Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0017638 (glioma)
 30,880 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Embryonic rat hippocampal neurons were cultured in a serum-free defined medium (MEM/N3) either directly on poly-D-lysine (PDL) or on a confluent monolayer of postnatal cortical astrocytes, C6 glioma cells, or Rat2 fibroblasts. Neurons on PDL were grown in MEM/N3 or in MEM/N3 conditioned for 24 h by astrocytes or C6 cells. Membrane capacitance (Cm) and gamma-aminobutyric acid (GABA)-, glycine-, kainate-, and N-methyl-D-aspartate (NMDA)-induced currents were quantified using whole-cell patch-clamp recordings. Cm as well as the amplitude and the density of these currents in neurons cultured on astrocytes were significantly greater than those in neurons grown on PDL after 24 and 48 h. C6 cells mimicked astrocytes in promoting Cm and GABA-, glycine-, and NMDA-evoked, but not kainate-evoked, currents. Cm and currents in neurons grown on Rat2 cells were comparable to those in neurons on PDL. Astrocytes maintained in culture for 3 months were noticeably less effective than freshly prepared ones just grown to confluence. Suppression of spontaneous cytoplasmic Ca2+ (Ca[c]2+) elevations in astrocytes by 1,2-bis(2-aminophenoxy) ehane-N, N, N, N-tetraacetic acid acetoxymethyl ester (BAPTA-AM) loaded intracellularly blocked the observed modulatory effects. Medium conditioned by either astrocytes or C6 cells mimicked the effects of direct coculture of neurons on these cells in promoting Cm and amino acid-evoked currents. Inclusion of antagonists at GABA and glutamate receptors in coculture experiments blocked the observed effects. Thus, diffusible substances synthesized and/ or secreted by astrocytes in a Ca(c)2+-dependent manner can regulate neuronal growth and aminoacid receptor function, and these effects may involve neuronal GABA and glutamate receptors.
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PMID:Astrocytes regulate amino acid receptor current densities in embryonic rat hippocampal neurons. 936 56

Glioma cells in acute slices and in primary culture, and glioma-derived human cell lines were screened for the presence of functional GABA(A) receptors. Currents were measured in whole-cell voltage clamp in response to gamma-aminobutyric acid (GABA). While cells from the most malignant glioma, the glioblastoma multiforme, did not respond to GABA, an inward current (under our experimental conditions with high Cl- concentration in the pipette) was induced in gliomas of lower grades, namely in 71% of oligodendroglioma cells and in 62% of the astrocytoma cells. Glioma cell lines did not express functional GABA(A) receptors, irrespective of the malignancy of the tumour they originate from. The currents elicited by application of GABA were due to activation of GABA(A) receptors; the specific agonist muscimol mimicked the response, the antagonists bicuculline and picrotoxin blocked the GABA-activated current and the benzodiazepine receptor agonist flunitrazepam augmented the GABA-induced current and the benzodiazepine inverse agonist DMCM decreased the GABA current. Cells were heterogeneous with respect to the direction of the current flow as tested in gramicidin perforated patches: in some cells GABA hyperpolarized the membrane, while in the majority it triggered a depolarization. Moreover, GABA triggered an increase in [Ca2+]i in the majority of the tumour cells due to the activation of Ca2+ channels. Our results suggest a link between the expression of GABA receptors and the growth of glioma cells as the disappearance of functional GABA(A) receptors parallels unlimited growth typical for malignant tumours and immortal cell lines.
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PMID:Functional GABA(A) receptors on human glioma cells. 975 31

