Plasminogen activator inhibitor 2 and urokinase-type plasminogen activator in plasma and leucocytes in patients with severe sepsis

Fungi Fibrinolytic Compound 1 Plays a Core Role in Modulating Fibrinolysis, Altering Plasma Clot Structure, and Promoting Susceptibility to Lysis

Fibrin clot structure and function are major determinants of venous and arterial thromboembolic diseases, as well as the key determinants of the efficiency of clot lysis. Studies have revealed that fungi fibrinolytic compound 1 (FGFC1) is a novel marine pyranisoindolone natural product with fibrinolytic activity. Here, we explore the impacts of FGFC1 on clot structure, lysis, and plasminogen activation in vitro using turbidimetric, enzyme-linked immunosorbent assay, confocal and electron microscopy, urokinase, or plasmin chromogenic substrate. Clots formed in the presence of FGFC1 expressed reduced fibrin polymerization rate and maximum turbidity; however, they did not influence the lag phase of fibrin polymerization. In the absence of scu-PA (single-chain urokinase plasminogen activator), microscopy revealed that FGFC1 increased the number of protofibrils within fibrin fiber and the pore diameter between protofibrils, inducing clots to form a region of thinner and looser networks separated by large pores. The effects of FGFC1 on scu-PA-mediated plasma clot structure were similar to those in the absence of scu-PA. In addition, FGFC1 promoted the lysis of clots and increased the D-dimer concentration in lysate. FGFC1 increased the generation rate of p-nitroaniline in plasma. These results show that FGFC1 has fibrinolytic activity in plasma, leading to interference with the release of fibrinopeptide B to affect lateral aggregation of protofibrils and increase clot susceptibility to fibrinolysis by altering its structure.

Extreme obesity is a strong predictor for in-hospital mortality and the prevalence of long-COVID in severe COVID-19 patients with acute respiratory distress syndrome

Acute Respiratory Distress Syndrome (ARDS) is common in COVID-19 patients and is associated with high mortality. The aim of this observational study was to describe patients' characteristics and outcome, identifying potential risk factors for in-hospital mortality and for developing Long-COVID symptoms. This retrospective study included all patients with COVID-19 associated ARDS (cARDS) in the period from March 2020 to March 2021 who were invasively ventilated at the intensive care unit (ICU) of the University Hospital Dresden, Germany. Between October 2021 and December 2021 patients discharged alive (at minimum 6 months after hospital discharge-midterm survival) were contacted and interviewed about persistent symptoms possibly associated with COVID-19 as well as the quality of their lives using the EQ-5D-5L-questionnaire. Long-COVID was defined as the occurrence of one of the symptoms at least 6 months after discharge. Risk factors for mortality were assessed with Cox regression models and risk factors for developing Long-COVID symptoms by using relative risk (RR) regression. 184 Patients were included in this study (male: n = 134 (73%), median age 67 (range 25-92). All patients were diagnosed with ARDS according to the Berlin Definition. 89% of patients (n = 164) had severe ARDS (Horovitz-index < 100 mmHg). In 27% (n = 49) extracorporeal membrane oxygenation was necessary to maintain gas exchange. The median length of in-hospital stay was 19 days (range 1-60). ICU mortality was 51%, hospital mortality 59%. Midterm survival (median 11 months) was 83% (n = 55) and 78% (n = 43) of these patients presented Long-COVID symptoms with fatigue as the most common symptom (70%). Extreme obesity (BMI > 40 kg/m²) was the strongest predictor for in-hospital mortality (hazard ratio: 3.147, confidence interval 1.000-9.897) and for developing Long-COVID symptoms (RR 1.61, confidence interval 1.26-2.06). In-hospital mortality in severe cARDS patients was high, but > 80% of patients discharged alive survived the midterm observation period. Nonetheless, most patients developed Long-COVID symptoms. Extreme obesity with BMI > 40 kg/m² was identified as independent risk factor for in-hospital mortality and for developing Long-COVID symptoms.Trial registration DRKS-ID DRKS00027856.

The role of plasminogen activator inhibitor-2 in pneumococcal meningitis

Pneumococcal meningitis is associated with dysregulation of the coagulation cascade. Previously, we detected upregulation of cerebral plasminogen activator inhibitor-2 (PAI-2) mRNA expression during pneumococcal meningitis. Diverse functions have been ascribed to PAI-2, but its role remains unclear. We analyzed the function of SERPINB2 (coding for PAI-2) in patients with bacterial meningitis, in a well-established pneumococcal meningitis mouse model, using Serpinb2 knockout mice, and in vitro in wt and PAI-2-deficient bone marrow-derived macrophages (BMDMs). We measured PAI-2 in cerebrospinal fluid of patients, and performed functional, histopathological, protein and mRNA expression analyses in vivo and in vitro. We found a substantial increase of PAI-2 concentration in CSF of patients with pneumococcal meningitis, and up-regulation and increased release of PAI-2 in mice. PAI-2 deficiency was associated with increased mortality in murine pneumococcal meningitis and cerebral hemorrhages. Serpinb2−/− mice exhibited increased C5a levels, but decreased IL-10 levels in the brain during pneumococcal infection. Our in vitro experiments confirmed increased expression and release of PAI-2 by wt BMDM and decreased IL-10 liberation by PAI-2-deficient BMDM upon pneumococcal challenge. Our data show that PAI-2 is elevated during in pneumococcal meningitis in humans and mice. PAI-2 deficiency causes an inflammatory imbalance, resulting in increased brain pathology and mortality.

