Neurotoxicity of Magnetic Nanoparticles

描述（由申请人提供）：工程氧化铁超顺磁性纳米颗粒（MNP）提供了靶向的尖端诊断和治疗平台，因为它们能够被外部磁场引导、功能化并穿透细胞和组织屏障。在研究MNP在磁力作用下延长分化的PC 12细胞中神经突生长的能力时，我们观察到MNP诱导的去分化、神经突的丧失和细胞死亡随着氧化铁浓度的增加而增加，但不包括用于MNP涂层的二巯基琥珀酸（DMSA）。越来越多的证据表明，增强的反应面积，渗透性和耐生物降解的纳米颗粒促进其细胞毒性潜力相对于分子或散装同行，牵连氧化应激（OS）作为一个关键的范例纳米毒性。OS是一个3级过程，表现为活性氧（ROS）和抗氧化防御（I级）的激活、促炎反应（II级）和导致细胞凋亡的DNA损伤（III级）。在其体内应用时，纳米颗粒迅速受到巨噬细胞的攻击，这既缓冲了纳米颗粒的潜在纳米毒性，又减少了其治疗和诊断用途所需的循环时间。在一系列初步体内研究中，我们使用大鼠坐骨神经作为组合模型，用于评估直接神经毒性和周围神经特有的有效神经元内巨噬细胞浸润。在束内显微注射高度稳定、水溶性和抗凝聚的阴离子DMSA包被的MNP（AMNP）的48小时内，我们观察到巨噬细胞的强烈流入，血红素加氧酶-1、白细胞介素-12、基质金属蛋白酶（MMP）-9和半胱天冬酶3的活化，所有这些都与氧化应激范例一致。相反，在相应的假手术、对照DMSA和葡聚糖包被的氧化铁MNP显微注射中仅观察到轻度神经毒性变化。利用工程和生物在体外和体内的方法相结合，该计划的目的是确定的机制和靶细胞的氧化铁MNP诱导的中枢和外周神经毒性。重点将放在研究表面化学（DMSA，葡聚糖和金）在体外和体内激活氧化应激信号和生物分布的作用。将使用SQUID磁力测定、光、电子和共聚焦神经病理学、ROS介导的促炎和促凋亡细胞信号传导分析以及体内感觉和运动行为评估的组合。该提案的总体目标是开发和测试MNP在神经系统治疗和诊断平台中使用安全的工程策略。 公共卫生相关性 磁性纳米颗粒（MNP）为包括神经科学在内的所有医学领域提供了尖端的药物输送、分子成像和组织工程工具。然而，它们的反应面积、渗透性和抗生物降解性的增强，提高了它们的潜在毒性。该提案旨在确定MNP神经毒性的机制，防御巨噬细胞系统的免疫激活，并开发先进的MNP制剂，用于神经系统的诊断，治疗和研究用途。

DESCRIPTION (provided by applicant): Engineered iron oxide superparamagnetic nanoparticles (MNPs) offer targeted cutting- edge diagnostic and therapeutic platforms due to their ability to be guided by an external magnetic field, be functionalized and penetrate cell and tissue barriers. In studying the capacity of MNPs to extend neurite outgrowth in differentiated PC12 cells under magnetic force, we observed MNP-induced de-differentiation, loss of neurites, and cell death with increasing concentration of iron oxide, but not dimercaptosuccinic acid (DMSA) used for MNP coating. Mounting evidence suggests that enhanced reactive area, permeability and resistance to biodegradation of nanoparticles promote their cytotoxic potential relative to molecular or bulk counterparts, implicating oxidative stress (OS) as a key paradigm of nanotoxicity. A 3-tier process, OS manifests in activation of reactive oxygen species (ROS) and antioxidant defense (tier I), pro-inflammatory response (tier II) and DNA damage leading to apoptosis (tier III). Upon their in vivo application, nanoparticles are quickly challenged by macrophages, which both buffer potential nanotoxicity of nanoparticles and reduce circulation time necessary for their therapeutic and diagnostic use. In a series of pilot in vivo studies, we used rat sciatic nerve as a combination model for assessment of direct neurotoxicity and effective intraneuronal macrophage infiltration that is unique to peripheral nerve. Within 48 hours of intrafascicular microinjection of anionic DMSA-coated MNPs (AMNPs) that are highly stable, water soluble and resistant to agglomeration, we observed a robust influx of macrophages, activation of heme oxygenase-1, interleukin-12, matrix metalloproteinase (MMP)-9 and caspase 3, all consistent with the oxidative stress paradigm. In contrast, only mild neurotoxic changes were seen in the corresponding sham procedures, control DMSA and dextran-coated iron oxide MNPs microinjections. Utilizing a combination of engineering and biological in vitro and in vivo approaches, this program aims to determine the mechanisms and target cells of central and peripheral neurotoxicity induced by iron oxide MNPs. Emphasis will be made on studying the role of surface chemistry (DMSA, dextran and gold) on activating oxidative stress signaling and biodistribution in vitro and in vivo. A combination of SQUID magnetometry, light, electron and confocal neuropathology, ROS-mediated pro- inflammatory and pro-apoptotic cell signaling analyses and in vivo sensory and motor behavioral assessments will be used. The overall goal of this proposal is to develop and test the engineering strategies that are safe for MNP use in therapeutic and diagnostic platforms in the nervous system. PUBLIC HEALTH RELEVANCE Magnetic nanoparticles (MNPs) offer cutting-edge drug delivery, molecular imaging and tissue engineering tools for all areas of medicine, including neurosciences. However, their enhanced reactive area, permeability and resistance to biodegradation promote their toxic potential. This proposal aims to determine the mechanisms of MNP neurotoxicity, immune activation of defense macrophage system, and develop advanced MNP formulation that are safe and robust for diagnostic, therapeutic and research use in the nervous system.