Inhibition of neutrophil elastase reduces lung injury and bacterial count in hamsters

Neutrophil Elastase Inhibition by Sivelestat (ONO-5046) Attenuates AngII-Induced Abdominal Aortic Aneurysms in Apolipoprotein E-Deficient Mice

BACKGROUND

Abdominal aortic aneurysm (AAA) is an arterial disease characterized by dilatation of the aortic wall. It has been suggested that neutrophil counts and neutrophil elastase activity are associated with AAA. We investigated whether a neutrophil elastase (NE) inhibitor, sivelestat (Siv), had a protective effect against angiotensin II (AngII)-induced AAAs.

METHODS

Male apolipoprotein E-deficient mice were assigned into three groups: Vehicle + saline, AngII + saline, and AngII + Siv. All mice were administered intraperitoneally with either Siv or vehicle twice daily after AngII infusion.

RESULTS

In the 4-week AngII infusion study, plasma NE concentration (P = 0.041) and its activity (P = 0.011) were elevated by AngII. These increases were attenuated by Siv (concentration:P = 0.010, activity:P = 0.027). Further, plasma elastase activity was closely correlated with aortic width (R = 0.6976, P < 0.001). In the 1-week AngII infusion study, plasma and tissue elastase activity increased by AngII (plasma:P = 0.034, tissue:P < 0.001), but were reduced by Siv (plasma:P = 0.014, tissue:P = 0.024). AngII increased aortic width (P = 0.011) but was attenuated by co-administration of Siv (P = 0.022). Moreover, Siv decreased the incidence of AAAs (P = 0.009). Elastin fragmentation induced by AngII was reduced by Siv. Many inflammatory cells that were either CD68 or Gr-1 positive were observed in the AngII + saline group, whereas few inflammatory cells were accumulated in the AngII + Siv group. MMP-2 and MMP-9 were enhanced by AngII, but were reduced by Siv. In vitro, MMP-2 activity was induced by human NE (medium:P < 0.001, cells:P = 0.001), which was attenuated by co-incubation of Siv in medium (P < 0.001) and protein of human aortic smooth muscle cells (P = 0.001).

CONCLUSIONS

Siv attenuated AngII-induced AAA through the inhibition of NE.

A comprehensive overview of investigational elastase inhibitors for the treatment of acute respiratory distress syndrome

INTRODUCTION

Excessive activity of neutrophil elastase (NE), the main enzyme present in azurophil granules in the neutrophil cytoplasm, may cause tissue injury and remodeling in various lung diseases, including acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), in which it is crucial to the immune response and inflammatory process. Consequently, NE is a possible target for therapeutic intervention in ALI/ARDS.

AREAS COVERED

The protective effects of several NE inhibitors in attenuating ALI/ARDS in several models of lung injury are described. Some of these NE inhibitors are currently in clinical development, but only sivelestat has been evaluated as a treatment for ALI/ARDS.

EXPERT OPINION

Preclinical research has produced encouraging information about using NE inhibitors. Nevertheless, only sivelestat has been approved for this clinical indication, and only in Japan and South Korea because of the conflicting results of clinical trials and likely also because of the potential adverse events. Identifying subsets of patients with ARDS most likely to benefit from NE inhibitor treatment, such as the hyperinflammatory phenotype, and using a more advanced generation of NE inhibitors than sivelestat could enable better clinical results than those obtained with elastase inhibitors.

Degradation of EGFR on lung epithelial cells by neutrophil elastase contributes to the aggravation of pneumococcal pneumonia

Streptococcus pneumoniae is the main cause of bacterial pneumonia. S. pneumoniae infection has been shown to cause elastase, an intracellular host defense factor, to leak from neutrophils. However, when neutrophil elastase (NE) leaks into the extracellular environment, it can degrade host cell surface proteins such as epidermal growth factor receptor (EGFR) and potentially disrupt the alveolar epithelial barrier. In this study, we hypothesized that NE degrades the extracellular domain of EGFR in alveolar epithelial cells and inhibits alveolar epithelial repair. Using SDS-PAGE, we showed that NE degraded the recombinant EGFR extracellular domain and its ligand EGF, and that the degradation of these proteins was counteracted by NE inhibitors. Furthermore, we confirmed the degradation by NE of EGFR expressed in alveolar epithelial cells in vitro. We show intracellular uptake of EGF and EGFR signaling were downregulated in alveolar epithelial cells exposed to NE, and found cell proliferation was inhibited in these cells These negative effects of NE on cell proliferation were abolished by NE inhibitors. Finally, we confirmed the degradation of EGFR by NE in vivo. Fragments of the extracellular domain of EGFR were detected in bronchoalveolar lavage fluid from pneumococcal pneumonia mice, and the percentage of cells positive for a cell proliferation marker Ki67 in lung tissue was reduced. In contrast, administration of an NE inhibitor decreased EGFR fragments in bronchoalveolar lavage fluid and increased the percentage of Ki67-positive cells. These findings suggest that degradation of EGFR by NE could inhibit the repair of alveolar epithelium and cause severe pneumonia.

