Science.gov

Sample records for acidic protein-positive astrocytes

  1. Astrocytes.

    ERIC Educational Resources Information Center

    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)

  2. Astrocytes Release Polyunsaturated Fatty Acids by Lipopolysaccharide Stimuli.

    PubMed

    Aizawa, Fuka; Nishinaka, Takashi; Yamashita, Takuya; Nakamoto, Kazuo; Koyama, Yutaka; Kasuya, Fumiyo; Tokuyama, Shogo

    2016-01-01

    We previously reported that levels of long-chain fatty acids (FAs) including docosahexaenoic acids (DHA) increase in the hypothalamus of inflammatory pain model mice. However, the precise mechanisms underlying the increment of free fatty acids (FFAs) in the brain during inflammation remains unknown. In this study, we characterized FFAs released by inflammatory stimulation in rat primary cultured astrocytes, and tested the involvement of phospholipase A2 (PLA2) on these mechanisms. Lipopolysaccharide (LPS) stimulation significantly increased the levels of several FAs in the astrocytes. Under these conditions, mRNA expression of cytosolic PLA2 (cPLA2) and calcium-independent PLA2 (iPLA2) in LPS-treated group increased compared with the control group. Furthermore, in the culture media, the levels of DHA and arachidonic acid (ARA) significantly increased by LPS stimuli compared with those of a vehicle-treated control group whereas the levels of saturated FAs (SFAs), namely palmitic acid (PAM) and stearic acid (STA), did not change. In summary, our findings suggest that astrocytes specifically release DHA and ARA by inflammatory conditions. Therefore astrocytes might function as a regulatory factor of DHA and ARA in the brain. PMID:27374285

  3. Medium-chain fatty acids inhibit mitochondrial metabolism in astrocytes promoting astrocyte-neuron lactate and ketone body shuttle systems.

    PubMed

    Thevenet, Jonathan; De Marchi, Umberto; Domingo, Jaime Santo; Christinat, Nicolas; Bultot, Laurent; Lefebvre, Gregory; Sakamoto, Kei; Descombes, Patrick; Masoodi, Mojgan; Wiederkehr, Andreas

    2016-05-01

    Medium-chain triglycerides have been used as part of a ketogenic diet effective in reducing epileptic episodes. The health benefits of the derived medium-chain fatty acids (MCFAs) are thought to result from the stimulation of liver ketogenesis providing fuel for the brain. We tested whether MCFAs have direct effects on energy metabolism in induced pluripotent stem cell-derived human astrocytes and neurons. Using single-cell imaging, we observed an acute pronounced reduction of the mitochondrial electrical potential and a concomitant drop of the NAD(P)H signal in astrocytes, but not in neurons. Despite the observed effects on mitochondrial function, MCFAs did not lower intracellular ATP levels or activate the energy sensor AMP-activated protein kinase. ATP concentrations in astrocytes were unaltered, even when blocking the respiratory chain, suggesting compensation through accelerated glycolysis. The MCFA decanoic acid (300 μM) promoted glycolysis and augmented lactate formation by 49.6%. The shorter fatty acid octanoic acid (300 μM) did not affect glycolysis but increased the rates of astrocyte ketogenesis 2.17-fold compared with that of control cells. MCFAs may have brain health benefits through the modulation of astrocyte metabolism leading to activation of shuttle systems that provide fuel to neighboring neurons in the form of lactate and ketone bodies.-Thevenet, J., De Marchi, U., Santo Domingo, J., Christinat, N., Bultot, L., Lefebvre, G., Sakamoto, K., Descombes, P., Masoodi, M., Wiederkehr, A. Medium-chain fatty acids inhibit mitochondrial metabolism in astrocytes promoting astrocyte-neuron lactate and ketone body shuttle systems.

  4. Medium-chain fatty acids inhibit mitochondrial metabolism in astrocytes promoting astrocyte-neuron lactate and ketone body shuttle systems.

    PubMed

    Thevenet, Jonathan; De Marchi, Umberto; Domingo, Jaime Santo; Christinat, Nicolas; Bultot, Laurent; Lefebvre, Gregory; Sakamoto, Kei; Descombes, Patrick; Masoodi, Mojgan; Wiederkehr, Andreas

    2016-05-01

    Medium-chain triglycerides have been used as part of a ketogenic diet effective in reducing epileptic episodes. The health benefits of the derived medium-chain fatty acids (MCFAs) are thought to result from the stimulation of liver ketogenesis providing fuel for the brain. We tested whether MCFAs have direct effects on energy metabolism in induced pluripotent stem cell-derived human astrocytes and neurons. Using single-cell imaging, we observed an acute pronounced reduction of the mitochondrial electrical potential and a concomitant drop of the NAD(P)H signal in astrocytes, but not in neurons. Despite the observed effects on mitochondrial function, MCFAs did not lower intracellular ATP levels or activate the energy sensor AMP-activated protein kinase. ATP concentrations in astrocytes were unaltered, even when blocking the respiratory chain, suggesting compensation through accelerated glycolysis. The MCFA decanoic acid (300 μM) promoted glycolysis and augmented lactate formation by 49.6%. The shorter fatty acid octanoic acid (300 μM) did not affect glycolysis but increased the rates of astrocyte ketogenesis 2.17-fold compared with that of control cells. MCFAs may have brain health benefits through the modulation of astrocyte metabolism leading to activation of shuttle systems that provide fuel to neighboring neurons in the form of lactate and ketone bodies.-Thevenet, J., De Marchi, U., Santo Domingo, J., Christinat, N., Bultot, L., Lefebvre, G., Sakamoto, K., Descombes, P., Masoodi, M., Wiederkehr, A. Medium-chain fatty acids inhibit mitochondrial metabolism in astrocytes promoting astrocyte-neuron lactate and ketone body shuttle systems. PMID:26839375

  5. Effect of fatty acids isolated from edible oils like mustard, linseed or coconut on astrocytes maturation.

    PubMed

    Joardar, Anindita; Das, Sumantra

    2007-12-01

    The omega-3 polyunsaturated fatty acid, docosahexaenoic acid (DHA, 22:6n-3) has been previously shown to facilitate some of the vital functions of astrocytes. Since some dietary oils contain alpha-linolenic acid (ALA, 18:3n-3), which is a precursor of DHA, we examined their effect on astrocyte development. Fatty acids (FAs) were isolated from commonly used oils and their compositions were determined by GLC. FAs from three oils, viz. coconut, mustard and linseed were studied for their effect on astrocyte morphology. Parallel studies were conducted with FAs from the same oils after heating for 72 h. Unlike coconut oil, FAs from mustard and linseed, both heated and raw, caused significant morphogenesis of astrocytes in culture. ss-AR binding was also substantially increased in astrocytes treated with FAs from raw mustard and linseed oils as compared to astrocytes grown in normal medium. The expression profile of the isoforms of GFAP showed that astrocyte maturation by FAs of mustard and linseed oil was associated with appearance of acidic variants of GFAP and disappearance of some neutral isoforms similar to that observed in cultures grown in serum containing medium or in the presence of DHA. Taken together, the study highlights the contribution of specific dietary oils in facilitating astrocyte development that can have potential impact on human health.

  6. Astrocyte fatty acid binding protein-7 is a marker for neurogenic niches in the rat hippocampus.

    PubMed

    Young, John K; Heinbockel, Thomas; Gondré-Lewis, Marjorie C

    2013-12-01

    Recent research has determined that newborn neurons in the dentate gyrus of the hippocampus of the macaque are frequently adjacent to astrocytes immunoreactive for fatty acid binding protein-7 (FABP7). To investigate if a similar relationship between FABP7-positive (FABP7+) astrocytes and proliferating cells exists in the rodent brain, sections of brains from juvenile rats were stained by immunohistochemistry to demonstrate newborn cells (antibody to Ki67 protein) and FABP7+ astrocytes. In rat brains, FABP7+ astrocytes were particularly abundant in the dentate gyrus of the hippocampus and were frequently close to dividing cells immunoreactive for Ki67 protein. FABP7+ astrocytes were also present in the olfactory bulbs, arcuate nucleus of the hypothalamus, and in the dorsal medulla subjacent to the area postrema, sites where more modest numbers of newborn neurons can also be found. These data suggest that regional accumulations of FABP7+ astrocytes may represent reservoirs of cells having the potential for neurogenesis. Because FABP7+ astrocytes are particularly abundant in the hippocampus, and since the gene for FABP7 has been linked to Alzheimer's disease, age-related changes in FABP7+ astrocytes (mitochondrial degeneration) may be relevant to age-associated disorders of the hippocampus.

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

    PubMed

    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

  8. Aspects of astrocyte energy metabolism, amino acid neurotransmitter homoeostasis and metabolic compartmentation.

    PubMed

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

    2012-04-27

    Astrocytes are key players in brain function; they are intimately involved in neuronal signalling processes and their metabolism is tightly coupled to that of neurons. In the present review, we will be concerned with a discussion of aspects of astrocyte metabolism, including energy-generating pathways and amino acid homoeostasis. A discussion of the impact that uptake of neurotransmitter glutamate may have on these pathways is included along with a section on metabolic compartmentation.

  9. [Glial fibrillary acidic protein: the component of intermediate filaments in the vertebrate brain astrocytes].

    PubMed

    Sukhorukova, E G; Kruzhevskiĭ, D É; Alekseeva, O S

    2015-01-01

    Glial fibrillary acidic protein (GFAP) refers to the type III intermediate filament proteins and is the essential component of the cytoskeleton in astrocytes of all vertebrates. This review presents current data on the molecular organization of GFAP in a comparative aspect. The results of most relevant studies using immunocytochemical labeling of the protein are summarized. The data on the changes in expression of GFAP in Alexander disease caused by the primary pathology of astrocytes are presented.

  10. Astrocytic Acid-Sensing Ion Channel 1a Contributes to the Development of Chronic Epileptogenesis.

    PubMed

    Yang, Feng; Sun, Xiaolong; Ding, Yinxiu; Ma, Hui; Yang, Tangpeng Ou; Ma, Yue; Wei, Dong; Li, Wen; Xu, Tianle; Jiang, Wen

    2016-01-01

    Unraveling mechanisms underlying epileptogenesis after brain injury is an unmet medical challenge. Although histopathological studies have revealed that reactive astrogliosis and tissue acidosis are prominent features in epileptogenic foci, their roles in epileptogenesis remain unclear. Here, we explored whether astrocytic acid-sensing ion channel-1a (ASIC1a) contributes to the development of chronic epilepsy. High levels of ASIC1a were measured in reactive astrocytes in the hippocampi of patients with temporal lobe epilepsy (TLE) and epileptic mice. Extracellular acidosis caused a significant Ca(2+) influx in cultured astrocytes, and this influx was sensitive to inhibition by the ASIC1a-specific blocker psalmotoxin 1 (PcTX1). In addition, recombinant adeno-associated virus (rAAV) vectors carrying a GFAP promoter in conjunction with ASIC1a shRNA or cDNA were generated to suppress or restore, respectively, ASIC1a expression in astrocytes. Injection of rAAV-ASIC1a-shRNA into the dentate gyrus of the wide type TLE mouse model resulted in the inhibition of astrocytic ASIC1a expression and a reduction in spontaneous seizures. By contrast, rAAV-ASIC1a-cDNA restored astrocytic ASIC1a expression in an ASIC1a knock-out TLE mouse model and increased the frequency of spontaneous seizures. Taken together, our results reveal that astrocytic ASIC1a may be an attractive new target for the treatment of epilepsy. PMID:27526777

  11. Astrocytic Acid-Sensing Ion Channel 1a Contributes to the Development of Chronic Epileptogenesis

    PubMed Central

    Yang, Feng; Sun, Xiaolong; Ding, Yinxiu; Ma, Hui; Yang, Tangpeng Ou; Ma, Yue; Wei, Dong; Li, Wen; Xu, Tianle; Jiang, Wen

    2016-01-01

    Unraveling mechanisms underlying epileptogenesis after brain injury is an unmet medical challenge. Although histopathological studies have revealed that reactive astrogliosis and tissue acidosis are prominent features in epileptogenic foci, their roles in epileptogenesis remain unclear. Here, we explored whether astrocytic acid-sensing ion channel-1a (ASIC1a) contributes to the development of chronic epilepsy. High levels of ASIC1a were measured in reactive astrocytes in the hippocampi of patients with temporal lobe epilepsy (TLE) and epileptic mice. Extracellular acidosis caused a significant Ca2+ influx in cultured astrocytes, and this influx was sensitive to inhibition by the ASIC1a-specific blocker psalmotoxin 1 (PcTX1). In addition, recombinant adeno-associated virus (rAAV) vectors carrying a GFAP promoter in conjunction with ASIC1a shRNA or cDNA were generated to suppress or restore, respectively, ASIC1a expression in astrocytes. Injection of rAAV-ASIC1a-shRNA into the dentate gyrus of the wide type TLE mouse model resulted in the inhibition of astrocytic ASIC1a expression and a reduction in spontaneous seizures. By contrast, rAAV-ASIC1a-cDNA restored astrocytic ASIC1a expression in an ASIC1a knock-out TLE mouse model and increased the frequency of spontaneous seizures. Taken together, our results reveal that astrocytic ASIC1a may be an attractive new target for the treatment of epilepsy. PMID:27526777

  12. Lauric Acid Stimulates Ketone Body Production in the KT-5 Astrocyte Cell Line.

    PubMed

    Nonaka, Yudai; Takagi, Tetsuo; Inai, Makoto; Nishimura, Shuhei; Urashima, Shogo; Honda, Kazumitsu; Aoyama, Toshiaki; Terada, Shin

    2016-08-01

    Coconut oil has recently attracted considerable attention as a potential Alzheimer's disease therapy because it contains large amounts of medium-chain fatty acids (MCFAs) and its consumption is thought to stimulate hepatic ketogenesis, supplying an alternative energy source for brains with impaired glucose metabolism. In this study, we first reevaluated the responses of plasma ketone bodies to oral administration of coconut oil to rats. We found that the coconut oil-induced increase in plasma ketone body concentration was negligible and did not significantly differ from that observed after high-oleic sunflower oil administration. In contrast, the administration of coconut oil substantially increased the plasma free fatty acid concentration and lauric acid content, which is the major MCFA in coconut oil. Next, to elucidate whether lauric acid can activate ketogenesis in astrocytes with the capacity to generate ketone bodies from fatty acids, we treated the KT-5 astrocyte cell line with 50 and 100 μM lauric acid for 4 h. The lauric acid treatments increased the total ketone body concentration in the cell culture supernatant to a greater extent than oleic acid, suggesting that lauric acid can directly and potently activate ketogenesis in KT-5 astrocytes. These results suggest that coconut oil intake may improve brain health by directly activating ketogenesis in astrocytes and thereby by providing fuel to neighboring neurons.

  13. Lauric Acid Stimulates Ketone Body Production in the KT-5 Astrocyte Cell Line.

    PubMed

    Nonaka, Yudai; Takagi, Tetsuo; Inai, Makoto; Nishimura, Shuhei; Urashima, Shogo; Honda, Kazumitsu; Aoyama, Toshiaki; Terada, Shin

    2016-08-01

    Coconut oil has recently attracted considerable attention as a potential Alzheimer's disease therapy because it contains large amounts of medium-chain fatty acids (MCFAs) and its consumption is thought to stimulate hepatic ketogenesis, supplying an alternative energy source for brains with impaired glucose metabolism. In this study, we first reevaluated the responses of plasma ketone bodies to oral administration of coconut oil to rats. We found that the coconut oil-induced increase in plasma ketone body concentration was negligible and did not significantly differ from that observed after high-oleic sunflower oil administration. In contrast, the administration of coconut oil substantially increased the plasma free fatty acid concentration and lauric acid content, which is the major MCFA in coconut oil. Next, to elucidate whether lauric acid can activate ketogenesis in astrocytes with the capacity to generate ketone bodies from fatty acids, we treated the KT-5 astrocyte cell line with 50 and 100 μM lauric acid for 4 h. The lauric acid treatments increased the total ketone body concentration in the cell culture supernatant to a greater extent than oleic acid, suggesting that lauric acid can directly and potently activate ketogenesis in KT-5 astrocytes. These results suggest that coconut oil intake may improve brain health by directly activating ketogenesis in astrocytes and thereby by providing fuel to neighboring neurons. PMID:27430387

  14. GABAB receptor-mediated activation of astrocytes by gamma-hydroxybutyric acid

    PubMed Central

    Gould, Timothy; Chen, Lixin; Emri, Zsuzsa; Pirttimaki, Tiina; Errington, Adam C.; Crunelli, Vincenzo; Parri, H. Rheinallt

    2014-01-01

    The gamma-aminobutyric acid (GABA) metabolite gamma-hydroxybutyric acid (GHB) shows a variety of behavioural effects when administered to animals and humans, including reward/addiction properties and absence seizures. At the cellular level, these actions of GHB are mediated by activation of neuronal GABAB receptors (GABABRs) where it acts as a weak agonist. Because astrocytes respond to endogenous and exogenously applied GABA by activation of both GABAA and GABABRs, here we investigated the action of GHB on astrocytes on the ventral tegmental area (VTA) and the ventrobasal (VB) thalamic nucleus, two brain areas involved in the reward and proepileptic action of GHB, respectively, and compared it with that of the potent GABABR agonist baclofen. We found that GHB and baclofen elicited dose-dependent (ED50: 1.6 mM and 1.3 µM, respectively) transient increases in intracellular Ca2+ in VTA and VB astrocytes of young mice and rats, which were accounted for by activation of their GABABRs and mediated by Ca2+ release from intracellular store release. In contrast, prolonged GHB and baclofen exposure caused a reduction in spontaneous astrocyte activity and glutamate release from VTA astrocytes. These findings have key (patho)physiological implications for our understanding of the addictive and proepileptic actions of GHB. PMID:25225100

  15. Is there in vivo evidence for amino acid shuttles carrying ammonia from neurons to astrocytes?

    PubMed

    Rothman, Douglas L; De Feyter, Henk M; Maciejewski, Paul K; Behar, Kevin L

    2012-11-01

    The high in vivo flux of the glutamate/glutamine cycle puts a strong demand on the return of ammonia released by phosphate activated glutaminase from the neurons to the astrocytes in order to maintain nitrogen balance. In this paper we review several amino acid shuttles that have been proposed for balancing the nitrogen flows between neurons and astrocytes in the glutamate/glutamine cycle. All of these cycles depend on the directionality of glutamate dehydrogenase, catalyzing reductive glutamate synthesis (forward reaction) in the neuron in order to capture the ammonia released by phosphate activated glutaminase, while catalyzing oxidative deamination of glutamate (reverse reaction) in the astrocytes to release ammonia for glutamine synthesis. Reanalysis of results from in vivo experiments using (13)N and (15)N labeled ammonia and (15)N leucine in rats suggests that the maximum flux of the alanine/lactate or branched chain amino acid/branched chain amino acid transaminase shuttles between neurons and astrocytes are approximately 3-5 times lower than would be required to account for the ammonia transfer from neurons to astrocytes needed for glutamine synthesis (amide nitrogen) to sustain the glutamate/glutamine cycle. However, in the rat brain both the total ammonia fixation rate by glutamate dehydrogenase and the total branched chain amino acid transaminase activity are sufficient to support a branched chain amino acid/branched chain keto acid shuttle, as proposed by Hutson and coworkers, which would support the de novo synthesis of glutamine in the astrocyte to replace the ~20 % of neurotransmitter glutamate that is oxidized. A higher fraction of the nitrogen needs of total glutamate neurotransmitter cycling could be supported by hybrid cycles in which glutamate and tricarboxylic acid cycle intermediates act as a nitrogen shuttle. A limitation of all in vivo studies in animals conducted to date is that none have shown transfer of nitrogen for glutamine amide

  16. RNA-binding protein QKI regulates Glial fibrillary acidic protein expression in human astrocytes.

    PubMed

    Radomska, Katarzyna J; Halvardson, Jonatan; Reinius, Björn; Lindholm Carlström, Eva; Emilsson, Lina; Feuk, Lars; Jazin, Elena

    2013-04-01

    Linkage, association and expression studies previously pointed to the human QKI, KH domain containing, RNA-binding (QKI) as a candidate gene for schizophrenia. Functional studies of the mouse orthologue Qk focused mainly on its role in oligodendrocyte development and myelination, while its function in astroglia remained unexplored. Here, we show that QKI is highly expressed in human primary astrocytes and that its splice forms encode proteins targeting different subcellular localizations. Uncovering the role of QKI in astrocytes is of interest in light of growing evidence implicating astrocyte dysfunction in the pathogenesis of several disorders of the central nervous system. We selectively silenced QKI splice variants in human primary astrocytes and used RNA sequencing to identify differential expression and splice variant composition at the genome-wide level. We found that an mRNA expression of Glial fibrillary acidic protein (GFAP), encoding a major component of astrocyte intermediate filaments, was down-regulated after QKI7 splice variant silencing. Moreover, we identified a potential QKI-binding site within the 3' untranslated region of human GFAP. This sequence was not conserved between mice and humans, raising the possibility that GFAP is a target for QKI in humans but not rodents. Haloperidol treatment of primary astrocytes resulted in coordinated increases in QKI7 and GFAP expression. Taken together, our results provide the first link between QKI and GFAP, two genes with alterations previously observed independently in schizophrenic patients. Our findings for QKI, together with its well-known role in myelination, suggest that QKI is a hub regulator of glia function in humans.

  17. High molecular weight hyaluronic acid limits astrocyte activation and scar formation after spinal cord injury

    NASA Astrophysics Data System (ADS)

    Khaing, Zin Z.; Milman, Brian D.; Vanscoy, Jennifer E.; Seidlits, Stephanie K.; Grill, Raymond J.; Schmidt, Christine E.

    2011-08-01

    A major hurdle for regeneration after spinal cord injury (SCI) is the ability of axons to penetrate and grow through the scar tissue. After SCI, inflammatory cells, astrocytes and meningeal cells all play a role in developing the glial scar. In addition, degradation of native high molecular weight (MW) hyaluronic acid (HA), a component of the extracellular matrix, has been shown to induce activation and proliferation of astrocytes. However, it is not known if the degradation of native HA actually enhances glial scar formation. We hypothesize that the presence of high MW HA (HA with limited degradation) after SCI will decrease glial scarring. Here, we demonstrate that high MW HA decreases cell proliferation and reduces chondroitin sulfate proteoglycan (CSPG) production in cultured neonatal and adult astrocytes. In addition, stiffness-matched high MW HA hydrogels crosslinked to resist degradation were implanted in a rat model of spinal dorsal hemisection injury. The numbers of immune cells (macrophages and microglia) detected at the lesion site in animals with HA hydrogel implants were significantly reduced at acute time points (one, three and ten days post-injury). Lesioned animals with HA implants also exhibited significantly lower CSPG expression at ten days post-injury. At nine weeks post-injury, animals with HA hydrogel implants exhibited a significantly decreased astrocytic response, but did not have significantly altered CSPG expression. Combined, these data suggest that high MW HA, when stabilized against degradation, mitigates astrocyte activation in vitro and in vivo. The presence of HA implants was also associated with a significant decrease in CSPG deposition at ten days after SCI. Therefore, HA-based hydrogel systems hold great potential for minimizing undesired scarring as part of future repair strategies after SCI.

  18. High molecular weight hyaluronic acid limits astrocyte activation and scar formation after spinal cord injury.

    PubMed

    Khaing, Zin Z; Milman, Brian D; Vanscoy, Jennifer E; Seidlits, Stephanie K; Grill, Raymond J; Schmidt, Christine E

    2011-08-01

    A major hurdle for regeneration after spinal cord injury (SCI) is the ability of axons to penetrate and grow through the scar tissue. After SCI, inflammatory cells, astrocytes and meningeal cells all play a role in developing the glial scar. In addition, degradation of native high molecular weight (MW) hyaluronic acid (HA), a component of the extracellular matrix, has been shown to induce activation and proliferation of astrocytes. However, it is not known if the degradation of native HA actually enhances glial scar formation. We hypothesize that the presence of high MW HA (HA with limited degradation) after SCI will decrease glial scarring. Here, we demonstrate that high MW HA decreases cell proliferation and reduces chondroitin sulfate proteoglycan (CSPG) production in cultured neonatal and adult astrocytes. In addition, stiffness-matched high MW HA hydrogels crosslinked to resist degradation were implanted in a rat model of spinal dorsal hemisection injury. The numbers of immune cells (macrophages and microglia) detected at the lesion site in animals with HA hydrogel implants were significantly reduced at acute time points (one, three and ten days post-injury). Lesioned animals with HA implants also exhibited significantly lower CSPG expression at ten days post-injury. At nine weeks post-injury, animals with HA hydrogel implants exhibited a significantly decreased astrocytic response, but did not have significantly altered CSPG expression. Combined, these data suggest that high MW HA, when stabilized against degradation, mitigates astrocyte activation in vitro and in vivo. The presence of HA implants was also associated with a significant decrease in CSPG deposition at ten days after SCI. Therefore, HA-based hydrogel systems hold great potential for minimizing undesired scarring as part of future repair strategies after SCI.

  19. High molecular weight hyaluronic acid limits astrocyte activation and scar formation after spinal cord injury.

    PubMed

    Khaing, Zin Z; Milman, Brian D; Vanscoy, Jennifer E; Seidlits, Stephanie K; Grill, Raymond J; Schmidt, Christine E

    2011-08-01

    A major hurdle for regeneration after spinal cord injury (SCI) is the ability of axons to penetrate and grow through the scar tissue. After SCI, inflammatory cells, astrocytes and meningeal cells all play a role in developing the glial scar. In addition, degradation of native high molecular weight (MW) hyaluronic acid (HA), a component of the extracellular matrix, has been shown to induce activation and proliferation of astrocytes. However, it is not known if the degradation of native HA actually enhances glial scar formation. We hypothesize that the presence of high MW HA (HA with limited degradation) after SCI will decrease glial scarring. Here, we demonstrate that high MW HA decreases cell proliferation and reduces chondroitin sulfate proteoglycan (CSPG) production in cultured neonatal and adult astrocytes. In addition, stiffness-matched high MW HA hydrogels crosslinked to resist degradation were implanted in a rat model of spinal dorsal hemisection injury. The numbers of immune cells (macrophages and microglia) detected at the lesion site in animals with HA hydrogel implants were significantly reduced at acute time points (one, three and ten days post-injury). Lesioned animals with HA implants also exhibited significantly lower CSPG expression at ten days post-injury. At nine weeks post-injury, animals with HA hydrogel implants exhibited a significantly decreased astrocytic response, but did not have significantly altered CSPG expression. Combined, these data suggest that high MW HA, when stabilized against degradation, mitigates astrocyte activation in vitro and in vivo. The presence of HA implants was also associated with a significant decrease in CSPG deposition at ten days after SCI. Therefore, HA-based hydrogel systems hold great potential for minimizing undesired scarring as part of future repair strategies after SCI. PMID:21753237

  20. Changes in the morphology and proliferation of astrocytes induced by two modalities of chemically functionalized single-walled carbon nanotubes are differentially mediated by glial fibrillary acidic protein.

    PubMed

    Gottipati, Manoj K; Bekyarova, Elena; Brenner, Michael; Haddon, Robert C; Parpura, Vladimir

    2014-07-01

    Alterations in glial fibrillary acidic protein (GFAP) levels accompany the changes in the morphology and proliferation of astrocytes induced by colloidal solutes and films of carbon nanotubes (CNTs). To determine if GFAP is required for the effects of CNTs on astrocytes, we used astrocytes isolated from GFAP null mice. We find that selected astrocytic changes induced by CNTs are mediated by GFAP, i.e., perimeter, shape, and cell death for solutes, and proliferation for films.

  1. Astrocytes are mainly responsible for the polyunsaturated fatty acid enrichment in blood-brain barrier endothelial cells in vitro.

    PubMed

    Bernoud, N; Fenart, L; Bénistant, C; Pageaux, J F; Dehouck, M P; Molière, P; Lagarde, M; Cecchelli, R; Lecerf, J

    1998-09-01

    To determine the respective roles of endothelial cells from brain capillaries and astrocytes in the conversion of circulating 18:2n-6 and 18:3n-3 into 20:4n-6 and 22:6n-3, respectively, a coculture of the two cell types mimicking the in vivo blood-brain barrier was used. During the culture period, endothelial cells cultured on an insert were set above the medium of a Petri dish containing or not a stabilized culture of astrocytes. Five days after confluence, labeled 18:2n-6 and 18:3n-3 (10 microM each) were added to the endothelial cells and incubated for 48 h. Analogous experiments were also performed by using each cell type cultured alone in the culture device. The distribution of radioactivity in lipids and fatty acids was studied in all the compartments of the culture device. Endothelial cells cultured alone weakly converted the precursor fatty acids into 20:4n-6 and 22:6n-3. When endothelial cells were cocultured with astrocytes, their content of polyunsaturated fatty acids increased dramatically. This effect was associated with the uptake of polyunsaturated fatty acids from the lower medium (astrocyte medium). These fatty acids were released by astrocytes after they were synthesized from the precursor fatty acids that passed through the endothelial cell monolayer into the lower medium. Polyunsaturated fatty acids were released by astrocytes as unesterified fatty acids and as phospholipids (mainly phosphatidylcholine and lysophosphatidylcholine) even when the medium was devoid of serum. These results suggest that astrocytes could play a major role in the delivery of essential polyunsaturated fatty acids to the barrier itself and to the brain.

  2. The phosphorylation status and cytoskeletal remodeling of striatal astrocytes treated with quinolinic acid

    SciTech Connect

    Pierozan, Paula; Ferreira, Fernanda; Ortiz de Lima, Bárbara; Gonçalves Fernandes, Carolina; Totarelli Monteforte, Priscila; Castro Medaglia, Natalia de; Bincoletto, Claudia; Soubhi Smaili, Soraya; Pessoa-Pureur, Regina

    2014-04-01

    Quinolinic acid (QUIN) is a glutamate agonist which markedly enhances the vulnerability of neural cells to excitotoxicity. QUIN is produced from the amino acid tryptophan through the kynurenine pathway (KP). Dysregulation of this pathway is associated with neurodegenerative conditions. In this study we treated striatal astrocytes in culture with QUIN and assayed the endogenous phosphorylating system associated with glial fibrillary acidic protein (GFAP) and vimentin as well as cytoskeletal remodeling. After 24 h incubation with 100 µM QUIN, cells were exposed to {sup 32}P-orthophosphate and/or protein kinase A (PKA), protein kinase dependent of Ca{sup 2+}/calmodulin II (PKCaMII) or protein kinase C (PKC) inhibitors, H89 (20 μM), KN93 (10 μM) and staurosporin (10 nM), respectively. Results showed that hyperphosphorylation was abrogated by PKA and PKC inhibitors but not by the PKCaMII inhibitor. The specific antagonists to ionotropic NMDA and non-NMDA (50 µM DL-AP5 and CNQX, respectively) glutamate receptors as well as to metabotropic glutamate receptor (mGLUR; 50 µM MCPG), mGLUR1 (100 µM MPEP) and mGLUR5 (10 µM 4C3HPG) prevented the hyperphosphorylation provoked by QUIN. Also, intra and extracellular Ca{sup 2+} quelators (1 mM EGTA; 10 µM BAPTA-AM, respectively) prevented QUIN-mediated effect, while Ca{sup 2+} influx through voltage-dependent Ca{sup 2+} channel type L (L-VDCC) (blocker: 10 µM verapamil) is not implicated in this effect. Morphological analysis showed dramatically altered actin cytoskeleton with concomitant change of morphology to fusiform and/or flattened cells with retracted cytoplasm and disruption of the GFAP meshwork, supporting misregulation of actin cytoskeleton. Both hyperphosphorylation and cytoskeletal remodeling were reversed 24 h after QUIN removal. Astrocytes are highly plastic cells and the vulnerability of astrocyte cytoskeleton may have important implications for understanding the neurotoxicity of QUIN in neurodegenerative

  3. Quinolinic acid induces disrupts cytoskeletal homeostasis in striatal neurons. Protective role of astrocyte-neuron interaction.

    PubMed

    Pierozan, Paula; Ferreira, Fernanda; de Lima, Bárbara Ortiz; Pessoa-Pureur, Regina

    2015-02-01

    Quinolinic acid (QUIN) is an endogenous metabolite of the kynurenine pathway involved in several neurological disorders. Among the several mechanisms involved in QUIN-mediated toxicity, disruption of the cytoskeleton has been demonstrated in striatally injected rats and in striatal slices. The present work searched for the actions of QUIN in primary striatal neurons. Neurons exposed to 10 µM QUIN presented hyperphosphorylated neurofilament (NF) subunits (NFL, NFM, and NFH). Hyperphosphorylation was abrogated in the presence of protein kinase A and protein kinase C inhibitors H89 (20 μM) and staurosporine (10 nM), respectively, as well as by specific antagonists to N-methyl-D-aspartate (50 µM DL-AP5) and metabotropic glutamate receptor 1 (100 µM MPEP). Also, intra- and extracellular Ca(2+) chelators (10 µM BAPTA-AM and 1 mM EGTA, respectively) and Ca(2+) influx through L-type voltage-dependent Ca(2+) channel (10 µM verapamil) are implicated in QUIN-mediated effects. Cells immunostained for the neuronal markers βIII-tubulin and microtubule-associated protein 2 showed altered neurite/neuron ratios and neurite outgrowth. NF hyperphosphorylation and morphological alterations were totally prevented by conditioned medium from QUIN-treated astrocytes. Cocultured astrocytes and neurons interacted with one another reciprocally, protecting them against QUIN injury. Cocultured cells preserved their cytoskeletal organization and cell morphology together with unaltered activity of the phosphorylating system associated with the cytoskeleton. This article describes cytoskeletal disruption as one of the most relevant actions of QUIN toxicity in striatal neurons in culture with soluble factors secreted by astrocytes, with neuron-astrocyte interaction playing a role in neuroprotection.

  4. Glial fibrillary acidic protein (GFAP) and the astrocyte intermediate filament system in diseases of the central nervous system.

    PubMed

    Hol, Elly M; Pekny, Milos

    2015-02-01

    Glial fibrillary acidic protein (GFAP) is the hallmark intermediate filament (IF; also known as nanofilament) protein in astrocytes, a main type of glial cells in the central nervous system (CNS). Astrocytes have a range of control and homeostatic functions in health and disease. Astrocytes assume a reactive phenotype in acute CNS trauma, ischemia, and in neurodegenerative diseases. This coincides with an upregulation and rearrangement of the IFs, which form a highly complex system composed of GFAP (10 isoforms), vimentin, synemin, and nestin. We begin to unravel the function of the IF system of astrocytes and in this review we discuss its role as an important crisis-command center coordinating cell responses in situations connected to cellular stress, which is a central component of many neurological diseases.

  5. Induction of glial fibrillary acidic protein expression in astrocytes by nitric oxide.

    PubMed

    Brahmachari, Saurav; Fung, Yiu K; Pahan, Kalipada

    2006-05-01

    Increased expression of glial fibrillary acidic protein (GFAP) represents astroglial activation and gliosis during neurodegeneration. However, the molecular mechanism behind increased expression of GFAP in astrocytes is poorly understood. The present study was undertaken to explore the role of nitric oxide (NO) in the expression of GFAP. Bacterial lipopolysachharides (LPSs) induced the production of NO and the expression of GFAP in mouse primary astrocytes. Either a scavenger of NO [2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO)] or an inhibitor of inducible nitric oxide synthase [l-N6-(I-iminoethyl)-lysine hydrochloride] blocked this induction of GFAP expression. Similarly, other inducers of NO production such as interferon-gamma, interleukin-1beta, human immunodeficiency virus type 1 gp120, fibrillar amyloid beta peptides, and double-stranded RNA (polyinosinic-polycytidilic acid) also induced the expression of GFAP through NO. The role of NO in the expression of GFAP was supported further by increased expression of GFAP by S-nitroso glutathione (GSNO), an NO donor. Interestingly, inhibition of nuclear factor kappaB (NF-kappaB) suppressed LPS- but not GSNO-induced expression of GFAP, suggesting that NO does not require NF-kappaB to induce GFAP and that NF-kappaB functions upstream of NO production. However, inhibition of LPS- and GSNO-induced expression of GFAP either by NS-2028 [a specific inhibitor of guanylate cyclase (GC)] or by KT5823 [a specific inhibitor of cGMP-activated protein kinase (PKG)], and induction of GFAP expression by either 8-Br cGMP (a cell-permeable cGMP analog) or MY-5445 (a specific inhibitor of cGMP phosphodiesterase) suggests that NO induces GFAP via GC-cGMP-PKG. This study illustrates a novel biological role of NO in regulating the expression of GFAP in astrocytes through the GC-cGMP-PKG pathway that may participate in the pathogenesis of neurodegenerative disorders.

  6. Morphological changes in glial fibrillary acidic protein immunopositive astrocytes in the hippocampus of dietary-induced obese mice.

    PubMed

    Cano, Victoria; Valladolid-Acebes, Ismael; Hernández-Nuño, Francisco; Merino, Beatriz; Del Olmo, Nuria; Chowen, Julie A; Ruiz-Gayo, Mariano

    2014-06-01

    Long-term consumption of a high-fat diet (HFD) has been shown to trigger both metabolic and cardiovascular diseases. In contrast, the effect of this type of dietary regime on the central nervous system, particularly outside the hypothalamus, has been investigated poorly. Astrocytes, the most abundant population of glial cells in the brain, are pivotal in regulating glutamatergic transmission as they are responsible for most of the glutamate uptake and metabolism. Mice on an HFD show deficits in learning and memory, together with neurochemical and electrophysiological changes compatible with the impairment in hippocampal glutamatergic activity. Because astrocyte function and morphology have been shown to be interdependent, we speculated whether HFD would trigger changes in astrocyte morphology. For this purpose, we have used a model of diet-induced obesity in mice. We have analyzed astrocyte morphology and density by glial fibrillary acidic protein immunohistochemistry, as well as the expression of the glutamate transporters, GLT-1 (glutamate transporter type-1), and GLAST (astrocyte glutamate transporter), in the CA3 area of the hippocampus. We found that astrocytes from HFD mice showed longer and less abundant projections. These changes were accompanied by the upregulation of both GLT-1 and GLAST. Our data show that the functional impairment detected previously in HFD mice is concomitant with morphological changes within the hippocampus.

  7. Glial fibrillary acidic protein as a marker of astrocytic activation in the cerebrospinal fluid of patients with amyotrophic lateral sclerosis.

    PubMed

    Benninger, Felix; Glat, Micaela J; Offen, Daniel; Steiner, Israel

    2016-04-01

    Glial fibrillary acidic protein (GFAP) has been shown to be increased in the cerebrospinal fluid (CSF) of patients suffering from neurological diseases involving the activation of astrocytes, but has not been studied in amyotrophic lateral sclerosis (ALS) patients to our knowledge. CSF samples of patients with definite ALS and of those with other neurological diseases were evaluated for their GFAP concentrations. CSF-GFAP concentrations of patients with ALS were significantly elevated by 53% compared to patients with other neurologic diseases. GFAP might serve as a biomarker in ALS. Our findings support the concept that astrocytes play a role in ALS pathogenesis.

  8. Andrographolide attenuates interleukin-1β-stimulated upregulation of chemokine CCL5 and glial fibrillary acidic protein in astrocytes.

    PubMed

    Wong, Siew-Ying; Chan, Su-Jing; Wong, W S Fred; Wong, Peter T-H; Lai, Mitchell K P

    2014-08-20

    Andrographolide is a bioactive molecule isolated from Andrographis paniculata with anticancer and anti-inflammatory activities. In this study, we tested the effects of andrographolide on astrocyte-mediated neuroinflammatory responses. Cultured rat primary astrocytes were treated with proinflammatory cytokine interleukin 1β with or without pretreatment with andrographolide, and then processed for measurements of chemokine C-C motif ligand 5 (CCL5) and glial fibrillary acidic protein. The activation status of nuclear factor-κB activation that may underlie CCL5 upregulation was also measured. Andrographolide pretreatment was found to attenuate the upregulation of CCL5 and glial fibrillary basic protein as well as reduce the phosphorylation of nuclear factor-κB p65 and IκBα after interleukin 1β stimulation. These data suggest that andrographolide should be evaluated further as a therapeutic for central nervous system diseases characterized by astrocyte-mediated neuroinflammatory processes.

  9. Epoxyeicosatrienoic acids pretreatment improves amyloid β-induced mitochondrial dysfunction in cultured rat hippocampal astrocytes.

    PubMed

    Sarkar, Pallabi; Zaja, Ivan; Bienengraeber, Martin; Rarick, Kevin R; Terashvili, Maia; Canfield, Scott; Falck, John R; Harder, David R

    2014-02-15

    Amyloid-β (Aβ) has long been implicated as a causative protein in Alzheimer's disease. Cellular Aβ accumulation is toxic and causes mitochondrial dysfunction, which precedes clinical symptoms of Alzheimer's disease pathology. In the present study, we explored the possible use of epoxyeicosatrienoic acids (EETs), epoxide metabolites of arachidonic acid, as therapeutic target against Aβ-induced mitochondrial impairment using cultured neonatal hippocampal astrocytes. Inhibition of endogenous EET production by a selective epoxygenase inhibitor, MS-PPOH, caused a greater reduction in mitochondrial membrane potential in the presence of Aβ (1, 10 μM) exposure versus absence of Aβ. MS-PPOH preincubation also aggravated Aβ-induced mitochondrial fragmentation. Preincubation of the cells with either 14,15- or 11,12-EET prevented this mitochondrial depolarization and fragmentation. EET pretreatment also further improved the reduction observed in mitochondrial oxygen consumption in the presence of Aβ. Preincubation of the cells with EETs significantly improved cellular respiration under basal condition and in the presence of the protonophore, carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP). The uncoupling of ATP synthase from the electron transfer chain that occurred in Aβ-treated cells was also prevented by preincubation with EETs. Lastly, cellular reactive oxygen species production, a hallmark of Aβ toxicity, also showed significant reduction in the presence of EETs. We have previously shown that Aβ reduces EET synthesis in rat brain homogenates and cultured hippocampal astrocytes and neurons (Sarkar P, Narayanan J, Harder DR. Differential effect of amyloid beta on the cytochrome P450 epoxygenase activity in rat brain. Neuroscience 194: 241-249, 2011). We conclude that reduction of endogenous EETs may be one of the mechanisms through which Aβ inflicts toxicity and thus supplementing the cells with exogenous EETs improves mitochondrial dynamics and

  10. Diphenylarsinic acid increased the synthesis and release of neuroactive and vasoactive peptides in rat cerebellar astrocytes.

    PubMed

    Negishi, Takayuki; Takahashi, Masaki; Matsunaga, Yuki; Hirano, Seishiro; Tashiro, Tomoko

    2012-06-01

    An incident of poisoning occurred in Japan in 2003 when high-level contamination with arsenic, mainly diphenylarsinic acid (DPAA), was found in well water. People using this water particularly experienced cerebellar symptoms. In the present study, we investigated the adverse effects of DPAA on the cerebellum in vitro and in vivo to understand the biological mechanisms that cause cerebellar symptoms. Comprehensive gene expression analyses in primary cultured ratcerebellar cells exposed to 10 μM DPAA for 24 hours indicated significant alterations in the mRNA expression of genes encoding antioxidative stress proteins (heme oxigenase 1 and heat shock protein72) and neuroactive and vasoactive peptides (neuropeptide Y, adrenomedullin, monocyte chemoattractant protein 1, and fibroblast growth factor 2). Further analyses of proteins revealed that cultured cerebellar astrocytes expressed these antioxidative stress proteins and peptides in response to exposure to DPAA. In addition, these adverseeffects were also observed in the cerebellum exposed in vivo to DPAA (100 mg/L) for 21 days. These results suggested that cerebellarastrocytes irregularly secrete neuroactive and vasoactive peptidesagainst DPAA-induced oxidative stress, which leads to abnormal neural functions and disrupted cerebellar autoregulation dynamics and results in the onset of cerebellar symptoms.

  11. Manganese accumulation in membrane fractions of primary astrocytes is associated with decreased γ-aminobutyric acid (GABA) uptake, and is exacerbated by oleic acid and palmitate.

    PubMed

    Fordahl, Steve C; Erikson, Keith M

    2014-05-01

    Manganese (Mn) exposure interferes with GABA uptake; however, the effects of Mn on GABA transport proteins (GATs) have not been identified. We sought to characterize how Mn impairs GAT function in primary rat astrocytes. Astrocytes exposed to Mn (500 μM) had significantly reduced (3)H-GABA uptake despite no change in membrane or cytosolic GAT3 protein levels. Co-treatment with 100 μM oleic or palmitic acids (both known to be elevated in Mn neurotoxicity), exacerbated the Mn-induced decline in (3)H-GABA uptake. Mn accumulation in the membrane fraction of astrocytes was enhanced with fatty acid administration, and was negatively correlated with (3)H-GABA uptake. Furthermore, control cells exposed to Mn only during the experimental uptake had significantly reduced (3)H-GABA uptake, and the addition of GABA (50 μM) blunted cytosolic Mn accumulation. These data indicate that reduced GAT function in astrocytes is influenced by Mn and fatty acids accumulating at or interacting with the plasma membrane.

  12. Mechanism of toxicity of the branched-chain fatty acid phytanic acid, a marker of Refsum disease, in astrocytes involves mitochondrial impairment.

    PubMed

    Reiser, Georg; Schönfeld, Peter; Kahlert, Stefan

    2006-01-01

    Phytanic acid is a saturated branched-chain fatty acid, which is formed by bacterial degradation of chlorophyll in the intestinal tract of ruminants. The methyl group in beta-position prevents degradation of phytanic acid by the beta-oxidation pathway. Therefore, degradation of phytanic acid is initiated by alpha-oxidation in peroxisomes. The inherited peroxisomal disorder Refsum disease is characterised by accumulation of phytanic acid. Unusually high concentrations of phytanic acid can be found in the plasma of Refsum disease patients, who suffer from neurodegeneration and muscle dystrophy. Phytanic acid has been suggested to be causally involved in the clinical symptoms. To elucidate the pathogenic mechanism, we investigated the influence of phytanic acid in rat hippocampal astrocytes by monitoring the cytosolic Ca(2+) concentration, the mitochondrial membrane potential (Deltapsi(m)), the generation of reactive oxygen species as well as the cellular ATP level. In response to phytanic acid (100 microM) cytosolic Ca(2+) was quickly increased. The phytanic acid-evoked Ca(2+) response was transient and involved activation of intracellular Ca(2+) stores. In isolated rat brain mitochondria, phytanic acid dissipated Deltapsi(m) in a reversible and dose-dependent manner. Moreover, phytanic acid released cytochrome c from mitochondria. Depending on the mitochondrial activity state, phytanic acid either stimulated or inhibited the electron flux within the respiratory chain. In addition, phytanic acid induced substantial generation of reactive oxygen species in isolated mitochondria as well as in intact cells. Phytanic acid caused cell death of astrocytes within a few hours of exposure. In conclusion, we suggest that phytanic acid initiates astrocyte cell death by activating the mitochondrial route of apoptosis.

  13. Neuron-astrocyte interactions in spinal cord dorsal horn in neuropathic pain development and docosahexaenoic acid therapy.

    PubMed

    Manzhulo, Igor V; Ogurtsova, Olga S; Kipryushina, Yuliya O; Latyshev, Nikolay A; Kasyanov, Sergey P; Dyuizen, Inessa V; Tyrtyshnaia, Anna A

    2016-09-15

    The analgesic activity of docosahexaenoic acid (DHA, 22:6 n-3) was studied using a chronic constriction injury (CCI) rat model. Animals were subcutaneously injected with DHA emulsion at a dose of 4.5mg/kg (125mМ/kg) daily during 2weeks after surgery. We characterized the dynamics of GFAP-positive astrocyte, substance P (SP) and nNOS-positive neurons activity in the spinal cord dorsal horn (SCDH) superficial lamina. We found that DHA treatment decrease the intensity and duration of neurogenic pain syndrome, results in earlier stabilization of weight distribution, prevents the cold allodynia and dystrophic changings in denervated limb tissue. DHA treatment reduced the reactive astrocyte number, decrease SP-immunopositive fibers and nNOS-positive neurons number in the SCDH in neuropathic pain. PMID:27609281

  14. Reversed electrogenic sodium bicarbonate cotransporter 1 is the major acid loader during recovery from cytosolic alkalosis in mouse cortical astrocytes

    PubMed Central

    Theparambil, Shefeeq M; Naoshin, Zinnia; Thyssen, Anne; Deitmer, Joachim W

    2015-01-01

    Recovery of intracellular pH from cytosolic alkalosis has been attributed primarily to Cl– coupled acid loaders/base extruders such as Cl–/HCO3– or Cl–/OH– exchangers. We have studied this process in cortical astrocytes from wild-type and transgenic mouse models with gene deletion for the electrogenic sodium bicarbonate cotransporter 1 (NBCe1) and for carbonic anhydrase (CA) isoform II. An acute cytosolic alkalosis was induced by the removal of either CO2/HCO3– or butyric acid, and the subsequent acid loading was analysed by monitoring changes in cytosolic H+ or Na+ using ion-sensitive fluorescent dyes. We have identified that NBCe1 reverses during alkalosis and contributes more than 70% to the rate of recovery from alkalosis by extruding Na+ and HCO3–. After CA inhibition or in CAII-knockout (KO) cells, the rate of recovery was reduced by 40%, and even by 70% in the nominal absence of CO2/HCO3–. Increasing the extracellular K+ concentration modulated the rate of acid loading in wild-type cells, but not in NBCe1-KO cells. Removing chloride had only a minor effect on the recovery from alkalosis. Reversal of NBCe1 by reducing pH/[HCO3–] was demonstrated in astrocytes and in Xenopus oocytes, in which human NBCe1 was heterologously expressed. The results obtained suggest that reversed NBCe1, supported by CAII activity, plays a major role in acid-loading cortical astrocytes to support recovery from cytosolic alkalosis. PMID:25990710

  15. Aquaporin 4-dependent expression of glial fibrillary acidic protein and tenascin-C in activated astrocytes in stab wound mouse brain and in primary culture.

    PubMed

    Ikeshima-Kataoka, Hiroko; Abe, Yoichiro; Yasui, Masato

    2015-01-01

    We previously reported that aquaporin 4 (AQP4) has a neuroimmunological function via astrocytes and microglial cells involving osteopontin. AQP4 is a water channel localized in the endofoot of astrocytes in the brain, and its expression is upregulated after a stab wound to the mouse brain or the injection of methylmercury in common marmosets. In this study, the correlation between the expression of AQP4 and the expression of glial fibrillary acidic protein (GFAP) or tenascin-C (TN-C) in reactive astrocytes was examined in primary cultures and brain tissues of AQP4-deficient mice (AQP4/KO). In the absence of a stab wound to the brain or of any stimulation of the cells, the expressions of both GFAP and TN-C were lower in astrocytes from AQP4/KO mice than in those from wild-type (WT) mice. High levels of GFAP and TN-C expression were observed in activated astrocytes after a stab wound to the brain in WT mice; however, the expressions of GFAP and TN-C were insignificant in AQP4/KO mice. Furthermore, lipopolysaccharide (LPS) stimulation activated primary culture of astrocytes and upregulated GFAP and TN-C expression in cells from WT mice, whereas the expressions of GFAP and TN-C were slightly upregulated in cells from AQP4/KO mice. Moreover, the stimulation of primary culture of astrocytes with LPS also upregulated inflammatory cytokines in cells from WT mice, whereas modest increases were observed in cells from AQP4/KO mice. These results suggest that AQP4 expression accelerates GFAP and TN-C expression in activated astrocytes induced by a stab wound in the mouse brain and LPS-stimulated primary culture of astrocytes.

  16. Sodium para-aminosalicylate protected cultured basal ganglia astrocytes from manganese-induced DNA damages and alteration of amino acid neurotransmitter levels.

    PubMed

    Li, Shao-Jun; Luo, Yi-Ni; Li, Yong; Chen, Jing-Wen; Mo, Yu-Huan; Yuan, Zong-Xiang; Ou, Shi-Yan; Ou, Chao-Yan; Jiang, Yue-Ming; Deng, Xiang-Fa

    2016-01-01

    Sodium para-aminosalicylate (PAS-Na) was first applied successfully in clinical treatment of two manganism patients with good prognosis. However, the mechanism of how PAS-Na protects against Mn-induced neurotoxicity is still elusive. The current study was conducted to explore the effects of PAS-Na on Mn-induced basal ganglia astrocyte injury, and the involvement of amino acid neurotransmitter in vitro. Basal ganglia astrocytes were exposed to 500 μM manganese chloride (MnCl2) for 24 hr, following by 50, 150, or 450 μM PAS-Na treatment for another 24 hr. MnCl2 significantly decreased viability of astrocytes and induced DNA damages via increasing the percentage of tail DNA and Olive tail moment of DNA. Moreover, Mn interrupted amino acid neurotransmitters by decreasing Gln levels and increasing Glu, Gly levels. In contrast, PAS-Na treatment reversed the aforementioned Mn-induced toxic effects on basal ganglia astrocytes. Taken together, our results demonstrated that excessive Mn exposure may induce toxic effects on basal ganglia astrocytes, while PAS-Na could protect basal ganglia astrocytes from Mn-induced neurotoxicity. PMID:27665767

  17. Increased in vitro glial fibrillary acidic protein expression, telomerase activity, and telomere length after productive human immunodeficiency virus-1 infection in murine astrocytes.

    PubMed

    Ojeda, Diego; López-Costa, Juan José; Sede, Mariano; López, Ester María; Berria, María Isabel; Quarleri, Jorge

    2014-02-01

    Although HIV-associated neurocognitive disorders (HAND) result from injury and loss of neurons, productive infection routinely takes place in cells of macrophage lineage. In such a complex context, astrocytosis induced by local chemokines/cytokines is one of the hallmarks of HIV neuropathology. Whether this sustained astrocyte activation is able to alter telomere-aging process is unknown. We hypothesized that interaction of HIV with astrocytes may impact astrocyte telomerase activity (TA) and telomere length in a scenario of astrocytic activation measured by expression of glial fibrillary acidic protein (GFAP). To test this hypothesis, cultured murine astrocytes were challenged with pseudotyped HIV/vesicular stomatitis virus (HIV/VSV) to circumvent the absence of viral receptors; and GFAP, telomerase activity, and telomere length were quantified. As an early and transient event after HIV infection, both TA activity and telomere length were significantly augmented (P < 0.001). Later, a strong negative correlation (-0.8616, P < 0.0001) between virus production and telomerase activity was demonstrated. Once HIV production had reached a peak (7 dpi), the TA decreased, showing levels similar to those of noninfected cells. In contrast, the astrocyte became activated, exhibiting significantly increased levels of GFAP expression directly related to the level of HIV/VSV replication (P < 0.0001). Our results suggest that HIV-infected astrocytes exhibit early disturbance in their cellular functions, such as telomerase activity and telomere length, that may attenuate cell proliferation and enhance the astrocyte dysregulation, contributing to HIV neuropathogenesis. Understanding the mechanisms involved in HIV-mediated persistence by altering the telomere-related aging processes could aid in the development of therapeutic modalities for neurological complications of HIV infection.

  18. Effects of carboxylic acids on the uptake of non-transferrin-bound iron by astrocytes.

    PubMed

    Keenan, Belinda M; Robinson, Stephen R; Bishop, Glenda M

    2010-01-01

    The concentrations of non-transferrin-bound iron are elevated in the brain during pathological conditions such as stroke and Alzheimer's disease. Astrocytes are specialised for sequestering this iron, however little is known about the mechanisms involved. Carboxylates, such as citrate, have been reported to facilitate iron uptake by intestinal cells. Citrate binds iron and limits its redox activity. The presence of high citrate concentrations in the interstitial fluid of the brain suggests that citrate may be an important ligand for iron transport by astrocytes. This study investigates whether iron accumulation by cultured rat astrocytes is facilitated by citrate or other carboxylates. Contrary to expectations, citrate, tartrate and malate were found to block iron accumulation in a concentration-dependent manner; alpha-ketoglutarate had limited effects, while fumarate, succinate and glutarate had no effect. This blockade was not due to an inhibition of ferric reductase activity. Instead, it appeared to be related to the capacity of these carboxylates to bind iron, since phosphate, which also binds iron, diminished the capacity of citrate, tartrate and malate to block the cellular accumulation of iron. These findings raise the possibility that citrate may have therapeutic potential in the management of neurodegenerative conditions that involve cellular iron overload.

  19. Glial fibrillary acidic protein gene promoter is differently modulated by transforming growth factor-beta 1 in astrocytes from distinct brain regions.

    PubMed

    Sousa, Vivian de Oliveira; Romão, Luciana; Neto, Vivaldo Moura; Gomes, Flávia Carvalho Alcantara

    2004-04-01

    The expression of glial fibrillary acidic protein (GFAP), the major intermediate filament protein of mature astrocytes, is regulated under developmental and pathological conditions. Recently, we have investigated GFAP gene modulation by using a transgenic mouse bearing part of the GFAP gene promoter linked to the beta-galactosidase reporter gene. We demonstrated that cerebral cortex neurons activate the GFAP gene promoter, inducing transforming growth factor-beta 1 (TGF-beta 1) secretion by astrocytes. Here, we report that cortical neurons or conditioned medium derived from them do not activate the GFAP gene promoter of transgenic astrocytes derived from midbrain and cerebellum suggesting a neuroanatomical regional specificity of this phenomenon. Surprisingly, they do induce synthesis of TGF-beta 1 by these cells. Western blot and immunocytochemistry assays revealed wild distribution of TGF receptor in all subpopulations of astrocytes and expression of TGF-beta 1 in neurons derived from all regions, thus indicating that the unresponsiveness of the cerebellar and midbrain GFAP gene to TGF-beta 1 is not due to a defect in TGF-beta 1 signalling. Together, our data highlight the great complexity of neuron-glia interactions and might suggest a distinct mechanism underlying modulation of the GFAP gene in the heterogeneous population of astrocytes throughout the central nervous system.

  20. The Refsum disease marker phytanic acid, a branched chain fatty acid, affects Ca2+ homeostasis and mitochondria, and reduces cell viability in rat hippocampal astrocytes.

    PubMed

    Kahlert, Stefan; Schönfeld, Peter; Reiser, Georg

    2005-02-01

    The saturated branched chain fatty acid, phytanic acid, a degradation product of chlorophyll, accumulates in Refsum disease, an inherited peroxisomal disorder with neurological clinical features. To elucidate the pathogenic mechanism, we investigated the influence of phytanic acid on cellular physiology of rat hippocampal astrocytes. Phytanic acid (100 microM) induced an immediate transient increase in cytosolic Ca2+ concentration, followed by a plateau. The peak of this biphasic Ca2+ response was largely independent of extracellular Ca2+, indicating activation of cellular Ca2+ stores by phytanic acid. Phytanic acid depolarized mitochondria without causing in situ swelling of mitochondria. The slow decrease of mitochondrial potential is not consistent with fast and simultaneous opening of the mitochondrial permeability transition pore. However, phytanic acid induced substantial generation of reactive oxygen species. Phytanic acid caused astroglia cell death after a few hours of exposure. We suggest that the cytotoxic effect of phytanic acid seems to be due to a combined action on Ca2+ regulation, mitochondrial depolarization, and increased ROS generation in brain cells.

  1. The influence of the branched-chain fatty acids pristanic acid and Refsum disease-associated phytanic acid on mitochondrial functions and calcium regulation of hippocampal neurons, astrocytes, and oligodendrocytes.

    PubMed

    Rönicke, Sabine; Kruska, Nicol; Kahlert, Stefan; Reiser, Georg

    2009-11-01

    Pristanic acid and phytanic acid are branched-chain fatty acids, which play an important role in diseases with peroxisomal impairment, like Refsum disease (MIM 266500), Zellwegers syndrome and alpha-methylacyl-CoA racemase deficiency (MIM 604489). Several studies revealed that the toxic activity of phytanic acid is mediated by multiple mitochondrial dysfunctions. However, the action of pristanic acid on brain cells is still completely unknown. Here, we exposed astrocytes, oligodendrocytes and neurons in mixed culture to pristanic acid and phytanic acid to analyse cellular consequences. Pristanic acid exerts a strong cytotoxic activity on brain cells, displayed by dramatic Ca2+ deregulation, in situ mitochondrial depolarization and cell death. Interestingly, pristanic acid strongly induced generation of reactive oxygen species (ROS), whereas phytanic acid exerts weaker effects on ROS production. In conclusion, pristanic acid as well as phytanic acid induced a complex array of toxic activities with mitochondrial dysfunction and Ca2+ deregulation.

  2. Neuroprotective effect of suppression of astrocytic activation by arundic acid on brain injuries in rats with acute subdural hematomas.

    PubMed

    Wajima, Daisuke; Nakagawa, Ichiro; Nakase, Hiroyuki; Yonezawa, Taiji

    2013-06-26

    Acute subdural hematoma (ASDH) can cause massive ischemic cerebral blood flow (CBF) underneath the hematoma, but early surgical evacuation of the mass reduces mortality. The aim of this study was to evaluate whether arundic acid improves the secondary ischemic damage induced by ASDH. Our results confirmed that arundic acid decreases the expression of S100 protein produced by activated astrocytes around ischemic lesions due to cytotoxic edema after ASDH as well as reducing infarction volumes and numbers of apoptotic cells around the ischemic lesions. In this study, we also evaluate the relationship of brain edema and the expression of Aquaporin 4 (AQP4) in an ASDH model. The expression of AQP4 was decreased in the acute phase after ASDH. Cytotoxic edema, assumed to be the main cause of ASDH, could also cause ischemic lesions around the edema area. Arundic acid decreased the infarction volume and number of apoptotic cells via suppression of S100 protein expression in ischemic lesions without changing the expression of AQP4.

  3. Neuroprotective Effect of Uncaria rhynchophylla in Kainic Acid-Induced Epileptic Seizures by Modulating Hippocampal Mossy Fiber Sprouting, Neuron Survival, Astrocyte Proliferation, and S100B Expression

    PubMed Central

    Liu, Chung-Hsiang; Lin, Yi-Wen; Tang, Nou-Ying; Liu, Hsu-Jan; Hsieh, Ching-Liang

    2012-01-01

    Uncaria rhynchophylla (UR), which is a traditional Chinese medicine, has anticonvulsive effect in our previous studies, and the cellular mechanisms behind this are still little known. Because of this, we wanted to determine the importance of the role of UR on kainic acid- (KA-) induced epilepsy. Oral UR for 6 weeks can successfully attenuate the onset of epileptic seizure in animal tests. Hippocampal mossy fiber sprouting dramatically decreased, while neuronal survival increased with UR treatment in hippocampal CA1 and CA3 areas. Furthermore, oral UR for 6 weeks significantly attenuated the overexpression of astrocyte proliferation and S100B proteins but not γ-aminobutyric acid A (GABAA) receptors. These results indicate that oral UR for 6 weeks can successfully attenuate mossy fiber sprouting, astrocyte proliferation, and S100B protein overexpression and increase neuronal survival in KA-induced epileptic rat hippocampus PMID:21837247

  4. Enhanced GLT-1 mediated glutamate uptake and migration of primary astrocytes directed by fibronectin-coated electrospun poly-L-lactic acid fibers

    PubMed Central

    Zuidema, Jonathan M.; Hyzinski-García, María C.; Vlasselaer, Kristien Van; Zaccor, Nicholas; Plopper, George E.; Mongin, Alexander A.; Gilbert, Ryan J.

    2014-01-01

    Bioengineered fiber substrates are increasingly studied as a means to promote regeneration and remodeling in the injured central nervous system (CNS). Previous reports largely focused on the ability of oriented scaffolds to bridge injured regions and direct outgrowth of axonal projections. In the present work, we explored the effects of electrospun microfibers on the migration and physiological properties of brain astroglial cells. Primary rat astrocytes were cultured on either fibronectin-coated poly-l-lactic acid (PLLA) films, fibronectin-coated randomly oriented PLLA electrospun fibers, or fibronectin-coated aligned PLLA electrospun fibers. Aligned PLLA fibers strongly altered astrocytic morphology, orienting cell processes, actin microfilaments, and microtubules along the length of the fibers. On aligned fibers, astrocytes also significantly increased their migration rates in the direction of fiber orientation. We further investigated if fiber topography modifies astrocytic neuroprotective properties, namely glutamate and glutamine transport and metabolism. This was done by quantifying changes in mRNA expression (qRT-PCR) and protein levels (Western blotting) for a battery of relevant biomolecules. Interestingly, we found that cells grown on random and/or aligned fibers increased the expression levels of two glutamate transporters, GLAST and GLT-1, and an important metabolic enzyme, glutamine synthetase, as compared to the fibronectin-coated films. Functional assays revealed increases in glutamate transport rates due to GLT-1 mediated uptake, which was largely determined by the dihydrokainate-sensitive GLT-1. Overall, this study suggests that aligned PLLA fibers can promote directed astrocytic migration, and, of most importance, our in vitro results indicate for the first time that electrospun PLLA fibers can positively modify neuroprotective properties of glial cells by increasing rates of glutamate uptake. PMID:24246642

  5. In vitro astrocytic differentiation from embryoid bodies of an experimental mouse testicular teratoma.

    PubMed Central

    VandenBerg, S. R.; Ludwin, S. K.; Herman, M. M.; Bignami, A.

    1976-01-01

    Astrocytic differentiation in monolayer cultures of ascitic embryoid bodies from the experimental teratoma OTT-6050 was studied by conventional light microscopy and by indirect immunofluorescence with antisera to glial fibrillary acidic (GFA) protein, a protein specific for astorcytes. Primitive neuroepithelial cells were identified in 24-hour cultures. Within 72 hours, two cell types diverged. One cell type, with a flattened epithelial morphology in early cultures, demonstrated delicate GFA protein-positive fibrils within 48 hours. In later cultures, this type progressively displayed more typical stellate astrocytic features, with denser, more compact GFA protein-positive fluorescence in the perinuclear cytoplasm and cell processes. As indicated by GFA protein expression, the appearance of astrocytes of typical morphology therefore was preceded by biochemical differentiation. The second cell type, interpreted as neuroblastic, failed to demonstrate GFA protein and had a small perikaryon with slender bipolar processes that were argyrophilic with Bodian's protargol in late cultures. Divergent neuroepithelial differentiation occurred within mitotically active cell populations and proceeded without apparent tissue relationships to other germ layer derivatives. Images Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 PMID:776002

  6. Notch1–STAT3–ETBR signaling axis controls reactive astrocyte proliferation after brain injury

    PubMed Central

    LeComte, Matthew D.; Shimada, Issei S.; Sherwin, Casey; Spees, Jeffrey L.

    2015-01-01

    Defining the signaling network that controls reactive astrogliosis may provide novel treatment targets for patients with diverse CNS injuries and pathologies. We report that the radial glial cell antigen RC2 identifies the majority of proliferating glial fibrillary acidic protein-positive (GFAP+) reactive astrocytes after stroke. These cells highly expressed endothelin receptor type B (ETBR) and Jagged1, a Notch1 receptor ligand. To study signaling in adult reactive astrocytes, we developed a model based on reactive astrocyte-derived neural stem cells isolated from GFAP-CreER-Notch1 conditional knockout (cKO) mice. By loss- and gain-of-function studies and promoter activity assays, we found that Jagged1/Notch1 signaling increased ETBR expression indirectly by raising the level of phosphorylated signal transducer and activator of transcription 3 (STAT3), a previously unidentified EDNRB transcriptional activator. Similar to inducible transgenic GFAP-CreER-Notch1-cKO mice, GFAP-CreER-ETBR-cKO mice exhibited a defect in reactive astrocyte proliferation after cerebral ischemia. Our results indicate that the Notch1–STAT3–ETBR axis connects a signaling network that promotes reactive astrocyte proliferation after brain injury. PMID:26124113

  7. Increased adenosine levels in mice expressing mutant glial fibrillary acidic protein in astrocytes result in failure of induction of LTP reversal (depotentiation) in hippocampal CA1 neurons.

    PubMed

    Fujii, Satoshi; Tanaka, Kenji F; Ikenaka, Kazuhiro; Yamazaki, Yoshihiko

    2014-08-26

    Astrocytes regulate the activity of neighboring neurons by releasing chemical transmitters, including ATP. Adenosine levels in the cerebrospinal fluid of mice that express a mutant human glial fibrillary acidic protein in astrocytes are slightly elevated compared to those in wild type mice and this might result from the observed increased release by mutant astrocytes of ATP, which can be used to produce adenosine. Using hippocampal slices from these mutant mice, we examined whether the increased endogenous adenosine levels in the hippocampus modulate the reversal of long-term potentiation (LTP), i.e. depotentiation (DP), in CA1 neurons. In hippocampal slices from wild type mice, a stable LTP was induced by tetanic stimulation consisting of 100 pulses at 100 Hz, and this was reversed by a train of low frequency stimulation (LFS) of 500 pulses at 1 Hz applied 30 min later. This induction of DP was inhibited by application of either 100 nM adenosine or 0.5 nM N(6)-cyclopentyladenosine, an adenosine A1 receptor agonist, during LFS, indicating that the increase in extracellular adenosine levels attenuated DP induction by acting on adenosine A1 receptors. In contrast, although a stable LTP was also induced in hippocampal slices from mutant mice, induction of DP was inhibited, but DP could be induced by application, during LFS, of 50 nM 8-cyclopentyltheophylline, an adenosine A1 receptor antagonist. These results suggest that a small increase in extracellular adenosine levels resulting from increased ATP release by astrocytes results in attenuation of DP in hippocampal CA1 neurons in the mutant mice.

  8. Diphenylarsinic Acid Induced Activation of Cultured Rat Cerebellar Astrocytes: Phosphorylation of Mitogen-Activated Protein Kinases, Upregulation of Transcription Factors, and Release of Brain-Active Cytokines.

    PubMed

    Negishi, Takayuki; Matsumoto, Mami; Kojima, Mikiya; Asai, Ryota; Kanehira, Tomoko; Sakaguchi, Fumika; Takahata, Kazuaki; Arakaki, Rina; Aoyama, Yohei; Yoshida, Hikari; Yoshida, Kenji; Yukawa, Kazunori; Tashiro, Tomoko; Hirano, Seishiro

    2016-03-01

    Diphenylarsinic acid (DPAA) was detected as the primary compound responsible for the arsenic poisoning that occurred in Kamisu, Ibaraki, Japan, where people using water from a well that was contaminated with a high level of arsenic developed neurological (mostly cerebellar) symptoms and dysregulation of regional cerebral blood flow. To understand the underlying molecular mechanism of DPAA-induced cerebellar symptoms, we focused on astrocytes, which have a brain-protective function. Incubation with 10 µM DPAA for 96 h promoted cell proliferation, increased the expression of antioxidative stress proteins (heme oxygenase-1 and heat shock protein 70), and induced the release of cytokines (MCP-1, adrenomedullin, FGF2, CXCL1, and IL-6). Furthermore, DPAA overpoweringly increased the phosphorylation of three major mitogen-activated protein kinases (MAPKs) (ERK1/2, p38MAPK, and SAPK/JNK), which indicated MAPK activation, and subsequently induced expression and/or phosphorylation of transcription factors (Nrf2, CREB, c-Jun, and c-Fos) in cultured rat cerebellar astrocytes. Structure-activity relationship analyses of DPAA and other related pentavalent organic arsenicals revealed that DPAA at 10 µM activated astrocytes most effective among organic arsenicals tested at the same dose. These results suggest that in a cerebellum exposed to DPAA, abnormal activation of the MAPK-transcription factor pathway and irregular secretion of these neuroactive, glioactive, and/or vasoactive cytokines in astrocytes can be the direct/indirect cause of functional abnormalities in surrounding neurons, glial cells, and vascular cells: This in turn might lead to the onset of cerebellar symptoms and disruption of cerebral blood flow. PMID:26645585

  9. Increased adenosine levels in mice expressing mutant glial fibrillary acidic protein in astrocytes result in failure of induction of LTP reversal (depotentiation) in hippocampal CA1 neurons.

    PubMed

    Fujii, Satoshi; Tanaka, Kenji F; Ikenaka, Kazuhiro; Yamazaki, Yoshihiko

    2014-08-26

    Astrocytes regulate the activity of neighboring neurons by releasing chemical transmitters, including ATP. Adenosine levels in the cerebrospinal fluid of mice that express a mutant human glial fibrillary acidic protein in astrocytes are slightly elevated compared to those in wild type mice and this might result from the observed increased release by mutant astrocytes of ATP, which can be used to produce adenosine. Using hippocampal slices from these mutant mice, we examined whether the increased endogenous adenosine levels in the hippocampus modulate the reversal of long-term potentiation (LTP), i.e. depotentiation (DP), in CA1 neurons. In hippocampal slices from wild type mice, a stable LTP was induced by tetanic stimulation consisting of 100 pulses at 100 Hz, and this was reversed by a train of low frequency stimulation (LFS) of 500 pulses at 1 Hz applied 30 min later. This induction of DP was inhibited by application of either 100 nM adenosine or 0.5 nM N(6)-cyclopentyladenosine, an adenosine A1 receptor agonist, during LFS, indicating that the increase in extracellular adenosine levels attenuated DP induction by acting on adenosine A1 receptors. In contrast, although a stable LTP was also induced in hippocampal slices from mutant mice, induction of DP was inhibited, but DP could be induced by application, during LFS, of 50 nM 8-cyclopentyltheophylline, an adenosine A1 receptor antagonist. These results suggest that a small increase in extracellular adenosine levels resulting from increased ATP release by astrocytes results in attenuation of DP in hippocampal CA1 neurons in the mutant mice. PMID:25017946

  10. Mathematical modelling of the citric acid cycle for the analysis of glutamine isotopomers from cerebellar astrocytes incubated with [1(-13)C]glucose.

