Intravenous extended infusion of recombinant human soluble thrombomodulin prevented tissue factor-induced disseminated intravascular coagulation in rats

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.

Combined therapy with gas gangrene antitoxin and recombinant human soluble thrombomodulin for Clostridium perfringens sepsis in a rat model

Cases of Clostridium perfringens septicemia, such as liver abscess, often develop a rapidly progressive intravascular hemolysis and coagulation; the mortality rate with current standard care including antibiotics and surgery is high. Herein, we firstly investigated the effects of gas gangrene antitoxin (GGA) (antitoxin against C. perfringens) and recombinant human soluble thrombomodulin (rTM) on the hemolysis, coagulation status, inflammatory process, and mortality in α-toxin-treated rats. Male 11-week-old Sprague Dawley rats were randomly divided into five groups: control group, α-toxin group, GGA group, rTM group, and combined GGA and rTM (combination group). After α-toxin injection, mortality and platelet counts, and hemolysis were observed for 6 h. The fibrin/fibrinogen degradation products (FDP), and plasma high-mobility group box 1 (HMGB1) were also measured at 6 h. The combination group demonstrated 100% survival compared with 50% survival in the α-toxin group and demonstrated significantly improved hemolysis, platelet counts, and lactate levels compared with those in the α-toxin group (p < .01). The FDP and HMGB1 levels in the combination therapy group were significantly lower than those in the α-toxin group (p < .05). Combination therapy with GGA and rTM administration is applicable as adjunct therapy for fatal C. perfringens sepsis.

Soluble Thrombomodulin Ameliorates Ischemia-Reperfusion Injury of Liver Grafts by Modulating the Proinflammatory Role of High-Mobility Group Box 1

Transplantation using grafts obtained after cardiac death (CD) is considered a promising solution for graft shortages. However, no standard criteria for organ preservation have been established for CD donors. High-mobility group box 1 (HMGB1) is a DNA-binding protein that is released from dying hepatocytes as an early mediator of inflammation and organ tissue damage. HMGB1 stimulates immunocytes to produce inflammatory cytokines, thereby amplifying the inflammatory response. Thrombomodulin is an integral membrane protein that functions as an endothelial anticoagulant cofactor, and it binds HMGB1 through the extracellular domain. We investigated the effects of ART-123, recombinant human soluble thrombomodulin, on warm ischemia-reperfusion injury in liver grafts. Male Wistar rats were divided into four ex vivo groups: heart-beating (HB) group, in which livers were isolated from HB donors; CD group, in which livers were isolated from CD donors exposed to apnea-induced conditions and warm ischemic conditions for 30 min after cardiac arrest; and two CD groups pretreated with ART-123 (1 or 5 mg/kg). Each isolated liver was reperfused for 1 h after cold preservation for 6 h. The perfusate levels of HMGB1, LDH, TNF-α, and IL-6 were significantly lower in the CD group pretreated with ART-123 (5 mg/kg) than in the CD group. Bile production was significantly higher in the CD group pretreated with ART-123 (5 mg/kg) than in the CD group. The sinusoidal spaces were significantly narrower in the CD group than in the other groups. We propose that ART-123 maintains sinusoidal microcirculation by reducing endothelial cell damage during warm ischemia-reperfusion injury.

Recombinant thrombomodulin of different domains for pharmaceutical, biomedical, and cell transplantation applications

Thrombomodulin (TM) is a membrane glycoprotein mainly expressed by vascular endothelial cells and is involved in many physiological and pathological processes, such as coagulation, inflammation, cancer development, and embryogenesis. Human TM consists of 557 amino acids divided into five distinct domains: N-terminal lectin-like domain (designated as TMD1); six epidermal growth factor (EGF)-like domain (TMD2); Ser/Thr-rich domain (TMD3); transmembrane domain (TMD4); and cytoplasmic tail domain (TMD5). The different domains are responsible for different biological functions of TM. In the past decades, various domains of TM have been cloned and expressed for TM structural and functional study. Further, recombinant TMs of different domains show promising antithrombotic and anti-inflammatory activity in both rodents and primates and a recombinant soluble TM has been approved for therapeutic application. This review highlights recombinant TMs of diverse structures and their biological functions, as well as the complex interactions of TM with factors involved in the related biological processes. Particularly, recent advances in exploring recombinant TM of different domains for pharmaceutical, biomedical, and cell transplantation applications are summarized.