Frontline workers: Mediators of mucosal immunity in community acquired pneumonia and COVID-19

The current COVID-19 pandemic has highlighted a need to further understand lung mucosal immunity to reduce the burden of community acquired pneumonia, including that caused by the SARS-CoV-2 virus. Local mucosal immunity provides the first line of defence against respiratory pathogens, however very little is known about the mechanisms involved, with a majority of literature on respiratory infections based on the examination of peripheral blood. The mortality for severe community acquired pneumonia has been rising annually, even prior to the current pandemic, highlighting a significant need to increase knowledge, understanding and research in this field. In this review we profile key mediators of lung mucosal immunity, the dysfunction that occurs in the diseased lung microenvironment including the imbalance of inflammatory mediators and dysbiosis of the local microbiome. A greater understanding of lung tissue-based immunity may lead to improved diagnostic and prognostic procedures and novel treatment strategies aimed at reducing the disease burden of community acquired pneumonia, avoiding the systemic manifestations of infection and excess morbidity and mortality.

The Yin and Yang of Pneumolysin During Pneumococcal Infection

Pneumolysin (PLY) is a pore-forming toxin produced by the human pathobiont Streptococcus pneumoniae, the major cause of pneumonia worldwide. PLY, a key pneumococcal virulence factor, can form transmembrane pores in host cells, disrupting plasma membrane integrity and deregulating cellular homeostasis. At lytic concentrations, PLY causes cell death. At sub-lytic concentrations, PLY triggers host cell survival pathways that cooperate to reseal the damaged plasma membrane and restore cell homeostasis. While PLY is generally considered a pivotal factor promoting S. pneumoniae colonization and survival, it is also a powerful trigger of the innate and adaptive host immune response against bacterial infection. The dichotomy of PLY as both a key bacterial virulence factor and a trigger for host immune modulation allows the toxin to display both "Yin" and "Yang" properties during infection, promoting disease by membrane perforation and activating inflammatory pathways, while also mitigating damage by triggering host cell repair and initiating anti-inflammatory responses. Due to its cytolytic activity and diverse immunomodulatory properties, PLY is integral to every stage of S. pneumoniae pathogenesis and may tip the balance towards either the pathogen or the host depending on the context of infection.

Clarithromycin Inhibits Pneumolysin Production via Downregulation of ply Gene Transcription despite Autolysis Activation

Streptococcus pneumoniae, the most common cause of community-acquired pneumonia, causes severe invasive infections, including meningitis and bacteremia. The widespread use of macrolides has been reported to increase the prevalence of macrolide-resistant S. pneumoniae (MRSP), thereby leading to treatment failure in patients with pneumococcal pneumonia. However, previous studies have demonstrated that several macrolides and lincosamides have beneficial effects on MRSP infection since they inhibit the production and release of pneumolysin, a pneumococcal pore-forming toxin released during autolysis. In this regard, we previously demonstrated that the mechanisms underlying the inhibition of pneumolysin release by erythromycin involved both the transcriptional downregulation of the gene encoding pneumolysin and the impairment of autolysis in MRSP. Here, using a cell supernatant of the culture, we have shown that clarithromycin inhibits pneumolysin release in MRSP. However, contrary to previous observations in erythromycin-treated MRSP, clarithromycin upregulated the transcription of the pneumococcal autolysis-related lytA gene and enhanced autolysis, leading to the leakage of pneumococcal DNA. On the other hand, compared to erythromycin, clarithromycin significantly downregulated the gene encoding pneumolysin. In a mouse model of MRSP pneumonia, the administration of both clarithromycin and erythromycin significantly decreased the pneumolysin protein level in bronchoalveolar lavage fluid and improved lung injury and arterial oxygen saturation without affecting bacterial load. Collectively, these in vitro and in vivo data reinforce the benefits of macrolides on the clinical outcomes of patients with pneumococcal pneumonia.

IMPORTANCE Pneumolysin is a potent intracellular toxin possessing multiple functions that augment pneumococcal virulence. For over 10 years, sub-MICs of macrolides, including clarithromycin, have been recognized to decrease pneumolysin production and release from pneumococcal cells. However, this study indicates that macrolides significantly slowed pneumococcal growth, which may be related to decreased pneumolysin release recorded by previous studies. In this study, we demonstrated that clarithromycin decreases pneumolysin production through downregulation of ply gene transcription, regardless of its inhibitory activity against bacterial growth. Additionally, administration of clarithromycin resulted in the amelioration of lung injury in a mouse model of pneumonia induced by macrolide-resistant pneumococci. Therefore, therapeutic targeting of pneumolysin offers a good strategy to treat pneumococcal pneumonia.

