Endotoxemia-induced Lung Injury Research Articles

Engineered Albumin Nanoparticles Targeting Inflammatory Neutrophils in Human Lungs Mitigate Endotoxemia-Induced Lung Injury

Engineered Albumin Nanoparticles Targeting Inflammatory Neutrophils in Human Lungs Mitigate Endotoxemia-Induced Lung Injury

DOCK2 contributes to endotoxemia-induced acute lung injury in mice by activating proinflammatory macrophages

Dedicator of cytokinesis 2 (DOCK2), an atypical Rac activator, has important anti-inflammatory properties in blepharitis, enteric bacterial infection and colitis. However, the roles of DOCK2 in macrophage activation and acute lung injury (ALI) are still poorly elucidated. In vitro studies demonstrated that DOCK2 was essential for the nucleotide-sensing Toll-like receptor (TLR) 4-mediated inflammatory response in macrophages. We also confirmed that exposure of macrophages to LPS induced Rac activation through a TLR4-independent, DOCK2-dependent mechanism. Phosphorylation of IκB kinase (IKK) β and nuclear translocation of transcription factor nuclear factor kappa B (NF-κB) were impaired in Ad-shDOCK2-expressing macrophages, resulting in a decreased inflammatory response. Similar results were obtained when EHop-016 (a Rac inhibitor) was used to treat uninfected macrophages. In summary, these data indicate that the DOCK2-Rac signaling pathway acts in parallel with TLR4 engagement to control IKKβ activation for inflammatory cytokine release. Next, we investigated whether pharmacological inhibition of DOCK2 protects against endotoxemia-induced lung injury in mice. Treatment with 4-[3′-(2″-chlorophenyl)-2′-propen-1′-ylidene]-1-phenyl-3,5-pyrazolidinedione (CPYPP), a small-molecule inhibitor of DOCK2, reduced the severity of lung injury, as indicated by decreases in the lung injury score and myeloperoxidase (MPO) activity. Moreover, CPYPP attenuated LPS-induced proinflammatory cytokine release in mice. Our studies suggest that inhibition of DOCK2 may suppress LPS-induced macrophage activation and that DOCK2 may be a novel target for treating endotoxemia-related ALI.

Caspase-11-mediated endothelial pyroptosis underlies endotoxemia-induced lung injury.

Acute lung injury is a leading cause of death in bacterial sepsis due to the wholesale destruction of the lung endothelial barrier, which results in protein-rich lung edema, influx of proinflammatory leukocytes, and intractable hypoxemia. Pyroptosis is a form of programmed lytic cell death that is triggered by inflammatory caspases, but little is known about its role in EC death and acute lung injury. Here, we show that systemic exposure to the bacterial endotoxin lipopolysaccharide (LPS) causes severe endothelial pyroptosis that is mediated by the inflammatory caspases, human caspases 4/5 in human ECs, or the murine homolog caspase-11 in mice in vivo. In caspase-11-deficient mice, BM transplantation with WT hematopoietic cells did not abrogate endotoxemia-induced acute lung injury, indicating a central role for nonhematopoietic caspase-11 in endotoxemia. Additionally, conditional deletion of caspase-11 in ECs reduced endotoxemia-induced lung edema, neutrophil accumulation, and death. These results establish the requisite role of endothelial pyroptosis in endotoxemic tissue injury and suggest that endothelial inflammatory caspases are an important therapeutic target for acute lung injury.

