Progranulin对糖尿病视网膜病变神经血管单元的保护作用及机制

Neuron degeneration and microangiopathy are both involved in diabetic retinopathy (DR) . DR is a retinal neurovascular unit (NVU) injury essentially. Currently, there are less researches on the overall treatment of NVU aiming to improve neuron and micrangium function. Progranulin is a multifunctional growth factor. It has the effect of immunomodulatory and neuron protection. The preliminary work found that Progranulin is expressed in the mice retina and downregulated in diabetic model. We also found that exogenous Progranulin could alleviate photoreceptors injury and retinal vascular adherent leukocytes under the hypoxic conditions. This protection effect is related with TLR4-NOX4 signaling pathway. Based on the preliminary experiment and research background, we propose the hypothesis that Progranulin could inhibit the retinal neurons and microvascular lesion through regulating the retinal TLR4-NOX4 signaling pathway under the diabetic conditions so as to protect the retinal NVU from high glucose damage. We will use animal and cell experiments by the means of electroretinogram and blood-retina barrier breakdown assays et al. We aim to investigate the protective role of Progranulin in DR and illustrate the mechanism of TLR4-NOX4 signaling pathway in the protection effect. Our work focused on the dual protection effect of neuron degeneration and microangiopathy by a single substance and would provide a new approach for the treatments of diabetic NVU injury.

糖尿病视网膜病变(DR)涉及视网膜神经元与微血管双重病变，其本质是视网膜神经血管单元(NVU)的损伤，但目前旨在同时改善神经元与微血管功能的研究非常缺乏。Progranulin是一种具有免疫调节与神经保护作用的多功能生长因子。申请者前期发现：该蛋白存在于视网膜，其表达在糖尿病小鼠视网膜中显著降低；添加该蛋白可显著减轻缺氧条件导致的小鼠光感受器损伤与视网膜血管白细胞粘滞度，该保护作用与TLR4-NOX4信号通路相关。据此我们假设Progranulin能同时改善DR的神经元与微血管病变。本项目将采用动物和细胞实验，应用视网膜电图与屏障渗漏分析等方法，拟：1）研究Progranulin在DR条件下对神经元与微血管病变的保护作用；2）阐明TLR4-NOX4信号通路在上述保护作用中的机制。本申请研究单一物质对DR中神经元与微血管病变的双重保护作用，有望为DR的NVU病变提供治疗新途径和新思路。

Progranulin是一种多功能的生长因子，既往研究发现Progranulin在肿瘤发生、炎症应答、神经细胞存活和调控轴突生长等多种病理生理过程起着重要作用，但其在视网膜神经退行性病变和微血管病变中的作用尚不明确。本项目探讨了Progranulin在视网膜神经-血管病变中的作用。我们通过视网膜电图检查、免疫荧光共定位法、视网膜血管白细胞粘、免疫印迹法等一系列检测了小鼠的视网膜结构和功能改变。结果发现在实验组小鼠视网膜电图振幅均较正常条件组显著下降，但PBS注射眼的振幅较Progranulin注射眼下降更为明显，差异有统计学意义。形态学检查发现实验组小鼠PBS注射眼较Progranulin注射眼其视杆细胞数量减少，视锥细胞排列稀疏，外节形态短小。此外还发现实验组小鼠Progranulin注射眼粘滞的白细胞数量尽管比正常条件组小鼠多，但仅为PBS注射眼总数的52.31%。信号通路筛查发现Progranulin是通过抑制TLR4-NOX4信号通路发挥对视网膜的保护作用，以上结果表明Progranulin对小鼠光感受器的功能和形态具有保护作用，同时还能减少视网膜血管炎症反应，Progranulin是通过抑制TLR4-NOX4信号通路而发挥作用的。本项目成果为寻找视网膜病变的治疗靶点提供了实验理论依据。