Blockade of glycoprotein IIb/IIIa mediates the antithrombotic activity of butanol fraction of Actinostemma lobatum Maxim

Aim of the study: Actinostemma lobatum Maxim, a wildlife plant of Cucurbitaceae family, has been utilized for the prevention or treatment of cardiovascular diseases as a folk remedy in Korea. However, its scientific evidence remains unclear. Thus, in the present study, we examined the effects of butanol fraction of Actinostemma lobatum Maxim (BFALM) on the in vitro and in vivo antithrombotic activity and possible mechanisms were elucidated for the first time. Material and methods: To elucidate the antithrombotic mechanism of BFALM, platelet aggregation assay, coagulation assay, glycoprotein IIb/IIIa assay, thromboxane A₂ assay and in vivo pulmonary thromboembolism experiment were performed. Results: BFALM significantly inhibited collagen, adenosine diphosphate (ADP) and thrombin-induced platelet aggregation in a concentration dependent manner. Consistently, oral administration of BFALM resulted in a dose-dependent increase of survival rates of mice with pulmonary thromboembolism induced by intravenous injection of collagen and epinephrine. In mechanism assays for the antithrombotic activity of BFALM, BFALM significantly inhibited the fibrinogen binding to the platelet surface Glycoprotein IIb/IIIa (GP IIb/IIIa) receptor in a concentration dependent fashion, as well as reduced the level of thromboxane A₂ at 400 μg/ml. Furthermore, BFALM significantly prolonged the prothrombin time (PT) and activated partial thromboplastin time (APTT) compared with untreated control. Conclusions: These results suggest that BFALM may exert antithrombotic activity through inhibition of platelet aggregation via GP IIb/IIIa and thromboxane A₂ pathways, along with anticoagulatory activity through intrinsic and extrinsic pathways.