The team found that Salmonella is able to regulate the vitamin D receptor, increasing its activity and determining where in the colon the receptor is active. In the presence of Salmonella, the receptor was more prevalent than usual deep within folded intestinal structures known as crypts.
Sun's team also discovered that the vitamin D receptor plays a key role in defending the body from assault by Salmonella and squelching inflammation. The receptor stops a molecule known as NF-Kappa B, a well-known master player in the world of inflammation, by binding to it and preventing it from activating other inflammatory molecules. While scientists have known that the receptor interacts with NF-Kappa B, details of the interaction modulated by bacteria in the colon are new.
The scientists found that Salmonella was much more virulent and aggressive in mice in which the vitamin D receptor had been turned off. These mice showed higher levels of activity of inflammatory molecules, and they lost weight more quickly and were much more likely to die in response to infection.
"We live together in a mutually beneficial state with most of the bacteria in our gut," said Sun, assistant professor in the Gastroenterology and Hepatology Division of the Department of Medicine. "They help us digest foods like fruits and vegetables, and we provide them a place to live and thrive. We co-exist peacefully most of the time.
"But we aren't able to culture most of these bacteria in the laboratory, and we don't know what most of them are doing. We need to understand our gut flora much more than we do. This is particularly important for understanding
|Contact: Tom Rickey|
University of Rochester Medical Center