Protein C pathway in sepsis

Prothrombin Complex Concentrate for Trauma Induced Coagulopathy: A Systematic Review and Meta-Analysis

Background

Optimal management for trauma-induced coagulopathy (TIC) is a clinical conundrum. In conjunction with the transfusion of fresh-frozen plasma (FFP), additional administration of prothrombin complex concentrate (PCC) was proposed to bring about further coagulative benefit. However, investigations evaluating the efficacy as well as corresponding side effects were scarce and inconsistent. The aim of this study was to systematically review current literature and to perform a meta-analysis comparing FFP+PCC with FFP alone.

Methods

Web search followed by manual interrogation was performed to identify relevant literatures fulfilling the following criteria, subjects as TIC patients taking no baseline anticoagulants, without underlying coagulative disorders, and reported clinical consequences. Those comparing FFP alone with PCC alone were excluded. Comprehensive Meta-analysis software was utilized, and statistical results were delineated with odd ratio (OR), mean difference (MD), and 95% confidence interval (CI). I² was calculated to determine heterogeneity. The primary endpoint was set as all-cause mortality, while the secondary endpoint consisted of international normalized ratio (INR) correction, transfusion of blood product, and thrombosis rate.

Results

One hundred and sixty-four articles were included for preliminary evaluation, 3 of which were qualified for meta-analysis. A total of 840 subjects were pooled for assessment. Minimal heterogeneity was present in the comparisons (I² < 25%). In the PCC + FFP cohort, reduced mortality rate was observed (OR: 0.631; 95% CI: 0.450-0.884, p = 0.007) after pooling. Meanwhile, INR correction time was shorter under PCC + FFP (MD: -608.300 mins, p < 0.001), whilst the rate showed no difference (p = 0.230). The PCC + FFP group is less likely to mandate transfusion of packed red blood cells (p < 0.001) and plasma (p < 0.001), but not platelet (p = 0.615). The incidence of deep vein thrombosis was comparable in the two groups (p = 0.460).

Conclusions

Compared with FFP only, PCC + FFP demonstrated better survival rate, favorable clinical recovery and no elevation of thromboembolism events after TIC.

Co-administration of iloprost and eptifibatide in septic shock (CO-ILEPSS)-a randomised, controlled, double-blind investigator-initiated trial investigating safety and efficacy

BACKGROUND

Part of the pathophysiology in septic shock is a progressive activation of the endothelium and platelets leading to widespread microvascular injury with capillary leakage, microthrombi and consumption coagulopathy. Modulating the inflammatory response of endothelium and thrombocytes might attenuate this vicious cycle and improve outcome.

METHOD

The CO-ILEPSS trial was a randomised, placebo-controlled, double-blind, pilot trial. Patients admitted to the intensive care unit with septic shock were randomised and allocated in a 2:1 ratio to active treatment with dual therapy of iloprost 1 ng/kg/min and eptifibatide 0.5 μg/kg/min for 48 h or placebo. The primary outcomes were changes in biomarkers reflecting endothelial activation and disruption, platelet consumption and fibrinolysis. We compared groups with mixed models, post hoc Wilcoxon signed-rank test and Mann-Whitney U test.

RESULTS

We included 24 patients of which 18 (12 active, 6 placebo) completed the full 7-day trial period and were included in the per-protocol analyses of the primary outcomes. Direct comparison between groups showed no differences in the primary outcomes. Analyses of within-group delta values revealed that biomarkers of endothelial activation and disruption changed differently between groups with increasing levels of thrombomodulin (p = 0.03) and nucleosomes (p = 0.02) in the placebo group and decreasing levels of sE-Selectin (p = 0.007) and sVEGFR1 (p = 0.005) in the active treatment group. Platelet count decreased the first 48 h in the placebo group (p = 0.049) and increased from baseline to day 7 in the active treatment group (p = 0.023). Levels of fibrin monomers declined in the active treatment group within the first 48 h (p = 0.048) and onwards (p = 0.03). Furthermore, there was a significant reduction in SOFA score from 48 h (p = 0.024) and onwards in the active treatment group. Intention-to-treat analyses of all included patients showed no differences in serious adverse events including bleeding, use of blood products or mortality.

CONCLUSION

Our results could indicate benefit from the experimental treatment with reduced endothelial injury, reduced platelet consumption and ensuing reduction in fibrinolytic biomarkers along with improved SOFA score. The results of the CO-ILEPSS trial are exploratory and hypothesis generating and warrant further investigation in a large-scale trial.

TRIAL REGISTRATION

Clinicaltrials.com, NCT02204852 (July 30, 2014); EudraCT no. 2014-002440-41.

Acute Traumatic Coagulopathy: The Value of Histone in Pediatric Trauma Patients

OBJECTIVE

Acute traumatic coagulopathy occurs after trauma with impairment of hemostasis and activation of fibrinolysis. Some endogenous substances may play roles in this failure of the coagulation system. Extracellular histone is one such molecule that has recently attracted attention. This study investigated the association between plasma histone-complexed DNA (hcDNA) fragments and coagulation abnormalities in pediatric trauma patients.

MATERIALS AND METHODS

This prospective case-control study was conducted in pediatric patients with trauma. Fifty trauma patients and 30 healthy controls were enrolled. Demographic data, anatomic injury characteristics, coagulation parameters, computerized tomography findings, trauma, and International Society on Thrombosis and Haemostasis disseminated intravascular coagulation (ISTH DIC) scores were recorded. Blood samples for hcDNA were collected and assessed by enzyme-linked immunosorbent assay.

RESULTS

Thirty-two patients had multiple trauma, while 18 patients had isolated brain injury. hcDNA levels were significantly higher in trauma patients than healthy controls (0.474 AU and 0.145 AU, respectively). There was an association between plasma hcDNA levels and trauma severity. Thirteen patients had acute coagulopathy of trauma shock (ACoTS). ACoTS patients had higher plasma histone levels than those without ACoTS (0.703 AU and 0.398 AU, respectively). Plasma hcDNA levels were positively correlated with the ISTH DIC score and length of stay in the intensive care unit and were negatively correlated with fibrinogen level.

CONCLUSION

This study indicated that hcDNA levels were increased in pediatric trauma patients and associated with the early phase of coagulopathy. Further studies are needed to clarify the role of hcDNA levels in mortality and disseminated intravascular coagulation.

Coagulopathy of Trauma

Coagulopathy is common after injury and develops independently from iatrogenic, hypothermic, and dilutional causes. Despite considerable research on the topic over the past decade, trauma-induced coagulopathy (TIC) continues to portend poor outcomes, including decreased survival. We review the current evidence regarding the diagnosis and mechanisms underlying trauma induced coagulopathy and summarize the debates regarding optimal management strategy including product resuscitation, potential pharmacologic adjuncts, and targeted approaches to hemostasis. Throughout, we will identify areas of continued investigation and controversy in the understanding and management of TIC.

