytes are often referred to, and historically have been regarded as, support cells of the mammalian CNS. Work over the last decade suggests otherwise, that astrocytes may in fact play a more active role in higher neural processing than previously recognized. Because astrocytes can potentially serve as novel therapeutic targets, it is critical to understand how astrocytes execute their diverse supportive tasks while maintaining neuronal health. To that end, this review will focus on the s...

  17. Injury and repair of astrocyte after ionizing radiation

    International Nuclear Information System (INIS)

    Astrocyte is the most glial cell in the central nervous system. In the present experiment, radiation injury to the central nervous system (CNS) triggers a large network of cellular changes including neuron, glial cell and endothelial cell in morphology and metabolism and function. Astrocyte changes rapidly after ionizing radiation. There is a relationship between astrocyte and the pathologic process and function recover of damaged brain tissue following CNS injury. This suggests that astrocyte plays an important role in cure of clinical radiation injury

  18. Epigenetic Regulation of HIV-1 Latency in Astrocytes

    OpenAIRE

    Narasipura, Srinivas D.; Kim, Stephanie; Al-Harthi, Lena

    2014-01-01

    HIV infiltrates the brain at early times postinfection and remains latent within astrocytes and macrophages. Because astrocytes are the most abundant cell type in the brain, we evaluated epigenetic regulation of HIV latency in astrocytes. We have shown that class I histone deacetylases (HDACs) and a lysine-specific histone methyltransferase, SU(VAR)3-9, play a significant role in silencing of HIV transcription in astrocytes. Our studies add to a growing body of evidence demonstrating that ast...

  19. Astrocytes contribute to gamma oscillations and recognition memory

    OpenAIRE

    Lee, Hosuk Sean; Ghetti, Andrea; Pinto-Duarte, António; Xin WANG; Dziewczapolski, Gustavo; Galimi, Francesco; Huitron-Resendiz, Salvador; Piña-Crespo, Juan C.; Roberts, Amanda J.; Verma, Inder M.; Sejnowski, Terrence J.; Heinemann, Stephen F.

    2014-01-01

    Astrocytes are well placed to modulate neural activity. However, the functions typically attributed to astrocytes are associated with a temporal dimension significantly slower than the timescale of synaptic transmission of neurons. Consequently, it has been assumed that astrocytes do not play a major role in modulating fast neural network dynamics known to underlie cognitive behavior. By creating a transgenic mouse in which vesicular release from astrocytes can be reversibly blocked, we found...

  20. Target cell-specific modulation of neuronal activity by astrocytes

    OpenAIRE

    Kozlov, A. S.; Angulo, M. C.; Audinat, E.; Charpak, S

    2006-01-01

    Interaction between astrocytes and neurons enriches the behavior of brain circuits. By releasing glutamate and ATP, astrocytes can directly excite neurons and modulate synaptic transmission. In the rat olfactory bulb, we demonstrate that the release of GABA by astrocytes causes long-lasting and synchronous inhibition of mitral and granule cells. In addition, astrocytes release glutamate, leading to a selective activation of granule-cell NMDA receptors. Thus, by releasing excitatory and inhibi...

  1. Glutamate release from astrocytic gliosomes under physiological and pathological conditions.

    Science.gov (United States)

    Milanese, Marco; Bonifacino, Tiziana; Zappettini, Simona; Usai, Cesare; Tacchetti, Carlo; Nobile, Mario; Bonanno, Giambattista

    2009-01-01

    Glial subcellular particles (gliosomes) have been purified from rat cerebral cortex or mouse spinal cord and investigated for their ability to release glutamate. Confocal microscopy showed that gliosomes are enriched with glia-specific proteins, such as GFAP and S-100 but not neuronal proteins, such as PSD-95, MAP-2, and beta-tubulin III. Furthermore, gliosomes exhibit labeling neither for integrin-alphaM nor for myelin basic protein, specific for microglia and oligodendrocytes, respectively. The gliosomal fraction contains proteins of the exocytotic machinery coexisting with GFAP. Consistent with ultrastructural analysis, several nonclustered vesicles are present in the gliosome cytoplasm. Finally, gliosomes represent functional organelles that actively export glutamate when subjected to releasing stimuli, such as ionomycin, high KCl, veratrine, 4-aminopyridine, AMPA, or ATP by mechanisms involving extracellular Ca2+, Ca2+ release from intracellular stores as well as reversal of glutamate transporters. In addition, gliosomes can release glutamate also by a mechanism involving heterologous transporter activation (heterotransporters) located on glutamate-releasing and glutamate transporter-expressing (homotransporters) gliosomes. This glutamate release involves reversal of glutamate transporters and anion channel opening, but not exocytosis. Both the exocytotic and the heterotransporter-mediated glutamate release were more abundant in gliosomes prepared from the spinal cord of transgenic mice, model of amyotrophic lateral sclerosis, than in controls; suggesting the involvement of astrocytic glutamate release in the excitotoxicity proposed as a cause of motor neuron degeneration. The results support the view that gliosomes may represent a viable preparation that allows to study mechanisms of astrocytic transmitter release and its regulation in healthy animals and in animal models of brain diseases. PMID:19607977

  2. Effects of supplementation with free glutamine and the dipeptide alanyl-glutamine on parameters of muscle damage and inflammation in rats submitted to prolonged exercise.

    Science.gov (United States)

    Cruzat, Vinicius Fernandes; Rogero, Marcelo Macedo; Tirapegui, Julio

    2010-01-01

    In this study, we investigated the effect of the supplementation with the dipeptide L-alanyl-L-glutamine (DIP) and a solution containing L-glutamine and L-alanine on plasma levels markers of muscle damage and levels of pro-inflammatory cytokines and glutamine metabolism in rats submitted to prolonged exercise. Rats were submitted to sessions of swim training for 6 weeks. Twenty-one days prior to euthanasia, the animals were supplemented with DIP (n = 8) (1.5 g.kg(-1)), a solution of free L-glutamine (1 g.kg(-1)) and free L-alanine (0.61 g.kg(-1)) (G&A, n = 8) or water (control (CON), n = 8). Animals were killed at rest before (R), after prolonged exercise (PE-2 h of exercise). Plasma concentrations of glutamine, glutamate, tumour necrosis factor-alpha (TNF-alpha), prostaglandin E2 (PGE2) and activity of creatine kinase (CK), lactate dehydrogenase (LDH) and muscle concentrations of glutamine and glutamate were measured. The concentrations of plasma TNF-alpha, PGE2 and the activity of CK were lower in the G&A-R and DIP-R groups, compared to the CON-R. Glutamine in plasma (p glutamine and glutamate in soleus (p glutamine and the dipeptide LL-alanyl-LL-glutamine represents an effective source of glutamine, which may attenuate inflammation biomarkers after periods of training and plasma levels of CK and the inflammatory response induced by prolonged exercise. PMID:19885855

  3. Astrocytic mGluR5 and the tripartite synapse.

    Science.gov (United States)

    Panatier, A; Robitaille, R

    2016-05-26

    In the brain, astrocytes occupy a key position between vessels and synapses. Among their numerous functions, these glial cells are key partners of neurons during synaptic transmission. Astrocytes detect transmitter release through receptors and transporters at the level of their processes, which are in close proximity to the tow neuronal elements of synapses. In response to transmitter-mediated activation, glial cells in turn regulate synaptic transmission and neuronal excitability. This process has been reported to involve several glial receptors. One of the best known of such receptors is the metabotropic glutamatergic receptor subtype 5 (mGluR5). In the present review we will discuss the implication of mGluR5s as detectors of synaptic transmission. In particular, we will discuss how the functional properties and localization of these receptors permit the detection of the synaptic signal in a defined temporal window and a given spatial area around the synapse. Furthermore, we will review the impact of their activation on synaptic transmission. PMID:25847307

  4. Laser-scanning astrocyte mapping reveals increased glutamate-responsive domain size and disrupted maturation of glutamate uptake following neonatal cortical freeze-lesion

    OpenAIRE

    Chris Dulla

    2014-01-01

    Astrocytic uptake of glutamate shapes extracellular neurotransmitter dynamics, receptor activation, and synaptogenesis. During development, glutamate transport becomes more robust. How neonatal brain insult affects the functional maturation of glutamate transport remains unanswered. Neonatal brain insult can lead to developmental delays, cognitive losses, and epilepsy; the disruption of glutamate transport is known to cause changes in synaptogenesis, receptor activation, and seizure. Usin...

  5. Effect of parenteral glutamine supplementation in premature infants

    Institute of Scientific and Technical Information of China (English)

    LI Zheng-hong; WANG Dan-hua; DONG Mei

    2007-01-01

    Background Glutamine, proposed to be conditionally essential for critically ill patients, is not added routinely to parenteral amino acid formulations for premature infants and is provided in only small quantities by the enteral route when enteral feeding is Iow. Parenteral feeding is the basic way of nutrition in the first days of life of premature infants. In this study, we evaluated the effects of glutamine supplemented parenteral nutrition for premature infants on growth and development, feeding toleration, and infective episodes.Methods From December 2002 to July 2006, 53 premature infants were given either standard or glutamine supplemented parenteral nutrition for more than 2 weeks. Twenty-eight infants were in glutamine supplemented group, whose gestational age (31.4±2.0) weeks, birth weight range (1386±251) g; twenty-five infants were in control group, gestational age (31.1 ± 1.7) weeks, with birth weight range (1346± 199) g. There were no differences between the two groups. Various growth and biochemical indices were monitored throughout the duration of hospital stay. Data between groups were analyzed with Student's t test. Nonparametric data were analyzed using a Chi-square test. A two-tailed P value < 0.05 was considered statistically significant.Results The level of serum albumin was lower in the glutamine groups on the second week (3.0 vs 3.2 g/dl, P=0.028), and blood urea nitrogen was higher in glutamine groups on the fourth week (8.1 vs 4.9 mg/dl, P=0.014), but normal. Glutamine group infants took fewer days to regain birth weight (8.1 vs 10.4 days, P=0.017), required fewer days on parenteral nutrition (24.8 vs 30.8 days, P=0.035), with shorter stays in hospital (32.1 vs 38.6 days, P=0.047). Episodes of hospital acquired infection in glutamine supplemented infants were lower than that in control group (0.96 vs 1.84 times, P=0.000).Conclusion Parenteral glutamine supplementation in premature infants can shorten days on parenteral nutrition and

  6. Astrocyte heterogeneity in the brain: from development to disease

    Directory of Open Access Journals (Sweden)

    Marcos R Costa

    2015-03-01

    Full Text Available In the last decades, astrocytes have risen from passive supporters of neuronal activity to central players in brain function and cognition. Likewise, the heterogeneity of astrocytes starts to become recognized in contrast to the homogeneous population previously predicted. In this review, we focused on astrocyte heterogeneity in terms of their morphological, protein expression and functional aspects and debate in a historical perspective the diversity encountered in glial progenitors and how they may reflect mature astrocyte heterogeneity. We discussed data that show that different progenitors may have unsuspected roles in developmental processes. We have approached the functions of astrocyte subpopulations on the onset of psychiatric and neurological diseases.

  7. Local production of astrocytes in the cerebral cortex.

    Science.gov (United States)

    Ge, W-P; Jia, J-M

    2016-05-26

    Astrocytes are the largest glial population in the mammalian brain. Astrocytes in the cerebral cortex are reportedly generated from four sources, namely radial glia, progenitors in the subventricular zone (SVZ progenitors), locally proliferating glia, and NG2 glia; it remains an open question, however, as to what extent these four cell types contribute to the substantial increase in astrocytes that occurs postnatally in the cerebral cortex. Here we summarize all possible sources of astrocytes and discuss their roles in this postnatal increase. In particular, we focus on astrocytes derived from local proliferation within the cortex. PMID:26343293

  8. New Tools for Investigating Astrocyte-to-Neuron Communication

    Directory of Open Access Journals (Sweden)

    Dongdong eLi

    2013-10-01

    Full Text Available Grey matter protoplasmic astrocytes extend very thin processes and establish close contacts with synapses. It has been suggested that the release of neuroactive gliotransmitters at the tripartite synapse contributes to information processing. However, the concept of calcium (Ca2+-dependent gliotransmitter release from astrocytes, and the release mechanisms are being debated.Studying astrocytes in their natural environment is challenging because: i astrocytes are electrically silent; ii astrocytes and neurons express an overlapping repertoire of transmembrane receptors; iii astrocyte processes in contact with synapses are below confocal and two-photon microscope resolution; iv bulk-loading techniques using fluorescent Ca2+ indicators lack cellular specificity.In this review, we will discuss some limitations of conventional methodologies and highlight the interest of novel tools and approaches for studying gliotransmission. Genetically encoded Ca2+ indicators (GECIs, light-gated channels, and exogenous receptors are being developed to selectively read out and stimulate astrocyte activity. Our review discusses emerging perspectives on: i the complexity of astrocyte Ca2+ signalling revealed by GECIs; ii new pharmacogenetic and optogenetic approaches to activate specific Ca2+ signalling pathways in astrocytes; iii classical and new techniques to monitor vesicle fusion in cultured astrocytes; iv possible strategies to express specifically reporter genes in astrocytes.

  9. The computational power of astrocyte mediated synaptic plasticity

    Directory of Open Access Journals (Sweden)

    Rogier Min

    2012-11-01

    Full Text Available Research in the last two decades has made clear that astrocytes play a crucial role in the brain beyond their functions in energy metabolism and homeostasis. Many studies have shown that astrocytes can dynamically modulate neuronal excitability and synaptic plasticity, and might participate in higher brain functions like learning and memory. With the plethora of astrocyte-mediated signaling processes described in the literature today, the current challenge is to identify which of these processes happen under what physiological condition, and how this shapes information processing and, ultimately, behavior. To answer these questions will require a combination of advanced physiological, genetical and behavioral experiments. Additionally, mathematical modeling will prove crucial for testing predictions on the possible functions of astrocytes in neuronal networks, and to generate novel ideas as to how astrocytes can contribute to the complexity of the brain. Here, we aim to provide an outline of how astrocytes can interact with neurons. We do this by reviewing recent experimental literature on astrocyte-neuron interactions, discussing the dynamic effects of astrocytes on neuronal excitability and short- and long-term synaptic plasticity. Finally, we will outline the potential computational functions that astrocyte-neuron interactions can serve in the brain. We will discuss how astrocytes could govern metaplasticity in the brain, how they might organize the clustering of synaptic inputs, and how they could function as memory elements for neuronal activity. We conclude that astrocytes can enhance the computational power of neuronal networks in previously unexpected ways.

  10. Recent molecular approaches to understanding astrocyte function in vivo

    Directory of Open Access Journals (Sweden)

    Todd A Fiacco

    2013-12-01

    Full Text Available Astrocytes are a predominant glial cell type in the nervous systems, and are becoming recognized as important mediators of normal brain function as well as neurodevelopmental, neurological, and neurodegenerative brain diseases. Although numerous potential mechanisms have been proposed to explain the role of astrocytes in the normal and diseased brain, research into the physiological relevance of these mechanisms in vivo is just beginning. In this review, we will summarize recent developments in innovative and powerful molecular approaches, including knockout mouse models, transgenic mouse models, and astrocyte-targeted gene transfer/expression, which have led to advances in understanding astrocyte biology in vivo that were heretofore inaccessible to experimentation. We will examine the recently improved understanding of the roles of astrocytes - with an emphasis on astrocyte signaling - in the context of both the healthy and diseased brain, discuss areas where the role of astrocytes remains debated, and suggest new research directions.

  11. Glutaminase enzyme biosensor for determination of glutamine in cerebrospinal fluid, human serum and l-glutamine capsule

    International Nuclear Information System (INIS)

    Ammonium-selective glutamine biosensor was prepared by immobilizing glutaminase on poly(vinylchloride) (PVC) ammonium membrane electrode containing palmitic acid prepared by using nonactine. The response of glutamine biosensor was linear over the concentration range of 1.0x10-11.0x10-4M and slope was Nernstian. We determined optimum working conditions of the biosensor such as buffer concentration, buffer pH, lifetime, response time, linear working range and other response characteristics. The optimum buffer concentration and pH of proposed glutamine biosensor were determined as 20mM and pH 7.5, respectively. The interference effects of some ions and amino acids that may be present in body fluids were also investigated. The Km and Vmax values of glutaminase were determined. Additionally, glutamine assay in several biological samples such as healthy human serum, cerebrospinal fluid (CSF) and commercial glutamine capsule were also successfully carried out by using the standard addition method. The results were good agreement with previously reported values. (author)

  12. The effect of glutamine infusion on the inflammatory response and HSP70 during human experimental endotoxaemia

    DEFF Research Database (Denmark)

    Andreasen, Anne Sofie; Pedersen-Skovsgaard, Theis; Mortensen, Ole Hartvig;

    2009-01-01

    INTRODUCTION: Glutamine supplementation has beneficial effects on morbidity and mortality in critically ill patients, possibly in part through an attenuation of the proinflammatory cytokine response and a stimulation of heat shock protein (HSP)70. We infused either alanine-glutamine or saline...... an infusion of alanine-glutamine at a rate of 0.025 g/(kg body weight x hour) or saline for 10 hours. After 2 hours, an intravenous bolus of Escherichia coli endotoxin (0.3 ng/kg) was administered. Blood samples were collected hourly for the following 8 hours. HSP70 protein content in isolated blood...... mononuclear cells (BMNCs) was measured by Western blotting. RESULTS: Plasma glutamine increased during alanine-glutamine infusion. Endotoxin reduced plasma glutamine during both trials, but plasma glutamine levels remained above baseline with alanine-glutamine supplementation. Endotoxin injection...

  13. Glutamine analogs promote cytoophidium assembly in human and Drosophila cells

    Institute of Scientific and Technical Information of China (English)

    Kangni Chen; Jing Zhang; (O)mür Yilmaz Tastan; Zillah Anne Deussen; Mayte Yu-Yin Siswick; Ji-Long Liu

    2011-01-01

    CTP synthase is compartmentalized within a subcellular structure,termed the cytoophidium,in a range of organisms including bacteria,yeast,fruit fly and rat.Here we show that CTP synthase is also compartmentalized into cytoophidia in human cells.Surprisingly,the occurrence of cyloophidia in human cells increases upon treatment with a glutamine analog 6-diazo-5-oxo-L-norleucine (DON),an inhibitor of glutaminedependent enzymes including CTP synthase.Experiments in flies confirmned that DON globally promotes cytoophidium assembly.Clonal analysis via CTP synthase RNA interference in somatic cells indicates that CTP synthase expression level is critical for the formation of cytoophidia.Moreover,DON facilitates cytoophidium assembly even when CTP synthase level is low.A second glutamine analog azaserine also promotes cytoophidum formation.Our data demonstrate that glutamine analogs serve as useful tools in the study of cytoophidia.

  14. Glutathione-Dependent Detoxification Processes in Astrocytes

    DEFF Research Database (Denmark)

    Dringen, Ralf; Brandmann, Maria; Hohnholt, Michaela C;

    2015-01-01

    component in many of the astrocytic detoxification processes is the tripeptide glutathione (GSH) which serves as electron donor in the GSH peroxidase-catalyzed reduction of peroxides. In addition, GSH is substrate in the detoxification of xenobiotics and endogenous compounds by GSH-S-transferases which...

  15. Astrocytes: a central element in neurological diseases

    NARCIS (Netherlands)

    M. Pekny; M. Pekna; A. Messing; C. Steinhäuser; J.M. Lee; V. Parpura; E.M. Hol; M.V. Sofroniew; A. Verkhratsky

    2016-01-01

    The neurone-centred view of the past disregarded or downplayed the role of astroglia as a primary component in the pathogenesis of neurological diseases. As this concept is changing, so is also the perceived role of astrocytes in the healthy and diseased brain and spinal cord. We have started to unr

  16. Characterization of astrocytic and neuronal benzodiazepine receptors

    Energy Technology Data Exchange (ETDEWEB)

    Bender, A.S.

    1988-01-01

    Primary cultures of astrocytes and neurons express benzodiazepine receptors. Neuronal benzodiazepine receptors were of high-affinity, K{sub D} values were 7.5-43 nM and the densities of receptors (B{sub max}) were 924-4131 fmol/mg protein. Astrocytes posses a high-affinity benzodiazepine receptor, K{sub D} values were 6.6-13 nM. The B{sub max} values were 6,033-12,000 fmol/mg protein. The pharmacological profile of the neuronal benzodiazepine receptor was that of the central-type benzodiazepine receptor, where clonazepam has a high-affinity and Ro 5-4864 (4{prime}-chlorodiazepam) has a low-affinity. Whereas astrocytic benzoidazepine receptor was characteristic of the so called peripheral-type benzodiazepine receptors, which shows a high-affinity towards Ro 5-4863, and a low-affinity towards clonazepam. The astrocytic benzodiazepine receptors was functionally correlated with voltage dependent calcium channels, since dihydropyridines and benzodiazepines interacted with ({sup 3}H) diazepam and ({sup 3}H) nitrendipine receptors with the same rank order of potency, showing a statistically significant correlation. No such correlation was observed in neurons.

  17. Astrocytes : a central element in neurological diseases

    NARCIS (Netherlands)

    Pekny, Milos; Pekna, Marcela; Messing, Albee; Steinhäuser, Christian; Lee, Jin Moo; Parpura, Vladimir; Hol, Elly M.; Sofroniew, Michael V.; Verkhratsky, Alexei

    2016-01-01

    The neurone-centred view of the past disregarded or downplayed the role of astroglia as a primary component in the pathogenesis of neurological diseases. As this concept is changing, so is also the perceived role of astrocytes in the healthy and diseased brain and spinal cord. We have started to unr

  18. Lrp4 in astrocytes modulates glutamatergic transmission.

    Science.gov (United States)

    Sun, Xiang-Dong; Li, Lei; Liu, Fang; Huang, Zhi-Hui; Bean, Jonathan C; Jiao, Hui-Feng; Barik, Arnab; Kim, Seon-Myung; Wu, Haitao; Shen, Chengyong; Tian, Yun; Lin, Thiri W; Bates, Ryan; Sathyamurthy, Anupama; Chen, Yong-Jun; Yin, Dong-Min; Xiong, Lei; Lin, Hui-Ping; Hu, Jin-Xia; Li, Bao-Ming; Gao, Tian-Ming; Xiong, Wen-Cheng; Mei, Lin

    2016-08-01

    Neurotransmission requires precise control of neurotransmitter release from axon terminals. This process is regulated by glial cells; however, the underlying mechanisms are not fully understood. We found that glutamate release in the brain was impaired in mice lacking low-density lipoprotein receptor-related protein 4 (Lrp4), a protein that is critical for neuromuscular junction formation. Electrophysiological studies revealed compromised release probability in astrocyte-specific Lrp4 knockout mice. Lrp4 mutant astrocytes suppressed glutamatergic transmission by enhancing the release of ATP, whose level was elevated in the hippocampus of Lrp4 mutant mice. Consequently, the mutant mice were impaired in locomotor activity and spatial memory and were resistant to seizure induction. These impairments could be ameliorated by blocking the adenosine A1 receptor. The results reveal a critical role for Lrp4, in response to agrin, in modulating astrocytic ATP release and synaptic transmission. Our findings provide insight into the interaction between neurons and astrocytes for synaptic homeostasis and/or plasticity. PMID:27294513

  19. 3-bromopyruvate inhibits glycolysis, depletes cellular glutathione, and compromises the viability of cultured primary rat astrocytes.

    Science.gov (United States)

    Ehrke, Eric; Arend, Christian; Dringen, Ralf

    2015-07-01

    The pyruvate analogue 3-bromopyruvate (3-BP) is an electrophilic alkylator that is considered a promising anticancer drug because it has been shown to kill cancer cells efficiently while having little toxic effect on nontumor cells. To test for potential adverse effects of 3-BP on brain cells, we exposed cultured primary rat astrocytes to 3-BP and investigated the effects of this compound on cell viability, glucose metabolism, and glutathione (GSH) content. The presence of 3-BP severely compromised cell viability and slowed cellular glucose consumption and lactate production in a time- and concentration-dependent manner, with half-maximal effects observed at about 100 µM 3-BP after 4 hr of incubation. The cellular hexokinase activity was not affected in 3-BP-treated astrocytes, whereas within 30 min after application of 3-BP the activity of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was inhibited, and cellular GSH content was depleted in a concentration-dependent manner, with half-maximal effects observed at about 30 µM 3-BP. The depletion of cellular GSH after exposure to 100 µM 3-BP was not prevented by the presence of 10 mM of the monocarboxylates lactate or pyruvate, suggesting that 3-BP is not taken up into astrocytes predominantly by monocarboxylate transporters. The data suggest that inhibition of glycolysis by inactivation of GAPDH and GSH depletion contributes to the toxicity that was observed for 3-BP-treated cultured astrocytes. PMID:25196479

  20. The dynamics of cysteine, glutathione and their disulphides in astrocyte culture medium.

    Science.gov (United States)

    Yoshiba-Suzuki, Sachiko; Sagara, Jun-ichi; Bannai, Shiro; Makino, Nobuo

    2011-07-01

    Glutathione (GSH) plays an important neuroprotective role, and its synthesis depends on the amount of available cysteine (CSH) in the cells. Various kinds of evidence suggest that astrocytes can provide CSH or GSH to neurons, but the delivery mechanism of the thiol-compounds has not been elucidated. In this study, the dynamics of CSH, GSH and their disulphides in astrocyte culture medium were investigated by following the time-course of concentration changes and by computer simulation and curve fitting to experimental data using a mathematical model. The model consists of seven reactions and three transports, which are grouped into four categories: autoxidation of thiols into disulphides, thiol-disulphide exchange and reactions of thiols with medium components, as well as the cellular influx and efflux of thiols and disulphides. The obtained results are interpreted that cystine (CSSC) after entering astrocyte is reduced to CSH, most of which is released to medium and autoxidized to CSSC. The efflux of GSH was estimated to be considerably slower than that of CSH, and most of the excreted GSH is converted to cysteine-glutathione disulphide principally through the thiol-disulphide exchange. The results seem to indicate that astrocytes provide neurons mainly with CSH, rather than GSH, as the antioxidant material for neuroprotection. PMID:21436138

  1. MiRNAs in Astrocyte-Derived Exosomes as Possible Mediators of Neuronal Plasticity.

    Science.gov (United States)

    Lafourcade, Carlos; Ramírez, Juan Pablo; Luarte, Alejandro; Fernández, Anllely; Wyneken, Ursula

    2016-01-01

    Astrocytes use gliotransmitters to modulate neuronal function and plasticity. However, the role of small extracellular vesicles, called exosomes, in astrocyte-to-neuron signaling is mostly unknown. Exosomes originate in multivesicular bodies of parent cells and are secreted by fusion of the multivesicular body limiting membrane with the plasma membrane. Their molecular cargo, consisting of RNA species, proteins, and lipids, is in part cell type and cell state specific. Among the RNA species transported by exosomes, microRNAs (miRNAs) are able to modify gene expression in recipient cells. Several miRNAs present in astrocytes are regulated under pathological conditions, and this may have far-reaching consequences if they are loaded in exosomes. We propose that astrocyte-derived miRNA-loaded exosomes, such as miR-26a, are dysregulated in several central nervous system diseases; thus potentially controlling neuronal morphology and synaptic transmission through validated and predicted targets. Unraveling the contribution of this new signaling mechanism to the maintenance and plasticity of neuronal networks will impact our understanding on the physiology and pathophysiology of the central nervous system. PMID:27547038

  2. Disrupting astrocyte-neuron lactate transfer persistently reduces conditioned responses to cocaine.

    Science.gov (United States)

    Boury-Jamot, B; Carrard, A; Martin, J L; Halfon, O; Magistretti, P J; Boutrel, B

    2016-08-01

    A central problem in the treatment of drug addiction is the high risk of relapse often precipitated by drug-associated cues. The transfer of glycogen-derived lactate from astrocytes to neurons is required for long-term memory. Whereas blockade of drug memory reconsolidation represents a potential therapeutic strategy, the role of astrocyte-neuron lactate transport in long-term conditioning has received little attention. By infusing an inhibitor of glycogen phosphorylase into the basolateral amygdala of rats, we report that disruption of astrocyte-derived lactate not only transiently impaired the acquisition of a cocaine-induced conditioned place preference but also persistently disrupted an established conditioning. The drug memory was rescued by L-Lactate co-administration through a mechanism requiring the synaptic plasticity-related transcription factor Zif268 and extracellular signal-regulated kinase (ERK) signalling pathway but not the brain-derived neurotrophic factor (Bdnf). The long-term amnesia induced by glycogenolysis inhibition and the concomitant decreased expression of phospho-ERK were both restored with L-Lactate co-administration. These findings reveal a critical role for astrocyte-derived lactate in positive memory formation and highlight a novel amygdala-dependent reconsolidation process, whose disruption may offer a novel therapeutic target to reduce the long-lasting conditioned responses to cocaine. PMID:26503760

  3. Glucose-coated gold nanoparticles transfer across human brain endothelium and enter astrocytes in vitro.

    Directory of Open Access Journals (Sweden)

    Radka Gromnicova

    Full Text Available The blood-brain barrier prevents the entry of many therapeutic agents into the brain. Various nanocarriers have been developed to help agents to cross this barrier, but they all have limitations, with regard to tissue-selectivity and their ability to cross the endothelium. This study investigated the potential for 4 nm coated gold nanoparticles to act as selective carriers across human brain endothelium and subsequently to enter astrocytes. The transfer rate of glucose-coated gold nanoparticles across primary human brain endothelium was at least three times faster than across non-brain endothelia. Movement of these nanoparticles occurred across the apical and basal plasma membranes via the cytosol with relatively little vesicular or paracellular migration; antibiotics that interfere with vesicular transport did not block migration. The transfer rate was also dependent on the surface coating of the nanoparticle and incubation temperature. Using a novel 3-dimensional co-culture system, which includes primary human astrocytes and a brain endothelial cell line hCMEC/D3, we demonstrated that the glucose-coated nanoparticles traverse the endothelium, move through the extracellular matrix and localize in astrocytes. The movement of the nanoparticles through the matrix was >10 µm/hour and they appeared in the nuclei of the astrocytes in considerable numbers. These nanoparticles have the correct properties for efficient and selective carriers of therapeutic agents across the blood-brain barrier.

  4. Expression, purification and preliminary crystallographic analysis of recombinant human small glutamine-rich tetratricopeptide-repeat protein

    International Nuclear Information System (INIS)

    The production and crystallization of the tetratricopeptide-repeat domain of human small glutamine-rich tetratricopeptide-repeat protein are reported. A 2.4 Å native diffraction data set has been obtained. Human small glutamine-rich tetratricopeptide-repeat protein (hSGT) is a 35 kDa protein implicated in a number of biological processes that include apoptosis, cell division and intracellular cell transport. The tetratricopeptide-repeat (TPR) domain of hSGT has been cloned and expressed in Escherichia coli and purified. Here, the crystallization and preliminary diffraction analysis of the TPR domain of hSGT is reported. X-ray diffraction data were processed to a resolution of 2.4 Å. Crystals belong to space group P21212, with unit-cell parameters a = 67.82, b = 81.93, c = 55.92 Å, α = β = γ = 90°

  5. Astrocyte Reactivity: A Biomarker for Retinal Ganglion Cell Health in Retinal Neurodegeneration

    OpenAIRE

    Formichella, Cathryn R; Abella, Simone K; Sims, Stephanie M; Cathcart, Heather M; Sappington, Rebecca M.

    2014-01-01

    Retinal ganglion cell (RGC) loss in glaucoma is sectorial in nature and preceded by deficits in axonal transport. Neuroinflammation plays an important role in the pathophysiology of glaucoma in the retina, optic nerve and visual centers of the brain, where it similarly appears to be regulated spatially. In a murine model, we examined the spatial characteristics of astrocyte reactivity (migration/proliferation, hypertrophy and GFAP expression) in healthy retina, retina with two glaucoma-relate...

  6. Systematic colocalization errors between acridine orange and EGFP in astrocyte vesicular organelles

    OpenAIRE

    Nadrigny, F.; Li, D.; Kemnitz, K; Ropert, N.; Koulakoff, A; Rudolph, S.; Vitali, M.; Giaume, C.; Kirchhoff, F.; Oheim, M

    2007-01-01

    Dual-color imaging of acridine orange (AO) and EGFP fused to a vesicular glutamate transporter or the vesicle-associated membrane proteins 2 or 3 has been used to visualize a supposedly well-defined subpopulation of glutamatergic astrocytic secretory vesicles undergoing regulated exocytosis. However, AO metachromasy results in the concomitant emission of green and red fluorescence from AO-stained tissue. Therefore, the question arises whether AO and EGFP fluorescence can be distinguished reli...

