Molecular mechanisms mediating anti-angiogenic action of the urokinase receptor-derived peptide UPARANT in human retinal endothelial cells

PURPOSE. To investigate the molecular mechanisms of the anti-angiogenic activity of UPARANT, an antagonist of the urokinase-type plasminogen activator receptor (uPAR), on primary human retinal endothelial cells (HREC) as a model of in vitro angiogenesis.METHODS. The anti-angiogenic activity of UPARANT was evaluated on endothelial cell migration, invasion and tube formation. HREC were further analyzed for viability, trans-endothelial electrical resistance (TEER) and tight junction (TJ) expression at the protein and mRNA levels. VEGF-related signaling molecules were also analyzed by western and northern blots. RESULTS. UPARANT inhibited in a dose-dependent fashion HREC motility, invasion and tube formation stimulated by VEGF-A, in a range of doses (1 to 100 nM) that had no effect on cell viability and proliferation. UPARANT also prevented the loss of permeability induced by VEGF-A, restoring normal TEER values and TJ protein expression. At the molecular level, UPARANT inhibited VEGFR-2 and STAT3 phosphorylation, thus decreasing VEGF and HIF-1 expression, finally resulting in decreased activation of MEK/ERK, JNK, p38 and AKT signaling proteins.CONCLUSIONS. These findings indicate that UPARANT exerts its anti-angiogenic effects through the inhibition of the downstream signaling activated by angiogenic factors such as VEGF-A.