Dose-dependent toxic effects of dietary TCDD on juvenile zebrafish

Juvenile zebrafish were fed Biodiet starter (4% body weight per day) for 42 d with TCDD added at 0 ppb, 0.1 ppb, 1 ppb, 10 ppb or 100 ppb. Fish were collected, sexed, weighed and length measured at 0, 7, 14, 28 or 42 d for TCDD assessment, histopathologic and microarray analysis. Microarray experiments were conducted in TCDD-treated (at 0, 0.1, 1, 10 and 100 ppb) for male and female sexed zebrafish at 28 d. NimbleGen Gene Expression 12X135K zebrafish microarrays and One-Color DNA labeling Kit (NimbleGen, WI) were used for genome-wide expression analysis of TCDD-treated zebrafish. TCDD accumulated in a dose- and time-dependent manner and 100 ppb TCDD caused TCDD accumulation in female (15.49 ppb) and male (18.04 ppb) fish at 28 d post exposure. TCDD caused multiple lesions in liver, kidney, intestine and ovary of zebrafish and functional dysregulation such as depletion of glycogen in liver, retrobulbar edema, degeneration of neurosensory epithelium, underdevelopment of intestine, and diminution in the fraction of ovarian follicles containing vitellogenic oocytes. Microarray gene expression analysis comparing control to post TCDD diet revealed dysregulated genes located in pathways associated with cardiac necrosis/cell death, cardiac fibrosis, renal necrosis/cell death and liver necrosis/cell death. These baseline toxicological effects provide evidence for the potential biomarkers, mechanisms and pathology of TCDD induced dysregulation. Juvenile wild-type zebrafish (stock originally purchased from EkkWill Waterlife Resources, Ruskin, FL) (0.16 g, 2.10 cm) were were reared in 28 °C dechlorinated, filtered municipal water (DFMW) in the NIEHS Children's Environmental Health Sciences Core Center (CEHSC) animal facility. Zebrafish were fed Biodiet starter (4% body weight per day) for 42 d with TCDD added at 0 ppb, 0.1 ppb, 1 ppb, 10 ppb or 100 ppb (nominal concentration, ethanol used as vehicle). Fish were collected, sexed, weighed and length measured at 0, 7, 14, 28 or 42 d for TCDD assessment and microarray analysis. Miicroarray experiments were conducted in TCDD-treated (at 0, 0.1, 1, 10 and 100 ppb) for male and female sexed zebrafish at 28 d. Zebrafish were were randomly selected from each group for the microarray experiments. NimbleGen Gene Expression 12X135K zebrafish microarrays and One-Color DNA labeling Kit (NimbleGen, WI) were used for genome-wide expression analysis of TCDD-treated zebrafish. Differential expression analysis was performed with Bayesian Estimation of Temporal Regulation (BETR) method using Multiple Array Viewer (MeV, Dana-Farber Cancer Institute, MA) software, version 4.8.1.