Multifunctional nanoformulations for diagnostic imaging of atherosclerosis

描述（由申请人提供）：尽管心血管护理取得了进展，但动脉粥样硬化仍然是美国和世界范围内死亡的主要原因。绝大多数心血管事件，如中风或心肌梗死，是由易损动脉粥样硬化斑块的破裂或侵蚀引起的。这些斑块的特征在于高和活跃的巨噬细胞含量。使用非侵入性成像方法准确地体内跟踪斑块脆弱性和进展，可以早期识别高危患者，并促进早期干预决策过程和监测干预措施的有效性。然而，目前的成像方式，包括磁共振（MR）成像的特点，解剖和结构的特点，而不是斑块的内容。造影剂（例如钆基造影剂（GBCA））通常用于心血管MR成像，以增强组织之间的对比度。巨噬细胞特异性递送GBCA将允许早期检测易损斑块和易损患者的风险分层。这也将使GBCA剂量最小化，从而降低肾源性系统性纤维化的风险，这是GBCA的主要不良后果，可能导致残疾或死亡。最近，高密度脂蛋白（HDL）被建议作为GBCA的递送纳米载体。我们假设，载脂蛋白（apo）A-I，HDL的主要蛋白质成分的氧化修饰，可用于直接GBCA携带HDL（GBCA-HDL）的巨噬细胞丰富的斑块。这是合理的，因为这种修饰发生在体内，并将HDL转化为巨噬细胞的底物。因此，它可以增强斑块内巨噬细胞对HDL的摄取。拟议项目的长期目标是开发一种新的方法来早期检测和评估易损斑块。I期研究的主要目标是证明基于HDL的MR成像剂中apo A-I的修饰增加了动物模型系统中斑块内巨噬细胞的检测。第一阶段的具体目标是：1）产生并表征含有修饰的apo A-I的GBCA-HDL纳米制剂，和2）在动脉粥样硬化的小鼠模型中测试最佳GBCA-HDL制剂。我们将合成含有修饰的载脂蛋白A-I的GBCA-HDL颗粒，对其进行表征并评估体外巨噬细胞摄取。我们将改变GBCA：脂质：apo A-I比率，并基于最大Gd含量和最高巨噬细胞摄取选择最佳制剂。我们将使用载脂蛋白E基因敲除小鼠模型来评估最佳制剂在体内斑块成像中的MR功效。预计该阶段研究将确定新型MR造影剂，为动脉粥样硬化成像提供强大的平台。第一阶段的数据将用于在第二阶段计划中改进这项技术。重要的是，不仅成像剂，而且治疗剂都可以并入所提出的平台中。因此，第一阶段的成功完成将为开发用于诊断和治疗的靶向递送的新的多功能纳米制剂提供概念证明。 公共卫生相关性：动脉粥样硬化是心血管疾病的主要原因，心血管疾病是全球头号死亡原因。拟议的研究将导致新的成像技术的发展，可以大大提高动脉粥样硬化的早期诊断和治疗，允许在症状发生之前进行诊断，识别风险较高的个体，并监测对治疗的反应。

DESCRIPTION (provided by applicant): Despite advances in cardiovascular care, atherosclerosis remains the leading cause of mortality in the United States and worldwide. A vast majority of cardiovascular events such as stroke or myocardial infarction result from rupture or erosion of vulnerable atherosclerotic plaques. These plaques are characterized by high and active macrophage content. Accurate in vivo tracking of plaque vulnerability and progression using non-invasive imaging approaches allows early identification of high-risk patients as well as facilitates early intervention decision-making process and monitoring of the effectiveness of interventions. However, current imaging modalities including magnetic resonance (MR) imaging characterize anatomic and structural features of the plaque rather than its content. Contrast agents such as gadolinium-based contrast agents (GBCAs) are often used in cardiovascular MR imaging to enhance contrast between tissues. Macrophage-specific delivery of GBCAs will allow early detection of vulnerable plaques and risk stratification of vulnerable patients. This wil also minimize the GBCA dose, thus diminishing the risk of nephrogenic systemic fibrosis, a major adverse consequence of GBCAs that may lead to disability or death. Recently, high density lipoproteins (HDLs) were suggested as delivery nanocarriers for GBCAs. We hypothesize that oxidative modification of apolipoprotein (apo) A-I, the major protein constituent of HDL, can be used to direct GBCA-carrying HDL (GBCA-HDL) to macrophage-rich plaques. This is rationalized by the fact that this modification occurs in vivo and converts HDL into a substrate for macrophages. Thus, it may enhance intraplaque macrophage uptake of HDL. The long-term objective of the proposed project is to develop a novel approach to early detection and evaluation of vulnerable plaques. The major goal of the Phase I study is to demonstrate that modification of apo A-I in HDL-based MR imaging agents increases the detection of intraplaque macrophages in animal model system. Phase I specific aims are: 1) generate and characterize GBCA-HDL nanoformulations that contain modified apo A-I, and 2) test the optimal GBCA-HDL formulation in a mouse model of atherosclerosis. We will synthesize GBCA-HDL particles that contain modified apo A-I, characterize them and assess macrophage uptake in vitro. We will vary the GBCA:lipid:apo A-I ratios and choose the optimal formulation based upon maximum Gd content and highest macrophage uptake. We will use apo E-knockout mouse model to assess MR efficacy of the optimal formulation in plaque imaging in vivo. It is anticipated that the Phase study will identify novel MR contrast agents that will provide a powerful platform for imaging of atherosclerosis. The Phase I data will be used to improve this technology in a Phase II program. Importantly, not only imaging but also therapeutic agents can be incorporated into the proposed platform. Thus, successful completion of Phase I will provide the proof of concept for the development of new multifunctional nanoformulations for targeted delivery of diagnostics and therapeutics. PUBLIC HEALTH RELEVANCE: Atherosclerosis is the major cause of cardiovascular disease, the number one leading cause of death worldwide. The proposed research will result in the development of novel imaging techniques that could substantially improve early diagnosis and treatment of atherosclerosis, allowing for diagnosis before symptoms occur, identification of those individuals with higher risk, and for monitoring response to treatment.