Marked difference in pathophysiology between tissue factor- and lipopolysaccharide-induced disseminated intravascular coagulation models in rats

Effect of NOS Inhibitors and Anticoagulants on Nitric Oxide Production in a Tissue-factor Induced Rat DIC Model

BACKGROUND/AIM

We examined the mechanism of nitric oxide (NO) production in a tissue-factor (TF)-induced disseminated intravascular coagulation (DIC) model in rats, using inducible nitric oxide synthase (iNOS) inhibitor (L-NIL), endothelial nitric oxide synthase (eNOS) inhibitor (L-NAME), Factor Xa inhibitor (DX-9065a), and thrombin inhibitor argatroban.

MATERIALS AND METHODS

Experimental DIC was induced by sustained infusion of 3.75 U/kg TF for 4 h via the tail vein. We then investigated the effect of these four agents on TF-induced DIC.

RESULTS

Administration of L-NIL or L-NAME during induction of TF-induced DIC did not affect hemostatic markers, whereas elevated plasma levels of NO metabolites (NOX) were significantly suppressed by co-administration of L-NAME. A significant increase in eNOS-mRNA expression was observed in the TF-induced DIC model. Argatroban almost completely suppressed eNOS-mRNA expression.

CONCLUSION

eNOS plays an important role in the NO production in the TF-induced DIC, and thrombin is a key stimulant of eNOS-mRNA expression in this model.

Monitoring Compound-Related Effects on Coagulability in Rats and Cynomolgus and Rhesus Monkeys by Thrombin Generation Kinetic Measurement

Thrombin generation assay (TGA) is a sensitive method for the assessment of the global clotting potential of plasma. This kinetic assay can detect both hypocoagulable and hypercoagulable conditions: delayed or reduced thrombin generation leading to a prolonged clotting time, or induced thrombin activity, shifting the coagulation cascade toward thrombosis. The purpose of this study is to qualify the TGA in nonhuman primates (NHP) and rats for its use during nonclinical in vivo and in vitro studies. Blood was drawn from nonanesthetized animals, and platelet-poor plasma was obtained after double centrifugation; coefficients of variation were <10% for all derived parameters of thrombin generation assessed with 5 pM of tissue factor. Thrombin generation was evaluated in vitro in rat and NHP plasmas with ascending doses of unfractionated heparin (UFH), recombinant tissue factor, and anticoagulant compounds. Thrombin generation was decreased with UFH and anticoagulant compounds, but was increased in the presence of tissue factor, in a dose-dependent manner. In a rat model of inflammation, animals were administered a low dose of lipopolysaccharides. Thrombin generation measurements were decreased 3 hours post-LPS administration with a nadir at 24 hours, while thrombin-antithrombin complexes reached a peak at 8 hours, supporting an earlier production of thrombin. In conclusion, these data demonstrated that TGA can be performed in vitro for screening of compounds expected to have effects on coagulation cascade, and thrombin generation can be measured at interim time points during nonclinical in vivo studies in rats and NHP.

Activation of autophagy is involved in the protective effect of 17β-oestradiol on endotoxaemia-induced multiple organ dysfunction in ovariectomized rats

Oestrogens have been reported to attenuate acute inflammation in sepsis. In this study, the effects of long-term oestrogen replacement with 17β-oestradiol (E2 ) on endotoxaemia-induced circulatory dysfunction and multiple organ dysfunction syndrome were evaluated in ovariectomized (Ovx) rats. E2 (50 μg/kg, s.c., 3 times/week) was administered for 8 weeks, followed by the induction of endotoxaemia by intravenous infusion of lipopolysaccharides (LPS; 30 mg/kg/4 hrs). Oestrogen deficiency induced by ovariectomy for 9 weeks augmented the LPS-induced damage, including endotoxic shock, myocardial contractile dysfunction, renal dysfunction and rhabdomyolysis. Cardiac levels of NF-κB p65, iNOS and oxidized glutathione, free radical production in skeletal muscles, myoglobin deposition in renal tubules, and plasma levels of plasminogen activator inhibitor-1, TNF-α, and IL-6 were more pronounced in the Ovx + LPS group than in the Sham + LPS group. Long-term treatment of E2 prevented this amplified damage in Ovx rats. Six hours after LPS initiation, activation of the autophagic process, demonstrated by increases in Atg12 and LC3B-II/LC3B-I ratios, and induction of haem oxygenase (HO)-1 and heat-shock protein (HSP) 70 protein expression in myocardium were increased significantly in the Ovx + E2  + LPS group. These results suggest that activation of autophagy and induction of HO-1 and HSP70 contribute to the protective effect of long-term E2 replacement on multiple organ dysfunction syndrome in endotoxaemia.