Thrombomodulin: a bifunctional modulator of inflammation and coagulation in sepsis

Deregulated interplay between inflammation and coagulation plays a pivotal role in the pathogenesis of sepsis. Therapeutic approaches that simultaneously target both inflammation and coagulation hold great promise for the treatment of sepsis. Thrombomodulin is an endogenous anticoagulant protein that, in cooperation with protein C and thrombin-activatable fibrinolysis inhibitor, serves to maintain the endothelial microenvironment in an anti-inflammatory and anticoagulant state. A recombinant soluble form of thrombomodulin has been approved to treat patients suffering from disseminated intravascular coagulation (DIC) and has thus far shown greater therapeutic potential than heparin. A phase II clinical trial is currently underway in the USA to study the efficacy of thrombomodulin for the treatment of sepsis with DIC complications. This paper focuses on the critical roles that thrombomodulin plays at the intersection of inflammation and coagulation and proposes the possible existence of interactions with integrins via protein C. Finally, we provide a rationale for the clinical application of thrombomodulin for alleviating sepsis.

Thrombomodulin and its role in inflammation

The goal is to provide an extensive review of the physiologic role of thrombomodulin (TM) in maintaining vascular homeostasis, with a focus on its anti-inflammatory properties. Data were collected from published research. TM is a transmembrane glycoprotein expressed on the surface of all vascular endothelial cells. Expression of TM is tightly regulated to maintain homeostasis and to ensure a rapid and localized hemostatic and inflammatory response to injury. By virtue of its strategic location, its multidomain structure and complex interactions with thrombin, protein C (PC), thrombin activatable fibrinolysis inhibitor (TAFI), complement components, the Lewis Y antigen, and the cytokine HMGB1, TM exhibits a range of physiologically important anti-inflammatory, anti-coagulant, and anti-fibrinolytic properties. TM is an essential cofactor that impacts on multiple biologic processes. Alterations in expression of TM and its partner proteins may be manifest by inflammatory and thrombotic disorders. Administration of soluble forms of TM holds promise as effective therapies for inflammatory diseases, and infections and malignancies that are complicated by disseminated intravascular coagulation.

Animal models of DIC and their relevance to human DIC: a systematic review

Disseminated intravascular coagulation (DIC) is a severe clinical condition with activation of coagulation and fibrinolysis. Its diagnosis is based on the International Society of Thrombosis and Haemostasis (ISTH) scoring system of DIC. Animal models of DIC, used to investigate pathophysiology and evaluate treatments, have not been developed in a standardized way, which impedes comparison between models and translation to the human setting. In the current review of animal models of DIC an overview of species, inducers, and dosing regimens is provided. Diagnostic approaches are compared in the light of the ISTH score and treatments tested in animal models of DIC are summarized. Systematic analysis revealed that the rat is by far the preferred species amongst animal models of DIC and lipopolysaccharides (LPS) the preferred inducer of DIC. An overview of the reporting of ISTH DIC score parameters elucidated that only about 25% of the studies measure all of the four parameters necessary for the implementation the ISTH scoring system. Furthermore, most therapeutic interventions tested in animal models of DIC are administered prophylactically, which may be irrelevant to the clinical setting and could explain why compounds effective in preclinical animal models often fail in clinical trials. It is concluded that Implementation of a scoring system in animal models of DIC may increase the ability to compare DIC amongst animal models and improve the translational aspect of treatment effect.

