Targeting COPD: advances on low-molecular-weight inhibitors of human neutrophil elastase

The Rise of Boron-Containing Compounds: Advancements in Synthesis, Medicinal Chemistry, and Emerging Pharmacology

Boron-containing compounds (BCC) have emerged as important pharmacophores. To date, five BCC drugs (including boronic acids and boroles) have been approved by the FDA for the treatment of cancer, infections, and atopic dermatitis, while some natural BCC are included in dietary supplements. Boron's Lewis acidity facilitates a mechanism of action via formation of reversible covalent bonds within the active site of target proteins. Boron has also been employed in the development of fluorophores, such as BODIPY for imaging, and in carboranes that are potential neutron capture therapy agents as well as novel agents in diagnostics and therapy. The utility of natural and synthetic BCC has become multifaceted, and the breadth of their applications continues to expand. This review covers the many uses and targets of boron in medicinal chemistry.

Sivelestat (Neutrophil Elastase Inhibitor) as an Anti-inflammatory and Anti-viral Agent: An In Silico Study

Background Sivelestat is a potent and specific neutrophil elastase inhibitor. It is clinically used in treating lung injury and respiratory distress syndrome. This engaged us to undertake the present study in which sivelestat was studied as an anti-inflammatory and anti-viral agent. Methodology The docking study of sivelestat on matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-9 (MMP-9), chikungunya virus nonstructural protein-2 (CVnsP2) protease, and influenza A (H1N9) virus neuraminidase was assessed using the Chemistry at Harvard Macromolecular Mechanics (CHARMM) Dock (CDOCK) method. Furthermore, molecular physicochemical; bioactivity; absorption, distribution, metabolism, and excretion (ADME); toxicity; and Search Tool for Interacting Chemicals (STITCH) analyses were performed by using the Molinspiration (Molinspiration Cheminformatics, Slovensky Grob, Slovak Republic), SwissADME SwissADME (Swiss Institute of Bioinformatics, Quartier Sorge - Bâtiment Amphipôle, Switzerland), pkCSM (University of Melbourne, Melbourne, Australia), and STITCH-free online tools. Results The molecular physicochemical assessment of the ligand (sivelestat) showed no (zero) violation and agreed with the thumb rule of five, otherwise known as Lipinski's rule of five. ADME prediction of the ligand (sivelestat) is shown to possess a low gastrointestinal absorption (GIA) property. Similarly, toxicity analysis of the ligand (sivelestat) is predicted to have a hepatotoxicity effect. STITCH analysis reveals that the ligand (sivelestat) has exhibited interactions with the three human proteins. Conclusions The present molecular docking studies showed that the ligand (sivelestat) has successfully docked with all four enzymes of interest. Hence, the current finding has provided a good understanding of sivelestat as an effective suppressor activity against all four enzymes: MMP-2, MMP-9, CVnsP2 protease, and influenza neuraminidase.

Human neutrophil elastase inhibitors: Classification, biological-synthetic sources and their relevance in related diseases

BACKGROUND

Human neutrophil elastase is a multifunctional protease enzyme whose function is to break the bonds of proteins and degrade them to polypeptides or amino acids. In addition, it plays an essential role in the immune mechanism against bacterial infections and represents a key mediator in tissue remodeling and inflammation. However, when the extracellular release of this enzyme is dysregulated in response to low levels of its physiological inhibitors, it ultimately leads to the degradation of proteins, in particular elastin, as well as other components of the extracellular matrix, producing injury to epithelial cells, which can promote sustained inflammation and affect the innate immune system, and, therefore, be the basis for the development of severe inflammatory diseases, especially those associated with the cardiopulmonary system.

OBJECTIVE

This review aims to provide an update on the elastase inhibitory properties of several molecules, either synthetic or biological sources, as well as their classification and relevance in related pathologies since a clear understanding of the function of these molecules with the inhibitory capacity of this protease can provide valuable information for the development of pharmacological therapies that manage to modify the prognosis and survival of various inflammatory diseases.

METHODS

Collected data from scientific databases, including PubMed, Google Scholar, Science Direct, Nature, Wiley, Scopus, and Scielo. Articles published in any country and language were included.

RESULTS

We reviewed and included 132 articles conceptualizing neutrophil elastase activity and known inhibitors.

CONCLUSION

Understanding the mechanism of action of elastase inhibitors based on particular aspects such as their kinetic behavior, structure-function relationship, chemical properties, origin, pharmacodynamics, and experimental progress has allowed for a broad classification of HNE inhibitors.

Desmosine as a biomarker for the emergent properties of pulmonary emphysema

Developing an effective treatment for pulmonary emphysema will require a better understanding of the molecular changes responsible for distention and rupture of alveolar walls. A potentially useful approach to studying this process involves the concept of emergence in which interactions at different levels of scale induce a phase transition comprising a spontaneous reorganization of chemical and physical systems. Recent studies in our laboratory provide evidence of this phenomenon in pulmonary emphysema by relating the emergence of airspace enlargement to the release of elastin-specific desmosine and isodesmosine (DID) crosslinks from damaged elastic fibers. When the mean alveolar diameter exceeded 400 μm, the level of peptide-free DID in human lungs was greatly increased, reflecting rapid acceleration of elastin breakdown, alveolar wall rupture, and a phase transition to an active disease state that is less responsive to treatment. Based on this finding, it is hypothesized that free DID in urine and other body fluids may serve as a biomarker for early detection of airspace enlargement, thereby facilitating timely therapeutic intervention and reducing the risk of respiratory failure.

Unlocking the Potential of Octocoral-Derived Secondary Metabolites against Neutrophilic Inflammatory Response

Inflammation is a critical defense mechanism that is utilized by the body to protect itself against pathogens and other noxious invaders. However, if the inflammatory response becomes exaggerated or uncontrollable, its original protective role is not only demolished but it also becomes detrimental to the affected tissues or even to the entire body. Thus, regulating the inflammatory process is crucial to ensure that it is resolved promptly to prevent any subsequent damage. The role of neutrophils in inflammation has been highlighted in recent decades by a plethora of studies focusing on neutrophilic inflammatory diseases as well as the mechanisms to regulate the activity of neutrophils during the overwhelmed inflammatory process. As natural products have demonstrated promising effects in a wide range of pharmacological activities, they have been investigated for the discovery of new anti-inflammatory therapeutics to overcome the drawbacks of current synthetic agents. Octocorals have attracted scientists as a plentiful source of novel and intriguing marine scaffolds that exhibit many pharmacological activities, including anti-inflammatory effects. In this review, we aim to provide a summary of the neutrophilic anti-inflammatory properties of these marine organisms that were demonstrated in 46 studies from 1995 to the present (April 2023). We hope the present work offers a comprehensive overview of the anti-inflammatory potential of octocorals and encourages researchers to identify promising leads among numerous compounds isolated from octocorals over the past few decades to be further developed into anti-inflammatory therapeutic agents.

