Abstract
The effect of confined and isolated experience on astronauts’ health is an important factor to consider for future space exploration missions. The more confined and isolated humans are, the more likely they are to develop negative behavioral or cognitive conditions such as a mood decline, sleep disorder, depression, fatigue and/or physiological problems associated with chronic stress. Molecular mediators of chronic stress, such as cytokines, stress hormones or reactive oxygen species (ROS) are known to induce cellular damage including damage to the DNA. In view of the growing evidence of chronic stress-induced DNA damage, we conducted an explorative study and measured DNA strand breaks in 20 healthy adults. The participants were grouped into five teams (missions). Each team was composed of four participants, who spent 45 days in isolation and confinement in NASA’s Human Exploration Research Analog (HERA). Endogenous DNA integrity, ex-vivo radiation-induced DNA damage and the rates of DNA repair were assessed every week. Our results show a high inter-individual variability as well as differences between the missions, which cannot be explained by inter-individual variability alone. The ages and sex of the participants did not appear to influence the results.
Highlights
There is no doubt that stress caused by long-term isolation and confinement negatively influences our physical and mental health
The overarching message from these studies is that physical and mental stress induced by isolation can be manifested in altered stress hormones, release of inflammatory molecules and production of reactive oxidative species (ROS), all of which are recognized mediators of DNA damage [8,9,10,11,12,13,14,15,16,17]
No significant changes were observed in the DNA integrity (DNAI) in blood cells from subjects during missions 1 and 4 (Figure 1a,b), while it changed significantly during missions 3 and 5 (Figure 1c,d)
Summary
There is no doubt that stress caused by long-term isolation and confinement negatively influences our physical and mental health. Oxidative stress markers in the hypothalamus were increased in rats as early as two weeks after social isolation [5]. An isolation period of 42 days increased glucocorticoid levels, oxidative damage and telomere degradation in prairie voles [6], while individually housed rats for 28 days showed higher levels of adrenocorticotropic hormone (ACTH), as well as in the cytokines tumor necrosis factor alpha (TNF-α), inteleukin-4 (IL-4) and interleukin-10 (IL-10) [7]. The overarching message from these studies is that physical and mental stress induced by isolation can be manifested in altered stress hormones, release of inflammatory molecules and production of reactive oxidative species (ROS), all of which are recognized mediators of DNA damage [8,9,10,11,12,13,14,15,16,17]. 8-hydroxy-2-deoxyguanosine (8OhdG), a DNA damage marker, has been detected in the hypothalamus of rats isolated for 2 weeks [5]
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