21 results on '"Horvat, Anemari"'
Search Results
2. Astrocytes with TDP-43 inclusions exhibit reduced noradrenergic cAMP and Ca2+ signaling and dysregulated cell metabolism
- Author
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Velebit, Jelena, Horvat, Anemari, Smolič, Tina, Prpar Mihevc, Sonja, Rogelj, Boris, Zorec, Robert, and Vardjan, Nina
- Published
- 2020
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3. Astrocyte Specific Remodeling of Plasmalemmal Cholesterol Composition by Ketamine Indicates a New Mechanism of Antidepressant Action
- Author
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Lasič, Eva, Lisjak, Marjeta, Horvat, Anemari, Božić, Mićo, Šakanović, Aleksandra, Anderluh, Gregor, Verkhratsky, Alexei, Vardjan, Nina, Jorgačevski, Jernej, Stenovec, Matjaž, and Zorec, Robert
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- 2019
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4. Adrenergic activation attenuates astrocyte swelling induced by hypotonicity and neurotrauma
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Vardjan, Nina, Horvat, Anemari, Anderson, Jamie E., Yu, Dou, Croom, Deborah, Zeng, Xiang, Lužnik, Zala, Kreft, Marko, Teng, Yang D., Kirov, Sergei A., and Zorec, Robert
- Published
- 2016
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5. Excitation-energy coupling and vesicle-based signaling in astrocytes: SYM.062
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Vardjan, Nina, Kreft, Marko, Chowdhury, Helena H, Horvat, Anemari, Stenovec, Matjaž, Lasič, Eva, Lisjak, Marjeta, Rituper, Boštjan, Jorgačevski, Jernej, Potokar, Maja, Gabrijel, Mateja, and Zorec, Robert
- Published
- 2016
6. The Activation of GPR27 Increases Cytosolic L-Lactate in 3T3 Embryonic Cells and Astrocytes.
- Author
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Dolanc, Dorian, Zorec, Tomaž M., Smole, Zala, Maver, Anja, Horvat, Anemari, Pillaiyar, Thanigaimalai, Trkov Bobnar, Saša, Vardjan, Nina, Kreft, Marko, Chowdhury, Helena Haque, and Zorec, Robert
- Subjects
MONOCARBOXYLATE transporters ,FLUORESCENCE resonance energy transfer ,ORPHANS ,ASTROCYTES - Abstract
G-protein-coupled receptors (GPCRs) represent a family with over 800 members in humans, and one-third of these are targets for approved drugs. A large number of GPCRs have unknown physiologic roles. Here, we investigated GPR27, an orphan GPCR belonging to the family of super conserved receptor expressed in the brain, with unknown functions. Cytosolic levels of L-lactate ([lactate]
i ), the end product of aerobic glycolysis, were measured with the Laconic fluorescence resonance energy transfer nanosensor. In single 3T3 wild-type (WT) embryonic cells, the application of 8535 (1 µM), a surrogate agonist known to activate GPR27, resulted in an increase in [lactate]i . Similarly, an increase was recorded in primary rat astrocytes, a type of neuroglial cell abundant in the brain, which contain glycogen and express enzymes of aerobic glycolysis. In CRISPR-Cas9 GPR27 knocked out 3T3 cells, the 8535-induced increase in [lactate]i was reduced compared with WT controls. Transfection of the GPR27-carrying plasmid into the 3T3KOGPR27 cells rescued the 8535-induced increase in [lactate]i . These results indicate that stimulation of GPR27 enhances aerobic glycolysis and L-lactate production in 3T3 cells and astrocytes. Interestingly, in the absence of GPR27 in 3T3 cells, resting [lactate]i was increased in comparison with controls, further supporting the view that GPR27 regulates L-lactate homeostasis. [ABSTRACT FROM AUTHOR]- Published
- 2022
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7. Astrocyte arborization enhances Ca2+ but not cAMP signaling plasticity.
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Pirnat, Samo, Božić, Mićo, Dolanc, Dorian, Horvat, Anemari, Tavčar, Petra, Vardjan, Nina, Verkhratsky, Alexei, Zorec, Robert, and Stenovec, Matjaž
- Published
- 2021
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8. Lactate as an Astroglial Signal Augmenting Aerobic Glycolysis and Lipid Metabolism.
