Targeting P2RX7 Signaling as a Biomarker for ADRD

标题：靶向P2 RX 7信号转导作为ADRD的生物标志物 摘要 大脑中的炎症被认为是一系列神经退行性疾病的早期预测因子 如阿尔茨海默病（AD）和相关痴呆、帕金森病、缺血-再灌注损伤 癫痫、肌萎缩侧索硬化和创伤性脑损伤。生物标志物的鉴定和开发 将允许研究人员和临床医生识别这些疾病的“风险”对象， 评估疾病阶段的严重程度和可能治疗的有效性。以往的工作对显像剂 监测神经炎症导致了次优放射性药物， 自然为了克服这些局限性，我们建议靶向在中枢神经系统中发现的P2 X7受体（P2 X7 R）。 神经系统，主要在免疫细胞上表达。这些受体被激活， 神经退行性疾病，并且是监测疾病进展和治疗反应的理想靶标。 先前开发针对该靶点的配体的努力由于P451 L突变的存在而受阻 导致P2 X7 R信号传导功能障碍的常见动物模型。近期发展及 野生型小鼠组的表征显示与人神经炎症高度重叠， 这可能是由于保留了功能性P2 X7 R，使其成为推进配体对抗 这个受体。我们假设神经炎症是神经退行性疾病的主要引发剂， 其中P2 X7受体发挥核心作用;开发针对该受体的新型PET示踪剂 将使衰老过程中的表型和治疗评估成为可能。我们的目标是描述第三个 在基于人细胞的测定中，以及在急性和慢性试验中， 神经炎症模型。在目的1中，我们将在体外表征[18F]-GSK 14821604在人iPSC衍生物中的表达。 在APOEE 3/E3或APOEE 4/E4中表达人P2 X7 R（hP 2X 7 R）的小胶质细胞，以理解：a）放射性配体 Ki的耗尽条件（Aim 1.1）; B）kon、koff、Kd、Bmax（Aim 1.2）和Bp通过饱和的结合动力学， 结合/解离动力学（目标1.3）。了解P2 X7 R在急性和慢性胰腺炎中的作用 在目标2中，我们将在女性CAST/EiJ的横断面队列中使用动态PET/CT， PWK/PhJ、PWK.APP/PS1和CAST.APP/PS1小鼠。使用动态PET/CT，我们将确定急性 (Aim 2.2）和慢性（目标2.4）炎症，其中生物分布（目标2.3），从而允许异速生长器官 首次在人体研究中进行剂量测定。此外，为了验证该配体的灵敏度和特异性，（目标2.5） 将在峰值P2 X7 R表达时进行动态[18 F]-GSK 1482160 PET/CT，以确定 最大（CAST.APP/PS1）和非特异性（CAST.APP/PS1 P2 X7 R-/-）结合相对于稳态水平 小胶质细胞（CAST/EiJ）。最后，为了建立重测信度（目标2.6），我们将在相同的条件下重复成像。 受试者间隔1周。在所有情况下，死后大脑将进行Autorad和IHC离体检测， 确认.结合这些数据将首先支持与ADNI合作的人体成像研究。

TITLE: Targeting P2RX7 Signaling as a Biomarker for ADRD ABSTRACT Inflammation in the brain has been proposed to be an early predictor for a range of neurodegenerative diseases such as Alzheimer’s disease (AD) and related dementias, Parkinson’s disease, ischemia-reperfusion injury, epilepsy, amyotrophic lateral sclerosis, and traumatic brain injury. Identification and development of biomarkers of neuroinflammation would permit researchers and clinicians to identify “at risk” subjects for these disorders, evaluate severity of disease stage, and effectiveness of possible treatments. Previous work on imaging agents to monitor neuroinflammation has resulted in sub-optimal radiopharmaceuticals that are only correlative in nature. To overcome these limitations, we propose to target the P2X7 receptor (P2X7R) found within the central nervous system and expressed primarily on immune cells. These receptors become activated in neurodegenerative diseases, and are an ideal target to monitor disease progression and therapy response. Previous efforts to develop ligands against this target have been stymied by the presence of P451L mutations that cause dysfunctional P2X7R signaling commonly used animal models. Recent development and characterization of a wild-derived mouse panel showed a high degree of overlap with human neuroinflammation, which is likely due to the retention of functional P2X7R, making them an ideal tool to advance ligands against this receptor. We hypothesize that neuroinflammation is a major initiator of neurodegenerative disease, where P2X7 receptors play a central role; and that developing a novel PET tracer against this receptor will enable phenotypic and therapeutic assessment during aging. Our goal is to characterize the third generation agent (i.e. [18F]GSK1482160) in human cell based assays, and in acute and chronic neuroinflammation models. In Aim 1, we will characterize [18F]-GSK14821604 in vitro in human iPSC derived microglia expressing human P2X7R (hP2X7R) in the APOEE3/E3 or APOEE4/E4 to understand: a) the radioligand depletion conditions for Ki (Aim 1.1); b) binding kinetics for kon, koff, Kd, Bmax (Aim 1.2), and Bp via saturation and association/dissociation kinetics (Aim 1.3). To understand the role of P2X7R in acute and chronic neuroinflammation, in Aim 2, we will use dynamic PET/CT in cross-sectional cohorts of female CAST/EiJ, PWK/PhJ, PWK.APP/PS1 and CAST.APP/PS1 mice. Using dynamic PET/CT we will determine the role of acute (Aim 2.2) and chronic (Aim 2.4) inflammation, where biodistribution (Aim 2.3), thus permitting allometric organ dosimetry for first in human studies. In addition, to validate the sensitivity and specificity of this ligand, (Aim 2.5) dynamic [18F]-GSK1482160 PET/CT at peak P2X7R expression will be conducted, allowing determination of maximum (CAST.APP/PS1) and non-specific (CAST.APP/PS1P2X7R-/-) binding relative to homeostatic levels of microglia (CAST/EiJ). Lastly, to establish test-retest reliability (Aim 2.6) we will repeat imaging in the same subjects separated by 1 week. In all cases, post-mortem brains will undergo Autorad and IHC ex vivo for confirmation. Combined these data will support first in human imaging studies in collaboration with the ADNI.