Common garden, pet pesticide linked to Parkinson's disease

[Guest guest]

http://www.ottawacitizen.com/national/001106/4817135.html

Common garden, pet pesticide linked to Parkinson's disease

Sharon Kirkey, with files from Tom Spears

The Ottawa Citizen

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 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.