Research On The Estrogen/Thyroid Hormone Receptor Mediated Effects Of Typical Environmental Endocrine Disruptors

In recent years, endocrine disruptor is one of the most polular topics studied in the field of environment research. At present, our country has not established an effective list of endocrine disruptors, and also lacked the platform for high-throughput screening the endocrine disrupting effects of compounds. The present study constructed a estrogen receptor α(ERα)/ thyroid hormone receptor β(TRβ)mediated dual-luciferase reporter gene system using the host CHO-K1 cells, combined with the other two methods — — T-screen assay and molecular docking, to qualitatively and quantitatively evaluate the endocrine disrupting effects of fipronil and its metabolites, 20 polychlorinated biphenyls(PCBs) and 9 organophosphorous flame retardants(OPFRs). The main work and achievements of the current research were shown as followed:(1) Results from the detection of endocrine disrupting effects demonstrated that fipronil sulfone exhibited both the ERα and TRβ antagonistic activity, but fipronil only had the antiestrogenic effect. Therefore, fipronil metabolite —— sulfone showed more significant endocrine disrupting effect than its parent compound. In addition, study of molecular docking found that fipronil sulfone may possess a greater thyroid hormone disrupting potential as a consequence of its higher affinity to bind to TRβ,which also effectively supported the results of report gene assay.(2) Of 20 PCBs tested, PCB44, PCB52, PCB101, PCB110 and PCB180 exhibited thyroid hormone activity, while PCB99, PCB118, PCB128, PCB138, PCB163, PCB180, PCB187, PCB194 and PCB199 showed anti-thyroid hormone activity. In particular, PCB 180 behaved both agonist and antagonist via TRβ. Furthermore, the underlying reason on the difference in the activities of PCBs was explored by molecular docking. From the analysis of structure-activity relationship, chlorine numbers and subtitution positions may affect on the interaction between PCBs and TRβ.(3) In TRβ mediated reporter gene assay, only TBP, TCP, TDCPP and TCPP induced anti-thyroid hormone activity, and the order of relative potencies according to RIC20 was TCP> TBP> TCPP> TDCPP. Moreover, T-screen assay was employed to further investigate the antagonistic activity of these 4 OPFRs. Results from molecular docking indicated that the different binding modes between TRβ and OPFRs partly resulted in the different activites of OPFRs. Furthermore, OPFRs with the structure containing benzene ring, halogen and short chain may be easier to show the antagonistic effect through TRβ.