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

Discriminatory ability and prognostic evaluation of presepsin for sepsis-related acute respiratory distress syndrome

Sepsis-related acute respiratory distress syndrome (ARDS) has worse clinical outcomes than non-sepsis-related ARDS. Presepsin is known to be elevated in sepsis, but little is known about its discriminatory ability and prognostic evaluation in patients with sepsis-related ARDS. This study was a multicenter prospective cohort study of 225 consecutive ARDS patients. Patients with sepsis-related ARDS had higher presepsin levels than patients with non-sepsis-related ARDS (P < 0.001). The area under the receiver operating characteristic (ROC) curve of presepsin (0.81) was significantly greater than that of PCT (0.62) in diagnosing sepsis-related ARDS (P = 0.001). Among patients with sepsis-related ARDS, presepsin levels were significantly higher in non-survivors than in survivors (P < 0.001). Presepsin was found to be an independent predictor of in-hospital mortality in sepsis-related ARDS. Based on ROC analysis, the addition of presepsin improved discrimination based on SOFA or APACHE II scores from 0.77 to 0.87 or 0.73 to 0.85 (all P < 0.05), respectively. The levels of plasma presepsin were positively correlated with disease severity, as determined by the SOFA score in the sepsis-related ARDS group (P < 0.001). Presepsin is a valuable biomarker for early stratification of sepsis-related ARDS. Higher plasma presepsin levels are associated with increased mortality in sepsis-related ARDS.

Disseminated Intravascular Coagulopathy (DIC): Pathophysiology, Laboratory Diagnosis, and Management

Disease entities such as sepsis, shock, obstetric complications, and neoplasms share the process of disseminated intravascular coagulopathy (DIC) as a secondary complication. Regardless of the initiating event, DIC results from the activation of the virtually unregulated coagulation cascade, characterized by the generation of thrombin with fibrin deposition within the micro- and macrovascular systems (i.e., multiple thrombi), combined with a hemorrhagic diathesis. The counteraction by the fibrinolytic cascade is variable and is characterized by the conversion of plasminogen to plasmin, the latter functioning as a potent proteolytic enzyme, capable of degrading fibrinogen, fibrin, and several clotting factors. The kinin and complement cascades also partake in the promotion of DIC. In addition, antithrombin (AT), proteins C and S, antiplasmin, and plasminogen activator inhibitor 1, play a functional role in curtailing the activation of the coagulation and fibrinolytic mechanisms, but they too may be affected by the DIC process, particularly because a marked decrease in AT takes place in severe cases.

The laboratory findings of DIC are as variable as the underlying clinical presentation and usually include elevation of D-dimer (a product of lysed fibrin), fibrinogen degradation products (FDP), as well as prolongation of prothrombin time (PT), partial thromboplastin time (PTT), and thrombin time, accompanied by thrombocytopenia and hypofibrinogenemia (noted mostly in obstetrical cases). Because some of these assays are not specific for the diagnosis of DIC, we propose the use of a new, simple, and cost effective panel: D-dimer, FDP, and AT. Elevations in FDP and D-dimer are sensitive for the diagnosis of DIC and a marked drop in AT establishes a poor prognosis.

Aside from the treatment of the underlying triggering event, a consensus with regard to the most effective management of DIC has not been established. Herein we summarize the rationale for the use of conventional therapeutic modalities such as fresh frozen plasma, cryoprecipitate, platelet and clotting factor concentrates, as well as the use of new alternatives. The use of AT infusions to maintain plasma levels of 150% of normal shows great promise in severe cases.

A fundamental understanding of the pathophysiology of DIC combined with an appreciation for efficient laboratory testing will allow for the most comprehensive diagnostic and therapeutic alternatives.

