Elevated amyloid ¦Â production in senescent retinal pigment epithelium, a possible mechanism of subretinal deposition of amyloid ¦Â in age-related macular degeneration
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- 作者：Jiying Wang ; Kyoko Ohno-Matsui ; Ikuo Morita
- 关键词：A¦Â ; amyloid ¦Â ; APP ; amyloid precursor protein ; RPE ; retinal pigment epithelium ; AMD ; age-related macular degeneration ; AD ; Alzheimer&rsquo ; s disease ; NEP ; neprilysin ; BACE ; beta-site amyloid precursor protein cleaving enzyme
- 刊名：Biochemical and Biophysical Research Communications
- 出版年：2012
- 出版时间：22 June, 2012
- 年：2012
- 卷：423
- 期：1
- 页码：73-78
- 全文大小：307 K
文摘
Age-related macular degeneration (AMD) is the most common cause of legal blindness in the elderly individuals in developed countries. Subretinally-deposited amyloid ¦Â (A¦Â) is a main contributor of developing AMD. However, the mechanism causing A¦Â deposition in AMD eyes is unknown. Aging is the most significant risk of AMD, thus, we examined the effect of aging on subretinal A¦Â deposition. mRNAs and cell lysates were isolated from retinal pigment epithelial (RPE) cells derived from 24-month-old (24M RPE) and 2-month-old (2M RPE) C57BL/6 mice. A¦Â concentration in culture supernatants was measured by ELISA. Activity and expression of proteins that regulate A¦Â level were examined by activity assay and real time PCR. Effect of ¦Â-secretase (BACE) on A¦Â production was examined by siRNA silencing. A¦Â amounts in supernatants of 24M RPE were significantly higher than 2M RPE. Activity and mRNA levels of neprilysin, an A¦Â degrading enzyme, were significantly decreased in 24M RPE compared to 2M RPE. PCR analysis found that BACE2 was significantly more abundantly expressed than BACE1 in RPE cells, however, inactivation of BACE2 gene did not affect A¦Â production. BACE1 protein amounts did not differ between 24M and 2M RPE, however, BACE1 activity was significantly higher in 24M RPE compared to 2M RPE. There were no significant changes in the activities of ¦Á- or ¦Ã-secretase between 2M and 24M RPE. In conclusion, RPE cells produce more amounts of A¦Â when they are senescent, and this is probably caused by a decrease in A¦Â degradation due to a reduction in the expression and activity of neprilysin and an increase in A¦Â synthesis due to increased activity of BACE1.