    PubMed

    Merle, M; Martin, M; Villégier, A; Canioni, P

    1996-08-01

    A mathematical model of the citric acid cycle devoted to the analysis of 13C-NMR data was developed for determining the relative flux of molecules through the anaplerotic versus oxidative pathways and the relative pyruvate carboxylase versus pyruvate dehydrogenase activities. Different variants of the model were considered depending on the reversibility of the conversion of fumarate into malate and oxaloacetate. The model also included the possibility of orientation-conserved transfer of the four-carbon citric acid cycle intermediates, leading to conversion of succinyl-CoA C1 into either malate C1 or C4. It was used to analyse NMR data from glutamine isotopomers produced by cerebellar astrocytes incubated with [1-13C]glucose. Partial cycling (39%) between oxaloacetate and fumarate was evident from the analysis. Application of the model to glutamate isotopomers from granule cells incubated with [1-13C]glucose [Martin, M.. Portais, J.C.. Labouesse. J., Canioni. P, & Merle, M. (1993) Eur. J. Biochem. 217, 617-625] indicated that total cycling of oxaloacetate into fumarate was, in this case, required to get the best fit. The results emphasized some important differences in carbon metabolism between cerebellar astrocytes and granule cells concerning the sources of carbon fuelling the citric acid cycle and the carbon fluxes on different pathways.

  11. Increased arachidonic acid-containing phosphatidylcholine is associated with reactive microglia and astrocytes in the spinal cord after peripheral nerve injury.

    PubMed

    Xu, Dongmin; Omura, Takao; Masaki, Noritaka; Arima, Hideyuki; Banno, Tomohiro; Okamoto, Ayako; Hanada, Mitsuru; Takei, Shiro; Matsushita, Shoko; Sugiyama, Eiji; Setou, Mitsutoshi; Matsuyama, Yukihiro

    2016-01-01

    Peripheral nerve injury (PNI) triggers cellular and molecular changes in the spinal cord. However, little is known about how the polyunsaturated fatty acid-containing phosphatidylcholines (PUFA-PCs) are regulated in the spinal cord after PNI and the association of PUFA-PCs with the non-neuronal cells within in the central nervous system (CNS). In this study, we found that arachidonic acid-containing phosphatidylcholine (AA-PC), [PC(16:0/20:4)+K](+), was significantly increased in the ipsilateral ventral and dorsal horns of the spinal cord after sciatic nerve transection, and the increased expression of [PC(16:0/20:4)+K](+) spatiotemporally resembled the increase of reactive microglia and the astrocytes. From the lipidomics point of view, we conclude that [PC(16:0/20:4)+K](+) could be the main phospholipid in the spinal cord influenced by PNI, and the regulation of specific phospholipid molecule in the CNS after PNI is associated with the reactive microglia and astrocytes. PMID:27210057

  12. Increased arachidonic acid-containing phosphatidylcholine is associated with reactive microglia and astrocytes in the spinal cord after peripheral nerve injury

    PubMed Central

    Xu, Dongmin; Omura, Takao; Masaki, Noritaka; Arima, Hideyuki; Banno, Tomohiro; Okamoto, Ayako; Hanada, Mitsuru; Takei, Shiro; Matsushita, Shoko; Sugiyama, Eiji; Setou, Mitsutoshi; Matsuyama, Yukihiro

    2016-01-01

    Peripheral nerve injury (PNI) triggers cellular and molecular changes in the spinal cord. However, little is known about how the polyunsaturated fatty acid-containing phosphatidylcholines (PUFA-PCs) are regulated in the spinal cord after PNI and the association of PUFA-PCs with the non-neuronal cells within in the central nervous system (CNS). In this study, we found that arachidonic acid-containing phosphatidylcholine (AA-PC), [PC(16:0/20:4)+K]+, was significantly increased in the ipsilateral ventral and dorsal horns of the spinal cord after sciatic nerve transection, and the increased expression of [PC(16:0/20:4)+K]+ spatiotemporally resembled the increase of reactive microglia and the astrocytes. From the lipidomics point of view, we conclude that [PC(16:0/20:4)+K]+ could be the main phospholipid in the spinal cord influenced by PNI, and the regulation of specific phospholipid molecule in the CNS after PNI is associated with the reactive microglia and astrocytes. PMID:27210057

  13. Reduction of glial fibrillary acidic protein-immunoreactive astrocytes in some brain areas of old hairless rhino-j mice (hr-rh-j).

    PubMed

    San Jose, I; García-Atares, N; Pelaez, B; Cabo, R; Esteban, I; Vega, J A; Represa, J

    2001-08-24

    Mutations in the hairless (hr) gene of mice result in hair follicle and other epithelial defects. The hr gene is expressed at high levels in the brain where it probably participates in the survival and maintenance of some neuronal populations, but whether it also supports glial populations of the central nervous system has been not investigated. To clarify this, quantitative immunohistochemistry for astrocytes (glial fibrillary acidic protein (GFAP)) and microglial cells (CD11b macrophage antigen) was used in the brain of a mutant mouse strain, the hairless (hr-rh-j) type, which carries the homozygous hr gene rhino mutation. The glial cell density was assessed in the cerebral cortex, hippocampus, striatum, hypothalamus and cerebellum of young (3 months) and old (9 months) hr-rh-j mice. No significant differences were found between young wild-type and hr-rh-j mice. The density of GFAP immunoreactive astrocytes normally increased as a function of age, but in older hr-rh-j mice there was a severe reduction (P<0.01) in the striatum, hypothalamus, and hippocampus. Conversely, the microglial cells were insensible to aging or to hr-rh-j mutation. These results suggest that the hr gene is involved in the maintenance of the GFAP immunoreactive cells in some cerebral areas. Nevertheless, because these animals do not show any neurological signs, the functional significance of the present findings remains to be established.

  14. The effect of gallic acid on cytotoxicity, Ca(2+) homeostasis and ROS production in DBTRG-05MG human glioblastoma cells and CTX TNA2 rat astrocytes.

    PubMed

    Hsu, Shu-Shong; Chou, Chiang-Ting; Liao, Wei-Chuan; Shieh, Pochuen; Kuo, Daih-Huang; Kuo, Chun-Chi; Jan, Chung-Ren; Liang, Wei-Zhe

    2016-05-25

    Gallic acid, a polyhydroxylphenolic compound, is widely distributed in various plants, fruits and foods. It has been shown that gallic acid passes into blood brain barrier and reaches the brain tissue of middle cerebral artery occlusion rats. However, the effect of gallic acid on Ca(2+) signaling in glia cells is unknown. This study explored whether gallic acid affected Ca(2+) homeostasis and induced Ca(2+)-associated cytotoxicity in DBTRG-05MG human glioblastoma cells and CTX TNA2 rat astrocytes. Gallic acid (20-40 μM) concentration-dependently induced cytotoxicity and intracellular Ca(2+) level ([Ca(2+)]i) increases in DBTRG-05MG cells but not in CTX TNA2 cells. In DBTRG-05MG cells, the Ca(2+) response was decreased by half by removal of extracellular Ca(2+). In Ca(2+)-containing medium, gallic acid-induced Ca(2+) entry was inhibited by store-operated Ca(2+) channel inhibitors (2-APB, econazole and SKF96365). In Ca(2+)-free medium, pretreatment with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin abolished gallic acid-induced [Ca(2+)]i increases. Conversely, incubation with gallic acid also abolished thapsigargin-induced [Ca(2+)]i increases. Inhibition of phospholipase C with U73122 abolished gallic acid-induced [Ca(2+)]i increases. Gallic acid significantly caused cytotoxicity in DBTRG-05MG cells, which was partially prevented by prechelating cytosolic Ca(2+) with BAPTA-AM. Moreover, gallic acid activated mitochondrial apoptotic pathways that involved ROS production. Together, in DBTRG-05MG cells but not in CTX TNA2 cells, gallic acid induced [Ca(2+)]i increases by causing Ca(2+) entry via 2-APB, econazole and SKF96365-sensitive store-operated Ca(2+) entry, and phospholipase C-dependent release from the endoplasmic reticulum. This Ca(2+) signal subsequently evoked mitochondrial pathways of apoptosis that involved ROS production.

  15. The effect of gallic acid on cytotoxicity, Ca(2+) homeostasis and ROS production in DBTRG-05MG human glioblastoma cells and CTX TNA2 rat astrocytes.

    PubMed

    Hsu, Shu-Shong; Chou, Chiang-Ting; Liao, Wei-Chuan; Shieh, Pochuen; Kuo, Daih-Huang; Kuo, Chun-Chi; Jan, Chung-Ren; Liang, Wei-Zhe

    2016-05-25

    Gallic acid, a polyhydroxylphenolic compound, is widely distributed in various plants, fruits and foods. It has been shown that gallic acid passes into blood brain barrier and reaches the brain tissue of middle cerebral artery occlusion rats. However, the effect of gallic acid on Ca(2+) signaling in glia cells is unknown. This study explored whether gallic acid affected Ca(2+) homeostasis and induced Ca(2+)-associated cytotoxicity in DBTRG-05MG human glioblastoma cells and CTX TNA2 rat astrocytes. Gallic acid (20-40 μM) concentration-dependently induced cytotoxicity and intracellular Ca(2+) level ([Ca(2+)]i) increases in DBTRG-05MG cells but not in CTX TNA2 cells. In DBTRG-05MG cells, the Ca(2+) response was decreased by half by removal of extracellular Ca(2+). In Ca(2+)-containing medium, gallic acid-induced Ca(2+) entry was inhibited by store-operated Ca(2+) channel inhibitors (2-APB, econazole and SKF96365). In Ca(2+)-free medium, pretreatment with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin abolished gallic acid-induced [Ca(2+)]i increases. Conversely, incubation with gallic acid also abolished thapsigargin-induced [Ca(2+)]i increases. Inhibition of phospholipase C with U73122 abolished gallic acid-induced [Ca(2+)]i increases. Gallic acid significantly caused cytotoxicity in DBTRG-05MG cells, which was partially prevented by prechelating cytosolic Ca(2+) with BAPTA-AM. Moreover, gallic acid activated mitochondrial apoptotic pathways that involved ROS production. Together, in DBTRG-05MG cells but not in CTX TNA2 cells, gallic acid induced [Ca(2+)]i increases by causing Ca(2+) entry via 2-APB, econazole and SKF96365-sensitive store-operated Ca(2+) entry, and phospholipase C-dependent release from the endoplasmic reticulum. This Ca(2+) signal subsequently evoked mitochondrial pathways of apoptosis that involved ROS production. PMID:27060209

  16. Astrocytes and mitochondria from adrenoleukodystrophy protein (ABCD1)-deficient mice reveal that the adrenoleukodystrophy-associated very long-chain fatty acids target several cellular energy-dependent functions.

    PubMed

    Kruska, Nicol; Schönfeld, Peter; Pujol, Aurora; Reiser, Georg

    2015-05-01

    X-linked adrenoleukodystrophy (X-ALD) is a severe neurodegenerative disorder resulting from defective ABCD1 transport protein. ABCD1 mediates peroxisomal uptake of free very-long-chain fatty acids (VLCFA) as well as their CoA-esters. Consequently, VLCFA accumulate in patients' plasma and tissues, which is considered as pathogenic X-ALD triggering factor. Clinical symptoms are mostly manifested in neural tissues and adrenal gland. Here, we investigate astrocytes from wild-type control and a genetic X-ALD mouse model (Abcd1-knockout), exposed to supraphysiological VLCFA (C22:0, C24:0 and C26:0) concentrations. They exhibit multiple impairments of energy metabolism. Furthermore, brain mitochondria from Abcd1(-/-) mice and wild-type control respond similarly to VLCFA with increased ROS generation, impaired oxidative ATP synthesis and diminished Ca(2+) uptake capacity, suggesting that a defective ABCD1 exerts no adaptive pressure on mitochondria. In contrast, astrocytes from Abcd1(-/-) mice respond more sensitively to VLCFA than wild-type control astrocytes. Moreover, long-term application of VLCFA induces high ROS generation, and strong in situ depolarization of mitochondria, and, in Abcd1(-/-) astrocytes, severely diminishes the capability to revert oxidized pyridine nucleotides to NAD(P)H. In addition, observed differences in responses of mitochondria and astrocytes to the hydrocarbon chain length of VLCFA suggest that detrimental VLCFA activities in astrocytes involve defective cellular functions other than mitochondria. In summary, we clearly demonstrate that VLCFA increase the vulnerability of Abcd1(-/-) astrocytes.

  17. Retinoic acid isomers up-regulate ATP binding cassette A1 and G1 and cholesterol efflux in rat astrocytes: implications for their therapeutic and teratogenic effects.

    PubMed

    Chen, Jing; Costa, Lucio G; Guizzetti, Marina

    2011-09-01

    Recent studies suggest that retinoids may be effective in the treatment of Alzheimer's disease, although exposure to an excess of retinoids during gestation causes teratogenesis. Cholesterol is essential for brain development, but high levels of cholesterol have been associated with Alzheimer's disease. We hypothesized that retinoic acid may affect cholesterol homeostasis in rat astrocytes, which regulate cholesterol distribution in the brain, through the up-regulation of cholesterol transporters ATP binding cassette (Abc)a1 and Abcg1. Tretinoin, 13-cis retinoic acid (13-cis-RA), 9-cis-RA, and the selective retinoid X receptor (RXR) agonist methoprene significantly increased cholesterol efflux induced by cholesterol acceptors and protein levels of Abca1 by 2.3- (± 0.25), 3.6- (± 0.42), 4.1- (± 0.5), and 1.75- (± 0.43) fold, respectively, and Abcg1 by 2.1- (± 0.26), 2.2- (± 0.33), 2.5- (± 0.23), and 2.2- (± 0.21) fold, respectively. 13-cis-RA and 9-cis-RA also significantly increased mRNA levels of Abca1 (maximal induction 7.3 ± 0.42 and 2.7 ± 0.17, respectively) and Abcg1 (maximal induction 2.0 ± 0.18 and 1.8 ± 0.09, respectively), and the levels of membrane-bound Abca1 (2.5 ± 0.3 and 2.5 ± 0.40-fold increase, respectively), whereas they significantly decreased intracellular cholesterol content without affecting cholesterol synthesis. The effect of 9-cis-RA on cholesterol homeostasis in astrocytes can be ascribed to the activation of RXR, whereas the effects of 13-cis-RA and tretinoin were independent of either RXRs or retinoic acid receptors. These findings suggest that retinoids affect cholesterol homeostasis in astrocytes and that this effect may be involved in both their therapeutic and teratogenic actions.

  18. Astrocyte elevated gene-1 is a novel modulator of HIV-1-associated neuroinflammation via regulation of nuclear factor-κB signaling and excitatory amino acid transporter-2 repression.

    PubMed

    Vartak-Sharma, Neha; Gelman, Benjamin B; Joshi, Chaitanya; Borgamann, Kathleen; Ghorpade, Anuja

    2014-07-11

    Astrocyte elevated gene-1 (AEG-1), a novel human immunodeficiency virus (HIV)-1 and tumor necrosis factor (TNF)-α-inducible oncogene, has generated significant interest in the field of cancer research as a therapeutic target for many metastatic aggressive tumors. However, little is known about its role in astrocyte responses during HIV-1 central nervous system (CNS) infection and whether it contributes toward the development of HIV-associated neurocognitive disorders (HAND). Therefore, in this study, we investigated changes in AEG-1 CNS expression in HIV-1-infected brain tissues and elucidated a potential mechanism of AEG-1-mediated regulation of HAND. Immunoblotting and immunohistochemical analyses of HIV-1 seropositive and HIV-1 encephalitic human brain tissues revealed significantly elevated levels of AEG-1 protein. Immunohistochemical analyses of HIV-1 Tat transgenic mouse brain tissues also showed a marked increase in AEG-1 staining. Similar to in vivo observations, cultured astrocytes expressing HIV-1 Tat also revealed AEG-1 and cytokine up-regulation. Astrocytes treated with HAND-relevant stimuli, TNF-α, interleukin (IL)-1β, and HIV-1, also significantly induced AEG-1 expression and nuclear translocation via activation of the nuclear factor (NF)-κB pathway. Co-immunoprecipitation studies demonstrated IL-1β- or TNF-α-induced AEG-1 interaction with NF-κB p65 subunit. AEG-1 knockdown decreased NF-κB activation, nuclear translocation, and transcriptional output in TNF-α-treated astrocytes. Moreover, IL-1β treatment of AEG-1-overexpressing astrocytes significantly lowered expression of excitatory amino acid transporter 2, increased expression of excitatory amino acid transporter 2 repressor ying yang 1, and reduced glutamate clearance, a major transducer of excitotoxic neuronal damage. Findings from this study identify a novel transcriptional co-factor function of AEG-1 and further implicate AEG-1 in HAND-associated neuroinflammation.

  19. Electrophilic nitro-fatty acids prevent astrocyte-mediated toxicity to motor neurons in a cell model of familial amyotrophic lateral sclerosis via nuclear factor erythroid 2-related factor activation.

    PubMed

    Diaz-Amarilla, Pablo; Miquel, Ernesto; Trostchansky, Andrés; Trias, Emiliano; Ferreira, Ana M; Freeman, Bruce A; Cassina, Patricia; Barbeito, Luis; Vargas, Marcelo R; Rubbo, Homero

    2016-06-01

    Nitro-fatty acids (NO2-FA) are electrophilic signaling mediators formed in tissues during inflammation, which are able to induce pleiotropic cytoprotective and antioxidant pathways including up regulation of Nuclear factor erythroid 2-related factor 2 (Nrf2) responsive genes. Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disease characterized by the loss of motor neurons associated to an inflammatory process that usually aggravates the disease progression. In ALS animal models, the activation of the transcription factor Nrf2 in astrocytes confers protection to neighboring neurons. It is currently unknown whether NO2-FA can exert protective activity in ALS through Nrf2 activation. Herein we demonstrate that nitro-arachidonic acid (NO2-AA) or nitro-oleic acid (NO2-OA) administrated to astrocytes expressing the ALS-linked hSOD1(G93A) induce antioxidant phase II enzyme expression through Nrf2 activation concomitant with increasing intracellular glutathione levels. Furthermore, treatment of hSOD1(G93A)-expressing astrocytes with NO2-FA prevented their toxicity to motor neurons. Transfection of siRNA targeted to Nrf2 mRNA supported the involvement of Nrf2 activation in NO2-FA-mediated protective effects. Our results show for the first time that NO2-FA induce a potent Nrf2-dependent antioxidant response in astrocytes capable of preventing motor neurons death in a culture model of ALS. PMID:27012417

  20. Electrophilic nitro-fatty acids prevent astrocyte-mediated toxicity to motor neurons in a cell model of familial amyotrophic lateral sclerosis via nuclear factor erythroid 2-related factor activation.

    PubMed

    Diaz-Amarilla, Pablo; Miquel, Ernesto; Trostchansky, Andrés; Trias, Emiliano; Ferreira, Ana M; Freeman, Bruce A; Cassina, Patricia; Barbeito, Luis; Vargas, Marcelo R; Rubbo, Homero

    2016-06-01

    Nitro-fatty acids (NO2-FA) are electrophilic signaling mediators formed in tissues during inflammation, which are able to induce pleiotropic cytoprotective and antioxidant pathways including up regulation of Nuclear factor erythroid 2-related factor 2 (Nrf2) responsive genes. Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disease characterized by the loss of motor neurons associated to an inflammatory process that usually aggravates the disease progression. In ALS animal models, the activation of the transcription factor Nrf2 in astrocytes confers protection to neighboring neurons. It is currently unknown whether NO2-FA can exert protective activity in ALS through Nrf2 activation. Herein we demonstrate that nitro-arachidonic acid (NO2-AA) or nitro-oleic acid (NO2-OA) administrated to astrocytes expressing the ALS-linked hSOD1(G93A) induce antioxidant phase II enzyme expression through Nrf2 activation concomitant with increasing intracellular glutathione levels. Furthermore, treatment of hSOD1(G93A)-expressing astrocytes with NO2-FA prevented their toxicity to motor neurons. Transfection of siRNA targeted to Nrf2 mRNA supported the involvement of Nrf2 activation in NO2-FA-mediated protective effects. Our results show for the first time that NO2-FA induce a potent Nrf2-dependent antioxidant response in astrocytes capable of preventing motor neurons death in a culture model of ALS.

  1. ASTROCYTES: EMERGING STARS IN LEUKODYSTROPHY PATHOGENESIS

    PubMed Central

    Lanciotti, Angela; Brignone, Maria Stefania; Bertini, Enrico; Petrucci, Tamara C.; Aloisi, Francesca; Ambrosini, Elena

    2013-01-01

    Astrocytes are the predominant glial cell population in the central nervous system (CNS). Once considered only passive scaffolding elements, astrocytes are now recognised as cells playing essential roles in CNS development and function. They control extracellular water and ion homeostasis, provide substrates for energy metabolism, and regulate neurogenesis, myelination and synaptic transmission. Due to these multiple activities astrocytes have been implicated in almost all brain pathologies, contributing to various aspects of disease initiation, progression and resolution. Evidence is emerging that astrocyte dysfunction can be the direct cause of neurodegeneration, as shown in Alexander’s disease where myelin degeneration is caused by mutations in the gene encoding the astrocyte-specific cytoskeleton protein glial fibrillary acidic protein. Recent studies point to a primary role for astrocytes in the pathogenesis of other genetic leukodystrophies such as megalencephalic leukoencephalopathy with subcortical cysts and vanishing white matter disease. The aim of this review is to summarize current knowledge of the pathophysiological role of astrocytes focusing on their contribution to the development of the above mentioned leukodystrophies and on new perspectives for the treatment of neurological disorders. PMID:24340223

  2. Targeting astrocytes in bipolar disorder.

    PubMed

    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

  3. Growth of purified astrocytes in a chemically defined medium

    SciTech Connect

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

    1981-11-01

    Astrocytes purified from primary cultures of neonatal rat cerebrum can not be grown in a synthetic medium supplemented with putrescine, prostaglandin F/sub 2//sub ..cap alpha../, insulin, fibroblast growth factor, and hydrocortisone. These five supplements have a marked synergistic effect on growth when used in combination but have little effect when used individually. Astrocytes grown in the defined medium exhibit dramatic changes in morphological characteristics in comparison to cells grown in serum-free or serum-supplemented medium. In addition, these cells express the astrocyte-specific marker glial fibrillary acidic protein and are estimated by several criteria to be greater than 95% astrocytes.

  4. Expression of zonula occludens-1 (ZO-1) and the transcription factor ZO-1-associated nucleic acid-binding protein (ZONAB)-MsY3 in glial cells and colocalization at oligodendrocyte and astrocyte gap junctions in mouse brain.

    PubMed

    Penes, Mihai C; Li, Xinbo; Nagy, James I

    2005-07-01

    The PDZ domain-containing protein zonula occludens-1 (ZO-1) interacts with several members of the connexin (Cx) family of gap junction-forming proteins and has been localized to gap junctions, including those containing Cx47 in oligodendrocytes. We now provide evidence for ZO-1 expression in astrocytes in vivo and association with astrocytic connexins by confocal immunofluorescence demonstration of ZO-1 colocalization with astrocytic Cx30 and Cx43, and by ZO-1 coimmunoprecipitation with Cx30 and Cx43. Evidence for direct interaction of Cx30 with ZO-1 was obtained by pull-down assays that indicated binding of Cx30 to the second of the three PDZ domains in ZO-1. Further, we investigated mouse Y-box transcription factor MsY3, the canine ortholog of which has been termed ZO-1-associated nucleic acid-binding protein (ZONAB) and previously reported to interact with ZO-1. By immunofluorescence using specific antimouse ZONAB antibody, ZONAB was found to be associated with oligodendrocytes throughout mouse brain and spinal cord, and to be colocalized with oligodendrocytic Cx47 and Cx32 as well as with astrocytic Cx43. Our results extend the CNS cell types that express the multifunctional protein ZO-1, demonstrate an additional connexin (Cx30) that directly interacts with ZO-1, and show for the first time the association of a transcription factor (ZONAB) with ZO-1 localized to oligodendrocyte and astrocyte gap junctions. Given previous observations that ZONAB and ZO-1 in combination regulate gene expression, our results suggest roles of glial gap junction-mediated anchoring of signalling molecules in a wide variety of glial homeostatic processes. PMID:16045494

  5. Elusive roles for reactive astrocytes in neurodegenerative diseases

    PubMed Central

    Ben Haim, Lucile; Carrillo-de Sauvage, Maria-Angeles; Ceyzériat, Kelly; Escartin, Carole

    2015-01-01

    Astrocytes play crucial roles in the brain and are involved in the neuroinflammatory response. They become reactive in response to virtually all pathological situations in the brain such as axotomy, ischemia, infection, and neurodegenerative diseases (ND). Astrocyte reactivity was originally characterized by morphological changes (hypertrophy, remodeling of processes) and the overexpression of the intermediate filament glial fibrillary acidic protein (GFAP). However, it is unclear how the normal supportive functions of astrocytes are altered by their reactive state. In ND, in which neuronal dysfunction and astrocyte reactivity take place over several years or decades, the issue is even more complex and highly debated, with several conflicting reports published recently. In this review, we discuss studies addressing the contribution of reactive astrocytes to ND. We describe the molecular triggers leading to astrocyte reactivity during ND, examine how some key astrocyte functions may be enhanced or altered during the disease process, and discuss how astrocyte reactivity may globally affect ND progression. Finally we will consider the anticipated developments in this important field. With this review, we aim to show that the detailed study of reactive astrocytes may open new perspectives for ND. PMID:26283915

  6. Endothelin, Astrocytes and Glaucoma

    PubMed Central

    Prasanna, Ganesh; Krishnamoorthy, Raghu; Yorio, Thomas

    2010-01-01

    It has become increasingly clear that astrocytes may play an important role in the genesis of glaucoma. Astrogliosis occurs in response to ocular stress or the presence of noxious stimuli. Agents that appear to stimulate reactive gliosis are becoming increasingly clear. One class of agents that is emerging is the endothelins (ETs; specifically, ET-1). In this review we examine the interactions of ET-1 with astrocytes and provide examples where ET-1 appears to contribute to activation of astrocytes and play a role in the neurodegenerative effects that accompany such reactivation resulting in astrogliosis. These actions are presented in the context of glaucoma although information is also presented with respect to ET-1's role in the central nervous system and brain. While much has been learned with respect to ET-1/astrocyte interactions, there are still a number of questions concerning the potential therapeutic implications of these findings. Hopefully this review will stimulate others to examine this potential. PMID:20849847

  7. Transcriptional Regulation of the Astrocytic Excitatory Amino Acid Transporter 1 (EAAT1) via NF-κB and Yin Yang 1 (YY1)*

    PubMed Central

    Karki, Pratap; Kim, Clifford; Smith, Keisha; Son, Deok-Soo; Aschner, Michael; Lee, Eunsook

    2015-01-01

    Astrocytic glutamate transporter excitatory amino acid transporter (EAAT) 1, also known as glutamate aspartate transporter (GLAST) in rodents, is one of two glial glutamate transporters that are responsible for removing excess glutamate from synaptic clefts to prevent excitotoxic neuronal death. Despite its important role in neurophysiological functions, the molecular mechanisms of EAAT1 regulation at the transcriptional level remain to be established. Here, we report that NF-κB is a main positive transcription factor for EAAT1, supported by the following: 1) EAAT1 contains two consensus sites for NF-κB, 2) mutation of NF-κB binding sites decreased EAAT1 promoter activity, and 3) activation of NF-κB increased, whereas inhibition of NF-κB decreased EAAT1 promoter activity and mRNA/protein levels. EGF increased EAAT1 mRNA/protein levels and glutamate uptake via NF-κB. The transcription factor yin yang 1 (YY1) plays a role as a critical negative regulator of EAAT1, supported by the following: 1) the EAAT1 promoter contains multiple consensus sites for YY1, 2) overexpression of YY1 decreased EAAT1 promoter activity and mRNA/protein levels, and 3) knockdown of YY1 increased EAAT1 promoter activity and mRNA/protein levels. Manganese decreased EAAT1 expression via YY1. Epigenetic modifiers histone deacetylases (HDACs) served as co-repressors of YY1 to further decrease EAAT1 promoter activity, whereas inhibition of HDACs reversed manganese-induced decrease of EAAT1 expression. Taken together, our findings suggest that NF-κB is a critical positive regulator of EAAT1, mediating the stimulatory effects of EGF, whereas YY1 is a negative regulator of EAAT1 with HDACs as co-repressors, mediating the inhibitory effects of manganese on EAAT1 regulation. PMID:26269591

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

    PubMed

    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

  9. Glycyrrhizic acid prevents astrocyte death by neuromyelitis optica-specific IgG via inhibition of C1q binding.

    PubMed

    Kim, Ji-Sun; Cheon, Soyoung; Kim, Seung Woo; Kim, Boram; Kim, Heejaung; Park, Ki Duk; Kim, Sung-Min

    2016-09-16

    Neuromyelitis optica (NMO) is an inflammatory demyelinating disease of the central nervous system and is mediated by complement-dependent cytotoxicity (CDC) of NMO-specific immunoglobulin G (IgG) antibodies (NMO-IgG). Glycyrrhizic acid (GA) has numerous pharmacological effects including inhibition of the complement pathway. We aimed to study the influence of GA on NMO-IgG-induced CDC. NMO-IgG samples from 7 patients with NMO, together with human complement, induced CDC in an aquaporin 4 M23-overexpressing glial cell line, an in vitro NMO model. GA attenuated NMO-IgG-induced CDC in a dose-dependent manner. The mechanism of the GA-related CDC inhibition was sequentially dissected and found to involve inhibition of C1q binding to NMO-IgG. Consequently, GA attenuates NMO-IgG-induced CDC and may be a promising novel therapeutic agent against NMO. PMID:27462020

  10. PKC signaling mediates global enhancement of excitatory synaptogenesis in neurons triggered by local contact with astrocytes.

    PubMed

    Hama, Hiroshi; Hara, Chikako; Yamaguchi, Kazuhiko; Miyawaki, Atsushi

    2004-02-01

    Here we provide evidence that astrocytes affect neuronal synaptogenesis by the process of adhesion. Local contact with astrocytes via integrin receptors elicited protein kinase C (PKC) activation in individual dissociated neurons cultured in astrocyte-conditioned medium. This activation, initially focal, soon spread throughout the entire neuron. We then demonstrated pharmacologically that the arachidonic acid cascade, triggered by the integrin reception, is responsible for the global activation of PKC. Local astrocytic contact also facilitated excitatory synaptogenesis throughout the neuron, a process which could be blocked by inhibitors of both integrins and PKC. Thus, propagation of PKC signaling represents an underlying mechanism for global neuronal maturation following local astrocyte adhesion.

  11. Form follows function: astrocyte morphology and immune dysfunction in SIV neuroAIDS.

    PubMed

    Lee, Kim M; Chiu, Kevin B; Renner, Nicole A; Sansing, Hope A; Didier, Peter J; MacLean, Andrew G

    2014-10-01

    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 glial fibrillary acidic protein (GFAP)-labeled astrocytes per square millimeter and the proportion of astrocytes immunopositive for Toll-like receptor 2 (TLR2) to examine innate immune activation in astrocytes. We also performed detailed morphometric analyses of gray and white matter astrocytes in the frontal and parietal lobes of rhesus macaques infected with simian immunodeficiency virus (SIV), both with and without encephalitis, an established model of AIDS neuropathogenesis. Protoplasmic astrocytes (gray matter) and fibrous astrocytes (deep white matter) were imaged, and morphometric features were analyzed using Neurolucida. Gray matter and white matter astrocytes showed no change in cell body size in animals infected with SIV regardless of encephalitic status. In SIV-infected macaques, both gray and white matter astrocytes had shorter, less ramified processes, resulting in decreased cell arbor compared with controls. SIV-infected macaques with encephalitis showed decreases in arbor length in white matter astrocytes and reduced complexity in gray matter astrocytes compared to controls. These results provide the first evidence that innate immune activation of astrocytes is linked to altered cortical astrocyte morphology in SIV/HIV infection. Here, we demonstrate that astrocyte remodeling is correlated with infection. Perturbed neuron-glia signaling may be a driving factor in the development of HAND.

  12. Brain oligomeric β-amyloid but not total amyloid plaque burden correlates with neuronal loss and astrocyte inflammatory response in amyloid precursor protein/tau transgenic mice.

    PubMed

    DaRocha-Souto, Bibiana; Scotton, Thomas C; Coma, Mireia; Serrano-Pozo, Alberto; Hashimoto, Tadafumi; Serenó, Lidia; Rodríguez, Marta; Sánchez, Belen; Hyman, Bradley T; Gómez-Isla, Teresa

    2011-05-01

    It has long been assumed that β-amyloid (Aβ) had to assemble into fibrillar amyloid plaques to exert its neurotoxic effects in Alzheimer disease. An alternative hypothesis is that soluble oligomers ofAβ play a much larger role in neuronal damage than the insoluble component. We have tested these competing hypotheses in vivo by studying the clinicopathologic correlates of oligomeric Aβ species and classic fibrillar amyloid plaques in the brains of double-transgenic APP-tau mice up to 17 months of age. Biochemical and immunohistochemical measures of brain oligomeric Aβ exponentially increased with age. Oligomeric Aβ load correlated with morphological markers of fibrillar Aβ deposition. In contrast to total amyloid plaque burden, the amount of oligomeric Aβ deposits labeled by the conformational epitope-specific antibody Nab61 closely correlated with neuronal loss and numbers of astrocytes in the entorhinal cortex and the CA1 hippocampal subfield. However, like other morphological Aβ measurements, brain oligomeric Aβ burden did not correlate well with memory deficits in these mice. The number of glial fibrillary acidic protein-positive astrocytes in entorhinal cortex and CA1 most tightly correlated with memory impairment and neuronal cell loss. Based on these findings, we hypothesize that the astrocyte response, which is likely triggered by brain oligomeric Aβ accumulation, adversely affects cognition and might also contribute to neuronal cell death in this model.

  13. Caffeic acid phenethyl ester induces adrenoleukodystrophy (Abcd2) gene in human X-ALD fibroblasts and inhibits the proinflammatory response in Abcd1/2 silenced mouse primary astrocytes.

    PubMed

    Singh, Jaspreet; Khan, Mushfiquddin; Singh, Inderjit

    2013-04-01

    X-linked adrenoleukodystrophy (X-ALD) is a peroxisomal disorder caused by mutations in the ABCD1 gene. Accumulation of very long chain fatty acids (VLCFA) that have been attributed to reduced peroxisomal VLCFA β-oxidation activity are the hallmark of the disease. Overexpression of ABCD2 gene, the closest homolog of ABCD1, has been shown to compensate for ABCD1, thus correcting the VLCFA derangement. The accumulation of VLCFA leads to a neuroinflammatory disease process associated with demyelination of the cerebral white matter. The present study underlines the importance of caffeic acid phenethyl ester (CAPE) in inducing the expression of ABCD2 (ALDRP), and normalizing the peroxisomal β-oxidation as well as the levels of saturated and monounsaturated VLCFAs in cultured human skin fibroblasts of X-ALD patients. The expression of ELOVL1, the single elongase catalyzing the synthesis of both saturated VLCFA (C26:0) and mono-unsaturated VLCFA (C26:1), was also reduced by CAPE treatment. Importantly, CAPE upregulated Abcd2 expression and peroxisomal β-oxidation and lowered the VLCFA levels in Abcd1-deficient U87 astrocytes and B12 oligodendrocytes. In addition, using Abcd1/Abcd2-silenced mouse primary astrocytes we examined the effects of CAPE in VLCFA-induced inflammatory response. CAPE treatment decreased the inflammatory response as the expression of inducible nitric oxide synthase, inflammatory cytokine, and activation of NF-κB in Abcd1/Abcd2-silenced mouse primary astrocytes was reduced. The observations indicate that CAPE corrects both the metabolic disease of VLCFA as well as secondary inflammatory disease; therefore, it may be a potential drug candidate to be tested for X-ALD therapy in humans.

  14. Impairments of astrocytes are involved in the D-galactose-induced brain aging

    SciTech Connect

    Lei Ming; Hua Xiangdong; Xiao Ming Ding Jiong; Han Qunying Hu Gang

    2008-05-16

    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.

  15. Kappa Opioid Receptor Activation of p38 MAPK Is GRK3- and Arrestin-dependent in Neurons and Astrocytes*

    PubMed Central

    Bruchas, Michael R.; Macey, Tara A.; Lowe, Janet D.; Chavkin, Charles

    2007-01-01

    AtT-20 cells expressing the wild-type kappa opioid receptor (KOR) increased phospho-p38 MAPK following treatment with the kappa agonist U50,488. The increase was blocked by the kappa antagonist norbinaltorphimine and not evident in untransfected cells. In contrast, U50,488 treatment of AtT-20 cells expressing KOR having alanine substituted for serine-369 (KSA) did not increase phospho-p38. Phosphorylation of serine 369 in the KOR carboxyl terminus by G-protein receptor kinase 3 (GRK3) was previously shown to be required for receptor desensitization, and the results suggest that p38 MAPK activation by KOR may require arrestin recruitment. This hypothesis was tested by transfecting arrestin3-(R170E), a dominant positive form of arrestin that does not require receptor phosphorylation for activation. AtT-20 cells expressing both KSA and arrestin3-(R170E) responded to U50,488 treatment with an increase in phospho-p38 consistent with the hypothesis. Primary cultured astrocytes (glial fibrillary acidic protein-positive) and neurons (γ-aminobutyric acid-positive) isolated from mouse striata also responded to U50,488 by increasing phospho-p38 immunolabeling. p38 activation was not evident in either striatal astrocytes or neurons isolated from KOR knock-out mice or GRK3 knock-out mice. Astrocytes pretreated with small interfering RNA for arrestin3 were also unable to activate p38 in response to U50,488 treatment. Furthermore, in striatal neurons, the kappa-mediated phospho-p38 labeling was colocalized with arrestin3. These findings suggest that KOR may activate p38 MAPK in brain by a GRK3 and arrestin-dependent mechanism. PMID:16648139

  16. Metabolic pathways for glucose in astrocytes.

    PubMed

    Wiesinger, H; Hamprecht, B; Dringen, R

    1997-09-01

    Cultured astroglial cells are able to utilize the monosaccharides glucose, mannose, or fructose as well as the sugar alcohol sorbitol as energy fuel. Astroglial uptake of the aldoses is carrier-mediated, whereas a non-saturable transport mechanism is operating for fructose and sorbitol. The first metabolic step for all sugars, including fructose being generated by enzymatic oxidation of sorbitol, is phosphorylation by hexokinase. Besides glucose only mannose may serve as substrate for build-up of astroglial glycogen. Whereas glycogen synthase appears to be present in astrocytes as well as neurons, the exclusive localization of glycogen phosphorylase in astrocytes and ependymal cells of central nervous tissue correlates well with the occurrence of glycogen in these cells. The identification of lactic acid rather than glucose as degradation product of astroglial glycogen appears to render the presence of glucose-6-phosphatase in cultured astrocytes an enigma. The colocalization of pyruvate carboxylase, phosphenolpyruvate carboxykinase and fructose-1,6-bisphosphatase points to astrocytes as being the gluconeogenic cell type of the CNS. PMID:9298844

  17. Differentiation of purified astrocytes in a chemically defined medium

    SciTech Connect

    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.

  18. Lead induces increased water permeability in astrocytes expressing aquaporin 4.

    PubMed

    Gunnarson, E; Axehult, G; Baturina, G; Zelenin, S; Zelenina, M; Aperia, A

    2005-01-01

    The water channel aquaporin 4 (AQP4) is abundantly expressed in astrocytes. There is now compelling evidence that AQP4 may contribute to an unfavorable course in brain edema. Acute lead intoxication is a condition that causes brain damage preceded by brain edema. Here we report that lead increases AQP4 water permeability (P(f)) in astrocytes. A rat astrocyte cell line that does not express aquaporin 4 was transiently transfected with aquaporin 4 tagged with green fluorescent protein (GFP). Using confocal laser scanning microscopy we measured water permeability in these cells and in AQP4-negative cells located on the same plate. AQP4-expressing astrocytes had a three-fold higher water permeability than astrocytes not expressing AQP4. Lead exposure induced a significant, 40%, increase in water permeability in astrocytes expressing AQP4, but had no effect on P(f) in astrocytes not expressing AQP4. The increase in water permeability persisted after lead washout, while treatment with a lead chelator, meso-2,3-dimercaptosuccinic acid, abolished the lead-induced increase in P(f). The effect of lead was attenuated in the presence of a calcium (Ca(2+))/calmodulin-dependent protein kinase II (CaMKII) inhibitor, but not in the presence of a protein kinase C inhibitor. In cells expressing AQP4 where the consensus site for CaMKII phosphorylation was mutated, lead failed to increase water permeability. Lead exposure also increased P(f) in rat astroglial cells in primary culture, which express endogenous AQP4. Lead had no effect on P(f) in astrocytes transfected with aquaporin 3. In situ hybridization studies on rat brain after oral lead intake for three days showed no change in distribution of AQP4 mRNA. It is suggested that lead-triggered stimulation of water transport in AQP4-expressing astrocytes may contribute to the pathology of acute lead intoxication.

  19. Gintonin stimulates gliotransmitter release in cortical primary astrocytes.

    PubMed

    Kim, Hyunsook; Lee, Byung-Hwan; Choi, Sun-Hye; Kim, Hyeon-Joong; Jung, Suk-Won; Hwang, Sung-Hee; Rhim, Hyewon; Kim, Hyung-Chun; Cho, Ik-Hyun; Nah, Seung-Yeol

    2015-08-31

    Lysophosphatidic acid (LPA) is a simple and minor phospholipid, but serves as a lipid-derived neurotransmitter via activation of G protein-coupled LPA receptors. Astrocytes abundantly express LPA receptors and contain gliotransmitters that modulate astrocyte-neuron interactions. Gintonin is a novel ginseng-derived G protein-coupled LPA receptor ligand. Gintonin induces [Ca(2+)]i transients in neuronal and non-neuronal cells via activation of LPA receptors, which regulate calcium-dependent ion channels and receptors. A line of evidence shows that neurotransmitter-mediated [Ca(2+)]i elevations in astrocytes are coupled with gliotransmitter release. However, little is known about whether gintonin-mediated [Ca(2+)]i transients are coupled to gliotransmitter release in astrocytes. In the present study, we examined the effects of gintonin on adenosine triphosphate (ATP) and glutamate release in mouse cortical primary astrocytes. Application of gintonin to astrocytes induced [Ca(2+)]i transients in a concentration-dependent and reversible manner. However, ginsenosides, other active ingredients in ginseng, had no effect on [Ca(2+)]i transients. The induction of gintonin-mediated [Ca(2+)]i transients was attenuated/blocked by the LPA1/3 receptor antagonist Ki16425, a phospholipase C inhibitor, an inositol 1,4,5-triphosphate receptor antagonist, and an intracellular Ca(2+) chelator. Gintonin treatment on astrocytes increased ATP and glutamate release in a concentration- and time-dependent manner. BAPTA and Ki16425 attenuated gintonin-mediated ATP and glutamate release in astrocytes. The present study shows that gintonin-mediated [Ca(2+)]i transients are coupled to gliotransmitter release via LPA receptor activation. Finally, gintonin-mediated [Ca(2+)]i transients and gliotransmitter release from astrocytes via LPA receptor activation might explain one mechanism of gintonin-mediated neuromodulation in the central nervous system. PMID:26191656

  20. Dynamic volume changes in astrocytes are an intrinsic phenomenon mediated by bicarbonate ion flux.

    PubMed

    Florence, Clare M; Baillie, Landon D; Mulligan, Sean J

    2012-01-01

    Astrocytes, the major type of non-neuronal cells in the brain, play an important functional role in extracellular potassium ([K(+)](o)) and pH homeostasis. Pathological brain states that result in [K(+)](o) and pH dysregulation have been shown to cause astrocyte swelling. However, whether astrocyte volume changes occur under physiological conditions is not known. In this study we used two-photon imaging to visualize real-time astrocyte volume changes in the stratum radiatum of the hippocampus CA1 region. Astrocytes were observed to swell by 19.0±0.9% in response to a small physiological increase in the concentration of [K(+)](o) (3 mM). Astrocyte swelling was mediated by the influx of bicarbonate (HCO(3-)) ions as swelling was significantly decreased when the influx of HCO(3-) was reduced. We found: 1) in HCO(3-) free extracellular solution astrocytes swelled by 5.4±0.7%, 2) when the activity of the sodium-bicarbonate cotransporter (NBC) was blocked the astrocytes swelled by 8.3±0.7%, and 3) in the presence of an extracellular carbonic anhydrase (CA) inhibitor astrocytes swelled by 11.4±0.6%. Because a significant HCO(3-) efflux is known to occur through the γ-amino-butyric acid (GABA) channel, we performed a series of experiments to determine if astrocytes were capable of HCO(3-) mediated volume shrinkage with GABA channel activation. Astrocytes were found to shrink -7.7±0.5% of control in response to the GABA(A) channel agonist muscimol. Astrocyte shrinkage from GABA(A) channel activation was significantly decreased to -5.0±0.6% of control in the presence of the membrane-permeant CA inhibitor acetazolamide (ACTZ). These dynamic astrocyte volume changes may represent a previously unappreciated yet fundamental mechanism by which astrocytes regulate physiological brain functioning. PMID:23226475

  1. Effects of aspartame metabolites on astrocytes and neurons.

    PubMed

    Rycerz, Karol; Jaworska-Adamu, Jadwiga Elżbieta

    2013-01-01

    Aspartame, a widespread sweetener used in many food products, is considered as a highly hazardous compound. Aspartame was discovered in 1965 and raises a lot of controversy up to date. Astrocytes are glial cells, the presence and functions of which are closely connected with the central nervous system (CNS). The aim of this article is to demonstrate the direct and indirect role of astrocytes participating in the harmful effects of aspartame metabolites on neurons. The artificial sweetener is broken down into phenylalanine (50%), aspartic acid (40%) and methanol (10%) during metabolism in the body. The excess of phenylalanine blocks the transport of important amino acids to the brain contributing to reduced levels of dopamine and serotonin. Astrocytes directly affect the transport of this amino acid and also indirectly by modulation of carriers in the endothelium. Aspartic acid at high concentrations is a toxin that causes hyperexcitability of neurons and is also a precursor of other excitatory amino acid - glutamates. Their excess in quantity and lack of astrocytic uptake induces excitotoxicity and leads to the degeneration of astrocytes and neurons. The methanol metabolites cause CNS depression, vision disorders and other symptoms leading ultimately to metabolic acidosis and coma. Astrocytes do not play a significant role in methanol poisoning due to a permanent consumption of large amounts of aspartame. Despite intense speculations about the carcinogenicity of aspartame, the latest studies show that its metabolite - diketopiperazine - is cancirogenic in the CNS. It contributes to the formation of tumors in the CNS such as gliomas, medulloblastomas and meningiomas. Glial cells are the main source of tumors, which can be caused inter alia by the sweetener in the brain. On the one hand the action of astrocytes during aspartame poisoning may be advantageous for neuro-protection while on the other it may intensify the destruction of neurons. The role of the glia in

  2. A Novel Subtype of Astrocytes Expressing TRPV4 (Transient Receptor Potential Vanilloid 4) Regulates Neuronal Excitability via Release of Gliotransmitters*

    PubMed Central

    Shibasaki, Koji; Ikenaka, Kazuhiro; Tamalu, Fuminobu; Tominaga, Makoto; Ishizaki, Yasuki

    2014-01-01

    Astrocytes play active roles in the regulation of synaptic transmission. Neuronal excitation can evoke Ca2+ transients in astrocytes, and these Ca2+ transients can modulate neuronal excitability. Although only a subset of astrocytes appears to communicate with neurons, the types of astrocytes that can regulate neuronal excitability are poorly characterized. We found that ∼30% of astrocytes in the brain express transient receptor potential vanilloid 4 (TRPV4), indicating that astrocytic subtypes can be classified on the basis of their expression patterns. When TRPV4+ astrocytes are activated by ligands such as arachidonic acid, the activation propagates to neighboring astrocytes through gap junctions and by ATP release from the TRPV4+ astrocytes. After activation, both TRPV4+ and TRPV4− astrocytes release glutamate, which acts as an excitatory gliotransmitter to increase synaptic transmission through type 1 metabotropic glutamate receptor (mGluR). Our results indicate that TRPV4+ astrocytes constitute a novel subtype of the population and are solely responsible for initiating excitatory gliotransmitter release to enhance synaptic transmission. We propose that TRPV4+ astrocytes form a core of excitatory glial assembly in the brain and function to efficiently increase neuronal excitation in response to endogenous TRPV4 ligands. PMID:24737318

  3. Regulation of astrocyte activity via control over stiffness of cellulose acetate electrospun nanofiber.

    PubMed

    Min, Seul Ki; Jung, Sang Myung; Ju, Jung Hyeon; Kwon, Yeo Seon; Yoon, Gwang Heum; Shin, Hwa Sung

    2015-10-01

    Astrocytes are involved in neuron protection following central nervous system (CNS) injury; accordingly, engineered astrocytes have been investigated for their usefulness in cell therapy for CNS injury. Nanofibers have attracted a great deal of attention in neural tissue engineering, but their mechanical properties greatly influence physiology. Cellulose acetate (CA) has been studied for use in scaffolds owing to its biocompatibility, biodegradability, and good thermal stability. In this study, stiffness of CA nanofibers controlled by heat treatment was shown to regulate astrocyte activity. Adhesion and viability increased in culture as substrate became stiffer but showed saturation at greater than 2 MPa of tensile strength. Astrocytes became more active in terms of increasing intermediate filament glial fibrillary acidic protein (GFAP). The results of this study demonstrate the effects of stiffness alone on cellular behaviors in a three-dimensional culture and highlight the efficacy of heat-treated CA for astrocyte culture in that the simple treatment enables control of astrocyte activity. PMID:26091629

  4. Regulation of astrocyte activity via control over stiffness of cellulose acetate electrospun nanofiber.

    PubMed

    Min, Seul Ki; Jung, Sang Myung; Ju, Jung Hyeon; Kwon, Yeo Seon; Yoon, Gwang Heum; Shin, Hwa Sung

    2015-10-01

    Astrocytes are involved in neuron protection following central nervous system (CNS) injury; accordingly, engineered astrocytes have been investigated for their usefulness in cell therapy for CNS injury. Nanofibers have attracted a great deal of attention in neural tissue engineering, but their mechanical properties greatly influence physiology. Cellulose acetate (CA) has been studied for use in scaffolds owing to its biocompatibility, biodegradability, and good thermal stability. In this study, stiffness of CA nanofibers controlled by heat treatment was shown to regulate astrocyte activity. Adhesion and viability increased in culture as substrate became stiffer but showed saturation at greater than 2 MPa of tensile strength. Astrocytes became more active in terms of increasing intermediate filament glial fibrillary acidic protein (GFAP). The results of this study demonstrate the effects of stiffness alone on cellular behaviors in a three-dimensional culture and highlight the efficacy of heat-treated CA for astrocyte culture in that the simple treatment enables control of astrocyte activity.

  5. Astrocyte-mediated ischemic tolerance.

    PubMed

    Hirayama, Yuri; Ikeda-Matsuo, Yuri; Notomi, Shoji; Enaida, Hiroshi; Kinouchi, Hiroyuki; Koizumi, Schuichi

    2015-03-01

    Preconditioning (PC) using a preceding sublethal ischemic insult is an attractive strategy for protecting neurons by inducing ischemic tolerance in the brain. Although the underlying molecular mechanisms have been extensively studied, almost all studies have focused on neurons. Here, using a middle cerebral artery occlusion model in mice, we show that astrocytes play an essential role in the induction of brain ischemic tolerance. PC caused activation of glial cells without producing any noticeable brain damage. The spatiotemporal pattern of astrocytic, but not microglial, activation correlated well with that of ischemic tolerance. Interestingly, such activation in astrocytes lasted at least 8 weeks. Importantly, inhibiting astrocytes with fluorocitrate abolished the induction of ischemic tolerance. To investigate the underlying mechanisms, we focused on the P2X7 receptor as a key molecule in astrocyte-mediated ischemic tolerance. P2X7 receptors were dramatically upregulated in activated astrocytes. PC-induced ischemic tolerance was abolished in P2X7 receptor knock-out mice. Moreover, our results suggest that hypoxia-inducible factor-1α, a well known mediator of ischemic tolerance, is involved in P2X7 receptor-mediated ischemic tolerance. Unlike previous reports focusing on neuron-based mechanisms, our results show that astrocytes play indispensable roles in inducing ischemic tolerance, and that upregulation of P2X7 receptors in astrocytes is essential. PMID:25740510

  6. Role of Astrocytes in Epilepsy

    PubMed Central

    Coulter, Douglas A.; Steinhäuser, Christian

    2016-01-01

    Astrocytes express ion channels, transmitter receptors, and transporters and, thus, are endowed with the machinery to sense and respond to neuronal activity. Recent studies have implicated that astrocytes play important roles in physiology, but these cells also emerge as crucial actors in epilepsy. Astrocytes are abundantly coupled through gap junctions allowing them to redistribute elevated K+ and transmitter concentrations from sites of enhanced neuronal activity. Investigation of specimens from patients with pharmacoresistant temporal lobe epilepsy and epilepsy models revealed alterations in expression, localization, and function of astroglial K+ and water channels. In addition, malfunction of glutamate transporters and the astrocytic glutamate-converting enzyme, glutamine synthetase, has been observed in epileptic tissue. These findings suggest that dysfunctional astrocytes are crucial players in epilepsy and should be considered as promising targets for new therapeutic strategies. PMID:25732035

  7. Astrocytes: Key Regulators of Neuroinflammation.

    PubMed

    Colombo, Emanuela; Farina, Cinthia

    2016-09-01

    Astrocytes are crucial regulators of innate and adaptive immune responses in the injured central nervous system. Depending on timing and context, astrocyte activity may exacerbate inflammatory reactions and tissue damage, or promote immunosuppression and tissue repair. Recent literature has unveiled key factors and intracellular signaling pathways that govern astrocyte behavior during neuroinflammation. Here we have re-visited in vivo studies on astrocyte signaling in neuroinflammatory models focusing on evidences obtained from the analysis of transgenic mice where distinct genes involved in ligand binding, transcriptional regulation and cell communication have been manipulated in astrocytes. The integration of in vivo observations with in vitro data clarifies precise signaling steps, highlights the crosstalk among pathways and identifies shared effector mechanisms in neuroinflammation.

  8. Neighborly interactions of metabolically-activated astrocytes in vivo.

    PubMed

    Dienel, Gerald A; Cruz, Nancy F

    2003-01-01

    Metabolic responses of brain cells to a stimulus are governed, in part, by their enzymatic specialization and interrelationships with neighboring cells, and local shifts in functional metabolism during brain activation are likely to be influenced by the neurotransmitter system, subcellular compartmentation, and anatomical structure. Selected examples of functional activation illustrate the complexity of metabolic interactions in working brain and of interpretation of changes in brain lactate levels. The major focus of this article is the disproportionately higher metabolism of glucose compared to oxygen in normoxic brain, a phenomenon that occurs during activation in humans and animals. The glucose utilized in excess of oxygen is not fully explained by accumulation of glucose, lactate, or glycogen in brain or by lactate efflux from brain to blood. Thus, any lactate derived from the excess glucose could not have been stoichiometrically exported to and metabolized by neighboring neurons because oxygen consumption would have otherwise increased and matched that of glucose. Metabolic labeling of tricarboxylic acid cycle-derived amino acids increased during brief sensory stimulation, reflecting a rise in oxidative metabolism. Brain glycogen is mainly in astrocytes, and its level falls throughout the stimulus and early post-activation interval. Glycogenolysis cannot be accounted for by lactate accumulation or oxidation; there must be rapid product clearance. Glycogen restoration is slow and diversion of glucose from oxidative pathways for its re-synthesis could reduce the global O(2)/glucose uptake ratio; astrocytes could downshift this ratio for up to an hour after 5 min stimulus. Morphological studies of astrocytes reveal a paucity of cytoplasm and organelles in the fine processes that surround synapses and form gap junction connections with neighboring astrocytes. Specialized regions of astrocytes, e.g. their endfeet and thin peripheral lamellae, are likely to have

  9. [Novel function of astrocytes revealed by optogenetics].

    PubMed

    Beppu, Kaoru; Matsui, Ko

    2014-12-01

    Astrocytes respond to neuronal activity. However, whether astrocytic activity has any significance in brain function is unknown. Signaling pathway leading from astrocytes to neurons would be required for astrocytes to participate in neuronal functions and, here, we investigated the presence of such pathway. Optogenetics was used to manipulate astrocytic activity. A light-sensitive protein, channelrhodopsin-2 (ChR2), was selectively expressed in astrocytes. Photostimulation of these astrocytes induced glutamate release which modulated neuronal activity and animal behavior. Such glutamate release was triggered by intracellular acidification produced by ChR2 photoactivation. Astrocytic acidification occurs upon brain ischemia, and we found that another optogenetic tool, archaerhodopsin (ArchT), could counter the acidification and suppress astrocytic glutamate release. Controlling of astrocytic pH may become a therapeutic strategy upon ischemia.

  10. Astrocyte-neuronal interactions in epileptogenesis.

    PubMed

    Hadera, Mussie Ghezu; Eloqayli, Haytham; Jaradat, Saied; Nehlig, Astrid; Sonnewald, Ursula

    2015-07-01

    Pentylenetetrazol, kainic acid, or pilocarpine can be used to induce seizures in animal models of epilepsy. The present Review describes disturbances in astrocyte-neuron interactions in the acute, latent, and chronic phases analyzed by magnetic resonance spectroscopy of brain tissue extracts from rats injected with [1-(13)C]glucose and [1,2-(13)C]acetate. The most consistent change after onset of seizures was the decrease in (13)C labeling of glutamate (GLU) from [1-(13) C]glucose regardless of brain area, severity, or duration of the period with seizures and toxin used. In most cases this decrease was accompanied by a reduction in glutamine (GLN) labeling from [1-(13)C]glucose, presumably as a direct consequence of the reduction in labeling of GLU and the GLU-GLN cycle. Amounts of GLN were never changed. Reduction in the content of N-acetyl aspartate (NAA) was first detectable some time after status epilepticus but before the occurrence of spontaneous seizures. This decrease can be an indication of neuronal death and/or mitochondrial impairment and might indicate beginning gliosis. It is known that gliosis occurs in the chronic phase of temporal lobe epilepsy in hippocampus, but astrocyte metabolism appears normal in this phase, indicating that the gliotic astrocytes have a somewhat reduced metabolism per volume. A decrease in (13)C labeling of GLU from [1-(13)C]glucose is a very sensitive measure for the onset of epileptogenesis, whereas reduction of NAA is first detectable later. In the chronic phases of the hippocampal formation, astrocyte metabolism is upregulated given that the number of neurons is reduced. PMID:25782696

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

    NASA Astrophysics Data System (ADS)

    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. Ballistic labeling and dynamic imaging of astrocytes in organotypic hippocampal slice cultures.

    PubMed

    Benediktsson, Adrienne M; Schachtele, Scott J; Green, Steven H; Dailey, Michael E

    2005-01-30

    Protoplasmic astrocytes in mammalian CNS tissues in vivo have a highly complex 3D morphology, but in dissociated cell cultures they often assume a flattened, fibroblast-like morphology bearing only a few, simple processes. By fluorescent labeling and confocal reconstruction we show that many astrocytes in organotypic hippocampal slice cultures exhibit a more native complex cytoarchitecture. Although astrocytes at the surface of slice cultures show a reactive form with several thick glial fibrillary acidic protein (GFAP)-positive processes, astrocytes situated in deeper portions of tissue slices retain a highly complex 3D morphology with many fine spine- or veil-like protrusions. Dozens of astrocytes can be labeled in single slice cultures by gene gun-mediated ballistic delivery of gold or tungsten particles carrying cDNAs (Biolistics), lipophilic dyes (DiOlistics), or fluorescent intracellular calcium indicators (Calistics). Expression of a membrane-targeted form of eGFP (Lck-GFP) is superior to soluble eGFP for resolving fine astrocytic processes. Time-lapse confocal imaging of Lck-GFP transfected astrocytes or "calistically" labeled astrocytes show structural remodeling and calcium transients, respectively. This approach provides an in vitro system for investigating the functional architecture, development and dynamic remodeling of astrocytes and their relationships to neurons and glia in live mammalian brain tissues. PMID:15585287

  13. Astrocyte morphology, heterogeneity, and density in the developing African giant rat (Cricetomys gambianus).

    PubMed

    Olude, Matthew A; Mustapha, Oluwaseun A; Aderounmu, Oluwatunde A; Olopade, James O; Ihunwo, Amadi O

    2015-01-01

    Astrocyte morphologies and heterogeneity were described in male African giant rats (AGR; Cricetomys gambianus, Waterhouse) across three age groups (five neonates, five juveniles, and five adults) using Silver impregnation method and immunohistochemistry against glial fibrillary acidic protein. 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 ± 5.4 μm and 75 ± 1.9 μm 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, 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 possible

  14. Astrocyte pathology in major depressive disorder: insights from human postmortem brain tissue.

    PubMed

    Rajkowska, Grazyna; Stockmeier, Craig A

    2013-10-01

    The present paper reviews astrocyte pathology in major depressive disorder (MDD) and proposes that reductions in astrocytes and related markers are key features in the pathology of MDD. Astrocytes are the most numerous and versatile of all types of glial cells. They are crucial to the neuronal microenvironment by regulating glucose metabolism, neurotransmitter uptake (particularly for glutamate), synaptic development and maturation and the blood brain barrier. Pathology of astrocytes has been consistently noted in MDD as well as in rodent models of depressive-like behavior. This review summarizes evidence from human postmortem tissue showing alterations in the expression of protein and mRNA for astrocyte markers such as glial fibrillary acidic protein (GFAP), gap junction proteins (connexin 40 and 43), the water channel aquaporin-4 (AQP4), a calcium-binding protein S100B and glutamatergic markers including the excitatory amino acid transporters 1 and 2 (EAAT1, EAAT2) and glutamine synthetase. Moreover, preclinical studies are presented that demonstrate the involvement of GFAP and astrocytes in animal models of stress and depressive-like behavior and the influence of different classes of antidepressant medications on astrocytes. In light of the various astrocyte deficits noted in MDD, astrocytes may be novel targets for the action of antidepressant medications. Possible functional consequences of altered expression of astrocytic markers in MDD are also discussed. Finally, the unique pattern of cell pathology in MDD, characterized by prominent reductions in the density of astrocytes and in the expression of their markers without obvious neuronal loss, is contrasted with that found in other neuropsychiatric and neurodegenerative disorders. PMID:23469922

  15. Modulation of morpho-functional characteristics of astrocytes using chemically-functionalized water-soluble single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Gottipati, Manoj K.

    In this thesis, I report the use of chemically functionalized water-soluble single-walled carbon nanotubes (ws-SWCNTs) for the modulation of morpho-functional characteristics of astrocytes. When added to the culturing medium, ws-SWCNTs were able to make astrocytes larger and stellate/mature, changes associated with the increase in glial fibrillary acidic protein immunoreactivity. Thus, ws-SWCNTs could have more beneficial effects at the injury site than previously thought; by affecting astrocytes, they could provide for a more comprehensive re-establishment of the brain computational power. Keywords: Carbon nanotubes, graft copolymers, astrocytes, glial fibrillary acidic protein.

  16. Volume transmission signalling via astrocytes

    PubMed Central

    Hirase, Hajime; Iwai, Youichi; Takata, Norio; Shinohara, Yoshiaki; Mishima, Tsuneko

    2014-01-01

    The influence of astrocytes on synaptic function has been increasingly studied, owing to the discovery of both gliotransmission and morphological ensheathment of synapses. While astrocytes exhibit at best modest membrane potential fluctuations, activation of G-protein coupled receptors (GPCRs) leads to a prominent elevation of intracellular calcium which has been reported to correlate with gliotransmission. In this review, the possible role of astrocytic GPCR activation is discussed as a trigger to promote synaptic plasticity, by affecting synaptic receptors through gliotransmitters. Moreover, we suggest that volume transmission of neuromodulators could be a biological mechanism to activate astrocytic GPCRs and thereby to switch synaptic networks to the plastic mode during states of attention in cerebral cortical structures. PMID:25225097

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

    PubMed

    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.

  18. Active sulforhodamine 101 uptake into hippocampal astrocytes.

    PubMed

    Schnell, Christian; Hagos, Yohannes; Hülsmann, Swen

    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 ventrolateral medulla. Although carbenoxolone is able to decrease the SR101-labeling of astrocytes in the hippocampus, it is unlikely that SR101 is taken up via gap-junction hemichannels because mefloquine, a blocker for pannexin and connexin hemichannels, was unable to prevent SR101-labeling of hippocampal astrocytes. However, SR101-labeling of the hippocampal astrocytes was significantly reduced by substrates of organic anion transport polypeptides, including estron-3-sulfate and dehydroepiandrosterone sulfate, suggesting that SR101 is actively transported into hippocampal astrocytes.

  19. Rat nucleus accumbens core astrocytes modulate reward and the motivation to self-administer ethanol after abstinence.

    PubMed

    Bull, Cecilia; Freitas, Kelen C C; Zou, Shiping; Poland, Ryan S; Syed, Wahab A; Urban, Daniel J; Minter, Sabrina C; Shelton, Keith L; Hauser, Kurt F; Negus, S Stevens; Knapp, Pamela E; Bowers, M Scott

    2014-11-01

    Our understanding of the active role that astrocytes play in modulating neuronal function and behavior is rapidly expanding, but little is known about the role that astrocytes may play in drug-seeking behavior for commonly abused substances. Given that the nucleus accumbens is critically involved in substance abuse and motivation, we sought to determine whether nucleus accumbens astrocytes influence the motivation to self-administer ethanol following abstinence. We found that the packing density of astrocytes that were expressing glial fibrillary acidic protein increased in the nucleus accumbens core (NAcore) during abstinence from EtOH self-administration. No change was observed in the nucleus accumbens shell. This increased NAcore astrocyte density positively correlated with the motivation for ethanol. Astrocytes can communicate with one another and influence neuronal activity through gap-junction hemichannels. Because of this, the effect of blocking gap-junction hemichannels on the motivation for ethanol was examined. The motivation to self-administer ethanol after 3 weeks abstinence was increased following microinjection of gap-junction hemichannel blockers into the NAcore at doses that block both neuronal and astrocytic channels. In contrast, no effect was observed following microinjection of doses that are not thought to block astrocytic channels or following microinjection of either dose into the nucleus accumbens shell. Additionally, the motivation for sucrose after 3 weeks abstinence was unaffected by NAcore gap-junction hemichannel blockers. Next, Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) were selectively expressed in NAcore astrocytes to test the effect of astrocyte stimulation. DREADD activation increased cytosolic calcium in primary astrocytes, facilitated responding for rewarding brain stimulation, and reduced the motivation for ethanol after 3 weeks abstinence. This is the first work to modulate drug-seeking behavior with

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

    PubMed

    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

  1. Effects of diabetes mellitus on astrocyte GFAP and glutamate transporters in the CNS.

    PubMed

    Coleman, Elaine; Judd, Robert; Hoe, Lori; Dennis, John; Posner, Philip

    2004-11-01

    Diabetes mellitus increases the risk of central nervous system (CNS) disorders such as stroke, seizures, dementia, and cognitive impairment. The cellular mechanisms responsible for the increased risk of these disorders are incompletely understood. Astrocytes are proving critical for normal CNS function, and alterations in their activity could contribute to diabetes-related disturbances in the brain. We examined the effects of streptozotocin (STZ)-induced diabetes in rats on the level of the astrocyte intermediate filament protein, glial fibrillary acidic protein (GFAP), number of astrocytes, and levels of the astrocyte glutamate transporters, glutamate transporter-1 (GLT-1) and glutamate/aspartate transporter (GLAST), in the cerebral cortex, hippocampus, and cerebellum by Western blotting (WB) and immunohistochemistry (IH). Studies were carried out at 4 and 8 weeks of diabetes duration. Diabetes resulted in a significant decrease in GFAP protein levels (WB) in the hippocampus and cerebellum at 4 weeks and in the cerebral cortex, hippocampus and cerebellum by 8 weeks. Attenuated GFAP immunoreactivity (IH) was evident in the hippocampus, cerebellum and white matter regions such as the corpus callosum and external capsule at both 4 and 8 weeks of diabetes. Astrocyte cell counts of adjacent sections immunoreactive for S-100B were not different between control and diabetic animals. No significant differences were noted in astrocyte glutamate transporter levels in the cerebral cortex, hippocampus, or cerebellum at either time period (WB, IH). With the expanding list of astrocyte functions in the CNS, the role of astrocytes in diabetes-induced CNS disorders clearly warrants further investigation.

  2. Imbalance between Glutamate and GABA in Fmr1 Knockout Astrocytes Influences Neuronal Development

    PubMed Central

    Wang, Lu; Wang, Yan; Zhou, Shimeng; Yang, Liukun; Shi, Qixin; Li, Yujiao; Zhang, Kun; Yang, Le; Zhao, Minggao; Yang, Qi

    2016-01-01

    Fragile X syndrome (FXS) is a form of inherited mental retardation that results from the absence of the fragile X mental retardation protein (FMRP), the product of the Fmr1 gene. Numerous studies have shown that FMRP expression in astrocytes is important in the development of FXS. Although astrocytes affect neuronal dendrite development in Fmr1 knockout (KO) mice, the factors released by astrocytes are still unclear. We cultured wild type (WT) cortical neurons in astrocyte-conditioned medium (ACM) from WT or Fmr1 KO mice. Immunocytochemistry and Western blotting were performed to detect the dendritic growth of both WT and KO neurons. We determined glutamate and γ-aminobutyric acid (GABA) levels using high-performance liquid chromatography (HPLC). The total neuronal dendritic length was reduced when cultured in the Fmr1 KO ACM. This neurotoxicity was triggered by an imbalanced release of glutamate and GABA from Fmr1 KO astrocytes. We found increased glutaminase and GABA transaminase (GABA-T) expression and decreased monoamine oxidase B expression in Fmr1 KO astrocytes. The elevated levels of glutamate contributed to oxidative stress in the cultured neurons. Vigabatrin (VGB), a GABA-T inhibitor, reversed the changes caused by glutamate and GABA release in Fmr1 KO astrocytes and the abnormal behaviors in Fmr1 KO mice. Our results indicate that the imbalance in the astrocytic glutamate and GABA release may be involved in the neuropathology and the underlying symptoms of FXS, and provides a therapeutic target for treatment. PMID:27517961

  3. Combination of nanoparticle-delivered siRNA for Astrocyte elevated gene-1 (AEG-1) and all-trans retinoic acid (ATRA): an effective therapeutic strategy for hepatocellular carcinoma (HCC)

    PubMed Central

    Rajasekaran, Devaraja; Srivastava, Jyoti; Ebeid, Kareem; Gredler, Rachel; Akiel, Maaged; Jariwala, Nidhi; Robertson, Chadia L.; Shen, Xue-Ning; Siddiq, Ayesha; Fisher, Paul B.; Salem, Aliasger K.; Sarkar, Devanand

    2016-01-01

    Hepatocellular carcinoma (HCC) is a fatal cancer with no effective therapy. Astrocyte elevated gene-1 (AEG-1) plays a pivotal role in hepatocarcinogenesis and inhibits retinoic acid-induced gene expression and cell death. Combination of a lentivirus expressing AEG-1 shRNA and all-trans retinoic acid (ATRA) profoundly and synergistically inhibited subcutaneous human HCC xenografts in nude mice. We now have developed liver-targeted nanoplexes by conjugating poly(amidoamine) (PAMAM) dendrimers with polyethylene glycol (PEG) and lactobionic acid (Gal) (PAMAM-PEG-Gal) which were complexed with AEG-1 siRNA (PAMAM-AEG-1si). The polymer conjugate was characterized by 1H-NMR, MALDI and mass spectrometry, and optimal nanoplex formulations were characterized for surface charge, size and morphology. Orthotopic xenografts of human HCC cell QGY-7703 expressing luciferase (QGY-luc) were established in the livers of athymic nude mice and tumor development was monitored by bioluminescence imaging (BLI). Tumor-bearing mice were treated with PAMAM-siCon, PAMAM-siCon+ATRA, PAMAM-AEG-1si and PAMAM-AEG-1si+ATRA. In the control group the tumor developed aggressively. ATRA showed little effect due to high AEG-1 levels in QGY-luc cells. PAMAM-AEG-1si showed significant reduction in tumor growth and the combination of PAMAM-AEG-1si+ATRA showed profound and synergistic inhibition so that the tumors were almost undetectable by BLI. A marked decrease in AEG-1 level was observed in tumor samples treated with PAMAM-AEG-1si. The group treated with PAMAM-AEG-1si+ATRA nanoplexes showed increased necrosis, inhibition of proliferation and increased apoptosis when compared to other groups. Liver is an ideal organ for RNAi therapy and ATRA is an approved anti-cancer agent. Our exciting observations suggest that the combinatorial approach might be an effective way to combat HCC. PMID:26079152

  4. D-Serine Is a Substrate for Neutral Amino Acid Transporters ASCT1/SLC1A4 and ASCT2/SLC1A5, and Is Transported by Both Subtypes in Rat Hippocampal Astrocyte Cultures

    PubMed Central

    Foster, Alan C.; Farnsworth, Jill; Lind, Genevieve E.; Li, Yong-Xin; Yang, Jia-Ying; Dang, Van; Penjwini, Mahmud; Viswanath, Veena; Staubli, Ursula; Kavanaugh, Michael P.

