Daily News Archives
From February 1, 2005
Exposure Heightens Brain Cell Vulnerability to Parkinson’s Disease
(Beyond Pesticides, February 1, 2005) University of Rochester
scientists investigating the link between PCBs, pesticides and Parkinson’s
disease demonstrated new and intricate reactions that occur in certain
brain cells, making them more vulnerable to injury after exposures.
In two papers published in the journal NeuroToxicology (December
2004 and February
2005), the group describes how Polychlorinated biphenyls (PCBs)
disrupt dopamine neurons, which are the cells that degenerate during
the course of Parkinson’s disease. Researchers also show that
low levels of maneb, a fungicide commonly used in farming, can injure
the antioxidant system in those same types of cells. Environmental contaminants
might make dopamine cells more vulnerable to damage from normal aging,
infection, or subsequent exposure to pollutants, researchers say.
The UR investigation is part of a nationwide race to better understand
every aspect of Parkinson’s disease, which affects up to 1 million
Americans. It is a progressive neurological disorder that occurs when
certain nerve cells in the substantia nigra region of the brain die
or can no longer produce the brain chemical dopamine. A lack of dopamine
is what causes patients to experience tremors, stiffness in the limbs
and trunk, and impaired movement or balance.
In the 1990s scientists reported that the brains of Parkinson’s
patients contained elevated levels of PCBs and certain pesticides. While
researchers believe that genetics, the aging process and exposure to
toxicants all play a role in the development of Parkinson’s, the
UR group led by Lisa Opanashuk, Ph.D., is focused on environmental exposures.
The National Institutes of Health is funding the work.
“If we can identify the mechanisms by which PCBs or pesticides
perturb dopamine neuron function, it may lead to the development of
therapies that can prevent, slow or stop the progression of Parkinson’s,”
says Opanashuk, an assistant professor of Environmental Medicine.
PCBs create havoc in the body’s cellular system by producing free
radicals, which leads to a process known as oxidative stress (OS). Oxidative
stress is thought to be one of the main causes of cell degeneration.
Normally, antioxidants can balance the damage done by OS. But toxic
pesticide exposure, combined with the normal aging process, shifts the
equilibrium toward oxidative stress and neurodegeneration.
The UR studies demonstrate, for the first time, the intricate OS and
antioxidant responses to PCBs in dopamine neurons. Investigators treated
dopamine cells and other brain cells with PCBs and documented the activation
of oxidative-stress related pathways. Further research will evaluate
how PCBs become risk factors for disease.
PCBs, used as industrial coolants and lubricants, were banned in 1977
but remain widespread in the environment due to their improper disposal.
They linger in the food chain, particularly in wild and farmed salmon
and other fish. PCBs accumulate in the body in fat and brain cells and
other tissues. The potential adverse health effects of PCBs are dependent
upon many factors, such as the levels of exposure, the toxicities of
individual chemicals present in any given mixture, and their interactive
Pesticides such as maneb remain in farmed soil for 20-75 days following
application and can be found on produce for more than three weeks, even
after washing, according to researchers. Until now, the effect of maneb
on oxidative stress responses in dopamine neurons was unknown.
But Opanashuk’s group shows that just as in exposure to PCBs,
cells treated with low levels of maneb also undergo changes that disturb
the balance in the antioxidant defense system. Another concern is whether
maneb causes more damage when people are exposed in combination with
other pesticides, which occurs in rural communities. Opanashuk hopes
the research will lead to developing safety guidelines and determining
more closely the role that maneb plays in neurological diseases.
Besides Opanashuk, the research group included Donna W. Lee and Mary
Williamson, fifth year graduate students in the Toxicology PhD. Program,
technician Bryan Thompson, and former UR scientists Brian K. Barlow
and Deborah Cory-Slechta, who are now associated with the Robert Wood
Johnson Medical School in New Jersey. The UR is also home to the Parkinson’s
Disease Data and Organizing Center, directed by Roger Kurlan, M.D.,
a nationwide network of 12 institutions, and the Parkinson Study Group,
a consortium of experts founded and headed by UR neurologist Ira Shoulson,
TAKE ACTION: Write to U.S.EPA Acting Administrator
Stephen Johnson to let
him know that they have a duty to alert the public to the scientific
findings (laboratory and epidemiologic) that link pesticides with Parkinson's
disease. In addition, urge these EPA officials to initiate an urgent
and expedited review of pesticides' link to Parkinson's.