Guo Hua, Zhang Jing, Boudreau Mary, Meng Jie, Yin Jun-jie, Liu Jian, Xu Haiyan
Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China.
National Center for Toxicological Research, US Food and Drug Administration, Jefferson, AR, 72079, USA.
Part Fibre Toxicol. 2016 Apr 29;13:21. doi: 10.1186/s12989-016-0133-9.
Administration of silver nanoparticles (AgNPs) to mice could result in their distribution and accumulation in multiple organs, with notable prominence in liver, lungs, and kidneys. However, how AgNPs transport through blood vesicular system to reach the target organs is unclear, and the precise differences in the mechanisms of toxicity between AgNPs and silver ions still remain elusive. In the present research, the pathological changes on these target organs with a focus on inter-endothelial junction was investigated to gain a new insight of AgNPs toxicity by comparing the mechanisms of action of AgNPs and AgNO3.
We investigated the in vitro cytotoxicity of either citrated-coated AgNPs (10, 75, and 110 nm) or silver nitrate (AgNO3) following 24 h incubations (1-40 μg/mL) in the presence of primary human umbilical vein endothelial cells (HUVEC). Meanwhile, we detected the effects of AgNPs on intercellular conjunction and intracellular ROS by VE-cadherin staining and 2', 7'-dichlorodihydrofluorescein diacetate (DCFH-DA) assay, respectively. To assess in vivo toxicity, we administered single or multiple intravenous injections (25 μg Ag for AgNPs and 2.5 μg Ag for AgNO3 per dose) to mice.
In the in vitro study, the TEM observation showed that AgNPs were taken up by endothelial cells while AgNO3 was taken up little. Meanwhile AgNPs incubation induced the elevation of intracellular ROS and down-regulation of VE-cadherin between the endothelial cells and affected the cytoskeleton actin reorganization, which could be rescued by antioxidant N-acetylcysteine. In contrast, AgNO3 caused direct cell death when the concentration was higher than 20 μg/mL and without ROS induction at lower concentration. The release of AgNPs from leaking vessels induced peripheral inflammation in the liver, lungs, and kidneys, and the severity increased in proportion to the diameter of the AgNPs used.
It is AgNPs but not AgNO3 that were taken up by vascular endothelial cells and induced intracellular ROS elevated, which was closely related to disruption of the integrity of endothelial layer. The AgNPs-induced leakiness of endothelial cells could mediate the common peripheral inflammation in liver, kidney and lung through intravenous exposure.
给小鼠施用银纳米颗粒（AgNPs）会导致其在多个器官中分布和积累，在肝脏、肺和肾脏中尤为显著。然而，AgNPs如何通过血管系统转运至靶器官尚不清楚，并且AgNPs与银离子毒性机制的确切差异仍不明确。在本研究中，通过比较AgNPs和AgNO₃的作用机制，以血管内皮连接为重点，研究这些靶器官的病理变化，从而深入了解AgNPs的毒性。
我们在原代人脐静脉内皮细胞（HUVEC）存在的情况下，对柠檬酸盐包被的AgNPs（10、75和110纳米）或硝酸银（AgNO₃）进行24小时孵育（1 - 40μg/mL），研究其体外细胞毒性。同时，我们分别通过VE-钙黏蛋白染色和2',7'-二氯二氢荧光素二乙酸酯（DCFH-DA）测定法检测AgNPs对细胞间连接和细胞内活性氧（ROS）的影响。为评估体内毒性，我们给小鼠单次或多次静脉注射（每剂量AgNPs为25μg银，AgNO₃为2.5μg银）。
在体外研究中，透射电子显微镜观察显示内皮细胞摄取了AgNPs，而AgNO₃摄取很少。同时，AgNPs孵育诱导细胞内ROS升高，内皮细胞间VE-钙黏蛋白下调，并影响细胞骨架肌动蛋白重排，这可通过抗氧化剂N-乙酰半胱氨酸挽救。相比之下，当浓度高于20μg/mL时，AgNO₃导致直接细胞死亡，且在较低浓度下无ROS诱导。从渗漏血管释放的AgNPs在肝脏、肺和肾脏中引发外周炎症，炎症严重程度与所用AgNPs的直径成正比。
被血管内皮细胞摄取并诱导细胞内ROS升高的是AgNPs而非AgNO₃，这与内皮细胞层完整性的破坏密切相关。静脉暴露时，AgNPs诱导的内皮细胞渗漏可介导肝脏、肾脏和肺中的共同外周炎症。
