Figure 1.
Induction of ROS production by HP-NAP in ATRA-induced differentiated HL-60 cells but not in DMSO-induced differentiated HL-60 cells. (A) Effect of HP-NAP on ROS production in undifferentiated and ATRA- and DMSO-induced differentiated HL-60 cells. HL-60 cells were treated with 1 μM ATRA or 1.25% DMSO for 4 days to induce the differentiation. Undifferentiated HL-60 cells and differentiated HL-60 (dHL-60) cells at a density of 1 × 106 cells/mL were stimulated with 1 μM HP-NAP, D-PBS, pH 7.2, as the unstimulated control, 0.32 μM PMA, or DMSO as the vehicle control for PMA, at 37 °C for 30 min. ROS produced by these cells were measured by NBT reduction assay as described in Materials and Methods and expressed as percentage of NBT-positive cells. Data are expressed as mean ± SD of at least three independent experiments. (B) Dose-response effect of HP-NAP on ROS production by ATRA-induced differentiated HL-60 cells. ATRA-induced differentiated HL-60 cells at a density of 1 × 106 cells/mL were stimulated with the indicated concentrations of HP-NAP in the range of 0.25 μM to 1.5 μM or 1 μM fMLP as a positive control at 37 °C for 30 min. ROS production was determined by NBT reduction assay as described in A. Data are expressed as mean ± SD of six independent experiments. *: p value < 0.05, **: p value < 0.01, ***: p value < 0.001 as compared with the unstimulated control for HP-NAP-stimulated cells or the vehicle control for PMA-stimulated cells.