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

Figure 11

Proposed mechanisms for the development of radioadaptive responses and bystander effect. Irradiation induces primary oxidative stress and oxidation of genomic DNA → apoptosis of some irradiated cells → release of oxidized cfDNAoxR → reactive oxygen species (ROS) production → ROS induces oxidative modifications of nuclear DNA, rapidly repaired DNA breaks, short-term arrest of the cell cycle → activation of DNA reparation systems and antioxidant response → inhibition of apoptosis. Thus, we conclude that cfDNAox that appears after irradiation is a signaling molecule in the stress signaling that mediates radiation-induced bystander effects.