Helicobacter pylori in the mouse stomach put the brakes on colitis by reducing the immune response in the lower GI tract, U-M study shows
Ann Arbor, Mich. -Helicobacter pylori, a common stomach bacterium, reduced the severity of inflammation of the colon caused by Salmonella in mice, according to research from U-M Medical School scientists.
More than half the people in the world are infected with H. pylori, although the incidence is much lower in the United States. National Institutes of Health sponsored research efforts at the University of Michigan led by John Kao, M.D.assistant professor of Gastroenterology, have focused on investigating the protective benefit of H. pylori infection. The team of scientists assembled by Kao published their findings last week in the journal Inflammatory Bowel Diseases demonstrating the direct effect of the bacteria in inhibiting lower gut inflammation.
"If we have evolved to live with certain bugs, maybe there is a reason," said Peter Higgins, M.D., Ph.D. MSc, a collaborator and assistant professor of Gastroenterology in U-M's Department of Internal Medicine. "This research demonstrates that having H. pylori in your stomach could have beneficial immune effects in other parts of the body."
In the study, researchers infected mice with H. pylori first and then co-infected them with Salmonella, which induces the inflammatory bowel disease colitis. The data provided the first evidence that H. pylori infection in the stomach alters the immunological environment of the lower gastrointestinal tract and reduced the severity of Salmonella-induced colitis, says Jay Luther, M.D. a research fellow on the team.
"This was surprising because H. pylori infects the stomach, not the colon. It appears to have a more global effect on the gut immune system," says Kao. "But it may explain why people in regions with lots of H. pylori infection - such as Asia and Africa - get fewer inflammatory bowel diseases, like ulcerative colitis and Crohn's disease."
It also may explain why H. pylori infection is so common, Higgins says. Salmonella was historically a rampant fatal infection that caused the plague of Athens, which led to rise of Sparta. It also likely led to the early death of Alexander the Great. So it would make sense that many humans carry the H. pylori bacteria, if it truly reduces the severity of inflammation caused by Salmonella, Higgins says.
The H. pylori infection is now more commonly found in developing countries or those with poor sanitation, where Salmonella and inflammatory bowel diseases are more common. Most people contract H. pylori in their first seven years of life, most commonly through exposure to feces.
Kao does not recommend that physicians withhold treatment against H. pylori in patients with H. pylori-associated stomach problems, such as gastric ulcers or malignancies. However, he cautioned against global vaccination programs to eradicate H. pylori.
"Several studies have also reported negative associations between H. pylori infection and chronic inflammatory conditions such as lupus and asthma. More studies are underway in the Kao Laboratory to understand how H. pylori induces global immune suppression."
About U-M's Division of Gastroenterology: U-M is one of the largest gastroenterology practices in the country and is a leader in the prevention, diagnosis, and treatment of diseases of the gastrointestinal tract and liver. Our 50-plus physicians are experts in the diagnosis and treatment of all diseases of the gastrointestinal system, from simple to complex, including those of the esophagus, stomach, small intestine, colon, rectum, liver, gallbladder, pancreas and biliary tract.
In addition to being leaders in the clinic, our faculty are also leaders in their respective areas of research, which span such varied interests as the role of peptides in the brain-gut interactions in functional bowel diseases to innovative treatments of viral hepatitis and liver cancer.
Additional authors: Laura A. Johnson, research specialist; Jay Luther, M.D.; Min Zhang, research specialist; all from the U-M Department of Internal Medicine.