Acute, Low-Dose Neutron Exposures Adversely Impact Central Nervous System Function

Abstract

A recognized risk of long-duration space travel arises from the elevated exposure astronauts face from galactic cosmic radiation (GCR), which is composed of a diverse array of energetic particles. There is now abundant evidence that exposures to many different charged particle GCR components within acute time frames are sufficient to induce central nervous system deficits that span from the molecular to the whole animal behavioral scale. Enhanced spacecraft shielding can lessen exposures to charged particle GCR components, but may conversely elevate neutron radiation levels. We previously observed that space-relevant neutron radiation doses, chronically delivered at dose-rates expected during planned human exploratory missions, can disrupt hippocampal neuronal excitability, perturb network long-term potentiation and negatively impact cognitive behavior. We have now determined that acute exposures to similar low doses (18 cGy) of neutron radiation can also lead to suppressed hippocampal synaptic signaling, as well as decreased learning and memory performance in male mice. Our results demonstrate that similar nervous system hazards arise from neutron irradiation regardless of the exposure time course. While not always in an identical manner, neutron irradiation disrupts many of the same central nervous system elements as acute charged particle GCR exposures. The risks arising from neutron irradiation are therefore important to consider when determining the overall hazards astronauts will face from the space radiation environment.

Galactic cosmic radiation exposure causes multifaceted neurocognitive impairments

“…Hippocampal slices for extracellular field recording and whole cell electrophysiology experiments were prepared as previously described and are detailed in the SI [ 3 , 15 ]. Extracellular field recordings were performed for both male and female mice at 5 months after the completion of irradiations.…”

Complex 33-beam simulated galactic cosmic radiation exposure impacts cognitive function and prefrontal cortex neurotransmitter networks in male mice

“…By using a complex 33-beam GCR simulation we more accurately reproduce the physiologically relevant conditions, which may produce differing results from simpler, less representative models. However, we emphasize that past work using complex GCR 34 , mixed field 5 ion studies 26 , 51 and even acute 52 and chronic low dose neutron 47 studies suggest multiple disruptions across interconnected brain regions. Moreover, chronic GCR exposure increased levels of all K+-stimulated neurotransmitters compared to controls, indicating global PFC changes that compromised all neurotransmitter systems; these effects were less significant after acute GCR.…”

Editorial to the Special Issue: “Dysregulation of Human Molecular and Metabolic Mechanisms Resulting in Oxidative Stress and Damage Generation in the Space Environment”

“…To address multiple OSaD factors in chorus with one another, the choice of research model is critical and certainly the likelihood that multiple models may need to be employed is warranted. The current scientific literature documents have extensively employed rodent and human physiological platforms to evaluate OSaD generated toxic effects, spanning many different physiological and analytical subsystem models [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ].…”

“…A great deal of excellent work has been accomplished in the last 12 years, illuminating the heretofore unrealized fragility resident in the mammalian brain. Klein et al in 2021 and Krishnan et al in 2021 described how even low dose neutron radiation through the generation of RONS damages the normal operation of the CNS and that chronic low dose exposure negatively effects the hippocampus and the prefrontal cortex, due to altered neurotransmission [ 14 , 15 ]. These studies illuminate the disruption of cellular processes at the DNA and molecular genetic levels [ 15 , 16 , 17 ].…”