Enantioselective Toxicities Of Chiral PCBs In Zebrafish Embryos By Metabolomics

Polychlorinated biphenyls(PCBs) are persistent environmental pollutants, which are prohibited in the global scope in 1970 s. At present, a lot of PCBs still exists in the environment, because it’s difficult to biodegrade, easy to accumulate and migrates long distance. There are many reports about PCBs toxicity research in zebrafish. The biological and toxicological characteristics of enantiomers of chiral PCBs may differ, but these enantioselective effects of PCBs have not been fully characterized. This is the first report about enantioselective effects of PCBs in zebrafish embryos by metabolomics.In this study, 19 stable chiral polychlorinated biphenyls(PCBs) were enantioselectively separated on five different chiral columns packed with polysaccharides derivatives, using normal-phase high-performance liquid chromatography. Satisfactory separations were obtained on Lux Cellulose-1, Cellulose-3 and Cellulose-4, while Cellulose-2 and Amylose-2 showed very poor enantioselective discriminability for these chiral PCBs. Except for PCB197, the other PCBs were baseline or partially separated. In the range of 5-30, the separations of chiral PCBs were driven by enthalpy, meaning that low temperature was advantageous to separation. In addition, the enantioseparation and elution orders were associated with the number and position of chlorine substituted in the benzene ring of chiral PCBs.Then, we performed target analysis using UPLC-Qtrap to investigate the enantioselective toxic effects of PCB95 in zebrafish(Danio rerio) embryos. A total of 26 metabolites were selected as potential marker metabolites, including amino acids, organic acids, nucleosides, betaine and choline. The biomarker metabolites exhibited different dose-response relationships with increasing doses. The changes in these biomarkers were dependent on the enantiomer-specific structures of PCB95. The effects of many nervous and immune system-related metabolites were confirmed to be significantly altered by exposure to PCB95. These metabolic changes indicated that the toxic effects of PCB95 may be related to its interactions with the nervous and immune systems, disorders of energy metabolism, and disruption of liver function.We performed metabolic profiling using UPLC-Qtof to investigate the enantioselective toxic effects of PCB95 and 136 in zebrafish embryos. A total of 460 metabolites were selected as potential marker metabolites, while 22 marker metabolites were identified, including amino acids, organic acids, phospholipid and compounds related to sugar metabolism. PCBs95 and 136 have significant toxicity on zebrafish embryos, and the influence of PCB136 is larger than that of PCB95.(+)-,(-)- and rac-PCB136 have similar toxic effects on zebrafish embryos,(-)- and rac-PCB95 also have similar toxic effects.In conclution, this study proves that the LC/MS-MS metabolomics technology can be effectively used for the analysis of enantioselective effects of PCBs and biological markers screening. This study provides a new method for enantioselective toxicity reaserch of environmental pollutants from the perspective of metabolomics.