Water Extract from Rice Bran Fermented with Lactobacillus plantarum Hong Inhibits Thromboxane A2 Production Associated Microsomal Enzyme Activity in Human Platelets

In this study, we investigated the effect of rice bran water extract fermented with Lactobacillus plantarum Hong (RBLw), on activities of cyclooxygenase-1 (COX-1) and thromboxane A₂ synthase (TXAS), thromboxane A₂ (TXA₂) production associated microsomal enzymes and evaluated its the antiplatelet effect. RBLw, containing 13.5 mg of ferulic acid, dose-dependently inhibited ADP-induced platelet aggregation, and inhibited the production of TXA₂, an aggregation molecule. In addition, RBLw directly inhibited COX-1 activity in a dose-dependent manner, but not TXAS activity in platelet microsomal fraction having cytochrome c reductase (an endoplasmic reticulum marker enzyme) activity and expressing COX-1 (72 kDa) and TXAS (60.5 kDa) proteins. These results suggest that RBLw selectively inhibited the activity of COX-1 rather than TXAS to attenuate TXA₂ production in ADP-activated platelets. Thus, we demonstrate that RBLw might have direct COX-1 antagonistic function for platelet aggregation-mediated diseases, such as thrombosis, myocardial infarction, atherosclerosis, and ischemic cerebrovascular disease.