A University of Toledo neuroscientist has received nearly $3 million from the National Institutes of Health to continue his investigation of the potential link between a commonly used pesticide and autism spectrum disorder.
Dr. James Burkett, a neuroscientist and assistant professor in the UToledo College of Medicine and Life Sciences, has previously led research that found exposing both mice and prairie voles to insecticides called pyrethroids while in the womb resulted in hyperactivity, repetitive behaviors and social and cognitive deficits — all characteristics of autism in humans.
Dr. James Burkett, a neuroscientist and assistant professor in the UToledo College of Medicine and Life Sciences, recently received a $2.94 million grant from the National Institutes of Health to continue his research into how a common insecticide may raise the risk of developmental disorders.
Notably, those studies used levels of the insecticide equivalent to what would currently be considered safe for humans under federal environmental guidelines.
With the new funding, Burkett will investigate whether similar effects are seen from lower levels of pyrethroid exposure. He’ll also dive deeply into understanding the specific mechanisms responsible for the pesticide’s effect on brain development.
“I think we’re very close to being able to say that this pesticide is a real danger at the levels to which people are currently exposed,” he said. “The critical part of this study is determining what a safe dose of this pesticide is, or if there even is a safe dose.”
Pyrethroids are widely used, appearing in everything from municipal mosquito fogging concentrations and home insecticide sprays to dog collars and factory-treated specialty clothing meant to repel ticks.
Though generally viewed as safer than other, older insecticides that have now been phased out of regular use, there is a growing body of evidence that pyrethroids may play a role in a range of developmental disorders.
In addition to Burkett’s work in animals, epidemiological studies have documented higher rates of neurodevelopmental disorders, including autism, in areas where the pesticides were used.
“Autism spectrum disorder is a complex condition and there is no one single cause. The current belief is that it’s the result of some combination of genetic and environmental factors,” Burkett said. “Pyrethroids are something that nearly everyone is exposed to at some level. Not everyone exposed to pyrethroids will develop autism, but I think there is very convincing evidence that pyrethroids are a real environmental risk factor.”
The new study, which is funded by the NIH’s National Institute of Environmental Health Sciences, will follow the model of Burkett’s prior work by exposing pregnant and lactating prairie voles to a pyrethroid called deltamethrin.
Unlike the previous studies, which looked at a single level of exposure, the upcoming work will expose different study groups to progressively lower levels of deltamethrin to see what level of exposure has no discernable impact to the animals’ laboratory behaviors, natural behaviors and brain biology.
In addition to better establishing a safe level of exposure to pyrethroids, the study, Burkett said, will allow researchers to see if different levels of exposure might cause different symptoms.
“We might see a very, very low dose cause symptoms that we think look like ADHD, but that it only causes symptoms that look like autism at these higher doses,” he said. “That’s the kind of information we can infer from this dose study.”
Prairie voles are particularly well suited for this type of research, Burkett said, because their complex social structures enable researchers to better see social deficits that are analogous to autism in humans.
Burkett’s prior work also has shown that pyrethroid exposure disrupts the prairie vole’s circadian rhythms. That, he said, is noteworthy, given that 50% to 85% of individuals with autism have comorbid sleep disorders.
As part of the new study, Burkett and his team plan to see if treating those voles’ sleep disruptions very early on might reduce the severity of their symptoms later on in life — potentially opening a new strategy for treating young children who have been diagnosed with autism spectrum disorder.
“Autism is a neurodevelopmental disorder. By the time those individuals are adults, their brain is already developed in an atypical way,” he said. “That’s why I want to look at treatments early in life where we can intervene and maybe reduce their symptoms in adulthood. To me, that’s the goal.”
