When mouse-derived brain cells were exposed to certain fungicides, the cells displayed altered patterns of gene expression often seen in individuals with neurological conditions, including autism and Alzheimer’s disease. While the researchers have identified this link, they cannot say for certain whether fungicides are the cause of these conditions.
According to Dr. Mark Zylka, an associate professor of cell biology and physiology at the University of North Carolina (UNC) School of Medicine, and the study’s senior author, more studies should be to further investigate this association. The research was published in the journal, Nature Communications.
The researchers conducted an analysis of 300 chemicals to determine their effect on mice neurons. Several of these chemicals were fungicides – compounds mainly used by the agricultural industry to prevent the growth of fungi on their crops.
By comparing RNA sequencing data collected from neurons that were exposed to each chemical, with neurons that were not treated, the researchers were able to determine which compounds influenced gene expression. Zylka and his colleagues found that six chemical groups – including pesticides like rotenone, pyridaben and fenpyroximate, and strobilurins fungicides – which altered gene expression in the mouse neurons.
Strobilurins are a relatively new class of fungicides which includes chemicals like pyraclostrobin, trifloxystrobin, fenamidone and famoxadone. These compounds were introduced into the US market in the late 1990s.
“We found that chemicals within each group altered expression in a common manner,” said Zylka. “One of these groups of chemicals altered the levels of many of the same genes that are altered in the brains of people with autism or Alzheimer’s disease.”
These chemicals lowered expression of genes that are critical to inerneuronal communication and brain functioning. In addition, the fungicides were found to increase expression of genes involved in inflammatory responses in the nervous system – a symptom characteristic of autism.
The chemicals also increased the release of damaging free radicals within the cell, interfering with microtubule functioning. “Disrupting microtubules affects the function of synapses in mature neurons and can impair the movement of cells as the brain develops,” said Zylka. “We know that deficits in neuron migration can lead to neurodevelopmental abnormalities. We have not yet evaluated whether these chemicals impair brain development in animal models or people.”
Green, leafy vegetables – including spinach, lettuce and kale – are most often exposed to high levels of strobilurins. According to Zylka, these chemicals are increasingly being sprayed onto other fruits and vegetables due to their high effectiveness against fungi growth.
“Virtually nothing is known about how these chemicals impact the developing or adult brain,” said Zylka. “Yet these chemicals are being used at increasing levels on many of the foods we eat.”