Wada Kunio, Katoh Yoshitaka, Ohnuma-Koyama Aya, Takahashi Naofumi, Yamada Masami, Matsumoto Kyomu
Toxicology Division, The Institute of Environmental Toxicology, 4321, Uchimoriya-machi, Joso-shi, Ibaraki 303-0043, Japan.
Toxicology Division, The Institute of Environmental Toxicology, 4321, Uchimoriya-machi, Joso-shi, Ibaraki 303-0043, Japan.
Mutat Res Genet Toxicol Environ Mutagen. 2017 Apr;816-817:18-23. doi: 10.1016/j.mrgentox.2017.03.002. Epub 2017 Mar 27.
2-Nitroanisole (2-NA) is used in the manufacturing of azo dyes and causes cancer, mainly in the urinary bladder. Previous in vivo genotoxic data seems to be insufficient to explain the mechanism through which 2-NA induces carcinogenesis, and several bladder carcinogens were reported to induce oxidative DNA damage. Thus, we examined the potential induction of oxidative DNA damage by 2-NA using bacterial strain YG3008, a mutM-deficient derivative of strain TA100. Consequently, strain YG3008, when compared with strain TA100, was found to be more sensitive to 2-NA, indicating oxidative DNA damage in bacterial cells. For further investigation, we performed the comet assay using the urinary bladder and liver of rats, with and without human 8-oxoguanine DNA-glycosylase 1 (hOGG1), to confirm the potential of 2-NA for inducing oxidative DNA damage. Simultaneously, we conducted a micronucleus test using bone marrow from rats to assess the genotoxicity of 2-NA in vivo. 2-NA was administered orally to male Fischer 344 rats for 3 consecutive days. The rats were divided into 6 treatment groups: 3 groups treated with 2-NA at doses of 125, 250, and 500mg/kg; a group treated with the combination of 2-NA and glutathione-SH (GSH); a negative control group; and a positive control group. The comet assay without hOGG1 detected no DNA damage in the liver or urinary bladder, and the micronucleus test did not show clastogenic effects in bone marrow cells. However, the comet assay with hOGG1 was positive in the urinary bladder samples, indicating the induction of oxidative DNA damage in the urinary bladder for the group treated with 2-NA at 500mg/kg. Moreover, an antioxidant of GSH significantly reduced oxidative DNA damage caused by 2-NA. These results indicate that oxidative DNA damage is a possible mode of action for carcinogenesis in the urinary bladder of rats treated with 2-NA.
2-硝基苯甲醚（2-NA）用于制造偶氮染料，可引发癌症，主要是膀胱癌。以往的体内遗传毒性数据似乎不足以解释2-NA诱导致癌作用的机制，并且有报道称几种膀胱致癌物可诱导氧化性DNA损伤。因此，我们使用YG3008菌株（TA100菌株的mutM缺陷衍生物）研究了2-NA对氧化性DNA损伤的潜在诱导作用。结果发现，与TA100菌株相比，YG3008菌株对2-NA更敏感，表明细菌细胞中存在氧化性DNA损伤。为进一步研究，我们使用大鼠的膀胱和肝脏进行彗星试验，分别添加和不添加人8-氧代鸟嘌呤DNA糖基化酶1（hOGG1），以确认2-NA诱导氧化性DNA损伤的可能性。同时，我们使用大鼠骨髓进行微核试验，以评估2-NA在体内的遗传毒性。对雄性Fischer 344大鼠连续3天口服给予2-NA。将大鼠分为6个处理组：3个组分别给予125、250和500mg/kg剂量的2-NA；1个组给予2-NA与谷胱甘肽-SH（GSH）的组合；1个阴性对照组；以及1个阳性对照组。不添加hOGG1的彗星试验未在肝脏或膀胱中检测到DNA损伤，微核试验也未显示骨髓细胞有断裂效应。然而，添加hOGG1的彗星试验在膀胱样本中呈阳性，表明给予500mg/kg 2-NA的组膀胱中存在氧化性DNA损伤。此外，GSH抗氧化剂显著降低了2-NA引起的氧化性DNA损伤。这些结果表明，氧化性DNA损伤可能是2-NA处理的大鼠膀胱致癌作用的一种作用方式。
