Dioxin-like pcb126 mediated estrogenicity in fish in vitro system involves both receptor activation and receptor-protein stability

Agonists of the aryl hydrocarbon receptor (AhR) have generally been thought to have anti-estrogenic activities. We proposed and have since established that these activities are exceptions, rather than the rule. In the present study, we evaluate mechanistically, the estrogenic effect of the dioxin-like PCB126. Primary salmon hepatocytes were exposed to PCB126 (0.001, 0.01 and 0.05 μM) or the estrogen receptor (ER) agonist estradiol-17β (E2; 0.001 μM) singly and in combination with ER-antagonist (ICI182780), AhR inhibitor (3’,4’- dimethoxyflavone; DMF) or protein synthesis inhibitor (cycloheximide; CyH). Hepatocytes were exposed for 6, 12 and 24 hours. The expression of genes and proteins involved in ER (ERα, ERβ and vitellogenin) and AhR (CYP1A1, AhR-repressor, AhR-isotypes and cofactors) pathways were analysed using quantitative PCR and immunochemical methods. Biochemical assay methods were used for CYP1A1 and proteasomal activities. In general, our data showed the involvement of activated AhR on PCB126-mediated estrogenicity and that this involvement was negatively influenced by protein and receptor inhibitors, respectively. The complex interactions between these two different classes of ligand-activated receptors have provided novel mechanistic insights in signalling pathways.