Neutrophil serine proteases fine-tune the inflammatory response

Cathepsin C inhibition reduces neutrophil serine protease activity and improves activated neutrophil-mediated disorders

Cathepsin C (CatC) is an enzyme which regulates the maturation of neutrophil serine proteases (NSPs) essential for neutrophil activation. Activated neutrophils are key players in the innate immune system, and are also implicated in the etiology of various inflammatory diseases. This study aims to demonstrate a therapeutic potential for CatC inhibitors against disorders in which activated neutrophil-derived neutrophil extracellular traps (NETs) play a significant role. We demonstrate that a CatC inhibitor, MOD06051, dose-dependently suppresses the cellular activity of NSPs, including neutrophil elastase (NE), in vitro. Neutrophils derived from MOD06051-administered rats exhibit significantly lower NE activity and NET-forming ability than controls. Furthermore, MOD06051 dose-dependently ameliorates vasculitis and significantly decreases NETs when administered to a rat model of myeloperoxidase (MPO)-antineutrophil cytoplasmic antibody-associated vasculitis (AAV). These findings suggest that CatC inhibition is a promising strategy to reduce neutrophil activation and improve activated neutrophil-mediated diseases such as MPO-AAV.

Genetics of Cardiac Aging Implicate Organ-Specific Variation

Heart structure and function change with age, and the notion that the heart may age faster for some individuals than for others has driven interest in estimating cardiac age acceleration. However, current approaches have limited feature richness (heart measurements; radiomics) or capture extraneous data and therefore lack cardiac specificity (deep learning [DL] on unmasked chest MRI). These technical limitations have been a barrier to efforts to understand genetic contributions to age acceleration. We hypothesized that a video-based DL model provided with heart-masked MRI data would capture a rich yet cardiac-specific representation of cardiac aging. In 61,691 UK Biobank participants, we excluded noncardiac pixels from cardiac MRI and trained a video-based DL model to predict age from one cardiac cycle in the 4-chamber view. We then computed cardiac age acceleration as the bias-corrected prediction of heart age minus the calendar age. Predicted heart age explained 71.1% of variance in calendar age, with a mean absolute error of 3.3 years. Cardiac age acceleration was linked to unfavorable cardiac geometry and systolic and diastolic dysfunction. We also observed links between cardiac age acceleration and diet, decreased physical activity, increased alcohol and tobacco use, and altered levels of 239 serum proteins, as well as adverse brain MRI characteristics. We found cardiac age acceleration to be heritable (h2g 26.6%); a genome-wide association study identified 8 loci related to linked to cardiomyopathy (near TTN, TNS1, LSM3, PALLD, DSP, PLEC, ANKRD1 and MYO18B) and an additional 16 loci (near MECOM, NPR3, KLHL3, HDGFL1, CDKN1A, ELN, SLC25A37, PI15, AP3M1, HMGA2, ADPRHL1, PGAP3, WNT9B, UHRF1 and DOK5). Of the discovered loci, 21 were not previously associated with cardiac age acceleration. Mendelian randomization revealed that lower genetically mediated levels of 6 circulating proteins (MSRA most strongly), as well as greater levels of 5 proteins (LXN most strongly) were associated with cardiac age acceleration, as were greater blood pressure and Lp(a). A polygenic score for cardiac age acceleration predicted earlier onset of arrhythmia, heart failure, myocardial infarction, and mortality. These findings provide a thematic understanding of cardiac age acceleration and suggest that heart- and vascular-specific factors are key to cardiac age acceleration, predominating over a more global aging program.

Aprotinin (I): Understanding the Role of Host Proteases in COVID-19 and the Importance of Pharmacologically Regulating Their Function

Proteases are produced and released in the mucosal cells of the respiratory tract and have important physiological functions, for example, maintaining airway humidification to allow proper gas exchange. The infectious mechanism of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), takes advantage of host proteases in two ways: to change the spatial conformation of the spike (S) protein via endoproteolysis (e.g., transmembrane serine protease type 2 (TMPRSS2)) and as a target to anchor to epithelial cells (e.g., angiotensin-converting enzyme 2 (ACE2)). This infectious process leads to an imbalance in the mucosa between the release and action of proteases versus regulation by anti-proteases, which contributes to the exacerbation of the inflammatory and prothrombotic response in COVID-19. In this article, we describe the most important proteases that are affected in COVID-19, and how their overactivation affects the three main physiological systems in which they participate: the complement system and the kinin-kallikrein system (KKS), which both form part of the contact system of innate immunity, and the renin-angiotensin-aldosterone system (RAAS). We aim to elucidate the pathophysiological bases of COVID-19 in the context of the imbalance between the action of proteases and anti-proteases to understand the mechanism of aprotinin action (a panprotease inhibitor). In a second-part review, titled "Aprotinin (II): Inhalational Administration for the Treatment of COVID-19 and Other Viral Conditions", we explain in depth the pharmacodynamics, pharmacokinetics, toxicity, and use of aprotinin as an antiviral drug.

Exogenous serpin B1 restricts immune complex-mediated NET formation via inhibition of a chymotrypsin-like protease and enhances microbial phagocytosis

Immune complex (IC)-driven formation of neutrophil extracellular traps (NETs) is a major contributing factor to the pathogenesis of autoimmune diseases including systemic lupus erythematosus (SLE). Exogenous recombinant human serpin B1 (rhsB1) can regulate NET formation; however, its mechanism(s) of action is currently unknown as is its ability to regulate IC-mediated NET formation and other neutrophil effector functions. To investigate this, we engineered or post-translationally modified rhsB1 proteins that possessed specific neutrophil protease inhibitory activities and pretreated isolated neutrophils with them prior to inducing NET formation with ICs derived from patients with SLE, PMA, or the calcium ionophore A23187. Neutrophil activation and phagocytosis assays were also performed with rhsB1 pretreated and IC-activated neutrophils. rhsB1 dose-dependently inhibited NET formation by all three agents in a process dependent on its chymotrypsin-like inhibitory activity, most likely cathepsin G. Only one variant (rhsB1 C344A) increased surface levels of neutrophil adhesion/activation markers on IC-activated neutrophils and boosted intracellular ROS production. Further, rhsB1 enhanced complement-mediated neutrophil phagocytosis of opsonized bacteria but not ICs. In conclusion, we have identified a novel mechanism of action by which exogenously administered rhsB1 inhibits IC, PMA, and A2138-mediated NET formation. Cathepsin G is a well-known contributor to autoimmune disease but to our knowledge, this is the first report implicating it as a potential driver of NET formation. We identified the rhsB1 C334A variant as a candidate protein that can suppress IC-mediated NET formation, boost microbial phagocytosis, and potentially impact additional neutrophil effector functions including ROS-mediated microbial killing in phagolysosomes.

Expression and purification of human neutrophil proteinase 3 from insect cells and characterization of ligand binding

Neutrophil proteinase 3 (PR3) is an important drug target for inflammatory lung diseases such as chronic obstructive pulmonary disease and cystic fibrosis. Drug discovery efforts targeting PR3 require active enzyme for in vitro characterization, such as inhibitor screening, enzymatic assays, and structural studies. Recombinant expression of active PR3 overcomes the need for enzyme supplies from human blood and in addition allows studies on the influence of mutations on enzyme activity and ligand binding. Here, we report the expression of recombinant PR3 (rPR3) using a baculovirus expression system. The purification and activation process described resulted in highly pure and active PR3. The activity of rPR3 in the presence of commercially available inhibitors was compared with human PR3 by using a fluorescence-based enzymatic assay. Purified rPR3 had comparable activity to the native human enzyme, thus being a suitable alternative for enzymatic studies in vitro. Further, we established a surface plasmon resonance-based assay to determine binding affinities and kinetics of PR3 ligands. These methods provide valuable tools for early drug discovery aiming towards treatment of lung inflammation.

