The practice of diagnosing and reporting transfusion-associated circulatory overload: a national survey among physicians and haemovigilance officers.

OBJECTIVES: This study aims at identifying factors that disciplines consider when diagnosing and reporting transfusion-associated circulatory overload ('TACO'). BACKGROUND: TACO is a clinical diagnosis based mainly on subjective factors. Therefore, TACO could be an underreported complication of blood transfusion. METHODS: A survey was conducted among critical care physicians, anaesthesiologists, haematologists, transfusion medicine physicians and haemovigilance officers using case vignettes and a questionnaire. Factors that may affect diagnosing TACO were investigated using conjoint analysis. A positive B-coefficient indicates a positive preference for diagnosing TACO. Participants rated factors influencing reporting TACO on a 0- to 100-point scale. RESULTS: One hundred and seven surveys were returned (62%). Vignettes showed preferences in favour of diagnosing TACO with the onset of symptoms within 2 h [ß 0·4(-0·1-1·0)], positive fluid balance [ß 0·9(0·4-1·5)] and history of renal failure [ß 0·6(0·1-1·2)]. Compared with transfusion of a single unit of red blood cells (RBC), respondents showed a preference for diagnosing TACO following a single unit of solvent/detergent (S/D) plasma or pooled platelet concentrate (PPC) [ß 0·3(-0·2-0·7) resp. 0·5(-0·1-1·2)]. Multiple transfusion (6 RBC + 4 S/D plasma) was a strong preference for diagnosing TACO compared to 1 RBC and 1 S/D plasma [ß 0·3(-0·8-1·3)]. Respondents did not fully take into account new hypertension and tachycardia when reporting TACO [median 70 (IQR 50-80) resp. 60 (IQR 50-80)]. No differences were observed between disciplines involved. CONCLUSION: When diagnosing and reporting TACO, physicians and haemovigilance officers do consider known risk factors for TACO. Reporting could be improved by increasing the awareness of haemodynamic variables in future education programmes.

Characterization of buffy coat-derived granulocytes for clinical use: a comparison with granulocyte colony-stimulating factor/dexamethasone-pretreated donor-derived products.

BACKGROUND AND OBJECTIVES: Buffy coat-derived granulocytes have been described as an alternative to the apheresis product from donors pretreated with dexamethasone and granulocyte colony-stimulating factor (G-CSF). The latter is - dependent on the local and national settings - obtained following a demanding and time-consuming procedure, which is undesirable in critically ill septic patients. In contrast, buffy coat-derived products have a large volume and are often heavily contaminated with red cells and platelets. We developed a new pooled buffy coat-derived product with high purity and small volume, and performed a comprehensive functional characterization of these granulocytes. MATERIALS AND METHODS: We pooled ten buffy coats following the production of platelet concentrates. Saline 0·9% was added to decrease the viscosity and the product was split into plasma, red cells and a 'super' buffy coat. Functional data of the granulocytes were compared to those obtained with granulocytes from healthy controls and G-CSF/dexamethasone-pretreated donors. RESULTS: Buffy coat-derived granulocytes showed adhesion, chemotaxis, reactive oxygen species production, degranulation, NETosis and in vitro killing of Staphylococcus aureus, Escherichia coli and Aspergillus species comparable to control and G-CSF/dexamethasone-derived granulocytes. Candida killing was superior compared to G-CSF/dexamethasone-derived granulocytes. Immunophenotyping was normal; especially no signs of activation in the buffy coat-derived granulocytes were seen. Viability was reduced. Buffy coats are readily available in the regular blood production process and would take away the concerns around the apheresis product. CONCLUSION: The product described appears a promising alternative for transfusion purposes.

Strategies to reduce wastage of red blood cell units.

