New research from scientists at the UK Dementia Research Institute at University College London has revealed how Parkinson’s disease may spread from the gut to the brain.
This discovery, made through studies in mice, could help doctors find new ways to stop the disease before it seriously harms the brain.
For a long time, researchers have suspected that Parkinson’s might begin in the gut.
This is partly because one of the first brain regions affected in Parkinson’s is the dorsal motor nucleus of the vagus nerve—a part of the brain directly connected to the gut.
However, no one fully understood how the disease actually moves from the gut into the brain.
Now, the study offers a new explanation: the disease may be getting help from the body’s own immune system.
Specifically, scientists discovered that immune cells called macrophages play a key role. These cells normally act as “first responders,” protecting the body by eating and destroying harmful substances. But in this study, the researchers found that gut macrophages were actually helping to move toxic proteins—called alpha-synuclein—from the gut to the brain.
These proteins, when misfolded, are known to build up in the brains of people with Parkinson’s, leading to the death of brain cells and the movement problems the disease is known for.
In the study, researchers took tiny amounts of alpha-synuclein from the brains of people who had died with Parkinson’s. They then injected these proteins into the small intestines of mice and watched what happened next.
The gut macrophages quickly engulfed the toxic proteins, but their waste-clearing systems stopped working properly. As a result, the macrophages began to malfunction.
The macrophages then sent signals to other immune cells known as T cells. These T cells, now activated in the gut, traveled through the bloodstream and into the brain—bringing along with them the toxic alpha-synuclein.
When the scientists reduced the number of macrophages in the gut before injecting the proteins, they noticed something remarkable: the toxic alpha-synuclein didn’t spread to the brain as much, and the mice showed fewer symptoms. This suggests that stopping or changing how these immune cells work could help prevent Parkinson’s from reaching the brain.
This could be a major breakthrough. Up to 90% of people with Parkinson’s experience digestive symptoms like constipation years or even decades before they notice movement problems.
Scientists now group patients into “body-first” and “brain-first” Parkinson’s depending on where the disease starts. This research offers an explanation for how body-first cases begin—and how they might be stopped early.
The team now hopes to explore how the body’s immune system influences brain diseases in general. They are also working on ways to use signs of inflammation in the blood as early warning signals for Parkinson’s.
Co-lead author Dr. Soyon Hong said the research shows that immune cells are not just innocent bystanders in Parkinson’s. Instead, they are reacting—but in the wrong way. By finding ways to correct their response, we may be able to slow or even stop the disease from spreading.
Dr. Tim Bartels, another lead author, said that Parkinson’s develops slowly over many years. If we can detect it before it damages the brain, we may be able to use blood tests to catch it early. This could give patients a better chance of getting help before serious symptoms begin.
This research opens new doors to understanding how Parkinson’s starts, spreads, and how it might one day be stopped—before it reaches the brain at all.
If you care about Parkinson’s disease, please read studies that Vitamin B may slow down cognitive decline, and Mediterranean diet could help lower risk of Parkinson’s.
For more information about brain health, please see recent studies that blueberry supplements may prevent cognitive decline, and results showing Plant-based diets could protect cognitive health from air pollution.
The study is published in Nature.
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