The mast cells - Cytokines axis in Autism Spectrum Disorder

Autism Spectrum Disorder (ASD) is a neurodevelopmental disturbance, diagnosed in early childhood. It is associated with varying degrees of dysfunctional communication and social skills, repetitive and stereotypic behaviors. Regardless of the constant increase in the number of diagnosed patients, there are still no established treatment schemes in global practice. Many children with ASD have allergic symptoms, often in the absence of mast cell (MC) positive tests. Activation of MCs may release molecules related to inflammation and neurotoxicity, which contribute to the pathogenesis of ASD. The aim of the present paper is to enrich the current knowledge regarding the relationship between MCs and ASD by providing PPI network analysis-based data that reveal key molecules and immune pathways associated with MCs in the pathogenesis of autism. Network and enrichment analyzes were performed using receptor information and secreted molecules from activated MCs identified in ASD patients. Our analyses revealed cytokines and key marker molecules for MCs degranulation, molecular pathways of key mediators released during cell degranulation, as well as various receptors. Understanding the relationship between ASD and the activation of MCs, as well as the involved molecules and interactions, is important for elucidating the pathogenesis of ASD and developing effective future treatments for autistic patients by discovering new therapeutic target molecules.

In vitro immune-depression and anti-inflammatory activities of cantharidin on gilthead seabream (Sparus aurata) leucocytes activated by λ-carrageenan

Cantharidin is a natural compound with known therapeutic applications in humans. The aim of this study was to investigate the in vitro effects of cantharidin on gilthead seabream (Sparus aurata) head kidney leucocytes (HKL) stimulated with λ-carrageenan. HKLs were incubated for 24 h with cantharidin (0, 2.5 and 5 μg mL-1) and λ-carrageenan (0 and 1000 μg mL-1). The results showed that HKL viability only decreased by 15.2% after incubated with 5 μg mL-1 of cantharidin and λ-carrageenan. Cantharidin increased the peroxidase activity of HKLs only when incubated in combination with λ-carrageenan. Besides this, cantharidin inhibited the respiratory burst and phagocytic activities. Furthermore, cantharidin induced morphological changes in HKLs (apoptotic and vacuolization signs) that were enhanced when incubated with λ-carrageenan. Considering the analysis of the selected gene expression studied in HKLs [NF-κB subunits (rela, relb, crel, nfkb1, nfkb2), proinflammatory cytokines (il1b, tnfa), anti-inflammatory cytokines (il10, tgfb) and caspases (casp1, casp3, casp8, casp9)], although λ-carrageenan up-regulated the expression of the proinflammatory gene il1b, λ-carrageenan and cantharidin down-regulated its expression in HKLs. In addition, cantharidin up-regulated casp3 and casp9 expression. The casp3 and casp9 gene expression was down-regulated while casp1 gene expression was up-regulated in HKLs incubated with both cantharidin and λ-carrageenan. All the effects of cantharidin are related to its inhibitory effect on protein phosphatases, which induce apoptosis at long exposure times, and minimize the effects of λ-carrageenan. The present results provide detailed insight into the immune-depressive and anti-inflammatory properties of cantharidin on immune cells, which could be of interest to the aquaculture sector.

Neutrophils in Physiology and Pathology

Infections, cardiovascular disease, and cancer are major causes of disease and death worldwide. Neutrophils are inescapably associated with each of these health concerns, by either protecting from, instigating, or aggravating their impact on the host. However, each of these disorders has a very different etiology, and understanding how neutrophils contribute to each of them requires understanding the intricacies of this immune cell type, including their immune and nonimmune contributions to physiology and pathology. Here, we review some of these intricacies, from basic concepts in neutrophil biology, such as their production and acquisition of functional diversity, to the variety of mechanisms by which they contribute to preventing or aggravating infections, cardiovascular events, and cancer. We also review poorly explored aspects of how neutrophils promote health by favoring tissue repair and discuss how discoveries about their basic biology inform the development of new therapeutic strategies.

Discovery of dual-target natural inhibitors of meprins α and β metalloproteases for inflammation regulation: pharmacophore modelling, molecular docking, ADME prediction, and molecular dynamics studies

Meprins, zinc-dependent metalloproteinases belonging to the metzincin family, have been associated with various inflammatory diseases due to their abnormal expression and activity. In this study, we utilized pharmacophore modelling to identify crucial features for discovering potential dual inhibitors targeting meprins α and β. We screened four pharmacophoric features against a library of 270,540 natural compounds from the Zinc database, resulting in 84,092 matching compounds. Molecular docking was then performed on these compounds, targeting the active sites of meprins α and β. Docking results revealed six compounds capable of interacting with both isoforms, with binding affinities ranging from -10.0 to -10.5 kcal/mol and -6.9 to -9.9 kcal/mol for meprin α and β, respectively. Among these compounds, ZINC000008790788 and ZINC000095099469 displayed superior docking scores and MM-GBSA binding free energy compared to reference ligands. Furthermore, these two compounds exhibited acceptable predicted pharmacokinetic properties and stable interactions with meprins α and β during molecular dynamics simulations. This study presents a comprehensive approach for identifying potential dual inhibitors of meprin α and β, offering insights into the development of therapeutic interventions for inflammatory diseases associated with meprin dysregulation.

Pharmacological inhibition of the cysteine protease cathepsin C improves graft function after heart transplantation in rats

BACKGROUND

Heart transplantation (HTX) is the standard treatment for end-stage heart failure. However, reperfusion following an ischemic period can contribute to myocardial injury. Neutrophil infiltration, along with the subsequent release of tissue-degrading neutrophil elastase (NE)-related serine proteases and oxygen-derived radicals, is associated with adverse graft outcomes. The inhibition of cathepsin C (CatC) has been shown to block NE-related protease activation. We hypothesized that the CatC inhibitor BI-9740 improves graft function after HTX.

METHODS

In a rat model of HTX, the recipient Lewis rats were orally administered with either a placebo (n = 12) or BI-9740 (n = 11, 20 mg/kg) once daily for 12 days. Donor hearts from untreated Lewis rats were explanted, preserved in a cardioplegic solution, and subsequently heterotopically implanted. In vivo left-ventricular (LV) graft function was assessed after 1 h of reperfusion. The proteolytic activity of neutrophil serine proteases was determined in bone marrow lysates from BI-9740-treated and control rats. Additionally, myocardial morphological changes were examined, and heart samples underwent immunohistochemistry and western blot analysis.

RESULTS

The NE-related proteolytic activity in bone marrow cell lysates was markedly decreased in the BI-9740-treated rats compared to those of the placebo group. Histopathological lesions, elevated CatC and myeloperoxidase-positive cell infiltration, and nitrotyrosine immunoreactivity with an increased number of poly(ADP-ribose) polymerase (PARP)-1-positive cells were lowered in the hearts of animals treated with BI-9740 compared to placebo groups. Regarding the functional parameters of the implanted graft, improvements were observed in both systolic function (LV systolic pressure 110 ± 6 vs 74 ± 6 mmHg; dP/dtmax 2782 ± 149 vs 2076 ± 167 mmHg/s, LV developed pressure, at an intraventricular volume of 200 µl, p < 0.05) and diastolic function in the hearts of BI-9740 treated animals compared with those receiving the only placebo. Furthermore, the administration of BI-9740 resulted in a shorter graft re-beating time compared to the placebo group. However, this study did not provide evidence of DNA fragmentation, the generation of both superoxide anions and hydrogen peroxide, correlating with the absence of protein alterations related to apoptosis, as evidenced by western blot in grafts after HTX.

CONCLUSIONS

We provided experimental evidence that pharmacological inhibition of CatC improves graft function following HTX in rats.

