糖尿病视网膜病变是糖尿病严重的并发症之一。血浆激肽释放酶（plasma kallikrein， PK）增加糖尿病视网膜血管通透性和加重黄斑水肿。我们前期研究首次发现PK可以酶切截短N-甲基-D-天门冬氨酸（NMDA）受体1（NR1），导致NMDA和钙离子内流，促进大脑皮质神经元细胞凋亡；还发现PK眼球内注射降低糖尿病SD大鼠视网膜神经电位，增加视网膜casepase 3表达，降低Brn3a表达；这提示PK可通过酶切NR1调控糖尿病视网膜视神经损伤和变性。本课题研究外源性PK、PK缺失和PK抑制剂ASP440对糖尿病视网膜神经节细胞（RGCs）凋亡和神经功能的影响；采用MTT-8法、流式细胞仪、膜片钳，阐明PK促进RGCs凋亡的作用及机制；体内和体外实验探讨PK在过表达截短的NR1对糖尿病RGCs和视网膜神经功能的影响，揭示糖尿病视网膜神经变性新的发病机制，为防治开辟新靶点。

Diabetic retinopathy (DR) is a common and sight-threatening complication of diabetes mellitus, and also the leading cause of new cases of blindness among adults. Plasma kallikrein contributes to excessive retinal vascular permeability and diabetic macular edema. In our preliminary results, we have shown that PK induced cortical neuronal cell death mediated by the cleavage at Arg323 extracellular domains of N-methyl-D-aspartate (NMDA) receptor 1 (NR1), which increase NMDA current and NMDA-induced Ca2+ influx. We also found that intravitreal (IVT) injections of activated PK in diabetic rats decreased Brn3a and increased caspase 3 expression in retinal extracts, and exacerbated electroretinography (ERG) defects. Based on these new preliminary data, we hypothesize that PK could induce retinal neuron degeneration and promote diabetic retinopathy through cleavage-dependent activation of the NR1 subunit of the NMDA receptor. This proposal will characterize the effects of plasma kallikrein on the neuroretina in diabetes using both gain-of-function (PK IVT injections) and loss-of-function approaches (PK deficiency mice and PK inhibitors ASP440); investigate the potential effects and mechanisms of PK on retinal ganglion cells (RGCs) death by using MTT-8, flow cytometry, whole cell patch clamp technique, and calcium imaging; and characterize the effect of truncated NR1 on RGCs apoptosis and neuroretinal function in vivo and vitro. In conclusion, the aim of this study is to reveal new mechanisms and find new potential target of PK for prevention and treatment of diabetic neuroretinal degeneration and dysfunction.