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。虽然脑损伤的影响已在成人中进行了广泛的研究，但对新生儿/婴儿的了解较少。与幼年猪相比，液压冲击脑损伤（FPI）后新生猪的脑血流量（CBF）福尔斯下降和软脑膜动脉收缩更多，这支持了新生猪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）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着至关重要的作用。尿激酶和组织型纤溶酶原激活物（uPA和tPA）是丝氨酸蛋白酶，其对脑血流动力学调节的贡献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而导致兴奋性毒性神经元细胞死亡。术语神经血管单位（NVU）关注脑血管和神经元之间的相互作用。tPA治疗矛盾可能与血管舒张有关。纤溶酶原激活剂血管活性由低密度脂蛋白受体（LRP）介导。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抑制剂的给药部分阻止了FPI诱导的NMDA扩张抑制和软脑膜动脉直径以年龄依赖性方式减小。我们建议，纤溶酶原激活剂改变MAPK亚型的表达/激活曲线的LRP依赖的过程中，引起初始充血和NMDA损伤的脑血流动力学产生显着的组织病理学损伤后的新生儿，但只有NMDA损伤的脑血流动力学和适度的组织病理学在青少年。假设FPI后纤溶酶原激活剂释放产生充血，并以年龄依赖性方式抑制NMDA受体介导的对CBF的作用，导致脑血流动力学受损和水肿，随后神经元细胞丢失。tPA治疗性治疗悖论可能与MAPK亚型表达谱的变化有关。将在新生和幼年猪中研究三个具体目标：1.描述FPI后脑血流动力学中纤溶酶原激活剂和NMDA受体激活之间的关系，作为年龄的函数。2.研究MAPK亚型和LRP作为纤溶酶原激活剂和NMDA受体激活控制FPI后脑血流动力学的机制的作用，作为年龄的函数; MAPK亚型表达谱的变化导致损伤后脑血流动力学受损和神经元细胞丢失。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。将进行免疫组织化学、纤溶酶原激活物和MAPK表达检测以及通过放射性标记微球测定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.