Thrombomodulin alfa attenuates thrombin-induced leakage of antithrombin through suppression of endothelial vascular hyperpermeability

Targeting Endothelial Dysfunction in Acute Critical Illness to Reduce Organ Failure

During hyperinflammatory conditions that can occur in acute critical illness, such as shock or hypoperfusion, inflammatory mediators activate the endothelium, fueling a proinflammatory host-response as well as procoagulant processes. These changes result in shedding of the glycocalyx, endothelial hyperpermeability, edema formation, and lead to disturbed microcirculatory perfusion and organ failure. Different fluid strategies that are used in shock may have differential effects on endothelial integrity. Collectively, low protein content fluids seem to have negative effects on the endothelial glycocalyx, aggravating endothelial hyperpermeability, whereas fluids containing albumin or plasma proteins may be superior to normal saline in protecting the glycocalyx and endothelial barrier function. Targeting the endothelium may be a therapeutic strategy to limit organ failure, which hitherto has not received much attention. Treatment targets aimed at restoring the endothelium should focus on maintaining glycocalyx function and/or targeting coagulation pathways or specific endothelial receptors. Potential treatments could be supplementing glycocalyx constituents or inhibiting glycocalyx breakdown. In this review, we summarize mechanisms of endothelial dysfunction during acute critical illness, such as the systemic inflammatory response, shedding of the glycocalyx, endothelial activation, and activation of coagulation. In addition, this review focuses on the effects of different fluid strategies on endothelial permeability. Also, potential mechanisms for treatment options to reduce endothelial hyperpermeability with ensuing organ failure are evaluated. Future research is needed to elucidate these pathways and to translate these data to the first human safety and feasibility trials.

Thrombomodulin alfa prevents oxaliplatin-induced neuropathic symptoms through activation of thrombin-activatable fibrinolysis inhibitor and protein C without affecting anti-tumor activity

Oxaliplatin, a platinum-based chemotherapeutic agent, is widely used to treat colorectal cancer, but it induces peripheral neuropathy as a serious dose-limiting side effect. Recently, thrombomodulin alfa, a recombinant human soluble thrombomodulin, was reported to prevent oxaliplatin-induced peripheral neuropathy in a clinical phase 2 study. Here we conducted preclinical pharmacology studies. Rats were given oxaliplatin (6 mg/kg) intravenously to induce mechanical hyperalgesia associated with peripheral neuropathy. Single intravenous administration of thrombomodulin alfa (0.1, 0.3, 1 mg/kg) dose dependently prevented the development of oxaliplatin-induced mechanical hyperalgesia, with no sex difference in the efficacy. The preventative effect of thrombomodulin alfa on mechanical hyperalgesia was attenuated by antithrombin or carboxypeptidase inhibitor. In addition, carboxypeptidase B, a homolog of activated thrombin-activatable fibrinolysis inhibitor (TAFI) and human-derived activated protein C, prevented mechanical hyperalgesia, whereas antithrombin or other anti-coagulants did not. These results suggest that thrombomodulin alfa prevents sensory symptoms of oxaliplatin-induced peripheral neuropathy through the activation of TAFI and protein C by modulating thrombin activity, but the effects are independent of an anticoagulant effect. On the other hand, thrombomodulin alfa did not affect the anti-cancer activity of oxaliplatin on human colon cancer cell lines or mice transplanted with HCT116 cells. These results indicate that thrombomodulin alfa prevents sensory symptoms of oxaliplatin-induced peripheral neuropathy without affecting the anti-tumor activity of oxaliplatin. Therefore, thrombomodulin alfa is a promising drug to prevent the symptoms of oxaliplatin-induced peripheral neuropathy.

Thrombomodulin alfa prevents the decrease in platelet aggregation in rat models of disseminated intravascular coagulation

INTRODUCTION

Disseminated intravascular coagulation (DIC), a deadly complication characterized by uncontrolled hypercoagulation, causes a decrease in the platelet count and impairs platelet aggregation. Thrombomodulin (TM) alfa, a recombinant human soluble TM, reduces hypercoagulation in DIC patients. However, the effects of TM alfa on impaired platelet aggregation remain to be determined. In this study, we aim to investigate the effects of TM alfa on platelet aggregation using lipopolysaccharide (LPS)-induced and tissue factor (TF)-induced DIC rat models.

MATERIALS AND METHODS

Sprague-Dawley rats were administered TF or LPS intravenously, with or without TM alfa before the injection. Six hours after LPS injection or 1 h after TF infusion, blood samples were obtained, and platelet-rich plasma was prepared. Collagen or adenosine diphosphate-induced platelet aggregation was measured using an aggregometer. In the other experiments, platelets were transfused 1 h after the TF infusion. Five minutes after transfusion, collagen-induced platelet aggregation was also measured.

RESULTS

The amplitude of platelet aggregation in platelet-rich plasma was decreased in LPS- and TF-treated rats. TM alfa inhibited the decrease in platelet aggregation in a dose-dependent manner. The washed platelet aggregation amplitude was not decreased in TF-treated rats. Suspension of normal platelets in plasma obtained from TF-treated rats reduced platelet aggregation. Platelet transfusion for TF-treated rats increased the platelet count but was unable to improve platelet aggregation.

CONCLUSIONS

TM alfa attenuated impairment of platelet aggregation in LPS- and TF-induced DIC rat models. The changes in plasma composition played a role in the decrease of platelet aggregation in TF-treated rats.