Spaceflight caused DNA to leak out of astronauts' cell powerhouse

By Thor Christensen, American Heart Association News

PASIEKA/Science Photo Library, Getty Images
(PASIEKA/Science Photo Library, Getty Images)

Scientists already knew radiation exposure and a lack of gravity stress the bodies of astronauts. But new research may offer a better idea of what's driving some of that. It's a clue that could help them measure the physical impact of space travel to detect problems earlier.

It involves mitochondria, known as the powerhouse of the cell because these tiny structures inside cells produce energy. Mitochondria have their own DNA, and when they undergo stress or other damage, that DNA is released and causes cellular damage and other problems elsewhere in the body.

Previous research shows increased levels of this circulating cell-free mitochondrial DNA can help predict how people with diabetes, rheumatoid arthritis and cardiovascular diseases will fare. And a breakdown in the normal activity of mitochondria has been linked to the development and progression of heart failure.

In the new study published Wednesday in the Journal of the American Heart Association, researchers examined blood samples of 14 NASA astronauts who took five- to 13-day missions to the International Space Station between 1998 and 2001. Blood samples were taken three times: 10 days before the launch, the day of their return and three days after the landing.

All 14 astronauts had increased levels of free-floating mitochondrial DNA in the blood on the day of landing and three days after, ranging from two to 355 times higher than pre-space travel.

That huge range makes it hard to draw any conclusions, said the study's senior author Dr. David Goukassian. Still, he said, the increased levels are possibly harmful because mitochondrial DNA drives inflammation when it leaks into the rest of the body.

The researchers, funded in part by NASA and the American Heart Association, also looked at astronauts' white blood cells. They found a significant increase in markers of inflammation, DNA damage and oxidative stress, which is a disruption in the balance of molecules that harm healthy tissue in the body and antioxidant defenses that neutralize them.

"It's a vicious circle: Radiation may induce DNA damage, which may induce oxidative stress, which leads to inflammation, which can lead to DNA damage," said Goukassian, a professor of cardiology at the Icahn School of Medicine at Mount Sinai in New York City.

As NASA plans to send astronauts back to the moon and to Mars, scientists need a better understanding of how people are affected by radiation, the relative lack of gravity in space, and issues like confinement and erratic sleep cycles, Goukassian said.

"Deep space exploration is dangerous for many reasons, but we need to know as much as possible about the adverse health effects so we can protect humans from stressors before, during and after exploration-type space missions."

Jamila Siamwala, a researcher on NASA's Twins Study, said the new study was limited by its small size, short length and lack of information about the astronauts' health.

Still, the findings are another key part of a growing body of evidence about the risks of human spaceflight, said Siamwala, an assistant professor of molecular pharmacology, physiology and biotechnology at Brown University in Providence, Rhode Island. She was not involved in the new research.

She said even as scientists look for ways to put astronauts into artificial hibernation to travel deeper into space, they still don't fully understand how space disrupts blood flow in a species that's so accustomed to gravity.

"I cannot tell you how important these studies are," Siamwala said. "Before we start thinking about commercial spaceflight or establishing factories in space, we need to understand how the body responds to these drastic conditions in such a hostile place."

If you have questions or comments about this story, please email editor@heart.org.


American Heart Association News Stories

American Heart Association News covers heart disease, stroke and related health issues. Not all views expressed in American Heart Association News stories reflect the official position of the American Heart Association.

Copyright is owned or held by the American Heart Association, Inc., and all rights are reserved. Permission is granted, at no cost and without need for further request, for individuals, media outlets, and non-commercial education and awareness efforts to link to, quote, excerpt or reprint from these stories in any medium as long as no text is altered and proper attribution is made to American Heart Association News.

Other uses, including educational products or services sold for profit, must comply with the American Heart Association’s Copyright Permission Guidelines. See full terms of use. These stories may not be used to promote or endorse a commercial product or service.

HEALTH CARE DISCLAIMER: This site and its services do not constitute the practice of medical advice, diagnosis or treatment. Always talk to your health care provider for diagnosis and treatment, including your specific medical needs. If you have or suspect that you have a medical problem or condition, please contact a qualified health care professional immediately. If you are in the United States and experiencing a medical emergency, call 911 or call for emergency medical help immediately.