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Sonia Lavisse,
Martine Guillermier,
Anne-Sophie Hérard,
Fanny Petit,
Marion Delahaye,
Nadja Van Camp,
Lucile Ben Haim,
Vincent Lebon,
Philippe Remy,
Frédéric Dollé,
Thierry Delzescaux, Gilles Bonvento,
Philippe Hantraye,
Carole Escartin
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ABSTRACT: Astrocytes and microglia become reactive under most brain pathological conditions, making this neuroinflammation process a surrogate marker of neuronal dysfunction. Neuroinflammation is associated with increased levels of translocator protein 18 kDa (TSPO) and binding sites for TSPO ligands. Positron emission tomography (PET) imaging of TSPO is thus commonly used to monitor neuroinflammation in preclinical and clinical studies. It is widely considered that TSPO PET signal reveals reactive microglia, although a few studies suggested a potential contribution of reactive astrocytes. Because astrocytes and microglia play very different roles, it is crucial to determine whether reactive astrocytes can also overexpress TSPO and yield to a detectable TSPO PET signal in vivo. We used a model of selective astrocyte activation through lentiviral gene transfer of the cytokine ciliary neurotrophic factor (CNTF) into the rat striatum, in the absence of neurodegeneration. CNTF induced an extensive activation of astrocytes, which overexpressed GFAP and become hypertrophic, whereas microglia displayed minimal increase in reactive markers. Two TSPO radioligands, [(18)F]DPA-714 [N,N-diethyl-2-(2-(4-(2-[(18)F]fluoroethoxy)phenyl)-5,7-dimethylpyrazolo[1,5-a]pyrimidin-3-yl)acetamide] and [(11)C]SSR180575 (7-chloro-N,N-dimethyl-5-[(11)C]methyl-4-oxo-3-phenyl-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-acetamide), showed a significant binding in the lenti-CNTF-injected striatum that was saturated and displaced by PK11195 [N-methyl-N-(1-methylpropyl)-1-(2-chlorophenyl)-isoquinoline-3-carboxamide]. The volume of radioligand binding matched the GFAP immunopositive volume. TSPO mRNA levels were significantly increased, and TSPO protein was overexpressed by CNTF-activated astrocytes. We show that reactive astrocytes overexpress TSPO, yielding to a significant and selective binding of TSPO radioligands. Therefore, caution must be used when interpreting TSPO PET imaging in animals or patients because reactive astrocytes can contribute to the signal in addition to reactive microglia.
Journal of Neuroscience 08/2012; 32(32):10809-18. · 7.11 Impact Factor
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Laurie Galvan,
Nad'a Lepejová,
Marie-Claude Gaillard,
Carole Malgorn,
Martine Guillermier,
Diane Houitte, Gilles Bonvento,
Fanny Petit,
Noëlle Dufour,
Patrick Héry,
Matthieu Gérard,
Jean-Marc Elalouf,
Nicole Déglon,
Emmanuel Brouillet,
Michel de Chaldée
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ABSTRACT: Genes selectively expressed in the striatum may be involved in the preferential vulnerability of striatal neurons to Huntington's disease (HD). Here, we investigated whether perturbations of Capucin expression, which is enriched in the striatum and downregulated in Huntington's disease models, could modify the neurotoxicity induced by the injection of a lentiviral vector encoding a short N-terminal fragment of mutant Huntingtin (mHtt) into the mouse striatum. Neither constitutive Capucin deficiency in knockout mice nor lentiviral vector-mediated Capucin overexpression in the striatum of adult wild type mice significantly modified vulnerability to the mHtt fragment in vivo, suggesting that Capucin has no impact on mHtt toxicity.
