Prostaglandin E2 Regulates Angiogenesis via Activation of Fibroblast Growth Factor Receptor-1

Federica Finetti,Raffaella Solito,Lucia Morbidelli,Antonio Giachetti,Marina Ziche,Sandra Donnini

doi:10.1074/jbc.m703090200

Abstract

Prostaglandin E(2) (PGE(2)) behaves as a mitogen in epithelial tumor cells as well as in many other cell types. We investigated the actions of PGE(2) on microvascular endothelial cells (capillary venular endothelial cells) with the purpose of delineating the signaling pathway leading to the acquisition of the angiogenic phenotype and to new vessel formation. PGE(2) (100 nM) produced activation of the fibroblast growth factor receptor 1 (FGFR-1), as measured by its phosphorylation, but not of vascular endothelial growth factor receptor 2. PGE(2) stimulated the EP3 subtype receptor, as deduced by abrogation of EP3 Galpha(i) subunit activity through pertussis toxin. Consistent with this result, in human umbilical venular endothelial cells missing the EP3 receptor, PGE(2) did not phosphorylate FGFR-1. Upon binding to its receptor, PGE(2) initiated an autocrine/paracrine signaling cascade involving the intracellular activation of c-Src, activation of matrix metalloproteinase (predominantly MMP2), which in turn caused the mobilization of membrane-anchored fibroblast growth factor-2 (FGF-2). In fact, in cells unable to release FGF-2 the transfection with both FGFR-1 and EP3 did not result in FGFR-1 phosphorylation in response to PGE(2). Relevance for the FGF2-FGFR-1 system was highlighted by confocal analysis, showing receptor internalization after cell exposure to the prostanoid. ERK1/2 appeared to be the distal signal involved, its phosphorylation being sensitive to either cSrc inhibitor or FGFR-1 blocker. Finally, PGE(2) stimulated cell migration and capillary formation in aortic rings, which were severely reduced by inhibitors of signaling molecules or by receptor antagonist. In conclusion, this study provides evidence for the involvement of FGFR-1 through FGF2 in eliciting PGE(2) angiogenic responses. This signaling pattern is similar to the autocrine-paracrine mechanism which operates in endothelial cells to support neovascular growth.

Highlights

A wealth of experimental studies has delineated the molecular mechanisms utilized by Prostaglandin E2 (PGE2) to induce tumor proliferation
In this work we have investigated the action of PGE2 on microvascular endothelial cells examining both their functional properties relevant for angiogenesis and signals involved in producing the angiogenic phenotype, such as activation of ERK1/2 and of the growth factor receptor, fibroblast growth factor receptor 1 (FGFR-1)
In light of these results we wondered whether PGE2 activity might involve canonical pathways of angiogenesis such as those elicited by the fibroblast growth factor-2 (FGF-2) or the vascular endothelial growth factors (VEGF)

Summary

Introduction

A wealth of experimental studies has delineated the molecular mechanisms utilized by PGE2 to induce tumor proliferation. Experimental evidence shows that the overexpression of cyclooxygenase-2, which characterizes many epithelial tumors as well as their endothelial population, is accompanied by enhanced expression and production of angiogenic factors such as vascular endothelial growth factors (VEGF), fibroblast growth factor-2 (FGF-2), hypoxia-inducible factor-1, matrix-degrading enzymes (e.g. matrix metalloproteinases (MMPs)), vascular remodeling ligands (i.e. angiopoietins), and adhesion receptors of the integrin families (9 –15). It appears that in experimental breast tumors, characterized by high output of PGE2 through forced expression of cyclooxygenase-2, angiogenesis proceeds tumor development [16]. The functional and molecular mechanisms necessary for PGE2-induced angiogenesis are not completely understood

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