Endogenous active plasminogen activator inhibitor 1 (PAI-1) was targeted in vivo with monoclonal antibodies (mAbs) that redirect its reaction with proteinases to the substrate branch. mAbs were used as an adjunct to prourokinase (single-chain [sc] urokinase [uPA]) intrapleural fibrinolytic therapy (IPFT) of tetracycline-induced pleural injury in rabbits. Outcomes of scuPA IPFT (0.25 or 0.0625 mg/kg) with 0.5 mg/kg of mouse IgG or mAbs (MA-33H1F7 and MA-8H9D4) were assessed at 24 hours. Pleural fluid (PF) was collected at 0, 10, 20, and 40 minutes and 24 hours after IPFT and analyzed for plasminogen activating (PA), uPA, fibrinolytic activities, levels of total plasmin/plasminogen, a-macroglobulin (aM), mAbs/IgG antigens, free active uPA, and aM/uPA complexes. Anti-PAI-1 mAbs, but not mouse IgG, delivered with an eightfold reduction in the minimal effective dose of scuPA (from 0.5 to 0.0625 mg/kg), improved the outcome of IPFT (P , 0.05). mAbs and IgG were detectable in PFs at 24 hours. Compared with identical doses of scuPA alone or with IgG, treatment with scuPA and anti-PAI-1 mAbs generated higher PF uPA amidolytic and PA activities, faster formation of aM/uPA complexes, and slower uPA inactivation. However, PAI-1 targeting did not significantly affect intrapleural fibrinolytic activity or levels of total plasmin/plasminogen and aM antigens. Targeting PAI-1 did not induce bleeding, and rendered otherwise ineffective doses of scuPA able to improve outcomes in tetracycline-induced pleural injury. PAI-1-neutralizing mAbs improved IPFT by increasing the durability of intrapleural PA activity. These results suggest a novel, well-tolerated IPFT strategy that is tractable for clinical development. Keywords: plasminogen activator inhibitor 1; fibrinolytic therapy; animal model; prourokinase; monoclonal antibodies Clinical RelevanceOrganizing pleural injury remains an important clinical problem for which fibrinolytic therapy has been used with variable results for children and adults. This study demonstrates, for the first time, that the targeting of active plasminogen activator inhibitor 1 enhances the ability of relatively low doses of intrapleural single-chain urokinase to clear pleural effusions after induction of organizing injury. This work defines a new, well-tolerated approach for intrapleural fibrinolytic therapy that is promising and tractable for clinical trial testing.The results of Multicenter Intrapleural Sepsis Trials 1 and 2 demonstrated that intrapleural fibrinolytic therapy (IPFT) with either streptokinase, or tissue-type plasminogen activator (tPA) alone were ineffective (1, 2). In contrast, there is a growing body of clinical reports demonstrating the successful use of IPFT, including tPA,. It is likely that the disparate results of IPFT trials, which are largely successful in children (2, 6) and variably effective in adults (6, 7), relate to the lack of formal toxicological and dose-escalation studies, resulting in empiric dosing. A further impediment to the field is an incomplete underst...

Elevated concentrations of plasminogen activator inhibitor-1 (PAI-1) are associated with pleural injury, but its effects on pleural organization remain unclear. A method of adenovirus-mediated delivery of genes of interest (expressed under a cytomegalovirus promoter) to rabbit pleura was developed and used with lacZ and human (h) PAI-1. Histology, b-galactosidase staining, Western blotting, enzymatic and immunohistochemical analyses of pleural fluids (PFs), lavages, and pleural mesothelial cells were used to evaluate the efficiency and effects of transduction. Transduction was selective and limited to the pleural mesothelial monolayer. The intrapleural expression of both genes was transient, with their peak expression at 4 to 5 days. On Day 5, hPAI-1 (40-80 and 200-400 nM of active and total hPAI-1 in lavages, respectively) caused no overt pleural injury, effusions, or fibrosis. The adenovirus-mediated delivery of hPAI-1 with subsequent tetracycline-induced pleural injury resulted in a significant exacerbation of the pleural fibrosis observed on Day 5 (P ¼ 0.029 and P ¼ 0.021 versus vehicle and adenoviral control samples, respectively). Intrapleural fibrinolytic therapy (IPFT) with plasminogen activators was effective in both animals overexpressing hPAI-1 and control animals with tetracycline injury alone. An increase in intrapleural active PAI-1 (from 10-15 nM in control animals to 20-40 nM in hPAI-1-overexpressing animals) resulted in the increased formation of PAI-1/plasminogen activator complexes in vivo. The decrease in intrapleural plasminogen-activating activity observed at 10 to 40 minutes after IPFT correlates linearly with the initial concentration of active PAI-1. Therefore, active PAI-1 in PFs affects the outcome of IPFT, and may be both a biomarker of pleural injury and a molecular target for its treatment.Keywords: pleural injury; plasminogen activator inhibitor-1; intrapleural fibrinolytic therapyThe incidence of complicated pleural infection and empyema, a serious infection of the pleural space often associated with pneumonia, is increasing in the United States (1) and other countries, in both adult and pediatric populations (2-5). The exact cause of this increase is unknown, although the increased prevalence of antibiotic-resistant bacteria, changes in empyema management, and changes in causative bacterial agents have been implicated (1,3,6). Pleural infections, empyema, or complicated parapneumonic effusions develop in approximately 80,000 patients in the United States and the United Kingdom annually (7). In the United Kingdom, a 20% mortality rate was reported for patients with empyema, and 20% of patients require surgical intervention after developing a pleural infection (7). When pleural effusions occur in association with high-grade inflammation, they can organize with the development of loculation, where an effusion becomes trapped behind partly fused visceral and parietal pleura, with pleural thickening (8-10). Persistent pleural loculation and fibrosis increase morbidity and mortality an...

