Pesticides, Genes Combine to Increase Risk of Parkinson’s Disease

(Beyond Pesticides, June 16, 2010)

Men with certain genetic variations who were exposed to some toxic pesticides that are now largely banned run an increased risk of developing Parkinson’s disease, French scientists said Monday.

In a study published in Archives of Neurology, entitled “Interaction Between ABCB1 and Professional Exposure to Organochlorine Insecticides in Parkinson Disease,” French researchers found that among men exposed to pesticides such as DDT, carriers of the gene variants are three and a half times more likely to develop Parkinson’s than those with the more common version of the gene.

The scientists think the brains of people with the gene variant fail to flush out toxic chemicals as efficiently as those with common versions of the gene, suggesting that environmental as well as genetic factors are important in the risk of Parkinson’s.

Alexis Elbaz, MD, PhD and Fabien Dutheil, PhD, of France’s National Institute for Health and Medical Research (INSERM) studied 101 men with Parkinson’s and 234 without the disease to look at links between organochlorine exposure and Parkinson’s disease.

The study includes only men, and all of them had high levels of exposure to pesticides through their work as farmers. The scientists found the link was around 3.5 times stronger in men who carried two copies of a gene known as ABCB1, which plays a role in helping the brain flush out dangerous chemicals.

“The gene encodes for a kind of pump in the brain, and in people who have the (two copy) variation, this pump doesn’t work as well,” Dr. Elbaz said. “It seems therefore that people who have these variations would have higher levels of insecticides in the brain because the brain’s pump is not clearing them out properly.”

Parkinson’s is a neurodegenerative disease that affects one to two percent of people over the age of 65. Sufferers have tremors, sluggish movement, muscle stiffness, and difficulty with balance. Although medical treatments may improve symptoms, there are none that can slow down or halt the progression of the disease. Dr. Elbaz said his work supported a growing body of evidence that genetic factors alone were not to blame for Parkinson’s, but that when they combined with factors in the environment, the risk could significantly increase.

Several published research within the past year have found that exposures to pesticides can increase the risk of developing Parkinson’s. In a similar study individuals with the variant MM PONI1-55 genotype that are exposed to organophosphates exhibited more than twice the risk of Parkinson’s disease compared to carriers of wildtype or heterozygous genotype and no exposure. Farmworkers have nearly double the risk for the disease if exposed to pesticides, with a dose-effect for the number of years of exposure. Another recent publication found that rural residents who drank contaminated well water had an increased (up to 90 percent) risk of developing Parkinson’s. Exposure to the pesticides, paraquat and maneb, within 500 meters of an individual’s home, increased the risk of developing Parkinson’s by 75 percent, according to a University of California, Berkeley study. The Institute of Medicine (IOM) found suggestive but limited evidence that exposure to Agent Orange and other herbicides used during the Vietnam War is associated with an increased chance of developing ischemic heart disease and Parkinson’s disease in Vietnam veterans.

For more on Parkinson’s disease, please read “Pesticides Trigger Parkinson’s Disease,” a review of published toxicological and epidemiological studies that link exposure to pesticides, as well as gene-pesticide interactions, to Parkinson’s disease and published in Pesticides and You (Spring 2008).

Source: Reuters