Endocrine Disrupting Effects And Mechanisms Of Chlorinated Polyfluorinated Ether Sulfonate On Rare Minnows

Chlorinated polyfluorinated ether sulfonate（Cl-PFESA）,with commercial name F-53B,a typical alternative to perfluorooctane sulfonate（PFOS）,is used as a chrome mist suppressant,with extremely limited knowledge on its environmental and health risks.In the present study,rare minnow,a Chinese native species,was selected as the text model.Juvenile fishes were exposed to Cl-PFESA for 4 weeks followed by a 12 weeks of depuration.The toxicokinetics of Cl-PFESA in the fishes,as well as the disrupting effects on thyroid hormone and sex hormone and the mechanisms induced by the chronic developmental exposure of Cl-PFESA in rare minnow juveniles.The main contents and results are as follows,（1）The toxicokinetic characteristics of Cl-PFESA in rare minnows were analyzed.High performance liquid chromatography-tandem mass spectrometry was used to measure Cl-PFESA in the fishes.After 4 weeks of Cl-PFESA exposure,the bioconcentration factors of C8 Cl-PFESA and C10 Cl-PFESA were 2.49 and 3.53,respectively.During the followed 12weeks of depuration,the clearance rate constants were 0.025 d^-11 and 0.015 d^-1,respectively,for C8 Cl-PFESA and C10 Cl-PFESA.The half-life of C8 Cl-PFESA and C10 Cl-PFESA were 28.9 days and 43.1 days,respectively.C10 Cl-PFESA was more easily to be enriched in the fishes than C8 Cl-PFESA.（2）The thyroid hormones disrupting effect of Cl-PFESA on in rare minnow and the mechanisms were studied.Enzyme-linked immunosorbent assay was used to analyzed thyroid hormones contents,and Real-time quantitative PCR was used to analyze the expression of key genes regulating thyroid hormones.After 4 weeks of exposure to Cl-PFESA at 86.5μg/L and 162μg/L,the levels of thyroid hormones T3 and fT3 increased significantly.Meanwhile,mRNA expression of genes regulating thyroid hormone synthesis（CRH,THSβ,NIS,TG,and TPO）,transport（TTR）,deiodinase（Dio1,Dio2）and receptor（TRαand TRβ）were decreased.UGT1A gene,regulating THs metabolism,was also decreased.After the followed 12 weeks of depuration,thyroid hormones contents of T4 and fT3 increased in the adult fishes.The expression of genes involved in hypothalamic-pituitary-thyroid（HPT）axis remained at disturbed levels.Different with PFOS,Cl-PFESA may cause hyperthyroidism-like effects by repressing expression of genes regulating the metabolism and transport of thyroid hormones.（3）The sex hormones disrupting effects of Cl-PFESA on rare minnow were evaluated.The body weight and length of rare minnow juvenile were stimulated by 4 weeks of exposure to Cl-PFESA.Several key gene regulating sex hormones,including GnRH3,LHβ,were down-regulated.Aromatase P450 gene（CYP19a）,regulating estrogen rate-limiting enzyme,was also repressed.Gene expression levels of estrogen receptor（ERα）and androgen receptor（AR）were significantly up-regulated.After the followed 12 weeks of depuration,the gonad index of female fish ovaries was reduced.The expression levels of the genes involved in hypothalamic-pituitary-gonad axis in both female and male fishes were up-regulated.Moreover,VTG genes in both the livers and gonads of male fishes were up-regulated,which suggested that Cl-PFESA caused potential estrogen effects to rare minnows.Results of the present study suggested that Cl-PFESA exhibited a relatively strong bioaccumulation potency in rare minnows.Chronic developmental exposure to Cl-PFESA in juvenile fish resulted in long-term effects on the regulation of thyroid hormones and sex hormones.Cl-PFESA may affect thyroid hormones in fishes via different modes of action compared with PFOS,with similar disrupting effects on sex hormones regulating with PFOS.It is suggested that a comprehensive ecological risk assessment and appropriate regulation was urgently needed for Cl-PFESA.