The effect of Derinat on UVB induced intracellular ROS production in skin cells. (A) KCs and (B) HDF were pretreated with Derinat and 0.5 mM NAC for 24 h and then irradiated with UVB. EDTA (1 mM) was applied after UVB exposure. The ROS generation was measured after 30 min of UVB irradiation by using 5 μM dihydroethidium (DHE) staining. The intracellular ROS production level with an average fluorescence intensity of more than 150 cells from (A) and (B) is quantified in (C) KCs and (D) HDF (***, p < 0.001; *, p < 0.01). To further investigate the intracellular ROS generation in (E) KCs and (F) HDF, the cells were cultured in normal medium for 24 h after UVB-exposure, and the intracellular ROS production was detected with a confocal microscope using DHE staining. The quantification of intracellular ROS production from (E,F) is shown in (G,H) (***, p <0.001).