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

脑血管痉挛是蛛网膜下腔出血(SAH)后预后的重要决定因素之一。根据我们先前的发现，1-磷酸鞘氨醇在脑血管痉挛中激活Rho/Rho-激酶通路，Rho和RhoKinase的激活和上调在脑血管痉挛的发病机制中起重要作用，本研究探讨了另一种有效的痉挛物质之一凝血酶的作用以及Rho/Rho-Kinase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在兔蛛网膜下腔出血模型痉挛基底动脉收缩反应中的作用。在痉挛的动脉中，凝血酶上调凝血酶受体的表达，并诱导对凝血酶本身的过度收缩反应。凝血酶受体脱敏受损也是痉挛动脉收缩过度的原因之一。其次，我们研究了Rhokinase在牛大脑中动脉钙敏化中的作用。血栓素A_2类似物是一种特殊的致痉挛物质，它通过增强动脉对钙离子的敏感性而引起动脉的持续收缩，这种作用是通过肌球蛋白抗链磷酸化依赖和非依赖性途径实现的。第三，我们发现氧化应激通过激活Rho/Rho-Kinase通路和内皮功能障碍来诱导大脑动脉对生理性血管舒张剂缓激肽的收缩反应，从而提示在氧化应激改变SAH下内皮依赖的松弛丧失。我们的基础研究表明Rho/Rho-Kinase通路的激活在脑血管痉挛发病的分子机制中具有重要意义。特别是，Rho/Rho-Kinase通路上游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.