Targeting neutrophil elastase is a promising direction for future cancer treatment

Neutrophil elastase (NE) is a proteolytic enzyme released extracellular during the formation of neutrophil extracellular traps (NETs) through degranulation. In addition to participating in the body's inflammatory response, NE also plays an important role in cancer. It can promote tumor proliferation, migration, and invasion, induce epithelial-mesenchymal transition (EMT), and change the tumor microenvironment (TME) to promote tumor progression. Concurrently, NE promotes systemic treatment resistance by inducing EMT. However, it can also selectively kill cancer cells and attenuate tumor development. Sivelestat is a specific NE inhibitor that can be used in the perioperative period of esophageal cancer patients to reduce the incidence of postoperative complications after esophagectomy. In addition, the combination of sivelestat and trastuzumab can enhance the efficacy of human epidermal growth factor receptor 2(HER 2) positive breast cancer patients. Meanwhile, targeting the human antibody domains and fragments of NE is also a new way to treat cancer and inflammation-related diseases. This review provides valuable insights into the role of NE in cancer treatment. Additionally, we discuss the challenges associated with the clinical application of sivelestat. By shedding light on the promising potential of NE, this review contributes to the advancement of cancer treatment strategies.

Clinical Significance of Serum Elafin in Children with Inflammatory Bowel Disease

BACKGROUND

The role of elafin in the pathophysiology of inflammatory bowel disease (IBD) has not been not elucidated. We aimed to evaluate serum elafin in children with IBD and assess its relationship with disease activity.

METHODS

We enrolled children with IBD in the study group and children with functional abdominal pain in the control group. We evaluated serum elafin using enzyme-linked immunosorbent assay kits.

RESULTS

In children with IBD, serum elafin (mean ± SD: 4.192 ± 1.424 ng/mL) was significantly elevated compared with controls (mean ± SD: 3.029 ± 1.366 ng/mL) (p = 0.0005). Elafin was significantly increased in children in the active phase of IBD (mean ± SD: 4.424 ± 1.449 ng/mL) compared with the control group (p = 0.0003). In IBD remission, only children with ulcerative colitis (mean ± SD: 4.054 ± 1.536 ng/mL) had elevated elafin compared with controls (p = 0.004). ROC analysis revealed that the area under the curve (AUC) of serum elafin was 0.809 while discriminating patients with ulcerative colitis from the control group, and the AUC was 0.664 while differentiating patients with Crohn's disease from the control group.

CONCLUSIONS

Serum elafin was found to be elevated in our cohort of children with IBD, depending on disease activity. Serum elafin was increased in the active phases of both ulcerative colitis and Crohn's disease, but only in the remission of ulcerative colitis. Elafin appears to be a potential candidate for a biomarker of ulcerative colitis.

Flavonoids as inhibitors of human neutrophil elastase

Elastase is a proteolytic enzyme belonging to the family of hydrolases produced by human neutrophils, monocytes, macrophages, and endothelial cells. Human neutrophil elastase is known to play multiple roles in the human body, but an increase in its activity may cause a variety of diseases. Elastase inhibitors may prevent the development of psoriasis, chronic kidney disease, respiratory disorders (including COVID-19), immune disorders, and even cancers. Among polyphenolic compounds, some flavonoids and their derivatives, which are mostly found in herbal plants, have been revealed to influence elastase release and its action on human cells. This review focuses on elastase inhibitors that have been discovered from natural sources and are biochemically characterised as flavonoids. The inhibitory activity on elastase is a characteristic of flavonoid aglycones and their glycoside and methylated, acetylated and hydroxylated derivatives. The presented analysis of structure-activity relationship (SAR) enables the determination of the chemical groups responsible for evoking an inhibitory effect on elastase. Further study especially of the in vivo efficacy and safety of the described natural compounds is of interest in order to gain better understanding of their health-promoting potential.

Human Inflammatory Neutrophils Express Genes Encoding Peptidase Inhibitors: Production of Elafin Mediated by NF-κB and CCAAT/Enhancer-Binding Protein β

The concept of plasticity of neutrophils is highlighted by studies showing their ability to transdifferentiate into APCs. In this regard, transdifferentiated neutrophils were found at inflammatory sites of autoimmune arthritis (AIA). Exposure of neutrophils to inflammatory stimuli prolongs their survival, thereby favoring the acquisition of pathophysiologically relevant phenotypes and functions. By using microarrays, quantitative RT-PCR, and ELISAs, we showed that long-lived (LL) neutrophils obtained after 48 h of culture in the presence of GM-CSF, TNF, and IL-4 differentially expressed genes related to apoptosis, MHC class II, immune response, and inflammation. The expression of anti-inflammatory genes mainly of peptidase inhibitor families is upregulated in LL neutrophils. Among these, the PI3 gene encoding elafin was the most highly expressed. The de novo production of elafin by LL neutrophils depended on a synergism between GM-CSF and TNF via the activation and cooperativity of C/EBPβ and NF-κB pathways, respectively. Elafin concentrations were higher in synovial fluids (SF) of patients with AIA than in SF of osteoarthritis. SF neutrophils produced more elafin than blood counterparts. These results are discussed with respect to implications of neutrophils in chronic inflammation and the potential influence of elafin in AIA.

Roles of neutrophil granule proteins in orchestrating inflammation and immunity

Neutrophil granulocytes form the first line of host defense against invading pathogens and tissue injury. They are rapidly recruited from the blood to the affected sites, where they deploy an impressive arsenal of effectors to eliminate invading microbes and damaged cells. This capacity is endowed in part by readily mobilizable proteins acquired during granulopoiesis and stored in multiple types of cytosolic granules with each granule type containing a unique cargo. Once released, granule proteins contribute to killing bacteria within the phagosome or the extracellular milieu, but are also capable of inflicting collateral tissue damage. Neutrophil-driven inflammation underlies many common diseases. Research over the last decade has documented neutrophil heterogeneity and functional versatility far beyond their antimicrobial function. Emerging evidence indicates that neutrophils utilize granule proteins to interact with innate and adaptive immune cells and orchestrate the inflammatory response. Granule proteins have been identified as important modulators of neutrophil trafficking, reverse transendothelial migration, phagocytosis, neutrophil life span, neutrophil extracellular trap formation, efferocytosis, cytokine activity, and autoimmunity. Hence, defining their roles within the inflammatory locus is critical for minimizing damage to the neighboring tissue and return to homeostasis. Here, we provide an overview of recent advances in the regulation of degranulation, granule protein functions, and signaling in modulating neutrophil-mediated immunity. We also discuss how targeting granule proteins and/or signaling could be harnessed for therapeutic benefits.

