In a new study, researchers found that serotonin, a chemical known for its role in producing feelings of well-being and happiness in the brain, can reduce the ability of some intestinal pathogens to cause deadly infections.
The findings could offer a new way to fight gut infections for which few truly effective treatments currently exist.
The research was conducted by UT Southwestern scientists.
Although the vast majority of research on serotonin has centered on its effects in the brain, about 90% of this neurotransmitter – a chemical that nerve cells use to communicate with each other – is produced in the gut.
In humans, trillions of bacteria live within this space.
Most of these gut bacteria are beneficial, but pathogenic bacteria can also colonize the gastrointestinal tract, causing serious and potentially fatal infections.
Because gut bacteria are strongly affected by their environment, the team wondered whether the serotonin produced in the gut can affect the virulence of pathogenic bacteria that infect the gastrointestinal tract.
The researchers worked with Escherichia coli O157, a species of bacteria that causes periodic outbreaks of often deadly foodborne infection.
The team grew these pathogenic bacteria in petri dishes in the lab, then exposed them to serotonin.
They found that serotonin strongly reduced the expression of a group of genes that these bacteria use to cause infections.
Additional experiments using human cells showed that the bacteria could no longer cause infection-associated lesions on the cells if these bacteria were exposed to serotonin.
Next, the researchers examined how serotonin affected virulence in living hosts.
They studied how serotonin might change the ability for a mouse gut bacterium often used as an analog for E. coli in humans to infect and sicken their hosts.
They found that treating mice with fluoxetine (sold under the brand name Prozac) to increase serotonin levels prevented them from getting sick.
Further experiments showed that it’s possible that serotonin could have wide-ranging effects on gut bacterial health.
The team says treating bacterial infections, especially in the gut, can be very difficult.
If scientists could repurpose Prozac or other drugs in the same class, it could give people a new weapon to fight these challenging infections.
One author of the study is Vanessa Sperandio, Ph.D., a professor of microbiology and biochemistry at UT Southwestern Medical Center.
The study is published in Cell Host & Microbe.
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