The Response of Mouse Microglia Cells SIM-A9 to γ-Radiation

Purpose: Characterization of the response of mouse microglia cells of the SIM-A9 line to the γ-irradiation. Material and methods: Irradiation of the cells in suspension was carried out using a GUT-200M installation (cobalt-60 γ-radiation source). The radiosensitivity of cells was assessed by the number of surviving cells and their clonogenic activity. The effect of γ-radiation on the phenotype and expression of colony-stimulating growth factor receptor-1 and of epidermal growth factor, which are required to stimulate microglial cells proliferation, was studied using flow cytometry after staining the cells with appropriate fluorescently labeled CD11b, CD45, TMEM119, CSF-1R и EGFR antibodies. Analysis of the relative expression of mRNA genes for the cytokines IL-1β, IL-6, and TNFα in response to γ-radiation was performed using RT-PCR. Statistical analysis was carried out using Student’s t-test in the Origin program. Results: High radiosensitivity of SIM-A9 cells has been demonstrated. When analyzing the dependence of the clonogenic activity of cells on the radiation dose, it was shown that the D37 value for these cells was equal to 1 Gy. Irradiation caused a cell cycle block in the G0/G1 phase with a decrease in the proportion of cells in the S– and G2/M-phases. The cell death of irradiated SIM-A9 cells occurred by apoptosis. The peculiarity of SIM-A9 cells compared to brain microglia is their phenotype of activated microglia CD11b+/CD45high with an insignificant content of CD11b+/CD45-/low cells and no change in it after irradiation. An increase in the level of mRNA expression of the proinflammatory cytokine genes IL-1β, IL-6 and TNFα in response to γ-irradiation of SIM-A9 cells was shown, which reflects their activation and corresponds to the response of brain microglia cells during total mice irradiation and local cranial irradiation. Conclusion: The obtained patterns indicate the possibility of using the SIM-A cell line in model radiobiological studies, including the study of intercellular interactions of brain cells of different types with microglia cells.