  7. Functional importance of the astrocytic glycogen-shunt and glycolysis for maintenance of an intact intra/extracellular glutamate gradient

    DEFF Research Database (Denmark)

    Schousboe, Arne; Sickmann, Helle M; Walls, Anne B;

    2010-01-01

    importance of this as well as the significance of ATP formed in glycolysis versus that formed by the concerted action of the tricarboxylic acid (TCA) cycle processes and oxidative phosphorylation for maintenance of glutamate transport capacity in astrocytes is discussed. It is argued that glycolytically...

  8. Study on the effects of thrombin on AQP4 mRNA and AQP4 protein expression in rat primary astrocytes

    Institute of Scientific and Technical Information of China (English)

    Jinghua Zhou; Xuebing Cao; Shenggang Sun

    2006-01-01

    Objective: To study the biologic effects of various concentrations of thrombin on aquaporin 4 (AQP4) expression in rat primary cultured astrocytes, and to explore the regulation mechanism of transmembrane water transportation in astrocytes after intracerebral hemorrhage (ICH). Methods: Primary cultured astrocytes were incubated in culture mediums containing various concentrations of thrombin for 24 h and harvested. AQP4 mRNA and AQP4 protein expression were determined by reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemical technique. Cell apoptosis was detected by TdT-mediated dUTP nick end labeling (TUNEL) technique. Cell morphology was observed by phase contrast microscope, and cell viability was assayed by MTT. Results: AQP4 mRNA and AQP4 protein showed a low expression in normal astrocytes. The expression of AQP4 mRNA and AQP4 protein significantly increased in the astrocytes treated with 100 U/ml or 200 U/ml thrombin (P < 0.01),and these astrocytes swelled. The number of TUNEL positive cells significantly increased. On the other hand, AQP4 mRNA and AQP4 protein expression were down-regulated in the astrocytes treated with 0.5 U/ml or l U/ml thrombin (P < 0.05),and the cell morphology did not change. Few TUNEL positive cells were observed. Conclusion: AQP4 over-expression induced by high concentrations of thrombin causes an increased permeability of water in astrocytic membrane. On the contrary, the decreased AQP4 expression prevents the astrocytes from swelling and apoptosis.

  9. Manganese inhibits the ability of astrocytes to promote neuronal differentiation

    International Nuclear Information System (INIS)

    Manganese (Mn) is a known neurotoxicant and developmental neurotoxicant. As Mn has been shown to accumulate in astrocytes, we sought to investigate whether Mn would alter astrocyte-neuronal interactions, specifically the ability of astrocytes to promote differentiation of neurons. We found that exposure of rat cortical astrocytes to Mn (50-500 μM) impaired their ability to promote axonal and neurite outgrowth in hippocampal neurons. This effect of Mn appeared to be mediated by oxidative stress, as it was reversed by antioxidants (melatonin and PBN) and by increasing glutathione levels, while it was potentiated by glutathione depletion in astrocytes. As the extracellular matrix protein fibronectin plays an important role in astrocyte-mediated neuronal neurite outgrowth, we also investigated the effect of Mn on fibronectin. Mn caused a concentration-dependent decrease of fibronectin protein and mRNA in astrocytes lysate and of fibronectin protein in astrocyte medium; these effects were also antagonized by antioxidants. Exposure of astrocytes to two oxidants, H2O2 and DMNQ, similarly impaired their neuritogenic action, and led to a decreased expression of fibronectin. Mn had no inhibitory effect on neurite outgrowth when applied directly onto hippocampal neurons, where it actually caused a small increase in neuritogenesis. These results indicate that Mn, by targeting astrocytes, affects their ability to promote neuronal differentiation by a mechanism which is likely to involve oxidative stress.

  10. Role of astrocytic leptin receptor subtypes on leptin permeation across hCMEC/D3 human brain endothelial cells

    OpenAIRE

    Hsuchou, Hung; Kastin, Abba J; Tu, Hong; Abbott, N Joan; Couraud, Pierre-Olivier; Pan, Weihong

    2010-01-01

    Astrocytic leptin receptors (ObR) can be upregulated in conditions such as adult-onset obesity. To determine whether the levels and subtypes of astrocytic ObR modulate leptin transport, we co-cultured hCMEC/D3 human brain endothelial cells and C6 astrocytoma cells in the Transwell system, and tested leptin permeation from apical to basolateral chambers. In comparison with hCMEC alone, co-culture of C6 cells reduced the permeability of paracellular markers and leptin. Unexpectedly, ObRb overex...

  11. Pyk2 is essential for astrocytes mobility following brain lesion.

    Science.gov (United States)

    Giralt, Albert; Coura, Renata; Girault, Jean-Antoine

    2016-04-01

    Proline-rich tyrosine kinase 2 (Pyk2) is a calcium-dependent, non-receptor protein-tyrosine kinase of the focal adhesion kinase (FAK) family. Pyk2 is enriched in the brain, especially the forebrain. Pyk2 is highly expressed in neurons but is also present in astrocytes, where its role is not known. We used Pyk2 knockout mice (Pyk2(-/-) ) developed in our laboratory to investigate the function of Pyk2 in astrocytes. Morphology and basic properties of astrocytes in vivo and in culture were not altered in the absence of Pyk2. However, following stab lesions in the motor cortex, astrocytes-mediated wound filling was slower in Pyk2(-/-) than in wild-type littermates. In an in vitro wound healing model, Pyk2(-/-) astrocytes migrated slower than Pyk2(+/+) astrocytes. The role of Pyk2 in actin dynamics was investigated by treating astrocytic cultures with the actin-depolymerizing drug latrunculin B. Actin filaments re-polymerization after latrunculin B treatment was delayed in Pyk2(-/-) astrocytes as compared with wild-type astrocytes. We mimicked wound-induced activation by treating astrocytes in culture with tumor-necrosis factor alpha (TNFα), which increased Pyk2 phosphorylation at Tyr402. TNFα increased PKC activity, and Rac1 phosphorylation at Ser71 similarly in wild-type and Pyk2-deficient astrocytes. Conversely, we found that gelsolin, an actin-capping protein known to interact with Pyk2 in other cell types, was less enriched at the leading edge of migrating Pyk2(-/-) astrocytes, suggesting that its lack of recruitment mediated in part the effects of the mutation. This work shows the critical role of Pyk2 in astrocytes migration during wound healing. GLIA 2016;64:620-634. PMID:26663135

  12. Effect of dexamethasone on fetal hepatic glutamine-glutamate exchange

    NARCIS (Netherlands)

    M. Timmerman (Michelle); C. Teng; R.B. Wilkening; P.V. Fennessey (Paul); F.C. Battaglia (Frederick); G. Meschia

    2000-01-01

    textabstractIntravenous infusion of dexamethasone (Dex) in the fetal lamb causes a two- to threefold increase in plasma glutamine and other glucogenic amino acids and a decrease of plasma glutamate to approximately one-third of normal. To explore the underlying mechanis

  13. Glutamine: precursor or nitrogen donor for citrulline synthesis?

    Science.gov (United States)

    Glutamine (Gln) is considered the main precursor for citrulline (Cit) synthesis, but no attempts have been made to differentiate the contribution of Gln carbon (Gln-C) skeleton vs. the nonspecific contribution through NH3 and CO2. To study the contribution of dietary Gln-N to the synthesis of Cit, t...

  14. Intravenous glutamine enhances COX-2 activity giving cardioprotection.

    LENUS (Irish Health Repository)

    McGuinness, Jonathan

    2009-03-01

    Preconditioning, a highly evolutionary conserved endogenous protective response, provides the most powerful form of anti-infarct protection known. We investigated whether acute intravenous glutamine, through an effect on cyclooxygenase (COX)-2 and heat shock protein (HSP) 72, might induce preconditioning.

  15. Spatial and temporal correlation in progressive degeneration of neurons and astrocytes in contusion-induced spinal cord injury

    Directory of Open Access Journals (Sweden)

    Min Kyoung-Jin

    2012-05-01

    Full Text Available Abstract Background Traumatic spinal cord injury (SCI causes acute neuronal death followed by delayed secondary neuronal damage. However, little is known about how microenvironment regulating cells such as microglia, astrocytes, and blood inflammatory cells behave in early SCI states and how they contribute to delayed neuronal death. Methods We analyzed the behavior of neurons and microenvironment regulating cells using a contusion-induced SCI model, examining early (3–6 h to late times (14 d after the injury. Results At the penumbra region close to the damaged core (P1 neurons and astrocytes underwent death in a similar spatial and temporal pattern: both neurons and astrocytes died in the medial and ventral regions of the gray matter between 12 to 24 h after SCI. Furthermore, mRNA and protein levels of transporters of glutamate (GLT-1 and potassium (Kir4.1, functional markers of astrocytes, decreased at about the times that delayed neuronal death occurred. However, at P1 region, ramified Iba-1+ resident microglia died earlier (3 to 6 h than neurons (12 to 24 h, and at the penumbra region farther from the damaged core (P2, neurons were healthy where microglia were morphologically activated. In addition, round Iba-1/CD45-double positive monocyte-like cells appeared after neurons had died, and expressed phagocytic markers, including mannose receptors, but rarely expressed proinflammatory mediators. Conclusion Loss of astrocyte function may be more critical for delayed neuronal death than microglial activation and monocyte infiltration.

  16. Protective effect of glutamine pretreatment on ischemia-reperfusion injury of spinal cord in rabbits

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Objective To investigate the effect of glutamine(Gln)on the content of reduced glutathione hormone(GSH)and aminoglutaminic acid(Glu)of spinal cord following ischemia-reperfusion injury.Methods Totally 40 healthy adult male rabbits were randomly divided into five groups:sham-operation group(S group),ischemia-reperfusion injury group(I/R group),low-dose glutamine group(L Gln group),median-dose glutamine group(M Gln group)and high-dose glutamine group(H Gln group).After glutamine preconditioning,the model of s...

  17. Astrocyte mega-domain hypothesis of the autistic savantism.

    Science.gov (United States)

    Mitterauer, Bernhard J

    2013-01-01

    Individuals with autism who show high abilities are called savants. Whereas in their brains a disconnection in and between neural networks has been identified, savantism is yet poorly understood. Focusing on astrocyte domain organization, it is hypothesized that local astrocyte mega-organizations may be responsible for exerting high capabilities in brains of autistic savants. Astrocytes, the dominant glial cell type, modulate synaptic information transmission. Each astrocyte is organized in non-overlapping domains. Formally, each astrocyte contacting n-neurons with m-synapses via its processes generates dynamic domains of synaptic interactions based on qualitative computation criteria, and hereby it structures neuronal information processing. If the number of processes is genetically significantly increased, these astrocytes operate in a mega-domain with a higher complexitiy of computation. From this model savant abilities are deduced. PMID:23098371

  18. Dosing and efficacy of glutamine supplementation in human exercise and sport training.

    Science.gov (United States)

    Gleeson, Michael

    2008-10-01

    Some athletes can have high intakes of l-glutamine because of their high energy and protein intakes and also because they consume protein supplements, protein hydrolysates, and free amino acids. Prolonged exercise and periods of heavy training are associated with a decrease in the plasma glutamine concentration and this has been suggested to be a potential cause of the exercise-induced immune impairment and increased susceptibility to infection in athletes. However, several recent glutamine feeding intervention studies indicate that although the plasma glutamine concentration can be kept constant during and after prolonged strenuous exercise, the glutamine supplementation does not prevent the postexercise changes in several aspects of immune function. Although glutamine is essential for lymphocyte proliferation, the plasma glutamine concentration does not fall sufficiently low after exercise to compromise the rate of proliferation. Acute intakes of glutamine of approximately 20-30 g seem to be without ill effect in healthy adult humans and no harm was reported in 1 study in which athletes consumed 28 g glutamine every day for 14 d. Doses of up to 0.65 g/kg body mass of glutamine (in solution or as a suspension) have been reported to be tolerated by patients and did not result in abnormal plasma ammonia levels. However, the suggested reasons for taking glutamine supplements (support for immune system, increased glycogen synthesis, anticatabolic effect) have received little support from well-controlled scientific studies in healthy, well-nourished humans. PMID:18806122

  19. Astrocytic role in synapse formation after injury.

    Science.gov (United States)

    Li, Ying; Li, Daqing; Raisman, Geoffrey

    2016-08-15

    In 1969 a paper entitled Neuronal plasticity in the septal nuclei of the adult rat proposed that new synapses are formed in the adult brain after injury (Raisman, 1969). The quantitative electron microscopic study of the timed responses to selective partial denervation of the neuropil of the adult rat septal nuclei after distant transection of the hippocampal efferent axons in the fimbria showed that the new synapses arise by sprouting of surviving adjacent synapses which selectively take over the previously denervated sites and thus restore the number of synapses to normal. This article presents the evidence for the role of perisynaptic astrocytic processes in the removal and formation of synapses and considers its significance as one of the three major divisions of the astrocytic surface in terms of the axonal responses to injury and regeneration. This article is part of a Special Issue entitled SI:50th Anniversary Issue. PMID:26746338

  20. Fluxes of lactate into, from, and among gap junction-coupled astrocytes and their interaction with noradrenaline

    Directory of Open Access Journals (Sweden)

    Leif eHertz

    2014-09-01

    Full Text Available Lactate is a versatile metabolite with important roles in modulation of brain glucose utilization rate (CMRglc, diagnosis of brain-injured patients, redox- and receptor-mediated signaling, memory, and alteration of gene transcription. Neurons and astrocytes release and accumulate lactate using equilibrative monocarboxylate transporters that carry out net transmembrane transport of lactate only until intra- and extracellular levels reach equilibrium. Astrocytes have much faster lactate uptake than neurons and shuttle more lactate among gap junction-coupled astrocytes than to nearby neurons. Lactate diffusion within syncytia can provide precursors for oxidative metabolism and glutamate synthesis and facilitate its release from endfeet to perivascular space to stimulate blood flow. Lactate efflux from brain during activation underlies the large underestimation of CMRglc with labeled glucose and fall in CMRO2/CMRglc ratio. Receptor-mediated effects of lactate on locus coeruleus neurons include noradrenaline release in cerebral cortex and c-AMP-mediated stimulation of astrocytic gap junctional coupling, thereby enhancing its dispersal and release from brain. Lactate transport is essential for its multifunctional roles.

  1. The importance of cytosolic glutamine synthetase in nitrogen assimilation and recycling

    Energy Technology Data Exchange (ETDEWEB)

    Bernard, S.M.; Habash, D.Z.

    2009-07-02

    Glutamine synthetase assimilates ammonium into amino acids, thus it is a key enzyme for nitrogen metabolism. The cytosolic isoenzymes of glutamine synthetase assimilate ammonium derived from primary nitrogen uptake and from various internal nitrogen recycling pathways. In this way, cytosolic glutamine synthetase is crucial for the remobilization of protein-derived nitrogen. Cytosolic glutamine synthetase is encoded by a small family of genes that are well conserved across plant species. Members of the cytosolic glutamine synthetase gene family are regulated in response to plant nitrogen status, as well as to environmental cues, such as nitrogen availability and biotic/abiotic stresses. The complex regulation of cytosolic glutamine synthetase at the transcriptional to post-translational levels is key to the establishment of a specific physiological role for each isoenzyme. The diverse physiological roles of cytosolic glutamine synthetase isoenzymes are important in relation to current agricultural and ecological issues.

  2. An Astrocyte-Specific Proteomic Approach toInflammatory Responses in Experimental Rat Glaucoma

    OpenAIRE

    Tezel, Gülgün; Yang, Xiangjun; Luo, Cheng; Cai, Jian; Powell, David W.

    2012-01-01

    This study introduces an astrocyte-specific approach, validates its sensitivity to quantitatively identify astrocyte responses in experimental rat glaucoma, and highlights various immune mediators/regulators characteristic of the inflammatory responses of ocular hypertensive astrocytes.

  3. Synchronization analysis of cultured epileptic human astrocytes

    Science.gov (United States)

    Balazsi, Gabor; Cornell-Bell, Ann; Neiman, Alexander; Moss, Frank

    2001-03-01

    Astrocyte cultures from severely epileptic patients were cultured, and the fluctuations of the intracellular calcium ion concentration were visualized using the fluorescent dye Fluo-3. The resulting image sequences were analyzed by methods of stochastic synchronization. Increased synchronization was observed in the epileptic tissues, when compared to normal tissues from rats. The more pathological the tissue, the more synchronized the calcium oscillations. The results might lead to a better understanding of intracellular calcium dynamics and could help drug development.

  4. Taurine Biosynthesis by Neurons and Astrocytes*

    OpenAIRE

    Vitvitsky, Victor; Garg, Sanjay K.; Banerjee, Ruma

    2011-01-01

    The physiological roles of taurine, a product of cysteine degradation and one of the most abundant amino acids in the body, remain elusive. Taurine deficiency leads to heart dysfunction, brain development abnormalities, retinal degradation, and other pathologies. The taurine synthetic pathway is proposed to be incomplete in astrocytes and neurons, and metabolic cooperation between these cell types is reportedly needed to complete the pathway. In this study, we analyzed taurine synthesis capab...

  5. Astrocytes and diffusive spread of substances in brain extracellular space

    OpenAIRE

    Sherpa, Ang D.; Hrabetova, Sabina

    2016-01-01

    Brain function is based on communication between individual cells, neurons and glia. From a traditional point of view, neurons play a central role in the fast transfer of information in the central nervous system while astrocytes, major type of glia, serve as housekeeping elements maintaining homeostasis of the extracellular microenvironment. This view has dramatically changed in recent years as many findings ascribe new roles to astrocytes. It is becoming evident that astrocytes communica...

  6. Immune and inflammatory responses in the CNS : Modulation by astrocytes

    DEFF Research Database (Denmark)

    Penkowa, Milena; aschner, michael; hidalgo, juan

    2008-01-01

    Beyond their long-recognized support functions, astrocytes are active partners of neurons in processing information, synaptic integration, and production of trophic factors, just to name a few. Both microglia and astrocytes produce and secrete a number of cytokines, modulating and integrating the...... experimental evidence on the role of astroglia in the etiology of neurological diseases will be highlighted, along with (5) the role of oxidative stressors generated within astrocytes in this process....

  7. Metabolic dysfunction in the brain: implications of astrocyte activation

    OpenAIRE

    Sonia Luz Albarracin

    2015-01-01

    Astrocytes are the most abundant cells in the central nervous system (CNS). They participate in different processes such as maintaining the blood–brain barrier and ion homeostasis, uptake and turnover of neurotransmitters, and formation of synapses. In addition, astrocytes also respond to brain insults to prevent the damage. For instance, astrocyte activation plays a central role in the cellular response to brain insults like trauma, infections, stroke, tumorigenesis, and neurodegeneration....

  8. Astrocyte Form and Function in the Developing CNS

    OpenAIRE

    Chaboub, Lesley S.; Deneen, Benjamin

    2013-01-01

    Astrocytes have long been forgotten entities in our quest to understand brain function. Over the last few decades there has been an exponential increase in our knowledge of CNS function and consequently astrocytes have emerged as key figures in CNS physiology and disease. Indeed, several pediatric neurological disorders have recently been linked to astrocyte dysregulation including, leukodystrophies, autism spectrum disorders, and epilepsy. Given that pediatric disorders are rooted in develop...

  9. Astrocyte heterogeneity in the brain: from development to disease

    OpenAIRE

    Costa, Marcos R.; Cecilia Hedin-Pereira

    2015-01-01

    In the last decades, astrocytes have risen from passive supporters of neuronal activity to central players in brain function and cognition. Likewise, the heterogeneity of astrocytes starts to become recognized in contrast to the homogeneous population previously predicted. In this review, we focused on astrocyte heterogeneity in terms of their morphological, protein expression and functional aspects, and debate in a historical perspective the diversity encountered in glial progenitors and how...

  10. Astrocytes Are an Early Target in Osmotic Demyelination Syndrome

    OpenAIRE

    Gankam Kengne, Fabrice; Nicaise, Charles; Soupart, Alain; Boom, Alain; Schiettecatte, Johan; Pochet, Roland; Brion, Jean Pierre; Decaux, Guy

    2011-01-01

    Abrupt osmotic changes during rapid correction of chronic hyponatremia result in demyelinative brain lesions, but the sequence of events linking rapid osmotic changes to myelin loss is not yet understood. Here, in a rat model of osmotic demyelination syndrome, we found that massive astrocyte death occurred after rapid correction of hyponatremia, delineating the regions of future myelin loss. Astrocyte death caused a disruption of the astrocyte-oligodendrocyte network, rapidly upregulated infl...

  11. Fatal encephalopathy with astrocyte inclusions in GFAP transgenic mice.

    OpenAIRE

    Messing, A; Head, M.W.; Galles, K.; Galbreath, E. J.; Goldman, J. E.; Brenner, M.

    1998-01-01

    Increased expression of glial fibrillary acidic protein (GFAP) is a hallmark of gliosis, the astrocytic hypertrophy that occurs during a wide variety of diseases of the central nervous system. To determine whether this increase in GFAP expression per se alters astrocyte function, we generated transgenic mice that carry copies of the human GFAP gene driven by its own promoter. Astrocytes of these mice are hypertrophic, up-regulate small heat-shock proteins, and contain inclusion bodies identic...

  12. Astrocytes mediate the neuroprotective effects of Tibolone following brain injury

    OpenAIRE

    Luis Miguel Garcia-Segura; Barreto, George E.

    2015-01-01

    Recently, astrocytes have become a key central player in mediating important functions in the brain. These physiological processes include neurotransmitter recycling, energy management, metabolic shuttle, immune sensing, K+ buffer, antioxidant supply and release of neurotrophic factors and gliotransmitters. These astrocytic roles are somehow altered upon brain injury, therefore strategies aimed at better protecting astrocytes are an essential asset to maintain brain homeostasis. In this cont...

  13. Transcriptomic analyses of primary astrocytes under TNFα treatment

    OpenAIRE

    Birck, Cindy; Koncina, Eric; Heurtaux, Tony; Glaab, Enrico; Michelucci, Alessandro; Heuschling, Paul; Grandbarbe, Luc

    2016-01-01

    Astrocytes, the most abundant glial cell population in the central nervous system, have important functional roles in the brain as blood brain barrier maintenance, synaptic transmission or intercellular communications [1], [2]. Numerous studies suggested that astrocytes exhibit a functional and morphological high degree of plasticity. For example, following any brain injury, astrocytes become reactive and hypertrophic. This phenomenon, also called reactive gliosis, is characterized by a set o...

  14. Astrocytes conspire with neurons during progression of neurological disease

    OpenAIRE

    McGann, James C.; Lioy, Daniel T.; Mandel, Gail

    2012-01-01

    As astrocytes are becoming recognized as important mediators of normal brain function, studies into their roles in neurological disease have gained significance. Across mouse models for neurodevelopmental and neurodegenerative diseases, astrocytes are considered key regulators of disease progression. In Rett syndrome and Parkinson’s disease, astrocytes can even initiate certain disease phenotypes. Numerous potential mechanisms have been offered to explain these results, but research into the ...

  15. The Neurogenic Potential of Astrocytes Is Regulated by Inflammatory Signals.

    Science.gov (United States)

    Michelucci, Alessandro; Bithell, Angela; Burney, Matthew J; Johnston, Caroline E; Wong, Kee-Yew; Teng, Siaw-Wei; Desai, Jyaysi; Gumbleton, Nigel; Anderson, Gregory; Stanton, Lawrence W; Williams, Brenda P; Buckley, Noel J

    2016-08-01

    Although the adult brain contains neural stem cells (NSCs) that generate new neurons throughout life, these astrocyte-like populations are restricted to two discrete niches. Despite their terminally differentiated phenotype, adult parenchymal astrocytes can re-acquire NSC-like characteristics following injury, and as such, these 'reactive' astrocytes offer an alternative source of cells for central nervous system (CNS) repair following injury or disease. At present, the mechanisms that regulate the potential of different types of astrocytes are poorly understood. We used in vitro and ex vivo astrocytes to identify candidate pathways important for regulation of astrocyte potential. Using in vitro neural progenitor cell (NPC)-derived astrocytes, we found that exposure of more lineage-restricted astrocytes to either tumor necrosis factor alpha (TNF-α) (via nuclear factor-κB (NFκB)) or the bone morphogenetic protein (BMP) inhibitor, noggin, led to re-acquisition of NPC properties accompanied by transcriptomic and epigenetic changes consistent with a more neurogenic, NPC-like state. Comparative analyses of microarray data from in vitro-derived and ex vivo postnatal parenchymal astrocytes identified several common pathways and upstream regulators associated with inflammation (including transforming growth factor (TGF)-β1 and peroxisome proliferator-activated receptor gamma (PPARγ)) and cell cycle control (including TP53) as candidate regulators of astrocyte phenotype and potential. We propose that inflammatory signalling may control the normal, progressive restriction in potential of differentiating astrocytes as well as under reactive conditions and represent future targets for therapies to harness the latent neurogenic capacity of parenchymal astrocytes. PMID:26138449

  16. Imaging neurotransmitter uptake and depletion in astrocytes

    Energy Technology Data Exchange (ETDEWEB)

    Tan, W. [Ames Laboratory-USDOE and Department of Chemistry, Iowa State University, Ames, Iowa 50011 (United States)]|[Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200 (United States); Haydon, P.G. [Department of Zoology and Genetics, Laboratory of Cellular Signaling, Iowa State University, Ames, Iowa 50011 (United States); Yeung, E.S. [Ames Laboratory-USDOE and Department of Chemistry, Iowa State University, Ames, Iowa 50011 (United States)

    1997-08-01

    An ultraviolet (UV) laser-based optical microscope and charge-coupled device (CCD) detection system was used to obtain chemical images of biological cells. Subcellular structures can be easily seen in both optical and fluorescence images. Laser-induced native fluorescence detection provides high sensitivity and low limits of detection, and it does not require coupling to fluorescent dyes. We were able to quantitatively monitor serotonin that has been taken up into and released from individual astrocytes on the basis of its native fluorescence. Different regions of the cells took up different amounts of serotonin with a variety of uptake kinetics. Similarly, we observed different serotonin depletion dynamics in different astrocyte regions. There were also some astrocyte areas where no serotonin uptake or depletion was observed. Potential applications include the mapping of other biogenic species in cells as well as the ability to image their release from specific regions of cells in response to external stimuli. {copyright} {ital 1997} {ital Society for Applied Spectroscopy}

  17. Decoding astrocyte heterogeneity: New tools for clonal analysis.

    Science.gov (United States)

    Bribián, A; Figueres-Oñate, M; Martín-López, E; López-Mascaraque, L

    2016-05-26

    The importance of astrocyte heterogeneity came out as a hot topic in neurosciences especially over the last decades, when the development of new methodologies allowed demonstrating the existence of big differences in morphological, neurochemical and physiological features between astrocytes. However, although the knowledge about the biology of astrocytes is increasing rapidly, an important characteristic that remained unexplored, until the last years, has been the relationship between astrocyte lineages and cell heterogeneity. To fill this gap, a new method called StarTrack was recently developed, a powerful genetic tool that allows tracking astrocyte lineages forming cell clones. Using StarTrack, a single astrocyte progenitor and its progeny can be specifically labeled from its generation, during embryonic development, to its final fate in the adult brain. Because of this specific labeling, astrocyte clones, exhibiting heterogeneous morphologies and features, can be easily analyzed in relation to their ontogenetic origin. This review summarizes how astrocyte heterogeneity can be decoded studying the embryonic development of astrocyte lineages and their clonal relationship. Finally, we discuss about some of the challenges and opportunities emerging in this exciting area of investigation. PMID:25917835

  18. Astrocyte Mitogen Inhibitor Related to Epidermal Growth Factor Receptor

    Science.gov (United States)

    Nieto-Sampedro, Manuel

    1988-06-01

    Epidermal growth factor (EGF) is a well-characterized polypeptide hormone with diverse biological activities, including stimulation of astrocyte division. A soluble astrocyte mitogen inhibitor, immunologically related to the EGF receptor, is present in rat brain. Injury to the brain causes a time-dependent reduction in the levels of this inhibitor and the concomitant appearance of EGF receptor on the astrocyte surface. Intracerebral injection of antibody capable of binding the inhibitor caused the appearance of numerous reactive astrocytes. EGF receptor-related inhibitors may play a key role in the control of glial cell division in both normal and injured brain.

  19. A Digital Realization of Astrocyte and Neural Glial Interactions.

    Science.gov (United States)

    Hayati, Mohsen; Nouri, Moslem; Haghiri, Saeed; Abbott, Derek

    2016-04-01

    The implementation of biological neural networks is a key objective of the neuromorphic research field. Astrocytes are the largest cell population in the brain. With the discovery of calcium wave propagation through astrocyte networks, now it is more evident that neuronal networks alone may not explain functionality of the strongest natural computer, the brain. Models of cortical function must now account for astrocyte activities as well as their relationships with neurons in encoding and manipulation of sensory information. From an engineering viewpoint, astrocytes provide feedback to both presynaptic and postsynaptic neurons to regulate their signaling behaviors. This paper presents a modified neural glial interaction model that allows a convenient digital implementation. This model can reproduce relevant biological astrocyte behaviors, which provide appropriate feedback control in regulating neuronal activities in the central nervous system (CNS). Accordingly, we investigate the feasibility of a digital implementation for a single astrocyte constructed by connecting a two coupled FitzHugh Nagumo (FHN) neuron model to an implementation of the proposed astrocyte model using neuron-astrocyte interactions. Hardware synthesis, physical implementation on FPGA, and theoretical analysis confirm that the proposed neuron astrocyte model, with significantly low hardware cost, can mimic biological behavior such as the regulation of postsynaptic neuron activity and the synaptic transmission mechanisms. PMID:26390499

  20. Astrocyte scar formation aids central nervous system axon regeneration.

    Science.gov (United States)

    Anderson, Mark A; Burda, Joshua E; Ren, Yilong; Ao, Yan; O'Shea, Timothy M; Kawaguchi, Riki; Coppola, Giovanni; Khakh, Baljit S; Deming, Timothy J; Sofroniew, Michael V

    2016-04-14

    Transected axons fail to regrow in the mature central nervous system. Astrocytic scars are widely regarded as causal in this failure. Here, using three genetically targeted loss-of-function manipulations in adult mice, we show that preventing astrocyte scar formation, attenuating scar-forming astrocytes, or ablating chronic astrocytic scars all failed to result in spontaneous regrowth of transected corticospinal, sensory or serotonergic axons through severe spinal cord injury (SCI) lesions. By contrast, sustained local delivery via hydrogel depots of required axon-specific growth factors not present in SCI lesions, plus growth-activating priming injuries, stimulated robust, laminin-dependent sensory axon regrowth past scar-forming astrocytes and inhibitory molecules in SCI lesions. Preventing astrocytic scar formation significantly reduced this stimulated axon regrowth. RNA sequencing revealed that astrocytes and non-astrocyte cells in SCI lesions express multiple axon-growth-supporting molecules. Our findings show that contrary to the prevailing dogma, astrocyte scar formation aids rather than prevents central nervous system axon regeneration. PMID:27027288

  1. Development of a Novel Method for the Purification and Culture of Rodent Astrocytes

    OpenAIRE

    Foo, Lynette C.; Allen, Nicola J.; Bushong, Eric A.; Ventura, P. Britten; Chung, Won-Suk; Zhou, Lu; Cahoy, John D.; Daneman, Richard; Zong, Hui; Ellisman, Mark H.; Barres, Ben A.

    2011-01-01

    The inability to purify and culture astrocytes has long hindered studies of their function. Whereas astrocyte progenitor cells can be cultured from neonatal brain, culture of mature astrocytes from postnatal brain has not been possible. Here we report a new method to prospectively purify astrocytes by immunopanning. These astrocytes undergo apoptosis in culture, but vascular cells and HBEGF promote their survival in serum-free culture. We found that some developing astrocytes normally undergo...

