Carbon Monoxide May Protect Brain Following Hemorrhagic Stroke

Carbon monoxide is commonly referred to as “the silent killer”, resulting in hundreds of deaths and catastrophic brain injuries each year. However, a group of researchers indicate that they may have found a potentially life-saving application for toxic gas.

Researchers from Beth Israel Deaconess Medical Center at Harvard report that animal testing shows carbon monoxide gas may be used to treat hemorrhagic strokes. Their findings were published online on May 26 in the Journal of Clinical Investigation (JCI). 

The study involved testing on mice that inhaled small levels of carbon monoxide following a subarachnoid hemorrhage (SAH), a type of stroke that affects about 40,000 Americans each year and has a 50% mortality rate. The researchers found that carbon monoxide was a key element used by the body to remove dangerous heme pigments that build up in the brain after a SAH stroke.

Heme build up can cause inflammation in the brain, furthering stroke brain damage. An estimated 30-40% of SAH stroke survivors suffer long-term brain damage.

One of the co-lead study authors, Dr. Leo E. Otterbein, an investigator in the Transplant Institute at Beth Israel, has been investigating potential therapeutic uses of carbon monoxide for more than 15 years. He says he has found potential CO treatments that could help with pulmonary hypertension, shrink cancerous tumors and help bodies accept newly transplanted organs.

“My laboratory has been studying the properties of carbon monoxide for years, but we’ve never investigated a possible therapeutic role for CO in the brain,” Otterbein said in a press release issued by the medical center.

The researchers say that brain cells, known as microglia, appear to be tasked with removing “trash,” such as unwanted proteins, that collect in the brain. They attack heme, a hemoglobin protein that escapes from red blood cells following a stroke, using carbon monoxide. The findings suggest that small additional amounts of inhaled carbon monoxide help clear out the heme pigment proteins faster, possibly preventing long-term brain damage.

The findings come amid increased awareness about the risks of carbon monoxide exposure, which is one of the leading causes of fatal poisonings in the United States.

Carbon monoxide is a significantly toxic gas that has no irritating factors that can allow someone to detect its presence. Because people often fail to promptly recognize symptoms of carbon monoxide, gas leaks often result in prolonged exposure and potentially severe brain damage when detectors or alarms are not present.

According to the U.S. Centers for Disease Control and Prevention, carbon monoxide poisoning kills about 500 people in the U.S. annually, and is linked to about 15,000 emergency room visits. In many cases, the injuries or deaths could have been prevented by the use of carbon monoxide detectors and proper maintenance of heating systems and generators.