• Asian Pacific Journal of Cancer Prevention
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• v.16 no.15
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• pp.6335-6338
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• 2015

Background: Cancers have dysfunctional redox regulation resulting in production of reactive oxygen species (ROS), damaging DNA, RNA and free NTPs, and causing the accumulation of oxidative nucleic acids in cytoplasm. The major types are 8-oxo-7,8-dihydroguanine(8-oxoGsn) in RNA and 8-oxo-7,8-dihydro-2' deoxyguanosine(8-oxodGsn) in Mt-DNA. The MTH1 protein sanitizes oxidized nucleotide pools from NTPs to monophosphates, preventing the occurrence of transversion mutations. This study concerned cytoplasmic 8-oxodGsn/Gsn and MTH1 expression in gastric cancer and para-cancer tissues and elucidated roles of nucleic-acid oxidation and anti-oxidation. Materials and Methods: A polymer HRP detection system was used to detect 8-oxo-Gsn/dGsn and MTH1 expression in 51 gastric cancer and para-cancer tissue samples. Analyses of patient clinical and pathological data were also performed. Results: The expression of MTH1 and the 8-oxo-dGsn/Gsn ratio were significantly higher in cancer tissues than para-cancer tissues (P<0.05). Cytoplasmic 8-oxo-Gsn and MTH1 were both found to positively correlate (P<0.05) with tumor differentiation, while no significant associations were found with gender, age, invasion depth, lymph node metastasis and clinical stage (P>0.05). Conclusions: We found 8-oxo-dGsn/Gsn and MTH1 are both highly expressed in gastric cancer tissues, especially in well differentiated lesions. In addition, oxidated mtDNA is prevalently expressed in gastric cancers, while 8-oxo-Gsn expression in cytoplasmic RNA is a bit lower, but more selectively.

• Journal of Applied Biological Chemistry
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• v.43 no.3
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• pp.156-160
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• 2000

The possible mechanism of the DNA strand breaking activity of the hot-water extract of Fructus Chaenomelis (dried fruit of Chaenomeles sinensis) in a closed circular duplex replica form DNA (RFI DNA) was studied through agarose gel electrophresis under various conditions. Induction of DNA strand scission by the hot-water extract of C. sinensis occurred in dose and time-dependent manners. $Cu^{2+}$ was indispensable for the induction of DNA strand breakage. Exogeneous chelating agents inhibited the DNA breaking activity, conforming the catalytic action of $Cu^{2+}$ on generation of free radicals responsible for oxidative damage. Antioxidant enzymes and some radical scavengers were used to investigate the major radical species triggering the DNA strand scission, demonstrating that a highest inhibitory activity was found in the presence of catalase, while less in the presence of tiron (a scavenger for superoxide radical), 2-aminoethyl-isothiuroniumbromide-HBr, cysteamine (scavengers for hydroxyl radical), and 1,4-diazabicyclo [2,2,2] octane (a scavenger for singlet oxygen) in decreasing order. The findings implied that oxygen radical species generated in presence of transition divalent cation during the oxidation of some compounds contained in the hot-water extract of C. sinensis is mainly responsible for inducing genotoxicity.

• Journal of Life Science
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• v.21 no.5
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• pp.693-699
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• 2011

Spermidine is a ubiquitous polycation that is synthesized from putrescine, which serves as a precursor of spermine. In recent years, spermidine was found to be a polyamine that plays an important role in longevity. Reactive oxygen species (ROS) such as hydroxyl radical, superoxide and hydrogen peroxide have been shown to be involved in various pathogenic processes as well as aging. The direct scavenging effect of spermidine on DPPH radical, $H_2O_2$ and hydroxyl radical, and its protective effect against DNA oxidation related to oxidative stress were evaluated in vitro. It was observed that spermidine exhibits scavenging activities on DPPH radical and H2O2 above 500 ${\mu}M$. Spermidine was especially effective in exerting a scavenging activity on hydroxyl radical. In addition, spermidine at 1000 ${\mu}M$ showed a clear protective effect against DNA oxidation. Furthermore, the expression level of anti-oxidant enzymes such as superoxide dismutase in humam dermal fibroblasts increased in the presence of spermidine compared with blank group. These results suggest that spermidine can be used as an antioxidant to prevent ROS-related diseases including inflammation, cancer and aging.