Cervicovaginal natural antimicrobial expression in pregnancy and association with spontaneous preterm birth

There is much interest in the role of innate immune system proteins (antimicrobial peptides) in the inflammatory process associated with spontaneous preterm birth (sPTB). After promising pilot work, we aimed to validate the association between the antimicrobial peptides/proteins elafin and cathelicidin and sPTB. An observational cohort study of 405 women at high-risk, and 214 women at low-risk of sPTB. Protein concentrations of elafin and cathelicidin, and the enzyme human neutrophil elastase (HNE) were measured in over 1,000 cervicovaginal fluid (CVF) samples (10 to 24 weeks’ gestation). Adjusted CVF cathelicidin and HNE concentrations (but not elafin) were raised in high-risk women who developed cervical shortening and who delivered prematurely and were predictive of sPTB < 37 weeks, with an area under the curve (AUC) of 0.75 (95% CI 0.68 to 0.81) for cathelicidin concentration at 14 to 15⁺⁶ weeks. Elafin concentrations were affected by gestation, body mass index and smoking. CVF elafin in early pregnancy was modestly predictive of sPTB < 34 weeks (AUC 0.63, 0.56–0.70). Alterations in innate immune response proteins in early pregnancy are predictive of sPTB. Further investigation is warranted to understand the drivers for this, and their potential to contribute towards clinically useful prediction techniques.

Ulinastatin treatment for acute respiratory distress syndrome in China: a meta-analysis of randomized controlled trials

BACKGROUND

Epidemiologic studies have shown inconsistent conclusions about the effect of ulinastain treatment for acute respiratory distress syndrome (ARDS). It is necessary to perform a meta-analysis of ulinastatin's randomized controlled trials (RCTS) to evaluate its efficacy for treating ARDS.

METHODS

We searched the published RCTs of ulinastatin treatment for ARDS from nine databases (the latest search on April 30th, 2017). Two authors independently screened citations and extracted data. The meta-analysis was performed using Rev. Man 5.3 software.

RESULTS

A total of 33 RCTs involving 2344 patients satisfied the selection criteria and were included in meta-analysis. The meta-analysis showed that, compared to conventional therapy, ulinastatin has a significant benefit for ARDS patients by reducing mortality (RR = 0.51, 95% CI:0.43~0.61) and ventilator associated pneumonia rate (RR = 0.50, 95% CI: 0.36~0.69), and shortening duration of mechanical ventilation (SMD = -1.29, 95% CI: -1.76~-0.83), length of intensive care unit stay (SMD = -1.38, 95% CI: -1.95~-0.80), and hospital stay (SMD = -1.70, 95% CI:-2.63~-0.77). Meanwhile, ulinastatin significantly increased the patients' oxygenation index (SMD = 2.04, 95% CI: 1.62~2.46) and decreased respiratory rate (SMD = -1.08, 95% CI: -1.29~-0.88) and serum inflammatory factors (tumor necrosis factor-α: SMD = -3.06, 95% CI:-4.34~-1.78; interleukin-1β: SMD = -3.49, 95% CI: -4.64~-2.34; interleukin-6: SMD = -2.39, 95% CI: -3.34~-1.45; interleukin-8: SMD = -2.43, 95% CI: -3.86~-1.00).

CONCLUSIONS

Ulinastatin seemly showed a beneficial effect for ARDS patients treatment and larger sample sized RCTs are needed to confirm our findings.

Neutrophil elastase inhibitory effects of pentacyclic triterpenoids from Eriobotrya japonica (loquat leaves)

ETHNOPHARMACOLOGICAL RELEVANCE

Eriobotrya japonica, a traditional herbal medicine in China and Japan, has long been used to treat chronic bronchitis and coughs.

AIM OF THE STUDY

Pentacyclic triterpenoids (PTs), especially ursolic acid (UA), have been found as reversibly and competitively human neutrophil elastase (HNE) inhibitors. However, the limited solubility and poor bioavailability of PTs hinder their clinical use. Crude plant extracts may have a greater activity than isolated constituents of the equivalent dosage. In this study, an Eriobotrya japonica (loquat leaves) extract (triterpenoid composition of loquat leaves, TCLL) with enriched PTs such as UA was prepared. The study aims to compare the HNE inhibitory (HNEI) effect in vitro and the therapeutic effect on acute lung injury (ALI) in vivo between TCLL and UA.

MATERIALS AND METHODS

An HNEI activity bioassay was performed with Sivelestat sodium hydrate as a positive control. A lipopolysaccharide (LPS)-induced lung inflammatory model was established to evaluate TCLL's therapeutic effect on ALI in vivo. The absorption of UA in TCLL and in UA alone was determined using a Caco-2 cell uptake model and LC-MS.

RESULTS

The IC₅₀ values of TCLL and UA for the HNEI effect were 3.26 ± 0.56 μg/mL and 8.49 ± 0.42 μg/mL (P < 0.01), respectively. TCLL significantly improved the inflammatory cells and inflammatory cytokine production in mice compared with the LPS group (P < 0.05). Additionally, it performed better than the UA alone group (P < 0.05). Moreover, the uptake by Caco-2 cells of UA in TCLL was higher than that in UA alone (P < 0.05).

CONCLUSION

TCLL has a significant HNEI effect in vitro and a therapeutic effect on LPS-induced inflammation in a mouse model. Both the effects are more efficient than UA. Improved absorption of PTs in TCLL may be one explanation for these results.

