Figure 4.

Leukotoxin causes a decrease in acidity and an increase in cathepsin D release in M1 cells. (A) Cells were treated with 10 µg/mL leukotoxin for 4 h, stained with LysoTracker Green (75 nM), and analyzed by flow cytometry. (B) M1 cells were pretreated with the cathepsin D inhibitor pepstatin A (10 µM) for 1 h and treated with various concentrations of leukotoxin for 24 h. Cell death was measured as the sum of annexin V⁺7AAD^– and annexin V⁺7AAD⁺ cells. Data are representative of 3 independent experiments, and error bars represent 1 SD. †, Value is significantly (P ≤ 0.01) different from that for untreated cells.