Figure 4. Simvastatin induced oxidative stress. (A) The ROS level showed effects in MDA-MB-231 cells with simvastatin or DMSO treatment for 24h as determined by fluorescence intensity of DCFH-DA (ROS probe). (B) simvastatin induced ROS elevation accompanied by a continuous decline of GSH/GSSG ratio in MDA-MB-231 cells within 24 hours. (C) The effect of simvastatin and NAC on NRF1 expression as detected by qPCR and western blot. (D) DNA oxidative damage marker 8-OH-dG was measured by ICC/IF in MDA-MB-231 cells treated with simvastatin(1-5µM) for 24h. The p-values were calculated using standard Student t-tests. Error bars represent mean±SEM of three individual experiments. *** P ≤ 0.001, ** P ≤ 0.01.