Two-stage response to endotoxin infusion into normal human subjects: Correlation of blood phagocyte luminescence with clinical and laboratory markers of the inflammatory, hemostatic response

Effects of enhanced adsorption haemofiltration versus haemoadsorption in severe, refractory septic shock with high levels of endotoxemia: the ENDoX bicentric, randomized, controlled trial

BACKGROUND

Endotoxin adsorption is a promising but controversial therapy in severe, refractory septic shock and conflicting results exist on the effective capacity of available devices to reduce circulating endotoxin and inflammatory cytokine levels.

METHODS

Multiarm, randomized, controlled trial in two Swiss intensive care units, with a 1:1:1 randomization of patients suffering severe, refractory septic shock with high levels of endotoxemia, defined as an endotoxin activity ≥ 0.6, a vasopressor dependency index ≥ 3, volume resuscitation of at least 30 ml/kg/24 h and at least single organ failure, to a haemoadsorption (Toraymyxin), an enhanced adsorption haemofiltration (oXiris) or a control intervention. Primary endpoint was the difference in endotoxin activity at 72-h post-intervention to baseline. In addition, inflammatory cytokine, vasopressor dependency index and SOFA-Score dynamics over the initial 72 h were assessed inter alia.

RESULTS

In the 30, out of 437 screened, randomized patients (10 Standard of care, 10 oXiris, 10 Toraymyxin), endotoxin reduction at 72-h post-intervention-start did not differ among interventions (Standard of Care: 12 [1-42]%, oXiris: 21 [10-51]%, Toraymyxin: 23 [10-36]%, p = 0.82). Furthermore, no difference between groups could be observed neither for reduction of inflammatory cytokine levels (p = 0.58), nor for vasopressor weaning (p = 0.95) or reversal of organ injury (p = 0.22).

CONCLUSIONS

In a highly endotoxemic, severe, refractory septic shock population neither the Toraymyxin adsorber nor the oXiris membrane could show a reduction in circulating endotoxin or cytokine levels over standard of care. Trial registration ClinicalTrials.gov. NCT01948778. Registered August 30, 2013. https://clinicaltrials.gov/study/NCT01948778.

Immunostimulation and Coagulopathy in COVID-19 Compared to Patients With H1N1 Pneumonia or Bacterial Sepsis

BACKGROUND/AIM

Multiple reports from all over the world link COVID-19 with endothelial/coagulation disorders as well as a dysregulated immune response. This study tested the hypothesis that immunostimulation will be greater in COVID-19 patients than in patients with H1N1 infection or bacterial sepsis. Also, whether an increase in immune stimulation will be accompanied by a more severely affected endothelium/coagulation system was examined.

PATIENTS AND METHODS

Twenty-three septic patients, admitted in the Intensive Care Unit (ICU), were enrolled (9 with SARS-CoV-2, 5 with H1N1 pneumonia, 9 with bacterial sepsis). Myeloperoxidase (MPO) activity along with certain endothelial/coagulation factors were assessed on admission (time point 1) and at either improvement or deterioration (time point 2).

RESULTS

MPO levels were significantly higher in COVID-19 patients compared to both other groups. Furthermore, in patients with COVID-19, vWF levels did not differ significantly, fVIII levels were lower while ADAMTS-13 activity was higher compared to patients with H1N1 pneumonia and bacterial sepsis (a trend in the latter).

CONCLUSION

Increased immunostimulation was noted in COVID-19 patients compared to other septic patients; however, this was not accompanied by greater disturbance of the clotting system and/or more severe endothelial injury.

Variation of endothelium-related hemostatic factors during sepsis

OBJECTIVE

The thrombomodulin/protein C and VWF/ADAMTS-13 pathways are disturbed in sepsis and have been implicated in the coagulation disorders that characterize the septic syndrome. We aimed to assess the variation of these endothelial parameters during sepsis and their putative association with outcome, in critically ill, septic patients.

