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)

Transfection of C6 glioma cells with connexin43 (Cx43) cDNA under a constitutive promoter resulted in expression of Cx43 protein, an increase in functional gap junctions, and reduced growth under in vitro and in vivo conditions (D. Zhu et al., Proc. Natl. Acad. Sci. USA, 88: 1883-1887, 1991). To allow for precise temporal and quantitative control of Cx43 gene expression, the Cx43 cDNA was inserted into an expression vector [pSV2M(2)6] containing a modified metallothionein promoter. Upon transfection of this vector into C6 cells, clones were isolated that expressed increased levels of inducible Cx43 protein and dye coupling. The level of induction of Cx43 expression increased with increasing concentration of Zn2+, thus enabling the use of the same clone with different levels of gap junctions present. Although we observed no change in cell growth under in vitro conditions following exposure to Zn2+ or Cd2+, clones with inducible expression of Cx43 were characterized by reduced growth in vivo. Within tumors, the level of expression of Cx43 mRNA and protein corresponded to that seen in vitro following the addition of Zn2+. The suppression of tumor growth in vivo correlated with the level of induced Cx43 expression.
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PMID:Analysis of connexin43 expression under the control of a metallothionein promoter. 889 44

Antibody to galactocerebroside (GalC) evokes a Ca2+ response in cultured glioma U-87 MG cells. The rise in intracellular calcium [Ca2+]i occurs largely due to the influx of Ca2+ through a plasma membrane channel, though the release of Ca2+ from intracellular stores also contributes. We characterized the channel activated by anti-GalC. The channel activity was transient and the inactivation appeared to be Ca2+ dependent. The channel was impermeant to monovalent ions Na+ and K+ and also to Mn2+. Ni2+ and Co2+ neither permeate through the channel nor inhibit the Ca2+ influx. In contrast Cd2+ the most potent inorganic blocker of Ca2+ channels permeated through this channel. The Ca2+ influx was inhibited by verapamil with IC50 of 65 +/- 8 microM. The Ca2+ influx as well as the intracellular release were markedly inhibited by neomycin sulfate and phorbol dibutyrate, suggesting that the Ca2+ influx may be mediated by IP3 (1). Depletion of intracellular Ca2+ stores by thapsigargin was followed by Ca2+ influx. This represents the capacitative Ca2+ entry pathway and is distinct from the channel activated by anti -GalC.
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PMID:A novel type of Ca2+ channel in U-87 MG cells activated by anti-galactocerebroside. 944 38

A hospital case-control study of meningioma was conducted in Heilongjiang Province in northeast China between September 1989 and December 1996. It included 183 cases of newly diagnosed primary meningioma and 366 individually matched hospital controls with non-neoplastic and non-neurological disease selected from six major hospitals. Cases and controls were matched by sex, age and area of residence and interviewed in the hospital wards to obtain information on medical history, occupation and lifestyle. No association with liquor or beer consumption was apparent. Cigarette smoking was positively associated with meningioma risk in women but not in men. In women, compared with non-smokers, the adjusted OR for pack-years of smoking above the median (124) was 6.2 (CI 2.04-18.87). Both of these observations contrast with the results of a study of glioma in the same population, using similar methods. The risk of meningioma was positively associated with reported occupational exposure to lead, tin, cadmium and ionising radiation in both genders.
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PMID:Risk factors for meningioma in adults: a case-control study in northeast China. 1049 19