Liposomal Formulations of Thrombomodulin Increase Engraftment after Intraportal Islet Transplantation

Early destruction of donor islet grafts due to an instant blood-mediated inflammatory reaction (IBMIR) remains a major obstacle in islet transplantation. Thrombomodulin plays an important role in limiting coagulation and inflammatory events through a variety of effects. In this study, we investigated the ability of thrombomodulin (TM), when reconstituted as a liposomal formulation, to enhance early syngeneic islet engraftment by minimizing or abrogating the IBMIR. Administration of TM significantly improved early engraftment of syngeneic islets after intraportal transplantation in diabetic mice. In the absence of treatment, conversion to euglycemia was observed among 46.6% (7/15) of recipients. In contrast, administration of TM led to euglycemia in 93.3% (14/15) of recipients ( p = 0.0142). Recipients that received TM exhibited a lower incidence of primary nonfunction and better glucose control over a 30-day period after transplantation. Fibrin deposition ( p < 0.05), neutrophil infiltration ( p < 0.05), expression of TNF-α and IL-β mRNA ( p < 0.05), as well as NF-κB activity ( p < 0.05) were significantly reduced in the liver of islet recipients having been treated with liposomal TM. These data demonstrate that TM significantly improves early syngeneic islet engraftment through effects that target both coagulation and inflammatory pathways.

Recombinant human soluble thrombomodulin decreases the plasma high-mobility group box-1 protein levels, whereas improving the acute liver injury and survival rates in experimental endotoxemia

OBJECTIVE

In addition to the hyperactivation of the inflammatory cytokines, high-mobility group box-1 protein (HMGB1), recently identified as a lethal late-phase mediator is suspected to be closely correlated with the development of sepsis. Therefore, the therapeutic efficacy of recombinant human soluble thrombomodulin (ART-123) administration on the production of inflammatory cytokines and the plasma level of HMGB1 was investigated in experimental endotoxemia.

DESIGN

Prospective, comparative, experimental study.

SETTING

Laboratory animal research center at a university.

SUBJECTS

Male Sprague-Dawley rats (250-300 g).

INTERVENTIONS

Endotoxemia was induced in rats by a bolus intravenous injection of lipopolysaccharide (LPS) at a dosage of 4 mg/kg (LPS group). ART-123 (1 mg/kg) was administered as a bolus injection 30 minutes before or 4 hours after injection of LPS (ART-123 pretreated/treated group). As a control, an equal volume of physiologic saline was administered instead of LPS and ART-123 (control group).

MEASUREMENTS AND MAIN RESULTS

Rats were randomly divided into ART-123 pretreated group, ART-123 treated group, and LPS group, respectively. After the injection of LPS, the levels of inflammatory cytokines and thrombin-antithrombin III complex, plasma HMGB1 concentrations, liver immunohistochemical and histopathologic characteristics, liver dysfunction, and survival rate were examined. The increased levels of inflammatory cytokines and plasma HMGB1 induced by LPS in this rat model were improved by the administration of ART-123; additionally, reduced liver dysfunction and increased survival rate were observed.

CONCLUSIONS

This study demonstrated that ART-123 inhibits the expression of inflammatory cytokines and decreases the plasma HMGB1 levels in experimental endotoxemia. In addition, ART-123 administration markedly reduced liver dysfunction and mortality even with delayed treatment of ART-123. The use of ART-123 may therefore be a beneficial treatment for septic patients.

Thrombomodulin improves early outcomes after intraportal islet transplantation

Primary islet nonfunction due to an instant blood mediated inflammatory reaction (IBMIR) leads to an increase in donor islet mass required to achieve euglycemia. In the presence of thrombin, thrombomodulin generates activated protein C (APC), which limits procoagulant and proinflammatory responses. In this study, we postulated that liposomal formulations of thrombomodulin (lipo-TM), due to its propensity for preferential uptake in the liver, would enhance intraportal engraftment of allogeneic islets by inhibiting the IBMIR. Diabetic C57BL/6J mice underwent intraportal transplantation with B10.BR murine islets. In the absence of treatment, conversion to euglycemia was observed among 29% of mice receiving 250 allo-islets. In contrast, a single infusion of lipo-TM led to euglycemia in 83% of recipients (p = 0.0019). Fibrin deposition (p < 0.0001), neutrophil infiltration (p < 0.0001), as well as expression TNF-alpha and IL-beta (p < 0.03) were significantly reduced. Significantly, thrombotic responses mediated by human islets in contact with human blood were also reduced by this approach. Lipo-TM improves the engraftment of allogeneic islets through a reduction in local thrombotic and inflammatory processes. As an enzyme-based pharmacotherapeutic, this strategy offers the potential for local generation of APC at the site of islet infusion, during the initial period of elevated thrombin production.