Acute traumatic coagulopathy and trauma-induced coagulopathy: an overview

Hemorrhage is the most important contributing factor of acute-phase mortality in trauma patients. Previously, traumatologists and investigators identified iatrogenic and resuscitation-associated causes of coagulopathic bleeding after traumatic injury, including hypothermia, metabolic acidosis, and dilutional coagulopathy that were recognized as primary drivers of bleeding after trauma. However, the last 10 years has seen a widespread paradigm shift in the resuscitation of critically injured patients, and there has been a dramatic evolution in our understanding of trauma-induced coagulopathy. Although there is no consensus regarding a definition or an approach to the classification and naming of trauma-associated coagulation impairment, trauma itself and/or traumatic shock-induced endogenous coagulopathy are both referred to as acute traumatic coagulopathy (ATC), and multifactorial trauma-associated coagulation impairment, including ATC and resuscitation-associated coagulopathy is recognized as trauma-induced coagulopathy. Understanding the pathophysiology of trauma-induced coagulopathy is vitally important, especially with respect to the critical issue of establishing therapeutic strategies for the management of patients with severe trauma.

New understandings of post injury coagulation and resuscitation

Coagulopathy following injury is common and it predicts poor outcomes and increased mortality. For many decades, coagulopathy in trauma was considered as an iatrogenic phenomenon, and clinical practice focused on a resuscitation strategy using large volume crystalloid and packed red blood cells. The discovery of Acute Traumatic Coagulopathy as a distinct pathophysiologic state coupled with a transition towards balanced product resuscitation has fundamentally changed the paradigm of trauma care and represents one of the most active areas of current research in the field of trauma. In this review, we examine the development and current understanding of the mechanisms, implicated mediators, and physiology of Acute Traumatic Coagulopathy, with an emphasis on the role of the activated Protein C pathway. We will also review the state of resuscitation practice including the evidence for balanced product administration and the previously under-appreciated importance of platelet count and function. Importantly, we highlight ongoing knowledge deficits in traumatic coagulopathy and resuscitation as directions for future investigation in order to facilitate further insight into these rapidly evolving fields.

Pro- and anticoagulant properties of factor V in pathogenesis of thrombosis and bleeding disorders

Factor V (FV) serves an important role in the regulation of blood coagulation, having both pro- and anticoagulant properties. The circulating high molecular weight single-chain FV molecule undergoes a series of proteolytic cleavages during both activation of coagulation and during anticoagulant regulation of coagulation by activated protein C (APC). It is noteworthy that mutations in the factor V gene (F5) either cause thrombosis or bleeding. New insights into the importance and complexity of FV functions have been generated from elucidation of the pathogenic mechanisms of two familial mutations in the F5 gene. The first mutation was identified as a result of the discovery of APC resistance as the most common risk factor for venous thrombosis. The mutation (FV Leiden) predicts the Arg(506) Gln replacement, which impairs the normal regulation of FVa by APC, as the Arg506 site is an important APC cleavage site. In addition, elucidation of APC resistance resulted in the discovery of the anticoagulant APC cofactor activity of FV. The second FV mutation (FV(A2440G) ), identified in a family with an autosomal dominant bleeding disorder, has led to the discovery of an alternative splicing generating a previously unidentified FV isoform (FV-Short), which inhibits coagulation via an unexpected and intriguing mechanism involving the coagulation inhibitor TFPI-α. These are naturally occurring mutations in the F5 gene that have generated new knowledge on the role of FV in regulation of coagulation and the importance of genetic risk factors for thrombosis and bleeding.

Recombinant soluble human thrombomodulin (thrombomodulin alfa) in the treatment of neonatal disseminated intravascular coagulation

Recombinant soluble human thrombomodulin (TM-α) has been shown to be useful in the treatment of disseminated intravascular coagulation (DIC) in a heparin-controlled study and has been available for clinical use in Japan since 2008. However, data on its use for neonatal DIC have not been reported from any clinical studies, so efficacy and safety were analyzed in 60 neonatal DIC patients identified in post-marketing surveillance. The DIC resolution rate as of the day after last administration of TM-α was 47.1 %, and the survival rate at 28 days after last administration was 76.7 %. Hemostatic test result profiles revealed decreased levels of fibrin/fibrinogen degradation products and increased platelet counts and antithrombin activity. Incidences of adverse drug reactions, bleeding-related adverse drug reactions, and bleeding-related adverse events were 6.7, 6.7, and 16.7 %, respectively, with no significant differences between neonatal, pediatric (excluding neonates), and adult DIC patients.

CONCLUSION

This surveillance provided real-world data on the safety and effectiveness of TM-alpha in the treatment of neonatal DIC in general practice settings.

Modulation of Protein C Activation by Histones, Platelet Factor 4, and Heparinoids

Objective—

Histones are detrimental in late sepsis. Both activated protein C (aPC) and heparin can reverse their effect. Here, we investigated whether histones can modulate aPC generation in a manner similar to another positively charged molecule, platelet factor 4, and how heparinoids (unfractionated heparin or oxygen-desulfated unfractionated heparin with marked decrease anticoagulant activity) may modulate this effect.

Approach and Results—

We measured in vitro and in vivo effects of histones, platelet factor 4, and heparinoids on aPC formation, activated partial thromboplastin time, and murine survival. In vitro, histones and platelet factor 4 both affect thrombin/thrombomodulin aPC generation following a bell-shaped curve, with a peak of >5-fold enhancement. Heparinoids shift these curves rightward. Murine aPC generation studies after infusions of histones, platelet factor 4, and heparinoids supported the in vitro data. Importantly, although unfractionated heparin and 2-O, 3-O desulfated heparin both reversed the lethality of high-dose histone infusions, only mice treated with 2-O, 3-O desulfated heparin demonstrated corrected activated partial thromboplastin times and had significant levels of aPC.

Conclusions—

Our data provide a new contextual model of how histones affect aPC generation, and how heparinoid therapy may be beneficial in sepsis. These studies provide new insights into the complex interactions controlling aPC formation and suggest a novel therapeutic interventional strategy.

Extracellular histone release in response to traumatic injury: implications for a compensatory role of activated protein C

BACKGROUND

Tissue injury leads to the release of DAMPs (damage-associated molecular patterns) that may drive a sterile inflammatory response; however, the role of extracellular histone levels after traumatic injury remains unexplored. We hypothesized that extracellular histone levels would be increased and associated with poor outcomes after traumatic injury.

METHODS

In this prognostic study, plasma was prospectively collected from 132 critically injured trauma patients on arrival and 6 hours after admission to an urban Level I trauma intensive care unit. Circulating extracellular histone levels and plasma clotting factors were assayed and linked to resuscitation and outcome data.

RESULTS

Of 132 patients, histone levels were elevated to a median of 14.0 absorbance units (AU) on arrival, declining to 6.4 AU by 6 hours. Patients with elevated admission histone levels had higher ISS (Injury Severity Score), lower admission GCS (Glasgow Coma Scale) score, more days of mechanical ventilation, and higher incidences of multiorgan failure, acute lung injury, and mortality (all p ≤ 0.05). Histone levels correlated with prolonged international normalized ratio and partial thromboplastin time, fibrinolytic markers D-dimer and tissue-type plasminogen activator, and anticoagulants tissue factor pathway inhibitor and activated protein C (aPC; all p < 0.03). Increasing histone level from admission to 6 hours was a multivariate predictor of mortality (hazard ratio, 1.005; p = 0.013). When aPC level trends were included, the impact of histone level increase on mortality was abrogated (p = 0.206) by a protective effect of increasing aPC levels (hazard ratio, 0.900; p = 0.020).

