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87万人死亡(2004年的统计数字)。由于发展中国家的病例也在增加，管理受影响人口的相关费用增加将产生全球影响，迫切需要改变诊断和监测疾病发展的方式。在这项建议中，我们建议开发和应用新的分子成像探针来检测作为心血管疾病进展的早期信号的血管壁局部炎症典型的细胞产生的介质的变化。髓过氧化物酶(MPO)是中性粒细胞通过胞吐作用释放的成分之一，是炎症部位独特的催化活性标记物，与血管病变的进展有关，如不稳定的动脉粥样硬化。我们以前开发并应用了MR信号放大技术，以GdDTPA的顺磁性双酰胺为MPO的还原底物，用于MPO酶活性的成像。由于MPO结合到细胞表面并被保留在炎症部位，MPO成像的潜在应用非常广泛，从中风成像到血管壁病理成像。在前人研究的基础上，我们将MR和核成像应用于血管壁炎元凶的可视化研究，我们建议对MPO分子成像探针进行优化，重点放在探针的稳定性和潜在的研究翻译上。我们还提出了设计用于MPO成像的新型双功能传感器。血管病变中MPO活性受局部过氧化氢产生速率的限制。过氧化氢是分布于血管壁的多种细胞(中性粒细胞、单核细胞和内皮细胞)通过超氧化物/过氧化氢途径激活的产物，这些细胞通过激活细胞内的NADPH氧化酶进行反应。我们建议合成并在模型体系中测试基于提供额外过氧化氢的顺磁性Mn(II)和Gd(III)的顺磁性超氧化物歧化酶(SOD)模拟MPO底物，同时报道由于能够与细胞表面和细胞外基质的蛋白质结合而产生的MPO活性。我们提出了优化步骤，使用放射性同位素方法进行可行性测试，并在活体成像之前进行毒性测试。该提案将追求三个主要目标：1)开发新的合成方法和构建块，以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、歧化酶模拟性质和体外稳定性；3)测试用于体内氧化反应成像的分子探针。 公共卫生相关性： 病变的血管壁经常发生病变，可能会变得不稳定和破裂。破裂会导致脑和心脏组织的血液供应受阻和死亡，并可能导致衰弱的疾病和生命的损失。我们建议开发能够报告血管不稳定区域并对导致不稳定的一些反应分子解毒的试剂，这有助于通过识别携带不稳定病变的患者以及谁可以从这种不稳定病变的早期治疗中受益来预防心脏病发作和中风。

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.