Prevention of Retinal Degeneration by Crystallins in Experimental Uveitis

描述(由主要研究人员提供)：眼内炎症，通常被称为葡萄膜炎，是视网膜光感受器细胞凋亡导致失明的主要原因。一种与人类葡萄膜炎非常相似的葡萄膜炎动物模型是实验性自身免疫性葡萄膜视网膜炎(EAU)。免疫早期，免疫后5-7天(P.I.)葡萄膜抗原，晚期/扩增阶段，12-14天P.I.在晚期，巨噬细胞/中性粒细胞渗入视网膜，组织学发现光感受器受损。早期阶段，在白细胞渗透之前，视网膜中由Th1和Th17驱动的细胞因子，光感受器中的细胞色素c(Cyto C)因线粒体氧化应激而硝化，硝化的Cyto c释放到胞浆中。已知这种细胞c的释放会导致细胞凋亡。然而，细胞凋亡不是早期EAU的一个特征，这表明EAU视网膜中存在一种保护机制(S)，该机制阻止光感受器凋亡。目前的初步研究表明，这种保护是由1A晶状体蛋白上调提供的，这是光感受器所独有的，并不是由公认的抗凋亡蛋白介导的，包括1B晶状体蛋白、热休克蛋白27和其他热休克蛋白。值得注意的是，早期EAU的晶体蛋白基因敲除小鼠视网膜中有显著的细胞凋亡；而野生型EAU小鼠中完全没有这种细胞凋亡。这些数据揭示了1A晶状体蛋白在防止视网膜细胞凋亡中的意义。此外，它还表明，与其他组织不同，光感受器在EAU早期选择性地利用1A晶体蛋白来防止氧化应激介导的损伤，这是在光感受器中观察到的一种新的保护机制。根据我们的初步研究，我们假设：1)上调1A晶体蛋白是光感受器对线粒体氧化应激的反应的特征；2)上调的1A晶体蛋白与氧化应激诱导的硝化细胞色素c相互作用，阻断caspase的激活，阻止光感受器的凋亡。这些假说将通过三个特定的目标得到验证：1)确定EAU过程中1A晶体蛋白在视网膜中上调的免疫机制；2)确定EAU中1A晶体蛋白对光感受器细胞凋亡的预防作用；3)确定iNOS在EAU中诱导光感受器氧化应激。深入分析1A晶状体蛋白在EAU中上调的免疫机制(S)及其保护性的抗凋亡功能将加深我们的理解，阐明晶状体蛋白上调不仅在葡萄膜炎中的光感受器保护中的重要性，而且在其他氧化应激介导的视网膜变性中也是如此。此外，目前的提议表明，1A晶体蛋白可能是一种很有前途的治疗药物，可以防止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，包括老年性黄斑变性、视网膜静脉阻塞和青光眼。与公共健康相关的AlphaA晶体蛋白是一种存在于眼睛和其他组织中的独特蛋白质。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.