Caspase-11–mediated endothelial pyroptosis underlies endotoxemia-induced lung injury

Caspase-11–mediated endothelial pyroptosis underlies endotoxemia-induced lung injury

Abstract 12320: Inhibition of DNA Methylation and Histone Acetylation Changes the Macrophage Polarization During Endotoxemia-induced Lung Injury

Introduction: Acute lung injury (ALI) during sepsis is characterized by bilateral alveolar infiltrates, lung edema, and respiratory failure. The exact molecular mechanism for ALI is poorly understood. Although chemical epigenetic modifiers can potentially limit lung inflammation, to date no study has examined the efficacy of DNA methyl transferase inhibitor 5-Aza 2-deoxycytidine (Aza) and histone deacetylase inhibitor Trichostatin A (TSA) combination therapy (Aza+TSA) on the polarization of macrophages. Hypothesis: We hypothesized that therapy with Aza+TSA would reduce inflammation in ALI and will stimulate the production of M2 macrophages. Methods and Results: In LPS-induced mouse ALI, post-treatment with a single dose of Aza+TSA showed a substantial attenuation of adverse lung inflammation and histopathological changes. Flow cytometry data showed a significant decrease in expression of CD14 and CD40, and increased expression of CD23 and CD124 in Aza+TSA-treated cells compared with untreated LPS-induced primary bone marrow derived macrophages (BMDMs) or LPS-induced BMDMs treated with either drug alone (Fig panel A). This was further confirmed by Western analysis for M1 marker NOS2 and M2 marker CD206. Our data showed lesser expression of NOS2 (Fig panel B) and higher expression of CD206 (Fig panel C) in LPS-challenged BMDMs treated with Aza+TSA than in the BMDMs treated with either Aza or TSA alone. These data support that Aza+TSA treatment promotes an M2 phenotype in LPS-stimulated macrophages, which secrete anti-inflammatory cytokines. Conclusions: This novel treatment with combined epigenetic modifiers has therapeutic potential for patients with sepsis-induced ALI by reducing inflammation and generation of alternatively activated M2 macrophages with more abilities of pathogen clearance.

Lack of cyclophilin D protects against the development of acute lung injury in endotoxemia

Sepsis caused by LPS is characterized by an intense systemic inflammatory response affecting the lungs, causing acute lung injury (ALI). Dysfunction of mitochondria and the role of reactive oxygen (ROS) and nitrogen species produced by mitochondria have already been proposed in the pathogenesis of sepsis; however, the exact molecular mechanism is poorly understood. Oxidative stress induces cyclophilin D (CypD)-dependent mitochondrial permeability transition (mPT), leading to organ failure in sepsis. In previous studies mPT was inhibited by cyclosporine A which, beside CypD, inhibits cyclophilin A, B, C and calcineurin, regulating cell death and inflammatory pathways. The immunomodulatory side effects of cyclosporine A make it unfavorable in inflammatory model systems. To avoid these uncertainties in the molecular mechanism, we studied endotoxemia-induced ALI in CypD−/− mice providing unambiguous data for the pathological role of CypD-dependent mPT in ALI. Our key finding is that the loss of this essential protein improves survival rate and it can intensely ameliorate endotoxin-induced lung injury through attenuated proinflammatory cytokine release, down-regulation of redox sensitive cellular pathways such as MAPKs, Akt, and NF-κB and reducing the production of ROS. Functional inhibition of NF-κB was confirmed by decreased expression of NF-κB-mediated proinflammatory genes. We demonstrated that impaired mPT due to the lack of CypD reduces the severity of endotoxemia-induced lung injury suggesting that CypD specific inhibitors might have a great therapeutic potential in sepsis-induced organ failure. Our data highlight a previously unknown regulatory function of mitochondria during inflammatory response.

Protective effect of resveratrol against endotoxemia-induced lung injury involves the reduction of oxidative/nitrative stress

