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%的患有糖尿病的退伍军人不仅患急性缺血性卒中的风险高2至6倍，而且还患有不利的卒中结局和恢复不良。组织纤溶酶原激活剂（tPA）再灌注治疗是缺血性卒中的唯一治疗方法;然而，这种治疗增加了糖尿病患者脑出血（出血性转化，HT）的风险。在这一高危人群中开发新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卒中结局和恢复的了解。本次更新申请的具体目标是通过定义HT损害糖尿病缺血性卒中后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型糖尿病患者的大脑存在强大的病理性新血管形成，B）叠加在这种病理上的再灌注损伤放大了HT和神经功能缺损，而不增加梗死面积，c）在没有再灌注的情况下，对照组和糖尿病动物之间没有HT，功能结局也没有差异。这些新的结果指导我们确定脑血管和HT作为糖尿病缺血性卒中的治疗靶点。危险相关分子模式（DAMP），细胞死亡时释放的细胞内分子，是一个新兴的概念，参与通过Toll样受体（TLR）激活先天免疫系统。基于这一基础，中心假设是，出血进入大脑，瘀点或占位，损害神经血管恢复和糖尿病的结果，通过激活TLR-4过量的铁，一种新的DAMP。为了实现我们的总体目标，目标1将测试这一假设，即即使是点状非占位性HT也会损害神经血管的恢复性修复，并导致糖尿病患者的神经功能缺损。目的2将验证糖尿病患者HT增加导致的铁沉积损害神经血管可塑性和缺血性卒中结局的假设。目的3验证HT刺激TLR 4信号通路和炎症恶化对糖尿病缺血性脑卒中后修复和恢复的影响。从我们的翻译研究中获得的数据将产生以下结果：a）我们将挑战 现有的范例，即仅占位性HT损害结果并证明任何脑出血都是有害的，因为损害血管和神经元修复，B）我们将通过使用糖尿病或中风动物模型的各种组合来概括临床状况，产生与糖尿病如何减弱神经元和内皮修复过程的机制相关的新的和重要的数据，和c）我们将鉴定铁作为新的DAMP，并表明铁螯合和/或下游TLR 4抑制是中风治疗/恢复中有希望的治疗靶点。该项目将对卒中研究、人类健康和VA使命产生重大影响，因为它将1）确定神经血管保护和恢复策略以改善卒中结局，2）推进我们对脑血管在卒中修复中的作用的认识，3）提供关于糖尿病卒中恢复的具体信息，糖尿病卒中发生在每年80万卒中患者中的30%以上。我们已经准备好迎接这一挑战，因为我们已经与VA科学家建立了合作关系，为这一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.