The Role of Neutrophils and Neutrophil Elastase in Pneumococcal Pneumonia

Streptococcus pneumoniae, also known as pneumococcus, is a Gram-positive diplococcus and a major human pathogen. This bacterium is a leading cause of bacterial pneumonia, otitis media, meningitis, and septicemia, and is a major cause of morbidity and mortality worldwide. To date, studies on S. pneumoniae have mainly focused on the role of its virulence factors including toxins, cell surface proteins, and capsules. However, accumulating evidence indicates that in addition to these studies, knowledge of host factors and host-pathogen interactions is essential for understanding the pathogenesis of pneumococcal diseases. Recent studies have demonstrated that neutrophil accumulation, which is generally considered to play a critical role in host defense during bacterial infections, can significantly contribute to lung injury and immune subversion, leading to pneumococcal invasion of the bloodstream. Here, we review bacterial and host factors, focusing on the role of neutrophils and their elastase, which contribute to the progression of pneumococcal pneumonia.

Proteolytic cleavage of HLA class II by human neutrophil elastase in pneumococcal pneumonia

Bacterial and viral respiratory infections can initiate acute lung injury and acute respiratory distress syndrome. Neutrophils and their granule enzymes, including neutrophil elastase, are key mediators of the pathophysiology of acute respiratory failure. Although intracellular neutrophil elastase functions as a host defensive factor against pathogens, its leakage into airway spaces induces degradation of host connective tissue components. This leakage disrupts host innate immune responses via proteolytic cleavage of Toll-like receptors and cytokines. Here, we investigated whether neutrophils possess proteases that cleave adaptive immune molecules. We found that expression of the human leukocyte antigen (HLA) class II molecule HLA-DP β1 was decreased in THP-1-derived macrophages treated with supernatants from dead neutrophils. This decreased HLA-DP β1 expression was counteracted by treatment with neutrophil elastase inhibitor, suggesting proteolytic cleavage of HLA-DP β1 by neutrophil elastase. SDS-PAGE showed that neutrophil elastase cleaved recombinant HLA-DP α1, -DP β1, -DQ α1, -DQ β1, -DR α, and -DR β1. Neutrophil elastase also cleaved HLA-DP β1 on extracellular vesicles isolated from macrophages without triggering morphological changes. Thus, leakage of neutrophil elastase may disrupt innate immune responses, antigen presentation, and T cell activation. Additionally, inhibition of neutrophil elastase is a potential therapeutic option for treating bacterial and viral pneumonia.

Treatment of severe pneumonia by hinokitiol in a murine antimicrobial-resistant pneumococcal pneumonia model

Streptococcus pneumoniae is often isolated from patients with community-acquired pneumonia. Antibiotics are the primary line of treatment for pneumococcal pneumonia; however, rising antimicrobial resistance is becoming more prevalent. Hinokitiol, which is isolated from trees in the cypress family, has been demonstrated to exert antibacterial activity against S. pneumoniae in vitro regardless of antimicrobial resistance. In this study, the efficacy of hinokitiol was investigated in a mouse pneumonia model. Male 8-week-old BALB/c mice were intratracheally infected with S. pneumoniae strains D39 (antimicrobial susceptible) and NU4471 (macrolide resistant). After 1 h, hinokitiol was injected via the tracheal route. Hinokitiol significantly decreased the number of S. pneumoniae in the bronchoalveolar lavage fluid (BALF) and the concentration of pneumococcal DNA in the serum, regardless of whether bacteria were resistant or susceptible to macrolides. In addition, hinokitiol decreased the infiltration of neutrophils in the lungs, as well as the concentration of inflammatory cytokines in the BALF and serum. Repeated hinokitiol injection at 18 h intervals showed downward trend in the number of S. pneumoniae in the BALF and the concentration of S. pneumoniae DNA in the serum with the number of hinokitiol administrations. These findings suggest that hinokitiol reduced bacterial load and suppressed excessive host immune response in the pneumonia mouse model. Accordingly, hinokitiol warrants further exploration as a potential candidate for the treatment of pneumococcal pneumonia.

Neutrophil elastase inhibitor (sivelestat) may be a promising therapeutic option for management of acute lung injury/acute respiratory distress syndrome or disseminated intravascular coagulation in COVID-19

WHAT IS KNOWN AND OBJECTIVE

This article summarizes the effects of sivelestat on acute lung injury/acute respiratory distress syndrome (ALI/ARDS) or ARDS with coagulopathy, both of which are frequently seen in patients with COVID-19.

COMMENT

COVID-19 patients are more susceptible to thromboembolic events, including disseminated intravascular coagulation (DIC). Various studies have emphasized the role of neutrophil elastase (NE) in the development of DIC in patients with ARDS and sepsis. It has been shown that NE inhibition by sivelestat mitigates ALI through amelioration of injuries in alveolar epithelium and vascular endothelium, as well as reversing the neutrophil-mediated increased vascular permeability.

