Identification of membrane calcium channels essential for cytoplasmic and nuclear calcium elevations induced by vascular endothelial growth factor inhuman endothelial cells

Vascular endothelial growth factor (VEGF) is mitogenic for endothelial cell s and has been shown to induce angiogenesis and endothelial cell migration through stimulation of endothelial tyrosine-kinase receptors. Here, using c onfocal. microscopy and the patch-damp technique on endothelial cells, memb rane permeability to calcium as wen as cytoplasmic and nuclear free calcium levels have been investigated in the first stages of tyrosine-kinase recep tor activation by VEGF. VEGF (0.5 nM) as well, as inositol trisphosphate (I P3) induced an activation of membrane calcium-permeable channels exhibiting a similar low conductance in the range of 10 pS. The VEGF-triggered activa tion of these calcium channels, mediated by IP3 and involving the intracell ular calcium stores, results in an increase in both cytoplasmic and nuclear calcium levels in endothelial. cells, potentially modulating gene expressi on. Finally, the effect of Ni2+, a calcium channel blocker, on endothelial cell proliferation has been studied. The results show that inhibition of ex tracellular calcium influx significantly inhibits VEGF-induced cell prolife ration. In the process of cell stimulation by VEGF, and possibly by other g rowth factors, activation of calcium channels could then be a key step in c alcium-regulated gene expression and cell activation. These results suggest that the use of calcium channel blockers could be a novel way of preventio n or reversion of VEGF-induced tumoral angiogenesis.