Neurobiology of aging 02/2012; 33(8):1845.e5-6. · 5.94 Impact Factor
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ABSTRACT: Several recent findings have shown that neurons as well as astrocytes are organized into networks. Indeed, astrocytes are interconnected through connexin-formed gap junction channels allowing exchanges of ions and signaling molecules. The aim of this study is to characterize astrocyte network properties in mouse olfactory glomeruli where neuronal connectivity is highly ordered. Dye-coupling experiments performed in olfactory bulb acute slices (P16-P22) highlight a preferential communication between astrocytes within glomeruli and not between astrocytes in adjacent glomeruli. Such organization relies on the oriented morphology of glomerular astrocytes to the glomerulus center and the enriched expression of two astroglial connexins (Cx43 and Cx30) within the glomeruli. Glomerular astrocytes detect neuronal activity showing membrane potential fluctuations correlated with glomerular local field potentials. Accordingly, gap junctional coupling of glomerular networks is reduced when neuronal activity is silenced by TTX treatment or after early sensory deprivation. Such modulation is lost in Cx30 but not in Cx43 KO mice, indicating that Cx30-formed channels are the molecular targets of this activity-dependent modulation. Extracellular potassium is a key player in this neuroglial interaction, because (i) the inhibition of dye coupling observed in the presence of TTX or after sensory deprivation is restored by increasing [K(+)](e) and (ii) treatment with a K(ir) channel blocker inhibits dye spread between glomerular astrocytes. Together, these results demonstrate that extracellular potassium generated by neuronal activity modulates Cx30-mediated gap junctional communication between glomerular astrocytes, indicating that strong neuroglial interactions take place at this first relay of olfactory information processing.
Proceedings of the National Academy of Sciences 11/2011; 108(45):18442-6. · 9.68 Impact Factor
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Mathilde Faideau,
Jinho Kim,
Kerry Cormier,
Richard Gilmore,
Mackenzie Welch,
Gwennaelle Auregan,
Noelle Dufour,
Martine Guillermier,
Emmanuel Brouillet,
Philippe Hantraye,
Nicole Déglon,
Robert J Ferrante, Gilles Bonvento
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ABSTRACT: 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.
Human Molecular Genetics 08/2010; 19(15):3053-67. · 7.64 Impact Factor
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ABSTRACT: Biomarkers and technologies similar to those used in humans are essential for the follow-up of Alzheimer's disease (AD) animal models, particularly for the clarification of mechanisms and the screening and validation of new candidate treatments. In humans, changes in brain metabolism can be detected by 1-deoxy-2-[(18)F] fluoro-D-glucose PET (FDG-PET) and assessed in a user-independent manner with dedicated software, such as Statistical Parametric Mapping (SPM). FDG-PET can be carried out in small animals, but its resolution is low as compared to the size of rodent brain structures. In mouse models of AD, changes in cerebral glucose utilization are usually detected by [(14)C]-2-deoxyglucose (2DG) autoradiography, but this requires prior manual outlining of regions of interest (ROI) on selected sections. Here, we evaluate the feasibility of applying the SPM method to 3D autoradiographic data sets mapping brain metabolic activity in a transgenic mouse model of AD. We report the preliminary results obtained with 4 APP/PS1 (64+/-1 weeks) and 3 PS1 (65+/-2 weeks) mice. We also describe new procedures for the acquisition and use of "blockface" photographs and provide the first demonstration of their value for the 3D reconstruction and spatial normalization of post mortem mouse brain volumes. Despite this limited sample size, our results appear to be meaningful, consistent, and more comprehensive than findings from previously published studies based on conventional ROI-based methods. The establishment of statistical significance at the voxel level, rather than with a user-defined ROI, makes it possible to detect more reliably subtle differences in geometrically complex regions, such as the hippocampus. Our approach is generic and could be easily applied to other biomarkers and extended to other species and applications.