WHAT IS NEW AND CONCLUSIONS

Sivelestat, a selective NE inhibitor, has not been evaluated for its possible therapeutic effects against SARS-CoV-2 infection. Based on its promising beneficial effects in underlying complications of COVID-19, sivelestat could be considered as a promising modality for better management of COVID-19-induced ALI/ARDS or coagulopathy.

Combination of sivelestat and N-acetylcysteine alleviates the inflammatory response and exceeds standard treatment for acetaminophen-induced liver injury

Hepatocyte death during acetaminophen (APAP) intoxication elicits a reactive inflammatory response, with hepatic recruitment of neutrophils and monocytes, which further aggravates liver injury. Neutrophil elastase (NE), secreted by activated neutrophils, carries degradative and cytotoxic functions and maintains a proinflammatory state. We investigated NE as a therapeutic target in acetaminophen-induced liver injury (AILI). C57BL/6 mice were administered a toxic dose of APAP, 2 h prior to receiving the NE inhibitor sivelestat, N-acetylcysteine (NAC), or a combination therapy, and were euthanized after 24 and 48 h. Upon APAP overdose, neutrophils and monocytes infiltrate the injured liver, accompanied by increased levels of NE. Combination therapy of NAC and sivelestat significantly limits liver damage, as evidenced by lower serum transaminase levels and less hepatic necrosis compared to mice that received APAP only, and this to a greater extent than NAC monotherapy. Lower hepatic expression of proinflammatory markers was observed in the combination treatment group, and flow cytometry revealed significantly less monocyte influx in livers from mice treated with the combination therapy, compared to untreated mice and mice treated with NAC only. The potential of NE to induce leukocyte migration was confirmed in vitro. Importantly, sivelestat did not impair hepatic repair. In conclusion, combination of NE inhibition with sivelestat and NAC dampens the inflammatory response and reduces liver damage following APAP overdose. This strategy exceeds the standard of care and might represent a novel therapeutic option for AILI.

Aggregatibacter actinomycetemcomitans induces detachment and death of human gingival epithelial cells and fibroblasts via elastase release following leukotoxin-dependent neutrophil lysis

Aggregatibacter actinomycetemcomitans is considered to be associated with periodontitis. Leukotoxin (LtxA), which destroys leukocytes in humans, is one of this bacterium's major virulence factors. Amounts of neutrophil elastase (NE), which is normally localized in the cytoplasm of neutrophils, are reportedly increased in the saliva of patients with periodontitis. However, the mechanism by which NE is released from human neutrophils and the role of NE in periodontitis is unclear. In the present study, it was hypothesized that LtxA induces NE release from human neutrophils, which subsequently causes the breakdown of periodontal tissues. LtxA-treatment did not induce significant cytotoxicity against human gingival epithelial cells (HGECs) or human gingival fibroblasts (HGFs). However, it did induce significant cytotoxicity against human neutrophils, leading to NE release. Furthermore, NE and the supernatant from LtxA-treated human neutrophils induced detachment and death of HGECs and HGFs, these effects being inhibited by administration of an NE inhibitor, sivelestat. The present results suggest that LtxA mediates human neutrophil lysis and induces the subsequent release of NE, which eventually results in detachment and death of HGECs and HGFs. Thus, LtxA-induced release of NE could cause breakdown of periodontal tissue and thereby exacerbate periodontitis.

Neutrophil Elastase Subverts the Immune Response by Cleaving Toll-Like Receptors and Cytokines in Pneumococcal Pneumonia

Excessive activation of neutrophils results in the release of neutrophil elastase (NE), which leads to lung injury in severe pneumonia. Previously, we demonstrated a novel immune subversion mechanism involving microbial exploitation of this NE ability, which eventually promotes disruption of the pulmonary epithelial barrier. In the present study, we investigated the effect of NE on host innate immune response. THP-1-derived macrophages were stimulated with heat-killed Streptococcus pneumoniae or lipopolysaccharide in the presence or absence of NE followed by analysis of toll-like receptor (TLR) and cytokine expression. Additionally, the biological significance of NE was confirmed in an in vivo mouse intratracheal infection model. NE downregulated the gene transcription of multiple cytokines in THP-1-derived macrophages through the cleavage of TLRs and myeloid differentiation factor 2. Additionally, NE cleaved inflammatory cytokines and chemokines. In a mouse model of intratracheal pneumococcal challenge, administration of an NE inhibitor significantly increased proinflammatory cytokine levels in bronchoalveolar lavage fluid, enhanced bacterial clearance, and improved survival rates. Our work indicates that NE subverts the innate immune response and that inhibition of this enzyme may constitute a novel therapeutic option for the treatment of pneumococcal pneumonia.

