Novel derivatives of vitamin D3 and lumisterol reduce oxidant formation in UVB-irradiated keratinocytes. Keratinocytes were pretreated with the indicated vitamin D3 and lumisterol hydroxy-derivatives for 24 h prior to UV irradiation (50 mJ/cm2). The irradiated cells were further incubated for an additional 4 h with the hydroxy-derivatives or ethanol vehicle, while non-irradiated cells were treated with the ethanol vehicle (comparison presented as insert, top right). Oxidant formation was examined using the DCFDA reagent at 4 h post UVB irradiation. Data are presented as the percentage of the control (mean ± SD). The statistical significance of differences was evaluated by one-way ANOVA, * P < 0.05, ** P < 0.01, *** P < 0.001 for all conditions.