A bioengineered protein may someday treat carbon monoxide poisoning

An antidote for carbon monoxide poisoning could come from bacteria.

Mice treated with a tweaked version of a bacterial protein rapidly cleared carbon monoxide from their blood, safely eliminating it through urine, researchers report in the Aug. 12 Proceedings of the National Academy of Sciences.

“The most common poisoning in the world is carbon monoxide poisoning,” says biochemist Mark Gladwin of the University of Maryland in Baltimore. In the United States alone, more than 50,000 people seek emergency care every year and roughly 1,500 die. “And we really don’t have an antidote.”

The colorless, odorless gas — which comes from fires, car fumes and more — binds tightly to hemoglobin, the oxygen-carrying protein in red blood cells. When it does, the oxygen is ousted, depriving tissues and leading to symptoms such as headache, dizziness and confusion.

The only treatment is supplemental oxygen, from a mask or in a hyperbaric chamber, which reduces the amount of time it takes for carbon monoxide to naturally come off red blood cells. But delays in diagnosis and treatment mean that some patients still end up with lasting heart and brain problems. Drugs that instead directly pluck carbon monoxide from blood cells could speed up recovery.

One solution may come from bacteria called Paraburkholderia xenovorans.

These microbes use a protein called RcoM to detect low levels of carbon monoxide and convert it to energy. “We said, ‘Wow, this is something in nature that’s known to bind [carbon monoxide] very tightly,’” Gladwin says. What’s more, the protein does not bind to oxygen or nitric oxide, a molecule that in mice and people is involved in regulating blood pressure.

With some molecular tweaks, the team engineered a version of RcoM that in lab dishes removed half the carbon monoxide from red blood cells in under a minute. Poisoned mice treated with the protein quickly removed the gas in their pee, with no impact on blood pressure.

The goal is to develop a drug that first responders can administer as soon as they suspect carbon monoxide poisoning, says biochemist Jesus Tejero of the University of Pittsburgh. “As long as [the drug] is safe, even if you’re not 100 percent sure that this person has [carbon monoxide] poisoning, you can administer to them.”

People could receive supplemental oxygen at the same time, because RcoM doesn’t strongly bind to oxygen, Tejero says. The team now needs to demonstrate the treatment’s effectiveness and safety in larger animals such as pigs or rats before clinical trials can start in people.