The Tanguay group uses the embryonic zebrafish model to demonstrate the utility of high throughput screening for toxicology studies. The group evaluated the 1060 US EPA ToxCast Phase 1 and 2 compounds on 18 distinct outcomes. With four doses for each compound the group generated a dizzying number of data points highlighting the importance of bioinformatics analysis in these types of studies. The study shows how it is now possible to screen many of the tens of thousands of untested chemicals using a whole animal model in which one can literally see developmental malformations. —Gary W. Miller
Abstract
There are tens of thousands of man-made chemicals in the environment; the inherent safety of most of these chemicals is not known. Relevant biological platforms and new computational tools are needed to prioritize testing of chemicals with limited human health hazard information. We describe an experimental design for high-throughput characterization of multidimensional in vivo effects with the power to evaluate trends relating to commonly cited chemical predictors. We evaluated all 1060 unique U.S. EPA ToxCast phase 1 and 2 compounds using the embryonic zebrafish and found that 487 induced significant adverse biological responses. The utilization of 18 simultaneously measured endpoints means that the entire system serves as a robust biological sensor for chemical hazard. The experimental design enabled us to describe global patterns of variation across tested compounds, evaluate the concordance of the available in vitro and in vivo phase 1 data with this study, highlight specific mechanisms/value-added/novel biology related to notochord development, and demonstrate that the developmental zebrafish detects adverse responses that would be missed by less comprehensive testing strategies.
CORVALLIS, Ore. – Researchers at Oregon State University have discovered novel compounds produced by certain types of chemical reactions – such as those found in vehicle exhaust or grilling meat – that are hundreds of times more mutagenic than their parent compounds which are known carcinogens.
These compounds were not previously known to exist, and raise additional concerns about the health impacts of heavily-polluted urban air or dietary exposure. It’s not yet been determined in what level the compounds might be present, and no health standards now exist for them.
The compounds were identified in laboratory experiments that mimic the type of conditions which might be found from the combustion and exhaust in cars and trucks, or the grilling of meat over a flame.
“Some of the compounds that we’ve discovered are far more mutagenic than we previously understood, and may exist in the environment as a result of heavy air pollution from vehicles or some types of food preparation,” said Staci Simonich, a professor of chemistry and toxicology in the OSU College of Agricultural Sciences.
Dr. Staci Simonich, Project 5 Leader with the OSU Superfund Research Program
“We don’t know at this point what levels may be present, and will explore that in continued research,” she said.
The parent compounds involved in this research are polycyclic aromatic hydrocarbons, or PAHs, formed naturally as the result of almost any type of combustion, from a wood stove to an automobile engine, cigarette or a coal-fired power plant. Many PAHs, such as benzopyrene, are known to be carcinogenic, believed to be more of a health concern that has been appreciated in the past, and are the subject of extensive research at OSU and elsewhere around the world.
The PAHs can become even more of a problem when they chemically interact with nitrogen to become “nitrated,” or NPAHs, scientists say. The newly-discovered compounds are NPAHs that were unknown to this point.
This study found that the direct mutagenicity of the NPAHs with one nitrogen group can increase 6 to 432 times more than the parent compound. NPAHs based on two nitrogen groups can be 272 to 467 times more mutagenic. Mutagens are chemicals that can cause DNA damage in cells that in turn can cause cancer.
For technical reasons based on how the mutagenic assays are conducted, the researchers said these numbers may actually understate the increase in toxicity – it could be even higher.
These discoveries are an outgrowth of research on PAHs that was done by Simonich at the Beijing Summer Olympic Games in 2008, when extensive studies of urban air quality were conducted, in part, based on concerns about impacts on athletes and visitors to the games.
Beijing, like some other cities in Asia, has significant problems with air quality, and may be 10-50 times more polluted than some major urban areas in the U.S. with air concerns, such as the Los Angeles basin.
An agency of the World Health Organization announced last fall that it now considers outdoor air pollution, especially particulate matter, to be carcinogenic, and cause other health problems as well. PAHs are one of the types of pollutants found on particulate matter in air pollution that are of special concern.
Concerns about the heavy levels of air pollution from some Asian cities are sufficient that Simonich is doing monitoring on Oregon’s Mount Bachelor, a 9,065-foot mountain in the central Oregon Cascade Range. Researchers want to determine what levels of air pollution may be found there after traveling thousands of miles across the Pacific Ocean.
Steven O’Connell sampling at the Portland Harbor Superfund Site
In the past few years, our Center has been conducting research to learn more about oxygenated polycyclic aromatic hydrocarbons (OPAHs). OPAHs are one of the degradation products of parent PAHs. OPAHs are studied because they are present in the environment and pose an unknown hazard to human health.
