Background  : Dark chocolate is reported to decrease platelet activation but the underlying mechanism is still undefined. Dark chocolate is rich of polyphenols that could exert an antiplatelet action via inhibition of oxidative stress. Aim of the study was to assess if dark chocolate inhibits platelet reactive oxidant species (ROS) formation and platelet activation.Methods  : Twenty healthy subjects (HS) and 20 smokers were randomly allocated to receive 40 g of dark (cocoa >85%) or milk chocolate (cocoa <35%) in a cross-over, single blind study. There was an interval of 7 days between the two phases of the study. At baseline and 2 hours after chocolate ingestion platelet recruitment (PR), platelet ROS,  platelet isoprostane 8-ISO-prostaglandin F2a (8-iso-PGF2a), Thromboxane (TxA2) and   platelet activation of NOX2, the catalytic sub-unit of NADPH oxidase, and serum epicatechin  were measured.Results:  Compared to HS, smokers showed enhanced PR, platelet formation of ROS and eicosanoids and NOX2 activation. After dark chocolate platelet ROS (-48%, p<0.001), 8-iso-PGF2a (-10%, p<0.001) and NOX2 activation (-22%, p<0.001) significantly decreased; dark chocolate did not affect platelet variables in HS. No effect of milk chocolate was detected in both groups. Serum epicatechin increased after dark chocolate in HS (from 0.454+/-0.3nanoM to 118.3+/-53.7nanoM) and smokers (from 0.5+/-0.28 nanoM to 120.9+/-54.2 nanoM). Platelet incubation with 0.1-10microM catechin significantly reduced PR, platelet 8-iso-PGF2a and ROS formation and NOX2 activation only in platelets from smokers.Conclusions  : Dark chocolate inhibits platelet function by lowering oxidative stress only in smokers; this effect  seems to be dependent on its  polyphenolic content.

Dark chocolate inhibits platelet isoprostanes via nox2 down-regulation in smokers

243rd National Meeting (2012)

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