The environmental estrogen, 4-nonylphenol modulates brain estrogen-receptor- and aromatase (CYP19) isoforms gene expression patterns in Atlantic salmon (Salmo salar)

The modulations of reproductive biomarker responses, such as vitellogenin (Vtg) and zona radiata protein (Zr-protein) by xenoestrogens are mediated through the estrogen receptors (ERs). The ERα and ERβ belong to the nuclear receptor (NR) superfamily of ligand activated transcription factors that modulate specific gene expression. By interacting with estrogen and estrogen like molecules (including estrogen mimics), the ERs exert a diverse array of biological effects. In addition to their effect as direct agonist to the ERs, the endocrine-disrupting effects of environmental chemicals are sometimes interpreted as interference with steroidogenesis through the aromatase enzyme (CYP19 or P450arom). The aim of this study was to investigate the effects of nonylphenol on the expression patterns of ER and aromatase (P450arom) isoform genes in the brain as sensitive molecular biomarker of response to endocrine disrupting chemicals. Immature Atlantic salmon were exposed to continuous nominal waterborne nonylphenol at 15 μg/L. Brain samples were collected after 7 days exposure. A quantitative RT-PCR method was used to analyze mRNA expression patterns. Nonylphenol caused a significant induction of P450arom and ER isoform patterns in the brain and represent quantitative gene expression biomarkers of exposure to endocrine disrupting chemicals in the environment.