Novel o-Toluidine Metabolite in Rat Urine Associated with Urinary Bladder Carcinogenesis
Novel o-Toluidine Metabolite in Rat Urine Associated with Urinary Bladder Carcinogenesis
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大鼠尿液中新型邻甲苯胺代谢物与膀胱癌发生相关
DOI：
10.1021/acs.chemrestox.0c00098
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发表时间：
2020
影响因子：
4.1
通讯作者：
Miyoshi Noriyuki
中科院分区：
文献类型：
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作者：
Tajima Yuya;Toyoda Takeshi;Hirayama Yuichiro;Matsushita Kohei;Yamada Takanori;Ogawa Kumiko;Watanabe Kenji;Takamura-Enya Takeji;Totsuka Yukari;Wakabayashi Keiji;Miyoshi Noriyuki
邻甲苯胺（o-Tol）是一种单环芳香胺，可引起人类和实验动物的膀胱癌，因此被归类为第1类致癌物（IARC），其中o-Tol的致癌性与代谢活化、DNA损伤和DNA加合物形成有关。在DNA加合物形成机制中，邻甲苯通过N-羟基化、N-乙酰氧基化、然后脱乙酰氧基化代谢，以产生亲电氮离子，其能够结合到DNA碱基，例如dG-C8。因此，dG-C8-o-Tol被认为是fo-Tol暴露的合理DNA加合物。然而，尚未报道直接检测生物样品中的dG-C8-o-Tol。在这里，我们表明，novelo-Tol代谢产物，2-甲基-N1-（2-甲基苯基）苯-1，4-二胺（MMBD），二聚体通过头到尾结合，首次被确定为ino-Tol暴露大鼠尿液。在fo-Tol和S9混合物的反应中也检测到MMBD，表明该形成由酶促反应催化。与o-Tol相比，MMBD对N-乙酰基转移酶高表达的鼠伤寒沙门氏菌具有更强的致突变性，对人膀胱癌T24细胞和人脾淋巴母细胞TK 6细胞具有更强的细胞毒性。此外，在小牛胸腺DNA与含有MMBD的大鼠尿液的反应中检测到对应于dG-MMBD的DNA加合物（m/z478.1），并且还在用o-Tol处理的大鼠的肝DNA中检测到。因此，这些结果表明，Tol诱导的膀胱癌发生可能至少部分归因于MMBD的形成。在评价接触后膀胱癌发生的风险时，应考虑单环芳香胺可能的二聚作用。
o-Toluidine (o-Tol), a monocyclic aromatic amine, causes bladder cancer in humans and experimental animals and is therefore classified as a Group 1 carcinogen (IARC) in which the carcinogenicity ofo-Tol is involved in metabolic activation, DNA damage, and DNA adduct formation. In the DNA adduct formation mechanism,o-Tol is metabolized byN-hydroxylation,N-acetoxylation, and then deacetoxylation to produce an electrophilic nitrenium ion, which is able to bind to a DNA base, such as dG-C8. Therefore, dG-C8-o-Tol is thought to be a plausible DNA adduct ofo-Tol exposure. However, direct detection of dG-C8-o-Tol in biological samples has not been reported yet. Here, we show that a novelo-Tol metabolite, 2-methyl-N1-(2-methylphenyl)benzene-1,4-diamine (MMBD), a dimer by head-to-tail binding, was identified for the first time ino-Tol-exposed rat urine. MMBD was also detected in a reaction ofo-Tol and S9 mix, indicating the formation was catalyzed by an enzymatic reaction. Moreover, MMBD showed a potent stronger mutagenicity inN-acetyltransferase overexpressedSalmonella typhimuriumstrains,and cytotoxicity in human bladder carcinoma T24 cells and human spleen lymphoblastoid TK6 cells compared witho-Tol. Furthermore, a DNA adduct (m/z478.1) corresponding to dG-MMBD was detected in the reaction of calf thymus DNA with rat urine containing MMBD, and also in hepatic DNA of rats treated witho-Tol. These results therefore suggested thato-Tol-induced bladder carcinogenesis could be at least partly attributed to MMBD formation. The possible dimerization of monocyclic aromatic amines should be considered in the evaluation of the risk of bladder carcinogenesis after exposure.