The LISA Pathfinder Mission
- Paper number
IAC-04-Q.4.06
- Author
Mr. Giuseppe D. Racca, European Space Agency (ESA)/ESTEC, The Netherlands
- Year
2004
- Abstract
Ionizing space radiation poses a dangerous risk for astronauts on deep space mission due the potential of accumulating high dose exposure levels. There is a definite need for research investigating the biological effects of chronic radiation exposures. Ionizing radiation leads to oxidative stress in biological organisms. Oxidative stress is believed to be a culprit for cellular death, DNA damage, and possibly cancer induction. However, low levels of oxidative stress have been shown to also be an induction mechanism for a beneficial radioadaptive response. We speculated that oxidative stress produced by repeated low dose diagnostic CT scans (10 mGy/scan, 2d/wk, 10 wk) could protect mice (C57BL/6) from detrimental effects of high dose radiation (1Gy, 2Gy). We also postulated that additional oxidative stress produced by exercise (12 metres/min for 1hr, 3d/wk, 10wk) could further enhance the adaptive response.
Using flow cytometry, DNA double strand break (DSB) levels (assessed by γH2AX foci formation) and genomic damage to stem cells were examined to evaluate the damage induced or prevented by CT scans and exercise. Following a challenge dose (1 Gy) in vitro, cells from CT-only and exercise-only mice had a significant decrease (14%) in DNA DSBs compared to control mice (p<0.035). A higher 2 Gy challenge dose further showed a significant reduction (16%) in DNA DSBs in CT-only and exercise-only mice compared to controls (p=0.002). When genomic damage was assessed via mirconucleated reticulocyte production, mice that exercised and mice that had repeated CT scans did not have higher genomic damage compared to controls (p=0.963). Interestingly, mice with both CT+exercise treatment had significantly lower spontaneous levels of genomic damage than control mice (p<0.028). After an in vivo 2 Gy challenge dose, control mice and CT-only mice had similar high levels of genomic damage, but there was a significant genomic damage reduction in the exercise-only (6%) and CT+exercise (14%) mice (p<0.025).
This research suggests that oxidative stress induced by repeated CT scans and exercise can adapt cells to withstand high dose exposure to ionizing radiation. Furthermore, when CT scans and exercise treatment are combined, the adaptive effects appear to be additive, if not synergistic. With respect to the aerospace industry, our results indicate that routine CT scans and rigorous physical activity can significantly protect astronauts from the adverse biological effects of high dose radiation that accumulates during deep space missions.
- Abstract document