Cyclosporine-induced detachment of vascular endothelial cells initiates the intrinsic coagulation system in plasma and whole blood

Cyclosporine A (CsA) is supposed to alter the metabolism of vascular endothelial cells, leading to a prothrombotic state. We examined by which mechanism human umbilical vein endothelial cells (HUVECs) treated with CsA would promote coagulation in human plasma and in whole blood. Treatment of HUVECs with CsA at concentrations clinically used led to dose-dependent cell detachment, with the subsequent exposure of the highly procoagulant connective tissue. As determined by scanning electron microscopy, cell counting of detached and adherent cells, and antigenic measurement of collagen exposure, HUVECs treated with 0.4 mu g/ml CsA (or more) for 4 days exhibited significant amounts of subendothelial areas. On CsA-treated HUVEC monolayers, the clotting time of recalcified citrated platelet-rich plasma (PRP), but not platelet-poor plasma (PPP), was dose-dependently shortened. Likewise, the onset of thrombin generation was significantly earlier. Except at a high concentration of 8.0 mu g/ml CsA, there was no procoagulant effect when PPP was used. To investigate CsA-treated HUVECs in whole blood, cells were cultivated on globular microcarriers and were incubated with nonanticoagulated whole blood. When untreated cells were used, generation of factor Xa, thrombin, and kallikrein was completely suppressed for 30 minutes. HUVEC beads treated with 0.4 and 0.8 mu g/ml CsA, however, led to a dose-dependent generation of all three coagulation factors, with peak values at 2.5 to 5 minutes. Extrinsic activation was excluded, since CsA treatment did not induce tissue factor activity in HUVECs. Furthermore, the thrombomodulin activity of HUVECs was not altered by CsA. In conclusion, treatment of HUVECs with CsA for 4 days at concentrations clinically used leads to the exposure of subendothelial areas that induce activation of the intrinsic coagulation in recalcified PRP and nonanticoagulated whole blood.