Scientists Discover How Pomegranate Triggers the Gut’s Own Repair System
Crohn’s disease and ulcerative colitis both involve a gut lining that has lost its ability to keep bacteria contained, leaving the body’s immune system in a state of chronic overdrive. Scientists may have found a way to fix that. They’ve identified a specific chain of molecular events triggered by a compound the body makes from pomegranate-related foods that appears to strengthen that wall and calm the chaos, a discovery that could point researchers toward a new treatment strategy for inflammatory bowel disease.
Urolithin A is a substance the gut produces when it breaks down ellagitannins, plant compounds found in pomegranates and certain other foods. That does not mean pomegranates or Urolithin A supplements have been shown to treat IBD in people. Researchers had previously shown that Urolithin A can protect against gut inflammation, but the exact biological steps it follows to do that remained a mystery. A new study published in Nature Communications has mapped that path in detail, revealing a precise chain reaction that reinforces the gut’s lining and turns down the inflammatory alarm.
What sets this discovery apart is its specificity. Urolithin A doesn’t broadly suppress inflammation. Instead, it activates a specific protein in the cells lining the gut, a molecular switch called the aryl hydrocarbon receptor, which then triggers a cascade of protective signals that reinforces the gut’s defenses, at least in experimental models and lab-prepared cells from intestinal biopsies from people with IBD.
Pomegranate Compound Urolithin A Triggers a Step-by-Step Gut Repair Sequence
Specifically, Urolithin A activates the aryl hydrocarbon receptor in the cells that form the lining of the intestine. Once that switch is flipped, it activates another protein called NLRP6, which acts like a sensor inside the cell. Activating NLRP6 leads to the controlled release of a signaling molecule called interleukin-18, or IL-18, a chemical messenger that helps keep the gut environment stable.
Critically, the researchers found that Urolithin A triggered the release of IL-18 but not a closely related, more inflammatory molecule called IL-1β. That distinction matters because IL-18 at the right level is protective, while too much of it, or releasing the wrong molecules, can actually make gut inflammation worse. Urolithin A appears to hit a kind of sweet spot, promoting just enough IL-18 to start a healing cascade without tipping into damage.
That IL-18 signal then travels to another group of immune cells in the gut lining, which respond by producing a second messenger called interleukin-22, or IL-22. IL-22 is a well-established repair signal: it stimulates the cells responsible for producing the gut’s protective mucus layer and ramps up production of proteins that help keep harmful bacteria in check.
Urolithin A’s Protective Effects Vanish When Key Links in the Chain Are Removed
Researchers then set out to confirm that each step of this chain was truly necessary. Mice engineered to lack the aryl hydrocarbon receptor in their gut lining cells showed no protective benefit from Urolithin A at all, while mice that lacked it only in immune cells were still protected, a result that pinpointed the gut lining as the critical site of action. Mice in the study were exposed to a chemical that induces colitis, a standard approach in IBD research. Similar knockout experiments then removed NLRP6, then IL-18, then IL-22 from the equation. In each case, removing a single piece of the chain broke the protective effect, confirming that every step is essential.
Scientists also prepared single-cell suspensions from intestinal biopsies collected from patients with IBD, taken from both inflamed and non-inflamed areas. When these cell preparations were exposed to Urolithin A in the lab for 24 hours, the compound triggered increased IL-18 in intestinal lining cells and increased IL-22 from immune cells, mirroring the mouse model results. Blocking the aryl hydrocarbon receptor using a chemical inhibitor eliminated that IL-22 response, supporting the receptor’s role in human cells as well. Notably, other known activators of the same receptor did not produce the same IL-18 response, suggesting Urolithin A engages it in a more targeted way.
Source : https://studyfinds.com/pomegranate-hidden-gut-defense/
