ER Stress and Diabetic Retinopathy

 描述（由申请人提供）：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视网膜内皮细胞和周细胞，导致视网膜毛细血管的损失。在晚期，广泛的毛细血管脱落导致严重的血液供应减少和向神经视网膜的氧气输送缺陷。这反过来又刺激视网膜表达和促血管生成因子的产生，促血管生成因子促进血管渗漏和新血管生长，导致视网膜水肿和增殖性视网膜病。显然，视网膜内皮损伤，如果不可逆地导致随后的毛细血管损失，是发展中的中心事件。 然而，迄今为止，没有有效的治疗方法可用于预防糖尿病诱导的视网膜血管损伤。我们项目的目标是通过识别和利用内源性保护因子来提高视网膜细胞存活率并改善糖尿病患者的血管功能，从而解决这一关键差距。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（XBP 1）。XBP 1是未折叠蛋白反应（UPR）核心信号通路中的转录因子，广泛参与ER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XBP 1介导的UPR在维持内皮细胞稳态对抗炎症中的基本作用。此外，我们发现，XBP 1-null视网膜细胞对氧化损伤和凋亡敏感。引人注目的是，我们的新结果表明，XBP 1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，XBP 1是一个中央调节器的细胞适应糖尿病的压力，通过协调ER和线粒体的稳态。我们提出了3个具体的目标来验证这一假设，重点是在视网膜内皮细胞的线粒体调节中的作用。在目标1中，我们将研究是否XBP 1参与线粒体重塑，以及是否增强XBP 1表达可以逆转糖尿病诱导的线粒体生物合成缺陷。在目标2中，我们将描述XBP 1是否通过调节ER-线粒体接触和钙运输来调节线粒体能量产生。最后，在目标3中，我们将确定XBP 1是否是必不可少的， 线粒体ROS解毒，从而减少氧化损伤和细胞凋亡。该申请在概念上和技术上都是创新的，因为它将阐明由ER应激诱导的传统UPR蛋白XBP 1在调节线粒体活性中的新功能，并使用新的RNA-seq和蛋白质组学方法来鉴定新的XBP 1特异性靶基因和关键参与这些过程的蛋白质。该项目还具有很高的翻译潜力，通过确定新的治疗靶点，以增强视网膜细胞的适应 糖尿病压力和预防/逆转糖尿病视网膜损伤。

 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.