BackgroundResveratrol, a natural plant polyphenol, has received increasing attention because its varied bioactivities, including the inhibition of tumorigenesis, lipid modification and calorie-restriction. We aimed to investigate the effect of resveratrol on oxidative/nitrative stress in endotoxemia-associated acute lung injury. MethodsMice were injected with lipopolysaccharide (LPS, 5 mg/kg, ip). Resveratrol at a dose of 0.3 mg/kg was administered alone or immediately before injection of LPS. Twenty four hours later, lung tissues were collected for histopathologic examination, and determination of malondialdehyde (MDA), H2O2, reduced/oxidized glutathione (GSH/GSSG) ratio, total antioxidant capacity (T-AOC), superoxide dismutase (SOD) activity, catalase (CAT) activity, inducible nitric oxide synthase (iNOS) expression, nitric oxide (NO) and peroxynitrite production. ResultsResveratrol treatment improves histopathological changes in the lung during endotoxemia. Increased oxidative stress in endotoxemic lung was reversed by resveratrol treatment, as evidenced by the decreases of pro-oxidant biomarker (MDA and H2O2), and the increases of anti-oxidant biomarkers (GSH/GSSG ratio, T-AOC, CAT and SOD activity). Treatment with resveratrol inhibited endotoxemia-induced iNOS expression and NO production. Moreover, peroxynitrite formation in endotoxemic lung was significantly attenuated after resveratrol treatment. ConclusionsResveratrol exerts protective effects against acute endotoxemia-associated lung injury. These beneficial effects may be due to both the anti-oxidant and anti-nitrative properties of resveratrol. These findings support the potential for resveratrol as a possible pharmacological agent to reduce acute lung injury resulting from oxidative/nitrative damage.

Inhaled unfractionated heparin improves abnormalities of alveolar coagulation, fibrinolysis and inflammation in endotoxemia-induced lung injury rats

Background Acute lung injury/acute respiratory distress syndrome presents with not only local inflammation, but also pulmonary coagulopathy which is characterized by an alveolar procoagulant response, anticoagulant inhibition, fibrinolytic supression and fibrin deposition. We thus had hypothesized that if aerosolized unfractionated heparin was inhaled into alveolar spaces, it could block the procoagulant tendency, lessen depletion of coagulation factors, and even influence the inflammatory response. We also assessed the effects of different administration regimens of heparin. Methods Male Wistar rats were given inhaled heparin starting 30 minutes before (prophylactic heparin) or 2 hours after (therapeutic heparin) intravenous lipopolysaccharide (LPS) was administered at 6-hour intervals; control groups received inhaled normal saline with or without being exposed to LPS. Thrombin-antithrombin complexes, activated protein C, tissue type and urokinase type plasminogen activators (t-PA/u-PA), plasminogen activator inhibitor-1 (PAI-1), tumor necrosis factor-α, interleukin-6 in bronchoalveolar lavage, and lung tissue myeloperoxidase activity, and histology score were measured at three time-points. PAI-1/(t-PA + u-PA) was calculated based on the before-mentioned parameters. Statistical analysis was made using one-way analysis of variance (ANOVA) with post hoc test or Student's t test in the case of heterogeneity of variance. Results An alveolar procoagulant reaction, depressed fibrinolysis, and inflammatory response occurred in endotoxemia-induced lung injury. Local prophylactic application of heparin attenuated coagulation and early inflammation, promoted fibrinolysis, and reduced the histology score. Therapeutic application of heparin had similar, but weaker effects. Conclusions Intrapulmonary application of unfractionated heparin by inhalation might inhibit alveolar procoagulant reaction and the early inflammatory response, promote fibrinolysis, and alleviate pulmonary pathology in endotoxemia-induced lung injury rats. Administration of heparin before LPS challenge was more efficacious. Chin Med J 2013;126 (2): 318-324

Distant effects of nitric oxide inhalation in lavage‐induced lung injury in anaesthetised pigs