CONCLUSION

Extracellular histone levels are elevated in response to traumatic injury and correlate with fibrinolysis and activation of anticoagulants. An increase in histone levels from admission to 6 hours is predictive of mortality, representing evidence of ongoing release of intracellular antigens similar to that seen in sepsis. Concomitant elevation of aPC abrogates this effect, suggesting a possible role for aPC in mitigating the sterile inflammatory response after trauma through the proteolysis of circulating histones.

LEVEL OF EVIDENCE

Prognostic study, level III.

Low circulating protein C levels are associated with lower leg ulcers in patients with diabetes

Activated protein C (APC) promotes angiogenesis and reepithelialisation and accelerates healing of diabetic ulcers. The aim of this study was to determine the relationship between the incidence of lower leg ulcers and plasma levels of APC's precursor, protein C (PC), in diabetic patients. Patients with diabetes who had a lower leg ulcer(s) for >6 months (n = 36) were compared with age-, type of diabetes-, and sex-matched subjects with diabetes but without an ulcer (n = 36, controls). Total PC was assessed using a routine PC colorimetric assay. There was a significantly (P < 0.001) lower level of plasma PC in patients with ulcers (103.3 ± 22.7, mean ± SD) compared with control (127.1 ± 34.0) subjects, when corrected for age and matched for gender and type of diabetes. Ulcer type (neuropathic, ischaemic, or mixed) was not a significant covariate for plasma PC levels (P = 0.35). There was no correlation between PC levels and gender, type of diabetes, HbA1c, or C-reactive protein in either group. In summary, decreased circulating PC levels are associated with, and may predispose to, lower leg ulceration in patients with diabetes.

Soluble thrombomodulin levels in plasma of multiple sclerosis patients and their implication

Thrombomodulin (TM) on the cell-surface of cerebrovascular endothelial cells (CECs) is released into blood upon CEC damage. TM promotes activation of protein C (APC), an anticoagulant, anti-inflammatory, neuroprotective molecule that protects CECs and impedes inflammatory cell migration across the blood-brain barrier (BBB). Multiple sclerosis (MS) is associated with CEC damage and BBB dysfunction. We evaluated soluble TM (sTM) levels as a biomarker of BBB integrity and whether glatiramer acetate (GA) influenced sTM levels in MS patients. sTM levels quantified by 2-site ELISA from sera of healthy controls and systemic lupus erythematosus (SLE) patients (CEC-damage positive control) were compared with levels from patients with relapsing-remitting (RRMS) or secondary-progressive MS (SPMS), stratified as: RRMS/GA/no relapse, RRMS/GA/in relapse, RRMS no GA/no relapse, RRMS/no GA/in relapse; and SPMS/no GA. Additionally, soluble endothelial protein C receptor (sEPCR) levels were assessed in the non-stratified MS group, SLE patients, and controls. sTM levels were highest in RRMS patients taking GA with or without relapse, followed in decreasing order by SLE, RRMS/no GA/in relapse, SPMS, RRMS/no GA/no relapse, healthy controls. sEPCR levels were highest in MS patients, then SLE, then controls. sTM may be a useful biomarker of BBB integrity in RRMS patients. Further evaluation of sEPCR is needed. The finding that the highest sTM levels were in RRMS patients taking GA is interesting and warrants further investigation.

Thrombomodulin domains attenuate atherosclerosis by inhibiting thrombin-induced endothelial cell activation

AIMS

Thrombin modulates the formation of atherosclerotic lesions by stimulating a variety of cellular effects through protease-activated receptor-1 (PAR-1) activation. Thrombomodulin (TM) inhibits thrombin effects by binding thrombin through its domains 2 and 3 (TMD23). We investigated whether recombinant TMD23 (rTMD23) could inhibit atherosclerosis via its thrombin-binding ability.

METHODS AND RESULTS

Wild-type mouse rTMD23 and three mutants with altered thrombin-binding sites, rTMD23 (I425A), rTMD23 (D424A/D426A), and rTMD23 (D424A/I425A/D426A), were expressed and purified in the Pichia pastoris expression system. Wild-type rTMD23 and rTMD23 (D424A/D426A) could effectively bind thrombin, activate protein C, and prolong thrombin clotting time, whereas rTMD23 (I425A) and rTMD23 (D424A/I425A/D426A) lost these functions. Wild-type rTMD23, but not rTMD23 (I425A), decreased both the thrombin-induced surface PAR-1 internalization and the increase in cytoplasmic Ca(2+) concentrations in endothelial cells (ECs). Wild-type rTMD23 and rTMD23 (D424A/D426A) also inhibited thrombin-induced adhesion molecules and monocyte chemoattractant protein-1 expression and increased permeability in ECs, whereas rTMD23 (I425A) and rTMD23 (D424A/I425A/D426A) had no such effects. Furthermore, wild-type rTMD23 and rTMD23 (D424A/D426A) were effective in reducing carotid ligation-induced neointima formation in C57BL/6 mice and atherosclerotic lesion formation in apolipoprotein E-deficient (ApoE-/-) mice, whereas rTMD23 with the I425A mutation showed impairment of this function. Wild-type rTMD23, but not rTMD23 (I425A), also markedly suppressed the PAR-1, the adhesion molecules expression, and the macrophage content in the carotid ligation model and ApoE-/- mice.

CONCLUSION

rTMD23 protein significantly reduces atherosclerosis and neointima formation through its thrombin-binding ability.

Early rise in circulating endothelial protein C receptor correlates with poor outcome in severe sepsis

PURPOSE

The endothelial protein C receptor (EPCR) negatively regulates the coagulopathy and inflammatory response in sepsis. Mechanisms controlling the expression of cell-bound and circulating soluble EPCR (sEPCR) are still unclear. Moreover, the clinical impact of EPCR shedding and its potential value to predict sepsis progression and outcome remain to be established.

METHODS

We investigated the time course of plasma sEPCR over the 5 first days (D) of severe sepsis in 40 patients.

RESULTS

No significant difference was observed when comparing sEPCR at admission (D1) to healthy volunteers and to patients with vasculitis. We report that the kinetics profile of plasma sEPCR in patients was almost stable at the onset of sepsis with no change from D1 to D4 and then a significant decrease at D5. This pattern of release was consistently observed whatever the level of sEPCR at D1. Characteristics of patients or of infections (except Gram negative) had no or little critical influence on the sEPCR profile. However, we found that sEPCR kinetics was clearly associated with patient's outcome (D28 survival). We demonstrate that a significant but moderate (<15% of basal level) and transient increase in sEPCR level at D2 is associated with poor outcome at D28.

CONCLUSION

Severe sepsis, at the onset, only triggers moderate quantitative changes in plasma sEPCR levels. Our findings suggest that in severe sepsis, an early (at D2), transient but significant increase in circulating sEPCR may be detrimental suggesting that sEPCR could provide an early biological marker of sepsis outcome.

