Genomic and proteomic responses to environmentally relevant exposures to dieldrin: indicators of neurodegeneration?

Dieldrin is a persistent organochlorine pesticide that induces neurotoxicity in the vertebrate central nervous system and impairs reproductive processes in fish. This study examined the molecular events produced by subchronic dietary exposures to 2.95 mg dieldrin/kg feed in the neuroendocrine brain of largemouth bass, an apex predator. Microarrays, proteomics, and pathway analysis were performed to identify genes, proteins, and cell processes altered in the male hypothalamus. Fifty-four genes were induced, and 220 genes were reduced in steady-state levels (p < 0.001; fold change greater than +/- 1.5). Functional enrichment analysis revealed that the biological gene ontology categories of stress response, nucleotide base excision repair, response to toxin, and metabolic processes were significantly impacted by dieldrin. Using isobaric tagging for relative and absolute quantitation, 90 proteins in the male hypothalamus were statistically evaluated for changes in protein abundance. Several proteins altered by dieldrin are known to be associated with human neurodegenerative diseases, including apolipoprotein E, microtubule-associated tau protein, enolase 1, stathmin 1a, myelin basic protein, and parvalbumin. Proteins altered by dieldrin were involved in oxidative phosphorylation, differentiation, proliferation, and cell survival. This study demonstrates that a subchronic exposure to dieldrin alters the abundance of messenger RNAs and proteins in the hypothalamus that are associated with cell metabolism, cell stability and integrity, stress, and DNA repair.