BACKGROUND AND OBJECTIVES: Wastage of red blood cell units (RBCs) due to their inappropriate storage at the clinical ward has become both a financial and ethical challenge in the daily hospital practice. This study was aimed at identifying the extent of RBC wastage and evaluating the effects of various interventions in reducing this wastage. MATERIALS AND METHODS: From January 2011 to March 2011, baseline wastage level was evaluated using temperature-sensitive labels. Following this initial analysis, various interventions were implemented, including modifying the transfusion practice, intensifying training of and communication with the medical staff and improving the transport conditions. The impact of these interventions on wastage was measured during two periods, and results were compared with baseline wastage level. RESULTS: Based on the extent of label colouring, 7·5% of the units dispensed by the transfusion laboratory were determined as non-reusable at baseline. After implementation of the various interventions, wastage decreased to 1% of the units dispensed, potentially leading to an annual saving for our hospital of approximately €208·000/$230·600 on the total number of RBCs dispensed. CONCLUSION: Relative straightforward interventions, such as raising awareness among medical staff and particularly improving transport conditions, had a clear impact on the level of RBC wastage, accommodating the financial issue not to waste public money as well as the ethical issue that RBC wastage should be as low as possible.

The effect of C1-inhibitor in a murine model of transfusion-related acute lung injury.

BACKGROUND AND OBJECTIVE: Transfusion-related acute lung injury (TRALI) is the leading cause of transfusion-related morbidity and mortality. Specific therapy is lacking. We assessed whether C1-inhibitor attenuates lung injury in a 'two-hit' TRALI model. METHODS: Mice were primed with lipopolysaccharide, subsequently TRALI was induced by MHC-I antibodies. In the intervention group, C1-inhibitor was infused concomitantly. Mice were supported with mechanical ventilation. After 2 h, mice were killed, lungs were removed and bronchoalveolar lavage fluid (BALF) was obtained. RESULTS: Injection of MHC-I antibodies induced TRALI, illustrated by an increase in wet-to-dry ratio of the lungs, in BALF protein levels and in lung injury scores. TRALI was further characterized by complement activation, demonstrated by increased BALF levels of C3a and C5a. Administration of C1-inhibitor resulted in increased pulmonary C1-inhibitor levels with high activity. C1-inhibitor reduced pulmonary levels of complement C3a associated with improved lung injury scores. However, levels of pro-inflammatory mediators were unaffected. CONCLUSION: In a murine model of TRALI, C1-inhibitor attenuated pulmonary levels of C3a associated with improved lung injury scores, but with persistent high levels of inflammatory cytokines.

GATA2 haploinsufficient patients lack innate lymphoid cells that arise after hematopoietic cell transplantation.

Innate lymphoid cells (ILC) are important barrier tissue immune regulators. They play a pivotal role in early non-specific protection against infiltrating pathogens, regulation of epithelial integrity, suppression of pro-inflammatory immune responses and shaping the intestinal microbiota. GATA2 haploinsufficiency causes an immune disorder that is characterized by bone marrow failure and (near) absence of monocytes, dendritic cells, B cells and natural killer (NK) cells. T cells develop normally, albeit at lower numbers. Here, we describe the absence of ILCs and their progenitors in blood and bone marrow of two patients with GATA2 haploinsufficiency and show that all subsets of ILCs appear after allogeneic hematopoietic stem cell transplantation, irrespective of the preparative conditioning regimen. Our data indicate that GATA2 is involved in the development of hematopoietic precursor cells (HPC) towards the ILC lineage.

Halting targeted and collateral damage to red blood cells by the complement system.

The complement system is an important defense mechanism against pathogens; however, in certain pathologies, the system also attacks human cells, such as red blood cells (RBCs). In paroxysmal nocturnal hemoglobinuria (PNH), RBCs lack certain complement regulators which sensitize them to complement-mediated lysis, while in autoimmune hemolytic anemia (AIHA), antibodies against RBCs may initiate complement-mediated hemolysis. In recent years, complement inhibition has improved treatment prospects for these patients, with eculizumab now the standard of care for PNH patients. Current complement inhibitors are however not sufficient for all patients, and they come with high costs, patient burden, and increased infection risk. This review gives an overview of the underlying pathophysiology of complement-mediated hemolysis in PNH and AIHA, the role of therapeutic complement inhibition nowadays, and the high number of complement inhibitors currently under investigation, as for almost every complement protein, an inhibitor is being developed. The focus lies with novel therapeutics that inhibit complement activity specifically in the pathway that causes pathology or those that reduce costs or patient burden through novel administration routes.

