Taku Miyasho

The Anti-Inflammatory and Proresolving Mediator Resolvin E1 Protects Mice from Bacterial Pneumonia and Acute Lung Injury

Whereas pneumonia is the most common cause of death and disability worldwide, most cases of pneumonia spontaneously resolve. Mechanisms that promote pneumonia resolution remain to be determined. Resolvin E1 (RvE1) is an endogenous mediator that displays proresolving actions in sterile inflammation. In this study, we developed a new model of aspiration pneumonia to evaluate the effect of RvE1 on acute lung injury caused by acid aspiration and subsequent bacterial challenge. Mice received hydrochloric acid into the left lung followed by the enteric pathogen Escherichia coli. I.v. administration of RvE1 (∼0.005 mg/kg) prior to acid injury selectively decreased lung neutrophil accumulation by 55% and enhanced clearance of E. coli. RvE1 significantly decreased lung tissue levels of several proinflammatory chemokines and cytokines, including IL-1β, IL-6, HMGB-1, MIP-1α, MIP-1β, keratinocyte-derived chemokine, and MCP-1, in a manner independent of the anti-inflammatory mediators IL-10 and lipoxin A4. In addition, animals treated with RvE1 had a marked improvement in survival. These findings in experimental aspiration pneumonia have uncovered protective roles for RvE1 in pathogen-mediated inflammation that are both anti-inflammatory for neutrophils and protective for host defense, suggesting that RvE1 represents the first candidate for a novel therapeutic strategy for acute lung injury and pneumonia that harnesses natural resolution mechanisms.

Role of high-mobility group box 1 protein in post-infarction healing process and left ventricular remodelling

AIMS High-mobility group box 1 protein (HMGB1) is one of the recently defined damage-associated molecular pattern molecules derived from necrotic cells and activated macrophages. We investigated clinical implications of serum HMGB1 elevation in patients with acute myocardial infarction (MI). Then, we evaluated the effect of HMGB1 blockade on post-MI left ventricular (LV) remodelling in a rat MI model. METHODS AND RESULTS Serum HMGB1 levels were examined in patients with ST-elevation MI (n = 35). A higher peak serum HMGB1 level was associated with pump failure, cardiac rupture, and in-hospital cardiac death. Then, an experimental MI model was induced in male Wistar rats. The mRNA and protein expression of HMGB1 were increased in the infarcted area compared with those values observed in sham-operated rats. We administered neutralizing anti-HMGB1 antibody (MI/anti-H) or control antibody (MI/C) to MI rats subcutaneously for 7 days. The mRNA levels of tumour necrosis factor-alpha and interleukin-1beta and the number of macrophages in the infarcted area were reduced on day 3 in MI/anti-H rats compared with MI/C rats. Interestingly, HMGB1 blockade resulted in thinning and expansion of the infarct scar and marked hypertrophy of the non-infarcted area on day 14. CONCLUSION Elevated serum HMGB1 levels were associated with adverse clinical outcomes in patients with MI. However, HMGB1 blockade in a rat MI model aggravated LV remodelling, possibly through impairment of the infarct-healing process. HMGB1, a novel predictor of adverse clinical outcomes after MI, may have an essential role in the appropriate healing process after MI.

Role of soluble receptor for advanced glycation end products on endotoxin-induced lung injury