Pathogen proteases and host protease inhibitors in molluscan infectious diseases

The development of infectious diseases represents an outcome of dynamic interactions between the disease-producing agent's pathogenicity and the host's self-defense mechanism. Proteases secreted by pathogenic microorganisms and protease inhibitors produced by host species play an important role in the process. This review aimed at summarizing major findings in research on pathogen proteases and host protease inhibitors that had been proposed to be related to the development of mollusk diseases. Metalloproteases and serine proteases respectively belonging to Family M4 and Family S8 of the MEROPS system are among the most studied proteases that may function as virulence factors in mollusk pathogens. On the other hand, a mollusk-specific family (Family I84) of novel serine protease inhibitors and homologues of the tissue inhibitor of metalloprotease have been studied for their potential in the molluscan host defense. In addition, research at the genomic and transcriptomic levels showed that more proteases of pathogens and protease inhibitor of hosts are likely involved in mollusk disease processes. Therefore, the pathological significance of interactions between pathogen proteases and host protease inhibitors in the development of molluscan infectious diseases deserves more research efforts.

Synthesis, biological evaluation, and molecular modelling studies of potent human neutrophil elastase (HNE) inhibitors

We report the synthesis and biological evaluation of a new series of 3- or 4-(substituted)phenylisoxazolones as HNE inhibitors. Due to tautomerism of the isoxazolone nucleus, two isomers were obtained as final compounds (2-NCO and 5-OCO) and the 2-NCO derivatives were the most potent with IC₅₀ values in the nanomolar range (20–70 nM). Kinetic experiments indicated that 2-NCO 7d and 5-OCO 8d are both competitive HNE inhibitors. Molecular modelling on 7d and 8d suggests for the latter a more crowded region about the site of the nucleophilic attack, which could explain its lowered activity. In addition molecular dynamics (MD) simulations showed that the isomer 8d appears more prone to form H-bond interactions which, however, keep the reactive sites quite distant for the attack by Ser195. By contrast the amide 7d appears more mobile within the active pocket, since it makes single H-bond interactions affording a favourable orientation for the nucleophilic attack.

Involvement of a newly identified atypical type II crustin (SpCrus5) in the antibacterial immunity of mud crab Scylla paramamosain

Crustins, the main AMP family in Crustacea, are generated as isoforms in many species and implicated in innate immune responses, but their detailed molecular mechanisms on susceptible bacteria remain largely unclear. Type II and type I crustins are distinguished by glycine-rich region (GRR), which is a major marker motif, and some type II crustins exhibit stronger antibacterial activities than their GRR deletion mutants. In the present study, a novel crustin, namely, SpCrus5, was functionally characterized from a commercially valuable crab Scylla paramamosain. SpCrus5 contained a typical cysteine-rich domain at the N-terminus, a conserved WAP domain in the center, and a special GRR at the C-terminus, which is located in a site that differs from that of GRRs in typical type II crustins found between signal peptides and cysteine-rich domains. SpCrus5 shared high similarities with most type II crustins, and it was more closely related to type II crustins than to other retrieved crustins. SpCrus5 was predominantly expressed in gills and remarkably upregulated after the crabs were challenged with Vibrio parahemolyticus or Staphylococcus aureus, suggesting that SpCrus5 might participate in antibacterial immune responses. To further elucidate how this C-terminal GRR affects the function of SpCrus5, we harvested a GRR deletion mutant (SpCrus5-ΔGRR) by deleting the GRR. Liquid growth inhibition assays demonstrated that the antimicrobial activity of SpCrus5 was stronger than that of SpCrus5-ΔGRR, and the antibacterial spectrum of the former toward Gram-negative bacteria was broader than that of the latter. Binding assays revealed that the microorganism-binding ability and polysaccharide-binding activity of SpCrus5 were stronger than those of SpCrus5-ΔGRR. SpCrus5 or SpCrus5-ΔGRR agglutinated all tested Gram-positive bacteria. Therefore, the antibacterial activities of SpCrus5 were stronger and broader than those of SpCrus5-ΔGRR, and the binding ability and agglutination activity might contribute to the antimicrobial activity of SpCrus5. These results revealed that the C-terminal GRR was necessary to produce an efficient antibacterial activity of SpCrus5. SpCrus5 was highly identical with most type II crustins and it functioned as many type II crustins did, indicating that SpCrus5 was more likely an atypical type II crustin than a type I crustin. This study revealed that SpCrus5 participated as an essential antimicrobial effector in immune responses and provided new insights into the underlying mechanisms of the sequence and function diversity of crustins.

Synthesis and analytical characterization of new thiazol-2-(3H)-ones as human neutrophil elastase (HNE) inhibitors

Human neutrophil elastase (HNE) is a potent serine protease belonging to the chymotrypsin family and is involved in a variety of pathologies affecting the respiratory system. Thus, compounds able to inhibit HNE proteolytic activity could represent effective therapeutics. We present here the synthesis of new thiazol-2-(3H)-ones as an elaboration of potent HNE inhibitors with an isoxazol-5-(2H)-one scaffold that we recently identified. Two-dimensional NMR spectroscopic techniques and tandem mass spectrometry allowed us to correctly assign the structure of the final compounds arising from both tautomers of the thiazol-2-(3H)-one nucleus (N-3 of the thiazol-2-(3H)-one and 3-OH of the thiazole). All new compounds were tested as HNE inhibitors, and no activity was found at the highest concentration used (40 µM), demonstrating that the thiazol-2-(3H)-one is not a good scaffold for HNE inhibitors. Molecular modelling experiments indicate that the low-energy pose might limit the nucleophilic attack on the endocyclic carbonyl group of the thiazolone-based compounds by HNE catalytic Ser195, in contrast to isoxazol-5-(2H)-one analogues.

Homeostasis of the gut barrier and potential biomarkers

The gut barrier plays a crucial role by spatially compartmentalizing bacteria to the lumen through the production of secreted mucus and is fortified by the production of secretory IgA (sIgA) and antimicrobial peptides and proteins. With the exception of sIgA, expression of these protective barrier factors is largely controlled by innate immune recognition of microbial molecular ligands. Several specialized adaptations and checkpoints are operating in the mucosa to scale the immune response according to the threat and prevent overreaction to the trillions of symbionts inhabiting the human intestine. A healthy microbiota plays a key role influencing epithelial barrier functions through the production of short-chain fatty acids (SCFAs) and interactions with innate pattern recognition receptors in the mucosa, driving the steady-state expression of mucus and antimicrobial factors. However, perturbation of gut barrier homeostasis can lead to increased inflammatory signaling, increased epithelial permeability, and dysbiosis of the microbiota, which are recognized to play a role in the pathophysiology of a variety of gastrointestinal disorders. Additionally, gut-brain signaling may be affected by prolonged mucosal immune activation, leading to increased afferent sensory signaling and abdominal symptoms. In turn, neuronal mechanisms can affect the intestinal barrier partly by activation of the hypothalamus-pituitary-adrenal axis and both mast cell-dependent and mast cell-independent mechanisms. The modulation of gut barrier function through nutritional interventions, including strategies to manipulate the microbiota, is considered a relevant target for novel therapeutic and preventive treatments against a range of diseases. Several biomarkers have been used to measure gut permeability and loss of barrier integrity in intestinal diseases, but there remains a need to explore their use in assessing the effect of nutritional factors on gut barrier function. Future studies should aim to establish normal ranges of available biomarkers and their predictive value for gut health in human cohorts.

