Uncovers Cause
of Pesticide Exposure, Parkinson’s Link
A
new University of Guelph study has discovered why exposure to pesticides
increases some people’s risk of developing Parkinson’s disease.
Previous
studies have found an association between two commonly used agrochemicals
(paraquat and maneb) and Parkinson’s disease.
Now
U of G professor Scott Ryan has determined that low-level exposure to the
pesticides disrupts cells in a way that mimics the effects of mutations known
to cause Parkinson’s disease.
Adding
the effects of the chemicals to a predisposition for Parkinson’s disease
drastically increases the risk of disease onset, said Ryan.
“People
exposed to these chemicals are at about a 250-per-cent higher risk of
developing Parkinson’s disease than the rest of the population,” said Ryan, a
professor in the Department of Molecular and Cellular Biology.
“We wanted to investigate what is happening in this susceptible population that results in some people developing the disease.”
Used
on a variety of Canadian crops, paraquat is used on crops as they grow, and
maneb prevents post-harvest spoiling.
Published
in the journal Federation of
American Societies for Experimental Biology, this study used
stem cells from people with Parkinson’s disease with a mutation in a gene
called synuclein that is highly associated with increased risk of Parkinson’s
disease, as well as normal embryonic stem cells in which the risk-associated
mutation was introduced by gene editing.
“Until
now, the link between pesticides and Parkinson’s disease was based primarily on
animal studies as well as epidemiological research that demonstrated an
increased risk among farmers and others exposed to agricultural chemicals,”
said Ryan. “We are one of the first to investigate what is happening inside
human cells.”
From
the two types of stem cells, Ryan and his team made dopamine-producing neurons
— the specific neurons affected in Parkinson’s disease — and exposed them to
the two agrochemicals.
That
exposure prevented energy-producing mitochondria from moving to where they were
needed inside the cell, depleting the neurons of energy.
Neurons
from the Parkinson’s patients and those in which the genetic risk factor was
introduced were impaired at doses below the U.S. Environmental Protection
Agency’s reported lowest observed effect level. Higher doses are needed to
impair function in normal neurons.
“People
with a predisposition for Parkinson’s disease are more affected by these low
level exposures to agrochemicals and therefore more likely to develop the
disease,” said Ryan. “This is one of the reasons why some people living near
agricultural areas are at a higher risk.”
He
said the findings indicate that we need to reassess current acceptable levels
for these two agrochemicals.
“This
study shows that everyone is not equal, and these safety standards need to be
updated in order to protect those who are more susceptible and may not even
know it.”