TWEAK-Induced Neuroinflammation and Cerebral Edema

描述（由申请人提供）： 血脑屏障（BBB）通透性的调节是一个动态过程，包括内皮细胞、基底膜和星形胶质细胞终足突起之间的相互作用。脑缺血的发作在BBB中诱导一组复杂的变化，其导致炎性细胞从血管内空间进入与脑水肿的发展相关的内皮细胞-基底膜-星形胶质细胞界面的近腔侧，这是急性中风患者死亡的主要原因（在一些系列中高达80%）。肿瘤坏死因子样弱凋亡诱导因子（TWEAK）是肿瘤坏死因子超家族的成员，其通过与称为成纤维细胞生长因子诱导因子14（Fn 14）的细胞表面受体结合而作用于应答细胞。我们以前已经证明，在大脑中，TWEAK和Fn 14主要在血管周围星形胶质细胞和内皮细胞中表达，并且脑内注射重组TWEAK诱导这些细胞中的NF-：B途径活化以及基质金属蛋白酶-9（MMP-9）活性和BB B渗透性的剂量依赖性增加。我们还发现，大脑中动脉闭塞（MCAO）后，缺血区域中TWEAK和Fn 14的表达增加，并且通过施用Fn 14-Fc诱饵受体或通过Fn 14的遗传缺陷抑制MCAO后的TWEAK活性导致NF-：B活化的抑制和BB B的结构和屏障功能的保留。考虑到下面讨论的这些和其他发现，在本申请中，我们假设在脑缺血期间，TWEAK和Fn 14之间的相互作用是调节BBB通透性的关键分子机制。更具体地，我们提出在缺血性损伤开始后早期，TWEAK与内皮细胞-基底膜-星形胶质细胞界面中的Fn 14的结合导致以下事件顺序：B介导的趋化因子MCP-1（CCL 2）及其受体CCR 2的表达增加，形成趋化因子梯度，导致炎性细胞浸润到BBB的近腔侧，ii）炎性细胞衍生的MMP-9活性增加，和iii）MMP-9介导的BBB渗透性的增加伴随脑水肿的发展。在本提案的最后一个目的中，我们将研究用Fn 14-Fc诱饵抑制TWEAK-Fn 14结合是否在缺血条件下保护BBB的屏障功能，所述Fn 14-Fc诱饵用纳米载体递送至内皮细胞-基底膜-星形胶质细胞界面。如果成功，这些临床相关研究不仅将揭示这种新途径的生物学，而且可能导致发现脑水肿发展的新机制。重要的是，如果我们的假设是正确的，我们的研究结果应该表明抑制TWEAK-Fn 4结合是否是治疗急性缺血性卒中患者的有效新靶点。 公共卫生相关性： 缺血性中风发作后早期，细胞因子TWEAK及其受体Fn 14之间的相互作用诱导脑肿胀（水肿），这是缺血性中风患者死亡的一个非常常见的原因。中风在美国退伍军人中的相关性已得到广泛认可。事实上，一些研究报告称，美国退伍军人因缺血性中风导致的死亡率高于一般人群，特别是在该国南部各州。在本申请中，我们研究了TWEAK和Fn 14之间的相互作用诱导脑水肿的机制，并测试了TWEAK-Fn 14通路抑制剂治疗急性缺血性中风的疗效。因此，如果成功，本申请中提出的研究可能会降低美国退伍军人的发病率和死亡率。

DESCRIPTION (provided by applicant): The regulation of the permeability of the blood-brain barrier (BBB) is a dynamic process that includes the interaction between endothelial cells, the basement membrane and astrocytic end-feet processes. The onset of cerebral ischemia induces a complex set of changes in the BBB that leads to the passage of inflammatory cells from the intravascular space into the abluminal side of the endothelial cell-basement membrane- astrocyte interface associated with the development of cerebral edema, which is a leading cause of mortality in acute stroke patients (up to 80% in some series). Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) is a member of the tumor necrosis factor superfamily that acts on responsive cells via binding to a cell surface receptor known as fibroblast growth factor-inducible 14 (Fn14). We have previously demonstrated that in the brain TWEAK and Fn14 are expressed mainly in perivascular astrocytes and endothelial cells, and that the intracerebral injection of recombinant TWEAK induces NF-:B pathway activation in these cells and a dose-dependent increase in both matrix metalloproteinase-9 (MMP-9) activity and the permeability of the BBB. We have also found that following middle cerebral artery occlusion (MCAO) the expression of TWEAK and Fn14 increases in the ischemic area, and that inhibition of TWEAK activity following MCAO either by administration of a Fn14-Fc decoy receptor or by genetic deficiency of Fn14 results in inhibition of NF-:B activation and preservation of the structure and barrier function of the BBB. In consideration of these and other findings discussed below, in this application we hypothesize that during cerebral ischemia the interaction between TWEAK and Fn14 is a key molecular mechanism that regulates the permeability of the BBB. More specifically, we propose that early after the onset of the ischemic insult the binding of TWEAK to Fn14 in the endothelial cell- basement membrane-astrocyte interface results in the following sequence of events: i) NF-:B-mediated increased expression of the chemokine MCP-1 (CCL2) and its receptor CCR2 with the formation of a chemokine gradient that leads to the infiltration of inflammatory cells into the abluminal side of the BBB, ii) increase in inflammatory cell- derived MMP-9 activity, and iii) MMP-9-mediated increase in the permeability of the BBB with development of cerebral edema. In the last Aim of this proposal we will study whether inhibition of TWEAK-Fn14 binding with Fn14-Fc decoy delivered to the endothelial cell-basement membrane-astrocyte interface with a nanocarrier protects the barrier function of the BBB during ischemic conditions. If successful, these clinically relevant studies not only will shed light into the biology of this novel pathway but also may lead to the discovery of a new mechanism underlying the development of cerebral edema. Importantly, if our hypothesis is correct, our findings should indicate whether inhibition of TWEAK-Fn4 binding is a valid new target for the treatment of patients with acute ischemic stroke. PUBLIC HEALTH RELEVANCE: Early after the onset of ischemic stroke the interaction between the cytokine TWEAK and its receptor Fn14 induces brain swelling (edema), which is a very common cause of death among patients with ischemic stroke. The relevance of stroke among USA Veterans has been widely recognized. In fact, some studies have reported that the mortality due to ischemic stroke among USA Veterans is higher than in the general population, particularly in southern states of the country. In this application we study the mechanism whereby the interaction between TWEAK and Fn14 induces brain edema, and test the therapeutic efficacy of inhibitors of the TWEAK-Fn14 pathway for the treatment of acute ischemic stroke. Thus, if successful, the studies proposed in this application may lead to a decrease in the morbility and mortality among USA Veterans.