Poster Session 2 - R2
1Emma McIlwraith, 1Neruja Loganathan, 1,2Denise 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
Phoenixin (PNX) is a highly conserved, amidated 20 amino acid peptide expressed most highly in the hypothalamus. In hypothalamic neurons, PNX upregulates gonadotropin-releasing hormone and kisspeptin expression and is therefore a positive regulator of the hypothalamic-pituitary-gonadal axis. However, how PNX and its receptor, GPR173, are regulated is unknown and will be important for determining possible additional functions, such as energy homeostasis. We hypothesize that expression of the PNX gene, Smim20, and PNX receptor gene, Gpr173, will be affected by the sex hormone, 17 beta-estradiol (E2); the endocrine disrupting chemical, bisphenol A (BPA); the fatty acids, palmitate, oleate, docosahexaenoic acid (DHA) and palmitoleate; and by the activation of individual signaling pathways. Gene expression was measured from 2 to 24 hours with quantitative PCR in hypothalamic cell lines. E2, DHA and palmitoleate had no effect on PNX; however, BPA significantly decreased Smim20 and Gpr173 mRNA levels by 16 hours. Palmitate and oleate significantly upregulated Smim20 mRNA, while palmitate downregulated Gpr173 expression. Activation of protein kinase C (12-O-tetradecanoylphorbol-13-acetate), elevated levels of cAMP (forskolin), the nitric oxide donor sodium nitroprusside (SNP), and induction of neuroinflammatory signaling (lipopolysaccharide) had no effect on Smim20 gene expression over 24 hours, while SNP slightly increased Gpr173 at 24 hours. We will continue to investigate the effects of these compounds using enzyme immunoassays to determine PNX peptide levels. An understanding of how PNX is regulated will aid in determining its physiologic function at the hypothalamic level, and its potential for therapeutic applications.