Pretreatment of curcumin attenuates coagulopathy and renal injury in LPS-induced endotoxemia

Disseminated intravascular coagulation (DIC) is a lethal situation in severe infections, characterized by the systemic formation of microthrombi complicated with bleeding tendency and organ dysfunction. Current clinical trials are not promising. In this study, we investigated the protective effect of curcumin in a lipopolysaccharide (LPS)-induced DIC model in rats. Experimental DIC was induced by sustained infusion of LPS (10 mg/kg body weight) for 4 h through the tail vein. Curcumin (60 mg/kg body weight) was given intraperitoneally 3 h before LPS infusion. Results showed that, in vivo, curcumin reduced the mortality rate of LPS-infused rats by decreasing the circulating TNF-α levels and the consumption of peripheral platelets and plasma fibrinogen. Furthermore, in vivo curcumin also has the effect of preventing the formation of fibrin deposition in the glomeruli of kidney. These results reveal the therapeutic potential of curcumin in infection-related coagulopathy of DIC.

17-DMAG, an HSP90 Inhibitor, Ameliorates Multiple Organ Dysfunction Syndrome via Induction of HSP70 in Endotoxemic Rats

Sepsis is a systemic inflammatory disorder, accompanied with elevated oxidative stress, leading to multiple organ dysfunction syndrome (MODS), and disseminated intravascular coagulation. 17-Dimethylaminoethylamino- 17-demethoxygeldanamycin (17-DMAG), a heat shock protein (HSP) 90 inhibitor, has been reported to possess anti-inflammatory effects. In this study, the beneficial effects of 17-DMAG on lipopolysaccharide (LPS) induced MODS and DIC was evaluated in anesthetized rats. 17-DMAG (5 mg/kg, i.p.) was significantly increased survival rate, and prevented hypotension in LPS (30 mg/kg i.v. infused for 4 h) induced endotoxemia. The elevated levels of alanine aminotransferase (ALT), creatine phosphokinase (CPK), lactate dehydrogenase, creatinine, nitric oxide (NO) metabolites, IL-6, and TNF-α in LPS-exposed rat plasma were significantly reduced by 17-DMAG. Moreover, 17-DMAG suppressed LPS-induced superoxide anion production and caspase 3 activation in heart tissues. LPS induced the prolongation of prothrombin time, and a pronounced decrease in platelet count, which were improved by 17-DMAG. 17-DMAG markedly induced HSP70 and heme oxygenase (HO)-1, and suppressed inducible nitric oxide synthase (iNOS) and phosphorylated NF-κB p65 protein expression in organs 6 h after LPS initiation. Pretreatment with high dose of quercetin (300 mg/kg, i.p.), as an HSP70 inhibitor, reversed the beneficial effects of 17-DMAG on survival rate, plasma levels of ALT, CPK, creatinine, IL-6, and NO metabolites, iNOS induction, and caspase-3 activation in LPS-treated rats. In conclusion, 17-DMAG possesses the anti-inflammatory and antioxidant effects that were proved through LPS-induced acute inflammation, which is associated with induction of HSP70 and HO-1, leading to prevent MODS in sepsis.

Effects of gabexate mesilate on coagulopathy and organ dysfunction in rats with endotoxemia: a potential use of thrombelastography in endotoxin-induced sepsis

Sepsis and its associated multiple organ failure are related to high mortality in critical patients. Several studies have reported that gabexate mesilate, a synthetic inhibitor of trypsin-like serine protease, protects tissues/organs against injury in the models of endotoxemia. The aim of this study was to examine whether gabexate mesilate could attenuate coagulopathy and organ dysfunction in lipopolysaccharide (LPS)-induced sepsis model by using thrombelastography (TEG). LPS (7.5  mg/kg/h, intravenouly for 4  h) was administered to male adult Wistar rats. Some of the LPS rats received a continuous infusion of gabexate mesilate (10  mg/kg/h, intravenously for 8.5  h) for 30  min before the LPS administration. Variable parameters of hemodynamics, biochemistry, hemostasis and inflammatory response were measured for 6  h after the LPS infusion. TEG variables (R-time, K-time, α-angle, and maximal amplitude) were also measured. The pretreatment of LPS rats with gabexate mesilate significantly attenuated the lung, liver and kidney dysfunction, consumptive coagulopathy, the increases in serum tumor necrosis factor-α, interleukin-6, plasma thrombin-antithrombin complex and plasminogen activator inhibitor-1, and neutrophils infiltration score in lung, liver and kidney, compared with the LPS alone group. In addition, TEG parameters correlated with tissue and liver injury in the late phase of endotoxemia. In particular, a strong negative correlation between maximal amplitude at 4  h and Ln (lactate dehydrogenase) at 6  h after LPS infusion was noted (r = -0.752, P < 0.001, R = 0.566). These results indicate that beneficial effects of anticoagulants (e.g. gabexate mesilate) in endotoxemia could be monitored by TEG per se.

