Administration of truncated secretory leukoprotease inhibitor ameliorates bleomycin-induced pulmonary fibrosis in hamsters

Knockdown of Long Noncoding RNA H19 Represses the Progress of Pulmonary Fibrosis through the Transforming Growth Factor β/Smad3 Pathway by Regulating MicroRNA 140

Long noncoding RNAs (lncRNAs) are involved in various human diseases. Recently, H19 was reported to be upregulated in fibrotic rat lung and play a stimulative role in bleomycin (BLM)-induced pulmonary fibrosis in mice. However, its expression in human fibrotic lung tissues and mechanism of action remain unclear. Here, our observations showed that H19 expression was significantly upregulated and that of microRNA 140 (miR-140) was markedly reduced in pulmonary fibrotic tissues from idiopathic pulmonary fibrosis (IPF) patients and transforming growth factor β1 (TGF-β1)-induced HBE and A549 cells. Moreover, the expression of H19 was negatively correlated with the expression of miR-140 in IPF tissues. H19 knockdown attenuated TGF-β1-induced pulmonary fibrosis in vitro Furthermore, animal experiments showed that H19 knockdown attenuated BLM-induced pulmonary fibrosis in mice. The study of molecular mechanisms showed that H19 functioned via reduction of miR-140 expression by binding to miR-140. The increase of miR-140 inhibited TGF-β1-induced pulmonary fibrosis, and H19 upregulation diminished the inhibitory effects of miR-140 on TGF-β1-induced pulmonary fibrosis, which was involved in the TGF-β/Smad3 pathway. Taken together, our findings showed that H19 knockdown attenuated pulmonary fibrosis via the regulatory network of lncRNA H19-miR-140-TGF-β/Smad3 signaling, and H19 and miR-140 might represent therapeutic targets and early diagnostic and prognostic biomarkers for patients with pulmonary fibrosis.

The impaired proteases and anti-proteases balance in Idiopathic Pulmonary Fibrosis

Idiopathic Pulmonary Fibrosis (IPF) is a devastating chronic, progressive and irreversible disease that remains refractory to current therapies. Matrix metalloproteinases (MMPs) and their inhibitors, tissue inhibitors of MMPs (TIMPs), have been implicated in the development of pulmonary fibrosis since decades. Coagulation signalling deregulation, which influences several key inflammatory and fibro-proliferative responses, is also essential in IPF pathogenesis, and a growing body of evidence indicates that Protease-Activated Receptors (PARs) inhibition in IPF may be promising for future evaluation. Therefore, proteases and anti-proteases aroused great biomedical interest over the past years, owing to the identification of their potential roles in lung fibrosis. During these last decades, numerous other proteases and anti-proteases have been studied in lung fibrosis, such as matriptase, Human airway trypsin-like protease (HAT), Hepatocyte growth factor activator (HGFA)/HGFA activator inhibitor (HAI) system, Plasminogen activator inhibitor (PAI)-1, Protease nexine (PN)-1, cathepsins, calpains, and cystatin C. Herein, we provide a general overview of the proteases and anti-proteases unbalance during lung fibrogenesis and explore potential therapeutics for IPF.

The role of whey acidic protein four-disulfide-core proteins in respiratory health and disease

Members of the whey acidic protein (WAP) or WAP four-disulfide-core (WFDC) family of proteins are a relatively under-explored family of low molecular weight proteins. The two most prominent WFDC proteins, secretory leukocyte protease inhibitor (SLPI) and elafin (or the precursor, trappin-2), have been shown to possess multiple functions including anti-protease, anti-bacterial, anti-viral and anti-inflammatory properties. It is therefore of no surprise that both SLPI and elafin/trappin-2 have been developed as potential therapeutics. Given the abundance of SLPI and elafin/trappin-2 in the human lung, most work in the area of WFDC research has focused on the role of WFDC proteins in protecting the lung from proteolytic attack. In this review, we will outline the current evidence regarding the expanding role of WFDC protein function with a focus on WFDC activity in lung disease as well as emerging data regarding the function of some of the more recently described WFDC proteins.

Lung fibrosis: drug screening and disease biomarker identification with a lung slice culture model and subtracted cDNA Library

Pulmonary fibrosis is a progressive and irreversible disorder with no appropriate cure. A practical and effective experimental model that recapitulates the disease will greatly benefit the research community and, ultimately, patients. In this study, we tested the lung slice culture (LSC) system for its potential use in drug screening and disease biomarker identification. Fibrosis was induced by treating rat lung slices with 1ng/ml TGF-β1 and 2.5μM CdCl2, quantified by measuring the content of hydroxyproline, and confirmed by detecting the expression of collagen type III alpha 1 (Col3α1) and connective tissue growth factor (CTGF) genes. The anti-fibrotic effects of pirfenidone, spironolactone and eplerenone were assessed by their capability to reduce hydroxyproline content. A subtractive hybridisation technique was used to create two cDNA libraries (subtracted and unsubtracted) from lung slices. The housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was employed to assess the subtraction efficiency of the subtracted cDNA library. Clones from the two libraries were sequenced and the genes were identified by performing a BLAST search on the NCBI GenBank database. Furthermore, the relevance of the genes to fibrosis formation was verified. The results presented here show that fibrosis was effectively induced in cultured lung slices, which exhibited significantly elevated levels of hydroxyproline and Col3α1/CTGF gene expression. Several inhibitors have demonstrated their anti-fibrotic effects by significantly reducing hydroxyproline content. The subtracted cDNA library, which was enriched for differentially expressed genes, was used to successfully identify genes associated with fibrosis. Collectively, the results indicate that our LSC system is an effective model for the screening of drug candidates and for disease biomarker identification.

Neutrophil elastase promotes myofibroblast differentiation in lung fibrosis

IPF is a progressive lung disorder characterized by fibroblast proliferation and myofibroblast differentiation. Although neutrophil accumulation within IPF lungs has been negatively correlated with outcomes, the role played by neutrophils in lung fibrosis remains poorly understood. We have demonstrated previously that NE promotes lung cancer cell proliferation and hypothesized that it may have a similar effect on fibroblasts. In the current study, we show that NE(-/-) mice are protected from asbestos-induced lung fibrosis. NE(-/-) mice displayed reduced fibroblast and myofibroblast content when compared with controls. NE directly both lung fibroblast proliferation and myofibroblast differentiation in vitro, as evidenced by proliferation assays, collagen gel contractility assays, and αSMA induction. Furthermore, αSMA induction occurs in a TGF-β-independent fashion. Treatment of asbestos-recipient mice with ONO-5046, a synthetic NE antagonist, reduced hydroxyproline content. Thus, the current study points to a key role for neutrophils and NE in the progression of lung fibrosis. Lastly, the study lends rationale to use of NE-inhibitory approaches as a novel therapeutic strategy for patients with lung fibrosis.

