Panax notoginseng saponins inhibit platelet activation and thrombosis while preserving hemostasis: involvement of platelet oxylipin metabolic reprogramming.

BACKGROUND: Platelets play a central role in hemostasis and thrombosis. Panax notoginseng saponins (PNS), the bioactive components of Panax notoginseng, have demonstrated promising potential in regulating platelet function. Platelet oxylipins are critically involved in thrombotic and pro-coagulant activities. This study aimed to investigate the impact of PNS on platelet function, thrombosis and hemostasis and to explore the mechanisms regarding platelet oxylipin metabolism regulation.

METHODS: The effects of PNS on platelet function and ischemia-induced myocardial injury were evaluated in a rat acute myocardial infarction (AMI) model. Agonist-induced platelet GPIIb/IIIa activation, degranulation and aggregation were tested by flow cytometry and light transmission aggregometry. Myocardial injury, infarct expansion and cardiac function post-myocardial infarction (MI) were evaluated by histopathology, 2,3,5-triphenyl tetrazolium chloride staining and echocardiography. In vivo analysis of thrombus formation was conducted by FeCl3-injured mesenteric arteriole thrombosis model. Bleeding time and coagulation function were assessed in a mouse tail bleeding model. Platelet oxylipin metabolism was characterized by targeted lipidomic analysis.

RESULTS: Enhanced platelet reactivity was observed post AMI. PNS dose-dependently inhibited platelet activation and aggregation via suppressing platelet degranulation, which was partly attributed to down-regulation of GPIIb/IIIa activation. Interestingly, high-dose PNS exhibited superior inhibition of platelet aggregation induced by adenosine diphosphate compared with aspirin. PNS ameliorated myocardial injury, MI expansion and ischemia-related heart failure. These findings were consistent with PNS-mediated attenuation of in vivo thrombus formation. Moreover, various doses of PNS preserved basal hemostasis in phycological conditions, which might be associated with shortened activated partial thromboplastin time. Platelet lipidomic analysis revealed perturbation of oxylipin profile post AMI, demonstrated by significant upregulation of thromboxane B2, 12-hydroxyeicosatetraenoic acid (12-HETE) and leukotrienes (LTs), indicating propagation of thrombo-inflammation. PNS favored generation of anti-thrombotic lipids and mitigated pro-inflammatory cascades, facilitating the resolution of thrombo-inflammatory milieu.

CONCLUSIONS: PNS exerted anti-platelet and anti-thrombotic effects in arterial ischemic conditions while preserving basal hemostasis, which was mechanistically linked to alleviation of thrombo-inflammation via reprogramming platelet oxylipin metabolism and regulation of coagulation. The findings unraveled therapeutic potential of PNS in the management of thrombotic cardiovascular diseases.