Molecular Imaging Probes for Reporting on Vascular Oxidative Response

描述（由申请人提供）： 心血管疾病是发达国家死亡的主要原因，仅在美国每年就有870，000例死亡（2004年统计数据）。随着发展中国家病例的增加，以及管理受影响人口的相关费用增加，将产生全球影响，迫切需要改变模式，以诊断和监测疾病进展。在这个建议中，我们建议开发和应用新的分子成像探针，用于检测血管壁局部炎症典型的细胞产生的介质库的变化，作为心血管疾病进展的早期信号。髓过氧化物酶（MPO，由PMNs通过触发胞吐作用释放的组分之一）是炎症部位的独特催化活性标记物，涉及血管病理学的进展，例如不稳定的动脉粥样化。我们以前开发和应用磁共振信号放大策略成像的MPO酶活性使用顺磁性双酰胺GdDTPA作为还原底物的MPO。由于MPO与细胞表面结合并保留在炎症部位的事实，MPO成像的潜在应用是众多的，并且范围从中风成像到血管壁病变的成像。基于我们先前应用MR和核成像可视化血管壁炎症元凶的研究，我们建议对MPO分子成像探针进行优化，重点关注探针稳定性和我们研究的潜在转化。我们还建议设计新的双功能传感器的MPO成像。血管病变中MPO活性受局部过氧化氢产生速率的限制。过氧化氢是许多细胞（PMN、单核细胞和内皮细胞）中超氧化物/过氧化氢途径激活的产物，这些细胞通过激活细胞内NADPH氧化酶来响应。我们建议在模型系统的顺磁性超氧化物歧化酶（SOD）模拟MPO基板的基础上螯合顺磁性锰（II）和Gd（III），提供额外的过氧化氢合成和测试，并同时报告MPO活性由于能够结合到细胞表面和细胞外基质的蛋白质。我们提出了优化步骤，使用放射性同位素方法的可行性测试和体内成像前的毒性测试。该提案将追求三个主要目标：1）开发新的合成方法和构建模块，用于优化髓过氧化物酶报告探针（MPO特异性顺磁性螯合物）; 2）表征所开发的分子成像探针：酶报告，歧化酶模拟特性和体外稳定性; 3）进行体内氧化反应成像分子探针的测试。 公共卫生相关性： 受损的血管壁经常发生病变，可能变得不稳定并破裂。破裂导致血液供应阻塞和大脑和心脏组织死亡，并可能导致衰弱性疾病和生命损失。我们建议开发能够报告血管不稳定区域的药物，并对导致不稳定的一些反应性分子进行解毒，这对通过识别携带不稳定病变的患者以及可以从早期治疗这种不稳定病变中受益的患者来预防心脏病发作和中风具有重要意义。

DESCRIPTION (provided by applicant): Cardiovascular disease is the major cause of mortality in developed countries claiming 870,000 deaths/year in US alone (year 2004 statistics). With cases on the rise in the developing countries as well the associated raising costs in managing the afflicted population will have global implications and urgently require paradigm-shifting approaches to diagnosis and monitoring of disease progression. In this proposal we suggest to develop and apply novel molecular imaging probes for detecting the changes in the repertoire of cell-generated mediators typical of local inflammation in the vascular wall as the early signal of cardiovascular disease progression. Myeloperoxidase (MPO, one of the components released by PMNs via triggered exocytosis) is a unique catalytically active marker of inflammation sites, implicated in progression of vascular pathologies, e.g. unstable atheroma. We previously developed and applied MR signal amplification strategy for imaging of MPO enzymatic activity using paramagnetic bisamides of GdDTPA as reducing substrates of MPO. Due to the fact that MPO binds to the cell surface and is retained at the site of inflammation, the potential applications of MPO imaging are numerous and range from stroke imaging to imaging of vascular wall pathologies. Building on our previous research applying MR and nuclear imaging to visualization of culprits of inflammation of the vascular wall we propose to perform optimization of MPO molecular imaging probe with the focus on probe stability and potential translation of our research. We also propose to design novel dual-function sensors for MPO imaging. MPO activity in vascular lesions is rate-limited by the rates of local hydrogen peroxide production. Hydrogen peroxide is a product of superoxide/hydrogen peroxide pathway activation in many cells populating blood vessel wall (PMN, monocytes and endothelial cells), which respond by activating intracellular NADPH oxidase. We propose to synthesize and test in model systems paramagnetic superoxide dismutase (SOD) mimic-MPO substrates based on chelated paramagnetic Mn(II) and Gd(III), which supply additional hydrogen peroxide, and simultaneously report on MPO activity due to the ability to bind to proteins of cell surface and extracellular matrix. We propose optimization steps, feasibility testing using radioisotope methods and toxicity testing before in vivo imaging. The proposal will pursue three major aims: 1) develop novel synthetic approaches and building blocks for optimizing myeloperoxidase reporter probes (MPO-specific paramagnetic chelates); 2) characterize the developed molecular imaging probes: enzyme reporting, dismutase mimic properties and stability in vitro; 3) perform testing of molecular probes for imaging oxidative response in vivo. PUBLIC HEALTH RELEVANCE: Diseased blood vessel walls frequently develop lesions that can become unstable and rupture. The rupture leads to blocking blood supply and death of tissues in the brain and heart and may result in debilitating disease and loss of life. We propose to develop agents that can report on areas of instability in blood vessels and detoxify some of the reactive molecules that cause instability, which has implications in preventing heart attacks and strokes by identifying patients who carry unstable lesions and who can benefit from early treatment of such unstable lesions.