fibrin and Pneumonia--Bacterial

Topics: Acute Disease; Aged; Chlamydophila Infections; Chlamydophila pneumoniae; Cryptogenic Organizing Pneumonia; Fatal Outcome; Female; Fibrin; Humans; Multiple Organ Failure; Pneumonia, Bacterial; Pulmonary Alveoli; Respiratory Insufficiency

Essentials Immunity and coagulation are linked during sepsis but the role of thrombin is not fully elucidated. We investigated the effect of thrombin inhibition on murine Klebsiella pneumosepsis outcome. Thrombin is crucial for survival and limiting bacterial growth in pneumonia derived sepsis. Thrombin improves host defense via fibrin and enhancement of platelet-neutrophil interactions.. Background Innate immunity and coagulation are closely linked during sepsis. Their interaction can be detrimental to the outcome because of microvascular failure but can also enhance host defense. The role of thrombin therein has not been fully elucidated. Objective We aimed to investigate the contribution of thrombin to the host response during pneumonia-derived sepsis. Methods Mice treated with the specific thrombin inhibitor dabigatran or control chow were infected with the common human sepsis pathogen Klebsiella (K.) pneumoniae via the airways. In subsequent infection experiments, mice were additionally treated with ancrod to deplete fibrinogen. Ex vivo Klebsiella growth was assessed by incubating human whole blood or specific blood components in various conditions with Klebsiella. Results Thrombin inhibition by dabigatran enhanced bacterial outgrowth and spreading, and accelerated mortality. Thrombin inhibition did not influence neutrophil recruitment to the lung or activation or neutrophil extracellular trap formation. Dabigatran reduced D-dimer formation and fibrin deposition in the lung. Fibrin depletion also enhanced bacterial outgrowth and spreading, and thrombin inhibition had no additional effect. Both thrombin and fibrin polymerization inhibited ex vivo Klebsiella outgrowth in human whole blood, which was neutrophil dependent, and the effect of thrombin required the presence of platelets and platelet protease activated receptor-1. In vivo thrombin inhibition reduced platelet-neutrophil complex formation and endothelial cell activation, but did not prevent sepsis-induced thrombocytopenia or organ damage. Conclusions These results suggest that thrombin plays an important role in protective immunity during pneumonia-derived sepsis by fibrin polymerization and enhancement of platelet-neutrophil interactions.

Topics: Animals; Blood Coagulation; Blood Platelets; Cell Communication; Dabigatran; Extracellular Traps; Female; Fibrin; Fibrinogen; Flow Cytometry; Humans; Immune System; Immunity, Innate; Klebsiella Infections; Klebsiella pneumoniae; Lung; Mice; Mice, Inbred C57BL; Microcirculation; Neutrophils; Pneumonia, Bacterial; Sepsis; Thrombin

ExoU, a Pseudomonas aeruginosa cytotoxin with phospholipase A2 activity, was shown to induce vascular hyperpermeability and thrombus formation in a murine model of pneumosepsis. In this study, we investigated the toxin ability to induce alterations in pulmonary fibrinolysis and the contribution of the platelet activating factor (PAF) in the ExoU-induced overexpression of plasminogen activator inhibitor-1 (PAI-1).. Mice were intratracheally instilled with the ExoU producing PA103 P. aeruginosa or its mutant with deletion of the exoU gene. After 24 h, animal bronchoalveolar lavage fluids (BALF) were analyzed and lung sections were submitted to fibrin and PAI-1 immunohistochemical localization. Supernatants from A549 airway epithelial cells and THP-1 macrophage cultures infected with both bacterial strains were also analyzed at 24 h post-infection.. In PA103-infected mice, but not in control animals or in mice infected with the bacterial mutant, extensive fibrin deposition was detected in lung parenchyma and microvasculature whereas mice BALF exhibited elevated tissue factor-dependent procoagulant activity and PAI-1 concentration. ExoU-triggered PAI-1 overexpression was confirmed by immunohistochemistry. In in vitro assays, PA103-infected A549 cells exhibited overexpression of PAI-1 mRNA. Increased concentration of PAI-1 protein was detected in both A549 and THP-1 culture supernatants. Mice treatment with a PAF antagonist prior to PA103 infection reduced significantly PAI-1 concentrations in mice BALF. Similarly, A549 cell treatment with an antibody against PAF receptor significantly reduced PAI-1 mRNA expression and PAI-1 concentrations in cell supernatants, respectively.. ExoU was shown to induce disturbed fibrin turnover, secondary to enhanced procoagulant and antifibrinolytic activity during P. aeruginosa pneumosepsis, by a PAF-dependent mechanism. Besides its possible pathophysiological relevance, in vitro detection of exoU gene in bacterial clinical isolates warrants investigation as a predictor of outcome of patients with P. aeruginosa pneumonia/sepsis and as a marker to guide treatment strategies.

