Pregnancy

Activation of Multiple Signaling Pathways is Critical for Fibroblast Growth Factor 2- and Vascular Endothelial Growth Factor-Stimulated Ovine Fetoplacental Endothelial Cell Proliferation

Abstract
Fibroblast growth factor-2 (FGF2) and vascular endothelial growth factor (VEGF) are two key regulators of placental angiogenesis. The potent vasodilator nitric oxide (NO) could also act as a key mediator of FGF2- and VEGF-induced angiogenesis. However, the postreceptor signaling pathways governing these FGF2- and VEGF- induced placental angiogenic responses are poorly understood. In this study, we assessed the role of endogenous NO, mitogen activated protein kinase 3/1 (MAPK3/1), and v-akt murine thymoma viral oncogene homolog 1 (AKT1) in FGF2- and VEGF-stimulated proliferation of ovine fetoplacental endothelial (OFPAE) cells. Both FGF2- and VEGF time-dependently stimulated (p < 0.05) NO production and activated AKT1. Both FGF2- and VEGF-stimulated cell proliferation was dose-dependently inhibited (p < 0.05) by N^G-monomethyl-L-arginine (L-NMMA; a NO synthase inhibitor), PD98059 (a selective MAPK3/1 kinase 1 and 2 [MAP2K1/2] inhibitor), or LY294002 (a selective phosphatidylinositol 3 kinase [PI3K] inhibitor), but not by phenyl-4,4,5,5 tetramethylimidazoline-1-oxyl 3-oxide (PTIO; a potent extracellular NO scavenger). At the maximal inhibitory dose without cytotoxicity, PD98059 and LY294002 completely inhibited VEGF-, but only partially attenuated (p < 0.05) FGF2-induced cell proliferation. PD98059 and LY294002 also inhibited (p < 0.05) FGF2- and VEGF-induced phosphorylation of MAPK3/1 and AKT1, respectively. L-NMMA did not significantly affect FGF2- and VEGF-induced phosphorylation of either MAPK3/1 or AKT1. Thus, in OFPAE cells, both FGF2- and VEGF-stimulated cell proliferation is partly mediated via NO as an intracellular and downstream signal of MAPK3/1 and AKT1 activation. Moreover, activation of both MAP2K1/2/MAPK3/1 and PI3K/AKT1 pathways is critical for FGF2-stimulated cell proliferation, whereas activation of either one pathway is sufficient for mediating the VEGF-induced maximal cell proliferation, indicating that these two kinase pathways differentially mediate the FGF2- and VEGF-stimulated OFPAE cell proliferation.

Key words: Pregnancy • Growth factors • Kinases • Nitric oxide

This article has been cited by other articles:

				K. Wang, Y. Song, D.-B. Chen, and J. Zheng Protein Phosphatase 3 Differentially Modulates Vascular Endothelial Growth Factor- and Fibroblast Growth Factor 2-Stimulated Cell Proliferation and Signaling in Ovine Fetoplacental Artery Endothelial Cells Biol Reprod, October 1, 2008; 79(4): 704 - 710. [Abstract] [Full Text] [PDF]