Indiana University-Purdue University Indianapolis (IUPUI) / Polybrominated diphenyl ethers (PBDEs) are widely used flame retardants suspected to act as endocrine disruptors. We tested the commercial PBDE mixture DE-71 and its in vivo metabolites for estrogenic activity. MCF-7 breast cancer cells culture, ERE-luciferase gene expression, 3H-β-estradiol displacement from recombinant ERα, and ovariectomized (OVX) mice served as bioassays. Although DE-71 did not bind ERα, it was able to increase MCF-7 cell proliferation and this was prevented by the antiestrogen fulvestrant. DE-71 co-treatment reduced the effect of estradiol in MCF-7 cells. In the OVX mouse (BALB/c) 3-day assay, DE-71 administered alone had no effect on uterine or vaginal tissues but when administered subcutaneously potentiated estradiol’s effect on uterine weight in a dose-dependent manner. DE-71 administered SQ to BALB/c mice for 34 days slightly increased uterine epithelial height (UEH), vaginal epithelial thickness (VET) and mammary ductal lumen area, and attenuated the estradiol-induced increase in UEH; these effects were not seen in C57BL/6 mice. DE-71 increased liver weight in BALB/c, C57BL/6 and estrogen receptor-alpha knockout (ERαKO) mice. Liver cytochrome P450 1A (CYP1A) and CYP2B activities increased 2.5-fold and 7-fold respectively when DE-71 was administered PO, but only CYP2B increased (5-fold) after SQ treatment. Six OH-PBDE metabolites were found in mice after 34-day DE-71 treatment and all were able to bind recombinant ERα. Para-hydroxylated metabolites displayed a 10- to 30-fold higher affinity for ERα compared to ortho-hydroxylated PBDEs. Para-OH-PBDEs induced ERE-luciferase and produced an additive effect when coadministered with β-estradiol. DE-71 was also additive with β-estradiol. At high concentrations (≥ 5x10-5 M), ortho-OH-PBDEs were antiestrogenic in the ERE-luciferase assay. In conclusion, DE-71 behaves as a weak estrogen in both MCF-7 breast cancer cells and ovariectomized adult mice. Mice strain, treatment route and duration determined if DE-71 was estrogenic. BALB/c mice are more susceptible to DE-71 effects in estrogen target tissues than C57BL/6 mice. DE-71 increased liver weight, 5%-51% depending on mouse strain and treatment regime, independently of ERα. The observations that the DE-71 mixture does not displace 3H-β-estradiol from ERα while the hydroxylated metabolites do, suggest that the cellular and tissue effects were due to a metabolic activation of individual congeners.
| Identifer | oai:union.ndltd.org:IUPUI/oai:scholarworks.iupui.edu:1805/1603 |
| Date | 05 March 2008 |
| Creators | Mercado-Feliciano, Minerva |
| Contributors | Bigsby, Robert M., Klaunig, James E., Jeng, Meei-Huey, Kamendulis, Lisa, Skaar, Todd, Sullivan, William J., Jr. |
| Source Sets | Indiana University-Purdue University Indianapolis |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
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