Margatoxin inhibits VEGF-induced hyperpolarization, proliferation and nitric oxide production of human endothelial cells

Ali Erdogan, Justus Liebig University of Giessen, Germany.
Christian Alexander Schaefer, Justus Liebig University of Giessen, Germany.
Matthias Schaefer, Justus Liebig University of Giessen, Germany.
Doerte Wiebke Luedders, Justus Liebig University of Giessen, Germany.
Florian Stockhausen, Justus Liebig University of Giessen, Germany.
Yaser Abdallah, Aga Khan University

This work was published before the author joined Aga Khan University.



Vascular endothelial growth factor (VEGF) induces proliferation of endothelial cells (EC) in vitro and angiogenesis in vivo. Furthermore, a role of VEGF in K(+) channel, nitric oxide (NO) and Ca(2+) signaling was reported. We examined whether the K(+) channel blocker margatoxin (MTX) influences VEGF-induced signaling in human EC.


Fluorescence imaging was used to analyze changes in the membrane potential (DiBAC), intracellular Ca(2+) (FURA-2) and NO (DAF) levels in cultured human EC derived from human umbilical vein EC (HUVEC). Proliferation of HUVEC was examined by cell counts (CC) and [(3)H]-thymidine incorporation (TI).


VEGF (5--50 ng/ml) caused a dose-dependent hyperpolarization of EC, with a maximum at 30 ng/ml (n=30, p<0.05). This effect was completely blocked by MTX (5 micromol/l). VEGF caused an increase in transmembrane Ca(2+) influx (n=30, p<0.05) that was sensitive to MTX and the blocker of transmembrane Ca(2+) entry 2-aminoethoxydiphenyl borate (APB, 100 micromol/l). VEGF-induced NO production was significantly reduced by MTX, APB and a reduction in extracellular Ca(2+) (n=30, p<0.05). HUVEC proliferation, examined by CC and TI, was significantly increased by VEGF and inhibited by MTX (CC: -58%, TI --121%); APB (CC --99%, TI--187%); N-monomethyl-L-arginine (300 micromol/l: CC: -86%, TI --164%).


VEGF caused an MTX-sensitive hyperpolarization which results in an increased transmembrane Ca(2+) entry that is responsible for the effects on endothelial proliferation and NO production.