uPA/uPAR系统介导脑室出血后血脑屏障损伤的机制研究

Most of research in intraventricular hemorrhage (IVH) have focused on the pathophysiology of secondary chronic hydrocephalus and the treatment strategy against it. However, no improved functional outcome have been obtained by intraventricular fibrinolysis from recent clinical trials although obstructive hydrocephalus could be resolved.Recently, we found blood-brain barrier (BBB) disruption may also be important pathophysiology following IVH beside hydrocephalus. The urokinase plasminogen activator / receptor (uPA/uPAR) system represents a family of serine proteases that are involved in the degradation of basement membrane and the extracellular matrix, which was found to be involved in ischemic brain injury. Our preliminary data show that increased uPAR expression following IVH, though the effect is unknown. Base on these findings,there is a substantial evidence to suggest that uPA/uPAR play a role in the BBB injury, and has the potential to be a therapeutic target against brain injury after IVH. Therefore,our main hypotheses are that upregulation of uPA/uPAR after IVH may be an important mechanism for BBB injury. We propose 2 specific aims to address the hypotheses: ①to examine if uPA/uPAR cause BBB damage by activating plasminogen activation system and the matrix metalloprotease (MMP) cascade? ② to examine if uPAR is induced via TGF-β1-mediated Smad2/3 activation after IVH. The information and knowledge gained from this study may provide novel insight in developing new protective strategies against brain injury after IVH.

慢性脑积水是既往脑室出血（IVH）防治研究的重点，但目前临床研究表明单纯减轻脑积水未能改善预后，我们前期研究显示早期血脑屏障损害可能是除脑积水外的又一重要损伤环节。近期研究发现尿激酶型纤溶酶原激活物及受体（uPA/uPAR）可能与中风后脑损伤关系密切，我们亦发现IVH后脑内uPAR表达上调，但机制不清。据此，基于uPA/uPAR相关研究进展，我们推测IVH后uPA/uPAR上调并活化纤溶酶-MMP级联反应可能是血脑屏障损伤的重要机制。本项目拟通过体内外实验，研究IVH后uPA/uPAR上调及其致血脑屏障损伤的机制，以阐明：①uPA/uPAR上调并活化PA-纤溶酶-MMP级联反应通路是否是IVH后血脑屏障损伤的关键机制？②TGF-β1/Smad2/3信号通路是否为uPAR表达上调的主要机制？本项目是首次从血脑屏障损害环节探讨IVH后急性脑损伤机制，有望为IVH继发脑损伤防治研究提供新的思路。

基本按计划执行，总结国内外研究进展，改良了脑室出血（IVH）大鼠模型，课题组首次建立脑出血合并脑室出血（ICH/IVH）模型，本模型更贴近临床。从现象到机制研究对比了uPA与tPA对脑出血纤溶治疗的效果，探索了uPA对交通性脑积水的治疗效应及机制。通过“大鼠脑室出血模型”重点研究IVH后BBB结构异常和功能障碍的特点，确定uPA/uPAR活化、PA-纤溶酶-MMP活性变化及其与BBB损伤间的关系，验证了本项目主要假设：抑制uPA/uPAR系统可以减轻IVH后BBB损伤，uPA/uPAR抑制后可降低PA-纤溶酶-MMP活性，减少紧密连接蛋白降解和基底膜损伤，从而改善BBB结构和功能损害及神经功能。验证TGF-β1/Smad2/3通路介导IVH后uPAR表达的推测的结果尚在整理之中。本研究是首次从BBB损伤的新角度对IVH后早期脑损伤环节展开研究，有望拓展对IVH后脑损伤机制的认识，并为继发脑损伤的防治研究提供新的思路。