Characterization of molecular properties and regulatory pathways of CrustinPm1 and CrustinPm7 from the black tiger shrimp Penaeus monodon

CrustinPm1 and crustinPm7 are the two most abundant isoforms of crustins identified from the hemocytes of the black tiger shrimp, Penaeus monodon. CrustinPm1 inhibits only Gram-positive bacteria, while crustinPm7 acts against both Gram-positive and Gram-negative bacteria. This work aims to characterize the molecular properties of recombinant crustinPm1 and crustinPm7, and the regulatory pathways of these two crustins. Circular dichroism spectroscopy revealed that crustinPm1 contained 40.81% alpha-helix and 22.34% beta-sheet, whereas crustinPm7 is made up of 32.86% alpha-helix and 27.53% beta-sheet. CrustinPm1 and crustinPm7 bound to phosphatidic acid (PA) with positive cooperativity of Hill slope (H) > 2, indicating that at least two molecules of crustins bind with one PA molecule. It is worth noting that both crustins bound to PA with significantly higher affinity than to lipoteichoic acid (LTA) and lipopolysaccharide (LPS). We speculate that crustin might also achieve antimicrobial activity by targeting PA, a signaling lipid. Regulatory pathways of crustinPm1 and crustinPm7 were investigated by knockdown of PmRelish and PmMyD88. This study demonstrated that crustinPm1 is mediated through the Toll signaling pathway, while crustinPm7 is regulated via both Toll and Imd pathways.

Review seed biopharmaceutical cyclic peptides: From discovery to applications

Mini-proteins (or peptides) with disulfide bond/s and a cyclic backbone offer exciting opportunities for applications in medicine, as these ribosomally synthesized and posttranslationally modified peptides are exceptionally stable and amenable to grafting epitopes with desirable activities. Here I discuss important aspects of the discovery and applications of disulfide-bonded cyclic peptides from seeds, i.e., the trypsin inhibitor cyclotides and the preproalbumin with sunflower trypsin inhibitor-derived peptides, focusing on bioanalytical methods for and insights generated from their discovery as well as their potential use as engineering scaffolds for peptide-based drug design. The recent discovery of their precursors and processing enzymes could potentially enable in planta production of designer disulfide-bonded cyclic peptides, preferably in edible seeds, and address the demand for new biopharmaceutical peptides in a cost-effective manner.

Inhibition of human neutrophil elastase by pentacyclic triterpenes

SCOPE

Inhibiting human neutrophil elastase (HNE) is a promising strategy for treating inflammatory lung diseases, such as H1N1 and SARS virus infections. The use of sivelestat, the only clinically registered synthesized HNE inhibitor, is largely limited by its risk of organ toxicity because it irreversibly inhibits HNE. Therefore, potent reversible HNE inhibitors are promising alternatives to sivelestat.

METHODS AND RESULTS

An in vitro HNE inhibition assay was employed to screen a series of triterpenes. Six pentacyclic triterpenes, but not tetracyclic triterpenes, significantly inhibited HNE. Of these pentacyclic triterpenes, ursolic acid exhibited the highest inhibitory potency (IC50 = 5.51 µM). The HNE inhibitory activity of ursolic acid was further verified using a mouse model of acute smoke-induced lung inflammation. The results of nuclear magnetic resonance and HNE inhibition kinetic analysis showed that the pentacyclic triterpenes competitively and reversibly inhibited HNE. Molecular docking experiments indicated that the molecular scaffold, 28-COOH, and a double bond at an appropriate location in the pentacyclic triterpenes are important for their inhibitory activity.

CONCLUSION

Our results provide insights into the effects of pentacyclic triterpenes on lung inflammatory actions through reversible inhibition of HNE activity.

A lack of secretory leukocyte protease inhibitor (SLPI) causes defects in granulocytic differentiation

We identified diminished levels of the natural inhibitor of neutrophil elastase (NE), secretory leukocyte protease inhibitor (SLPI), in myeloid cells and plasma of patients with severe congenital neutropenia (CN). We further found that downregulation of SLPI in CD34(+) bone marrow (BM) hematopoietic progenitors from healthy individuals resulted in markedly reduced in vitro myeloid differentiation accompanied by cell-cycle arrest and elevated apoptosis. Reciprocal regulation of SLPI by NE is well documented, and we previously demonstrated diminished NE levels in CN patients. Here, we found that transduction of myeloid cells with wild-type NE or treatment with exogenous NE increased SLPI messenger RNA and protein levels, whereas transduction of mutant forms of NE or inhibition of NE resulted in downregulation of SLPI. An analysis of the mechanisms underlying the diminished myeloid differentiation caused by reduced SLPI levels revealed that downregulation of SLPI with short hairpin RNA (shRNA) upregulated nuclear factor κB levels and reduced phospho-extracellular signal-regulated kinase (ERK1/2)-mediated phosphorylation and activation of the transcription factor lymphoid enhancer-binding factor-1 (LEF-1). Notably, microarray analyses revealed severe defects in signaling cascades regulating the cell cycle, including c-Myc-downstream signaling, in myeloid cells transduced with SLPI shRNA. Taken together, these results indicate that SLPI controls the proliferation, differentiation, and cell cycle of myeloid cells.

