In the study, it was found that inflammatory reactions can alter the brain's immune cells in the long term, which means that these cells have an "immunological memory." This memory may affect the development of neurological disorders that occur over time. It is, therefore, a previously unknown factor that could affect the severity of these diseases.
A team of researchers at the German Center for Neurodegenerative Diseases (DZNE), the Hertie Institute for Clinical Brain Research (HIH), and the University of Tuebingen wanted to find out whether environmental factors change microglia, the immune cells that only occur in the brain, over time. The research team also wanted to identify what effects this can have on the brain. Previous studies have shown that infectious diseases and inflammation experienced during a lifetime can influence the severity of Alzheimer's disease much later in life.
Microglia protects the brain by eliminating intruders and toxic substances in the brain. However, there are instances wherein they can also cause harm. Because of this, they have been suspected of contributing to neurodegenerative diseases.
"We therefore asked ourselves whether an immunological memory in these long-lived microglia could be communicating this risk," explained Dr. Jonas Neher, leader of the study and a scientist at the DZNE and the HIH.
Thus, the research team stimulated an immune reaction in the brain by triggering inflammation in mice, outside their brains. Although it was known that such inflammation could trigger an immune reaction in the brain, it was unclear whether microglia might be able to remember a previous inflammation.
As a result, they were able to cause two different states in the microglia – training and tolerance. The first inflammatory stimulus trained the microglia, which made them react more violently to the second. After a fourth stimulus, however, tolerance occurred, and the microglia barely responded.
After that, the team tested how microglia training and tolerance influenced the formation of amyloid plaques in the long term. These plaques are toxic deposits that build up in the brains of people with Alzheimer's disease. With the use of a mouse model of Alzheimer's pathology, they found that trained microglia intensified the formation of plaques even months after their immunological memory had been triggered. In turn, this increased the severity of the disease. On the other hand, tolerant microglia decreased plaque load. Similar effects also appeared in a mouse model of stroke.
To further understand these effects, they also examined epigenetic changes in the microglia. With that, they found that both the trained and the tolerant immune cells showed specific epigenetic changes and corresponding changes in gene activation, even months after the initial stimulus. These changes affected crucial functions in the microglia, including their ability to get rid of amyloid plaques.
"It is possible that also in humans, inflammatory diseases that primarily develop outside the brain could trigger epigenetic reprogramming inside the brain," Neher said.
Cutting inflammatory disease risk
A study by the Fred Hutchinson Cancer Research Center suggested that a low glycemic diet reduces inflammatory blood marker by almost a quarter. In addition to diet, there are other ways to reduce the risk of inflammation.
- Refrain from taking antibiotics, antacids, and NSAIDS as these could cause changes in the gut that can harm your microbiome.
- Try a simple meditation practice as that can significantly improve your health.
- Exercise regularly.
- Lessen your exposure to toxins as these can affect your immune system.
- Get enough sleep because lacking even a few hours of sleep each night can trigger pro-inflammatory changes.
- Get exposed to the sun for 10 to 15 minutes each day.
- Get a therapeutic massage.
Read more news stories and studies on the brain by going to Brain.news.
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