Predictive ability of viscoelastic testing using ClotPro® for short-term outcome in patients with severe Covid-19 ARDS with or without ECMO therapy: a retrospective study

BACKGROUND

SARS-CoV-2 infections are suspected to trigger the coagulation system through various pathways leading to a high incidence of thromboembolic complications, hypercoagulation and impaired fibrinolytic capacity were previously identified as potentially mechanisms. A reliable diagnostic tool for detecting both is still under discussion. This retrospective study is aimed to examine the prognostic relevance of early viscoelastic testing compared to conventional laboratory tests in COVID-19 patients with acute respiratory distress syndrome (ARDS).

METHODS

All mechanically ventilated patients with COVID-19 related ARDS treated in our intensive care unit (ICU) between January and March 2021 were included in this study. Viscoelastic testing (VET) was performed using the ClotPro® system after admission to our ICU. Prevalence of thromboembolic events was observed by standardized screening for venous and pulmonary thromboembolism using complete compression ultrasound and thoracic computed tomography pulmonary angiography at ICU admission, respectively. We examined associations between the severity of ARDS at admission to our ICU, in-hospital mortality and the incidence of thromboembolic events comparing conventional laboratory analysis and VET. ECMO related coagulopathy was investigated in a subgroup analysis. The data were analyzed using the Mann-Whitney U test.

RESULTS

Of 55 patients enrolled in this study, 22 patients required treatment with ECMO. Thromboembolic complications occurred in 51% of all patients. Overall hospital mortality was 55%. In patients with thromboembolic complications, signs of reduced fibrinolytic capacity could be detected in the TPA assay with prolonged lysis time, median 460 s (IQR 350-560) vs 359 s (IQR 287-521, p = 0.073). Patients with moderate to severe ARDS at admission to our ICU showed increased maximum clot firmness as a sign of hypercoagulation in the EX-test (70 vs 67 mm, p < 0.05), FIB-test (35 vs 24 mm, p < 0.05) and TPA-test (52 vs 36 mm, p < 0.05) as well as higher values of inflammatory markers (CRP, PCT and IL6). ECMO patients suffered more frequently from bleeding complications (32% vs 15%).

CONCLUSION

Although, the predictive value for thromboembolic complications or mortality seems limited, point-of-care viscoelastic coagulation testing might be useful in detecting hypercoagulable states and impaired fibrinolysis in critically ill COVID-19 ARDS patients and could be helpful in identifying patients with a potentially very severe course of the disease.

Clotting Dysfunction in Sepsis: A Role for ROS and Potential for Therapeutic Intervention

Sepsis is regarded as one of the main causes of death among the critically ill. Pathogen infection results in a host-mediated pro-inflammatory response to fight infection; as part of this response, significant endogenous reactive oxygen (ROS) and nitrogen species (RNS) production occurs, instigated by a variety of sources, including activated inflammatory cells, such as neutrophils, platelets, and cells from the vascular endothelium. Inflammation can become an inappropriate self-sustaining and expansive process, resulting in sepsis. Patients with sepsis often exhibit loss of aspects of normal vascular homeostatic control, resulting in abnormal coagulation events and the development of disseminated intravascular coagulation. Diagnosis and treatment of sepsis remain a significant challenge for healthcare providers globally. Targeting the drivers of excessive oxidative/nitrosative stress using antioxidant treatments might be a therapeutic option. This review focuses on the association between excessive oxidative/nitrosative stress, a common feature in sepsis, and loss of homeostatic control at the level of the vasculature. The literature relating to potential antioxidants is also described.

Fibrinogen and Antifibrinolytic Proteins: Interactions and Future Therapeutics

Thrombus formation remains a major cause of morbidity and mortality worldwide. Current antiplatelet and anticoagulant therapies have been effective at reducing vascular events, but at the expense of increased bleeding risk. Targeting proteins that interact with fibrinogen and which are involved in hypofibrinolysis represents a more specific approach for the development of effective and safe therapeutic agents. The antifibrinolytic proteins alpha-2 antiplasmin (α2AP), thrombin activatable fibrinolysis inhibitor (TAFI), complement C3 and plasminogen activator inhibitor-2 (PAI-2), can be incorporated into the fibrin clot by FXIIIa and affect fibrinolysis by different mechanisms. Therefore, these antifibrinolytic proteins are attractive targets for the development of novel therapeutics, both for the modulation of thrombosis risk, but also for potentially improving clot instability in bleeding disorders. This review summarises the main properties of fibrinogen-bound antifibrinolytic proteins, their effect on clot lysis and association with thrombotic or bleeding conditions. The role of these proteins in therapeutic strategies targeting the fibrinolytic system for thrombotic diseases or bleeding disorders is also discussed.

Fibrinolytic Alterations in Sepsis: Biomarkers and Future Treatment Targets

Sepsis is a life-threatening condition which develops as a dysregulated immune response in the face of infection and which is associated with profound hemostatic disturbances and in the most extreme cases disseminated intravascular coagulation (DIC). In addition, the fibrinolytic system is subject to alterations during infection and sepsis, and impaired fibrinolysis is currently considered a key player in sepsis-related microthrombus formation and DIC. However, we still lack reliable biomarkers to assess fibrinolysis in the clinical setting. Furthermore, drugs targeting the fibrinolytic system have potential value in sepsis patients with severe fibrinolytic disturbances, but these are still being tested in the preclinical stage. The present review provides an overview of key fibrinolytic changes in sepsis, reviews the current literature on potential laboratory markers of altered fibrinolysis in adult sepsis patients, and discusses future perspectives for diagnosis and treatment of fibrinolytic disturbances in sepsis patients.

