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L. Chen, S.S. M. Zhang, J. Tombran–Tink, C.J. Barnstable; PEDF Inhibits VEGF–Induced Cytoprotection of Endothelial Cell via Inhibition of VEGF–R2/KDR Phosphorylation . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3108.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: PEDF is a potent endogenous angiogenesis inhibitor and in many ocular diseases there is reciprocity between levels of PEDF and the pro–angiogenesis factor VEGF. Mechanisms by which PEDF exerts its anti–angiogenic function include impairing proliferation, migration, and permeability of endothelial cells stimulated by VEGF and downregulating expression of VEGF receptor RNA. This study examined the mechanism by which PEDF blocks the cytoprotective action of VEGF on human endothelial cells. Methods: Human umbilical vein endothelial cells (HUVECs) were cultured under serum deprived conditions. Cell viability, proliferation, and apoptosis assays were used to investigate the function of PEDF and VEGF. Immunoprecipitation, western blotting and PI–3 kinase assays were used to understand the molecular mechanism of PEDF action. Results: HUVEC survival depends on the relative concentrations of VEGF and PEDF. When the concentration of PEDF is above 100ng/ml, and VEGF is below 20ng/ml, the cytoprotection of VEGF is abrogated; when PEDF is below 100ng/ml, and VEGF is above 20ng/ml, the cytoprotection of VEGF predominates. The protection of VEGF is not associated with proliferation. The blocking of the cytoprotection of VEGF by PEDF is caspase dependent. PEDF induced apoptosis of HUVECs was predominantly mediated through the p38 MAPK pathway as it was blocked by an inhibitor of p38 MAPK (SB203580). PEDF inhibited the activation of phosphatidylinositol 3–kinase/Akt pathway in a dose–dependent pattern. The inhibition of PI–3K/ Akt activation correlates with a PEDF–mediated decrease in VEGF–R2/KDR phopshorylation induced by VEGF. Conclusions: PEDF can impair the cytoprotection of VEGF by inhibiting the PI–3K/Akt pathway and promoting the activation of p38 MAPK. This action of PEDF may be initiated at the VEGF receptor where it antagonizes the action of VEGF. These results lend further support to the idea of a special relationship between PEDF and VEGF and to the value of exploring the use of PEDF and its analogues for therapeutic inhibition of neovascular disease.
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