Structure-activity relationship of per- and Polyfluoroalkyl substances as inhibitors of human and rat 17β-Hydroxysteroid dehydrogenase 3

Per - and polyfluoroalkyl substances (PFAS) are a group of synthetic chemicals as carboxylic acid (PFCA) and sulfonic acid (PFSA) found in everyday products, from non-stick cookware to waterproof clothing, and are potential endocrine disruptors. However, whether they inhibit 17β-hydroxysteroid dehydrogenase 3 (17β-HSD3) and structure-activity relationship (SAR) and mode of action remains unclear. In this study, we screened 18 PFAS (11 PFCAs and 7 PFSAs) with different carbon-chain lengths from C4 to C14 to inhibit human and rat 17β-HSD3 from HSD17B3 -overexpressed LNCaP cells and rat testicular microsomes. Of the 11 PFCAs, 6 compounds significantly inhibited human 17β-HSD3, with IC 50 values ranging from 5.36 (C10) to 145.15 μM (C8) and a V-shaped turn at C10, and of the 7 PFSAs, only perfluorooctanesulfonic acid markedly inhibited this enzyme (IC 50 , 5.87 μM). Of the 18 PFAS, only 6 PFCAs inhibited rat 17β-HSD3, with IC 50 values ranging from 14.2 (C10) to no inhibition at 100 μM (C8). These PFAS are mixed/noncompetitive inhibitors of human and rat 17β-HSD3 enzymes. Molecular docking studies suggest that the degree of inhibition is linked to the carbon-chain length of the PFAS molecule. 3D-QSAR indicates that structural hydrophobic regions determine the inhibitory potency up to C10 (PFDA). Our in vitro observation of 17β-HSD3 inhibition represents a putative upstream mechanistic factor that may contribute to elevated reproductive dysfunction and hypogonadism risk reported in existing human epidemiological PFAS exposure cohorts. In conclusion, PFAS inhibit human and rat 17β-HSD3 with clear SAR and carbon-chain length determines their inhibitory potency, and C10 PFCA is the most potent inhibitor of human and rat 17β-HSD3.