Neutrophil elastase modulates cytokine expression: contribution to host defense against Pseudomonas aeruginosa-induced pneumonia

Current Mouse Models of Intracranial Aneurysms: Analysis of Pharmacological Agents Used to Induce Aneurysms and Their Impact on Translational Research

Intracranial aneurysms (IAs) are rare vascular lesions that are more frequently found in women. The pathophysiology behind the formation and growth of IAs is complex. Hence, to date, no single pharmacological option exists to treat them. Animal models, especially mouse models, represent a valuable tool to explore such complex scientific questions. Genetic modification in a mouse model of IAs, including deletion or overexpression of a particular gene, provides an excellent means for examining basic mechanisms behind disease pathophysiology and developing novel pharmacological approaches. All existing animal models need some pharmacological treatments, surgical interventions, or both to develop IAs, which is different from the spontaneous and natural development of aneurysms under the influence of the classical risk factors. The benefit of such animal models is the development of IAs in a limited time. However, clinical translation of the results is often challenging because of the artificial course of IA development and growth. Here, we summarize the continuous improvement in mouse models of IAs. Moreover, we discuss the pros and cons of existing mouse models of IAs and highlight the main translational roadblocks and how to improve them to increase the success of translational IA research.

Saturated fatty acid-enriched small extracellular vesicles mediate a crosstalk inducing liver inflammation and hepatocyte insulin resistance

Background & Aims

Lipotoxicity triggers non-alcoholic fatty liver disease (NAFLD) progression owing to the accumulation of toxic lipids in hepatocytes including saturated fatty acids (SFAs), which activate pro-inflammatory pathways. We investigated the impact of hepatocyte- or circulating-derived small extracellular vesicles (sEV) secreted under NAFLD conditions on liver inflammation and hepatocyte insulin signalling.

Methods

sEV released by primary mouse hepatocytes, characterised and analysed by lipidomics, were added to mouse macrophages/Kupffer cells (KC) to monitor internalisation and inflammatory responses. Insulin signalling was analysed in hepatocytes exposed to conditioned media from sEV-loaded macrophages/KC. Mice were i.v. injected sEV to study liver inflammation and insulin signalling. Circulating sEV from mice and humans with NAFLD were used to evaluate macrophage-hepatocyte crosstalk.

Results

Numbers of sEV released by hepatocytes increased under NAFLD conditions. Lipotoxic sEV were internalised by macrophages through the endosomal pathway and induced pro-inflammatory responses that were ameliorated by pharmacological inhibition or deletion of Toll-like receptor-4 (TLR4). Hepatocyte insulin signalling was impaired upon treatment with conditioned media from macrophages/KC loaded with lipotoxic sEV. Both hepatocyte-released lipotoxic sEV and the recipient macrophages/KC were enriched in palmitic (C16:0) and stearic (C18:0) SFAs, well-known TLR4 activators. Upon injection, lipotoxic sEV rapidly reached KC, triggering a pro-inflammatory response in the liver monitored by Jun N-terminal kinase (JNK) phosphorylation, NF-κB nuclear translocation, pro-inflammatory cytokine expression, and infiltration of immune cells into the liver parenchyma. sEV-mediated liver inflammation was attenuated by pharmacological inhibition or deletion of TLR4 in myeloid cells. Macrophage inflammation and subsequent hepatocyte insulin resistance were also induced by circulating sEV from mice and humans with NAFLD.

Conclusions

We identified hepatocyte-derived sEV as SFA transporters targeting macrophages/KC and activating a TLR4-mediated pro-inflammatory response enough to induce hepatocyte insulin resistance.

Impact and Implications

Small extracellular vesicles (sEV) released by the hepatocytes under non-alcoholic fatty liver disease (NAFLD) conditions cause liver inflammation and insulin resistance in hepatocytes via paracrine hepatocyte-macrophage-hepatocyte crosstalk. We identified sEV as transporters of saturated fatty acids (SFAs) and potent lipotoxic inducers of liver inflammation. TLR4 deficiency or its pharmacological inhibition ameliorated liver inflammation induced by hepatocyte-derived lipotoxic sEV. Evidence of this macrophage-hepatocyte interactome was also found in patients with NAFLD, pointing to the relevance of sEV in SFA-mediated lipotoxicity in NAFLD.

Chronic Exposure to Secondary Organic Aerosols Causes Lung Tissue Damage

Recently, secondary organic aerosols (SOAs) emerged as a predominant component of fine particulate matter. However, the pathogenic mechanism(s) of SOAs are still poorly understood. Herein, we show that chronic exposure of mice to SOAs resulted in lung inflammation and tissue destruction. Histological analyses found lung airspace enlargement associated with massive inflammatory cell recruitment predominated by macrophages. Concomitant with such cell influx, our results found changes in the levels of a series of inflammatory mediators in response to SOA. Interestingly, we observed that the expression of the genes encoding for TNF-α and IL-6 increased significantly after one month of exposure to SOAs; mediators that have been largely documented to play a role in chronic pulmonary inflammatory pathologies. Cell culture studies confirmed these in vivo findings. Of importance as well, our study indicates increased matrix metalloproteinase proteolytic activity suggesting its contribution to lung tissue inflammation and degradation. Our work represents the first in vivo study, which reports that chronic exposure to SOAs leads to lung inflammation and tissue injury. Thus, we hope that these data will foster new studies to enhance our understanding of the underlying pathogenic mechanisms of SOAs and perhaps help in the design of therapeutic strategies against SOA-mediated lung injury.

The Direct Anti-Virulence but Not Bactericidal Activity of Human Neutrophil Elastase against Moraxella catarrhalis

Neutrophil elastase (NE) contributes to innate antibacterial defense at both the intracellular (phagocytosis) and extracellular (degranulation, NETosis) levels. Moraxella catarrhalis, a human respiratory pathogen, can exist in an inflammatory milieu which contains NE. No data are available on the action of NE against M. catarrhalis or on the counteraction of NE-dependent host defenses by this pathogen. Using time-kill assays we found that bacteria are able to survive and replicate in the presence of NE. Transmission electron microscopy and flow cytometry studies with NE-treated bacteria revealed that while NE admittedly destabilizes the outer membrane leaflet, it does not cause cytoplasmic membrane rupture, suggesting that the enzyme does not target components that are essential for cell integrity. Using LC-MS/MS spectroscopy we determined that NE cleaved at least three virulent surface proteins in outer membrane vesicles (OMVs) of M. catarrhalis, including OMP CD, McaP, and TbpA. The cleavage of OMP CD contributes to the significant decrease in resistance to serum complement in the complement-resistant strain Mc6. The cleavage of McaP did not cause any sensitization to erythromycin nor did NE disturb its drug action. Identifying NE as a novel but subtle anti-virulence agent together with its extracellularly not-efficient bactericidal activity against M. catarrhalis may facilitate the pathogen’s existence in the airways under inflammation.

Gene Signatures of Symptomatic and Asymptomatic Clinical-Immunological Profiles of Human Infection by Leishmania (L.) chagasi in Amazonian Brazil

Individuals infected with Leishmania (L.) chagasi may present different asymptomatic and symptomatic stages of infection, which vary in the clinical–immunological profiles that can be classified as asymptomatic infection (AI), subclinical resistant infection (SRI), indeterminate initial infection (III), subclinical oligosymptomatic infection (SOI), and symptomatic infection (SI) (=American visceral leishmaniasis, AVL). However, little is known about the molecular differences between individuals having each profile. Here, we performed whole-blood transcriptomic analyses of 56 infected individuals from Pará State (Brazilian Amazon), covering all five profiles. We then identified the gene signatures of each profile by comparing their transcriptome with those of 11 healthy individuals from the same area. Symptomatic individuals with SI (=AVL) and SOI profiles showed higher transcriptome perturbation when compared to those asymptomatic III, AI and SRI profiles, suggesting that disease severity may be associated with greater transcriptomic changes. Although the expression of many genes was altered on each profile, very few genes were shared among the profiles. This indicated that each profile has a unique gene signature. The innate immune system pathway was strongly activated only in asymptomatic AI and SRI profiles, suggesting the control of infection. In turn, pathways such as MHC Class II antigen presentation and NF-kB activation in B cells seemed to be specifically induced in symptomatic SI (=AVL) and SOI profiles. Moreover, cellular response to starvation was down-regulated in those symptomatic profiles. Overall, this study revealed five distinct transcriptional patterns associated to the clinical–immunological (symptomatic and asymptomatic) profiles of human L. (L.) chagasi-infection in the Brazilian Amazon.