- Author
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Horvat, Anemari, Zorec, Robert, and Vardjan, Nina
- Subjects
LIPID metabolism ,LACTATION ,G protein coupled receptors ,GLYCOLYSIS ,HOMEOSTASIS - Abstract
Astrocytes, heterogeneous neuroglial cells, contribute to metabolic homeostasis in the brain by providing energy substrates to neurons. In contrast to predominantly oxidative neurons, astrocytes are considered primarily as glycolytic cells. They take up glucose from the circulation and in the process of aerobic glycolysis (despite the normal oxygen levels) produce L-lactate, which is then released into the extracellular space via lactate transporters and possibly channels. Astroglial L-lactate can enter neurons, where it is used as a metabolic substrate, or exit the brain via the circulation. Recently, L-lactate has also been considered to be a signaling molecule in the brain, but the mechanisms of L-lactate signaling and how it contributes to the brain function remain to be fully elucidated. Here, we provide an overview of L-lactate signaling mechanisms in the brain and present novel insights into the mechanisms of L-lactate signaling via G-protein coupled receptors (GPCRs) with the focus on astrocytes. We discuss how increased extracellular L-lactate upregulates cAMP production in astrocytes, most likely via L-lactate-sensitive G
s -protein coupled GPCRs. This activates aerobic glycolysis, enhancing L-lactate production and accumulation of lipid droplets, suggesting that L-lactate augments its own production in astrocytes (i.e., metabolic excitability) to provide more L-lactate for neurons and that astrocytes in conditions of increased extracellular L-lactate switch to lipid metabolism. [ABSTRACT FROM AUTHOR]- Published
- 2021
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9. Astrocytes in stress accumulate lipid droplets.
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Smolič, Tina, Tavčar, Petra, Horvat, Anemari, Černe, Urška, Halužan Vasle, Ana, Tratnjek, Larisa, Kreft, Mateja Erdani, Scholz, Nicole, Matis, Maja, Petan, Toni, Zorec, Robert, and Vardjan, Nina
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- 2021
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10. PROCEEDINGS OF VOLGA NEUROSCIENCE MEETING 2016 AND VOLGA NEUROSCIENCE SCHOOL 2016 Section CELLULAR NEUROSCIENCE
- Author
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Yasuda, Ryohei, Rose, Christine R., Davies, H.A., Mizuno, K., Kirby, A., Giese, K.P., Aziz, W., Kraev, I., Stewart, M.G., Demyanenko, S.V., Uzdensky, A.B., Nikulin, Vadim, Nazarova, Maria, Fedele, Tommaso, Blagovechtchenski, Evgeni, Zorec, Robert, Gabrijel, Mateja, Potokar, Maja, Jorgacevski, Jernej, Rituper, Bostjan, Lisjak, Marjeta, Lasic, Eva, Stenovec, Matjaz, Horvat, Anemari, Chowdhury, Helena H., Kreft, Marko, Vardjan, Nina, Revishchin, A., Kovalzon, V., Panteleev, D., Kust, N., Shamadykova, Dz., Pavlova, G., Semyanov, Alexey, Fejtova, A., Montenegro-Venegas, C., Dirks, A., Ivanova, D., Gundelfinger, E.D., Kavalali, Ege T., Monteggia, Lisa M., Nosyreva, Elena, Kaczmarek, Leszek, Petersen, J., Cordelieres, F., Hangen, E., Coussen, F., Lim, D., Rouach, Nathalie, Bezzi, Paola, Edwards, R., Giros, B., Deglon, N., Kirchhoff, F., Dellerac, G., Cali, C., Petrelli, F., Tamara, Z., Pucci, L., Kettenmann, Helmut, Volynski, Kirill, Oertner, Thomas G., Schulze, Christian, Wiegert, J. Simon, Durst, Celine, Mothet, Jean-Pierre, Roche, Katherine, Henley, Jeremy, Choquet, Daniel, Yoshioka, Yusaku, Noda, Mami, Rusakov, D.A., Schmidt, Hartmut, Gerkau, Niklas, Kleinhans, Christian, and Kafitz, Karl W.