Covid-19-Associated Coagulopathy: Biomarkers of Thrombin Generation and Fibrinolysis Leading the Outcome

Background: Coronavirus Disease 2019 (COVID-19)-associated coagulopathy is characterized by a prothrombotic state not yet comprehensively studied. We investigated the coagulation pattern of patients with COVID-19 acute respiratory distress syndrome (ARDS), comparing patients who survived to those who did not. Methods: In this prospective cohort study on 20 COVID-19 ARDS patients, the following biomarkers were measured: thrombin generation (prothrombin fragment 1 + 2 (PF 1 + 2)), fibrinolysis activation (tissue plasminogen activator (tPA)) and inhibition (plasminogen activator inhibitor 2 (PAI-2)), fibrin synthesis (fibrinopeptide A) and fibrinolysis magnitude (plasmin–antiplasmin complex (PAP) and D-dimers). Measurements were done upon intensive care unit (ICU) admission and after 10–14 days. Results: There was increased thrombin generation; modest or null release of t-PA; and increased levels of PAI-2, fibrinopeptide A, PAP and D-dimers. At baseline, nonsurvivors had a significantly (p = 0.014) higher PAI-2/PAP ratio than survivors (109, interquartile range (IQR) 18.1–216, vs. 8.7, IQR 2.9–12.6). At follow-up, thrombin generation was significantly (p = 0.025) reduced in survivors (PF 1 + 2 from 396 pg/mL, IQR 185–585 to 237 pg/mL, IQR 120–393), whereas it increased in nonsurvivors. Fibrinolysis inhibition at follow-up remained stable in survivors and increased in nonsurvivors, leading to a significant (p = 0.026) difference in PAI-2 levels (161 pg/mL, IQR 50–334, vs. 1088 pg/mL, IQR 177–1565). Conclusion: Severe patterns of COVID-19 ARDS are characterized by a thrombin burst and the consequent coagulation activation. Mechanisms of fibrinolysis regulation appear unbalanced toward fibrinolysis inhibition. This pattern ameliorates in survivors, whereas it worsens in nonsurvivors.

Clinical significance of measuring plasminogen activator inhibitor-1 in sepsis

Background

Disseminated thrombotic process in the microcirculation is considered to be an important cause of multiple organ dysfunction in sepsis. The fundamental purpose of this prothrombotic change was believed to be in the host defense against microbial dissemination. In that process, antifibrinolytic property plays an important role.

Main body

For the understanding of pathophysiology of sepsis, it is quite useful to grasp the alterations in coagulation/fibrinolytic parameters, i.e., plasminogen activator and plasminogen activator inhibitor-1. They play crucial roles in the development of clot formation and disseminated intravascular coagulation that leads to fatal organ dysfunction. Basically, fibrinolysis is a simple system compared to the complex coagulation cascade. Plasmin is the only factor that regulates fibrinolysis, and this enzyme is modulated by several factors including plasminogen activators and plasminogen activator inhibitor-1. However, recent studies have elucidated the complex regulation of the production, activation, and inactivation of these fibrinolytic factors.

Conclusion

The dynamic change of the fibrinolytic system plays a crucial role in the pathophysiology of sepsis. In this commentary, we introduce the recent advances of the research regarding fibrinolytic system.

Plasminogen activator inhibitor-1 stimulates macrophage activation through Toll-like Receptor-4

While inflammation is often associated with increased Plasminogen Activator Inhibitor-1 (PAI-1), the functional consequences of PAI-1 in inflammation have yet to be fully determined. The aim of this study was to establish the in vivo relevance of PAI-1 in inflammation. A mouse model of systemic inflammation was employed in wild-type (WT) and PAI-1 deficient (PAI-1(-/-)) mice. Mice survival, macrophage infiltration into the lungs, and plasma levels of pro-inflammatory cytokines were assessed after lipopolysaccharide (LPS) infusion. In vitro experiments were conducted to examine changes in LPS-induced inflammatory responses after PAI-1 exposure. PAI-1 was shown to regulate inflammation, in vivo, and affect macrophage infiltration into lungs. Further, PAI-1 activated macrophages, and increased pro-inflammatory cytokines at both the mRNA and protein levels in these cells. The effect of PAI-1 on macrophage activation was dose-dependent and LPS-independent. Proteolytic inhibitory activity and Lipoprotein Receptor-related Protein (LRP) and vitronectin (VN) binding functions, were not involved in PAI-1-mediated activation of macrophages. However, the effect of PAI-1 on macrophage activation was partially blocked by a TLR4 neutralizing antibody. Furthermore, PAI-1-induced Tumor Necrosis Factor-alpha (TNF-α) and Macrophage Inflammatory Protein-2 (MIP-2) expression was reduced in TLR4(-/-) macrophages compared to WT macrophages. These results demonstrate that PAI-1 is involved in the regulation of host inflammatory responses through Toll-like Receptor-4 (TLR4)-mediated macrophage activation.

Neuromuscular Blocking Agent Cisatracurium Attenuates Lung Injury by Inhibition of Nicotinic Acetylcholine Receptor-α1

Background

Neuromuscular blocking agents (NMBAs) bind the nicotinic acetylcholine receptor α1 (nAChRα1) that also contributes to inflammatory signaling. Thus, the author hypothesized that the use of NMBA mitigates lung injury by improving ventilator synchrony and decreasing inflammatory responses.

Methods

Lung injury was induced by intratracheal instillation of hydrogen chloride in rats that were randomized to receive no NMBA with evidence of asynchronous ventilation (noNMBA/aSYNC, n = 10); no NMBA with synchronous ventilation (noNMBA/SYNC, n = 10); cisatracurium (CIS, n = 10); or pancuronium (PAN, n = 10). Mechanical ventilation was set at a tidal volume of 6 ml/kg and positive end-expiratory pressure 8 cm H2O for 3 h. Human lung epithelial, endothelial, and CD14+ cells were challenged with mechanical stretch, lipopolysaccharide, lung lavage fluids (bronchoalveolar lavage fluid), or plasma obtained from patients (n = 5) with acute respiratory distress syndrome, in the presence or absence of CIS or small-interfering RNA and small hairpin RNA to attenuate the cell expression of nAChRα1.

