title: Glucocorticoid activity detected by in vivo zebrafish assay and in vitro glucocorticoid receptor bioassay at environmental relevant concentrations.
abstract: Glucocorticoids are pharmaceutical contaminants of emerging concern due to their incomplete removal during wastewater treatment, increased presence in aquatic environment and their biological potency. The zebrafish is a popular model for aquatic toxicology and environmental risk assessment. This study aimed to determine if glucocorticoids at environmental concentrations would perturb expression of selected glucocorticoid-responsive genes in zebrafish and to investigate their potentials as an in vivo zebrafish assay in complementing in vitro glucocorticoid receptor bioassay. The relative expression of eleven glucocorticoid-responsive genes in zebrafish larvae and liver of adult male zebrafish exposed to three representative glucocorticoids (dexamethasone, prednisolone and triamcinolone) was determined. The expression of pepck, baiap2 and pxr was up-regulated in zebrafish larvae and the expression of baiap2, pxr and mmp-2 was up-regulated in adult zebrafish exposed to glucocorticoids at concentrations equivalent to total glucocorticoids reported in environmental samples. The responsiveness of the specific genes were sufficiently robust in zebrafish larvae exposed to a complex environmental sample detected with in vitro glucocorticoid activity equivalent to 478 pM dexamethasone (DEX-EQ) and confirmed to contain low concentration (0.2 ng/L or less) of the targeted glucocorticoids, and possibly other glucocorticoid-active compounds. The findings provided in vivo relevance to the in vitro glucocorticoid activity and suggested that the environmental sample can perturb glucocorticoid-responsive genes in its original, or half the diluted, concentration as may be found in the environment. The study demonstrated the important complementary roles of in vivo zebrafish and in vitro bioassays coupled with analytical chemistry in monitoring environmental glucocorticoid contaminants.
authors.affiliation: NUS Environmental Research Institute, National University of Singapore, 5A Engineering Drive 1, 117411, Singapore.
authors.forename: Qiyu
authors.initials: Q
authors.lastname: Chen
authors.affiliation: University of Arizona, 1133 E. James E. Rogers Way, Harshbarger 108, Tucson, AZ 85721-0011, USA.
authors.forename: Ai
authors.initials: A
authors.lastname: Jia
authors.affiliation: University of Arizona, 1133 E. James E. Rogers Way, Harshbarger 108, Tucson, AZ 85721-0011, USA.
authors.forename: Shane A
authors.initials: SA
authors.lastname: Snyder
authors.affiliation: Department of Biological Science, National University of Singapore, 14 Science Drive 4, 117543, Singapore.
authors.forename: Zhiyuan
authors.initials: Z
authors.lastname: Gong
authors.affiliation: NUS Environmental Research Institute, National University of Singapore, 5A Engineering Drive 1, 117411, Singapore; Department of Biological Science, National University of Singapore, 14 Science Drive 4, 117543, Singapore. Electronic address: dbslsh@nus.edu.sg.
authors.forename: Siew Hong
authors.initials: SH
authors.lastname: Lam
mesh_terms: D000818:Animals; D001681:Biological Assay; D004305:Dose-Response Relationship, Drug; D004625:Embryo, Nonmammalian / Q000187:drug effects* / Q000378:metabolism; D004784:Environmental Monitoring / Q000379:methods*; D015870:Gene Expression / Q000187:drug effects; D005938:Glucocorticoids / Q000032:analysis / Q000494:pharmacology*; D007814:Larva / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D011965:Receptors, Glucocorticoid / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D062065:Wastewater / Q000737:chemistry*; D015027:Zebrafish / Q000196:embryology / Q000235:genetics / Q000378:metabolism*
chemical_list: D005938:Glucocorticoids; D011965:Receptors, Glucocorticoid; D062065:Wastewater
keywords: Environmental glucocorticoid contaminants; Gene expression; In vitro glucocorticoid receptor bioassay; In vivo zebrafish assay