Intravenous administration of activated protein C in Pseudomonas-induced lung injury: impact on lung fluid balance and the inflammatory response

Difference in hematocrit and plasma albumin levels as an additional biomarker in the diagnosis of infectious disease

INTRODUCTION

In clinical practice, it has been observed that patients with severe infections show changes to their hematocrit (HCT) and serum albumin (ALB) levels. This study aimed to evaluate whether the difference of HCT and ALB (HCT-ALB) levels can be used as an additional biomarker for fast diagnosis of severe infections.

MATERIAL AND METHODS

This was a retrospective case-control study which included adult patients with severe infections, patients with non-infective conditions and healthy individuals. A total of 7,117 individuals were recruited in Yunnan Province, China, from January 2012 to January 2018, and were divided into three groups: 1,033 patients with severe infections (group 1); 1,081 patients with non-infective conditions (group 2); and 5,003 healthy individuals from the general population (group 3). The potential diagnostic threshold of HCT-ALB for severe infectious patients was determined by the receiver operating characteristic (ROC) curve analysis. Group 3 was used as the reference to draw the ROC curves of the HCT-ALB value in group 1 or group 2.

RESULTS

HCT-ALB values in each group were significantly different. We found that the area under the ROC curve (AUC) of group 1 reached 0.87 (95% CI: 0.86-0.89), whereas the AUC of group 2 was 0.60 (95% CI: 0.58-0.62). To reach a higher specificity of 99.0% (95% CI: 98.8-99.3%, and with sensitivity of 37.5%, 95% CI: 34.5-40.5%), a HCT-ALB value of 10.25 was recommended as the standard for diagnosis of severe infection.

CONCLUSIONS

The HCT-ALB value was increased in patients with infectious disease. The measurement of the HCT-ALB value (> 10.25) might be useful in the fast diagnosis of infectious disease.

Understanding Infection-Induced Thrombosis: Lessons Learned From Animal Models

Thrombosis is a common consequence of infection that is associated with poor patient outcome. Nevertheless, the mechanisms by which infection-associated thrombosis is induced, maintained and resolved are poorly understood, as is the contribution thrombosis makes to host control of infection and pathogen spread. The key difference between infection-associated thrombosis and thrombosis in other circumstances is a stronger inflammation-mediated component caused by the presence of the pathogen and its products. This inflammation triggers the activation of platelets, which may accompany damage to the endothelium, resulting in fibrin deposition and thrombus formation. This process is often referred to as thrombo-inflammation. Strikingly, despite its clinical importance and despite thrombi being induced to many different pathogens, it is still unclear whether the mechanisms underlying this process are conserved and how we can best understand this process. This review summarizes thrombosis in a variety of models, including single antigen models such as LPS, and infection models using viruses and bacteria. We provide a specific focus on Salmonella Typhimurium infection as a useful model to address all stages of thrombosis during infection. We highlight how this model has helped us identify how thrombosis can appear in different organs at different times and thrombi be detected for weeks after infection in one site, yet largely be resolved within 24 h in another. Furthermore, we discuss the observation that thrombi induced to Salmonella Typhimurium are largely devoid of bacteria. Finally, we discuss the value of different therapeutic approaches to target thrombosis, the potential importance of timing in their administration and the necessity to maintain normal hemostasis after treatment. Improvements in our understanding of these processes can be used to better target infection-mediated mechanisms of thrombosis.

Recombinant activated protein C attenuates coagulopathy and inflammation when administered early in murine pneumococcal pneumonia

Recombinant human activated protein C (APC), which has both anticoagulant and anti-inflammatory properties, improves survival of patients with severe sepsis. This beneficial effect is especially apparent in patients with pneumococcal pneumonia. Earlier treatment with APC in sepsis has been associated with a better therapeutic response as compared to later treatment. In a mouse model it was recently confirmed that recombinant murine (rm-)APC decreases coagulation activation and improves survival in pneumococcal pneumonia; however, APC did not impact on the inflammatory response. The aim of this study was to determine the effect of APC treatment instigated early in infection on activation of coagulation and inflammation after induction of pneumococcal pneumonia. Mice were infected intranasally with viable S. pneumoniae. Mice were treated with rm-APC (125 μg) or vehicle intraperitoneally 12 hours after infection and were sacrificed after 20 hours, after which blood and organs were harvested for determination of bacterial outgrowth, coagulation activation and inflammatory markers. In this early treatment model, rm-APC treatment inhibited pulmonary and systemic activation of coagulation as reflected by lower levels of throm-bin-antithrombin complexes and D-dimer. Moreover, rm-APC reduced the levels of a large number of cytokines and chemokines in the lung. When administered early in pneumococcal pneumonia, rm-APC inhibits systemic and pulmonary activation of coagulation and moreover exerts various anti-inflammatory effects in the lung.

Anticoagulant Therapy in Sepsis. The Importance of Timing

Sepsis associated coagulopathy is due to the inflammation-induced activation of coagulation pathways concomitant with dysfunction of anticoagulant and fibrinolytic systems, leading to different degrees of haemostasis dysregulation. This response is initially beneficial, contributing to antimicrobial defence, but when control is lost coagulation activation leads to widespread microvascular thrombosis and subsequent organ failure. Large clinical trials of sepsis-related anticoagulant therapies failed to show survival benefits, but posthoc analysis of databases and several smaller studies showed beneficial effects of anticoagulants in subgroups of patients with early sepsis-induced disseminated intravascular coagulation. A reasonable explanation could be the difference in timing of anticoagulant therapy and patient heterogeneity associated with large trials. Proper selection of patients and adequate timing are required for treatment to be successful. The time when coagulation activation changes from advantageous to detrimental represents the right moment for the administration of coagulation-targeted therapy. In this way, the defence function of the haemostatic system is preserved, and the harmful effects of overwhelming coagulation activation are avoided.