Results

The use of CIS and PAN improved respiratory compliance (7.2 ± 0.7 in noNMBA/aSYNC, 6.6 ± 0.5 in noNMBA/SYNC, 5.9 ± 0.3 in CIS, and 5.8 ± 0.4 cm H2O/l in PAN; P &lt; 0.05), increased Pao2 (140 ± 54, 209 ± 46, 269 ± 31, and 269 ± 54 mmHg, respectively, P &lt; 0.05), and decreased the plasma levels of tumor necrosis factor-α (509 ± 252 in noNMBA, 200 ± 74 in CIS, and 175 ± 84 pg/ml in PAN; P &lt; 0.05) and interleukin-6 (5789 ± 79, 1608 ± 534, and 2290 ± 315 pg/ml, respectively; P &lt; 0.05). The use of CIS and PAN or silencing the receptor nAChRα1 resulted in decreased cytokine release in the human cells in response to a variety of stimuli mentioned earlier.

Conclusions

The use of NMBA is lung protective through its antiinflammatory properties by blocking the nAChRα1.

Plasminogen Activator Inhibitor-2 Plays a Leading Prognostic Role among Protease Families in Non-Small Cell Lung Cancer

Background

In lung cancer, uPA, its receptor (uPAR), and the inhibitors PAI-1 and PAI-2 of the plasminogen activator family interact with MMP-2 and MMP-9 of the MMP family to promote cancer progression. However, it remains undetermined which of these markers plays the most important role and may be the most useful indicator to stratify the patients by risk.

Methods

We determined the individual prognostic value of these 6 markers by analyzing a derivation cohort with 98 non-small cell lung cancer patients by immunohistochemical staining. The correlation between the IHC expression levels of these markers and disease prognosis was investigated, and an immunohistochemical panel for prognostic prediction was subsequently generated through prognostic model analysis. The value of the immunohistochemical panel was then verified by a validation cohort with 91 lung cancer patients.

Results

In derivation cohort, PAI-2 is the most powerful prognostic factor (HR = 2.30; P = 0.001), followed by MMP-9 (HR = 2.09; P = 0.019) according to multivariate analysis. When combining PAI-2 and MMP-9, the most unfavorable prognostic group (low PAI-2 and high MMP-9 IHC expression levels) showed a 6.40-fold increased risk of a poor prognosis compared to the most favorable prognostic group (high PAI-2 and low MMP-9 IHC expression levels). PAI-2 and MMP-9 IHC panel could more precisely identify high risk patients in both derivation and validation cohort.

Conclusions

We revealed PAI-2 as the most powerful prognostic marker among PA and MMP protease family even after considering their close relationships with each other. By utilizing a combination of PAI-2 and MMP-9, more precise prognostic information than merely using pathological stage alone can be obtained for lung cancer patients.

Effect of ascorbate on fibrinolytic factors in septic mouse skeletal muscle

Plugging of the capillary bed in tissues correlates with organ failure during sepsis. In septic mouse skeletal muscle, we showed that blood in capillaries becomes hypercoagulable and that ascorbate injection inhibits capillary plugging. In the present study, we hypothesized that ascorbate promotes fibrinolysis, reversing this plugging. Sepsis in mice was induced by fecal injection into peritoneum. Mice were injected intravenously with a bolus of streptokinase (fibrinolytic agent) or ascorbate at 5-6 h. Both agents reversed capillary plugging in muscle at 7 h. Sepsis increased mRNA expression of urokinase plasminogen activator (u-PA) (profibrinolytic) and plasminogen activator inhibitor 1 (PAI-1) (antifibrinolytic) in muscle and liver homogenates at 7 h. Ascorbate did not affect u-PA mRNA in either tissue, but it inhibited PAI-1 mRNA in muscle, suggesting enhanced fibrinolysis in this tissue. However, ascorbate did not affect increased PAI-1 mRNA in the liver (dominant source of soluble PAI-1 in systemic blood). Consistently, ascorbate affected neither elevated PAI-1 protein/enzymatic activity in septic liver nor lowered plasmin antiplasmin level in septic blood. Furthermore, hypocoagulability of septic blood revealed by thrombelastography and thrombin-induced PAI-1 release from isolated platelets (ex-vivo model of sepsis) were not affected by ascorbate. Based on the PAI-1 protein data, the present study does not support the hypothesis that ascorbate promotes fibrinolysis in sepsis.

Host response biomarkers in the diagnosis of sepsis: a general overview

Critically ill patients who display a systemic inflammatory response syndrome (SIRS) are prone to develop nosocomial infections. The challenge remains to distinguish as early as possible among SIRS patients those who are developing sepsis. Following a sterile insult, damage-associated molecular patterns (DAMPs) released by damaged tissues and necrotic cells initiate an inflammatory response close to that observed during sepsis. During sepsis, pathogen-associated molecular patterns (PAMPs) trigger the release of host mediators involved in innate immunity and inflammation through identical receptors as DAMPs. In both clinical settings, a compensatory anti-inflammatory response syndrome (CARS) is concomitantly initiated. The exacerbated production of pro- or anti-inflammatory mediators allows their detection in biological fluids and particularly within the bloodstream. Some of these mediators can be used as biomarkers to decipher among the patients those who developed sepsis, and eventually they can be used as prognosis markers. In addition to plasma biomarkers, the analysis of some surface markers on circulating leukocytes or the study of mRNA and miRNA can be helpful. While there is no magic marker, a combination of few biomarkers might offer a high accuracy for diagnosis.