Serine protease inhibitor derived from Trichinella spiralis (TsSERP) inhibits neutrophil elastase and impairs human neutrophil functions

During early infection with Trichinella spiralis, host neutrophils destroy newborn larvae migrating in the bloodstream, preventing infection. However, parasites secrete various immunomodulatory molecules to escape the host’s defense mechanisms, allowing them to infect the host and live for long periods. T. spiralis secretes serine protease inhibitors (TsSERPs), which are key inhibitory molecules that regulate serine proteases involved in digestion and inflammation. However, the modulatory roles of TsSERP in the inhibition of neutrophil serine proteases (NSPs) and neutrophil functions are unknown. Therefore, the immunomodulatory properties of recombinant TsSERP1 (rTsSERP1) on NSPs and neutrophil functions were investigated in this study. rTsSERP1 preferentially inhibited human neutrophil elastase (hNE). In addition, incubation of rTsSERP1 with fMLP-induced neutrophils impaired their phagocytic ability. The formation of neutrophil extracellular traps (NETs) was activated with phorbol myristate acetate (PMA), and NETs were dramatically reduced when treated with rTsSERP1. Furthermore, rTsSERP1 suppressed the production of proinflammatory cytokines and chemokines during neutrophil activation, which are essential for neutrophil-mediated local or systemic inflammation regulation. In conclusion, T. spiralis immune evasion mechanisms are promoted by the inhibitory properties of TsSERP1 against neutrophil elastase and neutrophil defense functions, and these might be promising alternative treatment targets for inflammatory disorders.

Plant polysaccharides with anti-lung injury effects as a potential therapeutic strategy for COVID-19

When coronavirus disease 2019 (COVID-19) develops into the severe phase, lung injury, acute respiratory distress syndrome, and/or respiratory failure could develop within a few days. As a result of pulmonary tissue injury, pathomorphological changes usually present endothelial dysfunction, inflammatory cell infiltration of the lung interstitium, defective gas exchange, and wall leakage. Consequently, COVID-19 may progress to tremendous lung injury, ongoing lung failure, and death. Exploring the treatment drugs has important implications. Recently, the application of traditional Chinese medicine had better performance in reducing fatalities, relieving symptoms, and curtailing hospitalization. Through constant research and study, plant polysaccharides may emerge as a crucial resource against lung injury with high potency and low side effects. However, the absence of a comprehensive understanding of lung-protective mechanisms impedes further investigation of polysaccharides. In the present article, a comprehensive review of research into plant polysaccharides in the past 5 years was performed. In total, 30 types of polysaccharides from 19 kinds of plants have shown lung-protective effects through the pathological processes of inflammation, oxidative stress, apoptosis, autophagy, epithelial–mesenchymal transition, and immunomodulation by mediating mucin and aquaporins, macrophage, endoplasmic reticulum stress, neutrophil, TGF-β1 pathways, Nrf2 pathway, and other mechanisms. Moreover, the deficiencies of the current studies and the future research direction are also tentatively discussed. This research provides a comprehensive perspective for better understanding the mechanism and development of polysaccharides against lung injury for the treatment of COVID-19.

Mutant allele knockout with novel CRISPR nuclease promotes myelopoiesis in ELANE neutropenia

Severe congenital neutropenia (SCN) is a life-threatening marrow failure disorder, usually caused by heterozygous mutations in ELANE. Potential genetic treatment strategies include biallelic knockout or gene correction via homology-directed repair (HDR). Such strategies, however, involve the potential loss of the essential function of the normal allele product or limited coverage of diverse monogenic mutations within the patient population, respectively. As an alternative, we have developed a novel CRISPR-based monoallelic knockout strategy that precisely targets the heterozygous sites of single-nucleotide polymorphisms (SNPs) associated with most ELANE mutated alleles. In vitro studies demonstrate that patients’ unedited hematopoietic CD34⁺ cells have significant abnormalities in differentiation and maturation, consistent with the hematopoietic defect in SCN patients. Selective knockout of the mutant ELANE allele alleviated these cellular abnormalities and resulted in about 50%–70% increase in normally functioning neutrophils (p < 0.0001). Genomic analysis confirmed that ELANE knockout was specific to the mutant allele and involved no off-targets. These results demonstrate the therapeutic potential of selective allele editing that may be applicable to SCN and other autosomal dominant disorders.

Neutrophil elastase promotes neointimal hyperplasia by targeting toll-like receptor 4 (TLR4)-NF-κB signalling

BACKGROUND AND PURPOSE

Neointimal hyperplasia (NIH) is the fundamental cause for vascular diseases and vascular smooth muscle cell (VSMC) dysregulation has been widely implicated in NIH. Neutrophil elastase is a potential therapeutic target for multiple diseases. We investigated the role of neutrophil elastase in VSMC functions and injury-induced NIH and explored the therapeutic potential of targeting neutrophil elastase in NIH.

EXPERIMENTAL APPROACH

VSMCs were used to analyse the effects of neutrophil elastase. Proteomic analysis was used to identify potential neutrophil elastase targets. Artery injury model and neutrophil elastase inhibitor GW311616A were used to investigate the role of neutrophil elastase in NIH.

KEY RESULTS

TNF-α up-regulated neutrophil elastase in VSMCs through modulating GAPBα/Runx1/CEBPα/c-Myb signalling. Up-regulated neutrophil elastase promoted VSMC migration, proliferation and inflammation. Toll-like receptor 4 (TLR4) was identified as a target protein for neutrophil elastase in VSMCs and the TLR4/MyD88/IRAK1/TRAF6/NF-κB regulatory axis was shown to be the signalling pathway for neutrophil elastase in VSMC pathology. Importantly, TLR4 inhibition abolished neutrophil elastase-mediated VSMC dysregulation. Injury-induced NIH was significantly reduced in both neutrophil elastase-deficient mice and mice treated with GW311616A. The formation of neutrophil extracellular traps was impaired in injured arteries from neutrophil elastase-deficient mice. Finally, a similar role for neutrophil elastase in human VSMC pathology was confirmed and we observed higher expression levels of neutrophil elastase but lower expression levels of TLR4 in human atherosclerotic lesions.

CONCLUSION AND IMPLICATIONS

We provide new insight into the molecular mechanisms underlying NIH and identify neutrophil elastase as a potential therapeutic target for vascular disease.

Reduced ELANE and SLPI expression compromises dental pulp cell activity

Background

Patients with ELANE variants and severe congenital neutropenia (SCN) commonly develop oral complications. Whether they are caused only by low neutrophil count or the combination of neutropenia and aberrant dental cells is unknown.

Methods

Genetic variant was identified with exome sequencing. Dental pulp cells isolated from the SCN patient with an ELANE mutation were investigated for gene expression, enzyme activity, proliferation, colony formation, wound healing, apoptosis, ROS, attachment, spreading and response to lipopolysaccharide.

Results

ELANE cells had diminished expression of ELANE and SLPI and reduced neutrophil elastase activity. Moreover, ELANE cells exhibited impaired proliferation, colony forming, migration, attachment and spreading; and significantly increased ROS formation and apoptosis, corresponding with increased Cyclin D1 and MMP2 levels. The intrinsic levels of TGF‐β1 and TNF‐α were significantly increased; however, IL‐6, IL‐8 and NF‐kB1 were significantly decreased in ELANE cells compared with those in controls. After exposure to lipopolysaccharide, ELANE cells grew larger, progressed to more advanced cell spreading stages and showed significantly increased SLPI, TNF‐α and NF‐kB1 and tremendously increased IL‐6 and IL‐8 expression, compared with controls.

