Targeting the apoE/ABeta Interaction as a Novel AD Therapy

描述（由申请人提供）：我们的主要假设是，阻断载脂蛋白E和？-淀粉样蛋白将有效地减少和预防6-淀粉样蛋白（A？）阿尔茨海默病（AD）的相关病理学。？-淀粉样蛋白（A？）级联假说认为，积累的A？？在AD的早期发病机制中，肽的表达是一个关键事件。A的过量？组装成有毒的寡聚体，随后进入沉积在脑实质和血管壁产生脑淀粉样血管病（CAA）。载脂蛋白E（apoE）是促进A？apoE/AB相互作用的大小似乎是同种型特异性的，为apoE 4等位基因与散发性AD风险增加之间的联系提供了一种解释。我们已经证明，阻断apoE/AB结合与合成肽- A？12- 28 P，模拟A？并被修饰用于体内应用，降低了实质AB沉积物和CAA的负担，以及预防AD转基因（Tg）小鼠的记忆损伤（Sadowski等，AJP，2004; 165：937; Sadowski等，PNAS，2006; 103：18787）。相反，抗A？疫苗接种方法只能预防实质性A？不影响CAA负担的沉积。此外，疫苗接种似乎增加了血管周围血管扩张的风险，这是不存在的AD Tg动物治疗A？12- 28点。在这项资助计划中，我们计划开发无毒的apoE/A？互动，这将是基于A？12-28序列。目的是提高治疗效果、BBB渗透性和生物稳定性。由于肽模拟物固有的仿生特性、它们对降解的抗性和易于化学修饰，这种策略在过去已成功地用于开发许多有治疗前景的化合物。将在AD Tg模型（包括表达不同人apoE同种型的模型）中测试选定的拟肽化合物。这将用于预测各种人apoE同种型携带者的治疗反应。为了确定这种形式的治疗是否可以减少已经存在的A？存款，我们将在体内进行成像的A？使用经颅双光子显微镜观察AD Tg小鼠中的斑块。虽然阻断apoE/A？互动是为了防止A？原纤组装和沉积我们在本申请中研究的这种方法还有几个其它潜在的优点。因此，我们将确定阻断apoE/A？A上的交互作用？和apoE通过血脑屏障的清除，A？寡聚体和原纤维的形成，以及apoE/A的神经元内积累？配合物该提案的总体目标是使这种新的治疗方法更接近临床研究，并确定一种先导肽模拟物化合物，该化合物可以进一步开发用于人类的安全，长期应用。

DESCRIPTION (provided by applicant): Our main hypothesis is that a therapeutic agent blocking the interaction between apolipoprotein E and ?-amyloid will be effective in reducing and preventing 6-amyloid (A?) related pathology of Alzheimer's disease (AD).The ?-amyloid (A?) cascade hypothesis maintains that accumulation of the A??peptide constitutes a critical event in the early pathogenesis of AD. An excess of A? assembles into toxic oligomers and subsequently into deposits in the brain's parenchyma and in walls of vessels producing cerebral amyloid angiopathy (CAA).The direct binding between A? and apolipoprotein E (apoE) has been identified as an important factor promoting the deposition of A? in the CMS and regulating its clearance across the blood-brain-barrier (BBB).The magnitude of apoE/AB interaction appears to be isoform specific, providing one explanation for the linkage between the apoE4 allele and an increased risk of sporadic AD. We have demonstrated that blocking the apoE/AB binding with a synthetic peptide - A?12-28P, that mimics the apoE binding site on A? and was modified for in vivo application, reduces the burden of parenchynal AB deposits and CAA, as well as preventing memory impairment in AD transgenic (Tg) mice (Sadowski et al. AJP, 2004; 165:937; Sadowski et al., PNAS, 2006; 103:18787). In contrast, anti-A? vaccination approaches prevent only parenchymal A? deposition without affecting the CAA burden. In addition, vaccination appears to increase the risk of perivascular hemorrhages which were absent in AD Tg animals treated with A?12-28P. In this grant proposal, we are planning to develop non-toxic peptidomimetic antagonists of the apoE/A? interaction which will be based on the A?12-28 sequence. The objectives are to improve therapeutic efficacy, BBB penetration, and biostability. Due to the inherent biomimetic character of peptidomimetics, their resistance to degradation, and ease of chemical modification, this strategy has been successfully employed in the past to develop a number of therapeutically promising compounds. Selected peptidomimetic compounds will be tested in AD Tg models including those expressing differing human apoE isoforms. This will be done to predict the therapeutic response in carriers of the various human apoE isoforms. To determine whether this form of therapy can lead to a reduction of already existing A? deposits we will perform in vivo imaging of A? plaques in AD Tg mice using transcranial two-photon microscopy. Although the primary goal of blocking the apoE/A? interaction is to prevent A? fibrillar assembly and deposition there are also several other potential benefits of this approach which we investigate in this application. Thus, we will determine the effect of blocking the apoE/A? interaction on A? and apoE clearance across the BBB, the equilibrium between A? oligomers and fibril formation, and intraneuronal accumulation of apoE/A? complexes. The overall goal of this proposal is to bring this novel therapeutic approach closer to clinical studies and to identify a lead peptidomimetic compound, which could be further developed for safe, long-term application in humans.