8-hydroxy-2--deoxyguanosine and Glioma

DNA modifications can be used to monitor pathological processes. We have previously shown that estimating the amount of the main DNA epigenetic mark, 5-methylcytosine (m

Topics: 5-Methylcytosine; 8-Hydroxy-2'-Deoxyguanosine; Adult; Aged; Aged, 80 and over; Biomarkers, Tumor; Brain Neoplasms; DNA; DNA Damage; DNA Methylation; Female; Glioma; Humans; Male; Middle Aged; Oxidative Stress; Reactive Oxygen Species; Young Adult

To understand the interaction between oxidative stress and autophagy in gliomas of different grades.. In the present study, we analyzed levels of oxidative stress in 45 human glioma tumors, using the DNA oxidation marker 8-hydroxydeoxyguanosine (8-OHdG). In addition, we determined activation of autophagy in gliomas samples by assessing expression of microtubule-associated protein 1 light chain-3B (LC3B). To confirm our in vivo findings, in vitro studies using U87 cells were conducted.. It was determined that the grade of gliomas, that is, different malignant degrees according to WHO classification, significantly affected level of 8-OHdG. High levels of 8-OHdG were present in high-grade gliomas. This trend was significant in male patients and in young adult patients (<50 years old). Further study showed increased expression of LC3B in high-grade gliomas. In addition, levels of 8-OHdG and expression of LC3B were positively correlated. Reducing autophagic activity by 3-methyladenine resulted in significantly increased intracellular reactive oxygen species (ROS) in U87 cells.. Our study provides evidence that high levels of oxidative stress in high-grade gliomas are associated with autophagy activation that may play a protective role promoting the survival of high-grade gliomas under severe oxidative stress.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Adult; Aged; Autophagy; Brain Neoplasms; Cell Line, Tumor; Deoxyguanosine; Female; Glioma; Humans; Male; Middle Aged; Oxidative Stress; Young Adult

Reactive oxygen species (ROS) are mainly produced by mitochondria which can cause oxidative stress. It has been considered that mitochondrial damage induced by oxidative stress is related to Alzheimer's disease (AD). Besides, mitochondrial DNA (mtDNA) is more vulnerable to oxidative damage than other biomacromolecules, causing serious dysfunction to mitochondria. β-amyloid peptides (Aβ) is a main factor responsible for the occurrence and development of AD. Astrocytes is an important target cell for Aβ' toxicity and can be activated to neglect their normal fountain in the central nervous system. Genistein (Gen), a main active ingredient of soybean isoflavone, has been shown to have neuroprotective effects by antagonizing oxidative damage induced by Aβ. Thus, in the present study, we evaluated Aβ25-35 induced mitochondrial DNA (mtDNA) damage and the protective effect of Gen in C6 glioma cells (C6 cells). The study design was consisted of four groups: control group (vehicle), Aβ group treated with Aβ25-35, Gen + Aβ group treated with Gen + Aβ25-35 and Gen group treated with Gen only. C6 cells were pre-incubated with or without Gen (50 μM) for 2 h followed by the incubation with Aβ25-35 (25 μM) for another 24 h. Then the cells were harvested and processed to perform the analysis according to protocols. The mitochondrial ROS in C6 cells were measured by fluorescence spectrometer. Enzyme-linked immunosorbent assay (ELISA) was used to detect the mitochondrial reduced glutathione (GSH) and oxidized glutathione (GSSG) in C6 cells, then the ratio of GSH and GSSG was calculated. The levels of 8-hydroxydeoxyguanosine (8-OHdG) in C6 cells was also detected by ELISA. In addition, mtDNA deletion was detected by polymerase chain reaction (PCR). The mRNA and protein expression of 8-oxoguanine DNA glycosylase (OGG1) in both C6 cells and its mitochondria, and manganese superoxide dismutase (MnSOD) in mitochondria were detected by using reverse transcription-PCR and Western blot. The results showed that the increased mitochondrial ROS accumulation in C6 cells induced by Aβ was profoundly reversed by pre-treaded with Gen (p < 0.05). The ratio of GSH and GSSG in mitochondria was significantly increased in both Gen + Aβ group and Gen group compared with Aβ group (p < 0.05). The levels of 8-OHdG in C6 cells and mtDNA deletion were decreased after pre-treated with Gen (p < 0.05). Gen could also up-regulate the mRNA and protein expression of OGG1 in both C6 cells and its mitochond

