Fig. 6.

LysoSensor Yellow/Blue DND-160 staining of macrophages shows that enrichment of THP-1 macrophages with TG maintains and/or restores active lysosome pH. A: After 6 days in culture, untreated lysosomes maintained an active pH (pH < 4.8), as indicated by a yellow fluorescence pattern. B: After 6 days of incubation with 100 μg aggLDL protein/ml, most lysosomes displayed a predominantly blue fluorescence, indicating an increase in pH to levels above 4.8. At this pH, CE hydrolysis is inhibited. C: Macrophages treated with 100 μg VLDL protein/ml maintained a large population of active lysosomes (pH < 4.8). D: Similarly, when cells were simultaneously incubated with 100 μg aggLDL protein/ml and 100 μg VLDL protein/ml, the lysosomes maintained activity, as evidenced by predominantly yellow fluorescence. E: When macrophages were incubated with 100 μg VLDL protein/ml after the cells were first incubated with 100 μg aggLDL protein/ml, the VLDL treatment was able to restore the pH of the lysosomes back to normal levels. F: Quantification of the percentage of active (pH 4.8) vesicles following the various treatment conditions. Magnification of A–E = 500×.