Low-dose paclitaxel ameliorates pulmonary fibrosis by suppressing TGF-β1/Smad3 pathway via miR-140 upregulation

Abnormal TGF-β1/Smad3 activation plays an important role in the pathogenesis of pulmonary fibrosis, which can be prevented by paclitaxel (PTX). This study aimed to investigate an antifibrotic effect of the low-dose PTX (10 to 50 nM in vitro, and 0.6 mg/kg in vivo). PTX treatment resulted in phenotype reversion of epithelial-mesenchymal transition (EMT) in alveolar epithelial cells (AECs) with increase of miR-140. PTX resulted in an amelioration of bleomycin (BLM)-induced pulmonary fibrosis in rats with reduction of the wet lung weight to body weight ratios and the collagen deposition. Our results further demonstrated that PTX inhibited the effect of TGF-β1 on regulating the expression of Smad3 and phosphorylated Smad3 (p-Smad3), and restored the levels of E-cadherin, vimentin and α-SMA. Moreover, lower miR-140 levels were found in idiopathic pulmonary fibrosis (IPF) patients, TGF-β1-treated AECs and BLM-instilled rat lungs. Through decreasing Smad3/p-Smad3 expression and upregulating miR-140, PTX treatment could significantly reverse the EMT of AECs and prevent pulmonary fibrosis of rats. The action of PTX to ameliorate TGF-β1-induced EMT was promoted by miR-140, which increased E-cadherin levels and reduced the expression of vimentin, Smad3 and p-Smad3. Collectively, our results demonstrate that low-dose PTX prevents pulmonary fibrosis by suppressing the TGF-β1/Smad3 pathway via upregulating miR-140.

Fra-1/AP-1 transcription factor negatively regulates pulmonary fibrosis in vivo

The Fra-1/AP-1 transcription factor plays a key role in tumor epithelial cell progression; however, its role in pathogenic lung fibrosis remains unclear. In the present study, using a genetic approach (Fra-1 deficient mice), we have demonstrated a novel regulatory (protective) role for Fra-1 in lung fibrosis. We found greater levels of progressive interstitial fibrosis, characterized by increased levels of inflammation, collagen accumulation, and profibrotic and fibrotic gene expression in the lungs of Fra-1^Δ/Δ mice than in those of Fra-1^+/+ mice following bleomycin treatment. Fra-1 knockdown in human lung epithelial cells caused the upregulation of mesenchymal marker N-cadherin, concomitant with a downregulation of the epithelial phenotype marker E-cadherin, under basal conditions and in response to bleomycin and TGF-β1. Furthermore, Fra-1 knockdown caused an enhanced expression of type 1 collagen and the downregulation of collagenase (MMP-1 and MMP-13) gene expression in human lung epithelial cells. Collectively, our findings demonstrate that Fra-1 mediates anti-fibrotic effects in the lung through the modulation of proinflammatory, profibrotic and fibrotic gene expression, and suggests that the Fra-1 transcription factor may be a potential target for pulmonary fibrosis, a progressive disorder with poor prognosis and treatment.

Relative α₁-anti-trypsin deficiency in systemic sclerosis

Objective. Neutrophil elastase is secreted by neutrophils during activation and circulates in the plasma where it can play a role in inflammation and fibrosis. This study examines the role of neutrophil elastase in SSc, a systemic CTD that is typified by vascular dysfunction, tissue fibrosis and inflammation.

Methods. Serum neutrophil elastase and α₁-anti-trypsin concentrations were assessed in SSc patients and healthy controls by ELISA. Serum neutrophil elastase activity was assessed by the elastase-dependent conversion of methoxy-succinyl-alanyl-alanyl-prolyl-valyl-p-nitroanilide to p-nitroanilide using a colourimetric assay. Elastase concentration and activity were correlated with clinical disease features.

Results. Serum neutrophil elastase concentration and activity were equivalent in patients and controls; however, in SSc serum, there was an increase in elastase activity for each unit of elastase concentration (P = 0.03). This was due to a decrease in serum α₁-anti-trypsin concentrations (P = 0.04). Serum elastase concentration (P = 0.03) and activity (P = 0.02) were significantly lower in RNP-positive patients and serum elastase concentrations were lower in ANA-positive patients (P = 0.003).

Conclusions. Relative deficiency in serum α₁-anti-trypsin concentrations in SSc could have important and pathogenically relevant effects since elastase has pro-inflammatory and pro-fibrotic roles. Elastase inhibitors are available in clinical practice and could represent potential therapeutic options in SSc.

Innate immunity and disorders of the female reproductive tract

Sexually transmitted infections, and their associated sequelae, such as tubal infertility, ectopic pregnancy and preterm labour, are a major worldwide health problem. Chlamydia trachomatis infection is thought to be the leading global cause of tubal infertility and tubal ectopic pregnancy. Preterm birth occurs in around 10% of all deliveries, and nearly 30% of preterm deliveries are associated with intrauterine infection. The mucosal innate immune system of the female reproductive tract has evolved to eliminate such sexually transmitted pathogens whilst maintaining its ability to accommodate specialized physiological functions that include menstruation, fertilization, implantation, pregnancy and parturition. The aim of this review was to describe the role and distribution of key mediators of the innate immune system, the natural antimicrobial peptides (secretory leukocyte protease inhibitor, elafin and the defensins) and the pattern recognition toll-like receptors in the normal female reproductive tract and in the context of these pathological processes.

Escape from the matrix: multiple mechanisms for fibroblast activation in pulmonary fibrosis

Lung fibrosis is a recognized feature of many chronic lung diseases and is central to the pathogenesis of idiopathic pulmonary fibrosis, a disease that carries a prognosis worse than many cancers. Current research into this condition is defining the key pathways of activation either in resident fibroblasts, matrix-producing cells derived from circulating fibrocytes, or epithelial cells that appear to transdifferentiate to fibroblast-like cells. The downstream signaling pathways are also being delineated as well as the gene interactions leading to altered cell phenotype. These studies have led to an appreciation that multiple pathways, including inflammatory and coagulation cascades, are involved in the pathogenesis of idiopathic pulmonary fibrosis. As these facts come to light, we are exploring promising new approaches to treat fibroses and halt the inexorable progression that is a feature of these disorders. This article reviews these findings and our current concepts of the key molecular events leading to tissue damage and excessive matrix deposition in lung fibrosis. It also highlights the need for new studies to delineate alternative pathogenetic mechanisms and integrate these pathways so we have a framework to better understand their importance in individual patients.

