BPA sex-reverses behavior in turtles

Turtles could help determine how exposure to harmful chemicals during development affects male and female brains
Jeff Sossamon | MU News

Bisphenol A (BPA) is a chemical used in many consumer products including water bottles, metal food storage products and certain resins. Often, aquatic environments such as rivers and streams become reservoirs for BPA, affecting turtle habitats. Last year, a team of researchers led by the University of Missouri determined that BPA can disrupt sexual function in painted turtles, causing males to develop female sex organs. Now, the team has shown that BPA also can induce behavioral changes in turtles, reprogramming male turtle brains to show behavior common in females. Researchers worry this could lead to population declines in painted turtles.

“Previously, our research team found that BPA and ethinyl estradiol (EE2), a hormone found in birth control pills, could ‘sex-reverse’ turtles from males to females,” said Cheryl Rosenfeld,  an associate professor of biomedical sciences in the MU College of Veterinary Medicine and an investigator in the Bond Life Sciences Center. “Painted turtles and other reptiles lack sex chromosomes. The gender of painted turtles and other reptiles is determined by the incubation temperature of the egg during development. Studies have shown that exposure to endocrine-disrupting chemicals (EDCs), such as BPA, can override incubation temperature and switch the sex of males to females. In our latest study, we found that BPA also affects how the male brain is ‘wired,’ potentially inducing males to show female type behavioral patterns.”

Researchers applied a liquid form of BPA and ethinyl estradiol to painted turtle eggs and incubated the eggs at a temperature that typically results in males. Five months after hatching, turtles were tested with a spatial navigation test that included four food containers, only one of which was baited with food. Each turtle was randomly assigned one food container that did not change over the trial period.

Researchers predicted that male turtles exposed to BPA and EE2 would exhibit improved navigational ability — similar to behaviors observed in female turtles. Results showed that developmental exposure to BPA and EE2 improved spatial navigational learning and memory in males, as evidenced by increased number of times spent in the correct target zone and greater likelihood of solving the maze compared to control turtles, who were male based on the lower incubation temperature.

“Previous studies have found that female turtles are much more adept at spatial navigation — think of female sea turtles that return many years later to the same beaches where they hatched to lay their own eggs,” Rosenfeld said. “We found that developmental exposure to BPA essentially overrides the brain development of male turtles as indicated by the enhanced navigational ability of the turtles we studied. While improved spatial navigation might be considered a good thing, it also may suggest that when they reach adulthood male turtles will not exhibit courtship behaviors needed to attract a mate and reproduce, which could result in dramatic population declines.”

Rosenfeld notes that this is the first study to show that these harmful chemicals not only reverse the physical sex-characteristics but also affect the brain in a turtle species. Turtles are known as an “indicator species” because they can be used as a barometer for the health of the entire ecosystem. By understanding the possible effects EDCs have on turtles, researchers might be able to understand the possible effects the chemicals have on other wildlife species and humans, Rosenfeld said.

Effects of developmental exposure to bisphenol A and ethinyl estradiol on spatical navigational learning and memory in painted turtles (Chrysemys picta),” recently was published in the journal, Hormones and Behavior. Lindsey Manshack, a student at the time in Rosenfeld’s lab in MU’s Bond Life Sciences Center authored the study. Dawn Holliday, adjunct assistant professor of pathology and anatomical sciences in the MU School of Medicine and assistant professor of biology at Westminster College in Fulton, Mo., and Sharon Deem, director of the Saint Louis Zoo Institute for Conservation Medicine, contributed to the study. Funding was provided by Mizzou Advantage, the Office of Research and the Bond Life Sciences Center at the University of Missouri. The content is solely the responsibility of the authors and does not necessarily represent the official views of the funding agencies.

Research Core offers new capabilities

Grand opening highlights specialty of large-scale metabolite profiling
By Phillip Sitter | Bond LSC

Dr. Zhentian Lei , assistant director and assistant research professor of the MU Metabolomics Center, provides an overview of an ultra high-pressure liquid chromatograph coupled to mass spectrometry for the large-scale profiling of metabolites at the University of Missouri Metabolomics Center open house on Aug. 12. | photo by Zivile Raskauskaite, Bond LSC

Dr. Zhentian Lei , assistant director and assistant research professor of the MU Metabolomics Center, provides an overview of an ultra high-pressure liquid chromatograph coupled to mass spectrometry for the large-scale profiling of metabolites at the University of Missouri Metabolomics Center open house on Aug. 12. | photo by Zivile Raskauskaite, Bond LSC

You might think you’ve entered the inside of a pinball machine for a moment when you enter lab 243 at the Bond Life Sciences Center.