Infectious Mechanisms Regulating Susceptibility to Acute Exacerbations of COPD

Acute exacerbations of COPD (AECOPD) are defined by clinical criteria, outlined in the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines [1]. These include an acute increase in one or more of the following cardinal symptoms, beyond day to day variability: dyspnea, increased frequency or severity of cough and increased volume or change in character of sputum, which represent an acute increase in airway inflammation. The role of infection in the pathogenesis of COPD, acute exacerbation and disease progression has been a clinical and research question for many years, and the pendulum has swung from infection as a major cause of acute exacerbation and COPD (British Hypothesis) [2], to infection as an unrelated epiphomenon in acute exacerbation [3–5], and back again to infection as integral in the development of AECOPD and likely an important contributor to COPD progression [6–19]. Upwards of 80 % of AECOPD are driven by infectious stimuli, with 40–50 % associated with bacterial infection and 30–50 % associated with acute viral infection, with some exacerbations having dual bacterial and viral causation [20]. Much of the advancement in our understanding of the role of infection is AECOPD is due to the advancement of clinical and research tools that have allowed researchers to accurately characterize the microbial pathogens, and better understand the host-pathogen interactions (Table 1).

Enzyme-degradable self-assembled hydrogels from polyalanine-modified poly(ethylene glycol) star polymers

The generation of a range of star-shaped block copolymers composed of a biocompatible poly(ethylene glycol) (PEG) core tethered to a polyalanine (PAla) shell that possesses the capability to (reversibly) self-assemble in water is described. The hydrogels formed offer a hydrophilic environment ideal for biological processes involving proteins and are able to withhold albumin for prolonged periods before its triggered release following the targeted material degradation by the proteolytic enzyme elastase. Consequently, the materials formed offer significant promise for the delivery of proteins, and possibly inhibitors, in response to a proteolytic enzyme overexpressed in chronic wounds.

Proinflammatory macrophages enhance the regenerative capacity of human myoblasts by modifying their kinetics of proliferation and differentiation

Macrophages have been shown to be essential for muscle repair by delivering trophic cues to growing skeletal muscle precursors and young fibers. Here, we investigated whether human macrophages, either proinflammatory or anti-inflammatory, coinjected with human myoblasts into regenerating muscle of Rag2(-/-) γC(-/-) immunodeficient mice, could modify in vivo the kinetics of proliferation and differentiation of the transplanted human myogenic precursors. Our results clearly show that proinflammatory macrophages improve in vivo the participation of injected myoblasts to host muscle regeneration, extending the window of proliferation, increasing migration, and delaying differentiation. Interestingly, immunostaining of transplanted proinflammatory macrophages at different time points strongly suggests that these cells are able to switch to an anti-inflammatory phenotype in vivo, which then may stimulate differentiation during muscle regeneration. Conceptually, our data provide for the first time in vivo evidence strongly suggesting that proinflammatory macrophages play a supportive role in the regulation of myoblast behavior after transplantation into preinjured muscle, and could thus potentially optimize transplantation of myogenic progenitors in the context of cell therapy.

The N-terminal glycine-rich and cysteine-rich regions are essential for antimicrobial activity of crustinPm1 from the black tiger shrimp Penaeus monodon

An antimicrobial protein crustinPm1 from Penaeus monodon is a WAP domain-containing protein with an antimicrobial activity against Gram-positive bacteria but does not have antiproteinase activity. The lack of antiproteinase is speculated to be due to the P(1)' Met and/or the length of spacing between the conserved Cys2 and Cys3 while the antimicrobial activity may be due to the N-terminal Gly-rich and Cys-rich regions. In this study, the P(1)-P(1)' and the N-terminal Gly-rich and Cys-rich regions of crustinPm1 were mutated by amino acid substitution or deletion. Substitutions of P(1)-P(1)' from Pro-Pro to Leu-Leu, Leu-His, Leu-Met, Leu-Ala and P(1)' from Pro to Met did not make the protein inhibitory to subtilisin, trypsin, chymotrypsin and elastase. The mutations at P(1)-P(1)' positions in rcrustinPm1 had no effect on antibacterial activity. The WAP domain mutant with both Gly-rich and Cys-rich regions deleted did not exhibit antibacterial activity against Staphylococcus aureus while the deletion mutants of either Gly-rich or Cys-rich regions exhibited lower antibacterial activity than the wild type crustinPm1. Therefore, both Gly-rich and Cys-rich regions attached to a WAP domain are essential for efficient antibacterial activity of crustinPm1.

Proteomic analysis of bronchoalveolar lavage fluid proteins from mice infected with Francisella tularensis ssp. novicida

Francisella tularensis causes the zoonosis tularemia in humans and is one of the most virulent bacterial pathogens. We utilized a global proteomic approach to characterize protein changes in bronchoalveolar lavage fluid from mice exposed to one of three organisms, F. tularensis ssp. novicida, an avirulent mutant of F. tularensis ssp. novicida (F.t. novicida-ΔmglA), and Pseudomonas aeruginosa. The composition of bronchoalveolar lavage fluid (BALF) proteins was altered following infection, including proteins involved in neutrophil activation, oxidative stress, and inflammatory responses. Components of the innate immune response were induced including the acute phase response and the complement system; however, the timing of their induction varied. F. tularensis ssp. novicida infected mice do not appear to have an effective innate immune response in the first hours of infection; however, within 24 h, they show an upregulation of innate immune response proteins. This delayed response is in contrast to P. aeruginosa infected animals which show an early innate immune response. Likewise, F.t. novicida-ΔmglA infection initiates an early innate immune response; however, this response is diminished by 24 h. Finally, this study identifies several candidate biomarkers, including Chitinase 3-like-1 (CHI3L1 or YKL-40) and peroxiredoxin 1, that are associated with F. tularensis ssp. novicida but not P. aeruginosa infection.

Protease-activated receptor-2 (PAR2) in human gastric mucosa as mediator of proinflammatory effects in Helicobacter pylori infection

INTRODUCTION

Protease-activated receptors (PAR) are seven transmembrane receptors that are expressed throughout the gastrointestinal tract. In vitro experiments using gastric tumor cell lines, murine models and one clinical study provided evidence for a potential role of PAR2 in Helicobacter pylori-induced gastritis.

AIM

To investigate PAR2 expression in H. pylori-infected patients and correlation with proinflammatory IL-8, IL-1β as well as histologic changes of the mucosa. Furthermore, PAR2 expression was studied in context to mucosal amounts of secretory leukocyte protease inhibitor (SLPI), a putative regulator of PAR2.