SYNERGISTIC EFFECTS OF RECOMBINANT HUMAN SOLUBLE THROMBOMODULIN AND FLUID-VOLUME RESUSCITATION IN A RAT LETHAL CRUSH INJURY MODEL

Severe crush injury results in a high mortality rate because of acute circulatory failure and hyperkalemia. The purpose of this study was to evaluate whether administration of prophylactic-recombinant human soluble thrombomodulin (rhsTM) and/or fluid-volume resuscitation before reperfusion attenuates severe crush injury in rats. Both hindlimbs of anesthetized rats were compressed for 6 h under blocks weighing 3.5 kg each, followed by 3 h of reperfusion. In the first group, fluid resuscitation with normal saline (1 mL/kg/h) was performed throughout the experiment. In the second group, volume resuscitation treatment with normal saline (10 mL/kg/h) was initiated 60 min before the end of the crush period and was continued until the end of the experiment. In the third group, normal saline-resuscitation treatment plus rhsTM (3 mg/kg) was performed. In the fourth group, volume resuscitation treatment plus rhsTM was performed. Blood samples were collected 6 h after the end of the crush period. Complete blood count and platelets were measured. In addition, serum lactate, base deficit, serum potassium, creatine phosphokinase, blood urea nitrogen, creatinine, myoglobin, and some cytokines were evaluated. In another experiment, survival of each group was monitored for 72 h after the end of the crush period. Combined administration of rhsTM and volume resuscitation significantly decreased hemoconcentration and hyperkalemia. The serum interleukin-6 level and mortality were also significantly improved in the combination group compared with those in the other groups. We conclude that prophylactic combination of rhsTM administration and volume resuscitation may be an effective therapy for severe crush injury.

Soluble thrombomodulin is antithrombotic in the presence of neutralising antibodies to protein C and reduces circulating activated protein C levels in primates

We studied whether there was a relationship between the anticoagulant effects of recombinant human soluble thrombomodulin (rhsTM) and activation of protein C in a primate model of acute vascular graft thrombosis in 11 baboons (Papio species). Baboons were pretreated with 0.1, 1 and 5 mg/kg of rhsTM, with or without co-injection of a neutralising monoclonal antibody to protein C (HPC4) in the 1 mg/kg rhsTM group. Subsequently, thrombogenic polyester grafts were deployed for 3 h into chronic exteriorised arteriovenous shunts. Thrombus growth in the graft, plasma-activated protein C (APC) levels, coagulation and thrombosis markers were determined. In untreated baboons, baseline circulating APC levels more than doubled and graft thrombi propagated until reaching equilibrium in about 1 h. Treatment with rhsTM reduced thrombus propagation rates, prolonged the clotting and bleeding times, decreased thrombin-antithrombin complex, beta-thromboglobulin and fibrinopeptide A levels, and, surprisingly, also decreased systemic APC levels, in a dose-dependent manner. In the presence of HPC4 antibody to inhibit APC generation, the acute antithrombotic activity of rhsTM on graft thromboses was not attenuated for up to 80 min, but sustained thrombus accumulation was observed over a 180-min period. These findings suggest that, in contrast to the prevailing hypotheses, the primary antithrombotic activity of rhsTM is independent of protein C, at least in this primate model. Direct inhibition of thrombin's prothrombotic activity upon complex formation with rhsTM might explain the molecular mechanism of the observed antithrombotic effect.

Limited generation of activated protein C during infusion of the protein C activator thrombin analog W215A/E217A in primates