Activated complement is more extensively present in diseased aortic valves than naturally occurring complement inhibitors: a sign of ongoing inflammation.

BACKGROUND: Recent studies indicate a role for complement in the pathogenesis of aortic valve disease. However, the role of naturally occurring anti-complement mediators in this context is unknown. In this study, we have analysed this in three different pathological conditions of the aortic valve: degeneration, atherosclerosis and bacterial endocarditis. MATERIALS AND METHODS: Human aortic valves were obtained at autopsy (n = 30): 5 control valves, 10 aortic valves with atherosclerotic changes, 10 aortic valves with degenerative changes and 5 degenerative changed aortic valves with bacterial infection. These valves were analysed immunohistochemically for the presence of activated complement (C3d and C5b9) and the complement inhibitors C1-inh and clusterin. Areas of positivity were then quantified. RESULTS: C3d, C5b9 and the complement inhibitors C1-inh and clusterin depositions were mainly found in the endothelium and extracellular matrix in aortic valves. All these mediators were already present in control valves, but the area of positivity increased significantly in response to the different diseases, with the highest increase in response to bacterial endocarditis. Interestingly, in all three aortic diseases, the depositions of complement were significantly more widespread than that of their inhibitors. CONCLUSIONS: Our study indicates that anti-complement mediators (C1-inh and clusterin) are deposited in diseased aortic valves together with activated complement, indicating an existing counter response against complement locally in the valve. However, deposition of activated complement is significantly more widespread than that of its inhibitors, which could explain ongoing inflammation in those diseased aortic valves.

ADAMTS-13, von Willebrand factor and related parameters in severe sepsis and septic shock.

BACKGROUND: Insufficient control of von Willebrand factor (VWF) multimer size as a result of severely deficient ADAMTS-13 activity results in thrombotic thrombocytopenic purpura associated with microvascluar thrombosis and platelet consumption, features not seldom seen in severe sepsis and septic shock. METHODS: ADAMTS-13 activity and VWF parameters of 40 patients with severe sepsis or septic shock were compared with those of 40 healthy controls of the same age and gender and correlated with clinical findings and sepsis outcome. RESULTS: ADAMTS-13 activity was significantly lower in patients than in healthy controls [median 60% (range 27-160%) vs. 110% (range 63-200%); P < 0.001]. VWF parameters behaved reciprocally and both VWF ristocetin cofactor activity (RCo) and VWF antigen (VWF:Ag) were significantly (P < 0.001) higher in patients compared with controls. Neither ADAMTS-13 activity nor VWF parameters correlated with disease severity, organ dysfunction or outcome. However, a contribution of acute endothelial dysfunction to renal impairment in sepsis is suggested by the significantly higher VWF propeptide and soluble thrombomodulin levels in patients with increased creatinine values as well as by their strong positive correlations (creatinine and VWF propeptide r(s) = 0.484, P < 0.001; creatinine and soluble thrombomodulin r(s) = 0.596, P < 0.001). CONCLUSIONS: VWF parameters are reciprocally correlated with ADAMTS-13 activity in severe sepsis and septic shock but have no prognostic value regarding outcome.

Therapeutic use of transferrin to modulate anemia and conditions of iron toxicity.

As the main iron transporter, transferrin delivers iron to target tissues like the bone marrow for erythropoiesis. Also, by binding free iron, transferrin prevents formation of reactive oxygen species. Transferrin deficiency due to congenital hypotransferrinemia is characterized by anemia as well as oxidative stress related to toxic free iron. Transferrin supplementation may be beneficial in two ways. First, transferrin can correct anemia by modulating the amount of iron that is available for erythropoiesis. This is obvious for patients that suffer from hypotransferrinemia, but may also have beneficial effects for ß-thalassemia patients. Second, under conditions of iron overload, transferrin reduces oxidative stress by binding free iron in the circulation and in tissues. Hereby, transferrin protects the host against the reactive oxygen species that can be formed as a consequence of free iron. This beneficial effect is shown in hematological patients undergoing chemotherapy and stem cell transplantation. Transferrin may also be beneficial in lung injury, ischemia-reperfusion injury and hypomyelination. This review summarizes the preclinical and clinical data on the efficacy of exogenous transferrin administration to modulate certain forms of anemia and to prevent the toxic effects of free iron. Thereby, we show that transferrin has promising therapeutic potential in a wide variety of conditions.

