A new study of rat brain cells shows that the herbicide Agent Orange can damage the central nervous system in a similar way to neurodegenerative diseases.
During the Vietnam War, U.S. military forces sprayed Agent Orange in Vietnam to remove dense vegetation that provided cover for enemy forces and to destroy crops that might feed the enemy. However, its widespread use resulted in severe environmental contamination and long-term health effects for both military personnel and civilians exposed to it.
"The first people who screamed alarm were mothers who gave birth to these infants with many mutations," Suzanne De La Monte, a scientist specializing in neuropathology at Brown University, told Tech Times in an interview. "They weren't even involved in the war; they were just civilians nearby."
Agent Orange contains two main components: 2,4-D and 2,4,5-T. While 2,4-D is still used today as a herbicide to control broadleaf weeds in various environments such as lawns, agricultural fields, and forestry sites, it has been linked to adverse health effects. Meanwhile, 2,4,5-T was banned due to toxicity concerns, and its use was phased out beginning in the late 1970s.
Recent research has shown that exposure to Agent Orange may be linked to a higher risk of Alzheimer's disease and other neurodegenerative diseases in Vietnam War veterans and civilians exposed to Agent Orange during the war. In an earlier study, De La Monte and her colleagues saw that short-term exposure of immature human brain cells to 2,4-D or 2,4,5-T caused various types of damage to the cells and triggered early signs of degeneration. The chemicals altered the expression of certain proteins that are typically disrupted in Alzheimer's disease.
Now, the team built on this knowledge and looked at how the herbicide affects brain tissue. They used slices of rat brains to understand how the herbicide toxins would interact with the many components of brain tissue, including brain cells, blood vessels, and tissue structures. The researchers used a combination of 2,4-D and 2,4,5-T to simulate the effects of Agent Orange. The scientists were attempting to understand the impact of exposure on both military personnel and civilians who were exposed to Agent Orange over many years due to its lingering presence in the environment.
"We exposed brain tissue to these Agent Orange toxins, one by one, and then together and then looked at the consequences focusing on exactly the same things that take place in Alzheimer's disease," adds De La Monte.
When asked if the doses used in the lab represent realistic environmental or wartime exposures, De La Monte believes they do, based on the calculations she and her team performed. "The doses we used were probably comparable to what someone would get if they were spraying or right in the vicinity of being sprayed," she explains.
Their results showed that both 2,4-D and 2,4,5-T caused damage and degeneration to neurons, the cells responsible for transmitting signals in the brain. The chemicals also led to the death of endothelial cells, which line blood vessels. Additionally, they resulted in damage to the white matter in the brain's tissue.
When it comes to Alzheimer's disease, the researchers found higher levels of two key proteins, amyloid-beta protein precursor and amyloid-beta, in the brain samples that had been treated with 2,4-D, 2,4,5-T, or a combination of the two. In Alzheimer's disease, these proteins tend to accumulate in the brain, forming the plaques that are a hallmark of the disease. The increase in these two proteins after exposure to the chemicals suggests a possible link between their presence and the development of Alzheimer ''s-like symptoms.
To Ray Dorsey, a physician specializing in neurology who wasn't involved in the study, these results are yet another piece of evidence about the impact of toxins on brain health. "This is just the latest study to tie environmental toxicants in our food, water, and air to brain diseases, which are the world's leading source of disability," he says. "If we see this with Agent Orange and Alzheimer's disease in the lab, we should be asking what is occurring with other pesticides in humans in our environment. What other weed killers are contributing to what other diseases?"
As for the next steps, De La Monte is working on looking at the combined effect of other factors, such as drinking and smoking, and how that plays with Agent Orange's impact on human health. "I feel very strongly about supporting the veterans," De La Monte concludes. "They gave their lives, they did whatever they were told, and at least we can give them back health care for their bad health that resulted from having been exposed."
Bárbara Pinho is a freelance science journalist. Her work work has appeared in New Scientist, Chemistry World, Discover, Chemistry & Industry News, National Geographic. Her website is https://www.barbarapinho.com/
