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Alzheimer's disease is transmitted from neuron to neuron
Last reviewed: 01.07.2025
Scientists from the Van Andel Research Institute (VARI) and Lund University, Sweden, have published a study that clarifies how Parkinson’s disease spreads throughout the brain. Experiments in a rat model of the neurodegenerative disease reveal a process that has previously been used to explain mad cow disease: the migration of misfolded proteins from diseased to healthy cells. This model has never been demonstrated so clearly in a living organism, and the scientists’ breakthrough brings us one step closer to drugs that can actively intervene in Parkinson’s disease.
“Parkinson’s disease is the second most common neurodegenerative disorder after Alzheimer’s disease,” said study leader Patrik Brundin, MD, PhD. “A major unmet medical need is a treatment that slows the progression of the disease. We aim to better understand how Parkinson’s disease progresses and thereby identify new molecular targets for disease-modifying drugs.”
Previous studies had shown that young, healthy neurons transplanted into the brains of Parkinson's patients gradually develop a misfolded protein known as alpha-synuclein. This discovery led to Dr. Brundin's group's hypothesis that the protein was being transferred from cell to cell, which was later demonstrated in laboratory experiments.
In a study published in the journal Public Library of Science One, the scientists were able to track for the first time the events in a recipient cell as it ingests a pathological protein that passes through the cell’s outer membrane. In addition, the experiments showed that ingested alpha-synuclein attracts proteins from the host cell, inducing abnormal intracellular folding or aggregation. “This cellular process likely drives the pathological process of Parkinson’s disease progression, and as the patient’s condition worsens, it spreads to more and more brain regions,” suggests the study’s lead author Elodie Angot, PhD.
"In our experiments, we showed a core of abnormal human alpha-synuclein protein surrounded by alpha-synuclein produced by the rat itself. This means that the misfolded protein not only moves between cells, but also acts as a 'seed' that attracts proteins made by the rat's brain cells," said Jennifer Steiner, PhD, another lead author of the study.
However, it remains unclear how exactly alpha-synuclein gains access from the extracellular space into the cell's cytoplasm, in turn becoming a template for misfolding naturally occurring alpha-synuclein there. Further research is needed to elucidate this important step in the process.
The discovery does not reveal the root cause of Parkinson's disease, but when combined with disease models developed at Lund University and elsewhere, it could help find new drug targets to alleviate symptoms or slow the progression of the disease, which today affects more than 1% of the population over the age of 65.
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