JNK-ATF-2 inhibits thrombomodulin (TM) expression by recruiting histone deacetylase4 (HDAC4) and forming a transcriptional repression complex in the TM promoter

Thrombomodulin (TM) is an important vascular protective molecule that has anticoagulant, anti-inflammatory and anti-apoptotic properties. TM is downregulated in many thrombotic and vascular diseases. However, the mechanisms responsible for TM suppression are not completely understood. In this study, we investigated the mechanism involved in fatty acid-induced suppression of TM expression in human aortic endothelial cells. We found that palmitic acid inhibited TM expression through the JNK and p38 pathways. ATF-2, a JNK and p38 target transcription factor, was involved in the suppression. ATF-2 can bind to the TM promoter, recruit HDAC4 and form a transcriptional repression complex in the promoter, which may lead to chromatin condensation and transcriptional arrest. This study provides novel insight into TM down-regulation by stress signaling pathways.

The coagulopathy of trauma: a review of mechanisms

BACKGROUND

Bleeding is the most frequent cause of preventable death after severe injury. Coagulopathy associated with severe injury complicates the control of bleeding and is associated with increased morbidity and mortality in trauma patients. The causes and mechanisms are multiple and yet to be clearly defined.

METHODS

Articles addressing the causes and consequences of trauma-associated coagulopathy were identified and reviewed. Clinical situations in which the various mechanistic causes are important were sought along with quantitative estimates of their importance.

RESULTS

Coagulopathy associated with traumatic injury is the result of multiple independent but interacting mechanisms. Early coagulopathy is driven by shock and requires thrombin generation from tissue injury as an initiator. Initiation of coagulation occurs with activation of anticoagulant and fibrinolytic pathways. This Acute Coagulopathy of Trauma-Shock is altered by subsequent events and medical therapies, in particular acidemia, hypothermia, and dilution. There is significant interplay between all mechanisms.

CONCLUSIONS

There is limited understanding of the mechanisms by which tissue trauma, shock, and inflammation initiate trauma coagulopathy. Acute Coagulopathy of Trauma-Shock should be considered distinct from disseminated intravascular coagulation as described in other conditions. Rapid diagnosis and directed interventions are important areas for future research.

Activated protein C in sepsis: the promise of nonanticoagulant activated protein C

PURPOSE OF REVIEW

To discuss the potential use of recombinant activated protein C (aPC) variants with altered bioactivity in sepsis therapy.

RECENT FINDINGS

Since the initial Protein C Worldwide Evaluation in Severe Sepsis trial demonstrating efficacy of aPC therapy to reduce mortality of severe sepsis, follow-up studies have failed to resolve concerns about the low overall risk-to-benefit ratio of this therapy and suggest that it might only be effective in severely ill patients with the most aggravated forms of coagulopathy. New studies begin to shed light on the potential mechanisms of how aPC therapy may alter sepsis outcome, and how recombinant aPC variants with altered bioactivities may improve the efficacy and safety of this therapy.

SUMMARY

aPC variants with selectively diminished antithrombotic activity, but normal cytoprotective potential, may allow more efficient dosing without increasing adverse bleeding effects and therefore provide a safer and possibly more efficient alternative to normal aPC. Critical questions about the precise mechanisms by which aPC therapy reduces mortality remain to be resolved in order to identify patients most likely to benefit from it and to reevaluate potential efficacy of aPC therapy in children and patients with less than severe sepsis.

Acute traumatic coagulopathy: initiated by hypoperfusion: modulated through the protein C pathway?

OBJECTIVES

Coagulopathy following major trauma is conventionally attributed to activation and consumption of coagulation factors. Recent studies have identified an acute coagulopathy present on admission that is independent of injury severity. We hypothesized that early coagulopathy is due to tissue hypoperfusion, and investigated derangements in coagulation associated with this.

METHODS

This was a prospective cohort study of major trauma patients admitted to a single trauma center. Blood was drawn within 10 minutes of arrival for analysis of partial thromboplastin and prothrombin times, prothrombin fragments 1+2, fibrinogen, thrombomodulin, protein C, plasminogen activator inhibitor-1, and D-dimers. Base deficit (BD) was used as a measure of tissue hypoperfusion.

RESULTS

A total of 208 patients were enrolled. Patients without tissue hypoperfusion were not coagulopathic, irrespective of the amount of thrombin generated. Prolongation of the partial thromboplastin and prothrombin times was only observed with an increased BD. An increasing BD was associated with high soluble thrombomodulin and low protein C levels. Low protein C levels were associated with prolongation of the partial thromboplastin and prothrombin times and hyperfibrinolysis with low levels of plasminogen activator inhibitor-1 and high D-dimer levels. High thrombomodulin and low protein C levels were significantly associated with increased mortality, blood transfusion requirements, acute renal injury, and reduced ventilator-free days.

CONCLUSIONS

Early traumatic coagulopathy occurs only in the presence of tissue hypoperfusion and appears to occur without significant consumption of coagulation factors. Alterations in the thrombomodulin-protein C pathway are consistent with activated protein C activation and systemic anticoagulation. Admission plasma thrombomodulin and protein C levels are predictive of clinical outcomes following major trauma.

Management of sepsis

Severe sepsis remains a common cause of death in surgical patients. Eradication of the septic source and supportive care has long been the mainstay of treatment. In recent years, however, early goal-directed therapy, tighter glucose control, administration of drotrecogin alfa (activated), and steroid replacement have produced improved morbidity and mortality. In the future, a better understanding of the pathophysiology of sepsis and clinical studies may further improve outcomes from severe sepsis.

Activated protein C promotes breast cancer cell migration through interactions with EPCR and PAR-1

Activated protein C (APC) is a serine protease that regulates thrombin (IIa) production through inactivation of blood coagulation factors Va and VIIIa. APC also has non-hemostatic functions related to inflammation, proliferation, and apoptosis through various mechanisms. Using two breast cancer cell lines, MDA-MB-231 and MDA-MB-435, we investigated the role of APC in cell chemotaxis and invasion. Treatment of cells with increasing APC concentrations (1-50 microg/ml) increased invasion and chemotaxis in a concentration-dependent manner. Only the active form of APC increased invasion and chemotaxis of the MDA-MB-231 cells when compared to 3 inactive APC derivatives. Using a modified "checkerboard" analysis, APC was shown to only affect migration when plated with the cells; therefore, APC is not a chemoattractant. Blocking antibodies to endothelial protein C receptor (EPCR) and protease-activated receptor-1 (PAR-1) attenuated the effects of APC on chemotaxis in the MDA-MB-231 cells. Finally, treatment of the MDA-MB-231 cells with the proliferation inhibitor, Na butyrate, showed that APC did not increase migration by increasing cell number. Therefore, APC increases invasion and chemotaxis of cells by binding to the cell surface and activating specific signaling pathways through EPCR and PAR-1.

Markers for sepsis diagnosis: what is useful?

