The neurotoxic effects have important implications for the long-term brain health of all people exposed to biologically similar herbicides.
Agent Orange, an herbicide used during the Vietnam War, is a known toxin with wide-ranging health effects. Even though it hasn’t been used for decades, there is increasing interest in its effects on the brain health of aging veterans. A recent study in the Journal of Alzheimer’s Disease shows that exposures to herbicidal chemicals damage frontal lobe brain tissue of laboratory rats with molecular and biochemical abnormalities that are similar to those found in early-stage Alzheimer’s.
The findings could have important implications for Vietnam veterans who were exposed to Agent Orange, says study author Suzanne M. De La Monte, MD, MPH. But they have much broader significance, she adds, because the same toxins are also present in common herbicides.
“These chemicals don’t just affect veterans; they affect our entire population,” says De La Monte, a professor of pathology and laboratory medicine and of neurosurgery.
Research has revealed associations between Agent Orange exposures and later development of neurodegenerative diseases, and significantly higher rates and earlier onsets of dementia. However, in the absence of a proved causal link, there has been a need for studies that improve understanding of the process by which the herbicide affects the brain.
The analysis, conducted by De La Monte and Ming Tong, MD, a research associate in medicine, builds upon their recent studies of exposure to Agent Orange chemicals on immature human cells showing that short-term exposure has neurotoxic and early degenerative effects related to Alzheimer’s.
De La Monte and Tong investigated the effects of the two main constituents of Agent Orange on markers of Alzheimer’s neurodegeneration using samples from the frontal lobes of laboratory rats. The scientists treated the samples to cumulative exposure to Agent Orange, and observed the underlying mechanisms and molecular changes. They found that treatment with Agent Orange and its constituents caused changes in the brain tissue corresponding to brain cell degeneration, and molecular and biochemical abnormalities indicative of cytotoxic injury, DNA damage, and other issues.
The approach helped De La Monte and Tong better characterize the consequences of Agent Orange exposures in young, otherwise healthy brains, as would have been the case for Vietnam War-era military personnel.
“Looking for the early effects tells us that there is a problem that is going to cause trouble later on,” De La Monte says. “If you were going to intervene, you would know to focus on that early effect.”