    2016-01-01

    N-methyl-D-aspartate (NMDA) receptors play critical roles in synaptic transmission and plasticity. Activation of NMDA receptors by synaptically released L-glutamate also requires occupancy of co-agonist binding sites in the tetrameric receptor by either glycine or D-serine. Although D-serine appears to be the predominant co-agonist at synaptic NMDA receptors, the transport mechanisms involved in D-serine homeostasis in brain are poorly understood. In this work we show that the SLC1 amino acid transporter family members SLC1A4 (ASCT1) and SLC1A5 (ASCT2) mediate homo- and hetero-exchange of D-serine with physiologically relevant kinetic parameters. In addition, the selectivity profile of D-serine uptake in cultured rat hippocampal astrocytes is consistent with uptake mediated by both ASCT1 and ASCT2. Together these data suggest that SLC1A4 (ASCT1) may represent an important route of Na-dependent D-serine flux in the brain that has the ability to regulate extracellular D-serine and thereby NMDA receptor activity. PMID:27272177

  5. Glutamate Mediated Astrocytic Filtering of Neuronal Activity

    PubMed Central

    Herzog, Nitzan; De Pittà, Maurizio; Jacob, Eshel Ben; 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 astrocytes specifically respond to the frequency of neuronal stimulation by intracellular Ca2+ transients, with a clear onset of astrocytic activation at neuron firing rates around 3-5 Hz. The cell-to-cell heterogeneity of the astrocyte Ca2+ response was however large and increasing with stimulation frequency. Astrocytic activation by neurons was abolished with antagonists of type I metabotropic glutamate receptor, validating the glutamate-dependence of this neuron-to-astrocyte pathway. Using a realistic biophysical model of glutamate-based intracellular calcium signaling in astrocytes, we suggest that the stepwise response is due to the supralinear dynamics of intracellular IP3 and that the heterogeneity of the responses may be due to the heterogeneity of the astrocyte-to-astrocyte couplings via gap junction channels. Therefore our results present astrocyte intracellular Ca2+ activity as a nonlinear integrator of glutamate-dependent neuronal activity. PMID:25521344

  6. Functional Oxygen Sensitivity of Astrocytes.

    PubMed

    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

  7. Persistent oxygen-glucose deprivation induces astrocytic death through two different pathways and calpain-mediated proteolysis of cytoskeletal proteins during astrocytic oncosis.

    PubMed

    Cao, Xu; Zhang, Ying; Zou, Liangyu; Xiao, Haibing; Chu, Yinghao; Chu, Xiaofan

    2010-07-26

    Astrocytes are thought to play a role in the maintenance of homeostasis and the provision of metabolic substrates for neurons as well as the coupling of cerebral blood flow to neuronal activity. Accordingly, astrocytic death due to various types of injury can critically influence neuronal survival. The exact pathway of cell death after brain ischemia is under debate. In the present study, we used astrocytes from rat primary culture treated with persistent oxygen-glucose-deprivation (OGD) as a model of ischemia to examine the pathway of cell death and the relevant mechanisms. We observed changes in the cellular morphology, the energy metabolism of astrocytes, and the percentage of apoptosis or oncosis of the astrocytes induced by OGD. Electron microscopy revealed the co-existence of ultrastructural features in both apoptosis and oncosis in individual cells. The cellular ATP content was gradually decreased and the percentages of apoptotic and oncotic cells were increased during OGD. After 4h of OGD, ATP depletion to less than 35% of the control was observed, and oncosis became the primary pathway for astrocytic death. Increased plasma membrane permeability due to oncosis was associated with increased calpain-mediated degradation of several cytoskeletal proteins, including paxillin, vinculin, vimentin and GFAP. Pre-treatment with the calpain inhibitor 3-(4-iodophenyl)-2-mercapto-(Z)-2-propenoic acid (PD150606) could delay the OGD-induced astrocytic oncosis. These results suggest that there is a narrow range of ATP that determines astrocytic oncotic death induced by persistent OGD and that calpain-mediated hydrolysis of the cytoskeletal-associated proteins may contribute to astrocytes oncosis. PMID:20493926

  8. H1-antihistamines induce vacuolation in astrocytes through macroautophagy

    SciTech Connect

    Hu, Wei-Wei; Yang, Ying; Wang, Zhe; Shen, Zhe; Zhang, Xiang-Nan; Wang, Guang-Hui; Chen, Zhong

    2012-04-15

    H1-antihistamines induce vacuolation in vascular smooth muscle cells, which may contribute to their cardiovascular toxicity. The CNS toxicity of H1-antihistamines may also be related to their non-receptor-mediated activity. The aim of this study was to investigate whether H1-antihistamines induce vacuolation in astrocytes and the mechanism involved. The H1-antihistamines induced large numbers of giant vacuoles in astrocytes. Such vacuoles were marked with both the lysosome marker Lysotracker Red and the alkalescent fluorescence dye monodansylcadaverine, which indicated that these vacuoles were lysosome-like acidic vesicles. Quantitative analysis of monodansylcadaverine fluorescence showed that the effect of H1-antihistamines on vacuolation in astrocytes was dose-dependent, and was alleviated by extracellular acidification, but aggravated by extracellular alkalization. The order of potency to induce vacuolation at high concentrations of H1-antihistamines (diphenhydramine > pyrilamine > astemizole > triprolidine) corresponded to their pKa ranking. Co-treatment with histamine and the histamine receptor-1 agonist trifluoromethyl toluidide did not inhibit the vacuolation. Bafilomycin A1, a vacuolar (V)-ATPase inhibitor, which inhibits intracellular vacuole or vesicle acidification, clearly reversed the vacuolation and intracellular accumulation of diphenhydramine. The macroautophagy inhibitor 3-methyladenine largely reversed the percentage of LC3-positive astrocytes induced by diphenhydramine, while only partly reversing the number of monodansylcadaverine-labeled vesicles. In Atg5{sup −/−} mouse embryonic fibroblasts, which cannot form autophagosomes, the number of vacuoles induced by diphenhydramine was less than that in wild-type cells. These results indicated that H1-antihistamines induce V-ATPase-dependent acidic vacuole formation in astrocytes, and this is partly mediated by macroautophagy. The pKa and alkalescent characteristic of H1-antihistamines may be the

  9. The Effect of Glutamate Receptor Agonists on Mouse Retinal Astrocyte [Ca2+]i

    PubMed Central

    Blandford, Stephanie N.

    2016-01-01

    Calcium-imaging techniques were used to determine if mouse retinal astrocytes in situ respond to agonists of ionotropic (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, AMPA; N-methyl-D-aspartate, NMDA) and metabotropic (S-3,5-dihydroxyphenylglycine, DHPG; trans-1-amino-1,3-cyclopentanedicarboxylic acid, ACPD) glutamate receptors. In most cases we found no evidence that retinal astrocyte intracellular calcium ion concentration ([Ca2+]i) increased in response to these glutamate agonists. The one exception was AMPA that increased [Ca2+]i in some, but not all, mouse retinal astrocytes in situ. However, AMPA did not increase [Ca2+]i in mouse retinal astrocytes in vitro, suggesting that the effect of AMPA in situ may be indirect. PMID:27413752

  10. Methamphetamine Inhibits the Glucose Uptake by Human Neurons and Astrocytes: Stabilization by Acetyl-L-Carnitine

    PubMed Central

    Szlachetka, Adam M.; Haorah, James

    2011-01-01

    Methamphetamine (METH), an addictive psycho-stimulant drug exerts euphoric effects on users and abusers. It is also known to cause cognitive impairment and neurotoxicity. Here, we hypothesized that METH exposure impairs the glucose uptake and metabolism in human neurons and astrocytes. Deprivation of glucose is expected to cause neurotoxicity and neuronal degeneration due to depletion of energy. We found that METH exposure inhibited the glucose uptake by neurons and astrocytes, in which neurons were more sensitive to METH than astrocytes in primary culture. Adaptability of these cells to fatty acid oxidation as an alternative source of energy during glucose limitation appeared to regulate this differential sensitivity. Decrease in neuronal glucose uptake by METH was associated with reduction of glucose transporter protein-3 (GLUT3). Surprisingly, METH exposure showed biphasic effects on astrocytic glucose uptake, in which 20 µM increased the uptake while 200 µM inhibited glucose uptake. Dual effects of METH on glucose uptake were paralleled to changes in the expression of astrocytic glucose transporter protein-1 (GLUT1). The adaptive nature of astrocyte to mitochondrial β-oxidation of fatty acid appeared to contribute the survival of astrocytes during METH-induced glucose deprivation. This differential adaptive nature of neurons and astrocytes also governed the differential sensitivity to the toxicity of METH in these brain cells. The effect of acetyl-L-carnitine for enhanced production of ATP from fatty oxidation in glucose-free culture condition validated the adaptive nature of neurons and astrocytes. These findings suggest that deprivation of glucose-derived energy may contribute to neurotoxicity of METH abusers. PMID:21556365

  11. Expression and Activation of STAT3 in the Astrocytes of Optic Nerve in a Rat Model of Transient Intraocular Hypertension

    PubMed Central

    Zhang, Shaodan; Li, Weiyi; Wang, Wenqian; Zhang, Samuel S.; Huang, Ping; Zhang, Chun

    2013-01-01

    Lamina cribosa, an astrocyte-rich region, is the origin of axonal degeneration in glaucomatous neuropathy. Astrocytes are particularly activated during optic nerve (ON) degeneration and are likely to contribute to the pathogenesis of glaucomatous optic neuropathy. Signalling mechanisms that regulate different aspects of astrocyte reactiviation in response to intraocular hypertensive injury are not well defined. Signal transducer and activator of transcription protein-3 (STAT3) is a transcription factor that participates in many biological processes and has been implicated as activator of reactive astrogliosis. In this study, we investigated the role of STAT3 in regulating the activation of astrocytes to transient intraocular hypertension in vivo by using a rat ocular hypertension model. ON astrocytes hypertrophy was observed early after intraocular hypertensive stress. Morphological changes in glial fibrillary acidic protein (GFAP) positive cells coupled with axon loss in the optic nerve was detected at day 7 after the injury. Nestin was significantly upregulated in ON astrocytes as early as day 2 post injury and kept elevated through post injury day 7. Phosphorylated STAT3 (pSTAT3) was markedly upregulated in ON astrocytes at post injury day 1, prior to the reactivation of ON astrocytes. These findings indicate that STAT3 signalling is involved in the initiation of astrocyte reactivation in optic nerve injury. PMID:23383263

  12. Intermediate filaments are important for astrocyte response to oxidative stress induced by oxygen-glucose deprivation and reperfusion.

    PubMed

    de Pablo, Yolanda; Nilsson, Michael; Pekna, Marcela; Pekny, Milos

    2013-07-01

    As a response to central nervous system injury, astrocytes become reactive. Two cellular hallmarks of reactive gliosis are hypertrophy of astrocyte processes and upregulation of intermediate filament (nanofilament) proteins glial fibrillary acidic protein (GFAP), vimentin, nestin, and synemin. Astrocytes in mice devoid of GFAP and vimentin (GFAP (-/-) Vim (-/-)) do not form cytoplasmic intermediate filaments. GFAP (-/-) Vim (-/-) mice develop larger infarcts after ischemic stroke (Li et al. in J Cereb Blood Flow Metab 28(3):468-481, 2008). Here, we attempted to analyze the underlying mechanisms using oxygen-glucose deprivation (OGD), an in vitro ischemia model, examining a potential link between astrocyte intermediate filaments and reactive oxygen species (ROS). We observed a reorganization of the intermediate filament network in astrocytes exposed to OGD. ROS accumulation was higher in GFAP (-/-) Vim (-/-) than wild-type astrocytes when exposed to OGD followed by reperfusion or when exposed to hydrogen peroxide. These results indicate that the elimination of ROS is impaired in the absence of the intermediate filament system. Compared to wild-type astrocytes, GFAP (-/-) Vim (-/-) astrocytes exposed to OGD and reperfusion exhibited increased cell death and conferred lower degree of protection to cocultured neurons. We conclude that the astrocyte intermediate filament system is important for the cell response to oxidative stress induced by OGD followed by reperfusion.

  13. H1-antihistamines induce vacuolation in astrocytes through macroautophagy.

    PubMed

    Hu, Wei-Wei; Yang, Ying; Wang, Zhe; Shen, Zhe; Zhang, Xiang-Nan; Wang, Guang-Hui; Chen, Zhong

    2012-04-15

    H1-antihistamines induce vacuolation in vascular smooth muscle cells, which may contribute to their cardiovascular toxicity. The CNS toxicity of H1-antihistamines may also be related to their non-receptor-mediated activity. The aim of this study was to investigate whether H1-antihistamines induce vacuolation in astrocytes and the mechanism involved. The H1-antihistamines induced large numbers of giant vacuoles in astrocytes. Such vacuoles were marked with both the lysosome marker Lysotracker Red and the alkalescent fluorescence dye monodansylcadaverine, which indicated that these vacuoles were lysosome-like acidic vesicles. Quantitative analysis of monodansylcadaverine fluorescence showed that the effect of H1-antihistamines on vacuolation in astrocytes was dose-dependent, and was alleviated by extracellular acidification, but aggravated by extracellular alkalization. The order of potency to induce vacuolation at high concentrations of H1-antihistamines (diphenhydramine>pyrilamine>astemizole>triprolidine) corresponded to their pKa ranking. Co-treatment with histamine and the histamine receptor-1 agonist trifluoromethyl toluidide did not inhibit the vacuolation. Bafilomycin A1, a vacuolar (V)-ATPase inhibitor, which inhibits intracellular vacuole or vesicle acidification, clearly reversed the vacuolation and intracellular accumulation of diphenhydramine. The macroautophagy inhibitor 3-methyladenine largely reversed the percentage of LC3-positive astrocytes induced by diphenhydramine, while only partly reversing the number of monodansylcadaverine-labeled vesicles. In Atg5⁻/⁻ mouse embryonic fibroblasts, which cannot form autophagosomes, the number of vacuoles induced by diphenhydramine was less than that in wild-type cells. These results indicated that H1-antihistamines induce V-ATPase-dependent acidic vacuole formation in astrocytes, and this is partly mediated by macroautophagy. The pKa and alkalescent characteristic of H1-antihistamines may be the major

  14. Modulation of extracellular signal-related kinase, cyclin D1, glial fibrillary acidic protein, and vimentin expression in estradiol-pretreated astrocyte cultures treated with competence and progression growth factors.

    PubMed

    Bramanti, Vincenzo; Grasso, Sonia; Tibullo, Daniele; Giallongo, Cesarina; Raciti, Giuseppina; Viola, Maria; Avola, Roberto

    2015-09-01

    The present study seeks to elucidate the interactions between the "competence" growth factor basic fibroblast growth factor (bFGF) and/or estrogen 17β-estradiol and the "progression" growth factors epidermal growth factor (EGF), insulin-like growth factor-I (IGF-I), and insulin (INS) on DNA labeling and also cyclin D1, extracellular signal-related kinase 1/2 (ERK1/2), glial fibrillary acidic protein (GFAP), and vimentin expression in astroglial cultures under different experimental conditions. Pretreatment for 24 hr with bFGF and subsequent exposure for 36 hr to estradiol (E2 ) and EGF, IGF-I, or INS stimulated DNA labeling in the last 12 hr, especially when the cultures were treated with progression growth factors. bFGF pretreatment and subsequent treatment with E2 for 36 hr stimulated DNA labeling. The 36-hr E2 treatment alone did not significantly decrease DNA labeling, but contemporary addition of E2 with two or three growth factors stimulated DNA labeling remarkably. When E2 was coadded with growth factors, a significantly increased DNA labeling was observed, demonstrating an astroglial synergistic mitogenic effect evoked by contemporary treatment with growth factors in the presence of estrogens. Cyclin D1 expression was markedly increased when astrocyte cultures were pretreated for 36 hr with E2 and subsequently treated with two or three competence and progression growth factors. A highly significant increase of ERK1/2 expression was observed after all the treatments (EGF, bFGF, INS, IGF-I alone or in combination with two or three growth factors). GFAP and vimentin expression was markedly increased when the cultures were treated with two or three growth factors. In conclusion, our data demonstrate estradiol-growth factor cross-talk during astroglial cell proliferation and differentiation in culture.

  15. Laminin is produced by early rat astrocytes in primary culture

    PubMed Central

    1983-01-01

    The production of laminin by early rat astrocytes in primary culture was investigated by double immunofluorescence staining for laminin and the glial fibrillary acidic protein (GFAP), a defined astrocyte marker. In early cultures (3 d in vitro; 3 DIV) cytoplasmic laminin was detected in all the GFAP-positive cells which formed the major population (80%) of the nonneuronal cells present in cultures from 20- 21-d embryonic, newborn, or 5-d-old rat brains. Monensin treatment (10 microM, 4 h) resulted in accumulation of laminin in the Golgi region, located using labeled wheat germ agglutinin. Laminin started gradually to disappear from the cells with the time in culture, was absent in star-shaped, apparently mature astrocytes, but remained as pericellular matrix deposits. The disappearance of cellular laminin was dependent on the age of the animal and the time in culture so that it started earlier in cultures from 5-d-old rat brains (5 DIV) and approximately following the in vivo age difference in cultures from newborn (12 DIV) and embryonic (14 DIV) rat brains. Our results indicate that laminin is a protein of early astrocytes and also deposited by them in primary culture, thus suggesting a role for this glycoprotein in the development of the central nervous system. PMID:6339524

  16. Genetic control of astrocyte function in neural circuits

    PubMed Central

    Jahn, Hannah M.; Scheller, Anja; Kirchhoff, Frank

    2015-01-01

    During the last two decades numerous genetic approaches affecting cell function in vivo have been developed. Current state-of-the-art technology permits the selective switching of gene function in distinct cell populations within the complex organization of a given tissue parenchyma. The tamoxifen-inducible Cre/loxP gene recombination and the doxycycline-dependent modulation of gene expression are probably the most popular genetic paradigms. Here, we will review applications of these two strategies while focusing on the interactions of astrocytes and neurons in the central nervous system (CNS) and their impact for the whole organism. Abolishing glial sensing of neuronal activity by selective deletion of glial transmitter receptors demonstrated the impact of astrocytes for higher cognitive functions such as learning and memory, or the more basic body control of muscle coordination. Interestingly, also interfering with glial output, i.e., the release of gliotransmitters can drastically change animal’s physiology like sleeping behavior. Furthermore, such genetic approaches have also been used to restore astrocyte function. In these studies two alternatives were employed to achieve proper genetic targeting of astrocytes: transgenes using the promoter of the human glial fibrillary acidic protein (GFAP) or homologous recombination into the glutamate-aspartate transporter (GLAST) locus. We will highlight their specific properties that could be relevant for their use. PMID:26347607

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

    PubMed

    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

  18. Mutant Disrupted-In-Schizophrenia 1 in astrocytes: focus on glutamate metabolism

    PubMed Central

    Abazyan, Sofya; Yang, Eun Ju; Abazyan, Bagrat; Xia, Meng; Yang, Chunxia; Rojas, Camilo; Slusher, Barbara; Sattler, Rita; Pletnikov, Mikhail

    2014-01-01

    Disrupted-In-Schizophrenia 1 (DISC1) is a genetic risk factor that has been implicated in major mental disorders. DISC1 binds to and stabilizes serine racemase (SR) to regulate production of D-serine by astrocytes, contributing to glutamate (GLU) neurotransmission. However, the possible involvement of astrocytic DISC1 in synthesis, metabolism, re-uptake or secretion of GLU remains unexplored. Thus, we studied the effects of dominant-negative mutant DISC1 on various aspects of GLU metabolism using primary astrocyte cultures and the hippocampal tissue from transgenic mice with astrocyte-restricted expression of mutant DISC1. While mutant DISC1 had no significant effects on astrocyte proliferation, GLU re-uptake, Glutaminase or Glutamate carboxypeptidase II activity, expression of mutant DISC1 was associated with increased levels of alanine-serine-cysteine transporter 2, vesicular glutamate transporters 1 and 3 in primary astrocytes and in the hippocampus as well as elevated expression of the NR1 subunit and diminished expression of the NR2A subunit of NMDA receptors in the hippocampus at postnatal day 21. Our findings indicate that decreased D-serine production by astrocytic mutant DISC1 may lead to compensatory changes in levels of the amino acid transporters and NMDA receptors in the context of tripartite synapse. PMID:25131692

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

    PubMed Central

    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

  20. Content and traffic of taurine in hippocampal reactive astrocytes.

    PubMed

    Junyent, Fèlix; De Lemos, Luisa; Utrera, Juana; Paco, Sonia; Aguado, Fernando; Camins, Antoni; Pallàs, Mercè; Romero, Rafael; Auladell, Carme

    2011-02-01

    Taurine is one of the most abundant free amino acids in the mammalian central nervous system, where it is crucial to proper development. Moreover, taurine acts as a neuroprotectant in various diseases; in epilepsy, for example, it has the capacity to reduce or abolish seizures. In the present study, taurine levels has been determine in mice treated with Kainic Acid (KA) and results showed an increase of this amino acid in hippocampus but not in whole brain after 3 and 7 days of KA treatment. This increase occurs when gliosis was observed. Moreover, taurine transporter (TAUT) was found in astrocytes 3 and 7 days after KA treatment, together with an increase in cysteine sulfinic acid decarboxylase (csd) mRNA, that codifies for the rate-limiting enzyme of taurine synthesis, in the hippocampus at the same times after KA treatment. Glial cultures enriched in astrocytes were developed to demonstrate that these cells are responsible for changes in taurine levels after an injury to the brain. The cultures were treated with proinflammatory cytokines to reproduce gliosis. In this experimental model, an increase in the immunoreactivity of GFAP was observed, together with an increase in CSD and taurine levels. Moreover, an alteration in the taurine uptake-release kinetics was detected in glial cells treated with cytokine. All data obtained indicate that astrocytes could play a key role in taurine level changes induced by neuronal damage. More studies are, therefore, needed to clarify the role taurine has in relation to neuronal death and repair. PMID:20082296

  1. HCO3(-)-independent pH regulation in astrocytes in situ is dominated by V-ATPase.

    PubMed

    Hansen, Daniel Bloch; Garrido-Comas, Nestor; Salter, Mike; Fern, Robert

    2015-03-27

    The mechanisms of HCO3(-)-independent intracellular pH (pHi) regulation were examined in fibrous astrocytes within isolated neonatal rat optic nerve (RON) and in cultured cortical astrocytes. In agreement with previous studies, resting pHi in cultured astrocytes was 6.82 ± 0.06 and inhibition of the V-ATPase H(+) pump by Cl(-) removal or via the selective inhibitor bafilomycin had only a small effect upon resting pHi and recovery following an acid load. In contrast, resting pHi in RON astrocytes was 7.10 ± 0.04, significantly less acidic than that in cultured cells (p < 0.001), and responded to inhibition of V-ATPase with profound acidification to the 6.3-6.5 range. Fluorescent immuno-staining and immuno-gold labeling confirmed the presence V-ATPase in the cell membrane of RON astrocyte processes and somata. Using ammonia pulse recovery, pHi recovery in RON astrocyte was achieved largely via V-ATPase with sodium-proton exchange (NHE) playing a minor role. The findings indicate that astrocytes in a whole-mount preparation such as the optic nerve rely to a greater degree upon V-ATPase for HCO3(-)-independent pHi regulation than do cultured astrocytes, with important functional consequences for the regulation of pH in the CNS.

  2. Heterogeneity in expression of functional ionotropic glutamate and GABA receptors in astrocytes across brain regions: insights from the thalamus

    PubMed Central

    Höft, Simon; Griemsmann, Stephanie; Seifert, Gerald; Steinhäuser, Christian

    2014-01-01

    Astrocytes may express ionotropic glutamate and gamma-aminobutyric acid (GABA) receptors, which allow them to sense and to respond to neuronal activity. However, so far the properties of astrocytes have been studied only in a few brain regions. Here, we provide the first detailed receptor analysis of astrocytes in the murine ventrobasal thalamus and compare the properties with those in other regions. To improve voltage-clamp control and avoid indirect effects during drug applications, freshly isolated astrocytes were employed. Two sub-populations of astrocytes were found, expressing or lacking α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. AMPA receptor-bearing astrocytes displayed a lower Kir current density than cells lacking the receptors. In contrast, all cells expressed GABAA receptors. Single-cell RT-PCR was employed to identify the receptor subunits in thalamic astrocytes. Our findings add to the emerging evidence of functional heterogeneity of astrocytes, the impact of which still remains to be defined. PMID:25225096

  3. Astrocyte calcium signaling: the third wave.

    PubMed

    Bazargani, Narges; Attwell, David

    2016-02-01

    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.

  4. Astrocytes Control Synapse Formation, Function, and Elimination

    PubMed Central

    Chung, Won-Suk; Allen, Nicola J.; Eroglu, Cagla

    2015-01-01

    Astrocytes, through their close associations with synapses, can monitor and alter synaptic function, thus actively controlling synaptic transmission in the adult brain. Besides their important role at adult synapses, in the last three decades a number of critical findings have highlighted the importance of astrocytes in the establishment of synaptic connectivity in the developing brain. In this article, we will review the key findings on astrocytic control of synapse formation, function, and elimination. First, we will summarize our current structural and functional understanding of astrocytes at the synapse. Then, we will discuss the cellular and molecular mechanisms through which developing and mature astrocytes instruct the formation, maturation, and refinement of synapses. Our aim is to provide an overview of astrocytes as important players in the establishment of a functional nervous system. PMID:25663667

  5. Astrocytes in the tempest of multiple sclerosis.

    PubMed

    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

  6. Involvement of astrocytes in neurovascular communication.

    PubMed

    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

  7. Effects of subcytotoxic cadmium on morphology of glial fibrillary acidic protein network in astrocytes derived from murine neural stem/progenitor cells.

    PubMed

    Mori, Hideki; Sasaki, Go; Nishikawa, Mayu; Hara, Masayuki

    2015-09-01

    The susceptibility of mouse neural stem/progenitor cells (NSPCs) to heavy-metal cytotoxicity was assessed by measuring cell viability following exposure to heavy metal chlorides (ZnCl2, CdCl2, CuCl2, and HgCl2, respectively). We determined half-maximal inhibitory concentration (IC50) values, subcytotoxic doses, capacity for neural differentiation, and morphological features of glial fibrillary acidic protein (GFAP) network at the subcytotoxic doses of heavy metal ions. Experiments were performed using two protocols for the exposure at subcytotoxic doses of heavy metal ions; these protocols included simultaneous exposure with the induction of NSPC differentiation and sequential exposure after the induction for 1 week. Exposure to HgCl2 using both protocols reduced the ratio of neuronal NSPC differentiation. Although sequential exposure to CdCl2 reduced the size of GFAP network, simultaneous exposure did not induce any change. In conclusion, image analyses of the cytoskeletal morphology of NSPCs as a novel tool for assessing neurodevelopmental cytotoxicity enabled us to obtain new information about the localization of cytoskeletal proteins.

  8. Astrocytic glycogenolysis: mechanisms and functions.

    PubMed

    Hertz, Leif; Xu, Junnan; Song, Dan; Du, Ting; Li, Baoman; Yan, Enzhi; Peng, Liang

    2015-02-01

    Until the demonstration little more than 20 years ago that glycogenolysis occurs during normal whisker stimulation glycogenolysis was regarded as a relatively uninteresting emergency procedure. Since then, a series of important astrocytic functions has been shown to be critically dependent on glycogenolytic activity to support the signaling mechanisms necessary for these functions to operate. This applies to glutamate formation and uptake and to release of ATP as a transmitter, stimulated by other transmitters or elevated K(+) concentrations and affecting not only other astrocytes but also most other brain cells. It is also relevant for astrocytic K(+) uptake both during the period when the extracellular K(+) concentration is still elevated after neuronal excitation, and capable of stimulating glycogenolytic activity, and during the subsequent undershoot after intense neuronal activity, when glycogenolysis may be stimulated by noradrenaline. Both elevated K(+) concentrations and several transmitters, including the β-adrenergic agonist isoproterenol and vasopressin increase free cytosolic Ca(2+) concentration in astrocytes, which stimulates phosphorylase kinase so that it activates the transformation of the inactive glycogen phosphorylase a to the active phosphorylase b. Contrary to common belief cyclic AMP plays at most a facilitatory role, and only when free cytosolic Ca(2+) concentration is also increased. Cyclic AMP is not increased during activation of glycogenolysis by either elevated K(+) concentrations or the stimulation of the serotonergic 5-HT(2B) receptor. Not all agents that stimulate glycogenolysis do so by directly activating phophorylase kinase--some do so by activating processes requiring glycogenolysis, e.g. for synthesis of glutamate. PMID:24744118

  9. Astrocytes: Everything but the glue

    PubMed Central

    Gonzalez-Perez, Oscar; Lopez-Virgen, Veronica; Quiñones-Hinojosa, Alfredo

    2015-01-01

    The current knowledge in neuroscience indicates that neural tissue has two major cell populations: neurons and glia (term derived from the Greek word for glue). Neuronal population is characterized by the capacity to produce action potentials, whereas glial cells are typically identified as the subordinate cell population of neurons. To date, this point of view has changed dramatically and growing evidence indicates that glial cells play a crucial role in normal mental functions and the pathogenesis of neurological diseases. Classically, glial cells include four major populations clearly discernible in the adult brain: astrocytes, oligodendrocytes, microglia cells and NG2 glia. Astrocytes, also referred as to astroglia, are by far the most abundant cell lineage in the adult brain. These cells are in close contact with several tissue components of the brain parenchyma including neurons, vasculature, extracellular matrix and other glial populations. Hence, the number and strategic position of astrocytes provide them with exceptional capacity for modulating multiple functions in the neural tissue. PMID:25938129

  10. Role of astrocytes as neural stem cells in the adult brain

    PubMed Central

    Gonzalez-Perez, Oscar; Quiñones-Hinojosa, Alfredo

    2012-01-01

    In the adult mammalian brain, bona fide neural stem cells were discovered in the subventricular zone (SVZ), the largest neurogenic niche lining the striatal wall of the lateral ventricles of the brain. In this region resides a subpopulation of astrocytes that express the glial fibrillary acidic protein (GFAP), nestin and LeX. Astonishingly, these GFAP-expressing progenitors display stem-cell-like features both in vivo and in vitro. Throughout life SVZ astrocytes give rise to interneurons and oligodendrocyte precursors, which populate the olfactory bulb and the white matter, respectively. The role of the progenies of SVZ astrocytes has not been fully elucidated, but some evidence indicates that the new neurons play a role in olfactory discrimination, whereas oligodendrocytes contribute to myelinate white matter tracts. In this chapter, we describe the astrocytic nature of adult neural stem cells, their organization into the SVZ and some of their molecular and genetic characteristics. PMID:23619383

  11. Disentangling calcium-driven astrocyte physiology.

    PubMed

    Rusakov, Dmitri A

    2015-04-01

    Astrocytes seem to rely on relatively sluggish and spatially blurred Ca(2+) waves to communicate with fast and point-precise neural circuits. This apparent discrepancy could, however, reflect our current inability to understand the microscopic mechanisms involved. Difficulties in detecting and interpreting astrocyte Ca(2+) signals may have led to some prominent controversies in the field. Here, we argue that a deeper understanding of astrocyte physiology requires a qualitative leap in our experimental and analytical strategies.

  12. Astrocytes are involved in trigeminal dynamic mechanical allodynia: potential role of D-serine.

    PubMed

    Dieb, W; Hafidi, A

    2013-09-01

    Trigeminal neuropathic pain affects millions of people worldwide. Despite decades of study on the neuronal processing of pain, mechanisms underlying enhanced pain states after injury remain unclear. N-methyl-D-aspartate (NMDA) receptor-dependent changes play a critical role in triggering central sensitization in neuropathic pain. These receptors are regulated at the glycine site through a mandatory endogenous co-agonist D-serine, which is synthesized by astrocytes. Therefore, the present study was carried out to determine whether astrocytes are involved, through D-serine secretion, in dynamic mechanical allodynia (DMA) obtained after chronic constriction of the infraorbital nerve (CCI-IoN) in rats. Two weeks after CCI-IoN, an important reaction of astrocytes was present in the medullary dorsal horn (MDH), as revealed by an up-regulation of glial fibrillary acidic protein (GFAP) in allodynic rats. In parallel, an increase in D-serine synthesis, which co-localized with its synthesis enzyme serine racemase, was strictly observed in astrocytes. Blocking astrocyte metabolism by intracisternal delivery of fluorocitrate alleviated DMA. Furthermore, the administration of D-amino-acid oxidase (DAAO), a D-serine-degrading enzyme, or that of L-serine O-sulfate (LSOS), a serine racemase inhibitor, significantly decreased pain behavior in allodynic rats. These results demonstrate that astrocytes are involved in the modulation of orofacial post-traumatic neuropathic pain via the release of the gliotransmitter D-serine.

  13. Trafficking of astrocytic vesicles in hippocampal slices

    SciTech Connect

    Potokar, Maja; Kreft, Marko; Lee, So-Young; Takano, Hajime; Haydon, Philip G.; Zorec, Robert

    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.

  14. Astrocytic Actions on Extrasynaptic Neuronal Currents

    PubMed Central

    Pál, Balázs

    2015-01-01

    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 (CNS), 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. PMID:26696832

  15. Activation of glutamate transport evokes rapid glutamine release from perisynaptic astrocytes

    PubMed Central

    Uwechue, Nneka M; Marx, Mari-Carmen; Chevy, Quentin; Billups, Brian

    2012-01-01

    Stimulation of astrocytes by neuronal activity and the subsequent release of neuromodulators is thought to be an important regulator of synaptic communication. In this study we show that astrocytes juxtaposed to the glutamatergic calyx of Held synapse in the rat medial nucleus of the trapezoid body (MNTB) are stimulated by the activation of glutamate transporters and consequently release glutamine on a very rapid timescale. MNTB principal neurones express electrogenic system A glutamine transporters, and were exploited as glutamine sensors in this study. By simultaneous whole-cell voltage clamping astrocytes and neighbouring MNTB neurones in brainstem slices, we show that application of the excitatory amino acid transporter (EAAT) substrate d-aspartate stimulates astrocytes to rapidly release glutamine, which is detected by nearby MNTB neurones. This release is significantly reduced by the toxins l-methionine sulfoximine and fluoroacetate, which reduce glutamine concentrations specifically in glial cells. Similarly, glutamine release was also inhibited by localised inactivation of EAATs in individual astrocytes, using internal dl-threo-β-benzyloxyaspartic acid (TBOA) or dissipating the driving force by modifying the patch-pipette solution. These results demonstrate that astrocytes adjacent to glutamatergic synapses can release glutamine in a temporally precise, controlled manner in response to glial glutamate transporter activation. Since glutamine can be used by neurones as a precursor for glutamate and GABA synthesis, this represents a potential feedback mechanism by which astrocytes can respond to synaptic activation and react in a way that sustains or enhances further communication. This would therefore represent an additional manifestation of the tripartite relationship between synapses and astrocytes. PMID:22411007

  16. Radiotherapy and temozolomide for anaplastic astrocytic gliomas

    PubMed Central

    Nayak, Lakshmi; Panageas, Katherine S.; Reiner, Anne S.; Huse, Jason T.; Pentsova, Elena; Braunthal, Stephanie G.; Abrey, Lauren E.; DeAngelis, Lisa M.

    2015-01-01

    We previously reported results of a phase II non-comparative trial that randomized patients with glioblastoma following radiotherapy to one of two different temozolomide schedules, followed by 13-cis-retinoic acid (RA) maintenance. Here we report the results of an exploratory cohort of patients accrued with anaplastic astrocytic tumors. Patients with newly diagnosed anaplastic astrocytoma (AA) or anaplastic oligo-astrocytoma (AOA) were treated with concurrent radiotherapy (60 Gy over 6 weeks) and temozolomide (75 mg/m2), and six adjuvant 28-day cycles of either dose-dense (150 mg/m2, days 1–7, 15–21) or metronomic (50 mg/m2, days 1–28) temozolomide. Subsequently, maintenance RA (100 mg/m2, days 1–21/28) was administered until disease progression. All outcome measures were descriptive without intention to compare between treatment arms. Survival was measured by the Kaplan–Meier method. There were 31 patients (21 men, 10 women) with median age 48 years (range 28–74), median KPS 90 (range 60–100). Extent of resection was gross-total in 35 %, subtotal 23 %, and biopsy 42 %. Histology was AA in 90 %, and AOA in 10 %. MGMT promoter methylation was methylated in 20 %, unmethylated in 50 %, and uninformative in 30 % of 30 tested. Median progression-free survival was 2.1 years (95 % CI 0.95–Not Reached), and overall survival 2.9 years (95 % CI 2.0–Not Reached). We report outcomes among a homogeneously treated population with anaplastic astrocytic tumors. Survival was unexpectedly short compared to other reports. These data may be useful as a contemporary historic control for other ongoing or future randomized trials. PMID:25920709

  17. Radiotherapy and temozolomide for anaplastic astrocytic gliomas.

    PubMed

    Nayak, Lakshmi; Panageas, Katherine S; Reiner, Anne S; Huse, Jason T; Pentsova, Elena; Braunthal, Stephanie G; Abrey, Lauren E; DeAngelis, Lisa M; Lassman, Andrew B

    2015-05-01

    We previously reported results of a phase II non-comparative trial that randomized patients with glioblastoma following radiotherapy to one of two different temozolomide schedules, followed by 13-cis-retinoic acid (RA) maintenance. Here we report the results of an exploratory cohort of patients accrued with anaplastic astrocytic tumors. Patients with newly diagnosed anaplastic astrocytoma (AA) or anaplastic oligo-astrocytoma (AOA) were treated with concurrent radiotherapy (60 Gy over 6 weeks) and temozolomide (75 mg/m(2)), and six adjuvant 28-day cycles of either dose-dense (150 mg/m(2), days 1-7, 15-21) or metronomic (50 mg/m(2), days 1-28) temozolomide. Subsequently, maintenance RA (100 mg/m(2), days 1-21/28) was administered until disease progression. All outcome measures were descriptive without intention to compare between treatment arms. Survival was measured by the Kaplan-Meier method. There were 31 patients (21 men, 10 women) with median age 48 years (range 28-74), median KPS 90 (range 60-100). Extent of resection was gross-total in 35%, subtotal 23%, and biopsy 42%. Histology was AA in 90%, and AOA in 10%. MGMT promoter methylation was methylated in 20%, unmethylated in 50%, and uninformative in 30% of 30 tested. Median progression-free survival was 2.1 years (95% CI 0.95-Not Reached), and overall survival 2.9 years (95 % CI 2.0-Not Reached). We report outcomes among a homogeneously treated population with anaplastic astrocytic tumors. Survival was unexpectedly short compared to other reports. These data may be useful as a contemporary historic control for other ongoing or future randomized trials. PMID:25920709

  18. Three-dimensional culture conditions differentially affect astrocyte modulation of brain endothelial barrier function in response to transforming growth factor β1.

    PubMed

    Hawkins, Brian T; Grego, Sonia; Sellgren, Katelyn L

    2015-05-22

    Blood-brain barrier (BBB) function is regulated by dynamic interactions among cell types within the neurovascular unit, including astrocytes and endothelial cells. Co-culture models of the BBB typically involve astrocytes seeded on two-dimensional (2D) surfaces, which recent studies indicate cause astrocytes to express a phenotype similar to that of reactive astrocytes in situ. We hypothesized that the culture conditions of astrocytes would differentially affect their ability to modulate BBB function in vitro. Brain endothelial cells were grown alone or in co-culture with astrocytes. Astrocytes were grown either as conventional (2D) monolayers, or in a collagen-based gel which allows them to grow in a three-dimensional (3D) construct. Astrocytes were viable in 3D conditions, and displayed a marked reduction in their expression of glial fibrillary acidic protein (GFAP), suggesting reduced activation. Stimulation of astrocytes with transforming growth factor (TGF)β1 decreased transendothelial electrical resistance (TEER) and reduced expression of claudin-5 in co-cultures, whereas treatment of endothelial cells in the absence of astrocytes was without effect. The effect of TGFβ1 on TEER was significantly more pronounced in endothelial cells cultured with 3D astrocytes compared to 2D astrocytes. These results demonstrate that astrocyte culture conditions differentially affect their ability to modulate brain endothelial barrier function, and suggest a direct relationship between reactive gliosis and BBB permeability. Moreover, these studies demonstrate the potential importance of physiologically relevant culture conditions to in vitro modeling of disease processes that affect the neurovascular unit.

  19. Astrocytes and Developmental White Matter Disorders

    ERIC Educational Resources Information Center

    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…

  20. Nitric Oxide in Astrocyte-Neuron Signaling

    SciTech Connect

    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

  1. Changes in the Transcriptome of Human Astrocytes Accompanying Oxidative Stress-Induced Senescence

    PubMed Central

    Crowe, Elizabeth P.; Tuzer, Ferit; Gregory, Brian D.; Donahue, Greg; Gosai, Sager J.; Cohen, Justin; Leung, Yuk Y.; Yetkin, Emre; Nativio, Raffaella; Wang, Li-San; Sell, Christian; Bonini, Nancy M.; Berger, Shelley L.; Johnson, F. Brad; Torres, Claudio

    2016-01-01

    Aging is a major risk factor for many neurodegenerative disorders. A key feature of aging biology that may underlie these diseases is cellular senescence. Senescent cells accumulate in tissues with age, undergo widespread changes in gene expression, and typically demonstrate altered, pro-inflammatory profiles. Astrocyte senescence has been implicated in neurodegenerative disease, and to better understand senescence-associated changes in astrocytes, we investigated changes in their transcriptome using RNA sequencing. Senescence was induced in human fetal astrocytes by transient oxidative stress. Brain-expressed genes, including those involved in neuronal development and differentiation, were downregulated in senescent astrocytes. Remarkably, several genes indicative of astrocytic responses to injury were also downregulated, including glial fibrillary acidic protein and genes involved in the processing and presentation of antigens by major histocompatibility complex class II proteins, while pro-inflammatory genes were upregulated. Overall, our findings suggest that senescence-related changes in the function of astrocytes may impact the pathogenesis of age-related brain disorders.

  2. Astrocyte reactivity after brain injury—: The role of galectins 1 and 3

    PubMed Central

    Sirko, Swetlana; Irmler, Martin; Gascón, Sergio; Bek, Sarah; Schneider, Sarah; Dimou, Leda; Obermann, Jara; De Souza Paiva, Daisylea; Poirier, Francoise; Beckers, Johannes; Hauck, Stefanie M.; Barde, Yves‐Alain

    2015-01-01

    Astrocytes react to brain injury in a heterogeneous manner with only a subset resuming proliferation and acquiring stem cell properties in vitro. In order to identify novel regulators of this subset, we performed genomewide expression analysis of reactive astrocytes isolated 5 days after stab wound injury from the gray matter of adult mouse cerebral cortex. The expression pattern was compared with astrocytes from intact cortex and adult neural stem cells (NSCs) isolated from the subependymal zone (SEZ). These comparisons revealed a set of genes expressed at higher levels in both endogenous NSCs and reactive astrocytes, including two lectins—Galectins 1 and 3. These results and the pattern of Galectin expression in the lesioned brain led us to examine the functional significance of these lectins in brains of mice lacking Galectins 1 and 3. Following stab wound injury, astrocyte reactivity including glial fibrillary acidic protein expression, proliferation and neurosphere‐forming capacity were found significantly reduced in mutant animals. This phenotype could be recapitulated in vitro and was fully rescued by addition of Galectin 3, but not of Galectin 1. Thus, Galectins 1 and 3 play key roles in regulating the proliferative and NSC potential of a subset of reactive astrocytes. GLIA 2015;63:2340–2361 PMID:26250529

  3. Distinct regulation of MHC molecule expression on astrocytes and microglia during viral encephalomyelitis.

    PubMed

    Hamo, Ludwig; Stohlman, Stephen A; Otto-Duessel, Maya; Bergmann, Cornelia C

    2007-08-15

    The potential interplay of glial cells with T cells during viral induced inflammation was assessed by comparing major histocompatibility complex molecule upregulation and retention on astrocytes and microglia. Transgenic mice expressing green fluorescent protein under control of the astrocyte-specific glial fibrillary acidic protein promoter were infected with a neurotropic coronavirus to facilitate phenotypic characterization of astrocytes and microglia using flow cytometry. Astrocytes in the adult central nervous system up-regulated class I surface expression, albeit delayed compared with microglia. Class II was barely detectable on astrocytes, in contrast to potent up-regulation on microglia. Maximal MHC expression in both glial cell types correlated with IFN-gamma levels and lymphocyte accumulation. Despite a decline of IFN-gamma concomitant to virus clearance, MHC molecule expression on glia was sustained. These data demonstrate distinct regulation of both class I and class II expression by microglia and astrocytes in vivo following viral induced inflammation. Furthermore, prolonged MHC expression subsequent to viral clearance implies a potential for ongoing presentation.

  4. Changes in the Transcriptome of Human Astrocytes Accompanying Oxidative Stress-Induced Senescence

    PubMed Central

    Crowe, Elizabeth P.; Tuzer, Ferit; Gregory, Brian D.; Donahue, Greg; Gosai, Sager J.; Cohen, Justin; Leung, Yuk Y.; Yetkin, Emre; Nativio, Raffaella; Wang, Li-San; Sell, Christian; Bonini, Nancy M.; Berger, Shelley L.; Johnson, F. Brad; Torres, Claudio

    2016-01-01

    Aging is a major risk factor for many neurodegenerative disorders. A key feature of aging biology that may underlie these diseases is cellular senescence. Senescent cells accumulate in tissues with age, undergo widespread changes in gene expression, and typically demonstrate altered, pro-inflammatory profiles. Astrocyte senescence has been implicated in neurodegenerative disease, and to better understand senescence-associated changes in astrocytes, we investigated changes in their transcriptome using RNA sequencing. Senescence was induced in human fetal astrocytes by transient oxidative stress. Brain-expressed genes, including those involved in neuronal development and differentiation, were downregulated in senescent astrocytes. Remarkably, several genes indicative of astrocytic responses to injury were also downregulated, including glial fibrillary acidic protein and genes involved in the processing and presentation of antigens by major histocompatibility complex class II proteins, while pro-inflammatory genes were upregulated. Overall, our findings suggest that senescence-related changes in the function of astrocytes may impact the pathogenesis of age-related brain disorders. PMID:27630559

  5. HIV-1, Methamphetamine and Astrocyte Glutamate Regulation: Combined Excitotoxic Implications for Neuro-AIDS

    PubMed Central

    Cisneros, Irma E; Ghorpade, Anuja

    2012-01-01

    Glutamate, the most abundant excitatory transmitter in the brain can lead to neurotoxicity when not properly regulated. Excitotoxicity is a direct result of abnormal regulation of glutamate concentrations in the synapse, and is a common neurotoxic mediator associated with neurodegenerative disorders. It is well accepted that methamphetamine (METH), a potent central nervous stimulant with high abuse potential, and human immunodeficiency virus (HIV)-1 are implicated in the progression of neurocognitive malfunction. Both have been shown to induce common neurodegenerative effects such as astrogliosis, compromised blood brain barrier integrity, and excitotoxicity in the brain. Reduced glutamate uptake from neuronal synapses likely leads to the accumulation of glutamate in the extracellular spaces. Astrocytes express the glutamate transporters responsible for majority of the glutamate uptake from the synapse, as well as for vesicular glutamate release. However, the cellular and molecular mechanisms of astrocyte-mediated excitotoxicity in the context of METH and HIV-1 are undefined. Topics reviewed include dysregulation of the glutamate transporters, specifically excitatory amino acid transporter-2, metabotropic glutamate receptor(s) expression and the release of glutamate by vesicular exocytosis. We also discuss glutamate concentration dysregulation through astrocytic expression of enzymes for glutamate synthesis and metabolism. Lastly, we discuss recent evidence of various astrocyte and neuron crosstalk mechanisms implicated in glutamate regulation. Astrocytes play an essential role in the neuropathologies associated with METH/HIV-1-induced excitotoxicity. We hope to shed light on common cellular and molecular pathways astrocytes share in glutamate regulation during drug abuse and HIV-1 infection. PMID:22591363

  6. HIV-1, methamphetamine and astrocyte glutamate regulation: combined excitotoxic implications for neuro-AIDS.

    PubMed

    Cisneros, Irma E; Ghorpade, Anuja

    2012-07-01

    Glutamate, the most abundant excitatory transmitter in the brain can lead to neurotoxicity when not properly regulated. Excitotoxicity is a direct result of abnormal regulation of glutamate concentrations in the synapse, and is a common neurotoxic mediator associated with neurodegenerative disorders. It is well accepted that methamphetamine (METH), a potent central nervous stimulant with high abuse potential, and human immunodeficiency virus (HIV)-1 are implicated in the progression of neurocognitive malfunction. Both have been shown to induce common neurodegenerative effects such as astrogliosis, compromised blood brain barrier integrity, and excitotoxicity in the brain. Reduced glutamate uptake from neuronal synapses likely leads to the accumulation of glutamate in the extracellular spaces. Astrocytes express the glutamate transporters responsible for majority of the glutamate uptake from the synapse, as well as for vesicular glutamate release. However, the cellular and molecular mechanisms of astrocyte-mediated excitotoxicity in the context of METH and HIV-1 are undefined. Topics reviewed include dysregulation of the glutamate transporters, specifically excitatory amino acid transporter-2, metabotropic glutamate receptor(s) expression and the release of glutamate by vesicular exocytosis. We also discuss glutamate concentration dysregulation through astrocytic expression of enzymes for glutamate synthesis and metabolism. Lastly, we discuss recent evidence of various astrocyte and neuron crosstalk mechanisms implicated in glutamate regulation. Astrocytes play an essential role in the neuropathologies associated with METH/HIV-1-induced excitotoxicity. We hope to shed light on common cellular and molecular pathways astrocytes share in glutamate regulation during drug abuse and HIV-1 infection.

  7. Astrocytes in the Rat Medial Amygdala Are Responsive to Adult Androgens

    PubMed Central

    Johnson, Ryan T.; Schneider, Amanda; DonCarlos, Lydia L.; Breedlove, S. Marc; Jordan, Cynthia L.

    2014-01-01

    The posterodorsal medial amygdala (MePD) exhibits numerous sex differences including differences in volume and in the number and morphology of neurons and astroctyes. In adulthood, gonadal hormones, including both androgens and estrogens, have been shown to play a role in maintaining the masculine character of many of these sex differences, but whether adult gonadal hormones maintain the increased number and complexity of astrocytes in the male MePD was unknown. To answer this question we examined astrocytes in the MePD of male and female Long Evans rats that were gonadectomized as adults and treated for 30 days with either testosterone or a control treatment. At the end of treatment brains were collected and immunostained for glial fibrillary acidic protein. Stereological analysis revealed that adult androgen levels influenced the number and complexity of astrocytes in the MePD of both sexes, but the specific effects of androgens were different in males and females. However, sex differences in the number and complexity of adult astrocytes persisted even in the absence of gonadal hormones in adulthood, suggesting that androgens also act earlier in life to determine these adult sex differences. Using immunofluorescence and confocal microscopy, we found robust androgen receptor immunostaining in a subpopulation of MePD astrocytes, suggesting that testosterone may act directly on MePD astrocytes to influence their structure and function. PMID:22581688

  8. Changes in the Transcriptome of Human Astrocytes Accompanying Oxidative Stress-Induced Senescence.

    PubMed

    Crowe, Elizabeth P; Tuzer, Ferit; Gregory, Brian D; Donahue, Greg; Gosai, Sager J; Cohen, Justin; Leung, Yuk Y; Yetkin, Emre; Nativio, Raffaella; Wang, Li-San; Sell, Christian; Bonini, Nancy M; Berger, Shelley L; Johnson, F Brad; Torres, Claudio

    2016-01-01

    Aging is a major risk factor for many neurodegenerative disorders. A key feature of aging biology that may underlie these diseases is cellular senescence. Senescent cells accumulate in tissues with age, undergo widespread changes in gene expression, and typically demonstrate altered, pro-inflammatory profiles. Astrocyte senescence has been implicated in neurodegenerative disease, and to better understand senescence-associated changes in astrocytes, we investigated changes in their transcriptome using RNA sequencing. Senescence was induced in human fetal astrocytes by transient oxidative stress. Brain-expressed genes, including those involved in neuronal development and differentiation, were downregulated in senescent astrocytes. Remarkably, several genes indicative of astrocytic responses to injury were also downregulated, including glial fibrillary acidic protein and genes involved in the processing and presentation of antigens by major histocompatibility complex class II proteins, while pro-inflammatory genes were upregulated. Overall, our findings suggest that senescence-related changes in the function of astrocytes may impact the pathogenesis of age-related brain disorders. PMID:27630559

  9. Deletion of Monoglyceride Lipase in Astrocytes Attenuates Lipopolysaccharide-induced Neuroinflammation*

    PubMed Central

    Grabner, Gernot F.; Eichmann, Thomas O.; Wagner, Bernhard; Gao, Yuanqing; Farzi, Aitak; Taschler, Ulrike; Radner, Franz P. W.; Schweiger, Martina; Lass, Achim; Holzer, Peter; Zinser, Erwin; Tschöp, Matthias H.; Yi, Chun-Xia; Zimmermann, Robert

    2016-01-01

    Monoglyceride lipase (MGL) is required for efficient hydrolysis of the endocannabinoid 2-arachidonoylglyerol (2-AG) in the brain generating arachidonic acid (AA) and glycerol. This metabolic function makes MGL an interesting target for the treatment of neuroinflammation, since 2-AG exhibits anti-inflammatory properties and AA is a precursor for pro-inflammatory prostaglandins. Astrocytes are an important source of AA and 2-AG, and highly express MGL. In the present study, we dissected the distinct contribution of MGL in astrocytes on brain 2-AG and AA metabolism by generating a mouse model with genetic deletion of MGL specifically in astrocytes (MKOGFAP). MKOGFAP mice exhibit moderately increased 2-AG and reduced AA levels in brain. Minor accumulation of 2-AG in the brain of MKOGFAP mice does not cause cannabinoid receptor desensitization as previously observed in mice globally lacking MGL. Importantly, MKOGFAP mice exhibit reduced brain prostaglandin E2 and pro-inflammatory cytokine levels upon peripheral lipopolysaccharide (LPS) administration. These observations indicate that MGL-mediated degradation of 2-AG in astrocytes provides AA for prostaglandin synthesis promoting LPS-induced neuroinflammation. The beneficial effect of astrocyte-specific MGL-deficiency is not fully abrogated by the inverse cannabinoid receptor 1 agonist SR141716 (Rimonabant) suggesting that the anti-inflammatory effects are rather caused by reduced prostaglandin synthesis than by activation of cannabinoid receptors. In conclusion, our data demonstrate that MGL in astrocytes is an important regulator of 2-AG levels, AA availability, and neuroinflammation. PMID:26565024

  10. Differential Acute and Chronic Effects of Leptin on Hypothalamic Astrocyte Morphology and Synaptic Protein Levels

    PubMed Central

    García-Cáceres, Cristina; Fuente-Martín, Esther; Burgos-Ramos, Emma; Granado, Miriam; Frago, Laura M.; Barrios, Vicente; Horvath, Tamas

    2011-01-01

    Astrocytes participate in neuroendocrine functions partially through modulation of synaptic input density in the hypothalamus. Indeed, glial ensheathing of neurons is modified by specific hormones, thus determining the availability of neuronal membrane space for synaptic inputs, with the loss of this plasticity possibly being involved in pathological processes. Leptin modulates synaptic inputs in the hypothalamus, but whether astrocytes participate in this action is unknown. Here we report that astrocyte structural proteins, such as glial fibrillary acidic protein (GFAP) and vimentin, are induced and astrocyte morphology modified by chronic leptin administration (intracerebroventricular, 2 wk), with these changes being inversely related to modifications in synaptic protein densities. Similar changes in glial structural proteins were observed in adult male rats that had increased body weight and circulating leptin levels due to neonatal overnutrition (overnutrition: four pups/litter vs. control: 12 pups/litter). However, acute leptin treatment reduced hypothalamic GFAP levels and induced synaptic protein levels 1 h after administration, with no effect on vimentin. In primary hypothalamic astrocyte cultures leptin also reduced GFAP levels at 1 h, with an induction at 24 h, indicating a possible direct effect of leptin. Hence, one mechanism by which leptin may affect metabolism is by modifying hypothalamic astrocyte morphology, which in turn could alter synaptic inputs to hypothalamic neurons. Furthermore, the responses to acute and chronic leptin exposure are inverse, raising the possibility that increased glial activation in response to chronic leptin exposure could be involved in central leptin resistance. PMID:21343257

  11. Bestrophin-1 encodes for the Ca2+-activated anion channel in hippocampal astrocytes.

    PubMed

    Park, Hyungju; Oh, Soo-Jin; Han, Kyung-Seok; Woo, Dong Ho; Park, Hyekyung; Mannaioni, Guido; Traynelis, Stephen F; Lee, C Justin

    2009-10-14

    In mammalian brain, neurons and astrocytes are reported to express various chloride and anion channels, but the evidence for functional expression of Ca(2+)-activated anion channel (CAAC) and its molecular identity have been lacking. Here we report electrophysiological evidence for the CAAC expression and its molecular identity by mouse Bestrophin 1 (mBest1) in astrocytes of the mouse brain. Using Ca(2+) imaging and perforated-patch-clamp analysis, we demonstrate that astrocytes displayed an inward current at holding potential of -70 mV that was dependent on an increase in intracellular Ca(2+) after G(alphaq)-coupled receptor activation. This current was mediated mostly by anions and was sensitive to well known anion channel blockers such as niflumic acid, 5-nitro-2(3-phenylpropylamino)-benzoic acid, and flufenamic acid. To find the molecular identity of the anion channel responsible for the CAAC current, we analyzed the expression of candidate genes and found that the mRNA for mouse mBest1 is predominantly expressed in acutely dissociated or cultured astrocytes. Whole-cell patch-clamp analysis using HEK293T cells heterologously expressing full-length mBest1 showed a Ca(2+)-dependent current mediated by mBest1, with a complete impairment of the current by a putative pore mutation, W93C. Furthermore, mBest1-mediated CAAC from cultured astrocytes was significantly reduced by expression of mBest1-specific short hairpin RNA (shRNA), suggesting that the CAAC is mediated by a channel encoded by mBest1. Finally, hippocampal CA1 astrocytes in hippocampal slice also showed mBest1-mediated CAAC because it was inhibited by mBest1-specific shRNA. Collectively, these data provide molecular evidence that the mBest1 channel is responsible for CAAC function in astrocytes.

  12. Large-scale recording of astrocyte activity

    PubMed Central

    Nimmerjahn, Axel; Bergles, Dwight E.

    2015-01-01

    Astrocytes are highly ramified glial cells found throughout the central nervous system (CNS). They express a variety of neurotransmitter receptors that can induce widespread chemical excitation, placing these cells in an optimal position to exert global effects on brain physiology. However, the activity patterns of only a small fraction of astrocytes have been examined and techniques to manipulate their behavior are limited. As a result, little is known about how astrocytes modulate CNS function on synaptic, microcircuit, or systems levels. Here, we review current and emerging approaches for visualizing and manipulating astrocyte activity in vivo. Deciphering how astrocyte network activity is controlled in different physiological and pathological contexts is critical for defining their roles in the healthy and diseased CNS. PMID:25665733

  13. Probing the Complexities of Astrocyte Calcium Signaling.

    PubMed

    Shigetomi, Eiji; Patel, Sandip; Khakh, Baljit S

    2016-04-01

    Astrocytes are abundant glial cells that tile the entire central nervous system and mediate well-established functions for neurons, blood vessels, and other glia. These ubiquitous cells display intracellular Ca(2+) signals, which have been intensely studied for 25 years. Recently, the use of improved methods has unearthed the panoply of astrocyte Ca(2+) signals and a variable landscape of basal Ca(2+) levels. In vivo studies have started to reveal the settings under which astrocytes display behaviorally relevant Ca(2+) signaling. Studies in mice have emphasized how astrocyte Ca(2+) signaling is altered in distinct neurodegenerative diseases. Progress in the past few years, fueled by methodological advances, has thus reignited interest in astrocyte Ca(2+) signaling for brain function and dysfunction. PMID:26896246

  14. Three-Dimensional Environment Sustains Morphological Heterogeneity and Promotes Phenotypic Progression During Astrocyte Development.

    PubMed

    Balasubramanian, Swarnalatha; Packard, John A; Leach, Jennie B; Powell, Elizabeth M

    2016-06-01

    Astrocytes are critical for coordinating normal brain function by regulating brain metabolic homeostasis, synaptogenesis and neurotransmission, and blood-brain barrier permeability and maintenance. Dysregulation of normal astrocyte ontogeny contributes to neurodevelopmental and neurodegenerative disorders, epilepsies, and adverse responses to injury. To achieve these multiple essential roles, astrocyte phenotypes are regionally, morphologically, and functionally heterogeneous. Therefore, the best regenerative medicine strategies may require selective production of distinct astrocyte subpopulations at defined maturation levels. However, little is known about the mechanisms that direct astrocyte diversity or whether heterogeneity is represented in biomaterials. In vitro studies report lack of normal morphologies and overrepresentation of the glial scar type of reactive astrocyte morphology and expression of markers, questioning how well the in vitro astrocytes represent glia in vivo and whether in vitro tissue engineering methods are suitable for regenerative medicine applications. Our previous work with neurons suggests that the three-dimensional (3D) environment, when compared with standard two-dimensional (2D) substrate, yields cellular and molecular behaviors that more closely approximately normal ontogeny. To specifically study the effects of dimensionality, we used purified glial fibrillary acidic protein (GFAP)-expressing primary cerebral cortical astrocyte cultures from single pups and characterized the cellular maturation profiles in 2D and 3D milieu. We identified four morphological groups in vitro: round, bipolar, stellate, and putative perivascular. In the 3D hydrogel culture environment, postnatal astrocytes transitioned from a population of nearly all round cells and very few bipolar cells toward a population with significant fractions of round, stellate, and putative perivascular cells within a few days, following the in vivo ontogeny. In 2D, however

  15. Astrocytes are the primary source of tissue factor in the murine central nervous system. A role for astrocytes in cerebral hemostasis.

    PubMed Central

    Eddleston, M; de la Torre, J C; Oldstone, M B; Loskutoff, D J; Edgington, T S; Mackman, N

    1993-01-01

    Hemostasis in the brain is of paramount importance because bleeding into the neural parenchyma can result in paralysis, coma, and death. Consistent with this sensitivity to hemorrhage, the brain contains large amounts of tissue factor (TF), the major cellular initiator of the coagulation protease cascades. However, to date, the cellular source for TF in the central nervous system has not been identified. In this study, analysis of murine brain sections by in situ hybridization demonstrated high levels of TF mRNA in cells that expressed glial fibrillary acidic protein, a specific marker for astrocytes. Furthermore, primary mouse astrocyte cultures and astrocyte cell lines from mouse, rat, and human constitutively expressed TF mRNA and functional protein. These data indicated that astrocytes are the primary source of TF in the central nervous system. We propose that astrocytes forming the glia limitans around the neural vasculature and deep to the meninges are intimately involved in controlling hemorrhage in the brain. Finally, we observed an increase in TF mRNA expression in the brains of scrapie-infected mice. This modulation of TF expression in the absence of hemorrhage suggested that TF may function in processes other than hemostasis by altering protease generation in normal and diseased brain. Images PMID:8326003

  16. Exposure of rat hippocampal astrocytes to Ziram increases oxidative stress.

    PubMed

    Matei, Ann-Marie; Trombetta, Louis D

    2016-04-01

    Pesticides have been shown in several studies to be the leading candidates of environmental toxins and may contribute to the pathogenesis of several neurodegenerative diseases. Ziram (zinc-bis(dimethyldithiocarbamate)) is an agricultural dithiocarbamate fungicide that is used to treat a variety of plant diseases. In spite of their generally acknowledged low toxicity, dithiocarbamates are known to cause a wide range of neurobehavioral effects as well as neuropathological changes in the brain. Astrocytes play a key role in normal brain physiology and in the pathology of the nervous system. This investigation studied the effects of 1.0 µM Ziram on rat hippocampal astrocytes. The thiobarbituric acid reactive substance assay performed showed a significant increase in malondialdehyde, a product of lipid peroxidation, in the Ziram-treated cells. Biochemical analysis also revealed a significant increase in the induction of 70 kDa heat shock and heme oxygenase 1 stress proteins. In addition, an increase of glutathione peroxidase (GPx) and a significant increase in oxidized glutathione (GSSG) were observed in the Ziram-treated cells. The ratio GSH to GSSG calculated from the treated cells was also decreased. Light and transmission electron microscopy supported the biochemical findings in Ziram-treated astrocytes. This data suggest that the cytotoxic effects observed with Ziram treatments may be related to the increase of oxidative stress. PMID:24193059

  17. Octanol, a gap junction uncoupling agent, changes intracellular [H+] in rat astrocytes.

    PubMed

    Pappas, C A; Rioult, M G; Ransom, B R

    1996-01-01

    Octanol rapidly closes gap junction channels but its mechanism of action is not known. Because intracellular [H+], pHi, also affects the conductance of gap junctions, we studied octanol's effects on pHi in cultured rat astrocytes, which are highly coupled cells. Octanol (1 mM) caused an acid shift in the pHi of 90% of rat hippocampal astrocytes which averaged -0.19 +/- 0.09 pH units in magnitude. In 58% of the cells tested, a biphasic change in pHi was seen; octanol produced an initial acidification lasting approximately 10 min that was followed by a persistent alkalinization. The related gap junction uncoupling agent, heptanol, had similar effects on pHi. Octanol-induced changes in pHi were similar in nominally HCO(3-)-free and HCO(3-)-containing solutions, although the rate of initial acidification was significantly greater in the presence of HCO3-. The initial acidification was inhibited in the presence of the stilbene DIDS, an inhibitor of Na+/HCO3- cotransport, indicating that octanol caused acidification by blocking this powerful acid extruder. The alkalinization was inhibited by amiloride which blocks the Na+/H+ exchanger (NHE), an acid extruder, suggesting that the alkaline shift induced by octanol was caused by stimulation of NHE. As expected, octanol's effects on astrocytic pHi were prevented by removal of external Na+, which blocks both Na+/HCO3- cotransport and NHE. Octanol had only small effects on intracellular Ca2+ (Ca2+i) in astrocytes. Hepatocytes which, like astrocytes, are strongly coupled to one another, showed no change in pHi with octanol application. Fluorescence recovery after photobleaching (FRAP) was used to study the effect of changes in astrocyte pHi on degree of coupling in hippocampal astrocytes. Coupling was decreased by intracellular acid shifts approximately -0.2 pH units in size. Octanol's effects on astrocyte pHi were complex but a prompt initial acidification was nearly always seen and could contribute to the uncoupling action of

  18. Effects of homocysteine on metabolic pathways in cultured astrocytes.

    PubMed

    Jin, Ying; Brennan, Lorraine

    2008-06-01

    Homocysteine is an amino acid that is an important risk factor for several neurodegenerative diseases such as Alzheimer's and Parkinson's disease. Increased homocysteine levels induce neuronal cell death in a variety of neuronal types. However, very few studies have probed the effects of homocysteine in astrocytes. The present study investigated the effects of homocysteine on primary cultures of astrocytes by exposing astrocytes to 400 microM homocysteine for 20 h. Metabolic extracts of cells were prepared following a 4-h incubation in minimum medium with 5.5 mM [U-(13)C]glucose in the presence or absence of homocysteine and analysed using (13)C NMR. The expression level of pyruvate dehydrogenase kinase isoform 2 (PDK-2), NAD(P)H levels and mitochondrial membrane potential responses were investigated following culture with homocysteine. Metabolomic analysis was performed using (1)H NMR spectroscopy and pattern recognition analysis. Following incubation with homocysteine there was a significant decrease (48%) in the ratio of flux through pyruvate carboxylase (PC) and pyruvate dehydrogenase (PDH) which was due to an increased flux through PDH. In addition, homocysteine culture resulted in a significant reduction in PDK-2 protein expression. Following stimulation with glucose there was a significant increase in NAD(P)H levels and an impaired hyperpolarisation of the mitochondrial membrane in homocysteine-treated cells. Metabolomic analysis showed that the most discriminating metabolites following homocysteine treatment were choline and hypotaurine. In summary, the results demonstrated that sub-lethal concentrations of homocysteine caused significant metabolic changes and altered mitochondrial function in primary cultures of astrocytes. PMID:18417255

  19. The pathophysiological role of astrocytic endothelin-1.

    PubMed

    Hostenbach, Stéphanie; D'haeseleer, Miguel; Kooijman, Ron; De Keyser, Jacques

    2016-09-01

    In the normal central nervous system, endothelin-1 (ET-1) is found in some types of neurons, epithelial cells of the choroid plexus, and endothelial cells of microvessels, but it is usually not detectable in glial cells. However, in different pathological conditions, astrocytes adapting a reactive phenotype express high levels of ET-1 and its receptors, mainly the ETB receptor. ET-1 released by reactive astrocytes appears mainly to have neurodeleterious effects by mechanisms that include constriction of cerebral arterioles leading to impairment of the cerebral microcirculation, increase of blood brain barrier permeability, inflammation, excitotoxicity, impairment of fast axonal transport, and astrogliosis. A few studies in rodents found that ET-1 increased the astrocytic expression of brain-derived neurotrophic factor, glial cell-line derived neurotrophic factor and neurotropin-3, and the production of endocannabinoids. However, whether this occurs in physiological or pathological conditions is unclear. This review summarizes current knowledge about the role of the astrocytic ET-1 system in acute and chronic neurological conditions, including multiple sclerosis, ischemic stroke and hypoxic/ischemic brain injury, traumatic brain injury, subarachnoid hemorrhage, Alzheimer's disease, Binswanger's disease and post-stroke dementia, amyotrophic lateral sclerosis, and CNS infections. Counteracting the harmful effects of astrocytic ET-1 may represent a promising therapeutic target for mitigating secondary brain damage in a variety of neurological diseases. We also briefly address the role of astrocytic ET-1 in astrocytic tumors and pain. PMID:27132521

  20. Astrocytes regulate cortical state switching in vivo.

    PubMed

    Poskanzer, Kira E; Yuste, Rafael

    2016-05-10

    The role of astrocytes in neuronal function has received increasing recognition, but disagreement remains about their function at the circuit level. Here we use in vivo two-photon calcium imaging of neocortical astrocytes while monitoring the activity state of the local neuronal circuit electrophysiologically and optically. We find that astrocytic calcium activity precedes spontaneous circuit shifts to the slow-oscillation-dominated state, a neocortical rhythm characterized by synchronized neuronal firing and important for sleep and memory. Further, we show that optogenetic activation of astrocytes switches the local neuronal circuit to this slow-oscillation state. Finally, using two-photon imaging of extracellular glutamate, we find that astrocytic transients in glutamate co-occur with shifts to the synchronized state and that optogenetically activated astrocytes can generate these glutamate transients. We conclude that astrocytes can indeed trigger the low-frequency state of a cortical circuit by altering extracellular glutamate, and therefore play a causal role in the control of cortical synchronizations. PMID:27122314

  1. Astrocytes regulate cortical state switching in vivo

    PubMed Central

    Poskanzer, Kira E.; Yuste, Rafael

    2016-01-01

    The role of astrocytes in neuronal function has received increasing recognition, but disagreement remains about their function at the circuit level. Here we use in vivo two-photon calcium imaging of neocortical astrocytes while monitoring the activity state of the local neuronal circuit electrophysiologically and optically. We find that astrocytic calcium activity precedes spontaneous circuit shifts to the slow-oscillation–dominated state, a neocortical rhythm characterized by synchronized neuronal firing and important for sleep and memory. Further, we show that optogenetic activation of astrocytes switches the local neuronal circuit to this slow-oscillation state. Finally, using two-photon imaging of extracellular glutamate, we find that astrocytic transients in glutamate co-occur with shifts to the synchronized state and that optogenetically activated astrocytes can generate these glutamate transients. We conclude that astrocytes can indeed trigger the low-frequency state of a cortical circuit by altering extracellular glutamate, and therefore play a causal role in the control of cortical synchronizations. PMID:27122314

  2. Artificial astrocytes improve neural network performance.

    PubMed

    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

  3. Artificial Astrocytes Improve Neural Network Performance

    PubMed Central

    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

  4. pH-Sensitive K(+) Currents and Properties of K2P Channels in Murine Hippocampal Astrocytes.