  2. Insulin Attenuates Beta-Amyloid-Associated Insulin/Akt/EAAT Signaling Perturbations in Human Astrocytes.

    Science.gov (United States)

    Han, Xiaojuan; Yang, Liling; Du, Heng; Sun, Qinjian; Wang, Xiang; Cong, Lin; Liu, Xiaohui; Yin, Ling; Li, Shan; Du, Yifeng

    2016-08-01

    The excitatory amino acid transporters 1 and 2 (EAAT1 and EAAT2), mostly located on astrocytes, are the main mediators for glutamate clearance in humans. Malfunctions of these transporters may lead to excessive glutamate accumulation and subsequent excitotoxicity to neurons, which has been implicated in many kinds of neurodegenerative disorders including Alzheimer's disease (AD). Yet, the specific mechanism of the glutamate system dysregulation remains vague. To explore whether the insulin/protein kinase B (Akt)/EAAT signaling in human astrocytes could be disturbed by beta-amyloid protein (Aβ) and be protected by insulin, we incubated HA-1800 cells with varying concentrations of Aβ1-42 oligomers and insulin. Then the alterations of several key substrates in this signal transduction pathway were determined. Our results showed that expressions of insulin receptor, phospho-insulin receptor, phospho-protein kinase B, phospho-mammalian target of rapamycin, and EAAT1 and EAAT2 were decreased by the Aβ1-42 oligomers in a dose-dependent manner (p  0.05), and the mRNA levels of EAAT1 and EAAT2 were also unchanged (p > 0.05). Taken together, this study indicates that Aβ1-42 oligomers could cause disturbances in insulin/Akt/EAAT signaling in astrocytes, which might be responsible for AD onset and progression. Additionally, insulin can exert protective functions to the brain by modulating protein modifications or expressions. PMID:26358886

  3. Expression of apical Na(+)-L-glutamine co-transport activity, B(0)-system neutral amino acid co-transporter (B(0)AT1) and angiotensin-converting enzyme 2 along the jejunal crypt-villus axis in young pigs fed a liquid formula

    Science.gov (United States)

    Gut apical amino acid (AA) transport activity is high at birth and during suckling, thus being essential to maintain luminal nutrient-dependent mucosal growth through providing AA as essential metabolic fuel, substrates and nutrient stimuli for cellular growth. Because system-B(0) Na(+)-neutral AA c...

  4. Serum glutamine, set-shifting ability and anorexia nervosa

    Directory of Open Access Journals (Sweden)

    Collier David A

    2010-06-01

    Full Text Available Abstract Background Set-shifting is impaired in people with anorexia nervosa (AN, but the underlying physiological and biochemical processes are unclear. Animal studies have established that glutamatergic pathways in the prefrontal cortex play an important role in set-shifting ability. However, it is not yet understood whether levels of serum glutamatergic amino acids are associated with set-shifting performance in humans. The aim of this study was to determine whether serum concentrations of amino acids related to glutamatergic neurotransmission (glutamine, glutamate, glycine, l-serine, d-serine are associated with set-shifting ability in people with acute AN and those after recovery. Methods Serum concentrations of glutamatergic amino acids were measured in 27 women with current AN (AN group, 18 women recovered from AN (ANRec group and 28 age-matched healthy controls (HC group. Set-shifting was measured using the Wisconsin Card Sorting Test (WCST and the Trail Making Task (TMT. Dimensional measures of psychopathology were used, including the Eating Disorder Examination Questionnaire (EDEQ, the Maudsley Obsessive-Compulsive Inventory (MOCI and the Hospital Anxiety and Depression Scale (HADS. Results Serum glutamine concentrations in the AN group (1,310.2 ± 265.6 μM, mean ± SD were significantly higher (by approximately 20% than those in the HC group (1,102.9 ± 152.7 μM, mean ± SD (F(2, 70 = 6.3, P = 0.003, 95% CI 61.2 to 353.4. Concentrations of serum glutamine were positively associated with markers of the illness severity: a negative correlation was present between serum glutamine concentrations and body mass index (BMI and lowest BMI and a positive correlation was found between duration of illness and EDEQ. The AN group showed significantly impaired set shifting in the WCST, both total errors, and perseverative errors. In the AN group, there were no correlations between serum glutamine concentrations and set shifting. Conclusions Serum

  5. Expression of apical Na(+)-L-glutamine co-transport activity, B(0)-system neutral amino acid co-transporter (B(0)AT1) and angiotensin-converting enzyme 2 along the jejunal crypt-villus axis in young pigs fed a liquid formula.

    Science.gov (United States)

    Yang, Chengbo; Yang, Xiaojian; Lackeyram, Dale; Rideout, Todd C; Wang, Zirong; Stoll, Barbara; Yin, Yulong; Burrin, Douglas G; Fan, Ming Z

    2016-06-01

    Gut apical amino acid (AA) transport activity is high at birth and during suckling, thus being essential to maintain luminal nutrient-dependent mucosal growth through providing AA as essential metabolic fuel, substrates and nutrient stimuli for cellular growth. Because system-B(0) Na(+)-neutral AA co-transporter (B(0)AT1, encoded by the SLC6A19 gene) plays a dominant role for apical uptake of large neutral AA including L-Gln, we hypothesized that high apical Na(+)-Gln co-transport activity, and B(0)AT1 (SLC6A19) in co-expression with angiotensin-converting enzyme 2 (ACE2) were expressed along the entire small intestinal crypt-villus axis in young animals via unique control mechanisms. Kinetics of Na(+)-Gln co-transport activity in the apical membrane vesicles, prepared from epithelial cells sequentially isolated along the jejunal crypt-villus axis from liquid formula-fed young pigs, were measured with the membrane potential being clamped to zero using thiocyanate. Apical maximal Na(+)-Gln co-transport activity was much higher (p < 0.05) in the upper villus cells than in the middle villus (by 29 %) and the crypt (by 30 %) cells, whereas Na(+)-Gln co-transport affinity was lower (p < 0.05) in the upper villus cells than in the middle villus and the crypt cells. The B(0)AT1 (SLC6A19) mRNA abundance was lower (p < 0.05) in the crypt (by 40-47 %) than in the villus cells. There were no significant differences in B(0)AT1 and ACE2 protein abundances on the apical membrane among the upper villus, the middle villus and the crypt cells. Our study suggests that piglet fast growth is associated with very high intestinal apical Na(+)-neutral AA uptake activities via abundantly co-expressing B(0)AT1 and ACE2 proteins in the apical membrane and by transcribing the B(0)AT1 (SLC6A19) gene in the epithelia along the entire crypt-villus axis. PMID:26984322

  6. Liposomal clodronate selectively eliminates microglia from primary astrocyte cultures

    Directory of Open Access Journals (Sweden)

    Kumamaru Hiromi

    2012-05-01

    Full Text Available Abstract Background There is increasing interest in astrocyte biology because astrocytes have been demonstrated to play prominent roles in physiological and pathological conditions of the central nervous system, including neuroinflammation. To understand astrocyte biology, primary astrocyte cultures are most commonly used because of the direct accessibility of astrocytes in this system. However, this advantage can be hindered by microglial contamination. Although several authors have warned regarding microglial contamination in this system, complete microglial elimination has never been achieved. Methods The number and proliferative potential of contaminating microglia in primary astrocyte cultures were quantitatively assessed by immunocytologic and flow cytometric analyses. To examine the utility of clodronate for microglial elimination, primary astrocyte cultures or MG-5 cells were exposed to liposomal or free clodronate, and then immunocytologic, flow cytometric, and gene expression analyses were performed. The gene expression profiles of microglia-eliminated and microglia-contaminated cultures were compared after interleukin-6 (IL-6 stimulation. Results The percentage of contaminating microglia exceeded 15% and continued to increase because of their high proliferative activity in conventional primary astrocyte cultures. These contaminating microglia were selectively eliminated low concentration of liposomal clodronate. Although primary microglia and MG-5 cells were killed by both liposomal and free clodronate, free clodronate significantly affected the viability of astrocytes. In contrast, liposomal clodronate selectively eliminated microglia without affecting the viability, proliferation or activation of astrocytes. The efficacy of liposomal clodronate was much higher than that of previously reported methods used for decreasing microglial contamination. Furthermore, we observed rapid tumor necrosis factor-α and IL-1b gene induction in

  7. Selenoprotein S expression in reactive astrocytes following brain injury.

    Science.gov (United States)

    Fradejas, Noelia; Serrano-Pérez, Maria Del Carmen; Tranque, Pedro; Calvo, Soledad

    2011-06-01

    Selenoprotein S (SelS) is an endoplasmic reticulum (ER)-resident protein involved in the unfolded protein response. Besides reducing ER-stress, SelS attenuates inflammation by decreasing pro-inflammatory cytokines. We have recently shown that SelS is responsive to ischemia in cultured astrocytes. To check the possible association of SelS with astrocyte activation, here we investigate the expression of SelS in two models of brain injury: kainic acid (KA) induced excitotoxicity and cortical mechanical lesion. The regulation of SelS and its functional consequences for neuroinflammation, ER-stress, and cell survival were further analyzed using cultured astrocytes from mouse and human. According to our immunofluorescence analysis, SelS expression is prominent in neurons and hardly detectable in astrocytes from control mice. However, brain injury intensely upregulates SelS, specifically in reactive astrocytes. SelS induction by KA was evident at 12 h and faded out after reaching maximum levels at 3-4 days. Analysis of mRNA and protein expression in cultured astrocytes showed SelS upregulation by inflammatory stimuli as well as ER-stress inducers. In turn, siRNA-mediated SelS silencing combined with adenoviral overexpression assays demonstrated that SelS reduces ER-stress markers CHOP and spliced XBP-1, as well as inflammatory cytokines IL-1β and IL-6 in stimulated astrocytes. SelS overexpression increased astrocyte resistance to ER-stress and inflammatory stimuli. Conversely, SelS suppression compromised astrocyte viability. In summary, our results reveal the upregulation of SelS expression in reactive astrocytes, as well as a new protective role for SelS against inflammation and ER-stress that can be relevant to astrocyte function in the context of inflammatory neuropathologies. PMID:21456042

  8. Resistance to BRAF inhibitors induces glutamine dependency in melanoma cells

    Science.gov (United States)

    Baenke, Franziska; Chaneton, Barbara; Smith, Matthew; Van Den Broek, Niels; Hogan, Kate; Tang, Haoran; Viros, Amaya; Martin, Matthew; Galbraith, Laura; Girotti, Maria R.; Dhomen, Nathalie; Gottlieb, Eyal; Marais, Richard

    2016-01-01

    BRAF inhibitors can extend progression-free and overall survival in melanoma patients whose tumors harbor mutations in BRAF. However, the majority of patients eventually develop resistance to these drugs. Here we show that BRAF mutant melanoma cells that have developed acquired resistance to BRAF inhibitors display increased oxidative metabolism and increased dependency on mitochondria for survival. Intriguingly, the increased oxidative metabolism is associated with a switch from glucose to glutamine metabolism and an increased dependence on glutamine over glucose for proliferation. We show that the resistant cells are more sensitive to mitochondrial poisons and to inhibitors of glutaminolysis, suggesting that targeting specific metabolic pathways may offer exciting therapeutic opportunities to treat resistant tumors, or to delay emergence of resistance in the first-line setting. PMID:26365896

  9. Glutamine synthetase gene evolution: A good molecular clock

    International Nuclear Information System (INIS)

    Glutamine synthetase gene evolution in various animals, plants, and bacteria was evaluated by a general stationary Markov model. The evolutionary process proved to be unexpectedly regular even for a time span as long as that between the divergence of prokaryotes from eukaryotes. This enabled us to draw phylogenetic trees for species whose phylogeny cannot be easily reconstructed from the fossil record. The calculation of the times of divergence of the various organelle-specific enzymes led us to hypothesize that the pea and bean chloroplast genes for these enzymes originated from the duplication of nuclear genes as a result of the different metabolic needs of the various species. The data indicate that the duplication of plastid glutamine synthetase genes occurred long after the endosymbiotic events that produced the organelles themselves

  10. The pivotal role of astrocytes in an in-vitro stroke model of the blood-brain barrier

    Directory of Open Access Journals (Sweden)

    Winfried Neuhaus

    2014-10-01

    Full Text Available Stabilization of the blood-brain barrier during and after stroke can lead to less adverse outcome. For elucidation of underlying mechanisms and development of novel therapeutic strategies validated in-vitro disease models of the blood-brain barrier could be very helpful. To mimic in-vitro stroke conditions we have established a blood-brain barrier in-vitro model based on mouse cell line cerebEND and applied oxygen/glucose deprivation (OGD. The role of astrocytes in this disease model was investigated by using cell line C6. Transwell studies pointed out that addition of astrocytes during OGD increased the barrier damage significantly in comparison to the endothelial monoculture shown by changes of transendothelial electrical resistance as well as fluorescein permeability data. Analysis on mRNA and protein levels by qPCR, western blotting and immunofluorescence microscopy of tight junction molecules claudin-3,-5,-12, occludin and ZO-1 revealed that their regulation and localisation is associated with the functional barrier breakdown. Furthermore, soluble factors of astrocytes, OGD and their combination were able to induce changes of functionality and expression of ABC-transporters Abcb1a (P-gp, Abcg2 (bcrp and Abcc4 (mrp4. Moreover, the expression of proteases (matrixmetalloproteinases MMP-2, MMP-3 and MMP-9 and t-PA as well as of their endogenous inhibitors (TIMP-1, TIMP-3, PAI-1 was altered by astrocyte factors and OGD which resulted in significant changes of total MMP and t-PA activity. Morphological rearrangements induced by OGD and treatment with astrocyte factors were confirmed at a nanometer scale using atomic force microscopy. In conclusion, astrocytes play a major role in blood-brain barrier breakdown during OGD in vitro.

  11. Stretch induced endothelin-1 secretion by adult rat astrocytes involves calcium influx via stretch-activated ion channels (SACs)

    Energy Technology Data Exchange (ETDEWEB)

    Ostrow, Lyle W., E-mail: lostrow1@jhmi.edu [Department of Neurology, Johns Hopkins School of Medicine, Baltimore, MD 21205 (United States); Suchyna, Thomas M.; Sachs, Frederick [Department of Physiology and Biophysical Sciences, State University of New York at Buffalo, Buffalo, NY 14214 (United States)

    2011-06-24

    Highlights: {yields} Endothelin-1 expression by adult rat astrocytes correlates with cell proliferation. {yields} Stretch-induced ET-1 is inhibited by GsMtx-4, a specific inhibitor of Ca{sup 2+} permeant SACs. {yields} The less specific SAC inhibitor streptomycin also inhibits ET-1 secretion. {yields} Stretch-induced ET-1 production depends on a calcium influx. {yields} SAC pharmacology may provide a new class of therapeutic agents for CNS pathology. -- Abstract: The expression of endothelins (ETs) and ET-receptors is often upregulated in brain pathology. ET-1, a potent vasoconstrictor, also inhibits the expression of astrocyte glutamate transporters and is mitogenic for astrocytes, glioma cells, neurons, and brain capillary endothelia. We have previously shown that mechanical stress stimulates ET-1 production by adult rat astrocytes. We now show in adult astrocytes that ET-1 production is driven by calcium influx through stretch-activated ion channels (SACs) and the ET-1 production correlates with cell proliferation. Mechanical stimulation using biaxial stretch (<20%) of a rubber substrate increased ET-1 secretion, and 4 {mu}M GsMTx-4 (a specific inhibitor of SACs) inhibited secretion by 30%. GsMTx-4 did not alter basal ET-1 levels in the absence of stretch. Decreasing the calcium influx by lowering extracellular calcium also inhibited stretch-induced ET-1 secretion without effecting ET-1 secretion in unstretched controls. Furthermore, inhibiting SACs with the less specific inhibitor streptomycin also inhibited stretch-induced ET-1 secretion. The data can be explained with a simple model in which ET-1 secretion depends on an internal Ca{sup 2+} threshold. This coupling of mechanical stress to the astrocyte endothelin system through SACs has treatment implications, since all pathology deforms the surrounding parenchyma.

  12. Variable Glutamine-Rich Repeats Modulate Transcription Factor Activity

    OpenAIRE

    Gemayel, Rita; Chavali, Sreenivas; Pougach, Ksenia; Legendre, Matthieu; Zhu, Bo; Boeynaems, Steven; van der Zande, Elisa; Gevaert, Kris; Rousseau, Frederic; Schymkowitz, Joost; Babu, M Madan; Verstrepen, Kevin J.

    2015-01-01

    Summary Excessive expansions of glutamine (Q)-rich repeats in various human proteins are known to result in severe neurodegenerative disorders such as Huntington’s disease and several ataxias. However, the physiological role of these repeats and the consequences of more moderate repeat variation remain unknown. Here, we demonstrate that Q-rich domains are highly enriched in eukaryotic transcription factors where they act as functional modulators. Incremental changes in the number of repeats i...

  13. The glutamine synthetase gene family in Populus

    OpenAIRE

    Cánovas Francisco M; Kirby Edward G; Avila Concepción; Canales Javier; García-Gutiérrez Angel; Castro-Rodríguez Vanessa

    2011-01-01

    Abstract Background Glutamine synthetase (GS; EC: 6.3.1.2, L-glutamate: ammonia ligase ADP-forming) is a key enzyme in ammonium assimilation and metabolism of higher plants. The current work was undertaken to develop a more comprehensive understanding of molecular and biochemical features of GS gene family in poplar, and to characterize the developmental regulation of GS expression in various tissues and at various times during the poplar perennial growth. Results The GS gene family consists ...

  14. Glutamine Supplementation in Sick Children: Is It Beneficial?

    OpenAIRE

    Elise Mok; Régis Hankard

    2011-01-01

    The purpose of this review is to provide a critical appraisal of the literature on Glutamine (Gln) supplementation in various conditions or illnesses that affect children, from neonates to adolescents. First, a general overview of the proposed mechanisms for the beneficial effects of Gln is provided, and subsequently clinical studies are discussed. Despite safety, studies are conflicting, partly due to different effects of enteral and parenteral Gln supplementation. Further insufficient evide...

  15. Glutamine supplementation and immune function during heavy load training.

    Science.gov (United States)

    Song, Qing-Hua; Xu, Rong-Mei; Zhang, Quan-Hai; Shen, Guo-Qing; Ma, Ming; Zhao, Xin-Ping; Guo, Yan-Hua; Wang, Yi

    2015-05-01

    Athletes with heavy training loads are prone to infectious illnesses, suggesting that their training may suppress immune function. This study sought to determine whether supplementation with the amino acid glutamine, which supports immune health, alters immune function in athletes during heavy load training. 24 athletes were randomly assigned to either an experimental group (n = 12) or a control group (n = 12). Athletes exercised using heavy training loads for 6 weeks. Athletes in the experimental group took 10 g glutamine orally once a day beginning 3 weeks after initial testing, while athletes in the control group were given a placebo. Immune function was assessed by measuring the following immunity markers: CD4⁺ and CD8⁺ T cell counts, serum IgA, IgG, and IgM levels, and natural killer (NK) cell activity both before and after the completion of training. The percentages of circulating CD8⁺ T cells were significantly different before (39.13 ± 5.87%) and after (26.63 ± 3.95%) training in the experimental group (p glutamine supplementation may be able to restore immune function and reduce the immunosuppressive effects of heavy-load training. PMID:25740264

  16. Neuroimmunological Implications of AQP4 in Astrocytes.

    Science.gov (United States)

    Ikeshima-Kataoka, Hiroko

    2016-01-01

    The brain has high-order functions and is composed of several kinds of cells, such as neurons and glial cells. It is becoming clear that many kinds of neurodegenerative diseases are more-or-less influenced by astrocytes, which are a type of glial cell. Aquaporin-4 (AQP4), a membrane-bound protein that regulates water permeability is a member of the aquaporin family of water channel proteins that is expressed in the endfeet of astrocytes in the central nervous system (CNS). Recently, AQP4 has been shown to function, not only as a water channel protein, but also as an adhesion molecule that is involved in cell migration and neuroexcitation, synaptic plasticity, and learning/memory through mechanisms involved in long-term potentiation or long-term depression. The most extensively examined role of AQP4 is its ability to act as a neuroimmunological inducer. Previously, we showed that AQP4 plays an important role in neuroimmunological functions in injured mouse brain in concert with the proinflammatory inducer osteopontin (OPN). The aim of this review is to summarize the functional implication of AQP4, focusing especially on its neuroimmunological roles. This review is a good opportunity to compile recent knowledge and could contribute to the therapeutic treatment of autoimmune diseases through strategies targeting AQP4. Finally, the author would like to hypothesize on AQP4's role in interaction between reactive astrocytes and reactive microglial cells, which might occur in neurodegenerative diseases. Furthermore, a therapeutic strategy for AQP4-related neurodegenerative diseases is proposed. PMID:27517922

  17. Investigation on the suitable pressure for the preservation of astrocyte

    International Nuclear Information System (INIS)

    The effects of pressure on the survival rate of astrocytes in growth medium (DMEM) were investigated at room temperature and at 40C, in an effort to establish the best conditions for the preservation. Survival rate at 40C was found to be higher than that at room temperature. The survival rate of astrocytes preserved for 4 days at 40C increased with increasing pressure up to 1.6 MPa, but decreased with increasing pressure above 1.6 MPa. At 10 MPa, all astrocytes died. The survival rate of cultured astrocytes decreased significantly following pressurization for 2 hours and the subsequent preservation for 2 days at atmospheric pressure. Therefore, it is necessary to maintain pressure when preserving astrocytes. These results indicate that the cells can be stored at 40C under pressurization without freezing and without adding cryoprotective agents. Moreover, it may be possible to use this procedure as a new preservation method when cryopreservation is impractical.

  18. Astrocytes Control Neuronal Excitability in the Nucleus Accumbens

    Directory of Open Access Journals (Sweden)

    Tommaso Fellin

    2007-01-01

    Full Text Available Though accumulating evidence shows that the metabotropic glutamate receptor 5 (mGluR5 mediates some of the actions of extracellular glutamate after cocaine use, the cellular events underlying this action are poorly understood. In this review, we will discuss recent results showing that mGluR5 receptors are key regulators of astrocyte activity. Synaptic release of glutamate activates mGluR5 expressed in perisynaptic astrocytes and generates intense Ca2+ signaling in these cells. Ca2+ oscillations, in turn, trigger the release from astrocytes of the gliotransmitter glutamate, which modulates neuronal excitability by activating NMDA receptors. By integrating these results with the most recent evidence demonstrating the importance of astrocytes in the regulation of neuronal excitability, we propose that astrocytes are involved in mediating some of the mGluR5-dependent drug-induced behaviors.

  19. Optical modulation of astrocyte network using ultrashort pulsed laser

    Science.gov (United States)

    Yoon, Jonghee; Ku, Taeyun; Chong, Kyuha; Ryu, Seung-Wook; Choi, Chulhee

    2012-03-01

    Astrocyte, the most abundant cell type in the central nervous system, has been one of major topics in neuroscience. Even though many tools have been developed for the analysis of astrocyte function, there has been no adequate tool that can modulates astrocyte network without pharmaceutical or genetic interventions. Here we found that ultrashort pulsed laser stimulation can induce label-free activation of astrocytes as well as apoptotic-like cell death in a dose-dependent manner. Upon irradiation with high intensity pulsed lasers, the irradiated cells with short exposure time showed very rapid mitochondria fragmentation, membrane blebbing and cytoskeletal retraction. We applied this technique to investigate in vivo function of astrocyte network in the CNS: in the aspect of neurovascular coupling and blood-brain barrier. We propose that this noninvasive technique can be widely applied for in vivo study of complex cellular network.

  20. Spatiotemporal characteristics of calcium dynamics in astrocytes

    OpenAIRE

    Kang, Minchul; Othmer, Hans G.

    2009-01-01

    Although Cai2+ waves in networks of astrocytes in vivo are well documented, propagation in vivo is much more complex than in culture, and there is no consensus concerning the dominant roles of intercellular and extracellular messengers [inositol 1,4,5–trisphosphate (IP3) and adenosine-5′-triphosphate (ATP)] that mediate Cai2+ waves. Moreover, to date only simplified models that take very little account of the geometrical struture of the networks have been studied. Our aim in this paper is to ...

  1. Glutamine availability as a target for the control of Glutamine-Synthetase negative human cancers: the case of oligodendroglioma

    OpenAIRE

    Ottaviani, Laura

    2015-01-01

    The amino acid Glutamine (Gln) is a nutrient of fundamental importance for cell metabolism. It is involved in many metabolic pathways, such as the synthesis of non essential amino acids, nucleotides and hexosamines, the regulation of cell volume, the response to oxidative stress (through the maintenance of intracellular glutathione). Moreover, it refuels the Krebs cycle with carbon moieties (anaplerosis) and activates mTOR, possibly through the energization of leucine influx. It has been k...

  2. Stimulation of glycogen synthesis and lipogenesis by glutamine in isolated rat hepatocytes.

    OpenAIRE

    Lavoinne, A; Baquet, A.; Hue, Louis

    1987-01-01

    Glutamine stimulated glycogen synthesis and lactate production in hepatocytes from overnight-fasted normal and diabetic rats. The effect, which was half-maximal with about 3 mM-glutamine, depended on glucose concentration and was maximal below 10 mM-glucose. beta-2-Aminobicyclo[2.2.1.]heptane-2-carboxylic acid, an analogue of leucine, stimulated glutaminase flux, but inhibited the stimulation of glycogen synthesis by glutamine. Various purine analogues and inhibitors of purine synthesis were ...

  3. Astrocytic vesicles and gliotransmitters: Slowness of vesicular release and synaptobrevin2-laden vesicle nanoarchitecture.

    Science.gov (United States)

    Zorec, R; Verkhratsky, A; Rodríguez, J J; Parpura, V

    2016-05-26

    Neurotransmitters released at synapses activate neighboring astrocytes, which in turn, modulate neuronal activity by the release of diverse neuroactive substances that include classical neurotransmitters such as glutamate, GABA or ATP. Neuroactive substances are released from astrocytes through several distinct molecular mechanisms, for example, by diffusion through membrane channels, by translocation via plasmalemmal transporters or by vesicular exocytosis. Vesicular release regulated by a stimulus-mediated increase in cytosolic calcium involves soluble N-ethyl maleimide-sensitive fusion protein attachment protein receptor (SNARE)-dependent merger of the vesicle membrane with the plasmalemma. Up to 25 molecules of synaptobrevin 2 (Sb2), a SNARE complex protein, reside at a single astroglial vesicle; an individual neuronal, i.e. synaptic, vesicle contains ∼70 Sb2 molecules. It is proposed that this paucity of Sb2 molecules in astrocytic vesicles may determine the slow secretion. In the present essay we shall overview multiple aspects of vesicular architecture and types of vesicles based on their cargo and dynamics in astroglial cells. PMID:25727638

  4. Guanosine effect on cholesterol efflux and apolipoprotein E expression in astrocytes.

    Science.gov (United States)

    Ballerini, Patrizia; Ciccarelli, Renata; Di Iorio, Patrizia; Buccella, Silvana; D'Alimonte, Iolanda; Giuliani, Patricia; Masciulli, Arianna; Nargi, Eleonora; Beraudi, Alina; Rathbone, Michel P; Caciagli, Francesco

    2006-11-01

    The main source of cholesterol in the central nervous system (CNS) is represented by glial cells, mainly astrocytes, which also synthesise and secrete apolipoproteins, in particular apolipoprotein E (ApoE), the major apolipoprotein in the brain, thus generating cholesterol-rich high density lipoproteins (HDLs). This cholesterol trafficking, even though still poorly known, is considered to play a key role in different aspects of neuronal plasticity and in the stabilisation of synaptic transmission. Moreover, cell cholesterol depletion has recently been linked to a reduction in amyloid beta formation. Here we demonstrate that guanosine, which we previously reported to exert several neuroprotective effects, was able to increase cholesterol efflux from astrocytes and C6 rat glioma cells in the absence of exogenously added acceptors. In this effect the phosphoinositide 3 kinase/extracellular signal-regulated kinase 1/2 (PI3K/ERK1/2) pathway seems to play a pivotal role. Guanosine was also able to increase the expression of ApoE in astrocytes, whereas it did not modify the levels of ATP-binding cassette protein A1 (ABCA1), considered the main cholesterol transporter in the CNS. Given the emerging role of cholesterol balance in neuronal repair, these effects provide evidence for a role of guanosine as a potential pharmacological tool in the modulation of cholesterol homeostasis in the brain. PMID:18404467

  5. Increased phase synchronization of spontaneous calcium oscillations in epileptic human versus normal rat astrocyte cultures

    Science.gov (United States)

    Balázsi, Gábor; Cornell-Bell, Ann H.; Moss, Frank

    2003-06-01

    Stochastic synchronization analysis is applied to intracellular calcium oscillations in astrocyte cultures prepared from epileptic human temporal lobe. The same methods are applied to astrocyte cultures prepared from normal rat hippocampus. Our results indicate that phase-repulsive coupling in epileptic human astrocyte cultures is stronger, leading to an increased synchronization in epileptic human compared to normal rat astrocyte cultures.

  6. Fine Astrocyte Processes Contain Very Small Mitochondria: Glial Oxidative Capability May Fuel Transmitter Metabolism.

    Science.gov (United States)

    Derouiche, Amin; Haseleu, Julia; Korf, Horst-Werner

    2015-12-01

    The peripheral astrocyte process (PAP) is the glial compartment largely handling inactivation of transmitter glutamate, and supplying glutamate to the axon terminal. It is not clear how these energy demanding processes are fueled, and whether the PAP exhibits oxidative capability. Whereas the GFAP-positive perinuclear cytoplasm and stem process are rich in mitochondria, the PAP is often considered too narrow to contain mitochondria and might thus not rely on oxidative metabolism. Applying high resolution light microscopy, we investigate here the presence of mitochondria in the PAPs of freshly dissociated, isolated astrocytes. We provide an overview of the subcellular distribution and the approximate size of astrocytic mitochondria. A substantial proportion of the astrocyte's mitochondria are contained in the PAPs and, on the average, they are smaller there than in the stem processes. The majority of mitochondria in the stem and peripheral processes are surprisingly small (0.2-0.4 µm), spherical and not elongate, or tubular, which is supported by electron microscopy. The density of mitochondria is two to several times lower in the PAPs than in the stem processes. Thus, PAPs do not constitute a mitochondria free glial compartment but contain mitochondria in large numbers. No juxtaposition of mitochondria-containing PAPs and glutamatergic synapses has been reported. However, the issue of sufficient ATP concentrations in perisynaptic PAPs can be seen in the light of (1) the rapid, activity dependent PAP motility, and (2) the recently reported activity-dependent mitochondrial transport and immobilization leading to spatial, subcellular organisation of glutamate uptake and oxidative metabolism. PMID:25894677

  7. Effect of the association l-glutamine – ethylene glycol In equine semen cryopreservation

    Directory of Open Access Journals (Sweden)

    Jorge Alberto Neira

    2007-12-01

    Full Text Available In order to improve the effectiveness in the cryopreservation of horse sperm, the effect of association L-glutamine with Ethylenglicole and Glycerol in the freezing media spermatozoa was evaluated. 4 Colombian native stallions were used to complete a total of 21 samples which were frozen in two different media: INRA 97 and cryoprotectant. The following study was done: L-glutamine 80mM + Etilenglicol 2.5% (protocol 1, L-glutamine 80 mM + Glycerol 2.5% (protocol 2, Etilenglicol 2.5% (protocol 3 and glycerol 2.5% (protocol 4. The freezing methodology was: 60 minutes to descend the temperature from 38°C to 5°C (0.55°C/min during the transport. The samples were centrifuged at 600G/10min., and the semen was diluted with the four protocols in straws of 0.5 ml. Then, 60 minutes of equilibrium in refrigeration; 20 minutes in liquid nitrogen vapors and then immersed. In the progressive motility evaluation there was not any significant difference between protocols at 0 time (p ≤ 0.6383, at 30 minutes (p ≤ 0.511, and at 60 minutes (p ≤ 0.1659. The motility averages for the 4 protocols at 0 time were (1 29,6 ± 15,1; (2 28,1 ± 13,5; (3 28,4 ± 12,3 and (4 30,8 ± 11,1; at the 30 minutes: (1 25,1 ± 13,6; (2 22,3 ± 13,0; (3 24,9 ± 12,4 and (4 25,5 ± 11,6, and at 60 minutes (1 17,1 ± 10,2; (2 15,4 ± 11,7; (3 19,9 ± 11,5 and (4 17,6 ± 10,4. The spermatic survival was evaluated with eosine-nigrosine coloration, after thawing and there was not any significant difference among the protocols (p≤ 0.6336, the average measures were (1 30,7; (2 28,8; (3 28,7 and (4 31,7. As a conclusion, although significant difference was not demonstrated among the protocols; the tendency to the highest average was presented by the protocol 4 (glycerol 2.5%.

