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