Inhibitory effects of total saponin from Korean red ginseng via vasodilator-stimulated phosphoprotein-Ser¹⁵⁷phosphorylation on thrombin-induced platelet aggregation

Abstract

In this study, we have investigated the effects of total saponin from Korean red ginseng (TSKRG) on thrombin-induced platelet aggregation. TSKRG dose-dependently inhibited thrombin-induced platelet aggregation with IC50 value of about 81.1 μg/mL. In addition, TSKRG dose-dependently decreased thrombin-elevated the level of cytosolic-free Ca2+ ([Ca2+]i), one of aggregation-inducing molecules. Of two Ca2+-antagonistic cyclic nucleotides as aggregation-inhibiting molecules, cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), TSKRG significantly dose-dependently elevated intracellular level of cAMP, but not cGMP. In addition, TSKRG dose-dependently inhibited thrombin-elevated adenosine triphosphate (ATP) release from platelets. These results suggest that the suppression of [Ca2+]i elevation, and of ATP release by TSKRG are associated with upregulation of cAMP. TSKRG elevated the phosphorylation of vasodilator-stimulated phosphoprotein (VASP)-Ser157, a cAMP-dependent protein kinase (A-kinase) substrate, but not the phosphorylation of VASP-Ser239, a cGMPdependent protein kinase substrate, in thrombin-activated platelets. We demonstrate that TSKRG involves in increase of cAMP level and subsequent elevation of VASP-Ser157 phosphorylation through A-kinase activation to inhibit [Ca2+]i mobilization and ATP release in thrombin-induced platelet aggregation. These results strongly indicate that TSKRG is a beneficial herbal substance elevating cAMP level in thrombin-platelet interaction, which may result in preventing of platelet aggregation-mediated thrombotic diseases.

In vitro and in vivo anti-inflammatory activity of Phyllanthus acidus methanolic extract

“…Sequence (5´to 3´) (Lee et al, 2013a). Immunoprecipitations were performed from whole cell lysates as previously described and immunoprecipitated proteins were analysed by immunoblotting.…”

Nobiletin, a citrus flavonoid, activates vasodilator-stimulated phosphoprotein in human platelets through non-cyclic nucleotide-related mechanisms

“…As VASP is a common downstream target of various signaling pathways, an increasing attention to this molecule has been paid in platelet studies (12–14). Cyclic AMP-dependent protein kinase (PKA; also known as protein kinase A) is considered the main mediator of the numerous effects associated with increased cyclic AMP levels.…”

PDK1 in NF-κB signaling is a target of Xanthium strumarium methanolic extract-mediated anti-inflammatory activities

“…Nuclear lysates were prepared in a three-step procedure (Lee et al, 2013b). Total and phosphorylated levels of transcription factors (p65 and p50), Akt, IκBα, PDK1, and β-actin (as a control) were visualized according to a previously published method (Lee et al, 2013a). Immunoprecipitations were performed from whole cell lysates as previously described and immunoprecipitated proteins were analyzed by immunoblotting.…”