Kruppel-like factor 11 and ischemic stroke

描述(申请人提供)：血脑屏障(BBB)是脑缺血损伤的主要靶点之一，由此导致的BBB功能障碍被公认为缺血性中风的主要标志。脑微血管内皮细胞(BMECs)作为血脑屏障的主要组成部分，与脑微血管内皮细胞之间的紧密连接(TJ)一起，在调节血脑屏障完整性和细胞旁通透性方面起着主导作用。广泛的研究表明，血脑屏障的破坏引发了一系列破坏性的事件，导致了脑缺血时的脑炎症反应、血管源性水肿、出血性转化和最终的神经元丢失。因此，确定在缺血性卒中期间减少血脑屏障完整性丧失的机制是很重要的。Kruppel样因子(KLFs)是锌指转录因子家族的成员，由17个成员组成，已被证明在细胞生长和分化中发挥关键作用。最近的研究表明，部分KLF家族成员(KLF2、KLF4、KLF5、KLF6和KLF11)与发育和病理血管过程有关。然而，KLF家族在脑血管系统中的功能在很大程度上还没有被探索。KLF11是KLF家族的一员，在血管内皮细胞中高表达。KLF11基因突变或变异导致7岁以下青年成熟期糖尿病(MODY7)，并与人类2型糖尿病密切相关，2型糖尿病是中风的主要危险因素。在此之前，我们首次报道了在脑缺血损伤中，过氧化体增殖物激活受体g介导的脑血管保护需要KLF11作为其关键的辅助激活因子，这表明KLF11在卒中病理中是一个潜在的介导物。然而，KLF11本身作为一种新的糖尿病相关转录因子在调节脑血管发病机制中的功能意义和机制在缺血性卒中中的作用尚不清楚。在我们的初步研究中，我们发现KLF11基因缺陷导致小鼠大脑中动脉闭塞后血脑屏障通透性增加，以及血管壁上白细胞-内皮细胞滚动和黏附增加。此外，我们还证实了通过腺病毒获得KLF11功能可以抑制缺氧缺糖后BMEC的死亡。此外，我们还在选择性内皮紧密连接的启动子区域发现了几个KLF11结合位点，KLF11在小鼠中的基因缺失显著降低了Claudin5和ZO-1mRNAs的脑表达。这些发现为我们的中心假设提供了基础，即KLF11在BBB病理中作为一种新的主调节因子发挥作用，并减轻缺血性中风后的脑损伤。这项提案将实现三个目标。目的1：明确KLF11在缺血性卒中后血脑屏障功能障碍和脑损伤中的作用；目的2：明确KLF11调节缺血诱导的血脑屏障功能障碍的分子机制；目的3：明确KLF11活性在缺血性卒中的治疗和转录调节中的作用。

DESCRIPTION (provided by applicant): The blood brain barrier (BBB) is one of the primary targets of cerebral ischemic insults, and resultant BBB dysfunction is well-recognized as a major hallmark of ischemic stroke. As a major component of BBB, brain microvascular endothelial cells (BMECs), together with the tight junctions (TJs) between BMECs, play a dominant role in modulating BBB integrity and paracellular permeability. Extensive studies have shown that breakdown of BBB initiates a devastating cascade of events, contributing to cerebral inflammatory responses, vasogenic edema, hemorrhagic transformation, and eventual neuronal loss in cerebral ischemia. Thus, it is important to identify mechanisms by which loss of BBB integrity can be reduced during ischemic stroke. Kruppel-like factors (KLFs) are members of the zinc finger family of transcription factors and consist of 17 members that have been shown to play key roles in cellular growth and differentiation. Recent studies have documented that partial KLF family members (KLF2, KLF4, KLF5, KLF6, and KLF11) are implicated in developmental and pathological vascular processes. However, the function of the KLF family in the cerebral vasculature is largely unexplored. KLF11 is a member of the KLF family with high expression in vascular endothelium. Mutations or variations in KLF11 gene result in Maturity Onset Diabetes of the Young 7 (MODY7), and are closely associated with human type 2 diabetes mellitus, a major risk factor for stroke. Previously, we reported for the first time that peroxisome proliferatr-activated receptor g-mediated cerebral vascular protection during ischemic insults needs recruitment of KLF11 as its critical coactivator, suggesting KLF11 as a potential mediator in stroke pathologies. However, the functional significance and mechanisms of KLF11 itself as a novel diabetes mellitus-associated transcription factor in regulating cerebrovascular pathogenesis are totally unknown in ischemic stroke. In our preliminary studies, we have shown that KLF11 genetic deficiency leads to increased BBB permeability in mouse brain after middle cerebral artery occlusion as well as increased leukocyte-endothelial rolling and adhesion in the vascular wall. Moreover, we also demonstrated that gain-of-KLF11 function by adenovirus can inhibit BMEC death after oxygen glucose deprivation. Furthermore, we also found several KLF11 binding sites in the promoter region of selective endothelial tight junctions, and genetic deletion of KLF11 in mouse significantly reduced cerebral expression of Claudin 5 and ZO-1 mRNAs. These findings have provided the basis for our Central Hypothesis that KLF11 functions as a novel master regulator in BBB pathologies and attenuates brain injury after ischemic stroke. Three aims will be performed in this proposal. Aim 1: Define the role of KLF11 in BBB dysfunction and brain injury after ischemic stroke; Aim 2: Define the molecular mechanisms of KLF11 in regulating ischemia-induced BBB dysfunction; Aim 3: Define the therapeutic and transcriptional modulation of KLF11 activities in ischemic stroke.