Link made with increased prevalence of Alzheimer's disease in agricultural communities that use this chemical
Neurodegenerative illnesses, such as Alzheimer’s disease, are among the most perplexing in medical science. The underlying causes of such diseases range from genetic factors and overall cardiovascular health to dietary influences and lifestyle choices.
Various environmental contaminants have also been implicated as possible players in the development or advancement of neurodegenerative disease. Among these is glyphosate herbicide, which is used in massive amounts on GMO glyphosate-tolerant crops. Each year, around 250 million pounds of glyphosate are applied to agricultural crops in the US alone.
In a new study, Arizona State University (ASU) Graduate Research Assistant Joanna Winstone, Assistant Professor Ramon Velazquez and their colleagues at the Translational Genomics Research Institute explored the effects of glyphosate exposure on the brains of mice.
Their research demonstrates for the first time that glyphosate successfully crosses the blood-brain barrier and infiltrates the brain, according to a news report by Arizona State University.
Once there, it acts to enhance levels of a critical factor known as TNF-α.TNF-α is a molecule with two faces. This pro-inflammatory cytokine performs vital functions in the neuroimmune system, acting to enhance the immune response and protect the brain.
When levels of TNF-α are dysregulated, however, a host of diseases linked with neuroinflammation can result. Among these is Alzheimer’s disease.
The study further demonstrates in cell culture studies that glyphosate exposure appears to increase the production of soluble beta amyloid (Aβ) and reduce the viability of neurons. The accumulation of soluble beta amyloid, the sticky protein responsible for the formation of soluble beta amyloid plaques, is one of the central diagnostic hallmarks of Alzheimer’s disease.
Further evidence suggestive of potential hazards to neurological health were observed when the researchers examined changes in gene expression via RNA sequencing in the brains of mice following glyphosate exposure.
These RNA transcripts hinted at disruptions in the expression of genes related to neurodegenerative disease, including dysregulation of a class of brain cells responsible for producing the myelin sheath critical for proper neuronal communication. These cells, known as oligodendrocytes, are affected by elevated levels of TNF-α.
“We find increases in TNF-α in the brain, following glyphosate exposure,” said Velazquez, the senior author of the paper. “While we examined (Alzheimer’s disease) pathology, this might have implications for many neurodegenerative diseases, given that neuroinflammation is seen in a variety of brain disorders.”
Velazquez and Winstone, the first author on the study, are researchers with the ASU-Banner Neurodegenerative Disease Research Center and Arizona State University's School of Life Sciences.
The research appears in the current issue of the Journal of Neuroinflammation.
The blood-brain barrier is a layer of cells preventing dissolved substances in the circulating bloodstream from readily passing into the extracellular fluid of the central nervous system, where the brain’s neurons reside.
Risks to brain health posed by glyphosate should be critically evaluated, particularly for those consistently exposed to the herbicide.
“The Alzheimer’s connection is that there's a much higher prevalence of Alzheimer's disease in agricultural communities that are using this chemical,” Winstone said. “We're trying to establish a more molecular-science based link between the two.”
The study exposed mice to high doses of glyphosate, then detected elevated levels of TNF-α in their brains. The researchers then exposed extracted mouse neurons in petri dishes to the same levels of glyphosate detected in the brains of mice, observing elevated amyloid beta and cell death in cortical neurons. Dysregulated oligodendrocyte RNA transcripts, which could indicate disruption of myelination, were detected in brain tissue.
Taken together, the results demonstrate a correlation between glyphosate exposure and classic symptoms of Alzheimer's disease, though the authors stress that much more work will be required before a causative link can be established.
Nevertheless, the widespread use of the chemical and the disturbing effects highlighted in the current study underscore the need for intensified investigation. Among the pressing questions still to be answered are:
* How does prolonged, low-dose exposure to glyphosate affect the brain?
* Does glyphosate act synergistically with other chemicals present in common herbicides? and
* Can glyphosate be detected post-mortem in patients who died of Alzheimer’s disease?
Main source: ASU
Image by the authors of the new study, downloadable via URL above