Stimulatory effects of interleukin-1 beta on development of porcine uterine epithelial cell are mediated by activation of the ERK1/2 MAPK cell signaling cascade

Successful establishment of pregnancy depends on timely changes in the conceptus (embryo and associated extra-embryonic membranes) and uterine endometrium orchestrated by molecules from both the conceptus and uterus. Interleukin-1 beta (IL-1β) is an important mediator of that communication regulating development of the peri-implantation conceptus and opening the window of implantation during early pregnancy. However, little is known about IL-1β-mediated intracellular signaling cascades and functional effects in uterine luminal epithelium (LE) during the peri-implantation period of pregnancy in pigs. Therefore, this study determined, using an immortalized porcine LE (pLE) cell line from day 12 pregnant gilts: 1) the intracellular signaling cascade responsible for activities of IL-1β in pLE cells, and 2) the changes in cellular activities induced by IL-1β. IL-1β stimulated phosphorylation of ERK1/2 proteins in pLE cells in a dose-dependent manner. Ten ng/ml IL-1β increased levels of phosphorylated (p)-ERK1/2 proteins in pLE cells within 15 min post-treatment, and this IL-1β-induced phosphorylated status was inhibited by increasing doses of U0126 (ERK1/2 inhibitor). In addition IL-1β increased p-P70S6K, p-P90S6K, p-S6, and p-P38 proteins in a time-dependent manner, but IL-1β-induced activation of P70S6K and S6 proteins was significantly decreased in the presence of pharmacological inhibitors for ERK1/2 (U0126), MTOR (rapamycin), and P38 (SB203580). Moreover, IL-1β treatment potently increased the abundance of p-ERK1/2 proteins in the nucleus and cytoplasm. Similarly cytoplasmic p-S6 proteins were localized abundantly in the pLE cells treated with IL-1β. Furthermore, IL-1β increased proliferation of pLE cells by approximately 200%, and pretreatment of pLE cells with U0126 significantly inhibited this stimulatory effect. Collectively, results of this study indicate that IL-1β plays an important role in development of uterine LE by stimulating cell proliferation, and that these effects are coordinately regulated by activation of the ERK1/2 and P38 MAPK cell signaling cascades.