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

描述(申请人提供)：阿尔茨海默病(AD)在我们的老龄化人口中日益流行，对公共卫生构成了重大挑战。目前的AD药物疗法在减少最近记忆丧失(AD最常见的早期症状)方面疗效不佳，但改变潜在神经变性的能力微乎其微。我们的长期目标是开发一种安全的药物，既能治疗早期有症状的记忆丧失，又能减少潜在的神经变性。虽然许多努力都集中在分泌酶抑制剂的开发上，但很少有药物策略专注于a分泌酶，这种酶能裂解跨膜淀粉样前体蛋白(APP)，产生一种无毒的片段，Sappa，淀粉样前体蛋白的可溶性形式。已知蛋白激酶C的激活剂可以增加A-分泌酶的活性，包括大环内酯类内酯Bryostatin，它也可以增强大鼠的迷宫学习和兔的点滴膜条件作用。Bryostatin从未被用于治疗AD。作为一种抗肿瘤药物，它显示出最小的疗效，但对人体的毒性也最小，剂量为30g/m2/周。中心假设是，间歇服用低剂量的bryostatin将导致最大限度地激活PKC同工酶a和e以及MAP激酶ERK1/2，而对人类的毒性最小。这一建议的基本原理是，认知增强和神经保护是由于Bryostatin对PKC的有效激活和对MAP激酶ERK1/2合成的长期促进。为了验证这一假说并实现我们的目标，我们将追求以下具体目标：1)测定Bryostatin-1(和“Bryologs”)对细胞膜和胞质蛋白激酶C同工酶和α-分泌酶(S)的体内外生化影响，并根据最大PKC活性、α-分泌酶同工酶和蛋白质合成时间确定毒性最小的给药方案；2)评估Bryostatin和Bryolos对幼年和老年正常大鼠的认知增强作用和体内疗效；3)通过空间迷宫测试确定AD转基因小鼠129S6.Cg-TG(APPswe)2576 Kha的认知增强和体内神经保护效果，并测量减少的神经变性，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。这项研究将为计划中的Bryostatin临床试验提供基础，作为一种改善AD症状的新疗法，并可能提供神经保护，对抗这种毁灭性的疾病。

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.