METHODS

We monitored 34 septic patients, 23 of whom improved (group A) while 11 deteriorated (group B). We assessed ADAMTS-13 levels, VWF activity, soluble thrombomodulin, and protein C activity upon admission to the ICU (time point 0) and at the time of a change in the clinical condition (remission or deterioration, time point 1).

RESULTS

In group A, thrombomodulin and VWF increased at time point 1 compared to time point 0 (P = 0.011, P = 0.028, respectively). In group B, protein C and ADAMTS-13 significantly decreased (P = 0.023, P = 0.026, respectively), while VWF, VWF/ADAMTS-13 ratio, and the thrombomodulin/protein C ratio increased (P = 0.02, P = 0.002, P = 0.01, respectively). Protein C (> or ≤17%) and ADAMTS-13 percentage difference (> or ≤22%) were independently associated with sepsis outcome among the endothelial variables tested.

CONCLUSIONS

An ongoing endothelial/hemostatic disorder was established during sepsis, observed even at clinical improvement. Among the variables tested, protein C and ADAMTS-13 change were associated with outcome.

Peptidoglycan induces disseminated intravascular coagulation in baboons through activation of both coagulation pathways

Anthrax infections exhibit progressive coagulopathies that may contribute to the sepsis pathophysiology observed in fulminant disease. The hemostatic imbalance is recapitulated in primate models of late-stage disease but is uncommon in toxemic models, suggesting contribution of other bacterial pathogen-associated molecular patterns (PAMPs). Peptidoglycan (PGN) is a bacterial PAMP that engages cellular components at the cross talk between innate immunity and hemostasis. We hypothesized that PGN is critical for anthrax-induced coagulopathies and investigated the activation of blood coagulation in response to a sterile PGN infusion in primates. The PGN challenge, like the vegetative bacteria, induced a sepsis-like pathophysiology characterized by systemic inflammation, disseminated intravascular coagulation (DIC), organ dysfunction, and impaired survival. Importantly, the hemostatic impairment occurred early and in parallel with the inflammatory response, suggesting direct engagement of coagulation pathways. PGN infusion in baboons promoted early activation of contact factors evidenced by elevated protease-serpin complexes. Despite binding to contact factors, PGN did not directly activate either factor XII (FXII) or prekallikrein. PGN supported contact coagulation by enhancing enzymatic function of active FXII (FXIIa) and depressing its inhibition by antithrombin. In parallel, PGN induced de novo monocyte tissue factor expression in vitro and in vivo, promoting extrinsic clotting reactions at later stages. Activation of platelets further amplified the procoagulant state during PGN challenge, leading to DIC and subsequent ischemic damage of peripheral tissues. These data indicate that PGN may be a major cause for the pathophysiologic progression of Bacillus anthracis sepsis and is the primary PAMP behind the pathogen-induced coagulopathy in late-stage anthrax.

Changes in plasma levels of natural anticoagulants in disseminated intravascular coagulation: high prognostic value of antithrombin and protein C in patients with underlying sepsis or severe infection

BACKGROUND

Dysfunctional natural anticoagulant systems enhance intravascular fibrin formation in disseminated intravascular coagulation (DIC), and plasma levels of natural anti coagulants can be used in the diagnosis and prognosis of DIC. Herein, the diagnostic value of 4 natural anticoagulants was assessed, and the prognostic value of antithrombin and protein C were validated in a large population.

METHODS

Part 1 study included 126 patients with clinically suspected DIC and estimated plasma levels of 4 candidate anticoagulant proteins: antithrombin, protein C, protein S, and protein Z. Part 2 comprised 1,846 patients, in whom plasma antithrombin and protein C levels were compared with other well-known DIC markers according to the underlying dis eases. The 28-day mortality rate was used to assess prognostic outcome.

RESULTS

Antithrombin and protein C showed higher areas under the ROC curve than protein S and protein Z. In part 2 of the study, antithrombin and protein C levels significantly correlated with DIC score, suggesting that these factors are good indicators of DIC severity. Antithrombin and protein C showed significant prognostic power in Kaplan-Meier analyses. In patients with sepsis/severe infection, antithrombin and protein C showed higher hazard ratios than D-dimer. Platelet count showed the highest hazard ratio in patients with hemato logic malignancy. In patients with liver disease, the hazard ratio for antithrombin levels was significantly high.

