New drug could prevent brain damage caused by cosmic rays

Scientists have identified a drug that could prevent the brain damage caused by exposure to cosmic radiation.

In the study published in the journal Scientific Reports, researchers found that the drug prevents memory impairment in mice exposed to simulated space radiation.

Humans venturing beyond the Earth's protective magnetic fields will be exposed to levels of cosmic radiation estimated to be 1000 times higher than what we experience on Earth or even in the International Space Station's low-Earth orbit.

Protecting astronauts from this harmful radiation will be key to making deep space exploration - and perhaps one day colonisation - possible.

The researchers at The University of California, San Francisco (UCSF) in the US have previously found that exposing mice to simulated space radiation causes problems with memory, social interactions, and anxiety.

They have also linked these symptoms of radiation exposure to activation of cells called microglia - part of the brain's immune system.

Activated microglia drive brain inflammation similar to what is seen in neurodegenerative disorders such as Alzheimer's disease.

Researchers exposed mice for a day to a dose of radiation comparable to what they might experience in deep space.

A week later, some of the mice were treated for 15 days with PLX5622, a drug shown to prevent cognitive deficits in a mouse model of cancer radiation therapy when administered prior to irradiation of the brain.

The irradiated animals initially displayed no cognitive deficits, but after three months they began showing signs of memory impairment.

Animals that had been treated with PLX5622 soon after being exposed to radiation performed just like healthy mice on the memory task.

The researchers examined the animals' brains and showed that while the brains of untreated mice were full of activated microglia and had lost significant numbers of synapses, the brains of treated mice looked just like normal.

The researchers hypothesise that by forcing the brain to replace irritable, radiation-exposed microglia with new, healthy microglia, the drug had allowed the animals avoid the cognitive consequences of radiation.

"This is really neat evidence, first that rebooting the brain's microglia can protect cognitive function following radiation exposure, and second that we don't necessarily need to treat immediately following the radiation exposure for the drug to be effective," said UCSF neuroscientist Susanna Rosi.