Lectin-like domain of thrombomodulin binds to its specific ligand Lewis Y antigen and neutralizes lipopolysaccharide-induced inflammatory response

Thrombomodulin (TM), a widely expressing glycoprotein originally identified in vascular endothelium, is an important cofactor in the protein C anticoagulant system. TM appears to exhibit anti-inflammatory ability through both protein C-dependent and -independent pathways. We presently have demonstrated that recombinant N-terminal lectinlike domain of TM (rTMD1) functions as a protective agent against sepsis caused by Gram-negative bacterial infections. rTMD1 caused agglutination of Escherichia coli and Klebsiella pneumoniae and enhanced the macrophage phagocytosis of these Gram-negative bacteria. Moreover, rTMD1 bound to the Klebsiella pneumoniae and lipopolysaccharide (LPS) by specifically interacting with Lewis Y antigen. rTMD1 inhibited LPS-induced inflammatory mediator production via interference with CD14 and LPS binding. Furthermore, rTMD1 modulated LPS-induced mitogen-activated protein kinase and nuclear factor-kappaB signaling pathway activations and inducible nitric oxide synthase expression in macrophages. Administration of rTMD1 protected the host by suppressing inflammatory responses induced by LPS and Gram-negative bacteria, and enhanced LPS and bacterial clearance in sepsis. Thus, rTMD1 can be used to defend against bacterial infection and inhibit LPS-induced inflammatory responses, suggesting that rTMD1 may be valuable in the treatment of severe inflammation in sepsis, especially in Gram-negative bacterial infections.

Protein C is an autocrine growth factor for human skin keratinocytes

The protein C (PC) pathway plays an important role in coagulation and inflammation. Many components of the PC pathway have been identified in epidermal keratinocytes, including endothelial protein C receptor (EPCR), which is the specific receptor for PC/activated PC (APC), but the core member of this pathway, PC, and its function in keratinocytes has not been defined. In this study, we reveal that PC is strongly expressed by human keratinocytes at both gene and protein levels. When endogenous PC was blocked by siRNA the proliferation of keratinocytes was significantly decreased. This inhibitory effect was restored by the addition of recombinant APC. PC siRNA treatment also increased cell apoptosis by 3-fold and inhibited cell migration by more than 20%. When keratinocytes were pretreated with RCR252, an EPCR-blocking antibody, or PD153035, an epidermal growth factor receptor (EGFR) inhibitor, cell proliferation was hindered by more than 30%. These inhibitors also completely abolished recombinant APC (10 mug/ml)-stimulated proliferation. Blocking PC expression or inhibiting its binding to EPCR/EGFR decreased the phosphorylation of ERK1/2 but increased p38 activation. Furthermore, inhibition of ERK decreased cell proliferation by approximately 30% and completely abolished the stimulatory effect of APC on proliferation. Taken together, these results indicate that keratinocyte-derived PC promotes cell survival, growth, and migration in an autocrine manner via EPCR, EGFR, and activation of ERK1/2. Our results highlight a novel role for the PC pathway in normal skin physiology and wound healing.

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.

Activated protein C prevents inflammation yet stimulates angiogenesis to promote cutaneous wound healing

Activated protein C (APC) is a serine protease that plays a central role in physiological anticoagulation, and has more recently been shown to be a potent anti-inflammatory mediator. Using cultured human cells, we show here that APC up-regulates the angiogenic promoters matrix metalloproteinase-2 in skin fibroblasts and umbilical vein endothelial cells, vascular endothelial growth factor in keratinocytes and fibroblasts, and monocyte chemoattractant protein-1 in fibroblasts. In the chick embryo chorioallantoic membrane assay, APC promoted the granulation/remodeling phases of wound healing by markedly stimulating angiogenesis as well as promoting reepithelialization. In a full-thickness rat skin-healing model, a single topical application of APC enhanced wound healing compared to saline control. APC-treated wounds had markedly more blood vessels on day 7 and a significantly lower infiltration of neutrophils at days 4 and 7. The broad spectrum matrix metallo-proteinase, GM6001, prevented the ability of APC to promote wound healing. In summary, our results show that APC promotes cutaneous wound healing via a complex mechanism involving stimulation of angiogenesis and inhibition of inflammation. These unique properties of APC make it an attractive therapeutic agent to promote the healing of chronic wounds.

