Common Agricultural Chemicals Shown to Change Mice Neurons in Ways Similar to Alzheimer’s Disease

Margarida Azevedo, MSc avatar

by Margarida Azevedo, MSc |

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pesticides, fungicides and Alzheimer's

Researchers haveĀ identified a group of agricultural chemicals ā€” pesticides and fungicides ā€” that constitute environmental risk factors for neurological and neurodegenerative diseases. A recentĀ studyĀ found that a number of these chemicalsĀ produce gene expression changes in mouse neurons similar to thoseĀ observed in people with autism, Alzheimerā€™s disease, and otherĀ conditions.

The paper, ā€œIdentification of chemicals that mimic transcriptional changes associated with autism, brain aging and neurodegeneration,ā€ was published in Nature Communications.

Retrospective epidemiological studies have linked a number of environmental factors, such as pesticides used in agriculture, to risks of autism and neurodegenerative disease. Such chemicals include pyraclostrobin, which has beenĀ found in potentially dangerous levels in food in a study by the U.S. Environmental Protection Agency, the pesticide rotenone, which has been associated with Parkinsonā€™s disease risk in both animal experiments and human epidemiological studies, and the fungicides trifloxystrobin and picoxystrobin, shown to impair motor activity in rats.

Researchers from the University of North Carolina (UNC) School of Medicine exposed cultures of mouse neurons to about 300 different chemicals commonly found in the environment and food, and proceeded toĀ sequence RNA extracted from animals’Ā neuronsĀ toĀ assess gene expression profiles of exposed brain cells. These experiments allowed researchers to identify which chemicals caused changes in gene expression. This included rotenone and certain fungicides, including pyraclostrobin, trifloxystrobin, famoxadone and fenamidone, that produce transcriptional changesĀ in vitroĀ similar to those seen in brain samples from peopleĀ with autism and neurodegenerative diseases such as Alzheimerā€™s and Huntingtonā€™s. Moreover, these chemicals accounted for theĀ reduced expression of genes involved in synapse transmission, stimulated free radical production, and disrupted microtubules within neurons, impairing cellular movement upon brain developmentĀ and leading to neuro-developmental abnormalities.

Information from U.S. regulatory agencies was also reviewed, such as the Ā Geological Survey, Food and Drug Administration and the Department of Agriculture, onĀ the use of specific chemicals, observing that pyridaben use has decreased since 2000 and rotenone use has remained the same. OverallĀ fungicide use has increased over the last decade, mainly due to itsĀ effectiveness in reducing fungal invasion in food crops.

The study team hopes these findings will encourage other scientists and regulatory agenciesĀ to investigate the consequencesĀ of Ā long-term exposure to the chemicals and their cumulative effects on the brain.

“We cannot say that these chemicals cause these conditions in people,”Ā Dr. Mark Zylka,Ā the study’sĀ senior author and an associate professor of cell biology and physiology at UNC, said in aĀ news release. “Many additional studies will be needed to determine if any of these chemicals represent real risks to the human brain.”

He added: ā€œThe real tough question is: if you eat fruits, vegetables or cereals that contain these chemicals, do they get into your blood stream and at what concentration? That information doesn’t exist.ā€