A novel probe for imaging apoptosis

描述(由申请人提供)：许多疾病与细胞死亡途径的改变有关。过度的细胞死亡会导致进行性器官功能障碍，如缺血性疾病和神经变性。细胞死亡不足是癌症的一个标志，并导致某些自身免疫性疾病。此外，许多药物的有益或有害作用可以归因于它们对细胞死亡的影响。因此，评估细胞死亡的非侵入性方法将为临床医生提供关于疾病活动性和治疗效果的关键信息。到目前为止，还没有被批准用于临床对细胞凋亡进行成像的探针。我们出人意料地发现，在经历细胞凋亡和坏死的过程中，各种脱氢酶蛋白特异性地积累。例如，重组乳酸脱氢酶(LDH)，当荧光标记时，特异性地染色早期凋亡和晚期凋亡/坏死细胞。虽然已知乳酸脱氢酶是一种从死亡细胞中泄漏出来的细胞内蛋白，但我们发现，外源应用的基于乳酸脱氢酶的探针专门在死亡细胞中积累。我们发现，与Annexin V相比，LDH探针具有几个优点，包括不需要钙和血清蛋白对染色的影响。Annexin V目前正在进行细胞凋亡成像的临床试验。这些特征表明，对于细胞死亡的活体成像，基于LDH的探针可能优于Annexin V。在这项提议中，我们试图建立一种优化的基于LDH的探针来成像细胞凋亡。我们将首先建立与凋亡细胞结合的全长LDH放射性配基的体外和体内特征，并进行体内成像。在第一个特定目标中，然后我们将使用系统突变来定义基于LDH的探针染色凋亡细胞所必需的和充分的结构元素。在第二个具体目标中，我们将开发一系列基于LDH的放射性配体探针，并表征它们在小鼠体内的生物分布。在第三个具体目标中，我们将使用三种小鼠凋亡模型来确定一种优化的基于LDH的探针，用于细胞死亡的PET成像。最后，优化的LDH探针的性能将直接与Annexin V的性能进行比较，以进行细胞死亡的活体成像。总之，这些研究的成功将为使用新的基于乳酸脱氢酶的探针对细胞凋亡进行成像提供概念验证，并将为继续进行人类临床测试奠定基础。 公共卫生相关性：非侵入性成像细胞死亡的能力将为诊断多种疾病和监测药物治疗的疗效提供一个关键工具。目前尚无探针被批准用于细胞凋亡的临床成像，这突显了对新的灵敏和特异的探针的巨大需求。拟议的研究试图开发一种全新的细胞凋亡成像方法，并使该探针准备好用于人类临床测试。

DESCRIPTION (provided by applicant): A number of diseases are associated with alterations in cell death pathways. Excessive cell death leads to progressive organ dysfunction, such as ischemic diseases and neurodegeneration. Inadequate cell death is a hallmark of cancer, and contributes to certain autoimmune diseases. Furthermore, the beneficial or detrimental effects of many drugs can be attributed to their effects on cell death. Therefore, non-invasive methods for assessing cell death would provide clinicians with critical information on disease activity and therapeutic efficacy. To date, there are no probes approved for clinical imaging of apoptosis. We have unexpectedly found that a variety of dehydrogenase proteins specifically accumulate in cells undergoing apoptosis and necrosis. For example, recombinant lactate dehydrogenase (LDH), when fluorescently labeled, specifically stains both early apoptotic and late apoptotic/necrotic cells. While LDH is known to be an intracellular protein that leaks out of dying cells, we find that exogenously applied LDH- based probes specifically accumulate within dead cells. We have found that LDH probes have several advantages over Annexin V, which is currently in clinical trials for imaging of apoptosis, including no requirement for calcium and no effect of serum proteins on staining. These characteristics suggest that LDH-based probes may be superior to Annexin V for in vivo imaging of cell death. In this proposal, we seek to establish an optimized LDH-based probe for imaging apoptosis. We will first establish the in vitro and in vivo characteristics of a full length LDH radioligand for binding to apoptotic cells and in vivo imaging. In the first Specific Aim, we will then use systematic mutagenesis to define the structural elements necessary and sufficient for LDH-based probes to stain apoptotic cells. In the second Specific Aim, we will develop a series of LDH-based radioligand probes, and characterize their biodistribution in mice. In the third Specific Aim, we will use three mouse models of apoptosis to identify an optimized LDH-based probe for PET-imaging of cell death. Finally, the performance of an optimized LDH probe will be directly compared to that of Annexin V for iin vivoi imaging of cell death. Together, success in these studies would provide proof-of-concept for imaging apoptosis using novel LDH-based probes, and would establish the rationale for proceeding with human clinical testing. PUBLIC HEALTH RELEVANCE: The ability to non-invasively image cell death would provide a critical tool for diagnosing multiple diseases and monitoring the efficacy of drug treatments. No probes have yet been approved for the clinical imaging of apoptosis, underscoring the great unmet need for new sensitive and specific probes. The proposed studies seek to develop an entirely novel method for imaging apoptosis, and to bring this probe to readiness for human clinical testing.