Activated protein C stimulates proliferation, migration and wound closure, inhibits apoptosis and upregulates MMP-2 activity in cultured human keratinocytes

Activated protein C (APC) is a physiological serine protease that regulates blood clotting and inflammation. Keratinocytes are a major cell type of human skin and play a fundamental role in normal skin metabolism and cutaneous wound healing. In this study, we investigated the regulatory role of APC on the function of human primary cultured keratinocytes. In an in vitro wounding assay, APC accelerated wound closure which was due jointly to increased cell proliferation and migration. APC attenuated calcium-induced cell death via prevention of cell apoptosis, as indicated by a decrease in both active caspase-3 and morphologically apoptotic cells. APC dramatically enhanced the expression and activation of MMP-2 by keratinocytes, whilst having no effect on MMP-9. GM6001, a broad spectrum MMP inhibitor, abolished cell migration in a dose-dependent manner and delayed in vitro wound healing. APC also significantly increased the production of IL-6 and IL-8 and suppressed calcium- and LPS-stimulated NF-kappaB activity. These results demonstrate a central role for APC in promoting cell proliferation and migration, preventing apoptosis and increasing MMP-2 activity in cultured keratinocytes. This regulatory activity implicates APC as having potential to promote re-epithelialisation during wound healing.

6,7-Dihydroxy-3-phenylcoumarin inhibits thromboplastin induced disseminated intravascular coagulation

6,7-Dihydroxy-3-phenylcoumarin (DHPC) was tested to determine whether it had any effect on vitamin K inhibition, by investigating the prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen level and platelet count. The anticoagulant and antithrombotic effects of DHPC were compared with those of warfarin by conducting a 4 h acute trial on thromboplastin-induced disseminated intravascular coagulation (DIC), investigating various haemostatic and antioxidant system parameters and performing a haemogram. Of most significance was that in the 5-d DHPC trial on healthy controls, PT, APTT, fibrinogen, platelet count remained within normal levels. In the 4-h DIC trial, both DHPC (0.025 mg/kg, i.v.) and warfarin (0.25 mg/kg, i.v.) significantly inhibited DIC, by reducing the PT, APTT, and fibrin degradation products and increasing fibrinogen levels and platelet count. In the DIC drug groups, lipid peroxidation significantly increased only in the warfarin group and glutathione significantly increased only in the DHPC group. However leucocyte count was significantly higher in the DHPC than the warfarin group. Further investigation is required for why DHPC is effective on the parameters investigated, at doses one-tenth of those of warfarin.

Rationale for restoration of physiological anticoagulant pathways in patients with sepsis and disseminated intravascular coagulation

OBJECTIVE

In the pathogenesis of disseminated intravascular coagulation, dysfunctional natural anticoagulant pathways appear to play a pivotal role. In this article, we will address the mechanisms that contribute to this defect in the regulation of coagulation activation. Furthermore, we will explore the experimental and clinical evidence that restoration of these anticoagulant pathways results in clinical improvement.

DATA SOURCES

We have searched and reviewed published articles on experimental studies of disseminated intravascular coagulation models in animals and clinical studies in patients with disseminated intravascular coagulation.

DATA SYNTHESIS

All three major anticoagulant pathways, that is, the antithrombin pathway, the protein C system, and tissue factor pathway inhibitor, are defective in sepsis and disseminated intravascular coagulation. Several mechanisms contribute to this defect. Restoration of these pathways, in principle, by administration of coagulation inhibitor concentrates or recombinant anticoagulant factors, appears to ameliorate the coagulation disorder and, more important, result in improvement of clinically relevant outcomes, such as a reduction of organ failure and mortality.