Pilot trial of a novel two-step therapy protocol using nebulized tranexamic acid and recombinant factor VIIa in children with intractable diffuse alveolar hemorrhage

BACKGROUND AND OBJECTIVES

Diffuse alveolar hemorrhage (DAH) is a life threatening condition with very limited, often unsuccessful, therapeutic options. This study aimed at exploring the feasibility and efficacy of nebulized tranexamic acid TXA (n-TXA) and nebulized recombinant factor VIIa (n-rFVIIa) when used in a two-step therapy protocol in children with intractable DAH in a pediatric intensive care unit.

METHODS

In a prospective trial, n-TXA (250 mg/dose for children < 25 kg and 500 mg/dose for children > 25 kg) was administered to 18 children (median age [interquartile range]; 24.0 months [11.3, 58.5]) with intractable DAH. N-rFVIIa (35 micro g/kg/dose for children < 25 kg, and 50 micro g/kg/dose for children > 25 kg) was added if no or minimal response was seen after 3 to 4 doses (18 to 24 hours) of n-TXA.

RESULTS

DAH was stopped in 10 (55.6%) children with n-TXA alone within 24 hours of therapy. Documented concomitant respiratory infection showed a significant negative association with response to n-TXA in a step.wise regression analysis (OR=0.06; 95% CI=0.01-0.74). In the other 8 (44.4%) children, n-rFVIIa was added due to n-TXA failure. Six (75.0%) showed complete cessation of DAH, while two children failed to respond with the addition of n-rFVIIa (25.0%). None of the children who responded to therapy showed recurrence of DAH after therapy termination. No complications related to therapy were recorded.

CONCLUSIONS

n-TXA and n-rFVIIa were effective and safe when used in a two-step-therapy protocol to control intractable DAH in pediatric patients in intensive care settings. This therapy modality warrants further exploration through larger multicenter clinical trials.

Hematological and morphological investigation of thrombogenic mechanisms in the lungs of phenylhydrazine-treated rats

Abnormality in hematological condition including hemolytic disorders has been suggested one of the risk factor of pulmonary thrombosis. We previously reported that phenylhydrazine (PHZ) could induce acute thrombosis in the rat lung. In this study, time-related hematological and histopathological changes were evaluated in PHZ-treated rats to reveal the pathogenesis of pulmonary thrombosis in hemolytic condition. Male Sprague-Dawley rats were administered PHZ at 40 mg/kg/day daily for up to 4 days (n=6). At 24 h after the last administration (i.e. on days 1, 2, 3, or 4), animals were euthanized and samples were subjected to hematology, light microscopy, and electron microscopy. PHZ-treated rats developed severe anemia on day 1 or later. On day 2 and after, congestion in the alveolar septa corresponding to accumulation of deformed/ghost erythrocytes in the alveolar capillaries was observed, which was the earliest change that preceded thrombus formation. Focal fibrin deposition in the alveolar septa was noted on day 3 and it expanded widely by day 4, while endothelial injury were minimally noted just on day 4. These congestive/thrombotic changes were predominant in the pulmonary capillaries. Changes in hemostatic parameters were noted only on day 4; which were prolonged prothrombin time and activated partial thromboplastin time, greatly increased plasma thrombin-antithrombin complex levels with statistical significance, and slightly decreased fibrinogen levels. In conclusion, the trigger of acute pulmonary thrombosis in PHZ-treated rats was considered to be regional stasis resulting from blockage caused by the deformed erythrocytes, and subsequent systemic hemostatic disruption.

