The role of platelet-derived spasmogens and Rho/Rho-kinase pathway in the pathogenesis of cerebral vasospasm.

脑血管痉挛是影响蛛网膜下腔出血（SAH）预后的重要因素之一。我们以前发现1-磷酸鞘氨醇激活Rho/Rho激酶通路在脑血管痉挛中起作用，Rho和Rho激酶的激活和上调在脑血管痉挛的发病机制中起重要作用。在本研究中，我们研究了凝血酶（另一种强有力的痉挛剂）和Rho/Rho激酶通路在脑血管痉挛中的作用。首先，我们研究了凝血酶及其受体表达在兔SAH模型痉挛基底动脉过度收缩反应中的作用。凝血酶上调凝血酶受体的表达，并诱导痉挛动脉对凝血酶本身的高收缩反应。凝血酶受体失敏受损也是痉挛动脉高收缩的原因之一。第二，我们研究了Rhokinase在牛大脑中动脉Ca^2+增敏中的作用。血栓素A_2类似物是一种较好的致痉剂，它能引起动脉持续收缩，并增强动脉对Ca^2+的敏感性，这种作用既依赖于肌球蛋白链磷酸化，也不依赖于肌球蛋白磷酸化。第三，我们发现氧化应激通过激活Rho/Rho激酶通路和内皮功能障碍诱导脑动脉对缓激肽的收缩反应，提示SAH后氧化应激引起的内皮依赖性舒张功能丧失，我们的基础研究表明Rho/Rho激酶通路激活在脑血管痉挛发病机制中的重要性。特别是Rho/Rho激酶通路上游的凝血酶受体的调节被认为是预防脑血管痉挛的一个新的治疗靶点。

Cerebral vasospasm is one of the major critical determinants of the prognosis alter subarachnoid hemorrhage (SAH). As shown in our previous discovery that sphingosine-1-phosphate activates the Rho/Rho-kinase pathway in cerebral vasospasm, the activation and up-regulation of Rho and Rhokinase have been suggested to play an important role in the pathogenesis of cerebral vasospasm,In the present study, we investigated the roles of thrombin, one of the other potent spasmogens, and the roles of Rho/Rho-kinase pathway in cerebral vasospasm. First, we investigated the effect of thrombin and its receptor expression in the hypercontractil response of spastic basilar artery of a rabbit SAH model. Thrombin up-regulated the expression of thrombin receptor and induced a hypercontractile response to thrombin itself in the spastic artery. The impaired desensitization of thrombin receptor also contributed to the hyperoontractiliy of the spastic artery. Second, we investigated the role of Rhokinase in Ca^<2+> sensitization in bovine middle cerebral artery. Thromboxane A_2 analogue, one of the patent spasmogens, induced the sustained contraction with enhanced Ca^<2+> sensitivity of the artery, which was achieved both in myosin fight chain phosphorylation-dependent and -independent manners. Third, we discovered that oxidative stress induced the contractile response of cerebral artery to bradykinin, a physiological vasorelaxant, through the activation of Rho/Rho-kinase pathway and endothelial dysfunction, which thus suggested a loss of endothelium-dependent relaxation under an oxidative stress alter SAH.Our basic researches showed the importance of Rho/Rho-kinase pathway activation in the molecular mechanisms underlying pathogenesis of cerebral vasospasm. In particular, the regulation of thrombin receptor in the upstream of Rho/Rho-kinase pathways was indicated to be a novel therapeutic target for the prophylactic managemert of cerebral vasospasm.