Dynamics of von Willebrand factor reactivity in sickle cell disease during vaso-occlusive crisis and steady state.

Essentials The role of von Willebrand Factor (VWF) in the pathophysiology of sickle cell disease is unclear. We assessed markers of VWF during admission for vaso-occlusive crisis (VOC) and steady state. VWF reactivity was higher during VOC and was associated with inflammation and neutrophil activation. Hyper-adhesive VWF may promote VOC in sickle cell disease. SUMMARY: Background Endothelial activation plays a central role in the pathophysiology of vaso-occlusion in sickle cell disease (SCD), facilitating adhesive interactions with circulating blood cells. Upon activation, various adhesive molecules are expressed, including von Willebrand factor (VWF). Increased VWF levels have been observed in patients with SCD during steady state. However, the role of VWF in the pathogenesis of SCD vaso-occlusion is unclear. Objectives To longitudinally assess the quantity and reactivity of VWF and its regulating protease ADAMTS-13 during vaso-occlusive crisis (VOC). Methods In this observational study, we obtained sequential blood samples in adult SCD patients during VOC. Results VWF reactivity was significantly higher during VOC (active VWF, VWF glycoprotein Ib-binding activity, and high molecular weight multimers), whereas platelet count and levels of ADAMTS-13 antigen and ADAMTS-13 activity were concomitantly lower than during steady state. Levels of VWF antigen, VWF propeptide (VWF:pp) and ADAMTS-13 specific activity did not change during VOC. VWF reactivity correlated strongly with markers of inflammation and neutrophil activation, and was inversely correlated with the platelet count. In patients who developed acute chest syndrome, levels of VWF, VWF:pp and active, hyperadhesive VWF were significantly higher, whereas ADAMTS-13 activity was lower, than in patients without this complication. Conclusions We provide the first evidence that VOC in SCD is associated with increased reactivity of VWF, without a pronounced ADAMTS-13 deficiency. This hyper-reactivity may be explained by resistance of VWF to proteolysis, secondary to processes such as inflammation and oxidative stress. Hyperadhesive VWF, scavenging blood cells in the microcirculation, may thereby amplify and sustain VOC in SCD.

Neutrophil activation and nucleosomes as markers of systemic inflammation in paroxysmal nocturnal hemoglobinuria: effects of eculizumab.

BACKGROUND: Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by complement-mediated hemolysis and a high risk of life-threatening venous and arterial thrombosis. Uncontrolled complement activation and the release of cell-free heme may result in systemic inflammation, neutrophil activation, and the release of procoagulant neutrophilic proteases. Eculizumab, an antibody to complement factor C5, inhibits hemolysis and reduces thrombotic risk. OBJECTIVES: To study neutrophil activation and nucleosome levels in relation to thrombosis in PNH patients before and during treatment with eculizumab. PATIENTS/METHODS: In 51 untreated PNH patients, including 20 patients before and after commencing eculizumab treatment, we have assessed neutrophil activation by measuring elastase-α1 -antitrypsin (EA) complexes and circulating nucleosomes, as established markers for systemic inflammation and cell death. RESULTS: Nucleosomes (median; range; 95% confidence interval [CI]), but not EA complexes, were higher in PNH patients with a history of thrombosis (16; 7-264; 0.3-94 U mL(-1) , n = 12) than in those without (6; 6-35; 7-11 U mL(-1) , n = 39) or controls (8; 6-23; 7-12 U mL(-1) , n = 17). EA complexes, but not nucleosomes, decreased promptly and markedly upon eculizumab treatment. EA complexes (estimated marginal means; 95% CI) remained low at ≥ 12 weeks (50; 34-67) compared with baseline (12; -6 to 29). CONCLUSIONS: The increased nucleosome levels in PNH patients with a history of thrombosis suggest systemic inflammation and/or cell death. Neutrophil activation markers did not differ between patients with and without a history of thrombosis and healthy controls. Interestingly, basal neutrophil activation in PNH patients significantly decreases on treatment with eculizumab, indicating that neutrophil activation is C5a driven.

