ascorbic-acid and Astrocytoma

Glutathione (GSH) is one of the major antioxidants in the brain. GSH is secreted by astrocytes and this extracellular GSH is used by neurones to maintain and increase their intracellular GSH levels. For efficient GSH trafficking between astrocytes and neurones, GSH needs to be maintained in the reduced form. In model systems, GSH trafficking has been shown to be essential for neuroprotection against a variety of stress conditions. Previously we and others have shown that GSH and thiols are unstable in cell culture media and are easily oxidised. In the present study it is shown that nanomolar concentrations of copper (II) ions can cause decay of GSH in cell culture media. Increased free or redox active copper has been implicated in a variety of diseases and degradation of extracellular GSH is a possible mechanism by which it exerts its harmful effects. Rat astrocytes, a human astrocytoma cell line and astrocyte-conditioned media, in the absence of cells, are able to retard this copper-catalysed decay of GSH and maintain GSH in its reduced form. The protective effect of astrocytes appears to be a combination of copper removing and antioxidant mechanisms. The importance of these protective mechanisms is discussed with regards to neurodegenerative diseases.

Topics: Animals; Ascorbic Acid; Astrocytes; Astrocytoma; Brain Neoplasms; Catalysis; Cell Line, Tumor; Cells, Cultured; Chelating Agents; Copper; Culture Media, Conditioned; Extracellular Space; Fluorescent Dyes; Glutathione; Humans; L-Lactate Dehydrogenase; Male; Pentetic Acid; Phenanthrolines; Rats; Rats, Wistar

Arsenic trioxide (As2O3, Trisenox) is used to treat patients with refractory or relapsed acute promyelocytic leukemia (APL). Its ability to induce apoptosis in various malignant cell lines has made it a potential treatment agent for other malignancies and many clinical trials are currently in progress to evaluate its clinical usefulness for multiple myeloma and glioblastoma cancer. In the present study, we investigated the metabolism of As2O3 regarding its cellular biotransformation and interaction with metallothionein (MT) as a possible protective responses of cells to arsenic-induced cytotoxicity. The study was performed on two types of cell treated with As2O3: (1) human astrocytoma (glioblastoma) cell line U87MG treated with 0.6 microM arsenic for 0, 3, 12, 24, and 48 h or 12 microM arsenic for 3, 6, 12, 24, and 48 h and (2) bone marrow cells (BM) from two patients with multiple myeloma (MM) treated with 7 microM arsenic for 0, 43, and 67 h. Cotreatment with vitamin C (1 mg/mL) was tested in longer exposure of MM BM cells. Traces of methylation products (mainly monomethylarsenic acid) were detected in cell lysates of both cell types and in pellets of U87 MG cells, although we found problems with column-sample interactions in cases where methanol pretreatment of the sample was not used. Pentavalent inorganic arsenic (AsV) was identified in both cell types, and up to 80% of total As in MM bone marrow cell lysates was present as AsV. Such an occurrence (generation) of pentavalent arsenic after As2O3 treatment demonstrates the presence of biological oxidation of trivalent arsenic, which could represent an additional protective mechanism of the cell. Vitamin C decreased As cell content and increased the percentage of pentavalent inorganic arsenic (in the growth medium and cells). The presence of metallothionein (MT) and its response to arsenic treatment was checked in all U87 MG cells, in the control, and in one exposed sample of MM BM cells. During 48 h exposure to 0.6 or 12 muM arsenic MTI/II levels increased in U87 MG cells, but with variable Zn levels, increased Cu levels, and As binding observed in traces only. Involvement of the MT-III isoform was negligible. In contrast, 43 h exposure to 7 microMarsenic did not increase MT content in multiple myeloma cells, and the levels even decreased with respect to the control. To evaluate the importance of the observed processes, MTs in U87 and AsIII-AsV conversion in MM BM cells, which could represent a resista

Topics: Antineoplastic Agents; Apoptosis; Arsenic Trioxide; Arsenicals; Ascorbic Acid; Astrocytoma; Biotransformation; Bone Marrow Cells; Cell Line, Tumor; Chromatography, Ion Exchange; Humans; Models, Chemical; Multiple Myeloma; Oxides; Reactive Oxygen Species; Time Factors

