Investigation of Zinc Neurochemistry by Optical Sensing and MRI

描述(申请人提供)：这项研究的长期目标是设计分子传感器，用于结合、可视化和定量神经生物系统中的移动锌。在生理刺激下，大脑海马神经元突触前囊泡中的内源性锌被释放出来，在学习和记忆中发挥着不完全确定的作用。类似的移动锌储存存在于嗅球(OB)过程中，气味信息通过更直接的信号通路从鼻子传递。大脑中不受控制的锌释放与癫痫、脑缺血或钝性头部创伤后的损伤有关。为了研究这些神经化学现象，锌离子响应传感器需要能够跟踪被激活离子在生理和病理刺激下的时空分布。传感器的设计、综合、评价和优化是本研究项目的主要组成部分。每个传感器最多将有三个模块。最低限度，将有锌绑定和锌报告单位。结合模块通常包括具有可变的锌亲和力的多齿配体，在神经元组织中对锌的选择性高于竞争离子，以及快速、可逆的配位以监测毫秒时间尺度上的生物变化。锌报告模块将是荧光或磷光的，用于光学成像(OI)实验，或能够改变水松弛速率，用于磁共振成像(MRI)研究。荧光记者包括黄原酮和单壁碳纳米管衍生物。磷光传感器是基于环金属化的Ir(III)配合物。磁共振成像结构利用锰(III)卟啉。采用的策略是附加可选的第三个模块，以将基于光致发光的锌传感器定位到编程的细胞靶标上，以研究生理或病理刺激后信号转导途径中特定位置的锌的动力学。一个相关的目标是制备锌选择性的、快速的螯合剂，用于研究流动的锌的生物功能。锌传感器和络合剂的热力学、动力学、光物理和理论研究将指导合成方向，以改进和优化其在应用中的应用。具体的应用包括通过OI评估有关移动锌在海马苔藓纤维突触和OB的肾小球的神经传递中的作用的假说，以及在生理和病理条件下用MRI显示海马区的移动锌活动。该项目与公众健康相关，因为它将提供测试有关大脑中可移动锌功能的理论的方法，以及评估不受控制的锌水平与神经退行性疾病(如阿尔茨海默氏症)和更急性毒性脑病的假设关联的方法。设计的化学还将促进开发工具来测量其他组织中发生的移动锌储存，如前列腺和胰腺，在这些组织中，移动锌2的定量有可能及早发现涉及这些器官的疾病。

DESCRIPTION (provided by applicant): The long-term goal of this research is to devise molecular sensors for binding, visualizing, and quantifying mobile zinc in neurobiological systems. Endogenous stores of zinc in presynaptic vesicles of hippocampal neurons in the brain are released upon physiological stimulation to perform an incompletely defined role in learning and memory. Similar mobile zinc stores present in the olfactory bulb (OB) process odorant information trans- mitted from the nose in a more direct signaling pathway. Uncontrolled Zn2+ release in the brain is associated with damage following seizure, ischemia, or blunt head trauma. In order to study these neurochemical phenomena, Zn2+ responsive sensors are required that can track the spatial and temporal distribution of the mobilized ion in response to physiological and pathological stimuli. The design, synthesis, evaluation, and optimization of the sensors constitute the major components of this research project. Each sensor will have up to three modules. Minimally, there will be zinc-binding and zinc-reporting units. The binding modules typically comprise multidentate ligands with variable Zn2+ affinity, selectivity for Zn2+ over competing ions in neuronal tissue, and fast, reversible coordination to monitor biological changes on the ms time scale. The zinc-reporting module will be either fluorescent or phosphorescent, for use in optical imaging (OI) experiments, or capable of altering water relaxation rates, for use in magnetic resonance imaging (MRI) studies. Fluorescent reporters include xanthenone and single-walled carbon nanotube derivatives. Phosphorescent sensors are based on cyclometalated iridium(III) complexes. MRI constructs utilize manganese(III) porphyrins. Strategies are adopted for attaching an optional third module to localize photoluminescence-based zinc sensors to programmed cellular targets to investigate Zn2+ dynamics at specific sites in a signal transduction pathway following physiological or pathological stimulation. An associated objective is to prepare zinc-selective, rapid chelating agents to be used in conjunction with investigations of the biological functions of mobile Zn2+. Thermodynamic, kinetic, photophysical, and theoretical studies of the zinc sensors and chelators will guide synthetic directions for making improvements to optimize their utility in applications. Specific applications include the evaluation by OI of hypotheses concerning the roles of mobile zinc in neurotransmission at mossy fiber synapses in the hippocampus and at glomeruli in the OB and the visualization by MRI of mobile zinc activity in the hippocampus under physiological and pathological conditions. This project is relevant to public health, for it will provide the means to test theories about the functions of mobile Zn2+ in the brain as well as the means by which to assess the postulated association of uncontrolled zinc levels with neurodegenerative diseases, such as Alzheimer's, and with more acute toxic encephalopathies. The chemistry devised will also facilitate the development of tools to measure mobile zinc stores that occur in other tissues such as the prostate and pancreas, where quantitation of mobile Zn2+ has the potential for early detection of diseases involving these organs.