基于血管舒缓素-激肽系统研究纳米银穿透血脑屏障产生神经毒性的分子作用机制

Silver nanoparticles are now being widely used in various fields because of their excellent antibacterial characteristics. However, their toxicological effects and the molecular mechanisms still remain unclear. In recent 10 years, we have been studing the toxicities of metal nanoparticles based on in vitro and in vivo tests. The results showed that silver nanoparticles could cause toxicities in experimental fish and rodent animals. Silver nanoparticles could also induce oxidative stress and cause apoptosis in rat cerebellum grandule cells, thus leading to potential neurotoxicities in the animals. It is thus very important to identify how silver nanoparticles penetrate the blood-brain barrier, so that we may explain their toxicological mechanisms. We will use in vitro, ex vivo and in vivo experiments to investigate silver nanoparticles induced kallikrein-kinin system activation, dysfunction of the tight junction in cerebral microvascular endothelial cells,increased permeability of the cerebral microvasculature and blood-brain barrier damage. The stress caused by silver nanoparticles and the activated plasma serine protease will be studied in rat cerebellum granule cells and astrocytes to elucidate the corresponding neurotoxicities. The mechanisms for silver nanoparticles induced vasular permeability and the corresponding neurotoxicity will be discussed. The strategy for improving silver nanoparticle induced neurotoxicity outcome will be explored by blocking the key plasma serine protease and inhibiting vasuclar permeability. It may help to reduce the unnecessary environmental harzards and human health risk from the unexpected silver nanoparticles exposure.

由于纳米银优越的抗菌性能，在医学、纺织等领域得到了广泛的使用，然而其毒性效应与作用机制尚不清晰。近十年间，我们课题组基于离体与活体模型对金属纳米材料毒理学效应开展了深入研究，发现纳米银可对鱼类与哺乳类动物产生毒性作用。纳米银通过诱导氧化胁迫可引起大鼠小脑颗粒细胞凋亡，具有潜在的神经毒性效应。因此，探讨这种纳米材料穿透血脑屏障进入脑组织的生物学过程对于揭示其致毒机制具有重要意义。本项目拟基于离体与活体暴露实验，通过血管舒缓素-激肽系统，研究纳米银对关键血浆丝氨酸蛋白酶的激活效应，评价脑微血管内皮细胞功能受损导致的血管通透性改变与纳米银颗粒穿透血脑屏障的效应，进而分析纳米银与血浆丝氨酸蛋白酶异位表达对脑神经细胞的损伤作用。通过这些研究，阐明纳米银穿过血脑屏障产生神经毒性效应的分子生物学作用机制，进而通过阻断信号通路中关键丝氨酸蛋白酶作用，抑制血管通透性改变，探讨纳米银毒性效应的拮抗方案。

纳米银由于优越的抗菌活性，目前已在医疗等多个领域应用，纳米银广泛的应用可造成人体不可避免的接触与暴露，研究纳米银进入血液穿透血管屏障达到靶组织产生毒性效应对于客观评价纳米银等金属纳米材料的健康风险具有重要意义。本项目围绕纳米银，探讨了其通过调控血浆关键酶原影响血管通透性，靶向性进入脑组织产生神经毒性作用的分子机制，并进而评价了调控包括纳米银与纳米金在内的典型金属纳米材料生物学效应的关键理化因子。研究发现，表面带有负电荷的纳米银可调控血管舒缓素-激肽系统中起始酶原FXII自激活，从而触发KKS的级联活化，引起血管内皮细胞粘合连接蛋白的细胞内化降解，导致血管通透性显著增加。经鼻给药的纳米银可靶向性进入大鼠脑组织，并且与其它组织不同的是，银在脑组织中可长期滞留。脑组织中的纳米银可通过抑制大鼠小脑颗粒细胞中钙通道蛋白的表达，产生脑神经组织病理学显著改变，从而引起实验动物神经行为学变化。通过大鼠大脑皮层星形胶质细胞模型的研究发现，纳米银可引起细胞氧化损伤导致细胞凋亡，而银离子则可通过破坏细胞膜完整性诱导细胞坏死为主的细胞毒性。在同等细胞毒性暴露剂量下，纳米银可引起细胞释放细胞因子调控神经免疫反应，表现出独特的颗粒效应。金属纳米材料的表面配体、电荷等可以有效影响其杀菌、血液毒性以及透皮行为。以上成果一方面揭示了纳米银的毒性效应与作用机制，另一方面也为效应调控的生物安全性纳米材料的设计与合成提供了科学思路。