Atypical presentation of livedo racemosa in a factor V Leiden heterozygous positive patient with Pseudomonas aeruginosa urosepsis

Impairment of the protein C pathway, detectable by reduced plasma levels of activated protein C (APC), are risk factors for venous thrombosis. Activated protein C maintains clotting homeostasis by regulation of pro-coagulant factors Va and VIIIa. Both infection and the factor V Leiden mutation reduce the formation of APC from protein C in the blood. With low levels of APC, excess factors Va and VIIIa exist, increasing the risk of thrombus formation. Livedo racemosa is characterised by a striking, violaceous branch-like pattering of the skin. It is similar to livedo reticularis, but with a different morphology and histopathology. In this case report we present the first case of livedo racemosa, in an 89-year-old factor V Leiden-positive patient with a Pseudomonas aeruginosa urinary tract infection. The cutaneous biopsies demonstrated vasculopathy with intraluminal thrombi in subcutaneous vessels with no evidence of inflammatory vasculitis.

THE ENDOTHELIUM IN SEPSIS

Sepsis affects practically all aspects of endothelial cell (EC) function and is thought to be the key factor in the progression from sepsis to organ failure. Endothelial functions affected by sepsis include vasoregulation, barrier function, inflammation, and hemostasis. These are among other mechanisms often mediated by glycocalyx shedding, such as abnormal nitric oxide metabolism, up-regulation of reactive oxygen species generation due to down-regulation of endothelial-associated antioxidant defenses, transcellular communication, proteases, exposure of adhesion molecules, and activation of tissue factor. This review covers current insight in EC-associated hemostatic responses to sepsis and the EC response to inflammation. The endothelial cell lining is highly heterogeneous between different organ systems and consequently also in its response to sepsis. In this context, we discuss the response of the endothelial cell lining to sepsis in the kidney, liver, and lung. Finally, we discuss evidence as to whether the EC response to sepsis is adaptive or maladaptive. This study is a result of an Acute Dialysis Quality Initiative XIV Sepsis Workgroup meeting held in Bogota, Columbia, between October 12 and 15, 2014.

Mechanisms of phagocytosis and host clearance of Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic bacterial pathogen responsible for a high incidence of acute and chronic pulmonary infection. These infections are particularly prevalent in patients with chronic obstructive pulmonary disease and cystic fibrosis: much of the morbidity and pathophysiology associated with these diseases is due to a hypersusceptibility to bacterial infection. Innate immunity, primarily through inflammatory cytokine production, cellular recruitment, and phagocytic clearance by neutrophils and macrophages, is the key to endogenous control of P. aeruginosa infection. In this review, we highlight recent advances toward understanding the innate immune response to P. aeruginosa, with a focus on the role of phagocytes in control of P. aeruginosa infection. Specifically, we summarize the cellular and molecular mechanisms of phagocytic recognition and uptake of P. aeruginosa, and how current animal models of P. aeruginosa infection reflect clinical observations in the context of phagocytic clearance of the bacteria. Several notable phenotypic changes to the bacteria are consistently observed during chronic pulmonary infections, including changes to mucoidy and flagellar motility, that likely enable or reflect their ability to persist. These traits are likewise examined in the context of how the bacteria avoid phagocytic clearance, inflammation, and sterilizing immunity.

Protein C and acute inflammation: a clinical and biological perspective

The protein C system plays an active role in modulating severe systemic inflammatory processes such as sepsis, trauma, and acute respiratory distress syndrome (ARDS) via its anticoagulant and anti-inflammatory properties. Plasma levels of activated protein C (aPC) are lower than normal in acute inflammation in humans, except early after severe trauma when high plasma levels of aPC may play a mechanistic role in the development of posttraumatic coagulopathy. Thus, following positive results of preclinical studies, a clinical trial (PROWESS) with high continuous doses of recombinant human aPC given for 4 days demonstrated a survival benefit in patients with severe sepsis. This result was not confirmed by subsequent clinical trials, including the recently published PROWESS-SHOCK trial in patients with septic shock and a phase II trial with patients with nonseptic ARDS. A possible explanation for the major difference in outcome between PROWESS and PROWESS-SHOCK trials is that lung-protective ventilation was used for the patients included in the recent PROWESS-SHOCK, but not in the original PROWESS trial. Since up to 75% of sepsis originates from the lung, aPC treatment may not have added enough to the beneficial effect of lung-protective ventilation to show lower mortality. Thus whether aPC will continue to be used to modulate the acute inflammatory response in humans remains uncertain. Because recombinant human aPC has been withdrawn from the market, a better understanding of the complex interactions between coagulation and inflammation is needed before considering the development of new drugs that modulate both coagulation and acute inflammation in humans.

Activated protein C in the treatment of acute lung injury and acute respiratory distress syndrome

BACKGROUND

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) frequently necessitate mechanical ventilation in the intensive care unit. The syndromes have a high mortality rate and there is at present no treatment specifically directed at the underlying pathogenesis. Central in the pathophysiology of ALI/ARDS is alveolocapillary inflammation leading to permeability edema. As a result of the crosstalk between inflammation and coagulation, activation of proinflammatory and procoagulant/antifibrinolytic pathways contributes to disruption of the endothelial barrier. Protein C (PC) plays a central role in maintaining the equilibrium between coagulation and inflammation. Additionally, natural anticoagulants, such as PC, are depleted, both in blood as well as in the lung. Therefore, the PC system is of interest as a therapeutic target in patients with ALI/ARDS.

METHOD

This review is based on a Medline search of relevant basic and clinical studies.

OBJECTIVE

It discusses the potential role of activated PC in modulating the proinflammatory/procoagulant state for enhancing endothelial barrier function in animal models and human ALI/ARDS.

Nebulized fibrinolytic agents improve pulmonary fibrinolysis but not inflammation in rat models of direct and indirect acute lung injury

BACKGROUND

Critically ill patients frequently develop acute lung injury (ALI). Disturbed alveolar fibrin turnover, a characteristic feature of ALI, is the result of both activation of coagulation and inhibition of fibrinolysis. Nebulized fibrinolytic agents could exert lung-protective effects, via promotion of fibrinolysis as well as anti-inflammation.