    PubMed

    Weller, Johannes; Steinhäuser, Christian; Seifert, Gerald

    2016-01-01

    Based on their intimate spatial association with synapses and the capillary, astrocytes are critically involved in the control of ion, transmitter, and energy homeostasis as well as regulation of the cerebral blood flow. Under pathophysiological conditions, dysfunctional astrocytes can no longer assure homeostatic control although the underlying mechanisms are poorly understood. Specifically, neurological diseases are often accompanied by acidification of the extracellular space, but the properties of astrocytes in such an acidic environment are still a matter of debate. To meet the homeostatic requirements, astrocytes are equipped with intercellular gap junctions, inwardly rectifying K(+) (Kir) channels, and two-pore domain K(+) (K2P) channels. One goal of the present study was to overview current knowledge about astrocyte K(+) channel function during acidosis. In addition, we combined functional and molecular analyses to clarify how low pH affects K(+) channel function in astrocytes freshly isolated from the developing mouse hippocampus. Extracellular acidification led to a decrease of K(+) currents in astrocytes, probably due to modulation of Kir4.1 channels. After blocking Kir4.1 channels, low pH enhanced K(+) current amplitudes. This current activation was mimicked by modulators of TREK-1 channels, which belong to the K2P channels family. We found no evidence for the presence of acid-sensitive ion channels and transient receptor potential vanilloid receptors in hippocampal astrocytes. In conclusion, the assembly of astrocytic K(+) channels allows tolerating short, transient acidification, and glial Kir4.1 and K2P channels can be considered promising new targets in brain diseases accompanied by pH shifts. PMID:26920692

  5. Hippocampus-based contextual memory alters the morphological characteristics of astrocytes in the dentate gyrus.

    PubMed

    Choi, Moonseok; Ahn, Sangzin; Yang, Eun-Jeong; Kim, Hyunju; Chong, Young Hae; Kim, Hye-Sun

    2016-07-26

    Astrocytes have been reported to exist in two states, the resting and the reactive states. Morphological changes in the reactive state of astrocytes include an increase in thickness and number of processes, and an increase in the size of the cell body. Molecular changes also occur, such as an increase in the expression of glial fibrillary acidic protein (GFAP). However, the morphological and molecular changes during the process of learning and memory have not been elucidated. In the current study, we subjected Fvb/n mice to contextual fear conditioning, and checked for morphological and molecular changes in astrocytes. 1 h after fear conditioning, type II and type III astrocytes exhibited a unique status with an increased number of processes and decreased GFAP expression which differed from the typical resting or reactive state. In addition, the protein level of excitatory excitatory amino acid transporter 2 (EAAT2) was increased 1 h to 24 h after contextual fear conditioning while EAAT1 did not show any alterations. Connexin 43 (Cx43) protein was found to be increased at 24 h after fear conditioning. These data suggest that hippocampus-based contextual memory process induces changes in the status of astrocytes towards a novel status different from typical resting or reactive states. These morphological and molecular changes may be in line with functional changes.

  6. Knockdown of apoptosis signal-regulating kinase 1 affects ischaemia-induced astrocyte activation and glial scar formation.

    PubMed

    Cheon, So Yeong; Cho, Kyoung Joo; Song, Juhyun; Kim, Gyung Whan

    2016-04-01

    Reactive astrocytes play an essential role in determining the tissue response to ischaemia. Formation of a glial scar can block the neuronal outgrowth that is required for restoration of damaged tissue. Therefore, regulation of astrocyte activation is important; however, the mediator of this process has not been fully elucidated. Apoptosis signal-regulating kinase 1 (ASK1) is an early responder to oxidative stress, and plays a pivotal role in the intracellular signalling pathway of apoptosis, inflammation, and differentiation. To confirm whether ASK1 mediates astrocyte activation and leads to glial scar formation after cerebral ischaemia, we conducted in vivo and in vitro experiments. C57BL/6 mice were subjected to occlusion of the middle cerebral artery, and astrocyte cultures were exposed to oxygen-glucose deprivation. After silencing of ASK1 , astrocyte-associated genes were downregulated, as seen with the use of microarrays. The glial fibrillary acidic protein (GFAP) level was decreased, and correlated with the reduction in the ASK1 level. In astrocytes, reduction in the ASK1 level decreased the activity of the p38 pathway, and the levels of transcription factors for GFAP and GFAP transcripts after hypoxia. In the chronic phase, ASK1 depletion reduced glial scar formation and conserved neuronal structure, which may lead to better functional recovery. These data suggest that ASK1 may be an important mediator of ischaemia-induced astrocyte activation and scar formation, and could provide a potential therapeutic target for treatment after ischaemic stroke. PMID:26797817

  7. Astrocytes as Gatekeepers of GABAB Receptor Function

    PubMed Central

    Beenhakker, Mark P.; Huguenard, John R.

    2010-01-01

    The long-lasting actions of the inhibitory neurotransmitter γ-aminobutyric acid (GABA) result from the activation of metabotropic GABAB receptors. Enhanced GABAB-mediated inhibitory postsynaptic currents (IPSCs) are critical for the generation of generalized thalamocortical seizures. Here, we demonstrate that GABAB-mediated inhibitory postsynaptic currents (IPSCs) recorded in the thalamus are largely defined by GABA diffusion and activation of distal extrasynaptic receptors potentially up to tens of μm from synapses. We also show that this diffusion is differentially regulated by two astrocytic GABA transporters, GAT1 and GAT3, which are localized near and far from synapses, respectively. A biologically constrained model of GABA diffusion and uptake shows how the two GATs differentially modulate amplitude and duration of GABAB IPSCs. Specifically, the perisynaptic expression of GAT1 enables it to regulate GABA levels near synapses and selectively modulate peak IPSC amplitude, which is largely dependent on perisynaptic receptor occupancy. GAT3 expression, on the other hand, is broader and includes distal extrasynaptic regions. As such, GAT3 acts as a gatekeeper to prevent diffusion of GABA away from synapses towards extrasynaptic regions that contain a potentially enormous pool of GABAB receptors. Targeting this gatekeeper function may provide new pharmacotherapeutic opportunities to prevent the excessive GABAB receptor activation that appears necessary for thalamic seizure generation. PMID:21068331

  8. Astrocytes: The missing link in neurological disease?

    PubMed Central

    Lin, Chia-Ching John; Deneen, Benjamin

    2013-01-01

    The central nervous system (CNS) is comprised of numerous cell types that work in concert to facilitate proper function and homeostasis. Disruption of these carefully orchestrated networks results in neuronal dysfunction, manifesting itself in a variety of neurological disorders. While neuronal dysregulation is causative of symptoms manifest in the clinic, the etiology of these disorders is often more complex than simply a loss of neurons or intrinsic dysregulation of their function. In the adult brain, astrocytes comprise the most abundant cell type and play key roles in CNS physiology, therefore it stands to reason that dysregulation of normal astrocyte function contributes to the etiology and progression of varied neurological disorders. We review here some neurological disorders associated with an astrocyte factor and discuss how the related astrocyte dysfunction contributes to the etiology and/or progression of these disorders. PMID:24365571

  9. Modulation of neuritogenesis by astrocyte muscarinic receptors.

    PubMed

    Guizzetti, Marina; Moore, Nadia H; Giordano, Gennaro; Costa, Lucio G

    2008-11-14

    Astrocytes have been shown to release factors that have promoting or inhibiting effects on neuronal development. However, mechanisms controlling the release of such factors from astrocytes are not well established. Astrocytes express muscarinic receptors whose activation stimulates a robust intracellular signaling, although the role of these receptors in glial cells is not well understood. Acetylcholine and acetylcholine receptors are present in the brain before synaptogenesis occurs and are believed to be involved in neuronal maturation. The present study was undertaken to investigate whether stimulation of muscarinic receptors in astrocytes would modulate neurite outgrowth in hippocampal neurons. Rat hippocampal neurons, co-cultured with rat cortical astrocytes previously exposed to the cholinergic agonist carbachol, displayed longer neurites. The effect of carbachol in astrocytes was due to the activation of M3 muscarinic receptors. Exposure of astrocytes to carbachol increased the expression of the extracellular matrix proteins fibronectin and laminin-1 in these cells. This effect was mediated in part by an increase in laminin-1 and fibronectin mRNA levels and in part by the up-regulation of the production and release of plasminogen activator inhibitor-1, an inhibitor of the proteolytic degradation of the extracellular matrix. The inhibition of fibronectin activity strongly reduced the effect of carbachol on the elongation of all the neurites, whereas inhibition of laminin-1 activity reduced the elongation of minor neurites only. Plasminogen activator inhibitor-1 also induced neurite elongation through a direct effect on neurons. Taken together, these results demonstrate that cholinergic muscarinic stimulation of astrocytes induces the release of permissive factors that accelerate neuronal development.

  10. Impaired Autophagy in APOE4 Astrocytes.

    PubMed

    Simonovitch, Shira; Schmukler, Eran; Bespalko, Alina; Iram, Tal; Frenkel, Dan; Holtzman, David M; Masliah, Eliezer; Michaelson, Danny M; Pinkas-Kramarski, Ronit

    2016-01-01

    Alzheimer's disease (AD) is the most prevalent form of dementia in elderly. Genetic studies revealed allelic segregation of the apolipoprotein E (ApoE) gene in sporadic AD and in families with higher risk of AD. The mechanisms underlying the pathological effects of ApoE4 are not yet entirely clear. Several studies indicate that autophagy, which plays an important role in degradation pathways of proteins, organelles and protein aggregates, may be impaired in AD. In the present study, we investigated the effects of ApoE4 versus the ApoE3 isoform on the process of autophagy in mouse-derived astrocytes. The results obtained reveal that under several autophagy-inducing conditions, astrocytes expressing ApoE4 exhibit lower autophagic flux compared to astrocytes expressing ApoE3. Using an in situ model, we examined the role of autophagy and the effects thereon of ApoE4 in the elimination of Aβ plaques from isolated brain sections of transgenic 5xFAD mice. This revealed that ApoE4 astrocytes eliminate Aβ plaques less effectively than the corresponding ApoE3 astrocytes. Additional experiments showed that the autophagy inducer, rapamycin, enhances Aβ plaque degradation by ApoE4 astrocytes whereas the autophagy inhibitor, chloroquine, blocks Aβ plaque degradation by ApoE3 astrocytes. Taken together, these findings show that ApoE4 impairs autophagy in astrocyte cultures and that this effect is associated with reduced capacity to clear Aβ plaques. This suggests that impaired autophagy may play a role in mediating the pathological effects of ApoE4 in AD.

  11. Altered astrocytic swelling in the cortex of α-syntrophin-negative GFAP/EGFP mice.

    PubMed

    Anderova, Miroslava; Benesova, Jana; Mikesova, Michaela; Dzamba, David; Honsa, Pavel; Kriska, Jan; Butenko, Olena; Novosadova, Vendula; Valihrach, Lukas; Kubista, Mikael; Dmytrenko, Lesia; Cicanic, Michal; Vargova, Lydia

    2014-01-01

    Brain edema accompanying ischemic or traumatic brain injuries, originates from a disruption of ionic/neurotransmitter homeostasis that leads to accumulation of K(+) and glutamate in the extracellular space. Their increased uptake, predominantly provided by astrocytes, is associated with water influx via aquaporin-4 (AQP4). As the removal of perivascular AQP4 via the deletion of α-syntrophin was shown to delay edema formation and K(+) clearance, we aimed to elucidate the impact of α-syntrophin knockout on volume changes in individual astrocytes in situ evoked by pathological stimuli using three dimensional confocal morphometry and changes in the extracellular space volume fraction (α) in situ and in vivo in the mouse cortex employing the real-time iontophoretic method. RT-qPCR profiling was used to reveal possible differences in the expression of ion channels/transporters that participate in maintaining ionic/neurotransmitter homeostasis. To visualize individual astrocytes in mice lacking α-syntrophin we crossbred GFAP/EGFP mice, in which the astrocytes are labeled by the enhanced green fluorescent protein under the human glial fibrillary acidic protein promoter, with α-syntrophin knockout mice. Three-dimensional confocal morphometry revealed that α-syntrophin deletion results in significantly smaller astrocyte swelling when induced by severe hypoosmotic stress, oxygen glucose deprivation (OGD) or 50 mM K(+). As for the mild stimuli, such as mild hypoosmotic or hyperosmotic stress or 10 mM K(+), α-syntrophin deletion had no effect on astrocyte swelling. Similarly, evaluation of relative α changes showed a significantly smaller decrease in α-syntrophin knockout mice only during severe pathological conditions, but not during mild stimuli. In summary, the deletion of α-syntrophin markedly alters astrocyte swelling during severe hypoosmotic stress, OGD or high K(+). PMID:25426721

  12. Altered Astrocytic Swelling in the Cortex of α-Syntrophin-Negative GFAP/EGFP Mice

    PubMed Central

    Anderova, Miroslava; Benesova, Jana; Mikesova, Michaela; Dzamba, David; Honsa, Pavel; Kriska, Jan; Butenko, Olena; Novosadova, Vendula; Valihrach, Lukas; Kubista, Mikael; Dmytrenko, Lesia; Cicanic, Michal; Vargova, Lydia

    2014-01-01

    Brain edema accompanying ischemic or traumatic brain injuries, originates from a disruption of ionic/neurotransmitter homeostasis that leads to accumulation of K+ and glutamate in the extracellular space. Their increased uptake, predominantly provided by astrocytes, is associated with water influx via aquaporin-4 (AQP4). As the removal of perivascular AQP4 via the deletion of α-syntrophin was shown to delay edema formation and K+ clearance, we aimed to elucidate the impact of α-syntrophin knockout on volume changes in individual astrocytes in situ evoked by pathological stimuli using three dimensional confocal morphometry and changes in the extracellular space volume fraction (α) in situ and in vivo in the mouse cortex employing the real-time iontophoretic method. RT-qPCR profiling was used to reveal possible differences in the expression of ion channels/transporters that participate in maintaining ionic/neurotransmitter homeostasis. To visualize individual astrocytes in mice lacking α-syntrophin we crossbred GFAP/EGFP mice, in which the astrocytes are labeled by the enhanced green fluorescent protein under the human glial fibrillary acidic protein promoter, with α-syntrophin knockout mice. Three-dimensional confocal morphometry revealed that α-syntrophin deletion results in significantly smaller astrocyte swelling when induced by severe hypoosmotic stress, oxygen glucose deprivation (OGD) or 50 mM K+. As for the mild stimuli, such as mild hypoosmotic or hyperosmotic stress or 10 mM K+, α-syntrophin deletion had no effect on astrocyte swelling. Similarly, evaluation of relative α changes showed a significantly smaller decrease in α-syntrophin knockout mice only during severe pathological conditions, but not during mild stimuli. In summary, the deletion of α-syntrophin markedly alters astrocyte swelling during severe hypoosmotic stress, OGD or high K+. PMID:25426721

  13. S100b counteracts effects of the neurotoxicant trimethyltin on astrocytes and microglia.

    PubMed

    Reali, Camilla; Scintu, Franca; Pillai, Rita; Donato, Rosario; Michetti, Fabrizio; Sogos, Valeria

    2005-09-01

    Central nervous system degenerative diseases are often characterized by an early, strong reaction of astrocytes and microglia. Both these cell types can play a double role, protecting neurons against degeneration through the synthesis and secretion of trophic factors or inducing degeneration through the secretion of toxic molecules. Therefore, we studied the effects of S100B and trimethyltin (TMT) on human astrocytes and microglia with two glial models, primary cultures of human fetal astrocytes and a microglia cell line. After treatment with 10(-5) M TMT, astrocytes showed morphological alterations associated with an increase in glial fibrillary acidic protein (GFAP) expression and changes in GFAP filament organization. Administration of S100B before TMT treatment prevented TMT-induced changes in morphology and GFAP expression. A decrease in inducible nitric oxide synthase expression was observed in astrocytes treated with TMT, whereas the same treatment induced iNOS expression in microglia. In both cases, S100B prevented TMT-induced changes. Tumor necrosis factor-alpha mRNA expression in astrocytes was not modified by TMT treatment, whereas it was increased in microglia cells. S100B pretreatment blocked the TMT-induced increase in TNF-alpha expression in microglia. To trace the mechanisms involved in S100B activity, the effect of BAY 11-7082, an inhibitor of nuclear factor-kappaB (NF-kappaB) activation, and of PD98059, an inhibitor of MEK-ERK1/2, were investigated. Results showed that the protective effects of S100B against TMT toxicity in astrocytes depend on NF-kappaB, but not on ERK1/2 activation. These results might help in understanding the role played by glial cells in brain injury after exposure to chemical neurotoxicants and support the view that S100B may protect brain cells in case of injury. (c) 2005 Wiley-Liss, Inc.

  14. Exocytosis of gliotransmitters from cortical astrocytes: implications for synaptic plasticity and aging.

    PubMed

    Lalo, Ulyana; Rasooli-Nejad, Seyed; Pankratov, Yuriy

    2014-10-01

    Maintaining brain function during aging is very important for mental and physical health. Recent studies showed a crucial importance of communication between two major types of brain cells: neurons transmitting electrical signals, and glial cells, which maintain the well-being and function of neurons. Still, the study of age-related changes in neuron-glia signalling is far from complete. We have shown previously that cortical astrocytes are capable of releasing ATP by a quantal soluble N-ethylmaleimide-sensitive factor-attachment protein receptor (SNARE) complex-dependent mechanism. Release of ATP from cortical astrocytes can be activated via various pathways, including direct UV-uncaging of intracellular Ca²⁺ or G-protein-coupled receptors. Importantly, release of both ATP and glutamate from neocortical astrocytes was not observed in brain slices of dominant-negative SNARE (dnSNARE) mice, expressing dnSNARE domain selectively in astrocytes. We also discovered that astrocyte-driven ATP can cause significant attenuation of synaptic inhibition in the pyramidal neurons via Ca²⁺-interaction between the neuronal ATP and γ-aminobutyric acid (GABA) receptors. Furthermore, we showed that astrocyte-derived ATP can facilitate the induction of long-term potentiation of synaptic plasticity in the neocortex. Our recent data have shown that an age-related decrease in the astroglial Ca²⁺ signalling can cause a substantial decrease in the exocytosis of gliotransmitters, in particular ATP. Age-related impairment of ATP release from cortical astrocytes can cause a decrease in the extent of astroglial modulation of synaptic transmission in the neocortex and can therefore contribute to the age-related impairment of synaptic plasticity and cognitive decline. Combined, our results strongly support the physiological relevance of glial exocytosis for glia-neuron communications and brain function. PMID:25233403

  15. 6-Hydroxydopamine and lipopolysaccharides induced DNA damage in astrocytes: involvement of nitric oxide and mitochondria.

    PubMed

    Gupta, Sonam; Goswami, Poonam; Biswas, Joyshree; Joshi, Neeraj; Sharma, Sharad; Nath, C; Singh, Sarika

    2015-01-15

    The present study was conducted to investigate the effect of the neurotoxins 6-hydroxydopamine and lipopolysaccharide on astrocytes. Rat astrocyte C6 cells were treated with different concentration of 6-hydroxydopamine (6-OHDA)/lipopolysaccharides (LPS) for 24 h. Both neurotoxins significantly decreased the viability of astrocytes, augmented the expression of inducible nitric oxide synthase (iNOS) and the astrocyte marker--glial fibrillar acidic protein. A significantly decreased mitochondrial dehydrogenase activity, mitochondrial membrane potential, augmented reactive oxygen species (ROS) level, caspase-3 mRNA level, chromatin condensation and DNA damage was observed in 6-OHDA/LPS treated astroglial cells. 6-OHDA/LPS treatment also caused the significantly increased expression of iNOS and nitrite level. Findings showed that 6-OHDA/LPS treatment caused mitochondrial dysfunction mediated death of astrocytes, which significantly involve the nitric oxide. Since we have observed significantly increased level of iNOS along with mitochondrial impairment and apoptotic cell death in astrocytes, therefore to validate the role of iNOS, the cells were co-treated with iNOS inhibitor aminoguanidine (AG, 100 μM). Co-treatment of AG significantly attenuated the 6-OHDA/LPS induced cell death, mitochondrial activity, augmented ROS level, chromatin condensation and DNA damage. GFAP and caspase-3 expression were also inhibited with co-treatment of AG, although the extent of inhibition was different in both experimental sets. In conclusion, the findings showed that iNOS mediated increased level of nitric oxide acts as a key regulatory molecule in 6-OHDA/LPS induced mitochondrial dysfunction, DNA damage and apoptotic death of astrocytes.

  16. PAR1-Activated Astrocytes in the Nucleus of the Solitary Tract Stimulate Adjacent Neurons via NMDA Receptors

    PubMed Central

    Vance, Katie M.; Rogers, Richard C.

    2015-01-01

    Severe autonomic dysfunction, including the loss of control of the cardiovascular, respiratory, and gastrointestinal systems, is a common comorbidity of stroke and other bleeding head injuries. Previous studies suggest that this collapse of autonomic control may be caused by thrombin acting on astrocytic protease-activated receptors (PAR1) in the hindbrain. Using calcium imaging and electrophysiological techniques, we evaluated the mechanisms by which astrocytic PAR1s modulate the activity of presynaptic vagal afferent terminals and postsynaptic neurons in the rat nucleus of the solitary tract (NST). Our calcium-imaging data show that astrocytic and neuronal calcium levels increase after brain slices are treated with the PAR1 agonist SFLLRN-NH2. This increase in activity is blocked by pretreating the slices with the glial metabolic blocker fluorocitrate. In addition, PAR1-activated astrocytes communicate directly with NST neurons by releasing glutamate. Calcium responses to SFLLRN-NH2 in the astrocytes and neurons significantly increase after bath application of the excitatory amino acid transporter blocker dl-threo-β-benzyloxyaspartic acid (TBOA) and significantly decrease after bath application of the NMDA receptor antagonist dl-2-amino-5-phosphonopentanoic acid (dl-AP5). Furthermore, astrocytic glutamate activates neuronal GluN2B-containing NMDA receptors. Voltage-clamp recordings of miniature EPSCs (mEPSCs) from NST neurons show that astrocytes control presynaptic vagal afferent excitability directly under resting and activated conditions. Fluorocitrate significantly decreases mEPSC frequency and SFLLRN-NH2 significantly increases mEPSC frequency. These data show that astrocytes act within a tripartite synapse in the NST, controlling the excitability of both postsynaptic NST neurons and presynaptic vagal afferent terminals. PMID:25589770

  17. PAR1-activated astrocytes in the nucleus of the solitary tract stimulate adjacent neurons via NMDA receptors.

    PubMed

    Vance, Katie M; Rogers, Richard C; Hermann, Gerlinda E

    2015-01-14

    Severe autonomic dysfunction, including the loss of control of the cardiovascular, respiratory, and gastrointestinal systems, is a common comorbidity of stroke and other bleeding head injuries. Previous studies suggest that this collapse of autonomic control may be caused by thrombin acting on astrocytic protease-activated receptors (PAR1) in the hindbrain. Using calcium imaging and electrophysiological techniques, we evaluated the mechanisms by which astrocytic PAR1s modulate the activity of presynaptic vagal afferent terminals and postsynaptic neurons in the rat nucleus of the solitary tract (NST). Our calcium-imaging data show that astrocytic and neuronal calcium levels increase after brain slices are treated with the PAR1 agonist SFLLRN-NH2. This increase in activity is blocked by pretreating the slices with the glial metabolic blocker fluorocitrate. In addition, PAR1-activated astrocytes communicate directly with NST neurons by releasing glutamate. Calcium responses to SFLLRN-NH2 in the astrocytes and neurons significantly increase after bath application of the excitatory amino acid transporter blocker DL-threo-β-benzyloxyaspartic acid (TBOA) and significantly decrease after bath application of the NMDA receptor antagonist DL-2-amino-5-phosphonopentanoic acid (DL-AP5). Furthermore, astrocytic glutamate activates neuronal GluN2B-containing NMDA receptors. Voltage-clamp recordings of miniature EPSCs (mEPSCs) from NST neurons show that astrocytes control presynaptic vagal afferent excitability directly under resting and activated conditions. Fluorocitrate significantly decreases mEPSC frequency and SFLLRN-NH2 significantly increases mEPSC frequency. These data show that astrocytes act within a tripartite synapse in the NST, controlling the excitability of both postsynaptic NST neurons and presynaptic vagal afferent terminals. PMID:25589770

  18. Characterization and astrocytic modulation of system L transporters in brain microvasculature endothelial cells.

    PubMed

    Omidi, Yadollah; Barar, Jaleh; Ahmadian, Somaieh; Heidari, Hamid Reza; Gumbleton, Mark

    2008-04-01

    Brain trafficking of amino acids is mainly mediated by amino acids transport machineries of the blood-brain barrier (BBB), where astrocytes play a key maintenance role. However, little is known about astrocytes impacts on such transport systems, in particular system L that consists of large and small neutral amino acids (NAAs) transporters, that is, LAT1/4F2hc and LAT2/4F2hc, respectively. In the current investigation, functionality and expression of system L were studied in the immortalized mouse brain microvascular endothelial b.End3 cells cocultured with astrocytes or treated with astrocyte-conditioned media (ACM). LAT2/4F2hc mediated luminal uptake of L-phenylalanine and L-leucine resulted in significantly decreased affinity of system L in b.End3 cells treated with ACM, while LAT2/4F2hc mediated luminal uptake of L-alanine remained unchanged. Gene expression analysis revealed marked upregulation of LAT1 and 4F2hc, but downregulation of LAT2 in b.End3 cells cultured with ACM. The basal to apical transport of L-phenylalanine and L-alanine appeared to be significantly greater than that of the apical to basal direction in b.End3 cells indicating an efflux functionality of system L. No marked influence was observed for transport of L-phenylalanine in b.End3 cells cocultured with astrocytes, while a slight decrease was seen for L-alanine in the basal to apical direction. Based on our findings, we propose that system L functions as influx and/or efflux transport machinery displaying a greater propensity for the outward transport of large and small NAAs. Astrocytes appeared to modulate the transcriptic expression and uptake functionalities of system L, but not the transport activities. PMID:18210381

  19. Astrocytic vesicle mobility in health and disease.

    PubMed

    Potokar, Maja; Vardjan, Nina; Stenovec, Matjaž; Gabrijel, Mateja; Trkov, Saša; Jorgačevski, Jernej; Kreft, Marko; Zorec, Robert

    2013-01-01

    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.

  20. Astrocytic Vesicle Mobility in Health and Disease

    PubMed Central

    Potokar, Maja; Vardjan, Nina; Stenovec, Matjaž; Gabrijel, Mateja; Trkov, Saša; Jorgačevski, Jernej; Kreft, Marko; Zorec, Robert

    2013-01-01

    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. PMID:23712361

  1. Astrocyte Aquaporin Dynamics in Health and Disease.

    PubMed

    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

  2. Stargazing: Monitoring subcellular dynamics of brain astrocytes.

    PubMed

    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

  3. Astrocyte Aquaporin Dynamics in Health and Disease

    PubMed Central

    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. Signal Transduction in Astrocytes during Chronic or Acute Treatment with Drugs (SSRIs, Antibipolar Drugs, GABA-ergic Drugs, and Benzodiazepines) Ameliorating Mood Disorders

    PubMed Central

    Li, Baoman; Du, Ting; Xu, Junnan; Chen, Ye; Peng, Liang

    2014-01-01

    Chronic treatment with fluoxetine or other so-called serotonin-specific reuptake inhibitor antidepressants (SSRIs) or with a lithium salt “lithium”, carbamazepine, or valproic acid, the three classical antibipolar drugs, exerts a multitude of effects on astrocytes, which in turn modulate astrocyte-neuronal interactions and brain function. In the case of the SSRIs, they are to a large extent due to 5-HT2B-mediated upregulation and editing of genes. These alterations induce alteration in effects of cPLA2, GluK2, and the 5-HT2B receptor, probably including increases in both glucose metabolism and glycogen turnover, which in combination have therapeutic effect on major depression. The ability of increased levels of extracellular K+ to increase [Ca2+]i is increased as a sign of increased K+-induced excitability in astrocytes. Acute anxiolytic drug treatment with benzodiazepines or GABAA receptor stimulation has similar glycogenolysis-enhancing effects. The antibipolar drugs induce intracellular alkalinization in astrocytes with lithium acting on one acid extruder and carbamazepine and valproic acid on a different acid extruder. They inhibit K+-induced and transmitter-induced increase of astrocytic [Ca2+]i and thereby probably excitability. In several cases, they exert different changes in gene expression than SSRIs, determined both in cultured astrocytes and in freshly isolated astrocytes from drug-treated animals. PMID:24707399

  5. Store-operated Ca2+ channels blockers inhibit lipopolysaccharide induced astrocyte activation.

    PubMed

    Li, Jian-Hua; Zhao, Shen-Ting; Wu, Cui-Ying; Cao, Xiong; Peng, Miao-Ru; Li, Shu-Ji; Liu, Xiao-Ai; Gao, Tian-Ming

    2013-10-01

    The destruction of calcium homeostasis is an important factor leading to neurological diseases. Store-operated Ca(2+) (SOC) channels are essential for Ca(2+) homeostasis in many cell types. However, whether SOC channels are involved in astrocyte activation induced by lipopolysaccharide (LPS) still remains unknown. In this study, we used LPS as an exogenous stimulation to investigate the role of SOC channels in astrocyte activation. Using calcium imaging technology, we first found that SOC channels blockers, 1-[h-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole (SKF-96365) and 2-aminoethyldiphenyl borate (2-APB), inhibited LPS induced [Ca(2+)]i increase, which prompted us to speculate that SOC channels may be involved in LPS induced astrocyte activation. Further experiments confirmed our speculation shown as SOC channels blockers inhibited LPS induced astrocyte activation characterized as cell proliferation by MTS and BrdU assay, raise in glial fibrillary acidic protein expression by immunofluorescence and Western Blot and secretion of interleukin 6 (IL-6) and interleukin 1β (IL-1β) by ELISA. So, our studies showed that SOC channels are involved in LPS-induced astrocyte activation.

  6. Neuroprotective Peptide humanin inhibits inflammatory response in astrocytes induced by lipopolysaccharide.

    PubMed

    Zhao, Shen-Ting; Zhao, Li; Li, Jian-Hua

    2013-03-01

    Humanin (HN) has been proved to be an extensive neuroprotective peptide against AD-related and unrelated insults, but little is know about the effect of HN in inflammation response. Current studies indicated the receptors of HN have a close relationship with immune system, which led us to hypothesize HN might have a role in inflammatory response. In this study, we used lipopolysaccharide (LPS) to induce astrocyte inflammation response. This model in vitro allowed us to study the effect of HN on the pure response of astrocyte without the exogenous influence between cells in vivo. Our results showed that 1.0 μg/ml LPS induced a significant activation of astrocyte, shown as the marked increase in the glial fibrillary acidic protein (GFAP) expression, the cell viability and the number of 5-bromo-2'-deoxyuridine (BrdU)-positive living cells. Pretreatment with HN (5, 10, 20 μM) led to a significant inhibition in astrocyte overactivation in a concentration dependent manner. We also found pretreatment with HN decreased the level of proinflammatory cytokines, interleukin (IL)-6, IL-1β and tumor necrosis factor α (TNFα) induced by LPS. Furthermore, we noticed HN couldn't completely reverse the above inflammatory injury. Our findings imply that HN partly antagonizes inflammation injury induced by LPS and the protective effect of HN on astrocyte is concentration-dependent.

  7. Astrocytic response in hippocampus and cerebral cortex in an experimental epilepsy model.

    PubMed

    Girardi, Elena; Ramos, Alberto Javier; Vanore, Gabriela; Brusco, Alicia

    2004-02-01

    Astrocytes are very sensitive to alterations in the brain environment and respond showing a phenomenon known as astroglial reaction. S100beta is an astroglial derived neurotrophic factor, seems to be involved in neuroplasticity. The aim of this work was to study the astrocytic response in rat hippocampus and cerebral cortex after repetitive seizures induced by 3-mercaptopropionic acid (MP) administration. Immunocytochemical studies were performed to analyze GFAP and S100beta expression. Both studied areas showed hypertrophied astrocytes with enlarged processes and increased soma size. Astrocyte hyperplasia was observed only in the cerebral cortex. A significant decrease in the astrocytic S100beta immunostaining occurs after MP treatment. These results indicate that MP administration induces an astroglial reaction with reduced intracellular S100beta level. The observed reduction in astroglial S100beta could be related to the release of this factor to the extracellular space, where it may produce neurotrophic or deleterious effects accordingly to the concentration achieved. The mechanism of this remains to be elucidated.

  8. Label-free optical activation of astrocyte in vivo

    NASA Astrophysics Data System (ADS)

    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.

  9. Dynamic transition of neuronal firing induced by abnormal astrocytic glutamate oscillation

    PubMed Central

    Li, Jiajia; Tang, Jun; Ma, Jun; Du, Mengmeng; Wang, Rong; Wu, Ying

    2016-01-01

    The gliotransmitter glutamate released from astrocytes can modulate neuronal firing by activating neuronal N-methyl-D-aspartic acid (NMDA) receptors. This enables astrocytic glutamate(AG) to be involved in neuronal physiological and pathological functions. Based on empirical results and classical neuron-glial “tripartite synapse” model, we propose a practical model to describe extracellular AG oscillation, in which the fluctuation of AG depends on the threshold of calcium concentration, and the effect of AG degradation is considered as well. We predict the seizure-like discharges under the dysfunction of AG degradation duration. Consistent with our prediction, the suppression of AG uptake by astrocytic transporters, which operates by modulating the AG degradation process, can account for the emergence of epilepsy. PMID:27573570

  10. Opioid-dependent growth of glial cultures: Suppression of astrocyte DNA synthesis by met-enkephalin

    SciTech Connect

    Stiene-Martin, A.; Hauser, K.F. )

    1990-01-01

    The action of met-enkephalin on the growth of astrocytes in mixed-glial cultures was examined. Primary, mixed-glial cultures were isolated from 1 day-old mouse cerebral hemispheres and continuously treated with either basal growth media, 1 {mu}M met-enkephalin, 1 {mu}M met-enkephalin plus the opioid antagonist naloxone, or naloxone alone. Absolute numbers of neural cells were counted in unstained preparations, while combined ({sup 3}H)-thymidine autoradiography and glial fibrillary acid protein (GFAP) immunocytochemistry was performed to identify specific changes in astrocytes. When compared to control and naloxone treated cultures, met-enkephalin caused a significant decrease in both total cell numbers, and in ({sup 3}H)-thymidine incorporation by GFAP-positive cells with flat morphology. These results indicate that met-enkephalin suppresses astrocyte growth in culture.

  11. Induction of neural stem cell-like cells (NSCLCs) from mouse astrocytes by Bmi1

    SciTech Connect

    Moon, Jai-Hee; Yoon, Byung Sun; Kim, Bona; Park, Gyuman; Jung, Hye-Youn; Maeng, Isaac; Jun, Eun Kyoung; Yoo, Seung Jun; Kim, Aeree; Oh, Sejong; Whang, Kwang Youn; Kim, Hyunggee; Kim, Dong-Wook; Kim, Ki Dong; You, Seungkwon

    2008-06-27

    Recently, Bmi1 was shown to control the proliferation and self-renewal of neural stem cells (NSCs). In this study, we demonstrated the induction of NSC-like cells (NSCLCs) from mouse astrocytes by Bmi1 under NSC culture conditions. These NSCLCs exhibited the morphology and growth properties of NSCs, and expressed NSC marker genes, including nestin, CD133, and Sox2. In vitro differentiation of NSCLCs resulted in differentiated cell populations containing astrocytes, neurons, and oligodendrocytes. Following treatment with histone deacetylase inhibitors (trichostatin A and valproic acid), the potential of NSCLCs for proliferation, dedifferentiation, and self-renewal was significantly inhibited. Our data indicate that multipotent NSCLCs can be generated directly from astrocytes by the addition of Bmi1.

  12. Dynamic transition of neuronal firing induced by abnormal astrocytic glutamate oscillation.

    PubMed

    Li, Jiajia; Tang, Jun; Ma, Jun; Du, Mengmeng; Wang, Rong; Wu, Ying

    2016-01-01

    The gliotransmitter glutamate released from astrocytes can modulate neuronal firing by activating neuronal N-methyl-D-aspartic acid (NMDA) receptors. This enables astrocytic glutamate(AG) to be involved in neuronal physiological and pathological functions. Based on empirical results and classical neuron-glial "tripartite synapse" model, we propose a practical model to describe extracellular AG oscillation, in which the fluctuation of AG depends on the threshold of calcium concentration, and the effect of AG degradation is considered as well. We predict the seizure-like discharges under the dysfunction of AG degradation duration. Consistent with our prediction, the suppression of AG uptake by astrocytic transporters, which operates by modulating the AG degradation process, can account for the emergence of epilepsy. PMID:27573570

  13. Characterization of astrocyte reactivity and gene expression on biomaterials for neural electrodes.

    PubMed

    Ereifej, Evon S; Khan, Saida; Newaz, Golam; Zhang, Jinsheng; Auner, Gregory W; VandeVord, Pamela J

    2011-10-01

    Neural electrode devices hold great promise to help people with the restoration of lost functions. However, research is lacking in the biomaterial design of a stable, long-term device. Glial scarring is initiated when a device is inserted into brain tissue and an inflammatory response ensues. Astrocytes become hypertrophic, hyperplastic, and upregulate glial-fibrillary acidic protein. This study was designed to investigate the astrocyte proliferation, viability, morphology, and gene expression to assess the reactive state of the cells on different material surfaces. Although platinum and silicon have been extensively characterized both in vivo and in vitro for their biocompatibility with neuronal cells, this study used the novel usage of PMMA and SU-8 in neural electrodes by comparative analysis of materials' biocompatibility. This study has shown evidence of noncytotoxicity of SU-8. We have also confirmed the biocompatibility of PMMA with astrocytes. Moreover, we have established sound guidelines of which neural implant materials should meet to be depicted biocompatible. PMID:21812095

  14. Dynamic transition of neuronal firing induced by abnormal astrocytic glutamate oscillation

    NASA Astrophysics Data System (ADS)

    Li, Jiajia; Tang, Jun; Ma, Jun; Du, Mengmeng; Wang, Rong; Wu, Ying

    2016-08-01

    The gliotransmitter glutamate released from astrocytes can modulate neuronal firing by activating neuronal N-methyl-D-aspartic acid (NMDA) receptors. This enables astrocytic glutamate(AG) to be involved in neuronal physiological and pathological functions. Based on empirical results and classical neuron-glial “tripartite synapse” model, we propose a practical model to describe extracellular AG oscillation, in which the fluctuation of AG depends on the threshold of calcium concentration, and the effect of AG degradation is considered as well. We predict the seizure-like discharges under the dysfunction of AG degradation duration. Consistent with our prediction, the suppression of AG uptake by astrocytic transporters, which operates by modulating the AG degradation process, can account for the emergence of epilepsy.

  15. Opiates selectively increase intracellular calcium in developing type-1 astrocytes: role of calcium in morphine-induced morphologic differentiation.

    PubMed

    Stiene-Martin, A; Mattson, M P; Hauser, K F

    1993-12-17

    Endogenous opioids and opiate drugs inhibit nervous system maturation, in part, by affecting the growth of astrocytes. Opiates inhibit astrocyte proliferation and cause premature differentiation. The emerging importance of Ca2+ in astrocyte function prompted us to explore whether opiates might affect astrocyte development by altering Ca2+ homeostasis. Astrocyte-enriched cultures were derived from newborn ICR mouse cerebra. Quantitative fluorescent measurements of intracellular free Ca2+ ([Ca2+]i) using Fura-2 as well as fluo-3 and computer-aided image analysis showed that 1 microM morphine significantly increased [Ca2+]i in flat, polyhedral, glial fibrillary acidic protein (GFAP) immunoreactive astrocytes at 2 and 6 min, and at 72 h. Co-administration of 3 microM naloxone blocked morphine-dependent increases in [Ca2+]i. Treatment with 1 microM concentrations of the kappa-opioid receptor agonist, U69,593, but not equimolar amounts of mu ([D-Ala2,MePhe4,Gly(ol)5]enkephalin)- or delta ([D-Pen2,D-Pen5]enkephalin)-opioid receptor agonists, significantly increased [Ca2+]i in astrocytes. To assess the role of Ca2+ in morphine-induced astrocyte differentiation, untreated and 1 microM morphine-treated astrocyte cultures were incubated for 5 days in < 0.01, 0.3, 1.0, or 3.0 mM extracellular Ca2+ ([Ca2+]o), or incubated with 1.0 mM [Ca2+]o in the presence of 1 microM of the Ca2+ ionophore, A23187. The areas of single astrocytes were measured and there was a positive correlation between astrocyte area and [Ca2+]o. Morphine had an additive effect on area and form factor measures when [Ca2+]o was 1.0 mM. High [Ca2+]o (3.0 mM) alone mimicked the action of morphine. Morphine alone had no effect on astrocyte area in the presence of 3.0 mM Ca2+.(ABSTRACT TRUNCATED AT 250 WORDS)

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

    PubMed Central

    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

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

    PubMed Central

    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 means of desmosomes, and to neuronal processes by means of zonulae occludens. The functional significance of these arrangements is discussed. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 PMID:7364663

  18. In vivo expression of polyglutamine-expanded huntingtin by mouse striatal astrocytes impairs glutamate transport: a correlation with Huntington's disease subjects.

    PubMed

    Faideau, Mathilde; Kim, Jinho; Cormier, Kerry; Gilmore, Richard; Welch, Mackenzie; Auregan, Gwennaelle; Dufour, Noelle; Guillermier, Martine; Brouillet, Emmanuel; Hantraye, Philippe; Déglon, Nicole; Ferrante, Robert J; Bonvento, Gilles

    2010-08-01

    Huntington's disease (HD) is a neurodegenerative disorder previously thought to be of primary neuronal origin, despite ubiquitous expression of mutant huntingtin (mHtt). We tested the hypothesis that mHtt expressed in astrocytes may contribute to the pathogenesis of HD. To better understand the contribution of astrocytes in HD in vivo, we developed a novel mouse model using lentiviral vectors that results in selective expression of mHtt into striatal astrocytes. Astrocytes expressing mHtt developed a progressive phenotype of reactive astrocytes that was characterized by a marked decreased expression of both glutamate transporters, GLAST and GLT-1, and of glutamate uptake. These effects were associated with neuronal dysfunction, as observed by a reduction in DARPP-32 and NR2B expression. Parallel studies in brain samples from HD subjects revealed early glial fibrillary acidic protein expression in striatal astrocytes from Grade 0 HD cases. Astrogliosis was associated with morphological changes that increased with severity of disease, from Grades 0 through 4 and was more prominent in the putamen. Combined immunofluorescence showed co-localization of mHtt in astrocytes in all striatal HD specimens, inclusive of Grade 0 HD. Consistent with the findings from experimental mice, there was a significant grade-dependent decrease in striatal GLT-1 expression from HD subjects. These findings suggest that the presence of mHtt in astrocytes alters glial glutamate transport capacity early in the disease process and may contribute to HD pathogenesis. PMID:20494921

  19. Evidence for a novel functional role of astrocytes in the acute homeostatic response to high-fat diet intake in mice

    PubMed Central

    Buckman, Laura B.; Thompson, Misty M.; Lippert, Rachel N.; Blackwell, Timothy S.; Yull, Fiona E.; Ellacott, Kate L.J.

    2014-01-01

    Objective Introduction of a high-fat diet to mice results in a period of voracious feeding, known as hyperphagia, before homeostatic mechanisms prevail to restore energy intake to an isocaloric level. Acute high-fat diet hyperphagia induces astrocyte activation in the rodent hypothalamus, suggesting a potential role of these cells in the homeostatic response to the diet. The objective of this study was to determine physiologic role of astrocytes in the acute homeostatic response to high-fat feeding. Methods We bred a transgenic mouse model with doxycycline-inducible inhibition of NFkappaB (NFκB) signaling in astrocytes to determine the effect of loss of NFκB-mediated astrocyte activation on acute high-fat hyperphagia. ELISA was used to measure the levels of markers of astrocyte activation, glial-fibrillary acidic protein (GFAP) and S100B, in the medial basal hypothalamus. Results Inhibition of NFκB signaling in astrocytes prevented acute high-fat diet-induced astrocyte activation and resulted in a 15% increase in caloric intake (P < 0.01) in the first 24 h after introduction of the diet. Conclusions These data reveal a novel homeostatic role for astrocytes in the acute physiologic regulation of food intake in response to high-fat feeding. PMID:25685690

  20. 4-Hydroxyhexenal (HHE) impairs glutamate transport in astrocyte cultures.

    PubMed

    Lovell, Mark A; Bradley, Melissa A; Fister, Shuling X

    2012-01-01

    Multiple studies show elevations of α,β-unsaturated aldehydic by-products of lipid peroxidation including 4-hydroxynonenal and acrolein in vulnerable brain regions of subjects throughout the progression of Alzheimer's disease (AD). More recently 4-hydroxyhexenal (HHE), a diffusible α,β-unsaturated aldehyde resulting from peroxidation of ω-3 polyunsaturated fatty acids, was shown to be elevated in the hippocampus/parahippocampal gyrus (HPG) of subjects with preclinical AD (PCAD) and in late stage AD (LAD). HHE treatment of primary rat cortical neuron cultures led to a time- and concentration-dependent decrease in survival and glucose uptake. To determine if HHE also impairs glutamate uptake, primary rat astrocyte cultures were exposed to HHE for 4 hours and glutamate transport measured. Results show subtoxic (2.5 μM) HHE concentrations significantly (p < 0.05) impair glutamate uptake in primary astrocytes. Immunoprecipitation of excitatory amino acid transporter-2 (EAAT-2), the primary glutamate transporter in brain, from normal control, mild cognitive impairment (MCI), PCAD, and LAD HPG followed by quantification of HHE immunolabeling showed a significant increase in HHE positive EAAT-2 in MCI and LAD HPG. Together these data suggest HHE can significantly impair glutamate uptake and may play a role in the pathogenesis of AD. PMID:22766736

  1. Sodium signaling and astrocyte energy metabolism.

    PubMed

    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

  2. Spinal astrocytes produce and secrete dynorphin neuropeptides.

    PubMed

    Wahlert, Andrew; Funkelstein, Lydiane; Fitzsimmons, Bethany; Yaksh, Tony; Hook, Vivian

    2013-04-01

    Dynorphin peptide neurotransmitters (neuropeptides) have been implicated in spinal pain processing based on the observations that intrathecal delivery of dynorphin results in proalgesic effects and disruption of extracellular dynorphin activity (by antisera) prevents injury evoked hyperalgesia. However, the cellular source of secreted spinal dynorphin has been unknown. For this reason, this study investigated the expression and secretion of dynorphin-related neuropeptides from spinal astrocytes (rat) in primary culture. Dynorphin A (1-17), dynorphin B, and α-neoendorphin were found to be present in the astrocytes, illustrated by immunofluorescence confocal microscopy, in a discrete punctate pattern of cellular localization. Measurement of astrocyte cellular levels of these dynorphins by radioimmunoassays confirmed the expression of these three dynorphin-related neuropeptides. Notably, BzATP (3'-O-(4-benzoyl)benzoyl adenosine 5'-triphosphate) and KLA (di[3-deoxy-D-manno-octulosonyl]-lipid A) activation of purinergic and toll-like receptors, respectively, resulted in stimulated secretion of dynorphins A and B. However, α-neoendorphin secretion was not affected by BzATP or KLA. These findings suggest that dynorphins A and B undergo regulated secretion from spinal astrocytes. These findings also suggest that spinal astrocytes may provide secreted dynorphins that participate in spinal pain processing.

  3. Unraveling the complex metabolic nature of astrocytes.

    PubMed

    Bouzier-Sore, Anne-Karine; Pellerin, Luc

    2013-01-01

    Since the initial description of astrocytes by neuroanatomists of the nineteenth century, a critical metabolic role for these cells has been suggested in the central nervous system. Nonetheless, it took several technological and conceptual advances over many years before we could start to understand how they fulfill such a role. One of the important and early recognized metabolic function of astrocytes concerns the reuptake and recycling of the neurotransmitter glutamate. But the description of this initial property will be followed by several others including an implication in the supply of energetic substrates to neurons. Indeed, despite the fact that like most eukaryotic non-proliferative cells, astrocytes rely on oxidative metabolism for energy production, they exhibit a prominent aerobic glycolysis capacity. Moreover, this unusual metabolic feature was found to be modulated by glutamatergic activity constituting the initial step of the neurometabolic coupling mechanism. Several approaches, including biochemical measurements in cultured cells, genetic screening, dynamic cell imaging, nuclear magnetic resonance spectroscopy and mathematical modeling, have provided further insights into the intrinsic characteristics giving rise to these key features of astrocytes. This review will provide an account of the different results obtained over several decades that contributed to unravel the complex metabolic nature of astrocytes that make this cell type unique.

  4. Unraveling the complex metabolic nature of astrocytes

    PubMed Central

    Bouzier-Sore, Anne-Karine; Pellerin, Luc

    2013-01-01

    Since the initial description of astrocytes by neuroanatomists of the nineteenth century, a critical metabolic role for these cells has been suggested in the central nervous system. Nonetheless, it took several technological and conceptual advances over many years before we could start to understand how they fulfill such a role. One of the important and early recognized metabolic function of astrocytes concerns the reuptake and recycling of the neurotransmitter glutamate. But the description of this initial property will be followed by several others including an implication in the supply of energetic substrates to neurons. Indeed, despite the fact that like most eukaryotic non-proliferative cells, astrocytes rely on oxidative metabolism for energy production, they exhibit a prominent aerobic glycolysis capacity. Moreover, this unusual metabolic feature was found to be modulated by glutamatergic activity constituting the initial step of the neurometabolic coupling mechanism. Several approaches, including biochemical measurements in cultured cells, genetic screening, dynamic cell imaging, nuclear magnetic resonance spectroscopy and mathematical modeling, have provided further insights into the intrinsic characteristics giving rise to these key features of astrocytes. This review will provide an account of the different results obtained over several decades that contributed to unravel the complex metabolic nature of astrocytes that make this cell type unique. PMID:24130515

  5. Disentangling the Role of Astrocytes in Alcohol Use Disorder.

    PubMed

    Adermark, Louise; Bowers, M Scott

    2016-09-01

    Several laboratories recently identified that astrocytes are critical regulators of addiction machinery. It is now known that astrocyte pathology is a common feature of ethanol (EtOH) exposure in both humans and animal models, as even brief EtOH exposure is sufficient to elicit long-lasting perturbations in astrocyte gene expression, activity, and proliferation. Astrocytes were also recently shown to modulate the motivational properties of EtOH and other strongly reinforcing stimuli. Given the role of astrocytes in regulating glutamate homeostasis, a crucial component of alcohol use disorder (AUD), astrocytes might be an important target for the development of next-generation alcoholism treatments. This review will outline some of the more prominent features displayed by astrocytes, how these properties are influenced by acute and long-term EtOH exposure, and future directions that may help to disentangle astrocytic from neuronal functions in the etiology of AUD. PMID:27476876

  6. Molecular approaches for manipulating astrocytic signaling in vivo

    PubMed Central

    Xie, Alison X.; Petravicz, Jeremy; McCarthy, Ken D.

    2015-01-01

    Astrocytes are the predominant glial type in the central nervous system and play important roles in assisting neuronal function and network activity. Astrocytes exhibit complex signaling systems that are essential for their normal function and the homeostasis of the neural network. Altered signaling in astrocytes is closely associated with neurological and psychiatric diseases, suggesting tremendous therapeutic potential of these cells. To further understand astrocyte function in health and disease, it is important to study astrocytic signaling in vivo. In this review, we discuss molecular tools that enable the selective manipulation of astrocytic signaling, including the tools to selectively activate and inactivate astrocyte signaling in vivo. Lastly, we highlight a few tools in development that present strong potential for advancing our understanding of the role of astrocytes in physiology, behavior, and pathology. PMID:25941472

  7. Disentangling the Role of Astrocytes in Alcohol Use Disorder.

    PubMed

    Adermark, Louise; Bowers, M Scott

    2016-09-01

    Several laboratories recently identified that astrocytes are critical regulators of addiction machinery. It is now known that astrocyte pathology is a common feature of ethanol (EtOH) exposure in both humans and animal models, as even brief EtOH exposure is sufficient to elicit long-lasting perturbations in astrocyte gene expression, activity, and proliferation. Astrocytes were also recently shown to modulate the motivational properties of EtOH and other strongly reinforcing stimuli. Given the role of astrocytes in regulating glutamate homeostasis, a crucial component of alcohol use disorder (AUD), astrocytes might be an important target for the development of next-generation alcoholism treatments. This review will outline some of the more prominent features displayed by astrocytes, how these properties are influenced by acute and long-term EtOH exposure, and future directions that may help to disentangle astrocytic from neuronal functions in the etiology of AUD.

  8. Neuroinflammatory TNFα Impairs Memory via Astrocyte Signaling.

    PubMed

    Habbas, Samia; Santello, Mirko; Becker, Denise; Stubbe, Hiltrud; Zappia, Giovanna; Liaudet, Nicolas; Klaus, Federica R; Kollias, George; Fontana, Adriano; Pryce, Christopher R; Suter, Tobias; Volterra, Andrea

    2015-12-17

    The occurrence of cognitive disturbances upon CNS inflammation or infection has been correlated with increased levels of the cytokine tumor necrosis factor-α (TNFα). To date, however, no specific mechanism via which this cytokine could alter cognitive circuits has been demonstrated. Here, we show that local increase of TNFα in the hippocampal dentate gyrus activates astrocyte TNF receptor type 1 (TNFR1), which in turn triggers an astrocyte-neuron signaling cascade that results in persistent functional modification of hippocampal excitatory synapses. Astrocytic TNFR1 signaling is necessary for the hippocampal synaptic alteration and contextual learning-memory impairment observed in experimental autoimmune encephalitis (EAE), an animal model of multiple sclerosis (MS). This process may contribute to the pathogenesis of cognitive disturbances in MS, as well as in other CNS conditions accompanied by inflammatory states or infections. PMID:26686654

  9. Activity-dependent regulation of astrocyte GAT levels during synaptogenesis.

    PubMed

    Muthukumar, Allie K; Stork, Tobias; Freeman, Marc R

    2014-10-01

    Astrocytic uptake of GABA through GABA transporters (GATs) is an important mechanism regulating excitatory/inhibitory balance in the nervous system; however, mechanisms by which astrocytes regulate GAT levels are undefined. We found that at mid-pupal stages the Drosophila melanogaster CNS neuropil was devoid of astrocyte membranes and synapses. Astrocyte membranes subsequently infiltrated the neuropil coordinately with synaptogenesis, and astrocyte ablation reduced synapse numbers by half, indicating that Drosophila astrocytes are pro-synaptogenic. Shortly after synapses formed in earnest, GAT was upregulated in astrocytes. Ablation or silencing of GABAergic neurons or disruption of metabotropic GABA receptor 1 and 2 (GABA(B)R1/2) signaling in astrocytes led to a decrease in astrocytic GAT. Notably, developmental depletion of astrocytic GABA(B)R1/2 signaling suppressed mechanosensory-induced seizure activity in mutants with hyperexcitable neurons. These data reveal that astrocytes actively modulate GAT expression via metabotropic GABA receptor signaling and highlight the importance of precise regulation of astrocytic GAT in modulation of seizure activity.

  10. Antioxidants and NOS inhibitors selectively targets manganese-induced cell volume via Na-K-Cl cotransporter-1 in astrocytes.

    PubMed

    Alahmari, Khalid A; Prabhakaran, Harini; Prabhakaran, Krishnan; Chandramoorthy, Harish C; Ramugounder, Ramakrishnan

    2015-06-12

    Manganese has shown to be involved in astrocyte swelling. Several factors such as transporters, exchangers and ion channels are attributed to astrocyte swelling as a result in the deregulation of cell volume. Products of oxidation and nitration have been implied to be involved in the pathophysiology of swelling; however, the direct link and mechanism of manganese induced astrocyte swelling has not been fully elucidated. In the current study, we used rat primary astrocyte cultures to investigate the activation of Na-K-Cl cotransporter-1 (NKCC1) a downstream mechanism for free radical induced astrocyte swelling as a result of manganese toxicity. Our results showed manganese, oxidants and NO donors as potent inducer of oxidation and nitration of NKCC1. Our results further confirmed that manganese (50 μM) increased the total protein, phosphorylation and activity of NKCC1 as well as cell volume (p < 0.05 vs. control). NKCC1 inhibitor (bumetanide), NKCC1-siRNA, antioxidants; DMTU, MnTBAP, tempol, catalase and Vit-E, NOS inhibitor; L-NAME, peroxinitrite scavenger; uric acid all significantly reversed the effects of NKCC1 activation (p < 0.05). From the current investigation we infer that manganese or oxidants and NO induced activation, oxidation/nitration of NKCC1 play an important role in the astrocyte swelling.

  11. Evidence for a role of proline and hypothalamic astrocytes in the regulation of glucose metabolism in rats.

    PubMed

    Arrieta-Cruz, Isabel; Su, Ya; Knight, Colette M; Lam, Tony K T; Gutiérrez-Juárez, Roger

    2013-04-01

    The metabolism of lactate to pyruvate in the mediobasal hypothalamus (MBH) regulates hepatic glucose production. Because astrocytes and neurons are functionally linked by metabolic coupling through lactate transfer via the astrocyte-neuron lactate shuttle (ANLS), we reasoned that astrocytes might be involved in the hypothalamic regulation of glucose metabolism. To examine this possibility, we used the gluconeogenic amino acid proline, which is metabolized to pyruvate in astrocytes. Our results showed that increasing the availability of proline in rats either centrally (MBH) or systemically acutely lowered blood glucose. Pancreatic clamp studies revealed that this hypoglycemic effect was due to a decrease of hepatic glucose production secondary to an inhibition of glycogenolysis, gluconeogenesis, and glucose-6-phosphatase flux. The effect of proline was mimicked by glutamate, an intermediary of proline metabolism. Interestingly, proline's action was markedly blunted by pharmacological inhibition of hypothalamic lactate dehydrogenase (LDH) suggesting that metabolic flux through LDH was required. Furthermore, short hairpin RNA-mediated knockdown of hypothalamic LDH-A, an astrocytic component of the ANLS, also blunted the glucoregulatory action of proline. Thus our studies suggest not only a new role for proline in the regulation of hepatic glucose production but also indicate that hypothalamic astrocytes are involved in the regulatory mechanism as well. PMID:23274895

  12. Mdivi-1 Inhibits Astrocyte Activation and Astroglial Scar Formation and Enhances Axonal Regeneration after Spinal Cord Injury in Rats

    PubMed Central

    Li, Gang; Cao, Yang; Shen, Feifei; Wang, Yangsong; Bai, Liangjie; Guo, Weidong; Bi, Yunlong; Lv, Gang; Fan, Zhongkai

    2016-01-01

    After spinal cord injury (SCI), astrocytes become hypertrophic, and proliferative, forming a dense network of astroglial processes at the site of the lesion. This constitutes a physical and biochemical barrier to axonal regeneration. Mitochondrial fission regulates cell cycle progression; inhibiting the cell cycle of astrocytes can reduce expression levels of axon growth-inhibitory molecules as well as astroglial scar formation after SCI. We therefore investigated how an inhibitor of mitochondrial fission, Mdivi-1, would affect astrocyte proliferation, astroglial scar formation, and axonal regeneration following SCI in rats. Western blot and immunofluorescent double-labeling showed that Mdivi-1 markedly reduced the expression of the astrocyte marker glial fibrillary acidic protein (GFAP), and a cell proliferation marker, proliferating cell nuclear antigen, in astrocytes 3 days after SCI. Moreover, Mdivi-1 decreased the expression of GFAP and neurocan, a chondroitin sulfate proteoglycan. Notably, immunofluorescent labeling and Nissl staining showed that Mdivi-1 elevated the production of growth-associated protein-43 and increased neuronal survival at 4 weeks after SCI. Finally, hematoxylin-eosin staining, and behavioral evaluation of motor function indicated that Mdivi-1 also reduced cavity formation and improved motor function 4 weeks after SCI. Our results confirm that Mdivi-1 promotes motor function after SCI, and indicate that inhibiting mitochondrial fission using Mdivi-1 can inhibit astrocyte activation and astroglial scar formation and contribute to axonal regeneration after SCI in rats. PMID:27807407

  13. Sustained Na+/H+ exchanger activation promotes gliotransmitter release from reactive hippocampal astrocytes following oxygen-glucose deprivation.

    PubMed

    Cengiz, Pelin; Kintner, Douglas B; Chanana, Vishal; Yuan, Hui; Akture, Erinc; Kendigelen, Pinar; Begum, Gulnaz; Fidan, Emin; Uluc, Kutluay; Ferrazzano, Peter; Sun, Dandan

    2014-01-01

    Hypoxia ischemia (HI)-related brain injury is the major cause of long-term morbidity in neonates. One characteristic hallmark of neonatal HI is the development of reactive astrogliosis in the hippocampus. However, the impact of reactive astrogliosis in hippocampal damage after neonatal HI is not fully understood. In the current study, we investigated the role of Na(+)/H(+) exchanger isoform 1 (NHE1) protein in mouse reactive hippocampal astrocyte function in an in vitro ischemia model (oxygen/glucose deprivation and reoxygenation, OGD/REOX). 2 h OGD significantly increased NHE1 protein expression and NHE1-mediated H(+) efflux in hippocampal astrocytes. NHE1 activity remained stimulated during 1-5 h REOX and returned to the basal level at 24 h REOX. NHE1 activation in hippocampal astrocytes resulted in intracellular Na(+) and Ca(2+) overload. The latter was mediated by reversal of Na(+)/Ca(2+) exchange. Hippocampal astrocytes also exhibited a robust release of gliotransmitters (glutamate and pro-inflammatory cytokines IL-6 and TNFα) during 1-24 h REOX. Interestingly, inhibition of NHE1 activity with its potent inhibitor HOE 642 not only reduced Na(+) overload but also gliotransmitter release from hippocampal astrocytes. The noncompetitive excitatory amino acid transporter inhibitor TBOA showed a similar effect on blocking the glutamate release. Taken together, we concluded that NHE1 plays an essential role in maintaining H(+) homeostasis in hippocampal astrocytes. Over-stimulation of NHE1 activity following in vitro ischemia disrupts Na(+) and Ca(2+) homeostasis, which reduces Na(+)-dependent glutamate uptake and promotes release of glutamate and cytokines from reactive astrocytes. Therefore, blocking sustained NHE1 activation in reactive astrocytes may provide neuroprotection following HI.

  14. Differential response of GFAP-positive astrocytes in the rat prefrontal cortex following ethanol self-administration

    PubMed Central

    Bull, Cecilia; Syed, Wahab A.; Minter, Sabrina C.; Bowers, M. Scott

    2015-01-01

    Background Prefrontal cortex (PFC) dysfunction is believed to contribute to the transition from controlled substance use to abuse. Because astrocytes have been suggested to play a key role in the development and maintenance of drug-seeking behaviors, we sought to determine if PFC astrocytes are affected by ethanol self-administration. Methods Ethanol consumption was modeled in rats by three self-administration paradigms where ethanol was made concurrently available with water in the home cage either continuously (CEA) or intermittently (IEA). In the third paradigm, ethanol was only available in the operant chamber (OEA). To avoid the potential confound of acute ethanol effects, all rats were sacrificed either 24 h or 3 wks abstinence. In all groups, the effect of ethanol consumption on PFC astrocytes was measured using unbiased stereological counting of cells expressing the astrocyte marker glial fibrillary acidic protein (GFAP). GFAP immunoreactivity commonly changes in response to pharmacological insult or injury. Results GFAP-positive astrocyte number increased in the prelimbic and anterior cingulate cortex regions of the PFC after IEA. No change was found in the infralimbic or orbitofrontal cortex after IEA. After 3 weeks abstinence, there was a reduction of astrocytes in the prelimbic and orbitofrontal cortex of the CEA cohort as well as a reduction in the orbitofrontal cortex of the OEA cohort. Conclusion These findings demonstrate that discrete PFC subregions contain GFAP-positive astrocyte populations that respond differentially to distinct ethanol consumption paradigms. A better understanding of how specific astrocyte populations uniquely adapt to ethanol consumption could provide insight for targeted therapeutic interventions. PMID:25833026

  15. Deletion of Monoglyceride Lipase in Astrocytes Attenuates Lipopolysaccharide-induced Neuroinflammation.

    PubMed

    Grabner, Gernot F; Eichmann, Thomas O; Wagner, Bernhard; Gao, Yuanqing; Farzi, Aitak; Taschler, Ulrike; Radner, Franz P W; Schweiger, Martina; Lass, Achim; Holzer, Peter; Zinser, Erwin; Tschöp, Matthias H; Yi, Chun-Xia; Zimmermann, Robert

    2016-01-01

    Monoglyceride lipase (MGL) is required for efficient hydrolysis of the endocannabinoid 2-arachidonoylglyerol (2-AG) in the brain generating arachidonic acid (AA) and glycerol. This metabolic function makes MGL an interesting target for the treatment of neuroinflammation, since 2-AG exhibits anti-inflammatory properties and AA is a precursor for pro-inflammatory prostaglandins. Astrocytes are an important source of AA and 2-AG, and highly express MGL. In the present study, we dissected the distinct contribution of MGL in astrocytes on brain 2-AG and AA metabolism by generating a mouse model with genetic deletion of MGL specifically in astrocytes (MKO(GFAP)). MKO(GFAP) mice exhibit moderately increased 2-AG and reduced AA levels in brain. Minor accumulation of 2-AG in the brain of MKO(GFAP) mice does not cause cannabinoid receptor desensitization as previously observed in mice globally lacking MGL. Importantly, MKO(GFAP) mice exhibit reduced brain prostaglandin E2 and pro-inflammatory cytokine levels upon peripheral lipopolysaccharide (LPS) administration. These observations indicate that MGL-mediated degradation of 2-AG in astrocytes provides AA for prostaglandin synthesis promoting LPS-induced neuroinflammation. The beneficial effect of astrocyte-specific MGL-deficiency is not fully abrogated by the inverse cannabinoid receptor 1 agonist SR141716 (Rimonabant) suggesting that the anti-inflammatory effects are rather caused by reduced prostaglandin synthesis than by activation of cannabinoid receptors. In conclusion, our data demonstrate that MGL in astrocytes is an important regulator of 2-AG levels, AA availability, and neuroinflammation.

  16. Deletion of Monoglyceride Lipase in Astrocytes Attenuates Lipopolysaccharide-induced Neuroinflammation.

    PubMed

    Grabner, Gernot F; Eichmann, Thomas O; Wagner, Bernhard; Gao, Yuanqing; Farzi, Aitak; Taschler, Ulrike; Radner, Franz P W; Schweiger, Martina; Lass, Achim; Holzer, Peter; Zinser, Erwin; Tschöp, Matthias H; Yi, Chun-Xia; Zimmermann, Robert

    2016-01-01

    Monoglyceride lipase (MGL) is required for efficient hydrolysis of the endocannabinoid 2-arachidonoylglyerol (2-AG) in the brain generating arachidonic acid (AA) and glycerol. This metabolic function makes MGL an interesting target for the treatment of neuroinflammation, since 2-AG exhibits anti-inflammatory properties and AA is a precursor for pro-inflammatory prostaglandins. Astrocytes are an important source of AA and 2-AG, and highly express MGL. In the present study, we dissected the distinct contribution of MGL in astrocytes on brain 2-AG and AA metabolism by generating a mouse model with genetic deletion of MGL specifically in astrocytes (MKO(GFAP)). MKO(GFAP) mice exhibit moderately increased 2-AG and reduced AA levels in brain. Minor accumulation of 2-AG in the brain of MKO(GFAP) mice does not cause cannabinoid receptor desensitization as previously observed in mice globally lacking MGL. Importantly, MKO(GFAP) mice exhibit reduced brain prostaglandin E2 and pro-inflammatory cytokine levels upon peripheral lipopolysaccharide (LPS) administration. These observations indicate that MGL-mediated degradation of 2-AG in astrocytes provides AA for prostaglandin synthesis promoting LPS-induced neuroinflammation. The beneficial effect of astrocyte-specific MGL-deficiency is not fully abrogated by the inverse cannabinoid receptor 1 agonist SR141716 (Rimonabant) suggesting that the anti-inflammatory effects are rather caused by reduced prostaglandin synthesis than by activation of cannabinoid receptors. In conclusion, our data demonstrate that MGL in astrocytes is an important regulator of 2-AG levels, AA availability, and neuroinflammation. PMID:26565024

  17. Density of GFAP-immunoreactive astrocytes is decreased in left hippocampi in major depressive disorder.

    PubMed

    Cobb, J A; O'Neill, K; Milner, J; Mahajan, G J; Lawrence, T J; May, W L; Miguel-Hidalgo, J; Rajkowska, G; Stockmeier, C A

    2016-03-01

    Neuroimaging and postmortem studies of subjects with major depressive disorder (MDD) reveal smaller hippocampal volume with lengthening duration of illness. Pathology in astrocytes may contribute significantly to this reduced volume and to the involvement of the hippocampus in MDD. Postmortem hippocampal tissues were collected from 17 subjects with MDD and 17 psychiatrically-normal control subjects. Sections from the body of the hippocampus were immunostained for glial fibrillary acidic protein (GFAP), a marker of intermediate filament protein expressed in astrocytes. The density of GFAP-immunoreactive astrocytes was measured in the hippocampus using 3-dimensional cell counting. Hippocampal subfields were also assessed for GFAP-immunoreactive area fraction. In CA1, there was a significant positive correlation between age and either density or area fraction in MDD. The density of astrocytes in the hilus, but not CA1 or CA2/3, was significantly decreased only in depressed subjects not taking an antidepressant drug, but not for depressed subjects taking an antidepressant drug. The area fraction of GFAP-immunoreactivity was significantly decreased in the dentate gyrus in women but not men with depression. In CA2/3, the area fraction of GFAP-immunoreactivity was inversely correlated with the duration of depression in suicide victims. Astrocyte contributions to neuronal function in the hilus may be compromised in depressed subjects not taking antidepressant medication. Due to the cross-sectional nature of the present study of postmortem brain tissue, it remains to be determined whether antidepressant drug treatment prevented a decrease in GFAP-immunoreactive astrocyte density or restored cell density to normal levels.

  18. HIV protease inhibitors disrupt astrocytic glutamate transporter function and neurobehavioral performance

    PubMed Central

    Vivithanaporn, Pornpun; Asahchop, Eugene L.; Acharjee, Shaona; Baker, Glen B.; Power, Christopher

    2016-01-01

    Objective: The neurotoxic actions of the HIV protease inhibitors, amprenavir (APV) and lopinavir (LPV) were investigated. Design: With combination antiretroviral therapy (cART), HIV-infected persons exhibit neurocognitive impairments, raising the possibility that cART might exert adverse central nervous system (CNS) effects. We examined the effects of LPV and APV using in-vitro and in-vivo assays of CNS function. Methods: Gene expression, cell viability and amino-acid levels were measured in human astrocytes, following exposure to APV or LPV. Neurobehavioral performance, amino-acid levels and neuropathology were examined in HIV-1 Vpr transgenic mice after treatment with APV or LPV. Results: Excitatory amino-acid transporter-2 (EAAT2) expression was reduced in astrocytes treated with LPV or APV, especially LPV (P < 0.05), which was accompanied by reduced intracellular l-glutamate levels in LPV-treated cells (P < 0.05). Treatment of astrocytes with APV or LPV reduced the expression of proliferating cell nuclear antigen (PCNA) and Ki-67 (P < 0.05) although cell survival was unaffected. Exposure of LPV to astrocytes augmented glutamate-evoked transient rises in [Cai] (P < 0.05). Vpr mice treated with LPV showed lower concentrations of l-glutamate, l-aspartate and l-serine in cortex compared with vehicle-treated mice (P < 0.05). Total errors in T-maze assessment were increased in LPV and APV-treated animals (P < 0.05). EAAT2 expression was reduced in the brains of protease inhibitor-treated animals, which was associated with gliosis (P < 0.05). Conclusion: These results indicated that contemporary protease inhibitors disrupt astrocyte functions at therapeutic concentrations with enhanced sensitivity to glutamate, which can lead to neurobehavioral impairments. ART neurotoxicity should be considered in future therapeutic regimens for HIV/AIDS. PMID:26558720

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

    NASA Astrophysics Data System (ADS)

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

    2006-06-01

    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 inhibitory neurotransmitters, astrocytes exert a complex modulatory control on the olfactory network. glutamate | GABA | inhibition | olfactory bulb | synchronization

  20. Role of astrocytes in brain function and disease.

    PubMed

    Sidoryk-Wegrzynowicz, Marta; Wegrzynowicz, Michal; Lee, Eunsook; Bowman, Aaron B; Aschner, Michael

    2011-01-01

    Astrocytes assume multiple roles in maintaining an optimally suited milieu for neuronal function. Select astrocytic functions include the maintenance of redox potential, the production of trophic factors, the regulation of neurotransmitter and ion concentrations, and the removal of toxins and debris from the cerebrospinal fluid (CSF). Impairments in these and other functions, as well as physiological reactions of astrocytes to injury, can trigger or exacerbate neuronal dysfunction. This review addresses select metabolic interactions between neurons and astrocytes and emphasizes the role of astrocytes in mediating and amplifying the progression of several neurodegenerative disorders, such as Parkinson's disease (PD), hepatic encephalopathy (HE), hyperammonemia (HA), Alzheimer's disease (AD), and ischemia.