CONCLUSIONS

Decreased plasma anticoagulant levels reflect florid consumption of the physiologic defense system against DIC-induced hypercoagulation. Plasma antithrombin and protein C levels are powerful prognostic markers of DIC, especially in patients with sepsis/severe infection.

The sepsis model: an emerging hypothesis for the lethality of inhalation anthrax

Inhalation anthrax is often described as a toxin-mediated disease. However, the toxaemia model does not account for the high mortality of inhalation anthrax relative to other forms of the disease or for the pathology present in inhalation anthrax. Patients with inhalation anthrax consistently show extreme bacteraemia and, in contrast to animals challenged with toxin, signs of sepsis. Rather than toxaemia, we propose that death in inhalation anthrax results from an overwhelming bacteraemia that leads to severe sepsis. According to our model, the central role of anthrax toxin is to permit the vegetative bacteria to escape immune detection. Other forms of B. anthracis infection have lower mortality because their overt symptoms early in the course of disease cause patients to seek medical care at a time when the infection and its sequelae can still be reversed by antibiotics. Thus, the sepsis model explains key features of inhalation anthrax and may offer a more complete understanding of disease pathology for researchers as well as those involved in the care of patients.

Whole-blood tissue factor procoagulant activity is elevated in type 1 diabetes: effects of hyperglycemia and hyperinsulinemia

OBJECTIVE

To determine tissue factor procoagulant activity (TF-PCA) in patients with type 1 diabetes and to examine effects of hyperglycemia and hyperglycemia plus hyperinsulinemia on TF-PCA.

RESEARCH DESIGN AND METHODS

We have determined circulating TF-PCA and other coagulation factors under basal (hyperglycemic) conditions, after acute correction of hyperglycemia, in response to 24 h of selective hyperglycemia, and in response to 24 h of hyperglycemia plus hyperinsulinemia in nine type 1 diabetic patients and in seven nondiabetic control subjects.

RESULTS

As shown previously in patients with type 2 diabetes, basal TF-PCA and plasma coagulation factor VIIa (FVIIa) were higher in patients with type 1 diabetes than in nondiabetic control subjects. However, in contrast with type 2 diabetes, normalizing glucose did not decrease the elevated TF-PCA levels, and raising glucose or glucose plus insulin levels did not increase TF-PCA.

CONCLUSIONS

Patients with type 1 diabetes have elevated circulating TF-PCA and FVIIa levels and are in a procoagulant state that may predispose them to acute cardiovascular events. The mechanisms regulating TF-PCA in patients with type 1 and type 2 diabetes are different and should be further explored.

Effects of a cytokine inhibitor, JTE-607, on the response to endotoxin in healthy human volunteers

It is generally regarded that the excessive production of cytokines plays an important role in the pathology of autoimmune diseases and septic shock. We have investigated the ability of JTE-607, a novel inhibitor of cytokine production, to modulate the inflammatory response to endotoxin in healthy human volunteers. Three cohorts of healthy male volunteers were recruited for a randomized, placebo-controlled, double-blind study. Within each cohort, 6 subjects received a single 8-hour intravenous infusion of JTE-607 (either 0.03, 0.1 or 0.3 mg/kg/h) and 3 subjects received a placebo infusion. Two hours after the start of the JTE-607 infusion, all subjects received a 30 unit/kg bolus infusion of endotoxin. JTE-607 administration resulted in the decrease in endotoxin-induced IL-10 production with mean % difference from placebo of -79.5% (P=0.040) and -86.2% (P=0.026) at 0.1 and 0.3 mg/kg/h dose, respectively. The production of endotoxin-mediated interleukin (IL)-1 receptor antagonist was significantly inhibited at 0.3 mg/kg/h dose with mean % difference from placebo of -60% (P=0.0037). Endotoxin-induced C-reactive protein decreased with the increasing dose of JTE-607 with mean % difference from placebo of -32.1% (P=0.322), -82.9% (P=0.0001) and -90.3% (P<0.0001) at 0.03, 0.1 and 0.3 mg/kg/h dose, respectively. In conclusion, this study describes a cytokine modulator JTE-607, which inhibits production of IL-10, IL-1ra and C-reactive protein in a human model of endotoxemia.

