Initiating Events in AMD: a mouse model for the human disease

描述(申请人提供)：年龄相关性黄斑变性(AMD)是一种老年人的祸害，在美国，这种潜在的致盲疾病在大约三分之一的75岁以上的人中存在。有大量证据表明，AMD是一种涉及补体途径调节失调的炎症性疾病。我们发现，由二十二碳六烯酸(DHA)氧化损伤产生的半抗原CEP(羧乙基吡咯)以加合物的形式存在于AMD供体眼的玻璃体蛋白上。此外，与年龄匹配的非AMD患者相比，AMD患者的循环(血浆)中抗CEP自身抗体更为丰富。由于DHA在外层视网膜中含量丰富，光线和高氧水平为氧化损伤提供了允许的环境，因此该组织可能是CEP加合物的来源。由于CEP加合物是抗原性的，我们推测，随着外层视网膜产生这些加合物，免疫系统对这些新的表位产生反应，随着时间的推移，开始攻击作为该片段来源的细胞。为了验证这一假设，我们用CEP加成的小鼠血清白蛋白(CEP-MSA)免疫正常小鼠。我们的预测是，CEP的系统免疫将使小鼠对正常衰老过程中外视网膜产生的内源性CEP加合物敏感。反过来，免疫系统会通过攻击最容易产生CEP表位的细胞来做出反应。我们发现，免疫的小鼠产生CEP抗体，在Bruchs膜上固定补体成分-3，在衰老过程中在RPE下方堆积苔藓，并在RPE中形成类似于地理性萎缩的病变，这是干性AMD的终末期症状。本研究利用这一小鼠模型对补体激活途径在病理发生中的作用、抗体在所观察到的损伤中的作用以及通过操纵补体激活或抑制口服耐受的病理来预防损伤的可能性进行了机制研究。这些研究的结果有可能导致确定预防AMD的新治疗途径。

DESCRIPTION (provided by applicant): Age-related macular degeneration (AMD) is a scourge of the elderly, with some stage of this potentially blinding disease present in approximately a third of individuals over 75 years of age in the US. There is substantial evidence that AMD is an inflammatory disease involving dysregulation of the complement pathway. We found that the hapten, CEP (carboxyethylpyrrole), generated by oxidative damage to docosahexaenoic acid (DHA), is present as an adduct on drusen proteins in AMD donor eyes. In addition, autoantibodies against CEP were more abundant in the circulation (plasma) of individuals with AMD than in age-matched individuals without AMD. Because DHA is abundant in the outer retina where light and high oxygen levels provide a permissive environment for oxidative damage, this tissue is a likely source of CEP-adducts. Since CEP-adducts is antigenic, we speculated that as the outer retina generates these adducts, the immune system becomes responsive to these new epitopes and over time begins to attack the cells that are the source of this fragment. To test this hypothesis we immunized normal mice with CEP-adducted mouse serum albumin (CEP-MSA). Our prediction was that systemic immunization with CEP would sensitize mice to endogenous CEP-adducts generated in the outer retina during the normal course of aging. In turn the immune system would respond by attacking the cells where CEP epitopes are most readily generated. We found that immunized mice develop antibodies to CEP, fix complement component-3 in Bruch's membrane, accumulate drusen below the RPE during aging, and develop lesions in the RPE mimicking geographic atrophy, the end-stage condition characteristic of dry AMD. The research proposed here uses this mouse model for mechanistic studies on the role of complement activation pathways in producing the pathology, the role of antibody in causing the lesions observed, and the possibility of prevention of the lesions through manipulation of complement activation or suppression of the pathology with oral tolerance. Outcomes from these studies have the potential to lead to the identification of new therapeutic pathways to prevent AMD.