Abnormal inflammation leads to maternal coagulopathies associated with placental haemostatic alterations in a rat model of foetal loss

Spontaneous pregnancy loss is often associated with aberrant maternal inflammation and systemic coagulopathies. However, the role of inflammation in the development of obstetric coagulopathies is poorly understood. Further, questions remain as to whether systemic coagulopathies are linked to placental haemostatic alterations, and whether these local alterations contribute to a negative foetal outcome. Using a model of spontaneous foetal loss in which pregnant rats are given a single injection of bacterial lipopolysaccharide (LPS), we characterised the systemic maternal coagulation status following LPS administration using thromboelastography (TEG), a global haemostatic assay that measures the kinetics of clot formation. Systemic maternal coagulopathy was evident in 82% of LPS-treated rats. Specifically, we observed stage-I, -II, and -III disseminated intravascular coagulation (DIC) and hypercoagulability. Modulation of inflammation through inhibition of tumour necrosis factor α with etanercept resulted in a 62% reduction in the proportion of rats exhibiting coagulopathy. Moreover, inflammation-induced systemic coagulopathies were associated with placental haemostatic alterations, which included increased intravascular, decidual, and labyrinth fibrin deposition in cases of DIC-I and hypercoagulability, and an almost complete absence of fibrin deposition in cases of DIC-III. Furthermore, systemic and placental haemostatic alterations were associated with impaired utero-placental haemodynamics, and inhibition of these haemostatic alterations by etanercept was associated with maintenance of utero-placental haemodynamics. These findings indicate that modulation of maternal inflammation may be useful in the prevention of coagulopathies associated with complications of pregnancy.

Diagnostic criteria and laboratory tests for disseminated intravascular coagulation

Disseminated intravascular coagulation (DIC) is associated with organ failure and it is often fatal condition. The main underlying diseases are infection, hematological malignancy and solid cancer. DIC is subclassified into overt DIC and non-overt DIC. The International Society on Thrombosis and Haemostasis (ISTH) and the Japanese Association for Acute Medicine (JAAM) published the diagnostic criteria for DIC after several recent clinical trials. These diagnostic criteria are modified versions of the Japanese Ministry of Health, Labor and Welfare (JMHLW) criteria. The JAAM diagnostic criteria demonstrated excellent sensitivity for mortality but low specificity. The mechanisms of onset of DIC vary based on the underlying diseases, and depend on tissue factor, cytokines, etc. Early diagnosis and early treatment for DIC are important, and the use of hemostatic molecular markers is necessary to successfully make an early and rapid diagnosis. The mortality of DIC might be improved by the administration of recombinant activated protein C or recombinant thrombomodulin. Further investigation to improve the mortality of DIC is required, including new methods for diagnosing and treating the disease.

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.

Thromboembolism and delayed cerebral ischemia after subarachnoid hemorrhage: an autopsy study

OBJECTIVE

Recent findings have cast doubt on vasospasm as the sole cause of delayed cerebral ischemia after subarachnoid hemorrhage.

METHODS

We reviewed the medical records of 29 patients who died after subarachnoid hemorrhage. Brain sections were taken from the insula, cingulate gyrus, and hippocampus. Adjacent sections were stained with hematoxylin-eosin and immunostained for thromboemboli. The density (burden) of the latter was calculated blindly and correlated with evidence for ischemia and with the amount of subarachnoid blood.

RESULTS

There is a strong correlation between microclot burden and delayed cerebral ischemia. Patients with clinical or radiological evidence of delayed ischemia had mean microclot burdens of 10.0/cm2 (standard deviation [SD], +/-6.6); those without had mean burdens of 2.8 (SD, +/-2.6), a highly significant difference (P = 0.002). There is also significant association (P = 0.001) between microclot burden and histological evidence of ischemia, with the mean burdens being 10.9 in sections exhibiting severe ischemia and 4.1 in those in which ischemia was absent. Microclot burden is high in patients who died within 2 days of hemorrhage, decreasing on Days 3 and 4. In delayed ischemia, the numbers rise again late in the first week and remain high until after the second week. In contrast, the average clot burden is low in patients dying without developing delayed ischemia. The amount of blood on an individual slide influenced the microclot burden on that slide to a highly significant extent (P < 0.001).

CONCLUSION

Thromboembolism after subarachnoid hemorrhage may contribute to delayed cerebral ischemia, which parallels that caused by vasospasm. The pathogenesis of thromboembolism is discussed.

Low dose endotoxin priming is accountable for coagulation abnormalities and organ damage observed in the Shwartzman reaction. A comparison between a single-dose endotoxemia model and a double-hit endotoxin-induced Shwartzman reaction

The clinical response of sepsis to a systemic inflammatory infection may be complicated by disseminated intravascular coagulation or DIC. In order to experimentally study the syndrome of DIC, we aimed for a severe sepsis model complicated by disseminated coagulation. Most -simplified- experimental models describing coagulation abnormalities as a consequence of sepsis are based on single dose endotoxemia. The so called-Shwartzman reaction contrarily, is elicited by a low dose endotoxin priming followed by an LPS challenge and is characterized by pathological manifestations that represent the syndrome of DIC. In order to investigate whether the Shwartzman reaction is superior to a single endotoxin challenge as a model for sepsis-induced DIC and to determine what the pathological effect is of an encounter of low endotoxin prior to an LPS challenge, we undertook the present study.