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

INTRODUCTION

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

AREAS COVERED

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

EXPERT OPINION

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

A Biocompatible Probe for the Detection of Neutrophil Elastase Free from the Interference of Structural Changes and Its Application to Ratiometric Photoacoustic Imaging In Vivo

Neutrophil elastase (NE) plays a key role in chronic inflammation and acute responses to infection and injury. Effective disease interventions thus call for precise identification of NE to aid the clinical treatment of such diseases. However, the detection process suffers from the interference of structural changes of NE. Herein, we introduce a molecular probe with high biocompatibility to overcome the interference, which was achieved by combining theoretical calculations and experimental studies, that permits highly specific and sensitive detection of NE in cells and in vivo. The upregulated NE accumulation was specifically measured in inflammation by ratiometric photoacoustic and near-infrared fluorescence imaging, providing a new method for developing more specific fluorogenic probes for other enzymes.

Polysulfone Membranes Doped with Human Neutrophil Elastase Inhibitors: Assessment of Bioactivity and Biocompatibility

The use of polysulfone (PSU) hemodialysis (HD) membranes modified with bioactive compounds has gained relevance in chronic kidney disease (CKD) management. Compounds based on the 4-oxo-β-lactam scaffold have outstanding inhibitory ability and selectivity for human neutrophil elastase (HNE). The present work aimed to evaluate the bioactivity and biocompatibility of PSU-based HD membranes doped with HNE inhibitors (HNEIs). For this, two 4-oxo-β-lactam derivates (D4L-1 and D4L-2) synthesized in house were used, as well as a commercial HNEI (Sivelestat), for comparison purposes. Their HNE inhibition efficacy was evaluated in in vitro and ex vivo (incubations with human plasma) assay conditions. All biomaterials were bioactive and hemocompatible. The inhibitory capacity of the HNEIs and HNEI-PSU membranes in vitro was D4L-1 > D4L-2 > Sivelestat and D4L-2 > Sivelestat > D4L-1, respectively. In ex vivo conditions, both HNEIs and HNEI-PSU materials presented the same relative inhibitory ability (D4L-1 > D4L-2 > Sivelestat). The difference observed between in vitro and ex vivo conditions is most likely due to the inherent lipophilicity/hydrophobicity of each HNEI influencing their affinity and accessibility to HNE when trapped in the membrane. Compared to Sivelestat, both D4L-1 and D4L-2 (and the respective doped membranes) have more potent inhibition capabilities. In conclusion, this work reports the successful development of PSU membranes functionalized with HNEIs.

Neutrophil elastase: From mechanisms to therapeutic potential

Neutrophil elastase (NE), a major protease in the primary granules of neutrophils, is involved in microbicidal activity. NE is an important factor promoting inflammation, has bactericidal effects, and shortens the inflammatory process. NE also regulates tumor growth by promoting metastasis and tumor microenvironment remodeling. However, NE plays a role in killing tumors under certain conditions and promotes other diseases such as pulmonary ventilation dysfunction. Additionally, it plays a complex role in various physiological processes and mediates several diseases. Sivelestat, a specific NE inhibitor, has strong potential for clinical application, particularly in the treatment of coronavirus disease 2019 (COVID-19). This review discusses the pathophysiological processes associated with NE and the potential clinical applications of sivelestat.

Inhibition of neutrophil elastase prevents cigarette smoke exposure-induced formation of neutrophil extracellular traps and improves lung function in a mouse model of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is an important public health challenge worldwide, and is usually caused by significant exposure to noxious agents, particularly cigarette smoke. Recent studies have revealed that excessive production of neutrophil extracellular traps (NETs) in the airways is associated with disease severity in COPD patients. NETs are extracellular neutrophil-derived structures composed of chromatin fibers decorated with histones and granule proteases including neutrophil elastase (NE). However, the effective prevention of NET formation in COPD remains elusive. Here, we demonstrated that treatment with GW311616A, a potent and selective inhibitor of NE, prevented cigarette smoke extract (CSE)-induced NET formation in human neutrophils by blocking NE nuclear translocation and subsequent chromatin decondensation. Inhibition of NE also abrogated CSE-induced ROS production and migration impairment of neutrophils. Administration of GW311616A in vivo substantially reduced pulmonary generation of NETs while attenuating the key pathological changes in COPD, including airway leukocyte infiltration, mucus-secreting goblet cell hyperplasia, and emphysema-like alveolar destruction in a mouse model of COPD induced by chronic cigarette smoke exposure. Mice treated with GW311616A also showed significant attenuation of neutrophil numbers and percentages and the levels of neutrophil chemotactic factors (LTB4, KC, and CXCL5) and proinflammatory cytokines (IL-1β, and TNF-α) in bronchoalveolar lavage fluid compared to mice treated with cigarette smoke exposure only. Furthermore, GW311616A treatment considerably improved lung function in the COPD mouse model, including preventing the decline of FEV₁₀₀/FVC and delta PEF as well as inhibiting the increase in FRC, TLC, and FRC/TLC. Overall, our study suggests that NE plays a critical role in cigarette smoke-induced NET formation by neutrophils and that inhibition of NE is a promising strategy to suppress NET-mediated pathophysiological changes in COPD.

N-Acylamino Saccharin as an Emerging Cysteine-Directed Covalent Warhead and Its Application in the Identification of Novel FBPase Inhibitors toward Glucose Reduction

With a resurgence of covalent drugs, there is an urgent need for the identification of new moieties capable of cysteine bond formation. Herein, we report on the N-acylamino saccharin moieties capable of novel covalent reactions with cysteine. Their utility as alternative electrophilic warheads was demonstrated through the covalent modification of fructose-1,6-bisphosphatase (FBPase), a promising target associated with cancer and type 2 diabetes. The cocrystal structure of title compound W8 bound with FBPase unexpectedly revealed that the N-acylamino saccharin moiety worked as an electrophile warhead that covalently modified the noncatalytic C128 site in FBPase while releasing saccharin, suggesting a previously undiscovered covalent reaction mechanism of saccharin derivatives with cysteine. Treatment of title compound W8 displayed potent inhibition of glucose production in vitro and in vivo. This newly discovered reactive warhead supplements the current repertoire of cysteine covalent modifiers while avoiding some of the limitations generally associated with established moieties.