  1. Regional astrocyte allocation regulates CNS synaptogenesis and repair.

    PubMed

    Tsai, Hui-Hsin; Li, Huiliang; Fuentealba, Luis C; Molofsky, Anna V; Taveira-Marques, Raquel; Zhuang, Helin; Tenney, April; Murnen, Alice T; Fancy, Stephen P J; Merkle, Florian; Kessaris, Nicoletta; Alvarez-Buylla, Arturo; Richardson, William D; Rowitch, David H

    2012-07-20

    Astrocytes, the most abundant cell population in the central nervous system (CNS), are essential for normal neurological function. We show that astrocytes are allocated to spatial domains in mouse spinal cord and brain in accordance with their embryonic sites of origin in the ventricular zone. These domains remain stable throughout life without evidence of secondary tangential migration, even after acute CNS injury. Domain-specific depletion of astrocytes in ventral spinal cord resulted in abnormal motor neuron synaptogenesis, which was not rescued by immigration of astrocytes from adjoining regions. Our findings demonstrate that region-restricted astrocyte allocation is a general CNS phenomenon and reveal intrinsic limitations of the astroglial response to injury.

  2. Bioimpedance modeling to monitor astrocytic response to chronically implanted electrodes

    NASA Astrophysics Data System (ADS)

    McConnell, G. C.; Butera, R. J.; Bellamkonda, R. V.

    2009-10-01

    The widespread adoption of neural prosthetic devices is currently hindered by our inability to reliably record neural signals from chronically implanted electrodes. The extent to which the local tissue response to implanted electrodes influences recording failure is not well understood. To investigate this phenomenon, impedance spectroscopy has shown promise for use as a non-invasive tool to estimate the local tissue response to microelectrodes. Here, we model impedance spectra from chronically implanted rats using the well-established Cole model, and perform a correlation analysis of modeled parameters with histological markers of astroglial scar, including glial fibrillary acid protein (GFAP) and 4',6-diamidino-2- phenylindole (DAPI). Correlations between modeled parameters and GFAP were significant for three parameters studied: Py value, Ro and |Z|1 kHz, and in all cases were confined to the first 100 µm from the interface. Py value was the only parameter also correlated with DAPI in the first 100 µm. Our experimental results, along with computer simulations, suggest that astrocytes are a predominant cellular player affecting electrical impedance spectra. The results also suggest that the largest contribution from reactive astrocytes on impedance spectra occurs in the first 100 µm from the interface, where electrodes are most likely to record electrical signals. These results form the basis for future approaches where impedance spectroscopy can be used to evaluate neural implants, evaluate strategies to minimize scar and potentially develop closed-loop prosthetic devices.

  3. Extracellular matrix glycoproteins and diffusion barriers in human astrocytic tumours.

    PubMed

    Zámecník, J; Vargová, L; Homola, A; Kodet, R; Syková, E

    2004-08-01

    The extracellular matrix (ECM) and changes in the size and geometry of the extracellular space (ECS) in tumour tissue are thought to be of critical importance in influencing the migratory abilities of tumour cells as well as the delivery of therapeutic agents into the tumour. In 21 astrocytic neoplasms, the ECM composition was investigated in situ by the immunohistochemical detection of ECM glycoproteins (tenascin, laminin, vitronectin, fibronectin, collagen types I-VI). To explain the changes in ECS size and to detect barriers to diffusion in the tumour tissue, the ECM composition, the cellularity, the density of glial fibrillary acidic protein (GFAP)-positive tumour cell processes and the proliferative activity of the tumours were compared with the size and geometry of the ECS. The ECS volume fraction and the complex of hindrances to diffusion in the ECS (i.e. the tortuosity) were revealed by the real-time iontophoretic tetramethylammonium method. Increased proliferative activity of the tumours correlated with increased ECS volume fraction and tortuosity. The tortuosity of the tumour tissue was not significantly influenced by tumour cell density. Higher tortuosity was found in low-grade astrocytomas associated with the presence of a dense net of GFAP-positive fibrillary processes of the tumour cells. The increase in tortuosity in high-grade tumours correlated with an increased accumulation of ECM molecules, particularly of tenascin. We conclude that the increased malignancy of astrocytic tumours correlates with increases in both ECS volume and ECM deposition.

  4. New tools for investigating astrocyte-to-neuron communication

    PubMed Central

    Li, Dongdong; Agulhon, Cendra; Schmidt, Elke; Oheim, Martin; Ropert, Nicole

    2013-01-01

    Gray 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) the size of astrocyte processes in contact with synapses are below the resolution of confocal and two-photon microscopes (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+ signaling revealed by GECIs; (ii) new pharmacogenetic and optogenetic approaches to activate specific Ca2+ signaling 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. PMID:24194698

  5. Activity-dependent regulation of astrocyte GAT levels during synaptogenesis

    PubMed Central

    Muthukumar, Allie K.; Stork, Tobias; Freeman, Marc R.

    2014-01-01

    Astrocytic uptake of GABA through GABA transporters (GATs) is an important mechanism regulating excitatory/inhibitory balance in the nervous system, however mechanisms by which astrocytes regulate GAT levels are undefined. Here we show at mid-pupal stages the Drosophila CNS neuropil is devoid of astrocyte membranes and synapses. Astrocyte membranes subsequently infiltrate the neuropil coordinate with synaptogenesis and a strocyte ablation reduces synapse numbers by half, indicating that Drosophila astrocytes are pro-synaptogenic. Shortly after synapses form in earnest, the GABA transporter, GAT, is up-regulated in astrocytes. Ablation or silencing of GABAergic neurons or disruption of metabotropic GABA receptor (GABABR1/2) signaling in astrocytes leads to decreased astrocytic GAT levels. Interestingly, developmental depletion of astrocytic GABABR1/2 signaling suppresses mechanosensory-induced seizure activity in mutants with hyperexcitable neurons. These data reveal astrocytes actively modulate GAT expression via metabotropic GABA receptor signaling, and highlight the importance of precise regulation of astrocytic GAT in modulation of seizure activity. PMID:25151265

  6. Effect of stress and peripheral immune activation on astrocyte activation in transgenic bioluminescent Gfap-luc mice.

    PubMed

    Biesmans, Steven; Acton, Paul D; Cotto, Carlos; Langlois, Xavier; Ver Donck, Luc; Bouwknecht, Jan A; Aelvoet, Sarah-Ann; Hellings, Niels; Meert, Theo F; Nuydens, Rony

    2015-07-01

    Neuroinflammation and the accompanying activation of glial cells is an important feature of many neurodegenerative conditions. It is known that factors such as peripheral infections and stress can influence immune processes in the brain. However, the effect of these stressors on astrocyte activation in vivo remains elusive. In this study, transgenic Gfap-luc mice expressing the luciferase gene under the transcriptional control of the glial fibrillary acidic protein promoter were used to quantify the kinetics of in vivo astrocyte activation following immune challenges relevant to clinical inflammation. It was found that astrocytes respond rapidly to peripheral immune activation elicited by either bacterial lipopolysaccharide (LPS) or the viral mimetic polyinosinic:polycytidylic acid (poly(I:C)). By measuring bioluminescence and 18-kDa translocator protein radioligand binding in the same animal it was observed that LPS induces both astrocyte as well as microglial activation at 6 h post-administration. Furthermore, the astrocyte response decreased upon repeated systemic LPS injections, indicating development of tolerance to the LPS challenge. Finally, restraining Gfap-luc mice for 1 h daily on 5 consecutive days did not affect brain bioluminescence, thereby indicating that sub-chronic stress does not influence astrocyte activation under unchallenged conditions. However, stressed animals showed a reduced response to a subsequent systemic LPS injection, suggesting that the immune system is compromised in these animals. Here, we demonstrate that Gfap-luc mice can be used to study astrocyte activation in response to stimuli relevant for clinical inflammation and that this approach may provide a more complete characterization of existing and novel models of neuroinflammation

  7. Recent molecular approaches to understanding astrocyte function in vivo

    PubMed Central

    Davila, David; Thibault, Karine; Fiacco, Todd A.; Agulhon, Cendra

    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 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. PMID:24399932

  8. Non-cell autonomous influence of the astrocyte system xc- on hypoglycaemic neuronal cell death.

    PubMed

    Jackman, Nicole A; Melchior, Shannon E; Hewett, James A; Hewett, Sandra J

    2012-02-08

    Despite longstanding evidence that hypoglycaemic neuronal injury is mediated by glutamate excitotoxicity, the cellular and molecular mechanisms involved remain incompletely defined. Here, we demonstrate that the excitotoxic neuronal death that follows GD (glucose deprivation) is initiated by glutamate extruded from astrocytes via system xc---an amino acid transporter that imports L-cystine and exports L-glutamate. Specifically, we find that depriving mixed cortical cell cultures of glucose for up to 8 h injures neurons, but not astrocytes. Neuronal death is prevented by ionotropic glutamate receptor antagonism and is partially sensitive to tetanus toxin. Removal of amino acids during the deprivation period prevents--whereas addition of L-cystine restores--GD-induced neuronal death, implicating the cystine/glutamate antiporter, system xc-. Indeed, drugs known to inhibit system xc- ameliorate GD-induced neuronal death. Further, a dramatic reduction in neuronal death is observed in chimaeric cultures consisting of neurons derived from WT (wild-type) mice plated on top of astrocytes derived from sut mice, which harbour a naturally occurring null mutation in the gene (Slc7a11) that encodes the substrate-specific light chain of system xc- (xCT). Finally, enhancement of astrocytic system xc- expression and function via IL-1β (interleukin-1β) exposure potentiates hypoglycaemic neuronal death, the process of which is prevented by removal of l-cystine and/or addition of system xc- inhibitors. Thus, under the conditions of GD, our studies demonstrate that astrocytes, via system xc-, have a direct, non-cell autonomous effect on cortical neuron survival.

  9. Astrocytic dysfunction in epileptogenesis: consequence of altered potassium and glutamate homeostasis?

    PubMed

    David, Yaron; Cacheaux, Luisa P; Ivens, Sebastian; Lapilover, Ezequiel; Heinemann, Uwe; Kaufer, Daniela; Friedman, Alon

    2009-08-26

    Focal epilepsy often develops following traumatic, ischemic, or infectious brain injury. While the electrical activity of the epileptic brain is well characterized, the mechanisms underlying epileptogenesis are poorly understood. We have recently shown that in the rat neocortex, long-lasting breakdown of the blood-brain barrier (BBB) or direct exposure of the neocortex to serum-derived albumin leads to rapid upregulation of the astrocytic marker GFAP (glial fibrillary acidic protein), followed by delayed (within 4-7 d) development of an epileptic focus. We investigated the role of astrocytes in epileptogenesis in the BBB-breakdown and albumin models of epileptogenesis. We found similar, robust changes in astrocytic gene expression in the neocortex within hours following treatment with deoxycholic acid (BBB breakdown) or albumin. These changes predict reduced clearance capacity for both extracellular glutamate and potassium. Electrophysiological recordings in vitro confirmed the reduced clearance of activity-dependent accumulation of both potassium and glutamate 24 h following exposure to albumin. We used a NEURON model to simulate the consequences of reduced astrocytic uptake of potassium and glutamate on EPSPs. The model predicted that the accumulation of glutamate is associated with frequency-dependent (>100 Hz) decreased facilitation of EPSPs, while potassium accumulation leads to frequency-dependent (10-50 Hz) and NMDA-dependent synaptic facilitation. In vitro electrophysiological recordings during epileptogenesis confirmed frequency-dependent synaptic facilitation leading to seizure-like activity. Our data indicate a transcription-mediated astrocytic transformation early during epileptogenesis. We suggest that the resulting reduction in the clearance of extracellular potassium underlies frequency-dependent neuronal hyperexcitability and network synchronization.

  10. Astrocyte arachidonate and palmitate uptake and metabolism is differentially modulated by dibutyryl-cAMP treatment.

    PubMed

    Seeger, D R; Murphy, C C; Murphy, E J

    2016-07-01

    Astrocytes play a vital role in brain lipid metabolism; however the impact of the phenotypic shift in astrocytes to a reactive state on arachidonic acid metabolism is unknown. Therefore, we determined the impact of dibutyryl-cAMP (dBcAMP) treatment on radiolabeled arachidonic acid ([1-(14)C]20:4n-6) and palmitic acid ([1-(14)C]16:0) uptake and metabolism in primary cultured murine cortical astrocytes. In dBcAMP treated astrocytes, total [1-(14)C]20:4n-6 uptake was increased 1.9-fold compared to control, while total [1-(14)C]16:0 uptake was unaffected. Gene expression of long-chain acyl-CoA synthetases (Acsl), acyl-CoA hydrolase (Acot7), fatty acid binding protein(s) (Fabp) and alpha-synuclein (Snca) were determined using qRT-PCR. dBcAMP treatment increased expression of Acsl3 (4.8-fold) and Acsl4 (1.3-fold), which preferentially use [1-(14)C]20:4n-6 and are highly expressed in astrocytes, consistent with the increase in [1-(14)C]20:4n-6 uptake. However, expression of Fabp5 and Fabp7 were significantly reduced by 25% and 45%, respectively. Acot7 (20%) was also reduced, suggesting dBcAMP treatment favors acyl-CoA formation. dBcAMP treatment enhanced [1-(14)C]20:4n-6 (2.2-fold) and [1-(14)C]16:0 (1.6-fold) esterification into total phospholipids, but the greater esterification of [1-(14)C]20:4n-6 is consistent with the observed uptake through increased Acsl, but not Fabp expression. Although total [1-(14)C]16:0 uptake was not affected, there was a dramatic decrease in [1-(14)C]16:0 in the free fatty acid pool as esterification into the phospholipid pool was increased, which is consistent with the increase in Acsl3 and Acsl4 expression. In summary, our data demonstrates that dBcAMP treatment increases [1-(14)C]20:4n-6 uptake in astrocytes and this increase appears to be due to increased expression of Acsl3 and Acsl4 coupled with a reduction in Acot7 expression. PMID:27255639

  11. Astrocyte-Derived BDNF Supports Myelin Protein Synthesis after Cuprizone-Induced Demyelination

    PubMed Central

    Fulmer, Clifton G.; VonDran, Melissa W.; Stillman, Althea A.; Huang, Yangyang; Hempstead, Barbara L.

    2014-01-01

    It is well established that BDNF may enhance oligodendrocyte differentiation following a demyelinating lesion, however, the endogenous sources of BDNF that may be harnessed to reverse deficits associated with such lesions are poorly defined. Here, we investigate roles of astrocytes in synthesizing and releasing BDNF. These cells are known to express BDNF following injury in vivo. In culture, they increase BDNF synthesis and release in response to glutamate metabotropic stimulation. Following cuprizone-elicited demyelination in mice, astrocytes contain BDNF and increase levels of metabotropic receptors. The metabotropic agonist, trans-(1S,3R)-1-amino-1,3-cyclopentanedicarboxylic acid (ACPD), was therefore injected into the demyelinating lesion. Increases in BDNF, as well as myelin proteins, were observed. Effects of ACPD were eliminated by coinjection of trkB-Fc to locally deplete BDNF and by deletion of astrocyte-derived BDNF. The data indicate that astrocyte-derived BDNF may be a source of trophic support that can be used to reverse deficits elicited following demyelination. PMID:24920623

  12. Striatal adenosine signaling regulates EAAT2 and astrocytic AQP4 expression and alcohol drinking in mice.

    PubMed

    Lee, Moonnoh R; Ruby, Christina L; Hinton, David J; Choi, Sun; Adams, Chelsea A; Young Kang, Na; Choi, Doo-Sup

    2013-02-01

    Adenosine signaling is implicated in several neuropsychiatric disorders, including alcoholism. Among its diverse functions in the brain, adenosine regulates glutamate release and has an essential role in ethanol sensitivity and preference. However, the molecular mechanisms underlying adenosine-mediated glutamate signaling in neuroglial interaction remain elusive. We have previously shown that mice lacking the ethanol-sensitive adenosine transporter, type 1 equilibrative nucleoside transporter (ENT1), drink more ethanol compared with wild-type mice and have elevated striatal glutamate levels. In addition, ENT1 inhibition or knockdown reduces glutamate transporter expression in cultured astrocytes. Here, we examined how adenosine signaling in astrocytes contributes to ethanol drinking. Inhibition or deletion of ENT1 reduced the expression of type 2 excitatory amino-acid transporter (EAAT2) and the astrocyte-specific water channel, aquaporin 4 (AQP4). EAAT2 and AQP4 colocalization was also reduced in the striatum of ENT1 null mice. Ceftriaxone, an antibiotic compound known to increase EAAT2 expression and function, elevated not only EAAT2 but also AQP4 expression in the striatum. Furthermore, ceftriaxone reduced ethanol drinking, suggesting that ENT1-mediated downregulation of EAAT2 and AQP4 expression contributes to excessive ethanol consumption in our mouse model. Overall, our findings indicate that adenosine signaling regulates EAAT2 and astrocytic AQP4 expressions, which control ethanol drinking in mice.

  13. Astrocytic estrogen receptors and impaired neurotrophic responses in a rat model of perimenopause

    PubMed Central

    Morgan, Todd E.; Finch, Caleb E.

    2015-01-01

    In a perimenopausal model of middle-aged rats, the astrocyte estrogen receptor-alpha (ERa): ER-beta (ERb) ratio increased with the onset of acyclicity (constant estrus, CE) in association with impaired neurotrophic responses to estradiol (E2). We report additional data on irregular cycling (IR) from this study of 9 month old perimenopausal subgroups. In particular, irregular cyclers (IR) also show increased ERa:ERb ratio in cerebral cortex astrocytes comparable to acyclic individuals in CE. In mixed glial cultures from these same cycling subgroups, the E2-dependent neurotrophic activity and glial fibrillary acidic protein (GFAP) repression by E2 were impaired in IR to the same degree as in CE-derived glia. The greater importance of cycling status than age during the perimenopause to astrocyte ERs are attributable to individual variations of the residual ovarian follicle pool, which determine the onset of acyclicity. The corresponding loss of E2-dependent GFAP repression and E2-dependent neurotrophic activity add further to the inverse relationship of GFAP expression and astrocyte neurotrophic activity across aging in both sexes. These findings are relevant to impairments of spatial learning and of hippocampal long-term potentiation during the onset of IR in middle-aged rats, and to perimenopausal factors mediating the higher risk of women for Alzheimer disease. PMID:26483679

  14. Uptake of dimercaptosuccinate-coated magnetic iron oxide nanoparticles by cultured brain astrocytes

    NASA Astrophysics Data System (ADS)

    Geppert, Mark; Hohnholt, Michaela C.; Thiel, Karsten; Nürnberger, Sylvia; Grunwald, Ingo; Rezwan, Kurosch; Dringen, Ralf

    2011-04-01

    Magnetic iron oxide nanoparticles (Fe-NP) are currently considered for various diagnostic and therapeutic applications in the brain. However, little is known on the accumulation and biocompatibility of such particles in brain cells. We have synthesized and characterized dimercaptosuccinic acid (DMSA) coated Fe-NP and have investigated their uptake by cultured brain astrocytes. DMSA-coated Fe-NP that were dispersed in physiological medium had an average hydrodynamic diameter of about 60 nm. Incubation of cultured astrocytes with these Fe-NP caused a time- and concentration-dependent accumulation of cellular iron, but did not lead within 6 h to any cell toxicity. After 4 h of incubation with 100-4000 µM iron supplied as Fe-NP, the cellular iron content reached levels between 200 and 2000 nmol mg - 1 protein. The cellular iron content after exposure of astrocytes to Fe-NP at 4 °C was drastically lowered compared to cells that had been incubated at 37 °C. Electron microscopy revealed the presence of Fe-NP-containing vesicles in cells that were incubated with Fe-NP at 37 °C, but not in cells exposed to the nanoparticles at 4 °C. These data demonstrate that cultured astrocytes efficiently take up DMSA-coated Fe-NP in a process that appears to be saturable and strongly depends on the incubation temperature.

  15. Blast shockwaves propagate Ca(2+) activity via purinergic astrocyte networks in human central nervous system cells.

    PubMed

    Ravin, Rea; Blank, Paul S; Busse, Brad; Ravin, Nitay; Vira, Shaleen; Bezrukov, Ludmila; Waters, Hang; Guerrero-Cazares, Hugo; Quinones-Hinojosa, Alfredo; Lee, Philip R; Fields, R Douglas; Bezrukov, Sergey M; Zimmerberg, Joshua

    2016-01-01

    In a recent study of the pathophysiology of mild, blast-induced traumatic brain injury (bTBI) the exposure of dissociated, central nervous system (CNS) cells to simulated blast resulted in propagating waves of elevated intracellular Ca(2+). Here we show, in dissociated human CNS cultures, that these calcium waves primarily propagate through astrocyte-dependent, purinergic signaling pathways that are blocked by P2 antagonists. Human, compared to rat, astrocytes had an increased calcium response and prolonged calcium wave propagation kinetics, suggesting that in our model system rat CNS cells are less responsive to simulated blast. Furthermore, in response to simulated blast, human CNS cells have increased expressions of a reactive astrocyte marker, glial fibrillary acidic protein (GFAP) and a protease, matrix metallopeptidase 9 (MMP-9). The conjoint increased expression of GFAP and MMP-9 and a purinergic ATP (P2) receptor antagonist reduction in calcium response identifies both potential mechanisms for sustained changes in brain function following primary bTBI and therapeutic strategies targeting abnormal astrocyte activity. PMID:27162174

  16. Blast shockwaves propagate Ca2+ activity via purinergic astrocyte networks in human central nervous system cells

    PubMed Central

    Ravin, Rea; Blank, Paul S.; Busse, Brad; Ravin, Nitay; Vira, Shaleen; Bezrukov, Ludmila; Waters, Hang; Guerrero-Cazares, Hugo; Quinones-Hinojosa, Alfredo; Lee, Philip R.; Fields, R. Douglas; Bezrukov, Sergey M.; Zimmerberg, Joshua

    2016-01-01

    In a recent study of the pathophysiology of mild, blast-induced traumatic brain injury (bTBI) the exposure of dissociated, central nervous system (CNS) cells to simulated blast resulted in propagating waves of elevated intracellular Ca2+. Here we show, in dissociated human CNS cultures, that these calcium waves primarily propagate through astrocyte-dependent, purinergic signaling pathways that are blocked by P2 antagonists. Human, compared to rat, astrocytes had an increased calcium response and prolonged calcium wave propagation kinetics, suggesting that in our model system rat CNS cells are less responsive to simulated blast. Furthermore, in response to simulated blast, human CNS cells have increased expressions of a reactive astrocyte marker, glial fibrillary acidic protein (GFAP) and a protease, matrix metallopeptidase 9 (MMP-9). The conjoint increased expression of GFAP and MMP-9 and a purinergic ATP (P2) receptor antagonist reduction in calcium response identifies both potential mechanisms for sustained changes in brain function following primary bTBI and therapeutic strategies targeting abnormal astrocyte activity. PMID:27162174

  17. Chronic stress-induced disruption of the astrocyte network is driven by structural atrophy and not loss of astrocytes.

    PubMed

    Tynan, Ross J; Beynon, Sarah B; Hinwood, Madeleine; Johnson, Sarah J; Nilsson, Michael; Woods, Jason J; Walker, Frederick R

    2013-07-01

    Chronic stress is well recognized to decrease the number of GFAP⁺ astrocytes within the prefrontal cortex (PFC). Recent research, however, has suggested that our understanding of how stress alters astrocytes may be incomplete. Specifically, chronic stress has been shown to induce a unique form of microglial remodelling, but it is not yet clear whether astrocytes also undergo similar structural modifications. Such alterations may be significant given the role of astrocytes in modulating synaptic function. Accordingly, in the current study we have examined changes in astrocyte morphology following exposure to chronic stress in adult rats, using three-dimensional digital reconstructions of astrocytes. Our analysis indicated that chronic stress produced profound atrophy of astrocyte process length, branching and volume. We additionally examined changes in astrocyte-specific S100β, which are both a putative astrocyte marker and a protein whose expression is associated with astrocyte distress. While we found that S100β levels were increased by stress, this increase was not correlated with atrophy. We further established that while chronic stress was associated with a decrease in astrocyte numbers when GFAP labelling was used as a marker, we could find no evidence of a decrease in the total number of cells, based on Nissl staining, or in the number of S100β⁺ cells. This finding suggests that chronic stress may not actually reduce astrocyte numbers and may instead selectively decrease GFAP expression. The results of the current study are significant as they indicate stress-induced astrocyte-mediated disturbances may not be due to a loss of cells but rather due to significant remodeling of the astrocyte network.

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

    SciTech Connect

    Giordano, Gennaro; Pizzurro, Daniella; VanDeMark, Kathryn; Guizzetti, Marina; Costa, Lucio G.

    2009-10-15

    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 {mu}M) 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, H{sub 2}O{sub 2} 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.

  19. Estradiol regulation of hypothalamic astrocyte adenosine 5'-monophosphate-activated protein kinase activity: role of hindbrain catecholamine signaling.

    PubMed

    Tamrakar, Pratistha; Briski, Karen P

    2015-01-01

    Recent work challenges the conventional notion that metabolic monitoring in the brain is the exclusive function of neurons. This study investigated the hypothesis that hypothalamic astrocytes express the ultra-sensitive energy gauge adenosine 5'-monophosphate-activated protein kinase (AMPK), and that the ovarian hormone estradiol (E) controls activation of this sensor by insulin-induced hypoglycemia (IIH). E- or oil (O)-implanted ovariectomized (OVX) rats were pretreated by caudal fourth ventricular administration of the catecholamine neurotoxin 6-hydroxydopamine (6-OHDA) prior to sc insulin or vehicle injection. Individual astrocytes identified in situ by glial fibrillary acidic protein immunolabeling were laser-microdissected from the ventromedial (VMH), arcuate (ARH), and paraventricular (PVH) nuclei and the lateral hypothalamic area (LHA), and pooled within each site for Western blot analysis of AMPK and phosphoAMPK (pAMPK) protein expression. In the VMH, baseline astrocyte AMPK and pAMPK levels were respectively increased or decreased in OVX+E versus OVX+O; these profiles did not differ between E and O rats in other hypothalamic loci. In E animals, astrocyte AMPK protein was reduced [VMH] or augmented [PVH; LHA] in response to either 6-OHDA or IIH. IIH increased astrocyte pAMPK expression in each structure in vehicle-, but not 6-OHDA-pretreated E rats. Results provide novel evidence for hypothalamic astrocyte AMPK expression and hindbrain catecholamine-dependent activation of this cell-specific sensor by hypoglycemia in the presence of estrogen. Further research is needed to determine the role of astrocyte AMPK in reactivity of these glia to metabolic imbalance and contribution to restoration of neuro-metabolic stability.

  20. P2Y1 receptor inhibits GABA transport through a calcium signalling-dependent mechanism in rat cortical astrocytes.

    PubMed

    Jacob, Pedro F; Vaz, Sandra H; Ribeiro, Joaquim A; Sebastião, Ana M

    2014-08-01

    Astrocytes express a variety of purinergic (P2) receptors, involved in astrocytic communication through fast increases in [Ca(2+) ]i . Of these, the metabotropic ATP receptors (P2Y) regulate cytoplasmic Ca(2+) levels through the PLC-PKC pathway. GABA transporters are a substrate for a number of Ca(2+) -related kinases, raising the possibility that calcium signalling in astrocytes impact the control of extracellular levels of the major inhibitory transmitter in the brain. To access this possibility we tested the influence of P2Y receptors upon GABA transport into astrocytes. Mature primary cortical astroglial-enriched cultures expressed functional P2Y receptors, as evaluated through Ca(2+) imaging, being P2Y1 the predominant P2Y receptor subtype. ATP (100 μM, for 1 min) caused an inhibition of GABA transport through either GAT-1 or GAT-3 transporters, decreasing the Vmax kinetic constant. ATP-induced inhibition of GATs activity was still evident in the presence of adenosine deaminase, precluding an adenosine-mediated effect. This, was mimicked by a specific agonist for the P2Y1,12,13 receptor (2-MeSADP). The effect of 2-MeSADP on GABA transport was blocked by the P2 (PPADS) and P2Y1 selective (MRS2179) receptor antagonists, as well as by the PLC inhibitor (U73122). 2-MeSADP failed to inhibit GABA transport in astrocytes where intracellular calcium had been chelated (BAPTA-AM) or where calcium stores were depleted (α-cyclopiazonic acid, CPA). In conclusion, P2Y1 receptors in astrocytes inhibit GABA transport through a mechanism dependent of P2Y1 -mediated calcium signalling, suggesting that astrocytic calcium signalling, which occurs as a consequence of neuronal firing, may operate a negative feedback loop to enhance extracellular levels of GABA. PMID:24733747

  1. Physiopathologic dynamics of vesicle traffic in astrocytes.

    PubMed

    Potokar, Maja; Stenovec, Matjaž; Kreft, Marko; Gabrijel, Mateja; Zorec, Robert

    2011-02-01

    The view of how astrocytes, a type of glial cells, contribute to the functioning of the central nervous system (CNS) has changed greatly in the last decade. Although glial cells outnumber neurons in the mammalian brain, it was considered for over a century that they played a subservient role to neurons. This view changed. Functions thought to be exclusively present in neurons, i.e. excitability mediated release of chemical messengers, has also been demonstrated in astrocytes. In this process, following an increase in cytosolic calcium activity, membrane bound vesicles, storing chemical messengers (gliotransmitters), fuse with the plasma membrane, a process known as exocytosis, permitting the exit of vesicle cargo into the extracellular space. Vesicles are delivered to and are removed from the site of exocytosis by an amazingly complex set of processes that we have only started to learn about recently. In this paper we review vesicle traffic, which is subject to physiological regulation and may be changed under pathological conditions.

  2. Astrocyte glutamine synthetase: pivotal in health and disease.

    PubMed

    Rose, Christopher F; Verkhratsky, Alexei; Parpura, Vladimir

    2013-12-01

    The multifunctional properties of astrocytes signify their importance in brain physiology and neurological function. In addition to defining the brain architecture, astrocytes are primary elements of brain ion, pH and neurotransmitter homoeostasis. GS (glutamine synthetase), which catalyses the ATP-dependent condensation of ammonia and glutamate to form glutamine, is an enzyme particularly found in astrocytes. GS plays a pivotal role in glutamate and glutamine homoeostasis, orchestrating astrocyte glutamate uptake/release and the glutamate-glutamine cycle. Furthermore, astrocytes bear the brunt of clearing ammonia in the brain, preventing neurotoxicity. The present review depicts the central function of astrocytes, concentrating on the importance of GS in glutamate/glutamine metabolism and ammonia detoxification in health and disease.

  3. Functions of astrocytes and their potential as therapeutic targets

    PubMed Central

    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 supportive roles of astrocytes, a line of study relevant to essentially all acute and chronic neurological diseases. Furthermore, this review will critically re-evaluate our concepts of the functional properties of astrocytes and relate these tasks to their intricate morphology. PMID:20880499

  4. Enhancement of FGF-1 release along with cytosolic proteins from rat astrocytes by hydrogen peroxide.

    PubMed

    Ito, Jin-Ichi; Nagayasu, Yuko; Hoshikawa, Mariko; Kato, Koichi H; Miura, Yutaka; Asai, Kiyofumi; Hayashi, Hideki; Yokoyama, Shinji; Michikawa, Makoto

    2013-07-19

    We previously observed that the production and release of fibroblast growth factor (FGF-1) are increased in rat astrocytes during in vitro long-term culture, that FGF-1 enhances the generation of apoE-containing high density lipoproteins (apoE/HDL), and that the wound healing of brain cryoinjury delays in apoE-deficient mouse. The detail mechanism underlying these phenomena remains unknown. In this study, we examined effects of oxidative stress on release of FGF-1 from cultured rat astrocytes. The treatment of rat astrocytes with 100µM hydrogen peroxide (H2O2) for 10min enhanced FGF-1 release without inducing apoptosis. The conditioned medium prepared from the cells cultured in a fresh medium after the treatment with H2O2 had the FGF-1-like activities, which enhanced cholesterol synthesis, signalings to phosphorylate Akt and ERK, and apoE secretion. The oxidative stress induced by H2O2 enhanced the release of cytosolic proteins such as HSP70 and HSP90 in addition to FGF-1. Antioxidants such as ascorbic acid and ebselen suppressed the release of cytosolic proteins induced by H2O2 treatment. The addition of lipoproteins such as low density lipoproteins (LDL), furthermore, canceled H2O2-induced release of FGF-1 and cytosolic proteins. Proteolysis of cytosolic proteins in the H2O2-treated rat astrocytes was enhanced in the presence of exogenous trypsin, which was attenuated by the pretreatment with LDL, suggesting that H2O2 increases the permeability of the membrane of cells, which was prevented by the addition of lipoproteins. These findings suggest that oxidative stress is one of the candidates which triggers FGF-1 release from astrocytes in the brain, and that the lipid homeostasis in the cell membrane may regulate H2O2-induced release of FGF-1. PMID:23727614

  5. Amyloid-β peptide induces temporal membrane biphasic changes in astrocytes through cytosolic phospholipase A2

    PubMed Central

    Hicks, Jacob B.; Lai, Yinzhi; Sheng, Wenwen; Yang, Xiaoguang; Zhu, Donghui; Sun, Grace Y.; Lee, James C-M

    2008-01-01

    Oligomeric amyloid-β peptide (Aβ) is known to induce cytotoxic effects and to damage cell functions in Alzheimer’s disease. However, mechanisms underlying the effects of Aβ on cell membranes have yet to be fully elucidated. In this study, Aβ 1–42 (Aβ42) was shown to cause a temporal biphasic change in membranes of astrocytic DITNC cells using fluorescence microscopy of Laurdan. Aβ42 made astrocyte cell membranes became more molecularly-disordered within the first 30 minutes to 1 hour, but gradually changed to more molecularly-ordered after 3 hours. However, Aβ42 caused artificial membranes of vesicles made of rat whole brain lipid extract to become more disordered only. The trend for more molecularly-ordered membranes in astrocytes induced by Aβ42 was abrogated by either an NADPH oxidase inhibitor, apocynin, or an inhibitor of cytosolic phospholipase A2 (cPLA2), but not by an inhibitor of calcium-independent PLA2 (iPLA2). Apocynin also suppressed the increased production of superoxide anions (O2.−) and phosphorylation of cPLA2 induced by Aβ42. In addition, hydrolyzed products of cPLA2, arachidonic acid (AA), but not lysophosphatidylcholine (LPC) caused astrocyte membranes to become more molecularly-ordered. These results suggest (1) a direct interaction of Aβ42 with cell membranes making them more molecularly-disordered, and (2) Aβ42 also indirectly makes membranes become more molecularly-ordered by triggering the signaling pathway involving NADPH oxidase and cPLA2 in astrocytes. PMID:18725190

  6. Neuron-astrocyte interactions, pyruvate carboxylation and the pentose phosphate pathway in the neonatal rat brain.

    PubMed

    Morken, Tora Sund; Brekke, Eva; Håberg, Asta; Widerøe, Marius; Brubakk, Ann-Mari; Sonnewald, Ursula

    2014-01-01

    Glucose and acetate metabolism and the synthesis of amino acid neurotransmitters, anaplerosis, glutamate-glutamine cycling and the pentose phosphate pathway (PPP) have been extensively investigated in the adult, but not the neonatal rat brain. To do this, 7 day postnatal (P7) rats were injected with [1-(13)C]glucose and [1,2-(13)C]acetate and sacrificed 5, 10, 15, 30 and 45 min later. Adult rats were injected and sacrificed after 15 min. To analyse pyruvate carboxylation and PPP activity during development, P7 rats received [1,2-(13)C]glucose and were sacrificed 30 min later. Brain extracts were analysed using (1)H- and (13)C-NMR spectroscopy. Numerous differences in metabolism were found between the neonatal and adult brain. The neonatal brain contained lower levels of glutamate, aspartate and N-acetylaspartate but similar levels of GABA and glutamine per mg tissue. Metabolism of [1-(13)C]glucose at the acetyl CoA stage was reduced much more than that of [1,2-(13)C]acetate. The transfer of glutamate from neurons to astrocytes was much lower while transfer of glutamine from astrocytes to glutamatergic neurons was relatively higher. However, transport of glutamine from astrocytes to GABAergic neurons was lower. Using [1,2-(13)C]glucose it could be shown that despite much lower pyruvate carboxylation, relatively more pyruvate from glycolysis was directed towards anaplerosis than pyruvate dehydrogenation in astrocytes. Moreover, the ratio of PPP/glucose-metabolism was higher. These findings indicate that only the part of the glutamate-glutamine cycle that transfers glutamine from astrocytes to neurons is operating in the neonatal brain and that compared to adults, relatively more glucose is prioritised to PPP and pyruvate carboxylation. Our results may have implications for the capacity to protect the neonatal brain against excitotoxicity and oxidative stress.

  7. Ligustilide attenuates inflammatory pain via inhibition of NFκB-mediated chemokines production in spinal astrocytes.

    PubMed

    Zhao, Lin-Xia; Jiang, Bao-Chun; Wu, Xiao-Bo; Cao, De-Li; Gao, Yong-Jing

    2014-04-01

    Ligustilide (LIG) is a major component of Radix Angelica Sinensis, and reportedly has neuroprotective and anti-inflammatory effects. Recent studies have demonstrated that spinal astrocyte-mediated neuroinflammation plays an important role in the pathogenesis of chronic pain. Here we investigated the anti-nociceptive effect of systemic treatment with LIG on chronic inflammatory pain and explored possible mechanisms. Unilateral hindpaw injection of complete Freund's adjuvant (CFA) induced persistent pain hypersensitivity. Repeated daily intravenous treatment with LIG, either before or after CFA injection, attenuated CFA-induced thermal hyperalgesia and mechanical allodynia. The same treatment also inhibited CFA-induced keratinocyte-derived chemokine (KC) and monocyte chemoattractant protein-1 (MCP-1) mRNA and protein increases in astrocytes of the spinal cord. In vitro study showed LIG dose-dependently reduced lipopolysaccharide (LPS)-induced upregulation of KC and MCP-1 mRNA in astrocyte cultures. Interestingly, LIG treatment did not affect CFA- or LPS-induced glial fibrillary acidic protein upregulation, but did inhibit CFA-induced phosphorylated nuclear factor-κB (p-NFκB) upregulation in spinal astrocytes. Furthermore, intrathecal injection of NFκB inhibitor attenuated CFA-induced pain hypersensitivity and upregulation of KC and MCP-1 in the spinal cord. Finally, single intravenous injection of LIG attenuated intrathecal injection of LPS-induced mechanical allodynia. The same treatment also decreased LPS-induced NFκB activation and KC and MCP-1 upregulation in the spinal cord. These data indicate that LIG attenuates chronic inflammatory pain potentially via inhibiting NFκB-mediated chemokines production in spinal astrocytes. These results provide direct evidence of the anti-nociceptive and anti-inflammatory effects of LIG, suggesting a new application of LIG for the treatment of chronic inflammatory pain.

  8. Differential microglial and astrocytic response to bacterial and viral infection in the developing hippocampus of neonatal rats.

    PubMed

    Patro, Nisha; Singh, Kavita; Patro, Ishan

    2013-08-01

    Polyinosinic:polycytidylic acid (Poly I:C; 5 mg/kg body weight, ip) and lipopolysaccharide (LPS; 0.3 mg/kg body weight, ip) induced microglial and astrocytic activation in Sprague Dawley rats. Higher microglial and astrocytic activities were noticed in Poly I:C infused rats throughout the hippocampus till postnatal day 21 with a comparatively weaker response in LPS group. However, LPS induced inflammation persisted even after postnatal day 21, indicating thereby, that the Poly I:C (viral mimic) produces an acute inflammation, while LPS (bacterial endotoxin) produces chronic inflammation when exposed during early neonatal life.

  9. Imaging neurotransmitter uptake and depletion in astrocytes

    SciTech Connect

    Tan, W. |; Haydon, P.G.; Yeung, E.S.

    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}

  10. Mechanisms of Astrocyte-Mediated Cerebral Edema

    PubMed Central

    Stokum, Jesse A.; Kurland, David B.; Gerzanich, Volodymyr; Simard, J. Marc

    2014-01-01

    Cerebral edema formation stems from disruption of blood brain barrier (BBB) integrity and occurs after injury to the CNS. Due to the restrictive skull, relatively small increases in brain volume can translate into impaired tissue perfusion and brain herniation. In excess, cerebral edema can be gravely harmful. Astrocytes are key participants in cerebral edema by virtue of their relationship with the cerebral vasculature, their unique compliment of solute and water transport proteins, and their general role in brain volume homeostasis. Following the discovery of aquaporins, passive conduits of water flow, aquaporin 4 (AQP4) was identified as the predominant astrocyte water channel. Normally, AQP4 is highly enriched at perivascular endfeet, the outermost layer of the BBB, whereas after injury, AQP4 expression disseminates to the entire astrocytic plasmalemma, a phenomenon termed dysregulation. Arguably, the most important role of AQP4 is to rapidly neutralize osmotic gradients generated by ionic transporters. In pathological conditions, AQP4 is believed to be intimately involved in the formation and clearance of cerebral edema. In this review, we discuss aquaporin function and localization in the BBB during health and injury, and we examine post-injury ionic events that modulate AQP4- dependent edema formation. PMID:24996934

  11. Astrocyte Contributions to Flow/Pressure-Evoked Parenchymal Arteriole Vasoconstriction

    PubMed Central

    Kim, Ki Jung; Iddings, Jennifer A.; Stern, Javier E.; Blanco, Víctor M.; Croom, Deborah; Kirov, Sergei A.

    2015-01-01

    Basal and activity-dependent cerebral blood flow changes are coordinated by the action of critical processes, including cerebral autoregulation, endothelial-mediated signaling, and neurovascular coupling. The goal of our study was to determine whether astrocytes contribute to the regulation of parenchymal arteriole (PA) tone in response to hemodynamic stimuli (pressure/flow). Cortical PA vascular responses and astrocytic Ca2+ dynamics were measured using an in vitro rat/mouse brain slice model of perfused/pressurized PAs; studies were supplemented with in vivo astrocytic Ca2+ imaging. In vitro, astrocytes responded to PA flow/pressure increases with an increase in intracellular Ca2+. Astrocytic Ca2+ responses were corroborated in vivo, where acute systemic phenylephrine-induced increases in blood pressure evoked a significant increase in astrocytic Ca2+. In vitro, flow/pressure-evoked vasoconstriction was blunted when the astrocytic syncytium was loaded with BAPTA (chelating intracellular Ca2+) and enhanced when high Ca2+ or ATP were introduced to the astrocytic syncytium. Bath application of either the TRPV4 channel blocker HC067047 or purinergic receptor antagonist suramin blunted flow/pressure-evoked vasoconstriction, whereas K+ and 20-HETE signaling blockade showed no effect. Importantly, we found TRPV4 channel expression to be restricted to astrocytes and not the endothelium of PA. We present evidence for a novel role of astrocytes in PA flow/pressure-evoked vasoconstriction. Our data suggest that astrocytic TRPV4 channels are key molecular sensors of hemodynamic stimuli and that a purinergic, glial-derived signal contributes to flow/pressure-induced adjustments in PA tone. Together our results support bidirectional signaling within the neurovascular unit and astrocytes as key modulators of PA tone. PMID:26019339

  12. Astrocyte contributions to flow/pressure-evoked parenchymal arteriole vasoconstriction.

    PubMed

    Kim, Ki Jung; Iddings, Jennifer A; Stern, Javier E; Blanco, Víctor M; Croom, Deborah; Kirov, Sergei A; Filosa, Jessica A

    2015-05-27

    Basal and activity-dependent cerebral blood flow changes are coordinated by the action of critical processes, including cerebral autoregulation, endothelial-mediated signaling, and neurovascular coupling. The goal of our study was to determine whether astrocytes contribute to the regulation of parenchymal arteriole (PA) tone in response to hemodynamic stimuli (pressure/flow). Cortical PA vascular responses and astrocytic Ca(2+) dynamics were measured using an in vitro rat/mouse brain slice model of perfused/pressurized PAs; studies were supplemented with in vivo astrocytic Ca(2+) imaging. In vitro, astrocytes responded to PA flow/pressure increases with an increase in intracellular Ca(2+). Astrocytic Ca(2+) responses were corroborated in vivo, where acute systemic phenylephrine-induced increases in blood pressure evoked a significant increase in astrocytic Ca(2+). In vitro, flow/pressure-evoked vasoconstriction was blunted when the astrocytic syncytium was loaded with BAPTA (chelating intracellular Ca(2+)) and enhanced when high Ca(2+) or ATP were introduced to the astrocytic syncytium. Bath application of either the TRPV4 channel blocker HC067047 or purinergic receptor antagonist suramin blunted flow/pressure-evoked vasoconstriction, whereas K(+) and 20-HETE signaling blockade showed no effect. Importantly, we found TRPV4 channel expression to be restricted to astrocytes and not the endothelium of PA. We present evidence for a novel role of astrocytes in PA flow/pressure-evoked vasoconstriction. Our data suggest that astrocytic TRPV4 channels are key molecular sensors of hemodynamic stimuli and that a purinergic, glial-derived signal contributes to flow/pressure-induced adjustments in PA tone. Together our results support bidirectional signaling within the neurovascular unit and astrocytes as key modulators of PA tone. PMID:26019339

  13. Responses of astrocytes in culture after low dose laser irradiation

    SciTech Connect

    Yew, D.T.; Zheng, D.R.; Au, C.; Li, W.W. )

    1990-03-01

    The effect of Helium-Neon low dose laser on astrocytes was investigated in cultures of isolated astrocytes from albino neonatal rats. The laser appeared to inhibit the growth of astrocytes as exemplified by the smaller sizes of the cells and the decreased leucine uptake in each cell after treatment. Temporary decrease in the number of mitoses was also observed, but this trend was reversed soon after. Electron microscopic studies revealed an increase in buddings from cell bodies and processes (branches) after irradiation.

  14. Motor neuron-astrocyte interactions and levels of Cu,Zn superoxide dismutase in sporadic amyotrophic lateral sclerosis.

    PubMed

    O'Reilly, S A; Roedica, J; Nagy, D; Hallewell, R A; Alderson, K; Marklund, S L; Kuby, J; Kushner, P D

    1995-02-01

    Copper, zinc superoxide dismutase (SOD1) is involved in neutralizing free radicals within cells, and mutant forms of the enzyme have recently been shown to occur in about 20% of familial cases of amyotrophic lateral sclerosis (ALS). To explore the mechanism of SOD1 involvement in ALS, we have analyzed SOD1 in sporadic ALS using activity assays and immunocyto-chemistry. Analyses of SOD1 activity in washed erythrocytes revealed no difference between 13 ALS cases and 4 controls. Spinal cord sections from 6 ALS cases, 1 primary lateral sclerosis (PLS) case, and 1 control case were stained using three different antibodies to SOD1. Since astrocytes are closely associated with motor neurons, antibodies to glial fibrillary acidic protein (GFAP) and vimentin were used as independent monitors of astrocytes. The principal findings from localizations are: (1) normal motor neurons do not have higher levels of SOD1 than other neurons, (2) there was no detectable difference in SOD1 levels in motor neurons of ALS cases and controls, (3) ALS spinal cord displayed a reduction or absence of SOD1-reactive astrocytes compared to the control and PLS cases, and (4) examination of GFAP-stained sections and morphometry showed that the normal close association between astrocytic processes and motor neuron somata was decreased in the ALS and PLS cases. These results indicate the disease mechanism in sporadic ALS may involve alterations in spinal cord astrocytes.

  15. Glutamine synthetase stability and subcellular distribution in astrocytes are regulated by γ-aminobutyric type B receptors.

    PubMed

    Huyghe, Deborah; Nakamura, Yasuko; Terunuma, Miho; Faideau, Mathilde; Haydon, Philip; Pangalos, Menelas N; Moss, Stephen J

    2014-10-17

    Emerging evidence suggests that functional γ-aminobutyric acid B receptors (GABABRs) are expressed by astrocytes within the mammalian brain. GABABRs are heterodimeric G-protein-coupled receptors that are composed of R1/R2 subunits. To date, they have been characterized in neurons as the principal mediators of sustained inhibitory signaling; however their roles in astrocytic physiology have been ill defined. Here we reveal that the cytoplasmic tail of the GABABR2 subunit binds directly to the astrocytic protein glutamine synthetase (GS) and that this interaction determines the subcellular localization of GS. We further demonstrate that the binding of GS to GABABR2 increases the steady state expression levels of GS in heterologous cells and in mouse primary astrocyte culture. Mechanistically this increased stability of GS in the presence of GABABR2 occurs via reduced proteasomal degradation. Collectively, our results suggest a novel role for GABABRs as regulators of GS stability. Given the critical role that GS plays in the glutamine-glutamate cycle, astrocytic GABABRs may play a critical role in supporting both inhibitory and excitatory neurotransmission.

  16. Development of a method for the purification and culture of rodent astrocytes.

    PubMed

    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

    2011-09-01

    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 apoptosis in vivo and that the vast majority of astrocytes contact blood vessels, suggesting that astrocytes are matched to blood vessels by competing for vascular-derived trophic factors such as HBEGF. Compared to traditional astrocyte cultures, the gene profiles of the cultured purified postnatal astrocytes much more closely resemble those of in vivo astrocytes. Although these astrocytes strongly promote synapse formation and function, they do not secrete glutamate in response to stimulation.

  17. Evidence for involvement of the astrocytic benzodiazepine receptor in the mechanism of action of convulsant and anticonvulsant drugs

    SciTech Connect

    Bender, A.S.; Hertz, L.

    1988-01-01

    The anticonvulsant drugs carbamazepine, phenobarbital, trimethadione, valproic acid and ethosuximide at pharmacologically relevant concentrations inhibit (/sup 3/H)diazepam binding to astrocytes in primary cultures but have much less effect on a corresponding preparation of neurons. Phenytoin as well as pentobarbital (which is not used chronically as an anticonvulsant) are equipotent in the two cell types. The convulsants picrotoxinin and pentylenetetrazol, the convulsant benzodiazepine RO 5-3663 and the two convulsant barbiturates DMBB and CHEB similarly inhibit diazepam binding to astrocytes but have little effect on neurons. On the basis of these findings it is suggested that these convulsants and anticonvulsants owe at least part of their effect to an interaction with the astrocytic benzodiazepine receptor, perhaps by interference with a calcium channel.

  18. Handling of iron oxide and silver nanoparticles by astrocytes.

    PubMed

    Hohnholt, Michaela C; Geppert, Mark; Luther, Eva M; Petters, Charlotte; Bulcke, Felix; Dringen, Ralf

    2013-02-01

    Metal-containing nanoparticles (NPs) are currently used for various biomedical applications. Since such NPs are able to enter the brain, the cells of this organ have to deal with NPs and with NP-derived metal ions. In brain, astrocytes are considered to play a key function in regulating metal homeostasis and in protecting other brain cells against metal toxicity. Thus, among the different types of brain cells, especially astrocytes are of interest regarding the uptake and the handling of metal-containing NPs. This article summarizes the current knowledge on the consequences of an exposure of astrocytes to NPs. Special focus will be given to magnetic iron oxide nanoparticles (IONPs) and silver nanoparticles (AgNPs), since the biocompatibility of these NPs has been studied for astrocytes in detail. Cultured astrocytes efficiently accumulate IONPs and AgNPs in a time-, concentration- and temperature-dependent manner by endocytotic processes. Astrocytes are neither acutely damaged by the exposure to high concentrations of NPs nor by the prolonged intracellular presence of large amounts of accumulated NPs. Although metal ions are liberated from accumulated NPs, NP-derived iron and silver ions are not exported from astrocytes but are rather stored in proteins such as ferritin and metallothioneins which are synthesized in NP-treated astrocytes. The efficient accumulation of large amounts of metal-containing NPs and the upregulation of proteins that safely store NP-derived metal ions suggest that astrocytes protect the brain against the potential toxicity of metal-containing NPs.

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

    PubMed

    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

  20. The multifaceted role of astrocytes in regulating myelination.

    PubMed

    Kıray, Hülya; Lindsay, Susan L; Hosseinzadeh, Sara; Barnett, Susan C

    2016-09-01

    Astrocytes are the major glial cell of the central nervous system (CNS), providing both metabolic and physical support to other neural cells. After injury, astrocytes become reactive and express a continuum of phenotypes which may be supportive or inhibitory to CNS repair. This review will focus on the ability of astrocytes to influence myelination in the context of specific secreted factors, cytokines and other neural cell targets within the CNS. In particular, we focus on how astrocytes provide energy and cholesterol to neurons, influence synaptogenesis, affect oligodendrocyte biology and instigate cross-talk between the many cellular components of the CNS.

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

    PubMed

    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

  2. Astrocyte Reactivity Following Blast Exposure Involves Aberrant Histone Acetylation

    PubMed Central

    Bailey, Zachary S.; Grinter, Michael B.; VandeVord, Pamela J.

    2016-01-01

    Blast induced neurotrauma (BINT) is a prevalent injury within military and civilian populations. The injury is characterized by persistent inflammation at the cellular level which manifests as a multitude of cognitive and functional impairments. Epigenetic regulation of transcription offers an important control mechanism for gene expression and cellular function which may underlie chronic inflammation and result in neurodegeneration. We hypothesize that altered histone acetylation patterns may be involved in blast induced inflammation and the chronic activation of glial cells. This study aimed to elucidate changes to histone acetylation occurring following injury and the roles these changes may have within the pathology. Sprague Dawley rats were subjected to either a 10 or 17 psi blast overpressure within an Advanced Blast Simulator (ABS). Sham animals underwent the same procedures without blast exposure. Memory impairments were measured using the Novel Object Recognition (NOR) test at 2 and 7 days post-injury. Tissues were collected at 7 days for Western blot and immunohistochemistry (IHC) analysis. Sham animals showed intact memory at each time point. The novel object discrimination decreased significantly between two and 7 days for each injury group (p < 0.05). This is indicative of the onset of memory impairment. Western blot analysis showed glial fibrillary acidic protein (GFAP), a known marker of activated astrocytes, was elevated in the prefrontal cortex (PFC) following blast exposure for both injury groups. Analysis of histone protein extract showed no changes in the level of any total histone proteins within the PFC. However, acetylation levels of histone H2b, H3, and H4 were decreased in both groups (p < 0.05). Co-localization immunofluorescence was used to further investigate any potential correlation between decreased histone acetylation and astrocyte activation. These experiments showed a similar decrease in H3 acetylation in astrocytes exposed to a 17

  3. Astrocyte Reactivity Following Blast Exposure Involves Aberrant Histone Acetylation.

    PubMed

    Bailey, Zachary S; Grinter, Michael B; VandeVord, Pamela J

    2016-01-01

    Blast induced neurotrauma (BINT) is a prevalent injury within military and civilian populations. The injury is characterized by persistent inflammation at the cellular level which manifests as a multitude of cognitive and functional impairments. Epigenetic regulation of transcription offers an important control mechanism for gene expression and cellular function which may underlie chronic inflammation and result in neurodegeneration. We hypothesize that altered histone acetylation patterns may be involved in blast induced inflammation and the chronic activation of glial cells. This study aimed to elucidate changes to histone acetylation occurring following injury and the roles these changes may have within the pathology. Sprague Dawley rats were subjected to either a 10 or 17 psi blast overpressure within an Advanced Blast Simulator (ABS). Sham animals underwent the same procedures without blast exposure. Memory impairments were measured using the Novel Object Recognition (NOR) test at 2 and 7 days post-injury. Tissues were collected at 7 days for Western blot and immunohistochemistry (IHC) analysis. Sham animals showed intact memory at each time point. The novel object discrimination decreased significantly between two and 7 days for each injury group (p < 0.05). This is indicative of the onset of memory impairment. Western blot analysis showed glial fibrillary acidic protein (GFAP), a known marker of activated astrocytes, was elevated in the prefrontal cortex (PFC) following blast exposure for both injury groups. Analysis of histone protein extract showed no changes in the level of any total histone proteins within the PFC. However, acetylation levels of histone H2b, H3, and H4 were decreased in both groups (p < 0.05). Co-localization immunofluorescence was used to further investigate any potential correlation between decreased histone acetylation and astrocyte activation. These experiments showed a similar decrease in H3 acetylation in astrocytes exposed to a 17

  4. Toll like receptor 9 antagonism modulates spinal cord neuronal function and survival: Direct versus astrocyte-mediated mechanisms.

    PubMed

    Acioglu, Cigdem; Mirabelli, Ersilia; Baykal, Ahmet Tarik; Ni, Li; Ratnayake, Ayomi; Heary, Robert F; Elkabes, Stella

    2016-08-01

    Toll like receptors (TLRs) are expressed by cells of the immune system and mediate the host innate immune responses to pathogens. However, increasing evidence indicates that they are important contributors to central nervous system (CNS) function in health and in pathological conditions involving sterile inflammation. In agreement with this idea, we have previously shown that intrathecal administration of a TLR9 antagonist, cytidine-phosphate-guanosine oligodeoxynucleotide 2088 (CpG ODN 2088), ameliorates the outcomes of spinal cord injury (SCI). Although these earlier studies showed a marked effect of CpG ODN 2088 on inflammatory cells, the expression of TLR9 in spinal cord (SC) neurons and astrocytes suggested that the antagonist exerts additional effects through direct actions on these cells. The current study was undertaken to assess the direct effects of CpG ODN 2088 on SC neurons, astrocytes and astrocyte-neuron interactions, in vitro. We report, for the first time, that inhibition of TLR9 in cultured SC neurons alters their function and confers protection against kainic acid (KA)-induced excitotoxic death. Moreover, the TLR9 antagonist attenuated the KA-elicited endoplasmic reticulum (ER) stress response in neurons, in vitro. CpG ODN 2088 also reduced the transcript levels and release of chemokine (C-X-C) motif ligand 1 (CXCL1) and monocyte chemotactic protein 1 (MCP-1) by astrocytes and it diminished interleukin-6 (IL-6) release without affecting transcript levels in vitro. Conditioned medium (CM) of CpG ODN 2088-treated astroglial cultures decreased the viability of SC neurons compared to CM of vehicle-treated astrocytes. However, this toxicity was not observed when astrocytes were co-cultured with neurons. Although CpG ODN 2088 limited the survival-promoting effects of astroglia, it did not reduce neuronal viability compared to controls grown in the absence of astrocytes. We conclude that the TLR9 antagonist acts directly on both SC neurons and astrocytes

  5. Role of astrocytic glutamate transporter in alcohol use disorder

    PubMed Central

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

    2016-01-01

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

  6. Neuron-glia interactions through the Heartless FGF receptor signaling pathway mediate morphogenesis of Drosophila astrocytes.

    PubMed

    Stork, Tobias; Sheehan, Amy; Tasdemir-Yilmaz, Ozge E; Freeman, Marc R

    2014-07-16

    Astrocytes are critically important for neuronal circuit assembly and function. Mammalian protoplasmic astrocytes develop a dense ramified meshwork of cellular processes to form intimate contacts with neuronal cell bodies, neurites, and synapses. This close neuron-glia morphological relationship is essential for astrocyte function, but it remains unclear how astrocytes establish their intricate morphology, organize spatial domains, and associate with neurons and synapses in vivo. Here we characterize a Drosophila glial subtype that shows striking morphological and functional similarities to mammalian astrocytes. We demonstrate that the Fibroblast growth factor (FGF) receptor Heartless autonomously controls astrocyte membrane growth, and the FGFs Pyramus and Thisbe direct astrocyte processes to ramify specifically in CNS synaptic regions. We further show that the shape and size of individual astrocytes are dynamically sculpted through inhibitory or competitive astrocyte-astrocyte interactions and Heartless FGF signaling. Our data identify FGF signaling through Heartless as a key regulator of astrocyte morphological elaboration in vivo.

  7. Astrocytes Enhance Streptococcus suis-Glial Cell Interaction in Primary Astrocyte-Microglial Cell Co-Cultures.

    PubMed

    Seele, Jana; Nau, Roland; Prajeeth, Chittappen K; Stangel, Martin; Valentin-Weigand, Peter; Seitz, Maren

    2016-06-13

    Streptococcus (S.) suis infections are the most common cause of meningitis in pigs. Moreover, S. suis is a zoonotic pathogen, which can lead to meningitis in humans, mainly in adults. We assume that glial cells may play a crucial role in host-pathogen interactions during S. suis infection of the central nervous system. Glial cells are considered to possess important functions during inflammation and injury of the brain in bacterial meningitis. In the present study, we established primary astrocyte-microglial cell co-cultures to investigate interactions of S. suis with glial cells. For this purpose, microglial cells and astrocytes were isolated from new-born mouse brains and characterized by flow cytometry, followed by the establishment of astrocyte and microglial cell mono-cultures as well as astrocyte-microglial cell co-cultures. In addition, we prepared microglial cell mono-cultures co-incubated with uninfected astrocyte mono-culture supernatants and astrocyte mono-cultures co-incubated with uninfected microglial cell mono-culture supernatants. After infection of the different cell cultures with S. suis, bacteria-cell association was mainly observed with microglial cells and most prominently with a non-encapsulated mutant of S. suis. A time-dependent induction of NO release was found only in the co-cultures and after co-incubation of microglial cells with uninfected supernatants of astrocyte mono-cultures mainly after infection with the capsular mutant. Only moderate cytotoxic effects were found in co-cultured glial cells after infection with S. suis. Taken together, astrocytes and astrocyte supernatants increased interaction of microglial cells with S. suis. Astrocyte-microglial cell co-cultures are suitable to study S. suis infections and bacteria-cell association as well as NO release by microglial cells was enhanced in the presence of astrocytes.

  8. Astrocytes Enhance Streptococcus suis-Glial Cell Interaction in Primary Astrocyte-Microglial Cell Co-Cultures

    PubMed Central

    Seele, Jana; Nau, Roland; Prajeeth, Chittappen K.; Stangel, Martin; Valentin-Weigand, Peter; Seitz, Maren

    2016-01-01

    Streptococcus (S.) suis infections are the most common cause of meningitis in pigs. Moreover, S. suis is a zoonotic pathogen, which can lead to meningitis in humans, mainly in adults. We assume that glial cells may play a crucial role in host-pathogen interactions during S. suis infection of the central nervous system. Glial cells are considered to possess important functions during inflammation and injury of the brain in bacterial meningitis. In the present study, we established primary astrocyte-microglial cell co-cultures to investigate interactions of S. suis with glial cells. For this purpose, microglial cells and astrocytes were isolated from new-born mouse brains and characterized by flow cytometry, followed by the establishment of astrocyte and microglial cell mono-cultures as well as astrocyte-microglial cell co-cultures. In addition, we prepared microglial cell mono-cultures co-incubated with uninfected astrocyte mono-culture supernatants and astrocyte mono-cultures co-incubated with uninfected microglial cell mono-culture supernatants. After infection of the different cell cultures with S. suis, bacteria-cell association was mainly observed with microglial cells and most prominently with a non-encapsulated mutant of S. suis. A time-dependent induction of NO release was found only in the co-cultures and after co-incubation of microglial cells with uninfected supernatants of astrocyte mono-cultures mainly after infection with the capsular mutant. Only moderate cytotoxic effects were found in co-cultured glial cells after infection with S. suis. Taken together, astrocytes and astrocyte supernatants increased interaction of microglial cells with S. suis. Astrocyte-microglial cell co-cultures are suitable to study S. suis infections and bacteria-cell association as well as NO release by microglial cells was enhanced in the presence of astrocytes. PMID:27304968

  9. Novel metabotropic glutamate receptor negatively coupled to adenylyl cyclase in cultured rat cerebellar astrocytes.

    PubMed

    Kanumilli, Srinivasan; Toms, Nick J; Roberts, Peter J

    2004-04-01

    Several excitatory amino acid ligands were found potently to inhibit forskolin-stimulated cAMP accumulation in rat cultured cerebellar astrocytes: L-cysteine sulfinic acid (L-CSA) = L-aspartate > L-glutamate >/= the glutamate uptake inhibitor, L-PDC. This property did not reflect activation of conventional glutamate receptors, since the selective ionotropic glutamate receptor agonists NMDA, AMPA, and kainate, as well as several mGlu receptor agonists [(1S,3R)-ACPD, (S)-DHPG, DCG-IV, L-AP4, L-quisqualate, and L-CCG-I], were without activity. In addition, the mGlu receptor antagonists, L-AP3, (S)-4CPG, Eglu, LY341495, (RS)-CPPG, and (S)-MCPG failed to reverse 30 microM glutamate-mediated inhibitory responses. L-PDC-mediated inhibition was abolished by the addition of the enzyme glutamate-pyruvate transaminase. This finding suggests that the effect of L-PDC is indirect and that it is mediated through endogenously released L-glutamate. Interestingly, L-glutamate-mediated inhibitory responses were resistant to pertussis toxin, suggesting that G(i)/G(o) type G proteins were not involved. However, inhibition of protein kinase C (PKC, either via the selective PKC inhibitor GF109203X or chronic PMA treatment) augmented glutamate-mediated inhibitory responses. Although mGlu3 receptors (which are negatively coupled to adenylyl cyclase) are expressed in astrocyte populations, in our study Western blot analysis indicated that this receptor type was not expressed in cerebellar astrocytes. We therefore suggest that cerebellar astrocytes express a novel mGlu receptor, which is negatively coupled to adenylyl cyclase, and possesses an atypical pharmacological profile. PMID:14999808

  10. Motor neuron death in ALS – programmed by astrocytes?

    PubMed Central

    Pirooznia, Sheila K.; Dawson, Valina L.; Dawson, Ted M.

    2014-01-01

    Motor neurons in ALS die via cell-autonomous and non-cell autonomous mechanisms. Using adult human astrocytes and motor neurons, Re et al (2014) discover that familial and sporadic ALS derived human adult astrocytes secrete neurotoxic factors that selectively kill motor neurons through necroptosis, suggesting a new therapeutic avenue. PMID:24607221

  11. Ghrelin Regulates Glucose and Glutamate Transporters in Hypothalamic Astrocytes

    PubMed Central

    Fuente-Martín, Esther; García-Cáceres, Cristina; Argente-Arizón, Pilar; Díaz, Francisca; Granado, Miriam; Freire-Regatillo, Alejandra; Castro-González, David; Ceballos, María L.; Frago, Laura M.; Dickson, Suzanne L.; Argente, Jesús; Chowen, Julie A.

    2016-01-01

    Hypothalamic astrocytes can respond to metabolic signals, such as leptin and insulin, to modulate adjacent neuronal circuits and systemic metabolism. Ghrelin regulates appetite, adiposity and glucose metabolism, but little is known regarding the response of astrocytes to this orexigenic hormone. We have used both in vivo and in vitro approaches to demonstrate that acylated ghrelin (acyl-ghrelin) rapidly stimulates glutamate transporter expression and glutamate uptake by astrocytes. Moreover, acyl-ghrelin rapidly reduces glucose transporter (GLUT) 2 levels and glucose uptake by these glial cells. Glutamine synthetase and lactate dehydrogenase decrease, while glycogen phosphorylase and lactate transporters increase in response to acyl-ghrelin, suggesting a change in glutamate and glucose metabolism, as well as glycogen storage by astrocytes. These effects are partially mediated through ghrelin receptor 1A (GHSR-1A) as astrocytes do not respond equally to desacyl-ghrelin, an isoform that does not activate GHSR-1A. Moreover, primary astrocyte cultures from GHSR-1A knock-out mice do not change glutamate transporter or GLUT2 levels in response to acyl-ghrelin. Our results indicate that acyl-ghrelin may mediate part of its metabolic actions through modulation of hypothalamic astrocytes and that this effect could involve astrocyte mediated changes in local glucose and glutamate metabolism that alter the signals/nutrients reaching neighboring neurons. PMID:27026049

  12. Ghrelin Regulates Glucose and Glutamate Transporters in Hypothalamic Astrocytes.

    PubMed

    Fuente-Martín, Esther; García-Cáceres, Cristina; Argente-Arizón, Pilar; Díaz, Francisca; Granado, Miriam; Freire-Regatillo, Alejandra; Castro-González, David; Ceballos, María L; Frago, Laura M; Dickson, Suzanne L; Argente, Jesús; Chowen, Julie A

    2016-03-30

    Hypothalamic astrocytes can respond to metabolic signals, such as leptin and insulin, to modulate adjacent neuronal circuits and systemic metabolism. Ghrelin regulates appetite, adiposity and glucose metabolism, but little is known regarding the response of astrocytes to this orexigenic hormone. We have used both in vivo and in vitro approaches to demonstrate that acylated ghrelin (acyl-ghrelin) rapidly stimulates glutamate transporter expression and glutamate uptake by astrocytes. Moreover, acyl-ghrelin rapidly reduces glucose transporter (GLUT) 2 levels and glucose uptake by these glial cells. Glutamine synthetase and lactate dehydrogenase decrease, while glycogen phosphorylase and lactate transporters increase in response to acyl-ghrelin, suggesting a change in glutamate and glucose metabolism, as well as glycogen storage by astrocytes. These effects are partially mediated through ghrelin receptor 1A (GHSR-1A) as astrocytes do not respond equally to desacyl-ghrelin, an isoform that does not activate GHSR-1A. Moreover, primary astrocyte cultures from GHSR-1A knock-out mice do not change glutamate transporter or GLUT2 levels in response to acyl-ghrelin. Our results indicate that acyl-ghrelin may mediate part of its metabolic actions through modulation of hypothalamic astrocytes and that this effect could involve astrocyte mediated changes in local glucose and glutamate metabolism that alter the signals/nutrients reaching neighboring neurons.

  13. Astrocytes are central in the pathomechanisms of vanishing white matter

    PubMed Central

    Dooves, Stephanie; Bugiani, Marianna; Postma, Nienke L.; Polder, Emiel; Land, Niels; Horan, Stephen T.; van Deijk, Anne-Lieke F.; van de Kreeke, Aleid; Jacobs, Gerbren; Vuong, Caroline; Klooster, Jan; Kamermans, Maarten; Wortel, Joke; Wisse, Lisanne E.; Scheper, Gert C.; Abbink, Truus E.M.; Heine, Vivi M.; van der Knaap, Marjo S.

    2016-01-01

    Vanishing white matter (VWM) is a fatal leukodystrophy that is caused by mutations in genes encoding subunits of eukaryotic translation initiation factor 2B (eIF2B). Disease onset and severity are codetermined by genotype. White matter astrocytes and oligodendrocytes are almost exclusively affected; however, the mechanisms of VWM development remain unclear. Here, we used VWM mouse models, patients’ tissue, and cell cultures to investigate whether astrocytes or oligodendrocytes are the primary affected cell type. We generated 2 mouse models with mutations (Eif2b5Arg191His/Arg191His and Eif2b4Arg484Trp/Arg484Trp) that cause severe VWM in humans and then crossed these strains to develop mice with various mutation combinations. Phenotypic severity was highly variable and dependent on genotype, reproducing the clinical spectrum of human VWM. In all mutant strains, impaired maturation of white matter astrocytes preceded onset and paralleled disease severity and progression. Bergmann glia and retinal Müller cells, nonforebrain astrocytes that have not been associated with VWM, were also affected, and involvement of these cells was confirmed in VWM patients. In coculture, VWM astrocytes secreted factors that inhibited oligodendrocyte maturation, whereas WT astrocytes allowed normal maturation of VWM oligodendrocytes. These studies demonstrate that astrocytes are central in VWM pathomechanisms and constitute potential therapeutic targets. Importantly, astrocytes should also be considered in the pathophysiology of other white matter disorders. PMID:26974157

  14. Neuroimmunological Implications of AQP4 in Astrocytes.

    PubMed

    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

  15. Neuroimmunological Implications of AQP4 in Astrocytes

    PubMed Central

    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

  16. Calcium dynamics in astrocyte processes during neurovascular coupling

    PubMed Central

    Otsu, Yo; Couchman, Kiri; Lyons, Declan G; Collot, Mayeul; Agarwal, Amit; Mallet, Jean-Maurice; Pfrieger, Frank W; Bergles, Dwight E; Charpak, Serge

    2015-01-01

    Enhanced neuronal activity in the brain triggers a local increase in blood flow, termed functional hyperemia, via several mechanisms, including calcium (Ca2+) signaling in astrocytes. However, recent in vivo studies have questioned the role of astrocytes in functional hyperemia because of the slow and sparse dynamics of their somatic Ca2+ signals and the absence of glutamate metabotropic receptor 5 in adults. Here, we reexamined their role in neurovascular coupling by selectively expressing a genetically encoded Ca2+ sensor in astrocytes of the olfactory bulb. We show that in anesthetized mice, the physiological activation of olfactory sensory neuron (OSN) terminals reliably triggers Ca2+ increases in astrocyte processes but not in somata. These Ca2+ increases systematically precede the onset of functional hyperemia by 1–2 s, reestablishing astrocytes as potential regulators of neurovascular coupling. PMID:25531572

  17. Expression of familial Alzheimer disease presenilin 1 gene attenuates vesicle traffic and reduces peptide secretion in cultured astrocytes devoid of pathologic tissue environment.

