Figure 5. Cholesterol crystals (CHCs) cause destabilization of lysosomes and leakage of cathepsin B into the cytoplasm.

CHC-treated or untreated live THP-1 macrophages were stained with cathepsin B substrate z-Arg-Arg-cresyl violet (panels i, iii) or with acridine orange (panels ii, iiii). The fluorescent cresyl violet group of z-Arg-Arg-cresyl violet is dequenched upon cleavage of one or both of the arginines by cathepsin B. Acridine orange aggregates in the acidic pH of lysosomes, which changes the fluorescence emission of the dye from green to red. The images are representative of 3 experiments.