RATIONALE The interaction of receptor for advanced glycation end products (RAGE) and its ligands often leads to inflammatory processes or tissue injury, although the effect of the blockade of RAGE signaling on lung injury remains to be investigated. OBJECTIVES Using a murine model of lung injury induced by intratracheal lipopolysaccharide (LPS), we evaluated RAGE expression in the airspace and the effect of recombinant soluble RAGE (sRAGE) on LPS-induced lung injury. METHODS First, the expression of sRAGE in bronchoalveolar lavage (BAL) fluid was determined at 24 hours after intratracheal instillation of LPS or phosphate-buffered saline. Next, to evaluate the effect of sRAGE, BAL fluid was collected for cell counting and measurements of lung permeability and cytokine concentrations 24 hours after intratracheal LPS in the mice with or without intraperitoneal administration of sRAGE 1 hour after the instillation. In another series, lungs were sampled for histopathology and detection of apoptotic cells. The activation of nuclear factor (NF)-kappaB was analyzed 4 hours after LPS instillation. MEASUREMENTS AND MAIN RESULTS In response to LPS challenge, a RAGE isoform of 48 kD was detected in the BAL fluid. Treatment with sRAGE significantly attenuated the increases in neutrophil infiltration, lung permeability, production of inflammatory cytokines, NF-kappaB activation, and apoptotic cells in the lung as well as development of pathologic changes after LPS instillation. CONCLUSIONS RAGE plays an important role in the pathogenesis of LPS-induced lung injury in mice. It was suggested that sRAGE should be tested as a treatment modality in other models of acute lung injury.

Cyclooxygenase-2/Prostaglandin D2/CRTH2 Pathway Mediates Double-Stranded RNA-Induced Enhancement of Allergic Airway Inflammation

Respiratory RNA viruses responsible for the common cold often worsen airway inflammation and bronchial responsiveness, two characteristic features of human asthma. We studied the effects of dsRNA, a nucleotide synthesized during viral replication, on airway inflammation and bronchial hyperresponsiveness in murine models of asthma. Intratracheal instillation of poly I:C, a synthetic dsRNA, increased the airway eosinophilia and enhanced bronchial hyperresponsiveness to methacholine in OVA-sensitized, exposed rats. These changes were associated with induction of cyclooxygenase-2 (COX-2) expression and COX-2-dependent PGD2 synthesis in the lungs, particularly in alveolar macrophages. The direct intratracheal instillation of PGD2 enhanced the eosinophilic inflammation in OVA-exposed animals, whereas pretreatment with a dual antagonist against the PGD2 receptor-(CRTH2) and the thromboxane A2 receptor, but not with a thromboxane A2 receptor-specific antagonist, nearly completely eliminated the dsRNA-induced worsening of airway inflammation and bronchial hyperresponsiveness. CRTH2-deficient mice had the same degree of allergen-induced airway eosinophilia as wild-type mice, but they did not exhibit a dsRNA-induced increase in eosinophil accumulation. Our data demonstrate that COX-2-dependent production of PGD2 followed by eosinophil recruitment into the airways via a CRTH2 receptor are the major pathogenetic factors responsible for the dsRNA-induced enhancement of airway inflammation and responsiveness.

Association between cytokine removal by polymyxin B hemoperfusion and improved pulmonary oxygenation in patients with acute exacerbation of idiopathic pulmonary fibrosis

Acute exacerbation of idiopathic pulmonary fibrosis (AE-IPF) is characterized by severe worsening dyspnea of unknown etiology and high mortality without effective treatment. Recently, direct hemoperfusion with polymyxin B (PMX)-immobilized fiber cartridge (PMX-DHP) has been reported to improve pulmonary oxygenation and survival in patients with AE-IPF although its mechanism of action remains unknown. To gain insights into the pathobiology of AE-IPF through the beneficial effects of PMX-DHP, we analyzed the profile of cytokines adsorbed onto PMX-fibers used in 9 AE-IPF patients. In addition, the sera of these AE-IPF patients collected immediately before and after PMX-DHP, 9 stable IPF patients and 8 healthy individuals were also analyzed. The serum levels of cytokines including IL-9, IL-12, IL-17, PDGF and VEGF were significantly decreased immediately after PMX-DHP (P<0.02), and VEGF and IL-12 were most prominently reduced. In addition to PDGF and VEGF, IL-1β, IL-1ra, IL-8, IL-23, FGF basic, GM-CSF, IP-10, RANTES and TGF-β were eluted from used PMX-fibers. Interestingly, improved pulmonary oxygenation after PMX-DHP was correlated well with the quantities of eluted VEGF. These results suggest that adsorption of proinflammatory, profibrotic and proangiogenic cytokines onto PMX-fibers is one of the mechanisms of action of PMX-DHP in AE-IPF. Notably, removal of VEGF by PMX-DHP may contribute to the rapid improvement in oxygenation by suppressing vascular permeability in the lung.

