Radiation Response in Primary Murine Astrocytes

Kurzfassung

Background: Ionizing radiation, as part of space radiation, is still the limiting factor in astronautic space exploration, as it is able to induce severe cellular damage. Due to its limited regenerative potential, especially the central nervous system is very vulnerable towards radiation-induced damage. Astrocytes, as the most abundant glial cell type in the central nervous system, exhibit diverse crucial functions for neuronal survival and are in general responsible for the maintenance of the normal function of the central nervous system and were therefore chosen as focus of the investigations in this study. Methods: Primary murine astrocytes were irradiated with different doses of X-rays, used as reference radiation quality, and the radiation response was subsequently analyzed with regard to different biological endpoints. DNA damage and repair was assessed for different doses and over time with an immunofluorescence based approach and analysis via microscopy or flow cytometry. Furthermore, the cell cycle progression was investigated on the basis of the DNA content, using flow cytometry. In addition to that, also radiationinduced changes in gene expression levels were investigated by PCR. Results: Analysis of the radiation-induced DNA double strand breaks and the respective repair revealed a clear dose- and time-dependency. With higher X-ray doses the total amount of damage was observed to increase significantly, reaching a maximum at 1 h postexposure, which subsequently was found to be decreasing, mainly due to DNA damage repair and at later time points only minor fractions of residual damage remained unrepaired. Furthermore, a non-significant tendency towards upregulated gene expression of cell-cycleand inflammation-associated genes was found. Cell cycle progression was observed to be mostly unaffected, although after exposure to high X-ray doses a trend towards an increased fraction of cells in S-phase was shown. Conclusion: Astrocytes were shown to exhibit high repair capacity in response to radiation induced DNA damage and were in general observed to be relatively radio-resistant.