Oxidative stress has been involved in various neurological disorders and, in the central nervous system, astrocytes represent the cell type that contributes to neuroprotection via glutathione (GSH) metabolism, GSH-metabolizing enzymes like gamma-glutamyltransferase (GGT), and apoE secretion. In this study, using IL-1beta, a proinflammatory and prooxidant cytokine that is increased in numerous pathological situations, cells of astrocytoma cell line U373-MG were exposed to an oxidative stress, leading to c-Jun and c-Fos activation. IL-1beta decreased both GGT activity and intracellular GSH content and increased apoE secretion, initiating astroglial response to injury. We observed that antioxidants inhibit IL-1beta effects on c-Jun and c-Fos proteins, GGT activity and the GSH pool but not on apoE secretion. Our results allow us to conclude that neurological disorders associated with an IL-1beta-induced oxidative stress could be, at least experimentally, reversible in the presence of one antioxidant, N-acetylcysteine.

Topics: Acetylcysteine; Apolipoproteins E; Ascorbic Acid; Astrocytoma; Blotting, Western; Cell Survival; Dose-Response Relationship, Drug; Enzyme Activation; Free Radical Scavengers; gamma-Glutamyltransferase; Glutathione; Humans; Interleukin-1; Oxidative Stress; Proto-Oncogene Proteins c-fos; Proto-Oncogene Proteins c-jun; Tumor Cells, Cultured; Vitamin E

We investigated the effect of EPC-K1, which is a phosphodiester compound of vitamin E and vitamin C, on NF-kappaB activity in human cultured astrocytoma cells T98G. In TNFalpha-stimulated T98G cells, treatment with EPC-K1 inhibited both DNA binding activity and transactivation of NF-kappaB in a dose-dependent manner, and the suppressive effect of EPC-K1 was stronger than either that of vitamin E or vitamin C. Moreover, we showed that in TNFalpha-stimulated T98G cells treatment with EPC-K1 repressed NF-kappaB-dependent activation of the human immunodeficiency virus 1 promoter. In contrast, TNFalpha-induced activation of the human immunodeficiency virus 1 promoter was not completely inhibited by either treatment with vitamin E or vitamin C. We, thus, suggest that EPC-K1 is considered to be one of the inhibitory agents of NF-kappaB.

Topics: Antioxidants; Ascorbic Acid; Astrocytoma; DNA, Viral; Dose-Response Relationship, Drug; Free Radical Scavengers; Gene Expression Regulation, Viral; Genes, Reporter; HIV-1; Humans; NF-kappa B; Plasmids; Promoter Regions, Genetic; Transcription, Genetic; Transfection; Tumor Cells, Cultured; Tumor Necrosis Factor-alpha; Vitamin E

The aim of the present study was to investigate the oxidative status in astrocytoma. Samples of brain tissue from the centre to the periphery of the tumor were obtained from 11 astrocytoma patients undergoing computer tomography-guided stereotaxic operation, who had been previously treated with the corticosteroid dexamethasone. Part of the sample was investigated histologically for clarification of tumor type, and the presence of neoplastic and non-neoplastic tissue and necrosis. The rest was used for the quantification of the antioxidants ascorbic acid, uric acid, glutathione and cysteine by high performance liquid chromatography, and for quantification of DNA. Levels of antioxidants were calculated as micrograms/g fresh tissue and mumol/g DNA, a parameter related to cell content. There was significantly more DNA in neoplastic samples than in non-neoplastic ones, indicating increased cell density. Uric acid (micrograms/g fresh tissue) was significantly increased in neoplastic compared with non-neoplastic tissue, and levels were even higher in necrotic tissue. There were no significant differences between neoplastic and non-neoplastic tissue levels of ascorbic acid, glutathione or cysteine, expressed as micrograms/g fresh tissue. However, when levels of these three compounds were expressed as mumol/g DNA, i.e. taking into account the higher cell density, ascorbic acid, glutathione and cysteine were significantly reduced in neoplastic samples compared with non-neoplastic ones. Results thus show that there are differences between the antioxidant levels in astrocytoma and non-neoplastic tissue, providing additional support for the hypothesis that free radicals play a role in tumor growth.