Anticoagulation with activated protein C (APC) reduces the mortality of severe sepsis. We investigated whether the circulating protein C (PC) pool could be utilized for sustained anticoagulation by endogenous APC. To generate APC without procoagulant effects, we administered the anticoagulant thrombin mutant W215A;E217A (WE) to baboons. In preliminary studies, administration of high dose WE (110 microg kg(-1) i.v. bolus every 120 min; n = 2) depleted PC levels by 50% and elicited transient APC bursts and anticoagulation. The response to WE became smaller with each successive injection. Low dose WE infusion (5 microg kg(-1) loading + 5 microg kg(-1) h(-1) infusion; n = 5) decreased plasma PC activity by 15%, from 105% to 90%, to a new equilibrium within 60 min. APC levels increased from 7.5 ng mL(-1) to 86 ng mL(-1) by 40 min, then declined, but remained elevated at 34 ng mL(-1) at 240 min. A 22-fold higher dose WE (n = 5) decreased PC levels to 60% by 60 min without significant further depletion in 5 h. The APC level was 201 ng mL(-1) at 40 min and decreased to 20 ng mL(-1) within 120 min despite continued activator infusion. Co-infusion of WE and equimolar soluble thrombomodulin (n = 5) rapidly consumed about 80% of the PC pool with significant temporal increase in APC generation. In conclusion, low-grade PC activation by WE produced sustained, clinically relevant levels of circulating APC. Limited PC consumption in WE excess was consistent with the rapid depletion of cofactor activity before depletion of the PC zymogen. Reduced utilization of circulating PC might have similar mechanism in some patients.

Molecular cloning of canine thrombomodulin cDNA and expression in normal tissues

Thrombomodulin (TM) is a glycoprotein localized mainly on endothelial cell surfaces, and is a major regulator of vascular thromboresistance. The entire open reading frame of canine TM cDNA comprises 1737 bp, encoding 578 amino acid residues. Comparison of the deduced amino acid sequence from canine TM with those of human, mouse, rat, rabbit and bovine (partial) TM sequences revealed 73.1%, 69.1%, 65.8%, 74.3% and 69.5% identity, respectively. Canine TM mRNA expression was confirmed by RT-PCR analysis in lung, liver, spleen, kidney, pancreas and lymph node, and was relatively low in heart, cerebrum, urinary bladder and uterus. The present results provide valuable data for research into canine coagulation disorders.

Thrombomodulin-protein C-EPCR system: integrated to regulate coagulation and inflammation

Late in the 18th century, William Hewson recognized that the formation of a clot is characteristic of many febrile, inflammatory diseases (Owen C. A History of Blood Coagulation. Rochester, Minnesota: Mayo Foundation; 2001). Since that time, there has been steady progress in our understanding of coagulation and inflammation, but it is only in the past few decades that the molecular mechanisms linking these 2 biologic systems have started to be delineated. Most of these can be traced to the vasculature, where the systems most intimately interact. Thrombomodulin (TM), a cell surface-expressed glycoprotein, predominantly synthesized by vascular endothelial cells, is a critical cofactor for thrombin-mediated activation of protein C (PC), an event further amplified by the endothelial cell protein C receptor (EPCR). Activated PC (APC), in turn, is best known for its natural anticoagulant properties. Recent evidence has revealed that TM, APC, and EPCR have activities that impact not only on coagulation but also on inflammation, fibrinolysis, and cell proliferation. This review highlights recent insights into the diverse functions of this complex multimolecular system and how its components are integrated to maintain homeostasis under hypercoagulable and/or proinflammatory stress conditions. Overall, the described advances underscore the usefulness of elucidating the relevant molecular pathways that link both systems for the development of novel therapeutic and diagnostic targets for a wide range of inflammatory diseases.

Statins increase thrombomodulin expression and function in human endothelial cells by a nitric oxide-dependent mechanism and counteract tumor necrosis factor alpha-induced thrombomodulin downregulation

Expression of functionally active thrombomodulin (TM) on the luminal surface of endothelial cells is critical for vascular thromboresistance. TM maintains thrombohemorrhagic homeostasis by forming a complex with thrombin, which subsequently loses its procoagulant properties and instead activates protein C. Acquired deficiency of endothelial TM is of particular pathophysiological significance in sepsis and related disorders. We show here that two different 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins), atorvastatin and simvastatin, strongly increase the expression and functional activity of TM in human umbilical vein endothelial cells, human coronary artery endothelial cells, and EA.hy926 endothelial cells. The increase in endothelial TM conferred by statin was prevented by the addition of mevalonic acid, geranylgeranyl-pyrophosphate, and nitric oxide scavenger, and was mimicked by the addition of a specific inhibitor of geranylgeranyl transferase, as well as by nitric oxide donors. Moreover, statin counteracted tumor necrosis factor alpha-induced downregulation of endothelial cell TM. The increase in endothelial cell TM activity in response to statin constitutes a novel pleiotropic (non-lipid-related) effect of these commonly used compounds, and may be of clinical significance in disorders where deficient endothelial TM and protein C activation play a pathophysiological role.