Timely diagnosis of the different severities of septic inflammation is potentially lifesaving because therapies that have been shown to lower mortality should be initiated early. Sepsis and severe sepsis are accompanied by clinical and laboratory signs of systemic inflammation but patients with inflammation caused by noninfectious causes may present with similar signs and symptoms. It is important to identify markers for an early diagnosis of sepsis and organ dysfunction. This article presents currently interesting sepsis biomarkers. Other novel markers and their potential role are discussed.

Does the oxidation of methionine in thrombomodulin contribute to the hypercoaguable state of smokers and diabetics?

The leading cause of premature death in smokers is cardiovascular disease. Diabetics also suffer from increased cardiovascular disease. This results, in part, from the hypercoagulable state associated with these conditions. However, the molecular cause(s) of the elevated risk of cardiovascular disease and the prothrombotic state of smokers and diabetics remain unknown. It is well known that oxidative stress is increased in both conditions. In smokers, it is established that oxidation of methionine residues takes place in alpha(1)-antitrypsin in lungs and that this leads to emphysema. Thrombomodulin is a key regulator of blood clotting and is found on the endothelium. Oxidation of methionine 388 in thrombomodulin is known to slow the rate at which the thrombomodulin-thrombin complex activates protein C, a protein which, in turn, degrades the factors which activate thrombin and lead to clot formation. In analogy to the cause of emphysema, it is hypothesized that oxidation of this methionine is elevated in smokers relative to non-smokers and, perhaps, in conditions such as diabetes that impose oxidative stress on the body. Evidence for the hypothesis that such an oxidation and concomitant reduction in activated protein C levels would lead to elevated cardiovascular risk is presented.

A novel ELISA for mouse activated protein C in plasma

The Protein C pathway plays a crucial role in the regulation of thrombosis and inflammation. One of the tools that researchers presently use to elucidate mechanisms of action of activated protein C (APC) is the use of transgenic or gene deletion murine models. To correlate observations in these murine models with the APC levels, there is a need for a sensitive and specific assay for circulating murine APC in plasma. We developed an immunological assay to measure the physiological and pharmacologic levels of circulating murine APC. The sandwich ELISA uses an anti-murine anti-protein C antibody capture antibody and human protein C inhibitor (PCI) as a detection reagent, taking advantage of the facts that the mouse lacks plasma PCI and that human PCI forms a 1/1 stable complex with mouse APC. The amount of complex APC:PCI is detected with an anti-human PCI monoclonal antibody. The assay shows improved sensitivity versus enzyme immunocapture assays commonly used to detect human APC and considerably reduces the processing time.

Severe sepsis and septic shock: review of the literature and emergency department management guidelines

Severe sepsis and septic shock are as common and lethal as other acute life-threatening conditions that emergency physicians routinely confront such as acute myocardial infarction, stroke, and trauma. Recent studies have led to a better understanding of the pathogenic mechanisms and the development of new or newly applied therapies. These therapies place early and aggressive management of severe sepsis and septic shock as integral to improving outcome. This independent review of the literature examines the recent pathogenic, diagnostic, and therapeutic advances in severe sepsis and septic shock for adults, with particular relevance to emergency practice. Recommendations are provided for therapies that have been shown to improve outcomes, including early goal-directed therapy, early and appropriate antimicrobials, source control, recombinant human activated protein C, corticosteroids, and low tidal volume mechanical ventilation.

Oral streptococci and cardiovascular disease: searching for the platelet aggregation-associated protein gene and mechanisms of Streptococcus sanguis-induced thrombosis

BACKGROUND

Pathogenic mechanisms in infective endocarditis, disseminated intravascular coagulation, and cardiovascular events involve the aggregation of platelets into thrombi. Attendant infection by oral bacteria contributes to these diseases. We have been studying how certain oral streptococci induce platelet aggregation in vitro and in vivo. Streptococcus sanguis expresses a platelet aggregation-associated protein (PAAP), which contributes little to adhesion to platelets. When specific antibodies or peptides block PAAP, S. sanguis fails to induce platelet aggregation in vitro or in vivo.

METHODS

We used subtractive hybridization to identify the gene encoding for PAAP.

RESULTS

After subtraction of strain L50 (platelet aggregation-negative), four strain 133-79 specific sequences were characterized. Sequence agg4 encoded a putative collagen-binding protein (CbpA), which was predicted to contain two PAAP collagen-like octapeptide sequences. S. sanguis CbpA- mutants were constructed and tested for induction of platelet aggregation in vitro. Platelet aggregation was substantially inhibited when compared to the wild-type using platelet-rich plasma from the principal donor, but adhesion was unaffected. Other donor platelets responded normally to the CbpA- strain, suggesting additional mechanisms of response to S. sanguis. In contrast, CshA- and methionine sulfoxide reductase-negative (MsrA-) strains neither adhered nor induced platelet aggregation.

CONCLUSIONS

CbpA was suggested to contribute to site 2 interactions in our two-site model of platelet aggregation in response to S. sanguis. Platelet polymorphisms were suggested to contribute to the thrombogenic potential of S. sanguis.

Endothelial protein C receptor-dependent inhibition of migration of human lymphocytes by protein C involves epidermal growth factor receptor

The protein C pathway is an important regulator of the blood coagulation system. Protein C may also play a role in inflammatory and immunomodulatory processes. Whether protein C or activated protein C affects lymphocyte migration and possible mechanisms involved was tested. Lymphocyte migration was studied by micropore filter assays. Lymphocytes that were pretreated with protein C (Ceprotin) or activated protein C (Xigris) significantly reduced their migration toward IL-8, RANTES, MCP-1, and substance P, but not toward sphingosine-1-phosphate. The inhibitory effects of protein C or activated protein C were reversed by Abs against endothelial protein C receptor and epidermal growth factor receptor. Evidence for the synthesis of endothelial protein C receptor by lymphocytes is shown by demonstration of receptor mRNA expression and detection of endothelial protein C receptor immunoreactivity on the cells' surface. Data suggest that an endothelial protein C receptor is expressed by lymphocytes whose activation with protein C or activated protein C arrests directed migration. Exposure of lymphocytes to protein C or activated protein C stimulates phosphorylation of Tyr845 of epidermal growth factor receptor, which may be relevant for cytoprotective effects of the protein C pathway.

Early and innovative interventions for severe sepsis and septic shock: taking advantage of a window of opportunity

The pathogenic, diagnostic and therapeutic landscape of sepsis is no longer confined to the intensive care unit: many patients from other portals of entry to care, both outside and within the hospital, progress to severe disease. Approaches that have led to improved outcomes with other diseases (e.g., acute myocardial infarction, stroke and trauma) can now be similarly applied to sepsis. Improved understanding of the pathogenesis of severe sepsis and septic shock has led to the development of new therapies that place importance on early identification and aggressive management. This review emphasizes approaches to the early recognition, diagnosis and therapeutic management of sepsis, giving the clinician the most contemporary and practical approaches with which to treat these patients.