A number of thiosemicarbazones have been tested previously and herein are included three bis(thiosemicarbazones) for comparison to the previous derivatives. In general the uncomplexed thiosemicarbazones were more potent in the cytotoxic screens than the bis(thiosemicarbazone) except in the murine L1210 and the human colon SW480 screens. Mode of action studies have only demonstrated slight differences in the effects of the two types of compounds on nucleic acid metabolism. The symmetrical and unsymmetrical bis(thiosemicarbazones) complexes of copper, nickel, zinc, and cadmium have been examined to compare them to the heterocyclic N(4)-substituted thiosemicarbazones metal complexes. These new derivatives demonstrated excellent activity against the growth of suspended lymphomas and leukemias although it should be pointed out that generally they were not as active as the copper complexes of N(4)-substituted thiosemicarbazones. Nevertheless, selected bis(thiosemicarbazones) complexes were active against the growth of human lung MB9812, KB nasopharynx, epidermoid A431, glioma UM-86, colon SW480, ovary 1-A9, breast MCK-7, and osteosarcoma Saos-2. In human HL-60 promyelocytic leukemia cells the complexes preferentially inhibited DNA and purine syntheses over 60 min. The regulatory enzyme of the de novo purine pathway, IMP dehydrogenase, appeared to be a major target of the complexes. However, minor inhibition of the activities of DNA polymerase alpha, PRPP-amido transferase, ribonucleotide reductase, and nucleoside kinases occurred over the same time period. No doubt these effects of the complexes on nucleic acid metabolism were additive since the d[NTP] pool levels were reduced after 60 min as was DNA synthesis. The symmetrical and unsymmetrical bis(thiosemicarbazones) and their metal complexes did not cause as severe DNA fragmentation as the heterocyclic N(4)-substituted thiosemicarbazone metal complexes; furthermore, their metabolic effects in the tumor cell were more focused on a single synthetic pathway.
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PMID:The cytotoxicity of symmetrical and unsymmetrical bis(thiosemicarbazones) and their metal complexes in murine and human tumor cells. 1096 96

The induction of apoptotic cell death by cadmium was investigated in eight mammalian cell lines. Great differences in the cytotoxicity of cadmium were found with different cell lines: Rat C6 glioma cells turned out to be most sensitive with an IC50-value of 0.7 microM, while human A549 adenocarcinoma cells were relatively resistant with an IC50-value of 164 microM CdCl2. The mode of cadmium-induced cellular death was identified to involve apoptotic DNA fragmentation in three cell lines, i.e., in C6 glioma cells, E367 neuroblastoma cells and NIH3T3 fibroblasts. In C6 glioma cells, this process was investigated in detail. Internucleosomal DNA-fragmentation occurred 40 h after application of CdCl2 and was concentration-dependent between 1-100 microM CdCl2, followed by a decrease at higher concentrations due to necrotic processes. Apoptotic chromatin-condensation and nuclear fragmentation was observed 48 h after application of 2.5 microM CdCl2. Furthermore, cadmium (1 microM, 48 h) caused a breakdown of the mitochondrial membrane potential as shown by the decline in mitochondrial uptake of rhodamine 123. Also, we found an activation of caspase 9, a protease known to be activated in apoptotic processes following mitochondrial damage. Besides Cd2+, other toxic heavy metal ions (Hg2+, Pb2+, Ni2+, Fe2+, CrO4(2-), Cu2+ or Co2+) did not induce apoptotic DNA fragmentation in C6 cells. The only exception was Zn2+ which caused apotosis at high concentrations (>150 microM) whereas it protected against cadmium-induced apoptosis at low concentrations (10-50 microM).
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PMID:Cadmium-induced apoptosis in C6 glioma cells: mediation by caspase 9-activation. 1186 19

In various mammalian cells, two group IIb metals, cadmium and zinc, induce several morphological and biochemical effects that are salient features of programmed cell death. In C6 rat glioma cells, cadmium caused externalization of phosphatidylserine, breakdown of the mitochondrial membrane potential, activation of caspase-9, internucleosomal DNA fragmentation, chromatin condensation, and nuclear fragmentation. In NIH3T3 murine fibroblasts, cadmium-induced apoptosis was inhibited by overexpression of the antiapoptotic protein Bcl-2. Cadmium-induced DNA fragmentation in C6 cells was independent of inhibition of protein kinase A (PKA), protein kinase C (PKC), mitogen-activated protein kinase (MAPK), phosphatidylinositol-3-kinase, Ca-calmodulin-dependent protein kinase, and protein kinase G. Zinc at moderate concentrations (10-50 microM) protected against programmed cell death induced by cadmium, whereas deprivation of zinc by the membrane-permeable chelator N,N,N',N-terakis-(2-pyridylmethyl)ethylenediamine (TPEN) caused cell death with features characteristic of apoptosis. On the other hand, at elevated extracellular levels (150-200 microM), zinc alone caused programmed cell death in C6 cells. Zinc-induced apoptosis was independent of inhibition of PKA, PKC, guanylate cyclase and MAPK, but it was suppressed in the presence of 100 microM lanthanum chloride.
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PMID:Induction of apoptosis in mammalian cells by cadmium and zinc. 1242 48