Establishment of a standard assay method for human thrombomodulin and determination of the activity of the Japanese reference standard

This study was undertaken to establish a standard method for determination of the activity of human (h) thrombomodulin (TM). The reactions mainly consisted of formation of a h-TM and h-thrombin complex, activation of h-protein C by the complex and digestion of substrate by activated h-protein C. Linear time-dependent formation of p -nitroaniline from the substrate, S-2366, was observed up to 12 min during measurement of the activity of urinary h-TM (uh-TM) reference material by the standard method. Therefore, 10 minutes was established as the reaction time in the standard method. In the standard method, we defined the activity of h-TM forming 0.1 micromol of p -nitroaniline per min in the reaction as 1 JRS Unit. Recombinant h-TM (rh-TM) and uh-TM reference material gave rectilinear dose-response curves within a certain range of specific activities by their original methods in the standard method. The validity of the standard method was assessed based on the coefficients of variation (CV) obtained in the various measurements of h-TM. Intra-batch precision (CV) of h-thrombin and h-protein C was 2.90% and 6.57%, respectively, in the measurement of uh-TM activity. The intra-sample, inter-day, and inter-laboratory precision (CV) was 1.30%, 1.63% and 5.02%, respectively, in the measurement of the first Japanese reference standard for h-TM coded TJRS1. In these assays, the activity of the first Japanese standard was also determined and found to be 205 JRS units per ampoule. When the stability of the Japanese reference standard was assessed by measuring of the standard stored under various thermal conditions, the predicted loss of activity assuming monomolecular degradation according to the Arrhenius equation was less than 3.0% during 103 years at -20 degrees C. These results indicate that the standard method is appropriate for determination of the activity of h-TM and that the Japanese reference standard for h-TM, whose activity was determined here, can be stored at -20 degrees C for long periods without loss of activity.

Factor Xa-inhibitor (DX-9065a) modulates the leukocyte-endothelial cell interaction in endotoxemic rat

Abnormalities of vascular endothelial function and coagulation play important roles in the development of septic organ dysfunction. DX-9065a is a novel Factor Xa inhibitor that is expected to modulate both coagulation and endothelial function. The purpose of this study is to examine the effect of DX-9065a on leukocyte-endothelial interaction. Rats were injected with 1.0 mg/kg of endotoxin simultaneously with saline, (placebo group), 0.3 mg/kg DX-9065a (low-dose group), or 3.0 mg/kg DX-9065a (high-dose group; n = 6 in each group). At 1 and 3 h after injection, the mesenteric microcirculation was observed under intravital microscopy. In addition, TNF, IL-6, alanine aminotransferase (ALT), blood urea nitrogen (BUN), and lactate levels were measured. The number of leukocytes adhering to the endothelium was significantly reduced in both the high-dose and low-dose groups (P < 0.05 for both, compared to the control group). A comparison of the cytokine levels showed that the peak levels in the treatment groups tended to be lower. Markers of organ damage also showed less increase in the treatment groups (P < 0.05 for both treatment groups compared to the control group). In summary, the Factor Xa inhibitor DX-9065a showed a protective effect on the microcirculation of endotoxemic rats by attenuating leukocyte-endothelial interaction. Although the mechanism for this effect could not be fully elucidated, suppression of both excessive coagulation and cytokine production appear to play a role.

The effects of danaparoid, dalteparin and heparin on tissue factor-induced experimental disseminated intravascular coagulation and bleeding time in the rat

Danaparoid and heparin, on the basis of anti-activated factor X (anti-FXa) activity, were equipotent in accelerating the rate of interaction of FXa and antithrombin III. In rat tissue factor-induced disseminated intravascular coagulation (DIC) models, an intravenous administration of danaparoid inhibited the decrease in plasma fibrinogen and platelet counts and the increase in serum fibrinogen degradation products. Expressed on the basis of anti-FXa activity, these effects were comparable with those of dalteparin and heparin. In rat mesenteric small artery and vein, less bleeding was observed after intravenous administration of danaparoid than after dalteparin or heparin. Danaparoid did not affect adenosine diphosphate- or collagen-induced platelet aggregation, and showed weaker inhibitory effects on aggregation induced by thrombin, or collagen + thrombin, than did dalteparin or heparin. These findings suggest that danaparoid may be useful for the prevention of DIC and has less tendency to cause bleeding than dalteparin or heparin, probably as a result of its weaker ability to inhibit platelet aggregation.