METHODS

Rats were challenged intratracheally with Pseudomonas aeruginosa, resulting in pneumonia as a model for direct ALI, or received an intravenous bolus infusion of lipopolysaccharide, as a model for indirect ALI. Rats were randomized to nebulization of normal saline (placebo), recombinant tissue plasminogen activator (rtPA), or monoclonal antibodies against plasminogen activator inhibitor-type 1 (anti-PAI-1).

RESULTS

Nebulized rtPA or anti-PA1-1 enhanced the bronchoalveolar fibrinolytic system, as reflected by a significant reduction of PAI-1 activity levels in bronchoalveolar lavage fluid, and a consequent increase in plasminogen activator activity (PAA) levels to supranormal values. Both treatments also significantly affected systemic fibrinolysis as reflected by a significant increase in PAA levels in plasma to supranormal levels. Neither nebulized rtPA nor anti-PA1-1 affected pulmonary inflammation. Neither treatment affected bacterial clearance of P. aeruginosa from the lungs in case of pneumonia.

CONCLUSIONS

Local treatment with rtPA or anti-PA1-1 affects pulmonary fibrinolysis but not inflammation in models of direct or indirect ALI in rats.

Nebulized anticoagulants for acute lung injury - a systematic review of preclinical and clinical investigations

Background

Data from interventional trials of systemic anticoagulation for sepsis inconsistently suggest beneficial effects in case of acute lung injury (ALI). Severe systemic bleeding due to anticoagulation may have offset the possible positive effects. Nebulization of anticoagulants may allow for improved local biological availability and as such may improve efficacy in the lungs and lower the risk of systemic bleeding complications.

Method

We performed a systematic review of preclinical studies and clinical trials investigating the efficacy and safety of nebulized anticoagulants in the setting of lung injury in animals and ALI in humans.

Results

The efficacy of nebulized activated protein C, antithrombin, heparin and danaparoid has been tested in diverse animal models of direct (for example, pneumonia-, intra-pulmonary lipopolysaccharide (LPS)-, and smoke inhalation-induced lung injury) and indirect lung injury (for example, intravenous LPS- and trauma-induced lung injury). Nebulized anticoagulants were found to have the potential to attenuate pulmonary coagulopathy and frequently also inflammation. Notably, nebulized danaparoid and heparin but not activated protein C and antithrombin, were found to have an effect on systemic coagulation. Clinical trials of nebulized anticoagulants are very limited. Nebulized heparin was found to improve survival of patients with smoke inhalation-induced ALI. In a trial of critically ill patients who needed mechanical ventilation for longer than two days, nebulized heparin was associated with a higher number of ventilator-free days. In line with results from preclinical studies, nebulization of heparin was found to have an effect on systemic coagulation, but without causing systemic bleedings.

Conclusion

Local anticoagulant therapy through nebulization of anticoagulants attenuates pulmonary coagulopathy and frequently also inflammation in preclinical studies of lung injury. Recent human trials suggest nebulized heparin for ALI to be beneficial and safe, but data are very limited.

Severe sepsis, coagulation, and fibrinolysis: dead end or one way?

It was suggested more than 30 yrs ago that inhibition of the clotting cascade by natural anticoagulants could decrease the high mortality observed in patients suffering from severe sepsis and septic shock. Unfortunately, this therapeutic "paradigm" has led to a dead end, illustrated by the failure of all randomized trials and the recent withdrawal of recombinant activated protein C. Should we now definitely give up trying to treat septic coagulation disturbances or is there any therapeutic alternative?

The effect of influenza virus A on th1/th2 balance and alveolar fluid clearance in pregnant rats

ABSTRACT Pregnant women are more prone to H1N1 infection and often with severe complications. The authors studied the influence of H1N1 infection on T-helper cell type 1/type 2 (Th1/Th2) balance and alveolar fluid clearance (AFC) in pregnant rats. The pregnant rats were infected intranasally with influenza virus. Peripheral blood interferon-γ (IFN-γ) and interleukin-4 (IL-4) were measured by enzyme-linked immunosorbent assay (ELISA) and AFC was estimated by albumin concentration in alveolar lavage. The ratio of IFN-γ/IL-4 in nonpregnant rats was 21 ± 7. There was significant increase in both cytokines in infected pregnant rats compared with noninfected counterparts, with dramatic reduction in IFN-γ/IL-4 ratio (8 ± 3) compared to that (15 ± 8) in normal pregnant group. AFC of normal nonpregnant rats was 17% ± 3% and H1N1 infection reduced it to 11% ± 2%. AFC of normal pregnant rats was 22% ± 2% and H1N1 infection reduced it to 10% ± 2%. Dexamethasone reversed AFC in both nonpregnant and pregnant groups (14% ± 4% and 13% ± 2%, respectively). These results show that influenza virus A infection leads to Th2-biased immunity and reduces AFC in normal rats, and further worsens these in pregnant rats. Dexamethasone reverses these effects in both pregnant and nonpregnant rats.

Severe protein C deficiency is associated with organ dysfunction in patients with severe sepsis

PURPOSE

The aim of this study was to assess the relationship between protein C levels and temporal changes in organ dysfunction.

MATERIALS AND METHODS

Using data from the placebo arm of Recombinant Human Activated PROtein C Worldwide Evaluation in Severe Sepsis trial (N = 775), we compared the development of organ dysfunction over time, in adult severe sepsis patients with and without severe protein C deficiency.

