PB0826 - Broccoli sulforaphane potentiates prostaglandins on preventing human platelet aggregation

Background: Sulforaphane, an isothiocyanate found in broccoli and other cruciferous vegetables, has been shown to exert beneficial effects in animal thrombosis models. Epidemiological studies have revealed dietary intake of broccoli is associated with reduced risk of coronary heart disease mortality. In a previous study (Thromb Haemost. 2013;109:1120-30), we have demonstrated that sulforaphane prevented human platelet aggregation caused by various activators and reduced thrombus formation on a collagen-coated surface under whole blood flow conditions. However, it is unclear if sulforaphane can exert its antiplatelet effect through the interaction with prostaglandin I2 (PGI2), which is the endogenous antiplatelet substance released from vascular endothelial cells.

Aims: In the present study, the enhancement of antiplatelet effects of prostaglandins PGI2 and PGE1 by sulforaphane as well as the underlying mechanisms were investigated.

Methods: Platelet aggregation was measured by using light transmission aggregometry. The contents of platelet cyclic nucleotides were determined by using ELISA assay. Western blotting and Fura-2 fluorescence were applied for measuring the activation of signaling molecules and cytosolic Ca2+ mobilization respectively.

Results: Sulforaphane enhanced a PGI2 analog (iloprost) and PGE1 to inhibit platelet aggregation caused by protease activated receptor-1 (PAR1) agonist and thromboxane A2 receptor agonist (U46619). Sulforaphane did not enhance the increase in platelet cAMP levels by PGE1. Furthermore, the protein kinase A (PKA) inhibitor H89 did not reverse the inhibition of platelet aggregation caused by sulforaphane plus PGE1. Therefore, the enhancement of antiplatelet activity of PGE1 by sulforaphane is not mainly related to the cAMP/PKA pathway. Investigation of the signaling pathways involved in platelet activation revealed that sulforaphane enhanced PGE1 to inhibit the activation of phosphoinositide-3 kinase (PI3K)/Akt pathway, but not PKC/Ca2+ pathway, caused by PAR1 agonist.

Conclusion(s): Our results suggest that sulforaphane enhances the antiplatelet effect of prostaglandins that may be mediated through inhibition of PI3K/Akt pathway.