New Insights into Alzheimer’s Brain Inflammation

ROCKVILLE, MD – Brain inflammation, while a crucial part of the body’s immune response, takes on a detrimental role in Alzheimer’s disease. Unlike the acute, short-lived inflammation that combats infection, the inflammation associated with Alzheimer’s becomes chronic and persistent. Scientists have been trying to understand why this happens. 

New research reveals key differences in how the brain’s immune system responds to the disease compared to a bacterial infection. The work will be presented at the 69th Biophysical Society Annual Meeting, to be held February 15 – 19, 2025 in Los Angeles.

The study focuses on how immune cells react to amyloid-beta (Aβ) plaques, a hallmark of Alzheimer’s, and how this immune response differs from the reaction to bacterial toxins. “Bacteria cannot enter our brain because of the blood brain barrier,” said Arpan Dey, PhD, a postdoctoral associate in the lab of Professor David Klenerman at the University of Cambridge in the United Kingdom. “But small proteins could be acting like bacteria in our brain and giving rise to neuroinflammation, which could be contributing to dementia,” he added.

Dey and colleagues used a model system of immune cells and exposed the cells to Aβ aggregates or lipopolysaccharide (LPS), a component of bacterial cell walls that triggers a strong immune response. They focused on the formation of structures called myddosomes, which are crucial for initiating inflammation.

The team discovered that larger Aβ clumps trigger more myddosome formation in immune cells. Smaller Aβ clumps, even after longer exposure, failed to trigger this response. This suggests that the size of the Aβ clump is critical for activating the immune system in Alzheimer’s.

In contrast, LPS triggered a much faster and stronger myddosome response than even the large Aβ aggregates. This difference in timing and intensity may explain why inflammation in Alzheimer’s is chronic and drawn-out, whereas the response to a bacterial infection is typically more acute and resolves more quickly.

“Our findings reveal a crucial distinction in how the brain’s immune system reacts to a bacterial infection versus Aβ clumps,” said Dey. “The slower, more sustained immune activation by large Aβ aggregates may contribute to the chronic inflammation seen in Alzheimer’s disease.”

The team’s next step is to start looking at markers of myddosomes in blood samples from people with dementia and brain samples from the UK Brain Bank.

By understanding the mechanisms driving inflammation in Alzheimer’s, they hope to contribute to the development of new therapies that can specifically target the chronic inflammation associated with the disease, potentially slowing its progression.

“This work opens up new avenues for drug discovery,” Dey said, he added, “by understanding and targeting the pathways involved in the inflammatory response, we may be able to develop treatments for Alzheimer’s and other neurodegenerative diseases.” 

Image Caption:

Myddosome formation (shown in yellow-green) is triggered by Aβ aggregates (shown in red) in macrophages. Image courtesy of Arpan Dey.

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The Biophysical Society, founded in 1958, is a professional, scientific Society established to lead development and dissemination of knowledge in biophysics. The Society promotes growth in this expanding field through its annual meeting, publications, and committee and outreach activities. Its 7,000 members are located throughout the United States and the world, where they teach and conduct research in colleges, universities, laboratories, government agencies, and industry.