RESULTS

At study enrollment (baseline), patients with and without severe protein C deficiency were similar in age and likelihood of comorbidities. Patients with severe protein C deficiency had lower arterial blood pressure (P = .0006), greater serum creatinine concentration (P < .0001), elevated markers of thrombosis and inflammation, and impairment of fibrinolysis (P < .0001). The baseline PaO(2)/FiO(2) ratio was not significantly different between the 2 groups. Seven days after study enrollment, cardiovascular and renal function remained significantly worse in patients with severe protein C deficiency (P < .0001), and respiratory dysfunction was greater (P < .0001). Baseline protein C deficiency was seen to be associated with subsequent pulmonary, renal, and hematologic organ failure.

CONCLUSIONS

Severe protein C deficiency in patients with severe sepsis is associated with both the incidence and severity of organ dysfunction and subsequent worsening of organ function and may be a useful predictor of organ failure in severe sepsis.

Impact of endogenous protein C on pulmonary coagulation and injury during lethal H1N1 influenza in mice

Influenza accounts for 5-10% of community-acquired pneumonia cases, and is a major cause of mortality. Sterile and bacterial lung injury are associated with procoagulant and inflammatory derangements in the lungs and down-regulation of the protein C (PC) pathway has been correlated with disease severity and mortality in severe bacterial pneumonia and sepsis. In addition, during lethal influenza pneumonia, pulmonary and systemic coagulation are activated, which can be attenuated by the administration of recombinant activated (A) PC. We here determined the role of endogenous PC in lethal H1N1 influenza A infection. Male C57BL/6 mice pretreated with an inhibitory monoclonal antibody directed against murine PC or a control antibody were intranasally infected with a lethal dose of a mouse-adapted H1N1 influenza A strain. Mice were killed at 48 or 96 hours after infection, after which lungs and bronchoalveolar lavage fluid were harvested, or observed for up to 9 days. Anti-PC antibody treatment aggravated pulmonary activation of coagulation as compared with control antibody treatment, as reflected by increased lung concentrations of thrombin-antithrombin complexes and fibrin degradation products, as well as intravascular thrombus formation. Anti-PC antibody treatment aggravated lung histopathology, but lowered bronchoalveolar neutrophil influx and total protein levels, and delayed mortality. In conclusion, endogenous PC has strong effects on the host response to lethal influenza A infection, inhibiting pulmonary coagulopathy and inflammation on the one hand, but facilitating neutrophil influx and protein leak and accelerating mortality on the other hand.

Cytoprotective-selective activated protein C attenuates Pseudomonas aeruginosa-induced lung injury in mice

Inhibition of the small GTPase RhoA attenuates the development of pulmonary edema and restores positive alveolar fluid clearance in a murine model of Pseudomonas aeruginosa pneumonia. Activated protein C (aPC) blocks the development of an unfavorably low ratio of small GTPase Rac1/RhoA activity in lung endothelium through endothelial protein C receptor (EPCR)/protease-activated receptor-1 (PAR-1)-dependent signaling mechanisms that include transactivating the sphingosine-1-phosphate (S1P) pathway. However, whether aPC's cytoprotective effects can attenuate the development of pulmonary edema and death associated with P. aeruginosa pneumonia in mice remains unknown. Thus, we determined whether the normalization of a depressed ratio of activated Rac1/RhoA by aPC would attenuate the P. aeruginosa-mediated increase in protein permeability across lung endothelial and alveolar epithelial barriers. Pretreatment with aPC significantly reduced P. aeruginosa-induced increases in paracellular permeability across pulmonary endothelial cell and alveolar epithelial monolayers via an inhibition of RhoA activation and a promotion of Rac1 activation that required the EPCR-PAR-1 and S1P pathways. Furthermore, pretreatment with aPC attenuated the development of pulmonary edema in a murine model of P. aeruginosa pneumonia. Finally, a cytoprotective-selective aPC mutant, aPC-5A, which lacks most of aPC's anticoagulant activity, reproduced the protective effect of wild-type aPC by attenuating the development of pulmonary edema and decreasing mortality in a murine model of P. aeruginosa pneumonia. Taken together, these results demonstrate a critical role for the cytoprotective activities of aPC in attenuating P. aeruginosa-induced lung vascular permeability and mortality, suggesting that cytoprotective-selective aPC-5A with diminished bleeding risks could attenuate the lung damage caused by P. aeruginosa in critically ill patients.

Activated protein C action in inflammation

Activated protein C (APC) is a natural anticoagulant that plays an important role in coagulation homeostasis by inactivating the procoagulation factor Va and VIIIa. In addition to its anticoagulation functions, APC also has cytoprotective effects such as anti-inflammatory, anti-apoptotic, and endothelial barrier protection. Recently, a recombinant form of human APC (rhAPC or drotrecogin alfa activated; known commercially as 'Xigris') was approved by the US Federal Drug Administration for treatment of severe sepsis associated with a high risk of mortality. Sepsis, also known as systemic inflammatory response syndrome (SIRS) resulting from infection, is a serious medical condition in critical care patients. In sepsis, hyperactive and dysregulated inflammatory responses lead to secretion of pro- and anti-inflammatory cytokines, activation and migration of leucocytes, activation of coagulation, inhibition of fibrinolysis, and increased apoptosis. Although initial hypotheses focused on antithrombotic and profibrinolytic functions of APC in sepsis, other agents with more potent anticoagulation functions were not effective in treating severe sepsis. Furthermore, APC therapy is also associated with the risk of severe bleeding in treated patients. Therefore, the cytoprotective effects, rather than the anticoagulant effect of APC are postulated to be responsible for the therapeutic benefit of APC in the treatment of severe sepsis.

Amino acid residues 201-205 in C-terminal acidic tail region plays a crucial role in antibacterial activity of HMGB1

Background

Antibacterial activity is a novel function of high-mobility group box 1 (HMGB1). However, the functional site for this new effect is presently unknown.

