Cerebral Arteriole Function during Hyperglycemic Stroke

描述(申请人提供)：缺血性中风是美国每年影响超过75万人的最常见的病理生理事件之一。约20%的卒中患者存在既往的高血糖，这种高血糖与脑缺血后再灌注损伤的加强有关，包括显著更高的发生率和严重程度的脑梗塞和水肿形成。虽然大多数研究都集中在高血糖卒中时的代谢紊乱或神经元组织损伤，但我们的初步数据表明，葡萄糖对血管系统有直接影响，导致缺血和再灌注(I/R)期间血流灌注不良和血管损伤增加。我们的初步数据还表明，高血糖上调了血管壁内的信号分子，包括我们假设的蛋白激酶C(PKC)和活性氧物种(ROS)，这对血管功能(张力、通透性)有影响，从而减少再灌注并增强I/R期间的血管源性水肿。此外，高血糖卒中时产生的缺血加剧导致再灌注损伤加剧，从而进一步损害血管系统。这项建议侧重于了解1)卒中前血糖升高如何影响脑血管功能，从而影响缺血再灌注和卒中预后，以及2)高血糖与I/R结合如何增加血管损伤。大鼠大脑中动脉阻塞模型将在正常血糖和高血糖条件下诱导受控I/R，然后从脑组织中解剖穿透脑实质小动脉，并在加压动脉造影术系统中进行体外研究，该系统允许控制血管内压，测量管腔直径，并用荧光和电子密度示踪剂灌流以确定通透性。该方案的目的1将研究葡萄糖诱导的PKC激活和ROS产生在卒中前调节小动脉功能变化中的作用，以及这些变化如何影响卒中预后。目标2将确定中风期间高血糖如何影响血管完整性，包括血管平滑肌和内皮细胞损伤。这项研究首次专门研究了I/R和高血糖对穿透性脑小动脉的直接影响，这些小动脉与大脑中的其他细胞类型密切相关，包括星形胶质细胞、周细胞和神经元，这些细胞与血管系统有显著的相互作用，并可以影响灌流、通透性和卒中结果。

DESCRIPTION (provided by applicant): Ischemic stroke is one of the most common pathophysiologic events affecting more than 750,000 people per year in the US. Preexisting hyperglycemia, present in ~20% of all stroke patients, is associated with enhanced reperfusion injury in the postischemic brain, including a significantly higher incidence and severity of cerebral infarction and edema formation. While most studies have focused on metabolic derangements or neuronal tissue damage during hyperglycemic stroke, our preliminary data demonstrate that there is a direct effect of glucose on the vasculature that leads to poor perfusion and increased vascular damage during ischemia and reperfusion (I/R). Our preliminary data also demonstrate that hyperglycemia upregulates signaling molecules within the vascular wall, including protein kinase C (PKC) and reactive oxygen species (ROS) that we have hypothesized has an effect on vascular function (tone, permeability) to decrease reperfusion and enhance vasogenic edema during I/R. In addition, augmented ischemia created during hyperglycemic stroke leads to enhanced reperfusion injury that further damages the vasculature. This proposal is focused on understanding 1) how elevated glucose prior to stroke affects cerebrovascular function in a way that influences postischemic reperfusion and stroke outcome, and 2) how hyperglycemia, in combination with I/R, augments vascular damage. The middle cerebral artery occlusion model in rats will be used under normoglycemic and hyperglycemic conditions to induce controlled I/R, after which penetrating brain parenchymal arterioles will be dissected from the brain tissue and studied in vitro in a pressurized arteriograph system that allows for control over intravascular pressure, measurement of lumen diameter, and perfusion with fluorescent and electron dense tracers for determination of permeability. Aim 1 of this proposal will investigate the role of glucose-induced PKC activation and ROS production in mediating changes in arteriole function prior to stroke and how those changes influence stroke outcome. Aim 2 will determine how hyperglycemia during stroke affects vascular integrity, including vascular smooth muscle and endothelial cell damage. The proposed studies are the first to specifically investigate the direct effect of I/R and hyperglycemia on small penetrating brain arterioles that are in close association with other cell types in the brain, including astrocytes, pericytes and neurons that are known to have significant interaction with the vasculature and can influence perfusion, permeability, and stroke outcome.