Lead is an important neurobehavioral toxicant and may interfere with developmental processes in the brain resulting in impairment of its functions. U-373MG, a human glioma cell line, was cultured in Dulbecco's modified Eagles' medium supplemented with either 20 or 10% FBS (fetal bovine serum) to explore the possible indications for lead-induced toxicity. Although lead did not affect cell growth rate in concentrations ranging from 0.01 to 10 microM, it substantially altered gene expression analyzed by reverse-transcription polymerase chain reaction. With 10% FBS culture, lead affected the gene expression in a dose-dependent relationship. It enhanced the expression of tumor necrosis factor-alpha (TNF-alpha), but decreased those of interleukin-1beta (IL-1beta), interleukin-6 (IL-6), gamma-aminobutyric acid (GABA) transaminase, and glutamine synthetase. With 20% FBS culture, lead also profoundly increased TNF-alpha and IL-1beta; however, it did not extensively affect the other genes examined above. Thus, the highly sensitive changes of gene expression of these cytokines or metabolic enzymes after treatments with lead acetate evidenced their usefulness as indicators for in vitro measurement of lead-induced neurotoxicity.
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PMID:In vitro aberrant gene expression as the indicator of lead-induced neurotoxicity in U-373MG cells. 1083 33

We have established a new line of immortalized rat astrocytes through transfection of plasmid pSV3-neo encoding the large T antigen of simian virus 40 into normal astrocytes. One of these immortalized astrocytes (ACT-57) with a flat and polygonal cell shape, exhibited stable growth in a chemically defined medium (modified N-2 medium) as well as in medium containing ordinary serum. ACT-57, retained a detectable level of expression of glial fibrillary acidic protein (GFAP) and its mRNA, and exhibited a stronger expression of nerve growth factor (NGF) mRNA than that of normal rat astrocytes or C6 glioma cells. NGF mRNA was significantly up-regulated by phorbol ester (12-O-tetradecanoylphorbol 13-acetate, TPA) and gamma-amino-n-butyric acid (GABA) but not by hydrocortisone. None of stimulants (TPA, dibutyryl cyclic AMP (db-cAMP), hydrocortisone, L-glutamate, carbacol, GABA, dopamine, or isoproterenol) changed the expression level of either brain-derived neurotrophic factor (BDNF) or neurotrophin-3 (NT-3). There was a discrete difference between ACT-57 and normal astrocytes in the response to GABA and isoproterenol. These findings imply that normal cortical astrocytes possess a functional heterogeneity whereas the clonal astrocyte, ACT-57, does not, indicating that ACT-57 cells may be useful for in vitro studies of neuron-astrocyte interactions involving the induction of neurotrophic factors such as NGF.
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PMID:Isolation and characterization of a new immortal rat astrocyte with a high expression of NGF mRNA. 1122 66

Poly(A(+)) RNA was extracted from the temporal lobe (TL) of medically intractable epileptic patients which underwent surgical TL resection. Injection of this mRNA into Xenopus oocytes led to the expression of ionotropic receptors for gamma-aminobutyric acid (GABA), kainate (KAI) and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA). Membrane currents elicited by GABA inverted polarity at -15 mV, close to the oocyte's chloride equilibrium potential, were inhibited by bicuculline, and were potentiated by pentobarbital and flunitrazepam. These basic characteristics were also displayed by GABA currents elicited in oocytes injected with mRNAs isolated from human TL glioma (TLG) or from mouse TL. However, the GABA receptors expressed by the epileptic TL mRNA exhibited some unusual properties, consisting in a rapid current run-down after repetitive GABA applications and a large EC(50) (125 microM). AMPA alone evoked very small or nil currents, whereas KAI induced larger currents. Nevertheless, upon cyclothiazide treatment, AMPA elicited substantial currents that, like the KAI currents, were inhibited by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). Furthermore, the glutamate receptor 5 (GluR5) agonist, ATPA, failed to evoke an obvious current although both RT-PCR and Western blot analyses showed GluR5 expression in the epileptic TL. Oocytes injected with mouse TL or human TLG mRNAs generated KAI and AMPA currents similar to those evoked in oocytes injected with epileptic TL mRNA but, in contrast to these, the mouse TL and human TLG oocytes were also responsive to ATPA. Our findings are in accord with the concept that both a depression of GABA inhibition and a dysfunction of the KAI-receptor system maintain a high neuronal excitability that results in epileptic seizures.
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PMID:Expression of human epileptic temporal lobe neurotransmitter receptors in Xenopus oocytes: An innovative approach to study epilepsy. 1240 14

