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

项目摘要 亨廷顿病(HD)是一种常染色体显性遗传性神经退行性疾病，其特征是非自愿 运动功能障碍，认知和精神症状，最终导致死亡。虽然 诊断测试可用于HD，但仍迫切需要客观的临床标记物来表征 疾病的发生和发展。为了开发有效的治疗方法来支持早期干预和 为了防止衰退，我们需要了解疾病发生在活着的大脑中的早期生物学变化 转换。正电子发射断层扫描(PET)成像有助于活体纵向测量 随着病理学的演变而表现出来的分子变化。然而，到目前为止，还没有生成PET配体 以预测HD的疾病转归或帮助预后。最近的研究表明，神经胶质细胞的激活可以 在HD患者出现症状时或之前被检测到，可能会引发 这样的配基。此外，从神经退行性疾病模型中有新的证据表明， 大脑的常驻免疫细胞在一些最早的病理事件中发挥着重要作用，包括 突触丢失。我们的初步数据显示HD患者和 HD小鼠模型脑(尸检)，表明它有望成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COX-2的升高，这是一种早期的病理事件 许多神经退行性疾病。此外，我们还看到，COX-2在小胶质细胞中特异性增加。 人类HD死后脑组织中受疾病影响的区域。真正理解这一角色的唯一途径 环氧合酶-2在HD中的作用是检查其在人脑中的存在和动态过程 疾病。因此，我们建议开发一种用于活体PET成像的选择性放射性示踪剂来研究COX-2 在活脑中的失调，并在小胶质细胞中开展COX-2的体外机制研究。我们 将合成新型的COX-2选择性配体，优化亲和力、靶向选择性、高脑摄取率和 对碳-11或氟-18放射性标记的适应性。这些配体将经历严格的物理化学过程 以及生化图谱，包括评估COX-2-亚型选择性的分析，以及预测血-脑的分析 障碍穿透。铅化合物将被放射性标记，并使用体外放射自显影进行评估 人类HD死后脑组织评估特异性和可饱和性结合。这之后将在体内进行。 用PET对啮齿动物进行成像，以评估脑摄取、放射性示踪剂动力学和放射性代谢。同时，我们 将阐明COX-2在HD小鼠模型小胶质细胞中的生化机制，并探讨其作用 COX-2在改变小胶质细胞功能中发挥作用。到奖助期结束时，我们的团队将有能力 使用翻译成像工具研究活体大脑中的COX-2，使人们能够更好地理解HD 病理生理学和加速新疗法的开发。

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.