Investigating The Endocrine Disrupting Effect Of HO-/MeO-PBDEs Based On MD Simulation And Target Prediction

As flame retardants, polybrominated diphenyl ethers (PBDEs) are a class of chemicals widely used in many manufactured items. PBDEs have received substantial attention due to their widely distribution and potential toxicity. Recently, more and more environmental scientists and toxicologists began to research their analogues Hydroxylated/Methoxylated-PBDEs (HO/MeO-PBDEs). Some studies involved their endocrine disrupting effects, such as estrogenic activity, anti-androgenic activity, thyroid hormone activity and aryl hydrocarbon receptor (AHR) activity, have been performed. However, the details of the interactions between these chemicals and related receptors have not been fully explored. What’s more, it was almost impossible to test the activities of hundreds kinds of HO/MeO-PBDEs. Therefore, it was very important to understand the interactions and develop models and simulation methods to predict activities based on the mechanism. HO/MeO-PBDEs and other chemicals could disrupt endocrine system via many other mechanisms. Omics was a good choice to identify the mechanism, but it was very expensive. Here we developed a tool to predict the potential targets of chemicals and performed the prediction on HO-/MeO-PBDEs.A brief description, the environmental occurrence and endocrine disrupting effects of HO/MeO-PBDEs was given. Meanwhile, some researches about their endocrine disrupting effects based on computational methods were introduced. Two main methods used in this thesis, signaling pathway and molecular structure about studied receptors were also described in this chapter.MDA-kb2cell-based assay and MD simulation were combinbed to study the anti-androgenic activity of16HO-/MeO-PBDEs. Helixl2(H12) of androgen receptor ligand binding domain (AR-LBD) was identified as a marker for screening active chemicals. H12s in active ligands occupied LBD would locate in an area stably, while the H12s in other complexes would keep fluctating. The rate involved stabilizing of H12was characteristic of anti-androgenic potencies of the tested chemicals. Then interactions between HO-PBDEs and thyroid hormone receptor β (TRβ) were studied based on MD simulation and the effect of nuclear receptor co-repressor (NCOR) on the interactions was also observed. No features were identified TRβ active chemicals when we only simulate the systems of ligands and receptors. However, after adding NCOR into our simulation, H12s in active ligands occupied TRP-LBD locate in an area stably, while the H12s in other complexes will keep fluctuating. The avtivating process of TRβ and AR were different, we should analysis them based on different strategies. In other words, to make simulation more reliable, proper protocols should be performed on different simulated systems.The effect of17HO-/MeO-PBDEs on AHR1of Chicken and Japanese quail has been studied in our previous research. Seven of17tested chemicals can activate AHR1of Chicken, while14of tested chemicals can activate AHR1of Japanese quail. Cell-based assay, sequence alignment, molecular docking and MD simulation were combined to explain the activity and the sensitivity difference of species. The movement of H4in LBD was the decisive factor for avtivating AHR1. What’s more, the sensitivity difference of species could be owed to the difference of324th amino acid of two receptors. The difference between Isoleucine and Valine induced the difference of H4s’ fluctuation in two AHR1s. H4following Val324can fluctuate more easily, therefore, AHR1of Japanese quail could be activated more easily. However, the used structures of AHRls were constructed by homology modeling, thus the obtained results should be used more carefully.Finally,94endocrine disrupting-related proteins were selected to develop a prediction tool named System for Predicting Endocrine disrupting-related Targets (SPET).After a series of validation of this system, the potential endocrine disrupting-related proteins of BDE-47,6-HO-BDE-47and6-MeO-BDE-47were predicted. There were high binding affinity between all of these chemicals and3proteins of activin receptor2A, adrenergic receptor and oxidosqualene-lanosterol cyclase based on our prediction. Similar endocrine disruption potential were detected between6-HO-BDE-47and6-MeO-BDE-47according to analysis their TOP20proteins. The obtained results were important for investigating and evaluating the endocrine disrupting effect of HO-/MeO-PBDEs based on experiments.Many innovative computational methods were provided to comprehensively evaluate the endocrine disrupting effect and safet of chemicals in this thesis. Considering about current problems in evaluation of chemical safety, this research will promote the use of molecular simulation in environmental toxicology and ecotoxicology.