Space: Science & Technology Article Explains Why Astronauts Are Vulnerable to Depression

BEIJING, Oct. 19, 2021 /PRNewswire/ -- Space travel and exploration is bound to become more common in the future, and astronauts will most certainly have to spend more time in space during missions. By now, it is well established that prolonged exposure to the harsh conditions of space environments is harmful to the mind and body. Besides bone and muscle problems, cardiovascular complications, and immune system malfunctioning, staying in space for too long can cause depression in astronauts. However, the underlying biological mechanisms that cause this remain unclear.

In an effort to address this knowledge gap, a team of scientists led by Professors Yongqian Zhang and Yulin Deng from Beijing Institute of Technology, China, conducted a study using rats as an animal model. Unlike previous studies, which focused mainly on the effects of simulated microgravity, the researchers exposed the rats to other intricacies of an extreme and complex space environment. This included a combination of microgravity, noise, isolation, and circadian rhythm alterations via short light/dark cycles. In this way, the scientists ensured that subsequent behavioral experiments and protein expression analyses more accurately mirrored the effects that a prolonged stay in space environments could have in astronauts. The study was published online in Space: Science & Technology on 27 May 2021.

First, to confirm depression in the rats subjected to the simulated complex space environment (SCSE), the team conducted three different experiments: sucrose preference tests, forced swimming tests, and open-field tests. These served to quantify lack of appetite, desperation, and motivation, respectively. As expected, the scores on the tests collectively indicated depression-like behavior in the rats exposed to the SCSE, but not in the control group.

Then, the scientists delved directly into the meat of the problem. After painlessly sacrificing the animals, they took tissue samples from the hippocampus, a major component of the brain that is highly vulnerable to long-term stress and is associated with depression. The team conducted two mass-spectrometry based techniques?quantitative proteomics and multiple reaction monitoring?to create an accurate profile of the cell membrane proteins that were differently expressed in SCSE rats compared with the control group.

The results of these analyses provided much insight into what proteins and biological functions are affected by exposure to space environments. "We found that the development of the nervous system may be disturbed under the SCSE, especially the formation of synapses and neuron regeneration," explains Professor Zhang, "Moreover, we found downregulated proteins that are involved in synaptic transmission and synaptic vesicular transport."

Overall, this study will be key for developing preventive drugs and measures aimed at astronauts in the future, as Professor Deng concludes, "The differentially expressed proteins that we identified will be used as biomarkers for future research and might provide helpful clues for formulating strategies to maintain the mental and physical health of astronauts during missions." Hopefully, science will let us find ways to prevent space travel from taking a toll on astronauts' minds and bodies.

Reference

Title of original paper: Deep Membrane Proteome Profiling of Rat Hippocampus in Simulated Complex Space Environment by SWATH
Journal: Space: Science & Technology
DOI: https://doi.org/10.34133/2021/9762372

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SOURCE Space: Science & Technology