Urokinase-type Plasminogen Activator in the Ischemic Brain

摘要 可溶性A-β诱导的突触功能障碍导致阿尔茨海默病(AD)患者进行性认知能力下降 病人。这是一个早于神经元死亡的早期事件，因此可以接受治疗干预。 在发展为不可逆转的脑损伤之前。尿激酶型纤溶酶原激活物(UPA)是一种丝氨酸 当与其受体(UPAR)结合时，不仅产生纤溶酶，而且激活细胞信号。 小路。由支持此行政补充申请的有效奖励资助的工作显示 UPA广泛存在于大脑皮质II/III和V层兴奋性神经元的突触中。 成熟的小鼠、非人类灵长类动物和人脑，其释放由突触活动触发， 促进突触接触的形成和因缺血损伤而受损的突触的修复。 Wnt-β-Catenin通路的激活对突触的形成和突触结构的保存至关重要 和功能。可溶性A-β抑制AD患者脑内Wnt-β-Catenin通路及其产物 β-连环蛋白信号障碍导致突触功能障碍，淀粉样蛋白的形成过程 前体蛋白(APP)、tau磷酸化和记忆丧失。根据这些观察，恢复 WnT-β-连环蛋白通路功能可预防可溶性A-β诱导的突触功能障碍和认知功能下降。在这 行政补充申请，我们将使用体外和体内的实验方法来测试 假设uPA通过激活突触来保护突触免受可溶性A-β的有害影响 WnT-β-连环蛋白途径不需要纤溶酶的产生。我们的 假设是在积极奖励的范围内，并得到下列观察结果的支持 这一应用的初步研究：1)阿尔茨海默病突触内uPA的丰度显著降低 患者；ii)uPA是大脑皮层神经元Wnt-β-Catenin通路的有效激活剂，通过 不需要产生纤溶酶的机制；III)uPA可消除可溶性Aβ对血管内皮细胞生长的抑制作用 4)uPA通过激活Wnt-β-Catenin通路来阻止β诱导的突触丢失。 和v)用重组uPA(RUPA)治疗保护突触免受可溶性Aβ的有害影响。 重要的是，uPA在AD发病机制中的相关性得到了核苷酸的支持 尿激酶型纤溶酶原激活剂编码基因的多态性与晚发性阿尔茨海默病的发病有关，并且uPA的活性 抑制物[纤溶酶原激活物抑制物-1(PAI-1)]在AD患者脑组织中升高。因此，假设 这将在此行政补充申请中进行测试，这是新颖的，可能会导致新的发现 AD的病理生理机制和保护AD患者突触的潜在治疗靶点。

ABSTRACT Soluble Aβ-induced synaptic dysfunction causes progressive cognitive decline in Alzheimer’s disease (AD) patients. This is an early event that precedes neuronal death and thus is amenable to therapeutic interventions before the progression to irreversible brain damage. Urokinase-type plasminogen activator (uPA) is a serine proteinase that upon binding to its receptor (uPAR) not only generates plasmin but also activates cell signaling pathways. Work funded by the active award supporting this Administrative Supplement application has revealed that uPA is abundantly found in synapses of excitatory neurons located in the II/III and V cortical layers of the mature murine, non-human primate and human brain, and that its release, triggered by synaptic activity, promotes the formation of synaptic contacts and the repair of synapses damaged by an ischemic injury. Activation of the Wnt-β-catenin pathway is crucial for synapse formation and preservation of synaptic structure and function. Soluble Aβ inhibits the Wnt-β-catenin pathway in the brain of AD patients, and the resultant impairment of β-catenin signaling causes synaptic dysfunction, amyloidogenic processing of the amyloid precursor protein (APP), tau phosphorylation and memory loss. In line with these observations, restoration of Wnt-β-catenin pathway function prevents soluble Aβ-induced synaptic dysfunction and cognitive decline. In this Administrative Supplement application we will use in vitro and in vivo experimental approaches to test the hypothesis that uPA protects the synapse from the harmful effects of soluble Aβ by its ability to activate the Wingless/Int1 (Wnt)-β-catenin pathway via a mechanism that does not require plasmin generation. Our hypothesis is within the scope of the active award, and supported by the following observations described in Preliminary Studies of this application: i) the abundance of uPA is significantly decreased in the synapse of AD patients; ii) uPA is an efficient activator of the Wnt-β-catenin pathway in cerebral cortical neurons by a mechanism that does not require plasmin generation; iii) uPA abrogates the inhibitory effect of soluble Aβ on the Wnt-β-catenin pathway; iv) uPA prevents Aβ-induced synaptic loss via Wnt-β-catenin pathway activation. And v) treatment with recombinant uPA (ruPA) protects the synapse from the harmful effects of soluble Aβ. Importantly, the relevance of uPA in the pathogenesis of AD is supported by findings that nucleotide polymorphisms of the uPA encoding gene are associated with late onset AD, and that the activity of uPA’s inhibitor [plasminogen activator inhibitor–1 (PAI-1)] is increased in the brain of AD patients. Thus, the hypothesis that will be tested in this Administrative Supplement application is novel and may lead to the discovery a new pathophysiological mechanism of AD and a potential therapeutic target to protect the synapse of AD patients.