Alpha Secretase Activation by Bryostatin for the Treatment of Alzheimer's Disease

描述（由申请人提供）：老年人口中阿尔茨海默病（AD）患病率的增加对公共卫生构成了重大挑战。目前的阿尔茨海默病药物治疗对减少近期记忆丧失（阿尔茨海默病最常见的早期症状）有一定的疗效，但对改变潜在的神经退行性变的能力很小。我们的长期目标是开发一种安全的药物，既能治疗早期症状性记忆丧失，又能减少潜在的神经变性。虽然在开发-分泌酶抑制剂方面已经付出了很多努力，但很少有药物策略关注于-分泌酶，它可以切割跨膜淀粉样前体蛋白（APP），产生无毒片段sAPPa，即淀粉样前体蛋白的可溶性形式。a-分泌酶活性已知可通过蛋白激酶C的激活剂，包括苔藓虫素（一种大环内酯内酯），提高大鼠迷宫学习能力和家兔硝化膜调节。苔藓虫素从未被用于治疗阿尔茨海默病。作为一种抗肿瘤药物，在剂量< 30¿g/m2/周时，其疗效最小，但人体毒性最小。中心假设是，间歇性给药低剂量苔藓虫素将导致PKC同工酶a和e和MAP激酶Erk1/2的最大激活，而人体毒性最小。这一建议的基本原理是，苔藓抑素对PKC的有效激活和MAP激酶Erk1/2合成的长期增强是认知增强和神经保护的结果。为了验证这一假设并实现我们的目标，我们将追求以下具体目标：1)测量苔藓虫抑素-1（和“苔藓虫”）对膜和胞质PKC同工酶和a-分泌酶的体外和体内生化效应，并根据最大PKC激活、a-分泌酶同工酶和延长的蛋白质合成确定毒性最小的给药方案；2)评估苔藓抑素和苔藓素对幼龄和老年正常大鼠的认知增强作用及其体内疗效；3)通过空间迷宫测试检测AD转基因小鼠129S6的认知增强和体内神经保护作用。Cg-Tg(APPSWE)2576Kha与减少神经变性的测量，包括死亡率，sAPP分泌，A¿1-42和A¿1-40水平，淀粉样斑块负荷和tau磷酸化。这项研究将为苔藓虫素作为一种新的治疗方法改善阿尔茨海默病的症状和潜在的神经保护提供计划的临床试验奠定基础。

DESCRIPTION (provided by applicant): The increasing prevalence of Alzheimer's disease (AD) in our aging population poses a significant challenge to public health. Current AD drug therapies have modest efficacy for reducing the loss of recent memory, the most common early symptom of AD, but have minimal ability to modify the underlying neurodegeneration. Our long range goal is to develop a safe drug to treat both the early symptomatic loss of memory and to reduce the underlying neurodegeneration. While much effort has gone into the development of ¿-secretase inhibitors, few drug strategies have focused on the a-secretases which cleave the transmembrane ¿ amyloid precursor protein (APP) to generate a nontoxic fragment, sAPPa, the soluble form of amyloid precursor protein. a-Secretase activity is known to be increased by activators of protein kinase C, including bryostatin, a macrolide lactone, that also enhances rat maze learning and rabbit nictitating membrane conditioning. Bryostatin has never been used to treat AD. As an anti-tumor agent, it shows minimal efficacy but also minimal human toxicity in doses < 30 ¿g/m2/week. The central hypothesis is that intermittent administration of low doses of bryostatin will cause maximal activation of PKC isozymes a and e and MAP kinase Erk1/2 with minimal human toxicity. The rationale for this proposal is that cognitive enhancement and neuroprotection result from bryostatin's potent activation of PKC and long-term enhancement of MAP kinase Erk1/2 synthesis. To test this hypothesis and accomplish our objectives, we will pursue the following Specific Aims: 1) to measure the in vitro and in vivo biochemical effects of bryostatin-1 (and "bryologs") on membrane and cytosolic PKC isozymes and a-secretase(s) and to determine dosing regimens with minimal toxicity based on maximal PKC activation, a-secretase isozymes, and prolonged protein synthesis; 2) to assess cognitive enhancement of bryostatin and bryologs and their efficacy in vivo in young and aged normal rats; and 3) to determine cognitive enhancement with spatial maze testing and neuroprotective efficacy in vivo in AD transgenic mice 129S6.Cg-Tg(APPSWE)2576Kha with measurements of reduced neurodegeneration that include mortality, sAPP secretion, levels of A¿1-42, and A¿1-40, amyloid plaque burden and tau phosphorylation. This research will provide a foundation for planned clinical trials of bryostatin as a novel therapy to improve the symptoms of AD and potentially offer neuroprotection against this devastating disease.