Methods and Results

In this study, recombinant human HMGB1 A box and B box (rHMGB1 A box, rHMGB1 B box), recombinant human HMGB1 (rHMGB1) and the truncated C-terminal acidic tail mutant (tHMGB1) were prepared by the prokaryotic expression system. The C-terminal acidic tail (C peptide) was synthesized, which was composed of 30 amino acid residues. Antibacterial assays showed that both the full length rHMGB1 and the synthetic C peptide alone could efficiently inhibit bacteria proliferation, but rHMGB1 A box and B box, and tHMGB1 lacking the C-terminal acidic tail had no antibacterial function. These results suggest that C-terminal acidic tail is the key region for the antibacterial activity of HMGB1. Furthermore, we prepared eleven different deleted mutants lacking several amino acid residues in C-terminal acidic tail of HMGB1. Antibacterial assays of these mutants demonstrate that the amino acid residues 201-205 in C-terminal acidic tail region is the core functional site for the antibacterial activity of the molecule.

Conclusion

In sum, these results define the key region and the crucial site in HMGB1 for its antibacterial function, which is helpful to illustrating the antibacterial mechanisms of HMGB1.

Nebulized antithrombin limits bacterial outgrowth and lung injury in Streptococcus pneumoniae pneumonia in rats

INTRODUCTION

Disturbed alveolar fibrin turnover is a cardinal feature of severe pneumonia. Clinical studies suggest that natural inhibitors of coagulation exert lung-protective effects via anticoagulant and possibly also anti-inflammatory pathways. Intravenous infusion of the natural anticoagulants increases the risk of bleeding. Local administration may allow for higher treatment dosages and increased local efficacy while at the same time reducing the risk of bleeding. We evaluated the effect of nebulized anticoagulants on pulmonary coagulopathy and inflammation in a rat model of Streptococcus pneumoniae pneumonia.

METHODS

In this randomized controlled in vivo laboratory study rats were challenged intratracheally with S. pneumoniae, inducing pneumonia, and randomized to treatment with normal saline (placebo), recombinant human activated protein C (rh-APC), plasma-derived antithrombin (AT), heparin or danaparoid, by means of nebulization.

RESULTS

S. pneumoniae infection increased pulmonary levels of thrombin-antithrombin complexes and fibrin degradation products. All nebulized anticoagulants significantly limited pulmonary coagulopathy. None of the agents except danaparoid resulted in changes in systemic coagulopathy. Treatment with plasma-derived AT reduced outgrowth of S. pneumoniae and histopathologic damage in lungs. In vitro experiments confirmed outgrowth was reduced in bronchoalveolar lavage fluid (BALF) from rats treated with plasma-derived AT compared with placebo. Neutralizing of cationic components in BALF diminished the inhibitory effects on bacterial outgrowth of BALF, suggesting a role for cationic antimicrobial proteins.

CONCLUSIONS

Nebulization of anticoagulants attenuates pulmonary coagulopathy during S. pneumoniae pneumonia in rats while only danaparoid affects systemic coagulation. Nebulized plasma-derived AT reduces bacterial outgrowth and exerts significant lung-protective effects.

Protective mechanisms of activated protein C in severe inflammatory disorders

The protein C system is an important natural anticoagulant mechanism mediated by activated protein C (APC) that regulates the activity of factors VIIIa and Va. Besides well-defined anticoagulant properties, APC also demonstrates anti-inflammatory, anti-apoptotic and endothelial barrier-stabilizing effects that are collectively referred to as the cytoprotective effects of APC. Many of these beneficial effects are mediated through its co-receptor endothelial protein C receptor, and the protease-activated receptor 1, although exact mechanisms remain unclear and are likely pleiotropic in nature. Increased insight into the structure-function relationships of APC facilitated design of APC variants that conserve cytoprotective effects and reduce anticoagulant features, thereby attenuating the risk of severe bleeding with APC therapy. Impairment of the protein C system plays an important role in acute lung injury/acute respiratory distress syndrome and severe sepsis. The pathophysiology of both diseases states involves uncontrolled inflammation, enhanced coagulation and compromised fibrinolysis. This leads to microvascular thrombosis and organ injury. Administration of recombinant human APC to correct the dysregulated protein C system reduced mortality in severe sepsis patients (PROWESS trial), which stimulated further research into its mechanisms of action. Several other clinical trials evaluating recombinant human APC have been completed, including studies in children and less severely ill adults with sepsis as well as a study in acute lung injury. On the whole, these studies have not supported the use of APC in these populations and challenge the field of APC research to search for additional answers.

Protection of vascular barrier integrity by activated protein C in murine models depends on protease-activated receptor-1

Protease activated receptor-1 (PAR1) mediates barrier protective signalling of activated protein C (APC) in human endothelial cells in vitro and may contribute to APC's beneficial effects in patients with severe sepsis. Mouse models are of key importance for translational research but species differences may limit conclusions for the human system. We analysed whether mouse APC can cleave, activate and induce signalling through murine PAR1 and tested in newly established mouse models if long-term infusion of APC prevents from vascular leakage. Cell surface immunoassays demonstrated efficient cleavage of endogenous murine endothelial PAR1 by either murine or human APC. Pharmacological concentrations of APC of either species had powerful barrier protective effects on cultured murine endothelial cells that required PAR1 cleavage. Vascular endothelial growth factor-mediated hyperpermeability in the skin was reduced by either endogenously generated as well as directly infused recombinant mouse APC in wild-type mice. However APC did not significantly alter the vascular barrier function in PAR1-deficient mice. In endotoxin-challenged mice, infused APC significantly prevented from pulmonary fluid accumulation in the wild-type mice but not in mice lacking PAR1. Our results directly show that murine APC cleaves and signals through PAR1 in mouse endothelial cells. APC reduces vascular permeability in mouse models and PAR1 plays a major role in mediating these effects. Our data in vitro and in vivo support the paradigm that PAR1 contributes to protective effects of APC on vascular barrier integrity in sepsis.