Critical roles of platelets in lipopolysaccharide-induced lethality: effects of glycyrrhizin and possible strategy for acute respiratory distress syndrome

Within a few minutes of an intravenous injection of a lipopolysaccharide (LPS) into mice, platelets accumulate, largely in the lung. At higher doses, LPS induces rapid shock (within 10 min), leading to death within 1 h. This type of shock differs from so-called endotoxin shock, in which shock signs and death occur several hours or more later. Here, we found that platelet depletion (by a monoclonal anti-platelet antibody) prevented LPS-induced rapid shock, but increased delayed lethality. In Japan, glycyrrhizin (GL), a compound isolated from licorice, is daily and slowly infused intravenously into chronic hepatitis C patients. A single bolus intravenous injection into mice of GL (200 mg/kg or less) shortly before (or simultaneously with) LPS injection reduced the pulmonary platelet accumulation and the severity of the rapid shock, and prevented death in both the early and later periods. GL itself, at 400 mg/kg, produced no detectable abnormalities in the appearance or activity of mice. Intraperitoneal injection of aspirin or dexamethasone had only marginal effects on LPS-induced platelet responses and lethality. These results suggest that platelets play important roles in the development of both the rapid and delayed types of shock induced by LPS. Although the mechanism by which GL suppresses platelet responses and delayed lethality remains to be clarified, GL might provide a strategy for alleviating the acute respiratory distress syndrome seen in sepsis. Our results may also support the proposal by Cinatl et al. [Cinatl J, Morgenstern B, Bauer G, Chandra P, Ravenau H, Doerr HW. Glycyrrhizin, an active component of liquorice roots, and replication of SARS-associated coronavirus. Lancet 2003; 361: 2045–6.] that GL may be an effective drug against severe acute respiratory syndrome.

Mice with a severe deficiency in protein C display prothrombotic and proinflammatory phenotypes and compromised maternal reproductive capabilities

Anticoagulant protein C (PC) is important not only for maintenance of normal hemostasis, but also for regulating the host immune response during inflammation. Because mice with a designed total genetic deficiency in PC (PC-/- mice) die soon after birth, attempts to dissect PC function in various coagulation/inflammation-based pathologies through use of mice with less than 50% of normal PC levels have not been successful to date. In the current investigation, we have used a novel transgenic strategy to generate different mouse models expressing 1-18% of normal PC levels. In contrast to PC-/- mice, mice with only partial PC deficiency survived beyond birth and also developed thrombosis and inflammation. The onset and severity of these phenotypes vary significantly and are strongly dependent on plasma PC levels. Our findings additionally provide the first evidence that maternal PC is vital for sustaining pregnancy beyond 7.5 days postcoitum, likely by regulating the balance of coagulation and inflammation during trophoblast invasion. These low PC-expressing transgenic mouse lines provide novel animal models that can be used to elucidate the importance of PC in maintenance of the organism and in disease.

Endothelial thrombomodulin (CD 141) in a rabbit burn model

Thrombomodulin (CD 141) is an endothelial surface transmembrane glycoprotein. It is involved in the activation of protein C in the inactivation of thrombin. In severe sepsis CD 141 is shed from the endothelial surface. This leads to disseminated intravascular coagulation (DIC), disturbed organ functions and multi organ failure (MOF). In this study, we investigated if endothelial bound thrombomodulin is shed in thermal injuries.

MATERIAL AND METHODS

In 10 New Zealand white rabbits full thickness and superficial partial thickness burns were produced. Dermal blood flow was analyzed by measuring the fluorescence of intravenously injected indocyanine green. Skin-biopsies were taken from the burn wounds from the zones of stasis between full thickness burns and from unburned skin 72 h post burn. Specimens were processed for immunoperoxidase staining using a specific monoclonal antibody against CD 141.

RESULTS

Dermal blood flow was reduced in burned skin areas and in the zones of stasis. Thrombomodulin was only detectable on the surface of capillary endothelial cells in specimens taken from unburned skin areas. No thrombomodulin was detectable in specimens taken from burn wounds or from the zones of stasis. Thus, shedding of thrombomodulin was detectable in areas with reduced dermal blood flow.

CONCLUSION

Thermal injuries affect the dermal endothelial surfaces resulting in a shedding of thrombomodulin. This mechanism might be involved in the development of progressive skin damage in the zone of stasis. Disseminated intravascular coagulation following inactivation of thrombomodulin might lead to multiple organ dysfunctions in severe burn injuries.

PAR1 Cleavage and Signaling in Response to Activated Protein C and Thrombin

Activated protein C (APC), a natural anticoagulant protease, can trigger cellular responses via protease-activated receptor-1 (PAR1), a G protein-coupled receptor for thrombin. Whether this phenomenon contributes to the physiological effects of APC is unknown. Toward answering this question, we compared the kinetics of PAR1 cleavage on endothelial cells by APC versus thrombin. APC did cleave PAR1 on the endothelial surface, and antibodies to the endothelial protein C receptor inhibited such cleavage. Importantly, however, APC was approximately 10(4)-fold less potent than thrombin in this setting. APC and thrombin both triggered PAR1-mediated responses in endothelial cells including expression of antiapoptotic (tumor necrosis factor-alpha-induced a20 and iap-1) and chemokine (interleukin-8 (il-8) and cxcl3) genes, but again, APC was approximately 10(4)-fold less potent than thrombin. The addition of zymogen protein C to endothelial cultures did not alter the rate of PAR1 cleavage at low or high concentrations of thrombin, and PAR1 cleavage was substantial at thrombin concentrations too low to trigger detectable conversion of protein C to APC. Thus, locally generated APC did not contribute to PAR1 cleavage beyond that effected by thrombin in this system. Although consistent with reports that sufficiently high concentrations of APC can cleave and activate PAR1 in culture, our data suggest that a significant physiological role for PAR1 activation by APC is unlikely.

CCR1 and CC chemokine ligand 5 interactions exacerbate innate immune responses during sepsis

CCR1 has previously been shown to play important roles in leukocyte trafficking, pathogen clearance, and the type 1/type 2 cytokine balance, although very little is known about its role in the host response during sepsis. In a cecal ligation and puncture model of septic peritonitis, CCR1-deficient (CCR1(-/-)) mice were significantly protected from the lethal effects of sepsis when compared with wild-type (WT) controls. The peritoneal and systemic cytokine profile in CCR1(-/-) mice was characterized by a robust, but short-lived and regulated antibacterial response. CCR1 expression was not required for leukocyte recruitment, suggesting critical differences extant in the activation of WT and CCR1(-/-) resident or recruited peritoneal cells during sepsis. Peritoneal macrophages isolated from naive CCR1(-/-) mice clearly demonstrated enhanced cytokine/chemokine generation and antibacterial responses compared with similarly treated WT macrophages. CCR1 and CCL5 interactions markedly altered the inflammatory response in vivo and in vitro. Administration of CCL5 increased sepsis-induced lethality in WT mice, whereas neutralization of CCL5 improved survival. CCL5 acted in a CCR1-dependent manner to augment production of IFN-gamma and MIP-2 to damaging levels. These data illustrate that the interaction between CCR1 and CCL5 modulates the innate immune response during sepsis, and both represent potential targets for therapeutic intervention.