Ixodes scapularis nymph saliva protein blocks host inflammation and complement-mediated killing of Lyme disease agent, Borrelia burgdorferi

Tick serine protease inhibitors (serpins) play crucial roles in tick feeding and pathogen transmission. We demonstrate that Ixodes scapularis (Ixs) nymph tick saliva serpin (S) 41 (IxsS41), secreted by Borrelia burgdorferi (Bb)-infected ticks at high abundance, is involved in regulating tick evasion of host innate immunity and promoting host colonization by Bb. Recombinant (r) proteins were expressed in Pichia pastoris, and substrate hydrolysis assays were used to determine. Ex vivo (complement and hemostasis function related) and in vivo (paw edema and effect on Bb colonization of C3H/HeN mice organs) assays were conducted to validate function. We demonstrate that rIxsS41 inhibits chymase and cathepsin G, pro-inflammatory proteases that are released by mast cells and neutrophils, the first immune cells at the tick feeding site. Importantly, stoichiometry of inhibition analysis revealed that 2.2 and 2.8 molecules of rIxsS41 are needed to 100% inhibit 1 molecule of chymase and cathepsin G, respectively, suggesting that findings here are likely events at the tick feeding site. Furthermore, chymase-mediated paw edema, induced by the mast cell degranulator, compound 48/80 (C48/80), was blocked by rIxsS41. Likewise, rIxsS41 reduced membrane attack complex (MAC) deposition via the alternative and lectin complement activation pathways and dose-dependently protected Bb from complement killing. Additionally, co-inoculating C3H/HeN mice with Bb together with rIxsS41 or with a mixture (rIxsS41 and C48/80). Findings in this study suggest that IxsS41 markedly contributes to tick feeding and host colonization by Bb. Therefore, we conclude that IxsS41 is a potential candidate for an anti-tick vaccine to prevent transmission of the Lyme disease agent.

Serum and Synovial Levels of Cathepsin G and Cathepsin K in Patients with Psoriatic Arthritis and Their Correlation with Disease Activity Indices

This retrospective case-control study examined the relationship between the serum and synovial levels of cathepsin G (CatG) and cathepsin K (CatK) in patients with psoriatic arthritis (PsA) and their association with disease activity. Methods: This case-control study involved 156 PsA patients, 50 patients with gonarthrosis (GoA), and 30 healthy controls. The target parameters were measured using enzyme-linked immunosorbent assay (ELISA) kits. The serum levels of CatG and CatK were found to be significantly higher in PsA patients compared to both control groups (p < 0.001). Moreover, they could distinguish PsA patients from healthy controls with 100% accuracy. Synovial fluid CatG and CatK were positively associated with the following indicators of disease activity: the VAS (rs = 0.362, rs = 0.391); the DAPSA (rs = 0.191, rs = 0.182); and the mCPDAI (rs = 0.378, rs = 0.313). Our results suggest that serum and synovial fluid CatG and CatK levels could serve as biomarkers for PsA. In PsA patients with synovial fluid crystals, elevated synovial CatG levels demonstrated a sensitivity of 89.54% and a specificity of 86.00% in distinguishing them from PsA patients without crystals. Similarly, elevated synovial CatK levels had a sensitivity of 93.67% and a specificity of 94.34% for distinguishing PsA patients with synovial fluid crystals from those without. Furthermore, the synovial fluid levels of both CatG and CatK showed positive associations with key indicators of disease activity, including the visual analog scale (VAS) (rs = 0.362, rs = 0.391), the disease activity in psoriatic arthritis (DAPSA) (rs = 0.191, rs = 0.182), and the modified composite psoriatic disease activity index (mCPDAI) (rs = 0.378, rs = 0.313). In conclusion, our findings suggest that the serum and synovial fluid levels of CatG and CatK hold promise as potential biomarkers for assessing disease activity in psoriatic arthritis.

Not all vaping is the same: differential pulmonary effects of vaping cannabidiol versus nicotine

RATIONALE

Vaping has become a popular method of inhaling various psychoactive substances. While evaluating respiratory effects of vaping have primarily focused on nicotine-containing products, cannabidiol (CBD)-vaping is increasingly becoming popular. It currently remains unknown whether the health effects of vaping nicotine and cannabinoids are similar.

OBJECTIVES

This study compares side by side the pulmonary effects of acute inhalation of vaporised CBD versus nicotine.

METHODS

In vivo inhalation study in mice and in vitro cytotoxicity experiments with human cells were performed to assess the pulmonary damage-inducing effects of CBD or nicotine aerosols emitted from vaping devices.

MEASUREMENTS AND MAIN RESULTS

Pulmonary inflammation in mice was scored by histology, flow cytometry, and quantifying levels of proinflammatory cytokines and chemokines. Lung damage was assessed by histology, measurement of myeloperoxidase activity and neutrophil elastase levels in the bronchoalveolar lavage fluid and lung tissue. Lung epithelial/endothelial integrity was assessed by quantifying BAL protein levels, albumin leak and pulmonary FITC-dextran leak. Oxidative stress was determined by measuring the antioxidant potential in the BAL and lungs. The cytotoxic effects of CBD and nicotine aerosols on human neutrophils and human small airway epithelial cells were evaluated using in vitro air-liquid interface system. Inhalation of CBD aerosol resulted in greater inflammatory changes, more severe lung damage and higher oxidative stress compared with nicotine. CBD aerosol also showed higher toxicity to human cells compared with nicotine.

CONCLUSIONS

Vaping of CBD induces a potent inflammatory response and leads to more pathological changes associated with lung injury than vaping of nicotine.

The pharmacokinetic profile of brensocatib and its effect on pharmacodynamic biomarkers including NE, PR3, and CatG in various rodent species

Brensocatib is a novel, oral, selective, reversible inhibitor of dipeptidyl peptidase 1 (DPP1), which activates several neutrophil serine proteases (NSPs), including neutrophil elastase (NE), proteinase 3 (PR3), and cathepsin G (CatG) in the bone marrow during the early stage of neutrophil maturation. These NSPs are associated with pathogen destruction and inflammatory mediation; their dysregulated activation can result in excess secretion of active NSPs causing damaging inflammation and contributing to neutrophil-mediated inflammatory and autoimmune diseases. Pharmacological inhibition of DPP1 in the bone marrow could therefore represent an attractive strategy for these neutrophil-driven diseases. A completed Phase 2 trial in non-cystic fibrosis bronchiectasis patients (ClinicalTrials.gov number NCT03218917; EudraCT number: 2017-002533-32) indeed demonstrated that administration of brensocatib attenuated the damaging effects of chronic inflammation by inhibiting the downstream activation of NSPs. To support a range of preclinical programs and further understand how rodent species and strains may affect brensocatib's pharmacokinetic (PK) profile and its pharmacodynamic (PD) effects on NE, PR3, and CatG, an extensive naïve dosing study with brensocatib at different dosing levels, frequencies, and durations was undertaken. Dose-dependent PK exposure responses (AUC and Cmax) were observed regardless of the rodent species and strain. Overall, mice showed greater reduction in NSP activities compared to rats. Both mice and rats dosed once daily (QD) had equivalent NSP activity reduction compared to BID (twice a day) dosing when the QD dose was 1.5-times the BID daily dose. For both mouse strains, CatG activity was reduced the most, followed by NE, then PR3; whereas, for both rat strains, PR3 activity was reduced the most, followed by CatG, and then NE. Maximum reduction in NSP activities was observed after ∼7 days and recoveries were nearly symmetrical. These results may facilitate future in vivo brensocatib study dosing considerations, such as the timing of prophylactic or therapeutic administration, choice of species, dosage and dosing frequency.

Brensocatib, an oral, reversible inhibitor of dipeptidyl peptidase 1, mitigates interferon-α-accelerated lupus nephritis in mice

Neutrophils have been implicated in initiating and perpetuating systemic lupus erythematosus and the resultant kidney damage in lupus nephritis (LN) patients, in part through an excessive release of neutrophil serine proteases (NSPs). NSP zymogens are activated by dipeptidyl peptidase 1 (DPP1) during neutrophil maturation and released by mature neutrophils in response to inflammatory stimuli. Thus, a potential strategy to attenuate disease progression in LN would be to inhibit DPP1. We tested whether brensocatib, a highly selective and reversible DPP1 inhibitor, could mitigate LN progression in an interferon-alpha (IFNα)-accelerated NZB/W F1 mouse model. To confirm brensocatib's pharmacodynamic effect on NSPs in this mouse strain, repeated dose studies were conducted for 7 and 14 days in naïve NZB/W F1 mice via oral gavage twice a day. Brensocatib at 2 and 20 mg/kg/day achieved a significant reduction in bone marrow NSP activities after 7 days of daily administration. To initiate LN disease progression, the mice were injected with an IFNα-expressing adenovirus. After 2 weeks, three brensocatib doses (or vehicle) were administered for 6 more weeks. Throughout the 8-week study, brensocatib treatment (20 mg/kg/day) significantly reduced the occurrence of severe proteinuria compared to the vehicle control. Brensocatib treatment also entailed a significant reduction in the urine albumin-to-creatinine ratio, indicating decreased kidney damage, as well as a significant reduction in blood urea nitrogen level, suggesting improved renal function. Based on kidney histopathology analysis, brensocatib treatment significantly lowered both the renal tubular protein score and the nephropathy score compared to the vehicle group. A trend towards reduced glomerulonephritis score with brensocatib treatment was also observed. Lastly, brensocatib significantly reduced LN mouse kidney infiltration by various inflammatory cells. In conclusion, these results suggest that brensocatib alters disease progression in LN mice and warrant further evaluation of DPP1 inhibition in LN.