Conclusion

This study, for the first time, suggests that in addition to neutropenia, the aberrant levels and functions of ELANE, SLPI and their downstream molecules in pulp cells play an important role in oral complications in SCN patients. In addition, pulp cells with diminished neutrophil elastase and SLPI are highly responsive to inflammation.

Neutrophil elastase-regulated macrophage sheddome/secretome and phagocytic failure

Patients with cystic fibrosis (CF) have defective macrophage phagocytosis and efferocytosis. Several reports demonstrate that neutrophil elastase (NE), a major inflammatory protease in the CF airway, impairs macrophage phagocytic function. To date, NE-impaired macrophage phagocytic function has been attributed to cleavage of cell surface receptors or opsonins. We applied an unbiased proteomic approach to identify other potential macrophage targets of NE protease activity that may regulate phagocytic function. Using the murine macrophage cell line, RAW 264.7, human blood monocyte-derived macrophages, and primary alveolar macrophages from Cftr-null and wild-type littermate mice, we demonstrated that NE exposure blocked phagocytosis of Escherichia coli bio-particles. We performed liquid chromatography-tandem mass spectroscopy (LC-MS/MS) proteomic analysis of the conditioned media from RAW264.7 treated either with active NE or inactive (boiled) NE as a control. Out of 840 proteins identified in the conditioned media, active NE upregulated 142 proteins and downregulated 211 proteins. NE released not only cell surface proteins into the media but also cytoskeletal, mitochondrial, cytosolic, and nuclear proteins that were detected in the conditioned media. At least 32 proteins were associated with the process of phagocytosis including 11 phagocytic receptors [including lipoprotein receptor-related protein 1 (LRP1)], 7 proteins associated with phagocytic cup formation, and 14 proteins involved in phagocytic maturation (including calpain-2) and phagolysosome formation. NE had a broad effect on the proteome required for regulation of all stages of phagocytosis and phagolysosome formation. Furthermore, the NE sheddome/secretome included proteins from other macrophage cellular domains, suggesting that NE may globally regulate macrophage structure and function.

Protease-Antiprotease Imbalance in Bronchiectasis

Airway inflammation plays a central role in bronchiectasis. Protease-antiprotease balance is crucial in bronchiectasis pathophysiology and increased presence of unopposed proteases activity may contribute to bronchiectasis onset and progression. Proteases' over-reactivity and antiprotease deficiency may have a role in increasing inflammation in bronchiectasis airways and may lead to extracellular matrix degradation and tissue damage. Imbalances in serine proteases and matrix-metallo proteinases (MMPs) have been associated to bronchiectasis. Active neutrophil elastase has been associated with disease severity and poor long-term outcomes in this disease. Moreover, high levels of MMPs have been associated with radiological and disease severity. Finally, severe deficiency of α1-antitrypsin (AAT), as PiSZ and PiZZ (proteinase inhibitor SZ and ZZ) phenotype, have been associated with bronchiectasis development. Several treatments are under study to reduce protease activity in lungs. Molecules to inhibit neutrophil elastase activity have been developed in both oral or inhaled form, along with compounds inhibiting dipeptydil-peptidase 1, enzyme responsible for the activation of serine proteases. Finally, supplementation with AAT is in use for patients with severe deficiency. The identification of different targets of therapy within the protease-antiprotease balance contributes to a precision medicine approach in bronchiectasis and eventually interrupts and disrupts the vicious vortex which characterizes the disease.

Pathogenesis and Management of COVID-19

COVID-19, occurring due to SARS-COV-2 infection, is the most recent pandemic disease that has led to three million deaths at the time of writing. A great deal of effort has been directed towards altering the virus trajectory and/or managing the interactions of the virus with its subsequent targets in the human body; these interactions can lead to a chain reaction-like state manifested by a cytokine storm and progress to multiple organ failure. During cytokine storms the ratio of pro-inflammatory to anti-inflammatory mediators is generally increased, which contributes to the instigation of hyper-inflammation and confers advantages to the virus. Because cytokine expression patterns fluctuate from one person to another and even within the same person from one time to another, we suggest a road map of COVID-19 management using an individual approach instead of focusing on the blockbuster process (one treatment for most people, if not all). Here, we highlight the biology of the virus, study the interaction between the virus and humans, and present potential pharmacological and non-pharmacological modulators that might contribute to the global war against SARS-COV-2. We suggest an algorithmic roadmap to manage COVID-19.

Neutrophil elastase inhibitor (MPH-966) improves intestinal mucosal damage and gut microbiota in a mouse model of 5-fluorouracil-induced intestinal mucositis

BACKGROUND

5-Fluorouracil (5-FU)-based chemotherapy is first-line chemotherapy for colorectal cancer. However, 5-FU-induced intestinal mucositis (FUIIM) is a common adverse effect that severely impairs drug tolerance and results in poor patient health.

METHODS

Male C57BL/6 mice were given 5-FU (50 mg/kg/day, i.p.) and treated with MPH-966 (5 and 7.5 mg/kg/day, p.o.) for five days. The body weight loss and the amount of food intake, and histopathological findings were recorded and analyzed. In addition, the neutrophil infiltration, levels of neutrophil serine proteases and pro-inflammatory cytokines, and tight junction proteins expression in intestinal tissues were determined. The ecology of gut microbiota was performed through next-generation sequencing technologies.

RESULTS

Neutrophil elastase (NE) overexpression is a key feature in FUIIM. This study showed that treatment with the specific NE inhibitor MPH-966 (7.5 mg/kg/day, p.o.) significantly reversed 5-FU-induced loss in body weight and food intake; reversed villous atrophy; significantly suppressed myeloperoxidase, NE, and proteinase 3 activity; and reduced pro-inflammatory cytokine expression in an FUIIM mouse model. In addition, MPH-966 prevented 5-FU-induced intestinal barrier dysfunction, as indicated by the modulated expression of the tight junction proteins zonula occludin-1 and occludin. MPH-966 also reversed 5-FU-induced changes in gut microbiota diversity and abundances, specifically the Firmicutes-to-Bacteroidetes ratio; Muribaculaceae, Ruminococcaceae, and Eggerthellaceae abundances at the family level; and Candidatus Arthromitus abundance at the genus level.

CONCLUSION

These data indicate that NE inhibitor is a key treatment candidate to alleviate FUIIM by regulating abnormal inflammatory responses, intestinal barrier dysfunction, and gut microbiota imbalance.

Alpha-1 antitrypsin deficiency and recombinant protein sources with focus on plant sources: Updates, challenges and perspectives

Alpha-1 antitrypsin deficiency (A1ATD) is an autosomal recessive disease characterized by low plasma levels of A1AT, a serine protease inhibitor representing the most abundant circulating antiprotease normally present at plasma levels of 1-2 g/L. The dominant clinical manifestations include predispositions to early onset emphysema due to protease/antiprotease imbalance in distal lung parenchyma and liver disease largely due to unsecreted polymerized accumulations of misfolded mutant A1AT within the endoplasmic reticulum of hepatocytes. Since 1987, the only FDA licensed specific therapy for the emphysema component has been infusions of A1AT purified from pooled human plasma at the 2020 cost of up to US $200,000/year with the risk of intermittent shortages. In the past three decades various, potentially less expensive, recombinant forms of human A1AT have reached early stages of development, one of which is just reaching the stage of human clinical trials. The focus of this review is to update strategies for the treatment of the pulmonary component of A1ATD with some focus on perspectives for therapeutic production and regulatory approval of a recombinant product from plants. We review other competitive technologies for treating the lung disease manifestations of A1ATD, highlight strategies for the generation of data potentially helpful for securing FDA Investigational New Drug (IND) approval and present challenges in the selection of clinical trial strategies required for FDA licensing of a New Drug Approval (NDA) for this disease.

