Poster Session 1 - E1
1Ashkan Salehi, 1,2,3Denise D. Belsham
1 Dept. of Physiology, University of Toronto; 2 Dept. of Obstetrics and Gynaecology, University of Toronto; 3 Dept. of Medicine, University of Toronto, Toronto, ON, Canada
Endocrine disrupting chemicals, such as bisphenol A (BPA), have been linked to obesity. However, the effect of BPA on hypothalamic pro-opiomelanocortin (POMC) neurons remains unexplored. POMC neurons produce the anorexigenic peptide αMSH and altering POMC expression disrupts energy homeostasis, leading to weight gain. We hypothesized that BPA alters POMC gene expression via induction of neuroinflammatory and nuclear receptor signaling, ultimately impairing feeding regulation. To examine this, POMC-expressing hypothalamus neuronal models, mHypoA-POMC/GFP-2, mHypoE-43/5, mHypoA-Bmal1WT and mHypoA-Bmal1KO, were treated with 100 μM BPA. The transcription of the POMC gene, circadian clock genes, pro-inflammatory genes, endoplasmic reticulum (ER) stress markers, estrogen and related receptor genes, peroxisome proliferator-activated receptor gamma gene (PPAR), and inducible nitric oxide synthase (iNOS) gene were examined using real-time quantitative PCR (RT-qPCR). BPA upregulated the mRNA levels of POMC, pro-inflammatory NFkB, IL6, TNF and IkB, estrogen related receptor gamma (ERR), PPAR, iNOS, and ER stress markers CHOP, GRP78 and Bax/Bcl2 at 4h, whereas BPA downregulated GPR30 mRNA levels at 4h. The effect of BPA on POMC expression demonstrates a dose-dependent increase. The circadian gene Bmal1 was upregulated by BPA at 4 hours, and downregulated at 16 and 24 hours. BPA downregulated the circadian clock genes Per2 and Rev-Erb⍺ at 24 hours. The dysregulation of POMC by BPA was rescued after pre-treatment with anti-inflammatory compounds GnRH, the IkB Kinase/NFkB inhibitor PS1145, and a combination of metformin and melatonin. BPA-induced dysregulation of POMC was also rescued by pretreatment with PPAR antagonist T0070907, and the ERR inverse agonist, GSK5182. It was determined that BPA does not have a Bmal1-dependent mechanism of action on the POMC gene, as BPA-induced POMC dysregulation was still observed in the Bmal1 knockout mHypoA-Bmal1KO cell line. In conclusion, our study is the first to explore the direct effects of BPA on POMC neuronal cell models, demonstrating altered expression of inflammatory and ER stress markers, steroid receptors, circadian clock and POMC genes. In addition, our study is the first to demonstrate that BPA operates through inflammatory and nuclear receptor mechanisms of action in POMC neurons. This study demonstrates that BPA can have direct effects on POMC neurons in the hypothalamus and that this region may be linked to the BPA-mediated alterations in energy homeostasis.