Effects of caffeic acid phenethyl ester (CAPE) on membrane potential and intracellular calcium in human endothelial cells

M. Kamil Burgazli, N. Aydogdu, A. Rafiq, M. Mericliler, R. Chasan, A. Erdogan

Department of Internal Medicine, Wuppertal Research and Medical Center, Angiology Wuppertal, Germany. prof.erdogan@gempraxbalserstift.de

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• Pharmacology

BACKGROUNG AND OBJECTIVES: Caffeic acid phenethyl ester (CAPE) is an active component of the resin propolis obtained from beehives. Propolis has a long history of medicinal use and a number of studies have already reported on some of its pharmaceutical properties. This study aimed to explore the effects of CAPE on the cytosolic Ca2+ concentration, cell proliferation, membrane potential and NO levels in human endothelial cells.

MATERIALS AND METHODS: Isolated human umbilical vein endothelial cells (HUVEC) were incubated with CAPE (1-100 µM) at 37°C for 48 hours. Cell proliferation was estimated by counting cell numbers with use of a Neubauer chamber. The effect of CAPE (1-100 µM) on the membrane potential was measured with the fluorescence dye DIBAC4(3) whereas its effect on the cytosolic Ca2+ concentration was measured by use of the fluorescence probe Fluo-3 AM (Invitrogen, Leiden, Netherlands). NO production was assayed using the flourophore DAF~AM (Invitrogen, Leiden, Netherlands). Changes in fluorescence intensity was determined with the GENios plate reader (Genios, Tecan, Austria).

RESULTS: A dose-dependent hyperpolarization of the endothelial cell membrane was observed with CAPE stimulation. The initial increase in the intracellular Ca2+ concentration showed a subsequent decrease over time. CAPE stimulation also resulted in an increase in NO production; however, at higher doses a decrease in NO levels was observed. HUVEC proliferation was inhibited by CAPE.

CONCLUSIONS: Here we report on the effect of CAPE stimulation on the cytosolic Ca2+ concentration, cell proliferation, membrane potential and NO production in HUVEC in a dose-dependent manner. These findings provide important insights into some potential key roles that both calcium and the membrane potential play in the CAPE activation of endothelial cells in a concentration-dependent manner.

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