Dissecting common and divergent molecular pathways elicited by CdSe/ZnS quantum dots in freshwater and marine sentinel invertebrates

Water ecosystems represent main targets of unintentional contamination of nanomaterials, due to industrial waste or other anthropogenic activities. Nanoparticle insult to living organisms may occur in a sequential way, first by chemical interactions of the material with the target membrane, then by progressive internalisation and interaction with cellular structures and organelles. These events trigger a signal transduction, through which cells modulate molecular pathway in order to respond and survive to the external elicitation. Therefore, the analysis of the global changes of the molecular machinery, possibly induced in an organism upon exposure to a given nanomaterial, may provide unique clues for proper and exhaustive risk assessment. Here, we tested the impact of core/shell CdSe/ZnS QDs coated by a positively charged polymer on two aquatic species, the polyp Hydra vulgaris and the coral S. pistillata, representative of freshwater and sea habitats, respectively. By using reliable approaches based on animal behaviour and physiology together with a whole transcriptomic profiling, we determined several toxicity endpoints. Despite the difference in the efficiency of uptake, both species were severely affected by QD treatment, resulting in dramatic morphological damages and tissue bleaching. Global transcriptional changes were also detected in both organisms, but presenting different temporal dynamics, suggesting both common and divergent functional responses in the two sentinel organisms. Due to the striking conservation of structure and genomic organisation among animals throughout evolution, our expression profiling offers new clues to identify novel molecular markers and pathways for comparative transcriptomics of nanotoxicity.

水生生态系统是纳米材料意外污染的主要靶标，此类污染多由工业废弃物或其他人为活动引发。纳米颗粒对生物体的侵害可循序发生：首先是材料与靶细胞膜发生化学相互作用，随后逐步完成内化，并与细胞结构及细胞器产生相互作用。此类事件会触发信号转导过程，细胞借此调控分子通路以响应外界刺激并维持存活。因此，对生物体暴露于特定纳米材料后可能引发的分子系统全局变化进行分析，可为开展精准且全面的风险评估提供独特线索。本研究针对经带正电聚合物包覆的核壳型CdSe/ZnS量子点（Quantum Dots, QDs），检验其对两种水生生物的影响：分别为淡水生境代表物种普通水螅（*Hydra vulgaris*）以及海水生境代表物种柱形珊瑚（*S. pistillata*）。本研究依托基于动物行为与生理特征的可靠实验手段，并结合全转录组分析，确定了多项毒性终点指标。尽管两种生物的纳米颗粒摄取效率存在差异，但均在QD处理后受到严重影响，出现显著的形态损伤与组织白化现象。两种生物体内均检测到全局转录水平的变化，但呈现出不同的时间动态特征，表明这两种指示生物既存在共通的功能响应，也存在分化的功能应答模式。鉴于动物在演化过程中其结构与基因组组织结构具有高度保守性，本研究的表达谱分析结果可为识别纳米毒性比较转录组学所需的新型分子标记及通路提供全新线索。