Fibrin(ogen)-alpha M beta 2 interactions regulate leukocyte function and innate immunity in vivo

In addition to its well-characterized role in hemostasis, fibrin(ogen) has been proposed to be a central regulator of the inflammatory response. Multiple in vitro studies have demonstrated that this hemostatic factor can alter leukocyte function, including cell adhesion, migration, cytokine and chemokine expression, degranulation, and other specialized processes. One important link between fibrin(ogen) and leukocyte biology appears to be the integrin receptor alpha(M)beta(2)/Mac-1, which binds to immobilized fibrin(ogen) and regulates leukocyte activities. Although it is well established that fibrin(ogen) is a ligand for alpha(M)beta(2), the precise molecular determinants that govern this interaction are only now becoming clear. A novel line of mice expressing a mutant form of fibrinogen (Fib gamma(390-396A)) has revealed that gamma chain residues 390-396 are important for the high-affinity engagement of fibrinogen by alpha(M)beta(2) and leukocyte function in vivo. Fibrinogen gamma(390-396A) failed to support alpha(M)beta(2)-mediated adhesion of primary neutrophils, monocytes, and macrophages, and mice expressing this fibrinogen variant were found to exhibit a major defect in the host inflammatory response following acute challenges. Most notably, Fib gamma(390-396A) mice display a profound impediment in Staphylococcus aureus elimination by leukocytes following intraperitoneal inoculation. These findings have positively established the physiological importance of fibrin(ogen) as a ligand for alpha(M)beta(2) and illustrate that the fibrin(ogen) gamma chain residues 390-396 constitute a critical feature of the alpha(M)beta(2) binding motif. Finally, the Fib gamma(390-396A) mice represent a valuable system for better defining the contribution of fibrin(ogen) to the inflammatory response in the absence of any confounding alteration in clotting function.

[Recombinant human activated protein C in the treatment of children with meningococcal purpura fulminans]

Meningococcal purpura fulminans (MPF) produces high mortality and morbidity, despite appropriate standard therapy. Administration of recombinant human activated protein C (rhAPC) has been successfully applied in adults with MPF and pediatric studies are under way. We report three pediatric patients with MPF treated with rhAPC as compassionate therapy. In two of these patients, positive clinical and laboratory effects were observed and both children achieved full recovery. The remaining patient died after 36 hours from refractory multiorgan failure. No rhAPC-related adverse effects were detected. The reported cases highlight the usefulness of rhAPC in children with MPF at least as a rescue compassionate treatment. Further clinical trials are needed to better delineate its efficacy and administration schedule in children.

Cardiovascular effects in patrol officers are associated with fine particulate matter from brake wear and engine emissions

BACKGROUND: Exposure to fine particulate matter air pollutants (PM2.5) affects heart rate variability parameters, and levels of serum proteins associated with inflammation, hemostasis and thrombosis. This study investigated sources potentially responsible for cardiovascular and hematological effects in highway patrol troopers. RESULTS: Nine healthy young non-smoking male troopers working from 3 PM to midnight were studied on four consecutive days during their shift and the following night. Sources of in-vehicle PM2.5 were identified with variance-maximizing rotational principal factor analysis of PM2.5-components and associated pollutants. Two source models were calculated. Sources of in-vehicle PM2.5 identified were 1) crustal material, 2) wear of steel automotive components, 3) gasoline combustion, 4) speed-changing traffic with engine emissions and brake wear. In one model, sources 1 and 2 collapsed to a single source. Source factors scores were compared to cardiac and blood parameters measured ten and fifteen hours, respectively, after each shift. The "speed-change" factor was significantly associated with mean heart cycle length (MCL, +7% per standard deviation increase in the factor score), heart rate variability (+16%), supraventricular ectopic beats (+39%), % neutrophils (+7%), % lymphocytes (-10%), red blood cell volume MCV (+1%), von Willebrand Factor (+9%), blood urea nitrogen (+7%), and protein C (-11%). The "crustal" factor (but not the "collapsed" source) was associated with MCL (+3%) and serum uric acid concentrations (+5%). Controlling for potential confounders had little influence on the effect estimates. CONCLUSION: PM2.5 originating from speed-changing traffic modulates the autonomic control of the heart rhythm, increases the frequency of premature supraventricular beats and elicits pro-inflammatory and pro-thrombotic responses in healthy young men.

The response to activated protein C after cardiopulmonary bypass: impact of factor V leiden

Activated protein C (aPC) resistance is a recognized hypercoagulable phenotype that is associated with increased risk for thrombosis in multiple clinical settings. Factor V Leiden (FVL) represents a specific inherited cause of aPC resistance, but the perioperative thrombotic risk of FVL is unclear. In this investigation, we sought to quantify whether cardiopulmonary bypass produces alterations in aPC resistance in FVL carriers and noncarrier controls, testing the hypothesis that FVL is associated with a relatively hypercoagulable postoperative state. Two-hundred-five adult cardiac surgery patients were prospectively enrolled into a genetic registry whose purpose was to study the impact of genetic variables on clinical outcomes. For this study, 8 subjects heterozygous for FVL were identified (group L), as well as 2 control groups: group MC, matched controls, 18 matched subjects without FVL; and group UC, unmatched controls, 11 consecutive subjects without FVL. Plasma was sampled at the beginning of surgery, 10 min after protamine administration, and on postoperative day 1, and assayed for resistance to aPC (normal aPC ratio is >2.0). Both MC and UC groups exhibited normal aPC ratio at baseline (2.40 and 2.36, respectively), which increased significantly (to 2.76 and 2.75, P = 0.007 and 0.021, respectively) on postoperative day 1, indicating increased postoperative sensitivity to aPC. Conversely, group L subjects exhibited aPC resistance at baseline (aPC ratio 1.80), and did not change significantly postoperatively (P = 0.867). Patients without FVL therefore show laboratory evidence consistent with relative protection from postoperative thrombosis, whereas FVL carriers do not. These findings provide mechanistic support for previous speculations of increased postoperative thrombotic risk associated with FVL.

Coagulation in Sepsis

Activation of the coagulation cascade during invasive infection can result in purpura fulminans, with rapid progression of tissue ischemia, or may manifest as abnormal clotting indices alone. Although severe derangements in coagulation are associated with organ dysfunction and increased mortality, the contribution of coagulopathy to the pathophysiology of sepsis remains incompletely understood. Over the past decade, investigators have evaluated several therapeutic anticoagulant strategies in sepsis, and manipulation of the coagulation system has emerged as a key concept in the current management of this disease. Clinical observations during treatment of septic patients with the endogenous anticoagulant activated protein C have stimulated additional study of interactions between endothelial injury, coagulation, and inflammation. This review describes clotting abnormalities during sepsis and discusses the clinical experience with therapeutic strategies intended to oppose excessive coagulation.

Coagulation-dependent mechanisms and asthma

In several clinical disorders, there are interactions between inflammation-dependent tissue injury and thrombin formation, fibrin deposition, and impaired fibrinolysis. New evidence generated from a mouse model of allergic airway hyperreactivity suggests that disordered coagulation and fibrinolysis may contribute to the pathogenesis of asthma. The inflammatory mechanisms that lead to airway smooth muscle contraction and airway hyperresponsiveness may be associated with accumulation of extravascular fibrin, plasma exudates, and inflammatory cells that can lead to airway closure.

