Scientists have demonstrated in mouse studies that specially designed probiotics can reduce brain inflammation associated with diseases like multiple sclerosis. The study points to new potential therapies for hard-to-treat chronic conditions that may be as simple as popping a pill.
They might seem pretty separate, but a growing body of research is showing that the gut and the brain are more deeply intertwined than we thought. Neurological diseases like Parkinson’s and Alzheimer’s might actually begin in the gut, and health appears to be a two-way street between them.
In the new study, researchers from Harvard Medical School’s Brigham and Women’s Hospital investigated how targeting the gut could help treat MS. As an autoimmune disease, MS occurs when a patient’s immune system mistakenly attacks the protective myelin coating around nerves. It can be tricky to treat, thanks to the important, impassable blood-brain barrier that blocks most molecules, drugs included.
The team studied dendritic cells – immune cells that are common in the gastrointestinal tract and spaces around the brain – which help the immune system differentiate between dangerous pathogens and harmless molecules, including the body’s own cells. In doing so, they discovered a biochemical pathway that dendritic cells can use to prevent autoimmune damage.
“The mechanism we found is like a brake for the immune system,” said Francisco Quintana, lead author of the study. “In most of us, it’s activated, but in people with autoimmune diseases, there are problems with this brake system, which means the body has no way to protect itself from its own immune system.”
On closer inspection, the researchers found that dendritic cells produce a molecule called lactate to trigger this braking system. So, they genetically engineered bacteria to produce lactate, and then tested them in mice with an MS-like disease to see if they could be used as a probiotic to reduce the ill effects.
And sure enough, they found that the lactate suppressed the autoimmune attacks of the animals’ T cells, reducing the effects of the disease in the brain. Importantly, none of the bacteria were found in the bloodstream, indicating that there was some kind of biochemical signaling occurring between the gut and brain.
Of course, the results of mouse studies don’t necessarily translate to humans, so much more work will need to be done before such a therapy might be used in the clinic. But the team hopes that eventually, controlling MS and other autoimmune diseases could be as simple as popping pills.
“We’ve learned in recent decades that the microbes of the gut have a significant impact on the central nervous system,” said Quintana. “One of the reasons we focused on multiple sclerosis in this study was to determine whether we can leverage this effect in treating autoimmune diseases of the brain. The results suggest we can.
“The ability to use living cells as a source of medicine in the body has tremendous potential to make more personalized and precise therapies. If these microbes living in the gut are powerful enough to influence inflammation in the brain, we’re confident we’ll be able to harness their power elsewhere as well.”
The research was published in the journal Nature.