Background/Aims: CpG-oligodeoxynucleotides (ODNs) are synthetic DNA sequences containing unmethylated cytosine-guanine motifs with potent immunomodulatory effects. Previous reports showed a powerful protective effect of CpG-ODN against the damage induced by low-LET γ-rays. In this study, we explored whether CpG-ODN also protects against the damage induced by high-LET irradiation. Parallel experiments were performed with low-LET irradiation. Methods: RAW264.7 cells were incubated with 1 μM of CpG-ODN after γ-ray or carbon-beam irradiation. Cell death was then measured by PI/DAPI double staining, cell survival was assessed by colony-formation assays, DNA damage was evaluated by comet assays, cell cycle was monitored by flow cytometry, and the levels of apoptosis-related proteins were detected by western blots. Results: When irradiated cells were treated with the CpG-ODN, cell viability decreased, cell survival increased, DNA damage and G₂/M-phase arrest were ameliorated, and apoptosis was inhibited. Conclusions: The CpG-ODN showed protective effects against low-LET γ-ray and high-LET carbon-beam irradiation. These effects might be associated with the repair of DNA damage and inhibition of apoptosis.

Background: Heavy ion radiation constitutes a major health risk for astronaut in space flight, potential damage to healthy tissues surrounding the tumor target along its penetrating path should still be considered in hydrotherapy. Therefore, there is a demand for reliable countermeasure against heavy ions radiation. In this study, we will estimate the radiomitigative effect of CpG-ODN on immune tissues after carbon ions radiation (CIR). Methods: Firstly, the 30 days’ survival of mice was observed, peripheral blood cell was counted, the injury of three principal immune tissues (including bone marrow, thymus and spleen) was evaluated by histological examination, apoptosis and double strand breaks (DSB) were detected by TUNEL staining and γ-H2AX immunohistochemistry respectively, and cytokine (G-CSF, IL-6 and TNF-α) was measured by ELISA assay. Results: the 30 days’ survival improved, the injury of three principal immune tissues were obviously ameliorated, the number of γ-H2AX foci and TUNEL-positive nuclei decreased, and G-CSF, IL-6 and TNF-α expression increased by CpG-ODN treatment after CIR. Conclusion: CpG-ODN could enhanced mice survival, and ameliorate immune tissues injury, the mechanism may be that CpG-ODN induced cytokines production and inhibited the double strand breaks (DSB) and apoptosis in order to stimulate the generation and mobilization of the immune cells and reestablish immune system to combat bacterial infections.