纳米银用于胶质瘤放射增敏及细胞受控自噬的研究

发布时间：2018-04-19 01:22

本文选题：纳米银 + 自噬　；参考：《东南大学》2016年博士论文

【摘要】：胶质瘤是发病率最高的神经系统肿瘤,且致死率最高。胶质瘤的治疗目前仍是医疗难题。胶质瘤的治疗方案包括手术、化疗和放疗。其中放疗是胶质瘤辅助治疗的金标准。然而在临床实践中,由于胶质瘤的浸润生长难以完全切除,另外恶性胶质瘤对放疗及化疗的敏感性较低,导致胶质瘤患者的预后很差,平均中位生存期约为14.6个月。因此我们急需寻找一种有效的治疗胶质瘤的方案。由于纳米材料有着卓越的物理化学性能,今年来被广泛用于肿瘤治疗,尤其在放化疗增敏以及肿瘤诊断方面。纳米银具有优异的表面增强拉曼特性以及广谱抗菌性,在生物医学方面的应用引起了广泛关注。最近研究表明纳米银也具有显著的抗肿瘤作用,其抗肿瘤机制主要是通过造成氧化应激压力、DNA损伤、细胞周期阻滞进而引起细胞凋亡或坏死。此外,纳米银还可被用作放疗的增敏剂,本组已在体外和体内分别证实了纳米银对胶质瘤的放射增敏作用,然而其放射增敏的深层机制仍待进一步阐明。本文主要研究了表面包覆PVP的纳米银的细胞毒性、诱导自噬效应、放射增敏效应及其相关机制,期望为纳米银用于胶质瘤治疗提供一定的数据基础。主要工作包括以下几个方面:1.系统研究了纳米银在U251细胞中的摄取及定位。发现纳米银对U251细胞具有浓度和尺寸依赖性的细胞毒性。此外,纳米银还可增加细胞中活性氧自由基(reactive oxygen species,ROS)的生成,降低线粒体膜电位。抗氧化剂预处理可逆转其对细胞内ROS生成以及线粒体膜电位的影响。2.系统研究了纳米银诱导U251细胞自噬的作用。并通过P62蛋白表达的研究证明纳米银引起的自噬体的积累是通过从上游促进自噬体的形成而非阻断自噬下游降解来实现的,即完整的细胞自噬。3.明确自噬与纳米银放射增敏作用的关系,并初步探讨了其机制。发现自噬在纳米银放射增敏过程中的作用为保护性,抑制自噬可进一步提高纳米银与X射线造成的细胞死亡和凋亡。此外,还发现ERK、JNK信号通路在纳米银诱导自噬及放射增敏过程中起重要作用。4.证实纳米银与X射线联合/单独作用造成的自噬以及纳米银的放射增敏作用均依赖于ROS生成。发现抑制保护性自噬提高放疗效果的实质是ROS水平的进一步升高。
[Abstract]:Glioma is the highest incidence of nervous system tumors, and the highest fatality rate.The treatment of glioma is still a medical problem.Treatment options for gliomas include surgery, chemotherapy and radiotherapy.Radiotherapy is the gold standard for adjuvant treatment of gliomas.However, in clinical practice, the invasion and growth of glioma is difficult to be completely resected, and the sensitivity of malignant glioma to radiotherapy and chemotherapy is low, which leads to poor prognosis of glioma patients, and the median survival time is about 14.6 months.Therefore, we urgently need to find an effective treatment for glioma.Because of their excellent physical and chemical properties, nanomaterials have been widely used in tumor therapy this year, especially in radio-chemosensitization and tumor diagnosis.Due to its excellent surface enhanced Raman and wide spectrum antimicrobial properties, silver nanoparticles have attracted wide attention in biomedical applications.Recent studies have shown that nano-silver also has a significant anti-tumor effect, its anti-tumor mechanism is mainly caused by oxidative stress stress caused by DNA damage, cell cycle arrest and cell apoptosis or necrosis.In addition, silver nanoparticles can be used as radiosensitizers for radiotherapy. The radiosensitization of silver nanoparticles to gliomas has been confirmed in vitro and in vivo, but the deep mechanism of the radiosensitization of silver nanoparticles remains to be further elucidated.In this paper, the cytotoxicity, induced autophagy, radiosensitization and the mechanisms of silver nanoparticles coated with PVP were studied in order to provide a data basis for the application of silver nanoparticles in glioma therapy.The main work includes the following aspects: 1.The uptake and localization of silver nanoparticles in U251 cells were systematically studied.It was found that silver nanoparticles were concentration-and size dependent cytotoxic to U251 cells.In addition, silver nanoparticles also increased the production of reactive oxygen speciesof Ros, and decreased the mitochondrial membrane potential.Antioxidant pretreatment could reverse the effects of antioxidant pretreatment on intracellular ROS production and mitochondrial membrane potential.The effect of silver nanoparticles on autophagy of U251 cells was studied systematically.The study of P62 protein expression showed that the accumulation of autophagy induced by nano-silver was achieved by promoting the formation of autophagy from upstream rather than blocking the degradation of autophagy downstream, that is, complete cell autophagy.The relationship between autophagy and the radiosensitization of silver nanoparticles was clarified and its mechanism was discussed.It was found that autophagy plays a protective role in the radiosensitization of silver nanoparticles, and inhibition of autophagy can further increase cell death and apoptosis induced by nano-silver and X-ray.In addition, ERKN JNK signaling pathway plays an important role in the process of silver induced autophagy and radiosensitization.It is confirmed that both the autophagy induced by the combination of silver nanoparticles and X-ray and the radiosensitization of silver nanoparticles are dependent on the formation of ROS.It was found that the essence of inhibiting protective autophagy to improve the effect of radiotherapy was the further increase of ROS level.
【学位授予单位】：东南大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：R739.41;TB383.1

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