Abstract
Increased risk of thromboembolism and platelet hyperreactivity has been reported in patients receiving thalidomide therapy. Whether thalidomide induces platelet activation directly or through other factors remains unclear. The aim of this study was to evaluate the effect of thalidomide on platelet activation under resting conditions in vitro and in vivo. Isolated human or mouse platelets were treated with different concentrations of thalidomide (10, 50 and 100 μg/ml) for 60 min at 37°C followed by analysis of platelet surface expression of platelet receptors GPIbα, GPVI, αIIbβ3 and P-selectin, and PAC-1 or fibrinogen binding, by flow cytometry and collagen- or ADP-induced platelet aggregation. In addition, thalidomide (200 mg/kg) was intraperitoneally injected into mice for analysis of the effect of thalidomide on platelet activation in vivo. No increased expression of P-selectin, PAC-1 or fibrinogen binding was observed in either human and mouse platelets after thalidomide treatment in vitro for 60 min at 37°C. Thalidomide treatment also did not affect expression of GPIbα, GPVI or αIIbβ3, nor did it affect collagen- or ADP-induced platelet aggregation at threshold concentrations. However, while mice injected with thalidomide displayed no increased surface expression of platelet P-selectin or αIIbβ3, there was a significantly shortened tail bleeding time, thrombin time, prothrombin time together with higher levels of Factor IX and fibrinogen. In conclusion, thalidomide at therapeutic doses does not directly induce platelet activation under resting conditions in vitro or in vivo, but results in increased procoagulant activity, which could explain the thalidomide-dependent prothrombotic tendency in patients.
Highlights
As a synthetic glutamic acid derivative, thalidomide was originally prescribed as a sedative and antinausea medicine in pregnant women, but was withdrawn from the market as severe birth defects were observed in patients receiving thalidomide [1, 2]
Apart from the endothelium, aberrant activation of platelets was reported in MM patients receiving thalidomide as shown by increased platelet surface P-selectin expression [15], PAC-1 binding [16] and platelet aggregation [17]
We investigate the potential role of thalidomide on platelet activation in vitro and in vivo, by directly treating isolated human or mouse platelets with thalidomide, and by analyzing platelets and coagulation markers following injection of thalidomide into mice
Summary
As a synthetic glutamic acid derivative, thalidomide was originally prescribed as a sedative and antinausea medicine in pregnant women, but was withdrawn from the market as severe birth defects were observed in patients receiving thalidomide [1, 2]. Given the association of thalidomide with increased thrombotic risk [9], the precise mechanism by which thalidomide induces thrombogenesis in vivo remains poorly understood. A previous study reported that increased endothelial activation was observed in MM patients treated with thalidomide as demonstrated by elevated levels of von Willebrand factor [12], a surrogate marker of endothelial cell injury [13]. Increased expression of phosphatidylserine, tissue factor and enhanced thrombin generation were observed in cultured human umbilical vein endothelial cells treated with thalidomide and plasma from MM patients [14], suggesting thalidomide potentially induces thrombogenesis by disrupting the balance between procoagulant and anticoagulant proteins on the surface of endothelial cells. Our findings support a mechanism involving a predominantly procoagulant effect rather than a direct effect on platelets, with implications for the future clinical use of thalidomide
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