BPA may affect the developing brain by disrupting gene regulation

Exposure to BPA may disrupt development of the central nervous system by slowing down the removal of chloride from neurons. As an organism matures and the brain develops, chloride levels inside nerve cells drop. However, when exposed to BPA, the chloride is removed more slowly from neurons. Researchers also found female neurons to be more susceptible to the effects of BPA. Credit: Michele Yeo, Duke Medicine

Environmental exposure to bisphenol A (BPA), a widespread chemical found in plastics and resins, may suppress a gene vital to nerve cell function and to the development of the central nervous system, according to a study led by researchers at Duke Medicine.

The researchers published their findings - which were observed in of mice, rats and humans - in the journal on Feb. 25, 2013.

"Our study found that BPA may impair the development of the , and raises the question as to whether exposure could predispose animals and humans to ," said lead author Wolfgang Liedtke, M.D., PhD, associate professor of medicine/neurology and neurobiology at Duke.

BPA, a molecule that mimics estrogen and interferes with the body's , can be found in a wide variety of manufactured products, including thermal printer paper, some and the lining of metal cans. The chemical can be ingested if it seeps into the contents of food and .

Research in animals has raised concerns that exposure to BPA may cause health problems such as behavioral issues, endocrine and reproductive disorders, obesity, cancer and immune system disorders. Some studies suggest that infants and young children may be the most vulnerable to the effects of BPA, which led the U.S. to ban the use of the chemical in baby bottles and cups in July 2012.

While BPA has been shown to affect the developing nervous system, little is understood as to how this occurs. The research team developed a series of experiments in rodent and human nerve cells to learn how BPA induces changes that disrupt gene regulation.

During early development of neurons, high levels of chloride are present in the cells. These levels drop as neurons mature, thanks to a chloride transporter protein called KCC2, which churns out of the cells. If the level of chloride within neurons remains elevated, it can damage neural circuits and compromise a developing nerve cell's ability to migrate to its proper position in the brain.

Exposing neurons to minute amounts of BPA alters the chloride levels inside the cells by somehow shutting down the Kcc2 gene, which makes the KCC2 protein, thereby delaying the removal of chloride from neurons.

MECP2, another protein important for normal brain function, was found to be a possible culprit behind this change. When exposed to BPA, MECP2 is more abundant and binds to the Kcc2 gene at a higher rate, which might help to shut it down. This could contribute to problems in the developing brain due to a delay in chloride being removed.

These findings raise the question of whether BPA could contribute to neurodevelopmental disorders such as Rett syndrome, a severe autism spectrum disorder that is only found in girls and is characterized by mutations in the gene that produces MECP2.

While both male and female neurons were affected by BPA in the studies, female neurons were more susceptible to the chemical's toxicity. Further research will dig deeper into the sex-specific effects of BPA exposure and whether certain sex hormone receptors are involved in BPA's effect on KCC2.

"Our findings improve our understanding of how environmental exposure to BPA can affect the regulation of the Kcc2 gene. However, we expect future studies to focus on what targets aside from Kcc2 are affected by BPA," Liedtke said. "This is a chapter in an ongoing story."

Related Stories

France bans contested chemical BPA in food packaging

Dec 13, 2012

The French parliament voted Thursday to ban the use of bisphenol A, a chemical thought to have a toxic effect on the brain and nervous system, in baby food packaging next year and all food containers in 2015.

BPA exposure effects may last for generations

Jun 15, 2012

Exposure to low doses of Bisphenol A (BPA) during gestation had immediate and long-lasting, trans-generational effects on the brain and social behaviors in mice, according to a recent study accepted for publication in the ...

France sees labelling of contested chemical BPA

Sep 27, 2011

France's ecology minister on Tuesday said she would seek labelling requirements for food containers made with bisphenol A (BPA) after a watchdog agency sharpened its concern about this chemical.

Exposure to BPA has been underestimated, new research says

Jun 06, 2011

A new University of Missouri study shows that the exposure to the controversial chemical Bisphenol A (BPA) through diet has been underestimated by previous lab tests. In the study, researchers compared BPA concentrations ...

BPA lowers male fertility: report

Jun 06, 2011

Daily exposure to a chemical that is prevalent in the human environment, bisphenol A (BPA), causes lowered fertility in male mice, according to the results of a new study that will be presented Saturday at The Endocrine Society's ...

Recommended for you

A better way to track emerging cell therapies using MRIs

1 hour ago

Cellular therapeutics – using intact cells to treat and cure disease – is a hugely promising new approach in medicine but it is hindered by the inability of doctors and scientists to effectively track the movements, destination ...

New biomedical implants accelerate bone healing

8 hours ago

A major success in developing new biomedical implants with the ability to accelerate bone healing has been reported by a group of scientists from the Department of Restorative Dentistry, University of Malaya. ...

User comments

Adjust slider to filter visible comments by rank

Display comments: newest first

VendicarE
not rated yet Feb 26, 2013
And once again, the U.S. was among the last industrialized nation to ban BPA in drinking bottles.

I take that as ample proof of the claimed brain damage done by BPA.