Summary
Sulforaphane, a dietary isothiocyanate found in cruciferous vegetables, has been shown
to exert beneficial effects in animal models of cardiovascular diseases. However,
its effect on platelet aggregation, which is a critical factor in arterial thrombosis,
is still unclear. In the present study, we show that sulforaphane inhibited human
platelet aggregation caused by different receptor agonists, including collagen, U46619
(a thromboxane A2 mimic), protease-activated receptor 1 agonist peptide (PAR1-AP), and an ADP P2Y12 receptor agonist. Moreover, sulforaphane significantly reduced thrombus formation
on a collagen-coated surface under whole blood flow conditions. In exploring the underlying
mechanism, we found that sulforaphane specifically prevented phosphatidylinositol
3-kinase (PI3K)/Akt signalling, without markedly affecting other signlaling pathways
involved in platelet aggregation, such as protein kinase C activation, calcium mobilisation,
and protein tyrosine phosphorylation. Although sulforaphane did not directly inhibit
the catalytic activity of PI3K, it caused ubiquitination of the regulatory p85 subunit
of PI3K, and prevented PI3K translocation to membranes. In addition, sulforaphane
caused ubiquitination and degradation of phosphoinositide-dependent kinase 1 (PDK1),
which is required for Akt activation. Therefore, sulforaphane is able to inhibit the
PI3K/Akt pathway at two distinct sites. In conclusion, we have demonstrated that sulforaphane
prevented platelet aggregation and reduced thrombus formation in flow conditions;
our data also support that the inhibition of the PI3K/Akt pathway by sulforaphane
contributes it antiplatelet effects.
Keywords
Platelet aggregation - sulforaphane - phosphatidylinositol 3-kinase - ubiquitination