Cocoa and wine polyphenols modulate platelet activation and function

There is speculation that dietary polyphenols can provide cardioprotective effects due to direct antioxidant or antithrombotic mechanisms. We report i n vitro and postingestion ex vivo effects of cocoa procyanidins, a procyani din-rich cocoa beverage and dealcoholized red wine (DRW) on human platelet activation. In a series of in vitro studies, cocoa procyanidin trimers, pen tamers or DRW (3 and 10 mu mol/L) were incubated with citrated peripheral w hole blood in the presence and absence of platelet agonists. Platelet activ ation was detected using fluorescent-labeled monoclonal antibodies recogniz ing the fibrinogen binding conformation of GPIIb-IIIa (referred to herein a s PAC-1 binding) and the activation-dependent platelet epitope CD62P (P-sel ectin). The percentage of CD42a-positive platelets coexpressing PAC-1 bindi ng and/or CD62P was determined by multiparameter flow cytometry. Procyanidi n trimers, pentamers and DRW added to whole blood in vitro increased PAC-1 binding and P-selectin expression. In contrast, procyanidin trimers, pentam ers and DRW inhibited the platelet activation in response to epinephrine. T he effects on platelet activation of cocoa beverage and DRW consumption wer e also studied in healthy subjects. Citrated blood was obtained before and 2 and 6 h after the ingestion of a cocoa beverage, a caffeine-containing be verage, DRW or water. Platelet activation was measured by flow cytometry. T he consumption of DRW did not affect the expression of activation-dependent platelet antigens, either unstimulated or after ex vivo activation with ep inephrine. However, the consumption of DRW increased PAC-I binding in respo nse to 100 mu mol/L ADP ex vivo. Cocoa consumption reduced platelet respons e to agonists ex vivo. The ingestion of water had no effect on platelet act ivation, whereas a caffeine-containing beverage augmented the response of p latelets to epinephrine. In summary, select cocoa procyanidins and DRW adde d to whole blood in vitro increased expression of platelet activation marke rs in unstimulated platelets but suppressed the platelet activation respons e to epinephrine. In contrast, cocoa consumption suppressed unstimulated an d stimulated platelet activation in whole blood. This suppressive effect ob served on platelet reactivity may explain in part the reported cardioprotec tive effects of dietary polyphenols.