Exposure to Deepwater Horizon Oil and Corexit 9500 at Low Concentrations Induces Transcriptional Changes and Alters Immune Transcriptional Pathways in Sheepshead Minnows

To investigate molecular effects in fish following exposure to environmentally relevant concentrations of dispersants and DWH oil, we exposed adult sheepshead minnows (Cyprinodon variegatus) to Corexit 9500™ and two concentrations of high-energy water-accommodated fraction (HEWAF) or chemically enhanced water-accommodated fraction (CEWAF) for 7 and 14 days. Resulting changes in hepatic gene expression were measured using Agilent 8x15K microarrays. We observed significant changes to gene expression in all treatments (relative to controls), with Corexit and CEWAF having a greater effect on expression patterns in the liver than HEWAF treatments. Sub-network enrichment analysis of biological pathways revealed that the greatest number of altered pathways in high dose HEWAF and CEWAF treatments occurred following a 7-day exposure. Pathways related to immunity comprised the majority of pathways affected in each treatment, followed by pathways related to blood and circulation processes. Adult Sheepshead minnows were exposed to two doses of oil, dispersed oil, or a single dose of dispersant for 7 or 14 days. Each treatment consisted of four tanks with one individual sampled from each tank for this study. After exposure, fish were sacrificed , liver tissue collected, and samples stored in RNA Later at -80 until further analysis. Total RNA was extracted, labeled with Cy3, and hybridized to Agilent 8 x 15k micorarrays to measure changes in gene expression.