  8. Sex differences in hypothalamic astrocyte response to estradiol stimulation

    Directory of Open Access Journals (Sweden)

    Kuo John

    2010-11-01

    Full Text Available Abstract Background Reproductive functions controlled by the hypothalamus are highly sexually differentiated. One of the most dramatic differences involves estrogen positive feedback, which leads to ovulation. A crucial feature of this positive feedback is the ability of estradiol to facilitate progesterone synthesis in female hypothalamic astrocytes. Conversely, estradiol fails to elevate hypothalamic progesterone levels in male rodents, which lack the estrogen positive feedback-induced luteinizing hormone (LH surge. To determine whether hypothalamic astrocytes are sexually differentiated, we examined the cellular responses of female and male astrocytes to estradiol stimulation. Methods Primary adult hypothalamic astrocyte cultures were established from wild type rats and mice, estrogen receptor-α knockout (ERKO mice, and four core genotype (FCG mice, with the sex determining region of the Y chromosome (Sry deleted and inserted into an autosome. Astrocytes were analyzed for Sry expression with reverse transcription PCR. Responses to estradiol stimulation were tested by measuring free cytoplasmic calcium concentration ([Ca2+]i with fluo-4 AM, and progesterone synthesis with column chromatography and radioimmunoassay. Membrane estrogen receptor-α (mERα levels were examined using surface biotinylation and western blotting. Results Estradiol stimulated both [Ca2+]i release and progesterone synthesis in hypothalamic astrocytes from adult female mice. Male astrocytes had a significantly elevated [Ca2+]i response but it was significantly lower than in females, and progesterone synthesis was not enhanced. Surface biotinylation demonstrated mERα in both female and male astrocytes, but only in female astrocytes did estradiol treatment increase insertion of the receptor into the membrane, a necessary step for maximal [Ca2+]i release. Regardless of the chromosomal sex, estradiol facilitated progesterone synthesis in astrocytes from mice with ovaries

  9. Phosphoinositide metabolism and adrenergic receptors in astrocytes

    International Nuclear Information System (INIS)

    Agonist-induced phosphoinositide (PI) breakdown functions as a signal generating system. Diacylglycerol, one breakdown product of phosphotidylinositol-4,5-diphosphate hydrolysis, can stimulate protein kinase C, whereas inositol triphosphate, the other product, has been proposed to be a second messenger for Ca++ mobilization. Using purified astrocyte cultures from neonatal rat brain, the effects of adrenergic agonists and antagonists at 10-5 M were measured on PI breakdown. Astrocytes grown in culture were prelabeled with (3H)inositol, and basal (3H) inositol phosphate (IP1) accumulation was measured in the presence of Li+. Epinephrine > norepinephrine (NE) were the most active stimulants of IP1 production. The α1 adrenoreceptor blockers, phentolamine and phenoxybenzamine, added alone had no effect on IP1 production was reduced below basal levels. Propranolol partially blocked the effects of NE. Clonidine and isoproterenol, separately added, reduced IP1 below basal levels and when added together diminished IP1 accumulation even further. The role of adrenergic stimulation in the production of c-AMP

  10. Astrocytic gap junctional communication is reduced in amyloid-β-treated cultured astrocytes, but not in Alzheimer's disease transgenic mice

    Directory of Open Access Journals (Sweden)

    Gerald A Dienel

    2010-08-01

    Full Text Available Alzheimer's disease is characterized by accumulation of amyloid deposits in brain, progressive cognitive deficits and reduced glucose utilization. Many consequences of the disease are attributed to neuronal dysfunction, but roles of astrocytes in its pathogenesis are not well understood. Astrocytes are extensively coupled via gap junctions, and abnormal trafficking of metabolites and signalling molecules within astrocytic syncytia could alter functional interactions among cells comprising the neurovascular unit. To evaluate the influence of amyloid-β on astrocyte gap junctional communication, cultured astrocytes were treated with monomerized amyloid-β1–40 (1 μmol/l for intervals ranging from 2 h to 5 days, and the areas labelled by test compounds were determined by impaling a single astrocyte with a micropipette and diffusion of material into coupled cells. Amyloid-β-treated astrocytes had rapid, sustained 50–70% reductions in the area labelled by Lucifer Yellow, anionic Alexa Fluor® dyes and energy-related compounds, 6-NBDG (a fluorescent glucose analogue, NADH and NADPH. Amyloid-β treatment also caused a transient increase in oxidative stress. In striking contrast with these results, spreading of Lucifer Yellow within astrocytic networks in brain slices from three regions of 8.5–14-month-old control and transgenic Alzheimer's model mice was variable, labelling 10–2000 cells; there were no statistically significant differences in the number of dye-labelled cells among the groups or with age. Thus amyloid-induced dysfunction of gap junctional communication in cultured astrocytes does not reflect the maintenance of dye transfer through astrocytic syncytial networks in transgenic mice; the pathophysiology of Alzheimer's disease is not appropriately represented by the cell culture system.

  11. Transport

    International Nuclear Information System (INIS)

    Transport is one of the major causes of environmental damage in Austria. Energy consumption, pollutants emissions, noise emissions, use of surfaces, sealing of surfaces, dissection of ecosystems and impact on landscape are the most significant environmental impacts caused by it. An overview of the transport development of passengers and freight in Austria is presented. Especially the energy consumption growth, carbon dioxide and nitrogen oxide emissions by type of transport, and the emissions development (HC, particle and carbon monoxide) of goods and passengers transport are analyzed covering the years 1980 - 1999. The health cost resulting from transport-related air pollution in Austria is given and measures to be taken for an effective control of the transport sector are mentioned. Figs. 8, Table 1. (nevyjel)

  12. Bacterial Type I Glutamine Synthetase of the Rifamycin SV Producing Actinomycete, Amycolatopsis mediterranei U32, is the Only Enzyme Responsible for Glutamine Synthesis under Physiological Conditions

    Institute of Scientific and Technical Information of China (English)

    Wen-Tao PENG; Jin WANG; Ting WU; Jian-Qiang HUANG; Jui-Shen CHIAO; Guo-Ping ZHAO

    2006-01-01

    The structural gene for glutamine synthetase, glnA, from Amycolatopsis mediterranei U32 was cloned via screening a genomic library using the analog gene from Streptomyces coelicolor. The clone was functionally verified by complementing for glutamine requirement of an Escherichia coli glnA null mutant under the control of a lac promoter. Sequence analysis showed an open reading frame encoding a protein of466 amino acid residues. The deduced amino acid sequence bears significant homologies to other bacterial type I glutamine synthetases, specifically, 71% and 72% identical to the enzymes of S. coelicolor and Mycobacterium tuberculosis, respectively. Disruption of this glnA gene in A. mediterranei U32 led to glutamine auxotrophy with no detectable glutamine synthetase activity in vivo. In contrast, the cloned glnA+ gene can complement for both phenotypes in trans. It thus suggested that in A. mediterranei U32, the glnA gene encoding glutamine synthetase is uniquely responsible for in vivo glutamine synthesis under our laboratory defined physiological conditions.

  13. Direct Signaling from Astrocytes to Neurons in Cultures of Mammalian Brain Cells

    Science.gov (United States)

    Nedergaard, Maiken

    1994-03-01

    Although astrocytes have been considered to be supportive, rather than transmissive, in the adult nervous system, recent studies have challenged this assumption by demonstrating that astrocytes possess functional neurotransmitter receptors. Astrocytes are now shown to directly modulate the free cytosolic calcium, and hence transmission characteristics, of neighboring neurons. When a focal electric field potential was applied to single astrocytes in mixed cultures of rat forebrain astrocytes and neurons, a prompt elevation of calcium occurred in the target cell. This in turn triggered a wave of calcium increase, which propagated from astrocyte to astrocyte. Neurons resting on these astrocytes responded with large increases in their concentration of cytosolic calcium. The gap junction blocker octanol attenuated the neuronal response, which suggests that the astrocytic-neuronal signaling is mediated through intercellular connections rather than synaptically. This neuronal response to local astrocytic stimulation may mediate local intercellular communication within the brain.

  14. Simultaneous neuron- and astrocyte-specific fluorescent marking

    Energy Technology Data Exchange (ETDEWEB)

    Schulze, Wiebke [Laboratory of Molecular Neuropharmacology, Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871 (Japan); Hayata-Takano, Atsuko [Molecular Research Center for Children' s Mental Development, United Graduate School of Child Development, Osaka University, Kanazawa University, Hamamatsu University School of Medicine, Chiba University and University of Fukui, 2-2 Yamadaoka, Suita, Osaka 565-0871 (Japan); Kamo, Toshihiko [Laboratory of Molecular Neuropharmacology, Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871 (Japan); Nakazawa, Takanobu, E-mail: takanobunakazawa-tky@umin.ac.jp [iPS Cell-based Research Project on Brain Neuropharmacology and Toxicology, Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871 (Japan); Nagayasu, Kazuki [iPS Cell-based Research Project on Brain Neuropharmacology and Toxicology, Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871 (Japan); Kasai, Atsushi; Seiriki, Kaoru [Laboratory of Molecular Neuropharmacology, Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871 (Japan); Interdisciplinary Program for Biomedical Sciences, Institute for Academic Initiatives, Osaka University, 1-1 Yamadaoka, Suita, Osaka 565-0871 (Japan); Shintani, Norihito [Laboratory of Molecular Neuropharmacology, Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871 (Japan); Ago, Yukio [Laboratory of Medicinal Pharmacology, Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871 (Japan); Farfan, Camille [Laboratory of Molecular Neuropharmacology, Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871 (Japan); and others

    2015-03-27

    Systematic and simultaneous analysis of multiple cell types in the brain is becoming important, but such tools have not yet been adequately developed. Here, we aimed to generate a method for the specific fluorescent labeling of neurons and astrocytes, two major cell types in the brain, and we have developed lentiviral vectors to express the red fluorescent protein tdTomato in neurons and the enhanced green fluorescent protein (EGFP) in astrocytes. Importantly, both fluorescent proteins are fused to histone 2B protein (H2B) to confer nuclear localization to distinguish between single cells. We also constructed several expression constructs, including a tandem alignment of the neuron- and astrocyte-expression cassettes for simultaneous labeling. Introducing these vectors and constructs in vitro and in vivo resulted in cell type-specific and nuclear-localized fluorescence signals enabling easy detection and distinguishability of neurons and astrocytes. This tool is expected to be utilized for the simultaneous analysis of changes in neurons and astrocytes in healthy and diseased brains. - Highlights: • We develop a method for the specific fluorescent labeling of neurons and astrocytes. • Neuron-specific labeling is achieved using Scg10 and synapsin promoters. • Astrocyte-specific labeling is generated using the minimal GFAP promoter. • Nuclear localization of fluorescent proteins is achieved with histone 2B protein.

  15. Curcumin alleviates oxidative stress and mitochondrial dysfunction in astrocytes.

    Science.gov (United States)

    Daverey, Amita; Agrawal, Sandeep K

    2016-10-01

    Oxidative stress plays a critical role in various neurodegenerative diseases, thus alleviating oxidative stress is a potential strategy for therapeutic intervention and/or prevention of neurodegenerative diseases. In the present study, alleviation of oxidative stress through curcumin is investigated in A172 (human glioblastoma cell line) and HA-sp (human astrocytes cell line derived from the spinal cord) astrocytes. H2O2 was used to induce oxidative stress in astrocytes (A172 and HA-sp). Data show that H2O2 induces activation of astrocytes in dose- and time-dependent manner as evident by increased expression of GFAP in A172 and HA-sp cells after 24 and 12h respectively. An upregulation of Prdx6 was also observed in A172 and HA-sp cells after 24h of H2O2 treatment as compared to untreated control. Our data also showed that curcumin inhibits oxidative stress-induced cytoskeleton disarrangement, and impedes the activation of astrocytes by inhibiting upregulation of GFAP, vimentin and Prdx6. In addition, we observed an inhibition of oxidative stress-induced inflammation, apoptosis and mitochondria fragmentation after curcumin treatment. Therefore, our results suggest that curcumin not only protects astrocytes from H2O2-induced oxidative stress but also reverses the mitochondrial damage and dysfunction induced by oxidative stress. This study also provides evidence for protective role of curcumin on astrocytes by showing its effects on attenuating reactive astrogliosis and inhibiting apoptosis. PMID:27423629

  16. Calcineurin proteolysis in astrocytes: Implications for impaired synaptic function.

    Science.gov (United States)

    Pleiss, Melanie M; Sompol, Pradoldej; Kraner, Susan D; Abdul, Hafiz Mohmmad; Furman, Jennifer L; Guttmann, Rodney P; Wilcock, Donna M; Nelson, Peter T; Norris, Christopher M

    2016-09-01

    Mounting evidence suggests that astrocyte activation, found in most forms of neural injury and disease, is linked to the hyperactivation of the protein phosphatase calcineurin. In many tissues and cell types, calcineurin hyperactivity is the direct result of limited proteolysis. However, little is known about the proteolytic status of calcineurin in activated astrocytes. Here, we developed a polyclonal antibody to a high activity calcineurin proteolytic fragment in the 45-48kDa range (ΔCN) for use in immunohistochemical applications. When applied to postmortem human brain sections, the ΔCN antibody intensely labeled cell clusters in close juxtaposition to amyloid deposits and microinfarcts. Many of these cells exhibited clear activated astrocyte morphology. The expression of ΔCN in astrocytes near areas of pathology was further confirmed using confocal microscopy. Multiple NeuN-positive cells, particularly those within microinfarct core regions, also labeled positively for ΔCN. This observation suggests that calcineurin proteolysis can also occur within damaged or dying neurons, as reported in other studies. When a similar ΔCN fragment was selectively expressed in hippocampal astrocytes of intact rats (using adeno-associated virus), we observed a significant reduction in the strength of CA3-CA1 excitatory synapses, indicating that the hyperactivation of astrocytic calcineurin is sufficient for disrupting synaptic function. Together, these results suggest that proteolytic activation of calcineurin in activated astrocytes may be a central mechanism for driving and/or exacerbating neural dysfunction during neurodegenerative disease and injury. PMID:27212416

  17. Simultaneous neuron- and astrocyte-specific fluorescent marking

    International Nuclear Information System (INIS)

    Systematic and simultaneous analysis of multiple cell types in the brain is becoming important, but such tools have not yet been adequately developed. Here, we aimed to generate a method for the specific fluorescent labeling of neurons and astrocytes, two major cell types in the brain, and we have developed lentiviral vectors to express the red fluorescent protein tdTomato in neurons and the enhanced green fluorescent protein (EGFP) in astrocytes. Importantly, both fluorescent proteins are fused to histone 2B protein (H2B) to confer nuclear localization to distinguish between single cells. We also constructed several expression constructs, including a tandem alignment of the neuron- and astrocyte-expression cassettes for simultaneous labeling. Introducing these vectors and constructs in vitro and in vivo resulted in cell type-specific and nuclear-localized fluorescence signals enabling easy detection and distinguishability of neurons and astrocytes. This tool is expected to be utilized for the simultaneous analysis of changes in neurons and astrocytes in healthy and diseased brains. - Highlights: • We develop a method for the specific fluorescent labeling of neurons and astrocytes. • Neuron-specific labeling is achieved using Scg10 and synapsin promoters. • Astrocyte-specific labeling is generated using the minimal GFAP promoter. • Nuclear localization of fluorescent proteins is achieved with histone 2B protein

  18. Arginine deiminase resistance in melanoma cells is associated with metabolic reprogramming, glucose dependence, and glutamine addiction.

    Science.gov (United States)

    Long, Yan; Tsai, Wen-Bin; Wangpaichitr, Medhi; Tsukamoto, Takashi; Savaraj, Niramol; Feun, Lynn G; Kuo, Macus Tien

    2013-11-01

    Many malignant human tumors, including melanomas, are auxotrophic for arginine due to reduced expression of argininosuccinate synthetase-1 (ASS1), the rate-limiting enzyme for arginine biosynthesis. Pegylated arginine deiminase (ADI-PEG20), which degrades extracellular arginine, resulting in arginine deprivation, has shown favorable results in clinical trials for treating arginine-auxotrophic tumors. Drug resistance is the major obstacle for effective ADI-PEG20 usage. To elucidate mechanisms of resistance, we established several ADI-PEG20-resistant (ADI(R)) variants from A2058 and SK-Mel-2 melanoma cells. Compared with the parental lines, these ADI(R) variants showed the following characteristics: (i) all ADI(R) cell lines showed elevated ASS1 expression, resulting from the constitutive binding of the transcription factor c-Myc on the ASS1 promoter, suggesting that elevated ASS1 is the major mechanism of resistance; (ii) the ADI(R) cell lines exhibited enhanced AKT signaling and were preferentially sensitive to PI3K/AKT inhibitors, but reduced mTOR signaling, and were preferentially resistant to mTOR inhibitor; (iii) these variants showed enhanced expression of glucose transporter-1 and lactate dehydrogenase-A, reduced expression of pyruvate dehydrogenase, and elevated sensitivity to the glycolytic inhibitors 2-deoxy-glucose and 3-bromopyruvate, consistent with the enhanced glycolytic pathway (the Warburg effect); (iv) the resistant cells showed higher glutamine dehydrogenase and glutaminase expression and were preferentially vulnerable to glutamine inhibitors. We showed that c-Myc, not elevated ASS1 expression, is involved in upregulation of many of these enzymes because knockdown of c-Myc reduced their expression, whereas overexpressed ASS1 by transfection reduced their expression. This study identified multiple targets for overcoming ADI-PEG resistance in cancer chemotherapy using recombinant arginine-degrading enzymes. PMID:23979920

  19. Regulation of the intersubunit ammonia tunnel in Mycobacterium tuberculosis glutamine-dependent NAD[superscript +] synthetase

    Energy Technology Data Exchange (ETDEWEB)

    Chuenchor, Watchalee; Doukov, Tzanko I.; Resto, Melissa; Chang, Andrew; Gerratana, Barbara (SSRL); (Maryland)

    2012-08-31

    Glutamine-dependent NAD{sup +} synthetase is an essential enzyme and a validated drug target in Mycobacterium tuberculosis (mtuNadE). It catalyses the ATP-dependent formation of NAD{sup +} from NaAD{sup +} (nicotinic acid-adenine dinucleotide) at the synthetase active site and glutamine hydrolysis at the glutaminase active site. An ammonia tunnel 40 {angstrom} (1 {angstrom} = 0.1 nm) long allows transfer of ammonia from one active site to the other. The enzyme displays stringent kinetic synergism; however, its regulatory mechanism is unclear. In the present paper, we report the structures of the inactive glutaminase C176A variant in an apo form and in three synthetase-ligand complexes with substrates (NaAD{sup +}/ATP), substrate analogue {l_brace}NaAD{sup +}/AMP-CPP (adenosine 5'-[{alpha},{beta}-methylene]triphosphate){r_brace} and intermediate analogues (NaAD{sup +}/AMP/PPi), as well as the structure of wild-type mtuNadE in a product complex (NAD{sup +}/AMP/PPi/glutamate). This series of structures provides snapshots of the ammonia tunnel during the catalytic cycle supported also by kinetics and mutagenesis studies. Three major constriction sites are observed in the tunnel: (i) at the entrance near the glutaminase active site; (ii) in the middle of the tunnel; and (iii) at the end near the synthetase active site. Variation in the number and radius of the tunnel constrictions is apparent in the crystal structures and is related to ligand binding at the synthetase domain. These results provide new insight into the regulation of ammonia transport in the intermolecular tunnel of mtuNadE.

  20. New developments in glutamine delivery%谷氨酰胺给药的新进展

    Institute of Scientific and Technical Information of China (English)

    PeterFuerst,MD

    2001-01-01

    Free glutamine-a critical issueNumerous studies demonstrate that free glutamine can be added to commercially available crystalline amino acid based preparations prior to their administration.Instability during heat sterilization and prolonged storage and linited solubility (35 g/L at 20℃) hampers the use of free glutamine in routine clinical setting.Indeed,there are many well controlled and valuable trials with free glutamine,yet its use is restricted to clinical research.How to solve the problem?The obvious linitations of using free glutamine initiated an intensive search for alternative substrates.Indeed,glutamic acid is a poor precursor;its in vivo transformation to glutamine is restricted to yield only 5-6%.Similarly,the transformation of α-ketoglutarate or the salt ornthine-α-ketoglutarate to glutamine is confined since they are primarily precursors for glutamic acid.Parenterally supplied acetyl glutamine is poorly utilized in man;the large urinary excretion (45-50%) being associated with considerable accumulation of acetyl glutamine in body fluids.It can be concluded that N-acetylated glutamine is not suitable as alternative glutamine source in humans due to restricted acylase capacities.Synthetic glutamine dipeptides are stable under heat sterilization and highly soluble;these properties qualify the dipeptides as suitable constituents of nutritional preparations.Industrial production of these dipeptides at a reasonable price is an essential prerequisite for implications of dipeptide-containing solutions in clinical practice.Recent development of novel synthesis procedures allows increased capacity in industrial-scale production.Basic studies with synthetic glutamine-containing short-chain peptides provide convincing evidence that these new substrates are rqpidly cleared from plasma after parenteral administration,without being accumulated in tissues,and with negligible loss of urine.The presence of membrane-bound as well as tissue free extracellular

  1. p53 isoforms regulate astrocyte-mediated neuroprotection and neurodegeneration.

    Science.gov (United States)

    Turnquist, C; Horikawa, I; Foran, E; Major, E O; Vojtesek, B; Lane, D P; Lu, X; Harris, B T; Harris, C C

    2016-09-01

    Bidirectional interactions between astrocytes and neurons have physiological roles in the central nervous system and an altered state or dysfunction of such interactions may be associated with neurodegenerative diseases, such as Alzheimer's disease (AD) and amyotrophic lateral sclerosis (ALS). Astrocytes exert structural, metabolic and functional effects on neurons, which can be either neurotoxic or neuroprotective. Their neurotoxic effect is mediated via the senescence-associated secretory phenotype (SASP) involving pro-inflammatory cytokines (e.g., IL-6), while their neuroprotective effect is attributed to neurotrophic growth factors (e.g., NGF). We here demonstrate that the p53 isoforms Δ133p53 and p53β are expressed in astrocytes and regulate their toxic and protective effects on neurons. Primary human astrocytes undergoing cellular senescence upon serial passaging in vitro showed diminished expression of Δ133p53 and increased p53β, which were attributed to the autophagic degradation and the SRSF3-mediated alternative RNA splicing, respectively. Early-passage astrocytes with Δ133p53 knockdown or p53β overexpression were induced to show SASP and to exert neurotoxicity in co-culture with neurons. Restored expression of Δ133p53 in near-senescent, otherwise neurotoxic astrocytes conferred them with neuroprotective activity through repression of SASP and induction of neurotrophic growth factors. Brain tissues from AD and ALS patients possessed increased numbers of senescent astrocytes and, like senescent astrocytes in vitro, showed decreased Δ133p53 and increased p53β expression, supporting that our in vitro findings recapitulate in vivo pathology of these neurodegenerative diseases. Our finding that Δ133p53 enhances the neuroprotective function of aged and senescent astrocytes suggests that the p53 isoforms and their regulatory mechanisms are potential targets for therapeutic intervention in neurodegenerative diseases. PMID:27104929

  2. Inducing Alignment In Astrocyte Tissue Constructs By Surface Ligands Patterned On Biomaterials

    OpenAIRE

    Meng, Fanwei; Hlady, Vladimir; Tresco, Patrick A.

    2011-01-01

    Planar substrates with patterned ligands were used to induce astrocyte alignment whereas substrates with uniform fields of ligand were used to produce random cell orientation. DRG neurons plated on top of oriented astrocyte monolayers exhibited directional outgrowth along aligned astrocytes, demonstrating that purely biological cues provided by the oriented astrocytes were sufficient to provide guidance cues. Antibody blocking studies demonstrated that astrocyte associated FN played a major m...

  3. Connexin 43 stabilizes astrocytes in a stroke-like milieu to facilitate neuronal recovery

    OpenAIRE

    Wu, Le-yu; Yu, Xue-li; Feng, Lin-yin

    2015-01-01

    Aim: Connexin 43 (Cx43) is a member of connexin family mainly expressed in astrocytes, which forms gap junctions and hemichannels and maintains the normal shape and function of astrocytes. In this study we investigated the role of Cx43 in astrocytes in facilitating neuronal recovery during ischemic stroke. Methods: Primary culture of astrocytes or a mixed culture of astrocytes and cortical neurons was subjected to oxygen glucose deprivation and reperfusion (OGD/R). The expression of Cx43 and ...

  4. mGluR5 protect astrocytes from ischemic damage in postnatal CNS white matter

    OpenAIRE

    Vanzulli, Ilaria; Butt, Arthur M

    2015-01-01

    Astrocytes perform essential neuron-supporting functions in the central nervous system (CNS) and their disruption has devastating effects on neuronal integrity in multiple neuropathologies. Although astrocytes are considered resistant to most pathological insults, ischemia can result in astrocyte injury and astrocytes in postnatal white matter are particularly vulnerable. Metabotropic glutamate receptors (mGluR) are neuroprotective in ischemia and are widely expressed by astrocytes throughout...

  5. Response of transgenic poplar overexpressing cytosolic glutamine synthetase to phosphinothricin.

    Science.gov (United States)

    Pascual, María Belén; Jing, Zhong Ping; Kirby, Edward G; Cánovas, Francisco M; Gallardo, Fernando

    2008-01-01

    Glutamine synthetase (GS) is the main enzyme involved in ammonia assimilation in plants and is the target of phosphinothricin (PPT), an herbicide commonly used for weed control in agriculture. As a result of the inhibition of GS, PPT also blocks photorespiration, resulting in the depletion of leaf amino acid pools leading to the plant death. Hybrid transgenic poplar (Populus tremula x P. alba INRA clone 7171-B4) overexpressing cytosolic GS is characterized by enhanced vegetative growth [Gallardo, F., Fu, J., Cantón, F.R., García-Gutiérrez, A., Cánovas, F.M., Kirby, E.G., 1999. Expression of a conifer glutamine synthetase gene in transgenic poplar. Planta 210, 19-26; Fu, J., Sampalo, R., Gallardo, F., Cánovas, F.M., Kirby, E.G., 2003. Assembly of a cytosolic pine glutamine synthetase holoenzyme in leaves of transgenic poplar leads to enhanced vegetative growth in young plants. Plant Cell Environ. 26, 411-418; Jing, Z.P., Gallardo, F., Pascual, M.B., Sampalo, R., Romero, J., Torres de Navarra, A., Cánovas, F.M., 2004. Improved growth in a field trial of transgenic hybrid poplar overexpressing glutamine synthetase. New Phytol. 164, 137-145], increased photosynthetic and photorespiratory capacities [El-Khatib, R.T., Hamerlynck, E.P., Gallardo, F., Kirby, E.G., 2004. Transgenic poplar characterized by ectopic expression of a pine cytosolic glutamine synthetase gene exhibits enhanced tolerance to water stress. Tree Physiol. 24, 729-736], enhanced tolerance to water stress (El-Khatib et al., 2004), and enhanced nitrogen use efficiency [Man, H.-M., Boriel, R., El-Khatib, R.T., Kirby, E.G., 2005. Characterization of transgenic poplar with ectopic expression of pine cytosolic glutamine synthetase under conditions of varying nitrogen availability. New Phytol. 167, 31-39]. In vitro plantlets of GS transgenic poplar exhibited enhanced resistance to PPT when compared with non-transgenic controls. After 30 days exposure to PPT at an equivalent dose of 275 g ha(-1), growth

  6. Astrocytic beta(2)-adrenergic receptors: from physiology to pathology.

    Science.gov (United States)

    Laureys, Guy; Clinckers, Ralph; Gerlo, Sarah; Spooren, Anneleen; Wilczak, Nadine; Kooijman, Ron; Smolders, Ilse; Michotte, Yvette; De Keyser, Jacques

    2010-07-01

    Evidence accumulates for a key role of the beta(2)-adrenergic receptors in the many homeostatic and neuroprotective functions of astrocytes, including glycogen metabolism, regulation of immune responses, release of neurotrophic factors, and the astrogliosis that occurs in response to neuronal injury. A dysregulation of the astrocytic beta(2)-adrenergic-pathway is suspected to contribute to the physiopathology of a number of prevalent and devastating neurological conditions such as multiple sclerosis, Alzheimer's disease, human immunodeficiency virus encephalitis, stroke and hepatic encephalopathy. In this review we focus on the physiological functions of astrocytic beta(2)-adrenergic receptors, and their possible impact in disease states. PMID:20138112

  7. Contributions of Glycogen to Astrocytic Energetics during Brain Activation

    OpenAIRE

    Dienel, Gerald A.; Nancy F Cruz

    2014-01-01

    Glycogen is the major store of glucose in brain and is mainly in astrocytes. Brain glycogen levels in unstimulated, carefully-handled rats are 10-12 mol/g, and assuming that astrocytes account for half the brain mass, astrocytic glycogen content is twice as high. Glycogen turnover is slow under basal conditions, but it is mobilized during activation. There is no net increase in incorporation of label from glucose during activation, whereas label release from pre-labeled glycogen exceeds net g...

  8. Pyk2 is essential for astrocytes mobility following brain lesion

    OpenAIRE

    Giralt, Albert; Coura, Renata; Girault, Jean-Antoine

    2016-01-01

    Proline-rich tyrosine kinase 2 (Pyk2) is a calcium-dependent, non-receptor protein-tyrosine kinase of the focal adhesion kinase (FAK) family. Pyk2 is enriched in the brain, especially the forebrain. Pyk2 is highly expressed in neurons but is also present in astrocytes, where its role is not known. We used Pyk2 knockout mice (Pyk2−/−) developed in our laboratory to investigate the function of Pyk2 in astrocytes. Morphology and basic properties of astrocytes in vivo and in culture were not alte...

  9. Computational models of neuron-astrocyte interaction in epilepsy

    Directory of Open Access Journals (Sweden)

    Vladislav eVolman

    2012-08-01

    Full Text Available Astrocytes actively shape the dynamics of neurons and neuronal ensembles by affecting several aspects critical to neuronal function, such as regulating synaptic plasticity, modulating neuronal excitability and maintaining extracellular ion balance. These pathways for astrocyte-neuron interaction can also enhance the information-processing capabilities of brains, but in other circumstances may lead the brain on the road to pathological ruin. In this article, we review the existing computational models of astrocytic involvement in epileptogenesis, focusing on their relevance to existing physiological data.

  10. Astrocyte elevated gene-1 regulates astrocyte responses to neural injury: implications for reactive astrogliosis and neurodegeneration

    OpenAIRE

    Vartak-Sharma Neha; Ghorpade Anuja

    2012-01-01

    Abstract Background Reactive astrogliosis is a ubiquitous but poorly understood hallmark of central nervous system pathologies such as trauma and neurodegenerative diseases. In vitro and in vivo studies have identified proinflammatory cytokines and chemokines as mediators of astrogliosis during injury and disease; however, the molecular mechanism remains unclear. In this study, we identify astrocyte elevated gene-1 (AEG-1), a human immunodeficiency virus 1 or tumor necrosis factor α-inducible...

  11. Physiological hypercortisolemia increases proteolysis, glutamine, and alanine production

    International Nuclear Information System (INIS)

    Physiological elevations of plasma cortisol levels, as are encountered in stress and severe trauma, were produced in six normal subjects by infusing them with hydrocortisone for 64 h. Amino acid kinetics were measured in the postabsorptive state using three 4-h infusions of L-[1-13C]leucine, L-phenyl[2H5]phenylalanine, L-[2-15N]glutamine, and L-[1-13C]alanine tracers (1) before, (2) at 12 h, and (3) at 60 h of cortisol infusion. Before and throughout the study, the subjects ate a normal diet of adequate protein and energy intake. The cortisol infusion raised plasma cortisol levels significantly from 10 ± 1 to 32 ± 4 μg/dl, leucine flux from 83 ± 3 to 97 ± 3 μmol·kg-1·h-1, and phenylalanine flux from 34 ± 1 to 39 ± 1 (SE) μmol·kg-1·h-1 after 12 h of cortisol infusion. These increases were maintained until the cortisol infusion was terminated. These nearly identical 15% increases in two different essential amino acid appearance rates are reflective of increased whole body protein breakdown. Glutamine flux rose by 12 h of cortisol infusion and remained elevated at the same level at 64 h. The increase in flux was primarily due to a 55% increase in glutamine de novo synthesis. Alanine flux increased with acute hypercortisolemia and increased further at 60 h of cortisol infusion, a result primarily of increased alanine de novo synthesis. Insulin, alanine, and lactate plasma levels responded similarly with significant rises between the acute and chronic periods of cortisol infusion. Thus hypercortisolemia increases both protein breakdown and the turnover of important nonessential amino acids for periods of up to 64 h

  12. Physiological hypercortisolemia increases proteolysis, glutamine, and alanine production

    Energy Technology Data Exchange (ETDEWEB)

    Darmaun, D.; Matthews, D.E.; Bier, D.M. (Washington Univ. School of Medicine, St. Louis, MO (USA) Cornell Univ. Medical College, New York, NY (USA))

    1988-09-01

    Physiological elevations of plasma cortisol levels, as are encountered in stress and severe trauma, were produced in six normal subjects by infusing them with hydrocortisone for 64 h. Amino acid kinetics were measured in the postabsorptive state using three 4-h infusions of L-(1-{sup 13}C)leucine, L-phenyl({sup 2}H{sub 5})phenylalanine, L-(2-{sup 15}N)glutamine, and L-(1-{sup 13}C)alanine tracers (1) before, (2) at 12 h, and (3) at 60 h of cortisol infusion. Before and throughout the study, the subjects ate a normal diet of adequate protein and energy intake. The cortisol infusion raised plasma cortisol levels significantly from 10 {plus minus} 1 to 32 {plus minus} 4 {mu}g/dl, leucine flux from 83 {plus minus} 3 to 97 {plus minus} 3 {mu}mol{center dot}kg{sup {minus}1}{center dot}h{sup {minus}1}, and phenylalanine flux from 34 {plus minus} 1 to 39 {plus minus} 1 (SE) {mu}mol{center dot}kg{sup {minus}1}{center dot}h{sup {minus}1} after 12 h of cortisol infusion. These increases were maintained until the cortisol infusion was terminated. These nearly identical 15% increases in two different essential amino acid appearance rates are reflective of increased whole body protein breakdown. Glutamine flux rose by 12 h of cortisol infusion and remained elevated at the same level at 64 h. The increase in flux was primarily due to a 55% increase in glutamine de novo synthesis. Alanine flux increased with acute hypercortisolemia and increased further at 60 h of cortisol infusion, a result primarily of increased alanine de novo synthesis. Insulin, alanine, and lactate plasma levels responded similarly with significant rises between the acute and chronic periods of cortisol infusion. Thus hypercortisolemia increases both protein breakdown and the turnover of important nonessential amino acids for periods of up to 64 h.

