Around 10 million people worldwide have Parkinson's disease, a progressive nervous system disorder that affects movement. Now, scientists have found exposure to diesel fumes can increase a person's risk of developing the disease.
Earlier research had already shown that people who live in areas with high levels of traffic-related pollution are more likely to get Parkinson's. Researchers from UCLA tested the effects of diesel exhaust fumes on zebrafish under lab conditions to understand why this happens.
As neurons in zebrafish interact in a similar way to those in humans, they can be useful analogs for understanding how certain chemicals and processes affect the brain. Also, as the fish are transparent, scientists can easily see and measure their biological processes as they happen without killing them.
For the study, the researchers added chemicals found in diesel fumes to a fish tank. They soon noticed that the chemicals changed their behavior. Closer inspection of their brains confirmed that this was likely happening as neurons died off.
After this, they investigated how the neuronal pathways linked to Parkinson's disease reacted to the same phenomenon. They found exposure to diesel particles led their brains to be less able to rid themselves of alpha-synuclein and other old proteins.
Causing these proteins to clump around neurons, a process associated with Parkinson's, the researchers began to suspect that this mechanism may explain why people in high-traffic areas are more likely to develop the disease.
To confirm whether the same may happen among human neurons, the researchers conducted the same experiment on a cluster of human cells. They found a similar result.
"It's really important to be able to demonstrate whether air pollution is actually the thing that's causing the effect or whether it's something else in urban environments," says Dr. Jeff Bronstein, one of the authors of the study. "Overall, this report shows a plausible mechanism of why air pollution may increase the risk of Parkinson's disease."