METHODS

Twenty-two H. pylori-infected patients and 72 H. pylori-negative subjects underwent upper GI endoscopy. In antrum-derived mucosal biopsies, PAR2, IL-1β, IL-8, and SLPI expression was analyzed by quantitative RT-PCR, and in part by ELISA and immunohistochemistry. Histopathologic evaluation of gastritis was performed according to the updated Sydney classification.

RESULTS

IL-8 gene expression was 5-fold increased in the mucosa of H. pylori-infected patients compared with non-infected (p < .0001), whereas no differences for PAR2 and IL-1β mRNA amounts were observed between both groups. PAR2 gene expression correlated positively with transcript levels of IL-8, IL-1β as well mucosal SLPI levels in H. pylori-infected patients (r: 0.47-0.84; p < .0001), whereas no correlation was found with the degree of gastritis.

CONCLUSIONS

PAR2 represents an additive pathway of IL-8 secretion and proinflammatory effects in H. pylori-induced gastritis. Reduced SLPI levels leading to higher serine protease activities in the mucosa of infected subjects might regulate PAR2 activation.

Mucosal Progranulin expression is induced by H. pylori, but independent of Secretory Leukocyte Protease Inhibitor (SLPI) expression

Background

Mucosal levels of Secretory Leukocyte Protease Inhibitor (SLPI) are specifically reduced in relation to H. pylori-induced gastritis. Progranulin is an epithelial growth factor that is proteolytically degraded into fragments by elastase (the main target of SLPI). Considering the role of SLPI for regulating the activity of elastase, we studied whether the H. pylori-induced reduction of SLPI and the resulting increase of elastase-derived activity would reduce the Progranulin protein levels both ex vivo and in vitro.

Methods

The expression of Progranulin was studied in biopsies of H. pylori-positive, -negative and -eradicated subjects as well as in the gastric tumor cell line AGS by ELISA, immunohistochemistry and real-time RT-PCR.

Results

H. pylori-infected subjects had about 2-fold increased antral Progranulin expression compared to H. pylori-negative and -eradicated subjects (P < 0.05). Overall, no correlations between mucosal Progranulin and SLPI levels were identified. Immunohistochemical analysis confirmed the upregulation of Progranulin in relation to H. pylori infection; both epithelial and infiltrating immune cells contributed to the higher Progranulin expression levels. The H. pylori-induced upregulation of Progranulin was verified in AGS cells infected by H. pylori. The down-regulation of endogenous SLPI expression in AGS cells by siRNA methodology did not affect the Progranulin expression independent of the infection by H. pylori.

Conclusions

Taken together, Progranulin was identified as novel molecule that is upregulated in context to H. pylori infection. In contrast to other diseases, SLPI seems not to have a regulatory role for Progranulin in H. pylori-mediated gastritis.

Micro-encapsulated secretory leukocyte protease inhibitor decreases cell-mediated immune response in autoimmune orchitis

AIMS

We previously reported that recombinant human Secretory Leukocyte Protease Inhibitor (SLPI) inhibits mitogen-induced proliferation of human peripheral blood mononuclear cells. To determine the relevance of this effect in vivo, we investigated the immuno-regulatory role of SLPI in an experimental autoimmune orchitis (EAO) model.

MAIN METHODS

In order to increase SLPI half life, poly-ε-caprolactone microspheres containing SLPI were prepared and used for in vitro and in vivo experiments. Multifocal orchitis was induced in Sprague-Dawley adult rats by active immunization with testis homogenate and adjuvants. Microspheres containing SLPI (SLPI group) or vehicle (control group) were administered s.c. to rats during or after the immunization period.

KEY FINDINGS

In vitro SLPI-release microspheres inhibited rat lymphocyte proliferation and retained trypsin inhibitory activity. A significant decrease in EAO incidence was observed in the SLPI group (37.5%) versus the control group (93%). Also, SLPI treatment significantly reduced severity of the disease (mean EAO score: control, 6.33±0.81; SLPI, 2.72±1.05). In vivo delayed-type hypersensitivity and ex vivo proliferative response to testicular antigens were reduced by SLPI treatment compared to control group (p<0.05).

SIGNIFICANCE

Our results highlight the in vivo immunosuppressive effect of released SLPI from microspheres which suggests its feasible therapeutic use.

A double WAP domain-containing protein PmDWD from the black tiger shrimp Penaeus monodon is involved in the controlling of proteinase activities in lymphoid organ

A homolog of mammalian secretory leucocyte proteinase inhibitor or SLPI known as a double WAP domain (DWD) protein has been found in penaeid shrimp and believed to play an important role in innate immune system of the shrimp. The PmDWD identified from the Penaeus monodon EST database was investigated for its expression under pathogen infection. Infections by Vibrio harveyi and white spot syndrome virus (WSSV) up-regulated the expression of the PmDWD, which was peaked at about 24 h post infection and, then, subsided to more or less normal level. The PmDWD was expressed in various tissues of normal, 24-h WSSV-injected and leg-amputated shrimp, predominantly in the hemocytes. The expression was dramatically increased in lymphoid organ upon WSSV infection and leg amputation. The recombinant PmDWD (rPmDWD) was not active against the commercial proteinases: trypsin, chymotrypsin, elastase and subtilisin while its mutant rPmDWD_F70R was active against the subtilisin. By using agar diffusion assay, the rPmDWD inhibited the crude proteinases from lymphoid organs of leg-amputated and WSSV-infected shrimp. It inhibited the crude proteinases from Bacillus subtilis as well. Unlike the mammalian SLPIs, the rPmDWD had no antimicrobial activity against various bacteria.

Effects of bacterial infection on airway antimicrobial peptides and proteins in COPD

BACKGROUND

Pathogenic bacteria colonize the airways of 30% to 40% of patients with COPD and cause approximately 50% of exacerbations. New strains of nontypeable Haemophilus influenzae (NTHI) and Moraxella catarrhalis are associated with exacerbations. Antimicrobial protein/peptides (AMPs) play important roles in innate lung defense against pathogens. To our knowledge, the changes in AMP baseline levels in respiratory secretions during bacterial colonization and exacerbation have not been described. The objective of this study was to elucidate the effects of the acquisition of a new strain of pathogenic bacteria on the airway levels of AMPs in patients with COPD.