Gradual Increase of High Mobility Group Protein B1 in the Lungs after the Onset of Acute Exacerbation of Idiopathic Pulmonary Fibrosis

The pathogenesis of acute exacerbation of idiopathic pulmonary fibrosis (IPF) remains to be elucidated. To evaluate the roles of inflammatory mediators in acute exacerbation, the concentrations of high mobility group protein B1 (HMGB1), a chief mediator of acute lung injury, and 18 inflammatory cytokines were measured in the bronchoalveolar lavage fluid, serially sampled from seven IPF patients after the onset of acute exacerbation. HMGB1 gradually increased in the alveolar fluid after the onset of acute exacerbation, in positive correlation with monocytes chemotactic protein-1 (MCP-1), a potent fibrogenic mediator. In the lung tissues of eight IPF patients autopsied after acute exacerbation, intense cytoplasmic staining for HMGB1 was observed in the alveolar epithelial cells in alveolar capillary augmented lesions, where the capillary endothelial cells remarkably reduced the expression of thrombomodulin, an intrinsic antagonist of HMGB1. These results suggest pathogenic roles for HMGB1 and MCP-1 in the late phase of acute exacerbation of IPF.

Neutrophil elastase inhibitor improves survival of rats with clinically relevant sepsis.

Sivelestat sodium hydrate is a selective inhibitor of neutrophil elastase, which is effective in acute lung injury associated with systemic inflammatory response syndrome. However, the effectiveness of sivelestat in sepsis has not been fully examined. In the present study, the effect of sivelestat on severe sepsis in a rat cecal ligation and puncture (CLP) model was investigated. Adult male Sprague-Dawley rats underwent CLP and were randomly divided into two groups: sivelestat-treated group and saline-treated controls. The serum concentrations of several inflammatory mediators were measured. Hematoxylin-eosin staining, and immunohistochemical staining for high-mobility group box chromosomal protein 1 (HMGB1), IL-8, and CD68 were performed on the lungs to assess pathological changes found 12 h after the CLP procedure. Treatment with sivelestat significantly improved the survival rate of the post-CLP septic animals (P = 0.030). Sivelestat also induced a significant reduction in serum IL-1&bgr; (P = 0.038) and IL-10 (P = 0.008) levels in these CLP rats. Serum HMGB1 levels had no significant difference between the sivelestat-treated and the control group. The lungs from sivelestat-treated rats exhibited less severe pathological changes and decreased the numbers of HMGB1, IL-8, and CD68-positive cells (P < 0.001). Sivelestat significantly improved survival rate of rats with clinically relevant sepsis, possibly by attenuating sepsis-induced systemic inflammatory response and lung injury. This may explain the implicated health benefits of sivelestat in reducing morbidity and mortality from sepsis.ABBREVIATIONS-NE-neutrophil elastase; ALI-acute lung injury; HMGB1-high-mobility group box chromosomal protein 1; CLP-cecal ligation and puncture; SIRS-systemic inflammatory response syndrome; POD-postoperative day; GM-CSF-granulocyte-macrophage colony-stimulating factor; IFN-interferon; POH-postoperative hour; H&E-hematoxylin and eosin; CD-cluster of differentiation; CARS-compensatory anti-inflammatory response syndrome

Protective effect of high-mobility group box 1 blockade on acute liver failure in rats

