Indole Glyoxylamides Peripheral Benzodiazepine Receptor

本研究项目的目标是定义配体的结构和放射性标记，其将允许通过正电子（PET）或单光子（SPECT）发射断层扫描的外部成像定量测量活脑中的外周苯二氮卓受体（PBR）。特异性结合PBR的放射性示踪剂将在神经精神障碍如脑损伤、神经退行性疾病、焦虑和应激障碍的诊断、监测治疗和病因学研究中具有很大的实用性。PBR被认为与许多生物学功能相关，包括调节细胞增殖、免疫调节、卟啉转运、血红素生物合成、阴离子转运、调节类固醇生成和凋亡。例如，在HIV/AIDS、阿尔茨海默病、亨廷顿病、多发性硬化和神经胶质增生患者的脑组织中观察到PBR增加。对艾滋病患者的PET研究显示，皮质和皮质下PBR受体结合增加，支持胶质细胞活化在艾滋病痴呆患者中的作用。这项研究强调了目前使用的放射性配体的局限性，并指出需要进一步优化PBR的定量。我们发现某些吲哚甘氨酰胺衍生物对PBR显示出纳摩尔亲和力。然而，其中两个与123 I标记的脑摄取低，在非人灵长类动物。这些结果提出的关键问题是：a）PBR的亲和力和选择性是否可以增加，同时降低不同杂环取代基的亲脂性？和B）匀浆结合结果是否适用于体内摄取和分布？在本申请中，我们提出测试以下假设：1）在吲哚的2-位上具有适当官能化的杂环取代基的N，N-二烷基吲哚基甘氨酰胺将有利于与PBR相对于CBR的结合;和2）引入这些杂芳环将改变我们的化合物的亲脂性，从而具有较低的非特异性结合和较高的脑摄取。 我们将合成一系列N，N-二烷基-2-杂环取代吲哚基甘氨酰胺类化合物。将用F-18或I-123放射性标记对PBR的结合亲和力低于10 nM且相对维斯CBR的选择性高于100的候选物，并测量其亲脂性（log D）。将在非人灵长类动物中通过在对照条件下和特定药理学挑战下对放射性示踪剂的局部脑分布进行成像来测量体内结合。将评价log D、体外亲和力和体内选择性的相关性。 在本项目结束时，我们希望已经确定了一种放射性配体，适用于NeuroAIDS，痴呆症和其他疾病的PBR成像。

The goal of this research project is to define the structure and radioactive label for ligands that will permit quantitative measurement of the peripheral benzodiazepine receptor (PBR ) in living brain by external imaging with positron (PET) or single photon (SPECT) emission tomography. A radio-tracer binding specifically to PBR would be of great utility in diagnosis, monitoring treatment, and etiological research of neuropsychiatric disorders such as brain damage, neurodegenerative diseases, anxiety and stress disorders. The PBR is thought to be associated with many biological functions, including the regulation of cellular proliferation, immunomodulation, porphyrin transport, heme biosynthesis, anion transport, regulation of steroidogenesis, and apoptosis. For example, increases in PBR have been observed in brain tissue from patients with HIV/AIDS, Alzheimer's disease, Huntington's disease, multiple sclerosis, and gliosis. A PET study in patients with AIDS showed increased cortical and subcortical PBR receptor binding, supporting the role of glial cell activation in HIV patients with dementia. This study highlights the limitations of current radioligands used and points out the need to further optimize quantitation of PBR. We found that certain indole glyoxylamide derivatives showed nanomolar affinity to PBR. However, brain uptake of two of them labeled with 123I was low in nonhuman primate. Key questions posed by these results are: a) Can PBR affinity and selectivity be increased while reducing lipophilicity with different heterocyclic substituents? And b) are the homogenate binding results applicable to in vivo uptake and distribution? In this application we propose to test the following hypotheses: 1) N,N-dialkyl indolylglyoxylamides with appropriately functionalized heterocyclic substituents on the 2-position of indole will favor binding to PBR relative to CBR; and 2) introduction of these heteroaromatic rings will alter the lipophilicity of our compounds so as to have lower nonspecific binding and higher brain uptake. We will synthesize a series of N,N-dialkyl-2-heterocyclic substituted indolylglyoxylamides. The candidates with binding affinities below 10 nM for PBR and selectivity vis-a-vis CBR above 100 will be radiolabeled with F-18 or I-123 and their lipophilicity (log D) will be measured. In vivo binding will be measured in nonhuman primates by imaging regional brain distribution of the radio-tracer under control conditions and with specific pharmacological challenges. Correlation of log D, in vitro affinity, and in vivo selectivity will be evaluated. At the conclusion of this project period, we expect to have identified a radioligand suitable for imaging the PBR in NeuroAIDS, dementia and other diseases.