Antiplatelet activity of chrysin via inhibiting platelet αIIbβ3-mediated signaling pathway

Scope: Propolis is thought to help prevent thrombotic and related cardiovascular diseases in humans. Chrysin, a bioflavonoids compound found in high levels in propolis and in honey, has been reported to possess antiplatelet activity. However, the mechanism by which it inhibits platelet function is unclear. Methods and results: The effects of chrysin on agonist-activated platelet-aggregation, granule-secretion, and integrin alpha IIb beta 3 activation were examined. Its effects on the phosphorylation of Akt, GSK3 beta, MAPKs, and several proteins of the glycoprotein VI (GPVI) signaling pathway were also studied on collaged-activated platelets. In addition, human platelet spreading on immobilized fibrinogen was also tested. We found that chrysin dose dependently inhibited platelet aggregation and granule secretion induced by collagen, as well as platelet aggregation induced by ADP, thrombin, and U46619. Chrysin also markedly reduced the number of adherent platelets and the single platelet spreading area on immobilized fibrinogen. Biochemical analysis revealed that chrysin inhibited collagen-induced activation of Syk, PLC gamma 2, PKC, as well as the phosphorylation of Akt and ERK1/2. Additionally, chrysin attenuated phosphorylation of molecules such as Fc gamma RIIa, FAK, Akt, and GSK3 beta in platelet spreading on immobilized fibrinogen. Conclusions: Our findings indicate that chrysin suppresses not only integrin alpha IIb beta 3-mediated inside-out signaling, but also the outside-in signal transmission. This implies that chrysin may represent a potential candidate for an antiplatelet agent.