An absence of platelet activation following thalidomide treatment in vitro or in vivo

// Jianlin Qiao 1, 2, 3, * , Yulu Wu 1, * , Xiaoqing Wu 1, * , Yun Liu 1 , Xiaoqian Li 2 , Wen Ju 1, 2, 3 , Kunming Qi 2 , Depeng Li 2 , Elizabeth E. Gardiner 4 , Robert K. Andrews 5 , Lingyu Zeng 1, 3 , Kailin Xu 1, 2, 3 1 Blood Diseases Institute, Xuzhou Medical University, Xuzhou, China 2 Department of Hematology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, China 3 Key Laboratory of Bone Marrow Stem Cell, Jiangsu Province, Xuzhou, China 4 Department of Cancer Biology and Therapeutics, John Curtin School of Medical Research, Australian National University, Canberra, Australia 5 Australian Centre for Blood Diseases, Monash University, Melbourne, Australia * These authors contributed equally to this work Correspondence to: Kailin Xu, email: lihmd@163.com Lingyu Zeng, email: zengly2000@163.com Keywords: thalidomide, platelet activation, blood coagulation, thrombosis, multiple myeloma Received: January 20, 2017      Accepted: March 01, 2017      Published: March 15, 2017 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, α IIb β 3 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 o C. Thalidomide treatment also did not affect expression of GPIbα, GPVI or α IIb β 3 , 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 α IIb β 3 , 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.