PB0753 - Tryptanthrin inhibits platelet functions and thrombosis

Background: Tryptanthrin is a naturally occurring compound isolated from Isatidis Radix. In previous studies, Isatidis Radix was reported to be an inhibitor of ADP-induced platelet aggregation.

Aims: The objective of this study was to explore the biological functions of tryptanthrin in platelets and its underlying mechanism.

Methods: Platelet functions, including spreading, aggregation, and clot retraction were measured in the presence or absence of tryptanthrin. With the use of oral gavage in mice, thrombus formation at a shear rate and FeCl3-induced carotid artery thrombosis were induced. To explore the mechanism by which tryptanthrin inhibits platelet functions, the 4D-DIA quantitative proteomics method was applied.

Results: Confocal microscopy images demonstrated that increasing doses of tryptanthrin reduced platelet adhesion to immobilized fibrinogen and collagen. Tryptanthrin dose- and time-dependently inhibited thrombin-induced clot retraction. Tryptanthrin dose-dependently inhibited platelet aggregation with ADP thrombin, collagen, and U46619 stimulation. Tryptanthrin dose-dependently reduced platelet ATP release, reflecting the secretion of dense granules upon platelet activation. The activation of integrin αIIbβ3 or surface P-selectin expression decreased with increasing doses of tryptanthrin. Moreover, platelet thrombosis was suppressed by tryptanthrin both in vitro and in vivo. Tryptanthrin restrained thrombus size in a dose-dependent manner when it was applied via a microfluidic platform at shear rates of 500 s-1 and 1500 s-1. We applied a model of left carotid FeCl3-induced thrombosis to determine whether tryptanthrin dose-dependently decelerated carotid thrombus formation. In addition, we identified 35 differentially expressed proteins, especially Gp1ba, Dcn and Bgn, in platelets treated with or without tryptanthrin through proteomics. GSEA revealed that tryptanthrin reduced platelet activation, aggregation, hemostasis and thrombosis.

Conclusion(s): Our findings indicated that tryptanthrin inhibited platelet function and thrombosis both in vitro and in vivo. Tryptanthrin might exert its antiplatelet effects via a decrease in Gp1ba expression in platelets.