The bleomycin animal model: a useful tool to investigate treatment options for idiopathic pulmonary fibrosis?

Different animal models of pulmonary fibrosis have been developed to investigate potential therapies for idiopathic pulmonary fibrosis (IPF). The most common is the bleomycin model in rodents (mouse, rat and hamster). Over the years, numerous agents have been shown to inhibit fibrosis in this model. However, to date none of these compounds are used in the clinical management of IPF and none has shown a comparable antifibrotic effect in humans. We performed a systematic review of publications on drug efficacy studies in the bleomycin model to evaluate the value of this model regarding transferability to clinical use. Between 1980 and 2006 we identified 240 experimental studies describing beneficial antifibrotic compounds in the bleomycin model. 222 of those used a preventive regimen (drug given < or =7 days after last bleomycin application), only 13 were therapeutic trials (>7 days after last bleomycin application). In 5 studies we did not find enough details about the timing of drug application to allow inter-study comparison. It is critical to distinguish between drugs interfering with the inflammatory and early fibrogenic response from those preventing progression of fibrosis, the latter likely much more meaningful for clinical application. All potential antifibrotic compounds should be evaluated in the phase of established fibrosis rather than in the early period of bleomycin-induced inflammation for assessment of its antifibrotic properties. Further care should be taken in extrapolation of drugs successfully tested in the bleomycin model due to partial reversibility of bleomycin-induced fibrosis over time. The use of alternative and more robust animal models, which better reflect human IPF, is warranted.

Relationships between early inflammatory response to bleomycin and sensitivity to lung fibrosis: a role for dipeptidyl-peptidase I and tissue inhibitor of metalloproteinase-3?

RATIONALE

Different sensitivities to profibrotic compounds such as bleomycin are observed among mouse strains.

OBJECTIVES

To identify genetic factors contributing to the outcome of lung injury.

METHODS

Physiological comparison of C57BL/6 (sensitive) and BALB/c (resistant) mice challenged by intratracheal bleomycin instillation revealed several early differences: global gene expression profiles were thus established from lungs derived from the two strains, in the absence of any bleomycin administration.

MEASUREMENTS AND MAIN RESULTS

Expression of 25 genes differed between the two strains. Among them, two molecules, not previously associated with pulmonary fibrosis, were identified. The first corresponded to dipeptidyl-peptidase I (DPPI), a cysteine peptidase (also known as cathepsin C) essential for the activation of serine proteinases produced by immune/inflammatory cells. The second corresponded to tissue inhibitor of matrix metalloproteinase-3, which also inhibits members of the ADAM (a disintegrin and metalloproteinase) family, such as the tumor necrosis factor-converting enzyme. In functional studies performed in the bleomycin-induced lung fibrosis model, the level of expression of these two genes was closely correlated with specific early events associated with lung fibrosis, namely activation of polymorphonuclear neutrophil-derived serine proteases and tumor necrosis factor-alpha-dependent inflammatory syndrome. Surprisingly, genetic deletion of DPPI in the context of a C57BL/6 genetic background did not protect against bleomycin-mediated fibrosis, suggesting additional function(s) for this key enzyme.

CONCLUSIONS

This study highlights the importance of the early inflammatory events that follow bleomycin instillation in the development of lung fibrosis, and describes for the first time the roles that DPPI and tissue inhibitor of matrix metalloproteinase-3 may play in this process.

Development of affinity chromatography using a bioactive peptide as a ligand

By repeatedly introducing hydrophilic polyethylene glycol (PEG) spacer (2) onto affinity resin bearing a bioactive peptide (1/2 secretory leukocyte protease inhibitor, 1/2SLPI) as a ligand, the adsorption of nonspecific binding proteins was effectively reduced and the purification efficacy of elastase, which is one of the target molecules for 1/2SLPI, from a protein mixture was improved. Moreover, using this resin, we also successfully detected L-plastin, as an endogenous target molecule for SLPI, from HL-60 cell lysate.

SLPI and elafin: one glove, many fingers

Elafin and SLPI (secretory leucocyte protease inhibitor) have multiple important roles both in normal homoeostasis and at sites of inflammation. These include antiprotease and antimicrobial activity as well as modulation of the response to LPS (lipopolysaccharide) stimulation. Elafin and SLPI are members of larger families of proteins secreted predominantly at mucosal sites, and have been shown to be modulated in multiple pathological conditions. We believe that elafin and SLPI are important molecules in the controlled functioning of the innate immune system, and may have further importance in the integration of this system with the adaptive immune response. Recent interest has focused on the influence of inflamed tissues on the recruitment and phenotypic modulation of cells of the adaptive immune system and, indeed, the local production of elafin and SLPI indicate that they are ideally placed in this regard. Functionally related proteins, such as the defensins and cathelicidins, have been shown to have direct effects upon dendritic cells with potential alteration of their phenotype towards type I or II immune responses. This review addresses the multiple functions of elafin and SLPI in the inflammatory response and discusses further their roles in the development of the adaptive immune response.

Is neutrophil elastase the missing link between emphysema and fibrosis? Evidence from two mouse models

BACKGROUND

The separation of emphysema from fibrosis is not as clear-cut as it was thought in early studies. These two pathologies may be present at the same time in human lungs and in mice either instilled with elastolytic enzymes or bleomycin or exposed to cigarette-smoke. According to a current view, emphysema originates from a protease/antiprotease imbalance, and a role for antiproteases has also been suggested in the modulation of the fibrotic process. In this study we investigate in experimental animal models of emphysema and fibrosis whether neutrophil elastase may constitute a pathogenic link between these two pathologies.

METHODS

This study was done in two animal models in which emphysema and fibrosis were induced either by bleomycin (BLM) or by chronic exposure to cigarette-smoke. In order to assess the protease-dependence of the BLM-induced lesion, a group mice was treated with 4-(2-aminoethyl)-benzenesulfonyl fluoride hydrochloride, a serine proteinase inhibitor active toward neutrophil elastase. Lungs from each experimental group were used for the immunohistochemical assessment of transforming growth factor-beta (TGF-beta) and transforming growth factor-alpha (TGF-alpha) and for determination of the mean linear intercept as well as the percent volume densities of fibrosis and of emphysematous changes. Additionally, the lungs were also assessed for desmosine content and for the determination of elastase levels in the pulmonary interstitium by means of immunoelectron microscopy.

