Space radiobiology and the new era of induced radioresistance: Should traditional concepts be moved to science history museums?

Abstract

Energetic solar particle events (SPE) which are among the main sources of ionizing radiation can be life threatening to astronauts who are not adequately protected. To date, physical shielding of spacecrafts and inducing radioresistance by using radioprotectors have been proposed by different investigators. Mortazavi et al. have previously reported that screening of the candidates of long-term space missions by conducting Ground-based in vitro adaptive response studies before any mission identifies the individuals who respond well to low levels of ionizing radiation and reveal high magnitudes of radioadaptive response. On the other hand, Mortazavi et al. have recently showed that radiofrequency-induced adaptive response can be used as a method for decreasing the risk of infection caused by immunosuppression during deep space missions. Furthermore, over the past years the radioresistance induced by a wide variety of radioprotectors has been studied. According to classical radiobiology, chemical radioprotective agents must be administered before irradiation or at the time of irradiation, to increase the mean survival rate of the exposed individuals. A revolution in this paradigm was started in 2010, when investigators reported that a diet supplemented with antioxidants administered starting 24 h after total-body irradiation is more effective than if given soon after the exposure (radiation mitigation). This finding along with the above mentioned interventions open new horizons in inducing biological radioresistance against unpredictable high levels of radiation due to solar particle events. This wide time window indeed enables astronauts to firstly evaluate their radiation doses before making any decision on the type of intervention. As major solar particle events last for hours, astronauts will be able to consult distinguished radiation biologists via satellite telecommunication before choosing any medical intervention.

Donor-Specific Cell-Based Assays in Studying Sensitivity to Low-Dose Radiation: A Population-Based Perspective

“…In this setting, individual variability can arise both from genetic predisposition that determines intrinsic radiosensitivity and individual exposures to different factors. For example, differences in diet ( 41 – 43 ), tobacco use ( 44 , 45 ), or prescribed medications ( 46 ) can affect individual response ( 47 ). Such confounding background factors cannot be easily controlled, compromising comparisons of radiation responses between individuals in vivo .…”

Non-Linear Adaptive Phenomena which Decrease the Risk of Infection after Pre-Exposure to Radiofrequency Radiation

“…Finally as discussed above in detail, we recently showed that pre-exposure of mice to radiofrequency radiation emitted by a GSM mobile phone increased their resistance to a subsequent Escherichia coli infection. Altogether, we can come Non-linear Adaptive Phenomena and Risk of Infection to this conclusion that exposure of astronauts to low levels of radiofrequency radiations emitted by an appropriate source or chronic space radiation can increase their resistance against infections caused by lifethreatening microorganisms (Mortazavi et al 2012, Mortazavi 2013b.…”

Poor Understanding of Radiation Profiles in Deep Space Causes Inaccurate Findings and Misleading Conclusions

“…In addition, the experimental conditions used in this study do not include microgravity, the duration of the space mission, and effects of radioadaptation. Moreover, the assumed dose of gamma and neutron radiation is not representative of the solar particle events (SPE) and galactic cosmic radiation (GCR) [2-7]. In this light, this cannot be a good rationale for designing a study on the combined effects of exposure to neutron and gamma.…”

“…Radioadaptation increases the body’s resistance to higher doses of radiation after a pre-exposure to a lower dose. The role of pre-exposures and induction of adaptive response phenomena in decreasing the risk of radiation in deep space missions has previously been discussed in detail by Mortazavi et al [7-12]. Citing reports authored by Mortazavi et al and other researchers about the importance of radioadaptation in deep space missions, a 2016 NASA report [13] states it is realistic to expect that cells will be exposed to multiple hits of protons before being traversed by an HZE particle.…”