Daphnia magna exposed to narcotics and polar narcotics - isopropanol

Structural analogues are assumed to elicit toxicity via similar predominant modes of action (MOAs). Currently, MOA categorization of chemicals in environmental risk assessment is mainly based on the physico-chemical properties of potential toxicants. It is often not known whether such classification schemes are also supported by mechanistic biological data. In this study, the toxic effects of two groups of structural analogues (alcohols and anilines) with predefined MOA (narcotics and polar narcotics) were investigated at different levels of biological organization (gene transcription, energy reserves and growth). Chemical similarity was not indicative of a comparable degree of toxicity and a similar biological response. Categorization of the test chemicals based on the different biological responses (growth, energy use and gene transcription) did not result in a classification of the predefined narcotics versus the predefined polar narcotics. Moreover, gene transcription based clustering profiles were indicative of the observed effects at higher level of biological organization. Furthermore, a small set of classifier genes could be identified that was discriminative for the clustering pattern. These classifier genes co-varied with the organismal and physiological responses. Compared to the physico-chemistry based MOA classification, integrated biological multi-level effect assessment can provide the necessary MOA information that is crucial in high-quality environmental risk assessment. Our findings support the view that transcriptomics tools hold considerable promise to be used in biological response based mechanistic profiling of potential (eco)toxicants. The hybridization design was a universal reference design (a mixture of aliquots from control and exposed samples), which is recommended when class discovery is the main purpose of the experiment. One of the three biological replicates of each exposure condition was labeled with one dye, the remaining two samples were labeled with the second dye.

结构类似物被认为通过相似的主要作用模式（Modes of Action，MOAs）引发毒性。当前，环境风险评估中化学品的作用模式分类主要基于潜在有毒物质的理化性质。目前尚不清楚此类分类体系是否也能得到机制生物学数据的支撑。本研究针对两组预设作用模式分别为麻醉型毒物与极性麻醉型毒物的结构类似物（醇类与苯胺类），在不同生物组织水平（基因转录、能量储备与生长）下的毒性效应展开了探究。结果显示，化学品的结构相似性并不能反映其毒性程度与生物学响应的相似性。基于不同生物学响应（生长、能量利用与基因转录）对受试化学品进行分类，并未得到与预设的麻醉型毒物和极性麻醉型毒物相匹配的分类结果。此外，基于基因转录的聚类特征能够反映更高生物组织水平下观测到的效应。进一步可识别出一组小型分类基因集合，该集合可对聚类模式进行区分。这些分类基因与生物体整体及生理响应呈共变关系。相较于基于理化性质的作用模式分类方法，整合式生物学多水平效应评估能够提供高质量环境风险评估所需的关键作用模式信息。本研究结果佐证了这一观点：转录组学工具在基于生物学响应的潜在（生态）有毒物质机制表征方面具有可观的应用前景。本实验采用的杂交设计为通用参考设计（即对照组与暴露组样品的等分试样混合物），当实验的主要目的为类别发现时，该设计是推荐使用的方案。每个暴露条件的三个生物学重复中，一个样品使用一种荧光染料标记，剩余两个样品使用另一种荧光染料标记。