Caspase-8 inhibition improves the outcome of bacterial infections in mice by promoting neutrophil activation

During differentiation, neutrophils undergo a spontaneous pro-inflammatory program that is hypothesized here to be under caspase-8 control. In mice, intraperitoneal administration of the caspase-8 inhibitor z-IETD-fmk is sufficient to unleash the production of pro-inflammatory cytokines and neutrophil influx in the absence of cell death. These effects are due to selective inhibition of caspase-8 and require tonic interferon-β (IFN-β) production and RIPK3 but not MLKL, the essential downstream executioner of necroptotic cell death. In vitro, stimulation with z-IETD-fmk is sufficient to induce significant cytokine production in murine neutrophils but not in macrophages. Therapeutic administration of z-IETD-fmk improves clinical outcome in models of lethal bacterial peritonitis and pneumonia by augmenting cytokine release, neutrophil influx, and bacterial clearance. Moreover, the inhibitor protects mice against high-dose endotoxin shock. Collectively, our data unveil a RIPK3- and IFN-β-dependent pathway that is constitutively activated in neutrophils and can be harnessed therapeutically using caspase-8 inhibition.

Neutrophil extracellular trap-associated carbamylation and histones trigger osteoclast formation in rheumatoid arthritis

OBJECTIVE

Neutrophil infiltration into the synovial joint is a hallmark of rheumatoid arthritis (RA), a disease characterised by progressive bone erosion. However, the mechanisms by which neutrophils participate in bone destruction remain unclear. Carbamylation is a posttranslational modification linked to increased bone erosion in RA and we previously showed that carbamylation is present in RA neutrophil extracellular traps (NETs). However, it remains unclear whether NETs and their carbamylated protein cargo directly promote bone destruction and alter osteoclast biology.

METHODS

NETs and carbamylated NETs (cNETs) were assessed for their capacity to induce osteoclast formation in CD14+ monocytes. Chemical inhibitors and neutralising antibodies were used to elucidate the pathway by which NETs induce osteoclastogenesis. HLA-DRB1*04:01 mice received intra-articular injection of cNETs for 4 weeks. Joints were isolated and assessed for osteoclast formation. Plasma and synovial fluid samples from patients with RA (n=32) were assessed for the presence of carbamylated histone, and correlations to disease specific outcomes were performed.

RESULTS

We found that NETs, when cNETs, instruct monocytes to undergo rapid osteoclast formation. NET-mediated osteoclastogenesis appears to depend on Toll-like receptor 4 signalling and NET-associated proteins including histones and neutrophil elastase. In vivo, we identified that the number of osteoclasts increased following immunisation with cNETs in HLA-DRB1*04:01 transgenic mice. Furthermore, carbamylated histones are increased in plasma and synovial fluid from patients with RA and correlate with active bone resorption and inflammatory markers.

CONCLUSIONS

Our results suggest that NETs have a direct role in RA-associated bone erosion by promoting osteoclast formation.

Homogeneous, Synthetic, Non-Saccharide Glycosaminoglycan Mimetics as Potent Inhibitors of Human Cathepsin G

Cathepsin G (CatG) is a pro-inflammatory neutrophil serine protease that is important for host defense, and has been implicated in several inflammatory disorders. Hence, inhibition of CatG holds much therapeutic potential; however, only a few inhibitors have been identified to date, and none have reached clinical trials. Of these, heparin is a well-known inhibitor of CatG, but its heterogeneity and bleeding risk reduce its clinical potential. We reasoned that synthetic small mimetics of heparin, labeled as non-saccharide glycosaminoglycan mimetics (NSGMs), would exhibit potent CatG inhibition while being devoid of bleeding risks associated with heparin. Hence, we screened a focused library of 30 NSGMs for CatG inhibition using a chromogenic substrate hydrolysis assay and identified nano- to micro-molar inhibitors with varying levels of efficacy. Of these, a structurally-defined, octasulfated di-quercetin NSGM 25 inhibited CatG with a potency of ~50 nM. NSGM 25 binds to CatG in an allosteric site through an approximately equal contribution of ionic and nonionic forces. Octasulfated 25 exhibits no impact on human plasma clotting, suggesting minimal bleeding risk. Considering that octasulfated 25 also potently inhibits two other pro-inflammatory proteases, human neutrophil elastase and human plasmin, the current results imply the possibility of a multi-pronged anti-inflammatory approach in which these proteases are likely to simultaneously likely combat important conditions, e.g., rheumatoid arthritis, emphysema, or cystic fibrosis, with minimal bleeding risk.

Synthesis and screening of cyclic diketone indanedione derivatives as future scaffolds for neutrophil elastase inhibition

Human neutrophil elastase (HNE) and proteinase 3 (Pr3) released from neutrophils at inflammatory sites are the major causes of pathogens in chronic obstructive pulmonary disease (COPD) and various lung tissue derangements, among which cystic fibrosis and blockade of airway passages are chronic. These proteolytic mediatory agents combined with induced oxidative reactions sustain pathogenicity. Cyclic diketone indane-1,3-dione derivatives were designed, and toxicity evaluation predictions were performed in silico. Benzimidazole and hydrazide derivatives of indanedione were synthesized and characterized. Synthesized compounds were run using neutrophil elastase inhibition assay protocols. The compounds exhibit considerable inhibition of neutrophil elastase enzymes.

Neutrophils drive pulmonary vascular leakage in MHV-1 infection of susceptible A/J mice

Background

Lung inflammation, neutrophil infiltration, and pulmonary vascular leakage are pathological hallmarks of acute respiratory distress syndrome (ARDS) which can lethally complicate respiratory viral infections. Despite similar comorbidities, however, infections in some patients may be asymptomatic while others develop ARDS as seen with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections for example.

Methods

In this study, we infected resistant C57BL/6 and susceptible A/J strains of mice with pulmonary administration of murine hepatitis virus strain 1 (MHV-1) to determine mechanisms underlying susceptibility to pulmonary vascular leakage in a respiratory coronavirus infection model.

Results

A/J animals displayed increased lung injury parameters, pulmonary neutrophil influx, and deficient recruitment of other leukocytes early in the infection. Moreover, under basal conditions, A/J neutrophils overexpressed primary granule protein genes for myeloperoxidase and multiple serine proteases. During infection, myeloperoxidase and elastase protein were released in the bronchoalveolar spaces at higher concentrations compared to C57BL/6 mice. In contrast, genes from other granule types were not differentially expressed between these 2 strains. We found that depletion of neutrophils led to mitigation of lung injury in infected A/J mice while having no effect in the C57BL/6 mice, demonstrating that an altered neutrophil phenotype and recruitment profile is a major driver of lung immunopathology in susceptible mice.

Conclusions

These results suggest that host susceptibility to pulmonary coronaviral infections may be governed in part by underlying differences in neutrophil phenotypes, which can vary between mice strains, through mechanisms involving primary granule proteins as mediators of neutrophil-driven lung injury.

Nafamostat has anti-asthmatic effects associated with suppressed pro-inflammatory gene expression, eosinophil infiltration and airway hyperreactivity

Introduction

Asthma is characterized by an imbalance between proteases and their inhibitors. Hence, an attractive therapeutic option could be to interfere with asthma-associated proteases. Here we exploited this option by assessing the impact of nafamostat, a serine protease inhibitor known to neutralize mast cell tryptase.

Methods

Nafamostat was administered in a mouse model for asthma based on sensitization by house dust mite (HDM) extract, followed by the assessment of effects on airway hyperreactivity, inflammatory parameters and gene expression.