In this study we demonstrate that low-dose endotoxin priming prior to an LPS challenge in the Shwartzman reaction is accountable for micro-vascular thrombosis in lung and liver and subsequent (multi-) organ failure, not observed after a single-dose endotoxin challenge, which indicates that the Shwartzman reaction is well suited-model to study sepsis-induced DIC adversities. Remarkably, only minor differences in the innate immune response were established between the single-dose endotoxin challenge and the Shwartzman reaction.

Nafamostat Attenuated the Impairment of Fibrinolysis in Animal Sepsis Model by Suppressing the Increase of Plasminogen Activator Inhibitor Type 1

BACKGROUND

In endotoxemia, plasminogen activator inhibitor-1 (PAI-1) increases and develops clinical symptoms by suppressing fibrinolysis. We analyzed therapeutic advantage of nafamostat, a broad-range protease inhibitor, on fibrinolysis in an animal sepsis model.

METHODS

Male Wister rats infused with lipopolysaccharide (LPS) (50 mg/kg) alone or together with nafamostat (0.1 mg/kg/hr) for 4 hours were analyzed.

RESULTS

Plasma PAI-1 (4.2: 4.0-5.0 ng/mL, median and interquartile range) increased after LPS infusion (3700: 3400-4000), which was attenuated by nafamostat (2300: 2100-2600, p < 0.05). Fibrin(ogen) degradation products after LPS injection (173: 152-182 microg/mL) were further elevated by nafamostat (205: 205-228, p < 0.05), Nafamostat attenuated polymorphonuclear neutrophils infiltration in the liver, and tended to suppress plasma tumor necrosis factor-alpha levels. Nafamostat did not affect thrombin generation, platelet count, markers of liver and kidney function, and overall mortality.

CONCLUSIONS

Nafamostat appeared to improve impaired fibrinolysis by suppressing the increase of PAI-1 in plasma, though it did not largely improve clinical parameters.

Thrombocytopenia in the experimental leptospirosis of guinea pig is not related to disseminated intravascular coagulation

Background

Thrombocytopenia is commonly observed in severe leptospirosis. However, previous studies on coagulation alterations during leptospirosis resulted in inconsistent conclusions. Some findings showed that the prominent levels of thrombocytopenia observed in severe leptospirosis did not reflect the occurrence of disseminated intravascular coagulation (DIC) syndrome, while the others reached the conclusion that the hemorrhages observed in leptospirosis were due to DIC. The aim of this study is to elucidate whether DIC is an important feature of leptospirosis.

Methods

The leptospirosis model of guinea pig was established by intraperitoneal inoculation of Leptospira interrogans strain Lai. Hematoxylin and eosin (HE) staining, electron microscopy and immunohistochemistry staining were used to detect the pathologic changes. Platelet thrombus or fibrin thrombus was detected by HE, Martius Scarlet Blue (MSB) staining and electron microscopy. Hemostatic molecular markers such as 11-dehydrogenate thromboxane B2 (11-DH-TXB2), thrombomodulin (TM), thrombin-antithrombin III complex (TAT), D-Dimer and fibrin (ogen) degradation products (FDPs) in the plasma were examined by quantitative enzyme-linked immunosorbent assay (ELISA) to evaluate the hematological coagulative alterations in leptospirosis models.

Results

Pulmonary hemorrhage appeared in the model guinea pig 24 hours after leptospires intraperitoneal inoculation, progressing to a peak at 96 hours after the infection. Leptospires were detected 24 hours post-inoculation in the liver, 48 hours in the lung and 72 hours in the kidney by immunohistochemistry staining. Spiral form of the bacteria was initially observed in the liver, lung and kidney suggestive of intact leptospires, granular form of leptospires was seen as the severity increased. Platelet aggregation in hepatic sinusoid as well as phagocytosis of erythrocytes and platelets by Kupffer cells were both observed. Neither platelet thrombus nor fibrin thrombus was found in the liver, lung or kidney via morphological observation. Thrombocytopenia was observed in all infected guinea pigs of our experimental leptospirosis study. Analysis of hematologic molecular markers showed that 11-DH-TXB2 and TM in the plasma were elevated significantly. TAT that reflects the thrombin activation had a trend of decline after infection. Although D-dimer and FDPs increased statistically, the increasing may not bear clinical significance.

