DNA Damage Baseline Predicts Space Radiation and Radio-Therapeutic Resilience

The radiation environment in deep space, where astronauts are behind the shelter provided by the Earth’s magnetosphere, is a major health concern. Galactic cosmic rays (GCR) and solar particle events (SPE) are two basic sources of space radiation in the solar system. The health risks of exposure to high levels of space radiation can be observed either as acute and delayed effects. Zhang et al. in their recently published paper entitled “γ-H2AX responds to DNA damage induced by long-term exposure to combined low-dose-rate neutron and γ-ray radiation” have addressed the effects of different cumulative radiation doses on peripheral blood cell, subsets of T cells of peripheral blood lymphocytes and DNA damage repair. These researchers exposed animals to low dose rate 60Co-rays at 0.0167 Gy h−1for 2 h/d and 252Cf neutrons at 0.028 mGy h−1for 20 h/d for 15, 30, or 60 consecutive days. They reported that the mRNA of H2AX increased significantly, and showed a positive correlation with dose. Despite strengths, this paper has several shortcomings such as poor definition of low dose radiation as well as space and reactor radiation environments. Another shortcoming of this paper comes from this point that blood cell studies do not represent the biological effects of ionizing radiation on the total body. Moreover, the effects of the human immune system and DNA repair mechanisms are not included in the study. The role of pre-exposures and induction of adaptive response phenomena in decreasing the risk of radiation in deep space missions are also ignored.

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Repair Kinetics of DNA Double Strand Breaks Induced by Simulated Space Radiation

Life ◽

10.3390/life10120341 ◽

2020 ◽

Vol 10 (12) ◽

pp. 341

Author(s):

Takashi Oizumi ◽

Rieko Ohno ◽

Souichiro Yamabe ◽

Tomoo Funayama ◽

Asako J. Nakamura

Keyword(s):

Dna Damage ◽

Ion Irradiation ◽

Space Radiation ◽

Double Strand Breaks ◽

Dependent Manner ◽

Dna Double Strand Breaks ◽

Dsb Repair ◽

Strand Breaks ◽

Carbon Ion ◽

Kinetics Of

Radiation is unavoidable in space. Energetic particles in space radiation are reported to induce cluster DNA damage that is difficult to repair. In this study, normal human fibroblasts were irradiated with components of space radiation such as proton, helium, or carbon ion beams. Immunostaining for γ-H2AX and 53BP1 was performed over time to evaluate the kinetics of DNA damage repair. Our data clearly show that the repair kinetics of DNA double strand breaks (DSBs) induced by carbon ion irradiation, which has a high linear energy transfer (LET), are significantly slower than those of proton and helium ion irradiation. Mixed irradiation with carbon ions, followed by helium ions, did not have an additive effect on the DSB repair kinetics. Interestingly, the mean γ-H2AX focus size was shown to increase with LET, suggesting that the delay in repair kinetics was due to damage that is more complex. Further, the 53BP1 focus size also increased in an LET-dependent manner. Repair of DSBs, characterized by large 53BP1 foci, was a slow process within the biphasic kinetics of DSB repair, suggesting non-homologous end joining with error-prone end resection. Our data suggest that the biological effects of space radiation may be significantly influenced by the dose as well as the type of radiation exposure.

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Healthy offspring from freeze-dried mouse spermatozoa held on the International Space Station for 9 months

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1701425114 ◽

2017 ◽

Vol 114 (23) ◽

pp. 5988-5993 ◽

Cited By ~ 27

Author(s):

Sayaka Wakayama ◽

Yuko Kamada ◽

Kaori Yamanaka ◽

Takashi Kohda ◽

Hiromi Suzuki ◽

...

Keyword(s):

Dna Damage ◽

International Space Station ◽

Room Temperature ◽

Space Station ◽

Space Radiation ◽

Reproductive Technology ◽

International Space ◽

Sperm Dna ◽

Freeze Dried ◽

Generation Sequencing

If humans ever start to live permanently in space, assisted reproductive technology using preserved spermatozoa will be important for producing offspring; however, radiation on the International Space Station (ISS) is more than 100 times stronger than that on Earth, and irradiation causes DNA damage in cells and gametes. Here we examined the effect of space radiation on freeze-dried mouse spermatozoa held on the ISS for 9 mo at –95 °C, with launch and recovery at room temperature. DNA damage to the spermatozoa and male pronuclei was slightly increased, but the fertilization and birth rates were similar to those of controls. Next-generation sequencing showed only minor genomic differences between offspring derived from space-preserved spermatozoa and controls, and all offspring grew to adulthood and had normal fertility. Thus, we demonstrate that although space radiation can damage sperm DNA, it does not affect the production of viable offspring after at least 9 mo of storage on the ISS.

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