Prevention of Retinal Degeneration by Crystallins in Experimental Uveitis

描述（由主要研究者提供）：眼内炎症，通常被称为葡萄膜炎，是视网膜感光细胞凋亡导致失明的主要原因。实验性自身免疫性葡萄膜视网膜炎（EAU）是一种与人类葡萄膜炎非常相似的葡萄膜炎动物模型。其特征分为两个阶段：早期阶段，用葡萄膜源性抗原刺激后5-7天，晚期/扩增期，12-14天。在后期，巨噬细胞/中性粒细胞浸润视网膜，组织学上注意到光感受器损伤。在白细胞浸润之前的早期阶段，视网膜中出现Th1-和th17驱动的细胞因子，线粒体氧化应激导致光感受器中的细胞色素c （cyto c）硝化，硝化后的细胞c释放到细胞质中。已知这种细胞c释放会引起细胞凋亡。然而，凋亡并不是早期EAU视网膜的特征，这表明在EAU视网膜中存在一种防止光受体凋亡的保护机制。目前的初步研究表明，这种保护作用是由1A晶体蛋白上调提供的，这是光感受器所特有的，而不是由公认的抗凋亡蛋白介导的，包括1B晶体蛋白、热休克蛋白27和其他热休克蛋白。值得注意的是，早期EAU的1A结晶蛋白敲除小鼠的视网膜出现明显的细胞凋亡；这种凋亡在野生型小鼠中完全不存在。这些数据揭示了1A晶体蛋白在防止视网膜细胞凋亡中的重要意义。此外，这表明与其他组织不同，光感受器选择性地利用1A晶体蛋白来预防早期EAU中氧化应激介导的损伤，这是光感受器中观察到的一种新的保护机制。基于我们的初步研究，我们假设：1)1A晶体蛋白的上调是光感受器响应线粒体氧化应激的一个特征；2) 1A晶体蛋白上调与氧化应激诱导的硝化细胞c相互作用，阻断半胱天冬酶的激活，防止光感受器凋亡。这些假设将通过三个特定目的进行验证：1)确定EAU期间视网膜1A结晶蛋白上调的免疫机制；2)确定1A晶体蛋白对EAU中光受体凋亡的预防作用；3)确定iNOS对EAU中光受体氧化应激的诱导作用。深入分析EAU中1A结晶蛋白上调的免疫机制及其保护性抗凋亡功能，将有助于我们进一步认识，阐明结晶蛋白上调不仅在葡萄膜炎中，而且在其他氧化应激介导的视网膜变性中对光感受器的保护作用。此外，目前的研究表明，1A晶体蛋白可能是一种有前途的治疗药物，可预防氧化应激介导的光感受器损伤。这种氧化损伤与各种致盲疾病有关，包括年龄相关性黄斑变性、视网膜静脉闭塞和青光眼。α结晶蛋白是存在于眼睛和其他组织中的一种独特蛋白。缺乏这种蛋白质会导致失明，补充这种蛋白质可以预防几种致盲疾病。

DESCRIPTION (provided by principal investigator): Intraocular inflammation, commonly referred to as uveitis, is a leading cause of blindness from retinal photoreceptor cell apoptosis. A robust animal model of uveitis that closely resembles human uveitis is experimental autoimmune uveoretinitis (EAU). It is characterized by two phases: the early phase, 5-7 days postimmunization (p.i.) with an uveitogenic antigen, and the late/amplification phase, 12-14 days p.i. During the late phase, macrophages/neutrophils infiltrate the retina, and photoreceptor damage is noted histologically. The early phase, preceding the leukocyte infiltration, reveals Th1- and Th17-driven cytokines in the retina, nitration of cytochrome c (cyto c) in the photoreceptors from mitochondrial oxidative stress, and the release of nitrated cyto c into the cytosol. Such cyto c release is known to cause apoptosis. However, apoptosis is not a feature of early EAU, suggesting the presence of a protective mechanism(s) in the EAU retina that prevents photoreceptor apoptosis. Current preliminary studies suggest that the protection is offered by 1A crystallin upregulation and that this is unique to the photoreceptors and are not mediated by well-recognized anti-apoptotic proteins, including 1B crystallin, heat shock protein 27 and other heat shock proteins. Significantly, 1A crystallin knockout mice with early EAU show prominent apoptosis in the retina; such apoptosis is totally absent in the wild type mice with EAU. The data reveal the significance of 1A crystallin in preventing apoptosis in the retina. Moreover, it indicates that unlike other tissues, the photoreceptors utilize 1A crystallins selectively in the prevention of oxidative stress-mediated damage in early EAU, a novel protective mechanism observed in the photoreceptors. Based on our preliminary studies we hypothesize that 1) upregulation of 1A crystallin is a feature of the photoreceptors in response to mitochondrial oxidative stress; 2) upregulated 1A crystallin interacts with the oxidative stress-induced nitrated cyto c, blocking the activation of caspases, and preventing apoptosis of photoreceptors. These hypotheses will be tested by three specific aims: 1) Determine the immune mechanism of 1A crystallin upregulation in the retina during EAU; 2) Determine prevention of photoreceptor apoptosis by 1A crystallin in EAU and 3) Determine photoreceptor oxidative stress induction by iNOS in EAU. In-depth analysis of the immune mechanism(s) of 1A crystallin upregulation in EAU and its protective anti- apoptotic function will enhance our understanding, by clarifying the importance of crystallin upregulation in photoreceptor protection not only in uveitis, but in other oxidative stress-mediated retinal degenerations as well. Moreover the current proposal suggests that 1A crystallin can be a promising therapeutic agent for preventing oxidative stress-mediated photoreceptor damage. Such oxidative damage has been implicated in various blinding diseases, including age-related macular degeneration, retinal vein occlusion, and glaucoma. PUBLIC HEALTH RELEVANCE AlphaA crystallin is a unique protein present in the eye and other tissues. Lack of this protein can cause blindness, and supplement of this protein can prevent several blinding diseases.