Reduced life expectancy model for effects of long term exposure on lethal toxicity with fish

Determination and reduced life expectancy model and molecular docking analyses of estrogenic potentials of 17β-estradiol, bisphenol A and nonylphenol on expression of vitellogenin gene (vtg1) in zebrafish

This study determined and evaluated the estrogenic potentials on hepatic vitellogenin gene (vtg1) of adult male zebrafish which were exposed to low level concentrations (ng/L-μg/L levels) of individual and binary mixtures of 17β-estradiol (E₂), bisphenol A (BPA) and nonylphenol (NP) through the use of reduced life expectancy (RLE) model and molecular docking analysis. The order of in vivo estrogenic potentials of individual and binary exposure of E₂, BPA and NP was as follows: E₂+BPA＞E₂＞E₂+NP＞BPA＞BPA + NP >>>NP. Binary mixtures of E₂, BPA and NP had weak synergistic effects under the exposure concentration ranges. With the expression of hepatic vtg1 gene, the hepatic toxicity was analyzed by using the RLE model. All plots of the linear RLE model had negative slopes indicating that EC₅₀ was negatively correlated with the natural logarithm of exposure time (lnET₅₀). The RLE model analyses can be useful to evaluate the exposure time effects of zebrafish by using EC₅₀ as toxicity endpoint. Molecular docking analysis revealed that the interaction potential of E₂ (Binding energy: -10.1 kcal/mol) for the zebrafish ERα-LBD was the most potent (stable), followed by BPA (-8.0 kcal/mol) and NP (-6.8 kcal/mol). Molecular docking analysis can be useful to understand interactive effects of E₂, BPA and NP.