Bisphenol A Linked to Damage in Developing Brain Tissue

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Bisphenol A (BPA) has been linked to damage in developing brain tissue

Medical Research News

Published: Friday, 2-Dec-2005

The chemical bisphenol A (BPA), widely used in products such as food cans,

milk container linings, water pipes and even dental sealants, has now been

found to disrupt important effects of estrogen in the developing brain.

A University of Cincinnati (UC) research team, headed by Belcher, PhD,

reports in two articles in the December 2005 edition of the journal

Endocrinology that BPA shows negative effects in brain tissue " at

surprisingly low doses. "

The research was supported by funding from the National Institutes of Health

and the Pediatric Brain Tumor Foundation.

" These new studies are also the first to show that estrogen's rapid

signaling mechanisms are active in the developing and maturing brain in

regions not thought to be involved with sexual differences or reproductive

functions, " Dr. Belcher said.

BPA has often been implicated in disease or developmental problems.

Long known to act as an artificial estrogen, the primary hormone involved in

female sexual development, BPA has already been shown to increase breast

cancer cell growth, and in the January 2005 edition of the journal Cancer

Research, another UC research team reported that it increased the growth of

some prostate cancer cells as well. Warnings about other possible long-term

health risks associated with fetal exposures to BPA have also been discussed

in recent scientific literature.

" BPA molecules are linked into polymers used to create polycarbonate

plastics and epoxy resins that are widely used in many products, " said Dr.

Belcher, an associate professor in the pharmacology and cell biophysics

department at UC College of Medicine. " While plastics are typically thought

of as being stable, scientists have known for many years that the chemical

linkage between BPA molecules was unstable, and that BPA leaches into food

or beverages in contact with the plastics. "

Dr. Belcher and his colleagues worked with rats at a period in their

development equivalent to the third trimester of human fetal development

through to the first few years of childhood.

Although best known for its function as a female sex hormone, Dr. Belcher

explained, estrogen also has very important roles in the developing brain of

both males and females.

In the absence of estrogen, Dr. Belcher said, BPA alone was found to mimic

the actions of estrogen in developing neurons, and very low doses of BPA

completely inhibited the activity of estrogen. Because estrogen normally

increases the growth and regulates viability of developing neurons, he said,

these results support the idea that BPA may harm developing brain cells.

In fact, Dr. Belcher said, while high doses cause little effect, analysis of

cellular and molecular markers of estrogen signaling revealed that

near-maximal effects of BPA on rat brain neurons not only occurred " at

surprisingly low " doses of 0.23 parts per trillion, they also happened in a

matter of minutes.

" From other studies it's clear that these low concentrations are in line

with human fetal exposures, and at levels one might even see in the water

supply, " said Dr. Belcher.

This " low-dose " effect of BPA is troubling, Dr. Belcher points out, since

its maximal effects occur at the level typical of human exposure. This means

that the harmful effects of BPA could easily be missed using standard

approaches for determining the risks of chemical exposure.

" These are important considerations in view of the widespread presence of

low concentrations of BPA in the environment, " said Dr. Belcher

In earlier research, which showed estrogens could control the survival of

maturing neurons in the brain region involved in movement and coordination,

Dr. Belcher and his co-workers found the effects of estrogen were the same

in both males and females.

" Estrogen's actions on these neurons appear to be a double-edged sword, " he

said. " During certain periods of development estrogen can kill specific

subsets of neurons, but at a later developmental stage it actually appears

to increase their viability. " Disruption of either of these actions of

estrogen could be considered potentially harmful, he added.

" We have now shown that environmental estrogens like BPA appear to alter, in

a very complicated fashion, the normal way estrogen communicates with

immature nerve cells, " Dr. Belcher explained. " The developmental effects

that we studied are known to be important for brain development and also for

normal function of the adult brain, " he said.

What remains unclear, he said, is how inappropriate hormone signaling, or

blocking the normal signaling at a critical time during development, will

influence later life.

In the face of more than 100 studies published in peer-reviewed journals

showing the detrimental effects of BPA, Dr. Belcher said, the chemical

industry and federal regulatory agencies have resisted banning BPA from

plastics used as food and beverage containers, despite the fact that

plastics free of BPA and other toxic chemicals are available.