For many years, scientists have known that inflammation plays a major role in Alzheimer’s disease.
Brain scans, laboratory studies, and patient samples have repeatedly shown signs of ongoing inflammation in people with the condition.
Yet one important question has remained unanswered: what keeps the inflammation going long after it should have stopped?
A new study from Scripps Research may provide an important answer. Researchers have identified a molecular switch that appears to push the brain’s immune system into overdrive, creating a self-sustaining cycle of inflammation and damage.
Their findings were published in Cell Chemical Biology and could point to a completely new treatment strategy for Alzheimer’s disease.
Alzheimer’s disease affects memory, thinking, and behavior. It is characterized by the accumulation of abnormal protein clumps in the brain, including amyloid-beta plaques and other toxic protein aggregates. These changes are believed to damage brain cells and gradually interfere with communication between different parts of the brain.
In recent years, scientists have realized that the immune system is deeply involved in this process. The brain contains specialized immune cells that constantly monitor their surroundings.
Their job is to remove waste, respond to injury, and protect nerve cells. But in Alzheimer’s disease, these cells often remain activated for long periods, producing inflammatory chemicals that can worsen damage.
The new study focused on a protein called STING, which stands for Stimulator of Interferon Genes. STING is an important part of the body’s defense system and helps detect signs of infection and cellular stress. Normally, it turns on briefly when needed and then settles down once the threat has passed.
The researchers discovered that Alzheimer’s disease may change this normal behavior through a chemical process called S-nitrosylation. During this process, a nitric-oxide-related molecule attaches to a specific site on the STING protein.
This small chemical change has major consequences. The modified STING proteins begin gathering together into clusters that trigger powerful inflammatory signals. Instead of acting as a temporary alarm system, STING becomes chronically activated.
The team found high levels of this altered form of STING in brain tissue from people who had Alzheimer’s disease. Similar results appeared in human brain immune cells grown in the laboratory and in mice engineered to develop Alzheimer’s-like symptoms.
One of the most interesting findings involved the relationship between protein clumps and inflammation. The researchers discovered that amyloid-beta and alpha-synuclein, two proteins linked to neurodegenerative disease, can trigger the S-nitrosylation of STING.
This creates what researchers describe as a feed-forward cycle. Protein clumps trigger inflammation. Inflammation produces nitric oxide. Nitric oxide modifies STING. Overactive STING then drives even more inflammation, which may further increase protein-related damage.
To test whether this cycle could be broken, the scientists engineered a version of STING that lacked the specific site required for S-nitrosylation. This modified protein could not be pushed into its harmful overactive state.
The results were encouraging. Mice carrying the modified protein showed significantly lower levels of neuroinflammation. Their brain immune cells were calmer, and the synapses connecting nerve cells remained healthier.
Synapses are especially important because they allow brain cells to communicate with one another. Scientists believe that the loss of these connections is one of the strongest predictors of cognitive decline in Alzheimer’s disease. Preserving synapses may therefore help preserve memory and thinking abilities.
The research team is now working on developing small molecules that specifically block the critical site on STING. Their goal is to prevent excessive activation without disabling the normal protective functions of the immune system.
This research offers an important advance because it identifies a precise biological mechanism linking protein aggregates, inflammation, and synapse loss in Alzheimer’s disease. The findings were replicated across human tissue samples, stem-cell-based models, and animal studies, increasing confidence in the results.
A major advantage of the proposed strategy is that it targets only the harmful overactivation of STING rather than shutting down the immune system entirely. However, the work remains experimental, and no treatment based on this approach has yet been tested in people.
Human clinical studies will be necessary to determine whether targeting STING can slow cognitive decline or alter the course of Alzheimer’s disease. Even so, the discovery represents a promising new direction in the search for effective Alzheimer’s therapies.
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