Increased Levels Of 8-hydroxydeoxyguanosine Research Articles

Halobenzoquinone-Induced Developmental Toxicity, Oxidative Stress, and Apoptosis in Zebrafish Embryos.

The developmental toxicity of water disinfection byproducts remains unclear. Here we report the study of halobenzoquinone (HBQ)-induced in vivo developmental toxicity and oxidative stress using zebrafish embryos as a model. Embryos were exposed to 0.5-10 μM of individual HBQs and 0.5-5 mM haloacetic acids for up to 120 h postfertilization (hpf). LC50 values of the HBQs at 24 hpf were 4.6-9.8 μM, while those of three haloacetic acids were up to 200 times higher at 1900-2600 μM. HBQ exposure resulted in significant developmental malformations in larvae, including failed inflation of the gas bladder, heart malformations, and curved spines. An increase in reactive oxygen species was observed,together with a decrease in superoxide dismutase activity and glutathione content. Additionally, the antioxidant N-acetyl-l-cysteine significantly mitigated all HBQ-induced effects, supporting that oxidative stress contributes to HBQ toxicity. Further experiments examined HBQ-induced effects on DNA and genes. HBQ exposure increased 8-hydroxydeoxyguanosine levels, DNA fragmentation, and apoptosis in larvae, with apoptosis induction related to changes in the gene expression of p53 and mdm2. These results suggest that HBQs are acutely toxic, causing oxidative damage and developmental toxicity to zebrafish larvae.

Pathological and Clinical Pathological Changes Induced by Four-week, Repeated-dose, Oral Administration of the Wood Preservative Chromated Copper Arsenate in Wistar Rats.

Chromated copper arsenate (CCA) is used as a wood preservative worldwide. Exposure to it may adversely affect human health. Some events have increased human exposure to CCA, including the Great East Japan Earthquake, which generated a large amount of lumber debris from CCA-treated woods. We elucidated the toxicity due to daily exposure to CCA over a 4-week period at doses of 0, 8, 40, and 80 mg/kg/day in Wistar Hannover rats. Chromium (Cr) and arsenic (As), but not copper, were detected in the plasma samples of rats treated with various doses of CCA. Males and females showed sedation, and males had poor body weight gain. The clinical pathologies observed in both sexes included hypochromic and microcytic anemia, hepatic and renal dysfunction, and changes in lipid and glucose levels. Histopathologically, males and females showed forestomach hyperkeratosis, mucosal epithelial hyperplasia in the small intestine, rectal goblet cell hypertrophy, and lipofuscin deposition in the proximal renal tubule. Females showed diffuse hepatocellular hypertrophy with increased 8-hydroxydeoxyguanosine levels. These results indicated that oral administration of CCA mainly affected hematopoietic, gastrointestinal, hepatic, and renal systems owing to the toxic effects of As and/or Cr. Major toxic effects were observed in both sexes receiving 40 and 80 mg/kg/day.

Aluminum chloride caused liver dysfunction and mitochondrial energy metabolism disorder in rat

Aluminum (Al) is known to exert hepatotoxicity. However, the mechanisms mostly are unclear. Liver is a metabolism organ that maintains the energy level and structural stability of body, mitochondria are the main sites of energy metabolism, thus, we hypothesized that mitochondrial energy metabolism disorder contributes to liver dysfunction in aluminum chloride (AlCl3) treatment rat. To verify the hypothesis, forty male Wistar rats were randomly allocated and orally exposed to 0, 64mg/kg, 128mg/kg and 256mg/kg body weight AlCl3 in drinking water for 120days, respectively. We found that AlCl3 exposure reduced the electron transport chain complexes I–V activities and adenosine triphosphate (ATP) level, as well as disturbed mitochondrial DNA transcript, presenting as the inhibited mRNA expressions of NADH dehydrogenase 1, NADH dehydrogenase 2, cytochrome b, cytochrome c oxidase subunit 1, cytochrome c oxidase subunit 3 and ATP synthase 6, indicating that AlCl3 exposure disturbs the mitochondrial energy metabolism, and it caused an increase in liver enzymes (Aspartate aminotransferase and Alanine aminotransferase) and histopathological lesions. Additionally, we found that reactive oxygen species accumulation and decreased superoxide dismutase activity in mitochondria, and increased 8-Hydroxydeoxyguanosine levels in mitochondrial DNA, demonstrating AlCl3 exposure promotes mitochondrial oxidative stress, which may be a contributing factor to mitochondrial energy metabolism disorder and liver dysfunction. The study displayed that mitochondria are the potential target of liver damage induced by AlCl3, providing considerable direction for the prevention and clinical intervention of liver diseases.