RESULTS

We demonstrate that in BLM-treated mice (i) the development of elastolytic emphysema precedes that of fibrosis; (ii) significant amount of elastase in alveolar interstitium is associated with an increased expression of TGF-beta and TGF-alpha; and finally, (iii) emphysematous and fibrotic lesions can be significantly attenuated by using a protease inhibitor active against neutrophil elastase. Also, in a strain of mice that develop both emphysema and fibrosis after chronic cigarette-smoke exposure, the presence of elastase in alveolar structures is associated with a positive immunohistochemical reaction for reaction for both TGF-beta and TGF-alpha.

CONCLUSION

The results of the present study strongly suggest that neutrophil elastase may represent a common pathogenic link between emphysema and fibrosis. Proteases and in particular neutrophil elastase could act as regulatory factors in the generation of soluble cytokines with mitogenic activity for mesenchymal cells resulting either in emphysema or in fibrosis or both.

Oxidative stress in pulmonary fibrosis: a possible role for redox modulatory therapy

Idiopathic ulmonary fibrosis (histopathology of usual interstitial pneumonia) is a progressive lung disease of unknown etiology. No treatment has been shown to improve the prognosis of the patients with this disease. Recent evidence, including the observations that the patients with idiopathic pulmonary fibrosis have higher levels of oxidant stress than control patients, and a recent multicenter European study examining the effect of the antioxidant N-acetylcysteine on the progression of idiopathic pulmonary fibrosis suggest that the cellular redox state may play a significant role in the progression of this disease. These complex mechanisms include activation of growth factors as well as regulation of matrix metalloproteinases and protease inhibitors. Potential future approaches for the therapy of interstitial pulmonary fibrosis may involve synthetic agents able to modulate cellular redox state. Investigation into therapeutic approaches to inhibit oxidant-mediated reactions in the initiation and progression of pulmonary fibrosis may provide hope for the future treatment of this disease.

Beneficial effect of an inhibitor of leukocyte elastase (EPI-hNE-4) in presence of repeated lung injuries

Persistence of alveolar neutrophil influx and activation may enhance the fibrotic process after acute lung injury. On the other hand, elastase has an antimicrobial activity and could participate in neutrophil migration, both events being critically important in host defense, explaining the controversial issue of therapeutic elastase inhibition in the setting of acute lung injury. We assessed the effect of a neutrophil elastase inhibitor, EPI-hNE-4, in single (bleomycin, 1.2 mg/rat intratracheally) and repeated (bleomycin, 1.2 mg/rat plus endotoxin and 1 mg/kg intratracheally 24 h later) lung injuries to assess the role of neutrophil in fibrosis. Subsequently, the effect of EPI-hNE-4 on bacterial clearance was evaluated during Pseudomonas aeruginosa-induced pneumonia. In the single injury model, despite a dramatic reduction of alveolar neutrophil influx with EPI-hNE-4 treatment, no significant inhibition of the decrease in respiratory system compliance, an index of lung fibrosis, was demonstrated at day 14. In the repeated injury model, EPI-hNE-4 treatment afforded a significant protective effect on compliance and alveolar inflammation at day 14. During bacterial pneumonia, EPI-hNE4 did not modify alveolar neutrophil recruitment or bacterial clearance from bronchoalveolar lavage fluid and lung homogenate. In conclusion, EPI-hNE-4, a specific inhibitor of leukocyte elastase, afforded a partial protective effect on the respiratory system compliance during repeated lung injuries, and had no detrimental effect during a gram-negative bacterial pneumonia.

C-type natriuretic peptide attenuates bleomycin-induced pulmonary fibrosis in mice

C-type natriuretic peptide (CNP) has been shown to play an important role in the regulation of vascular tone and remodeling. However, the physiological role of CNP in the lung remains unknown. Accordingly, we investigated whether CNP infusion attenuates bleomycin (BLM)-induced pulmonary fibrosis in mice. After intratracheal injection of BLM or saline, mice were randomized to receive continuous infusion of CNP or vehicle for 14 days. CNP infusion significantly reduced the total number of cells and the numbers of macrophages, neutrophils, and lymphocytes in bronchoalveolar lavage fluid. Interestingly, CNP markedly reduced bronchoalveolar lavage fluid IL-1beta levels. Immunohistochemical analysis demonstrated that CNP significantly inhibited infiltration of macrophages into the alveolar and interstitial regions. CNP infusion significantly attenuated BLM-induced pulmonary fibrosis, as indicated by significant decreases in Ashcroft score and lung hydroxyproline content. CNP markedly decreased the number of Ki-67-positive cells in fibrotic lesions of the lung, suggesting antiproliferative effects of CNP on pulmonary fibrosis. Kaplan-Meier survival curves demonstrated that BLM mice treated with CNP had a significantly higher survival rate than those given vehicle. These results suggest that continuous infusion of CNP attenuates BLM-induced pulmonary fibrosis and improves survival in BLM mice, at least in part by inhibition of pulmonary inflammation and cell proliferation.

Proteases and lung injury

OBJECTIVE

Acute respiratory distress syndrome (ARDS) represents an inflammatory process that is initiated by diverse systemic and/or pulmonary insults, resulting in a clinical syndrome of severe respiratory distress and refractory hypoxemia. Neutrophils and their cytotoxic products, including oxidants and proteases, such as elastase, have been implicated as playing a key role in the pathophysiology of ARDS. This article reviews some of the physiologic actions of proteases, specifically elastase, the evidence for neutrophil elastase involvement in ARDS, and the potential therapeutic use of neutrophil elastase inhibitors in lung injury.

DATA SOURCE

A review of published literature (original articles and reviews) in English from 1965 to 2002.

CONCLUSION

Although the data support a key role for neutrophil elastase in the pathogenesis of ARDS, further study is needed to fully define the actions of neutrophil elastase, and how these actions affect host functions, before we can exploit this knowledge for therapeutic benefit.

