Common Angiogenic Signaling Pathways Induced by Monomeric C - reactive protein and FGF-2 through MAPK and PI3K

Excessive angiogenesis (i.e. neovascularization) inatherosclerotic lesions, sites of dissociation of theinflammatory biomarker pentameric C-reactive protein(pCRP) into monomeric CRP (mCRP), represents a focus ofplaque instability with haemorrhagic complications. Wepreviously demonstrated mCRP pro-angiogenic effects oncultured aortic endothelial cells. However, mCRP effects incombination with FGF-2, pro-angiogenic factor released byactivated macrophages infiltrating developing lesions, havenot yet been described. Here, we examined in vitro theangiogenic capabilities of mCRP combined with FGF-2 byperforming endothelial cell proliferation, migration, anddifferentiation including tube formation and spheroidsprouting assays. The signaling pathways were alsoinvestigated by Western blotting and all the cell-basedassays were used with or without pharmacologicalinhibitors of mitogen-activated protein kinase (MAPK),phosphatidylinositol-3 kinase (PI3K) and I³-secretase,considered as key regulators of angiogenesis. We showedthat mCRP-induced endothelial cell proliferation andmigration required activation of PI3K pathway. MAPKpathway was essential in mCRP-induced endothelial cellproliferation and spheroid sprouting while I³-secretaseactivity was indispensable for mCRP-induced tube formationonly. MAPK pathway was required in all FGF-2-stimulatedangiogenic assays whereas I³-secretase slightly inhibitedFGF-2 angiogenic effects. PI3K pathway was necessary forFGF-2 angiogenic activities except for cell differentiation. Inmost of the assays, the additive pro-angiogenic effects ofmCRP combined to FGF-2 were mainly attenuated by PI3Kand MAPK inhibitors. Altogether, mCRP and FGF-2 havecommon angiogenic signaling pathways through PI3K andMAPK. Thus, the therapeutic use of PI3K and MAPKinhibitors may inhibit this increased vascularization whilstreducing the haemorrhagic complications from unstableplaques.