Abstract
The aim of the present study was to evaluate whether blackcurrant leaf extract (BLE) modulates endothelium antithrombotic function, namely increases the expression/activity of ADPase (CD39) and augments the production of nitric oxide in human umbilical vein endothelial cells (HUVEC). It was found that BLE with proanthocyanidins (60 % of the total polyphenol content) increased the CD39-positive endothelial cell fraction (up to 10 % for 2.5 μg/ml, and up to 33 % for 15 μg/ml, p < 0.05 or less) in a concentration-dependent manner, and enhanced endothelial nitric oxide synthase (eNOS) activation (T495 phosphorylation decreased by 31 ± 6 % for 2.5 μg/ml and 48 ± 6 % for 15 μg/ml; S1177 phosphorylation increased by 13 ± 3 % for 2.5 μg/ml and 18 ± 7 % for 15 μg/ml, compared to untreated cells, p < 0.05 or less). Additionally, incubation for 24 or 48 h with BLE at a lower range of polyphenol concentrations, significantly increased cell viability with a maximal effect at 2.5 μg/ml (viability increased by 24.8 ± 1.0 % for 24 h and by 32.5 ± 2.7 % for 48-h time incubation, p < 0.0001). The increased CD39 expression and the increased eNOS activation in HUVEC can be regarded as the beneficial markers of the improvement of antiplatelet action of endothelial cells. Unexpectedly, these assumptions were not confirmed in the experimental model of platelet-endothelial cell interactions. These observations lead to the conclusion that BLE may improve endothelial cell viability at low physiological concentrations without affecting the antiplatelet action of endothelium.
Highlights
The endothelium mediates a number of responses of arteries and veins from animals and humans, but the special role of endothelial cells is the regulation of blood platelet functions
The results demonstrated that blackcurrant extract rich in proanthocyanidins, used at a concentration of 2.5 to 15 μg/ml, increased the CD39positive cell fraction and enhanced endothelial nitric oxide synthase (eNOS) activation by increasing serine 1177 (S1177) phosphorylation and decreasing threonine 495 (T495) phosphorylation in the eNOS molecule
The results showed that flavanols were the most common phenolic compounds, representing 68 % of the total polyphenols present in extract and that proanthocyanidins accounted for almost 90 % of total flavanol content
Summary
The endothelium mediates a number of responses (relaxation or contraction) of arteries and veins from animals and humans, but the special role of endothelial cells is the regulation of blood platelet functions. In general, appear to be designed to adhere to the vessel wall only when endothelial integrity is disrupted and several mechanisms, such as the secretion of nitric oxide (NO) and prostacyclin, evolved to prevent their adhesion to the intact endothelium. Both mediators are potent inhibitors of platelet adhesion and activation. Under conditions of disrupted homeostasis such as those found in inflammatory states, platelets can even bind to the intact endothelium This is partly because endothelium-dependent mechanisms of platelet inhibition are impaired, and partly because new adhesion molecules are expressed on the surface of activated endothelial cells. Vascular protection may be due to the direct action of polyphenols on the endothelial function [24]
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