用于阿尔茨海默症早期诊断的氟标小分子MRI成像用Aβ探针的研究

Alzheimer's disease (AD) which is characterized by neurodegeneration and cognitive impairment serious harm to the health of the elderly. Currently, cognitive and neuropathological examination is difficult to early diagnose AD. With the approve of fluorine 18-AV45 by FDA, PET imaging of Aβ probes has been achieved early diagnosis of AD. MRI is more secure and cheap than PET. Fluorine 19 (19F) labeled small molecular probes have outstanding advantages in MRI brain imaging. Scatter distributed Aβ plaques are pathological specific in the early stage of AD brain. However, they could not be detected by FSB and other existing MRI 19F Aβ probes animal MRI imaging, probably due to insufficient amount of 19F atoms and an oversize molecular weight in the existing probes. This study intends to use more fluorine atoms labeling strategies. The probe will be labeled more amount of 19F atoms while keeping a smaller molecular weight. Previous work of the applicant showed that the indanone derivatives were able to bind to the Aβ plaques specifically and with fine affinity and brain uptake. The derivatives had an attractive prospect. In this study, the 18F which is a radioactivity isotope of 19F will be labeled to the probe. Then the related techniques such as the receptor binding assay, autoradiography and so on will be used to screen and evaluate the 19F labeled probes quickly and accurately. It is expected to get the probe which could image the scatter distributed Aβ plaques accurately and clearly. And it will provide new techniques for early diagnosis of AD by MRI molecular imaging test. This study was not found to be reported at home and abroad.

阿茨海默症（AD）以神经退行性病变和认知障碍为主要特征，严重危害老年人健康。目前，认知和神经病理检查均难以早期诊断AD。随着氟18-AV45等获FDA批准，PET用Aβ探针的显像已实现AD的早期诊断。MRI较PET更安全经济，氟19小分子探针在MRI脑显像中有突出优势。但现有氟19Aβ探针如FSB等,在动物MRI成像中均未显示出AD早期病理性特异的散在分布的Aβ斑块。原因可能是现有氟标探针的氟原子数较少，且分子量过大。本课题拟采用多氟标记策略，既保持探针的小分子量，又标记上多个氟原子。申请人前期筛选的茚酮衍生物能特异结合Aβ斑块，拥有良好的亲和力和脑摄取量，有诱人的应用前景。本研究拟用氟19的放射性同位素氟18标记，利用受体结合、放射自显影等技术，快速准确地筛选评价待测探针。预期将能实现对散在分布的Aβ斑块进行准确清晰的MRI成像，为AD 的MRI早期诊断提供新技术。本研究国内外未见报道。

阿尔茨海默病（AD）是一种严重威胁人类健康的神经退行性疾病，认知和病理检查无法早期诊断AD,PET用Aβ探针能实现AD的早期诊断，MRI比PET更安全、便宜，氟19探针在MRI脑显像中有突出优势。本课题目的是采取小分子量的前提下进行多氟标记的策略，研究用于MRI成像的小分子Aβ探针。.根据计划，我们完成了以下几方面研究：.1. 合成和表征了茚酮类及AV-45类似的多氟化合物及氟标前体，开展了亲和力测定和脑片染色等生物评价。创新性地开发了基于质谱平台的受体结合分析（MSBA）用于小分子与Aβ结合的亲和力的测定，MSBA测定的IMPY与Aβ1-40及1-42纤维的Kd及Ki值与文献中RBA的数据相似。MSBA用于Aβ探针亲和力测定国内外暂未见报道。MSBA测定的优选的氟标茚酮类及AV-45类似化合物的Kd及Ki值在0.1-100 nM级别。结果提示多氟标记的茚酮类化合物是一类较有潜力的Aβ成像用MRI探针。.2. 为筛选(E)-肉桂醛衍生物作为Aβ探针，我们建立了通过无金属DDQ介导的烯丙基芳烃氧化转化的全新方法并合成了一系列(E)-肉桂醛衍生物，后续将测定其与Aβ的亲和力及其抗菌活性。.3. 该课题还支持了星形胶质细胞（Astrocyte）在AD的病理生理和治疗中的作用的研究。结果显示APP/PS1小鼠的Astrocyte分泌高水平的可溶性Aβ40和Aβ42，而后两者在体内和体外均显示出突触毒性。这些结果为Astrocyte在APP/PS1小鼠的病理生理学中的重要作用提供了直接证据，而这可能与FAD的发病机理直接相关。此外，氟西汀治疗可有效抑制Astrocyte产生可溶性Aβ40和Aβ42，显著改善了后两者对神经元的突触毒性，从而防止APP/PS1小鼠在记忆测试中的行为缺陷。这些结果凸显Astrocyte在产生神经毒性Aβ中的重要作用，并且提供了一个AD治疗的潜在途径。.4. 该课题还支持了茚酮衍生物作为PET成像探针的研究，该研究合成了一系列6-甲氧基茚酮衍生物，在AD脑切片染色、RBA实验均显示出对Aβ的高亲和力，生物分布实验中表现出高初始脑摄取率（5.29％ID/g）以及快速清除的能力。放射自显影实验AD脑片及APP/PS1转基因小鼠（体内和体外）的脑切片均显示出对Aβ斑块的高结合能力。结果显示该类探针是一类有潜力的Aβ探针。