Hormone Activity of Hydroxylated Polybrominated Diphenyl Ethers on Human Thyroid Receptor-β: In Vitro and In Silico Investigations

BACKGROUND: Hydroxylated polybrominated diphenyl ethers (HO-PBDEs) may disrupt thyroid hormone status because of their structural similarity to thyroid hormone. However, the molecular mechanisms of interactions with thyroid hormone receptors (TRs) are not fully understood. OBJECTIVES: We investigated the interactions between HO-PBDEs and TRβ to identify critical structural features and physicochemical properties of HO-PBDEs related to their hormone activity, and to develop quantitative structure–activity relationship (QSAR) models for the thyroid hormone activity of HO-PBDEs. METHODS: We used the recombinant two-hybrid yeast assay to determine the hormone activities to TRβ and molecular docking to model the ligand–receptor interaction in the binding site. Based on the mechanism of action, molecular structural descriptors were computed, selected, and employed to characterize the interactions, and finally a QSAR model was constructed. The applicability domain (AD) of the model was assessed by Williams plot. RESULTS: The 18 HO-PBDEs tested exhibited significantly higher thyroid hormone activities than did PBDEs (p < 0.05). Hydrogen bonding was the characteristic interaction between HO-PBDE molecules and TRβ, and aromaticity had a negative effect on the thyroid hormone activity of HO-PBDEs. The developed QSAR model had good robustness, predictive ability, and mechanism interpretability. CONCLUSIONS: Hydrogen bonding and electrostatic interactions between HO-PBDEs and TRβ are important factors governing thyroid hormone activities. The HO-PBDEs with higher ability to accept electrons tend to have weak hydrogen bonding with TRβ and lower thyroid hormone activities.