METHODS

One hundred fifty-three samples from 11 patients were selected from COPD sputum samples collected prospectively over 6 years. Samples were grouped as culture-negative (no pathogenic bacteria), colonization, and exacerbation due to new strains of NTHI and M catarrhalis. Levels of lysozyme, lactoferrin, LL-37, and secretory leukocyte protease inhibitor (SLPI) were measured by enzyme-linked immunosorbent assay and compared among groups by paired analysis.

RESULTS

Compared with baseline, sputum lysozyme levels were significantly lower during colonization and exacerbation by NTHI (P = .001 and P = .013, respectively) and M catarrhalis (P = .007 and P = .018, respectively); SLPI levels were lower with exacerbation due to NTHI and M catarrhalis (P = .002 and P = .004, respectively), and during colonization by M catarrhalis (P = 032). Lactoferrin levels did not change significantly; LL-37 levels were higher during exacerbation by NTHI and M catarrhalis (P = .001 and P = .018, respectively).

CONCLUSIONS

Acquisition of NTHI and M catarrhalis is associated with significant changes in airway levels of AMPs, with larger changes in exacerbation. Airway AMP levels are likely to be important in pathogen clearance and clinical outcomes of infection in COPD.

Gastroesophageal reflux disease does not lead to changes in the secretory leukocyte protease inhibitor expression in esophageal mucosa

OBJECTIVES

Secretory leukocyte protease inhibitor (SLPI) serves as a 'defense shield' against serine proteases in inflammation. Gastroesophageal reflux disease (GERD) is associated with chronic inflammation and histomorphological alterations of the gastroesophageal junction and esophageal mucosa. Here, it was investigated whether the presence of GERD was associated with changes of mucosal SLPI expression.

METHODS

Ninety-five patients with GERD-related symptoms and 27 patients lacking those symptoms were included. Endoscopic and histological evaluation was done according to the Los Angeles and updated Sydney classifications. Multiple biopsies were taken from gastric and esophageal mucosa of each patient for histology, immunohistochemistry (IHC), and molecular analyses. SLPI expression was analyzed by quantitative reverse transcriptase-PCR, enzyme-linked immunoassay, and IHC, and the data were statistically analyzed with respect to endoscopic and clinical parameters.

RESULTS

Forty-four patients had nonerosive and 51 erosive reflux diseases, respectively. Histology revealed higher chronic inflammation (P=0.04) and significant alterations of the intercellular spaces, basal cell hyperplasia, and length of papilla (P<0.05) in patients with GERD. Mucosal SLPI levels were comparable among antrum, cardia, and esophagus ranging from 95 to 165 pg/mug protein and were not affected by the presence of GERD, whereas esophageal SLPI-transcript levels were three-fold induced in patients with GERD (P=0.002). IHC identified epithelial cells as major cellular source of mucosal SLPI expression in normal cardiac and esophageal mucosa, whereas infiltrating immune cells contributed to the SLPI expression in chronically inflamed tissue.

CONCLUSION

GERD, a chemically induced inflammation, does not affect mucosal SLPI expression in gastroesophageal mucosa.

The serine protease marapsin is expressed in stratified squamous epithelia and is up-regulated in the hyperproliferative epidermis of psoriasis and regenerating wounds

The trypsin-like serine protease marapsin is a member of the large protease gene cluster at human chromosome 16p13.3, which also contains the structurally related proteases testisin, tryptase epsilon, tryptase gamma, and EOS. To gain insight into the biological functions of marapsin, we undertook a detailed gene expression analysis. It showed that marapsin expression was restricted to tissues containing stratified squamous epithelia and was absent or only weakly expressed in all other tissues, including the pancreas. Marapsin was constitutively expressed in nonkeratinizing stratified squamous epithelia of human esophagus, tonsil, cervix, larynx, and cornea. In the keratinizing stratified squamous epidermis of skin, however, its expression was induced only during epidermal hyperproliferation, such as in psoriasis and in murine wound healing. In fact, marapsin was the second most strongly up-regulated protease in psoriatic lesions, where expression was localized to the upper region of the hyperplastic epidermis. Similarly, in the hyperproliferative epithelium of regenerating murine skin wounds, marapsin localized to the suprabasal layers, where keratinocytes undergo squamous differentiation. The transient up-regulation of marapsin, which closely correlated with re-epithelialization, was virtually absent in a genetic mouse model of delayed wound closure. These results suggested a function during the process of re-epithelialization. Furthermore, in reconstituted human epidermis, a model system of epidermal differentiation, members of the IL-20 subfamily of cytokines, such as IL-22, induced marapsin expression. Consistent with a physiologic role in marapsin regulation, IL-22 was also strongly expressed in re-epithelializing skin wounds. Marapsin's restricted expression, localization, and cytokine-inducible expression suggest a role in the terminal differentiation of keratinocytes in hyperproliferating squamous epithelia.

Secretory leukocyte protease inhibitor: a secreted pattern recognition receptor for mycobacteria

RATIONALE

Human secretory leukocyte protease inhibitor (SLPI) displays bactericidal activity against pathogens such as Escherichia coli and Streptococcus. Furthermore, it has been reported that murine SLPI shows potent antimycobacterial activity.

OBJECTIVES

The aim of the present study was to investigate whether human recombinant SLPI not only kills mycobacteria but also acts as a pattern recognition receptor for the host immune system.

METHODS

For the in vivo experiment, BALB/c mice were infected by intranasal instillation with Mycobacterium bovis BCG and viable BCG load in lung homogenates was later determined. For the in vitro experiments, SLPI was incubated overnight with a suspension of M. bovis BCG or the virulent strain Mycobacterium tuberculosis H37Rv, and the percentage survival as well as the binding of SLPI to mycobacteria was determined. Furthermore, bacteria phagocytosis was also determined by flow cytometry.

