NOX2-mediated arterial dysfunction in smokers: acute effect of dark chocolate

Background Cocoa seems to exert artery dilatation via oxidative stress inhibition but the mechanism is still unclear. Objectives To investigate whether in smokers, dark chocolate elicits artery dilatation via down-regulation of NOX2, the catalytic core of NADPH oxidase. Methods Flow-mediated dilatation (FMD), oxidative stress (as assessed by urinary isoprostanes excretion), nitric oxide generation (as assessed by serum levels of nitrite/nitrate (NOx)), NOX2 activity (as assessed by blood levels of soluble NOX2 derived peptide (sNOX2-dp)) and serum epicatechin were studied in 20 smokers and 20 healthy subjects (HS) in a crossover, single-blind study. Patients were randomly allocated to 40 g dark chocolate (>85% cocoa) or 40 g of milk chocolate (<= 35% cocoa). FMD, urinary isoprostanes, NOx and sNOX2-dp were assessed at baseline and 2 h after chocolate ingestion. Results Smokers had lower FMD and NOx and higher sNOX2-dp compared to HS. After dark chocolate intake, urinary isoprostanes and sNOX2-dp significantly decreased and FMD and NOx significantly increased in smokers but not in HS. No changes of the above variables were observed after milk chocolate intake. Multiple linear regression analysis showed that in smokers the only independent predictive variable associated with a change in FMD was a change in sNOX2-dp. Serum epicatechin increased in either group only after dark chocolate intake, reaching values higher than 0.1 mu M. Platelets from smokers (n=5), but not from HS (n=5), showed lower p47(phox) translocation to platelet membrane and higher NOx when incubated with 0.1-10 mu M epicatechin. Conclusion Results suggest that in smokers, cocoa enhances artery dilatation by lowering of NOX2 activation.