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- 2016
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11. Astroglial cAMP signalling in space and time.
- Author
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Horvat, Anemari and Vardjan, Nina
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Highlights • Genetically encoded fluorescent cAMP sensors have enabled the first measurements of the temporal dynamics of cAMP signalling in living astrocytes. • Compared with Ca2+ signalling with fast phasic dynamics, cAMP signalling in astrocytes -exhibits >4-fold slower tonic dynamics. • Ca2+ potentiates cAMP signalling -in astrocytes, indicating cross-talk between the Ca2+- and cAMP-signalling pathways. • Astroglial cAMP signalling in subcellular compartments needs to be evaluated in the future. Abstract To maintain a high level of specificity and normal cell function, the cyclic adenosine monophosphate (cAMP) pathway is tightly regulated in space and time. Recent advances in cAMP reporter technology have provided insights into spatio-temporal characteristics of cAMP signalling in individual living cells, including astrocytes. Astrocytes are glial cells in the central nervous system with many homeostatic functions. In contrast to neurons, astrocytes are electrically silent, but, in response to extracellular stimuli through activation of surface receptors, they can increase intracellular levels of secondary messengers, e.g. Ca2+ and cAMP. This enables them to communicate with neighbouring cells, such as neurons and endothelial cells of blood vessels. The dynamics of receptor-mediated Ca2+ signalling in astrocytes has been extensively studied in the past in contrast to cAMP signalling. Here, we present the first insights into the temporal dynamics of cAMP signalling in living astrocytes, which revealed that cAMP signals in astrocytes exhibit tonic dynamics and are slower than Ca2+ signals with phasic dynamics. We debate on the heterogeneity of basal cAMP levels in astrocytes and how hypotonicity-induced astrocyte swelling affects temporal dynamics of cAMP signalling. Understanding the spatio-temporal characteristics of cAMP signalling in astrocytes is of extreme importance because cAMP governs many important cellular processes and any malfunctions may lead to pathology. [ABSTRACT FROM AUTHOR]
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- 2019
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12. Enhancement of Astroglial Aerobic Glycolysis by Extracellular Lactate-Mediated Increase in cAMP.
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Vardjan, Nina, Chowdhury, Helena H., Horvat, Anemari, Velebit, Jelena, Malnar, Maja, Muhič, Marko, Kreft, Marko, Krivec, Špela G., Bobnar, Saša T., Miš, Katarina, Pirkmajer, Sergej, Offermanns, Stefan, Henriksen, Gjermund, Storm-Mathisen, Jon, Bergersen, Linda H., and Zorec, Robert
- Subjects
GLYCOLYSIS ,ASTROCYTES ,LACTATES - Abstract
Besides being a neuronal fuel, L-lactate is also a signal in the brain. Whether extracellular L-lactate affects brain metabolism, in particular astrocytes, abundant neuroglial cells, which produce L-lactate in aerobic glycolysis, is unclear. Recent studies suggested that astrocytes express low levels of the L-lactate GPR81 receptor (EC
50 ≈ 5 mM) that is in fat cells part of an autocrine loop, in which the Gi-protein mediates reduction of cytosolic cyclic adenosine monophosphate (cAMP). To study whether a similar signaling loop is present in astrocytes, affecting aerobic glycolysis, we measured the cytosolic levels of cAMP, D-glucose and L-lactate in single astrocytes using fluorescence resonance energy transfer (FRET)-based nanosensors. In contrast to the situation in fat cells, stimulation by extracellular L-lactate and the selective GPR81 agonists, 3-chloro-5-hydroxybenzoic acid (3Cl-5OH-BA) or 4-methyl-N-(5-(2-(4-methylpiperazin- 1-yl)-2-oxoethyl)-4-(2-thienyl)-1,3-thiazol-2-yl)cyclohexanecarboxamide (Compound 2), like adrenergic stimulation, elevated intracellular cAMP and L-lactate in astrocytes, which was reduced by the inhibition of adenylate cyclase. Surprisingly, 3Cl-5OH-BA and Compound 2 increased cytosolic cAMP also in GPR81-knock out astrocytes, indicating that the effect is GPR81-independent and mediated by a novel, yet unidentified, excitatory L-lactate receptor-like mechanism in astrocytes that enhances aerobic glycolysis and L-lactate production via a positive feedback mechanism. [ABSTRACT FROM AUTHOR]- Published
- 2018
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13. Adrenergic stimulation of single rat astrocytes results in distinct temporal changes in intracellular Ca2+ and cAMP-dependent PKA responses.