Circulating tissue factor procoagulant activity and thrombin generation in patients with type 2 diabetes: effects of insulin and glucose

CONTEXT

Type 2 diabetes mellitus (T2DM) is a hypercoagulable state. Tissue factor (TF) is the principal initiator of blood coagulation.

OBJECTIVE

Our objective was to examine the effects of hyperglycemia and hyperinsulinemia on the TF pathway of blood coagulation in T2DM.

DESIGN

Three study protocols were used: 1) acute correction of hyperglycemia (with iv insulin) followed by 24 h of euglycemia, 2) 24 h of selective hyperinsulinemia, and 3) 24 h of combined hyperinsulinemia and hyperglycemia.

SETTING

The study took place at a clinical research center.

STUDY PARTICIPANTS

Participants included 18 T2DM patients and 22 nondiabetic controls.

RESULTS

Basal TF-procoagulant activity (TF-PCA), monocyte TF mRNA, plasma coagulation factor VII (FVIIc), and thrombin-anti-thrombin complexes were higher in T2DM than in nondiabetic controls, indicating a chronic procoagulant state. Acutely normalizing hyperglycemia over 2-4 h resulted in a small ( approximately 7%) but significant decline in TF-PCA with no further decline over 24 h. Raising insulin levels alone raised TF-PCA by 30%, whereas raising insulin and glucose levels together increased TF-PCA (by 80%), thrombin-anti-thrombin complexes, and prothrombin fragment 1.2. Plasma FVIIa and FVIIc declined with increases in TF-PCA.

CONCLUSION

We conclude that the combination of hyperglycemia and hyperinsulinemia, common in poorly controlled patients with T2DM, contributes to a procoagulant state that may predispose these patients to acute cardiovascular events.

Toll-like receptors on hematopoietic progenitor cells stimulate innate immune system replenishment

Toll-like receptors (TLRs) are best known for their ability to recognize microbial or viral components and initiate innate immune responses. We showed here that TLRs and their coreceptors were expressed by multipotential hematopoietic stem cells, whose cell cycle entry was triggered by TLR ligation. TLR expression also extended to some of the early hematopoietic progenitors, although not the progenitor cells dedicated to megakaryocyte and erythroid differentiation. TLR signaling via the Myd88 adaptor protein drove differentiation of myeloid progenitors, bypassing some normal growth and differentiation requirements, and also drove lymphoid progenitors to become dendritic cells. CD14 contributed to the efficiency of lipopolysaccharide (LPS) recognition by stem and progenitor cells, and LPS interacted directly with the TLR4/MD-2 complex on these cells in bone marrow. Thus, the preferential pathogen-mediated stimulation of myeloid differentiation pathways may provide a means for rapid replenishment of the innate immune system during infection.

Effects of hyperglycemia and hyperinsulinemia on circulating tissue factor procoagulant activity and platelet CD40 ligand

Individuals with chronically elevated glucose and/or insulin levels, i.e., most patients with type 2 diabetes, have accelerated atherosclerosis and are prone to acute vascular events. We have tested the hypothesis that hyperglycemia and/or hyperinsulinemia singly or combined may increase tissue factor, the primary initiator of blood coagulation. We have determined changes in circulating tissue factor procoagulant activity (PCA) and other procoagulation proteins in healthy volunteers exposed to 24 h of selective hyperinsulinemia, selective hyperglycemia, or combined hyperinsulinemia and hyperglycemia. Combined elevations of plasma insulin and glucose levels for 24 h produced a ninefold increase in tissue factor PCA, which was associated with an increase in monocyte tissue factor protein (flow cytometry) and mRNA (RT-PCR), increases in plasma thrombin-antithrombin complexes, prothrombin fragment 1.2, factor VIII coagulant activity, and platelet CD40 ligand as well as decreases in factor VIIa, factor VII coagulant activities, and factor VII antigen. Effects of selective hyperinsulinemia and selective hyperglycemia were less striking but appeared to be additive. We conclude that hyperinsulinemia and hyperglycemia but particularly the combination of both create a prothrombotic state and in addition may be proinflammatory and proatherogenic because of the proinflammatory actions of CD40 ligand and tissue factor.