Conclusion

Pathologic and hematological studies for experimental leptospirosis of guinea pig indicated that the thrombocytopenia found in guinea pigs did not correlate with the occurrence of DIC. The platelet aggregation and Kupffer cells phagocytosis might be the potential causes of thrombocytopenia in severe leptospirosis.

Hemostatic activation in a chemically induced rat model of severe hemolysis and thrombosis

INTRODUCTION

In hemolytic diseases such as sickle cell disease and beta-thalassemia, the mechanisms of thrombosis are poorly understood, however erythrocyte/endothelium interactions are thought to play an important role. Appropriate animal models would increase our understanding of the pathophysiology of thrombosis and aid in the development of new therapeutic strategies. We previously reported that rats exposed to 2-butoxyethanol (2-BE) develop hemolysis and enhanced adherence of erythrocytes to the extracellular matrix, possibly secondary to the recruitment of cellular adhesion molecules at the erythrocyte/endothelium interface.

METHODS

We exposed rats to 250 mg/kg/day of 2-BE for 4 days, and collected blood for coagulation markers on each day.

RESULTS

As previously observed, erythrocytes dropped precipitously (8.0 to 1.8x10(6)/microl in 48 h), and diffuse microvascular thrombosis developed in the heart, lungs, liver, bones and eyes. Prothrombin times, activated partial thromboplastin times, fibrinogen, and antithrombin-III were unchanged between treated and control rats, indicating that hemostasis is largely unperturbed. However the thrombin-antithrombin III levels in the 2-BE treated rats for all days were 3-7 times greater than the control rats. The plasma intercellular adhesion molecule-1 (ICAM-1) levels of 2-BE treated animals were approximately twice that of the controls on days 2 and 3 and 1.5 times the controls on day 4 (P<0.05).

CONCLUSION

Our findings are consistent with the observations of increased erythrocyte aggregation, increased erythrocyte/endothelium interaction, and increased plasma ICAM-1 levels observed in sickle cell disease and beta-thalassemia patients. This model may be useful for studying therapeutic agents that disrupt erythrocyte/endothelium interactions.

Evaluation of new Japanese diagnostic criteria for disseminated intravascular coagulation in critically ill patients

New Japanese diagnostic criteria were prepared for disseminated intravascular coagulation (DIC) in critically ill patients and their usefulness was compared with the criteria of the International Society of Thrombosis and Haemostasis (ISTH) and those of the Japan Ministry of Health and Welfare (JMHW). In a retrospective study of patients with platelet counts of less than 150 x10(3)/mL, 52 cases (33.3%), 66 cases (42.3%), and 101 cases (64.7%) were diagnosed as DIC by the ISTH, JMHW, and new Japanese DIC criteria, respectively. The DIC state as diagnosed by the new Japanese DIC criteria included both DIC states as diagnosed by ISTH or JMHW criteria. Some DIC states diagnosed by the JMHW criteria included those diagnosed by ISHT criteria but this was not universal. The mortality of DIC as diagnosed by the ISTH or JMHW criteria was markedly high, compared to that for DIC diagnosed by the new Japanese criteria. The mortality of patients without DIC by ISTH was also high when they were diagnosed as DIC by the new Japanese criteria. The frequency of DIC by each set of diagnostic criteria was significantly higher in patients with infection than in those without infection. The mortality of DIC by each set of diagnostic criteria was significantly higher in patients with infection than in those without infection, and the mortality of overt-DIC by ISTH diagnostic criteria was also high in patients without infection.

Relationship between endothelin and the pathophysiology of tissue factor-induced and lipopolysaccharide-induced disseminated intravascular coagulation in rats: a study examining the effect of an endothelin receptor antagonist

We investigated the relationship between endothelin, a potent vasoconstrictor peptide, and the pathophysiology of disseminated intravascular coagulation (DIC), using two models of DIC. Experimental DIC was induced by sustained infusion of 50 mg/kg lipopolysaccharide (LPS), or 3.75 U/kg thromboplastin, for 4 h via the rat tail vein. The effect of administration of a non-selective endothelin receptor antagonist (TAK-044) (2, 10, or 50 mg/kg, from -0.5 to 4 h) on thromboplastin-induced DIC was not significant. However, LPS-induced elevation of alanine aminotransferase, creatinine and glomerular fibrin deposition was significantly suppressed by co-administration of TAK-044 in a dose-dependent manner, although no effect of TAK-044 was observed on the platelet count, fibrinogen concentration or the level of thrombin-antithrombin complex. Moreover, plasma levels of D-dimer, which reflect the grade of fibrinolysis of cross-linked fibrin, were significantly increased by co-administration of each dose of TAK-044 in the LPS-induced DIC model in rats. Our results suggest that vasoconstriction, as well as depressed fibrinolysis, contribute to severe organ dysfunction in LPS-induced, but not thromboplastin-induced, DIC, and that endothelin plays a role in the development of organ injury in LPS-induced DIC in rats.

