Combined space stressors induce independent behavioral deficits predicted by early peripheral blood monocytes

Abstract

Interplanetary space travel poses many hazards to the human body. To protect astronaut health and performance on critical missions, there is first a need to understand the effects of deep space hazards, including ionizing radiation, confinement, and altered gravity. Previous studies of rodents exposed to a single such stressor document significant deficits, but our study is the first to investigate possible cumulative and synergistic impacts of simultaneous ionizing radiation, confinement, and altered gravity on behavior and cognition. Our cohort was divided between 6-month-old female and male mice in group, social isolation, or hindlimb unloading housing, exposed to 0 or 50 cGy of 5 ion simplified simulated galactic cosmic radiation (GCRsim). We report interactions and independent effects of GCRsim exposure and housing conditions on behavioral and cognitive performance. Exposure to GCRsim drove changes in immune cell populations in peripheral blood collected early after irradiation, while housing conditions drove changes in blood collected at a later point. Female mice were largely resilient to deficits observed in male mice. Finally, we used principal component analysis to represent total deficits as principal component scores, which were predicted by general linear models using GCR exposure, housing condition, and early blood biomarkers.

Galactic Cosmic Irradiation Alters Acute and Delayed Species-Typical Behavior in Male and Female Mice

“…Previously, in open field, Raber et al observed that females had higher activity levels than males, but for all doses and sham exposures [ 18 ], where Lui et al found male mice were more susceptible to radiation-induced changes in activity levels than female mice after 10 or 50 cGy exposure of 56 Fe [ 37 ]. Rienecker et al did not observe any dose or sex differences in the time spent in the center of the open field arena [ 21 ]. Here, both males and females spent more time moving at the delayed timepoint than acute, regardless of dose.…”

“…Yet, there was a trend toward an effect of radiation where BDNF levels increased in the cortex of males but not females [ 19 ]. Rienceker et al (2023) observed behavioral deficits and elevated peripheral blood monocytes and Natural Killer cells in group-housed males but not females, after exposure to 50 cGy 5-ion GCRSim [ 21 ]. Given the sexually dimorphic nature of the behavioral responses, establishing a GCRSim dose–response curve is key to enabling the selection of a dose that evokes a midrange response in future studies of both sexes to avoid ceiling or floor effects.…”

Development of a payload for monitoring biological samples in microgravity and hypergravity conditions

“…Furthermore, the findings from these studies can contribute to addressing disturbances that may arise during spaceflights involving organisms [9]. Thus, it is essential to analyze the behavior of different species and cells under hypergravity conditions and evaluate any resultant changes to identify potential beneficial applications [10], [11]. To accomplish this, the changes can be monitored within a container equipped with an array of cameras, enabling subsequent image processing and analysis [12].…”