Endothelial Cell-Derived Microparticles in the Pathogenesis of Chemotherapy-Associated Hypercoagulability.

Background: Cisplatin-based chemotherapy is a risk factor of venous thromboembolism in cancer patients. The underlying pathogenesis remains unclear. We hypothesized an apoptotic effect of cisplatin on endothelial cells (EC) inducing a release of small membrane vesicles, so-called microparticles (MP) which are known to cause hemostasis activation.

Objectives:

1. To quantify the release of MP from EC following administration of cisplatin and

2. to investigate MP-associated procoagulant mechanisms.

Methods: Two EC lines (HUVEC, HMVEC-L) were exposed to cisplatin (1, 2.5, 5, 10, and 20 μM) for up to 120 h. Cell viability was assessed by quantification of mitochondrial dehydrogenase activity, counts and procoagulant activity of MP were measured by flow cytometry and a thrombin generation assay, respectively. Tissue factor (TF) antigen levels were determined by ELISA.

Results: EC viability decreased in a dose- and time-dependent manner and was accompanied by an increasing release of MP into culture media (maximum: HUVEC + 544%; HMVEC-L + 1738%). In parallel, procoagulant activity of media increased by up to 150% (HUVEC) and 493% (HMVEC-L), respectively. The procoagulant activity was almost abolished by annexin V but was not suppressed by a monoclonal TF-antibody. TF antigen levels on MP were persistently low even at high cisplatin concentrations.

Conclusion: At pharmacologically relevant concentrations, cisplatin induced a marked release of procoagulant MP from EC. Negatively charged phospholipids but not TF on MP were decisive for total thrombin generation. Further studies are warranted to investigate the cisplatin-induced release of EC-derived MP in vivo.