Azole fungicides: Potential endocrine disrupting effects and impact on placental steroidogenesis via inhibiting human and rat 3β-hydroxysteroid dehydrogenase.

Azole fungicides disrupt pregnancy, but their effects on placental 3β-hydroxysteroid dehydrogenases (3β-HSDs) and structure-activity relationships (SARs) remain unclear. This study evaluated 9 azole fungicides for their inhibitory potency, mechanism, SAR, and docking interactions with human 3β-HSD1 and rat 3β-HSD4. Bromuconazole, climbazole, cyproconazole, and etaconazole inhibited human 3β-HSD1 (IC50 = 6.21 μM to 104.83 μM), with climbazole being the most potent. These compounds acted as mixed/noncompetitive inhibitors and climbazole suppressed progesterone secretion in human JAr cells at ≥ 2.5 μM. They also inhibited rat 3β-HSD4, albeit with lower potency. Molecular docking revealed that these fungicides bind to the NAD+/steroid-binding site via hydrogen bonds, hydrophobic interactions, and van der Waals forces. A negative correlation between LogP and IC50 indicated that lipophilicity enhances inhibitory efficacy. 3D-QSAR analysis further confirmed the critical role of hydrogen bonding in binding affinity. In conclusion, climbazole exhibits the strongest inhibition of human 3β-HSD1, driven by its high lipophilicity. These findings highlight the endocrine-disrupting potential of azole fungicides and provide insights into their SAR and inhibition mechanisms, aiding risk assessment and regulatory decisions.