Prognostic significance of urokinase-type plasminogen activator and its receptor in patients with systemic inflammatory response syndrome

BACKGROUND

This study aimed to determine the plasma levels of urokinase-type plasminogen activator (uPA), urokinase-type plasminogen activator receptor (uPAR), D-dimer, IL-6 and TNF-α and observe the relations among uPA, uPAR, D-dimer, IL-6 and TNF-α in patients with systemic inflammatory response syndrome (SIRS).

METHODS

A prospective, clinical case-control study was conducted in patients with SIRS at age of more than 55 years old treated during 2008-2010 at Wuhan Central Hospital. Venous blood samples were collected by routine venipuncture. Eighty-five patients were divided into two groups according to diagnostic criteria of SIRS: SIRS patients from intensive care units (n=50), and non-SIRS patients from medical wards (n=35). Thirty healthy blood donors who visited the General Health Check-up Division at Wuhan Central Hospital served as controls. Excluded from the study were (1) those patients with pregnancy; (2) those with cancer; (3) those died after admission into the ICU in 7 days; (4) those received cardiopulmonary resuscitation; (5) those who had previous blood system diseases; and (6) those with SIRS before admission into the ICU. The levels of uPA, uPAR, D-D, IL-6 and TNF-α in blood were detected by commercial enzyme-linked immunosorbent assay (ELISA) kit. The data were analyzed using SPSS version 17.0 and expressed as mean ± standard. Student's t test and the Mann-Whitney U test were used in the analysis. The relations of uPA, uPAR and D-dimer, IL-6 TNF-α levels were analyzed using Spearman's rank-order correlation coefficient test.

RESULTS

The plasma levels of uPA, uPAR, D-dimer,IL-6 and TNF-α in the patients with SIRS were obviously higher than those in the non-SIRS patients and controls (P<0.001). Correlation analysis showed a positive correlation between uPAR and IL-6 levels (r=0.395, P=0.004) and between uPAR and TNF-α levels (r=0.606, P<0.001), but no correlation between uPAR and D-dimer levels (r=0.069, P=0.632). No correlation was observed between uPA, D-dimer, IL-6 and TNF-α levels (P>0.05). The establishment of ROC curve was based on the levels of uPAR, D-dimer, IL-6 and TNF-α in 24 hours for the diagnosis of multiple organ dysfunction syndrome (MODS), and the ROC areas under the curve were 0.76, 0.58, 0.86 and 0.83, respectively.

CONCLUSIONS

uPA and uPAR play a major role in patients with SIRS in the process of coagulation disorder, but the mechanism of SIRS is not the same. uPAR may play a central role in the development of SIRS to MODS.

Regulation of urokinase expression at the posttranscription level by lung epithelial cells

Urokinase-type plasminogen activator (uPA) is expressed by lung epithelial cells and regulates fibrin turnover and epithelial cell viability. PMA, LPS, and TNF-alpha, as well as uPA itself, induce uPA expression in lung epithelial cells. PMA, LPS, and TNF-alpha induce uPA expression through increased synthesis as well as stabilization of uPA mRNA, while uPA increases its own expression solely through uPA mRNA stabilization. The mechanism by which lung epithelial cells regulate uPA expression at the level of mRNA stability is unclear. To elucidate this process, we sought to characterize protein-uPA mRNA interactions that regulate uPA expression. Regulation of uPA at the level of mRNA stability involves the interaction of a ~40 kDa cytoplasmic-nuclear shuttling protein with a 66 nt uPA mRNA 3'UTR sequence. We purified the uPA mRNA 3'UTR binding protein and identified it as ribonucleotide reductase M2 (RRM2). We expressed recombinant RRM2 and confirmed its interaction with a specific 66 nt uPA 3'UTR sequence. Immunoprecipitation of cell lysates with anti-RRM2 antibody and RT-PCR for uPA mRNA confirmed that RRM2 binds to uPA mRNA. Treatment of Beas2B cells with uPA or LPS attenuated RRM2-endogenous uPA mRNA interactions, while overexpression of RRM2 inhibited uPA protein and mRNA expression through destabilization of uPA mRNA. LPS exposure of lung epithelial cells translocates RRM2 from the cytoplasm to the nucleus in a time-dependent manner, leading to stabilization of uPA mRNA. This newly recognized pathway could influence uPA expression and a broad range of uPA-dependent functions in lung epithelial cells in the context of lung inflammation and repair.

Glibenclamide reduces proinflammatory cytokines in an ex vivo model of human endotoxinaemia under hypoxaemic conditions

AIMS

In vivo application of the K(ATP)-channel blocker glibenclamide can reverse endotoxin-induced hypotension, vascular hyporeactivity and shock in experimental animals. The hypothesis of the present study is, that the drug effects might not only be based on direct inhibition of K(ATP)-channels of vascular smooth muscle cells, but might also reflect reduction of shock-induced excess proinflammatory cytokines and procoagulatory molecules produced in the blood monocytes.

MAIN METHODS

Human whole blood (normoxaemic or hypoxaemic) supplemented ex vivo with 100 ng/ml LPS was used to assess glibenclamide (3-100 μM) effects on IL-1 beta, IL-6, TNF-alpha, tissue factor, and plasminogen-activator-inhibitor-2 (PAI-2). Co-incubations with monocytes and erythrocytes and cytosolic calcium measurements were performed to reveal their purinergic intercellular interaction.

KEY FINDINGS

In heparinized blood, glibenclamide reduced LPS-induced release of IL-1 beta and TNF-alpha, tissue factor and PAI-2 mRNA in a concentration-dependent manner. When samples were subjected to strong hypoxemia using 95% N(2)/5% CO(2), these parameters became even more sensitive to the drug. No drug effect was observable in citrated blood or in isolated monocytes. IL-1 beta mRNA inhibition by glibenclamide appeared to be dependent on P2X7-receptor activation of monocytes by ATP-releasing erythrocytes during hypoxia. Cytosolic calcium values as well as the duration of calcium transients elicited by P2X7-receptor stimulation in isolated monocytes were strongly increased during hypoxia, both of which could be abolished by glibenclamide.