Komissarov AA, Florova G, Azghani A, Karandashova S, Kurdowska AK, Idell S. Active ␣-macroglobulin is a reservoir for urokinase after fibrinolytic therapy in rabbits with tetracycline-induced pleural injury and in human pleural fluids. Am J Physiol Lung Cell Mol Physiol 305: L682-L692, 2013. First published August 30, 2013 doi:10.1152/ajplung.00102.2013.-Intrapleural processing of prourokinase (scuPA) in tetracycline (TCN)-induced pleural injury in rabbits was evaluated to better understand the mechanisms governing successful scuPA-based intrapleural fibrinolytic therapy (IPFT), capable of clearing pleural adhesions in this model. Pleural fluid (PF) was withdrawn 0 -80 min and 24 h after IPFT with scuPA (0 -0.5 mg/kg), and activities of free urokinase (uPA), plasminogen activator inhibitor-1 (PAI-1), and uPA complexed with ␣-macroglobulin (␣M) were assessed. Similar analyses were performed using PFs from patients with empyema, parapneumonic, and malignant pleural effusions. The peak of uPA activity (5-40 min) reciprocally correlated with the dose of intrapleural scuPA. Endogenous active PAI-1 (10 -20 nM) decreased the rate of intrapleural scuPA activation. The slow step of intrapleural inactivation of free uPA (t1/2 ␤ ϭ 40 Ϯ 10 min) was dose independent and 6.7-fold slower than in blood. Up to 260 Ϯ 70 nM of ␣M/uPA formed in vivo [second order association rate (kass) ϭ 580 Ϯ 60 M Ϫ1 ·s Ϫ1 ]. ␣M/uPA and products of its degradation contributed to durable intrapleural plasminogen activation up to 24 h after IPFT. Active PAI-1, active ␣2M, and ␣2M/uPA found in empyema, pneumonia, and malignant PFs demonstrate the capacity to support similar mechanisms in humans. Intrapleural scuPA processing differs from that in the bloodstream and includes 1) dose-dependent control of scuPA activation by endogenous active PAI-1; 2) two-step inactivation of free uPA with simultaneous formation of ␣M/uPA; and 3) slow intrapleural degradation of ␣M/uPA releasing active free uPA. This mechanism offers potential clinically relevant advantages that may enhance the bioavailability of intrapleural scuPA and may mitigate the risk of bleeding complications. fibrinolytic therapy; rabbit model; pleural injury; urokinase; ␣-macroglobulin; human FIBRINOLYSINS, INCLUDING tissue type (tPA) and urokinase (active two-chain enzyme; tcuPA), are plasminogen activators (PAs) that have long been used to treat a variety of thrombotic conditions including acute myocardial infarction (23; 44), deep vein thrombosis (33, 40), ischemic stroke (1, 3), acute respiratory distress syndrome (ARDS) (20, 21), pulmonary emboli, and organizing pleural effusions (8,9,11,31,37,43). Although intrapleural fibrinolytic therapy (IPFT) has been in use for over 60 years, it has recently undergone reassessment in light of the disparate results seen in clinical trials (9, 11, 37). The efficacy of IPFT in adults remains a subject of ongoing debate. Intrapleural streptokinase was ineffective in patients with complicated parapneumonic pleural effusions and empyema (EMP), whereas ...

Pseudomonas. aeruginosa (PA) is a leading cause of nosocomial pneumonia in patients receiving mechanical ventilation with hyperoxia. Exposure to supraphysiological concentrations of reactive oxygen species during hyperoxia may result in macrophage damage that reduces their ability to phagocytose PA. We tested this hypothesis in cultured macrophage-like RAW 264.7 cells and alveolar macrophages from mice exposed to hyperoxia. Exposure to hyperoxia induced a similarly impaired phagocytosis of both the mucoid and non-mucoid forms of PA in alveolar macrophages and RAW cells. Compromised PA phagocytosis was associated with cytoskeleton disorganization and actin oxidation in hyperoxic macrophages. To test whether moderate concentrations of O 2 limit the loss of phagocytic function induced by ≥ 95% O 2 , mice and RAW cells were exposed to 65% O 2 . Interestingly, although the resulting lung injury/cell proliferation was not significant, exposure to 65% O 2 resulted in a marked reduction in PA phagocytosis that was comparable to that of ≥95% O 2 . Treatment with antioxidants, even post hyperoxic exposure, preserved actin cytoskeleton organization and phagocytosis of PA. These data suggest that hyperoxia reduces macrophage phagocytosis through effects on actin functions which can be preserved by antioxidant treatment. In addition, administration of moderate rather than higher concentrations of O 2 does not improve macrophage phagocytosis of PA.