Voltage-gated chloride channels have recently been implicated as being important for cell proliferation and invasive cell migration of primary brain tumors cells. In the present study we provide several lines of evidence that glioma Cl- currents are primarily mediated by ClC-2 and ClC-3, two genes that belong to the ClC superfamily. Transcripts for ClC-2 thru ClC-7 were detected in a human glioma cell line by PCR, whereas only ClC-2, ClC-3, and ClC-5 protein could be identified by Western blot. Prominent ClC-2, -3, and -5 channel expression was also detected in acute patient biopsies from low- and high-grade malignant gliomas. Immunogold electron microscopic studies as well as digital confocal imaging localized a portion of these ClC channels to the plasma membrane. Whole-cell patch-clamp recordings show the presence of two pharmacologically and biophysically distinct Cl- currents that could be specifically reduced by 48 hr exposure of cells to channel-specific antisense oligonucleotides. ClC-3 antisense selectively and significantly reduced the expression of outwardly rectifying current with pronounced voltage-dependent inactivation. Such currents were sensitive to DIDS (200-500 microm) and 5-nitro-2-(3-phenylpropylamino) benzoic acid (165 microm). ClC-2 antisense significantly reduced expression of inwardly rectifying currents, which were potentiated by hyperpolarizing prepulses and inhibited by Cd2+ (200-500 microm). Currents that were mediated by ClC-5 could not be demonstrated. We suggest that ClC-2 and ClC-3 channels are specifically upregulated in glioma membranes and endow glioma cells with an enhanced ability to transport Cl-. This may in turn facilitate rapid changes in cell size and shape as cells divide or invade through tortuous extracellular brain spaces.
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PMID:Expression of voltage-gated chloride channels in human glioma cells. 1284 58

Cadmium has recently been shown to induce apoptosis in C6 glioma cells via disruption of the mitochondrial membrane potential and subsequent caspase 9-activation. Here we show that both H2O2 and CdCl2 induced apoptotic DNA fragmentation in C6 cells. The employment of glutathione as an antioxidant prevented the induction of apoptotic DNA fragmentation by cadmium completely and catalase strongly reduced cadmium-induced DNA fragmentation suggesting that cadmium exerts its apoptotic effects at least partly via the production of H2O2. Apoptosis may be induced by cadmium indirectly through formation of oxidative stress, e.g., by inhibition of antioxidant enzymes. After incubation of C6 cells with cadmium for short times (up to 4 h), we analyzed the formation of intracellular reactive oxygen species and cellular lipid peroxidation. After 1 h of incubation with inreasing concentrations of CdCl2 (1-500 microM), no increase in dichlorofluorescein fluorescence was found. At variance, lipid peroxidation was slightly elevated after 2 h incubation with cadmium (50-100 microM). Furthermore, we analyzed the modulation of markers for oxidative stress after prolonged (24 h) exposure to cadmium. The intracellular glutathione content as measured using the fluorescent probe monobromobimane was decreased after incubation with CdCl2 (0.5-10 microM) for 24 h. Furthermore, we measured the effect of cadmium on the level of oxidized DNA lesions (predominantly 8-hydroxyguanine) using the bacterial Fpg-DNA-repair protein. After 24 h of incubation with 5 microM CdCl2 we found a sixfold increase in Fpg-sensitive DNA-lesions. We conclude that short time incubations with cadmium (up to 4 h) caused only slight or insignificant effects on the generation of reactive oxygen species (formation of thiobarbituric acid reactive substances, fluorescence of dichlorofluorescein), whereas incubation with this heavy metal for 24 h lead to a decrease in intracellular glutathione concentration and an increase in oxidative DNA-lesions. Our data demonstrate that cadmium as similar to H2O2 is a potent inducer of apoptosis in C6 cells. Even if cadmium unlike Fenton-type metals can not produce reactive oxygen species directly, the apoptotic effects of cadmium at least in part are mediated via induction of oxidative stress. Because both apoptosis and oxidative stress are thought to play important roles in neurodegenerative diseases, low concentrations of cadmium that initiate programmed cell death may lead to a selective cell death in distinct brain regions via generation of oxidative stress.
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PMID:Cadmium-induced apoptosis in C6 glioma cells: influence of oxidative stress. 1497 63

