Betulinic Acid Inhibits Collagen-Induced Platelet Adhesion and Activation Through Inhibition of Spleen Tyrosine Kinase (SYK) Phosphorylation.

Betulinic acid is a pentacyclic triterpenoid and is found in various plant species. Betulinic acid has been shown to exhibit several biological activities, such as antiviral, anticancer, immunomodulatory, anti-inflammatory, antimicrobial, anti-diabetic, anti-parasitic, and anti-HIV properties. Additionally, betulinic acid has shown antiplatelet effects against thrombin receptor activator peptide (TRAP), adenosine diphosphate (ADP), and arachidonic acid (AA)-induced platelet activation and aggregation. However, its effect on collagen-induced platelet activation and signaling pathways is not yet known. Therefore, we investigated the effect of betulinic acid on collagen-induced platelet adhesion and activation. Platelets were isolated from mice and labeled with CD41 PE-Cy7 at 37 °C for one hour and induced with various agonists to determine the platelet activation profile against different platelet agonists. Further, the concentration-dependent effect of betulinic acid (100 µM, 300 µM, 500 µM, or 1 mM) against collagen-induced platelet activation was assessed by flow cytometry. Moreover, platelets were labeled with CD41 PE-Cy7 and phospho-spleen tyrosine kinase (SYK) PE at 37 °C for one hour and incubated with betulinic acid (500 µM) or cytochalasin D (1 µg/mL) for 20 minutes, followed by the addition of collagen (25 µg/mL). Thereafter, samples were analyzed by flow cytometer (BD FACSCanto