The results clearly indicate that the Lipo-Ga-GEN formulation is more effective than gentamicin alone in eradicating antibiotic-resistant P. aeruginosa isolates growing in a planktonic or biofilm community.

Pseudomonas aeruginosa is inherently resistant to most conventional antibiotics. The mechanism of resistance of this bacterium is mainly associated with the low permeability of its outer membrane to these agents. We sought to assess the bactericidal efficacy of liposome-entrapped aminoglycosides against resistant clinical strains of P. aeruginosa and to define the mechanism of liposome-bacterium interactions. Aminoglycosides were incorporated into liposomes, and the bactericidal efficacies of both free and liposomal drugs were evaluated. To define the mechanism of liposome-bacterium interactions, transmission electron microscopy (TEM), flow cytometry, lipid mixing assay, and immunocytochemistry were employed. Encapsulation of aminoglycosides into liposomes significantly increased their antibacterial activity against the resistant strains used in this study (MICs of >32 versus <8 g/ml). TEM observations showed that liposomes interact intimately with the outer membrane of P. aeruginosa, leading to the membrane deformation. The flow cytometry and lipid mixing assays confirmed liposome-bacterial membrane fusion, which increased as a function of incubation time. The maximum fusion rate was 54.3% ؎ 1.5% for an antibiotic-sensitive strain of P. aeruginosa and 57.8% ؎ 1.9% for a drug-resistant strain. The fusion between liposomes and P. aeruginosa significantly enhanced the antibiotics' penetration into the bacterial cells (3.2 ؎ 2.3 versus 24.2 ؎ 6.2 gold particles/bacterium, P < 0.001). Our data suggest that liposome-entrapped antibiotics could successfully resolve infections caused by antibiotic-resistant P. aeruginosa through an enhanced mechanism of drug entry into the bacterial cells.

Lung injury in bacterial infection is a multifactorial phenomenon that involves bacterial metabolites and host factors. Primary isolates of type II pneumocytes and established cultures of Madin-Darby canine kidney (MDCK) cells were used to study effects of Pseudomonas aeruginosa exoproducts on epithelial paracellular permeability. The results indicate that elastase (PE) and exotoxin A (Exo A) have different, but complementary, actions that diminish epithelial barrier function. We measured transepithelial electrical resistance (TER) and permeability coefficient for mannitol (Pm) across cell monolayers plated on tissue culture membranes. Application of 100 ng/ml of Exo A to the basal side decreased TER from 1,405 +/- 106 to 462 +/- 50 ohm (omega) and increased Pm for mannitol 6-fold in 16 h (P < 0.05). Application of Exo A to the apical side did not affect either TER or Pm. In contrast, PE (6.5 U/ml) applied either apically or basolaterally reduced TER to 353 +/- 66 omega and increased Pm by 10-fold within 90 min (P < 0.05). The increase in permeability correlated with the number of bacteria that traversed the epithelial monolayers. Fluorescent staining and western immunoblot analysis of toxin-treated cells showed that two tight junctional proteins, ZO-1 and ZO-2, were depleted in monolayers treated with enzymatically active PE. The junctional proteins decreased in cells treated overnight with Exo A but were not depleted. Neither agent diminished cell viability as measured by trypan blue staining or release of radioactivity from 51 Cr-labeled cells. Elastase from P. aeruginosa thus seems to increase alveolar epithelial permeability by damaging tight junction-associated proteins. Exo A, through its effect on protein synthesis, may render the cells unable to restore the junctional proteins and thus the functional junctions.

The authors compared the ability of a single dose of the proenzyme single-chain urokinase (scuPA), low-molecular-weight urokinase, tissue plasminogen activator (tPA), or a mutant site-inactive scuPA to resolve intrapleural loculations at 72 to 96 hours after tetracycline-induced pleural injury in rabbits. Both scuPA and tPA reversed loculations at 96 hours after injury P < or = .001, whereas low-molecular-weight urokinase and the scuPA mutant were ineffective. scuPA and tPA generated inhibitor complexes, induced fibrinolytic activity, and quenched plasminogen activator-1 activity in pleural fluids. The authors conclude that scuPA reverses loculations as effectively as tPA at clinically applied intrapleural doses, whereas low-molecular-weight urokinase was ineffective.