    PubMed

    Stenovec, Matjaž; Trkov, Saša; Lasič, Eva; Terzieva, Slavica; Kreft, Marko; Rodríguez Arellano, José Julio; Parpura, Vladimir; Verkhratsky, Alexei; Zorec, Robert

    2016-02-01

    In the brain, astrocytes provide metabolic and trophic support to neurones. Failure in executing astroglial homeostatic functions may contribute to the initiation and propagation of diseases, including Alzheimer disease (AD), characterized by a progressive loss of neurones over years. Here, we examined whether astrocytes from a mice model of AD isolated in the presymptomatic phase of the disease exhibit alterations in vesicle traffic, vesicular peptide release and purinergic calcium signaling. In cultured astrocytes isolated from a newborn wild-type (wt) and 3xTg-AD mouse, secretory vesicles and acidic endosomes/lysosomes were labeled by transfection with plasmid encoding atrial natriuretic peptide tagged with mutant green fluorescent protein (ANP.emd) and by LysoTracker, respectively. The intracellular Ca(2+) concentration ([Ca(2+)]i) was monitored with Fluo-2 and visualized by confocal microscopy. In comparison with controls, spontaneous mobility of ANP- and LysoTracker-labeled vesicles was diminished in 3xTg-AD astrocytes; the track length (TL), maximal displacement (MD) and directionality index (DI) were all reduced in peptidergic vesicles and in endosomes/lysosomes (P < 0.001), as was the ATP-evoked attenuation of vesicle mobility. Similar impairment of peptidergic vesicle trafficking was observed in wt rat astrocytes transfected to express mutated presenilin 1 (PS1M146V). The ATP-evoked ANP discharge from single vesicles was less efficient in 3xTg-AD and PS1M146V-expressing astrocytes than in respective wt controls (P < 0.05). Purinergic stimulation evoked biphasic and oscillatory [Ca(2+)]i responses; the latter were less frequent (P < 0.001) in 3xTg-AD astrocytes. Expression of PS1M146V in astrocytes impairs vesicle dynamics and reduces evoked secretion of the signaling molecule ANP; both may contribute to the development of AD.

  18. Inhibition of glycogen synthase kinase-3β by lithium chloride suppresses 6-hydroxydopamine-induced inflammatory response in primary cultured astrocytes.

    PubMed

    Wang, Hong-Mei; Zhang, Ting; Li, Qiang; Huang, Jian-Kang; Chen, Rong-Fu; Sun, Xiao-Jiang

    2013-11-01

    An increasing amount of evidence has emerged to suggest that neuroinflammatory process is involved in the pathogenesis of Parkinson's disease (PD). Activated microglia and astrocytes are found in the substantia nigra (SN) of Parkinson's disease brains as well as in animal models of Parkinson's disease. Although reactive astrocytes are involved in the progression of PD, the role of reactive astrocytes in neuroinflammation of PD has received limited attention to date. Recently, Glycogen synthase kinase-3β (GSK-3β) was identified as a crucial regulator of the inflammatory response. The purpose of this study was to explore the mechanism by which 6-hydroxydopamine (6-OHDA) induces inflammatory response in astrocytes and observe the anti-inflammatory effect of lithium chloride (LiCl) on 6-OHDA-treated astrocytes. In the present study, we found that glial fibrillary acidic protein (GFAP) was markedly upregulated in the presence of 6-OHDA. Moreover, our results revealed that proinflammatory molecules including inducible nitric oxide synthase (iNOS), nitric oxide (NO), cyclooxygenase-2(COX-2), prostaglandins E2 (PGE2), and tumor necrosis factor-α (TNF-α) were obviously increased in astrocytes exposed to 6-OHDA. Western blot analysis revealed that 6-OHDA significantly increased dephosphorylation/activation of GSK-3β as well as the nuclear translocation of nuclear factor-κB (NF-κB) p65. Besides, GSK-3β inhibitor LiCl and SB415286 inhibited the GSK-3β/NF-κB signaling pathway, leading to the reduction of proinflammatory molecules in 6-OHDA-activated astrocytes. These results confirmed that GSK-3β inhibitor LiCl and SB415286 provide protection against neuroinflammation in 6-OHDA-treated astrocytes. Therefore, GSK-3β may be a potential therapeutic target for the treatment of PD.

  19. Expressional analysis of the astrocytic Kir4.1 channel in a pilocarpine–induced temporal lobe epilepsy model

    PubMed Central

    Nagao, Yuki; Harada, Yuya; Mukai, Takahiro; Shimizu, Saki; Okuda, Aoi; Fujimoto, Megumi; Ono, Asuka; Sakagami, Yoshihisa; Ohno, Yukihiro

    2013-01-01

    The inwardly rectifying potassium (Kir) channel Kir4.1 in brain astrocytes mediates spatial K+ buffering and regulates neural activities. Recent studies have shown that loss-of-function mutations in the human gene KCNJ10 encoding Kir4.1 cause epileptic seizures, suggesting a close relationship between the Kir4.1 channel function and epileptogenesis. Here, we performed expressional analysis of Kir4.1 in a pilocarpine-induced rat model of temporal lobe epilepsy (TLE) to explore the role of Kir4.1 channels in modifying TLE epileptogenesis. Treatment of rats with pilocarpine (350 mg/kg, i.p.) induced acute status epilepticus, which subsequently caused spontaneous seizures 7–8 weeks after the pilocarpine treatment. Western blot analysis revealed that TLE rats (interictal condition) showed significantly higher levels of Kir4.1 than the control animals in the cerebral cortex, striatum, and hypothalamus. However, the expression of other Kir subunits, Kir5.1 and Kir2.1, remained unaltered. Immunohistochemical analysis illustrated that Kir4.1-immunoreactivity-positive astrocytes in the pilocarpine-induced TLE model were markedly increased in most of the brain regions examined, concomitant with an increase in the number of glial fibrillary acidic protein (GFAP)-positive astrocytes. In addition, Kir4.1 expression ratios relative to the number of astrocytes (Kir4.1-positive cells/GFAP-positive cells) were region-specifically elevated in the amygdala (i.e., medial and cortical amygdaloid nuclei) and sensory cortex. The present study demonstrated for the first time that the expression of astrocytic Kir4.1 channels was elevated in a pilocarpine-induced TLE model, especially in the amygdala, suggesting that astrocytic Kir4.1 channels play a role in modifying TLE epileptogenesis, possibly by acting as an inhibitory compensatory mechanism. PMID:23922547

  20. Expressional analysis of the astrocytic Kir4.1 channel in a pilocarpine-induced temporal lobe epilepsy model.

    PubMed

    Nagao, Yuki; Harada, Yuya; Mukai, Takahiro; Shimizu, Saki; Okuda, Aoi; Fujimoto, Megumi; Ono, Asuka; Sakagami, Yoshihisa; Ohno, Yukihiro

    2013-01-01

    The inwardly rectifying potassium (Kir) channel Kir4.1 in brain astrocytes mediates spatial K(+) buffering and regulates neural activities. Recent studies have shown that loss-of-function mutations in the human gene KCNJ10 encoding Kir4.1 cause epileptic seizures, suggesting a close relationship between the Kir4.1 channel function and epileptogenesis. Here, we performed expressional analysis of Kir4.1 in a pilocarpine-induced rat model of temporal lobe epilepsy (TLE) to explore the role of Kir4.1 channels in modifying TLE epileptogenesis. Treatment of rats with pilocarpine (350 mg/kg, i.p.) induced acute status epilepticus, which subsequently caused spontaneous seizures 7-8 weeks after the pilocarpine treatment. Western blot analysis revealed that TLE rats (interictal condition) showed significantly higher levels of Kir4.1 than the control animals in the cerebral cortex, striatum, and hypothalamus. However, the expression of other Kir subunits, Kir5.1 and Kir2.1, remained unaltered. Immunohistochemical analysis illustrated that Kir4.1-immunoreactivity-positive astrocytes in the pilocarpine-induced TLE model were markedly increased in most of the brain regions examined, concomitant with an increase in the number of glial fibrillary acidic protein (GFAP)-positive astrocytes. In addition, Kir4.1 expression ratios relative to the number of astrocytes (Kir4.1-positive cells/GFAP-positive cells) were region-specifically elevated in the amygdala (i.e., medial and cortical amygdaloid nuclei) and sensory cortex. The present study demonstrated for the first time that the expression of astrocytic Kir4.1 channels was elevated in a pilocarpine-induced TLE model, especially in the amygdala, suggesting that astrocytic Kir4.1 channels play a role in modifying TLE epileptogenesis, possibly by acting as an inhibitory compensatory mechanism.

  1. Microglia-derived interleukin-6 and leukaemia inhibitory factor promote astrocytic differentiation of neural stem/progenitor cells.

    PubMed

    Nakanishi, Masaya; Niidome, Tetsuhiro; Matsuda, Satoru; Akaike, Akinori; Kihara, Takeshi; Sugimoto, Hachiro

    2007-02-01

    Neural stem/progenitor cells (NSPCs) proliferate and differentiate depending on their intrinsic properties and local environment. It has been recognized that astrocytes promote neurogenic differentiation of NSPCs, suggesting the importance of cell-cell interactions between glial cells and NSPCs. Recent studies have demonstrated that microglia, one type of glial cells, play an important role in neurogenesis. However, little is known about how activated microglia control the proliferation and differentiation of NSPCs. In this study, we investigated the possibility that microglia-derived soluble factors regulate the behaviour of NSPCs. To this end, NSPCs and microglial cultures were obtained from rat embryonic day 16 subventricular zone (SVZ) and rat postnatal 1 day cortex, respectively, and the conditioned medium from microglia was prepared. Microglial-conditioned medium had no significant effect on the proliferation of NSPCs. In contrast, it increased the percentage of cells positive for a marker of astrocytes, glial fibrillary acidic protein (GFAP) during differentiation. The induction of astrocytic differentiation by microglial-conditioned medium was reduced by the inhibition of the Janus kinase/signal transducer and activation of transcription (JAK/STAT) and mitogen-activated protein kinase (MAPK) pathways. Furthermore, microglia-derived interleukin (IL)-6 and leukaemia inhibitory factor (LIF) were identified as essential molecules for this astrocytic differentiation using neutralizing antibodies and recombinant cytokines. Our results suggest that microglia as well as astrocytes contribute to the integrity of the local environment of NSPCs, and at least IL-6 and LIF released by activated microglia promote astrocytic differentiation of NSPCs via the activation of the JAK/STAT and MAPK pathways.

  2. Transcriptomic analyses of primary astrocytes under TNFα treatment.

    PubMed

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

    2016-03-01

    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 of progressive gene expression and cellular changes [3]. Interestingly, in this context, astrocytes can re-acquire neurogenic properties. It has been shown that astrocytes can undergo dedifferentiation upon injury and inflammation, and may re-acquire the potentiality of neural progenitors [4], [5], [6], [7]. To assess the effect of inflammation on astrocytes, primary mouse astrocytes were treated with tumor necrosis factor α (TNFα), one of the main pro-inflammatory cytokines. The strength of this study is that pure primary astrocytes were used. As microglia are highly reactive immune cells, we used a magnetic cell sorting separation (MACS) method to further obtain highly pure astrocyte cultures devoid of microglia. Here, we provide details of the microarray data, which have been deposited in the Gene Expression Omnibus (GEO) under the series accession number GSE73022. The analysis and interpretation of these data are included in Gabel et al. (2015). Analysis of gene expression indicated that the NFκB pathway-associated genes were induced after a TNFα treatment. We have shown that primary astrocytes devoid of microglia can respond to a TNFα treatment with the re-expression of genes implicated in the glial cell development. PMID:26981349

  3. Astrocytes grown in oculo: Expression of cell morphologies on the iris as revealed by GFA immunohistochemistry.

    PubMed

    Björklund, H

    1984-01-01

    Using two experimental approaches, the morphology of central astrocytes growing in vivo with the iris as a substratum were studied. When irides with mature intraocular grafts of cortex cerebri or locus coeruleus were stretch-prepared as whole mounts and processed for immunohistochemistry with antiserum against glial fibrillary acidic protein (GFA), a restricted halo of fluorescent cells and fibers was seen surrounding the grafts. Similarly, injection into the anterior eye chamber of adult rats, of a cell suspension prepared from cortex cerebri of 10-day-old rat pups gave rise to both multiple GFA-positive astrocytic islets of different sizes and cell densities as well as scattered individual cells on the anterior surface of the host iris. In contrast, astrocytes from similar cell suspensions prepared from young adult animals survived very poorly. In both types of experiments, a large variation in cell morphology ranging from immature epitheloid, via large flat cells with few thick processes, to typical mature star-shaped astrocytes was observed. This morphological variation is in agreement with that reported for similar cells in tissue culture. Immature-looking cells always had a strong perinuclear fluorescence; an inverse correlation was observed between cell body size and development of cell processes. Likewise, the fluorescence intensity was higher in well-developed cells as compared to more immature ones. The morphology of individual cells did not seem to be dependent upon the time in oculo, since no difference was observed between GFA-positive cells on irides examined 10 days and 6 weeks after injection of a cell suspension. Similarly, a high number of immature-looking cells was seen in irides with locus coeruleus transplants grafted more than 6 months earlier. Instead, the cell density seemed to be the crucial factor. Thus, star-shaped, well-developed cells were seen growing singly or in less dense groups whereas denser areas contained mainly immature

  4. Astrocytes grown in oculo: Expression of cell morphologies on the iris as revealed by GFA immunohistochemistry.

    PubMed

    Björklund, H

    1984-01-01

    Using two experimental approaches, the morphology of central astrocytes growing in vivo with the iris as a substratum were studied. When irides with mature intraocular grafts of cortex cerebri or locus coeruleus were stretch-prepared as whole mounts and processed for immunohistochemistry with antiserum against glial fibrillary acidic protein (GFA), a restricted halo of fluorescent cells and fibers was seen surrounding the grafts. Similarly, injection into the anterior eye chamber of adult rats, of a cell suspension prepared from cortex cerebri of 10-day-old rat pups gave rise to both multiple GFA-positive astrocytic islets of different sizes and cell densities as well as scattered individual cells on the anterior surface of the host iris. In contrast, astrocytes from similar cell suspensions prepared from young adult animals survived very poorly. In both types of experiments, a large variation in cell morphology ranging from immature epitheloid, via large flat cells with few thick processes, to typical mature star-shaped astrocytes was observed. This morphological variation is in agreement with that reported for similar cells in tissue culture. Immature-looking cells always had a strong perinuclear fluorescence; an inverse correlation was observed between cell body size and development of cell processes. Likewise, the fluorescence intensity was higher in well-developed cells as compared to more immature ones. The morphology of individual cells did not seem to be dependent upon the time in oculo, since no difference was observed between GFA-positive cells on irides examined 10 days and 6 weeks after injection of a cell suspension. Similarly, a high number of immature-looking cells was seen in irides with locus coeruleus transplants grafted more than 6 months earlier. Instead, the cell density seemed to be the crucial factor. Thus, star-shaped, well-developed cells were seen growing singly or in less dense groups whereas denser areas contained mainly immature

  5. Developmental alcohol exposure leads to a persistent change on astrocyte secretome.

    PubMed

    Trindade, Pablo; Hampton, Brian; Manhães, Alex C; Medina, Alexandre E

    2016-06-01

    Fetal alcohol spectrum disorder is the most common cause of mental disabilities in the western world. It has been quite established that acute alcohol exposure can dramatically affect astrocyte function. Because the effects of early alcohol exposure on cell physiology can persist into adulthood, we tested the hypothesis that ethanol exposure in ferrets during a period equivalent to the last months of human gestation leads to persistent changes in astrocyte secretome in vitro. Animals were treated with ethanol (3.5 g/kg) or saline between postnatal day (P)10-30. At P31, astrocyte cultures were made and cells were submitted to stable isotope labeling by amino acids. Twenty-four hour conditioned media of cells obtained from ethanol- or saline-treated animals (ET-CM or SAL-CM) were collected and analyzed by quantitative mass spectrometry in tandem with liquid chromatography. Here, we show that 65 out of 280 quantifiable proteins displayed significant differences comparing ET-CM to SAL-CM. Among the 59 proteins that were found to be reduced in ET-CM we observed components of the extracellular matrix such as laminin subunits α2, α4, β1, β2, and γ1 and the proteoglycans biglycan, heparan sulfate proteoglycan 2, and lumican. Proteins with trophic function such as insulin-like growth factor binding protein 4, pigment epithelium-derived factor, and clusterin as well as proteins involved on modulation of proteolysis such as metalloproteinase inhibitor 1 and plasminogen activator inhibitor-1 were also reduced. In contrast, pro-synaptogeneic proteins like thrombospondin-1, hevin as well as the modulator of extracelular matrix expression, angiotensinogen, were found increased in ET-CM. The analysis of interactome maps through ingenuity pathway analysis demonstrated that the amyloid beta A4 protein precursor, which was found reduced in ET-CM, was previously shown to interact with ten other proteins that exhibited significant changes in the ET-CM. Taken together our results

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

    PubMed

    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

  7. Study of red wine neuroprotection on astrocytes.

    PubMed

    Gómez-Serranillos, M Pilar; Martín, Sara; Ortega, Teresa; Palomino, Olga M; Prodanov, Marín; Vacas, Visitación; Hernández, Teresa; Estrella, Isabel; Carretero, M Emilia

    2009-12-01

    Phenolic composition of wine depends not only on the grape variety from which it is made, but on some external factors such as winemaking technology. Red wine possesses the most antioxidant effect because of its high polyphenolic content. The aim of this work is to study for the first time, the neuroprotective activity of four monovarietal Spanish red wines (Merlot (ME), Tempranillo (T), Garnacha (G) and Cabernet-Sauvignon (CS)) through its antioxidant ability, and to relate this neuroprotection to its polyphenolic composition, if possible. The wine effect on neuroprotection was studied through its effect as free radical scavenger against FeSO4, H2O2 and FeSO4 + H2O2. Effect on cell survival was determined by 3(4,5-dimethyltiazol-2-il)-2,5-diphenyltetrazolium reduction assay (MTT) and lactate dehydrogenase (LDH) release assay on astrocytes cultures. Results showed that most of the studied wine varieties induced neuroprotection through their antioxidant ability in astrocytes, Merlot being the most active; this variety is especially rich in phenolic compounds, mainly catechins and oligomeric proanthocyanidins. Our results show that red wine exerts a protection against oxidative stress generated by different toxic agents and that the observed neuroprotective activity is related to their polyphenolic content.

  8. Translational potential of astrocytes in brain disorders.

    PubMed

    Verkhratsky, Alexei; Steardo, Luca; Parpura, Vladimir; Montana, Vedrana

    2016-09-01

    Fundamentally, all brain disorders can be broadly defined as the homeostatic failure of this organ. As the brain is composed of many different cells types, including but not limited to neurons and glia, it is only logical that all the cell types/constituents could play a role in health and disease. Yet, for a long time the sole conceptualization of brain pathology was focused on the well-being of neurons. Here, we challenge this neuron-centric view and present neuroglia as a key element in neuropathology, a process that has a toll on astrocytes, which undergo complex morpho-functional changes that can in turn affect the course of the disorder. Such changes can be grossly identified as reactivity, atrophy with loss of function and pathological remodeling. We outline the pathogenic potential of astrocytes in variety of disorders, ranging from neurotrauma, infection, toxic damage, stroke, epilepsy, neurodevelopmental, neurodegenerative and psychiatric disorders, Alexander disease to neoplastic changes seen in gliomas. We hope that in near future we would witness glial-based translational medicine with generation of deliverables for the containment and cure of disorders. We point out that such as a task will require a holistic and multi-disciplinary approach that will take in consideration the concerted operation of all the cell types in the brain.

  9. Astrocytes refine cortical connectivity at dendritic spines

    PubMed Central

    Risher, W Christopher; Patel, Sagar; Kim, Il Hwan; Uezu, Akiyoshi; Bhagat, Srishti; Wilton, Daniel K; Pilaz, Louis-Jan; Singh Alvarado, Jonnathan; Calhan, Osman Y; Silver, Debra L; Stevens, Beth; Calakos, Nicole; Soderling, Scott H; Eroglu, Cagla

    2014-01-01

    During cortical synaptic development, thalamic axons must establish synaptic connections despite the presence of the more abundant intracortical projections. How thalamocortical synapses are formed and maintained in this competitive environment is unknown. Here, we show that astrocyte-secreted protein hevin is required for normal thalamocortical synaptic connectivity in the mouse cortex. Absence of hevin results in a profound, long-lasting reduction in thalamocortical synapses accompanied by a transient increase in intracortical excitatory connections. Three-dimensional reconstructions of cortical neurons from serial section electron microscopy (ssEM) revealed that, during early postnatal development, dendritic spines often receive multiple excitatory inputs. Immuno-EM and confocal analyses revealed that majority of the spines with multiple excitatory contacts (SMECs) receive simultaneous thalamic and cortical inputs. Proportion of SMECs diminishes as the brain develops, but SMECs remain abundant in Hevin-null mice. These findings reveal that, through secretion of hevin, astrocytes control an important developmental synaptic refinement process at dendritic spines. DOI: http://dx.doi.org/10.7554/eLife.04047.001 PMID:25517933

  10. Translational potential of astrocytes in brain disorders.

    PubMed

    Verkhratsky, Alexei; Steardo, Luca; Parpura, Vladimir; Montana, Vedrana

    2016-09-01

    Fundamentally, all brain disorders can be broadly defined as the homeostatic failure of this organ. As the brain is composed of many different cells types, including but not limited to neurons and glia, it is only logical that all the cell types/constituents could play a role in health and disease. Yet, for a long time the sole conceptualization of brain pathology was focused on the well-being of neurons. Here, we challenge this neuron-centric view and present neuroglia as a key element in neuropathology, a process that has a toll on astrocytes, which undergo complex morpho-functional changes that can in turn affect the course of the disorder. Such changes can be grossly identified as reactivity, atrophy with loss of function and pathological remodeling. We outline the pathogenic potential of astrocytes in variety of disorders, ranging from neurotrauma, infection, toxic damage, stroke, epilepsy, neurodevelopmental, neurodegenerative and psychiatric disorders, Alexander disease to neoplastic changes seen in gliomas. We hope that in near future we would witness glial-based translational medicine with generation of deliverables for the containment and cure of disorders. We point out that such as a task will require a holistic and multi-disciplinary approach that will take in consideration the concerted operation of all the cell types in the brain. PMID:26386136

  11. The expression of CAP1 after traumatic brain injury and its role in astrocyte proliferation.

    PubMed

    Zhang, Haiyan; Liu, Yonghua; Li, Yao; Zhou, Ying; Chen, Dongjian; Shen, Jianhong; Yan, Yaohua; Yan, Song; Wu, Xinmin; Li, Aihong; Guo, Aisong; Cheng, Chun

    2014-12-01

    Adenylate cyclase-associated protein 1 (CAP1), a member of cyclase-associated proteins involved in the regulation of actin filaments, was recently reported to play a role in the pathology of sciatic nerves injury. However, the distribution and function of CAP1 in the central nervous system (CNS) remain unclear. To investigate whether CAP1 is involved in CNS injury and repair, we used an acute traumatic brain injury (TBI) model in adult rats. Western blot analysis and immunohistochemistry showed a significant upregulation of CAP1 in ipsilateral peritrauma cortex compared with the contralateral and sham-operated ones. Double immunofluorescence staining showed that CAP1 was co-expressed with glial fibrillary acidic protein (GFAP). In addition, we detected that Ki-67 had colocalization with GFAP and CAP1 after TBI. In vitro, during the process of lipopolysaccharide (LPS)-induced primary astrocyte proliferation, we observed enhanced expression of CAP1. Specially, CAP1-specific siRNA-transfected primary astrocytes show significantly decreased ability for proliferation. Together, all these data indicated that the change of CAP1 protein expression was associated with astrocyte proliferation after the trauma of the central nervous system (CNS).

  12. Glycogen distribution in the microwave-fixed mouse brain reveals heterogeneous astrocytic patterns.

    PubMed

    Oe, Yuki; Baba, Otto; Ashida, Hitoshi; Nakamura, Kouichi C; Hirase, Hajime

    2016-09-01

    In the brain, glycogen metabolism has been implied in synaptic plasticity and learning, yet the distribution of this molecule has not been fully described. We investigated cerebral glycogen of the mouse by immunohistochemistry (IHC) using two monoclonal antibodies that have different affinities depending on the glycogen size. The use of focused microwave irradiation yielded well-defined glycogen immunoreactive signals compared with the conventional periodic acid-Schiff method. The IHC signals displayed a punctate distribution localized predominantly in astrocytic processes. Glycogen immunoreactivity (IR) was high in the hippocampus, striatum, cortex, and cerebellar molecular layer, whereas it was low in the white matter and most of the subcortical structures. Additionally, glycogen distribution in the hippocampal CA3-CA1 and striatum had a 'patchy' appearance with glycogen-rich and glycogen-poor astrocytes appearing in alternation. The glycogen patches were more evident with large-molecule glycogen in young adult mice but they were hardly observable in aged mice (1-2 years old). Our results reveal brain region-dependent glycogen accumulation and possibly metabolic heterogeneity of astrocytes. GLIA 2016;64:1532-1545. PMID:27353480

  13. State-dependent changes in astrocyte regulation of extrasynaptic NMDA receptor signalling in neurosecretory neurons.

    PubMed

    Fleming, Tiffany M; Scott, Victoria; Naskar, Krishna; Joe, Natalie; Brown, Colin H; Stern, Javier E

    2011-08-15

    Despite the long-established presence of glutamate NMDA receptors at extrasynaptic sites (eNMDARs), their functional roles remain poorly understood. Factors influencing the concentration and time course of glutamate in the extrasynaptic space, such as the topography of the neuronal–glial microenvironment, as well as glial glutamate transporters, are expected to affect eNMDAR-mediated signalling strength. In this study, we used in vitro and in vivo electrophysiological recordings to assess the properties, functional relevance and modulation of a persistent excitatory current mediated by activation of eNMDARs in hypothalamic supraoptic nucleus (SON) neurons. We found that ambient glutamate of a non-synaptic origin activates eNMDARs to mediate a persistent excitatory current (termed tonic I(NMDA)), which tonically stimulates neuronal activity. Pharmacological blockade of GLT1 astrocyte glutamate transporters, as well as the gliotoxin α-aminodadipic acid, enhanced tonic I(NMDA) and neuronal activity, supporting an astrocyte regulation of tonic I(NMDA) strength. Dehydration, a physiological challenge known to increase SON firing activity and to induce neuroglial remodelling, including reduced neuronal ensheathment by astrocyte processes, resulted in blunted GLT1 efficacy, enhanced tonic I(NMDA) strength, and increased neuronal activity. Taken together, our studies support the view that glial modulation of tonic I(NMDA) activation contributes to regulation of SON neuronal activity, contributing in turn to neuronal homeostatic responses during a physiological challenge. PMID:21690192

  14. Astrocyte-secreted matricellular proteins in CNS remodelling during development and disease.

    PubMed

    Jones, Emma V; Bouvier, David S

    2014-01-01

    Matricellular proteins are secreted, nonstructural proteins that regulate the extracellular matrix (ECM) and interactions between cells through modulation of growth factor signaling, cell adhesion, migration, and proliferation. Despite being well described in the context of nonneuronal tissues, recent studies have revealed that these molecules may also play instrumental roles in central nervous system (CNS) development and diseases. In this minireview, we discuss the matricellular protein families SPARC (secreted protein acidic and rich in cysteine), Hevin/SC1 (SPARC-like 1), TN-C (Tenascin C), TSP (Thrombospondin), and CCN (CYR61/CTGF/NOV), which are secreted by astrocytes during development. These proteins exhibit a reduced expression in adult CNS but are upregulated in reactive astrocytes following injury or disease, where they are well placed to modulate the repair processes such as tissue remodeling, axon regeneration, glial scar formation, angiogenesis, and rewiring of neural circuitry. Conversely, their reexpression in reactive astrocytes may also lead to detrimental effects and promote the progression of neurodegenerative diseases.

  15. Extensive astrocyte infection is prominent in human immunodeficiency virus-associated dementia.

    PubMed

    Churchill, Melissa J; Wesselingh, Steven L; Cowley, Daniel; Pardo, Carlos A; McArthur, Justin C; Brew, Bruce J; Gorry, Paul R

    2009-08-01

    Astrocyte infection with human immunodeficiency virus (HIV) is considered rare, so astrocytes are thought to play a secondary role in HIV neuropathogenesis. By combining double immunohistochemistry, laser capture microdissection, and highly sensitive multiplexed polymerase chain reaction to detect HIV DNA in single astrocytes in vivo, we showed that astrocyte infection is extensive in subjects with HIV-associated dementia, occurring in up to 19% of GFAP+ cells. In addition, astrocyte infection frequency correlated with the severity of neuropathological changes and proximity to perivascular macrophages. Our data indicate that astrocytes can be extensively infected with HIV, and suggest an important role for HIV-infected astrocytes in HIV neuropathogenesis.

  16. Involvement of the Notch pathway in terminal astrocytic differentiation: role of PKA.

    PubMed

    Angulo-Rojo, Carla; Manning-Cela, Rebeca; Aguirre, Adán; Ortega, Arturo; López-Bayghen, Esther

    2013-12-23

    The Notch pathway is a highly conserved signaling system essential for modulating neurogenesis and promoting astrogenesis. Similarly, the cAMP signaling cascade can promote astrocytic commitment in several cell culture models, such as the C6 glioma cell line. These cells have the capacity to differentiate into oligodendrocytes or astrocytes, characteristics that allow their use as a glial progenitor model. In this context, we explore here the plausible involvement of cAMP in Notch-dependent signal transactions. The exposure of C6 cells to a non-hydrolysable cAMP analogue resulted in a sustained augmentation of Notch activity, as detected by nuclear translocation of its intracellular domain portion (NICD) and transcriptional activity. The cAMP effect is mediated through the activation of the γ-secretase complex, responsible for Notch cleavage and is sensitive to inhibitors of the cAMP-dependent protein kinase, PKA. As expected, Notch cleavage and nuclear translocation resulted in the up-regulation of the mRNA levels of one of its target genes, the transcription factor Hair and enhancer of split 5. Moreover, the glutamate uptake activity, as well as the expression of astrocytic markers such as glial fibrillary acidic protein, S100β protein and GLAST was also enhanced in cAMP-exposed cells. Our results clearly suggest that during the process of C6 astrocytic differentiation, cAMP activates the PKA/γ-secretase/NICD/RBPJ(κ) pathway and Notch1 expression, leading to transcriptional activation of the genes responsible for glial progenitor cell fate decision.

  17. Involvement of the Notch pathway in terminal astrocytic differentiation: role of PKA

    PubMed Central

    Angulo-Rojo, Carla; Manning-Cela, Rebeca; Aguirre, Adán; Ortega, Arturo; López-Bayghen, Esther

    2013-01-01

    The Notch pathway is a highly conserved signaling system essential for modulating neurogenesis and promoting astrogenesis. Similarly, the cAMP signaling cascade can promote astrocytic commitment in several cell culture models, such as the C6 glioma cell line. These cells have the capacity to differentiate into oligodendrocytes or astrocytes, characteristics that allow their use as a glial progenitor model. In this context, we explore here the plausible involvement of cAMP in Notch-dependent signal transactions. The exposure of C6 cells to a non-hydrolysable cAMP analogue resulted in a sustained augmentation of Notch activity, as detected by nuclear translocation of its intracellular domain portion (NICD) and transcriptional activity. The cAMP effect is mediated through the activation of the γ-secretase complex, responsible for Notch cleavage and is sensitive to inhibitors of the cAMP-dependent protein kinase, PKA. As expected, Notch cleavage and nuclear translocation resulted in the up-regulation of the mRNA levels of one of its target genes, the transcription factor Hair and enhancer of split 5. Moreover, the glutamate uptake activity, as well as the expression of astrocytic markers such as glial fibrillary acidic protein, S100β protein and GLAST was also enhanced in cAMP-exposed cells. Our results clearly suggest that during the process of C6 astrocytic differentiation, cAMP activates the PKA/γ-secretase/NICD/RBPJκ pathway and Notch1 expression, leading to transcriptional activation of the genes responsible for glial progenitor cell fate decision. PMID:24286475

  18. Dorsomedial hindbrain catecholamine regulation of hypothalamic astrocyte glycogen metabolic enzyme protein expression: Impact of estradiol.

    PubMed

    Tamrakar, P; Shrestha, P K; Briski, K P

    2015-04-30

    The brain astrocyte glycogen reservoir is a vital energy reserve and, in the cerebral cortex, subject among other factors to noradrenergic control. The ovarian steroid estradiol potently stimulates nerve cell aerobic respiration, but its role in glial glycogen metabolism during energy homeostasis or mismatched substrate supply/demand is unclear. This study examined the premise that estradiol regulates hypothalamic astrocyte glycogen metabolic enzyme protein expression during normo- and hypoglycemia in vivo through dorsomedial hindbrain catecholamine (CA)-dependent mechanisms. Individual astrocytes identified in situ by glial fibrillary acidic protein immunolabeling were laser-microdissected from the ventromedial hypothalamic (VMH), arcuate hypothalamic (ARH), and paraventricular hypothalamic (PVH) nuclei and the lateral hypothalamic area (LHA) of estradiol (E)- or oil (O)-implanted ovariectomized (OVX) rats after insulin or vehicle injection, and pooled within each site. Stimulation [VMH, LHA] or suppression [PVH, ARH] of basal glycogen synthase (GS) protein expression by E was reversed in the former three sites by caudal fourth ventricular pretreatment with the CA neurotoxin 6-hydroxydopamine (6-OHDA). E diminished glycogen phosphorylase (GP) protein profiles by CA-dependent [VMH, PVH] or -independent mechanisms [LHA]. Insulin-induced hypoglycemia (IIH) increased GS expression in the PVH in OVX+E, but reduced this protein in the PVH, ARH, and LHA in OVX+O. Moreover, IIH augmented GP expression in the VMH, LHA, and ARH in OVX+E and in the ARH in OVX+O, responses that normalized by 6-OHDA. Results demonstrate site-specific effects of E on astrocyte glycogen metabolic enzyme expression in the female rat hypothalamus, and identify locations where dorsomedial hindbrain CA input is required for such action. Evidence that E correspondingly increases and reduces basal GS and GP in the VMH and LHA, but augments the latter protein during IIH suggests that E regulates

  19. Simultaneous neuron- and astrocyte-specific fluorescent marking

    SciTech Connect

    Schulze, Wiebke; Hayata-Takano, Atsuko; Kamo, Toshihiko; Nakazawa, Takanobu; Nagayasu, Kazuki; Kasai, Atsushi; Seiriki, Kaoru; Shintani, Norihito; Ago, Yukio; Farfan, Camille; 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.

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

    PubMed

    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.

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

    PubMed

    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

  2. Ethanol inhibits neuritogenesis induced by astrocyte muscarinic receptors.

    PubMed

    Guizzetti, Marina; Moore, Nadia H; Giordano, Gennaro; VanDeMark, Kathryn L; Costa, Lucio G

    2010-09-01

    In utero alcohol exposure can lead to fetal alcohol spectrum disorders, characterized by cognitive and behavioral deficits. In vivo and in vitro studies have shown that ethanol alters neuronal development. We have recently shown that stimulation of M(3) muscarinic receptors in astrocytes increases the synthesis and release of fibronectin, laminin, and plasminogen activator inhibitor-1, causing neurite outgrowth in hippocampal neurons. As M(3) muscarinic receptor signaling in astroglial cells is strongly inhibited by ethanol, we hypothesized that ethanol may also inhibit neuritogenesis in hippocampal neurons induced by carbachol-stimulated astrocytes. In the present study, we report that the effect of carbachol-stimulated astrocytes on hippocampal neuron neurite outgrowth was inhibited in a concentration-dependent manner (25-100 mM) by ethanol. This effect was because of the inhibition of the release of fibronectin, laminin, and plasminogen activator inhibitor-1. Similar effects on neuritogenesis and on the release of astrocyte extracellular proteins were observed after the incubation of astrocytes with carbachol in the presence of 1-butanol, another short-chain alcohol, which like ethanol is a competitive substrate for phospholipase D, but not by tert-butanol, its analog that is not a substrate for this enzyme. This study identifies a potential novel mechanism involved in the developmental effects of ethanol mediated by the interaction of ethanol with cell signaling in astrocytes, leading to an impairment in neuron-astrocyte communication.

  3. Protective role of astrocytic leptin signaling against excitotoxicity.

    PubMed

    Jayaram, Bhavaani; Khan, Reas S; Kastin, Abba J; Hsuchou, Hung; Wu, Xiaojun; Pan, Weihong

    2013-03-01

    Both proconvulsive and anticonvulsive roles of leptin have been reported, suggesting cell-specific actions of leptin in different models of seizure and epilepsy. The goal of our study was to determine the regulation and function of astrocytic leptin receptors in a mouse model of epilepsy and glutamate-induced cytotoxicity. We show that in pilocarpine-challenged mice developing epilepsy with recurrent seizures after a latent period of 2 weeks, hippocampal leptin receptor (ObR) immunofluorescence was increased at 6 weeks. This was more pronounced in astrocytes than in neurons. In cultured astrocytes, glutamate increased ObRa and ObRb expression, whereas leptin pretreatment attenuated glial cytotoxicity by excess glutamate, reflected by better preserved adenosine triphosphate production. The protective role of astrocytic leptin signaling is further supported by the higher lethality of the astrocyte-specific leptin receptor knockout mice in the initial phase of seizure production. Thus, leptin signaling in astrocytes plays a protective role against seizure, and the effects are at least partially mediated by attenuation of glutamate toxicity. Astrocytic leptin signaling, therefore, may be a novel therapeutic target.

  4. Calcium oscillations encoding neuron-to-astrocyte communication.

    PubMed

    Zonta, Micaela; Carmignoto, Giorgio

    2002-01-01

    The observation that the excitatory neurotransmitter glutamate released from presynaptic terminals can activate, beside the post-synaptic neuron, the glial cell astrocyte, stimulated glial cell research like no other event since the recognition in the 1980s that astrocytes can express on their membrane many receptors for classical neurotransmitters. The properties and the functional role(s) of such a neuron-to-astrocyte signaling have now become the focus of intense research in neurobiology. Indeed, a growing body of evidence has recently highlighted the ability of astrocytes to work as sophisticated detectors of synaptic activity: by changing the frequency of [Ca(2+)](i) oscillations evoked by the synaptic release of glutamate, these cells display the remarkable capacity to discriminate between different levels and patterns of synaptic activity. Furthermore, the observation that astrocytes increase the frequency of [Ca(2+)](i) oscillations in response to repetitive episodes of high neuronal activity challenges the common concept that memory function in the brain is an exclusive property of neuronal cells. Glutamate-mediated [Ca(2+)](i) elevations can also trigger in astrocytes the release of glutamate that can ultimately affect neuronal transmission. Given the wide role played by glutamate in brain physiology, our view on how the brain operates needs now to be revised taking into account the bi-directional, glutamatergic communication between neurons and astrocytes.

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

    PubMed

    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.

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

    PubMed

    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

  7. Phosphorylation in the C-terminal domain of Aquaporin-4 is required for Golgi transition in primary cultured astrocytes

    SciTech Connect

    Kadohira, Ikuko; Abe, Yoichiro Nuriya, Mutsuo; Sano, Kazumi; Tsuji, Shoji; Arimitsu, Takeshi; Yoshimura, Yasunori; Yasui, Masato

    2008-12-12

    Aquaporin-4 (AQP4) is expressed in the perivascular and subpial astrocytes end-feet in mammalian brain, and plays a critical component of an integrated water and potassium homeostasis. Here we examine whether AQP4 is phosphorylated in primary cultured mouse astrocytes. Astrocytes were metabolically labeled with [{sup 32}P]phosphoric acid, then AQP4 was immunoprecipitated with anti-AQP4 antibody. We observed that AQP4 was constitutively phosphorylated, which is reduced by treatment with protein kinase CK2 inhibitors. To elucidate the phosphorylation of AQP4 by CK2, myc-tagged wild-type or mutant AQP4 was transiently transfected in primary cultured astrocytes. Substitution of Ala residues for four putative CK2 phosphorylation sites in the C terminus abolished the phosphorylation of AQP4. Immunofluorescent microscopy revealed that the quadruple mutant was localized in the Golgi apparatus. These observations indicate that the C-terminal domain of AQP4 is constitutively phosphorylated at least in part by protein kinase CK2 and it is required for Golgi transition.

  8. Controlled release of 6-aminonicotinamide from aligned, electrospun fibers alters astrocyte metabolism and dorsal root ganglia neurite outgrowth

    NASA Astrophysics Data System (ADS)

    Schaub, Nicholas J.; Gilbert, Ryan J.

    2011-08-01

    Following central nervous system (CNS) injury, activated astrocytes form a glial scar that inhibits the migration of axons ultimately leading to regeneration failure. Biomaterials developed for CNS repair can provide local delivery of therapeutics and/or guidance mechanisms to encourage cell migration into damaged regions of the brain or spinal cord. Electrospun fibers are a promising type of biomaterial for CNS injury since these fibers can direct cellular and axonal migration while slowly delivering therapy to the injury site. In this study, it was hypothesized that inclusion of an anti-metabolite, 6-aminonicotinamide (6AN), within poly-l-lactic acid electrospun fibers could attenuate astrocyte metabolic activity while still directing axonal outgrowth. Electrospinning parameters were varied to produce highly aligned electrospun fibers that contained 10% or 20% (w/w) 6AN. 6AN release from the fiber substrates occurred continuously over 2 weeks. Astrocytes placed onto drug-releasing fibers were less active than those cultured on scaffolds without 6AN. Dorsal root ganglia placed onto control and drug-releasing scaffolds were able to direct neurites along the aligned fibers. However, neurite outgrowth was stunted by fibers that contained 20% 6AN. These results show that 6AN release from aligned, electrospun fibers can decrease astrocyte activity while still directing axonal outgrowth.

  9. The role of astrocytes in the formation of cartilage in gliomas. An immunohistochemical study of four cases.

    PubMed Central

    Kepes, J. J.; Rubinstein, L. J.; Chiang, H.

    1984-01-01

    The occasional presence of focal cartilage in gliomas is generally attributed to metaplasia of the mesenchymal supportive elements. While this mechanism undoubtedly exists, the present report describes a different mode of development of cartilage in four gliomas occurring in young individuals. Two of the tumors were pontine astrocytomas, one was a mixed ependymoma and astrocytoma involving the fourth ventricle and the brainstem, and one was an extraspinal malignant astrocytoma in the lumbar region of a young boy who earlier had been diagnosed as having a pontine glioma for which he received radiation treatment. In all four tumors, transitions from astrocytic to cartilaginous elements were seen, characterized by an increasing deposition of chondroid ground substance between the astrocytes and a gradual morphologic changes of the glial cells to more rounded forms with a vacuolated cytoplasm, indistinguishable from chondrocytes of mesenchymal origin. Many of these cells retained positive staining for glial fibrillary acidic protein by the immunoperoxidase method, attesting to their astrocytic nature. The production of cartilage by neoplastic astrocytes may be related to their ability to secrete, in certain circumstances and occasionally in large amounts, basement membrane material and other forms of mucopolysaccharides, which may become condensed to form a chondroid ground substance. The process appears analogous to that of cartilage formation by epithelial cells in pleomorphic adenomas of the salivary glands. Images Figure 12 Figure 13 Figure 14 Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 PMID:6391192

  10. Concentration of astrocytic filaments at the retinal optic nerve junction is coincident with the absence of intra-retinal myelination: comparative and developmental evidence.

    PubMed

    Morcos, Y; Chan-Ling, T

    2000-09-01

    The structure of the lamina cribrosa (LC) and astrocytic density were examined in various species with and without intra-retinal myelination. Sections of optic nerve from various species were stained with Milligan's trichrome or antibodies to glial fibrillary acidic protein, myelin basic protein (MBP) and antibody O4. Marmoset, flying fox, cat, and sheep, which lack intraretinal myelination, were shown to possess a well-developed LC as well as a marked concentration of astrocytic filaments distal to the LC. Rat and mouse, which lack intraretinal myelination, lacked a well-developed LC but exhibited a marked concentration of astrocytic filaments in this region. Rabbit and chicken, which exhibit intraretinal myelination, lacked both a well-developed LC and a concentration of astrocytes at the retinal optic nerve junction (ROJ). A marked concentration of astrocytes at the ROJ of human fetuses was also apparent at 13 weeks of gestation, prior to myelination of the optic nerve; in contrast, the LC was not fully developed even at birth. This concentration of astrocytes was located distal to O4 and MBP immunoreactivity in human optic nerve, and coincided with the site of initial myelination of ganglion cell axons in marmoset and rat. Myelination proceeded from the chiasm towards the retinal end of the human optic nerve. Moreover, the outer limit of oligodendrocyte precursor cells (OPC) migration into the rabbit retina was restricted by the outer limit of astrocyte spread. These observations indicate that a concentration of astrocytic filaments at the ROJ is coincident with the absence of intraretinal myelination. Differential expression of tenascin-C by astrocytes at the ROJ appears to contribute to the molecular barrier to OPC migration (see Bartsch et al., 1994), while expression of the homedomain protein Vax 1 by glial cells at the optic nerve head appears to inhibit migration of retinal pigment epithelial cells into the optic nerve (see Bertuzzi et al., 1999). These

  11. Transfer of mitochondria from astrocytes to neurons after stroke.

    PubMed

    Hayakawa, Kazuhide; Esposito, Elga; Wang, Xiaohua; Terasaki, Yasukazu; Liu, Yi; Xing, Changhong; Ji, Xunming; Lo, Eng H

    2016-07-28

    Neurons can release damaged mitochondria and transfer them to astrocytes for disposal and recycling. This ability to exchange mitochondria may represent a potential mode of cell-to-cell signalling in the central nervous system. Here we show that astrocytes in mice can also release functional mitochondria that enter neurons. Astrocytic release of extracellular mitochondrial particles was mediated by a calcium-dependent mechanism involving CD38 and cyclic ADP ribose signalling. Transient focal cerebral ischaemia in mice induced entry of astrocytic mitochondria into adjacent neurons, and this entry amplified cell survival signals. Suppression of CD38 signalling by short interfering RNA reduced extracellular mitochondria transfer and worsened neurological outcomes. These findings suggest a new mitochondrial mechanism of neuroglial crosstalk that may contribute to endogenous neuroprotective and neurorecovery mechanisms after stroke. PMID:27466127

  12. Monitoring local synaptic activity with astrocytic patch pipettes

    PubMed Central

    Henneberger, Christian; Rusakov, Dmitri A

    2013-01-01

    Rapid signal exchange between astroglia and neurons has emerged as a key player in neural communication in the brain. To understand the mechanisms involved, it is often important to have access to individual astrocytes while monitoring the activity of nearby synapses. Achieving this with standard electrophysiological tools is not always feasible. The protocol presented here enables the monitoring of synaptic activity using whole-cell current-clamp recordings from a local astrocyte. This approach takes advantage of the fact that the low input resistance of electrically passive astroglia allows extracellular currents to pass through the astrocytic membrane with relatively little attenuation. Once the slice preparation is ready, it takes ~30 min to several hours to implement this protocol, depending on the experimental design, which is similar to other patch-clamp techniques. The technique presented here can be used to directly access the intracellular medium of individual astrocytes while examining synapses functioning in their immediate proximity. PMID:23196973

  13. Astrocytes mediate synapse elimination through MEGF10 and MERTK pathways

    NASA Astrophysics Data System (ADS)

    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.

  14. Astrocytes in Multiple Sclerosis: A Product of their Environment

    PubMed Central

    Nair, Aji; Frederick, Terra J.; Miller, Stephen D.

    2010-01-01

    It has long been thought that astrocytes, like other glial cells, simply provide a support mechanism for neuronal function in the healthy and inflamed central nervous system (CNS). However, recent evidence suggests that astrocytes play an active and dual role in CNS inflammatory diseases such as multiple sclerosis (MS). Astrocytes not only have the ability to enhance immune responses and inhibit myelin repair, but they can also be protective and limit CNS inflammation while supporting oligodendrocyte and axonal regeneration. The particular impact of these cells on the pathogenesis and repair of an inflammatory demyelinating process is dependent upon a number of factors, including the stage of the disease, the type and microenvironment of the lesion, and the interactions with other cell types and factors that influence their activation. In this review, we summarize recent data supporting the idea that astrocytes play a complex role in the regulation of CNS autoimmunity. PMID:18516496

  15. mGlu3 receptor and astrocytes: partners in neuroprotection.

    PubMed

    Durand, Daniela; Carniglia, Lila; Caruso, Carla; Lasaga, Mercedes

    2013-03-01

    Astrocytes are currently studied intensively because of their now highlighted relevance as key players with neurons that modulate a wide range of central functions, from synaptic plasticity and synaptogenesis to regulation of metabolic and neuroinflammatory processes. Since the discovery of mGlu3 receptors on astrocytes, accumulating evidence supports a role of these receptors not only in maintaining synaptic homeostasis and treating psychiatric disorders but also in promoting astrocyte survival in several pathologic conditions. This review focuses on providing up-to-date knowledge regarding effects of activating astroglial mGlu3 receptors on psychiatric disorders, astrocyte and neuronal survival, and neurodegenerative diseases. This article is part of a Special Issue entitled 'Metabotropic Glutamate Receptors'. PMID:22564439

  16. Aquaporin-4 expression in cultured astrocytes after fluid percussion injury.

    PubMed

    Rao, Kakulavarapu V Rama; Reddy, Pichili V B; Curtis, Kevin M; Norenberg, Michael D

    2011-03-01

    The development of cytotoxic brain edema resulting in increased intracranial pressure is a major cause of death occurring in the early phase of traumatic brain injury (TBI). Such edema predominantly develops as a consequence of astrocyte swelling. We recently documented that fluid percussion injury (FPI) to cultured astrocytes causes cell swelling. Since aquaporin-4 (AQP4) has been strongly implicated in the development of brain edema/astrocyte swelling in various neurological conditions, this study examined the effect of in vitro trauma on AQP4 protein expression in cultured astrocytes. Exposure of astrocytes to FPI resulted in a significant upregulation of AQP4 protein in the plasma membrane due to neosynthesis, as cycloheximide blocked the trauma-induced AQP4 upregulation. Silencing the aqp4 gene by siRNA resulted in a significant reduction in trauma-induced astrocyte swelling, indicating a critical role of AQP4 in this process. We recently documented that oxidative/nitrative stress (ONS), the mitochondrial permeability transition (mPT), and activation of mitogen-activated protein kinases (MAPKs), contribute to trauma-induced astrocyte swelling in culture. We now show that inhibition of these factors reduces the upregulation of AQP4 following trauma. Since TBI has been shown to activate nuclear factor-kappa B (NF-κB), as well as the Na(+),K(+),Cl(-) co-transporter (NKCC), both of which are implicated in brain edema/astrocyte swelling in other conditions, we also examined the effect of BAY 11-7082 and bumetanide, inhibitors of NF-κB and NKCC, respectively, and found that these agents also significantly inhibited the trauma-induced AQP4 upregulation. Our findings show that in vitro trauma upregulates AQP4, and that ONS, MAPKs, mPT, NF-κB, and NKCC are involved in its upregulation.

  17. Astrocyte structural reactivity and plasticity in models of retinal detachment.

    PubMed

    Luna, Gabriel; Keeley, Patrick W; Reese, Benjamin E; Linberg, Kenneth A; Lewis, Geoffrey P; Fisher, Steven K

    2016-09-01

    Although retinal neurodegenerative conditions such as age-related macular degeneration, glaucoma, diabetic retinopathy, retinitis pigmentosa, and retinal detachment have different etiologies and pathological characteristics, they also have many responses in common at the cellular level, including neural and glial remodeling. Structural changes in Müller cells, the large radial glia of the retina in retinal disease and injury have been well described, that of the retinal astrocytes remains less so. Using modern imaging technology to describe the structural remodeling of retinal astrocytes after retinal detachment is the focus of this paper. We present both a review of critical literature as well as novel work focusing on the responses of astrocytes following rhegmatogenous and serous retinal detachment. The mouse presents a convenient model system in which to study astrocyte reactivity since the Mϋller cell response is muted in comparison to other species thereby allowing better visualization of the astrocytes. We also show data from rat, cat, squirrel, and human retina demonstrating similarities and differences across species. Our data from immunolabeling and dye-filling experiments demonstrate previously undescribed morphological characteristics of normal astrocytes and changes induced by detachment. Astrocytes not only upregulate GFAP, but structurally remodel, becoming increasingly irregular in appearance, and often penetrating deep into neural retina. Understanding these responses, their consequences, and what drives them may prove to be an important component in improving visual outcome in a variety of therapeutic situations. Our data further supports the concept that astrocytes are important players in the retina's overall response to injury and disease. PMID:27060374

  18. Astrocyte structural reactivity and plasticity in models of retinal detachment.

    PubMed

    Luna, Gabriel; Keeley, Patrick W; Reese, Benjamin E; Linberg, Kenneth A; Lewis, Geoffrey P; Fisher, Steven K

    2016-09-01

    Although retinal neurodegenerative conditions such as age-related macular degeneration, glaucoma, diabetic retinopathy, retinitis pigmentosa, and retinal detachment have different etiologies and pathological characteristics, they also have many responses in common at the cellular level, including neural and glial remodeling. Structural changes in Müller cells, the large radial glia of the retina in retinal disease and injury have been well described, that of the retinal astrocytes remains less so. Using modern imaging technology to describe the structural remodeling of retinal astrocytes after retinal detachment is the focus of this paper. We present both a review of critical literature as well as novel work focusing on the responses of astrocytes following rhegmatogenous and serous retinal detachment. The mouse presents a convenient model system in which to study astrocyte reactivity since the Mϋller cell response is muted in comparison to other species thereby allowing better visualization of the astrocytes. We also show data from rat, cat, squirrel, and human retina demonstrating similarities and differences across species. Our data from immunolabeling and dye-filling experiments demonstrate previously undescribed morphological characteristics of normal astrocytes and changes induced by detachment. Astrocytes not only upregulate GFAP, but structurally remodel, becoming increasingly irregular in appearance, and often penetrating deep into neural retina. Understanding these responses, their consequences, and what drives them may prove to be an important component in improving visual outcome in a variety of therapeutic situations. Our data further supports the concept that astrocytes are important players in the retina's overall response to injury and disease.

  19. Leptin signaling in astrocytes regulates hypothalamic neuronal circuits and feeding.

    PubMed

    Kim, Jae Geun; Suyama, Shigetomo; Koch, Marco; Jin, Sungho; Argente-Arizon, Pilar; Argente, Jesús; Liu, Zhong-Wu; Zimmer, Marcelo R; Jeong, Jin Kwon; Szigeti-Buck, Klara; Gao, Yuanqing; Garcia-Caceres, Cristina; Yi, Chun-Xia; Salmaso, Natalina; Vaccarino, Flora M; Chowen, Julie; Diano, Sabrina; Dietrich, Marcelo O; Tschöp, Matthias H; Horvath, Tamas L

    2014-07-01

    We found that leptin receptors were expressed in hypothalamic astrocytes and that their conditional deletion led to altered glial morphology and synaptic inputs onto hypothalamic neurons involved in feeding control. Leptin-regulated feeding was diminished, whereas feeding after fasting or ghrelin administration was elevated in mice with astrocyte-specific leptin receptor deficiency. These data reveal an active role of glial cells in hypothalamic synaptic remodeling and control of feeding by leptin.

  20. Group B Streptococcal Infection and Activation of Human Astrocytes

    PubMed Central

    Stoner, Terri D.; Weston, Thomas A.; Trejo, JoAnn; Doran, Kelly S.

    2015-01-01

    Background 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. Methodology/Principal Findings 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. Conclusions/Significance 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. PMID:26030618

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

    PubMed

    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

  2. S100A6 (calcyclin) is a novel marker of neural stem cells and astrocyte precursors in the subgranular zone of the adult mouse hippocampus.

    PubMed

    Yamada, Jun; Jinno, Shozo

    2014-01-01

    S100A6 (calcyclin), an EF-hand calcium binding protein, is considered to play various roles in the brain, for example, cell proliferation and differentiation, calcium homeostasis, and neuronal degeneration. In addition to some limbic nuclei, S100A6 is distributed in the rostral migratory stream, one of the major neurogenic niches of the adult brain. However, the potential involvement of S100A6 in adult neurogenesis remains unclear. In this study, we aimed to elucidate the role of S100A6 in the other major neurogenic niche, the subgranular zone of the dentate gyrus in the adult mouse hippocampus. Immunofluorescent multiple labeling showed that S100A6 was highly expressed in neural stem cells labeled by sex determining region Y-box 2, brain lipid-binding protein protein and glial fibrillary acidic protein. S100A6+ cells often extended a long process typical of radial glial morphology. In addition, S100A6 was found in some S100β+ astrocyte lineage cells. Interestingly, proliferating cell nuclear antigen was detected in a fraction of S100A6+/S100β+ cells. These cells were considered to be lineage-restricted astrocyte precursors maintaining mitotic potential. On the other hand, S100A6 was rarely seen in neural lineage cells labeled by T-box brain protein 2, doublecortin, calretinin and calbindin D28K. Cell fate-tracing experiment using BrdU showed that the majority of newly generated immature astrocytes were immunoreactive for S100A6, while mature astrocytes lacked S100A6 immunoreactivity. Administration of S100 protein inhibitor, trifluoperazine, caused a reduction in production of S100β+ astrocyte lineage cells, but had no impact on neurogenesis. Overall, our data provide the first evidence that S100A6 is a specific marker of neural stem cells and astrocyte precursors, and may be especially important for generation of astrocytes in the adult hippocampus.

  3. Effects of arsenite in astrocytes on neuronal signaling transduction.

    PubMed

    Wang, Yan; Zhao, Fenghong; Liao, Yingjun; Jin, Yaping; Sun, Guifan

    2013-01-01

    The main purpose of this study was to test the hypothesis that arsenite induces neurotoxicity via effects on astrocytes. Astrocytes were exposed to 0, 5 or 10 μM arsenite in medium for 24 h, and then astrocyte-conditioned medium (ACM) was collected after incubation with fresh medium for 6 h. Primary neuron cultures were divided into four groups due to ACM, which were neurons without ACM exposure (group I) and neurons exposed to ACM from 0, 5 or 10 μM arsenite treated astrocytes (group II-IV). Protein expression of N-methyl-d-aspartate receptors (NR1, NR2A, NR2B), calmodulin-dependent protein kinase II (CaMKII) and adenylate cyclase (AC) in neurons were measured after incubation with ACM for 4, 8 or 12 h. Morphological changes and synaptic formation were observed after a 72 h-incubation with ACM. Compared to group II, synaptic formation and protein expression of NR2A, NR2B, CaMKII and AC in group III and IV were significantly suppressed. Moreover, synaptic formation and protein expression of CaMKII and AC in group II were significantly enhanced when compared with group I. Taken together, findings from this study suggested that arsenic in astrocytes might impair synaptic formation through disturbing astrocytic effects on neuronal signal transduction.

  4. Two-pore Domain Potassium Channels in Astrocytes

    PubMed Central

    Ryoo, Kanghyun

    2016-01-01

    Two-pore domain potassium (K2P) channels have a distinct structure and channel properties, and are involved in a background K+ current. The 15 members of the K2P channels are identified and classified into six subfamilies on the basis of their sequence similarities. The activity of the channels is dynamically regulated by various physical, chemical, and biological effectors. The channels are expressed in a wide variety of tissues in mammals in an isoform specific manner, and play various roles in many physiological and pathophysiological conditions. To function as channels, the K2P channels form dimers, and some isoforms form heterodimers that provide diversity in channel properties. In the brain, TWIK1, TREK1, TREK2, TRAAK, TASK1, and TASK3 are predominantly expressed in various regions, including the cerebral cortex, dentate gyrus, CA1-CA3, and granular layer of the cerebellum. TWIK1, TREK1, and TASK1 are highly expressed in astrocytes, where they play specific cellular roles. Astrocytes keep leak K+ conductance, called the passive conductance, which mainly involves TWIK1-TREK1 heterodimeric channel. TWIK1 and TREK1 also mediate glutamate release from astrocytes in an exocytosis-independent manner. The expression of TREK1 and TREK2 in astrocytes increases under ischemic conditions, that enhance neuroprotection from ischemia. Accumulated evidence has indicated that astrocytes, together with neurons, are involved in brain function, with the K2P channels playing critical role in these astrocytes. PMID:27790056

  5. Role of astrocytes in memory and psychiatric disorders.

    PubMed

    Moraga-Amaro, R; Jerez-Baraona, J M; Simon, F; Stehberg, J

    2014-01-01

    Over the past decade, the traditional description of astrocytes as being merely accessories to brain function has shifted to one in which their role has been pushed into the forefront of importance. Current views suggest that astrocytes:(1) are excitable through calcium fluctuations and respond to neurotransmitters released at synapses; (2) communicate with each other via calcium waves and release their own gliotransmitters which are essential for synaptic plasticity; (3) activate hundreds of synapses at once, thereby synchronizing neuronal activity and activating or inhibiting complete neuronal networks; (4) release vasoactive substances to the smooth muscle surrounding blood vessels enabling the coupling of circulation (blood flow) to local brain activity; and (5) release lactate in an activity-dependent manner in order to supply neuronal metabolic demand. In consequence, the role of astrocytes and astrocytic gliotransmitters is now believed to be critical for higher brain function and recently, evidence begins to gather suggesting that astrocytes are pivotal for learning and memory. All of the above are reviewed here while focusing on the role of astrocytes in memory and psychiatric disorders.

  6. Astrocytic modulation of blood brain barrier: perspectives on Parkinson's disease.

    PubMed

    Cabezas, Ricardo; Avila, Marcos; Gonzalez, Janneth; El-Bachá, Ramon Santos; Báez, Eliana; García-Segura, Luis Miguel; Jurado Coronel, Juan Camilo; Capani, Francisco; Cardona-Gomez, Gloria Patricia; Barreto, George E

    2014-01-01

    The blood-brain barrier (BBB) is a tightly regulated interface in the Central Nervous System (CNS) that regulates the exchange of molecules in and out from the brain thus maintaining the CNS homeostasis. It is mainly composed of endothelial cells (ECs), pericytes and astrocytes that create a neurovascular unit (NVU) with the adjacent neurons. Astrocytes are essential for the formation and maintenance of the BBB by providing secreted factors that lead to the adequate association between the cells of the BBB and the formation of strong tight junctions. Under neurological disorders, such as chronic cerebral ischemia, brain trauma, Epilepsy, Alzheimer and Parkinson's Diseases, a disruption of the BBB takes place, involving a lost in the permeability of the barrier and phenotypical changes in both the ECs and astrocytes. In this aspect, it has been established that the process of reactive gliosis is a common feature of astrocytes during BBB disruption, which has a detrimental effect on the barrier function and a subsequent damage in neuronal survival. In this review we discuss the implications of astrocyte functions in the protection of the BBB, and in the development of Parkinson's disease (PD) and related disorders. Additionally, we highlight the current and future strategies in astrocyte protection aimed at the development of restorative therapies for the BBB in pathological conditions. PMID:25136294

  7. Glucose Tightly Controls Morphological and Functional Properties of Astrocytes.

    PubMed

    Lee, Chun-Yao; Dallérac, Glenn; Ezan, Pascal; Anderova, Miroslava; Rouach, Nathalie

    2016-01-01

    The main energy source powering the brain is glucose. Strong energy needs of our nervous system are fulfilled by conveying this essential metabolite through blood via an extensive vascular network. Glucose then reaches brain tissues by cell uptake, diffusion and metabolization, processes primarily undertaken by astrocytes. Deprivation of glucose can however occur in various circumstances. In particular, ageing is associated with cognitive disturbances that are partly attributable to metabolic deficiency leading to brain glycopenia. Despite the crucial role of glucose and its metabolites in sustaining neuronal activity, little is known about its moment-to-moment contribution to astroglial physiology. We thus here investigated the early structural and functional alterations induced in astrocytes by a transient metabolic challenge consisting in glucose deprivation. Electrophysiological recordings of hippocampal astroglial cells of the stratum radiatum in situ revealed that shortage of glucose specifically increases astrocyte membrane capacitance, whilst it has no impact on other passive membrane properties. Consistent with this change, morphometric analysis unraveled a prompt increase in astrocyte volume upon glucose deprivation. Furthermore, characteristic functional properties of astrocytes are also affected by transient glucose deficiency. We indeed found that glucoprivation decreases their gap junction-mediated coupling, while it progressively and reversibly increases their intracellular calcium levels during the slow depression of synaptic transmission occurring simultaneously, as assessed by dual electrophysiological and calcium imaging recordings. Together, these data indicate that astrocytes rapidly respond to metabolic dysfunctions, and are therefore central to the neuroglial dialog at play in brain adaptation to glycopenia. PMID:27148048

  8. Astrocytes, Synapses and Brain Function: A Computational Approach

    NASA Astrophysics Data System (ADS)

    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.

  9. Glucose Tightly Controls Morphological and Functional Properties of Astrocytes

    PubMed Central

    Lee, Chun-Yao; Dallérac, Glenn; Ezan, Pascal; Anderova, Miroslava; Rouach, Nathalie

    2016-01-01

    The main energy source powering the brain is glucose. Strong energy needs of our nervous system are fulfilled by conveying this essential metabolite through blood via an extensive vascular network. Glucose then reaches brain tissues by cell uptake, diffusion and metabolization, processes primarily undertaken by astrocytes. Deprivation of glucose can however occur in various circumstances. In particular, ageing is associated with cognitive disturbances that are partly attributable to metabolic deficiency leading to brain glycopenia. Despite the crucial role of glucose and its metabolites in sustaining neuronal activity, little is known about its moment-to-moment contribution to astroglial physiology. We thus here investigated the early structural and functional alterations induced in astrocytes by a transient metabolic challenge consisting in glucose deprivation. Electrophysiological recordings of hippocampal astroglial cells of the stratum radiatum in situ revealed that shortage of glucose specifically increases astrocyte membrane capacitance, whilst it has no impact on other passive membrane properties. Consistent with this change, morphometric analysis unraveled a prompt increase in astrocyte volume upon glucose deprivation. Furthermore, characteristic functional properties of astrocytes are also affected by transient glucose deficiency. We indeed found that glucoprivation decreases their gap junction-mediated coupling, while it progressively and reversibly increases their intracellular calcium levels during the slow depression of synaptic transmission occurring simultaneously, as assessed by dual electrophysiological and calcium imaging recordings. Together, these data indicate that astrocytes rapidly respond to metabolic dysfunctions, and are therefore central to the neuroglial dialog at play in brain adaptation to glycopenia. PMID:27148048

  10. Unveiling astrocytic control of cerebral blood flow with optogenetics.

    PubMed

    Masamoto, Kazuto; Unekawa, Miyuki; Watanabe, Tatsushi; Toriumi, Haruki; Takuwa, Hiroyuki; Kawaguchi, Hiroshi; Kanno, Iwao; Matsui, Ko; Tanaka, Kenji F; Tomita, Yutaka; Suzuki, Norihiro

    2015-06-16

    Cortical neural activities lead to changes in the cerebral blood flow (CBF), which involves astrocytic control of cerebrovascular tone. However, the manner in which astrocytic activity specifically leads to vasodilation or vasoconstriction is difficult to determine. Here, cortical astrocytes genetically expressing a light-sensitive cation channel, channelrhodopsin-2 (ChR2), were transcranially activated with a blue laser while the spatiotemporal changes in CBF were noninvasively monitored with laser speckle flowgraphy in the anesthetised mouse cortex. A brief photostimulation induced a fast transient increase in CBF. The average response onset time was 0.7 ± 0.7 sec at the activation foci, and this CBF increase spread widely from the irradiation spot with an apparent propagation speed of 0.8-1.1 mm/sec. The broad increase in the CBF could be due to a propagation of diffusible vasoactive signals derived from the stimulated astrocytes. Pharmacological manipulation showed that topical administration of a K(+) channel inhibitor (BaCl2; 0.1-0.5 mM) significantly reduced the photostimulation-induced CBF responses, which indicates that the ChR2-evoked astrocytic activity involves K(+) signalling to the vascular smooth muscle cells. These findings demonstrate a unique model for exploring the role of the astrocytes in gliovascular coupling using non-invasive, time-controlled, cell-type specific perturbations.

  11. Arsenic Exposure Induces Unscheduled Mitotic S Phase Entry Coupled with Cell Death in Mouse Cortical Astrocytes

    PubMed Central

    Htike, Nang T. T.; Maekawa, Fumihiko; Soutome, Haruka; Sano, Kazuhiro; Maejima, Sho; Aung, Kyaw H.; Tokuda, Masaaki; Tsukahara, Shinji

    2016-01-01

    There is serious concern about arsenic in the natural environment, which exhibits neurotoxicity and increases the risk of neurodevelopmental disorders. Adverse effects of arsenic have been demonstrated in neurons, but it is not fully understood how arsenic affects other cell types in the brain. In the current study, we examined whether sodium arsenite (NaAsO2) affects the cell cycle, viability, and apoptosis of in vitro-cultured astrocytes isolated from the cerebral cortex of mice. Cultured astrocytes from transgenic mice expressing fluorescent ubiquitination-based cell cycle indicator (Fucci) were subjected to live imaging analysis to assess the effects of NaAsO2 (0, 1, 2, and 4 μM) on the cell cycle and number of cells. Fucci was designed to express monomeric Kusabira Orange2 (mKO2) fused with the ubiquitylation domain of hCdt1, a marker of G1 phase, and monomeric Azami Green (mAG) fused with the ubiquitylation domain of hGem, a marker of S, G2, and M phases. NaAsO2 concentration-dependently decreased the peak levels of the mAG/mKO2 emission ratio when the ratio had reached a peak in astrocytes without NaAsO2 exposure, which was due to attenuating the increase in the mAG-expressing cell number. In contrast, the mAG/mKO2 emission ratio and number of mAG-expressing cells were concentration-dependently increased by NaAsO2 before their peak levels, indicating unscheduled S phase entry. We further examined the fate of cells forced to enter S phase by NaAsO2. We found that most of these cells died up to the end of live imaging. In addition, quantification of the copy number of the glial fibrillary acidic protein gene expressed specifically in astrocytes revealed a concentration-dependent decrease caused by NaAsO2. However, NaAsO2 did not increase the amount of nucleosomes generated from DNA fragmentation and failed to alter the gene expression of molecules relevant to unscheduled S phase entry-coupled apoptosis (p21, p53, E2F1, E2F4, and Gm36566). These findings

  12. Astrocyte Ca2+ Signaling Drives Inversion of Neurovascular Coupling after Subarachnoid Hemorrhage.

    PubMed

    Pappas, Anthony C; Koide, Masayo; Wellman, George C

    2015-09-30

    Physiologically, neurovascular coupling (NVC) matches focal increases in neuronal activity with local arteriolar dilation. Astrocytes participate in NVC by sensing increased neurotransmission and releasing vasoactive agents (e.g., K(+)) from perivascular endfeet surrounding parenchymal arterioles. Previously, we demonstrated an increase in the amplitude of spontaneous Ca(2+) events in astrocyte endfeet and inversion of NVC from vasodilation to vasoconstriction in brain slices obtained from subarachnoid hemorrhage (SAH) model rats. However, the role of spontaneous astrocyte Ca(2+) signaling in determining the polarity of the NVC response remains unclear. Here, we used two-photon imaging of Fluo-4-loaded rat brain slices to determine whether altered endfoot Ca(2+) signaling underlies SAH-induced inversion of NVC. We report a time-dependent emergence of endfoot high-amplitude Ca(2+) signals (eHACSs) after SAH that were not observed in endfeet from unoperated animals. Furthermore, the percentage of endfeet with eHACSs varied with time and paralleled the development of inversion of NVC. Endfeet with eHACSs were present only around arterioles exhibiting inversion of NVC. Importantly, depletion of intracellular Ca(2+) stores using cyclopiazonic acid abolished SAH-induced eHACSs and restored arteriolar dilation in SAH brain slices to two mediators of NVC (a rise in endfoot Ca(2+) and elevation of extracellular K(+)). These data indicate a causal link between SAH-induced eHACSs and inversion of NVC. Ultrastructural examination using transmission electron microscopy indicated that a similar proportion of endfeet exhibiting eHACSs also exhibited asymmetrical enlargement. Our results demonstrate that subarachnoid blood causes a delayed increase in the amplitude of spontaneous intracellular Ca(2+) release events leading to inversion of NVC. Significance statement: Aneurysmal subarachnoid hemorrhage (SAH)--strokes involving cerebral aneurysm rupture and release of blood onto the

  13. The diagnostic value of immunohistochemistry and silver impregnation techniques for characterization of normal, reactive and tumoral astrocytes.