Bleomycin-induced pulmonary fibrosis is attenuated in gamma-glutamyl transpeptidase-deficient mice

To investigate repair mechanisms in bleomycin-induced pulmonary fibrosis, we used mice deficient in gamma-glutamyl transpeptidase (GGT-/-), a key enzyme in glutathione (GSH) and cysteine metabolism. Seventy-two hours after bleomycin (0.03 U/g), GGT-/- mice displayed a different inflammatory response to wild-type mice as judged by a near absence of neutrophils in lung tissue and bronchoalveolar lavage and a less pronounced rise in matrix metalloproteinase-9. Inflammation in GGT-/- mice consisted mainly of lymphocytes and macrophages. At 1 month, lungs from bleomycin-treated GGT-/- mice exhibited minimal areas of fibrosis compared with wild-type mice(light microscopy fibrosis index: 510 +/- 756 versus 1975 +/- 817, p < 0.01). Lung collagen content revealed a significant increase in bleomycin-treated wild-type (15.1 +/- 3.8 versus 8.5 +/- 0.7 microg hydroxy(OH)-proline/mg dry weight, p < 0.01) but not in GGT-/- (10.4 +/- 1.7 versus 8.8 +/- 0.8). Control lungs from GGT-/- showed a significant reduction of cysteine (0.03 +/- 0.005 versus 0.055 +/- 0.001, p < 0.02) and GSH levels (1.24 +/- 0.055 versus 1.79 +/- 0.065, p < 0.002). These values decreased after 72 hours of bleomycin in both GGT-/- and wild-type but reached their respective control values after 1 month. Supplementation with N-acetyl cysteine partially ameliorated the effects of GGT deficiency. These findings suggest that increased neutrophils and matrix metalloproteinase-9 during the early inflammatory response and adequate thiol reserves are key elements in the fibrotic response after bleomycin-induced pulmonary injury.

Effects of secretory leukocyte protease inhibitor on the tumor necrosis factor-alpha production and NF-kappaB activation of lipopolysaccharide-stimulated macrophages

It has been reported that lipopolysaccharide (LPS)-hyporesponsiveness of macrophages (Mphis) of C3H/HeJ mice with a mutated Lps gene (Lps(d)) is related to high-level expression of secretory leukocyte protease inhibitor (SLPI) in response to LPS, causing suppression of NF-kappaB activation and tumor necrosis factor-alpha (TNF-alpha) production. We thus examined the effects of SLPI on the TNF-alpha production by LPS-stimulated Mphis. Neither intact SLPI nor half-sized SLPI (1/2 SLPI) down-regulated Mphi TNF-alpha production. 1/2 SLPI weakly increased Mphi TNF-alpha production in response to LPS signaling and potentiated the LPS-induced activation of NF-kappaB, especially the binding of p65-p50 heterodimers to the DNA kappaB sites, suggesting that LPS-hyporesponsiveness of Lps(d) Mphis is not due to the overexpression of SLPI.

Fourteen-membered ring macrolides inhibit vascular cell adhesion molecule 1 messenger RNA induction and leukocyte migration: role in preventing lung injury and fibrosis in bleomycin-challenged mice

BACKGROUND AND OBJECTIVE

Although the pathogenesis of interstitial pneumonia and pulmonary fibrosis are not well understood, it has been reported that inflammatory cells, especially neutrophils, and the injurious substances produced by them play important roles in the progression of interstitial pneumonia and subsequent fibrosis. Erythromycin and other 14-membered ring macrolides (14-MRMLs) have been reported to improve the survival of patients with diffuse panbronchiolitis by antineutrophil and several other anti-inflammatory mechanisms. The present study was undertaken to investigate the effects of 14-MRMLs on an experimental model of bleomycin-induced acute lung injury and subsequent fibrosis in mice.

METHODS

Bleomycin was administered IV to ICR mice. At 28 days after bleomycin injection, fibrotic foci were histologically observed in left lung tissues, and hydroxyproline content in right lung tissues was chemically analyzed. The inhibitory effects of 14-MRMLs were assessed by overall comparison between control (normal saline solution [NS] alone), untreated (bleomycin alone), and treated (bleomycin plus 14-MRMLs) groups. For evaluation of early-phase inflammation, cell populations in BAL fluid and induction of messenger RNA (mRNA) of adhesion molecules (E-selectin, P-selectin, intercellular adhesion molecule 1 [ICAM-1], and vascular cell adhesion molecule 1 [VCAM-1]) in lung tissues were examined at 0 to 13 days after bleomycin treatment. These parameters were also compared with those for the control (NS alone), 14-MRML untreated (bleomycin alone), and 14-MRML pretreated (bleomycin plus 14-MRML pretreated) groups.

RESULTS

Bleomycin-induced pulmonary fibrosis was inhibited by erythromycin and other 14-MRMLs on day 28 after bleomycin injection in ICR mice, especially those pretreated with 14-MRMLs. Hydroxyproline content in lung tissues was also decreased in the 14-MRML-pretreated groups. The number of neutrophils in BAL fluid significantly increased, with two peaks at 1 day and 9 days (from 6 to 11 days) after bleomycin administration. 14-MRMLs significantly inhibited both peaks of neutrophil infiltration into the airspace. Changes in mRNA expression of adhesion molecules (E-selectin, P-selectin, ICAM-1, VCAM-1) were associated with leukocyte migration into the airspace. 14-MRMLs clearly inhibited the induction of VCAM-1 mRNA, and tended to attenuate that of ICAM-1 mRNA, but inhibited the induction of neither E-selectin mRNA nor P-selectin mRNA.

CONCLUSION

These findings indicate that attenuation of inflammatory cell migration into the airspace by 14-MRMLs, especially of neutrophils and macrophages, resulted in inhibition of lung injury and subsequent fibrosis. 14-MRMLs clearly attenuated the expression of VCAM-1 mRNA during the early phase of bleomycin-induced lung injury, and this might be one mechanism of inhibition of neutrophil and macrophage migration into the airspace by 14-MRMLs. This may be one mechanism of the anti-inflammatory and antifibrotic effects of 14-MRMLs. These findings suggest that prophylactic administration of 14-MRMLs may be clinically efficacious in preventing acute exacerbation of interstitial pneumonia and acute lung injury.

P-selectin upregulation in bleomycin induced lung injury in rats: effect of N-acetyl-L-cysteine

BACKGROUND

A number of adhesion molecules are involved in the process of neutrophil infiltration into the lung. P-selectin is one of these neutrophil-endothelial cell adhesion molecules. A study was undertaken to examine the involvement of P-selectin in the development of bleomycin induced inflammation and the ability of N-acetyl-L-cysteine to reduce the potential expression of this selectin in rats.

METHODS

N-acetyl-L-cysteine (3 mmol/kg po) was administered daily for seven days prior to bleomycin administration (2.5 U/kg). The kinetics of P-selectin expression and the effect of N-acetyl-L-cysteine after bleomycin treatment were measured using radiolabelled antibodies. P-selectin localisation was evaluated by immunohistochemistry and neutrophil infiltration was assessed by myeloperoxidase activity.

