University of Maine Student Funded by SOT Investigates Antimicrobial Toxicity during Summer 2022

By Julie Gosse posted 10-06-2022 15:34

Patrick Fleming standing near a desk and computer.
Patrick Fleming continues the work
begun on an SOT grant.

I am an Associate Professor in the Department of Molecular and Biomedical Sciences at the University of Maine (UMaine). UMaine is not only a PhD-granting research university but also an R15-eligible institution, which means there is a heavy emphasis on mentoring undergraduates in research.

During summer 2022, undergraduate Patrick Fleming was generously supported by an SOT Undergraduate Faculty Research Grant administered by the Faculty United for Toxicology Undergraduate Research and Education (FUTURE) Committee that provided wages for him while he investigated the eukaryotic toxicology of cetylpyridinium chloride (CPC). CPC is a cationic quaternary ammonium antimicrobial used widely in personal care and food products such as treated poultry. The widespread use of antibacterial agent CPC is accompanied by a striking lack of research assessing its eukaryotic toxicology.

Mast cells are important immune system players and are enriched at environmental interfaces, making them toxicant targets. Earlier, we found that low-µM, non-cytotoxic doses of CPC inhibit mast cell function degranulation, which is the release of bioactive substances such as histamine. We are investigating the molecular mechanisms underlying CPC inhibition of mast cells.

This summer, Patrick tested the hypothesis that CPC disrupts mast cells by electrostatically interfering with key players in degranulation, specifically tyrosine phosphorylation and phosphatidylinositol 4,5-bisphosphate (PIP2), a plasma membrane phospholipid key for mast cell and other immune function. He assessed the effects of CPC on tyrosine phosphorylation of enzymes involved in mast cell degranulation (via ELISA) as well as cation effects on direct PIP2-protein interactions. Overall, his results contributed to pinpointing the mechanism underlying CPC disruption of immune cell function to provide insights into CPC effects on human health.

In addition, our previously published work indicates CPC disruption of PIP2. One specific interaction partner of PIP2 is the influenza protein hemagglutinin. Patrick used molecular modeling to begin the process of simulating effects of CPC and other cations, including calcium ion (Ca2+), on PIP2-protein interactions. Molecular dynamic simulation GROMACS software was employed to test the effects of differing Ca2+ concentrations on PIP2 clustering and interaction with viral influenza protein hemagglutinin.

Patrick is currently enrolled in honors thesis research for this academic year, and we were awarded a National Institutes of Health (NIH) R15 grant that supports his thesis research. He is a co-author on a research article currently being written for submission for peer review and will be a co-author on a future article as well. An abstract describing research co-authored by Patrick has been submitted for the SOT Northeast Regional Chapter (NESOT) 2022 Annual Meeting and will be submitted for the 2023 SOT Annual Meeting and ToxExpo. We are grateful for this SOT funding that facilitated Patrick’s education and our NIH-funded research.

Editor’s note: the next deadline for SOT Undergraduate Faculty Research Grant applications is April 8, 2023.