Inhaling carbon monoxide (CO) can kill you, but it may also help prevent rejection of transplanted hearts and reclogging of arteries after angioplasty, according to the results of a study in rats.

Physical trauma to blood vessels during balloon angioplasty or immune-mediated damage after transplant often leads to dysregulated proliferation of smooth-muscle cells in these vessels. The resulting narrowing of the vessels, or stenosis, can curb or completely block blood flow, limiting the success of these lifesaving procedures.

Now, a group led by Leo E. Otterbein at the University of Pittsburgh School of Medicine (Pittsburgh, PA) reports that exposing rats to low levels of CO substantially reduces this vascular narrowing (Nature Medicine, February). The research team found that rats exposed to CO (250 p.p.m.) immediately after aortic transplantation and for the subsequent 56 days, exhibited ∼60% less stenosis than did control animals. Similarly, the research team found that stenosis was reduced by ∼75% in rats exposed to CO for an hour before undergoing a procedure similar to balloon angioplasty.

If similarly successful results can be obtained in humans, CO therapy could substantially improve the prognosis for patients undergoing transplant or angioplasty. As Otterbein tells Lab Animal, “The ease of delivery, the short exposure time, and reversibility of the therapy, combined with the over 100 years of understanding of how this molecule functions, not to mention the low cost to produce it, makes [CO] an ideal candidate for development and use as a potential therapy in not only vascular diseases, but a host of inflammatory disorders.”

According to Otterbein, his group is “currently testing the effects [of CO] in a pig model as well as carrying out some dose-ranging studies and time courses in rats to better understand the amount and length of exposure that will be optimal.” Based on the results of these tests, in addition to safety studies to determine if inhaling comparable doses of CO has untoward effects in humans, they hope to move to testing this therapy in angioplasty patients.