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TBI的常见和不祥的后遗症，其由血脑屏障（BBB）完整性的丧失和受影响区域的出血引起。该应用基于最近的数据，该数据显示tPA-/-小鼠在TBI后相对免受脑水肿和皮质坏死的发展，并且我们发现tPA通过纤维蛋白溶解外机制诱导血管舒张直接和间接地增加BBB通透性，所述纤维蛋白溶解外机制涉及通过低密度脂蛋白相关受体（LRP）和整联蛋白avb 3的信号转导。在这里，我们建议研究tPA的纤溶活性调节BBB通透性，血管内皮细胞，脑水肿和神经功能的结果在实验性TBI。我们的方法包括使用拮抗剂和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标分离其血管活性和催化特性。在具体目标1中，我们将研究avb 3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BBB通透性和血管舒张的机制。在具体目标2中，将使用分离tPA的纤维蛋白溶解和信号转导活性的方法来阐明血管内血栓形成对创伤后脑损伤发展的影响。在具体目标3中，将在野生型和tPA-/-小鼠中检查LRP和avb 3以及选择性缺乏纤溶或纤溶外功能的tPA变体的拮抗剂在TBI后遗症中的作用。此外，将使用表达血小板tPA的转基因小鼠来评估将tPA输送到创伤血管的新方法。总之，这些研究将为tPA在介导CNS损伤中的作用提供新的理解，并提供新的细胞靶点和可能改善临床结局的tPA新制剂。

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.