- Author
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Horvat, Anemari, Zorec, Robert, and Vardjan, Nina
- Abstract
During the arousal and startle response, locus coeruleus neurons, innervating practically all brain regions, release catecholamine noradrenaline, which reaches neural brain cells, including astrocytes. These glial cells respond to noradrenergic stimulation by simultaneous activation of the α- and β-adrenergic receptors (ARs) in the plasma membrane with increasing cytosolic levels of Ca 2+ and cAMP, respectively. AR-activation controls a myriad of processes in astrocytes including glucose metabolism, gliosignal vesicle homeostasis, gene transcription, cell morphology and antigen-presenting functions, all of which have distinct temporal characteristics. It is known from biochemical studies that Ca 2+ and cAMP signals in astrocytes can interact, however it is presently unclear whether the temporal properties of the two second messengers are time associated upon AR-activation. We used confocal microscopy to study AR agonist-induced intracellular changes in Ca 2+ and cAMP in single cultured cortical rat astrocytes by real-time monitoring of the Ca 2+ indicator Fluo4-AM and the fluorescence resonance energy transfer-based nanosensor A-kinase activity reporter 2 (AKAR2), which reports the activity of cAMP via its downstream effector protein kinase A (PKA). The results revealed that the activation of α 1 -ARs by phenylephrine triggers periodic (phasic) Ca 2+ oscillations within 10 s, while the activation of β-ARs by isoprenaline leads to a ∼10-fold slower tonic rise to a plateau in cAMP/PKA activity devoid of oscillations. Thus the concomitant activation of α- and β-ARs triggers the Ca 2+ and cAMP second messenger systems in astrocytes with distinct temporal properties, which appears to be tailored to regulate downstream effectors in different time domains. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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14. Memory Formation Shaped by Astroglia.
- Author
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Zorec, Robert, Horvat, Anemari, Vardjan, Nina, and Verkhratsky, Alexei
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ASTROCYTES ,MEMORY ,CENTRAL nervous system physiology ,PHYSIOLOGY - Abstract
Astrocytes, the most heterogeneous glial cells in the central nervous system (CNS), execute a multitude of homeostatic functions and contribute to memory formation. Consolidation of synaptic and systemic memory is a prolonged process and hours are required to form long-term memory. In the past, neurons or their parts have been considered to be the exclusive cellular sites of these processes, however, it has now become evident that astrocytes provide an important and essential contribution to memory formation. Astrocytes participate in the morphological remodeling associated with synaptic plasticity, an energy-demanding process that requires mobilization of glycogen, which, in the CNS, is almost exclusively stored in astrocytes. Synaptic remodeling also involves bidirectional astroglial-neuronal communication supported by astroglial receptors and release of gliosignaling molecules. Astroglia exhibit cytoplasmic excitability that engages second messengers, such as Ca
2+ , for phasic, and cyclic adenosine monophosphate (cAMP), for tonic signal coordination with neuronal processes. The detection of signals by astrocytes and the release of gliosignaling molecules, in particular by vesicle-based mechanisms, occurs with a significant delay after stimulation, orders of magnitude longer than that present in stimulus-secretion coupling in neurons. These particular arrangements position astrocytes as integrators ideally tuned to support time-dependent memory formation. [ABSTRACT FROM AUTHOR]- Published
- 2015
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15. Cover Image, Volume 69, Issue 12.
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Pirnat, Samo, Božić, Mićo, Dolanc, Dorian, Horvat, Anemari, Tavčar, Petra, Vardjan, Nina, Verkhratsky, Alexei, Zorec, Robert, and Stenovec, Matjaž
- Published
- 2021
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16. Ca2+ as the prime trigger of aerobic glycolysis in astrocytes.
