Cerebral arteriole structure/function in diabetic ischemic brain injury

描述(由申请人提供)： 超过7%的美国人口和20%的退伍军人患有糖尿病，不仅急性缺血性中风的风险高出2到6倍，而且中风预后不良和康复不良。组织纤溶酶原激活剂(TPA)再灌注治疗是治疗缺血性卒中的唯一方法；然而，这种治疗增加了糖尿病患者出血进入脑内(出血性转化，HT)的风险。在这一高危人群中开发新的治疗策略的一个关键障碍是缺乏对出血严重程度如何影响糖尿病患者卒中结局和康复的了解。这一更新应用的具体目标是通过确定糖尿病缺血性中风后羟色胺损害神经血管修复的影响和机制来解决这一关键障碍。在过去的资助期间，我们报道了a)2型糖尿病大鼠脑内有明显的病理性新生血管，b)在此基础上的再灌注损伤放大了羟色胺，加重了神经功能缺陷，而不增加梗塞面积，以及c)在没有再灌注的情况下，对照组和糖尿病动物之间没有高血压，功能结果也没有差异。这些新的结果指导我们确定脑血管系统和羟色胺作为糖尿病缺血性卒中的治疗靶点。危险相关分子模式(DAMP)是细胞死亡后释放的细胞内分子，是一个新兴的概念，涉及到通过Toll样受体(Toll-like Receptor，TLRs)激活天然免疫系统。在此基础上，中心假说是，出血进入大脑，无论是点状出血还是占位性出血，都会损害神经血管的恢复，并通过过量铁激活TLR-4来恶化糖尿病的预后。为了实现我们的总体目标，目标1将检验这一假设，即即使是点状非占位性高血压也会损害神经血管的恢复性修复，并加剧糖尿病患者的神经功能障碍。目的2验证糖尿病患者高血压引起的铁沉积损害神经血管可塑性和恶化缺血性卒中预后的假说。目的3将验证这一假说，即羟色胺刺激TLR4信号和炎症恶化糖尿病缺血性中风后的修复和恢复。我们从翻译研究中获得的数据将产生以下结果：a)我们将挑战 我们认为，只有占据空间的高血压才会恶化预后，并证明任何进入大脑的出血都会通过损害血管和神经元修复而有害；b)我们将产生新的重要数据，通过使用各种糖尿病或中风的动物模型的组合来总结临床情况，研究糖尿病如何减弱神经元和内皮修复过程的机制；以及c)我们将把铁确定为一种新的湿气，并证明铁螯合和/或其下游的TLR4抑制是中风治疗/康复中有希望的治疗靶点。该项目将对中风研究、人类健康和退伍军人管理局的使命产生重大影响，因为它将1)确定改善中风预后的神经血管保护和恢复策略，2)增进我们对脑血管在中风修复中作用的了解，3)提供糖尿病中风康复的具体信息，在每年80万中风患者中，超过30%的人患有糖尿病。我们已经做好了迎接这一挑战的准备，因为我们已经与退伍军人管理局的科学家建立了合作关系，为这项提案的目标提供了支持。

DESCRIPTION (provided by applicant): More than 7% of the US population and 20% of our veterans who have diabetes are not only at a 2 to 6-fold higher risk for having acute ischemic stroke but also suffer from unfavorable stroke outcome and poor recovery. Reperfusion therapy with tissue plasminogen activator (tPA) is the only therapy for ischemic stroke; however, this treatment increases the risk of bleeding into the brain (hemorrhagic transformation, HT) of diabetics. A critical barrier to progress in the development of new therapeutic strategies in this high-risk population is the lack of understanding how bleeding severity impacts stroke outcome & recovery in diabetes. The specific objective of this renewal application is to address this critical barrier by defining the impact and mechanisms by which HT impairs neurovascular repair after ischemic stroke in diabetes. During the past funding period we reported that a) there is robust pathological neovascularization of the brain in type 2 diabetes, b) a reperfusion injury superimposed on this pathology amplifies HT and worsens neurological deficits without increasing infarct size, and c) in the absence of reperfusion, there is no HT and no difference in functional outcome between control and diabetic animals. These novel results guided us to identify cerebral vasculature and HT as a therapeutic target in diabetic ischemic stroke. Danger-associated molecular patterns (DAMPs), intracellular molecules released upon cell death, is an emerging concept that is involved in the activation of the innate immune system via toll-like receptors (TLRs). Based on this foundation, the central hypothesis is that bleeding into the brain, petechial OR space-occupying, impairs neurovascular restoration and worsens outcome in diabetes via the activation of TLR-4 by excess iron, a novel DAMP. To achieve our overall goals, Aim 1 will test the hypothesis that even petechial nonspace-occupying HT impairs neurovascular restorative repair and worsens neurological deficits in diabetes. Aim 2 will test the hypothesis that iron deposition resulting from greater HT in diabetes impairs neurovascular plasticity and worsens outcome of ischemic stroke. Aim 3 will test the hypothesis that HT stimulates TLR4 signaling and inflammation worsening repair and recovery after diabetic ischemic stroke. The data obtained from our translational studies will yield the following outcomes: a) we will challenge the existing paradigm that only space-occupying HT worsens outcomes and demonstrate that any bleeding into the brain is detrimental by impairing vascular and neuronal repair, b) we will generate new and important data related to mechanisms of how diabetes attenuates neuronal and endothelial repair processes by using various combinations of animal models of diabetes or stroke to recapitulate the clinical condition, and c) we will identify iron as a new DAMP and show that iron chelation and/or downstream TLR4 inhibition are promising therapeutic targets in stroke treatment/recovery. This project will significantly impact stroke research, human health and VA mission because it will 1) identify neurovascular protection & restoration strategies to improve stroke outcomes, 2) advance our knowledge of the role of the cerebral vasculature in stroke repair, and 3) provide specific information on stroke recovery in diabetes which occurs in more than 30% of the 800,000 annual stroke victims. We are well poised to take this challenge since we have established collaborations with VA scientists that have provided support for the goals of this proposal.