A review of pulmonary coagulopathy in acute lung injury, acute respiratory distress syndrome and pneumonia

Enhanced bronchoalveolar coagulation is a hallmark of many acute inflammatory lung diseases such as acute lung injury, acute respiratory distress syndrome and pneumonia. Intervention with natural anticoagulants in these diseases has therefore become a topic of interest. Recently, new data on the role of pulmonary coagulation and inflammation has become available. The aim of this review is to summarize these findings. Furthermore, the results of anticoagulant therapeutic interventions in these disorders are discussed.

Recombinant human activated protein C in acute lung injury: what is the role of bronchial circulation?

Impairment of the protein C pathway plays a central role in the pathogenesis of sepsis. Treatment with recombinant human activated protein C (rhAPC) has been reported to increase survival from severe sepsis. Protein C levels also decrease markedly in acute lung injury, of both septic and nonseptic origin. Low levels of protein C in acute lung injury are associated with poor clinical outcome. The present article discusses the beneficial effects of rhAPC in oleic acid-induced lung injury as well as the controversies between different animal models and the timing of drug administration. The unique bronchial circulation in ovine models seems to be responsible for the beneficial effects of rhAPC when given simultaneously to the injury.

Identification of biofilm-associated cluster (bac) in Pseudomonas aeruginosa involved in biofilm formation and virulence

Biofilms are prevalent in diseases caused by Pseudomonas aeruginosa, an opportunistic and nosocomial pathogen. By a proteomic approach, we previously identified a hypothetical protein of P. aeruginosa (coded by the gene pA3731) that was accumulated by biofilm cells. We report here that a ΔpA3731 mutant is highly biofilm-defective as compared with the wild-type strain. Using a mouse model of lung infection, we show that the mutation also induces a defect in bacterial growth during the acute phase of infection and an attenuation of the virulence. The pA3731 gene is found to control positively the ability to swarm and to produce extracellular rhamnolipids, and belongs to a cluster of 4 genes (pA3729–pA3732) not previously described in P. aeruginosa. Though the protein PA3731 has a predicted secondary structure similar to that of the Phage Shock Protein, some obvious differences are observed compared to already described psp systems, e.g., this unknown cluster is monocistronic and no homology is found between the other proteins constituting this locus and psp proteins. As E. coli PspA, the amount of the protein PA3731 is enlarged by an osmotic shock, however, not affected by a heat shock. We consequently named this locus bac for biofilm-associated cluster.

Recombinant human activated protein C ameliorates oleic acid-induced lung injury in awake sheep

INTRODUCTION

Acute lung injury (ALI) may arise both after sepsis and non-septic inflammatory conditions and is often associated with the release of fatty acids, including oleic acid (OA). Infusion of OA has been used extensively to mimic ALI. Recent research has revealed that intravenously administered recombinant human activated protein C (rhAPC) is able to counteract ALI. Our aim was to find out whether rhAPC dampens OA-induced ALI in sheep.

METHODS

Twenty-two yearling sheep underwent instrumentation. After 2 days of recovery, animals were randomly assigned to one of three groups: (a) an OA+rhAPC group (n = 8) receiving OA 0.06 mL/kg infused over the course of 30 minutes in parallel with an intravenous infusion of rhAPC 24 mg/kg per hour over the course of 2 hours, (b) an OA group (n = 8) receiving OA as above, or (c) a sham-operated group (n = 6). After 2 hours, sheep were sacrificed. Hemodynamics was assessed by catheters in the pulmonary artery and the aorta, and extravascular lung water index (EVLWI) was determined with the single transpulmonary thermodilution technique. Gas exchange was evaluated at baseline and at cessation of the experiment. Data were analyzed by analysis of variance; a P value of less than 0.05 was regarded as statistically significant.

RESULTS

OA induced profound hypoxemia, increased right atrial and pulmonary artery pressures and EVLWI markedly, and decreased cardiac index. rhAPC counteracted the OA-induced changes in EVLWI and arterial oxygenation and reduced the OA-induced increments in right atrial and pulmonary artery pressures.

CONCLUSIONS

In ovine OA-induced lung injury, rhAPC dampens the increase in pulmonary artery pressure and counteracts the development of lung edema and the derangement of arterial oxygenation.

Role of coagulation pathways and treatment with activated protein C in hyperoxic lung injury

BACKGROUND

Activated protein C (APC) significantly decreases mortality in severe sepsis, but its role in acute lung injury from non-infectious aetiologies is unclear. The role of APC in hyperoxic acute lung injury was tested by studying the physiology of lung injury development, measurement of key coagulation proteins and treatment with murine APC (mAPC).

METHODS

Mice were continuously exposed to >95% oxygen and lung injury was assessed by extravascular lung water, lung vascular protein permeability and alveolar fluid clearance. Coagulation proteins were measured in bronchoalveolar lavage (BAL) fluid and plasma. Recombinant mAPC was administered in preventive and treatment strategies.

RESULTS

Hyperoxia produced dramatic increases in lung vascular permeability and extravascular lung water between 72 and 96 h. Lung fluid balance was also adversely affected by progressive decreases in basal and cAMP-stimulated alveolar fluid clearance. Plasma levels of APC decreased at 72 h and were 90% depleted at 96 h. There were significant increases in BAL fluid levels of thrombomodulin, thrombin-antithrombin complexes and plasminogen activator inhibitor-1 at later time points of hyperoxia. Lung thrombomodulin expression was severely decreased during late hyperoxia and plasma levels of APC were not restored by excess thrombin administration. Administration of recombinant mAPC failed to improve indices of lung injury.

CONCLUSIONS

Hyperoxic acute lung injury produces procoagulant changes in the lung with a decrease in plasma levels of APC due to significant endothelial dysfunction. Replacement of mAPC failed to improve lung injury.