Topics: 8-Hydroxy-2'-Deoxyguanosine; Amyloid beta-Peptides; Brain Neoplasms; Cell Line, Tumor; Deoxyguanosine; DNA Damage; DNA, Mitochondrial; Genistein; Glioma; Humans; Oxidative Stress; Peptide Fragments; Reactive Oxygen Species

Cancer stem-like cells (CSCs) possessing features of neural precursor cells (NPC) influence initiation, recurrence and chemoresistance of glioblastoma multiforme (GBM). As inflammation is crucial for glioblastoma progression we investigated the effect of chronic IL-1β treatment on CSCs derived from glioblastoma cell line U87MG. Exposure to IL-1β for 10 days increased (i) accumulation of 8-OHdG - a key biomarker of oxidative DNA damage; (ii) DNA damage response (DDR) indicators γH2AX, ATM and DNA-PK; (iii) nuclear and cytoplasmic p53 and COX-2 levels and (iv) interaction between COX-2 and p53. Despite upregulating p53 expression IL-1β had no effect on cell cycle progression, apoptosis or self renewal capacity of CSCs. COX-2 inhibitor Celecoxib reduced self renewal capacity and increased apoptosis of both control and IL-1β treated CSCs. Therefore the ability of COX-2 to regulate proliferation of CSCs irrespective of exposure to IL-1β, warrants further investigation of COX-2 as a potential anti-glioma target.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Apoptosis; Blotting, Western; Caspase 3; Cell Line, Tumor; Cell Proliferation; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Deoxyguanosine; Disease Progression; DNA Damage; DNA, Neoplasm; Flow Cytometry; Glioma; Histones; Humans; Interleukin-1beta; Neoplastic Stem Cells; Tumor Suppressor Protein p53

The present experiments have been carried out in order to study (comparatively) oxidative stress and its consequences (i.e. modifications of DNA bases and/or DNA fragmentation), cell cycle progression (through two generations) and apoptosis in C6 glioma cells (with normal p53 status) and p53-null mouse embryonic fibroblasts (MEF) after incubation with fumonisin B(1) (FB(1)). Further endpoints, including protein and DNA syntheses as well as cytotoxicity, have been also studied. The results show that FB(1) (incubation) produced a significant increase of malondialdehyde (MDA) production (suggestive of lipid peroxidation) which was prevented by antioxidant agents in both cell types. Moreover, FB(1) induced a significant and dose-related increase of 8-OH-dG and DNA fragmentation in both C6 glioma and MEF cells. Unlike MEF cells, apoptotic C6 glioma cells were observed after FB(1) incubation. Moreover, suppression of cell cycle progression was observed in C6 glioma but not in MEF cell incubated with FB(1). The results suggest a possible loss of protective mechanisms (such as p53-dependent apoptosis and cell cycle arrest) in FB(1)-damaged MEF cells and confirm that cells lacking of mechanisms governed by p53 gene would be more susceptible to neoplastic cascade or mutation following DNA lesions induced by this mycotoxin.

