 |
 |
Common garden, pet pesticide linked to Parkinson's disease Monday 6 November 2000 A widely used pesticide found in flea powders and plant sprays is being linked to Parkinson's in a new study that raises fresh concerns about the role of pesticides in the devastating brain disease. American scientists have found that the organic pesticide rotenone can produce the major symptoms of Parkinson's disease in rats. The animals didn't move around as much; they became stiff and slow and suffered the same damage to their brain cells as Parkinson's patients do. "What this means to me is that we're really on the track of what can cause Parkinson's disease," the study's lead author, Dr. Tim Greenamyre, of Emory University in Atlanta, said in an interview yesterday. And there's extra interest in this study because rotenone isn't one of the synthetic pesticides often attacked by environmentalists. It's a natural, organic compound widely used in garden insecticides and anti-flea shampoos for cats and dogs. The study will be published in the December issue of the journal Nature Neuroscience. About 100,000 Canadians suffer from Parkinson's disease, a degenerative disease of the central nervous system for which there is no known cure. The disease destroys brain cells that produce dopamine, a neurotransmitter that carries messages between nerve endings, allowing muscles to move. Its most famous victims include former prime minister Pierre Trudeau, Canadian-born actor Michael J. Fox and former heavyweight boxing champion Muhammad Ali. Although genes play a role, the majority of cases are unexplained. But researchers have long had some clues about what might be causing Parkinson's, said Dr. Greenamyre, a professor of neurology and pharmacology at Emory University. In large epidemiological studies, one of the possible risk factors that consistently "pops out" is exposure to pesticides, he said. "The other thing that pops out quite often is living in rural areas. The two might be related obviously, because more pesticides are used producing crops in rural areas." Scientists have also suspected that the mitochondria -- the energy generators or "power plants" of cells -- don't work properly in people with Parkinson's disease. And many pesticides such as rotenone are known to be mitochondrial toxins. "We decided to test both ideas at once," Dr. Greenamyre said. His team administered rotenone intravenously to rats at very low doses, but over a period of several weeks. "What happened was the rats became slow -- they didn't move around as much as a normal rat does," Dr. Greenamyre said. "And that looks a lot like Parkinson's." The rats exhibited the same stiffness as Parkinson's patients; a few even developed odd tremors "that I've never seen in a rat before, but Parkinson's patients have tremors as well," he said. The rats' brains later revealed exactly the same pattern of degeneration that occurs in people with Parkinson's. The same group of cells died in the rotenone-treated animals as die in Parkinson's disease. And when they looked closer at the cells that were dying, the researchers discovered the cells contained an abnormal accumulation of protein "that looked a whole lot like what are called Lewy bodies in Parkinson's disease," Dr. Greenamyre said. "And this has never been seen before in an animal model of Parkinson's." The researchers speculate that rotenone causes the mitochondria in brain cells to produce free radicals -- highly reactive molecules produced as the body metabolizes oxygen. Free radicals have been implicated in a wide range of diseases, including heart disease, stroke and certain cancers. If more research proves that the cells in the rotenone-infected rats are dying in the same way as in Parkinson's patients, "we can use our rat model to screen for new drugs that might protect our brain against Parkinson's disease," Dr. Greenamyre said. But he says it doesn't mean that rotenone should necessarily be banned. "You have to remember. We gave this drug in an artificial way. We gave it in very low doses -- it's not like giving rats saccharin as they did several years ago, and forcing pounds of saccharin down a rat. We gave tiny milligram doses intravenously and, obviously, that's not the way people are exposed to pesticides." And rotenone is just one of a large family of pesticides that act exactly the same way on the mitochondria. "We've only tested one, but I would be willing to bet a sizable amount of money that other (pesticides) would produce the same effect," Dr. Greenamyre said. He stressed that his research doesn't prove "in any way" that rotenone causes Parkinson's in humans. "What I am saying is that in rats, chronic exposure to this pesticide is sufficient to produce all the features of Parkinson's disease. It really hammers home the idea that environmental factors are likely to play a huge role in Parkinson's disease." But the research also implies genetic factors play a key role, too. Many people are exposed to the same environmental factors, but not everybody gets Parkinson's, Dr. Greenamyre noted. In some people, their liver "chops them up real fast" and they metabolize them quickly, so it takes more of certain toxins to harm them. Others, the slow metabolizers, are more sensitive. Still, "our work shows that things that are likely to be in the environment are sufficient to cause Parkinson's in an animal, and therefore very likely to do it in people." While he isn't advocating getting rid of pesticides "because they're absolutely essential for productive crops, we have to be mindful of their potential harmful effects, too." Just because rotenone is natural, it's assumed to be safe. But the study shows natural, organic pesticides aren't necessarily any safer than synthetic ones, said toxicology professor Len Ritter of the University of Guelph. "We call one natural and one synthetic. Biochemically, physiologically, biomedically, that doesn't mean anything. Your body or mine doesn't care if the toxicant originated in nature or if it came from a lab. It really doesn't make a whole lot of difference." Synthetic pesticides may actually be safer than organic ones, he argues, "because they are much better characterized in terms of their effects." "They are subject to very intensive regulation and typically the natural components are not," said Mr. Ritter, a former senior official in Health Canada's pesticides program. Sharon Kirkey, with files from Tom Spears The Ottawa Citizen http://www.ottawacitizen.com/national/001106/4817135.html janet paterson, an akinetic rigid subtype parkie 53 now /44 dx cd / 43 onset cd /41 dx pd / 37 onset pd TEL: 613 256 8340 URL: http://www.geocities.com/janet313/ EMAIL: [log in to unmask] SMAIL: POBox 171 Almonte Ontario K0A 1A0 Canada