The immune systems of astronauts threatened by prolonged space flight

NASA hopes to send humans to Mars by 2030 for a round-trip mission that could last up to three years, much longer than any human has ever traveled in space. According to a new study by researchers at the University of Arizona, such long-term space flights could negatively affect some cells of the astronauts' immune system.

"NASA and other space agencies are worried about whether the immune system will be compromised during very long spaceflight missions," said Richard Simpson, senior author and badociate professor of nutrition sciences at the Faculty of Agriculture and Life Sciences of the AU. "What are the clinical risks to astronauts during these missions when they are exposed to factors such as microgravity, radiation and isolation stress? Could this be catastrophic to the point that the astronaut is not able to carry out his mission? "

Simpson and researchers from the AU, the University of Houston, the Louisiana State University and the NASA Johnson Space Center have studied the effects of spaceflights of six months or more on NK cells, a type of white blood cell that kills cancer cells. in the body and prevents old viruses from reactivating.

"Cancer represents a significant risk to astronauts during very long space flight missions due to radiation exposure," Simpson said. "Are also very important for killing cells infected with the virus. When you're in the space station, the environment is very sterile – you probably will not get the flu, a rhinovirus or a community-type infection – but the problematic infections are the viruses already in your system . body. These are mostly viruses that cause things like shingles, mononucleosis or cold sores; they stay in your body for the rest of your life and reactivate when you're stressed. "

Scientists compared blood samples from eight crew members completing missions to the International Space Station with healthy individuals left on Earth. Blood samples were collected before launch, at several points during the mission and after the astronauts returned to Earth.

The results showed that NK cell function is altered in astronauts compared to pre-flight and ground control levels. At day 90, the cytotoxic activity of NK cells against leukemic cells in vitro was reduced by approximately 50% in crew members of the International Space Station.

"When we look at the function of astronaut samples in flight versus their own samples before they fly, it decreases. When we compare them to the controls that have remained on Earth, it keeps going down, "said Simpson. "I do not think there is any doubt about the fact that the function of NK cells decreases in the environment of spaceflights when it is badyzed in a cell culture system."

The effect seems to be more pronounced in novice astronauts, as opposed to those who have already been in space.

"Fortunately, we found that half of our crew members had already flown, and the other half had not done so," Simpson said. "So we were able to divide them in half to see if there was an effect, and there was one." The "recruits" had larger declines in NK cell function compared to veterans. "

The differences could be categorized by age or stress, said Simpson, finding that novice astronauts, generally younger than their experienced counterparts, would find trips in the space more stressful than those who do not. had already done.

While declining NK cell function makes astronauts more vulnerable to cancer, it remains to be seen whether the virus will reactivate, making viral reactivation even more difficult, Simpson said. He hopes to learn more about future studies.

"The next question would be: how can we mitigate these effects? How can we prevent the immune system from degrading during space travel? "To do this, you must first understand what causes the decline: is it stress? Is it microgravity? Is it a radiation? Is it a plethora of things? Once we understand this, we can try to find ways to directly target and mitigate these factors. "

Simpson and his colleagues at NASA Johnson Space Center, as well as European and Russian scientists, are already working on potential countermeasures that could help astronauts stay healthy in space, including nutritional or pharmacological interventions. and increased physical activity, all of which have proven effective. a positive effect on the functioning of the immune system.

Studies have shown that spending long periods off the Earth presents certain health risks, such as the loss of muscle and bone due to the effects of microgravity. But scientists did not know if the unique conditions encountered by astronauts had had an impact on the immune system until now. The document, Spaceflight Inhibits Function of NK Cells, was published in the Journal of Applied Physiology.

This article has been republished from documents provided by the University of Arizona. Note: Content may have changed for length and content. For more information, please contact the cited source.

Reference
The function of NK cells is impaired during long-duration space flights. Austin B. Bigley, Nadia H. Agha, Forrest L. Baker, William Spielmann, Hawley E. Kunz, Preteesh L. Mylabathula, Bridgette Rooney, Mitzi S. Laughlin, Duane L. Pierson, Satish K. Mehta and Brian E. Crucian . and Richard J. Simpson. January 28, 2019, www.physiology.org/journal/apsselect (195.099.213.082).