Focus on this class of compounds has really increased in the last few years, although it’s interesting to note that there were reports of some of these compounds in the 1970’s and earlier. There are several reasons researchers want to study these compounds. OPAHs seem to be found in similar concentrations to the highly studied parent PAHs in a variety of samples ranging from diesel exhaust to urban air. Additionally, not a lot is known about the toxicity of these compounds, although early evidence suggests that they may be on par with PAHs. That’s why the OPAH research of students Andrea Knecht and Britton Goodale in Dr. Robert Tanguay’s Lab (Project 3) has been so important.
Why measure OPAHs at the Portland Harbor Superfund Site?
It makes a lot of sense to try and measure OPAHs at Portland Harbor Superfund. PAHs have been responsible for remediation at some sites for years now, and are the precursors of OPAHs. In some cases, remediation approaches employ ultra violet (UV) light to try and degrade PAHs and thereby cleanup that site. However, it is possible that PAHs could degrade to OPAHs during the process. If no one is monitoring the products of this UV treatment, the site could remain hazardous. That’s why Norman Forsberg’s upcoming paper and Marc Elie’s work with ultra violet light in the Anderson laboratory (Project 4) is so interesting.
What still needs to be understood?
The formation and concentration of these compounds in the environment at contaminated sites are poorly understood. It is important to continue three areas of research that have been going on at OSU.
Detection: If the compounds are not present, then there’s less to worry about.
Good times with lab mates when Steven O’Connell (right) first started working in the Anderson lab.
Toxicity: Addresses concerns over compounds that are detected in environmental samples.
Processes by which OPAHs are made or degraded.
With that knowledge, it will become easier to understand potential risks with this compound class.
Why is this paper important in advancing the science?
My paper is very analytical. If you watch the television series Bones, I would be most like Hodgins, except there would be less talk of “particulates” and more talk of cleaning instrumentation. But seriously, by providing two methods on very different instrumentation to measure over 20 OPAHs, I provided a helpful platform for other scientists to use and build upon to measure this compound class in a variety of applications.
The recently produced CTUIR – OSU 2012-2013 Newsletter shares the background, summary, and findings of a collaborative research project to understand polycyclic aromatic hydrocarbon (PAH) exposure related to smoked salmon.
Salmon fillet
Salmon, a first food, is important to the subsistence of Native Americans living in the Pacific Northwest. Smoking salmon is one of the traditional ways to preserve this seasonally abundant food and make it available year round.
People can be exposed to PAHs from breathing contaminated air or eating smoked foods although many other exposure pathways exist.
Each volunteer wore air sampling equipment and turned it on every time they went into the smoking structures.
The data showed the air in the tipi and the smoke shed contained PAHs.
Pictured above from left: Traditional tipi, volunteer tending the fire in the tipi wearing an air sampler in black bag on his hip, traditional smoke shed.
Indigenous cultures perceive the natural environment as an essential link between traditional cultural practices, social connectedness, identity, and health. Many tribal communities face substantial health disparities related to exposure to environmental hazards. We asked 27 volunteers who were members of the CTUIR their opinions on meanings of health and how their environment interacts with their health.
The findings from the focus group discussions were published in the journal Environmental Justice.
Robert Tanguay, PhD (Project 3 ) focuses on examining the effects of selected chemicals and chemical classes on zebrafish development and associated gene expression pathways.
The Tanguay research group recently collaborated with Terrence J. Collins, PhD, a champion in the field of green chemistry at Carnegie Mellon University.
Collins and his collaborators showed that specific green chemicals (a group of molecules called TAML activators) used with hydrogen peroxide, can effectively remove steroid hormones from water after just one treatment. Steroid hormones are common endocrine disruptors found in almost 25 percent of streams, rivers, and lakes. Collins needed to understand the safety of TAML activators to move forward on this problem.
Tanguay’s group exposed zebrafish embryos to seven different types of TAML activators. None of the TAML’s impaired embryo development at concentrations typically used for decontaminating water.
The collaboration resulted in a new journal publication in Green Chemistry.
These are important findings that contribute toward TAML activators getting commercialized for water treatment.
Endocrine disruptors and human health
Endocrine disruptors can disrupt normal functions of the endocrine system and impair development, by mimicking or blocking the activities of hormones in wildlife. Several animal studies suggest that endocrine disruptors can also affect human health, and may be involved in cancers, learning disabilities, obesity, and immune and reproductive system disorders.
Robert Tanguay’s leadership in utilizing zebrafish
In 2012, Dr. Tanguay received an EPA grant award, “Toxicity Screening with Zebrafish Assay”. The award is for three years and almost two million dollars in funding to examine the developmental toxicology of at least 1000 chemicals.
Dr. Tanguay and his research team have tested over 3,000 compounds of interest to the National Toxicology Program (NTP), to complement the ongoing high-throughput screening efforts in the U.S. government’s multiagency Tox21 research program.
Citation:Truong L, DeNardo MA, Kundu S, Collins TJ, Tanguay RL. 2013. Zebrafish assays as developmental toxicity indicators in the green design of TAML oxidation catalysts. Green Chem; doi:10.1039/C3GC40376A [Online 15 July 2013].
Learn more about Tanguay’s zebrafish research
