Inhibitory Effects of Water Extract from Rice Bran Due to cAMP-dependent Phosphorylation of VASP () on ADP-induced Platelet Aggregation

In this study, we investigated the effect of water extract from rice bran (RB) on ADP ($20{\mu}M$)-stimulated platelet aggregation. RB dose-dependently inhibited ADP-induced platelet aggregation, and its $IC_{50}$ value was $224.0{\mu}g/mL$, which was increased by adenylate cyclase inhibitor SQ22536 and cAMP-dependent protein kinase (A-kinase) inhibitor Rp-8-Br-cAMPS. RB elevated the phosphorylation of VASP ($Ser^{157}$) which was also inhibited by SQ22536 and Rp-8-Br-cAMPS. It is thought that RB-elevated cAMP contributed to the phosphorylation of VASP ($Ser^{157}$) to inhibit ADP-induced platelet aggregation. Therefore, we demonstrate that RB has an antiplatelet effect via cAMP-dependent phosphorylation of VASP ($Ser^{157}$), and RB may have preventive or therapeutic potential for platelet aggregation-mediated diseases, such as thrombosis, myocardial infarction, atherosclerosis, and ischemic cerebrovascular disease.