  13. Astrocytic tracer dynamics estimated from [1-11C]-acetate PET measurements

    DEFF Research Database (Denmark)

    Arnold, Andrea; Calvetti, Daniela; Gjedde, Albert;

    2014-01-01

    We address the problem of estimating the unknown parameters of a model of tracer kinetics from sequences of positron emission tomography (PET) scan data using a statistical sequential algorithm for the inference of magnitudes of dynamic parameters. The method, based on Bayesian statistical...... of [1-11C]-acetate-derived tracer accumulation, estimating the transport rates in a three-compartment model of astrocytic uptake and metabolism of the tracer for a cohort of 18 volunteers from 3 groups, corresponding to healthy control individuals, cirrhotic liver and hepatic encephalopathy patients...

  14. Intercellular synchronization of diffusively coupled astrocytes

    CERN Document Server

    Alam, Md Jahoor; Devi, Gurumayum Reenaroy; Singh, Heisnam Dinachandra; Singh, R K Brojen; Sharma, B Indrajit

    2010-01-01

    We examine the synchrony of the dynamics of localized [Ca^{2+}]_i oscillations in internal pool of astrocytes via diffusing coupling of a network of such cells in a certain topology where cytosolic Ca^{2+} and inositol 1,4,5-triphosphate (IP3) are coupling molecules; and possible long range interaction among the cells. Our numerical results claim that the cells exhibit fairly well coordinated behaviour through this coupling mechanism. It is also seen in the results that as the number of coupling molecular species is increased, the rate of synchrony is also increased correspondingly. Apart from the topology of the cells taken, as the number of coupled cells around any one of the cells in the system is increased, the cell process information faster.

  15. Astrocyte and Oligodendrocyte Connexins of the Glial Syncytium in Relation to Astrocyte Anatomical Domains and Spatial Buffering

    OpenAIRE

    NAGY, JAMES I.; Rash, John E.

    2003-01-01

    Astroctyes express a set of three connexins (Cx26, Cx30, and Cx43) that are contained in astrocyte-to-astrocyte (A/A) gap junctions; oligodendrocytes express a different set of three connexins (Cx29, Cx32, and Cx47) that are contained in the oligodendrocyte side of necessarily heterotypic astrocyte-to-oligodendrocyte (A/O) gap junctions, and there is little ultrastructural evidence for gap junction formation between individual oligodendrocytes. In addition, primarily Cx29 and Cx32 are contain...

  16. Regulation of Amidase Formation in Mutants from Pseudomonas aeruginosa PAO Lacking Glutamine Synthetase Activity

    NARCIS (Netherlands)

    Janssen, Dick B.; Herst, Patricia M.; Joosten, Han M.L.J.; Drift, Chris van der

    1982-01-01

    The formation of amidase was studied in mutants from Pseudomonas aeruginosa PAO lacking glutamine synthetase activity. It appeared that catabolite repression of amidase synthesis by succinate was partially relieved when cellular growth was limited by glutamine. Under these conditions, a correlation

  17. Cysteine digestive peptidases function as post-glutamine cleaving enzymes in tenebrionid stored product pests

    Science.gov (United States)

    Cereals have storage proteins with high amounts of the amino acids glutamine and proline. Therefore, storage pests need to have digestive enzymes that are efficient in hydrolyzing these types of proteins. Post-glutamine cleaving peptidases (PGP) were isolated from the midgut of the stored product pe...

  18. Encapsulation of glutamine synthetase in mouse erythrocytes: a new procedure for ammonia detoxification.

    Science.gov (United States)

    Kosenko, Elena A; Venediktova, Natalia I; Kudryavtsev, Andrey A; Ataullakhanov, Fazoil I; Kaminsky, Yury G; Felipo, Vicente; Montoliu, Carmina

    2008-12-01

    There are a number of pathological situations in which ammonia levels increase leading to hyperammonemia, which may cause neurological alterations and can lead to coma and death. Currently, there are no efficient treatments allowing rapid and sustained decrease of ammonia levels in these situations. A way to increase ammonia detoxification would be to increase its incorporation in glutamine by glutamine synthetase. The aim of this work was to develop a procedure to encapsulate glutamine synthetase in mouse erythrocytes and to assess whether administration of these erythrocytes containing glutamine synthetase (GS) reduce ammonia levels in hyperammonemic mice. The procedure developed allowed the encapsulation of 3 +/- 0.25 IU of GS / mL of erythrocytes with a 70% cell recovery. Most metabolites, including ATP, remained unaltered in glutamine synthetase-loaded erythrocytes (named ammocytes by us) compared with native erythrocytes. The glutamine synthetase-loaded ammocytes injected in mice survived and retained essentially all of their glutamine synthetase activity for at least 48 h in vivo. Injection of these ammocytes into hyperammonemic mice reduced ammonia levels in the blood by about 50%. The results reported indicate that ammocytes are able to keep their integrity, normal energy metabolism, the inserted glutamine synthetase activity, and can be useful to reduce ammonia levels in hyperammonemic situations. PMID:19088795

  19. Reducing the serine availability complements the inhibition of the glutamine metabolism to block leukemia cell growth

    Science.gov (United States)

    Polet, Florence; Corbet, Cyril; Pinto, Adan; Rubio, Laila Illan; Martherus, Ruben; Bol, Vanesa; Drozak, Xavier; Grégoire, Vincent; Riant, Olivier; Feron, Olivier

    2016-01-01

    Leukemia cells are described as a prototype of glucose-consuming cells with a high turnover rate. The role of glutamine in fueling the tricarboxylic acid cycle of leukemia cells was however recently identified confirming its status of major anaplerotic precursor in solid tumors. Here we examined whether glutamine metabolism could represent a therapeutic target in leukemia cells and whether resistance to this strategy could arise. We found that glutamine deprivation inhibited leukemia cell growth but also led to a glucose-independent adaptation maintaining cell survival. A proteomic study revealed that glutamine withdrawal induced the upregulation of phosphoglycerate dehydrogenase (PHGDH) and phosphoserine aminotransferase (PSAT), two enzymes of the serine pathway. We further documented that both exogenous and endogenous serine were critical for leukemia cell growth and contributed to cell regrowth following glutamine deprivation. Increase in oxidative stress upon inhibition of glutamine metabolism was identified as the trigger of the upregulation of PHGDH. Finally, we showed that PHGDH silencing in vitro and the use of serine-free diet in vivo inhibited leukemia cell growth, an effect further increased when glutamine metabolism was blocked. In conclusion, this study identified serine as a key pro-survival actor that needs to be handled to sensitize leukemia cells to glutamine-targeting modalities. PMID:26625201

  20. {open_quotes}The effects of diabetes on the activity of the enzyme glutamine: fructose-6-phosphate amindotransferase{close_quotes}

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, S.P.

    1994-12-31

    Hexsoamine synthetic pathway (HexNSP) controls the supply of essential substrates for glycoprotein synthesis. In vitro studies suggest that increased flux of glucose via the hexsoamine synthetic pathway may play a role in glucose induced insulin resistance of glucose transport. Glutamine: fructose-6-phosphate amindotransferase (GFAT) controls flux into the hexsoamine synthetic pathway; the major products are UDPN-acetylhexosamines (UDP.HexNac=UDP.GlcNAc= UDP.GalNac). I examined whether diabetes ({approximately} 7 days post intravenous streptozotocin, and genetically linked) affects the activity of glutamine: fructose-6-phosphate in rat and mouse skeletal muscle in vivo. Nucleotide linked HexNAc were analyzed by high pressure liquid chromatography(HPLC) in deproteinized hind limb muscle extracts.

  1. Redefining the role of metallothionein within the injured brain: extracellular metallothioneins play an important role in the astrocyte-neuron response to injury

    DEFF Research Database (Denmark)

    Chung, Roger S; Penkowa, Milena; Dittmann, Justin;

    2008-01-01

    A number of intracellular proteins that are protective after brain injury are classically thought to exert their effect within the expressing cell. The astrocytic metallothioneins (MT) are one example and are thought to act via intracellular free radical scavenging and heavy metal regulation, and......-dependent axonal regeneration. First, we show that MT can be detected within the extracellular fluid of the injured brain, and that cultured astrocytes are capable of actively secreting MT in a regulatable manner. Second, we identify a receptor, megalin, that mediates MT transport into neurons. Third, we directly...

  2. Astrocyte regulation of sleep circuits: experimental and modeling perspectives

    Directory of Open Access Journals (Sweden)

    Tommaso eFellin

    2012-08-01

    Full Text Available Integrated within neural circuits, astrocytes have recently been shown to modulate brain rhythms thought to mediate sleep function. Experimental evidence suggests that local impact of astrocytes on single synapses translates into global modulation of neuronal networks and behavior. We discuss these findings in the context of current conceptual models of sleep generation and function, each of which have historically focused on neural mechanisms. We highlight the implications and the challenges introduced by these results from a conceptual and computational perspective. We further provide modeling directions on how these data might extend our knowledge of astrocytic properties and sleep function. Given our evolving understanding of how local cellular activities during sleep lead to functional outcomes for the brain, further mechanistic and theoretical understanding of astrocytic contribution to these dynamics will undoubtedly be of great basic and translational benefit.

  3. Overexpression of Eg5 correlates with high grade astrocytic neoplasm.

    Science.gov (United States)

    Liu, Liqiong; Liu, Xichun; Mare, Marcus; Dumont, Aaron S; Zhang, Haitao; Yan, Dong; Xiong, Zhenggang

    2016-01-01

    To investigate the relationship between Eg5 and histopathological grade of astrocytoma, Eg5 expression was evaluated by immunohistochemical examination on 88 specimens including 25 cases of glioblastoma (WHO grade IV), 22 cases of anaplastic astrocytoma (WHO grade III), 20 cases of diffuse astrocytoma (WHO grade II), and 21 cases of pilocytic astrocytoma (WHO grade I). The histopathological characteristics and Eg5 expression level of each tumor were assessed and statistically analyzed. Astrocytic tumors exhibited significant correlation of expression of Eg5 with higher WHO histopathological grades (p astrocytoma, 6-36% (mean 18.60%) of neoplastic cells in diffuse astrocytoma, and 2-28% (mean 13.48%) of neoplastic cells in pilocytic astrocytoma. In conclusion, overexpression of Eg5 associates with high-grade astrocytic neoplasm, and it may represent an independent diagnostic and prognostic factor in grading astrocytic tumors and predicting prognosis of astrocytic tumor patients. PMID:26456023

  4. Oxidative metabolism of astrocytes is not reduced in hepatic encephalopathy

    DEFF Research Database (Denmark)

    Iversen, Peter; Mouridsen, Kim; Hansen, Mikkel Bo;

    2014-01-01

    In patients with impaired liver function and hepatic encephalopathy (HE), consistent elevations of blood ammonia concentration suggest a crucial role in the pathogenesis of HE. Ammonia and acetate are metabolized in brain both primarily in astrocytes. Here, we used dynamic [(11)C]acetate PET of the...... brain to measure the contribution of astrocytes to the previously observed reduction of brain oxidative metabolism in patients with liver cirrhosis and HE, compared to patients with cirrhosis without HE, and to healthy subjects. We used a new kinetic model to estimate uptake from blood to astrocytes and...... astrocyte metabolism of [(11)C]acetate. No significant differences of the rate constant of oxidation of [(11)C]acetate (k 3) were found among the three groups of subjects. The net metabolic clearance of [(11)C]acetate from blood was lower in the group of patients with cirrhosis and HE than in the group of...

  5. Astrocytes mediate synapse elimination through MEGF10 and MERTK pathways

    Science.gov (United States)

    Chung, Won-Suk; Clarke, Laura E.; Wang, Gordon X.; Stafford, Benjamin K.; Sher, Alexander; Chakraborty, Chandrani; Joung, Julia; Foo, Lynette C.; Thompson, Andrew; Chen, Chinfei; Smith, Stephen J.; Barres, Ben A.

    2013-12-01

    To achieve its precise neural connectivity, the developing mammalian nervous system undergoes extensive activity-dependent synapse remodelling. Recently, microglial cells have been shown to be responsible for a portion of synaptic pruning, but the remaining mechanisms remain unknown. Here we report a new role for astrocytes in actively engulfing central nervous system synapses. This process helps to mediate synapse elimination, requires the MEGF10 and MERTK phagocytic pathways, and is strongly dependent on neuronal activity. Developing mice deficient in both astrocyte pathways fail to refine their retinogeniculate connections normally and retain excess functional synapses. Finally, we show that in the adult mouse brain, astrocytes continuously engulf both excitatory and inhibitory synapses. These studies reveal a novel role for astrocytes in mediating synapse elimination in the developing and adult brain, identify MEGF10 and MERTK as critical proteins in the synapse remodelling underlying neural circuit refinement, and have important implications for understanding learning and memory as well as neurological disease processes.

  6. Saturable Leptin Transport Across the BBB Persists in EAE Mice

    OpenAIRE

    Hsuchou, Hung; Pramod K. Mishra; Kastin, Abba J; Wu, Xiaojun; Wang, Yuping; Ouyang, Suidong; Pan, Weihong

    2013-01-01

    We have shown that mice with experimental autoimmune encephalomyelitis (EAE), a model of multiple sclerosis, have upregulated leptin receptor expression in reactive astrocytes of the hippocampus, a region involved in sickness behavior. Leptin can exacerbate EAE when its serum concentration is high. Although leptin receptors in astrocytes modulate leptin transport across cultured endothelial cell monolayers, it is not known how leptin transport in EAE mice is regulated. Here, we determined bra...

  7. Influence of glutamine on the effect of resistance exercise on cardiac ANP in rats

    Directory of Open Access Journals (Sweden)

    Romeu Rodrigues de Souza

    2015-03-01

    Full Text Available Various nutritional supplements (herbs, vitamins, and micronutrients improve responses and adaptations to resistance exercise. ANP is a heart hormone that contributes to fluid, electrolyte and blood pressure homeostasis through its natriuretic and vasodilative actions. In the present study, the adaptation of ANP in response to resistance exercise was investigated in rats supplemented with glutamine for five weeks. The results showed that supplementation with glutamine did not influence the number of ANP granules per atrial cardiocyte in sedentary animals. In exercised-trained rats, the number and diameter of the granules was significantly higher in comparison with the control group and in exercised animals supplemented with glutamine there was significant increase in the number and diameter of ANP granules compared with controls. Altogether, these data indicated that in resistance exercise rats, glutamine significantly enhances cardiac ANP thus implicating the beneficial effects of glutamine supplementation to the ANP system.

  8. Lack of cardioprotection from metabolic support with glutamine or glutamate in a porcine coronary occlusion model

    DEFF Research Database (Denmark)

    Kristensen, Jens; Mæng, Michael; Mortensen, Ulrik;

    2005-01-01

    OBJECTIVE: Previous experimental studies indicate that glutamine or glutamate may provide cardioprotection by improving the oxidative metabolism in myocardial ischemia. We investigated the effect of glutamine or glutamate, given during reperfusion, on resulting infarct size and hemodynamic recovery...... outcome measures were the hemodynamic variables. RESULTS: The infarct sizes as a proportion of the area at risk (mean+/-SD) were: control group, 0.64 +/- 0.19 (n = 9); glutamine group, 0.87 +/- 0.07 (p < 0.05 vs control group) (n = 8); glutamate group, 0.72 +/- 0.11 (n = 9). Glutamine increased systemic...... vascular resistance, while glutamate preserved cardiac output during infusion. CONCLUSION: Substrate supplementation with the anaplerotic precursors glutamine and glutamate is ineffective as adjunctive therapy for severe myocardial ischemia. Beneficial effects documented in less complex experimental...

  9. Key Roles of Glutamine Pathways in Reprogramming the Cancer Metabolism

    Science.gov (United States)

    Michalak, Krzysztof Piotr; Maćkowska-Kędziora, Agnieszka; Sobolewski, Bogusław; Woźniak, Piotr

    2015-01-01

    Glutamine (GLN) is commonly known as an important metabolite used for the growth of cancer cells but the effects of its intake in cancer patients are still not clear. However, GLN is the main substrate for DNA and fatty acid synthesis. On the other hand, it reduces the oxidative stress by glutathione synthesis stimulation, stops the process of cancer cachexia, and nourishes the immunological system and the intestine epithelium, as well. The current paper deals with possible positive effects of GLN supplementation and conditions that should be fulfilled to obtain these effects. The analysis of GLN metabolism suggests that the separation of GLN and carbohydrates in the diet can minimize simultaneous supply of ATP (from glucose) and NADPH2 (from glutamine) to cancer cells. It should support to a larger extent the organism to fight against the cancer rather than the cancer cells. GLN cannot be considered the effective source of ATP for cancers with the impaired oxidative phosphorylation and pyruvate dehydrogenase inhibition. GLN intake restores decreased levels of glutathione in the case of chemotherapy and radiotherapy; thus, it facilitates regeneration processes of the intestine epithelium and immunological system. PMID:26583064

  10. Galunisertib inhibits glioma vasculogenic mimicry formation induced by astrocytes

    OpenAIRE

    Chao Zhang; Wenliang Chen; Xin Zhang; Bin Huang; Aanjing Chen; Ying He; Jian Wang; Xingang Li

    2016-01-01

    Gliomas are among the most lethal primary brain tumors found in humans. In high-grade gliomas, vasculogenic mimicry is often detected and has been correlated with prognosis, thus suggesting its potential as a therapeutic target. Vasculogenic mimicry mainly forms vascular-like channels independent of endothelial cells; however, little is known about the relationship between astrocytes and vasculogenic mimicry. In our study, we demonstrated that the presence of astrocytes promoted vasculogenic ...

  11. Astrocytes as therapeutic targets of estrogenic compounds following brain injuries

    Directory of Open Access Journals (Sweden)

    George E. Barreto

    2015-03-01

    Full Text Available For decades, astrocytes have been considered to be non-excitable support cells that are relatively resistant to brain injury. This view has changed radically during the past twenty years. Multiple essential functions are performed by astrocytes in normal brain. Astrocytes are dynamically involved in synaptic transmission, metabolic and ionic homeostasis, and inflammatory maintenance of the blood brain barrier. Advances in our understanding of astrocytes include new observations about their structure, organization, and function. Astrocytes play an active and important role in the pathophysiology of brain damage. Brain injury impairs mitochondrial function and this is accompanied by increased oxidative stress, leading to prominent astrogliosis, which involves changes in gene expression and morphology, and therefore glial scar formation. Recent works have demonstrated a protective role of reactive astrocytes after brain injury. Nevertheless, others have pointed to an inhibitory role of astrocytes in axonal regeneration after injury. Reactive astrogliosis is a complex phenomenon that includes a mixture of positive and negative responses for neuronal survival and regeneration. Reactive astroglia maintains the integrity of the blood-brain barrier and the survival of the perilesional tissue, but may prevent axonal and damaged tissue regeneration. Neuroprotective strategies aiming at reducing gliosis and enhance brain plasticity are of potential interest for translational neuroscience research in brain injuries. In this context, neurosteroids have shown to be a promising strategy to protect brain against injury, as their effects may rely on reducing gliosis, brain inflammation and potentially modulating recovery from brain injury by engaging mechanisms of neural plasticity. In conclusion, in this work we will consider particularly the two-edged sword role of reactive astrocytes, which is an experimental paradigm helpful in discriminating destructive

  12. Recent molecular approaches to understanding astrocyte function in vivo

    OpenAIRE

    Fiacco, Todd A.; Cendra Agulhon

    2013-01-01

    Astrocytes are a predominant glial cell type in the nervous systems, and are becoming recognized as important mediators of normal brain function as well as neurodevelopmental, neurological, and neurodegenerative brain diseases. Although numerous potential mechanisms have been proposed to explain the role of astrocytes in the normal and diseased brain, research into the physiological relevance of these mechanisms in vivo is just beginning. In this review, we will summarize recent developments ...

  13. Computational models of neuron-astrocyte interaction in epilepsy

    OpenAIRE

    Vladislav Volman; Maxim Bazhenov; Sejnowski, Terrence J.

    2012-01-01

    Astrocytes actively shape the dynamics of neurons and neuronal ensembles by affecting several aspects critical to neuronal function, such as regulating synaptic plasticity, modulating neuronal excitability, and maintaining extracellular ion balance. These pathways for astrocyte-neuron interaction can also enhance the information-processing capabilities of brains, but in other circumstances may lead the brain on the road to pathological ruin. In this article, we review the existing computation...

  14. Neuroinflammation alters voltage-dependent conductance in striatal astrocytes

    OpenAIRE

    Karpuk, Nikolay; Burkovetskaya, Maria; Kielian, Tammy

    2012-01-01

    Neuroinflammation has the capacity to alter normal central nervous system (CNS) homeostasis and function. The objective of the present study was to examine the effects of an inflammatory milieu on the electrophysiological properties of striatal astrocyte subpopulations with a mouse bacterial brain abscess model. Whole cell patch-clamp recordings were performed in striatal glial fibrillary acidic protein (GFAP)-green fluorescent protein (GFP)+ astrocytes neighboring abscesses at postinfection ...

  15. A Mathematical Model of Tripartite Synapse: Astrocyte Induced Synaptic Plasticity

    OpenAIRE

    Tewari, Shivendra; Majumdar, Kaushik

    2011-01-01

    In this paper we present a biologically detailed mathematical model of tripartite synapses, where astrocytes modulate short-term synaptic plasticity. The model consists of a pre-synaptic bouton, a post-synaptic dendritic spine-head, a synaptic cleft and a peri-synaptic astrocyte controlling Ca2+ dynamics inside the synaptic bouton. This in turn controls glutamate release dynamics in the cleft. As a consequence of this, glutamate concentration in the cleft has been modeled, in which glutamate ...

  16. The astrocyte as a gatekeeper of synaptic information transfer

    OpenAIRE

    Volman, Vladislav; Ben-Jacob, Eshel; Levine, Herbert

    2006-01-01

    We present a simple biophysical model for the coupling between synaptic transmission and the local calcium concentration on an enveloping astrocytic domain. This interaction enables the astrocyte to modulate the information flow from presynaptic to postsynaptic cells in a manner dependent on previous activity at this and other nearby synapses. Our model suggests a novel, testable hypothesis for the spike timing statistics measured for rapidly-firing cells in culture experiments.

  17. Information Transmission in a Neuron-Astrocyte Coupled Model

    OpenAIRE

    Tang, Jun; Luo, Jin-Ming; Ma, Jun

    2013-01-01

    A coupled model containing two neurons and one astrocyte is constructed by integrating Hodgkin-Huxley neuronal model and Li-Rinzel calcium model. Based on this hybrid model, information transmission between neurons is studied numerically. Our results show that when the successive spikes are produced in neuron 1 (N1), the bursting-like spikes (BLSs) occur in two neurons simultaneously during the spikes being transferred to neuron 2 (N2). The existence of the astrocyte and a higher expression l...

  18. Astrocyte regulation of sleep circuits: experimental and modeling perspectives

    OpenAIRE

    Tommaso eFellin; Jeffrey M Ellenbogen; Maurizio eDe Pittà; Eshel eBen-Jacob; Michael M Halassa

    2012-01-01

    Integrated within neural circuits, astrocytes have recently been shown to modulate brain rhythms thought to mediate sleep function. Experimental evidence suggests that local impact of astrocytes on single synapses translates into global modulation of neuronal networks and behavior. We discuss these findings in the context of current conceptual models of sleep generation and function, each of which have historically focused on neural mechanisms. We highlight the implications and the challenges...

  19. Astrocytes Directly Influence Tumor Cell Invasion and Metastasis In Vivo

    OpenAIRE

    Wang, Ling; Cossette, Stephanie M.; Rarick, Kevin R.; Gershan, Jill; Michael B Dwinell; Harder, David R.; Ramchandran, Ramani

    2013-01-01

    Brain metastasis is a defining component of tumor pathophysiology, and the underlying mechanisms responsible for this phenomenon are not well understood. Current dogma is that tumor cells stimulate and activate astrocytes, and this mutual relationship is critical for tumor cell sustenance in the brain. Here, we provide evidence that primary rat neonatal and adult astrocytes secrete factors that proactively induced human lung and breast tumor cell invasion and metastasis capabilities. Among wh...

  20. Group B streptococcal infection and activation of human astrocytes.

    Directory of Open Access Journals (Sweden)

    Terri D Stoner

    Full Text Available Streptococcus agalactiae (Group B Streptococcus, GBS is the leading cause of life-threatening meningitis in human newborns in industrialized countries. Meningitis results from neonatal infection that occurs when GBS leaves the bloodstream (bacteremia, crosses the blood-brain barrier (BBB, and enters the central nervous system (CNS, where the bacteria contact the meninges. Although GBS is known to invade the BBB, subsequent interaction with astrocytes that physically associate with brain endothelium has not been well studied.We hypothesize that human astrocytes play a unique role in GBS infection and contribute to the development of meningitis. To address this, we used a well- characterized human fetal astrocyte cell line, SVG-A, and examined GBS infection in vitro. We observed that all GBS strains of representative clinically dominant serotypes (Ia, Ib, III, and V were able to adhere to and invade astrocytes. Cellular invasion was dependent on host actin cytoskeleton rearrangements, and was specific to GBS as Streptococcus gordonii failed to enter astrocytes. Analysis of isogenic mutant GBS strains deficient in various cell surface organelles showed that anchored LTA, serine-rich repeat protein (Srr1 and fibronectin binding (SfbA proteins all contribute to host cell internalization. Wild-type GBS also displayed an ability to persist and survive within an intracellular compartment for at least 12 h following invasion. Moreover, GBS infection resulted in increased astrocyte transcription of interleukin (IL-1β, IL-6 and VEGF.This study has further characterized the interaction of GBS with human astrocytes, and has identified the importance of specific virulence factors in these interactions. Understanding the role of astrocytes during GBS infection will provide important information regarding BBB disruption and the development of neonatal meningitis.

  1. A Common Progenitor for Retinal Astrocytes and Oligodendrocytes

    OpenAIRE

    Rompani, Santiago B.; Cepko, Constance L.

    2010-01-01

    Developing neural tissue undergoes a period of neurogenesis followed by a period of gliogenesis. The lineage relationships among glial cell types have not been defined for most areas of the nervous system. Here we use retroviruses to label clones of glial cells in the chick retina. We found that almost every clone had both astrocytes and oligodendrocytes. In addition, we discovered a novel glial cell type, with features intermediate between those of astrocytes and oligodendrocytes, which we h...

  2. P2X7 receptor activation in rat brain cultured astrocytes increases the biosynthetic release of cysteinyl leukotrienes.

    Science.gov (United States)

    Ballerini, P; Ciccarelli, R; Caciagli, F; Rathbone, M P; Werstiuk, E S; Traversa, U; Buccella, S; Giuliani, P; Jang, S; Nargi, E; Visini, D; Santavenere, C; Di Iorio, P

    2005-01-01

    Astrocytes have been recognized as important elements in controlling inflammatory as well as immune processes in the central nervous system (CNS). Recently, glial cells have been shown to produce cysteinyl leukotrienes (CysLTs) which are known lipid mediators of inflammation and whose extracellular concentrations rise under different pathological conditions in the brain. In the same conditions also extracellular concentrations of ATP dramatically increase reaching levels able to activate P2X7 ionotropic receptors for which an emerging role in neuroinflammation and neurodegeneration has been claimed. RTPCR analysis showed that primary cultures of rat brain astrocytes express P2X7 receptors. Application of the selective P2X7 agonist benzoyl benzoly ATP (BzATP) markedly increased [Ca2+]i which was mediated by a calcium influx from the extracellular milieu. The P2X7 antagonist, oATP, suppressed the BzATP-induced calcium increase. Consistent with the evidence that increased calcium levels activate the leukotriene biosynthetic pathway, challenge of astrocytes with either the calcium ionophore A23187 or BzATP significantly increased CysLT production and the cell pre-treatment with EGTA abolished these effects. Again the P2X7 antagonist prevented the BzATP-mediated CysLT efflux, whereas the astrocyte pretreatment with MK-571, a CysLT1 receptor antagonist, was ineffective. The astrocyte pre-treatment with a cocktail of inhibitors of ATP binding cassette (ABC) proteins reduced the BzATP-mediated CysLT production confirming that ABC transporters are involved in the release of CysLTs. The astrocyte P2X7- evoked rise of CysLT efflux was abolished in the presence of MK-886, an inhibitor of 5-lipoxygenase activating protein (FLAP) whose expression, along with that of 5-lipoxygenase (5-LO) was reported by Northern Blot analysis. The stimulation of P2X7 induced an up-regulation of FLAPmRNA that was reduced by the antagonist oATP. These data suggest that in rat brain cultured

  3. Astrocytes, Synapses and Brain Function: A Computational Approach

    Science.gov (United States)

    Nadkarni, Suhita

    2006-03-01

    Modulation of synaptic reliability is one of the leading mechanisms involved in long- term potentiation (LTP) and long-term depression (LTD) and therefore has implications in information processing in the brain. A recently discovered mechanism for modulating synaptic reliability critically involves recruitments of astrocytes - star- shaped cells that outnumber the neurons in most parts of the central nervous system. Astrocytes until recently were thought to be subordinate cells merely participating in supporting neuronal functions. New evidence, however, made available by advances in imaging technology has changed the way we envision the role of these cells in synaptic transmission and as modulator of neuronal excitability. We put forward a novel mathematical framework based on the biophysics of the bidirectional neuron-astrocyte interactions that quantitatively accounts for two distinct experimental manifestation of recruitment of astrocytes in synaptic transmission: a) transformation of a low fidelity synapse transforms into a high fidelity synapse and b) enhanced postsynaptic spontaneous currents when astrocytes are activated. Such a framework is not only useful for modeling neuronal dynamics in a realistic environment but also provides a conceptual basis for interpreting experiments. Based on this modeling framework, we explore the role of astrocytes for neuronal network behavior such as synchrony and correlations and compare with experimental data from cultured networks.

  4. Metabolic aspects of Neuronal – Oligodendrocytic - Astrocytic (NOA interactions

    Directory of Open Access Journals (Sweden)

    Ana I Amaral

    2013-05-01

    Full Text Available Whereas astrocytes have been in the limelight on the metabolic glucose interaction scene for a while, oligodendrocytes are still waiting for a place. We would like to call oligodendrocyte interaction with astrocytes and neurons: NOA (neuron – oligodendrocyte – astrocyte interactions. One of the reasons to find out more about oligodendrocyte interaction with neurons and astrocytes is to detect markers of healthy oligodendrocyte metabolism, to be used in diagnosis and treatment assessment in diseases such as Perinatal hypoxic-ischemic encephalopathy and multiple sclerosis in which oligodendrocyte function is impaired, possibly due to glutamate toxicity. Glutamate receptors are expressed in oligodendrocytes and also vesicular glutamate release in the white matter has received considerable attention. It is also important to establish if the glial precursor cells recruited to damaged areas are developing oligodendrocyte characteristics or those of astrocytes. Thus, it is important to study astrocytes and oligodendrocytes separately to be able to differentiate between them. This is of particular importance in the white matter where the number of oligodendrocytes is considerable. The present review summarizes the not very extensive information published on glucose metabolism in oligodendrocytes in an attempt to stimulate research into this important field.

