Topoisomerase poisons are known to stabilize covalent enzyme-DNA intermediates forming covalent cleavage complexes, which are highly cytotoxic especially for dividing cells and thus, make topoisomerases targets for cancer therapy. Topoisomerases have been extensively studied in mammalian model systems, whereas in other vertebrate models including zebrafish, they still remain less characterized. Here we show similarities in the genotoxic effects of zebrafish and mammalian systems towards topoisomerase I (Top1) poisons and PARP inhibitor - olaparib. On the other hand we observed that topoisomerase II (Top2) poisons (doxorubicin and etoposide) did not affect 1 day post fertilization embryo viability, however in cells isolated from Top2 drug treated embryos the formation of DNA cleavage complexes was observed by comet assay. We explain this by cellular drug uptake limitation in live zebrafish embryos versus unimpeded drug influx in cells isolated from Top2 poisons pre-treated embryos. We also demonstrate that EDTA facilitates the extraction of Top2 from zebrafish nuclei and recovers both, basal and Top2 poison induced DNA damage.

中文翻译：

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拓扑异构酶中毒的遗传毒性作用和对斑马鱼胚胎的PARP抑制作用。

已知拓扑异构酶毒物可稳定形成共价裂解复合物的共价酶-DNA中间体，共价裂解复合物具有很高的细胞毒性，尤其是对分裂细胞而言，因此成为拓扑异构酶的靶点，可用于癌症治疗。拓扑异构酶已在哺乳动物模型系统中进行了广泛研究，而在包括斑马鱼在内的其他脊椎动物模型中，它们的特征仍然较少。在这里，我们显示了斑马鱼和哺乳动物系统对拓扑异构酶I（Top1）毒物和PARP抑制剂-olaparib的遗传毒性作用的相似性。另一方面，我们观察到拓扑异构酶II（Top2）毒物（阿霉素和依托泊苷）不会影响受精后1天的胚胎活力，但是在通过Top2药物处理的胚胎分离的细胞中，通过彗星分析观察到了DNA裂解复合物的形成。我们通过在活的斑马鱼胚胎中的细胞药物吸收限制与从Top2毒物预处理的胚胎分离的细胞中不受阻碍的药物流入来解释这一点。我们还证明了EDTA有助于从斑马鱼细胞核中提取Top2，并恢复了基础毒物和Top2毒物诱导的DNA损伤。