14:00 26 January 2007
NewScientist.com news service
Roxanne Khamsi
Journal of Clinical Investigation
Miguel Soares, Gulbenkian Science Institute
In a novel experiment, moderate doses of carbon monoxide protected against the symptoms of multiple sclerosis in mice.
Researchers believe that the poisonous gas prevents the development of symptoms, such as paralysis, by stopping harmful molecules called free radicals from forming in the nervous symptom.
Miguel Soares at the Gulbenkian Science Institute in Oeiras, Portugal, and colleagues injected the animals with a protein mixture known to cause experimental autoimmune encephalomyelitis, a mouse model of multiple sclerosis (MS).
Ten days later some of the mice were placed in a chamber where they breathed carbon monoxide (CO) at a concentration of about 500 parts per million for 20 days. Soares notes that while the mice functioned normally at this level of CO exposure, a similar concentration of the gas can cause headaches and fainting in humans.
At the end of the trial, the mice that had breathed CO showed much greater mobility than their control counterparts. While the experimental mice had limp tails, the control mice suffered complete hind limb paralysis.
Free radicals
Soares suspects that CO works in this fashion because it promotes the binding of iron to heme molecules within the nervous system. Heme molecules that lack iron can increase the production of free radicals, which damage cells.
Immune cells produce free radicals in order to kill off bacteria. Soares suggests that disrupted immune cells in the nervous system of MS patients might overproduce free radicals, thereby causing the tissue damage that leads to paralysis. He believes that CO might work to counter this overproduction, thereby slowing the progression of disease.
Pharmaceutical companies are currently working on developing drugs that can deliver carbon monoxide locally within the nervous system, the researchers say. They stress that MS patients should under no circumstances try inhaling carbon monoxide – the gas can be lethal.
Journal reference: Journal of Clinical Investigation (DOI: 10.1172/JCI28844)
