Reactive oxygen species (ROS) are generated by environmental factors, such as ionizing radiation and chemical carcinogens, and also by endogenous processes, including energy metabolism in mitochondria. In 1984, Kasai and colleagues first reported the detection of 8-hydroxydeoxyguanosine (8-OH-dG), a type of oxidative damage in DNA formed by Fenton-type reagents and X-irradiation in vitro. Further studies of the mechanisms of 8-OH-dG formation by various carcinogens suggested that it is generated by a wide variety of agents with different mechanisms of action. 8-OH-dG is biologically significant, since it induces mutations and has specific repair systems. 8-OH-dG is one of the major forms of oxidative DNA damage, and it has been well studied because it is relatively easy to detect by using a high performance liquid chromatography-electrochemical detector (HPLC-ECD) system. In this review, we summarize the methods to analyze 8-OH-dG in cellular DNA and urine, and the free base, 8-hydroxyguanine (8-OH-Gua), in urine and serum.
Heirloom vegetables in Kyoto, termed Kyo-yasai, have had their seeds preserved by traditional cultivation methods. These heirloom vegetables offer a more distinctive flavor than conventional vegetables, and extracts from some Kyo-yasai are known to decrease ultraviolet light induced mutations in Escherichia coli B/r WP2 (trpE65) significantly more than extracts from their counterpart of conventional vegetables. 4-Methylthio-3-butenyl isothiocyanate which causes the pungency in daikon (Raphanus sativus), and 3-methylthiopropionic acid ethyl ester, which causes melon-like odor, were identified from heirloom vegetables in Kyoto to be antimutagens in Escherichia coli mutagenicity assays. These two chemicals also demonstrated in vivo animal cancer prevention, and induced differentiation, a chemotherapeutic strategy, in an in vitro human colon-cancer cell system. The heirloom daikon varieties in Kyoto produced 2.0-11.5 times higher levels of 4-methylthio-3-butenyl isothiocyanate as compared to the conventional Aokubi variety, because the conventional variety is grown for consumer preferences of milder flavor, which is corresponding to both quantity of 4-methylthio-3-butenyl isothiocyanate and quality associated with its antimutagenicity. The heirloom pickling melon in Kyoto, Katsura-uri (Cucumis melo var. conomon) began to produce 3-methylthiopropionic acid ethyl ester between the midripening to fully ripening stage of fruit development. Shiro-uri, a conventional variety for Katsura-uri, did not contain 3-methylthiopropionic acid ethyl ester. Results also indicate that antimutagenic and anticarcinogenic properties change over the ripening stage quantitatively. In this review, we discuss the value of retaining the original phenotypes of vegetables, including the flavors, to maximize the anticarcinogenic properties of these food products.
The frequency of micronucleated cells (MNCs) was measured in acridine orange (AO) stained kidney cells obtained from male and female medaka fish (Oryzias latipes) of known body weight before and after X-irradiation at a dose of 4 Gy. The MNC frequency in the kidney cells obtained from untreated and X-ray treated fish did not vary in correlation with the body weight in either gender, and neither did it show a significant gender-related difference. In both the untreated and treated groups, the number of MNCs in kidney cells per fish appeared to follow a Poisson distribution. These results are in agreement with those previously reported for the MNC frequency in gill cells of medaka fish. The average MNC frequency in kidney cells for the untreated fish was 0.4‰ (12/30000), which was significantly lower than 0.8‰ (24/30000) reported for gill cells. Similarly, a relatively lower frequency of X-ray-induced MNCs was evident for kidney cells (2.2‰; 69/30000) vs. gill cells (6.3‰; 191/30000). These results combined with previous reports support the use of AO to detect micronucleus formation in kidney cells, and further indicate that the kidney cell micronucleus assay can be used as a reliable and coincidently applied adjunct to the gill cell assay for medaka fish.
Plants are exposed to solar ultraviolet radiation (UV), which has deleterious effects on plant growth, development and physiology. Cyclobutane pyrimidine dimers (CPDs) are a major form of UV-induced DNA damage. It is conceivable that the reversal of CPDs is important for the reduction of lethal and mutagenic effects. Photoreactivation catalyzed by CPD photolyase is an efficient CPD repair system with a mechanism dependent on UV-A/visible light, which is contained in solar radiation. Photoreactivation presumably functions to protect plants from solar UV. We generated a CPD photolyase knock-down in Arabidopsis thaliana by RNA interference (RNAi) to investigate the role of CPD photorepair for protection of plants from solar UV. These knock-down lines exhibited hypersensitivity to UV-B and an increased occurrence of mutation induced by UV-B radiation compared with Arabidopsis proficient in CPD photolyase. Mutations induced by UV-B were determined by an rpsL mutation assay system. G:C to A:T transitions were frequently observed in CPD photolyase knock-down lines at the site of dipyrimidine sequences. A high incidence of frameshifts was observed in irradiated knock-down lines. These results indicate that CPD photoreactivation plays an important role for UV resistance of Arabidopsis and suppression of UV-induced mutagenesis.
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