Electroencephalographic recordings in cerebral cortex of mice given a single sub-convulsive dose of domoic acid exhibited typical spike and wave discharges. Administration of the anti-epileptic drugs sodium valproate, nimodipine, or 5 alpha-pregnan 3 alpha-ol-20-one as well as pyridoxine simultaneously with or after domoic acid treatment resulted in significantly less spike and wave activity. Administration of these same drugs 45 min prior to the administration of domoic acid also significantly reduced EEG background. Mechanistically, sodium valproate and pyridoxine significantly attenuated domoic acid-induced increase in levels of glutamate, increase in levels of calcium influx, decrease in levels of gamma-aminobutyric acid and increase in levels of the protooncogenes c-fos, jun-B and jun-D. In hippocampal cells, domoic acid-induced increases in glutamate and calcium influx were significantly decreased by pyridoxal phosphate or nimodipine. Similarly in neuroblastoma-glioma hybrid cells (NG 108/15), pyridoxine attenuated domoic acid-induced increases in glutamate, influx of extracellular calcium, and enhanced induction of oncoproteins regardless of whether cells were undifferentiated, differentiated or de-differentiated. Pyridoxine has anti-seizure and neuroprotective actions mediated through mechanisms similar to those targeted by current therapeutic strategies.
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PMID:Neuroprotective actions of pyridoxine. 1268 37

The neuronal glutamate transporter, EAAC1, appears to both limit spillover between excitatory synapses and provide precursor for the synthesis of the inhibitory neurotransmitter, gamma-aminobutyric acid. There is evidence for a large intracellular pool of EAAC1 from which transporter is redistributed to the cell surface following activation of protein kinase C (PKC) or platelet-derived growth factor (PDGF) receptor by seemingly independent pathways. A variety of biotinylation strategies were employed to measure trafficking of EAAC1 to and from the plasma membrane and to examine the effects of phorbol ester and PDGF on these events. Biotinylation of cell surface protein under trafficking-permissive conditions (37 degrees C) resulted in a 2-fold increase in the amount of biotinylated EAAC1 within 15 min in C6 glioma and in primary neuronal cultures, suggesting that EAAC1 has a half-life of approximately 5-7 min for residence at the plasma membrane. Both phorbol ester and PDGF increased the amount of transporter labeled under these conditions. Using a reversible biotinylation strategy, a similarly rapid internalization of EAAC1 was observed in C6 glioma. Phorbol ester, but not PDGF, blocked this measure of internalization. Incubation at 18 degrees C, which blocks some forms of intracellular membrane trafficking, inhibited PKC- and PDGF-dependent redistribution of EAAC1 but had no effect on basal trafficking of EAAC1. These studies suggest that both PKC and PDGF accelerate delivery of EAAC1 to the cell surface and that PKC has an additional effect on endocytosis. The data also suggest that basal and regulated pools of EAAC1 exist in distinct compartments.
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PMID:Rapid trafficking of the neuronal glutamate transporter, EAAC1: evidence for distinct trafficking pathways differentially regulated by protein kinase C and platelet-derived growth factor. 1519 83

Brain neurosteroids modulate gamma-aminobutyric acid type A (GABAA) receptor activity, thereby playing a role in mood disorders. Alterations in 17beta-estradiol (E2) and progesterone (P) are also known to play a significant role in psychopathology in women. The aim of the present study was to evaluate the synthesis of dihydroprogesterone (DHP), tetrahydroprogesterone (THP), and the activity of 5alpha-reductase (5alphaR) which regulates the reduction of P to DHP on exposure to supraphysiological levels of E2 in vitro (C6 glioma cells) and in vivo (mouse brain). The results showed that supraphysiological levels of E2 induced a decrease in the accumulation of both neurosteroids, probably by decreasing the activity of 5alphaR. We hypothesize that the high levels of E2 in pregnancy attenuate the increase in the conversion of P to THP in the brain and that the ratio of E2/P modulates the sedative effect of THP. This process may be relevant to psychopathological disorders that are ascribed to drastic alterations in estrogen levels, such as premenstrual syndrome, pregnancy-related mental disorders, and postpartum "blues".
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PMID:Influence of 17beta-estradiol on the synthesis of reduced neurosteroids in the brain (in vivo) and in glioma cells (in vitro): possible relevance to mental disorders in women. 1531 99