    PubMed

    Şovrea, Alina Simona; Boşca, Adina Bianca; Georgiu, Carmen; Constantin, Anne-Marie; Ben Abdalah, Mohamed Amine; Gheban, Dan

    2014-01-01

    Astrocytes represent a heterogeneous population of specialized glial cells responsible not only for accomplishing various important functions in the healthy nervous tissue, but also for reacting to all types of the central nervous system diseases and trauma. GFAP immunostaining is considered to be the most accurate of the routine techniques used for identifying astrocytes; however, silver impregnation techniques, which are inexpensive and approachable, might be a reliable alternative. The present research has brought into question and tried to assess the sensitivity and specificity of these classical methods for identifying and differentiating normal and reactive from tumoral astrocytes. Our study included 10 supratentorial gliomas specimens of various grade and two normal brain samples. We performed a histological study on consecutive seriated sections labeled using four methods: the immunostaining for GFAP (glial fibrillary acidic protein) and the three silver impregnation techniques: Ramón y Cajal, Bielschowsky-Cajal and Gömöri. For each tumoral case, two areas were examined: the tumoral parenchyma and the tumor borders (considered as reactive gliosis) and were both compared to healthy brain parenchyma; for each area, three microscopic fields were assessed and two parameters were recorded: a semi-quantitative score (the astrocytes' density) and a qualitative score (the color intensity). We used a complex statistical analysis in order to process the data and to compare the diagnostic value of silver impregnation techniques versus GFAP immunostaining (the reference method) in terms of tumoral grading and differentiating tumoral from normal and reactive astrocytes. Our results indicated that there data provided by both GFAP immunostaining and silver impregnation techniques were comparable.

  14. Neurogenic effect of VEGF is related to increase of astrocytes transdifferentiation into new mature neurons in rat brains after stroke.

    PubMed

    Shen, Shu-Wen; Duan, Chun-Ling; Chen, Xian-Hua; Wang, Yong-Quan; Sun, Xiao; Zhang, Qiu-Wan; Cui, Hui-Ru; Sun, Feng-Yan

    2016-09-01

    To study the cellular mechanism of vascular endothelial growth factor (VEGF)-enhanced neurogenesis in ischemic brain injury, we used middle cerebral artery occlusion (MCAO) model to induce transient focal ischemic brain injury. The results showed that ischemic injury significantly increased glial fibrillary acidic protein immunopositive (GFAP(+)) and nestin(+) cells in ipsilateral striatum 3 days following MCAO. Most GFAP(+) cells colocalized with nestin (GFAP(+)-nestin(+)), Pax6 (GFAP(+)-Pax6(+)), or Olig2 (GFAP(+)-Olig2(+)). VEGF further increased GFAP(+)-nestin(+) and GFAP(+)-Pax6(+) cells, and decreased GFAP(+)-Olig2(+) cells. We used striatal injection of GFAP targeted enhanced green fluorescence protein (pGfa2-EGFP) vectors combined with multiple immunofluorescent staining to trace the neural fates of EGFP-expressing (GFP(+)) reactive astrocytes. The results showed that MCAO-induced striatal reactive astrocytes differentiated into neural stem cells (GFP(+)-nestin(+) cells) at 3 days after MCAO, immature (GFP(+)-Tuj-1(+) cells) at 1 week and mature neurons (GFP(+)-MAP-2(+) or GFP(+)-NeuN(+) cells) at 2 weeks. VEGF increased GFP(+)-NeuN(+) and BrdU(+)-MAP-2(+) newborn neurons after MCAO. Fluorocitrate, an astrocytic inhibitor, significantly decreased GFAP and nestin expression in ischemic brains, and also reduced VEGF-enhanced neurogenic effects. This study is the first time to report that VEGF-mediated increase of newly generated neurons is dependent on the presence of reactive astrocytes. The results also illustrate cellular mechanism of VEGF-enhanced neural repair and functional plasticity in the brains after ischemic injury. We concluded that neurogenic effect of VEGF is related to increase of striatal astrocytes transdifferentiation into new mature neurons, which should be very important for the reconstruction of neurovascular units/networks in non-neurogenic regions of the mammalian brain. PMID:26603138

  15. Prenatal exposure to ethanol alters the postnatal development and transformation of radial glia to astrocytes in the cortex.

    PubMed

    Miller, M W; Robertson, S

    1993-11-01

    Postmitotic neurons migrate from a zone(s) near the ventricles to the neocortex. During this migration, neurons associate with radial glia. After serving their role as guides for neuronal migration, the radial glia transform into astrocytes. Prenatal exposure to ethanol causes abnormal neuronal migration. We examined the effects of gestational exposure to ethanol on radial glia and astrocytes. Radial glia were stained immunohistochemically with the antibody RAT-401, and astrocytes were labeled with an antibody directed against glial fibrillary acidic protein (GFAP). The subjects were the offspring of rats fed an ethanol-containing liquid diet (Et), pair-fed a liquid control diet (Ct), or fed chow and water (Ch). During the first postnatal week, radial glial fibers (in Et-treated rats and controls) stretched from the ventricular surface through the developing cerebral wall to the pial surface. In the Et-treated rats, the radial processes were less dense and more poorly fasciculated than they were in the Ch- and Ct-treated rats. Moreover, by postnatal day (P) 5, there was a significant reduction in RAT-401 immunostaining in the Et-treated rats, particularly in the superficial cortex. A similar reduction in control rats did not begin until P10. In all three treatment groups, GFAP-immunoreactive astrocytes were in the cortex throughout the period from P1 to P45. In neonates, GFAP-positive cells were distributed in the marginal zone (layer I) and the intermediate zone (the white matter). The number of GFAP-positive cells in the cortical plate increased steadily with time so that, by P26, GFAP-immunoreactive astrocytes were distributed evenly through all cortical laminae. Interestingly, between P5 and P12, the number of astrocytes was significantly greater in Et-treated rats than in controls. Thus prenatal exposure to ethanol induces the premature loss of RAT-401-positive processes and the precocious increase in GFAP immunostaining. These ethanol-induced changes in glial

  16. Reactive Astrocytes Expressing Intense Estrogen Receptor-alpha Immunoreactivities Have Much Elongated Cytoplasmic Processes: An Autopsy Case of Human Cerebellar Tissue with Multiple Genitourinary and Gastrointestinal Anomalies

    PubMed Central

    Kim, Eo-Jin; Oh, Chang Seok; Kim, Jaehyup; Kim, Wu Ho; Chung, Yoon Hee

    2007-01-01

    We performed an immunohistochemical study on the estrogen receptor alpha (ER-α) distribution in the cerebellum of a human neonate with multiple congenital anomalies, that had been acquired during autopsy. Although the exact pathology in the brain was not clearly elucidated in this study, an unidentified stressful condition might have induced the astrocytes into reactive states. In this immunohistochemical study on the neonatal cerebellum with multiple congenital anomalies, intense ER-α immunoreactivities (IRs) were localized mainly within the white matter even though ER-α IRs were known to be mainly localized in neurons. Double immunohistochemical staining showed that ER-α IR cells were reactive astrocytes, but not neurons. Interestingly, there were differences in the process length among the reactive astrocytes showing ER-α IRs. Our quantitative data confirmed that among the glial fibrillary acidic protein (GFAP)-expressing reactive astrocytes, the cells exhibiting intense ER-α IRs have much longer cytoplasmic processes and relatively weaker GFAP IRs. Taken together, the elongated processes of reactive astrocytes might be due to decreased expression of GFAP, which might be induced by elevated expression of ER-α even though the elucidation of the exact mechanism needs further studies. PMID:17982251

  17. Ornithine and Homocitrulline Impair Mitochondrial Function, Decrease Antioxidant Defenses and Induce Cell Death in Menadione-Stressed Rat Cortical Astrocytes: Potential Mechanisms of Neurological Dysfunction in HHH Syndrome.

    PubMed

    Zanatta, Ângela; Rodrigues, Marília Danyelle Nunes; Amaral, Alexandre Umpierrez; Souza, Débora Guerini; Quincozes-Santos, André; Wajner, Moacir

    2016-09-01

    Hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome is caused by deficiency of ornithine translocase leading to predominant tissue accumulation and high urinary excretion of ornithine (Orn), homocitrulline (Hcit) and ammonia. Although affected patients commonly present neurological dysfunction manifested by cognitive deficit, spastic paraplegia, pyramidal and extrapyramidal signs, stroke-like episodes, hypotonia and ataxia, its pathogenesis is still poorly known. Although astrocytes are necessary for neuronal protection. Therefore, in the present study we investigated the effects of Orn and Hcit on cell viability (propidium iodide incorporation), mitochondrial function (thiazolyl blue tetrazolium bromide-MTT-reduction and mitochondrial membrane potential-ΔΨm), antioxidant defenses (GSH) and pro-inflammatory response (NFkB, IL-1β, IL-6 and TNF-α) in unstimulated and menadione-stressed cortical astrocytes that were previously shown to be susceptible to damage by neurotoxins. We first observed that Orn decreased MTT reduction, whereas both amino acids decreased GSH levels, without altering cell viability and the pro-inflammatory factors in unstimulated astrocytes. Furthermore, Orn and Hcit decreased cell viability and ΔΨm in menadione-treated astrocytes. The present data indicate that the major compounds accumulating in HHH syndrome impair mitochondrial function and reduce cell viability and the antioxidant defenses in cultured astrocytes especially when stressed by menadione. It is presumed that these mechanisms may be involved in the neuropathology of this disease. PMID:27161368

  18. Ca(2+) -dependent endoplasmic reticulum stress correlates with astrogliosis in oligomeric amyloid β-treated astrocytes and in a model of Alzheimer's disease.

    PubMed

    Alberdi, Elena; Wyssenbach, Ane; Alberdi, María; Sánchez-Gómez, M V; Cavaliere, Fabio; Rodríguez, José J; Verkhratsky, Alexei; Matute, Carlos

    2013-04-01

    Neurotoxic effects of amyloid β peptides are mediated through deregulation of intracellular Ca(2+) homeostasis and signaling, but relatively little is known about amyloid β modulation of Ca(2+) homeostasis and its pathological influence on glia. Here, we found that amyloid β oligomers caused a cytoplasmic Ca(2+) increase in cultured astrocytes, which was reduced by inhibitors of PLC and ER Ca(2+) release. Furthermore, amyloid β peptides triggered increased expression of glial fibrillary acidic protein (GFAP), as well as oxidative and ER stress, as indicated by eIF2α phosphorylation and overexpression of chaperone GRP78. These effects were decreased by ryanodine and 2APB, inhibitors of ryanodine receptors and InsP3 receptors, respectively, in both primary cultured astrocytes and organotypic cultures of hippocampus and entorhinal cortex. Importantly, intracerebroventricular injection of amyloid β oligomers triggered overexpression of GFAP and GRP78 in astrocytes of the hippocampal dentate gyrus. These data were validated in a triple-transgenic mouse model of Alzheimer's disease (AD). Overexpression of GFAP and GRP78 in the hippocampal astrocytes correlated with the amyloid β oligomer load in 12-month-old mice, suggesting that this parameter drives astrocytic ER stress and astrogliosis in vivo. Together, these results provide evidence that amyloid β oligomers disrupt ER Ca(2+) homeostasis, which induces ER stress that leads to astrogliosis; this mechanism may be relevant to AD pathophysiology.

  19. Ornithine and Homocitrulline Impair Mitochondrial Function, Decrease Antioxidant Defenses and Induce Cell Death in Menadione-Stressed Rat Cortical Astrocytes: Potential Mechanisms of Neurological Dysfunction in HHH Syndrome.

    PubMed

    Zanatta, Ângela; Rodrigues, Marília Danyelle Nunes; Amaral, Alexandre Umpierrez; Souza, Débora Guerini; Quincozes-Santos, André; Wajner, Moacir

    2016-09-01

    Hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome is caused by deficiency of ornithine translocase leading to predominant tissue accumulation and high urinary excretion of ornithine (Orn), homocitrulline (Hcit) and ammonia. Although affected patients commonly present neurological dysfunction manifested by cognitive deficit, spastic paraplegia, pyramidal and extrapyramidal signs, stroke-like episodes, hypotonia and ataxia, its pathogenesis is still poorly known. Although astrocytes are necessary for neuronal protection. Therefore, in the present study we investigated the effects of Orn and Hcit on cell viability (propidium iodide incorporation), mitochondrial function (thiazolyl blue tetrazolium bromide-MTT-reduction and mitochondrial membrane potential-ΔΨm), antioxidant defenses (GSH) and pro-inflammatory response (NFkB, IL-1β, IL-6 and TNF-α) in unstimulated and menadione-stressed cortical astrocytes that were previously shown to be susceptible to damage by neurotoxins. We first observed that Orn decreased MTT reduction, whereas both amino acids decreased GSH levels, without altering cell viability and the pro-inflammatory factors in unstimulated astrocytes. Furthermore, Orn and Hcit decreased cell viability and ΔΨm in menadione-treated astrocytes. The present data indicate that the major compounds accumulating in HHH syndrome impair mitochondrial function and reduce cell viability and the antioxidant defenses in cultured astrocytes especially when stressed by menadione. It is presumed that these mechanisms may be involved in the neuropathology of this disease.

  20. Green-Fluorescent Protein(+) Astrocytes Attach to Beta-Amyloid Plaques in an Alzheimer Mouse Model and Are Sensitive for Clasmatodendrosis.

    PubMed

    Daschil, Nina; Humpel, Christian

    2016-01-01

    Alzheimer's disease (AD) is pathologically characterized by beta-amyloid (Aβ) plaques and Tau pathology. It is well-established that Aβ plaques are surrounded by reactive astrocytes, highly expressing glial fibrillary acidic protein (GFAP). In order to study the cellular interaction of reactive astrocytes with Aβ plaques, we crossbred mice overexpressing amyloid precursor protein (APP) with the Swedish-Dutch-Iowa mutations (APP-SweDI) with mice expressing green fluorescent protein (GFP) under the GFAP-promotor. Three-dimensional confocal microscopy revealed a tight association and intense sprouting of astrocytic finely branched processes towards Aβ plaques in 12 month old mice. In order to study phagocytosis, 110 μm thick brain slices from 12 month old crossbred mice were cultured overnight, however, we found that the GFP fluorescence faded, distal processes degenerated and a complete loss of astrocytic morphology was seen (clasmatodendrosis). In summary, our data show that GFP(+) reactive astrocytes make intense contact with Aβ plaques but these cells are highly vulnerable for degeneration. PMID:27092076

  1. Green-Fluorescent Protein+ Astrocytes Attach to Beta-Amyloid Plaques in an Alzheimer Mouse Model and Are Sensitive for Clasmatodendrosis

    PubMed Central

    Daschil, Nina; Humpel, Christian

    2016-01-01

    Alzheimer’s disease (AD) is pathologically characterized by beta-amyloid (Aβ) plaques and Tau pathology. It is well-established that Aβ plaques are surrounded by reactive astrocytes, highly expressing glial fibrillary acidic protein (GFAP). In order to study the cellular interaction of reactive astrocytes with Aβ plaques, we crossbred mice overexpressing amyloid precursor protein (APP) with the Swedish-Dutch-Iowa mutations (APP-SweDI) with mice expressing green fluorescent protein (GFP) under the GFAP-promotor. Three-dimensional confocal microscopy revealed a tight association and intense sprouting of astrocytic finely branched processes towards Aβ plaques in 12 month old mice. In order to study phagocytosis, 110 μm thick brain slices from 12 month old crossbred mice were cultured overnight, however, we found that the GFP fluorescence faded, distal processes degenerated and a complete loss of astrocytic morphology was seen (clasmatodendrosis). In summary, our data show that GFP+ reactive astrocytes make intense contact with Aβ plaques but these cells are highly vulnerable for degeneration. PMID:27092076

  2. Activation of Sonic Hedgehog Leads to Survival Enhancement of Astrocytes via the GRP78-Dependent Pathway in Mice Infected with Angiostrongylus cantonensis

    PubMed Central

    Chen, Kuang-Yao; Cheng, Chien-Ju; Wang, Lian-Chen

    2015-01-01

    Angiostrongylus cantonensis infection may cause elevation of ROS and antioxidants in the CSF of infected mice. Astrocytes may protect the surrounding neurons from oxidative stress-induced cell death by secreting Sonic hedgehog (Shh) via the PI3-K/AKT/Bcl-2 pathway. This study was conducted to determine the role of the Shh signaling pathway in A. cantonensis-infected BABL/c mice by coculturing astrocytes with living fifth-stage larvae or soluble antigens. The Shh pathway was activated with corresponding increases in the level of the Shh. Glial fibrillary acidic protein (GFAP) and Shh were increased in astrocyte cocultured with living fifth-stage larvae or soluble antigens. The survival of astrocytes pretreated with Shh was significantly elevated in cocultures with the antigens but reduced by its inhibitor cyclopamine. The expression of GRP78 and Bcl-2 was significantly higher in astrocytes pretreated with recombinant Shh. These findings suggest that the expression of Shh may inhibit cell death by activating Bcl-2 through a GRP78-dependent pathway. PMID:25961032

  3. Angiotensin II induces secretion of plasminogen activator inhibitor 1 and a tissue metalloprotease inhibitor-related protein from rat brain astrocytes

    SciTech Connect

    Olson, J.A. Jr.; Shiverick, K.T.; Ogilvie, S.; Buhi, W.C.; Raizada, M.K. )

    1991-03-01

    The present study investigates angiotensin (Ang) II effects on secretory protein synthesis in brain astrocytes cultured from neonatal and 21-day-old rats. Ang II-induced changes in the de novo synthesis of (35S)methionine-labeled secretory proteins were visualized using two-dimensional NaDodSO4/PAGE. Astrocytes from 21-day-old rat brain possess specific high-affinity receptors for Ang II. These cells express two Ang II-induced secretory proteins with Mr 55,000 (AISP-55K) and Mr 30,000 (AISP-30K), which were time- and dose-dependent (EC50, 1 nM). (Sar1, Ile8)Ang II (where Sar is sarcosine) inhibited Ang II-induced secretion of AISP-55K but not AISP-30K. N-terminal amino acid sequencing indicates that AISP-55K is identical to rat plasminogen activator inhibitor 1, whereas AISP-30K exhibits 72-81% identity to three closely related proteins: human tissue inhibitor of metalloproteases, a rat phorbol ester-induced protein, and the murine growth-responsive protein 16C8. Immunofluorescent staining with rat plasminogen activator inhibitor 1 antibody was induced in the majority of cells in culture after Ang II treatment of astrocytes from 21-day-old rat brains. Absence of this response to Ang II in astrocytes from neonatal rat brain provides evidence that this action of Ang II on astrocytes is developmentally regulated.

  4. Ceftriaxone reverses ketamine-induced lasting EEG and astrocyte alterations in juvenile mice

    PubMed Central

    Dodman, K.; Featherstone, R.E.; Bang, J.; Liang, Y.; Siegel, S.J.

    2015-01-01

    Background Ketamine, an N-Methyl-D-aspartate receptor antagonist, is used as a pediatric anesthetic because of its favorable safety profile. It is also being investigated as an antidepressant. Unfortunately, ketamine causes adverse reactions including hallucinations and is associated with a high prevalence of abuse among adolescents. Although chronic ketamine use has been shown to produce cognitive impairments even years following cessation, little is known about its long-term consequences on adolescents. The beta-lactam ceftriaxone has been shown to attenuate alcohol withdrawal, and alleviate early brain injury and memory impairments following subarachnoid hemorrhage. However, its ability to reverse the effects of adolescent ketamine exposure is not known. Previous data indicate that ketamine causes a reduction in the number of Excitatory Amino Acid Transporter Type 2 (EAAT2)-containing astrocytes. Additionally, the beta lactam antibiotic ceftriaxone increased expression of EAAT2. As EAAT2 is a principal mechanism of glutamate clearance from the synapse, the current study tests the hypothesis that ceftriaxone may reverse functional consequences of ketamine exposure. Methods We examined the effects of chronic ketamine in juvenile mice as well as reversal by ceftriaxone using electroencephalography (EEG). Subsequently, we assessed the effects of these treatments on markers of astrocyte proliferation, using Glial Fibrillary Acidic Protein (GFAP), and function, as evidenced by EAAT2. Results Juvenile mice exposed to chronic ketamine showed lasting alterations in EEG measurements as well as markers of astrocyte number and function. These alterations were reversed by ceftriaxone. Conclusions Data suggest that ceftriaxone may be able to ameliorate ketamine-induced long-term disturbances in adolescent brains. PMID:26442907

  5. Striatal astrocytes transdifferentiate into functional mature neurons following ischemic brain injury

    PubMed Central

    Duan, Chun‐Ling; Liu, Chong‐Wei; Shen, Shu‐Wen; Yu, Zhang; Mo, Jia‐Lin; Chen, Xian‐Hua

    2015-01-01

    To determine whether reactive astrocytes stimulated by brain injury can transdifferentiate into functional new neurons, we labeled these cells by injecting a glial fibrillary acidic protein (GFAP) targeted enhanced green fluorescence protein plasmid (pGfa2‐eGFP plasmid) into the striatum of adult rats immediately following a transient middle cerebral artery occlusion (MCAO) and performed immunolabeling with specific neuronal markers to trace the neural fates of eGFP‐expressing (GFP+) reactive astrocytes. The results showed that a portion of striatal GFP+ astrocytes could transdifferentiate into immature neurons at 1 week after MCAO and mature neurons at 2 weeks as determined by double staining GFP‐expressing cells with βIII‐tubulin (GFP+‐Tuj‐1+) and microtubule associated protein‐2 (GFP+‐MAP‐2+), respectively. GFP+ neurons further expressed choline acetyltransferase, glutamic acid decarboxylase, dopamine receptor D2‐like family proteins, and the N‐methyl‐d‐aspartate receptor subunit R2, indicating that astrocyte‐derived neurons could develop into cholinergic or GABAergic neurons and express dopamine and glutamate receptors on their membranes. Electron microscopy analysis indicated that GFP+ neurons could form synapses with other neurons at 13 weeks after MCAO. Electrophysiological recordings revealed that action potentials and active postsynaptic currents could be recorded in the neuron‐like GFP+ cells but not in the astrocyte‐like GFP+ cells, demonstrating that new GFP+ neurons possessed the capacity to fire action potentials and receive synaptic inputs. These results demonstrated that striatal astrocyte‐derived new neurons participate in the rebuilding of functional neural networks, a fundamental basis for brain repair after injury. These results may lead to new therapeutic strategies for enhancing brain repair after ischemic stroke. GLIA 2015;63:1660–1670 PMID:26031629

  6. A1R-A2AR heteromers coupled to Gs and G i/0 proteins modulate GABA transport into astrocytes.

    PubMed

    Cristóvão-Ferreira, Sofia; Navarro, Gemma; Brugarolas, Marc; Pérez-Capote, Kamil; Vaz, Sandra H; Fattorini, Giorgia; Conti, Fiorenzo; Lluis, Carmen; Ribeiro, Joaquim A; McCormick, Peter J; Casadó, Vicent; Franco, Rafael; Sebastião, Ana M

    2013-09-01

    Astrocytes play a key role in modulating synaptic transmission by controlling extracellular gamma-aminobutyric acid (GABA) levels via GAT-1 and GAT-3 GABA transporters (GATs). Using primary cultures of rat astrocytes, we show here that a further level of regulation of GABA uptake occurs via modulation of the GATs by the adenosine A1 (A1R) and A2A (A2AR) receptors. This regulation occurs through A1R-A2AR heteromers that signal via two different G proteins, Gs and Gi/0, and either enhances (A2AR) or inhibits (A1R) GABA uptake. These results provide novel mechanistic insight into how GPCR heteromers signal. Furthermore, we uncover a previously unknown mechanism where adenosine, in a concentration-dependent manner, acts via a heterocomplex of adenosine receptors in astrocytes to significantly contribute to neurotransmission at the tripartite (neuron-glia-neuron) synapse.

  7. Electrodiffusive Model for Astrocytic and Neuronal Ion Concentration Dynamics

    PubMed Central

    Halnes, Geir; Østby, Ivar; Pettersen, Klas H.; Omholt, Stig W.; Einevoll, Gaute T.

    2013-01-01

    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+. PMID:24367247

  8. Astrocyte sodium signaling and the regulation of neurotransmission.

    PubMed

    Kirischuk, Sergei; Héja, László; Kardos, Julianna; Billups, Brian

    2016-10-01

    The transmembrane Na(+) concentration gradient is an important source of energy required not only to enable the generation of action potentials in excitable cells, but also for various transmembrane transporters both in excitable and non-excitable cells, like astrocytes. One of the vital functions of astrocytes in the central nervous system (CNS) is to regulate neurotransmitter concentrations in the extracellular space. Most neurotransmitters in the CNS are removed from the extracellular space by Na(+) -dependent neurotransmitter transporters (NeuTs) expressed both in neurons and astrocytes. Neuronal NeuTs control mainly phasic synaptic transmission, i.e., synaptically induced transient postsynaptic potentials, while astrocytic NeuTs contribute to the termination of phasic neurotransmission and modulate the tonic tone, i.e., the long-lasting activation of extrasynaptic receptors by neurotransmitter that has diffused out of the synaptic cleft. Consequently, local intracellular Na(+) ([Na(+) ]i ) transients occurring in astrocytes, for example via the activation of ionotropic neurotransmitter receptors, can affect the driving force for neurotransmitter uptake, in turn modulating the spatio-temporal profiles of neurotransmitter levels in the extracellular space. As some NeuTs are close to thermodynamic equilibrium under resting conditions, an increase in astrocytic [Na(+) ]i can stimulate the direct release of neurotransmitter via NeuT reversal. In this review we discuss the role of astrocytic [Na(+) ]i changes in the regulation of uptake/release of neurotransmitters. It is emphasized that an activation of one neurotransmitter system, including either its ionotropic receptor or Na(+) -coupled co-transporter, can strongly influence, or even reverse, other Na(+) -dependent NeuTs, with potentially significant consequences for neuronal communication. GLIA 2016;64:1655-1666. PMID:26566753

  9. Astrocyte sodium signaling and the regulation of neurotransmission.

    PubMed

    Kirischuk, Sergei; Héja, László; Kardos, Julianna; Billups, Brian

    2016-10-01

    The transmembrane Na(+) concentration gradient is an important source of energy required not only to enable the generation of action potentials in excitable cells, but also for various transmembrane transporters both in excitable and non-excitable cells, like astrocytes. One of the vital functions of astrocytes in the central nervous system (CNS) is to regulate neurotransmitter concentrations in the extracellular space. Most neurotransmitters in the CNS are removed from the extracellular space by Na(+) -dependent neurotransmitter transporters (NeuTs) expressed both in neurons and astrocytes. Neuronal NeuTs control mainly phasic synaptic transmission, i.e., synaptically induced transient postsynaptic potentials, while astrocytic NeuTs contribute to the termination of phasic neurotransmission and modulate the tonic tone, i.e., the long-lasting activation of extrasynaptic receptors by neurotransmitter that has diffused out of the synaptic cleft. Consequently, local intracellular Na(+) ([Na(+) ]i ) transients occurring in astrocytes, for example via the activation of ionotropic neurotransmitter receptors, can affect the driving force for neurotransmitter uptake, in turn modulating the spatio-temporal profiles of neurotransmitter levels in the extracellular space. As some NeuTs are close to thermodynamic equilibrium under resting conditions, an increase in astrocytic [Na(+) ]i can stimulate the direct release of neurotransmitter via NeuT reversal. In this review we discuss the role of astrocytic [Na(+) ]i changes in the regulation of uptake/release of neurotransmitters. It is emphasized that an activation of one neurotransmitter system, including either its ionotropic receptor or Na(+) -coupled co-transporter, can strongly influence, or even reverse, other Na(+) -dependent NeuTs, with potentially significant consequences for neuronal communication. GLIA 2016;64:1655-1666.

  10. The Role of Astrocytes in Multiple Sclerosis Progression

    PubMed Central

    Correale, Jorge; Farez, Mauricio F.

    2015-01-01

    Multiple sclerosis (MS) is an inflammatory disorder causing central nervous system (CNS) demyelination and axonal injury. Although its etiology remains elusive, several lines of evidence support the concept that autoimmunity plays a major role in disease pathogenesis. The course of MS is highly variable; nevertheless, the majority of patients initially present a relapsing–remitting clinical course. After 10–15 years of disease, this pattern becomes progressive in up to 50% of untreated patients, during which time clinical symptoms slowly cause constant deterioration over a period of many years. In about 15% of MS patients, however, disease progression is relentless from disease onset. Published evidence supports the concept that progressive MS reflects a poorly understood mechanism of insidious axonal degeneration and neuronal loss. Recently, the type of microglial cell and of astrocyte activation and proliferation observed has suggested contribution of resident CNS cells may play a critical role in disease progression. Astrocytes could contribute to this process through several mechanisms: (a) as part of the innate immune system, (b) as a source of cytotoxic factors, (c) inhibiting remyelination and axonal regeneration by forming a glial scar, and (d) contributing to axonal mitochondrial dysfunction. Furthermore, regulatory mechanisms mediated by astrocytes can be affected by aging. Notably, astrocytes might also limit the detrimental effects of pro-inflammatory factors, while providing support and protection for oligodendrocytes and neurons. Because of the dichotomy observed in astrocytic effects, the design of therapeutic strategies targeting astrocytes becomes a challenging endeavor. Better knowledge of molecular and functional properties of astrocytes, therefore, should promote understanding of their specific role in MS pathophysiology, and consequently lead to development of novel and more successful therapeutic approaches. PMID:26347709

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

    PubMed

    Halnes, Geir; Ostby, Ivar; Pettersen, Klas H; Omholt, Stig W; Einevoll, Gaute T

    2013-01-01

    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(+). PMID:24367247

  12. Voluntary Exercise Induces Astrocytic Structural Plasticity in the Globus Pallidus

    PubMed Central

    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 Olig2CreER/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

  13. Voluntary Exercise Induces Astrocytic Structural Plasticity in the Globus Pallidus.

    PubMed

    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

  14. Defining pathways of loss and secretion of chemical messengers from astrocytes.

    PubMed

    Evanko, Daniel S; Zhang, Qi; Zorec, Robert; Haydon, Philip G

    2004-08-15

    It is becoming evident that glia, and astrocytes in particular, are intimately involved in neuronal signaling. Astrocytic modulation of signaling in neurons appears to be mediated by the release of neuroactive compounds such as the excitatory amino acid glutamate. Release of these transmitters appears to be driven by two different processes: (1) a volume regulatory response triggered by hypo-osmotic conditions that leads to the release of osmotically active solutes from the cytoplasm into the extracellular space, and (2) intracellular calcium-dependent vesicle-mediated excytotic release. The regulatory volume decrease may be mediated by any of several different pathways that increase membrane permeability, thus allowing osmolytes to travel down their concentration gradient into the extracellular space. Such pathways include anion channels, hemichannels, P2X receptor channels, and transporters or multidrug resistance proteins. The excytotic release process may use calcium triggered synaptic like vesicle fusion or alterations in constitutive vesicle trafficking to the membrane. Determining the contribution of any of these release mechanisms requires agents that can be used to specifically block pathways of interest. Currently, many of the pharmacological compounds being used exhibit a great deal of cross-reactivity between several of these pathways. For example, the popular anion channel inhibitor 5-nitro-2-(3-phenyl-propylamino)benzoic acid (NPPB) is an efficient blocker of both hemichannels and vesicle loading. This demonstrates the need to more fully characterize the activities of the agents currently available and to choose pathway blockers carefully when designing experiments.

  15. Autonomic control of neuronal-astrocytic interactions, regulating metabolic activities, and ion fluxes in the CNS.

    PubMed

    Hertz, L

    1992-01-01

    It is generally assumed that the brain, in contrast to all other organs, is not equipped with an autonomic nervous system, regulating blood supply, and cellular activities. This may be because systemic administration of most drugs acting on monoaminergic or cholinergic receptors have little or no effect on cerebral blood flow and metabolism. However, intrathecal administration of noradrenaline does, indeed, influence both blood flow and energy metabolism in the brain. The present review focuses on effects of noradrenaline or serotonin on energy metabolism, turnover of amino acid transmitters and ion homeostasis, with special emphasis on the cellular localization. Noradrenergic agonists stimulate brain metabolism in vivo as well as many aspects of energy metabolism, Na+,K(+)-ATPase activity and uptake of transmitter amino acids in astrocytes in primary cultures, with little or no effect on corresponding preparations of neurons. Serotonin acts differently, decreasing potassium-induced release of glutamate from both neurons and astrocytes. Little is known about the effects of acetylcholine. The functional significance of these effects is discussed. PMID:1393603

  16. In vitro synchronization of mammalian astrocytic cultures by serum deprivation.

    PubMed

    Chou, Richard C; Langan, Thomas J

    2003-07-01

    The study of the regulation of cell division cycle in vitro requires cell cultures growing in the same phase of the cycle. The procedure by which cells are arrested in specific phases of the cell cycle is termed synchronization. Synchronization is particularly important in the study of astrocyte biology, as its application allows astrocytes to re-enter the cell cycle from a state of quiescence (G(0)), and, under carefully defined experimental conditions, move together into subsequent phases such as the G(1) and S phases. A number of methods have been established to synchronize mammalian cell cultures, including centrifugal elutriation, mitotic shake-off, and chemically induced cell cycle arrest. Yet there are intrinsic limitations associated with these methods. In the present protocol, we describe a simple, reliable, and reversible procedure to synchronize astrocytic cultures from newborn rat brains by serum deprivation. This protocol consists essentially of two parts: (1) proliferation of astrocytes under optimal conditions in vitro until reaching desired confluence; and (2) synchronization of cultures by serum down-shift and arrested in the G(0) phase of the cell cycle. This procedure has recently been extended toward the study of cell cycle control in astroglioma cells and astrocytes from injured adult brains. Since it was also employed in recent precursor cloning studies in developmental biology, this procedure will certainly find increasing use in future research.

  17. Simultaneous neuron- and astrocyte-specific fluorescent marking.

    PubMed

    Schulze, Wiebke; Hayata-Takano, Atsuko; Kamo, Toshihiko; Nakazawa, Takanobu; Nagayasu, Kazuki; Kasai, Atsushi; Seiriki, Kaoru; Shintani, Norihito; Ago, Yukio; Farfan, Camille; Hashimoto, Ryota; Baba, Akemichi; Hashimoto, Hitoshi

    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.

  18. Targeting astrocytes in brain injuries: A translational research approach.

    PubMed

    Barreto, George E

    2016-09-01

    In the brain, the astrocentric view has increasingly changed in the past few years. The classical and old view of astrocytes as "just supporting cells" has assigned these cells some functions to help neurons maintain their homeostasis. This neuronal supportive function of astrocytes includes maintenance of ion and extracellular pH equilibrium, neuroendocrine signaling, metabolic support, clearance of glutamate and other neurotransmitters, and antioxidant protection. However, recent findings have shed some light on the new roles, some controversial though, performed by astrocytes that might change our view about the central nervous system functioning. Since astrocytes are important for neuronal survival, it is a potential approach to favor astrocytic functions in order to improve the outcome. Such translational strategies may include the use of genetically targeted proteins, and/or pharmacological therapies by administering androgens and estrogens, which have shown promising results in vitro and in vivo models. It is noteworthy that successful strategies reviewed in here shall be extrapolated to human subjects, and this is probably the next step we should move on.

  19. Study of curcumin immunomodulatory effects on reactive astrocyte cell function.

    PubMed

    Seyedzadeh, Mir Hadi; Safari, Zohreh; Zare, Ahad; Gholizadeh Navashenaq, Jamshid; Razavi, Seyed Alireza; Kardar, Gholam Ali; Khorramizadeh, Mohammad Reza

    2014-09-01

    Multiple sclerosis (MS) is considered an inflammatory and neurodegenerative disease of the central nervous system (CNS) which most often presents as relapsing-remitting episodes. Recent evidence suggests that activated astrocytes play a dual functional role in CNS inflammatory disorders such as MS. In this study, we tried to induce anti-inflammatory functions of astrocytes by curcumin. The effects of curcumin were examined on human a astrocyte cell line (U373-MG) induced by lipopolysaccharide (LPS) in vitro. Matrix metalloproteinase (MMP)-9 activity was assessed by gelatin zymography. Cytokine levels were evaluated by quantitative ELISA method and mRNA expression was measured by real-time PCR. We found that curcumin decreased the release of IL-6 and reduced MMP-9 enzyme activity. It down-regulated MCP-1 mRNA expression too. However, curcumin did not have significant effects on the expression of neurotrophin (NT)-3 and insulin-like growth factor (IGF)-1 mRNAs. Results suggest that curcumin might beneficially affect astrocyte population in CNS neuroinflammatory environment lean to anti-inflammatory response and help to components in respects of CNS repair. Our findings offer curcumin as a new therapeutic agent with the potential of regulating astrocyte-mediated inflammatory diseases in the CNS. PMID:24998635

  20. Astrocytes and NG2-glia: what's in a name?

    PubMed Central

    Nishiyama, Akiko; Yang, Zhongshu; Butt, Arthur

    2005-01-01

    Classic studies recognize two functionally segregated macroglial cell types in the central nervous system (CNS), namely astrocytes and oligodendrocytes. A third macroglial cell type has now been identified by its specific expression of the NG2 chondroitin sulphate proteoglycan (NG2-glia). These NG2-glia exist abundantly in both grey and white matter of the mature CNS and are almost as numerous as astrocytes. It is well established that NG2-glia give rise to oligodendrocytes. However, the majority of NG2-glia in the adult CNS proliferate very slowly and are non-motile. Both astrocytes and NG2-glia display a stellate morphology and express ion channels and receptors to neurotransmitters used by neurons. Both types of glia make intimate contacts with neurons in grey and white matter, and their functional differences and similarities are only beginning to be unravelled. Recent observations emphasize the need to examine the relationship between astrocytes and NG2-glia, and address the question of whether they represent overlapping or two distinct glial cell populations. To be of any relevance, this classification must relate to specific functions in the neural network. At present, the balance of evidence is that NG2-glia and astrocytes are functionally segregated populations. PMID:16367796

  1. Targeting astrocytes in brain injuries: A translational research approach.

    PubMed

    Barreto, George E

    2016-09-01

    In the brain, the astrocentric view has increasingly changed in the past few years. The classical and old view of astrocytes as "just supporting cells" has assigned these cells some functions to help neurons maintain their homeostasis. This neuronal supportive function of astrocytes includes maintenance of ion and extracellular pH equilibrium, neuroendocrine signaling, metabolic support, clearance of glutamate and other neurotransmitters, and antioxidant protection. However, recent findings have shed some light on the new roles, some controversial though, performed by astrocytes that might change our view about the central nervous system functioning. Since astrocytes are important for neuronal survival, it is a potential approach to favor astrocytic functions in order to improve the outcome. Such translational strategies may include the use of genetically targeted proteins, and/or pharmacological therapies by administering androgens and estrogens, which have shown promising results in vitro and in vivo models. It is noteworthy that successful strategies reviewed in here shall be extrapolated to human subjects, and this is probably the next step we should move on. PMID:27659056

  2. Interferon-Gamma Promotes Infection of Astrocytes by Trypanosoma cruzi

    PubMed Central

    Silva, Rafael Rodrigues; Mariante, Rafael M.; Silva, Andrea Alice; dos Santos, Ana Luiza Barbosa; Roffê, Ester; Santiago, Helton; Gazzinelli, Ricardo Tostes; Lannes-Vieira, Joseli

    2015-01-01

    The inflammatory cytokine interferon-gamma (IFNγ) is crucial for immunity against intracellular pathogens such as the protozoan parasite Trypanosoma cruzi, the causative agent of Chagas disease (CD). IFNγ is a pleiotropic cytokine which regulates activation of immune and non-immune cells; however, the effect of IFNγ in the central nervous system (CNS) and astrocytes during CD is unknown. Here we show that parasite persists in the CNS of C3H/He mice chronically infected with the Colombian T. cruzi strain despite the increased expression of IFNγ mRNA. Furthermore, most of the T. cruzi-bearing cells were astrocytes located near IFNγ+ cells. Surprisingly, in vitro experiments revealed that pretreatment with IFNγ promoted the infection of astrocytes by T. cruzi increasing uptake and proliferation of intracellular forms, despite inducing increased production of nitric oxide (NO). Importantly, the effect of IFNγ on T. cruzi uptake and growth is completely blocked by the anti-tumor necrosis factor (TNF) antibody Infliximab and partially blocked by the inhibitor of nitric oxide synthesis L-NAME. These data support that IFNγ fuels astrocyte infection by T. cruzi and critically implicate IFNγ-stimulated T. cruzi-infected astrocytes as sources of TNF and NO, which may contribute to parasite persistence and CNS pathology in CD. PMID:25695249

  3. Calcium Signaling and Gliotransmission in Normal vs. Reactive Astrocytes

    PubMed Central

    Agulhon, Cendra; Sun, Min-Yu; Murphy, Thomas; Myers, Timothy; Lauderdale, Kelli; Fiacco, Todd A.

    2012-01-01

    A prominent area of neuroscience research over the past 20 years has been the acute modulation of neuronal synaptic activity by Ca2+-dependent release of the transmitters ATP, D-serine, and glutamate (called gliotransmitters) by astrocytes. Although the physiological relevance of this mechanism is under debate, emerging evidence suggests that there are critical factors in addition to Ca2+ that are required for gliotransmitters to be released from astrocytes. Interestingly, these factors include activated microglia and the proinflammatory cytokine Tumor Necrosis Factor α (TNFα), chemotactic cytokine Stromal cell-Derived Factor-1α (SDF-1α), and inflammatory mediator prostaglandin E2 (PGE2). Of note, microglial activation and release of inflammatory molecules from activated microglia and reactive astrocytes can occur within minutes of a triggering stimulus. Therefore, activation of astrocytes by inflammatory molecules combined with Ca2+ elevations may lead to gliotransmitter release, and be an important step in the early sequence of events contributing to hyperexcitability, excitotoxicity, and neurodegeneration in the damaged or diseased brain. In this review, we will first examine evidence questioning Ca2+-dependent gliotransmitter release from astrocytes in healthy brain tissue, followed by a close examination of recent work suggesting that Ca2+-dependent gliotransmitter release occurs as an early event in the development of neurological disorders and neuroinflammatory and neurodegenerative diseases. PMID:22811669

  4. Accumulation of silver nanoparticles by cultured primary brain astrocytes

    NASA Astrophysics Data System (ADS)

    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.

  5. Adrenergic activation attenuates astrocyte swelling induced by hypotonicity and neurotrauma.

    PubMed

    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. PMID:27018061

  6. Interferon-gamma promotes infection of astrocytes by Trypanosoma cruzi.

    PubMed

    Silva, Rafael Rodrigues; Mariante, Rafael M; Silva, Andrea Alice; dos Santos, Ana Luiza Barbosa; Roffê, Ester; Santiago, Helton; Gazzinelli, Ricardo Tostes; Lannes-Vieira, Joseli

    2015-01-01

    The inflammatory cytokine interferon-gamma (IFNγ) is crucial for immunity against intracellular pathogens such as the protozoan parasite Trypanosoma cruzi, the causative agent of Chagas disease (CD). IFNγ is a pleiotropic cytokine which regulates activation of immune and non-immune cells; however, the effect of IFNγ in the central nervous system (CNS) and astrocytes during CD is unknown. Here we show that parasite persists in the CNS of C3H/He mice chronically infected with the Colombian T. cruzi strain despite the increased expression of IFNγ mRNA. Furthermore, most of the T. cruzi-bearing cells were astrocytes located near IFNγ+ cells. Surprisingly, in vitro experiments revealed that pretreatment with IFNγ promoted the infection of astrocytes by T. cruzi increasing uptake and proliferation of intracellular forms, despite inducing increased production of nitric oxide (NO). Importantly, the effect of IFNγ on T. cruzi uptake and growth is completely blocked by the anti-tumor necrosis factor (TNF) antibody Infliximab and partially blocked by the inhibitor of nitric oxide synthesis L-NAME. These data support that IFNγ fuels astrocyte infection by T. cruzi and critically implicate IFNγ-stimulated T. cruzi-infected astrocytes as sources of TNF and NO, which may contribute to parasite persistence and CNS pathology in CD. PMID:25695249

  7. Galunisertib inhibits glioma vasculogenic mimicry formation induced by astrocytes.

    PubMed

    Zhang, Chao; Chen, Wenliang; Zhang, Xin; Huang, Bin; Chen, Aanjing; He, Ying; Wang, Jian; Li, Xingang

    2016-03-15

    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.

  8. Glucocorticoids decrease astrocyte numbers by reducing glucocorticoid receptor expression in vitro and in vivo.

    PubMed

    Unemura, Kazuhiro; Kume, Toshiaki; Kondo, Minami; Maeda, Yuki; Izumi, Yasuhiko; Akaike, Akinori

    2012-01-01

    Glucocorticoids are stress hormones released from the adrenal cortex and their concentration is controlled by the hypothalamic-pituitary-adrenal axis. In this study, we investigated the effect of glucocorticoids on the number of astrocytes and glucocorticoid receptor (GR) expression in vitro and in vivo. Proliferation of cultured astrocytes was reduced following treatment with corticosterone and dexamethasone for 72 h. Corticosterone and dexamethasone also reduced GR expression in astrocytes. RU486, a GR antagonist, inhibited the reduction in both astrocyte proliferation and GR expression. Furthermore, GR knockdown by siRNA inhibited astrocyte proliferation. We also examined the effect of excessive glucocorticoid release on GR expression and the number of astrocytes in vivo by administering adrenocorticotropic hormone to rats for 14 days. GR expression was reduced in the prefrontal cortex and hippocampus and the number of astrocytes was reduced in the frontal cortex. Overall, our results suggest that glucocorticoids decrease the number of astrocytes by reducing GR expression.

  9. Methylene blue protects astrocytes against glucose oxygen deprivation by improving cellular respiration.

    PubMed

    Roy Choudhury, Gourav; Winters, Ali; Rich, Ryan M; Ryou, Myoung-Gwi; Gryczynski, Zygmunt; Yuan, Fang; Yang, Shao-Hua; Liu, Ran

    2015-01-01

    Astrocytes outnumber neurons and serve many metabolic and trophic functions in the mammalian brain. Preserving astrocytes is critical for normal brain function as well as for protecting the brain against various insults. Our previous studies have indicated that methylene blue (MB) functions as an alternative electron carrier and enhances brain metabolism. In addition, MB has been shown to be protective against neurodegeneration and brain injury. In the current study, we investigated the protective role of MB in astrocytes. Cell viability assays showed that MB treatment significantly protected primary astrocytes from oxygen-glucose deprivation (OGD) & reoxygenation induced cell death. We also studied the effect of MB on cellular oxygen and glucose metabolism in primary astrocytes following OGD-reoxygenation injury. MB treatment significantly increased cellular oxygen consumption, glucose uptake and ATP production in primary astrocytes. In conclusion our study demonstrated that MB protects astrocytes against OGD-reoxygenation injury by improving astrocyte cellular respiration.

  10. Isolation of intact astrocytes from the optic nerve head of adult mice

    PubMed Central

    Choi, Hee Joo; Sun, Daniel; Jakobs, Tatjana C.

    2015-01-01

    The astrocytes of the optic nerve head are a specialized subtype of white matter astrocytes that form the direct cellular environment of the unmyelinated ganglion cell axons. Due to their potential involvement in glaucoma, these astrocytes have become a target of research. Due to the heterogeneity of the optic nerve tissue, which also contains other cell types, in some cases it may be desirable to conduct gene expression studies on small numbers of well-characterized astrocytes or even individual cells. Here, we describe a simple method to isolate individual astrocytes. This method permits obtaining astrocytes with intact morphology from the adult mouse optic nerve and reduces contamination of the isolated astrocytes by other cell types. Individual astrocytes can be recognized by their morphology and collected under microscopic control. The whole procedure can be completed in 2-3 hours. We also discuss downstream applications like multiplex single-cell PCR and quantitative PCR (qPCR). PMID:26093274

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

    PubMed

    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.

  12. Melatonin modulates intercellular communication among cultured chick astrocytes.

    PubMed

    Peters, Jennifer L; Cassone, Vincent M; Zoran, Mark J

    2005-01-01

    Melatonin, a pineal neurohormone, mediates circadian and seasonal processes in birds and mammals. Diencephalic astrocytes are sites of action, at least in birds, since they express melatonin receptors and melatonin affects their metabolism. We tested whether astrocytic calcium waves are also modulated by melatonin. Calcium waves, which we found to be regulated in cultured chick glial cells by an IP(3)-dependent mechanism, were potentiated by physiological concentrations of melatonin. Melatonin also increased resting calcium levels and reduced gap junctional coupling among astrocytes, at concentrations that facilitated calcium waves. These modulatory effects were diminished by melatonin receptor blockade and pertussis toxin (PTX). Thus, melatonin induced a functional shift in the mode of intercellular communication, between junctional coupling and calcium waves, among glial cells. We suggest a mechanism where neuroglial physiology, involving GTP-binding protein signaling pathways, links rhythmic circadian outputs to pervasive neurobehavioral states. PMID:15621008

  13. Neuron–astrocyte interactions in neurodegenerative diseases: Role of neuroinflammation

    PubMed Central

    Rama Rao, Kakulavarapu V.; Kielian, Tammy

    2015-01-01

    Selective neuron loss in discrete brain regions is a hallmark of various neurodegenerative disorders, although the mechanisms responsible for this regional vulnerability of neurons remain largely unknown. Earlier studies attributed neuron dysfunction and eventual loss during neurodegenerative diseases as exclusively cell autonomous. Although cell-intrinsic factors are one critical aspect in dictating neuron death, recent evidence also supports the involvement of other central nervous system cell types in propagating non-cell autonomous neuronal injury during neurodegenerative diseases. One such example is astrocytes, which support neuronal and synaptic function, but can also contribute to neuroinflammatory processes through robust chemokine secretion. Indeed, aberrations in astrocyte function have been shown to negatively impact neuronal integrity in several neurological diseases. The present review focuses on neuroinflammatory paradigms influenced by neuron–astrocyte cross-talk in the context of select neurodegenerative diseases. PMID:26543505

  14. Are astrocytes executive cells within the central nervous system?

    PubMed

    Sica, Roberto E; Caccuri, Roberto; Quarracino, Cecilia; Capani, Francisco

    2016-08-01

    Experimental evidence suggests that astrocytes play a crucial role in the physiology of the central nervous system (CNS) by modulating synaptic activity and plasticity. Based on what is currently known we postulate that astrocytes are fundamental, along with neurons, for the information processing that takes place within the CNS. On the other hand, experimental findings and human observations signal that some of the primary degenerative diseases of the CNS, like frontotemporal dementia, Parkinson's disease, Alzheimer's dementia, Huntington's dementia, primary cerebellar ataxias and amyotrophic lateral sclerosis, all of which affect the human species exclusively, may be due to astroglial dysfunction. This hypothesis is supported by observations that demonstrated that the killing of neurons by non-neural cells plays a major role in the pathogenesis of those diseases, at both their onset and their progression. Furthermore, recent findings suggest that astrocytes might be involved in the pathogenesis of some psychiatric disorders as well. PMID:27556379

  15. Diverse subtypes of astrocytes and their development during corticogenesis

    PubMed Central

    Tabata, Hidenori

    2015-01-01

    Astrocytes are one of the most abundant cell types in the mammalian central nervous system, and are known to have a wide variety of physiological functions, including maintenance of neurons, formation of the blood brain barrier, and regulation of synapse functions. Although the migration and positioning of neurons has been extensively studied over the last several decades and many aspects have been uncovered, the process underlying glial development was largely unknown until recently due to the existence of multiple subtypes of glia and the sustained proliferative ability of these cells through adulthood. To overcome these difficulties, new gene transfer techniques and genetically modified mice were developed, and have been gradually revealing when and how astrocytes develop during corticogenesis. In this paper, I review the diversity of astrocytes and summarize our knowledge about their production and migration. PMID:25904839

  16. In vivo astrocytic Ca2+ signaling in health and brain disorders

    PubMed Central

    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. Intercellular Ca2+ waves in astrocytes can be evoked by a variety of stimulations. In animal models of some brain disorders, astrocytes can exhibit enhanced Ca2+ excitability featured as regenerative intercellular Ca2+ waves. This review first briefly summarizes the astrocytic Ca2+ signaling pathway and the procedure of in vivo two-photon Ca2+ imaging of astrocytes. It subsequently summarizes in vivo astrocytic Ca2+ signaling in health and brain disorders from experimental studies of animal models, and discusses the possible mechanisms and therapeutic implications underlying the enhanced Ca2+ excitability in astrocytes in brain disorders. Finally, this review summarizes molecular genetic approaches used to selectively manipulate astrocyte function in vivo and their applications to study the role of astrocytes in synaptic plasticity and brain disorders. PMID:24376372

  17. Contributions of Glycogen to Astrocytic Energetics during Brain Activation

    PubMed Central

    Dienel, Gerald A.; Cruz, Nancy F.

    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 glycogen consumption, which increases during stronger stimuli. Because glycogen level is restored by non-oxidative metabolism, astrocytes can influence the global ratio of oxygen to glucose utilization. Compensatory increases in utilization of blood glucose during inhibition of glycogen phosphorylase are large and approximate glycogenolysis rates during sensory stimulation. In contrast, glycogenolysis rates during hypoglycemia are low due to continued glucose delivery and oxidation of endogenous substrates; rates that preserve neuronal function in the absence of glucose are also low, probably due to metabolite oxidation. Modeling studies predict that glycogenolysis maintains a high level of glucose-6-phosphate in astrocytes to maintain feedback inhibition of hexokinase, thereby diverting glucose for use by neurons. The fate of glycogen carbon in vivo is not known, but lactate efflux from brain best accounts for the major metabolic characteristics during activation of living brain. Substantial shuttling coupled with oxidation of glycogen-derived lactate is inconsistent with available evidence. Glycogen has important roles in astrocytic energetics, including glucose sparing, control of extracellular K+ level, oxidative stress management, and memory consolidation; it is a multi-functional compound. PMID:24515302

  18. Astrocytes in Oligodendrocyte Lineage Development and White Matter Pathology

    PubMed Central

    Li, Jiasi; Zhang, Lei; Chu, Yongxin; Namaka, Michael; Deng, Benqiang; Kong, Jiming; Bi, Xiaoying

    2016-01-01

    White matter is primarily composed of myelin and myelinated axons. Structural and functional completeness of myelin is critical for the reliable and efficient transmission of information. White matter injury has been associated with the development of many demyelinating diseases. Despite a variety of scientific advances aimed at promoting re-myelination, their benefit has proven at best to be marginal. Research suggests that the failure of the re-myelination process may be the result of an unfavorable microenvironment. Astrocytes, are the most ample and diverse type of glial cells in central nervous system (CNS) which display multiple functions for the cells of the oligodendrocytes lineage. As such, much attention has recently been drawn to astrocyte function in terms of white matter myelin repair. They are different in white matter from those in gray matter in specific regards to development, morphology, location, protein expression and other supportive functions. During the process of demyelination and re-myelination, the functions of astrocytes are dynamic in that they are able to change functions in accordance to different time points, triggers or reactive pathways resulting in vastly different biologic effects. They have pivotal effects on oligodendrocytes and other cell types in the oligodendrocyte lineage by serving as an energy supplier, a participant of immunological and inflammatory functions, a source of trophic factors and iron and a sustainer of homeostasis. Astrocytic impairment has been shown to be directly linked to the development of neuromyelities optica (NMO). In addition, astroctyes have also been implicated in other white matter conditions such as psychiatric disorders and neurodegenerative diseases such as Alzheimer’s disease (AD), multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS). Inhibiting specifically detrimental signaling pathways in astrocytes while preserving their beneficial functions may be a promising approach for

  19. Astrocytes in Oligodendrocyte Lineage Development and White Matter Pathology.

    PubMed

    Li, Jiasi; Zhang, Lei; Chu, Yongxin; Namaka, Michael; Deng, Benqiang; Kong, Jiming; Bi, Xiaoying

    2016-01-01

    White matter is primarily composed of myelin and myelinated axons. Structural and functional completeness of myelin is critical for the reliable and efficient transmission of information. White matter injury has been associated with the development of many demyelinating diseases. Despite a variety of scientific advances aimed at promoting re-myelination, their benefit has proven at best to be marginal. Research suggests that the failure of the re-myelination process may be the result of an unfavorable microenvironment. Astrocytes, are the most ample and diverse type of glial cells in central nervous system (CNS) which display multiple functions for the cells of the oligodendrocytes lineage. As such, much attention has recently been drawn to astrocyte function in terms of white matter myelin repair. They are different in white matter from those in gray matter in specific regards to development, morphology, location, protein expression and other supportive functions. During the process of demyelination and re-myelination, the functions of astrocytes are dynamic in that they are able to change functions in accordance to different time points, triggers or reactive pathways resulting in vastly different biologic effects. They have pivotal effects on oligodendrocytes and other cell types in the oligodendrocyte lineage by serving as an energy supplier, a participant of immunological and inflammatory functions, a source of trophic factors and iron and a sustainer of homeostasis. Astrocytic impairment has been shown to be directly linked to the development of neuromyelities optica (NMO). In addition, astroctyes have also been implicated in other white matter conditions such as psychiatric disorders and neurodegenerative diseases such as Alzheimer's disease (AD), multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS). Inhibiting specifically detrimental signaling pathways in astrocytes while preserving their beneficial functions may be a promising approach for

  20. 1,3-Dinitrobenzene neurotoxicity - Passage effect in immortalized astrocytes.

    PubMed

    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

  1. Contributions of glycogen to astrocytic energetics during brain activation.

    PubMed

    Dienel, Gerald A; Cruz, Nancy F

    2015-02-01

    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 μmol/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 glycogen consumption, which increases during stronger stimuli. Because glycogen level is restored by non-oxidative metabolism, astrocytes can influence the global ratio of oxygen to glucose utilization. Compensatory increases in utilization of blood glucose during inhibition of glycogen phosphorylase are large and approximate glycogenolysis rates during sensory stimulation. In contrast, glycogenolysis rates during hypoglycemia are low due to continued glucose delivery and oxidation of endogenous substrates; rates that preserve neuronal function in the absence of glucose are also low, probably due to metabolite oxidation. Modeling studies predict that glycogenolysis maintains a high level of glucose-6-phosphate in astrocytes to maintain feedback inhibition of hexokinase, thereby diverting glucose for use by neurons. The fate of glycogen carbon in vivo is not known, but lactate efflux from brain best accounts for the major metabolic characteristics during activation of living brain. Substantial shuttling coupled with oxidation of glycogen-derived lactate is inconsistent with available evidence. Glycogen has important roles in astrocytic energetics, including glucose sparing, control of extracellular K(+) level, oxidative stress management, and memory consolidation; it is a multi-functional compound.

  2. Astrocytes in Oligodendrocyte Lineage Development and White Matter Pathology.

    PubMed

    Li, Jiasi; Zhang, Lei; Chu, Yongxin; Namaka, Michael; Deng, Benqiang; Kong, Jiming; Bi, Xiaoying

    2016-01-01

    White matter is primarily composed of myelin and myelinated axons. Structural and functional completeness of myelin is critical for the reliable and efficient transmission of information. White matter injury has been associated with the development of many demyelinating diseases. Despite a variety of scientific advances aimed at promoting re-myelination, their benefit has proven at best to be marginal. Research suggests that the failure of the re-myelination process may be the result of an unfavorable microenvironment. Astrocytes, are the most ample and diverse type of glial cells in central nervous system (CNS) which display multiple functions for the cells of the oligodendrocytes lineage. As such, much attention has recently been drawn to astrocyte function in terms of white matter myelin repair. They are different in white matter from those in gray matter in specific regards to development, morphology, location, protein expression and other supportive functions. During the process of demyelination and re-myelination, the functions of astrocytes are dynamic in that they are able to change functions in accordance to different time points, triggers or reactive pathways resulting in vastly different biologic effects. They have pivotal effects on oligodendrocytes and other cell types in the oligodendrocyte lineage by serving as an energy supplier, a participant of immunological and inflammatory functions, a source of trophic factors and iron and a sustainer of homeostasis. Astrocytic impairment has been shown to be directly linked to the development of neuromyelities optica (NMO). In addition, astroctyes have also been implicated in other white matter conditions such as psychiatric disorders and neurodegenerative diseases such as Alzheimer's disease (AD), multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS). Inhibiting specifically detrimental signaling pathways in astrocytes while preserving their beneficial functions may be a promising approach for

  3. Theophylline potentiates lipopolysaccharide-induced NO production in cultured astrocytes.

    PubMed

    Ogawa, Mizue; Takano, Katsura; Kawabe, Kenji; Moriyama, Mitsuaki; Ihara, Hideshi; Nakamura, Yoichi

    2014-01-01

    Elucidation of the functions of astrocytes is important for understanding of the pathogenic mechanism of various neurodegenerative diseases. Theophylline is a common drug for bronchial asthma and occasionally develops side-effects, such as acute encephalopathy; although the pathogenic mechanism of the side-effects is unknown. The lipopolysaccharide (LPS)-induced nitricoxide (NO) production is generally used for an index of the activation of astrocyte in vitro. In this study, in order to elucidate the effect of theophylline on the astrocytic functions, we examined the LPS-induced NO production and the expression of iNOS in cultured rat cortex astrocytes.Theophylline alone could not induce the NO production; however, NO production induced by LPS was enhanced by theophylline in a dose-dependent manner; and by isobutylmethylxanthine, a phosphodiesterase inhibitor. The theophylline enhancement of LPS-induced NO production was further increased by dibutyryl cyclic AMP, a membrane-permeable cAMP analog; and by forskolin, an adenylate cyclase activator. When the cells were preincubated with Rp-8-Br-cAMP, an inhibitor of protein kinase A, the theophylline enhancement of LPS-induced NO production was decreased. The extent of iNOS protein expression induced by LPS was also enhanced by theophylline.It is likely that phosphodiesterase inhibition is a major action mechanism for the theophylline enhancement of LPS-induced NO production in astrocytes. Theophylline-induced acute encephalopathy might be due to the hyper-activation of astrocytes via cAMP signaling to produce excess amount of NO.

  4. Dual role of astrocytes in perinatal asphyxia injury and neuroprotection.

    PubMed

    Romero, J; Muñiz, J; Logica Tornatore, T; Holubiec, M; González, J; Barreto, G E; Guelman, L; Lillig, C H; Blanco, E; Capani, F

    2014-04-17

    Perinatal asphyxia represents an important cause of severe neurological deficits including delayed mental and motor development, epilepsy, major cognitive deficits and blindness. However, at the moment, most of the therapeutic strategies were not well targeted toward the processes that induced the brain injury during perinatal asphyxia. Traditionally, experimental research focused on neurons, whereas astrocytes have been more related with the damage mechanisms of perinatal asphyxia. In this work, we propose to review possible protective as well as deleterious roles of astrocytes in the asphyctic brain with the aim to stimulate further research in this area of perinatal asphyxia still not well studied. PMID:24172702

  5. Dual role of astrocytes in perinatal asphyxia injury and neuroprotection.

    PubMed

    Romero, J; Muñiz, J; Logica Tornatore, T; Holubiec, M; González, J; Barreto, G E; Guelman, L; Lillig, C H; Blanco, E; Capani, F

    2014-04-17

    Perinatal asphyxia represents an important cause of severe neurological deficits including delayed mental and motor development, epilepsy, major cognitive deficits and blindness. However, at the moment, most of the therapeutic strategies were not well targeted toward the processes that induced the brain injury during perinatal asphyxia. Traditionally, experimental research focused on neurons, whereas astrocytes have been more related with the damage mechanisms of perinatal asphyxia. In this work, we propose to review possible protective as well as deleterious roles of astrocytes in the asphyctic brain with the aim to stimulate further research in this area of perinatal asphyxia still not well studied.

  6. Hydrolysis of polyphosphoinositides in astrocytes by platelet-activating factor.

    PubMed

    Murphy, S; Welk, G

    1990-06-12

    In primary astrocyte cultures, picomolar concentrations of platelet-activating factor (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine, PAF) evoked the formation of inositol phosphates (InsP), including inositol trisphosphate. This effect was not observed with the biologically inert lyso-PAF, nor in cells pretreated with phorbol myristate acetate to downregulate receptors. PAF at concentrations greater than or equal to 10(-9) M did not elevate InsP, suggesting some form of uncoupling of the receptor from phospholipase C. The responsiveness of astrocytes to PAF is further evidence for the role of these cells in the central nervous system response to trauma. PMID:2164941

  7. High effective cytosolic H+ buffering in mouse cortical astrocytes attributable to fast bicarbonate transport.

    PubMed

    Theparambil, Shefeeq M; Deitmer, Joachim W

    2015-09-01

    Cytosolic H(+) buffering plays a major role for shaping intracellular H(+) shifts and hence for the availability of H(+) for biochemical reactions and acid/base-coupled transport processes. H(+) buffering is one of the prime means to protect the cell from large acid/base shifts. We have used the H(+) indicator dye BCECF and confocal microscopy to monitor the cytosolic H(+) concentration, [H(+)]i, in cultured cortical astrocytes of wild-type mice and of mice deficient in sodium/bicarbonate cotransporter NBCe1 (NBCe1-KO) or in carbonic anhydrase isoform II (CAII-KO). The steady-state buffer strength was calculated from the amplitude of [H(+)]i transients as evoked by CO2/HCO3(-) and by butyric acid in the presence and absence of CO2/HCO3(-). We tested the hypotheses if, in addition to instantaneous physicochemical H(+) buffering, rapid acid/base transport across the cell membrane contributes to the total, "effective" cytosolic H(+) buffering. In the presence of 5% CO2/26 mM HCO3(-), H(+) buffer strength in astrocytes was increased 4-6 fold, as compared with that in non-bicarbonate, HEPES-buffered solution, which was largely attributable to fast HCO3 (-) transport into the cells via NBCe1, supported by CAII activity. Our results show that within the time frame of determining physiological H(+) buffering in cells, fast transport and equilibration of CO2/H(+)/HCO3(-) can make a major contribution to the total "effective" H(+) buffer strength. Thus, "effective" cellular H(+) buffering is, to a large extent, attributable to membrane transport of base equivalents rather than a purely passive physicochemical process, and can be much larger than reported so far. Not only physicochemical H(+) buffering, but also rapid import of HCO3(-) via the electrogenic sodium-bicarbonate cotransporter NBCe1, supported by carbonic anhydrase II (CA II), was identified to enhance cytosolic H(+) buffer strength substantially.

  8. Fluoro-jade B stains quiescent and reactive astrocytes in the rodent spinal cord.

    PubMed

    Anderson, Kevin J; Fugaccia, Isabella; Scheff, Stephen W

    2003-11-01

    In an attempt to label dying neurons in the injured spinal cord, we used the novel fluorescein derivative Fluoro-Jade B, which has been reported to specifically label dead or dying neurons in the brain. Rats and mice were subjected to a moderate level of spinal cord injury using an IH impact device and sacrificed at 1, 2, 4, 7, 14, and 21 days post injury. Spinal cord tissue was processed for Fluoro-Jade B histochemistry and included sections throughout the injured region of the cord. No Fluoro-Jade positive neurons were observed in sections from any time point postinjury at any level of the spinal cord. Instead, Fluoro-Jade labeled astrocytes in uninjured control animals and injured animals. The specificity of astrocytic staining was confirmed by co-localizaton of Fluoro-Jade with glial fibrillary acidic protein. We also subjected a group of rats to a sequential cortical contusion injury and spinal cord injury. Sections from these animals showed numerous Fluoro-Jade positive neurons in the hippocampal formation and thalamus underlying the cortical contusion; however, the staining pattern in the spinal cord was identical to those animals that had received spinal cord injury alone.

  9. Taurine release by astrocytes modulates osmosensitive glycine receptor tone and excitability in the adult supraoptic nucleus.

    PubMed

    Choe, Katrina Y; Olson, James E; Bourque, Charles W

    2012-09-01

    Cells can release the free amino acid taurine through volume-regulated anion channels (VRACs), and it has been hypothesized that taurine released from glial cells is capable of inhibiting action potential (AP) firing by activating neuronal glycine receptors (GlyRs) (Hussy et al., 1997). Although an inhibitory GlyR tone is widely observed in the brain, it remains unknown whether this specifically reflects gliotransmission because most neurons also express VRACs and other endogenous molecules can activate GlyRs. We found that VRACs are absent in neurons of the rat supraoptic nucleus (SON), suggesting that glial cells are the exclusive source of taurine in this nucleus. Application of strychnine to rat hypothalamic explants caused a depolarization of SON neurons associated with a decrease of chloride conductance and could excite these cells in the absence of fast synaptic transmission. This inhibitory GlyR tone was eliminated by pharmacological blockade of VRACs, by cellular taurine depletion, by metabolic inactivation of glia with fluorocitrate, and after retraction of astrocytic processes that intercalate neuronal somata and dendrites. Finally, GlyR tone varied inversely with extracellular fluid tonicity to mediate the osmotic control of AP firing by SON neurons. These findings establish taurine as a physiological gliotransmitter and show that gliotransmission is a spatially constrained process that can be modulated by the morphological rearrangement of astrocytes. PMID:22956842

  10. The role of attenuated astrocyte activation in infantile neuronal ceroid lipofuscinosis.

    PubMed

    Macauley, Shannon L; Pekny, Milos; Sands, Mark S

    2011-10-26

    Infantile neuronal ceroid lipofuscinosis (INCL) is an inherited neurodegenerative disorder affecting the CNS during infancy. INCL is caused by mutations in the CLN1 gene that lead to a deficiency in the lysosomal hydrolase, palmitoyl protein thioesterase 1 (PPT1). A murine model of INCL, the PPT1-deficient (PPT1(-/-)) mouse, is an accurate phenocopy of the human disease. The first pathological change observed in the PPT1(-/-) brain is regional areas of glial fibrillary acidic protein (GFAP) upregulation, which predicts future areas of neurodegeneration. We hypothesized that preventing GFAP and vimentin upregulation in reactive astrocytes will alter the CNS disease. To test this hypothesis, we generated mice simultaneously carrying null mutations in the GFAP, Vimentin, and PPT1 genes (GFAP(-/-)Vimentin(-/-)PPT1(-/-)). Although the clinical and pathological features of the GFAP(-/-)Vimentin(-/-)PPT1(-/-) mice are similar to INCL, the disease appears earlier and progresses more rapidly. One mechanism underlying this accelerated phenotype is a profound neuroinflammatory response within the CNS. Thus, our data identify a protective role for intermediate filament upregulation during astrocyte activation in INCL, a model of chronic neurodegeneration.

  11. Alterations in expression of genes coding for key astrocytic proteins in acute liver failure.

    PubMed

    Desjardins, P; Bélanger, M; Butterworth, R F

    2001-12-01

    Cerebral edema and hepatic encephalopathy are major complications of acute liver failure. Brain herniation caused by increased intracranial pressure as a result of cell swelling is the major cause of death in this condition. Evidence available currently suggests that the rapid accumulation of ammonia by the brain is the major cause of the central nervous system complications of acute liver failure. Increased brain ammonia may cause cell swelling via the osmotic effects of an increase in astrocytic glutamine concentrations or by inhibition of glutamate removal from brain extracellular space. Acute liver failure results in altered expression of several genes in brain, some of which code for important proteins involved in CNS function such as the glucose (GLUT-1) and glutamate (GLT-1) transporters, the astrocytic structural protein glial fibrillary acidic protein (GFAP) the "peripheral-type" benzodiazepine receptor (PTBR) and the water channel protein, aquaporin IV. Loss of expression of GLT-1 results in increased extracellular brain glutamate in acute liver failure. Experimental acute liver failure also results in post-translational modifications of the serotonin and noradrenaline transporters resulting in increased extracellular concentrations of these monoamines. Therapeutic measures currently used to prevent and treat brain edema and encephalopathy in patients with acute liver failure include mild hypothermia and the ammonia-lowering agent L-ornithine-L-aspartate. PMID:11746425

  12. Acetylcholine as a mitogen: muscarinic receptor-mediated proliferation of rat astrocytes and human astrocytoma cells.

