Exposure to the chemical herbicide glyphosate leads to brain inflammation, persists in tissues, and worsens neurodegenerative diseases.
Glyphosate, a common herbicide used in the U.S. and worldwide can cause severe inflammation of the brain leading to neurodegenerative disease (1✔ ✔Trusted Source
Glyphosate exposure exacerbates neuroinflammation and Alzheimer’s disease-like pathology despite a 6-month recovery period in mice
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The human is an adaptive organ that heals itself even from significant trauma. However, the effect of glyphosate can damage the brain and may persist long after direct exposure.
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Glyphosate’s Harmful Effects on Brain Health
A new study by Ramon Velazquez and his colleagues at the Translational Genomics Research Institute (TGen), part of the City of Hope, demonstrates that mice exposed to the herbicide glyphosate develop significant brain inflammation, which is associated with neurodegenerative disease. The findings suggest the brain may be much more susceptible to the damaging effects of the herbicide than previously thought. Glyphosate is one of the most pervasive herbicides used in the U.S. and worldwide.
The research, which appears today in the Journal of Neuroinflammation, identifies an association between glyphosate exposure in mice and symptoms of neuroinflammation, as well as accelerated Alzheimer’s disease-like pathology. This study tracks both the presence and impact of glyphosate’s byproducts in the brain long after exposure ends, showing an array of persistent, damaging effects on brain health.
Glyphosate exposure in mice also resulted in premature death and anxiety-like behaviors, which replicates findings by others examining glyphosate exposure in rodents. Further, the scientists discovered these symptoms persisted even after a 6-month recovery period during which exposure was discontinued. Additionally, the investigation demonstrated that a byproduct of glyphosate —aminomethylphosphonic acid—accumulated in brain tissue, raising serious concerns about the chemical’s safety for human populations.
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Who’s at Risk from Glyphosate Exposure?
According to the Centers for Disease Research, farm laborers, landscape workers, and others employed in agriculture are more likely to be exposed to glyphosate through inhalation or skin contact. Additionally, the new findings suggest that ingestion of glyphosate residues on foods sprayed with the herbicide potentially poses a health hazard. Most people living in the U.S. have been exposed to glyphosate during their lifetime.
“I hope that our work drives further investigation into the effects of glyphosate exposure, which may lead to a reexamination of its long-term safety and perhaps spark discussion about other prevalent toxins in our environment that may affect the brain,” Bartholomew says.
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Glyphosate and the Blood-Brain Barrier
The team’s findings build on earlier ASU research that demonstrates a link between glyphosate exposure and a heightened risk for neurodegenerative disorders.
The previous study showed that glyphosate crosses the blood-brain barrier, a protective layer that typically prevents potentially harmful substances from entering the brain. Once glyphosate crosses this barrier, it can interact with brain tissue and appears to contribute to neuroinflammation and other harmful effects on neural function.
The EPA considers certain levels of glyphosate safe for human exposure, asserting that the chemical is minimally absorbed into the body and is primarily excreted unchanged. However, recent studies, including this one, indicate that glyphosate, and its major metabolite aminomethylphosphonic acid, can persist in the body and accumulate in brain tissue over time, raising questions about existing safety thresholds and whether glyphosate use is safe at all.
Global Glyphosate Use and Health Risks
Glyphosate is the world’s most heavily applied herbicide, used on crops including corn, soybeans, sugar beets, alfalfa, cotton, and wheat. Since the introduction of glyphosate-tolerant crops (genetically engineered to be sprayed with glyphosate without dying) in 1996, glyphosate usage has surged, with applications predominately in agricultural settings.
The U.S. Geological Survey notes approximately 300 million pounds of glyphosate are used annually in the United States alone. Although glyphosate levels are regulated on foods imported into the United States, enforcement and specific limits can vary. Due to its widespread use, the chemical is found throughout the food chain. It persists in the air, accumulates in soils, and is found in surface and groundwater.
Despite being considered safe by the EPA, the International Agency for Research on Cancer classifies glyphosate as “possibly carcinogenic to humans,” and emerging research, including this study, points to its potential role in worsening neurodegenerative diseases by contributing to pathologies, like those seen in Alzheimer’s disease.
The chemical works by inhibiting a specific enzyme pathway in plants that is crucial for producing essential amino acids. However, its impact extends beyond the intended weed, grass, and plant targets, negatively affecting the biological systems in mammals, as demonstrated by its persistence in brain tissue and its role in inflammatory processes.
Glyphosate’s Link to Alzheimer’s Disease
The researchers hypothesized that glyphosate exposure would induce neuroinflammation in control mice and worsen neuroinflammation in Alzheimer’s model mice, causing elevated Amyloid-β and tau pathology and worsening spatial cognition after recovery. Amyloid-β and Tau are key proteins that comprise plaques and tau tangles, the classic diagnostic markers of Alzheimer’s disease. Plaques and tangles disrupt neural functioning and are directly linked to memory loss and cognitive decline.
The experiments were conducted over 13 weeks, followed by a six-month recovery period. The main metabolite, aminomethylphosphonic acid, was detected in the brains of both normal and transgenic mice with Alzheimer’s pathology. Transgenic mice are genetically modified to carry genes that cause them to develop Alzheimer-like symptoms as they age. This allows researchers to study the progression and effects of the disease in a controlled laboratory setting.
The researchers tested two levels of glyphosate exposure: a high dose, similar to levels used in earlier research, and a lower dose that is close to the limit used to establish the current acceptable dose in humans. This lower dose still led to harmful effects in the brains of mice, even after exposure ceased for months. While reports show that most Americans are exposed to glyphosate daily, these results show that even a short period could potentially cause neurological damage.
Glyphosate caused a persistent increase in inflammatory markers in the brain and blood, even after the recovery period. This prolonged inflammation could drive the progression of neurodegenerative diseases, including Alzheimer’s, indicating even temporary glyphosate exposure can lead to enduring inflammatory processes that affect brain health. The data emphasizes that glyphosate exposure may be a significant health concern for human populations. The researchers stress the need for continued vigilance and intensified surveillance of glyphosate’s neurological and other long-term negative health effects.
Reference:
- Glyphosate exposure exacerbates neuroinflammation and Alzheimer’s disease-like pathology despite a 6-month recovery period in mice – (https://jneuroinflammation.biomedcentral.com/articles/10.1186/s12974-024-03290-6)
Source-Eurekalert