RESULTS

Bleomycin administration resulted in an upregulation of P-selectin at 1 hour, returning to baseline at 3 hours. Myeloperoxidase activity showed a significant increase at 6 hours after bleomycin administration that lasted for 3 days. N-acetyl-L-cysteine treatment completely prevented these increases.

CONCLUSION

Upregulation of P-selectin in the lung is associated with neutrophil recruitment in response to bleomycin. The beneficial effect of N-acetyl-L-cysteine on bleomycin induced lung injury may be explained in part by the prevention of neutrophil recruitment in the inflammatory stage of the disease.

[Attenuated mRNA induction of molecules associated with neutrophil migration by 14-membered ring macrolides inhibits bleomycin induced acute lung injury in mice]

BACKGROUND

Although the pathogeneses of interstitial pneumonia are not well understood, it has been reported that inflammatory cells, especially neutrophils, and their injurious substances play important roles in the progression of interstitial pneumonia. Erythromycin and other 14-membered ring macrolides (14-MRMLs) have been reported to inhibit chronic airway inflammation by mechanisms of anti-neutrophil and several other anti-inflammatory activities. The present study was undertaken to investigate the effects and mechanisms of 14-MRMLs (erythromycin: EM; clarithromycin: CAM; roxithromycin: RXM) on an experimental model of bleomycin (BLM) -induced acute lung injury in mice.

METHODS

BLM was administered intravenously to ICR mice. For the evaluation of early-phase inflammation, cell populations in broncho-alveolar lavage fluid (BALF) and induction of mRNA of adhesion molecules (E-selectin, P-selectin, ICAM-1, VCAM-1) and TNF-alpha tested by RT-PCR in lung tissues were examined at 0 to 13 days after BLM. These parameters were also compared with those of the control (NS alone), 14-MRMLs-untreated (BLM alone) and-pre-treated (BLM+pre 14-MRMLs) groups.

RESULTS

The number of neutrophils, macrophages, and lymphocytes significantly increased in BAL. Neutrophils especially increased with two peaks after BLM administration. 14-MRMLs significantly inhibited both peaks of neutrophil. The increase in number of macrophages in BALF was significantly attenuated by EM and RXM, and slightly attenuated by CAM. Number of lymphocytes in BALF was significantly attenuated by EM and CAM, and slightly attenuated by RXM. Changes in mRNA expression of E-selectin, P-selectin, ICAM-1, VCAM-1, and TNF-alpha were associated with the number of neutrophils migrating into the airspace. 14-MRMLs clearly inhibited the induction of VCAM-1 mRNA, and tended to attenuate the induction of ICAM-1 and TNF-alpha mRNA, but did not inhibit the induction of E-selectin and P-selectin mRNA.

DISCUSSION

These findings show that 14-MRMLs clearly attenuated the expression of VCAM-1mRNA, and tended to attenuate the induction of ICAM-1 and TNF-alpha mRNA, and subsequently inhibited leucocyte, especially neutrophil migration into the airspace during the early phase of BLM-induced lung injury and finally inhibited lung fibrosis. This might be one potent mechanism of the anti-inflammatory effects of 14-MRMLs in BLM-induced acute lung injury. The findings suggest that prophylactic administration of 14-MRMLs may be clinically efficacious in preventing acute exacerbation of interstitial pneumonia and acute lung injury.

Protection against acute lung injury by intravenous or intratracheal pretreatment with EPI-HNE-4, a new potent neutrophil elastase inhibitor

Excessive accumulation of active neutrophil elastase (NE) in pulmonary fluids and tissues of patients with cystic fibrosis (CF) is thought to act on the lungs, compromising their structure and function. The aim of this study was to investigate the in vitro and in vivo protective effect of a new, rapidly acting, potent (Ki = 5.45 x 10(-12) M and Kon = 8 x 10(6) M(-1) s(-1)) and specific human NE inhibitor, EPI-HNE-4, engineered from the Kunitz domain. The results demonstrated that this inhibitor was able to (i) effectively inhibit in vitro the high levels of active NE present in a medium as complex as sputum from children with CF, with a measured IC(50) equal or close to the calculated IC(50) in 60% of cases, and (ii) almost completely block (91%) the N-formyl-methionine-leucine-phenylalanine-induced migration of purified human neutrophils across a Matrigel basement membrane. Intratracheal administration (250, 175, or 100 microg per rat) of the inhibitor 5 min before instillation of pure human NE (HNE) (150 microg per rat) to rats induced effective, dose-dependent protection of the lungs, 4 h later, from hemorrhage, serum albumin leakage, residual active NE, and discrete neutrophil influx in air spaces induced by instillation of pure HNE. Intravenous administration (3 mg per rat) of EPI-HNE-4, 15 min before instillation of the soluble fraction of pooled sputum (delivering 120 microg of active NE per rat) from children with CF, effectively reduced (64%), 4 h later, the massive neutrophil influx induced by sputum instillation. Overall, these data strongly suggest that associated aerosol and systemic administration of EPI-HNE-4 would be beneficial in the treatment of CF.

Genetic deficiency of alpha1-PI in mice influences lung responses to bleomycin

It has recently been suggested that proteinase inhibitors modulate the fibrotic response in the lung. This study investigated the development of bleomycin-induced pulmonary changes in pallid mice, deficient in serum alpha1-proteinase inhibitor, and with a lower elastase inhibitory capacity, and in congenic C57Bl/6J mice. Male pallid and C57Bl/6J mice received a single intratracheal instillation of either saline or bleomycin. The investigation was carried out by means of biochemical, morphological and morphometrical methods. In both strains, 21 and 72 h after bleomycin, the lungs showed foci of inflammatory cell infiltration associated with emphysema. Fibrosis developed with time after bleomycin. At 14 days fibrosis affected 23.46+/-9.48% (mean +/- SD) and 40.62+/-13.34% (p < 0.01) of the lungs of C57Bl/6J and pallid mice, respectively. Emphysema affected 3.68+/-3.11% and 12.57+/-4.13% (p<0.01) of lung in C57Bl/6J and pallid mice, respectively. In C57Bl/6J mice bleomycin increased lung hydroxyproline content by 34% and desmosine content by 44% (p < 0.01 for both). In pallid mice these increases were only 21% (p < 0.01) and 6% which may reflect parenchymal loss. Thus, the lung destructive response (emphysema) and the subsequent proliferative reaction (fibrosis) to bleomycin are potentiated in alpha1-proteinase inhibitor deficiency.

