Progesterone regulates GnRH secretion in bovine endometrial cells via Erk1/2-ARRB1 pathway modulation

In ruminants, progesterone is crucial for promoting uterine development and establishing a favorable environment for embryo implantation. However, the precise molecular mechanisms by which progesterone regulates the function of endometrial epithelial cells (BEECs), which are vital for uterine receptivity, remain largely undefined. Understanding these cellular pathways is essential for optimizing reproductive outcomes and addressing infertility challenges in livestock. This study addresses the gap in understanding how progesterone influences key signaling cascades like Erk1/2 and the secretion of gonadotropin-releasing hormone (GnRH) within these critical cells.

Researchers treated a bovine endometrial epithelial cell (BEEC) line with varying concentrations of progesterone (0, 5, 10, and 15 ng/mL) to investigate its effects on gene expression. After treatment, RNA sequencing (RNA-Seq) was performed to construct comprehensive mRNA expression profiles. To further elucidate the mechanism, a small interfering RNA (siRNA) approach was used to disrupt ARRB1 expression, allowing for observation of its impact on Erk1/2 expression and GnRH secretion.

Progesterone induced concentration-dependent gene expression changes in BEECs. Compared to control cells (0 ng/mL progesterone), 10 ng/mL and 15 ng/mL progesterone significantly upregulated interleukin 6 (IL6) expression (P < 0.05). Decreased expression of matrix metallopeptidase 9 (MMP9) (P < 0.05) and increased expression of vascular endothelial growth factor (VEGF) (P < 0.05) were observed in BEECs treated with 5, 10, and 15 ng/mL progesterone. In total, 138, 132, and 385 differentially expressed genes (DEGs) were identified at 5, 10, and 15 ng/mL progesterone, respectively, primarily associated with leukotriene and oxytocin signaling, cell surface receptor signaling, and GnRH secretion.

BEECs treated with 10 ng/mL progesterone showed increased β-arrestin 1 (ARRB1) gene expression, which inhibited the extracellular signal-regulated kinase 1/2 (Erk1/2) pathway and reduced gonadotropin-releasing hormone (GnRH) secretion. Subsequent siRNA-mediated suppression of ARRB1 expression promoted Erk1/2 expression and increased GnRH secretion.