Background Exposure to bisphenol A (BPA) in the early life period can induce developmental toxicity. Aryl hydrocarbon receptor (AhR) can regulate various developmental and physiological functions, and can be activated by BPA.
Objective This experiment uses zebrafish as a model animal to study the role of AhR in the developmental toxicity of zebrafish embryos induced by BPA.
Methods Zebrafish embryos were randomly divided into eight groups: DMSO control group, AhR inhibitor CH223191 (CH) control group, BPA exposure groups (1, 5, and 25 μmol·L-1), and CH+BPA (1, 5, and 25 μmol·L-1) groups. The exposure period was from 2 h post-fertilization (2 hpf) to 96 h post-fertilization (96 hpf). The mortality, hatching rate, malformation rate, heart rate, body length, and locomotor ability of zebrafish embryos were evaluated. The expressions of AhR-related genes (ahr2, cyp1a1, and cyp1b1), cardiac development-related genes (nkx2.5 and sox9b), and neurodevelopment-related genes (elavl3, gfap, mbp, and syn2a), and reactive oxygen species-related genes (nrf2, sod1, sod2, ho1, and nqo1) were detected by fluorescence quantitative PCR.
Results Compared with the DMSO control group, the zebrafish embryos in the 25 μmol·L-1 BPA group had delayed hatching, decreased heart rate, and elevated malformation rate, and the 5 μmol·L-1 and 25 μmol·L-1 groups showed shortened body length, increased mortality, and decreased movement distance (P < 0.05). Compared with corresponding BPA exposure groups, the heart rate, malformation rate, and locomotor ability of the zebrafish in the CH+25μmol·L-1 BPA group, and the body length of the CH+5μmol·L-1 BPA group and the CH+25μmol·L-1 BPA group all recovered (P < 0.05). However, the hatching rate and mortality rate were not affected by CH. The results of fluorescence quantitative PCR showed that AhR-related genes (ahr2, cyp1a1, and cyp1b1) were up-regulated in the BPA groups (P < 0.05), and CH combined treatment reduced the overexpression of ahr2 and cyp1a1 in each BPA group and cyp1b1 in the 25 μmol·L-1 BPA group (P < 0.05). The expression of cardiac development-related gene nkx2.5 was down-regulated in the 25 μmol·L-1 BPA group and that of sox9b was down-regulated in the 5 and 25 μmol·L-1 BPA groups, respectively (P < 0.05), and the expressions were recovered after the CH combined treatment (P < 0.05). The neurodevelopment-related gene elavl3 was down-regulated in the 25 μmol·L-1 BPA group (P < 0.05), gfap and syn2a were down-regulated in the 5 and 25 μmol·L-1 BPA groups (P < 0.05), and mbp was down-regulated in all BPA groups (P < 0.05); the above genes were recovered after the CH combined treatment (P < 0.05). The expressions of reactive oxygen species-related gene nrf2 was up-regulated in the 25μmol·L-1 BPA group, sod1, ho1, and nqo1 were up-regulated in the 5 and 25μmol·L-1 BPA groups, and sod2 was up-regulated in all BPA groups (P < 0.05); after the CH treatment, the expressions of these genes returned to normal levels (P < 0.05).
Conclusion BPA may activate AhR, up-regulate the expressions of cyp1a1 and cyp1b1 genes, and enhance the production of ROS, leading to the developmental toxicity in zebrafish embryos.
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