1. We tested whether pretreatment of reagents known to induce hypoxia-inducible factor-1 (HIF-1) may confer chemoresistance against cytotoxicity of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) to rat C6 glioma cells. We also studied which cytotoxic mechanism(s) of chloroethylnitrosoureas could be neutralized by cobalt preconditioning. 2. Preconditioning of rat C6 glioma cells with cobalt chloride (300 microm, 2 h) induced HIF-1 binding activity based on electrophoretic mobility shift assay (EMSA). Results from Western blotting confirmed a heightened HIF-1alpha level upon cobalt chloride exposure (300-400 microm, 2 h). Cobalt chloride (300 microm) pretreatment for 2 h substantially neutralized BCNU toxicity, leading to increases in glioma cell survival based on MTT assay. In addition, pre-exposure of C6 cells with desferrioxamine (DFO; 400 microm, 3 h), an iron chelator known to activate HIF-1, also induced HIF-1 binding and rendered the glioma cells resistant to cytotoxicity of BCNU. 3. Pre-incubation with cobalt chloride abolished the cytotoxicity of several carbamoylating agents including 2-chloroethyl isocyanate and cyclohexyl isocyanate, the respective carbamoylating metabolites of BCNU and 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea. The protective effect of cobalt exposure, however, was not observed when cells were challenged with alkylating agents including temozolomide. 4. Cadmium chloride (50 microm) effectively reversed cobalt-induced HIF-1 activation. Correspondingly, cadmium chloride suppressed carbamoylating chemoresistance mediated by cobalt chloride pretreatment. Furthermore, both double-stranded oligodeoxynucleotide (ODN) decoy with HIF-1 cognate sequence and antisense phosphorothioate ODNs against HIF-1alpha partially abolished the carbamoylating chemoresistance associated with cobalt preconditioning. 5. Our results suggest that cobalt- or DFO-preconditioning may enhance glioma carbamoylating chemoresistance that is dependent, at least in part, on induction of HIF-1.
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PMID:Carbamoylating chemoresistance induced by cobalt pretreatment in C6 glioma cells: putative roles of hypoxia-inducible factor-1. 1498 Sep 78

Heme oxygenase-1 (HO-1) is a 32-kDa stress induced enzyme that degrades heme to carbon monoxide (CO) and biliverdin. By employing RT-PCR and Western blotting techniques, we have examined the HO-1 induction in C6 glioma cells that were treated with cadmium chloride (CdCl(2)) or spermine NONOate (SPER/NO). By employing a cell viability assay, we have also examined the cytoprotective effect of HO-1 induction against the cytotoxicity caused by toxic dose of CdCl(2). In C6 glioma cells exposed to CdCl(2), expression of HO-1 (mRNA and protein) was increased in a dose- and time-dependent manner. Nitric oxide (NO) generated from SPER/NO very rapidly increased HO-1 mRNA expression in the C6 glioma cells. The induction of HO-1 by SPER/NO protected the cells from toxic dose of CdCl(2). The up-regulation of HO-1 mRNA expression by CdCl(2) was inhibited by a pre-incubation of the cells with actinomycin D, a potent inhibitor of mRNA transcription. Upon the inhibition of elevated HO-1 mRNA expression by the use of zinc protoporphyrin IX (ZnPP), an inhibitor of HO activity, the change of HO-1 mRNA expression by ZnPP was not observed. Thus, the glial cell may respond to CdCl(2) toxicity by enhancing the HO-1 expression in its effort to minimize the CdCl(2)-derived oxidative damage, and to survive. In the glioma cells, when the HO-1 expression was elevated by a prior incubation with SPER/NO, the cell viability against the cytotoxicity of CdCl(2) was significantly increased. When the results of our experiment are taken together, we discovered that NO provided a rapid enhancement of HO-1 expression, and it provided a protective effect against CdCl(2)-derived oxidative injury in the C6 rat glioma cells.
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PMID:Heme oxygenase-1-mediated partial cytoprotective effect by NO on cadmium-induced cytotoxicity in C6 rat glioma cells. 1558 53


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