The effect of genetic background and dose on non-targeted effects of radiation

Purpose: This work investigates the hypothesis that genetic background plays a significant role in the signalling mechanisms underlying induction and perpetuation of genomic instability following radiation exposure. Materials and methods: Bone marrow from two strains of mice (CBA and C57) were exposed to a range of X-ray doses (0, 0.01, 0.1, 1 and 3 Gy). Different cellular signalling endpoints: Apoptosis, cytokine levels and calcium flux, were evaluated at 2 h, 24 h and 7 d post-irradiation to assess immediate and delayed effects. Results: In CBA (radiosensitive) elevated apoptosis levels were observed at 24 h post X-irradiation, and transforming growth factor-β (TGF-β) levels which increased with time and dose. C57 showed a higher background level of apoptosis, and sustained apoptotic levels 7 days after radiation exposure. Levels of tumor necrosis factor-α (TNF-α were increased in C57 at day 7 for higher X-ray doses. TGF-β levels were higher in CBA, whilst C57 exhibited a greater TNF-α response. Calcium flux was induced in reporter cells on exposure to conditioned media from both strains. Conclusions: These results show genetic and dose specific differences in radiation-induced signalling in the initiation and perpetuation of the instability process, which have potential implications on evaluation of non-targeted effects in radiation risk assessment.