Topics: 5-Methylcytosine; 8-Hydroxy-2'-Deoxyguanosine; Animals; Apoptosis; Carcinogens, Environmental; Cell Cycle; Comet Assay; Cytosine; Deoxyguanosine; DNA; Fibroblasts; Flow Cytometry; Fumonisins; Glioma; Lipid Peroxidation; Malondialdehyde; Mice; Mice, Knockout; Oxidative Stress; Thiobarbituric Acid Reactive Substances; Tumor Cells, Cultured; Tumor Suppressor Protein p53

Organic mercury is a well-known neurotoxicant although its mechanism of action has not been fully clarified. In addition to a direct effect on neurons, much experimental evidence supports an involvement of the glial component. We assessed methylmercury hydroxide (MeHgOH) toxicity in a glial model, C6 glioma cells, exposed in the 10(-5)-10(-8) M range. The time course of the effects was studied by time-lapse confocal microscopy and supplemented with biochemical data. We have monitored cell viability and proliferation rate, reactive oxygen species (ROS), mitochondrial transmembrane potential, DNA oxidation, energetic metabolism and modalities of cell death. The earliest effect was a measurable ROS generation followed by oxidative DNA damage paralleled by a partial mitochondrial depolarization. The effect on cell viability was dose dependent. TUNEL, caspase activity and real-time morphological observation of calcein-loaded cells showed that apoptosis was the only detectable mode of cell death within this concentration range. N-acetyl-cysteine (NAC) or reduced glutathione (GSH) completely prevent the apoptotic effect of MeHgOH. The lowest effective MeHgOH concentration was 10(-7) M for ROS and DNA OH-adducts generation. The effect of submicromolar concentrations of MeHgOH on C6 cells could be relevant in the developmental neurotoxicity caused by low dose, long-term exposures, such as those of food origin. In addition, we have shown that the same concentrations are effective in the induction of DNA oxidative damage, with further potential pathogenetic implications.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Adenosine Triphosphate; Animals; Apoptosis; Cell Division; Cell Survival; Deoxyguanosine; DNA Damage; Fluoresceins; Glioma; In Situ Nick-End Labeling; Membrane Potentials; Methylmercury Compounds; Microscopy, Confocal; Mitochondria; Oxidative Stress; Rats; Time Factors; Tumor Cells, Cultured

It has been reported that glutamate decreased the intracellular glutathione (GSH) concentration and thereby induced cell death in C6 rat glioma cells. Polyunsaturated fatty acids such as arachidonic acid, gamma-linolenic acid, and linoleic acid enhanced lipid peroxidation promoting 8-hydroxy-2'-deoxyguanosine (8-OH-dG) formation under the glutamate-induced GSH-depletion. The enhancement of lipid peroxidation by polyunsaturated fatty acids was species-dependent. Some antioxidants capable of scavenging oxygen and lipid radicals and some iron or copper scavengers inhibited both the lipid peroxidation and the 8-OH-dG formation, consequently protecting against cell death induced by glutamate-induced GSH depletion. These results suggest that GSH depletion caused by glutamate induces lipid peroxidation and consequently 8-OH-dG formation and that polyunsaturated fatty acids enhance lipid peroxidation associated with mediated 8-OH-dG formation through a chain reaction.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Antioxidants; Cell Death; Chelating Agents; Deoxyguanosine; Fatty Acids, Unsaturated; Glioma; Glutamic Acid; Glutathione; Lipid Peroxidation; Rats; Tumor Cells, Cultured

Although paraquat has been shown to cause oxidative damage to neuronal cells, little is known about its effect on glial cells. Thus the effect of paraquat on glial cells was examined using rat C6 glioma cells as a model system. Paraquat reduced cell viability in a concentration- and time-dependent manner, and this toxic effect was not significantly attenuated by various kinds of antioxidants. Furthermore, paraquat failed to increase 8-hydroxy-deoxyguanosine formation in the cells. These results indicate that paraquat can be toxic to glial cells and suggest that this cytotoxic effect may not be associated with the oxidative damage to the cells.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Antioxidants; Ascorbic Acid; Cell Survival; Deoxyguanosine; DNA, Neoplasm; Dose-Response Relationship, Drug; Glioma; Glutathione; Herbicides; Oxidative Stress; Paraquat; Rats; Time Factors; Tumor Cells, Cultured; Vitamin E