Gene expression and DNA methylation changes in the hypothalamus and hippocampus of adult rats developmentally exposed to bisphenol A or ethinyl estradiol: a CLARITY-BPA consortium study

ABSTRACT

Bisphenol A (BPA), an endocrine disrupting chemical (EDC), is a ubiquitous pollutant. As part of the Consortium Linking Academic and Regulatory Insights on BPA Toxicity (CLARITY-BPA), we sought to determine whether exposure of Sprague-Dawley rats to 2,500 μg/kg/day BPA (BPA) or 0.5 μg/kg/day ethinyl estradiol (EE) from gestational day 6 through postnatal day 21 induces behavior-relevant gene expression and DNA methylation changes in hippocampus and hypothalamus at adulthood. RNA and DNA were isolated from both regions. Expression of ten genes (Dnmt1, Dnmt3a, Dnmt3b, Esr1, Esr2, Avp, Ar, Oxt, Otr, and Bdnf) presumably altered by early-life BPA/EE exposure was examined. Three genes (Bdnf, Dnmt3b, and Esr1) were studied for DNA methylation changes in their putative 5ʹ promoter regions. Molecular changes in hippocampus were correlated to prior Barnes maze performance, including sniffing correct holes, distance traveled, and velocity. Exposure to BPA and/or EE disrupted patterns of sexually dimorphic gene expression/promoter DNA methylation observed in hippocampus and hypothalamus of controls. In the hippocampus of female offspring, BPA exposure resulted in hypermethylation of the putative 5ʹ promoter region of Bdnf, while EE exposure induced hypomethylation. Bdnf methylation was weakly associated with Bdnf expression in hippocampi of female rats. Hippocampal Bdnf expression in females showed a weak negative association with sniffing correct hole in Barnes maze. Hippocampal expression of Avp, Esr2, Oxt, and Otr was strongly associated with velocity of control rats in Barnes maze. Findings suggest BPA exposure induced non-EE-like gene expression and epigenetic changes in adult rat hippocampi, a region involved in spatial navigation.

KEYWORDS:

• Endocrine disrupting chemicals
• brain
• rodent models
• epigenetics
• estrogen receptor
• developmental programming
• Dnmt3b
• Bdnf

Acknowledgments

The authors are grateful for Drs. K. Barry Delclos, Sherry A. Ferguson, and colleagues at National Center for Toxicological Research/Food and Drug Administration for their assistance in designing and collecting the brains as part of this CLARITY-BPA consortium project. The authors also acknowledge Dr. Thaddeus Schug and Dr. Retha Newbold of NIEHS for their assistance in coordinating and addressing any questions and concerns that arose during the project. The authors would also like to thank Ms. Natalie Ho for her assistance in designing Bdnf primers for bisulfite sequencing.

Disclaimer

The contents of this manuscript should not be interpreted as current or future policy of the FDA or NIEHS. The mention of any manufacturers or trade names is only for clarity and does not constitute endorsement.

Disclosure statement

No potential conflict of interest was reported by the authors.

SUPPLEMENTAL DATA

Supplemental data for this article can be accessed here.

Additional information

Funding

This study is part of the NIEHS CLARITY-BPA Consortium supported by NIEHS grant U01ES020929 to C.S.R., I01-BX000675, U01-ES020988, U01-ES019480 to S.M.H. The animal portion of this study was funded by the National Toxicology Program under an Interagency Agreement between FDA and NIEHS (FDA IAG # 224-17-0502 and NIH IAG #AES12013).