In vivo Probe for ionotropic glutamate signaling system: AMPA receptors

项目概述：我们将开发第一个亚型选择性正电子发射断层扫描探针，用于α-氨基-2，4-氨基-4-氨基-4-氨基-4-氨基-2，4-氨基-2，4，4，4，4，4，4，4，4，4，4，6-二氨基甲苯 3-羟基-5-甲基-4-异恶唑丙酸受体(AMPAR)在离子亲和性谷氨酸系统中的作用。 AMPAR功能障碍与精神分裂症等神经疾病的生理病理有关， 抑郁症、癫痫和帕金森氏症。AMPAR的药理调节可防止过度的神经元 激活，代表了一种有吸引力的治疗方法。作为一种非侵入性的化学探针，PET能够 量化体内的生化过程，以及合适的AMPAR PET探针将大大改善我们的 在正常和疾病条件下对基于AMPAR的离子型谷氨酸信号的理解 无法通过体外(破坏性)分析获得的。到目前为止，还没有成功的例子被演示到图像 Ampar，代表着我们在体内研究这个靶点的能力的一个重大缺陷。因此，我们建议 开发一种可以填补这一空白的PET探头，作为第一个平移AMPAR成像工具。 由于PAN AMPAR拮抗剂往往伴随着衰弱的不良反应，并且具有非常狭窄的 治疗性给药窗，通过调控亚型选择性AMPAR拮抗剂的最新进展 跨膜AMPA调节蛋白(TARP)。PI和他的团队开创了第一个 针对AMPAR亚基TARPɣ8，[11C]JNJ-486at MGH的亚型选择性AMPAR PET探针。[11C]JNJ-486 表现出对AMPAR TARPɣ8亚基的高体外特异性结合和靶向选择性，但被终止 由于大脑渗透率较低。通过我们建立的基于HEK293细胞的钙通量荧光分析，我们发现了一种 第二代化学铅。该化合物具有较高的效价和亚型选择性。一架11C- 然后合成了同位素，初步的PET研究证实，我们已经克服了两个主要的 AMPAR探针发展的障碍，即：1)合理的脑摄取和2)区域特异性摄取。 尽管这一先导是开发新的TARPPET 8靶向体内化学工具ɣ的一个很有前途的模板 最佳成像需要具有更高的效力和选择性以及更高的结合势(Bmax/Kd)的探针 以及在翻译的跨物种成像研究中对亚型选择性AMPAR进行量化。 在这项提案中，我们将设计和制备一系列精心挑选的亚型选择性AMPAR抑制剂，LABEL 11C或18F的最佳候选者，并评估他们在啮齿动物药物挑战期间量化AMPAR的能力 非人灵长类动物。这项工作的影响不仅仅是开发出第一个有效和选择性的AMPAR PET探针 为了研究与疾病相关的生物学过程，也最终要为潜在的临床准备这种活体工具 翻译和监测AMPAR治疗剂在大脑中的靶向反应。 相关性：这项提案有可能改善公共健康，帮助患有中枢神经系统疾病的患者 通过使用AMPAR PET探头发现神经治疗方法来治疗疾病/神经退行性疾病。

Project Summary: We will develop the first subtype-selective positron emission tomography (PET) probe for α-amino- 3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) in the ionotropic glutamate system. Dysfunction of AMPAR is implicated in the physiopathology of neurological diseases such as schizophrenia, depression, epilepsy and Parkinson’s disease. Pharmacological modulation of AMPAR prevents excessive neuronal activation, representing an attractive therapeutic approach. As a non-invasive chemical probe, PET is capable of quantifying biochemical processes in vivo, and a suitable AMPAR PET probe would substantially improve our understanding of AMPAR-based ionotropic glutamate signaling under normal and disease conditions otherwise inaccessible by ex vivo (destructive) analysis. To date, no successful examples have been demonstrated to image AMPAR, representing a significant deficiency of our ability to study this target in vivo. Therefore, we propose to develop a PET probe that can fill this void, as the first translational AMPAR imaging tool. As pan AMPAR antagonists are often accompanied by debilitating adverse effects and have a very narrow therapeutic dosing window, one recent advance focuses on subtype-selective AMPAR antagonists via modulating transmembrane AMPA regulatory proteins (TARPs). The PI and his team have pioneered the development of the first subtype-selective AMPAR PET probe targeting AMPAR subunit TARP ɣ8, [11C]JNJ-486 at MGH. [11C]JNJ-486 showed high in vitro specific binding and target selectivity towards AMPAR TARP ɣ8 subunit, but was discontinued due to low brain penetration. Through our established HEK293 cell-based Ca2+ flux fluorescent assay, we identified a second generation chemical lead. This compound showed high potency and high subtype selectivity. An 11C- isotopologue was then synthesized and preliminary PET studies confirmed that we have overcome the two major obstacles for AMPAR probe development, namely: 1) reasonable brain uptake and 2) regional-specific uptake. Though this lead is a promising template for the development of new TARP ɣ8-targeted in vivo chemical tool, PET probes with improved potency & selectivity, and increased binding potentials (Bmax/Kd) are needed for optimal imaging and quantification of subtype-selective AMPAR in translational cross-species imaging studies. In this proposal, we will design and prepare a series of carefully chosen subtype-selective AMPAR inhibitors, label top candidates with 11C or 18F, and evaluate their ability to quantify AMPAR during drug challenges in rodents and nonhuman primates. The impact of this work is not only to develop the first potent and selective AMPAR PET probe for the study of disease-related biological processes, but also ultimately, to prepare this in vivo tool for potential clinical translation and monitor target response of AMPAR therapeutic agents in the brain. Relevance: This proposal has the potential to improve public health and help patients suffering from CNS disorders/neurodegenerative diseases through the discovery of neurotherapeutics using AMPAR PET probes.