Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, 1-1-1 Tsushima, Okayama 700-8530, Japan.
Mutat Res. 2010 Sep 10;691(1-2):47-54. doi: 10.1016/j.mrfmmm.2010.07.002. Epub 2010 Jul 15.
We investigated the photo-mutagenicity and photo-genotoxicity of N-dialkylnitrosamines and its mechanisms of UVA activation. With simultaneous irradiation of UVA, photo-mutagenicity of seven N-dialkylnitrosamines was observed in Ames bacteria (Salmonella typhimurium TA1535) in the absence of metabolic activation. Mutagenicity of pre-irradiated N-dialkylnitrosamines was also observed with S. typhimurium hisG46, TA100, TA102 and YG7108 in the absence of metabolic activation. UVA-mediated mutation with N-nitrosodimethylamine (NDMA) and N-nitrosodiethylamine (NDEA) decreased by adding either the NO or OH radical scavenger. When superhelical DNA was irradiated with N-dialkylnitrosamines, nicked circular DNA appeared. Ten N-dialkylnitrosamines examined produced strand breaks in the treated DNA in the presence of UVA. The level of single-strand breaks in phiX174 DNA mediated by N-nitrosomorpholine (NMOR) and UVA decreased by adding either a radical scavenger or superoxide dismutase. When calf thymus DNA was treated with N-dialkylnitrosamines (NDMA, NDEA, NMOR, N-nitrosopyrrolidine (NPYR) and N-nitrosopiperidine (NPIP)) and UVA, the ratio of 8-oxodG/dG in the DNA increased. Action spectra were obtained to determine if nitrosamine acts as a sensitizer of UVA. Both mutation frequency and NO formation were highest at the absorption maximum of nitrosamines, approximately 340 nm. The plots of NO formation and mutation frequency align with the absorption curve of NPYR, NMOR and NDMA. A significant linear correlation between the optical density of N-dialkynitrosamines at 340 nm and NO formation in each irradiated solution was revealed by ANOVA. We would like to propose the hypothesis that the N-nitroso moiety of N-dialkylnitrosamines absorbs UVA photons, UVA-photolysis of N-dialkylnitrosamines brings release of nitric oxide, and subsequent production of alkyl radical cations and active oxygen species follow as secondary events, which cause DNA strand breaks, oxidative and alkylative DNA damages and mutation.
我们研究了 N-二烷基硝胺的光致突变性和光遗传毒性及其 UVA 激活机制。在没有代谢激活的情况下，用 UVA 同时辐照时，在艾姆斯细菌（鼠伤寒沙门氏菌 TA1535）中观察到七种 N-二烷基硝胺的光致突变性。在没有代谢激活的情况下，用 S. typhimurium hisG46、TA100、TA102 和 YG7108 也观察到了预辐照 N-二烷基硝胺的致突变性。用 N-亚硝二甲胺（NDMA）和 N-亚硝二乙胺（NDEA）进行 UVA 介导的突变时，添加 NO 或 OH 自由基清除剂可降低突变率。当超螺旋 DNA 受到 N-二烷基硝胺的辐照时，出现了缺口环状 DNA。在 UVA 存在的情况下，十种 N-二烷基硝胺处理的 DNA 产生了链断裂。在 N-亚硝吗啉（NMOR）和 UVA 介导的 phiX174 DNA 中单链断裂的水平通过添加自由基清除剂或超氧化物歧化酶降低。当小牛胸腺 DNA 用 N-二烷基硝胺（NDMA、NDEA、NMOR、N-亚硝基吡咯烷（NPYR）和 N-亚硝基哌啶（NPIP））和 UVA 处理时，DNA 中的 8-氧-dG/dG 比例增加。获得作用光谱以确定亚硝胺是否作为 UVA 的敏化剂。突变频率和 NO 形成均在亚硝胺的吸收最大值处最高，约为 340nm。NO 形成和突变频率的曲线与 NPYR、NMOR 和 NDMA 的吸收曲线一致。通过方差分析揭示了 340nm 处 N-二炔硝胺的光密度与每个辐照溶液中 NO 形成之间的显著线性相关性。我们想提出一个假设，即 N-二烷基硝胺的 N-亚硝基部分吸收 UVA 光子，UVA 光解 N-二烷基硝胺导致一氧化氮的释放，随后烷基自由基阳离子和活性氧物质的产生作为次级事件，导致 DNA 链断裂、氧化和烷基化 DNA 损伤和突变。