Diabetes-independent increase of factor VII-activating protease activation in patients with Gram-negative sepsis (melioidosis).

BACKGROUND: The plasma protease factor VII-activating protease (FSAP) can release nucleosomes from late apoptotic cells. Nucleosomes are markers of cell death, and extracellular cell-free DNA has been suggested to play an important role in inflammation and has been demonstrated to correlate with severity and outcome in sepsis patients. OBJECTIVE: To investigate FSAP activation in patients suffering from Burkholderia pseudomallei infection (melioidosis), an important cause of Gram-negative sepsis in Southeast Asia. As diabetes mellitus (DM) is the most important risk factor for both melioidosis and sepsis, we were also able to examine the role of DM in FSAP activation in this cohort of patients. METHODS: In a prospective observational study, complexes of FSAP with α2 -antiplasmin (AP) were assayed in 44 patients with melioidosis, 34 of whom were classified as diabetic. Eighty-two healthy subjects served as controls (52 with DM and 30 without). RESULTS: FSAP-AP complex levels were markedly elevated in patients as compared with controls. The FSAP level increased by 16.82 AU mL(-1) in patients with melioidosis after adjustment for the effect of DM in the regression model. As expected, FSAP activation was correlated with nucleosome release (slope = 0.74). No difference in FSAP activation on admission was seen between survivors and non-survivors, but the extent of FSAP activation correlated with stage of the disease; repeated testing during convalescence showed a return towards normal values (day 0 vs. day 28, 4.16 AU mL(-1) , 95% confidence interval [CI] 1.42-12.22). CONCLUSION: Patients with Gram-negative sepsis caused by B. pseudomallei have abundant FSAP activation, which significantly correlates with stage of disease. The presence of DM, however, does not influence the extent of FSAP activation.

Biomarker profiling of steroid-resistant acute GVHD in patients after infusion of mesenchymal stromal cells.

We performed a prospective phase II study to evaluate clinical safety and outcome in 48 patients with steroid-refractory grade II-IV acute graft-versus-host disease (aGVHD) treated with mesenchymal stromal cells (MSCs). Clinical outcomes were correlated to comprehensive analyses of soluble and cellular biomarkers. Complete resolution (CR) of aGVHD at day 28 (CR-28) occurred in 12 (25%) patients, CR lasting >1 month (CR-B) occurred in 24 (50%) patients. One-year overall survival was significantly improved in CR-28 (75 versus 33%, P=0.020) and CR-B (79 versus 8%, P<0.001) versus non-CR patients. A six soluble biomarker-panel was predictive for mortality (HR 2.924; CI 1.485-5.758) when measured before MSC-administration. Suppression of tumorigenicity 2 (ST2) was only predictive for mortality 2 weeks after but not before MSC-administration (HR 2.389; CI 1.144-4.989). In addition, an increase in immature myeloid dendritic cells associated with decreased mortality (HR 0.554, CI 0.389-0.790). Patients had persisting T-cell responses against defined virus- and leukemia-associated antigens. In conclusion, our data emphasize the need to carefully assess biomarkers in cohorts with homogeneous GVHD treatments. Biomarkers might become an additional valuable component of composite end points for the rapid and efficient testing of novel compounds to decrease lifecycle of clinical testing and improve the success rate of phase II/III trials.

Reevaluation of the incidence of thromboembolic complications in congenital factor XII deficiency--a study on 73 subjects from 14 Swiss families.

