Erythropoietin-producing hepatocellular A7 restrains estrogen-negative feedback of luteinizing hormone via ephrin A5 in the hypothalamus of female rats.

: We have previously shown that systemic injection of exogenous erythropoietin-producing hepatocellular (EPH) A7-Fc raises serum luteinizing hormone (LH) levels before ovulation in female rats, indicating the induction of EPHA7 in ovulation. In this study, we aimed to identify the mechanism and hypothalamus-pituitary-ovary (HPO) axis level underlying the promotion of LH secretion by EPHA7. Using an ovariectomized (OVX) rat model, in conjunction with low-dose estradiol (E2) treatment, we investigated the association between EPHA7-ephrin (EFN) A5 signaling and E2-negative feedback. Various rat models (OVX, E2-treated OVX, and abarelix-treated) were injected with the recombinant EPHA7-Fc protein through the caudal vein to investigate the molecular mechanism underlying the promotion of LH secretion by EPHA7. Efna5 was observed strongly expressed in the arcuate nucleus of the female rat using RNAscope in situ hybridization. Our results indicated that E2, combined with estrogen receptor (ER) α, but not ERβ, inhibited Efna5 and gonadotrophin-releasing hormone 1 (Gnrh1) expression in the hypothalamus. In addition, the systemic administration of EPHA7-Fc restrained the inhibition of Efna5 and Gnrh1 by E2, resulting in increased Efna5 and Gnrh1 expression in the hypothalamus, as well as increased serum LH levels. Collectively, our findings demonstrated the involvement of EPHA7-EFNA5 signaling in the regulation of LH and the E2-negative feedback pathway in the hypothalamus, highlighting the functional role of EPHA7 in female reproduction.