CRISPR-Cas9-Mediated ELANE Mutation Correction in Hematopoietic Stem and Progenitor Cells to Treat Severe Congenital Neutropenia

Severe congenital neutropenia (SCN) is a monogenic disorder. SCN patients are prone to recurrent life-threatening infections. The main causes of SCN are autosomal dominant mutations in the ELANE gene that lead to a block in neutrophil differentiation. In this study, we use CRISPR-Cas9 ribonucleoproteins and adeno-associated virus (AAV)6 as a donor template delivery system to repair the ELANEL172P mutation in SCN patient-derived hematopoietic stem and progenitor cells (HSPCs). We used a single guide RNA (sgRNA) specifically targeting the mutant allele, and an sgRNA targeting exon 4 of ELANE. Using the latter sgRNA, ∼34% of the known ELANE mutations can in principle be repaired. We achieved gene correction efficiencies of up to 40% (with sgELANE-ex4) and 56% (with sgELANE-L172P) in the SCN patient-derived HSPCs. Gene repair restored neutrophil differentiation in vitro and in vivo upon HSPC transplantation into humanized mice. Mature edited neutrophils expressed normal elastase levels and behaved normally in functional assays. Thus, we provide a proof of principle for using CRISPR-Cas9 to correct ELANE mutations in patient-derived HSPCs, which may translate into gene therapy for SCN.

Neutrophil elastase promotes macrophage cell adhesion and cytokine production through the integrin-Src kinases pathway

There are a number of respiratory diseases characterized by the presence of excess neutrophil elastase (NE) activity in tissues, including cystic fibrosis and chronic obstructive pulmonary disease (COPD). NE is considered a primary contributor to disease development, but the precise mechanism has yet to be fully determined. We hypothesized that NE alters the function of macrophages (Mɸ) which play a critical role in many physiological processes in healthy lungs. We demonstrate that monocyte-derived Mɸ exposed to NE releases active matrix metalloproteinases (MMPs), increase expression of pro-inflammatory cytokines TNFα, IL-1β, and IL-8, and reduce capacity to phagocytose bacteria. Changes in Mɸ function following NE treatment were accompanied by increased adhesion and cytoskeleton re-arrangement, indicating the possibility of integrin involvement. To support this observation, we demonstrate that NE induces phosphorylation of kinases from the Src kinase family, a hallmark of integrin signaling activation. Moreover, pretreatment of Mɸ with a specific Src kinase inhibitor, PP2 completely prevents NE-induced pro-inflammatory cytokine production. Taken together these findings indicate that NE participates in lung destruction not only through direct proteolytic degradation of matrix proteins, but also through activation of Mɸ inflammatory and proteolytic functions.

Anti-inflammatory effects of troxerutin are mediated through elastase inhibition

CONTEXT

Obesity is a chronic low-grade inflammatory state associated with immune cell infiltration into the adipose tissue (AT). We hypothesize that the anti-obesity and anti-inflammatory effects of troxerutin (TX) are mediated through inhibition of elastase.

OBJECTIVE

To determine the inhibitory effect of TX on elastase in vitro and in tumor necrosis factor alpha (TNFα) induced 3T3-L1 adipocytes and the molecular interaction of TX with human neutrophil elastase (HNE).

MATERIALS AND METHODS

Differentiated 3T3-L1 adipocytes were pretreated with TX, elastatinal (ELAS) or sodium salicylate (SAL) before exposure to TNFα. Lipid accumulation, reactive oxygen species (ROS) generation and oxidant-antioxidant balance were examined. The mRNA and protein expression of TNFα, interleukin-6, monocyte chemoattractant protein-1, adiponectin, leptin, resistin, chemerin, and elastase were analyzed. Elastase inhibition by TX and ELAS in a cell free system and docking studies for HNE with TX and ELAS were performed.

RESULTS

TX, ELAS or SAL pretreatment had lowered lipid droplets formation and TG content. TX suppressed ROS generation, oxidative stress and improved antioxidant status. The expression of inflammatory cytokines and elastase was downregulated while that of adiponectin was upregulated by TX. The concentration required to produce 50% inhibition in vitro (IC₅₀) was 11.5 μM for TX and 16.9 μM for ELAS. TX showed hydrogen bonding and hydrophobic interactions with elastase.

DISCUSSION

TNFα induces inflammation of 3T3-L1 cells through elastase activation. TX inhibits elastase activity, downregulates expression and binds with elastase.

CONCLUSION

The antioxidant and anti-inflammatory activities of TX in AT could be of relevance in the management of obesity.

Anti-cytokines as a Strategy in Alpha-1 Antitrypsin Deficiency

For many years, the lung disease associated with alpha-1 antitrypsin (AAT) deficiency (AATD) was perceived as being secondary to an imbalance between this serine protease inhibitor and the target protease, neutrophil elastase (NE). More recently, a greater understanding of the pathways leading to lung inflammation has shed light on new potential attributes and presented AATD as an inflammatory condition in which proteases and neutrophils still play a major role, but in which pro-inflammatory cytokines, either induced by the actions of NE or by other pro-inflammatory processes normally modulated by AAT, are involved. In this review, we will look at the various cytokines centrally involved in AATD lung disease, and how a greater understanding of their contribution may help development of targeted therapies.

IBD: Role of intestinal compartments in the mucosal immune response

BACKGROUND AND AIMS

Laser capture microdissection (LCM) is a powerful tool for the isolation of specific tissue compartments. We aimed to investigate the mucosal immune response that takes place in different intestinal compartments of IBD patients, dissected by LCM, analyzing cytokines expression profile and endoplasmic reticulum (ER) stress markers.

METHODS

Frozen sections of gut were obtained from patients with Crohn's disease (CD), ulcerative colitis (UC) and from controls. Using LCM, surface epithelium (SE) and lamina propria (LP) compartments were isolated and total RNA extracted. The relative expression of Th1, Th17 and Treg cytokines was evaluated by quantitative reverse transcriptase real-time PCR (qRT-PCR), in addition to the assessment of mRNA splicing of the transcription factor X-box binding protein-1 (XBP1). Human neutrophil elastase (HNE) and the transcription factor forkhead box P3 (Foxp3) were also analyzed by immunohistochemistry.

RESULTS

The increased expression of IL-17 was observed in both intestinal compartments of IBD patients when compared to controls. IFN- γ, TNF-α , IL-10, HNE and Foxp3 were overexpressed in the LP compartment of both IBD patients as compared to controls. An upregulation of IFN-γ and an infiltration of HNE+ cells was found in the SE of patients with UC. Splicing of XBP1 mRNA was recognized in both intestinal compartments of IBD patients when compared to controls.

CONCLUSIONS

In IBD patients, both intestinal compartments are involved in Th17 response, whereas, LP compartment plays a prominent role in Th1 and Treg immune responses. Nevertheless, high level of IFN- γ was found in the SE of UC patients, suggesting that this compartment is involved in the Th1 immune response. Our data also suggested that ER stress signalling is active in both LP and SE compartment of IBD patients, thus advocating that ER stress and immunity are intertwined.

Optical Molecular Imaging of Inflammatory Cells in Interventional Medicine-An Emerging Strategy

The optical molecular imaging of inflammation is an emerging strategy for interventional medicine and diagnostics. The host's inflammatory response and adaptation to acute and chronic diseases provides unique signatures that have the potential to guide interventions. Thus, there are emerging a suite of molecular imaging and sensing approaches for a variety of targets in this area. This review will focus on two key cellular orchestrators that dominate this area, neutrophils and macrophages, with recent developments in molecular probes and approaches discussed.

