Michal Werbner, Orly Avni and Yiftah Barsheshet.
(photo credit: Courtesy)
A study by Bar-Ilan University has found that chronic social and psychological stress is recognized by some of the bacteria in the gut, which causes them to become more “violent.” In response, the immune system kicks in and the result can be an increased risk for autoimmune disease in susceptible individuals.
“Many studies support the notion that stressful life events play a role in the etiopathogenesis of autoimmune disorders,” Orly Avni of the Azrieli Faculty of Medicine at Bar-Ilan University explained. “Stress-triggered neuroendocrine hormones lead to immune dysregulation, but considering the recently appreciated gut-brain-microbiota axis, and the well-known microbiota-immune interactions, we asked whether and how the brain-microbiota-immune triangle is involved in stress-promoting autoimmunity.”
The National Institutes of Health estimates that more than 20 million people in the United States, the vast majority of whom are women, have autoimmune disease. Worldwide, the incidence of autoimmune disease is estimated at 5%. Examples of autoimmune disease are multiple sclerosis, lupus, rheumatoid arthritis, juvenile diabetes, scleroderma, and pulmonary fibrosis.
The study, conducted by Avni with Ph.D. student Michal Werbner and lab manager Yiftah Barsheshet and published in mSystems, was conducted on two groups of mice. One was exposed to stress in the form of daily, threatening encounters with other “dominant and aggressive” mice. The other group was left alone. After 10 days, the researchers analyzed the gut microbiome of each group and found that the stressed mice had higher levels of some bacteria. Those included Bilophila and Dehalobacterium microbes, genera that have been observed at unusually high levels in patients with multiple sclerosis, for example.
Further, the study showed that stress led to the activation of bacterial genes related to potentially violent traits – including growth, motility and signals sent between a pathogen and a host. Microbes with these traits can travel to other parts of the body, including lymph nodes, and elicit an immune response.
“We know that there’s strong crosstalk between the immune system and the microbiota,” Avni said. This study showed that social stress changed both the composition and transcriptional patterns in the microbiota, “and the consequent immune response to that threat jeopardized the tolerance to self.”
In other words, researchers found that the onset of stress caused changes in the intestinal bacteria that, in turn, stimulated the activity of immune cells in a way that increased the likelihood that the body would attack itself.
Avni told The Jerusalem Pos
t that if this reaction could be better understood, it could offer opportunities for potential treatment, including through the use of pharmaceutical inhibitors.
“Life is stressful,” Avni said. “Most of us know that stress can affect our well being.”
The next step, she said, might be to examine how the effects of stress on the microbial composition and “behavior” could increase the risk of depression, and “how we can use our knowledge for diagnosis, and hopefully novel treatment modalities.”
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