Anti‐platelet effect of prednisolone is regulated by ERK‐mediated thromboxane generation

Abstract

Endogenous hypercortisolism is associated with increased risk of blood‐related diseases such as high blood pressure and hyperglycemia that result in fatal cardiovascular disorders. Platelet plays a major role in hemostasis and thrombosis. Although it is well known that glucocorticoids exert a significant effect on hemostasis, the effect of endogenous cortisol on platelet function is much less clear.We aimed to characterize the in vitro effect of prednisolone and its molecular basis on regulation of platelet function using murine platelets.We first evaluated the concentration‐dependent effect of prednisolone on 2‐MeSADP‐induced platelet function and found that 2‐MeSADP‐induced secondary wave of aggregation and dense granule secretion were completely inhibited from 500 nM prednisolone. Since 2‐MeSADP‐induced secretion and the resultant secondary wave of aggregation is mediated by thromboxane A2 (TxA2) generation, this result suggested a role of prednisolone on TxA2generation in platelets. Consistently, prednisolone did not affect the 2‐MeSADP‐induced aggregation in aspirin‐treated platelets, where the secondary wave of aggregation and secretion were blocked by eliminating the contribution of TxA2 generation by aspirin. In addition, AYPGKF‐ and thrombin‐induced platelet aggregation and secretion were inhibited in the presence of prednisolone by inhibiting the positive‐feedback effect of TxA2 generation on platelet function. Furthermore, prednisolone completely inhibited 2‐MeSADP‐induced TxA2 generation confirming the role of prednisolone on TxA2 generation. Finally, Western blot analysis revealed that prednisolone inhibited the 2‐MeSADP‐induced ERK phosphorylation.In conclusion, prednisolone affects platelet function by the inhibition of TxA2 generation through the regulation of ERK phosphorylation, thereby shedding light on the clinical characterization and its treatment efficacy in patients with cardiovascular disorders in the future.