Secretory leukoprotease inhibitor augments hepatocyte growth factor production in human lung fibroblasts

Secretory leukoprotease inhibitor (SLPI), an 11.7-kD nonglycosylated serine protease inhibitor, is produced and released into the fluids of mucosal surfaces including human lung. It comprises two domains with homologous amino acid sequences: the N-terminal domain possessing antibacterial activity, and the C-terminal domain with antiprotease activity. Here we report the positive regulation of hepatocyte growth factor (HGF) production in human lung fibroblasts exerted by SLPI or its C-terminal domain under physiologic concentrations (1 to 10 microM). This HGF production by SLPI was unaffected by the addition of interleukin (IL)-1 receptor antagonist. In contrast, human skin fibroblasts exerted no SLPI-stimulated increase in HGF production, despite the fact that IL-1beta increased HGF production with an intensity similar to that of human lung fibroblasts. Both the time-course and dose-response studies in human lung fibroblasts revealed that the induction of HGF messenger RNA (mRNA) and protein occurred in parallel, indicating that the mechanism existed at the steady-state mRNA level. A synthetic elastase inhibitor failed to induce HGF, but alpha(1)-antitrypsin also stimulated HGF production in lung fibroblasts. Inactivation of the antiprotease activity of SLPI or its C-terminal domain by an oxidizing agent (N-chlorosuccinimide) abolished their stimulatory effect on HGF production. These findings demonstrate that SLPI exerts a novel HGF induction and functions as an anti-inflammatory and regenerative factor in addition to its role in protease inhibition.

Effects of secretory leucocyte protease inhibitor on the production of the anti-inflammatory cytokines, IL-10 and transforming growth factor-beta (TGF-beta), by lipopolysaccharide-stimulated macrophages

We studied the effects of secretory leucocyte protease inhibitor (SLPI) on the production of the anti-inflammatory cytokines, IL-10 and TGF-beta, by lipopolysaccharide (LPS)-stimulated macrophages, using half-sized SLPI (1/2 SLPI) containing the C-terminal domain (Arg58-Ala107). ELISA testing of macrophage culture fluids showed a temporary production of IL-10 by the macrophages in the early phase (24 h) after LPS stimulation at low (1 ng/ml) or high (10 microg/ml) concentrations. On the other hand, TGF-beta production was initiated after day 3 and progressively increased. 1/2 SLPI significantly increased IL-10 and TGF-beta production by macrophages in response to a low dose as well as a high dose of LPS. Reverse transcription-polymerase chain reaction analysis showed that 1/2 SLPI caused a significant increase in the expression of both IL-10 and TGF-beta mRNAs by LPS-stimulated macrophages. Thus, although the profile of macrophage TGF-beta production by LPS-stimulated macrophages is markedly different from that of their IL-10 production, SLPI causes an up-regulation of the production of these anti-inflammatory cytokines by LPS-stimulated macrophages.

Roles of ICAM-1 for abnormal leukocyte recruitment in the microcirculation of bleomycin-induced fibrotic lung injury

To assess the importance of endothelial intercellular adhesion molecule-1 (ICAM-1) in microvascular leukocyte kinetics in diseased lungs, we investigated the transitional changes in ICAM-1 expression, vascular diameter, and leukocyte behavior in rat pulmonary microcirculation during the development of acute lung injury (ALI) and chronic fibrosis (FIB) evoked by bleomycin (BLM). Observations were made in the isolated perfused lung with a real-time confocal laser luminescence microscope. Microvascular cell kinetics were evaluated by measuring the behavior of fluorescence- labeled leukocytes and erythrocytes in the presence or absence of anti-ICAM-1 monoclonal antibody (1A29). Arteriolar ICAM-1 showed little change at any time after BLM treatment. Venular ICAM-1 was first enhanced at the initial phase of ALI followed by the second upregulation at the early phase of FIB. Capillary ICAM-1 showed a sustained increase at both ALI and FIB. Arteriolar and venular diameters were not altered but capillary diameter decreased during ALI and early FIB stages. Although firm adherence of leukocytes to arteriolar and venular walls was not observed, rolling leukocytes were increased in venules both at the initial phase of ALI and at the early phase of FIB. The leukocyte rolling in venules correlated well with transitional changes in ICAM-1 and was inhibited by 1A29. Sustained entrapment of leukocytes in capillaries was attributed to changes in vascular diameter as well as augmented ICAM-1. In conclusion, ICAM-1 plays an important role in microvascular leukocyte recruitment in both ALI and FIB in the BLM-injured lung.

Role of E-selectin in bleomycin induced lung fibrosis in mice

BACKGROUND

Bleomycin (BLM), a well known anti-cancer drug, often causes acute lung injury and fibrosis by mechanisms that are not well understood. It is suspected that some proteases and active oxygen species generated from inflammatory cells cause the lung injury and subsequent lung fibrosis. It was therefore hypothesised that inhibition of adhesion of inflammatory cells to the endothelium might prevent these developments.

METHODS

BLM (100 mg/kg) was injected into the tail veins of ICR mice to evaluate the induction of E-selectin, an adhesion molecule known to induce neutrophil attachment on endothelial cells. E-selectin mRNA induction was detected by reverse transcriptase polymerase chain reaction (RT-PCR). The myeloperoxidase (MPO) activities in the lung tissues of BLM treated and control mice were compared to evaluate neutrophil infiltration. Pathological changes in the lungs of soluble E-selectin transgenic mice (TG) and their TG negative (non-TG) littermates after BLM treatment were also compared. Serum samples of TG mice and non-TG mice were tested for their ability to block the binding of sialyl Lewis(x) to recombinant E-selectin in vitro.

RESULTS

E-selectin mRNA was maximally induced at six hours after BLM treatment in the ICR mice. The soluble form of E-selectin which can competitively inhibit the binding of sialylated antigens on inflammatory cells to E- and P-selectins on the endothelium was detected in the serum of TG mice. BLM induced lung fibrosis occurred in non-TG mice but not in TG mice. This result confirms the finding that the serum of TG mice inhibits the binding of sialyl Lewis(x) to E-selectin in vitro.

CONCLUSION

E-selectin plays an essential role in BLM induced lung fibrosis through the induction of neutrophil and other inflammatory cell accumulation, and soluble E-selectin may be of use in the prophylactic treatment of lung fibrosis.