The Neutrophilic Response to Pseudomonas Damages the Airway Barrier, Promoting Infection by Klebsiella pneumoniae

Pseudomonas aeruginosa and Klebsiella pneumoniae are two common gram-negative pathogens that are associated with bacterial pneumonia and can often be isolated from the same patient. We used a mixed-pathogen pneumonia infection model in which mice were infected with sublethal concentrations of P. aeruginosa and K. pneumoniae, resulting in significant lethality, outgrowth of both bacteria in the lung, and systemic dissemination of K. pneumoniae. Inflammation, induced by P. aeruginosa activation of Toll-like receptor 5, results in prolonged neutrophil recruitment to the lung and increased levels of neutrophil elastase in the airway, resulting in lung damage and epithelial barrier dysfunction. Live P. aeruginosa was not required to potentiate K. pneumoniae infection, and flagellin alone was sufficient to induce lethality when delivered along with Klebsiella. Prophylaxis with an anti-Toll-like receptor 5 antibody or Sivelestat, a neutrophil elastase inhibitor, reduced neutrophil influx, inflammation, and mortality. Furthermore, pathogen-specific monoclonal antibodies targeting P. aeruginosa or K. pneumoniae prevented the outgrowth of both bacteria and reduced host inflammation and lethality. These findings suggest that coinfection with P. aeruginosa may enable the outgrowth and dissemination of K. pneumoniae, and that a pathogen- or host-specific prophylactic approach targeting P. aeruginosa may prevent or limit the severity of such infections by reducing neutrophil-induced lung damage.

Proteases in Pemphigoid Diseases

Pemphigoid diseases are a subgroup of autoimmune skin diseases characterized by widespread tense blisters. Standard of care typically involves immunosuppressive treatments, which may be insufficient and are often associated with significant adverse events. As such, a deeper understanding of the pathomechanism(s) of pemphigoid diseases is necessary in order to identify improved therapeutic approaches. A major initiator of pemphigoid diseases is the accumulation of autoantibodies against proteins at the dermal-epidermal junction (DEJ), followed by protease activation at the lesion. The contribution of proteases to pemphigoid disease pathogenesis has been investigated using a combination of in vitro and in vivo models. These studies suggest proteolytic degradation of anchoring proteins proximal to the DEJ is crucial for dermal-epidermal separation and blister formation. In addition, proteases can also augment inflammation, expose autoantigenic cryptic epitopes, and/or provoke autoantigen spreading, which are all important in pemphigoid disease pathology. The present review summarizes and critically evaluates the current understanding with respect to the role of proteases in pemphigoid diseases.

Neutrophil elastase plays a non-redundant role in remodeling the venular basement membrane and neutrophil diapedesis post-ischemia/reperfusion injury

Ischemia/reperfusion (I/R) injury is a severe inflammatory insult associated with numerous pathologies, such as myocardial infarction, stroke and acute kidney injury. I/R injury is characterized by a rapid influx of activated neutrophils secreting toxic free radical species and degrading enzymes that can irreversibly damage the tissue, thus impairing organ functions. Significant efforts have been invested in identifying therapeutic targets to suppress neutrophil recruitment and activation post‐I/R injury. In this context, pharmacological targeting of neutrophil elastase (NE) has shown promising anti‐inflammatory efficacy in a number of experimental and clinical settings of I/R injury and is considered a plausible clinical strategy for organ care. However, the mechanisms of action of NE, and hence its inhibitors, in this process are not fully understood. Here we conducted a comprehensive analysis of the impact of NE genetic deletion on neutrophil infiltration in four murine models of I/R injury as induced in the heart, kidneys, intestine and cremaster muscle. In all models, neutrophil migration into ischemic regions was significantly suppressed in NE^−/− mice as compared with wild‐type controls. Analysis of inflamed cremaster muscle and mesenteric microvessels by intravital and confocal microscopy revealed a selective entrapment of neutrophils within venular walls, most notably at the level of the venular basement membrane (BM) following NE deletion/pharmacological blockade. This effect was associated with the suppression of NE‐mediated remodeling of the low matrix protein expressing regions within the venular BM used by transmigrating neutrophils as exit portals. Furthermore, whilst NE deficiency led to reduced neutrophil activation and vascular leakage, levels of monocytes and prohealing M2 macrophages were reduced in tissues of NE^−/− mice subjected to I/R. Collectively our results identify a vital and non‐redundant role for NE in supporting neutrophil breaching of the venular BM post‐I/R injury but also suggest a protective role for NE in promoting tissue repair. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Monocyte clearance of apoptotic neutrophils is unhindered in the presence of NETosis, but proteins of NET trigger ETosis in monocytes

Resolution of inflammation needs effective and timely removal of dead cells and other toxic products of neutrophils, monocytes, and macrophages. In this study, we evaluated the role of monocytes in the clearance of neutrophil extracellular trap (NET) and apoptotic neutrophils in the inflammation site. For this, monocytes were observed microscopically after exposing them with NETs and/or apoptotic bodies. A subset of monocytes exposed to NETs ejected extracellular traps and this was shown to be mediated by proteins like elastase and citrullinated histones present in NET supernatant. Monocytes showed a preference for the internalisation of the apoptotic body when both NET and apoptotic bodies were present in the medium. The study provides new insight into the role of monocytes in the clearance of NET and apoptotic neutrophils and this information may open up a way in formulating therapeutic strategies for accelerating resolution of inflammation.

Bldesin, the first functionally characterized pathogenic fungus defensin with Kv1.3 channel and chymotrypsin inhibitory activities

Fungus defensin is a kind of important natural peptide resource, such as plectasin from the soil fungus Pseudoplectania nigrella with potential application in the antimicrobial peptide lead drug discovery. Here, a fungus defensin named Bldesin with Kv1.3 channel and serine protease inhibitory activities was first explored. By GST-Bldesin fusion expression and enterokinase cleaving strategy, recombinant Bldesin was obtained successfully. Antimicrobial assays showed that Bldesin had potent activity against Gram-positive Staphylococcus aureus, but had no effect on Gram-negative Escherichia coli. Electrophysiological experiments showed that Bldesin had Kv1.3 channel inhibitory activity. Serine protease inhibitory associated experiments showed that Bldesin had unique chymotrypsin protease inhibitory, elastase protease inhibitory, and serine protease-associated coagulation inhibitory activities. To the best of our knowledge, Bldesin is the first functionally characterized pathogenic fungus defensin with Kv1.3 channel and chymotrypsin inhibitory activities and highlighted novel pharmacological effects of fungus-derived defensin peptides.

Inhibitors of elastase stimulate murine B lymphocyte differentiation into IgG- and IgA-producing cells

It is well established that dendritic cells and macrophages play a role in antigen presentation to B and T cells and in shaping B and T cell responses via cytokines they produce. We have previously reported that depletion of neutrophils improves the production of mucosal IgA after sublingual immunization with Bacillus anthracis edema toxin as adjuvant. These past studies also demonstrated that an inverse correlation exists between the number of neutrophils and production of IgA by B cells. Using specific inhibitors of elastase, we addressed whether the elastase activity of neutrophil could be the factor that interferes with production of IgA and possibly other immunoglobulin isotypes. We found that murine splenocytes and mesenteric lymph node cells cultured for 5 days in the presence of neutrophil elastase inhibitors secreted higher levels of IgG and IgA than cells cultured in the absence of inhibitors. The effect of the inhibitors was dose-dependent and was consistent with increased frequency of CD138⁺ cells expressing IgG or IgA. Finally, neutrophil elastase inhibitors increased transcription of mRNA for AID, IL-10, BAFF and APRIL, factors involved in B cell differentiation. These findings identify inhibitors of elastase as potential adjuvants for increasing production of antibodies.

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.