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Horvat, Anemari, Muhič, Marko, Smolič, Tina, Begić, Ena, Zorec, Robert, Kreft, Marko, and Vardjan, Nina
- Abstract
[Display omitted] • Ca
2+ signals are key triggers of augmented aerobic glycolysis in astrocytes. • cAMP aids to Ca2+ -driven increase in aerobic glycolysis in astrocytes. • Aerobic glycolysis in astrocytes depends on extracellular d -glucose. • Aerobic glycolysis in astrocytes depends on glycogen shunt activity. Astroglial aerobic glycolysis, a process during which d -glucose is converted to l -lactate, a brain fuel and signal, is regulated by the plasmalemmal receptors, including adrenergic receptors (ARs) and purinergic receptors (PRs), modulating intracellular Ca2+ and cAMP signals. However, the extent to which the two signals regulate astroglial aerobic glycolysis is poorly understood. By using agonists to stimulate intracellular α 1 -/β-AR-mediated Ca2+ /cAMP signals, β-AR-mediated cAMP and P 2 R-mediated Ca2+ signals and genetically encoded fluorescence resonance energy transfer-based glucose and lactate nanosensors in combination with real-time microscopy, we show that intracellular Ca2+ , but not cAMP, initiates a robust increase in the concentration of intracellular free d -glucose ([glc] i) and l -lactate ([lac] i), both depending on extracellular d -glucose, suggesting Ca2+ -triggered glucose uptake and aerobic glycolysis in astrocytes. When the glycogen shunt, a process of glycogen remodelling, was inhibited, the α 1 -/β-AR-mediated increases in [glc] i and [lac] i were reduced by ∼65 % and ∼30 %, respectively, indicating that at least ∼30 % of the utilization of d -glucose is linked to glycogen remodelling and aerobic glycolysis. Additional activation of β-AR/cAMP signals aided to α 1 -/β-AR-triggered [lac] i increase, whereas the [glc] i increase was unaltered. Taken together, an increase in intracellular Ca2+ is the prime mechanism of augmented aerobic glycolysis in astrocytes, while cAMP has only a moderate role. The results provide novel information on the signals regulating brain metabolism and open new avenues to explore whether astroglial Ca2+ signals are dysregulated and contribute to neuropathologies with impaired brain metabolism. [ABSTRACT FROM AUTHOR]- Published
- 2021
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17. ERNEST COST action overview on the (patho)physiology of GPCRs and orphan GPCRs in the nervous system.
- Author
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Birgül Iyison, Necla, Abboud, Clauda, Abboud, Dayana, Abdulrahman, Abdulrasheed O., Bondar, Ana‐Nicoleta, Dam, Julie, Georgoussi, Zafiroula, Giraldo, Jesús, Horvat, Anemari, Karoussiotis, Christos, Paz‐Castro, Alba, Scarpa, Miriam, Schihada, Hannes, Scholz, Nicole, Güvenc Tuna, Bilge, and Vardjan, Nina
- Abstract
G protein‐coupled receptors (GPCRs) are a large family of cell surface receptors that play a critical role in nervous system function by transmitting signals between cells and their environment. They are involved in many, if not all, nervous system processes, and their dysfunction has been linked to various neurological disorders representing important drug targets. This overview emphasises the GPCRs of the nervous system, which are the research focus of the members of ERNEST COST action (CA18133) working group ‘Biological roles of signal transduction’. First, the (patho)physiological role of the nervous system GPCRs in the modulation of synapse function is discussed. We then debate the (patho)physiology and pharmacology of opioid, acetylcholine, chemokine, melatonin and adhesion GPCRs in the nervous system. Finally, we address the orphan GPCRs, their implication in the nervous system function and disease, and the challenges that need to be addressed to deorphanize them. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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18. Inhibiting glycolysis rescues memory impairment in an intellectual disability Gdi1-null mouse
