Zipping to Mars could badly zap brain nerve cells

Particle blasts similar to cosmic radiation caused memory, learning woes in mice

BRAIN ZAP After radiation exposure, mouse dendrites (green) in the medial prefrontal cortex were shorter and branched less than those of mice not exposed to radiation, as seen in this digital reconstruction. Exposed dendrites also had fewer docking sites (red) that detect messages from other cells.

V. Parihar et al/Science Advances 2015

By Laura Sanders

May 1, 2015 at 2:00 pm

Like cannonballs slamming into stained glass, high-energy particles can shatter the delicate tendrils that connect nerve cells, a study on mice finds. This neural destruction left mice with memory and learning problems, a finding that has implications for intrepid space explorers.

The result is “worrisome, very worrisome,” says neuroscientist M. Kerry O’Banion of the University of Rochester Medical Center in New York. But figuring out the human brain’s fate on a long space trip is tricky, he notes.

In the study, Charles Limoli of University of California, Irvine and colleagues briefly exposed mice to a beam loaded with high-energy versions of either titanium or oxygen, particles an astronaut might encounter in deep space. Six weeks after the quick zap, the mice showed memory deficits. Compared with nonirradiated mice, zapped animals were worse at recognizing new toys and remembering where a particular toy used to be, the team reported May 1 in Science Advances.

Brain damage also occurred. Complex branches of nerve cells that receive messages were shorter and the cells had fewer branches after the radiation, the team found. “We weren’t expecting such dramatic effects from these charged particles,” says Limoli.

During a long-haul mission to Mars, astronauts would surely encounter these sorts of particles, Limoli says. This study suggests that these encounters could damage astronauts’ brains, perhaps in ways that lead to cognitive problems during the mission and afterward. “Over the course of a long-term mission, this may become very problematic,” Limoli says.

Translating the mouse study to people is difficult, O’Banion says. “There are big differences in the way the animals are exposed to the radiation versus how astronauts are,” he says. Space holds a more complex mixture of particles than those in the beam, and the doses differ, too. The biological response to radiation is, in many ways, “still a black box,” O’Banion says.

A deeper understanding of how these particles affect the body and brain may help scientists create better ways to shield vulnerable tissues from space radiation (SN: 7/26/14, p. 18).