But the wires and tubes strung around the room, connected to large instruments that produce sounds of whirring fans, humming motors and hissing pumps, are just part of the University of Missouri’s newest core facility, the MU Metabolomics Center.

At its grand opening and open house Friday, August 12, there was even a counter-top half-pipe with metal ball bearings to shoot down it as a demonstration of time of flight mass spectrometry.

This new center will serve as home of high-tech chemical analysis services that scientists in Bond LSC, across campus and the country can use to better understand the organisms they work with on a molecular level.

Lloyd Sumner, director of the MU Metabolomics Center, and Assistant Professor Ruthie Angelovici discuss the use of NMR for metabolite identification during the University of Missouri Metabolomics Center open house on Aug. 12. | photo by Zivile Raskauskaite, Bond LSC

Lloyd Sumner, director of the MU Metabolomics Center, and Assistant Professor Ruthie Angelovici discuss the use of NMR for metabolite identification during the University of Missouri Metabolomics Center open house on Aug. 12. | photo by Zivile Raskauskaite, Bond LSC

“We have a series of experiments that allow us to profile hundreds to thousands of different metabolites, and that gives people a large-scale, high resolution biochemical traits for whatever they’re looking at, whether it be plants, microbes or animals,” explained Lloyd Sumner, director of the center. “That is useful in understanding what is happening in response to stresses, disease, drug treatment or pest/pathogen interactions that occur in nature.”

Metabolites are the building blocks and energy sources that fuel your metabolism. In your body, what you eat and drink is processed and yields small molecules that are ready to become raw chemical material for construction processes and energy to fuel these processes, like energy stored in the form of fats and lipids, amino acids for the construction of proteins and enzymes. Metabolite are essentially the raw materials.

In order to be studied, complex metabolite mixtures are separated and observed as individual, uniquely identifiable molecules.

This separation can be accomplished in a couple different ways.

“We have instruments that couple chromatography with mass spectrometry. We use that for comparative profiling. Some of the instruments utilize gas chromatography, some of the instruments use liquid chromatography. Chromatography is the technology used to separate these complex mixtures into its individual components. Once we have the mixture’s components separated, we weigh them and that gives us an idea of their identification,” Sumner explained.

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These internal components of a triple quadrupole mass spectrometry are used for explaining how the instrument helps identify the metabolites within a sample during the University of Missouri Metabolomics Center open house on Aug. 12. | photo by Zivile Raskauskaite, Bond LSC

Mass spectrometry works by bombarding molecules with electrons. This bombardment process generates charged molecules that can also fragment into smaller, electrically-charged pieces. These charged pieces can then be “weighed,” or separated, according to their mass-to-charge ratio and identified.

“Something that we find a lot of the time is that we see metabolic differences, but we can’t always identify all of the metabolites associated with those differences. In those cases, we also use the gold standard for chemical identification of unknown molecules,” Sumner said of the nuclear magnetic resonance (NMR) spectrometer in the corner of the lab.

A person points at a 600 MHz Nuclear Magnetic Resonance Spectrometer used for metabolite identification during the University of Missouri Metabolomics Center open house on Aug. 12. | photo by Zivile Raskauskaite, Bond LSC

A person points at a 600 MHz Nuclear Magnetic Resonance Spectrometer used for metabolite identification during the University of Missouri Metabolomics Center open house on Aug. 12. | photo by Zivile Raskauskaite, Bond LSC

Placards warn people that when NMR produces a magnetic field 235,000 times stronger than the Earth’s — by comparison, a typical refrigerator magnet’s field is about 83 times as strong as the Earth’s.

Sumner explained that most people at Bond LSC won’t use the equipment directly themselves. The center’s Assistant Director Dr. Zhentian Lei and other staff will perform most analyses and training users to prepare, process and understand their data.

Sumner said “we train our core users to do their own sample preparation, data processing and data interpretation. Most of the equipment we have in here [cost] hundreds of thousands of dollars, and so we actually have staff that will do the data acquisition, and we try to make it more cost-effective for users by training them to prep their own samples and process their own data.”

The training workshop in metabolomics will be August 15 through 19. The training Monday through Thursday will be hands-on, and Friday will be a symposium day highlighting current metabolomics research. We will likely offer another training workshop in the Spring of 2017, and then annually thereafter.

