Modification of Vascular Signaling in the Brain by Reactive Oxygen Species

有越来越多的数据表明，活性氧和氮中间体参与启动/修改控制血管功能的信号事件。关于活性氧（ROS），最近的报道定义了O2-和H2 O2在血管内皮相互作用中的作用。低水平的氧化应激已被证明介导增殖事件，而高水平的氧化应激已被证明诱导细胞凋亡。本项目的目的是确定活性氧在启动或改变调节脑血流的信号事件中的作用。我们还将探讨ROS改变有丝分裂信号事件的假设，这些信号事件调节毛细血管密度以响应神经元的代谢需求。初步数据显示，H_（202）显著增加脑小动脉肌细胞K ~+通道活性。我们还提出的数据表明，细胞色素P450（P450）酶活性抑制氧化应激。实验计划确定的作用，ROS压力介导的肌张力，脑血流和离子通道电导系统控制肌细胞兴奋性的自动调节。我们实验室以前的工作表明，星形胶质细胞释放的P450环氧化物响应谷氨酸，通过增强K+通道活性和超极化血管肌肉，有效地扩张脑小动脉。我们将确定ROS是否通过对肌细胞K+通道的作用或通过干扰P450衍生的环氧化物产生来改变功能性充血。初步数据表明，自由基可以修改功能性充血，清除O2-注入SOD到麻醉大鼠的脑脊液改变基线脑血流量。最后，我们将定义ROS修饰毛细血管生成的能力。氧的产生对培养的脑毛细血管内皮细胞胸腺嘧啶掺入产生双相作用。短时间（60分钟）暴露于O2-增加胸腺嘧啶掺入的毛细血管内皮，而较长时间（8小时）暴露减少胸腺嘧啶掺入。我们将定义氧化应激改变毛细血管增殖和管形成的机制。本项目将使用各种分子、生物化学和功能技术，在分子、细胞和整个动物水平上确定ROS在改变脑血流、自动调节和对神经活动的反应中的作用。与本拟议项目编制补助金的其他项目有着强有力的互动，并广泛使用了核心资源。

There is a growing body of data demonstrating that reactive oxygen and nitrogen intermediates are involved in initiating/modifying signaling events controlling vascular function. With respect to reactive oxygen species (ROS) recent reports define a role for O2- and H2O2 in vascular endothelial interactions. Low levels of oxidant stress have been shown to mediate proliferative events, while high levels have been shown to induce apoptosis. The purpose of this Project is to define the actions of ROS in initiating or modifying signaling events which regulate cerebral blood flow. We will, also, explore the hypothesis that ROS modify mitogenic signaling events which regulate capillary density in response to neuronal metabolic demand. Preliminary data show that H202 markedly increase K+ channel activity in cerebral arteriolar muscle cells. We also present data demonstrating that cytochrome P450 (P450) enzyme activity is inhibited by oxidant stress. Experiments are planned to define the action of ROS on pressure-mediated myogenic tone, autoregulation of cerebral blood flow and ion channel conductance systems controlling muscle cell excitability. Previous work from our laboratory has shown that P450 epoxides released from astrocytes in response to glutamate potently dilate cerebral arterioles by enhancing K+ channel activity and hyperpolarizing vascular muscle. We will determine if ROS modify functional hyperemia via actions on muscle cell K+ channels or by interfering with P450 derived epoxide production. Preliminary data suggests that free radicals can modify functional hyperemia, and that scavenging of O2- by infusing SOD into the cerebral spinal fluid of anesthetized rats alters baseline cerebral blood flow. Finally, we will define the ability of ROS to modify capillary angiogenesis. Generation of O2- exerts biphasic actions on thymadine incorporation in cultured cerebral capillary endothelial cells. Short (60 minute) exposure of capillary endothelium to O2- increases thymadine incorporation, while longer (8 hours) exposure reduces thymidine incorporation. We will define the mechanisms through which oxidant stress alters capillary proliferation and tube formation. This Project will use a variety of molecular, biochemical and functional techniques to define the action of ROS in modifying cerebral blood flow, autoregulation and responses to neural activity at the molecular, cellular and whole animal level. There is strong interaction with the other Projects of this proposed PPG, and extensive use of Core resources.