High-mobility group box 1 (HMGB1) is a monocyte-derived inflammatory mediator that is released in some conditions including shock, tissue injury, and endotoxin-induced lethality. In this study, we determined the plasma and hepatic tissue levels of HMGB1 in a drug-induced rat acute liver failure (ALF) model and investigated the effect of HMGB1 blockade on ALF. Adult male Sprague-Dawley rats, weighing 250 to 300 g, were used for this study. d-galactosamine was injected into the penile vein to induce ALF. To determine HMGB1 levels, plasma and hepatic tissue samples were serially collected after the d-galactosamine injection. To test the effect of HMGB1 blockade, anti-HMGB1 polyclonal antibodies or control antibodies were injected into the penile vein right after injection of d-galactosamine. Levels of HMGB1 were increased in plasma and decreased in hepatic tissue after induction of ALF. Immunohistochemical examination for HMGB1 showed that liver from animals with ALF had little staining, whereas normal liver had strong staining in the nuclei. Injection of anti-HMGB1 antibodies resulted in significant suppression of plasma HMGB1 and hepatic enzymes, marked suppression of plasma inflammatory cytokines, marked improvement of histological findings, and significant improvement of survival. The decrease of hepatic HMGB1 was also significantly suppressed in the group injected with anti-HMGB1 antibodies. The present study suggests that in ALF, the liver may release HMGB1 into the plasma, and that neutralizing the released HMGB1 has a protective effect against injury.ABBREVIATIONS-ALF-acute liver failure; HMGB1-high-mobility group box 1; ELISA-enzyme-linked immunosorbent assay; anti-HMGB1 Ab-anti-HMGB1 polyclonal antibodies; control Ab-control IgY antibodies; AST-aspartate aminotransferase; ALT-alanine aminotransferase; LDH-lactic dehydrogenase; IL-interleukin; TNF-tumor necrosis factor

Role of Toll-like receptor 4 in hyperoxia-induced lung inflammation in mice.

Abstract.Objective:Prolonged exposure to hyperoxia causes lung inflammation, but the role of Toll-like receptor 4 (TLR4) in hyperoxia-induced signal transduction remains unclear.Material or subjects:We evaluated neutrophil accumulation, signal transduction and cytokine production during hyperoxia, comparing TLR4 mutant (C3H/HeJ) and wild type (C3H/HeN) mice.Methods:The mice were exposed to 80% oxygen in a hyperoxic chamber for 0 (control), 48, or 96 h. After the exposure, bronchoalveolar lavage (BAL) was performed for differential cell counting and cytokine measurement. In lung homogenate, activation of NF-κB and STAT1 was also examined.Results:In C3H/HeJ mice, hyperoxia-induced neutrophil accumulation in BAL fluid was significantly decreased compared with C3H/HeN. Hyperoxia for 96 h caused NF-κB translocation in C3H/HeN mice, which was significantly attenuated in C3H/HeJ mice (p < 0.05). In contrast, STAT1 activation occurred as early as after 48 h of oxygen exposure, which did not differ between the two strains. The levels of TNF-α, IL-6, and KC in BAL fluid were increased after oxygen exposure, which was suppressed by the lack of TLR4 signaling.Conclusion:These results suggest that TLR4-dependent NF-kB activation may be an important process of the upregulation of proinflammatory mediators and subsequent neutrophil accumulation into the lung during hyperoxia.

Role of high mobility group box chromosomal protein 1 in ischemia-reperfusion injury in the rat small intestine

BACKGROUND High mobility group box chromosomal protein 1 (HMGB1) has recently been shown to be an important late mediator of endotoxic shock and sepsis. The purpose of the present study was to investigate the role of HMGB1 in response to ischemia-reperfusion injury. METHODS Ischemia-reperfusion injury was induced in male Wistar rats by clamping the superior mesenteric artery for 60 min. Using this model, the serum concentrations and localization of HMGB1 were investigated. The histologic findings from reperfused intestines and the survival rates were compared between the anti-HMGB1 antibody treatment groups (group A treated with 6.0 mg/kg antibody and group B with 0.6 mg/kg antibody) and the control antibody treatment group (control group). RESULTS Serum HMGB1 concentrations increased early after reperfusion and peaked at 3 h. Immunohistochemistry for HMGB1 revealed a high degree of positive staining in the epithelial cells of the damaged villi. Anti-HMGB1 antibody treatment significantly reduced this damage (P < 0.05) and improved the 48-h survival rate (90% in group A versus 50% in the controls; P < 0.05). CONCLUSIONS These results suggest that HMGB1 plays a key role in small intestinal ischemia-reperfusion injury.