The Dynamic Contribution of Neutrophils in the Chronic Respiratory Diseases

Asthma, chronic obstructive pulmonary disease, and idiopathic pulmonary fibrosis are representative chronic respiratory diseases (CRDs). Although they differ in terms of disease presentation, they are all thought to arise from unresolved inflammation. Neutrophils are not only the first responders to acute inflammation, but they also help resolve the inflammation. Notably, emerging clinical studies show that CRDs are associated with systemic and local elevation of neutrophils. Moreover, murine studies suggest that airway-infiltrating neutrophils not only help initiate airway inflammation but also prolong the inflammation. Given this background, this review describes neutrophil-mediated immune responses in CRDs and summarizes the completed, ongoing, and potential clinical trials that test the therapeutic value of targeting neutrophils in CRDs. The review also clarifies the importance of understanding how neutrophils interact with other immune cells and how these interactions contribute to chronic inflammation in specific CRDs. This information may help identify future therapeutic strategies for CRDs.

Application of kojic acid scaffold in the design of non-tyrosinase enzyme inhibitors

Kojic acid (KA) is a hydroxypyranone natural metabolite mainly known as tyrosinase inhibitor. Currently, this compound is used as a whitening agent in cosmetics and as an anti-browning agent in food industry. Given the easy-manipulation in different positions of the KA molecule, many investigations have been carried out to find new tyrosinase inhibitors derived from KA. Beside anti-tyrosinase activity, many KA-based compounds have been designed for targeting other enzymes including human neutrophil elastase, catechol-O-methyltransferase, matrix metalloproteinases, monoamine oxidase, human lactate dehydrogenase, endonucleases, D-amino acid oxidase, and receptors such as histamine H₃ and apelin (APJ) receptors. This review could help biochemists and medicinal chemists in designing diverse KA-derived enzyme inhibitors.

The role of neutrophil elastase in aortic valve calcification

Background

Calcific aortic valve disease (CAVD) is the most commonly valvular disease in the western countries initiated by inflammation and abnormal calcium deposition. Currently, there is no clinical drug for CAVD. Neutrophil elastase (NE) plays a causal role in inflammation and participates actively in cardiovascular diseases. However, the effect of NE on valve calcification remains unclear. So we next explore whether it is involved in valve calcification and the molecular mechanisms involved.

Methods

NE expression and activity in calcific aortic valve stenosis (CAVD) patients (n = 58) and healthy patients (n = 30) were measured by enzyme-linked immunosorbent assay (ELISA), western blot and immunohistochemistry (IHC). Porcine aortic valve interstitial cells (pVICs) were isolated and used in vitro expriments. The effects of NE on pVICs inflammation, apoptosis and calcification were detected by TUNEL assay, MTT assay, reverse transcription polymerase chain reaction (RT-PCR) and western blot. The effects of NE knockdown and NE activity inhibitor Alvelestat on pVICs inflammation, apoptosis and calcification under osteogenic medium induction were also detected by RT-PCR, western blot, alkaline phosphatase staining and alizarin red staining. Changes of Intracellular signaling pathways after NE treatment were measured by western blot. Apolipoprotein E⁻/⁻ (APOE⁻/⁻) mice were employed in this study to establish the important role of Alvelestat in valve calcification. HE was used to detected the thickness of valve. IHC was used to detected the NE and α-SMA expression in APOE⁻/⁻ mice. Echocardiography was employed to assess the heat function of APOE⁻/⁻ mice.

Results

The level and activity of NE were evaluated in patients with CAVD and calcified valve tissues. NE promoted inflammation, apoptosis and phenotype transition in pVICs in the presence or absence of osteogenic medium. Under osteogenic medium induction, NE silencing or NE inhibitor Alvelestat both suppressed the osteogenic differentiation of pVICs. Mechanically, NE played its role in promoting osteogenic differentiation of pVICs by activating the NF-κB and AKT signaling pathway. Alvelestat alleviated valve thickening and decreased the expression of NE and α-SMA in western diet-induced APOE⁻/⁻ mice. Alvelestat also reduced NE activity and partially improved the heart function of APOE⁻/⁻mice.

Conclusions

Collectively, NE is highly involved in the pathogenesis of valve calcification. Targeting NE such as Alvelestat may be a potential treatment for CAVD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03363-1.

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.

Hindrance of the Proteolytic Activity of Neutrophil-Derived Serine Proteases by Serine Protease Inhibitors as a Management of Cardiovascular Diseases and Chronic Inflammation

During inflammation neutrophils become activated and segregate neutrophil serine proteases (NSPs) to the surrounding environment in order to support a natural immune defense. However, an excess of proteolytic activity of NSPs can cause many complications, such as cardiovascular diseases and chronic inflammatory disorders, which will be elucidated on a biochemical and immunological level. The application of selective serine protease inhibitors is the logical consequence in the management of the indicated comorbidities and will be summarized in this briefing.

Inflammatory microenvironment-targeted nanotherapies

Inflammatory microenvironments (IMEs) are common pathological characteristics and drive the development of multiple chronic diseases. Thus, IME-targeted therapies exhibit potential for the treatment of inflammatory diseases. Nanoplatforms have significant advantages in improving the efficiency of anti-inflammatory treatments. Owing to their improved therapeutic effects and reduced side effects, IME-targeted nanotherapies have recently drawn interest from the research community. This review introduces IMEs and discusses the application of IME-targeted nanotherapies for inflammatory diseases. The development of rational targeting strategies tailored to IMEs in damaged tissues can help promote therapies for chronic diseases.

