Researchers looked at how microorganisms can alter fruit flies' immune systems in outer space; the findings could help researchers gain insight into how to keep astronauts healthy in space.
The NASA/Johnson Space Flight Center suggests having gravity or hypergravity on a space station could help solve biological problems associated with space travel, such as weakened immune systems. Fruit flies have similar immune response mechanisms to humans, so they were perfect stand-ins for astronauts.
Researchers looked at the immunes response in Drosophila melanogaster (the common fruit fly) when experiencing changes in gravity.
"Immune response is central to health for essentially all organisms, and, not surprisingly, in the stressful space environment there are a variety of changes to how a person or other organisms can fight an infection," Deborah Kimbrell, Ph.D., at the University of California, Davis (UC Davis), said. "In order to try and understand those changes, my group used the simple fruit fly, well-studied for its immune response on Earth, as a model to help sort out at a cell-based level what happens to the immune response when an organism is in space."
The signaling pathways Toll and Imd are the "go-betweens" of immune responses to fungal and bacterial infections; this quality is shared in both fruit flies and humans.
The team sent flies to space for 12 days, allowing them to fully mature before bringing them back to Earth. The team found hypergravity and microgravity produced opposite immune responses in the flies. When exposed to increased gravity flies responded from infection by the fungus Beauveria bassiana through the Toll pathway; when the flies were in space their Toll pathway failed to respond to the fungal infection. The Imd pathway response to E. coli bacteria was successful in flies in both hypergravity and microgravity.
"What we found is that in one kind of infection in flies that were raised in space, they did fine, and in another kind of infection, they really didn't respond at all," Kimbrell. Said. "The pathway that did not respond, the Toll pathway, is critical in humans for all kinds of health-related issues, both for functioning and for over-functioning. The Toll pathway (TLR4) response is involved in sepsis, which is still a big problem in human health."
