Scientists warned about unexpected brain hazard from popular pesticide

Chlorpyrifos, a pesticide widely used in agriculture, can significantly increase the risk of developing Parkinson's disease. This conclusion was reached by scientists from the University of California, Los Angeles, who combined decades of epidemiological data with animal experiments.

As reported by BAKU.WS with reference to Molecular Neurodegeneration (MN), the study showed that chlorpyrifos disrupts the cellular mechanism for cleaning neurons, causing toxic proteins characteristic of Parkinson's disease to accumulate in the brain.

As a reminder, Parkinson's disease develops due to the gradual death of neurons that produce dopamine - a neurotransmitter responsible for movement control. As these cells are lost, patients develop tremors, muscle rigidity, and balance problems.

Chlorpyrifos is an organophosphate insecticide that has been used since the 1960s. Despite the fact that its household use was banned in the United States about 20 years ago, the product is still actively used in commercial agriculture.

In the first stage, scientists analyzed data from the Parkinson's Environment and Genes project, covering residents of three agricultural counties in California's Central Valley. Data from 829 patients with Parkinson's disease and 824 healthy volunteers were compared with government reports on pesticide use since 1974. The cumulative exposure to chlorpyrifos near participants' places of residence and work was assessed.

The results showed that people with the highest level of exposure to this pesticide had more than 2.5 times higher risk of developing Parkinson's disease compared to those who had little to no contact with the substance.

To test the direct effect of chlorpyrifos on neurons, researchers conducted experiments on mice. For 11 weeks, the animals were exposed to an aerosol, simulating inhalation of the chemical near farmlands. As a result, the mice developed motor disorders, and about 26% of dopamine neurons in the substantia nigra were lost in the brain. There was also an accumulation of pathological alpha-synuclein protein and signs of inflammation.

Further experiments on zebrafish (danio rerio) allowed researchers to determine the molecular mechanism of action. It was established that chlorpyrifos blocks autophagy - the cellular "disposal system" responsible for removing damaged proteins and organelles. When it is disrupted, toxic proteins begin to accumulate and lead to the death of neurons.

The key confirmation came from "rescue" experiments: stimulation of autophagy or removal of the gene associated with synuclein protected dopamine neurons even when exposed to the pesticide. This indicates that chlorpyrifos does not destroy the cells themselves directly, but rather the systems of their internal maintenance.