CONCLUSIONS

Restoration of disrupted physiologic anticoagulant pathways in disseminated intravascular coagulation is not only a logical point of impact in patients with sepsis and an activated coagulation system, but also is associated with an improved outcome in experimental and (initial) clinical studies.

Activated protein C reduces the ischemia/reperfusion-induced spinal cord injury in rats by inhibiting neutrophil activation

OBJECTIVE

To examine whether activated protein C (APC) reduces spinal cord injury in rats by inhibiting neutrophil activation after the transient ischemia.

SUMMARY BACKGROUND DATA

Ischemic spinal cord injury is an important pathologic mechanism leading to the paraplegia observed after surgery to repair aortic aneurysms. Activated neutrophils play a pivotal role in the development of ischemia/reperfusion-induced tissue injury. Recently, the authors have reported that APC, a physiologic anticoagulant, prevents lipopolysaccharide-induced pulmonary vascular injury by inhibiting neutrophil activation. These observations strongly suggest that APC reduces ischemia/reperfusion-induced spinal cord injury by inhibiting neutrophil activation.

METHODS

In rats, spinal cord ischemia was induced by using a balloon catheter placed into the aorta. After the transient ischemia, survival and motor function were evaluated, and histologic examination of the spinal cord was performed by using both hematoxylin-and-eosin staining and 2,3,5, -triphenyltetrazolium chloride (TTC) staining 24 hours after the ischemia. Tissue levels of myeloperoxidase and cytokines, including tumor necrosis factor-alpha (TNF-alpha) and rat interleukin-8, were measured in six experimental groups: sham-operated, control, APC (100 microg/kg, intravenous), dansyl glutamyl-glycyl-arginyl chloromethyl ketone-treated activated factor X (DEGR-F.Xa), a selective inhibitor of thrombin generation (1 mg/kg, intravenous), nitrogen mustard-induced leukocytopenia, and diisopropyl fluorophosphate-treated APC (DIP-APC), active site-blocked APC (100 microg/kg, intravenous). APC, DEGR-F.Xa, and DIP-APC were administered intravenously 30 minutes before aortic occlusion. Control and leukocytopenic rats received saline instead of other drugs.

RESULTS

Pretreatment with APC significantly reduced motor disturbances compared with those in control animals. In contrast, neither DEGR-F.Xa nor DIP-APC had any effect. Microinfarctions, evidenced by the absence of TTC staining and histologic change, were markedly reduced in animals given APC. The increases in the tissue levels of TNF-alpha, rat interleukin-8, and myeloperoxidase in the ischemic part of the spinal cord were significantly reduced in animals that received APC. These levels were not reduced in rats given DEGR-F.Xa or DIP-APC. Leukocytopenia produced effects similar to those of APC.

CONCLUSIONS

APC reduced the ischemia/reperfusion-induced spinal cord injury by inhibiting neutrophil activation. The therapeutic mechanisms of APC might depend on its inhibitory effect on the production of TNF-alpha, which is a potent activator of neutrophils. Although the anticoagulant effects of APC might not be related to its ability to inhibit TNF-alpha production, its serine protease activity appears to be essential in the therapeutic mechanism. APC appears to have potential as a therapeutic agent for prevention of spinal cord injury in patients undergoing aortic aneurysm repair.

Discrimination of infectious and noninfectious causes of early acute respiratory distress syndrome by procalcitonin

OBJECTIVE

To test the sepsis marker procalcitonin (PCT) for its applicability to discriminate between septic and nonseptic causes of acute respiratory distress syndrome (ARDS).

DESIGN

Prospective study, assessing the course of PCT serum levels in early (within 72 hrs after onset) ARDS. The three other inflammation markers neopterin, interleukin-6 (IL-6), and C-reactive protein (CRP) were tested in parallel.