Inhalation of nitric oxide (INO) exerts both local and distant effects. INO in healthy pigs causes down-regulation of endogenous nitric oxide (NO) production and vasoconstriction in lung regions not reached by INO, especially in hypoxic regions, which augments hypoxic pulmonary vasoconstriction. In contrast, in pigs with endotoxemia-induced lung injury, INO causes increased NO production in lung regions not reached by INO. The aim of this study was to investigate whether INO exerts distant effects in surfactant-depleted lungs. Twelve pigs were anaesthetised, and the left lower lobe (LLL) was separately ventilated. Lavage injury was induced in all lung regions, except the LLL. In six pigs, 40 ppm INO was given to the LLL (INO group), and the effects on endogenous NO production and blood flow in the lavage-injured lung regions were studied. Six pigs served as a control group. NO concentration in exhaled air (ENO), NO synthase (NOS) activity and cyclic guanosine monophosphate (cGMP) in lung tissue, and regional pulmonary blood flow were measured. The calcium (Ca(2+) )-dependent NOS activity was lower (P < 0.05) in the lavage-injured lung regions in the INO group than in the control group. There were no measurable differences between the groups for Ca(2+) -independent NOS activity, cGMP, ENO, or regional pulmonary blood flow. Regional INO did not increase endogenous NO production in lavage-injured lung regions not directly reached by INO, but instead down-regulated the constitutive calcium-dependent nitric oxide synthase activity, indicating that NO may inhibit its own synthesis.

The role of mitochondrial oxidation in endotoxin-induced liver-dependent swine pulmonary edema

We reported previously studies in an in situ perfused swine preparation demonstrating that endotoxemia induced lung injury required the presence of the liver and that the response was accompanied by oxidative stress. To determine whether lung and liver mitochondrial oxidative stress was important to the response, we compared the effects of equimolar amounts of two antioxidants, n-acetylcysteine, which does not replenish mitochondrial glutathione, and procysteine which does, on endotoxemia induced lung injury in the swine preparation. In a swine perfused liver–lung preparation, we measured physiologic, biochemical and cellular responses of liver and lung to endotoxemia with and without the drugs. Endotoxemia caused oxidation of the mitochondria-specific protein, thioredoxin-2, in both the lungs and the liver. Procysteine reduced thioredoxin-2 oxidation, attenuated hemodynamic, gas exchange, hepatocellular dysfunction, and cytokine responses and prevented lung edema. n-acetylcysteine had more modest effects and did not prevent lung edema. ConclusionsWe conclude that mitochondrial oxidation may be critical to the pathogenesis of endotoxemia-induced liver-dependent lung injury and that choices of antioxidant therapy for such conditions must consider the desired subcellular target in order to be optimally effective.

Nebulized Anticoagulants Limit Pulmonary Coagulopathy, But Not Inflammation, in a Model of Experimental Lung Injury

Pulmonary coagulopathy may contribute to an adverse outcome in lung injury. We assessed the effects of local anticoagulant therapy on bronchoalveolar and systemic haemostasis in a rat model of endotoxemia-induced lung injury. Male Sprague-Dawley rats were intravenously challenged with lipopolysaccharide (LPS) and treated with nebulized normal saline (placebo), recombinant human-activated protein C (APC), plasma-derived antithrombin (AT), heparin, or danaparoid. Intravenous administration of LPS resulted in lung injury associated with elevated bronchoalveolar levels of thrombin-antithrombin complex (TATc), 6.9 +/- 0.8 ng/mL (placebo) versus 0.5 +/- 0.2 ng/mL (healthy control) (p < 0.01), and elevated bronchoalveolar levels of fibrin degradation products (FDP), 555 +/- 74 ng/mL versus 27 +/- 12 ng/mL (p < 0.01). Nebulized APC, AT, and danaparoid all significantly limited the rise of bronchoalveolar levels of TATc, 2.4 +/- 0.7 ng/mL), 1.5 +/- 0.2, 3.8 +/- 0.7, and 3.2 +/- 0.9 ng/mL, respectively (all p < 0.01 vs. placebo), and fibrin degradation products, 243 +/- 77, 113 +/- 20, 317 +/- 74, and 300 +/- 42 ng/mL (all p < 0.01 vs. placebo). Heparin and danaparoid also significantly affected systemic coagulopathy. However, pulmonary inflammatory responses [neutrophil influx into the lungs, bronchoalveolar levels of myeloperoxidase, and bronchoalveolar levels of tumor necrosis factor (TNF), interleukin (IL)-6 and CINC-3], and histopathology of lungs were not affected by nebulization of anticoagulants. In conclusion, local treatment with APC, AT, heparin, or danaparoid attenuate pulmonary coagulopathy, but not inflammation, in rats with endotoxemia-induced lung injury.

