Recombinant human thrombomodulin attenuates human endothelial cell activation by human thrombin.
Two glycoforms of recombinant human thrombomodulin (TM; TMD1-105 and TMD1-75), an endothelial cell membrane protein, were tested for their ability to alter thrombin-induced activation of cultured human umbilical vein endothelial cells (HUVECs). After stimulation with 10 nmol/L thrombin, HUVEC generation of inositol-1,4,5-trisphosphate (IP3), a potent Ca(2+)-mobilizing second messenger, was dose-dependently blocked by TMD1-105. Both TMD1-105 (IC50 = 10 nmol/L) and TMD1-75 (IC50 = 100 nmol/L) blocked the enhanced prostacyclin synthesis by HUVEC monolayers treated with 10 nmol/L thrombin. HUVEC monolayer permeability to Evans blue dye-labeled albumin increased from 0.125 +/- 0.06 microL/min in control experiments to 0.380 +/- 0.09 microL/min after treatment with 100 nmol/L thrombin (P < .05). Incubation of HUVECs with TMD1-105 alone (600 nmol/L) had no effect (0.114 +/- 0.04 microL/min) on basal permeability. In contrast, incubation of 100 nmol/L thrombin with 600 nmol/L TMD1-105 reduced this increase in HUVEC permeability to almost control levels (0.142 +/- 0.06 microL/min). These results demonstrate that recombinant human TM, a potent in vitro anticoagulant, also functions as an antagonist of thrombin receptor-mediated HUVEC activation. In addition to its anticoagulant functions, the high-affinity endothelial cell receptor TM may play a role in modulating endothelial cell activation by thrombin.
Eli Lilly and Co, Indianapolis, Ind.
J F
JF
Parkinson
N U
NU
Bang
J G
JG
Garcia
D002463:Cell Membrane Permeability / Q000187:drug effects; D004730:Endothelium, Vascular / Q000166:cytology*; D011464:Epoprostenol / Q000096:biosynthesis; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000502:physiology*; D018179:Receptors, Thrombin; D011994:Recombinant Proteins / Q000494:pharmacology; D013917:Thrombin / Q000037:antagonists & inhibitors*; D014471:Umbilical Veins
D007295:Inositol Phosphates; D011956:Receptors, Cell Surface; D018179:Receptors, Thrombin; D011994:Recombinant Proteins; D011464:Epoprostenol; D013917:Thrombin