- Author
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Maja Malnar, Angela Bachi, Helena H. Chowdhury, Anemari Horvat, Patrizia D’Adamo, Antonia Gurgone, Saša Trkov Bobnar, Marko Muhič, Lorenzo Piemonti, Maria Lidia Mignogna, Michela Masetti, Jelena Velebit, Veronica Bianchi, Robert Zorec, Matjaž Stenovec, Alessia Mercalli, Katja Fink, Sara Belloli, Stefano Taverna, Maja Potokar, Marko Kreft, Rosa Maria Moresco, Nina Vardjan, Maddalena Ripamonti, Umberto Restuccia, D'Adamo, Patrizia, Horvat, Anemari, Gurgone, Antonia, Mignogna, Maria Lidia, Bianchi, Veronica, Masetti, Michela, Ripamonti, Maddalena, Taverna, Stefano, Velebit, Jelena, Malnar, Maja, Muhič, Marko, Fink, Katja, Bachi, Angela, Restuccia, Umberto, Belloli, Sara, Moresco, Rosa Maria, Mercalli, Alessia, Piemonti, Lorenzo, Potokar, Maja, Bobnar, Saša Trkov, Kreft, Marko, Chowdhury, Helena H, Stenovec, Matjaž, Vardjan, Nina, Zorec, R, D'Adamo, P, Horvat, A, Gurgone, A, Mignogna, M, Bianchi, V, Masetti, M, Ripamonti, M, Taverna, S, Velebit, J, Malnar, M, Muhic, M, Fink, K, Bachi, A, Restuccia, U, Belloli, S, Moresco, R, Mercalli, A, Piemonti, L, Potokar, M, Bobnar, S, Kreft, M, Chowdhury, H, Stenovec, M, and Vardjan, N
- Subjects
0301 basic medicine ,CTX, context memory ,Male ,Endocrinology, Diabetes and Metabolism ,Glucose uptake ,Intellectual disability ,FRET, Förster Resonance Energy Transfer ,SV, synaptic vesicle ,XLID, X-linked intellectual disability ,Mice ,0302 clinical medicine ,Endocrinology ,Basic Science ,GDI1 knockout mice ,Aerobic glycolysis ,Astrocytes ,cAMP ,Glycolysis ,Gdi1 KO, full knockout of Gdi1 ,Cells, Cultured ,Guanine Nucleotide Dissociation Inhibitors ,NA, noradrenaline ,Mice, Knockout ,Cultured ,3-Cl-5-OH-BA, 3-chloro-5-hydroxybenzoic acid ,Animals ,Brain ,Deoxyglucose ,Down-Regulation ,Glucose ,Intellectual Disability ,Maze Learning ,Memory ,Memory Disorders ,[18F]-FDG, [18F]-fluoro-2-deoxy-d-glucose ,Aerobic glycolysi ,cAMP, cyclic adenosine monophosphate ,GlastGdi1flox/Y, GLAST:CreERT2+/Gdi1lox/Y inducible astrocyte-specific Gdi1 KO male mice ,medicine.anatomical_structure ,intellectual disability ,Knockout mouse ,Astrocyte ,Gdi1 WT, wild type ,medicine.medical_specialty ,Cells ,Knockout ,030209 endocrinology & metabolism ,Biology ,2-DG, 2-deoxy-d-glucose ,sEPSCs, spontaneous excitatory postsynaptic currents ,CNS, central nervous system ,SEM, standard error of the mean ,03 medical and health sciences ,αGDI, α guanosine dissociation inhibitor protein coded by GDI1 gene ,CFP, cyan fluorescent protein ,Downregulation and upregulation ,Internal medicine ,medicine ,aerobic glycolysis ,GlastGdi1X/Y, male mice (Gdi1X/Y) carrying the GLAST:CreERT2 transgene ,GLUT1, d-glucose transporter ,Wild type ,astrocytes ,GFAP, glial fibrillary acidic protein ,PSD, postsynaptic density ,GDI1, guanosine dissociation inhibitor 1 gene ,YFP, yellow fluorescent protein ,030104 developmental biology ,GPCR, G-protein coupled receptor ,Anaerobic glycolysis ,GPR81, G-protein receptor 81 ,CS, conditional stimulus, tone ,PKA, protein kinase A ,MCTs, monocarboxylate transporters ,Homeostasis - Abstract
