Effect of Rpe65 knockout on accumulation of lipofuscin fluorophores in the retinal pigment epithelium.
Effect of Rpe65 knockout on accumulation of lipofuscin fluorophores in the retinal pigment epithelium.
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DOI：
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发表时间：
2001-11
影响因子：
4.4
通讯作者：
M. Katz;T Michael Redmond
中科院分区：
文献类型：
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作者：
M. Katz;T Michael Redmond
目的：迄今为止，在所有哺乳动物物种中，视网膜色素上皮（RPE）在衰老过程中积累了自身荧光溶酶体储存体（脂褐素）。大量证据表明，RPE视网膜复合体中的类维甲酸在RPE脂褐素的形成中起主要作用。事实上，至少有一种RPE脂褐素荧光团部分来源于维生素A醛。然而，类维生素a调节RPE脂褐素积累的确切机制尚未阐明。在没有功能性Rpe65基因的小鼠中，全反式到11-顺式视黄醇的异构化被阻断。进行实验以确定类视黄醇代谢的损害是否会改变RPE脂褐素的积累。方法比较12 ~ 13月龄Rpe65（+/+）、Rpe65（+/-）和Rpe65（-/-）小鼠RPE脂褐素荧光团的含量。用荧光定量法测定脂褐素荧光团的含量。用定量超微结构技术测定RPE脂褐素含量。结果在Rpe65（-/-）小鼠中，RPE脂褐素的荧光团积累几乎被消除。此外，在Rpe65（+/-）动物中还观察到脂褐素荧光团的积累显著减少。Rpe65（-/-）小鼠的RPE无法从RPE向视网膜光感受器提供11-顺式视网膜，这伴随着RPE中大量脂滴的积累，这些脂滴似乎含有大量的类视黄醇。结论：这些发现表明RPE脂褐素荧光团的形成几乎完全依赖于正常的视觉周期。Rpe65基因敲除小鼠的视网膜缺失（全反式和11-顺式）大大减少了这些动物中脂褐素荧光团的形成。即使在Rpe65基因敲除小鼠的RPE中过量积累视黄醇脂肪酸酯也不会导致脂褐素积累。
PURPOSE In all mammalian species examined to date the retinal pigment epithelium (RPE) has been found to accumulate autofluorescent lysosomal storage bodies (lipofuscin) during senescence. Substantial evidence indicates that retinoids in the RPE-retina complex play a major role in RPE lipofuscin formation. Indeed, at least one RPE lipofuscin fluorophore is derived in part from vitamin A aldehyde. However, the precise mechanisms by which retinoids modulate RPE lipofuscin accumulation have not been elucidated. In mice without a functional Rpe65 gene, isomerization of all-trans- to 11-cis-retinol is blocked. Experiments were performed to determine whether this impairment of retinoid metabolism alters RPE lipofuscin accumulation. METHODS RPE lipofuscin fluorophore content was compared in 12- to 13-month-old Rpe65(+/+), Rpe65(+/-), and Rpe65(-/-) mice. Lipofuscin fluorophore content was determined using quantitative fluorometric measurements. RPE lipofuscin content was also estimated with quantitative ultrastructural techniques. RESULTS In the Rpe65(-/-) mice, RPE lipofuscin fluorophore accumulation was almost abolished. In addition, a significantly reduced accumulation of lipofuscin fluorophores was also observed in the Rpe65(+/-) animals. The inability of the RPE of)Rpe65(-/-) mice to supply 11-cis-retinal from the RPE to the retinal photoreceptors was accompanied by a massive accumulation of lipid droplets in the RPE that appeared to contain substantial amounts of retinoids. CONCLUSIONS These findings indicate that formation of RPE lipofuscin fluorophores is almost completely dependent on a normal visual cycle. The absence of retinal (both all-trans and 11-cis) in Rpe65 knockout mice drastically reduced formation of lipofuscin fluorophores in these animals. Even an excessive accumulation of retinyl fatty acid esters in the RPE of Rpe65 knockout mice did not contribute to lipofuscin accumulation.