Results

We show that nafamostat efficiently suppressed the airway hyperreactivity in HDM-sensitized mice. This was accompanied by reduced infiltration of eosinophils and lymphocytes to the airways, and by lower levels of pro-inflammatory compounds within the airway lumen. Further, nafamostat had a dampening impact on goblet cell hyperplasia and smooth muscle layer thickening in the lungs of HDM-sensitized animals. To obtain deeper insight into the underlying mechanisms, a transcriptomic analysis was conducted. This revealed, as expected, that the HDM sensitization caused an upregulated expression of numerous pro-inflammatory genes. Further, the transcriptomic analysis showed that nafamostat suppressed the levels of multiple pro-inflammatory genes, with a particular impact on genes related to asthma.

Discussion

Taken together, this study provides extensive insight into the ameliorating effect of nafamostat on experimental asthma, and our findings can thereby provide a basis for the further evaluation of nafamostat as a potential therapeutic agent in human asthma.

Tryptase and Exogenous Trypsin: Mechanisms and Ophthalmic Applications

Ocular injuries caused by inflammation, surgery or accidents are subject to a physiological healing process that ultimately restores the structure and function of the damaged tissue. Tryptase and trypsin are essential component of this process and they play a role in promoting and reducing the inflammatory response of tissues, respectively. Following injury, tryptase is endogenously produced by mast cells and can exacerbate the inflammatory response both by stimulating neutrophil secretion, and through its agonist action on proteinase-activated receptor 2 (PAR2). In contrast, exogenously introduced trypsin promotes wound healing by attenuating inflammatory responses, reducing oedema and protecting against infection. Thus, trypsin may help resolve ocular inflammatory symptoms and promote faster recovery from acute tissue injury associated with ophthalmic diseases. This article describes the roles of tryptase and exogenous trypsin in affected tissues after onset of ocular injury, and the clinical applications of trypsin injection.

COVID-19 Pathology Sheds Further Light on Balance between Neutrophil Proteases and Their Inhibitors

Excessive neutrophil influx and activation in lungs during infections, such as manifest during the ongoing SARS CoV-2 pandemic, have brought neutrophil extracellular traps (NETs) and the concomitant release of granule contents that damage surrounding tissues into sharp focus. Neutrophil proteases, which are known to participate in NET release, also enable the binding of the viral spike protein to cellular receptors and assist in the spread of infection. Blood and tissue fluids normally also contain liver-derived protease inhibitors that balance the activity of proteases. Interestingly, neutrophils themselves also express the protease inhibitor alpha-1-antitrypsin (AAT), the product of the SERPINA-1 gene, and store it in neutrophil cytoplasmic granules. The absence of AAT or mutations in the SERPINA-1 gene promotes lung remodeling and fibrosis in diseases such as chronic obstructive pulmonary disease (COPD), and acute respiratory distress syndrome (ARDS) and increases the risk of allergic responses. Recent observations point to the fact that reduced activity of AAT presents a major susceptibility factor for severe COVID-19. Here, we focus attention on the mechanism of neutrophil elastase (NE) in NET release and its inhibition by AAT as an additional factor that may determine the severity of COVID-19.

Standardised Sonneratia apetala Buch.-Ham. fruit extract inhibits human neutrophil elastase and attenuates elastase-induced lung injury in mice

Chronic obstructive pulmonary disease (COPD) along with asthma is a major and increasing global health problem. Smoking contributes to about 80%-90% of total COPD cases in the world. COPD leads to the narrowing of small airways and destruction of lung tissue leading to emphysema primarily caused by neutrophil elastase. Neutrophil elastase plays an important role in disease progression in COPD patients and has emerged as an important target for drug discovery. Sonneratia apetala Buch.-Ham. is a mangrove plant belonging to family Sonneratiaceae. It is widely found in the Sundarban regions of India. While the fruits of this plant have antibacterial, antifungal, antioxidant and astringent activities, fruit and leaf extracts have been shown to reduce the symptoms of asthma and cough. The aim of this study is to find whether hydro alcoholic fruit extracts of S. apetala inhibit neutrophil elastase and thus prevent the progression of neutrophil elastase-driven lung emphysema. The hydroalcoholic extract, ethanol: water (90:10), of the S. apetala Buch.-Ham. fresh fruits (SAM) were used for neutrophil elastase enzyme kinetic assay and IC₅₀ of the extract was determined. The novel HPLC method has been developed and the extract was standardized with gallic acid and ellagic acid as standards. The extract was further subjected to LC-MS² profiling to identify key phytochemicals. The standardized SAM extract contains 53 μg/mg of gallic acid and 95 μg/mg of ellagic acid, based on the HPLC calibration curve. SAM also reversed the elastase-induced morphological change of human epithelial cells and prevented the release of ICAM-1 in vitro and an MTT assay was conducted to assess the viability. Further, 10 mg/kg SAM had reduced alveolar collapse induced by neutrophil elastase in the mice model. Thus, in this study, we reported for the first time that S. apetala fruit extract has the potential to inhibit human neutrophil elastase in vitro and in vivo.

Suppression of T-Cell Proliferation by Normal Density Granulocytes Led to CD183 Downregulation and Cytokine Inhibition in T-Cells

Normal density granulocytes (NDGs) can suppress T-cell responses in a similar way as myeloid-derived suppressor cells (MDSCs). In this study, we tested the hypothesis that NDGs from healthy donors preferentially inhibit T helper 1 (Th1) cells and investigated the myeloid-derived suppressive effect in different T-cell populations. We found that NDG-induced suppression of T-cell proliferation was contact dependent, mediated by integrin CD11b, and dependent on NDG-production of reactive oxygen species (ROS). The suppression was rapid and occurred within the first few hours of coculture. The suppression did not influence the CD8+/CD4+ ratio indicating an equal sensitivity in these populations. We further analyzed the CD4+ T helper subsets and found that NDGs induced a loss of Th1 surface marker, CD183, that was unrelated to ligand-binding to CD183. In addition, we analyzed the Th1, Th2, and Th17 cytokine production and found that all cytokine groups were suppressed when T-cells were incubated with NDGs. We therefore concluded that NDGs do not preferentially suppress Th1-cells. Instead, NDGs generally suppress Th cells and cytotoxic T-cells but specifically downregulate the Th1 marker CD183.

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

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

An optimized method of extracting and quantifying active Neutrophil serine proteases from human whole blood cells

Purpose

Neutrophil serine proteases (NSPs) are implicated in numerous inflammatory diseases. Thus, a robust methodology to monitor and quantify NSPs is important to study disease progression and evaluate the effect of pharmacological interventions. A comparison of the various methods used to extract NSPs from neutrophil granulocytes has not been published, providing the impetus to conduct this method optimization and comparison study.

Methods

Two NSP recovery methodologies were evaluated on samples from five human donors: zymosan stimulation and cell pellet extraction. For the zymosan stimulation method, 1 mL donor blood was added to zymosan and samples were incubated at 37°C for 30 min while shaking. Samples were then centrifuged, and the plasma was collected for quantitation of NSP activity. For the cell pellet extraction procedure, 2 mL whole blood samples were centrifuged into white blood cell pellets following red blood cell lysis. To each pellet, three sequential lysis steps were performed using either 0.05% Nonidet P-40 Substitute (NP40) or 0.02% Triton X-100 lysis buffers under agitation followed by centrifugation. NSP activities were quantified using an exogenous peptide substrate specific to each of the three NSPs being analyzed: neutrophil elastase, cathepsin G, and proteinase 3.

Results and discussion

The zymosan stimulation method resulted in lower recovery of active NSPs and was unable to stimulate significant release of active cathepsin G. In contrast, the NP40 pellet extraction method showed consistent inter-donor NSP release with greater recoveries of active NSPs than the Triton method or the zymosan stimulation method. Overall, the pellet extraction procedure provided 13.3-fold greater recovery of active neutrophil elastase, 283-fold greater recovery of active cathepsin G, and 2.9-fold greater recovery of active proteinase 3 than the zymosan method.

Conclusion

The NP40 cell pellet extraction method resulted in greater extraction of active NSPs compared to the other methods investigated here, which may allow for a more accurate and complete biomarker profile when evaluating human clinical samples.

