British scientist David Strachan first proposed the controversial "hygiene hypothesis" in 1989, suggesting that in our modern, sterile world, lack of exposure to microorganisms in childhood was leading to impaired immune systems and higher rates of allergies and asthma. Researchers have since refined that theory, suggesting that it is not lack of exposure to disease-causing germs at play, but rather to "old friends" -- beneficial microbes in soil and the environment that we have long lived alongside -- and that mental health is also impacted.
"The idea is that as humans have moved away from farms and an agricultural or hunter-gatherer existence into cities, we have lost contact with organisms that served to regulate our immune system and suppress inappropriate inflammation," said Lowry. "That has put us at higher risk for inflammatory disease and stress-related psychiatric disorders." . . .
One Lowry-authored study, published in the Proceedings of the National Academy of Sciences in 2016, showed that injections of M. vaccae prior to a stressful event could prevent a "PTSD-like" syndrome in mice, fending off stress-induced colitis and making the animals act less anxious when stressed again later.
"We knew it worked, but we didn't know why," said Lowry. "This new paper helps clarify that." . . .
"It seems that these bacteria we co-evolved with have a trick up their sleeve," said Lowry. "When they get taken up by immune cells, they release these lipids that bind to this receptor and shut off the inflammatory cascade."Lowry has long envisioned developing a "stress vaccine" from M. vaccae, which could be given to first responders, soldiers and others in high-stress jobs to help them fend off the psychological damage of stress."This is a huge step forward for us because it identifies an active component of the bacteria and the receptor for this active component in the host," he said. . ..
"This is just one strain of one species of one type of bacterium that is found in the soil but there are millions of other strains in soils," Lowry said. "We are just beginning to see the tip of the iceberg in terms of identifying the mechanisms through which they have evolved to keep us healthy. It should inspire awe in all of us."