Streptococcus pneumoniae disrupts pulmonary immune defence via elastase release following pneumolysin-dependent neutrophil lysis

Streptococcus pneumoniae is a leading cause of bacterial pneumonia and is the principal cause of morbidity and mortality worldwide. Previous studies suggested that excessive activation of neutrophils results in the release of neutrophil elastase, which contributes to lung injury in severe pneumonia. Although both pneumococcal virulence factors and neutrophil elastase contribute to the development and progression of pneumonia, there are no studies analysing relationships between these factors. Here, we showed that pneumolysin, a pneumococcal pore-forming toxin, induced cell lysis in primary isolated human neutrophils, leading to the release of neutrophil elastase. Pneumolysin exerted minimal cytotoxicity against alveolar epithelial cells and macrophages, whereas neutrophil elastase induced detachment of alveolar epithelial cells and impaired phagocytic activity in macrophages. Additionally, activation of neutrophil elastase did not exert bactericidal activity against S. pneumoniae in vitro. P2X₇ receptor, which belongs to a family of purinergic receptors, was involved in pneumolysin-induced cell lysis. These findings suggested that infiltrated neutrophils are the primary target cells of pneumolysin, and that S. pneumoniae exploits neutrophil-elastase leakage to induce the disruption of pulmonary immune defences, thereby causing lung injury.

Manipulating the air-filled zebrafish swim bladder as a neutrophilic inflammation model for acute lung injury

Acute lung injury (ALI) and its more severe form, acute respiratory distress syndrome (ARDS), are life-threatening diseases that are associated with high mortality rates due to treatment limitations. Neutrophils play key roles in the pathogenesis of ALI/ARDS by promoting the inflammation and injury of the alveolar microenvironment. To date, in vivo functional approaches have been limited by the inaccessibility to the alveolar sacs, which are located at the anatomical terminal of the respiratory duct in mammals. We are the first to characterize the swim bladder of the zebrafish larva, which is similar to the mammalian lung, as a real-time in vivo model for examining pulmonary neutrophil infiltration during ALI. We observed that the delivery of exogenous materials, including lipopolysaccharide (LPS), Poly IC and silica nanoparticles, by microinjection triggered significant time- and dose-dependent neutrophil recruitment into the swim bladder. Neutrophils infiltrated the LPS-injected swim bladder through the blood capillaries around the pneumatic duct or a site near the pronephric duct. An increase in the post-LPS inflammatory cytokine mRNA levels coincided with the in vivo neutrophil aggregation in the swim bladder. Microscopic examinations of the LPS-injected swim bladders further revealed in situ injuries, including epithelial distortion, endoplasmic reticulum swelling and mitochondrial injuries. Inhibitor screening assays with this model showed a reduction in neutrophil migration into the LPS-injected swim bladder in response to Shp2 inhibition. Moreover, the pharmacological suppression and targeted disruption of Shp2 in myeloid cells alleviated pulmonary inflammation in the LPS-induced ALI mouse model. Additionally, we used this model to assess pneumonia-induced neutrophil recruitment by microinjecting bronchoalveolar lavage fluid from patients into swim bladders; this injection enhanced neutrophil aggregation relative to the control. In conclusion, our findings highlight the swim bladder as a promising and powerful model for mechanistic and drug screening studies of alveolar injuries.

[Levels of surfactant proteins A and D in bronchoalveolar lavage fluid of children with pneumonia and their relationships with clinical characteristics]

OBJECTIVE

To observe the levels of pulmonary surfactant proteins A and D (SP-A, SP-D) in bronchoalveolar lavage fluid (BALF) of children with pneumonia, and to explore their relationships with clinical characteristics.

METHODS

Thirty-five children with pneumonia were enrolled in this study. Differential cell counts were obtained by Countstar counting board. The levels of SP-A and SP-D in BALF were detected using ELISA.

RESULTS

In children with pneumonia, SP-D levels were significantly higher than SP-A levels (P<0.001). SP-D levels were negatively correlated with the neutrophil percentage in BALF (r(s)=-0.5255, P<0.01). SP-D levels in BALF in children with increased blood C-reactive protein levels (>8 mg/L) were significantly lower than in those with a normal level of C-reactive protein (P<0.05). Compared with those in children without wheezing, SP-D levels in children with wheezing were significantly lower (P<0.01). There was no correlation between SP-A levels and clinical characteristics.

CONCLUSIONS

SP-D levels in BALF are significantly higher than SP-A levels, and have a certain correlation with clinical characteristics in children with pneumonia. As a protective factor, SP-D plays a more important role than SP-A in regulating the immune and inflammatory responses.

