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A Transcriptomic View of 6PPD & 6PPD-Q in Pimephales promelas
Citation:
Bush, K., M. Hazemi, J. Hoang, M. Le, B. Blackwell, K. Flynn, E. Stacy, AND Dan Villeneuve. A Transcriptomic View of 6PPD & 6PPD-Q in Pimephales promelas. Society of Environmental Toxicology and Chemistry (SETAC) North America 43rd Annual Meeting, Pittsburgh, PA, November 13 - 17, 2022. https://doi.org/10.23645/epacomptox.21395106
Impact/Purpose:
Poster presented to the Society of Environmental Toxicology and Chemistry (SETAC) North America 43rd Annual Meeting November 2022. The chemicals N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) and its transformation product chemical N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone (6PPD-quinone) are found in tire wear particles and can leach into watersheds, especially those adjacent to urban roadways. In the Pacific Northwest of the United States, sudden mortality of coho salmon after exposure to runoff has been linked to 6PPD-quinone toxicity. The toxicity appears to be largely species specific and the mode of action is an area of active research. The present study utilizes a high throughput assay with fathead minnow (Pimephales promelas) to characterize 6PPD and 6PPD-quinone acute toxicity and explore the genes that may be impacted to help elucidate toxic mode of action.
Description:
In the last few years, the world of aquatic toxicology has set its eyes on the chemicals N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) and its transformation product chemical N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone (6PPD-quinone) present in urban runoff for their impact on the coho salmon (Oncorhynchus kisutch) population. While the identification of these chemicals was a necessary breakthrough, a conclusive mode of action for their toxicity has yet to be elucidated. This study utilized a cost and time-efficient assay to explore the apical and transcriptomic impacts of both 6PPD and 6PPD-quinone on the standard freshwater test species, fathead minnow (Pimephales promelas). Five-day post-hatch larval fish were exposed to each of eight concentrations (½ log spacing) per chemical in 1 mL, 96 well plates for 24 hours at 25°C under a 16:8 hour, light on: light off regimen. Post-exposure survival was enumerated to calculate an LC50 value. Next, a transcriptomic library was produced and sequenced from total RNA extracted from individual fish. The resulting transcript abundance data were analyzed using BMDExpress3 and a custom analysis pipeline in R to obtain transcriptomic points of departure (tPODs) and a list of differentially expressed genes (DEGs). Both our apical and transcriptomic results suggest that fathead minnow are more sensitive to 6PPD than 6PPD-quinone. However, no mode of action was suggested by the list of DEGs. It is unclear at this time whether this suggests a non-specific mode of action or simply a lack of sensitivity of larval fathead minnows to 6PPD and 6PPD-quinone. The contents of this abstract neither constitute, nor necessarily reflect, official US EPA policy.
URLs/Downloads:
DOI: A Transcriptomic View of 6PPD & 6PPD-Q in Pimephales promelas
BUSH SETAC POSTER V5.PDF (PDF, NA pp, 1006.394 KB, about PDF)