Cavin Christophe, Delatour Thierry, Marin-Kuan Maricel, Holzhäuser Daisy, Higgins Larry, Bezençon Claudine, Guignard Gabriela, Junod Sylviane, Richoz-Payot Janique, Gremaud Eric, Hayes John D, Nestler Sandra, Mantle Peter, Schilter Benoît
Quality and Safety Department, Nestlé Research Center, CH-1000 Lausanne 26, Switzerland.
Toxicol Sci. 2007 Mar;96(1):30-9. doi: 10.1093/toxsci/kfl169. Epub 2006 Nov 16.
Ochratoxin A (OTA) is a renal carcinogen in rodents. Its human health significance is unclear. It likely depends upon the mechanism of carcinogenesis. In a previous microarray study a reduction in nuclear factor-erythroid 2 p45-related factor 2 (Nrf2)-dependent gene expression was observed in the kidney but not in the liver of rats fed OTA up to 12 months. Nrf2 regulates detoxification and antioxidant gene expression. The present report shows that OTA decreased the protein expression of several markers of the Nrf2-regulated gene battery in kidney in vivo indicating that the effects observed at mRNA level may be of biological significance. The OTA-mediated Nrf2 response could be reproduced in an NRK renal cell line and in primary hepatocyte cultures. In in vitro systems, an OTA-mediated inhibition of Nrf2 activity was demonstrated by electrophoretic mobility shift and Antioxidant Regulatory Element-driven luciferase reporter assays. The reduction of Nrf2-regulated gene expression resulted in oxidative DNA damage as evidenced by formation of abasic sites in vitro and confirmed in kidney in vivo. All OTA-mediated effects observed were prevented by pretreatment of cell cultures with inducers of Nrf2 activity. Our data suggest that reduction of cellular defense against oxidative stress by Nrf2 inhibition may be a plausible mechanism of OTA nephrotoxicity and carcinogenicity.
赭曲霉毒素A（OTA）是啮齿动物的一种肾致癌物。其对人类健康的影响尚不清楚。这可能取决于致癌机制。在之前的一项微阵列研究中，在长达12个月喂食OTA的大鼠的肾脏中观察到核因子红系2 p45相关因子2（Nrf2）依赖性基因表达降低，但在肝脏中未观察到。Nrf2调节解毒和抗氧化基因的表达。本报告表明，OTA在体内降低了肾脏中几种Nrf2调节基因标志物的蛋白质表达，表明在mRNA水平观察到的效应可能具有生物学意义。OTA介导的Nrf2反应可以在NRK肾细胞系和原代肝细胞培养物中重现。在体外系统中，通过电泳迁移率变动分析和抗氧化反应元件驱动的荧光素酶报告基因分析证明了OTA对Nrf2活性的抑制作用。Nrf2调节基因表达的降低导致了氧化性DNA损伤，体外无碱基位点的形成证明了这一点，并在体内肾脏中得到证实。用Nrf2活性诱导剂预处理细胞培养物可防止观察到的所有OTA介导的效应。我们的数据表明，通过抑制Nrf2降低细胞对氧化应激的防御可能是OTA肾毒性和致癌性的一种合理机制。
