Abstract Body: BACKGROUND: Per- and polyfluoroalkyl substances (PFAS), nicknamed “forever chemicals,” are persistent environmental contaminants. Human studies link PFAS exposure with subclinical atherosclerosis and inflammation. Evidence also shows impaired vaccine responses, suggesting that PFAS may disrupt trained immunity, a process driven by epigenetic and metabolic reprogramming. Independently, inflammatory priming, a similar reprogramming of monocytes toward a hyperreactive state, is known to hasten atherosclerotic progression. However, the mechanisms by which PFAS may change monocyte function to drive atherosclerosis remain unclear. We hypothesize that PFAS exposure causes inflammatory priming and monocyte dysfunction.
METHODS: To test our hypothesis, we exposed CD14+ monocytes from 6 healthy humans ex vivo to vehicle or physiologically relevant amounts of perfluorooctanoic acid (PFOA), followed by vehicle or lipopolysaccharide (LPS) to test inflammatory priming and secondary hyperreactivity. We measured cytokines by cytometric bead assay and assessed epigenomic and transcriptomic changes with paired ATAC- and RNA-sequencing. We used live-cell imaging of transendothelial migration and lipid and particle uptake to test functional effects of exposure to PFOA and LPS in monocytes.
RESULTS: PFOA exposure enhanced pro-inflammatory cytokine (IL-1β, IL-6, TNFα, IL-18) response to LPS challenge in primary human monocytes. RNAseq identified 494 differentially expressed genes after PFOA alone versus vehicle, enriching pathways related to aerobic glycolysis activation and inhibition of endocytosis. Priming with PFOA versus vehicle altered LPS-induced expression changes for 382 genes associated with dysregulated oxidative phosphorylation and mitochondrial dysfunction, phagosome formation, leukocyte adhesion and inflammatory signaling. ATACseq showed differential chromatin accessibility at loci related to atherosclerosis. Integrating ATAC- and RNAseq revealed a set of 283 genes whose LPS responsiveness was driven by PFOA. Functionally, PFOA alone and upon LPS challenge increased NF-kB activity and lipid uptake while impairing particle phagocytosis and transendothelial migration, without inducing cytotoxicity.
CONCLUSIONS: PFOA exposure changes epigenomic, transcriptomic, and functional responses to inflammatory stimulus in human monocytes. PFOA-primed monocytes show heightened inflammatory responses and dysfunction that may link PFAS exposure and atherosclerotic disease.