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.

Neutrophils as early immunologic effectors in hemorrhage- or endotoxemia-induced acute lung injury.

Acute lung injury is characterized by accumulation of neutrophils in the lungs, accompanied by the development of interstitial edema and an intense inflammatory response. To assess the role of neutrophils as early immune effectors in hemorrhage- or endotoxemia-induced lung injury, mice were made neutropenic with cyclophosphamide or anti-neutrophil antibodies. Endotoxemia- or hemorrhage-induced lung edema was significantly reduced in neutropenic animals. Activation of the transcriptional regulatory factor nuclear factor-kappaB after hemorrhage or endotoxemia was diminished in the lungs of neutropenic mice compared with nonneutropenic controls. Hemorrhage or endotoxemia was followed by increases in pulmonary mRNA and protein levels for interleukin-1beta (IL-1beta), macrophage inflammatory protein-2 (MIP-2), and tumor necrosis factor-alpha (TNF-alpha). Endotoxin-induced increases in proinflammatory cytokine expression were greater than those found after hemorrhage. The amounts of mRNA or protein for IL-1beta, MIP-2, and TNF-alpha were significantly lower after hemorrhage in the lungs of neutropenic versus nonneutropenic mice. Neutropenia was associated with significant reductions in IL-1beta and MIP-2 but not in TNF-alpha expression in the lungs after endotoxemia. These experiments show that neutrophils play a central role in initiating acute inflammatory responses and causing injury in the lungs after hemorrhage or endotoxemia.

The Lung Expression of Proinflammatory Cytokines, TNF-alpha and Interleukin 6, in Early Periods of Endotoxemia

Background: The immediate hoot to LPS is the production of proinflammatory cytokines that act as intercellular mediators in inflammatory reactions, including acute lung injury. These response cytokines transmit signals from recognition cells to target or effector cells. This host is further amplified by the expression of leukocyte chemoattractants, growth factors, and adhesion molecules, resulting in an array of proinflammatory events. This experiment was performed to define the lung origin of proinflammatory cytokines, such as TNF-, IL 6 in early periods of endotoxin induced acute lung injury (ALI). Method: The healthy male Sprague-Dawley, weighted 150 - 250g, were divided into saline control (NC) and endotoxemia-induced ALI (ETX-), and leukopenic endotoxemia-induced ALI (CPA-ETX-Group) which was induced by cyclophosphamide, 70 mg/kg i.p. injection. Acute lung injury was evoked by LPS, 5 mg/kg, intravenously administered. Bronchoalveolar lavage was performed at 0, 3, 6 h after LPS-treated to estimate the influx of phagocytes and concentration of total protein, and cytokines as TNF- and IL 6 by a bioassy using MIT method. We also examined the localization of TNF- and IL 6 protein in endotoxemia-challenged lung tissue by immunohistochemical stain (IH). Results: The total cell, macrophage and PMN count in BALF were elavated in ETX group compared to NC(p and IL 6 in BALF was significantly increased in the ETX- and CPA-ETX group compared to NC. There was no difference between ETX- and CPA-ETX group. In IH, anti-TNF-- and anti-IL 6 antibody was strongly localized at interstitial monocytes and alveolar macrophages in endotoxemia-challenged lung tissue. From above point of view, activated alveolar macrophage/monocyte considered as a prominent source of proinflammatory cytokines in endotoxemia-challenged lung injury. Conclusion: The prominent source of proinflammatory cytokines in early periods of endotoxemia-induced lung injury will be the activated resident macrophages like an alveolar macrophage and interstitial monocytes. The pulmonary macrophage/monocyte will impact the initiation and continuance of lung injury without PMNs's certain inflammatory role, particularly in endotoxemia-induced acute lung injury.