COX-2-selective PET imaging as an onset marker of Huntington's disease

项目摘要 亨廷顿氏病（HD）是一种常染色体显性遗传的神经退行性疾病，其特征在于不自主的 运动功能障碍以及认知和精神症状，最终导致死亡。虽然 尽管HD的诊断测试可用，但仍迫切需要客观的临床标志物来表征 疾病发作和进展。为了开发有效的治疗方法来支持早期干预， 为了防止衰退，我们需要了解疾病发生时活大脑中的早期生物学变化， 转换.正电子发射断层扫描（PET）成像有助于体内纵向测量 随着病理学的发展而出现的分子变化。然而，迄今为止，还没有PET配体产生 以预测HD的疾病转化或辅助预后。最近的研究表明，神经胶质细胞的激活可以 在HD患者症状发作时或即将发作前检测到，引起发生 这样的配体。此外，有来自神经退行性疾病模型的新证据表明小胶质细胞， 大脑的常驻免疫细胞在一些最早的病理事件中起着重要作用，包括 突触丧失我们的初步数据显示，HD患者和HD患者中的环氧合酶-2（考克斯-2）蛋白增加， HD小鼠模型脑（死后），表明它有希望作为一种新的临床标志物。临床前模型 在小胶质细胞介导的突触消除期间表现出升高的考克斯-2，这是病理学的早期事件 许多神经退行性疾病的症状此外，我们看到考克斯-2在小胶质细胞中特异性增加， 人类HD死后脑组织中的疾病影响区域。唯一能真正理解 考克斯-2在高清播放是检查它的存在和动态在整个过程中的人脑 疾病因此，我们建议开发一种用于体内PET成像的选择性放射性示踪剂来研究考克斯-2 在活体脑中的失调，并进行小胶质细胞中考克斯-2功能的离体机制研究。我们 将合成新的考克斯-2-选择性配体，优化亲和力，靶向选择性，高脑摄取， 易于用碳-11或氟-18进行放射性标记。这些配体将经历严格的物理化学过程， 和生化分析，包括评估考克斯-2-亚型选择性和预测血脑 势垒穿透将对先导化合物进行放射性标记，并使用体外放射自显影进行评价。 人HD死后脑组织以评价特异性和可饱和结合。随后将在体内 在啮齿类动物中使用PET进行成像，以评价脑摄取、放射性示踪剂动力学和放射性代谢。同时，我们 将阐明考克斯-2在HD小鼠模型中小胶质细胞中的生化机制，并研究其作用。 考克斯-2在改变小胶质细胞功能中起作用。在资助项目结束时，我们的团队将有能力 使用平移成像工具研究活体大脑中的考克斯-2，从而提高对HD的理解 病理生理学和加速新疗法的发展。

Project Summary Huntington’s Disease (HD) is an autosomal dominant, neurodegenerative disease characterized by involuntary movement dysfunction, and cognitive and psychiatric symptoms, ultimately resulting in death. Although diagnostic testing is available for HD, there remains a critical need for an objective clinical marker to characterize both disease onset and progression. In order to develop effective therapeutics to support early intervention and prevent decline, we need to understand the early-stage biological changes in the living brain that occur at disease conversion. Imaging with positron emission tomography (PET) facilitates in vivo longitudinal measurements of molecular changes that manifest with evolving pathology. To date however, no PET ligands have been generated to predict disease conversion or aid prognosis in HD. Recent studies have shown that glial cell activation can be detected either at or just prior to the onset of symptoms in HD patients, evoking potential for the development of such a ligand. In addition, there is emerging evidence from neurodegenerative disease models that microglia, the brain’s resident immune cells, play an important role in some of the earliest pathological events, including synaptic loss. Our preliminary data showing increased cyclooxygenase-2 (COX-2) protein in both HD patient and HD mouse model brains (postmortem), suggest it holds promise as a novel clinical marker. Preclinical models exhibit elevated COX-2 during periods of microglia-mediated synaptic elimination, an event early in the pathology of many neurodegenerative diseases. In addition, we see COX-2 is increased specifically in the microglia of disease-affected regions in human HD post-mortem brain tissue. The only way to truly understand the role that COX-2 plays in HD is to examine its presence and dynamics in the human brain throughout the course of disease. Therefore, we propose to develop a selective radiotracer for in vivo PET imaging to study COX-2 dysregulation in the living brain, and carry out ex vivo mechanistic studies of COX-2 function in microglia. We will synthesize novel COX-2-selective ligands, optimized for affinity, target selectivity, high brain uptake, and amenability to radiolabeling with carbon-11 or fluorine-18. These ligands will undergo rigorous physiochemical and biochemical profiling, including assays that evaluate COX-2-isoform selectivity, and that predict blood-brain barrier penetration. Lead compounds will be radiolabeled and evaluated with in vitro autoradiography using human HD post-mortem brain tissue to evaluate specific and saturable binding. This will be followed by in vivo imaging in rodents with PET to evaluate brain uptake, radiotracer kinetics, and radiometabolites. In parallel, we will elucidate biochemical mechanisms of COX-2 in microglia in HD mouse models, and investigate the role COX-2 plays in altering microglial function. By the end of the grant project period, our team will have the ability to study COX-2 in the living brain with translational imaging tools, enabling improved understanding of HD pathophysiology and accelerating development of novel therapeutics.