Sulfonated Nonsaccharide Heparin Mimetics Are Potent and Noncompetitive Inhibitors of Human Neutrophil Elastase

Human neutrophil elastase (HNE) is a serine protease that plays vital roles in inflammation, innate immune response, and tissue remodeling processes. HNE has been actively pursued as a drug target, particularly for the treatment of cardiopulmonary diseases. Although thousands of molecules have been reported to inhibit HNE, yet very few are being evaluated in early clinical trials, with sivelestat as the only approved HNE inhibitor. We report here a novel chemotype of sulfonated nonsaccharide heparin mimetics as potent and noncompetitive inhibitors of HNE. Using a chromogenic substrate hydrolysis assay, 14 sulfonated nonsaccharide heparin mimetics were tested for their inhibitory activity against HNE. Only 12 molecules inhibited HNE with IC₅₀ values of 0.22-88.3 μM. The inhibition of HNE by these molecules was salt-dependent. Interestingly, a specific hexa-sulfonated molecule inhibited HNE with an IC₅₀ value of 0.22 μM via noncompetitive mechanism, as demonstrated by Michaelis-Menten kinetics. The hexa-sulfonated derivative demonstrated at least 455-, 221-, 1590-, 21-, and 381-fold selectivity indices over other heparin-binding coagulation proteins including factors IIa, Xa, IXa, XIa, and FXIIIa, respectively. At the highest concentrations tested, the molecule also did not significantly inhibit other serine proteases of plasmin, trypsin, and chymotrypsin. Further supporting its selectivity, the molecule did not show heparin-like effects on clotting times of human plasma. The molecule also did not affect the proliferation of three cell lines at a concentration as high as 10 μM. Interestingly, the hexa-sulfonated molecule also inhibited cathepsin G with an IC₅₀ value of 0.57 μM alluding to a dual anti-inflammatory action. A computational approach was exploited to identify putative binding site(s) for this novel class of HNE inhibitors. Overall, the reported hexa-sulfonated nonsaccharide heparin mimetic serves as a new platform to develop potent, selective, and noncompetitive inhibitors of HNE for therapeutic purposes.

A 28-day clinical trial of aerosolized hyaluronan in alpha-1 antiprotease deficiency COPD using desmosine as a surrogate marker for drug efficacy

INTRODUCTION

A previous 2-week clinical trial of aerosolized hyaluronan (HA) in COPD showed a rapid reduction in lung elastic fiber breakdown, as measured by sputum levels of the unique elastin crosslinks, desmosine and isodesmosine (DID). To further assess the therapeutic efficacy of HA and the utility of DID as surrogate markers for the development of pulmonary emphysema, we have conducted a 28-day randomized, double-blind, placebo-controlled, phase 2 trial of HA involving 27 subjects with alpha-1 antiprotease deficiency COPD.

METHODS

The study drug consisted of a 3 ml inhalation solution containing 0.03% HA with an average molecular weight of 150 kDa that was self-administered twice daily. DID levels were measured in urine, sputum, and plasma using tandem mass spectrometry.

RESULTS

Free urine DID in the HA group showed a significant negative correlation with time between days 14 and 35 (r = -1.0, p = 0.023) and was statistically significantly decreased from baseline at day 35 (15.4 vs 14.2 ng/mg creatinine, p = 0.035). A marked decrease in sputum DID was also seen in the HA group between days 1 and 28 (0.96 vs 0.18 ng/mg protein), but the difference was not significant, possibly due to the small number of adequate specimens. Plasma DID remained unchanged following HA treatment and no significant reductions in urine, sputum, or plasma DID were seen in the placebo group.

CONCLUSIONS

The results support additional clinical trials to further evaluate the therapeutic effect of HA and the use of DID as a real-time marker of drug efficacy.

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.

Evaluation of Ionic Liquids and Ionic Liquids Active Pharmaceutical Ingredients Inhibition in Elastase Enzyme Activity

Human neutrophil elastase (HNE) is used as diagnostic biomarker for inflammation/infection. In this work, 10 ionic liquids (ILs) and 11 ionic liquids active pharmaceutical ingredients (ILs-APIs) were tested to evaluate the inhibition effect on the activity of porcine pancreatic elastase enzyme, frequently employed as a model for HNE. The insertion of ionic liquids in some drugs is useful, as the insertion of ILs with inhibitory capacity will also slow down all processes in which this enzyme is involved. Therefore, a spectrophotometric method was performed to the determination of EC₅₀ values of the compounds tested. EC₅₀ values of 124 ± 4 mM to 289 ± 11 mM were obtained, with the most toxic IL for elastase being tetrabutylammonium acetate and the least toxic 1-butyl-3-methylimidazolium acetate. Moreover, sodium salicylate (raw material) presented the lower and benzethonium bistriflimide the higher EC₅₀ when compared with all the IL-APIs tested. This work provides significant information about the effect of the studied IL and IL-APIs in elastase enzyme activity.

Characterization of ecotin homologs from Campylobacter rectus and Campylobacter showae

Ecotin, first described in Escherichia coli, is a potent inhibitor of a broad range of serine proteases including those typically released by the innate immune system such as neutrophil elastase (NE). Here we describe the identification of ecotin orthologs in various Campylobacter species, including Campylobacter rectus and Campylobacter showae residing in the oral cavity and implicated in the development and progression of periodontal disease in humans. To investigate the function of these ecotins in vitro, the orthologs from C. rectus and C. showae were recombinantly expressed and purified from E. coli. Using CmeA degradation/protection assays, fluorescence resonance energy transfer and NE activity assays, we found that ecotins from C. rectus and C. showae inhibit NE, factor Xa and trypsin, but not the Campylobacter jejuni serine protease HtrA or its ortholog in E. coli, DegP. To further evaluate ecotin function in vivo, an E. coli ecotin-deficient mutant was complemented with the C. rectus and C. showae homologs. Using a neutrophil killing assay, we demonstrate that the low survival rate of the E. coli ecotin-deficient mutant can be rescued upon expression of ecotins from C. rectus and C. showae. In addition, the C. rectus and C. showae ecotins partially compensate for loss of N-glycosylation and increased protease susceptibility in the related pathogen, Campylobacter jejuni, thus implicating a similar role for these proteins in the native host to cope with the protease-rich environment of the oral cavity.

Prospects for COPD treatment

The management of chronic obstructive pulmonary disease (COPD) is fundamentally still heavily dependent on the use of bronchodilators and corticosteroids. Therefore, there is a need for alternative, more effective and safer therapeutic approaches. In particular, since inflammation in COPD lungs is often poorly responsive to corticosteroid treatment, novel pharmacological anti-inflammatory approaches are needed to optimally treat COPD patients. There have been multiple attempts to develop drugs that inhibit recruitment and activation of inflammatory cells, such as macrophages, neutrophils and T-lymphocytes, in the lungs of patients with COPD or target inflammatory mediators that are important in the recruitment or activation of these inflammatory cells or released by such cells. This review article focuses on novel classes of anti-inflammatory drugs that have already been tested in humans as possible treatments for patients with COPD.