Systemic coagulation parameters in mice after treatment with vascular targeting agents

Background

Vascular targeting of malignant tumors has become a clinically validated new treatment approach with clear patient benefit. However clinical studies have also revealed that some types of vascular targeting agents (VTAs) are prone to coagulation system side effects. It is therefore essential to predetermine coagulation parameters in preclinical studies. As of to date, this has rarely been done, predominantly due to technical issues.

The goal of this study was to establish and apply a standardized process, whereby systemic coagulation activation can be routinely measured in mice.

Results

We have evaluated a number of sampling techniques and coagulation tests regarding their suitability for this purpose. We were able to adapt two assays measuring soluble fibrin, a marker for a prethrombotic status. Thus, soluble fibrin could be measured for the first time in mice. All assays were validated in a positive control model for systemic coagulation activation, i.e. lipopolysaccharide-induced endotoxemia.

Based on our results, we selected a panel of coagulation tests, which are both feasable and informative for preclinical testing of VTAs: soluble fibrin, thrombin-antithrombin complexes, free antithrombin III, white blood cell counts and platelet counts. The effect of tumor transplants on coagulation parameters was evaluated using this panel. We then applied this set of assays in treatment studies with a VTA developed in our laboratory to investigate a potential systemic coagulation activation.

Conclusion

We have established a standardized panel of assays that can be used to test murine blood samples for coagulation activation in preclinical studies. All tests are feasible to perform in any research laboratory without specialized equipment. In addition, this is the first report to measure soluble fibrin, an early marker of systemic coagulation activation, in mice. The panel was applied on tumor bearing mice and mice treated with a VTA. We suggest its general application for coagulation activation analyses in mice.

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.

Dysfonctionnement myocardique et choc septique

Myocardial dysfunction frequently accompanies severe sepsis and septic shock. It is now clear that such a myocardial depression, as evidenced by biventricular alteration, is present during the early phase of sepsis in most patients. Myocardial depression exists despite a fluid loading-dependent hyperdynamic state and usually recovers within 7 to 10 days in survivors. Myocardial dysfunction does not appear to be due to irreversible structural abnormalities nor to myocardial hypoperfusion, but rather linked to many circulating mediators including cytokines. At a cellular level, reduced myocardial contractility could be related in part to apoptosis and induced by both nitric oxide-dependent and nitric oxide-independent mechanisms. However, whatever the mechanism involved, it leads to calcium homeostasis abnormality. The present review describes both the diagnosis procedure and the molecular and cellular pathways of sepsis-induced myocardial depression.

Extracorporeal therapies in non-renal disease: treatment of sepsis and the peak concentration hypothesis

