Le Hegarat Ludovic, Puech Lilian, Fessard Valérie, Poul Jean Michel, Dragacci Sylviane
AFSSA, Laboratoire d'Etudes et de Recherches sur les Médicaments Vétérinaires et les Désinfectants, Unité de Toxicologie Alimentaire, BP 90203, F-35302 Fougères, France.
Mutagenesis. 2003 May;18(3):293-8. doi: 10.1093/mutage/18.3.293.
Okadaic acid (OA) is a major toxin involved in diarrhetic shellfish poisoning in humans and has been shown to be both a potent tumor promoter in rodent skin and stomach and an inhibitor of serine/threonine protein phosphatases, specifically PP1 and PP2A. The research on the genotoxic potential of OA amounts to only a few studies, which give conflicting results. In order to evaluate the ability of OA to induce DNA damage, the cytokinesis-block micronucleus assay was performed in the CHO-K1 cell line. A statistically significant induction of micronuclei without strong cytotoxicity was obtained after a 24 h treatment with 20 (approximately 5-fold) and 30 nM (approximately 10-fold) OA. Then, in order to discriminate between a clastogenic or aneugenic effect of OA, the micronucleus assay was carried out in combination with fluorescence in situ hybridization (FISH) using a (TTAGGG)(n) DNA probe for centromere detection. FISH analysis showed that OA mainly induced centromere-positive micronuclei (68.9% induction with 20 nM OA and 77.0% with 30 nM). Therefore, OA can be considered aneugenic. Using the same assay, biotransformation of OA was studied after a 4 h treatment with and without metabolic activation. The results show that reactive metabolites of OA were generated with a significant increase in genotoxic potential. The relationship between the different components involved in the mitotic process and OA inhibition of protein phosphatase is also discussed.
冈田酸（OA）是导致人类腹泻性贝类中毒的主要毒素，已被证明是啮齿动物皮肤和胃部的强效肿瘤促进剂，也是丝氨酸/苏氨酸蛋白磷酸酶（特别是PP1和PP2A）的抑制剂。关于OA遗传毒性潜力的研究仅有少数几项，结果相互矛盾。为了评估OA诱导DNA损伤的能力，在CHO-K1细胞系中进行了胞质分裂阻滞微核试验。用20 nM（约5倍）和30 nM（约10倍）OA处理24小时后，获得了微核的统计学显著诱导且无强烈细胞毒性。然后，为了区分OA的致断裂或非整倍体效应，将微核试验与荧光原位杂交（FISH）结合进行，使用（TTAGGG）（n）DNA探针检测着丝粒。FISH分析表明，OA主要诱导着丝粒阳性微核（20 nM OA诱导率为68.9%，30 nM为77.0%）。因此，OA可被认为具有非整倍体效应。使用相同的试验，在有和没有代谢活化的情况下处理4小时后研究了OA的生物转化。结果表明，OA的活性代谢产物生成，遗传毒性潜力显著增加。还讨论了有丝分裂过程中不同成分与OA对蛋白磷酸酶抑制之间的关系。
