Intracellular Ca2+ ([Ca2+]i) induces platelet aggregation, and influences the activation of aggregation associated-molecules. The increased [Ca2+]i activates both the Ca2+/calmodulin-dependent phosphorylation of the myosin light chain and the diacylglycerol-dependent phosphorylation of pleckstrin to trigger granule secretion (i.e., dense body and α-granule) and platelet aggregation. This study was carried out to elucidate the antagonistic effect of 20(S)-ginsenoside Rg3 (G-Rg3) present in Panax ginseng Mayer on Ca2+. G-Rg3 inhibited thrombin-induced human platelet aggregation in a dose-dependent manner and suppressed thrombin-induced elevation of [Ca2+]i mobilization. G-Rg3 increased the levels of cAMP, and subsequently, elevated the phosphorylation of inositol 1,4,5-triphosphate receptor I (Ser1756) during thrombin-induced human platelet aggregation. Moreover, G-Rg3 inhibited thapsigargin-induced Ca2+ influx and the thrombin-induced elevation of extracellular signal-regulated kinase 2 phosphorylation. G-Rg3 exhibited an inhibitory effect on [Ca2+]i levels leading to granule release and thus a therapeutic potential against platelet-mediated thrombotic disease is suggested.

Platelet hyperactivation is a major factor in thrombotic complications such as myocardial infarction and ischemic stroke. Ginsenoside Rg5 is a minor ginsenoside, and among its various beneficial pharmacological effects, its antithrombotic potential has not been extensively studied. Human platelets were isolated and treated with Rg5 (35-100 μM) before stimulation with agonists such as collagen, thrombin, and U46619. Platelet aggregation, granule secretion, calcium mobilization, thromboxane A₂ production, fibrinogen binding, and clot retraction were evaluated. The effects of Rg5 on signaling pathways were determined via Western blot analysis of key proteins. In vivo, the antithrombotic efficacy was assessed using ferric chloride (FeCl₃)-induced thrombosis in mice. Rg5 dose-dependently inhibited collagen-induced platelet aggregation (IC₅₀ = 42.5 μM) and selectively inhibited GPVI-mediated signaling compared to thrombin and U46619. Rg5 suppressed intracellular calcium mobilization, granule secretion, and thromboxane A₂ production, with no cytotoxicity observed. Rg5 downregulated key signaling proteins (p-PI3K, p-AKT, p-cPLA2, and p-p38) while upregulating p-VASP (S157 and S239), suggesting its role in elevating cyclic nucleotide signaling. Additionally, Rg5 inhibited CD162 expression that was induced in the presence of collagen and oxidized low-density lipoprotein. It also prevented fibrinogen and fibronectin binding and significantly reduced clot retraction. In vivo, Rg5 (20 mg/kg) significantly prolonged the carotid artery occlusion time and prevented thrombus formation, outperforming aspirin (100 mg/kg). Ginsenoside Rg5 exhibits potent antiplatelet activity by selectively targeting GPVI-mediated platelet activation and modulating key intracellular signaling pathways. These results suggest that Rg5 could be utilized to develop safer and natural antiplatelet therapies.

Hyuk-Woo Kwon. BSL 2018;24:253-62. https://doi.org/10.15616/BSL.2018.24.3.253

Seung Na Ko, Ji Won Son, Gyu Ri Kim, Min Seon Kim, Yea Jin Lee, Seung Ju Kim, Ji Hyeon Shin, Da In Jo, Woo Young Bok, Hye Gyo Oh and Hyuk-Woo Kwon. BSL 2023;29:242-8. https://doi.org/10.15616/BSL.2023.29.4.242

Glycoprotein IIb/IIIa (αIIb/β3) is the most abundant integrin on platelet surfaces, which is involved in interaction between platelets, and triggers an intracellular signaling cascade, platelet shape changes, granule secretion, and clot retraction. In this study, we evaluated the effect of ginsenoside Ro (G-Ro) on the binding of fibronectin and fibrinogen to αIIb/β3 and clot retraction. We found that G-Ro inhibited thrombin-induced platelet aggregation dose-dependently and attenuated the fibronectin-, and fibrinogen-binding to αIIb/β3 through the dephosphorylation of phosphoinositide 3-kinase p85 and Akt, which influence clot retraction, reflecting the intensification of thrombus. We observed that G-Ro is involved in αIIb/β3 in human platelets. These results suggest that G-Ro is beneficial, inhibiting fibronectin adhesion, fibrinogen binding, and clot retraction. Therefore, G-Ro in Panax ginseng may prevent platelet aggregation-mediated thrombotic disease.

Platelets play a very significant role in hemostasis while simultaneously posing a risk for the development of various cardiovascular diseases. Platelet-mediated issues can occur in blood vessels and trigger various medical problems. Therefore, controlling platelet function is important in the prevention of thrombosis. In this regard, we need to find compounds that provide potent antiplatelet activity with minimum side effects. Therefore, we examined the effect of 5-hydroxyindolin-2-one isolated from Protaetia brevitarsis larvae having antiplatelet properties and investigated different pathways that mediate the antiplatelet activity. We examined the effect of 5-hydroxyindolin-2-one (5-HI) on the regulation of phosphoproteins, thromboxane A₂ generation, and integrin αIIbβ3 action. Our data showed that human platelet aggregation was inhibited by 5-HI (75, 100, 150, 200 μM) without cytotoxicity, and it suppressed intracellular Ca²⁺ concentration through the regulation of inositol 1, 4, 5-triphosphate receptor I (Ser¹⁷⁵⁶) and extracellular signal-regulated kinase (ERK). Moreover, collagen-elevated thromboxane A₂ production and αIIbβ3 action were inhibited by 5-HI through the regulation of cytosolic phospholipase A₂ (cPLA₂), mitogen-activated protein kinase p38 (p38^MAPK), vasodilator-stimulated phosphoprotein (VASP), phosphoinositide 3-kinase (PI3K), and Akt (protein kinase B). Therefore, we suggested that 5-HI could be a potential substance for the prevention of thrombosis-mediated thrombosis.