New research from University of California-Davis and Washington State University suggests exposure to PCBs may increase the likelihood of autism in some children.
Dr. Pamela Lein, a developmental neurobiologist and professor of molecular biosciences in the UC Davis School of Veterinary Medicine, said PCBs can cause a disruption of nerve connections in the brain among children. “Impaired neuronal connectivity is a common feature of a number of conditions, including autism spectrum disorders.”
However, the PCBs alone are not believed to cause autism, but serve as an environmental trigger among genetically susceptible children.
Two related studies published in the journal Environmental Health Perspectives, present findings that underscore the developing brain’s vulnerability to environmental exposures and demonstrate how PCBs could add to autism risk.
“We don’t think PCB exposure causes autism,” Lein said, “but it may increase the likelihood of autism in children whose genetic makeup already compromises the processes by which neurons form connections.”
Gary Wayman, Ph.D., of Washington State University’s Program in Neuroscience, first described the molecular pathway that controls the calcium signaling in the brain that guides normal dendrite growth.
Wayman found that key cellular players are activated by increased calcium levels.
“The wiring of billions of neurons is dependent on the health of this cellular process and is crucial to proper development of virtually all complex behaviors, learning, memories and language.”
For the current studies, the team set out to determine if that pathway was altered by exposure to PCBs, focusing on neurons of the hippocampus — the brain region linked with learning and memory and known to suffer impaired connectivity in many neurodevelopmental disorders.
The scientists also focused on the effects of an understudied PCB subset known as non-dioxin-like PCBs, which have been shown to increase calcium levels in neurons.
Both non-dioxin-like PCBs and the more familiar dioxin-like subset were widely used in electrical equipment in the 1950s and 1960s. Banned in the 1970s because of the potential for dioxin-like PCBs to cause cancer, all PCBs are stable compounds that persist throughout the environment today.
“The new findings provide good evidence that PCBs could add to autism risk in genetically predisposed children,” said researchers.
“Understanding the fundamental mechanisms by which PCBs alter neural networks sets the stage for research on environmental contaminants that are structurally related to PCBs, including flame retardants, and their risks to susceptible populations.”
Source: UC Davis