To further elucidate the debated role of hereditary FXII deficiency as a thrombophilic risk factor this follow-up study on 65 subjects out of 12 Swiss families was undertaken (follow-up: 6 yrs). Fifteen severely FXII deficient subjects (FXII:C < 1%), 35 partially FXII deficient subjects (FXII:C > or = 1-59%), 10 with normal FXII values (FXII:C > or = 70%), and 5 non-classifiable subjects (FXII:C > or = 60-69%) were reevaluated. Eight subjects (4 severely and 3 partially FXII deficient, 1 non-classifiable) were newly enrolled. Four instances of deep vein thrombosis, one superficial vein thrombosis and one myocardial infarction were noted in 2 out of 19 severely FXII deficient subjects during a total life-time period of 866.6 patient-years. In 38 partially FXII deficient subjects (1862.8 patient-years) one ischemic cerebrovascular stroke and one superficial vein thrombosis were recorded in 2 individuals. The 10 subjects with normal FXII values (498.2 patient-years) remained thrombosis-free. One superficial vein thrombosis occurred in an unclassifiable woman. None of the 3 different FXII gene defects revealed in our patients was specifically associated with thromboembolic complications. Kaplan-Meier analysis of thrombosis-free survival suggests that hereditary partial (and probably severe) FXII deficiency does not constitute a thrombophilic condition.

Disseminated intravascular coagulation in meningococcal sepsis. Case 7.

We report on a man (age: 49 years), who died from severe meningococcal sepsis with disseminated intravascular coagulation (DIC), multiple organ dysfunction syndrome and extended skin necrosis. We discuss in detail the pathophysiology of the activation of coagulation and fibrinolysis during sepsis. The article discusses new therapeutic concepts in the treatment of disseminated intravascular coagulation in meningococcal sepsis, too.

[Derailed oral anticoagulation with very high INR values and poor response to oral vitamin K--cholestasis as a possible cause]. / Entgleiste orale Antikoagulation mit sehr hohen INR-Werten und schlechtem Ansprechen auf perorales Vitamin K--Cholestase als mögliche Ursache.

A 76-year-old man under long term oral anticoagulant treatment showed unclottable prothrombin time (PT) without overt bleeding. After oral administration of vitamin K1, PT remained severely prolonged and the patient was hospitalized. INR was 8.0 and responded to parenteral vitamin K. Cholestasis resulting in poor intestinal vitamin K resorption was assumed to have caused "overanticoagulation". Quick test is a global clotting test for the extrinsic and common pathways of the coagulation system. Increased PT, i.e. decreased Quick percentage, may be due to different conditions and should--if unexplained--be further analyzed by assaying factors II, V, VII, X and fibrinogen. Preanalytical problems, plasma dilution with clotting factor-free volume replacement, decreased vitamin K-dependent clotting factors (oral anticoagulation, intoxication with certain rodenticides, vitamin K deficiency), impaired liver synthetic capacity, disseminated intravascular coagulation, or massive heparin contamination may cause prolonged PT. Newborns physiologically have longer PT and should receive vitamin K prophylaxis.

[Isolated increased aPTT with anamnestic hemorrhagic diathesis--severe FXI deficiency]. / Isoliert verlängerte aPTT mit anamnestischer hämorrhagischer Diathese--Schwerer FXI-Mangel.

A 47-year-old patient with several episodes of bleeding after tonsillectomy, after an excision of a sacral dermoid and after urinary tract surgery presented with a mechanical ileus and was admitted to the department of visceral surgery. Preoperative analysis revealed a prolonged activated partial thromboplastin time (aPTT) of 93 seconds (normal range: 40-60 seconds), whereas the prothrombin time and thrombin time were normal. A mixture of 1 volume patient plasma and 1 volume normal plasma gave a normal aPTT, both before and after incubation of the plasma mixture at 37 degrees C for 1 hour. The patient's history and the prolonged aPTT as the only abnormal clotting test indicated deficiency of either factor VIII, factor IX, factor XI or von Willebrand factor with consecutively diminished factor VIII. Laboratory analysis revealed a factor XI of 4% indicating severe factor XI deficiency. Laparotomy was successfully performed without any hemorrhagic complications under fresh frozen plasma substitution.

[A patient with isolated prolongation of aPTT without hemorrhagic diathesis anamnesis: severe, hereditary factor XII deficiency]. / Eine Patientin mit isolierter Verlängerung der aPTT ohne Anamnese einer hämorrhagischen Diathese: schwerer hereditärer Faktor XII-Mangel.

