Abstract
Purpose:
Age-related macular degeneration (AMD) is caused by degeneration of the retinal pigment epithelium (RPE). This leads to loss of photoreceptor cells in dry AMD and choroidal neovascularization in wet AMD. A hallmark of human AMD is the accumulation of extracellular drusen waste products, such as oligomeric amyloid-beta (OAβ), between the RPE and Bruch's membrane. In a human RPE cell line (ARPE-19), OAβ disrupts tight junctions, but does not induce cell death. However, in human neuroblastoma cells (SH-SY5Y), OAβ increases intracellular Ca2+, which is known to induce apoptosis and cell death. The purpose of present study was to determine if OAβ in cultured monkey RPE cells increases intracellular Ca2+ and cell death.
Methods:
Monkey RPE cells were isolated and cultured with 10, 20, or 30 μM OAβ. Formation of OAβ peptide1-42 containing the critical C-terminal residues was detected by immunoblotting. Intracellular calcium imaging was performed by laser scanning confocal microscopy. RPE cell death was measured by the TUNEL assay and by staining with propidium iodide (PI).
Results:
Intracellular Ca2+ levels were increased in RPE cells cultured for 24 hrs with 30 μM OAβ. After 3 days, TUNEL-positive cells were observed. Some TUNEL-positive cells were also PI-positive, suggesting late-stage of apoptosis.
Conclusions:
OAβ induces late-onset apoptosis in monkey PRE cells. Increased intracellular Ca2+ may induce such apoptosis. This late-onset monkey cell model may be a relevant and useful aid for further studies on the role of intracellular Ca2+ in OAβ-induced cell death in AMD.