NeuroImage 03/2010; 51(2):586-98. · 5.89 Impact Factor
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ABSTRACT: Ciliary neurotrophic factor (CNTF) is a potent neuroprotective cytokine in different animal models of glutamate-induced excitotoxicity, although its action mechanisms are still poorly characterized. We tested the hypothesis that an increased function of glial glutamate transporters (GTs) could underlie CNTF-mediated neuroprotection. We show that neuronal loss induced by in vivo striatal injection of the excitotoxin quinolinic acid (QA) was significantly reduced (by approximately 75%) in CNTF-treated animals. In striatal slices, acute QA application dramatically inhibited corticostriatal field potentials (FPs), whose recovery was significantly higher in CNTF rats compared to controls (approximately 40% vs. approximately 7%), confirming an enhanced resistance to excitotoxicity. The GT inhibitor DL-threo-beta-benzyloxyaspartate greatly reduced FP recovery in CNTF rats, supporting the role of GT in CNTF-mediated neuroprotection. Whole-cell patch-clamp recordings from striatal medium spiny neurons showed no alteration of basic properties of striatal glutamatergic transmission in CNTF animals, but the increased effect of a low-affinity competitive glutamate receptor antagonist (gamma-D-glutamylglycine) also suggested an enhanced GT function. These data strongly support our hypothesis that CNTF is neuroprotective via an increased function of glial GTs, and further confirms the therapeutic potential of CNTF for the clinical treatment of progressive neurodegenerative diseases involving glutamate overflow.
PLoS ONE 01/2010; 5(1):e8550. · 4.09 Impact Factor
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Béchir Jarraya,
Sabrina Boulet,
G Scott Ralph,
Caroline Jan, Gilles Bonvento,
Mimoun Azzouz,
James E Miskin,
Masahiro Shin,
Thierry Delzescaux,
Xavier Drouot,
Anne-Sophie Hérard,
Denise M Day,
Emmanuel Brouillet,
Susan M Kingsman,
Philippe Hantraye,
Kyriacos A Mitrophanous,
Nicholas D Mazarakis,
Stéphane Palfi
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ABSTRACT: In Parkinson's disease, degeneration of specific neurons in the midbrain can cause severe motor deficits, including tremors and the inability to initiate movement. The standard treatment is administration of pharmacological agents that transiently increase concentrations of brain dopamine and thereby discontinuously modulate neuronal activity in the striatum, the primary target of dopaminergic neurons. The resulting intermittent dopamine alleviates parkinsonian symptoms but is also thought to cause abnormal involuntary movements, called dyskinesias. To investigate gene therapy for Parkinson's disease, we simulated the disease in macaque monkeys by treating them with the complex I mitochondrial inhibitor 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, which induces selective degeneration of dopamine-producing neurons. In this model, we demonstrated that injection of a tricistronic lentiviral vector encoding the critical genes for dopamine synthesis (tyrosine hydroxylase, aromatic L-amino acid decarboxylase, and guanosine 5'-triphosphate cyclohydrolase 1) into the striatum safely restored extracellular concentrations of dopamine and corrected the motor deficits for 12 months without associated dyskinesias. Gene therapy-mediated dopamine replacement may be able to correct Parkinsonism in patients without the complications of dyskinesias.
Science translational medicine 10/2009; 1(2):2ra4. · 7.80 Impact Factor
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ABSTRACT: There is increasing evidence that glial cells, in particular astrocytes, interact dynamically with neurons. The well-known anatomofunctional organization of neurons in the barrel cortex offers a suitable and promising model to study such neuroglial interaction. This review summarizes and discusses recent in vitro as well as in vivo works demonstrating that astrocytes receive, integrate, and respond to neuronal signals. In addition, they are active elements of brain metabolism and exhibit a certain degree of plasticity that affects neuronal activity. Altogether these findings indicate that the barrel cortex presents glial compartments overlapping and interacting with neuronal compartments and that these properties help define barrels as functional and independent units. Finally, this review outlines how the use of the barrel cortex as a model might in the future help to address important questions related to dynamic neuroglia interaction.
The Neuroscientist 07/2009; 15(4):351-66. · 4.57 Impact Factor
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Valérie Drouet,
Valérie Perrin,
Raymonde Hassig,
Noëlle Dufour,
Gwennaelle Auregan,
Sandro Alves, Gilles Bonvento,
Emmanuel Brouillet,
Ruth Luthi-Carter,
Philippe Hantraye,
Nicole Déglon
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ABSTRACT: Huntington's disease (HD) is a fatal autosomal dominant neurodegenerative disorder caused by a polyglutamine expansion in the huntingtin (htt) protein. No cure is available to date to alleviate neurodegeneration. Recent studies have demonstrated that RNA interference represents a promising approach for the treatment of autosomal dominant disorders. But whether an allele-specific silencing of mutant htt or a nonallele-specific silencing should be considered has not been addressed.
