Impact of Lipofuscin in Retinal Pigment Epithelial Cells

描述（由申请人提供）：随着年龄的增长，眼睛的视网膜色素上皮（RPE）细胞积累双视色素荧光团。这组色素，包括创始成员A2 E，由于视黄醇的无意反应而在感光细胞中形成。它们沉积在被吞噬的外节膜内的RPE中，并且它们以脂褐质的形式积累。这些化合物对RPE细胞的损伤作用涉及许多年龄相关的和早发性形式的黄斑疾病，包括隐性Stargardt病、BLVL 4相关疾病、best黄斑营养不良和年龄相关性黄斑变性。本申请中提出的研究的广泛目标是理解视网膜的双维甲酸类化合物促进威胁视力的疾病过程的机制。我们将讨论构成RPE脂褐素的双视色素和感光细胞中这些化合物的双视色素前体。这项工作将阐明治疗途径。此外，由于双维甲酸是眼底自发荧光的主要来源，这些研究将有助于眼底自发荧光图像的临床解释。在具体目标1中，我们将研究我们的初步观察，即双视黄酸的光裂解释放小的二羰基化合物（甲基乙二醛和乙二醛），这些化合物负责蛋白质的晚期糖基化终产物（AGE）修饰。布鲁赫膜和玻璃疣中的蛋白质易于被AGE修饰。布鲁赫膜的老化变化也被认为有助于年龄相关性黄斑变性的发作。我们提出，与糖尿病的情况不同，布鲁赫膜中的AGE加合物是从覆盖的RPE释放二羰基的结果。在具体目标2中，我们将探索RPE双视黄酸在体内光氧化相关光降解的证据。在具体目标3中，我们将探索位于感光细胞外节的双视黄酸荧光团，它们是RPE脂褐素的前体。我们将探测受损感光细胞中双视黄酸形成增加的倾向;我们将测试感光细胞双视黄酸介导感光细胞中脂质氧化和光损伤的能力;我们将证明感光细胞双视黄酸可导致眼底自发荧光图像中的自发荧光增强的条件。这些目标将通过使用动物和体外模型以及采用生物化学和组织学方法来实现。这项研究的完成将促进我们对玻璃疣形成的理解，并将阐明RPE脂褐素与布鲁赫膜衰老变化之间的联系，而布鲁赫膜衰老变化可能是AMD的前奏。这些研究将有助于了解光和氧化机制是如何在单基因视网膜疾病的感光细胞死亡的因素。

DESCRIPTION (provided by applicant): Retinal pigment epithelial (RPE) cells of the eye amass bisretinoid fluorophores with age. This group of pigments, including the founding member A2E, forms in photoreceptor cells due to inadvertent reactions of retinaldehyde. They are deposited in RPE within phagocytosed outer segment membrane and they accumulate as lipofuscin. The damaging effects of these compounds on RPE cells are implicated in a number of age-associated and early-onset forms of macular disease including recessive Stargardt disease, ELOVL4-related disease, best macular dystrophy and age-related macular degeneration. The broad objectives of the studies proposed in this application are to understand mechanisms by which bisretinoids of retina contribute to disease processes that threaten vision. We will address both the bisretinoid pigments constituting RPE lipofuscin and the bisretinoid precursors of these compounds in photoreceptor cells. This work will elucidate therapeutic avenues. Additionally since bisretinoids are the major source of fundus autofluorescence, these studies will contribute to clinical interpretations of fundus autofluorescence images. In Specific Aim 1, we will investigate our preliminary observation that photo-cleavage of bisretinoid releases the small dicarbonyls (methylglyoxal and glyoxal) that are responsible for advanced glycation end-product (AGE) - modifications of proteins. Proteins in Bruch's membrane and drusen are prone to AGE-modification. Aging changes in Bruch's membrane are also considered to contribute to onset of age-related macular degeneration. We propose that, unlike the case in diabetes, AGE-adducts in Bruch's membrane form as a consequence of dicarbonyl release from overlying RPE. In Specific Aim 2, we will probe for evidence of photooxidation-associated photodegradation of RPE bisretinoid in vivo. In Specific Aim 3 we will explore the bisretinoid fluorophores located in photoreceptor cell outer segments that are precursors of RPE lipofuscin. We will probe the propensity for increased formation of bisretinoid in impaired photoreceptor cells; we will test the ability of photoreceptor bisretinoids to mediate oxidation of lipid in photoreceptor cells and photo-damage; and we will demonstrate conditions under which photoreceptor bisretinoids can contribute to hyperautofluorescence in fundus autofluorescence images. These aims will be achieved by the use of animal and in vitro models and by employing biochemical and histological approaches. Completion of this research will advance our comprehension of drusen formation and will elucidate links between RPE lipofuscin and the aging changes in Bruch's membrane that can be a prelude to AMD. These studies will contribute to an understanding of how light and oxidative mechanisms are factors in photoreceptor cell death in monogenic retinal disorders.