Proteases and Their Potential Role as Biomarkers and Drug Targets in Dry Eye Disease and Ocular Surface Dysfunction

Dry eye disease (DED) is a multifactorial disorder that leads to ocular discomfort, visual disturbance, and tear film instability. DED is accompanied by an increase in tear osmolarity and ocular surface inflammation. The diagnosis and treatment of DED still present significant challenges. Therefore, novel biomarkers and treatments are of great interest. Proteases are present in different tissues on the ocular surface. In a healthy eye, proteases are highly regulated. However, dysregulation occurs in various pathologies, including DED. With this review, we provide an overview of the implications of different families of proteases in the development and severity of DED, along with studies involving protease inhibitors as potential therapeutic tools. Even though further research is needed, this review aims to give suggestions for identifying novel biomarkers and developing new protease inhibitors.

Novel benzoxazinone derivative as potent human neutrophil elastase inhibitor: Potential implications in lung injury

Neutrophil elastase, a powerful physiological defence tool, may serve as drug target for diverse diseases due to its bystander effect on host cells like chronic obstructive pulmonary disease (COPD). Here, we synthesised seven novel benzoxazinone derivatives and identified that these synthetic compounds are human neutrophil elastase inhibitor that was demonstrated by enzyme substrate kinetic assay. One such compound, PD05, emerged as the most potent inhibitor with lower IC₅₀ as compared to control drug sivelestat. While this inhibition is competitive based on substrate dilution assay, PD05 showed a high binding affinity for human neutrophil elastase (Kd = 1.63 nM) with faster association and dissociation rate compared to notable elastase inhibitors like ONO 6818 and AZD9668, and its interaction with human neutrophil elastase was fully reversible.Preclinical pharmacokinetic studies were performed in vitro where protein binding was found to be 72% with a high recovery rate, aqueous solubility of 194.7 μM, low permeability along with a favourable hERG. Experiments with cell line revealed that the molecule successfully prevented elastase induced rounding and retracted cell morphology and cell cytotoxicity. In mouse model PD05 is able to reduce the alveolar collapse induced by neutrophil elastase. In summary, we demonstrate the in situ, in vitro and in vivo anti-elastase potential of the newly synthesised benzoxazinone derivative PD05 and thus this could be promising candidate for further investigation as a drug for the treatment of COPD.

In vitro effects of cantharidin on gilthead seabream (Sparus aurata) head-kidney leucocytes

Cantharidin is a toxic vesicant terpene used in folk and traditional medicine due to its various therapeutic effects. Since there are no previous data on the effect of cantharidin in fish, this study aimed to investigate the in vitro related-inflammatory effects of cantharidin in gilthead seabream (Sparus aurata L.) head-kidney leucocytes (HKLs). In the first experiment, the HKLs were incubated with 0, 5 and 10 μg mL^-1 of cantharidin for 24 h to delimit its possible toxic effects. In a second experiment, leucocytes were incubated with ranging concentrations from 0 to 10 μg mL^-1 for 3, 6, or 12 h. Cell viability was higher in acidophilic granulocytes than in monocytes/macrophages and lymphocytes. Cantharidin caused apoptosis as was evidenced by transmission electron microscopy. In addition, cantharidin produced a time- and dose-dependent decrease of respiratory burst and phagocytic activities in HKLs, while their peroxidase activity was increased at 24 h of incubation with 5 and 10 μg mL^-1 of cantharidin. Different changes in the gene expression were observed after incubation with cantharidin. While the gene expression of tnfa, il1b and crel was up-regulated in HKLs, the nfkb1 and igmh genes were down-regulated in comparison to the expression found in control HKLs. Present results offer a first view of the possible effects and action mechanisms of cantharidin in HKLs, as well as its implication in the inflammatory process, which could be of interest not only for basic research but also in the aquaculture sector.

Fluid transport in the brain

The brain harbors a unique ability to, figuratively speaking, shift its gears. During wakefulness, the brain is geared fully toward processing information and behaving, while homeostatic functions predominate during sleep. The blood-brain barrier establishes a stable environment that is optimal for neuronal function, yet the barrier imposes a physiological problem; transcapillary filtration that forms extracellular fluid in other organs is reduced to a minimum in brain. Consequently, the brain depends on a special fluid [the cerebrospinal fluid (CSF)] that is flushed into brain along the unique perivascular spaces created by astrocytic vascular endfeet. We describe this pathway, coined the term glymphatic system, based on its dependency on astrocytic vascular endfeet and their adluminal expression of aquaporin-4 water channels facing toward CSF-filled perivascular spaces. Glymphatic clearance of potentially harmful metabolic or protein waste products, such as amyloid-β, is primarily active during sleep, when its physiological drivers, the cardiac cycle, respiration, and slow vasomotion, together efficiently propel CSF inflow along periarterial spaces. The brain's extracellular space contains an abundance of proteoglycans and hyaluronan, which provide a low-resistance hydraulic conduit that rapidly can expand and shrink during the sleep-wake cycle. We describe this unique fluid system of the brain, which meets the brain's requisites to maintain homeostasis similar to peripheral organs, considering the blood-brain-barrier and the paths for formation and egress of the CSF.

Phosphoproteomic Analysis of Haemaphysalis longicornis Saliva Reveals the Influential Contributions of Phosphoproteins to Blood-Feeding Success

Tick saliva, an essential chemical secretion of the tick salivary gland, is indispensable for tick survival owing to the physiological influence it exerts on the host defence mechanisms via the instrumentality of its cocktail of pharmacologically active molecules (proteins and peptides). Much research about tick salivary proteome has been performed, but how most of the individual salivary proteins are utilized by ticks to facilitate blood acquisition and pathogen transmission is not yet fully understood. In addition, the phosphorylation of some proteins plays a decisive role in their function. However, due to the low phosphorylation level of protein, especially for a small amount of protein, it is more difficult to study phosphorylation. Maybe, for this reason, the scarcity of works on the phosphorylated tick salivary proteomes still abound. Here, we performed a phosphoproteomic analysis of Haemaphysalis longicornis tick saliva via TiO₂ enrichment and the most advanced Thermo Fisher Orbitrap Exploris 480 mass spectrometer for identification. A total of 262 phosphorylated tick saliva proteins were identified and were subjected to functional annotation/enrichment analysis. Cellular and metabolic process terms accounted for the largest proportion of the saliva proteins, with the participation of these proteins in vital intracellular and extracellular transport-oriented processes such as vesicle-mediated transport, exocytic process, cell adhesion, and movement of cell/subcellular component. “Endocytosis”, “Protein processing in endoplasmic reticulum”, and “Purine metabolism” were the most significantly enriched pathways. The knockdown (RNAi) of Tudor domain-containing protein (TCP), actin-depolymerizing factors (ADF), programmed cell death protein (PD), and serine/threonine-protein kinase (SPK) resulted in the dissociation of collagen fibers and the pilosebaceous unit, increased inflammatory infiltrates/granulocytes (possibly heterophiles), and the depletion of the epithelium. Ticks injected with SPK dsRNA engorged normally but with a change in skin colour (possibly an autoimmune reaction) and the failure to produce eggs pointing to a possible role of SPK in reproduction and host immune modulation. Ticks injected with ADF dsRNA failed to acquire blood, underscoring the role of ADF in facilitating tick feeding. The results of this study showed the presence of phosphorylation in tick saliva and highlight the roles of salivary phosphoproteins in facilitating tick feeding.

The role of neutrophil extracellular traps in acute lung injury

Acute lung injury (ALI) is a heterogeneous inflammatory condition associated with high morbidity and mortality. Neutrophils play a key role in the development of different forms of ALI, and the release of neutrophil extracellular traps (NETs) is emerging as a common pathogenic mechanism. NETs are essential in controlling pathogens, and their defective release or increased degradation leads to a higher risk of infection. However, NETs also contain several pro-inflammatory and cytotoxic molecules than can exacerbate thromboinflammation and lung tissue injury. To reduce NET-mediated lung damage and inflammation, DNase is frequently used in preclinical models of ALI due to its capability of digesting NET DNA scaffold. Moreover, recent advances in neutrophil biology led to the development of selective NET inhibitors, which also appear to reduce ALI in experimental models. Here we provide an overview of the role of NETs in different forms of ALI discussing existing gaps in our knowledge and novel therapeutic approaches to modulate their impact on lung injury.

