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S. Wasmuth, M. Hennig, K. Lück, M. Zeimer, G. Spital, A. Lommatzsch, D. Pauleikhoff; Retinal Pigment Epithelial Cells are Impaired by Complement. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5153.
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Age-related macular degeneration (AMD) is a common cause of blindness in the elderly. During the development of the disease photoreceptor cells and retinal pigment epithelial (RPE) cells are damaged. Operative deficiencies in complement factor H, an inhibitor of the complement cascade, and an increased risk for AMD were recently confirmed. Consequently in this study the direct effects of complement on RPE cells were investigated.
ARPE-19 cells as a human RPE cell line were cultured and were challenged with different concentrations of complement. Lipopolysaccharide (LPS) activated RPE cells were used as a positive control. Immunohistochemistry staining was performed to study the expression of vitronectin and the formation of C5b-9 (terminal complement complex or membrane attack complex) on the cells. The viability of the cells was measured by MTT assay, the proliferation was assayed by the uptake of radioactive 3H thymidine. The cell culture supernatants were quantified for their IL-6 content by sandwich ELISA. All tests were performed in serum-containing media and under serum-deprived conditions.
LPS treated cells stained neither positively for C5b-9 nor for vitronectin. In contrast, both were detected after the addition of complement in a concentration-dependent manner. Complement exposure reduced viability and proliferation of ARPE-19 cells, while LPS induced only minor effects. Enhanced quantities of secreted IL-6 were found after complement as well as LPS treatment. The observed effects were more exceeded in serum free medium.
Decreased viability and proliferation, and the formation of C5b-9 on ARPE-19 cells indicate deleterious effects of activated complement. A higher secretion of proinflammatory IL-6 by ARPE-19 cells was measured by both complement and LPS addition thus indicating an activated phenotype of the cells. On the other hand the evidence of vitronectin was a complement-specific consequence. Taken together during the development of AMD complement activation can harm RPE cells and might contribute to the thickening of Bruch's membrane by the production of extracellular matrix components.
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