Identification of mechanisms by which cytisine and estrogen inhibit ER stress and exert neuroprotection in Parkinson's disease

帕金森病(PD)是第二种最常见的神经退行性疾病，预计影响超过12 到2040年，全球人口将达到100万。帕金森病无法治愈，目前的治疗只是对症治疗， 这突显了对神经保护药物的迫切需求和未得到满足的需求。一个主要的障碍是无法 开发有效的临床可翻译的神经保护药物是没有一个单一的动物模型总结的 帕金森病患者多巴胺能神经元丢失的复杂过程。因此，大多数成功的药物 临床前动物模型在帕金森病患者中不起作用。目前的提案通过将重点放在 高活性内质网应激是一种既定的汇聚机制 下游多种与帕金森氏病相关的毒性。ER压力由三个信号臂组成，最终以 三个关键蛋白-ATF6、XBP1和CHOP移位到DA神经元的核中。中等 ATF6和XBP1的激活是神经保护的，而这些蛋白的慢性、不受控制的激活导致 致地区检察官细胞死亡。相反，CHOP的激活总是会导致细胞死亡。实验表明， 烟碱类化合物可引起称为内质网出口部位(ERES)的特殊结构的上调，以及 这与ATF6和XBP1的抑制有关。令人惊讶的是，在6-羟基多巴胺(6-OHDA)诱导的帕金森病临床前毒素模型中的实验表明，胞二磷胆碱只对雌性小鼠具有神经保护作用。 另外的初步实验表明，17-β-雌二醇抑制DA神经元CHOP的表达，这是 在帕金森病的发病率和表型上观察到强烈的性别差异，男性更容易患上 发展中的帕金森病多于女性。基于这些数据，这项建议假设胞二磷胆碱和雌激素对 协同抑制ATF6、XBP1和CHOP对雌性小鼠的神经保护作用 多巴胺能神经元内质网应激过度激活。有人建议进行实验，以确定胱氨酸在多大程度上 需要ERES来发挥神经保护作用，具体方法是删除DA神经元中的ERES或使用尼古丁 不能上调ERES的化合物。雌性小鼠将被摘除卵巢以确定其机制 哪些特定的雌激素受体亚型对雌性小鼠起到神经保护作用。在完成时 在这一方案中的实验，关键的信号转导靶点，通过胞苷和雌激素进行调节 神经保护作用将得到确认。这项提案的成功将为实现以下长期目标奠定基础 发现临床可翻译的神经保护性帕金森病药物，对男性和女性都有效。

Parkinson’s disease (PD) is the second most common neurodegenerative disorder, predicted to affect over 12 million people worldwide by 2040. There is no cure for PD and current treatments are merely symptomatic, which underscores an urgent and unmet need for neuroprotective drugs. One major barrier for the inability to develop effective and clinically translatable neuroprotective drugs is that no single animal model recapitulates the complex process that leads to dopaminergic (DA) neuron loss in PD. Therefore, most drugs that succeed in preclinical animal models fail to work in PD patients. The current proposal addresses this barrier by focusing on hyperactivated endoplasmic reticulum (ER) stress, which is an established convergent mechanism downstream of multiple PD-related toxicities. ER stress consists of three signaling arms that culminate in the translocation of three key proteins – ATF6, XBP1, and CHOP into the nucleus of DA neurons. Moderate activation of ATF6 and XBP1 is neuroprotective, while chronic, uncontrolled activation of these proteins leads to DA cell death. By contrast, activation of CHOP invariably causes cell death. Experiments showed that the nicotinic compound cytisine causes an upregulation of specialized structures called ER exit sites (ERES), and this is associated with an inhibition of ATF6 and XBP1. Surprisingly, experiments in a 6-hydroxydopamine (6-OHDA)-induced preclinical toxin model of PD showed that cytisine is neuroprotective only in female mice. Additional preliminary experiments showed that 17-β-estradiol inhibits CHOP expression in DA neurons, which fits with strong sex-differences observed in the incidence and phenotype of PD, with men being more prone to developing PD than women. Based on these data, this proposal hypothesizes that cytisine and estrogen exert neuroprotection in female mice by synergistically inhibiting all three arms (ATF6, XBP1 and CHOP) of hyperactivated ER stress in DA neurons. Experiments are proposed to determine the extent to which cytisine requires ERES for exerting neuroprotection by specifically deleting ERES in DA neurons or by using nicotinic compounds that cannot upregulate ERES. Female mice will be ovariectomized to determine mechanisms by which specific subtypes of estrogen receptors exert neuroprotection in female mice. On completing experiments in this proposal, key signaling targets through which cytisine and estrogen mediate neuroprotective effects will be identified. Success in this proposal will lay groundwork for the long-term goal of discovering clinically translatable neuroprotective PD drugs that work in both men and women.