Low-Dose Ionizing Radiation Affects Mesenchymal Stem Cells via Extracellular Oxidized Cell-Free DNA: A Possible Mediator of Bystander Effect and Adaptive Response

Figure 2

(a) A plasmid containing a marker GFP-gene and containing (G)n repeats that are easy to oxidate penetrates into cells treated with 10 cGy of IR (fluorescent microscopy, 40x). (b–e) Both low-dose radiation (10 cGy) and cfDNAox fragments induce a short-term increase in ROS production. (a, b) Change of DCF fluorescence in the presence of 10 μM of H2DCFH-DA. (c) (1) SSC versus FSC and FL1-DCF versus SSC plots; (2) cumulative histogram of DCF intensity distribution measured by FACS; , nonparametric U test. (d) Ratio of I(DCF) change rate in treated samples (v) to the control samples (vk) (flow cytometry). The light-grey, dark-grey, and black bars correspond to 5, 10, and 60 min time points, respectively. Data points were averaged and represented as mean ± SD for three biological replicates. , nonparametric Mann–Whitney U test. (e) Increase in ROS level measured by fluorescence microscopy 10 min after 10 cGy irradiation or addition of cfDNAox fragments (50 ng/ml); 60 min after exposure ROS returns to control level.

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