ER Stress and Diabetic Retinopathy

 描述(申请人提供)：视网膜血管功能障碍和变性是糖尿病视网膜病变(DR)的早期特征。令人信服的证据表明，慢性糖尿病环境损害了视网膜内皮细胞和周细胞，导致视网膜毛细血管的丧失。在晚期，广泛的毛细血管丢失导致血液供应的严重减少和对神经视网膜的氧气输送的缺陷。这反过来刺激视网膜表达和产生促血管生成因子，促进血管渗漏和新血管生长，导致视网膜浮肿和增殖性视网膜病变。显然，视网膜内皮细胞损伤，如果不可逆转地导致随后的毛细血管丢失，是发展中的一个中心事件。 然而，到目前为止，还没有有效的治疗方法来预防糖尿病引起的视网膜血管损伤。我们项目的目标是通过识别和利用内源性保护因素来提高糖尿病患者的视网膜细胞存活率和改善血管功能，以解决这一关键差距。我们已发表的和初步的研究揭示了一个这样的保护因子，即X-box结合蛋白1(XBP1)。XBP1是未折叠蛋白反应(UPR)核心信号通路中的一个转录因子，广泛参与内质网生物发生、蛋白质折叠、免疫反应和脂质代谢。我们的数据证实了XBP1介导的UPR在维持内皮细胞抗炎平衡方面的基础作用。此外，我们还发现XBP1缺失的视网膜细胞对氧化损伤和细胞凋亡非常敏感。值得注意的是，我们的新结果表明XBP1在调节线粒体重塑和活性方面具有新的功能。因此，我们假设XBP1是通过协调内质网和线粒体稳态来调节细胞对糖尿病应激源的适应的中心调节因子。我们提出了3个特定的目标来检验这一假说，重点是XBP1的S在视网膜内皮细胞线粒体调控中的作用。在目标1中，我们将研究XBP1是否参与线粒体重塑，以及增强XBP1表达是否可以逆转糖尿病诱导的线粒体生物发生缺陷。在目标2中，我们将描述XBP1是否通过调节内质网-线粒体接触和钙转运来调节线粒体的能量产生。最后，在目标3中，我们将确定XBP1是否对 线粒体ROS解毒，从而减少氧化损伤和细胞凋亡。这项应用在概念和技术上都是创新的，因为它将阐明XBP1--一种由内质网应激诱导的传统UPR蛋白--在调节线粒体活动中的新功能，并使用新的RNA-SEQ和蛋白质组学方法来鉴定与这些过程有关的XBP1特异的新的靶基因和蛋白。该项目还通过确定新的治疗靶点来增强视网膜细胞的适应能力，从而具有很高的翻译潜力 减轻糖尿病压力，预防/逆转糖尿病患者的视网膜损伤。

 DESCRIPTION (provided by applicant): Retinal vascular dysfunction and degeneration are the early characteristics of diabetic retinopathy (DR). Compelling evidence suggests that the chronic diabetic milieu damages retinal endothelial cells and pericytes, resulting in loss of retinl capillaries. At the late stages, extensive capillary dropout leads to severe reduction in blood supply and defects in oxygen delivery to the neural retina. This, in turn, stimulates retinal expression and production of pro-angiogenic factors, which promote vascular leakage and new vessel growth leading to retinal edema and proliferative retinopathy. Clearly, retinal endothelial injury, if irreversibly leading to consequent capillary loss, is a central event in the development and progression of DR. However, to date, there is no effective therapy available to prevent diabetes-induced retinal vascular damage. The goal of our project is to address this critical gap by identifying and harnessing endogenous protective factors to enhance retinal cell survival and improve vascular function in diabetes mellitus. Our published and preliminary studies have revealed one such protective factor, namely X-box binding protein 1 (XBP1). XBP1 is a transcription factor in the core signaling pathways of the unfolded protein response (UPR) and is broadly implicated in ER biogenesis, protein folding, immune response, and lipid metabolism. Our data confirmed a fundamental role of the XBP1- mediated UPR in maintaining endothelial cell homeostasis against inflammation. In addition, we found that XBP1-null retinal cells are sensitive to oxidative damage and apoptosis. Strikingly, our new results suggest a novel function of XBP1 in regulation of mitochondrial remodeling and activity. Thus, we hypothesize that XBP1 is a central regulator of cell adaptation to diabetic stressors through coordinating ER and mitochondrial homeostasis. We propose 3 Specific Aims to test this hypothesis, focusing on XBP1's role in mitochondrial regulation in retinal endothelial cells. In Aim 1, we will examine if XBP1 is involved in mitochondrial remodeling and whether enhancing XBP1 expression can reverse diabetes-induced deficits in mitochondrial biogenesis. In Aim 2, we then will delineate if XBP1 regulates mitochondrial energy production through modulation of ER- mitochondrial contact and calcium trafficking. Finally, in Aim 3, we will establish whether XBP1 is essential for mitochondrial ROS detoxification, thereby reducing oxidative damage and apoptosis. This application is conceptually and technically innovative in that it will elucidate a novel function o XBP1, a traditional UPR protein induced by ER stress, in regulation of mitochondrial activities, and using novel RNA-seq and proteomic approaches to identify new XBP1-specific target genes and proteins that are critically involved in these processes. This project also has high translational potential by identifying novel therapeutic targets to enhance retinal cell adaptation to diabetic stresses and prevent/reverse retinal damage in diabetes.