In the setting of intensive care, patients with acute renal failure often present a clinical picture of the systemic inflammatory response syndrome (SIRS). SIRS can be caused by bacterial stimuli or by non-microbiological stimuli that induce a significant inflammatory response. When this response is exaggerated, the patient experiences multiple organ system failure and a condition of sepsis also defined as a systemic malignant inflammation. This is mostly characterized by an invasion of cytokines and other pro-inflammatory mediators into the systemic circulation where major biological effects take place, including vasopermeabilization, hypotension and shock. At the same time, the monocyte of the septic patient seems to be hyporesponsive to inflammatory stimuli to a certain extent. In this condition, the patient faces a situation of hyperinflammation but at the same time of immunodepression expressing a clinical entity defined as counter anti-inflammatory response syndrome. The general picture of the clinical disorder is therefore better characterized by an immunodysregulation than by a simple pro- or anti-inflammatory disorder. Due to the short half-life of cytokines and other mediators spilled over into the circulation, it is extremely difficult to approach the problem at the right moment with the right pharmacological agent. For these reasons, the peak concentration hypothesis suggests that continuous renal replacement therapies, due to their continuity and unspecific capacity of removal, might be beneficial in cutting the peaks of the concentrations of both pro- and anti-inflammatory mediators, restoring a situation of immunohomeostasis. Thus the patient may benefit from a lesser degree of immunodysregulation and he/she may restore a close-to-normal capacity of response to exogenous stimuli.

Protease-activated receptor signaling in the regulation of inflammation

OBJECTIVE

To discuss recent studies addressing the relationship between protease-activated receptor signaling, coagulation, and inflammation.

DATA EXTRACTION AND SYNTHESIS

This review article covers relevant original articles published until October 2003 dealing with animal models, clinical trial data, and in vitro experiments.

CONCLUSIONS

Although activation of protease-activated receptors has been implicated in the proinflammatory effects of the coagulation cascade, current data provide evidence that protease-activated receptor signaling plays a more complex role in the regulation of inflammation and endothelial homeostasis. Sensitive assays for coagulation activation have provided clear evidence that targeting the coagulation pathway effectively reduces the coagulopathy in sepsis. However, the effect of these anticoagulant agents on sepsis-associated inflammation is less clear. Further insight into this question will require the development or use of additional biomarkers for assessing pharmacologic interference with coagulation-related cell-signaling pathways.

Induction of microparticle- and cell-associated intravascular tissue factor in human endotoxemia

The precise role of intravascular tissue factor (TF) remains poorly defined, due to the limited availability of assays capable of measuring circulating TF procoagulant activity (PCA). As a model of inflammation-associated intravascular thrombin generation, we studied 18 volunteers receiving an infusion of endotoxin. A novel assay that measures microparticle (MP)-associated TF PCA from a number of cellular sources (but not platelets) demonstrated an 8-fold increase in activity at 3 to 4 hours after endotoxin administration (P <.001), with a return to baseline by 8 hours. TF antigen-positive MPs isolated from plasma were visualized by electron microscopy. Interindividual MP-associated TF response to lipopolysaccharide (LPS) was highly variable. In contrast, a previously described assay that measures total (cell and MP-borne) whole-blood TF PCA demonstrated a more modest increase, with a peak in activity (1.3-fold over baseline; P <.000 01) at 3 to 4 hours, and persistence for more than 24 hours. This surprisingly modest increase in whole-blood TF activity is likely explained by a profound although transient LPS-induced monocytopenia. MP-associated TF PCA was highly correlated with whole-blood TF PCA and total number of circulating MPs, and whole-blood TF PCA was highly correlated with TF mRNA levels.

Rôle de la dysfonction endothéliale dans la mortalité liée au sepsis

During the past decade, a unifying hypothesis has been developed to explain the vascular changes that occur in septic shock on the basis of the effect of inflammatory mediators on the vascular endothelium. The vascular endothelium plays a central role in the control of microvascular flow, and it has been proposed that widespread vascular endothelial activation, dysfunction and eventually injury occur in septic shock, ultimately resulting in multiorgan failure. This has been characterised in various models of experimental septic shock. Now, direct and indirect evidence for endothelial cell alteration in humans during septic shock is emerging. The present review details recently published literature on this rapidly evolving topic.