Clinical utility of the neutrophil elastase inhibitor sivelestat for the treatment of acute respiratory distress syndrome

Acute respiratory distress syndrome is a serious condition that can arise following direct or indirect lung injury. It is heterogeneous and has a high mortality rate. Supportive care is the mainstay of treatment and there is no definitive pharmacological treatment as yet. Sivelestat is a neutrophil elastase inhibitor approved in Japan and the Republic of Korea for acute lung injury, including acute respiratory distress syndrome in patients with systemic inflammatory response syndrome. The aim of this review is to examine the clinical utility of sivelestat in different disease states, using data from nonclinical and clinical studies. In nonclinical studies, sivelestat appears to show benefit in acute lung injury without inhibiting the host immune defense in cases of infection. Clinical studies do not yet provide a clear consensus. Phase III and IV Japanese studies have shown improvements in pulmonary function, length of intensive care unit stay, and mechanical ventilation, but a non-Japanese multicenter study did not demonstrate sivelestat to have an effect on ventilator-free days or 28-day all-cause mortality. Evidence of improvement in various parameters, including duration of stay in intensive care, mechanical ventilation, the ratio of partial pressure of arterial oxygen and fraction of inspired oxygen (PaO₂/F_IO₂ ratio) ratio, and lung injury scores, has been shown in patients with sepsis or gastric aspiration, and following the surgical treatment of esophageal cancer. To date, there are no particular concerns regarding adverse events, and the available data do not suggest that sivelestat might worsen infections. One study has analyzed cost-effectiveness, finding that sivelestat may reduce costs compared with standard care. The currently available evidence suggests that sivelestat may show some benefit in the treatment of acute lung injury/acute respiratory distress syndrome, although large, randomized controlled trials are needed in specific pathophysiological conditions to explore these potential benefits.

Improving effect of Sivelestat on lipopolysaccharide-induced lung injury in rats

Sepsis causes neutrophil sequestration in the lung, which leads to acute lung injury (ALI). Neutrophil elastase (NE) is thought to play an important role in the pathogenesis of ALI. This study investigated whether Sivelestat, a specific NE inhibitor, can attenuate ALI induced by lipopolysaccharide (LPS). In vivo, 30 male Wistar rats were divided into three groups (n = 10 each groups) on the basis of the reagent used, which were subjected to LPS injection with or without Sivelestat treatments to induce ALI model. Lung injury was assessed by pulmonary histology, lung wet-weight to dry-weight (W/D) ratio, immunohistochemical analysis of intercellular adhesion molecule-1 (ICAM-1), the number of myeloperoxidase (MPO)-positive cells, and gene expression of ICAM-1. In vitro, pulmonary microvascular endothelial cells (PMVECs) were stimulated with LPS in the presence and absence of Sivelestat; nuclear factor-κB (NF-κB) p65 was measured by immunocytochemistry staining and Western blotting. Infusion of LPS induced lung injury, in vivo, as demonstrated by pulmonary edema with infiltration of neutrophils, the increase in lung W/D ratio, the number of MPO-positive cells and enhanced expression of ICAM-1 and ICAM-1 gene. In vitro, the significant increased release of NF-κB p65 and its subsequent translocation into the nucleus in PMVECs. In contrast, Sivelestat treatment significantly ameliorated the LPS-induced lung injury, as judged by the marked improvement in all these indices. These results indicated that inhibition of NE attenuated LPS-induced lung injury through an inhibition of the inflammatory signaling pathway, besides the direct inhibitory effect on NE.

Effects of sivelestat treatment on acute lung injury in paraquat-intoxicated rats

Lung injury is the main cause of death in acute paraquat (PQ) intoxication. Sivelestat (SV), a neutrophil elastase inhibitor, is effective in reducing inflammation in acute lung injury. The aim of this study was to examine the effect of SV on acute lung injury in PQ-intoxicated rats. Seven-week-old male Sprague-Dawley rats were randomly assigned to four groups: (1) control group (group N; n = 5); (2) PQ + normal saline (group P; n = 6); (3) normal saline + SV (group S; n = 6) and (4) PQ + SV (group PS; n = 6). SV treatment (intraperitoneally [i.p.], 20 mg/kg) was performed 30 minutes after PQ injection (i.p., 100 mg/kg), and injections were continued every hour for a total of five doses. One hour after the last treatment, blood samples were obtained for analysis of interleukin (IL)-6 and tumor necrosis factor alpha (TNF-α). Lung sections were stained with hematoxylin--eosin for light microscopic analysis. Neutrophil infiltration score of group PS was significantly lower than that of group P (p < 0.05). But, other scores and total score had no significant differences. IL-6 of group PS did not differ, compared to group P. In addition, there were no differences among the four groups. TNF-α of group PS was reduced, in comparison to the level of group P. SV attenuated neutrophil infiltration in PQ-induced acute lung injury in rats. In addition, systemic inflammation was partially suppressed with SV treatment, suppressing TNF-α production. These results suggest that SV reduces paraquat-induced lung injury, at least partially, by inhibiting neutrophil infiltration and TNF-α secretion.

