How does radiation in space affect the brain?

Exposure to deep space poses many potential risks to the health of astronauts, but one of the biggest dangers is space radiation. Above Earth’s protective shielding, astronauts are exposed to radiation from energetic charged particles that increases their risk of cancer, damage to the central nervous system and a host of other health problems.

A new study has now investigated how chronic, space-like irradiation impacts the brain function of mice. To learn more, I spoke with Ivan Soltesz, PhD, a senior author on the study and a professor of neurosurgery and neurosciences at Stanford.

What was the goal of your study?

“Our basic question was ‘what happens to your brain during a mission to Mars?’ So far, only the Apollo astronauts have traveled far enough beyond the Earth’s protective magnetic field to be exposed to similar galactic cosmic radiation levels, albeit only for short durations.

In previous rodent studies, my lab observed that neuronal function is disrupted by low levels of radiation, a fraction of the dose used for cancer therapy. However, technical constraints required us to deliver the entire radiation dose within minutes, rather than across several months as during a mission to Mars. In the current study, we are the first to investigate the impact of prolonged radiation exposures, at Mars-relevant doses and dose rates, on the neurological function. We used a new neutron irradiation facility at Colorado State University.”

What part of the brain did you study?

“The hippocampus, which is critical for several important brain functions, including the formation of new memories and spatial navigation. And the medial prefrontal cortex, which is important for retrieving preexisting memories, making decisions and processing social information. Thus, deficits in either of these two brain regions could detrimentally impact the ability of astronauts to safely and successfully carry out a mission to Mars.”

What did you find?

“My lab at Stanford measured electrical properties of individual neurons from mice that were exposed to six months of chronic neutron radiation. We determined that after chronic radiation exposure, neurons in the hippocampus were less likely to respond to incoming stimuli and they received a reduced frequency of communication from neighboring neurons.

Our collaborators at UC, Irvine found that chronic neutron radiation also caused neuronal circuits in both the hippocampus and medial prefrontal cortex to no longer show long-lasting strengthening of their responses to electrical stimulation, normally referred to as long-term potentiation. Long-term potentiation is a cellular mechanism that allows memory formation.

Our collaborators also conducted behavioral tests. The mice displayed lasting deficits in learning, memory, anxiety and social behavior — even months after radiation exposure. Based on these results, our team predicts that nearly 1 in 5 astronauts would experience elevated anxiety behavior during a mission to Mars, while 1 in every 3 astronauts would struggle with memory recall.”

How can these findings facilitate safe space exploration?

“By understanding radiation risks, future missions can plan practical changes — such as locating astronaut sleeping spaces towards the center of the spacecraft where intervening material blocks more incoming radiation — that may help to mitigate the risks associated with interplanetary travel.

However, my lab believes the best way to protect astronauts from the harmful effects of space radiation is to understand at a basic science level how neuronal activity is disrupted by chronic radiation exposures.

One promising sign is that radiation exposures that occur in space rarely cause neurons in the brain to die, but rather cause smaller scale cellular changes. Thus, we should be able to develop strategies to modulate neuronal activity to compensate for radiation-induced changes. Our team is already starting a new set of chronic space-radiation experiments to test a candidate countermeasure drug.”

Would you ever go to space, given how harmful it is on the human body?

“The radiation risks we discovered are mostly a concern for travel beyond low earth orbit, such as months-long missions to Mars. Shorter trips to the moon — such as the Apollo missions — or months spent in Earth orbit aboard the International Space Station appear to pose a much lower risk of radiation-induced cognitive deficits. I would definitely like to go into space for at least a few quick orbits.

I’m also confident that my lab and others will expand our understanding of how chronic radiation impacts the nervous system and to develop the effective countermeasures needed to enable safe missions towards the moon or Mars within the next decade. However, I’m not sure I’m ready to leave my lab unattended for two years while I take a sabbatical to Mars.”

Photo by ColiN00B

This is a reposting of my Scope blog story, courtesy of Stanford School of Medicine.

Blasting radiation therapy into the future: New systems may improve cancer treatment

Image by Greg Stewart/SLAC National Accelerator Laboratory

As a cancer survivor, I know radiation therapy lasting minutes can seem much longer as you lie on the patient bed trying not to move. Future accelerator technology may turn these dreaded minutes into a fraction of a second due to new funding.

Stanford University and SLAC National Accelerator Laboratory are teaming up to develop a faster and more precise way to deliver X-rays or protons, quickly zapping cancer cells before their surrounding organs can move. This will likely reduce treatment side effects by minimizing damage to healthy tissue.

“Delivering the radiation dose of an entire therapy session with a single flash lasting less than a second would be the ultimate way of managing the constant motion of organs and tissues, and a major advance compared with methods we’re using today,” said Billy Loo, MD, PhD, an associate professor of radiation oncology at Stanford, in a recent SLAC news release.