We developed small hairpin RNA targeting mutant or wild-type htt transcripts, or both.
We confirmed the therapeutic potential of sihtt administered with lentiviral vectors in rodent models of HD and showed that initiation of small interfering RNA treatment after the onset of HD symptoms is still efficacious and reduces the HD-like pathology. We then addressed the question of the impact of nonallele-specific silencing and demonstrated that silencing of endogenous htt to 25 to 35% in vivo is altering several pathways associated with known htt functions but is not inducing overt toxicity or increasing striatal vulnerability up to 9 months after treatment.
These data indicate that the coincident silencing of the wild-type and mutant htt may be considered as a therapeutic tool for HD.
Annals of Neurology 04/2009; 65(3):276-85. · 11.09 Impact Factor
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ABSTRACT: Astrocytes are involved in key physiological brain processes, such as glutamatergic transmission and energy metabolism, often altered in neurodegenerative diseases. Targeted gene expression in astrocytes is needed to assess the contribution of these cells to physiological processes and for the development of new therapeutic strategies. However, most of the viral vectors currently used for gene transfer in the central nervous system (CNS) are highly neurotropic. We used mokola pseudotyping to shift the tropism of lentiviral vectors toward astrocytes and a detargeting strategy with miRNA to eliminate residual expression in neuronal cells. In primary cultures, we showed that incorporating target sequences for the neuron-specific miR124 effectively abolished transgene expression in neurons post-transcriptionally. Targeted expression of the LacZ reporter gene in astrocytes was achieved in the hippocampus, striatum, and cerebellum of the adult mouse in vivo. As a proof-of-principle, this new lentiviral vector was used to either overexpress or downregulate (RNA interference) the glial glutamate transporter GLAST into striatal astrocytes in vivo. These vectors provide new opportunities for cell type-specific gene transfer in the CNS.
Glia 11/2008; 57(6):667-79. · 4.82 Impact Factor
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ABSTRACT: Astrocytes are involved in many key physiological processes in the brain, including glutamatergic transmission, energy metabolism, and blood flow control. They become reactive in response to pathological situations, a response that involves well-described morphological alterations and less characterized functional changes. The functional consequences of astrocyte reactivity seem to depend on the molecular pathway involved and may result in the enhancement of several neuroprotective and neurotrophic functions. We propose that a selective and controlled activation of astrocytes may switch these highly pleiotropic cells into therapeutic agents to promote neuron survival and recovery. This may represent a potent therapeutic strategy for many brain diseases in which neurons would benefit from an increased support from activated astrocytes.
Molecular Neurobiology 11/2008; 38(3):231-41. · 5.74 Impact Factor
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ABSTRACT: PET scanners devoted to in vivo functional study have recently been developed, but autoradiography remains the reference technique for assessing cerebral glucose metabolism (CMRGlu) in rodents. Autoradiographs are conventionally subjected to region of interest (ROI) analysis, which is intrinsically hypothesis-driven and therefore not suitable for whole-brain investigation. Voxel-wise statistical methods of analysis have long been used to determine differences in brain activity during in vivo functional neuroimaging experiments. They have also recently been applied to 3D reconstructed autoradiographic volume images from rat brains. We present here a fully automated analysis for autoradiographic data combining (1) computerized procedures for the acquisition and 3D reconstruction of postmortem volume images and (2) spatial normalization followed by classical whole-brain voxel-wise statistical analysis. We also describe an additional procedure for characterizing functional differences between the right and left hemispheres of the brain. We compared two spatial normalization techniques and evaluated how the effect of choosing a particular normalization technique impacted on the statistical analysis. We also propose a small volume correction analysis to address the problem of multiple statistical comparisons. Lastly, we investigated the reliability of such analyses, by comparing their results qualitatively and quantitatively with those previously obtained with our semiautomated ROI-based analysis [Dubois, A., Dauguet, J., Herard, A.-S., Besret, L., Duchesnay, E., Frouin, V., Hantraye, P., Bonvento, G., Delzescaux, T., 2007. Automated three-dimensional analysis of histologic and autoradiographic rat brain sections: application to an activation study. J. Cereb. Blood Flow Metab. 27 (10), 1742-1755.]. Both voxel-wise statistical analyses led to the detection of consistent interhemispheric differences in CMRGlu. This work demonstrates the potential value and robustness of voxel-wise statistical methods for analyzing autoradiographic data sets.
