Altering the gut microbiota of mice can reduce brain damage after a stroke, reports a new study published online in Nature Medicine. These findings highlight a previously unrecognized link between the intestine and the brain.
Communities of microbes - the microbiome - colonize the gut and other barrier surfaces in the body early in life, and they have a pronounced influence on the development of the immune system and on metabolic processes. Alterations in the microbiome have been identified in several diseases, including inflammatory bowel disease, obesity and asthma, and they influence disease outcome.
Josef Anrather and colleagues used a mouse model of stroke to show that microbes in the gut regulate the development of pro-inflammatory immune cells, which migrate from the intestine to the brain after a stroke is induced. The authors treated mice with antibiotics, and found that this shifted the balance of pro- and anti-inflammatory immune cell types in the gut, increasing the number of anti-inflammatory, regulatory T (Treg) cells present. These microbial shifts ultimately reduce the number of pro-inflammatory cells that travel to the brain after stroke, which results in reduced brain damage. The transferal of microbes from mice treated with antibiotics to untreated mice provided similar protection from brain damage after stroke. The authors conclude that the subset of immune cells identified in the study and the cells' migration to the brain could potentially be targeted therapeutically to affect stroke outcomes, if this specific link between the intestine and the brain is also found in humans.