Figure 5. Alkalinization of ARPE-19 lysosomes by chronic treatment with A2E. A: Bafilomycin-A1 (BfA; 500 nM) and chloroquine (CQ; 1 and 100 µM) positive controls caused a large increase in lysosome pH from approximately 1 pH unit to approximately 2.6 pH units. B: Chronic treatment of ARPE-19 cells with A2E led to a moderate increase in lysosomal pH. Lysosomal pH was measured using LysoSensor DND160 calibrated against the control cells treated with KCl buffered at values from pH 4.4 to 6.0 in the presence of monensin and nigericin. n = 3 for each experimental condition.