  5. Inositol phospholipid hydrolysis in cultured astrocytes and oligodendrocytes

    International Nuclear Information System (INIS)

    Cultures of astrocytes and oligodendrocytes were prelabeled with 3H-inositol and the accumulation of 3H-inositol phosphates was determined following stimulation with a number of neuroactive substances. In astrocytes, norepinephrine (NE) produced the greatest stimulation with significant increase also observed with bradykinin. In oligodendrocytes, the greatest stimulation was produced by carbachol with significant increase also produced by bradykinin, histamine and NE. Carbachol was found to be ineffective in producing stimulation in astrocytes. The accumulation of 3H-inositol phosphates in astrocytes in response to NE was found to be dependent on the presence of Li+. The NE stimulation in astrocytes was dose-dependent and had an EC50 of 1.2 μM. This stimulation was blocked by the low concentration of the α1-adrenergic antagonist prazosin but not by the α2-adrenergic antagonist yohimbine. The NE-stimulated accumulation of 3H-inositol phosphates in astrocytes was inhibited by the cyclic nucleotide phosphodiesterase inhibitor isobutylmethylxanthine as well as by the cAMP analog dibutyryl cAMP. 34 references, 4 figures, 4 tables

  6. Reduced tonic inhibition in striatal output neurons from Huntington mice due to loss of astrocytic GABA release through GAT-3

    Directory of Open Access Journals (Sweden)

    Anna Maria Wójtowicz

    2013-11-01

    Full Text Available The extracellular concentration of the two main neurotransmitters glutamate and GABA is low but not negligible which enables a number of tonic actions. The effects of ambient GABA vary in a region-, cell-type and age-dependent manner and can serve as indicators of disease-related alterations. Here we explored the tonic inhibitory actions of GABA in Huntington's disease (HD. HD is a devastating neurodegenerative disorder caused by a mutation in the huntingtin gene. Whole cell patch clamp recordings from striatal output neurons (SONs in slices from adult wild type mice and two mouse models of HD (Z_Q175_KI homozygotes or R6/2 heterozygotes revealed an HD-related reduction of the GABA(A receptor-mediated tonic chloride current (ITonic(GABA along with signs of reduced GABA(B receptor-mediated presynaptic depression of synaptic GABA release. About half of ITonic(GABA depended on tetrodotoxin-sensitive synaptic GABA release, but the remaining current was still lower in HD. Both in WT and HD, ITonic(GABA was more prominent during the first four hours after preparing the slices, when astrocytes but not neurons exhibited a transient depolarization. All further tests were performed within 1 to 4 h in vitro. Experiments with SNAP5114, a blocker of the astrocytic GABA transporter GAT-3, suggest that in WT but not HD GAT-3 operated in the releasing mode. Application of a transportable substrate for glutamate transporters (D-aspartate 0.1 - 1 mM restored the non-synaptic GABA release in slices from HD mice. ITonic(GABA was also rescued by applying the hyperagonist gaboxadol (0.33 µM. The results lead to the hypothesis that lesion-induced astrocyte depolarization facilitates nonsynaptic release of GABA through GAT-3. However, the capacity of depolarized astrocytes to provide GABA for tonic inhibition is strongly reduced in HD.

  7. Deletion of oligodendrocyte Cx32 and astrocyte Cx43 causes white matter vacuolation, astrocyte loss and early mortality

    OpenAIRE

    Magnotti, Laura M.; Goodenough, Daniel A.; Paul, David L.

    2011-01-01

    CNS glia exhibit a variety of gap junctional interactions: between neighboring astrocytes, between neighboring oligodendrocytes, between astrocytes and oligodendrocytes, and as ‘reflexive’ structures between layers of myelin in oligodendrocytes. Together, these junctions are thought to form a network facilitating absorption and removal of extracellular K+ released during neuronal activity. In mice, loss of the two major oligodendrocyte connexins causes severe demyelination and early mortality...

  8. Freshly dissociated mature hippocampal astrocytes exhibit passive membrane conductance and low membrane resistance similarly to syncytial coupled astrocytes

    OpenAIRE

    Du, Yixing; Ma, Baofeng; Kiyoshi, Conrad M.; Alford, Catherine C.; Wang, Wei; Zhou, Min

    2015-01-01

    Mature astrocytes exhibit a linear current-to-voltage K+ membrane conductance (passive conductance) and an extremely low membrane resistance (Rm) in situ. The combination of these electrophysiological characteristics establishes a highly negative and stable membrane potential that is essential for basic functions, such as K+ spatial buffering and neurotransmitter uptake. However, astrocytes are coupled extensively in situ. It remains to be determined whether the observed passive behavior and ...

  9. Hyperglycaemia and diabetes impair gap junctional communication among astrocytes

    Directory of Open Access Journals (Sweden)

    Gautam K Gandhi

    2010-03-01

    Full Text Available Sensory and cognitive impairments have been documented in diabetic humans and animals, but the pathophysiology of diabetes in the central nervous system is poorly understood. Because a high glucose level disrupts gap junctional communication in various cell types and astrocytes are extensively coupled by gap junctions to form large syncytia, the influence of experimental diabetes on gap junction channel-mediated dye transfer was assessed in astrocytes in tissue culture and in brain slices from diabetic rats. Astrocytes grown in 15–25 mmol/l glucose had a slow-onset, poorly reversible decrement in gap junctional communication compared with those grown in 5.5 mmol/l glucose. Astrocytes in brain slices from adult STZ (streptozotocin-treated rats at 20–24 weeks after the onset of diabetes also exhibited reduced dye transfer. In cultured astrocytes grown in high glucose, increased oxidative stress preceded the decrement in dye transfer by several days, and gap junctional impairment was prevented, but not rescued, after its manifestation by compounds that can block or reduce oxidative stress. In sharp contrast with these findings, chaperone molecules known to facilitate protein folding could prevent and rescue gap junctional impairment, even in the presence of elevated glucose level and oxidative stress. Immunostaining of Cx (connexin 43 and 30, but not Cx26, was altered by growth in high glucose. Disruption of astrocytic trafficking of metabolites and signalling molecules may alter interactions among astrocytes, neurons and endothelial cells and contribute to changes in brain function in diabetes. Involvement of the microvasculature may contribute to diabetic complications in the brain, the cardiovascular system and other organs.

  10. The effects of trypsin on rat brain astrocyte activation.

    Directory of Open Access Journals (Sweden)

    Masoud Fereidoni

    2013-12-01

    Full Text Available Astrocytes are cells within the central nervous system which are activated in a wide spectrum of infections, and autoimmune and neurodegenerative diseases. In pathologic states, they produce inflammatory cytokines, chemokines, and nitric oxide (NO, and sometimes they induce apoptosis. Their protease-activated receptors (PARs can be activated by proteases, e.g. thrombin and trypsin, which are important in brain inflammation. The current study aimed to investigate the effects of different concentrations of trypsin (1 to 100U/ml on cultured astrocytes.In the present study, two-day rat infants' brains were isolated and homogenized after meninges removal, then cultivated in DMEM + 10% FBS medium. 10 days later, astrocytes were harvested and recultivated for more purification (up to 95%, using Immunocytochemistry method, in order to be employed for tests. They were affected by different concentrations of trypsin (1, 5, 10, 15, 20, 40, 60, 80, and 100 U/ml. To reveal the inflammation progress, NO concentrations (the Griess test were assessed after 24 and 48 hours.The results showed that trypsin concentration up to 20 U/ml caused a significant increase in NO, in a dose-dependent manner, on cultured astrocytes (P < 0.001. Trypsin 20 U/ml increased NO production fivefold the control group (P < 0.001. At higher concentrations than 20 U/ml, NO production diminished (P < 0.001. At 100 U/ml, NO production was less than the control group (P < 0.001.Inflammatory effects of trypsin 5-20 U/ml are probably due to the stimulation of astrocytes' PAR-2 receptors and the increasing of the activation of NF-κB, PKC, MAPKs. Stimulation of astrocytes' PAR-2 receptors causes an increase in iNOS activation which in turn leads to NO production. However, higher trypsin concentration possibly made astrocyte apoptosis; therefore, NO production diminished. These assumptions need to be further investigated.

  11. Voluntary Exercise Induces Astrocytic Structural Plasticity in the Globus Pallidus.

    Science.gov (United States)

    Tatsumi, Kouko; Okuda, Hiroaki; Morita-Takemura, Shoko; Tanaka, Tatsuhide; Isonishi, Ayami; Shinjo, Takeaki; Terada, Yuki; Wanaka, Akio

    2016-01-01

    Changes in astrocyte morphology are primarily attributed to the fine processes where intimate connections with neurons form the tripartite synapse and participate in neurotransmission. Recent evidence has shown that neurotransmission induces dynamic synaptic remodeling, suggesting that astrocytic fine processes may adapt their morphologies to the activity in their environment. To illustrate such a neuron-glia relationship in morphological detail, we employed a double transgenic Olig2(CreER/WT); ROSA26-GAP43-EGFP mice, in which Olig2-lineage cells can be visualized and traced with membrane-targeted GFP. Although Olig2-lineage cells in the adult brain usually become mature oligodendrocytes or oligodendrocyte precursor cells with NG2-proteoglycan expression, we found a population of Olig2-lineage astrocytes with bushy morphology in several brain regions. The globus pallidus (GP) preferentially contains Olig2-lineage astrocytes. Since the GP exerts pivotal motor functions in the indirect pathway of the basal ganglionic circuit, we subjected the double transgenic mice to voluntary wheel running to activate the GP and examined morphological changes of Olig2-lineage astrocytes at both the light and electron microscopic levels. The double transgenic mice were divided into three groups: control group mice were kept in a cage with a locked running wheel for 3 weeks, Runner group were allowed free access to a running wheel for 3 weeks, and the Runner-Rest group took a sedentary 3-week rest after a 3-week running period. GFP immunofluorescence analysis and immunoelectron microscopy revealed that astrocytic fine processes elaborated complex arborization in the Runner mice, and reverted to simple morphology comparable to that of the Control group in the Runner-Rest group. Our results indicated that the fine processes of the Olig2-lineage astrocytes underwent plastic changes that correlated with overall running activities, suggesting that they actively participate in motor

  12. Astrocytes as a source for Extracellular matrix molecules and cytokines

    Directory of Open Access Journals (Sweden)

    Stefan eWiese

    2012-06-01

    Full Text Available Research of the past 25 years has shown that astrocytes do more than participating and building up the blood brain barrier and detoxify the active synapse by reuptake of neurotransmitters and ions. Indeed, astrocytes express neurotransmitter receptors and, as a consequence, respond to stimuli. Deeper knowledge of the differentiation processes during development of the central nervous system (CNS might help explaining and even help treating neurological diseases like Alzheimer’s disease, Amyotrophic lateral sclerosis (ALS and psychiatric disorders in which astrocytes have been shown to play a role. Astrocytes and oligodendrocytes develop from a multipotent stem cell that prior to this has produced primarily neuronal precursor cells. This switch towards the more astroglial differentiation is regulated by a change in receptor composition on the cell surface and responsiveness of the respective trophic factors Fibroblast growth factor (FGF and Epidermal growth factor (EGF. The glial precursor cell is driven into the astroglial direction by signaling molecules like Ciliary neurotrophic factor (CNTF, Bone Morphogenetic Proteins (BMPs, and EGF. However, the early astrocytes influence their environment not only by releasing and responding to diverse soluble factors but also express a wide range of extracellular matrix (ECM molecules, in particular proteoglycans of the lectican family and tenascins. Lately these ECM molecules have been shown to participate in glial development. In this regard, especially the matrix protein Tenascin C (Tnc proved to be an important regulator of astrocyte precursor cell proliferation and migration during spinal cord development. On the other hand, ECM molecules expressed by reactive astrocytes are also known to act mostly in an inhibitory fashion under pathophysiological conditions. In this regard, we further summarize recent data concerning the role of chondroitin sulfate proteoglycans and Tnc under pathological

  13. Reduced Hsp70 and Glutamine in Pediatric Severe Malaria Anemia

    DEFF Research Database (Denmark)

    Kempaiah, Prakasha; Dokladny, Karol; Karim, Zachary;

    2016-01-01

    decreased HSPA1A, a heat shock protein (Hsp) 70 coding gene. Hsp70 is a ubiquitous chaperone that regulates Nuclear Factor-kappa B (NF-κB) signaling and production of pro-inflammatory cytokines known to be important in malaria pathogenesis (e.g., IL-1β, IL-6 and TNF-α). Since the role of host Hsp70 in...... malaria pathogenesis is unexplored, we investigated Hsp70 and molecular pathways in children with SMA. Validation experiments revealed that leukocytic HSP70 transcripts were reduced in SMA relative to non-severe malaria, and that intraleukocytic hemozoin (PfHz) was associated with lower HSP70. HSP70 was...... correlated with reticulocyte production and Hb. Since glutamine (Gln) up-regulates Hsp70, modulates NF-κB activation, and attenuates over-expression of pro-inflammatory cytokines, circulating Gln was measured in children with malaria. Reduced Gln was associated with increased risk of developing SMA...

  14. Glutamine supplementation in sick children: is it beneficial?

    Science.gov (United States)

    Mok, Elise; Hankard, Régis

    2011-01-01

    The purpose of this review is to provide a critical appraisal of the literature on Glutamine (Gln) supplementation in various conditions or illnesses that affect children, from neonates to adolescents. First, a general overview of the proposed mechanisms for the beneficial effects of Gln is provided, and subsequently clinical studies are discussed. Despite safety, studies are conflicting, partly due to different effects of enteral and parenteral Gln supplementation. Further insufficient evidence is available on the benefits of Gln supplementation in pediatric patients. This includes premature infants, infants with gastrointestinal disease, children with Crohn's disease, short bowel syndrome, malnutrition/diarrhea, cancer, severe burns/trauma, Duchenne muscular dystrophy, sickle cell anemia, cystic fibrosis, and type 1 diabetes. Moreover, methodological issues have been noted in some studies. Further mechanistic data is needed along with large randomized controlled trials in select populations of sick children, who may eventually benefit from supplemental Gln. PMID:22175008

  15. Glutamine Supplementation in Sick Children: Is It Beneficial?

    Directory of Open Access Journals (Sweden)

    Elise Mok

    2011-01-01

    Full Text Available The purpose of this review is to provide a critical appraisal of the literature on Glutamine (Gln supplementation in various conditions or illnesses that affect children, from neonates to adolescents. First, a general overview of the proposed mechanisms for the beneficial effects of Gln is provided, and subsequently clinical studies are discussed. Despite safety, studies are conflicting, partly due to different effects of enteral and parenteral Gln supplementation. Further insufficient evidence is available on the benefits of Gln supplementation in pediatric patients. This includes premature infants, infants with gastrointestinal disease, children with Crohn's disease, short bowel syndrome, malnutrition/diarrhea, cancer, severe burns/trauma, Duchenne muscular dystrophy, sickle cell anemia, cystic fibrosis, and type 1 diabetes. Moreover, methodological issues have been noted in some studies. Further mechanistic data is needed along with large randomized controlled trials in select populations of sick children, who may eventually benefit from supplemental Gln.

  16. Fatty acid oxidation and ketogenesis in astrocytes

    International Nuclear Information System (INIS)

    Astrocytes were derived from cortex of two-day-old rat brain and grown in primary culture to confluence. The metabolism of the fatty acids, octanoate and palmitate, to CO2 in oxidative respiration and to the formation of ketone bodies was examined by radiolabeled tracer methodology. The net production of acetoacetate was also determined by measurement of its mass. The enzymes in the ketogenic pathway were examined by measuring enzymic activity and/or by immunoblot analyses. Labeled CO2 and labeled ketone bodies were produced from the oxidation of fatty acids labeled at carboxy- and ω-terminal carbons, indicating that fatty acids were oxidized by β-oxidation. The results from the radiolabeled tracer studies also indicated that a substantial proportion of the ω-terminal 4-carbon unit of the fatty acids bypassed the β-ketothiolase step of the β-oxidation pathway. The [14C]acetoacetate formed from the [1-14C]labeled fatty acids, obligated to pass through the acetyl-CoA pool, contained 50% of the label at carbon 3 and 50% at carbon 1. In contrast, the [14C]acetoacetate formed from the (ω-1)labeled fatty acids contained 90% of the label at carbon 3 and 10% at carbon 1

  17. End products of glutamine oxidation in MC-29 virus-induced chicken hepatoma mitochondria.

    Science.gov (United States)

    Matsuno, T

    1989-10-01

    Products of glutamine metabolism were examined in the MC-29 virus-induced chicken hepatoma mitochondria incubated in vitro. Glutamine oxidation proceeded in the tumor mitochondria exclusively via a pathway involving glutamic-oxalacetic transaminase. Malate stimulated aspartate production from glutamine, while pyruvate exerted suppressive effect on aspartate production with little alanine formation. The mitochondria of this hepatoma are unique in that the metabolic pattern and response to malate and pyruvate are essentially inconsistent with those reported in normal cells as well as those proposed by Moreadith and Lehninger in various tumor cells. PMID:2571353

  18. Curative effect of parenteral nutrition and glutamine on post-surgical patients

    Directory of Open Access Journals (Sweden)

    Bangash TA

    2012-03-01

    Full Text Available Background: To evaluate the influence of parenteral nutrition and glutamine on nutritional status and prognosis of surgical critically ill patients. Methods: 32 cases were treated by parenteral nutrition plus alanyl-glutamine injection. The differences in liver function, weight and nutritional status were compared between, before and after medication. Results: Patients were either cured or relieved, and no complication including infection appeared. Total protein. Albumin, ferrohemoglobin and weight increased after medication, respectively. Conclusions: The use of parenteral nutrition plus glutamine is beneficial for ameliorating malnutrition and negative nitrogen balance caused by hypermetabolism, inhibiting bacterial translocation, preventing the complication, and increasing healing rate of disease.

  19. Role of astrocytic leptin receptor subtypes on leptin permeation across hCMEC/D3 human brain endothelial cells.

    Science.gov (United States)

    Hsuchou, Hung; Kastin, Abba J; Tu, Hong; Joan Abbott, N; Couraud, Pierre-Olivier; Pan, Weihong

    2010-12-01

    Astrocytic leptin receptors (ObR) can be up-regulated in conditions such as adult-onset obesity. To determine whether the levels and subtypes of astrocytic ObR modulate leptin transport, we co-cultured hCMEC/D3 human brain endothelial cells and C6 astrocytoma cells in the Transwell system, and tested leptin permeation from apical to basolateral chambers. In comparison with hCMEC alone, co-culture of C6 cells reduced the permeability of paracellular markers and leptin. Unexpectedly, ObRb over-expression in C6 cells increased leptin permeation whereas ObRa over-expression showed no effect when compared with the control group of pcDNA-transfected C6 cells. By contrast, the paracellular permeability to the sodium fluorescein control was unchanged by over-expression of ObR subtypes. Leptin remained intact after crossing the monolayer as shown by HPLC and acid precipitation, and this was not affected by C6 cell co-culture or the over-expression of different ObR subtypes. Thus, increased expression of ObRb (and to a lesser extent ObRe) in C6 cells specifically increased the permeation of leptin across the hCMEC monolayer. Consistent with the evidence that the most apparent regulatory changes of ObR during obesity and inflammation occur in astrocytes, the results indicate that astrocytes actively regulate leptin transport across the blood-brain barrier, a mechanism independent of reduction of paracellular permeability. PMID:20977476

  20. Effects of Hydro Alcoholic Extraction of Valeriana on Astrocyte Raphe Magnus in Adult Rats

    Directory of Open Access Journals (Sweden)

    sajad Hatami joni

    2014-12-01

    Conclusion: Oral administration of hydro alcoholic extract of valerian increases astrocytes number and decreases their size in nucleus of raphe Magna, which indicated the effect of this extraction on proliferation of astrocytes increasing.

  1. The metabolism of malate by cultured rat brain astrocytes

    International Nuclear Information System (INIS)

    Since malate is known to play an important role in a variety of functions in the brain including energy metabolism, the transfer of reducing equivalents and possibly metabolic trafficking between different cell types; a series of biochemical determinations were initiated to evaluate the rate of 14CO2 production from L-[U-14C]malate in rat brain astrocytes. The 14CO2 production from labeled malate was almost totally suppressed by the metabolic inhibitors rotenone and antimycin A suggesting that most of malate metabolism was coupled to the electron transport system. A double reciprocal plot of the 14CO2 production from the metabolism of labeled malate revealed biphasic kinetics with two apparent Km and Vmax values suggesting the presence of more than one mechanism of malate metabolism in these cells. Subsequent experiments were carried out using 0.01 mM and 0.5 mM malate to determine whether the addition of effectors would differentially alter the metabolism of high and low concentrations of malate. Effectors studied included compounds which could be endogenous regulators of malate metabolism and metabolic inhibitors which would provide information regarding the mechanisms regulating malate metabolism. Both lactate and aspartate decreased 14CO2 production from malate equally. However, a number of effectors were identified which selectively altered the metabolism of 0.01 mM malate including aminooxyacetate, furosemide, N-acetylaspartate, oxaloacetate, pyruvate and glucose, but had little or no effect on the metabolism of 0.5 mM malate. In addition, alpha-ketoglutarate and succinate decreased 14CO2 production from 0.01 mM malate much more than from 0.5 mM malate. In contrast, a number of effectors altered the metabolism of 0.5 mM malate more than 0.01 mM. These included methionine sulfoximine, glutamate, malonate, alpha-cyano-4-hydroxycinnamate and ouabain

  2. Galunisertib inhibits glioma vasculogenic mimicry formation induced by astrocytes.

    Science.gov (United States)

    Zhang, Chao; Chen, Wenliang; Zhang, Xin; Huang, Bin; Chen, Aanjing; He, Ying; Wang, Jian; Li, Xingang

    2016-01-01

    Gliomas are among the most lethal primary brain tumors found in humans. In high-grade gliomas, vasculogenic mimicry is often detected and has been correlated with prognosis, thus suggesting its potential as a therapeutic target. Vasculogenic mimicry mainly forms vascular-like channels independent of endothelial cells; however, little is known about the relationship between astrocytes and vasculogenic mimicry. In our study, we demonstrated that the presence of astrocytes promoted vasculogenic mimicry. With suspension microarray technology and in vitro tube formation assays, we identified that astrocytes relied on TGF-β1 to enhance vasculogenic mimicry. We also found that vasculogenic mimicry was inhibited by galunisertib, a promising TGF-β1 inhibitor currently being studied in an ongoing trial in glioma patients. The inhibition was partially attributed to a decrease in autophagy after galunisertib treatment. Moreover, we observed a decrease in VE-cadherin and smooth muscle actin-α expression, as well as down-regulation of Akt and Flk phosphorylation in galunisertib-treated glioma cells. By comparing tumor weight and volume in a xenograft model, we acquired promising results to support our theory. This study expands our understanding of the role of astrocytes in gliomas and demonstrates that galunisertib inhibits glioma vasculogenic mimicry induced by astrocytes. PMID:26976322

  3. Astrocyte activation in vivo during graded photic stimulation.

    Science.gov (United States)

    Dienel, Gerald A; Schmidt, Kathleen C; Cruz, Nancy F

    2007-11-01

    Astrocytes have important roles in control of extracellular environment, de novo synthesis of neurotransmitters, and regulation of neurotransmission and blood flow. All of these functions require energy, suggesting that astrocytic metabolism should rise and fall with changes in neuronal activity and that brain imaging can be used to visualize and quantify astrocytic activation in vivo. A unilateral photic stimulation paradigm was used to test the hypothesis that graded sensory stimuli cause progressive increases in the uptake coefficient of [2-(14)C]acetate, a substrate preferentially oxidized by astrocytes. The acetate uptake coefficient fell in deafferented visual structures and it rose in intact tissue during photic stimulation of conscious rats; the increase was highest in structures with monosynaptic input from the eye and was much smaller in magnitude than the change in glucose utilization (CMR(glc)) by all cells. The acetate uptake coefficient was not proportional to stimulus rate and did not correlate with CMR(glc) in resting or activated structures. Simulation studies support the conclusions that acetate uptake coefficients represent mainly metabolism and respond to changes in metabolism rate, with a lower response at high rates. A model portraying regulation of acetate oxidation illustrates complex relationships among functional activation, cation levels, and astrocytic metabolism. PMID:17725580

  4. Integrated Brain Circuits: Astrocytic Networks Modulate Neuronal Activity and Behavior

    Science.gov (United States)

    Halassa, Michael M.; Haydon, Philip G.

    2011-01-01

    The past decade has seen an explosion of research on roles of neuron-astrocyte interactions in the control of brain function. We highlight recent studies performed on the tripartite synapse, the structure consisting of pre- and postsynaptic elements of the synapse and an associated astrocytic process. Astrocytes respond to neuronal activity and neuro-transmitters, through the activation of metabotropic receptors, and can release the gliotransmitters ATP, D-serine, and glutamate, which act on neurons. Astrocyte-derived ATP modulates synaptic transmission, either directly or through its metabolic product adenosine. D-serine modulates NMDA receptor function, whereas glia-derived glutamate can play important roles in relapse following withdrawal from drugs of abuse. Cell type–specific molecular genetics has allowed a new level of examination of the function of astrocytes in brain function and has revealed an important role of these glial cells that is mediated by adenosine accumulation in the control of sleep and in cognitive impairments that follow sleep deprivation. PMID:20148679

  5. Astrocytes directly influence tumor cell invasion and metastasis in vivo.

    Directory of Open Access Journals (Sweden)

    Ling Wang

    Full Text Available Brain metastasis is a defining component of tumor pathophysiology, and the underlying mechanisms responsible for this phenomenon are not well understood. Current dogma is that tumor cells stimulate and activate astrocytes, and this mutual relationship is critical for tumor cell sustenance in the brain. Here, we provide evidence that primary rat neonatal and adult astrocytes secrete factors that proactively induced human lung and breast tumor cell invasion and metastasis capabilities. Among which, tumor invasion factors namely matrix metalloprotease-2 (MMP-2 and MMP-9 were partly responsible for the astrocyte media-induced tumor cell invasion. Inhibiting MMPs reduced the ability of tumor cell to migrate and invade in vitro. Further, injection of astrocyte media-conditioned breast cancer cells in mice showed increased invasive activity to the brain and other distant sites. More importantly, blocking the preconditioned tumor cells with broad spectrum MMP inhibitor decreased the invasion and metastasis of the tumor cells, in particular to the brain in vivo. Collectively, our data implicate astrocyte-derived MMP-2 and MMP-9 as critical players that facilitate tumor cell migration and invasion leading to brain metastasis.

  6. Adrenergic activation attenuates astrocyte swelling induced by hypotonicity and neurotrauma.

    Science.gov (United States)

    Vardjan, Nina; Horvat, Anemari; Anderson, Jamie E; Yu, Dou; Croom, Deborah; Zeng, Xiang; Lužnik, Zala; Kreft, Marko; Teng, Yang D; Kirov, Sergei A; Zorec, Robert

    2016-06-01

    Edema in the central nervous system can rapidly result in life-threatening complications. Vasogenic edema is clinically manageable, but there is no established medical treatment for cytotoxic edema, which affects astrocytes and is a primary trigger of acute post-traumatic neuronal death. To test the hypothesis that adrenergic receptor agonists, including the stress stimulus epinephrine protects neural parenchyma from damage, we characterized its effects on hypotonicity-induced cellular edema in cortical astrocytes by in vivo and in vitro imaging. After epinephrine administration, hypotonicity-induced swelling of astrocytes was markedly reduced and cytosolic 3'-5'-cyclic adenosine monophosphate (cAMP) was increased, as shown by a fluorescence resonance energy transfer nanosensor. Although, the kinetics of epinephrine-induced cAMP signaling was slowed in primary cortical astrocytes exposed to hypotonicity, the swelling reduction by epinephrine was associated with an attenuated hypotonicity-induced cytosolic Ca(2+) excitability, which may be the key to prevent astrocyte swelling. Furthermore, in a rat model of spinal cord injury, epinephrine applied locally markedly reduced neural edema around the contusion epicenter. These findings reveal new targets for the treatment of cellular edema in the central nervous system. GLIA 2016;64:1034-1049. PMID:27018061

  7. Astrocytes mediate the neuroprotective effects of Tibolone following brain injury

    Directory of Open Access Journals (Sweden)

    Luis Miguel Garcia-Segura

    2015-04-01

    Full Text Available Recently, astrocytes have become a key central player in mediating important functions in the brain. These physiological processes include neurotransmitter recycling, energy management, metabolic shuttle, immune sensing, K+ buffer, antioxidant supply and release of neurotrophic factors and gliotransmitters. These astrocytic roles are somehow altered upon brain injury, therefore strategies aimed at better protecting astrocytes are an essential asset to maintain brain homeostasis. In this context, estrogenic compounds, such as Tibolone, have attracted attention for their beneficial effects in acute and chronic degenerative diseases. Tibolone may act through binding to estrogen, androgen or progesterone receptors and exert protective effects by reducing astrocytes cell death and oxidative stress signaling mechanisms. Although Tibolone has a multifactorial effect in the brain, its mechanisms of action are not completely understood. In this work, we highlight the role of Tibolone in brain protection upon damage, how astrocytes might mediate part of its neuroprotective actions and discuss the effects of Tibolone in diminishing the harmful consequences of a metabolic insult and energy failure in the setting of a pathological event.

  8. Channel-Mediated Lactate Release by K+-Stimulated Astrocytes

    KAUST Repository

    Sotelo-Hitschfeld, T.

    2015-03-11

    Excitatory synaptic transmission is accompanied by a local surge in interstitial lactate that occurs despite adequate oxygen availability, a puzzling phenomenon termed aerobic glycolysis. In addition to its role as an energy substrate, recent studies have shown that lactate modulates neuronal excitability acting through various targets, including NMDA receptors and G-protein-coupled receptors specific for lactate, but little is known about the cellular and molecular mechanisms responsible for the increase in interstitial lactate. Using a panel of genetically encoded fluorescence nanosensors for energy metabolites, we show here that mouse astrocytes in culture, in cortical slices, and in vivo maintain a steady-state reservoir of lactate. The reservoir was released to the extracellular space immediately after exposure of astrocytes to a physiological rise in extracellular K+ or cell depolarization. Cell-attached patch-clamp analysis of cultured astrocytes revealed a 37 pS lactate-permeable ion channel activated by cell depolarization. The channel was modulated by lactate itself, resulting in a positive feedback loop for lactate release. A rapid fall in intracellular lactate levels was also observed in cortical astrocytes of anesthetized mice in response to local field stimulation. The existence of an astrocytic lactate reservoir and its quick mobilization via an ion channel in response to a neuronal cue provides fresh support to lactate roles in neuronal fueling and in gliotransmission.

  9. Investigation on the suitable pressure for the preservation of astrocyte

    Energy Technology Data Exchange (ETDEWEB)

    Sotome, S; Shimizu, A [Department of Environmental Engineering for Symbiosis, Soka University, 1-326 Tangi-cho, Hachioji, Tokyo 192-8577 (Japan); Nakajima, K [Department of Bioinformatics, Soka University, 1-326 Tangi-cho, Hachioji, Tokyo 192-8577 (Japan); Yoshimura, Y, E-mail: sotome_shinichi@yahoo.co.j [Department of Applied Chemistry, National Defence Academy, 1-10-20 Hashirimizu, Yokosuka, Kanagawa 239-8686 (Japan)

    2010-03-01

    The effects of pressure on the survival rate of astrocytes in growth medium (DMEM) were investigated at room temperature and at 4{sup 0}C, in an effort to establish the best conditions for the preservation. Survival rate at 4{sup 0}C was found to be higher than that at room temperature. The survival rate of astrocytes preserved for 4 days at 4{sup 0}C increased with increasing pressure up to 1.6 MPa, but decreased with increasing pressure above 1.6 MPa. At 10 MPa, all astrocytes died. The survival rate of cultured astrocytes decreased significantly following pressurization for 2 hours and the subsequent preservation for 2 days at atmospheric pressure. Therefore, it is necessary to maintain pressure when preserving astrocytes. These results indicate that the cells can be stored at 4{sup 0}C under pressurization without freezing and without adding cryoprotective agents. Moreover, it may be possible to use this procedure as a new preservation method when cryopreservation is impractical.

  10. Accumulation of silver nanoparticles by cultured primary brain astrocytes

    Science.gov (United States)

    Luther, Eva M.; Koehler, Yvonne; Diendorf, Joerg; Epple, Matthias; Dringen, Ralf

    2011-09-01

    Silver nanoparticles (AgNP) are components of various food industry products and are frequently used for medical equipment and materials. Although such particles enter the vertebrate brain, little is known on their biocompatibility for brain cells. To study the consequences of an AgNP exposure of brain cells we have treated astrocyte-rich primary cultures with polyvinylpyrrolidone (PVP)-coated AgNP. The incubation of cultured astrocytes with micromolar concentrations of AgNP for up to 24 h resulted in a time- and concentration-dependent accumulation of silver, but did not compromise the cell viability nor lower the cellular glutathione content. In contrast, the incubation of astrocytes for 4 h with identical amounts of silver as AgNO3 already severely compromised the cell viability and completely deprived the cells of glutathione. The accumulation of AgNP by astrocytes was proportional to the concentration of AgNP applied and significantly lowered by about 30% in the presence of the endocytosis inhibitors chloroquine or amiloride. Incubation at 4 °C reduced the accumulation of AgNP by 80% compared to the values obtained for cells that had been exposed to AgNP at 37 °C. These data demonstrate that viable cultured brain astrocytes efficiently accumulate PVP-coated AgNP in a temperature-dependent process that most likely involves endocytotic pathways.

