Vaccination with beneficial bacteria can have a lasting anti-inflammatory effect on the brain, increasing its resistance to physical and behavioral disturbances caused by stress, according to a study at the University of Colorado.
The findings, if replicated in clinical trials, could lead to a new probiotic immunization that protects against PTSD and anxiety and could help develop new treatments for depression.
“We found that the bacterium Mycobacterium vaccae creates an anti-inflammatory environment in the brains of rodents,” said study leader Matthew Frank. "If we can get the same result in humans, it will go a long way in neuroinflammatory disease."
Anxiety, post-traumatic stress disorder and other mental disorders caused by stress throughout life are noted in one in four. A growing body of research shows that stress-induced inflammation in the brain increases the risk of mental disorders by affecting mood-related neurotransmitters such as norepinephrine and dopamine.
“Many sources report that if you trigger an inflammatory-immune response in a person, then signs of depression and anxiety will quickly appear. Remember your mood when you were sick with the flu."
Research also suggests that trauma, illness, or surgery can increase the sensitivity of certain parts of the brain, making them instantly alert to subsequent stressors, which can lead to mood disorders and cognitive decline.
“We found that the bacterium Mycobacterium vaccae also blocks the sensitization effect of brain regions due to stress, creating a strong stress-resistant phenotype in the brain,” says Matthew Frank.
A previous study at the University of Colorado and published in the Proceedings of the US National Academy of Sciences found that mice injected with heat-killed Mycobacterium vacca bacteria and placed with a larger, aggressive male for 19 days showed less anxiety and a tendency toward intestinal or peripheral inflammation. fabrics.
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In this new study, published in the journal Behavior and Immunity, Frank and lead author Christopher Lowry, professor of psychology, set out to find out what exactly the bacteria Mycobacterium vacca do to the brain.
Male rats were injected three times with M. vaccae at one week intervals. As a result, eight days after the last injection, they significantly increased levels of the anti-excitatory protein interleukin-4 in the hippocampus, the brain region responsible for modulating cognitive functions, anxiety and fear.
After exposure to stress factors, the vaccinated animals also showed reduced levels of the stress-induced HMGB1 protein. This protein is thought to play a role in increasing the brain's sensitivity to inflammation, and in increasing the expression of CD200R1, a receptor that keeps glial cells (immune cells in the brain) anti-excitatory.
The vaccinated rats, as in the first study, showed calmer behavior after stress.
“When we look at probiotics in general, they have shown significant effects on cognitive function, anxiety and fear,” says Professor Lowry. "This work explains this effect by suggesting that these beneficial microbes, or the signals they receive from them, somehow get into the hippocampus and cause an anti-inflammatory state."
Lowry hopes that the day will come when Mycobacterium vacca (first isolated from Lake Kyoga silt in Uganda) will be injected into people at high risk for PTSD - pre-combat soldiers or emergency responders - to mitigate the effects of stress on the brain and body. They could also be used to prevent sepsis-induced cognitive impairment.
Lowry is now working with researchers at the University of Colorado to study whether veterans with PTSD can benefit from oral probiotics, which include another species of bacteria, Lactobacillus reuteri.
“Further research is required and it is possible that other strains of beneficial bacteria or probiotics have similar effects on the brain,” he said.
Vadim Tarabarko