Effect of anthocyanins and their microbiota metabolites on monocyte adhesion to endothelial cells at physiologically relevant concentrations

Epidemiological studies suggest a protective role of dietary anthocyanins, micronutrients present mainly in berries, against cardiovascular diseases. Clinical and pre-clinical studies showed effects on improvements in endothelial function, modulation of inflammation or decreased atherosclerosis development. However, the underlying cellular and molecular mechanisms still remain unknown. The aim of the present study was to investigate the effect of anthocyanins and their gut metabolites identified in plasma on monocyte adhesion to TNFα-stimulated endothelial cells, the initial step of atherosclerosis development. Human umbilical vein endothelial cells (HUVECs) were exposed to cyanidin-3-O-glucoside, cyanidin-3-O-galactoside, cyanidin-3-O-arabinoside, delphinidin-3-O-glucoside, peonidin-3-O-glucoside and 4-hydroxybenzaldehyde for 3 hours and to protocatechuic, ferulic, hippuric and vanillic acid for 18h at physiologically-relevant concentrations, all at 0.1μM, 0.2μM, 0.5μM, 1μM and 2μM. Subsequently, HUVECs were stimulated with TNFα (1ng/ml) for 4 hours followed by 15 minutes incubation with monocytes. Monocytes adhesion to HUVECs was determined using the flow cytometry. This study showed that exposure of HUVECs to cyanidin-3-O-galactoside, cyanidin-3-O-arabinoside, delphinidin-3-O-glucoside and peonidin-3-O-glucoside significantly attenuated monocyte adhesion at 0.1μM by 27.4% in average. Ferulic acid decreased adhesion at 1μM and 2μM by 28.5%, hippuric at 2μM by 18.1% and protocatechuic by 36.5% at all concentrations. Exposure of HUVECs to mixture of compounds used in 3-hour exposure period, resulted in adhesion decrease by 28.3%. In conclusion, this study showed the biological potency of plasma anthocyanins and their gut metabolites to modulate the adhesion of monocyte to endothelial cells at physiologically-relevant concentrations. The further investigation using nutrigenomics approaches is needed to decipher underlying molecular mechanisms of actio