  11. Staurosporine induces different cell death forms in cultured rat astrocytes

    International Nuclear Information System (INIS)

    Astroglial cells are frequently involved in malignant transformation. Besides apoptosis, necroptosis, a different form of regulated cell death, seems to be related with glioblastoma genesis, proliferation, angiogenesis and invasion. In the present work we elucidated mechanisms of necroptosis in cultured astrocytes, and compared them with apoptosis, caused by staurosporine. Cultured rat cortical astrocytes were used for a cell death studies. Cell death was induced by different concentrations of staurosporine, and modified by inhibitors of apoptosis (z-vad-fmk) and necroptosis (nec-1). Different forms of a cell death were detected using flow cytometry. We showed that staurosporine, depending on concentration, induces both, apoptosis as well as necroptosis. Treatment with 10−7 M staurosporine increased apoptosis of astrocytes after the regeneration in a staurosporine free medium. When caspases were inhibited, apoptosis was attenuated, while necroptosis was slightly increased. Treatment with 10−6 M staurosporine induced necroptosis that occurred after the regeneration of astrocytes in a staurosporine free medium, as well as without regeneration period. Necroptosis was significantly attenuated by nec-1 which inhibits RIP1 kinase. On the other hand, the inhibition of caspases had no effect on necroptosis. Furthermore, staurosporine activated RIP1 kinase increased the production of reactive oxygen species, while an antioxidant BHA significantly attenuated necroptosis. Staurosporine can induce apoptosis and/or necroptosis in cultured astrocytes via different signalling pathways. Distinction between different forms of cell death is crucial in the studies of therapy-induced necroptosis

  12. Investigation on the suitable pressure for the preservation of astrocyte

    Science.gov (United States)

    Sotome, S.; Nakajima, K.; Yoshimura, Y.; Shimizu, A.

    2010-03-01

    The effects of pressure on the survival rate of astrocytes in growth medium (DMEM) were investigated at room temperature and at 4°C, in an effort to establish the best conditions for the preservation. Survival rate at 4°C was found to be higher than that at room temperature. The survival rate of astrocytes preserved for 4 days at 4°C increased with increasing pressure up to 1.6 MPa, but decreased with increasing pressure above 1.6 MPa. At 10 MPa, all astrocytes died. The survival rate of cultured astrocytes decreased significantly following pressurization for 2 hours and the subsequent preservation for 2 days at atmospheric pressure. Therefore, it is necessary to maintain pressure when preserving astrocytes. These results indicate that the cells can be stored at 4°C under pressurization without freezing and without adding cryoprotective agents. Moreover, it may be possible to use this procedure as a new preservation method when cryopreservation is impractical.

  13. Accumulation of silver nanoparticles by cultured primary brain astrocytes

    International Nuclear Information System (INIS)

    Silver nanoparticles (AgNP) are components of various food industry products and are frequently used for medical equipment and materials. Although such particles enter the vertebrate brain, little is known on their biocompatibility for brain cells. To study the consequences of an AgNP exposure of brain cells we have treated astrocyte-rich primary cultures with polyvinylpyrrolidone (PVP)-coated AgNP. The incubation of cultured astrocytes with micromolar concentrations of AgNP for up to 24 h resulted in a time- and concentration-dependent accumulation of silver, but did not compromise the cell viability nor lower the cellular glutathione content. In contrast, the incubation of astrocytes for 4 h with identical amounts of silver as AgNO3 already severely compromised the cell viability and completely deprived the cells of glutathione. The accumulation of AgNP by astrocytes was proportional to the concentration of AgNP applied and significantly lowered by about 30% in the presence of the endocytosis inhibitors chloroquine or amiloride. Incubation at 4 0C reduced the accumulation of AgNP by 80% compared to the values obtained for cells that had been exposed to AgNP at 37 0C. These data demonstrate that viable cultured brain astrocytes efficiently accumulate PVP-coated AgNP in a temperature-dependent process that most likely involves endocytotic pathways.

  14. Accumulation of silver nanoparticles by cultured primary brain astrocytes

    Energy Technology Data Exchange (ETDEWEB)

    Luther, Eva M; Koehler, Yvonne; Dringen, Ralf [Center for Biomolecular Interactions Bremen, University of Bremen, PO Box 330440, D-28334 Bremen (Germany); Diendorf, Joerg; Epple, Matthias, E-mail: ralf.dringen@uni-bremen.de [Inorganic Chemistry and Center for Nanointegration Duisburg-Essen, University of Duisburg-Essen, Universitaetsstrasse 5-7, D-45117 Essen (Germany)

    2011-09-16

    Silver nanoparticles (AgNP) are components of various food industry products and are frequently used for medical equipment and materials. Although such particles enter the vertebrate brain, little is known on their biocompatibility for brain cells. To study the consequences of an AgNP exposure of brain cells we have treated astrocyte-rich primary cultures with polyvinylpyrrolidone (PVP)-coated AgNP. The incubation of cultured astrocytes with micromolar concentrations of AgNP for up to 24 h resulted in a time- and concentration-dependent accumulation of silver, but did not compromise the cell viability nor lower the cellular glutathione content. In contrast, the incubation of astrocytes for 4 h with identical amounts of silver as AgNO{sub 3} already severely compromised the cell viability and completely deprived the cells of glutathione. The accumulation of AgNP by astrocytes was proportional to the concentration of AgNP applied and significantly lowered by about 30% in the presence of the endocytosis inhibitors chloroquine or amiloride. Incubation at 4 {sup 0}C reduced the accumulation of AgNP by 80% compared to the values obtained for cells that had been exposed to AgNP at 37 {sup 0}C. These data demonstrate that viable cultured brain astrocytes efficiently accumulate PVP-coated AgNP in a temperature-dependent process that most likely involves endocytotic pathways.

  15. Novel cell separation method for molecular analysis of neuron-astrocyte co-cultures

    OpenAIRE

    Goudriaan, Andrea; Camargo, Nutabi; Carney, Karen E.; Oliet, Stéphane H. R.; Smit, August B.; Verheijen, Mark H. G.

    2014-01-01

    Over the last decade, the importance of astrocyte-neuron communication in neuronal development and synaptic plasticity has become increasingly clear. Since neuron-astrocyte interactions represent highly dynamic and reciprocal processes, we hypothesized that many astrocyte genes may be regulated as a consequence of their interactions with maturing neurons. In order to identify such neuron-responsive astrocyte genes in vitro, we sought to establish an expedited technique for separation of neuro...

  16. A cortical astrocyte subpopulation inhibits axon growth in vitro and in vivo

    OpenAIRE

    Liu, Rui; Wang, Zhe; Gou, Lin; XU, HANPENG

    2015-01-01

    Astrocytes are the most heterogeneous and predominant glial cell type in the central nervous system. However, the functional significance of this heterogeneity remains to be elucidated. Following injury, damaged astrocytes inhibit axonal regeneration in vivo and in vitro. Cultured primary astrocytes are commonly considered good supportive substrates for neuron attachment and axon regeneration. However, it is not known whether different populations of cells in the heterogeneous astrocyte cultu...

  17. Novel cell separation method for molecular analysis of neuron-astrocyte cocultures

    OpenAIRE

    Karen Carney; Oliet, Stéphane H. R.; Verheijen, Mark H. G.

    2014-01-01

    Over the last decade, the importance of astrocyte-neuron communication in neuronal development and synaptic plasticity has become increasingly clear. Since neuron-astrocyte interactions represent highly dynamic and reciprocal processes, we hypothesized that many astrocyte genes may be regulated as a consequence of their interactions with maturing neurons. In order to identify such neuron-responsive astrocyte genes in vitro, we sought to establish an expedite technique for separation of neuron...

  18. Significance of the astrocyte domain organization for qualitative information structuring in the brain

    OpenAIRE

    Bernhard J Mitterauer

    2010-01-01

    Astrocytes, the dominant glial cell type, modulate synaptic information transmission. Each astrocyte is organized in non-overlapping domains. Here, a formally based model of the possible significance of astrocyte domain organization is proposed. It is hypothesized that each astrocyte contacting n neurons with m synapses via its processes generates dynamic domains of synaptic interactions based on qualitative criteria so that it exerts a structuring of neuronal information processing. The form...

  19. Studies on astrocyte function : potential roles in brain water homeostasis and neuroprotection

    OpenAIRE

    Song, Yutong

    2012-01-01

    Astrocytes are essential in brain homeostasis and function, including maintenance of water and ion balance. Astrocytes express the water channel aquaporin 4 (AQP4), implicated in both physiological functions and injury processes associated with brain edema, a common consequence of brain diseases. As part of the tripartite synapse astrocytes are tightly coupled to normal brain function via neuron-astrocyte interactions and by providing metabolic support to neurons as well as con...

  20. Conditions and constraints for astrocyte calcium signaling in the hippocampal mossy fiber pathway

    OpenAIRE

    Haustein, Martin D.; Kracun, Sebastian; Lu, Xiao-Hong; Shih, Tiffany; Jackson-Weaver, Olan; Tong, Xiaoping; Xu, Ji; Yang, X William; O'Dell, Thomas J.; Marvin, Jonathan S.; Ellisman, Mark H.; Bushong, Eric A.; Looger, Loren L.; Khakh, Baljit S.

    2014-01-01

    The spatiotemporal activities of astrocyte Ca2+ signaling in mature neuronal circuits remain unclear. We used genetically encoded Ca2+ and glutamate indicators as well as pharmacogenetic and electrical control of neurotransmitter release to explore astrocyte activity in the hippocampal mossy fiber pathway. Our data revealed numerous localised spontaneous Ca2+ signals in astrocyte branches and territories, but these were not driven by neuronal activity or glutamate. Moreover, evoked astrocyte ...

  1. Regulated temporal-spatial astrocyte precursor cell proliferation involves BRAF signalling in mammalian spinal cord

    OpenAIRE

    Tien, An-Chi; Tsai, Hui-hsin; Molofsky, Anna V.; McMahon, Martin; Foo, Lynette C.; Kaul, Aparna; Dougherty, Joseph D.; Heintz, Nathaniel; Gutmann, David H.; Barres, Ben A.; Rowitch, David H.

    2012-01-01

    Expansion of astrocyte populations in the central nervous system is characteristic of evolutionarily more complex organisms. However, regulation of mammalian astrocyte precursor proliferation during development remains poorly understood. Here, we used Aldh1L1-GFP to identify two morphologically distinct types of proliferative astrocyte precursors: radial glia (RG) in the ventricular zone and a second cell type we call an ‘intermediate astrocyte precursor’ (IAP) located in the mantle region of...

  2. Neuroinflammation leads to region-dependent alterations in astrocyte gap junction communication and hemichannel activity

    OpenAIRE

    Karpuk, Nikolay; Burkovetskaya, Maria; Fritz, Teresa; Angle, Amanda; Kielian, Tammy

    2011-01-01

    Inflammation attenuates gap junction (GJ) communication in cultured astrocytes. Here we utilized a well-characterized model of experimental brain abscess as a tool to query effects of the CNS inflammatory milieu on astrocyte GJ communication and electrophysiological properties. Whole-cell patch-clamp recordings were performed on GFP-positive astrocytes in acute brain slices from GFAP-GFP mice at 3 or 7 days following S. aureus infection in the striatum. Astrocyte GJ communication was signific...

  3. Insulin Promotes Glycogen Storage and Cell Proliferation in Primary Human Astrocytes

    OpenAIRE

    Martin Heni; Hennige, Anita M.; Andreas Peter; Dorothea Siegel-Axel; Anna-Maria Ordelheide; Norbert Krebs; Fausto Machicao; Andreas Fritsche; Hans-Ulrich Häring; Harald Staiger

    2011-01-01

    INTRODUCTION: In the human brain, there are at least as many astrocytes as neurons. Astrocytes are known to modulate neuronal function in several ways. Thus, they may also contribute to cerebral insulin actions. Therefore, we examined whether primary human astrocytes are insulin-responsive and whether their metabolic functions are affected by the hormone. METHODS: Commercially available Normal Human Astrocytes were grown in the recommended medium. Major players in the insulin signaling pathwa...

  4. In vivo astrocytic Ca2+ signaling in health and brain disorders

    OpenAIRE

    Ding, Shinghua

    2013-01-01

    Astrocytes are the predominant glial cell type in the CNS. Although astrocytes are electrically nonexcitable, their excitability is manifested by their Ca2+ signaling, which serves as a mediator of neuron–glia bidirectional interactions via tripartite synapses. Studies from in vivo two-photon imaging indicate that in healthy animals, the properties of spontaneous astrocytic Ca2+ signaling are affected by animal species, age, wakefulness and the location of astrocytes in the brain. Intercellul...

  5. Spinal astrocyte gap junctions contribute to oxaliplatin-induced mechanical hypersensitivity

    OpenAIRE

    Yoon, Seo-Yeon; Robinson, Caleb R.; Zhang, Haijun; Dougherty, Patrick M.

    2013-01-01

    Spinal glial cells contribute to the development of many types of inflammatory and neuropathic pain. Here the contribution of spinal astrocytes and astrocyte gap junctions to oxaliplatin-induced mechanical hypersensitivity was explored. The expression of glial fibrillary acidic protein (GFAP) in spinal dorsal horn was significantly increased at day 7 but recovered at day 14 after oxaliplatin treatment, suggesting a transient activation of spinal astrocytes by chemotherapy. Astrocyte-specific ...

  6. Astrocyte pathology in the prefrontal cortex impairs the cognitive function of rats

    OpenAIRE

    Lima, A; Sardinha, Vanessa Morais; Oliveira, A. F.; Reis, M; Mota, Cristina de Fátima Sousa da; Silva, M. A.; Marques, Fernanda; Cerqueira, João; Pinto, Luisa; Sousa, Nuno; Oliveira, João F.

    2014-01-01

    Interest in astroglial cells is rising due to recent findings supporting dynamic neuron-astrocyte interactions. There is increasing evidence of astrocytic dysfunction in several brain disorders such as depression, schizophrenia or bipolar disorder; importantly these pathologies are characterized by the involvement of the prefrontal cortex and by significant cognitive impairments. Here, to model astrocyte pathology, we injected animals with the astrocyte specific toxin L-a-aminoadipate (L-AA) ...

  7. Transient acidification and subsequent proinflammatory cytokine stimulation of astrocytes induce distinct activation phenotypes

    OpenAIRE

    Renner, Nicole A.; Sansing, Hope A.; Inglis, Fiona M; Mehra, Smriti; Kaushal, Deepak; Lackner, Andrew A; Andrew G MacLean

    2013-01-01

    The foot processes of astrocytes cover over 60% of the surface of brain microvascular endothelial cells, regulating tight junction integrity. Retraction of astrocyte foot processes has been postulated to be a key mechanism in pathology. Therefore, movement of an astrocyte in response to a proinflammatory cytokine or even limited retraction of processes would result in leaky junctions between endothelial cells. Astrocytes lie at the gateway to the CNS and are instrumental in controlling leukoc...

  8. Phenotypic Heterogeneity and Plasticity of Isocortical and Hippocampal Astrocytes in the Human Brain

    OpenAIRE

    Sosunov, Alexander A.; Wu, Xiaoping; Tsankova, Nadejda M.; Guilfoyle, Eileen; Guy M McKhann; Goldman, James E.

    2014-01-01

    To examine the diversity of astrocytes in the human brain, we immunostained surgical specimens of temporal cortex and hippocampus and autopsy brains for CD44, a plasma membrane protein and extracellular matrix receptor. CD44 antibodies outline the details of astrocyte morphology to a degree not possible with glial fibrillary acidic protein (GFAP) antibodies. CD44+ astrocytes could be subdivided into two groups. First, CD44+ astrocytes with long processes were consistently found in the subpial...

  9. Dynamic inhibition of excitatory synaptic transmission by astrocyte-derived ATP in hippocampal cultures

    OpenAIRE

    Koizumi, Schuichi; Fujishita, Kayoko; Tsuda, Makoto; Shigemoto-Mogami, Yukari; Inoue, Kazuhide

    2003-01-01

    Originally ascribed passive roles in the CNS, astrocytes are now known to have an active role in the regulation of synaptic transmission. Neuronal activity can evoke Ca2+ transients in astrocytes, and Ca2+ transients in astrocytes can evoke changes in neuronal activity. The excitatory neurotransmitter glutamate has been shown to mediate such bidirectional communication between astrocytes and neurons. We demonstrate here that ATP, a primary mediator of intercellular Ca2+ signaling among astroc...

  10. Protoplasmic Astrocytes Enhance the Ability of Neural Stem Cells to Differentiate into Neurons In Vitro

    OpenAIRE

    Yuan Liu; Li Wang; Zaiyun Long; Lin Zeng; Yamin Wu

    2012-01-01

    Protoplasmic astrocytes have been reported to exhibit neuroprotective effects on neurons, but there has been no direct evidence for a functional relationship between protoplasmic astrocytes and neural stem cells (NSCs). In this study, we examined neuronal differentiation of NSCs induced by protoplasmic astrocytes in a co-culture model. Protoplasmic astrocytes were isolated from new-born and NSCs from the E13-15 cortex of rats respectively. The differentiated cells labeled with neuron-specific...

  11. Neuronal cadherin (NCAD) increases sensory neurite formation and outgrowth on astrocytes

    OpenAIRE

    Ferguson, Toby A.; Scherer, Steven S.

    2012-01-01

    We examined the neurite outgrowth of sensory neurons on astrocytes following the genetic deletion of N-cadherin (NCAD). Deletion abolished immunostaining for NCAD and the other classical cadherins, indicating that NCAD is likely the only classical cadherin expressed by astrocytes. Only 38% of neurons grown on NCAD-deficient astrocytes for 24 hours produced neurites, as compared to 74% of neurons grown on NCAD-expressing astrocytes. Of the neurons that produced neurites, those grown on NCAD-de...

  12. Don't fence me in: Harnessing the beneficial roles of astrocytes for spinal cord repair

    OpenAIRE

    White, Robin E.; Jakeman, Lyn B.

    2008-01-01

    Astrocytes comprise a heterogeneous cell population that plays a complex role in repair after spinal cord injury. Reactive astrocytes are major contributors to the glial scar that is a physical and chemical barrier to axonal regeneration. Yet, consistent with a supportive role in development, astrocytes secrete neurotrophic factors and protect neurons and glia spared by the injury. In development and after injury, local cues are modulators of astrocyte phenotype and function. When multipotent...

  13. GLUT2 Immunoreactivity in Gomori-positive Astrocytes of the Hypothalamus

    OpenAIRE

    Young, John K.; McKenzie, James C.

    2004-01-01

    A specialized subtype of astrocyte, the Gomori-positive (GP) astrocyte, is unusually abundant and prominent in the arcuate nucleus of the hypothalamus. GP astro-cytes possess cytoplasmic granules derived from degenerating mitochondria. GP granules are highly stained by Gomori's chrome alum hematoxylin stain, by the Perl's reaction for iron, or by toluidine blue. The source of the oxidative stress causing mitochondrial damage in GP astrocytes is uncertain, but such damage could arise from the ...

  14. Form Follows Function: Astrocyte Morphology and Immune Dysfunction in SIV neuroAIDS

    OpenAIRE

    Lee, Kim M.; Chiu, Kevin B.; Renner, Nicole A.; Sansing, Hope A.; Didier, Peter J.; Andrew G MacLean

    2014-01-01

    Cortical function is disrupted in neuroinflammatory disorders, including HIV-associated neurocognitive disorders (HAND). Astrocyte dysfunction includes retraction of foot processes from the blood-brain barrier and decreased removal of neurotransmitters from synaptic clefts. Mechanisms of astrocyte activation, including innate immune function and the fine neuroanatomy of astrocytes, however, remain to be investigated. We quantified the number of GFAP-labeled astrocytes per mm2 and the proporti...

  15. Phenotypic Conversions of “Protoplasmic” to “Reactive” Astrocytes in Alexander Disease

    OpenAIRE

    Sosunov, Alexander A.; Guilfoyle, Eileen; Wu, Xiaoping; Guy M McKhann; Goldman, James E.

    2013-01-01

    Alexander Disease (AxD) is a primary disorder of astrocytes, caused by heterozygous mutations in GFAP, which encodes the major astrocyte intermediate filament protein, glial fibrillary acidic protein (GFAP). Astrocytes in AxD display hypertrophy, massive increases in GFAP, and the accumulation of Rosenthal fibers, cytoplasmic protein inclusions containing GFAP and small heat shock proteins. To study the effects of GFAP mutations on astrocyte morphology and physiology we have examined hippocam...

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

    Institute of Scientific and Technical Information of China (English)

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

    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 shamoperated 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.

  17. Effects of Alpha-Ketoglutarate on Glutamine Metabolism in Piglet Enterocytes in Vivo and in Vitro.

    Science.gov (United States)

    He, Liuqin; Li, Huan; Huang, Niu; Tian, Junquan; Liu, Zhiqiang; Zhou, Xihong; Yao, Kang; Li, Tiejun; Yin, Yulong

    2016-04-01

    Alpha-ketoglutarate (AKG) plays a vital part in the tricarboxylic acid cycle and is a key intermediate in the oxidation of L-glutamine (Gln). The study was to evaluate effects of AKG on Gln metabolism in vivo and in vitro. A total of twenty-one piglets were weaned at 28 days with a mean body weight (BW) of 6.0 ± 0.2 kg, and randomly divided into 3 groups: corn soybean meal based diet (CON group); the basal diet with 1% alpha-ketoglutarate (AKG treatment group); and the basal diet with 1% L-glutamine (GLN treatment group). Intestinal porcine epithelial cells-1 (IPEC-1) were incubated to investigate effects of 0.5, 2, and 3 mM AKG addition on Gln metabolism. Our results showed that there were no differences (P > 0.05) among the 3 treatments in initial BW, final BW, and average daily feed intake. However, average daily gain (P = 0.013) and gain:feed (P = 0.041) of the AKG group were greater than those of the other two groups. In comparison with the CON group, the AKG and GLN groups exhibited an improvement in villus length, mucosal thickness, and crypt depth in the jejunum of piglets. Serum concentrations of Asp, Glu, Val, Ile, Tyr, Phe, Lys, and Arg in the piglets fed the 1% AKG or Gln diet were lower than those in the CON group. Compared with the CON group, the mRNA expression of jejunal and ileal amino acid (AA) transporters in the AKG and GLN groups were significantly increased (P < 0.05). Additionally, the in vitro study showed that the addition of 0.5, 2, and 3 mM AKG dose-dependently decreased (P < 0.05) the net utilization of Gln and formulation of ammonia, Glu, Ala, and Asp by IPEC-1. In conclusion, dietary AKG supplementation, as a replacement for Gln, could improve Gln metabolism in piglet enterocytes and enhance the utilization of AA. PMID:27018713

  18. Dynamical patterns of calcium signaling in a functional model of neuron-astrocyte networks

    DEFF Research Database (Denmark)

    Postnov, D.E.; Koreshkov, R.N.; Brazhe, N.A.;

    2009-01-01

    We propose a functional mathematical model for neuron-astrocyte networks. The model incorporates elements of the tripartite synapse and the spatial branching structure of coupled astrocytes. We consider glutamate-induced calcium signaling as a specific mode of excitability and transmission in...... astrocytic-neuronal networks. We reproduce local and global dynamical patterns observed experimentally....

  19. File list: ALL.Neu.50.AllAg.Astrocytes [Chip-atlas[Archive

    Lifescience Database Archive (English)

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  20. File list: ALL.Neu.10.AllAg.Astrocytes [Chip-atlas[Archive

    Lifescience Database Archive (English)

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  1. File list: Oth.Neu.20.AllAg.Astrocytes [Chip-atlas[Archive

    Lifescience Database Archive (English)

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    Lifescience Database Archive (English)

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  3. File list: ALL.Neu.20.AllAg.Astrocytes [Chip-atlas[Archive

    Lifescience Database Archive (English)

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    Lifescience Database Archive (English)

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    Lifescience Database Archive (English)

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  6. File list: ALL.Neu.05.AllAg.Astrocytes [Chip-atlas[Archive

    Lifescience Database Archive (English)

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  7. L-Arginine and L-Glutamine as Immunonutrients and Modulating Agents for Erysipelothrix rusiopathiae Infection

    Directory of Open Access Journals (Sweden)

    Haijun Wang

    2012-01-01

    Full Text Available L-arginine and L-glutamine were not only building blocks of proteins and polypeptides but also important regulators of key metabolic pathways that were necessary for maintenance, growth, reproduction and immunity in organisms. These compelling findings convinced us that L-arginine and L-glutamine play a vital role in virus and bacterium infection. However, scientific literature about its role on Erysipelothrix rhusiopathiae (E. rhusiopathiae infection was unavailable. Thus, this study was conduct to research the effect of dietary L-arginine and L-glutamine supplementation on E. rhusiopathiae infection. According to the exciting results, researchers concluded that dietary L-arginine and L-glutamine supplementation ameliorated the cytokines profile and blood parameters and delayed the development process of E. rhusiopathiae infection in mouse model.

  8. Effect of carbohydrate supplementation on plasma glutamine during prolonged exercise and recovery

    DEFF Research Database (Denmark)

    Van Hall, Gerrit; Saris, W H; Wagenmakers, A J

    1998-01-01

    Muscle glycogen and glucose have been suggested to be carbon-chain precursors for glutamine synthesis in skeletal muscle. Therefore, the aim of the present study is to investigate whether carbohydrate supplementation affects plasma glutamine and other amino acids during exercise and 7 h of recovery....... Eight well-trained subjects cycled at an alternating workload of 50 and 80% Wmax until exhaustion (59 to 140 min). During the exercise bout the subjects received either water (control) or a carbohydrate (CHO) drink (83 g CHO x l(-1), 2 ml x kg(-1) per kg body weight every 15 min). Plasma glutamine...... concentration appeared not to be affected by exercise, as a significant increase was only observed at some points in time during the control test. During recovery, however, plasma glutamine concentration decreased from 682+/-24 and 685+/-19 micromol x l(-1) at exhaustion to 552+/-19 and 534+/-12 micromol x l(-1...

  9. Effects of glutamine and curcumin on bacterial translocation in jaundiced rats

    OpenAIRE

    Karatepe, Oguzhan; Acet, Ersin; Battal, Muharrem; Adas, Gokhan; Kemik, Ahu; Altiok, Merih; Kamali, Gulcin; Koculu, Safiye; Catay, Atahan; Kamali, Sedat; Karahan, Servet

    2010-01-01

    AIM: To investigate the effect of curcumin on bacterial translocation and oxidative damage in an obstructive jaundice model and compare the results to glutamine, an agent known to be effective and clinically used.

  10. Comparison of the Gene Expression Profiles of Human Fetal Cortical Astrocytes with Pluripotent Stem Cell Derived Neural Stem Cells Identifies Human Astrocyte Markers and Signaling Pathways and Transcription Factors Active in Human Astrocytes

    OpenAIRE

    Nasir Malik; Xiantao Wang; Sonia Shah; Efthymiou, Anastasia G.; Bin Yan; Sabrina Heman-Ackah; Ming Zhan; Mahendra Rao

    2014-01-01

    Astrocytes are the most abundant cell type in the central nervous system (CNS) and have a multitude of functions that include maintenance of CNS homeostasis, trophic support of neurons, detoxification, and immune surveillance. It has only recently been appreciated that astrocyte dysfunction is a primary cause of many neurological disorders. Despite their importance in disease very little is known about global gene expression for human astrocytes. We have performed a microarray expression anal...

  11. Glutamine-Loaded Liposomes: Preliminary Investigation, Characterization, and Evaluation of Neutrophil Viability.

    Science.gov (United States)

    Costa, Larissa Chaves; Souza, Bárbara Nayane Rosário Fernandes; Almeida, Fábio Fidélis; Lagranha, Cláudia Jacques; Cadena, Pabyton Gonçalves; Santos-Magalhães, Nereide Stela; Lira-Nogueira, Mariane Cajubá de Britto

    2016-04-01

    Glutamine has received attention due to its ability to ameliorate the immune system response. Once conventional liposomes are readily recognized and captured by immune system cells, the encapsulation of glutamine into those nanosystems could be an alternative to reduce glutamine dosage and target then to neutrophils. Our goals were to nanoencapsulate glutamine into conventional liposomes (Gln-L), develop an analytical high-performance liquid chromatography (HPLC) method for its quantification, and evaluate the viability of neutrophils treated with Gln-L. Liposomes were prepared using the thin-film hydration technique followed by sonication and characterized according to pH, mean size, zeta potential, and drug encapsulation efficiency (EE%). We also aimed to study the effect of liposomal constituent concentrations on liposomal characteristics. The viability of neutrophils was assessed using flow cytometry after intraperitoneal administration of free glutamine (Gln), Gln-L, unloaded-liposome (UL), and saline solution as control (C) in healthy Wistar rats. The selected liposomal formulation had a mean vesicle size of 114.65 ± 1.82 nm with a polydispersity index of 0.30 ± 0.00, a positive surface charge of 36.30 ± 1.38 mV, and an EE% of 39.49 ± 0.74%. The developed chromatographic method was efficient for the quantification of encapsulated glutamine, with a retention time at 3.8 min. A greater viability was observed in the group treated with glutamine encapsulated compared to the control group (17%), although neutrophils remain viable in all groups. Thus, glutamine encapsulated into liposomes was able to increase the number of viable neutrophils at low doses, thereby representing a promising strategy for the treatment of immunodeficiency conditions. PMID:26228746

  12. The effect of glutamine infusion on the inflammatory response and HSP70 during human experimental endotoxaemia

    OpenAIRE

    Andreasen, Anne Sofie; Pedersen-Skovsgaard, Theis; Mortensen, Ole Hartvig; van Hall, Gerrit; Moseley, Pope Lloyd; Pedersen, Bente Klarlund

    2009-01-01

    Introduction Glutamine supplementation has beneficial effects on morbidity and mortality in critically ill patients, possibly in part through an attenuation of the proinflammatory cytokine response and a stimulation of heat shock protein (HSP)70. We infused either alanine-glutamine or saline during endotoxin challenge and measured plasma cytokines and HSP70 protein expression. Methods This crossover study, conducted in eight healthy young men, was double-blind, randomized and placebo-controll...

  13. The effect of glutamine and synbiotics on the healing of colonic anastomosis

    OpenAIRE

    Nikolaos Sapidis; Chrysostomos Tziouvaras; Orestis Ioannidis; Ioanna Kalaitsidou; Dimitrios Botsios

    2014-01-01

    Introduction: Intestinal wound healing is an essential process for surgical reconstruction of the digestive tract. The purpose of this study is to evaluate the effect of perioperative administration of glutamine and synbiotics on the biological behavior of intestinal mucosal barrier and the healing of colonic anastomosis in rats. Material and methods: 80 Wistar rats were divided in five groups. A: Control. B: Mechanical bowel preparation and antibiotics. C: Glutamine. D: Synbiotics. E: Glutam...

  14. Influence of glutamine on the effect of resistance exercise on cardiac ANP in rats

    OpenAIRE

    Romeu Rodrigues de Souza; Cleomara Angélica Vieira Caldeira; Patrícia Oliva Carbone; Eduardo Victor Pianca

    2015-01-01

    Various nutritional supplements (herbs, vitamins, and micronutrients) improve responses and adaptations to resistance exercise. ANP is a heart hormone that contributes to fluid, electrolyte and blood pressure homeostasis through its natriuretic and vasodilative actions. In the present study, the adaptation of ANP in response to resistance exercise was investigated in rats supplemented with glutamine for five weeks. The results showed that supplementation with glutamine did not influence the n...

  15. Protection from radiation injury by elemental diet: does added glutamine change the effect?

    OpenAIRE

    McArdle, A. H.

    1994-01-01

    The feeding of a protein hydrolysate based 'elemental' diet supplemented with added glutamine did not provide superior protection to the small intestine of dogs subjected to therapeutic pelvic irradiation. Comparison of diets with and without the added glutamine showed significant protection of the intestine from radiation injury. Both histological examination and electron microscopy showed lack of tissue injury with both diets. The activity of the free radical generating enzymes, scavengers,...

  16. Glutamate/glutamine and neuronal integrity in adults with ADHD: a proton MRS study

    OpenAIRE

    Maltezos, S.; Horder, J; Coghlan, S; Skirrow, C; O'Gorman, R; Lavender, T J; Mendez, M A; Mehta, M.; Daly, E.; Xenitidis, K; Paliokosta, E; Spain, D; M. Pitts; Asherson, P.; Lythgoe, D J

    2014-01-01

    There is increasing evidence that abnormalities in glutamate signalling may contribute to the pathophysiology of attention-deficit hyperactivity disorder (ADHD). Proton magnetic resonance spectroscopy ([1H]MRS) can be used to measure glutamate, and also its metabolite glutamine, in vivo. However, few studies have investigated glutamate in the brain of adults with ADHD naive to stimulant medication. Therefore, we used [1H]MRS to measure the combined signal of glutamate and glutamine (Glu+Gln; ...

