Gene Expression Profiling of Zebrafish (Danio rerio) Exposed to the Steroidogenesis Inhibitor Ketoconazole

Abstract

Ketoconazole (KTC) has been shown to alter the reproductive function of small fish through inhibition of enzymes in the steroid biosynthesis pathway. The purpose of this research was to examine the transcriptomic response of adult zebrafish (Danio rerio) to KTC exposure. Zebrafish were treated up to 96 h with 400 µg/L KTC in a flow‐through system. Total RNA was isolated from brain, liver and gonad and gene expression changes were identified using a two color, high density zebrafish microarray. Differentially‐expressed genes were identified (p<0.05; FDR<30%) then were analyzed by gene ontology term clustering, gene set enrichment analysis (GSEA) and Ingenuity Pathway Analysis (IPA). Results in liver showed a possible disruption of cholesterol and steroid biosynthesis and activation of cytokine signaling pathways. Analyses of brain gene expression demonstrated oxidative stress, down regulation of an oxioreductase and increase in estrogen receptor 2b (esr2b). In ovary, oxidative stress response, oxidative phosphorylation and hormone receptor regulated cholesterol metabolism were enriched along with an increase in esr2b expression. Pathways known to be effected by inhibition via KTC; cholesterol biosynthesis, steroid biosynthesis and xenobiotic metabolism, are finely controlled at multiple levels of regulation. The results presented here provide insight into the transcriptional regulation of these broad and interactive processes at an isolated time point.