Neuroprotection with serpins during cardiac surgery

描述（由申请人提供）：成人和儿童在心脏手术期间和之后都会发生脑损伤。它可以采取局灶性或整体神经损伤的形式，如中风或舞蹈手足徐动症。或者，它可以表现为认知和运动技能的普遍下降。抑肽酶，一种“SERPIN”（丝氨酸蛋白酶抑制剂），可减少心肺转流术（CPB）后出血。一项对心脏手术文献的广泛荟萃分析得出结论，抑肽酶也降低了CPB后卒中的发生率，尽管最近一项有影响力的报告表明脑损伤的风险增加。尽管先前的工作已经证明抑肽酶可以保护内皮功能，但体外循环期间抑肽酶的直接神经和神经血管作用机制在很大程度上尚未探索。此外，最近在神经科学文献中应用细胞培养模型的报告表明，一些丝氨酸蛋白酶抑制剂可能通过抑制兴奋性毒性而具有神经保护作用。拟议的研究将检验抑肽酶在CPB环境中具有神经保护作用的假设。将采用幼年仔猪模型，暴露于不同程度的流量减少至已知导致脑损伤的程度。术后4天的存活率允许通过盲法观察者的行为评估以及盲法神经病理学家确定的有意义的组织学来评估脑损伤的功能证据。将使用活体显微镜研究血管完整性，活体显微镜可直接观察脑微循环。将通过近红外光谱法监测脑氧输送的准确性。将采用几种剂量水平的抑肽酶来确定最佳剂量。本研究的第二部分将检验抑肽酶具有神经保护作用的一种机制是通过抑制兴奋性毒性的假设。将采用神经元细胞培养模型。将不同剂量的抑肽酶与先前已证明具有神经保护作用的其他丝氨酸蛋白酶抑制剂进行比较。新的丝氨酸蛋白酶抑制剂，可能有一个应用在心脏外科手术也将研究与细胞培养模型。在研究的第三阶段，将在CPB的整个动物模型中详细研究发现具有保护作用的丝氨酸蛋白酶抑制剂。最后阶段将研究抑肽酶提供的血管保护机制。这项研究有可能降低儿童和成人接受心脏手术时脑损伤的风险。

DESCRIPTION (provided by applicant): Brain injury occurs during and after cardiac surgery in both adults and children. It can take the form of either a focal or global neurological insult such as stroke or choreoathetosis. Alternatively it can manifest itself as a generalized decline in cognitive and motor skills. Aprotinin, a "SERPIN" (serine protease inhibitor), reduces bleeding after cardiopulmonary bypass (CPB). An extensive metaanalysis of the cardiac surgery literature concluded that aprotinin also decreases the incidence of stroke after CPB though a recent influential report suggests an increased risk of brain injury. Direct neuronal and neurovascular mechanisms of action of aprotinin during CPB remain largely unexplored though previous work has demonstrated protection of endothelial function by aprotinin. Furthermore recent reports in the neuroscience literature applying cell culture models suggest that some serpins may be neuroprotective through inhibition of excitotoxicity. The proposed study will test the hypothesis that aprotinin is neuroprotective in the setting of CPB. A juvenile piglet model will be employed with exposure to various degrees of flow reduction to a degree known to cause brain injury. Survival for 4 days postoperatively allows assessment of functional evidence of brain injury through behavioral assessment by a blinded observer as well as meaningful histology determined by a blinded neuropathologist. Vascular integrity will be studied with intravital microscopy which allows direct observation of the cerebral microcirculation. Adequacy of cerebral oxygen delivery will be monitored by near infrared spectroscopy. Several dosage levels of aprotinin will be employed to determine optimal dose. The second component of the study will test the hypothesis that one mechanism by which aprotinin is neuroprotective is through inhibition of excitotoxicity. Neuronal cell culture models will be employed. Aprotinin at various dosages will be compared with other serpins which have previously been demonstrated to be neuroprotective. Novel serpins which may have an application in cardiac surgery will also be studied with the cell culture model. Serpins which are found to be protective will be studied in detail in the whole animal model of CPB in the third phase of the study. The final phase will study mechanisms of vascular protection afforded by aprotinin. The proposed study has the potential to reduce the risk of brain injury in children and adults undergoing heart surgery.