Topics: Adult; Aged; Antioxidants; Artifacts; Ascorbic Acid; Astrocytoma; Biopsy; Brain Chemistry; Brain Edema; Brain Neoplasms; Combined Modality Therapy; Cysteine; Dexamethasone; DNA, Neoplasm; Female; Free Radicals; Glioblastoma; Glutathione; Humans; Male; Middle Aged; Necrosis; Neoplasm Proteins; Oxidation-Reduction; Oxidative Stress; Phenytoin; Solubility; Stereotaxic Techniques; Tomography, X-Ray Computed; Uric Acid; Water

Exposure of postconfluent 1321N1 human astrocytoma cells to 1.0 microM isoproterenol for 12-24 hr results in a 90% loss of beta-adrenergic receptors. Upon removal of agonist, recovery of beta-receptors to control levels occurs within 72 hr. The recovery of receptors is completely blocked by cycloheximide [R. C. Doss, J. P. Perkins, and T. K. Harden, J. Biol. Chem. 256:12281-12286 (1981)]. In contrast cycloheximide does not block recovery of beta-receptors after down-regulation in preconfluent cultures. To determine unambiguously if beta-receptor synthesis accounts for the recovery of receptors after down-regulation, post confluent cultures were incubated with isoproterenol and then transferred to agonist-free medium containing either normal or "heavy" (2H, 13C, 15N) amino acids. The rate and extent of beta-receptor recovery were similar in both normal and heavy amino acid-containing medium. When beta-receptors that had recovered in the heavy amino acid-containing medium were labeled with 125I-cyanopindolol, solubilized in Lubrol PX, and subjected to centrifugation on a 5-15% sucrose density gradient, they exhibited an increased mass compared to beta-receptors that recovered in the presence of normal amino acids. These results confirm that the density shift method is a useful approach for the study of beta-receptor synthesis and that new receptor synthesis occurs during recovery of beta-receptors from catecholamine-induced down-regulation in postconfluent cultures.

Topics: Ascorbic Acid; Astrocytoma; Cell Line; Humans; Iodocyanopindolol; Isoproterenol; Kinetics; Pindolol; Receptors, Adrenergic, beta

Topics: 2,2'-Dipyridyl; Ascorbic Acid; Astrocytoma; Cell Line; Collagen; Fluorescent Antibody Technique; Humans; Molecular Weight; Pepsin A; Procollagen

Topics: Adenosine; Ascorbic Acid; Astrocytoma; Calcium; Carbachol; Cell Line; Cyclic AMP; Drug Interactions; Humans; Isoproterenol; Lidocaine; Parasympatholytics; Phentolamine; Prostaglandins E; Thiourea

To assess their carcinogenic effects, the ethylnitrosourea (ENU) precursors, ethylurea and sodium nitrite, [were administered to pregnant hamsters as a single intragastic] dose on day 15 of gestation, or introduced into the cecum on day 14. Since sodium ascorbate (NaASC) inhibits the biosynthesis of nitrosamides, identical doses of the precursors were given concomitantly with NaASC. Progeny of mothers treater intragastrically developed significant incidences of neurogenic tumors of the peripheral nervous system, with a predominance in females. The concurrent administration of NaASC with ENU precursors prevented carcinogenic effects in the progency, whereas the simultaneous inoculation of the precursors into the cecum produced no carcinogenic effects in the offspring.

Topics: Animals; Ascorbic Acid; Astrocytoma; Brain Neoplasms; Cecum; Cricetinae; Ethylnitrosourea; Female; Intubation, Gastrointestinal; Male; Maternal-Fetal Exchange; Neoplasms, Experimental; Nitrites; Nitroso Compounds; Peripheral Nervous System Neoplasms; Pons; Pregnancy; Sex Factors; Urea

Topics: Arachnoid; Ascorbic Acid; Astrocytoma; Ependymoma; Glioblastoma; Glioma; Hemangioendothelioma; Histocytochemistry; Humans; Medulloblastoma; Meningioma; Neoplasms, Nerve Tissue

Topics: Ascorbic Acid; Ascorbic Acid Deficiency; Astrocytoma; Cerebral Hemorrhage; Congenital Abnormalities; Humans; Intracranial Aneurysm; Subarachnoid Hemorrhage