Currently, most radiation therapy systems work by accelerating electrons through a meter-long tube using radiofrequency fields that travel in the same direction. These electrons then collide with a heavy metal target to convert their energy into high energy X-rays, which are sharply focused and delivered to the tumors.

Now, researchers are developing a new way to more powerfully accelerate the electrons. The key element of the project, called PHASER, is a prototype accelerator component (shown in bronze in this video) that delivers hundreds of times more power than the standard device.

In addition, the researchers are developing a similar device for proton therapy. Although less common than X-rays, protons are sometimes used to kill tumors and are expected to have fewer side effects particularly in sensitive areas like the brain. That’s because protons enter the body at a low energy and release most of that energy at the tumor site, minimizing radiation dose to the healthy tissue as the particles exit the body.

However, proton therapy currently requires large and complex facilities. The Stanford and SLAC team hopes to increase availability by designing a compact, power-efficient and economical proton therapy system that can be used in a clinical setting.

In addition to being faster and possibly more accessible, animal studies indicate that these new X-ray and proton technologies may be more effective.

“We’ve seen in mice that healthy cells suffer less damage when we apply the radiation dose very quickly, and yet the tumor-killing is equal or even a little better than that of a conventional longer exposure,” Loo said in the release. “If the results hold for humans, it would be a whole new paradigm for the field of radiation therapy.”

This is a reposting of my Scope blog story, courtesy of Stanford School of Medicine.

New Portable Device Quickly Measures Radiation Exposure

Scientists are developing a portable device that can measure a person's radiation exposure in minutes using radiation-induced changes in the concentrations of certain blood proteins. This image shows a magneto-nanosensor chip reader station, chip cartridge, and chip. (Credit: S. Wang)
Scientists are developing a portable device that can measure a person’s radiation exposure in minutes. This image shows a magneto-nanosensor chip reader station, chip cartridge, and chip. (Credit: S. Wang)

Picture the scene of the Fukushima nuclear accident. The Daiichi nuclear reactors were hit by an earthquake of magnitude 9.0 and flooded by the resulting tsunami, which caused a nuclear meltdown and release of radioactive materials. Over 100,000 people were evacuated from their homes due to the threat of radiation contamination.

In a large-scale radiological incident like this, emergency medical personnel need a rapid way to assess radiation exposure so they can identify the people who need immediate care. This radiation-dosimetry technology needs to be sensitive, accurate, fast and easy to use in a non-clinical setting.

Local scientists have developed a small, portable device that can quickly test the level of radiation exposure victims have suffered in such emergencies. This technology was developed by scientists from Berkeley Lab, Stanford University and several other institutions, as reported in a journal article recently published in Scientific Reports. The lead researchers were Dr. Shan Wang from Stanford University and Dr. Andrew Wyrobek from Berkeley Lab.

This new dosimetry device is a novel type of immunoassay. Immunoassays are chemical tests used to detect or measure the quantity of a specific substance in a body fluid sample using a reaction of the immune system. For example, a common immunoassay test for pregnancy measures the concentration of the human chorionic gonadotropin hormone in a woman’s blood or urine sample.

In order to measure a person’s radiation dose, the new device measures a blood sample for the concentration of particular proteins that change after radiation exposure. Scientists, including those in Wyrobek’s group, have previously identified these target proteins as excellent biological markers for radiation dosimetry. Basically, blood exposed to radiation has a special biochemical signature.

But scientists needed more than just target proteins. They also needed an accurate, sensitive way to quickly measure the proteins’ concentrations in a few drops of blood. So at the heart of the new device is a biochip developed by Wang’s group.

The biochip system relies on a sandwich structure where a target protein is trapped between a capture antibody and a detection antibody. The capture antibodies are immobilized on the surface of the biochip sensor. When a drop of blood is placed on the biochip, those antibodies capture the target proteins and the other proteins are washed away. Detection antibodies labeled with magnetic nanoparticles are then added, forming a sandwich structure that traps the target proteins. When an external oscillating magnetic field is then applied, the magnetic nanoparticles generate an electrical signal that is read out. This signal measures the number of magnetic nanoparticles bound to the surface, and this indicates the number of target proteins that have been trapped.

The researchers tested the biochip system using blood from mice that had been exposed to varying levels of radiation. Their novel immunoassay results were validated by comparing them to conventional ELISA immunoassay measurements. Overall the scientists demonstrated that the new biochip dosimetry system is fast, accurate, sensitive and robust. In addition, the whole system is the size of a shoebox so it is very portable.

“You add a drop of blood, wait a few minutes, and get results,” explained Wyrobek in a press release. “The chip could lead to a much-needed way to quickly triage people after possible radiation exposure.” Although the technology is still under development, hopefully it will be available before the next radiological accident or terrorist attack occurs.

For more information about this biochip system, check out my KQED Science blog.