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BACKGROUND: Previous studies have uncovered heightened prostatic susceptibility to hormone-induced neoplasia from early-life exposure to low dose bisphenol A (BPA). However, significant data gaps remain that are essential to address for biological relevance and necessary risk assessment.

OBJECTIVES: A complete BPA dose response analysis of prostate lesions across multiple prostatic lobes was conducted that included internal BPA dosimetry, progression to adenocarcinoma with aging and mechanistic connections to epigenetically reprogramed genes.

METHODS: Male neonatal Sprague-Dawley rats were briefly exposed to 0.1 to 5,000 mu g BPA/kg BW on postnatal days (PND) 1, 3, and 5. Individual prostate lobes plus periurethral prostatic ducts were evaluated at 7 mo or 1 y of age without or with adult testosterone plus estradiol (T + E) to promote carcinogenesis. DNA methylation of live genes was quantified by bisullite genomic sequencing in d-200 dorsal prostates across BPA doses. Serum free-BPA and BPA-glucuronide were quantitated in sera of individual PND 3 pups collected 1 hr postexposure utilizing ultra-high-pressure tandem mass spectrometry (UHPLC-MS-MS).

RESULTS: The lowest BPA dose initiated maximal hormonal carcinogenesis in lateral prostates despite undetectable free BPA 1 hr postexposure. Further, prostatic intraepithelial neoplasia (PIN) progressed to carcinoma in rats given neonatal low-close BPA with adult T + E but not in rats given adult T + E alone. The dorsal and ventral lobes and periurethral prostatic ducts exhibited a nonmonotonic dose response with peak PIN, proliferation and apoptotic values at 10-100 mu g/kg BW. This was paralleled by nonmonotonic and dose-specific DNA hypomethylation of genes that confer carcinogenic risk, with greatest hypomethylation at the lowest BPA doses.

CONCLUSIONS: Developmental BPA exposures heighten prostate cancer susceptibility in a complex dose- and lobe-specific manner. Importantly, elevated carcinogenic risk is found at doses that yield undetectable serum free BPA. Dose-specific epigenetic modifications of selected genes provide a mechanistic framework that may connect early-life BPA to later-life predisposition to prostate carcinogenesis.