title: Polyphenols enhance platelet nitric oxide by inhibiting protein kinase C-dependent NADPH oxidase activation: effect on platelet recruitment.
abstract: Several studies demonstrated an inverse association between polyphenol intake and cardiovascular events. Platelet recruitment is an important phase of platelet activation at the site of vascular injury, but it has never been investigated whether polyphenols influence platelet recruitment. The aim of the study was to analyze in vitro whether two polyphenols, quercetin and catechin, were able to affect platelet recruitment. Platelet recruitment was reduced by NO donors and by NADPH oxidase inhibitors and was enhanced by L-NAME, an inhibitor of NO synthase. Quercetin and catechin, but not single polyphenol, significantly inhibited platelet recruitment in a concentration-dependent fashion. The formation of superoxide anion was significantly inhibited in platelets incubated with quercetin and catechin but was unaffected by a single polyphenol. Incubation of platelets with quercetin and catechin resulted in inhibition of PKC and NADPH oxidase activation. Treatment of platelets with quercetin and catechin resulted in an increase of NO and also down-regulated the expression of GpIIb/IIIa glycoprotein. This study shows that the polyphenols quercetin and catechin synergistically act in reducing platelet recruitment via inhibition of PKC-dependent NADPH oxidase activation. This effect, resulting in NO-mediated platelet glycoprotein GpIIb/IIIa down-regulation, could provide a novel mechanism through which polyphenols reduce cardiovascular disease.
authors.affiliation: Divisione IV Clinica Medica, Dipartimento di Medicina Interna, Università di Roma Tor Vergata, Rome, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Pignatelli
authors.forename: S
authors.initials: S
authors.lastname: Di Santo
authors.forename: B
authors.initials: B
authors.lastname: Buchetti
authors.forename: V
authors.initials: V
authors.lastname: Sanguigni
authors.forename: A
authors.initials: A
authors.lastname: Brunelli
authors.forename: F
authors.initials: F
authors.lastname: Violi
mesh_terms: D000328:Adult; D000975:Antioxidants / Q000494:pharmacology*; D001792:Blood Platelets / Q000187:drug effects* / Q000201:enzymology; D002392:Catechin / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005419:Flavonoids / Q000494:pharmacology*; D006801:Humans; D008297:Male; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D018384:Oxidative Stress; D010636:Phenols / Q000494:pharmacology*; D010974:Platelet Aggregation / Q000187:drug effects*; D059808:Polyphenols; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011794:Quercetin / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism
chemical_list: D000975:Antioxidants; D004791:Enzyme Inhibitors; D005419:Flavonoids; D020030:Nitric Oxide Donors; D010636:Phenols; D059808:Polyphenols; D013481:Superoxides; D009569:Nitric Oxide; D002392:Catechin; D011794:Quercetin; D019255:NADPH Oxidases; D011493:Protein Kinase C; D019331:NG-Nitroarginine Methyl Ester