Activated Protein C Protection from Lung Inflammation in Endotoxin-Induced Injury

We studied the protection of recombinant human activated protein C (rhAPC) in endotoxin-induced lung inflammation and injury and whether this effect is correlated with modulation of lung matrix metalloproteinase (MMP) activity. We randomly assigned 12 Large White pigs to receive intravenous Escher-ichia coli lipopolysaccharide (LPS; 40 μ g/kg/hr), rhAPC (24 μ g/ kg/hr), or both. We monitored respiratory mechanics and function, cell counts, and cytokine concentrations in bron-choalveolar lavage fluid (BALF). Lung samples were collected for the zymography of MMP-2 and MMP-9 activities and for histology. In septic pigs, rhAPC decreased proMMP-9 release as well as MMP-9 activation, and increased proMMP-2 presence without any evident activation compared with specimens that were given LPS alone. In addition, lung injury in rhAPC-treated animals was significantly attenuated, as shown by higher respiratory compliance, delayed increase in tumor necrosis alfa and interleukin-1β as well as neutrophil recruitment in the BALF, reduced lung edema, and histologic changes. In conclusion, rhAPC is beneficial in acute lung injury, and the protection may depend, at least in part, on modulation of MMP-2/9 activity.

Augmentation of Pulmonary Epithelial Cell IL-8 Expression and Permeability by Pre-B-cell Colony Enhancing Factor

Background

Previous studies in our lab have identified Pre-B-cell colony enhancing factor (PBEF) as a novel biomarker in acute lung injury (ALI). The molecular mechanism of PBEF involvement in the pathogenesis of ALI is still incompletely understood. This study examined the role of PBEF in regulating pulmonary alveolar epithelial cell IL-8 expression and permeability.

Methods

Human pulmonary alveolar epithelial cells (cell line and primary cells) were transfected with human PBEF cDNA or PBEF siRNA and then cultured in the presence or absence of TNFα. PBEF and IL-8 expression were analyzed by RT-PCR and Western blotting. In addition, changes in pulmonary alveolar epithelial and artery endothelial cell barrier regulation with altered PBEF expression was evaluated by an in vitro cell permeability assay.

Results

Our results demonstrated that, in human pulmonary alveolar epithelial cells, the overexpression of PBEF significantly augmented basal and TNFα-stimulated IL-8 secretion by more than 5 to 10-fold and increased cell permeability by >30%; the knockdown of PBEF expression with siRNA significantly inhibited basal and TNFα-stimulated IL-8 secretion by 70% and IL-8 mRNA levels by 74%. Further, the knockdown of PBEF expression also significantly attenuated TNFα-induced cell permeability by 43%. Similar result was observed in human pulmonary artery endothelial cells.

Conclusion

These results suggest that PBEF may play a vital role in basal and TNFα-mediated pulmonary inflammation and pulmonary epithelial barrier dysfunction via its regulation of other inflammatory cytokines such as IL-8, which could in part explain the role of PBEF in the susceptibility and pathogenesis of ALI. These results lend further support to the potential of PBEF to serve as a diagnostic and therapeutic target to ALI.

Anticoagulant therapy in acute lung injury: a useful tool without proper operating instruction?

Activation of the coagulation cascade resulting in alveolar fibrin deposition is recognized as a hallmark of acute lung injury (ALI). Anticoagulant treatment with recombinant human activated protein C (rhAPC) appears promising, because – like in sepsis – there is a deficiency of protein C in ALI, which is correlated with poor outcome in both syndromes. Recently in Critical Care, Waerhaug and colleagues confirmed the beneficial effects of rhAPC on pulmonary function in ovine endotoxin-induced ALI. Notably, the authors reported no differences in hemorrhage in histologic analyses between rhAPC-treated and untreated animals. However, a recently reported randomized, placebo-controlled, multicenter trial in ALI patients without severe sepsis failed to identify any differences in the number of ventilator-free days or 60 day-mortality between the rhAPC and placebo group. In addition to (or perhaps because of) the complex pathogenesis, the discrepancy between clinical and experimental results in ALI is another common feature with sepsis. The future challenge will be to transfer our theoretical knowledge adequately into daily clinical practice. Anticoagulant therapy might be a useful tool in the treatment of ALI; however the proper operating instruction remains to be defined.

Treatment of sepsis-induced acquired protein C deficiency reverses Angiotensin-converting enzyme-2 inhibition and decreases pulmonary inflammatory response

The protein C (PC) pathway plays an important role in vascular and immune function, and acquired deficiency during sepsis is associated with increased mortality in both animal models and in clinical studies. However, the association of acquired PC deficiency with the pathophysiology of lung injury is unclear. We hypothesized that low PC induced by sepsis would associate with increased pulmonary injury and that replacement with activated protein C (APC) would reverse the activation of pathways associated with injury. Using a cecal ligation and puncture (CLP) model of polymicrobial sepsis, we examined the role of acquired PC deficiency on acute lung injury assessed by analyzing changes in pulmonary pathology, chemokine response, inducible nitric-oxide synthase (iNOS), and the angiotensin pathway. Acquired PC deficiency was strongly associated with an increase in lung inflammation and drivers of pulmonary injury, including angiotensin (Ang) II, thymus and activation-regulated chemokine, plasminogen activator inhibitor (PAI)-1, and iNOS. In contrast, the protective factor angiotensin-converting enzyme (ACE)-2 was significantly suppressed in animals with acquired PC deficiency. The endothelial protein C receptor, required for the cytoprotective signaling of APC, was significantly increased post-CLP, suggesting a compensatory up-regulation of the signaling receptor. Treatment of septic animals with APC reduced pulmonary pathology, suppressed the macrophage inflammatory protein family chemokine response, iNOS expression, and PAI-1 activity and up-regulated ACE-2 expression with concomitant reduction in AngII peptide. These data demonstrate a clear link between acquired PC deficiency and pulmonary inflammatory response in the rat sepsis model and provide support for the concept of APC as a replacement therapy in acute lung injury associated with acquired PC deficiency.

Effect of activated protein C on pulmonary blood flow and cytokine production in experimental acute lung injury

OBJECTIVE

In acute lung injury (ALI) activated protein C (APC) may reopen occluded lung vessels and minimize lung inflammation. We aimed at assessing the effect of APC on regional lung perfusion, aerated lung volume, cytokine production and oxygenation in experimental ALI.

