In two papers published in the journal NeuroToxicology (Dec. 2004 and Feb. 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 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 group led by Lisa Opanashuk, Ph.D., is focused on environmental exposures. The National Institute of Environmental Health Sciences 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.