Objectives GDI1 gene encodes for αGDI, a protein controlling the cycling of small GTPases, reputed to orchestrate vesicle trafficking. Mutations in human GDI1 are responsible for intellectual disability (ID). In mice with ablated Gdi1, a model of ID, impaired working and associative short-term memory was recorded. This cognitive phenotype worsens if the deletion of αGDI expression is restricted to neurons. However, whether astrocytes, key homeostasis providing neuroglial cells, supporting neurons via aerobic glycolysis, contribute to this cognitive impairment is unclear. Methods We carried out proteomic analysis and monitored [18F]-fluoro-2-deoxy-d-glucose uptake into brain slices of Gdi1 knockout and wild type control mice. d-Glucose utilization at single astrocyte level was measured by the Förster Resonance Energy Transfer (FRET)-based measurements of cytosolic cyclic AMP, d-glucose and L-lactate, evoked by agonists selective for noradrenaline and L-lactate receptors. To test the role of astrocyte-resident processes in disease phenotype, we generated an inducible Gdi1 knockout mouse carrying the Gdi1 deletion only in adult astrocytes and conducted behavioural tests. Results Proteomic analysis revealed significant changes in astrocyte-resident glycolytic enzymes. Imaging [18F]-fluoro-2-deoxy-d-glucose revealed an increased d-glucose uptake in Gdi1 knockout tissue versus wild type control mice, consistent with the facilitated d-glucose uptake determined by FRET measurements. In mice with Gdi1 deletion restricted to astrocytes, a selective and significant impairment in working memory was recorded, which was rescued by inhibiting glycolysis by 2-deoxy-d-glucose injection. Conclusions These results reveal a new astrocyte-based mechanism in neurodevelopmental disorders and open a novel therapeutic opportunity of targeting aerobic glycolysis, advocating a change in clinical practice., Highlights • Mutations in human Gdi1, encoding αGDI, a protein controlling vesicle traffic, are responsible for Intellectual Disability. • Gdi1 knockout revealed significant changes in astrocyte-resident glycolytic enzymes and facilitated D-glucose utilization. • Astrocyte-selective Gdi1 deletion impairs working memory, which can be rescued by administration of 2-deoxy-D-glucose. • Astrocyte-based glycolysis is a new target to treat Intellectual Disability.
- Published
- 2021
19. Astrocyte arborization enhances Ca 2+ but not cAMP signaling plasticity.
- Author
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Pirnat S, Božić M, Dolanc D, Horvat A, Tavčar P, Vardjan N, Verkhratsky A, Zorec R, and Stenovec M
- Subjects
- Calcium Signaling physiology, Cells, Cultured, Astrocytes metabolism, Signal Transduction
- Abstract
The plasticity of astrocytes is fundamental for their principal function, maintaining homeostasis of the central nervous system throughout life, and is associated with diverse exposomal challenges. Here, we used cultured astrocytes to investigate at subcellular level basic cell processes under controlled environmental conditions. We compared astroglial functional and signaling plasticity in standard serum-containing growth medium, a condition mimicking pathologic conditions, and in medium without serum, favoring the acquisition of arborized morphology. Using opto-/electrophysiologic techniques, we examined cell viability, expression of astroglial markers, vesicle dynamics, and cytosolic Ca
2+ and cAMP signaling. The results revealed altered vesicle dynamics in arborized astrocytes that was associated with increased resting [Ca2+ ]i and increased subcellular heterogeneity in [Ca2+ ]i , whereas [cAMP]i subcellular dynamics remained stable in both cultures, indicating that cAMP signaling is less prone to plastic remodeling than Ca2+ signaling, possibly also in in vivo contexts., (© 2021 The Authors. GLIA published by Wiley Periodicals LLC.)- Published
- 2021
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20. Ca 2+ as the prime trigger of aerobic glycolysis in astrocytes.