SETTING

Twenty-four-bed medical intensive care unit of a 1,990-bed primary hospital, providing health care for an estimated 39,000 patients.

PATIENTS

Twenty-seven patients, 18 male and nine female, aged 16-85 yrs, with early ARDS of known cause (17 with septic and ten with nonseptic ARDS) were enrolled in a prospective study between May 1994 and May 1995.

INTERVENTIONS

Serum samples were drawn every 4-6 hrs for measurement of PCT, neopterin, IL-6, and CRP concentrations. Blood cultures, tracheal aspirates, and urine samples were obtained every 12-24 hrs. In 24 of 27 patients, bronchoscopic cultures were also obtained. Clinical sepsis criteria as defined by the American College of Chest Physicians/Society of Critical Care Medicine Consensus Conference were checked daily.

MEASUREMENTS AND MAIN RESULTS

Assessment of inflammation marker serum levels in septic vs. nonseptic ARDS. PCT serum levels were significantly higher (p < .0005) in the patients with septic ARDS than in patients with nonseptic ARDS within 72 hrs after onset of ARDS. There was no overlap between the two groups. Also, neopterin allowed a differentiation (p < .005), although a substantial overlap between serum levels of septic and nonseptic patients was observed. No discrimination could be achieved by determination of CRP and IL-6 levels.

CONCLUSION

PCT determination in early ARDS could help to discriminate between septic and nonseptic underlying disease.

Pharmacologic adjuncts to mechanical ventilation in acute respiratory distress syndrome

This article reviews pharmacologic approaches to treating acute respiratory distress syndrome (ARDS). The authors discuss the therapeutic effects of ketoconazole, antioxidants, corticosteroids, surfactant, ketanserin, pentoxifylline, bronchodilators, and almitrine in ARDS. Current animal data and proposed mechanics which may foster future pharmacologic therapies are also examined.

Disseminated intravascular coagulation: clinical and laboratory aspects

Disseminated intravascular coagulation (DIC) is a complex acquired coagulopathy resulting from excessive thrombin formation. Abnormal tissue factor (TF) expression is a major mechanism initiating DIC in many disorders, including obstetrical complications, sepsis, cancer, and trauma. Numerous laboratory tests are available to monitor DIC, but most patients are adequately managed using only routine hemostasis screening tests, and assays for fibrinogen and D-dimer. Treatment of DIC should focus on reversing the underlying disorder initiating the coagulopathy. Novel treatments are being investigated for treating DIC; many of these experimental modalities target the excessive TF activity that characterizes DIC.

Species specificity of the anticoagulant activity of human urinary soluble thrombomodulin

The anticoagulant activities of human urinary soluble thrombomodulin (UTM) in blood taken from various species using several anticoagulant assay systems were compared; it was examined which coagulant assay system is appropriate for evaluation of the antithrombotic effects of UTM and how the species specificity of UTM is involved in the mechanisms of action of UTM. When anticoagulant activities were compared using activated partial thromboplastin time (APTT), thromboelastography (TEG), and thrombin generation test (TGT), the effect of UTM was found to be the strongest in humans among various species tested. Among the anticoagulant assays tested, TGT reflecting protein C (PC) activation by UTM, appeared to be more sensitive than APTT and TEG in detection of thrombomodulin activity. In the study of the mechanisms of action of UTM, UTM exhibited nearly the same antithrombin activity against human and rat thrombin; the rate of activation of human PC by thrombin/UTM complex was much higher than that of rat PC. Therefore, the species specificity of the anticoagulant activity of UTM may be attributable to thrombin/UTM-PC interaction, but not to UTM-thrombin interaction. From these results, we concluded that TGT reflecting PC activation by UTM will be a more useful assay than APTT and TEG for estimating the antithrombotic effects of UTM in humans. Furthermore, our findings suggest that UTM will exhibit more potent antithrombotic effects in humans than those in rats by strongly enhancing thrombin-catalyzed PC activation.