SIGNIFICANCE

We conclude that the anti-inflammatory effect of glibenclamide is mainly based on the reduction of calcium entry by drug-induced depolarization of hypoxic monocytes. Thus, glibenclamide possesses a potentially beneficial shock-specific anti-inflammatory action.

Plasma soluble vascular endothelial growth factor receptor-1 levels predict outcomes of pneumonia-related septic shock patients: a prospective observational study

INTRODUCTION

Despite recent advances in the management of septic shock, mortality rates are still unacceptably high. Early identification of the high-mortality risk group for early intervention remains an issue under exploration. Vascular endothelial growth factor (VEGF), soluble vascular endothelial growth factor receptor-1 (sVEGFR1) and urokinase plasminogen activator (uPA) have diverse effects in the pathogenesis of sepsis, which involve pro-inflammation, anti-inflammation, endothelial cell repair, and vascular permeability change. Their roles in predicting mortality and organ dysfunction remain to be clarified.

METHODS

Pneumonia-related septic shock patients from medical intensive care units were enrolled for this prospective observational study. We also included 20 patients with pneumonia without organ dysfunction for comparison. Plasma levels of VEGF and sVEGFR1 and uPA activity within 24 hours of shock onset were measured. We compared plasma levels of these biomarkers with APACHE II scores between subgroups of patients, and evaluated their predictive value for 28-day mortality and organ dysfunction.

RESULTS

A total of 101 patients, including 81 with pneumonia-related septic shock and 20 with pneumonia without organ dysfunction, were enrolled. Non-survivors of septic shock had significantly higher plasma sVEGFR1 levels (659.3 ± 1022.8 vs. 221.1 ± 268.9 pg/mL, respectively, P < 0.001) and uPA activity (47.2 ± 40.6 vs. 27.6 ± 17.2 units, respectively, P = 0.001) when compared with those of the survivors. Kaplan-Meier survival analysis demonstrated significantly higher mortality in patients with higher levels of sVEGFR1 (P < 0.001) and uPA activity (P = 0.031). In Cox regression analysis, plasma sVEGFR1 level was independently associated with, and best predicted, the 28-day mortality of septic shock (HR: 1.55, 95% CI: 1.05-2.30). Plasma sVEGFR1 level and uPA activity had good correlation with renal dysfunction, metabolic acidosis, and hematologic dysfunction; their levels significantly increased when the number of organ dysfunctions increased. In multivariate analysis, plasma sVEGFR1 level (HR: 2.82, 95% CI: 1.17-6.81) and uPA activity (HR: 2.75, 95% CI: 1.06-7.13) were independent predictors of the presence of concomitant multi-organ dysfunction. The predictive value of VEGF for mortality and organ dysfunction was limited in pneumonia-related septic shock patients.

CONCLUSIONS

High plasma sVEGFR1 level in the early stage of pneumonia-related septic shock independently predicted 28-day mortality and multi-organ dysfunction.

Urokinase-type plasminogen activator inhibits efferocytosis of neutrophils

RATIONALE

Phagocytosis of apoptotic cells, also called efferocytosis, plays an essential role in the resolution of inflammation. Urokinase-type plasminogen activator (uPA) is a multifunctional protein that has been implicated in inflammatory conditions, including pneumonia and severe infection, which are often accompanied by the development of acute lung injury. However, the role of uPA in modulating efferocytosis of apoptotic neutrophils has not been defined.

OBJECTIVES

To characterize the role of uPA in regulation of efferocytosis and to delineate the underlying mechanisms involved in this process.

METHODS

In vitro and in vivo phagocytosis, immunoprecipitation, and Western blotting assays.

MEASUREMENTS AND MAIN RESULTS

The phagocytosis of apoptotic neutrophils by macrophages was significantly inhibited by uPA. Mutant uPA lacking the growth factor domain and catalytically inactive uPA had similar inhibitory effects on efferocytosis, as did wild-type uPA. In contrast, absence of the kringle domain abrogated the ability of uPA to diminish efferocytosis. Both the α(V)β₃ integrin and vitronectin seemed to be involved in the inhibition of efferocytosis by uPA. Incubation of macrophages with uPA also diminished activation of the small GTPase Rac-1, which normally occurs during ingestion of apoptotic neutrophils. Under in vivo conditions in the lungs, uPA decreased the uptake of apoptotic neutrophils by alveolar macrophages.

CONCLUSIONS

Our data demonstrate a novel role for uPA in which it is able to diminish the uptake of apoptotic neutrophils by macrophages under both in vitro and in vivo conditions.

The protein C pathway and pathologic processes

Alterations in expression of protein C (PC) pathway components have been identified in patients with active inflammatory disease states. While the PC pathway plays a pivotal role in regulating coagulation and fibrinolysis, activated PC (aPC) also exhibits cytoprotective properties. For example, PC-deficient mice challenged in septic/endotoxemic models exhibit phenotypes that include hypotension, disseminated intravascular coagulation, elevated inflammatory mediators, neutrophil adhesion to the microvascular endothelium, and loss of protective endothelial and epithelial cell barriers. Further, inflammatory bowel disease has been correlated with diminished endothelial PC receptor and thrombomodulin levels in the intestinal mucosa. Downregulated expression of the cofactor, protein S, as well as PC, is also associated with ischemic stroke. Studies to elucidate further the structural elements that differentiate the various functions of PC will serve to identify novel therapeutic approaches toward regulating these and other diseases.