Extended cleavage specificity of human neutrophil cathepsin G: A low activity protease with dual chymase and tryptase-type specificities

Human neutrophils express at least four active serine proteases, cathepsin G, N-elastase, proteinase 3 and neutrophil serine protease 4 (NSP4). They have all been extensively studied due to their importance in neutrophil biology and immunity. However, their extended cleavage specificities have never been determined in detail. Here we present a detailed cleavage specificity analysis of human cathepsin G (hCG). The specificity was determined by phage display analysis and the importance of individual amino acids in and around the cleavage site was then validated using novel recombinant substrates. To provide a broader context to this serine protease, a comparison was made to the related mast cell protease, human chymase (HC). hCG showed similar characteristics to HC including both the primary and extended specificities. As expected, Phe, Tyr, Trp and Leu were preferred in the P1 position. In addition, both proteases showed a preference for negatively charged amino acids in the P2´ position of substrates and a preference for aliphatic amino acids both upstream and downstream of the cleavage site. However, overall the catalytic activity of hCG was ~10-fold lower than HC. hCG has previously been reported to have a dual specificity consisting of chymase and tryptase-type activities. In our analysis, tryptase activity against substrates with Lys in P1 cleavage position was indeed only 2-fold less efficient as compared to optimal chymase substrates supporting strong dual-type specificity. We hope the information presented here on extended cleavage specificities of hCG and HC will assist in the search for novel in vivo substrates for these proteases as well as aid in the efforts to better understand the role of hCG in immunity and bacterial defence.

Differential susceptibility of Dectin-1 isoforms to functional inactivation by neutrophil and fungal proteases

Patients with cystic fibrosis (CF) experience chronic or recurrent bacterial and fungal lung infections. Many patients with CF cannot effectively clear Aspergillus from their lungs. This may result in IgE sensitization and the development of allergic bronchopulmonary aspergillosis, or invasive infections, such as Aspergillus bronchitis. Lung disease in patients with CF is associated with neutrophil-dominated inflammation and elevated levels of the serine protease, neutrophil elastase (NE). Various C-type lectin-like receptors (CLRs), including Dectin-1 and Dectin-2, are involved in the immune response to Aspergillus. Here, we show that purified NE cleaves Dectin-1 in an isoform-specific manner. Bronchoalveolar lavage fluid from patients with CF, which contains high NE activity, induces Dectin-1 cleavage. Similarly, filtrate from a protease-producing strain of Aspergillus fumigatus induces isoform-specific cleavage of Dectin-1. Dectin-1 knockout (KO) cells and NE-treated cells demonstrated reduced phagocytosis of zymosan, a fungal cell wall preparation. In addition, NE cleaves 2 other CLRs, Dectin-2 and Mincle, and fungal-induced cytokine production was reduced in Dectin-1 KO cells, Dectin-2 KO cells, and NE-treated cells. Thus, Dectin-1 and Dectin-2 cleavage by NE and/or A. fumigatus–derived proteases results in an aberrant antifungal immune response that likely contributes to disease pathology in patients with CF.—Griffiths, J. S., Thompson, A., Stott, M., Benny, A., Lewis, N. A., Taylor, P. R., Forton, J., Herrick, S., Orr, S. J., McGreal, E. P. Differential susceptibility of Dectin-1 isoforms to functional inactivation by neutrophil and fungal proteases.

Granulomatous lung inflammation is nanoparticle type-dependent

BACKGROUND

Nanoparticles are increasingly suspected as a strong etiologic factor of granuloma formation.

AIM OF THE STUDY

The aim of our study was to compare lung inflammatory response and histology changes following exposure of mice to two widely used nanoparticles: carbon nanotubes (MWCNT) and cadmium-based nanoparticles (QDOT705) in an attempt to better our understanding of granulomatous inflammation.

MATERIALS AND METHODS

Various groups of mice were included: control mice and mice that were intranasally instilled with QDOT or MWCNT. At defined time points post-challenge, bronchoalveolar lavages (BALs) and lung tissues were collected to study inflammatory and histologic changes.

RESULTS

Analyses of lung BAL fluids and tissues of nanoparticles-challenged mice in comparison to controls found: (1) increased cellularity in BALs, (2) increase of total protein concentration, LDH activity and proteolytic activity in BALs; (3) patchy granulomas, (4) macrophages, CD3 ± T, Treg and B cell infiltration in granulomatous areas; and (5) altered regulation of key inflammatory mediators and receptors. Importantly, these changes were nanoparticle type-dependent.

CONCLUSION

Our work enhances understanding of nanoparticles-induced lung inflammatory and histological changes that result in granuloma formation. We provide compelling evidence that not only exposure to nanoparticles leads to granulomatous lung inflammation, but the severity of this latter is nanostructure type-dependent. Of importance, while nanotechnology has the potential to revolutionize various fields including medicine, nanoparticles form the potential for an entirely new lung health risk that it is necessary to take seriously into consideration by setting up and/or reinforcing adequate safety measures.

An anti-Propionibacterium acnes antibody shows heterologous resistance to an Actinobacillus pleuropneumoniae infection independent of neutrophils in mice

Porcine contagious pleuropneumonia is a highly fatal respiratory disease that is caused by Actinobacillus pleuropneumoniae (APP) and results in tremendous economic losses for the pig breeding industry worldwide. Previous studies have demonstrated that Propionibacterium acnes (PA) could effectively prevent APP infection in mice and pigs. The humoral immune response played a primary role during this process and anti-PA antibody could mediate macrophages to kill the bacteria. However, the role of neutrophils in this process is currently unknown. In this study, mice were injected with cyclophosphamide to deplete neutrophils and then passively immunized with anti-PA serum or negative serum. Mice were subsequently challenged with APP serotype 1. The results showed that the mice exhibited less bacterial colonization, less lung damage, and a high survival rate, which were immunized with the anti-PA antibody whether neutrophils were depleted or not. Worse still, the presence of neutrophils increased the damage to the mice after challenge. These results suggest that the activity of the anti-PA antibody against APP infection was independent of neutrophils. These findings have important significance for understanding the mechanisms of humoral immunity conferred by heterologous immunization and lay a good foundation for preventing APP infection.

Prophylactic inhibition of neutrophil elastase prevents the development of chronic neuropathic pain in osteoarthritic mice

Background

A subset of osteoarthritis (OA) patients experience joint pain with neuropathic characteristics. Mediators such as neutrophil elastase, a serine proteinase, may be released during acute OA inflammatory flares. We have previously shown that local administration of neutrophil elastase causes joint inflammation and pain via activation of proteinase-activated receptor-2 (PAR2). The aim of this study was to examine the contribution of endogenous neutrophil elastase and PAR2 to the development of joint inflammation, pain, and neuropathy associated with monoiodoacetate (MIA)-induced experimental OA.

Methods

MIA (0.3 mg/10 μl) was injected into the right knee joint of male C57BL/6 mice (20–34 g). Joint inflammation (edema, leukocyte kinetics), neutrophil elastase proteolytic activity, tactile allodynia, and saphenous nerve demyelination were assessed over 14 days post-injection. The effects of inhibiting neutrophil elastase during the early inflammatory phase of MIA (days 0 to 3) were determined using sivelestat (50 mg/kg i.p.) and serpinA1 (10 μg i.p.). Involvement of PAR2 in the development of MIA-induced joint inflammation and pain was studied using the PAR2 antagonist GB83 (5 μg i.p. days 0 to 1) and PAR2 knockout animals.

Results

MIA caused an increase in neutrophil elastase proteolytic activity on day 1 (P < 0.0001), but not on day 14. MIA also generated a transient inflammatory response which peaked on day 1 (P < 0.01) then subsided over the 2-week time course. Joint pain appeared on day 1 and persisted to day 14 (P < 0.0001). By day 14, the saphenous nerve showed signs of demyelination. Early treatment with sivelestat and serpinA1 blocked the proteolytic activity of neutrophil elastase on day 1 (P < 0.001), and caused lasting improvements in joint inflammation, pain, and saphenous nerve damage (P < 0.05). MIA-induced synovitis was reversed by early treatment with GB83 and attenuated in PAR2 knockout mice (P < 0.05). PAR2 knockout mice also showed reduced MIA-induced joint pain (P < 0.0001) and less nerve demyelination (P = 0.81 compared to saline control).

