January 23, 2013
Bisphenol S Shown To Disrupt Hormone Activity
Brett Smith for redOrbit.com - Your Universe Online
After numerous research studies raised questions over its safety, several states and countries began banning the sale of products containing bisphenol A (BPA), prompting companies in the plastics industry to begin producing products that were “BPA free.”
However, a new study from the University of Texas Medical Branch at Galveston (UTMB) shows that a widely used BPA substitute, bisphenol S (BPS), has the same negative effect as the original organic compound–blocking the cellular responses to the hormone estrogen.
"Our studies show that BPS is active at femtomolar to picomolar concentrations just like endogenous hormones – that's in the range of parts per trillion to quadrillion," said senior researcher Cheryl Watson, a UTMB professor. “Those are levels likely to be produced by BPS leaching from containers into their contents."
In the late 1990s, several different studies began linking BPA, which is used to make plastic bottles, to various ailments, including diabetes, asthma, cancer, and altered prostate development. One study showed that very weak concentrations of BPA are able to produce a negative effect in the human testicle.
As the evidence against the additive began to mount, many governments around the world adopted regulations to protect their people against the potential threat. In the United States public pressure began to grow, and the FDA and state legislatures were considering legislation to restrict the use of BPA. These developments led to an industry-wide shift away from BPA to BPS.
In the UTMB study, which was recently published in Environmental Health Perspectives, Watson and her colleague RenÃ© ViÃ±as conducted in vitro experiments to test the effects of BPS on estrogen signaling on the cell's outer membrane instead of the cell nucleus. Membrane signaling was chosen for study because a response can be measured in seconds or minutes, while nuclear signaling interactions can take hours or days to gauge.
The two researchers focused their study on certain biochemical pathways that are usually stimulated when estrogen activates membrane receptors, and that could be problematic if disrupted. One signaling mechanism, involving a protein known as ERK, is associated to cell growth, and another, called JNK, is involved in the death of a cell. They also examined the effects of BPS on proteins called caspases, also linked to cell death, and the release of the sex hormone prolactin, which promotes lactation among other functions.
"These pathways form a complicated web of signals, and we're going to need to study them more closely to fully understand how they work," Watson said. "On its own, though, this study shows us that very low levels of BPS can disrupt natural estrogen hormone actions in ways similar to what we see with BPA. That's a real cause for concern."
If BPS is found to be harmful to humans, it could have a wide impact as the organic compound is used in everything from currency to receipt paper. The degree of human exposure to BPS was demonstrated in a 2012 study that showed urine samples taken in the U.S., Japan, China and five other Asian countries contained the substance.