Role of Mitogen-Activated Protein Kinase in Prostaglandin F_2αAction in Human Granulosa-Luteal Cells¹

Abstract

In the ovary it has been demonstrated that PGF(2alpha) activates the phospholipase C (PLC)/diacylglycerol/protein kinase C pathway. However, little is known about the downstream signaling events that mediate subsequent cellular responses such as steroidogenesis. The present study was designed to examine the effect of PGF(2alpha) on activation of the mitogen-activated protein kinase (MAPK) signaling pathway and its physiological role in human granulosa-luteal cells (hGLCs). Human GLCs, obtained from women undergoing in vitro fertilization-embryo transfer, were treated with increasing concentrations of PGF(2alpha) (10 nmol/L to 10 micromol/L) for 5 min. For time-course experiments, hGLCs were treated with 1 micromol/L PGF(2alpha) for 1, 5, 10, or 20 min. Western blot analysis, using a monoclonal antibody that detected the phosphorylated forms of extracellular signal-regulated kinases 1 and 2 (p42(mapk) and p44(mapk), respectively), demonstrated that PGF(2alpha) activated MAPK in hGLCs in a dose- and time-dependent manner. Treatment of the cells with neomycin (10 mmol/L; a PLC inhibitor), bisindolylmaleimide I (5 micromol/L; a PKC inhibitor), or PD98059 (50 micromol/L; a MEK inhibitor and a MAPK kinase inhibitor) significantly attenuated the PGF(2alpha)-induced activation of MAPK. In contrast, MAPK activation was not significantly affected by pertussis toxin (200 ng/mL; a G(i) inhibitor) pretreatment. To determine the role of MAPK in steroidogenesis, hGLCs were treated with PGF(2alpha) (1 micromol/L), hCG (1 IU/mL), or PGF(2alpha) plus hCG in the presence or absence of PD98059. Progesterone levels in the culture medium were examined by RIA. Treatment of hGLCs with PGF(2alpha) significantly inhibited hCG-induced progesterone production. The presence of the MEK inhibitor, PD98059, reversed the inhibitory effect of PGF(2alpha) on hCG-induced progesterone production. To our knowledge, it is the first demonstration of PGF(2alpha)-induced activation of the MAPK signaling pathway in the human ovary. These results indicated that PGF(2alpha) activated MAPK subsequent to PLC and PKC activation through pertussis toxin-insensitive G protein in hGLCs. Further, we demonstrated that PGF(2alpha)-induced MAPK activation is associated with modulation of progesterone production. These results support the idea that the MAPK signaling pathway is involved in mediating PGF(2alpha) actions in the human ovary.

Phospholipase C inhibits apoptosis of porcine primary granulosa cells cultured in vitro

“…The activation of PLC β could increase intracellular Ca 2+ [38], which is in line with this study that PLC activator increased the intracellular Ca 2+ concentration and PLC inhibitor decreased the intracellular Ca 2+ concentration. The PKC activator PLC could be activated by prostaglandin f (2alpha) in the ovary [39]. It was reported that the Wnt/Ca 2+ signaling pathway could reduce cisplatin resistance, and CaMKII might be an underlying therapeutic target in chemoresistant ovarian cancers [40].…”

The effects of phospholipase C on oestradiol and progesterone secretion in porcine granulosa cells cultured in vitro

“…As for the regulation of PLC at the hormone level, scientific reports have shown that parathyroid hormone (PTH) could promote fracture healing and callus hardness in ovariectomized mice by increasing callus formation and reconstructing trabecular bone via a PLC‐independent pathway (Li, Yu, Huang, & Pang, ), and the activity of diapause hormone could be mediated through the Gαq‐PLC‐PKC cascade (Jiang et al, ). The binding of PGF2α to its receptor coupled to a PTX‐insensitive G protein could subsequently lead to PLC, PKC and MAPK activation (Tai, Kang, Choi, Tzeng, & Leung, ).…”