NASA Johnson Space Center, Houston, TX, USA; University of Houston Clear Lake, Houston, TX, USA.
NASA Kennedy Space Center, Cape Canaveral, FL, USA.
Life Sci Space Res (Amst). 2017 Feb;12:24-31. doi: 10.1016/j.lssr.2016.12.004. Epub 2016 Dec 24.
Although charged particles in space have been detected with radiation detectors on board spacecraft since the discovery of the Van Allen Belts, reports on the effects of direct exposure to space radiation in biological systems have been limited. Measurement of biological effects of space radiation is challenging due to the low dose and low dose rate nature of the radiation environment, and due to the difficulty in distinguishing the radiation effects from microgravity and other space environmental factors. In astronauts, only a few changes, such as increased chromosome aberrations in their lymphocytes and early onset of cataracts, are attributed primarily to their exposure to space radiation. In this study, cultured human fibroblasts were flown on the International Space Station (ISS). Cells were kept at 37°C in space for 14 days before being fixed for analysis of DNA damage with the γ-H2AX assay. The 3-dimensional γ-H2AX foci were captured with a laser confocal microscope. Quantitative analysis revealed several foci that were larger and displayed a track pattern only in the Day 14 flight samples. To confirm that the foci data from the flight study was actually induced from space radiation exposure, cultured human fibroblasts were exposed to low dose rate γ rays at 37°C. Cells exposed to chronic γ rays showed similar foci size distribution in comparison to the non-exposed controls. The cells were also exposed to low- and high-LET protons, and high-LET Fe ions on the ground. Our results suggest that in G1 human fibroblasts under the normal culture condition, only a small fraction of large size foci can be attributed to high-LET radiation in space.
尽管自发现范艾伦带以来，航天器上的辐射探测器已经探测到太空中的带电粒子，但关于生物系统直接暴露于空间辐射的影响的报告一直有限。由于辐射环境的剂量低、剂量率低，以及难以将辐射效应与微重力和其他空间环境因素区分开来，因此测量空间辐射的生物效应具有挑战性。在宇航员中，只有少数变化，如淋巴细胞染色体畸变增加和白内障早期发病，主要归因于他们暴露于空间辐射。在这项研究中，培养的人类成纤维细胞在国际空间站（ISS）上飞行。细胞在太空中保持 37°C 14 天，然后固定，用 γ-H2AX 测定法分析 DNA 损伤。用激光共聚焦显微镜捕获 3 维 γ-H2AX 焦点。定量分析显示，仅在第 14 天飞行样本中，有几个焦点更大，并呈现出轨道模式。为了确认飞行研究中的焦点数据实际上是由空间辐射暴露引起的，培养的人类成纤维细胞在 37°C 下接受低剂量率γ射线照射。与未暴露的对照相比，暴露于慢性γ射线的细胞显示出相似的焦点大小分布。这些细胞还在地面上暴露于低和高 LET 质子和高 LET Fe 离子下。我们的结果表明，在 G1 期人类成纤维细胞的正常培养条件下，只有一小部分大尺寸焦点可以归因于空间中的高 LET 辐射。
