C2 (TFA) – C10 PFAS: An in vitro comparison of toxicological mode of action

Varying carbon chain length and functional head-group of PFAS can affect their physicochemical properties, resulting in different toxicological properties.  A paper by Sodani et al. [1] investigated C₂ (TFA) to C₁₀ PFAS using in vitro assays. The paper demonstrated that the carbon chain length of PFAS can determine their in vitro toxicity and that ultrashort-chain PFAS (TFA) was found to be less toxic when compared to long-chain PFAS.

ToxProfiler, a human in vitro assay was used by Sodani et al. to visualize and quantify activation of the major cellular stress pathways for 8 PFAS from C₂ (TFA) to C₁₀ (PFDA). ToxProfiler [2] is a quantitative in vitro reporter assay that can accurately provide insight into the toxicological MoA (mode of action) of compounds, thereby assisting in the future mechanism-based safety assessment of chemicals. Cellular injury is usually considered a trigger of a toxic effect manifestation. Such cell injury initiates cell stress response signaling pathways, of which strong activation reflects the onset of toxicity. The ToxProfiler platform consists of a panel of seven reporter cell lines, in which specific biomarkers of these cell stress response pathways have been tagged with a fluorophore (GFP- green fluorescent protein). The data reported by Sodani et al. showed a clear correlation between ToxProfiler stress pathway activation potency and carbon length of PFAS, which is also corroborated by increased in vitro toxicity. They reported that C₄ to C₁₀ PFAS induced one or more cellular stress signal pathways at various levels, with autophagy (natural process within cells to remove damaged cell components) and endoplasmic reticulum (ER- a membrane system within certain cells) stress signals being common pathways being induced by them, but in contrast, ultrashort-chain PFAS (C₂-C₃: TFA and PFPrA, CF₃CF₂COOH) did not significantly induce any stress pathway.

To assess and compare developmental toxicity potential of TFA against PFOA, Sodai et al. used ReproTracker, a novel human stem cell based biomarker assay. ReproTracker [3] is a human induced pluripotent stem cells (hiPSCs)-based biomarker assay that is shown to identify the teratogenicity potential of new pharmaceuticals and chemicals reliably. Sodani et al. reported that ReproTracker data could confirm developmental toxicity effects of PFOA (C₈), while TFA (C₂) was found to be non-teratogenic in the assay. However, the authors added that, in vivo data on TFA indicates species-specific developmental malformation of retinal folding in foetuses of NZW Rabbits with NOAEL of 60mg/kg/day [4], and the authors discussed this and related findings.

References

[1] Sodani, K., ter Braak, B., Hartvelt, S., Boelens, M., Jamalpoor, A., and Mukhi, S. Toxicological mode-of-action and developmental toxicity of different carbon chain length PFAS, Toxicology Letters Volume 405, March 2025, Pages 59-66, https://doi.org/10.1016/j.toxlet.2025.02.003

[2] ter Braak, B., Loonstra-Wolters, L., Elbertse, K., Osterlund, T., Hendriks, G., Jamalpoor, A., 2024. ToxProfiler: a novel human-based reporter assay for in vitro chemical safety assessment. Toxicology 509. https://doi.org/10.1016/j. tox.2024.153970.

[3] Moreau, M., Jamalpoo, A., Hall, J.C., Fisher, J., Hartvelt, S., Hendriks, G., Nong, A., 2023. Animal-free assessment of developmental toxicity: combining PBPK modeling with the ReproTracker assay. Toxicology 500, 153684. https://doi.org/10.1016/j.tox.2023.153684

[4] European Chemical Agency, ECHA. 2023. Registration dossier for trifluoroacetic acid EC number: 200-929-3; CAS number: 76-05-1. https://echa.europa.eu/de/registration-dossier/-/registered-dossier/5203/7/1