Nox4 was involved in Dex-induced ROS production. (A) MC3T3-E1 cells were treated with Dex for 24 h with or without a 30-min pre-treatment with the following inhibitors: NAC (10 mM), DPI (10 μM), apocynin (100 μM), rotenone (10 μM), allopurinol (100 μM) or plumbagin (10 μM). Representative images for cells loaded with DCFH-DA (5 μmol/L) was captured with a fluorescence microscopy. (B) Quantitative analysis of DCF fluorescence intensity in (A). (C) The cells were transfected with Nox4 siRNA for different concentrations (5, 10, 20, 80 nM) or negative siRNA (Negative) for 24 h. The efficiencies of siRNA were detected by western blot. (D) MC3T3-E1 cells were transiently transfected with Nox4 siRNA (20 nM) for 24 h, and then treated with Dex for another 24 h. Intracellular ROS was detected by DCFH-DA fluorescent dye. (E) Quantitative analysis of DCF fluorescence intensity in (D). Data were presented asmean ± SEM. **P<0.01 vs. control; ##P<0.01 vs. Dex treatment alone, n=4.