Human Neutrophil Elastase Activated Fluorescent Probe for Pulmonary Diseases Based on Fluorescence Resonance Energy Transfer Using CdSe/ZnS Quantum Dots

There is an increasing demand for effective noninvasive diagnosis against common pulmonary diseases, which are rising sharply due to the serious air pollution. Human neutrophil elastase (HNE), a typical protease highly involved in pulmonary inflammatory diseases and lung cancer, is a potential predictor for disease progression. Currently, few of the HNE-targeting probes are applicable in vivo due to the limitation in sensitivity and biocompatibility. Herein, we reported the achievement of in vitro detection and in vivo imaging of HNE by incorporating the HNE-specific peptide substrate, quantum dots (QDs), and organic dyes into the fluorescence resonance energy transfer (FRET) system. The refined nanoprobe, termed QDP, could specifically measure the HNE with excellent sensitivity of 7.15 pM in aqueous solution and successfully image the endogenous and exogenous HNE in living cells. In addition, this nanoprobe enabled HNE imaging in mouse models of lung cancer and acute lung injury, and the HNE activity at high temporal and spatial resolution was continuously monitored. Most importantly, QDP successfully discriminated the serums of patients with lung diseases from those of the healthy controls based on the HNE activity determination. Overall, this study demonstrates the advantages of a FRET-system-based nanoprobe in imaging performance and provides an applicable tool for in vivo HNE detection and pulmonary disease diagnosis.

Novel and Modified Neutrophil Elastase Inhibitor Loaded in Topical Formulations for Psoriasis Management

Human neutrophil elastase (HNE) is a serine protease that degrades matrix proteins. An excess of HNE may trigger several pathological conditions, such as psoriasis. In this work, we aimed to synthesize, characterize and formulate new HNE inhibitors with a 4-oxo-β-lactam scaffold with less toxicity, as well as therapeutic index in a psoriasis context. HNE inhibitors with 4-oxo-β-lactam scaffolds were synthesized and characterized by NMR, FTIR, melting point, mass spectrometry and elemental analysis. In vitro cytotoxicity and serine protease assays were performed. The compound with the highest cell viability (AAN-16) was selected to be incorporated in an emulsion (AAN-16 E) and in a microemulsion (AAN-16 ME). Formulations were characterized in terms of organoleptic properties, pH, rheology, droplet size distribution, in vitro drug release and in vivo psoriatic activity. All compounds were successfully synthesized according to analytical methodology, with good yields. Both formulations presented suitable physicochemical properties. AAN-16 E presented the most promising therapeutic effects in a murine model of psoriasis. Overall, new HNE inhibitors were synthesized with high and selective activity and incorporated into topical emulsions with potential to treat psoriasis.

Iterative Optimization of the Cyclic Peptide SFTI-1 Yields Potent Inhibitors of Neutrophil Proteinase 3

Neutrophils produce at least four serine proteases that are packaged within azurophilic granules. These enzymes contribute to antimicrobial defense and inflammation but can be destructive if their activities are not properly regulated. Accordingly, they represent therapeutic targets for several diseases, including chronic obstructive pulmonary disease, cystic fibrosis, and rheumatoid arthritis. In this study, we focused on proteinase 3 (PR3), a neutrophil protease with elastase-like specificity, and engineered potent PR3 inhibitors based on the cyclic peptide sunflower trypsin inhibitor-1 (SFTI-1). We used an iterative optimization approach to screen targeted substitutions at the P1, P2, P2', and P4 positions of SFTI-1, and generated several new inhibitors with K _i values in the low nanomolar range. These SFTI-variants show high stability in human serum and are attractive leads for further optimization.

Neutrophilic Dermatoses and Their Implication in Pathophysiology of Asthma and Other Respiratory Comorbidities: A Narrative Review

Neutrophilic dermatoses (ND) are a polymorphous group of noncontagious dermatological disorders that share the common histological feature of a sterile cutaneous infiltration of mature neutrophils. Clinical manifestations can vary from nodules, pustules, and bulla to erosions and ulcerations. The etiopathogenesis of neutrophilic dermatoses has continuously evolved. Accumulating genetic, clinical, and histological evidence point to NDs being classified in the spectrum of autoinflammatory conditions. However, unlike the monogenic autoinflammatory syndromes where a clear multiple change in the inflammasome structure/function is demonstrated, NDs display several proinflammatory abnormalities, mainly driven by IL-1, IL-17, and tumor necrosis factor-alpha (TNF-a). Additionally, because of the frequent association with extracutaneous manifestations where neutrophils seem to play a crucial role, it was plausible also to consider NDs as a cutaneous presentation of a systemic neutrophilic condition. Neutrophilic dermatoses are more frequently recognized in association with respiratory disorders than by chance alone. The combination of the two, particularly in the context of their overlapping immune responses mediated primarily by neutrophils, raises the likelihood of a common neutrophilic systemic disease or an aberrant innate immunity disorder. Associated respiratory conditions can serve as a trigger or may develop or be exacerbated secondary to the uncontrolled skin disorder. Physicians should be aware of the possible pulmonary comorbidities and apply this knowledge in the three steps of patients' management, work-up, diagnosis, and treatment. In this review, we attempt to unravel the pathophysiological mechanisms of this association and also present some evidence for the role of targeted therapy in the treatment of both conditions.

Further modifications of 1H-pyrrolo[2,3-b]pyridine derivatives as inhibitors of human neutrophil elastase

Human neutrophil elastase (HNE) is a potent protease that plays an important physiological role in many processes and is considered to be a multifunctional enzyme. HNE is also 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 a new series of pyrrolo[2,3-b]pyridine derivatives of our previously reported potent HNE inhibitors. Our results show that position 2 of the pyrrolo[2,3-b]pyridine scaffold must be unsubstituted, and modifications of this position resulted in loss of HNE inhibitory activity. Conversely, the introduction of certain substituents at position 5 was tolerated, with retention of HNE inhibitory activity (IC₅₀  = 15-51 nM) after most substitutions, indicating that bulky and/or lipophilic substituents at position 5 probably interact with the large pocket of the enzyme site and allow Michaelis complex formation. The possibility of Michaelis complex formation between Ser195 and the ligand carbonyl group was assessed by molecular docking, and it was found that highly active HNE inhibitors are characterized by geometries favorable for Michaelis complex formation and by relatively short lengths of the proton transfer channel via the catalytic triad.

