Role of toll-like receptor signaling in retinal ischemia

描述（由申请人提供）：缺血-再灌注（IR）损伤与视网膜中的大量病理状况有关，包括青光眼、糖尿病性视网膜病变、前部缺血性视神经病变和创伤性视神经病变。因此，了解缺血性神经元损伤所涉及的事件可以为我们提供临床有效的治疗方法， 许多视网膜疾病。虽然这种损伤的原因是多因素的，但越来越多的实验性 证据表明先天免疫系统在引发导致视网膜功能的有害/有害变化的炎性级联反应中起重要作用。Toll样受体（TLR）被认为是病原体诱导的炎症和最近损伤诱导的炎症的主要贡献者之一。从损伤/坏死细胞释放的内源性配体可以激活TLR，即使在没有病原体的情况下也引发炎症反应。我们发表的结果表明，Toll样受体4（TLR 4）的内源性配体的水平在视网膜IR中增加，并且通过TLR 4的活化，参与由缺血性损伤引发的视网膜损伤和炎症。重要的是，我们的初步结果表明，介导视网膜缺血性损伤的机制不仅是由星形胶质细胞，小胶质细胞或浸润性免疫细胞诱导的炎症，而且还通过激活视网膜神经节细胞（RGC）本身的TLR 4。然而，视网膜IR损伤后TLR 4信号诱导的炎症和损伤的确切机制仍不清楚。在这个项目中，我们假设TLR 4信号通过直接和/或间接促进RGCs的损伤在视网膜IR损伤的发病机制中起重要作用。这一假设将在以下具体目标所概述的一系列实验中得到检验：1）确定TLR 4是否协调视网膜对IR损伤的免疫应答~ 2）确定TLR 4信号传导的沉默是否减少缺血视网膜中的血视网膜渗透性和白细胞浸润~ 3）确定TLR 4介导的信号是否直接损伤RGC ~ 4）确定TLR 4配体在缺血后视网膜中的作用。这些特定目标的完成可能会导致发现创新策略，以帮助预防患有视网膜缺血的患者的视力丧失，因为选择性靶向TLR 4及其配体可能比靶向细胞内途径更有效地用于开发预防IR损伤的治疗工具。 公共卫生相关性：视网膜缺血再灌注（IR）损伤与大量病理状况有关，其中炎症是疾病的标志。Toll样受体（TLR）被认为是病原体诱导的炎症和最近损伤诱导的炎症的主要贡献者之一。对TLR在视网膜IR损伤中的作用的更好理解可能有助于开发特异性TLR靶向治疗剂来治疗视网膜中的这些病症，这对于开发预防IR损伤的治疗工具可能比靶向细胞内途径更有效。

DESCRIPTION (provided by applicant): Ischemia-reperfusion (IR) injury is implicated in a large array of pathological conditions in the retina including glaucoma, diabetic retinopathy, anterior ischemic optic neuropathy and traumatic optic neuropathy. Thus, understanding the events involved in ischemic neuronal injury can provide us with clinically effective treatments for many retinal diseases. Although the cause of this injury is multifactorial, increasing experimental evidence suggests an important role for the innate immune system in initiating the inflammatory cascade leading to detrimental/deleterious changes in retinal function. Toll-like receptors (TLRs) are recognized as one of the main contributors to pathogen-induced inflammation and, more recently, injury-induced inflammation. Endogenous ligands liberated from injured/necrotic cells can activate TLRs, initiating an inflammatory response even in the absence of pathogens. Our published results indicate that the level of endogenous ligands for toll- like receptor 4 (TLR4) increases in retinal IR and, through activation of TLR4, are involved in retinal damage and inflammation triggered by ischemic injury. Importantly, our preliminary results suggest that the mechanisms mediating ischemic damage in the retina are facilitated not only by inflammation induced by astrocytes, microglia, or infiltrating immune cells, but also by activation of TLR4 in retinal ganglion cells (RGCs) themselves. However, the exact mechanism of TLR4 signaling-induced inflammation and damage after retinal IR injury remains unknown. In this project we hypothesize that TLR4 signaling plays a significant role in the pathogenesis of retinal IR injury by directly and/or indirectly contributing to the injury of RGCs. This hypothesis will be tested ina series of experiments outlined in the following specific aims: 1) to determine whether TLR4 coordinates the immune response of the retina to IR injury~ 2) to determine whether silencing of TLR4 signaling reduces blood retinal permeability and infiltration of leukocytes in the ischemic retina~ 3) to determine whether TLR4-mediated signals directly injure RGCs~ 4) to define the role of TLR4 ligands in the post-ischemic retina. Completion of these specific aims could lead to the discovery of innovative strategies to help prevent the loss of vision in patients suffering fro retinal ischemia, as selective targeting of both TLR4 and its ligands may be more effective for the development of therapeutic tools to prevent IR injury than targeting the intracellular pathways. PUBLIC HEALTH RELEVANCE: Ischemia-reperfusion (IR) injury of the retina is implicated in a large array of pathological conditions in which inflammation is a hallmark of disease. Toll-like receptors (TLRs) are recognized as one of the main contributors to pathogen-induced inflammation and, more recently, injury-induced inflammation. A greater understanding of the role of TLRs in retinal IR injury may aid in the development of specific TLR-targeted therapeutics to treat these conditions in the retina, which may be more effective for the development of therapeutic tools to prevent IR injury than targeting the intracellular pathways.