On Monday, April 21st, the Superfund Research Programs at UC Davis (UCD) and the University of Arizona (UA) collaborated to showcase cell-based tools for environmental assessment in the seminar series titled: “New Research on Toxicity Screening Methods.” Dr. Scott Boitano (UA) described how he conducts Real Time Cell Analysis (RTCA) using the XCELLigence system, while Dr. Michael Denison explained his technology called the Chemically-Activated Luciferase Expression (CALUX) Bioassay. Both technologies are radically new means in which scientists can measure human cell responses after exposure to varying levels of environmental toxins.

The "Live at EPA Region 9" lecture series provides a platform for NIEHS Superfund Research Program (SRP) researchers to share their research findings with scientists in the Pacific Southwest (EPA Region IX). The lecture is presented at Region 9 headquarters in San Francisco to EPA staff and invited attendees, and is coordinated by Michael Gill, Superfund and Technology Liaison, in collaboration with UA and UCD Research Translation Core Leaders. Approximately one month after the live seminar at Region 9, the researchers will publically broadcast another live presentation via webinar through the EPA CLU-IN website (date: TBD; check the CLU-IN website for the most recent information). 

In the interest of science: What can cells-based technologies do for environmental regulators?

For Dr. Scott Boitano, cell-based technologies help him examine dangers found in air pollution. At the cellular level, there already exist methods to detect cytotoxicity (cell death caused by toxins). Dr. Boitano uses RTCA, which provides a way to measure non-lethal changes in the cell when exposed to toxins. The ability to observe these phenomena is highly relevant for studies examining chronic, long-term environmental exposure of the air we breathe, as the levels of contaminants humans are exposed to on a daily basis may not cause immediate cell death but may affect other biological functions.

Dr. Boitano’s research focuses on the toxicity of inhaled engineered nanoparticles, metals, and metalloids on the epithelial lining of the respiratory tract and uses a human, immortal epithelial cell line in his RTCA assays. RTCA allows for taking time points in intervals as short as 30 seconds and for running the assay for as long as needed, three weeks in Dr. Boitano’s experiments. RTCA is a valuable tool for evaluating the toxicity of chronic, low-level toxin exposure from air pollution because it can detect cell signaling abnormalities that contribute to the negative health outcomes observed in humans.

Dr. Michael Denison, on the other hand, uses cell-based technologies to tell him if a common consumer product or an environmental sample contains toxins that interfere with natural biological functions, such as hormone regulation. His CALUX bioassays are designed to detect gene expression induced by chemicals that mimic endogenous ligands for specific receptors. By inserting the gene that produces the fluorescent compound in fireflies, luciferase, next to the genes that respond to these ligands, researchers can quantify the potency of a sample based on the fluorescence level expressed in the cell. Dr. Denison’s research has shown that CALUX bioassays can predict toxicity in animal studies more accurately than strictly analytical means because the results are based on whether the pathway is activated, not solely on the presence or absence of a particular chemical.

CALUX bioassays are more useful for analyzing unknown chemicals from the environment, which usually contain mixtures of chemicals. Using CALUX, Dr. Denison’s lab evaluated a range of everyday products for estrogenic activity. They found that all but one sunscreen brand of those sampled had estrogenic activity, and that children’s plastic cups and plates showed estrogenic activity. A particularly concerning finding showed that some of the plastics leached potent estrogenics into pure water without any heating or chemical treatment, with color-changing sippy cups as the worst offenders. Dr. Denison advocates for using the CALUX bioassay as a fast and inexpensive tool for screening new chemicals for their biological potency. It is estimated that new chemicals are introduced into commerce at a rate of 7 chemicals/day*!

*CA Dept of Toxic Substances Control