Manuka Honey Modulates the Inflammatory Behavior of a dHL-60 Neutrophil Model under the Cytotoxic Limit

Recent work has shown that Manuka honey, an increasingly popular wound additive with potent antibacterial properties, also has anti-inflammatory properties. However, little research has been done examining its effect on neutrophils. This study investigates the hypothesis that Manuka honey reduces neutrophil superoxide release and chemotaxis and reduces the activation of the inflammatory nuclear factor-κB (NF-κB) signaling pathway under honey's cytotoxic limit. A differentiated HL-60 cell line was used as a neutrophil model and cultured in various concentrations of Manuka honey for 3 and 24 hours to measure cytotoxicity via mitochondrial activity and visual trypan-exclusion count. Cytochrome C and Boyden chamber assays were used to measure the effect of Manuka honey on superoxide release and chemotaxis toward fMLP, respectively. Additionally, a Western blot for NF-κB inhibitor α (IκBα) was performed to measure Manuka honey's effect on the NF-κB pathway via IκBα phosphorylation. The results indicate a cytotoxic limit of 3-5% v/v. The presence of 1% honey decreased superoxide release at 24 hours. The 0.5, 1, and 3% honey concentrations reduced chemotaxis and IκBα phosphorylation in a dose-dependent fashion. These results suggest that Manuka honey significantly reduces neutrophil recruitment and inflammatory behavior in the wound site in a dose-dependent fashion under the cytotoxic limit.

COPD Pathogenesis: Finding the Common in the Complex

Developing an effective treatment for COPD, and especially pulmonary emphysema, will require an understanding of how fundamental changes at the molecular level affect the macroscopic structure of the lung. Currently, there is no accepted model that encompasses the biochemical and mechanical processes responsible for pulmonary airspace enlargement. We propose that pulmonary emphysematous changes may be more accurately described as an emergent phenomenon, involving alterations at the molecular level that eventually reach a critical structural threshold where uneven mechanical forces produce alveolar wall rupture, accompanied by advanced clinical signs of COPD. The coupling of emergent morphologic changes with biomarkers to detect the process, and counteract it therapeutically, represents a practical approach to the disease.

Diazaborines as New Inhibitors of Human Neutrophil Elastase

Boronic acids (BAs) are a prominent functionality extensively used to design biologically active compounds and functional biomaterials. Boronic acids open shell can lead to unspecific reactivity of BAs with endogenous nucleophiles and to undesired off-target effects. Here, diazaborines are presented as a new class of boron-based warheads for serine proteases inhibition, in which the boron function is stabilized in the form of an aromatic boron-based heterocycle. In this study, diazaborines were readily synthesized in a single step in yields up to 96%, without any chromatographic operation and were shown to reversibly inhibit human neutrophil elastase (HNE) serine protease with IC₅₀ values in the low μM range. Diazaborines were also selective toward HNE, as no inhibition was observed against a panel of five closely related serine proteases. Synthetic and theoretical studies performed on this system suggest that, similar to BAs, the reaction mechanism involves the formation of a reversible covalent bond between the diazaborine boron center and the catalytic serine oxygen. Finally, different from BAs, diazaborines were shown to be very stable in pH 7.4 phosphate buffer and human plasma.

Neutrophil Elastase Inhibitors and Chronic Kidney Disease

End-stage renal disease (ESRD), the last stage of chronic kidney disease (CKD), is characterized by chronic inflammation and oxidative stress. Neutrophils are the front line cells that mediate an inflammatory response against microorganisms as they can migrate, produce reactive oxygen species (ROS), secrete neutrophil serine proteases (NSPs), and release neutrophil extracellular traps (NETs). Serine proteases inhibitors regulate the activity of serine proteases and reduce neutrophil accumulation at inflammatory sites. This review intends to relate the role of neutrophil elastase in CKD and the effects of neutrophil elastase inhibitors in predicting or preventing inflammation.

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.

A BODIPY-Tagged Phosphono Peptide as Activity-Based Probe for Human Leukocyte Elastase

Human leukocyte elastase plays a crucial role in a variety of inflammatory disorders and represents an important subject of biomedical studies. The chemotype of peptidic phosphonates was employed for the design of a new activity-based probe for human leukocyte elastase. Its structure combines the phosphonate warhead with an adequate peptide portion and a BODIPY fluorophore with a clickable ethinylphenyl moiety at meso position. The probe 6 was assembled by copper-catalyzed alkyne-azide 1,3-dipolar cycloaddition. It was characterized as an active site-directed elastase inhibitor exhibiting a second-order rate constant of inactivation of 88400 M^-1s^-1. The suitability of 6 as a fluorescent probe for human leukocyte elastase was demonstrated by in-gel fluorescence analysis. Labeling experiments and inhibition data toward a panel of related proteases underlined the selectivity of the probe for the targeted leukocyte elastase.

Neutrophil Adhesion Is a Prerequisite for Antibody-Mediated Proteolytic Tissue Damage in Experimental Models of Epidermolysis Bullosa Acquisita

Although uncontrolled proteolytic activity mediated by activated neutrophils is a major reason for tissue damage, therapeutic approaches using protease inhibitors are inefficient. Here, we investigated the role of the immune complex-induced neutrophil adhesion and protease release in tissue damage. We show both in vitro and in vivo that immune complex-mediated neutrophil adhesion to the target tissue depends on β₂ integrins. Without affecting elastase or reactive oxygen species release, blocking of adhesion drastically inhibited tissue damage in an experimental model of autoantibody-mediated skin blistering disease. By using a cell-bound fluorescent resonance energy transfer-based elastase sensor, we detected elastase enzyme activity on the surface of adherent cells resistant to protease inhibitors. Inhibitor resistance was lost by CD18 blockade or deficiency in vitro and in vivo. Immune complex-induced neutrophil adhesion created an enclosed protected space between the cell and its target structure where proteinases and reactive oxygen species can execute their tissue-damaging effect. Because immune complex-induced neutrophil adhesion represents an indispensable step for tissue damage of many diseases, our findings may facilitate the development of strategies for the treatment of such disorders.

Starch nanocapsules containing a novel neutrophil elastase inhibitor with improved pharmaceutical performance

Psoriasis and atopic dermatitis patients show an excessive amount of elastase in peripheral blood neutrophils due to an imbalance between this proteolytic enzyme and its endogenous inhibitors, the search for new human neutrophil elastase (HNE) inhibitors are required. The HNE is an attractive therapeutic target and inhibitors with new molecular architectures have been extensively investigated. In this context a promising novel synthetic human neutrophil elastase inhibitor (ER143) was associated to a starch-based nanoparticulate system (StNC) with improved pharmaceutical performance, using a quality by design approach to support product development and optimization. The resulting formulation was characterized in terms of and in vitro release, permeation and retention studies in newborn pig skin, using Franz diffusion cells revealing the StNC have the ability to control the drug release rate and contribute to a high skin retention and/or permeation profiles. The anti-inflammatory activity accessed in vivo using the croton oil-induced ear inflammation model in mice showed that erythema and edema were attenuated in 98% following local application. These observations suggest the association of ER143 to the StNC promotes a deeper skin penetration and retention, also confirming StNC as a potential topical delivery system.

