Endothelial cell surface limits coagulation without modulating the antithrombin potency.

Antithrombin (AT) binds in vitro and in vivo to endothelial cells through various receptors, including heparan sulphate glycosaminoglycan (HSPG) that could modulate the AT activity. A thrombin generation assay (TGA) was set up at the surface of HUVEC and HMVEC evaluating their participation in the coagulation-anticoagulation processes. TGA induced by 0.5 pM Tissue Factor was performed in normal or AT-deficient plasma spiked with various amounts of recombinant or plasma-derived AT (0, 0.1, 0.5 and 1.0 U/ml). To evaluate the role of HSPG or cellular anticoagulant receptors, cells were treated or not with heparin, a mix of heparanase I, II and III, a neutralizing anti-Endothelial Protein C Receptor (EPCR) or with an anti-Tissue Factor Pathway Inhibitor (TFPI) antibody. The presence of the cells diminished the TG in normal plasma and maintained anticoagulation in AT-deficient plasma. Spiking the AT-deficient plasma with different doses of AT demonstrated that the cells did not amplify the anticoagulant activity of AT. The recombinant AT binds the cells with a higher avidity than the plasma-derived one but this did not affect its anticoagulant potency. Moreover both bindings are independent of the HSPG. The antithrombotic activity kept in absence of AT was not inhibited by blocking antibodies directed against EPCR or TFPI. Our data did not reveal a major co-factor activity for AT from endothelial cells that could have been mediated by HSPG. In contrast, it reveals the presence of alternative anti-coagulant system(s) in two venous cell types that maintain an antithrombotic activity.

Comparison of antioxidant properties of different therapeutic albumin preparations.

Albumin displays several important functions for homeostasis amongst which the maintenance of the plasma redox-state. The study aim was to compare the redox state of pharmaceutical human albumin preparations since it reflects the oxidation-reduction status of the surrounding environment. Using an array of analytical methods, four commercially available albumins were compared with respect to their structural characteristics (cobalt ion binding, glycation, spectrophotometric and fluorometric profiles) and their ability to scavenge hydroxyl, peroxyl or free radicals. The different albumins exhibited a similar structural profile as well as hydroxyl and peroxyl scavenging activities. By contrast, the albumin from LFB (Vialebex(®)) possessed a significantly higher capacity to transfer electrons to DPPH, as compared with other albumins that was correlated with the level of free cysteine-34. Commercially available albumins differed for some of their antioxidant properties. The albumin preparation possessing the highest level of free cysteine-34 exhibited the highest antioxidant potential.