tPA in traumatic brain injury

描述（由申请人提供）：创伤性脑损伤（TBI）仍然是死亡和长期发病的主要原因。脑水肿是严重创伤性脑损伤的一种常见的不良后果，它是由血脑屏障完整性丧失和患处出血引起的。这一应用是基于最近的数据表明tPA-/-小鼠在TBI后相对保护不发生脑水肿和皮质坏死，以及我们发现tPA通过低密度脂蛋白相关受体（LRP）和整合素avb3信号转导的纤溶外机制诱导血管松弛，直接或间接地增加血脑屏障通透性。在此，我们拟研究tPA的纤溶活性如何调节实验性TBI的血脑屏障通透性、血管舒张、脑水肿和神经预后。我们的方法包括利用拮抗剂和tPA变体对tPA介导的信号转导机制进行基础研究，这些拮抗剂和tPA变体通过三个相互关联的特定目的分离其血管活性和催化特性。在Specific Aim 1中，我们将研究avb3和LRP之间形成复合物所需的分子决定因素，以及tPA破坏这些复合物并诱导血脑屏障通透性和血管松弛的机制。在专项目标2中，血管内血栓形成对创伤后脑损伤发展的影响将通过分离tPA的纤溶和信号转导活性的方法来阐明。在Specific Aim 3中，我们将在野生型和tPA-/-小鼠中检测TBI后遗症中选择性缺乏纤溶或纤溶外功能的LRP、avb3和tPA变体拮抗剂的作用。此外，我们还将利用表达血小板tPA的转基因小鼠来评估一种将tPA输送到损伤血管的新方法。总之，这些研究将为tPA在介导中枢神经系统损伤中的作用提供新的认识，并提供新的细胞靶点和新的tPA配方，可能会改善临床结果。

DESCRIPTION (provided by applicant): Traumatic brain injury (TBI) remains a major cause of death and long-term morbidity. Cerebral edema is a common and ominous sequel of severe TBI which results from loss of blood-brain-barrier (BBB) integrity and hemorrhage in the affected zone. This application is predicated on recent data showing that tPA-/- mice are relatively protected from developing cerebral edema and cortical necrosis after TBI and our finding that tPA increases BBB permeability both directly and indirectly by inducing vasorelaxation through extra-fibrinolytic mechanisms that involve signal transduction through the low density lipoprotein related receptor (LRP) and the integrin avb3. Here, we propose to study how the extra-fibrinolytic activities of tPA modulate BBB permeability, vasorelexation, cerebral edema and neurological outcome in experimental TBI. Our approach includes basic research into the mechanism of tPA-mediated signal transduction using antagonists and tPA variants that dissociate its vasoactive and catalytic properties through three inter-related specific aims. In Specific Aim 1 we will study the molecular determinants required to form complexes between avb3 and LRP and mechanism by which tPA disrupts these complexes and induces BBB permeability and vasorelaxation. In Specific Aim 2 the effect of intravascular thrombosis on the development of post-traumatic brain injury will be elucidated using approaches to isolate the fibrinolytic and signal transduction activities of tPA. In Specific Aim 3 the effect of antagonists to LRP and avb3 and tPA variants selectively lacking fibrinolytic or extra-fibrinolytic function in the sequelae of TBI will be examined in wild type and tPA-/- mice. Also, a new approach to deliver tPA to traumatized vessels will be evaluated using platelet-tPA expressing transgenic mice. Together, these studies will provide new understanding of the role of tPA in mediating CNS injury and novel cellular targets and new formulations of tPA that may improve clinical outcome.