Design of an Activity-Based Probe for Human Neutrophil Elastase: Implementation of the Lossen Rearrangement To Induce Förster Resonance Energy Transfers

Human neutrophil elastase is an important regulator of the immune response and plays a role in host defense mechanisms and further physiological processes. The uncontrolled activity of this serine protease may cause severe tissue alterations and impair inflammatory states. The design of an activity-based probe for human neutrophil elastase reported herein relies on a sulfonyloxyphthalimide moiety as a new type of warhead that is linker-connected to a coumarin fluorophore. The inhibitory potency of the activity-based probe was assessed against several serine and cysteine proteases, and the selectivity for human neutrophil elastase (K_i = 6.85 nM) was determined. The adequate fluorescent tag of the probe allowed for the in-gel fluorescence detection of human neutrophil elastase in the low nanomolar range. The coumarin moiety and the anthranilic acid function of the probe, produced in the course of a Lossen rearrangement, were part of two different Förster resonance energy transfers.

Potential Anti-inflammatory Effects of the Fruits of Paulownia tomentosa

As part of an ongoing search for new natural products from medicinal plants to treat respiratory disease, six new compounds, a dihydroflavonol (1) and five C-geranylated flavanones (3, 6, 8, 13, and 14), and 13 known compounds were isolated from mature fruits of Paulownia tomentosa. The structures of the new compounds were determined via interpretation of their spectroscopic data (1D and 2D NMR, UV, IR, ECD, and MS). In biological activity assays with human alveolar basal epithelial cells, the expression of TNF-α-induced proinflammatory cytokines (IL-8 and IL-6) was reduced significantly by the EtOAc fraction of a P. tomentosa extract as well as by the new compounds isolated from this fraction. Furthermore, the majority of the isolates (1-19 except 5-7) were found to inhibit human neutrophil elastase (HNE) activity, with IC₅₀ values ranging from 2.4 ± 1.0 to 74.7 ± 8.5 μM. In kinetic enzymatic assays with the HNE substrate MeOSuc-AAPV-pNA, compound 17 exhibited the highest inhibitory activity (K_i = 3.2 μM) via noncompetitive inhibition. These findings suggest that the flavanone constituents of P. tomentosa fruits may be valuable for the development of new drug candidates to treat airway inflammation.

A pilot clinical trial to determine the safety and efficacy of aerosolized hyaluronan as a treatment for COPD

A novel therapy for COPD involving the use of aerosolized hyaluronan (HA) was tested on a small cohort of COPD patients to determine both its safety and efficacy in reducing levels of desmosine and isodesmosine (DID), biomarkers for elastin degradation. In a 2-week, randomized, double-blind trial, 8 patients receiving 150 kDa HA (mean molecular weight) and 3 others given placebo did not show significant adverse effects with regard to spirometry, electrocardiograms, and hematological indices. Furthermore, measurements of DID in plasma from HA-treated patients indicated a progressive decrease over a 3-week period following initiation of treatment (r=−0.98; p=0.02), whereas patients receiving placebo showed no reduction in DID (r=−0.70; p=0.30). Measurements of sputum in the HA-treated group also revealed a progressive decrease in DID (r=−0.97; p=0.03), but this finding was limited by the absence of similar measurements in the placebo group. Nevertheless, the results of this small, pilot study support a longer-term trial of HA in a larger population of COPD patients.

Isoxazol-5(2H)-one: a new scaffold for potent human neutrophil elastase (HNE) inhibitors

Human neutrophil elastase (HNE) is an important target for the development of novel and selective inhibitors to treat inflammatory diseases, especially pulmonary pathologies. Here, we report the synthesis, structure-activity relationship analysis, and biological evaluation of a new series of HNE inhibitors with an isoxazol-5(2H)-one scaffold. The most potent compound (2o) had a good balance between HNE inhibitory activity (IC₅₀ value =20 nM) and chemical stability in aqueous buffer (t_1/2=8.9 h). Analysis of reaction kinetics revealed that the most potent isoxazolone derivatives were reversible competitive inhibitors of HNE. Furthermore, since compounds 2o and 2s contain two carbonyl groups (2-N-CO and 5-CO) as possible points of attack for Ser195, the amino acid of the active site responsible for the nucleophilic attack, docking studies allowed us to clarify the different roles played by these groups.

Proteases Revisited: Roles and Therapeutic Implications in Fibrosis

Proteases target many substrates, triggering changes in distinct biological processes correlated with cell migration, EMT/EndMT and fibrosis. Extracellular protease activity, demonstrated by secreted and membrane-bound protease forms, leads to ECM degradation, activation of other proteases (i.e., proteolysis of nonactive zymogens), decomposition of cell-cell junctions, release of sequestered growth factors (TGF-β and VEGF), activation of signal proteins and receptors, degradation of inflammatory inhibitors or inflammation-related proteins, and changes in cell mechanosensing and motility. Intracellular proteases, mainly caspases and cathepsins, modulate lysosome activity and signal transduction pathways. Herein, we discuss the current knowledge on the multidimensional impact of proteases on the development of fibrosis.

Inhibitors and Antibody Fragments as Potential Anti-Inflammatory Therapeutics Targeting Neutrophil Proteinase 3 in Human Disease

Proteinase 3 (PR3) has received great scientific attention after its identification as the essential antigenic target of antineutrophil cytoplasm antibodies in Wegener's granulomatosis (now called granulomatosis with polyangiitis). Despite many structural and functional similarities between neutrophil elastase (NE) and PR3 during biosynthesis, storage, and extracellular release, unique properties and pathobiological functions have emerged from detailed studies in recent years. The development of highly sensitive substrates and inhibitors of human PR3 and the creation of PR3-selective single knockout mice led to the identification of nonredundant roles of PR3 in cell death induction via procaspase-3 activation in cell cultures and in mouse models. According to a study in knockout mice, PR3 shortens the lifespan of infiltrating neutrophils in tissues and accelerates the clearance of aged neutrophils in mice. Membrane exposure of active human PR3 on apoptotic neutrophils reprograms the response of macrophages to phagocytosed neutrophils, triggers secretion of proinflammatory cytokines, and undermines immune silencing and tissue regeneration. PR3-induced disruption of the anti-inflammatory effect of efferocytosis may be relevant for not only granulomatosis with polyangiitis but also for other autoimmune diseases with high neutrophil turnover. Inhibition of membrane-bound PR3 by endogenous inhibitors such as the α-1-protease inhibitor is comparatively weaker than that of NE, suggesting that the adverse effects of unopposed PR3 activity resurface earlier than those of NE in individuals with α-1-protease inhibitor deficiency. Effective coverage of PR3 by anti-inflammatory tools and simultaneous inhibition of both PR3 and NE should be most promising in the future.

