Direct inhibition of bisphenols on human and rat 1113-hydroxysteroid dehydrogenase 2: Structure-activity relationship and docking analysis

Bisphenols (BPs) as endocrine-disrupting compounds have drawn attention to their health hazards. Whether a BP interferes with glucocorticoid metabolism remains unclear. 1113-Hydroxysteroid dehydrogenase 2 (1113-HSD2) is a key glucocorticoid-metabolizing enzyme that controls fetal glucocorticoid levels across the placental barrier and mineralocorticoid receptor specificity in the kidney. In this study, 11 BPs were tested to inhibit human placental and rat renal 1113-HSD2 and were analyzed for inhibitory potency, mode action, and docking parameters. BPs had inhibitory potency against human 1113-HSD2: BPFL>BPAP>BPZ>BPB>BPC>BPAF>BPA>TDP and the IC10 values were 0.21, 0.55, 1.04, 2.04, 2.43, 2.57, 14.43, and 22.18 mu M, respectively. All BPs are mixed inhibitors except BPAP, which is a competitive inhibitor for human 1113-HSD2. Some BPs also inhibited rat renal 1113-HSD2, with BPB (IC50, 27.74 +/- 0.95) > BPZ (42.14 +/- 0.59) > BPAF (54.87 +/- 1.73) > BPA (77.32 +/- 1.20) > other BPs (about 100 mu M). Docking analysis showed that all BPs bound to the steroid-binding site, interacting with the catalytic residue Tyr232 of both enzymes and the most potent human 1113-HSD2 inhibitor BPFL acts possibly due to its large fluorene ring that has hydrophobic interaction with residues Glu172 and Val270 and n-stacking interaction with catalytic residue Tyr232. The increase in the size of substituted alkanes and halogenated groups in the methane moiety of the bridge of BPs increases its inhibitory potency. Regressions of the lowest binding energy with inhibition constant indicated that there was an inverse regression. These results indicated that BPs significantly inhibited human and rat 1113-HSD2 activity and that there were speciesdependent differences.