FIGURE 6.

Viability of retinoid-laden ARPE19 and HEK293 cells. A, retinoid-laden ARPE19 cells were produced by the published methods (34, 35) with modifications. Cells were incubated for 16 h at 37 °C with a 30 μm concentration of the indicated retinoids followed by 3 days of incubation with medium alone. Cells then were either exposed or not exposed to blue light (440 nm; X-Cite120 Fluorescence illumination system with 440-nm filters) for 5 min, and MTT assays were performed after 16 h of additional incubation in the dark. Some blue light-dependent cell death was observed with A2E-loaded cells, whereas nearly all cells loaded with either 9-cis-retinal (9cRAL) or all-trans-retinal (atRAL) died whether or not they were exposed to light. Means ± S.E. are shown (n > 3). B, A2E, all-trans-retinal dimer (RALdi), and oxidized RALdi-laden HEK293 cells (human renal epithelial cells) and ARPE19 cells (human RPE cells) were produced by a 16-h incubation with a 30 μm concentration of the indicated retinoids followed by a 3-day incubation with fresh medium. 9-cis-Retinal and all-trans-retinal were added to the medium just before cells were either exposed or not exposed to blue light (440 nm) for 5 min and then analyzed by MTT assays. Strong cytotoxicity was evidenced by 9-cis-retinal- and all-trans-retinal-laden HEK293 cells independent of light exposure (left). Blue light-dependent cell death was noted in all-trans-retinal dimer-loaded ARPE19 cells (right). Means ± S.E. are shown (n > 5).