Monday, May 16, 2011

Arsenic trioxide induces procoagulant activity through phosphatidylserine exposure and microparticle generation in endothelial cells.

Thromb Res. 2011 May;127(5):466-72. Epub 2011 Jan 26.
Zhou J, Li H, Fu Y, Shi J, Hou J, Zhang Y, Liu X, Song P.
Department of Hematology, the First Affiliated Hospital, Harbin Medical University, Harbin 150001, China.
Abstract: BACKGROUND: Coagulopathy is a major cause of early death when arsenic trioxide (As(2)O(3)) therapy fails. In addition to the procoagulant properties of blast cells, the cytotoxic therapy may contribute to the coagulation disorders. The aim of the present study was to evaluate the possible impact of As(2)O(3) on membrane alterations, including phosphatidylserine (PS) exposure and microparticle generation, and the consequent procoagulant properties of endothelial cells. METHODS: Procoagulant activity (PCA) of human umbilical vein endothelial cells (HUVECs) was assessed by measuring clotting time and through purified coagulation complex assays. PS exposure on HUVEC membrane was observed by confocal microscopy and quantified with flow cytometry. In addition, counts and PCA of endothelial microparticles were determined by flow cytometry and plasma coagulation assay. RESULTS: As(2)O(3) increased the ability of HUVECs to accelerate coagulation process and promote formation of coagulation complexes. Procoagulant activity corresponded to PS exposed on HUVECs. In coincidence with the PS externalization, As(2)O(3) increased the production of PS-bearing microparticles, which then accelerated fibrin strand formation significantly. By blocking PS, lactadherin was able to inhibit over 90% of the intrinsic tenase/prothrombinase activity of As(2)O(3)-treated HUVECs, and restored coagulation times of As(2)O(3)-treated cells and microparticles to control levels. CONCLUSIONS: As(2)O(3) increases PCA of HUVECs through PS exposure and PS-bearing microparticle generation, which might cause thrombosis and act as a contributing factor in As(2)O(3) therapy-related coagulopathy.

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