University of Pittsburgh researchers say it appears carbon monoxide, a component of cigarette smoke, helps shut down the intestinal inflammation that causes ulcerative colitis.
The study, published in the Dec. 19 issue of The Journal of Experimental Medicine, says small amounts of CO are produced in the human body as a normal byproduct of metabolism. High dose CO gas is lethal, because it robs the body of oxygen, but in low concentrations it acts as an anti-inflammatory agent.
Scott Plevy and his colleagues at the University of Pittsburgh tested the theory on mice and found that inhaled CO inhibited the production of interleukin (IL)-12 by immune cells.
IL-12 is normally produced during infection and helps activate the immune cells that fight off the invading pathogens. But chronic production of IL-12 also drives the inflammation that causes ulcerative colitis.
While inhaled CO might provide some relief for patients with ulcerative colitis, Plevy said cigarette smoking is a risk factor not only for heart disease and cancer but also for Crohn's disease, another form of inflammatory bowel disease.