Bisphenol AF Induces Prostatic Dorsal Lobe Hyperplasia in Rats through Activation of the NF-κB Signaling Pathway

Abstract

Bisphenol AF (BPAF) represents a common environmental estrogenic compound renowned for its capacity to induce endocrine disruptions. Notably, BPAF exhibits an enhanced binding affinity to estrogen receptors, which may have more potent estrogenic activity compared with its precursor bisphenol A (BPA). Notwithstanding, the existing studies on BPAF-induced prostate toxicity remain limited, with related toxicological research residing in the preliminary stage. Our previous studies have confirmed the role of BPAF in the induction of ventral prostatic hyperplasia, but its role in the dorsal lobe is not clear. In this study, BPAF (10, 90 μg/kg) and the inhibitor of nuclear transcription factor-κB (NF-κB), pyrrolidinedithiocarbamate (PDTC, 100 mg/kg), were administered intragastrically in rats for four weeks. Through comprehensive anatomical and pathological observations, as well as the assessment of PCNA over-expression, we asserted that BPAF at lower doses may foster dorsal prostatic hyperplasia in rats. The results of IHC and ELISA indicated that BPAF induced hyperplastic responses in the dorsal lobe of the prostate by interfering with a series of biomarkers in NF-κB signaling pathways, containing NF-κB p65, COX-2, TNF-α, and EGFR. These findings confirm the toxic effect of BPAF on prostate health and emphasize the potential corresponding mechanisms.

Keywords: bisphenol AF; cyclooxygenase-2; nuclear transcription factor-κB; prostatic hyperplasia.

Figure 1

Weight gain and pathological changes of prostates in rats. Effect of exposure to bisphenol AF (BPAF) and the inhibitor of nuclear transcription factor-κB (NF-κB), pyrrolidinedithiocarbamate (PDTC), for 4 weeks on the prostate organ coefficient (A) and prostate–brain coefficient (B), n = 10. (C) The pathological changes of the tissues (200×, scale bar = 100 µm) and the prostate epithelium are pointed to with arrows. (D) The immunohistochemical images of proliferating cell nuclear antigen (PCNA) (400×, scale bar = 20 µm). Arrows indicate the positive expression. (E) The height of prostate epithelium of ventral prostates, n = 6. (F) Immunohistochemistry (IHC) quantification of PCNA is presented as the ratio of the positively expressed nucleus to the total nucleus, n = 8. Results are presented as means ± SD, analyzed using ANOVA, followed by LSD post hoc test. Comparison of the individual-administration group and the control: * p < 0.05, ** p < 0.01; comparison of the combined-administration group and the individual-administration group: ## p < 0.01. Prostate organ coefficient = 1000 × total prostate weight/terminal body weight. Prostate–brain coefficient = 100 × total prostate weight/terminal brain weight.

Figure 2

Localization observation of phosphorylated NF-κB p65 (p-NF-κB p65), cyclooxygenase-2 (COX-2), tumor necrosis factor-α (TNF-α), and epidermal-growth-factor-receptor (EGFR) expression in DLP. Immunohistochemical images of p-NF-κB p65, COX-2, TNF-α, and EGFR of the prostate tissues in the rats treated using BPA, BPAF, and PDTC (400×, scale bar = 20 µm). Arrows indicate positive expression.

Figure 3

BPAF and PDTC induced the quantitative changes of p-NF-κB p65, COX-2, TNF-α, and EGFR in DLP. Effect of exposure to BPAF and PDTC on the rate of positive expression of p-NF-κB p65 (A); the semiquantitative expression levels of COX-2 (B), TNF-α (C), and EGFR (D) in the dorsal lobe of the prostate (DLP). Results are presented as means ± SD, analyzed using ANOVA, followed by LSD post hoc test, n = 8. Contents of NF-κB p65 (E), COX-2 (F), TNF-α (G), and EGFR (H) were obtained using enzyme-linked immunosorbent assay (ELISA). Results are presented as means ± SD, analyzed using ANOVA, followed by LSD post hoc test, n = 4. Comparison of the individual-administration group and the control: * p < 0.05, ** p < 0.01; comparison of the combined-administration group and the individual-administration group: # p < 0.05, ## p < 0.01.