Plasminogen activators and NMDA after brain injury

描述（由申请人提供）：创伤性损伤是婴儿和儿童死亡的主要原因，头部损伤的死亡率大大增加。虽然脑损伤对成人的影响已被广泛研究，但对新生儿/婴儿的影响知之甚少。新生儿的脑血流（CBF）下降和脑动脉收缩更明显，这支持了新生儿对创伤性血管性脑损伤更敏感的观点。n -甲基- d -天冬氨酸（NMDA）谷氨酸受体亚型的激活被认为在兴奋性毒性神经元细胞死亡中起关键作用。尿激酶和组织纤溶酶原激活剂（uPA和tPA）是丝氨酸蛋白酶，它们对脑血流动力学的调节作用尚未得到很好的表征。tPA可能通过增强NMDA受体介导的信号传导促进兴奋性神经元细胞死亡。神经血管单元（NVU）一词关注的是脑血管与神经元之间的相互作用。tPA治疗悖论可能与血管舒张有关。纤溶酶原激活剂的血管活性是由低密度脂蛋白受体介导的。我们发现tPA和uPA在病理生理浓度下引起血管舒张，而tPA和uPA抑制剂的施用部分阻止了FPI诱导的NMDA扩张抑制和动脉直径的减少，并以年龄依赖的方式。我们提出纤溶酶原激活剂在LRP依赖过程中改变MAPK亚型的表达/激活谱，从而引起新生儿初始充血和脑血流动力学的NMDA损伤，在新生儿损伤后产生明显的组织病理学，但在青少年中仅产生NMDA损伤的脑血流动力学和轻度组织病理学。假设FPI后的纤溶酶原激活剂释放产生充血并以年龄依赖的方式抑制NMDA受体介导的CBF作用，导致脑血流动力学受损和水肿，随后是神经元细胞损失。tPA治疗悖论可能与MAPK异构体表达谱的变化有关。将在新生猪和幼猪中研究三个具体目标：描述纤溶酶原激活剂和NMDA受体在FPI后脑血流动力学中的激活与年龄的关系。2. 探讨MAPK亚型和LRP在纤溶酶原激活剂和NMDA受体激活控制FPI后脑血流动力学的作用机制；MAPK异构体表达谱的改变导致脑血流动力学受损和神经元细胞损失。和3。确定纤溶酶原激活剂和NMDA受体诱导的FPI后脑血流动力学和组织病理学损伤与年龄的关系。免疫组织化学，检测纤溶酶原激活剂和MAPK的表达，并通过放射性微球测定CBF。

DESCRIPTION (provided by applicant): Traumatic injury is the leading cause of death for infants and children and mortality is greatly increased in the presence of head injury. While the effects of brain injury have been extensively investigated in the adult, less is known in the newborn/infant. Cerebral blood flow (CBF) falls and pial arteries constrict more in newborn versus juvenile pigs after fluid percussion brain injury (FPI), supporting the idea that the newborn is more sensitive to traumatic vascular brain injury. Activation of the N-methyl-D-aspartate (NMDA) glutamatergic receptor subtype is thought to play a crucial role in excitotoxic neuronal cell death. Urokinase and tissue plasminogen activator (uPA and tPA) are serine proteases whose contributions to the regulation of cerebral hemodynamics are not well characterized. tPA may contribute to excitoxic neuronal cell death via enhancement of NMDA receptor mediated signaling. The term neurovascular unit (NVU) focuses attention on the interactions between cerebral blood vessels and neurons. The tPA treatment paradox could relate to vasodilation. Plasminogen activator vascular activity is mediated by the low density lipoprotein receptor (LRP). We show tPA and uPA elicit vasodilation at pathophysiologic concentrations while administration of tPA and uPA inhibitors partially prevented FPI induced inhibition of NMDA dilation and reductions in pial artery diameter in an age dependent manner. We propose that plasminogen activators change the MAPK isoform expression/activation profile in an LRP dependent process to elicit both initial hyperemia and NMDA impairment of cerebral hemodynamics producing marked histopathology post insult in the newborn but only NMDA impairment of cerebral hemodynamics and modest histopathology in the juvenile. The hypothesis is that plasminogen activator release following FPI produces hyperemia and inhibits NMDA receptor mediated effects on CBF in an age dependent manner leading to impaired cerebral hemodynamics and edema followed by neuronal cell loss. The tPA therapeutic treatment paradox may relate to changes in the MAPK isoform expression profile. Three specific aims will be investigated in newborn and juvenile pigs: 1. Characterize the relationship between the plasminogen activators and NMDA receptor activation in cerebral hemodynamics following FPI as a function of age. 2. Investigate the role of MAPK isoforms and LRP as the mechanism by which plasminogen activators and NMDA receptor activation control cerebral hemodynamics following FPI as a function of age; Changes in the MAPK isoform expression profile result in impaired cerebral hemodyanamics and neuron cell loss post insult. And 3. Determine the association between plasminogen activator and NMDA receptor induced impairment of cerebral hemodynamics and histopathology following FPI as a function of age. Immunohistochemistry, detection of plasminogen activator and MAPK expression, and CBF determination by radiolabled microspheres will be performed.