- Author
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Horvat A, Muhič M, Smolič T, Begić E, Zorec R, Kreft M, and Vardjan N
- Subjects
- Animals, Astrocytes drug effects, Cells, Cultured, Cerebral Cortex cytology, Cerebral Cortex drug effects, Cerebral Cortex metabolism, Female, Glycolysis drug effects, Isoproterenol pharmacology, Phenylephrine pharmacology, Rats, Rats, Wistar, Astrocytes metabolism, Calcium metabolism, Glucose metabolism, Glycolysis physiology
- Abstract
Astroglial aerobic glycolysis, a process during which d-glucose is converted to l-lactate, a brain fuel and signal, is regulated by the plasmalemmal receptors, including adrenergic receptors (ARs) and purinergic receptors (PRs), modulating intracellular Ca
2+ and cAMP signals. However, the extent to which the two signals regulate astroglial aerobic glycolysis is poorly understood. By using agonists to stimulate intracellular α1 -/β-AR-mediated Ca2+ /cAMP signals, β-AR-mediated cAMP and P2 R-mediated Ca2+ signals and genetically encoded fluorescence resonance energy transfer-based glucose and lactate nanosensors in combination with real-time microscopy, we show that intracellular Ca2+ , but not cAMP, initiates a robust increase in the concentration of intracellular free d-glucose ([glc]i ) and l-lactate ([lac]i ), both depending on extracellular d-glucose, suggesting Ca2+ -triggered glucose uptake and aerobic glycolysis in astrocytes. When the glycogen shunt, a process of glycogen remodelling, was inhibited, the α1 -/β-AR-mediated increases in [glc]i and [lac]i were reduced by ∼65 % and ∼30 %, respectively, indicating that at least ∼30 % of the utilization of d-glucose is linked to glycogen remodelling and aerobic glycolysis. Additional activation of β-AR/cAMP signals aided to α1 -/β-AR-triggered [lac]i increase, whereas the [glc]i increase was unaltered. Taken together, an increase in intracellular Ca2+ is the prime mechanism of augmented aerobic glycolysis in astrocytes, while cAMP has only a moderate role. The results provide novel information on the signals regulating brain metabolism and open new avenues to explore whether astroglial Ca2+ signals are dysregulated and contribute to neuropathologies with impaired brain metabolism., (Copyright © 2021 The Author(s). Published by Elsevier Ltd.. All rights reserved.)- Published
- 2021
- Full Text
- View/download PDF
21. Targeting Astrocytes for Treating Neurological Disorders: Carbon Monoxide and Noradrenaline-Induced Increase in Lactate.
- Author
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Horvat A, Vardjan N, and Zorec R
- Subjects
- Animals, Astrocytes drug effects, Drug Delivery Systems methods, Drug Delivery Systems trends, Humans, Nervous System Diseases drug therapy, Neuroprotection drug effects, Astrocytes metabolism, Carbon Monoxide administration & dosage, Lactic Acid metabolism, Nervous System Diseases metabolism, Neuroprotection physiology, Norepinephrine administration & dosage
- Abstract
There are at least three reasons why brain astrocytes represent a new target for treating neurological disorders. First, although the human neocortex represents over 80% of brain mass, neurons are outnumbered by non-neuronal cells, including astrocytes, a neuroglial cell type. Second, as in neurons, vesicle-based release of transmitters is present in astrocytes, however with much slower kinetics than in neurons. Third, astrocytes contain glycogen, which can be transformed to L-lactate in glycolysis. L-lactate is considered to be a fuel and a signalling molecule involved in cognition and neuroprotection. The mechanisms of neuroprotection are unclear but may be linked to carbon monoxide, a product of the heme oxygenase, an evolutionarily conserved cellular cytoprotectant. Increased levels of local carbon monoxide arising from heme oxygenase activity may increase L-lactate, but direct measurements of cytosolic L-lactate are lacking. A fluorescence resonance energy transfer-based nanosensor selective for L-lactate was used to monitor cytosolic levels of L-lactate while cultured astrocytes were exposed to carbon monoxide. The results revealed that in astrocytes exposed to carbon monoxide there is no significant increase in L-lactate, however, when noradrenaline, a potent glycogenolytic agent, is applied, cytosolic levels of Llactate are increased, but strongly attenuated in astrocytes pretreated with carbon monoxide. These first measurements of carbon monoxide-modulated L-lactate levels in astrocytes provide evidence that the L-lactate and heme oxygenase neuroprotective systems may interact. In conclusion, not only the abundance of astrocytes but their signalling capacity using vesicles and metabolites, such as L-lactate, are valid targets for neurological disorders., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.)
- Published
- 2017
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