Real time imaging of immune cells and glutamate dynamics by PET and metabolic MRI

摘要 免疫细胞的激活在多发性硬化症(MS)的发生和发展中起着关键作用，导致 到中枢神经系统(CNS)的进行性神经变性。虽然谷氨酸失衡一直是 在多发性硬化症大脑中描述，并被认为有助于轴突损伤和组织破坏， 谷氨酸动力学和疾病进展过程中的免疫激活之间的关系尚不清楚。 目前，缺乏临床可用的非侵入性成像方法来检测免疫细胞和谷氨酸 代谢限制了我们对MS发病机制的理解和对治疗反应的监测。 用于正电子发射断层扫描(PET)的放射性示踪剂的最新发展显示出巨大的潜力 星形胶质细胞兴奋性氨基酸对免疫系统细胞的检测及谷氨酸再摄取的成像 酸转运蛋白2(EAAT2)。具体地说，2‘-deoxy-2’-[18F]fluoro-9-β-D-arabinofuranosylguanine([18F]F-Arag) 能够在炎症性疾病和癌症模型中检测激活的T细胞。[18F]氟- 荧基天冬氨酸酰胺([18F]FFAA)已经证明有能力测量中枢神经系统中EAAT2的活性。 超极化~(13)C磁共振波谱成像是一种新兴的成像技术 它实时测量体内的酶反应。幽门螺杆菌13C丙酮酸已被证明可高度检测 外周和中枢神经系统炎症模型中来自天然免疫系统的糖酵解细胞。最近，丙酮酸 标记在第二碳位置上的[2-13C]丙酮酸为监测谷氨酸的产生提供了一种新的方法 人类的大脑。 本项目建议验证这些创新的无创PET和MR方法，以提供一种新的方法 探讨先天性和获得性免疫反应与谷氨酸动态的关系 临床前多发性硬化症模型。该项目的指导阶段将开发和验证新的神经成像 技术：Aim 1将研究[18F]F-Arag和[18F]FFAA PET成像显示激活的可能性 T细胞和谷氨酸在疾病进展过程中的重新摄取。AIM 2将开发和验证HP[2-13C]丙酮酸 作为一种同时检测促炎性先天免疫细胞和确定实时脑功能的方法 谷氨酸生产。该项目的独立阶段将建立在这些初步成果的基础上，目标3将 评估这种多模式PET和MRI方法监测免疫反应、谷氨酸的潜力 治疗后的生产和星形胶质细胞的功能。这项提议成功的关键，古列尔梅蒂博士 将得到成熟的神经成像专家小组的支持和指导，特别是HP 13C 磁共振技术(Myriam Chaumeil博士和Peder Larson博士)和PET成像(Henry VanBrocklin博士)也是如此 如神经免疫学和多发性硬化症(Ari Green博士和Zamvil博士)，为她提供必要的技能来 开始独立科学家的职业生涯。

ABSTRACT Activation of immune cells plays a critical role in initiation and progression of multiple sclerosis (MS), leading to progressive neurodegeneration of the central nervous system (CNS). While glutamate imbalance has been described in MS brains and has been proposed to contribute to axonal damage and tissue destruction, the relationships between glutamate dynamics and immune activation during disease progression remain unclear. Presently, the lack of clinically available noninvasive imaging methods to detect immune cells and glutamate metabolism limits our understanding of MS pathogenesis and monitoring of responses to therapies. Recent development of radiotracers for positron emission tomography (PET) have shown great potential for detection of cells from the immune system and for imaging glutamate reuptake by astroglial excitatory amino acid transporter-2 (EAAT2). Specifically, 2'-deoxy-2'-[18F]fluoro-9-β-D-arabinofuranosylguanine ([18F]F-AraG) enables the detection of activated T-cells in inflammatory diseases and cancer models. [18F]Fluoro- fluorenylaspartyl amide ([18F]FFAA) has demonstrated the ability to measure EAAT2 activity in the CNS. Hyperpolarized 13C magnetic resonance spectroscopic imaging (HP 13C MRSI) is an emerging imaging technique which measures enzymatic reactions in vivo in real-time. HP 13C pyruvate has been shown to detect highly glycolytic cells from the innate immune system in peripheral and CNS inflammation models. Recently, pyruvate labelled on the second carbon position, [2-13C]pyruvate, provided a new way to monitor glutamate production in the human brain. This project proposes to validate these innovative noninvasive PET and MR methods to provide a new way to investigate the relationships between innate and adaptive immune responses and glutamate dynamics in preclinical MS models. The mentored phase of this project will develop and validate new neuroimaging technologies: Aim 1 will investigate the potential of [18F]F-AraG and [18F]FFAA PET imaging to visualize activated T-cells and glutamate reuptake during disease progression. Aim 2 will develop and validate HP [2-13C]pyruvate as a method to simultaneously detect pro-inflammatory innate immune cells and determine real-time brain glutamate production. The independent phase of this project will build on these initial results and Aim 3 will evaluate the potential of this multimodal PET and MRI approach to monitor immune responses, glutamate production, and astrocyte functions following therapy. Central to the success of this proposal, Dr. Guglielmetti will have the support and guidance from an established group of experts in neuroimaging, particularly HP 13C MR technology (Dr. Myriam Chaumeil and Dr. Peder Larson) and PET imaging (Dr. Henry VanBrocklin) as well as in neuroimmunology and MS (Dr. Ari Green and Dr. Zamvil), providing her with the necessary skillsets to embark on a career as an independent scientist.