Polymorphonuclear Neutrophils and Tumors: Friend or Foe?

Tumor microenvironment (TME) is a dynamic network that apart from tumor cells includes also cells of the immune system, e.g., neutrophils, which are recruited from blood circulation. In TME, neutrophils are strongly implicated in the direct and indirect interactions with tumor cells or other immune cells, and they play roles in both preventing and/or facilitating tumor progression and metastasis. The dual role of neutrophils is determined by their high plasticity and heterogeneity. Analogous to the macrophages, neutrophils can express antitumoral (N1) and protumoral (N2) phenotypes which differ substantially in morphology and function. N1 phenotype characterizes with a high cytotoxic and proinflammatory activities, while N2 phenotype with immunosuppressive and prometastatic properties. The antitumoral effect of neutrophils includes for example the production of reactive oxygen species or proapoptotic molecules. The protumoral action of neutrophils relies on releasing of proangiogenic and prometastatic mediators, immunosuppressive factors, as well as on direct helping tumor cells in extravasation process. This chapter summarizes the heterogeneity of neutrophils in TME, as well as their dual role on tumor cells.

Neutrophils and their role in the aetiopathogenesis of type 1 and type 2 diabetes

Multiple and complex aetiological processes underlie diabetes mellitus, which invariably result in the development of hyperglycaemia. Although there are two prevalent distinct forms of the disease, that is, type 1 and type 2 diabetes, accumulating evidence indicates that these syndromes share more aetiopathological mechanisms than originally thought. This compels a rethinking of the approaches to prevent and treat the different manifestations of what eventually becomes a hyperglycaemic state. This review aims to address the involvement of neutrophils, the most abundant type of granulocytes involved in the initiation of the acute phase of inflammation, in the aetiopathogenesis of diabetes mellitus, with a focus on type 1 and type 2 diabetes. We review the evidence that neutrophils are the first leucocytes to react to and accumulate inside target tissues of diabetes, such as the pancreas and insulin-sensitive tissues. We then review available data on the role of neutrophils and their functional alteration, with a focus on NETosis, in the progression towards clinical disease. Finally, we review potential approaches as secondary and adjunctive treatments to limit neutrophil-mediated damage in the prevention of the progression of subclinical disease to clinical hyperglycaemia.

Hyperactive neutrophils infiltrate vital organs of tumor bearing host and contribute to gradual systemic deterioration via upregulated NE, MPO and MMP-9 activity

Cancer is known to have systemic impact by targeting various organs that ultimately compromises the overall physiology of the host. Several reports have demonstrated the role of neutrophils in cancer wherein the focus has been drawn on the elevated neutrophil count in blood or at tumor loci. However, their role in mediating systemic effects during cancer progression has not been deciphered so far. Therefore, it is worthwhile to explore whether and how neutrophils contribute to systemic deterioration in cancer. To discern their systemic role, we evaluated neutrophil count and function at different stages of tumor growth in Dalton's Lymphoma mice model. Notably, our results displayed a gradual increase in Ly6G⁺ neutrophils in peripheral blood and their infiltration in vital organs including liver, lungs, spleen, kidney, lymph nodes and peritoneum of tumor bearing host. We showed remarkable alterations in histoarchitecture and serum enzyme levels that aggravated with tumor progression. We next examined neutrophil function by assessing its granular cargoes including neutrophil elastase (NE), myeloperoxidase (MPO), and matrix metalloproteinases (MMP-8 and MMP-9). Interestingly, blood neutrophils of tumor bearing mice exhibited a marked change in morphology with gradual increase in NE and MPO expression with tumor growth. In addition, we observed upregulated expression of NE, MPO, MMP-8 and MMP-9 in the vital organs of tumor bearing host. Taken together, our results demonstrate heightened infiltration and function of neutrophils in vital organs of tumor bearing host which possibly account for gradual systemic deterioration during cancer progression. Our findings thus implicate neutrophils as a potential therapeutic target that may help to reduce the overall fatality rate of cancer.

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.

Zebrafish intestinal transcriptome highlights subdued inflammatory responses to dietary soya bean and efficacy of yeast β-glucan

Anti-nutritional factors in dietary components can have a negative impact on the intestinal barrier. Here, we present soya bean-induced changes in the intestine of juvenile zebrafish and the effect of yeast β-glucan through a transcriptomic approach. The inclusion of soya bean meal affected the expression of several intestinal barrier function-related genes like arl4ca, rab25b, rhoub, muc5ac, muc5d, clcn2c and cltb in zebrafish. Several metabolic genes like cyp2x10.2, cyp2aa2, aldh3a2b, crata, elovl4, elovl6, slc51a, gpat2 and ATP-dependent peptidase activity (lonrf, clpxb) were altered in the intestinal tissue. The expression of immune-related genes like nlrc3, nlrp12, gimap8, prdm1 and tph1a, and genes related to cell cycle, DNA damage and DNA repair (e.g. spo11, rad21l1, nabp1b, spata22, tdrd9) were also affected in the soya bean fed group. Furthermore, our study suggests the plausible effect of yeast β-glucan through the modulation of several genes that regulate immune responses and barrier integrity. Our findings indicate a subdued inflammation in juvenile zebrafish fed soya bean meal and the efficacy of β-glucan to counter these subtle inflammatory responses.

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

BACKGROUND AND PURPOSE

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

EXPERIMENTAL APPROACH

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

KEY RESULTS

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

CONCLUSION AND IMPLICATIONS

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

Identification of sustainable trypsin active-site inhibitors from Nigrospora sphaerica strain AVA-1

Trypsin is a protein-digesting enzyme that is essential for the growth and regeneration of bone, muscle, cartilage, skin, and blood. The trypsin inhibitors have various role in diseases such as inflammation, Alzheimer's disease, pancreatitis, rheumatoid arthritis, cancer prognosis, metastasis and so forth. From 10 endophytic fungi isolated, we were able to screen only one strain with the required activity. The fungus with activity was obtained as an endophyte from Dendrophthoe falcata and was later identified as Nigrospora sphaerica. The activity was checked by enzyme assays using trypsin. The fungus was fermented and the metabolites were extracted and further purified by bioassay-guided chromatographic methods and the compound isolated was identified using gas chromatography-mass spectrometry. The compound was identified as quercetin. Docking studies were employed to study the interaction. The absorption, distribution, metabolism, and excretion analysis showed satisfactory results and the compound has no AMES and hepatotoxicity. This study reveals the ability of N. sphaerica to produce bioactive compound quercetin has been identified as a potential candidate for trypsin inhibition. The present communication describes the first report claiming that N. sphaerica strain AVA-1 can produce quercetin and it can be considered as a sustainable source of trypsin active-site inhibitors.

Tick host immunity: vector immunomodulation and acquired tick resistance

Ticks have an unparalleled ability to parasitize diverse land vertebrates. Their natural persistence and vector competence are supported by the evolution of sophisticated hematophagy and remarkable host immune-evasion activities. We analyze the immunomodulatory roles of tick saliva which facilitates their acquisition of a blood meal from natural hosts and allows pathogen transmission. We also discuss the contrasting immunological events of tick-host associations in non-reservoir or incidental hosts, in which the development of acquired tick resistance can deter tick attachment. A critical appraisal of the intricate immunobiology of tick-host associations can plant new seeds of innovative research and contribute to the development of novel preventive strategies against ticks and tick-transmitted infections.

The relationship of neutrophil elastase and proteinase 3 with risk factors, and chronic complications in type 2 diabetes: A Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) sub-study

INTRODUCTION

Neutrophil elastase (NE) and proteinase 3 (PR3) are novel inflammation biomarkers. We investigated their associations with chronic complications, determinants of biomarker levels and effects of fenofibrate in patients with type 2 diabetes mellitus (T2DM) from Fenofibrate Intervention and Event Lowering in Diabetes study.

METHODS

Plasma NE and PR3 levels were quantified at baseline (n = 2000), and relationships with complications over 5-years assessed. Effects of fenofibrate on biomarker levels (n = 200) were determined at four follow-up visits.

