20(S)-Panaxadiol Enhances Hemostatic Effect on Activated Platelet by Affecting Calcium Signaling

Abstract

\n Background: Panax notoginseng (Burk.) F.H. Chen has long been used to stop bleeding for hundreds of years in China. At present, only dencichine and notoginsenoside Ft1 showed the hemostatic effect. Other ingredients from Panax notoginseng need to be further investigated. This study evaluates the hemostatic effect of 20(S)-panaxadiol (PD) and reveals its mechanism. Methods: We performed an in vivo study to measure PD on the hemostatic effect of mouse tail amputation and liver scratch models, and routine blood. Plasma coagulation parameters were measured using a blood analyzer. Platelet aggregation rate and adenosine triphosphate (ATP) release were analyzed by platelet aggregometer. Subsequently, degranulation marker P-selectin (CD62P), PAC-1 (activated GP IIb/IIIa receptor marker), the concentrations of cytosolic Ca2+ ([Ca2+]i) and cyclic adenosine monophosphate (cAMP) were also assessed. Results: PD shorted bleeding time on the mouse tail amputation and liver scratch models and mainly increased blood platelet count in the rats after subcutaneous injection of 4 h. Meanwhile, PD decreased APTT, increased FIB content, and directly induced platelet aggregation. In the absence of Ca2+, PD promoted the increase of [Ca2+]i and ATP, slightly increased CD62P expression and PAC-1 binding of platelets. After the addition of Ca2+, PD treatment markedly promoted platelet activation by releasing ATP level, increasing CD62P expression and PAC-1 binding, and decreasing cAMP level in platelets. Besides, PD increased phosphorylation of phosphoinositide 3-kinase (PI3K), protein kinase B (PKB or Akt), and glycogen synthase kinase 3β (GSK3β) in human platelets. Excitingly, PD-induced changes included platelet aggregation, a decrease of the cAMP content, and the increases of ATP, CD62P and PAC-1, which were significantly reversed by vorapaxar, which showed a similar function as thrombin. Conclusions: PD is an essential hemostatic ingredient in Panax notoginseng for promoting hematopoiesis and thrombopoiesis. PD induces platelet aggregation by affecting calcium signaling and activating PI3K/Akt/GSK3β signaling pathway, which could contribute to the new insight for the treatment of hemorrhagic disease.