Interpreting the mechanisms of continuous renal replacement therapy in sepsis: the peak concentration hypothesis

Severe sepsis and septic shock are the primary causes of multiple organ dysfunction syndrome (MODS), which is the most frequent cause of death in intensive care unit patients. Many water-soluble mediators with pro- and anti-inflammatory action such as TNF, IL-6, IL-8, and IL-10 play a strategic role in septic syndrome. In intensive care medicine, blocking any one mediator has not led to a measurable outcome improvement in patients with sepsis. CRRT is a continuously acting therapy, which removes in a nonselective way pro- and anti-inflammatory mediators; "the peak concentration hypothesis" is the concept of cutting peaks of soluble mediators through continuous hemofiltration. Furthermore, there is evidence of increased efficacy of high-volume hemofiltration compared to conventional CVVH, and other blood purification techniques that utilize large-pore membranes or sorbent plasmafiltration are conceptually interesting.

Reduced neutrophil CD10 expression in nonhuman primates and humans after in vivo challenge with E. coli or lipopolysaccharide

CD10, also known as neutral endopeptidase or CALLA, is a major metalloproteinase that regulates levels of biologically active peptides that initiate inflammatory, cardiovascular, and neurogenic responses. Relative tissue expression levels of CD10, its peptide substrates, and their receptors constitute the basic regulatory mechanism. Neutrophils contain abundant CD10 and are rapid responders to an inflammatory septic challenge. Expression of neutrophil surface antigens in response to inflammation was studied in the primate model of Escherichia coli-mediated sepsis and in human volunteers injected with lipopolysaccharide (LPS). There was a rapid and profound (up to 95%) reduced baboon neutrophil CD10 expression in response to E. coli injections of 5.71 x 106 CFU/kg to 2.45 x 109 CFU/kg that gradually resolved to preinjection levels. The reduction was both dose and time dependent. Reduced CD10 antigen on mature baboon neutrophils and bands was observed by immunohistochemistry. Human volunteers challenged with 4ng/kg LPS experienced transient chills, nausea, fever, and myalgia. Up to approximately 20% of their neutrophils had reduced CD10 expression, peaking at 2 to 8 h after injection. By 24 h, neutrophil CD10 expression resolved to preinjection levels. In contrast, in both the baboon and human studies, other neutrophil surface antigens were only slightly decreased (CD11a) or increased (CD11b, CD18, CD35, CD66b, and CD63). These data present the novel observation that neutrophil CD10 expression decreases significantly in response to in vivo inflammatory challenge. This decrease appears to be unique to CD10 and may contribute to a reduced regulation of bioactive peptides released in response to inflammatory challenge.

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.

Acute renal failure and multiple organ dysfunction in the ICU: from renal replacement therapy (RRT) to multiple organ support therapy (MOST)

Renal replacement therapy (RRT) has evolved from the concept that we need to treat the dysfunction of a single organ (the kidney). As intensive care units have become more and more complex, it has become clear that the majority of patients with acute renal failure often have dysfunction of several other organs. In order to facilitate single organ support in this setting, continuous renal replacement therapy (CRRT) techniques have been developed. However, CRRT has opened the door to the concept that targeting renal support as the only goal of extracorporeal blood purification may be a simplistic view of our therapeutic aims. In this article we argue that it is now time to move from the simple goal of achieving adequate renal support. The proper goal of extracorporeal blood purification in ICU should be multi-organ support therapy (MOST). We explain why MOST represents the most logical future conceptual and practical evolution of CRRT and illustrates the biological rationale, supplying animal and clinical evidence that confirms the need to move rapidly in this direction theoretically, practically and technologically.

Artificial organ treatment for multiple organ failure, acute renal failure, and sepsis: recent new trends

Sepsis remains the major cause of mortality worldwide, claiming millions of lives each year. The past decade has seen major advances in the understanding of the biological mechanisms involved in this complex process. Unfortunately, no definitive therapy yet exists that can successfully treat sepsis and its complications. At variance with targeting single mediators, therapeutic intervention aimed at the nonselective removal of pro- and anti-inflammatory mediators seems a rational concept and a possible key to successful extracorporeal therapies. A further advantage may lie in the continuous nature of such therapy. With such continuous therapy, sequentially appearing peaks of systemic mediator overflow may be attenuated and persistently high plasma levels reduced. This theoretical framework is proposed as the underlying biological rationale for a series of innovative modalities in sepsis. In this editorial, we will review recent animal and human trials that lend support to this concept. We will also review the importance of treatment dose during continuous renal replacement therapy as a major factor affecting survival in critically ill patients with acute renal failure. Additionally, we will review novel information related to other blood purification techniques using large pore membranes or plasma filtration with adsorbent perfusion. Although these approaches are still in the early stages of clinical testing, they are conceptually promising and might represent an important advance.

