Abstract
BackgroundAmyloid 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.MethodsCells 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.ResultsThe 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.ConclusionsExposure 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.
Highlights
Amyloid beta (Aβ) is a constituent of drusen that is a common sign of age-related macular degeneration (AMD)
The adult RPE (ARPE)-19 cells were incubated for 48 h with different concentrations of Aβ 1–40, and the number of living cells were determined by the WST8 assay
Because receptor-for-advanced glycation end products (RAGE) is expressed on the surface of retinal pigment epithelial (RPE) cells and is increased under AMD conditions, we examined whether the Aβ-RAGE pathway is involved in the development of neovascular macular diseases with the expression of some cytokines
Summary
Amyloid beta (Aβ) is a constituent of drusen that is a common sign of age-related macular degeneration (AMD). Age-related macular degeneration (AMD) is a progressive eye disorder that can proceed to irreversible blindness [1]. Yellowish-white protuberant lesions seen in the fundus ophthalmoscopically and are considered to be the initial change in eyes with AMD. In spite of the well-known relationship between drusen and AMD, there are still some unanswered questions, e.g., how drusen form and how drusen interact with the RPE and photoreceptor cells. It was recently reported that amyloid beta (Aβ), a peptide associated with the neurodegenerative events in Alzheimer’s disease, is an important constituent of drusen [3]. Aβ is a toxic protein that affects nerve cells and is associated with many neurodegenerative disorders [4]
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