Leukocyte engagement of fibrin(ogen) via the integrin receptor alphaMbeta2/Mac-1 is critical for host inflammatory response in vivo

The leukocyte integrin alpha(M)beta(2)/Mac-1 appears to support the inflammatory response through multiple ligands, but local engagement of fibrin(ogen) may be particularly important for leukocyte function. To define the biological significance of fibrin(ogen)-alpha(M)beta(2) interaction in vivo, gene-targeted mice were generated in which the alpha(M)beta(2)-binding motif within the fibrinogen gamma chain (N(390)RLSIGE(396)) was converted to a series of alanine residues. Mice carrying the Fibgamma(390-396A) allele maintained normal levels of fibrinogen, retained normal clotting function, supported platelet aggregation, and never developed spontaneous hemorrhagic events. However, the mutant fibrinogen failed to support alpha(M)beta(2)-mediated adhesion of primary neutrophils, macrophages, and alpha(M)beta(2)-expressing cell lines. The elimination of the alpha(M)beta(2)-binding motif on fibrin(ogen) severely compromised the inflammatory response in vivo as evidenced by a dramatic impediment in leukocyte clearance of Staphylococcus aureus inoculated into the peritoneal cavity. This defect in bacterial clearance was due not to diminished leukocyte trafficking but rather to a failure to fully implement antimicrobial functions. These studies definitively demonstrate that fibrin(ogen) is a physiologically relevant ligand for alpha(M)beta(2), integrin engagement of fibrin(ogen) is critical to leukocyte function and innate immunity in vivo, and the biological importance of fibrinogen in regulating the inflammatory response can be appreciated outside of any alteration in clotting function.

Progress in the Understanding of the Protein C Anticoagulant Pathway

A natural anticoagulant pathway denoted the protein C system provides specific and efficient control of blood coagulation. Protein C is the key component of the system and circulates in the blood as a zymogen to an anticoagulant serine protease. Activation of protein C is achieved on the surface of endothelial cells by thrombin bound to the membrane protein thrombomodulin. The endothelial protein C receptor stimulates the activation of protein C on the endothelium. Activated protein C (APC) modulates blood coagulation by cleaving a limited number of peptide bonds in factor VIIIa (FVIIIa) and factor Va (FVa), cofactors in the activation of factor X and prothrombin, respectively. Vitamin K-dependent protein S stimulates the APC-mediated regulation of coagulation. Not only is protein S involved in the degradation of FVIIIa, but so is FV, which in recent years has been found to be a Janus-faced protein with both procoagulant and anticoagulant potentials. A number of genetic defects affecting the anticoagulant function of the protein C system, eg, APC resistance (Arg506Gln or FV Leiden) and deficiencies of protein C and protein S constitute major risk factors of venous thrombosis. The protein C system also has anti-inflammatory and antiapoptotic potentials, the molecular mechanisms of which are beginning to be unraveled. APC has emerged in recent years as a useful therapeutic compound in the treatment of severe septic shock. The beneficial effect of APC is believed be due to both its anticoagulant and its anti-inflammatory properties.

Immunomodulatory role of CXCR2 during experimental septic peritonitis

The loss of CXCR2 expression by neutrophils is a well-described, but poorly understood, consequence of clinical sepsis. To address the potential impact of this CXCR2 deficit during the septic response, we examined the role of CXCR2 in a murine model of septic peritonitis provoked by cecal ligation and puncture (CLP). CLP-induced mouse mortality was significantly attenuated with i.v. or i.p. administration of an affinity-purified murine CXCR2-specific polyclonal Ab. Mouse survival required Ab administration before and every 2 days following CLP. Furthermore, mice deficient in CXCR2 (CXCR2(-/-)) were significantly protected against CLP-induced mortality compared with control (CXCR2(+/+)) mice. The anti-CXCR2 Ab treatment delayed, but did not completely inhibit, the recruitment of leukocytes, specifically neutrophils, into the peritoneal cavity. Peritoneal macrophages from anti-CXCR2 Ab-treated mice exhibited markedly increased RNA and protein levels of several key proinflammatory cytokines and chemokines. Specifically, isolated preparations of these cells released approximately 11-fold more CXCL10 protein compared with peritoneal macrophages from control-treated or naive mice. CXCR2(-/-) mice had higher resting and CLP-induced levels of peritoneal CXCL10 compared with CXCR2(+/+) mice. Administration of a neutralizing, affinity-purified, murine CXCL10-specific polyclonal Ab before CLP in wild-type mice and every 2 days after surgery significantly increased mortality compared with control Ab-treated mice. Anti-CXCL10 treatment in CXCR2(-/-) mice negated the protective effect associated with the absence of CXCR2. In summary, these data demonstrate that the absence of CXCR2 protects mice from septic injury potentially by delaying inflammatory cell recruitment and enhancing CXCL10 expression in the peritoneum.

Comparison of mechanisms after post-hoc analyses of the drotrecogin alfa (activated) and antithrombin III trials in severe sepsis

Severe sepsis is a heterogeneous syndrome in a heterogeneous population. The current scheme of classification does not enable distinction between systemic inflammatory response syndrome, sepsis and severe sepsis on the basis of the underlying biochemical, immunological and abnormal coagulation features. Planning, implementation and assessment of results of intervention studies on severe sepsis thus present enormous challenges. Two such studies were published in the year 2001. The study investigating the drug drotrecogin alfa (activated) was positive in the day-28 mortality endpoint; however, post-hoc analyses have raised controversies regarding the manner in which the study was carried out, the consistency of results presented, and the suggested mechanism of action. On the other hand, the KyberSept study that investigated antithrombin III reported negative results for the day-28 mortality endpoint, despite correct performance of the study. This, however, was not interpreted to mean proof of therapeutic inefficacy of administering antithrombin III and post-hoc analyses raise the suspicion of an undesirable drug interaction between antithrombin III and heparin. Apparently, neither of the sepsis studies meets the criteria which lie at the basis of critical assessment of the success or failure of clinical trials that could more significantly affect clinical treatment decisions.

The role of pharmacology in spinal cord protection during thoracic aortic reconstruction

Surgery of the thoracic aorta continues to have a significant risk of neurologic complication. Several strategies to minimize this risk are emerging. Pharmacologic protection from these complications continues to be researched, but at this point few medications are being used clinically. This article reviews the pathophysiology of ischemic spinal cord injury and summarizes the investigational pharmacology that may prevent these serious complications.

Inhibition of staurosporine-induced apoptosis of endothelial cells by activated protein C requires protease-activated receptor-1 and endothelial cell protein C receptor

In a model of staurosporine-induced apoptosis using EAhy926 endothelial cells, inhibition of apoptosis by activated protein C was dose-dependent and required the enzyme's active site, implicating activated protein C-mediated proteolysis. Consistent with this implication, both protease-activated receptor-1 (PAR-1) and endothelial cell protein C receptor (EPCR) were required for the anti-apoptotic effects of activated protein C.