Abstract 181: Common Angiogenic Signalling Pathways Induced by Monomeric c-Reactive Protein and FGF-2 Through Phosphatidylinositol 3-kinase

Abstract

Angiogenesis is the process of new blood vessel growth from pre-existing vascular structures. The new vessels from atherosclerotic lesions may be a focus of instability, since they facilitate the infiltration of inflammatory cells and due to their tendency to leak, they may produce haemorrhagic complications. Pentameric C-reactive protein (CRP), a strong marker of inflammation, is a risk factor for cardiovascular diseases with a direct role in the development of atherosclerotic lesions. In hypoxic tissue damage, CRP dissociates irreversibly into monomeric CRP (mCRP), which was previously demonstrated to be pro-angiogenic on bovine aortic endothelial cells (BAEC). Our main study was to examine the vessel forming capability of CRP in the presence of other angiogenic factors known to be present in the micro-environment of unstable plaques with immature vasculature. Here we studied the effects of mCRP in presence or absence of FGF-2 on BAEC proliferation, migration, tube formation in Matrigel and on the vascular remodelling using spheroids, a tri-dimensional system of endothelial cell culture embedded in collagen gel. A significant synergic effect of mCRP combined with FGF-2 was observed in all angiogenesis assays used, compared to the effect of mCRP or FGF-2 alone. Using the spheroids, both mCRP and FGF-2 stimulated the length of sprouts with endothelial cells more dispersed giving an aspect of thin structures. For a better understanding of the molecular mechanisms involved, the signalling pathways were investigated by Western blotting and all the assays were performed in the presence or absence of pharmacological inhibitors of MAPK (PD98059), γ-secretase (DAPT inhibitor) and phosphatidylinositol 3-kinase (PI3K) pathways (LY294002). We showed mCRP-induced endothelial cell proliferation, migration and tube formation required activation of the PI3K pathway. MAPK activation was essential in mCRP-induced cell proliferation and differentiation (tube formation and sprouting from the core of spheroids) and γ-secretase activity was required for mCRP-induced tube formation only. For its pro-angiogenic activity, FGF-2 required all of these key pathways with the exception that γ-secretase activity was not associated with FGF-2-induced cell migration. In all assays including the over-expression of phospho-ERK, the synergistic pro-angiogenic effect of mCRP added to FGF-2 was completely inhibited by LY294002. Thus, mCRP and FGF-2 have a common signalling pathway through PI3K and an eventual deregulation of their pro-angiogenic effects due to an excessive inflammation inducing a hyper-vascularisation which could contribute to formation of unstable plaque with haemorrhagic risk, and therefore, might be prevented by targeting the key proteins of the PI3K pathway.