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

描述（由申请人提供）：老年痴呆症（AD）在我们老龄化人口中的患病率不断增加，对公共卫生构成了重大挑战。目前的AD药物疗法对于减少近期记忆丧失（AD最常见的早期症状）具有适度的功效，但是具有最小的改变潜在神经变性的能力。我们的长期目标是开发一种安全的药物来治疗早期症状性记忆丧失并减少潜在的神经退行性变。虽然许多努力已经投入到β-分泌酶抑制剂的开发中，但很少有药物策略集中在α-分泌酶上，该α-分泌酶切割跨膜β-淀粉样前体蛋白（APP）以产生无毒片段sAPPa，淀粉样前体蛋白的可溶形式。已知α-分泌酶活性可通过蛋白激酶C的激活剂而增加，包括苔藓抑素（bryostatin），一种大环内酯内酯，其也可增强大鼠迷宫学习和兔瞬膜调节。苔藓抑素从未被用于治疗AD。作为一种抗肿瘤剂，它显示出最小的功效，但在剂量< 30 μ g/m2/周时也显示出最小的人体毒性。中心假设是低剂量苔藓抑素的间歇给药将导致PKC同工酶a和e以及MAP激酶Erk 1/2的最大激活，而人体毒性最小。该建议的基本原理是，认知增强和神经保护来自苔藓抑素对PKC的有效激活和MAP激酶Erk 1/2合成的长期增强。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）测量苔藓抑素-1的体外和体内生化作用（和“bryologs”）对膜和细胞溶质PKC同工酶和α-分泌酶的作用，并基于最大PKC活化、α-分泌酶同工酶和延长的蛋白质合成确定具有最小毒性的给药方案; 2）评估苔藓抑素和苔藓素的认知增强作用及其在年轻和老年正常大鼠中的体内功效;和3）在AD转基因小鼠129 S6.Cg-Tg（APPSWE）2576 Kha中用空间迷宫测试确定认知增强和体内神经保护功效，测量减少的神经变性，包括死亡率，sAPP分泌，水平A？1-42，A？1-40，淀粉样斑块负荷和tau磷酸化。这项研究将为苔藓抑素作为一种新型疗法的临床试验提供基础，以改善AD的症状，并可能提供针对这种毁灭性疾病的神经保护。

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.