By virtue of a severely prolonged aPTT with a normal thromboplastin time (prothrombin time) and a normal thrombin time, severe FXII deficiency has been diagnosed in a woman without a bleeding diathesis or a history of thromboembolic complications. A deficiency of a factor of the contact activation system (FXII, prekallikrein, high molecular weight kininogen) is usually diagnosed during routine coagulation tests demonstrating a prolonged aPTT. The severe and partial deficiency of FXII, of prekallikrein or high molecular weight kininogen is not associated with a bleeding tendency. In contrast, severely factor XI deficient subjects may suffer from a mild hemorrhagic diathesis, whereas FVIII deficiency (hemophilia A, autoimmune "hemophilia", von Willebrand disease) and FIX deficiency (hemophilia B) are associated with a bleeding tendency of varying severity, depending on the clotting activity of FVIII or FIX, respectively. An isolated prolongation of the aPTT due to a lupus anticoagulant, however, is frequently associated with arterial and/or venous thrombosis. Therefore, in case of a prolongation of the aPTT, its cause has to be determined.

Plasma-derived human C1-esterase inhibitor does not prevent mechanical ventilation-induced pulmonary complement activation in a rat model of Streptococcus pneumoniae pneumonia.

Mechanical ventilation has the potential to cause lung injury, and the role of complement activation herein is uncertain. We hypothesized that inhibition of the complement cascade by administration of plasma-derived human C1-esterase inhibitor (C1-INH) prevents ventilation-induced pulmonary complement activation, and as such attenuates lung inflammation and lung injury in a rat model of Streptococcus pneumoniae pneumonia. Forty hours after intratracheal challenge with S. pneumoniae causing pneumonia rats were subjected to ventilation with lower tidal volumes and positive end-expiratory pressure (PEEP) or high tidal volumes without PEEP, after an intravenous bolus of C1-INH (200 U/kg) or placebo (saline). After 4 h of ventilation blood, broncho-alveolar lavage fluid and lung tissue were collected. Non-ventilated rats with S. pneumoniae pneumonia served as controls. While ventilation with lower tidal volumes and PEEP slightly amplified pneumonia-induced complement activation in the lungs, ventilation with higher tidal volumes without PEEP augmented local complement activation more strongly. Systemic pre-treatment with C1-INH, however, failed to alter ventilation-induced complement activation with both ventilation strategies. In accordance, lung inflammation and lung injury were not affected by pre-treatment with C1-INH, neither in rats ventilated with lower tidal volumes and PEEP, nor rats ventilated with high tidal volumes without PEEP. Ventilation augments pulmonary complement activation in a rat model of S. pneumoniae pneumonia. Systemic administration of C1-INH, however, does not attenuate ventilation-induced complement activation, lung inflammation, and lung injury.

Endogenous protein C has a protective role during Gram-negative pneumosepsis (melioidosis).

BACKGROUND: Activated protein C (APC) exerts anticoagulant effects via inactivation of factors Va and VIIIa and cytoprotective effects via protease activated receptor (PAR)1. Inhibition of endogenous APC in endotoxemia and sepsis results in exacerbation of coagulation and inflammation, with consequent enhanced lethality. OBJECTIVES: We here sought to dissect the distinct roles of the anticoagulant and cytoprotective functions of endogenous APC in severe Gram-negative pneumonia-derived sepsis (melioidosis). METHODS: We infected wild-type (WT) mice with Burkholderia pseudomallei, a common sepsis pathogen in southeast Asia, and treated them with antibodies inhibiting both the anticoagulant and cytoprotective functions of APC (MPC1609) or the anticoagulant functions of APC (MAPC1591) only. Additionally, we administered SEW2871 (stimulating the S1P1-pathway downstream from PAR1) to control and MPC1609-treated mice. RESULTS: MPC1609, but not MAPC1591, significantly worsened survival, increased coagulation activation, facilitated bacterial growth and dissemination and enhanced the inflammatory response. The effects of MPC1609 could not be reversed by SEW2871, suggesting that S1P1 does not play a major role in this model. CONCLUSIONS: These results suggest that the mere inhibition of the anticoagulant function of APC does not interfere with its protective role during Gram-negative pneumosepsis, suggesting a more prominent role for cytoprotective effects of APC .