Abstract
Abstract: :
Purpose: To investigate the expression and signaling of ephrin B2 in human retinal endothelial cells. Methods: Human retinal endothelial cells were stimulated with an Eph B4/Fc chimera and probed for members of the phosphatidylinositol-3-kinase (PI3K), Src and mitogen activated protein kinase (MAPK) pathways. Endothelial cell proliferation and migration were also investigated after Eph B4/Fc stimulation in the presence of various pathway inhibitors. Results: Human retinal endothelial cells express ephrin B2, with little expression of Eph B4. Treatment of these cells with EphB4/Fc chimera resulted in phosphorylation of PI3K, Src, and extracellular signal-regulated kinase (ERK1/2) of the MAPK pathway. Intracellular calcium was not altered by Eph B4/Fc administration. Eph B4-stimulated endothelial cell proliferation was mediated via the PI3K pathway, with subsequent activation of nitric oxide synthase and ERK1/2. Src was not involved in retinal endothelial cell proliferation. Blockade of the Src-PI3K pathways produced significant attenuation of Eph B4/Fc-stimulated invasion. Conclusions: These results demonstrate for the first time that ephrin B2 is present in human retinal endothelial cells. Additionally, it appears that vascular growth may be modulated in the retina through activation of the PI3K pathway and its downstream components since LY294002, the PI3K inhibitor, in the presence of Eph B4/Fc prevented both proliferation and migration. This information suggests that inhibition of ephrin B2 activation or modulation of PI3K signaling may prove a novel treatment for disease involving retinal angiogenesis.
Keywords: growth factors/growth factor receptors • neovascularization • signal transduction: pharmacology/physiology