Friday, July 13, 2012

New Evidence of Flame Retardant's Role In Autism

By Jennifer Wolstenholme
Fri, Jul 13, 2012 at 7:12 AM

For the first time, scientists have reported that the environment and genetics can work together to create autism-like symptoms in mice exposed in the womb to a flame retardant. According to a new study published in Human Molecular Genetics, female mice — born to mothers that are genetically more susceptible to develop autistic behaviors — were less social and had impaired memories and learning skills after their mothers were exposed to a brominated compound known as a PBDE.

A mother's exposure to a flame retardant before, during, and after pregnancy interacted with a known genetic mutation to impair learning and memory and decrease social behaviors in her offspring, a study with mice has found. Female mice were more sensitive to the exposure, which altered the on/off switches in the epigenetic code.

This is the first study to link genetic, epigenetic, and behavioral changes to a flame retardant chemical in females with a high genetic risk for autism spectrum disorders. The study is important because it focused on a specific gene mutation linked to Rett's syndrome — a condition on the autism spectrum that primarily affects females.

The results suggest that genetic risk for social deficits can interact with an environmental chemical to tip the balance toward exacerbated autistic behaviors. An individual with genetic risks for other health-related problems or diseases may also be more sensitive to these environmental chemicals than the overall general population.

During the past 25 years, brominated flame retardants — including polybrominated diphenyl ethers (PBDEs) — have been used in home furnishings and electronics to slow their burning during a fire. PBDEs are routinely detected in household dust, food, and air.

PBDEs have a similar chemical structure to thyroid hormone and can mimic thyroid actions, which can lead to changes in brain development. Rodent studies show that early life PBDE exposure increases activity, impairs learning, and alters motor development. Some of the cell populations in the brain affected in autism are also sensitive to thyroid hormone regulation, and thus may be affected by PBDEs. Thyroid hormone acts on most cells in the body and plays a wide-ranging role in metabolism, growth, and development.

Hallmarks of autism spectrum disorder (ASD) include deficiencies in social behaviors, cognition, and communication, often with repetitive behaviors. Recent evidence in the United States places ASD at as high as 1 in 88 children.

It is known that environmental exposures and genetic susceptibility work in concert to increase the risk of developing disorders along the autism spectrum. PBDEs have been accumulating in the environment at the same time as the accelerating rise in ASDs. Because changes in the brain and other symptoms are similar in PBDE exposures and autism, the authors suggest that the two may be related.

In the study, the researchers explored the interactions between genetics and environment. Adult female mice with a known genetic mutation were exposed orally every day for ten weeks to one type of PBDE before, during, and after pregnancy.

Importantly, this study shows that in a genetically susceptible population, PBDE exposure can have strong effects and can tip the balance toward an autistic pattern of behaviors. The researchers examined the role of a single environmental chemical in autistic behaviors but did not design their experiments to prove cause and effect with flame retardants. This study is an important step in showing that low dose chemical exposures can be important risk factors in sensitive populations for social and neurological diseases.

A longer version of this report was originally published at EnvironmentalHealthNews.org

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