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Low doses of carbon monoxide to help after a stroke?
Carbon monoxide could help patients after a stroke. Nils Schallner from the Department of Anaesthesiology and Intensive Care Medicine at the University Medical Center Freiburg and colleagues from the Beth Israel Deaconess Medical Center (BIDMC) and the Harvard Medical School in Boston (USA) found that small amounts of carbon monoxide protect the brain, reduce brain damage and improve brain function improve a stroke.
Carbon monoxide is actually known to be a toxic gas that can cause brain damage, confusion, memory loss and, in the worst case, death. However, the international team of researchers, including scientists from the Freiburg University Hospital, has now been able to demonstrate that low doses have a positive effect in the event of a stroke. Low doses of carbon monoxide could protect the brain from damage that occurs after a bleeding-related stroke, the scientists report. They have published their results in the journal "Clinical Investigation".
Heme molecule causes damage after bleeding from the brain
According to the researchers, around 10,000 people suffer from subarachnoid hemorrhage (SAB for short) every year. This particular form of stroke is due to a ruptured artery in the brain with subsequent blood leakage. Suddenly a very severe headache is the central symptom. Women between the ages of 45 and 55 are particularly affected, according to the Freiburg University Hospital. Only every second affected person survives longer than a year after SAB and many have long-term impairments of brain function. The molecule heme is responsible for a large part of the damage after a hemorrhage, which is important for the oxygen transport in the red blood cells, but is highly toxic outside the cells.
Tests on mice show the positive effects of carbon monoxide
The SAB is doubly dangerous for the patients because on the one hand there is an undersupply of oxygen and on the other hand the leaked blood is toxic to the brain, the scientists report. In the current study, the team led by Professor Dr. Khalid Hanafy, Neurological Director of the BIDMC Neurointensive Unit, and Dr. Leo E. Otterbein, a researcher at the BIDMC's Transplant Institute, is now investigating how two groups of mice recovered after bleeding from the brain, with one group kept in normal breathing air for a week and the other group with a small daily additional hour for a week Amount of carbon monoxide received. In the subsequent tests on spatial memory, "the animals that had inhaled carbon monoxide performed significantly better," reports Dr. Schallner from Freiburg University Hospital.
Basis for clinical studies
According to the researchers, the damage to the brain tissue and the cognitive restrictions in the stroke mice were significantly reduced by the administration of carbon monoxide. "From this we concluded that the normally toxic gas carbon monoxide in small doses could improve recovery after a stroke," explains Dr. Nils Schallner. The scientists had already demonstrated “that special brain cells, called microglia, detoxify the heme by the enzyme heme oxygenase 1 (HO-1)” and that “during this breakdown, carbon monoxide is released,” according to the Freiburg University Hospital. However, the gas is not only a by-product of the breakdown, but also has a positive effect on the heme breakdown. For example, animals that did not produce HO-1 and accordingly also no carbon monoxide would also have benefited from the administration of carbon monoxide. A carbon monoxide dose "from the outside" can compensate for a lack of the body's own carbon monoxide production, according to Dr. Schallner. According to the researchers, the current results could in future serve as the basis for clinical studies with patients who have had a bleeding-related stroke. (fp)