Alzheimer’s disease is the most common cause of dementia and affects millions of people around the world. It slowly damages memory, thinking and the ability to perform everyday tasks.
Although scientists have learned a great deal about the disease, there is still no cure, and current medicines can only ease symptoms or slow the disease for a limited time. Researchers are therefore searching for new ways to stop the illness before it spreads through the brain.
A team of scientists at University of Utah Health has now discovered an unexpected clue. Their findings were published in the journal Cell. The research suggests that a normal brain protein called Arc may accidentally help Alzheimer’s disease spread from one brain cell to another.
One of the main causes of Alzheimer’s disease is the buildup of an abnormal protein called Tau. Healthy brain cells contain Tau, which normally helps support the cell’s internal structure. In Alzheimer’s disease, however, Tau changes shape and sticks together into harmful clumps that damage and eventually kill neurons.
As brain cells become sick, these harmful Tau clumps can break into tiny pieces known as Tau seeds. These seeds can move into nearby healthy neurons and trigger normal Tau proteins to become harmful as well. This chain reaction allows the disease to spread to new parts of the brain over time.
The researchers wanted to understand how Tau travels between brain cells. They studied mice with Alzheimer’s disease and compared animals that produced the Arc protein with mice that did not. Arc normally plays an important role in learning and memory by helping neurons communicate with each other.
The team discovered that Arc packs itself into tiny bubble-like structures called extracellular vesicles. These microscopic sacs naturally carry messages between brain cells. Unfortunately, harmful Tau appears to take advantage of this normal communication system by attaching itself to Arc and travelling inside these vesicles.
When the scientists removed Arc, the amount of Tau moving between brain cells dropped dramatically. Disease spread was almost completely blocked. This finding suggests that Arc is a key part of the process that allows toxic Tau to reach healthy neurons.
However, the researchers also found that Arc has an important protective role. By helping damaged neurons release excess Tau, Arc reduces the buildup of toxic protein inside those cells. Without Arc, diseased neurons died more quickly because the harmful Tau remained trapped inside them.
This means future treatments may need a more careful approach. Instead of stopping Arc completely, scientists may be able to block the harmful vesicles after they leave diseased neurons but before they enter healthy ones. This could slow the spread of Alzheimer’s while still allowing the original cells to remove some toxic protein.
This study provides an important new understanding of how Alzheimer’s disease progresses. A major strength is that it explains a possible biological pathway rather than simply describing disease changes.
However, the work was carried out mainly in mice, so much more research is needed before the findings can be applied to people. If confirmed in human studies, this discovery could lead to new therapies that slow brain damage and help preserve memory for longer.
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Source: University of Utah Health.
