Investigating the Influence of Sex Hormones on OLFR558
Authors: Medcalf Alexandra D. , Xu Jiaojiao , Moore Brittni N. , Pluznick Jennifer L. 
Published: May 2024

Premenopausal women have blood pressure that is ~10mmHg lower than age-matched men. Women incur cardiovascular disease risk at lower blood pressures than men, implying that this sex difference in blood pressure is functionally important; however, clinical management of blood pressure is identical in men and women (Ji et al Circulation 2021). Recently, a study from our lab examined an olfactory receptor (OLFR558) that is expressed in renal juxtaglomerular cells, as well as in all renal blood vessels and a subset of extrarenal blood vessels. We find that OLFR558 is required for sex differences in blood pressure, as sex differences in blood pressure are entirely absent in Olfr558 knockout mice (Xu et al BioRxiv 2022). However, there is a gap in our knowledge regarding how OLFR558 influences blood pressure, and, in the mechanism underlying the blood pressure differences between the sexes. We hypothesize that sex hormones act to modulate OLFR558 signaling. To pursue this, we examined whether sex hormones may act as agonists or antagonists of OLFR558; in parallel, we also examined the human ortholog of OLFR558 (OR51E1). Green Up cADDis cyclic AMP assays were performed (olfactory receptors elevate cAMP upon activation) in technical triplicates, and each experiment was repeated four times. A known agonist (butyrate) activated OLFR558 at 0.5mM (0.175±0.035 cAMP production ± SD), 1mM (0.208±0.038), 2mM (0.264±0.014) and 5mM (0.238±0.028) vs baseline (0.061±0.009); all comparisons significant vs baseline by one-way ANOVA, p<0.0001. We first tested estrone (E1), estradiol (E2), estriol (E3), progesterone (P), testosterone (T), follicle stimulating hormone (FSH), and luteinizing hormone (LH) as potential agonists for OLFR558. We find that none of these compounds activate OLFR558 (p values vs baseline/PBS: 50 nM estrogen: E1, p>0.999; E2, p=0.999; E3, p=0.938 35nM T: p>0.999, 50 nM P: p>0.999, 10 mIU FSH: p=0.9348, 100 mIU FSH: p-value=0.8429, 10 mIU LH: p value >0.999, 56 mIU LH: p value> 0.999). We then tested these compounds as potential antagonists for OLFR558 by measuring cAMP responses to butyrate in the presence of each hormone. Estrogen, P, and T were tested at two different butyrate doses (0.1mM and 0.2 mM), and LH and FSH were tested at four different butyrate doses (0.5mM, 1mM, 2mM, and 5mM). We find that estrogen and T do not act as antagonists (p-value vs. matched doses of butyrate alone are 0.650-0.725 for 50 nM estrogen, 0.625-0.653 for 50 nM P and 0.708-0.883 for 35 nM T). Similarly, we find that LH and FSH do not antagonize OLFR558 at any of the four butyrate doses tested (p value for hormone+butyrate vs. matched doses of butyrate alone is p-value 0.4275-0.9069 for 10 mIU LH, p-value 0.5225-0.9921 for 56mIU LH, p-value 0.1235-0.9732 for 10mIU FSH, and p-value 0.5610-0.9358 for 100 mIU FSH). Similarly, we find that the human ortholog OR51E1 is significantly activated by known ligand butyrate (0.5 mM: 0.176± 0.011 cAMP production ± SD, 1mM: 0.225±0.001, 2mM: 0.242±0.027, 5mM:0.249±0.021 versus baseline 0.087±0.003 by one-way ANOVA, p<0.0001), but is neither agonized nor antagonized by estrogen, P, T, LH or FSH. Looking ahead, we plan to investigate additional sex hormones and related metabolites, as well as alternative explanations for the phenotype. Better understanding of the relationship between sex hormones, blood pressure, and OLFR558/OR51E1 is pertinent to how physicians treat elevated blood pressure in men and women. Funding: American Heart Association Established Investigator Award (to JLP) and R21AG081683 (to JLP). ADM is supported by NIH PREP grant R25GM109441. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.