Topics: Animals; Bacterial Proteins; Blood Coagulation; Bronchoalveolar Lavage Fluid; Cell Line, Tumor; Disease Models, Animal; Epithelial Cells; Female; Fibrin; Humans; Immunohistochemistry; Macrophages; Mice; Mutation; Plasminogen Activator Inhibitor 1; Platelet Activating Factor; Pneumonia, Bacterial; Pseudomonas aeruginosa; Pseudomonas Infections; Pulmonary Alveoli; Respiratory Mucosa; RNA, Messenger; Sepsis; Time Factors; Up-Regulation

In children, pleural empyema is a recognized complication of severe pneumonia and is characterized by loculated effusions with fibrin septations. The aim of this study was to evaluate the relationship between proinflammatory cytokines [tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and IL-6], intrapleural fibrinolytic system enzymes [tissue-type plasminogen activator (tPA) and plasminogen activator inhibitor type 1 (PAI-1)], and common biochemical indices during pleural infection.. Children with pneumonia complicated by para-pneumonic effusions were enrolled into our study and underwent real-time chest sonography. The patients were divided into 3 groups by ultrasound using a recognized staging system of pleural effusions. Staging of progressive pleural infection was used to correlate with the characteristics of pleural effusions. The correlation of various pleural variables with the formation of complicated para-pneumonic effusions (CPE) was performed and pleural variables for predicting subsequent intervention procedures were also analyzed.. A total of 57 patients were enrolled in the present study. Univariate analysis revealed that the amounts of biochemical indices (pH, glucose, lactate dehydrogenase), proinflammatory cytokines (TNF-alpha, IL-1beta, IL-6), and fibrinolytic system enzymes (tPA, PAI-1) were significantly different with the progressive stages of para-pneumonic effusions (Ptrend < 0.05). For all proinflammatory cytokines, a positive correlation was found with lactate dehydrogenase and PAI-1, whereas a negative correlation was found with pH, glucose, and tPA. Moreover, these cytokines were also significantly correlated with PAI-1 in both non-CPE and CPE. The pleural fluid findings of IL-1beta (> or =50 pg/mL), PAI-1 (> or =1252 ng/mL), and pH (< or =7.30) were the most significant predictive factors for subsequent intervention procedures (P < 0.001).. The increased release of proinflammatory cytokines in pleural fluid caused by bacteria may result in an imbalance of the fibrinolytic system, which can subsequently lead to fibrin deposition and intervention procedures.