Deranged blood coagulation equilibrium as a factor of massive liver necrosis following endotoxin administration in partially hepatectomized rats

Activated Kupffer cells provoke massive liver necrosis after endotoxin stimulation through microcirculatory disturbance caused by sinusoidal fibrin deposition in rats undergoing 70% hepatectomy. In these rats, serum activities of purine nucleoside phosphorylase (PNP) and alanine transaminase (ALT) were increased at 1 and 5 hours, respectively, following endotoxin administration. When 70% resected liver was perfused with Dulbecco's modified Eagle medium (DMEM) containing heat-inactivated fetal calf serum, the increase in both enzyme activities was not affected by addition of endotoxin during perfusion, suggesting that activated Kupffer cells injured neither sinusoidal endothelial cells nor hepatocytes. The activity of tissue factor, an initiator of blood coagulation cascade, was much higher in Kupffer cells isolated from partially hepatectomized rats than in those from normal rats. In contrast, mRNA expressions of tissue factor pathway inhibitor (TFPI) as well as thrombomodulin were almost undetectable in normal and partially resected livers. When recombinant human TFPI was injected intravenously in 70% hepatectomized rats, TFPI was markedly stained on the surfaces of sinusoidal endothelial cells and microvilli of hepatocytes on immunohistochemistry. In these rats, endotoxin-induced liver injury was significantly attenuated compared with rats given no TFPI. Similar attenuation was also found in rats receiving recombinant human thrombomodulin. These results suggest that fibrin deposition developing in 70% hepatectomized rats after endotoxin administration may be caused by deranged blood coagulation in the hepatic sinusoids through increasing tissue factor activity in Kupffer cells and minimal TFPI and thrombomodulin in endothelial cells. The destruction of sinusoidal endothelial cells as well as hepatocytes may occur as a result of microcirculatory disturbance caused by such sinusoidal fibrin deposition.

The sepsis-coagulant axis: a review

Activation of coagulation is a normal component of the acute inflammatory response. Inflammatory cytokines initiate coagulation events locally at sites of inflammation by converting endothelium from an antithrombotic surface to a prothrombotic surface; by stimulating tissue factor production, which activates both the extrinsic and intrinsic coagulation systems; and by stimulating production of platelet-activating factors. The fibrinolytic system is initially activated but is subsequently inhibited. This results in a marked imbalance in coagulation and fibrinolysis resulting in a net procoagulant state. When thrombin generation and platelet activation exceed the body's capacity to inactivate or remove these factors, disseminated intravascular coagulation (DIC) results. DIC directly contributes to multiple organ failure and death associated with sepsis. Presently available treatments (i.e., heparin and aspirin) are relatively ineffective in treating DIC; however, newer, more potent drugs may soon be available for clinical use.

A novel recombinant soluble human thrombomodulin, ART-123, activates the protein C pathway in healthy male volunteers

The effect of a novel recombinant soluble human thrombomodulin, ART-123, on protein C activation was investigated by measuring plasma prothrombinase activity in four healthy male volunteers. ART-123 at a dose of 0.3 mg was administered as a bolus intravenous injection for 1 minute. Plasma ART-123 concentration and prothrombinase activity were determined before and immediately, 24, and 48 hours after injection, and thromboelastography was recorded before and immediately and 24 hours after injection. The mean elimination half-life was 19.82 +/- 2.10 hours. Compared with pretreatment levels, ART-123 reduced prothrombinase activity by 44.2 +/- 11.7%, 52.1 +/- 10.8%, and 61.0 +/- 14.7%, respectively, immediately, 24, and 48 hours after injection, suggesting that ART-123 activated the protein C pathway. ART-123 did not affect thromboelastography values. There were no abnormal findings for objective signs or laboratory tests, including blood pressure, heart rate, electrocardiogram, body temperature, hematology, coagulation and hemostatic parameters, blood chemistry, and urinalysis. Based on these observations, ART-123 at a dose of 0.3 mg can activate the protein C pathway in healthy volunteers.

