A role for thrombomodulin in the pathogenesis of thrombin-induced thromboembolism in mice

Abstract

The antithrombotic action of thrombomodulin was studied in mice. Rat and mouse thrombomodulin were isolated from lung acetone powders, and anti-rat thrombomodulin antibodies were prepared in rabbits. The antibodies neutralized both mouse (Kd approximately 150 nM) and rat thrombomodulin (Kd approximately 50 nM). A role for thrombomodulin in vivo was shown in mice injected intravenously (IV) with thrombin. All mice injected with 15 U thrombin (bolus) died of thromboembolism (mean survival 55 minutes), whereas those injected with a lower dosage survived. Prior injection with anti-rat thrombomodulin (1.8 mg IgG/mouse) potentiated the lethal effects of subsequent thrombin, whereas injection of thrombomodulin (isolated from mouse lung) prior to thrombin prolonged survival in a thrombomodulin concentration-dependent manner. The protective effect of thrombomodulin persisted for 30 minutes but after one hour thrombin injection was as toxic as in control animals. The half life (t1/2) for plasma clearance of 125I- mouse lung thrombomodulin was nine minutes. The major site of clearance was the liver, although thrombomodulin accumulated in several organs ten minutes after injection. The mechanism by which antithrombomodulin antibodies potentiated the lethal effects of thrombin was studied by measuring the protein C activating cofactor activity on vena cava removed from animals injected with antibodies. Protein C activation was inhibited by antibodies, suggesting a role for activated protein C in prevention of lethal thromboembolism. We found no effect of antibodies on the clearance of thrombin from mouse plasma, suggesting that blockade of endothelial endocytosis of thrombin does not play a significant role in the effects of antibodies. These results indicate that thrombomodulin participates in the defense against thrombosis in vivo.

Cardiac xenografts show reduced survival in the absence of transgenic human thrombomodulin expression in donor pigs

“…However, administration of hTBM attenuates the consequences of thrombin‐induced thromboembolism in mice and rats . Thrombomodulin has been shown to be involved in the regulation of coagulation, complement, and anti‐inflammation and cell proliferation, which have a protective role against microvascular thrombosis . Furthermore, our results presented earlier also suggest that hTBM expression in the donor organ along with anti‐CD40 mAb treatment may help to prolong the xenograft survival …”

High‐mobility group box 1 protein promotes development of microvascular thrombosis in rats

“…As the plasma or serum levels of HMGB1 in DIC or septic patients have been reported to range from 0 to 10 n m [7,16,17], the percentage inhibition of APC generation in such patients may be about 10%. Considering that 40% inhibition of APC generation or heterozygous deletion of TM was previously reported to cause thrombosis in animal models [29,30], HMGB1 in septic patients at a concentration of about 1 n m may not be sufficient to cause thrombosis through inhibition of APC generation alone. It is therefore possible that other mechanisms, such as increased tissue factor expression, are also important in the aggravation of DIC by HMGB1.…”

Thrombomodulin Improves Early Outcomes After Intraportal Islet Transplantation

“…As an alternative approach, several studies have documented that various forms of solubilized TM are capable of activating protein C in vivo . For example, Kumada et al (36) observed that TM prolonged the survival of mice in a model of thrombin‐induced thromboembolism. Other studies have demonstrated that administration of TM reduces endotoxin induced lung injury (37,38) and thrombosis from disseminated intravascular coagulation (DIC) in rats and monkeys (39–41), limits thrombosis in an arteriovenous shunt model in rats (42), attenuates thrombotic glomerulonephritis in rats (43) and decreases trauma induced spinal cord injury (44).…”