Posted on Jun 09, 2017, 10 a.m.
Certain types of bacteria in the gut can leverage the immune system to decrease the severity of stroke.
Stroke is currently the second leading cause of death worldwide. The most common type is ischemic stroke, during which a blocked blood vessel prevents blood from reaching the brain. Researchers at Memorial Sloan Kettering Cancer Center induced ischemic stroke in mice two weeks after administering a combination of antibiotics. The mice treated with antibiotics had a stroke that was approximately 60 percent smaller than the mice that did not receive antibiotics. The microbial environment in the gut instructed the immune cells present there to protect the brain, shielding it from the stroke’s full force. "Our experiment shows a new relationship between the brain and the intestine," stated Dr. Josef Anrather, the Finbar and Marianne Kenny Research Scholar in Neurology and an associate professor of neuroscience in the Feil Family Brain and Mind Research Institute at Weill Cornell Medicine. "The intestinal microbiota shape stroke outcome, which will impact how the medical community views stroke and defines stroke risk." These findings open up the possibility that altering the macrobiotic makeup of the gut could become a new method of preventing stroke. For high-risk patients, such as those who are having cardiac surgery or those who have multiple obstructed blood vessels in the brain, this could be particularly beneficial. Further exploration is required to figure out exactly which bacterial components generated their protective message. The researchers do know, however, that the bacteria did not interact with the brain chemically, but instead influenced neural survival by changing the behavior of the immune cells. The gut’s immune cells traveled up into the outer coverings of the brain, which are called the meninges. Here they organized and directed a response to the stroke. "One of the most surprising findings was that the immune system made strokes smaller by orchestrating the response from outside the brain, like a conductor who doesn't play an instrument himself but instructs the others, which ultimately creates music," said Dr. Costantino Iadecola, director of the Feil Family Brain and Mind Research Institute and the Anne Parrish Titzell Professor of Neurology at Weill Cornell Medicine. This new gut-brain connection holds promise for preventing stroke in the future, which the researchers say may be achieved by changing at-risk patients’ nutrition.
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Nature Medicine, DOI: 10.1038/nm.4068 Commensal microbiota affects ischemic stroke outcome by regulating intestinal γδ T cells