[Influence of fibrinolitic potential reduction in ischemic brain disease development]

INTRODUCTION

Vascular brain disease are the third leading cause of morbidity and mortality today. Among them ischemic brain disease caused mostly by cerebral atherosclerosis makes almost 80%. The main risk factors for this disease are arterial hypertension, dislipoproteinemia and diabetes but, recently hemostatic system disorders have also been underlined, especially fibrinolytic disorders. PHYSIOLOGY OFFIBRINOLYSIS: The primary role of fibrinolytic system is to make blood vessels passable by prevention of thromb forming or by removing the existing ones. This role is enabled by constant dynamic balance between activators and inhibitors of fibrinolysis. The leading activators are tissue plasminogen activator (t-PA) and urokinase plasminogen activator (u-PA) and the most important inhibitors are 2-antiplasmin, plasminogen activator inhibitor 1 (PAI-1) and thrombin activated fibrinolytic inhibitor (TAFI).

FIBRINOLYSIS AND THROMBOSIS

In patients with atherosclerosis there is clear insufficiency of fibrinolysis caused mainly by the increased activity of fibrinolytic inhibitors. There is evidence that the level of PAI-1 connected to fibrin directly affects thromb resistance to fibrinolysis and that velocity of thromb lysis in vitro predominantly depends on TAFI concentration. Factor XIII also has influence on thromb structure and stability and Lp(a) lipoprotein is one more factor that is responsible for resistence of thromb to fibrinolysis.

FIBRINOLYSIS IN ISCHEMIC BRAIN DISEASE

Reduced fibrinolytic capacity is noticed in patients with ischemic brain disease resulting from the increased PAI-1 activity. Higher risk for ischemic brain disease is veryfied among people with 4G/4G PAI-1 genotype. Raised level of t-PA anti-gene can also induce reduction of endogenous fibrinolysis.

CONCLUSION

In conclusion we want to underline that a possible pathophysiological significance of fibrinolytic system is assumed in a high percentage of patients with ischemic brain disease. Because of that we need further investigations to establish precise role of fibrinolytic mechanisms in genesis of this disease.

Sepsis

Sepsis is a clinical syndrome defined by a systemic response to infection. With progression to sepsis-associated organ failure (ie, severe sepsis) or hypotension (ie, septic shock) mortality increases. Sepsis is a cause of considerable mortality, morbidity, cost, and health care utilization. Abnormalities in the inflammation, immune, coagulation, oxygen delivery, and utilization pathways play a role in organ dysfunction and death. Early identification of septic patients allows for evidence-based interventions, such as prompt antibiotics, goal-directed resuscitation, and activated protein C. Appropriate care for sepsis may be more easily delivered by dividing this clinical entity into various stages and with changes in structures of delivery that extend across traditional boundaries. Better description of the molecular basis of the disease process also will allow for more targeted therapies.

Inhibition of urokinase plasminogen activator with a novel enzyme inhibitor, WXC-340, ameliorates endotoxin and surgery-accelerated growth of murine metastases

The urokinase plasminogen activator (u-PA) is intimately associated with tumour invasion and metastases. Surgery facilitates accelerated metastatic tumour growth in murine models, a phenomenon related to elevated perioperative bacterial lipopolysaccaride (LPS) and inflammatory cytokine levels. The objectives of the study were to examine the role of u-PA in cytokine-enhanced tumour cell invasion in vitro and surgery-induced accelerated metastatic tumour growth in vivo and to assess the potential benefit of a novel selective u-PA inhibitor WXC-340 in this setting. CT-26 murine colorectal carcinoma cells were stimulated with LPS, tumour necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6). Cell supernatant u-PA expression and activity were determined using a colorimetric assay and Western blot analysis, respectively. Baseline and cytokine-stimulated in vitro invasion were assessed using ECmatrix invasion chambers. Two established murine models of accelerated metastatic tumour growth were used to investigate the consequences of u-PA inhibition on postoperative metastatic tumour burden. The effect of u-PA inhibition in vitro and in vivo was examined using the novel selective u-PA inhibitor, WXC-340. Proinflammatory cytokine stimulation significantly enhanced in vitro u-PA expression, activity and extracellular matrix invasion by approximately 50% compared to controls (P<0.05). This was abrogated by WXC-340. In vivo WXC-340 almost completely ameliorated both LPS- and surgery-induced, metastatic tumour growth compared to controls (P>0.05). In conclusion, u-PA cascade is actively involved in cytokine-mediated enhanced tumour cell invasion and LPS and surgery-induced metastatic tumour growth. Perioperative u-PA inhibition with WXC-340 may represent a novel therapeutic paradigm.

Lipoprotein (a): A link between thrombogenesis and atherogenesis

Introduction It is well known that numerous mechanisms of thrombogenesis can participate in every stage of atherosclerotic disease. The discovery of Lp(a) lipoprotein and its structural similarity with plasminogen suggests another pathogenic link between atherogenesis and thrombogenesis. Some characteristics of Lp(a) lipoprotein This lipoprotein is present in the whole human population in a wide range of plasma concentrations. It has numerous different isoforms. Its synthesis occurs in the liver, but it is practically metabolically independent from other lipoproteins. Today, Lp(a) lipoprotein is considered to be an independent risk factor for heart and brain ischemic disease. Fibrinolytic mechanisms The primary role of the fibrinolytic mechanism is to prevent thrombus formation during circulation and to remove already formed ones. Plasmin has a central role in this process, due to the inactive proenzyme plasminogen. Its basic activators are tissue-type plasminogen activator (t-PA) and urokinase plasminogen activator (u-PA). The most important inhibitors of plasminogen are alpha2-antiplasmin and plasminogen activator inhibitors 1 and 2 (PAI-1 and PAI-2). Structural similarity of Lp(a) and plasminogen The apo(a) and plasminogen genes are very closely linked on the long arm of chromosome 6. Because of that they are structuraly very similar and they have a cross immunological reactivity. Their common elements are so-called "kringle" structures. The key difference in structure of Lp(a) and plasminogen is replacement of Arg with Ser at position 560. This prevents splitting of apo(a) by plasminogen activators. Lp(a) and fibrinolysis Lp(a) lipoprotein inhibits activation of plasminogen by streptokinase. It is also a competitive inhibitor of plasminogen for its binding to plasminogen receptors. Furthermore, it successfully achieves competitive inhibition of plasminogen for binding to tetranectin and thrombospondin. Also, Lp(a) inhibits activation of transforming growth factor alpha (TGF-alpha). It positively correlates with PAI-1 and it is assumed that it promotes release of tissue factor pathway inhibitor (TFPI) from endothelial cell surfaces. Conclusion In regulation of the hemostatic system via apolipoprotein(a) antifibrinolytic effects, Lp(a) lipoprotein offers a molecular solution to the link between thrombogenesis and atherogenesis.

