Deciphering PFAS Potency: Cracking the Code with Gene Expression Profiles of Liver Toxic and Non-Liver-Toxic Reference Compounds

Understanding the mechanisms by which environmental chemicals cause toxicity is necessary for effective human health risk assessment. High-Throughput Transcriptomics (HTTr) can be used to inform risk assessment on toxicological mechanisms, hazards, and potencies. We applied HTTr to elucidate the molecular mechanisms by which Per- and Polyfluoroalkyl Substances (PFAS) cause liver toxicity. We contrasted transcriptomic profiles of four prototype PFAS against transcriptomic profiles from liver-toxic and non-liver-toxic reference compounds, alongside chemicals that activate peroxisome proliferator-activated receptors (PPARs). Our analysis was conducted on metabolically competent 3-D human liver spheroids produced from primary cells of 10 donors. Pathway analysis showed that PFOS and PFDS perturb many of the same pathways as the liver-toxic compounds in the spheroids, and that the cholesterol biosynthesis pathways are significantly affected by exposure to these compounds. PFOA alters lipid metabolism-related pathways but its expression profile does not closely match reference compounds. PFBS upregulates many degradation-related pathways and targets many of the same pathways as the PPAR agonists and acetaminophen. Our transcriptional analysis does not support that these PFAS are DNA damaging in this model. A multidimensional scaling analysis revealed that PFOS, PFOA, and PFDS cluster together in the same 3-D space as liver-damaging compounds; whereas, PFBS clusters more closely with the non-liver-damaging compounds. Benchmark concentration-response modeling predicts that all the PFAS are sufficiently bioactive to be liver-toxic. Overall, our results show that these PFAS produce unique transcriptional changes as well as altering pathways associated with established liver-toxic chemicals in this liver spheroid model. Deciphering PFAS Potency: Cracking the Code with Gene Expression Profiles of Liver Toxic and Non-Liver-Toxic Reference Compounds