My grandfather's Parkinson's was pretty far along by the time I knew him. I remember as a 4-year-old straining to understand his tremoring voice which — when combined with his thick Swedish accent — was almost impossible for me and my sister to understand. Even as a small child, I could tell it broke his heart.
In a study released last week, researchers explain exactly how pesticides can interact with the brain to trigger this incurable disease. Their findings may help prevent and treat Parkinson's for future generations.
After Alzeimer's, Parkinson's is our most common disease of the nervous system. One in every 200 people in their 60s have the disease; for those in their 80s, the number jumps to 8 in 200. Farmers and farmworkers suffer at especially high rates, which is one of the flags that sparked early research into the role pesticides may play.
Pesticide exposure has been linked to Parkinson's for years. Scientists tell us that genetics explain fewer than 5% of Parkinson's cases.
Just how do pesticides increase risk?
People with Parkinson's don't produce enough dopamine, a chemical that helps the brain coordinate movement of our muscles. Lack of dopamine leads to slow movement, muscle stiffness and shaking. Symptoms get worse over time.
Genes explain fewer than 5% of Parkinson's cases.
Those with Parkinson's are also more likely to suffer both dementia and depression.
Scientists already know that lower levels of dopamine are caused by damage to nerve cells caused in turn by unstable atoms or molecules — a process dubbed "oxidative stress."
Researchers at the University of Missouri School of Medicine wanted to understand more.
As Assistant Professor Zezong Gu and his colleagues report in Molecular Degeneration, they figured out how exposure to a variety of pesticides — including rotenone and paraquat — causes a brain protein called "parkin" to malfunction.
Parkin, which regulates the function of other proteins, clusters together due to oxidative stress caused by exposure to the pesticides. It then fails at its job of cleaning up other proteins that are damaged, and this malfunction triggers the process of degeneration.
Protecting future grandparents
Professor Gu and his colleagues are hopeful that their findings will mean a breakthrough in the battle against Parkinson's: "Knowing this, we can find ways to correct, prevent and reduce the incidence of this disease."
Our grandfather came across the Atlantic on a boat when he was 19, and got a job as a railroad carpenter in a small town in western Michigan. We'll never know whether his lifetime of exposure to the wood preservatives and herbicides commonly used by the railroad company contributed to his Parkinson's.
Understanding just how pesticides cause this heartbreaking disease makes it easier to push for smart policies that will protect future generations of grandparents.