Red grape extracts protective effects on endothelial progenitor cells function and improvement of their polyphenols bioavaibility.

Purpose: Maintenance of endothelial integrity and function are greatly affected by circulating endothelial progenitor cells (EPC) number and functional activities. Compounds that can prevent or ameliorate EPC dysfunction are of special clinical interest. Grapes are receiving growing attention as material for potential drug formulation due to the high polyphenolic content. However, polyphenols positive health effects strongly depend on their bioavailability. Aim of this work was to evaluate the ability of grape skin and seeds to protect EPC from oxidative stress induced by hyperglycaemia (HG) compared to red wine and to enhance polyphenols absorption across the intestinal epithelium. Methods: human EPCs were cultured from peripheral blood and characterized by the presence of double positive cells for DiI-Ac-LDL uptake and lectin binding and by expression of cell surface markers. Dry extracts from fresh vegetal material and red wine were obtained by Sangiovese grape variety (doc-Montecucco, Italy). Total polyphenols were determined using the Folin–Ciocalteau micro method. EPCs were incubated with different concentration of total polyphenols content (5 µg, 50 µg, 150 µg) of grape skin, seed and red wine. Cell viability, migration and reactive oxygen species (ROS) production were assayed using the tetrazolium salt reduction (WST-1) assay, modified Boyden chamber assay and with a fluorescent probe CM-H2DCFDA, respectively. Intestinal red grape polyphenols permeation were tested by Ussing-type chamber in the absence or presence of 1% (w/v) of the quaternary ammonium-chitosan conjugates polymer (N+(60)-Ch). Results: grape skin, seed and red wine all increased EPC proliferation, adhesion and migration in a dose-dependent manner, preventing the HG effect (p<0.01). Moreover, the effect of grape skin and seed was comparable to red wine. However, ROS production resulted significantly reduced only by grape seed and red wine (p<0.05). Finally, N+(60)-Ch is an effective enhancer of polyphenols permeability across the excised rat intestine. Conclusions: These data suggest that red grape seed significantly improve EPC dysfunction induced by hyperglycaemia; the use of chitosan derivate protect polyphenols from enzymatic degradation and guarantee their bioavailability. These results might have the potential for innovative therapeutic systems in diabetes and oxidative stress related-cardiovascular disease.