NeuroImage 05/2008; 40(2):482-94. · 5.89 Impact Factor
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ABSTRACT: Besides the newly developed positron emission tomography scanners (microPET) dedicated to the in vivo functional study of small animals, autoradiography remains the reference technique widely used for functional brain imaging and the gold standard for the validation of in vivo results. The analysis of autoradiographic data is classically achieved in two dimensions (2D) using a section-by-section approach, is often limited to few sections and the delineation of the regions of interest to be analysed is directly performed on autoradiographic sections. In addition, such approach of analysis does not accommodate the possible anatomical shifts linked to dissymmetry associated with the sectioning process. This classic analysis is time-consuming, operator-dependent and can therefore lead to non-objective and non-reproducible results. In this paper, we have developed an automated and generic toolbox for processing of autoradiographic and corresponding histological rat brain sections based on a three-step approach, which involves: (1) an optimized digitization dealing with hundreds of autoradiographic and histological sections; (2) a robust reconstruction of the volumes based on a reliable registration method; and (3) an original 3D-geometry-based approach to analysis of anatomical and functional post-mortem data. The integration of the toolbox under a unified environment (in-house software BrainVISA, http://brainvisa.info) with a graphic interface enabled a robust and operator-independent exploitation of the overall anatomical and functional information. We illustrated the substantial qualitative and quantitative benefits obtained by applying our methodology to an activation study (rats, n=5, under unilateral visual stimulation).
Journal of Cerebral Blood Flow & Metabolism 11/2007; 27(10):1742-55. · 5.01 Impact Factor
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Carole Escartin,
Karin Pierre,
Angélique Colin,
Emmanuel Brouillet,
Thierry Delzescaux,
Martine Guillermier,
Marc Dhenain,
Nicole Déglon,
Philippe Hantraye,
Luc Pellerin, Gilles Bonvento
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ABSTRACT: High energy demands of neurons make them vulnerable to adverse effects of energy impairment. Recently, astrocytes were shown to regulate the flux of energy substrates to neurons. In pathological situations, astrocytes are activated but the consequences on brain energy metabolism are still poorly characterized. We found that local lentiviral-mediated gene transfer of ciliary neurotrophic factor (CNTF), a cytokine known to activate astrocytes, induced a stable decrease in the glycolytic flux in the rat striatum in vivo as measured by 2-[18F]-2-deoxy-D-glucose autoradiography and micro-positron emission tomography imaging. The activity of the mitochondrial complex IV enzyme cytochrome oxidase was not modified, suggesting maintenance of downstream oxidative steps of energy production. CNTF significantly increased the phosphorylation level of the intracellular energy sensor AMP-activated protein kinase (AMPK), supporting a specific reorganization of brain energy pathways. Indeed, we found that different key enzymes/transporters of fatty acids beta-oxidation and ketolysis were overexpressed by CNTF-activated astrocytes within the striatum. In primary striatal neuron/astrocyte mixed cultures exposed to CNTF, the AMPK pathway was also activated, and the rate of oxidation of fatty acids and ketone bodies was significantly enhanced. This metabolic plasticity conferred partial glial and neuronal protection against prolonged palmitate exposure and glycolysis inhibition. We conclude that CNTF-activated astrocytes may have a strong protective potential to face severe metabolic insults.
