Central Nervous System Responses to Simulated Galactic Cosmic Rays.

Egle Cekanaviciute,Susanna Rosi,Sylvain Costes

doi:10.3390/ijms19113669

Abstract

In preparation for lunar and Mars missions it is essential to consider the challenges to human health that are posed by long-duration deep space habitation via multiple stressors, including ionizing radiation, gravitational changes during flight and in orbit, other aspects of the space environment such as high level of carbon dioxide, and psychological stress from confined environment and social isolation. It remains unclear how these stressors individually or in combination impact the central nervous system (CNS), presenting potential obstacles for astronauts engaged in deep space travel. Although human spaceflight research only within the last decade has started to include the effects of radiation transmitted by galactic cosmic rays to the CNS, radiation is currently considered to be one of the main stressors for prolonged spaceflight and deep space exploration. Here we will review the current knowledge of CNS damage caused by simulated space radiation with an emphasis on neuronal and glial responses along with cognitive functions. Furthermore, we will present novel experimental approaches to integrate the knowledge into more comprehensive studies, including multiple stressors at once and potential translation to human functions. Finally, we will discuss the need for developing biomarkers as predictors for cognitive decline and therapeutic countermeasures to prevent CNS damage and the loss of cognitive abilities.

Highlights

Astronauts on the International Space Station (ISS) are somewhat protected from galactic cosmic rays (GCRs) by the magnetic field of the Earth
The hypothesized interaction between central nervous system (CNS) and peripheral inflammation mediated by a leaky blood-brain barrier in response to HZE ions may account for the fact that whole body 1 GeV/n 16O irradiation has been shown to lead to worse behavioral impairments than head irradiation alone in rats [39], and for the fact that peripheral immune cells can serve as biomarkers for the severity of radiation-induced behavioral deficits in response to 0.25 Gy of 600 MeV/n 16O irradiation in mice [22]
Long-term responses to 28Si irradiation showed a worse reduction in new neuron survival in male than in female mice [30], though one previous study has indicated the opposite effect of higher doses of 56Fe irradiation: Impaired memory responses in female mice, but improved in male mice [57]

Summary

Introduction

Astronauts on the International Space Station (ISS) are somewhat protected from galactic cosmic rays (GCRs) by the magnetic field of the Earth. 1.5 Gy doses of 56Fe has been reported to dysregulate it starting at 7 months and continuing to up to 15 months after exposure [25,26], indicating that HZE ion exposure may alter the dopaminergic system Another cognitive test that relies on the functions of the dopaminergic system, the psychomotor vigilance test, is based on increasing the waiting time before response and measures premature responses that can reflect a drop in sustained attention and increased impulsivity. The hypothesized interaction between CNS and peripheral inflammation mediated by a leaky blood-brain barrier in response to HZE ions may account for the fact that whole body 1 GeV/n 16O irradiation has been shown to lead to worse behavioral impairments than head irradiation alone in rats [39], and for the fact that peripheral immune cells can serve as biomarkers for the severity of radiation-induced behavioral deficits in response to 0.25 Gy of 600 MeV/n 16O irradiation in mice [22]. ROS production and neuronal damage have been shown by multiple studies to be accompanied by microglial activation [42]

Time After Exposure

Findings

Conclusions