State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, People's Republic of China.
Toxicol Sci. 2010 Jan;113(1):60-9. doi: 10.1093/toxsci/kfp248. Epub 2009 Oct 12.
Microcystin-LR (MCLR) is the most toxic and most frequently encountered hepatotoxin in the aquatic environment. This study investigated the protein profiles of zebrafish (Danio rerio) livers chronically exposed to MCLR concentrations (2 or 20 microg/l) using the proteomic approach as well as cell ultrastructure, protein phosphatase (PP) activity, protein phosphatase 2A (PP2A) abundance, and toxin content analysis of the hepatic tissue. The results showed that, after 30-day exposure, the presence of MCLR strikingly enhanced toxin accumulation and the PP activity in zebrafish livers. However, the PP2A amounts were independent of toxin treatments. MCLR caused a noticeable damage to liver ultrastructure, a widespread swelling in the rough endoplasmatic reticulum and mitochondria was observed in the MCLR-exposed hepatocytes, and a honeycomb-like structure was formed in the treated nucleoli. Comparison of two-dimensional electrophoresis (2-DE) protein profiles of MCLR-exposed and nonexposed zebrafish livers revealed that the abundance of 22 proteins, measured by 2-DE, was remarkably altered in response to toxin exposure. These proteins were involved in cytoskeleton assembly, macromolecule metabolism, oxidative stress, and signal transduction, indicating that MCLR toxicity in fish liver is complex and diverse. Thus, proteomics provides a new insight into MCLR toxicity, that chronic toxicity of MCLR is different from acute toxicity, and we speculate that the reactive oxygen species pathway might be the main toxic pathway instead of the PP one. Moreover, even a low concentration of MCLR in water could significantly interrupt cellular processes, and more care should be taken in determining the criterion for MCLR content in drinking water.
微囊藻毒素-LR（MCLR）是水生环境中最具毒性和最常遇到的肝毒素。本研究采用蛋白质组学方法研究了斑马鱼（Danio rerio）肝脏在慢性暴露于 MCLR 浓度（2 或 20 微克/升）下的蛋白质谱，以及肝组织的细胞超微结构、蛋白磷酸酶（PP）活性、蛋白磷酸酶 2A（PP2A）丰度和毒素含量分析。结果表明，在 30 天暴露后，MCLR 的存在显著增强了斑马鱼肝脏中毒素的积累和 PP 活性。然而，PP2A 量与毒素处理无关。MCLR 对肝脏超微结构造成明显损伤，暴露于 MCLR 的肝细胞中内质网和线粒体广泛肿胀，处理后的核仁中形成蜂窝状结构。暴露于和未暴露于 MCLR 的斑马鱼肝脏的二维电泳（2-DE）蛋白质谱比较表明，2-DE 测量的 22 种蛋白质的丰度因毒素暴露而显著改变。这些蛋白质参与细胞骨架组装、大分子代谢、氧化应激和信号转导，表明鱼类肝脏中 MCLR 的毒性是复杂多样的。因此，蛋白质组学为 MCLR 毒性提供了新的见解，即 MCLR 的慢性毒性不同于急性毒性，我们推测活性氧途径可能是主要的毒性途径，而不是 PP 途径。此外，即使水中的 MCLR 浓度很低，也能显著干扰细胞过程，在确定饮用水中 MCLR 含量的标准时应更加小心。
