Chlorinated bis-phenolic disinfectants inhibit human and rat aromatase.

Chlorinated bis-phenolic disinfectants (CBPDs) are widely used compounds. However, whether they disrupt the endocrine system by inhibiting human and rat aromatase (CYP19A1) remains unclear. The objective of this study was to investigate the effects of CBPDs on human and rat CYP19A1 activity in placental microsomes. CBPDs showed structure-dependent inhibition of CYP19A1, with the human enzyme exhibiting 1.3-1.8-fold higher sensitivity than the rat ortholog. Since lower IC50 values correspond to stronger inhibitory potency, the compounds were ranked as follows: hexachlorophene (5.47 μM) > bithionol (7.60 μM) > bromochlorophene (9.57 μM) > fenticlor (14.44 μM) > dichlorophene (20.05 μM) > clorophene (22.53 μM). Enzyme kinetics and Lineweaver-Burk plot analyses indicated that they exhibited mixed/competitive inhibition, suggesting that CBPDs primarily bind free enzymes. In human BeWo cells, noncytotoxic CBPD concentrations reduced estradiol secretion, supporting endocrine-disrupting potential. Structure-activity relationship analyses revealed that hydrophobicity (LogP) and halogen atom number critically influence inhibition potency. Molecular docking confirmed CBPD binding at the steroid-heme interface, interacting with catalytic residue Met374. Network toxicology analysis linked CBPDs to estrogen signaling disruption in hypertensive disorders of pregnancy. These findings emphasize the structure-activity dependency of CBPD-mediated CYP19A1 inhibition and its implications for endocrine risk assessment.