DESIGN AND SETTING

Prospective, controlled study in an imaging facility.

PARTICIPANTS

Pigs tracheotomized and mechanically ventilated.

INTERVENTION

Pigs were randomly given intravenously APC (n = 8) or saline (n = 8). Thirty minutes later, ALI was induced by injecting oleic acid.

MEASUREMENTS AND RESULTS

Lung perfusion and aerated lung volume measured with positron emission tomography, plasma cytokines and arterial blood gas were determined just before ALI and 110 and 290 min thereafter. Lung cytokines were measured at the end of the experiment. PaO2 under F I O2 1 was significantly lower in the APC group before lung injury (473+/-129 vs. 578+/-54 mmHg) and 110 min (342+/-138 vs. 446+/-103 mmHg) and 290 min (303+/-171 vs. 547+/-54 mmHg) thereafter (p < 0.05). Lung perfusion nonsignificantly tended to redistribute towards dorsal lung regions with APC. Total aerated lung volume was not different between APC and control before ALI (10.0+/-1.5 vs. 11.0+/-2.5 ml/kg) (p > 0.05) or thereafter. Plasma IL-6 and IL-8 at 110 min were greater with APC (p < 0.05).

CONCLUSIONS

In contrast to studies using other models, pretreatment with APC was associated with worsening oxygenation in the present investigation. This might be due to ventilation-perfusion mismatch, with more perfusion to dependent nonaerated areas.

Recombinant activated protein C in sepsis: endothelium protection or endothelium therapy?

Endothelium dysfunction is one of the hallmarks of sepsis. Looney and Mattay, in the previous issue of Critical Care, highlight the role of activated protein C (APC) as a protective endothelial drug in septic situations. Nevertheless, the results of in vivo studies are less explicit and it remains uncertain whether these properties are relevant in human septic shock. Before considering recombinant APC (rAPC) as a therapeutic drug for the endothelium, we have to demonstrate its efficiency to protect or to reduce endothelium injury when infused a long time after the septic challenge. Nevertheless, if rAPC is efficient when infused in the early phase of septic challenge, we thus need to treat our patients earlier. At the least, genetically engineered variants have been designed with greater anti-apoptotic activity and reduced anticoagulant activity relative to wild-type APC. Further studies are needed to demonstrate the usefulness of these variants in septic shock therapy.

Recombinant human activated protein C inhibits local and systemic activation of coagulation without influencing inflammation during Pseudomonas aeruginosa pneumonia in rats

OBJECTIVE

Alveolar fibrin deposition is a hallmark of pneumonia. It has been proposed that recombinant human activated protein C exerts lung-protective effects via anticoagulant and anti-inflammatory pathways. We investigated the role of the protein C system in pneumonia caused by Pseudomonas aeruginosa, the organism that is predominantly involved in ventilator-associated pneumonia.

DESIGN

An observational clinical study and a controlled, in vivo laboratory study.

SETTING

Multidisciplinary intensive care unit and a research laboratory of a university hospital.

PATIENTS AND SUBJECTS

Patients with unilateral ventilator-associated pneumonia and male Sprague-Dawley rats.

INTERVENTIONS

Bilateral bronchoalveolar lavage was performed in five patients with unilateral ventilator-associated pneumonia. A total of 62 rats were challenged with intratracheal P. aeruginosa (10 colony-forming units), inducing pneumonia. Rats were randomized to treatment with normal saline, recombinant human activated protein C, heparin, or recombinant tissue plasminogen activator.

MEASUREMENTS AND MAIN RESULTS

Patients with pneumonia demonstrated suppressed levels of protein C and activated protein C in bronchoalveolar lavage fluid obtained from the infected site compared with the contralateral uninfected site. Intravenous administration of recombinant human activated protein C in rats with P. aeruginosa pneumonia limited bronchoalveolar generation of thrombin-antithrombin complexes, largely preserving local antithrombin activity. However, recombinant human activated protein C did not have effects on neutrophil influx and activity, expression of pulmonary cytokines, or bacterial clearance.

CONCLUSIONS

In patients with ventilator-associated pneumonia, the pulmonary protein C pathway is impaired at the site of infection, and local anticoagulant activity may be insufficient. Recombinant human activated protein C prevents procoagulant changes in the lung; however, it does not seem to alter the pulmonary host defense against P. aeruginosa pneumonia.

Alveolar fluid clearance in acute lung injury: what have we learned from animal models and clinical studies?

Background

Acute lung injury and the acute respiratory distress syndrome continue to be significant causes of morbidity and mortality in the intensive care setting. The failure of patients to resolve the alveolar edema associated with these conditions is a major contributing factor to mortality; hence there is continued interest to understand the mechanisms of alveolar edema fluid clearance.

Discussion

The accompanying review by Vadász et al. details our current understanding of the signaling mechanisms and cellular processes that facilitate clearance of edema fluid from the alveolar compartment, and how these signaling processes may be exploited in the development of novel therapeutic strategies. To complement that report this review focuses on how intact organ and animal models and clinical studies have facilitated our understanding of alveolar edema fluid clearance in acute lung injury and acute respiratory distress syndrome. Furthermore, it considers how what we have learned from these animal and organ models and clinical studies has suggested novel therapeutic avenues to pursue.

Bench-to-bedside review: the role of activated protein C in maintaining endothelial tight junction function and its relationship to organ injury

Activated protein C (APC) has emerged as a novel therapeutic agent for use in selected patients with severe sepsis, even though the mechanism of its benefit is not well established. APC has anticoagulant, anti-inflammatory, antiapoptotic, and profibrinolytic properties, but it is not clear through which of these mechanisms APC exerts its benefit in severe sepsis. Focus has recently turned to the role of APC in maintaining endothelial barrier function, and in vitro and in vivo studies have examined this relationship. This article critically reviews these studies, with a focus on potential mechanisms of action.