Pharmacokinetics and safety of a novel recombinant soluble human thrombomodulin, ART-123, in healthy male volunteers

The safety and pharmacokinetics of a novel recombinant soluble human thrombomodulin, ART-123 were evaluated in single- and multiple-dose studies involving 16 healthy male volunteers. ART-123 was administered by intravenous infusion over 2 hours. The single-dose study indicated that plasma ART-123 levels at doses of 0.03, 0.1, and 0.3 mg declined biexponentially and those half-lives were approximately 4 hours (t1/2 alpha) and 20 hours (t1/2 beta), respectively. The mean plasma peak concentration and area under the plasma concentration-time curves increased in proportion to the given doses. Mean urinary recovery within the first 48 hours was between 54.3% and 59.8% of dose. In the multiple-dose study, ART-123 was administered at a dose of 0.2 mg once daily for 3 days. ART-123 did not accumulate as judged from plasma concentrations and urinary recovery. There were no abnormal findings in objective symptoms and laboratory findings, including blood pressure, heart rate, electrocardiogram, body temperature, hematology, bleeding time, coagulation and hemostatic parameters, blood chemistry, and urinalysis. There were no significant adverse reactions or abnormalities in physical and laboratory examinations that could definitely be attributed to the drug at a dose of 0.3 mg as a single administration and at a dose of 0.2 mg once daily for 3 days. These results indicate that ART-123 is safe at doses up to 0.2 mg once daily for 3 days and may have clinical application. Further studies are needed, however, to evaluate the safety and pharmacokinetics of ART-123 in the targeted population.

Effect of human urinary thrombomodulin on endotoxin-induced intravascular coagulation and pulmonary vascular injury in rats

Adult respiratory distress syndrome (ARDS) and disseminated intravascular coagulation (DIC) are serious complications of sepsis. Thrombomodulin, an important endothelial anticoagulant, binds thrombin to generate activated protein C (APC). To determine whether thrombomodulin purified from human urine (urinary thrombomodulin, UTM) is useful for the treatment of DIC and ARDS in sepsis, we examined the effect of UTM on endotoxin (ET)-induced coagulation abnormalities and pulmonary vascular injury in rats. Intravenous administration of UTM prevented the ET-induced pulmonary accumulation of leukocytes and the increase in pulmonary vascular permeability, as well as ET-induced histological changes such as leukocyte infiltration and pulmonary interstitial edema. On the other hand, dansyl-Glu-Gly-Arg-chloromethyl ketone-treated factor Xa (DEGR-Xa), a selective inhibitor of thrombin generation, did not prevent these effects of ET. UTM did not prevent ET-induced pulmonary accumulation of leukocytes and pulmonary vascular injury in rats pretreated with DEGR-Xa. Our findings suggest that UTM attenuates ET-induced coagulation abnormalities and pulmonary vascular injury. Furthermore, the latter effect may be dependent on the capacity of UTM to activate protein C.

Antithrombotic effects of recombinant human soluble thrombomodulin (rhs-TM) on arteriovenous shunt thrombosis in rats

We examined the antithrombotic effect of recombinant human soluble thrombomodulin (rhs-TM) using an arteriovenous shunt thrombosis model and its influence on hemostasis in rats. Intravenous administration of rhs-TM (0.5-4 mg/kg) significantly inhibited thrombus formation and prolonged ex vivo activated partial thromboplastin time (APTT) in a dose-dependent manner. Thrombus formation was inhibited to the same extent in animals treated with heparin (25-200 U/kg) and in those treated with rhs-TM (0.5-4 mg/kg), but heparin had a much stronger effect on prolonging APTT. In the hemorrhagic study using the rat template bleeding time method, rhs-TM exhibited the prolongation of the bleeding time only at the highest effective dose (rhs-TM; 4 mg/kg) of the thrombosis experiments. Thus, rhs-TM exhibits the inhibitory effect on thrombus formation with less APTT prolongation in comparison with heparin and without significant pertubation of hemostasis.