RESULTS

Higher waist-to-hip ratio, homocysteine and C-reactive protein and lower apoA-II were determinants of higher NE and PR3 levels. Higher NE levels were associated with on-trial stroke and cardiovascular mortality, and higher PR3 levels with on-trial stroke, but associations were not significant after adjustment for confounding factors. Although higher NE and PR3 levels were associated with baseline total microvascular disease, only NE levels were associated with on-trial neuropathy or amputation. These associations were not significant after adjusting for multiple comparisons. NE and PR3 levels did not change with fenofibrate.

CONCLUSIONS

In T2DM plasma NE and PR3 levels are associated with vascular risk factors, and total microvascular disease at baseline, but on rigorous analyses were not associated with on-trial complications. Levels were not changed by fenofibrate.

Elastolytic activity is associated with inflammation in bladder cancer

Cancer development and progression is often associated with inflammation. Late diagnosis of inflammation that directly leads to the development of neoplasm - cancer is associated with a reduction in the chance of successful treatment or is associated with therapeutic difficulties. A panel of chromogenic substrates was used for the qualitative determination of specific activity of enzymes in urine of patients with confirmed inflammatory reaction and/or epithelial neoplasms in particular tumors at various stages of development. Urine of people with excluded inflammation was used as a control group. Proteolytic activity was determined in urine samples collected from patients with epithelial neoplasms and/or inflammation. What is more, we determine human neutrophil elastase (HNE) activity related inflammation based on the examination of urine samples. We suspect that the proteolytical activity of urine samples is due to neutrophil response to inflammation, which is directly related to cancer. This is the first study to determine elastolytic activity in bladder cancer urine samples. It supports wider use of urine for inflammation screening.

Reduced neutrophil granular proteins and post-treatment modulation in tuberculous lymphadenitis

Background

Neutrophils are important for host innate immune defense and mediate inflammatory responses. Pulmonary tuberculosis (PTB) is associated with increased neutrophil granular protein (NGP) levels in the circulation. However, the systemic levels of neutrophil granular proteins were not examined in tuberculous lymphadenitis (TBL) disease.

Methods

We measured the systemic levels of NGP (myeloperoxidase [MPO], elastase and proteinase 3 [PRTN3]) in TBL and compared them to latent tuberculosis (LTB) and healthy control (HC) individuals. We also measured the pre-treatment (Pre-T) and post-treatment (Post-T) systemic levels of neutrophil granular proteins in TBL individuals upon anti-tuberculosis treatment (ATT) completion. In addition, we studied the correlation and discriminatory ability of NGPs using receiver operating characteristic (ROC) analysis.

Results

Our data suggests that systemic levels of NGPs (MPO, PRTN3, elastase) were significantly reduced in TBL individuals compared to LTB and HC individuals. Similarly, after ATT, the plasma levels of MPO and elastase but not PRTN3 were significantly elevated compared to pre-treatment levels. NGPs (except PRTN3) were positively correlated with absolute neutrophil count of TBL, LTB and HC individuals. Further, NGPs were able to significantly discriminate TBL from LTB and HC individuals.

Conclusion

Hence, we conclude reduced neutrophil granular protein levels might be associated with disease pathogenesis in TBL.

B Cell Activation and Escape of Tolerance Checkpoints: Recent Insights from Studying Autoreactive B Cells

Autoreactive B cells are key drivers of pathogenic processes in autoimmune diseases by the production of autoantibodies, secretion of cytokines, and presentation of autoantigens to T cells. However, the mechanisms that underlie the development of autoreactive B cells are not well understood. Here, we review recent studies leveraging novel techniques to identify and characterize (auto)antigen-specific B cells. The insights gained from such studies pertaining to the mechanisms involved in the escape of tolerance checkpoints and the activation of autoreactive B cells are discussed. In addition, we briefly highlight potential therapeutic strategies to target and eliminate autoreactive B cells in autoimmune diseases.

Recent sexual violence exposure is associated with immune biomarkers of HIV susceptibility in women

PROBLEM

HIV/AIDS and sexual violence act synergistically and compromise women's health. Yet, immuno-biological mechanisms linking sexual violence and increased HIV susceptibility are poorly understood.

METHODS

We conducted a cross-sectional pilot study of HIV-uninfected women, comparing 13 women exposed to forced vaginal penetration within the past 12 weeks (Exposed) with 25 Non-Exposed women. ELISA assays were conducted for 49 biomarkers associated with HIV pathogenesis in plasma and cervicovaginal lavage (CVL). Differences between Exposed and Non-Exposed were analyzed by linear and logistic regression, using propensity score weighting to control for age, race, socioeconomic status, menstrual cycle, and contraceptive use.

RESULTS

In CVL, Exposed women had significantly reduced chemokines MIP-3α (p < .01), MCP-1 (p < .01), and anti-HIV/wound-healing thrombospondin-1 (p = .03). They also had significantly increased inflammatory cytokine IL-1α (p < 0.01) and were more likely to have detectable wound-healing PDGF (p = .02). In plasma, Exposed women had reduced chemokines MIP-3α (p < .01) and IL-8 (p < .01), anti-inflammatory cytokine TGF-β (p = .02), anti-HIV/antimicrobial HBD-2 (p = .02), and wound-healing MMP-1 (p = 0.02). They also had increased thrombospondin-1 (p < .01) and Cathepsin B (p = .01). After applying the stringent method of false discovery rate adjustment, differences for IL-1α (p = .05) and MCP-1 (p = .03) in CVL and MIP-3α (p = .03) in plasma remained significant.

CONCLUSIONS

We report systemic and mucosal immune dysregulation in women exposed to sexual violence. As these biomarkers have been associated with HIV pathogenesis, dysregulation may increase HIV susceptibility.

Mice Deficient in the IL-1β Activation Genes Prtn3, Elane, and Casp1 Are Protected Against the Development of Obesity-Induced NAFLD

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease. Inflammatory pathways contribute to disease pathogenesis; however, regulation of the underlying mechanism is not completely understood. IL-1β, a pro-inflammatory cytokine, participates in the development and progression of NAFLD. To become bioactive, IL-1β requires enzymatic processing. Mechanisms that activate IL-1β include the classical NLRP3 inflammasome-caspase-1 and the neutrophil serine proteases, neutrophil elastase, and proteinase-3. Several studies have shown that both caspase-1 and the neutrophil serine proteases are important for NAFLD development. However, it is unknown whether these pathways interact and if they have a synergistic effect in promoting NAFLD. In the present study, we developed a novel and unique mouse model by intercrossing caspase-1/11 knockout mice with neutrophil elastase/proteinase-3 double knockout mice. Subsequently, these mice were examined regarding the development of high-fat diet–induced NAFLD. Our results show that mice deficient in caspase-1, neutrophil elastase, and proteinase-3 were protected from developing diet-induced weigh gain, liver steatosis, and adipose tissue inflammation when compared with controls. We conclude that pathways that process pro-IL-1β to bioactive IL-1β play an important role in promoting the development of NAFLD and obesity-induced inflammation. Targeting these pathways could have a therapeutic potential in patients with NAFLD.

Prolyl endopeptidase contributes to early neutrophilic inflammation in acute myocardial transplant rejection

Altered inflammation and tissue remodeling are cardinal features of cardiovascular disease and cardiac transplant rejection. Neutrophils have increasingly been understood to play a critical role in acute rejection and early allograft failure; however, discrete mechanisms that drive this damage remain poorly understood. Herein, we demonstrate that early acute cardiac rejection increases allograft prolyl endopeptidase (PE) in association with de novo production of the neutrophil proinflammatory matrikine proline-glycine-proline (PGP). In a heterotopic murine heart transplant model, PGP production and PE activity were associated with early neutrophil allograft invasion and allograft failure. Pharmacologic inhibition of PE with Z-Pro-prolinal reduced PGP, attenuated early neutrophil graft invasion, and reduced proinflammatory cytokine expression. Importantly, these changes helped preserve allograft rejection-free survival and function. Notably, within 2 independent patient cohorts, both PGP and PE activity were increased among patients with biopsy-proven rejection. The observed induction of PE and matrikine generation provide a link between neutrophilic inflammation and cardiovascular injury, represent a potential target to reduce allogenic immune responses, and uncover a mechanism of cardiovascular disease that has been previously unrecognized to our knowledge.