Journal of Neuroscience 08/2007; 27(27):7094-104. · 7.11 Impact Factor
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ABSTRACT: An adequate and timely production of ATP by brain cells is of cardinal importance to support the major energetic cost of the rapid processing of information via synaptic and action potentials. Recently, evidence has been accumulated to support the view that the regulation of brain energy metabolism is under the control of an intimate dialogue between astrocytes and neurons. In vitro studies on cultured astrocytes and in vivo studies on rodents have provided evidence that glutamate and Na(+) uptake in astrocytes is a key triggering signal regulating glucose use in the brain. With the advent of NMR spectroscopy, it has been possible to provide experimental evidence to show that energy consumption is mainly devoted to glutamatergic neurotransmission and that glutamate-glutamine cycling is coupled in a approximately 1 : 1 molar stoichiometry to glucose oxidation, at least in the cerebral cortex. This improved understanding of neuron-astrocyte metabolic interactions offers the potential for developing novel therapeutic strategies for many neurological disorders that include a metabolic deficit.
Journal of Neurochemistry 11/2006; 99(2):393-401. · 4.06 Impact Factor
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ABSTRACT: According to the "indirect" excitotoxicity hypothesis, mitochondrial defects increase Ca2+ entry into neurons by rendering NMDA-R hypersensitive to glutamate. We tested this hypothesis by investigating in the rat striatum and cultured striatal cells how partial mitochondrial complex II inhibition produced by 3-nitropropionic acid (3NP) modifies the toxicity of the NMDA-R agonist quinolinate (QA). We showed that nontoxic 3NP treatment, leading to partial inhibition of complex II activity, greatly exacerbated striatal degeneration produced by slightly toxic QA treatment through an "all-or-nothing" process. The potentiation of QA-induced cell death by 3NP was associated with increased calpain activity and massive calpain-mediated cleavage of several postsynaptic proteins, suggesting major neuronal Ca2+ deregulation in the striatum. However, Ca2+ anomalies probably do not result from NMDA-R hypersensitivity. Indeed, brain imaging experiments using [(18)F]fluorodeoxyglucose indirectly showed that 3NP did not increase QA-induced ionic perturbations at the striatal glutamatergic synapses in vivo. Consistent with this, the exacerbation of QA toxicity by 3NP was not related to an increase in the QA-induced entry of 45Ca2+ into striatal neurons. The present results demonstrate that the potentiation of NMDA-R-mediated excitotoxicity by mitochondrial defects involves primarily intracellular Ca2+ deregulation, in the absence of NMDA-R hypersensitivity.
The FASEB Journal 06/2006; 20(7):1021-3. · 5.71 Impact Factor
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Carole Escartin,
Emmanuel Brouillet,
Paolo Gubellini,
Yaël Trioulier,
Carine Jacquard,
Claire Smadja,
Graham W Knott,
Lydia Kerkerian-Le Goff,
Nicole Déglon,
Philippe Hantraye, Gilles Bonvento
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ABSTRACT: To study the functional role of activated astrocytes in glutamate homeostasis in vivo, we used a model of sustained astrocytic activation in the rat striatum through lentiviral-mediated gene delivery of ciliary neurotrophic factor (CNTF). CNTF-activated astrocytes were hypertrophic, expressed immature intermediate filament proteins and highly glycosylated forms of their glutamate transporters GLAST and GLT-1. CNTF overexpression produced a redistribution of GLAST and GLT-1 into raft functional membrane microdomains, which are important for glutamate uptake. In contrast, CNTF had no detectable effect on the expression of a number of neuronal proteins and on the spontaneous glutamatergic transmission recorded from striatal medium spiny neurons. These results were replicated in vitro by application of recombinant CNTF on a mixed neuron/astrocyte striatal culture. Using microdialysis in the rat striatum, we found that the accumulation of extracellular glutamate induced by quinolinate (QA) was reduced threefold with CNTF. In line with this result, CNTF significantly increased QA-induced [(18)F]-fluoro-2-deoxyglucose uptake, an indirect index of glutamate uptake by astrocytes. Together, these data demonstrate that CNTF activation of astrocytes in vivo is associated with marked phenotypic and molecular changes leading to a better handling of increased levels of extracellular glutamate. Activated astrocytes may therefore be important prosurvival agents in pathological conditions involving defects in glutamate homeostasis.
