July 18, 2013
Modified Forms Of BPA Alter Hormone Signaling In New, Disturbing Ways
April Flowers for redOrbit.com - Your Universe Online
Bisphenol A (BPA) has been a worry for scientists for years. It is known as an "endocrine disruptor," a substance that interferes with the body's hormone signaling system. BPA is found in everything from plastic drink bottles to the linings of food and drink cans to the thermal paper used for cash register receipts - it is even present in the urine of 92.6 percent of Americans over the age of six. BPA has also been associated with diseases such as diabetes, asthma and ovarian dysfunction. Because of the dangers, the FDA banned BPA from use in the production of baby bottles and drinking cups in 2012.The ubiquitous presence of BPA in the environment led researchers to question what it might be doing in publicly supplied drinking water, which is contaminated at its source by BPA-laden discarded plastic. The water picks up more of the chemical when it passes through PVC plastic pipes. Because most public water supplies are chlorinated to kill bacteria, the BPA also becomes chlorinated - acquiring one or more chlorine atoms from the surrounding water. The research team, led by University of Texas Medical Branch at Galveston professor Cheryl Watson, wanted to understand how this chlorinated BPA reacts in the body.
The team used cell-culture experiments to find the answer - chlorinated BPA produces different, but no less profound, effects. "We found that when you modify the BPA it works just as dramatically but in different ways on the same systems," said Watson.
Watson, along with graduate student Rene Vinas, looked at both chlorinated BPA and BPA that had undergone sulfonation and glucuronodation - two processes the body uses to make a compound easier to excrete. All three modified forms of BPA worked through membrane estrogen receptors to deactivate key signaling enzymes known as ERK and JNK kinases.
"These kinases are major control centers, gathering all the cell signals, making decisions and then expediting them," Watson said. "If you change the dynamic by inactivating kinases, you can mess up cell signaling."
In a phenomenon commonly seen with membrane receptors, only very low levels of modified BPA were needed to produce the results. The responses followed a non-monotonic pattern, which varies irregularly when different concentrations of modified BPA were tested. This variable pattern made a large number of experimental procedures necessary. These were facilitated by a BIOMEK-FX robot, which Vinas programmed to considerably increase the efficiency and precision of the process.
"The robot cuts down on the experimenter time required, because it does so much of the mechanical work, and it makes results more replicable, because the robot does things exactly the same every time," Watson said. "It gives us hope that we can make an impact even with the sheer volume of chemicals that we have to study and the detail we have to study them in."
The results of their study were recently published online in the journal Endocrine Disruptors.