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，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，是由易损的动脉粥样硬化斑块破裂或侵蚀引起的。这些斑块的特点是巨噬细胞含量高且活跃。使用非侵入性成像方法对斑块易损性和进展进行准确的体内跟踪，可以早期识别高风险患者，并促进早期干预决策过程和干预有效性的监测。然而，目前的成像方式，包括磁共振（MR）成像表征斑块的解剖和结构特征，而不是其内容。造影剂如钆基造影剂（gbca）常用于心血管MR成像以增强组织间的造影剂。巨噬细胞特异性递送gbca将允许易损斑块的早期检测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可能导致残疾或死亡的主要不良后果。近年来，高密度脂蛋白（hdl）被认为是gbca的纳米递送载体。我们假设载脂蛋白（apo） A-I （HDL的主要蛋白质成分）的氧化修饰可用于指导携带gbca的HDL （GBCA-HDL）到达富含巨噬细胞的斑块。这种修饰发生在体内，并将HDL转化为巨噬细胞的底物，这一事实是合理的。因此，它可以增强斑块内巨噬细胞对HDL的摄取。该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在基于hdl的MR显像剂中修饰载脂蛋白A-I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)生成和表征含有修饰载脂蛋白a -I的GBCA-HDL纳米配方，以及2)在动脉粥样硬化小鼠模型中测试最佳的GBCA-HDL配方。我们将合成含有修饰载脂蛋白A-I的GBCA-HDL颗粒，对其进行表征并评估巨噬细胞的体外摄取。我们将改变GBCA：脂质：载脂蛋白A-I比率，并根据最大Gd含量和最高巨噬细胞摄取来选择最佳配方。我们将使用载脂蛋白e敲除小鼠模型来评估最佳配方在斑块成像中的MR有效性。预计该阶段研究将确定新的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的项目中改进这项技术。重要的是，不仅成像，而且治疗剂也可以纳入提议的平台。因此，第一阶段的成功完成将为开发新的多功能纳米制剂提供概念证明，用于诊断和治疗的靶向递送。

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.