• Proceedings of the PSK Conference
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• 2002.10a
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• pp.317.2-317.2
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• 2002

Peroxynitrite, formed from the reaction of .O2- and .NO, is a cytotoxic species that can oxidize several cellular components such as proteins. lipids and DNA. Oxidative stress is considered to be the major cause of aging and many age-related diseases including Alzheimer's disease. rheumatoid arthritis. cancer. and atherosclerosis. ONO-, a powerful oxidant, can cause damage of proteins, lipid and DNA through nitration and oxidation. (omitted)

• Environmental Mutagens and Carcinogens
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• v.25 no.2
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• pp.71-75
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• 2005

Green tea and their major constituents such as catechins are famous materials for their anti-oxidative and anti-carcinogenic activity, but many compounds with reducing power can promote the oxidation in their oxidized form or in the presence of metal ion. We investigated the pro-oxidative effect of the ethanol extract equivalent up to 30mg of dried weight of green tea leaves in four in vitro systems which could be used for detecting DNA damage. Although ethanol extract of green tea did not show significant mutagenicity in Salmonella typhimurium TA102, which is sensitive strain to oxidative stress, it degraded deoxyribose extensively in the presence of $FeCl_3-EDTA$ complex, promoted 8-oxoguanine formation in the live bacteria cell, Salmonella typhimurium TAI04, and cleaved super coiled DNA strand with the help of copper ion. It suggested that green tea, famous anti-oxidative material, can be pro-oxidant according to the condition of extraction or metal existence.

• Environmental Mutagens and Carcinogens
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• v.25 no.3
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• pp.97-103
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• 2005

The genotoxic effect of antimalarial drugs amodiaquine (AQ), mefloquine (MQ) and halofantrine (HF) was investigated in.at liver cells using the alkaline comet assay. AQ, MQ and HF at concentrations between $0-1000{\mu}mol/L$ significantly increased DNA strand breaks of rat liver cells dose-dependently. The order of induction of strand breaks was AQ>MQ>HF. The rat liver cells exposed to AQ and HF (200 and 400 ${\mu}mol/L$) and treated with (Fpg) the bacterial DNA repair enzyme that recognizes oxidized purine showed greater DNA damage than those not treated with the enzyme, providing evidence that AQ and HF induced oxidation of purines. Such an effect was not observed when MQ was treated with the enzyme. Treatment of cells with catalase, an enzyme inactivating hydrogen peroxide, decreased significantly the extent of DNA damage induced by AQ, and HF but not the one induced by MQ. Similarly quercetin, an antioxidant flavonoid at $50{\mu}mol/L$ attenuated the extent of the formation of DNA strand breaks by both AQ and HE. Quercetin, however, did not modify the effects of MQ. These results indicate the genotoxicity of AQ, MQ and HF in rat liver cells. In addition, the results suggest that reactive oxygen species may be involved in the formation of DNA lesions induced by AQ and HF and that, free radical scavengers may elicit protective effects against genotoxicity of these antimalarial drugs.

• Applied Biological Chemistry
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• v.48 no.2
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• pp.155-160
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• 2005

Electrolyzed reduced water (ERW), showing extremely negative oxidation-reduction potential, was used to investigate the effects of paraquat-induced damages on DNA from human lymphocyte. The effect of ERW on paraquat-induced oxidative DNA damage in human lymphocytes was evaluated by Comet assay (single-cell gel electrophoresis) quantified as percentage fluorescence in tail. Comet assay has been used widely to assess the level of the DNA damage in individual cells. Lymphocytes were oxidatively challenged with various concentrations of paraquat for 30 min at $37^{\circ}C$, and were then treated with electrolyzed reduced water for 30 min. The oxidative DNA damage by paraquat, as indicated by the fluorescent tail in DNA, increased in a dose-dependent manner. However, oxidative damage of the DNA was almost completely prevented upon treatment with electrolyzed reduced water.