Topics: Adolescent; Child; Child, Preschool; Cytokines; Female; Fibrin; Glucose; Humans; Hydrogen-Ion Concentration; Infant; Inflammation; L-Lactate Dehydrogenase; Male; Plasminogen Activator Inhibitor 1; Pleural Effusion; Pneumonia, Bacterial; Pneumonia, Pneumococcal; Tissue Plasminogen Activator; Ultrasonography

Severe pneumonia is associated with a local inhibition of fibrinolysis in the lung as reflected by strongly reduced pulmonary plasminogen activator activity.. To study the effect of elevation of local plasminogen activator activity during pneumonia caused by the common respiratory pathogen Klebsiella pneumoniae.. Female C57Bl/6 mice were inoculated intranasally with a replication-defective adenoviral vector expressing human tissue-type plasminogen activator or a control vector 24 h before intranasal infection with K. pneumoniae.. Mice infected with Klebsiella via the airways developed overt pneumonia, which was accompanied by a downregulation of pulmonary tissue-type plasminogen activator levels at protein and mRNA levels. Pulmonary overexpression of human tissue-type plasminogen activator resulted in increased fibrinolytic activity in the lungs during pneumonia, as indicated by higher D-dimer levels and reduced fibrin deposition. Interestingly, overexpression of tissue-type plasminogen activator markedly improved host defense against pneumonia: mice treated with the tissue-type plasminogen activator vector displayed less bacterial growth and dissemination, attenuated distant organ injury and a reduced mortality.. These data demonstrate that local elevation of plasminogen activator activity in the lungs improves host defense against severe gram-negative pneumonia and sepsis.

Topics: Adenoviridae; Administration, Intranasal; Animals; Female; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinolysis; Genetic Vectors; Humans; Immunity, Innate; Klebsiella Infections; Klebsiella pneumoniae; Lung; Mice; Mice, Inbred C57BL; Pneumonia, Bacterial; Recombinant Fusion Proteins; RNA, Messenger; Sepsis; Tissue Plasminogen Activator; Transgenes

Changes in the alveolar hemostatic balance in severe pneumonia were compared with those in the acute respiratory distress syndrome (ARDS). Analysis was performed in bronchoalveolar lavage fluids (BALF) of patients with ARDS triggered by nonpulmonary underlying events in the absence of lung infection (ARDS; n = 25), pneumonia demanding mechanical ventilation (PNEU-vent; n = 114), spontaneously breathing patients with pneumonia (PNEU-spon; n = 40), and ARDS in combination with lung infection (ARDS+PNEU; n = 43); comparison with healthy control subjects (n = 35) was performed. In all groups of patients, BALF total procoagulant activity was increased by nearly two orders of magnitude, being largely attributable to the tissue factor pathway of coagulation. Concomitantly, markedly reduced overall fibrinolytic capacity (fibrin plate assay) was noted in the lavage fluids of all patients. BALF levels of urokinase-type plasminogen activator were significantly reduced throughout, whereas the lavage concentrations of tissue-type plasminogen activator did not differ from those in control subjects. In addition, markedly enhanced levels of plasminogen activator- inhibitor I and alpha(2)-antiplasmin were noted in ARDS, ARDS+PNEU, and PNEU-vent, but not in PNEU-spon. In all groups of patients, the changes in the lavage enzymatic activities were paralleled by manifold increased BALF concentrations of fibrinopeptide A and D-dimer, reflecting in vivo coagulation processes. Within the overall number of patients with pneumonia, changes in the alveolar hemostatic balance were more prominent in alveolar and interstitial pneumonia than in bronchopneumonia. Acute inflammatory lung injury, whether triggered by nonpulmonary systemic events or primary lung infection, is thus consistently characterized by both enhanced procoagulant and depressed fibrinolytic activities in the alveolar lining layer, with the appearance of fibrin formation in this compartment. Profile and extent of changes in severe pneumonia demanding respirator therapy are virtually identical to those in ARDS, whereas somewhat less prominent alterations of the alveolar hemostatic balance are noted in spontaneously breathing patients with pneumonia.

Topics: Adolescent; Adult; Aged; Bronchoalveolar Lavage Fluid; Critical Care; Diagnosis, Differential; Female; Fibrin; Fibrinolysis; Humans; Male; Middle Aged; Pneumonia, Bacterial; Pulmonary Alveoli; Respiration, Artificial; Respiratory Distress Syndrome