Washington D.C.: Turns out the much-dreaded diarrhea actually does serve some purpose. After years of speculation about whether it helps clear bacteria causing gastrointestinal infections, or is merely a symptom of a disease that should be prevented as much as possible, new research sheds light on its role in our body.
In a new study from Brigham and Women’s Hospital, investigators explore the immune mechanism that drives diarrhea, concluding that it does play a critical role in pathogen clearance in the early stages of infection. The new study, published in Cell Host and Microbe, also uncovers a previously unrecognized role for interleukin-22, an immune system molecule, in the host’s defense against infection.
“The hypothesis that diarrhea clears intestinal pathogens has been debated for centuries,” said corresponding author Jerrold Turner, MD, PhD, of the BWH Departments of Pathology and Medicine, adding, “Its impact on the progression of intestinal infections remains poorly understood. We sought to define the role of diarrhea and to see if preventing it might actually delay pathogen clearance and prolong disease.”
To investigate, researchers used a mouse model infected with Citrobacter rodentium, the mouse equivalent of an E. coli infection. Using this model, they saw an increase in the permeability of the intestinal barrier within just two days of infection — well before inflammation and epithelial damage. In particular, they uncovered a critical role for interleukin-22, that in turn influences another molecule called claudin-2, previously known to be involved in causing diarrhea.