X-ray-induced chromosome aberrations in human lymphocytes in vitro are potentiated under simulated microgravity conditions (Clinostat).

The influence of simulated microgravity weightlessness on the outcome of radiation-induced chromosomal aberrations was investigated using the clinostat as a tool to simulate weightlessness conditions. Treatments were performed in the G0 phase of human lymphocytes with 1.5 Gy of X-rays alone or in combination with the DNA synthesis inhibitor of 1-beta-D-arabinofuranosylcytosine (ara-C) to check also for possible specific radiation-induced DNA repair processes impairment (excision repair caused by base damage) under microgravity conditions. The results obtained, which confirmed previous findings, showed significantly higher increases of aberrant cells and hence total number of aberrations compared to the parallel treatments performed 'on ground'. For what concern ara-C its contribution in terms of potentiation in the induction of aberrant cells was equivalent in absolute terms under simulated microgravity conditions and 'on ground' indicating that excision repair caused by base damage and inhibited by ara-C is not affected by simulated microgravity. A possible explanation for this outcome could quote two major factors: i) Enhanced probability that under simulated microgravity conditions the reactive DSB are spatially brought together to better interact, hence increasing the probability of mis-rejoining. ii) Alternatively chromatin structure could be modified under simulated microgravity conditions generating different quality and quantities of DNA lesions compared to treatments performed 'on ground'.