Regulatory Effects of Endogenous Protease Inhibitors in Acute Lung Inflammatory Injury

Inflammatory lung injury is probably regulated by the balance between proteases and protease inhibitors together with oxidants and antioxidants, and proinflammatory and anti-inflammatory cytokines. Rat tissue inhibitor of metalloprotease-2 (TIMP-2) and secreted leukoprotease inhibitor (SLPI) were cloned, expressed, and shown to be up-regulated at the levels of mRNA and protein during lung inflammation in rats induced by deposition of IgG immune complexes. Using immunoaffinity techniques, endogenous TIMP-2 in the inflamed lung was shown to exist as a complex with 72- and 92-kDa metalloproteinases (MMP-2 and MMP-9). In inflamed lung both TIMP-2 and SLPI appeared to exist as enzyme inhibitor complexes. Lung expression of both TIMP-2 and SLPI appeared to involve endothelial and epithelial cells as well as macrophages. To assess how these endogenous inhibitors might affect the lung inflammatory response, animals were treated with polyclonal rabbit Abs to rat TIMP-2 or SLPI. This intervention resulted in significant intensification of lung injury (as revealed by extravascular leak of albumin) and substantially increased neutrophil accumulation, as determined by cell content in bronchoalveolar lavage (BAL) fluids. These events were correlated with increased levels of C5a-related chemotactic activity in BAL fluids, while BAL levels of TNF-α and chemokines were not affected by treatment with anti-TIMP-2 or anti-SLPI. The data suggest that endogenous TIMP-2 and SLPI dynamically regulate the intensity of lung inflammatory injury, doing so at least in part by affecting the generation of the inflammatory mediator, C5a.

Therapeutic effects of benzoxazinorifamycin KRM-1648 administered alone or in combination with a half-sized secretory leukocyte protease inhibitor or the nonsteroidal anti-inflammatory drug diclofenac sodium against Mycobacterium avium complex infection in mice

The effects of half-sized secretory leukocyte protease inhibitor or diclofenac sodium administered alone or in combination with the benzoxazinorifamycin KRM-1648 on the therapeutic efficacy of KRM-1648 against Mycobacterium avium complex (MAC) in mice were studied. Neither of the two anti-inflammatory drugs affected the efficacy of KRM-1648, while they exerted significant modulating effects on tumor necrosis factor alpha production by MAC-infected macrophages.

Pulmonary fibrosis correlates with duration of tissue neutrophil activation

The role of inflammatory cells such as neutrophil granulocytes in the pathogenesis of pulmonary scarring is unclear. We determined the metabolic activity of neutrophils with positron emission tomography (PET) to measure regional uptake of (18F)-2-fluoro-2-deoxy-D-glucose (18FDG) following its intravenous injection. Fibrogenic or nonfibrogenic substances were instilled into the right upper lobe of rabbit lungs. Time course and intensity of the 18FDG signal in the affected region varied markedly, depending on the stimulus. Time to peak signal (Tmax) and rate constant for its decline (k) for the test substances were, respectively: C5a 10 h (Tmax), 0.045 +/- 0.030 h-1 (k); Streptococcus pneumoniae 15 h, 0.068 +/- 0.012 h-1; bleomycin 28 h, 0.002 +/- 0.001 h-1; microcrystalline silica (microXSiO2), 90 h, 0.0012 +/- 0.0007 h-1; amorphous silica (aSiO2), no response. Response to the nonfibrogenic agents C5a, S. pneumoniae and aSiO2 was brief or nonexistent, falling to baseline values within 3 d, whereas that to the fibrogenic agents bleomycin and microXSiO2 persisted for up to 4 wk. Neutrophil numbers in the lung were proportional to the 18FDG signal following C5a and S. pneumoniae, but not bleomycin and microXSiO2. Autoradiography of lungs following administration of (3H)-deoxyglucose [(3H)-DG] showed specific localization to neutrophils in all models. Thus, 18FDG uptake provides a remarkably specific measure of neutrophil activity in situ, and the development of pulmonary fibrosis may be related to persistence of this activity.

Preventive effect of erythromycin on experimental bleomycin-induced acute lung injury in rats

BACKGROUND

Erythromycin has been reported to have an inhibitory effect on chronic inflammatory airway disease and chronic infiltration of neutrophils into the airway. Bleomycin (BLM) often induces interstitial lung fibrosis following acute lung injury. A study was undertaken to investigate the effects of erythromycin (EM) on experimental bleomycin-induced acute lung injury in rats.

METHODS

Bleomycin-induced lung injury was assessed by light microscopic examination, measurement of neutrophil elastase activity and of the interleukin 8 (IL-8) content in bronchoalveolar lavage (BAL) fluid. The potential inhibitory effect of erythromycin was assessed by overall comparison of erythromycin untreated (BLM alone), concurrently treated (BLM + EM), and pretreated (BLM + pre-EM) groups.

RESULTS

The neutrophil count and concentration of neutrophil-derived elastase in BAL fluid were significantly different in the three groups. The morphological changes of lung injury were also less extensive in rats pretreated with erythromycin. However, these protective effects were not marked in the group concurrently treated with erythromycin. Moreover, the concentration of IL-8 in the BAL fluid tended to be less in the erythromycin treated groups; however, there were no significant differences between the bleomycin-treated groups.

CONCLUSION

Erythromycin exhibits a prophylactic effect on acute lung injury induced by intratracheal administration of bleomycin, which is possibly associated with a downregulation of neutrophil-derived elastase.

Effects of neutrophil elastase inhibitor on bleomycin-induced pulmonary fibrosis in mice

Neutrophils play an important role in the pathogenesis of idiopathic pulmonary fibrosis (IPF). To elucidate the possible involvement of neutrophil elastase (NE) in pulmonary fibrosis, we investigated the efficacy of a new specific NE inhibitor (ONO-5046 Na) in a murine model of human IPF, bleomycin-induced pulmonary fibrosis. Bronchoalveolar lavage (BAL) and histopathological analysis were performed on bleomycin-treated mice (group A), bleomycin and ONO-5046 Na-treated mice (group B), and saline control groups at 1, 15, and 29 d after the end of bleomycin treatment. At 29 d, multifocal fibrosis was observed in group A, whereas no fibrotic regions were observed in group B. Interleukin-1 beta and macrophage inflammatory protein-2 mRNA levels in BAL cells on day 1, and platelet-derived growth factor-A and insulin-like growth factor-1 mRNA levels on days 1 and 15, were significantly lower in group B than in group A. Thus, we demonstrated an inhibitory effect of ONO-5046. Na on pulmonary fibrosis in mice, indicating the involvement of NE in the pathogenesis of pulmonary fibrosis. We propose that this effect might be related to suppressed expression of particular cytokines in alveolar macrophages and that this specific NE inhibitor could be a novel therapeutic agent for IPF.