Complement factor H modulates lipoprotein clearance in AMD

摘要 在发达国家，年龄相关性黄斑变性（AMD）是导致不可逆失明的主要原因 大多数老年人没有治疗方法。早期AMD的特征是 形成富含蛋白质和脂质的视网膜下色素上皮（RPE）沉积物。这些沉积物含有 许多成分可归因于补体级联和脂蛋白的激活 新陈代谢.此外，补体和脂蛋白途径基因已独立地与 AMD在多种方面，包括遗传风险关联和流行病学研究。努力去了解 脂质代谢/运输和补体失调对AMD的贡献部分受到 缺乏忠实地概括疾病的这些致病方面的年龄依赖性体内模型。的 所提出的研究的目的是利用使用我们所拥有的新型AMD动物模型获得的数据， 开发这些模型引起高龄、补体失调和脂质/胆固醇扰动， 所有已知的导致人类AMD风险的因素。具体地说，我们根据大多数 与AMD风险相关的复制遗传风险变体，氨基酸序列中的酪氨酸（Y）替换为组氨酸（H）， 人补体因子H的酸性位置402（Y 402 H），替代补体的可溶性调节剂 通路只有表达人H402 AMD风险变体（CFH-H/H）的小鼠发展出AMD表型 与表达正常人Y 402 CFH变体的小鼠相比。值得注意的是， 与血液和RPE/Bruch膜（BrM）/脉络膜中脂蛋白水平的变化相关 复杂.因此，我们首次在体内观察到Y 402 H多态性的功能性后果， 促进AMD样病变并影响老年小鼠的脂蛋白水平。此外，我们分析了ApoA-1， 含有从老年人供体的BrM和血浆中分离的脂蛋白，发现它们具有非常高的 不同的蛋白质组成。最显著的差异是ApoB的浓度显著较高， BrM中的ApoE和ApoE，已知它们与糖胺聚糖（GAG）结合， 沉积到BrM GAG上;可能引发导致RPE功能障碍/死亡的下游效应。 基于这些观察和其他研究，我们假设异常RPE源性高密度 脂蛋白（HDL）样脂蛋白分泌有助于AMD的发展，并且由CFH调节。因此，在本发明中， 所提出的研究的目标是使用我们的新的AMD动物模型和人类诱导多能 干细胞衍生的RPE（1）阐明CFH调节AMD中脂蛋白清除的机制 发病机制和（2）测试是否增加正常CFH和/或增强局部HDL清除， 治疗AMD的可行策略。 这些研究的结果将从机制上确定两个风险因素的相互作用，CFH和 本发明的目的是研究脂蛋白在AMD中的作用，并建立这些因子作为AMD治疗靶点的概念证明。

ABSTRACT In developed countries, age-related macular degeneration (AMD) is the leading cause of irreversible blindness in the elderly and there are no treatments for the majority of patients. Early AMD is characterized by the formation of protein- and lipid-rich, sub-retinal pigmented epithelium (RPE) deposits. These deposits contain many constituents that are attributable to both the activation of the complement cascade and lipoprotein metabolism. In addition, complement and lipoprotein pathway genes have been independently associated with AMD in multiple ways including genetic risk association and epidemiological studies. Efforts to understand how lipid metabolism/trafficking and complement dysregulation contribute to AMD have been limited in part by the lack of age-dependent in vivo models that faithfully recapitulate these pathogenic aspects of the disease. The aim of the proposed studies is to leverage data derived using novel animal models of AMD that we have developed. These models invoke advanced age, complement dysregulation and lipid/cholesterol perturbation, all known contributors to human AMD risk. Specifically, we generated mouse models based on the most replicated genetic risk variant associated with AMD risk, the tyrosine (Y) to histidine (H) substitution at amino acid position 402 (Y402H) of human complement factor H, the soluble regulator of the alternative complement pathway. Only mice expressing the human H402 AMD risk variant (CFH-H/H) develop an AMD phenotype compared to mice expressing the normal human Y402 CFH variant. Significantly, the AMD phenotype correlates with changes in lipoprotein levels in blood, and in the RPE/Bruch’s membrane (BrM)/choroid complex. Thus, we are the first to observe a functional consequence of the Y402H polymorphism in vivo, which promotes an AMD-like pathology and affects lipoprotein levels in aged mice. In addition, we analyzed ApoA-1 containing lipoproteins isolated from BrM and plasma of elderly human donors and found they have very different protein compositions. The most striking difference is the significantly higher concentration of ApoB and ApoE in BrM, which are known to bind to glycosaminoglycans (GAGs) and could promote lipoprotein deposition onto BrM GAGs; likely initiating downstream effects that contribute to RPE dysfunction/death. Based on these observations and other studies we hypothesize that aberrant RPE-derived high-density lipoprotein (HDL)-like lipoprotein secretion contributes to AMD development, and is modulated by CFH. Thus, the goals of the proposed studies are to use our novel animal models of AMD and human induced pluripotent stem cell-derived RPE to (1) elucidate the mechanism by which CFH modulates lipoprotein clearance in AMD pathogenesis and (2) to test whether augmenting normal CFH and/or enhancing local HDL clearance are viable strategies for treating AMD. Outcomes from these studies will mechanistically determine the interaction of two risk factors, CFH and lipoproteins in AMD and establish proof of concept for these factors as therapeutic targets for AMD.