Sphingolipid Metabolism and Signaling in the Retina

项目概要/摘要： 鞘脂是膜脂家族，在调节细胞膜脂代谢中具有重要的结构作用。 脂双层，特别是脂筏的流动性和子域结构。神经酰胺（Cer）是其关键代谢产物 所有鞘脂的生物合成。Cer及其代谢产物鞘氨醇-1-磷酸（S1 P）是 鞘脂;涉及与炎症，肿瘤发生，糖尿病， 和神经退化Cer信号主要用于细胞凋亡，而S1 P在细胞凋亡中具有相反的细胞内作用。 细胞存活S1 P还通过其受体（S1 P1 -5）进行细胞旁信号传导，所述受体主要存在于血管中。 内皮细胞和T细胞以及粘附、迁移、炎症和新血管形成的信号。 与其在细胞凋亡中的作用一致，神经酰胺最近被证明参与感光细胞 死亡我们的初步数据显示，在几种模型中，神经酰胺水平在视网膜变性过程中增加 遗传和压力导致的视网膜退化我们还观察到S1 P水平和表达增加 退化的视网膜已知S1 P对神经酰胺合成具有抑制作用。在试点研究中，我们 确定S1 P也是另一组酶--鞘磷脂酶（SMase）的竞争性抑制剂 负责细胞中神经酰胺的产生，表明S1 P在Cer的调节反馈中的作用 生产当我们将Cer注射到大鼠玻璃体中时，我们观察到严重的炎症， 视网膜功能和感光细胞死亡。我们进一步发现，FTY 720，一种新的Cer合成抑制剂， 阻断大鼠视网膜中的Cer产生并保护视杆免受光诱导的变性。我们的初步 结果显示，视网膜中的鞘脂代谢活跃，并表明 神经酰胺和S1 P在维持正常视网膜结构和功能中是重要的。在本提案中，我们将测试 假设视网膜中Cer和S1 P之间的平衡失调导致视网膜病变， 炎症和细胞死亡。在四个具体目标中提出的实验将侧重于阐明 Cer在视网膜退行性疾病中的生理作用，了解Cer水平如何调节， 探索靶向Cer合成或可降解Cer的酶的抑制剂的治疗潜力， 确定S1 P如何与视网膜中的Cer代谢相关，以及Cer和 S1 P在维持视网膜稳态和功能中的作用 该提案将探讨神经酰胺和S1 P在视网膜生理和疾病中的作用。这是一 视网膜研究的新的和不足的领域，并与许多形式的人类视网膜营养不良 包括年龄相关性黄斑变性、糖尿病性视网膜病和色素性视网膜炎。机制研究 将有可能为治疗干预确定新的途径和新的靶点。

Project Summary/Abstract: Sphingolipids are a family of membrane lipids with important structural roles in the regulation of the fluidity and subdomain structure of the lipid bilayer, especially lipid rafts. Ceramide (Cer) is the key metabolite for all sphingolipid biosynthesis. Cer and its metabolite sphingosine-1-phosphate (S1P) are signaling sphingolipids; implicated in several human diseases associated with inflammation, tumorigenesis, diabetes, and neurodegeneration. Cer signals primarily for apoptosis, whereas S1P has an opposing intracellular role in cell survival. S1P also signals paracellularly via its receptors (S1P1-5), which are mostly present in vascular endothelial cells and T cells and signals for adhesion, migration, inflammation, and neovascularization. Consistent with its role in apoptosis, ceramide has recently been shown to be involved in photoreceptor cell death. Our preliminary data show ceramide levels are increased during retinal degeneration in several models of inherited and stress-induced retinal degeneration. We also observed increased S1P levels and expression in degenerating retinas. S1P is known to have inhibitory effect on ceramide synthesis. In pilot studies, we determined that S1P is a competitive inhibitor of sphingomyelinase (SMase) also, another group of enzymes responsible for ceramide production in cells, suggesting a role for S1P in the regulated feedback of Cer production. When we injected Cer into the rat vitreous, we observed severe inflammation followed by loss of retinal function and photoreceptor cell death. We further found that FTY720, a de novo Cer synthesis inhibitor, blocked Cer production in the rat retina and protected rods from light-induced degeneration. Our preliminary results show an active sphingolipid metabolism in the retina and suggest that the delicate balance between ceramide and S1P is important in maintaining normal retinal structure and function. In this proposal we will test the hypothesis that the dysregulated balance between Cer and S1P in the retina leads to retinal inflammation and cell death. The experiments proposed in four specific aims will focus on elucidating the physiological role of Cer in retinal degenerative diseases, understanding how Cer levels are regulated, exploring the therapeutic potential of inhibitors that target Cer synthesis or the enzymes that can degrade Cer, determining how S1P is related to Cer metabolism in the retina, and how important is the balance of Cer and S1P in maintaining retinal homeostasis and function. This proposal will explore the role of Ceramide and S1P in retinal physiology and diseases. This is a novel and underserved area of retinal research and has relevance to many forms of human retinal dystrophies including age-related macular degeneration, diabetic retinopathy, and retinitis pigmentosa. Mechanistic studies will likely identify novel pathways and novel targets for therapeutic intervention.