COX2-Derived Cyclopentenone Prostaglandins Exacerbate Hypoxic Ischemic Brain Inju

描述（由申请人提供）：环氧化酶-2 （COX-2）是一种负责产生前列腺素的酶，已被确定为缺氧缺血后脑损伤的重要因素。不幸的是，据报道COX-2抑制剂会导致患者的脑和心脏血栓形成，这使得COX-2抑制剂作为一种治疗缺血性事件恢复患者的吸引力降低。因此，了解COX-2介导的神经元损伤机制对于开发更有针对性的治疗方法非常重要。最近，前列腺素的下游产物，特别是环戊酮前列腺素已被确定为缺血性损伤的潜在贡献者。环戊酮前列腺素具有高度亲电性，可与暴露的蛋白质巯基形成共价键。这种化学反应可以通过靶向新生和变性蛋白来加剧再灌注神经元的恢复，从而导致内质网（ER）应激。内质网应激被认为是缺血性损伤的重要组成部分。此外，据报道，环戊烯酮结合并灭活内质网应激反应的关键成分。内质网应激反应包括：1)暂时停止大多数mRNA的翻译（限制新形成的未折叠蛋白质的负载）2)伴侣蛋白的选择性翻译以促进蛋白质折叠，以及3)蛋白质降解途径的招募，包括泛素化，蛋白体和自噬，以清除错误折叠的蛋白质。环戊酮前列腺素已被证明与内质网应激反应的关键成分结合并使其失活，包括硫氧还蛋白、硫氧还蛋白还原酶、蛋白酶体亚基和泛素水解酶。我们已经确定了这一途径的一个潜在的新靶点，即蛋白质二硫异构酶（PDI），这是一种丰富的内质网蛋白，负责新生或错误折叠蛋白质中二硫键的正确折叠。我们也是第一个在缺血后的脑组织中测量环戊烯酮。我们已经能够使用质谱法在产后17天（PND 17）从窒息性心脏骤停恢复的大鼠大脑中检测到这种高活性化合物。PND 17大鼠作为这项研究的模型是有吸引力的，因为它具有非常高的COX-2组成表达，并且使用具有类似幼儿发育质量的大鼠来模仿儿童心脏骤停（窒息）的最常见原因。因此，我们提出了一系列实验，旨在研究COX-2衍生的环戊烯酮在窒息性心脏骤停的PND17大鼠中加重内质网应激的假设，部分原因是通过抑制PDI。这些实验有可能为心脏骤停后脑损伤的儿童确定新的治疗策略。公共卫生相关性：本项目将研究窒息性心脏骤停后脑损伤的新机制。我们将使用啮齿动物模型模拟儿童心脏骤停继发机制，如溺水。该项目有可能为患有心脏骤停的儿童的脑损伤找到治疗方法。

DESCRIPTION (provided by applicant): Cyloxygenase-2 (COX-2), the enzyme responsible for production of prostaglandins, has been identified as an important contributor to brain damage following hypoxia-ischemia. Unfortunately, COX-2 inhibitors have been reported to cause cerebral and cardiac thrombosis in patients, making COX-2 inhibition less attractive as a therapy for patients recovering from ischemic events. Thus, it is important to understand the mechanisms of COX-2 mediated neuronal injury so that more targeted therapies can be developed. Recently, downstream products of prostaglandins, specifically cyclopentenone prostaglandins have been identified as potential contributors to ischemic injury. The cyclopentenone prostaglandins are highly electrophilic and can form covalent bonds with exposed sulfhydryl groups of proteins. This chemical reaction can exacerbate recovery in reperfusing neurons by targeting nascent and denatured proteins thus contributing to endoplasmic reticulum (ER) stress. ER stress has been reported as an important component of ischemic injury. Further, cyclopentenones have been reported to bond and inactivate key component of the ER stress response. The ER stress response involves: 1) temporary cessation of translation of most mRNA (limiting the load of newly-formed, unfolded proteins) 2) selective translation of chaperone proteins to facilitate protein folding, and 3) recruitment of protein degradation pathways, including ubiquitination, the proteosome, and autophagy, to clear misfolded proteins. Cyclopentenone prostaglandins have been shown to bind with and inactivate key components of the ER stress response including thioredoxin, thioredoxin reductase, proteosome subunits, and ubiquitin hydrolase. We have identified a potential new target of this pathway, namely protein disulfide isomerase (PDI), an abundant ER protein responsible for proper folding of disulfide bonds in nascent or misfolded proteins. We are also the first to measure a cyclopentenone in post-ischemic brain tissue. We have been able to detect this highly reactive compound by using mass spectrometry in post-natal day 17 (PND 17) rat brains recovering from asphyxial cardiac arrest. The PND 17 rat is attractive as a model for this inquiry because it has very high constitutive expression of COX-2 and the insult mimics the most common cause of pediatric cardiac arrest (asphyxia) using a rat with developmental qualities similar to a toddler. Accordingly, we propose a series of experiments designed to investigate the hypothesis that COX-2 derived cyclopentenones worsen ER stress, in part by inhibiting PDI, in PND17 rats with asphyxial cardiac arrest. These experiments have the potential to identify new strategies for therapy in children suffering from brain injury following cardiac arrest. PUBLIC HEALTH RELEVANCE: This project will investigate a novel mechanism of brain injury following asphyxial cardiac arrest. We will use a rodent model mimicking pediatric cardiac arrest secondary to mechanisms such as drowning. The project has potential to identify therapies for brain injury in children suffering from cardiac arrest.