    PubMed

    Guizzetti, M; Costa, P; Peters, J; Costa, L G

    1996-02-22

    The mitogenic effect of muscarinic receptor agonists in glial cells has been characterized in rat cortical astrocytes and human 132 1N1 astrocytoma cells. The muscarinic receptor agonist carbachol caused a dose- and time-dependent increase in proliferation, as measured by [3H]thymidine incorporation. The mitogenic effect was mimicked by several muscarinic, but not nicotinic receptor agonists, and was blocked by muscarinic receptor antagonists. Reverse transcription-polymerase chain reaction (RT-PCR) experiments indicated the presence of m2, m3 and to a lesser degree, m5 muscarinic receptor mRNA in both astrocytes and astrocytoma cells. Proliferation experiments with subtype-specific muscarinic receptor antagonists suggest that carbachol-induced proliferation is due to activation of muscarinic M3 receptors. The phorbol ester 12-O-tetradecanoyl-phorbol 13-acetate (TPA) also stimulated glial cell proliferation. Down-regulation of protein kinase C, or the protein kinase C antagonist 1,5-(isoquinolynsulfanyl)-2-methylpiperazine dihydrochloride (H7) blocked proliferation induced by either TPA or carbachol. Of other neurotransmitters tested, histamine caused glial cell proliferation, norepinephrine and gamma-aminobutyric acid were ineffective, while serotonin and glutamate inhibited basal or serum-stimulated proliferation. PMID:8666059

  13. Astrocytic cytoskeletal atrophy in the medial prefrontal cortex of a triple transgenic mouse model of Alzheimer's disease

    PubMed Central

    Kulijewicz-Nawrot, Magdalena; Verkhratsky, Alexei; Chvátal, Alexander; Syková, Eva; Rodríguez, José J

    2012-01-01

    Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by the loss of cognitive functions, reflecting pathological damage to the medial prefrontal cortex (mPFC) as well as to the hippocampus and the entorhinal cortex. Astrocytes maintain the internal homeostasis of the CNS and are fundamentally involved in neuropathological processes, including AD. Here, we analysed the astrocytic cytoskeletal changes within the mPFC of a triple transgenic mouse model of AD (3 × Tg-AD) by measuring the surface area and volume of glial fibrillary acidic protein (GFAP)-positive profiles in relation to the build-up and presence of amyloid-β (Aβ), and compared the results with those found in non-transgenic control animals at different ages. 3 × Tg-AD animals showed clear astroglial cytoskeletal atrophy, which appeared at an early age (3 months; 33% and 47% decrease in GFAP-positive surface area and volume, respectively) and remained throughout the disease progression at 9, 12 and 18 months old (29% and 36%; 37% and 35%; 43% and 37%, respectively). This atrophy was independent of Aβ accumulation, as only a few GFAP-positive cells were localized around Aβ aggregates, which suggests no direct relationship with Aβ toxicity. Thus, our results indicate that the progressive reduction in astrocytic branching and domain in the mPFC can account for the integrative dysfunction leading to the cognitive deficits and memory disturbances observed in AD. PMID:22738374

  14. Immunohistochemical evaluation of hippocampal CA1 region astrocytes in 10-day-old rats after monosodium glutamate treatment.

    PubMed

    Krawczyk, A; Jaworska-Adamu, J; Rycerz, K

    2015-01-01

    High concentration of glutamate (Glu) is excitotoxic for nervous system structures. This may lead to glial reactivity ie. increased expression of glial fibrillary acidic protein (GFAP) and S100β protein, and also to hypertrophy and proliferation of cells which are determined by the presence of Ki-67 antigen. The aim of the study was to analyse the immunoreactivity of the GFAP, S100β and Ki-67 proteins in astrocytes of hippocampal CA1 region in young rats after administration of monosodium glutamate (MSG) at two doses: 2 g/kg b.w. (I group) and 4 g/kg b.w. (II group). In rats from I and II group morphologically altered astrocytes with the GFAP expression were observed in the SLM of the hippocampal CA1 region. The cells had eccentrically located nuclei and on the opposite site of the nuclei there were single or double, long and weakly branched processes. Moreover, in the SLM the increase of the number of GFAP and S100β immunopositive astrocytes and nuclei with Ki-67 expression, in contrary to control individuals, was observed. These results suggest the increased expression of the proteins in early reactions or hyperplasia which, together with cell hypertrophy, indicate late reactivity of astroglia in response to glutamate noxious effect. PMID:26812818

  15. Silencing of Abcd1 and Abcd2 genes sensitizes astrocytes for inflammation: implication for X-adrenoleukodystrophy*

    PubMed Central

    Singh, Jaspreet; Khan, Mushfiquddin; Singh, Inderjit

    2009-01-01

    X-linked adrenoleukodystrophy is a metabolic disorder arising from a mutation/deletion in the ABCD1 gene, leading to a defect in the peroxisomal adrenoleukodystrophy protein (ALDP), which inhibits the oxidation of very long chain fatty acids (VLCFAs). Thus, these VLCFAs accumulate. In a cerebral form of ALD (cALD), VLCFA accumulation induces neuroinflammation that leads to loss of oligodendrocytes and myelin, which ultimately shortens the lifespan. To establish a relationship between the metabolic disease and inflammatory disease induction, we document that small interfering RNA (siRNA)-mediated silencing of Abcd1 (ALDP) and Abcd2 [adrenoleukodystrophy-related protein (ALDRP)] genes in mice primary astrocyte cultures resulted in accumulation of VLCFA and induction of an inflammatory response characteristic of human cALD. Correction of the metabolic defect using monoenoic FAs in Abcd1/Abcd2-silenced cultured astrocytes decreased inducible nitric oxide synthase and inflammatory cytokine expression, suggesting a link between VLCFA accumulation and inflammation. The inflammatory response was found to be mediated by transcription factors NF-κB, AP-1, and C/EBP in Abcd1/Abcd2-silenced mouse primary astrocytes. Although mechanisms of VLCFA-mediated induction of the inflammatory response have been investigated here in vitro, the in vivo mediators remain elusive. Our data represent the first study to suggest a direct link between the accumulation of VLCFA and the induction of inflammatory mediators. PMID:18723473

  16. Astrocytic cytoskeletal atrophy in the medial prefrontal cortex of a triple transgenic mouse model of Alzheimer's disease.

    PubMed

    Kulijewicz-Nawrot, Magdalena; Verkhratsky, Alexei; Chvátal, Alexander; Syková, Eva; Rodríguez, José J

    2012-09-01

    Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by the loss of cognitive functions, reflecting pathological damage to the medial prefrontal cortex (mPFC) as well as to the hippocampus and the entorhinal cortex. Astrocytes maintain the internal homeostasis of the CNS and are fundamentally involved in neuropathological processes, including AD. Here, we analysed the astrocytic cytoskeletal changes within the mPFC of a triple transgenic mouse model of AD (3 × Tg-AD) by measuring the surface area and volume of glial fibrillary acidic protein (GFAP)-positive profiles in relation to the build-up and presence of amyloid-β (Aβ), and compared the results with those found in non-transgenic control animals at different ages. 3 × Tg-AD animals showed clear astroglial cytoskeletal atrophy, which appeared at an early age (3 months; 33% and 47% decrease in GFAP-positive surface area and volume, respectively) and remained throughout the disease progression at 9, 12 and 18 months old (29% and 36%; 37% and 35%; 43% and 37%, respectively). This atrophy was independent of Aβ accumulation, as only a few GFAP-positive cells were localized around Aβ aggregates, which suggests no direct relationship with Aβ toxicity. Thus, our results indicate that the progressive reduction in astrocytic branching and domain in the mPFC can account for the integrative dysfunction leading to the cognitive deficits and memory disturbances observed in AD.

  17. Morphological transformation and proliferation of rat astrocytes as induced by sulfated polysaccharides from the sea cucumber Stichopus japonicus.

    PubMed

    Sheng, Xiehuang; Zhang, Nannan; Song, Shuliang; Li, Min; Liang, Hao; Zhang, Yuejie; Wang, Yunshan; Ji, Aiguo

    2011-09-26

    In this report, we demonstrate that the sulfated polysaccharide, Haishen (HS), which was isolated from the body wall of the sea cucumber Stichopus japonicus can induce morphological transformation and proliferation of astrocytes in vitro when combined with basic fibroblast growth factor 2 (FGF-2). Cell morphology showed no change when induced by HS or FGF-2 alone. However, combinational treatment of HS and FGF-2 promoted transformation of normal astrocyte into a stella morphology (stellation), along with an increase in the expression and rearrangement of glial fibrillary acidic protein (GFAP). Further analysis of HS- and FGF-2-treated cells indicated a reduced percentage of cells in the G0/G1 phase, whereas the cell proliferation index (S phase) was increased. The proportion of 5-bromo-2-deoxyuridine (BrdU)-positive cells increased in response to the combination of HS and FGF-2. With respect to cell cycle signaling, immunoblotting assay demonstrated an accumulation of Cyclin D1. These observations suggest that HS may play a role in astrocyte morphological transformation and proliferation, and this activation requires a synergism with FGF-2.

  18. Astrocytes regulate inhibitory synapse formation via Trk-mediated modulation of postsynaptic GABAA receptors.

    PubMed

    Elmariah, Sarina B; Oh, Eun Joo; Hughes, Ethan G; Balice-Gordon, Rita J

    2005-04-01

    Astrocytes promote the formation and function of excitatory synapses in the CNS. However, whether and how astrocytes modulate inhibitory synaptogenesis are essentially unknown. We asked whether astrocytes regulate the formation of inhibitory synapses between hippocampal neurons during maturation in vitro. Neuronal coculture with astrocytes or treatment with astrocyte-conditioned medium (ACM) increased the number of inhibitory presynaptic terminals, the frequency of miniature IPSCs, and the number and synaptic localization of GABA(A) receptor (GABA(A)R) clusters during the first 10 d in vitro. We asked whether neurotrophins, which are potent modulators of inhibitory synaptic structure and function, mediate the effects of astrocytes on inhibitory synapses. ACM from BDNF- or tyrosine receptor kinase B (TrkB)-deficient astrocytes increased inhibitory presynaptic terminals and postsynaptic GABA(A)R clusters in wild-type neurons, suggesting that BDNF and TrkB expression in astrocytes is not required for these effects. In contrast, although the increase in the number of inhibitory presynaptic terminals persisted, no increase was observed in postsynaptic GABA(A)R clusters after ACM treatment of hippocampal neurons lacking BDNF or TrkB. These results suggest that neurons, not astrocytes, are the relevant source of BDNF and are the site of TrkB activation required for postsynaptic GABA(A)R modulation. These data also suggest that astrocytes may modulate postsynaptic development indirectly by stimulating Trk signaling between neurons. Together, these data show that astrocytes modulate inhibitory synapse formation via distinct presynaptic and postsynaptic mechanisms.

  19. Metabolic Dysfunction of Astrocyte: An Initiating Factor in Beta-amyloid Pathology?

    PubMed Central

    Yan, Liang-Jun; Xiao, Ming; Chen, Ran; Cai, Zhiyou

    2013-01-01

    Astrocytes, the most important energy regulator in the brain, support brain energy needs. In the meantime, numerous studies have demonstrated that impaired brain glucose metabolism is closely linked to abnormal astrocytic metabolism in AD. Indeed, the interaction between amyloid plaques and perturbed astrocytic homeostasis contributes to AD pathogenesis and astrocytic metabolic dysfunction is thought to be a trigger for Aβ pathology through oxidative stress and neuroinflammation Moreover, astrocytic metabolic dysfunction may regulate Aβ generation via modulating proteolytic processing of amyloid precursor protein (APP) by β-secretase, γ-secretase, and α-secretase, and may also modulate APP post-translational modifications such as glycosylation, phosphorylation, and tyrosine sulfation. While it is known that metabolic dysfunction of astrocytes contributes to the failure of Aβ clearance, it has also been reported that such dysfunction has neuroprotective property and exhibits no detrimental outcomes. Therefore, the exact role of astrocytic metabolic dysfunction in Aβ pathology remains to be further investigated. PMID:24443714

  20. Autophagy-related gene Atg5 is essential for astrocyte differentiation in the developing mouse cortex

    PubMed Central

    Wang, Shukun; Li, Baoguo; Qiao, Huimin; Lv, Xiaohui; Liang, Qingli; Shi, Zixiao; Xia, Wenlong; Ji, Fen; Jiao, Jianwei

    2014-01-01

    Astrocyte differentiation is essential for late embryonic brain development, and autophagy is active during this process. However, it is unknown whether and how autophagy regulates astrocyte differentiation. Here, we show that Atg5, which is necessary for autophagosome formation, regulates astrocyte differentiation. Atg5 deficiency represses the generation of astrocytes in vitro and in vivo. Conversely, Atg5 overexpression increases the number of astrocytes substantially. We show that Atg5 activates the JAK2-STAT3 pathway by degrading the inhibitory protein SOCS2. The astrocyte differentiation defect caused by Atg5 loss can be rescued by human Atg5 overexpression, STAT3 overexpression, and SOCS2 knockdown. Together, these data demonstrate that Atg5 regulates astrocyte differentiation, with potential implications for brain disorders with autophagy deficiency. PMID:25227738

  1. A critical role for palladin in astrocyte morphology and response to injury.

    PubMed

    Boukhelifa, Malika; Hwang, Se Jin; Valtschanoff, Juli G; Meeker, Rick B; Rustioni, Aldo; Otey, Carol A

    2003-08-01

    Astrocytes respond to injury of the CNS with a dramatic change in morphology, contributing to the formation of a glial scar. We recently identified a novel actin-associated protein named palladin, which possesses the features of a potent cytoskeletal scaffold. Palladin expression was assayed in two populations of cultured astrocytes, polygonal versus stellate, and was detected at high levels in polygonal astrocytes and low levels in stellate astrocytes. When stellate astrocyte monolayers were wounded, palladin was rapidly upregulated along the edge of the wound, coordinate with an increase in actin assembly. Palladin upregulation occurred along a similar rapid time course following injury to the cerebral cortex of adult rats. To explore palladin function more directly, palladin cDNA was transfected into stellate astrocytes, which acquired a spread morphology and prominent actin bundles. These results suggest that palladin upregulation following injury may be a key step in the acquisition of the reactive astrocyte morphology.

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

    PubMed

    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. PMID:26643508

  3. Acetazolamide Mitigates Astrocyte Cellular Edema Following Mild Traumatic Brain Injury

    NASA Astrophysics Data System (ADS)

    Sturdivant, Nasya M.; Smith, Sean G.; Ali, Syed F.; Wolchok, Jeffrey C.; Balachandran, Kartik

    2016-09-01

    Non-penetrating or mild traumatic brain injury (mTBI) is commonly experienced in accidents, the battlefield and in full-contact sports. Astrocyte cellular edema is one of the major factors that leads to high morbidity post-mTBI. Various studies have reported an upregulation of aquaporin-4 (AQP4), a water channel protein, following brain injury. AZA is an antiepileptic drug that has been shown to inhibit AQP4 expression and in this study we investigate the drug as a therapeutic to mitigate the extent of mTBI induced cellular edema. We hypothesized that mTBI-mediated astrocyte dysfunction, initiated by increased intracellular volume, could be reduced when treated with AZA. We tested our hypothesis in a three-dimensional in vitro astrocyte model of mTBI. Samples were subject to no stretch (control) or one high-speed stretch (mTBI) injury. AQP4 expression was significantly increased 24 hours after mTBI. mTBI resulted in a significant increase in the cell swelling within 30 min of mTBI, which was significantly reduced in the presence of AZA. Cell death and expression of S100B was significantly reduced when AZA was added shortly before mTBI stretch. Overall, our data point to occurrence of astrocyte swelling immediately following mTBI, and AZA as a promising treatment to mitigate downstream cellular mortality.

  4. Acetazolamide Mitigates Astrocyte Cellular Edema Following Mild Traumatic Brain Injury

    PubMed Central

    Sturdivant, Nasya M.; Smith, Sean G.; Ali, Syed F.; Wolchok, Jeffrey C.; Balachandran, Kartik

    2016-01-01

    Non-penetrating or mild traumatic brain injury (mTBI) is commonly experienced in accidents, the battlefield and in full-contact sports. Astrocyte cellular edema is one of the major factors that leads to high morbidity post-mTBI. Various studies have reported an upregulation of aquaporin-4 (AQP4), a water channel protein, following brain injury. AZA is an antiepileptic drug that has been shown to inhibit AQP4 expression and in this study we investigate the drug as a therapeutic to mitigate the extent of mTBI induced cellular edema. We hypothesized that mTBI-mediated astrocyte dysfunction, initiated by increased intracellular volume, could be reduced when treated with AZA. We tested our hypothesis in a three-dimensional in vitro astrocyte model of mTBI. Samples were subject to no stretch (control) or one high-speed stretch (mTBI) injury. AQP4 expression was significantly increased 24 hours after mTBI. mTBI resulted in a significant increase in the cell swelling within 30 min of mTBI, which was significantly reduced in the presence of AZA. Cell death and expression of S100B was significantly reduced when AZA was added shortly before mTBI stretch. Overall, our data point to occurrence of astrocyte swelling immediately following mTBI, and AZA as a promising treatment to mitigate downstream cellular mortality. PMID:27623738

  5. A new concept affecting restoration of inflammation-reactive astrocytes.

    PubMed

    Block, L; Björklund, U; Westerlund, A; Jörneberg, P; Biber, B; Hansson, E

    2013-10-10

    Long-lasting pain may partly be a consequence of ongoing neuroinflammation, in which astrocytes play a significant role. Following noxious stimuli, increased inflammatory receptor activity, influences in Na(+)/K(+)-ATPase activity and actin filament organization occur within the central nervous system. In astrocytes, the Ca(2+) signaling system, Na(+) transporters, cytoskeleton, and release of pro-inflammatory cytokines change during inflammation. The aim of this study was to restore these cell parameters in inflammation-reactive astrocytes. We found that the combination of (1) endomorphin-1, an opioid agonist that stimulates the Gi/o protein of the μ-opioid receptor; (2) naloxone, an opioid antagonist that inhibits the Gs protein of the μ-opioid receptor at ultralow concentrations; and (3) levetiracetam, an anti-epileptic agent that counteracts the release of IL-1β, managed to activate the Gi/o protein and Na(+)/K(+)-ATPase activity, inhibit the Gs protein, and decrease the release of IL-1β. The cell functions of astrocytes in an inflammatory state were virtually restored to their normal non-inflammatory state and it could be of clinical significance and may be useful for the treatment of long-term pain.

  6. Microglia is activated by astrocytes in trimethyltin intoxication

    SciTech Connect

    Roehl, Claudia . E-mail: claudia.roehl@gmx.net; Sievers, Jobst

    2005-04-01

    Microglia participates in most acute and chronic neuropathologies and its activation appears to involve interactions with neurons and other glial cells. Trimethyltin (TMT)-induced brain damage is a well-characterized model of neurodegeneration, in which microglial activation occurs before neuronal degeneration. The aim of this in vitro study was to investigate the role of astroglia in TMT-induced microgliosis by using nitric oxide (NO), inducible NO synthase (iNOS), and morphological changes as parameters for microglial activation. Our investigation discusses (a) whether microglial cells can be activated directly by TMT; (b) if astroglial cells are capable of triggering or modulating microglial activation; (c) how the morphology and survival of microglia and astrocytes are affected by TMT treatment; and (d) whether microglial-astroglial interactions depend on direct cell contact or on soluble factors. Our results show that microglia are more vulnerable to TMT than astrocytes are and cannot be activated directly by TMT with regard to the examined parameters. In bilayer coculture with viable astroglial cells, microglia produce NO in significant amounts at subcytotoxic concentrations of TMT (20 {mu}mol/l). At these TMT concentrations, microglial cells in coculture convert into small round cells without cell processes, whereas flat, fibroblast-like astrocytes convert into thin process bearing stellate cells with a dense and compact cell body. We conclude that astrocytes trigger microglial activation after treatment with TMT, although the mechanisms of this interaction remain unknown.

  7. How do astrocytes shape synaptic transmission? Insights from electrophysiology

    PubMed Central

    Dallérac, Glenn; Chever, Oana; Rouach, Nathalie

    2013-01-01

    A major breakthrough in neuroscience has been the realization in the last decades that the dogmatic view of astroglial cells as being merely fostering and buffering elements of the nervous system is simplistic. A wealth of investigations now shows that astrocytes actually participate in the control of synaptic transmission in an active manner. This was first hinted by the intimate contacts glial processes make with neurons, particularly at the synaptic level, and evidenced using electrophysiological and calcium imaging techniques. Calcium imaging has provided critical evidence demonstrating that astrocytic regulation of synaptic efficacy is not a passive phenomenon. However, given that cellular activation is not only represented by calcium signaling, it is also crucial to assess concomitant mechanisms. We and others have used electrophysiological techniques to simultaneously record neuronal and astrocytic activity, thus enabling the study of multiple ionic currents and in depth investigation of neuro-glial dialogues. In the current review, we focus on the input such approach has provided in the understanding of astrocyte-neuron interactions underlying control of synaptic efficacy. PMID:24101894

  8. Acetazolamide Mitigates Astrocyte Cellular Edema Following Mild Traumatic Brain Injury.

    PubMed

    Sturdivant, Nasya M; Smith, Sean G; Ali, Syed F; Wolchok, Jeffrey C; Balachandran, Kartik

    2016-01-01

    Non-penetrating or mild traumatic brain injury (mTBI) is commonly experienced in accidents, the battlefield and in full-contact sports. Astrocyte cellular edema is one of the major factors that leads to high morbidity post-mTBI. Various studies have reported an upregulation of aquaporin-4 (AQP4), a water channel protein, following brain injury. AZA is an antiepileptic drug that has been shown to inhibit AQP4 expression and in this study we investigate the drug as a therapeutic to mitigate the extent of mTBI induced cellular edema. We hypothesized that mTBI-mediated astrocyte dysfunction, initiated by increased intracellular volume, could be reduced when treated with AZA. We tested our hypothesis in a three-dimensional in vitro astrocyte model of mTBI. Samples were subject to no stretch (control) or one high-speed stretch (mTBI) injury. AQP4 expression was significantly increased 24 hours after mTBI. mTBI resulted in a significant increase in the cell swelling within 30 min of mTBI, which was significantly reduced in the presence of AZA. Cell death and expression of S100B was significantly reduced when AZA was added shortly before mTBI stretch. Overall, our data point to occurrence of astrocyte swelling immediately following mTBI, and AZA as a promising treatment to mitigate downstream cellular mortality. PMID:27623738

  9. Water entry into astrocytes during brain edema formation.

    PubMed

    Nase, Gabriele; Helm, P Johannes; Enger, Rune; Ottersen, Ole P

    2008-06-01

    The process of brain edema formation has been studied extensively at the macroscopic level. In contrast, little is known about water fluxes and volume changes at the cellular level in the initial phase of brain edema. Insight in these "microscopic" events could pave the way for more efficient prevention and therapy. Here, we report measurements of brain cell volume responses recorded in vivo in a model of systemic hyponatremia. Transgenic mice expressing fluorescent proteins in astrocytes were subjected to hypo-osmotic stress and two photon laser scanning microscopy. Volume measurements of glial cells in the cerebellum and the visual cortex indicate that individual astrocytes undergo a position-dependent increase in cell volume by a factor of two or more during edema formation. Our data are the first to show that volume changes can be monitored at the cellular level in vivo and demonstrate that astrocytes are sites of water entry in the initial phase of brain edema formation. The uptake of water in astrocytes is likely to reflect the strong expression of aquaporin-4 in these cells.

  10. A new concept affecting restoration of inflammation-reactive astrocytes.

    PubMed

    Block, L; Björklund, U; Westerlund, A; Jörneberg, P; Biber, B; Hansson, E

    2013-10-10

    Long-lasting pain may partly be a consequence of ongoing neuroinflammation, in which astrocytes play a significant role. Following noxious stimuli, increased inflammatory receptor activity, influences in Na(+)/K(+)-ATPase activity and actin filament organization occur within the central nervous system. In astrocytes, the Ca(2+) signaling system, Na(+) transporters, cytoskeleton, and release of pro-inflammatory cytokines change during inflammation. The aim of this study was to restore these cell parameters in inflammation-reactive astrocytes. We found that the combination of (1) endomorphin-1, an opioid agonist that stimulates the Gi/o protein of the μ-opioid receptor; (2) naloxone, an opioid antagonist that inhibits the Gs protein of the μ-opioid receptor at ultralow concentrations; and (3) levetiracetam, an anti-epileptic agent that counteracts the release of IL-1β, managed to activate the Gi/o protein and Na(+)/K(+)-ATPase activity, inhibit the Gs protein, and decrease the release of IL-1β. The cell functions of astrocytes in an inflammatory state were virtually restored to their normal non-inflammatory state and it could be of clinical significance and may be useful for the treatment of long-term pain. PMID:23892009

  11. Astrocyte-Secreted Factors Modulate the Developmental Distribution of Inhibitory Synapses in Nucleus Laminaris of the Avian Auditory Brainstem

    PubMed Central

    Korn, Matthew J.; Koppel, Scott J.; Li, Lan H.; Mehta, Divya; Mehta, Sonia B.; Seidl, Armin H.; Cramer, Karina S.

    2014-01-01

    Nucleus laminaris (NL) neurons in the avian auditory brainstem are coincidence detectors necessary for the computation of interaural time differences used in sound localization. In addition to their excitatory inputs from nucleus magnocellularis, NL neurons receive inhibitory inputs from the superior olivary nucleus (SON) that greatly improve coincidence detection in mature animals. The mechanisms that establish mature distributions of inhibitory inputs to NL are not known. We used the vesicular GABA transporter (VGAT) as a marker for inhibitory presynaptic terminals to study the development of inhibitory inputs to NL between embryonic day 9 (E9) and E17. VGAT immunofluorescent puncta were first seen sparsely in NL at E9. The density of VGAT puncta increased with development, first within the ventral NL neuropil region and subsequently throughout both the ventral and dorsal dendritic neuropil, with significantly fewer terminals in the cell body region. A large increase in density occurred between E13–15 and E16–17, at a developmental stage when astrocytes that express glial fibrillary acidic protein (GFAP) become mature. We cultured E13 brainstem slices together with astrocyte-conditioned medium (ACM) obtained from E16 brainstems and found that ACM, but not control medium, increased the density of VGAT puncta. This increase was similar to that observed during normal development. Astrocyte-secreted factors interact with the terminal ends of SON axons to increase the number of GABAergic terminals. These data suggest that factors secreted from GFAP-positive astrocytes promote maturation of inhibitory pathways in the auditory brainstem. PMID:22020566

  12. Cytotoxicity of the diterpene 14-O-methyl-ryanodanol from Erythroxylum passerinum in an astrocytic cells model.

    PubMed

    Menezes-Filho, Noélio de Jesus; Souza, Cleide dos Santos; Costa, Tereza Cristina Silva; Da Silva, Victor Diógenes Amaral; Ribeiro, Cátia Suse de Oliveira; Barreiros, Marizeth Liborio; Costa, Jose Fernando Oliveira; David, Jorge Mauricio; David, Juceni P L; Costa, Silvia Lima

    2014-09-01

    Plant secondary metabolites, such as, specifically, alkaloids and terpenes, may present psychoactive properties that modify the function of the central nervous system (CNS) and induce neurotoxicity. Neurotoxicity involves the response of glial cells, mainly astrocytes, which play a fundamental role in the control of homeostasis of the CNS. Some Erythroxylum species are indigenous to the state of Bahia in Brazil. This study investigated the cytotoxic activity of the diterpene AEP-1, extracted from the fruit of E. passerinum in a GL-15 cell line, astrocytic, glial cells model. The effects on cell viability, analyzed by the MTT assay, demonstrated a dose-dependent cytotoxic effect, with maximum effect at 500 μg/mL of AEP-1, and with a reduction of about 40 and 47% on cellular viability after 24 h and 72 h treatment, respectively. Evidence for induction of apoptosis by AEP-1 was first obtained when GL-15 glial cells were incubated with 250 μg/mL AEP-1 causing reniform and/or pyknotic nuclei and apoptotic bodies revealed by chromatin staining with Hoechst 33258. Increase in DNA fragmentation was also observed by comet assays in cells incubated with 500 μg/mL of AEP-1. Moreover, cells exposed to a sub toxic dose of AEP-1 (250 μg/mL) showed significant changes in morphology--contraction of the cytoplasm and expansion of cellular projections--signifying the presence of astrocytic cytoskeletal protein and glial fibrillary acidic protein (GFAP). These findings indicated astrocytic cells as the target for terpene AEP-1 and suggest the involvement of glial cells with psychoactive symptoms observed in humans and animals after consumption of fruits of plants of the genus Erythroxylum. PMID:25918783

  13. Shifts in excitatory/inhibitory balance by juvenile stress: A role for neuron-astrocyte interaction in the dentate gyrus.

    PubMed

    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. PMID:26875694

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

    PubMed

    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.

  15. Astrocytes in the optic nerve head express putative mechanosensitive channels

    PubMed Central

    Choi, Hee Joo; Sun, Daniel

    2015-01-01

    Purpose To establish whether optic nerve head astrocytes express candidate molecules to sense tissue stretch. Methods We used conventional PCR, quantitative PCR, and single-cell reverse transcription PCR (RT–PCR) to assess the expression of various members of the transient receptor potential (TRP) channel family and of the recently characterized mechanosensitive channels Piezo1 and 2 in optic nerve head tissue and in single, isolated astrocytes. Results Most TRP subfamilies (TRPC, TRPM, TRPV, TRPA, and TRPP) and Piezo1 and 2 were expressed in the optic nerve head of the mouse. Quantitative real-time PCR analysis showed that TRPC1, TRPM7, TRPV2, TRPP2, and Piezo1 are the dominant isoforms in each subfamily. Single-cell RT–PCR revealed that many TRP isoforms, TRPC1–2, TRPC6, TRPV2, TRPV4, TRPM2, TRPM4, TRPM6–7, TRPP1–2, and Piezo1–2, are expressed in astrocytes of the optic nerve head, and that most astrocytes express TRPC1 and TRPP1–2. Comparisons of the TRPP and Piezo expression levels between different tissue regions showed that Piezo2 expression was higher in the optic nerve head and the optic nerve proper than in the brain and the corpus callosum. TRPP2 also showed higher expression in the optic nerve head. Conclusions Astrocytes in the optic nerve head express multiple putative mechanosensitive channels, in particular the recently identified channels Piezo1 and 2. The expression of putative mechanosensitive channels in these cells may contribute to their responsiveness to traumatic or glaucomatous injury. PMID:26236150

  16. Effects of Ranolazine on Astrocytes and Neurons in Primary Culture

    PubMed Central

    Aldasoro, Martin; Guerra-Ojeda, Sol; Aguirre-Rueda, Diana; Mauricio, Mª Dolores; Vila, Jose Mª; Marchio, Patricia; Iradi, Antonio; Aldasoro, Constanza; Jorda, Adrian; Obrador, Elena; Valles, Soraya L.

    2016-01-01

    Ranolazine (Rn) is an antianginal agent used for the treatment of chronic angina pectoris when angina is not adequately controlled by other drugs. Rn also acts in the central nervous system and it has been proposed for the treatment of pain and epileptic disorders. Under the hypothesis that ranolazine could act as a neuroprotective drug, we studied its effects on astrocytes and neurons in primary culture. We incubated rat astrocytes and neurons in primary cultures for 24 hours with Rn (10−7, 10−6 and 10−5 M). Cell viability and proliferation were measured using trypan blue exclusion assay, MTT conversion assay and LDH release assay. Apoptosis was determined by Caspase 3 activity assay. The effects of Rn on pro-inflammatory mediators IL-β and TNF-α was determined by ELISA technique, and protein expression levels of Smac/Diablo, PPAR-γ, Mn-SOD and Cu/Zn-SOD by western blot technique. In cultured astrocytes, Rn significantly increased cell viability and proliferation at any concentration tested, and decreased LDH leakage, Smac/Diablo expression and Caspase 3 activity indicating less cell death. Rn also increased anti-inflammatory PPAR-γ protein expression and reduced pro-inflammatory proteins IL-1 β and TNFα levels. Furthermore, antioxidant proteins Cu/Zn-SOD and Mn-SOD significantly increased after Rn addition in cultured astrocytes. Conversely, Rn did not exert any effect on cultured neurons. In conclusion, Rn could act as a neuroprotective drug in the central nervous system by promoting astrocyte viability, preventing necrosis and apoptosis, inhibiting inflammatory phenomena and inducing anti-inflammatory and antioxidant agents. PMID:26950436

  17. Effects of Ranolazine on Astrocytes and Neurons in Primary Culture.

    PubMed

    Aldasoro, Martin; Guerra-Ojeda, Sol; Aguirre-Rueda, Diana; Mauricio, M Dolores; Vila, Jose M; Marchio, Patricia; Iradi, Antonio; Aldasoro, Constanza; Jorda, Adrian; Obrador, Elena; Valles, Soraya L

    2016-01-01

    Ranolazine (Rn) is an antianginal agent used for the treatment of chronic angina pectoris when angina is not adequately controlled by other drugs. Rn also acts in the central nervous system and it has been proposed for the treatment of pain and epileptic disorders. Under the hypothesis that ranolazine could act as a neuroprotective drug, we studied its effects on astrocytes and neurons in primary culture. We incubated rat astrocytes and neurons in primary cultures for 24 hours with Rn (10-7, 10-6 and 10-5 M). Cell viability and proliferation were measured using trypan blue exclusion assay, MTT conversion assay and LDH release assay. Apoptosis was determined by Caspase 3 activity assay. The effects of Rn on pro-inflammatory mediators IL-β and TNF-α was determined by ELISA technique, and protein expression levels of Smac/Diablo, PPAR-γ, Mn-SOD and Cu/Zn-SOD by western blot technique. In cultured astrocytes, Rn significantly increased cell viability and proliferation at any concentration tested, and decreased LDH leakage, Smac/Diablo expression and Caspase 3 activity indicating less cell death. Rn also increased anti-inflammatory PPAR-γ protein expression and reduced pro-inflammatory proteins IL-1 β and TNFα levels. Furthermore, antioxidant proteins Cu/Zn-SOD and Mn-SOD significantly increased after Rn addition in cultured astrocytes. Conversely, Rn did not exert any effect on cultured neurons. In conclusion, Rn could act as a neuroprotective drug in the central nervous system by promoting astrocyte viability, preventing necrosis and apoptosis, inhibiting inflammatory phenomena and inducing anti-inflammatory and antioxidant agents. PMID:26950436

  18. Decreased functions of astrocytes on carbon nanofiber materials.

    PubMed

    McKenzie, Janice L; Waid, Michael C; Shi, Riyi; Webster, Thomas J

    2004-01-01

    Carbon nanofibers possess excellent conductivity properties, which may be beneficial in the design of more effective neural prostheses; however, limited evidence on their cytocompatibility properties currently exists. The objective of the present in vitro study was to determine cytocompatibility properties of formulations containing carbon nanofibers pertinent to neural implant applications. Substrates were prepared from four different types of carbon fibers, two with nanoscale diameters (nanophase, or less than or equal to 100 nm) and two with conventional diameters (or greater than 100 nm). Within these two categories, both a high and a low surface energy fiber were investigated and tested. Carbon fibers were compacted in a manual hydraulic press via a uniaxial loading cycle. Astrocytes (glial scar tissue-forming cells) were seeded onto the substrates for adhesion, proliferation, and long-term function studies (such as total intracellular protein and alkaline phosphatase activity). Results provided the first evidence that astrocytes preferentially adhered and proliferated on carbon fibers that had the largest diameter and the lowest surface energy. Based on these results, composite substrates were also formed using different weight percentages (0-25 wt%) of the nanophase, high surface energy fibers in a polycarbonate urethane matrix. Results provided the first evidence of decreased adhesion of astrocytes with increasing weight percents of the high surface energy carbon nanofibers in the polymer composite; this further demonstrates that formulations containing carbon fibers in the nanometer regime may limit astrocyte functions leading to decreased glial scar tissue formation. Positive interactions with neurons, and, at the same time, limited astrocyte functions leading to decreased gliotic scar tissue formation are essential for increased neuronal implant efficacy.

  19. Astrocyte signaling in the presence of spatial inhomogeneities

    NASA Astrophysics Data System (ADS)

    Stamatakis, Michail; Mantzaris, Nikos V.

    2007-09-01

    Astrocytes, a special type of glial cells, were considered to have just a supporting role in information processing in the brain. However, several recent studies have shown that they can be chemically stimulated by various neurotransmitters, such as ATP, and can generate Ca2+ and ATP waves, which can propagate over many cell lengths before being blocked. Although pathological conditions, such as spreading depression and epilepsy, have been linked to abnormal wave propagation in astrocytic cellular networks, a quantitative understanding of the underlying characteristics is still lacking. Astrocytic cellular networks are inhomogeneous, in the sense that the domain they occupy contains passive regions or gaps, which are unable to support wave propagation. Thus, this work focuses on understanding the complex interplay between single-cell signal transduction, domain inhomogeneity, and the characteristics of wave propagation and blocking in astrocytic cellular networks. The single-cell signal transduction model that was employed accounts for ATP-mediated IP3 production, the subsequent Ca2+ release from the ER, and ATP release into the extracellular space. The model is excitable and thus an infinite range of wave propagation is observed if the domain of propagation is homogeneous. This is not always the case for inhomogeneous domains. To model wave propagation in inhomogeneous astrocytic networks, a reaction-diffusion framework was developed and one-gap as well as multiple-gap cases were simulated using an efficient finite-element algorithm. The minimum gap length that blocks the wave was computed as a function of excitability levels and geometric characteristics of the inhomogeneous network, such as the length of the active regions (cells). Complex transient patterns, such as wave reflection, wave trapping, and generation of echo waves, were also predicted by the model, and their relationship to the geometric characteristics of the network was evaluated. Therefore, the

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

    PubMed

    Korenić, Andrej; Boltze, Johannes; Deten, Alexander; Peters, Myriam; Andjus, Pavle; Radenović, Lidija

    2014-01-01

    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. PMID:24587410

  1. Novel neuronal and astrocytic mechanisms in thalamocortical loop dynamics.

    PubMed

    Crunelli, Vincenzo; Blethyn, Kate L; Cope, David W; Hughes, Stuart W; Parri, H Rheinallt; Turner, Jonathan P; Tòth, Tibor I; Williams, Stephen R

    2002-12-29

    In this review, we summarize three sets of findings that have recently been observed in thalamic astrocytes and neurons, and discuss their significance for thalamocortical loop dynamics. (i) A physiologically relevant 'window' component of the low-voltage-activated, T-type Ca(2+) current (I(Twindow)) plays an essential part in the slow (less than 1 Hz) sleep oscillation in adult thalamocortical (TC) neurons, indicating that the expression of this fundamental sleep rhythm in these neurons is not a simple reflection of cortical network activity. It is also likely that I(Twindow) underlies one of the cellular mechanisms enabling TC neurons to produce burst firing in response to novel sensory stimuli. (ii) Both electrophysiological and dye-injection experiments support the existence of gap junction-mediated coupling among young and adult TC neurons. This finding indicates that electrical coupling-mediated synchronization might be implicated in the high and low frequency oscillatory activities expressed by this type of thalamic neuron. (iii) Spontaneous intracellular Ca(2+) ([Ca(2+)](i)) waves propagating among thalamic astrocytes are able to elicit large and long-lasting N-methyl-D-aspartate-mediated currents in TC neurons. The peculiar developmental profile within the first two postnatal weeks of these astrocytic [Ca(2+)](i) transients and the selective activation of these glutamate receptors point to a role for this astrocyte-to-neuron signalling mechanism in the topographic wiring of the thalamocortical loop. As some of these novel cellular and intracellular properties are not restricted to thalamic astrocytes and neurons, their significance may well apply to (patho)physiological functions of glial and neuronal elements in other brain areas.

  2. Advanced glycation end product-induced astrocytic differentiation of cultured neurospheres through inhibition of Notch-Hes1 pathway-mediated neurogenesis.

    PubMed

    Guo, Yijing; Wang, Pin; Sun, Haixia; Cai, Rongrong; Xia, Wenqing; Wang, Shaohua

    2014-01-01

    This study aims to investigate the roles of the Notch-Hes1 pathway in the advanced glycation end product (AGE)-mediated differentiation of neural stem cells (NSCs). We prepared pLentiLox3.7 lentiviral vectors that express short hairpin RNA (shRNA) against Notch1 and transfected it into NSCs. Cell differentiation was analyzed under confocal laser-scanning microscopy. The percentage of neurons and astrocytes was quantified by normalizing the total number of TUJ1+ (Neuron-specific class III β-tubulin) and GFAP+ (Glial fibrillary acidic protein) cells to the total number of Hoechst 33342-labeled cell nuclei. The protein and gene expression of Notch-Hes1 pathway components was examined via western blot analysis and real-time PCR. After 1 week of incubation, we found that AGE-bovine serum albumin (BSA) (400 μg/mL) induced the astrocytic differentiation of cultured neurospheres and inhibited neuronal formation. The expression of Notch-Hes1 pathway components was upregulated in the cells in the AGE-BSA culture medium. Immunoblot analysis indicated that shRNA silencing of Notch1 expression in NSCs significantly increases neurogenesis and suppresses astrocytic differentiation in NSCs incubated with AGE-BSA. AGEs promote the astrocytic differentiation of cultured neurospheres by inhibiting neurogenesis through the Notch-Hes1 pathway, providing a potential therapeutic target for hyperglycemia-related cognitive deficits.

  3. IL-17A induces MIP-1α expression in primary astrocytes via Src/MAPK/PI3K/NF-kB pathways: implications for multiple sclerosis.

    PubMed

    Yi, Hongwei; Bai, Ying; Zhu, Xinjian; Lin, Lin; Zhao, Lei; Wu, Xiaodong; Buch, Shilpa; Wang, Longxin; Chao, Jie; Yao, Honghong

    2014-12-01

    Neuroinflammation plays critical roles in multiple sclerosis (MS). In addition to the part played by the lymphocytes, the underlying mechanisms could, in part, be also attributed to activation mediated by astrocytes. Macrophage inflammatory protein-1α (MIP-1α) has been implicated in a number of pathological conditions, specifically attributable to its potent chemottractant effects. Its modulation by IL-17, however, has received very little attention. In the present study, we demonstrated IL-17-mediated induction of MIP-1α in rat primary astroctyes through its binding to the cognate IL-17RA. Furthermore, this effect was mediated via the activation of Src, mitogen-activated protein kinases (MAPKs), PI3K/Akt and NF-kB pathways, culminating ultimately into increased expression of MIP-1α. Exposure of primary mouse astrocytes to IL-17 resulted in increased expression of glial fibrillary acidic protein and, this effect was abrogated in cells cultured in presence of the MIP-1α neutralizing antibody, thus underscoring its role in the activation of astrocytes. In vivo relevance of these findings was further corroborated in experimental autoimmune encephalomyelitis mice that demonstrated significantly increased activation of astrocytes with concomitant increased expression of MIP-1α in the corpus callosum compared with control group. Understanding the regulation of MIP-1α expression may provide insights into the development of potential therapeutic targets for neuroinflammation associated with multiple sclerosis.

  4. Different responses of astrocytes and neurons to nitric oxide: The role of glycolytically generated ATP in astrocyte protection

    PubMed Central

    Almeida, Angeles; Almeida, Julia; Bolaños, Juan P.; Moncada, Salvador

    2001-01-01

    It was recently proposed that in Jurkat cells, after inhibition of respiration by NO, glycolytically generated ATP plays a critical role in preventing the collapse of mitochondrial membrane potential (Δψm) and thus apoptotic cell death. We have investigated this observation further in primary cultures of rat cortical neurons and astrocytes—cell types that differ greatly in their glycolytic capacity. Continuous and significant (≈85%) inhibition of respiration by NO (1.4 μM at 175 μM O2) generated by [(z)-1-[2-aminoethyl]-N-[2-ammonioethyl]amino]diazen-1-ium-1,2 diolate (DETA-NO) initially (10 min) depleted ATP concentrations by ≈25% in both cell types and increased the rate of glycolysis in astrocytes but not in neurons. Activation of glycolysis in astrocytes, as judged by lactate production, prevented further ATP depletion, whereas in neurons, which do not invoke this mechanism, there was a progressive decrease in ATP concentrations over the next 60 min. During this time, there was a persistent mitochondrial hyperpolarization and absence of apoptotic cell death in astrocytes, whereas in the neurons there was a progressive fall in Δψm and increased apoptosis. After glucose deprivation or treatment with inhibitors of the F1F0-ATPase and adenine nucleotide translocase, astrocytes responded to NO with a fall in Δψm and apoptotic cell death similar to the response in neurons. Finally, although treatment of astrocytes with NO partially prevented staurosporin-induced collapse in Δψm and cell death, NO and staurosporin synergized in decreasing Δψm and inducing apoptosis in neurons. These results demonstrate that although inhibition of cellular respiration by NO leads to neurotoxicity, it may also result in initial neuroprotection, depending on the glycolytic capacity of the particular cell. PMID:11742096

  5. Don't fence me in: Harnessing the beneficial roles of astrocytes for spinal cord repair

    PubMed Central

    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 cells are transplanted into the injured spinal cord, they differentiate into astrocytes and other glial cells as opposed to neurons, which is commonly viewed as a challenge to be overcome in developing stem cell technology. However, several examples show that astrocytes provide support and guidance for axonal growth and aid in improving functional recovery after spinal cord injury. Notably, transplantation of astrocytes of a developmentally immature phenotype promotes tissue sparing and axonal regeneration. Furthermore, interventions that enhance endogenous astrocyte migration or reinvasion of the injury site result in greater axonal growth. These studies demonstrate that astrocytes are dynamic, diverse cells that have the capacity to promote axon growth after injury. The ability of astrocytes to be supportive of recovery should be exploited in devising regenerative strategies. PMID:18820411

  6. Calcium Imaging of Living Astrocytes in the Mouse Spinal Cord following Sensory Stimulation

    PubMed Central

    Cirillo, Giovanni; De Luca, Daniele; Papa, Michele

    2012-01-01

    Astrocytic Ca2+ dynamics have been extensively studied in ex vivo models; however, the recent development of two-photon microscopy and astrocyte-specific labeling has allowed the study of Ca2+ signaling in living central nervous system. Ca2+ waves in astrocytes have been described in cultured cells and slice preparations, but evidence for astrocytic activation during sensory activity is lacking. There are currently few methods to image living spinal cord: breathing and heart-beating artifacts have impeded the widespread application of this technique. We here imaged the living spinal cord by two-photon microscopy in C57BL6/J mice. Through pressurized injection, we specifically loaded spinal astrocytes using the red fluorescent dye sulforhodamine 101 (SR101) and imaged astrocytic Ca2+ levels with Oregon-Green BAPTA-1 (OGB). Then, we studied astrocytic Ca2+ levels at rest and after right electrical hind paw stimulation. Sensory stimulation significantly increased astrocytic Ca2+ levels within the superficial dorsal horn of the spinal cord compared to rest. In conclusion, in vivo morphofunctional imaging of living astrocytes in spinal cord revealed that astrocytes actively participate to sensory stimulation. PMID:23091738

  7. Overexpression of Swedish mutant APP in aged astrocytes attenuates excitatory synaptic transmission.

    PubMed

    Katsurabayashi, Shutaro; Kawano, Hiroyuki; Ii, Miyuki; Nakano, Sachiko; Tatsumi, Chihiro; Kubota, Kaori; Takasaki, Kotaro; Mishima, Kenichi; Fujiwara, Michihiro; Iwasaki, Katsunori

    2016-01-01

    Amyloid precursor protein (APP), a type I transmembrane protein, has different aspects, namely, performs essential physiological functions and produces β-amyloid peptide (Aβ). Overexpression of neuronal APP is responsible for synaptic dysfunction. In the central nervous system, astrocytes - a major glial cell type - have an important role in the regulation of synaptic transmission. Although APP is expressed in astrocytes, it remains unclear whether astrocytic overexpression of mutant APP affects synaptic transmission. In this study, the effect of astrocytic overexpression of a mutant APP on the excitatory synaptic transmission was investigated using coculture system of the transgenic (Tg) cortical astrocytes that express the human APP695 polypeptide with the double mutation K670N + M671L found in a large Swedish family with early onset Alzheimer's disease, and wild-type hippocampal neuron. Significant secretion of Aβ 1-40 and 1-42 was observed in cultured cortical astrocytes from the Tg2576 transgenic mouse that genetically overexpresses Swedish mutant APP. Under the condition, Tg astrocytes did not affect excitatory synaptic transmission of cocultured wild-type neurons. However, aged Tg astrocytes cultured for 9 weeks elicited a significant decrease in excitatory synaptic transmission in cocultured neurons. Moreover, a reduction in the number of readily releasable synaptic vesicles accompanied a decrease in the number of excitatory synapses in neurons cocultured with aged Tg astrocytes. These observations indicate that astrocytic expression of the mutant APP is involved in the downregulation of synaptic transmission with age. PMID:26733247

  8. Astrocyte-secreted thrombospondin-1 modulates synapse and spine defects in the fragile X mouse model.

    PubMed

    Cheng, Connie; Lau, Sally K M; Doering, Laurie C

    2016-01-01

    Astrocytes are key participants in various aspects of brain development and function, many of which are executed via secreted proteins. Defects in astrocyte signaling are implicated in neurodevelopmental disorders characterized by abnormal neural circuitry such as Fragile X syndrome (FXS). In animal models of FXS, the loss in expression of the Fragile X mental retardation 1 protein (FMRP) from astrocytes is associated with delayed dendrite maturation and improper synapse formation; however, the effect of astrocyte-derived factors on the development of neurons is not known. Thrombospondin-1 (TSP-1) is an important astrocyte-secreted protein that is involved in the regulation of spine development and synaptogenesis. In this study, we found that cultured astrocytes isolated from an Fmr1 knockout (Fmr1 KO) mouse model of FXS displayed a significant decrease in TSP-1 protein expression compared to the wildtype (WT) astrocytes. Correspondingly, Fmr1 KO hippocampal neurons exhibited morphological deficits in dendritic spines and alterations in excitatory synapse formation following long-term culture. All spine and synaptic abnormalities were prevented in the presence of either astrocyte-conditioned media or a feeder layer derived from FMRP-expressing astrocytes, or following the application of exogenous TSP-1. Importantly, this work demonstrates the integral role of astrocyte-secreted signals in the establishment of neuronal communication and identifies soluble TSP-1 as a potential therapeutic target for Fragile X syndrome. PMID:27485117

  9. Purification and Characterization of Progenitor and Mature Human Astrocytes Reveals Transcriptional and Functional Differences with Mouse.

    PubMed

    Zhang, Ye; Sloan, Steven A; Clarke, Laura E; Caneda, Christine; Plaza, Colton A; Blumenthal, Paul D; Vogel, Hannes; Steinberg, Gary K; Edwards, Michael S B; Li, Gordon; Duncan, John A; Cheshier, Samuel H; Shuer, Lawrence M; Chang, Edward F; Grant, Gerald A; Gephart, Melanie G Hayden; Barres, Ben A

    2016-01-01

    The functional and molecular similarities and distinctions between human and murine astrocytes are poorly understood. Here, we report the development of an immunopanning method to acutely purify astrocytes from fetal, juvenile, and adult human brains and to maintain these cells in serum-free cultures. We found that human astrocytes have abilities similar to those of murine astrocytes in promoting neuronal survival, inducing functional synapse formation, and engulfing synaptosomes. In contrast to existing observations in mice, we found that mature human astrocytes respond robustly to glutamate. Next, we performed RNA sequencing of healthy human astrocytes along with astrocytes from epileptic and tumor foci and compared these to human neurons, oligodendrocytes, microglia, and endothelial cells (available at http://www.brainrnaseq.org). With these profiles, we identified novel human-specific astrocyte genes and discovered a transcriptome-wide transformation between astrocyte precursor cells and mature post-mitotic astrocytes. These data represent some of the first cell-type-specific molecular profiles of the healthy and diseased human brain.

  10. DISC1, astrocytes and neuronal maturation: a possible mechanistic link with implications for mental disorders.

    PubMed

    Xia, Meng; Zhu, Shanshan; Shevelkin, Alexey; Ross, Christopher A; Pletnikov, Mikhail

    2016-08-01

    Disrupted-In-Schizophrenia 1 (DISC1) is a genetic risk factor implicated in major mental disorders that involve disrupted neurodevelopment and synaptic signaling. Glial cells such as astrocytes can regulate neuronal and synaptic maturation. Although astrocytes express DISC1, the role of astrocyte DISC1 in synaptic regulation remains unknown. We expressed a pathogenic, dominant-negative form of DISC1, mutant DISC1, in astrocytes to elucidate the roles of astrocytic DISC1 in maturation of dendrites and excitatory and inhibitory synapses using a co-culture model. We found that wild-type primary neurons exhibited less elaborated dendritic arborization when co-cultured with astrocytes that express mutant DISC1, compared to control astrocytes. We observed significantly decreased density of excitatory but not inhibitory synapses on wild-type primary neurons that were co-cultured with astrocytes that express mutant DISC1, compared to control astrocytes. Treatment of co-cultures with D-serine restored dendritic development and density of excitatory synapses. Our findings show for the first time that mutant DISC1 diminished the capacity of astrocytes to support dendritic and synaptic maturation in co-cultured neurons, and that D-serine can restore the dendritic and synaptic abnormalities. The results provide a new insight into the mechanisms whereby genetic risk factors within astrocytes could contribute the pathogenesis of psychiatric disorders. Expression of mutant DISC1 (mDISC1) in astrocytes (A) decreases binding of endogenous DISC1 to serine racemase (SR) and production of D-serine (blue triangles) from L-serine (red triangles). As a result, neurons co-cultured with mutant DISC1 astrocytes exhibit diminished dendritic arborization (DIV10) and decreased linear density of VGLUT+(red)/PSD95 +  (green) excitatory synapses (DIV14). Filled circles with arrows denote membrane transporters for D-serine. Read the Editorial Highlight for this article on doi: 10.1111/jnc.13699

  11. Transplantation of specific human astrocytes promotes functional recovery after spinal cord injury.

    PubMed

    Davies, Stephen J A; Shih, Chung-Hsuan; Noble, Mark; Mayer-Proschel, Margot; Davies, Jeannette E; Proschel, Christoph

    2011-03-02

    Repairing trauma to the central nervous system by replacement of glial support cells is an increasingly attractive therapeutic strategy. We have focused on the less-studied replacement of astrocytes, the major support cell in the central nervous system, by generating astrocytes from embryonic human glial precursor cells using two different astrocyte differentiation inducing factors. The resulting astrocytes differed in expression of multiple proteins thought to either promote or inhibit central nervous system homeostasis and regeneration. When transplanted into acute transection injuries of the adult rat spinal cord, astrocytes generated by exposing human glial precursor cells to bone morphogenetic protein promoted significant recovery of volitional foot placement, axonal growth and notably robust increases in neuronal survival in multiple spinal cord laminae. In marked contrast, human glial precursor cells and astrocytes generated from these cells by exposure to ciliary neurotrophic factor both failed to promote significant behavioral recovery or similarly robust neuronal survival and support of axon growth at sites of injury. Our studies thus demonstrate functional differences between human astrocyte populations and suggest that pre-differentiation of precursor cells into a specific astrocyte subtype is required to optimize astrocyte replacement therapies. To our knowledge, this study is the first to show functional differences in ability to promote repair of the injured adult central nervous system between two distinct subtypes of human astrocytes derived from a common fetal glial precursor population. These findings are consistent with our previous studies of transplanting specific subtypes of rodent glial precursor derived astrocytes into sites of spinal cord injury, and indicate a remarkable conservation from rat to human of functional differences between astrocyte subtypes. In addition, our studies provide a specific population of human astrocytes that

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

    PubMed Central

    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 Ephrin-A4 in astrocytes was detected using immunocytochemical staining and Western blot assays. Intercellular Ca2+ concentration was determined with Fluo-4 AM fluorescent staining. Middle cerebral artery occlusion (MCAO) model rats were used for in vivo studies. Results: OGD/R treatment of cultured astrocytes caused a decrement of Cx43 expression and translocation of Cx43 from cell membrane to cytoplasm, accompanied by cell retraction. Furthermore, OGD/R increased intracellular Ca2+ concentration, activated CaMKII/CREB pathways and upregulated expression of Ephrin-A4 in the astrocytes. All these changes in OGD/R-treated astrocytes were alleviated by overexpression of Cx43. In the cortical neurons cultured with astrocytes, OGD/R inhibited the neurite growth, whereas overexpression of Cx43 or knockdown of Ephrin-A4 in astrocytes restored the neurite growth. In MCAO model rats, neuronal recovery was found to be correlated with the recuperation of Cx43 and Ephrin-A4 in astrocytes. Conclusion: Cx43 can stabilize astrocytes and facilitate the resistance to the deleterious effects of a stroke-like milieu and promote neuronal recovery. PMID:26095039

  13. Modifications in astrocyte morphology and calcium signaling induced by a brain capillary endothelial cell line.

    PubMed

    Yoder, Elizabeth J

    2002-04-15

    Astrocytes extend specialized endfoot processes to perisynaptic and perivascular regions, and thus are positioned to mediate the bidirectional flow of metabolic, ionic, and other transmissive substances between neurons and the blood stream. While mutual structural and functional interactions between neurons and astrocytes have been documented, less is known about the interactions between astrocytes and cerebrovascular cells. For example, although the ability of astrocytes to induce structural and functional changes in endothelial cells is established, the reciprocity of brain endothelial cells to induce changes in astrocytes is undetermined. This issue is addressed in the present study. Changes in primary cultures of neonatal mouse cortical astrocytes were investigated following their coculture with mouse brain capillary endothelial (bEnd3) cells. The presence of bEnd3 cells altered the morphology of astrocytes by transforming them from confluent monolayers into networks of elongated multicellular columns. These columns did not occur when either bEnd3 cells or astrocytes were cocultured with other cell types, suggesting that astrocytes undergo specific morphological consequences when placed in close proximity to brain endothelial cells. In addition to these structural changes, the pharmacological profile of astrocytes was modified by coculture with bEnd3 cells. Astrocytes in the cocultures showed an increased Ca2+ responsiveness to bradykinin and glutamate, but no change in responsiveness to ATP, as compared to controls. Coculturing the astrocytes with a neuronal cell line resulted in increased responsiveness of the glial responses to glutamate but not to bradykinin. These studies indicate that brain endothelial cells induce changes in astrocyte morphology and pharmacology.

  14. Astrocytic gap junctional networks suppress cellular damage in an in vitro model of ischemia

    SciTech Connect

    Shinotsuka, Takanori; Yasui, Masato; Nuriya, Mutsuo

    2014-02-07

    Highlights: • Astrocytes exhibit characteristic changes in [Ca{sup 2+}]{sub i} under OGD. • Astrocytic [Ca{sup 2+}]{sub i} increase is synchronized with a neuronal anoxic depolarization. • Gap junctional couplings protect neurons as well as astrocytes during OGD. - Abstract: Astrocytes play pivotal roles in both the physiology and the pathophysiology of the brain. They communicate with each other via extracellular messengers as well as through gap junctions, which may exacerbate or protect against pathological processes in the brain. However, their roles during the acute phase of ischemia and the underlying cellular mechanisms remain largely unknown. To address this issue, we imaged changes in the intracellular calcium concentration ([Ca{sup 2+}]{sub i}) in astrocytes in mouse cortical slices under oxygen/glucose deprivation (OGD) condition using two-photon microscopy. Under OGD, astrocytes showed [Ca{sup 2+}]{sub i} oscillations followed by larger and sustained [Ca{sup 2+}]{sub i} increases. While the pharmacological blockades of astrocytic receptors for glutamate and ATP had no effect, the inhibitions of gap junctional intercellular coupling between astrocytes significantly advanced the onset of the sustained [Ca{sup 2+}]{sub i} increase after OGD exposure. Interestingly, the simultaneous recording of the neuronal membrane potential revealed that the onset of the sustained [Ca{sup 2+}]{sub i} increase in astrocytes was synchronized with the appearance of neuronal anoxic depolarization. Furthermore, the blockade of gap junctional coupling resulted in a concurrent faster appearance of neuronal depolarizations, which remain synchronized with the sustained [Ca{sup 2+}]{sub i} increase in astrocytes. These results indicate that astrocytes delay the appearance of the pathological responses of astrocytes and neurons through their gap junction-mediated intercellular network under OGD. Thus, astrocytic gap junctional networks provide protection against tissue damage

  15. Modifications in astrocyte morphology and calcium signaling induced by a brain capillary endothelial cell line.

    PubMed

    Yoder, Elizabeth J

    2002-04-15

    Astrocytes extend specialized endfoot processes to perisynaptic and perivascular regions, and thus are positioned to mediate the bidirectional flow of metabolic, ionic, and other transmissive substances between neurons and the blood stream. While mutual structural and functional interactions between neurons and astrocytes have been documented, less is known about the interactions between astrocytes and cerebrovascular cells. For example, although the ability of astrocytes to induce structural and functional changes in endothelial cells is established, the reciprocity of brain endothelial cells to induce changes in astrocytes is undetermined. This issue is addressed in the present study. Changes in primary cultures of neonatal mouse cortical astrocytes were investigated following their coculture with mouse brain capillary endothelial (bEnd3) cells. The presence of bEnd3 cells altered the morphology of astrocytes by transforming them from confluent monolayers into networks of elongated multicellular columns. These columns did not occur when either bEnd3 cells or astrocytes were cocultured with other cell types, suggesting that astrocytes undergo specific morphological consequences when placed in close proximity to brain endothelial cells. In addition to these structural changes, the pharmacological profile of astrocytes was modified by coculture with bEnd3 cells. Astrocytes in the cocultures showed an increased Ca2+ responsiveness to bradykinin and glutamate, but no change in responsiveness to ATP, as compared to controls. Coculturing the astrocytes with a neuronal cell line resulted in increased responsiveness of the glial responses to glutamate but not to bradykinin. These studies indicate that brain endothelial cells induce changes in astrocyte morphology and pharmacology. PMID:11948807

  16. Acceleration of astrocytic differentiation in neural stem cells surviving X-irradiation.

    PubMed

    Ozeki, Ayumi; Suzuki, Keiji; Suzuki, Masatoshi; Ozawa, Hiroki; Yamashita, Shunichi

    2012-03-28

    Neural stem cells (NSCs) are highly susceptible to DNA double-strand breaks; however, little is known about the effects of radiation in cells surviving radiation. Although the nestin-positive NSCs predominantly became glial fibrillary acidic protein (GFAP)-positive in differentiation-permissive medium, little or no cells were GFAP positive in proliferation-permissive medium. We found that more than half of the cells surviving X-rays became GFAP positive in proliferation-permissive medium. Moreover, localized irradiation stimulated differentiation of cells outside the irradiated area. These results indicate for the first time that ionizing radiation is able to stimulate astrocyte-specific differentiation of surviving NSCs, whose process is mediated both by the direct activation of nuclear factor-κB and by the indirect bystander effect induced by X-irradiation.

  17. Assessment of C-phycocyanin effect on astrocytes-mediated neuroprotection against oxidative brain injury using 2D and 3D astrocyte tissue model

    PubMed Central

    Min, Seul Ki; Park, Jun Sang; Luo, Lidan; Kwon, Yeo Seon; Lee, Hoo Cheol; Jung Shim, Hyun; Kim, Il-Doo; Lee, Ja-Kyeong; Shin, Hwa Sung

    2015-01-01

    Drugs are currently being developed to attenuate oxidative stress as a treatment for brain injuries. C-phycocyanin (C-Pc) is an antioxidant protein of green microalgae known to exert neuroprotective effects against oxidative brain injury. Astrocytes, which compose many portions of the brain, exert various functions to overcome oxidative stress; however, little is known about how C-Pc mediates the antioxidative effects of astrocytes. In this study, we revealed that C-Pc intranasal administration to the middle cerebral artery occlusion (MCAO) rats ensures neuroprotection of ischemic brain by reducing infarct size and improving behavioral deficits. C-Pc also enhanced viability and proliferation but attenuated apoptosis and reactive oxygen species (ROS) of oxidized astrocytes, without cytotoxicity to normal astrocytes and neurons. To elucidate how C-Pc leads astrocytes to enhance neuroprotection and repair of ischemia brain, we firstly developed 3D oxidized astrocyte model. C-Pc had astrocytes upregulate antioxidant enzymes such as SOD and catalase and neurotrophic factors BDNF and NGF, while alleviating inflammatory factors IL-6 and IL-1β and glial scar. Additionally, C-Pc improved viability of 3D oxidized neurons. In summary, C-Pc was concluded to activate oxidized astrocytes to protect and repair the ischemic brain with the combinatorial effects of improved antioxidative, neurotrophic, and anti-inflammatory mechanisms. PMID:26399322

  18. Assessment of C-phycocyanin effect on astrocytes-mediated neuroprotection against oxidative brain injury using 2D and 3D astrocyte tissue model.

    PubMed

    Min, Seul Ki; Park, Jun Sang; Luo, Lidan; Kwon, Yeo Seon; Lee, Hoo Cheol; Shim, Hyun Jung; Kim, Il-Doo; Lee, Ja-Kyeong; Shin, Hwa Sung

    2015-01-01

    Drugs are currently being developed to attenuate oxidative stress as a treatment for brain injuries. C-phycocyanin (C-Pc) is an antioxidant protein of green microalgae known to exert neuroprotective effects against oxidative brain injury. Astrocytes, which compose many portions of the brain, exert various functions to overcome oxidative stress; however, little is known about how C-Pc mediates the antioxidative effects of astrocytes. In this study, we revealed that C-Pc intranasal administration to the middle cerebral artery occlusion (MCAO) rats ensures neuroprotection of ischemic brain by reducing infarct size and improving behavioral deficits. C-Pc also enhanced viability and proliferation but attenuated apoptosis and reactive oxygen species (ROS) of oxidized astrocytes, without cytotoxicity to normal astrocytes and neurons. To elucidate how C-Pc leads astrocytes to enhance neuroprotection and repair of ischemia brain, we firstly developed 3D oxidized astrocyte model. C-Pc had astrocytes upregulate antioxidant enzymes such as SOD and catalase and neurotrophic factors BDNF and NGF, while alleviating inflammatory factors IL-6 and IL-1β and glial scar. Additionally, C-Pc improved viability of 3D oxidized neurons. In summary, C-Pc was concluded to activate oxidized astrocytes to protect and repair the ischemic brain with the combinatorial effects of improved antioxidative, neurotrophic, and anti-inflammatory mechanisms. PMID:26399322

  19. Ebselen alters cellular oxidative status and induces endoplasmic reticulum stress in rat hippocampal astrocytes.

    PubMed

    Santofimia-Castaño, Patricia; Izquierdo-Alvarez, Alicia; de la Casa-Resino, Irene; Martinez-Ruiz, Antonio; Perez-Lopez, Marcos; Portilla, Juan C; Salido, Gines M; Gonzalez, Antonio

    2016-05-16

    Ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one) is an organoselenium radical scavenger compound, which has strong antioxidant and anti-inflammatory effects. Because of its properties, it may be protective against injury to the nervous tissue. However, evidence suggests that its glutathione peroxidase activity could underlie certain deleterious actions on cell physiology. In this study we have analyzed the effect of ebselen on rat hippocampal astrocytes in culture. Cellular oxidative status, cytosolic free-Ca(2+) concentration ([Ca(2+)]c), setting of endoplasmic reticulum stress and phosphorylation of glial fibrillary acidic protein and major mitogen-activated protein kinases were analyzed. Our results show that ebselen induced a concentration-dependent increase in the generation of reactive oxygen species in the mitochondria. We observed a concentration-dependent increase in global cysteine oxidation and in the level of malondialdehyde in the presence of ebselen. We also detected increases in catalase, glutathione S-transferase and glutathione reductase activity. Ebselen also evoked a concentration-dependent increase in [Ca(2+)]c. Moreover, we observed a concentration-dependent increase in the phosphorylation of the unfolded protein response markers, eukaryotic translation initiation factor 2α and X-box binding protein 1. Finally, ebselen also induced an increase in the phosphorylation of glial fibrillary acidic protein, SAPK/JNK, p38 MAPK and p44/42 MAPK. Our results provide strong evidence that implicate endoplasmic reticulum stress and activation of crucial mitogen-activated protein kinases in an oxidative damage of cells in the presence of ebselen. The compound thus might exert deleterious actions on astrocyte physiology that could compromise their function. PMID:27282967

  20. Diverse FGF receptor signaling controls astrocyte specification and proliferation

    SciTech Connect

    Kang, Kyungjun; Song, Mi-Ryoung

    2010-05-07

    During CNS development, pluripotency neuronal progenitor cells give rise in succession to neurons and glia. Fibroblast growth factor-2 (FGF-2), a major signal that maintains neural progenitors in the undifferentiated state, is also thought to influence the transition from neurogenesis to gliogenesis. Here we present evidence that FGF receptors and underlying signaling pathways transmit the FGF-2 signals that regulate astrocyte specification aside from its mitogenic activity. Application of FGF-2 to cortical progenitors suppressed neurogenesis whereas treatment with an FGFR antagonist in vitro promoted neurogenesis. Introduction of chimeric FGFRs with mutated tyrosine residues into cortical progenitors and drug treatments to specifically block individual downstream signaling pathways revealed that the overall activity of FGFR rather than individual autophosphorylation sites is important for delivering signals for glial specification. In contrast, a signal for cell proliferation by FGFR was mainly delivered by MAPK pathway. Together our findings indicate that FGFR activity promotes astrocyte specification in the developing CNS.

  1. Biomechanical and proteomic analysis of INF- β-treated astrocytes

    NASA Astrophysics Data System (ADS)

    Vergara, Daniele; Martignago, Roberta; Leporatti, Stefano; Bonsegna, Stefania; Maruccio, Giuseppe; De Nuccio, Franco; Santino, Angelo; Cingolani, Roberto; Nicolardi, Giuseppe; Maffia, Michele; Rinaldi, Ross

    2009-11-01

    Astrocytes have a key role in the pathogenesis of several diseases including multiple sclerosis and were proposed as the designed target for immunotherapy. In this study we used atomic force microscopy (AFM) and proteomics methods to analyse and correlate the modifications induced in the viscoleastic properties of astrocytes to the changes induced in protein expression after interferon- β (IFN-β) treatment. Our results indicated that IFN-β treatment resulted in a significant decrease in the Young's modulus, a measure of cell elasticity, in comparison with control cells. The molecular mechanisms that trigger these changes were investigated by 2DE (two-dimensional electrophoresis) and confocal analyses and confirmed by western blotting. Altered proteins were found to be involved in cytoskeleton organization and other important physiological processes.

  2. Astrocyte Intermediaries of Septal Cholinergic Modulation in the Hippocampus.

    PubMed

    Pabst, Milan; Braganza, Oliver; Dannenberg, Holger; Hu, Wen; Pothmann, Leonie; Rosen, Jurij; Mody, Istvan; van Loo, Karen; Deisseroth, Karl; Becker, Albert J; Schoch, Susanne; Beck, Heinz

    2016-05-18

    The neurotransmitter acetylcholine, derived from the medial septum/diagonal band of Broca complex, has been accorded an important role in hippocampal learning and memory processes. However, the precise mechanisms whereby acetylcholine released from septohippocampal cholinergic neurons acts to modulate hippocampal microcircuits remain unknown. Here, we show that acetylcholine release from cholinergic septohippocampal projections causes a long-lasting GABAergic inhibition of hippocampal dentate granule cells in vivo and in vitro. This inhibition is caused by cholinergic activation of hilar astrocytes, which provide glutamatergic excitation of hilar inhibitory interneurons. These results demonstrate that acetylcholine release can cause slow inhibition of principal neuronal activity via astrocyte intermediaries. PMID:27161528

  3. How astrocyte networks may contribute to cerebral metabolite clearance

    PubMed Central

    Asgari, Mahdi; de Zélicourt, Diane; Kurtcuoglu, Vartan

    2015-01-01

    The brain possesses an intricate network of interconnected fluid pathways that are vital to the maintenance of its homeostasis. With diffusion being the main mode of solute transport in cerebral tissue, it is not clear how bulk flow through these pathways is involved in the removal of metabolites. In this computational study, we show that networks of astrocytes may contribute to the passage of solutes between tissue and paravascular spaces (PVS) by serving as low resistance pathways to bulk water flow. The astrocyte networks are connected through aquaporin-4 (AQP4) water channels with a parallel, extracellular route carrying metabolites. Inhibition of the intracellular route by deletion of AQP4 causes a reduction of bulk flow between tissue and PVS, leading to reduced metabolite clearance into the venous PVS or, as observed in animal studies, a reduction of tracer influx from arterial PVS into the brain tissue. PMID:26463008

  4. BMPs as Therapeutic Targets and Biomarkers in Astrocytic Glioma

    PubMed Central

    González-Gómez, Pilar; Anselmo, Nilson Praia; Mira, Helena

    2014-01