Regulation of the Novel Reproductive Peptide, Phoenixin, By Bisphenol a and Palmitate, but Not 17β-Estradiol, in Hypothalamic Cell Models

Presentation Number: SUN 488
Date of Presentation: April 2nd, 2017

Emma McIlwraith*1, Neruja Loganathan2 and Denise D Belsham3
1University of Toronto, Toronto, ON, CANADA, 2Univeristy of Toronto, Toronto, ON, CANADA, 3University of Toronto, Toronto, ON, Canada

Abstract

Phoenixin (PNX) is a novel reproductive peptide implicated in control of the reproductive axis through regulation of gonadotropin-releasing hormone and kisspeptin in the hypothalamus, and leutinizing hormone in the pituitary. This amidated 20-amino acid peptide is cleaved from small integral membrane protein 20 (SMIM20) and is most highly expressed in the hypothalamus. The PNX receptor, GPR173, is expressed in the brain, pituitary, and gonads, which further suggests involvement of PNX in reproduction. However, it is currently unknown how PNX is regulated at the gene level. Because PNX is linked to the reproductive axis, we investigated whether 17β-estradiol, necessary for HPG feedback control, affects SMIM20 gene expression. We also examined the effect of the putative estrogen mimic, bisphenol A (BPA), a prevalent environmental chemical reported to disrupt reproductive function. Finally, because nutritional status has been linked to reproductive success, we analyzed the effect of the dietary saturated fatty acid, palmitate, on SMIM20 expression. Using RT-PCR, we observed that 100 nM 17β-estradiol had no effect on SMIM20 expression from 4 to 48 hours in embryonic- or adult-derived PNX-expressing, immortalized hypothalamic cell lines from female mice (mHypoE-41 and mHypoA-59, respectively). In contrast, 100 uM BPA induced SMIM20 expression from 2 to 24 hours in these cell lines, with a 1.5 fold increase at 16 and 24 hours in the mHypoE-41 cells. These differential results indicate that BPA may be acting through a pathway independent of estrogen. Additionally, we found that in male embryonic- and adult-derived, mHypoE-46 and mHypoA-2/12 cell lines, respectively, 50 uM palmitate increased expression of SMIM20 by 1.5 fold at 16 and 24 hours. Interestingly, treatment with BPA increased GPR173 expression at 2 and 4 hours in the mHypoE-41 and mHypoA-59 cell lines, respectively, then attenuated expression at 16 and 24 hours in both lines. Similarly, palmitate significantly repressed GPR173 expression by 20% at 16 hours and by 15% at 24 hours in mHypoE-46 cells. In addition to altering SMIM20 and GPR173 mRNA levels, treatment with BPA and palmitate induced expression of inflammatory and endoplasmic reticulum stress markers, and may therefore modulate PNX expression through activation of these pathways. We continue to investigate the mechanisms through which BPA and palmitate affect SMIM20 expression, and thus PNX expression. Uncovering hormones and/or nutrients that regulate the PNX gene will lead to a better understanding of reproductive control mechanisms in the hypothalamus.

 

Nothing to Disclose: EM, NL, DDB