Styliani Papadaki, Sofia Sidiropoulou, Vasileios Chantzichristos, Minas Paschopoulos, Alexandros Tselepis
Background: Thrombin is the key serine protease of the coagulation cascade which also exerts cellular non-haemostatic effects that are primarily mediated by the protease-activated receptor-1 (PAR-1).
Aim: In the present study we investigated the effect of thrombin on the membrane expression of adhesion molecule ICAM-1 on CD34+-derived late-outgrowth endothelial cells (OECs) and human umbilical vein endothelial cells (HUVECs).
Methods: CD34+ cells were isolated from cord blood mononuclear cells using human CD34 Microbead Kit and appropriately cultured for the formation of OECs. HUVECs were purchased from Lonza. Confluent OECs (passage 4) and HUVECs (passage 3) were incubated for various time intervals up to 24 h with 1-8 U/mL thrombin and the effect of thrombin-induced ICAM-1 expression (anti-CD54-PE) was evaluated using flow cytometry. PECAM-1 (anti-CD31-FITC) was used as an endothelial marker.
Results: Thrombin (8 U/mL) significantly increased ICAM-1 expression on OECs by 3.3-fold, after 24 h of incubation. In the resting state, ICAM-1 expression was significantly higher by 2.1-fold on OECs, compared with HUVECs. On the contrary, the % increase of ICAM-1 expression following activation with thrombin was significantly lower on OECs, compared with HUVECs.
Conclusions: Thrombin is a mediator of ICAM-1 expression on endothelial progenitor cells and this expression at baseline and after thrombin activation is different compared with HUVECs. The biochemical basis of this difference, as well as its pathophysiological significance remain to be established in future studies.
Keywords: thrombin, protease-activated receptor-1, endothelial progenitor cells, ICAM-1