Adequate Intakes of Vitamin E and Protein Prevent Increases of Oxidative Damage to DNA, Lipids, and Protein Induced by Total Body Irradiation in Mice

: We examined the influence of the level of dietary protein or vitamin E (VE) on oxidative damage to DNA, lipids, and protein in the liver after total body irradiation (TBI) with X-rays at 1 or 4 Gy. Levels of 8-hydroxydeoxyguanosine, thiobarbituric acid-reactive substances, and protein carbonyls in the liver did not differ among the groups that did not receive TBI. However, oxidative damage to lipids and protein was increased by TBI only in the 1% protein group. DNA damage, lipid peroxidation, or protein oxidation in the liver was increased by TBI in a dose-dependent manner, and the damage was consistently higher in the 1% than in the 20% protein group. In the 1% protein group, a greater decrease in relative spleen weight by TBI was also observed. Concentrations of antioxidants (vitamins C and E and glutathione) in the liver were lower and the concentration of nonheme iron in the liver was higher in the 1% than in the 20% protein group. Mice fed a 1% protein diet became susceptible to TBI-induced oxidative damage, and decreases in antioxidant levels and an increase in iron level were involved in the mechanism of this susceptibility. These results suggest that dietary VE and protein can prevent oxidative damage to DNA, lipid, and protein in mice subjected to TBI. Consumption of a VE-free diet significantly increased 8-hydroxydeoxyguanosine levels in DNA from mice fed the 1% protein diet with TBI, but such changes were not detected in DNA from mice fed the 20% protein diet.

Exposure to hexavalent chromium does not increase 8-hydroxydeoxyguanosine levels in Korean chromate pigment workers.

This study was performed to determine whether chromium exposure increased 8-hydroxydeoxyguanosine levels in respiratory epithelial and white blood cells of chromate pigment workers. The subjects of this study were 22 chromium pigment workers and 16 controls in a chromate pigments factory. To estimate the level of exposure, hexavalent chromium concentrations in the factory air were measured. Chrominum concentrations of venous blood and spot urine, and 8-hydroxydeoxyguanosine levels in DNA extracted from sputum and white blood cells were determined. Correlation coefficients were calculated between them and their statistical significance was tested. Hexavalent chromium concentration in the factory air ranged from below limit of detection to 0.5150 mg/m3. Chromium levels in blood and 8-hydroxydeoxyguanosine levels in DNA extracted from venous blood and sputum were not statistically different between the two groups. Urine chromium level was significantly higher among workers. Among the correlation coefficients between blood chromium concentration, urine chromium concentration, blood 8-OH-dG level, and sputum 8-OH-dG level, none was statistically significant for workers, controls, and total subjects. Duration of employment did not show any significant correlation with those four variables, either. These results suggest that neither the hydroxyl radical nor 8-hydroxydeoxyguanosine is formed by the reduction of hexavalent chromium, or that one or both of these is formed and then effectively removed by oxygen free radical scavengers or 8-hydroxydeoxyguanosine repair enzymes. Since increased exposure to hexavalent chromium did not result in increased 8-hydroxydeoxyguanosine levels, it is unlikely that hexavalent chromium induces lung cancer through 8-hydroxydeoxyguanosine formation.

Lung cancer patients have increased 8-hydroxydeoxyguanosine levels in peripheral lung tissue DNA.

