Perturbation of Mitosis through Inhibition of Histone Acetyltransferases: The Key to Ochratoxin A Toxicity and Carcinogenicity?
Perturbation of Mitosis through Inhibition of Histone Acetyltransferases: The Key to Ochratoxin A Toxicity and Carcinogenicity?
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DOI：
10.1093/toxsci/kfr110
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发表时间：
2011-08-01
影响因子：
3.8
通讯作者：
Mally, Angela
中科院分区：
文献类型：
--
作者：
Czakai, Kristin;Mueller, Katja;Mally, Angela
赭曲霉毒素A（OTA）是迄今为止研究的最强的啮齿动物肾脏致癌物之一。虽然关于OTA遗传毒性的争议性结果已经发表，但现在广泛接受OTA不是致突变的DNA反应性致癌物。相反，来自体内和体外研究的越来越多的证据表明，OTA可能通过干扰细胞分裂促进基因组不稳定性和肿瘤发生。本研究的目的是提供进一步的支持，有丝分裂的破坏作为OTA毒性的关键事件，并了解OTA如何介导这些影响。用OTA处理永生化的人肾上皮细胞（IHKE），并通过微分干涉相差显微镜监测15小时。图像分析证实，OTA在浓度>= 5 μ M时，与大鼠在致癌条件下的血浆浓度相关，导致持续的有丝分裂停滞，并在没有核或细胞分裂的情况下退出有丝分裂。有丝分裂染色体的特征是异常浓缩和过早的姐妹染色单体分离，与核心组蛋白的磷酸化和乙酰化改变有关。为了测试OTA是否直接干扰调节组蛋白和非组蛋白的赖氨酸乙酰化的组蛋白乙酰转移酶（HAT），使用IHKE细胞的总核提取物进行无细胞HAT活性测定。在本试验中，OTA以浓度依赖性方式显著阻断HAT活性。总体而言，本研究的结果进一步支持OTA致癌性机制，包括干扰有丝分裂机制，并表明HAT是OTA的主要细胞靶点。
Ochratoxin A (OTA) is one of the most potent rodent renal carcinogens studied to date. Although controversial results regarding OTA genotoxicity have been published, it is now widely accepted that OTA is not a mutagenic, DNA-reactive carcinogen. Instead, increasing evidence from both in vivo and in vitro studies suggests that OTA may promote genomic instability and tumorigenesis through interference with cell division. The aim of the present study was to provide further support for disruption of mitosis as a key event in OTA toxicity and to understand how OTA mediates these effects. Immortalized human kidney epithelial cells (IHKE) were treated with OTA and monitored by differential interference contrast microscopy for 15 h. Image analysis confirmed that OTA at concentrations >= 5 mu M, which correlate with plasma concentrations in rats under conditions of carcinogenesis, causes sustained mitotic arrest and exit from mitosis without nuclear or cellular division. Mitotic chromosomes were characterized by aberrant condensation and premature sister chromatid separation associated with altered phosphorylation and acetylation of core histones. To test if OTA directly interferes with histone acetyltransferases (HATs) which regulate lysine acetylation of histones and nonhistone proteins, a cell-free HAT activity assay was conducted using total nuclear extracts of IHKE cells. In this assay, OTA significantly blocked HAT activity in a concentration-dependent manner Overall, results from this study provide further support for a mechanism of OTA carcinogenicity involving interference with the mitotic machinery and suggest HATs as a primary cellular target of OTA.