Early administration of sivelestat, the neutrophil elastase inhibitor, in adults for acute lung injury following gastric aspiration

Gastric aspiration is the major cause of acute lung injury (ALI) and acute respiratory distress syndrome. Aspiration-induced ALI is believed to be, at least in part, facilitated by neutrophil-derived mediators and toxic molecules. We conducted a prospective cohort study based on the hypothesis that sivelestat, a specific neutrophil elastase inhibitor, is effective for treating ALI following gastric aspiration. Forty-four ALI patients who showed evidence of aspiration were observed within 12 h before intensive care unit admission and who had been mechanically ventilated within 12 h after admission were included in this study. Lung injury score (LIS) and PAO2/FiO2 (P/F) ratio on day 7 were defined as the primary outcomes of the study. Twenty-three patients were assigned to the sivelestat group and 21 to the control group. In univariate analyses, the proportions of patients with LIS lower than 1.0 on day 7 and a P/F greater than 300 on day 7 were significantly higher in the sivelestat group than in the control group (60.9% vs. 26.3%, P = 0.03; 87.0% vs. 36.8%, P = 0.001). In the logistic regression model, the use of sivelestat was an independent predictor for LIS lower than 1.0 on day 7 (relative risk, 7.4; 95% confidence interval [CI], 1.51-36.48) and for a P/F ratio higher than 300 on day 7 (relative risk, 18.5; 95% CI, 2.72-126.46). In the Cox proportional hazards model, the use of sivelestat was associated with a lower cumulative proportion of patients who received mechanical ventilation during the initial 14 days (hazard ratio, 2.6; 95% CI, 1.17-5.55).

Inhaled neutrophil elastase inhibitor reduces oleic acid-induced acute lung injury in rats

RATIONALE

Neutrophil elastases (NE) play an important role in the pathogenesis of acute lung injury (ALI). NE activities are significantly increased in serums and lungs of patients or animals with ALI. Intravenous infusion (IV) of Sivelestat, an NE inhibitor, can reduce ALI. Through inhalation, drugs reach lungs directly and in high concentration. We hypothesized that inhaled Sivelestat would alleviate oleic acid (OA)-induced ALI in rats.

METHODS

Rats were anesthetized and mechanically ventilated, and then ALI was induced by OA injection. One hour later, the animals were randomized to receive either Sivelestat (3 mg/kg/h) or saline inhalation. The effect of Sivelestat IV (3 mg/kg/h) was also investigated. All animals were ventilated and observed for 6 h.

RESULTS

OA injection increased NE activities in lung tissues and serums. The increase of NE activities in lung tissues and serums markedly reduced by 77%, and 29%, respectively, by the inhalation of Sivelestat; and 53.8%, and 80%, respectively, by Sivelestat IV. Additionally, inhaled Sivelestat resulted in ameliorated lung injury by reducing edema and infiltration of neutrophils in the lung, improved oxygenation and survival.

CONCLUSIONS

An over increased NE activity in lungs may play a vital effect in the pathogenesis of OA-induced ALI in rats. Topical application of nebulized Sivelestat, an NE inhibitor, may reduce OA-induced ALI in rats. Sivelestat inhalation can be developed as a novel treatment for ALI.

Polyphenol fatty acid esters as serine protease inhibitors: a quantum-chemical QSAR analysis

We investigated the ability of polyphenol fatty acid esters to inhibit the activity of serine proteases trypsin, thrombin, elastase and urokinase. Potent protease inhibition in micromolar range was displayed by rutin and rutin derivatives esterified with medium and long chain, mono- and polyunsaturated fatty acids (1e-m), followed by phloridzin and esculin esters with medium and long fatty acid chain length (2a-d, 3a-d), while unmodified compounds showed only little or no effect. QSAR study of the compounds tested provided the most significant parameters for individual inhibition activities, i.e. number of hydrogen bond donors for urokinase, molecular volume for thrombin, and solvation energy for elastase. According to the statistical analysis, the action of elastase inhibitors is opposed to those of urokinase and thrombin. Cluster analysis showed two groups of compounds: original polyphenols together with rutin esters with short fatty acid chain length and rutin esters with long fatty acid chain length.

In vivo efficacy of KRP-109, a novel elastase inhibitor, in a murine model of severe pneumococcal pneumonia

KRP-109 is a novel specific inhibitor of neutrophil elastase (NE). Various studies suggest that NE inhibitors reduce lung injury associated with systemic inflammatory response syndrome (SIRS). In this study, the efficacy of KRP-109 was examined using a murine model of severe pneumonia induced by Streptococcus pneumoniae (S. pneumoniae). Female mice (CBA/J, aged 5 weeks) were inoculated intranasally with penicillin-susceptible S. pneumoniae (ATCC49619 strain, 2.5 × 10(8) CFU/mouse). KRP-109 (30 or 50 mg/kg) or physiological saline as a control was administered intraperitoneally every 8 h beginning at 8 h after inoculation, and survival rate was evaluated over 7 days. Histopathological and bacteriological analyses of the lung, and bronchoalveolar lavage were performed at 48 h post-infection. The mice treated with KRP-109 (KRP-109 mice) tended to have higher survival rate than those given saline. The lung tissues of the KRP-109 mice had few neutrophils in the alveolar walls and less inflammation. Furthermore, KRP-109 decreased significantly total cell and neutrophil counts, and cytokine levels (interleukin 1β and macrophage inflammatory protein 2) in bronchoalveolar lavage fluid. Viable bacterial numbers in lung were not influenced by treatment of KRP-109. The present results indicate that KRP-109 reduces lung inflammation in a murine model, and that KRP-109 may be useful for the treatment of patients with severe pneumonia.