The 8‐hydroxydeoxyguanosine (8‐OH‐dG) levels in the peripheral parts of human lung tissues were compared between lung cancer patients (n=70) and non‐cancer patient controls (n=15). An increased level of 8‐OH‐dG was observed in the lung cancer group, in both the adenocarcinoma and non‐adenocarcinoma (mainly squamous cell carcinoma) groups, as compared to the non‐cancer control group. This result suggests that reactive oxygen species are partly involved in the induction of lung carcinomas (both adenocarcinoma and non‐adenocarcinoma).

Detection of DNA damage induced by human carcinogens in acellular assays: Potential application for determining genotoxic mechanisms

Positive outcomes of in vitro genotoxicity tests may not always occur as a consequence of direct reaction of a compound or a metabolite with DNA. To follow-up positive responses in in vitro test, we developed two supplemental, cell-free assays to examine the potential of compounds and metabolites to directly damage DNA. Calf thymus DNA was used as the target for the direct detection of adducts by 32P-postlabeling/TLC and electrochemical detection, and alkaline gel electrophoresis was used to detect single-strand breakage of bacteriophage λ DNA. To show that these assays would detect damage from relevant compounds, we examined nine human carcinogens (aflatoxin B 1, busulfan, chlorambucil, cyclophosphamide, diethylstilbestrol, melphalan, 2-naphthylamine, phenacetin and potassium chromate). Each of the nine compounds produced a positive result for one or both endpoints. Using multifraction contact-transfer TLC, we detected 32P-labeled DNA adducts produced by aflatoxin B 1, chlorambucil, diethylstilbestrol, melphalan, 2-naphthylamine, and potassium chromate (plus hydrogen peroxide). Aflatoxin B 1, diethylstilbestrol and 2-naphthylamine required metabolic activation (induced rat liver S9) to generate DNA adducts. Although potassium chromate alone induced a slight increase in the content of 8-hydroxydeoxyguanosine (a promutagenic adduct produced by reactive oxygen species), addition of hydrogen peroxide greatly increased 8-hydroxydeoxyguanosine levels. The damage to λ DNA by each human carcinogen (or metabolites), except diethylstilbestrol, was sufficient to generate single-strand breaks after neutral thermal hydrolysis at 70°C. Chromate was a weak inducer of DNA fragmentation, but adding hydrogen peroxide to the reaction mixtures dramatically increased the DNA strand breakage. Our data suggest that these non-routine, acellular tests for determining direct DNA damage may provide valuable mechanistic insight for positive responses in cell-based genetic toxicology tests.

Crocidolite asbestos increased 8-hydroxydeoxyguanosine levels in cellular DNA of a human promyelocytic leukemia cell line, HL60.

Crocidolite, one of the most carcinogenic asbestos fibers, induces the release of reactive oxygen species (ROS) from neutrophils and macrophages. Using HPLC combined with electrochemical detection, we determined that 8-hydroxydeoxyguanosine (8OHdG), a molecule typical of mutagenic oxidative DNA damage, was induced in the cellular DNA of a human promyelocytic leukemia cell line, HL60, incubated with crocidolite. Crocidolite increased 8OHdG in the cellular DNA of phorbol myristate acetate (PMA)-differentiated HL60, which phagocytosed crocidolite. PMA-differentiated HL60 released ROS spontaneously, as determined by ESR with 5,5-dimethylpyrrolone-N-oxide as a spin trap. However, the release of ROS from the cell line did not increase after the addition of crocidolite. The addition of superoxide dismutase at a sufficient concentration to scavenge ROS released from the cell did not inhibit the 8OHdG increase induced by crocidolite. Cytochalasin B, which inhibited phagocytosis, did not inhibit the release of ROS. However, it inhibited the crocidolite-induced 8OHdG increase by 48.3%. Contrary to PMA-differentiated HL60, undifferentiated HL60 neither phagocytosed crocidolite nor showed a crocidolite-induced increase in 8OHdG formation. The 8OHdG increase induced by crocidolite was not correlated with ROS release, but with the internalization of crocidolite, suggesting that the increase was not due to an increase in ROS release from the cell but was due to the conversion of relatively inert ROS to highly reactive ROS, such as hydroxyl radicals, by crocidolite that was internalized and close to DNA.