Disseminated intravascular coagulation

The diagnosis of disseminated intravascular coagulation (DIC) was initially based on the detection of microthrombi. Current diagnosis involves laboratory assessment of hemostatic abnormalities although additional studies may often be necessary. DIC is characterized by hypercoagulability and hyperfibrinolysis and is caused by high offense factors or low defense factors. DIC is divided two stages: overt-DIC and non-overt-DIC. The diagnosis of overt-DIC state is based on the criteria developed by the International Society of Thrombosis Haemostasis in conjunction with the Japanese Ministry Health and Welfare. However, no criteria are currently available for the diagnosis of non-overt DIC. Although scientifically supported modalities for treatment of DIC are few, the use of activated protein C (APC) and low-molecular-weight heparin appear to hold promise.

Significance of Decreased Plasma D-Dimer Levels following Lipopolysaccharide-Induced Disseminated Intravascular Coagulation in Rats

Plasma D-dimer (DD) is considered to be one of the most useful markers in the diagnosis and assessment of disseminated intravascular coagulation (DIC). The present study was performed to clarify the role of DD in a rat model of lipopolysaccharide (LPS)-induced DIC in which low-molecular-weight heparin (LMWH) and tranexamic acid (TA) were used. We investigated whether a relationship exists between plasma DD levels and severity of DIC. Experimental DIC was induced in rats by a sustained 4-hour infusion of 30 mg/kg LPS administered via the tail vein (LPS group). Rats received either LPS alone (LPS group) or LPS combined with 200 U/kg LMWH (LPS+LMWH group) or 50 mg/kg TA (LPS+TA group) from -30 minutes to 4 hours. Blood was drawn from each rat at 4, 8, and 12 hours. Plasma levels of thrombin-antithrombin complex (TAT) and creatinine were suppressed in the LPS+LMWH group, and less glomerular fibrin deposition was observed compared with the LPS group. On the other hand, an increased level of creatinine and increased glomerular fibrin deposition were observed in the LPS+TA group compared with the LPS group. LMWH demonstrated a protective effect against LPS-induced DIC, resulting in increased survival at 12 hours, whereas TA had the opposite effect. From these results, it appears that LMWH protects against LPS-induced DIC, but TA exacerbates LPS-induced DIC. It was interesting that plasma levels of DD were almost completely suppressed by concurrent administration of either TA or LMWH in this LPS-induced DIC model. This finding suggested that plasma levels of DD were suppressed by inhibition of coagulation (reduced deposition of fibrin) in the LPS+LMWH group and that DD levels were also suppressed by inhibition of fibrinolysis (reduced degradation of fibrin by plasmin) in the LPS+TA group. Thus care should be taken when evaluating the significance of plasma DD levels, because suppressed levels can occur with progressive fibrin deposition and worsening organ dysfunction or improvement in the course of DIC.

BLOOD COAGULATION TESTS IN TOXICOLOGICAL STUDIES-REVIEW OF METHODS AND THEIR SIGNIFICANCE FOR DRUG SAFETY ASSESSMENT-

In general toxicological studies, prothrombin time and activated partial thromboplastin time are routinely measured to assess blood coagulation. Special (problem-driven) tests for blood coagulation are of significance to detect abnormalities and investigate the mechanism of toxicity in detail. In this review, we compiled widely scattered information on blood coagulation testing from different fields in the biological area, and reviewed the methods available and their significance in toxicological studies. The relevant literature cited here reports large species differences in platelet aggregation, coagulation factors or fibrinolysis, and technical limitations. However, the following tests are basically applicable to laboratory animals; (1) assays for individual coagulation factors and protein induced by vitamin K absence or antagonists (PIVKA) to investigate coagulation factor abnormalities; (2) platelet aggregation-, platelet adhesion-, platelet release-tests and von Willebrand factor assay to screen and/or investigate platelet dysfunction; (3) fibrin/fibrinogen degradation products (FDP), D-dimer and thromboelastogram to detect fibrinolitic abnormalities, and assays for plasminogen, plasmin and their activator/inhibitor to investigate fibrinolysis in detail; and (4) bleeding-time to grossly evaluate blood coagulation capability in vivo. An appropriate battery of these tests provides significant information for risk assessment of drugs.

