Space travel was found to increase levels of inflammation in the blood, and produce more exertion from leg muscles, with differing effects on the body depending on gender
A study has revealed that space can wreak havoc on the body, including on blood, cells and the immune system.
The study gathered information from the SpaceX Inspiration4 mission, which saw two men and two women orbit Earth for three days in 2021.
It found that space travel disrupts the immune system, triggering inflammatory responses and major disruption to the cells. The high-altitude, short-duration spaceflight prompted the production of documented and never-before-seen cytokines.
Cytokines, produced by the immune system, are crucial for immune responses and muscle regulation but are not normally linked to inflamation.
Some of these cytokines were identified as exerkines, proteins produced by muscles during exercise. There were also significant increases in myokines, proteins from skeletal muscle cells, indicating a physiological response to microgravity rather than purely an immune response.
Non-muscle tissues showed no changes in inflammation-related proteins. However, the soleus muscle in the back of the leg exhibited a significant increase in muscle exertion. Additionally, the tibialis anterior muscle in the front of the leg showed an increase in interleukins, vital for immune cell activation.
On landing, the most substantial increase was seen in the pro-inflammatory cytokine Interleukin 5, further implicating muscles as the source of the cytokines in the Inspiration4 crew.
Blood samples collected before and after the trip revealed cell-specific and sex-specific responses to spaceflight. Increases in Interleukin 6, Interleukin 10, and MCP-1, a pro-inflammatory molecule, aligned with changes seen in astronauts from longer missions. Several other pro-inflammatory proteins significantly increased. However, proteins like fibrinogen, crucial for blood clot formation, and hemoglobin, which carries oxygen, did not change significantly.
Scientists also noted that B-cell receptor mutations increased post-flight. These mutations, often caused by inflammatory stimuli or antigens, suggest that B-cells become more active after space travel, producing antibodies to neutralize harmful substances.
Cell differentiation, where young cells take on specialized roles, was reduced in CD4 and CD8 T cells, a type of white blood cell critical for infection defense. Upon returning to Earth, the astronauts showed higher concentrations of inflammation-related cytokines, balanced by an increase in anti-inflammatory cytokines.
The researchers also noted significant changes in proteins related to the migration of monocytes and neutrophils, which travel to injury sites.
Prior studies have suggested that women might be more resilient to space travel's stresses and recover faster upon returning to Earth. This study aimed to test that theory, comparing gene activity between males and females. The results showed more disrupted gene activity in males, suggesting women might be more resistant to space travel stressors.
Overall, the study provided evidence of an immune response to space travel in the Inspiration4 data. "We found that 18 cytokines/chemokines related to inflammation, aging, and muscle homeostasis changed after spaceflight," the researchers wrote. Despite the small sample size, consistent cellular and molecular responses indicate valuable insights for future studies and countermeasures for space travelers.
The Inspiration4 mission wasn't designed to assess spaceflight safety for all civilians, but the findings could help refine targets for future research.