Direct interaction between caffeic acid phenethyl ester and human neutrophil elastase inhibits the growth and migration of PANC-1 cells

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignant tumors of the digestive system, but the mechanisms of its development and progression are unclear. Inflammation is thought to be fundamental to pancreatic cancer development and caffeic acid phenethyl ester (CAPE) is an active component of honey bee resin or propolis with anti-inflammatory and anticancer activities. We investigated the inhibitory effects of CAPE on cell growth and migration induced by human neutrophil elastase (HNE) and report that HNE induced cancer cell migration at low doses and growth at higher doses. In contrast, lower CAPE doses inhibited migration and higher doses of CAPE inhibited the growth induced by HNE. HNE activity was significantly inhibited by CAPE (7.5-120 µM). Using quantitative real-time PCR and western blotting, we observed that CAPE (18-60 µM) did not affect transcription and translation of α1-antitrypsin (α1-AT), an endogenous HNE inhibitor. However, in an in silico drug target docking model, we found that CAPE directly bound to the binding pocket of HNE (25.66 kcal/mol) according to CDOCKER, and the residue of the catalytic site stabilized the interaction between CAPE and HNE as evidenced by molecular dynamic simulation. Response unit (RU) values of surface plasmon resonance (SPR) significantly increased with incremental CAPE doses (7.5-120 µM), indicating that CAPE could directly bind to HNE in a concentration-dependent manner. Thus, CAPE is an effective inhibitor of HNE via direct interaction whereby it inhibits the migration and growth of PANC-1 cells in a dose-dependent manner.

Design of Potent and Selective Cathepsin G Inhibitors Based on the Sunflower Trypsin Inhibitor-1 Scaffold

Neutrophils are directly responsible for destroying invading pathogens via reactive oxygen species, antimicrobial peptides, and neutrophil serine proteases (NSPs). Imbalance between NSP activity and endogenous protease inhibitors is associated with chronic inflammatory disorders, and engineered inhibitors of NSPs are a potential therapeutic pathway. In this study we characterized the extended substrate specificity (P4-P1) of the NSP cathepsin G using a peptide substrate library. Substituting preferred cathepsin G substrate sequences into sunflower trypsin inhibitor-1 (SFTI-1) produced a potent cathepsin G inhibitor (K_i = 0.89 nM). Cathepsin G's P2' preference was determined by screening against a P2' diverse SFTI-based library, and the most preferred residue at P2' was combined in SFTI-1 with a preferred substrate sequence (P4-P2) and a nonproteinogenic P1 residue (4-guanidyl-l-phenylalanine) to produce a potent (K_i = 1.6 nM) and the most selective (≥360-fold) engineered cathepsin G inhibitor reported to date. This compound is a promising lead for further development of cathepsin G inhibitors targeting chronic inflammatory disorders.

Concomitant elevations of MMP-9, NGAL, proMMP-9/NGAL and neutrophil elastase in serum of smokers with chronic obstructive pulmonary disease

A growing body of evidence points towards smoking‐related phenotypic differences in chronic obstructive pulmonary disease (COPD). As COPD is associated with systemic inflammation, we determined whether smoking status is related to serum levels of matrix metalloproteinase‐9 (pro‐ and active MMP‐9), neutrophil gelatinase‐associated lipocalin (NGAL) and the proMMP‐9/NGAL complex in patients with COPD. Serum samples were collected in 100 stable‐phase COPD patients (82 smokers, 18 never‐smokers) and 28 healthy adults (21 smokers, 7 never‐smokers). Serum levels of studied factors were measured in ELISA. Our data provide the first evidence of simultaneously elevated serum levels of MMP‐9, NGAL and proMMP‐9/NGAL in COPD smokers. While the triad discriminated between smokers and non‐smokers in the COPD group, MMP‐9 and proMMP‐9/NGAL (but not NGAL) discriminated between smokers with and without COPD. Adjustment for age and smoking pack‐years did not alter the findings. Serum MMP‐9, NGAL and proMMP‐9/NGAL levels were not correlated with the GOLD stage or FEV1 decline. Furthermore, serum levels of neutrophil elastase (NE) and MMP‐3 (but not of IL‐6 and MMP‐12) were also higher in COPD smokers than in healthy smokers before and after adjustment for age and pack‐years. Among COPD smokers, levels of MMP‐9, NGAL and proMMP‐9/NGAL were positively correlated with NE (P < 0.0001) but not with the remaining factors. Gelatin zymography detected proMMP‐9 in serum samples of healthy and COPD smoking groups. Our results suggest that associated serum levels of proMMP‐9, NGAL, proMMP‐9/NGAL and NE may reflect the state of systemic inflammation in COPD related to cigarette smoking.

Pharmacological and genetic reappraisals of protease and oxidative stress pathways in a mouse model of obstructive lung diseases

Protease-antiprotease imbalance and oxidative stress are considered to be major pathophysiological hallmarks of severe obstructive lung diseases including chronic obstructive pulmonary disease (COPD) and cystic fibrosis (CF), but limited information is available on their direct roles in the regulation of pulmonary phenotypes. Here, we utilized βENaC-transgenic (Tg) mice, the previously established mouse model of severe obstructive lung diseases, to produce lower-mortality but pathophysiologically highly useful mouse model by backcrossing the original line with C57/BL6J mice. C57/BL6J-βENaC-Tg mice showed higher survival rates and key pulmonary abnormalities of COPD/CF, including mucous hypersecretion, inflammatory and emphysematous phenotypes and pulmonary dysfunction. DNA microarray analysis confirmed that protease- and oxidative stress-dependent pathways are activated in the lung tissue of C57/BL6J-βENaC-Tg mice. Treatments of C57/BL6J-βENaC-Tg mice with a serine protease inhibitor ONO-3403, a derivative of camostat methylate (CM), but not CM, and with an anti-oxidant N-acetylcystein significantly improved pulmonary emphysema and dysfunction. Moreover, depletion of a murine endogenous antioxidant vitamin C (VC), by genetic disruption of VC-synthesizing enzyme SMP30 in C57/BL6J-βENaC-Tg mice, exaggerated pulmonary phenotypes. Thus, these assessments clarified that protease-antiprotease imbalance and oxidative stress are critical pathways that exacerbate the pulmonary phenotypes of C57/BL6J-βENaC-Tg mice, consistent with the characteristics of human COPD/CF.