Conclusions

Neutrophil elastase and PAR2 contribute significantly to the development of joint inflammation, pain, and peripheral neuropathy associated with experimental OA, suggesting their potential as therapeutic targets.

Sharpening Host Defenses during Infection: Proteases Cut to the Chase

The human immune system consists of an intricate network of tightly controlled pathways, where proteases are essential instigators and executioners at multiple levels. Invading microbial pathogens also encode proteases that have evolved to manipulate and dysregulate host proteins, including host proteases during the course of disease. The identification of pathogen proteases as well as their substrates and mechanisms of action have empowered significant developments in therapeutics for infectious diseases. Yet for many pathogens, there remains a great deal to be discovered. Recently, proteomic techniques have been developed that can identify proteolytically processed proteins across the proteome. These “degradomics” approaches can identify human substrates of microbial proteases during infection in vivo and expose the molecular-level changes that occur in the human proteome during infection as an operational network to develop hypotheses for further research as well as new therapeutics. This Perspective Article reviews how proteases are utilized during infection by both the human host and invading bacterial pathogens, including archetypal virulence-associated microbial proteases, such as the Clostridia spp. botulinum and tetanus neurotoxins. We highlight the potential knowledge that degradomics studies of host–pathogen interactions would uncover, as well as how degradomics has been successfully applied in similar contexts, including use with a viral protease. We review how microbial proteases have been targeted in current therapeutic approaches and how microbial proteases have shaped and even contributed to human therapeutics beyond infectious disease. Finally, we discuss how, moving forward, degradomics research can greatly contribute to our understanding of how microbial pathogens cause disease in vivo and lead to the identification of novel substrates in vivo, and the development of improved therapeutics to counter these pathogens.

Neutrophil elastase cleaves epithelial cadherin in acutely injured lung epithelium

Background

In acutely injured lungs, massively recruited polymorphonuclear neutrophils (PMNs) secrete abnormally neutrophil elastase (NE). Active NE creates a localized proteolytic environment where various host molecules are degraded leading to impairment of tissue homeostasis. Among the hallmarks of neutrophil-rich pathologies is a disrupted epithelium characterized by the loss of cell-cell adhesion and integrity. Epithelial-cadherin (E-cad) represents one of the most important intercellular junction proteins. E-cad exhibits various functions including its role in maintenance of tissue integrity. While much interest has focused on the expression and role of E-cad in different physio- and physiopathological states, proteolytic degradation of this structural molecule and ensuing potential consequences on host lung tissue injury are not completely understood.

Methods

NE capacity to cleave E-cad was determined in cell-free and lung epithelial cell culture systems. The impact of such cleavage on epithelial monolayer integrity was then investigated. Using mice deficient in NE in a clinically relevant experimental model of acute pneumonia, we examined whether degraded E-cad is associated with lung inflammation and injury and whether NE contributes to E-cad cleavage. Finally, we checked for the presence of both degraded E-cad and NE in bronchoalveolar lavage samples obtained from patients with exacerbated COPD, a clinical manifestation characterised by a neutrophilic inflammatory response.

Results

We show that NE is capable of degrading E-cad in vitro and in cultured cells. NE-mediated degradation of E-cad was accompanied with loss of epithelial monolayer integrity. Our in vivo findings provide evidence that NE contributes to E-cad cleavage that is concomitant with lung inflammation and injury. Importantly, we observed that the presence of degraded E-cad coincided with the detection of NE in diseased human lungs.

Conclusions

Active NE has the capacity to cleave E-cad and interfere with its cell-cell adhesion function. These data suggest a mechanism by which unchecked NE participates potentially to the pathogenesis of neutrophil-rich lung inflammatory and tissue-destructive diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-016-0449-x) contains supplementary material, which is available to authorized users.

Ilex kaushue and Its Bioactive Component 3,5-Dicaffeoylquinic Acid Protected Mice from Lipopolysaccharide-Induced Acute Lung Injury

Acute lung injury (ALI) is a severe respiratory disease with high mortality rates worldwide. Recent reports suggest that human neutrophil elastase (HNE) plays a key role in the inflammatory response that is characteristic of ALI, which indicates that the development of HNE inhibitors could be an efficient treatment strategy. In the current study, an enzyme-based screening assay was used to identify effective HNE inhibitors from a number of traditional Chinese medicines (TCMs). Among them, a water extract of Ilex kaushue (IKWE) effectively inhibited HNE activity (IC₅₀, 11.37 ± 1.59 μg/mL). Using bioactivity-guided fractionation, one new compound and 23 known compounds were identified. Compound 6 (identified as 3,5-dicaffeoylquinic acid; 3,5-DCQA) exerted the most potent and selective inhibitory effect on HNE activity (IC₅₀, 1.86 ± 0.06 μM). In a cell-based assay, 3,5-DCQA not only directly reduced superoxide generation and elastase activity but also attenuated the Src family kinase (SRKs)/Vav signaling pathway in N-formyl-L-Met-L-Leu-L-Phe (fMLF)-stimulated human neutrophils. In an animal disease model, both 3,5-DCQA and standardized IKWE protected against lipopolysaccharide-induced ALI in mice, which provides support for their potential as candidates in the development of new therapeutic agents for neutrophilic inflammatory diseases.

Application of multiplex immunoassay technology to investigations of ocular disease

Eye-derived fluids, including tears, aqueous humour and vitreous humour often contain molecular signatures of ocular disease states. These signatures can be composed of cytokines, chemokines, growth factors, proteases and soluble receptors. However, the small quantities (<10 µl) of these fluids severely limit the detection of these proteins by traditional enzyme-linked immunosorbent assay or Western blot. To maximise the amount of information generated from the analysis of these specimens, many researchers have employed multiplex immunoassay technologies for profiling the expression or modification of multiple proteins from minute sample volumes.

Elastase levels and activity are increased in dystrophic muscle and impair myoblast cell survival, proliferation and differentiation

In Duchenne muscular dystrophy, progressive loss of muscle tissue is accompanied by fibrosis, chronic inflammation and reduced muscle regenerative capacity. Although much is known about the development of fibrosis and chronic inflammation in muscular dystrophy, less is known about how they are mechanistically linked to loss of muscle regenerative capacity. We have developed a proteomics method to discover dystrophy-associated changes in the muscle progenitor cell niche, which identified serine proteases, and especially neutrophil elastase, as candidates. We show that elastase activity is increased in dystrophic (mdx^4cv) muscle and impairs myoblast survival in culture. While the effect of elastase on C2C12 cell survival correlates with the kinetics of elastase-mediated degradation of the substrate to which the cells adhere, the effect of elastase on satellite cell-derived primary myoblast growth and differentiation is substrate-independent and even more dramatic than the effect on C2C12 cells, suggesting a detrimental role for elastase on myogenesis in vivo. Additionally, elastase impairs differentiation of both primary and C2C12 myoblasts into myotubes. Our findings evidence the importance of neutrophil-mediated inflammation in muscular dystrophy and indicate elastase-mediated regulation of myoblast behaviour as a potential mechanism underlying loss of regenerative capacity in dystrophic muscle.

Degranulating Neutrophils Promote Leukotriene B4 Production by Infected Macrophages To Kill Leishmania amazonensis Parasites

Neutrophils mediate early responses against pathogens, and they become activated during endothelial transmigration toward the inflammatory site. In the current study, human neutrophils were activated in vitro with immobilized extracellular matrix proteins, such as fibronectin (FN), collagen, and laminin. Neutrophil activation by FN, but not other extracellular matrix proteins, induces the release of the granules' contents, measured as matrix metalloproteinase 9 and neutrophil elastase activity in culture supernatant, as well as reactive oxygen species production. Upon contact with Leishmania amazonensis-infected macrophages, these FN-activated neutrophils reduce the parasite burden through a mechanism independent of cell contact. The release of granule proteases, such as myeloperoxidase, neutrophil elastase, and matrix metalloproteinase 9, activates macrophages through TLRs, leading to the production of inflammatory mediators, TNF-α and leukotriene B4 (LTB4), which are involved in parasite killing by infected macrophages. The pharmacological inhibition of degranulation reverted this effect, abolishing LTB4 and TNF production. Together, these results suggest that FN-driven degranulation of neutrophils induces the production of LTB4 and TNF by infected macrophages, leading to the control of Leishmania infection.

