Data from: Comparative genotoxicity of TEMPO and three of its derivatives in mouse lymphoma cells

TEMPO and its derivatives are stable free radical nitroxides widely used in the field of chemistry, biology, and pharmacology. TEMPO was previously found to be mutagenic and to induce micronuclei in mammalian cells. In the present study, we investigated and quantified the genotoxicity of four structurally similar nitroxides, TEMPO and three of its derivatives (4-hydroxy-TEMPO, 4-oxo-TEMPO, and 4-methoxy-TEMPO), using the mouse lymphoma assay (MLA) and Comet assay in L5178Y Tk+/- cells. The results showed that all tested nitroxides were cytotoxic and mutagenic in the MLA, both in the presence and absence of S9, with metabolic activation significantly enhancing the cytotoxicity and/or mutagenicity. In addition, the four nitroxides caused DNA strand breakage. The mutagenicity and DNA damaging dose-responses of the test articles were compared using the PROAST benchmark dose (BMD) software package. The potency ranking of the four nitroxides for mutagenicity was different from the ranking of the DNA damaging effects. The mode of action (MoA) analysis by a multi-endpoint DNA damage pathway assay classified all four nitroxides as clastogens. In addition, the majority of the induced Tk mutants showed loss of heterozygosity (LOH) at the Tk and D11Mit42 loci (i.e., chromosome damage <31 Mbp). These results suggest that TEMPO and its three derivatives are cytotoxic and mutagenic in mouse lymphoma cells through a mechanism that involves strand breakage and large alterations to DNA. The potency rankings indicate that the different TEMPO derivatives vary in their mutagenic and DNA damaging potential.TEMPO及其衍生物均为稳定自由基型硝酰化合物（nitroxides），广泛应用于化学、生物学与药理学领域。此前已有研究发现，TEMPO具有致突变性，并可诱导哺乳动物细胞产生微核。本研究采用小鼠淋巴瘤试验（MLA）与彗星试验（Comet assay），在L5178Y Tk+/-细胞中对四种结构相似的硝酰化合物——TEMPO及其三种衍生物（4-羟基-TEMPO、4-氧代-TEMPO与4-甲氧基-TEMPO）的遗传毒性进行了研究与定量分析。试验结果显示，在添加与不添加S9代谢活化体系的情况下，所有受试硝酰化合物在MLA中均表现出细胞毒性与致突变性，且代谢活化可显著增强其细胞毒性和/或致突变性。此外，四种受试硝酰化合物均可造成DNA链断裂。本研究采用PROAST基准剂量（BMD）软件包，对受试物的致突变性与DNA损伤剂量反应关系进行了比较分析。四种硝酰化合物的致突变性效力排序与DNA损伤效应排序存在差异。通过多终点DNA损伤通路试验开展的作用模式（MoA）分析将四种受试硝酰化合物均归类为致染色体断裂剂。此外，多数诱导产生的Tk突变体在Tk与D11Mit42基因位点均表现出杂合性缺失（LOH），即染色体损伤范围小于31 Mbp。上述结果表明，TEMPO及其三种衍生物可通过引发DNA链断裂与大范围DNA改变的机制，在小鼠淋巴瘤细胞中表现出细胞毒性与致突变性。效力排序结果显示，不同的TEMPO衍生物在致突变性与DNA损伤潜力方面存在差异。