A protein C deficiency exacerbates inflammatory and hypotensive responses in mice during polymicrobial sepsis in a cecal ligation and puncture model

During the systemic inflammatory state induced by sepsis, the potential for coagulopathy exists because of up-regulation of natural procoagulants and anti-fibrinolytics, and down-regulation of natural anti-coagulants, with protein C (PC) being a critical example of the latter case. PC functions as an anti-coagulant, profibrinolytic, and anti-inflammatory agent, and, thus, its administration or deficiency may affect the course and outcome of sepsis in patients. In this study, a cecal ligation and puncture model of septic peritonitis was applied to wild-type mice and littermates with a targeted heterozygous deficiency of PC (PC(+/-)) to characterize the importance of a PC-deficiency on polymicrobial sepsis. An enhanced mortality rate was found to accompany a PC deficiency. Plasma cytokines, as well as organ-specific expression of cytokine transcripts, were elevated in PC(+/-) mice. No signs of severe disseminated intravascular coagulation (DIC) were observed in wild-type or PC(+/-) mice, as indicated by an increase in fibrinogen levels and the invariability of platelet counts after cecal ligation and puncture. Consumption of coagulation factors was similar in both genotypes and a decrease in the PC mRNA and protein levels was more prominent in PC(+/-) mice. Renal and organ muscle damage was enhanced in PC(+/-) mice, as shown by increases in plasma blood urea nitrogen, creatinine, and creatinine kinase. Hypotension and bradycardia were more enhanced in PC(+/-) mice than in wild-type mice, thus provoking a more severe septic shock response. Thus, the hemodynamic role of PC during sepsis is of critical importance to the outcome of the disease.

Polymorphonuclear leukocytes from patients with severe sepsis have lost the ability to degrade fibrin via u-PA

Fibrin persistence in the vasculature is an important complication of sepsis that can often lead to mortality. We have previously established that polymorphonuclear leukocytes (PMN) from healthy individuals have the capacity to degrade fibrin via urokinase-type plasminogen activator (u-PA). We have also demonstrated an increase in u-PA antigen in the plasma of patients suffering from septic shock. In this study, we investigate the hypothesis that PMN from patients with sepsis have lost their fibrinolytic ability and that this might contribute to the persistence of fibrin deposits. We show here that PMN from these patients do not express any u-PA activity, despite retaining some u-PA antigen. Additionally, thrombi prepared from the whole blood of the patients exhibit reduced endogenous lysis compared with those from healthy individuals. These data indicate that loss of fibrinolytic activity from PMN may be a contributing factor in fibrin persistence in the microvasculature in sepsis.

Urokinase-type plasminogen activator potentiates lipopolysaccharide-induced neutrophil activation

Urokinase plasminogen activator (uPA) is a serine protease that catalyzes the conversion of plasminogen to plasmin. Although increased circulating levels of uPA are present in endotoxemia and sepsis, conditions in which activated neutrophils contribute to the development of acute organ dysfunction, the ability of uPA to participate directly in LPS-induced neutrophil activation has not been examined. In the present experiments, we show that uPA can enhance activation of neutrophils exposed to submaximal stimulatory doses of LPS. In particular, uPA increased LPS-induced activation of intracellular signaling pathways, including Akt and c-Jun N-terminal kinase, nuclear translocation of the transcriptional regulatory factor NF-kappa B, and expression of proinflammatory cytokines, including IL-1 beta, macrophage-inflammatory protein-2, and TNF-alpha. There was no effect of uPA on LPS-induced activation of p38 mitogen-activated protein kinase in neutrophils. Transgenic mice unable to produce uPA (uPA(-/-)) were protected from endotoxemia-induced lung injury, as determined by development of lung edema, pulmonary neutrophil accumulation, lung IL-1 beta, macrophage-inflammatory protein-2, and TNF-alpha cytokine levels. These results demonstrate that uPA can potentiate LPS-induced neutrophil responses and also suggest that such effects are sufficiently important in vivo to play a major contributory role in neutrophil-mediated inflammatory responses, such as the development of acute lung injury.

Comparing functional genomic datasets: lessons from DNA microarray analyses of host-pathogen interactions

Functional genomic technologies such as high density DNA microarrays allow biologists to study the structure and behavior of thousands of genes in a single experiment. One of the fields in which microarrays have had an increasingly important impact is host-pathogen interactions. Early investigations in this area over the past two years not only emphasize the utility of this approach, but also highlight the stereotyped gene expression responses of different host cells to diverse infectious stimuli, and the potential value of broad dataset comparisons in revealing fundamental features of innate immunity. The comparative analysis of recently published datasets involving human gene expression responses to two bacterial respiratory pathogens illustrates many of these points. Comparisons between these large, highly parallel sets of experimental observations also emphasize important technical and experimental design issues as future challenges.