Effects of concentration of amyloid β (Aβ) on viability of cultured retinal pigment epithelial cells.
BACKGROUND
Amyloid beta (Aβ) is a constituent of drusen that is a common sign of age-related macular degeneration (AMD). The purpose of this study was to investigate the effect of Aβ on human retinal pigment epithelial (RPE) cells in culture.


METHODS
Cells from a human RPE cell line (ARPE-19) were exposed to 0 to 25 μM of Aβ 1-40 for 48 h, and the number of living cells was determined by WST-8 cleavage. Replicative DNA synthesis was measured by the incorporation of 5'-bromo-2'-deoxyuridine. The cell death pathway was investigated by the WST-8 cleavage assay after the addition of caspase-9 inhibitor, an anti-apoptotic factor. Real-time qRT-PCR was performed using Aβ-exposed cellular RNA to determine the level of vascular endothelial growth factor (VEGF)-A and pigment epithelium derived factor (PEDF). To determine the effect of receptor-for-advanced glycation end products (RAGE), the siRNA for RAGE was inserted into ARPE-19 treated with Aβ, and the levels of expression of VEGF-A and PEDF were determined.


RESULTS
The number of living ARPE-19 cells was increased by exposure to 5 μM Aβ but was decreased by exposure to 25 μM of Aβ. Replicative DNA synthesis by ARPE-19 cells exposed to 25 μM of Aβ was significantly decreased indicating that 25 μM of Aβ inhibited cell proliferation. Real-time RT-PCR showed that the level of the mRNA of PEDF was increased by exposure to 5 μM Aβ, and the levels of the mRNAs of PEDF and VEGF-A were also increased by exposure to 25 μM Aβ. The addition of an inhibitor of caspase-9 blocked the decrease the number of ARPE-19 cells exposed to 25 μM Aβ. Exposure to si-RAGE attenuated the increase of VEGF-A and PEDF mRNA expression in ARPE-19 exposed to Aβ.


CONCLUSIONS
Exposure of ARPE-19 cells to low concentrations of Aβ increases the level of PEDF which then inhibits the apoptosis of ARPE-19 cells leading to RPE cell proliferation. Exposure to high concentrations of Aβ induces RPE cell death and enhances the expression of the mRNA of VEGF-A in RPE cells. The Aβ-RAGE pathway may lead to the expression VEGF-A and PEDF in RPE cells. These results suggest that Aβ is strongly related to the pathogenesis of choroidal neovascularization.
['Masuda|Naonori|N|', 'Tsujinaka|Hiroki|H|', 'Hirai|Hiromasa|H|', 'Yamashita|Mariko|M|', 'Ueda|Tetsuo|T|', 'Ogata|Nahoko|N|']
D016229:Amyloid beta-Peptides D016923:Cell Death D002478:Cells, Cultured D004305:Dose-Response Relationship, Drug D004847:Epithelial Cells D005136:Eye Proteins D006801:Humans D009414:Nerve Growth Factors D000067759:Receptor for Advanced Glycation End Products D055213:Retinal Pigment Epithelium D015843:Serpins D042461:Vascular Endothelial Growth Factor A
Retinal pigment epithelial cells Amyloid beta Age-related macular degeneration Vascular endothelial growth factor Pigment epithelium-derived factor Receptor for advanced glycation end products