Production of IL-8, VEGF and Elastase by Circulating and Intraplaque Neutrophils in Patients with Carotid Atherosclerosis

Objectives

Polymorphonuclear neutrophils (PMN) in atherosclerotic plaques have been identified only recently, and their contribution to plaque development is not yet fully understood. In this study, production of elastase, interleukin (IL)-8 and vascular endothelial growth factor (VEGF) by PMN was investigated in subjects with carotid stenosis undergoing carotid endarterectomy (CEA).

Methods

The study enrolled 50 patients (Pts) and 10 healthy subjects (HS). Circulating PMN (cPMN) isolated from venous blood (in both Pts and HS) and from plaques (pPMN, in Pts) were cultured, alone or with 0.1 μM fMLP. Elastase, IL-8 and VEGF mRNA were analyzed by real-time PCR. In CEA specimens, PMN were localized by immunohistochemistry.

Results

In both Pts cPMN and pPMN, IL-8 mRNA was higher at rest but lower after fMLP (P<0.01 vs HS), and VEGF mRNA was higher both at rest and after fMLP (P<0.01 vs HS), while elastase mRNA was not significantly different. On the contrary, protein production was always higher in cPMN of HS with respect to values measured in cells of Pts. In CEA specimens, CD66b+ cells localized to areas with massive plaque formation close to neovessels. Pts with soft and mix plaques, as defined by computed tomography, did not differ in cPMN or pPMN IL-8, VEGF or elastase mRNA, or in intraplaque CD66b+ cell density. However, Pts with soft plaques had higher white blood cell count due to increased PMN.

Conclusions

In Pts with carotid plaques, both circulating and intraplaque PMN produce IL-8, VEGF and elastase, which are crucial for plaque development and progression. These findings suggest mechanistic explanations to the reported correlation between PMN count and cardiovascular mortality in carotid ATH.

Granulocyte-macrophage colony-stimulating factor primes interleukin-13 production by macrophages via protease-activated receptor-2

Chronic inflammation is often linked to the presence of type 2-polarized macrophages, which are induced by the T helper type 2 cytokines interleukin-4 and interleukin-13 (IL-13). IL-13 is a key mediator of tissue fibrosis caused by T helper type 2-based inflammation. Human neutrophil elastase (HNE) plays a pivotal role in the pathogenesis of pulmonary fibrosis. This study investigated the priming effect of granulocyte-macrophage colony-stimulating factor (GM-CSF) on IL-13 expression by macrophages stimulated with HNE. Adherent macrophages were obtained from primary cultures of human mononuclear cells. Expression of IL-13 mRNA and protein by GM-CSF-dependent macrophages was investigated after stimulation with HNE, using the polymerase chain reaction and enzyme-linked immunosorbent assay. GM-CSF had a priming effect on IL-13 mRNA and protein expression by macrophages stimulated with HNE, while this effect was not observed for various other cytokines. GM-CSF-dependent macrophages showed a significant increase in the expression of protease activated receptor-2 (PAR-2) mRNA and protein. The response of IL-13 mRNA to HNE was significantly decreased by pretreatment with alpha1-antitrypsin, a PAR-2 antibody (SAM11), or a PAR-2 antagonist (ENMD-1068). These findings suggest that stimulation with HNE can induce IL-13 production by macrophages, especially GM-CSF-dependent macrophages. Accordingly, neutrophil elastase may have a key role in fibrosis associated with chronic inflammation.

Neutrophil extracellular traps downregulate lipopolysaccharide-induced activation of monocyte-derived dendritic cells

Polymorphonuclear neutrophils (PMN) play a central role in inflammation and participate in its control, notably by modulating dendritic cell (DC) functions via soluble mediators or cell-cell contacts. Neutrophil extracellular traps (NETs) released by PMN could play a role in this context. To evaluate NET effects on DC maturation, we developed a model based on monocyte-derived DC (moDC) and calibrated NETs isolated from fresh human PMN. We found that isolated NETs alone had no discernable effect on moDC. In contrast, they downregulated LPS-induced moDC maturation, as shown by decreased surface expression of HLA-DR, CD80, CD83, and CD86, and by downregulated cytokine production (TNF-α, IL-6, IL-12, IL-23), with no increase in the expression of tolerogenic DC genes. Moreover, the presence of NETs during moDC maturation diminished the capacity of these moDC to induce T lymphocyte proliferation in both autologous and allogeneic conditions, and modulated CD4(+) T lymphocyte polarization by promoting the production of Th2 cytokines (IL-5 and IL-13) and reducing that of Th1 and Th17 cytokines (IFN-γ and IL-17). Interestingly, the expression and activities of the lymphoid chemokine receptors CCR7 and CXCR4 on moDC were not altered when moDC matured in the presence of NETs. Together, these findings reveal a new role for NETs in adaptive immune responses, modulating some moDC functions and thereby participating in the control of inflammation.

The role of oxidative stress during inflammatory processes

Abstract The production of various reactive oxidant species in excess of endogenous antioxidant defense mechanisms promotes the development of a state of oxidative stress, with significant biological consequences. In recent years, evidence has emerged that oxidative stress plays a crucial role in the development and perpetuation of inflammation, and thus contributes to the pathophysiology of a number of debilitating illnesses, such as cardiovascular diseases, diabetes, cancer, or neurodegenerative processes. Oxidants affect all stages of the inflammatory response, including the release by damaged tissues of molecules acting as endogenous danger signals, their sensing by innate immune receptors from the Toll-like (TLRs) and the NOD-like (NLRs) families, and the activation of signaling pathways initiating the adaptive cellular response to such signals. In this article, after summarizing the basic aspects of redox biology and inflammation, we review in detail the current knowledge on the fundamental connections between oxidative stress and inflammatory processes, with a special emphasis on the danger molecule high-mobility group box-1, the TLRs, the NLRP-3 receptor, and the inflammasome, as well as the transcription factor nuclear factor-κB.

Innate immunity to Leishmania infection: within phagocytes

Infection by Leishmania takes place in the context of inflammation and tissue repair. Besides tissue resident macrophages, inflammatory macrophages and neutrophils are recruited to the infection site and serve both as host cells and as effectors against infection. Recent studies suggest additional important roles for monocytes and dendritic cells. This paper addresses recent experimental findings regarding the regulation of Leishmania major infection by these major phagocyte populations. In addition, the role of IL-4 on dendritic cells and monocytes is discussed.

The landscape of protein biomarkers proposed for periodontal disease: markers with functional meaning

Periodontal disease (PD) is characterized by a deregulated inflammatory response which fails to resolve, activating bone resorption. The identification of the proteomes associated with PD has fuelled biomarker proposals; nevertheless, many questions remain. Biomarker selection should favour molecules representing an event which occurs throughout the disease progress. The analysis of proteome results and the information available for each protein, including its functional role, was accomplished using the OralOme database. The integrated analysis of this information ascertains if the suggested proteins reflect the cell and/or molecular mechanisms underlying the different forms of periodontal disease. The evaluation of the proteins present/absent or with very different concentrations in the proteome of each disease state was used for the identification of the mechanisms shared by different PD variants or specific to such state. The information presented is relevant for the adequate design of biomarker panels for PD. Furthermore, it will open new perspectives and help envisage future studies targeted to unveil the functional role of specific proteins and help clarify the deregulation process in the PD inflammatory response.