Abstract
Long term manned space missions are planned to implement within the first two decades of the 21st century. A mission of International Space Station (ISS) is in progress, and a plan to explore Moon as well as to visit the Mars is also underway. In space field, the plan will allow space man to live for long terms to do experiments to examine various space sciences. In space environment, 0.2~0.3 mSv a day of radiation exposure will affect cellular metabolisms. As such missions will inevitably result in a significant space radiation exposure on the astronauts, there is an increasing demand to examine their risk. Evaluation of realistic risk associated with the space mission will be in urgent demand to protect them adequately based on both physical and biological knowledge. Considering cellular metabolisms or homeostasis, which affect their risk, examinations of gene expression change would be important. In this study, a human neuron-like cell line, NB-1 was irradiated with 0.1 mGy, 1.0 mGy, 10 mGy, and 100 mGy in single exposure. Thirty minutes and 2 hours after the treatments, mRNA was isolated from the cells and gene expressions were studied with Quantitative RT-PCR analysis. The results showed that the both up- and downregulated gene expressions were seen among mitochondrial genome, electron transport and TCA cycle genes. On the other hand, beta-oxidation, ion transport, antioxidative enzymes and factors related gene expressions were downregulated. DNA repair, glycolysis, heat shock protein, and apoptosis related gene expressions were also downregulated except for some genes such as p53. The autophagy related gene, and necrosis related gene expressions were also downregulated. These results suggest that the space low-dose irradiation induce intracellular oxidative stress, and may decrease at least partial apoptosis-related gene expression changes, i.e., may increase potential risk of cancer or neuro-degenerative diseases.
