Age-Related Susceptibility to Apoptosis in Human Retinal Pigment Epithelial Cells Is Triggered by Disruption of p53-Mdm2 Association
Age-Related Susceptibility to Apoptosis in Human Retinal Pigment Epithelial Cells Is Triggered by Disruption of p53-Mdm2 Association
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DOI：
10.1167/iovs.12-10495
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发表时间：
2012-12-01
影响因子：
4.4
通讯作者：
Johnson, Leonard R.
中科院分区：
文献类型：
--
作者：
Bhattacharya, Sujoy;Chaum, Edward;Johnson, Leonard R.
目的。关于p53/Mdm2通路在视网膜色素上皮（RPE）细胞凋亡中的作用，或其与衰老RPE功能障碍或相关致盲疾病（如年龄相关性黄斑变性（AMD））的可能联系，我们知之甚少。在来自不同年龄的人供体眼睛的RPE培养物中评估了p53激活的年龄相关变化。凋亡通过半胱天冬酶的激活和DNA断裂来评估。使用基因特异性小干扰RNA敲低p53的表达。我们观察到p53依赖性细胞凋亡的基础率在人类RPE中以年龄依赖的方式增加。细胞凋亡的年龄依赖性增加与p53通路的几个方面的改变有关。通过刺激ATM-Ser1981， p53磷酸化Ser15增加。p53乙酰化Lys379通过抑制SIRT1/2而增加。这两种p53的翻译后修饰阻断了Mdm2对p53的隔离，从而通过增加PUMA （p53上调的凋亡调节剂）的表达和激活caspase-3，导致游离p53和p53刺激凋亡的增加。衰老的RPE细胞抗凋亡Bcl-2表达降低，导致细胞凋亡增加。这些研究中特别有趣的是，阻断p53磷酸化、乙酰化或表达的药物治疗能够保护RPE细胞免于凋亡。我们的研究表明，RPE中的衰老导致凋亡通路中特定检查点的改变，这可能是治疗RPE相关衰老疾病（如AMD）的重要分子靶点。（Invest Ophthalmol Vis Sci. 2012;53:8350-8366） DOI:10.1167/iovs.12-10495
PURPOSE. Relatively little is known about the contribution of p53/Mdm2 pathway in apoptosis of retinal pigment epithelial (RPE) cells or its possible link to dysfunction of aging RPE or to related blinding disorders such as age-related macular degeneration (AMD).METHODS. Age-associated changes in p53 activation were evaluated in primary RPE cultures from human donor eyes of various ages. Apoptosis was evaluated by activation of caspases and DNA fragmentation. Gene-specific small interfering RNA was used to knock down expression of p53.RESULTS. We observed that the basal rate of p53-dependent apoptosis increased in an age-dependent manner in human RPE. The age-dependent increase in apoptosis was linked to alterations in several aspects of the p53 pathway. p53 phosphorylation Ser15 was increased through the stimulation of ATM-Ser1981. p53 acetylation Lys379 was increased through the inhibition of SIRT1/2. These two posttranslational modifications of p53 blocked the sequestration of p53 by Mdm2, thus resulting in an increase in free p53 and of p53 stimulation of apoptosis through increased expression of PUMA (p53 upregulated modulator of apoptosis) and activation of caspase-3. Aged RPE also had reduced expression of antiapoptotic Bcl-2, which contributed to the increase in apoptosis. Of particular interest in these studies was that pharmacologic treatments to block p53 phosphorylation, acetylation, or expression were able to protect RPE cells from apoptosis.CONCLUSIONS. Our studies suggest that aging in the RPE leads to alterations of specific checkpoints in the apoptotic pathway, which may represent important molecular targets for the treatment of RPE-related aging disorders such as AMD. (Invest Ophthalmol Vis Sci. 2012;53:8350-8366) DOI:10.1167/iovs.12-10495