Characterization of molecular basis of anti‐platelet effect of daphnetin

Abstract

Coumarin derivates have been known for their antithrombotic, anti‐inflammatory, and antioxidant activities and daphnetin is one of the natural coumarin derivatives isolated from Daphne Korean Nakai. Although the pharmacological value of daphnetin is well documented in diverse biological activities, its antithrombotic effect is not studied till date.We investigated the functional role of daphnetin and its molecular basis on the regulation of platelet activation using murine platelets.In order to check the effect of daphnetin on GPVI‐mediated platelet response, we first measured the effect of daphnetin on collagen‐induced platelet aggregation and secretion. Collagen‐induced platelet aggregation and dense granule secretion were partially inhibited in the presence of daphnetin. Interestingly, 2‐MeSADP‐induced secondary wave of aggregation and secretion were completely inhibited in the presence of daphnetin. It has been known that 2‐MeSADP‐induced secretion and the resultant secondary wave of aggregation are mediated by positive‐feedback effect of thromboxane A2 (TxA2) generation, suggesting the important role of daphnetin on TxA2 generation in platelets. Consistently, daphnetin did not affect the 2‐MeSADP‐induced platelet aggregation in aspirin‐treated platelets where the contribution of TxA2 generation is blocked. Additionally, AYPGKF‐induced platelet aggregation and secretion were inhibited in the presence of daphnetin by blocking the positive‐feedback effect of TxA2 generation. Moreover, 2‐MeSADP‐induced TxA2 generation was completely inhibited in the presence of daphnetin confirming the role of daphnetin on TxA2 generation. Finally, 2‐MeSADP‐induced ERK phosphorylation was inhibited in the presence of daphnetin.We conclude that daphnetin plays a role in platelet function by inhibiting the TxA2 generation through the regulation of ERK phosphorylation.