With thousands of pesticides in use, the researchers’ new screening approach could make it easier to determine which ones are linked to the disease.
Researchers at the University of California, Los Angeles (
While environmental factors such as pesticide exposure have long been linked to Parkinson’s, it has been harder to pinpoint which pesticides may raise risk for the neurodegenerative disorder. Just in California, the nation’s largest agricultural producer and exporter, there are nearly 14,000 pesticide products with over 1,000 active ingredients registered for use.
Through a novel pairing of epidemiology and toxicity screening that leveraged California’s extensive pesticide use database, UCLA and Harvard researchers were able to identify 10 pesticides that were directly toxic to dopaminergic neurons. The neurons play a key role in voluntary movement, and the death of these neurons is a hallmark of Parkinson’s.
Further, the researchers found that co-exposure of pesticides that are typically used in combinations in cotton farming were more toxic than any single pesticide in that group.
For this study, published on May 16 in the journal
Researchers also tested the toxicity of multiple pesticides that are commonly applied in cotton fields around the same time, according to California’s pesticide database. Combinations involving trifluralin, one of the most commonly used herbicides in California, produced the most toxicity. Previous research in the Agricultural Health Study, a large research project involving pesticide applicators, had also implicated trifluralin in Parkinson’s.
Kimberly Paul, PhD, a lead author and assistant professor of neurology at UCLA, said the study demonstrated their approach could broadly screen for pesticides implicated in Parkinson’s and better understand the strength of these associations.
“We were able to implicate individual agents more than any other study has before, and it was done in a completely agnostic manner,” Paul said. “When you bring together this type of agnostic screening with a field-to-bench paradigm, you can pinpoint pesticides that look like they’re quite important in the disease.”
The researchers are next planning to study epigenetic and metabolomic features related to exposure using integrative omics to help describe which biologic pathways are disrupted among Parkinson’s patients who experienced pesticide exposure. More detailed mechanistic studies of the specific neuronal processes impacted by pesticides such as trifluralin and copper are also underway at the Harvard/Brigham and Women’s labs. The lab work is focused on distinct effects on dopamine neurons and cortical neurons, which are important for the movement and cognitive symptoms in Parkinson’s patients, respectively. The basic science is also expanding to studies of pesticides on non-neuronal cells in the brain – the glia – to better understand how pesticides influence the function of these critical cells.
Reference: “A pesticide and iPSC dopaminergic neuron screen identifies and classifies Parkinson-relevant pesticides” by Kimberly C. Paul, Richard C. Krolewski, Edinson Lucumi Moreno, Jack Blank, Kristina M. Holton, Tim Ahfeldt, Melissa Furlong, Yu Yu, Myles Cockburn, Laura K. Thompson, Alexander Kreymerman, Elisabeth M. Ricci-Blair, Yu Jun Li, Heer B. Patel, Richard T. Lee, Jeff Bronstein, Lee L. Rubin, Vikram Khurana and Beate Ritz, 16 May 2023, Nature Communications.
DOI: 10.1038/s41467-023-38215-z
Other authors include Edinson Lucumi Moreno, Jack Blank, Kristina M. Holton, Tim Ahfeldt, Melissa Furlong, Yu Yu, Myles Cockburn, Laura K. Thompson, Alexander Kreymerman, Elisabeth M. Ricci-Blair, Yu Jun Li, Heer B. Patel, Richard T Lee, Jeff Bronstein, Lee L. Rubin, Vikram Khurana, and Beate Ritz.