Glutamate transporters (also called excitatory amino acid transporters, EAAT) participate in maintaining extracellular homeostasis of glutamate, a major excitatory neurotransmitter, and regulating glutamate neurotransmission. EAAT3, the major neuronal EAAT, may also regulate gamma-aminobutyric acid-mediated inhibitory neurotransmission. Dysfunction of EAAT3 has been shown to induce seizure in rats. We hypothesize that carbamazepine, a commonly used antiepileptic agent, enhances EAAT3 activity. We tested this hypothesis using oocytes artificially expressing EAAT3 and C6 rat glioma cells expressing endogenous EAAT3. In oocytes, carbamazepine dose-dependently enhanced EAAT3 activity. The EC50 of this carbamazepine effect was 12.2muM. The concentrations of carbamazepine to significantly enhance EAAT3 activity were within the therapeutic serum levels (17-51muM) of carbamazepine for the antiepileptic effect. Carbamazepine decreased the Km but did not change the maximal response of EAAT3 to glutamate. Carbamazepine-increased EAAT3 activity was inhibited by wortmannin or LY-294002, phosphatidylinositol 3-kinase (PI3K) inhibitors, but was not affected by staurosporine, chelerythrine or calphostin C, protein kinase C inhibitors. In C6 cells, carbamazepine also enhanced the endogenous EAAT3 activity. However, carbamazepine did not affect the activity of EAAT4 expressed in Cos7 cells. These results suggest that carbamazepine at clinically relevant concentrations specifically enhances the affinity of EAAT3 for glutamate to increase EAAT3 activity via a PI3K-dependent pathway. EAAT3 may be a therapeutic target for carbamazepine in the central nervous system.
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PMID:Carbamazepine enhances the activity of glutamate transporter type 3 via phosphatidylinositol 3-kinase. 1615 May 75

Scorpion neurotoxins targeting the Na(v) channel can be classified into two classes: alpha- and beta-neurotoxins and are reported as highly active in mammalian brain. In this work, we evaluate the effects of Tityus serrulatus venom (Ts venom) and its alpha-neurotoxin TsTX-V on gamma-aminobutyric acid (GABA), dopamine (DA) and glutamate (Glu) uptake in isolated rat brain synaptosomes. TsTX-V was isolated from Ts venom by ion exchange chromatography followed by reverse-phase (C18) high-performance liquid chromatography. Neither Ts venom nor TsTX-V was able to affect (3)H-Glu uptake. On the other hand, Ts venom (0.13 microg/mg) significantly inhibited both (3)H-GABA and (3)H-DA uptake ( approximately 50%). TsTX-V showed IC(50) values of 9.37 microM and 22.2 microM for the inhibition of (3)H-GABA and (3)H-DA uptake, respectively. These effects were abolished by pre-treatment with tetrodotoxin (TTX, 1 microM), indicating the involvement of voltage-gated Na(+) channels in this process. In the absence of Ca(2+), and at low Ts venom concentrations, the reduction of (3)H-GABA uptake was not as marked as in the presence of Ca(2+). TsTX-V did not reduce (3)H-GABA uptake in COS-7 cells expressing the GABA transporters GAT-1 and GAT-3, suggesting that this toxin indirectly reduces the transport. The reduced (3)H-GABA uptake by synaptosomes might be due to rapid cell depolarization as revealed by confocal microscopy of C6 glioma cells. Thus, TsTX-V causes a reduction of (3)H-GABA and (3)H-DA uptake in a Ca(2+)-dependent manner, not directly affecting GABA transporters, but, in consequence of depolarization, involving voltage-gated Na(+) channels.
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PMID:Effects of Tityus serrulatus scorpion venom and its toxin TsTX-V on neurotransmitter uptake in vitro. 1704 77


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