MEASUREMENTS AND MAIN RESULTS

Intranasal SLPI treatment decreased the number of colony-forming units recovered from lung homogenates, indicating that SLPI interfered with M. bovis BCG infection. Moreover, SLPI decreased the viability of both M. bovis BCG and H37Rv. We demonstrated that SLPI attached to the surface of the mycobacteria by binding to pathogen-associated molecular pattern mannan-capped lipoarabinomannans and phosphatidylinositol mannoside. Furthermore, we found that in the sputum of patients with tuberculosis, mycobacteria were coated with endogenous SLPI. Finally, we showed that phagocytosis of SLPI-coated mycobacteria was faster than that of uncoated bacteria.

CONCLUSIONS

The present results demonstrate for the first time that human SLPI kills mycobacteria and is a new pattern recognition receptor for them.

Altered expression of antimicrobial molecules in cigarette smoke-exposed emphysematous mice lungs

BACKGROUND AND OBJECTIVE

The natural history of COPD, a disease usually caused by cigarette smoking, is associated with frequent respiratory infections. Consistent with human COPD, bacterial clearance in the lungs has been reported to be impaired in mice exposed to cigarette smoke. In the airways, several antimicrobial molecules such as surfactant proteins (SP), beta-defensins (BD), secretory leucocyte protease inhibitor (SLPI) and lysozyme play important roles in the defence against invading pathogens. This study evaluated the expression of antimicrobial molecules in mice lungs with cigarette smoke-induced emphysematous changes.

METHODS

Six B6C3F1 mice were exposed to cigarette smoke (2 cigarettes/day/mouse for 6 months) or room air. Gene expression within the lungs of mice in both groups was assessed by RT-PCR.

RESULTS

The expression of SP-A, BD2, BD3 and SLPI was significantly elevated in the lungs of cigarette smoke-exposed mice compared with air-exposed mice. BD1 expression decreased in the smoke-exposed mice and lysozyme expression was unchanged.

CONCLUSIONS

Chronic cigarette smoke exposure did not suppress the expression of antimicrobial molecules in the lung. Altered expression of antimicrobial molecules in this mouse model does not explain the impaired host defence against respiratory microbes seen in patients with COPD.

Human pre-elafin inhibits a Pseudomonas aeruginosa-secreted peptidase and prevents its proliferation in complex media

Pseudomonas aeruginosa is a life-threatening opportunist human pathogen frequently associated with lung inflammatory diseases, namely, cystic fibrosis. Like other species, this gram-negative bacteria is increasingly drug resistant. During the past decade, intensive research efforts have been focused on the identification of natural innate defense molecules with broad antimicrobial activities, collectively known as antimicrobial peptides. Human pre-elafin, best characterized as a potent inhibitor of neutrophil elastase with anti-inflammatory properties, was also shown to possess antimicrobial activity against both gram-positive and gram-negative bacteria, including P. aeruginosa. Its mode of action was, however, not known. Using full-length pre-elafin, each domain separately, and mutated variants of pre-elafin with attenuated antipeptidase activity toward neutrophil elastase, we report here that both pre-elafin domains contribute, through distinct mechanisms, to its antibacterial activity against Pseudomonas aeruginosa. Most importantly, we demonstrate that the whey acidic protein (WAP) domain specifically inhibits a secreted peptidase with the characteristics of arginyl peptidase (protease IV). This is the first demonstration that a human WAP-motif protein inhibits a secreted peptidase to prevent bacterial growth in vitro. Since several WAP-motif proteins from various species demonstrate antimicrobial function with variable activities toward bacterial species, we suggest that this mechanism may be more common than initially anticipated.

N-Benzoylpyrazoles Are Novel Small-Molecule Inhibitors of Human Neutrophil Elastase

Human neutrophil elastase (NE) plays an important role in the pathogenesis of pulmonary disease. Using high-throughput chemolibrary screening, we identified 10 N-benzoylpyrazole derivatives that were potent NE inhibitors. Nine additional NE inhibitors were identified through further screening of N-benzoylpyrazole analogues. Evaluation of inhibitory activity against a range of proteases showed high specificity for NE, although several derivatives were also potent inhibitors of chymotrypsin. Analysis of reaction kinetics and inhibitor stability revealed that N-benzoylpyrazoles were pseudoirreversible competitive inhibitors of NE. Structure-activity relationship (SAR) analysis demonstrated that modification of N-benzoylpyrazole ring substituents modulated enzyme selectivity and potency. Furthermore, molecular modeling of the binding of selected active and inactive compounds to the NE active site revealed that active compounds fit well into the catalytic site, whereas inactive derivatives contained substituents or conformations that hindered binding or accessibility to the catalytic residues. Thus, N-benzoylpyrazole derivatives represent novel structural templates that can be utilized for further development of efficacious NE inhibitors.

Attenuated induction of epithelial and leukocyte serine antiproteases elafin and secretory leukocyte protease inhibitor in Crohn's disease

Elafin (or skin-derived antileukoprotease) and secretory leukocyte protease inhibitor (SLPI) are serine antiproteases antagonizing human neutrophil elastase (HNE), thereby preventing tissue injury from excessive release of proteolytic enzymes by inflammatory cells. Furthermore, elafin and SLPI are "defensin-like" molecules with broad antimicrobial activity. The balance between proteases and antagonists may critically determine inflammatory processes in Crohn's disease (CD) and ulcerative colitis (UC). Real-time PCR was performed to quantitate colonic, proinflammatory cytokine IL-8, protease (HNE), and antiprotease mRNA (elafin and SLPI) in a total of 340 biopsies from 117 patients (47 CD, 45 UC, 25 controls). Histological inflammation was scored, and HNE, elafin, and SLPI were localized and semiquantified by immunostaining in 51 colonic paraffin sections (23 CD, 11 UC, 17 controls). Proinflammatory IL-8, degree of histological inflammation, and granulocyte content were similar in UC and CD. Elafin stained predominantly in the epithelium and SLPI in mucosal inflammatory cells. HNE mRNA levels and immunostaining were increased equally in both forms of inflammatory bowel disease. Levels of mRNA and immunostaining of the antiproteases elafin and SLPI were enhanced strongly in inflamed versus noninflamed UC. It is surprising that comparing inflamed versus noninflamed CD, this increase was significantly less pronounced for elafin and even lacking for SLPI. Despite comparable degrees of inflammation and protease levels, the induction of both antiproteases was attenuated in CD. This could contribute to the transmural depth of tissue destruction in CD. Elafin and SLPI may be added to the list of defensin-like peptides with diminished induction in CD versus UC.