S AN F rancisco - Smoking kills, it is true, but in at least one point, it seems to do a body good. Cigarette smokers are less likely to develop Parkinson's disease, a condition marked by the death of certain nerve cells that use the neurotransmitter dopamine, which causes a gradual loss of muscle control. At the meeting of the American Chemical Society last month, a team of researchers described a molecule in cigarette smoke that can offer protection.
Researchers suspect smokers have a lower risk of Parkinson's because something in tobacco keeps dopamine levels near normal, even if a smoker does start losing dopamine-producing cells. Most likely, this mysterious bodyguard protects dopamine by inhibiting an enzyme called monoamine oxidase in the brain (MAO) which breaks down the neurotransmitter. Indeed, doctors have long used other MAO inhibitors to treat Parkinson's disease. And in 1996, the brain scans by a Brookhaven National Laboratory team at Upton, New York, found that smokers had up to 40% less of the enzyme MAO in their brains than non-smokers.
Neal Castagnoli and Kay, a team of husband and wife chemists from the Virginia Polytechnic Institute and State University in Blacksburg, set out to find compounds MAO-blocking among thousands of other components in tobacco and tobacco smoke. They ground the tobacco leaves and tested representative samples in a test tube to see if they inhibit MAO. The fraction containing the inhibitor of MAO more powerful, they isolated a chemical known as 2,3,6-trimethyl-1,4-naphthoquinone.
To establish whether this was a key MAO inhibitor in cigarette smoke, the team of Castagnoli examined mice in which the dopamine-producing neurons were killed with a compound called MPTP is converted toxin moiety in the brain, causing symptoms much like the Parkinson's disease. Without naphthoquinone, dopamine levels in the mice that received MPTP fell 60% below normal. However, when mice were pretreated with naphthoquinone dopamine levels have dropped to just 40%. This suggests that naphtoquinone "is a good [MAO] inhibitor - not gangbusters, but a good inhibitor," says Castagnoli
naphthoquinone had already been found in tobacco smoke, but not related to dopamine .. The new discovery suggests that it might be to protect dopamine in smokers, but Castagnoli warns that the team is not sure yet. but the new work is exciting, said Janet Fowler, who led Brookhaven studies. "It is really interesting to find one of these substances, "says Fowler. And because the compound is unlike any previously known inhibitors, it could give pharmaceutical companies led to new drugs to treat Parkinson's disease, she said.
0 Komentar