有机磷农药毒死蜱与镉引发肝细胞复合毒性效应的作用机制

The contamination of organophosphorus pesticides and heavy metals, which are simultaneously distributed in diverse environmental media and the exposed population (even the general population), is rather serious and poses substantial risk on human health. Our previous research demonstrated that Chlorpyrifos (CPF) and cadmium (Cd) could form a complex, which would result in increased bioavailability of cadmium in liver cells. Besides, the joint exposure of CPF and Cd could also lead to obvious synergistic toxic effects, such as remarkable increase of intracellular ROS, considerable morphological changes of cells and destruction of membrane integrity as well as cell apoptosis. Nevertheless, the mechanisms of synergistic toxicities remain poorly understood thus far. Therefore, further studies will be conducted in this project to reveal the following issues, 1).the key mechanisms of changes in hepatic bioavailability of CPF and Cd under joint exposure compared to their individual effects, as well as the kinetics of uptake and release of the chemicals. 2).the subcellular distribution of the complex and the relationship between the damage of organelles and the overall cytotoxicity. 3). the effects on antioxidant function of hepatocytes and the mechanism of cell death. 4).the effects and mechanism of the joint exposure on liver-governed iron metabolism. Research objectives: to identify the mechanisms responsible for the synergistic hepatoxicity inudced by the joint exposure of CPF and Cd, and to clarify the effects of the joint exposure upon liver-conducted iron metabolism plus the primary signal pathways involved.

有机磷农药和重金属的污染形势严峻，这两类污染物在多种环境介质和高暴露人群（甚至普通人群）中同时存在，对人类的健康造成巨大威胁。本研究组前期的工作表明，毒死蜱（CPF）和镉可形成复合物，这一复合物显著提高肝细胞对镉的生物有效性；二者复合暴露产生明显的协同毒性，如胞内ROS显著升高、细胞形态明显改变、细胞膜完整性破坏和细胞凋亡等。然而，目前对于复合毒性机理尚不清楚。为此，本项目将深入揭示：1) CPF与镉复合暴露下肝细胞对目标污染物生物有效性变化的决定机制，以及复合物的进入和排出细胞的动力学；2) CPF与镉复合物的亚细胞分布，及细胞器的损伤与细胞毒性间的关联；3)复合暴露对肝细胞抗氧化功能的影响和诱导细胞死亡的机理；4)复合毒性对肝脏主导的铁代谢平衡的影响及分子作用机制。研究目标：明确CPF和镉复合暴露引发肝脏协同毒性效应的作用机理，阐明复合暴露对肝脏介导的铁代谢的影响与受累的主要信号通路。

目前对环境污染物毒性和作用机制的认识主要局限于对单一化合物的研究，但往往不能有效地评估复杂的环境混合物的毒性和相关机制。研究已证实，有机磷农药和重金属污染物在各种环境介质中和暴露人群（甚至普通人群）的体液和组织中均发现同时共存，同时，二者共同暴露可对低等水生生物产生联合毒性效应。但目前，这方面的研究尚未在人和哺乳动物细胞上深入开展，对二者复合毒性的机理更缺乏了解。为此，本课题深入探索了以毒死蜱(CPF)为代表的有机磷农药和以镉、铅等为代表的有毒重金属复合污染对肝脏和血液的毒理学效应以及分子机理，并通过铁代谢的调节途径将肝脏毒性和血液毒性结合起来，揭示两种毒性效应之间的关联和相关机理。本研究结果表明：（1）在单独暴露未出现毒性的条件下，镉和CPF复合暴露对肝脏细胞产生明显的毒性效应，包括降低存活率和增值水平、降低线粒体膜电位促进凋亡、引起形态的异常并干扰细胞的脂类代谢。（2）镉暴露上调巨噬细胞中铁输出蛋白ferroportin水平从而降低胞内铁水平，而CFP暴露除了通过上调巨噬细胞ferroportin，还下调肝脏细胞的hepcidin表达水平，使得这两种体内最主要的铁存储细胞均出现胞内铁水平下降，进而引发机体铁代谢紊乱。（3）镉暴露可通过lncRNA MT1DP诱发相应的肝脏细胞死亡效应，而Hri基因可通过诱导单核细胞和中性粒细胞生成在对镉暴露所引发的肝脏组织损伤的修复中起到促进作用。（4）镉暴露造成明显的血液毒性和造血障碍，而在对抗镉所诱导的血液毒性效应过程中，HRI-eIF2αP-ATF4信号通路起着关键的作用。（5）与镉类似，铅暴露可引发相应的毒性效应，包括溶血、造血障碍及铁代谢紊乱，而miR-214在对抗砷的血液毒性过程中发挥着重要的调节作用。