Fig. 4

Co-exposure of UVB with nIR leads to early strand breaks without detectable ROS formation. (A) Alkaline comet assay quantification of strand breaks. Co-exposure (blue line) leads to initial higher levels of strand breaks. (B) FPG modified comet assay, shows that oxidized bases are not induced in co-exposed cells. Points represent the median of at least three biological replicates. The error bars represent the standard error of the mean. Lines are single exponential fit functions. (C) Detection and quantification of ROS and superoxide in UVB, nIR, and co-exposed cells. Sample images of HaCaT cells exposed to either UVB, nIR or the combination of UVB and nIR, as well as the positive and negative control. Green fluorescence indicates the ROS formation, red fluorescence the superoxide levels. (D) Quantification of ROS levels after 3 doses of UVB (360–1440 J/m², purple), 3 doses of nIR (150–600 kJ/m², green) and the combination of both (orange). (E) Similar to (D), the quantification of superoxide with the same cells. (F) Detection of single strand breaks by means of Poly-ADP-ribose (green) and single stranded DNA by means of RPA70 (red). Sample images of HaCaT cells 0.25 h post exposure to either UVB, nIR or the combination. (G) Quantification of poly-ADP-ribose up to 24 h post irradiation either after UVB, nIR or UVB + nIR exposure. (H) RPA70 intensities per nucleus analogue to G. Boxplots represent the Q1 to Q3 distribution and whiskers represent 1.5 times the IQR data from three independent replicates. In F and G, individual cell measurements are shown as dots and the resulting boxplots as described above.