  17. 1,3-Dinitrobenzene neurotoxicity - Passage effect in immortalized astrocytes.

    Science.gov (United States)

    Maurer, Laura L; Latham, Jackelyn D; Landis, Rory W; Song, Dong Hoon; Epstein, Tamir; Philbert, Martin A

    2016-03-01

    Age-related disturbances in astrocytic mitochondrial function are linked to loss of neuroprotection and decrements in neurological function. The immortalized rat neocortical astrocyte-derived cell line, DI-TNC1, provides a convenient model for the examination of cellular aging processes that are difficult to study in primary cell isolates from aged brain. Successive passages in culture may serve as a surrogate of aging in which time-dependent adaptation to culture conditions may result in altered responses to xenobiotic challenge. To investigate the hypothesis that astrocytic mitochondrial homeostatic function is decreased with time in culture, low passage DI-TNC1 astrocytes (LP; #2-8) and high passage DI-TNC1 astrocytes (HP; #17-28) were exposed to the mitochondrial neurotoxicant 1,3-dinitrobenzene (DNB). Cells were exposed in either monoculture or in co-culture with primary cortical neurons. Astrocyte mitochondrial membrane potential, morphology, ATP production and proliferation were monitored in monoculture, and the ability of DI-TNC1 cells to buffer K(+)-induced neuronal depolarization was examined in co-cultures. In HP DI-TNC1 cells, DNB exposure decreased proliferation, reduced mitochondrial membrane potential and significantly decreased mitochondrial form factor. Low passage DI-TNC1 cells effectively attenuated K(+)-induced neuronal depolarization in the presence of DNB whereas HP counterparts were unable to buffer K(+) in DNB challenge. Following DNB challenge, LP DI-TNC1 cells exhibited greater viability in co-culture than HP. The data provide compelling evidence that there is an abrupt phenotypic change in DI-TNC1 cells between passage #9-16 that significantly diminishes the ability of DI-TNC1 cells to compensate for neurotoxic challenge and provide neuroprotective spatial buffering. Whether or not these functional changes have an in vivo analog in aging brain remains to be determined. PMID:26769196

  18. NT2 derived neuronal and astrocytic network signalling.

    Directory of Open Access Journals (Sweden)

    Eric J Hill

    Full Text Available A major focus of stem cell research is the generation of neurons that may then be implanted to treat neurodegenerative diseases. However, a picture is emerging where astrocytes are partners to neurons in sustaining and modulating brain function. We therefore investigated the functional properties of NT2 derived astrocytes and neurons using electrophysiological and calcium imaging approaches. NT2 neurons (NT2Ns expressed sodium dependent action potentials, as well as responses to depolarisation and the neurotransmitter glutamate. NT2Ns exhibited spontaneous and coordinated calcium elevations in clusters and in extended processes, indicating local and long distance signalling. Tetrodotoxin sensitive network activity could also be evoked by electrical stimulation. Similarly, NT2 astrocytes (NT2As exhibited morphology and functional properties consistent with this glial cell type. NT2As responded to neuronal activity and to exogenously applied neurotransmitters with calcium elevations, and in contrast to neurons, also exhibited spontaneous rhythmic calcium oscillations. NT2As also generated propagating calcium waves that were gap junction and purinergic signalling dependent. Our results show that NT2 derived astrocytes exhibit appropriate functionality and that NT2N networks interact with NT2A networks in co-culture. These findings underline the utility of such cultures to investigate human brain cell type signalling under controlled conditions. Furthermore, since stem cell derived neuron function and survival is of great importance therapeutically, our findings suggest that the presence of complementary astrocytes may be valuable in supporting stem cell derived neuronal networks. Indeed, this also supports the intriguing possibility of selective therapeutic replacement of astrocytes in diseases where these cells are either lost or lose functionality.

  19. p53 protein alterations in adult astrocytic tumors and oligodendrogliomas

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    Nayak Anupma

    2004-04-01

    Full Text Available BACKGROUND: p53 is a tumor suppressor gene implicated in the genesis of a variety of malignancies including brain tumors. Overexpression of the p53 protein is often used as a surrogate indicator of alterations in the p53 gene. AIMS: In this study, data is presented on p53 protein expression in adult cases (>15 years of age of astrocytic (n=152 and oligodendroglial (n=28 tumors of all grades. Of the astrocytic tumors, 86% were supratentorial in location while remaining 14% were located infratentorially - 8 in the the cerebellum and 13 in the brainstem. All the oligodendrogliomas were supratentorial. MATERIALS AND METHODS: p53 protein expression was evaluated on formalin-fixed paraffin-embedded sections using streptavidin biotin immunoperoxidase technique after high temperature antigen retrieval. RESULTS: Overall 52% of supratentorial astrocytic tumors showed p53 immunopositivity with no correlation to the histological grade. Thus, 58.8% of diffuse astrocytomas (WHO Grade II, 53.8% of anaplastic astrocytomas (WHO Grade III and 50% of glioblastomas (WHO Grade IV were p53 protein positive. In contrast, all the infratentorial tumors were p53 negative except for one brainstem glioblastoma. Similarly, pilocytic astrocytomas were uniformly p53 negative irrespective of the location. Among oligodendroglial tumors, the overall frequency of p53 immunopositivity was lower (only 28%, though a trend of positive correlation with the tumor grade was noted - 25% in Grade II and 31.5% in grade III (anaplastic oligodendroglioma. Interestingly, p53 labeling index (p53 LI did not correlate with the histopathological grade in both astrocytic and oligodendroglial tumors. CONCLUSIONS: Thus, this study gives an insight into the genetic and hence biological heterogeneity of gliomas, not only between astrocytic tumors vs. oligodendrogliomas but also within astrocytic tumors with regard to their grade and location. With p53 gene therapy trials in progress, this will

  20. Dysfunctional TCA-Cycle Metabolism in Glutamate Dehydrogenase Deficient Astrocytes

    DEFF Research Database (Denmark)

    Nissen, Jakob D; Pajęcka, Kamilla; Stridh, Malin H;

    2015-01-01

    synthesis of aspartate via pyruvate carboxylation. In the absence of glucose, lactate production from glutamate via malic enzyme was lower in GDH deficient astrocytes. In conclusions, our studies reveal that metabolism via GDH serves an important anaplerotic role by adding net carbon to the TCA cycle. A...... reduction in GDH activity seems to cause the astrocytes to up-regulate activity in pathways involved in maintaining the amount of TCA cycle intermediates such as pyruvate carboxylation as well as utilization of alternate substrates such as branched chain amino acids....

  1. CCL2 modulates cytokine production in cultured mouse astrocytes

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    Frugier Tony

    2010-10-01

    Full Text Available Abstract Background The chemokine CCL2 (also known as monocyte chemoattractant protein-1, or MCP-1 is upregulated in patients and rodent models of traumatic brain injury (TBI, contributing to post-traumatic neuroinflammation and degeneration by directing the infiltration of blood-derived macrophages into the injured brain. Our laboratory has previously reported that Ccl2-/- mice show reduced macrophage accumulation and tissue damage, corresponding to improved motor recovery, following experimental TBI. Surprisingly, Ccl2-deficient mice also exhibited delayed but exacerbated secretion of key proinflammatory cytokines in the injured cortex. Thus we sought to further characterise CCL2's potential ability to modulate immunoactivation of astrocytes in vitro. Methods Primary astrocytes were isolated from neonatal wild-type and Ccl2-deficient mice. Established astrocyte cultures were stimulated with various concentrations of lipopolysaccharide (LPS and interleukin (IL-1β for up to 24 hours. Separate experiments involved pre-incubation with mouse recombinant (rCCL2 prior to IL-1β stimulation in wild-type cells. Following stimulation, cytokine secretion was measured in culture supernatant by immunoassays, whilst cytokine gene expression was quantified by real-time reverse transcriptase polymerase chain reaction. Results LPS (0.1-100 μg/ml; 8 h induced the significantly greater secretion of five key cytokines and chemokines in Ccl2-/- astrocytes compared to wild-type cells. Consistently, IL-6 mRNA levels were 2-fold higher in Ccl2-deficient cells. IL-1β (10 and 50 ng/ml; 2-24 h also resulted in exacerbated IL-6 production from Ccl2-/- cultures. Despite this, treatment of wild-type cultures with rCCL2 alone (50-500 ng/ml did not induce cytokine/chemokine production by astrocytes. However, pre-incubation of wild-type astrocytes with rCCL2 (250 ng/ml, 12 h prior to stimulation with IL-1β (10 ng/ml, 8 h significantly reduced IL-6 protein and gene

  2. Glutamine supplementation in cancer patients receiving chemotherapy: a double-blind randomized study.

    Science.gov (United States)

    Bozzetti, F; Biganzoli, L; Gavazzi, C; Cappuzzo, F; Carnaghi, C; Buzzoni, R; Dibartolomeo, M; Baietta, E

    1997-01-01

    The purpose of this study was to evaluate the efficacy of glutamine in preventing doxifluridine-induced diarrhea and the potential impact of glutamine on the tumor growth. We investigated 65 patients with advanced breast cancer receiving doxifluridine in a double-blind randomized fashion: 33 patients took glutamine (30 g/d, divided in 3 doses of 10 g each) for 8 consecutive days (5-12h) during each interval between chemotherapy, which was administered from day 1 to 4. Thirty-two patients took an equal dose of placebo (maltodextrine). The incidence of diarrhea was registered after each cycle of chemotherapy and severity was scored by the National Cancer Institute (NCI), Bethesda, Maryland, classification. The tumor response was evaluated by the World Health Organization (WHO) criteria. A total of 278 and 259 cycles (median 10 cycles), respectively, were delivered in glutamine and placebo groups. There were 34 and 32 episodes of diarrhea in glutamine and placebo groups, with no statistical difference overall, in the severity and duration of tumor growth, there was no difference in the response rate (21% and 28% of complete or partial response, respectively), in median time to response (2 mo), or in median duration of response. In conclusion, glutamine did not prevent the occurrence of the doxifluridine-induced diarrhea and did not have any impact on tumor response to chemotherapy. PMID:9263281

  3. Enhanced mitochondrial glutamine anaplerosis suppresses pancreatic cancer growth through autophagy inhibition.

    Science.gov (United States)

    Jeong, Seung Min; Hwang, Sunsook; Park, Kyungsoo; Yang, Seungyeon; Seong, Rho Hyun

    2016-01-01

    Cancer cells use precursors derived from tricarboxylic acid (TCA) cycle to support their unlimited growth. However, continuous export of TCA cycle intermediates results in the defect of mitochondrial integrity. Mitochondria glutamine metabolism plays an essential role for the maintenance of mitochondrial functions and its biosynthetic roles by refilling the mitochondrial carbon pool. Here we report that human pancreatic ductal adenocarcinoma (PDAC) cells have a distinct dependence on mitochondrial glutamine metabolism. Whereas glutamine flux into mitochondria contributes to proliferation of most cancer cells, enhanced glutamine anaplerosis results in a pronounced suppression of PDAC growth. A cell membrane permeable α-ketoglutarate analog or overexpression of glutamate dehydrogenase lead to decreased proliferation and increased apoptotic cell death in PDAC cells but not other cancer cells. We found that enhanced glutamine anaplerosis inhibits autophagy, required for tumorigenic growth of PDAC, by activating mammalian TORC1. Together, our results reveal that glutamine anaplerosis is a crucial regulator of growth and survival of PDAC cells, which may provide novel therapeutic approaches to treat these cancers. PMID:27477484

  4. Pilot study with a glutamine-supplemented enteral formula in critically ill infants

    Directory of Open Access Journals (Sweden)

    Barbosa Eliana

    1999-01-01

    Full Text Available Seriously ill infants often display protein-calorie malnutrition due to the metabolic demands of sepsis and respiratory failure. Glutamine has been classified as a conditionally essential amino acid, with special usefulness in critical patients. Immunomodulation, gut protection, and prevention of protein depletion are mentioned among its positive effects in such circumstances. With the intent of evaluating the tolerance and clinical impact of a glutamine supplement in seriously ill infants, a prospective randomized study was done with nine patients. Anthropometric and biochemical determinations were made, and length of stay in the intensive care unit (ICU, in the hospital, and under artificial ventilation, and septic morbidity and mortality were tabulated. Infants in the treatment group (n=5 were enterally administered 0.3 g/kg of glutamine, whereas controls received 0.3 g/kg of casein during a standard period of five days. Septic complications occurred in 75% of the controls (3/4 versus 20% of the glutamine-treated group (1/5, p<=0.10, and two patients in the control group died of bacterial infections (50% vs. 0%, p<=0.10. Days in the ICU, in the hospital, and with ventilation numerically favored glutamine therapy, although without statistical significance. The supplements were usually well tolerated, and no patient required discontinuation of the program. The conclusion was that glutamine supplementation was safe and tended to be associated with less infectious morbidity and mortality in this high-risk population.

  5. L-type voltage-operated calcium channels contribute to astrocyte activation In vitro.

    Science.gov (United States)

    Cheli, Veronica T; Santiago González, Diara A; Smith, Jessica; Spreuer, Vilma; Murphy, Geoffrey G; Paez, Pablo M

    2016-08-01

    We have found a significant upregulation of L-type voltage-operated Ca(++) channels (VOCCs) in reactive astrocytes. To test if VOCCs are centrally involved in triggering astrocyte reactivity, we used in vitro models of astrocyte activation in combination with pharmacological inhibitors, siRNAs and the Cre/lox system to reduce the activity of L-type VOCCs in primary cortical astrocytes. The endotoxin lipopolysaccharide (LPS) as well as high extracellular K(+) , glutamate, and ATP promote astrogliosis in vitro. L-type VOCC inhibitors drastically reduce the number of reactive cells, astrocyte hypertrophy, and cell proliferation after these treatments. Astrocytes transfected with siRNAs for the Cav1.2 subunit that conducts L-type Ca(++) currents as well as Cav1.2 knockout astrocytes showed reduce Ca(++) influx by ∼80% after plasma membrane depolarization. Importantly, Cav1.2 knock-down/out prevents astrocyte activation and proliferation induced by LPS. Similar results were found using the scratch wound assay. After injuring the astrocyte monolayer, cells extend processes toward the cell-free scratch region and subsequently migrate and populate the scratch. We found a significant increase in the activity of L-type VOCCs in reactive astrocytes located in the growing line in comparison to quiescent astrocytes situated away from the scratch. Moreover, the migration of astrocytes from the scratching line as well as the number of proliferating astrocytes was reduced in Cav1.2 knock-down/out cultures. In summary, our results suggest that Cav1.2 L-type VOCCs play a fundamental role in the induction and/or proliferation of reactive astrocytes, and indicate that the inhibition of these Ca(++) channels may be an effective way to prevent astrocyte activation. GLIA 2016. GLIA 2016;64:1396-1415. PMID:27247164

  6. Fe2+-Tetracycline-Mediated Cleavage of the Tn10 Tetracycline Efflux Protein TetA Reveals a Substrate Binding Site near Glutamine 225 in Transmembrane Helix 7

    OpenAIRE

    McMurry, Laura M.; Aldema-Ramos, Mila L.; Levy, Stuart B.

    2002-01-01

    TetA specified by Tn10 is a class B member of a group of related bacterial transport proteins of 12 transmembrane alpha helices that mediate resistance to the antibiotic tetracycline. A tetracycline-divalent metal cation complex is expelled from the cell in exchange for a entering proton. The site(s) where tetracycline binds to this export pump is not known. We found that, when chelated to tetracycline, Fe2+ cleaved the backbone of TetA predominantly at a single position, glutamine 225 in tra...

  7. Astrocytes protect neurons against methylmercury via ATP/P2Y(1 receptor-mediated pathways in astrocytes.

    Directory of Open Access Journals (Sweden)

    Yusuke Noguchi

    Full Text Available Methylmercury (MeHg is a well known environmental pollutant that induces serious neuronal damage. Although MeHg readily crosses the blood-brain barrier, and should affect both neurons and glial cells, how it affects glia or neuron-to-glia interactions has received only limited attention. Here, we report that MeHg triggers ATP/P2Y1 receptor signals in astrocytes, thereby protecting neurons against MeHg via interleukin-6 (IL-6-mediated pathways. MeHg increased several mRNAs in astrocytes, among which IL-6 was the highest. For this, ATP/P2Y1 receptor-mediated mechanisms were required because the IL-6 production was (i inhibited by a P2Y1 receptor antagonist, MRS2179, (ii abolished in astrocytes obtained from P2Y1 receptor-knockout mice, and (iii mimicked by exogenously applied ATP. In addition, (iv MeHg released ATP by exocytosis from astrocytes. As for the intracellular mechanisms responsible for IL-6 production, p38 MAP kinase was involved. MeHg-treated astrocyte-conditioned medium (ACM showed neuro-protective effects against MeHg, which was blocked by anti-IL-6 antibody and was mimicked by the application of recombinant IL-6. As for the mechanism of neuro-protection by IL-6, an adenosine A1 receptor-mediated pathway in neurons seems to be involved. Taken together, when astrocytes sense MeHg, they release ATP that autostimulates P2Y1 receptors to upregulate IL-6, thereby leading to A1 receptor-mediated neuro-protection against MeHg.

  8. Human Brain Astrocytes Mediate TRAIL-mediated Apoptosis after Treatment with IFN-γ

    OpenAIRE

    Lee, Jeonggi; Shin, Jeon-Soo; Choi, In-Hong

    2006-01-01

    TNF-related apoptosis inducing ligand (TRAIL) expressions were studied in primary human brain astrocytes in response to pro-inflammatory cytokines. When astrocytes were treated with IL-1β, TNF-α or IFN-γ, TRAIL was induced in cultured fetal astrocytes. In particular, IFN-γ induced the highest levels of TRAIL in cultured astrocytes. When astrocytes were prereated with IFN-γ, they induced apoptosis in TRAIL-sensitive Peer cells. Our results suggest that IFN-γ modulates the expression of TRAIL i...

  9. Astrocyte-to-neuron signaling in response to photostimulation with a femtosecond laser

    Science.gov (United States)

    Zhao, Yuan; Liu, Xiuli; Zhou, Wei; Zeng, Shaoqun

    2010-08-01

    Conventional stimulation techniques used in studies of astrocyte-to-neuron signaling are invasive or dependent on additional electrical devices or chemicals. Here, we applied photostimulation with a femtosecond laser to selectively stimulate astrocytes in the hippocampal neural network, and the neuronal responses were examined. The results showed that, after photostimulation, cell-specific astrocyte-to-neuron signaling was triggered; sometimes the neuronal responses were even synchronous. Since photostimulation with a femtosecond laser is noninvasive, agent-free, and highly precise, this method has been proved to be efficient in activating astrocytes for investigations of astrocytic functions in neural networks.

  10. Shifts in excitatory/inhibitory balance by juvenile stress: A role for neuron-astrocyte interaction in the dentate gyrus.

    Science.gov (United States)

    Albrecht, Anne; Ivens, Sebastian; Papageorgiou, Ismini E; Çalışkan, Gürsel; Saiepour, Nasrin; Brück, Wolfgang; Richter-Levin, Gal; Heinemann, Uwe; Stork, Oliver

    2016-06-01

    Childhood trauma is a well-described risk factor for the development of stress-related psychopathology such as posttraumatic stress disorder or depression later in life. Childhood adversity can be modeled in rodents by juvenile stress (JS) protocols, resulting in impaired coping with stressful challenges in adulthood. In the current study, we investigated the long-lasting impact of JS on the expression of molecular factors for glutamate and γ-aminobutyric acid (GABA) uptake and turnover in sublayers of the dentate gyrus (DG) using laser microdissection and quantitative real-time polymerase chain reaction. We observed reduced mRNA expression levels after JS for factors mediating astrocytic glutamate and GABA uptake and degradation. These alterations were prominently observed in the dorsal but not ventral DG granule cell layer, indicating a lasting change in astrocytic GABA and glutamate metabolism that may affect dorsal DG network activity. Indeed, we observed increased inhibition and a lack of facilitation in response to paired-pulse stimulation at short interstimulus intervals in the dorsal DG after JS, while no alterations were evident in basal synaptic transmission or forms of long-term plasticity. The shift in paired-pulse response was mimicked by pharmacologically blocking the astrocytic GABA transporter GAT-3 in naïve animals. Accordingly, reduced expression levels of GAT-3 were confirmed at the protein level in the dorsal granule cell layer of rats stressed in juvenility. Together, these data demonstrate a lasting shift in the excitatory/inhibitory balance of dorsal DG network activity by JS that appears to be mediated by decreased GABA uptake into astrocytes. GLIA 2016;64:911-922. PMID:26875694

  11. The effect of free glutamine and peptide ingestion on the rate of muscle glycogen resynthesis in man

    DEFF Research Database (Denmark)

    Van Hall, Gerrit; Saris, W H; van de Schoor, P A;

    2000-01-01

    The present study investigated previous claims that ingestion of glutamine and of protein-carbohydrate mixtures may increase the rate of glycogen resynthesis following intense exercise. Eight trained subjects were studied during 3 h of recovery while consuming one of four drinks in random order....... Drinks were ingested in three 500 ml boluses, immediately after exercise and then after 1 and 2 h of recovery. Each bolus of the control drink contained 0.8 g x kg(-1) body weight of glucose. The other drinks contained the same amount of glucose and 0.3 g x kg(-1) body weight of 1) glutamine, 2) a wheat...... hydrolysate (26% glutamine) and 3) a whey hydrolysate (6.6% glutamine). Plasma glutamine, decreased by approximately 20% during recovery with ingestion of the control drink, no changes with ingestion of the protein hydrolysates drinks, and a 2-fold increase with ingestion of the free glutamine drinks. The...

  12. Isolation and characterization of glutamine synthetase genes in Chlamydomonas reinhardtii.

    Science.gov (United States)

    Chen, Q; Silflow, C D

    1996-11-01

    To elucidate the role of glutamine synthetase (GS) in nitrogen assimilation in the green alga Chlamydomonas reinhardtii we used maize GS1 (the cytosolic form) and GS2 (the chloroplastic form) cDNAs as hybridization probes to isolate C. reinhardtii cDNA clones. The amino acid sequences derived from the C. reinhardtii clones have extensive homology with GS enzymes from higher plants. A putative amino-terminal transit peptide encoded by the GS2 cDNA suggests that the protein localizes to the chloroplast. Genomic DNA blot analysis indicated that GS1 is encoded by a single gene, whereas two genomic fragments hybridized to the GS2 cDNA probe. All GS2 cDNA clones corresponded to only one of the two GS2 genomic sequences. We provide evidence that ammonium, nitrate, and light regulate GS transcript accumulation in green algae. Our results indicate that the level of GS1 transcripts is repressed by ammonium but induced by nitrate. The level of GS2 transcripts is not affected by ammonium or nitrate. Expression of both GS1 and GS2 genes is regulated by light, but perhaps through different mechanisms. Unlike in higher plants, no decreased level of GS2 transcripts was detected when cells were grown under conditions that repress photorespiration. Analysis of GS transcript levels in mutants with defects in the nitrate assimilation pathway show that nitrate assimilation and ammonium assimilation are regulated independently. PMID:8938407

  13. Glutamine: a precursor of glutathione and its effect on liver

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    AIM To investigate the relationship between alanyl-glutamine (ALA-GLN) and glutathione (GSH) biosynthesis in hepatic protection.METHODS Twenty male Wistar rats were randomly divided into two groups: one receiving standard parenteral nutrition (STD) and the other supplemented with or without ALA-GLN for 7 days. The blood and liver tissue samples were examined after 5-fluorouracil (5-FU) was injected peritoneally.RESULTS The concentration measurements were significantly higher in ALA-GLN group than in STD group in serum GLN (687 μmol/ L±50 μmol/ L vs 505 μmol/ L±39 μmol/ L, P<0.05), serum GSH (14 μmol/ L±5 μmol/ L vs 7 μmol/ L±3 μmol/ L, P<0.01) and in liver GSH content (6.9 μmol/ g±2.5 μmol/ g vs 4.4 μmol/ g±1.6 μmol/ g liver tissue, P<0.05). Rats in ALA-GLN group had lesser elevations in hepatic enzymes after 5-FU administration.CONCLUSION The supplemented nutrition ALA-GLN can protect the liver function through increasing the glutathione biosynthesis and preserving the glutathione stores in hepatic tissue.

  14. Overexpression of glutamine synthetases confers transgenic rice herbicide resistance

    Institute of Scientific and Technical Information of China (English)

    Sun Hui; Huang Qiman; Su Jin

    2005-01-01

    Glutamine synthetase (GS, E.C.6.3.1.2) is a key enzyme involved in the assimilation of inorganic nitrogen in higher plants and gram-negative microorganisms. GS is the targeting enzyme of a herbicide phosphinothricin (PPT) or Basta. In order to generate PPT-resistant transgenic rice via overexpression of GS, we constructed a plant expression vector p2GS harboring two different isoenzymes GS1 and GS2 cDNAs under the control of constitutive promoters of rice Act1 and maize Ubiquitin(Ubi) genes. The p2GS was introduced into rice genome by Agrobacterium-mediated transformation and confirmed by PCR and Southern blot hybridization. GS-transgene expression was first detected by Northern blot analyses. Results from Basta test indicated that GS-transgenic plants can tolerate as high as 0.3% Basta solution. In addition, our results also demonstrated that GS overexpression conferred transformed rice calli PPT resistance. Thus, GS cassette can serve as a selective marker gene instead of bar cassette for selection of PPT transformants.

  15. Glutamine synthetase and glutamyltransferase in developing chick and rat tissues

    Energy Technology Data Exchange (ETDEWEB)

    Herzfeld, A.; Raper, S.M.

    1975-01-01

    Concomitant determination of ..gamma..-glutamine-hydroxylamine-glutamyltransferase (GT) and ..gamma..-glutamyl hydroxamate synthetase (GS) activities in chick retina, brain and liver between the 13th day of incubation and a day after hatching showed that while both activities increased late in incubation, in neural tissues their rises were not simultaneous throughout development; in liver both activities were already high on the 14th day of incubation and changed in parallel thereafter. GS and GT activities could be evoked prematurely in all three tissues by cortisol, but GT activity showed higher responses to the hormone. GT and GS were separable by differential solubilization in chick liver but not in retina of chick or rat. The wide spread of the ratios of GT : GS activities in homogenates of a number of chick and rat tissues (1 : 1 to 73 : 1) indicates that the GS reaction is not catalyzed by the same protein that catalyzes the GT reactions. Relative amounts of GT(T) (free of GS activity) and of variants of GS (with different competences to catalyze the GT reaction) may govern the changes between the two activities during development and their distribution among different adult tissues in chick and rat.

  16. Glutamine Attenuates Acute Lung Injury Caused by Acid Aspiration

    Directory of Open Access Journals (Sweden)

    Chih-Cheng Lai

    2014-08-01

    Full Text Available Inadequate ventilator settings may cause overwhelming inflammatory responses associated with ventilator-induced lung injury (VILI in patients with acute respiratory distress syndrome (ARDS. Here, we examined potential benefits of glutamine (GLN on a two-hit model for VILI after acid aspiration-induced lung injury in rats. Rats were intratracheally challenged with hydrochloric acid as a first hit to induce lung inflammation, then randomly received intravenous GLN or lactated Ringer’s solution (vehicle control thirty min before different ventilator strategies. Rats were then randomized to receive mechanical ventilation as a second hit with a high tidal volume (TV of 15 mL/kg and zero positive end-expiratory pressure (PEEP or a low TV of 6 mL/kg with PEEP of 5 cm H2O. We evaluated lung oxygenation, inflammation, mechanics, and histology. After ventilator use for 4 h, high TV resulted in greater lung injury physiologic and biologic indices. Compared with vehicle treated rats, GLN administration attenuated lung injury, with improved oxygenation and static compliance, and decreased respiratory elastance, lung edema, extended lung destruction (lung injury scores and lung histology, neutrophil recruitment in the lung, and cytokine production. Thus, GLN administration improved the physiologic and biologic profiles of this experimental model of VILI based on the two-hit theory.

  17. Paracrine effect of carbon monoxide - astrocytes promote neuroprotection through purinergic signaling in mice.

    Science.gov (United States)

    Queiroga, Cláudia S F; Alves, Raquel M A; Conde, Sílvia V; Alves, Paula M; Vieira, Helena L A

    2016-08-15

    The neuroprotective role of carbon monoxide (CO) has been studied in a cell-autonomous mode. Herein, a new concept is disclosed - CO affects astrocyte-neuron communication in a paracrine manner to promote neuroprotection. Neuronal survival was assessed when co-cultured with astrocytes that had been pre-treated or not with CO. The CO-pre-treated astrocytes reduced neuronal cell death, and the cellular mechanisms were investigated, focusing on purinergic signaling. CO modulates astrocytic metabolism and extracellular ATP content in the co-culture medium. Moreover, several antagonists of P1 adenosine and P2 ATP receptors partially reverted CO-induced neuroprotection through astrocytes. Likewise, knocking down expression of the neuronal P1 adenosine receptor A2A-R (encoded by Adora2a) reverted the neuroprotective effects of CO-exposed astrocytes. The neuroprotection of CO-treated astrocytes also decreased following prevention of ATP or adenosine release from astrocytic cells and inhibition of extracellular ATP metabolism into adenosine. Finally, the neuronal downstream event involves TrkB (also known as NTRK2) receptors and BDNF. Pharmacological and genetic inhibition of TrkB receptors reverts neuroprotection triggered by CO-treated astrocytes. Furthermore, the neuronal ratio of BDNF to pro-BDNF increased in the presence of CO-treated astrocytes and decreased whenever A2A-R expression was silenced. In summary, CO prevents neuronal cell death in a paracrine manner by targeting astrocytic metabolism through purinergic signaling. PMID:27383770

  18. Impairments of astrocytes are involved in the D-galactose-induced brain aging

    International Nuclear Information System (INIS)

    Astrocyte dysfunction is implicated in course of various age-related neurodegenerative diseases. Chronic injection of D-galactose can cause a progressive deterioration in learning and memory capacity and serve as an animal model of aging. To investigate the involvement of astrocytes in this model, oxidative stress biomarkers, biochemical and pathological changes of astrocytes were examined in the hippocampus of the rats with six weeks of D-galactose injection. D-galactose-injected rats displayed impaired antioxidant systems, an increase in nitric oxide levels, and a decrease in reduced glutathione levels. Consistently, western blotting and immunostaining of glial fibrillary acidic protein showed extensive activation of astrocytes. Double-immunofluorescent staining further showed activated astrocytes highly expressed inducible nitric oxide synthase. Electron microscopy demonstrated the degeneration of astrocytes, especially in the aggregated area of synapse and brain microvessels. These findings indicate that impairments of astrocytes are involved in oxidative stress-induced brain aging by chronic injection of D-galactose

  19. IMPROVEMENT OF INTESTINAL PERMEABILITY WITH ALANYL-GLUTAMINE IN HIV PATIENTS: a randomized, double blinded, placebo-controlled clinical trial

    OpenAIRE

    Roberio Dias LEITE; Noelia Leal LIMA; Christiane Araujo Chaves LEITE; Calil Kairalla FARHAT; Guerrant, Richard Littleton; Aldo Angelo Moreira LIMA

    2013-01-01

    Context Glutamine is the main source of energy of the enterocyte and diarrhea and weight loss are frequent in HIV infected patients. Objective To determine the effect of alanyl-glutamine supplementation on intestinal permeability and absorption in these patients. Methods Randomized double-blinded, placebo-controlled study using isonitrogenous doses of alanyl-glutamine (24 g/day) and placebo (glycine, 25 g/day) during 10 days. Before and after this nutritional supplementation l...

  20. IMPROVEMENT OF INTESTINAL PERMEABILITY WITH ALANYL-GLUTAMINE IN HIV PATIENTS: a randomized, double blinded, placebo-controlled clinical trial

    OpenAIRE

    Roberio Dias LEITE; Noelia Leal LIMA; Christiane Araujo Chaves LEITE; Calil Kairalla FARHAT; Guerrant, Richard Littleton; Aldo Angelo Moreira LIMA

    2013-01-01

    Context Glutamine is the main source of energy of the enterocyte and diarrhea and weight loss are frequent in HIV infected patients. Objective To determine the effect of alanyl-glutamine supplementation on intestinal permeability and absorption in these patients. Methods Randomized double-blinded, placebo-controlled study using isonitrogenous doses of alanyl-glutamine (24 g/day) and placebo (glycine, 25 g/day) during 10 days. Before and after this nutritional supplementation lactulose and...