Neurotoxicity of Magnetic Nanoparticles

描述(申请人提供)：工程氧化铁超顺磁纳米颗粒(MNPs)提供了有针对性的尖端诊断和治疗平台，因为它们能够由外部磁场引导，被功能化，并穿透细胞和组织屏障。在研究MNPs在磁力作用下延长分化的PC12细胞突起的能力时，我们观察到MNP诱导的去分化、突起的丢失和细胞死亡随着氧化铁浓度的增加而增加，但用于MNP包被的二硫代丁二酸(DMSA)没有观察到。越来越多的证据表明，纳米颗粒的反应面积、渗透性和对生物降解的抵抗力增强了它们相对于分子或本体的细胞毒性潜力，这意味着氧化应激(OS)是纳米毒性的关键范例。OS是一个三层的过程，表现为活性氧簇(ROS)的激活和抗氧化防御(Tier I)、促炎反应(Tier II)和DNA损伤导致细胞凋亡(Tier III)。在体内应用后，纳米颗粒很快就会受到巨噬细胞的挑战，这既可以缓冲纳米颗粒潜在的纳米毒性，又可以减少治疗和诊断所需的循环时间。在一系列体内先导性研究中，我们使用大鼠坐骨神经作为组合模型来评估周围神经特有的直接神经毒性和有效的神经元内巨噬细胞浸润。在48小时内，我们观察到巨噬细胞大量涌入巨噬细胞，激活血红素加氧酶-1、白介素12、基质金属蛋白酶-9和半胱氨酸天冬氨酸氨基转移酶3，所有这些都与氧化应激范式一致。相比之下，在相应的假手术、对照DMSA和葡聚糖包被的氧化铁MNPs微量注射中，只有轻微的神经毒性变化。利用工程和生物学相结合的体外和体内方法，该计划旨在确定氧化铁MNPs诱导的中枢和外周神经毒性的机制和靶细胞。重点研究表面化学(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方面的作用。将结合SQUID磁学、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分析以及体内感觉和运动行为评估。这项提案的总体目标是开发和测试在神经系统治疗和诊断平台上使用MNP安全的工程策略。公共卫生相关性 磁性纳米颗粒(MNPs)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，它们增强的反应面积、渗透性和对生物降解的抵抗力提高了它们的毒性潜力。这项建议旨在确定MNP的神经毒性、防御巨噬细胞系统的免疫激活机制，并开发安全可靠的先进MNP制剂，用于神经系统的诊断、治疗和研究。

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.