For more information on using the MU Metabolomics Core or future training, email Director Lloyd Sumner at sumnerlw@missouri.edu or Assistant Director Zhentian Lei at leiz@missouri.edu.

Standing out through saliva

Bond LSC scientist internationally recognized for work on salivary glands and autoimmune disorders
By Phillip Sitter | Bond LSC

You might not think too highly of spit, but you would quickly regret not having any.

People with Sjögren’s syndrome suffer chronic dry mouth and eyes from an overzealous immune system that attacks salivary and tear ducts, causing serious health issues.

Gary Weisman’s research might hold the key to understanding and managing this immune response, leading to effective treatment or even prevention of this ailment.

For this, the International Association of Dental Research, or IADR, awarded him the 2016 Distinguished Scientist Award for Salivary Research. Weisman accepted the award in June at the opening ceremonies of the IADR conference in Seoul, Republic of Korea.

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Gary Weisman stands in his lab in Bond LSC where he studies the cellular mechanisms of auto-immune disease, specifically how the release of ATP from damaged cells signals receptors that trigger an immune response. | Phillip Sitter, Bond LSC

“We want the good, but not the bad,” said Weisman, a Bond Life Sciences Center investigator, of what we ideally want from our immune system’s functions.

Mice with un-checked autoimmune disease of their salivary glands have their glands destroyed. The disease can spread to other secretory organs next. An over-reactive immune system on a civil war-path can extend its damage to cause pancreatic failure and death.

The destruction wrought by Sjögren’s syndrome is self-inflicted, caused by an overreaction of our bodies’ defenses against infection and injury. This is what an autoimmune disease is.

But, our bodies’ immune cellular response team is complicated. Weisman said dozens of different cell types have been isolated and identified as part of the immune system, and he likens the immune system to fire, police and construction services in human society all working together.

While firefighters are meant to prevent further damage from an inferno, sometimes our bodies’ first responders start doing the equivalent of using dynamite to stop the spread of a fire.

In chronic inflammation, that autoimmune response can mean a burning, throbbing, constant pain. The key to a healthy immune response is balance. The balance has to be between containment and repair of damage caused by infection or injury and damage caused by chronic inflammation if that emergency response continues unabated.

Weisman has spent almost 30 years studying how to prevent our bodies’ immune system from over-reacting to threats and causing further harm.

Earlier in his career, Weisman studied how extracellular ATP plays a critical role in immune responses, and how too much of it can cause the over-reaction that leads to tissue destruction in autoimmune diseases. ATP, or adenosine 5’-triphosphate, is the main molecule used for energy in cellular activities inside cells. Weisman was one of the first scientists to study how damaged cells release ATP as a distress signal.

The released ATP signals receptors that “send out the alarm to the fire station” — the body’s immune cells, he said.

Once he understood this, Weisman began to manipulate the actions of released ATP to see how that would affect an immune response.

Mice with salivary gland autoimmune disease got healthy when the released ATP was prevented from activating their receptors on the surface of cells. Preventing the ATP receptors from being activated slowed down and even stopped the advance of autimmune disease.

Conversely, if you prevent the activation of the ATP receptors in lab mice with Alzheimer’s disease they die much more rapidly from the disease, Weisman said, suggesting that activation of immune cells by ATP is beneficial in slowing the progression of this disease.

Alzheimer’s disease and autoimmune diseases such as Sjögren’s syndrome are only some of the inflammatory diseases that Weisman has studied. With each of these diseases, the role of ATP receptors has to be investigated individually, suggesting that Weisman’s work may extend beyond salivary glands and the brain to other parts of the body.

“Our [ATP] receptor is also involved in heart disease,” Weisman said, and he added that other diseases like cystic fibrosis, cancer, lupus and arthritis have inflammatory components, too.

For now, we all fight a losing battle when it comes to our bodies’ management of the immune system. As we and our immune system age, it has the potential to destroy more than it protects and “eventually you could slip over to the dark side and die,” Weisman said.

In the meantime, Weisman said that a better understanding of the immune system could lead to more effective, targeted treatments of chronic inflammation and other autoimmune disorders. This could provide a new approach to control undesirable activation of the immune system beyond the use of with anti-histamines, anti-cytokines and ibuprofen.

Weisman is a Curator’s Distinguished Professor of Biochemistry. He began his salivary gland research at MU 27 years ago with Professor John Turner, before Turner’s retirement. Since then, his research has been continuously funded by the National Institutes of Health, where one of his recent grants was well scored and will likely be extended for another five years.