Molecular Basis of Retinal Angiogenesis

项目总结 过氧化物酶体增殖物激活受体(PPAR)是核受体超家族的成员。 配体激活的转录因子。三个子类型，PPAR-？、PPAR-？/？和PPAR-？，每个子类型由 单基因，已被鉴定。PPAR可以被各种配体激活，其中包括天然的 常见的脂肪酸、贝特类和前列腺素。在上一个项目期间，我们对角色的研究 前列腺素在视网膜血管生成中确认PPAR，特别是PPAR-？/？是潜在的治疗靶点。 三种PPAR均在血管内皮细胞中表达。在这方面，PPAR-？和PPAR-？通常 表现出抗炎、抗增殖和抗血管生成的作用。相比之下，我们所知的要少得多。 关于PPAR-，虽然已被证明能刺激血管内皮细胞的增殖，但其 在某些癌细胞中，激活会导致血管内皮生长因子的诱导，但在其他癌细胞中则不会。之前的工作清楚地表明 所有三种PPAR都通过高度多效性的机制影响血管功能，这些机制是组织和细胞- 具体的。因此，为了在视网膜血管生成的背景下理解这些机制，PPAR 表达和激活必须在涉及的特定视网膜细胞中进行表征。这些细胞是 产生血管生成因子的M？ler细胞和视网膜微血管内皮细胞(RMEC)， 它们对血管生成因子有反应。使用这两种细胞类型的原代培养，复杂的 可以研究PPAR、生长因子产生和血管生成细胞行为之间的相互作用 系统地，导致确定PPAR的适当治疗操作。我们的预赛 数据表明，在与早期和早期相关的条件下，PPAR-？/？在M？ler细胞和RMEC中被激活 晚期糖尿病视网膜病变(DR)。因此，我们建议使用一组工具来描述 视网膜血管疾病中的PPAR-？/？：1)从野生型和PPAR-？/？小鼠中分离的细胞的比较； 野生型小鼠细胞中高选择性激动剂和拮抗剂；3)野生型和 早期和晚期DR模型中的PPAR-/？-/-小鼠；以及4)在DR模型中的高特异性激动剂和拮抗剂 野生型小鼠和大鼠的DR。我们的活体模型被选中是因为它们与早期(STZ- 糖尿病)和晚期(氧源性视网膜病变)我们相信这一策略是有针对性的 全面，它将产生对我们对DR的基本理解和 开发合理的治疗方法。

PROJECT SUMMARY Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear receptor superfamily of ligand-activated transcription factors. Three subtypes, PPAR-¿, PPAR-¿/¿ and PPAR-¿, each encoded by a single gene, have been identified. PPARs can be activated by a variety of ligands that include naturally occurring fatty acids, fibrates and prostaglandins. During the last project period, our studies of the roles of prostaglandins in retinal angiogenesis identified PPARs, specifically PPAR-¿/¿, as potential therapeutic targets. All three PPARs are expressed in vascular endothelium. In this context, PPAR-¿ and PPAR-¿ generally demonstrate anti-inflammatory, anti-proliferative, and anti-angiogenic effects. In contrast, much less is known regarding PPAR-¿/¿, although it has been shown to stimulate proliferation of vascular endothelial cells, and its activation leads to VEGF induction in some cancer cell lines, but not others. Previous work clearly suggests that all three PPARs influence vascular function by highly pleiotropic mechanisms that are tissue- and cell- specific. Thus, in order to understand these mechanisms in the context of retinal angiogenesis, PPAR expression and activation must be characterized in the specific retinal cells that are involved. These cells are the M¿ller cells, which produce angiogenic factors, and the retinal microvascular endothelial cells (RMEC), which respond to the angiogenic factors. Using primary cultures of these two cell types, the complicated interactions between PPAR-¿/¿, growth factor production and angiogenic cell behaviors can be studied systematically, leading to the identification of appropriate therapeutic manipulations of PPARs. Our preliminary data indicate that PPAR-¿/¿ is activated in M¿ller cells and RMEC under conditions relevant to both early and late diabetic retinopathy (DR). Thus, we propose to use a combination of tools to characterize the role of PPAR-¿/¿ in retinal vascular disease: 1) comparisons of cells isolated from wild type and PPAR-¿/¿-/- mice; 2) highly selective agonists and antagonists in cells isolated from wild type mice; 3) comparisons of wild type and PPAR-¿/¿-/- mice in models of early and late DR; and 4) highly specific agonists and antagonists in models of DR in wild type mice and in rats. Our in vivo models have been selected for their relevance to early (STZ- induced diabetes) and late (oxygen-induced retinopathy) DR. We believe this strategy is focused and comprehensive, and it will yield information of importance to our fundamental understanding of DR and to the development of rational therapeutic approaches.