Bench-to-bedside review: endothelial cell dysfunction in severe sepsis: a role in organ dysfunction?

During the past decade a unifying hypothesis has been developed to explain the vascular changes that occur in septic shock on the basis of the effect of inflammatory mediators on the vascular endothelium. The vascular endothelium plays a central role in the control of microvascular flow, and it has been proposed that widespread vascular endothelial activation, dysfunction and eventually injury occurs in septic shock, ultimately resulting in multiorgan failure. This has been characterized in various models of experimental septic shock. Now, direct and indirect evidence for endothelial cell alteration in humans during septic shock is emerging. The present review details recently published literature on this rapidly evolving topic.

Staging of the pathophysiologic responses of the primate microvasculature to Escherichia coli and endotoxin: examination of the elements of the compensated response and their links to the corresponding uncompensated lethal variants

OBJECTIVE

Review of primate studies of Escherichia coli sepsis and endotoxemia with a reexamination of the rationale for diagnosis and treatment of these multistage disorders.

SETTING

Animal research and intensive care units in a university medical school.

SUBJECTS

Cyanocephalus baboons (E. coli) and normal human subjects (endotoxin).

INTERVENTIONS

Baboon studies: anti-tissue factor, protein C, endothelial protein C receptor, and anti-tumor necrosis factor antibodies, and active site inhibited factor recombinant VIIa and factor Xa.

RESULTS AND CONCLUSIONS

This review concerns the primate microvascular endothelial response to inflammatory and hemostatic stress. Studies of the impact of inflammatory and hemostatic stress on this microvasculature have fallen into four categories. First, studies of pure hemostatic stress using factor Xa phospholipid vesicles showed that blockade of protein C as well as protein C plus tissue plasminogen activator produced a severe but transient consumptive and a lethal thrombotic coagulopathy, respectively. These studies showed that the protein C and fibrinolytic systems can work in tandem to regulate even a severe response if the endothelium is not rendered dysfunctional by metabolic or inflammatory factors. Second, studies of compensated (nonlethal) inflammatory stress using E. coli or endotoxin in baboon and human subjects showed that even under minimal stress in which there is no evidence of overt disseminated intravascular coagulation, injury of the endothelium and activation of neutrophils and hemostatic factors are closely associated. This showed that molecular markers of hemostatic activity could be used to detect microvascular endothelial stress (nonovert disseminated intravascular coagulation) in patients who are compensated but at risk. These studies also showed that the compensated response to inflammatory stress could exhibit two stages, each with its unique inflammatory and hemostatic response signature. The first is driven by vasoactive peptides, cytokines, and thrombin, followed 12 to 14 hrs later by a second stage driven by C-reactive protein/complement complexes, tissue factor, and plasminogen activator inhibitor 1 secondary to oxidative stress after reperfusion. Third, studies of uncompensated (lethal) inflammatory stress using E. coli showed that irreversible thrombosis of the microvasculature was not a link in the lethal chain of events even though inhibition of components of the protein C network (protein C and endothelial protein C receptor) converted compensated responses to sublethal E. coli into uncompensated lethal responses. Fourth, these studies also showed that there were variants of the lethal response ranging from capillary leak and shock to recurrent sustained inflammatory disorders. We believe that each of these variants arises from their sublethal counterparts, depending on underlying or modulating host factors operating at the time of challenge. Such underlying conditions range from preexisting microvascular ischemia, reperfusion, and oxidative stress to alteration or reprogramming of monocyte/macrophage responses (tolerance to hyperresponsiveness). Characterization of these underlying conditions in patients who are at risk should aid in identifying and optimizing management of these variants.