Pathophysiology of disseminated intravascular coagulation (DIC) progresses at a different rate in tissue factor-induced and lipopolysaccharide-induced DIC models in rats

Tissue factor (TF) and lipopolysaccharide (LPS) are frequently used to induce disseminated intravascular coagulation (DIC) in experimental animal models. Although the pathophysiology of DIC may differ depending on which agent is used for induction, previous studies on models of DIC have not distinguished which DIC-inducing agent was used. In the present paper, we evaluate the characteristics of TF-induced and LPS-induced DIC using two types of DIC models, with special reference to selected hemostatic parameters and pathological findings within the kidney. Male Wistar rats were administered TF (3.75 U/kg; sustained infusion for 4 h) or LPS (30 mg/kg; sustained infusion for 4 h) via the tail vein, and blood sampling was performed at 0, 1, 3, 4, 5, 7, 9, 11, and 28 h. Judging from changes in the levels of thrombin-antithrombin complex, fibrinogen levels, and platelet counts, it is reasonable to conclude that the severity of both types of experimental DIC is similar with regard to hemostatic activation and consumption coagulopathy. A marked elevation in the level of D-dimer was noted without any organ dysfunction or much fibrin deposition in the kidney upon administration of TF. However, a markedly prolonged period of elevation in plasminogen activator inhibitor activity, a prolonged depression in antithrombin III activity, severe organ failure, and a markedly prolonged period of fibrin deposition in the kidney was observed following LPS administration. A modest number of the rats from the TF-induced DIC model died during the experimental period, whereas a large number of rats died during LPS-induced DIC, especially after 9 h. Since the time course of the pathophysiology differed remarkably among the TF-induced and LPS-induced DIC models in rats, we recommend that TF-induced and LPS-induced DIC be approached as distinct models in order to determine the implications of their experimental and clinical use.

Tissue factor-dependent coagulation protease signaling in acute lung injury

OBJECTIVES

To review the role of tissue factor-dependent coagulation in acute lung injury. To interpret preclinical and clinical data on therapeutic intervention of the coagulation cascade, focusing on the principles of proteolytic cell signaling of the coagulant and anticoagulant pathways.

DATA EXTRACTION AND SYNTHESIS

This review is based on published original research and relevant review articles on cell signaling by coagulation proteases and on experimental models that implicate the tissue factor-initiated coagulation cascade in acute lung injury and systemic inflammation.

CONCLUSIONS

The coagulation cascade signals via protease activated receptors in the tissue factor-initiation phase and downstream via the effector protease, thrombin. Bleomycin-induced acute lung injury is an example of thrombin signaling-dependent pathology. Frequently, thrombin signaling is a major contributor to inflammation in the extravascular space but intravascular thrombin signaling is a threshold-regulated event. At low concentrations, intravascular thrombin activates the protein C pathway by converting protein C (bound to endothelial cell protein C receptor) to activated protein C and this generates antiinflammatory signals along the activated protein C-endothelial cell protein C receptor-protease activated receptor 1 pathway on endothelial cells. Direct thrombin signaling only occurs when intravascular thrombin concentrations exceed a coagulant threshold. In systemic bacterial toxin-mediated inflammation, inhibition of thrombin is not sufficient to limit inflammation, whereas tissue factor inhibition interrupts a self-sustaining inflammatory escalation in acute lung injury. Therefore, in the vasculature, inflammatory signaling by the tissue factor initiation complex is favored over thrombin signaling.

Science review: role of coagulation protease cascades in sepsis

Cellular signaling by proteases of the blood coagulation cascade through members of the protease-activated receptor (PAR) family can profoundly impact on the inflammatory balance in sepsis. The coagulation initiation reaction on tissue factor expressing cells signals through PAR1 and PAR2, leading to enhanced inflammation. The anticoagulant protein C pathway has potent anti-inflammatory effects, and activated protein C signals through PAR1 upon binding to the endothelial protein C receptor. Activation of the coagulation cascade and the downstream endothelial cell localized anticoagulant pathway thus have opposing effects on systemic inflammation. This dichotomy is of relevance for the interpretation of preclinical and clinical data that document nonuniform responses to anticoagulant strategies in sepsis therapy.