Synthesis of complement factor H by retinal pigment epithelial cells is down-regulated by oxidized photoreceptor outer segments
Synthesis of complement factor H by retinal pigment epithelial cells is down-regulated by oxidized photoreceptor outer segments
复制标题
DOI：
10.1016/j.exer.2006.11.015
复制
发表时间：
2007-04-01
影响因子：
3.4
通讯作者：
Xu, Heping
中科院分区：
文献类型：
--
作者：
Chen, Mei;Forrester, John V.;Xu, Heping
补体激活被认为参与年龄相关性黄斑变性（AMD）的发病机制，部分原因是补体因子H（CFH）（替代补体激活途径的重要调节剂）中的某些基因多态性是AMD的高危因素。CFH如何在视网膜/脉络膜界面局部调节以及这如何有助于AMD发展仍然未知。在本研究中，我们已经证实，CFH是可检测的免疫组织化学在脉络膜中，并在低水平的RPE细胞和interphotoreceptor矩阵，但似乎集中在密集的补丁在布鲁赫膜。在体外培养的人和小鼠RPE细胞表达高水平的CFH，免疫组化和蛋白质印迹证明。使用稳定的小鼠RPE细胞系，我们证实了RPE细胞组成型合成CFH。CFH的合成没有受到短期（2小时）感光细胞外段（POS）治疗。然而，长期（24 - 48小时）处理的RPE细胞与氧化的POS（ox-POS），而不是正常的POS（n-POS）显着下调CFH mRNA的表达。ox-POS和n-POS的吞噬作用似乎降低了RPE培养物中细胞内CFH蛋白的表达。促炎细胞因子TNF-α和IL-6也在mRNA水平上降低了培养的RPE细胞合成CFH的能力。其他测试的细胞因子，包括IFN-γ，IL-1 α和IL-4显示对CFH蛋白或mRNA水平没有影响。我们的研究结果支持这样的观点，即RPE细胞合成和表达CFH，并可能是这种蛋白质在视网膜/脉络膜界面的主要本地来源，分泌CFH到interphotoreceptor基质以及布鲁赫膜。POS的长期吞噬作用，特别是如果通过炎症中发生的氧化过程进行修饰，似乎会显著损害CFH的合成和分泌，并可能丧失抵消活化补体的促炎作用的重要调节功能。(c)2006爱思唯尔有限公司保留所有权利。
Complement activation is thought to be involved in the pathogenesis of age-related macular degeneration (AMD), in part because certain gene polymorphisms in complement factor H (CFH), an important regulator of the alternative complement activation pathway, are high risk factors for AMD. How CFH is regulated locally at the retina/choroid interface and how this contributes to AMD development remain unknown. In the present study, we have confirmed that CFH was detectable by immunohistochemistry in the choroid, and at low levels in the RPE cell and interphotoreceptor matrix, but appeared to be concentrated in dense patches in Bruch's membrane. In vitro, cultured human and mouse RPE cells expressed high levels of CFH as evidenced by immunohistochemistry and western blot. Using a stabilized mouse RPE cell line, we confirmed that RPE cells constitutively synthesise CFH. Synthesis of CFH was not affected by a short-term (2 h) photoreceptor outer segment (POS) treatment. However, long-term (24-48 h) treatment of RPE cells with oxidised POS (ox-POS) but not normal POS (n-POS) markedly down-regulated CFH mRNA expression. Phagocytosis of both ox-POS and n-POS appeared to reduce intracellular CFH protein expression in RPE cultures. Synthesis of CFH by cultured RPE cells was also reduced at the mRNA level by the proinflammatory cytokines TNF-alpha and IL-6. Other cytokines tested including IFN-gamma, IL-1 alpha and IL-4 showed no effect on either CFH protein or mRNA levels. Our results support the view that RPE cells synthesise and express CFH and are probably a major local source of this protein at the retina/choroid interface, secreting CFH into the interphotoreceptor matrix as well as Bruch's membrane. Prolonged phagocytosis of POS, particularly if modified by oxidative processes as occurs in inflammation, appears to markedly impair synthesis and secretion of CFH, with potential loss of important regulatory functions in counteracting the pro-inflammatory effects of activated complement. (c) 2006 Elsevier Ltd. All rights reserved.