Journal of Neuroscience 06/2006; 26(22):5978-89. · 7.11 Impact Factor
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ABSTRACT: Mitochondrial dysfunction might potentiate NMDA-receptor (R)-mediated toxicity in neurodegenerative diseases. The aim of this work was to investigate in vivo whether the mechanisms of potentiation of excitotox-icity by inhibition of mitochondrial complex II were associated with 1) an "all-or-nothing" process, 2) an elevation of cytosolic Ca 2 concentrations, and 3) an increase in the entry of Ca 2 into neurons.
The FASEB Journal 01/2006; · 5.71 Impact Factor
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Carole Escartin,
Emmanuel Brouillet,
Paolo Gubellini,
Yaël Trioulier,
Carine Jacquard,
Claire Smadja,
Graham W Knott,
Lydia Kerkerian-Le,
Goff,
Nicole Déglon,
Philippe Hantraye, Gilles Bonvento
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[hide abstract]
ABSTRACT: To study the functional role of activated astrocytes in glutamate homeostasis in vivo, we used a model of sustained astrocytic activation in the rat striatum through lentiviral-mediated gene delivery of ciliary neurotrophic factor (CNTF). CNTF-activated astrocytes were hypertrophic, expressed immature intermediate filament proteins and highly glycosylated forms of their glutamate transporters GLAST and GLT-1. CNTF overexpression produced a redistribution of GLAST and GLT-1 into raft functional membrane microdomains, which are important for glutamate uptake. In contrast, CNTF had no detectable effect on the expression of a number of neuronal proteins and on the spontaneous glutamatergic transmission recorded from striatal medium spiny neurons. These results were replicated in vitro by application of recombinant CNTF on a mixed neuron/astrocyte striatal culture. Using microdialysis in the rat striatum, we found that the accumulation of extracellular glutamate induced by quinolinate (QA) was reduced threefold with CNTF. In line with this result, CNTF significantly increased QA-induced [ 18 F]-fluoro-2-deoxyglucose uptake, an indirect index of glutamate uptake by astrocytes. Together, these data demonstrate that CNTF activation of astrocytes in vivo is associated with marked phenotypic and molecular changes leading to a better handling of increased levels of extracellular glutamate. Activated astrocytes may therefore be important prosurvival agents in pathological conditions involving defects in glutamate homeostasis.
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Carole Escartin,
Emmanuel Brouillet,
Paolo Gubellini,
Yaël Trioulier,
Carine Jacquard,
Claire Smadja,
Graham W Knott,
Lydia Kerkerian-Le Goff,
Nicole Déglon,
Philippe Hantraye, Gilles Bonvento
[show abstract]
[hide abstract]
ABSTRACT: To study the functional role of activated astrocytes in glutamate homeostasis in vivo, we used a model of sustained astrocytic activation in the rat striatum through lentiviral-mediated gene delivery of ciliary neurotrophic factor (CNTF). CNTF-activated astrocytes were hypertrophic, expressed immature intermediate filament proteins and highly glycosylated forms of their glutamate transporters GLAST and GLT-1. CNTF overexpression produced a redistribution of GLAST and GLT-1 into raft functional membrane microdomains, which are important for glutamate uptake. In contrast, CNTF had no detectable effect on the expression of a number of neuronal proteins and on the spontaneous glutamatergic transmission recorded from striatal medium spiny neurons. These results were replicated in vitro by application of recombinant CNTF on a mixed neuron/astrocyte striatal culture. Using microdialysis in the rat striatum, we found that the accumulation of extracellular glutamate induced by quinolinate (QA) was reduced threefold with CNTF. In line with this result, CNTF significantly increased QA-induced [(18)F]-fluoro-2-deoxyglucose uptake, an indirect index of glutamate uptake by astrocytes. Together, these data demonstrate that CNTF activation of astrocytes in vivo is associated with marked phenotypic and molecular changes leading to a better handling of increased levels of extracellular glutamate. Activated astrocytes may therefore be important prosurvival agents in pathological conditions involving defects in glutamate homeostasis.
The Journal of neuroscience : the official journal of the Society for Neuroscience. 01/2006; 26(22):5978-89.
