Species Sensitivities Of Dioxin And Dioxin-like Compounds And Biological Screeningin Environmental Medium By The Luciferase Reporter Gene Assay

Dioxins and DLCs(Dioxin-like compounds,DLCs)are normally considered as a class of highly toxic compounds and their toxicological mechanisms have been extensively studied in the past decades.It is well accepted that all highly toxic dioxins and DLCs exert their toxic and biological interference effects through the binding and activation of Aryl hydrocarbon receptor(AhR).Recently increasing evidences showed that many emerging environmental pollutants had similar structure with dioxins and could potentially induce high toxicity.However,the common chemical method cannot be applied widely because of complicated operation and expensive cost.Biological method,especially the luciferase reporter gene assay(LRG),overcomes the limitation of chemical method and has been widely used.Currently,experiment technology of the H4IIE-luc luciferase reporter gene assay is very mature and has been used as a high throughput screening method of dioxin activity.But for ecological risk assessment of environmental dioxins to wildlife,especially birds,a bioassay based avian AhR should be exploited.Birds can be divided into three types according to sensitivity differences of dioxin compounds to different birds.So someone exploited an AhR-LRG assay based the three avian AhR.The objective of our present studies is to research the toxicity and sensitivity differences of dioxins and dioxins mixtures and to evaluate the application of the LRG assay(H4IIE-luc and avian AhR)in detecting dioxin activity in environmental medium.The main research results were as follows.1)The comparison of dixoins sensitivity differences among birds and rat by the LRG assay.The rank order of avian species sensitivities to dioxins was rat>chicken>ring-necked pheasant>Japanese quail.Effects of binary mixtures of TCDD,2,3,7,8-tetrachlorodibenzofuran(2,3,7,8-TCDF)and 2,3,4,7,8-pentachlorodibenzofuran(2,3,4,7,8-PeCDF)were strictly additive.Overall,the ReP and the species sensitivities of these chemicals could guide risk assessments to wild species when mixtures of dioxins and DLCs were exposured to in the environment.2)Screening of dioxin activity in environmental medium by LRG assay(H4?E-luc).Dioxin activity tests showed in sediment samples of the Tai Lake basin:the persistent AhR agonists were not dominant contributors to the overall AhR-mediated activity.PAHs,at most,only explained 40%the mixture effect in this labile AhR ligands fraction,warranting future investigations to take more attention to PAHs and identify the unresolved AhR ligands in the Tai Lake basin.For Nanjing chemical park samples(soil and sediment),the dioxin activity of most samples is low,showing low ecological risk.For Ningbo e-waste dismantling area(soil and sediment),all samples showed high dioxin activity.Biological toxic equivalents(TEQbio)of 4 sediment samples and 8 soil samples is respectively 13.8-149.4(ng TCDD/kg,dw)and 45.2-37611(ng TCDD/kg,dw).More attention should be taken on the e-waste disposal.3)Application of avian AhR-LRG assay in environmental samples.We evaluated the activity of dioxins of the typical fly ash samples by the avian AhR-LRG assay.Results indicated the dioxin activity of fly ash organic extracts could be detected by the avian AhR-LRG assay.Among the three avian AhR,TEQbio of fly ash organic extracts inducing the chicken AhR,reached 58.30-798.78 ng TCDD/g,dw.HRGC-HRMS analysis showed that TEQchem of the typical dioxin substances only contributed a small portion to the overall TEQbio value with the AhR-LRG assay.The result showed the avian AhR-LRG bioassay provided an useful bio-monitoring tools for dioxins activity in environmental medium for the protection of avian species.