• Animal cells and systems
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• v.9 no.2
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• pp.79-85
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• 2005

Oxidized abasic residues arise as a major class of DNA damage by a variety of agents involving free radical attack and oxidation of deoxyribose sugar components. 2-deoxyribonolactone (dL) is a C1'-oxidized abasic lesion implicated in DNA strand scission, mutagenesis, and covalent DNA-protein cross-link (DPC). We show here that mammalian cell-free extract give rise to stable DPC formation that is specifically mediated by dL residue. When a duplex DNA containing dL at the site-specific position was incubated with cell-free extracts of Po ${\beta}-proficient$ and -deficient mouse embryonic fibroblast cells, the formation of major dL-mediated DPC was dependent on the presence of DNA polymerase (Pol) ${\beta}$. Formation of dL-specific DPC was also observed with histones and FEN1 nuclease, although the reactivity in forming dL-mediated DPC was significantly higher with Pol ${\beta}$ than with histones or FEN1. DNA repair assay with a defined DPC revealed that the dL lesion once cross-linked with Pol ${\beta}$ was resistant to nucleotide excision repair activity of cell-free extract. Analysis of nucleotide excision repair utilizing a model DNA substrate containing a (6-4) photoproduct suggested that excision process for DPC was inhibited because of DNA single-strand incision at 5' of the lesion. Consequently DPC mediated by dL lesion may not be readily repaired by DNA excision repair pathway but instead function as unusual DNA damage causing a prolonged DNA strand break and trapping of the major base excision repair enzyme.

• Journal of Photoscience
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• v.9 no.2
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• pp.138-141
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• 2002

A photo-labile compound which is bioinactive but, upon irradiation with light, yields bioactive species is called as "caged compound". Photolysis of caged compounds generating bioactive species, has become a general method to produce a desired amounts of bioactive species in the specific time interval at the desired place or area of the target biological systems. For this purpose, we designed and synthesized caged hydroxyl radical., "Photo-Fenton Reagent" NP-IIl. NP-IIl has a strong absorption maximum at 377 nm and yields hydroxyl radicals upon UV light irradiation. The antioxidant activity of the ${\alpha}$ -lipoic acid and other naturally occurring compounds has been examined by using NP-IIl as a molecular probe. For example, upon photoirradiation of NP-lII with BSA or apolipoprotein of human low density (LDL), the significant oxidative modifications were observed in both cases. The oxidation was completely suppressed in the presence of ${\alpha}$-lipoic acid, which clearly demonstrates the strong hydroxyl radical scavenging activity of ${\alpha}$-lipoic acid. Other applications of NP-lII will also be described

• Journal of Food Hygiene and Safety
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• v.14 no.4
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• pp.415-421
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• 1999

The flavin-containing monooxygenases (FMOs) (EC 1.14. 13.8) are NADPH-dependent flavoenzymes that catalyze oxidation of soft nucleophilic heteroatom centers in a range of structurally diverse compounds including foods, drugs, pesticides, and other xenobiotics. In humans, FMOl appears to be the predominant form expressed in human fetal liver. cDNA-expressed human FMO and human liver microsomal FMO have been observed to N- and S-oxy-genate nucleophilic nitrogen- and sulfur-containing drugs and chemicals, respectively. In the present study, FMOl can be expressed in the baculovirus expression vector system at level of 2.68 nmol FMOl/mg of membrane protein. This isoform was examined for its capacity to metabolize methimazole to its S-oxide using thiocholine assay. Kinetic studies of its S-oxide by recombinant human FMO1 result in Km of 7.66 $\mu$M and Vmax of 17.79 nmol/min/mg protein.