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BBC
Parkinson's patients have changes in
their brains
A commonly-used
organic pesticide produced symptoms similar to Parkinson's
disease when small amounts were injected into rats over
time.
It adds weight to theories that repeated exposure to low
levels may also be causing cumulative damage to the human
brain.
The
pesticide Rotenone, frequently used as an insecticide and
as a method of killing fish, is considered relatively benign
compared to many commercially-available chemicals.
But
scientists now believe it interferes with cells in the brain
which produce a chemical called dopamine.
Lack
of dopamine produces the well-known Parkinsonism symptoms
such as tremor, rigidity and difficulty moving.
The
loss of these key brain cells is presently irreversible,
and worsens over time, eventually leading to death.
The
cause of Parkinson's Disease is largely unknown, with cases
appearing sporadically and apparently at random, leading
some scientists to think it could be caused by long-term
exposure to environmental toxins.
Because
of the current lack of knowledge about the origins of the
illness, the only acknowledged risk factor is age - the
older you are, the more likely you are to get it.
Approximately
1% of people over the age of 65 develop the illness.
To test
this, Dr Tim Greenamyre from the Emory University in Georgia,
US, administered Rotenone intravenously over a period of
weeks to rats.
Physical
symptoms
Not
only did the rats develop some of the physical symptoms
of Parkinson's, but scans revealed actual changes in their
brains which appear similar to changes in the brain of a
Parkinson's patient.
The
research was published in the journal Nature Neuroscience.
The
team believes Rotenone may be causing cell components called
mitochondriae to release damaging molecules called free
radicals, which go on to affect the dopamine-producing brain
cells.
Professor
Adrian Williams, chairman of the medical advisory panel
of the Parkinson's Disease Society, said it was possible
that pesticides did cause Parkinson's in some patients -
but the likelihood was it was only a small minority.
He said
it was possible a minority of patients had a genetic make-up
which made them more vulnerable to the effects of pesticides
than normal.
He told
BBC News Online: "It is unlikely that all cases of
Parkinson's are caused by pesticides, but it may be that
one or two in every hundred are.
"It
would be wrong to expect that a condition such as Parkinson's
is caused by a single factor."
Prof
Williams also warned of the dangers of drawing conclusions
based on experimental research on animals.
Separate
research, published in the journal Science, supports the
theory that this type of damage is behind the development
of Parkinson's.
A team
from the University of Pennsylvania School of Medicine has
identified a protein which, when damaged by free radicals,
could trigger the onset of Parkinson's.
When
the physical brain changes associated with Parkinson's were
examined, a protein, called alpha-synuclein, was found in
an altered state there, but not elsewhere.
This
change to the protein could have been caused by free radicals.
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