Salk Institute researchers say a single gene variant could predispose many people to develop a range of neurological disorders, ranging from attention deficit hyperactivity disorder (ADHD) to Gulf War syndrome, following exposure to certain pesticides. The researchers say their findings could explain anecdotal evidence of a link between pesticide exposure and neurological dysfunction.
Carrolee Barlow, Christopher Winrow and colleagues found that in mice, exposure to organophosphates (a group of chemicals that include nerve gas and certain pesticides) inhibits the activity of a gene called neuropathy target esterase, or NTE. Mice bred to lack the NTE gene died before birth, but those with only one copy of the gene exhibited marked ADHD-like behavior when exposed to organophosphates. Mice with two functional NTE genes also exhibited behavior similar to ADHD after organophosphate pesticide exposure, but their symptoms were far milder.
The researchers note that the mice with only one copy of the NTE gene had a 40 percent decrease in the enzyme produced by the gene, which is active in areas of the brain controlling movement (including the hippocampus, cerebellum, and spinal cord).
Barlow says, "NTE is a large gene. It's possible that we all have slightly different forms of the NTE enzyme, which may explain why some may get ADHD when they're exposed at young ages, and why some may get Gulf War syndrome at a later age, or why some of us have no symptoms at all. It appears to be a case of delayed toxicity, inhibiting the function of NTE."
The findings of Barlow and Winnow follow earlier research by Elizabeth Guillette and colleagues (see related article, Crime Times, 1998, Vol. 4, No. 3, Page 1) linking pesticide exposure to neurodevelopmental problems. Guillette et al. compared Yaqui Indian children exposed to high or low levels of agricultural pesticides, and found that the children with higher pesticide exposure showed learning disabilities, behavior problems, impaired memory, motor problems, and other signs of significant brain dysfunction.
"Loss of neuropathy target esterase in mice links organophosphate exposure to hyperactivity," Christopher J. Winrow, Matthew L. Hemming, Duane M. Allen, Gary B. Quistad, John E. Casida, and Carrolee Barlow, Nature Genetics, advance online publication, March 17, 2003. Address: Carrolee Barlow, email@example.com.
"Genetic link may tie together pesticides, ADHD, Gulf War syndrome and other disorders," press release, Salk Institute, March 17, 2003.