Targeting the apoE/ABeta Interaction as a Novel AD Therapy

描述（由申请人提供）：我们的主要假设是一种阻断载脂蛋白E和b -淀粉样蛋白相互作用的治疗药物将有效减少和预防阿尔茨海默病（AD）的6-淀粉样蛋白（AB）相关病理。b -淀粉样蛋白（AB）级联假说认为，AB肽的积累是AD早期发病的关键事件。过量的AB聚集成有毒的低聚物，随后沉积在脑实质和血管壁上，产生脑淀粉样血管病（CAA）。AB与载脂蛋白E （apoE）的直接结合被认为是促进AB在CMS中沉积并调节其通过血脑屏障（BBB）清除的重要因素。apoE/AB相互作用的程度似乎是同工异构体特异性的，这为apoE4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，用合成肽- AB 12-28P阻断apoE/AB的结合，该肽模仿AB上的apoE结合位点，并经过体内修饰，可以减少实质AB沉积和CAA的负担，并防止AD转基因（Tg）小鼠的记忆障碍（Sadowski等）。美国,2004;165:937;Sadowski et al.， PNAS, 2006；103:18787)。相反，抗AB疫苗接种方法只能预防实质AB沉积，而不影响CAA负担。此外，疫苗接种似乎增加了AD - Tg动物血管周围出血的风险，而AB 12-28P治疗的AD - Tg动物没有血管周围出血。在这项拨款申请中，我们计划开发基于AB 12-28序列的apoE/ AB相互作用的无毒肽类拮抗剂。目的是提高治疗效果、血脑屏障渗透和生物稳定性。由于肽模拟物固有的仿生特性，它们的抗降解性和易于化学修饰，这种策略在过去已经成功地用于开发许多有治疗前景的化合物。选定的拟肽化合物将在AD - Tg模型中进行测试，包括表达不同人类apoE亚型的模型。这将用于预测各种人类载脂蛋白e亚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AB沉积，我们将使用经颅双光子显微镜对AD Tg小鼠的AB斑块进行体内成像。虽然阻断apoE/ AB相互作用的主要目的是防止AB纤维的组装和沉积，但我们在本应用中研究了这种方法的其他几个潜在好处。因此，我们将确定阻断apoE/ AB相互作用对血脑屏障中AB和apoE清除、AB低聚物与纤维形成之间的平衡以及apoE/ AB复合物在神经元内积累的影响。这项提议的总体目标是使这种新的治疗方法更接近临床研究，并确定一种先导的拟肽化合物，这种化合物可以进一步开发用于安全、长期的人体应用

DESCRIPTION (provided by applicant): Our main hypothesis is that a therapeutic agent blocking the interaction between apolipoprotein E and B-amyloid will be effective in reducing and preventing 6-amyloid ( AB ) related pathology of Alzheimer's disease (AD).The B-amyloid ( AB ) cascade hypothesis maintains that accumulation of the AB peptide constitutes a critical event in the early pathogenesis of AD. An excess of AB 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 AB and apolipoprotein E (apoE) has been identified as an important factor promoting the deposition of AB 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 - AB 12-28P, that mimics the apoE binding site on AB 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- AB vaccination approaches prevent only parenchymal AB 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 AB 12-28P. In this grant proposal, we are planning to develop non-toxic peptidomimetic antagonists of the apoE/ AB interaction which will be based on the AB 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 AB deposits we will perform in vivo imaging of AB plaques in AD Tg mice using transcranial two-photon microscopy. Although the primary goal of blocking the apoE/ AB interaction is to prevent AB 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/ AB interaction on AB and apoE clearance across the BBB, the equilibrium between AB oligomers and fibril formation, and intraneuronal accumulation of apoE/ AB 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