Reevaluation of the efficacy and safety of the neutrophil elastase inhibitor, Sivelestat, for the treatment of acute lung injury associated with systemic inflammatory response syndrome; a phase IV study

INTRODUCTION

Sivelestat, a neutrophil elastase inhibitor, has been approved in Japan for the treatment of patients with acute lung injury (ALI) associated with systemic inflammatory response syndrome (SIRS). The Pharmaceuticals and Medical Devices Agency (PMDA) has ordered to conduct a postmarket clinical study in order to reevaluate the efficacy and safety of Sivelestat in actual clinical settings in Japan.

METHODS

According to the PMDA's order, we evaluated the efficacy and safety of Sivelestat in Japanese patients with ALI associated with SIRS using ventilator-free days (VFD) as the primary endpoint. The surrogate endpoints are ventilator-weaning rate, ICU discharge rate, and 180-day survival rate. Study design was an open-label, non-randomized, multi-center clinical trial. Sivelestat was intravenously administered at 0.2 mg/kg/h continuously for a maximum of 14 days. Sivelestat group and control group were compared by adjusting the outcome values using an inverse probability of treatment weighted method based on the propensity scores.

RESULTS

Four hundred and four Sivelestat group patients and 177 control group patients were enrolled. The adjusted mean number of VFD was 15.7 and 12.1 in the Sivelestat group and control group, respectively (P = 0.0022). Both the adjusted ventilator-weaning rate and ICU discharge rate were significantly higher in the Sivelestat group than in the control group (P = 0.0028 and P = 0.019, respectively). The adjusted 180-day survival rate was significantly higher in the Sivelestat group than in the control group (71.8 percent vs. 56.3 percent).

CONCLUSIONS

Sivelestat contributed to early weaning from the mechanical ventilation, while showing no negative effect on the long-term outcomes of ALI associated with SIRS. The results of this study suggest the clinical usefulness of Sivelestat in this patient population.

Contribution of neutrophils to acute lung injury

Treatment of acute lung injury (ALI) and its most severe form, acute respiratory distress syndrome (ARDS), remain unsolved problems of intensive care medicine. ALI/ARDS are characterized by lung edema due to increased permeability of the alveolar-capillary barrier and subsequent impairment of arterial oxygenation. Lung edema, endothelial and epithelial injury are accompanied by an influx of neutrophils into the interstitium and broncheoalveolar space. Hence, activation and recruitment of neutrophils are regarded to play a key role in progression of ALI/ARDS. Neutrophils are the first cells to be recruited to the site of inflammation and have a potent antimicrobial armour that includes oxidants, proteinases and cationic peptides. Under pathological circumstances, however, unregulated release of these microbicidal compounds into the extracellular space paradoxically can damage host tissues. This review focuses on the mechanisms of neutrophil recruitment into the lung and on the contribution of neutrophils to tissue damage in ALI.

Human neutrophils kill Streptococcus pneumoniae via serine proteases

Neutrophils, or polymorphonuclear leukocytes, comprise a crucial component of innate immunity, controlling bacterial and fungal infection through a combination of both oxidative and nonoxidative mechanisms. Indeed, neutrophils are believed to play an important role in controlling infection caused by the major human pathogen Streptococcus pneumoniae. However, the method by which neutrophils kill the pneumococcus as well as other Gram-positive bacteria, is not fully understood. We investigated human neutrophil killing of the pneumococcus in a complement-dependent opsonophagocytic assay. In contrast to other Gram-positive organisms, inhibition of the NADPH oxidase did not affect killing of S. pneumoniae. Supernatant from degranulated neutrophils killed the pneumococcus, suggesting a role for granular products. When neutrophil granule proteases were inhibited with either a protease mixture, or specific serine protease inhibitors 4-(2-Aminoethyl)benzenesulfonylfluoride and diisopropylfluorophosphate, killing by neutrophils was inhibited in a manner that correlated with increased intracellular survival. All three compounds inhibited intracellular activity of the three major neutrophil serine proteases: elastase, cathepsin G, and proteinase 3. Additionally, purified elastase and cathepsin G were sufficient to kill S. pneumoniae in a serine protease dependent-manner in in vitro assays. Inhibition studies using specific inhibitors of these serine proteases suggested that while each serine protease is sufficient to kill the pneumococcus, none is essential. Our findings show that Gram-positive pathogens are killed by human neutrophils via different mechanisms involving serine proteases.