Time-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 using 0 and 100 ppb-TCDD treated male and female sexed zebrafish at 7, 14, 28 and 42 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. At 42d, no mature female fish were observed. 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. Microarray experiments were conducted using 0 and 100 ppb-TCDD treated male and female sexed zebrafish at 7, 14, 28 and 42 d. Zebrafish 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.