28. The effects of the spaceflight environment on stress pathways

Abstract

In previous experiments, we have shown that spaceflight can alter leukocyte and lymphocyte population distributions and mitogen-induced cytokine expression. We hypothesize that these changes are a result of flight-induced physiological and psychological stress. On July 8, 2011, age- and weight-matched, female C57BL/6J mice were placed into Animal Enclosure Modules (AEMs) and flown on the Space Shuttle Atlantis (STS-135) for 13 days ( N = 6–7). Ground controls were housed at the Space Life Science Laboratory (SLSL) at Kennedy Space Center (KSC). Ground AEM control mice were placed into the same hardware used in flight and environmental parameters such as temperature and CO2 levels were matched as closely as possible based on 48 h delayed telemetry data ( N = 12–13). Vivarium control mice were housed in regular shoebox cages ( N = 4). Mice were euthanized and dissected within 3–5 h of landing. Adrenals were removed, snap frozen in liquid N2, and shipped on ice back to Loma Linda University via overnight courier for analysis. Although corticosterone levels were slightly elevated in spaceflight mice, with a corresponding decrease in phosphorylated adrenocorticotropic hormone (ACTH) levels, these changes were not enough to reach significance. Similarly, there were no significant changes in catecholamine levels. This suggests that there is no significant impact of spaceflight on stress pathways. However, closer examination of the data indicates that the circadian rhythm may have masked the overall effect of spaceflight.